| 摘要 |
1,228,381. Advancing mine roof supports. GULLICK, DOBSON Ltd. 18 July, 1968 [8 Nov., 1967], No. 50847/67. Heading E1P. In an advancing mine roof support comprising a prop 10 which is controlled by a release valve 15 responsive to the fluid pressure in a line 28, and, an advancing ram 11 which is controlled by a valve 16 connected to the line 28 through conduits 25, 27 as shown, an adjustable metering valve 17 is disposed in the line 25 to ensure that a predetermined time lapse ensues between the release of the prop 10 and its advancement. Line 28 may receive a hydraulic signal from an adjacent supportas described in Specifications 1,038,262 and 1,085,274. |
