Joy Global built the first all electric multi-motor shearing machine in the world in 1975. This innovation brought a new level of reliability and maintainability to the machine. The advantages of this modular all-electric concept and the benefit of eliminating complex, dirt sensitive hydraulic circuits from the underground environment are well recognized by the mining industry. The modular design consists of five main structural elements.
The body of the shearer normally consists of three high tensile steel fabrications bolted together to form a slim main section with no under-frame. This design provides maximum under-body clearance for material passage in a given seam thickness. The elimination of the under-frame also enhances underground transportation.
The controller case, which forms the center section, contains the electric control system including; vacuum contactors, transformers, OPTIDRIVE inverters and bus-supply for AC haulage, micro-processors, control circuitry and diagnostic data display screen. The design features gob-side access to the electrical controller section and motors which means that normal maintenance can be carried out in a safe working environment.
Two traction sections (housing a haulage motor, primary traction gear case and hydraulic system) are bolted and doweled to each end of the controller case. The hydraulic system raises and lowers the ranging arms and lumpbreaker and rotates the cowls. The secondary traction gearcases (or down-drives) are bolted to the traction cases in an arrangement that permits the custom fitting of the shearer within the AFC and roof support envelope. A wide selection of Joy Global designed and manufactured down-drives can be fitted to the shearer to suit mining conditions and AFC selection.
Two high tensile steel ranging arm castings house the cutter motors and cutter gearcases. Custom gear design for high power densities draws on many years of experience and the latest Finite Element Analysis (FEA) techniques. This coupled with Joy Global's exacting manufacturing standards, heat treatment processes, gear grinding capabilities, gear charting, metalurgical lab checks, % gears cut for test and Coordinate Measuring Machine (CMM) reporting has maximized performance, reliability and extended rebuild intervals.