Pulley 1 is fixed to the base. Flexible link 2 runs over the pulley and is connected at point A to slider 3 which moves along guide b of slotted link 4. When link 4 turns clockwise about fixed axis B, flexible link 2 winds on the pulley and moves slider 3 inward in guide b, compressing spring 5. When slider 3 reaches its extreme inward position, slotted link 4 begins to turn in the opposite direction (counterclockwise).
$1859$FL,4L$