US2284110A - Hydraulic pump or motor - Google Patents

Description

May Z6, 1942. H. F. vlcKERs f 2,284,110

I HYDRAULIC PUMP 0R MOTOR Filed June 28, 1959 HARRY F. VICKI-:Rs

BY f` @l /M ATTORN EY Patented May 2e, 1942A UNITED sTATEsPATENT OFFICE' HYDRAULIC PUMP OR MOTOR Harry F. Vickers, Detroit, Mich., assignoi'. to Vickers Incorporated, Detroit, Mich., a corporation of Michigan Application June 28, 1939, Serial No. 281,647

' s claims. (ci. 10s-162) This invention relates to power transmissions and more particularly to those of the type comprising two or more fluid pressure energy translating devices, one of which may function as a pump and another as a iiuid motor. In such devices of the type which comprise a revolving cylinder barrel having a plurality of parallel cylinder bores therein within which pistons are reciprocated by a swash plate device, it is customary to provide a rotary valving mechanisml which is operated by the rotation of the cylinder barrel itself for the purpose of alternately connectinga each cylinder bore with the inlet and outlet passages of the device. Many machines,

of this character utilize a plate typevalve formed by a ilat, surface of the .cylinder barrel which runs in abutting and in uid sealing relationship on a' stationary V ilat valve plate. The plate type valve may be so constructed that the cylinder barrel is constantly pressed into engagement with the valve plate sq that the clearance at the valve is automatically adjusted to take care of variations in' oil viscosityand to compensate for wear.. This is a distinct advantage and contributes much to the reliability and long life of machines employing a valve of this character.

It is customary with machines of this character to so proportion the size of the distributing ports in the end face oi the cylinder barrel relative to the piston area and to the area of the annular surface of contact 'with the valve plate as to provideA approximate hydraulic balance between the fluid pressure forces exerted by piston chine is designed for a very small net unbalance, it occasionally happens, due to manufacturing variations, that the net unbalance of the hydraulic forces on the barrel is in a direction has to overcome a gravity load and in which complete dependence upon the transmission isv placed for sustaining that load. In such cases it occasionally happens that the' critical pressure at-which the barrel will blow oif is slightly above the normal operating pressure required for lifting the usuai loads and that on raw. oc-

casions, due to snagging of hoisting lines or some other momentary small overload during hoisting, the critical pressure is exceeded causing the barrel to lift and resulting in dropping or the load with consequent damage thereto.4

It is an object of the present invention to provide a valve plate construction for a nuid pressure energy translating'device of the class dereaction `on the end faces of the cylinder bores and the fluid pressure separating forces exerted in the oil iilm between the cylinder barrel andvalve plate.` It is, ofI course, impossible in practice to provide an exact balance between these forces, and since it is necessary to provide some means for 4holding the barrel in contact with the valve plate while the machine is idle, a spring or other resilient means vis usually provided for urging the barrel into contact with the valve plate with a relativelylight force at all times.

It is extremely difficult to predetermine with precision the exact amount of hydraulic unbalance which will exist in a given machine since small variationsin; dimensions which are entirely within normal kmanufacturing tolerances produce large lchanges in the vhydraulic balance when the operating pressures are high. Ii! the net unbalance is in a direction holding the barrel in contactand is very large, then theunit bearing pressures at the valve plate are apt to be excessive. On the other hand, ii the mascribed in which the above problems are avoided Y bythe provision ofmeans for exerting a varia-l ble force tending to hold the barrel on the valve plate and proportional to leakage variations.

Further objects and advantages of the present invention will be apparent irom'theaiollowing description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

I n the drawing, the vsingle figure is a longitudinal cross section of a iiuid pressured energy vtranslating device incorporating a preferred iorm of the present invention.

