United States Patent [191 Coeurderoy 1 Dec.2, 1975 154] HYDRAULIC INSTALLATION WITH ENERGY STORING MEANS [75] inventor: Yves G. Coeurderoy, Lagny-le-Sec,

France [73] Assignee: Societe Anonyme: Poclain, Le

Plessis-Belleville, France 22 Filed: Dec. 23, 1974 [21] Appl. No.: 535,820

[301 Foreign Application Priority Data Jan. 14, 1974 France 74.01175 [52] US. Cl. 60/413; 60/418; 60/430; 60/486 [51] Int. Cl. FlSB 1/02 [58] Field of Search 60/413, 418, 430, 486

[56] References Cited UNITED STATES PATENTS 3,023,579 3/1962 Bookout et al. 60/418 3,355,994 12/1967 Malott 60/430 X Primary ExaminerEdgar W. Geoghegan Attorney, Agent, or Firm-Lewis H. Eslinger; Alvin Sinderbrand [5 7] ABSTRACT This invention relates to a hydraulic installation in which means are provided for storing energy when operating at low power and for restoring this energy for work at high power.

According to the invention, an auxiliary pump keyed to the driven shaft of a motor driving a group of main pumps, discharges into an accumulator. A first distributor may interrupt this flow and direct it towards a tank; a conduit connects the accumulator to the receiver conduit connected to the main pumps. A second distributor may interrupt this conduit. A pressure sensor is connected to the input of a logic unit whose outputs are connected to the control elements of the distributors. This logic unit controls the position of the distributors as a function of the pressure detected in the conduit. The invention is applicable to public works machines.

2 Claims, 2 Drawing Figures US. Patent Dec. 2, 1975 f P P P2 HYDRAULIC INSTALLATION WITH ENERGY STORING MEANS The present invention relates to a hydraulic installation in which means are provided for storing energy when the power used by the receiver apparatus is less than the installed capacity, and for restoring this energy as a supplement to the fully employed installed capacity for work where high power is required.

In certain types of devices, and in particular in public works machines, it is advantageous, for reasons of economy of operation, to use all the installed power of these machines as much as possible. Now, certain work or certain work phases do not require this maximum use of the installed power, particularly when the resistant stress is less than what the machine is capable of employing. Others, on the other hand, require an addition of power for a short time, for example to overcome resistance to the tearing up of a volume of earth which is slightly more than the maximum capacity of the machine.

The invention proposes to use at least a part of the installed capacity which is not devoted to the main task in the work of the first type mentioned above, to store it and restore it when work of the second typehas to be carried out.

To this end, it has for its object a hydraulic installation comprising a motor driving at least one so-called main pump and at least one so-called auxiliary pump, the main pump discharging into at least one receiver and the delivery pipe of the auxiliary pump being con nected to a pressure accumulator.

According to the invention, there is provided a first two-way distributor disposed in the delivery conduit of the auxiliary pump which ensures communication of said auxiliary pump, in its first position, with the accumulator and, in its second position, with a tank; between said first distributor and the accumulator there is tapped a pipe connected to the feed conduit of the receiver and provided with a second two-way distributor ensuring, in its first position the closure of said pipe and, in its second position, the opening thereof, whilst a fluid pressure sensor is disposed in the feed conduit of the receiver and controls, via a logic device, the selection of the positions of the first and second distributors.

The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which:

FIG. 1 is a diagram of a hydraulic installation according to the invention.

FIG. 2 is a graph showing a possible development of the power as a function of the pressure in a hydraulic installation according to the invention.

Referring now to the drawings, and firstly to FIG. 1, a motor 1 is shown on the driven shaft 2 on which are keyed, on the one hand, a group of n main pumps (1 n and, on the other hand, a group of auxiliary pumps of which only one has been shown, at 3, to facilitate understanding of the invention. The main pumps n are in communication via their inlet conduit (2 n with a tank 4 and via their exhaust conduit a n with a pipe 5 for feeding a receiver member 6.

An intermediate member 7 is provided at the junction of pipe 5 with each of conduits a 11 in order to ensure, in known manner, the correct, selective communication of these conduits with said pipe.

The auxiliary pump 3 is connected via its inlet conduit 3a to tank 4 and via its exhaust conduit 3b to a pressure accumulator 8. A two-way distributor is interposed in the exhaust conduit 312 between the pump 3 and the accumulator 8. In its first position, said distributor establishes the communication between the accumulator 8 and pump 3, whilst its second position establishes communication between conduit 3b and tank 4, whilst isolating accumulator 8.

A conduit 10 connected to conduit 312 between the accumulator 8 and distributor 9 establishes a connection between saidconduit 3b and pipe 5. This conduit 10 comprises a non-return valve 10a and a two-position, one-way distributor 11, ensuring, in its first position, the opening of conduit 10 and, in its second posi-' tion, the closure thereof.

Finally, a pressure sensor 12 is disposed in conduit 5 and is connected to the input of a logic unit 13 whose outputs are respectively connected to the control element 9a of the distributor 9 and to the control element 11a of the distributor 1 1.

