Looseness preventing device

Abstract

To provide a looseness preventing device which includes a protruded nut having a protrusion and a recessed nut having a recess, either the protrusion or the recess being eccentric to a screw hole, for preventing the looseness with the irregularity eccentric fitting of the protrusion and the recess while locating the gravity center of the whole device near the axis center of a screw shaft at the time of completing fastening.SOLUTION: A looseness preventing device has one of a construction A and a construction B: the construction A; an axis center E1 of a tapered inner peripheral face of a recess 22 is eccentric to an axis center O1 of a screw hole 23 of a recessed nut 2 and the gravity center G1 of the recessed nut 2 is located in the same direction as the axis center E1 of the tapered inner peripheral face of the recess 22 with respect to the axis center O1 of the screw hole 23 of the recessed nut 2, and the construction B; the axis center E2 of the tapered outer peripheral face of the protrusion 12 is eccentric to the axis center O2 of the screw hole 13 of the protruded nut 1 and the gravity center of the protruded nut 1 is located in the opposite direction to the axis center E2 of the tapered outer peripheral face of the protrusion 12 with respect to the axis center O2 of the screw hole 13.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an anti-loosening device consisting of two nuts that are eccentrically fitted together. [Background technology]

[0002] The applicant of the present application has been developing the Hard Lock Nut ("Hard Lock" is a registered trademark of the applicant of the present application), a double-nut type anti-loosening device that exhibits high anti-loosening performance, as disclosed, for example, in Patent Document 1 below. A thin Hard Lock Nut specialized for mounting bearings is manufactured and sold under the product name "HLB" (a registered trademark of the applicant of the present application).

[0003] This hard lock nut includes a first nut having a threaded hole that screws onto a screw shaft, and a second nut having a threaded hole that screws onto the screw shaft.

[0004] The first nut has a protrusion that protrudes axially toward the second nut, and the protrusion has a tapered outer circumferential surface with a predetermined taper angle. The screw hole of the first nut passes through the protrusion in the axial direction.

[0005] The second nut has a recess into which the protrusion fits, and the recess has a tapered inner circumferential surface having a predetermined taper angle. The screw hole of the second nut opens into a bottom surface of the recess.

[0006] Either the protrusion or the recess is eccentric with respect to the screw hole. That is, in one embodiment, the tapered outer peripheral surface of the protrusion is eccentric with respect to the screw hole of the first nut, and the tapered inner peripheral surface of the recess is concentric with respect to the screw hole of the second nut. In another embodiment, the tapered inner peripheral surface of the recess is eccentric with respect to the screw hole of the second nut, and the tapered outer peripheral surface of the protrusion is concentric with respect to the screw hole of the first nut.

[0007] With the above configuration, when the convex portion of the first nut screwed onto the screw shaft and the concave portion of the second nut screwed onto the screw shaft are eccentrically fitted together, the tapered outer peripheral surface of the convex portion and the tapered inner peripheral surface of the concave portion interfere with each other in a portion of the circumferential direction so that a pressing force is generated on the first and second nuts along the eccentric direction, and the pressing force becomes greater as the fitting depth of the convex portion relative to the concave portion becomes greater.

[0008] In this way, the eccentric fit between the convex portion and the concave portion creates a strong wedge action, and when the convex portion and the concave portion are engaged, the tapered outer surface of the convex portion and the tapered inner surface of the concave portion interfere with each other in part of the circumferential direction, generating large frictional forces at the contact areas between the convex portion and the concave portion, and between each of the first and second nuts and the screw shaft, thereby providing a strong anti-loosening effect. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Patent No. 6762591 Summary of the Invention [Problem to be solved by the invention]

[0010] In the above conventional locking devices, due to the eccentric structure of the convex or concave portion, the positions of the centers of gravity of the first and second nuts are shifted radially from the axis of the screw shaft when they are fastened to the screw shaft. This phenomenon, particularly when used as a fixing nut for a bearing, increases the load on the bearing and causes a shortening of the bearing's life, so improvement was desired. [Means for solving the problem]

[0011] The locking device of the present invention includes a first nut having a threaded hole that screws onto a screw shaft, and a second nut having a threaded hole that screws onto the screw shaft. The first nut has a protrusion that protrudes axially toward the second nut, and the protrusion has a tapered outer circumferential surface with a predetermined taper angle. The second nut has a recess into which the protrusion fits, and the recess has a tapered inner circumferential surface with a predetermined taper angle.

