Secondary self-locking screw and using method

Abstract

The invention relates to the technical field of mechanical connecting pieces, and discloses a two-stage self-locking screw and a using method.The two-stage self-locking screw comprises a screw body, a gasket is arranged on the outer wall of the screw body, a mounting base is arranged on the outer wall of the screw body, a pin is arranged in the mounting base, and the interior of the screw body is slidably connected to the outer wall of the pin; a groove and a through hole which are perpendicular to each other are formed in the end part of the screw body, the through hole and the screw body are concentric, and the wall thickness between the hole wall of the through hole and the outer cylindrical surface of the screw body is 0.8-1.2 mm. Through precise matching of the pin and the screw, the first conical surface is used for promoting plastic deformation of the hole wall to form the mechanical interference protrusion, mechanical vibration resistance and looseness prevention are achieved, the fracture groove is impacted to remove the gasket during disassembly, screwing continues to enable the second conical surface to strongly expand the hole wall, and the end of the screw is accurately cut off under bidirectional extrusion. And the integrity of internal threads of the mounting seat is protected, and the maintainability of equipment is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of mechanical connector technology, specifically to a two-stage self-locking screw and its usage method. Background Technology

[0002] In the field of mechanical connections, screws are widely used as basic fasteners in various equipment, especially in extreme working conditions such as automobiles, aerospace, and heavy machinery. Screws not only need stable connection performance to resist external forces such as vibration and impact, preventing loosening of connected components and ensuring normal equipment operation, but they also need to allow for convenient and efficient disassembly during equipment maintenance, while avoiding damage to critical structures such as the internal threads of the mounting base during disassembly, thus extending the overall service life of the equipment and improving maintainability. Traditional screw anti-loosening methods mostly rely on friction, such as using spring washers or double nuts, to increase the friction between the threads and prevent loosening. While this method can be effective under normal working conditions, under extreme conditions such as long-term vibration and high-frequency impact, the coefficient of friction is easily affected by factors such as temperature and wear, making it difficult to meet the requirements for anti-loosening reliability. It cannot effectively combat the continuous tendency of loosening, posing a safety hazard to equipment operation. Furthermore, traditional anti-loosening screws have significant shortcomings during disassembly. Some anti-loosening structures require special tools for forced removal, which is not only complex and time-consuming but also prone to scratching and deformation of the mounting base's internal threads, rendering the mounting base unusable and increasing equipment maintenance costs. Other removable anti-loosening structures, while avoiding serious damage to the mounting base, experience a significant decrease in anti-loosening performance after disassembly, making it difficult to meet reliable connection requirements again. Moreover, they cannot provide an efficient operating procedure in scenarios requiring rapid disassembly, thus hindering the improvement of equipment maintenance efficiency and maintainability. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a two-stage self-locking screw and its usage method, solving the problem that traditional screws struggle to balance anti-loosening reliability with ease of disassembly and structural protection.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a two-stage self-locking screw, comprising a screw body, a washer provided on the outer wall of the screw body, a mounting base provided on the outer wall of the screw body, a pin provided inside the mounting base, and the screw body being slidably connected to the outer wall of the pin.

[0005] By adopting the above technical solution: This invention utilizes the precise fit between the pin and the through hole at the end of the screw, and uses the first conical surface to cause the hole wall material to undergo controllable plastic expansion deformation, naturally forming a mechanical interference protrusion. This protrusion forms a rigid barrier with the internal thread structure of the mounting base, effectively resisting the tendency of rotational loosening caused by vibration and impact in a purely mechanical way. It achieves a reliability far exceeding that of traditional friction anti-loosening methods, and is particularly suitable for extreme working conditions. When disassembly is required, the washer can be quickly removed by impacting the preset fracture groove, providing critical stroke space for the screw to continue to be screwed in. The subsequent screwing action causes the second conical surface of the pin with a larger taper to forcefully expand the hole wall. Under the reverse synergistic effect of the inner groove of the mounting base, the screw end is precisely guided to undergo shear fracture at a predetermined position. This process is simple to operate and the damage is controllable. It can achieve rapid non-destructive disassembly while completely protecting the integrity of the internal thread of the mounting base, greatly improving the maintainability and service life of the equipment.

[0006] Preferably, the end of the screw body is provided with mutually perpendicular grooves and through holes, the through holes are concentric with the screw body, and the wall thickness between the hole wall and the outer cylindrical surface of the screw body is 0.8-1.2 mm.

