A lock nut and screw assembly

Abstract

The application discloses a kind of anti-loose nut and screw rod assembly, comprising: the nut body with axially extending inner hole;Non-metal insert is arranged in the adjacent position of inner hole opening end and forms axial through shaft hole, and the inner wall is provided with the anti-loose muscle that extends in the axial direction;And the screw rod with outer thread, the free end top area of one end of screw rod is equipped with the anti-loose ratchet for cooperating with shaft hole.Working, when screw rod appears relative loosening direction rotation tendency, anti-loose muscle occurs elastic embedding and forms one-way mechanical blocking with anti-loose ratchet, to inhibit loosening rotation and keep connection pre-tightening force.The structure realizes directional stop under the premise of not increasing complex metal mechanism, and assembly is smooth, low in cost, and is suitable for miniaturization and batch fastening connection under vibration working condition.Optionally, non-metal insert can use nylon and be fixedly matched with nut, and anti-loose muscle can be helically extended in the axial direction and be arranged in the circumferential direction corresponding with ratchet, to further improve anti-vibration and durability.

Description

Technical Field

[0001] This invention relates to the field of fasteners and mechanical connection technology, and in particular to an anti-loosening nut and its nut-screw assembly that employs a non-metallic insert in conjunction with a ratchet at the end of a screw. Background Technology

[0002] Threaded connections are widely used in machinery, electronics, and transportation. Under conditions of vibration, impact, thermal cycling, and load relaxation, threaded pairs are prone to lateral micro-slippage and relative rotation, causing a decrease in preload and leading to loosening. To suppress loosening, existing technologies have proposed various anti-loosening methods, mainly including: elastic washers, chemical locking, deformation self-locking, wedge locking with added parts, and self-locking nuts with non-metallic inserts.

[0003] Non-metallic insert self-locking nuts (commonly nylon inserts) utilize a section of non-metallic material at the nut inlet. During assembly, the screw thread compresses the insert, generating additional friction and elastic recovery force, thus creating a continuous self-locking torque. This type of solution is simple in structure, low in cost, and suitable for mass production. However, its anti-loosening mechanism is primarily based on "friction maintenance," offering limited resistance to cumulative loosening under vibration. After oil contamination, temperature increases, or repeated assembly, the friction coefficient and deformation recovery capacity of the insert surface decrease, resulting in a significant attenuation of the holding torque and increased torque dispersion.

[0004] To improve vibration resistance, existing technologies have also incorporated techniques such as textured, knurled, or micro-protrusioned designs on the inner wall of the nut to enhance engagement with the thread and dissipate energy. However, such inner wall modifications primarily involve roughening or morphological disturbance of the friction surface, and still fall under the category of friction locking.

[0005] Some solutions attempt to incorporate grooves, steps, or ratchet features at the screw end or thread surface to create a cooperative locking mechanism with the opposite part. However, existing solutions primarily focus on direct engagement with metal parts, resulting in high structural rigidity and demanding machining precision. When used with non-metallic inserts, unstable engagement or irreversible damage after engagement can easily occur, making it difficult to balance assembly smoothness and reusability in conventional small-sized fasteners (such as M2 to M4).

[0006] Self-locking solutions based on non-metallic inserts offer manufacturing and cost advantages, maintaining the self-locking torque through "symmetrical friction," but lack unidirectional geometric locking against the "relative loosening direction" of the screw. While check valve / eccentric solutions based on metal mechanisms or multi-part structures can provide unidirectional blocking, they suffer from complex parts, higher costs, and significant issues with fretting wear and assembly consistency. Current technology still lacks a simple structure that can achieve directional engagement and unidirectional blocking of the screw's free end while using non-metallic inserts, possesses good assembly ease of introduction, maintains relatively stable self-locking characteristics after multiple assembly and disassembly, and can be compatible with eccentric arrangements or helical extensions to improve adaptability and vibration resistance bandwidth. Summary of the Invention

[0007] Based on the above situation, the industry still hopes to provide a structure that can form a controllable embedding / engaging relationship between the non-metallic insert and the screw end features without significantly increasing the number of parts and manufacturing complexity. This structure would generate a clear unidirectional blockage in the relative loosening direction of the screw, thereby reducing the tendency to rotate and the attenuation of preload under vibration, while also taking into account the requirements of miniaturization, low cost and consistency in mass production.