FIG. 2 is a graph showing the curves of variation of the power used as a function of the pressure demanded, for various flows obtained by grouping several main pumps together. The Y-axis shows a power scale W and X-axis a pressure scale p. The different flows Q1, Q2, Q3 that may be obtained are shown in this graph by straight lines in view of the ratioW pQ in which Q may take several fixed values Q Q Q Wo represents the installed capacity of the machine. It corresponds'to the maxium useful power furnished by the motor driving the pumps. This graph clearly shows that it is sought always to operate as close as possible to the maximum installed capacity. Thus, when one is in a zone of low'pressure, the flow Q delivered by the main pumps is high. When the attained pressure I is such that P Q Wo, flow O is less'than Q so as not'to overload the motor. The same applies until the least flow On which may be discharged with the group of installed pumps.

However, it should be noted that the use of the maximum installed capacity is only punctual, corresponding to products Q p Q X 13 Q X p In all the intervals between these points, one always falls short of the maximum power. The invention seeks to use the available power to a maximum.

In zone A of the graph of FIG. 2, it is seen that, as long as pressure p in the receiver circuit has not been reached, operation is not carried out at maximum power. The value of the flow Q could be increased so that, by straightening up the inclined straight line by which it is represented, this zone A is reduced. However, one should expect a considerable loss of load if the flow is too strong and losses by very considerable frictions which constitute a limit higher than the value of this flow Q which guarantees a good yield.

One has therefore had to resort to an energy accumulation restitution system as described with regard to FIG. I. The auxiliary pump 3 may furnish a certain known fluid flow to fill the accumulator 8 whose maximum pressure is also known. The power Wa that the auxiliary pump 3 will consume at a maximum is therefore known. This power Wa has been shown on the graph of FIG. 2.

Assuming that the motor 1 is rotating, the n main pumps discharge into conduit 5 at flow-rate Q and the auxiliary pump 3 discharges through conduit 3b into accumulator 8, the distributor 9 being in its conduitopen position, and distributor 11 closing conduit 10. It is known that the power absorbed by the pump 3 will never exceed the value Wa; therefore, as long as the pressure prevailing in the conduit 5 has not reached value p (FIG. 2), the motor will not be overloaded. When the pressure sensor 12 detects this value P',, the logic unit 13 controls the distributor 9 in the sense of an interruption of conduit 3b. The auxiliary pump 3 then discharges in the direction of tank 4 and the power that it consumes is zero apart from the frictions. The power available at the output of the motor 1 on its shaft 2 is then devoted entirely to the n main pumps When the pressure in the conduit 5 reaches value P,, a new group operates within the n main pumps so as to obtain a flow Q As shown by the graph of FIG. 2, the power used between p and p is less than the installed capacity W0. Insofar as this power is less than W0 Wa, a part thereof may beused to make auxiliary pumps 3 discharge into accumulator 8. Therefore, when the pressure sensor 12 records the pressure p the logic unit 13 controls the opening of the conduit 3b by acting on the control element 9a of the distributor 9. At the pressure p' detected by the sensor 12, the same sequence of operations occurs as at pressure p and for the same reasons, i. e. communication of delivery of the pump 3 to the tank 4.

The device continues to function in the same way until the straight line of minimum flow has been achieved on the graph.

Assuming that the flow O is the minimum flow and that the pressurep is the maximum pressure attained by the installation at this flow rate, there may be an addition of power at this point due to the device of the invention. In fact, the distributor 9 is in its position where conduit 3b is closed and when the sensor 12 detects the pressure'p the logic unit 13 controls the opening of conduit through distributor 11. Two possibilities may then present themselves: either the accumulator 8 which is adjustably calibrated to a pressure higher than value p is completely filled and the fluid that it contains may flow through the non-return valve l0a towards conduit 5, this bringing the desired addition of power, or the accumulator 8 is not filled up entirely and the fluid that it contains is at too low a pressure to be able to pass through the valve 10a, and nothing happens. In this second case, the machine must return to phases of operation employing only a power less than Wo Wa in order that the available power can be used for completely filling the accumulator 8.

The device according to the invention is therefore capable of storing energy, using all or part of the installed capacity not used by the group of main pumps and of restoring it when the installed capacity is totally employed. This device has the advantage of improving the profitability of a hydraulic installation, particularly of a public works machine audit is in this latter domain that it finds advantageous application.

What is claimed is:

l. A hydraulic installation comprising a motor driving at least one so-called main pump and at least one ,so-called auxiliary pump, the main pump discharging into at least one receiver and the delivery conduit of the auxiliary pump being connected to a pressure accumulator, wherein a first two-way distributor disposed in the delivery conduit of the auxiliary pump ensures communication of said auxiliary pump, in its first position, with the accumulator, and in its second position with a tank, and wherein between said first distributor and the accumulator there is tapped a pipe connected to the feed conduit of the receiver and provided with a second two-way distributor ensuring, in its first position, the closure of said pipe and, in its second position, the opening thereof, whilst a fluid pressure sensor is disposed in the feed conduit of the receiver and controls, via a logic device, the selection of the positions of the first and second distributors.

2. An installation as claimed in claim 1, wherein a non-return valve is disposed in the said pipe preventing the circulation of the fluid in this pipe in the direction of said accumulator.