An elastic locking bolt suitable for a vibrating environment

Abstract

This invention discloses an elastic locking bolt suitable for vibration environments, relating to the field of bolt technology. It includes a bolt head and a threaded rod, the threaded rod having a smooth section and a threaded section. At least one axially non-through groove is formed on the outer circumferential surface of the smooth section, one end of which is near the head and the other end terminates in a closed end wall. After assembly, the groove and the wall of the mounting hole form a variable volume cavity. The smooth section also has a radial blind hole communicating with the groove, which sequentially accommodates an elastic element and a steel ball from the inside out. The steel ball protrudes from the outer circumferential surface and radially retracts when the variable volume cavity is compressed. This invention suppresses radial fretting wear of the smooth section through the elastic support of the steel ball, and delays preload decay through the damping effect of the variable volume cavity. The structure is simple and compact, and it possesses reliable anti-loosening and preload retention capabilities under vibration conditions.

Description

Technical Field

[0001] This invention relates to the field of bolt technology, specifically to an elastic locking bolt suitable for vibration environments. Background Technology

[0002] Bolted connections are prone to loosening and failure under vibration conditions. Existing anti-loosening technologies are mainly divided into two categories: friction anti-loosening and mechanical anti-loosening.

[0003] Friction-based anti-loosening relies on increasing the frictional torque of the threaded pair, but under high-frequency, low-amplitude vibration, fretting wear on the contact surface leads to a continuous decrease in preload, eventually causing rotational loosening. Mechanical anti-loosening can prevent macroscopic rotation, but it has no ability to inhibit the decrease in preload caused by fretting wear, and it involves many parts and is cumbersome to install.

[0004] The two types of technologies mentioned above face a common contradiction: structures that can suppress fretting wear lack mechanical locking capabilities, while structures that can mechanically lock cannot compensate for the preload loss caused by fretting wear. Especially for radial fretting between the bolt's smooth shank and the hole wall of the connected component, existing technologies lack simple and effective means of suppression, and this is precisely the critical interface for the transmission of lateral vibration loads. Therefore, this invention proposes an elastic locking bolt suitable for vibration environments. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing an elastic locking bolt suitable for vibration environments. It can provide damping suppression for high-frequency fretting and reliable locking when macroscopic rotational tendencies occur, thus solving the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An elastic locking bolt suitable for vibration environments includes a bolt head and a threaded rod. The threaded rod includes a smooth section and a threaded section. At least one non-through groove extending axially is formed on the outer peripheral surface of the smooth section. One end of the non-through groove extends to a position near the bolt head, and the other end terminates at a closed end wall before the junction of the smooth section and the threaded section, so that the non-through groove and the mounting hole wall of the connected part form a variable volume cavity. At least one radial blind hole is also formed on the smooth section. The radial blind hole communicates with the non-through groove. An elastic element and a steel ball are sequentially accommodated in the radial blind hole from the inside to the outside. The steel ball protrudes from the outer peripheral surface of the smooth section and retracts radially when the variable volume cavity is compressed.

[0007] Preferably, the polished rod section is also provided with an annular groove around its axis, the annular groove being located between the non-through groove and the bolt head; an open C-type elastic check ring is accommodated in the annular groove, the outer diameter of the C-type elastic check ring in the free state is greater than the outer diameter of the polished rod section and less than the maximum outer diameter of the bolt head, so that the outer edge of the C-type elastic check ring forms an interference contact with the wall of the mounting hole after assembly.

[0008] Preferably, the depth of the non-through groove gradually decreases axially from the end closest to the bolt head toward the closed end wall to form a wedge-shaped variable volume cavity.

[0009] Preferably, the variable volume cavity is pre-filled with high-viscosity grease.

[0010] Preferably, two non-through grooves are symmetrically arranged on the outer peripheral surface of the polished rod section.

[0011] Preferably, the elastic element is a pre-compression spring.

