Patent ID: 7478884

Claim:
A hydraulic switching mechanism for longwall supports comprising: one or more shields that can be actuated in the sense of support functions of setting and removing props for the support of a rock mass; one or more hydraulically actuated rams that are assigned to each of the shields for the execution of operational functions required for the support functions; one or more hydraulic control valves that can be actuated by positioning commands output to electromagnets and are each assigned to one of the rams for hydraulic triggering of the operational functions of the ram and are connected to it hydraulically; an electronic control unit for each of the shields for triggering positioning commands with the aid of support commands that can be input into the individual shield control; a pump line for feeding pressurizing medium to all the rams which is connected in each case via a pump branch line to at least one ram; a return flow line for draining pressurizing medium from the rams that is connected in each case via a return flow branch line to at least one ram; and a block valve located in the pump branch line that blocks a direction of flow from the respective ram to the pump line and that can be actuated independently of activation and switch positions of the hydraulic control valves.