Patent GB-996137-A (GB)
Title: Mining apparatus
Inventor: BOLTON DOUGLAS HERBERT HEWLETT
IPC: E21D23/26
Filed: 1963-04-22
Abstract: 996,137. Advancing mine roof supports. DOWTY MINING EQUIPMENT Ltd. April 14, 1964 [April 22, 1963], No. 15826/63. Heading F1P. A mine roof support assembly comprises a series of advanceable roof supports 4 each having at least one fluid-pressure operated support prop 6 and a support advancing jack 7 (Fig. 3), together controlled by a valve assembly 12 including a re-setting valve 53 actuated by the completion of a predetermined advance of the support to cause the support to reset against the roof, additional means being provided to cause re-setting of the support in the event of a support failing to advance the predetermined distance. The valve assembly 12 associated with each roof support 4 is connected by a branch supply line 13 to a supply line 11, and by a branch return line 15 to a return line 14. A pilot line 18 connected to a secondary pressure source 16 passes through the valve assembly 12 of each roof support 4 in turn and a control line 19 is connected to each valve assembly by branch control lines 21, 22. Fig. 3 shows the valve assembly 12 of a roof support also having associated therewith a double-acting jack 8 for advancing a conveyer (not shown) to which the advancing jacks 7 are connected. The valve assembly comprises valve units A, D and E controlling respectively the supply of hydraulic fluid for extending the jack 8 contracting the jacks 7, 8 and extending the support props 6. In the conveyer advancing condition of each valve assembly 12 a lever 32 is moved in an anti-clockwise direction either manually or by pressurisation of a line 65 connected to a valve unit B and is held in the anticlockwise position by a spring latch 66 to thereby maintain valve unit A open, whereby the conveyer advancing jack 8 is supplied with fluid through lines 11, 13 and 23. When the first support in the series is to be advanced, the upper left-hand portion of pilot line 18 is pressurised. Pressurisation of line 18 releases the latch 66 and operates on a valve unit C to cause clockwise movement of the lever 32 and a lever 33. As a result valve unit A closes thereby cutting off the supply to the jack 8 and valve unit B opens to allow fluid to pass from the jack 8 to the return lines 15, 14. At the same time valve unit C closes and valve unit D opens thereby connecting the contracting sides of the jacks 7, 8 through a line 24 and valve unit D to the branch supply line 13. Pressurisation of line 24 also pressurises a line 69 thereby causing a valve unit F to open, whereupon the props 6 retract from the roof, the fluid therein passing through a non-return valve 29, a line 28, and the valve F to the branch return line 15. The jack 7 then advances the support towards the conveyer until a trip 63 on the jack 7 opens the re-setting valve 53 so that a line 58 is pressurised from the line 24 to close valve unit F whereby fluid flows through a non-return valve 59, a restrictor 26 and a non- return valve 27 to extend the props 6. The pressure build-up in a line 43 which occurs after the props have reset against the roof is arranged to displace the piston 39 of a pilot valve 35 whereby the pilot line 18 is pressurised up to the valve assembly 12 of the second support of the group. In this way, each roof support in the series is advanced in turn. Pressurisation of the lower portion of pilot line 18 and a line 71 connected thereto closes valve unit D thereby returning the interconnected valves A, B, C to their original positions. The piston 39 is prevented from returning by fluid trapped by a non-return valve 44 and a locking valve 46. If any roof support fails to advance the predetermined amount, further advance of the series is prevented until the branch control line 22 is pressurised to a pre-determined lower value to operate on a piston 62 to open the re-setting valve 53. Alternatively valve unit E may be arranged to be operated either manually or by pressurisation of the branch control line 22 thereby pressurising a line 25 to extend the props. When all the roof supports 4 have advanced, the pilot valves 35 are unlocked by pressurising the branch control lines 21 to a predetermined higher value sufficient to open the locking valves 46. In a further arrangement a time-operated mechanism triggered by the receipt of the signal in pilot line 18 is operative, after a predetermined time, to actuate the resetting valve 53 or valve unit E unless rendered inoperative by subsequent pressurisation of the line 43 and props 6.