Axial piston device

Abstract

An axial piston device may be operated as a pump and includes a self-centering rotary valve. The device includes a stationary housing encompassing a shaft and the rotary valve. The rotary valve and the shaft are coupled to each other. Upon rotation, the rotary valve self-centers as a result of elimination of moments and forces within the pump. The inventive pump is a piston device. The valve is within a valve bore, which is a part of a manifold. A shaft is within the manifold and the shaft is attached at its distal end to a planar surface of the rotary valve. The shaft has a first axis of rotation and the rotary valve has a second axis of rotation. During operation of the pump, the first axis is often times offset from the second axis. The pump operates via a swashplate with reciprocating pistons while the housing remains stationary.

What is claimed is: 
     
         1 . A piston device comprising:
 a stationary cylinder block,   a shaft that is rotatable about its own axis within the stationary cylinder block, and the shaft comprising a plurality of passages configured to receive, direct and exhaust fluid, the shaft centrically and eccentrically rotatable during operation of the pump, and   a swash plate coupled to the shaft, the swash plate having a first side coupled to a first plurality of pistons.   
     
     
         2 . The piston device as recited in  claim 1  wherein the swash plate is configured to tilt about an axis perpendicular to the axis of the shaft. 
     
     
         3 . The piston device as recited in  claim 2  further comprising a means for tilting the swash plate. 
     
     
         4 . The piston device as recited in  claim 1  wherein fluid pressure on the passages in the shaft balances at least one force and/or moment. 
     
     
         5 . The piston device as recited in  claim 1  further comprising a respective plurality of slipper shoes each connected to a piston, and the swash plate comprising at least one active surface for interacting with the slipper shoes. 
     
     
         6 . The piston device as recited in  claim 1  wherein fluid flow throughout the pump creates at least one of a force and a moment on the shaft and the plurality of passages are configured on the shaft such that at least one of the forces or the moments on the shaft are balanced. 
     
     
         7 . The piston device as recited in  claim 6  further comprising a second plurality of pistons, each plurality of pistons contained within the cylinder block and arcuately positioned coaxial with the shaft on opposite ends of the cylinder block. 
     
     
         8 . The piston device as recited in  claim 7  further comprising a first active surface and a second active surface, the first and second active surfaces are on opposing sides of the swash plate. 
     
     
         9 . A piston device comprising:
 a stationary cylinder block;   a shaft extending through the stationary cylinder block and having a plurality of passages along a portion of the shaft; and   a valve enclosed within the stationary cylinder block, the valve comprising the shaft integrally coupled to the valve.   
     
     
         10 . The piston device as recited in  claim 9  further comprising a first plurality of pistons and a second plurality of pistons, each plurality of pistons arcuatley positioned coaxial with the shaft on opposite sides of the shaft. 
     
     
         11 . The piston device as recited in  claim 9  wherein the plurality of passages are configured to receive, direct and exhaust fluid flow throughout the pump. 
     
     
         12 . The piston device as recited in  claim 11  wherein the fluid flow throughout the pump creates at least one of a plurality of forces and a plurality of moments on the shaft and the plurality of passages are configured on the shaft such that the at least one of the plurality of forces and the plurality of moments is balanced. 
     
     
         13 . The piston device as recited in  claim 12  further comprising a plurality of slipper assemblies, each slipper assembly coupled to one piston of the plurality of pistons; and
 a swash plate coupled to the shaft and comprising at least one active surface for interacting with a respective slipper assembly. 
 
     
     
         14 . The piston device as recited in  claim 13  further comprising a first active surface and a second active surface, the first and second active surfaces are on opposing sides of the swash plate. 
     
     
         15 . A piston device comprising:
 a swash plate having a first side coupled to a first plurality of slipper shoes and a second side coupled to a second plurality of slipper shoes, the first side of the swash plate is generally parallel to the second side of the swash plate; and   a first portion of the pump on the first side of the swash plate and a second portion of the pump on the second side of the swash plate, the first portion of the pump on the first side of the swash plate is substantially symmetric about the swash plate with the second portion of the pump.   
     
