Patent GB-991011-A (GB)
Title: Roof support assembly
Inventor: POTTS MICHAEL CHARLES
IPC: E21D23/16
Filed: 1962-09-03
Abstract: 991,011. Advancing mine roof supports. DOWTY MINING EQUIPMENT Ltd. Aug. 19, 1963 [Sept. 3, 1962], No. 33755/62. Heading F1P. A mine roof support assembly comprises a series of fluid pressure operated roof supports advanceable in a predetermined sequence towards a conveyer (not shown) by an associated jack 7, controlled by an associated hydraulically operable control valve assembly 13 which is adapted to send an hydraulic-pressure signal through a pilot line 14 to the control valve assembly 13 of the next roof support in the sequence to thereby initiate its operation. Each roof support is comprised of a number, e.g. three hydraulic telescopic props 6, and every fourth support is provided with a conveyer advancing jack 8. Each control valve assembly 13 includes three valve units A, B, C, (Fig. 4) having ports 20-25 inter-connected by lines, as shown. An hydraulic power unit 9 is connected to each control valve assembly through a main pressure line 11, a return line 12, the pilot line 14 and a secondary pilot line 15. The power unit 9 comprises a main pressure source 56, a pilot pressure source 57 and a change-over valve 59 which includes two further valve units 63, 64 (Fig. 4). In operation with each of the valve units A, B, C of all of the control valve assemblies 13 in their neutral positions shown, wherein ports 22, 23 are connected, hydraulic pressure from the main line 11 passes via non-return valves 18, valve units C, lines 19, and non-return valves 27 to the props 6 which thereby support the roof. Branch lines 35 leading from the lines 19 communicate with the conveyer advancing jacks 8 so that the conveyer is advanced towards the receding mine face. To initiate the first advancing sequence the pilot pressure source 57 is switched on so that pressure is communicated through the change-over valve 59 to ports 24 of valve units B and C which are thereby operated to connect their ports 21, 22 which pressurises through valve unit B, lines 34, 36, 37 from the main line 11. Pressure in line 34 operates a prop release valve 32 so that the props 6 are connected through lines 26, 29, 30 & 33 to the return line 12, and pressure in the line 36 retracts jack 7 to cause the roof support to advance towards the conveyer. The conveyer advancing jack 8 is also retracted by pressure in the line 37. When the roof support is nearly fully advanced up to the conveyer a projection 45 carried by the jack 7 opens a valve unit 40 which causes a line 44 to become pressurised from the line 36 so that valve unit A is operated. Pilot pressure from line 14 therefore passes through now connected ports 21, 22 of valve unit A to a closed valve 46 and also through a non-return valve 43 and line 41 to port 24. Valve unit A is therefore locked in the operated position since valve 39 is closed and pressure is trapped in the port 24. Pilot pressure in line 14 is also communicated to ports 25 of valve units B and C which are thereby returned to their neutral positions, which causes the props to extend and the jack 8 to be pressurised through line 35 to once again urge the conveyer to advance. The attainment of a satisfactory pressure in the props 6 causes the valve 46 to open thus allowing pilot pressure in line 14 to pass on to the valve assembly 13 of the next roof support in the series which then undergoes an advancing operation. When the last support has advanced pilot pressure in the line 14 is applied through a non-return valve 71 to the secondary pilot line 15. The ports 20 of valve units 63, 64 are therefore pressurised and operate these units to break the pilot line 14 and connect the pilot pressure source 57 to the secondary pilot line 15. The valve units are held operated by pressure locked in line 66, the valve 67 being closed. Pressure in the secondary pilot line 15 acting through lines 38 opens the valve unit 39 in each control valve assembly 13 to connect their respective lines 41 to the return line 12 and thereby return the valve units A to their neutral positions. The fall in pressure in the pilot line 14 due to the operation of units 63, 64 opens a valve 55 to allow pressure in the secondary pilot line 15 to reach one side of the valves 48, 49. The valves 48, 49 are operated by a cam member 47 carried by the support advancing jack 7 when the jack has been extended by about three-quarters of its full extension due to advancement of the conveyer. Operation of the valves 48, 49 pressurises line 53 which opens a valve 67 thereby unlocking valve units 63, 64 and initiating another advancing operation of the roof supports. The valve units A, B, C 63 and 64 may be held in the operative position by mechanical instead of pressure locks. Excessive pressure in the props 6 is relieved through a valve 31.