Locking nuts and their tightening methods

Abstract

In a self-locking nut, the structure and shape for changing the relative position of the thread contact surface between the upper nut and the bolt are simplified to a structure suitable for mass production. [Solution] The lower nut 1 and the upper nut 2 are provided with tapered surfaces 1A and 2A at their joint surfaces, inclined at an angle of at least 1 / 2 pitch of the screw pitch with respect to a surface perpendicular to the axis of the bolt B. The upper nut 1 is provided with a flange-like portion 3 with the tapered surface 2A as its lower surface, formed by providing a groove 3a having a vertical width of 2.0 mm at a position 2.0 mm or more above the tapered surface 2A, with the depth of the groove 3a being such that the bottom of the groove 3a is at least 1.5 mm away from the inner circumference of the bolt hole of the nut.

Description

[Technical Field]

[0001] The present invention relates to a locking nut configured to be capable of preventing loosening of a nut that occurs after the nut is tightened onto a bolt with a simple structure. [Background Art]

[0002] It is known in practice that when a member to be fastened is fastened by a bolt and a nut threadedly engaged therewith, the nut loosens due to vibration of the machine, apparatus or the like adopting this fastening, which is inconvenient for practical use.

[0003] The fundamental reason why a tightened nut loosens is that a minute clearance (play) is provided between the threads of the bolt and the nut to allow the nut to rotate smoothly on the bolt. Therefore, even if the nut is tightened with a large torque, the frictional force acting between the member to be fastened and the bolt head, and between the nut and the member to be fastened is limited, and the tightened nut loosens due to vibration of a machine or the like.

[0004] As one of means for preventing loosening of a tightened nut, a locking double nut, which is also known from Patent Documents 1 to 3, is used, but a double nut that fully exerts a locking function can hardly be found.

[0005] Therefore, the locking action of the upper nut N in a locking double nut will be described with reference to FIG. 15. For convenience of explanation, FIG. 15 shows a state, in which the thickest part of the nut on the tapered surface of the upper nut N screwed onto the bolt B or the vicinity thereof receives a pressing force P from the thickest part of the nut on the tapered surface of the lower nut (not shown) or the vicinity thereof, schematically in the form of a normal nut.

[0006] In FIG. 15, L: the thickness of the upper nut N, D: the outer diameter of the upper nut N, d: the inner diameter of the upper nut N, P: the upward pressing force acting on the upper nut N from the lower nut (not shown) (generated by the contact between the tapered surface of the upper nut N and the tapered surface of the lower nut), R: the reaction force received by the upper nut N from the bolt B (generated by the pressing force P acting on the upper nut N).

[0007] As shown by the dotted line in Figure 15, the moment RL around the contact point A between the female thread Na of the upper nut N, which is tilted by the upward pressing force P on the tapered surface of the lower nut (not shown), and the male thread Ba of the bolt B is RL = P × 1 / 2(D + d). Therefore, the reaction force R is expressed as R = P × (D + d) × 1 / 2L.

[0008] From the above formula, to increase the reaction force R, it is possible to (a) increase the upward pressing force P of the lower nut, (b) increase the outer diameter D (inner diameter d) of the upper nut N, or (c) decrease the thickness (height) L of the upper nut N. Although not expressed in the above formula for the reaction force R, it is also possible to directly increase the reaction force R by deforming the upper nut N.

[0009] On the other hand, as an alternative to increasing the outer diameter D of the upper nut N, it is considered effective to not increase the outer diameter of the upper nut N itself and to attach a deformable flange to the nut N. Furthermore, reducing the thickness L of the upper nut N is also considered effective in order to deform the upper nut N. From the above considerations, it is thought that conventional anti-loosening nuts (double nuts) cannot fully perform their anti-loosening function for the following reasons.

[0010] The effect of the upward pressing force P acting at the contact point between the threads Na and Ba of the upper nut N and bolt B in the locking nut schematically shown in Figure 15 will be examined using Figures 16 and 17, focusing on one male thread (bolt) and one female thread (nut).

