Compact Eccentric Radial Piston Hydraulic Machine

Abstract

A high efficiency diametrically compact, radial oriented piston hydraulic machine includes a cylinder block with a plurality of cylinders coupled to a first port by a first valve and to a second port by a second valve. A drive shaft with an eccentric cam, is rotatably received in the cylinder block and a cam bearing extend around the eccentric cam. A separate piston is slideably received in each cylinder. A piston rod is coupled at one end to the piston and a curved shoe at the other end abuts the cam bearing. The curved shoe distributes force from the piston rod onto a relatively large area of the cam bearing and a retaining ring holds each shoe against the cam bearing. The cylinder block has opposing ends with a side surface there between through which every cylinder opens. A band engages the side surface closing the openings of the cylinders.

1 . A hydraulic machine comprising:
 a cylinder block with an first port, a second port, and an exterior surface, and having a plurality of cylinders disposed radially in the cylinder block with openings through the exterior surface;   a plurality of piston assemblies each slideably received in a different one of the plurality of cylinders;   a plurality of valve arrangements each coupling one of the plurality of cylinders to the first and second ports;   a drive shaft rotatably received in the cylinder block and having an eccentric cam for driving the plurality of piston assemblies within the plurality of cylinders; and   a closing band engaging the exterior surface and closing the openings of the plurality of cylinders.   
     
     
         2 - 4 . (canceled) 
     
     
         5 . The hydraulic machine as recited in  claim 1  wherein each of the plurality of piston assemblies comprises a piston and a piston rod wherein the piston rod comprises a stem with a curved shoe through which force is transferred to the eccentric cam, wherein the curved shoe has a surface with an area that is greater than a largest cross sectional area of the stem. 
     
     
         6 . The hydraulic machine as recited in  claim 5  further comprising a retaining ring extending around the drive shaft and engaging the curved shoe of every piston rod to constrain the curved shoe from moving away from the eccentric cam. 
     
     
         7 . The hydraulic machine as recited in  claim 5  further comprising two retaining rings each extending around the drive shaft and engaging the curved shoe of every piston rod on opposite sides of the stem. 
     
     
         8 . The hydraulic machine as recited in  claim 5  further comprising a cam bearing extending around the drive shaft and having an outer race with a plurality of rollers between the outer race and the eccentric cam, wherein the shoe of each piston rod has a surface that abuts the outer race of the bearing. 
     
     
         9 . The hydraulic machine as recited in  claim 1  wherein the piston rod has an end with a partially spherical head that engages a partially spherical depression in the piston. 
     
     
         10 . The hydraulic machine as recited in  claim 9  wherein piston has an interior cavity into which the partially spherical head of the piston rod is received. 
     
     
         11 . The hydraulic machine as recited in  claim 10  further comprising a retainer within the interior cavity and holding the partially spherical head in engagement with the piston. 
     
     
         12 . The hydraulic machine as recited in  claim 10  further comprising a spring within the interior cavity and engaging the partially spherical head of the piston rod and a slot in the piston. 
     
     
         13 . The hydraulic machine as recited in  claim 1  wherein the piston and the piston rod are formed as a single piece, and the piston has a partially spherical circumferential surface that engages a wall of the cylinder. 
     
     
         14 . The hydraulic machine as recited in  claim 1  wherein:
 the cylinder block includes a plurality of first bores in a first end surface and extending parallel to a longitudinal axis of the drive shaft, each of the plurality of first bores being in communication with the first port and opening into one of the plurality of cylinders, and the cylinder block also including a plurality of second bores in a second end surface and extending parallel to a longitudinal axis of the drive shaft, each of the plurality of second bores being in communication with the second port and opening into one of the plurality of cylinders; and 
 the valve arrangement comprises a plurality of first valves, each located in one of the first bores, and a plurality of second valves, each located in one of the second bores. 
 
     
     
         15 . The hydraulic machine as recited in  claim 14  further comprising a tubular sleeve within each one of the plurality of cylinders, wherein each tubular sleeve extends partially across openings of the first bore and the second bore into that one cylinder. 
     
     
         16 . The hydraulic machine as recited in  claim 14  wherein each of the first valves and the second valves is an electrically operated bidirectional valve. 
     
     
         17 . The hydraulic machine as recited in  claim 16  wherein each of the first valves and the second valves is a two-position, two-way valve. 
     