[0007] Preferably, the mounting base has an inner groove inside, the depth of which is greater than the thickness of the gasket, and the mounting base has a step inside.

[0008] Preferably, the circumferential surface of the pin is provided with a first conical surface and a second conical surface with different tapers, wherein the taper of the first conical surface is lower than the taper of the second conical surface.

[0009] Preferably, a transition zone is provided between the first conical surface and the second conical surface, the transition zone being used to determine the insertion depth of the pin during assembly.

[0010] Preferably, the minor diameter of the first conical surface is equal to the diameter of the through hole, the major diameter of the first conical surface is greater than the diameter of the through hole by a difference of 0.15-0.25 mm, the major diameter of the second conical surface is greater than the diameter of the through hole by a difference of 0.8-1.2 mm, and the length of the second conical surface is equal to the thickness of the gasket.

[0011] Preferably, the gasket has a threaded groove inside, which is located on the inner wall of the through hole. The threaded groove is used to enhance the frictional fit between the screw body and the pin. The outer wall of the gasket has a fracture groove.

[0012] Preferably, the mounting base has a countersunk hole inside, which communicates with the inner groove, and a screw is fixedly connected to the outer wall of the pin, with the screw's outer wall threaded into the interior of the mounting base.

[0013] Preferably, a method for using a two-stage self-locking screw involves first screwing the screw body into the mounting base. Through the engagement of the pin and the through hole, under the influence of the first conical surface, the through hole is squeezed outward, naturally forming a bulge with a radial diameter greater than the step. This mechanical interference prevents the screw body from loosening, thus forming a first-stage anti-loosening mechanism.

[0014] Preferably, in the first-level anti-loosening state, the washer can be quickly removed by impacting the fracture groove with external force, so that the screw body can continue to be screwed into the washer thickness. When screwing in, the second conical surface will cooperate with the through hole, squeezing the through hole to form a greater degree of outward expansion. Under the squeezing in both directions of the second conical surface and the inner groove, the material at the end of the screw body will break, and the anti-loosening of the step will fail. At this time, the screw body and the pin can be removed.

[0015] This invention provides a two-stage self-locking screw and its method of use. It has the following beneficial effects: 1. This invention utilizes the precise fit between the pin and the through hole at the end of the screw to induce a controllable plastic expansion deformation of the hole wall material through the first conical surface, naturally forming a mechanical interference protrusion. This protrusion forms a rigid barrier with the internal thread structure of the mounting base, effectively resisting the tendency of rotational loosening caused by vibration and impact, achieving a highly reliable mechanical anti-loosening mechanism, and overcoming the defect of traditional friction anti-loosening methods being prone to failure under extreme working conditions.

[0016] 2. This invention can quickly remove the washer by impacting the preset fracture groove, providing travel space for the screw to continue to be screwed in. The subsequent screwing action causes the second conical surface of the pin with a larger taper to forcefully expand the hole wall, and under the reverse action of the inner groove of the mounting seat, it causes the end of the screw to shear and break at a predetermined position. This process is simple and controllable, can achieve quick disassembly, and leaves the internal thread of the mounting seat intact, which greatly facilitates maintenance and replacement.

[0017] 3. This invention can also achieve the reuse of components through structural adjustments. By designing the screw end as a thin-walled section that can elastically recover, and in conjunction with a pin structure that can be unscrewed in the reverse direction, damage to any parts can be avoided during normal disassembly. This method not only ensures the reliability of anti-loosening, but also significantly reduces maintenance costs in scenarios that require frequent disassembly and maintenance. The original secondary fracture function serves as an emergency guarantee when the pin is accidentally locked, further improving the practicality and economy of the entire connection system. Attached Figure Description

[0018] Figure 1 This is a perspective view of a two-stage self-locking screw according to the present invention; Figure 2 This is a schematic diagram of the internal structure of the mounting base for a two-stage self-locking screw according to the present invention; Figure 3 This is a schematic diagram of the screw body of a two-stage self-locking screw according to the present invention; Figure 4 This is a schematic diagram of the groove of a two-stage self-locking screw according to the present invention; Figure 5 This is a schematic diagram of the through hole of a two-stage self-locking screw according to the present invention; Figure 6 This is a schematic diagram of the fracture groove of a two-stage self-locking screw according to the present invention; Figure 7 This is a schematic diagram of the inner groove of a two-stage self-locking screw according to the present invention; Figure 8 This is a three-dimensional schematic diagram of the pin of a two-stage self-locking screw according to the present invention; Figure 9 This is a schematic diagram of the pin plane of a two-stage self-locking screw according to the present invention; Figure 10 This is a schematic diagram of the steps of a two-stage self-locking screw according to the present invention; Figure 11 This is a three-dimensional schematic diagram of a washer for a two-stage self-locking screw according to the present invention; Figure 12 This is a schematic diagram of the washer plane of a two-stage self-locking screw according to the present invention; Figure 13 This is a schematic diagram of a two-stage self-locking screw according to the present invention; Figure 14 This is a planar schematic diagram of a two-stage self-locking screw according to the present invention.

