CN111734728A

CN111734728A - Anti-loosening nut with double anti-loosening and pretightening force estimation functions

Info

Publication number: CN111734728A
Application number: CN202010721091.3A
Authority: CN
Inventors: 冯鲁民
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2020-10-02

Abstract

An anti-loosening nut with double anti-loosening and pretightening force estimating functions comprises two bearing surfaces. The offset pivot points on the bearing surface ensure that the pretightening force can be completely pressed on the offset pivot points with less quantity on the bearing surface. In order to prevent the offset fulcrum from loosening the thread during slippage, an optimized fulcrum configuration exists in the form of a single ratchet, the forbidden direction of the ratchet being the loosening direction of the thread. Under the action of the pretightening force, the biased ratchet teeth enable the nut to generate a pair of strong radial force couple at the rod part of the bolt, and the force couple enables the threads of the nut and the bolt to generate huge friction force, so that the threads are prevented from loosening. Under the action of strong pre-tightening force, the tooth edges of the single ratchet can be embedded into the surface of the part to form a huge loosening prevention effect. The higher ratchet height enables the single ratchet to have enough residual height after being embedded into the surface of the part, and the residual value of the pre-tightening force can be estimated by measuring the distance between the lowest point on the supporting surface and the surface of the part.

Description

Anti-loosening nut with double anti-loosening and pretightening force estimation functions

Technical field the present invention relates to the field of mechanical or threaded fasteners, and in particular to the anti-loosening technique of fasteners or nuts.

Background artthe prior art fastener anti-loosening techniques fall into three broad categories, namely permanent anti-loosening, mechanical anti-loosening and friction anti-loosening. Wherein the permanent anti-loosening is to destroy the thread pair relationship and change the thread pair into a non-moving pair, thereby eliminating the possibility of relative movement of the thread pair, such as welding, punching, applying adhesive between the thread pair, and bending the screw portion above the nut after pre-tightening the nut. The permanent anti-loosening is a disposable fastening scheme because the fastener must be destroyed during disassembly; the mechanical anti-loosening is realized by adopting a metal element which is convenient to replace to restrain a thread pair, and the mechanical anti-loosening comprises a fixed thread pair such as a cotter pin, a stop washer and a steel wire rope. Mechanical anti-loosening is used repeatedly, but is complicated to apply. The friction anti-loosening is a technology for preventing the loosening of the thread by utilizing various ways of increasing friction force.

Chinese patent CN1114766C "washer for preventing nut from loosing" proposes a washer with inclined bearing surface using the principle of friction loosing prevention. The washer has the advantage that the nut on the washer can generate a force couple effect on the screw after being pre-tightened, so that the washer can generate an anti-loosening effect. However, under strong transverse vibration component, even if the friction force between the nut and the screw rod is large, transverse slip weak links are still generated between the surface of the part and the washer, and between the washer and the nut. Once such slippage occurs, the impact on the washer at the moment of switching between static and dynamic friction states is transmitted by the nut to the engagement between the nut and the screw, causing the nut to produce a back-out motion on the screw tending to reduce the pressure, resulting in the loosening of the threads. In addition, the technology is an application that the bearing surface of the washer is completely attached to the bearing surface of the nut, is a traditional application concept, and does not consider the requirements of the aspects of controlling and detecting the pre-tightening force.

Chinese patent CN101598168B "anti-loose and anti-theft bolt structure" proposes a ratchet structure for a bearing surface. The technique proposes in particular that the ratchet teeth are distributed on the bearing surface in an equiangular array, which, however, is too dependent on the pretension. Because the pretightening force has the characteristic of time variation caused by creep deformation, once the pretightening force is reduced, the pressure of the ratchet on the bearing surface is reduced, and the spontaneous loosening of the thread under the high-strength vibration environment is difficult to be restrained only by the ratchet structure.

The existing fastener anti-loosening technology is developed on the premise of keeping the axis of the screw straight and smooth, and although the schemes are numerous and effective, the engineering application needs to be continued to be better. In addition, the existing several anti-loosening technologies have the problems of complex processing, high cost and short service life of the self or accessories. Moreover, the existing anti-loosening technical scheme has a complex structure, so that the anti-loosening aspect of fasteners with small diameters or even micro diameters is difficult to be involved. Even so, most anti-loosening technologies have the possibility of accidental failure, and the technical reliability needs to be improved.

