Grinding mill control system

Claim 1

A mill drive system having a mill drum rotatably mounted between spaced bearings, a large gear connected thereto in driving relation, at least two pinion gears mounted in constant meshing relation with the large gear, at least two electric motors to drive the respective pinion gears, variable clutches to permit variation in transmission of torque between each motor and the respective pinion gear, and regulating means for selectively controlling the clutches, said system being subject while under steady state operation to recurrent cyclic imbalance in the instantaneous values of electrical power required by said motors, angular position indicating means located at a predetermined angular position on the large gear and datum indicating means positioned in predetermined angular relation adjacent the large gear to provide indication of the coincidence of the indicating means, and clutch control means for effecting locking-up of the clutches at a preselected angular position of the gear wheel whereby the cyclic variation in load of the motors may be selectively moderated.

Claim 4

The method of controlling the operation of a large gear directly connected in driving relation with a load, in a system having individual selectively variable clutches interposed in controllable connecting relation between a pair of pinion gears connected in constant meshing relation with the large gear and an individual electric motor connected in driving relation with each pinion gear through a said clutch, having each said motors initially running at synchronous speed including the steps of operating said clutches in a slipping mode on start-up of the load to limit the respective torque transmitted to a predetermined load value, and to permit cyclic equalization of load between said motors and then locking up the clutches at a predetermined angular position of the large gear relative to a fixed datum to preclude further slip and to synchronize operation of the motors to the gear whereby cyclic variations of loading on the motors due to non-uniform characteristic of the large gear are substantially minimized.

Claim 5

The method of controlling the operation of a large gear directly connected in driving relation with a load, in a system having individual selectively variable clutches interposed in controllable connecting relation between a pair of pinion gears connected in constant meshing relation with the large gear and an individual electric motor connected in driving relation with each pinion gear through a said clutch, having each said motors initially running at synchronous speed including the steps of operating said clutches in a slipping mode on start-up of the load to limit the respective torque transmitted to a predetermined load value, and to permit cyclic equalization of load between said motors and then locking up the clutches at a predetermined angular position of the large gear relative to a fixed datum to preclude further slip and to synchronize operation of the motors to the gear whereby cyclic variations of loading on the motors due to non-uniform characteristic of the large gear are substantially minimized.