JPH08177839A - Loosening prevention screw - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a loosening prevention screw that prevents the screw from loosening and that keeps the screwing torque low. [PROBLEMS] A loosening prevention screw comprising a screw part in which a screw thread (2) is formed in a spiral shape and a head part integrally formed with the screw part, wherein a height (H) of catching the screw thread (2) and a crest of the screw thread (2). The width m of is molded to a size that conforms to the standard reference mountain,
The pressure flank angle α is smaller than the flank angle of the internal thread, and the flank angle β on the play side is larger than the flank angle of the internal thread. [Effect] The loosening prevention screw of the present invention generates a gap between itself and the internal thread flank, and absorbs the deformation of the screw thread here. Therefore, the screwing torque at the time of screwing can be reduced. Further, since the top side of the pressure side flank and the valley bottom side of the play side flank contact the female thread flanks respectively, it is possible to prevent loosening after tightening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tightening screw, and more particularly to a loosening prevention screw for preventing loosening of a screw after tightening.

[0002]

2. Description of the Related Art Conventionally, tightening screws have been widely used for joining various plate materials or parts because of their ease of use. There was a forced problem. As means for preventing such screw loosening, in Japanese Unexamined Patent Publication (Kokai) No. 5-71524, the crest width of the male screw is made wider than the valley width in the threaded portion of the female screw, and the angle of the screw thread is a line perpendicular to the screw axis. When divided by, make the front angle of the male screw tightening direction almost the same as the rear angle of the female screw, and make the rear angle of the male screw tightening direction smaller than the front angle to assist the female screw side when tightening. Proposals have been made for loosening prevention screws that tap female threads.

[0003]

However, JP-A-5-7
In the loosening prevention screw of No. 1524, by tapping the auxiliary female screw, a resistance force from the female screw acts on the thread of the male screw, and the thread of the male screw is deformed to the front side in the tightening direction to some extent. At this time, the angle on the front side in the tightening direction of the male screw is almost the same as the angle on the rear side of the female screw, so the front slope is strongly pressed against the slope of the female screw.
Due to this frictional force, the screwing torque is extremely increased, and there is a problem that it is difficult to screw in a screw having a normal thread.

The present invention was created in view of the above problems, and an object of the present invention is to provide a loosening prevention screw which prevents the screw from loosening and keeps the screwing torque low.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a screw comprising a screw portion in which a screw thread is formed in a spiral shape, and a head portion integrally formed with the screw portion, the height of the thread being caught. And the width of the top of the crest is formed according to the standard reference crest, and the threads of the thread part are such that one flank angle is smaller than the flank angle of the female thread and the other flank angle is smaller than the flank angle of the female thread. It is a loosening prevention screw molded into a shape that also increases. The cross-sectional shape of the thread portion of the loosening prevention screw may be formed in a non-circular shape.

[0006]

When the loosening prevention screw is screwed into the internal thread, one flank digs into the thread of the internal thread, and the other flank of the other flank comes into contact with the vicinity of the top of the internal thread of the internal thread.
This increases the contact resistance generated between the loosening prevention screw and the female screw, and prevents the loosening after tightening. When one flank bites into the thread of an internal thread, pressing force due to deformation acts on the other flank, but there is a gap between the top of the other flank and the flank of the internal thread in this loosening prevention screw. Since this occurs, the pressing force is absorbed by this gap, and this makes it possible to obtain the effect of reducing the screwing torque. Further, by making the cross-sectional shape of the screw portion non-circular, the contact area with the female screw when screwed in is reduced, and the screwing torque of the loosening prevention screw can be significantly reduced in correlation with the absorption of the pressing force described above.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, reference numeral 1 denotes a loosening prevention screw, which is composed of a screw portion 3 in which a spiral thread 2 is formed, and a head 4 integrally formed above the screw portion 3, and is tightened on the upper surface of the head. A cross-shaped drive hole 4a with which a tool is engaged is formed.
The width m of the top of the thread 2 of the loosening prevention screw 1 and the catching height H when the thread is engaged with the female screw are dimensions conforming to the standard thread defined by JIS, and actually, the tolerance of the standard thread is close to the upper limit. The dimensions are preferred.

FIG. 1 is an enlarged cross-sectional view of a thread 2 of the main loosening prevention screw 1.
It is formed asymmetrically with respect to a vertical line drawn from the virtual contact points A of both flanks so as to be orthogonal to the axis of the screw part 3.
That is, in the thread 2, the flank angle α of the pressure flank 2a, which is one flank angle, is smaller than the flank angle of the female thread, and the flank angle β of the play side flank 2b, which is the other flank angle, is the flank angle of the female thread. It is set larger than. The loosening prevention screw 1 in the present embodiment corresponds to a female screw having a standard thread with a thread angle of 60 ° specified by JIS, and the flank angle α of the pressure side flank 2a is less than 30 ° and the play is reduced. The flank angle β of the side flank 2b is set to an angle larger than 30 °.

