Slotted link 4 has circular segment a. Pulley 3 is keyed on shaft D. Steel tapes 1 and 2 are attached by their ends b and c to pulley 3 and by their other ends b' and c' to segment a. When crank 5 of link-gear mechanism ACB rotates about fixed axis A, shaft D, on which pulley 3 is keyed, rotates alternately in both directions.
$1870$FL,6L$