US3391708A

US3391708A - Valve

Info

Publication number: US3391708A
Application number: US529473A
Authority: US
Inventors: Orval L Rice
Original assignee: General Signal Corp
Current assignee: SPX Technologies Inc
Priority date: 1966-02-23
Filing date: 1966-02-23
Publication date: 1968-07-09
Anticipated expiration: 1985-07-09
Also published as: FR1510663A; GB1120698A; DE1550432A1; SE308844B; DE1550432B2

Description

0. L. RlcE' July 9, 1968 VALVE Filed Feb. 23. 1966 E/ w mm mm W. 9p 9 Qt ORVAL L. R] C E ATTORNEYS United States Patent ice 3,391,708 VALVE Orval L. Rice, Kalamazoo, Mich, assignor to General Signal Corporation, a corporation of New York Filed Feb. 23, 1966, Ser. No. 529,473 Claims. (Cl. 137-596) This invention relates to hydraulic valves of the directional control type.

Valves of this kind are used frequently in hydraulic circuits for actuating double-acting motors. Each general ly includes an inlet passage which is connected with a pump, an exhaust passage which is connected with a reservoir, first and second motor passages which are connected with opposite sides of the double-acting motor or cylinder, and a movable valve element. The movable element has a neutral or hold position in which each motor passage is isolated from the other three passages, a raise position in which the first motor passage is connected with the inlet passage and the second motor passage is connected with the exhaust passage, and a lower position in which the connections between the motor passages and the inlet and exhaust passages are reversed. In some cases the movable valve element, or at least that portion of it controlling flow to and from the first motor passage, is of the hollow type, i.e., it contains an internal flow passage that forms part of the supply path to the motor in the raise position and part of the exhaust path from the motor in the lower position. This internal flow passage is provided with a spring biased check valve which, in the raise position, prevents dropping of the load acting on the motor whenever pump supply pressure is below the pressure in the side of the motor that is being contracted by the load.

When the load being positioned is large, it sometimes happens that the motor moves so fast that its flow demand exceeds the delivery rate of the pump, and the expanding side of the motor cavitates. One known way of combating this problem consists in splitting the return flow from the cylinder so that a portion of this flow is delivered directly to the expanding side of the cylinder through a regeneration path, and the balance of the flow is delivered to tank through the load drop check valve. The regeneration path may be uncontrolled, as in U.S. Patent 3,215,160, granted Nov. 2, 1965, or controlled by a by-pass valve that responds to supply pressure, as in U.S. Patent 3,006,- 372, granted Oct. 31, 1961, or in application Ser. No. 325,987, filed Nov. 26, 1963, now U.S. Patent No. 3,255; 277. In each of these prior schemes, the closing bias on the load drop check valve is increased above the normal value so that, in the lower position, the bacltpressure which this valve produces is adequate to force fluid through the regeneration path and to the expanding side of the cylinder. However, since the check valve creates this same backpressure in the raise position, it is evident that the pressure losses in the supply path in the raise position can be rather high.

The object of this invention is to provide an improved regeneration scheme which, like the prior schemes mentioned above, uses the backpressure created by the load drop check valve to force fluid through the regeneration path, but which includes means for automatically changing the magnitude of the closing bias on the check valve in accordance with the position of the movable valve element. When that element is in the raise position, the closing bias is set to the normal low value so that the supply flow to the cylinder is not unduly restricted. On the other hand, when the movable valve element is in the lower position, this bias is increased to a higher value which will insure that the backpressure created by the load drop check. valve is adequate to maintain the expanding side 3,391,798 Patented July 9, 1968 of the cylinder liquid-filled. Since this invention allows the closing bias on the check valve to be matched to the requirements of the particular function which that valve is performing, it is obvious that it represents a more efiicient way of satisfying the needs of the hydraulic circuits in which the directional control valve is used.

The preferred embodiment of the invention is described herein with reference to the accompanying drawing in which:

FIG. 1 is a sectional view of one unit of a multi-plunger directional control valve of the tandem type incorporating the invention, the valve plunger being shown in the neutral position.

FIG. 2 and 3 are sectional views similar to FIG. 1 but showing the valve plunger in the raise and lower positions, respectively.