The invention provides an anti-loosening nut with double anti-loosening and pretightening force estimating functions. Such a release nut has two bearing surfaces, at least one of which has an asymmetry with respect to the thread axis. The asymmetric configuration includes a configuration in which the bearing surface is not perpendicular to the thread axis and a fulcrum or ratchet offset from the thread axis is provided on the bearing surface, or a combination of three configurations of a sloped bearing surface, an offset fulcrum and an offset ratchet. The fulcrum may be simply a projection or may be the highest point on the inclined support surface. I.e. the highest point on the inclined support surface, is a special form of offset fulcrum. The offset fulcrum on the bearing surface ensures that the pretension is fully pressed against the offset fulcrum of the bearing surface in order to obtain a greater moment and to embed the ratchet teeth deeper into the surface of the part. A biased ratchet is a particular form of biased fulcrum. In order to prevent the offset fulcrum from loosening the thread during the sliding movement, the fulcrum is in the form of a single ratchet, the forbidden direction of the ratchet being the loosening direction of the thread. Under the action of the pretightening force, the biased ratchet teeth enable the nut to generate a pair of strong radial force couple at the rod part of the bolt, and the force couple generates huge friction force between the threads of the nut and the bolt, so that the threads are prevented from loosening. Even if the couple acts on the polish rod, huge friction force is generated, so that the movement of the acting point of the couple is avoided, and the couple acts on the thread. Under the action of strong pre-tightening force, the sharp ratchet tooth edges of the single ratchet can be embedded into the surface of the part, and a huge loosening prevention effect is formed in the mode of scraping the surface of a material. The higher ratchet height allows a sufficient residual height after the single ratchet is embedded in the surface of the part, and the residual value of the pre-tightening force can be estimated by measuring the height between the lowest point on the bearing surface and the surface of the part by using a plug gauge.

The technical form of the nut has the advantages that the difference between the processing cost and the common nut can be almost completely ignored, the production procedures are completely the same, and the service life is the same as that of the common nut.

Description of the drawings:

FIG. 1 is an inclined bearing surface configuration of a first preferred embodiment of the present invention;

FIG. 2 is a second preferred embodiment of the biased ratchet configuration of the present invention;

FIG. 3 is a bevel ratchet configuration of a third preferred embodiment of the present invention;

the reference numbers are exemplary: 1. a common nut; 13. a head end bearing surface; 15. a thread axis; 2. an inclined bearing surface; 21. the highest point of the inclined plane; 22. the lowest point of the inclined plane; 3. a ratchet; 31. a ratchet tooth blade; 32. a ratchet tooth back; 33. ratchet tooth flanks.

The specific implementation mode is as follows: in a first preferred embodiment of the present invention, the head end bearing surface is an inclined bearing surface. As shown in fig. 1, the head end bearing surface (13) of the nut (1) is not perpendicular to the nut internal thread axis (15). The head end bearing surface (13) is the bearing surface of the nut (1) which is in contact with the part or the bearing surface of the nut which is in contact with the nut, while the other bearing surface of the nut is usually non-load bearing, i.e. a free end which is not in contact with any object.

A slope peak (21) is provided on the head end bearing surface (13). The highest point (21) of the inclined plane is the point on the head end bearing surface which is farthest from the other bearing surface of the nut along the axis of the internal thread of the nut. When the nut is pre-tightened, the highest point (21) on the bearing surface of the head end of the nut first contacts the surface of the part perpendicular to the axis of the thread. The lowest point (22) of the chamfer on the head end bearing surface is the point on the nut head end bearing surface (13) that will eventually contact the surface of the part perpendicular to the thread axis (15), or the point on the nut head end bearing surface that is farthest from another bearing surface of the nut perpendicular to the thread axis (15).

The highest point (21) of the inclined plane bears all the pretightening force, so that the nut (1) generates huge bending moment on the bolt rod part at the meshing position, and the force effect generated by the moment is expressed in the form of force couple. Huge couple produces huge frictional force on bolt shank screw thread, makes the screw thread avoid the pine to take off.

When the nut (1) is screwed until the highest point (21) of the inclined plane contacts with the surface of the part, the pretightening force begins to increase. Because the highest point (21) of the inclined plane deviates from the axis (15) of the internal thread of the nut, and the distance between the lowest point (22) of the inclined plane and the surface of the part, after the nut (1) is pre-tightened, the highest point (21) of the inclined plane contacts the surface of the part, and the lowest point (22) of the inclined plane is closer to the surface of the part along with the increasing pre-tightening force. The phenomenon is that the highest point (21) of the inclined surface is pressed into the surface of the part to be deeper and deeper, but the pressing depth is in a micro-variable level with huge elastic modulus; secondly, gaps among the threads are used up when the pretightening force begins to lift, and the threads begin to elastically deform; thirdly, along with the increase of pretightening force, the effect of elastic bending of bolt pole portion increases gradually. The three factors jointly enable the distance between the lowest point (22) of the inclined plane on the head end bearing surface (13) of the nut (1) and the surface of the part to be smaller and smaller, and the pretightening force is monotonous relative to the distance between the lowest point (22) of the inclined plane and the surface of the part. Since the bending elastic modulus of the bolt shank is much smaller than the compression elastic modulus of the surface of the part below the ratchet tooth edge, the value of the preload can be estimated by measuring the distance of the lowest point (22) of the inclined surface with respect to the surface of the part, and even by roughly estimating the distance, it can be judged whether the bolt has been loosened.

