US3237007A - Retarder control systems - Google Patents

Description

2 Sheets-Sheet 1 A. R. CRAWFORD RETARDER CONTROL SYSTEMS 6 a D a j in m 5 M F 7T w 7 SN 6 A n l -.1 l m R 2 8 H M, NR 6 R x 3 1 \@C R z Tu 6 U AD H Rs P m m V GM mmmm A M RN 9 ARH 6 TEC 3 2 2 a K! 2 MM R /L 7 H mm 2 I; My RT 2 5 TM n l u 2 l 0 m5 M/ m 2 m m ,2 m M m M Feb. 22, 1966 Filed April 2, 1965 VIBRATION TRANSDUCER Feb. 22, 1966 A. R. CRAWFORD RETARDER CONTROL SYSTEMS 2 Sheets-Sheet 2 Filed April 2, 1965 United States Patent 3,237,007 RETARDER CONTROL SYSTEMS Arthur B. Crawford, Columbus, Ohio, assignor to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Filed Apr. 2, 1965, Ser. No. 447,602 18 Claims. (Cl. 246-182) This invention relates to a new and improved method and apparatus for braking railroad cars in the operation of a railroad classification yard or the like. More particularly, the invention relates to a method of controlling an electrically actuable car retarder and to control apparatus for actuating the car retarder.

This application is a continuation-in-part of application Serial No. 138,382 filed September 15, 1961.

In the operation of a railroad classification yard, railroad cars are ordinarily pushed over the top of an incline or hump and roll down the incline into the branching tracks of the yard. It is usually necessary to provide some means for braking the cars at one or more points along the gang track or feeder track; in other instances, it may also be necessary to provide additional braking on the classification tracks of the yard. Track brakes or car retarders are employed for this purpose, usually in the form of pairs of brakes shoes of elongated rail-like construction that engages the sides of the car 'wheels. Braking installations of this kind are necessary to prevent coupling at excessive speed because it is virtually impossible to release the car from the top of the incline Without some variations in velocity. Moreover, in a long yard the cars may well develop excessive velocity as they roll through the various stages of the yard.

Relatively elaborate control systems have been proposed, in the past, for afiording centralized control of all of the car retarders in a classification yard. On the other hand, a much simpler system has been suggested that entails the use of independent track brakes together with individual control means for operating each retarder independently of the others in the yard. In an arrangement of this kind, each car is braked to a virtual standstill in each car retarder, after which the retarder is opened :and the car is permitted to resume movement along the incline track. With judicious location of the retarders in the yard, an arrangement of this kind can be elfect-ive to limit the speed of each car to a safe value.

The use of independently operated ear retarders, each of which is effective to stop and then to release a car passing therethrough, presents some substantial problems, particuarly where the control is to be entirely automatic. Thus, means must be provided to assure maintenance of the car retarder in closed condition upon the entrance of each car or cut of cars. On the other hand, the retarder must be held open long enough to permit each cut of cars to roll free of the retarder. Thus, if a given car does not pass out of the retarder, but is caught and held therein upon re-closing of the track brake, the next approaching car finds the retarder in partially open or released condition. When this occurs, the second car collides with the first stationary car, which may lead to substantial damage both to the cars and their contents. The difiiculty presented by the necessity for permitting complete release of each car from the retarder is compounded by the fact that railroad cars exhibit very substantial variations in their rolling characteristics. Thus, a light free-rolling car may move out of the car retarder in a minor fraction of the time required for the clearance of a heavy car with poor rolling characteristics. Mechanical sensing devices may be utilized to maintain surveillance of the position of each car in the 3,237,007 Patented Feb. 22, 1966 "ice retarder, but the operating speeds of devices of this kind are relatively low, so that they may substantially reduce the rate at which cars may be classified. Furthermore, some mechanical sensing switches or similar apparatus are subject to some limitations with respect to the accuracy of operation, particularly with respect to determination of the car position, due to variations in the number of Wheels on each car.

It is a principal object of the present invention, therefore, to provide a new and improved method and apparatus for independent control and actuation of one or more car retarders, in a railroad classification or like application, to enable each car retarder independently to brake any car or cut of cars that enters the retarder and to release the car or cars for subsequent movement in an expeditious yet safe manner.

A particular object of the invention is to provide a new and improved method of braking railroad cars, using an electrically actuatatble car retarder, based upon the sensing of the actual movement of each car rather than upon timing controls or the position of the car. I

An additional object of the invention is to provide a new and improved method and apparatus for controlling the operation of a track brake or car retarder to assure immediate release of the car once it has been braked to a predetermined release velocity, to maintain the brake in released condition until the car has cleared the re tarder, and immediately to restore the retarder to braking condition to receive another car.

A further object of the invention is to utilize a vibration signal representative of the movement of the car into a car retarder, in a unique manner, first to establish and maintain the retarder in braking condition and subsequently to establish and maintain the retarder in released condition.

Another object of the invention is to provide a new and improved method and apparatus for automatic operation of a car retarder that stops each car or cut of cars, and then releases the car or cars for further movement, and that includes automatic compensation for single or multiple car conditions.

Thus, the present invention relates to a method of braking railroad cars, utilizing a car retarder located on a given section of track and electrically actuatable between a braking condition and a released condition." In accordance with the method of the invention, the car retarder is initially established in its braking condition. Movement of the car along the track section comprising the retarder is sensed to develop a control signal having a given parameter representative of the velocity of car movement. In the preferred method described in detail hereinafter, vibration of the traffic rail is sensed to develop a control signal having an amplitude representative of car velocity. The control signal is initially utilized to maintain the retarder in braking condition when the control signal parameter is above a threshold value indicative of the presence of a car moving along the retarder track section at a velocity above a predetermined release velocity. Preferably, the release velocity is established at approximately zero velocity. The method further includes actuating the retarder to its released condition When the control signal parameter drops below the aforementioned threshold. Thus, when a car approaches the retarder and the latter is placed in braking condition, the control signal is utilized to maintain the retarder in braking condition until the signal drops suffioiently to indicate that the car is approximately stopped. When the car resumes movement, the same control signal is utilized to hold the retarder open until the signal again falls below the threshold, indicating that the car has cleared the retarder track section. In addition, the method of the invention may provide for actuating the retarder to its braking condition whenever the control signal remains below the aforementioned threshold value for a predetermined time interval. This is done to protect the retarder against a failure to develop a control signal at the time the car rolls out of the retarder, which might otherwise leave the retarder in open condition.

The apparatus of the present invention comprises a control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like. This control system comprises retarder operating means having braking and releasing operating conditions for actuating the retarder to braking and releasing positions respectively. Gate means are connected to the retarder operating means, these gate means being actuatable from a normal operating condition, in which the gate means actuates the retarder operating means to braking condition, to an actuated condition in which the gate means permits the retarder operating means to change to its releasing condition. Sensing means, usually one or more vibration transducers, are provided for developing a control signal indicative of movement of a railroad car along the retarder track section. In addition, the control system comprises control means coupled to all of the aforementioned retarder operating, gate, and sensing means. This control means is actuatable between first and second operating conditions in response to variations in the control signal above and below a given threshold value. The control means actuates the gate means to its actuated condition whenever the control signal exceeds the threshold value. In addition, the control means maintains the retarder operating means in whichever operating condition the latter is in at the time the control signal exceeds the threshold value until the control signal falls below threshold.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a partially schematic plan view of a railway car retarder actuated and controlled in accordance with the present invention;

FIG. 2 is a combination block diagram and schematic circuit diagram of one form of retarder control system constructed in accordance with the invention;

FIG. 3 is a detail schematic diagram of a modification of the circuit of FIG. 2; and

FIG. 4 is a combination block diagram and schematic circuit diagram of another form of control system constructed in accordance with the invention.

FIG. 1 illustrates a substantially conventional railroad car retarder to which the present invention may be applied. The car retarder 10 includes a relatively short section of track comprising the trafiic rails 11 and 12. The railroad track in which the rail sections 11 and 12 are incorporated is inclined to permit cars to roll through the retarder 10 in the direction indicated by the arrow A. A pair of car-retarding rails or brake shoes 13 are disposed immediately adjacent the rail 11 in position to engage the opposite sides of a car wheel as the wheel traverses the track section 11. A similar pair of retarder rails 14 may be disposed adjacent the traffic rail section 12 in position to engage the sides of a car wheel moving along this portion of the track. It will be understood that one pair of retarder rails may be used if desired; it is not essential to brake along both trafiic rails.

Suitable means are provided for actuating the retarder rails or brake shoes 13 and 14 between braking and released positions, this mechanism being generally indicated in FIG. 1 as the retarder operating mechanism 15. The retarder operating mechanism 15 may comprise any suitable electrical, mechanical, pneumatic, or hydraulic mechanism capable of moving the retarder rails .13 and 14 between an open or released condition and a closed or re tarding condition. Regardless of the basic drive employed in the operating mechanism 15, however, it is preferable that this apparatus be constructed to provide for electrical actuation.

When the retarder 10 is in its open or released operating condition, the rails 13 and 14 are spread to permit a car rolling along the track sect-ion 11, 12 to continue its movement without impedance from the retarder. When the retarder 1D is actuated to its closed or braking condition, however, the retarder rails in each of pairs 13 and 14 are moved toward each other. As a consequence, the retarder rails engage the sides of the wheels of any car that enters the retarder and provide a substantial braking effect on the rolling car.

