Bethlehem Steel Corporation

William S Locks

Francis G Miller

Edwin B Wilson

James C Weimer

An intrinsically safe system controls all miner hydraulic and electrical functions from a hand held miner remote control pendant. Pendant control devices provide on/off control signals to interfaces with miner drive and pump controllers, as well as a group of .+-.6 VDC differential proportional and on/off control signals to respective electronic valve drivers. Valve driver outputs are fed to respective force motors on pilot stage valves which control each hydraulic function. Each valve driver output is modified by offset and dither signals to overcome power stage valve dead band and frictional characteristics. Pilot stage valves have an internal feedback sleeve coacting with a pilot valve spool in a hydraulic servo circuit. Pilot stage valves operate in a pilot oil system which may be isolated from power oil systems.

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Bethlehem, PA, United States of America

William S Locks