A pilot type switching valve includes: a housing bore formed in a valve body, the housing bore having an opening end; a spool slidably housed in the housing bore, the spool being configured to allow or block a flow of the working fluid to a first relief valve; a pilot chamber to which pilot pressure biasing the spool in the valve opening direction is guided; and a spring configured to bias the spool in the valve closing direction. The spool has a bottom surface on which the pilot pressure acts in such a manner that the spool is biased in the valve opening direction, and the area of the bottom surface is smaller than the sectional area of the housing bore.

A control valve includes a housing formed with first and second supply ports, first and second actuator ports, and a pilot port, and a spool accommodated slidably in the housing, and the spool is configured to allow the first supply port and the pilot port to communicate with each other both at the first communication position and the second communication position.

A control valve for an automatic parking brake having an inlet for coupling to a source a brake pipe pressure, an outlet for coupling to a control inlet of the automatic parking brake and a pilot for coupling to the source of brake pipe pressure. The control valve is moveable between a first position where the inlet is in communication with the outlet and a second position where the inlet and the outlet are isolated from each other in response to a predetermined amount of brake pipe pressure at the pilot. The control valve includes a spring biasing the control valve into the first position.

The invention relates to a control apparatus for a hydraulic variable-pitch propeller (12) of an aircraft, land vehicle or water vehicle, comprising: a hydraulic oil feed line (24); a control line (16) which can be connected to the variable-pitch propeller (12); a pressure generating device (73) which is connected to the hydraulic oil feed line (24) and provides hydraulic oil with a basic pressure; a servo valve (78) which is arranged downstream of the pressure generating device (73), the input pressure to which servo valve is the basic pressure and the output pressure from which servo valve during normal operation defines a control pressure in the control line (16) and which servo valve is connected to a controller (28) which delivers a control signal for changing the control pressure; and pressure reducing means which are arranged downstream of the servo valve (78) and upstream of the control line (16), which are mechanically actuated and which, in the event of a failure of the servo valve (78), change the control pressure in the control line (16).

A first case accommodating a first check valve of a switching valve switching a flow of hydraulic fluid to one of a first chamber and a second chamber of a cylinder device, an inside of which is segmented into the first chamber and the second chamber by a piston, and a second case which is stacked on the first case and in which a first actuation valve of the switching valve is accommodated to be displaced in a direction of stacking the first case are provided. A first valve chamber, accommodating the first actuation valve, of the second case has a pressure receiving surface on which pressure of hydraulic fluid that acts on the first valve chamber acts toward the first case.

A compressed-air feed system for operating a pneumatic system includes a compressed-air supply, a compressed-air connection to the pneumatic system, at least one ventilation connection to surroundings, and a pneumatic main line between the compressed-air supply and the compressed-air connection. The pneumatic main line has an air dryer and a regeneration throttle. The compressed-air feed system further includes a first ventilation line between the pneumatic main line and the at least one ventilation connection. The first ventilation line has a first ventilation valve and a ventilation throttle. The compressed-air feed system additionally includes a second ventilation line between the compressed-air connection and the at least one ventilation connection. The second ventilation line has a second ventilation valve formed as a 2/2 directional valve. The compressed-air feed system is designed to provide an operating mode in which the second ventilation valve is open over a predetermined time period.

A pilot type switching valve includes: a housing bore formed in a valve body, the housing bore having an opening end; a spool slidably housed in the housing bore, the spool being configured to allow or block a flow of the working fluid to a first relief valve; a pilot chamber to which pilot pressure biasing the spool in the valve opening direction is guided; and a spring configured to bias the spool in the valve closing direction. The spool has a bottom surface on which the pilot pressure acts in such a manner that the spool is biased in the valve opening direction, and the area of the bottom surface is smaller than the sectional area of the housing bore.

A method of controlling a plurality of downhole tools in a wellbore, using first and second codes transmitted by hydraulic line to first address and then actuate the desired tool. A dedicated line is provided for terminating all actuated tools.

A portable hydraulic power unit includes a frame, a fluid tank supported by the frame, and a manifold supported by the frame. The fluid tank is configured to store a supply of hydraulic fluid for powering a hydraulically-driven tool. A reciprocating pump is mounted on the exterior of the fluid tank and on the exterior of the manifold. The reciprocating pump is secured to the fluid tank and the manifold with fasteners extending through a cylinder body of the reciprocating pump.

A portable hydraulic power unit includes a frame, a fluid tank supported by the frame, and a manifold supported by the frame. The fluid tank is configured to store a supply of hydraulic fluid for powering a hydraulically-driven tool. A reciprocating pump is mounted on the exterior of the fluid tank and on the exterior of the manifold. The reciprocating pump is secured to the fluid tank and the manifold with fasteners extending through a cylinder body of the reciprocating pump.