Bucyrus Erie Company

Becor Western Inc.

Donald M Mains

Richard A Jasinski

James H Treiber

Edward H Christian

Richard G Currier

A dual automatic leveling system for a blast hole drill during raising and lowering which includes 'fine' level sensors to detect an attitude within a fine level range and 'coarse' level sensors to detect an attitude outside a coarse level range which is greater than that of the first. A controller is connected to the sensors as well as to appropriate valving with a pressurized fluid source so as to operate hydraulic jacks. The jacks are activated in a first mode in conjunction with the 'fine' sensors and in a second mode in conjunction with the 'coarse' sensors. In a preferred manner, the 'fine' and 'coarse' level sensors are positioned as front, rear, and end level sensors mounted on the main frame of the blast hole drill. The 'fine' level sensors in conjunction with a programmable logic control will initially level the drilling platform within a .+-.0.5.degree. (both transverse and longitudinally). If during the raising or lowering process the platform becomes out of level by 2.degree. or more, the 'coarse' level sensors in conjunction with the programmable logic control will cause the raising or lowering process to stop and a re-leveling to .+-.0.5.degree. is effected before a raising or lowering is continued.

Automatic leveling system for blast hole drills and the like

A motor drive system for a mining shovel includes three a.c. motors which are driven by associated inverter circuits that receive power from a common d.c. bus. The d.c. bus connects to the a.c. power lines through a rectifier circuit and large variations in power occur during various portions of the digging cycle. To limit the peak power demanded during a digging cycle a peak power limiter system comprised of a fourth inverter driven a.c. motor is attached to the d.c. bus. This a.c. motor drives a flywheel which is operated to store energy during periods of low power demand and which is operated to regenerate stored energy to the d.c. bus when power demanded from the a.c. power lines exceeds a preset amount.

Peak power limiter system for excavator

A Ward-Leonard drive system for a dragline excavator includes a feedback circuit which connects to the motor-generator armature loop to sense a signal proportional to motor armature counter emf and rate of change of armature current. The feedback circuit takes the second derivative of this signal and applies it to a circuit which controls motor speed and torque. The feedback circuit alters the response of the drive system to sudden increases in motor load caused by rough digging and thereby reduces transient loading on the mechanical elements of the drive system.

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Greendale, WI, United States of America

Donald M Mains