[0011] In this case, when the pressing force P = Σp is set in Figure 17, the force ph parallel to the screw threads is almost balanced at the left and right screw threads Ba and Na of the bolt B and nut N. Therefore, even if a pressing force P acts in the vertical direction, if the force ph parallel to the screw threads Ba and Na is balanced at the contact surfaces of the left and right screw threads Ba and Na, there is no change in the relative position of the contact surfaces of the screw threads Ba and Na. If there is no change in the relative position, a large "crimping force" cannot be obtained, and therefore strong crimping is not possible. In Figure 17, p is the pressing force acting on one screw thread, and Pn is the component force acting perpendicular to the contact surfaces of one screw thread Ba and Na.

[0012] The inventors of the present invention previously proposed a self-loosening nut that can solve the above-mentioned problems of self-loosening nuts in Patent No. 7403170 (Patent Document 4). The invention employs a structure in which the lower nut and upper nut of a locking nut (double nut) can change the relative position of the contact surfaces of the threads that generate a large crimping force between the threads of the upper nut and the threads of the bolt, thereby achieving a sufficient locking effect. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 53-110765 [Patent Document 2] Special Publication No. 62-049489 [Patent Document 3] Patent No. 3574698 [Patent Document 4] Patent No. 7403170 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] The anti-loosening nut previously proposed by the inventor of this application in Patent Document 4 has a lower nut and an upper nut with tapered surfaces formed at a desired angle. The lower nut is screwed onto the bolt with the tapered surfaces of both nuts in close contact and tightened to the object to be fastened. Then, the upper nut is rotated approximately half a turn in the loosening direction, thereby changing the relative position of the thread contact surfaces between the upper nut and the bolt, which results in a large crimping force. However, through prototype testing and other means, it was found that there were issues that needed to be resolved. The issue was to simplify the structure for changing the relative position of the thread contact surfaces between the upper nut and the bolt to obtain an anti-loosening effect, so that it could be applied to precision nuts with diameters smaller than M2 (e.g., 1 mm diameter) as well as nuts with diameters of M30 or larger, and to obtain an anti-loosening nut that is also low cost and suitable for mass production. [Means for solving the problem]

[0015] One configuration of the anti-loosening nut of the present invention, which was made with the aim of solving the above problems, is: A locking nut comprising a lower nut and an upper nut that are screwed onto a bolt, The lower nut and the upper nut are provided with their opposing surfaces formed as tapered surfaces inclined at an angle of at least 1 / 2 the screw pitch with respect to a surface perpendicular to the axis of the bolt. The lower nut and the upper nut are characterized in that one of the nuts has a flange-like portion that includes the tapered surface of the nut, formed by providing a groove parallel to the tapered surface and surrounding the bolt hole of the nut.

[0016] In the anti-loosening nut of the present invention, the lower surface of the upper nut is formed as an inclined tapered surface, while the upper surface of the lower nut remains a horizontal surface. In this case, the flange portion is formed including the inclined tapered surface of the upper nut. Furthermore, in this invention, there are also cases where the angle of inclination of the tapered surfaces formed on the upper surface of the lower nut and the lower surface of the upper nut are different.

[0017] The angle of inclination of the tapered surfaces of the lower and upper nuts in the aforementioned anti-loosening nut is preferably between 1 / 2 and 11 degrees, or more, of the pitch angle of the bolt's thread. The size of the angle of inclination of the upper and lower nuts is proportional to the diameter of the nut or the pitch angle of its thread. Therefore, the angle of inclination of the tapered surface of the nut is appropriately determined according to the diameter of the upper and lower nuts or the pitch angle of their thread. Incidentally, the angle of inclination of the tapered surface increases as the diameter of the upper and lower nuts increases, and decreases as the diameter of the upper and lower nuts decreases. Furthermore, in the present invention, by cutting the middle section of a long nut with a large vertical width (height or length) at the angle of inclination of the tapered surface, it is possible to obtain upper and lower nut components that can be used as lower and upper nuts having tapered surfaces with the same angle of inclination.

