A work machine includes an electric drive system. The work machine includes a prime mover, a machine controller, and a hydraulic control system. The hydraulic control system includes a pump, a control valve and a retarding control valve. The pump is configured to supply pressurized fluid to the hydraulic control system via a supply line. The control valve is fluidly coupled to the pump via the supply line, and includes a pressure relief valve. The retarding control valve is fluidly connected to the pump and the control valve. The retarding control valve includes a solenoid valve, an orifice and a check valve. The solenoid valve is coupled to the machine controller, the orifice restricts a flow of the pressurized fluid through the supply line, and the check valve is coupled to a discharge line, which branches from a point along the supply line between the solenoid valve and the orifice.

Hydraulic pressure compensator units and hydraulic systems incorporating hydraulic pressure compensator units. The pressure compensator units include a main valve body defining a central axis and a first central passage, a compensation valve member positioned in the first central passage and defining a second central passage, the first central passage being in selective fluid communication with a port of hydraulic actuator. A load sense check component is positioned within the second central passage and adapted to move in a first axial direction to selectively open a fluid communication between a pump output and a load sense line. A reverse flow check component is positioned within the second central passage and adapted to move in a second axial direction opposite the first axial direction to selectively open a fluid communication between the hydraulic actuator and a tank line.

An example valve assembly is configured: generate a valve load-sense pressure signal indicative of a pressure level at a workport of an actuator; generate a pilot fluid signal to be communicated to a worksection of a valve assembly to enable shifting a spool in the worksection; compare a first pressure level of the valve load-sense pressure signal to a second pressure level of the pilot fluid signal; and communicate the pilot fluid signal to a load-sense port fluidly coupled to a load-sensing source of pressurized fluid when the second pressure level of the pilot fluid signal exceeds the first pressure level of the valve load-sense pressure signal.

A control device is disclosed for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and a control valve (34) supplied with a pilot pressure, the device comprising an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Said control device is characterised in that both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by means of the pilot solenoid valve (16) via the additional valve (14).

A downhole tractor having a hydraulic system for driving a plurality of hydraulic cylinders and a plurality of hydraulic motors. The system comprises: a hydraulic power pack; a first hydraulic supply line for supplying hydraulic fluid to the plurality of hydraulic cylinders; a second hydraulic supply line for supplying hydraulic fluid to plurality of hydraulic motors; a valve section comprising a respective part of first hydraulic supply line and a further respective part of second hydraulic supply line, valve section further comprising an inlet for receiving hydraulic fluid, and a set of valves, and a hydraulic bypass supply line coupled to hydraulic power pack for supplying hydraulic fluid directly to the inlet of valve section bypassing at least part of first hydraulic supply line and second hydraulic supply line. The first and the second hydraulic supply line each comprise two parts connected via respective part in the valve section. Each respective part is connected to a respective sub-set of plurality of hydraulic components. The valve section configured for individually controlling flow of hydraulic fluid into each respective part of hydraulic supply lines.

A hydraulic lifting mechanism suspension has a main valve in the activation position whereof at least one hydraulic accumulator is connected to a connection line of the lifting mechanism suspension acting in the lifting direction or to working line of the lifting mechanism suspension acting in the lifting direction. The lifting mechanism suspension is deactivated via a deactivation position of the main valve, while at the same time a connection for recharging or filling the hydraulic accumulator is opened.

A downhole tractor having a hydraulic system for driving a plurality of hydraulic cylinders and a plurality of hydraulic motors. The system comprises: a hydraulic power pack; a first hydraulic supply line for supplying hydraulic fluid to the plurality of hydraulic cylinders; a second hydraulic supply line for supplying hydraulic fluid to plurality of hydraulic motors; a valve section comprising a respective part of first hydraulic supply line and a further respective part of second hydraulic supply line, valve section further comprising an inlet for receiving hydraulic fluid, and a set of valves, and a hydraulic bypass supply line coupled to hydraulic power pack for supplying hydraulic fluid directly to the inlet of valve section bypassing at least part of first hydraulic supply line and second hydraulic supply line. The first and the second hydraulic supply line each comprise two parts connected via respective part in the valve section. Each respective part is connected to a respective sub-set of plurality of hydraulic components. The valve section configured for individually controlling flow of hydraulic fluid into each respective part of hydraulic supply lines.

An example valve includes: a piston movable between a neutral position and an actuated position, wherein in the neutral position: a second port of the valve is fluidly coupled to a first port, and a third port is fluidly decoupled from the second port; a solenoid actuator sleeve movable between an unactuated state and an actuated state, wherein in the actuated state, the solenoid actuator sleeve allows pilot fluid to apply a fluid force on a piston in a distal direction; a first feedback spring; and a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move to the actuated position based on a relationship between the fluid force and the biasing force.

An example valve includes: a piston movable between a neutral position and an actuated position, wherein in the neutral position: a second port of the valve is fluidly coupled to a first port, and a third port is fluidly decoupled from the second port; a solenoid actuator sleeve movable between an unactuated state and an actuated state, wherein in the actuated state, the solenoid actuator sleeve allows pilot fluid to apply a fluid force on a piston in a distal direction; a first feedback spring; and a second feedback spring disposed in series with the first feedback spring, wherein the first feedback spring and the second feedback spring cooperate to apply a biasing force in a proximal direction on the piston against the fluid force, wherein the piston is configured to move to the actuated position based on a relationship between the fluid force and the biasing force.

Hydraulic pressure compensator units and hydraulic systems incorporating hydraulic pressure compensator units. The pressure compensator units include a main valve body defining a central axis and a first central passage, a compensation valve member positioned in the first central passage and defining a second central passage, the first central passage being in selective fluid communication with a port of hydraulic actuator. A load sense check component is positioned within the second central passage and adapted to move in a first axial direction to selectively open a fluid communication between a pump output and a load sense line. A reverse flow check component is positioned within the second central passage and adapted to move in a second axial direction opposite the first axial direction to selectively open a fluid communication between the hydraulic actuator and a tank line.