[0008] This invention provides an anti-loosening nut and screw assembly for suppressing loosening of a screw under vibration and impact conditions. The assembly includes: a nut body having an axially extending inner hole; a non-metallic insert disposed near the opening end of the inner hole and forming an axially penetrating shaft hole, the insert having an axially extending anti-loosening rib on its inner wall; and a screw having an external thread and a free end top region, the free end top being provided with an anti-loosening ratchet for engaging with the shaft hole. During operation, when the screw tends to rotate relative to the "loosening direction," the anti-loosening rib elastically deforms and embeds into the ratchet's tooth valley, forming a unidirectional mechanical block, thereby effectively suppressing loosening rotation; in the tightening direction, smooth assembly is achieved through the guide surface.

[0009] In some embodiments, the anti-loosening ratchet can be formed by dividing the thread into multiple tooth segments through grooves opened along the axial direction of the external thread at the free end of the screw; in the assembled state, the anti-loosening rib is at least partially embedded in the ratchet tooth valley to improve locking reliability. To further enhance the self-tightening capability, the non-metallic insert can be designed with a structure having a preset eccentricity relative to the axis of the nut body, and the anti-loosening rib is preferably arranged on the side with the minimum radial clearance in the eccentric direction. The insert is preferably made of non-metallic materials such as nylon. To balance lead-in and matching, the anti-loosening rib can extend spirally along the axial direction, and the anti-loosening ratchet can also be arranged in a ring array along the circumference and correspond to the circumferential distribution of the anti-loosening rib; the ends of the anti-loosening rib can be provided with lead-in chamfers or fillets to reduce assembly resistance; when the ratchet is arranged at spiral pitch intervals along the axial direction, its lead can match the spiral lead of the anti-loosening rib. The insert and the nut body are preferably fixedly fitted to ensure long-term stability.

[0010] The beneficial effects of this invention are as follows: while maintaining the simplicity, low cost, and ease of mass production of non-metallic inserts, it achieves clear blocking of the loosening direction through the unidirectional embedding and locking relationship of "anti-loosening rib - anti-loosening ratchet", which has stronger anti-vibration and anti-rotation capabilities than the traditional self-locking method that relies on friction; and through geometric refinement such as eccentric arrangement, spiral matching and end introduction, it can further improve the assembly smoothness and the stability of the holding torque, making it suitable for small-sized fasteners and high-consistency application scenarios. Attached Figure Description

[0011] Figure 1 This is a three-dimensional schematic diagram of the overall assembly of the anti-loosening nut and screw assembly of the present invention.

[0012] Figure 2 This is an exploded structural diagram of the present invention, showing the relative positional relationship of the nut body 10, the non-metallic insert 20 (with anti-loosening ribs 21 on the inner wall) and the screw 30.

[0013] Figure 3 The top view from the entrance shows the circumferential distribution of the eccentric holes of the insert 20 and the anti-loosening ribs 21, and the section line AA is marked.

[0014] Figure 4 The cross-sectional view along AA shows the fit between the non-metallic insert 20 and the thread 31, as well as the engagement relationship between the anti-loosening rib 21 and the thread / ratchet.

[0015] Figure 5 This is an enlarged schematic diagram of the top region 32 of the free end of the screw 30, showing the annular anti-loosening ratchet 33 formed by axial grooves. Detailed Implementation

[0016] The following combination Figures 1-5 The structure shown illustrates specific embodiments of the present invention. It should be understood that the following is intended to be illustrative and not limiting; materials, dimensions, tolerances, processes, and assembly sequences can be reasonably substituted or optimized without departing from the core concept defined in the claims.

