The electro-hydrostatic actuator system for raising and lowering aircraft landing gear (1) is provided with at least one hydraulic actuator (21, 22) that is constituted so as to perform retraction and deployment of landing gear (11), a hydraulic circuit (33), a hydraulic pump (32), an electric motor (31), a controller (4) constituted so as to control the operation of the electric motor upon receiving an instruction relating to retraction of the landing gear or an instruction relating to deployment of the landing gear, and a sensor (34) that detects the discharge pressure of the hydraulic pump. The controller feeds back the discharge pressure that the sensor has detected, and controls the operation of the electric motor so that the discharge pressure of the hydraulic pump becomes a target discharge pressure.

A soil processing machine includes a hydraulic drive system including an electrohydraulic pressurized fluid source with at least one electric motor and at least one hydraulic drive pump, a hydraulic drive circuit fed with pressurized fluid by the at least one hydraulic drive pump, at least one hydraulic drive motor fed with pressurized fluid from the hydraulic drive circuit, and a discharge valve assembly for discharging fluid from the hydraulic drive circuit to a fluid reservoir. The hydraulic drive system is designed to operate the discharge valve assembly as a function of at least one of the following parameters: a temperature of the fluid in the hydraulic drive circuit, an ambient temperature, a viscosity of the fluid in the hydraulic drive circuit, a degree of contamination of the fluid in the hydraulic drive circuit, a period of time since the last start-up of the hydraulic drive system, a period of time since the last fluid was discharged from the hydraulic drive circuit.

A hydraulic leak detection system includes a leak detection switch responsive to a level of hydraulic fluid in a tank used by a hydraulic mowing circuit and a lift and lower circuit of a grass mowing machine. The system includes a controller that activates a warning indicator if the leak detection switch indicates the level of hydraulic fluid in the tank is low, but allows the hydraulic mowing circuit and the lift and lower circuit to continue operating until the lift and lower circuit reaches a fully raised position. A solenoid valve may control the level of hydraulic fluid in the tank based on temperature of the hydraulic fluid.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic system includes a hydraulic circuit, a heater, a temperature sensor, and a controller. The hydraulic circuit includes a reservoir configured to store hydraulic fluid, a pump coupled to the reservoir, a driver positioned to drive the pump to pump the hydraulic fluid from the reservoir and throughout the hydraulic circuit, and an actuator positioned to selectively receive the hydraulic fluid from the pump to operate a controllable machine component. The driver is independent of a prime mover of the machine. The heater is positioned to facilitate selectively heating the hydraulic fluid. The temperature sensor is positioned to acquire temperature data indicative of a temperature of the hydraulic fluid. The controller is configured to monitor the temperature of the hydraulic fluid and selectively activate at least one of the heater or the pump to thermally regulate the hydraulic fluid to maintain the hydraulic fluid within a target temperature range.

A hydraulic system includes a hydraulic circuit, a heater, a temperature sensor, and a controller. The hydraulic circuit includes a reservoir configured to store hydraulic fluid, a pump coupled to the reservoir, a driver positioned to drive the pump to pump the hydraulic fluid from the reservoir and throughout the hydraulic circuit, and an actuator positioned to selectively receive the hydraulic fluid from the pump to operate a controllable machine component. The driver is independent of a prime mover of the machine. The heater is positioned to facilitate selectively heating the hydraulic fluid. The temperature sensor is positioned to acquire temperature data indicative of a temperature of the hydraulic fluid. The controller is configured to monitor the temperature of the hydraulic fluid and selectively activate at least one of the heater or the pump to thermally regulate the hydraulic fluid to maintain the hydraulic fluid within a target temperature range.

A hydrostatic drive includes at least one hydrostatic pump configured to supply at least one hydrostatic consumer and an apparatus for an energy recovery procedure of at least a part of the energy that is output by the consumer. An electronic control unit or at least one software component is further included, with which the energy recovery procedure is controlled in a variable manner and depends upon detected influencing variables.

A hydrostatic drive includes at least one hydrostatic pump configured to supply at least one hydrostatic consumer and an apparatus for an energy recovery procedure of at least a part of the energy that is output by the consumer. An electronic control unit or at least one software component is further included, with which the energy recovery procedure is controlled in a variable manner and depends upon detected influencing variables.

A valve body defines a work passage, a high-pressure channel fluidly connected to the work passage, a tank passage, and a cavity disposed between the high-pressure channel and the tank passage. The cavity fluidly connects the high-pressure channel and the tank passage. The cavity is defined at least in part by a first portion within which a relief valve threadedly engages, a second portion disposed adjacent to the high-pressure channel, and an annulus interposed between the first portion and the second portion. The annulus fluidly connects to the tank passage. A surface area of the relief valve exposed to the annulus is greater than a cross-sectional area of the high-pressure channel.