A lift apparatus and method for driving a downhole reciprocating pump is disclosed and includes a hydraulic cylinder having a piston and a hydraulic fluid port, the piston being coupled to a rod for driving the reciprocating pump, the piston being moveable between first and second ends of the cylinder in response to a flow of hydraulic fluid through the hydraulic fluid port. A variable displacement hydraulic pump is responsive to a displacement control signal to draw hydraulic fluid from a reservoir and to produce a controlled flow of hydraulic fluid at the outlet. The apparatus also includes a valve connected between the hydraulic fluid port and the reservoir, the valve being responsive to a valve control signal for controlling discharge of hydraulic fluid from the hydraulic fluid port of the cylinder back to the reservoir to facilitate movement of the piston through a downstroke away from the second end toward the first end of the cylinder. The apparatus further includes a first sensor located proximate the first end of the cylinder and operable to produce a first signal indicating a proximity of the piston to the first sensor, a second sensor located proximate the second end of the cylinder and operable to produce a second signal indicating a proximity of the piston to the second sensor, and a controller operably configured to generate the displacement control signal and the valve control signal in response to receiving the first signal and the second signal.

A variable displacement axial pump, including: a housing including first and second inlet ports and first and second outlet ports; a shaft arranged to receive rotational torque; an axis of rotation for the shaft; swash plate located in the housing; a first cylinder block located in the housing and including first and second through-bores and first and second pistons at least partly disposed in the first and second through-bores, respectively, and connected to the swash plate; and a second cylinder block located in the housing and including third and fourth through-bores and third and fourth pistons at least partly disposed in the third and fourth through-bores, respectively, and connected to the swash plate. The shaft is arranged to rotate, with respect to the swash plate, the first and second cylinder blocks about the axis of rotation.

A pump volume control apparatus includes: a tilting piston; a pump volume switching valve configured to adjust a tilt driving pressure by a movement of a spool; a flow rate control spring configured to bias the spool in accordance with a tilt angle; a horsepower control piston configured to move in accordance with a pump discharge pressure; and a horsepower control spring configured to bias the horsepower control piston in accordance with the tilt angle. The tilt driving pressure is adjusted by means of the movement of the spool in accordance with a force acting on the spool in response to a flow rate controlling signal pressure in a flow rate controlled state, and is adjusted by means of the movement of the spool in accordance with a force acting on the horsepower control piston in response to the pump discharge pressure in a horsepower controlled state.

The present invention relates to an electronically controlled valve for a variable displacement pump, a hydraulic pump and a hydraulic pump system with switchable control functions. Multiple control functions of different types of hydraulic pumps can be implemented via one single electronically controlled valve combined with control elements and sensors. The hydraulic pump systems can be easily integrated into the overall application systems for intelligent control.

Provided is a variable displacement pump which sucks and discharges a working fluid by moving a piston with a stroke in response to an inclination angle of a swash plate, the variable displacement pump including: a control piston which includes a columnar piston portion pressing the swash plate and adjusts the inclination angle of the swash plate between a maximal inclination angle in which a discharge capacity of the working fluid becomes maximal and a minimal inclination angle in which the discharge capacity of the working fluid becomes minimal; a piston accommodation portion which is formed in the housing and accommodates the piston portion; and a pressed portion which is disposed between the swash plate and the piston portion and is pressed toward the swash plate by the piston portion, in which when the inclination angle of the swash plate is an intermediate inclination angle in which the discharge capacity of the working fluid becomes an intermediate amount between the maximal amount and the minimal amount, a contact point between the piston portion and the pressed portion is located at a center portion including an axis center of the piston portion in an end surface on the side of the swash plate in the piston portion.

Provided is a variable displacement pump which includes a cylinder block including a plurality of cylinder bores formed in a rotation shaft in a circumferential direction and rotating together with the rotation shaft, a piston provided inside each of the plurality of cylinder bores to be slidable, and a swash plate supported to be tiltable with respect to the rotation shaft while a distal end portion of the piston is slidable thereon and which sucks and discharges a working fluid by moving the piston in a reciprocating manner with a stroke in accordance with an inclination angle of the swash plate, the variable displacement pump including: a control piston which includes a piston portion pressing the swash plate and controls the inclination angle of the swash plate; a piston accommodation portion which is formed in the housing and accommodates the piston portion; and a hollow cylindrical guide portion which is disposed between the piston accommodation portion and the piston portion and includes an inner peripheral surface supporting the piston portion to be slidable thereon, in which the housing is formed of a material having higher fatigue strength than the guide portion and the guide portion is formed of a material harder than the housing.

A hydraulic axial-piston machine achieves a control cut-off by an additional control edge of a control valve of an actuating mechanism for swiveling a swash plate.

A hydrostatic axial piston machine of swashplate type of construction includes a rotatable cylinder drum that has a plurality of cylinder bores, which are arranged approximately axially, formed in the cylinder drum. A piston is inserted into each cylinder bore at one side. At the other side, each cylinder bore is freely connected via a respective passage opening to a face surface of the cylinder drum. The face surface bears against a static distributor disk. The respective mouths arranged at the face surface, or the passage openings as a whole, have a cross section that has two or four widenings with rounded corners so as to enlarge the cross-sectional area in relation to the circular shape.

A pump injection arrangement can inject a medium at least one process position into a high-pressure process, in particular at least two different pressure levels. The pump injection arrangement includes injection pump apparatuses for the medium and a regulating unit coupled to the injection pump apparatuses and configured for regulating the injection by at least two of the injection pump apparatuses. The pump injection arrangement is configured for synchronized regulation of the injection pump apparatuses with dependence on one another. At least two of the synchronously regulated injection pump apparatuses are double acting bidirectionally operating high-pressure pumps that are functionally coupled with at least single redundancy to the regulating unit such that pressure can be generated via at least two shafts and the pressurized medium can be made available for injection via a joint high-pressure conduit. In this way, advantageous pressure and pumping characteristics can be achieved.

An electroproportional pressure control valve of cartridge-type construction is screwed into a housing bore of a hydrostatic pump. The cartridge includes an adjusting pressure port, a pump port, and a tank port. The adjusting pressure port is relieved to the tank port in a normal position of a spring-biased valve plunger of the pressure control valve. A connection from the pump port to the adjusting pressure port is opened counter to the force of the spring by increasing a current of an electromagnet and increasing the pump pressure at the pump port. The spring, the electromagnet, and the resultant force of the pump pressure act along a common axis of movement of the valve plunger. A first nozzle connects the adjusting pressure port to an adjusting pressure chamber. A second nozzle connects the adjusting pressure port to the tank port.