Tripping device for an overload circuit breaker

In an overload circuit breaker including a housing, a tripping device supported in the housing and having a helically wound, current-carrying bimetal strip having an axis and composed of two face-to-face arranged metal components situated, respectively, at the inside and at the outside of the bimetal strip;

• and a tripping portion forming part of the bimetal strip;
• the tripping portion executing a tripping motion as the bimetal strip undergoes deformation under the effect of heat generated by an excess current flowing through the bimetal strip;
• the improvement wherein said bimetal strip is formed of two electrically serially connected, oppositely wound bimetal helices each having an outer end constituting the opposite ends of said bimetal strip;
• securing means for affixing said bimetal strip to said housing at both said opposite ends;
• the bimetal helices each having an inner end connected to one another by a coupling part constituting said tripping portion of said bimetal strip;
• and further wherein said inner ends of said bimetal helices are bent radially inwardly towards said axis and said tripping portion projects radially outwardly from said axis and is situated within an envelope circumscribable about said bimetal helices.