US3212523A

US3212523A - Fluid system and relief valve assembly therefor

Info

Publication number: US3212523A
Application number: US312215A
Authority: US
Inventors: George J Martin
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 1963-09-27
Filing date: 1963-09-27
Publication date: 1965-10-19
Anticipated expiration: 1982-10-19

Description

G. J. MARTIN Oct. 19, 1965 FLUID SYSTEM AND RELIEF VALVE ASSEMBLY THEREFOR Filed Sept. 2'7, 1963

FlG

2 ,3 s v a I Willi INVENTOR.

GEORGE J. MARTIN FIG 5 BY 1 AiTORNES United States Patent 3,212,523 FLUID SYSTEM AND RELIEF VALVE ASSEMBLY THEREFOR George J. Martin, Lyndhurst, Ohio, assignor to Parker- I-Iannifin Corporation, Cleveland, Ohio, a corporation of Ohio Filed Sept. 27, 1963, Ser. No. 312,215 14 Claims. (Cl. 137596.13)

The present invention relates generally as indicated to a fluid system and relief valve assembly therefor and more particularly to a fluid system that comprises a pump, a reservoir, one or more fluid motors, one or more directional control valves for said motor or motors, and a relief valve assembly that has different relief pressures depending on directional control valve actuation.

In fluid systems such as those associated with front end loaders, bulldozers, load handling, and like equipment, it

is desired to have available different maximum fluid pres- 'in the case of a system including either an open center or closed center directional control valve for a double acting fluid motor, is so arranged that one motor port of the valve is relievedat the normal high pressure setting of the relief valve, whereas the other motor port connected with a con- .trol port of the relief valve is relieved at a lower pressure.

It is another object of this invention to provide a fluid system and relief valve therefor which, in the case of an open center system comprising a plurality of directional control valves for corresponding single or double acting fluid motors, is so arranged that the upstream directional control valve or valves nearest the pressure inlet have their motor ports relieved at the normalhigh pressure setting of the relief valve and the downstream directional control valve or valves have their motor ports relieved at a lower pressure.

.It is another object of this invention to provide a fluid system and relief valve therefor in which the latter is provided with means for adjusting the higher relief pressure at which the relief valve will be opened, and the mini- .mum control pressure needed to decrease the relief pres- .sure to a lower value.

It is another object of this invention to provide a fluid system and relief valve therefor in which the latter is ,provided with means for adjusting the normal high pressure at which the relief valve will be opened and the control pressure at which the relief valve will be actuated to relieve at predetermined lower pressures.

It is still another object of this invention to provide a fluid system and relief valve therefor in which the main .relief pressure will continue to be lowered a predetermined amount for each increment of increase of control pressure over and above that required to initially lower 'the relief pressure from its high setting to a lower setting.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings ice setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a cross-section view of one form of relief valve assembly which may be employed in fluid systems as schematically depicted in FIGS. 3, 4, and

FIG. 2 is a cross-section view similar to FIG. 1 illustrating another form of relief valve assembly usable in the fluid systems of FIGS. 3, 4, and 5; and

FIGS. 3, 4, and 5 are schematic diagrams of fluid systems employing the relief valves of either FIGS. 1 or 2 to provide high and low relief pressures according to how a directional control valve is actuated or according to which of a plurality of directional control valves is actuated.

Refering now more particularly to the drawing, and first to FIG. 1, the relief valve assembly 1 therein comprises a body or housing 2 having a pressure supply passage 3 therethrough terminating at one end in a port 4 to which the pressure delivery port of the pump P (see FIG. 5) is connected and terminating at the other end in a port 5 which connects with the inlet port of a directional control valve 6, as shown for example, in FIG. 5. Intersecting the through passage 3 is the relief passage 7 leading to a tank T. The relief passage 7 has therein a tubular seat member 8 which is closed by the main relief valve member 9 which is biased by spring 10 and by fluid pressure in the chamber 11 tending to hold said main relief valve member 9 in engagement with the seat member 8.

