US3205788A - Control valve devices for hydraulic rams - Google Patents

Description

Sept. 14, 1965 J. E. LIMBRICK I CONTROL VALVE DEVICES FOR HYDRAULIC RAMS Filed June 11, 1962 mml United States Patent 3,205,788 CONTROL VALVE DEVICES FOR HYDRAULIC RAMS John Ernest Limbrick, Swindon, England, assignor to The Plessey Company Limited, Ilford, England, a British company Filed June 11, 1962, Ser. No. 202,644 6 Claims. (Cl. 91-419) This invention relates to the control of the operation of a hydraulic ram cylinder and has for an object to provide an improved control valve device in which the rate of operation of the ram is variable in accordance with the position of a control valve element and is independent of variations in the ram load.

According to the present invention the valve device comprises a valve element adapted to open, when moved from its neutral position, a metering aperture for the flow to or from a ram cylinder in such manner that the aperture increases progressively with the displacement of the valve, and a spring-loaded flow valve controlling a variable aperture determining a return flow for excess fluid supplied, said flow valve being acted upon in such manner by the pressure drop in said variable aperture of the control valve as to keep said pressure drop constant by variation of said return flow.

Preferably the valve element is arranged to progressively open, according to the direction in which it is moved from its neutral position, separate flow paths including separate variable metering apertures respectively for the flow from the source to the ram cylinder and for the return flow from the ram cylinder during the return stroke of the latter, a separate flow valve being provided in each of the two paths. A restricted orifice is preferably interposed in the connection between the down-stream side of the metering aperture and the spring-loaded side of the supply-controllingflow valve, a safety release pilot valve being arranged at a point between said restricted orifice and the spring loaded side of the flow valve.

According to another aspect of the present invention the pressure drop across an adjustable metering port controlling the admission of liquid from a supply line leading from a constant rate source a hydraulic cylinder is maintained substantially constant by a spill valve actuated by a piston element which is spring-loaded to the closed position, and the two sides of the piston element being respectively acted upon by the pressures on the upstream and downstream sides of said adjustable port, the downstream pressure being admitted to the piston element by a restricted passage, and auxiliary pilot valve means being provided which vent the latter side of the piston element when a physical feature of the hydraulic liquid reaches a safety limit.

Preferably a non-return valve is interposed 'betweensaid adjustable port and the hydraulic cylinder, and a piston controlled discharge-control valve, spring biased to the open position is interposed in a discharge line between the cylinder and an adjustable discharge-control port to prevent the pressure at the upstream side of said dischargecontrol port from exceeding a predetermined value.

The accompanying drawing is a somewhat diagrammatic elevation partly in section, showing the device as applied to the hydraulic implement lift-cylinder of an implement supporting agricultural or horticultural tractor.

Referring now to the drawing, a hydraulic ram cylinder 1 contains a piston 2 which is coupled by a piston rod 3 to the lift arm 41 of an implement-supporting system provided on a tractor. A flow of liquid supplied at a connection 4 from a positive-displacement pump 32 is made available for application to the cylinder 1 by a control valve A which comprises a valve element 6 operating in 3,205,788 Patented Sept. 14, 1965 a cylindrical bore 7 of a valve housing 5. Both ends of the bore are open to low pressure, for example to the inlet sump 33 of the hydraulic pump 32. The valve element 6 has two annular recesses 8 and 9, of which the former communicates permanently with the pressure inlet 4 while the recess 9 is drained to low pressure through a passage 10 leading to one of the end surfaces of the valve element. The bore 7 of the valve housing has two enlarged portions forming annular chambers 11 and 12 which respectively communicate with two pipelines 13 and 14. When operative according to the position of the valve element 6, pipe line 13 will admit liquid from pump connection 4 to the cylinder 1 While pipe line 14, when operative, will release pressure fluid from the said cylinder to the low-pressure outlet. To control the rate of flow in these two cases, the annular recess 8 is formed with a tapered extension 15 decreasing in radial depth from the recess 8 towards the chamber 11, and the end of valve element 6 adjacent to chamber 12 is tapered as shown at 16. When the implement-supporting arm 41 is to be raised by piston 2 in response to operation of a manual control element 34 in the direction of arrow 35 or to a feed-back impulse provided by a cam 36 on arm 41 or by the movement of a draught measuring element 37 loaded by a spring 44 a floating lever 38 being provided for transmitting all these impulses to the valve element 6, the valve element 6 is displaced in the direction of arrow 17 by an amount determined by the magnitude of the displacement of the control element or by the magnitude of the pulse received, and the tapered extension 15 of the recess 8 will accordingly overlap to a greater or smaller extent the adjacent edge of the chamber 11 of the valve housing, thus allowing hydraulic liquid, at a rate determined by the amount of displacement of the valve element, to flow from liquidsupply inlet 4 to pipe line 13 and from there, via a non-return valve 18 and a service-selector valve 19 (which will be assumed to be premanently in the illustrated position) to ram cylinder 1.

