A super bolt and nut for gravity support

Abstract

This invention belongs to the field of fastener technology and discloses a super bolt nut for gravity support, comprising a double-ended stud. A nut and a preload are threaded onto both ends of the double-ended stud, respectively. A hardened washer is movably fitted onto the outer surface of the double-ended stud near the end of the preload. A push screw is threaded uniformly onto the inside of the preload. A push block is installed at the end of the push screw near the hardened washer. The end face of the nut near the hardened washer has an arc surface. This invention achieves efficient force transmission and uniform stress distribution through an innovative elastic nut internal thread design, reducing inter-thread pressure, minimizing the risk of thread seizure, and extending bolt life. The stress distribution is optimal, especially at a 6° tilt angle, improving structural stability and safety. The nut is an elastic nut; the arc surface deforms under force, resulting in more complete contact.

Description

Technical Field

[0001] This invention belongs to the field of fastener technology, specifically a super bolt and nut for gravity support. Background Technology

[0002] Traditional bolts, when under load, may lack sufficient deformation coefficients in their internal thread design, preventing effective force transmission to subsequent threads. This can lead to some threads being overstressed while others are understressed, reducing overall force transmission efficiency. Uneven bolt stress can cause some threads to bear excessive stress, becoming stress concentration points. These areas are more prone to fatigue failure, leading to premature bolt failure. Uneven stress can also cause uneven pressure distribution between threads, with some threads bearing excessive pressure, increasing the risk of thread seizure. This not only affects bolt disassembly and replacement but can also damage equipment and systems. Under high loads, bolts with uneven stress may fracture or fail due to excessive local stress, threatening the structural stability and safety of equipment and systems. Bolt failure and damage caused by uneven stress may require more frequent maintenance and replacement, increasing maintenance costs and potentially impacting normal equipment operation and production efficiency. Therefore, a gravity-supported super bolt with uniform stress distribution is needed. Summary of the Invention

[0003] The purpose of this invention is to provide a super bolt nut for gravity support to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a super bolt nut for gravity support, comprising a double-ended stud, wherein a nut and a preload are respectively threaded onto both ends of the double-ended stud, a hardened washer is movably fitted onto the outer surface of the double-ended stud near one end of the preload, a push screw is uniformly threaded onto the inside of the preload, a push block is installed at the end of the push screw near the hardened washer, and the end face of the nut near the hardened washer has an arc surface.

[0005] Preferably, the inner wall of the nut is uniformly fixed with inclined blocks, the bottom end of the inclined blocks is provided with protrusions, and the outer surface of the double-ended stud is threaded with a fastening sleeve located inside the nut.

[0006] Preferably, one end of the fastening sleeve and the inclined surface of the inclined block are on the same slope, and their contact surfaces are in parallel contact.

[0007] Preferably, the protrusion is made of rubber asphalt material, which deforms when compressed and fits tightly with the thread at the end of the double-ended stud.

[0008] Preferably, the arc surface undergoes slight deformation under stress to ensure uniform stress distribution.

[0009] Preferably, the nut is an elastic nut with a settlement value of 0.24 mm. When the angle of the nut is 6°, the stress difference is minimized, and the maximum stress is also minimized, resulting in more uniform force distribution.

[0010] Preferably, the deformation coefficient of the internal thread of the nut is higher than that of the external thread, so that the elastic deformation of the thread can better transmit the force to the next thread and make the force distribution more uniform.

[0011] Preferably, the thread tolerance grade of the nut is 6g-6H, 2A-2B.

[0012] Preferably, the hardness of the hardened washer is selected to be within the range of hardness greater than that of the nut and less than that of the stud.

[0013] Preferably, the inclined blocks and protrusions are grouped together, with a total of ten groups evenly distributed on the inner wall of the nut.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. This invention utilizes the internal thread design of the elastic nut, which has a higher deformation coefficient. Compared to traditional bolts, it can more effectively transmit force to the next thread stage. The elastic deformation between threads not only ensures uniform force distribution and avoids the problem of excessive force on a single thread stage, but also significantly reduces the pressure between threads, thereby reducing the risk of thread seizure and extending the bolt's service life.

