J23 is a mechanical rigid clutch. Its working principle is that when the cam stop rotates, the key tail is dragged into the working groove of the middle sleeve of the flywheel (gear), thus driving the flywheel (gear) to transmit power to the crankshaft and driving the slider to move up and down. On the left side of the crankshaft, a braking band is generally installed, which does not stop the slider, but stops the slider by resetting the cam stopper to block the key tail, so that it can be separated from the middle sleeve groove. We know that there is inertia when a certain mass of matter moves from a moving state to a stopped state. When the slider stops moving, its inertia is great. If this part of inertia is not overcome, it will impact the key tail and cam, and it will damage this part for a long time. If this part of inertia can be eliminated, the impact will be much smaller, and the life of the parts will not be affected basically. Therefore, a braking band is designed on the left side of the crankshaft to overcome the inertia of motion, and the braking band tightens the friction (braking) on the way from the bottom dead center to the top dead center.