A nut and a fastener

Abstract

The application provides a nut, which comprises a fastening nut and an anti-loosening nut, the fastening nut and the anti-loosening nut respectively comprise a body and an extension section, the rotation directions of the two bodies are opposite to each other, and the two extension sections are connected in a sleeved mode; the extension section of the fastening nut and the extension section of the anti-loosening nut are respectively provided with fastening teeth and anti-loosening teeth which are in a clearance fit. The nut provided by the application is connected in a sleeved mode through the extension sections provided with the fastening teeth and the anti-loosening teeth on the peripheral wall, so that the progressive mutual engagement between the two kinds of teeth in the use process can be realized, the anti-loosening effect is good, the adaptability is strong, the processing is easy, and the manufacturing cost is low. The application further provides a fastener comprising the nut and a bolt, and the fastener provided by the application has the advantages of good anti-loosening effect, strong adaptability, long service life, easy processing, low manufacturing cost, etc.

Description

Technical Field

[0001] This invention relates to the field of mechanical fastening technology, specifically to a nut and a fastener. Background Technology

[0002] Threaded connections are currently the most commonly used connection method. Their advantages over other connections include convenient connection, simple structure, and easy disassembly, making them a common connection method in mechanical structures. However, because the vibration-resistant loosening life of fasteners is shorter than the fatigue life of materials and structures, loosening occurs before fatigue fracture. In high-speed, high-vibration mechanical equipment, serious incidents caused by loosening, detachment, and fatigue fracture of threaded connections occur frequently. With the continuous improvement of mechanization, the continuous development of industrial scale, and the advancement of aerospace technology, higher requirements are being placed on the anti-loosening of threaded fastener connections.

[0003] Furthermore, bolted connections are also an indispensable connection method in overhead transmission lines tasked with transmitting and distributing electrical energy. Shear bolts (non-fastening bolts) that rely on cotter pins / closed pins to prevent nut loosening and fastening bolts play a major role in transmission line connections. Among line fasteners such as bolts, nuts, and washers, the use of nuts and bolts together is a convenient fastening method. In harsh field service environments, fatigue loads such as conductor galloping and wind vibration, as well as high temperatures and large temperature variations, can cause the friction and preload of threaded connections to gradually decrease or even disappear, leading to loosening and eventually failure of the threaded connections. This undoubtedly poses a challenge to the safe operation of transmission lines. For example, in the case of diverter plates, thermal defects caused by oxidation corrosion, loose joints, or poor installation quality can cause temperature increases during energized operation, accelerating aging, increasing contact resistance, and causing overheating at the joints. This can lead to burnout of transmission line joints and cause major power grid safety accidents such as large-scale sudden power outages.

[0004] Different anti-loosening methods will have different anti-loosening performance for threaded connections. Commonly used anti-loosening methods in engineering practice include:

[0005] Friction-based anti-loosening involves longitudinally or laterally compressing the threaded pair, with additional pressure less affected by load, thus maintaining a certain frictional torque, such as nut pairs, eccentric nuts, and spring washers; mechanical anti-loosening uses additional components to prevent the bolt or nut from rotating, such as cotter pins and slotted nuts, locking washers, and connecting wires; anti-loosening by disrupting the motion relationship of the threaded pair, making the threaded connection non-removable, such as riveting anti-loosening, welding anti-loosening, and expansion bolt connections; and anti-loosening by changing the tooth shape, altering the internal force mechanism of the threaded connection to improve its anti-loosening performance, such as Spiral and Tang bolts.

[0006] Nut pair (e.g.)Figure 1 As shown, the spring washer is currently the main anti-loosening method for fastening bolts in UHV transmission line hardware. It utilizes the counter-actuating force of the nuts to subject the bolts to additional tensile and frictional forces. After the two nuts are tightened, an additional counter-actuating force is generated between them. This counter-actuating force, together with the preload, produces a large radial expansion force on the nuts, which is far from the external radial force, making it difficult for the upper nut to rotate.

