Cam 1 rotates about fixed axis A and consists of two rings, 3 and 5, with internal lobe members b and c. The r ings can be turned with respect to each other and clamped in the required position by a bolt passing through slots d on the rings and wing nut 4, thereby increasinlglower or decreasing the length of concentric circular arc a-a. Follower 2 oscillates about fixed axis B and carries roller 6 which rolls a long the working surface of cam 1. Follower 2 has a dwell that can be varied when roller 6 is on the circular surface a-a of the cam. Roller 6 is held in contact with cam 1 by spring 7.
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