In order to provide for braking of railroad cars, in the retarder 10, in accordance with the present invention, it is necessary to sense the movement of a railroad car or cars along the track section 11, .12. This is done in order to provide a means for developing a control signal generally representative of the velocity of car movement. It is not necessary to provide for accurate measurement of the car speed. Rather, what is required is, essentially, the sensing of the presence of a car moving at some velocity above a predetermined threshold value. Usually this threshold speed is quite low and, indeed, it is suflicient if the sensing means can detect whether the ear is actually moving or has come to a virtual halt.

As shown in FIG. 1, the necessary sensing operation may be effected by a vibration transducer 21 mounted upon one of the traffic rails, in this instance the track section 11. The vibration transducer 21 may be of conventional construction and, for example, may be essentially similar to the operating mechanism of an ordinary microphone except that the vibratile element of the mechanism is mechanically connected to the rail 11 instead of to a diaphragm. Vibration detecting devices of this kind are well-known in the art and, accordingly, no detailed description of the construction of the transducer 21 is provided herein. It should be understood that other forms of vibration detector can be substituted for the transducer 21. Moreover, other suitable means of sensing the presence of a moving car may be utilized instead of this type of transducer. Transducer 21 is electrically connected to a retarder control unit 22 which is utilized to actuate the retarder operating mechanism 15.

The method of operation that comprises one important aspect of the present invention entails the initial step of establishing the car retarder 10 in its braking condition. That is, the retarder operating mechanism 15 is normally actuated to hold the retarder rails 13 and 14 in position to engage the wheels of any car that enters the retarder. Depending upon the construction of the mechanism 15, this may require application of an electrical signal to the operating mechanism 15 to cause that mechanism to drivev the retarder rails inwardly toward the tratfic rails against some form of bias, usually provided by relatively heavy springs. On the other hand, the retarder apparatus may be constructed to afford a normal braking condition, with the retarder rails urged toward the trafiic rails by some biasing means, which may again comprise springs. In the latter instance, the step of initially establishing the car retarder in its braking condition is effected by preventing actuation of the retarder operating mechanism 15, since the latter is used to afford a positive drive to bring the retarder rails to released condition.

The approach of a railroad car along the track section 11, 12 is sensed by the vibration transducer 21 or by other Suitable sensing means. Upon the detection of movement of a car onto the track section 11, 12, a control signal is developed that is generally representative of the velocity of the car. The parameter of the control signal indicative of car velocity may be the signal amplitude, particularly where vibration of one of the trafiic rails is taken as the starting point for the sensing operation. This is not critical, however, and some other control signal parameter such as frequency of vibration may be employed. It should be emphasized that it is not necessary or even particularly desirable to provide a control signal that is precisely proportional to or otherwise represents a precise function of car speed. Rather, it is sufficient to develop a control signal having some reasonable amplitude (or frequency) in the presence of a moving car and a substantially different amplitude (or frequency) when no car is present or when the car is stopped or is nearly stopped. Stated differently, the critical aspect of the control signal is that it exceed some threshold value whenever the car velocity exceeds a predetermined release velocity and that it be less than that threshold whenever the car is braked below the release velocity. In the preferred application of the invention, the release velocity is taken as nearly as possible to zero.

Further in accordance with the method of the present invention, as soon as a control signal exceeding the aforementioned threshold is developed, this control signal is initially utilized to maintain the retarder in braking condition. When the car first approaches the retarder, the retarder is established in its braking condition, as noted above. The control signal is employed to maintain the retarder 10 in braking condition, by suitably actuating operating mechanism 15, as long as the control signal remains above the threshold value. As soon as the control signal drops below the threshold, however, the retarder is actuated to its alternate condition. In this instance, the retarder is released when the incoming car has been braked to an extent sufiicient to indicate that its movement has been interrupted.

When the retarder 10 is actuated to released condition, however, the car is again free to roll. As it picks up speed, the resulting vibration of the rail 11 is again sensed, developing a control signal in the same manner as described above. As soon as the control signal exceeds the selected threshold value, the control signal is utilized to maintain the retarder in its released condition. As before, the retarder is maintained in this particular operating condition until such time as the control signal is again reduced below threshold value, which occurs when the car has rolled clear of the track section 11, 12 and the vibration of the rail 11 is consequently much reduced. At this point, the reduction of the controlsignal below its threshold may again be utilized to actuate the retarder to its braking condition if a normally closed retarder operation is desired. Accordingly, the retarder is restored to braking condition, from released condition, and is ready to receive the next car. Alternatively, the retarder may be left open and the next incidence of the control signal, caused by the next approaching car, may be employed to trigger the retarder closed.

In addition to the steps of the method as set forth above, it is desirable to actuate the retarder 10 to its braking condition whenever the control signal remains below the aforementioned threshold value for a predetermined time interval, Where normally-closed operation is desired. This is a safety provision to prevent the retarder 10 from remaining in open condition in the event that the vibration pickup 21 fails to detect the relatively slow movement of the car out of the retarder. This happens only on rare occasions, as when a particularly smooth rolling car is present in the retarder and there is no artificial means to develop distinctive vibrations. It may also be desirable to interrupt the development of the control signal for a short time interval on those occasions when the retarder is actuated from its braking condition to its released condition. In the course of a braking operation, relatively light cars may ride up between the retarder rails and out of contact with the traffic rails. Moreover, considerable vibration of the entire retarder may occur when the retarder is opened or closed, particularly if a fast-acting retarder operating mechanism is employed. Thus, it is frequently desirable to prevent spurious operation of the retarder or damage to the sensing apparatus or the associated operating circuits of the control unit 22 by effectively blanking the control signal circuits under these circumstances.

The method of the present invention, as described above, permits effective and rapid car retarder operation based upon the sensing of the actual movement of a railroad car and without the use of position-sensing devices. The method does not depend upon the position of a car, other than its efiective engagement with the retarder traific rail. Furthermore, the method of the invention permits the use of very rapid acting sensing devices, thereby materially increasing the effective capacity of the retarder. Operation of the retarder is made independent of the number of cars that may enter the retarder in a single cut. That is, the operation proceeds in the same manner regardless of whether one car or a plurality of coupled cars is released to roll intothe retarder.

FIG. 2 illustrates, in substantial detail, one embodiment of a control system constructed in accordance with the present invention and designated generally by the reference character 22 to indicate that it will be utilized as the retarder control unit 22 in FIG. 1. The control system 22 includes an input amplifier 24 that is coupled to the output of the vibration transducer 21. The amplifier 24 may be of conventional construction; for example, this amplifier may comprise a simple two-stage A.C.-coupled transistor amplifier. Accordingly, the details of the amplifier circuit are not shown in the drawings. Preferably, the amplifier should be provided with a gain control to permit adjustment of the operating level and thereby establish a working threshold for the control system 22.

The output terminal 25 of the amplifier 24 is returned to ground through a diode 26 and is coupled through a diode 27 to the base electrode of a transistor 28. The input circuit to the transistor 28 further includes a parallel RC circuit comprising a capacitor 29 and a resistor 31 connected from the base electrode to ground.

The transistor 28 is utilized as a gating device and comprises one of the operating elements of a control circuit generally indicated by the reference character 32. The emitter of the transistor 28 is connected to system ground. The collector of the transistor is connected to one terminal of the operating coil 33 of a control relay 34. The other terminal of the relay coil 33 is connected to a unidirectional negative-polarity operating source herein designated as C. The relay 33 is provided with a first movable contact 35 that is normally engaged with a fixed contact 36 but which engages a second fixed contact 37 when the relay is energized. In addition, the relay 34 includes a second movable contact 41 that is normally engaged with a fixed contact 42 but is engageable with another fixed contact 43 upon actuation of the relay.

The first fixed contact 37 of the relay 34 is returned to ground through a relatively small resistor 44. The contact 37 is connected to a negative polarity D.C. supply, herein designated as D, through a resistor 45. The movable contact 35 of the relay is returned to ground through a capacitor 46. The movable contact 35 is also connected, by means of a series circuit comprising a neon discharge device 47 .and a resistor 48, to the base electrode of a second gating transistor 49. The input circuit to the transistor 49 further includes a load resistor 51 that is connected between the 'base electrode and ground.

The gate transistor 49 constitutes a part of a gate device generally designated by the reference numeral 52. The emitter of the transistor is connected to system ground. The collector of the transistor is connected to one terminal of the operating coil 53 of a relay 54 inc-orporated in the gate means 52. The other terminal of the coil 53 is connected to the C- supply.

The relay 54 includes a first movable contact 55 that is engageable alternately with the fixed contacts 56 and 57. The relay further includes a second movable contact 61 that is alternately engageable with two fixed contacts 62 and 63. The relay is shown in de-energized condition, with the movable contacts 55 and 61 engaged with the fixed contacts 56 .and 62 respectively. The movable contact 55 of the relay 54 is connected to an RC timing circuit comprising a resistor 65 and a capacitor 66. The resistor '65 is connected to the D supply whereas the capacitor 66 is returned to system ground. The movable contact 61 of the gate relay 54, on the other hand, is connected directly to ground.

The normally closed contact 56 of the relay 54 is connected through a series circuit comprising a neon bulb 67 and a resistor 68 to an additional gate transistor 69, being connected to the base electrode of the transistor. The transistor base is also returned to ground through an input resistor 71. The emitter of the transistor 69 is returned to system ground. The collector electrode is connected to one terminal of the operating coil 73 of a relay 74. The other terminal of the relay coil 73 is connected to the C- supply.

