US3255777A

US3255777A - Directional control valve

Info

Publication number: US3255777A
Application number: US325987A
Authority: US
Inventors: Orval L Rice; Robert C Westveer
Original assignee: New York Air Brake LLC
Current assignee: New York Air Brake LLC
Priority date: 1963-11-26
Filing date: 1963-11-26
Publication date: 1966-06-14
Anticipated expiration: 1983-06-14
Also published as: GB1008324A

Description

0. L. RICE ETAL DIRECTIONAL CONTROL VALVE Filed Nov. 26, 1963 JHUHHQ 14, 1966 INVENTORS ATTORNEYS United States Patent 3,255,777 DIRECTIONAL CONTROL VALVE ()rval 1.. Rice and Robert C. Westveer, Kalamazoo, Mich.,

assignors to The New York Air Brake Company, a corporation of New Jersey Filed Nov. 26, 1963, Ser. No. 325,987 3 Claims. (Cl. 137-62568) This invention relates to hydraulic valves of the directional control type.

Valves of this type are frequently used in hydraulic circuits for actuating double-acting motors. In general, the valve 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 the opposite sides of the double-acting motor, and a movable valve element which 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 part of it controlling flow to and from the first motor passage, is of the hollow type, i.e., it contains an internal fiow 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 usually provided with a spring biased check valve that prevents dropping of the load acting on the motor whenever pump supply pressure is below the pressure in the side of the motor that would be contracted by the load.

When circuits of this kind are used to lower large loads, it sometimes happens that the motor moves so fast that its flow demand exceeds the delivery rate of the pump. This condition causes cavitation in the expanding side of the double-acting motor and obviously is undesirable. The co-pending application of Orval L. Rice, Serial No. 247,- 974, filed December 28, 1962, discloses a hollow plunger directional control valvewhich, in the lower position, splits the return flow from the contracting side of the motor so that at least a portion of that fluid passes through a regeneration path leading to the expanding side of the motor and the balance is delivered to the reservoir. This supplemental flow to the expanding side of the motor maintains a positive pressure in that side and prevents cavitation. While this valve is satisfactory in installations wherein the load imposed by the device being actuated always tends to contract one and the same side of the motor, it cannot be used in installations wherein the direction of action of the load reverses during movement of the actuated device because it connects both sides of the motor with the reservoir and thus precludes development of a high Working pressure.

The object of the present invention is to provide an improvement in the regeneration scheme of application Serial No. 247,974 that permits that scheme to be used in installations wherein the load exerted by the actuated device is bidirectional, i.e., it may tend to contract either side of the motor. According to this invention, the regeneration path includes a check valve whose seat is defined by a transverse end face of one of the plunger lands, and whose head is an annular member that encircles the plunger and is positioned in an annular peripheral groove formed in the plunger between that land and one of the other plunger lands. In the lower position of the plunger, the downstream side of the annular valve head communicates with the inlet passage of the directional control valve so that the head remains seated, and thus closes the regeneration path, whenever a high working pressure is required in that side of the motor which normally receives supplemental delivery. This arrangement enables the motor to move a load through an overcenter position, i.e., through a position in which its direction of action reverses. When the load moves beyond this position, and its direction of action reverses, the supply pressure decreases, the check valve opens, and normal regeneration action is resumed.

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

FIG. 1 is a cross-sectional view of the improved directional control valve including, in schematic form, the other circuit components with which it is used.

FIG. 2 is a sectional view, on enlarged scale, taken on line 22 of FIG. 1.

As shown in FIG. 1, the improved directional control valve 11 is employed in a circuit for actuating a doubleacting motor 12 that raises and lowers the bucket-carrying boom 13 of a loader. The valve 11 includes an inlet port 14 which is connected with a pump 15, an exhaust port 16 which is connected with a reservoir 17, and a pair of motor ports (not shown) which are connected with the rod and head ends of motor 12 through conduits 18 and 19, respectively. The housing of valve 11 contains a through valve bore which is intersected by seven long i tudinally spaced annular chambers 21-27. Annular chambers 23 and 25 are connected with inlet port 14 by a branched supply passage 28, annular chambers 21, 24 and 27 are connected with exhaust port 16 by manifold 29, and annular chambers 22 and 26 are connected with the motor ports (not shown). Annular chamber 22 is provided with a longitudinal extension 31 which, as explained in application Serial No. 247,974, forms part of the regeneration path. As in the usual control valve, a relief valve 32 is interposed between supply passage 28 and the exhaust manifold 29.

