US2673528A - Pump valve actuation - Google Patents

Description

March 1954 A. SENKOWSKI ET AL PUMP VALVE ACTUATION 4 Shets-Sheet 1 Filed Nov. 10. 1949 INVENTOR! March 30, 1954 A. SENKQWSKI ET AL PUMP VALVE ACTUATION 4 Sheets-Sheet 5 Filed Nov. 10. 1949 INVE M EXANDER SE n// ram cum/0c BY NTORS' KOWSK/ March 1954 A. SENKOWSKI ET AL PUMP VALVE ACTUATION 4 Sheets-Sheet 4 Filed NOV. 10, 1949 INV RS SEN AZ [FYI/V059 w/rom c224 BY 6M Patented Mar. 30, 1954 2,673,528 PUMP VALVE AoTUarIoN Alexander Senkowski, Earlsdon,

Coventry, and

Witold Czarnocki, Coventry, England, assignors to Harry Ferguson, Limited, Coventry, England Application November 10, 1949, Serial N 0. 126,603 Claims priority, application Great Britain November 19,

4 Claims. g l

The invention relates to improvements in the control of power operated systems for tractor hitch linkages and more particularly to systems of the pressure fluid, operated type in which the operation is controlled by means of a valve actuated in response to changes in thedraft or other force imposed on the hitch linkage. The basic principles of such a system are disclosedin the Ferguson Patent No. 2,118,180, issued May 24, 1.938.

In systems of the above general character, a pump driven from the tractor engine supplies pressure fluid such as oil under control of a plunger type ,valve to a hydraulic ram operatively associated with the hitch linkage. The valve plunger is arranged, within a casing for axial movements relative to a series of ports opening through the walls of the casing to regulate or interrupt the flow of pressure fluid through the ports. At times therefore the sides of the valve plunger are subjected to substantial pressure, often on the order of two thousand to three thousand pounds per square inch. At such high pressures there is a tendency for the valve plunger to stick, due apparently to fluid creeping around one side of the plunger and pushing it into an eccentric results in a breaking of the oil film and allows metal-to-metal contact between casing with consequent sticking of the plunger; Such sticking is especially undesirable in systems of the type under consideration since the automatic depth or draft control for which they are commonly used calls for frequent and instantaneous movement of the control valve in response to changes in the forces imposed on the linkage.

The object of the present invention is to provide a simple, inexpensive and highly effective arrangement for preventing the sticking of the control valve plunger in pressure fluid operated systems of the above general character.

Other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiments illustrated in the accompanying drawings, in which:

Figure 1 is a sectional view through the center housing of a tractor equipped with a power operated system and controls embodying the features of the invention.

. Fig. 2 is a vertical sectional view through the pump and control valve of the system.

Fig. 3 is a sectional view taken in oiT-set vertitical planes substantially on the line 33 of Fig. 2.

Fig. 4 is a sectional view of a modified form of control mechanism.

position in the casing. This the plunger and been incorporated in a 2 For purposes of illustration the invention has lightweight tractor similar to that disclosed in the Ferguson Patent No. 2,118,180 above referred to. At the rear end of the tractor is mounted a hitch linkage of the type shown in that Ferguson patent comprising a pair of lower hitch links I0 (Fig. 1) and a top link II. The lower links are arranged side by side and their forward ends are pivotally secured as at l2 to the rear housing l3 0f the tractor A for vertically swinging movement about a transverse horizontal axis below and slightly forward of the axis of the rear axle [4 of the tractor.

The pivots l2 permit lateral swinging of the hitch links as well as vertical swinging movement.

The top link II is secured for universal pivotal movement at its forward end to the rearwardly of pressure on projecting arm on a rocker or clevis l5 pivoted on the housing l3. Forward thrust on the top link ll tends to swing the rocker IS in a clockwise direction as viewed in Fig. 1, while relief the top link tends to permit it to retreat rearwardly under the thrust of a control spring [6.

Raising and lowering of the hitch links 10 and the implement attached thereto are effected by a hydraulic power unit including a one-way ram comprising a cylinder l1 suitably supported in the housing [3. The cylinder I! opens to the rear of the tractor and working therein is a piston l8 having arod l9 projecting rearwardly and received in the socketedlower end of an arm 20 rigid with a transverse rockshaft 2| journalled in the upper rear portion of the housing. The rockshaft 2| is fitted with radially projecting crank arms 22 connected with the hitch links Ill by means of drop links 23. The arrangement is such that admission of pressure fluid to the forward end of the cylinder ll forces the piston I8 rearwardly to rock the crank arms 22 upwardly and thereby raise the hitch links l0. Upon exhaust of fluid from I8 is permitted to retreat into the cylinder under the urge of the gravity load on the hitchlinks and any implement attached to those links so that the latter swing downwardly in a lowering direction.

