Point E of connecting rod 2 of four-bar linkage ABCD describes a path of which portion y-y, shown by a heavy continuous line, approximates a straight line. When crank 1 rotates about fixed axis A, link 2, connected by turning pair E to slider 4, drives link 5 which rotates with dwells. The dwell of link 5 corresponds to the motion of point E of slider 4 along portion y-y of its path. Groove a of the upright, along which slider 4 travels when linkage ABCD is in an extreme (dead centre) position, prevents unintentional motion of link 5 during the dwell period.
$1346$LG,D$