At one end of lever 4 is eccentric cam b which slides along fixed flat surface c-c when lever 4 is turned. Pin e of the eccentric cam is in slot f of link 1 which has plunger d at its other end. Spring 3 is arranged between the plunger and its fixed housing. Disk 2, turning about fixed axis A, has holes a. Disk 2 is held in the required indexed position by plunger d of link 1 which enters the corresponding hole a of the disk, being actuated by spring 3. When lever 4 is turned counterclockwise, eccentric cam b withdraws plunger d from hole a.
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