The lengths of the links comply with the conditions: r₁=r₂, where r₁ and r₂ are the radii of pulleys 1 and 2; and the distance from point C to line AB is d=r₁. Pulley 1 rotates about fixed axis A and, through flexible link 3, rotates pulley 2 about fixed axis B. Pin a of flexible link 3 slides along slot b of slotted link 4 which turns about fixed axis C. When pulley 1 rotates about axis A, slotted link 4 oscillates about axis C. When pin a travels along straight portion df of its path, slotted link 4 has a dwell in its upper extreme position.
$1936$FL,D$