As shown in FIG. 1, the invention is incorporated in one valve plunger 11 of a multi-plunger directional control valve of the series-parallel or tandem type. The plunger 11 reciprocates in a valve bore 12 which extends through the housing of the valve, and which is encircled by seven longitudinally spaced, annular chambers 13-19; the chambers 15-17 forming part of the open center by-pass path of the directional control valve, the

chambers

13 and 19 being connected by an exhaust manifold (not shown) with tank 21, and the

chambers

14 and 18 being connected with the opposite sides of a doubleacting cylinder 22. Valve plunger 11 is formed with a pair of annular peripheral grooves 23 and 24 which cooperate with

chambers

15, 16 and 17 to complete the open center by-pass path, and which define three valve lands 2527. In the illustrated neutral position, lands 25 and 27 serve to isolate

motor chambers

14 and 18 from each other and from the other chambers.

Extending into the right end of valve plunger 11 is a stepped axial bore whose open end is closed and sealed by a plug 28, and which is divided into two separate portions 29 and 31 by a sealed plug 32. Bore portion 29 is intersected by two spaced sets of radial passages 33 and 34 which open through the outer surface of land 27 and are positioned to register, respectively, with

chambers

17 and 18 in the lower position and with

chambers

18 and 19 in the raise position. A conventional load drop check valve 35, which seats on a step in bore portion 29, controls interpassage flow through bore portion 29. Bore portion 31 cooperates with a pair of spaced sets of radial passages 35 and 37 to define a regenerative flow path which is controlled by by-pass valve 38. These radial passages are so positioned that they register with chambers 14 and 15, respectively, in the lower position and are isolated from the supply chambers 15 and 17 in the raise position. The bypass valve 38 is adapted to seat on a step in bore portion 31 and is urged toward that seat by a coil compression spring 39 and by the fluid pressure in space 41 which communicates with radial passages 37 through radial and axial passages formed in the valve. The by-pass valve 38 is shifted in the opening direction by the pressure in radial passages 36 which acts upon its nose 42.

Extending into the left end of valve plunger 11 is a second, stepped axial bore 43 whose open end is closed and sealed by plug 44 and which is intersected by three spaced sets of radial passages 45-47.

Passages

45 and 46 are positioned to register, respectively, with chambers 15 and 14- in the raise position, and

passages

45 and 47 are positioned to register with

chambers

14 and 13, respectively, in the lower position. In the lower position, radial passages 46 are closed by the wall of the bore 12. Mounted in the axial bore 43 in plunger 11 are a pair of coaxial poppet valves 43 and 49; the valve 48 being a load drop check valve which is adapted to seat on a step in bore a 43 located between passages 45 and as, and the valve 49 serving to control the bias on the check valve 48 and being arranged to seat on a step located between

passages

46 and 47. Check valve 48 is biased closed by a light, coil compression spring 51 and by the fluid pressure in radial passages 46. These passages communicate with the space 52 behind the check valve through the radial clearance between the outer periphery of the stem of the check valve 43 and the wall of the axial recess in control valve 49 in which this stem is received. The check valve is urged in the opening direction by the pressure in radial passages 45 which acts upon its nose 53. Control valve 45 on the other hand, is biased closed by coil compression spring 54 and by the fluid pressure in radial passages 47, and is urged in the opening direction by the pressure in radial passages 46 which acts upon its annular nose 55. Longitudinally extending grooves formed in the outer periphery of valve 49 connect radial passages 47 with the space 56 behind the valve. Spring 54 exerts a greater biasing force than spring 51, and therefore, it maintains valve 49 on its seat against the unseating action of spring 51 which reacts against it.

When the valve is put in service, chambers and 17 are connected with a supply pump 57, and chamber 16 is connected with tank 21. Either connection may be made directly through a housing port and a conduit, or indirectly through a path that includes the open center by-pass path provided by another valving unit. With the valve plunger 11 in the illustrated neutral position, flow to and from

chambers

14 and 13 is blocked by lands and 27, and the oil delivered by pump 57 passes to tank 21 via chambers 15 and 17, plunger grooves 23 and 24, and chamber 16. Therefore, cylinder 22 is hydraulically locked, and pump 57 is unloaded.