Pressure fluid such as oil is supplied to the actuator or ram cylinder I! by way of a conduit 25 from a four-cylinder oil pump 26 having a shaft 21 driven continuously from the tractor engine. As shown in Fig. 2, the shaft 21 carries two eccentrics 28 on which are mounted blocks or slippers 29 adapted to actuate frames 30 each of which carries two opposed pump pistons (not shown) the cylinder [1, the piston The supply of oil to and exhaust of oil from the ram cylinder for raising and lowering the hitch linkage is controlled by means of a valve mechanism 3 I. This valve mechanism comprises relatively axially slidable plunger and easing elements 32 and 33. In the exemplary system, the casing 33 is stationarily mounted in the housing 34 of the pump and the valve plunger 32 is slidable axially in a bore in thecasing to control a set of intake ports 35 for the pump 26 and a set of bleed or exhaust ports 36 communicating with the conduit 25 leading from the pump to the ram cylinder 11. There are a plurality of the ports 36 spaced apart circumferentially of the valve plunger, the spacing preferably being substantially uniform.

As will be seen by reference to Fig. 2, the plunger 32 is dimensioned lengthwise so as to cover both sets of ports when in a central or neutral position and to maintain one set of ports blocked off when the other set is opened by appropriate axial movement of the plunger.

Shifting of the valve plunger 32 is effected by a system of levers operable manually and automatically in accordance with the forces imposed on the hitch linkage. As herein shown, the valve plunger is of hollow construction and is held on the ball end of a rod 31 by means of a compression spring 38. This rod is connected to a crossbar 39 at the lower end of a duplex floating lever 40 (Fig. 1) which is rotatable about one or the other of two pivots adjacent its upper end. The uppermost pivot is an eccentric 4| against which the top of the lever rests and which is adjustable by a hand lever '42 in well known manner. The other pivot 43 forms a connection with a stirrup 44 connected by means of a plunger 45 with the rocker l whereby the pivotal connection is shifted fore and aft in response to variations in the force imposed on the hitch linkage.

Rocking of the floating lever 46 in clockwise direction is effected either by the eccentric or by the connection with the rocker member l5 against the force exerted by a spring- 46 connected between the lever and a stationary part of the tractor. To prevent damage to the lever when it is rocked beyond a limit position defined by a fixed stop 41, the lever is constructed in two parts, namely, a lower part 48 pivotally connected as at-49 to an upper part 50. The lower part 48 of the lever has an-extension'or finger piece 5| to which the spring 46 is anchored and which engages a cross piece 52 on the upper part of the lever to form a knuckle joint permitting the parts of the lever to rock about the pivot 49 against the action of the spring 46 when the lower end ofthe'lever engages the stop 41.

The normal rocking movements of; the floating lever 40 serve to shift the valve plunger 32 axially within the casing 33 to control the ports 35 and 36. When the valve plunger is moved to the left from the central position in which it is shown in Fig. 2, it uncovers the ports 35 so that oil may be drawn from the sump 53 (in'which the pump is mounted) through a passage 54 and into the pump cylinders'from which the oil is delivered under pressure into a chamber 55. The latter chamber communicates by way of a passage 56 with a chamber 51 connected by a cored passage 58 with the supply conduit 25 leading to the ram cylinder. The passage 56 as shown iscontrolled by a check valve 58 with which is embodied as a unit a pressure responsive valve 59 for relieving the system in the-event that excessive pressure is developed therein.

- ticularly undesirable since It will be observed that the ports 36 in the valve casing 33 communicate with the chamber 51 so that fluid may exhaust from the ram when the ports are uncovered. When the valve plunger 32 is'positioned for at raising operation or for holding the hitch linkage in a selected position, it blocks those ports. Upon shifting of the valve plunger to the right from the position shown in Fig. 2, the intake ports 35 are blocked thus shutting off the supply of fluid from the pump and thereby terminating the supply to the ram. The ports 36 are uncovered thus allowing the oil in the ram cylinder to exhaust therethrough and effect a lowering of the hitch linkage.

When the valve plunger is in its central or neutral position, as shown, both sets of ports 35 and 36 are blocked and the hitch linkage and implement attached thereto are held against movement in either a raising or lowering direction.