The relay 74 and the gate transistor 69 comprise the principal elements of a retarder operating device 72. The retarder operating relay 74 comprises four sets of contacts. The first contact set comprises a movable contact 75 engageable with a normally closed fixed contact '76 and a normally open contact 77. The second set of contacts comprises the movable contact 81 which is normally engaged with a fixed contact 82 but is engageable with a second fixed contact 83. The third set of contacts includes a movable contact 85 engageable with a normally closed contact 86 and a normally open. contact -87. The fourth contact stage of the relay comprises the movable contact 91, which is engageable with the contacts 92 and 93. The movable contact 75 of the retarder operating relay 74 is connected through a resistor 95 to the base-electrode of the retarde-r operating gate transistor 69. The base electrode of this transistor is also connected to the fixed contact 43 of the control relay 32. The normally closed contact 76 of the reta-rder operating relay is left open-ci-rcui ted. The normally open contact 77 is connected .to a parallel RC timing circuit comprising a resistor 97 and a capacitor 96. The capacitor 96 is returned to system ground Whereas the resistor 97 is connected to the C- supply. In addition, the relay contact 77 is connected to the fixed contact 63 in the gate relay -4, the related fixed contact 62 of the gate relay being left open-circuited.

The second movable contact 81 of the relay 74 is connected to system ground. The normally closed contact 82 associated with the movable contact 81 is connected to the movable contact 41 of the control relay 34. These two contacts are also connected to the C supply through a resistor 98. The normally open contact 83 associated with the movable contact 81 in the retarder operating relay 74 is connected back to the fixed contact 57 of the relay for the gate means 52.

In the fourth set of contacts of the retarder operating relay 74, the fixed contact 92 is left open-circuited. The contacts 91 and 93, on the other hand, are connected to the brake mechanism 15. In this particular control system, the actuation of the brake operating mechanism to its braking condition is effected by energization of the relay 74 to close the movable contact 91 upon the fixed contact 93. When the relay is deenergized, as shown in FIG. 2, the brake operating mechanism 15 is maintained in its released condition.

The normally closed contact 86 in the third set of contacts of the retarder control relay 74 is connected to a parallel RC combination comprising a capacitor 101 and a resistor 102. The capacitor 101 is returned to system ground and the resistor 102 is connected to the D- supply. A similar circuit arrangement is provided for the normally open contact 87, this contact being returned to ground through a capacitor 103 and being connected to the D supply through a resistor 104. The movable contact that is associated with the fixed contacts 86 and 87, on the other hand, is connected through a series resistor 105 to the base electrode of a gate transistor 106. The contact 85 is also returned to ground through a shunt resistor 107.

The gate transistor 106 comprises a principal operating component of a blanking means generally designated by the reference numeral 112. The blanking means 112 further includes a blanking relay 114 having an operating coil 113. One terminal of the coil 113 is connected to the C- supply and the other terminal of the relay coil is connected to the collector of the gate transistor 196. The emitter of the transistor is returned to system ground.

The relay 114 further includes a movable contact 115 that is engageable with a normally closed contact 116 and a normally open contact 117. The relay is also provided with a second set .of contacts comprising a movable contact 121 that is engageable with a normally closed contact 122 and a normally open contact 123. The movable contact 121 is connected to system ground. The normally open contact 123 is connected to the coupling circuit between the vibration transducer 21 and the amplifier 24, as shown, or to one of the stages of the amplifier. The normally closed contact 122 of this portion of the relay is connected through a series circuit comprising a neon bulb 127 and a resistor 128 to the base electrode of a transistor 129. The base electrode of the transistor 129 is also connected to an input resistor 131 that is returned to system ground.

There is a further interconnection from the contacts of the relay 114 to the base electrode of the transistor 129. This connection is provided through the contacts 115-117 of the relay 114. Thus, the movable contact 115 of the relay is connected to the D- supply. The normally closed contact 116 is left open-circuited but the normally open contact 117 is connected to one terminal of a resistor 142. The resistor 142 comprises a portion of an RC timing circuit that further includes a capacitor 141. The capacitor 141 is connected from the remaining terminal of the resistor 142 to ground. The common terminal of the capacitor 141 and the resistor 142 is connected to the neon bulb 127 in the input circuit to the transistor 129.

The transistor 129 comprises a part of a cut-off device 132 which also includes a relay 134 having an operating coil 133. One terminal of the relay coil 133 is connected to the C supply and the other terminal is connected to the collector of the transistor 129. The emitter of the transistor is grounded. The relay 134 includes a movable contact 135 that is engageable with a normally closed contact 136 but can also be engaged with a normally open contact 137 when the relay is energized. The movable contact 135 is connected through a resistor 138 back to the normally open contact 117 of the blanking relay 114. The normally open contact 137 is left open-circuited. The normally closed contact 136 is connected directly to the base electrode of the transistor 106 in the input circuit to the blanking means 112 to alford a holding circuit for the relay 114.

In the circuit diagram of FIG. 2, no power supply is illustrated. The power supply for the circuit may be of conventional construction; for this reason, it has not been shown in detail. It will be helpful in understanding operation of the circuit, however, to recognize. that the C and D power supplies do not represent equal voltages. Instead, the negative voltage afforded by the D supply is substantially greater than that of the C- supply. In a practical application, using the circuit parameters set forth in detail hereinafter, the C- supply is approximately thirty volts and the D supply is ninety volts.

When the control system 22 of FIG. 2 is placed in operation, the capacitor 66 of the time-delay circuit comprising this capacitor and the resistor 65 starts to charge toward the maximum voltage of the D supply. In the specific example constructed with the circuit parameters set forth hereinafter, the D supply is approximately ninety volts. As the capacitor 66 charges, it reaches the threshold voltage for the initiation of a discharge through the neon bulb 67. In this instance, the breakdown voltage for the neon bulb is seventy-five volts. When the device 67 fires, a substantial negative-going signal is supplied to the base electrode of the transistor 69, rendering the transistor conductive and energizing the operating coil 73 of the retarder operating relay 74. According, the relay is actuated from the de-energized condition illustrated in FIG. 2, the released condition for the relay, to its alternate actuated condition. As a consequence, the contacts 91, 93 are closed, completing an operating circuit for the brake operating mechanism 15 and establishing the retarder (FIG. 1) in its braking position. Hereinafter, the energized operating condition for the retarder operating relay 74 is referred to as the braking condition for this relay.

The resistor 65 and the capacitor 66 are selected to afford a substantial time delay in the firing of the neon tube 67 and the consequent actuation of the retarder operating relay 74 to its braking condition. The duration of the time delay is not particularly important when the control system is first placed in operation, but is of consequence in subsequent operations as described in detail hereinafter. In a typical circuit, this time delay may be of the order of sixteen seconds. Once the retarder operating relay 74 has been actuated to its braking condition, the closing of the contacts 75, 77 completes a holding circuit for the relay. This holding circuit, bebeginning at the base electrode of the gate transistor 69, extends through the resistor 95, through the contacts 75 and 77, and thence to the timing circuit 96, 97. The capacitor 96 and the resistor 97 are selected to afford a relatively short charging time for the capacitor 96, as compared with the charging time for the capacitor 66, so that substantially full C- voltage is available from the timing circuit 96, 97 as soon as the transistor 69 is triggered to conduction.

As long as no railroad car approaches the retarder 10 (FIG. 1), only the relay 74 of the control system 22 is actuated. All of the other relays remain in their initial or de-ene-rgized operating conditions with their contacts in the positions shown in FIG. 2. A railroad car entering the retarder, however, is detected by the vibration transducer 21. The sensing means comprising the transducer 21 and the amplifier 24 develops a control signal having an amplitude indicative of movement of a railroad car on to the track section at Which the retarder is located. The output signal from the amplifier 24 is rectified by the diodes 26 and 27 and is applied to the base electrode of the gate transistor 28 in the input to the control means 32.

The amplifier 24, the gate 28, and the relay 34 are adjusted to provide for actuation of the control relay 34 from its first or de-energized operating condition to its second or actuated operating condition in the presence of relatively low amplitude vibration signals from the transducer 21. This is done to permit actuation of the control system 22 in response to even relatively slow movements of a car along the track section 11, 12. Consequently, the generation of virtually any vibration signal by the transducer 21 actuates the relay 34 to its second operating condition. Upon closing of the relay, the contacts 35 and 37 are closed and the connection between the contact 35 and the contact 36 is broken. This com-.

pletes an energizing circuit for the gate means 52, this energizing circuit including the resistor 45 that is connected to the D supply, the capacitor 46, the neon bulb 47, and the resistors 48 and 51. The incorporation of the RC circuit 45, 46 in the input to the gate device 52 prevents instantaneous actuation of the gate relay 54 upon actuation of the control relay 34. Thus, a predetermined time interval is required to charge the capacitor 46 to a voltage sufficient to effect conduction through the neon tube 47. The resistor 45 and the capacitor 46 are selected to provide relatively short but appreciable time delay; for example, this time delay may be of the order of two seconds.

This input circuit arrangement for the gate relay 54 is employed to prevent spurious operation of the control system 22 as the result of short-duration vibration signals on the traffic rail 11. Signals of this kind, which might be caused by a car going over a rough track joint at a point up the track substantially displaced from the track section 11, 12, or by some foreign object striking the rail, could cause a completely erroneous and potentially dangerous actuation of the control system. The incorporation of the delay circuit 45, 46 in the input to the gate means 52 protects the control system against spurious operation from this source without interfering with effective operation when a car is actually rolling into the retarder 10 (FIG. 1). A similar effect could be accomplished by utilizing an amplifier 24 having a relatively slow response characteristic. This expedient, however, would also slow down the drop-out of the control relay 34 and would prolong the time that a car is held in the retarder 10 after braking has been completed, as will be apparent from the description of operation set forth in further detail hereinafter.