When the plunger 11 is shifted to the raise position shown in PEG. 2, lands 25 and 26 interrupt flow from chambers 15 and 17 to chamber 16, and thus close the open center by-pass, and

radial passages

33, 34, and 46 register with

chambers

18, 19, 15 and 14, respectively. The pump 57 now communicates with the rod end of cylinder 22 along a supply path including chamber 15, radial passages 45, check valve 48, radial passages 46, and motor chamber 14, and the head end of cylinder 22 is vented to tank 21 along an exhaust path including chamber 18, radial passages 33, bore portion 29, check valve 35, radial passages 34, and chamber 19. Opening of these flow paths causes cylinder 22 to move the load upward. In this position of plunger 11, check valve 48 is opened initially, and then maintained open, by a pressure differential between

passages

45 and 46 whose magnitude is a function of the small biasing force exerted by spring 51. Therefore, the pressure losses in the supply path to the rod end of cylinder 22 are no greater than those encountered in a conventional hollow plunger valve equipped with a load drop check valve.

Cylinder 22 moves the load downward when valve plunger 11 is shifted to the lower position shown in FIG. 3. In this position, lands 26 and 27 close the open center by-pass path, fluid from pump 57 is delivered to the head end of cylinder 22 along a path comprising chamber 17, radial passages 33, bore portion 29, check valve 35, radial passages 34 and chamber 13, and the return flow from the rod end of the cylinder is delivered to the axial bore 43 and bore portion 31 through chamber 14 and

radial passages

45 and 36, respectively. The pressure acting on the nose 53 of check valve 48 tends to unseat the check valve, but, since radial passages 46 are now closed by the Wall of the plunger bore 12, the check valve cannot open until the pressure in the return path from cylinder 22, and consequently the reflected pressure in the space 52 behind the check valve, rises to a value high enough to develop on the nose 55 of valve 49 a force greater than the bias of spring 54. When the control valve 49 opens, it destroys the temporary hydraulic loci: holding valve 4ft closed, thereby allowing the last mentioned valve o open. Now. the return llow entering bore i?) through radial passages ii 45 can how to tank 21 through check valve 43, control valve 45 radial passages 47, and chamber 13.

With plunger 11 in its 3 position, the space 41 behind by-pass valve 38 is connected with the supply path to the head end of cylinder 22 through radial passages 37, plunger groove 23-, and chamber 15. If the load acting on cylinder 22 opposes downward movement of its piston 225a, or assists such movement but is small, the pressure in the supply path to the head end will be high, and by pass valve 33 will remain closed. Therefore, under these conditions, all of the tiuid returning to the directional control valve from the rod end of cyuinder 22 will be directed to tank 21 through check valve id. On the other hand, if the load is large, and it acts in a direction to contract the rod end of the cylinder 22, the piston 22:; wiil tend to move at a speed greater than that with which pump can keep pace, and the supply pressure will decrease to a relatively low value. In this situation, the bacl-ipressure which is developed in the return path by check valve 48, and which acts on the valve nose 42, will cause lay-pass valve 33 to shift away from its seat and open the regeneration path. As a result, a portion of the return flow is diverted to the supply path through radial passages 36, here portion 31, bypass valve 38, radial ges 37, plunger groove 23, and chamber 15. The fluid 1g tirough this path supplements that delivered by pump 57 and insures that the head end of cylinder 22 is maintained liquid-filled.

it is assumed in this description that regenerative flow from the head end to the rod end of cylinder 22 is not required in the raise position because, in the usual case, the flow demand of the rod end is so much less than that of the head end that the pump capacity is sutlicient to maintain it liquid-tilled. However, if it is found that cavitation is a problem in both directions of movement, it will be apparent that this can be cured by using two regeneration circuits, and that the teachings of this invention may be embodied in each of those circuits.

As stated previously, the drawing and description relate only to the preferred embodiment of the invention. Since changes can be made in the structure of this embodiment without departing from the inventive concept, the following claims should provide the sole measure of the scope of the invention.

