The invention relates to a hydraulic cylinder, for example for use with a hydraulic tool, which hydraulic tool is provided with a frame and an element which is movable with respect to the frame by means of the hydraulic cylinder. A hydraulic tool which is operated by means of a hydraulic cylinder as described above is known from, for example, European patent no. 0641618. This patent discloses a frame which is coupleable to a jib of an excavator or the like and to which an assembly of two jaws can be coupled. One of the jaws is pivotable with respect to the other jaw by means of a hydraulic adjusting cylinder (a double-acting piston/cylinder combination).

An output member (7) is inserted in a housing (5) so as to be movable in a left-right direction. A lock chamber (20) is provided to the right of the output member (7), as a first actuation chamber. Compressed air is supplied to and discharged from the lock chamber (20) through a first supply and discharge passage (24) provided in the housing (5). A first holding valve (30) provided to an intermediate portion of the first supply and discharge passage (24) is configured to close and open the first supply and discharge passage (24).

A hydraulic drive unit for a stretcher has a hydraulic circuit with a differential cylinder, a pump, a tank and a valve assembly. The differential cylinder includes a rod working chamber and a piston working chamber. The valve assembly is switchable into at least a first state and a second state, wherein the rod working chamber is connected to the tank in the first state and to the pump in the second state, and wherein the piston working chamber is connected to the pump in the first state and to the tank in the second state. The tank is a tank separated from the atmosphere with a variable tank volume, so that the hydraulic circuit is configured as a closed hydraulic circuit. A stretcher having such a hydraulic drive unit is also provided.

A hydraulic system (600) and method for reducing boom dynamics of a boom (30), while providing counter-balance valve protection, includes a hydraulic actuator (110), first and second counter-balance valves (300, 400), first and second control valves (700, 800), and first and second blocking valves (350, 450). A net load (90) is supported by a first chamber (116, 118) of the hydraulic actuator, and a second chamber (118, 116) of the hydraulic actuator may receive fluctuating hydraulic fluid flow from the second control valve to produce a vibratory response (950) that counters environmental vibrations (960) on the boom. The first blocking valve prevents the fluctuating hydraulic fluid flow from opening the first counter-balance valve. The first blocking valve may drain leakage from the first counter-balance valve.

The present invention relates to an electrohydrostatic system having a hydraulic cylinder comprising a first cylinder chamber and a second cylinder chamber. Furthermore, the electrohydrostatic system has a fluid hydraulic supply device for providing a hydraulic fluid, a fluid hydraulic motor pump unit, designed to provide a fluid hydraulic volume flow in order to move the hydraulic cylinder. A motor control device is designed to provide a rated current for an electrical drive of the fluid hydraulic motor pump unit. Moreover, the electrohydrostatic system has at least one fluid hydraulic safety valve, which on a first valve side is connected to one of the cylinder chambers of the hydraulic cylinder and on a second valve side is connected to the fluid hydraulic motor pump unit. The fluid hydraulic safety valve can be bridged via a bypass connection with a fixed orifice plate, wherein the bypass connection is connected to the first valve side and to the second valve side of the at least one fluid hydraulic safety valve. Moreover, the electrohydrostatic system has a pressure sensor that is connected to one of the cylinder chambers of the hydraulic cylinder. The pressure sensor is designed to detect a fluid hydraulic pressure on one of the cylinder chambers and, according to the detected fluid hydraulic pressure, to provide an enabling signal for the motor control device to provide the rated current for the electrical drive of the fluid hydraulic motor pump unit.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.

A hydraulic control system for linear actuation that includes an electric motor connected to a hydraulic pump and a hydraulic cylinder connected to the pump by a first flow line. A pressure transducer, a pressure control valve, and a check valve are connected to the first flow line between the pump and the cylinder and a tank is connected to the pump by a second flow line and the cylinder by a return line. A control valve is connected between the first flow line and the return line.

A device for holding a hydraulic cylinder stem in position includes a hydraulic block having series-connected primary and secondary check valves. The latter includes a secondary control stem having a secondary valve body and a seal. A first throttle upstream and a second throttle downstream are closed in a secondary control stem closed position where the seal tightly blocks the secondary check valve, each throttle having a tiny throttle closing gap, preferably 0.1 mm or less. The control stem can move axially into an intermediate position where the throttles remain closed, that is, have a tiny closing gap, but valve body and seal are lifted from a secondary valve seat. The control stem can be moved further into an opening position where the throttles are open, each having an opening gap much larger than the closing gap, and the valve body and seal are lifted from the valve seat.

Submersible hydraulic power units with interchangeable manifolds for hydraulic systems are provided. In one embodiment, submersible hydraulic power unit (“SHPU”) for moving hydraulic fluid between a first chamber and a second chamber of a hydraulic device is provided, the SHPU comprising: a tank for storing hydraulic fluid, wherein the tank houses: a motor submerged in the hydraulic fluid, the motor having a powered on and a powered off configuration based on at least one command signal; and a pump submerged in the hydraulic fluid and connected to the motor, wherein the motor drives the pump to route the hydraulic fluid in and out of the tank; and a lid attached to the tank, wherein the lid comprises at least one opening allowing an interchangeable manifold to connect to the pump.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.