A bushing 12 screwed into said body 2 is provided with a tubular seat member 14 for the pilot valve member 15 which, when seated, as shown, closes communication between the chamber 11 and the passage 16 which leads to the tank T via relief passage 7. The pilot valve member 15 is biased against the seat member 14 by the spring 17 and, as evident, when the fluid pressure in the chamber 11 acting on the exposed area of the pilot valve member 15 overcomes the seating effect of the spring 17, the pilot valve member 15 will be urged away from seat member 14 to vent the chamber 11 to the tank T. Because the flow capacity of the orifice 18 in the main valve member 9 is less than the flow capacity through the pilot member 14, the pressure in the chamber 11 will drop with respect to the pressure in the passage 3, whereby the main valve member 9 will be moved away from the seat member 8 to valve spring 17.

When the fluid pressure in the control port 24 is of magnitude suflicient to urge the plunger downwardly against spring 21, the follower 19 moves downwardly a corresponding distance thereby permitting partial decompression of the pilot valve spring 17. The control port pressure required to move the plunger 20 downwardly the distance D is usually considerably less than the minimum or low pressure relief setting of the valve 1.

The low relief pressure setting is adjusted by turning the bushing while the plunger 20 is down against backup member 26 closing gap D, this being done as by loosening the screw 27 which bears on spring 21. The pressure differential above the desired low setting which is the high pressure setting of the valve 1 is determined by the magnitude of the gap D which is usually factory pre-set. After making the low pressure setting as aforesaid, the plunger spring 21 is reset by turning screw 27 until the pressure gauge (not shown) in the pressure line from pump P shows no further rise in relief pressure, thus indicating that the plunger 20 has engaged stop sleeve 23 and has moved the distance D away from backup member 26.

Referring now to FIG. 2, the relief valve assembly 31 there shown may be the same as shown in FIG. 1 insofar as the body 2, main relief valve member 9, pilot valve member 15, etc. are concerned, as evidenced by like reference numerals employed in both FIGS. 1 and 2. A primary difference between the FIGS. 1 and 2 relief valve assemblies 1 and 31 resides in the construction of FIG. 2 in which the high relief pressure setting is made by turning the control port body 32 which is in threaded engagement with the pilot valve bushing 34 and locking it at the desired adjusted position by means of the lock nut 35. When so turning the control port body 32, the follower 36 of plunger 37 is held against shoulder 38.

The cap 39 threaded on body 32 is turned to adjust the follower spring 40 thus to determine what magnitude of fluid pressure in control port 41 will cause downward movement of plunger 37 and consequent partial decompression of pilot valve spring 17.

Accordingly, with fluid pressure in control port 41 insuflicient to move the plunger 37 downwardly against the spring 40. the parts will be in the position shown in FIG. 2 and a predetermined maximum pressure in the through passage 3 and in the chamber 11 will be relieved when that pressure is sufficient to unseat the pilot valve member 15 thereby creating the unbalance in pressures in the through passage 3 and in the chamber 11 to cause opening movement of the main relief valve member 9. Assuming now that there is suflicient pressure in control port 41, to move the plunger 37 downwardly thereby compressing the spring 40, such downward movement of the plunger 37 will effect relaxation of the pilot valve spring 17 so that the through passage 3 will be relieved at a lower pressure.

By way of example, the high pressure setting through adjustment of the control port body 32 may be anywhere between 500 and 3,000 p.s.i. The compression on the plunger actuator spring 40 is adjusted by turning the spring backup cap 39 in either direction and locking it at adjusted positions by means of the lock nut 42. The arrangement may be such that the unloading or control pressure may be adjusted between 500 and 2500 p.s.i. pressure and so that the relief pressure will decrease, say, 500 p.s.i. for each 100 p.s.i. increase in control port pressure above the initial setting of the plunger spring 40.

As an example, if the pilot valve spring 17 is set to relieve the pressure in the through passage 3 at 2000 p.s.i. and the plunger spring 40 is set to permit actuation of the plunger 37 at 1000 p.s.i. control port pressure, a rise in control port pressure to 1100 p.s.i. will permit relief of the passage 3 at 1500 p.s.i. As the control port pressure further increases, each 100 p.s.i. increase will result in a 500 p.s.i. decrease in the pressure at which the main relief valve 9 will relieve the through passage 3.