[0019] Among them, 1. Washer; 2. Screw body; 3. Mounting base; 4. Pin; 5. Groove; 6. Through hole; 7. Inner groove; 8. First conical surface; 9. Second conical surface; 10. Step; 11. Fracture groove; 12. Transition zone; 13. Thread groove; 14. Screw; 15. Countersunk hole. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see the appendix Figure 1 - Appendix Figure 3 This invention provides a two-stage self-locking screw, including a screw body 2, a washer 1 disposed on the outer wall of the screw body 2, a mounting base 3 disposed on the outer wall of the screw body 2, a pin 4 disposed inside the mounting base 3, and the screw body 2 being slidably connected to the outer wall of the pin 4.

[0022] Specifically, the screw body 2 is the core load-bearing component of the entire structure and provides the basis for assembling other parts, thus playing the role of bearing and connecting various components, thereby achieving the effect of stably assembling related components together; the washer 1 is set on the outer wall of the screw body 2 and can be separated from the screw body 2. At the same time, the washer 1 plays the role of transmitting preload and dispersing pressure, thereby enhancing the stability of the overall connection. The washer 1 is a thin metal sheet after heat treatment, which is a brittle material; the mounting base 3 plays the role of supporting and limiting the screw body 2, and also plays a guiding role, ensuring the stability of installation; at the same time, the pin 4 also plays the role of precisely guiding the movement trajectory of the screw body 2, thereby ensuring that the components maintain the correct relative position relationship throughout the entire working process, ultimately achieving a comprehensive effect of reliable first-level anti-loosening and convenient second-level disassembly.

[0023] Please see the appendix Figure 3 - Appendix Figure 5 The end of the screw body 2 is provided with mutually perpendicular grooves 5 and through holes 6. The through holes 6 are concentric with the screw body 2, and the wall thickness between the hole wall of the through holes 6 and the outer cylindrical surface of the screw body 2 is 0.8-1.2mm.

[0024] Specifically, by setting mutually perpendicular grooves 5 and through holes 6, the end of the screw body 2 is guided to deform in a specific direction when subjected to force, thereby enabling the end of the screw body 2 to form a regular and reliable anti-loosening protrusion when squeezed by the pin 4. The through hole 6 is concentric with the screw body 2, which ensures that the force is evenly distributed when the screw body 2 is inserted, thus avoiding the instability of the anti-loosening effect caused by eccentric force. The wall thickness between the hole wall of the through hole 6 and the outer cylindrical surface of the screw body 2 is controlled within the range of 0.8-1.2mm, which balances the screw strength and fractureability: it ensures that there is sufficient strength to withstand the extrusion deformation in the first stage of anti-loosening, and that it can break smoothly under the predetermined torque in the second stage of disassembly, thus achieving a unity of anti-loosening reliability and disassembly convenience.

[0025] Please see the appendix Figure 7 The mounting base 3 has an inner groove 7 inside, the depth of which is greater than the thickness of the gasket 1, and the mounting base 3 has a step 10 inside.

[0026] Specifically, the inner groove 7 provides a precise installation and positioning space for the washer 1, thereby ensuring that the washer 1 can be stably placed in the predetermined position during assembly. The depth of the inner groove 7 is greater than the thickness of the washer 1. By maintaining this dimensional gap, it provides the necessary travel space for the screw body 2 to continue to be screwed in, thus providing conditions for the secondary disassembly operation. The step 10 forms a mechanical limit with the end face of the screw body 2, thereby limiting the final screw-in position and providing a reliable interference contact surface for the expansion protrusion formed during the first-stage anti-loosening, ultimately achieving the effect of effectively preventing the screw from rotating and loosening under vibration.

