In our daily lives, springs have different shapes and serve us everywhere. Common springs are helical, called coil springs. The spring scales used in mechanics experiments and the springs of chest expanders are all coil springs. Coil springs are long and short, thick and thin: the spring of the chest expander is thicker and longer than the spring scale; in the drawer lock, the spring is short and thin, about a few millimeters long; there is a spring used to tighten the nut The washer has only one turn and cannot be separated from it when tightening screws and nuts. When the coil spring is stretched or compressed, it must produce elastic force against external forces, and within the elastic limit, the greater the deformation, the greater the elastic force generated; once the external force disappears, the deformation also disappears. Some springs are made of leaf or plate, called reeds or leaf springs. There are copper reeds in harmonicas and accordions. There are also copper reeds in many electrical switches. The springs in toys or clocks are steel leaf springs. There are also steel plates under the truck compartment. reed. They have a tendency to return to their original shape when they are bent, and the stronger the bending, the stronger this tendency. Some springs are coiled like mosquito coils. For example, such springs are installed in electrical measuring instruments (current meters, voltmeters) in laboratories and mechanical clocks. This kind of spring also tends to return to its original shape when it is twisted, and is called a torsion spring.
All kinds of springs play different functions in different occasions:
1. Measurement function
We know that within the elastic limit, the extension (or compression) of the spring is proportional to the external force. The spring balance can be made using the nature of the spring.
2. Squeeze function
Observing various electrical switches, you will find that one of the two contacts of the switch must be equipped with a spring to ensure that the two contacts are in close contact and make good conduction. If the contact is not good, the resistance at the contact will increase, and the heat generated when the current passes will increase. In severe cases, the metal at the contact will melt. The two metal posts of the bayonet base are equipped with springs for good contact; as for the central metal piece of the screw base and the plug-in metal pieces of all sockets are reeds, their function is to bring the two sides into close contact to ensure guidance. Good communication. In the cassette tape, there is a reed made of phosphor bronze, which uses the elastic force generated when it is bent and deformed to make the magnetic head closely contact the tape. There is a long coil spring in the stapler. On the one hand, it is used to tighten the staples. On the other hand, when the front staple is pushed out, the back staples can be pushed out to the front to prepare for staples. , In this way, one by one nails can be automatically pushed to the front until all the nails are used up. Many machines feed automatically, and the automatic loading of bullets in automatic rifles relies on this function of springs. In addition, like the clips for holding clothes, the clips on ballpoint pens and pen covers are all clamped on clothes by the pressing function of springs.
3. Reset function
The spring is deformed under the action of external force, and after the external force is removed, the spring can return to its original state. Many tools and equipment use springs to reset. For example, the hinges of the doors of many buildings are equipped with return springs. After people enter and exit, the doors will automatically reset. People also use this function to make automatic umbrellas, automatic pencils and other supplies, which is very convenient. In addition, a return spring is indispensable for various buttons and keys.
4. Drive function
Mechanical clocks and clockwork toys are driven by winding up the clockwork. When the mainspring is tightened, the mainspring is bent and deformed, storing a certain amount of elastic potential energy. After release, the elastic potential energy is transformed into kinetic energy, which drives the hour, minute, second hand or wheel to rotate through the transmission device. Many toy guns are equipped with springs. After the spring is compressed, it has potential energy. Pull the trigger, the spring is released, and the potential energy is converted into kinetic energy, and the ball hits and shoots along the barrel. Starting guns and military guns used in track and field competitions also use the elastic potential energy of the spring to be released into kinetic energy to hit the fuse of the starting paper or bullet to complete the task of starting or firing.
5. Buffer function
Springs are installed between the locomotive, automobile frame and the wheels, and the elasticity of the spring is used to slow down the bumps of the vehicle.
6. Vibration and sound function
When air flows from the reed holes in the harmonica and accordion, it impacts the reeds and vibrates to produce sound.