US3200841A - Valve - Google Patents

Description

Aug 17, 1955 A. A. BEUTLER 3,200,841

VALVE Filed June 2o, 196s Tlv I8 al 24 ATTORNEYS 3,200,841 VALVE Arthur A. Beutler, Kalamazoo, Mich., assigner to The New York Air Brake Company, a corporation of New Jersey Filed .lune 20, 1963, Ser. No. 289,295 2 Claims. (Cl. 137-596) This invention relates to valve-s for controlling the flow of fluid to and from hydraulic motors.

A typical actuation circuit for a double-acting piston motor includes a pump, a sump and a three-position directional control valve having inlet and exhaust ports connected with the pump and sump, respectively, and a pair of motor ports connected with opposite sides of the motor. The directional control valve has a neutral position in which each motor port is isolated from the other three ports and the rnotor is hydraulically locked, a second position in which it establishes a supply path from the inlet port to the first motor port and an exhaust path from the second motor port to the exhaust port, and a third position in which it establishes a supply path from the inlet port to the second motor port and an exhaust path from the irst motor port to the exhaust port. In some installations, for example, the blade raising and lowering circuit of a bulldozer, the load being actuated tends t contract oney side of the motor, and in other installations, for instance, the mast tilting circuit of a fork lift truck, the load may tend to contract either side of the motor. In installations such as these, if the directional control valve is in a position to establish a supply path to the motor port connected with the coutracting side of the motor when supply pressure falls be-low load pressure, as a result, for example, of failure of the pump or a break in the supply line connecting the pump with the directional control valve, the motor will drop the load. Because of this, it is necessary to include in one or both supply paths a check valve which serves to sustain the load by preventing reverse flow through the supply path.

Another problem encountered in circuits of this kind is that of preventing the development of excessive pressures in the contracting side of the motor when the directional control valve is in neutral position. Although these actuation circuits include a system relief valve, this valve is located upstream of the actual valving mechanism in the directional control valve and thus is isolated from the motor ports when that valve is in neutral position. Therefore, the system relief valve is not effective to relieve excessive pressures in one or both sides of the motor resulting from external loads applied to the motor when the directional control valve is in neutral position, or from the momentum of the actuated load itself in those cases where the operator suddenly returns the directional control valve to neutral position when the load is in motion. Because of this, one or both sides of the motor frequently are provided with overload relief valves.

From the standpoint of versatility and simplicity, it is desirable to locate both the load drop check valve and the overload relief valve for one or both sides of the motor in the movable member of the directional control valve. One such arrangement is disclosed in Ruhl Patent 2,946,347, issued July 26, 1960. However, in the combined check and relief valve shown in this patent, both sides of the pilot poppet are subjected to substantially the same pressure once the main relief valve opens and it has been found that this changes the relief characteristics and makes the unit erratic.

The object of this invention is to provide an improved form of check and relief valve which is mounted in the movable member of the directional control valve and i. United States Patent O 3,299,841 Patented Aug. 17, 1965 which eliminates the disadvantage of the device shown in the Ruhl patent mentioned above. In addition, the combined check and relief valve of this invention is less cost-ly, simpler and more reliable than its predecessor.

The preferred form of the invention is described herein with reference to the accompanying drawing whose single figure is a cross-sectional view of a threeposition, sliding plunger, directional control valve of the open center type incorporating the invention.

As shown in the drawing, the directional control valve comprises a housing 11 containing inlet and exhaust ports 12 and 13, respectively, and a through valve bore 14. The bore 14 is encircled by seven longitudinally spaced chambers 15 through 19, 21 and 22. Annular chambers 15, 18 and 22 communicate with exhaust port 13 through exhaust manifold 23, and annular chambers 17 and 19 communicate with inlet port 12 through inlet manifold 24. Annular chambers 16 and 21 are connected with a pair of motor ports (not shown). A conventional, pilot-operated system relief valve 25 limits the pressure in inlet manifold 24 by bypassing fluid to the exhaust manifold 23.

