US2689513A - Hydraulic control system - Google Patents

Description

P 1954 H. G. FERGUSON ETAL 2,689,513

HYDRAULIC CONTROL SYSTEM Fvyl HENRY GEORGE FERGUSON JOHN A4. CHAMBERS W. L /A M JOHN SANDS INVENTORS ATTORNEYS Sept. 21, 1954 H. s. FERGUSON ETAL 2,689,513

HYDRAULIC CONTRQL SYSTEM Filed March 3, 1948 3 Sheets-Sheet 2 N JOHN M. CHAM ERS W/LL/AM JOHN SANDS INVENTORJ ATTORNEYS Sept. 21, 1954 H. G. FERGUSON ETAL 2,639,513

HYDRAULIC CONTROL SYSTEM Filed March 3, 1948 3 Sheets-Sheet 3 HENRY GEORGE FERGUSON JOHN M CHAMBERS W/lL/AM JOHN SANDS INVENTORS A T TORNE Y5 Patented Sept. 21, 1954 UNITED STATES? PATENT OFFICE HYDRAULIC CONTROL SYSTEM Henry George Ferguson, Stow-on-the-Wold, and

John M.

Chambers, Leamington, Sp and William John Sands, Lisburn,

, England, Northern Ireland; said Chambers and said Sands assignors to Harry Ferguson Holdings Limited, Stow-on-the-Wold, England, a British company Application March 3, 1948, Serial No. 12,884

This invention relates to hydraulic control systems which comprise a source of pressurized fluid, for example, a pump, a load-sustaining or operating device actuable by fiuid from the said source,

and valve means whereby the fluid may be caused though the pump is continuously driven, it has the disadvantage that when the draft operates the control valve there will be a certain amount of lag before the pump actually begins to raise the implement in cases where the draft has increased, and the implement is to be correctively raised to the predetermined depth or draft. This lag is due to the fact that there is a vacuum inside the pump which has effective delivery of oil. There is also the further to be filled before there is disadvantage that when the control valve has again closed the'pump inlet as the implement draft or depth reaches thepredetermined value the pump will deliver its contents and will thus actually cause the implement to be raised too much and this may entail a or draft correction and so further cycle of depth on. An object of the invention is to obviate or mitigate the above disadvantages. Another object is to provide in a hydraulic system which includes a continuously driven pressure pump, a load-sustaining or actuating device actuable by pressure fluid from the pump and valve means controlling an admission port on the suction side of the pump and a discharge port ,whereby the fluidmay be caused to be admitted 'to and exhausted from the device; a vessel for pressure fluid, which is chargeable up to a predetermined pressure. from the pump and is connected to provide in the system a reserve supply of fluid under pressure.

In further accordance with theyinvention, we provide in a tractor a hydraulic control system for automatic depth or draft or position control of implements attached to the tractor which embodies a new anduseful, combination including a pressure fluid responsive, device, for example, a

ram, for lifting, lowering and supportingtheimplement on the tractor, valve means'controlling admission and release port means forsaid device 4 Claims. (Cl. 97-46207) and movable in accordance with the depth of cut of the implement or its position relative to the tractor to admit or release fluid to or from the device respectively as the implement goes deeper or shallower with respect to a desired depth or as the implement moves in either direction away from a predetermined position relatively to the tractor, and means containing fluid under a pre- I determined pressure for supplying the fluid to said valve means so that on opening thereof there is instantaneous admission of pressure fluid to the device.

More particularly stated, another object of the invention is to provide a new and improved hydraulic control system for an agricultural tractor or the like having a fluid-operable actuatingor load-sustaining device for a soil-engaging or agricultural implement to be controlled, valve means movable under the opposed influence of balance means, such as, a. spring and the soil pressure or draft on the implement to admit or release fluid to said device automatically to maintain said implement at a predetermined depth or draft, and a source of pressurized fluid which includes a chamber or container for the fluid, a pump or the like for supplying fluid to said chamber and a control member, for example, a valve on the admission side of the pump, which is operable by the pressure in said chamber to put the pump automatically into or out of effective operation to maintain the fluid at a predetermined pressure in said chamber.

While the invention is susceptible of various modifications and. alternative constructions, a preferred embodiment has been shown in the drawings and will be herein described in some detail, but it is to be understood that there is no intention to limit the invention to the specific form disclosed, the intention being, on the contrary, to cover all modificationsand alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Fig. 1 is an elevation of a known tractor with plow attached and controlled by a hydraulic system embodying the features of the invention, the near rear wheel being omitted for the sake of clarity.

Fig. 2 is a sectional view taken longitudinally of the rear end of the tractor and showing on an enlarged scale a control system embodying the invention.

