Importance

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Abstract

A coal cutting machine 13, a conveyor 12 and a plurality of mine roof supports 10 extend along the face 11 of a coal mine. The operation of the hydraulic jacks of the roof supports are controlled by pilot valves which are electrically powered and rotationally driven. For example, motorized or cam operated pilot valves can be used. Such pilot valves use much less energy than valves controlled conventionally by solenoids, and the electricity supply can thus be at an intrinsically safe level. The operation of the pilot valves include unitary operation of a given support, remote operation of one support from another and sequential operation of a series of supports. When the system controls a plurality of supports sequentially, sensing means sensitive to a first pressure level in a first support when the first support is set to a mine roof activate another support in the sequence when the first pressure level has been sensed in the first support, while continuing the raising of the pressure in the first support until a second, higher pressure level is detected. A group of supports is controlled by a control station positioned at a face end, and in addition each support has its own individual control position. The control station incorporates a microprocessor which may be reprogrammed underground.

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First Claim