US2284109A - Hydraulic pump or motor - Google Patents

Description

HYDRAULIC PUMP on MoToR Filed June 28,'1939 5%# z. 7M ATTORNEY HARRY F. VICKERS Patented May 26, 1942 HYDRAULIC PUMP 0R MOTOR Harry F. Vickers, Detroit, Mich., assigner to Vickers Incorporated, Detroit, Mich., a corporation of Michigan i Application June s, 1939, seria1N0.2s1,s46

4 Claims.

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 uid motor. In such devices of the type which comprise a revolving cylinder barrel having a pluralityof parallel cylinder bores therein within which pistons are reciprocated by a swash plate device, it is customary to provide a rotary valving mechanism which is operated by the rotation of the cylinder barrel itself for the purpose of alternately connecting each cylinder bore with the inlet and outlet passages of the device. Many machines of this character utilize a plate type valve formed by a` dat surface of the cylinder barrel which runs in abutting and in fluid sealing relationship on a stationary at valve plate. The plate type valve may be so constructed that the cylinder barrel is constantly pressed into engagement with the valve plate so that the clearance at the valve is automatically adjusted to take care of variations in oil viscosity and 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 of the cylinder barrel relative to the piston area and to the area of the annular surface of contact with the valve plate as to pmvide approximate hydraulic balance between the uid pressure forces exerted by piston reaction on' the end faces of the cylinder bores and the fluid pressure separating forces exerted in the oil lm between the cylinder barrel and valve plate. It is, of course, impossible in practice to provide an exact balance between these forces, and since it is necessary to provide some means for holding the barrel in contact with the valve plate while the machine is idle, a spring or other resilient meansy is usually provided for urging the barrel into contact with the valve plate with a relatively light force at-all times.

mum. When this maximum is exceeded, however, the barrel lifts away from the valve plate, and since the valve is thereby rendered ineffective, the power drive .through the transmission is completely and suddenly interrupted, This difficulty can be extremely troublesome at times, particularly where the transmission is used to operate a device, such as a hoist, which has to overcome a gravity load and in which completey -dependence upon the transmission is placed for sustaining that load In such cases it occasionally happens that the critical pressure at which the barrel will blow offis slightly above the normal operating pressure required for lifting the usual loads and that on rare occasions, due to snagging Aof 'hoisting lines or some other momentary small overload during hoisting, the critical pressure is exceeded causing the barrel to lift and resulting in dropping of the load with consequent damage thereto.

It is an object of the present invention to provide a valve plate construction for a fluid pressure energy translating device of the class described in which the above problems are avoided by the provision of means for exerting a variable force. tending to hold the barrel on the valve plate and proportional to leakage variations.

produce large changes in the hydraulic balance(y Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

In the drawing, the single figure is a longitudinal cross section of a fluid pressure energy translating device incorporating a preferred form 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 comprises generally a mainring-like frame member Il] 'hav-- ing 'a mounting flange I2 thereon and provided with bearings I4 on which a main shaft I6 is journalled. The shaft I 6 is provided with a socket flange I8 carrying a plurality of ball sockets 28 in which are mounted ball-ended connecting rods 22 carrying reciprocating pistons 24. Rigidly secured to the frame member I8 by suitable bolts not shown are a pair of plates 26 provided with bearings 28 'and with uid connections 38. Journalled on the bearings-28 isv a swinging yoke generally designated as 32 comprising a valve plate 34 with rigidly attached ,hollow arms 36 providing trunnions for the yoke and connected to the fluid connection 38 by sealing sleeves 38.-

The valve plate 34 is provided with an arcuate raised sealing surface 48 against which runs the flat end face 42 of a cylinder barrel 44 provided with a plurality of cylinder bores 46 therein. Formed in the valve plate 34 are two arcuate fluid distributing ports 46 each of which extends through an arc somewhat less than 180 degrees and communicates with the passages in the hollow arms 36. Formed at the left-hand end of the cylinder bores 48 are a plurality of fluid distributing ports 58 opening into the flat face 42 and adapted to alternately register with each of the distributing ports 48. A shaft 52 provided with universal joints 54 'at its opposite ends connects the barrel 44 to rotate with the shaft I6 in any position of the yoke 32. The parts thus far described are in a broad aspect well known in the art and per set form no part of the present invention.

The hydraulic balance of the cylinder barrel 44 is, of course,determined by suitable proportioning of the radial width of the dat pressure surface 48 relative to the total area of all of the ports 58 and the total area of all of 4the pistons 24. With the present invention these areas are so proportioned as to produce a netfluid pressure forceon the cylinder barrel 44 tending to lift the barrel out of contact with the surface 48. This unbalance is preferably, though not necessarily, made small, and` is, of course, proportional to the operating pressure.

According to the invention, means is provided for imposing an additional force tending to urge.

the barrel into contact with the surface 48, which force is vdetermined by the amount of leakage taking place at the valve plate surface. For this purpose the valve plate is formed with a cylindrical recess 86 in which a cylindrical projection58 formed integrally with the cylinder barrel 44 is rotatably mounted. A suitable oil seal .may be provided at 88. 'There is thus formed an annular chamber 82 radially inward of the annular valve plate surface 48.

