Abstract: A spring drive mechanism for switchgear, in particular for a circuit breaker. The mechanism has an engagement shaft that is rotatable about its axis, a large toothed-wheel mounted on said shaft, a small toothed-wheel meshing with said large toothed-wheel to put an engagement spring under stress, and a mechanism which prevents the large toothed-wheel and the small toothed-wheel jamming each other mutually after the shaft has been released. The mechanism which prevents jamming includes the shape of the teeth of said small toothed-wheel and the shape of the teeth of the large toothed-wheel. In the teeth of the large toothed-wheel there is a first gap followed, in the direction of rotation, by a first retractable tooth that is retractable along the axis of the tooth against bias from a spring. This tooth is followed by a second gap extending over a length that is not less than two gear pitch steps and is slightly less than an integer number of steps.