GB2105005A - Valve detent and stop - Google Patents

Abstract

A housing (10) adapted to be integral with a pump housing has a low pressure chamber (13), a high pressure chamber (14) and a cylinder chamber (15) which are spaced apart and generally parallel to one another. The chambers are intersected by a transverse bore (16), in which a valve member (17) is movable axially. The valve member (17) has an annular groove (18) intermediate its ends and is movable between a first position in which the low and high pressure chambers are in fluid communication, a second position in which all of the chambers are in fluid communication and a third position in which none of the chambers are in fluid communication. A detent co-operates with detent engaging means (19) in the groove (18) intermediate its ends, and means (24) extend into the bore and groove on opposite sides of the detent to engage the ends of the groove (18) to limit the stroke of the valve member (17). <IMAGE>

Description

SPECIFICATION Valves The invention relates to valves and particularly to valves for use in integral hydraulic pump and valve assemblies.

The use of integral hydraulic pump and valve assemblies is not itself new. There are several forms of such assemblies on the market. In one form the valve body circuitry is an integral part of the pump and cover. In another form the valve body circuitry is a separate casting which is attached to the end cover of a pump. Two of the important considerations in such structures are compactness and simplicity. In all such structures it is necessary to have a detent mechanism acting on the valve spool and a stop mechanism for limiting the movement in each direction. It has been conventional in these mechanisms, as in ordinary control valves, to add a detent mechanism on one end of the spool and a stop mechanism such as snap rings and retainer rings on the two ends of the spool outside the spool housing.These expedients necessarily add length to the spool beyond that needed for the primary function of directing the flow of hydraulic fluid. In addition the snap rings and/or retainer rings are externally exposed which increases the potential of a ring coming off, thereby permitting the spool to over-travel.

The invention provides a valve in or for a hydraulic pump and valve assembly, the valve comprising a valve housing integral with or for integration with a pump housing, the valve housing having spaced apart low pressure and high pressure ports corresponding to the low pressure inlet port and high pressure outlet port of the pump housing, a low pressure chamber, a high pressure chamber and a cylinder chamber in the valve housing spaced apart and generally parallel to one another, a transverse bore in the valve housing intersecting the low pressure, high pressure and cylinder chambers, a valve member having an annular groove intermediate its ends and being axially movable in the transverse bore between a first neutral position in which the low and high pressure chambers are in fluid communication through the bore, a second position in which the low pressure, high pressure and cylinder chambers are all in fluid communication through the bore, and a third position in which there is no fluid communication through the bore between any of the low pressure, high pressure and cylinder chambers, a detent extending into the bore for cooperation with detent engaging means in the annular groove intermediate its ends, and means extending into the bore on opposite sides of the detent for engaging the ends of the annular groove to limit the stroke of the valve member.

In the valve according to the invention the problems of additional length and exposed stop members are eliminated. The detent en gages the spool in a reduced centre area of the spool and a cartridge carrying the detent acts as an internal stop in each direction.

Preferably the detent is a spring loaded poppet movable in the stroke limiting means.

The stroke limiting means is preferably a hollow cylindrical member threaded into the housing and extending into the bore. The valve member is preferably symmetrical about the detent engaging means therein so that it may be inserted either way in the bore.

The invention is illustrated by the drawings of which: Figure 1 is an end elevation of a valve according to the invention; Figure 2 is an elevation of the valve of Fig.

1 from the opposite end, showing the oil connection to a pump; Figure 3 is a sectional view taken about the line Ill-Ill of Fig 1; Figure 4 is a sectional view taken about the line IV-IV of Fig 1; and Figure 5 is a sectional view taken through the stroke limiting means of the valve of Fig.

1.

Referring to the drawings, there is provided a valve for integration in a hydraulic pump and valve assembly. The control valve com prises a housing 10 for integration with one end of a pump housing (not shown) and having a low pressure port 11 and a high pressure port 1 2 spaced apart on one end of the housing to match the low pressure and high pressure ports of the pump. The housing 10 has, generally parallel, a low pressure chamber 13, a high pressure chamber 14 and a cylinder chamber 1 5. A transverse bore 1 6 extends through the housing 10 from side to side intersecting all the chambers 13, 14 and 1 5. A valve member 1 7 having a central groove 1 8 is slidable in the bore 16.The groove 1 8 is provided with an annular detent engaging slot 1 9 midway between its ends.