The pressure in the ram cylinder which resists the load imposed on the hitch linkage is substantial. This pressure is exerted on the sides of the valve plunger 32 through the circumferentially spaced ports 36 and as stated heretofore tends to cause the plunger to bind or stick in the casing 33. Such sticking is parmovements of the valve plunger are not effected under positive control but under the yielding action of the springs 38 and 46. In effect therefore there is a two-way spring loaded lost motion connection in the valve operating lever system. Moreover, any tendency of the valve plunger to stick is objectionable since the effective automatic adjustment of the hitch linkage in response to load variations requires frequent and rapid movement of the valve plunger.

In accordance with the invention, the tendency of the valve plunger 32 to bind or stick in the casing 33 is effectively overcome by the provision of a novel arrangement for relatively oscillating the valve plunger and the casing through a comparatively small angle and at a relatively high frequency. In the exemplary systems the valve casing is stationarily mounted on the pump housing 34 and the valve plunger is oscillated about its central axis.

Preferably oscillation of the plunger is effected through the medium of a driving connection with the pump drive shaft 21. In the embodiment illustrated in Figs. 2 and 3 of the drawings, the valve 3| is mounted in the pump housing with the axis of the control plunger 32 disposed parallel to the axis of the pump shaft 21. With this arrangement, thedriving connection between the pump shaft and the valve plunger is provided by a lever 60 having a hollow hub portion 6| at its lower end journaled in a boss 62 upstanding from the bottom of the pump housing 13. The upper end of the lever 60 is forked as at 63 to straddle one of the eccentrics 28 on the shaft 21, preferably the front eccentric which is widened to accommodate the lever and thus serve as a driver for the plunger. The lever 60 is accordingly oscillated about the axis of its hub 6| incident to the rotation of the pump shaft.

As will be seen by reference to Fig. 2 of the drawings, the axis of the hub BI is located coincident with the axis of the valve plunger 32. A driving connection between the lever and the plunger is provided on this axis by a thin, torsionally flexible shaft 64. This shaft has atone end a plug 65 fitted into the hollow plunger 32 s eve-ices:

and securedthereto as by a cross other end the shaft 64 is fitted with a shank 61 of-non-circular cross section, preferably square, slidably received in a complemental hole in the I hub 6| of the lever 60 coincident with the pivotal The connection thus provided sional flexibility of the shaft 64, damage to the valve mechanism or other parts is prevented in the event that the valve becomes stuck through. the accumulation of an excessive amount of dirt or by rust which might form when the tractor is allowed to stand idle for a substantial period.

The arrangement above described substantially eliminates or materially reduces the tendency of the valve plunger .32 to stick and renders the control very sensitive. Ithas been found, for example, that a force of a fraction of an ounce is to move the valve plunger axially even with pressures in the neighborhood of three thousand pounds per square inch obtaining in a hydraulic system. It appears that this oscillatory movement of the valve plunger spreads an oil film entirely around the plunger, or at least to such extent as to prevent metal-to-metal contact between the plunger and the casing. A surprising. feature is that this beneficial effect is obtained with an oscillatory movement of only about 10 or 12 amplitude which is less than half the angle subtended by the nearest points of the opposed ports 36. Apparently the relatively high frequency of the oscillation compensates for its small amplitude. The frequency, incidentally, may be as low as 150 cycles per minute which correspond approximately to an engine idling speed of 500 R. P. M. but, in practice, the pump shaft is usually rotating at a higher speed which enhances the beneficial action of the plunger oscillation. It should be noted that there is a substantial practical advantage in employing low amplitude oscillations since it permits the use of the simple lever drive above described.

In the modified form of the system shown in Fig. 4, a valve 10 controls the operation of the pump 26 in the same manner as the valve 3| heretofore described. In this particular system, the valve is arranged with its axis substantially perpendicular to the axis of the pump shaft 21.

As in the previously described construction, the valve 10 comprises a casing 1| with a central bore in which a valve plunger 12 is slidable axially to control suction or pump intake ports 13 and exhaust ports 14. The latter ports communicate with the pressure chamber 51 from which the cored passage 58 and core duct 25 carry fluid to the ram cylinder |1. Check valve 58 and relief valve 59 are associated with the pressure system a before explained.

The valve plunger 10 may be shifted axially by the floating lever mechanism heretofore described, the lever being connected with the plunger in this instance through the medium of a spool 15 fitted on the upper end of the plunger.