[0007] Nord-Lock anti-loosening washers from Sweden are wedge-type locking double-layer washers, such as... Figure 2 As shown, this type of anti-loosening washer consists of a set of two identical washers, each with different serrations on its upper and lower surfaces. One side has large, cam-shaped teeth with a slope angle α greater than the bolt thread angle β, while the other side has smaller, more closely spaced teeth. When installing the washers, the large tooth surfaces should face each other, in pairs. The smaller tooth surfaces contact the nut and the fastened component, respectively. The radial serrations on the outer surface of the wedge-type locking washer engage with the surface of the workpiece it contacts. When the anti-loosening system encounters a dynamic load, displacement can only occur on the inner surface of the washer. When tightening the bolt or nut, the radial serrations tightly grip the contact surfaces, fixing the washer in place and allowing only relative movement between the large tooth surfaces. Any tendency for the bolt or nut to loosen is prevented by this wedge-like effect of the large serrations. The lifting distance between the two washers is greater than the lifting distance of the bolt or nut caused by thread slippage. However, this can damage the surface of the clamping component.

[0008] Existing Japanese Hard-lock anti-loosening nuts combine and improve upon the anti-loosening principles of nut sets and raised face nuts. For example... Figure 3 As shown, the upper nut is a concave nut, machined according to standard nut methods, and is not off-center. The lower nut is a convex nut, machined with its center slightly off-center to create a wedge-like effect in the gap, preventing the threads from loosening. With the lower nut off-center, the upper nut presses against it, increasing the clamping force. Even under vibration, if the nut shifts laterally, the upper nut will still press against the lower nut in any direction. Hard-lock nuts have high machining precision but are expensive. Summary of the Invention

[0009] To overcome the problems of poor anti-loosening effect and poor economic benefits of existing anti-loosening nuts, this invention provides a nut and fastener with good anti-loosening effect, strong adaptability and low manufacturing cost.

[0010] The present invention provides a nut, which includes a fastening nut 20 and a locking nut 10; the fastening nut 20 and the locking nut 10 each include a body and an extension, and the bodies of the fastening nut 20 and the locking nut 10 have opposite rotation directions; in use, the extensions of the fastening nut 20 and the extensions of the locking nut 10 are sleeved together.

[0011] The extension of the fastening nut 20 has fastening teeth 201 on its peripheral wall; the extension of the anti-loosening nut 10 has anti-loosening teeth 101 on its peripheral wall; during assembly, the fastening teeth 201 and the anti-loosening teeth 101 are in clearance fit; during anti-loosening, the fastening teeth 201 and the anti-loosening teeth 101 mesh with each other.

[0012] Furthermore, the outer peripheral wall of the extension of the fastening nut 20 is provided with fastening teeth 201; the inner peripheral wall of the extension of the anti-loosening nut 10 is provided with anti-loosening teeth 101.

[0013] Furthermore, the inner peripheral wall of the extension of the fastening nut 20 is provided with fastening teeth 201; the outer peripheral wall of the extension of the anti-loosening nut 10 is provided with anti-loosening teeth 101.

[0014] Furthermore, the inner diameter of the anti-loosening nut 10 is smaller than the inner diameter of the fastening nut 20.

[0015] Furthermore, both the fastening tooth 201 and the anti-loosening tooth 101 are straight teeth.

[0016] Furthermore, both the fastening tooth 201 and the anti-loosening tooth 101 are helical teeth, and the fastening tooth 201 and the anti-loosening tooth 101 have opposite rotation directions.

[0017] Furthermore, the length of the extension of the fastening nut 20 is greater than the length of the extension of the anti-loosening nut 10.

[0018] Furthermore, the length of the extension of the fastening nut 20 is greater than or equal to the length of the fastening section of the fastening nut 10.

[0019] The present invention also provides a fastener comprising a bolt and a nut as described above, wherein the bolt comprises an end, a middle section 41 and a tail section 42 arranged sequentially; the diameter of the middle section 41 is larger than the diameter of the tail section 42; the thread direction of the middle section 41 is the same as the thread direction of the fastening section of the fastening nut; and the thread direction of the tail section 42 is the same as the thread direction of the fastening section of the anti-loosening nut.