Fig. 3 is a sectional elevation to a further enlarged scale showing the valve arrangement of the system.

Figs. 4 and 5 are sectional views respectively on the lines 44 and 5-5 of Fig. 3.

Fig. 6 is a diagrammatic view of the hydraulic circuit.

Referring especially to Fig. 1', the tractor is of known type embodying the Ferguson System of. a hitch linkage and an implement hydraulic control system operating on the principle set forth in said prior patents. The tractor comprises a body housing i and the usual rear ground wheels 2, the nearer wheel being omitted for clearness. The link.- age system comprises an upper compression link 3 and two laterally spaced lower draft links 4, the links being triangularly spaced and universally attached to the tractor and implement. The tractor embodies a hydraulic system, described later, which operates two cranks E on the cross shaft 5A and serves to raise and lower the links A through the drop links 6A and thus raise and lower the implement. As shown, the implement is a plow but it may be any agricultural or other implement adapted to be attached to the links.

The known hydraulic system includes an oil ram consistin of a cylinder 6 to which oil under pressure can be supplied under control of valve means from a pump 28 which may comprise a piston or pistons 20A (Fig. 6) actuated by an cecentric or' eccentrics 25213 which are continuously driven by a shaft ZG'C iron the tractor engine. The cylinder contains a ram or piston l connected to the crank 5. Admission of oil moves the. pistonv to the right (as seen in Fig. 2) and raises the linkage while release of oil allows the implement to lower under its own weight. The system can becontroll'ed both by the operator or automatically by the implement itself to maintain the implement at a predetermined depth. Briefly the control mechanism comprises a duplex floating lever 8, substantially similar to that disclosed in prior patent No. Re. 22,642, pivoted at 9 on the. yoke or'stirrup lil connected to the rod H which in turn is. connected to the top link 3 through a rocker or bell crank 3A. The upper end of the lever B ismaintained by the tension spring 12' against. an eccentric it which is under control of the control handle I' l (Figs. 1 and 2) actuable by the operator; To raise the link (and an implement carried thereby) to the position shown in Fig; 2 the handle is moved to the position. shown so as to move. the eccentric l3 to rotate the lever clockwise aboutthef pivot 9. This allows a valve means connected with the lower end of the lever 8'to be moved by spring l2; from its neutra position, which the oil supply to the pump is cut off and the oil is trapped in the-cylinder, to an intakepositionfor admitting oil' to. the cylinder. The upward. limit of lift is. determined. by projections. it on. the lever 8 which are engaged by the ram 1 as it moves out of the cylinder to rotate the lever 8 counterclockwise to cut off the supply of. oil by moving the valve means back to its neutral position.

Automatic control of the depth is effected through the top-link 3, rod. H and yoke Ill. If the implem nt goes too deep or too shallow the increased or decreased draft further corn-presses a'balance spring it (arranged to resist inward movement of the rod I!) or allowsit to expand and the lever 8 is: swung clockwise or counter clockwise about its top end to cause admission or. release of oil and raising or lowering ofthe implement. Such. implement movement in turn reduces or increases the draft and causes the balance compression spring ll to extend or be compressed and swing the lever 8 counterclockwise or clockwise until the valve means again reaches the neutral position. The above briefly described arrangement is well known, the valve means being arranged on the suction side of the pump to avoid continuous pumpin of the oil.

A system embodying the present invention is shown diagrammatically in Fig. 6. A main control' valve 21, which is responsive to variations in implement draft, is located in the delivery line 22 from the pump. A pressure fluid accumulator 26 is also in communication through line 722A- with the line 22 on the pump side of the valve. The inlet port 23 to the pump, which is located on the suction side thereof, is controlled by a piston valve 24 which is under the opposed influence or control of a resilient resistant, such as a spring 25, and the pressure (through line 48) of the fluid in the pressure fluid accumulator 25'. To this end,v the valve 2 is engaged by a piston plunger 2 3A which constitutes a member connected so as to be continuously subjected to fluid at the pressure prevailing at'the discharge side of the pump, the plunger 24A being slidable in a bore to which the line 48 is connected. The accumulator as mentioned above, connected to the delivery side 21' of the pump. and also to the admission side ii! of the implement-controlled valve 21. It may consist of a device wherein the stored fluid is pressurized for subsequent delivery by entrapped air or by spring means. The pump has the usual inlet and outlet non-return valves 29,

The actual construction of the arrangement is shown more clearly in Figs. 2'to 5. This construction uses the existing pumpand associated castlllg 26D with its existing passages as at present in use on tractors sold under the trade-mark Ferguson.

