Abstract: A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.

Abstract: A pump system including a prevention mechanism for preventing excessive fluid temperature buildup of system fluid. The overheat prevention mechanism includes a thermally-responsive control component (130) made with a thermally-responsive material. The thermally-responsive control component is located in the pump system (112) such that the thermally-responsive material is in thermal communication with the system fluid for effecting a change in temperature of the thermally-responsive material. The thermally-responsive material is configured to have an activation temperature that is a predefined amount less than a maximum operating temperature of the system fluid. The thermally-responsive control component is configured to cooperate with a pump control mechanism in the system to decrease pump output pressure in response to the thermally-responsive material being heated by the fluid to a temperature that is equal to or greater than the activation temperature of the thermally-responsive material.

Abstract: A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.

Abstract: An engine driven pump includes a drive apparatus that is assisted into the disengaged condition prior to disconnect by the ported pressure in the pump. A spring-biased actuator assembly is fluidly connected to a depressure valve of the pump, and along with its spring bias, urges a yoke into a disengaged position to disengage the gear faces of the mechanism. A trigger link held by a solenoid plunger normally retains the yoke in an engaged position. A drive socket can be accessed to return the yoke, and hence the gear faces, into the engaged position. The pump can be disengaged under command during flight or when the aircraft is on the ground, and can only be re-engaged when the aircraft is on the ground. The drive apparatus has few rotating components to reduce rotational inertia; and is enclosed within a housing with no exposed components with all parts continually lubricated.

Abstract: An electrohydrostatic actuator including an unbalanced area actuator whereby movement of an actuator piston causes a greater change in displacement on a first side of the actuator piston having a first area than on a second side of the actuator piston having a second area. The actuator includes a four-port, dual displacement hydraulic pump having a first pair of ports and a second pair of ports. If an axial piston pump is used, the pistons may be arranged in first and second rings of pistons arranged concentrically about a central axis. The pump has a port plate with a first pair of ports associated with the first ring of pistons and a second pair of ports associated with the second ring of pistons. At least one of the first pair of ports and at least one of the second pair of ports are connected to the first side of the actuator piston. At least one of the first pair of ports is connected to the second side of the actuator piston.