[0017] like Figure 1 and Figure 2 As shown, the anti-loosening nut and screw assembly of this embodiment mainly includes a nut body 10, a non-metallic insert 20, and a screw 30. The nut body 10 has a conventional hexagonal shape, and an inner hole 11 is provided through it along the axial direction. The non-metallic insert 20 is fixed to the part near the opening end of the inner hole 11, that is, the position away from the nut assembly entrance. A through shaft hole 22 is formed inside the non-metallic insert 20. Figure 2 and Figure 4 As shown, several anti-loosening ribs 21 are arranged axially on the inner wall of the shaft hole 22. In this embodiment, the anti-loosening ribs 21 are long and thin strips, and the cross-section can be trapezoidal, triangular, wedge-shaped, etc.

[0018] Preferably, such as Figure 4 As shown in (AA), the shaft hole 22 of the non-metallic insert 20 is a micro-conical structure that gradually narrows from the inlet to the inside: the inlet hole diameter D1 is larger than the inner hole diameter D2, the hole wall is a linear conical surface and is evenly distributed with anti-loosening ribs extending along the axial direction; when tightening, the larger D1 provides smooth introduction first, and then the tapered gradually forms a progressive interference, so that the insert generates a continuously increasing radial pressure and friction on the thread; when a slight rotation occurs in the loosening direction, the "wedge-shaped self-tightening" component force generated by the conical surface causes the anti-loosening rib to fall to the ratchet tooth valley at the free end of the screw, realizing one-way locking, thereby suppressing rotational loosening.

[0019] Preferably, the cone angle θ ≈ 1°~15° and the cone segment length L k ≈0.1d~0.5d (d is the thread diameter).

[0020] The screw 30 has an external thread 31 machined on it, and a free end top region 32 is formed at one end of the screw 30. The free end top region 32 is as follows: Figure 5 The assembly includes anti-loosening ratchet teeth 33 for engaging with the shaft hole 22. Preferably, the anti-loosening ratchet teeth 33 form a circumferential array. During assembly, the screw 30 is screwed into the nut body 10 from the inlet end. The external thread 31 makes surface contact with the anti-loosening rib 21 of the shaft hole 22, forcing the non-metallic insert 20 to undergo slight elastic radial compression, thereby establishing basic self-locking friction. Under the combined action of elastic deformation and guidance, the anti-loosening rib 21 actively enters the tooth valley position of the anti-loosening ratchet teeth 33 and forms a partial embedding, thus establishing a mechanical locking engagement in the loosening direction. In the tightening direction, the anti-loosening rib 21 contacts the driving surface of the ratchet teeth 33 and is guided by the inclined surface, resulting in less assembly resistance than in the loosening direction, thereby achieving a unidirectional blocking anti-loosening mechanism. Compared with traditional nylon lock nuts that rely on symmetrical friction, this significantly improves the ability to suppress micro-rotation caused by vibration and reduces preload attenuation.

[0021] Furthermore, the anti-loosening ratchet 33 is not a separately added independent toothed component, but rather directly utilizes the external thread 31 at the free end of the screw 30, achieved by creating a groove perpendicular to the thread axis, such as... Figure 5As shown. These grooves are preferably arranged at equal intervals in the circumferential position of the top region 32 of the free end, dividing several thread segments of the free end into multiple tooth segments. The outer edge of each tooth segment constitutes the blocking surface of the ratchet, while the bottom of the groove constitutes the tooth valley of the ratchet. The grooves can be formed by CNC milling, laser etching, rolling extrusion, or cold punching. For the M3×0.5 specification, the width of the groove can be 0.20–0.35 mm, the groove depth can be 0.10–0.25 mm, and the number of grooves can be, for example, 12–24, to maintain a sufficient number of teeth without significantly weakening the thread load-bearing capacity. Preferably, the blocking surface of each tooth segment forms a large included angle α with respect to the end face of the free end, for example, 20°–60°, and the driving surface forms a smaller included angle β, for example, 5°–25°, satisfying α > β, to ensure that the locking torque in the loosening direction is significantly greater than the guiding resistance in the tightening direction. Furthermore. Preferably, the end of the groove should be rounded to avoid stress concentration, and the outer edge of the tooth segment can maintain the original rounded corner of the thread or be appropriately sharpened. This helps to reliably engage with the anti-loosening rib 21, and prevents the insert material from being cut during repeated disassembly and assembly.