In the transverse vibration process, due to the sliding phenomenon of the bearing surface, the highest point (21) of the inclined surface is used as a bias fulcrum, the impact of the cyclic and initial transition between the sliding friction force and the static friction force can be repeatedly received, and the phenomenon that the fulcrum drives the nut to do circumferential torsional vibration can occur. Since the thread is always easy to wind out, less wind-up than loosening will necessarily occur as soon as torsional vibration occurs. This means loosening of the thread.

In a second embodiment of the invention, a set of ratchet teeth are provided on the bearing surface of the conventional nut offset from the axis of the thread.

As shown in fig. 2, in order to produce a bending moment on the screw, on the basis of a conventional nut (1), a set of ratchet teeth (3) is provided offset from the thread axis (15) on its head end bearing surface (13) perpendicular to the thread axis (15). The set of ratchet teeth (3) comprises at least one ratchet tooth.

The present embodiment is provided with two one-way prohibiting ratchets. The ratchet has a ratchet tooth blade (31), a ratchet tooth back (32), and a ratchet tooth surface (33), and the prohibiting direction is a thread loosening direction. The ratchet tooth blade (31) is the highest point (21) of the bearing surface of the embodiment, and the corresponding point on the bearing surface at the symmetrical position of the two ratchets (3) relative to the thread axis (15) is the lowest point (22) of the bearing surface of the embodiment. Under the preset pretightening force, the two ratchets (3) stably bear the pressure required by being pressed into the surface of the part without being crushed. Because of the residual height of the ratchets, the lowest point (22) on the bearing surface does not contact the surface of the part, so that under the action of a pre-tightening force, the nut inclines to one side of the axis by taking the two ratchets (3) as fulcrums, and a bending moment is generated on the screw rod. The generation of the bending moment accumulates the pressure on the ratchet, so that the pressure acting on the ratchet is not reduced sharply even if the nut (1) loosens slightly and sensitive strain force is lost.

In any case, the ratchet teeth only generate indentation with different degrees during the screwing process and can not seriously damage the surface of the part, and the ratchet teeth pressed into the surface of the part can only seriously scratch the surface of the part during the unscrewing process. Therefore, the nut with the ratchet can be used as a factory packaging mark of a product, and a product customer service staff can confirm whether the product shell is opened by a user without permission according to whether the surface of the shell has scars caused by the ratchet when the nut is loosened.

A third preferred embodiment of the present invention is another technical form of the ratchet tooth blade disposed at the highest point of the slope.

As shown in fig. 3, the head end bearing surface of the nut (1) is an inclined bearing surface (2) which is sectioned in a direction perpendicular to the thread axis (15) between the highest point (21) and the lowest point (22) of the inclined surface to form a quarter of a plateau and three quarters of a form of an inclined surface. The ratchet tooth edge (31) is a part of the dividing line of the two, the ratchet tooth surface (33) is a vertical surface on the dividing line, and the rest inclined supporting surface (2) is a ratchet tooth back (32). The ratchet of this configuration ensures that the ratchet tooth blade (31) is located at the highest point (21) of the inclined support surface and simultaneously reinforces the strength of the ratchet tooth blade (31).

The ratchet teeth, or a closely spaced set of offset ratchet teeth, on the bearing surface of the head end of the nut limit circumferential displacement of the ratchet tooth contact points but do not limit radial displacement parallel to the ratchet tooth edges. Thus, if the ratchet position is selected in a predetermined lateral vibration direction at the end of the pretensioning, such as the length direction of a bridge truss, the vibration in that direction can be immune, avoiding the effect of the lateral vibration component in that direction on the loosening of the nut.

The configuration of the angled bearing surfaces and ratchet combination of this embodiment also provides the possibility for the double nut application of this embodiment. The same is possible with the configuration of the first preferred embodiment. In a double nut application, the contacting surfaces of the parts are the common bearing surfaces of the first nut perpendicular to the axis of the threads, and the second nut with its ratchet bearing surface facing upward. The second nut, even if a common nut, has the capability of bending the bolt rod part due to the fact that the second nut is pre-tightened on the inclined supporting surface of the first nut, and a strong couple is generated, so that the second nut cannot be loosened. The two nuts cannot be loosened from each other due to the embedded contact of the ratchet teeth formed on the first nut and the bearing surface of the head end of the second nut. Therefore, the anti-loosening mode of the double nuts is achieved, and the situation that the ratchet hurts the surface of a valuable part is avoided.

To avoid interference of the angled bearing surface with the threading, the preferred embodiment clears the angled bearing surface of the thread that is in interference with the angled bearing surface.