     
         18 . The hydraulic machine as recited in  claim 1  wherein:
 the cylinder block includes a plurality of bores in a first end surface and extending parallel to a longitudinal axis of the drive shaft, each of the plurality of bores in fluid communication with the first port, the second port, and a different one of the plurality of cylinders; and 
 the valve arrangement comprises a plurality of electrically operated valves, each located in one of the plurality of bores for selectively connecting the associated cylinder with the first and second ports. 
 
     
     
         19 . The hydraulic machine as recited in  claim 18  wherein each of the plurality of electrically operated valves is a three-way valve. 
     
     
         20 . The hydraulic machine as recited in  claim 1  wherein the drive shaft has a passage with an opening in a surface of the eccentric cam for conveying fluid for lubrication. 
     
     
         21 . The hydraulic machine as recited in  claim 20  wherein the passage of the drive shaft is operably connected to receive fluid that enters the hydraulic machine through one of the first port and the second port. 
     
     
         22 . A hydraulic machine comprising:
 a cylinder block with an first port, a second port, and an exterior surface, and having a plurality of cylinders disposed radially in the cylinder block with openings through the exterior surface;   a closing band engaging the exterior surface and closing the openings of the plurality of cylinders;   a drive shaft rotatably received in the cylinder block and having an eccentric cam;   a cam bearing extending around the drive shaft and having an outer race with a plurality of rollers between the outer race and the eccentric cam;   a plurality of piston assemblies each slideably received in a different one of the plurality of cylinders and comprising a piston and a piston rod, wherein the piston rod comprises a stem with a curved shoe abutting the outer race;   a retaining ring extending around the drive shaft and engaging the curved shoe of every piston rod to hold the curved shoe against the outer race; and   a plurality of valve arrangements each selectively coupling one of the plurality of cylinders to the first and second ports.   
     
     
         23 - 26 . (canceled) 
     
     
         27 . The hydraulic machine as recited in  claim 22  wherein the valve arrangement comprises a plurality of first valves, each coupling one of the plurality of cylinders to the first port; and a plurality of second valves, each coupling one of the plurality of cylinders to the second port. 
     
     
         28 . The hydraulic machine as recited in  claim 27  wherein each of the plurality of first valves and the plurality of second valves is an electrically operated bidirectional valve. 
     
     
         29 . The hydraulic machine as recited in  claim 22  wherein the valve arrangement comprises a plurality of electrically operated, three-way valve, each selectively coupling one of the plurality of cylinders to the first and second ports. 
     
     
         30 - 36 . (canceled) 
     
     
         37 . A hydraulic machine comprising:
 a cylinder block having a first port, a second port, an end surface, a side surface, and a plurality of cylinders disposed radially in the cylinder block with openings through the side surface, the cylinder block further including a plurality of bores in the first end surface and each bore in fluid communication with the first port, the second port, and one of the plurality of cylinders;   a drive shaft having an eccentric cam and rotatably received in the cylinder block and projecting outward therefrom;   a plurality of piston assemblies slideably received in a different one of the plurality of cylinders; and   a plurality of valve arrangements, each located in one of the bores and selectively controlling fluid flow between the one of the plurality of cylinders and each of the first and second ports.   
     
     
         38 . The hydraulic machine as recited in  claim 37  further comprising a closing band engaging the side surface and closing the openings of the plurality of cylinders. 
     
     
         39 . The hydraulic machine as recited in  claim 37  wherein each of the plurality of valve arrangements is an electrically operated three-way valve. 
     
     
         40 . The hydraulic machine as recited in  claim 37  wherein each of the plurality of valve arrangements is a three-position, three-way valve. 
     
     
         41 . The hydraulic machine as recited in  claim 37  wherein each of the plurality of valve arrangements comprises:
 a plurality of first valves, each located in one of the bores and selectively controlling fluid flow between the first port and the one of the plurality of cylinders; and 
 a plurality of second valves, each located in one of the second bores and selectively controlling fluid flow between the second port and the one of the plurality of cylinders. 
 
     
     
         42 . The hydraulic machine as recited in  claim 37  wherein each of the plurality of piston assemblies comprises a piston, a piston rod having a stem with a curved shoe through which force is transferred to the eccentric cam, and a retaining ring extending around the drive shaft and engaging the curved shoe of every piston rod to constrain the curved shoe from moving away from the eccentric cam.