Rocker arm 1 oscillates about fixed axis D. Connecting rod 3 is connected by turning pairs B and C to link 2 and rocker arm 1. Link 2 has arc-shaped slot a which slides along arc- shaped guide block b whose radius equals A͞D. Upon oscillation of rocker arm 1, arc-shaped slotted link 2, having its centre at point A, slides along the fixed guide block. This mechanism is equivalent to four-bar double-swing linkage ABCD.
$581$LW,4L$