When cam 1 rotates clockwise about fixed axis A, finger 2 engages lug a of collar 3 and turns the collar together with vertical plunger 4. The plunger is rotated until end h of flange d on cam 1 comes In contact with the lower squared end of the plunger, continuing its rotation until It has completed its 90° movement. After this, the squared end enters between flanges b and d of cam 1, preventing further rotation. Plunger 4 turns with respect to plug 5 which is a free fit in a bore at the bottom of the plunger and carries roller 6. Roller 6 Is constrained by continuous groove c of cam 1. As cam 1 rotates further, roller 6 rolls along its working surface and plunger 4 is shifted by spring 7 to its lower position. When the roller reaches portion f of the cam, plunger 4 is raised again and finger 8 engages lug e of collar 3, turning it back again together with plunger 4. The corresponding end of flange b now completes the 90° movement. Then plunger 4 is lowered again. Gaps are provided in the flanges at the required places to permit the square end of plunger 4 to rotate. Thus, to each revolution of shaft 9 to which cam 1 is keyed, plunger 4 has two upstrokes and two downstrokes, and is turned 90° twice, first in one direction and then back again, at its extreme upper position.
$3158$SmC,FD$