Low profile multi-pole circuit breaker having multiple toggle springs

Abstract

A multi-pole circuit breaker includes a wide toggle shaft which spans all of the poles of the breaker and which is electrically neutral. The lower links of the toggle mechanism are made of phenolic or other insulating material which thus electrically insulates the wide toggle shaft spanning all of the poles of the breaker and makes the toggle shaft electrically neutral. A plurality of short toggle springs may therefore be connected between the wide toggle shaft and a handle arm of corresponding width. The plurality of short toggle springs provide as much tripping energy as the longer single or double toggle springs of prior art circuit breakers in which the springs are clustered together in alignment with one pole of the breaker to which they are electrically connected and whose polarity the toggle springs in such prior art breakers accordingly take. Thus by providing a tripping mechanism which can utilize a plurality of short toggle springs in place of one or two long ones, a lower profile circuit breaker is possible. In addition, the movable contact blade of each pole of the multi-pole breaker of this invention is biased independently toward a contact closed position. Each contact blade is pivotally mounted to the lower end of its corresponding insulated lower toggle link, with the end of the contact blade opposite the contact end being biased in one direction by a cantilever spring to urge the contact end in the opposite direction to the contact closed position. The biasing force is selected to permit the movable contact of each contact pair to separate by virtue of electrodynamic and thermodynamic 'blow-apart' forces occurring during a severe short circuit in the phase in which such pole is connected.