US2719218A - Apparatus for the control of highway crossing signals - Google Patents

Description

Sept. 27, 1955 A. B. MILLER 2,719,213

APPARATUS FOR THE CONTROL OF HIGHWAY CROSSING SIGNALS Filed Dec. 1'7, 1949 3 Sheets-Sheet l (P (e wbe wwg m wk NA 5 S M NN M TE MN AN Q Q\ N.\ w IS Nm mw T kwh l m fiwfi T Mai m y E 5 SW 7 Q m l W W NS a I Q s w l I m A. B. MILLER Sept. 27, 1955 APPARATUS FOR THE CONTROL OF HIGHWAY CROSSING SIGNALS 3 Sheets-Sheet 2 Filed Dec. 17, 1949 INVENTOR.

14mm! 6. M'llez? S m k United States Patent O APPARATUS FOR THE CONTROL OF HIGHWAY CROSSING SIGNALS Alfred B. Miller, Edgewood, Pa., assignor to Westinghouse Air Brake Company, a corporation of Pennsylvania Application December 17, 1949, Serial No. 133,562

7 Claims. (Cl. 246130) is necessary to provide an adequate Warning period of the signal prior to the arrival of the train at the intersection and it is generally agreed that the absolute minimum warning time should be of the order of 20 seconds because this is the time required by a loaded motor vehicle, starting from rest, to clear a single track crossing. For a multiple track crossing the minimum warning period should be increased above 20 seconds by the order of 5 seconds for each additional track of the crossing. The maximum warning time that may be provided is an arbitrary figure but it should be determined by practical consideration of the length of time a highway user may be expected to wait at a crossing before the arrival of the train. Thus an ideal highway crossing protection system should provide an equal warning time for all trains, the warning period being not less than 20 seconds.

Systems have been proposed for providing a substantially uniform warning period irrespective of the speed of a train below a prescribed maximum permissible speed for all trains. These systems generally involve the installation of a measuring track section immediately preceding a warning or operating track section with means for determining the speed of a train in the measuring section and means for introducing a delay time interval in the starting of the warning operation of the crossing signal after the train enters the warning section, the delay interval depending upon and varying inversely with the speed of the train in the measuring section. The length of the warning section depends upon the maximum permissible train speed and the prescribed warning period of the signal prior to the arrival of the train at the crossing, the warning section being just long enough to insure the given warning period for a train moving at the maximum permissible speed. The measuring section is made of any convenient length. It is clear that with this arrangement referred to above the prescribed warning time is obtained only if the train speed is constant throughout both the measuring and the warning sections because if a train travels the measuring'section at a given average speed and thereby establishes a corresponding delay period in the starting of the warning operation and the train accelerates to travel the warning section at an average speed higher than that for which the delay period has been established, the train will be so close to the crossing when the warning signal is started that the prescribed warning time period prior to the arrival of a train at the crossing would not be obtained. In fact, a train with a high rate of acceleration may reach the crossing before the warning signal is started.

It is evident therefore that a very serious and dangerous condition can result with a so-called constant warning 2 time system if a train is advancing with a relatively high rate of acceleration. In the case of deceleration no serious or dangerous condition will result but the warning period may become excessively long and irksome for the highway user.

Again, systems have been proposed wherewith the conditions of acceleration and deceleration are checked and the warning period modified either by the use of a positive operating track section or the equivalent thereof. Since a constant warning time scheme is vulnerable to acceleration and must be modified in a manner which to a large extent eliminates the constant warning time feature, other forms of control of highway crossing signals have been proposed.

Another proposed arrangement is that by which minimum and maximum warning time limits are provided for the operation of the signal. In these schemes it is first necessary to determine the speed of each train before the train reaches the point which will provide the minimum warning time at the maximum speed. Having determined the train speed, a point is selected at which it is necessary to start the warning operation of the crossing signal to provide a warning period that comes within the prescribed limits. In these latter systems the track in the approach to the highway crossing is arranged with measuring and warning track sections and there are provided means controlled by a train as it travels each section in the approach to the intersection to start the warning operation of the signal when a train exceeds a speed predetermined for each section, the warning operation being initiated when the train enters the section next toward the crossing from the section in which the train has exceeded the prescribed limit.

In other words, these schemes use no delay time feature and employ positive warning sections together with means for automatically shifting the point for starting the warning signal from one warning section to another dependent upon the speed of the train. Thus, with prescribed minimum and maximum warning time limits the different lengths of the consecutive track sections are determined. However, the former arrangements of this type, as far as I am aware, have proposed track section lengths which are determined by considering constant train speeds through the approach to the crossing. That is, the track sections are determined by considering that each train approaches the intersection at some constant speed falling within theprescribe'd speed range. It is clear that acceleration may vary the operation of the apparatus to such a degree that the warning time may not be kept above the prescribed minimum warning time limit. Train operating rules which prohibit acceleration in the approach section to a highway crossing have been proposed for these systems but it is well known that at low speed, rates of acceleration that could hardly be detected without speed indicating devices on the locomotives, could result in a shortening of the warning time of the crossing signal to such an extent that an unsafe condition could exist. With any amount of acceleration this shortening of the warning time is present to a certain extent at all speeds but it becomes pronounced at the lower speeds.

Accordingly, a feature of my invention is the provision of an improved method for the predetermining of the layout and the lengths of track sections in the approach of a highway crossing for providing warning periods of the highway crossing signal within prescribed limits for all trains regardless of speed and acceleration of the train.

Another feature of my invention is the provision of improved apparatus for the control of highway crossing signals and wherewith the warning time of the highway crossing signal prior to the arrival of a train at the intersection is kept within prescribed limits regardless of the speed and acceleration of the train.

A further feature of my invention is the provision of highway crossing signal control apparatus incorporating means whereby the effect of deceleration on the warning period is taken into account and when a train is decelerating in a measuring section and the train stops before reaching the warning point that corresponds to the average speed of the train, the warning signal is not initiated until the train again proceeds and passes that warning point.

Other features, objects and advantages of my invention will appear as the specification progresses.

The foregoing objects, features and advantages of my invention I provide by laying out the stretch of railway track in the approach to a highway crossing into measuring and warning sections according to a method that takes into consideration the average speed of a train and the maximum possible rate of acceleration that a train can attain in traversing this stretch of railway. This improved method provides an arrangement of track sections that guarantees a warning period which falls within predetermined minimum and maximum warning time intervals. Furthermore, the arrangement of track sections established according to my invention is such that excessively long warning times due to deceleration and train stops in the approach stretch are to a large extent eliminated.

