GB2093952A

GB2093952A - Hydraulic valves

Info

Publication number: GB2093952A
Application number: GB8124020A
Authority: GB
Original assignee: Commercial Shearing Inc
Current assignee: Commercial Shearing Inc
Priority date: 1981-02-23
Filing date: 1981-08-06
Publication date: 1982-09-08
Also published as: AU7488981A; JPS57143181A; FR2500563B1; FR2500563A1; GB2093952B; IT1142899B; AU549665B2; DE3131067A1; CA1150590A; IT8149499A0

Abstract

A valve for controlling the output of a variable displacement piston pump, alone or in parallel with a gear pump, is baded upon an open centre valve but uses a special spool which provides the necessary signal and flow and pressure compensation. A valve 10 has a central outlet chamber 11 and successively to each side inlet chambers 13, 14, parallel chambers 16, 17, work chambers 20, 21, and exhaust chambers 24, 25. A valve spool 31 has axial bores 35, 36 and radial passages 37, 38 and 39, 40 for connecting one of the work chambers 20, 21 to the outlet chamber 11 in a work position. <IMAGE>

Description

SPECIFICATION Hydraulic valves The invention relates to valves for controlling the output of a variable displacement piston pump alone or in parallel with a gear pump.

A valve according to the invention comprises an elongate housing, a central outlet chamber in the housing, a pair of parallel inlet pressure chambers on opposite sides of the outlet chamber, a pair of work chambers on opposite sides of the parallel chambers, a pair of exhaust chambers on opposite sides of the work chambers, a bore extending longitudinally through the housing intersecting all the chambers, and a spool movable in the bore, the spool having an axial bore at each end, a pair of spaced radial passages through the spool into each axial bore for connecting one of the work chambers to the outlet chamber when the spool is moved to a work position connecting one of the parallel chambers to the work chamber, the outlet pressure chamber providing a pressure signal from the work chamber for controlling the displacement of the pump.

This valve structure is based upon an open centre valve but uses a special spool which provides the necessary signal and a flow and pressure compensation without the loss of horsepower normally associated with fixed displacement gear pumps.

Drawings Figure 1 is a section through a valve according to the invention; Figure 2 is a schematic drawing of a pump circuit including a number of the valves of Figure 1; Figure 3 is similar to Figure 2 but includes a gear pump; and Figure 4 is a section through a second valve according to the invention.

With particular reference to Figure 1, a valve housing 10 of open centre, parallel passage design having a centre chamber 11, connected to an outlet port 12, a pair of inlet chambers 13 and 14 on opposite sides of centre chamber 11 connected to an inlet port 15, a pair of parallel chambers 16 and 17 on opposite sides of chambers 13 and 14 connected to an inlet port 18 and an outlet port 19, a pair of work chambers 20 and 21 on opposite sides of the parallel chambers having corresponding work ports 22 and 23, and a pair of exhaust chambers 24 and 25 on opposite sides of the work chambers 22 and 23 and connected to ports 26 and 27.

A central elongate bore 30 extends from end to end of the housing 10, intersecting all the chambers 11,13,14,16, 17,20,21,24and25.

An elongate spool 31 is movable in the bore 30.

Spool 31 has a central groove 32 which connects the chambers 1 1, 13 and 14, and a pair of grooves 33 and 34 on opposite sides of the central groove 32 and-within the work chambers 22 and 23 in the neutral position. Spool 31 has axial bores 35 and 36 at its opposite ends, spaced radial passages 37 and 38 from bores 35 and 36 adjacent the inner ends 35a and 36a of the bores 35 and 36 and spaced radial passages 39 and 40 respectively from bores 35 and 36 to the grooves 33 and 34. Each of the bores 35 and 36 is divided between passages 37 and 38 and 39 and 40 by plugs 41 and 42 with central axial passages 43 and 44 which are normally closed by springloaded balls 45 and 46.

The valve may be used alone or in multiples as illustrated in Figures 2 and 3 to control the displacement of a variable displacement piston pump. In Figure 2, a variable displacement piston pump 50 delivers pressure fluid to the parallel chambers 1 6 and 1 7 of successive valves through an inlet section 51 and a block plate 52. The plate 52 permits inlet pressure fluid from pump 50 to go to parallel passages only and blocks normal inlet chambers 13 and 14 and inlet port 1 5. The centre chamber 11 and outlet port 12 are connected by a line 59 to a control compensator 60 on the pump 50 which controls the displacement of the pump. The control compensator 60 is connected through a line 61 to the output of pump 50. The pressure difference between line 59 and line 61 causes the compensator 60 to adjust the displacement of the pump 50.

In Figure 3, a gear pump 70 and a variable displacement piston pump 71 in parallel deliver fluid to a special compensated inlet valve 72 which connects an input line 73 with the parallel chambers 1 6 and 17 and the open centre passages 13 and 14 with a pump compensator 75 on the pump 71 through a line 76. The compensator inlet valve also is provided with a relief valve portion which by-passes fluid to the exhaust chambers of the valve because of the gear pump 70 and the constant volume which it provides.

In Figure 4, a cylindrical cartridge 80 containing a ball, spring and seat is substituted for the ball, spring and seat of Figure 1. 11 other parts are the same.

