Anti-loosening thread of arc structure

Abstract

An anti-loosening thread of an arc structure, which thread belongs to the technical field of threads. The anti-loosening thread of an arc structure comprises an internal thread (1) and an external thread (2), wherein a root (1-3, 2-3) of at least one of the internal thread (1) and the external thread (2) is of an arc thread structure having a root arc, and the external thread (2) has a contact crest (2-1), which is in abutting contact with the root arc of the internal thread (1) when the internal and external threads are in fitted connection, or the internal thread (1) has a contact crest (1-1), which is in abutting contact with the root arc of the external thread (2) when the internal and external threads are in fitted connection. Contact positions between the internal and external threads are the root arc and the contact crest (1-1, 2-1) instead of linear segments, and therefore compared with the linear segments, the position of a contact point is closer to the lowest point of the root arc. In this way, under the same external load, the included angle between the supporting force between the internal and external threads, and the radial direction of the thread is reduced, that is, the angle of α1 is reduced, and then sinα1 is reduced. Therefore, the supporting force N1 between the internal and external threads is increased, and then the friction force between the internal and external threads is increased, thereby improving the anti-loosening performance.

Description

A circular arc structure anti-loosening thread Technical Field

[0001] The invention relates to an arc structure anti-loosening thread, belonging to the technical field of threads. Background Art

[0002] Threaded connection is a common connection method in industry and is widely used in wind power generation, shipbuilding, automobile manufacturing, aerospace, mechanical products and other fields. Threaded connection has the characteristics of strong connection performance, easy disassembly, and easy manufacturing, and has become the most common connection method. When the threaded connection is disturbed by the outside world, the bolts often loosen and fail, which may cause major safety accidents. Existing anti-loosening theory shows that the main reason for thread loosening is the lack of friction between the internal and external threads, resulting in relative slippage. The supporting force generated between the internal and external threads of traditional metric threads, MJ threads, etc. is only 1.15 times the axial force, and is prone to loosening under vibration loads.

[0003] Arc-shaped threads also exist in the prior art. For example, Chinese utility model patent CN209818480U discloses a high-strength arc-shaped threaded connection pair. This threaded connection pair includes a bolt and a nut. The external thread on the bolt is composed of an upper crest arc, a straight line segment, a lower root arc, and a straight line segment, connected in sequence. The radius of the upper crest arc is equal to the radius of the lower root arc, and the straight line segment is tangent to the upper crest arc and the lower root arc, respectively. The internal thread on the nut is composed of an upper semicircular arc, a straight line segment, and a crest, connected in sequence. The crest is flat, and the straight line segment is tangent to the upper semicircular arc.

[0004] The bottom of the above-mentioned internal and external threads both adopt a large arc thread structure, which can effectively improve the fatigue performance and load-bearing performance of the connection by-products. However, the internal and external threads on the bolts and nuts are in surface contact, that is, as shown in Figure 1, the straight segment of the internal thread 1 is in contact with the straight segment of the external thread 2, and the supporting force N1 of the internal thread 1 on the external thread 2 is N1 = F0 / sinα1, where F0 is the external load acting on the external thread 2, and α1 is the angle between N1 and the thread radial direction, which is numerically equal to the thread tooth angle of 60°. The action direction of N1 is perpendicular to the straight segment. Due to the limitation of the α1 angle, the supporting force N1 is limited. Therefore, the anti-loosening performance of the arc thread connection by-product is not significantly improved compared with the traditional metric thread. The supporting force between the internal and external threads is also about 1.15 times the axial force, resulting in insufficient friction and poor anti-loosening effect.

[0005] Summary of the Invention

[0006] The purpose of the present invention is to provide an arc structure anti-loosening thread to solve the problem that the internal and external threads of the existing arc structure thread contact through a straight line segment, resulting in limited supporting force and thus poor anti-loosening performance.

