HYDRAULIC PISTON PUMP HAVING DISTRIBUTION THROUGH A BI-DIRECTIONAL PORT PLATE

Abstract

A hydraulic pump having a plurality of pistons sliding in bores formed in a barrel mounted in rotation in a casing of the pump, the barrel bearing against a distribution port plate borne by a cylinder head. Two drainage channels place an inner space of the casing in respective communication with two suction/delivery orifices of the cylinder head. Each drainage channel is provided with a valve able to close the drainage channel in response to an overpressure in the suction/delivery orifice such that, according to the direction of rotation of the pump, the inner space of the casing is in communication through one of the drainage channels with the suction line; whereas the communication through the other drainage channel between the delivery side and the inner space of the casing is closed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application claims priority to Patent Application No. 1360278 filed Oct. 22, 2013 in France, the disclosure of which is incorporated herein by reference and to which priority is claimed.

FIELD OF THE INVENTION

The present invention relates to a hydraulic piston pump and more particularly a hydraulic piston pump in which distribution takes place by means of a port plate.

BACKGROUND OF THE INVENTION

To allow a piston pump having distribution through a port plate to be able to rotate either to the right or to the left, it is necessary to construct this pump, on the one hand, by designing a symmetrical distribution port plate such that the delivery zone of the pump can become a suction zone and vice versa and, on the other hand, by incorporating orifices in the pump which can receive either a suction connection or a delivery connection.

According to the direction of rotation of the pump, each of the two orifices of the pump will become either a suction orifice or a delivery orifice.

In such an arrangement, the leaks of the distribution port plate on the delivery side of the pump, which is the pressure side, will be collected by the casing of the pump.

To evacuate these leaks, it is necessary to provide a connection of the casing of the pump toward the supply reservoir of the pump by installing a drainage circuit.

This need to have a drainage circuit is a disadvantage.

FR-A-2988143 describes a hydraulic motor with internal drainage. The hydraulic motor has a drainage orifice communicating with an inner space of the casing of the motor, an intermediate pipe into which the drainage orifice of the casing opens, a first nonreturn valve arranged between the intermediate pipe and a first bi-directional hydraulic port and able to open under the effect of a positive pressure differential between the intermediate pipe and the first bi-directional hydraulic port, and a second nonreturn valve arranged between the intermediate pipe and a second bi-directional hydraulic port and able to open under the effect of a positive pressure differential between the intermediate pipe and the second bi-directional hydraulic port. Such an arrangement makes it possible for the liquid arising from the internal leaks of the motor to be evacuated from the casing through the one of the two nonreturn valves which is connected to the return port of the motor. In this device, the valves are closed by default.

SUMMARY OF THE INVENTION

The object of the present invention is to produce a piston pump which can rotate either to the right or to the left without having to put in place a specific pump drainage circuit.

To achieve this aim, the pump according to the present invention has a plurality of pistons sliding in bores formed in a barrel mounted in rotation in a casing of the pump, said barrel bearing against a distribution port plate borne by a cylinder head, said distribution port plate being provided with two symmetrical crescents serving alternately as a suction crescent and a delivery crescent according to the direction of rotation of the pump, and is characterized in that the cylinder head is provided with two drainage channels placing an inner space of the casing in respective communication with two suction/delivery orifices of said cylinder head; each drainage channel being provided with a valve able to close the drainage channel in response to an overpressure in the suction/delivery orifice such that, according to the direction of rotation of the pump, the inner space of the casing is in communication through one of the drainage channels with the suction line; whereas the communication through the other drainage channel between the delivery side and the inner space of the casing is closed.

According to one embodiment, the valve has in each case a compression spring housed in the drainage channel so as to maintain the valve in an open position by default.

The invention will be better understood, and other aims, details, features and advantages thereof will become more clearly apparent during the following description of a number of particular embodiments of the invention given purely by way of nonlimiting illustrative example with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In these drawings:

FIG. 1 is a view in longitudinal section of a known type of hydraulic piston pump.

FIG. 2 is a view in section on line D-D of FIG. 1.

FIG. 3 is a perspective view of the pump of FIG. 1 rotating to the right.

FIG. 4 is a perspective view of the pump of FIG. 1 rotating to the left.

FIG. 5 is a partial view, in longitudinal section, illustrating the operation of the suction zone of the pump according to the invention.

