Movement No. 156 converts continuous circular motion of a rotating disk into variable alternating rectilinear motion using a crank-pin working in the slot of a bell-crank (elbow-lever). A crank-pin (wrist pin) is fixed on the face of a continuously rotating disk. This pin rides inside a slot cut along one arm of a bell-crank lever, which pivots about a fixed fulcrum. As the disk rotates, the crank-pin traces a circular path and slides within the slot, causing the bell-crank to oscillate about its pivot. The other arm of the bell-crank converts this oscillation into alternating rectilinear motion of a connected rod or slide. Because the crank-pin’s circular motion produces a non-uniform angular sweep of the bell-crank, the resulting linear output is variable in speed — moving faster at mid-stroke and slower at the ends. The variable velocity profile of this mechanism can be tuned by adjusting the crank radius, slot angle, and bell-crank arm lengths to suit different application requirements.
156. Circular motion into variable alternating rectilinear motion, by the wrist or crank-pin on the rotating disk working in the slot of the bell-crank or elbow-lever.