Anti-loosening device for seated nut

Abstract

Provided is an anti-loosening nut that can produce an outstanding anti-loosening effect on an ordinary nut that is seated.　The present invention unitarily comprises: a body section 3 having a threaded hole 2 that screws onto a bolt B above a seated nut N; and a cylindrical section 4 that fits exteriorly onto an upper-end portion of the seated nut N. The inner circumferential surface of the cylindrical section 4 is constituted by a tapered surface that gradually flares diametrically heading downward, and is eccentric with respect to the threaded hole 2 in such a way that along a part of the circumference direction, the inner circumference of the cylindrical section 4 and a corner-portion upper end of the hexagonally shaped seated nut N interfere, producing a pressuring force that is orthogonal to the axis direction of the seated nut N.

Description

Device to prevent loosening of existing nuts

[0001] The present invention relates to a locking nut as a device for preventing loosening of an existing 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 present invention is a locking nut that prevents loosening of an existing nut fastened to a bolt, and comprises a main body portion having a threaded hole that screws onto the bolt above the existing nut, and a cylindrical portion that fits onto the upper end of the existing nut.The inner surface of the cylindrical portion is configured as a tapered surface that gradually becomes larger in diameter as it extends downward, and is eccentric with respect to the threaded hole so that, in part of the circumferential direction, the inner circumference of the cylindrical portion and the outer circumference of the existing nut interfere with each other, generating a pressing force on the existing nut perpendicular to the axial direction.

[0012] According to the present invention, when the anti-loosening nut of the present invention is fastened to a bolt above an existing nut (ordinary nut) that is fastened to the bolt, the outer periphery of the existing nut and the inner periphery of the main body interfere with each other in a portion of the circumferential direction, generating a pressing force perpendicular to the axial direction of the existing nut, and as a reaction force, a pressing force in the opposite direction is generated on the anti-loosening nut.The pressing forces generated by the wedge action on the existing nut and the anti-loosening nut provide an excellent anti-loosening effect to the existing nut and the anti-loosening nut.

[0013] The threaded hole may be open downward, and the main body may have a top portion that closes the upper end of the threaded hole, thereby preventing rainwater and the like from entering the threaded hole and preventing corrosion of the nut and bolt.

[0014] Preferably, the inclination angle θ of the tapered surface constituting the inner peripheral surface of the cylindrical portion with respect to the axis is 15° or more, and more preferably 20° or more. This makes it possible to absorb relatively large manufacturing errors in the outer peripheral shape of the existing nut and dimensional changes due to aging, corrosion, etc., due to the large inclination angle of the tapered surface, thereby reliably generating the axial pressing force.

[0015] In the present invention, the existing nut is a hexagonal nut, and the inner peripheral surface of the cylindrical portion interferes with the upper ends of the hexagonal corners of the hexagonal nut.

[0016] The outer periphery of the locking nut body may be cylindrical or frusto-conical. This prevents the locking nut from being tampered with using a standard wrench or box wrench. The locking nut can be fastened using a special tool that fits the outer periphery of the locking nut.

[0017] According to the present invention, it is possible to provide a locking nut that can easily and quickly provide an excellent locking effect on an existing nut.

[0018] 1 is a longitudinal cross-sectional view showing a locking nut according to an embodiment of the present invention in a state before installation, and FIG. 2 is a longitudinal cross-sectional view showing the locking nut in an installed state.

[0019] 1 and 2 show a locking nut 1 according to one embodiment of the present invention, which is attached to an existing nut N fastened to a bolt B and an existing fastener consisting of the bolt B to prevent the existing nut N from loosening. The existing nut N is a general nut that conforms to public standards and is typically a hexagonal nut.

[0020] The locking nut 1 integrally comprises a main body 3 having a threaded hole 2 that threads onto a bolt B above the existing nut N, and a cylindrical portion 4 that fits over the upper end of the existing nut N. The outer peripheral surface of the main body 3 may have any suitable shape, for example, a hexagonal nut shape similar to that of the existing nut N. The inner peripheral surface of the cylindrical portion 4 is configured as a tapered surface that gradually increases in diameter as it extends downward. The cylindrical portion 4 is eccentric with respect to the threaded hole 2 so that, in a portion of the circumferential direction (left side in the figure), the inner periphery of the cylindrical portion 4 and the upper end of the hexagonal corner of the existing nut N interfere with each other, generating a pressing force perpendicular to the axial direction on the existing nut N. As a reaction force to the pressing force acting on the existing nut N, a pressing force acts on the locking nut 1 in the opposite direction. The top 3a of the main body 3 is closed, and the threaded hole 2 is open downward.

[0021] According to the locking nut 1 of this embodiment, by additionally fastening the upper end of the bolt B to which the existing nut N is fastened, a wedge action is created by the eccentric fit between the inner peripheral surface of the cylindrical portion 4 and the outer periphery of the upper end of the existing nut N, and large opposing horizontal pressing forces are generated on the existing nut N and the locking nut 1, thereby providing excellent locking functionality. Also, by closing the upper end of the threaded hole 2 with the apex 3a, rainwater and the like can be prevented from entering the threaded hole 2, preventing corrosion and the like.

[0022] The present invention is not limited to the above-described embodiment, and the design can be modified as appropriate.

[0023] 1 Locking nut 2 Screw hole 3 Body 3a Top 4 Cylindrical part

Claims

1. An anti-loosening nut that prevents an existing nut fastened to a bolt from loosening, comprising: a main body portion having a threaded hole that screws onto the bolt above the existing nut; and a cylindrical portion that fits onto the upper end of the existing nut, the inner surface of the cylindrical portion being configured as a tapered surface that gradually becomes larger in diameter as it extends downward, and is eccentric with respect to the threaded hole so that, at one portion in the circumferential direction, the inner circumference of the cylindrical portion and the outer circumference of the existing nut interfere with each other, generating a pressing force on the existing nut perpendicular to the axial direction.

2. A locking nut as claimed in claim 1, wherein the screw hole is open downward, and the body has a top portion closing the upper end of the screw hole.

3. A locking nut as claimed in claim 1, wherein the inclination angle of the tapered surface constituting the inner peripheral surface of the cylindrical portion with respect to the axis is 15° or more.

4. A locking nut as claimed in claim 1, wherein the inclination angle of the tapered surface constituting the inner peripheral surface of the cylindrical portion with respect to the axis is 20° or more.

5. A locking nut according to claim 1, wherein the existing nut is a hexagonal nut, and the inner peripheral surface of the cylindrical portion interferes with the upper end of a corner of the hexagonal shape of the hexagonal nut.

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