Ratchet mechanism follower motion classification can be divided into single-action ratchet mechanism, double ratchet mechanism and bi-directional ratchet mechanism. Single-action ratchet mechanism when active on a swing in one direction, to set the ratchet turning. Double ratchet mechanism, master remote pole swung in both directions in the process, two pawl drive respectively, twice promoted a ratchet wheel rotation. Double ratchet mechanism is often used to load large ratchet size limited, fewer teeth, and active rocker swing angle is smaller than the ratchet teeth from the occasion. The ratchet mechanism described above, can only one direction for one-way intermittent motion. Bi-directional ratchet mechanism by changing the pawl of the swing direction, achieving a ratchet wheel rotation in both directions. Two bi-directional ratchet mechanism in the form shown, two-way ratchet mechanism must be symmetric tooth form.