[0020] The technical solution provided by this invention has the following superior effects:

[0021] 1. In the technical solution provided by the present invention, both the fastening nut and the anti-loosening nut are provided with extension sections. During use, the extension sections of the fastening nut and the anti-loosening nut are sleeved together. The peripheral wall of the extension section of the fastening nut is provided with fastening teeth, and the peripheral wall of the extension section of the anti-loosening nut is provided with anti-loosening teeth. When sleeved together, the fastening teeth and the anti-loosening teeth between the inner and outer walls of the two extension sections are in clearance fit. That is, when the fastening nut or the anti-loosening nut gradually loosens during use, the position between the sleeved fastening teeth and the anti-loosening teeth will also gradually change and become misaligned. The fastening teeth and the anti-loosening teeth, which were originally in clearance fit, gradually mesh or lock together as the misalignment occurs. Moreover, the rotation directions of the fastening nut body and the anti-loosening nut body are opposite to each other, which prevents the relative movement between the anti-loosening nut and the fastening nut. This connection method can not only significantly improve the anti-loosening effect, but also has good adaptability. This invention cleverly utilizes the misalignment that occurs during the loosening of the fastening nut or anti-loosening nut, so that the fastening teeth and anti-loosening teeth, which are originally fitted together, gradually mesh and lock together. This not only overcomes the problem of high machining precision in the existing hard-lock anti-loosening nut, but also enhances the anti-loosening effect and facilitates processing and assembly.

[0022] 2. By interlocking the extensions of the fastening nut and the anti-loosening nut, the constraint strength between the two nuts is improved. The constraint range between the two nuts increases from two-dimensional to three-dimensional. Even under extreme lateral vibration conditions during use, which may cause loosening, the long anti-loosening teeth and fastening teeth on the inner and outer peripheral walls of the sleeve extensions provide high constraint strength. This unique constraint condition between the two nuts ensures that they remain in an anti-loosening state throughout the entire service life. It also avoids the drawback of existing technologies where nuts easily damage the surface of the assembly, thus providing better protection for the assembly surface.

[0023] 3. The present invention provides a connection between the extension of the fastening nut and the extension of the anti-loosening nut, and the teeth of the inner and outer walls of the two contacts each other, which reduces the requirements for the size and tolerance of the assembly to be clamped. The length of the extension of the two can be determined according to the specifications of the assembly to be clamped.

[0024] 4. In addition, the nuts and fasteners provided by the present invention have low manufacturing costs and simple processes. The mutual cooperation between the extension of the fastening nut and the extension of the anti-loosening nut greatly reduces the requirements for fitting accuracy. The longitudinal cooperation of the extension can also make up for the loss of fitting accuracy. They are easy to process and manufacture and have good economic benefits.

[0025] 5. When both the fastening teeth and the anti-loosening teeth are helical teeth, the anti-loosening effect is more prominent. This is because, compared to teeth perpendicular to the axial direction, the longitudinal length of the locking or meshing between the fastening teeth and the anti-loosening teeth between the inner and outer peripheral walls of the two extension sections is longer, and the fastening effect of the fastening nut on the assembly is also better.

[0026] 6. The extension section provided at one adjacent end of the fastening nut and the anti-loosening nut of the present invention also facilitates the connection of bolts with two diameters and two rotating threads on one bolt, so as to further improve the fastening effect of the fastening nut in the longitudinal or axial direction, thereby changing the traditional concept of using washers to increase the fastening effect of the fastening nut in the prior art. Attached Figure Description

[0027] Figure 1 A schematic diagram of an existing nut assembly;

[0028] Figure 2 A schematic diagram of Nord-Lock anti-loosening washers from Sweden;

[0029] Figure 3 This is a schematic diagram of a Japanese Hard-lock anti-loosening nut;

[0030] Figure 4 This is an exploded view of the nut of the present invention in use;

[0031] Figure 5 This is a diagram showing the usage state of the fasteners according to the present invention;

[0032] Figure 6 This is a perspective view of the fastening nut of the present invention;

[0033] Figure 7 This is a perspective view of the anti-loosening nut of the present invention.

