Self-tightening spring and anti-loose thread pair

Abstract

This utility model discloses a self-tightening spring and an anti-loosening threaded assembly. The self-tightening spring includes a tension spring body, a bolt hook, and a nut hook. The tension spring body is a cold-rolled cylindrical helical tension spring. The bolt hook is a straight hook, with one end connected to the helical coil of the tension spring body and the other end being a straight pry hook for inserting into the bolt hook hole and holding it in place. The nut hook is an "L"-shaped hook, with its end for inverted insertion into the nut hook hole. The anti-loosening threaded assembly includes a bolt, a nut, and the aforementioned self-tightening spring. The bolt has a bolt hook hole on the thread protruding from the nut, and the nut has a nut hook hole on its hexagonal side. The pry hook of the self-tightening spring is inserted into the bolt hook hole and held in place, while the "L"-shaped nut hook is inverted inserted into the nut hook hole. The tension spring body is stretched around the bolt, and the tension of the tension spring body causes the nut to tend to rotate in the direction of thread tightening. This invention utilizes the elastic tension of the self-tightening spring to continuously provide tightening torque, ensuring reliable anti-loosening and allowing for reusability.

Description

Technical Field

[0001] This utility model relates to the field of fastener anti-loosening technology, specifically to a self-tightening spring and an anti-loosening threaded pair using the self-tightening spring. Background Technology

[0002] A cold-rolled cylindrical helical tension spring, or simply a tension spring, is a helical spring that bears axial tensile force. Made of a circular cross-section material, when not under load, the coils of the tension spring are tightly wound with no gaps. Under tension, the coils are pulled apart, creating gaps, and the entire spring stretches under stress, entering a state of contraction and self-tightening. Under a certain degree of tension, the tension spring possesses an initial tension that determines the tightness of the coiling. Typically, tension springs have open annular hooks at both ends to ensure the source of the tensile force. When the ends of the tension spring are pulled apart, the spring will bring these ends to their closest distance; the tension spring also absorbs and stores energy.

[0003] In threaded pairs consisting of a nut and a bolt, under conditions of strong vibration, the internal thread of the nut may vibrate and rotate against the external thread of the bolt, causing it to loosen. This loosening occurs when the nut is in a free state during vibration, momentarily overcoming friction and undergoing reverse rotational loosening, because at this time the nut lacks a continuous preload in the helical tightening direction. A small, continuous preload can overcome the force of reverse rotational loosening in each vibration cycle, thus ensuring it does not loosen. Currently, this anti-loosening method has not been fully explored and utilized.

[0004] Existing anti-loosening threaded pairs mostly rely on increasing the friction between the nut and the bolt to achieve the purpose of preventing loosening, such as thread coating, double-layer self-locking washers, and lock nuts. However, all of them have the problem that as the number of vibrations increases, the residual axial force continuously decreases, eventually leading to the loosening of the anti-loosening threaded pair. Utility Model Content

[0005] The purpose of this invention is to overcome the problem that existing anti-loosening threaded pairs are prone to loosening due to vibration under strong vibration conditions, causing the nut to rotate back on the bolt, and to provide a self-tightening spring and anti-loosening threaded pair to ensure that the nut will not loosen for a long time.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A self-tightening spring includes a spring body, a bolt hook, and a nut hook. The spring body is a cold-coil cylindrical helical tension spring. The bolt hook is a straight hook, with one end connected to the helical coil of the spring body and the other end being a straight pry hook. The pry hook is used to insert into the bolt hook hole of the bolt and does not come out when the spring body is under full load, thus prying and holding the spring body. The nut hook is an "L"-shaped hook, with its end used to be inserted backward into the nut hook hole on the hexagonal side of the nut. In use, the spring body is stretched around one side of the bolt from the bolt hook hole to the nut hook hole, and the tension of the spring body is within its elastic range, keeping the nut in a self-tightening state.

[0008] Furthermore, the self-tightening spring is made of an elastic metal selected from high-carbon steel wire, phosphor bronze, austenitic stainless steel, nickel-based alloys, or titanium alloys.

