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.

A pump draws fluid from a reservoir and drives the fluid downstream to a spray tip where the fluid is applied to a surface. A piston is driven in a reciprocating manner to pump the fluid. A check valve is disposed downstream of the piston to regulate a flow of the fluid downstream from the piston. The pump is initially dry and is primed with fluid prior to operation. To facilitate priming, the piston is dimensioned to impact the ball and unseat a valve member of the check valve during a priming stroke, thereby ejecting any air from the pump through the check valve. With the air ejected from the pump, a vacuum is formed during a suction stroke of the piston, which draws fluid downstream from the reservoir to prime the pump.

The present invention concerns an axial piston pump (1, 1, 1,1) for the pumping of a liquid comprising: a head (20) in which there is at least partially made a plurality of cylinders (25) in a number greater than three, with central axes parallel between them, a plurality of pistons (75) each of which slide in a respective cylinder (25) of the plurality of cylinders (25) for the pumping of the liquid, and a suction channel of the liquid to pump, which is equipped with a primary duct (140) and a plurality of branch ducts (145, 145,145), each of said branch ducts (145, 145,145) being adapted to place the primary duct (140) in fluid communication with a respective cylinder (25) of the plurality of cylinders (25), in which the primary duct (140) is positioned between the central axes of the cylinders (25).

The present invention concerns an axial piston pump (1, 1, 1,1) for the pumping of a liquid comprising: a head (20) in which there is at least partially made a plurality of cylinders (25) in a number greater than three, with central axes parallel between them, a plurality of pistons (75) each of which slide in a respective cylinder (25) of the plurality of cylinders (25) for the pumping of the liquid, and a suction channel of the liquid to pump, which is equipped with a primary duct (140) and a plurality of branch ducts (145, 145,145), each of said branch ducts (145, 145,145) being adapted to place the primary duct (140) in fluid communication with a respective cylinder (25) of the plurality of cylinders (25), in which the primary duct (140) is positioned between the central axes of the cylinders (25).

A submersible pumping system has an electric motor, a rotary hydraulic pump driven by the electric motor, and a linear hydraulic pump that is configured to move a production fluid. The rotary hydraulic pump produces a pressurized working fluid that drives the linear hydraulic pump. In another aspect, a method is disclosed for controlling the temperature of an electric motor within a submersible pumping system disposed in a wellbore. The method includes the steps of circulating motor lubricant through a hydraulically driven production pump to reduce the temperature of the motor lubricant.

This plunger pump includes a pressurization chamber that has a tubular inner circumferential wall and a plunger that has a substantially cylindrical outer circumferential surface. The inner circumferential wall has, in a part thereof in a circumferential direction about an axis of the plunger, a suction opening, which communicates with the pressurization chamber and is for introducing a fuel into the pressurization chamber. The inner circumferential wall is formed with an enlarged gap portion having a larger dimension than a dimension, at a position of the suction opening, from the outer circumferential surface of the plunger to an inner circumferential surface of the inner circumferential wall along a radial direction of the plunger, in at least a part of the inner circumferential wall at a position away from the position of the suction opening in the circumferential direction.

A pump draws fluid from a reservoir and drives the fluid downstream to a spray tip where the fluid is applied to a surface. A piston is driven in a reciprocating manner to pump the fluid. A check valve is disposed downstream of the piston to regulate a flow of the fluid downstream from the piston. The pump is initially dry and is primed with fluid prior to operation. To facilitate priming, the piston is dimensioned to impact the ball and unseat a valve member of the check valve during a priming stroke, thereby ejecting any air from the pump through the check valve. With the air ejected from the pump, a vacuum is formed during a suction stroke of the piston, which draws fluid downstream from the reservoir to prime the pump.

The present disclosure relates to a piston assembly, the piston assembly comprising a cylinder extending along an axis and having an open axial end, a cap assembly closing the cylinder at its open axial end, wherein the cap assembly comprises an insertion portion received in the cylinder at its open axial end, and a piston axially movably disposed within the cylinder and partially received in the insertion portion of the cap assembly. The present disclosure further relates to a variable displacement hydraulic unit including said piston assembly.

The present disclosure relates to a piston assembly, the piston assembly comprising a cylinder extending along an axis and having an open axial end, a cap assembly closing the cylinder at its open axial end, wherein the cap assembly comprises an insertion portion received in the cylinder at its open axial end, and a piston axially movably disposed within the cylinder and partially received in the insertion portion of the cap assembly. The present disclosure further relates to a variable displacement hydraulic unit including said piston assembly.

A pump plunger is disclosed. The plunger may include a proximal end and a distal end opposite the proximal end. The plunger may also include a body portion extending between the proximal end and a second transition datum, and additionally include a transition section extending between a first transition datum and the second transition datum. The transition section may have a non-linear geometric profile. A first shoulder portion may be positioned adjacent to the transition section that may extend between the second transition datum and a third datum. The third datum may be positioned radially inward of the second transition datum. The plunger may also include a tip portion positioned adjacent to the first shoulder portion that may extend between the third datum and a fourth datum positioned at the distal end. The fourth datum may be positioned radially inward of the third datum.