[0034] Among them: 10 anti-loosening nut; 101 anti-loosening tooth; 20 fastening nut; 201 fastening tooth; 30 assembly; 40 bolt; 41 middle section; 42 tail section. Detailed Implementation

[0035] Example 1

[0036] The fastening nut 20 and the anti-loosening nut 10 constituting the nut of the present invention are shown in Figure 4 , Figure 6 and Figure 7 .

[0037] The fastening nut 20 and the anti-loosening nut 10 each include a body and an extension. The bodies of the fastening nut 20 and the anti-loosening nut 10 have opposite rotation directions. In use, the fastening nut 20 and the anti-loosening nut 10 are connected by sleeves through the extensions. The peripheral wall of the extension of the fastening nut 20 is provided with fastening teeth 201. The peripheral wall of the extension of the anti-loosening nut 10 is provided with anti-loosening teeth 101. During assembly, the fastening teeth 201 and the anti-loosening teeth 101 are in clearance fit. When preventing loosening, the fastening teeth 201 and the anti-loosening teeth 101 mesh with each other.

[0038] The term "socket connection" means that the lock nut 10 and the fastening nut 20 are connected as follows: Figure 5The assembly relationship shown is that the lock nut 10 and the fastening nut 20 are fitted together during use. Under normal assembly conditions, the lock nut 10 and the fastening nut 20 are fitted with a clearance fit. The assembly of the lock nut 10 and the fastening nut 20 is achieved by setting the radial distance between the inner and outer walls of the extensions of the lock nut 10 and the fastening nut 20. When the lock nut 10 or the fastening nut 20 becomes loose, the extensions of the lock nut 10 and the fastening nut 20 engage with each other through the locking teeth 101 and the fastening teeth 201.

[0039] Under normal assembly conditions, the lock nut 10 and the fastening nut 20 are in a clearance fit, meaning the tooth-to-tooth fit between their inner and outer peripheral walls is a clearance fit with tolerances of H / f, H / h, and H / g, specifically H5 / F6, H8 / f7, or H8 / h8. Preferably, the outer diameter of the extension of the fastening nut 20 is equal to the inner diameter of the extension of the lock nut 10; or the inner diameter of the extension of the fastening nut 20 is equal to the outer diameter of the extension of the lock nut 10. In other words, the inner diameter of one extension of the lock nut 10 and the fastening nut 20 is equal to the outer diameter of the other extension. The inner diameter and outer diameter refer to the distance between the center of the cross-section of the extension of the lock nut 10 and the tip of the lock tooth, or the distance between the center of the cross-section of the extension of the fastening nut 20 and the tip of the fastening tooth.

[0040] The extension of the fastening nut 20 is provided with fastening teeth 201 on its peripheral wall; the extension of the anti-loosening nut 10 is provided with anti-loosening teeth 101 on its peripheral wall, so as to satisfy the clearance fit between the fastening teeth 201 and the anti-loosening teeth 101.

[0041] The fastening nut 20 may have fastening teeth 201 on the outer peripheral wall of its extension, and the anti-loosening nut 10 may have anti-loosening teeth 101 on the inner peripheral wall of its extension.

[0042] Alternatively, the inner peripheral wall of the extension of the fastening nut 20 may be provided with fastening teeth 201; the outer peripheral wall of the extension of the anti-loosening nut 10 may be provided with anti-loosening teeth 101.

[0043] During service, the body of the fastening nut 20 and the body of the anti-loosening nut 10 are respectively engaged with the middle section 41 and the tail section 42 of the bolt. The cross-sections of the body of the anti-loosening nut 10 and the body of the fastening nut 20 are both regular hexagonal.

[0044] In this embodiment, the body of the anti-loosening nut 10 has a reverse thread, and the body of the fastening nut 20 has a forward thread. The inner diameter of the body of the anti-loosening nut 10 is smaller than the inner diameter of the body of the fastening nut 20 to facilitate the installation of the fastening nut 20.

