A hydrostatic axial piston machine includes a housing, a connection plate closing the housing, working connections formed on the connection plate, a drive shaft, a swashplate, a cylinder drum coupled to the shaft in the direction of rotation, bores formed in the drum and each including a piston, a control plate against which the drum bears, a retraction plate for removing a piston from the bores, and a retraction ball arranged in front of the first end face of the drum which surrounds a drum neck of the drum and the shaft and by which the retraction plate is loaded in the direction of the swashplate. A pressure chamber is defined by seals between the retraction ball, the drum, and the shaft, and is configured to be acted upon by a pressure above a housing pressure. The retraction ball is sealed against the drum neck and against the shaft.

An ultra-long stroke multi-cylinder reciprocating pump comprises a small gear, a large gear, a crankshaft, connecting rods, fixed racks, a frame, translation pinions, movable racks, clamps, piston rods, cylinder sleeves, pistons, suction valves, liquid discharging valves, guide rails, a prime motor, a coupling, and a small gear shaft. When the prime motor rotates, the small gear is meshed with the large gear to drive the crankshaft to rotate, an axial center of the translation pinion is driven by the connecting rod to move reciprocally, the translation pinion is meshed with the fixed rack and the movable rack simultaneously, and a distance of reciprocating motion of the movable rack is twice a distance of reciprocating motion of a rotation center of the translation pinion, so that an ultra-long stroke is realized.

An ultra-long stroke multi-cylinder reciprocating pump comprises a small gear, a large gear, a crankshaft, connecting rods, fixed racks, a frame, translation pinions, movable racks, clamps, piston rods, cylinder sleeves, pistons, suction valves, liquid discharging valves, guide rails, a prime motor, a coupling, and a small gear shaft. When the prime motor rotates, the small gear is meshed with the large gear to drive the crankshaft to rotate, an axial center of the translation pinion is driven by the connecting rod to move reciprocally, the translation pinion is meshed with the fixed rack and the movable rack simultaneously, and a distance of reciprocating motion of the movable rack is twice a distance of reciprocating motion of a rotation center of the translation pinion, so that an ultra-long stroke is realized.

A motor-hydraulic machine unit includes an electric motor, a hydraulic machine, and a connection body that has a planar connection surface which delimits first and second working connections. The first and second working connections are each in fluid exchange connection with the hydraulic machine via an assigned first fluid duct in the connection body. The electric motor and the hydraulic machine have a common axis of rotation which is arranged substantially parallel to the connection surface. The hydraulic machine and the electric motor are arranged on opposite sides of the connection body in the direction of the axis of rotation. The connection body is traversed by a drive aperture in the direction of the axis of rotation. The electric motor and the hydraulic machine are in rotary drive connection in a region of the drive aperture.

A motor-hydraulic machine unit includes an electric motor, a hydraulic machine, and a connection body that has a planar connection surface which delimits first and second working connections. The first and second working connections are each in fluid exchange connection with the hydraulic machine via an assigned first fluid duct in the connection body. The electric motor and the hydraulic machine have a common axis of rotation which is arranged substantially parallel to the connection surface. The hydraulic machine and the electric motor are arranged on opposite sides of the connection body in the direction of the axis of rotation. The connection body is traversed by a drive aperture in the direction of the axis of rotation. The electric motor and the hydraulic machine are in rotary drive connection in a region of the drive aperture.

A hydrostatic piston machine unit, which is in particular designed as a hydrostatic axial piston machine unit, comprises at least two driving mechanisms that can be driven synchronously and have displacement pistons which each perform a reciprocating motion in operation and are provided for delivery into a common pressure line. The hydrostatic piston machine unit has a jointly assigned precompression volume for the at least two driving mechanisms.

Provided is an electro/hydraulic valve for use in a hydrocarbon production well, an electrically surface-controlled subsurface safety valve, and a method of operating an electrically surface-controlled subsurface safety valve. The electro/hydraulic valve for use in a hydrocarbon production well, in one aspect, includes a fluid chamber and an electro/mechanical pump having a fluid inlet and a fluid outlet, and further wherein an inlet check valve is positioned in fluid communication between the fluid chamber and the fluid inlet and an outlet check valve is positioned in fluid communication between the fluid outlet and a hydraulically controlled actuation member.

Provided is an electro/hydraulic valve for use in a hydrocarbon production well, an electrically surface-controlled subsurface safety valve, and a method of operating an electrically surface-controlled subsurface safety valve. The electro/hydraulic valve for use in a hydrocarbon production well, in one aspect, includes a fluid chamber and an electro/mechanical pump having a fluid inlet and a fluid outlet, and further wherein an inlet check valve is positioned in fluid communication between the fluid chamber and the fluid inlet and an outlet check valve is positioned in fluid communication between the fluid outlet and a hydraulically controlled actuation member.

A pumping system includes at least three electrically driven pumping units. Each pumping unit includes a linear actuator driven by at least one electric motor and driving a shaft. Pistons on each end of the shaft move within fixed cylinders to draw fluid from an inlet and expel the fluid to an outlet. Each pumping unit draws fluid at one end while expelling an equal quantity of fluid at the opposite end. The shaft velocity is controlled such that a total flow of the pumping system is constant, eliminating flow ripple.

A pumping system includes at least three electrically driven pumping units. Each pumping unit includes a linear actuator driven by at least one electric motor and driving a shaft. Pistons on each end of the shaft move within fixed cylinders to draw fluid from an inlet and expel the fluid to an outlet. Each pumping unit draws fluid at one end while expelling an equal quantity of fluid at the opposite end. The shaft velocity is controlled such that a total flow of the pumping system is constant, eliminating flow ripple.