Furthermore, I provide a timing device that has operating periods individual for each measuring section and which device includes an individual circuit controlling contact member for each warning section. This timing device is controlled by and functions in conjunction with a group of train controlled relays to determine the average speed of a train in the different measuring sections and to automatically shift the warning point from one warning section to another dependent upon the average train speed. Preferably the timing device consists of a motor driven cam shaft to which several cams are secured and each of which cams operates a circuit controlling contact member according to the position of the cam. The complete movement of this timing device is one full revolution of the cam shaft and this complete movement is subdivided into several different operating periods.

For a more complete understanding of the method of determining the location of the warning points for a highway crossing signal and the control apparatus embodying my invention, reference may be had to the accompanying drawings in which Figs. 1a and 1b when taken together with the bottom of Fig. 1a placed at the top of Fig. 1b are diagrammatic views showing warning points determined by my improved method and a preferred form of apparatus embodying the invention when used with one track of a railway which is intersected by a highway at which crossing signals are provided. Figs. 2 and 3 are diagrams illustrating operating characteristics of apparatus embodying the invention.

In each of the different views like reference characters are used to designate similar parts.

Referring to the drawings, the reference characters 1a and 1b indicate the track rails of an eastbound track of a railway on which trains normally move east, that is, from left to right in the drawing. This track is intersected at grade by highway H at which intersection two highway crossing signals S1 and S2 are located. These highway crossing signals are illustrated by the symbol commonly used to indicate a flashing light type of signal but it will be understood that other forms of highway crossing signals, such as bells, gates, or barriers can be used.

This stretch of railway is formed with three insulated track sections 1T, 2T, and ST by the usual insulating rail joints 2. As shown, the section IT is located to the left of the crossing, the section 2T is located at the crossing, and the section 3T is located to the right of the crossing. Thus, the section IT is the approach section to the highway crossing for eastbound trains, the exit end F of the section being adjacent the crossing and the entrance end A of the section being a distance from the crossing predetermined in a manner to be described hereinafter. The section 2T is of a length just sufficient to include the crossing and the section ST is a receding section for eastbound trains and it may be of any suitable length. Each of these track sections 1T, 2T, and 3T is provided with a track circuit that includes a battery 3 connected across the rails at one end of the section and a track relay designated R plus a prefix corresponding to the section connected across the rails at the other end of the section.

As an aid in the understanding of the method by which points are preselected in the approach section IT for starting the operation of the signals S1 and S2 and for a better understanding of the control apparatus provided for the control of the signals S1 and S2, I shall assume a minimum warning time of 20 seconds for the signals prior to the arrival of a train at the crossing, a maximum warning time of 60 seconds, a maximum permissible speed for all trains of 100 miles per hour, a minimum train speed of 11.9 miles per hour and a maximum rate of acceleration of .8 mile per hour per second for speeds below 50 miles per hour and a maximum rate of acceleration of .3 mile per hour per second for speeds above 50 miles per hour. In other words, it is here assumed for the purpose of illustration that the apparatus will maintain the warning time of the highway crossing signals prior to the arrival of a train at the crossing within the time limits of 20 and 60 seconds over a speed range of 100 to 11.9 miles per hour and for all rates of acceleration between 0 and the rates specified above.

It will be understood that the invention is not limited to the above assumption of warning time limits, speed range and rate of acceleration and it will become apparent as the specification progresses that other speed ranges and different warning time limits and different rates of acceleration can be used.

The section IT is divided into control or subsections by any suitable means well-known for subdividing a track section. As here shown the section IT is divided into control sections by coils located at selected points B, C, D, and E, the coils being designated by the reference character C plus a prefix corresponding to its location. Each of the coils is mounted near to and preferably under the rail 1b to be in inductive relation with the rails so that an electromotive force is induced in the coil in response to an alternating current flowing in the rails. For example, when a source of alternating current the terminals of which are indicated at BX and NX is connected across the rails adjacent the exit end P of section 1T due to the closing of front contacts 4 and S of a relay 38K? to be referred to later, and a train enters the section at the entrance end A to shunt the rails, an alternating current will flow in the rails and this current flowing in the rail 1b will induce an electromotive force in each of the coils C. Furthermore, when this alternating current is coded by being periodically interrupted by a coder CD which is of standard form and arranged to open and close its contacts and 66 at a given code rate of, say, times per minute, the electromotive force picked up by each coil C will have a like code. Again, when the train advances to the right and its leading pair of wheels and axle are to the right of the location B the alternating current is shunted away from the coil BC and no electromotive force is induced in that coil. Similarly, the electromotive force induced in each of the other coils CC, DC, and EC will be cut oflf as the leading pair of wheels and axle of the train advance to the right of the respective location of the coil.

Directional control which is usually effected for highway crossing signals is here provided by means of two stick relays ISR and 38R, the relay 18R being associated with westbound trafiic and the relay 35R being associated with eastbound trafiic. Looking at the relay 38R, this relay is provided with a pickup circuit that includes terminal B of a source of direct current, front contact 6 of track relay 3TR, back contact 7 of track relay lTR, back lTR and front contact 6 of relay 3TR.

contact 8 of the opposing directional relay 1 SR, winding of relay 38R and terminal N of the same source of current. The stick relay 38R is provided with a stick circuit including two paths one of which paths include-s its own front contact 10 and back contact 9 of the track relay 2TR, and the other of which paths includes front contact 7 of relay 1TR, back contact 6 of relay 3TR and front contact 11 of the relay 35R. Thus the directional stick relay 3SR is picked up in response to an eastbound train entering the section IT to shunt relay 1TR providing the sections 2T and 3T are unoccupied, and the relay 3SR is then retained picked up by its stick circuit while the train passes over the crossing and recedes through the track section 3T. Similarly, the directional relay 1SR is controlled by a westbound train, the relay 1SR being provided with a pickup circuit that includes terminal B, front contact 7 of relay lTR, back contact 6 of relay 3TR, back contact 11 of relay 38R, winding of the relay ISR and the terminal N of the current source. The stick circuit for relay 1SR comprises two alternative path-s, one-of which paths includes back contact 9 of the relay 2TR and its own front contact 81, and the other of which paths includes its own front contact 8, back contact 7 of relay The directional stick relay 3SR governs a repeater relay SSRP, the circuit for relay 3SRP including terminal B, front contact 12 of relay 3SR, back contact 13 of relay lSR, back Contact 14 of relay lTR, winding of relay 3SRP and terminal N. The repeater relay 3SRP on picking up closes its front contacts 4 and 5 which connect the source of coded alternating current across the rails of the section IT, as explained hereinbefore. Relay 3SRP also controls the connection of the individual coils C to corresponding code following relays. For example, the closing of front contacts 15 and 16 of the relay 3SRP completes a connection of the coil BC to the input of an amplifier 17 to the output of which amplifier a code following relay BR is connected. Similarly, the coil CC is connected to a code following relay CR through front contacts 18 and 19 of relay 3SRP and an amplifier 20, the coil DC is coupled to a code following relay DR through front contacts 21 and 22 of relay 3SRP and an amplifier 23, and the coil EC is connected to a code following relay ER through front contacts 24 and 25 of relay 3SRP and an amplifier 26.