Having thus described two embodiments of the relief valve assembly, reference will now be made to the systems shown schematically in FIGS. 3, 4, and illustrating how these relief valves 1 and 31 may be used in fluid systems to provide high and low relief pressures of the system according to which way a particular directional control valve is actuated or which one of a plurality of directional control valves is actuated. Although the relief valves 1 and 31 herein shown are each provided with its own body 2 for connection with the inlet port of a directional control valve housing, it is to be understood that either relief valve assembly may be incorporated in a directional control valve housing in a manner disclosed, for example, in the Patent to George J. Markovich 3,023,584 dated March 6, 1962 and in my copending application Ser. No. 159,413, filed December 14, 1961 now Patent No. 3,160,076 dated Dec. 8, 1964. Such incorporation of the relief valve assembly 1 or 31 as a part of the directional control valve housing is shown herein in FIGS. 3 and 4.

With reference to FIG. 3, the fluid system comprises a pump P having its pressure delivery port connected by conduit 50 to the inlet port of the housing of a directional control valve 51, a relief valve assembly 1 or 31 in accordance with either FIG. 1 or FIG. 2, having its

control port

24 or 41 communicated by way of conduit 52 with one of the two

motor ports

53, 53 of the directional control valve 51. As aforesaid, the body 2 of the relief valve assembly is herein shown as an integral part of the housing of the directional control valve 51, whereby the relief passage 7 and the return passage 16 lead to a return port in valve 51 which, in turn, is connected by conduit 54 with the tank T. The control valve 51 shown in FIG. 3 may be of the open center, or closed center type and when it is of the open center type the movable valve member thereof when in a neutral position blocking flow of fluid under pressure from the inlet to both

motor ports

53, 53 permits the pump output to freely flow through a bypass in valve 51 to the return port and tank T. The

motor ports

53, 53 may be connected in well known manner to the opposite ends of a double acting fluid motor, whereby when the valve member 56 is shifted to communicate the fluid pressure inlet with the lower motor port 53 to actuate the motor in one direction, the return pressure in the upper motor port 53 will not be suflicient to overcome the force exerted by the

spring

21 or 40 against the

plunger

20 or 37 and, therefore, a maximum pressure can be built up in the pressure circuit as determined by the setting of the pilot valve spring 17. However, when the control valve member 56 is shifted to a position communicating the pressure circuit with the upper motor port 53 to actuate the motor in the opposite direction, the pressure which builds up in the upper motor port 53 will, through the conduit 52, reach the

control port

24 or 41 of the relief valve 1 or 31 and will cause it to be moved downwardly to effect partial decompression of the pilot valve spring 17 with the result that the relief pressure of the pressure circuit will be decreased when the motor is actuated by fluid under pressure in the upper motor port 53. As shown in dotted lines in FIG. 3, additional one or more directional control valves 57 may be provided to control additional fluid motors and in that case the relief valve 1 or 31 will relieve the pressure circuits at the higher pressure setting of the relief valve, since the relief valve actuating pressure through the

control port

24 or 41 will not be sufficient in the case of the other directional control valve or valves 57 to move the

plunger

20 or 37 to effect a lower pressure setting of the main relief valve 9.

FIG. 4 is generally similar to FIG. 3 except that the control port conduit 60 is connected in the bypass circuit of the open center system so that when either of the upstream directional control valves 61 is actuated the relief pressure will be the maximum for which the pilot valve spring 17 has been set and so that when either of the downstream directional control valves 62 is actuated, the bypass line becomes the pressure supply line and consequently pressure builds up in the control port conduit 60 to cause movement of the

plunger

20 or 37 that effects partial decompression of the pilot valve spring 17 to thus provide a lower relief pressure in the pressure circuits of the downstream directional control valves 62.

FIG. 5 illustrates a fluid system utilizing either relief valve assembly 1 or 31 as it is shown in FIG. 1, or FIG. 2 in connection with a plurality of directional control valves 6 that have separate housings and a bypass conduit 65 leading from one valve 6 to the other. Accordingly, when the upstream directional control valve 6 is actuated, the motor connected to the motor ports thereof is actuated at the maximum pressure for which the pilot valve member 15 is set by spring 17 and when the downstream directional control valve 6 is actuated, the pressure inlet circuit from the pump P through the body 2 of relief valve 1 or 31, through the bypass of the upstream directional control valve 6, through bypass conduit 65, to either motor port of the downstream valve 6 will be decreased by reason of fluid pressure in the control port conduit 67 acting on the

plunger

20 or 37 to effect partial decompression of the pilot valve spring 17.

