金属弹簧的复位功能
Return function of metal spring
弹簧在外力作用下发生形变，撤去外力后，弹簧就能恢复状态。很多工具和设备都是利用弹簧这一性质来复位的。例如，许多建筑物大门的合页上都装了复位弹簧人们进出后，门会自动复位。人们还利用这一功能制成了自动伞、自动铅笔等用品，十分方便。此外，各种按钮和按键也少不了复位弹簧。
The spring deforms under the action of external force. After the external force is removed, the spring can recover. Many tools and equipments use the spring to reset. For example, many building doors are equipped with a return spring on their hinges. When people enter or leave, the doors will automatically return. People also use this function to make automatic umbrella, automatic pencil and other supplies, which is very convenient. In addition, all kinds of buttons and keys can not do without a return spring.