Abstract: Forming a hole between lower and upper parallel galleries formed in a mine by boring upwardly from the lower gallery a bore hole having a first length equal to a fraction of the distance between the lower and upper galleries, then casing the bore hole by thrusting upwardly at least one pipe section having a diameter sufficient to be gripped by the shrinkage of the bore hole into the bore hole.

Abstract: Steep dip strong-coal deposits can be broken in an explosive mine environment utilizing a succession of explosive units each of which comprises a core tube surrounded by a body of explosive material which, in turn, is surrounded by an arc-suppressing heat-dissipating fluid. Igniters in the explosive charges have conductors which are lead back out of the bore hole through the tubes of the explosive units which are anchored at spaced locations along the bore hole.

Abstract: A workpiece clamping device for the fast, central clamping of workpieces provided with holes of various number and pitch diameter and/or with a central hole, such device being adapted for the balancing of vehicle wheels. The device consists of a fixing mechanism, releasing mechanism and a clamping unit attachable to them with the workpiece. The clamping unit contains a central mandrel with a threaded end, a pressure element movable on the mandrel in an axial direction and secured against turning with respect thereto, and one or more locating elements connected to the pressure element and fitting into the hole or holes of the workpiece as well as a threaded clamping element supported by the pressure element. The fixing mechanism contains a sleeve receiving the mandrel of the clamping unit; the fixing device is provided with a selectively operated releasing mechanism. Operation of the releasing mechanism automatically disables the motor which drives the balancing mechanism.

Abstract: Floor tiles are disclosed which comprise a carrier layer and a superimposed floor surface forming layer which is provided with a decorative wear resistant surface. In one embodiment the carrier layer protrudes beyond the floor surface layer on two sides and the floor surface layer protrudes beyond the carrier layer on the other two sides and the floor surface forming layer defines an angular groove and a bevelled tongue to enable adjacent tiles to be interlocked. In an alternative embodiment of the invention the groove and tongue are formed to have different angles.