Although both relief valves 1 and 31 herein disclosed employ pilot operated relief valves, it is to be understood that a conventional spring biased main relief valve member may be provided, and in this case, the backup member for the spring would be the fluid pressure actuated

plunger

20 or 37, also backed up by a

spring

21 or 40 to maintain a predetermined compression on the main valve spring for the higher pressure relief setting.

In the case of an arrangement such as shown in FIG. 5 the

directional control valves

6, 6 may be joined together in well-known manner in parallel or series-parallel and in either event, the actuation of the upstream valve 6 provides for the higher relief pressure; and the actuation of the downstream valve 6 provides for the lower relief pressure. In a parallel circuit simultaneous actuation of the

valves

6, 6 results in the lower relief pressures at the inlet and this is true even though the valve member of the upstream valve 6 is in a metering position. In the series-parallel circuit when both

valves

6, 6 are simultaneously actuated the higher relief pressure setting is in effect for the upstream valve 6 with no pressure available at the downstream valve 6, and when the upstream valve 6 is in a metering position while the downstream valve 6 is actuated, the lower relief pressure setting will be in effect.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In combination, a directional control valve assembly having an inlet port for fluid communication with a pump and providing two pressure circuits from said inlet port for fluid motor actuation; valve means in said assembly selecting either one of said circuits for motor actua-' tion; a relief valve having a relief port in fluid communication with said inlet port and a control port in fluid communication with but one pressure circuit, said relief valve comprising a movable relief valve member therein, spring means biasing said relief valve member to a position closing said relief port, and a fluid pressure actuated means bearing on said spring means in a direction for yieldably holding said relief valve member in a position closing said relief port, said fluid pressure actuated means being exposed to fluid under pressure in said control port and movable thereby to decrease the spring bias on said relief valve member whereby the latter opens said relief port to said inlet port at a lower fluid pressure when said one circuit is selected for motor actuation than when the other circuit is selected for motor actuation.

2. The combination of claim 1 wherein said directional control valve assembly comprises a four-Way valve having a pair of motor ports constituting said pressure circuits for actuation of a double acting fluid motor.

3. The combination of claim 1 wherein said directional control valve assembly comprises at least two valves with passages thereto constituting said pressure circuits for actuation of a corresponding number of fluid motors.

4. In combination, a directional control valve assembly having an inlet port for fluid communication with a pump and providing two pressure circuits from said inlet port for fluid motor actuation; valve means in said assembly selecting either one of said circuits for motor actuation; a relief valve having a relief port in fluid communication with said inlet port and a control port in fluid communication with but one pressure circuit; said relief valve comprising a movable relief valve member therein, spring means biasing said relief valve member to a position closing said relief port, a fluid pressure actuated member exposed to fluid under pressure in said control port, and another spring means biasing said fluid pressure actuated member in a direction bearing on said spring means for holding said relief valve member in a position closing said relief port when said other circuit is selected for motor actuation, said another spring means yielding under the influence of fluid pressure in said control port acting on said fluid pressure actuated member to permit movement of the latter to decrease the spring bias on said relief valve member, whereby said relief valve member opens said relief port to said inlet port at a lower fluid pressure when said one circuit is selected for motor actuation than when the other circuit is selected for motor actuation.

5. The combination of claim 4 wherein stop means are provided in said relief valve for engagement by said fluid pressure actuated member to determine the maximum relief pressure when said other circuit is selected for motor actuation.

6. The combination of claim 5 wherein additional stop means are provided in said relief valve for engagement by said fluid pressure actuated member to determine the minimum relief pressure when said one circuit is selected for motor actuation.

7. The combination of claim 5 wherein said another spring means yields in proportion to the increase in fluid pressure in said control port when said one circuit is selected for motor actuation thus to proportionately decrease the bias of said first-mentioned spring means on said relief valve member.

