Classification of ratchet mechanism according to its structure can be divided into tooth ratchet mechanism and friction ratchet mechanism. Tooth ratchet mechanism is simple in structure, convenient manufacturing; and stopping time than may be achieved through choosing the right drive mechanism. The disadvantage is the motion of the body can only be adjusted; noise, shock and wear larger, it is not appropriate for high speed. Friction type ratchet mechanism Friction type ratchet mechanism Friction type ratchet mechanism is partial in fan-shaped wedges instead of the pawl in the tooth ratchet mechanism, to replace ratchet tooth friction-free. Is characterized by smooth transmission, no noise; stroke can be adjusted Steplessly. But due to friction driven, slipping occurs, although you can play a role in security, but driving accuracy is not high. Applies to low speed for light duty applications.