US3267961A

US3267961A - Valve

Info

Publication number: US3267961A
Application number: US360294A
Authority: US
Inventors: Orval L Rice
Original assignee: New York Air Brake LLC
Current assignee: New York Air Brake LLC
Priority date: 1964-04-16
Filing date: 1964-04-16
Publication date: 1966-08-23
Anticipated expiration: 1983-08-23
Also published as: GB1029470A

Description

Aug. 23, 1966 o. L. RICE 3,267,961

VALVE Filed April 16, 1964 2 Sheets-Sheet 1 L N R ORVAL L. RICE I I5 i BY ATTORNEYS INVENTOR 0. L. RICE Aug. 23, 1966 VALVE 2 Sheets-Sheet 2 Filed April 16. 1964 FIG .2

INVENTOR ORVAL L. RICE PUMP ATTORNEYS;

United States Patent 3,267,961 VALVE Orval L. Rice, Kalamazoo, Mich, assignor to The New York Air Brake Company, a corporation of New Jersey Filed Apr. 16, 1964, Ser. No. 360,294 3 Claims. (Cl. 137596) This invention relates to valves for hydraulic systems used to actuate double-acting, differential are-a piston motors.

In systems of this kind, the piston motor is controlled by a multi-position directional control valve having an inlet port connected with a pump, an exhaust port connected with a reservoir or tank, and a pair of motor ports which are connected with the opposite sides of the piston motor. The directional control valve has at least a neutral or hold position in which each motor port is isolated from the other three ports, a raise portion in which one motor port is connected with the inlet port and the other motor port is connected with the exhaust port, and a lower position in which the connections between the motor ports and the inlet and exhaust ports are reversed. The valve may also have a float position in which all four ports are interconnected.

These systems are used frequently on loaders and bulldozers to control the hoist motors which raise and lower the bucket and blade, respectively, and one of the problems encountered in this service is that of maintaining the expanding side of the piston motor liquid-filled, and thus avoiding cavitation, during implement dropping operations without retarding unduly the rate of movement. One solution to this problem is disclosed in US. Patent 3,049,101, granted August 14, 1962, and includes a bypass valve which is mounted on or near the piston motor and which is triggered to open and interconnect the contracting and expandingsides of the motor when the directional control valve is shifted to float position. While this scheme affords the desired results in cases where the directional control valve is shifted to float position to effect dropping of the implement, it affords little protection against cavitation in cases where the implement is dropped as a result of shifting the directional control valve to the lower position. Furthermore, the valving device disclosed in that patent is not suitable for use in installations wherein quick dropping of the implement is required when the directional control valve is in the lower position.

The object of this invention is to provide an improved version of the valving device disclosed in the patent mentioned above which allows by-passing of oil from the contracting to the expanding side of the motor in either the lower or the float position of the directional control valve, and which, in the latter case, also affords anti-cavitation flow control action when the directional control valve is in the lower position.

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

FIG. 1 is a diagram, partly in schematic form, showing the automatic version of the improved valving device and a typical circuit with which it is used.

FIG. 2 is a diagram, also partly in schematic form, showing the triggered version of the improved valving device and a typical circuit with which it is used.

As shown in FIG. 1, the improved valving device 11 is incorporated in a circuit for actuating a double-acting piston motor 12 which is arranged to raise and lower the blade 13 of a bulldozer. The circuit includes a threeposition, sliding plunger, directional control valve 14 having an inlet port connected with pump 15, an exhaust port connected with tank 16, and a pair of

motor ports

17 and 18. The letters N, R and L indicate the neutral,

Patented August 23, 1966 raise and lower positions, respectively, of valve 14.