The duplex lever 8 is connected by links 3| to a fork 32 mounted between its ends'to' rock on a bracket 33and' pivotally connected at its lower end to a link 34 which is pivoted to the valve 2!. The valve 2| in this instance comprises a central cylindrical part and two frusto-conical end parts (see Fig. 3'), the central part cooperating with one or more radial ports 35 in a bushing 31 communicating with an annular chamber 36 which is connected by the conduit 38 (Figs; 2 and 6) with; the cylinder 6. The valve has a tailpiece 39 thereon cooperating with the bushing 3-1 to define an annular transfer passage 39A which communicates through ports 40 with an annular chamber 4| which is connected to the pump delivery and the accumulator through the conduit 22- and distributor connection 22A.

The pump. valve 24 is located below the valve 2| in a bushing 42 and is adapted to control a port' 23' which is connected by a passage in the casting 20D to the pump through pump: inlet valve 29 (see Fig. 6). The valve 24 has a plurality of openings 43 (Fig. 3) bored therein and the reduced diameter plunger 24A is attached thereto for sliding movement in a bore passage 44 in a plug 45 which is screwed into and closes oneend of the bushing 4-2. Radial passages- 46 connect vthepassage 44 with an annular chamber'fl which in turnis connected by the conduit with the accumulator 26. The spring 25 bears against the end of the'valve opposite the plunger 24A and against a pin 42A disposed crosswise of'the bushing 42. The valve 24' is thus subject on; the: one end to the force of the pressure ex.- isting in the accumulator, which force is; op-

posed bythat of the compression spring 25. The valve is located in an oil sump 49. In the event the pressure in the accumulator falls below a predetermined value, the spring 25'wil1'move the valve 24'to the right (as viewed in Figs. 2

and 3) to open port 23 and admit fluid through .the open end of the bushing 42 to the intake valve 29 on the suction side of the pump. 1 Ports 50 may be provided in the bushing to allow free movement of the valve and also to allow inflow of and lower parts adapted to break in jackknife fashion if it is rotatedmore than the stop 5| will allow. l V l The accumulator or pressurizing device 26 is of the well known type and need not be fully described. The form shown consists of a sphere containing a resilient diaphragm 52 dividing the sphere into an oil chamber 53 and an air-trap chamber 54 having a loaded air-admission valve 55 whereby any desired initial air pressure may be attained. An alternative known form may consist of a cylinder divided into oil and air chambers by a piston and a further known alternative may consist of an oil vessel containing a collapsible air sac.

With the arrangement herein shown and described, the continually-running pump 20 will deliver oil to the accumulator 26 past valve 30 and through lines 21, 22A and 48 until the pressure rise is sumcient to close valve 24 against the force of spring 25. l The valve 24 is of course open whenever the line pressure is down. While the system is under accumulated pressure with both valves 24 and 2| closed, the pump will run idly under substantially no load, yet a supply of fluid under pressure will be available in chamber 39A at opened. Wheneverthe line to the ram is opened by movement of valve 2| from its illustrated neutral position (Fig. 6) to connect lines 22 and 38 through chamber 39A, the accumulated pressure fluid will supply the ram during the relatively brief lag preceding the delivery of fluid directly thereto from the pump. Such movement of the valve 2| will, of course, be in response to a shift of the control lever and linkage 8, 3|, 32 which follows either the operation of the control system when the implement goes too deep and draft increases or a manual operation of the control system to raise the hitch links 4 and an implement thereon. Consequently, the system will be instantaneously actuated without lag. Moreover, there will be no over-delivery of fluid to the ram since when the valve 2| closes port 35 (as when the control system is automatically restored to its preset balanced condition or when the valve is moved'to neutral by the engagement of lugs IS on lever 8 by the end of the piston 'I), the pump will then supply fluid to the accumulator until the pressure rise in that portion of the system closes valve 24 to prevent further delivery of fluid to the pump.

When the system is reversely actuated to exhaust fluid from the ram for lowering the hitch links and implement, the valve 2| is shifted to the left (Fig. 6) from its neutral position either automatically or manually. Fluid then flows from the ram through line 38 and the righthand end of bushing 31. The accumulated pressure fluid remains available since the portion of valve 2| for use the instant t he valve 2| is I 6 the system in which it is stored is not affected by the movement of the valve 2| to exhaust fluid from the ram. It will be noted that the accumulator system will replenish automatically any incidental leakage since resulting pressure loss thereinwill allow valve 24 to move and open the pump supply line. T

It will also be understood that the accumulator system may be used to provide an immediately available supply of pressurized oil, for example, through a branch conduit48A (Fig. 6) for actuation of auxiliary devices, for instance, for lifting and lowering an implement mounted'at the front of the tractor and which may be subject to automatic depth control as above described. f 3

The capacity of the accumulator and the pressure on the fluid in that systemmay be varied in accordance with requirements and it will be understood that in some cases there need be no especially large accumulator vessel, the minimum requirement being a pressurizing device between the pump delivery and the implement controlled valve which has suiflcient capacity to deliver enough pressurized fluid to maintain an actuating pressure until the pump has filled and is effectively deliveringthe oil.

