Abstract: An interlock scheme is provided for preventing access to a draw-out mechanism of a drawout circuit breaker which is in a contact "closed" position and preventing the contacts from being closed when the circuit breaker is only partially connected to the power bus. A sliding door, carried by the front cover of the circuit breaker, is movable between a first position providing access to a driver shaft assembly for operation of the drawout mechanism and a second position preventing access to the driver shaft assembly. A plunger and slider assembly is operable associated with the access door to prevent the door from being moved from the second position to the first position unless the contacts within the circuit breaker are open. A trip arm prevents the contacts from being closed when the circuit breaker is only partially connected to the power bus.

Abstract: An assembly for protecting a circuit breaker drawout mechanism from damage which may be caused if excessive torque is applied to operate the mechanism. The invention relates to drawout circuit breakers of the type utilizing a worm gear assembly (34, 36) to operate a driven shaft (12) to move the circuit breaker into and out of an electrical compartment. A two-part driver shaft assembly (38) is used which includes a head (50) and a driver shaft (62). The head has a collar portion (52) which includes a ridge (54) and the driver shaft is provided with a channel (68) adapted to receive the ridge. A shoulder screw (60) connects the head to the driver shaft while a coil spring (66) encircling the screw biases the head against the driver shaft, retaining the ridge within the channel unless an excessive amount of torque is applied to the head causing the ridge to slip from the channel and preventing additional torque from being imparted to the worm.