Slidable in bore 14 is a valve plunger 26 formed with two spaced grooves 27 and 28 that define three lands 29, 31 and 32. Extending inward from opposite ends of plunger 26 are a pair of axial bores 33 and 34 whose outer ends are closed and sealed by threaded plugs 35 and 36, respectively. Axial bore 33 is intersected by two spaced sets of radial passages 37 and 38, and axial bore 34 is` intersected by two similar sets of passages 39 and 41. However, it will be observed that unlike its counterpart 37 at the left side of plunger 26, passages 41 register with the associated motor chamber 21 when the plunger 62 is in the illustrated neutral position. Each axial bore is provided with a step 42 that. serves as a seat for the load drop check valve. Since it is assumed in this embodiment that the load drop check valve is required only in that side of the plunger 26 controlling ilow to and from motor chamber 21, the seat in bore 33 actually is not required.

Reciprocable in axial bore 34 is a load drop check valve 43 having a beveled end 44 that serves as the head of the check valve and is arranged to seat on step 42. Bore 34 also contains a reciprocable sleeve 45 formed with an end wall 46 that faces the left end of check valve 43. The space within bore 34 between the adjacent ends of sleeve 45 and check valve 43 is connected with radial passages 41 through axial and radial passages 47 and 4S, respectively, formed in the check valve. End wall 45 contains an axial port 49, the right edge of which serves as a seat for the relief poppet 51 located within sleeve 45. The interior of sleeve 45, which is the downstream side of the relief poppet, is in continuous communication with exhaust port 13 through registering radial passages 52 and 53 formed in sleeve 45 and plunger 26, respectively, chamber 22 and exhaust manifold 23. A coil compression spring 54, reacting between plug 36 and poppet 51, urges the relief valve closed and, through sleeve 45, also urges check valve 43 in the closing direction. Thus, this single spring furnishes closing bias for both valves.

Operation In a typical installation, inlet port 12 is connected with a pump 55, exhaust port 13 is connected wtin a sump 56, and the motor ports communicating with annular chambers 16 and 21 are connected by conduits 57 and 58, respectively, with the opposite sides of a double-acting piston motor 59. For purposes of this description, it is assumed that the device actuated by motor 59 exerts a load that tends to contract the rod end of the motor and thus to pressurize annular chamber 21.

When valve plunger 26 is in the illustrated neutral position, the ffuid delivered to inlet port l2 from pump 55 flows directly to sump 56 through inlet manifold 24, annular chambers 17 and 19, plunger grooves 27 and 28, annular chamber 1S, exhaust manifold 23 and exhaust port 13.` Lands 29 and 31 isolate motor chambers 16 and 2i, respectively, from communication with each other and with the other chambers. At this time, the load pressure in chamber 2l is transmitted to axial port 49 in sleeve 45 via radial passages 41 and 48 and axial passage 47 where it acts upon the nose of poppet 51. Normally, this load pressure is inadequate to unseat the poppet against the opposing bias of spring 54. However, when excessive pressures are developed in the rod end of motor 59, poppet 5l moves to the right and opens a relief path to sump including the interior of sleeve 4S, radial passages 52 and 53, chamber 22, exhaust manifold 23 and exhaust port 13. When the overload condition has subsided, poppet 51 moves to the left under the action of spring 54 and closes this relief path.

Rightward movement of motor 59 is effected by shifting valve plunger 26 to the right to its second position in 4which radial passages 37, 3S, 39 and 4l register, respectively, with annular chambers 16, 17, 21 and 22, and lands 29 and '3i interrupt the open center unloading path between pump 55 and sump 56. The fluid delivered by pump 55 may now fiow to the head end of motor 59 along a supply path comprising inlet port 12, inlet manifold 24, annular chamber i7, radial passages 38, axial bore 33, radial passages 37, annular chamber 16, and conduit 57. The fiuid displaced from the rod end of motor 59 is transmitted to axial bore 34 through conduit 5S, annular chamber 21 and radial passages 39 where it acts upon the left end of check valve 43. Since the space Within sleeve 45 is in continuous communication with annular chamber 22, check` valve 43 and sleeve 45 are shifted to the right against the bias of spring 54 by the fluid in the left end of bore 34, thereby opening a return path to sump 56 including radial passages 41, annular chamber 22, exhaust manifold 23 and exhaust port 13. Inasmuch as the cross-sectional area of the left end of check valve 43 is much greater than the cross-sectional area of port 49, a very small pressure differential is required to open the check valve even though this valve and relief poppet 51 are biased closed by the same spring.