To prevent sticking of the valve plunger 12, provision is made for oscillating it in timed relation to the rotation of the pump shaft 21. For this purpose the pump shaft is formed with a driver in the form of a generally spherical extension 16 having an oblique cam groove 11 in its peripheral surface which is engaged by two the oscillatory movements of diametrically opp sed ballsor pegs 18 mounted;

in a ring 19 fitted Within an opening in a driving member 80. The member has a cylindrical shank 8|. disposed substantially perpendicular to the axis ofthe ring 19 and supported for oscillation in a bearing extension 82 of the pump nous-P ing. The bearing in axially with the valve ber is drivingly connected with the plunger by means of a torsionally flexible rod or shaft 83 anchored at one end to the shank 8| of the member. The shaft 83 extends axially into the valve the extension 82 is alined plunger and has a non-circular (in this instancesquare) driving portion 84 engaging in a complementally shaped passage in the plunger.

rotation of the pump shaft. As explained here-;

tofore, this oscillation of the valve plunger through a relatively small angle but at a comparatively high frequency effectively eliminates any tendency of the plunger to stick.

We claim as our invention:

1. In a hydraulic system for tractors and the like, in combination, a pressure fluid pump having a rotatably driven shaft, a valve controlling the flow of pressure fluid from said pump, said valve comprising a casing having a cylindrical bore disposed with its axis parallel with and at one side of the axis of the pump shaft, said bore having a plurality of ports in its walls substantially uniformly spaced apart circumferentially of the bore and communicating with the outlet of the pump, a valve member slidable axially of said bore to open or close said ports, a driving member supported adjacent one end of said casing for oscillation about an axis coincident with the axis of said bore, said driving member having a forked end straddling said pump shaft, a driver on said pump shaft cooperating with the forked end of said driving member for oscillating the member, and a flexible torque transmitting element disposed in axial alinement with said bore and having connections with said driving member and said valve member, one of said connections permitting relative axial sliding movement of the flexible element relative to the connected member so as to enable the element to transmit oscillating movement to the valve member without impeding its axial movements.

2. In a hydraulic system for tractors and the like, in combination, a pressure fluid pump having a rotatably driven shaft, a valve controlling the flow of pressure fluid from said pump, said valve comprising a casing having a cylindrical bore disposed with its axis parallel to and at one side of the axis of the pump shaft, a valve member slidable axially of said bore to control the flow of pressure fluid therethrough, a driving member supported adjacent one end of said casing for oscillation about an axis coincident with the axis of said bore, said driving member having one end disposed adjacent said pump shaft, a driver on said pump shaft cooperating with said one end of said driving member for oscillating the memplunger 1| and the mem-- This arrangement provides a sliding connection per-,

is transmitted to the valve,

ber, and a torque transmitting element disposed in axial alignment with said bore and having connections with said driving member and said valve member, one of said connections permitting relative axial sliding movement of the ele ment relative to the connected member so as to enable the element to transmit oscillating move ment to the valve member without impeding its axial movements.

3. In a hydraulic system for tractors and the like, in combination, a pressure fluid pump having a rotatably driven shaft, a fluid flow control valve operatively associated with said pump, said valve comprising a casing having a cylindrical bore, a valve member slidable axially of said bore, a driving member supported adjacent one end of said casing for oscillation about an axis coincident with the axis of said bore, said member having one end disposed adjacent said pump shaft, a driver on said pump shaft cooperating with said one end of said driving member for oscillating the member, and a torque transmitting element disposed in axial alinement with said bore and having connections with said driving member and said valve member, one of said connections per mitting relative axial sliding movement of the element relative to the connected member so as to enable the element to transmit oscillating movements to the valve member without impeding its axial movements.

4. In a hydraulic system for tractors and the like, in combination, a pressure fluid pump having a rotatably driven shaft, a fluid flow control valve operatively associated with said pump, said valve comprising a casing having a cylindrical bore, a valve member slidable axially of said bore to control the flow of fluid therethrough, a driving member supported in spaced relation to one end of said casing for oscillation about an axis coincident with the axis of said bore, a driver on the pump shaft cooperating with said driving member for oscillating the member, and an elongated ilexible element disposed in axial alinement with said bore and having torque transmitting connections with said driving member and said valve member, one of said connections permitting relative axial sliding movement of the element relative to the connected member so as to enable the element to transmit oscillating movement to the valve member without impeding its axial movements.

ALEXANDER SENKOWSKI. WITOLD CZARNOCKI References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,512,804 Roucka Oct. 21, 1924 2,065,702 Hubbard Dec. 29, 1936 2,099,443 Kraft Nov. 16, 1937 2,324,514 Kalin July 20, 1943 2,368,628 Bates Feb. 6, 1945 2,455,315 Rose et al Nov. 30, 1948

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