The relays BR, CR, DR, and ER are of any suitable form of code following relay and consequently when an eastbound train enters the section 1T causing the relay 3SRP to be picked up and coded alternating current supplied to the rails, each of the relays BR, CR, DR, and ER is operated in response to the electromotive force picked up by the respective track coil. Also, each of the code following relays will cease to be operated when the train arrives at the location of the respective track coil. It is to be noted that the amplifiers 17, 20, 23, and 26 are shown conventionally since they may be of standard arrangement. 6

Each of the code following relays in turn governs a corresponding train controlled relay. Locking at the code following relay BR, for example, a capacitor 27 is charged from the source of direct current B-N through back contact 28 of relay BR. Then when relay BR is picked up in response to an on code period of electromotive force received from the track coil BC, the capacitor 27 is disconnected from the current source and is connected across the winding of a relay BFSA and the capacitor discharges to supply the relay BFSA with a pulse of energizing current, this current serving to energize the relay and causeit to be picked up. On the next off period of the code, the relay BR releases to close its back contact 28 and the capacitor 27 is recharged. Thus, the relay BFSA is energized with pulses of current in step with the code operation of the relay. BR, the relay BFSA being slightly slow releasing in character and remaining picked up from one code pulse to the next. Similarly, train controlled relays CFSA and DFSA are energized in response to code operation. of relays CR and DR, respectively. A fourth train controlled relay EFSA is also energized in response to code operation of relay ER except the relay EFSA is provided with a pickup circuit governed in a manner to be described when the operation of the apparatus is taken up and then when relay EFSA is once picked up closing its own front contact 29 and a relay TP, to be referred to later, is released closing its back contact 30, the relay EFSA is controlled by code operation of the relay ER. These relays BFSA, CFSA, DFSA, and EFSA are in effect track relays responsive to a train moving through the track section in the approach to the highway crossing, and these relays will be referred to hereinafter as track relays.

It is to be noted that the track coils C, the amplifiers and the code following relays are only one arrangement by which track relays can be controlled by a train approaching the crossing and it is clear that these track relays can be controlled by conventional forms of insulated track sections if desired.

A relay TP is also provided for the apparatus and this relay is energized normally by a circuit that includes terminal B, front contact of relay 3TR, front contact 54 of relay lTR, front contact 73 of relay 2TR, winding of relay TP and terminal N. Two alternative paths, are provided for energizing relay TP, one of which includes front contact 74 of relay 3SR, and the other of which includes front contact 82 of relay 1SR.

The apparatus also includes a timing device which is indicated as a whole by the reference character TD. This timing device may take different forms and includes a motor means and a plurality of ditferent circuit controlling contact members each of which has an operating period individual for the member. Preferably the construction of the timing device TD comprises a motor driven cam shaft indicated by a dotted line 31, on which shaft eight cams No. 1 to No. 8, inclusive, are secured, Each cam is provided with a spring biased contactmemher, the contact members 35, 40, 41, 42, 43, 44, 45, and 46 being associated with the cams No. 1, No. 2, No. 3, No. 4,'No. 5, No. 6, No. 7, and No'. 8, respectively. Looking at the contact member 35, for example, this member is pivoted at 36 and is biased by a' spring 47 to the vertical position, that is, to the position illustrated in the drawing. The member 35 is provided with a roller 38 which rides on the periphery of the cam No. l, the arrangement being such that at times the member 35 is forced to the left against the force of the bias spring 47 due to the shape of the cam surface. Similarly, each of the other contact members is spring biased to a vertical position and is rotated about a pivot in opposition to the spring bias by the cam surface engaging a roller secured to the contact member as will be understood by an inspection of the drawing.

The cam shaft 31 is driven by a constant speed synchronous motor 32 through a clutch and gear train 33. While a synchronous motor is preferred, other formsof constant speed motors can be used. A complete operation of the timing device is one revolution of the shaft 31 and the No. 1 cam in cooperation with a starting magnet 34 divides the complete movement into several different operations. The member 35 is pin connected at an intermediate point to the armature 37 of the starting magnet 34 and its locking roller 38 is adapted to fit a notch or recess 1N in cam No. 1 and thereby the shaft is locked in an initial position, that is, the position shown in the drawing when the magnet is deenergized and the member held by the bias spring. When the starting magnet 34 is momentarily energized in a manner to later appear, it attracts its armature 37 to the left and draws the member 35 against the force of the bias spring 47 so that the roller 38 is lifted out of the cam recess IN. The member 35 also engages a contact 39. The closing of the contact39 completes an obvious circuit by which the source of alternating current BX-NX is connected to the motor 32 and the motor is operated to drive the cam shaft in a counterclockwise direction as indicated by an arrow through the clutch and gear train 33. With the No. 1 cam moved away from its initial position, the contact member 35 is held to the left to engage the contact 39 due to the roller 38 riding on the periphery of the cam and operation of the motor 32 is continued although the starting magnet 34 is in the meantime deenergized. When rotation of the cam No. 1 has proceeded, an angle predetermined in a manner to later appear, a second recess 2N aligns with the roller 38 and the contact member 35 is snapped back to its vertical position due to its bias spring. This operation of the contact member 35 opens the contact 39 in the motor circuit and the operation is stopped, the roller 38 engaging the recess 2N to lock the cam in this new position. The clutch portion of the clutch and gear train 33 serves to avoid any severe shock to the construction due to the stopping of the cam shaft. At a second energizing of the starting magnet 34, the contact member 35 is again drawn to the left to complete the motor circuit and unlock the No. 1 cam so that a second operation of the cam shaft takes place. This second operation will be continued after the deenergizing of the magnet 34 due to the roller 38 riding on the cam No. 1. When the cam No. l is rotated another predetermined angle and the recess 3N aligns with the roller 38, the contact member 35 is snapped back into its vertical position by the bias spring and the motor stopped with the cam shaft locked in this position. Similarly, a third operation of the cam shaft 31 to a third position is effected by means of a fourth recess 4N formed in the No. 1 cam. A final operation of the cam shaft back to its initial position is effected through the No. 2 cam in a manner to be explained hereinafter.