[0022] Furthermore, after the screw 30 reaches the designed preload, the non-metallic insert 20 is in an elastically compressed state, and the radial interference of the shaft hole 22 relative to the thread makes the anti-loosening rib 21 form a stable fit with the thread side. When the assembly is subjected to external vibration, causing the screw 30 to attempt to rotate in the loosening direction, due to the large angle of the blocking surface of the anti-loosening ratchet 33, the anti-loosening rib 21 generates a resultant force decomposition component along the axial and radial directions on the blocking surface, causing the anti-loosening rib 21 to locally deflect and "jump in" towards the tooth valley. This process is equivalent to the transformation from a friction pair to a local "claw-rat" meshing pair, so that the rotation in the loosening direction is restricted by geometric engagement. In order to ensure smooth assembly and reliable locking, this embodiment controls the embedding depth h of the end of the anti-loosening rib 21 into the tooth valley to be in the range of 0.05 to 0.20 mm; when the anti-loosening rib 21 adopts a wedge-shaped section, it provides compliant guidance in the assembly direction and sufficient geometric engagement in the loosening direction.

[0023] Figure 3A top-view diagram from the nut inlet end is provided, showing that the shaft hole 22 of the non-metallic insert 20 has a predetermined eccentricity relative to the geometric axis of the nut body 10, forming an "eccentric hole" layout. In this arrangement, there are a minimum radial clearance side and a maximum radial clearance side between the shaft hole 22 and the thread 31 in the circumferential direction. Preferably, the anti-loosening rib 21 is preferentially arranged on the minimum radial clearance side in the eccentric direction, and the rib height can be appropriately increased or the local hole diameter reduced on this side. During assembly, the screw 30 is screwed in along the driving direction and automatically aligned, and the non-metallic insert 20 fits relatively uniformly under elastic deformation. Once rotation occurs along the loosening direction, the geometric relationship of the thread relative to the shaft hole 22 will drive the contact area to "climb" towards the minimum radial clearance side, which is equivalent to converting the rotational trend into radial compression of the insert, thus forming a "tightening as it loosens" wedge-shaped self-tightening effect. For nuts of sizes M2-M8, the eccentricity can be 0.02d to 0.08d (d is the nominal diameter of the thread), preferably 0.03d to 0.05d.

[0024] Furthermore, the non-metallic insert 20 is preferably made of nylon material, such as PA66, PA46, PA6T, or their copolymerized modification system. Nylon material has good wear resistance, elastic modulus, and recovery characteristics, and can maintain stable deformation recovery and interlocking after repeated assembly and disassembly; compared with polyoxymethylene or polycarbonate, nylon exhibits higher heat resistance and fatigue resistance under dry friction conditions with metal threads.

[0025] Preferably, except that the anti-loosening reinforcement 21 is designed as a straight reinforcement in the same direction as the axial direction (e.g. Figure 4 As shown in the figure, in this embodiment, it is more preferable that the spiral extends along the axial direction. The spiral ribs make the contact state between the ribs and the threads linear and progressive during the tightening process, and the assembly torque is smoother. In the loosening direction, the spiral path decomposes the rotational motion into micro-displacement along the axial direction, making it easier for the anti-loosening rib 21 to cross the blocking surface of the ratchet 33 and fall stably into the tooth valley position, thereby improving the locking consistency.

[0026] like Figure 5As shown, the anti-loosening ratchet 33 is preferably arranged in a ring array along the circumference, and the number can be selected according to the diameter, the required holding torque, and the smoothness of assembly. The number of ratchet teeth is, for example, 12 to 24, corresponding to the number N (e.g., 4 to 8) of the anti-loosening ribs 21. In this embodiment, in order to obtain reliable insertion at any assembly angle, the circumferentially arrayed ratchet teeth 33 and the spirally or linearly distributed anti-loosening ribs 21 are arranged in a corresponding manner in the circumferential direction: specifically, N anti-loosening ribs 21 can be arranged at equal angular intervals when the insert 20 is formed, and M tooth segments are distributed at equal angular intervals in the top region 32 of the free end of the screw (M is usually an integer multiple of N). In this way, when the screw 30 enters the insert 20 and is pre-tightened, regardless of the initial phase, at least one or more distribution positions will achieve effective insertion of the rib-tooth. A "staggered array" method can also be used, so that two adjacent sets of ratchet teeth are staggered at a certain angle (e.g., 10° to 30°) in the circumferential direction to avoid systematic "gaps" caused by local wear after multiple assembly and disassembly.

