Anti-loosening device for nut

Abstract

Provided is an anti-loosening device capable of producing an excellent anti-loosening action on existing ordinary nuts.　An anti-loosening device 1 for a nut according to the present disclosure comprises a cover member 2 and a lock nut member 3. The cover member 2 has a cylindrical part 21 that is externally fitted to a nut N fastened to a bolt B, and a flange part 22 that engages with an upper surface of the nut N. The lock nut member 3 has a screw hole 31 that is screwed together with a threaded shaft of the bolt B above the nut N. The flange part 22 is provided with a through-hole 23 through which the bolt B is inserted. The lock nut member 3 has a projection part 32 fitted to the through-hole 23. The projection part 32 is eccentric with respect to the through-hole 23 such that an outer periphery of the projection part 32 interferes with an inner periphery of the through-hole 23 in a portion in the circumferential direction, and a pressing force orthogonal to the axial direction occurs at the nut N.

Description

Nut locking device

[0001] The present invention relates to a device for preventing loosening of a nut fastened to a bolt.

[0002] The applicant of the present application has been developing a Hard Lock Nut ("Hard Lock" is a trademark of the applicant of the present application), which is a locking nut that exhibits high locking performance, and these have been disclosed, for example, in Patent Documents 1 to 4 described below.

[0003] This Hardlock Nut is composed of a lower nut having a threaded hole that screws onto the screw shaft, and an upper nut having a threaded hole that screws onto the screw shaft.

[0004] One of the lower nut and upper nut has a truncated cone-shaped convex portion that protrudes axially toward the other nut. The convex portion has a tapered outer surface with a predetermined taper angle that gradually reduces in diameter toward the tip. The screw hole passes through the convex portion along the axial direction. A nut with a convex portion is called a "convex nut."

[0005] The other nut has a recess into which the protrusion fits. The recess has a tapered inner circumferential surface with a taper angle that matches the taper angle of the outer circumferential surface of the protrusion, preferably the same taper angle. The screw hole of the other nut opens to the bottom surface of the recess. A nut with a recess is called a "recessed nut."

[0006] The Hardlock Nut's eccentric fit between a convex portion and a concave portion creates a stress state that is just like driving a wedge between the outer periphery of the screw shaft and the inner periphery of the nut's threaded hole, and this wedge action provides a powerful anti-loosening effect.

[0007] The eccentric fit between the convex portion and the concave portion is achieved by forming the outer peripheral surface of the convex portion eccentrically with respect to the screw hole of the convex nut, or by forming the inner peripheral surface of the concave portion eccentrically with respect to the screw hole of the concave nut. When the outer peripheral surface of the convex portion is eccentric, the inner peripheral surface of the concave portion and the screw hole of the concave nut are made concentric. On the other hand, when the inner peripheral surface of the concave portion is eccentric, the outer peripheral surface of the convex portion and the screw hole of the convex nut are made concentric.

[0008] With a Hardlock Nut, when the convex and concave portions of the upper and lower nuts threaded onto the screw shaft are eccentrically fitted together, the outer peripheral surface of the convex portion and the 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 each of the upper and lower nuts in the eccentric direction.

[0009] Japanese Patent No. 6762591 JP 2016-125622 A JP 2016-133136 A JP 2002-195236 A JP 2011-174600 A

[0010] Replacing existing standard nuts with Hard Lock Nuts can provide excellent locking effects, but in cases where there are a large number of existing nuts, the process of removing the existing nuts is time-consuming and requires a long total work time, so simple locking clips such as those shown in JP 2011-174600 A (Patent Document 5) have been used instead. However, users have been demanding a locking device that can apply the principles of Hard Lock Nuts to lock existing standard nuts.

[0011] The nut locking device of the present invention locks a nut fastened to a bolt and includes a cover member having a cylindrical portion fitted over the nut and a flange portion engaging the upper surface of the nut, and a lock nut member having a threaded hole above the nut that screws onto the threaded shank of the bolt. The flange portion is provided with a through hole through which the bolt is inserted. The lock nut member has a protrusion that fits into the through hole. The protrusion is eccentric with respect to the through hole so that the outer periphery of the protrusion and the inner periphery of the through hole interfere with each other at a portion of the circumferential direction, generating a pressing force on the nut perpendicular to the axial direction.

[0012] According to the nut locking device of the present invention, when a cover member is fitted over an existing nut (a standard nut) fastened to a bolt and a lock nut member is fastened to the bolt above the nut, the outer periphery of the protrusion interferes with the inner periphery of the through hole in a circumferential portion, pressing the cover member in a direction perpendicular to the axial direction. This causes the inner circumferential surface of the cover member to come into strong contact with the outer circumferential surface of the nut in a portion diametrically opposed to the circumferential portion, generating a pressing force perpendicular to the axial direction on the nut. In addition, this interference generates a pressing force on the lock nut member that opposes the pressing force on the nut. These pressing forces due to the wedge action on the nut and lock nut member provide excellent locking effects on the nut and lock nut member.