The timing device TD is controlled by the track relays and it functions with these relays to determine the average train speed in the different track sections and to automatically determine the point at which the warning operation of the signals is to be initiated. To this end, the track relays, the timing device and the slow release relay TP cooperate to govern a signal controlling relay XR. Normally, that is, when no train is approaching the intersection, the relay XR is energized by a pickup circuit which includes a front contact 48 of the relay TP. When relay TP is released in response to a train entering the section 1T, the relay XR can be energized over a stick circuit that includes its own front contact 49 and a plurality of alternative paths governed by the timing device and by the track relays, as will be pointed out when the operation of the apparatus is explained. The signal controlling relay XR when released closing back contact 50 completes an obvious operating circuit for a flasher relay EOR which is of a standard form and which relay EOR is operated in the well-known manner to alternately close its contacts 51 and 52, the contacts 51 and 52 being included in the signal lamp circuits for the signals S1 and S2 to alternately flash the lamps in response to alternate operation of the contacts 51 and 52.

It is believed that the method of predetermining the layout of the control track sections can best be explained by a description of the operation of the apparatus. Normally, that is, when no train is approaching the crossing the apparatus occupies the position illustrated in the drawings. I shall first assume that an eastbound train enters the section IT and proceeds over the crossing. The shunting of the rails of section 1T causes relay 1TR to be released and the release of relay lTR closing back contact 7 causes the directional stick relay 38R to be picked up and which directional relay on closing front contact 12 causes the repeater relay 3SRP to be energized and picked up. With relay 3SRP picked up, coded alternating current is supplied to the rails of the section 1T and each of the track coils BC, CC, DC, and EC picks up an electromotive force coded due to the coder CD. The code following relays BR, CR, DR, and ER are now operated due to the coded electromotive force picked up by the track coils in response to the coded alternating current flowing in the rails. Code operation of relays BR, CR, and DR at once picks up the track relays BFSA, CFSA, and DFSA, respectively.

The release of the track relay 1TR opening its front contact 54 removes current from relay TP, but relay TP does not release until the end of its predetermined slow release period. Subsequent to the release of relay lTR and before the release of relay TP, the pickup circuit for the relay EFSA is formed, the circuit being traced from terminal B through back contact 55 of relay lTR, back contact 56 of relay lSR, wire 57, the contact of contact member 41 of the timing device and which contact is closed because the roller 58 of the element 41 engages the raised portion of No. 3 cam at the initial position, front contact 30 of relay TP, and winding of relay EFSA to terminal N. Subsequent to the release of relay TP, the relay EFSA is energized due to the code operation of its associated relay ER.

With the release of the track relay lTR, current is supplied to the starting magnet 34 of the timing device during the slow release period of the relay TP, current flowing from terminal B through back contact 55 of relay 11' R, back contact 56 of relay ISR, wire 57, front contact 53 of relay TP and the winding of magnet 34 to terminal N. When the magnet 34 is energized it releases the No. 1 cam and closes the operating circuit for the motor 32 and the cam shaft 31 is rotated counterclockwise by operation of the motor. Winding magnet 34 is deenergized when the relay TP is released opening front contact 53 but the motor circuit is held closed due to the roller 38 riding on the surface of the cam No. l. The motor continues to drive the cam shaft at a constant speed until the second recess 2N on the No. l cam aligns with roller 38 and the contact member 35 is snapped back to its vertical position by its bias spring, the movement being stopped at this point. Since all of the cams are secured to the shaft 31, the movement of the shaft just described causes all cams to assume a new position corresponding to the position of the No. 1 cam. In the second position of the cam shaft the raised portion of cam No. 3 moves out from under the roller 58 and the contact member 41 is pulled back to its vertical position by its bias spring. The raised portion of cam No. 4 engages the roller 59 of the contact member 42, forcing this member to the left against its bias to close the corresponding contact, and the raised portion of No. 6 cam engages the roller 60 of contact member 44 to close its contact.

It is to be noted that the release of the relay TP to open its front contact 48 opens the circuit for the signal control relay XR, but relay XR is then supplied with current over its stick circuit path which includes the front contacts 61, 62, 63, and 64 of the track relays BFSA, CFSA, DFSA, and EFSA, respectively.

Referring now to the layout of the approach track section, the first warning point B, the point at which the warning signal must start for a train traveling at a maximum speed here assumed to be miles per hour, must be located 2933 feet in advance of the crossing, this distance being equal to the distance the train can travel at the maximum speed in the assumed minimum warning time of 20 seconds. Since a maximum warning time of 60 seconds has been assumed, the point B can remain the warning point for all train speeds between 100 miles per hour and 33.3 miles per hour, the speed at which the running time of this distance BF becomes equal to the maximum warning time of 60 seconds. For speeds below 33.3 miles per hour, the warning point, however, must be shifted closer to the crossing in order not to exceed the maximum warning time.

The shifting of the warning point from point B to some new point, such as point C, and the method of determining the location of this point C with respect to the crossing are effected as follows. The measuring track section AB immediately preceding the warning point B is used in conjunction with the timing device TD to determine the speed of the train as it approaches the point B. This measuring section AB canbe any convenient length so long as the timing device is proportioned accordingly. As here illustrated, the section AB is made 733 feet which is the distance a train can travel in seconds at 33.3 miles per hour, the speed at which the warning point must be shifted from point B. The time of 15 seconds is an arbitrary value and the timing device is proportioned so that its cam shaft 31 is rotated from its initial position to its second position where the locking roller 38 engages the second recess 2N in 15 seconds. That is, the timing device will have operated to the position where recess 2N aligns with the locking roller 38 and the timing device has stopped just when a train traveling at the everage speed of 33.3 miles per hour in section AB has reached the point B.

