Hydraulic and earth engineering – Earth treatment or control – Shoring – bracing – or cave-in prevention
Patent
1981-09-28
1984-01-24
Corbin, David H.
Hydraulic and earth engineering
Earth treatment or control
Shoring, bracing, or cave-in prevention
405299, 405302, E21D 1514, E21D 2318, E21D 2326
Patent
active
044273215
ABSTRACT:
A longwall mineral mining installation has a conveyor and a plurality of roof support units positioned side-by-side on the goaf side of the conveyor. Each roof support unit has a roof shield having an advanceable shield extension. Each unit has a first hydraulic ram for extending its shield extension, and a second hydraulic ram for advancing the conveyor. The extension of each first ram is controlled in dependence upon the retraction of one of the second rams (either the second ram of the same unit or that of an adjacent unit). This control is effected by controlling the supply of pressurized hydraulic fluid to the first rams. In one embodiment this is carried out by a control valve which has a spring-loaded plunger which engages with a series of equispaced cams on the movable cylinder of the associated second ram. In another embodiment, the piston rods of the rams are provided with series of equispaced magnets. The cylinders of the rams are provided with sensors, which sense the magnets and generate control signals. A control box is provided to direct the control signals to control valves associated with the rams, so that the first rams are extended by the same distance as that through which the second rams are retracted.
REFERENCES:
patent: 3436922 (1969-04-01), Irresberger et al.
patent: 4192632 (1980-03-01), Von Viebahn et al.
patent: 4217067 (1980-08-01), Lagodka et al.
patent: 4307981 (1981-12-01), Weirich et al.
Becker Kunibert
Rosenberg Harry
Weirich Walter
Corbin David H.
Gewerkschaft Eisenhutte Westfalia
Pistel Nancy J.
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