| 摘要 |
969,085. Mines etc.; blasting. W. H. DUNN & SON Ltd. May 21, 1963 [May 30, 1962], No. 20735/62. Heading E1F. A shot-firing curtain comprises mesh screens 20, 21 fastened at each side of a mine road and horizontally extensible towards each other, and a mesh screen 25 horizontally mounted and extensible downwardly to overlap and cover any gap between the screens 20, 21. The screens which are arranged to slide on rails 10, 11 are surmounted by a screen 27. The screen 25 may be supported in a raised position by clips 26. |