[0009] An anti-loosening threaded assembly includes a bolt, a nut, and the aforementioned self-tightening spring. The bolt has a bolt hook hole on its exposed thread at the tail end, which is a radial through hole with a diameter larger than the thread diameter of the tension spring body. Alternatively, the bolt has at least one radially open bolt hook groove at its tail end. The nut has at least one nut hook hole on its hexagonal side, which is a blind hole extending inward from the hexagonal side with a diameter larger than the thread diameter of the tension spring body. A straight pry hook of the self-tightening spring is inserted into the bolt hook hole or bolt hook groove and holds the nut in place. The end of the "L"-shaped nut hook is inserted backward into the nut hook hole. The tension spring body is tightened, with one end connected to the bolt and the other end connected to the nut. The tension of the spring body causes the nut to tend to rotate in the direction of thread tightening.

[0010] The beneficial effects of this invention are as follows: Utilizing the elastic tension of the self-tightening spring, the bolt and nut are elastically linked through the prying action of the straight pry hook in the bolt hole and the inverted insertion action of the "L"-shaped hook in the blind hole on the side of the nut, providing a continuous tightening torque and effectively preventing loosening. The structure is simple, installation is convenient, no changes to the main structure of the bolt and nut are required, and it can maintain its anti-loosening performance for a long time. Attached Figure Description

[0011] Figure 1 This is the front view of the self-tightening spring;

[0012] Figure 2 yes Figure 1 Top view;

[0013] Figure 3 yes Figure 1 The left view;

[0014] Figure 4 yes Figure 1 The right view;

[0015] Figure 5 yes Figure 1 A bottom view;

[0016] Figure 6 yes Figure 1 Rear view;

[0017] Figure 7 This is a schematic diagram showing a hook hole at the end of a bolt;

[0018] Figure 8 yes Figure 7 The left view;

[0019] Figure 9 yes Figure 7 The right view;

[0020] Figure 10 This is a schematic diagram showing a blind hole on the hexagonal side of a nut;

[0021] Figure 11 yes Figure 10 The left view;

[0022] Figure 12 yes Figure 10 The right view;

[0023] Figure 13 yes Figure 10 Top view;

[0024] Figure 14 This is the front view of the anti-loosening threaded pair;

[0025] Figure 15 yes Figure 14 The left view;

[0026] Figure 16 yes Figure 14 The right view;

[0027] Figure 17 yes Figure 14 Rear view;

[0028] Figure 18 yes Figure 14 Top view;

[0029] Figure 19 yes Figure 14 A bottom view;

[0030] Figure 20 This is a schematic diagram of a bolt with a bolt hook groove.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Self-tightening spring; 2. Bolt hook; 3. Nut hook; 4. Bolt hook hole; 5. Nut hook hole; 6. Bolt; 7. Screw; 8. Bolt head; 9. Nut; 10. Bolt external thread; 11. Nut internal thread; 12. Screw hole; 13. Thread clearance; 14. Upper fastener; 15. Lower fastener; 16. Circular plane at one end of the nut; 17. Bolt tail end; 23. Bolt hook groove; 24. Tension spring body; 25. Anti-loosening thread pair; 26. Steel wire; 27. Fold-back transition section; 28. Fold-back barb; 29. ​​Hexagonal side; 30. Blind hole. Detailed Implementation

[0033] The present invention will now be further described in conjunction with the accompanying drawings and embodiments.

[0034] The working principle of the self-tightening spring 1 is as follows: through the elastic deformation of the material, a reaction force is generated when it is stretched, storing and releasing elastic potential energy to achieve the reset function. When the two ends of the self-tightening spring 1 are subjected to tension, the self-tightening spring 1 undergoes extension deformation, and a restoring force opposite to the direction of tension is generated inside the material, causing the tension spring body 24 to attempt to return to the original shortest closed state.

[0035] like Figures 1-6 As shown, the self-tightening spring 1 consists of three parts: a bolt hook 2, a tension spring body 24, and a nut hook 3. These three parts are connected by the same circular cross-section steel wire, which is wound and cut by a universal spring machine. The tension spring body 24 is a cold-coiled cylindrical helical tension spring. The bolt hook 2 is a straight hook, with one end connected to the tangent of the helical coil of the tension spring body 24, and the other end is a straight pry hook. The nut hook 3 is an "L"-shaped hook, with a section 27 folded back at a right angle to the tension spring body 24 tangent at the other end. This folded-back section is then folded back parallel to the axial direction of the tension spring body 24 to form a back hook 28, which is used for inverted insertion into the nut hook hole 5.