[0027] Please see the appendix Figure 3 Appendix Figure 8 and attached Figure 9 The circumferential surface of the pin 4 is provided with a first conical surface 8 and a second conical surface 9 with different tapers. The taper of the first conical surface 8 is lower than that of the second conical surface 9. A transition area 12 is provided between the first conical surface 8 and the second conical surface 9. The transition area 12 is used to position the insertion depth of the pin 4 during assembly. The minor diameter of the first conical surface 8 is equal to the diameter of the through hole 6, and the major diameter of the first conical surface 8 is greater than the diameter of the through hole 6, with a difference of 0.15-0.25mm. The major diameter of the second conical surface 9 is greater than the diameter of the through hole 6, with a difference of 0.8-1.2mm. The length of the second conical surface 9 is equal to the thickness of the washer 1.

[0028] Specifically, by employing a phased double-conical surface design, differentiated extrusion effects are achieved on the through hole 6 at different operational stages: the first conical surface 8 uses a smaller taper, guiding the hole wall material to gradually deform outwards with relatively gentle force, thus achieving a uniform and stable first-level locking effect with anti-loosening protrusions; the second conical surface 9 uses a larger taper, generating strong expansion force during disassembly, thus providing sufficient radial stress for shearing the screw tip; the transition zone 12 provides tactile and visual positioning references during assembly, ensuring that the pin 4 is inserted to a uniform standard depth each time, guaranteeing the consistency of the first-level anti-loosening effect; the minor diameter of the first conical surface 8 is equal to... The diameter of the through hole 6 is such that the major diameter of the first conical surface 8 is larger than the diameter of the through hole 6, with a difference of 0.15-0.25mm. By precisely controlling this small interference, the pin 4 can be smoothly inserted while generating the necessary compressive force, thereby causing sufficient plastic deformation of the hole wall material to form a reliable anti-loosening limit. The major diameter of the second conical surface 9 is larger than the diameter of the through hole 6, with a difference of 0.8-1.2mm, and the length of the second conical surface 9 is equal to the thickness of the washer 1. By designing the length of the second conical surface 9 in relation to the thickness of the washer 1, the screw's continued screwing stroke can be precisely controlled, thereby ensuring that the huge expansion force generated during the disassembly stage is applied precisely to the predetermined fracture position, achieving a controllable and clean fracture effect.

[0029] Please see the appendix Figure 10 - Appendix Figure 12 The inside of the washer 1 is provided with a threaded groove 13, which is located on the inner wall of the through hole 6. The threaded groove 13 is used to enhance the frictional fit between the screw body 2 and the pin 4. The outer wall of the washer 1 is provided with a fracture groove 11.

[0030] Specifically, the threaded groove 13 increases the coefficient of friction and anti-rotation capability of the contact surface, thereby effectively preventing relative rotation between the washer 1 and the screw body 2 during pre-tightening and vibration. The threaded groove 13 also enhances the bonding strength between the pin 4 and the screw body 2, ensuring that the pin 4 remains stable during operation and will not accidentally fall off. The threaded groove 13 enhances the frictional fit between the screw body 2 and the pin 4, thus providing an auxiliary anti-loosening function and improving overall reliability. The fracture groove 11 on the outer wall of the washer 1 guides stress concentration, allowing the washer 1 to break neatly at a predetermined position when subjected to external impact, facilitating quick removal of the washer 1 during disassembly and improving operational convenience.

[0031] Please see the appendix Figure 13 and attached Figure 14 The mounting base 3 has a countersunk hole 15 inside, which communicates with the inner groove 7. The outer wall of the pin 4 is fixedly connected to a screw 14, and the outer wall of the screw 14 is threaded into the inside of the mounting base 3.

[0032] Specifically, another implementation method can be achieved by setting the countersunk hole 15 and the screw 14, thereby enabling the reuse of the screw body 2. In this case, the one-time fracture structure of the screw body 2 needs to be changed to an elastic deformation structure. Specifically, the groove 5 at the end of the screw body 2 needs to be designed to be deeper and wider, thus forming an elastic thin-walled section. Its wall thickness can ensure that large elastic deformation rather than plastic deformation or fracture can occur, which just allows the pin 4 to slide in it. The depth of the countersunk hole 15 is the same as the length of the first conical surface 8. During assembly, the screw body 2 is screwed in to tighten the washer 1, and then the screw 14 is screwed in to screw in the pin 4. Its first conical surface 8 expands the elastic thin-walled section, causing it to expand outward to form an anti-loosening limit. When disassembly is required, rotating screw 14 in the reverse direction will cause pin 4 to rotate, thereby disengaging its first conical surface 8 and retracting the elastic thin-walled section. At this point, the anti-loosening limit disappears, and screw body 2 can be directly unscrewed. All parts are intact and can be reused. If screw 14 cannot be unscrewed due to rust or other reasons, the original solution can be used: after removing washer 1, continue to tighten screw body 2. The second conical surface 9 of pin 4 will forcefully open the elastic thin-walled section, causing it to break, thereby disengaging the connection. Through this implementation scheme, reusability is achieved, thereby reducing maintenance costs in frequent repair scenarios. At the same time, the secondary disassembly function is retained as a guarantee, improving overall reliability.