[0012] Preferably, the radial blind hole is formed at the bottom of the non-through groove.

[0013] Preferably, the threaded section is a self-tapping thread, and the non-through groove extends from the smooth section to the root region of the threaded section.

[0014] Preferably, the portion of the non-through groove located at the root region of the thread segment constitutes a chip-receiving groove and a closed air cavity.

[0015] Preferably, the cross-section of the C-type elastic check ring is circular, and the axial width of the annular groove is greater than the axial thickness of the C-type elastic check ring, so as to allow the C-type elastic check ring to rotate and expand radially within the groove.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention creates a variable volume cavity between the bolt and the hole wall of the connected component by setting a non-through groove and a radial steel ball elastic support structure on the smooth rod section, thereby applying a radial elastic preload. Under lateral vibration, the steel ball remains in contact with the hole wall under the push of the elastic element, effectively suppressing radial fretting wear between the smooth rod section and the mounting hole, reducing the preload attenuation caused by fretting at the source. At the same time, the pressure change in the variable volume cavity can absorb some vibration energy, delaying the loosening process of the threaded pair. This device further incorporates the structural design of a C-type elastic check ring. After assembly, the bolt forms a reliable interference contact with the hole wall and a one-way mechanical lock, preventing macroscopic rotation and loosening of the bolt even when the preload is partially lost. The check ring can also adaptively rotate and radially expand within the annular groove, avoiding local jamming caused by installation eccentricity or vibration offset, thus achieving a synergistic function of mechanical anti-loosening and wear compensation. This solution integrates fretting wear suppression and mechanical locking into a single structure of the bolt's smooth shank, eliminating the need for additional washers, cotter pins, or other parts. It is easy to install and has a compact structure. The closed air chamber and chip-holding space formed by the non-through groove further enhance its applicability in blind hole conditions such as self-tapping threads. Overall, it offers a comprehensive advantage in vibration environments, possessing strong preload retention, radial positioning stability, and high anti-loosening reliability. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the overall structure of the present invention from another perspective; Figure 3 This is a schematic cross-sectional view of the overall structure of the present invention; Figure 4 for Figure 3 Enlarged view of point A in the middle; Figure 5 This is a schematic diagram showing the position of the C-type elastic check ring of the present invention; Figure 6 This is a schematic diagram of the variable volume cavity structure of the present invention; Figure 7 This is a schematic diagram of a bolt structure in which the threaded section is a self-tapping thread, according to the present invention. Figure 8 This is a cross-sectional schematic diagram of a non-through groove in a bolt with a self-tapping thread section according to the present invention.

[0019] Drawing number explanation: 1. Bolt head; 2. Plain section; 3. Threaded section; 4. Non-through groove; 5. Radial blind hole; 6. Elastic element; 7. Steel ball; 8. Annular groove; 9. C-type elastic check ring; 10. Closed end wall; 11. Variable volume cavity. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings.

[0021] The following description is intended to disclose the invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious modifications will be apparent to those skilled in the art. The basic principles of the invention defined in the following description can be used in other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0022] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or position based on the orientation or positional relationship shown in the accompanying drawings. They are merely simplifications for the convenience of describing this invention and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this invention.

