Mine roof support

In a mine roof support with a pair of spaced-apart floor-engageable skids, a roof-engageable structure, hydraulic prop means operably disposed between the skids and the roof-engageable structure, a shifting and guide means composed of a floor rail and a shifting ram disposed above the floor rail for advancing the support relative to a mineral face, a bridge member interconnecting front end regions of the skids relative to a mineral face, a lower surface of the bridge member being disposed above the floor rail and in confronting relationship thereto and a lifting mechanism comprising an upstanding piston and cylinder unit, the unit being extendible to engage on the floor rail to effect at least partially raising of the skids when the shifting ram is operated to advance the support, and means for detachably connecting the unit to the bridge member in a plurality of alternative height positions relative to the bridge member;

• the improvement comprising a stop member operably associated with the bridge member to provide a lower surface below that of the bridge member in confronting relationship to the floor rail to ensure when the unit is retracted it is maintained above the lower surface of the bridge member or the stop member in all the alternative positions of the unit.