[0033] Please see the appendix Figure 1 - Appendix Figure 14 A method for using a two-stage self-locking screw, for the aforementioned two-stage self-locking screw, firstly, the screw body 2 is screwed into the mounting base 3. Through the cooperation of the pin 4 and the through hole 6, under the influence of the first conical surface 8, the through hole 6 is squeezed outward, naturally forming a bulge with a radial diameter greater than the step 10, which can then prevent the screw body 2 from loosening by mechanical interference, forming a first-stage anti-loosening state. In the first-stage anti-loosening state, the washer 1 can be quickly removed by impacting the fracture groove 11 with external force, so that the screw body 2 can continue to be screwed in by the thickness of the washer 1. When screwing in, the second conical surface 9 will cooperate with the through hole 6, squeezing the through hole 6 to form a greater degree of outward expansion. Under the squeezing in two directions of the second conical surface 9 and the inner groove 7, the material at the end of the screw body 2 will break, and the anti-loosening of the step 10 will fail. At this time, the screw body 2 and the pin 4 can be removed.

[0034] Specifically, when the screw body 2 is screwed into the mounting base 3, the hole wall of the through hole 6 undergoes uniform plastic expansion deformation under the progressive compression of the first conical surface 8 through the engagement of the pin 4 and the through hole 6. This process, through the interference fit, causes the end of the screw body 2 to flow in a directional manner, thereby naturally forming a mechanical interference protrusion with a radial dimension larger than the mean diameter of the internal thread of the mounting base 3. This achieves a first-level anti-loosening effect by effectively preventing the screw body 2 from rotating and loosening through mechanical locking. Under the first-level anti-loosening state, the fracture groove 11 on the washer 1 is impacted by external force. Utilizing the stress concentration characteristics of brittle materials, the washer 1 is guided to break neatly along a predetermined path, thereby achieving rapid and complete removal of the washer 1 and creating conditions for subsequent operations. After the washer 1 is removed, the screw body 2 can continue to be screwed in by a distance equivalent to the thickness of the washer 1. By controlling the screwing stroke, it ensures that the second conical surface 9 passes completely through the through hole 6. During the continued screwing process, the second conical surface 9 engages with the through hole 6. Through its greater taper and dimensional difference, it exerts a secondary strong extrusion on the expanded through hole 6, thereby causing a greater degree of plastic deformation of the hole wall. At the same time, under the bidirectional extrusion action of the outward expansion of the second conical surface 9 and the inward limiting action of the bottom of the inner groove 7, the material at the end of the screw body 2 is sheared and fractured at a predetermined weak point, thereby achieving the failure of the anti-loosening limit and the disconnection. Ultimately, it achieves the dual effect of ensuring both connection reliability and disassembly.

[0035] Example 1: First, screw body 2 is screwed into mounting base 3. When screw body 2 is screwed into mounting base 3, under the progressive extrusion of the first conical surface 8, the hole wall of through hole 6 will produce uniform plastic expansion deformation, and then naturally form a mechanical interference protrusion with a radial dimension larger than the mean diameter of the internal thread of mounting base 3. In this way, the screw body 2 can be prevented from loosening by mechanical interference, forming a first-level anti-loosening. In the first-level anti-loosening state, the washer 1 can be quickly removed by impacting the fracture groove 11 on the washer 1 with external force. After the washer 1 is removed, the screw body 2 can continue to be screwed in a distance equivalent to the thickness of the washer 1. During the continued screwing process, the second conical surface 9 engages with the through hole 6. Through its larger taper and size difference, it can exert a secondary strong extrusion on the expanded through hole 6, thereby causing the hole wall to undergo greater plastic deformation. At the same time, under the bidirectional extrusion action of the second conical surface 9 expanding outward and the inner groove 7 limiting inward, the material at the end of the screw body 2 can be sheared and fractured at the predetermined weak position, thereby achieving the failure of the anti-loosening limit and the disconnection, ultimately achieving the dual effect of ensuring connection reliability and achieving disassembly.

