Cam 1 rotates about fixed axis A and has a helical groove with right- and left-hand turns. Half-nut 2, consisting of a single ridge, engages the groove of cam 1 and travels along its axis. When it reaches an extreme position, half-nut 2 is swivelled by the end turn of the groove and its travel is reversed. Follower 3, whose pin a slides along slot b of the half-nut, is imparted an oscillating motion with dwells at its extreme positions about an axis (not shown).
$3075$SmC,ML$