Valving device 11 includes a housing containing a pair of parallel through

bores

19 and 21 and four ports 22-25; the

ports

22 and 23 being connected with the

motor ports

17 and 18, respectively, of valve 14 by

conduits

26 and 27, and the

ports

24 and 25 being connected with the head and rods ends, respectively, of motor 12 by

conduits

28 and 29. A cored passage 31, having portions 31a and 31!) which encircle bores 19 and 21, respectively, establishes continuous communication between

ports

23 and 25, whereas

cored passages

32 and 33 connect

ports

22 and 24 with the longitudinally spaced annular chambers 32a and 33a, respectively, encircling bore 19. As in the case of cored passage 31, cored passage 33 has a portion 33b which encircles bore 21.

The opposite ends of valve bore 19 are closed and sealed by

plugs

34 and 35, and the bore contains a sliding valve plunger 36 formed with an annular groove 37 which defines two

valve lands

38 and 39. The left end of plunger 36 is enclosed by a chamber 41 which communicates with cored passage 32 through the restricted passage 42 extending through plug 43. The combined forces developed by the pressure in this chamber 41 and the coil compression spring 44 biases valve plunger 36 to the right to a position in which the plunger engages plug 35 and land 38 isolates chambers 32a and 33a from each other. The plunger 36 is shifted in the opposite direction by the pressure in cored passage 31 which acts upon its right end 45, and, as the plunger moves to the left, the throttling notches 46 formed in the right edge of land 38 progressively open communication between annular chambers 32a and 330:. When the plunger reaches its extreme leftward position wherein its left end abuts plug 34, annular groove 37 spans chambers 32a and 33a and establishes a substantially unrestricted flow path between them. Land 39 isolates annular chamber 32a from cored passage 31 in all positions of the valve plunger 36.

Valve plunger 36 contains an ,axial bore 47 Whose left end is closed and sealed by plug 48 and which is intersected by two sets of longitudinal-1y spaced radial passages 49 and 51 which register with annular chambers 32a and 33a, respectively, when the valve plunger is in the illustrated position. Flow through axial bore 47 is controlled by a check valve 52 which is biased closed by a coil compression spring 53 and by the pressure in the chamber 54 at its left end. Chamber 54 is connected with cored passage 33 by the axial and radial passages 55 and 56, respectively, in check valve 52 and by the radial passages 51 in valve plunger 36.

Valve bore 21, whose opposite ends are closed and sealed by plugs 57 and 58, contains a check valve 59 and a by-pass valve 61 which control communication between the central bore portion 62 and the

cored passages

31 and 33, respectively. Check valve 59 is biased closed by a coil compression spring 63 and by the pressure in chamber 64 which communicates with cored passage 31 through the axial and

radial passages

65 and 66, respectively, formed in the valve. This valve is opened by the pressure in bore portion 62 which acts upon its nose 67. By-pass valve 61, on the other hand, is biased closed by a coil compression spring 68 and by the pressure in chamber 69, and is urged in the opening direction by the pressure in cored passage 33 which acts upon an annular reaction surface 71 at its right end which is bounded by its seat 72 and its outer periphery. Chamber 69 communicates with cored passage 33 through the axial and restricted radial passages 73 and 74, respectively, in valve 61, and with the chamber 41 through the passage in the valve housing. The flow restriction afforded by passage 74 is greater than that afforded by the passage 42 in plug 43. As will be apparent from the following description of operation, by-pass valve 61 opens automatically when the rate of flow of the fluid from port 24 to port 22 through the pilot path including chambers 41 and 69 reaches a predetermined value.

