Abstract: Mine roof support comprising a base including a pair of skids, a roof engaging canopy, jacks acting between the base and the canopy, an auxiliary jack connected to the base for lifting or lowering at least part of the base when the support advances and a lost motion arrangement connected between the base and the auxiliary jack for aiding movement of the base and the roof engaging canopy toward each other. The lost motion arrangement is connected to each of the skids by a pivotal connection which permits the front end of one skid to move vertically to a limited extent with respect to the front end of the adjacent skid.

Abstract: A self-advancing mine roof support comprising a floor engaging base 11, a roof engaging canopy 12, hydraulic jacks 19a, 19b to urge the base and canopy apart, and a linkage system located towards the rear of the support. The linkage system comprises an inclined shield member 22 pivotally connected to the canopy 12, and at least two links 23, 24 interconnecting the shield and the base. The jacks 19a, 19b, are located substantially halfway along the length of the base and extend substantially vertically from the base. There is a hydraulic jack 18 operable between the roof engaging canopy 12 and the linkage system to effectively counterbalance the projection on the canopy 12 which extends forwardly of the jacks 19a, 19b.