[0012] In the first aspect of the present invention, the axis of the tapered inner peripheral surface of the recess is eccentric with respect to the axis of the screw hole of the second nut, and the center of gravity of the second nut is located in the same direction as the axis of the tapered inner peripheral surface of the recess with respect to the axis of the screw hole of the second nut. In this case, the axis of the tapered outer peripheral surface of the protrusion is preferably concentric with the axis of the screw hole of the first nut. Preferably, the second nut includes a nut body having the recess on its end surface, and the screw hole of the second nut is opened on the bottom surface of the recess. The adjustment of the center of gravity of the second nut can be performed by optimizing the outer peripheral shape of the nut body of the second nut, providing a cavity or cutout portion of an appropriate size and shape in the second nut, or the like.

[0013] More preferably, the distance d1 from the axis of the screw hole of the second nut to the center of gravity of the second nut is greater than P1 × tan θ1 × (1 / 5) and smaller than P1 × tan θ1 × (1 / 2), where P1 is the thread pitch of the screw hole of the second nut and θ1 is 1 / 2 of the taper angle of the tapered inner surface of the recess.

[0014] In a second aspect of the present invention, the axis of the tapered outer peripheral surface of the protrusion is eccentric with respect to the axis of the screw hole of the first nut, and the center of gravity of the first nut is located in the opposite direction to the axis of the tapered outer peripheral surface of the protrusion with respect to the axis of the screw hole. In this case, the axis of the tapered inner peripheral surface of the recess is preferably concentric with the axis of the screw hole of the second nut. Preferably, the first nut has a nut body, and the protrusion is provided so as to protrude in the axial direction from the nut body. The adjustment of the center of gravity of the first nut can be performed by optimizing the thickness and outer peripheral shape of the nut body and / or the protrusion of the first nut, or by providing a cavity or notch of an appropriate size and shape in the first nut.

[0015] More preferably, the distance d2 from the axis of the screw hole of the first nut to the center of gravity of the first nut is greater than P2 × tan θ2 × (1 / 5) and smaller than P2 × tan θ2 × (1 / 2), where P2 is the thread pitch of the screw hole of the first nut and θ2 is 1 / 2 the taper angle of the tapered outer peripheral surface of the convex portion.

[0016] Typically, the thread pitch P2 of the first nut and the thread pitch P1 of the second nut are equal, but may be slightly different. Typically, the taper angle of the outer peripheral surface of the protruding portion of the first nut and the taper angle of the inner peripheral surface of the recessed portion of the second nut are equal, but may be slightly different. Effect of the Invention

[0017] According to the present invention, when the first and second nuts are in a fastened state, the positions of their centers of gravity can be brought closer to the axis of the screw shaft. [Brief description of the drawings]

[0018] [Figure 1] 1A to 1C are three views of a first nut of the locking device according to the first embodiment of the present invention. [Diagram 2] 3A to 3C are three views of a second nut of the locking device according to the first embodiment. [Diagram 3]3 is a vertical cross-sectional view of the anti-loosening device according to the first embodiment in a fastened state of a first and second nut. FIG. [Figure 4] 11A to 11C are three views of a first nut of a locking device according to a second embodiment of the present invention. [Diagram 5] 13 is a three-view diagram of a second nut of the locking device according to the second embodiment. FIG. [Figure 6] 11 is a graph showing a transition of the center of gravity position during a second nut tightening process when the first nut has an eccentric structure and the center of gravity is not corrected. [Figure 7] 11 is a graph showing a transition of the center of gravity position during a second nut tightening process when the first nut has an eccentric structure and center of gravity correction is performed. [Figure 8] 11 is a graph showing a transition of the center of gravity position during a second nut tightening process in the case where the second nut has an eccentric structure and the center of gravity is not corrected. [Figure 9] 13 is a graph showing a transition of the center of gravity position during a second nut tightening process when the second nut has an eccentric structure and center of gravity correction is performed. [Figure 10] 13 is a graph showing the relationship between the amount of tightening rotation of a second nut and the transition of the center of gravity position in the process of fastening the second nut to the first nut in a model with a correction coefficient of 0.235. [Figure 11] 13 is a graph showing the relationship between the amount of tightening rotation of a second nut and the transition of the center of gravity position in the process of fastening the second nut to the first nut in a model with a correction coefficient of 0.205. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present inventors analyzed the shift in the center of gravity when the first nut and the second nut of a conventional anti-loosening device are fastened.

[0020] When the convex portion of the first nut is eccentric with respect to the screw hole, the center of gravity of the first nut is shifted in the same direction as the axis of the tapered outer peripheral surface of the convex portion with respect to the axis of the screw hole due to the eccentric structure. When the second nut is tightened into the first nut by finger force, the outer peripheral surface of the convex portion of the first nut and the inner peripheral surface of the concave portion of the second nut start to slide in part of the circumferential direction.

