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.

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.

An axial hydraulic pump-motor, in which a cylinder block having a plurality of cylinder bores on a valve plate having a high-pressure side port and a low-pressure side port for controlling an amount of reciprocation of a piston in each of the cylinder bores, the hydraulic pump-motor includes: a residual pressure release port provided on the valve plate and communicating until the cylinder bore on a top dead center side communicates with the low-pressure side port; a residual pressure acquisition portion obtaining a value of a residual pressure in the cylinder bore on the top dead center side; and a directional switching valve switching a flow path between the residual pressure release port and an hydraulic oil tank and a flow path between the residual pressure release port and the low-pressure side port.

An axial hydraulic pump-motor, in which a cylinder block having a plurality of cylinder bores on a valve plate having a high-pressure side port and a low-pressure side port for controlling an amount of reciprocation of a piston in each of the cylinder bores, the hydraulic pump-motor includes: a residual pressure release port provided on the valve plate and communicating until the cylinder bore on a top dead center side communicates with the low-pressure side port; a residual pressure acquisition portion obtaining a value of a residual pressure in the cylinder bore on the top dead center side; and a directional switching valve switching a flow path between the residual pressure release port and an hydraulic oil tank and a flow path between the residual pressure release port and the low-pressure side port.

A pump in desalination systems has four cylinders, each having a double acting piston. Each cylinder and piston defines a feed chamber and a recovery chamber. The pistons connect to a common drive. The connection to the common drive is such that the pistons reciprocate in a sequence equally spaced in time. Reciprocating valving for each piston is driven by the common drive to be 90 degrees out of phase with the respective piston. The valving connects the recovery chamber alternately to an inlet manifold for an intake stroke of the piston relative to the recovery chamber, and to an outlet manifold for a discharge stroke of the piston relative to the recovery chamber. A brief period of closure coincides with top dead centre and bottom dead centre of the piston, during which the recovery chamber is blocked off from both the inlet and outlet manifolds. The reciprocating valving is midway between its top dead centre and bottom dead centre during the period of closure.

A pump in desalination systems has four cylinders, each having a double acting piston. Each cylinder and piston defines a feed chamber and a recovery chamber. The pistons connect to a common drive. The connection to the common drive is such that the pistons reciprocate in a sequence equally spaced in time. Reciprocating valving for each piston is driven by the common drive to be 90 degrees out of phase with the respective piston. The valving connects the recovery chamber alternately to an inlet manifold for an intake stroke of the piston relative to the recovery chamber, and to an outlet manifold for a discharge stroke of the piston relative to the recovery chamber. A brief period of closure coincides with top dead centre and bottom dead centre of the piston, during which the recovery chamber is blocked off from both the inlet and outlet manifolds. The reciprocating valving is midway between its top dead centre and bottom dead centre during the period of closure.

Pump assemblies and pumping systems incorporating the pump assemblies are disclosed. In an embodiment, the pump assembly includes a power end including an output shaft having an output shaft axis. In addition, the pump assembly includes a fluid end including a piston configured to reciprocate to pressurize the working fluid. Further, the pump assembly includes a transmission coupled to each of the power end and the fluid end. The transmission includes a carriage coupled to the piston and a pivoting arm pivotably coupled to the carriage at a first connection about a first pivot axis. The first pivot axis extends in a perpendicular direction to a direction of the output shaft axis, and rotation of the output shaft about the output shaft axis is configured to cause the pivoting arm to pivot about the first pivot axis at the first connection and to cause the carriage to reciprocate

An axial piston motor having a cylinder housing, in which a plurality of cylinders are formed, and having pistons which are movably guided in the cylinders, wherein the pistons are attached to a swash plate and wherein a flow of a fluid that has entered via an inlet into the axial piston motor is controlled into and out of the cylinders by means of inlet and outlet valves, wherein the inlet and/or outlet valves comprise fluid change openings which are formed in a cylinder head plate and which can be temporarily released and covered by means of a rotary slide, for which purpose the rotary slide forms at least one passage opening.

A plunger pump fluid end housing assembly comprising: a fluid end housing, multiple plungers, a single in-line suction valve and seat corresponding with each said plunger, a discharge valve and seat corresponding with each said plunger; wherein axis of said suction valve and seat are parallel with said plunger, and the suction manifold is positioned to feed the fluid chamber opposite the power end of the fluid end. Plunger chamber of said fluid end housing is square or rectangular in cross section with large fillets at corners and flats between said fillets. Said flats are approximately equal in width to radii of said fillets.

An electric tool is configured that oil pressure can be rapidly increased while suppressing the load on a motor. The electric tool includes a main body in which a cylinder part, a hydraulic pump for feeding hydraulic oil to the cylinder part and an electric motor are disposed, and a tool head operated by a pressing force of a piston in the cylinder part. The hydraulic pump has a swash plate cam, a first plunger, a second plunger, a check valve and a relief valve, and until the pressure reaches the first pressure, a first liquid feeding amount of the first plunger is increased than a second liquid feeding amount of the second plunger.