[0023] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0024] Example 1: Please refer to Figure 1-6 A resilient locking bolt suitable for vibration environments is disclosed. The bolt comprises an integrally formed bolt head 1 and a threaded shank. The shank is axially divided into a smooth section 2 and a threaded section 3 from the bolt head 1 to the tail end. The smooth section 2 is a cylindrical section with an outer diameter slightly smaller than the diameter of the mounting hole of the connected parts. The threaded section 3 is used to engage with the internal threaded hole of one of the connected parts to generate an axial preload to clamp multiple connected parts. At least one axially extending non-penetrating groove 4, preferably two, is formed on the outer circumferential surface of the smooth section 2 and is symmetrically arranged along the axis of the smooth section 2. One end of each non-penetrating groove 4 extends to a position near the lower end face of the bolt head 1, but does not penetrate to the head end face. The other end terminates at a closed end wall 10 before the junction of the smooth section 2 and the threaded section 3. This closed end wall 10 is the solid material boundary of the non-penetrating groove 4 at its axial end, making the non-penetrating groove 4 an overall blind groove structure with one end open and the other end closed. When the smooth section 2 of the bolt is inserted into the mounting hole of the connected component, the open side of the non-through groove 4 is sealed by the wall of the mounting hole, thus forming a closed chamber with variable volume between the inner surface of the non-through groove 4 and the cylindrical surface of the hole wall. This chamber is called the variable volume cavity 11. The depth of the non-through groove 4 is not consistent throughout the axial direction, but gradually decreases from the end near the bolt head 1 towards the closed end wall 10, thus forming a wedge-shaped profile with decreasing depth along the axial direction. This results in the variable volume cavity 11 having a larger volume near the bolt head 1 and a smaller volume near the closed end wall 10, thereby constituting a wedge-shaped variable volume cavity.

[0025] In this design, after the bolt assembly is completed, when the smooth rod section 2 is subjected to lateral vibration load and undergoes radial displacement relative to the hole wall, the volume of the variable volume cavity 11 will change accordingly. The wedge-shaped profile with gradually varying depth of the non-through groove 4 makes the volume change and radial displacement have a non-linear relationship, which helps to provide differentiated damping responses under different amplitudes. To further enhance the dissipation capacity of vibration energy, the variable volume cavity 11 is pre-filled with high-viscosity grease before assembly. The viscous shear resistance of the grease can convert part of the vibration mechanical energy into heat energy during the cavity volume change, thereby suppressing fretting wear and delaying the decay of preload.

[0026] It should be noted that a radial blind hole 5 is also provided at the bottom of each non-penetrating groove 4 on the smooth rod section 2. The axis of the radial blind hole 5 extends radially along the smooth rod section 2 and intersects with the bolt axis. The internal space of the radial blind hole 5 is completely connected with the internal space of the non-penetrating groove 4, and the bottom of the blind hole terminates inside the material of the smooth rod section 2, without penetrating to the opposite surface of the smooth rod section 2. An elastic element 6 and a steel ball 7 are sequentially accommodated from bottom to outside in the radial blind hole 5. The elastic element 6 is specifically a pre-compressed helical spring, one end of which abuts against the bottom surface of the bottom hole of the radial blind hole 5, and the other end abuts against the bottom spherical surface of the steel ball 7. Under the preload of the spring, part of the spherical crown of the steel ball 7 protrudes beyond the outer circumference of the smooth rod section 2, that is, the steel ball 7 is higher than the outer circumference of the smooth rod section 2 in its free state. When the smooth section 2 of the bolt is inserted into the mounting hole, the protruding part of the steel ball 7 first contacts the hole wall and, under radial pressure, forces the spring to compress further. The steel ball 7 then retracts inward along the radial blind hole 5, allowing the smooth section 2 to pass smoothly through the mounting hole. After assembly, the spring still maintains a certain amount of compression, and the steel ball 7 continues to press against the mounting hole wall under the spring's restoring force, forming a radial elastic preload.

[0027] In this design, under vibration, when a lateral load attempts to separate or displace the smooth rod section 2 from the hole wall, the steel ball 7 and spring system respond in real time. The steel ball 7 floats radially with the displacement of the hole wall, and the volume of the variable volume cavity 11 changes accordingly. The damping effect of the internal grease and the elastic restoring force of the spring work together to absorb and dissipate vibration energy, suppressing radial fretting wear between the smooth rod section 2 and the hole wall. Since fretting wear is one of the important causes of the decrease in preload of threaded connections, this design delays the attenuation process of preload by suppressing fretting wear, thereby extending the effective service life of the bolt connection against loosening.

