Alternating flow hydraulic pump circuit

Abstract

A hydraulic pump assembly including a first pump, a second pump, a shaft, and fluid lines is disclosed. The first pump includes a first piston assembly. The second pump including a second piston assembly. Each piston assembly of the first and second pumps includes a cylinder and a piston slidably disposed in the cylinder. The shaft connects the first pump to the second pump and is configured to displace the pistons within the cylinders of the first and second piston assemblies. The fluid lines fluidly couple the first piston assembly with the second piston assembly to form paired piston assemblies. The first piston assembly is phase shifted from the second piston assembly.

What is claimed is: 
     
         1 . A hydraulic pump assembly, comprising:
 a first pump including a first piston assembly, wherein the first piston assembly includes a first cylinder and a first piston is slidably disposed in the first cylinder;   a second pump including a second piston assembly, wherein the second piston assembly includes a second cylinder and a second piston is slidably disposed in the second cylinder;   a shaft connecting the first pump to the second pump and configured to displace the first and second pistons within the first and second cylinders; and   fluid lines to fluidly couple the first piston assembly with the second piston assembly to form paired piston assemblies,   wherein the first piston assembly is phase shifted from the second piston assembly.   
     
     
         2 . The assembly of  claim 1 , wherein the first and second pumps each include at least two piston assemblies. 
     
     
         3 . The assembly of  claim 1 , wherein the first and second pumps are radial piston pumps. 
     
     
         4 . The assembly of  claim 1 , wherein the first and second piston assemblies each include three piston assemblies arranged radially at 120 degrees. 
     
     
         5 . The assembly of  claim 1 , wherein the first and second pumps are inline pumps. 
     
     
         6 . The assembly of  claim 1 , wherein the fluid lines include:
 an inflow source line for fluid flow into the first and second piston assemblies; and   an outflow source line for fluid flow out of the first and second piston assemblies.   
     
     
         7 . The assembly of  claim 6 , further comprising:
 active valves disposed along the inflow source line to control flow into the first and second piston assemblies.   
     
     
         8 . The assembly of  claim 2 , wherein each of the at least two piston assemblies of the first pump is fluidly coupled to one of the at least two piston assemblies of the second pump. 
     
     
         9 . The assembly of  claim 1 , further comprising:
 at least one additional first and second pumps including pump assemblies, wherein the shaft connects the at least one additional first and second pumps and wherein the fluid lines extend between the at least one additional first and second pumps to fluidly couple piston assemblies to form pairs of mated piston assemblies, and wherein the piston assemblies are phase shifted from one another.   
     
     
         10 . A hydraulic pump assembly, comprising:
 a first pump and a second pump each including:
 a piston assembly, 
 a translating mechanism to selectively move a piston within a cylinder of the piston assembly, and 
 a casing to house the translating mechanism and piston assembly; 
   a shaft coupled to the first and second pumps, the shaft to jointly rotate the translating mechanisms; and   a fluid line to fluidly couple the piston assemblies of the first and second pumps;   wherein the pistons are movable by the translating mechanisms to transfer fluid flow between the fluidly coupled piston assemblies.   
     
     
         11 . The assembly of  claim 10 , wherein the piston assembly of each of the first and second pumps includes at least two piston assemblies. 
     
     
         12 . The assembly of  claim 11 , wherein each of the at least two piston assemblies of the first pump is fluidly coupled to one of the at least two piston assemblies of the second pump. 
     
     
         13 . The assembly of  claim 10 , wherein first pump is phase shifted from the second pump along the shaft. 
     
     
         14 . The assembly of  claim 10 , wherein the casings of the first and second pumps are rotationally fixed along the shaft. 
     
     
         15 . The assembly of  claim 10 , wherein the first and second pumps each have an axis of rotation, wherein the translating mechanisms are rotatable around the axes of rotation to move the pistons of the piston assemblies. 
     
     
         16 . A method of operating a hydraulic pump assembly, comprising:
 supplying fluid to a first pump and a second pump mounted along a shaft, the first and second pumps each including a piston assembly, a translating mechanism to selectively move a piston within a cylinder of the piston assembly, and a casing to house the translating mechanism and piston assembly;   rotating the translating mechanism s of the first and second pump;   slidably moving the piston of the first pump within the cylinder in response to contacting the piston of the first pump with the translating mechanism;   transferring fluid from the piston assembly of the first pump to the piston assembly of the second pump;   slidably moving the piston of the second pump within the cylinder in response to contacting the piston of the first pump with the translating mechanism; and   transferring fluid from the piston assembly of the second pump to the piston assembly of the first pump.   
     
     
         17 . The method of  claim 16 , wherein the first pump is rotated relative to the second pump. 
     
     
         18 . The method of  claim 16 , wherein the translating mechanisms are rotated relative to the shaft and the first and second pumps are rotationally fixed to the shaft. 
     
     
         19 . The method of  claim 16 , wherein slidably moving the pistons of the first and second pumps includes radially reciprocally moving the pistons within the cylinders through a constant length stroke. 
     
     
         20 . The method of  claim 16 , wherein the first and second pumps are oriented at a phase shift angle.