Abstract: A 2-port, 2-directional hydraulic valve is disposed alongside a pulse generator in a casing, the actuating force of the pulse generator being transmitted to a push rod of the valve for actuating the latter via a two-armed lever mounted like the beam of a balance. A threaded bore in one lever arm receives a bush which is adjustable in the direction of actuation and contains a spring-loaded pressure member. A set screw can be used to pre-stress the spring and thus exactly adjust the transmitted actuating force, while the adjustable bush is used for pre-setting the actuating travel.

Abstract: The invention relates to a method and system for supplying devices which are charged with a fluid pressure medium as a working medium with electrical energy for actuating electrical parts of the device, wherein an energy converter is subjected to the fluid pressure medium in such a way that a fraction of the energy of the fluid pressure medium is converted into electrical energy which is then stored in an electric store.

Abstract: The invention concerns apparatus for the determination of the length of stroke of a piston in a working cylinder, especially in a hydraulic, walking, mine-roof support. For this purpose a piston shaft is rotatably mounted in one end portion of the working cylinder and extends into a hollow cylindrical piston rod of the piston. Through a pin on the piston or piston rod which engages in a helical guide groove on the piston shaft, the latter is rotated during movements of the piston. The piston shaft is connected to a code plate provided with a pattern of holes and displaceable on rotation of the shaft between light-emitting elements on one side and light-detecting diodes on the other side. The combination of irradiated and darkened light-detecting diodes represents a digitally-detectable binary numeral sequence which corresponds to a specific piston position.

Abstract: A change-over valve for hydraulic walking mine-roof supports comprises a valve housing containing a sealed-off operating piston in which a valve member supported on a helical spring is displaceably arranged, the piston being responsive to the supply of small quantities of hydraulic fluid through an end connection in the housing and having a sealing cone adapted to close a connection of large throughflow cross-section at the opposite end of the housing which also has a side connection for the supply of pressurized fluid to a working cylinder of a mine-roof support, the large throughflow cross-section at the connection thereby guaranteeing brisk pushing-in of a piston rod of a piston in the cylinder.