[0036] Example 2: The assembly process is the same as in Example 1. First, screw in the screw body 2 to press the washer 1 during assembly. Then, screw 14 to screw in the pin 4. Its first conical surface 8 opens the elastic thin-walled section, causing it to expand outward and form an anti-loosening limit. When disassembly is required, rotate the screw 14 in the opposite direction to drive the pin 4 to rotate, thereby causing its first conical surface 8 to exit and the elastic thin-walled section to retract. At this time, the anti-loosening limit disappears, and the screw body 2 can be directly unscrewed. At this time, all parts are intact and can be reused. If screw 14 cannot be unscrewed due to rust or other reasons, the original solution can be used: after removing washer 1, continue to tighten screw body 2. The second conical surface 9 of pin 4 will forcefully open the elastic thin-walled section and break it, thereby achieving the disconnection. Through this implementation scheme, reusability is achieved, thereby reducing maintenance costs in frequent maintenance scenarios. At the same time, the secondary disassembly function is retained as a guarantee, improving the overall reliability.

[0037] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A two-stage self-locking screw comprising a screw body (2), characterized in that: The outer wall of the screw body (2) is provided with a gasket (1), the outer wall of the screw body (2) is provided with a mounting seat (3), the inside of the mounting seat (3) is provided with a pin (4), and the inside of the screw body (2) is slidably connected to the outer wall of the pin (4).

2. A two-stage self-locking screw according to claim 1, characterized in that: The end of the screw body (2) is provided with a recess (5) and a through hole (6) perpendicular to each other, the through hole (6) is concentric with the screw body (2), and the wall thickness between the hole wall of the through hole (6) and the outer cylindrical surface of the screw body (2) is 0.8-1.2mm.

3. A two-stage self-locking screw according to claim 1, characterized in that: The inside of the mounting seat (3) is provided with an inner groove (7), the depth of the inner groove (7) is greater than the thickness of the gasket (1), and the inside of the mounting seat (3) is provided with a step (10).

4. The secondary self-locking screw according to claim 1, characterized in that: The circumference of the pin (4) is provided with a first taper surface (8) and a second taper surface (9) with different tapers, and the taper of the first taper surface (8) is lower than that of the second taper surface (9).

5. A two-stage self-locking screw according to claim 4, characterized in that: The first taper surface (8) and the second taper surface (9) are transitionally provided with a transition zone (12) for positioning the insertion depth of the pin (4) during assembly.

6. A two-stage self-locking screw according to claim 4, characterized in that: The small diameter of the first taper surface (8) is equal to the diameter of the through hole (6), the large diameter of the first taper surface (8) is greater than the diameter of the through hole (6), and the difference is 0.15-0.25mm, the large diameter of the second taper surface (9) is greater than the diameter of the through hole (6), and the difference is 0.8-1.2mm, and the length of the second taper surface (9) is equal to the thickness of the gasket (1).

7. The secondary self-locking screw according to claim 1, characterized in that: The inside of the gasket (1) is provided with a threaded groove (13), the threaded groove (13) is located on the inner wall of the through hole (6), the threaded groove (13) is used for enhancing the friction fit between the screw body (2) and the pin (4), and the outer wall of the gasket (1) is provided with a fracture groove (11).

8. The two-stage self-locking screw according to claim 1, wherein: The inside of the mounting seat (3) is provided with a counterbore (15) which is communicated with the inner groove (7), and the outer wall of the pin (4) is fixedly connected with a screw (14), and the outer wall of the screw (14) is threadedly connected in the inside of the mounting seat (3).

9. A method of using a two-stage self-locking screw, characterized in that, A two-stage self-locking screw according to any one of claims 1-8, first screw body (2) is screwed into the mounting seat (3), through the cooperation of the pin (4) and the through hole (6), under the influence of the first taper surface (8), the through hole (6) will be extruded and expanded, and a convex with a radial larger than the step (10) will be formed naturally, and then the screw body (2) can be blocked in a mechanical interference manner to form a first anti-loose.

10. The method of using a two-stage self-locking screw of claim 9, wherein: In the first anti-loose state, the gasket (1) can be quickly removed by external force impact on the fracture groove (11), so that the screw body (2) can continue to be screwed into the gasket (1) by the thickness of the gasket (1), when screwed in, the second taper surface (9) will cooperate with the through hole (6), the through hole (6) will be extruded to a larger extent, under the extrusion of the second taper surface (9) and the inner groove (7) in two directions, the material at the end of the screw body (2) will be broken, and then the anti-loose of the step (10) will be invalid, at this time, the screw body (2) and the pin (4) can be taken out.

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