In order to ensure that the rate of flow through the metering port established between extension 15 and chamber 11 is independent of the load acting on piston rod 3, a flow valve is provided which has a transversely subdivided valve sleeve 20 the cylindrical wall of which is provided with ports 21 open to pressure inlet 4 which control, according to the position of the valve sleeve, a return flow from pressure inlet 4 to a low-pressure exhaust 22. The flow valve is urged towards its illustrated closed position by a spring 23 and towards its open position by the pressure drop between recess 8 and the chamber 11 of valve 5, 6, i.e. between the inlet pressure which acts on valve sleeve 20 against the pressure of spring 23, and the pressure from line 13, which, after passing through a restriction 25, admitted by a passage 24 to the other side of the sleeve 20 to assist the action of spring 23. The rate of spring 23 is made relatively low, so that displacement of the valve sleeve 20 from the position in which ports 21 are closed to the position in which they are fully open will only involve a small increase in the pressure of spring 23; as a result the flow valve will cause so much of the pressure fluid supplied at 4 to be spilled from ports 21 that the pressure drop from chamber 8 to chamber '11 is equal to the loading of the spring 23. If, when the piston 2 has reached the end of its stroke so that it can move no further, valve 6 still remains in the implement-raising position, no more liquid can flow through line 13 to the cylinder 1, and since the outlet via ports 21 is closed, the pressure at both sides of valve 20 will tend torise. In order to limit this rise, a pressure responsive safety-release pilot valve 26 is arranged to co-operate with the chamber at that side of the flow-valve 20 which assists the action of the spring 23, this relief valve being set to open at a pressure just above the maximum pressure desired to act upon piston 2. When the pilot valve 26 opens, the restriction 25 produces a pressure difference between the two sides of the valve 20, so that the latter will open and allow the liquid delivered by the pump 32 to return to the sump by the exhaust port 22,

In order to avoid the risk of an undue rise in the temperature of the hydraulic medium, should discharge under maximum-pressure conditions take place for a considerable time, a temperature responsive further pilot valve 40, actuated for example by an expansion capsule 42, is arranged in parallel to the relief valve 26. This will cause free discharge of the liquid through ports 21 of flow valve 20 when the temperature of the liquid reaches a predetermined value.

When the control valve element 6 is in its illustrated neutral position, the extension 15 of recess 8 does not reach the chamber 11, and no flow from pressure inlet 4 will reach chamber 11, while on the other hand chamber 11 communicates with the recess 9 so that line 13 is drained through passage 10 of the valve element 6. Full pressure from inlet 4 will therefore act on the valve sleeve 20 to compress spring 23, and since the action of this spring is no longer assisted by any pressure in line 13, the valve 20 will fully open its ports 21 and allow the liquid delivered by the pump 32 to return to low pressure with minimum resistance. It will be appreciated that the drain connection from vannular chamber 11 to recess 9 is closed when valve element 6 is moved from the illustrated neutral position in the direction of the arrow 17 to raise the implement.