[0028] In this design, the polished rod segment 2 has an annular groove 8 that encircles the entire circumference of the polished rod segment 2 on the side of the non-through groove 4 near the bolt head 1. This annular groove 8 is located between the axial portion of the non-through groove 4 and the bearing surface of the bolt head 1, and its bottom diameter is smaller than the outer diameter of the polished rod segment 2. An open C-type elastic check ring 9 is housed within this annular groove 8. The C-type elastic check ring 9 is made of elastic metal material and has an open gap; its cross-sectional shape is preferably circular. In its free state, the outer diameter of the C-type elastic check ring 9 is designed to be larger than the outer diameter of the polished rod segment 2, but smaller than the maximum outer diameter of the bolt head 1. When the bolt is inserted into the mounting hole, the C-type elastic check ring 9 is constrained by the hole wall and elastically contracts, reducing the open gap and tightly fitting the outer edge of the ring against the hole wall. After assembly, the C-type elastic check ring 9 relies on its own elastic restoring force to form a stable interference contact between its outer edge and the wall of the mounting hole. The radial pressure and friction generated by the interference contact constitute a one-way mechanical locking mechanism: when the bolt is subjected to a reverse rotational torque that causes it to loosen in a vibrating environment, the frictional resistance between the C-type elastic check ring 9 and the hole wall prevents the bolt from rotating macroscopically. Even if the preload between the threaded pairs is partially lost due to fretting wear, the locking effect of the check ring can still prevent the bolt from loosening.

[0029] Furthermore, the axial width of the annular groove 8 is designed to be greater than the axial thickness of the C-type elastic check ring 9, and the groove depth of the annular groove 8 has a certain allowance in the radial direction. This allows the C-type elastic check ring 9 to rotate around its own axis within the groove, and also to expand and contract to a certain extent in the radial direction. This allowance enables the check ring to adaptively adjust its posture during installation, avoiding local jamming or concentrated deformation caused by installation eccentricity or misalignment between the smooth rod section 2 and the hole wall. This ensures that the check ring maintains reliable interference locking performance throughout its entire lifespan.

[0030] It should be noted that the installation and use process of the bolts in this embodiment is as follows: First, align and stack the connected parts, ensuring the mounting holes are aligned. Align one end of the threaded section 3 of the bolt with the mounting hole and push the smooth section 2 axially. During this pushing process, the steel ball 7 first contacts the hole wall, and after being compressed, retracts radially along the blind hole 5, further compressing the spring; simultaneously, the C-type elastic check ring 9, constrained by the hole wall, elastically contracts, its outer edge adhering to the hole wall and sliding into the hole. When the bearing surface of the bolt head 1 approaches the surface of the connected part, rotate the bolt to screw the threaded section 3 into the internal threaded hole of the lower connected part, and continue tightening until the design preload is reached.

[0031] After tightening, the bolt head 1 presses against the surface of the connected parts, and the smooth section 2 is completely located inside the mounting hole. At this time, the steel ball 7 remains in contact with the hole wall under the spring thrust, and the non-through groove 4 and the hole wall form a variable volume cavity 11. The grease in the cavity fills the space around the steel ball 7 and the non-through groove 4. The C-type elastic check ring 9 is in a constrained state in the annular groove 8, and its outer edge forms a reliable interference friction lock with the hole wall.

[0032] When the connecting structure is subjected to lateral vibration, the vibration load attempts to cause radial relative movement between the smooth rod section 2 and the hole wall. The radial elastic support formed by the steel ball 7 and the spring immediately responds: the steel ball 7 compresses or expands following the displacement of the hole wall, and the volume of the variable volume cavity 11 changes accordingly. The grease inside the cavity is squeezed and sheared, generating damping energy dissipation. At the same time, the frictional torque between the C-shaped elastic check ring 9 and the hole wall resists the rotation and loosening of the bolt. The design of the wedge-shaped variable volume cavity makes the volume change sensitive under micro-amplitude vibration and the damping effect significant; under large-amplitude vibration, the volume change gradient increases, and the radial compensation stroke of the steel ball 7 also increases accordingly, maintaining effective contact with the hole wall.