[0045] Both the fastening tooth 201 and the anti-loosening tooth 101 can be straight teeth or helical teeth, preferably helical teeth, as long as the fastening tooth 201 and the anti-loosening tooth 101 can mesh when the extensions of the fastening nut 20 and the anti-loosening nut 10 are engaged during service. When both the fastening tooth 201 and the anti-loosening tooth 101 are helical teeth, the directions of rotation of the fastening tooth 201 and the anti-loosening tooth 101 are opposite, that is, one is left-handed and the other is right-handed. The fastening tooth 201 and the anti-loosening tooth 101 can also be other teeth to satisfy the meshing relationship.

[0046] like Figure 4 As shown, cylindrical extensions are respectively provided at one of the adjacent ends of the anti-loosening nut 10 and the fastening nut 20; the length of the extension of the fastening nut 20 is greater than the length of the extension of the anti-loosening nut 10, and the specific difference between the two can be determined according to the specific specifications of the assembly. Therefore, the nut provided by the present invention has good adaptability.

[0047] Optionally, the length of the extension of the fastening nut 20 is greater than or equal to the length of the fastening section of the fastening nut 20, so as to provide better anti-loosening effect.

[0048] Example 2

[0049] In this embodiment, the fastening nut 20 consists of a body with a regular hexagonal cross-section and an extension with a circular cross-section. The thread on the inner wall of the body of the fastening nut 20 is a forward thread, and the outer peripheral wall of the extension is uniformly provided with fastening teeth 201, such as... Figure 6 As shown. In this embodiment, the fastening teeth are right-hand helical teeth. The length of the extension of the fastening nut is equal to or greater than the length of the fastening nut body. This length of the extension of the fastening nut is chosen to allow sufficient space for the rotation of the anti-loosening nut 10 and its gradual advancement into the body of the fastening nut 20 when installing the anti-loosening nut 10 and tightening the fitting 30, ensuring that the fastening effect of the fastening nut 20 on the fitting 30 is optimal and that the anti-loosening nut achieves the best anti-loosening effect. The tooth shape of the fastening teeth can also be convex and concave teeth.

[0050] In this embodiment, the anti-loosening nut 10 is composed of a regular hexagonal body and an extension section. The thread on the inner wall of the body of the anti-loosening nut 10 is a reverse thread, and the inner circumferential wall of the extension section is uniformly provided with anti-loosening teeth 101, as shown in the attached figure. Figure 7 As shown, the anti-loosening tooth 101 is a left-handed helical tooth with the same number of teeth as the fastening teeth of the fastening nut 20 but in the opposite direction. The anti-loosening tooth 101 can also be a tooth with a convex-concave structure.

[0051] In this embodiment, the inner diameter of the extension of the anti-loosening nut 10 is equal to... Figure 6 The outer diameter of the extension of the locking nut shown. The length of the extension of the locking nut 10 is greater than the length of the body of the locking nut 10, but less than the length of the extension. Figure 6The length of the extension of the fastening nut 20 shown is designed to provide sufficient space for the rotation of the anti-loosening nut during installation to achieve the best anti-loosening effect.

[0052] Figure 4 The inner diameter of the extension of the lock nut 10 shown is equal to the outer diameter of the extension of the fastening nut. This allows the outer wall of the extension of the fastening nut 20 and the inner wall of the extension of the lock nut 10, both with teeth, to be connected by the sleeve of the extensions. Sufficient space is provided for the lock nut 10 to gradually advance into the body of the fastening nut 20, ensuring optimal fastening of the fastening nut 20 on the assembly 30 and optimal anti-loosening effect. The length of the extension can be increased or decreased as needed for tightening.

[0053] The fastening teeth 201 of the fastening nut 20 are preferably helical teeth, and the locking teeth of the locking nut 10 are preferably helical teeth. Both have the same number of helical teeth, but because... Figure 4 The helical teeth of the fastening nut 20 shown are located on the outer wall of its extension, while the helical teeth of the anti-loosening nut 10 are located on the inner wall of its extension. The fastening nut 20 and the anti-loosening nut 10 are connected by the sleeve of their respective extensions. The inner wall of the extension of the anti-loosening nut is located on the outer periphery of the outer wall of the extension of the fastening nut. Therefore, the width of the helical teeth of the anti-loosening section is greater than the width of the helical teeth of the fastening section.

