Hydraulic control system for mine supports - has combined unit operating double two=way valve system for roof and floor members

摘要

The control for mine supports adjacent to a face conveyor in the region of e.g. a coal plough includes a unit for operating a cylinder, controlling movement of floor members and another cylinder, controlling movement of roof supports, in a proportionate manner. The control unit has a main and a follower cylinder connected to a double two-way valve, controlling the supply from the pump to the floor and roof control members. The control unit also has connections between the pump and its two cylinders, communicating with annular chambers around the cylinders. The main cylinder controls flow to an annular chamber around the floor support control cylinder so that an auxiliary piston is extended, when the control cylinder operates. The follower cylinder similarly retracts an auxiliary piston for the roof member cylinder.