[0033] The entire system achieves the absorption and dissipation of lateral vibration energy and the locking of macroscopic rotation through the combined action of the stiffness of the elastic element 6, the viscosity of the damping medium, and the friction of the check ring. This ensures that reliable preload is maintained for a long time under vibration conditions, guaranteeing the safety of the bolt connection.

[0034] Example 2: In this solution, please refer to... Figure 7 and Figure 8For applications where the connected components are thin-plate structures and internal threaded holes cannot be pre-machined due to plate thickness limitations, a self-tapping elastic locking bolt is provided. This bolt is suitable for directly connecting two or more thin plates using the bolt's own tapping capability, eliminating the need for pre-drilling threads on the thin plates or installing a nut on the back. The bolt has a simple structure, consisting only of the self-tapping bolt body and a sealant layer pre-coated on the surface of the threaded section 3. The bolt body also includes a smooth section 2 and a threaded section 3, the difference being that the threaded section 3 uses a self-tapping thread profile, i.e., the thread crest is sharper and the flank angle is suitable for pressing or cutting the plate material to form an internal thread. A more important structural change is that the non-through groove 4 on the smooth section 2 does not terminate at the junction of the smooth section 2 and the threaded section 3 in the axial direction, but continues to extend towards the threaded section 3 until it enters the root region of the threaded section 3. Specifically, the non-through groove 4 starts near the bolt head 1, axially spans the entire smooth section 2, and extends a certain length along the thread root following the helical direction of the thread. The portion of the non-through groove 4 extending to the root region of thread segment 3 is part of the same continuous channel as the non-through groove 4 on the smooth section 2, but it serves a dual function. During the bolt's insertion into the smooth hole of the thin plate, the crest of the self-tapping thread compresses or slightly cuts the plate material, causing plastic flow and forming an internal thread profile that meshes with the bolt's external thread. This forming process generates metal debris and simultaneously creates a locally enclosed space between the thread root and the plate material. Because the non-through groove 4 in the root region of thread segment 3 provides additional chip-carrying space, the debris generated by compression or cutting is collected and contained within this non-through groove 4, preventing a sharp increase in the tapping torque or thread damage caused by debris accumulation at the thread interface.

[0035] Meanwhile, the air in the non-through groove 4 is gradually sealed within the non-through groove 4 at the root of the thread during the thread forming process, and cannot escape outward. When the bolt is fully tightened, the non-through groove 4 in the root region of the thread segment 3 is jointly sealed by the sheet material and the bolt body. The air sealed within the groove, together with the contained metal debris, constitutes a special metal-gas composite spring. This composite spring has non-linear stiffness characteristics. When the thin sheet structure is subjected to vibration excitation, the small relative displacement generated between the threaded pairs will compress or stretch the gas in the sealed air cavity. The mutual friction between the debris particles and the viscosity between the gas and the groove wall provide additional damping, thereby suppressing vibrations over a wide frequency range. This structure is particularly suitable for sheet metal chassis, thin-walled pipes, automotive body panels, and other applications where deep threaded holes cannot be installed due to thickness limitations. It is also easy to install and requires no additional auxiliary locking elements.