The embodiment of the invention selected for illustration comprises a pump of the same general class as that illustrated in the patent to Hans Thoma, No. 1,931,969, and comprisesgenerally a main ring-like frame member I0 having a mountingange I2 thereon and provided with bearings It on which a main shaft I6 Ais journalled. The shaft I6 is provided withv a socketA ilange I8 carrying a plurality o f ball 5 5 sockets -20 in which are mounted ball-ended connecting rods 22 carrying reciprocating pistons 24. A

Rigidly secured to the frame member I by suitable bolts not shown are a pair of 'plates 2t provided with bearings 20 and with ,iluid connections` 30. Journalled on the bearings 20 is a Swingin yoke generally designated as 02 comprising avalve plate 04 with rigidly attached hollow arms 00 providing trunnions for the yoke and connected to the uid connection 20 by sealing sleeves 30.

The valve plate'34 is provided with an arcuate raised sealingsurface 40 against which runs the flat end face 42 of a cylinder barrel 44 provided with a plurality of cylinder bres 46 therein. Formed in the valve plate 04 are-two` arcuate fluid distributing ports 4l each of which extends through an arc somewhat less than 180 degrees and communicates with the passages in the hollow arms 08. Formed at the left-hand fend of the cylinder bores 40 are a plurality of fluid distributing ports 50 opening into the flat face 42 and adapted to alternately register with each of the distributing ports 4B. A shaft l2 provided with universal joints 54 at its opposite ends connects the barrel 44 to rotate with the shaft |0 in any position of the yoke-02. The parts thus far described are in a broad aspect well known in the art and per se form no part of the present invention.

The hydraulic balance of the cylinder barrel 44 is, of course, determined by suitable proportioning oi' the radial width of the flat pressure surface 40 relative to the total area of all of the ports I0 and the total area of all of the pistons 24. With the present invention these areas are so proportioned as to produce a net fluid'pressure force on the cylinder barrel 44 tending to lift the barrel out of contact with the surface 40. This unbalance is preferably, though not necessarily, made small, and is, of course, proportional to the operating pressure. g

According to the invention, means is provided for imposing an additional force tending to urge the barrel into contact with the surface 40, which force is determined by the amount ot 'leakage 00 extends tothe left-hand end face oi' the cap member 00. Theend of the passage 88 is provided with a plug 00 having a restricted orifice A |00 of predetermined size. Slidably mounted in the bore 22 is a valve spool |02 having a bore |04 therein at its left-hand end for receiving a spring |06. An aperture plug |00 is provided at the left-hand end of bore 02 to provide a spring abutment while leaving the bore open to tank.

The valve-spool 02 is provided with a chamber ||0 at its right-hand end closed by a plug |l2. The walls of the chamber |I|l are provided with four large'orices ||4 adapted to register with the groove 80 and with four small elongated orifices I Ii adapted to partially register'with the chamber 84 depending upon the valve position.

In operation, assuming' that the conduits 3D are connected into a powerl transmission circuit in the usual manner so that the upper conduit 3o is the pressure supply connection while the lower one is the suction connection and that the shaft I8 is connected to a suitable prime mover and rotated thereby at a constant speed, with the,top moving away from the observer the pistons 24 are reciprocated in the cylinder bores 46 in the wellknown manner with a stroke depending upon the angular displacement of the yoke 32.

With the left-hand end of the yoke moved away from the observer each piston 24 will'travel to the left during its top-half revolution and will vbe withdrawn to the right during its bottom-half revolution, thus withdrawing fluid from the lower port 4t into the cylinder 46 and discharging it Y. out of them into the upper port 48.

taking place at the valve plate surface. For'this purpose the valve plate is formed with a cylindrical recess I0 in which a cylindrical projection I0 formed integrally with the cylinder barrel 44 is rotatably mounted. A suitable oil seal may be provided at 60. There is thus formed an annular chamber I2 radially inward of the annular valve plate surface 40.

