Cam 1 is keyed to driven shaft 8 and is connected by turning pair D to bellcrank lever 2, one arm of which is connected by spring 3 to cam 1. The spring tends to turn lever 2 but this motion is prevented by fixed prismatic member 4. Tie-rod 5 is pivoted to lever 2 and carries roller 6. Drum 7 is keyed to driving shaft 9. When lever 2 is released from the restraint of member 4, it turns counterclockwise so that roller 6 is jammed between drum 7 and cam 1, and the cam begins to rotate together with driven shaft 8.
$3192$CmL,D$