JP7567124B2 - Nuts for half-threaded bolts - Google Patents

Description

The present invention relates to a nut that is used in combination with a half-threaded bolt to secure multiple objects together.

Generally, when a bolt and nut are used to tighten and fix something, the axial force (tensile force) generated in the shaft of the bolt and the compressive force (clamping force) generated in the fastened parts are integrated, and the fastened state is maintained by balancing the two.

However, simply screwing a bolt and nut together and tightening them can cause initial loosening due to roughness of the contact area of the screw fastener, or back-rotation of the nut caused by static or dynamic fluctuations in the axial force, resulting in loosening of the fastener.

Therefore, various efforts have been made in the past. For example, grooved hex nuts, nylon nuts, nuts that utilize the wedge locking effect, and anti-loosening nuts that incorporate friction rings are well known.

A technology has also been disclosed that features a clutch piece that is a columnar body with a nearly elliptical cross section that comes into contact with the threaded portion of the bolt when the bolt is screwed in, and is positioned in contact with the threaded portion of the bolt (see Patent Document 1).

Japanese Unexamined Patent Publication No. 58-156712 Japanese Patent Application Publication No. 11-117954

However, according to the invention described in Patent Document 1, the tip of the clutch piece is crimped and engaged with the male thread of the bolt, and the contact area between the clutch piece and the thread is limited, so the effect of preventing loose rotation is limited. Furthermore, there is a risk of stripping the thread.
Therefore, further improvements have been desired to achieve a suitable fastening state without stripping the screw threads and to obtain a high degree of anti-loosening effect.

Therefore, the inventors of the present application conducted intensive research to solve these problems, and came up with a new idea that led to the completion of the present invention.

In order to solve the above problem, the invention described in claim 1 is a bolt and nut for clamping and fixing multiple objects together , the bolt being a half-threaded bolt whose bolt shaft is composed of a cylindrical portion and a male threaded portion, the nut having a nut hole with a female thread formed on a part of the inner surface thereof into which the male thread screws, and when the nut is screwed onto the male thread and fastened, a shell-type roller clutch type one-way rotation mechanism is fitted and fixed in a position opposite to a part of the cylindrical portion , and the nut hole is provided with a pad forming an annular convex wall .

The present invention makes it possible to achieve an appropriate tightening state of bolts and nuts without stripping the male screw threads, regardless of the skill level of the worker, and achieves a high degree of anti-loosening effect.

FIG. 2 is a perspective view of a nut for a half-threaded bolt according to one embodiment of the present invention. 1 is an explanatory diagram showing the structure of a nut for a half-threaded bolt according to one embodiment of the present invention. FIG. 1 is a side view of a nut for a half-threaded bolt according to one embodiment of the present invention. FIG. FIG. 2 is a partial cross-sectional view taken along line AA, showing the use state of the nut for a half-threaded bolt according to one embodiment of the present invention. 1 is a cross-sectional view of a nut for a half-threaded bolt according to an embodiment of the present invention taken along line BB. FIG. 2 is an exploded perspective view of a nut for a half-threaded bolt according to one embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described.
The size, shape, and positional relationship of each part constituting the present invention are described generally for the purpose of facilitating understanding of the present invention. Furthermore, the materials and qualities of each component are disclosed as preferred combinations, and modifications that can achieve the effects of the present invention without departing from the spirit of the present invention are not prohibited.

The nut 1 is composed of a nut body 10 having a female thread 101 on a portion of the inner circumferential surface 102 of the nut hole, and a one-way rotation mechanism 11 having a number of rollers 110. In this embodiment, a resin pad P is provided at the nut hole opening (the side that contacts the target object when fastening with the bolt) (Figs. 1, 2, and 6).

The bolt 2 is a half-thread bolt whose bolt shaft is made up of a cylindrical portion 21 and a male threaded portion 22. The roller 110 of the one-way rotation mechanism 11 is positioned opposite the cylindrical portion 21 in the area on the tip side of the bolt shaft. (Figure 4)

A typical structure and principle of a one-way rotation mechanism is, for example, as disclosed in the above-mentioned Patent Document 2, a mechanism used when one of two concentrically assembled members rotates in both directions and transmits only one of the two rotational motions to the other member. This mechanism is also called a "one-way clutch," and specifically, for example, a "shell-type roller clutch" sold by NSK Ltd. can be used.

The procedure for attaching object A to target object B (target object here refers to a machine, building, or other object to which object A is to be attached) is explained below. Note that object A and target object B are assumed to have holes with a diameter large enough to insert the cylindrical portion 21 of half-threaded bolt 2.

The object to be fixed A is aligned with the specified position of the object B, the bolt shaft of the half-threaded bolt 2 is inserted, and then the female threaded portion 101 of the nut 1 is screwed into the male threaded portion 22 at the tip of the bolt shaft, and the nut body 10 is tightened to obtain an integrated fastening state between the bolt head, the object to be fixed A, the object B, and the nut 1. (Figure 4)

At this time, by using the pad P, the nut is fixed in a biased state due to the elasticity of the pad P, and a more stable fastening state can be maintained. Furthermore, as shown in Figures 1, 2, 3, and 6, the pad P has an annular convex wall P1 facing the object B, and the elastic shape that is generated when fastening provides a waterproof effect for the nut hole. The pad P is preferably of hardness between 65 and 75 as measured with a type A durometer.