[0013] In the nut locking device according to the present invention, the threaded hole of the lock nut member may be open downward, and the lock nut may have a top portion that closes the upper end of the threaded hole. This prevents rainwater and the like from entering the threaded hole, and prevents corrosion of the threaded hole and the bolt.

[0014] The outer periphery of the locking nut member may be cylindrical or frusto-conical, which prevents the locking nut member from being tampered with using a standard wrench or box wrench, and allows the locking nut member to be fastened using a special tool that fits the outer periphery shape of the locking nut member.

[0015] The outer circumferential surface of the cover member may be cylindrical or frusto-conical, which can prevent the nut from being loosened by a common wrench or box wrench for tampering purposes.

[0016] The outer peripheral surface of the protrusion and the inner peripheral surface of the through hole may be configured in a truncated cone shape with a diameter gradually decreasing downward. By tapering the protrusion and the through hole in this manner, a large pressing force can be generated on the nut in accordance with the fastening force of the lock nut member, resulting in a greater wedge action.

[0017] The inner peripheral surface of the through hole may be concentric with the inner peripheral surface of the cylindrical portion, and the outer peripheral surface of the protrusion may be eccentric with respect to the screw hole. Alternatively, the inner peripheral surface of the through hole may be eccentric with respect to the inner peripheral surface of the cylindrical portion, and the outer peripheral surface of the protrusion may be concentric with the screw hole. Furthermore, the cover member and the locking nut member may be made of a hard material, preferably a metal such as a steel material having a strength equal to or greater than that of the existing nut.

[0018] According to the present invention, a nut locking device can be provided that can provide an excellent locking effect on existing general nuts.

[0019] Fig. 1 is a half-sectional vertical cross-sectional view showing a state before installation of a nut locking device according to a first embodiment of the present invention. Fig. 2 is a vertical cross-sectional view of a nut locking device according to the first embodiment in an installed state. Fig. 3 is a perspective view of the locking device in an installed state. Fig. 4 is a vertical cross-sectional view of a nut locking device according to a second embodiment of the present invention in a state before installation. Fig. 5 is a vertical cross-sectional view of the locking device in an installed state. Fig. 6 is a perspective view showing an example of a cover member of the locking device.

[0020] 1 to 3 show a nut loosening prevention device 1 according to a first embodiment of the present invention. The loosening prevention device 1 prevents a nut N fastened to a bolt B and prevents the nut N from loosening by being attached to the bolt B.

[0021] The locking device 1 includes a cover member 2 that is fitted onto the nut N, and a lock nut member 3 that is screwed onto the bolt B above the nut N.

[0022] The cover member 2 has a tubular portion 21 that fits around the nut N and a flange portion 22 that engages with the upper surface of the nut N. The tubular portion 21 is cylindrical, and its inner diameter is slightly larger than the maximum diameter portion of the nut N (i.e., the diameter of the corner portion of the hexagonal nut). The flange portion 22 may extend radially inward from the upper end of the tubular portion 21. The flange portion 22 is provided with a through hole 23 through which a bolt B is inserted. The through hole 23 has an inner diameter larger than the outer diameter of the bolt B, and is configured so that a protrusion 32 fits between the inner periphery of the through hole 23 and the outer periphery of the threaded shaft of the bolt B. The inner surface of the through hole 23 is formed in a truncated cone shape whose diameter gradually decreases downward. The axis of the inner surface of the through hole 23 is concentric with the axis of the inner surface of the tubular portion 21.

[0023] The locking nut member 3 has a threaded hole 31 that screws onto the threaded shaft of the bolt B above the nut B, and a protrusion 32 that fits into the through hole 23. The threaded hole 31 is open downward, and the upper end of the threaded hole 31 is closed by a vertex 33. The outer peripheral surface of the locking nut member 3 is formed in a truncated cone shape that gradually decreases in diameter as it extends upward. The protrusion 32 is configured in a truncated cone shape that gradually decreases in diameter as it extends downward.

[0024] The protrusion 32 of the lock nut member 3 threaded onto the bolt B is eccentric by a predetermined eccentricity amount d with respect to the through hole 23 of the cover member 2 fitted onto the nut N so that the outer peripheral surface of the protrusion 32 interferes with the inner peripheral surface of the through hole 23 in a portion of the circumferential direction (the left side of the bolt B in FIG. 2 ), generating a pressing force perpendicular to the axial direction on the nut N. Note that the above configuration may be realized by eccentrically positioning the protrusion 32 with respect to the screw hole 31, or by eccentrically positioning the through hole 23 with respect to the tubular portion 21.

[0025] According to the nut loosening prevention device 1 of the first embodiment, by fitting the cover member 2 onto an existing ordinary nut N fastened to a bolt B and fastening the lock nut member 3 to the bolt B above the nut N, a wedge action is generated by the eccentric fit between the through hole 23 of the cover member 2 and the convex portion of the lock nut member 3, and large opposing horizontal pressing forces are generated on the nut N and the lock nut member 3, thereby achieving excellent loosening prevention function. Furthermore, after the loosening prevention device 1 is installed, the entire structure is covered by a circumferential or conical surface as shown in Figure 3, making it impossible to use ordinary spanners or wrenches, and therefore preventing the nut N from being loosened by tampering, etc.

