| 摘要 |
1,254,594. Advancing mine roof supports. GULLICK DOBSON Ltd. 28 Jan., 1970 [13 Feb., 1969], No. 7998/69. Heading E1P. In an advancing mine roof support assembly for inclined seams, two adjacent roof supports are inter-connected by three extensible members, such as single or double acting rams 22, 22a, positioned relative to one another at the apices of a triangle. In a modification, see Figs. 4, 5 and 6 (not shown), one of the rams is replaced by a cam-like skid plate pivotally connected to one support and adjustably positioned thereon by a single- or double-acting ram. |