[0018] In the present invention, the flange portion formed by a groove provided on the upper or lower nut at an angle parallel to its tapered surface is determined by the position of the groove from the tapered surface, the width (vertical width) of the groove, and the depth (distance of the groove bottom from the inner circumference of the screw) corresponding to the screw diameter of the nut on which the flange portion is provided. This also determines the thickness of the flange portion. For example, in the case of M12 nuts, which are commonly used, a flange portion is formed by a groove with a vertical width of 2.0 mm at a position 2.0 mm away from the tapered surface, with the groove bottom located approximately 1.5 mm away from the inner circumference of the bolt hole (see Figures 1 and 2). In the case of precision nuts of M2 or smaller, the position (distance) of the groove from the tapered surface, the width, and the bottom (distance from the inner circumference of the screw) are smaller than in the above example.

[0019] In the present invention, the lower nut and upper nut are also characterized in that they are provided with an angle mark on the outer circumference of the tapered surface at the point where the thickness of the lower nut and upper nut is greatest (hereinafter referred to as the thickest point) or nearby, indicating the angle at which the upper nut is reversed in the loosening direction after the lower nut and upper nut have been screwed onto the bolt and tightened. However, in the present invention, the anti-loosening effect can be obtained even without providing a mark that functions as a marker.

[0020] Here, in the lower nut and the upper nut, markers formed as marks for obtaining the loosening prevention effect obtained by rotation of the upper nut, and for recognizing the angle of rotation of the upper nut toward the tightening side (forward rotation) or the angle of rotation toward the loosening side (reverse rotation) include three-dimensional markers formed as protrusions or recesses, planar markers such as coloring, adhesive stickers, engraved marks, and scribed lines, or markers that combine the three-dimensional marker and the planar marker.

[0021] For example, when the marker of the lower nut is a concave or convex three-dimensional marker formed on the outer circumferential surface of the upward tapered surface of the flange portion, the marker of the upper nut corresponding to the lower nut is a convex or concave three-dimensional marker formed on the outer circumference of the downward tapered surface and corresponding to the concave or convex marker of the lower nut.

[0022] The loosening prevention nut of the present invention includes a type in which the above-described flange portion is provided on the upper nut, and a type in which the flange portion is provided on the lower nut. Providing the flange portion on either nut exhibits equivalent loosening prevention effect. As an example of forming the flange portion provided on the upper nut, the specifications (arrangement method) of the groove in the case of M12 has been described in paragraph 0018. In the present invention, for the groove for forming the flange portion on the tapered surface, the distance from the tapered surface, the vertical width of the formed groove, the depth of the groove (the distance from the inner peripheral edge of the thread of the nut) can be appropriately set according to the size of the nut.

[0023] In the loosening prevention nut of the present invention, it is preferable to provide a marker serving as a mark for the rotation angle of the upper nut, but the marker may not be provided in some cases. For example, there is a tightening method in which the lower nut is first tightened to a predetermined torque, and then the upper nut is tightened. In this tightening method, the upper nut is tightened until the thickest point of the upper nut overlaps the thickest point of the lower nut or reaches a position immediately before overlapping, so a marker serving as a mark for the tightening angle is not required. Even in this case, it is optional to provide a marker for the tightening angle.

[0024] On the other hand, unlike the tightening method described above, there is a tightening method in which the lower nut and upper nut are tightened together with a socket wrench or similar tool to a predetermined torque while keeping their respective tapered surfaces in close contact, and then the upper nut is rotated approximately half a turn in the loosening direction until the thickest point of the lower nut and the thickest point of the upper nut overlap, or are just before they overlap. Here, the angle at which the upper nut is rotated in the loosening direction is selected from approximately 180 degrees to approximately 120 degrees, depending on the angle of the tapered surface. Incidentally, experiments have confirmed that for an M12 screw with an upper nut (or lower nut) having a flange-like portion with a tapered surface inclination angle of 6 degrees, the loosening rotation angle is approximately 120 degrees, and for a nut with a tapered surface inclination angle of 5.5 to 5.6 degrees, the loosening rotation angle is approximately 180 degrees. [Effects of the Invention]