Generally, when a high tightening force is required, the flank angle α of the pressure side flank 2a is set to a value close to 30 °, or the flank angle α of the pressure side flank 2a and the flank angle of the idle side flank 2b are set. It is preferable to replace the angle β. Actually, in order to obtain the effect of preventing loosening with respect to the female thread consisting of the reference mountain, the pressure flank 2
It is most effective to set the flank angle α of a to 15 ° while setting the flank angle β of the play side flank 2b to 35 °.

When the loosening prevention screw 1 is screwed into a female thread having a symmetrical thread and a reference thread shape having a thread angle of 60 °,
As shown in FIG. 3, the top side of the pressure side flank 2a bites into the trough side of the corresponding female thread flank, and the idle side flank 2b is in a state where its trough bottom side is in contact with the top side of the female thread flank. At this time, the top side of the play side flank 2b inevitably has a gap 2c with the female thread flank to some extent due to the flank angle.

Strictly speaking, when the internal thread is made of a material having the same or similar hardness as the material of the actual loosening prevention screw 1, as shown in FIG. 4, the pressure side flank 2a has a top side along the female thread flank. As a result of the deformation of the pressure flank 2a, the material flows in the direction of the play flank 2b. At this time, since the top side of the play side flank 2b has a gap 2c with the valley bottom side of the female thread flank, the material flows most to the top side of the play side flank 2b, and the pressure side flank 2a is deformed on the play side. It is absorbed by forming the raised portion 2d on the top side of the flank 2b.

Also, loosening after tightening is prevented by the pressure contact between the top side of the pressure side flank 2a and the bottom side of the female thread flank, and the contact between the bottom side of the idle side flank 2b and the top side of the female thread flank. It By strictly setting the flank angles of the pressure flank 2a and the play flank 2b according to the material forming the female screw, the raised portion 2d of the play flank 2b can be brought into contact with the female flank. Therefore, it is suitable in terms of preventing loosening.

This is not limited to the above when the female screw is made of a material softer than the main loosening prevention screw 1. When the main loosening prevention screw 1 is screwed, the thread 2 has a female flank on the pressure side flank 2a. An auxiliary female screw is formed on the female screw flank so as to be surely crimped to the pressure side flank 2a of the main loosening prevention screw 1. Even in such a case, the above-mentioned deformation of the thread is slightly generated, but it goes without saying that this deformation can be sufficiently absorbed by the gap 2c between the idle side flank 2b and the female thread flank.

The cross-sectional shape of the threaded portion 3 of the loosening prevention screw 1 may be the most general circular shape, or may be a non-circular shape such as a substantially triangular shape or a shape in which a relief groove is provided on the circumferential surface. Is also good. In particular, when the shape is a substantially triangular shape or a shape in which a relief groove is provided on the circumferential surface, the portion that comes into contact with the female screw is smaller than that of a circular shape, so there is an advantage that the tightening torque etc. can be suppressed, which is preferable. Is.

[0015]

As described above in detail, since the loosening prevention screw of the present invention has the asymmetrical thread formed by forming the flank angle on the pressure side at 15 ° and the flank angle on the idle side at 35 °,
By creating a gap between the female thread flank and absorbing the deformation of the thread, the top side of the pressure side flank and the valley bottom side of the play side flank can be brought into contact with the female thread flank, respectively. This can reduce the screwing torque when screwing and prevent loosening after tightening. Further, by making the cross-sectional shape of the screw portion non-circular, it is possible to reduce the contact portion between the screw thread and the female screw, and it is possible to further reduce the screwing torque.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a thread of a loosening prevention screw according to the present invention.

FIG. 2 is a front view of a loosening prevention screw according to the present invention.

FIG. 3 is an enlarged cross-sectional view of a main part of a screw portion when the loosening prevention screw according to the present invention is screwed into a female screw.

FIG. 4 is an enlarged sectional view of an essential part showing a deformed state of a screw thread when the loosening prevention screw according to the present invention is screwed into a female screw.

[Explanation of symbols]

 1 Loosening prevention screw 2 Thread 2a Pressure flank 2b Play flank 2c Gap 2d Raised part 3 Screw part 4 Head 4a Drive hole A Virtual contact H Height of catching m Top width α Pressure flank angle β Play Side flank angle

Claims (2)

[Claims] 1. A screw part in which a screw thread is formed in a spiral shape,
A screw consisting of this screw part and a head that is integrally molded.The height of the thread and the width of the crest of the screw thread are formed to the dimensions according to the normal reference thread, and The loosening prevention screw is characterized in that one of the flank angles is smaller than the flank angle of the internal thread and the other flank angle is larger than the flank angle of the internal thread. 2. The loosening prevention screw according to claim 1, wherein the cross-sectional shape of the screw portion is formed into a non-circular shape.