| 摘要 |
1,242,776. Advancing mine roof supports. GULLICK DOBSON Ltd. 30 Oct., 1969 [24 Dec., 1968], No. 53108/69. Heading E1P. To prevent sliding, down an inclined seam, two mine roof supports are interconnected by an extensible dash pot 6 such as a double acting piston and cylinder arrangement. The ends of the latter arrangement are pivotally connected to the supports and are interconnected via line 11 through a throttle and a closure valve 12, 13 provided on a further neighbouring support. The control system includes an accumulator 15 which can be bypassed by a valve 16, an air release valve 17 also being provided. |