[0025] The present invention provides a locking nut consisting of a lower nut and an upper nut, wherein the joint surfaces of both nuts are tapered surfaces inclined at an angle of at least 1 / 2 pitch of the screw pitch with respect to a surface perpendicular to the axis of the bolt to be screwed, and one of the nuts is provided with a flange-like portion formed by creating a groove parallel to the tapered surface and surrounding the bolt hole of this nut. As a first example, a marker portion is provided at or near the thickest point of both nuts on the outer circumference of the tapered surfaces of the lower and upper nuts to indicate the angle of reversal or forward rotation when the upper nut is reversed in the loosening direction after the lower and upper nuts have been fastened together to the bolt, or as a second example, when the lower nut is tightened to a predetermined torque first and then the upper nut is rotated in the forward direction relative to the lower nut in the tightening direction. This locking nut is thus designed to reliably obtain a crimping force that provides a locking effect by changing the relative position of the screw thread contact surface between the upper nut and the bolt. Furthermore, the present invention allows for a simpler structure for achieving the anti-loosening effect, thereby enabling the production of a low-cost anti-loosening nut suitable for mass production. [Brief explanation of the drawing]

[0026] [Figure 1](a) is a front view of the upper nut and lower nut having a flange-like portion on the upper nut in the anti-loosening nut of the present invention, and (b) is a plan view of the upper nut in Figure 1(a). [Figure 2] (a) is a front view of the upper and lower nuts in the anti-loosening nut of the present invention, in which the lower nut has a flange-like portion, and (b) is a plan view of the upper nut in Figure 2(a). [Figure 3] A plan view of the upper nut of Embodiment 1 of the anti-loosening nut of the present invention. [Figure 4] View of the upper nut in Figure 3, as seen by arrow AA. [Figure 5] A plan view of the lower nut of Embodiment 2 of the anti-loosening nut of the present invention. [Figure 6] View of the lower nut in Figure 5, as seen by arrow BB. [Figure 7] A plan view of the lower nut of Embodiment 3 of the anti-loosening nut of the present invention. [Figure 8] View of the lower nut in Figure 7, as seen by arrow CC. [Figure 9] A plan view of the upper nut of Embodiment 4 of the anti-loosening nut of the present invention. [Figure 10] View of the upper nut in Figure 9, as seen by the arrow DD. [Figure 11] A plan view of the lower nut of Embodiment 5 of the anti-loosening nut of the present invention. [Figure 12] View from arrow EE in Figure 11. [Figure 13] A plan view of the lower nut of Embodiment 6 of the anti-loosening nut of the present invention. [Figure 14] View of the lower nut in Figure 13, as seen by the FF arrow. [Figure 15] A schematic front view illustrating the force acting from the lower nut to the upper nut when the upper nut is rotated half a turn in the loosening direction in a locking nut (double nut) system. [Figure 16] Figure 15 shows a schematic cross-sectional view, enlarged, illustrating the relationship between the upper nut and the threads of the bolt. [Figure 17] A schematic diagram illustrating the forces acting on one thread of the upper nut and bolt in Figure 16. [Figure 18] A cross-sectional view illustrating the fastening situation using the anti-loosening nut of the present invention (before the upper nut is rotated half a turn in the loosening direction). [Modes for carrying out the invention]

[0027] Next, an example of an embodiment of the anti-loosening nut of the present invention will be described with reference to Figures 1 to 4.

[0028] In Figures 1(a) and 1(b), 1 is a lower nut with its upper surface formed as a tapered surface 1A, and 2 is an upper nut with its lower surface formed as a tapered surface 2A with the same inclination angle as the tapered surface 1A.