[0026] 4 to 6 show a nut loosening prevention device 1' according to a second embodiment of the present invention. The loosening prevention device 1' prevents loosening of a nut N fastened to a bolt B and the nut N when attached to the bolt B.

[0027] The locking device 1' includes a cover member 2' that fits over the nut N, and a lock nut member 3' that is screwed onto the bolt B above the nut N.

[0028] The cover member 2' has a cylindrical portion 21' that fits around the nut N and a flange portion 22' that engages with the upper surface of the nut N. The cylindrical portion 21' is hexagonal, and its inner peripheral surface is slightly larger than the outer peripheral surface of the nut N. The cover member 2' of this embodiment can be formed by bending the upper end of a thin-walled cylinder using a press or the like, as shown in Figure 6. The flange portion 22' extends radially inward from the upper end of the cylindrical portion 21' and downward at its radially inner end to form a through hole 23' through which a bolt B is inserted. The through hole 23' has an inner diameter larger than the outer diameter of the bolt B, and is configured so that a protrusion 32' fits between the inner periphery of the through hole 23' and the outer periphery of the threaded shaft of the bolt B. The inner peripheral surface of the through hole 23' is formed in a frusto-conical shape that gradually decreases in diameter as it extends downward. The axis of the inner peripheral surface of the through-hole 23' is arranged concentrically with the axis of the inner peripheral surface of the cylindrical portion 21'.

[0029] The locking nut member 3' has a threaded hole 31' that screws onto the threaded shaft of the bolt B above the nut B, and a protrusion 32' that fits into the through-hole 23'. The threaded hole 31' penetrates the locking nut member 3' in the vertical direction. The outer circumferential surface of the locking nut member 3' is hexagonal in plan view. The protrusion 32' is configured in the shape of a truncated cone whose diameter gradually decreases as it extends downward.

[0030] The convex portion 32' of the locking nut member 3' threaded onto the bolt B is eccentric by a predetermined eccentricity amount d with respect to the through hole 23' of the cover member 2' fitted onto the nut N so that the outer surface of the convex portion 32' interferes with the inner surface of the through hole 23' in a part of the circumferential direction (the left side of the bolt B in Figure 5), generating a pressing force on the nut N perpendicular to the axial direction.

[0031] A dome-shaped closing portion 4' is integrally formed on the top of the locking nut member 3'. By providing the closing portion 4' in this dome shape, even if the existing bolt protrudes somewhat significantly, the locking nut member 3' can be threaded onto the bolt while receiving the bolt protrusion. The threaded hole 31' can also be opened upward, and a separate closing member can be fitted into the threaded hole 31' of the locking nut member 3' from above to close the threaded hole 31'. Such a closing member 4' may be made of an elastic material such as rubber, or a hard material such as metal or plastic.

[0032] The nut locking device 1' according to the second embodiment can also provide the same excellent locking function as the first embodiment.

[0033] The present invention is not limited to the above-described embodiment, and the design can be modified as appropriate. For example, the outer peripheral surface of the convex portion and the inner peripheral surface of the through hole may be formed in a right cylindrical shape. In addition, in the above-described embodiment, the outer peripheral surface of the convex portion is eccentric with respect to the screw hole, and the through hole and the cylindrical portion are concentrically arranged. However, the convex portion and the screw hole may be concentrically arranged, and the inner peripheral surface of the through hole may be eccentric with respect to the inner peripheral surface of the cylindrical portion.

[0034] REFERENCE SIGNS LIST 1 Nut locking device 2 Cover member 21 Cylindrical portion 22 Flange portion 23 Through hole 3 Locking nut member 31 Threaded hole 32 Convex portion 33 Closure portion

Claims

1. A device for preventing loosening of a nut fastened to a bolt, comprising: a cover member having a cylindrical portion that fits over the nut and a flange portion that engages with the upper surface of the nut; and a locking nut member having a screw hole that screws into the screw shaft of the bolt above the nut, wherein the flange portion is provided with a through hole through which the bolt is inserted, and the locking nut member has a protrusion that fits into the through hole, and the protrusion is eccentric with respect to the through hole so that at a circumferential portion, the outer periphery of the protrusion and the inner periphery of the through hole interfere with each other at a portion of the circumference, generating a pressing force on the nut perpendicular to the axial direction.

2. A nut loosening prevention device as described in claim 1, wherein the screw hole of the locking nut member is open downward, and the locking nut has a top portion closing the upper end of the screw hole.

3. A nut loosening prevention device according to claim 1, wherein the outer peripheral surface of the locking nut member is cylindrical or frusto-conical.

4. A nut loosening prevention device according to claim 1, 2 or 3, wherein the outer peripheral surface of the cover member is cylindrical or frusto-conical.

5. A nut loosening prevention device as described in claim 1, wherein the outer peripheral surface of the protrusion and the inner peripheral surface of the through hole are configured in a truncated cone shape whose diameter gradually decreases toward the bottom.

Images