[0036] The self-tightening spring 1 is made of an elastic metal, which is selected from high-carbon steel wire (e.g., 65Mn, 50CrVA, with a hardness of HRC45-55 after heat treatment and a tensile strength of 1600-2000MPa), phosphor bronze (elastic modulus 110-130GPa), austenitic stainless steel (e.g., SUS304, SUS316, with corrosion resistance up to 5% salt spray test for 500 hours, operating temperature -200℃ to 400℃, suitable for chemical and marine environments), nickel-based alloys (e.g., Inconel 718), or titanium alloys. The specific material is selected according to the working conditions.

[0037] The diameter of the steel wire 26 in the tension spring body 24 is its wire diameter. The magnitude of the tension depends on the specifications of the anti-loosening thread pair 25 and the required preload, generally between 1N and 50KN; the tension spring body 24 can be either left-handed or right-handed. The length of the pry hook of the bolt hook 2, the length of the folded-back hook 28 of the nut hook 3, the direction and depth of insertion, etc., must all match the specifications of the bolt 6 and nut 9. The initial tension of the self-tightening spring 1 is equal to the force required to separate the tightly pressed spring coils, and the initial tension occurs after the spring is coiled. To eliminate uneven initial tension, the coils should be pre-tensioned with a slight gap between them during installation; the force required at this time is the initial tension.

[0038] The self-tightening spring 1 can be manufactured using commercially available cold-forming spring equipment. Steel wire 26, ranging from 0.3 to 14 mm, can be formed in one step on an 8-jaw forming machine. After forming, heat treatment and surface treatment are required. For example, the self-tightening spring 1 used in the M16 anti-loosening threaded pair 25 uses 0.6 mm diameter SUS304 stainless steel wire 26, a spring body 24 with an outer diameter of 5 mm and a length of 31 mm, a bolt hook 2 with a pry hook length of 10 mm, a fold-back transition section 27 with a length of 3 mm, and a fold-back barb 28 with a length of 8 mm. After cold working by winding and stamping, the stainless steel spring needs to undergo heat treatment (such as heating at 300–500℃ to relieve stress, or solution treatment at 900–1100℃) to improve its performance. The specific operations can be performed by those skilled in the art.

[0039] like Figures 7-9 As shown, a bolt hook hole 4 is provided at the tail end 17 of the bolt 6, which cooperates with the self-tightening spring 1. This hole is a radial through hole with a diameter larger than the wire diameter of the tension spring body 24, but not greater than 5 times the wire diameter. Bolt hooks 2 can be inserted into both openings of the radial through hole, facilitating alignment with the nut hook hole 5 on the nut 9. Alternatively, as shown... Figure 20 As shown, a bolt hook groove 23 with at least one radial opening is provided at the bolt tail end 17, which can also be used for hooking.

[0040] like Figures 10-13 As shown, at least one nut hook hole 5 is provided on the hexagonal side 29 of the nut 9, which is used in conjunction with the self-tightening spring 1. This hole is a blind hole 30 extending inward from the hexagonal side 29, with its opening direction being the chord direction of the nut and parallel to the hexagonal side 29 and the end face of the nut. The diameter of the blind hole 30 is larger than the wire diameter of the tension spring body 24, but not more than 5 times the wire diameter, and its depth is greater than the length of the folded-back hook 28. The direction of the blind hole 30 from the opening inward satisfies the following condition: after the "L"-shaped nut hook 3 is inserted backward, it can generate a torque in the thread tightening direction of the nut 9 when the self-tightening spring 1 is tightened. To facilitate the selection of the position after tightening, blind holes 30 can be provided on three consecutive hexagonal side 29. Since the diameter of the blind hole is very small (e.g., 0.3mm to 2mm), it can be machined using an electrical discharge machining (EDM) machine.

[0041] like Figures 14-19 As shown, the assembly method of the anti-loosening threaded pair 25 is as follows: After the tail end of the bolt 6 passes through the screw holes 12 of the lower fastener 15 and the upper fastener 14, screw on the nut 9 and pre-tighten it to the specified torque. When installing the self-tightening spring 1, first insert the straight pry hook of the bolt hook 2 into the bolt hook hole 4 (or bolt hook groove 23) of the bolt tail end 17, so that the pry hook is held in the hole and the other end does not protrude. Then tighten the tension spring body 24: when the thread of the bolt 6 is right-handed, turn the tension spring body 24 counterclockwise around the bolt 6 for about half a turn, hold the tension spring body 24 with your hand or needle-nose pliers, stretch it to about 1 / 5 to 1 / 3 longer than the free length, find the nut hook hole 5 on the hexagonal side of the nearest nut 9, tighten the back hook 28 of the "L" shaped nut hook 3 and insert it backwards into the hole; when the thread of the bolt 6 is left-handed, tighten it clockwise around the bolt 6, and similarly stretch and insert it backwards into the nearest nut hook hole 5. After release, the tension spring body springs back to its original position and tightens, completing the installation.

