Cam 1 rotates about fixed axis A. Follower 2 reciprocates in fixed guides D-D and carries two round rollers 3 and 4. Positive motion is achieved by designing pitch, or theoretical, curve a of cam 1 with a constant diameter, i.e. the length of any diameter of curve a, passing through centre A, is equal to distance C͞B between the centres of rollers 4 and 3.
$2981$SmC,3L$