When a sustained vibration signal causes the gate relay 54 to be actuated from its normal or open condition, as shown in FIG. 2, to its actuated or closed condition, the relay is held in the actuated condition by the input circuit to the gate transistor 49, described above, as long as the control relay 34 remains actuated. The closing of the gate relay 54 effectively opens the energizing circuit of the retarder operating relay 74. That is, the holding circuit for the retarder operating relay 74 is grounded out by the closing of the contacts 61 and 63, since this effectively grounds the circuit connection to the resistor 97 in the holding circuit for the relay 74. The relay 74 does not drop out, however. Rather, it is held in its actuated braking condition by means of a circuit extending from the C supply through the resistor 98 and through the contacts 41 and 43 of the control relay 34 to the base electrode of the gate transistor 69 in the relay operating circuit. Thus, as long as the control relay 34 remains energized by the vibration signal applied to the gate transistor 28, the control relay operates to maintain the retarder operating relay 74 in its energized condition, keeping the retarder in braking operation.

As the car, or cut of cars, continues to move into the retarder 10, its velocity is reduced by engagement with the retarder rails 13 and 14 (FIG. 1). Ultimately, however, the cut of cars is slowed to a stop, or to virtually stopped condition. As a consequence, the amplitude of the output signal from the transducer 21 drops below the operating threshold of the control means 32 comprising the amplifier 24, the gate device 28, and the relay 34 (FIG. 2). This threshold could be established at some relatively low car velocity as, for example, one or two miles per hour. Preferably, it is established at or near zero velocity for the railroad car. In any event, whenever the control signal produced by the transducer 21 drops below the threshold, the control relay 34 is eifectively de-energized and, consequently, is actuated back to its initial operating condition. When the relay 34 drops out, the gate relay 54 also drops out, since the energizing circuit for the gate relay is opened at the contacts 35-37 of the control relay. The gate relay 54 drops out virtually instantaneously upon drop-out of the control relay 34, the discharge resistor 44 for the capacitor 46 being quite small.

When the control relay 34 returns to its initial or unactuated condition, as noted above, signifying the interruption of movement of the car through the retarder, the retarder operating relay 74 also drops out. Thus, it will be recalled that the relay 74 is held in its actuated or braking condition, in the presence of the vibration signal signifying car movement, by means of an operating circuit which includes, in series, the contacts 41 and 43 of the control relay 34. When these contacts open, the temporary holding circuit for the operating relay 74 is opened, with the result that the retarder operating relay drops out.

When the gate relay 54 is returned to its normal or unactuated condition, as described above, the ground connection that had been provided through the contacts 55 and 57 of the gate relay and the contacts 81 and 83 of the retarder operating relay is opened. Consequently, the capacitor 66 again begins to charge through the resistor 65 and the connection afforded to the operating source D. Moreover, the return of the relay 54 to its initial operating condition removes the ground connection from the capacitor 96, permitting it to charge quickly to approximately the full value of the C- voltage. This begins the operations necessary to re-close the brakes, as described more fully hereinafter.

At the time the retarder operating relay 74 is deenergized, and thereby actuated to its brake-releasing condition, the resultant closing of the contacts 85 and 86 of the relay applies a pulse signal from the capacitor 101 through the coupling circuit comprising the resistors 105 and 107 to the base electrode of the gate transistor 106 in the blanking means 112. As a consequence, the blanking relay 114 is energized, closing the contacts 121 and 1-23 and grounding the coupling circuit from the transducer 21 to the amplifier 24. Thus, at the time the brakes begin to open, the vibration sensing means comprising the transducer 21 is effectively interrupted in its operation. As noted above, this is done to prevent overloading of the system or erroneous operation as the result of high-amplitude vibrations that may be produced if a car has ridden up on the retarder rails and is dropped abruptly on the traffic rails 11 and 12 (FIG. 1).

Actuation of the blanking relay 114 also closes the contacts 115 and 117. This completes an energizing circuit for the cut-off means 132, this circuit starting at the D supply and extending through the contacts 115 and 117 and the time delay circuit 141, 142 to the input circuit of the cut-cit means comprising the neon tube 127 and the resistors 128 and 131. The capacitor 141- is charged through the resistor 142 and, eventually, reaches a potential sufiicient to cause breakdown in the neon tube 127. That is, the time delay means afforded by the RC circuit 141, 142 eitectively completes an actuating circuit for the cut-off relay 134, through the gate transistor 129, a predetermined time interval after actuation of the blanking means 112. This time delay interval must be made shorter than the time delay of the RC circuit 65, 66 to prevent premature re-closing of the retarder. Typically, the time delay afforded by the circuit 141, 142 may be of, the order of one-half that provided by the timing circuit 65, 66; in this instance, the time delay is approximately eight seconds.

At the time the blanking relay 114 is energized, a holding circuit is established for the relay. This holding circuit is provided by the closing of the contacts 115 and 117, which completes a circuit from the D supply through the resistor 128 and the contacts 135 and 136 of the cut-off relay back to the base electrode of the gate transistor 106 in the blanking means 112. When the cut-ofl? relay 134 is energized, following the time delay interval provided by the delay circuit 141, 142, the contacts 135 and 136 are opened. As a consequence, the holding circuit for the blanking relay 114 is opened. The relay 114 then drops out, returning to the initial condition illustrated in FIG. 2 and removing the ground for the sensing transducer 21. Accordingly, the vibration sensing circuit comprising the transducer 21 and its connection to the amplifier 24 is restored to operation and effective utilization of the control signal developed by these circuits is again made possible.

Upon release of the retarder 10, as described above, which is eflected by the opening of the contacts 91 and 93 in the relay 74, the railroad car that has been stopped in the retarder again starts to roll. Acceleration may be relatively low, depending upon the inclination of the track section through the retarder. However, unless the car is virtually unusable because of poor rolling characteristics, it will achieve sufficient velocity to vibrate the rail 11 and produce an appreciable control signal before completion of the time delay interval of the gate means 52, established by the RC circuit 65, 66. The control signal from the transducer 21 is again supplied through the amplifier 24 and the rectifying and coupling circuit including the gate transistor 28 to the operating coil 33 of the control relay 34. Accordingly, the control relay is again actuated to its second operating condition, closing the contacts 41, 43 and 35, 37. The closing of the contacts 35, 37, after a short time interval, again actuates the gate relay 54 as described above. Thus, the gate means 52 is prevented, by closing of the relay 54, from supplying an energizing or actuating signal to the retarder operating means 72. In this instance, moreover, the closing of the contacts 41 and 43 of the control relay 34 efifectively grounds the base of the gate transistor 69 in the input circuit of the retarder operating means 72, the ground connection being completed through the contacts 81 and 82 of relay 74. Consequently, the retarder operating relay 74 cannot be actuated.

It is thus seen that the control means comprising the relay 34 operates to maintain the retarder operating means 72 in its released condition, this being the unactuated condition of the relay 74. Since, as previously described, the control relay 34 of the control means 32 originally was effective to maintain the retarder operating relay 74 in its braking condition, at the 'start of the braking cycle, it is seen that the control means 32 is effective to hold the operating means 72 in whichever operating condition the latter is in at the time the control means is actuated, this being the time that the control signal exceeds the aforementioned threshold value indicative of a car moving at a predetermined minimum velocity. In connection with the system 22, this minimum velocity is approximately zero.

As long as the vibration transducer 21 continues to develop a control signal having an amplitude sufficient to indicate the presence of a moving car, the control means 32 is retained in its second operating condition and operates to hold the retarder operating means 72 in the brake releasing condition. As the car rolls free of the retarder, the amplitude of the control signal reduces, until it again falls below the threshold value. When the vibration dies out the second time, as the car leaves the retarder, the control relay 34 again opens, thereby returning to the initial operating condition shown in FIG. 2. As a consequence, the gate relay 54 drops out, in the same manner as described above. The previously charged capacitor 66 already carries a charge suflicient to fire the neon tube 67, in most instances, so that the gate circuit 69 is actuate-d and the retarder operating relay 74 is energized, returning to its actuated or braking condition. If it happens that the car rolls out of the retarder very rapidly restoration of the retarder operating means 72 to braking condition may be delay until completion of the charging time for the capacitor 66. This can be prevented by making the time delay of the circuit 65, 66 less than the minimum time required for a car to clear the retarder, in this instance approximately sixteen seconds. Control system 22 is now restored to its initial operation condition and is ready to begin a new braking cycle with respect to the next car or cut of cars released for movement into the retarder 10.

Usually, the traflic rails 11 and 12 are connected in control signal.

13 vibration-transmitting relation to the retarder rails 13 and 14 by the operating mechanism of the retarder. Consequently, substantial vibration of the traflic rail may occur as the retarder operating mechanism 15 acts to restore the retarder rails to braking position. To protect the system 22 against spurious operation as a result of this vibration, it is desirable to again blank the output of the transducer 21 at the time the retarder is restored to braking position. This is accomplished by means of the charging circuit 103, 104, Thus, when the retarder operating relay 74 is again energized, a pulse signal is supplied from the capacitor 103 to the base electrode of the gate transistor 106 in the input of the blanking means 112. Accordingly, the blanking relay 114 is again actuated to ground the circuit connection between the transducer 21 and the amplifier 24. As before, this blanking effect is of relatively short duration, the blanking relay 114 being restored to its initial condition after a short time interval by operation of the cut-off relay 134 in the manner described above.

