Circuit breaker with improved trip mechanism

A circuit breaker mechanism which comprises:

• a contact arm forming a portion of an interruptable load current path through the circuit breaker mechanism and mounted with respect to a pivot axis for swinging motion to break the current path;
• an operating mechanism comprising, a toggle mechanism having an upper toggle and a lower toggle coupled at a toggle joint forming an axis about which the toggles can relatively pivot;
• the toggle joint being disposed in the path of travel of the contact arm as the contact arm swings to break the current path;
• and
• a surface formation that acts on the toggle joint radially of the pivot axis of the contact arm to cause force of the swinging contact arm to be delivered to the toggle joint along an arc whose shape is defined at least in part by the geometric shape of the surface formation such that a component of the contact arm force is directed so as to approximately maximize the effect of the swinging contact arm force on the toggle mechanism.

A circuit breaker comprising:

• a contact arm having a pivot axis, the contact arm forming a portion of an interruptable load current path through the circuit breaker;
• a mounting pivotally mounting the contact arm about the pivot axis for swinging motion to break the current path;
• an operating-mechanism for selectively positioning the contact arm to a circuit-making condition and to a circuit-breaking condition;
• a trip mechanism, including a trip actuator, that operates via the operating mechanism to cause the contact arm to swing from the circuit-making condition to the circuit-breaking condition upon occurrence of a fault detected by the trip actuator;
• the operating mechanism comprising a toggle mechanism having an upper toggle, a lower toggle, and a spring pin coupling the upper and lower toggles to create a toggle joint about which the toggles can relatively pivot coincident with a longitudinal axis of the spring pin, and a spring acting on the toggle mechanism for exerting a force that urges the contact arm toward the circuit-making condition when the upper and lower toggles are relatively pivoted to one side of an over-center condition of the operating mechanism and that urges the contact arm away from the circuit-making condition when the upper and lower toggles are relatively pivoted to the other side of the over-center condition;
• the toggle joint being disposed in the path of travel of the contact arm as the contact arm swings away from the circuit-making condition so as to be displaced by the swinging contact arm;
• and
• wherein the contact arm comprises a notch that acts on the toggle joint radially of the pivot axis of the contact arm to cause force of the swinging contact arm to be delivered to the toggle joint along an arc whose shape is defined at least in part by the geometric shape of the notch.