Abstract: A pilot-operated pressure shut-off valve having a main control piston which, when an upper system limit pressure in the hydraulic system is reached, connects an inlet, via which pressure medium can be fed to a hydraulic system, to an outlet by taking up a first switching position and, when a lower system limit pressure is reached, separates from the outlet by taking up a second switching position. The pressure shut-off valve has a pilot valve arrangement by which the fluidic connection of a control space adjacent to the main control piston can be changed in order to control the main control piston, and which has a valve housing, with a first pilot piston and a second pilot piston accommodated within the first pilot piston for compact construction and capability to adjust the two pilot pistons mechanically completely independently of each other.

Abstract: What is disclosed is a directly controlled pressure control valve comprising a seat piston in a longitudinal bore of a valve housing, which is radially guided in its guidance portion through the intermediary of two circular, spaced-apart guide members in the longitudinal bore.

Abstract: The invention relates to a pilot-operated pressure shut-off valve having a main control piston which, when an upper system limit pressure in the hydraulic system is reached, connects an inlet, via which pressure medium can be fed to a hydraulic system, to an outlet by taking up a first switching position and, when a lower system limit pressure is reached, separates from the outlet by taking up a second switching position.

Abstract: A precontrolled 3-way pressure control valve with a main valve having, in a valve housing, a valve bore with first, second and third control chambers connected with pressure connection, tank connection, and control connection, respectively, a control piston displaceable in a valve bore, wherein the third control chamber is connectable with the first or second control chambers, and subjectable in opposite direction to pressures from the control connection and pressure setting of a pilot valve. With deviation of pressure applied in control connection from pressure setting of the pilot valve, an imbalance of forces develops in the valve. Oblong holes, distributed over circumference of hollow control piston pass through the wall, are located in the wall radially delimiting its hollow chamber, which holes are longer than clearances between two control chambers.

Abstract: A precontrolled three-way pressure reduction valve having essentially vibration-free operation is encased in a cartridge and has a hollow control piston wherein a working fluid space is formed as a T-shaped cavity within the control piston. In the cavity, there are axial and transverse bores of approximately the same diameter. A groove encircles the control piston, and has a width which is slightly larger than a diameter of the transverse bore, the transverse bore communicating with the groove.