[0016] 2. The design of the elastic nut in this invention results in lower settlement under stress, with an overall inward contraction trend. This helps to distribute stress more evenly across the threads. In particular, when the elastic nut reaches a 6° tilt angle, the stress difference is minimized, and the maximum stress is also reduced to a minimum. This further demonstrates the superior performance of the new bolt in terms of stress uniformity, with the intermediate workpiece meeting the design conditions and the contact surface experiencing uniform stress.

[0017] 3. This invention, through its design, ensures more uniform stress distribution on each thread, resulting in higher structural stability and safety of the new bolt under high loads. This means that under extreme conditions, the new bolt is less prone to breakage or failure, thus ensuring reliable operation of equipment and systems. Due to its longer service life and lower failure rate, the new bolt reduces equipment maintenance costs. Furthermore, the reduced pressure between the threads lowers the risk of thread seizure, making bolt disassembly and replacement easier and faster. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2This is a partial cross-sectional schematic diagram of the present invention;

[0020] Figure 3 For the present invention Figure 2 Enlarged view of a portion of point A in the middle;

[0021] Figure 4 This is an exploded view of the fastening sleeve and nut of the present invention;

[0022] Figure 5 For the present invention Figure 4 Enlarged view of a section at point B in the middle;

[0023] Figure 6 This is a schematic diagram of the pretensioner structure of the present invention;

[0024] Figure 7 This is a schematic cross-sectional view of the nut of the present invention;

[0025] Figure 8 Diagrams showing thread deformation caused by various reasons in this invention;

[0026] Figure 9 This is a comparison chart of the elastic deformation coefficient values ​​of the thread teeth caused by various reasons according to the present invention.

[0027] Figure 10 This is a stress distribution diagram of the present invention;

[0028] Figure 11 This is a settlement analysis diagram of the present invention;

[0029] Figure 12 Stress analysis at the thread of this invention Figure 1 ;

[0030] Figure 13 Stress analysis at the thread of this invention Figure 2 ;

[0031] Figure 14 This is a table of stress analysis data at the threaded parts of the present invention.

[0032] In the diagram: 1. Double-ended stud; 2. Nut; 3. Preload; 4. Hardened washer; 5. Push screw; 6. Push block; 7. Wedge block; 8. Protrusion; 9. Fastening sleeve; 10. Curved surface. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below 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.

[0034] like Figures 1 to 14 As shown, this embodiment of the invention provides a super bolt nut for gravity support, including a double-ended stud 1. The two ends of the double-ended stud 1 are respectively threaded with a nut 2 and a preload 3. A hardened washer 4 is movably fitted on the outer surface of the double-ended stud 1 near one end of the preload 3. A push screw 5 is uniformly threaded inside the preload 3. A push block 6 is installed at the end of the push screw 5 near the hardened washer 4. The end face of the nut 2 near the hardened washer 4 is provided with an arc surface 10.

[0035] In use, the part to be fixed is placed between the nut 2 and the hardening washer 4. By rotating the nut 2, one end of the double-ended stud 1 is sealed. Then, the preload 3 is threaded onto the preload. By rotating the push screw 5, the push block 6 is moved closer to the hardening washer 4, so that the hardening washer 4 fits tightly against the part to be fixed. When under pressure, the arc surface 10 on the nut 2 will deform.

[0036] The inner wall of the nut 2 is uniformly fixed with inclined blocks 7, the bottom end of the inclined blocks 7 is provided with protrusions 8, and the outer surface of the double-ended stud 1 is threaded with a fastening sleeve 9 located inside the nut 2.

[0037] After determining the position of nut 2, fastening sleeve 9 is placed on double-ended stud 1. The fastening sleeve 9 presses against the inclined block 7, so that the protrusion 8 is in close contact with the thread on the surface of double-ended stud 1, preventing nut 2 from rotating accidentally.