[0021] When the second nut is further tightened using a tool, the second nut is pushed radially outward by the convex part and moves slightly radially outward because there is a fit gap (play) between the screw shaft and the screw hole, and the sliding part is strongly pressed radially outward by the eccentric convex part of the first nut, causing it to deform slightly. The screw hole of the second nut and the screw shaft are pressed radially as a reaction force to the internal stress generated by this deformation, and the friction force increases to prevent loosening. At the same time, the center of gravity of the second nut also moves due to the radial outward deformation and radial movement of the sliding part. Note that the first nut, which is fastened to the screw shaft first, is already under axial force when the second nut is fastened, so there is almost no radial movement associated with the fastening of the second nut.

[0022] Here, assuming that the center of gravity of the second nut alone is on the axis of the screw hole, when the first and second nuts are fastened to the screw shaft, the center of gravity of the entire anti-loosening device is shifted radially from the axis of the screw shaft due to the eccentricity of the convex part of the first nut. In addition, the center of gravity of the second nut is shifted radially outward from the axis of the screw shaft due to the second nut being pushed by the convex part of the first nut and moving slightly in the direction of the eccentricity of the convex part. In addition, the center of gravity of the second nut is shifted radially outward from the axis of the screw shaft due to the inner peripheral surface of the recess of the second nut being deformed radially outward by the convex part of the first nut. It is considered that the shift in the center of gravity due to the radial movement and deformation of the second nut increases almost in proportion to the amount of tightening of the second nut relative to the first nut, as shown in FIG. 6.

[0023] In order to reduce the amount of deviation of the center of gravity of the entire device relative to the axis of the screw shaft when fastening is complete, as shown in Figure 7, the center of gravity of the first nut, which has an eccentric structure, can be positioned in the opposite direction to the eccentricity of the convex part relative to the screw hole so that it balances with the center of gravity of the second nut when fastening is complete.

[0024] Next, we consider the case where the recess of the second nut is eccentric with respect to the screw hole. In this case, the center of gravity of the second nut is shifted in the opposite direction to the axis of the tapered inner surface of the recess with respect to the axis of the screw hole due to its eccentric structure. When the second nut is tightened against the first nut by finger force, the outer peripheral surface of the convex portion of the first nut and the inner peripheral surface of the recess of the second nut start to slide in part of the circumferential direction.

[0025] When the second nut is further tightened using a tool, the inner peripheral surface of the recess of the second nut is pressed radially outward by the sliding part, and the second nut moves slightly radially in the direction in which the deviation of the center of gravity position increases, and the sliding part deforms slightly radially outward, further increasing the deviation of the center of gravity position. The screw hole of the second nut and the screw shaft are pressed radially as a reaction force of the internal stress generated by this deformation, and the friction force increases to prevent loosening. At the same time, as shown in Figure 8, the deviation of the center of gravity position of the second nut increases due to the radial movement and deformation of the sliding part. Note that the first nut, which is fastened to the screw shaft first, is already under axial force when the second nut is fastened, so there is almost no radial movement due to the fastening of the second nut.

[0026] In order to reduce the amount of deviation of the center of gravity of the entire device relative to the axis of the screw shaft when fastening is complete, the center of gravity of the second nut having an eccentric structure can be positioned in the same direction as the eccentricity of the recess relative to the screw hole so that it is closer to the axis of the screw shaft when fastening is complete, as shown in Figure 9.

[0027] Next, the optimum value of the distance (amount of deviation of the center of gravity) between the center of gravity of the first or second nut having an eccentric structure and the axis of the screw hole is examined.

[0028] The amount of radial outward movement of the inner circumferential surface of the recess at the sliding portion between the convex portion and the concave portion due to the tightening of the second nut depends on the gradient angle θ of the sliding portion of the outer circumferential surface of the convex portion and the inner circumferential surface of the concave portion. The gradient angle θ is half the taper angle of the outer circumferential surface of the convex portion and the inner circumferential surface of the concave portion. Here, if the amount of axial movement due to tightening is δ, the amount of radial outward movement of the inner circumferential surface of the recess at the sliding portion can be expressed as δ x tan θ. Therefore, the amount of deviation of the center of gravity position can be expressed as k x δ x tan θ, where k is a correction coefficient.