When directional control valve 14 is in its neutral position, each of the

motor ports

17 and 18 is isolated from the other and from both the pump and the tank 16. At this time, the components of valve 11 assume their illustrated positions and motor 12 is hydraulically locked. Since valve 14 usually is of the open center type, it establishes an unrestricted unloading path from pump 15 to tank 16. In order to raise blade 13, the operator shifts directional control valve 14 to its raise position in which the open center unloading path is closed and

motor ports

17 and 18 are connected with pump 15 and tank 16, respectively. The fluid delivered to valve 14 by pump 15 now flows to the head end of motor 12 via motor port 17, conduit 26, port 22, cored passage 32, annular chamber 32a, radial passages 49, axial bore 47, check valve 52, radial passages 51, cored passage 33, port 24 and conduit 28. Simultaneously, the rod end of motor 12 is vented to tank 16 through a path including conduit 29, port 25, cored passage 31, port 23, conduit 27 and motor port 18. Since the head and rod ends of motor 12 are now pressurized and vented, respectively, the motor lifts blade 13. During this operation, the

valves

36, 59 and 61 in valving device 11 remain in their illustrated positions. When the blade 13 reaches the desired elevation, the operator returns directional control 14 to its neutral position and thereby interrupts the supply and vent paths and again hydraulically locks motor 12. Check valve 52 in valving device 11 now closes.

Lowering of blade -13 is effected by shifting directional control valve 14 to its lower position in which the open center unloading path is closed and

motor ports

17 and 18 are connected with tank 16 and pump 15, respectively. Now the fluid delivered by pump 15 is transferred to the rod end of motor 12 through a supply path including motor port 18, conduit 27, port 23, cored passage 31, port 25 and conduit 29. Since conduit 26, port 22 and cored passage 32 are now connected with tank 16 through the directional control valve, the pressure in chamber 41 decreases. As a result, the supply pressure in cored passage 31, which acts upon the right end 45 of valve plunger 36, shifts the valve plunger 36 to the left and causes throttling notches 46 to open communication between annular chambers 32a and 33a. Oil displaced from the head end of motor 12 now may flow to tank 16 along a path including conduit 28, port 24, cored pas sage 33, annular chamber 33a, throttling notches 46, annular chamber 32a, cored passage 32, port 22, conduit 26 and motor port 17. Therefore, motor 12 commences to lower blade 13.

Oil displaced from the head end of motor 12 also can flow to tank 16 along a second vent path including restricted passage 74, axial passage 73, chamber 69, passage 75, chamber 41 and restricted passage 42. The oil flowing along this pilot path experiences a drop in pressure as it passes through restricted passage 74 and this pressure drop increases as the rate of flow increases. When the flow rate reaches a predetermined value, the pressure differential between cored passage 33 and chamber 69 develops a force on by-pass valve 61 which overcomes the bias of spring 68 and causes that valve to open. When this happens, some of the oil returning from the head end of motor 12 is diverted to the rod end through bore portion 62, check valve 59, cored passage 31, port 25 and conduit 29. The fluid transferred from the contracting to the expanding end of motor 12 through this by-pass path maintains the rod end of motor 12 liquidfilled, and, since the length of this transfer path is relatively short, it imposes little flow resistance. As a result, blade 13 can drop rapidly without risk of cavitation. The amount of oil which follows the by-pass path depends upon the capacity of pump 15 and the magnitude of the load exerted on motor 12 by blade 13. If the load is large and motor 12 tends to move at a rate considerably greater than that with which the pump can keep pace, the pressure in cored passage 31 will decrease and plunger valve 36 will shift to the right and cause notches 46 to throttle further the return flow to the directional control valve 14. This increases the pressure in cored passage 33 and causes by-pass valve 61 to open further. As a result, a greater portion of the oil displaced from the head end of motor 12 will be diverted to the rod end through the by-pass path defined by bore portion 62. On the other hand, under reduced load conditions, the pressure in cored passage 31 will rise and cause valve plunger 36 to move to the left and reduce the throttling effect at notches 46. In this case, by-pass valve 61 moves in the closing direction and causes less fluid to be transferred to the rod end of motor 12 through the by-pass path. It is thus apparent that the

valves

36 and 61 act together to split the return flow from motor 12 so that the expanding side of motor 12 always receives sufficient oil to prevent cavitation. Since the effective area of the head end of motor 12 is greater than the effective area of the rod end, the quantity of oil being returned to valving device 11 is always greater than that demanded by the rod end. Consequently, some oil always returns to tank 16 through the plunger valve 36.

