Levers 4 and 5 turn about fixed axes A and B and have pins c that enter slots b of link 1. Link 2 turns about fixed axis D and has flat spring 3. One end of spring 3 engages pin d of link 1 and the other end engages pin e of link 2. When link 1 reciprocates, link 2 oscillates about axis D due to the action of spring 3. Projections a of levers 4 and 5 engage grooves in link 2, thereby indexing the link in its extreme positions.
$2117$EL,5L$