Coalface supports with datum beam - beam acted on by jacks releasably fixed to it, engaged by support shifting cylinders

摘要

Mine support chocks or shield chocks or shield units composed of floor-bars and props supporting roof canopies are allocated a datum beam which runs along the face and is divided into sections for horizontal and vertical movement and is additionally engaged by the extensible shifting rams forming part of the respective support units. The beam is acted on by jacks which are distributed over the length of the face and releasably associated with teh beam for this purpose. Preferably the hydraulic piston and cylinder units comprising the jacks can be locked onto the beam by means of their cylinder tube members, but rest on the floor at their piston rod bases by means of swivel plates of bowl design. The jacks can be integrated with the datum beam.