A liquid feed pump which increases the liquid flow velocity in a stagnation area in the pressure chamber of a plunger pump, thereby improving the liquid replacement speed in the plunger pump. When the liquid in the liquid feed pump is replaced, a first plunger slides back and forth in the space between a lower limit point and an upper limit point, and the second plunger stops at least temporarily at a position near to the upper limit point or slides back and forth for a shorter distance than when the liquid feed pump usually feeds the liquid.

A liquid feed pump which increases the liquid flow velocity in a stagnation area in the pressure chamber of a plunger pump, thereby improving the liquid replacement speed in the plunger pump. When the liquid in the liquid feed pump is replaced, a first plunger slides back and forth in the space between a lower limit point and an upper limit point, and the second plunger stops at least temporarily at a position near to the upper limit point or slides back and forth for a shorter distance than when the liquid feed pump usually feeds the liquid.

The invention relates to a hydraulic machine, in particular to a hydraulic motor with two working lines, from one of which a high pressure line and from the other one a low pressure line is branched off. An electronic control unit and a servo displacement unit are provided to control the displacement of the displacement volume of a drive mechanism of the hydraulic machine, wherein the displacement volume can be determinated by the displacement of a servo piston within the servo displacement unit. For this, the servo piston can be loaded at least on one side via a servo pressure line with hydraulic fluid under servo pressure, wherein the servo pressure level can be adjusted by a control spool arranged moveable within a control valve. For this, hydraulic fluid from the low pressure line or, perhaps, from the high pressure line is guidable via the control valve to the servo pressure line if a suitable control signal is available at a switching valve.

A pumping system having a pump includes a pump controller having a signal processor or processing module configured at least to: receive signaling containing information about pump differential pressure, flow rate and corresponding power data at motor maximum speed published by pump manufacturers, as well as instant motor power and speed; and determine corresponding signaling containing information about instant pump differential pressure and flow rate using a combined affinity equation and numerical interpolation algorithm to control the pump in the pumping system, based upon the signaling received.

A pumping system having a pump includes a pump controller having a signal processor or processing module configured at least to: receive signaling containing information about pump differential pressure, flow rate and corresponding power data at motor maximum speed published by pump manufacturers, as well as instant motor power and speed; and determine corresponding signaling containing information about instant pump differential pressure and flow rate using a combined affinity equation and numerical interpolation algorithm to control the pump in the pumping system, based upon the signaling received.

A fluid flow meter comprising a fluid pump to displace fluid with pumping strokes of one or more pumping stroke types wherein each of the one or more stroke types displaces a known volume of fluid, a sensor functionally associated with a fluid reservoir and adapted to generate a signal indicative of a fluid pumping condition within the fluid reservoir, which fluid reservoir is integral or functionally associated with the pump, and circuitry to trigger one or a sequence of strokes of the pump in response to a signal from the sensor.

A hydraulic pump includes a work port, a high-flow piston, multiple high-pressure pistons, and an unloading valve. The work port couples to a fluid supply line of a hydraulic tool. The high-flow piston supplies fluid along a first flow path to the work port. The high-pressure pistons supply fluid along a second flow path to the work port. The unloading valve is fluidly coupled to the first flow path and the second flow path, and actuatable between an open state and a closed state. The unloading valve is configured to (i) permit fluid to flow from the high-flow piston to the work port in the open state, (ii) inhibit fluid from flowing from the high-flow piston to the work port in the closed state, and (iii) actuate from the open state to the closed state when a pressure of the fluid in the second flow path exceeds a threshold pressure.

A hydraulic pump includes a work port, a high-flow piston, multiple high-pressure pistons, and an unloading valve. The work port couples to a fluid supply line of a hydraulic tool. The high-flow piston supplies fluid along a first flow path to the work port. The high-pressure pistons supply fluid along a second flow path to the work port. The unloading valve is fluidly coupled to the first flow path and the second flow path, and actuatable between an open state and a closed state. The unloading valve is configured to (i) permit fluid to flow from the high-flow piston to the work port in the open state, (ii) inhibit fluid from flowing from the high-flow piston to the work port in the closed state, and (iii) actuate from the open state to the closed state when a pressure of the fluid in the second flow path exceeds a threshold pressure.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.

Hydraulic axial piston unit having a rotational group for driving or being driven by a driving shaft, and a tiltable displacement element for adjusting the displacement volume of the rotational group. The rotational group includes a rotatable cylinder block in which working pistons are mounted reciprocally moveable in cylinder bores for conveying hydraulic fluid from an inlet port to an outlet port on a valve segment. At least two control ports are located on the valve segment each between the inlet port and the outlet port. The control ports can be brought sequentially in fluid connection with the cylinder bores when the cylinder block is rotating. At least one hydraulic fluid injector is connected fluidly to one control port, for sequentially injecting pressurized hydraulic fluid via the control port into the passing cylinder bores. Via the other control port hydraulic fluid can be drained from passing cylinder bores.