It should be noted here that the lower position of directional control valve 14 is also used during digging operations. In this case, the blade 13 encounters considerable resistance to movement so the pressure in the rod end of motor 12 and in cored passage 31 is high. Therefore, valve plunger 36 assume-s its leftmost position, in which it opens fully the return path to valve 14, and the .by-pass valve 61 and check valve 59 close. Under this condition, maximum system pressure is available to force the blade 13 into the ground.

It might be mentioned here that since the chamber 41 at the left end of valve plunger 36 is in communication with the other fluid-containing spaces of valving device 11 only through restricted

passages

42 and 74, this chamber and the left end of valve plunger 36 form a dashpot. The provision of this dashpot tends to stabilize the action of valve 36 and thus minimize valve chatter.

-In the FIG. 2 embodiment, the improved valving device 11 is incorporated in a circuit including a four-position directional control valve 14 having a float position, and wherein the double-acting motor 12' is so arranged that its rod end is contracted by the load exerted by blade 13'. Valvin-g device 1 1' is identical to its counterpart in FIG. 1 except that the chamber 69 behind the :by-pass valve 61 is isolated from the chamber 41' at the left end of plunger valve 36' and is provided with an outlet connection in the form of a tapped port formed in plug 57'. In this embodiment, the bypass action of valve 61 does not take place automatically upon the occurrence of a predetermined flow rate, but is triggered manually by shifting the directional control valve to a selected position, in this case the float position. This is accomplished by providing in the directional control valve 14 a vent valve 76 .which includes an annular chamber 77 that is connected with port 7 5' by a conduit 78 and an annular exhaust chamber 79 which communicates with tank 16. The plunger 14a of valve 14 norm-ally isolates chamber 77 from exhaust chamber 79, but is provided with an annular groove 81 that spans these chambers, and thus vents chamber 69', when it is shifted to the float position.

When the directional control valve 14 of FIG. 2 is shifted to its lower position and pump 15 and tank 16 are connected with conduits 27' and 26, respectively, oil is delivered to the head end of motor 12' through a supply path including port 23', cored passage 31', port 25 and conduit 29'. The pressure in this path acts upon the right end 45 of plunger valve 36 and develops a force which shifts it to the left and causes throttling notches 46 to interconnect annular chambers 32a and 33a. Oil displaced fromthe rod end of motor 12' may now flo'w to tank 16 along a vent path including conduit 28', port 24', cored passage 33', annular chamber 33a, throttling notches 46f, annular chamber 32a, cored passage 32, port 22' and conduit 26'. Since vent valve 76 is closed, by-pass valve 61 remains in its illustrated closed position and prevents transfer of fluid from the contracting to the expanding side of motor 12. However, since plunger valve 36' is responsive to the pressure in the cored passage 31 and varies the restriction afforded by notches 46' in inverse relation to that pressure, the valving device 11 does maintain a positive pressure in the supply path leading to the expanding side of motor 12 and insures that motor 12 moves at a rate that does not exceed the capability of pump 15'. Thus, while the rate of movement of motor 12' in the lower position of valve 14' is less than the rate of movement of motor 12 in the lower poist-ion of valve 14, protection against cavitation is provided.