Slidable in the valve bore is a hollow valve plunger 33 formed with two annular grooves 34 and 35 that define three valve lands 36, 37 and 38. A pair of

axial bores

39 and 41 extend into the valve plunger from its opposite ends and these bores are closed and sealed by threaded plugs 42 and 43, respectively. Axial bore 39 is intersected by two sets of longitudinally spaced, radial passages 44 and 45 and contains a spring-biased load-drop check valve 46 which is arranged to prevent flow through bore 39 from passages 44 to passages 45. Axial bore 41 is provided with similar sets of

radial passages

47 and 48 and a spring-biased load-drop, check valve 49. The transverse end faces of lands 36 and 38 contain conical undercuts 51 and 52, which are intersected by radial passages 53 and 54, respectively. These undercuts and passages are provided in accordance withthe teachings of Hodgson Reissue Patent 24,580, granted December 23, 1958, for reducing the axial components of the dynamic reaction forces acting on the valve plunger. In addition, undercut 51 and radial passages 53 cooperate with chamber exten sion 31 to define the regeneration flow path.

The directional control valve described thus far is essen tially the same as the one described in application Serial No. 247,974. However, in this case, the regeneration flow path is provided with a check valve whose seat is defined by the right transverse end face of valve land 36 and whose head is a split annular member 55 that encircles plunger 33 and is positioned within the annular peripheral groove 34. The two halves of theannular valve head 55 are held together by a Waldes Truarc interlocking snap ring 56. This head is guided for slid ing movement on the inner peripheral wall of groove 34 and is biased toward the transverse end face of land 36 by a coil compression spring 57, which also encircles plunger 33. Spring 57 is supported on steps formed on the right and left ends of head 55 and plunger land 37, respectively.

When valve plunger 33 is in the illustrated neutral position, lands 36 and 38 isolate annular chambers 22 and 26, respectively, from the other chambers, so doubleacting motor 12 is hydraulically locked. At this time, pump 15 is unloaded to reservoir 17 along a path comprising inlet port 14, supply passage 28, annular cham= bers 23 and 25, plunger grooves 34 and 35, annular chamber 24, exhaust manifold 29 and exhaust port 16.

In order to raise the boom 13, valve plunger 33 is shifted to the right to its raise position in which

radial passages

44, 45, 48 and 47 register, respectively, with

annular chambers

22, 23, 26 and 27, lands 36 and 37 isolate annular chamber 24 from annular chambers 23 and 25, respectively, and thus load the pump, and radial passages 53 register with annular chamber 24. Fluid under pressure now flows to the rod end of motor 12 along a path comprising inlet port 14, supply passage 28, annular chamber 23, radial passages 45, axial bore 39, check valve 46, radial passages 44, annular chamber 22 and conduit 18. Fluid expelled from the head end of motor 12 is returned to reservoir 17 along a path comprising conduit 19, annular chamber 26, radial passages 48, axial bore 41, check valve 49, radial passages 47, annular chamber 27, exhaust manifold 29 and exhaust port 16. It will be apparent to those skilled in the art that check valve 46 serves to prevent dropping of the boom 13 during the time required for pump 15 to build up operating pressure and also at such other times as supply pressure decreases below the pressure in the rod end of motor 12. After the boom 13 has been moved to the desired position, valve plunger 33 is returned to its neutral position to again hydraulically lock motor 12 and unload pump 15.

Lowering of the boom 13 is accomplished by shifting valve plunger 33 to the left to the lower position in which