Leading from the chamber 62 is a passage 64 of negligible resistance which opens in to a cylindrical chamber 66 formed at'the left-hand In operation, assuming that the conduits 38 are connected into a power transmission circuit in tne usual manner so that the upper conduit 38 is the pressure supply connection while the lower one is the suction connection and that the shaft I6 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 48 in the well-known `manner with a stroke depending upon the angular displacement of the yoke 82.

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 be withdrawn to the right during its bottomhalf revolution, thus withdrawing fluid from the lower port 48 into the cylinder 48 and discharging it out of them into the upper port 48.

' At zero operating pressure in the upper port `48 the hydraulic unbalance of the cylinder barrel is likewise zero so that the force of spring 18 transmitted through the bearing 12 to the cylinder barrel 44 is the sole force urging the barrel into contact with the valve plate. As the pressure in the upper port 48 increases and beforeh it reaches the critical pressure at which spring 18 can no longer hold barrel 44 against the surface 48, the spring 18 is 'able to overcome the net hydraulic unbalance of the barrel 44 and hold Vthe same in contact. In increasing to the critical pressure, however, if we assume that the clearance between surfaces 48 and 42 remains constant, the leakage from these surfaces radially inward to the chamber 82 will increase correspondingly.. This leakage passes through passage 64 into chamber 88 and out through passage 88.

So long as the amount of this leakage is so small as'to meet negligible resistance in the restricted passage. 88, the pressure in chamber 88 will be substantially zero. As the leakage gradually increases, however, the resistance imposed bypassage 88 increases causing the pressure in chamber 66 to risel and thereby impose additional force on vthe piston 88 urging the barrel 44 into closer abutment with the surface 48, thus decreasing the clearance between surfaces 48 and 42 anddecreasing the leakage. It will be seen that the greater the leakage into chamber 82,

side of the valve plate.34. Slidably mounted in chamber 66 is a piston 88 secured to a rod 18. An oil seal 1i is provided' around the rod 18. The latter carries a` thrust bearing 12 at its righthand end which abuts against a shoulder formed at the left-hand end of a recess 14 in the outlet of passage 88.

Y cylinder barrel into contact with the valve platev Cap members 88 the greater will be the force exerted on piston 88 so that under any conditions a balance `is reached such that the leakage is held downto a predetermined value.

It will be noted incidentally that the same pressure which is exerted in the chamber 88 against the piston 68 is also exerted in the chamber 62 in the opposite direction against the l at face 42 of cylinder barrel 44. Accordingly it is necessary that the net area of the chamber 68 be greater than the net area of chamber 82.

It will be seen that with the construction f shown and described, the total force (urging the is automatically regulated to control the leakage acrossv 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 follows:

l. In a fluid pressure energy translating device having a plurality of cylinders and pistons reciprocable therein, a rotary valve structure comprising two relatively rotatable members prov vided.with at, annular, sealing surfaces in runfaceA on the cylinder barrel adapted to abut `the ning engagement and containing iluid distributing 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 with force proportional to said pressure, means forming a chamber for.

collecting leakage from said valve, a restricted conduit for draining said chamber, said chamber lying between said conduit and the iiuid distributing ports, and means including a uidmo- Ator communicating with said chamber and connected to one of said members and responsive to pressure variations in said chamber for varying the total force applied to said one member.

2. In a uid pressure energy translating device having a plurality of cylinders and pistons reciprocable therein, a rotary kvalve structure comprising two relatively rotatable members pro valve, a restricted conduit for draining said chamber, said chamber lying between said conduit and the iiuid distributing ports, and means including a fluid motor communicating with said chamber and connected to one of said members and responsive to pressure variations in said chamber for varying the total force applied to said one member.

3. vIn a uid pressure energy translating derel with a plurality of cylinders therein and pistons reciprocable in the cylinders, a rotary valve structure comprising a stationary valve having a at annular surface with iiuid distributing ports therein, means forming a iiat annular survalve plate surface and provided with iiuid distributing ports therein, said barrel being provided' with fluid pressure areas exposed to the pressure in said cylinders 'for exerting a force on the barrel proportional to such pressure tending to urge the barrel into abutment with the valve plate, means forming a chamber. for collecting leakage from between said surfaces, a rel stricted conduit for draining said chamber, said chamber lying-between said conduit and the fluid distributing ports, and means including a fluid motor communicating with said chamber and connected to one of said members 'and responsive to pressure variations in said'chamber for varying the totalforce applied to the barrel.

4. In a fluid pressure energy translating device of the type having a revolving cylinder barrel with a plurality of cylinders therein and pistons reciprooable in the cylinders, a rotary valve structure comprising a stationary valve having l a flat annular surface with uid distributing pressure in said cylinders for exerting a force on the barrel proportional to such pressure tending to urge the barrel into abutment with the valve plate, resilient means for also urging the barrel into abutment with the valve plate, means forming achamber for collecting leakage from between said surfaces, a restricted ,conduit for I vice of the type having a revolving cylinder bardraining said chamber, said chamber lying between said conduit and the fluid distributing ports, and means including a iiuid-motor communicating with said chamber and connected to one of'said members and responsive to pressure variations in said chamber for varying the total force applied to the barrel.

HARRY r'. VICKERS.

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