Claims

1. A valve for controlling the output of a variable displacement piston pump comprising an elongate housing, a central outlet chamber in the housing, a pair of parallel inlet pressure chambers on opposite sides of the outlet chamber, a pair of work chambers on opposite sides of the parallel chambers, a pair of exhaust chambers on opposite sides of the work chambers, a bore extending longitudinally through the housing intersecting all the chambers, and a spool movable in the bore, the spool having an axial bore at each end, a pair of spaced radial passages through the spool into each axial bore for connecting one of the work chambers to the outlet chamber when the spool is moved to a work position connecting one of the parallel chambers to the work chamber, the outlet pressure chamber providing a pressure signal

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Hydraulic valves The invention relates to valves for controlling the output of a variable displacement piston pump alone or in parallel with a gear pump. A valve according to the invention comprises an elongate housing, a central outlet chamber in the housing, a pair of parallel inlet pressure chambers on opposite sides of the outlet chamber, a pair of work chambers on opposite sides of the parallel chambers, a pair of exhaust chambers on opposite sides of the work chambers, a bore extending longitudinally through the housing intersecting all the chambers, and a spool movable in the bore, the spool having an axial bore at each end, a pair of spaced radial passages through the spool into each axial bore for connecting one of the work chambers to the outlet chamber when the spool is moved to a work position connecting one of the parallel chambers to the work chamber, the outlet pressure chamber providing a pressure signal from the work chamber for controlling the displacement of the pump. This valve structure is based upon an open centre valve but uses a special spool which provides the necessary signal and a flow and pressure compensation without the loss of horsepower normally associated with fixed displacement gear pumps. Drawings Figure 1 is a section through a valve according to the invention; Figure 2 is a schematic drawing of a pump circuit including a number of the valves of Figure 1; Figure 3 is similar to Figure 2 but includes a gear pump; and Figure 4 is a section through a second valve according to the invention. With particular reference to Figure 1, a valve housing 10 of open centre, parallel passage design having a centre chamber 11, connected to an outlet port 12, a pair of inlet chambers 13 and 14 on opposite sides of centre chamber 11 connected to an inlet port 15, a pair of parallel chambers 16 and 17 on opposite sides of chambers 13 and 14 connected to an inlet port 18 and an outlet port 19, a pair of work chambers 20 and 21 on opposite sides of the parallel chambers having corresponding work ports 22 and 23, and a pair of exhaust chambers 24 and 25 on opposite sides of the work chambers 22 and 23 and connected to ports 26 and 27. A central elongate bore 30 extends from end to end of the housing 10, intersecting all the chambers 11,13,14,16, 17,20,21,24and25. An elongate spool 31 is movable in the bore 30. Spool 31 has a central groove 32 which connects the chambers 1 1, 13 and 14, and a pair of grooves 33 and 34 on opposite sides of the central groove 32 and-within the work chambers 22 and 23 in the neutral position. Spool 31 has axial bores 35 and 36 at its opposite ends, spaced radial passages 37 and 38 from bores 35 and 36 adjacent the inner ends 35a and 36a of the bores 35 and 36 and spaced radial passages 39 and 40 respectively from bores 35 and 36 to the grooves 33 and 34. Each of the bores 35 and 36 is divided between passages 37 and 38 and 39 and 40 by plugs 41 and 42 with central axial passages 43 and 44 which are normally closed by springloaded balls 45 and 46. The valve may be used alone or in multiples as illustrated in Figures 2 and 3 to control the displacement of a variable displacement piston pump. In Figure 2, a variable displacement piston pump 50 delivers pressure fluid to the parallel chambers 1 6 and 1 7 of successive valves through an inlet section 51 and a block plate 52. The plate 52 permits inlet pressure fluid from pump 50 to go to parallel passages only and blocks normal inlet chambers 13 and 14 and inlet port 1 5. The centre chamber 11 and outlet port 12 are connected by a line 59 to a control compensator 60 on the pump 50 which controls the displacement of the pump. The control compensator 60 is connected through a line 61 to the output of pump 50. The pressure difference between line 59 and line 61 causes the compensator 60 to adjust the displacement of the pump 50. In Figure 3, a gear pump 70 and a variable displacement piston pump 71 in parallel deliver fluid to a special compensated inlet valve 72 which connects an input line 73 with the parallel chambers 1 6 and 17 and the open centre passages 13 and 14 with a pump compensator 75 on the pump 71 through a line 76. The compensator inlet valve also is provided with a relief valve portion which by-passes fluid to the exhaust chambers of the valve because of the gear pump 70 and the constant volume which it provides. In Figure 4, a cylindrical cartridge 80 containing a ball, spring and seat is substituted for the ball, spring and seat of Figure 1. 11 other parts are the same. Claims

1. A valve for controlling the output of a variable displacement piston pump comprising an elongate housing, a central outlet chamber in the housing, a pair of parallel inlet pressure chambers on opposite sides of the outlet chamber, a pair of work chambers on opposite sides of the parallel chambers, a pair of exhaust chambers on opposite sides of the work chambers, a bore extending longitudinally through the housing intersecting all the chambers, and a spool movable in the bore, the spool having an axial bore at each end, a pair of spaced radial passages through the spool into each axial bore for connecting one of the work chambers to the outlet chamber when the spool is moved to a work position connecting one of the parallel chambers to the work chamber, the outlet pressure chamber providing a pressure signal from the work chamber for controlling the displacement of the pump.

2. A valve according to claim 1 wherein each bore in the spool is divided into two chambers by a plug insert having an axial passage and a springloaded ball normally closing the passage and opening on pressure from fluid flowing from a work chamber to the outlet chamber.

3. A valve as herein described with reference to Figure 1 or Figure 4 of the drawings.

4. A pump circuit comprising a variable displacement piston pump, a control compensator on the pump adapted to vary the displacement of the pump in response to a pressure difference between the pump output and a second pressure applied thereto, and a valve according to any preceding claim.

5. A pump circuit according to claim 4 having a number of like housings and spools, the outlet charnber of the last housing being connected to the pump control compensator.