| 摘要 |
<p>1,233,180. Advancing mine roof supports. GULLICK DOBSON Ltd. 22 Oct., 1968 [9 Dec., 1967; 4 Jan., 1968], Nos. 56100/67 and 621/68. Heading E1P. [Also in Division G3] In a longwall system of mining wherein the machine cuts at zero depth to start with and the depth of cut progressively increases as the machine travels along the face prior to a return cut in zig-zag fashion the conveyor advancing rams 10<SP>1</SP>..10<SP>n</SP> are each controlled by a metering device adapted to be adjusted differentially one from another. Each metering device has two chambers 14, 15 with a floating piston 16, 17 whose stroke may be limited by screws 18, 19 respectively. The chambers are divided by a wall 22 and each communicate with a conduit 24 leading to a control valve 26 having a spring-loaded poppet 27 controlling an outlet port 37 to the associated ram and pressure-supply passages 30, 32, the latter being connected to feed conduits 35, 36 arranged and controlled by valves 33, 34 as shown. The metering devices may be replaced by potentiometers each of which controls a solenoid determining the supply of fluid to the rams. Again, the piston rod of each ram may have a series of magnets disposed thereon to actuate reed switches thereby control the operation of such solenoids, see Figs. 9 and 10 (not shown). For other minor modifications and methods of operation the Specification should be referred to.</p> |
