Planetary overriding gearing and overriding driving for chain belts and the like, particularly for chain conveyors and chaindrawn mining machines

In a drive system for propelling an endless traction member of a mineral mining installation having main and auxiliary drives each composed of an electric asynchronous drive motor and a gearing unit;

• the improvement comprising a planetary gearing unit interposed between at least one of the motors and an associated gearing unit, a further control motor operably associated with the planetary gear unit, the planetary gearing unit comprising an input shaft with a first sun wheel, an output shaft with a second sun wheel, sets of planet wheels meshing with the respective first and second sun wheels with planet wheels of one set also meshing with planet wheels of the other set, a common carrier for the sets of planet wheels, means drivably coupling the carrier to the control motor and means for sensing a load parameter derived from loading of at least one of the drive motors and indicative of imbalance between the drives and for operating the control motor to rotate the carrier;
• whereby the sensing means and the control motor co-operate to regulate the planetary gearing drive ratio from a value of 1:1 when the control motor is inoperative to cause the planetary gearing to override the drive ratio of said associated gearing to compensate for the sensed load parameter.