[0029] The tapered surfaces 1A and 2A in Figure 1 are inclined at an angle of at least half a screw pitch with respect to a plane perpendicular to the axis of the bolt (not shown) into which both nuts 1 and 2 are screwed. In this invention, if the inclination angle of the tapered surfaces 1A and 2A is less than half a pitch, the anti-loosening effect of the upper nut 2 cannot be obtained. Furthermore, the inclination angle is preferably between half a pitch and about 11 degrees for practical purposes. In Figure 1, it is shown as 6 degrees. Note that the M12 upper nut 2 shown in Figure 1(a) is provided with a flange-like portion 3 having a vertical thickness of at least 2.0 mm above its tapered surface 2A, at a distance of at least 2.0 mm. Furthermore, the size of the inclination angle of the tapered surfaces of the upper and lower nuts is proportional to the diameter of the nut or the pitch angle of the screw, so the inclination angle of the tapered surfaces can be appropriately determined depending on the diameter of the upper and lower nuts or the pitch angle of the screw used.

[0030] In this invention, a flange-like portion 3 is formed on the nut by providing a groove of appropriate depth that is parallel to the tapered surface of the nut and surrounds the bolt hole of the nut. In Figure 1(a), the flange-like portion 3 of the upper nut 2 is formed by cutting a groove with a width of 2.0 mm (vertical width) with a cutter at a location at least 2.0 mm below the tapered surface 2A, but the method of forming the flange-like portion 3 may be other than cutting. The depth of the groove 3a is at least 1.5 mm away from the inner circumference of the bolt hole 2B.

[0031] The flange portion 3 of the lower M12 nut 1 shown in Figure 2(a) is formed as a flange 3b with a vertical thickness of at least 2.0 mm, located at least 2.0 mm below the tapered surface 1A.

[0032] The flange 3b of the flange-shaped portion 3 is formed in the same manner as in the case of the upper nut 2 described above. That is, the flange 3b is formed by cutting a groove 3a with a width of 2.0 mm (vertical direction) at least 2.0 mm below the tapered surface 1A using a cutter (not shown). In this case, the depth of the groove 3a (depth toward the center of the bolt hole) is at least 1.5 mm away from the inner circumference of the bolt hole 1B of the lower nut 1. For example, when the bolt hole 1B is 12.0 mm, the inner diameter of the groove 3a can be 15.0 mm. The bolt hole 1B has a female thread that screws onto the bolt B.

[0033] On the circumference of the flange 3b of the lower nut 1 shown in Figure 5, a surface 3c is formed that is approximately 0.5 mm higher than other parts in a counterclockwise direction from the thickest point Hx (hereinafter also referred to as the thickest point Hx) to the thinnest point Hy (hereinafter also referred to as the thinnest point Hy) of the lower nut 1, for example, in a 120° fan shape. Consequently, the remaining surface is formed as a lower surface 3d that is 0.5 mm lower than the higher surface 3c in a 240° range.

[0034] In Figure 3, the upper nut 2 has a tapered surface 2A formed on its lower surface with the same angle of inclination as the tapered surface 1A of the lower nut 1. In Figure 3, 2B is a bolt hole with a female thread.

[0035] In the upper nut 2, the point with the largest vertical width, Hx (thickest point Hx), and the point with the smallest vertical width, Hy (thinnest point Hy), are in a phase relationship that is 180° opposite to the two points Hx and Hy in the lower nut 1 (positions on the diagonal of a hexagon) (see Figure 1).

[0036] In Figure 3, at the thickest point Hx of the tapered surface 2A of the upper nut 2, a convex surface 2a with a height of 0.5 mm is provided in a 60° range adjacent in a clockwise direction, such that it rides up onto the higher surface 3c formed on the lower nut 1. Therefore, the remaining surface of the tapered surface 2A is a flat, lower surface 2b that is 0.5 mm lower than the convex surface 2a. Note that since Figure 3 is a plan view of the upper nut 2, the convex surface 2a and the lower surface 2b are formed on the tapered surface 2A of the lower surface of the upper nut 2 (see Figure 4). This point is the same in Figures 9 and 10, which will be described later.

[0037] In the lower nut 1 of Figure 5, the higher surface 3c is formed, for example, by cutting 240° off the original tapered surface 1A so that the lower surface 3d remains (see Figure 6). Note that the entire surface 3d is not at the same height; the 60° range adjacent to the higher surface 3c may be formed as a low triangular ramp section 3e (see Figures 7 and 8) with a cross-section where the height changes between 0 and 0.5 mm as the hypotenuse of a triangle. Of course, it is also acceptable for the entire surface 3d, in this case the 240° range, to be flat.