[0007] To achieve the above purpose, the arc structure anti-loosening thread in the present invention adopts the following technical solutions:

[0008] A circular arc structure anti-loosening thread includes an internal thread and an external thread, the root of at least one of the internal thread and the external thread is an arc thread structure with a root arc, the external thread has a contact crest that contacts the root arc of the internal thread when the internal and external threads are mated, or the internal thread has a contact crest that contacts the root arc of the external thread when the internal and external threads are mated.

[0009] The beneficial effect of the above technical solution is that: the present invention proposes an improved arc structure anti-loosening thread, the main improvement is that the external thread has a contact tooth top that contacts the top of the tooth bottom arc of the internal thread when the internal and external threads are matched and connected, or the internal thread has a contact tooth top that contacts the top of the tooth bottom arc of the external thread when the internal and external threads are matched and connected, that is, the contact position of the internal and external threads is the tooth bottom arc and the contact tooth top, rather than a straight line segment. Compared with the straight line segment, the position of the contact point is closer to the lowest point of the tooth bottom arc. In this way, under the same external load, the angle between the internal and external thread supporting force and the thread radial direction will be reduced, that is, the angle α1 will be reduced, and then sinα1 will be reduced, so the internal and external thread supporting force N1 will become larger, and then the friction between the internal and external threads will be increased, thereby improving the anti-loosening performance.

[0010] Furthermore, if the radial distance from the contact point between the tooth crest and the tooth bottom arc to the center of the tooth bottom arc is l, and the radius of the tooth bottom arc is r, then k = l / r, and the value range of k is 0.5 to 1. As a further optimization, the value range of k is 0.55-0.866. As a further optimization, the value range of k is 0.67-0.866. As a further optimization, the value range of k is 0.714-0.866.

[0011] The beneficial effect of the above technical solution is that it has good anti-loosening performance within this range.

[0012] Furthermore, the internal thread includes a crest, a first transition section, a root and a second transition section connected in sequence, and the external thread includes a crest, a third transition section, a root and a fourth transition section connected in sequence. The root of the internal thread has the described root arc, and the crest of the external thread constitutes the described contact crest.

[0013] The beneficial effect of the above technical solution is that the tooth top of the external thread contacts the tooth bottom of the internal thread in an arc, which facilitates manufacturing and assembly.

[0014] Furthermore, the contact tooth crest has a tooth crest arc.

[0015] The beneficial effect of the above technical solution is to reduce stress concentration and damage to the anti-corrosion coating.

[0016] Furthermore, the first transition section and the second transition section are both straight line sections.

[0017] The beneficial effect of the above technical solution is that it facilitates the transition between the tooth top and the tooth bottom.

[0018] Furthermore, the first transition section and the second transition section are respectively tangent to the root of the internal thread.

[0019] Furthermore, the third transition segment and the fourth transition segment are both straight line segments.

[0020] The beneficial effect of the above technical solution is that it facilitates the transition between the tooth top and the tooth bottom.

[0021] Furthermore, the internal thread includes a crest, a first transition section, a root and a second transition section connected in sequence, and the external thread includes a crest, a third transition section, a root and a fourth transition section connected in sequence. The root of the external thread has the described root arc, and the crest of the internal thread constitutes the described contact crest.

[0022] The beneficial effect of the above technical solution is that the tooth top of the internal thread contacts the tooth bottom arc of the external thread, which facilitates manufacturing and assembly.

[0023] Furthermore, the contact tooth top is a flat tooth top.

[0024] The beneficial effect of the above technical solution is that it is easy to process and manufacture.

[0025] Furthermore, the first transition section and the second transition section are both straight line sections.

[0026] The beneficial effect of the above technical solution is that it facilitates the transition between the tooth top and the tooth bottom.

[0027] Furthermore, the third transition segment and the fourth transition segment are both straight line segments.

[0028] Furthermore, the third transition section and the fourth transition section are tangent to the external thread crest and the external thread bottom respectively.