     
         16 . The piston device as recited in  claim 15  further comprising a shaft, the swash plate coupled to the shaft 
     
     
         17 . The piston device as recited in  claim 16  configured to be adjustable about an axis askew or perpendicular to an axis of the shaft. 
     
     
         18 . The piston device as recited in  claim 16  further comprising a means for balancing at least one of a plurality of forces and a plurality of moments acting on the shaft. 
     
     
         19 . The piston device as recited in  claim 17  further comprising a means for tilting the swash plate with respect to the shaft. 
     
     
         20 . The piston device as recited in  claim 16  further comprising a housing encasing the shaft, swash plate and slipper assemblies. 
     
     
         21 . A piston device comprising:
 a stationary cylinder block,   a valve-shaft assembly encompassed by the stationary cylinder block, the valve-shaft assembly comprising a valve connected to a shaft of the valve shaft assembly via interaction between a drive key and a valve keyway in the valve and a shaft keyway in the shaft, and wherein the interaction is configured to provide at least one degree of freedom for the valve relative to the shaft.   
     
     
         22 . The piston device as recited in  claim 21  wherein the valve is configured to balance within the cylinder block by controlled leakage rates of fluid within the hydraulic pump as a function of at least one of a force and a moment on the valve 
     
     
         23 . The piston device as recited in  claim 22  further comprising a swash plate connected to the shaft. 
     
     
         24 . The piston device as recited in  claim 23  further comprising a means for tilting the swash plate about an axis perpendicular to the axis of the shaft. 
     
     
         25 . The piston device as recited in  claim 24  wherein the swash plate comprises at least one active surface. 
     
     
         26 . The piston device as recited in  claim 25  wherein the swash plate comprises a plurality of slipper assemblies coupled to the at least one active surfaces of the swash plate. 
     
     
         27 . A piston device comprising:
 a housing and a manifold integral with the housing, and   a rotary valve encompassed by the manifold, the rotary valve comprising a shaft, a passaged section and a sealing section,   wherein the sealing section comprises a semicircular sealing ridge.   
     
     
         28 . The piston device as recited in  claim 27 , the rotary valve further comprising a first axial face seal on a first end of the rotary valve and a second axial face seal on a second end of the rotary valve. 
     
     
         29 . The piston device as recited in  claim 28 , the rotary valve further comprising a high pressure discharge section on a side of the rotary valve opposite the semicircular sealing ridge. 
     
     
         30 . The piston device as recited in  claim 29 , the rotary valve further comprising an intake section on the first end of the rotary valve. 
     
     
         31 . The piston device as recited in  claim 29  further comprising an operating gap formed between the high pressure discharge section and the manifold, the operating gap having a width that is dependent upon a force applied in the direction of the semi-circular sealing ridge at the high pressure discharge section. 
     
     
         32 . The piston device as recited in  claim 31  wherein the semicircular sealing ridge is configured to remain at a generally constant operating distance from the manifold. 
     
     
         33 . The piston device as recited in  claim 31  wherein the width of the operating gap is further dependent upon shaft speed and a circumference of the valve. 
     
     
         34 . The piston device as recited in  claim 27  wherein the rotary valve is generally cylindrical and the semicircular sealing ridge encompasses less than three hundred and sixty degrees of the rotary valve. 
     
     
         35 . The piston device as recited in  claim 34  wherein the semicircular sealing ridge comprises a manifold engaging portion and a recessed portion. 
     
     
         36 . The piston device as recited in  claim 28 , the rotary valve further comprising a low pressure suction section on a side of the rotary valve opposite the semicircular sealing ridge. 
     
     
         37 . A piston device comprising:
 a valve bore,   a rotary valve encompassed by the valve bore, the rotary valve comprising at least one axial face seal and at least one radial face seal,   an operating sealing clearance gap between the radial face seal and the valve bore,   wherein the operating sealing clearance gap maintains a generally constant thickness during operation of the rotary valve.   
     