[0038] One end of the fastening sleeve 9 is on the same slope as the inclined surface of the inclined block 7, and their contact surfaces are in parallel contact.

[0039] Among them, the protrusion 8 is made of rubber asphalt material, which deforms when squeezed and fits tightly with the thread at the end of the double-ended stud 1.

[0040] Among them, the arc surface 10 will undergo slight deformation under stress to ensure uniform stress distribution.

[0041] Among them, nut 2 is an elastic nut with a settlement value of 0.24mm. When the angle of nut 2 is 6°, the stress difference is the smallest, and the maximum stress is also the smallest, resulting in more uniform force distribution.

[0042] Among them, the deformation coefficient of the internal thread of nut 2 is higher than that of the external thread. The elastic deformation of the thread can better transmit the force to the next thread, making the force distribution more uniform.

[0043] Among them, the thread tolerance grade of nut 2 is 6g-6H, 2A-2B.

[0044] The hardness of the hardened washer 4 should preferably be selected within the range of hardness greater than that of the nut 2 and less than that of the stud 1.

[0045] Among them, the inclined block 7 and the protrusion 8 form a group, and there are ten groups evenly distributed on the inner wall of the nut 2.

[0046] Experimental verification:

[0047] Nut 2 Calculation Sheet:

[0048] Calculation: Thread specification of double-ended stud 1:

[0049] Minimum tensile strength Rm: 1230 (MPa)

[0050] Minimum yield strength Rpo.2: 1034 (MPa)

[0051]

[0052] d2: median diameter

[0053] d3: Trail

[0054] The formula for calculating thread dimensions can be found in GB / T196.

[0055] Stress cross-sectional area: A = 621 mm 2

[0056] Guaranteed load: F=763KN

[0057] According to GB / T3098.1, the load that the stud can withstand is 758 kN.

[0058] Nut thread specification: 7 / 16-20-UNF;

[0059] The load-bearing capacity is referenced from the data in GB / T3098.2 Fasteners Mechanical Strength - Nuts, 7 / 16-20-UNF and The internal thread ensures that the load meets the usage requirements.

[0060] Push screw specification: 7 / 16-20-UNF

[0061] According to test data, the nut provides a preload of 350KN~540KN, which meets the usage requirements.

[0062] Preload force: >35KN

[0063] Total preload FB: >350KN

[0064] Torque formula:

[0065]

[0066] P: Pitch

[0067] Hg: Thread friction coefficient (0.18)

[0068] k: Coefficient of friction of the contact surface (0.18)

[0069] Contact surface diameter under stress: 8.6mm

[0070] Based on calculation (3), the recommended torque is 90 (Nm) ~ 118 (Nm).

[0071] Torque tolerance ±10%.

[0072] Push screw verification:

[0073] Safety factor: 0.7

[0074] Preload: 65KN

[0075] The friction coefficient and formula meet the usage requirements and are referenced in "VDI2230 High Strength Bolt Connection System Calculation".

[0076] Number of screws: 10

[0077] Total preload force FB: >350KN.

[0078] according to Figure 8 and Figure 9 It can be seen that the deformation coefficient of internal threads is higher than that of external threads. The elastic deformation of the thread can better transmit the force to the next stage of the thread, thereby ensuring a more uniform force distribution, avoiding excessive force on a single stage of thread, reducing inter-thread pressure, improving stress conditions, reducing the risk of thread seizure, and increasing thread life.

[0079] in conclusion:

[0080] Based on the above calculations:

[0081] Screw yield strength ≥ 1200 MPa;

[0082] Stud yield strength ≥ 1034 MPa;

[0083] Nut body guaranteed load:

[0084] Referring to the data in GB / T3098.2 Fasteners Mechanical Strength - Nuts, 7 / 16-20-UNF and The internal thread ensures that the load meets the usage requirements.

[0085] Thread tolerance grades: 6g-6H, 2A-2B;

[0086] According to "Theory and Calculation of Threaded Connections", the engagement length should be >4.8mm at the screw and >18mm at the stud. This will meet the usage requirements.