When the train passes the point B, the alternating current is shunted away from the coil BC due to the train shunt and the relay BR is no longer operated with the result the track relay BFSA is deenergized and released. The release of relay BFSA opening its front contact 61 and closing its back contact 70 switches the control of the relay XR to a second alternative path of its stick circuit and which second path includes the contact 44 of the timing device and back contact 61 of the track relay BFSA. The signal controlling relay XR is thus released or retained energized after the train passes the point B depending upon whether or not the timing device has been operated to its second position. If the average speed of the train in the measuring section AB is greater than,33.3 miles per hour and it consumes less than 15 seconds in traveling the section, the timing device will not have reached its second position to close contact 44 and the relay XR is released to immediately start the warning operation of the signals S1 and S2. The warning operation of the signals once started, the operation is continued until the train passes over the crossing, as will be pointed out shortly. If the average speed of the train in section AB is less than 33.3 miles per hour and it consumes 15 seconds or more in passing through the section AB, the timing device will have reached its second position and stopped with the contact 44 closed so that the signal controlling relay XR is retained energized after the train passes the point B, at least the relay XR is retained energized until the train reaches another predetermined warning point, such as point C.

Since the warning point is shifted to point C at an average train speed in section AB- of 33.3 miles per hour, and since acceleration can be present, the location of the new warning point C with respect to the crossing must be such that the running time in the section C-F is equal to the minimum Warning time of seconds with an average speed in section AB of 33.3 miles per hour and with acceleration all the way from the point A to the crossing. Thus the maximum average speed for which. the point C can be the warning point is determined by using the average speed of 33.3 miles per hour in section AB and the assumed maximum rate of acceleration of .8 mile per hour per second at speeds below 50 miles per hour and .3 mile per hour per second at speeds above 50 miles per hour from the point A to the crossing. Knowing the length of the section AB and the time consumed in traveling the section as being 15 seconds, and using the maximum rate of acceleration of -.8 mile per hour per second or 1.17 feet per second per second, the initial speed, that is, the speed at point A, is determined by the equation s=Vot]- /z at where s equals the distance, V0 equals the initial speed, t equals the time in seconds and a equals the rate of acceleration. This gives the initial speed V at point A as 27.3 miles per hour. Using this initial speed and the maximum rate of acceleration, the time consumed when the train has attained the speed of 50 miles per hour, the speed at which the rate of acceleration is assumed as changing from a first value to a second value, is found by the equation V Vii-Fat, where V is the final speed, Vn the initial speed; a the acceleration and t the time, and in this instance the time is 28.3 seconds. Also, the distance advanced by the train by the time the speed of 50 miles per hour is attained is determined by the first mentioned equation and it is found to be 1603 feet. Since the total distance (AF) is 3666 feet there remains a distance of 2063 feet for the train to travel at the low value of assumed maximum rate of acceleration of .3 mile per hour per second or .44 feet per second per second. Using the distance of 2063 feet and the rate of acceleration of .44 feet per second per second, the time consumed by the train in moving to the point P after it has attained the speed of 50 miles per hour is determined by the first mentioned equation as being 26.1 seconds. Also, the speed the train will have attained at point F is computed by the second mentioned equation to be 57.8 miles per hour.

Then using the speed attained at point F, the average speed during the 20 second period just prior to the train reaching the crossing is computed as being 54.8 miles per hour or 80.45 feet per second. The distance traveled in 20 seconds at this average speed of 80.45 feet per second is 1609 feet and hence the point C must be located 1609 feet from the crossing or 1324 feet east of the point B in order that the minimum warning time of 20 seconds is guaranteed for trains having an average speed just under 33.3 miles per hour in section AB and the maximum assumed acceleration all the way from point A to point F.

The point C, therefore, becomes the new warning point for train speeds below 33.3 miles per hour and it can remain the warning point for all train speeds between 33.3 miles per hour and 18.3 miles per hour, the train speed at which the running time from points C to the crossing becomes equal to the maximum warning time of 60 seconds. For train speeds below 18.3 miles per hour, the warning point must be again shifted closer to the crossing in order not to exceed the maximum warning time.

The section BC, immediately preceding the Warning point C, is used as a measuring section for speeds below 33.3 miles per hour and this section BC in conjunction with the timing device determines the speed of the train as it approaches the point C. In other words, the measuring section BC now cooperates with the timing device in a manner similar to the manner in which the measuring section AB cooperated with the timing device. When the train passes the point B and coded alternating current is shunted from coil BC, causing the track relay BFSA to be deenergized and released, the starting magnet 34 is again energized by current flowing from terminal B through front contact 68 of relay EFSA, front contact 69 of relay CFSA, back contact 70 of relay BFSA, contact member 42 of cam No. 4, back contact 53 of relay TP, and the winding of magnet 34 to terminal N. The magnet 34 being energized, it draws the member 35 to the leftto release the cam No. 1 and also to close the energizing circuit for the motor 32 so that the cam shaft is rotated counterclockwise from its second position. The No. 4 cam at once moves its raised portion from under the roller 59 of member 42 and that member is pulled to its vertical position by the bias spring to open the magnet circuit but the motor circuit remains closed due to the roller 38 riding on the surface of cam No. 1 and the operation of. the cam shaft continues until the third recess 3N of the cam No. l aligns with the locking roller 38 and the member 35 is snapped back to its vertical position by the spring bias. At this third position the raised portions of cams No. 5 and No. 7 engage the respective rollers 71 and 72 of the respective contact members 43 and 45 to close these contacts.

The length of the section BC is 1324 feet and the running time of this section is 49.4 seconds at the average train speed of 18.3 miles per hour, the speed at which the warning point must be shifted from point C to some point D in order not to exceed the maximum warning time of 60 seconds. The recess 3N is formed in No. 1 cam at an angle such that the shaft is rotated to this point in 49.4 seconds. That is, the shaft is operated to its third position Where recess 3N aligns with the locking roller 38 and the operation is stopped just as the train traveling through the section BC at the average speed of 18.3 miles per hour reaches the point C.

When the train passes point C, coded alternating current is shunted from the coil CC with the result that the track relay CFSA is deenergized and released. The signal controlling relay XR is now retained energized by the path of its stick circuit that is completed through back contact 62 of relay CFSA and the contact of contact member 45 of cam No. 7 of the timing device. Thus, if the average speed of the train in section BC is above 18.3 miles per hour so that the contact member 45 is not operated to close its contact when the train reaches point C, the relay XR is released to start the operation of the signals S1 and S2. If the train speed is less than 18.3 miles per hour and the contact of the contact member 45 is closed when the train reaches point C, relay XR is retained energized, at least it is retained energized until the train reaches a selected point, such as point D.