[0042] The anti-loosening principle of the aforementioned anti-loosening threaded pair 25 is as follows: After installation, the self-tightening spring 1 stores potential energy through elastic deformation. Under strong vibration conditions, if the nut 9 has a tendency to loosen, the tension spring body 24 is further stretched, and its elastic contraction force will shorten the rotation distance between the nut hook hole 5 and the bolt hook hole 4, releasing the stored elastic potential energy, causing the nut 9 to rotate in the tightening direction, automatically compensating for the preload loss caused by vibration, shortening and restoring the loose displacement, thereby achieving the purpose of self-tightening and anti-loosening.

[0043] In addition to high strength and high elastic limit, reliable operation of self-tightening spring 1 also requires good fatigue limit, impact toughness, and heat treatment processability. In practice, carbon spring steel, low-manganese spring steel, silicon-manganese spring steel, chromium-vanadium steel, stainless steel, etc., can be selected based on a comprehensive consideration of load characteristics, operating temperature, medium, corrosion and magnetic resistance requirements, and processing economy.

[0044] Actual testing has proven that the residual axial force of the anti-loosening threaded pair 25 of this utility model can approach 100% of the initial axial force under strong vibration, and it remains unloose for a long time. It can be applied to vibrating mechanical equipment with high requirements for anti-loosening performance, such as wind power, nuclear power, and high-speed rail.

[0045] During disassembly, simply use a tool to hook the nut hook 3 and pull it out of the blind hole 30 to loosen the nut 9 normally. It can be reused.

[0046] The above description is merely a preferred embodiment of the present utility model and is not intended to limit the scope of protection of the present utility model. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present utility model should be included within the scope of protection of the present utility model.

Claims

1. A self-tightening spring, comprising a spring body (24), a bolt hook (2), and a nut hook (3), wherein the spring body (24) is a cold-coil cross-section cylindrical helical tension spring, characterized in that: The bolt hook (2) is a straight hook, one end of which is connected to the spiral ring of the tension spring body (24), and the other end is a straight pry hook; the pry hook is used to insert into the bolt hook hole (4) of the bolt (6), and does not come out when the tension spring body (24) is fully loaded with tension, and can pry and hang the tension spring body (24). The nut hook (3) is an "L" shaped hook, the end of which is used to be inserted backward into the nut hook hole (5) on the hexagonal side (29) of the nut (9); In use, the tension spring body (24) surrounds one side of a bolt (6) from the bolt hook hole (4) to the nut hook hole (5) and is tightened. The tension of the tension spring body (24) is within its elastic range, so that the nut (9) is in a state of elastic self-tightening.

2. The self-tightening spring of claim 1, wherein: The self-tightening spring is made of an elastic metal selected from high-carbon steel wire, phosphor bronze, austenitic stainless steel, nickel-based alloys, or titanium alloys.

3. A threaded assembly for preventing loosening, comprising a bolt (6), a nut (9), and a self-tightening spring (1) as described in claim 1 or 2, characterized in that: The bolt (6) has a bolt hook hole (4) on the thread protruding from the nut (9) at the tail end. The hole is a radial through hole with a diameter larger than the wire diameter of the tension spring body (24); or, the bolt (6) has at least one radially open bolt hook groove (23) at the tail end. The nut (9) has at least one nut hook hole (5) on its hexagonal side (29), which is a blind hole (30) extending inward from the hexagonal side (29) and has a diameter larger than the wire diameter of the tension spring body (24). The straight pry hook of the self-tightening spring (1) is inserted into the bolt hook hole (4) or bolt hook groove (23) and pryed in place. The end of the "L"-shaped nut hook (3) is inserted backward into the nut hook hole (5). The tension spring body (24) is tightened, with one end connected to the bolt (6) and the other end connected to the nut (9). The tension of the tension spring body (24) causes the nut (9) to have a tendency to rotate in the direction of thread tightening.

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