| 摘要 |
The multi-height pit prop proposed comprises an outer tube (1) fitted with a foot (4), a central piston rod (3) fitted with a head (6), an inner tube (2) with a floor (5) and guide bushes (12 and 13) located at the head end of the outer tube (1) and inner tube (2), respectively. In order to increase the scope of utility of the pit prop, the foot (4) and the head (6) are fitted detachably to the outer tube (1) and inner tube (2), respectively. To set up the pit prop, the foot (4) of the outer tube and the floor (5) of the inner tube are removed and the inner tube (2) and piston rod (3) pushed out through the hole in the floor of the outer tube (1) and inner tube (2), respectively. The guide bushes (12, 13) are integral components of the outer and inner tubes (1, 2). |
