GB823128A - Improvements in and relating to mine roof support systems - Google Patents

Abstract

823,128. Mine roof supports. DOWTY MINING EQUIPMENT Ltd. May 23, 1956 [Feb. 23, 1955], No. 16012/56. Divided out of 823,127. Class 20(2) Mine roof supports 19 and a flexible coal conveyer extending along the coal face adapted to be moved forward alternately by jacks 35 connected between them are controlled by trip valves 41 on the conveyer operated by movement of a cam 43 with the coal cutter so as to collapse the supports 19 after the coal cutter has passed them, advance the supports and extend them again. The supports are of two kinds arranged alternately along the coal face and a different control valve and jack is associated with each kind. One kind comprises a roof bar supported by two props and the other 17 by three props, and only the jacks associated with the three prop units move the conveyer. A two-prop support immediately behind the coal cutter is moved by its jack when a cam moving with the coal cutter initiates operation of the two-prop support control mechanism and a cable extending behind the coal cutter from this cam is connected to the cam 43 which is drawn along to initiate the operation of the control mechanism of a three-prop support 17 by depressing the plunger 42 of the trip valve 41 which is retained by a latch 91, pressure fluid is thus supplied to extend the jack 35 and move a part of the conveyer forward some distance behind the coal cutter, until the latch 91 is released by a rod 92 and a lug 93 on the jack whereupon pressure fluid is supplied by pipe 54 through the jack rod chamber 55, chamber 56 and control valve 61 to operate a release valve 82 to collapse the props of the support 17 and to contract the jack 35 which advances the support 17 until a stop 68 depresses the plunger 62 of the control valve 61 which supplies fluid to reset the props. The control mechanism of the two-prop supports is similar except that the piston chamber 52 is always connected to exhaust and for the omission of the latch 91 and consequent modification of the trip valve.