The one-way rotation mechanism 11 faces the cylindrical portion 21 of the bolt shaft, and when the cylindrical portion 21 rotates in one direction (Figure 5(A)), the rotational torque is not transmitted to the roller 110, but when it rotates in the other direction (Figure 5(B)), the rotational torque is transmitted.
In other words, when the nut body 10 is rotated in the tightening direction (clockwise rotation), the rotational torque is not transmitted to the roller 110, the nut body 10 rotates freely, and the screwing with the male threaded portion 22 progresses, but when an attempt is made to rotate the nut body 10 in the loosening direction (counterclockwise rotation), the rotational torque is transmitted to the roller 110 and the clutch mechanism is activated, preventing counterclockwise rotation.

After fastening by nut 1 is complete and an integrated fastening state is formed between the bolt head, fixed object A, object B and nut 1, the nut body 10 must be rotated counterclockwise to loosen it. However, since the torque in the same rotation direction is generated by the one-way rotation mechanism 11 according to the mechanism described above, the nut body 10 will not rotate counterclockwise unless a force strong enough to destroy the mechanism is applied.
That is, under normal use conditions, the nut for a half-thread bolt of the present invention will not loosen.

This embodiment makes it easy to tighten the nut, creates a proper tightening state, and provides a high degree of anti-loosening effect.

Comparative Example

A comparative test (NAS3350-compliant screw loosening evaluation test/JFE Techno-Research Corporation) was conducted using the present invention and a normal bolt and nut as comparative test specimens.
・Test equipment: Electrodynamic vibration test equipment (IMV i230)
・Test standard: US aviation standard NAS3350 accelerated vibration test <Test method>
The screw fastener is allowed to vibrate up and down freely within a long hole drilled in the jig body, and impact forces are repeatedly applied to the screw fastener. NAS3350 specifies the vibration frequency, vibration amplitude, impact amplitude, and vibration count as follows:
・Regulated frequency: 30Hz
・Specified vibration width: 11.4±0.4mmp-p
・Specified impact width: 19 mm
- Specified number of vibrations: 30,000 times (approximately 17 minutes)

<Test procedure>
(1) Attach the bolts and nuts to be tested to the test jig using the central long hole of the M8 slot.
(2) Tighten the test specimen with a tightening torque of 12.6 N.m (Newton meters). Range: 12.6 to 13.0 N.m.
(3) Mark the bolts and nuts.
(4) Conduct vibration testing under NAS3350 standard conditions (30,000 times).
(5) If any specimen becomes loose during the test, the vibration is stopped and the test is terminated. The approximate time from the start of the test until the specimen becomes loose is recorded.
(6) After the test, take a photograph of the match mark location.
(7) For specimens with no misalignment of the alignment marks, measure the loosening torque.

<Test Results>
The results of the NAS thread loosening test are shown below. The bolt and nut components of the test specimen loosened their threads in 1 minute 48 seconds of testing, causing the fastener to fall off, whereas the product of the present invention had a misalignment of the alignment marks of 360 degrees or less after 30,000 vibration tests, satisfying the pass criteria for the NAS3350 test.
Furthermore, the tightening torque was 12.6 Nm, while the loosening torque was a high 31.3 Nm. Although the relationship between tightening torque and loosening torque is influenced by various factors such as the material and the usage conditions, it is said that if tightened immediately, loosening will occur at about 70-80% of the torque at the time of tightening. From this, it is clear that the present invention can provide an extremely high loosening prevention effect.

The present invention does not rely on a strong tightening force to maintain the fastened state as with conventional bolts and nuts, but has a structure that uses a one-way rotation mechanism to prevent loosening after a certain fastened state is achieved, and is therefore particularly effective in cases where, for example, the object to be fixed A or the target object B is made of glass, brick, pottery, porcelain, or other materials that are fragile to physical forces.
It is also expected to be widely used in places where regular inspection is difficult once tightening construction has been completed.

Reference Signs List 1 Nut 10 Nut body 101 Female thread portion 102 Inner peripheral surface 11 One-way rotation mechanism 110 Roller 2 Half-thread bolt 21 Cylindrical portion 22 Male thread portion A Fixed object B Object P Pad P1 Annular convex wall

Claims (1)

A bolt and a nut for clamping and fixing a plurality of objects to each other ,
The bolt is a half- thread bolt having a bolt shaft consisting of a cylindrical portion and a male thread portion,
The nut has a female thread formed on a part of an inner circumferential surface of a nut hole, into which the male thread is screwed, and
When the nut is screwed onto the male screw and fastened, a shell-type roller clutch type one-way rotation mechanism is fitted and fixed at a position facing a part of the cylindrical portion ,
A half-threaded bolt and a nut for said bolt , each of which has a pad formed with an annular convex wall in the nut hole .

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