[0038] The above constitutes an embodiment of the anti-loosening nut of the present invention, and its usage will be described below.

[0039] An example of the anti-loosening nut of the present invention, as explained in Figures 1 to 8, is shown in Figure 18, illustrating an example of fastening it to a bolt B inserted through two plate materials 11 and 12.

[0040] With the tapered surfaces 1A and 2A of the lower nut 1 and upper nut 2 positioned parallel and close together as shown in Figure 1 (the thickest point Hx of the lower nut 1 and the thinnest point Hy of the upper nut 2 facing each other), the female threads of the respective bolt holes 1B and 2B are screwed onto the male thread of the bolt B using a socket wrench. In this state, the tapered surfaces 1A and 2A do not come into close contact due to the convex surface 2a on the tapered surface 2A of the upper nut 2 and the higher surface 3c on the tapered surface 1A of the lower nut 1.

[0041] Once the two nuts 1 and 2 are tightened to a predetermined torque using a socket wrench, and the lower surface 1C of the lower nut 1 is pressed against the upper surface of the plate material 11, the upper nut 2 is rotated in the opposite direction to the tightening direction (loosening direction), for example, by approximately 155°.

[0042] By rotating the upper nut 2 in the loosening direction, the convex surface 2a formed adjacent to the thickest point Hx of the upper nut 2 slides on the lower surface 3d formed on the tapered surface 1A of the lower nut 1, and rides up onto the higher surface 3c provided near the thickest point Hx of this tapered surface 1A. The convex surface 2a and the higher surface 3c described above serve as three-dimensional marker functions that determine the amount of rotation (angle) of approximately half a turn for preventing loosening.

[0043] In this invention, upper and lower nuts 1 and 2 are tightened onto bolts B inserted through bolt holes in plate materials 11 and 12 of the fastened material, with their tapered surfaces 1A and 2A in the phase relationship shown in Figure 1. Once tightening is complete, only the upper nut 1 is rotated approximately half a turn in the loosening direction (155° in the above example), so that the convex surface 2a provided on the thickest part Hx of the upper nut 2 rides up onto the higher surface 3c formed near the thickest part Hx of the lower nut 1, thereby completing the setting as a locking nut.

[0044] By tightening both nuts 1 and 2 in the positional relationship shown in Figure 1, and then by approximately half a turn of the upper nut 2 in the loosening direction, the component force pn, as explained in Figure 17, acts on the threads of the upper nut 2 and the bolt B. As a result, the component force pn on each thread can significantly change the relative position of the thread contact surfaces of the upper nut 2 and the bolt B, thereby providing a sufficient anti-loosening effect.

[0045] In the present invention, the same anti-loosening effect as in the above embodiment can also be obtained by forming a convex portion similar to the high surface 3c of the lower nut 1 near the thickest part Hx of the upper nut 2, while forming a convex portion similar to the convex portion 2a of the upper nut 2 on the upper surface of the flange 3b near the thickest part Hx of the lower nut 1.

[0046] Furthermore, as another configuration for obtaining the above-mentioned anti-loosening effect of the present invention, the upper nut 2 is provided with the configuration of the lower nut 1 in the above embodiment, i.e., the configuration of the flange portion 3, while the lower nut 1 is provided with the configuration of the upper nut 2 in the above embodiment, i.e., the convex surface 2a. In this configuration, the same anti-loosening effect as in the above embodiment can be obtained with the upper nut 2 and lower nut 1.

[0047] The above description was an example of a self-locking nut (first example) in which a lower nut 1 and an upper nut 2, both having the same angle of inclination as tapered surfaces 1A and 2A, are screwed onto bolt B together and tightened, and then the upper nut 2 is rotated by the required angle to loosen it. However, the self-locking nut of the present invention also has a type (second example) in which the lower nut 1 is screwed onto bolt B first and tightened to a predetermined torque, and then the upper nut 2 is screwed onto bolt B and tightened. The second example will be described below.

