Abstract: The control device is adapted to be inserted between the control valves of a pilot device and the pressure-medium consumers (hydraulic prop and hydraulic working cylinder) in an hydraulic self-advancing mine-roof support and is connected to a pressure-medium line and to a return line. The control device comprises a valve block with continuous longitudinal bores for connection to a multiple tubing line leading to the pilot device, the valve block having bores for receiving piloted 3/2-way valves and bores for connection to the directly-controlled working cylinders of the mine-roof support.

Abstract: A method of working coal seams to a defined preset cutting depth during ploughing with a cutter, a face conveyor moving along a face behind the cutter being advanced by the defined preset cutting depth and this advance being made by extension of self-advancing cylinders pivotally attached at one end to the face conveyor and at the other end to face supports disposed parallel to the face conveyor. The advance is controlled in dependence upon the piston stroke of the self-advancing cylinders, carried out in dependence upon individually defined partial strokes corresponding to the preset depth of cutting. After a predetermined maximum total piston stroke has been reached, the face support connected to the respective self-advancing cylinder is automatically disengaged, advanced by the maximum total piston stroke and then re-set (self-advancing process).

Abstract: A control system for longwall face support frames as used in mines, the system comprising pushing rams which are adapted to be actuated at two different pressures (for example, a low pressure of about 70 to 120 bar for non-defined cutting and a high pressure of 120 to 350 bar for defined cutting) with each pushing ram being individually actuatable by a respective non-return valve arrangement, the pushing rams being connected by a common pressure line to an hydraulic pressure unit.

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: A pressure-control valve is connected to a working cylinder of an hydraulic, walking, mine roof support on one side of the piston in the cylinder. In its function as a pressure-limiting valve, it regulates the pressure in the working cylinder in dependence upon a predetermined pressure in a control conduit which is connected to the pressure chamber of a prop of the mine roof support. Through it a spring-loaded control piston of the pressure-control valve is hydraulically loaded so as to act on a spring-loaded valve closure member in the pressure-control valve. The control piston holds the valve-closure member in the closure position if the pressure in the control conduit exceeds the predetermined pressure. If the pressure in the control conduit drops off, the valve-closure member then regulates the pressure in the working cylinder to a comparatively low value.

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.

Abstract: The control valve for the re-setting of the props at a predetermined minimum setting pressure is connected at respective junctions to a high pressure conduit, to the pressure chambers of the props, to the prop-setting conduit and to the return-flow conduit leading to the annular chambers of the props. The spring-loaded closure body is guided displaceably in the valve housing by journals on each of the two sides of the valve cone. The ends of the journals are formed as actuation faces. The valve cone seals off the high pressure junction and the junctions leading to the pressure chambers of the prop and opens only when a predetermined minimum setting pressure at the junction is exceeded. For closure, the control valve is loaded through the junction on the actuation area of the journal with the pressure fluid conducted to the annular chambers of the props.

Abstract: Valves regulating the supply of hydraulic fluid to hydraulic cylinders of an hydraulic walking mine-roof support are controlled by apparatus comprising an axially-movable switching shaft provided with cams which is rotatable into successive switching stations where it is immobilized by spring-loaded stop pins to that the cams bear on tappets to actuate the respective valves, there being a switching spring acting on the shaft to return the shaft to its initial position of rest after it has been axially displaced and rotated out of that position of rest.

Abstract: A pressure-limiting valve comprises a cylindrical actuator piston guided displaceably in a bore and held under the pressure of a spring in the closure position of the valve. Longitudinally-directed throughflow passages are formed in the actuator piston on the pressure-loaded end and are arranged concentrically with respect to the central axis and open into an annular groove extending around and in the circumferential surface of the actuator piston. This groove is sealed off by a gasket mounted in the bore wall. When the set pressure predetermined by the closure spring is exceeded, the actuator piston travels with the gasket over the annular groove so that the pressure medium can flow away through the outlet opening.

Abstract: An hydraulically-controlled non-return valve for the hydraulic cylinders of a walking mine-roof support is provided with a cylindrical valve-closing member which is spring-loaded in the closing direction and is guided in a valve case in a valve housing, the valve-closing member being sealed off therein by means of a seal. A space on one face of the valve-closing member is connected to a circulating duct by way of a stepped bore in the valve case, which bore contains a spring-loaded throttle member having through-flow bores of which one has a throttle-like reduced cross-section. During setting of the hydraulic cylinder pressurized fluid flows past the opened valve-closing member through inclined bores and, by way of the circulating duct, to the stroke space of the hydraulic cylinder. During retraction of the hydraulic cylinder, a control piston in the non-return valve is loaded at the same time as an annular space in the hydraulic cylinder.

Abstract: A pressure-limiting valve for hydraulic fluids comprises a stepped switching piston which is loaded by a closing spring to oppose high fluid pressure obtaining in an inflow duct of the valve. Radial transverse bores branch from an axially-extending bore in the switching piston. When the setting pressure established by the closing spring is exceeded, the transverse bores in the piston move past an O-ring seal as the piston compresses the spring, and pressure fluid thus flows from the axially-extending bore into a discharge duct of the valve. The stepped switching piston is guided in a pressure chamber by a portion of its cross-section which is greater than that in the zone of the O-ring seal. Adjacent the inflow duct, the axially-extending bore in the piston has a reduced flow cross-section. Further radial bores lead from the axially-extending bore in the piston in the region of the stepped portion of the latter.

Abstract: A control line connects an annular space in an auxiliary hydraulic cylinder of an hydraulically-movable mine-roof support (the auxiliary cylinder being provided to advance a forward, auxiliary, roof-support canopy in the direction of the working face of a mine) to the displacement space of an hydraulic measuring cylinder which is longitudinally displaceable in a direction parallel to the hydraulic advancing cylinder in order to advance the auxiliary roof-support canopy, which is pivoted to the main roof-support canopy, in synchronism with the advancing cylinder mounted in the base of the mine-roof support and attached to an abutment on the working face side of the support. A control valve is connected to the control line and responds to the control line pressure in such a way that, when the pressure falls, it supplies pressurized fluid into the pressure space of the auxiliary cylinder to extend the piston rod thereof, and shuts off again when the pressure increases.