This invention relates to a roof-supporting assembly for a hydraulic roof-supporting system for longwall faces, which roof-supporting assembly comprises three frames placed side by side of which either the two outer frames jointly or the frame in the middle can be advanced and wherein the frames are coupled by paired control cylinders operable in contrary directions for correcting the relative positions of the frames, the annular piston face in one of each pair of cylinders having the same effective cross-sectional area as the full piston face in the other cylinder and the chamber on the full piston face side in one control cylinder being connected to the chamber on the annular piston face side in the other cylinder for keeping the frames parallel.
The present invention is directed to a movable load support used for supporting the roof in underground excavations. The load support includes a primary roof support carried on a base frame and an auxiliary roof support also carried on said base frame but laterally disposed from the primary roof support. The auxiliary roof support is longitudinally and laterally moveable with respect to the primary roof support to successively provide roof support to adjacent areas of the roof.
