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US 4,307,981 AGranted
Mineral mining installation
AssigneeGewerkschaft Eisenhutte Westfalia
InventorsWalter Weirich, Harry Rosenberg, Kunibert Becker
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AssigneeGewerkschaft Eisenhutte Westfalia
InventorsWalter Weirich, Harry Rosenberg, Kunibert Becker
Estimating the term…
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.
A longwall mineral mining installation comprising a conveyor and a plurality of roof support units positioned side-by-side along the goaf side of the conveyor, each roof support unit having first and second double-acting hydraulic rams, wherein each first hydraulic ram is provided with control means responsive to the movement of one of the second hydraulic rams, and wherein each control means is such that the associated first ram moves through the same distance as said one second hydraulic ram.
A longwall mineral mining installation comprising a conveyor and a plurality of roof support units positioned side-by-side along the goaf side of the conveyor, each roof support unit having first and second double-acting hydraulic rams, wherein each first hydraulic ram is provided with control means responsive to the movement of one of the second hydraulic rams, and wherein each control means is such that the associated first ram moves through a distance proportional to that through which said one second hydraulic ram moves.
Dependencies are inferred from the claim text.