Patent GB-1095112-A (GB)
Title: Advancing roof supports
Inventor: BRUCE DONALD MARSH
IPC: E21D23/12
Filed: 1964-08-31
Abstract: 1, 095,112. Advancing mine roof supports. ELECTRO-HYDRAULICS Ltd. Aug. 27, 1965 [Aug. 31, 1964], No.35523/64. Heading F1P. In a control system for automatically advanceable, hydraulically operated, mine roof support units in which the united are associated with a conveyer and each unit undergoes the three operations of conveyer advance, support unit release and advance, and support unit reset; the supports are connected to common pressure, exhaust and control lines 15, 11, C and each support has a single solenoid operated valve 28 which is actuated on two separate occasions in sequence with pressurizing and de-pressurizing the control line C to cause its support to perform the three operations. In the majority of the embodiments the solenoid valve 28 is merely supplied with an electrical pulse of short duration but in certain of the embodiments the solenoid is maintained energized. Several different sequences of actuating the solenoid valve 28 and changing the pressure in the control line are described with reference to control systems comprising various arrangements of pilot operated control valves. Each of these control systems provides particular control features e.g. alternative left-to-right or rightto-left advance of the supports, power lowering of the support props, or advance of all left hand frames of a support unit followed by advance of all the right-hand frames of the unit. The system shown is for controlling the advance of an individual support comprising right and left frames connected to a return line P 1  and pressure line P 2  which may be reversed to operate a valve 77 and enable one or other of the frames to be selectively advanced. A shuttle valve 57 ensures that the pressure line 15 is always connected to the line P 1  or P 2  pressurized and non-return valves 58, 59 ensure that the exhaust line 11 is always connected to the line P 1  or P 2  unpressurized. With the control line C pressurized by, for example, operation of a valve actuated by the successful advance of an adjacent support unit, advance of the support is initiated by supplying an electrical pulse to the solenoid valve 28. Operation of the valve 28 pressurizes from pressure line 15 the pilot connections 13, 26 of valves 6, 22 to changeover the valve 6, but operation of the valve 22 is prevented by control pressure in its pilot connection 27. The changeover of the valve 6 applies pressure to the full area side of an advancing ram 3 to cause advance of the conveyer connected thereto. When the ram 3 has fully extended it is arranged to cause venting of the control line by, for example, operating a micro-switch and to also actuate for a second time the solenoid operated valve 28. The valve 22 is thus able to changeover so that the pressure line 23 leading to the prop(s) is vented to the exhaust line 11 and a conduit 95 is pressurized from the line 15. The pressurization of the line 95 causes a piston 88 to move fully to the right to rapidly displace hydraulic fluid through lines 94, 50A to open the lock valve(s) of the prop(s) of the left-hand frame and to rapidly retract them from the roof by a predetermined amount. The pressure in the line 95 acting through a line 96 and a pilot connection 17 returns the valve 6 after the solenoid valve 28 is de-energized whereby the full area side of the ram 3 is exhausted and the annular side is pressurized from the line 95 and a line 85 to advance the left-hand frame, the conveyer acting as an anchorage. When the lefthand frame is fully advanced pressure is reapplied to the control line C by e.g. operation of a micro-switch to reset valve 22 and thereby pressurize the line 23 thus restoring the frame to its roof supporting condition.