GB974501A - - Google Patents

Abstract

974,501. Stemming devices. COMMERCIAL PLASTICS Ltd. Nov. 15, 1960 [Nov. 17, 1959; July 28, 1960], Nos. 38981/59 and 26332/60. Heading F3A. [Also in Division B8] A shot-hole stemming bag comprises a flexible tube of water-resistant material, e.g. polyvinyl chloride, closed at one end by a valve 3 comprising a flexible tube which will admit water under pressure and seal against loss of water when a filler tube is withdrawn from the valve, the valve not extending for more than two-thirds the length of the tube. The stemming bags may be formed singly as in Fig. 1, from plastics sheeting which has been folded at 1 and severed from neighbouring bags by side cut-welds 2, or may be formed as a strip of bags as in Fig. 3 which may be filled while joined together,wherein semi-tear welds 15 replace the cut-welds 2. An inlet valve 3 is held by welds 4 at the mouth of the bag leaving a gap 5 for insertion of a filler tube, the valve being formed from two plastics sheets secured by welds 6 and 7 which leave an inlet 8 for the filler tube. The valve 3 may have a modified form as in Fig. 2 to which are shown shaped side welds 11 to facilitate the insertion of the filler tube through the central gap 5; a re-entrant pocket 10 for an explosive charge is also shown and is formed from a strip of plastics material folded at 12 and inserted into the tube such that the strip is caught in the side welds 2. The mouth of this pocket is welded to the bottom at 13 so defining the entry 14 for the explosive. The pocket 10 allows the explosive charge to be completely surrounded by water with the use of submersible charges. Specifications 265,518 and 714,224 are referred to.