This invention relates generally to electrical circuit breakers and more particularly to thermally responsive circuit breakers for interrupting electrical circuits on the occurrence of predetermined conditions in the circuits.
Thermally responsive electrical circuit breakers typically interrupt electrical circuits in response to the occurrence of selected overload conditions in the circuits to protect other equipment in the circuits from damage due to overheating or overcurrent or the like. In one particular advantageous breaker shown in U.S. Pat. No. 3,361,882 commonly assigned to the assignee of the present invention, and a similar breaker shown in U.S. Pat. No. 4,400,677, also assigned to the assignee of the present invention, a control mechanism manually moves movable contacts into and out of engagement with complementary contacts to open and close a circuit and a thermally response bimetallic member is operable to open the circuit in response to the occurrence of a selected overload current in the circuit. The bimetallic member is formed of metal materials having substantial electrical resistance properties and the member is disposed in the circuit breaker so that the member is self-heated and flexes to a selected extent to trip the mechanism to open the breaker circuit when selected overload current flows in the circuit for a selected period of time. The circuit breaker is adapted to be latched in open circuit position until manually reset after it has been manually open or has been opened in response to the occurrence of an overload current. It is also "trip free" in that the circuit breaker will open in response to the occurrence of an overload current even if the manual resetting means is manually held in the circuit closing position.
In some applications, for example when used as aircraft circuit breakers, it is desirable to provide a visual or other indication of the status of the circuit breaker. In such applications there may be provided a large number of circuit breakers so that the ability to readily discern which breakers are in the closed position and which ones are in the open position would be advantageous.