It may happen that the car, in rolling out of the retarder, may fail to produce suihcient vibration to exceed the threshold established by the control means 32, relative to the effective operating amplitude required of the This might happen, for example, with a car having antifriction bearings and virtually perfect Wheels. If this happens, of course, no control signal is developed, sufficient to actuate the control means 32, and

the gate means 52 remains in its normal operating condition, to which it has previously been restored upon completion of the braking operation. Under these circumstances, the brakes are automatically applied as soon as the capacitor 66 is charged to a level exceeding the breakdown voltage of the neon 67. Thus, the gate means 52 operates automatically to restore the retarder operating means 72 to braking condition whenever the control signal' remains below the aforementioned threshold for a predetermined time interval, this being the time interval established by the resistor 65 and the capacitor 66.

In order to afford a more complete illustration of the control system 22, certain circuit data are set forth in detail hereinafter. It should be understood that these data are provided solely for purposes of illustration and in no sense as a limitation on the invention.

RESISTORS 41, 51, 71, 107, 131 kilohms 18 44 "ohms" 500 45 ki1ohms 330 48, 68, 105, 128, 97 do 47 -65 megohms 2.5 95, 98 kilohms 10 102, 104 megohms 10 142 -kilohms 680 138'- do 470 CAPACITORS 46 microfarads 4 66 do 4 '96 do 4 101, 103 do 1 141 do 4 All transistors in FIG. 2 are Type 2N586; all of the neon discharge devices are Type NE76.

Becausethe control system 22 is actuated solely by a sensed signal that indicates the presence of a moving car in the retarder, and the reduction of velocity of the car below a predetermined critical value, the system enables the car retarder 10 to brake any car or cut of cars that enters the retarder, regardless of initial velocity or number of cars, providing only that the retarder itself has the capacity to effect a braking operation. No adjustment is needed to compensate for variations in the number of cars in a cut. The basic control is exercised in accordance with car movement, rather than employing timing controls to determine the normal releasing and re-closi-ng operations of the retarder. This makes it possible to brake more cars in a given time than can be accomplished Where timing controls are employed and must be set to accommodate the heaviest and fastest moving cars expected to be passed through the retarder. On the other hand, the control system assures maintenance of the retarder in released condition until a braked cut of cars is clear of the retarder, preventing a car from being trapped in the retarder and holding the retarder substantially open until another car enters and smashes into the first car. Nevertheless, the retarder is'irnmediately restored to braking operation as soon as each cut has been released from the retarder.

In some applications, it may be desirable to maintain the retarder in a normally open condition and to actuate the retarder to braking condition only when a car is actually present on the track. This can be accomplished by a relatively simple modification of the operating circuit of FIG. 2, the modification being illustrated in FIG. 3. In this system, an additional set of fixed contacts 202 and 203 is provided in the gate device relay 54. Contacts 202 and 203 are engageable by a movable contact 201. Contact 201 engages contact 202 when the relay 54 is de-energized but is brought into'engagement with contact 203 whenever the relay is actuated. Contact 203 is connected directly to contact 91 of the retarder operating device relay 74 (FIG. 2) and contact 201 is connected to the brake mechanism 15. Thus, contacts 201 and 203 are interposed in series in the actuating circuit for the retarder operating mechanism.

With the retarder control system 22 of FIG. 2 modified as shown in FIG. 3, energization of the systetm causes the retarder operating relay 74 to be energized, following the requisite time delay for charging capacitor 66, as described above. Initially, however, the retarder is not actuated to its closed or braking condition because the relay 54 of gate device 52 is not actuated when the system is initially energized and no car is moving along the retarder track. The contacts 201 and 203 are still open, since relay 54 is not energized until a control signal is developed indicative of the presence of a moving car on the track. Therefore, the retarder starts its operation in open or released condition.

When a railroad car enters the retarder, the vibration transducer 21 (FIG. 2) is again actuated and develops a control signal having an amplitude, frequency, or other parameter indicative of the movement of the car along the retarder track section. This control signal actuates the control circuit 32 as described above, energizing the relay 34 and closing contacts 35 and 37 to energize the relay 54 in gate device 52. Thus, relay 54 is energized as previously described. In this instance, actuation of the relay closes contacts 201 and 203, FIG. 3, complet ing the operating circuit for the brake mechanism 15 and actuating the retarder to braking condition.

When the car slows approximately to a stop and the control signal is interrupted, the relay 34 drops out as described above. As a consequence, the relays 54 and 74 are de-energized and drop out. Opening of the two relays opens the operating circuit for the retarder operating mechanism 15 at contacts 91 and 93 and at contacts 201 and 203 so that the retarder is actuated to released condition.

With the retarder released, the car starts to roll again, and the vibration transducer 21 again develops a control signal. The gate relay 54 is now energized but the retarder operating relay 74 remains de-energized as described above. Consequently, although the contacts 201 and 203 (FIG. 3) are closed, the operating circuit for the retarder operating mechanism 15 remains open at contacts 91 and 93 and the retarder remains in released condition. When the car subsequently clears the retarder, the control signal dies out and the relays 34 and 54 are again de-energized. After a given time interval,

15 and again in the manner described above, the relay 74 is energized and the system is ready for the next car to be passed through the retarder.

It is thus seen that the modification of the operating circuit 22 of FIG. 2 as illustrated in FIG. 3 affords a system that operates in the same manner as described above except that the retarder is now normally maintained in open condition when no car is present and is actuated to closed condition upon the first occurrence of the vibration control signal.

FIG. 4 illustrates a control system 522 for a railway car retarder constituting another embodiment of the present invention. The car retarder controlled by system 522 is somewhat different from that described and illustrated in FIG. 1 in that it includes two pairs of retarder rails 513A and 5133 that are located immediately adjacent each other longitudinally of the traffic rail 511. The two sets of braking elements or retarder rails, however, are controlled from a common retarder actuating mechanism 515. Moreover, the traffic rail 511 is provided with a multiplicity of equally-spaced shallow grooves or other surface discontinuities 516 beginning at a point 511A well ahead of the retarder rails 513A and 513B and ending at the point 5113 at the outlet of the retarder. Thus, the retarder mechanism is basically similar to that described above except that the retarder rails are divided into two longitudinal segments for convenience in construction and are located along only one of the trafiic rails. It should be noted that the surface notches or grooves 516 need not be provided in the rail 511 along which the retarder rails 513A and 513B are mounted; rather, the other rail of the railway may be provided with the requisite notches or other surface discontinuities.

Control system 522 comprises three individual pickup devices 521A, 521B and 521C mounted on rail 511. The initial pickup device 521A is located near the point 511A at which the individual cars or cuts of cars enter the retarder system. Pickup device 521B is located within the length of traffic rail 511 encompassed by the first pair of retarder rails 513A. Pickup 521C is located near the outlet end of the retarder on the portion of the traffic rail encompassed by the second pair of retarder rails 5133. All three of the pickup units 521A, 521B and 5210 are electrically coupled to an adder amplifier 519. Adder amplifier 519 is a simple adding circuit that combines and amplifies the three initial electrical signals from the pickup devices 521A, 521B and 521C to produce a combined control signal representative Olf movement of a railroad car or cars along trafiic rail 511.

The output of amplifier 519 is coupled to a rectifier and drive circuit 523. Drive circuit 523 is utilized to complete an operating circuit for and thus to energize the operating coil 524 of a control relay 525. Relay 525 comprises two sets of contacts, the contacts being shown in the normal or unenergized position for the relay. The first set of contacts comprises two fixed contacts 526 and 527 and a movable contact 528, movable contact 528 normally being engaged with contact 526. The second set of contacts of the relay includes a fixed contact 532 normally engaged by a movable contact 534, the movable contact engaging a second fixed contact 533 when the relay is energized.

Movable contact 528 in control relay 525 is returned to system ground through a resistor 536. The fixed contact 526 normally engaged by contact 528 is connected to the input of a rectifier and drive circuit 537 employed to actuate a retarder operating relay 538. That is, circuit 537 completes an operating circuit for the coil 539 of relay 538.

Relay 538 includes two sets of contacts. The first set of contacts comprises a fixed contact 542 that is normally engaged by a movable contact 544, the movable contact 544 being engageable with a second fixed contact 543 when the relay is energized. The second set of contacts comprises a fixed contact 546 normally engaged by a movable contact 548, the movable contact 548 being engageable with a second fixed contact 547 upon actuation of the relay.

The control system 522 further comprises a brake release relay 551 having an operating coil 552. The operating coil 552 of the relay is energized from a rectifier and drive circuit 553. The relay 551 includes at least two sets of contacts. One contact set includes a first fixed contact 554 that is normally engaged by a movable contact 556, the movable contact 556 being engageable with a second fixed contact 555 when the relay is actuated. The second set Olf contacts in the relay 551 includes a fixed contact 557 that is normally engaged by a movable contact 558. The movable contact 558 engages another fixed contact 559 when the relay is actuated.

The movable contact 556 of the release relay 551 is connected to the fixed contact 533 in the control relay 525. The normally closed contact 554 engaged by the movable contact 556 is connected in an input circuit to the rectifier and drive circuit 537. The other fixed con tact 555 that is engageable by the movable contact 556 upon energization of the relay 551 is connected in an input circuit to a drive amplifier 561. The output of the drive amplifier is connected to the input of the rectifier and drive circuit 553. To energize these circuits through actuation of the relay 525, the movable contact 534 in that relay is connected to a suitable A.C. supply. The contact 532 of the relay 525 is left open-circuited.

The remaining contact 527 in the relay 525 is connected through a resistor 562 to the fixed contact 542 of the retarder operating relay 538. In addition, a connection is provided from the resistor 562 through a diode 563 to an input circuit for the rectifier and drive circuit 553. The common terminal of the diode 563 and the resistor 562 is returned to ground through a resistor 56.