The configuration of the preferred embodiment is only a typical configuration, and typically the land area is a proportion of the ramp area, corresponding to the ratchet height. The ratchet height is selected in relation to the application scenario.

The invention is based on the structure that the offset fulcrums or ratchets with small quantity are arranged on the bearing surface, so that all pretightening force is borne on each fulcrum or ratchet, the purpose of embedding the fulcrums or ratchets into the surface of a part is achieved, and the first element for preventing the threads from loosening is achieved. The pre-tightening force is converted into torque by utilizing the offset distribution of the fulcrum or the ratchet and acts on the contact position of the nut and the bolt to generate a couple effect. And because the ratio of the force arm of the offset fulcrum to the thickness of the nut is greater than 1, the value of the force couple is greater than the pre-tightening force in the conversion, and in addition, the pre-tightening force is changed into two action effects greater than the pre-tightening force couple, so that the friction force generated by the force couple is far greater than the friction force generated by the pre-tightening force on the bearing surface, and a second element for preventing the thread from loosening is achieved.

In addition, the couple makes the screw rod produce elastic bending, and the degree of bending is directly relevant to the size of pretightening force. The bending of the screw rod and the joint action of the fulcrum or the ratchet embedded into the surface of the part reduce the distance between the lowest point on the bearing surface of the head end of the nut and the surface of the part under the same pretightening force. This distance may be greater than zero or equal to zero. A refined design may provide that the pretensioning force reaches exactly the preset value when the lowest point on the bearing surface contacts the surface of the component. If the lowest point is visually found to be separated from the surface of the part, the fact that the pretightening force is reduced can be judged.

The technique proposed by the present invention can be applied to nuts of various sizes. The angle of the slope and the remaining height of the ratchet should be determined depending on the application, wherein the strength of the structure or the thread itself is the limiting condition for determining the angle of the slope and the remaining height of the ratchet, and thus the optimization of the angle of the slope or the remaining height of the ratchet is not innovative for the present invention and the present invention will not be described in detail.

Claims

1. The utility model provides an anti-loosening nut with dual locking and estimate pretightning force function, includes two bearing surfaces, characterized by: at least one of the bearing surface configurations has an asymmetry with respect to the thread axis.

2. The anti-loosening nut with dual anti-loosening and preload estimation functions as claimed in claim 1, comprising two bearing surfaces, at least one of which is configured to be asymmetric with respect to the axis of the thread, wherein: the bearing surface is provided with a fulcrum offset relative to the thread axis.

3. A dual release and preload force estimation anti-loosening nut as claimed in claim 2, including two bearing surfaces, at least one of which is configured to be asymmetric with respect to the axis of the thread, the bearing surfaces being provided with a fulcrum offset with respect to the axis of the thread, wherein: the bearing surface is an inclined bearing surface, namely the bearing surface is not perpendicular to the thread axis, and the highest point of the inclined bearing surface is an offset fulcrum on the bearing surface.

4. A dual release and preload force estimation anti-loosening nut as claimed in claim 2, including two bearing surfaces, at least one of which is configured to be asymmetric with respect to the axis of the thread, the bearing surfaces being provided with a fulcrum offset with respect to the axis of the thread, wherein: the fulcrum on the bearing surface is at least one ratchet.

5. A dual release and preload force estimation anti-loosening nut as claimed in claim 2, including two bearing surfaces, at least one of which is configured to be asymmetric with respect to the axis of the thread, the bearing surfaces being provided with a fulcrum offset with respect to the axis of the thread, wherein: the bearing surface is provided with at least one projection offset with respect to the thread axis.

6. A double anti-loosening and pretension estimating anti-loosening nut as claimed in claims 3, 4 and 5, comprising two bearing surfaces, at least one of which is configured to be asymmetric with respect to the thread axis, and on which a fulcrum is provided which is offset with respect to the thread axis, characterized in that: the offset fulcrum on the bearing surface is any combination of the highest point of the inclined bearing surface, the bulge and the ratchet teeth.

7. The anti-loosening nut with dual anti-loosening and preload estimation functions as claimed in claim 4, comprising two bearing surfaces, at least one of which is configured to be asymmetric with respect to the axis of the thread, the bearing surfaces being perpendicular to the axis of the thread, wherein: at least one ratchet is provided on the bearing surface offset relative to the thread axis.

8. The anti-loosening nut with dual anti-loosening and preload estimation functions as claimed in claim 4, comprising two bearing surfaces, at least one bearing surface having an asymmetry with respect to the axis of the thread, the bearing surfaces being provided with at least one ratchet tooth offset with respect to the axis of the thread, wherein: the ratchet teeth on the bearing surface are cut by intersecting the bearing surface inclined with respect to the thread axis and a plane perpendicular to the thread axis.