Abstract: Methods and fluid supply systems are provided for supplying fluids while adjusting a pump discharge pressure to compensate for downstream pressure changes. The fluid supply system comprises a variable displacement piston (VDP) pump configured to supply a fluid at a pump discharge pressure, fuel metering units (FMUs) downstream of the VDP pump, each of the FMUs configured to receive the fluid from the VDP pump at the pump discharge pressure and supply the fluid at metered flow discharge pressures, and a pump compensator valve fluidically coupled with the FMUs to receive the fluid therefrom at the metered flow discharge pressures and configured to continuously, either fluidically or mechanically, adjust the pump discharge pressure of the VDP pump between a higher of a minimum pump discharge pressure and a floating ceiling pump discharge pressure, the floating ceiling pump discharge pressure based on a highest of the metered flow discharge pressures.

Abstract: A piston pump includes a ported member that is moveably disposed within an internal space of a housing between a rotating group and the housing. The ported member includes a first face facing the rotating group and a second face facing a fluid inlet and outlet. The ported member includes an intake port and a discharge port. Moreover, the ported member includes a balance aperture configured to pass fluid between the biasing member and a pump chamber as the rotating group rotates within the internal space such that the biasing member biases the ported member toward a balanced position within the internal space. The balance aperture has a rim at the first face. The rim is clefted at a relief feature of the first face. The relief feature is recessed into the first face.

Abstract: A piston pump includes a ported member that is moveably disposed within an internal space of a housing between a rotating group and the housing. The ported member includes a first face facing the rotating group and a second face facing a fluid inlet and outlet. The ported member includes an intake port and a discharge port. Moreover, the ported member includes a balance aperture configured to pass fluid between the biasing member and a pump chamber as the rotating group rotates within the internal space such that the biasing member biases the ported member toward a balanced position within the internal space. The balance aperture has a rim at the first face. The rim is clefted at a relief feature of the first face. The relief feature is recessed into the first face.

Abstract: A piston pump includes a rotor member with a bore therein. The bore is defined by an inner surface. The piston pump also includes a piston supported for reciprocating movement in an axial direction within the bore to change a volume of a pump chamber that is cooperatively defined by the piston and the rotor member. The piston has an outer surface that faces the inner surface with a leakage interface defined therebetween. The leakage interface is configured to receive a passive leakage flow of a fluid from the pump chamber through the leakage interface to provide cooling. Moreover, the outer surface includes a relief feature that is recessed into the outer surface to define, with the inner surface, a cooling pocket of the leakage interface. The cooling pocket moves in the axial direction relative to the inner surface with the reciprocating movement of the piston.

Abstract: Methods and apparatus are provided for lubricating a piston-to-shoe interface in a hydraulic motor or pump. Piston assemblies are installed in a housing that are each adapted to receive a reciprocating drive force and are each configured, in response thereto, to cyclically move between an intake direction and a discharge direction. Each piston assembly includes a piston and a piston shoe, and the piston, the piston shoe, or both have a plurality of pockets formed in a surface that defines a piston-to-shoe interface. When the pistons cyclically move, liquid is supplied to each piston-to-shoe interface to form a hydrostatic bearing at each piston-to-shoe interface. A portion of the liquid that is supplied to each piston-to-shoe interface is selectively supplied to and from one or more of the plurality of pockets.

Abstract: A direct metering fuel supply system includes a fuel pump, a burn flow fuel line, a servo flow fuel line, and a servo regulator. The fuel pump is adapted receive pump commands representative of a commanded fuel flow rate and is configured, in response to the pump commands, to discharge fuel at the commanded fuel flow rate. The burn flow fuel line is in fluid communication with the pump to receive a first portion of the fuel discharged therefrom. The servo flow fuel line is in fluid communication with the pump to receive a second portion of the fuel discharged therefrom. The servo regulator is mounted on the servo flow fuel line and configured to maintain fuel flow rate in the servo flow fuel line at a substantially constant fuel flow rate regardless of fuel flow rate in the burn flow fuel line.

Abstract: Methods and apparatus are provided for lubricating a piston-to-shoe interface in a hydraulic motor or pump. Piston assemblies are installed in a housing that are each adapted to receive a reciprocating drive force and are each configured, in response thereto, to cyclically move between an intake direction and a discharge direction. Each piston assembly includes a piston and a piston shoe, and the piston, the piston shoe, or both have a plurality of pockets formed in a surface that defines a piston-to-shoe interface. When the pistons cyclically move, liquid is supplied to each piston-to-shoe interface to form a hydrostatic bearing at each piston-to-shoe interface. A portion of the liquid that is supplied to each piston-to-shoe interface is selectively supplied to and from one or more of the plurality of pockets.

Abstract: A direct metering fuel supply system includes a fuel pump, a burn flow fuel line, a servo flow fuel line, and a servo regulator. The fuel pump is adapted receive pump commands representative of a commanded fuel flow rate and is configured, in response to the pump commands, to discharge fuel at the commanded fuel flow rate. The burn flow fuel line is in fluid communication with the pump to receive a first portion of the fuel discharged therefrom. The servo flow fuel line is in fluid communication with the pump to receive a second portion of the fuel discharged therefrom. The servo regulator is mounted on the servo flow fuel line and configured to maintain fuel flow rate in the servo flow fuel line at a substantially constant fuel flow rate regardless of fuel flow rate in the burn flow fuel line.

Abstract: A system and method is provided for controlling a variable displacement piston pump that supplies fluid to one or more loads. If fluid is being supplied through a metering valve to a load, then the variable displacement piston pump is controlled to operate in accordance with a variable flow/variable discharge pressure scheme. However, if fluid is not being supplied through the metering valve to the load, then the variable displacement piston pump is controlled to operate in accordance with a variable flow/constant discharge pressure scheme.

Abstract: An auxiliary cam assembly for an axial piston pump includes an auxiliary cam plate and an auxiliary cam retainer. The auxiliary cam plate is configured to be coupled a rotatable shaft. A central shaft opening extends through the auxiliary cam plate. A plurality of piston openings surround the central opening and extend through the auxiliary cam plate. A circumferential cut is formed in and extends around the outer peripheral surface of the auxiliary cam plate. The auxiliary cam retainer has a plurality of ramps formed therein, and each ramp slopes upwardly from a first end to a second end. A plurality of substantially flat pads are disposed between each of the ramps, and each pad extends between the first end of one ramp and the second end of another ramp.

Abstract: A system and method is provided for controlling a variable displacement piston pump that supplies fluid to one or more loads. If fluid is being supplied through a metering valve to a load, then the variable displacement piston pump is controlled to operate in accordance with a variable flow/variable discharge pressure scheme. However, if fluid is not being supplied through the metering valve to the load, then the variable displacement piston pump is controlled to operate in accordance with a variable flow/constant discharge pressure scheme.

Abstract: A rotary actuator includes one or more rotor vanes (40); an endplate (60); a corner seal (30) being positioned between the rotor vanes (40) and the endplate (60); a vane seal (20); a high pressure chamber and a low pressure chamber; and a single channel (22) extending from a lower portion of a vane seal groove (25) to a common channel (28) beneath the vane seal (20), wherein the high pressure chamber is in fluid communication with the corner seal (30) via the single channel (22) and the common channel (28). The common channel (28) may be formed in the rotor vane (40) or provided separately in a rotor vane flow sleeve (21) positioned along an interior surface of the rotor vane (40). The single channel (22) is machined from the bottom of the vane seal groove (25) to the area behind the corner seal (30).