radial passages

44, 45, 48 and 47 register, respectively, with annular chambers 21, 22, and 26, lands 36 and 38 isolate annular chamber 24 from annular chambers 23 and 25, respectively, and radial passages 53 register with chamber extension 31. In this position of the valve plunger 33, the fluid delivered to supply passage 28 by pump 15 is transmitted to the head end of motor 12 via annular chamber 25, radial passages 48, axial bore 41, check valve 49, radial passages 47, annular chamber 26 and conduit 19. The fluid displaced from the rod end of motor 12 is delivered to annular chamber 22 through conduit 18, whence, depending upon the position of check valve 50, either all of it is transmitted to reservoir 17 through a return path comprising radial passages 45, axial bore 39, check valve 46, radial passages 44, annular chamber 21, exhaust manifold 29 and exhaust port 16, or a part is transmitted to the reservoir along this path and the rest passes into the supply passage 28 through the regeneration path defined by chamber extension 31, radial passages 53, conical undercut 51, checkvalve 50, and annular chamber 23. When boom 13 is in the illustrated position, in which the center of gravity of bucket 58 is on the right side of the vertical plane passing through boom pivot 59, the load acting on motor 12 tends to contract its head end, and, therefore, the pressure in the supply path leading to this side of the motor is rather high. Under these conditions, the forces developed by spring 57 and by the supply pressure in annular chamber 23 hold annular valve head 55 on its seat against the opposing pressure force developed by the fluid in undercut 51 and thus maintain the regeneration path closed. Since the two sides of the motor 12 are now completely isolated from each other, the high pressure required to move bucket 58 over center can be developed in the supply path and all of the fluid returned to valve 11 from the rod end of motor 12 is transmitted to the reservoir 17.

As the center of gravity of the bucket 58 moves over center, i.e., through the vertical plane passing through pivot 59, the direction of action of the load imposed on motor 12 reverses. Since the load now tends to contract the rod end of motor 12, the pressure in the supply path leading to the head end, and consequently the closing force acting on annular valve head 55, decrease. When this closing bias becomes less than the opposing force developed by the fluid in undercut 51, annular valve head 55 shifts to the right and opens the regeneration flow path. Now some of the fluid being returned to annular chamber 22 flows into the supply passage 28 through extension 31, radial passages 53, conical undercut 51, and annular chamber 23, and check valve 46 moves in the closing direction. The supply pressure at which regenerative action occurs depends upon the back pressure created by check valve 46, and the spring used in this valve is so chosen that the back pressure is always sufiicient to maintain the head end of motor 12' liquid-filled, If not all of the fluid being returned to annular chamber 22 is required to maintain the desired supply pressure in the head end of motor 12, that portion which is not transmitted to the head end through the regeneration path is delivered to reservoir 17 through the return path mentioned previously.

It has been assumed in this description that regenerative flow from the head end to the rod end is not required in the raise position of valve plunger 33, even though bucket 58 can move over center, because of the substantial difference between the flow demands of the head and rod ends of motor 12. However, if it is found that cavitation does occur in the rod end of motor 12 as the center of gravity of bucket 58 moves in the clockwise direction beyond the vertical plane passing through pivot 59, it will be obvious that that condition can be eliminated by providing a second regeneration flow path. In this case, annular chamber 26 would be formed with an extension, corresponding to chamber extension 31, that cooperates with radial passages 54 and undercut 52 to define the flow path, and a second check valve 50, located in annular groove 35, would be-employed to selectively open and close it.

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 we claim is:

1. In combination (a) a valve housing containing a valve bore intersected by first, second, third and fourth longitudinally spaced passages, the third and fourth passages being intermediate the other two;

(b) a valve plunger reciprocable in the bore and formed with an annular peripheral groove that defines two spaced valve lands having opposing transverse end faces;

(0) a fifth passage formed in one of said lands;

((1) a separate sixth passage formed in said one land and terminating at its opposite ends at first and second openings formed in the outer peripheral surface and in the transverse end face, respectively, of said land;

(e) the valve plunger having a first position in which said one land isolates the third passage from the other passages and the peripheral groove interconnects the second and fourth passages, a second position in which said one land isolates the second passage from the fourth passage, the fifth passage interconnects the third and fourth passages, and the first opening registers with the second passage, and a third position in which the other land isolates the second passage from the fourth passage, the peripheral groove registers with the fourth passage, the fifth passage interconnects the first and third passages, and the first opening registers with the third passage; and

(f) an annular valve head encircling the plunger and located in said annular peripheral groove, said valve headv being guided for sliding movement along the inner peripheral surface of said groove between first and second positions in which, respectively, it closes and opens said second opening.

2. The combination defined in claim 1 including a coil spring located in said annular peripheral groove and encircling the plunger, said spring reacting between the transverse end face of the other of said lands and the valve head and urging the valve head toward said first position.

