A hydraulic pump assembly for a vehicle is provided, comprising an electrical motor, a hydraulic pump driven by the electrical motor, and a centrifugal regulator connected with a pressure overflow valve connected to the oil outlet of the hydraulic pump, characterized in that the pump assembly further comprises at least two input check valves and at least two output check valves arranged such that a first pressure outlet port is formed when the motor is rotating in a first direction, and a second pressure outlet port is formed when the motor is rotating in an opposite direction.

An electro hydrostatic actuator (EHA) comprises a hydraulic pump and an electric motor driving the hydraulic pump. The hydraulic pump comprises an inlet and an outlet for hydraulic fluid and an active fluid flow path arranged therebetween such that, in an active mode of operation when the pump is driven by the electric motor, hydraulic fluid is actively drawn in through the inlet and exhausted out through the outlet. The hydraulic pump further comprises a bypass flow path arranged between the pump inlet and outlet, such that, in a damping mode of operation, hydraulic fluid is able to freely flow between the inlet and outlet in either direction.

An electro hydrostatic actuator comprises a hydraulic pump driven by an electric motor to supply hydraulic fluid to a hydraulic actuator. The pump comprises an inlet and an outlet for the hydraulic fluid and an active flow path arranged therebetween such that, in an active mode of operation when the pump is driven by the electric motor, hydraulic fluid is actively drawn in through the inlet and exhausted out through the outlet. The pump further comprises a bypass flow path arranged to open between the inlet and outlet such that, in a damping mode of operation when the pump is not driven by the electric motor, hydraulic fluid is able to pass through the pump along the bypass flow path between the inlet and outlet.

A first bleeding passage 50 configured to allow a crank chamber 2 and a suction chamber 31 to constantly communicate with each other, and a second bleeding passage 60 configured to allow the crank chamber 2 and the suction chamber 31 to constantly communicate with each other are provided. The first bleeding passage 50 is made to communicate with the crank chamber 2 at least via a space (central hole space 54) defined by an insertion end portion of a shaft 7 in a central hole 12 that is formed in the center of a cylinder block 1 and into which the shaft 7 is inserted. The second bleeding passage 60 is opened in an end surface 1a of the cylinder block 1 that is opposed to a swash plate 19.

A first bleeding passage 50 configured to allow a crank chamber 2 and a suction chamber 31 to constantly communicate with each other, and a second bleeding passage 60 configured to allow the crank chamber 2 and the suction chamber 31 to constantly communicate with each other are provided. The first bleeding passage 50 is made to communicate with the crank chamber 2 at least via a space (central hole space 54) defined by an insertion end portion of a shaft 7 in a central hole 12 that is formed in the center of a cylinder block 1 and into which the shaft 7 is inserted. The second bleeding passage 60 is opened in an end surface 1a of the cylinder block 1 that is opposed to a swash plate 19.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits, each kit comprising a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.

A fluid end having its fluid flow bores sealed without threading a retaining nut into the walls of each bore. The fluid ends may be assembled using a plurality of different kits that each comprise a fluid end body, a component, a retainer element, and a fastening system. The retainer element holds the component within each of the bores formed in the fluid end body and the fastening system secures the retainer element to the body. The fastening system comprises a plurality of externally threaded studs, washers and nuts in some embodiments. In other embodiments, the fastening system comprises a plurality of screws.