[0029] The beneficial effect of the above technical solution is that it facilitates the transition between the tooth top and the tooth bottom. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a diagram showing the structure of the prior art in which both the internal and external threads are arc threads;

[0031] FIG2 is a structural diagram of Example 1 of an arc-structured anti-loosening thread according to the present invention;

[0032] FIG3 is an enlarged view of the fit between the external thread crest and the internal thread root in FIG2 ;

[0033] FIG4 is an enlarged view of the fit between the external thread bottom and the internal thread top of Example 2 of the arc structure anti-loosening thread in the present invention.

[0034] In the figure: 1, internal thread; 1-1, internal thread top; 1-2, first transition section; 1-3, internal thread bottom; 1-4, second transition section; 2, external thread; 2-1, external thread top; 2-2, third transition section; 2-3, external thread bottom; 2-4, fourth transition section. DETAILED DESCRIPTION

[0035] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0036] Example 1 of the arc structure anti-loosening thread in the present invention:

[0037] In this embodiment, the top of the external thread and the bottom of the internal thread are brought into contact with each other, and the position of the contact point is closer to the lowest point of the arc of the bottom of the thread. In this way, under the same external load, the angle between the supporting force of the internal and external threads and the radial direction of the thread will be reduced, that is, the angle α1 will be reduced, and then sinα1 will be reduced. Therefore, the supporting force N1 of the internal and external threads will become larger, and then the friction between the internal and external threads will be increased, thereby improving the anti-loosening performance.

[0038] As shown in Figures 2 and 3, the arc-shaped anti-loosening thread includes an internal thread 1 and an external thread 2, both of which are arc threads. The internal thread 1 includes a crest (i.e., internal thread crest 1-1), a first transition section 1-2, a root (i.e., internal thread root 1-3), and a second transition section 1-4, which are connected in sequence. The internal thread crest 1-1 is a flat crest, the internal thread root 1-3 is an arc thread structure with a root arc, and the first transition section 1-2 and the second transition section 1-4 are both straight segments and are tangent to the internal thread root 1-3.

[0039] The external thread 2 includes a crest (i.e., the external thread crest 2-1), a third transition section 2-2, a root (i.e., the external thread root 2-3) and a fourth transition section 2-4 connected in sequence, wherein the external thread crest 2-1 is an arc thread structure with a crest arc, the external thread root 2-3 is an arc thread structure with a bottom arc, the third transition section 2-2 and the fourth transition section 2-4 are both straight segments, and are tangent to the external thread crest 2-1 and the external thread root 2-3, respectively.

[0040] In this embodiment, as shown in Figure 2, when the internal thread 1 and the external thread 2 are mated and connected, when the internal thread 1 and the external thread 2 are loaded and move relative to each other and come into contact, the external thread crest 2-1 is in contact with the internal thread root 1-3, that is, the contact point between the root arc of the internal thread 1 and the crest of the external thread 2 is located on the root arc of the internal thread 1, and the external thread crest 2-1 constitutes a contact crest that is in contact with the root arc of the internal thread root 1-3.

[0041] Furthermore, the supporting force N2 exerted by the internal thread 1 on the external thread 2 is calculated as F0 / sinα2, where F0 is the external load acting on the external thread 2. Since α1>α2, N2>N1. That is, under the same external load F0, the change in the contact point position reduces the angle between the supporting force of the internal and external threads and the thread radial direction. This means that the angle α1 (shown in Figure 1) in the prior art will decrease, and thus sinα1 will decrease. Therefore, the supporting force N1 of the internal and external threads will increase (to N2), which in turn increases the friction between the internal and external threads and improves the anti-loosening performance.

[0042] In this embodiment, if the radial distance from the contact point of the contact crest of the external thread 2 and the tooth bottom arc of the internal thread 1 to the center of the tooth bottom arc of the internal thread 1 (i.e., the projected length of the line segment between the contact point and the tooth bottom arc center in the radial plane perpendicular to the secondary axis of the threaded connection) is l, and the radius of the tooth bottom arc of the internal thread 1 is r, then it can be concluded that k = l / r, and the value range of k is 0.5 to 1 (maximum range, tooth profile angle is 60°). In theory, the larger k is, the greater the support force generated between the internal thread 1 and the external thread 2. Preferably, the value of k can be 0.55, 0.67, 0.714, 0.866, which are all parameters of existing commonly used arc threads. Table 1 shows the support force corresponding to different k values.