In view of the foregoing it is evident that point C is the warning point for all train speeds between 33.3 miles per hour and 18.3 miles per hour and the Warning time will be within the warning limit of 20 and 60 seconds regardless of acceleration. Also, it is evident that the warning point must be shifted to some point closer to the crossing, such as point D, for train speeds below 18.3 miles per hour.

Since the warning point is shifted to point D at an average speed of 18.3 miles per hour in the measuring section BC and since acceleration may be present, the location of the Warning point D with respect to the crossing must be such that the warning time in section D-F is equal to the minimum Warning time of 20 seconds with an average train speed in section BC of 18.3 miles per hour and with the maximum rate of acceleration from point B to the crossing. Using the same method of calculation discussed in connection with determining the location of point C, it is found that a train speed of 52.6 miles per hour at point P can be attained when the average speed in the measuring section BC is 18.3 miles per hour and there is the maximum rate of acceleration all the way from point B to the crossing. Using this speed at point P and the assumed maximum rate of acceleration. it is found by the equation previously referred to that the train will travel 1406 feet in the 20 seconds just prior to the arrival of the train at the crossing. Thus the point D must be located 1406 feet from the crossing or 203 feet east of the point C. The point D, therefore, becomes the warning point for an average speed of 18.3 miles per hour in he measuring section BC and it remains the warning point for all train speeds between 18.3 miles I per hour and 15.9 miles per hour, the train speed at which the running time in the section DF becomes equal to the maximum warning period of 60 seconds. For train speeds below 15 .9 miles per hour, the warning point must again be shifted to some point closer to the crossing, such as point E in order not to exceed a maximum warning period.

The shifting of the warning point from point D to point E at 15.9 miles per hour is accomplished by using section CD as the measuring section in conjunction with the timing device. In this case, section CD which is 203 feet long, functions with the timing device to shift the warning point to point E at the proper speed. With the contact member 43 of No. cam closed at the third position of the cam shaft, it provides a circuit for the starting magnet 34 when the train passes point C and causes track relay CFSA to be released, and which circuit extends through front contact 68 of relay EFSA, back contact 69 of relay CFSA, contact member 43 and back contact 53 of relay TP. With the starting magnet 34 energized to release roiler 38 out of the recess 3N and to close the motor circuit, the motor is operated todrive the cam shaft counterclockwise through a movement to where the recess 4N aligns with the roller 38, causing the contact member 35 to be snapped back to its vertical position to open the motor circuit. It is to be noted that the raised portion of No. 5 cam moves out from under the roller 71 immediately after this movement is started so that the starting magnet is deenergized prior to the movement of the shaft to the fourth position. The train moving at 15.9 miles per hour would consume approximately 8.7 seconds in section CD and the recess 4N is formed for the cam shaft to be rotated at an angle where recess 4N aligns with roller 38 in 8.7 seconds. That is, the cam shaft is operated at its fourth position and stopped just prior to the train travelling at a speed of 15.9 miles per hour in section CD reaches the point D. The contact member 46 of No. 8 cam is arranged to close its contact when the recess 4N aligns with the roller 38 and thus when the train passes the point D to shunt the coded alternating current away from coil DC and cause the track relay DFSA to be deenergized, the signal controlling relay XR is provided with a new circuit path including back contact 63 of relay DFSA and the contact of contact member 46 to retain the relay XR energized.

The location of point E is determined in the manner already discussed for determining the locations of the points C and D. In this latter case the section CD is used as the measuring section, together with the average train speed of 15.9 miles per hour in the section and the maximum rate of acceleration from point D to the crossing. Using the method previously explained, the warning point E is found to be located 1049 feet from the crossing or 357 feet east of the point D in order to guarantee a minimum Warning time of 20 seconds. With point E located 1049 feet from the crossing, the maximum Warning time of 60 seconds will not be exceeded until the train speed in section E-F falls below 11.9 miles per hour which is the minimum speed assumed for the speed range of to 11.9 miles per hour.

From the foregoing it will be evident that with the control track sections arranged by the method described and the timing device constructed in the manner explained, the warning time of all trains moving within the assumed speed range of 100 to 11.9 miles per hour will be Within the warning time limits of 20 to 60 seconds for all rates of acceleration between zero and the maximum rate assumed. It will also be evident that the warning limits of 20 to 60 seconds can be provided for speeds lower than 11.9 miles per hour by installing additional control track sections and additional cams on the timing device. Furthermore, it will be evident that different warning time limits can be provided for the same rate of acceleration and the same speed range or for different rates of acceleration and different speed ranges by the same method of determining the control track sections and the same construction for the timing device.

When the train passes point E the coded alternating current is shunted from coil EC with the result that the track relay EFSA is deenergized and released. The opening of front contact 64 of relay EFSA opens the stick circuit for the signal controlling relay XR and that relay is released to start the operation of the signals.

When the train enters the section 2T to shunt track relay 2TR, the release of relay ZTR opening its front contact 73 opens the circuit for relay TP at a second point and the relay TP is retained released subsequent to the train clearing the section 1T. The closing of back contact 9 of relay ZTR completes an alternative path for directional stick relay 35R as explained hereinbefore. When the train has passed over the crossing and enters the section 3T the clearing of sections IT and 2T causes the relay TP to be reenergized with the result the operation of the crossing signals is stopped. However, the directional stick relay 35R is retained energized while the train passes through the section 3T.

Since the timing device TD was operated to its fourth position for control of relay XR at the section DE it becomes necessary to return the device to its initial position as soon as the train passes the point E. To this end the contact member 40 of No. 2 cam engages its contact at all positions of the cam shaft except at the starting position and an energizing circuit for the starting magnet 34 is provided from terminal B, through back contact 68 of relay EFSA, back contact 75 of relay TP, contact member 40 of the No. 2 cam and Winding of the magnet 34 to terminal N. With magnet 34 energized, the locking roller 38 is lifted out of the recess 4N and the motor circuit is closed and the motor operated to drive the shaft counterclockwise to its initial position. The recess in the cam No. 2 for roller 76 of member 40 is made a little long so that as the cam shaft approaches its initial position the member 40 is snapped back to its vertical position to deenergize the starting magnet in time to permit the motor to stop and the locking roller 38 to engage the recess 1N andretain the cam shaft at its initial position. In order to assure full return' of the timing device for a high speed train an alternative path for the starting magnet 34 is provided from terminal B through front contact 55 of relay ITR, front contact 77 of relay 3SR, wire 78, front contact 75 of relay TP and contact 40 of the No. 2 cam.

