Method of operating a pump/motor

Abstract

A method of operating a pump/motor includes pumping working fluid into a high-pressure manifold with a first piston/cylinder assembly while the piston in the first piston/cylinder assembly is displaced from a bottom dead center position to a top dead center position, and transferring working fluid from the high-pressure manifold to the cylinder of a second piston/cylinder assembly to displace the piston of the second piston/cylinder assembly from a top dead center position to a bottom dead center position, thereby imparting torque on a cam and an output shaft, within the same complete revolution of the cam and the output shaft in which working fluid is pumped into the high-pressure manifold by the first piston/cylinder assembly.

1 . A method of operating a pump/motor in a system including a high-pressure manifold and a low-pressure manifold, the pump/motor including an output shaft, a plurality of piston/cylinder assemblies, and a cam coupled to the output shaft and disposed between the output shaft and the piston/cylinder assemblies, each piston/cylinder assembly including a cylinder and a piston at least partially disposed in the cylinder and engaged with the cam, the method comprising:
 displacing the pistons of the respective piston/cylinder assemblies from a bottom dead center position to a top dead center position, and then back to the bottom dead center position, within each revolution of the cam and the output shaft;   pumping working fluid into the high-pressure manifold with a first piston/cylinder assembly while the piston in the first piston/cylinder assembly is displaced from the bottom dead center position to the top dead center position; and   transferring working fluid from the high-pressure manifold to the cylinder of a second piston/cylinder assembly to displace the piston of the second piston/cylinder assembly from the top dead center position to the bottom dead center position, thereby imparting torque on the cam and the output shaft, within the same complete revolution of the cam and the output shaft in which working fluid is pumped into the high-pressure manifold by the first piston/cylinder assembly.   
     
     
         2 . The method of  claim 1 , wherein the second piston/cylinder assembly is included in a group of piston/cylinder assemblies from which the first piston/cylinder assembly is excluded, and wherein the method further includes transferring working fluid from the high-pressure manifold to each of the cylinders of the group to displace the respective pistons in the group from the top dead center position to the bottom dead center position within the same complete revolution of the cam and the output shaft in which working fluid is pumped into the high-pressure manifold by the first piston/cylinder assembly. 
     
     
         3 . The method of  claim 2 , wherein transferring working fluid from the high-pressure manifold to each of the cylinders of the group includes opening a valve in each of the piston/cylinder assemblies of the group to fluidly communicate the respective cylinders of the group with the high-pressure manifold. 
     
     
         4 . The method of  claim 3 , further comprising exhausting working fluid to the low-pressure manifold with each of the piston/cylinder assemblies of the group when the pistons in the group are displaced from the bottom dead center position to the top dead center position within the same complete revolution of the cam and the output shaft in which working fluid is pumped into the high-pressure manifold by the first piston/cylinder assembly. 
     
     
         5 . The method of  claim 4 , wherein exhausting working fluid to the low-pressure manifold includes opening a second valve in each of the piston/cylinder assemblies of the group to fluidly communicate the respective cylinders of the group with the low-pressure manifold. 
     
     
         6 . The method of  claim 5 , further comprising driving each of the pistons of the group with the rotating cam from the bottom dead center position to the top dead center position while the second valve is open to exhaust working fluid from the respective cylinders of the group to the low-pressure manifold. 
     
     
         7 . The method of  claim 2 , further comprising at least partially filling the cylinder of a third piston/cylinder assembly excluded from the group with working fluid from the low-pressure manifold, thereby displacing the piston in the third piston/cylinder assembly from the top dead center position to the bottom dead center position, within the same complete revolution of the cam and the output shaft in which working fluid is pumped into the high-pressure manifold by the first piston/cylinder assembly. 
     
     
         8 . The method of  claim 7 , wherein at least partially filling the cylinder of the third piston/cylinder assembly with working fluid from the low-pressure manifold includes opening a valve in the third piston/cylinder assembly to fluidly communicate the cylinder of the third piston/cylinder assembly with the low-pressure manifold. 
     
     
         9 . The method of  claim 1 , wherein the first piston/cylinder assembly is included in a group of piston/cylinder assemblies from which the second piston/cylinder assembly is excluded, and wherein the method further includes pumping working fluid into the high-pressure manifold with each of the assemblies in the group within the same complete revolution of the cam and the output shaft in which working fluid is transferred from the high-pressure manifold to the second piston/cylinder assembly. 
     
     
         10 . The method of  claim 9 , wherein pumping working fluid into the high-pressure manifold with each of the piston/cylinder assemblies of the group includes opening a valve in each of the piston/cylinder assemblies of the group to fluidly communicate the respective cylinders of the group with the high-pressure manifold. 
     
     
         11 . The method of  claim 10 , further comprising driving each of the pistons of the group with the rotating cam from the bottom dead center position to the top dead center position while the valve is open to pump working fluid from the respective cylinders of the group to the high-pressure manifold. 
     
     
         12 . The method of  claim 10 , further comprising at least partially filling the respective cylinders of the group with low-pressure working fluid from the low-pressure manifold when the pistons in the group are displaced from the top dead center position to the bottom dead center position. 
     
     
         13 . The method of  claim 12 , wherein at least partially filling the respective cylinders of the group with low-pressure working fluid includes opening a second valve in each of the piston/cylinder assemblies of the group to fluidly communicate the respective cylinders of the group with the low-pressure manifold. 
     