[0054] Example 3

[0055] This embodiment provides a fastener. Figure 5 The diagram shows the usage state of the fastener, which includes the nut and bolt described in Embodiments 1 and 2. The bolt includes an end, a middle section 41, and a tail section 42 arranged sequentially. The diameter of the middle section 41 is larger than the diameter of the tail section 42. The thread direction of the middle section 41 is the same as the thread direction of the body of the fastening nut. The thread direction of the tail section 42 is the same as the thread direction of the body of the anti-loosening nut.

[0056] Specifically, the middle section 41 has a forward-facing thread, and the tail section 42 has a reverse-facing thread; the body of the fastening nut 20 has a forward-facing thread, and the body of the anti-loosening nut has a reverse-facing thread. The outer diameter of the extension of the fastening nut 20 is equal to the inner diameter of the extension of the anti-loosening nut 10; the inner circumferential wall of the extension of the fastening nut 20 is not threaded, and the outer circumferential wall is evenly distributed with left-handed helical teeth; the inner circumferential wall of the extension of the anti-loosening nut 10 is evenly distributed with right-handed helical teeth; the fastening nut 20 and the anti-loosening nut 10 achieve anti-loosening of the assembly 30 by the sleeve of their extensions with helical teeth evenly distributed on their inner and outer circumferential walls.

[0057] When using the fastener fastening fitting 30 of the present invention, insert the tail section 42 of the bolt 40 into the fitting 30, and tighten the body of the fastening nut 20 onto the middle section 41 of the bolt 40 until the fastening nut 20 fastens the fitting 30. Then, slip the extension of the anti-loosening nut 10 onto the tail section 42 of the bolt 40, and rotate the anti-loosening nut 10 in the opposite direction until the extension of the anti-loosening nut 10 is fitted onto the outer periphery of the extension of the fastening nut 20, thus completing the fastening process. Figure 5 The assembly of component 30 is shown.

[0058] When the fastening nut 20 provided by the present invention is fastened to one or more components 30 by bolts in a forward-rotating manner, the bolts will naturally loosen during the entire service life of the components 30. This is accompanied by a gradual engagement or meshing process between the convex and concave teeth or helical teeth between the inner and outer walls of the extension sections of the fastening nut 20 and the anti-loosening nut 10. Especially when both the fastening teeth 201 and the anti-loosening teeth 101 are helical teeth, the gradual engagement or meshing process will be longer. Since the bodies of the fastening nut 20 and the anti-loosening nut 10 have different rotation directions, the fastening teeth and the anti-loosening teeth resist each other during the meshing process, thereby restricting the relative movement of the bodies of the fastening nut 20 and the anti-loosening nut 10. This mutual constraint between the fastening nut 20 and the anti-loosening nut 10 results in a better fastening effect on the components 30 than the prior art.

[0059] In this invention, the fastening nut 20 and the anti-loosening nut 10 that make up the nut are connected by the sleeve of their respective extension sections. The inner and outer peripheral walls of the two sleeved extension sections are evenly distributed with helical teeth. In addition, the length of the extension sections of the fastening nut 20 and the anti-loosening nut 10 is axial or longitudinal and adjustable. Therefore, it is not only convenient to use, but also has a more prominent fastening effect on the assembly 30.

[0060] In use, given that the fastening nut 20 needs to withstand a greater preload than the anti-loosening nut 10, it requires more threads. The anti-loosening nut 10 is designed to prevent the fastening nut 20 from loosening due to various external influences during service. Considering that the anti-loosening nut withstands less force, it can use fewer threads. Therefore, the body length of the fastening nut 20 is greater than the body length of the anti-loosening nut 10.