When the eastbound train vacates the section 3T in receding from the crossing, the track relay 3TR is reenergized and the apparatus is fully restored to its normal position.

In accordance with the usual practice, the operation of the signals S1 and S2 is provided for a westbound train, but in this case the operation is not controlled according to the speed of the train. When a westboud trains enters the section 3T to shunt the track relay 3TR and sections 1T and 2T are unoccupied, the directional stick relay ISR is picked up and the relay TP is released. The release of relay TP to open its front contact 48 causes the signal controlling relay XR to be released and start the operation of the signals. When the westbound train advances into section 2T and then into section 1T, the directional stick relay ISR is retained energized by its stick circuit and with relay ISR energized to open back contact 13 the relay 3SRP is retained deenergized so that no coded alternating current is applied to the rails of section 1T to cause an operation of the associated apparatus by the westbound train. It is to be noted that section 3T can be arranged with track coils in the same way as section 1T and the crossing signals governed according to the speed and acceleration of trains moving from right to left over the crossing.

Deceleration, at least to a certain extent, is automatically taken care of in the control of the crossing signals.

If an eastbound train is decelerating in the measuring section AB, for example, and the train stops before it reaches the point C, it is quite likely that the average speed in the measuring section AB would be such as to shift the warning point to point C. With the train stopped in the section BC, it would thus not produce a warning signal. Under these circumstances, the timing device would operate to its third position where the locking roller 38 engages the recess 3N. When the train starts up again and passes the point C, the relay XR will be retained energized by the circuit path including the contact member 45 of the No. 7 cam. The apparatus will then function to determine the speed of the train with the section C-D as a measuring section and if the train exceeds the speed range predetermined for the section C-D, the warning operation will be initiated at point D. If the train travels the section C-D at a speed below the predetermined speed range for the section, then the warning point is shifted to point E. Thus we see that with the apparatus here provided an excessively long warning period when a train is decelerating will not ordinarily be established.

It follows from the foregoing description of the operation of the apparatus here provided that the warning times of the highway crossing signals are kept within prescribed limits by shifting the warning point from one section to another depending upon the speed and acceleration of the train in the measuring section. For example, the first measuring section A-B and the average speed of the train in the section will determine whether the warning point will be at point B or at point C or beyond. If the speed in the measuring section AB is low enough to shift the warning point to point C or beyond, then the section BC becomes the new measuring section, and the average speed of the train in this section BC determines whether the warning point will be at point C or beyond. Similarly, if the speed of the train in this measuring section BC is low enough to shift the warning point to point D or beyond, then section C-D becomes the measuring section to determine whether the warning point shall be at point D or at point E. In a similar manner, additional measuring and warning sections can be provided to extend the speed range.

This principle of control provided by the apparatus of Figs. 1a and lb is illustrated in Fig. 2 and it is to be observed that the five control sections serve the function of three measuring sections and four warning sections. For many highway crossings it is believed that three control sections will provide a sufiicient speed range for a desired warning time limit, and under this arrangement only the first measuring section AB would be required and the construction of the timing device can be simplified to comprise only four cams and four contact members.

In Fig. 3 there is illustrated a modification of the layout of the control tract sections that I may use to chain the control of the highway crossing signals affected by apparatus embodying the invention. In Fig. 3 the five control track sections are arranged to serve as three warning sections and two measuring sections, whereas in Fig. 2, the five control sections serve as four warning sections and three measuring sections. In the arrangement shown in Fig. 3 the warning points for starting the operation of the highway crossing signals would be determined by the samemethod used in connection with the layout illustrated in Fig. 2 and employed with the apparatus of Figs. 1a and 1b and which method takes into consideration the speed of the train and the different rates of acceleration. It is to be noted that in Fig. 3 the second measuring section is made independent of the warning section and it can be of any arbitrarily chosen length, the same as the first measuring section AB. In this way the second measuring section can be chosen to have equal running time for various warning time limits, speed ranges and rates of acceleration required at different crossing locations. Preferably the time intervals of the first and second measuring section of Fig. 3 would be equal and relatively short but unequal time measuring intervals for the two measuring sections can be used. It is clear that with only two measuring sections the construction of the timing device would be simplified. With the measuring section divorced from the warning section as shown in Fig. 3, the arrangement tends to still further simplify the design of the timing device because it eliminates the need for the various measuring section time intervals to he graduated in tenths of a second. Furthermore, the same construction of the timing device for the arrangement of Fig. 3 would serve for a relatively large number of different grade crossing layouts.

Although I have herein shown and described but one method and one form of apparatus for the control of highway crossing signals embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. The method of operating a highway crossing signal located at a crossing approached by a length of track which consists in actuating the signal at a first control point along the track at a distance from the crossing which provides a warning time interval between a given minimum and a given maximum time interval for train speeds between a given maximum average speed and a lower average speed determined by the maximum time interval, avoiding the signal actuation at the first control point for speeds below said lower determined speed, and actuating the signal at a second control point along the track at such a distance from the crossing that it provides said given minimum time interval at a speed which is substantially equal to the determined speed plus the increase in speed caused by an assumed rate of acceleration all the way from the first control point to the crossing,

2. The method of control of a highway crossing signal located at a crossing approached by a length of track to provide a warning period prior to the arrival of a train at the crossing that is within a given minimum and a given maximum time interval for all train speeds within a given maximum average and a given minimum speed and for all rates of acceleration between zero and an assumed maximum rate, which consists in providing a track section remote from said crossing of known length for measuring the average speed of a train approaching the highway crossing, actuating the signal at the crossing at a first control point along the track at a distance such as to provide the minimum interval for the maximum average speed when the measured speed of a train is between a given maximum average speed and an average speed determined by a given maximum time interval, holding in abeyance the actuation of said signal for average train speeds below said determined speed, and actuating the signal at a second control point at a distance along the track such as to provide the minimum time interval when the train is traveling at a speed corresponding to said determined average speed increased at the assumed maximum rate of acceleration and which second point provides said maximum warning time interval at a given average minimum speed.

