Abstract: The invention relates to an advance mechanism for a roof support assembly constituted by a plurality of roof support units positioned side-by-side along, for example, a longwall face of a mineral mining working. The advance mechanism comprises a pair of hydraulic advance rams and a pair of resilient, generally parallel guide rods. The guide rods are interconnected at one end by means of a head-piece which is attachable to a conveyor extending along the longwall face. The other end of each guide rod is attached to a respective slide piece which is slidably guided on a respective guide rail which is attached to a floor girder of a roof support unit. The hydraulic advance rams are each pivotally attached to one of the slide pieces and to one of said floor girders. The guide rods are provided, adjacent said one end, with outwardly projecting alignment members each of which co-operates with one of said floor girders to align an associated roof support unit during its advance.

Abstract: A mine roof support assembly comprises three basically similar mine roof support units positioned in a side-by-side relationship along a beam. The central unit is fastened to the beam for movement therewith, and the two outer units are flexibly connected to the beam by respective guide rod assemblies. Each of the outer units is provided with an alignment device, such as a short working stroke hydraulic ram, which acts on the beam in the direction of the longitudinal axis of the beam.

Abstract: A hydraulic control system for use with double-acting shifting rams in a mine working.The system has a pump for supplying pressure fluid and main and return feed lines or conduits connected to the pump and laid along the working. An adjustable pressure-regulating device or devices serves to provide fluid at variable pressure in a further feed line or conduit.Each ram has its working chambers connected to a control device which is in turn connected to the main and further feed lines or conduits and to the return line or conduit. The devices can each be set to various positions to operate the rams in order to extend one of the rams its associated device is set to connect the working chamber used for extension (having the larger piston working surface area) to the further feed line or conduit, and to connect the other working chamber used for retraction (having the smaller piston working surface area) to the to the main feed line or conduit.