[0027] Preferably, in order to balance assembly smoothness and embedding reliability, this embodiment provides an induction chamfer or rounded corner at the end of the anti-loosening rib. The induction structure provides a smooth guiding effect in the tightening direction, so that the first contact between the rib and the tooth gradually transitions from point / linear to surface contact, reducing the initial tightening peak torque and reducing scratches and crushing on the insert surface.

[0028] like Figure 2 and Figure 4 In summary, the non-metallic insert 20 and the nut body 10 are fixedly fitted to ensure that the insert will not rotate or move axially during repeated assembly and disassembly. This embodiment preferably employs a two-stage injection molding process: first, the nut body 10 undergoes surface pretreatment, and a positioning ring, knurling, or shallow groove is machined circumferentially at the inlet of the inner hole 11. Then, the nut is placed into the injection mold, and nylon material is injected to form a mechanical lock at the ring and knurling. Alternatively, a combination of press-fitting and partial riveting / adhesive bonding can be used: for example, the outer circle of the insert 20 is press-fitted into the inner hole 11 with an interference fit.

[0029] This invention introduces a unidirectional locking mechanism of "anti-loosening rib - anti-loosening ratchet" on the basis of traditional nylon insert self-locking. Simultaneously, optimizations such as eccentric self-tightening, helical phase matching, and rib end introduction ensure both smooth assembly in the assembly direction and resistance to loosening in the loosening direction. Compared with existing structures that rely solely on friction, this invention exhibits a lower rotation threshold and slower holding torque decay under harsh conditions such as random vibration, impact loads, and thermal cycling. Furthermore, the solution retains the advantages of fewer parts, lower manufacturing costs, and ease of mass production, making it particularly suitable for the highly consistent assembly and long-term stable application of small-sized fasteners. The above embodiments can be used individually or in any combination; any changes made to the rib shape, ratchet morphology, materials, and fixing methods within the spirit of the claims should be covered within the scope of protection of this invention.

Claims

1. A locking nut and screw assembly, characterized in that, It includes: The nut body has an inner hole extending axially; A non-metallic insert is disposed near the opening end of the inner hole and forms an axially penetrating shaft hole. The inner wall of the non-metallic insert is provided with an axially extending anti-loosening rib. A screw having an external thread and a free end top region at one end thereof, the free end top region being provided with anti-loosening ratchet teeth for engaging with the shaft hole; The anti-loosening rib and the anti-loosening ratchet engage in a one-way blocking action in the relative loosening direction of the screw, thereby preventing the screw from loosening and rotating.

2. The component as claimed in claim 1, wherein, The anti-loosening ratchet is formed by dividing the thread into multiple tooth segments by axially opening grooves on the thread surface of the external thread at the free end.

3. The component as claimed in claim 1 or 2, wherein, The anti-loosening rib is at least partially embedded in the groove of the anti-loosening ratchet in the assembled state.

4. The component as claimed in claim 1, wherein, The non-metallic insert has an eccentric structure, and the anti-loosening rib is located on the side with the minimum radial gap in the eccentric direction.

5. The component as claimed in claim 1, wherein, The non-metallic insert is made of nylon material.

6. The component of claim 1, wherein, The anti-loosening reinforcement extends spirally along the axial direction.

7. The component of claim 1, wherein, The anti-loosening ratchet teeth are arranged in a ring array along the circumference, corresponding to the distribution of the anti-loosening ribs in the circumference.

8. The component of claim 1, wherein, The end of the anti-loosening rib is provided with a guide chamfer or rounded corner to guide the anti-loosening ratchet and reduce assembly resistance.

9. The component of claim 1, wherein, The non-metallic insert is fixedly fitted to the nut body.

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