What I claim is:

1. A directional control valve including a housing containing (a) inlet and exhaust passages and first and second motor passages;

(b) a movable valving element having a first position in which it connects the first and second motor passages with the inlet and. exhaust passages, respectively, and a second position in which the connections between the motor passages and the other two passages are reversed, the valving element containing a load drop check valve which prevents flow from the first motor passage to the inlet passage in said first posilion and restricts flow from the first motor passage to the exhaust passage in the second position;

(c) means for establishing a replenishing path which leads from the first to the second motor passage when the valving element is in the second position; and

(d) means for exerting a closing bias on the load drop check valve which changes in accordance with the position of. the movable valving element, the larger bias being exerted when that element is in said second position.

2. A directional control valve as defined in claim 1 in which the bias exerting means comprises (a) a bias chamber in the valving element which is defined in part by the check valve itself so that the volume of the chamber decreases and increases as the check valve moves in the opening and closing directions, respectively;

(b) first and second control passages in the valving etement and communicating with the bias chamber;

(c) means carried by the valving element and the housing for connecting the first control passage With the first motor passage in said first position and for closing the first control passage in said second position;

(d) means carried by the valving element and the housing for connecting the second control passage with the exhaust passage in said second position; and

(e) a control valve normally closing the second control passage but adapted to open this passage in response to a predetermined pressure in the bias chamber.

3. A movable valving element for a directional control valve including a body containing (a) a bore having closed ends and intersected intermedi ate these ends by three longitudinaily spaced transverse passages which open through the surface of the body, there being first and second end passages and an intermediate third passage;

(b) first and second annular valve seats encircling the bore at points between the first and third passages and between the second and third passages, respectively;

(c) a check valve movable longitudinally of the bore and adapted to engage the first seat;

(d) a control valve movable longitudinally of the bore and adapted to engage the second seat, the opening and closing directions of the check and control valves being the same;

(e) a spring urging each of the check and control valves toward its seat;

(f) first and second opposed reaction surfaces on the check valve subject to the pressures in the first and third passages, respectively, the first reaction surface developing a force which urges the check valve in the opening direction; and

(g) third and fourth opposed reaction surfaces on the control valve subject to the pressure in the third and second passages, respectively, the third surface developing a force which urges the control valve in the opening direction.

4. A movable valving element as defined in claim 3 in which (a) the body is in the form of a sliding valve plunger;

(b) the bore is an axial bore in the plunger; and

(c) the check and control valves and the springs are coaxial with the bore.

5. A movable valving element are defined in claim 4 in which (a) the control valve is guided for movement by the wall of said bore and contains an axial recess;

(b) the check valve has a longitudinally extending stern which is received in said recess; and

(c) the spring biasing the check valve is seated on the control valve and exerts a smaller force than the spring biasing the control valve.

References Cited UNITED STATES PATENTS 3,200,841 8/1965 Beutler 137-596 3,213,880 10/1965 Donner 137-596 3,216,446 11/1965 Schmiel 137596 M. CARY NELSON, Primary Examiner.

R. J. MILLER, Assistant Examiner.

Claims

1. A DIRECTIONAL CONTROL VALVE INCLUDING A HOUSING CONTAINING (A) INLET AND EXHAUST PASSAGES AND FIRST AND SECOND MOTOR PASSAGES; (B) A MOVABLE VALVING ELEMENT HAVING A FIRST POSITION IN WHICH IT CONNECTS THE FIRST AND SECOND MOTOR PASSAGES WITH THE INLET AND EXHAUST PASSAGES, REPECTIVELY, AND A SECOND POSITION IN WHICH THE CONNECTIONS BETWEEN THE MOTOR PASSAGES AND THE OTHER TWO PASSAGES ARE REVERSED, THE VALVING ELEMENT CONTAINING A LOAD DROP CHECK VALVE WHICH PREVENTS FLOW FROM THE FIRST MOTOR PASSAGE TO THE INLET PASSAGE IN SAID FIRST POSITION AND RESTRICTS FLOW FROM THE FIRST MOTOR PASSAGE TO THE EXHAUST PASSAGE IN THE SECOND POSITION;