Fastening and anti-loosening
Anti-loosening refers to the ability of the connection to resist external shock, vibration or variable load after the threaded connection is properly tightened, as well as the ability of the connection to weaken when the high temperature or temperature change is large, rather than the comparison of the torque displayed when the thread is loosened.
With the continuous development of technology, the types of self-locking nuts are more and more. You are also welcome to add.
1. Nylon insert self-locking nut
Nylon insert self-locking nuts are a very common type of self-locking nuts that are widely used. Structurally, the nylon ring is embedded in the nut head. Its working principle is that when the non-metallic insert nut is screwed, the thread of the bolt will be naturally extruded into a spiral on the nylon ring, so that it forms a tight fit with the bolt and bolt teeth, and under the action of the elastic force of nylon, friction resistance is generated to achieve the purpose of anti-loosening.
The nylon insert self-locking nut has a simple structure and reliable anti-loosening performance, and the tightening will not damage the nut body, and it is also very suitable for application in places with vibration loads. Reusable, with the increase of the number of uses, the anti-loosening characteristics will be weakened, the screw Jun referred to the relevant technical information, the research shows that the number of uses of the nut is recommended not to exceed 5 times. Because nylon has weak resistance to heat and acids and alkalis, it is suitable for use in the range of -50 100, and the application environment avoids acids and alkalis.
2. Metal self-locking nut
Metal self-locking nuts are also a commonly used structure, and its structure diagram is shown in the figure below.
The working principle of the metal self-locking nut is through the deformation of the thread bottom hole or the deformation of the thread tooth, and when it is matched with the bolt, the interference fit relationship between the threads is generated, so as to increase the friction between the threads to achieve the purpose of anti-loosening.
Compared with nylon self-locking nuts, its application environment requirements are low, and it is suitable for application in high temperature, acid and alkali corrosion environments. Because the deformability of metal is poor compared to nylon, even if the dimensional deviation of the part is very small, its torque characteristics will deviate greatly. Therefore, its dimensional control accuracy is also required to be high, and it is not suitable for application in places with large vibration loads.
In general, its anti-loosening performance is better than that of nylon self-locking nuts, and the screw-in torque when tightening is also higher. Screw Jun referred to the relevant standards and learned that the number of reuses is recommended not to exceed 5 times.
3. Shi Bi firmly self-locking nut
Spirant self-locking nuts have an innovative self-locking internal thread profile with a unique 30° wedge-shaped bevel at the root of the thread. Due to the change of the angle of the tooth shape, the normal force generated on the contact surface between the threads forms a 60° angle with the bolt axis, which makes the axial clamping force transmit to the threaded contact area of the bolt and nut to produce a much greater friction force than the ordinary thread, so as to effectively improve the anti-loosening performance.
According to the characteristics of the thread structure of the Spitter nut, the thread tip of the Spike bolt is designed to be a 30° wedge surface that matches the thread of the Spitter nut, which makes the thread contact change from the previous line contact to the ribbon surface contact, which improves the stability of the contact. As a result, the clamping force is continuously constant.
In addition to providing superior anti-loosening performance, it can also prevent tooth slippage, prevent bolt breakage, anti-tripping, anti-torsion, and is a new type of high-reliability bolt pair.
The self-locking nut has good anti-loosening performance, can be reused, and has high efficiency, especially suitable for use under various temperature and shock and vibration conditions. However, the thread structure is relatively complex and the cost is relatively high, so it has not been widely used in the manufacturing industry.
Fourth, the flange surface with teeth self-locking nut
The bearing surface of the flange surface toothed self-locking nut is evenly distributed with a certain angle of "sawtooth" or arc-shaped tooth shape, and the compression force generated in the tightening process makes the tooth shape embedded in the surface of the connecting surface, thereby increasing the friction of the bearing surface and playing a good anti-loosening effect.
This kind of nut is generally suitable for applications with low strength of the opponent piece, and the tooth shape of the flange nut can be smoothly pressed into the opponent piece and form a tooth shape on the opponent piece.
Taking automobiles as an example, at present, lightweight materials aluminum alloy and magnesium alloy are more and more widely used, and the flange face toothed self-locking nut is very suitable for the application of these materials.
5. Slotted self-locking nut
When the bolt is screwed into the slotted closing self-locking nut, the tail end of the nut will be automatically opened, and under the action of the nut closing deformation force, the thread will fit tightly and produce friction resistance to achieve the purpose of anti-loosening.
The slotted and closed self-locking nut has good anti-loosening performance, can be applied to various occasions, can be reused 3-5 times, and the relaxation performance will decrease with the increase of use.
Make a rounded corner transition at the slotted closing place as much as possible to avoid the origin of cracks due to stress concentration during use, which will eventually lead to fracture.
Sixth, Tang's self-locking nut
The following figure is a schematic diagram of the anti-loosening method of Tang's self-locking nut. In the connection, two nuts with different rotational directions are used: the nut on the working bearing surface is called the fastening nut, and the nut on the non-supporting surface is called the lock nut. When using, pre-tighten the fastening nut first, and then pre-tighten the lock nut.
Down's bolts are compatible with two different rotation directions, so that the friction and tightening force can be converted into each other to achieve the purpose of restriction. The deloosening force of the right-handed nut is directly converted into the tightening force of the left-handed nut, and the two opposing forces are converted into mutual aid, and the thread structure that will not loosen is invented.
From the perspective of thread, the eccentric nut is still a traditional thread, which is a "single rotation, continuous, equal cross-section" thread, while the Down's thread is a "double-rotational, discontinuous, variable cross-section" thread, which completely breaks through the concept of traditional thread and is the most significant breakthrough in the field of threading.
7. Other self-locking nuts
For example, the nut is never loosened by hard-lock, and the additional torque in the radial plane is generated under the action of eccentricity to achieve the anti-loosening of the connection structure, as shown in the following figure.
Bump slope self-locking nut
When the nut is single-screwed, the two are axially opened and more compressed due to the effect of concave and convex slopes.
When the washer is screwed, due to the effect of the concave and convex slope, the washer drives the nut exactly the same as when the nut is screwed, so it is relatively easy to loosen.
At present, these two kinds of self-locking nuts are not widely used in industry, and are only used in some specific industries and specific structures.
The anti-loosening of fasteners is an important research topic in the industry, and certain anti-loosening measures need to be adopted for the connection position that bears alternating load and shear load, and the self-locking nut is a common anti-loosening method.
Today, the self-locking nuts introduced by Screw Jun include nylon insert self-locking nuts, metal self-locking nuts, Spitsafe self-locking nuts, flange surface toothed self-locking nuts, slotted closing self-locking nuts, Down's self-locking nuts, and other self-locking nuts, each of which has its application characteristics, such as: nylon insert self-locking nuts are suitable for applications in connections with certain impact loads, and the cost is low. Self-locking nut with teeth on the flange face for light metal connections. I hope to provide you with some inspiration and reference in the search for anti-loosening methods.
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