Quick dropping of the blade 13 in FIG. 2 is effected by shifting directional control valve 114' to its float position in which motor ports 17' and 18' are connected with each other and with both the pump 15 and the tank 16'. At this time, plunge-r groove 81 spans annular chambers 77 and 79 and opens a pilot path from chamber 69 to tank 16'. A small portion of the oil expelled from the rod end of motor 12 now flows through this pilot path and creates a pressure differential between cored passage 33' and chamber 69' which causes by-pass valve 61' to open against the opposing bias of spring 68. As a result, oil may now flow directly from the contracting to the expanding side of motor 12 through the bypass path defined by bore portion 62'. Because of the area differential between the rod .and head ends of motor 12, and the fact that pump 15' is unloaded in the float position of valve 14', all of the oil displaced from the rod end of motor .12, except that small portion flowing through the pilot path controlled by vent valve 76, may be required .to maintain the head end of motor 12 liquidfilled. Thus, it is possible that plunger valve 36' will assume a position in which land 38' interrupts flow to port 22. However, in the usual case, the back pressure imposed on pump 15 by the unloading path in valve 14' is high enough to cause a substantial part of the oil delivered by the pump to flow to motor 12. Therefore, in the normal case, the return fiow from the contracting side of motor 12' is split in the same way as in the bypassing operation of FIG. 1. In any event, valving device 1-1 permits motor 12 to move rapidly without risk of cavitation.

When directional control valve 14' is in its neutral position, the parts of valving device 11' assume their illustrated positions. Since chamber 69' is not connected with chamber 41', the load pressure in port 24 is not transmitted to port 22'. Therefore, unlike the valving device 11 of FIG. 1, valving device 11 afiords load drop protection and eliminates the need for a load drop check valve in directional control valve 14'. Thus, should supply pressure decrease, as a result, for example, of pump failure, when directional con-trol valve 14 is in its raise position, check valve 52' will close the only path between

ports

22 and 24 and prevent downward drifting of motor 12.

As stated previously, the drawings and description relate to the preferred embodiments of the invention. Since changes can be made in these embodiments 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 four ports;

(b) a valve bore intersected by two longitudinally spaced passages, there being a first passage which communicates with the first port and a second passage which communicates with the second port;

(0) a third passage interconnecting the third and fourth ports;

(d) a flow control valve reciprocable in the bore between first and second positions in which it closes and opens, respectively, communication between the first and second passages through the valve bore, the flow control valve carrying means which cooperates with the wall of the bore to throttle progressively said communication as the valve moves toward the first position;

(e) spring means biasing the flow control valve toward the first position;

(f) means defining a damping chamber in restricted communication with the second passage and enclosing one end of the flow control valve;

(g) means at the other end of the fiow control valve responsive to the pressure in the third passage for urging the flow control valve toward the second position;

(h) an internal passage in the fiow control valve intersected by first and second longitudinally spaced transverse passages that open through the outer periphery of the flow control valve and register with the first and second passages, respectively, when the flow control valve is in the first position;

(i) a first check valve located in the internal passage and arranged to prevent flow from the first transverse passage to the second transverse passage through the internal passage but to permit flow in the reverse direction;

(j) biasing means, including means responsive to the pressure in the first passage and a spring, urging the first check valve closed;

(k) a by-pass passage interconnecting the first and third passages;

v (l) a second check valve arranged to prevent flow from the third passage to the by-pass passage but to permit flow in the reverse direction;

(m) a control chamber having a restricted inlet connection leading to the first passage and an outlet connection;

(11) a by-pass valve controlling communication between the first passage and the bypass passage;

(0) spring means biasing the bypass valve closed; and

(p) means responsive to the pressure differential between the first passage and the control chamber for moving the by-pass valve in the opening direction.

2. A valve as defined in claim 1 wherein the outlet connection for the control chamber leads to said damping chamber; and the restricted inlet connection of the control chamber afiiords a higher degree of flow restriction than the restricted connection between said damping chamber and the second passage.

3. In combination (a) a valve as defined in claim 1; and

(b) a vent valve connected with the outlet connection of the control chamber and operable selectively to open and close this outlet connection.

References Cited by the Examiner UNITED STATES PATENTS 2,367,682 1/1945 Kehle 91-436 2,607,599 8/1952 Kanuch l37596.l2 2,704,087 3/1955 Lindsay 91-447 3,049,101 8/1962 Ruhl 91-420 M. CARY NELSON, Primary Examiner.