FIG. 6 is a partial view, in longitudinal section, illustrating the operation of the delivery zone of the pump according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 shows a hydraulic piston pump having a drive shaft 1 provided with a plate 2 against which there bear a plurality of pistons 3 which slide in bores 4 formed in a barrel 5 housed in a casing 6 provided with a drainage orifice 8 closed by a cap. The barrel 5 bears against a distribution port plate 7 borne by a cylinder head 9.

In FIG. 2, which is a view in section on D-D of FIG. 1, it can be seen that, in a known way, the distribution port plate 7 has two crescents 10 and 11 which are bean-shaped openings and which are symmetrical. According to the direction of rotation of the shaft 1, these crescents will serve alternately for suction or for delivery.

FIG. 3 shows the position of the suction pipe A when the drive shaft 1 is rotating to the right (or clockwise direction).

FIG. 4 shows the position of this suction pipe A when the drive shaft is rotating to the left (or counter clockwise direction).

A delivery line B, not shown in FIGS. 3 and 4, is connected to the other orifice of the cylinder head 9.

During the operation of the pump, hydraulic liquid leaks occur on the delivery side of the pump. These leaks are collected in the casing 6 and will be evacuated through the drainage orifice 8, which can be connected to a drainage circuit to return the liquid arising from the leaks to the reservoir.

One aim of the present invention is to dispense with this drainage circuit.

To achieve this aim, the cylinder head 9 is provided with two nonreturn valves 12 communicating with the suction/delivery orifices 20.

The effect of these two valves 12 is:

• • on the one hand, to allow the inner space 17 of the casing 6 to communicate freely through one of the valves 12 with the suction orifice 20 and the suction line A, as is illustrated in FIG. 5, thereby placing the inner space 17 of the casing 6 in connection with the suction side of the pump and implementing the drainage of the pump;
  • on the other hand, closing, through the other valve 12, the communication of the delivery orifice 20 with the inner space 17 of the casing 6, as is illustrated in FIG. 6.

More precisely, the nonreturn valve has a helical spring 13, a ball 12 serving as a valve, and a channel 14 formed in the cylinder head 9 so as to connect in each case the suction/delivery orifice 20 to the inner space 17 of the casing 6 of the pump. The channel 14 opens into the casing 6 in line with a peripheral portion of the distribution port plate 7 which has a fluid passage toward the inner space 17 of the casing 6.

The spring 13 is housed in a wide section of the channel 14, bearing between a shoulder of the channel 14 on the casing side and the ball 12 on the cylinder head side. By default, the spring 13 maintains the ball 12 at a distance from a valve seat 18 surrounding the inlet of the channel 14. Thus, the channel 14 is open unless there is an overpressure in the suction/delivery orifice 20 with respect to the inner space 17, which is normally at atmospheric pressure. The valve 12 is therefore a valve which is open by default and which closes the channel 14 in response to an overpressure in the suction/delivery orifice 20 of the cylinder head.

Although the invention has been described in conjunction with a number of particular embodiments, it is clearly obvious that it is in no way limited thereto and that it encompasses all the technical equivalents of the means described and combinations thereof where these fall within the scope of the invention.

The use of the verb “have”, “comprise” or “include” and its conjugated forms does not exclude the presence of elements or steps other than those stated in a claim. Unless stated otherwise, the use of the indefinite article “a” for an element does not exclude the presence of a plurality of such elements.

In the claims, any reference sign between parentheses should not be interpreted as a limitation of the claim.

Claims

1. A hydraulic piston pump of the type having a plurality of pistons sliding in bores formed in a barrel mounted in rotation in a casing of the pump, said barrel bearing against a distribution port plate borne by a cylinder head, said distribution port plate being provided with two symmetrical crescents serving alternately as a suction crescent and a delivery crescent according to the direction of rotation of the pump, in which the cylinder head is provided with two drainage channels placing an inner space of the casing in respective communication with two suction/delivery orifices of said cylinder head; each drainage channel being provided with a valve, wherein the valve has in each case a compression spring housed in the drainage channel so as to maintain the valve in an open position by default, the valve being able to close the drainage channel in response to an overpressure in the suction/delivery orifice such that, according to the direction of rotation of the pump, the inner space of the casing is in communication through one of the drainage channels with the suction line; whereas the communication through the other drainage channel between the delivery side and the inner space of the casing is closed.