Patent ID: 8242647
Filing Date: 2012-08-14
Classification: H02K

Abstract:
1. An overload protection device comprising: a chassis; a motor received in the chassis and comprising a stator having a spiral groove defined on the stator and a pair of electrical conductive contacts attached on the stator, and a rotor rotatably received in the stator at one end and protruding from the stator at another end; a pair of resilient members respectively positioned between two opposite ends of the motor and the chassis; at least one friction bump attached on the inner side of the chassis and frictionally engaged in the spiral groove of the motor; and a pair of electrodes separately attached on the inner side of the chassis and electrically coupled to electrical conductive contacts of the motor for supply power to the motor; wherein, when the motor operates at a rated load, an absolute value of a torque applied on the stator by a critical static friction between the stator and the friction bumps, is equal to an absolute value of a counter-torque applied on the stator by the rotor; and when the motor overloads, the counter-torque will be greater than the torque produced by the friction, so that the stator will rotate relative to the rotor and move forwards or backwards to disengage the electrical conductive contacts from the electrodes thereby shutting down the motor.