Carbon brush for commutator motor - has insulated signalling contact embedded in it to form closed circuit when brush needs changing

摘要

The carbon brush assembly, for an electric motor, has a contact embedded in its brush and insulated from it. The contact is exposed when the brush has worn down by an unacceptable amount. The exposed contact touches the collector and closes a circuit, which results in the generation of a signal indicating that the brush needs changing. The contact is sintered into the brush. The signalling circuit is made when the collector connects the brush and contact together electrically.