Trip adjustment means for instantaneous trip circuit breaker

Claim 1

In a magnetic trip circuit breaker, means for adjusting the airgap of the magnetic trip means comprising, in combination: an insulating casing for a circuit breaker, said casing having a primary opening and a plurality of secondary openings extending through an external surface of said circuit breaker casing, said secondary openings surrounding said primary opening and being radially spaced therefrom; a rotatable adjustment member supported within said circuit breaker casing, said adjustment member having a portion at one end thereof accessible through said primary opening and a cam portion on the inner end thereof; cam follower means biased into engagement with said cam portion and including means connecting with the armature of said magnetic trip means, said cam follower means moving said armature in a direction to increase the airgap in response to rotation of said adjustment member in one direction and moving said armature in a direction to decrease the airgap in response to rotation of said adjustment member in an opposite direction; means biasing said adjustment member in said opposite direction wherein said adjustment member normally assumes a position establishing the smallest airgap possible by said adjustment member, and means inserted into a selected one of said secondary openings and extending into said casing to engage said biasing means to render said biasing means inoperative upon said adjustment member and to limit rotation of said adjustment means in said one direction.