     
         38 . The piston device as recited in  claim 37  further comprising a discharge gap between the rotary valve and the bore, the rotary valve being biased by a force applied in the direction of the semi-circular sealing ridge, wherein the force determines a width of the operating sealing clearance gap. 
     
     
         39 . The piston device as recited in  claim 38 , the rotary valve further comprising a shaft, wherein the radial face seal comprises a semicircular sealing component and is generally coaxial about the shaft. 
     
     
         40 . The piston device as recited in  claim 39  further comprising a passaged section on the shaft. 
     
     
         41 . The piston device as recited in  claim 40  wherein the shaft comprises an inlet passage and a discharge passage. 
     
     
         42 . A piston device comprising:
 a housing having a valve bore and manifold,   a shaft within the manifold and a rotary valve within the valve bore, the shaft attached at a distal end to a planar surface of the rotary valve; and   the shaft having a first axis and the rotary valve having a second axis, the first axis being offset from the second axis.   
     
     
         43 . The piston device as recited in  claim 42 , wherein the second axis is coincident with an axis of the valve bore. 
     
     
         44 . The piston device as recited in  claim 43  wherein the first axis is offset from a centerline of the manifold. 
     
     
         45 . The piston device of  claim 42  wherein the rotary valve comprises a high pressure outlet. 
     
     
         46 . The piston device as recited in  claim 45  wherein the shaft is offset in a direction of the high pressure outlet of the rotary valve. 
     
     
         47 . The piston device as recited in  claim 46  wherein the shaft comprises a manifold contact surface. 
     
     
         48 . The piston device as recited in  claim 45  wherein the shaft is offset in a direction opposite the high pressure outlet of the rotary valve. 
     
     
         49 . The piston device as recited in  claim 42  further comprising a plurality of cylinders within the manifold arranged in parallel and in a circle around and coaxial with the valve bore. 
     
     
         50 . The piston device as recited in  claim 49  wherein the rotary valve is generally coaxial with the valve bore. 
     
     
         51 . The piston device as recited in  claim 50  wherein the shaft is not coaxial with the valve bore. 
     
     
         52 . The piston device as recited in  claim 42  the shaft being monolithic with the rotary valve. 
     
     
         53 . A piston device comprising
 a valve in a bore,   a radial face seal on a radial surface of the valve positioned between the valve and the bore and at least partially circumferencing the valve, the radial face seal comprising a sealing ridge and   an axial face seal on an axial surface of the valve, the axial face seal between the axial surface of the valve and the axial surface of the bore.   
     
     
         54 . The piston device as recited in  claim 53  wherein the sealing ridge protrudes toward
 the bore away from the radial surface of the valve. 
 
     
     
         55 . The piston device as recited in  claim 53  wherein the radial face seal is connected to
 the valve via at least one radial face seal torque transmitting device. 
 
     
     
         56 . The piston device as recited in  claim 55  wherein the radial face seal is biased away
 from the valve via at least one radial face seal spring. 
 
     
     
         57 . The piston device as recited in  claim 53  wherein the axial face seal is connected to
 the valve via at least one axial face seal torque transmitting device. 
 
     
     
         58 . The piston device as recited in  claim 57  wherein the at least one axial face seal is
 biased away from the valve via an axial face seal spring. 
 
     
     
         59 . The piston device as recited in  claim 53  wherein the sealing ridge further comprises
 a passage. 
 
     
     
         60 . A piston device comprising:
 a swash plate having a first side and a second side, the first side is generally parallel to the second side;   a first portion of the pump on the first side and a second portion of the pump on the second side,   the first portion comprising a first portion rotary valve encompassed by a first portion bore and the second portion comprising a second portion valve encompassed by a second portion bore,   wherein both valves comprise a shaft, a passaged section and a sealing ridge.   
     
     
         61 . The piston device as recited in  claim 60  wherein at least one of the portions further
 comprises a respective radial face seal connected to the respective valve and 
 providing a seal between the respective valve and the respective bore. 
 
     
     
         62 . The piston device as recited in  claim 61  further comprising torque translator
 connecting the respective radial face seal with the respective valve for transmitting rotational force from the valve to the respective radial face seal.