[0048] Figures 9 and 10 show a second example of the upper nut 2 when the upper nut 2 is tightened after the lower nut 1 has been tightened. In Figure 9, a convex surface 2a with a thickness of 0.5 mm is formed in a range of 60° counterclockwise from the thickest point Hx. Therefore, the remaining surface of the tapered surface 2A is a flat surface 2b that is 0.5 mm lower than the convex surface 2a.

[0049] On the other hand, Figures 11 and 12 show the lower nut 1, which corresponds to the upper nut 2 shown in Figures 9 and 10. Here, a high surface 3c with a height (thickness) of 0.5 mm is formed in a range of 120° clockwise from the thickest point Hx.

[0050] The reason why the shape of the higher surface 3c formed on the tapered surface 1A of the lower nut 1, as viewed from the plane, differs from the example in Figure 5 is that, after the lower nut 1 is fastened, the upper nut 2 is tightened onto the bolt B in a forward rotation on the tightening side. Therefore, near the end of the tightening of the upper nut 2, the convex surface 2a of the upper nut 2 can ride up onto the higher surface 3c of the lower nut 1.

[0051] In this second example as well, when the upper nut 2 is rotated (tightened) in the forward direction, the convex surface 2a of the upper nut 2 can be smoothly mounted onto the higher surface 3c of the lower nut 1. To achieve this, a low triangular cross-section mounting ramp 3e, as seen from the forward rotation side of the higher surface 3c, can be positioned on the near side (see Figures 7 and 8). In the second example of the anti-loosening nut described in paragraphs 0048-0051, the inclination angle of the tapered surface 1A of the lower nut 1 and the inclination angle of the tapered surface of the upper nut 2 may be the same as in the first example, but it is preferable to make them different angles in order to bring the thickest part of the upper nut 2 closer to the thickest part of the lower nut 1 (increasing the crimping effect).

[0052] In the present invention, instead of the three-dimensional marker function formed by the higher surface 3c of the lower nut 1 and the convex surface 2a of the upper nut 2 in the example described above, or together with the three-dimensional marker function, a planar marker function may be provided by coloring, scribing, or the like on the outer circumferential surface of the lower nut 1 where the higher surface 3c is provided and the outer circumferential surface of the upper marker 2 where the convex surface 2a is provided.

[0053] Furthermore, in the first embodiment of the present invention, when tightening the upper and lower nuts 1 and 2, the upper and lower nuts 1 and 2 are tightened together with a socket wrench, and then the upper nut 2 is rotated in the reverse direction to loosen it by approximately half a turn. However, in the second embodiment of the present invention, the lower nut 1 is first screwed onto the bolt B to a predetermined torque and tightened, and then the upper nut 2 is screwed onto the bolt B, bringing its tapered surface 2A closer to the tapered surface 1A of the lower nut 1, and the upper nut 2 is rotated in the forward direction so that the thickest parts Hx of both nuts 1 and 2 are brought closer together.

[0054] In this invention, the groove 3a, flange 3b, upper surface 3c, lower surface 3d formed on the tapered surface 1A, and the convex surface 2a and flat surface of the tapered surface 2A were described as being formed by cutting in the embodiment, but these can also be formed by processing methods other than cutting (for example, forging or pressing). Furthermore, although the upper and lower nuts 1 and 2 described above are hexagonal nuts, this invention can also be applied to nuts with octagonal or dodecagonal sides, or nuts with fewer or more sides.

[0055] The above description was an example of an embodiment of the anti-loosening nut of the present invention, in which a flange-shaped portion 3 is provided on the lower nut 1. However, the anti-loosening nut of the present invention also has an upper nut 2 with a flange-shaped portion 3 formed on it, and the function and operation of that flange-shaped portion 3 are the same as those provided on the lower nut 1.