3. In a highway crossing signal control apparatus of the type wherein the warning time provided by a highway crossing signal is kept within prescribed limits by shifting the point along a stretch of track in approach to the crossing at which said warning signal commences to operate when a train approaches the crossing in accordance with the time a train takes to traverse a predetermined length of the stretch in approach to the point, the combination comprising a first, second and third consecutive control sections provided in said stretch through which trafiic travels in the order named, said first section being of a predetermined length, the entrance end of said second section being located at a distance from said crossing equal to the product of an assumed maximum speed for the stretch times an assumed minimum safe warning time, said entrance end of said third section being located at a distance from said crossing equal to the product of the maximum average speed a train is permitted to travel from said entrance end of said third section to said crossing times said minimum warning time, said maximum average speed being the average of the maximum speed a train which is constantly accelerating at an assumed rate while it traverses said second section could enter said third section without having caused said signal to commence operating when said train entered said second section and of the speed said constantly accelerating train will achieve when it reaches said crossing, neither of said speeds to exceed said assumed maximum speed for the stretch, a control relay means for each of said control sections and each of said relay means being responsive to a train entering its respective section, a timing device including a motor element and a contact actuating memher, said timing device provided with drive means for said motor element to operate said contact actuating member for a time equal to the time it would take a train traveling at the minimum speed which would necessitate the commencing of operation of said signal when said train enters said second section and still prevent said signal from operating for more than an assumed maximum warning time, a first energizing circuit means for said signal including said control relay means associated with said second section and closed 'only if said motor element has not completed its operation when said second control relay means operates, and a second energizing circuit means for said signal including said control relay means for said third section.

4. In a highway crossing signal control apparatus of the type wherein the warning time provided by the highway crossing signal is kept within prescribed limits by shifting the point along a stretch of track in approach to the crossing at which said warning signal commences to operate when a train approaches the crossing in accordance with the time a train takes to traverse a predetermined length of said stretch in approach to said point, the combination comprising a measuring section and a first and second operating sections provided in said stretch through which a train travels in the order named in approaching the crossing, the measuring section being of a predetermined length, the entrance end of said first operating section being located at a distance from said crossing equal to the product of an assumed maximum speed for the stretch times an assumed minimum warning time, said entrance end of said second operating section being located a distance from said crossing equal to the product of the maximum average speed a train is permitted to travel from the entrance end of said second operating section to said crossing times said minimum warning time, said maximum average speed being the average of the maximum speed a train which is continuously accelerating from the entrance end of said first operating section at an assumed rate is permitted to enter said second operating section without having caused said signal to commence operating when said train entered said first operating section and of the speed said constantly accelerating train will achieve when it reaches said crossing, a control relay means associated with each of said sections and each control relay means responsive to a train entering its respective section, a control circuit including a contact of the control relay means of each of said operating sections for starting a warning operation of the signal, a timing device including a motor element, a starting magnet and a contact actuating member which is operatively connected to said motor element; an operating circuit connected to the motor element for energizing said motor element and including a contact closed when said starting magnet is energized, said timing device having an initial position and an operated position for its contact actuating member, said member being actuated by said motor element from its initial position to its operated position in a time interval equal to that consumed by a train traversing the measuring section at a preselected minimum average speed when the motor element is energized, a slow-release relay energized over a contact of the control relay means associated with said measuring section closed when that section is unoccupied, circuit means for energizing said starting magnet including a front contact of said slow-release relay and a contact of the control relay means of the measuring section closed when a train enters said measuring section, a circuit path including a contact closed only when said contact actuating member is actuated to its operated position to shunt said signal control circuit around the contacts of the control relay means of said first operating section, and means actuated by said contact actuating member to hold closed said contact of the motor element operating circuit between said initial and said operated positions.

5. A method of operating a highway crossing signal located at a crossing approached by a length of track, comprising measuring the speed of a train approaching the crossing, actuating the signal when the train reaches a first point along the track at a distance from the crossing such as to provide a warning period between predetermined maximum and minimum limits if the measured speed is between an assumed maximum and a lower speed fixed by the maximum warning period, and actuating the signal when the train reaches a second point at such a distance from the crossing as to provide the minimum warning period for a train having the lower measured speed and an assumed maximum acceleration from the first point to the crossing.

6. The method of operating a highway crossing signal to provide a warning of the approach of a train to the crossing, said Warning being provided for a variable period not less than a predetermined minimum period and not exceeding a predetermined maximum period, comprising the steps of measuring the average speed of trains approaching the crossing over a length of track remote from the crossing, operating a signal placed at the crossing when the train reaches a first point removed from the crossing by a distance equal to that which could be traveled by a train operating at a predetermined maximum first speed in the predetermined minimum period if the measured speed is greater than that second speed required for the train to reach the crossing from said first point in the predetermined maximum period, and operating the crossing signal when the train reaches a second point removed from the crossing by a distance equal to that which could be traveled in'said minimum period by a train operating from the beginning of said length of track to said crossing at an acceleration equal to a predetermined maximum and having an average speed over said length of track equal to said second speed if said measured speed is less than said second speed.

7. In highway crossing signal control apparatus, a crossing signal, operating means for said signal, a length of track approaching said crossing, first means responsive to the passage of a train across a first point along said track a predetermined distance away from said crossing, second means responsive to the passage of a train across a second point along said track between said first point and said crossing at a distance from said crossing equal to that which would be traversed by a train operating at an assumed maximum speed in a predetermined minimum warning time, timing means actuated by said first means for establishing a circuit to prevent the actuation of said operating means after a time equal to that required for a train to reach the second point from the first point at the assumed maximum speed, third means actuated by said second means to actuate said operating means, said third means being by-passed by said established circuit, and fourth means responsive to the passage of a train across a third point along said track at a distance from said crossing equal to that which would be covered in said minimum warning time by a train having an assumed maximum acceleration from said first point to said crossing and an average speed from the first point to the second point required to reach the crossing from the second point in a predetermined maximum warning time, said fourth means including means for actuating said operating means.

References Cited in the file of this patent UNITED STATES PATENTS 1,896,120 Young et al. Feb. 7, 1933 1,933,781 Williamson Nov. 7, 1933 2,028,370 Williamson Jan. 21, 1936 2,035,169 Lazich Mar. 24, 1936 2,035,170 Lazich Mar. 24, 1936 2,406,955 Lower Sept. 3, 1946

Images