Movement No. 131 converts continuous rotary motion into reciprocating rectilinear motion through a three-stage linkage: a crank-pin, a slotted arm, and a toothed sector driving a rack. A rotating disk carries a crank-pin that rides inside a slot cut along a swinging arm. As the disk turns, the crank-pin traces a circular path and slides within the slot, causing the arm to vibrate back and forth about its fixed pivot. The lower end of this slotted arm is formed as — or connected to — a toothed sector (a partial gear arc). As the arm swings, the toothed sector meshes with a horizontal rack at the bottom, converting the oscillating arc motion into reciprocating rectilinear motion of the rack. This three-stage conversion — rotary to oscillating to linear — produces a smooth rack motion with a variable velocity profile, and is useful in planing machines, shaping tools, and other applications requiring a driven linear slide from a rotary power source.
131. On rotating the disk carrying the crank-pin working in the slotted arm, reciprocating rectilinear motion is imparted to the rack at the bottom by the vibration of the toothed sector.