[0029] 10 and 11 show, in a polar coordinate system, the transition of the center of gravity of the entire locking device depending on the tightening rotation angle of the second nut relative to the first nut, starting from the point where the sliding between the convex portion and the concave portion starts. The thin spiral is a transition diagram of the center of gravity when the first and second nuts are fastened without performing center of gravity correction. FIG. 10 is a transition diagram when the correction coefficient a is set to 0.235, and FIG. 11 is a transition diagram when the correction coefficient a is set to 0.205. The thick line is a transition diagram of the center of gravity when center of gravity correction is performed on one of the first and second nuts having an eccentric structure. When center of gravity correction is not performed, as shown by the thin spiral, the center of gravity of the entire device moves radially outward in proportion to the amount of tightening rotation of the second nut, starting from the point where the sliding between the convex portion and the concave portion starts. On the other hand, when center of gravity correction is performed, as shown by the thick line, starting from the point at which the convex and concave portions start to slide, the center of gravity position of the entire device gradually approaches the origin as the amount of tightening rotation of the second nut increases, and once the amount of rotation increases beyond a certain level, the center of gravity position moves away from the origin.

[0030] 10, it can be seen that when the correction coefficient k is 0.235, the deviation amount of the center of gravity position is reduced by 1 to 2 rotations from the start of sliding due to the center of gravity correction. Also, with reference to Fig. 11, it can be seen that when the correction coefficient k is 0.205, the deviation amount of the center of gravity position is reduced by 1.5 to 2.5 rotations from the start of sliding due to the center of gravity correction.

[0031] The inventors of the present application have found that a hard lock nut can exhibit a sufficient anti-loosening effect by being tightened approximately one to 2.5 rotations from the start of sliding between the convex and concave portions. To produce a sufficient anti-loosening effect at 0.9 rotations from the start of sliding and minimize the amount of displacement of the center of gravity as much as possible, considering the model calculation shown in FIG. 10, it can be seen that the center of gravity correction amount may be set to 0.9×0.235×δ×tan θ≒0.2×δ×tan θ. Also, to minimize the amount of displacement of the center of gravity as much as possible at 1.5 to 2.5 rotations from the start of sliding, considering the model calculation shown in FIG. 11, it can be seen that the center of gravity correction amount may be set to 1.5×0.205×δ×tan θ≒0.3×δ×tan θ to 2.5×0.205×δ×tan θ≒0.5×δ×tan θ.

[0032] Since the axial movement amount δ corresponding to one rotation of the tightening rotation amount is equal to the screw pitch p, integrating the above formula for the center of gravity correction amount, the distance d from the screw hole axis of the center of gravity of the nut having an eccentric structure should satisfy p×tan θ×(1 / 5) < d < p×tan θ×(1 / 2). Thereby, while exerting a sufficient anti-loosening effect, the center of gravity of the entire device in the fastened state can be positioned near the axis of the screw.

[0033] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0034] FIGS. 1 to 3 show an anti-loosening device according to a first embodiment of the present invention. This device includes a first nut 1 (hereinafter referred to as a "convex nut") having a screw hole 13 screwed onto a screw shaft 3, and a second nut 2 (hereinafter referred to as a "concave nut") having a screw hole 23 screwed onto the screw shaft 3. In this embodiment, the convex nut 1 is used as the lower nut, and the concave nut 2 is screwed onto the screw shaft 3 above the convex nut 1. Note that the concave nut may be used as the lower nut, and the convex nut may be screwed onto the screw shaft above the concave nut.

[0035] The convex nut 1 has a nut body 11 in the shape of a hexagonal prism as a whole, and a frustum-shaped cylindrical convex portion 12 that protrudes axially from the upper surface of the nut body 11 toward the concave nut 2. The convex portion 12 has a tapered outer peripheral surface with a predetermined taper angle. The threaded hole 13 is provided across the nut body 11 and the convex portion 12. The axis of the outer peripheral surface of the convex portion 12 is concentric with the axis of the threaded hole 13. The center of gravity of the convex nut 1 alone is on the axis of the threaded hole 13.

[0036] The concave nut 2 has a nut body 21 in which a concave portion 22 into which the convex portion 12 fits is formed to open at the bottom surface. The concave portion 22 has a tapered inner peripheral surface with a predetermined taper angle. The taper angle of the inner peripheral surface of the concave portion 22 is equal to the taper angle of the outer peripheral surface of the convex portion 12.

[0037] The axis E1 of the inner peripheral surface of the concave portion 22 of the concave nut 2 is eccentric by a predetermined amount a with respect to the axis O1 of the threaded hole 23. If no centroid correction is performed, the center of gravity of the concave nut 2 will be located in the direction opposite to the axis E1 of the inner peripheral surface of the concave portion with respect to the axis O1 of the threaded hole 23. In this embodiment, by cutting out a part of the outer periphery of the nut body 21, the center of gravity G1 of the concave nut 2 is corrected so as to be located in the same direction as the axis E1 of the inner peripheral surface of the concave portion with respect to the axis O1 of the threaded hole.