[0087] To protect the screw and reduce the impact of washer deformation on the elastic deformation of the nut thread, the hardness of the washer should be selected within the hardness range that is greater than that of the nut but less than that of the screw.

[0088] According to the instruction manual Figure 11 It can be seen that the settlement value of the clamping component in the hexagonal nut assembly is 1.30mm, while the settlement value of the clamping component in the elastic nut assembly is 0.24mm, with the elastic nut showing an even lower settlement value. The clamping component as a whole exhibits a tendency to shrink inward.

[0089] According to the instruction manual Figure 12 It can be seen that the maximum local stress at the first three threads of the hexagonal nut assembly is 156.4 MPa (11.4 MPa for the last three threads), while the maximum local stress at the first three threads of the elastic nut assembly is 154.9 MPa (43.9 MPa for the last three threads). Although the stress values ​​of the first three threads are not significantly different, the stress values ​​of the last three threads are significantly different. The elastic nut distributes more stress across the last three threads, making the stress on each thread more even.

[0090] All materials are: Inconel 718

[0091] According to the instruction manual Figure 13 It can be seen that: compared with the elastic telescopic nut (3°), the elastic telescopic nut (6°) slightly reduces the maximum stress of the head meshing teeth and increases the maximum stress of the bottom meshing teeth, thus further reducing the stress difference. However, the assembly of the elastic telescopic nut (10°) shows that the maximum stress of the head meshing teeth increases compared with the elastic telescopic nut (6°), and the maximum stress at the bottom is also slightly reduced.

[0092] According to the instruction manual Figure 14 It can be seen that when the elastic nut is at 6°, the stress difference is the smallest, and the maximum stress is also the smallest, indicating that the force is more uniform than at other angles.

[0093] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0094] 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 super bolt nut for gravity support, comprising a double-ended stud (1), characterized in that: The two ends of the double-ended stud (1) are respectively threaded with a nut (2) and a preload (3). The outer surface of the double-ended stud (1) is movably fitted with a hardened washer (4) near one end of the preload (3). The inside of the preload (3) is uniformly threaded with a push screw (5). The end of the push screw (5) near the hardened washer (4) is fitted with a push block (6). The end face of the nut (2) near the hardened washer (4) is provided with an arc surface (10). The inner wall of the nut (2) is uniformly fixed with inclined blocks (7), and the bottom end of the inclined blocks (7) is provided with protrusions (8). The outer surface of the double-headed stud (1) is threaded with a fastening sleeve (9) located inside the nut (2). One end of the fastening sleeve (9) and the inclined surface of the inclined block (7) are on the same inclined surface with the same slope, and their contact surfaces are in parallel contact.

2. The super bolt nut for gravity support according to claim 1, characterized in that: The protrusion (8) is made of rubber asphalt material. It deforms when squeezed and fits tightly with the thread at the end of the double-ended stud (1).

3. The super bolt nut for gravity support according to claim 1, characterized in that: The arc surface (10) will undergo slight deformation under stress, ensuring uniform stress distribution.

4. The super bolt nut for gravity support according to claim 1, characterized in that: The nut (2) is an elastic nut with a settlement value of 0.24 mm. When the angle of the nut (2) is 6°, the stress difference is the smallest and the maximum stress is also the smallest, resulting in more uniform force distribution.

5. The super bolt nut for gravity support according to claim 1, characterized in that: The deformation coefficient of the internal thread of the nut (2) is higher than that of the external thread. The elastic deformation of the thread can better transmit the force to the next thread, making the force distribution more uniform.

6. The super bolt nut for gravity support according to claim 1, characterized in that: The thread tolerance grade of the nut (2) is 6g-6H, 2A-2B.

7. The super bolt nut for gravity support according to claim 1, characterized in that: The hardness of the hardened washer (4) is within the range that is greater than the hardness of the nut (2) but less than the hardness of the stud (1).

8. A super bolt nut for gravity support according to claim 1, characterized in that: The inclined block (7) and the protrusion (8) form a group, and there are ten groups evenly distributed on the inner wall of the nut (2).

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