Cam and follower mechanisms
A cam and follower is formed by the direct contact of two specially shaped links. The driving link is called the cam  and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of the camm and follower determines the movement of the mechanism. In general a cam follower mechanism's energy is transferred from cam to follower. The cam shaft is rotated and, according to the cam profile, the follower moves up and down.  The main benefit of this type of cam follower mechanism is that the follower moves a little bit and helps to rotate the cam 6 times more circumference length with 70% force!!!