It is to be understood that the above more specific embodiments'have been'described merely by way of example and that modification may be made without departing from the scope of the invention.

In the event of the implement striking an obstruction, the consequentl excessive movement of the lever 8 swings the projections 15 into contact with the cylinder 6 sothat the swinging movement of the lever is reversed to an anticlockwise movement as disclosed in said prior Patent No. Re. 22,642. The valve-2l is thus moved to the left to allow dis'chargeof oil from the cylinder 6, through the ports 35 and the righthand end of the bushing 31 into the sump 49. Thus the present invention admits of the overload release eifect as disclosed in the prior Patents Nos. 2,118,181 and Re. 22,642.

The invention is also applicable to hydraulic systems wherein the implement automatically controls the system to maintain the implement in a predetermined position with reference to the tractor as distinct from the above-described load or depth control. An example of such system is disclosed in a copending application filed by Ernest V. Bunting, Serial No. 712,125, new Patent No. 2,632,628.

We claim as our invention:

1. A hydraulic control system for an agricultural tractor or the like which comprises the combination of a fluid-operable actuating or loadsustaining device for a soil-engaging or agricultural implement which is to be controlled, valve means movable progressively to admit fluid to or release it from said device at a rate proportioned to the degree of movement thereof to correctively restore said implement to a predetermined depth or draft, and a source of pressurized fluid for actuating said load-sustaining device which includes a container for pressure fluid, a continuously driven pump, connections between said container, the discharge side of said pump and said valve means for supplying fluid from said pump to said container and said device simultaneously, or for supplying pressure fluid to the device from the container and pump simultaneously, and control means on the admission side of the pump responsive to the pressure either fluid in said container to put the pump automatically into or out of effective operation to maintain the fiuidat a predetermined pressure in. said container.

2. In. a hydraulic system for effecting an accurately proportioned response to displacement of a control member, the combination of a continuously driven pump, a single acting hydraulic actuator operable against a load by fluid supplied from said pump, a first control valve interposed between said actuator and the discharge of. said pump, said valve having relatively slidable plunger and housing elements with a port in. the'latter connected to said actuator, said elements being operatively associated with, the displaceable control member and relatively slidable thereby from a neutral position, in which said plunger substantially blocks said port, in opposite directions from such neutral position to open said port respectively to the discharge of said pump and to drain and with a progressive opening of said port in each direction, a second control. valve arranged to open and close the intake of said pump, said second control valve being spring biased to open position, and a fluid pressure operated member connected so as to be continuously subjected to fluid at the pressure prevailing at the discharge side of said pump and mechanically connected to said second control valve to close the latter against the influence of its spring bias in response to the establishment of a predetermined pressure head at the discharge side of the pump irrespective of the position of the first-control valve. I

,3. A system as set forth in claim 1, in which means is provided for supplying fluid out of the system to an auxiliary actuator or the like from a point intermediate said valve means and the discharge of said pump.

4-. In a hydraulic control system for a tractor having a trailing implement hitch, a single acti-ng hydraulic actuator for raising and lowering the hitch with an implement attached thereto and a'control member displaceable in proportion to the draft load onthe hitch, the combination. of a continuously driven pump connected for sup:- plyingj fluid under pressure to the. actuator, a first control valve interposed between said actuator and the discharge of said pump, said' valve having relatively slidable plunger and housing elements with a port in the latter connected to the actuator, said elements being, operatively as sociated with the displaceable control member and relatively slidable thereby from a neutral position, in which said plunger substantially blocks said port, in opposite directions from such neutral position to open said port respectively to the discharge of said pump and to drain andwith a progressive opening of said port in each direction, a second control valve arranged to open and close the intake of said pump, said second control valve being. spring biased to open position, and a fluid pressure operated member connected so as to be continuously subjected to fluid at the pressure prevailing at the discharge side of said pump and mechanically connected to. said second control valve to close the latter against the influence of its spring bias in responseto the establishment of a predetermined pressure head at the discharge side of the pump, irrespective of the position of the first control valve.

References Cited in the file of this patent UNITED STATES PATENTS Clark Sept. 5, 1,950

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