[0061] like Figure 6 , Figure 7As shown, the number of fastening helical teeth 201 is the same as the number of anti-loosening helical teeth 101, so that the fastening helical teeth 201 and anti-loosening helical teeth 101 gradually mesh with each other during service, so that the locking force between the fastening nut 20 and the anti-loosening nut 10 gradually increases; wherein, the width of the fastening helical teeth 201 on the peripheral wall of the extension section of the fastening nut 20 and the anti-loosening helical teeth 101 on the peripheral wall of the extension section of the anti-loosening nut 10 are both the length of the helical teeth perpendicular to the circumferential direction.

[0062] In another embodiment of the present invention, the middle section of the bolt has a reverse thread and the tail section has a forward thread, and the body of the fastening nut 20 that constitutes the nut has a reverse thread, while the body of the anti-loosening nut has a forward thread.

[0063] The fastener provided by this invention has both good fastening and anti-loosening effects, and can be adapted to different specifications of assemblies. It is highly adaptable, easy to process and manufacture, and economical.

[0064] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many modifications under the guidance of the present invention without departing from the spirit and scope of the claims. These modifications are all protected by the present invention.

Claims

1. A nut, characterized in that The nut comprises a fastening nut (20) and a lock nut (10); the fastening nut (20) and the lock nut (10) comprise a body and an extension section respectively, the body of the fastening nut (20) and the body of the lock nut (10) are opposite in rotation direction; in use, the fastening nut (20) and the lock nut (10) are connected through the extension section in a sleeved manner. The extension section of the fastening nut (20) is provided with fastening teeth (201) on the peripheral wall; the extension section of the lock nut (10) is provided with lock teeth (101) on the peripheral wall. The inner diameter of the extension section of one of the lock nut (10) and the fastening nut (20) is equal to the outer diameter of the extension section of the other; wherein the inner diameter and the outer diameter refer to the distance between the center of the cross section of the extension section of the lock nut (10) and the top of the lock teeth or the distance between the center of the cross section of the extension section of the fastening nut (20) and the top of the fastening teeth. In assembly, the fastening teeth (201) and the lock teeth (101) are in clearance fit; in locking, the fastening teeth (201) and the lock teeth (101) are engaged with each other. In use, when the fastening nut (20) or the lock nut (10) is gradually loosened, the position of the fastening teeth (201) and the lock teeth (101) connected in a sleeved manner will also gradually change and be misaligned, and the fastening teeth (201) and the lock teeth (101) originally in clearance fit will gradually engage or lock with each other due to the gradually occurring misalignment.

2. The nut of claim 1, wherein The extension section of the fastening nut (20) is provided with fastening teeth (201) on the peripheral wall; the extension section of the lock nut (10) is provided with lock teeth (101) on the inner peripheral wall.

3. The nut of claim 1, wherein The extension section of the fastening nut (20) is provided with fastening teeth (201) on the inner peripheral wall; the extension section of the lock nut (10) is provided with lock teeth (101) on the outer peripheral wall.

4. The nut of claim 1, wherein The inner diameter of the body of the lock nut (10) is smaller than the inner diameter of the body of the fastening nut (20).

5. Nut according to any one of claims 1-4, characterized in that The fastening teeth (201) and the lock teeth (101) are straight teeth.

6. Nut according to any one of claims 1-4, characterized in that The fastening teeth (201) and the lock teeth (101) are helical teeth, and the rotation directions of the fastening teeth (201) and the lock teeth (101) are opposite.

7. Nut according to any one of claims 1-4, characterized in that The length of the extension section of the fastening nut (20) is greater than the length of the extension section of the lock nut (10).

8. The nut of claim 7, wherein The length of the extension section of the fastening nut (20) is greater than the length of the body of the fastening nut (20).

9. A fastener, characterized by The fastener comprises a bolt and the nut according to any one of claims 1-8, the bolt comprises an end portion, a middle section (41) and a tail section (42) arranged in sequence; the diameter of the middle section (41) is greater than the diameter of the tail section (42); the rotation direction of the thread of the middle section (41) is the same as the rotation direction of the thread of the body of the fastening nut; the rotation direction of the thread of the tail section (42) is the same as the rotation direction of the thread of the body of the lock nut.

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