Leading from the chamber 62 is a passage 64 of negligible resistance which opensinto a cylindrical chamber formed at the left-hand side oi' the valve plate 04. Slidably mounted in chamber 00 is a piston 0I secured to a rod 10. An oil seal 1| is provided around the rod 10.' The latter carries a thrust bearing 'I2 at its right-hand end which abuts against a shoulder formed at the left-hand end ofa recess 14 in the barrel 44. The left-hand en d of thegrod I0 carries an adjustable spring abutment 'I6 against which is mounted a spring 10 serving as the normal cylinder barrel spring. Cap members 0|) and I2 having drain passages 04 and 00 lserve to enclose the spring 10 and the left-hand end of chamber 0i.

Formed in the cap member 0|! and in the valve plate. is a passage 00 communicating between At zero operating pressure in the upper port 40 the hydraulic unbalance of the cylinder barrel is likewise zero so that the force of spring 'I8 transmitted through the bearing 'l2 to the cylinder barrel 44 is the sole force urging the barrel into contact with thelvalvc plate. -As the pressure in the upper port 48 increases and before it reaches the critical pressure at which spring 18 can no longer, hold barrel 44 against the surface 40, the spring 10 is able to overcome the net hydraulic unbalance of the barrel 44 and hold the same in contact. In increasing to the critical pressure, however, if we assume that the clearance between surfaces 40 and 42 remains constant, the leakage `from these surfaces radially inward to the chamber 02 will increase correspondingly. This leak-- age passes through passage 04 into chamber 66 vand out through passage 00.

The valve spool |02 cooperating with the ilxed orice |00 acts tan-maintain a constant maximum rate of flow-through the passage 08. This maximum is equal to the leakage which it is desired to have take place at or near normal operating pressure. So long as the leakage is below this value it is permitted to pass through oriilce |00 with very little resistance, As soon as the leakage reaches 'or exceedsthis value,however, the

' valve |02 comes into effect and acts to therethe right-hand end of the chamben and a groove 00 formed in a bore 02 in the cap'member after maintain a constant pressure in the passage 96.

It will be noted lthat the left-hand end of the spool |02 is subject to the force of spring |06 only, the hydraulic pressure thereon beingatmospheric The right-hand end of spool |02 is subject to the pressure in conduit 06, however, and when the maximum rate of flow is reached, suillcient pressure is required to force this quantity through orlilce IIIII to overcome the force of spring |00 and movethe valve spool |02 to the left, thereby tending to close the orifices I |0 from is Provided chamber M from which a Passage chamber u. Accordingly the' valve spool Il: re-

2,2s4,11o' a 3 stricts the flow between groove 90 and chamber `barrel 44 tightly against the valve plate,A thus decreasing' the'clearance between surfaces 40 and 42 and decreasing the leakage. It will be seen that the greater the leakage into chamber 62, the greater will be the force exerted on piston 68 so that under vany conditions a balance is reached such that the leakage is held down to a predetermined value. v v

It will be noted incidentally that the same Apressure which is exerted in the chamber 66 against the piston 68 is also exerted in the chamber 62 in the opposite direction against the flat face 42 of cylinder barrel". Accordingly it is necessary that the net area of the chamber 66 be greater tharthe net area of chamber 62.

It will be seen that with the construction shown and described, the total force urging the cylinder barrel into contactwith the valve plate is automatically regulated to control -the leakage across the valve plate surfaces.

While the form of embodiment of the' inven- -tion as herein disclosed constitutes .a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as flollows:

1. In a uid pressure energy translating' de-` vice having a plurality of vcylinders and pistons reciprocable therein, a rotary valve Astructure comprising two relatively rotatable members provided with dat, annulansealing surfaces in running engagement and containing duid distributing ports'communicating .with said cylinqders, one ofv said members having anl area ex-y posed to fluid pressure from said cylinders tending to urge said members .into abutment with force proportional to said pressure, meansrforming a chamber for collecting kleakage from" said valve,` a restricted conduit for draining said chamber, said chamber lying between said conduit and the uid distributing ports, means including a uid motor communicating withsaidA .chamber and connected to one ofsaid members and responsive to pressure variations in said chamber for varying the total force appliedvto said one member, and'means for limiting the now through said conduitto a predetermined maximum irrespective of leakage from said valve.

