List more than 3 kinds of gear structure and give the purpose
Gear is meshing with each other of the teeth of the mechanical parts, the composition of the gear structure generally has teeth, tooth groove, face, normal face, tooth top circle, tooth root circle, base circle, graduated circle. Gears can be classified according to tooth shape, gear shape, tooth line shape, tooth surface and manufacturing method
The role of a gear is to transfer the rotation of one shaft to another, and it can also achieve deceleration, increase, change direction and reverse direction, etc.
Commonly used gear according to the relative position of the two axes is divided into the following three; 1, cylindrical gear 2, bevel gear 3, worm gear