When the valve element 6 is moved from its neutral position in the opposite direction to lower the ram, line 13 remains drained via recess 9, but the escape of liquid from cylinder 1 via line 13 is prevented by the non-return valve 18. On the other hand the tapered end portion 16 of the control-valve element 6 will co-oper-ate with the edge of annular chamber 12 to establish a drain orifice or restricted drain outlet from chamber 12. This outlet will increase in cross-section according to the amount by which valve 6 is displaced, and it allows liquid from cylinder 1 to escape past selector valve 19 through line 14 and the said variable drain outlet orifice at a rate determined by the amount by which the valve 6 has been displaced. In order to render the rate of this escape independent of the load acting on piston rod 3, a second flow valve is provided having a divided valve sleeve 28 of similar construction to valve sleeve 20 and the ports 29 of sleeve 28 are, in the illustrated normal position of the valve, fully opened to an annular chamber 30 which communicates with the cylinder 1 via the selector valve 19. The flow valve 28 is urged to its illustrated open position by a spring 31, against which the valve is urged by the pressure acting in line 14. The opposite side of the flow valve sleeve 28 communicates with low pressure by a restricted line 39, so that in practice the pressure difference acting upon the valve sleeve against the spring 31 is equal to the pressure drop from chamber 12 to low pressure via the tapered portion '16 of the valve 6. Any tendency of this pressure drop to increase above the value determined by the setting of spring 31 and thus any undesired rise in the rate at which the implement arm 41 is lowered, or permitted to be lowered, by the ram 1, 2, will therefore be countereacted by partial closing of the ports 29 in the path of the liquid flowing via line 14 to chamber 12.

The change-over valve 19 enables the hydraulic power from pump 32 to be selectively directed to operate some auxiliary hydraulic ram or the like, generally referred to as external service, connected to a service port 45. .When the valve element 19 is in the illustrated position,

it connects a line 43 leading to the implement-arm actuat- .ing cylinder via non-return valve and line 13 to the annular chamber 11 of the valve device A and via flowvalve ports 29 to discharge-control line 14, while isolating the external service port 45. By moving the valve element 19, this condition can be reversed, isolating service line 43 and establishing communication, via non-return valve 18, between external-service port 45 and line 11, and via flow valve ports 29, between port 45 and dischargecontrol line 14.

It will be evident to those skilled in the art that some details of the embodiment described and illustrated may be varied Within the scope of the invention. Thus instead of providing a tapered extensionlS to the recess 8, the recess 8 may be made without an extension if chamber 11 is instead provided with an extension tapering towards the edge of recess 8.

What I claim is:

1. A control valve device for the supply of liquid from a constant-rate source of liquid to a hydraulic ram cylinder and the release of liquid from such cylinder, said con trol valve device comprising a valve element which, when moved in one or the other of two opposite directions from a neutral position, respectively opens a variable metering aperture controlling a first flow path for the flow from said source to the ram cylinder and a variable metering aperture controlling a second flow path for the release of liquid from the ram cylinder, each said flow path being, for at least part of its way between said ram cylinder and the respective variable metering aperture, separate from the other flow path, a spring-loaded spill valve controlling a variable spill aperture from such separate part of said first flow path and arranged to be urged to an open position against its spring loading by the pressure drop in the metering aperture of the first flow path so as to keep said pressure drop constant by variation of the flow through said spill valve, and a springloaded throttle valve controlling a variable throttle aperture in such separate part of said second flow path, said throttle valve being arranged to be urged towards a closed position against its spring loading by the pressure drop in the metering aperture of the second flow path so as to reduce the effective size of said throttle aperture in response to an increase in said last-mentioned pressure drop.

2. A control valve device as claimed in claim 1, wherein a restricted orifice is interposed in a connection between the downstream side of the metering aperture of the first flow path and the spring-loaded side of the supply-controlling spill valve, the valve device further including a safety release pilot valve communicating with the spring loaded side of the spill valve independently of said restricted orifice.

3. A control valve device as claimed in claim 2, further comprising a second pilot valve connected to the springloaded side of the fiow control valve, and a heat sensitive control member causing said second pilot valve to vent the spring-loaded side of the flow control valve when the temperature rises above a predetermined level.

