Movement No. 81 converts continuous rotary motion into alternating rectilinear motion using a mutilated spur-gear. As the mutilated spur-gear (A) rotates continuously, its partial teeth engage the rack-rod (B) and push it forward in a straight line. When the toothed section of the gear passes and disengages from the rack, the spiral spring (C) pulls the rod back to its original position, ready for the next cycle. This elegant mechanism produces a repeated push-and-return linear stroke from a single rotating input, and is commonly used in intermittent feeding and stamping machinery.
81. Alternate rectilinear motion is given to the rack-rod, B, by the continuous revolution of the mutilated spur-gear, A, the spiral spring, C, forcing the rod back to its original position on the teeth of the gear, A, quitting the rack.