Abstract: A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields incorporates a pressure monitoring device in the pressure line between the load maintaining valve and the shield control valve. The pressure monitoring device can be a device for monitoring the piston position of the shield control valve which device signals a deviation of the set position predetermined by the shield control device from the measured actual position of the piston of the shield control valve in the form of a deviation signal. It may also be a pressure sensor which signals the deviation of the set pressure predetermined by the shield control device from the measured actual pressure in the form of a deviation signal. Signaling can be acoustic or optical.

Abstract: A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields includes in the annular piston line of each cylinder/piston unit a pressure sensor. The pressure sensor, upon reaching a predetermined maximum pressure activates a pressure deviation signal, causes the entire longwall to be depressurized by means of a longwall shut-off valve. The pressure deviation signal is blocked for one of the hydraulic valves against each triggering signal.

Abstract: The invention relates to a control device for an extracting unit in the face of a mine, for actuating the hydraulic actuator in the sense of drawing, stepping, setting, and having a plurality of main valves for connecting the actuator of the extracting unit to a main pressure line and a main return line, and a similar plurality of pilot valves, each associated with a main valve for adjusting same and connected to the main pressure line via a pilot pressure line common to all pilot valves and connected to the main return line via a return line common to the main valves and the pilot valves. The pilot pressure line can be shut off and the return line can be blocked off from the main return line and connected to a measuring device for measuring escaping hydraulic fluid.

Abstract: The invention relates to a control device for an extracting unit in the face of a mine, for actuating the hydraulic actuator in the sense of drawing, stepping, setting, and having a plurality of main valves for connecting the actuator of the extracting unit to a main pressure line and a main return line, and a similar plurality of pilot valves, each associated with a main valve for adjusting same and connected to the main pressure line via a pilot pressure line common to all pilot valves and connected to the main return line via a return line common to the main valves and the pilot valves. The pilot pressure line can be shut off and the return line can be blocked off from the main return line and connected to a measuring device for measuring escaping hydraulic fluid.

Abstract: A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields comprises in the annular piston line of each cylinder/piston unit a pressure sensor. Said pressure sensor upon reaching a predetermined maximum pressure activates a pressure deviation signal, which causes the entire longwall to be depressurized by means of a longwall shut-off valve. The pressure deviation signal is blocked for one of the hydraulic valves against each triggering signal.

Abstract: A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields comprises a pressure monitoring device in the pressure line between the load maintaining valve and the shield control valve. Said pressure monitoring device can be a device for monitoring the piston position of the shield control valve which device signals a deviation of the set position predetermined by the shield control device from the measured actual position of the piston of the shield control valve in the form of a deviation signal. It may also be a pressure sensor which signals the deviation of the set pressure predetermined by the shield control device from the measured actual pressure in the form of a deviation signal. Signaling can be acoustic or optical.