Axial pump and hydraulic drive system

Abstract

A hydraulic device having an input shaft and an output shaft, the device comprising: a housing having the input shaft mounted at one end and the output shaft mounted at the other end; an axially reciprocating hydraulic pump mounted on the input shaft within the housing, the axially reciprocating hydraulic pump having: a plurality of pistons located in respective piston bores and configured for axial reciprocation therein; a cam plate connected to the input shaft, the cam plate having a plurality of cam surfaces distributed about the cam plate for driving the plurality of pistons towards Top Dead Center (TDC) of the piston bores; a rotating hydraulic motor mounted on the output shaft within the housing for rotating with the output shaft; and a pair of shared fluid conduits, one of the pair directly and fluidly connecting a fluid outlet of the axially reciprocating hydraulic pump with a fluid inlet of the rotating hydraulic motor and the other of the pair for directly and fluidly connecting a fluid outlet of the rotating hydraulic motor with a fluid inlet of the axially reciprocating hydraulic pump, such that the pair are contained within the housing; wherein flow of hydraulic fluid between the axially reciprocating hydraulic pump and the rotating hydraulic motor bypasses any fluid reservoir external to the housing.

1 . A hydraulic device having an input shaft and an output shaft, the device comprising:
 a housing having the input shaft mounted at one end and the output shaft mounted at the other end;   an axially reciprocating hydraulic pump mounted on the input shaft within the housing, the axially reciprocating hydraulic pump having:
 a plurality of pistons located in respective piston bores and configured for axial reciprocation therein; 
 a cam plate connected to the input shaft, the cam plate having a plurality of cam surfaces distributed about the cam plate for driving the plurality of pistons towards Top Dead Center (TDC) of the piston bores; 
   a rotating hydraulic motor mounted on the output shaft within the housing for rotating with the output shaft; and
 a pair of shared fluid conduits, one of the pair directly and fluidly connecting a fluid outlet of the axially reciprocating hydraulic pump with a fluid inlet of the rotating hydraulic motor and the other of the pair for directly and fluidly connecting a fluid outlet of the rotating hydraulic motor with a fluid inlet of the axially reciprocating hydraulic pump, such that the pair are contained within the housing; 
 wherein flow of hydraulic fluid between the axially reciprocating hydraulic pump and the rotating hydraulic motor bypasses any fluid reservoir external to the housing. 
   
     
     
         2 . The device of  claim 1 , wherein the cam plate is connected to the input shaft at a fixed angle to the input shaft. 
     
     
         3 . The device of  claim 1 , wherein the other of the pair is fluidly connected to a second fluid conduit connecting the other of the pair to the fluid inlet of the hydraulic pump, the second fluid conduit located within a shell of the housing between the fluid inlet of the hydraulic pump and the fluid outlet of the hydraulic motor. 
     
     
         4 . The device of  claim 1 , wherein the fluid inlet of the hydraulic pump and the fluid outlet of the hydraulic motor are located within the shell of the housing. 
     
     
         5 . The device of  claim 1 , wherein each of the cam surfaces is opposite to a respective drive piston surface of each of the plurality of pistons, such that the cam surfaces and the drive piston surfaces can become decoupled from one another in a spaced apart manner based on an amount of the hydraulic fluid contained within the piston bores. 
     
     
         6 . The device of  claim 1 , wherein the amount of the hydraulic fluid injected into a selected piston bore of the piston bores can be inhibited via closing of a valve associated with a fluid line connected to the fluid inlet of the selected piston bore in order to inhibit axial reciprocation of the piston in the selected piston bore while maintaining an open state of a second valve associated with a second fluid line connected to the fluid inlet of a second piston bore of the piston bores in order to maintain axial reciprocation of a second piston in the second piston bore. 
     
     
         7 . The device of  claim 1 , further comprising a second set of pistons located in a second set piston bores and configured for axial reciprocation therein, second set of pistons opposed to the plurality of pistons to provide for configuration of the hydraulic pump as a double acting pump, such that the cam plate has a second set of cam surfaces distributed about the cam plate opposite the plurality of cam surfaces, the second set of cam surfaces for driving the plurality of pistons towards TDC of the second set of piston bores, fluid outlets of the second set of piston bores fluidly coupled to the one of the pair and fluid outlets of the second set of piston bores fluidly coupled to the other of the pair. 
     
     
         8 . The device of  claim 1 , further comprising a set of control valves for inhibiting injection of the hydraulic fluid into the fluid inlets of the second set of piston bores to provide for operation of the hydraulic pump as a single acting pump. 
     
     
         9 . The device of  claim 1 , further comprising a third set of pistons positioned in a corresponding set of piston bores in the housing a cam plate connected to the input shaft, the cam plate having a plurality of cam surfaces distributed about the cam plate for driving the plurality of pistons towards Top Dead Center (TDC) of the piston bores. 
     
     
         10 . The device of  claim 1 , wherein the output shaft and the input shaft are decoupled from one another and thus free to rotate independently with respect to one another. 
     
     
         11 . The device of  claim 1 , further comprising a linkage for coupling the output shaft to the input shaft to facilitate a braking mode.