[0056] As described above, the present invention provides a simple structure for the anti-loosening nut suitable for mass production, making it possible to manufacture and provide an anti-loosening nut with an extremely high anti-loosening effect at low cost and with ease. [Explanation of symbols]

[0057] 1. Lower nut 1A Tapered surface 1B Female thread 1C Bottom 3 Flange 3a groove 3b Flange 3c High-level face 3D lower surface 3e Overcoming slope section 2. Upper nut 2A Tapered surface 2B Female Thread 2a Convex Hx Thickest point of both nuts 1 and 2 Hy: Thinnest point of both nuts 1 and 2

Claims

1. A locking nut comprising a lower nut and an upper nut that are screwed onto a bolt, Both the lower nut and the upper nut, or the upper nut, are provided with tapered surfaces on the opposing surfaces of both nuts, or the lower surface of the upper nut, which are inclined at an angle of at least 1 / 2 pitch of the screw pitch with respect to a plane perpendicular to the axis of the bolt. A locking nut characterized in that one of the nuts, or the upper nut, has a flange-like portion including the tapered surface, formed by providing a groove parallel to the tapered surface and surrounding the bolt hole of the nut.

2. The anti-loosening nut according to claim 1, wherein the lower nut does not have a tapered surface and the upper nut does have a tapered surface.

3. The anti-loosening nut according to claim 1 or 2, wherein the inclination angle of the tapered surface is 1 / 2 or more of the screw pitch to 11 degrees.

4. The locking nut according to claim 1, wherein the inclination angle of the tapered surface is the same for both nuts, or different for both nuts.

5. The anti-loosening nut according to claim 1 or 2, wherein the inclination angle of the tapered surface increases as the diameters of the lower nut and upper nut increase, and decreases as the diameters of the lower nut and upper nut decrease.

6. The flange portion is a locking nut according to claim 1 or 2, wherein the upper nut is provided with its tapered surface facing downwards.

7. The anti-loosening nut according to claim 6, wherein the outer diameter (or outer shape) of the flange-shaped portion of the upper nut is formed to be larger than the outer diameter (or outer shape) of the lower nut.

8. The flange-like portion is a locking nut according to claim 1, wherein the lower nut is provided with its tapered surface facing upward.

9. The anti-loosening nut according to claim 1, wherein the lower nut and the upper nut are provided with a mark indicating the rotation angle when the upper nut is reversed or rotated forward, on the outer circumference of the tapered surface at the point where the thickness of the lower nut and the upper nut is greatest (hereinafter referred to as the thickest point) or in the vicinity thereof.

10. The locking nut according to claim 9, wherein the rotation angle mark on the upper nut indicates the rotation angle when the upper nut is rotated in the loosening direction after the lower nut and upper nut have been tightened together, or indicates the rotation angle when the upper nut is rotated in the tightening direction after the lower nut has been tightened first.

11. The anti-loosening nut according to claim 10, wherein the markings are provided on the outer circumference of the flange-shaped portion and on the outer circumference near the tapered surface of the nut that does not have the flange-shaped portion, using three-dimensional markers, planar markers, or a combination marker using both three-dimensional and planar markers.

12. A method for tightening a locking nut according to claim 1, wherein, after tightening the lower nut to a predetermined torque, the upper nut is tightened by rotating it in the forward direction, and the upper nut is tightened until the thickest point or vicinity of the lower nut and the thickest point or vicinity of the upper nut overlap, or until just before they overlap.

13. A method for tightening a locking nut according to claim 12, wherein the lower nut is a nut that does not have a tapered surface, and the upper nut is tightened to a predetermined torque.

14. A method for tightening a locking nut according to any of the claims in claim 1, wherein the lower nut and the upper nut are tightened together with a predetermined torque while their respective tapered surfaces are in contact, and then the upper nut is rotated (reverse rotation) in the loosening direction until the thickest point of the lower nut or its vicinity and the thickest point of the upper nut or its vicinity overlap or just before they overlap.

15. A method for tightening a locking nut according to claim 12, wherein the angle of inclination of the tapered surface of the lower nut and the angle of inclination of the tapered surface of the upper nut are the same or different.

16. A method for tightening a locking nut according to claim 11, wherein the angle of inclination of the tapered surfaces of the lower nut and the upper nut are the same or different, in the locking nut used in the tightening method of claim 14.

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