Abstract: A coupling gear for connecting two side-by-side, longitudinally extending shiftable skids of a divided footwall skid of a lemniscate shield timbering frame for actuation by a fluid pressure operated piston and cylinder combination which is adapted to be connected thereto, comprises, a double crank joint which includes first and second outer crank pins extending transversely between the skids with bracket means adapted to be positioned on the respective skids for rotatably supporting the outer crank pins on the respective skids and, wherein, the crank pins have outer ends rotatably supported in the bracket means and opposite inner ends and including first and second longitudinally extending, substantially parallel crank arms, one of which has a first end connected to the inner end of the first outer crank pin and the other of which has a first end freely rotatable on the second outer crank pin and with a central crank pin having a first end freely rotatable in the first crank pin arm opposite end and an opposi