s. 2. In av fluid pressure energy translating .device vhaving aplurality-of cylinders and lpistons I `reciprocable therein, a rotary valve structure comprising two relatively rotatable members provided with nat, annular, sealing surfaces in running engagement' and containing 'duid distributing ports communicatingv withv said cylin' ders, one of saidv members having an area exl,posed to -fluid pressure from said cylinderstendto urge said members into abutment with,V

force proportional to said pressure. means forming a chamber for lcollectingleakage from said valve, a conduit for draining said chamber, said chamber lying between said conduit and the fluid distributing ports, said conduit having a re- "mszmcteeeporuonggmerem, .fprersureA responsive' y means for maintaining va. 'predetermined pres- 'I5 cluding a duid motorlcommunicating with said l sure vdrop through the restricted portion, and means including a fluid motor. communicating with said chamber and connected toinne of said members and responsive to pressure variations in said-chamber for varying the total force applied to said one member.l s

3. In a uidV pressure energy-translating device having a plurality of cylinders and pistons reciprocable therein, a rotary valve structure comprising two relatively 'rotatable members provided with flat, annular, sealing surfaces in running engagement and containing fluid distribut- 1 ing ports communicating with said cylinders, one` of said members having an area exposed to fluid pressure from said cylinders tending to urge said members into abutment ywith force proportional to said pressure, means forming a chamber for v Y collecting leakage from said valve, means including a conduit for draining fluid fromsaid chamber at a xed maximum rate, said chamber lying between said conduit and the fluid distribut '4. In a fluid pressure energy translating device ofthe type having a revolving cylinder barrel with a plurality of cylinders thereinv and pistons' reciprocable in the cylinders, a rotary valve structurecomprising a stationary. valve lhaving a, at annular surface with nuid distributing ports therein, means forming a at annular surface on the cylinder barrel adapted to abut the. valve plate surface and provided with uid distributing ports therein, said barrel being provided with uid pressure areas exposed .to the pressure in'said cylinders for exerting a' force on the barrel proportional to such pressure 40 ,tending to urge the barrel into abutment with the valve plate, means forming a 'chamber for l collecting leakage fromi between said surfaces, a restricted conduit for' draining said chamber,

sponsive to pressure variations in said chamber. for varying the total force applied to the barrel, and means forlimiting the now through said conduit to a predetermined maximum irrespective of leakage from said valve.v

5. In a fluid pressure energy translating de'` vice of the type having a revolving cylinder barrel with a plurality of cylinders vtherein and pistons reciprocable in the cylinders, av rotary valve structure comprising la stationary valve having a flat annular surface withiluid distributing ports therein, means forming aflatvannular surface on the cylinder barrel adapted to abut the valve plate vsurface vand provided with fluid distributing ports therein, saidl barrel being provided withv iluid pressure areas exposed to the 'pressure in saidcylinders for exerting a force on the barrel proportional to such pressure'tenda ing to urge the` barrel into abutment withl the valve plate, means forming a chamber for.` collecting leakage from between said surfaces, a 'conduit for draining said chamber, said cham- .ber lying between said conduit and the fluid-distributing ports, said conduit having a restricted portion therein, pressure responsive means for maintaining a predetermined 'pressure ldrop through the restricted portiom and means inchamber and connected to one oi said members and responsive to pressure variations in said chamber for varying the total i'orce applied'to the barrel.

6. In a iluidl pressure energy translating device ci the type having `a. revolving cylinder barrel-with a plurality of cylinders therein and pistons reciprocable in the cylinders, a rotary valve structure comprising a stationary valve having a ilat annular surface with iiuid distributing ports therein, means forming a flat annulla.; surface on the cylinder barrel adapted to abut the valve plate surface and provided with fluid disl tributing ports therein; said barrel being provided with uid pressure areas exposed to the :insane HARRY F. VICKERS.

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