What are the anti-loosening measures for the bolt loosening physical device?

(1) Anti-loosening device with additional friction
The anti-loosening device with additional friction mainly has three structures: double nut tightening structure, spring washer tightening structure and self-locking nut tightening structure. Double nut tightening structure: first tighten the lower nut and then tighten the upper nut. After the two nuts are tightened to the top, the contact surfaces of the upper and lower nuts and the bolt threads are opposite, so that the screwed threads are always subject to additional pressure and friction, as shown in the figure. 2 shown. This frictional force still exists when the working load changes. Its simple structure is suitable for the connection of stable, low-speed and heavy-duty fixtures.

Spring washer tightening structure: Spring washers are widely used in assembly sites because of their simple structure, convenient use and low cost, and are generally used in conjunction with bolts or nuts. After the bolt or nut is tightened, the elastic reaction force generated by the flattening of the washer causes the screw threads to be compressed. At the same time, the tip of the washer beveled against the bolt or nut and the supporting surface of the connected part also has an anti-loosening effect.

However, this kind of tightening structure has poor anti-loosening effect under the action of vibration and impact load, and is generally used for unimportant connections. Self-locking nut tightening structure: There are generally two types of tightening structures, one is an all-metal locking nut. It is mainly after the upper end of the metal nut body is slotted and closed or non-circular closed. After the treatment, the nut thread will be partially deformed. When the nut is tightened, the closing will be opened. Compression between threads. This type of nut has a simple structure, reliable anti-loosening, and can be loaded and unloaded many times without reducing the anti-loosening performance. But it is not suitable for high-speed running parts.

The other type is the non-metallic insert lock nut, which mainly embeds a non-metallic insert (usually a nylon washer) on the upper end of the metal nut body. After the nut is tightened, the non-threaded nylon ring itself will be screwed into the pressure. The thread is extruded to form a stable friction force with high torque. This type has very good anti-loosening ability, especially in the environment of multi-vibration and multi-shock.

(2) Mechanical anti-loosening device
Mechanical anti-loosening methods mainly include: hexagonal slotted nut with split pin, series steel wire structure anti-loosening and stop washer structure anti-loosening.

Hexagonal slotted nut with cotter pin: the cotter pin passes through the slot of the nut and the pin hole at the end of the bolt, and the tail of the cotter pin is opened to the side of the nut, and the nut and bolt are locked. This method is reliable in preventing loosening, and can be used for severe impact and vibration parts.

Anti-loosening of series steel wire structure: the nuts or bolts are designed with safety holes, and the low carbon steel wires are inserted into them, and the screws are connected in series to make them brake each other, but pay attention to the penetration direction of the steel wires, as shown in Figure 4. Show. Although this method has excellent anti-loosening ability, it is very inconvenient to install and disassemble. Anti-looseness of the stop washer structure: Bend the single-ear or double-ear stop washer to the side of the nut and the connected part, respectively, to lock the nut, as shown in Figure 5. If the two bolts need to be double-locked, a double-lock washer can be used to brake the two nuts against each other. This method has good anti-loosening effect and is easy to use.

(3) Bonding anti-loosening device
The anaerobic adhesive is applied between the screwed threads. After tightening the nut, the adhesive hardens and fixes, which can firmly bond the matching threads to prevent the relative movement of the thread pair and achieve the effect of locking and anti-loosening. Anaerobic adhesives are divided into two types: liquid type and dry type. Liquid type is generally used for on-site application. The dry type is pre-coated and dried in advance for easy operation. Anaerobic adhesives are generally used for assembly parts that do not require disassembly or require infrequent disassembly.