     
         14 . The method of  claim 10 , further comprising exhausting low-pressure working fluid from the cylinder of a third piston/cylinder assembly excluded from the group to the low-pressure manifold when the piston of the third piston/cylinder assembly is displaced from the bottom dead center position to the top dead center position within the same complete revolution of the cam and the output shaft in which working fluid is transferred from the high-pressure manifold to the second piston/cylinder assembly. 
     
     
         15 . The method of  claim 14 , wherein exhausting low-pressure working fluid from the cylinder of the third piston/cylinder assembly includes
 opening a second valve in the third piston/cylinder assembly to fluidly communicate the cylinder of the third piston/cylinder assembly with the low-pressure manifold, and   driving the piston of the third piston/cylinder assembly with the rotating cam from the bottom dead center position to the top dead center position while the second valve is open to exhaust working fluid from the cylinder of the third piston/cylinder assembly to the low-pressure manifold.   
     
     
         16 . A method of operating a pump/motor in a system including a high-pressure manifold and a low-pressure manifold, the pump/motor including an output shaft, a plurality of piston/cylinder assemblies, and a cam coupled to the output shaft and disposed between the output shaft and the piston/cylinder assemblies, each piston/cylinder assembly including a cylinder and a piston at least partially disposed in the cylinder and engaged with the cam, a first valve selectively fluidly communicating the high-pressure manifold and the cylinder, and a second valve selectively fluidly communicating the low-pressure manifold and the cylinder, the method comprising:
 opening the first valve of a first group of piston/cylinder assemblies to at least partially fill each of the cylinders within the first group with high-pressure working fluid, thereby displacing the pistons within the respective cylinders in the first group from a top dead center position to a bottom dead center position;   rotating the output shaft and the cam with the pistons in the first group;   opening the second valve of a second group of piston/cylinder assemblies;   driving each of the pistons within the second group, with the rotating cam, from the bottom dead center position to the top dead center position to at least partially exhaust working fluid from each of the cylinders within the second group to the low-pressure manifold;   opening the first valve of a first piston/cylinder assembly not in either of the first and second groups while the respective first valves in the first group are opened; and   driving the piston in the first piston/cylinder assembly, with the rotating cam, from the bottom dead center position toward the top dead center position to pump working fluid into the high-pressure manifold while the first valve of the first piston/cylinder assembly is opened.   
     
     
         17 . The method of  claim 16 , wherein driving the piston in the first piston/cylinder assembly, with the rotating cam, from the bottom dead center position toward the top dead center position includes pumping working fluid from the cylinder of the first piston/cylinder assembly, through the first valve of the piston/cylinder assembly, and into the high-pressure manifold. 
     
     
         18 . The method of  claim 16 , wherein the piston/cylinder assemblies are arranged substantially symmetrically about a longitudinal axis of the pump/motor, wherein rotating the output shaft and the cam with the pistons in the first group includes rotating the output shaft and the cam about the longitudinal axis, and wherein opening the first valve of the first piston/cylinder assembly occurs within the same complete revolution of the output shaft and the cam about the longitudinal axis as opening the first valve of the first group of piston/cylinder assemblies. 
     
     
         19 . A method of operating a pump/motor in a system including a high-pressure manifold and a low-pressure manifold, the pump/motor including an output shaft, a plurality of piston/cylinder assemblies, and a cam coupled to the output shaft and disposed between the output shaft and the piston/cylinder assemblies, each piston/cylinder assembly including a cylinder and a piston at least partially disposed in the cylinder and engaged with the cam, a first valve selectively fluidly communicating the high-pressure manifold and the cylinder, and a second valve selectively fluidly communicating the low-pressure manifold and the cylinder, the method comprising:
 opening the first valve of a first group of piston/cylinder assemblies to fluidly communicate the cylinders in the first group with the high-pressure manifold;   rotating the output shaft and the cam, thereby displacing the pistons within the respective cylinders in the first group from a bottom dead center position to a top dead center position to pump working fluid in the respective cylinders in the first group into the high-pressure manifold;   opening the second valve of a second group of piston/cylinder assemblies;   at least partially filling the respective cylinders within the second group with working fluid from the low-pressure manifold, thereby displacing the pistons within the respective cylinders in the second group from the top dead center position to the bottom dead center position;   opening the first valve of a first piston/cylinder assembly not in either of the first and second groups, while the respective first valves in the first group are opened, to at least partially fill the cylinder of the first piston/cylinder assembly with high-pressure working fluid, thereby displacing the piston in the first piston/cylinder assembly from the top dead center position to the bottom dead center position; and   imparting a torque on the cam and the output shaft with the piston in the first piston/cylinder assembly as the piston in the first piston/cylinder assembly moves from the top dead center position to the bottom dead center position.   
     
     
         20 . The method of  claim 19 , wherein the piston/cylinder assemblies are arranged substantially symmetrically about a longitudinal axis of the pump/motor, wherein rotating the output shaft and the cam includes rotating the output shaft and the cam about the longitudinal axis, and wherein opening the first valve of the first piston/cylinder assembly occurs within the same complete revolution of the output shaft and the cam about the longitudinal axis as opening the first valve of the first group of piston/cylinder assemblies.