A lift apparatus and method for driving a downhole reciprocating pump is disclosed. The apparatus 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. The apparatus also includes a variable displacement hydraulic pump coupled to receive a substantially constant rotational drive from a prime mover for operating the hydraulic pump, the hydraulic pump having an outlet and being 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 hydraulic fluid line connected to deliver hydraulic fluid from the outlet of the hydraulic pump through the hydraulic fluid port to the cylinder for causing the piston to move through an upstroke away from the first end and toward the second end of the cylinder. The apparatus further 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 valve is operable to prevent flow of hydraulic fluid through the valve during the upstroke and the hydraulic pump is operable to prevent flow of hydraulic fluid back into the outlet of the hydraulic pump during the downstroke.

An adjustment device for regulating the torque of a hydrostatic piston machine with adjustable swept volume, comprises an adjustment piston delimiting an adjustment chamber, a regulation valve defining a valve bore and including a valve slide positioned in the valve bore that controls inflow and outflow of pressure medium, and first and second feedback springs configured to exert feedback force on the valve slide in first and second displacement directions dependent on a position of the adjustment piston. The device further includes a regulation spring configured to exert a force on the valve slide in a second displacement direction. During an adjustment of the adjustment piston in a direction of maximum swept volume of the piston machine, beyond a particular position of the adjustment piston, the first and second feedback springs exert an increased force on the valve slide determined only by a spring constant of the first feedback spring.

An adjustment device for regulating torque of a hydrostatic piston machine includes a piston delimiting a chamber, a regulation valve, feedback and regulation springs, and a member. The valve has a displaceable slide to enable pressure medium to flow into or out of the chamber, a measurement surface acted on by pressure from the piston machine, and a bore open to the chamber, a side facing the chamber acted on by a chamber pressure in a first direction. The feedback spring exerts force on the slide in the first direction, depending on a position of the piston. The regulation spring exerts force on the slide in a second direction opposite the first direction. The member has a surface as large as the side of the bore such that the chamber pressure exerts force on the slide in the second direction.

A pump control assembly for controlling a variable displacement hydraulic pump includes a spool mounted within a valve block. The spool is configured to move between a first and a second position within the valve block so as to selectively control the displacement of the attached pump. The pump control assembly further includes first and second chambers that each apply a force to opposite ends of the spool. The first chamber is positioned at a first end of the spool in fluid communication with a pump output port. The second chamber is positioned at a second end of the spool and in fluid communication with a hydraulic tank port and a proportional pressure reducing valve. The second chamber also includes a piston and first and second springs positioned on either side of the piston. The proportional pressure reducing valve provides a regulated pressure to a first side of the piston along with the first spring, and the hydraulic tank port provides a tank pressure on the opposite side of the piston along with the second spring. The pump control assembly also includes a stop structure having a positive stop that limits movement of the piston in a direction toward the first chamber.

A fluid delivery system for an engine is disclosed. The fluid delivery system comprises a pump, a valve module, a motor, and a displacement control module. The pump is operatively coupled with an engine and is adapted to provide a flow of a fluid. The valve module is provided in fluidic communication with the pump to control the flow of the fluid. The motor is provided in fluidic communication with the valve module to receive the flow of the fluid and generate mechanical power. The displacement control module is provided in fluidic communication with the pump and the valve module and is provided downstream of the pump and upstream of the valve module. The displacement control module controls a displacement of the pump for maintaining a constant flow rate of the fluid from the pump based, at least in part, on an engine speed regardless of compressor load.

A hydrostatic axial piston machine includes a swashplate with an oblique surface formed thereon. Working pistons, which revolve and are supported by the oblique surface, are axially positioned on the swashplate with respect to a drive shaft. An adjusting cylinder, coupled to the swashplate, is configured to produce a pivoting moment and pivot the swashplate about a pivoting axis. Displacement of the working cylinders per revolution around the drive shaft is adjustable by adjusting a pivoting angle of the oblique surface. The adjustment of the pivoting angle is configured to pass beyond zero degrees, such that the direction of rotation of the drive shaft is changeable. The pivoting axis is at a distance from an axis of rotation of the drive shaft, such that an internal counter pivoting moment counteracting the pivoting moment is produced during operation of the axial piston machine when the working pistons are subjected to pressure.

An oil-pressure driving system includes a variable displacement oil-pressure pump, a tilting angle adjuster, an electric motor, and a control device. In the control device, a target assist torque calculating portion calculates a target assist torque, a first torque limiting portion limits the target assist torque to an output value that is a virtual limit value or less, and a drive control portion controls the electric motor such that the electric motor outputs a command torque corresponding to the output value. Further, in the control device, a torque deficiency calculating portion calculates a torque deficiency by subtracting the output value from the target assist torque, a tilting angle calculating portion calculates a tilting angle command value by which the output torque of the oil-pressure pump is reduced by the torque deficiency, and a tilting angle control portion outputs a tilt signal corresponding to the tilting angle command value to the tilting angle adjuster.

A hydrostatic axial piston machine has a housing. In the housing of the hydrostatic axial piston machine, an actuating pressure cylinder is formed at an angle to the drive shaft. A control valve is inserted into the actuating pressure cylinder in a cartridge type of design. In order to enable maximum movement of an actuating piston in the direction toward the control valve, the cartridge is of shortened design. To this end, an actuating pressure port, which is arranged between a high-pressure port and a low-pressure port, and an actuating pressure passage are arranged completely inside the cartridge.

A hydrostatic axial piston machine has a housing. In the housing of the hydrostatic axial piston machine, an actuating pressure cylinder is formed at an angle to the drive shaft. A control valve is inserted into the actuating pressure cylinder in a cartridge type of design. In order to enable maximum movement of an actuating piston in the direction toward the control valve, the cartridge is of shortened design. To this end, an actuating pressure port, which is arranged between a high-pressure port and a low-pressure port, and an actuating pressure passage are arranged completely inside the cartridge.

A variable displacement pump comprising a pumping piston (10), cylinder head (2); a rotating shaft (3); regulating means (4) of the displacement of the pump, said means in turn comprising: a structure (41) having a variable inclination; a fluid-dynamic actuator (42) for regulating an inclination of said structure (41); command means (43) for the actuator (42), which assume a non-equilibrium and an equilibrium position, said command means (43) in turn comprising: a sliding body (431) being able to take at least a first position in which it places a chamber (420) acting on said actuator (42) in communication with a first zone (51) at least initially having a pressure that is different from a pressure present in said chamber (420); a sliding element (432) with respect to the sliding body (431) for resetting said equilibrium configuration, said sliding element (432) being distinct from said actuator (42) and being mechanically actuated in consequence of a variation of an inclination of said structure (41).