3. A directional control valve including (a) a housing containing inlet, exhaust, and first and second motor passages, and a valve bore intersected by at least four longitudinally spaced chambers, there being first and second exhaust chambers that are connected with the exhaust passage, 21 motor chamber located between the exhaust chambers and connected with the first motor passage, and a supply chamber located between the motor chamber and the first exhaust chamber and connected with the inlet passage;

(b) a valve plunger reciprocable in the valve bore and formed with at least two lands that are separated by an annular peripheral groove, the two lands having opposed transverse end faces;

(c) a longitudinal passage formed in the plunger and intersected by first and second longitudinally spaced transverse passages that open through the outer peripheral surface of the first of said lands,

(d) the plunger having a first position in which the first land isolates the motor chamber from the other chambers, a second position in which the first land interrupts communication between the supply chamher and the first exhaust chamber, and the first and second transverse passages register,'respective1y, with (e) a separate flow passage formed in the first land and terminating at it opposite ends in openings located in its outer peripheral surface and in the transverse end face, the opening in the outer peripheral surface being positioned so that it registers with the motor chamber in said third position, is isolated from the motor chamber in said first position, and is isolated from both the motor chamber and the supply chamber in said second position;

(f) an annular valve head encircling the plunger and located in said annular peripheral groove, the valve head being guided for sliding movement on the inner peripheral surface of said groove between first and second positions in which, respectively, it closes and opens said opening in the transverse end wall;

(g) a coil spring encircling the plunger and located in said annular peripheral groove, the spring reacting between the transverse end faceof the second land and the valve head and urging the valve head toward its first position; and

(b) means carried by the valve member and the housing for isolating the second motor passage from the other three passages when the plunger is in its first position, for connecting the second motor passage with the exhaust passage when the plunger is in its second position, and for connecting the second motor passage with the inlet passage when the plunger is in its third position.

References Cited by the Examiner UNITED STATES PATENTS 2,678,114 5/1954 De Koning et al. 137-4933 X 2,980,135 4/1961 Tennis 137-596.12 3,006,372 10/1961 Ruhl 137-6l2.l

MARTIN P. SCHWADRON, Acting Primary Examiner. M. CARY NELSON, Examiner.

Claims

1. IN COMBINATION (A) A VALVE HOUSING CONTAINING A VALVE BORE INTERSECTED BY FIRST, SECOND, THIRD AND FOURTH LONGITUDINALLY SPACED PASSAGES, THE THIRD AND FOURTH PASSAGES BEING INTERMEDIDATE THE OTHER TWO; (B) A VALVE PLUNGER RECIPROCABLE IN THE BORE AND FORMED WITH AN ANNULAR PERIPHERAL GROOVE THAT DEFINES TWO SPACED VALVE LANDS HAVING OPPOSING TRANSVERSE END FACES; (C) A FIFTH PASSAGE FORMED IN ONE OF SAID LANDS; (D) A SEPARATE SIXTH PASSAGE FORMED IN SAID ONE LAND AND TERMINATING AT ITS OPPOSITE ENDS AT FIRST AND SECOND OPENINGS FORMED IN THE OUTER PERIPHERAL SURFACE AND IN THE TRANSVERSE END FACE, RESPECTIVELY, OF SAID LAND; (E) THE VALVE PLUNGER HAVING, A FIRST POSITION IN WHICH SAID ONE LAND ISLOATES THE THIRD PASSAGE FROM THE OTHER PASSAGES AND THE PERIPHERAL GROOVE INTERCONNECTS THE SECOND AND FOURTH PASSAGES, A SECOND POSITION IN WHICH SAID ONE LAND ISOLATES THE SECOND PASSAGE FROM THE FOURTH PASSAGE, THE FIFTH PASSAGE INTERCONNECTS THE THIRD AND FOUTH PASSAGES, AND THE FIRST OPENING REGISTERS WITH THE SECOND PASSAGE, ANDA THIRD POSITION IN WHICH THE OTHER LAND ISOLATES THE SECOND PASSAGE FROM THE FOURTH PASSAGE, THE PERIPHERAL GROOVE REGISTERS WITH THE FOURTH PASSAGE, THE FIFTH PASSAGE INTERCONNECTS THE FIRST AND THIRD PASSAGES, AND THE FIRST OPENING REGISTERS WITH THE THIRD PASSAGE; AND (F) AN ANNULAR VALVE HEAD ENCIRCLING THE PLUNGER AND LOCATED IN SAID ANNULAR PERIPHERAL GROOVE, SAID VALVE HEAD BEING GUIDED FOR SLIDING MOVEMENT ALONG THE INNER PERIPHERAL SURFACE OF SAID GROOVE BETWEEN FIRST AND SECOND POSITIONS IN WHICH, RESPECTIVELY, IT CLOSES AND OPENS SAID SECOND OPENING.