Cam 1 rotates about fixed axis A and its theoretical, or pitch, curve is composed of two identical curves a that are designed to satisfy the condition of constant acceleration and deceleration of follower 2. Follower 2 reciprocates in fixed guides B-B and carries two rollers 3 and 4 which roll along the working curve a of cam 1. When cam 1 rotates at constant speed, follower 2 travels at constant acceleration and deceleration in its rise and return. Positive motion is achieved because the sums of all opposing radius vectors of the theoretical curves are equal to the distance between the centres of rollers 3 and 4.
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