The movable contact 554 in the relay 538 is connected to a capacitor 565 that is returned to systemground. The related fixed contact 543 is connected to a suitable direct current supply, designated as B+, through a resistor 566.

The remaining two sets of contacts in the relays 538 and 551 are utilized to complete an energizing circuit for the retarder actuating mechanism 515. The circuit arrangement is such that when this external relay circuit is completed, the retarder actuating mechanism 515, like mechanism 15, is energized to actuate the retarder to a braking condition. This circuit arrangement comprises a connection between the fixed contact 557 of the relay 551 and the movable contact 543 of the relay 538. The fixed contact 547 of the relay 538 is connected to the retarder actuating mechanism 515. The movable contact 558 of the relay 551 is also connected, through a separate path, to the retarder actuating mechanism. The relay contacts 546 and 559 are left open-circuited.

The notches, grooves, or other surface discontinuities 516 in the traffic rail 511 are employed to develop, in the transducers 521A, 521B and 521C, a relatively high-amplitude signal giving a positive indication of the movement of any railroad car along the traflic rail. An arrangement of this kind is more positive in action than the simple vibration sensing apparatus of FIG. 1. A speed control system based upon the notched or grooved traffic rail construction is described and claimed in the co-pending application of Richard E. Porter and Arthur R. Crawford, Serial No. 427,537, filed January 13, 1965.

When the system 522 is placed in operation, and the power supplies are energized, the three operating relays 525, 538 and 551 initially remain de-energized as illustrated in FIG. 4. As a car enters the retarder track section 511, a strong vibration signal is developed in the 17 velocity of the car but it is not necessary to control car movement in accordance with velocity changes in the present system. Consequently, and particularly where the car is to be stopped completely in the retarder, only the amplitude of the control signal output from adder-amplifier 519 is of real significance.

The rectifier and drive circuit 523 utilizes the initial control signal to actuate the control relay 525 whenever there is a car moving through the retarder system. Once the relay 525 is actuated (a short time delay may be utilized in the drive circuit 523 to prevent spurious action of the relay in response to transient signals) and operating circuit is completed through the contacts 533 and 534 from the A.C. supply to the rectifier and drive circuit 537. This circuit extends through the contacts 554 and 556 of the release relay 551, which is not energized at this time. The AC. signal supplied to the rectifier and drive circuit 537 is utilized to complete an operating circuit for the relay 533, actuating the contacts of this relay. Consequently, contacts 547 and 548 close to complete an operating circuit for the retarder actuating mechanism 515, actuating the retarder to its braking condition. At the same time, contacts 543 and 44 close, charging the capacitor 565 from the B+ supply.

When the car is braked to a virtual stop in the retarder of FIG. 4, the output signals from the transducers 521A 521C diminish in amplitude below a given threshold value. As a consequence, the control signal output from adder amplifier 519 is interrupted, with the result that the control relay 525 is de energized and drops out. When this occurs, the energizing signal to the rectifier and drive circuit 537, previously supplied through the contacts 533 and 534 of the control relay, is interrupted and the brake relay 538 drops out. This opens the contacts 547 and 548 and interrupts the operating circuit for the retarder actuating mechanism 515 so that the retarder reverts to its released or open condition.

When the brake relay 538 drops out, the charging connection for the capacitor 565 afiorded by the contacts 543 and 544 is opened. The movable contact 544 closes upon the closed contact 542 and the capacitor 565 is discharged through the diode 563 to the input circuit to the rectifier and drive circuit 553. In this manner, the rectifier and drive circuit 553 is actuated to energize the release relay 551. The discharge circuit for the capacitor 555 is constructed to afford a substantial time delay and to hold the release relay 551 energized for an appreciable time interval.

Upon release of the retarder by actuation of mechanism 515, the car begins to roll again and starts to accelerate, moving out of the retarder. This again produces a substantial vibration of the trafiic rail 511 that is detected by the transducers 521A-521C. The signals from the transducers are again supplied to the adder amplifier 519, developing an eiiective control signal that is employed in the rectifier and drive circuit 523 to again energize the control relay 525.

In this instance, when the relay 525 is energized, the closing of the contacts 533 and 534 of the relay completes an energizing circuit for the drive amplifier 561, since the release relay 551 has been energized and the contacts 555 and 556 are closed. Accordingly, as long as the control relay 525 is held actuated by the control signal from the sensing apparatus, the release relay 551 is maintained in actuated condition. Under these circumstances, the contacts 557 and 558 are held open so that it is not possible to again actuate the retarder actuating mechanism 515. Thus, the retarder is maintained released, by the control signal, until the control signal dies out after the car clears the retarder. During the time interval in which the car rolls out of the retarder, the brake relay 558 is not energized since the input connection to the rectifier and drive circuit 537 for this relay is open at contacts 554 and 556.

On the second actuation of the control relay 525, the

closing of the contacts 527 and 528 completes a discharge circuit for the capacitor 565. This discharge circuit, starting with the capacitor, extends through the contacts 544 and 542 of the brake relay 538 (now deenergized), through the resistor 562, through contacts 527 and 52S, and through the resistor 536 to ground. This arrangement assures discharge of the capacitor during the release cycle of operation and conditions the system for the next braking cycle. The connection of the relay contacts 526, 527 to the drive circuit 537 affords a grounding connection in the drive circuit input preventing erroneous actuation of the drive circuit when the control relay 525 is not actuated.

From the foregoing description, it will be apparent that the control system 522 of FIG. 4 operates in a manner quite similar to, though specifically different from, the embodiment of FIGS. 2 and 3, the control system 22.. In each, the sensing devices (21 in FIG. 2, 521A-521C in FIG. 4) and associated amplifier circuits develop a control signal indicative of movement of a railroad car along the track section comprising the retarder. Each embodiment further comprises control means including a control relay (relay 34 in FIG. 2, relay 525 in FIG. 4) that is actuated from first to second operating conditions, and back, in response to excursions of the control signal above and below a given threshold value, respectively.

The retarder operating means in each of the two embodiments is actuated between released and braking operating conditions in accordance with the operating conditions of the control means. In FIG. 4, the retarder operating relay 538 is energized directly by actuation of the control relay 525, provided the release relay 551 is not previously energized. In FIG. 2, the retarder operating relay 74 is energized through a separate time delay circuit, but cannot be actuated if the release relay, gate relay 54, has previously been actuated. In each instance, the retarder operating relay is energized through an interlocking circuit that includes one set of contacts in the release relay.

In each of the two embodiments, the release relay and other elements of the interlocking circuits between the relays establish and maintain the retarder in released condition whenever the control relay is actuated to its second operating condition within less than a given time interval after being actuated to its first operating condition. Thus, in FIG. 4 the release relay 551 is energized upon drop-out of the operating relay 538 caused by drop out of the control relay 525, and is held energized when the control relay 525 is again actuated Within the discharge time for capacitor 565. In FIGS. 2 and 3, drop-out of the gate or release relay 54 upon loss of the control signal opens contacts 201, 203 to release the retarder, and the operat ing relay 74 is de-energized by drop-out of the control relay 34 at the same time. Whenever the control and release relays are re-actuated before capacitor 66 can charge, relay 74 cannot re-close and hence maintains the retarder in released condition. Thus, in both circuits the retarder is first maintained in braking condition and subsequently maintained in released condition by consecutive control signals above the seelcted threshold, spaced by a control signal, of limited duration, below the threshold.

Hence, while preferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification.

I claim:

1. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder, located on a given section of track, and electrically actuatable between a braking condition and a released condition, comprising:

initially establishing said car retarder in its braking condition with no car on said track section;

sensing the movement of a car along said track section,

and developing a control signal having a given param- 119 eter representative of the velocity of car movement; maintaining said retarder in which ever operating condition the retarder is already in in response to an increase in said control signal parameter above a threshold indicating the presence of a car moving along said track section at a Velocity above a predetermined release velocity;

actuating said retarder to its alternate condition upon reduction of said control signal parameter below said threshold;

and actuating the retarder to its braking condition whenever said control signal parameter remains below said threshold tor a predetermined time interval.

2. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder, located on a given section of track, and electrically actuatable between a braking condition and a released condition, comprising:

initially establishing said car retarder in its braking condition with no car on said track section;

sensing the movement of a car along said track section,

by detecting vibration of the traflic rail, and developing a control signal having an amplitude representative of the velocity of car movement;

maintaining said retarder in whichever operating condition the retarder is already in, in response to an increase in said control signal amplitude above a given threshold, for a preselected minimum period, indicative of the presence of a car moving along said track section at a velocity above a predetermined release velocity;

actuating said retarder to its alternate condition, substantially instantaneously upon reduction of said control signal amplitude below said threshold;

and actuating the retarder to its braking condition whenever said control signal amplitude remains below said threshold for a predetermined time interval.

3. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder, located on a given section of track, and electrically actuatable between a braking condition and a released condition, comprising:

initially establishing said car retarder in its braking condition with no car on said track section;

sensing the movement of a car toward said retarder,

along said track section, and developing a control signal having a given parameter representatitve of the velocity of car movement; maintaining said retarder in Whichever operating condition the retarder is already in in response to an increase in said control signal parameter above a threshold indicating the presence of a car moving along said track section at a velocity above a predetermined release velocity; 1

actuating said retarder to its alternate condition upon reduction of said control signal parameter below said threshold; interrupting development of said control signal for a first predetermined time interval whenever said retarder is actuated from braking to released condition;

and actuating the retarder to its braking condition whenever said control signal parameter remains below said threshold for a second predetermined time interval, said second time interval being substantially longer than said first time interval.

4. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder, located on a given section of track, and electrically actuatable between a braking condition and a released condition, comprising the following steps:

actuating said car retarder to its braking condition with no car on said track section;

sensing vibration of said track section caused by the movement of a car toward said retarder, along said 20 track section, and developing a control signal indicative of said movement;

actuating said retarder to its released condition in response to a reduction in amplitude of said control signal indicating reduction of the car velocity approximately to zero;

sensing vibration of said track section caused by resumption of car movement along said track section to again develop said control signal;

maintaining said retarder in released condition, in response to said control signal, to permit the car to move out of the retarder; re-actuating the retarder to its braking condition in response to a reduction in amplitude of said control signal indicating movement of the car beyond said track section;

and actuating the retarder to braking condition a predetermined time interval after actuation to released condition if no control signal appears during the second sensing step.

5. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder located on a given section of track and electrically actuatable between a braking condition and a released condition, comprising:

sensing the movement of a car along said track section and developing a control signal having a given parameter representative of the velocity of car movement;

initially actuating said car retarder to its braking condition;

maintaining said car retarder in braking condition so long as said control signal parameter exceeds a given threshold value indicating the presence of a car moving along said track at more than a given minimum velocity;

actuating said retarder to released condition upon reduction of said control signal parameter below said threshold;

maintaining said car retarder in released condition whenever and so long as said control signal again exceeds said given threshold value Within a given time interval following actuation of said retarder to released condition;

and restoring said retarder to its original operating condition whenever said control signal again falls below said given threshold value.

6. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder located on a given section of track and electrically actuatable between a braking condition and a released condition, comprising:

establishing said car retarder in an original released condition with no car on said track section;

sensing the movement of a car approaching and moving along said track section and developing a control signal having a given parameter representative of the velocity of car movement; initially actuating said car retarder to its braking condition in response to a control signal in which said parameter exceeds a given threshold value;

thereafter maintaining said car retarder in braking condition so long as said control signal parameter exceeds said threshold value, indicating the presence of a car moving along said track section at more than a given minimum velocity;

actuating said retarder to released condition upon reduction of said control signal parameter below said threshold;

thereafter establishing and maintaining said car retarder in released condition whenever and so long as said control signal again exceeds said given threshold value within a given time interval following actuation of said retarder to released condition;

and restoring said retarder to its original operating condition whenever said control signal again falls below said given threshold value. 7. The method of braking railroad cars, in a railroad classification yard or the like including a car retarder located on a given section of track and electrically actuatable between a braking condition and a released condition, comprising:

sensing the movement of a car along said track section and developing a control signal having a given parameter representative of the velocity of car movement;

originally actuating said car retarder to its braking condition when no car is moving along said track section;

maintaining said car retarder in braking condition so long as said control signal parameter exceeds a given threshold value indicating the presence of a car moving along said track at more than a given minimum velocity;

actuating said retarder to released condition upon reduction of said control signal parameter below said threshold;

maintaining said car retarder in released condition whenever and so long as said control signal again exceeds said given threshold value within a given time interval following actuation of said retarder to released condition;

and restoring said retarder to its original braking condition whenever said control signal again falls below said given threshold value for a period greater than said time interval.

8. A control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like, comprising:

retarder operating means having braking and releasing operating conditions for actuating said retarder to braking and released conditions, respectively;

gate means coupled to said retarder operating means,

said gate means being actuatable from a normal operating condition, in which it applies a delayed actuating signal to said retarder operating means to actuate said retarder operating means to its braking condition, to an actuated condition in which said gate means permits said retarder operating means to change to its releasing condition;

sensing means for developing a control signal indicative of movement of a railroad car along said track section;

control means, coupled to all of the aforesaid means and actuatable between first and second operating conditions in response to variations in said control signal above and below a given threshold value, for actuating said gate means to its actuated condition whenever said control signal exceeds said threshold value, and for maintaining said retarder operating means in whichever operating condition the retarder operating means is in at the time the control signal exceeds said threshold value until the control signal falls below the threshold;

and blanking means, coupled to said retarder operating means and said sensing means, for effectively interrupting operation of said sensing means for a predetermined time interval upon actuation of said retarder operating means to its released condition.

9. A control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like, comprising:

retarder operating means, including a retarder operating relay having braking and releasing operating conditions, for actuating said retarder to braking and released conditions, respectively;

gate means including a gate relay having a set of contacts coupled to said retarder operating relay, said gate relay being actuatable from a normal operating condition, in which it is effective to apply an actuating signal to said retarder operating relay to actuate said retarder operating relay to its braking condi- 22 tion, to an actuated condition in which said gate relay interrupts said actuating signal to permit said retarder operating means to change to its releasing condition;

sensing means for developing a control signal indicative of movement of a railroad car along said track section;

and control means comprising a control relay having an operating coil coupled to said sensing means and having contacts coupled to said gate relay and said retarder operating relay, said control relay being actuatable between first and second operating conditions in response to variations in said control signal above and below a given threshold value, for actuating said gate relay to its actuated condition whenever said control signal exceeds said threshold value, and for maintaining said retarder operating relay in whichever operating condition the retarder operating relay is in at the time the control signal exceeds said threshold value until the control signal falls below the threshold.

10. A control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like, comprising:

retarder operating means having braking and releasing operating conditions for actuating said retarder to braking and released conditions, respectively;

gate means coupled to said retarder operating means,

said gate means being actuatable from a normal operating condition, in which it applies an actuating signal to said retarder operating means to actuate said retarder operating means to its braking condition, to an actuated condition in which said gate means permits said retarder operating means to change to its releasing condition;

sensing means for detecting vibration of said track section to develop a control signal indicative of movement of a railroad car along said track section;

control means, coupled to all of the aforesaid means and actuatable between first and second operating conditions in response to variations in said control signal below and above a given threshold value, re spectively, for actuating said gate means to its actuated condition whenever said control signal exceeds said threshold value, and for maintaining said retarder operating means in whichever operating condition the retarder operating means is in at the time the control signal exceeds said threshold value until the control signal falls below the threshold;

and a time delay circuit, included in said control means, for preventing actuation of said gate means except when said control means is held in its second operating condition for a predetermined time interval to prevent spurious actuation of the system in response to short-duration vibration of the track.

11. A control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like, comprising:

retarder operating means having braking and releasing operating conditions for actuating said retarder to braking and released conditions, respectively;

gate means coupled to said retarder operating means,

i said gate means being actuatable between a normal operating condition, in which it is eifective to actuate said retarder operating means to its braking condition, and an actuated condition in which said gate means permits said retarder operating means to change to its releasing condition;

sensing means for developing a control signal indicative of movement of a railroad car along said track ection;

control means coupled to all of the aforesaid means and actuatable between first and second operating conditions in response to variations in said control 23 signal below and above a given threshold value, for actuating said gate means to its actuated condition whenever said control signal exceeds said threshold value and back to normal condition when the control 13. A control system for an electrically actuatable car 24 mined time interval after actuation of the gate relay to normal conditions; sensing means for developing a control signal indicative of movement of a railroad car along said track signal drops below the threshold, and for maintainsection; ing said retarder operating means in whichever opand control means, coupled to all of the aforesaid erating condition the retarder operating means is in means and actuatable between first and second operat the time the control signal exceeds said threshold ating conditions in response to variations in said convalue until the control signal falls below the threshtrol signal above and below a given threshold value, old; for actuating said gate means to its actuated condiand time delay means, included in said gate means, for tion whenever said control signal exceeds said threshdelaying actuation of said retarder operating means old value for a limited time interval, and for mainto its braking condition for a predetermined time taining said retarder operating means in whichever interval following actuation of the gate means to operating condition the retarder operating means is its normal operating condition to allow a car braked in at the time the control signal exceeds said threshby the retarder to resume movement and prevent old value until the control signal falls below the premature restoration of the retarder operating means threshold. to braking condition. 14. A control system for an electrically actuatable car 12. A control system for an electrically actuatable car retarder located on a given section of track in a railroad retarder located on a given section of track in a railroad 2O classification yard or the like, comprising: classification yard or the like, comprising: retarder operating means having braking and releasing retarder operating means having braking and releasing operating conditions for actuating said retarder to operating conditions for actuating said retarder to braking and release/d conditions, respectively; braking and released positions, respectively; gate means coupled to said retarder operating means, gate means coupled to said retarder operating means, Said g means being actuatable from a normal said gate means being actuatable from a normal operating condition, in which the gate means applies erating condition, in which said gate means actuates all actuating Signal to Said retarder Operating means said retarder operating means to its braking condito actuate Said retarder Operating means t0 its bFakti to an actuated di i i hi h i gate 'ing condition, to an actuated condition in which said means permits said retarder operating means to gate means P Said retarder Operating means change to its releasing condition; to change to its releasing condition; vibration sensing means for sensing vibration of the Sensing means for detficting Vibration of Said flack t k d dgveloping a n- 1 i l h i an section to develop a control signal indicative of li d i di i f movement f a il movement of a railroad car along said track section; along id track i control means, coupled to all of the aforesaid means control means, coupled to all of the aforesaid means hh l between first selfond ppfirating d actuatable between fi t and second operating conditions 1n response to variations in said control conditions in response to variations in said control 5 below and abOVP a Elven thIesh'old valhe, signal above and below a given threshold value for fespectlvely, Q actua'flng Sald g means 9 Its actuating said gate means to its actuated condition 40 actuated fondlhoh Whenever Sald Control $5 when said control signal exceeds said threshold value, eXFeedS Sald threshhld Value f P malhtalnlhg and for maintaining said retarder operating means tq oPel'ahhg means m whlchever P in whichever operating condition the retarder operatmg {Ohdlhoh the hammer Operahng i 15 111 at ing means is in at the time the control signal exceeds mm h control slghahexceeds sald threshold said threshold value until the control signal falls be- Value the control slghal fans below the low the threshold; threshold; blanking means, connected to said retarder operating 'blankmg a cohplhd to sald retarder h h means and to said sensing means, for effectively inmeans sald Fehslhg h P effechvely terrupting operation of said sensing means for a first terruhtmg f h of Sa1d sensing means a predetermined time interval upon actuation of said first Predetermmed t1me,T1 Interval h actuahhh retarder operating means to either of its two operat- Sald h Ph' means to elther of lts ing conditions; two operating conditions; and timing means, included in said gate means, for a time delay circuit, ncluded in said control means, delaying actuation of said retarder operating means for delaymg actuhtlon 9 sa,ld gate means a from its releasing condition to its braking condition seconq predetf'rmmed ,tlme f T2 followmg for a second predetermined time interval longer than h 9 Sald control means to Its second operat' said first interval to permit said control means to hold mg condmon? the retarder operating means in releasing condition and a further tune. delay h Included m d gate as a car rolls out of the retarden means, for delaying actuation of sald retarder operatmg means to braking condition for a third predetermined time interval T following actuation of the retarder located on a given section of track in a railroad classification yard or the like, comprising:

retarder operating means having braking and releasing operating conditions for actuating said retard-er to braking and released conditions, respectively; gate means coupled to said retarder operating means, said gate means comprising a gate relay actuatable between an actuated condition, in which said gate means permits said retarder operating means to change to its releasing condition, and a normal condition, said gate means further including time delay gate means to normal operating condition, the relation of said time intervals being T T T 15. A control system for an electrically actuatable car 65 retarder located on a given section of track in a railroad classification yard or the like, comprising:

sensing means for developing a control signal indicative of movement of a railroad car along said track section; control means, coupled to said sensing means and actuatable from first to second operating conditions, and back, in response to excursions of said control means for applying an actuating signal to said retarder operating means to actuate said retarder operating means to its braking condition, a predeterand actuatable between a released operating condition and a braking operating condition, said retarder operating means being effective, in its released operating condition, to establish and maintain said car retarder in released condition, and said retarder operating means being effective, in its braking operating condition, to establish and maintain said car retarder in braking condition;

and interlocking circuit means, interconnecting said first operating condition to a second operating condition, said retarder operating means being eifective, when said release relay is actuated to its second operating condition, to establish and maintain said car retarder in released condition, and said retarder operating means further being effective, when said retarder operating relay is actuate-d to its second operating condition and said release relay remains in its first operating condition, to establish and tive of movement of a railroad car along said track section;

control means, coupled to said sensing means and actuatable from first to second operating conditions, and back, in response to excursions of said control signal above and below a given threshold value, respectively;

retarder operating means, coupled to said car retarder,

and actuatable between a released operating condi- C ut Ol means and Said retarder Operating means, tion and a braking operating condition, said reactuating Said retarder Operating means from tarder operating means being effective, in its released its released Operating condition to its braking op ratoperating condition, to establish and maintain said condition when Said Control means is actuated car retarder in released condition, and said retarder from its first operating condition to its second operato erating means being efiective, in its braking ing condition, and for actuating Said retarder p erating condition, to establish and maintain said ing means from its braking operating condition to car retarder i b ki diti its relfiased Operating condition when Said control said retarder operating means including a retarder means is actuated to its Second 0196f ating condition operating relay and a release relay with the retarder within less than a given time interval following actuaoperating relay energized h h a Set f t ts tion of said control means to its first operating coni h release l whereby Said Ietardel i5 first maintained in land interlocking circuit means, interconnecting said braking nond'ition and Subsequently maintainnd in control means and both of said relays of said rereleased condition by consecutive control signals tardeloperating means, f energizing Said above Said threshold Value Spaced by a control Signal tarder operating relay to establish and maintain said below said thr es-ho ld value and having a duration retarder operating means in braking operating conless than Sald tune lntel'valdition, through said contacts of said release relay A Control System for an electrically actuatable whenever said control means is actuated to its seccar retarder located on a given section of track in a 0nd operating condition and id release relay i railroad Classification Y of the like, comprising: in a first predetermined operating condition, and for sensing means for developing a control signal indicaactuating said release relay to a Second Operating cative of movement of a rallroad car along Said condition and maintaining said retarder operating track Sectlon; relay de-energized Whenever said control means is control means, Couplfid to sald senslng means actuated to its second operating condition within actuatable from first to second operating conditions, less than a given time interval f ll i actuation n back: in response to emulsions of said control of said control means to its first opearting condition, slgnal above and below a Elven threshold Value whereby said retarder is first maintained in braking respecuvely; condition and subsequently maintained in released retarder operating means, comprising a retarder condition by consecutive control signals above said )Peratmg relay and a release relay each coupled threshold value spaced by a control signal below to said car retarder, and each actuatable from a said threshold value and having a duration less than said time interval. 18. A control system for an electrically actuatable car retarder located on a given section of track in a railroad classification yard or the like, comprising:

sensing means for developing a control signal indicative of movement of a railroad car along said track section;

a control relay, coupled to said sensing means and actuatable from first to second operating conditions,

maintain said Car retarder in braking condition; and back, in response to excursions of said control and interlocking circuit means, interconnecting said signal above and bnlOW a given threshold Value,

control means and both of said relays of said Spectlvely; retarder operating means, for actuating said retarder retarder operatmg means coupled to sald Car f operating relay to its second operating condition 5 and .afztuatabk normial re1eae.d opeiatmg without actuating said release relay when said con condltlon to braking oppratmg l i q Said rem dmon and Said. .release relay 1S aklmdy Its first oar retarder in released condition, and said retarder operating condition, and for actuating said release operating means being effective in its braking p relay to its Second operating condition Whenever crating condition to establish and maintain said car said control means is actuated to its second operatretarder in braking condition; ing condition within less than a given interval folsaid retarder operating means including a retarder lowing actuation of Said brake relay from its second operating relay and a release relay with the retarder to its first operating condition, whereby said retarder Operating relay energized through a normally-closed is first established and maintained in braking condit f nta t in the release relay; tion and subsequently maintained in released conand interlocking circuit means, interconnecting said dition by cons u iv Contf 01 Signals above Said control relay and both of said relays of said retarder threshold value spaced by a control signal below operating means, for energizing said retarder opsaid threshold value and having a duration less han crating relay to establish and maintain said retarder said time interval. 17. A control system for an electrically actuatable car openating means in its braking operating condition through said normally-closed contacts of said reretarder located on a given section of track in a railroad classification yard or the like, comprising:

sensing means for developing a control signal indicalease relay, whenever said control relay is actuated to its second operating condition and said release relay is de-energized, and for energizing said release relay and opening the energizing circuit for said retarder operating relay whenever said control relay is actuated to its second operating condition within less than a given time interval following actuation of said control relay to its first operating condition;

said interlocking circuit means further including a capacitor, means for charging said capacitor upon encrgization of said retarder operating relay, and means for utilizing the charge on said capacitor to energize said release relay for said time interval upon de-energization of said retarder operating relay, whereby said retarder is first established and maintained in braking condition and subsequently established and maintained in released condition by consecutive control signals above said threshold value spaced by a control signal below said threshold value and having a duration less than said time interval.

References Cited by the Examiner FOREIGN PATENTS 3/1956 Great Britain.

OTHER REFERENCES A thesis prepared by Wilhelm Koth and titled Die, Lauf- 15 zielsteruerung In Der Abl'aufdynamikGermany-151 pages.

October 29, 1953.

Corresponding 131 page English translation of this thesis titled Humped Freight Cars.

ARTHUR L. LA POINT, Primary Examiner.

Claims (1)

1. THE METHOD OF BRAKING RAILROAD CARS, IN A RAILROAD CLASSIFICATION YARD OR THE LIKE INCLUDING A CAR RETARDER, LOCATED ON A GIVEN SECTION OF TRACK, AND ELECTRICALLY ACTUATABLE BETWEEN A BRAKING CONDITION AND A RELEASED CONDITION, COMPRISING: INITIALLY ESTABLISHING SAID CAR RETARDER IN ITS BRAKING CONDITION WITH NO CAR ON SAID TRACK SECTION, SENSING THE MOVEMENT OF A CAR ALONG SAID TRACK SECTION, AND DEVELOPING A CONTROL SIGNAL HAVING A GIVEN PARAMETER REPRESENTATIVE OF THE VELOCITY OF CAR MOVEMENT; MAINTAINING SAID RETARDER IN WHICH EVER OPERATING CONDITION THE RETARDER IS ALREADY IN IN RESPONSE TO AN INCREASE IN SAID CONTROL SIGNAL PARAMETER ABOVE A THRESHOLD INDICATING THE PRESENCE OF A CAR MOVING ALONG SAID TRACK SECTION AT A VELOCITY ABOVE A PREDETERMINED RELEASE VELOCITY; ACTUATING SAID RETARDER TO ITS ALTERNATE CONDITION UPON REDUCTION OF SAID CONTROL SIGNAL PARAMETER BELOW SAID THRESHOLD; AND ACTUATING THE RETARDER TO ITS BRAKING CONDITION WHENEVER SAID CONTROL SIGNAL PARAMETER REMAINS BELOW SAID THRESHOLD FOR A PREDETERMINED TIME INTERVAL.

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