US Patent 7535327 Circuit breaker

A circuit breaker includes a main case containing a contactor section, an arc-extinguishing device and an overcurrent tripping device; a middle cover laid on the main case, the middle cover having in a central section thereof a recess partitioned with a bottom wall for containing a switching mechanism and at least one interior attachment; and a top cover covering the top side of the recess in the middle cover. The main case, the middle cover and the top cover are arranged to be dividable from one another. The middle cover has an auxiliary cover, covering the switching mechanism, and the auxiliary cover has the top cover mounted thereon.