The lengths of the links comply with the condition: A͞D:B͞D=r₁:r₂, where r₁ and r₂ are the radii of pulleys 1 and 2. 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 D. When pulley 1 rotates about axis A, slotted link 4 oscillates about axis D. When pin a travels along straight portions df and gh of its path, slotted link 4 has dwells in its extreme positions.
$1931$FL,D$