Abstract: Examples of an operating mechanism of a circuit breaker are described. The operating mechanism includes a housing, a cam element installed on a mechanically driven first shaft, a transmission lever installed on a second shaft parallel to the first shaft, and a support assembly. The transmission lever is provided with a first roller element. The support assembly includes a fork joint that is to support a second roller element and a damper element coupled to the fork joint. During a closing operation of the circuit breaker, the cam element rotates to interact with the first roller element to cause rotation of the transmission lever to close the circuit breaker and rotates further to engage with the second roller element on the fork joint to initiate a closing damper stroke.