4. A control valve for the supply of liquid from a constant-rate source of liquid to a hydraulic ram cylinder and cylinder and the respective .variable metering aperture,

separate from the other flow path, a spring-loaded spill valve controlling a variable spill aperture from such separate part of said first flow path and arranged to be urged to an open position against its spring loading by the pressure drop in the said first metering aperture so as to keep said pressure drop constant by variation of the fiow through said spill valve, and a spring-loaded throttle valve controlling a variable throttle aperture in such separate part of said second flow path, said throttle valve being arranged to be urged towards a closed position against its spring loading by the pressure drop in the said second metering aperture so as to reduce the effective size of said throttle aperture in response to an increase in said lastmentioned pressure drop.

5. In a device for the raising and lowering of a tractordrawn agricultural or horticultural implement by means of a hydraulic ram cylinder, the combination comprising a ram cylinder and a control valve device as claimed in claim 4.

6. A control-valve device for the supply of liquid from a constant-rate source of liquid to a hydraulic ram cylinder and the release of liquid from such cylinder, comprising a control-valve forming an adjustable metering port for the admission of liquid from a supply line leading from a constant-rate source to a hydraulic cylinder, a spill valve actuated by a piston element which is spring-loaded to the closed position, the two sides of the piston element being respectively acted-upon by the pressures on the upstream and downstream sides of said adjustable port, the downstream pressure being admitted to one side of the piston element by a restricted passage, auxiliary pilot-valve means which vent the said one side of the piston element when a physical feature of the hydraulic liquid reaches a safety limit, a non-return valve interposed between said adjustable port and the hydraulic cylinder, and a piston-controlled discharge-control valve spring-biased to the open position and interposed in a discharge line between the cylinder and an adjustable discharge-control port to prevent the pressure at the upstream side of said dischargecontrol port from exceeding a predetermined value.

References Cited by the Examiner UNITED STATES PATENTS Re. 24,006 5/55 Acton 91-447 1,964,196 6/34 Cuttat 91-448 2,102,865 12/37 Vickers 137-501 2,236,700 4/41 Slater 91-419 2,328,979 9/43 Herman et a1. 91-447 2,373,773 4/45 Mercier 91-419 2,785,861 3/57 Kimm et al 236-92 2,856,900 10/58 Bosshard 91447 2,868,460 1/59 Hansen et a1. 236-92 2,964,908 12/60 Pomper et al. 9l-447 3,010,437 11/61 Andre 91-419 3,088,283 5/63 Furia et a1. 91-447 SAMUEL LEVINE, Primary Examiner.

FRED E. ENGELTHALER, Examiner.

Claims (1)

1. A CONTROL VALVE DEVICE FOR THE SUPPLY OF LIQUID FROM A CONSTANT-RATE SOURCE OF LIQUID TO A HYDRAULIC RAM CYLINDER AND THE RELEASE OF LIQUID FROM SUCH CYLINDER, SAID CONTROL VALVE DEVICE COMPRISING A VALVE ELMENT WHICH, WHEN MOVED IN ONE OR THE OTHER OF TWO OPPOSITE DIRECTIONS FROM A NEUTRAL POSITION, RESPECTIVELY OPENS A VARIABLE METERING APERTURE CONTROLLING A FIRST FLOW PATH FOR THE FLOW FROM SAID SOURCE TO THE RAM CYLINDER AND A VARIABLE METERING APERTURE CONTROLLING A SECOND FLOW PATH FOR THE RELEASE OF LIQUID FROM THE RAM CYLINDER, EACH SAID FLOW PATH BEING, FOR AT LEAST PART OF ITS WAY BETWEEN SAID RAM CYLINDER AND THE RESPECTIVE VARIABLE METERING APERTURE, SEPARATE FROM THE OTHER FLOW PATH, A SPRING-LOADED SPILL VALVE CONTROLLING A VARIABLE SPILL APERTURE FROM SUCH SEPARATE PART OF SAID FIRST FLOW PATH AND ARRANGED TO BE URGED TO AN OPEN POSITION AGAINST ITS SPRING LOADING BY THE

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