The operator stops rightward movement of motor 59 by returning valve plunger 26 to its neutral position. If the load acting on motor 59 is large and is moving rapidly, its momentum may develop excessive kpressures in the rod end of motor 55* if the return path from this side of the motor is interrupted suddenly. Should this happen, relief poppet Si will open in the manner described above and the overpressure will be dissipated.

Leftward movement of motor 59 is effected by shifting plunger 26 to the left to a third position in which radial passages 37, 3d, 39 and 41 register, respectively, with annular chambers 15, 16, 19 and 21, and lands 31 and 32 close the open center unloading path. Now, fluid delivered by the pump 55 is transmitted to axial bore 34 through inlet port l2, inlet manifold 24, annular chamber 19 and radial passages 39. When supply pressure rises to a value sufficient to overcome the combined bias of spring S4 and the pressure force developed by the load pressure acting on the right end of check valve 43, the check valve opens and allows the fluid in bore 34 to fioW to the rod end of motor 59 through radial passages 4l, annular chamber 2i and conduit 58. Simultaneously, valve plunger 26 opens an exhaust path from the head end of motor 59 to sump 56 comprising conduit 57, annular chamber lr6, radial passages 38, axial bore 33, radial passages 37, annular chamber 15, exhaust manifold 23 and exhaust port lf3. As in the previous case, movement of motor S@ is stopped by returning valve plunger 26 to its neutral position.

lt will be observed that when valve plunger 26 is in the third position, the load pressure in radial passages 4l acts on an annular area at the left end of check valve 43 having a radial width equal to the difference between the diameter of seat 42 and the outside diameter of the check valve, and develops a force that tends to open the check valve. However, since the entire right end of the check 'valve is subjected to the same pressure and develops a much larger force tending to close the valve7 it is apparent that should supply pressure fail While plunger 26 is in the third position, valve 43 will close and preclude dropping of the load. It will be apparent that since spring 54 also biases check valve 43 in the closing direction, it is not essential that load pressure develop on valve 43 a net force tending to close it, and that a balance of pressure forces is all that actually is required in the illustrated embodiment.

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 valve comprising (a) a housing containing a bore intersected by three spaced chambers, there being a supply chamber, an exhaust chamber and an intermediate motor chamber;

(b) a valve member movable in the bore and containing an internal passage intersected by first and second spaced through ports;

(c) the valve member having a first position in which the second through port registers with the motor chamber, a second position in which the rst, and second through ports register, respectively, with the supply and motor chambers, and a third position in which the first and second through ports register respectively with the motor and exhaust chambers;

(d) a check valve seat encircling the internal passage and located between the first and second through ports;

(e) a check valve head reciprocable in the internal passage between open and closed positions with respect to said seat for controlling flow from the first to the second through port;

(f) reaction surfaces on the check valve head subject to the pressure in the second through port for developing forces that urge the head in both the opening and the closing directions, the areas of the reaction surfaces being so proportioned that the force urging the head in the opening direction does not exceed the force urging the head in the closing direction;

(g) means defining a vent chamber within the valve member which communicates with the exhaust chamber at least when the valve member is in the first position;

(h) a relief passage connecting the vent chamber with the second through port, said relief passage constituting the sole fluid connection between the vent charnber and the second through port; and

(i) a relief valve normally preventing ffowrfrorn the second port to the vent chamber through the relief passage but being responsive to the differential between the pressures in the second port and the vent chamber for opening the relief passage when the differential reaches a predetermined value.