[0036] It should be noted that the installation steps of the bolt in this embodiment are similar to those of conventional self-tapping bolts, but due to the special internal structure, its performance is superior. Before installation, the bolt thread section 3 is pre-coated with sealant, which remains uncured during bolt storage. During installation, the holes of the plates to be connected are aligned, the front end of the thread section 3 of the self-tapping bolt is inserted into the hole, and the bolt head 1 is rotated using a tool. Under the combined action of axial thrust and rotational torque, the crest of the self-tapping thread gradually squeezes into the plate material, forming an internal thread. As the insertion depth increases, the non-penetrating groove 4 in the thread root region continuously transports and stores debris backward, while simultaneously sealing air within the groove. The tightening process ends when the bearing surface of the bolt head 1 presses against the surface of the connected parts. At this time, the closed air cavity and debris mixture in the non-penetrating groove 4 at the thread root of the thread section 3 form a metal-gas composite spring, the variable volume cavity 11 on the smooth rod section 2 and the steel ball 7 spring system form a radial elastic damping support, and the C-type elastic check ring 9 provides rotational locking friction torque in the hole area. The sealant gradually cures after the bolts are tightened, filling the gaps in the threaded joints. This not only enhances the anti-loosening torque of the threaded connection but also provides a sealing and corrosion-resistant function.

[0037] During subsequent vibration service, the radial damping system of the smooth rod section 2 suppressed fretting wear between the smooth rod section 2 and the wall of the thin plate hole, while the composite spring at the root of the threaded section 3 absorbed the vibration energy at the threaded interface. Through this structural configuration, the elastic locking bolt exhibits excellent preload retention capability and long-life anti-loosening reliability under thin plate vibration connection conditions.

[0038] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and structural principles of the present invention have been shown and explained in the embodiments, and any modifications or variations of the implementation of the present invention may be made without departing from the principles.

Claims

1. A resilient locking bolt suitable for vibration environments, comprising a bolt head (1) and a threaded rod, the threaded rod comprising a smooth section (2) and a threaded section (3); Its features are: At least one non-through groove (4) extending axially is provided on the outer peripheral surface of the smooth rod section (2). One end of the non-through groove (4) extends to a position close to the bolt head (1), and the other end terminates at the closed end wall (10) before the junction of the smooth rod section (2) and the threaded section (3), so that the non-through groove (4) and the mounting hole wall of the connected part form a variable volume cavity (11). At least one radial blind hole (5) is also provided on the smooth rod section (2). The radial blind hole (5) is connected to the non-through groove (4). The radial blind hole (5) contains an elastic element (6) and a steel ball (7) from the inside to the outside. The steel ball (7) protrudes from the outer circumference of the smooth rod section (2) and retracts radially when the variable volume cavity (11) is compressed.

2. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The smooth rod section (2) is also provided with an annular groove (8) around its axis. The annular groove (8) is located between the non-through groove (4) and the bolt head (1). An open C-type elastic check ring (9) is housed in the annular groove (8). The outer diameter of the C-type elastic check ring (9) in its free state is greater than the outer diameter of the smooth rod section (2) and smaller than the maximum outer diameter of the bolt head (1), so that the outer edge of the C-type elastic check ring (9) after assembly forms an interference contact with the wall of the mounting hole.

3. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The depth of the non-through groove (4) gradually decreases axially from the end near the bolt head (1) toward the closed end wall (10) to form a wedge-shaped variable volume cavity.

4. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The variable volume cavity (11) is pre-filled with high-viscosity grease.

5. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: Two non-through grooves (4) are symmetrically arranged on the outer peripheral surface of the smooth rod section (2).

6. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The elastic element (6) is a pre-compression spring.

7. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The radial blind hole (5) is opened at the bottom of the non-through groove (4).

8. The elastic locking bolt suitable for vibration environments according to claim 1, characterized in that: The threaded section (3) is a self-tapping thread, and the non-through groove (4) extends from the smooth section (2) to the root region of the threaded section (3).

9. A resilient locking bolt suitable for vibration environments according to claim 8, characterized in that: The portion of the non-through groove (4) located in the root region of the thread segment (3) constitutes a chip groove and a closed air cavity.

10. A resilient locking bolt suitable for vibration environments according to claim 2, characterized in that: The cross-section of the C-type elastic check ring (9) is circular, and the axial width of the annular groove (8) is greater than the axial thickness of the C-type elastic check ring (9) so as to allow the C-type elastic check ring (9) to rotate and expand radially within the groove.

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