MINE ROOF SUPPORT
1487553 Advancing mine roof supports DOWTY MINING EQUIPMENT Ltd 20 Sept 1974 [18 Oct 1973 20 July 1974] 48620/73 and 32251/74 Heading E1P In a mine roof support having an advancing jack 18 connectible to an anchorage such as a conveyor by a relay bar 13, the jack is arranged to exert on the support a force having one component parallel to the direction of advance and another component which lifts the support from the floor. The thrust exerted by jack 18 acts in a straight line between pivot joints 19, 21 as shown, a slot 35 providing a lost motion connection between the jack and the bar 13. The jack is enclosed by a pair of telescopic tubes 27, 28 loaded by a spring-actuated plunger 38. In a modification, see Figs. 4..7 (not shown), the forward end of the jack is pivoted to a bridge member [119] extending between the front edges of the floor beams of the support and the plunger of the jack is pivotally. connected to the end of the relay bar.