The groove 1 8 is arranged so that, with the valve member 1 7 in a first position (as shown in Fig. 3), the low pressure chamber 1 3 and the high pressure chamber 14 are connected through the bore 1 6. With the valve member 1 7 in a second position all the chambers 13, 1 4 and 1 5 are connected through the bore 16, and with the valve member 1 7 in a third position only the low pressure chamber 1 3 communicates with the bore 1 6. A cylinder port 20 is provided in the end of the housing 10 opposite the high pressure port 1 2 and the low pressure port 11.An inlet port 21 is provided in the same end of the housing 10 as the cylinder port 20. A check valve 22 is provided between the high pressure chamber 1 4 and the cylinder chamber 1 5 and a relief valve 23 is provided between the cylinder chamber 1 5 and the low pressure chamber 1 3. A hollow cylindrical stroke limiting member 24 is provided in the housing 10 intersecting the bore 1 6 and extending into the groove 1 8 to engage the ends thereof when the valve member 1 7 is moved axially in the bore 1 6 and thus limit the movement of the valve member 1 7 therein.A detent poppet 25 is movable in an axial passage 26 in the member 24 and is urged to a position extending out of the end of the passage 26 by spring 27 acting on an annular shoulder 28 of the poppet 25, until the shoulder 28 bears on stops 29 in the member 24. The detent poppet 25 engages a detent slot 1 9 in the valve member 1 7 in the neutral position of the valve member (the first position aforedescribed).Thus, the operator has an indicator of the neutral position and the valve is held there by the detent poppet 25 resting in the detent slot 1 9. Movement of the valve member 1 7 to the right, as shown in Fig. 3, until one end of the groove 1 8 abuts the stroke limiting means 24 places the valve in its second condition in which all chambers are connected, permitting fluid to return from the cylinder port 20 to te low pressure chamber 1 3. Movement of the valve member 1 7 to the left, as shown in Fig. 3, until the opposite end od the groove 1 8 abuts the stroke limiting means 24 places the valve in its third condition in which the bore 1 6 is ciosed to all chambers except chamber 1 3. This causes the high pressure fluid coming from the pump through the high pressure port 1 2 into the high pressure chamber 1 4 to open the check valve 22 and pass through the cylinder chamber 1 5 and out of the cylinder port 20 to a hydraulic cylinder or other working device.

Claims (5)

1. A valve in or for a hydraulic pump and valve assembly, the valve comprising a valve housing integral with or for integration with a pump housing, the valve housing having spaced apart low pressure and high pressure ports corresponding to the low pressure inlet port and high pressure outlet port of the pump housing, a low pressure chamber, a high pressure chamber and a cylinder chamber in the valve housing spaced apart and generally parallel to one another, a transverse bore in the valve housing intersecting the low pressure, high pressure and cylinder chambers, a valve member having an annular groove intermediate its ends and being axially movable in the transverse bore between a first neutral position in which the low and high pressure chambers are in fluid communication through the bore, a second position in which the low pressure, high pressure and cylinder chambers are all in fluid communication through the bore, and a third position in which there is no fluid communication through the bore between any of the low pressure, high pressure and cylinder chambers, a detent extending into the bore for cooperation with detent engaging means in the annular groove intermediate its ends, and means extending into the bore on opposite sides of the detent for engaging the ends of the annular groove to limit the stroke of the valve member.

2. A valve according to claim 1 wherein the stroke limiting means is a hollow cylindrical member surrounding the detent.

3. A valve according to claim 1 or claim 2 wherein the detent is a spring loaded poppet movable in a hollow bore in the stroke limiting means.

4. A valve according to any preceding claim wherein the valve member is symmetrical about the detent engaging means.

5. A valve in or for a hydraulic pump and valve assembly, the valve being substantially as described herein with reference to the drawings.