2. A valve'cornprising (a) a housing containing a bore intersected by three longitudinally spaced chambers, there being a supply chamber, an exhaust chamber and an intermediate motor chamber;

(b) a valve plunger reciprocable in the bore and containing a longitudinal bore intersected by first and second longitudinally spaced through ports;

(c) the plunger having a first position in which the second through lport registers with the motor charn-4 ber, a second position in which the rst and second through ports register, respectively, with the supply and motor chambers, and a third position in which the first and second through ports register, respectively, With the motor and exhaust chambers;

(d) -a check valve seat encircling the longitudinal bore and located between the first and second through ports;

(e) a check valve reciprocable in the longitudinal bore and carrying a head at one end arranged to engage said seat;

(f) a sleeve reciprocable in the longitudinal bore and having a closed end wall facing the end of the cheek Valve opposite the head;

(g) passage means connecting the second through port with the space in the longitudinal bore between the check Valve and the sleeve;

(h) a relief port formed through said end wall;

(i) a relief poppet within said sleeve and seated in said relief port;

(j) a spring reacting between the plunger and the p0ppet and urging the poppet toward its seat and the check Valve toward its seat; and

(k) means defining a relief passage connecting the interior of the sleeve with the exhaust chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,946,347 7/60 Ruhl 137-6l2.l

M. CARY NELSON, Primary Examiner.

15 HENRY T. KLINKSIEK,Exam1-ner.

Claims (1)

1. A VALVE COMPRISING (A) A HOUSING CONTAINING A BORE INTERSECTED BY THREE SPACED CHAMBERS, THERE BEING A SUPPLY CHAMBER, AN EXHAUST CHAMBER AND AN INTERMEDIATE MOTOR CHAMBER; (B) A VALVE MEMBER MOVALBE IN THE BORE AND CONTAINING AN INTERNAL PASSAGE INTERSECTED BY FIRST AND SECOND SPACED THROUGH PORTS; (C) THE VALVE MEMBER HAVING A FIRST POSITION IN WHICH THE SECOND THROUGH PORT REGISTERS WITH THE MOTOR CHAMBER, A SECOND POSITION IN WHICH THE FIRST, AND SECOND THROUGH PORTS REGISTER, RESPECTIVELY, WITH THE SUPPLY AND MOTOR CHAMBERS, AND A THIRD POSITION IN WHICH THE FIRSAT AND SECOND THROUGH PORTS REGISTER RESPECTIVELY WITH THE MOTOR AND EXHAUST CHAMBERS; (D) A CHECK VALVE SEAT ENCIRCLING THE INTERNAL PASSAGE AND LOCATED BETWEEN THE FIRST AND SECOND THROUGH PORTS; (E) A CHECK VALVE HEAD RECIPROCABLE IN THE INTERNAL PASSAGE BETWEEN OPEN AND CLOSED POSITIONS WISTH RESPECT TO SAID SEAT FOR CONTROLLING FLOW FROM THE FIRST TO THE SECOND THROUGH PORT; (F) REACTION SURFACES ON THE CHECK VALVE HEAD SUBJECT TO THE PRESSURE IN THE SECOND THROUGH PORT FOR DEVELOPING FORCES THAT URGE THE HEAD IN BOTH THE OPENING AND THE CLOSING DIRECTIONS, THE AREAS OF THE REACTION SURFACES BEING SO PROPORTIONED THAT THE FORCE URGING THE HEAD IN THE OPENING DIRECTION DOES NOT EXCEED THE FORCE URGING THE HEAD IN THE CLOSING DIRECTION; (G) MENS DEFINING A VENT CHAMBER WITHIN THE VALVE MEMBER WHICH COMMUNICATES WITH THE EXHAUST CHAMBER AT LEAST WHEN THE VALVE MEMBER IS IN THE FIRST POSITION; (H) A RELIEF PASSAGE CONNECTING THE VENT CHAMBER WITH THE SECOND THROUGH PORT, SAID RELIEF PASSAGE CONSTITUTING THE SOLE FLUID CONNECTION BETWEEN THE VENT CHAMBER AND THE SECOND THROUGH PORT; AND (I) A RELIEF VALVE NORMALLY PREVENTING FLOW FROM THE SECOND PORT TO THE VENT CHAMBER THROUGH THE RELIEF PASSAGE BUT BEING RESPONSIVE TO THE DIFFERENTIAL BETWEEN THE PRESSURES IN THE SECOND PORT AND THE VENT CHAMBER FOR OPENING THE RELIEF PASSAGE WHEN THE DIFFERENTIAL REACHES A PREDETERMINED VALUE.

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