8. The combination of claim 5 wherein means are provided for adjustment of the bias of said first-mentioned and another spring means on said relief valve and fluid pressure actuated members respectively.

9. A relief valve comprising a housing having an inlet port for connection with a fluid pressure source and a relief port for connection with a fluid reservoir; a relief valve member movable in said housing to open and close fluid communication between said inlet port and relief port according to the magnitude of fluid pressure in two fluid circuits with .which said inlet port is selectively adapted to be communicated; spring means biasing said member to a position closing such communication between said ports; a fluid pressure actuated member bearing on said spring means; said housing having a control port for connection with one fluid pressure circuit; said fluid pressure actuated member being exposed to fluid pressure in said control port and movable thereby to decrease the spring bias on said relief valve member; another spring means biasing said fluid pressure actuated member in a direction to increase the bias of said firstmentioned spring means on said relief valve member when the other circuit is selected whereby fluid pressure in said control port acting on said fluid pressure actuated member is insuflicient to move the latter against said another spring means; said relief valve member thus opening fluid communication between said inlet port and relief port at a lower pressure when said one circuit is selected than when the other circuit is selected.

10. The relief valve of claim 9 wherein stop means are provided in said housing for engagement by said fluid pressure actuated member to determine the maximum relief pressure when said other circuit is selected.

11. The relief valve of claim 9 wherein stop means are provided in said housing for engagement by said fluid pressure actuated member to determine the minimum relief pressure when said one circuit is selected.

12. The relief valve of claim 9 wherein said another spring means yields in proportion to the increase in pressure in said control port when said one circuit is selected thus to proportionately decrease the bias of said first mentioned spring means on said relief valve member.

13. The relief valve of claim 9 wherein means are provided for adjustment of the bias of said first-menti-oned and another spring means on said relief valve and fluid pressure actuated members respectively.

14. The relief valve of claim 9 wherein stop means are provided in said housing for engagement by said fluid pressure actuated member to determine the minimum and maximum relief pressures when said one or other circuit is selected.

References Cited by the Examiner UNITED STATES PATENTS Kupiec 137596.13 Earle 137529 XR Chattler 137596.13 XR Poundstone 137-522 Hancock et a1. 137-596.l3

M. CARY NELSON, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

Claims

1. IN COMBINATION, A DIRECTIONAL CONTROL VALVE ASSEMBLY HAVING AN INLET PORT FOR FLUID COMMUNICATION WITH A PUMP AND PROVIDING TWO PRESSURE CIRCUITS FROM SAID INLET PORT FOR FLUID MOTOR ACTUATION; VALVE MEANS IN SAID ASSEMBLY SELECTING EITHER ONE OF SAID CIRCUITS FOR MOTOR ACTUATION; A RELIEF VALVE HAVING A RELIEF PORT IN FLUID COMMUNICATION WITH SAID INLET PORT AND A CONTROL PORT IN FLUID COMMUNICATION WITH BUT ONE PRESSURE CIRCUIT, SAID RELIEF VALVE COMPRISING A MOVABLE RELIEF VALVE MEMBER THEREIN, SPRING MEANS BIASING SAID RELIEF VALVE MEMBER TO A POSITION CLOSING SAID RELIEF PORT, AND A FLUID PRESSURE ACTUATED MEANS BEARING ON SAID SPRING MEANS IN A DIRECTION FOR YIELDABLY HOLDING SAID RELIEF VALVE MEMBER IN A POSITION CLOSING SAID RELIEF PORT, SAID FLUID PRESSURE ACTUATED MEANS BEING EXPOSED TO FLUID UNDER PRESSURE IN SAID CONTROL PORT AND MOVABLE THEREBY TO DECREASE THE SPRING BIAS ON SAID RELIEF VALVE MEMBER WHEREBY THE LATTER OPENS SAID RELIEF PORT TO SAID INLET PORT AT A LOWER FLUID PRESSURE WHEN SAID ONE CIRCUIT IS SELECTED FOR MOTOR ACTUATION THAN WHEN THE OTHER CIRCUIT IS SELECTED FOR MOTOR ACTUATION.