HENRY T. KLINKSIEK, Assistant Examiner.

Claims

1. A VALVE COMPRISING (A) A HOUSING CONTAINING FOUR PORTS; (B) A VALVE BORE INTERSECTED BY TWO LONGITUDINALLY SPACED PASSAGES, THERE BEING A FIRST PASSAGE WHICH COMMUNICATES WITH THE FIRST PORT AND A SECOND PASSAGE WHICH COMMUNICATES WITH THE SECOND PORT; (C) A THIRD PASSAGE INTERCONNECTING THE THIRD AND FOURTH PORTS; (D) A FLOW CONTROL VALVE RECIPROCABLE IN THE BORE BETWEEN FIRST AND SECOND POSITIONS IN WHICH IT CLOSES AND OPENS, RESPECTIVELY, COMMUNICATION BETWEEN THE FIRST AND SECOND PASSAGES THROUGH THE VALVE BORE, THE FLOW CONTROL VALVE CARRYING MEANS WHICH COOPERATES WITH THE WALL OF THE BORE TO THROTTLE PROGRESSIVELY SAID COMMUNICATION AS THE VALVE MOVES TOWARD THE FIRST POSITION; (E) SPRING MEANS BIASING THE FLOW CONTROL VALVE TOWARD THE FIRST POSTION; (F) MEANS DEFINING A DAMPING CHAMBER IN RESTRICTED COMMUNICATION WITH THE SECOND PASSAGES AND ENCLOSING ONE END OF THE FLOW CONTROL VAVLE; (G) MEANS AT THE OTHER END OF THE FLOW CONTROL VALVE RESPONSIVE TO THE PRESSURE IN THE THIRD PASSAGE FOR URGING THE FLOW CONTROL VALVE TOWARD THE SECOND POSITION; (H) AN INTERNAL PASSAGE IN THE FLOW CONTROL VALVE INTERSECTED BY FIRST AND SECOND LONGITUDINALLY SPACED TRANSVERSE PASSAGES THAT OPEN THROUGH THE OUTER PERIPHERY OF THE FLOW CONTROL VALVE AND REGISTER WITH THE FIRST AND SECOND PASSAGES, RESPECTIVELY, WHEN THE FLOW CONTROL VALVE IS IN THE FIRST POSITION; (I) A FIRST CHECK VALVE LOCATED IN THE INTERNAL PASSAGE AND ARRANGED TO PREVENT FLOW FROM THE FIRST TRANSVERSE PASSAGE TO THE SECOND TRANSVERSE PASSAGE THROUGH THE INTERNAL PASSAGE BUT TO PERMIT FLOW IN THE REVERSE DIRECTION; (J) BIASING MEANS, INCLUDING MEANS RESPONSIVE TO THE PRESSURE IN THE FIRST PASSAGE AND A SPRING, URGING THE FIRST CHECK VALVE CLOSED; (K) A BY-PASS PASSAGE INTERCONNECTING THE FIRST AND THIRD PASSAGES; (L) A SECOND CHECK VALVE ARRANGED TO PREVENT FLOW FROM THE THIRD PASSAGE TO THE BY-PASS PASSAGE BUT TO PERMIT FLOW IN THE REVERSE DIRECTION; (M) A CONTROL CHAMBER HAVING A RESTRICTED INLET CONNECTION LEADING TO THE PASSAGE AND AN OUTLET CONNECTION; (N) A BY-PASS VALVE CONTROLLING COMMUNICATION BETWEEN THE FIRST PASSAGE AND THE BY-PASS PASSAGE; (O) SPRING BIASING THE BY-PASS VALVE CLOSED; AND (P) MEANS RESPONSIVE TO THE PRESSURE DIFFERENTIAL BETWEEN THE FIRST PASSAGE AND THE CONTROL CHAMBER FOR MOVING THE BY-PASS VALVE IN THE OPENING DIRECTION.