Circuit breaker and crank arm box for circuit breaker

The invention relates to the technical field of circuit breakers, in particular to a circuit breaker and a crank arm box for the circuit breaker. The crank arm box for the circuit breaker comprises a box body provided with a flange, the flange is used for being fixedly connected with one end of an arc extinguish chamber cylinder, a transmission shaft is rotationally installed on the box body, one end, penetrating out of the box body, of the transmission shaft is fixedly connected with an outer crank arm, and the outer crank arm is used for being in transmission connection with a circuit breaker operating mechanism; and the part of the transmission shaft in the box body is fixedly connected with three inner crank arms which are respectively connected with a three-phase pull rod of the circuit breaker so as to drive the pull rod to move synchronously. The driving force of the circuit breaker operating mechanism is steered by the crank arm box, so that the circuit breaker operating mechanism can be arranged at t