[0043] Table 1 Support forces corresponding to different k values

[0044] The correctness of the above conclusion will be demonstrated in combination with the specific dimensions of the arc thread. As shown in Figure 3, it is assumed that the arc radius of the internal thread bottom 1-3 is R = 2.8 mm (i.e., O1A = 2.8 mm), and the major diameter D of the internal thread 1 is 48.44 mm; the arc radius of the top of the external thread top 2-1 is r1 = 2 mm (i.e., O2A = 2 mm), the arc radius of the bottom of the external thread bottom 2-3 is r2 = 2 mm, and the major diameter d of the external thread 2 is 48.3 mm.

[0045] When the internal and external threads are engaged under load, the contact point A of the internal and external threads, the center O1 of the arc at the root of the internal thread root 1-3, and the center O2 of the arc at the tip of the external thread crest 2-1 are collinear. The distance from the center O1 of the internal thread root 1-3 to the secondary axis of the threaded connection is l1 = D / 2 - O1C1 = 24.22 - R = 24.22 - 2.8 = 21.42 mm. The distance from the center O2 of the external thread crest 2-1 to the secondary axis of the threaded connection is l2 = d / 2 - O2C2 = 24.15 - r1 = 24.15 - 2 = 22.15 mm. The radial distance between the center O1 of the internal thread root 1-3 and the center O2 of the external thread crest 2-1, i.e., the length of line segment O2B2, is l' = l2 - l1 = 22.15 - 21.42 = 0.73 mm. According to the geometric similarity relationship (O1O2 / O1A=l' / l, O1A-O2A=O1O2=0.8mm), the length of the line segment AB1 (i.e. the radial distance of AO1 in the radial plane of the threaded connection pair) can be obtained as l=2.555mm. According to the mathematical relationship, cosα2=l / R=0.913 (i.e. the k value is 0.913), so sinα2=(1-l 2 / R 2 ) 0.5 =0.408, and then according to N2=F0 / sinα2=F0 / 0.408, we can calculate the support force N2 exerted by the internal thread 1 on the external thread 2 = 2.45F0, which is greater than the support force of ordinary threads and Spirax threads. Table 2 compares the support force of the contact points of the threads of this application and the threads of the prior art. The solution process for the support force of ordinary threads and Spirax threads is based on the prior art and will not be repeated in this invention.

[0046] Table 2 Comparison of the supporting force of the contact points of the thread of the present application and the thread of the prior art

[0047] Example 2 of the arc structure anti-loosening thread in the present invention:

[0048] This embodiment achieves the same effect as Example 1 by bringing the external thread roots into contact with the internal thread crests. Specifically, as shown in FIG4 , the specific thread structures of the internal thread 1 and the external thread 2 in this embodiment are the same as those in Example 1 and will not be repeated here. The difference is that when the internal thread 1 and the external thread 2 are mated and connected, the external thread roots 2-3 and the internal thread crest 1-1 are in contact with each other. Therefore, the internal thread crest 1-1 forms a contact crest that is in contact with the arc of the root of the external thread roots 2-3. Of course, the contact crest is a flat crest.

[0049] Assume that the radius of the arc of the bottom of the external thread 2-3 is r2 = 2mm (i.e. OC = 2mm), the minor diameter of the external thread 2 is d3 = 41.7mm, the minor diameter of the internal thread 1 is D3 = 41.96mm, the distance from the center O of the arc of the bottom of the external thread 2-3 to the secondary axis of the threaded connection is l1 = d3 / 2 + OC = 41.7 / 2 + 2 = 20.85 + 2 = 22.85mm, the length of the line segment AB is l = l1-D3 / 2 = 22.85-41.96 / 2 = 22.85-20.98 = 1.87mm, and according to the mathematical relationship, cosα2 = l / r2 = 0.935 (i.e. the k value is 0.935), so sinα2 = (1-l 2 / r2 2 ) 0.5 =0.355, then we can calculate the supporting force N3 = F0 / sinα2 = F0 / 0.355 = 2.82F0 exerted by the internal thread 1 on the external thread 2, which is much greater than the supporting force of ordinary threads and Spirax threads.

