There is a pinion with only half tooth in the end of rotary axis. When it is rotated, the pinion uses its tooth to drive objects up and down.

• 转动轴的尾端有一个小齿轮，这个小齿轮只有半边有齿轮，当转动时，小齿轮利用齿轮部位来推动物体的上下运动。