Patent ID: 8876218

Claim:
A hydraulic circuit for longwall support for use in underground mining for supporting a longwall by means of a plurality of support shields where each support shield comprises: at least one hydraulic cylinder/piston unit configured to perform support functions such as removing timbering, progressing, and setting, wherein the at least one cylinder/piston unit is connected with a shield control valve by an unblockable check valve and a pressure line, wherein, upon demand by a shield control device that is assigned to each support shield, the at least one cylinder/piston unit is either connected by the shield control valve with a pump line, or, when the check valve is simultaneously unblocked, is connected with a return line, or is blocked against the pressure line by the check valve, wherein an annular piston line of the at least one cylinder/piston unit is monitored by means of a pressure sensor, which in turn activates a pressure deviation signal when a predetermined maximum pressure is reached, which causes the hydraulic circuit to be depressurized by means of a longwall shut-off valve such that the check valve remains blocked, and wherein the pressure deviation signal is locked against a triggering signal of the shield control device such that the pressure deviation signal does not cause the longwall shut-off valve to become depressurized if the triggering signal is present.