[0050] In other embodiments of the arc structure anti-loosening thread: the first transition section, the second transition section, the third transition section and the fourth transition section can also be arc surface transitions.

[0051] In other embodiments of the arc structure anti-loosening thread: the internal thread crest can also be an arc crest.

[0052] In other embodiments of the arc structure anti-loosening thread: the external thread crest may also be a flat crest.

[0053] In other embodiments of the arc structure anti-loosening thread: the root of only one of the internal thread and the external thread is an arc thread structure with a root arc.

[0054] In other embodiments of the arc structure anti-loosening thread: depending on the different tooth angles, the value of k can also be less than 0.5.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be based on the claims. Any equivalent structural changes made using the description and drawings of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A circular arc structure anti-loosening thread, comprising an internal thread and an external thread, wherein the root of at least one of the internal thread and the external thread is a circular arc thread structure having a root arc, characterized in that: The external thread has a contact crest that contacts the arc of the internal thread bottom when the internal and external threads are connected, or the internal thread has a contact crest that contacts the arc of the external thread bottom when the internal and external threads are connected.

2. The arc structure anti-loosening thread according to claim 1, characterized in that: If the radial distance from the contact point between the tooth top and the tooth bottom arc to the center of the tooth bottom arc is l, and the radius of the tooth bottom arc is r, it can be concluded that k=l / r, and the value range of k is 0.5-1.

3. The arc structure anti-loosening thread according to claim 2, characterized in that: The value range of k is 0.55-0.

866.

4. The arc structure anti-loosening thread according to claim 2, characterized in that: The value range of k is 0.67-0.

866.

5. The arc structure anti-loosening thread according to claim 2, characterized in that: The value range of k is 0.714-0.

866.

6. The arc structure anti-loosening thread according to any one of claims 1 to 5, characterized in that: The internal thread includes a crest, a first transition section, a root and a second transition section connected in sequence, and the external thread includes a crest, a third transition section, a root and a fourth transition section connected in sequence. The root of the internal thread has the described root arc, and the crest of the external thread constitutes the described contact crest.

7. The arc structure anti-loosening thread according to claim 6, characterized in that: The contact tooth crest has a tooth crest arc.

8. The arc structure anti-loosening thread according to claim 6, characterized in that: The first transition section and the second transition section are both straight line sections.

9. The arc structure anti-loosening thread according to claim 8, characterized in that: The first transition section and the second transition section are respectively tangent to the root of the internal thread.

10. The arc structure anti-loosening thread according to claim 6, characterized in that: The third transition segment and the fourth transition segment are both straight line segments.

11. The arc structure anti-loosening thread according to any one of claims 1 to 5, characterized in that: The internal thread includes a crest, a first transition section, a root and a second transition section connected in sequence, and the external thread includes a crest, a third transition section, a root and a fourth transition section connected in sequence. The root of the external thread has the described root arc, and the crest of the internal thread constitutes the described contact crest.

12. The arc structure anti-loosening thread according to claim 11, characterized in that: The contact tooth top is a flat tooth top.

13. The arc structure anti-loosening thread according to claim 11, characterized in that: The first transition section and the second transition section are both straight line sections.

14. The arc structure anti-loosening thread according to claim 11, characterized in that: The third transition segment and the fourth transition segment are both straight line segments.

15. The arc structure anti-loosening thread according to claim 14, characterized in that: The third transition section and the fourth transition section are tangent to the external thread crest and the external thread bottom respectively.

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