[0038] It is preferable that the distance d1 from the axis O1 of the threaded hole of the concave nut 2 to the center of gravity G1 of the concave nut 2 satisfies P1×tan θ1×(1 / 5) < d1 < P1×tan θ1×(1 / 2). Here, P1 is the thread pitch of the threaded hole 23 of the concave nut 2, and θ1 is 1 / 2 of the taper angle of the tapered inner peripheral surface of the concave portion 22.

[0039] According to the anti-loosening device of the first embodiment, in the state where the convex nut 1 and the concave nut 2 are fastened as shown in FIG. 3, it can exert a sufficient anti-loosening effect and locate the center of gravity of the entire device near the axis of the screw shaft 3.

[0040] Figs. 4 and 5 show the anti-loosening device according to the second embodiment of the present invention. For the components having the same configuration as those in the first embodiment, the same reference numerals are used and the detailed description thereof is omitted, and the different configurations, functions and effects will be described.

[0041] In the anti-loosening device according to the second embodiment, the convex portion 12 of the convex nut 1 is eccentric with respect to the screw hole 13. That is, the axis E2 of the outer peripheral surface of the convex portion 12 is eccentric with respect to the axis O2 of the screw hole 13 by a predetermined eccentricity a. Further, by cutting out a part of the outer periphery of the nut body 11, the center of gravity G2 of the convex nut 1 is corrected so as to be located in the diametrically opposite direction to the axis E2 of the outer peripheral surface of the convex portion with respect to the screw hole axis O2.

[0042] The distance d2 from the screw hole axis O2 of the convex nut 1 to the center of gravity G2 of the convex nut 1 preferably satisfies P2×tan θ2×(1 / 5) < d2 < P2×tan θ2×(1 / 2). Here, P2 is the screw pitch of the screw hole 1 of the convex nut 1, and θ2 is 1 / 2 of the taper angle of the tapered outer peripheral surface of the convex portion 12.

[0043] In the second embodiment, the axis of the inner peripheral surface of the concave portion 22 of the concave nut 2 is concentric with the axis of the screw hole 23, and the center of gravity of the concave nut 2 is located on the axis of the screw hole 23.

[0044] Also in this anti-loosening nut according to the second embodiment, a sufficient anti-loosening effect can be exerted, and the center of gravity of the entire device can be positioned near the axis of the screw shaft 3.

Description of Reference Numerals

[0045] 1 First nut 11 Nut body 12 Convex portion 13 Screw hole 2 Second nut 21 Nut body 22 Concave portion 23 Screw hole

Claims

1. A first nut having a screw hole screwed into a screw shaft, and a second nut having a screw hole screwed into the screw shaft, The first nut has a protruding portion protruding in an axial direction toward the second nut, and the protruding portion has a tapered outer peripheral surface having a predetermined taper angle, In the locking device, the second nut has a recess into which the protrusion is fitted, and the recess has a tapered inner circumferential surface having a predetermined taper angle, A loosening prevention device comprising any one of the following configurations A and B. Configuration A: The axis of the tapered inner surface of the recess is eccentric with respect to the axis of the screw hole of the second nut, and the center of gravity of the second nut is located in the same direction as the axis of the tapered inner surface of the recess with respect to the axis of the screw hole of the second nut. Configuration B: The axis of the tapered outer peripheral surface of the convex portion is eccentric with respect to the axis of the screw hole of the first nut, and the center of gravity of the first nut is located in the opposite direction to the axis of the tapered outer peripheral surface of the convex portion with respect to the axis of the screw hole.

2. The locking device according to claim 1, A loosening prevention device comprising the configuration A.

3. The locking device according to claim 2, an anti-loosening device in which a distance d1 from the axis of the screw hole of the second nut to the center of gravity of the second nut is greater than P1 × tan θ1 × (1 / 5) and smaller than P1 × tan θ1 × (1 / 2), where P1 is the thread pitch of the screw hole of the second nut and θ1 is 1 / 2 of the taper angle of the tapered inner surface of the recess.

4. The locking device according to claim 1, A loosening prevention device comprising the configuration B.

5. The locking device according to claim 4, an anti-loosening device wherein a distance d2 from the axis of the screw hole of the first nut to the center of gravity of the first nut is greater than P2 × tan θ2 × (1 / 5) and smaller than P2 × tan θ2 × (1 / 2), where P2 is the thread pitch of the screw hole of the first nut and θ2 is 1 / 2 of the taper angle of the tapered outer peripheral surface of the convex portion.

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