JP2001221216A - Unfastening prevention screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unfastening prevention screw imparted with a biting function and a positioning function for a turning tool in a screw head part independently of engagement means for the turning tool. SOLUTION: In this unfastening prevention screw 1, an end part of a screw shaft 2 has the head part 3, and the upper face of the head part 3 has the engagement means 4, 6, 7 engaging with the turning tool only to a fastening direction. A stop face center part of the head part 3 is formed with a conical recessed part 5 forming a biting face 8 and a positioning hole for the turning tool.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called one-way type screw which cannot be loosened by a general tightening tool such as a driver tool or a wrench once tightened.

[0002]

2. Description of the Related Art In general, anti-removable screws are used for assembling equipment or attaching objects that cannot be disassembled or removed by a third party for security reasons or to prevent leakage of security. It is used for

[0003] A detachment prevention screw of this kind is disclosed in, for example, Japanese Patent Publication No. 45-25445, Japanese Utility Model Publication No. 3-89221.
Various structures are known, such as those described in Japanese Patent Publication No. 1 and Japanese Utility Model Laid-Open No. 4-121515.

[0004]

Most of these screws for preventing removal are provided such that the engaging means of the rotating tool provided on the screw head engages the rotating tool only in the tightening direction, and is opposite to the tightening direction. In other words, the rotating tool does not engage in the loosening direction, but is detached from the screw head. As described above, most of the engaging means do not have the positioning means of the rotary tool and the biting function. For this reason, such anti-removable screws have drawbacks in terms of the tightening operation.

[0005] Since the engaging means does not have the function of biting the rotary tool, it is difficult and time-consuming to correctly engage the rotary tool concentrically with the screw head. Easy to fall off from power tools. In addition, when the rotating tool is not properly engaged with the screw head, especially when tightening with a power rotating tool such as an electric screwdriver, severe vibration occurs and the tightening is incomplete, and a predetermined tightening torque is obtained. Can not be obtained.

[0006] Such a drawback on the work surface becomes remarkable especially when the screw is a small screw and the screw is tightened using a power turning tool such as an electric screwdriver.
It is a problem to be solved in handling.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a detachment prevention screw in which a positioning function and a biting function of a rotary tool are added to a screw head separately from the engaging means. The purpose is to:

Another object of the present invention is to provide a detachment prevention screw provided with a tightening torque management function capable of making a tightening torque substantially constant, in addition to a positioning function and a biting function of a rotary tool. Is what you do.

[0009]

In order to achieve the above object, the present invention has a head at one end of a screw shaft, and a rotary tool is engaged with the upper surface of the head only in a tightening direction. A detachment prevention screw provided with an engagement means, wherein a conical recess forming a positioning hole and a biting surface of the rotary tool is provided in a central portion of a top surface of the head. I do.

[0010] In the invention according to a second aspect, the engagement means comprises:
The arc-shaped groove is formed by a plurality of arc-shaped grooves extending in a circumferential direction, and the bottom surface of the arc-shaped groove is formed by a central flat surface, and an inclined guide surface continuous to both sides of the central flat surface and extending to the upper surface of the head. In addition, the rotary tool is configured to be engaged with the protrusion protruding from the central flat surface only in the tightening direction.

According to a third aspect of the present invention, the projecting portion is broken or deformed by a fixed tightening torque of the rotating tool for engaging the projecting portion and tightening the screw, and the rotating tool is The present invention is characterized in that the inclined guide surface is configured to be disengaged from the arc-shaped groove by a cam action.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 show an embodiment of a detachment prevention screw according to the present invention. The removal prevention screw 1
Has a round head 3 at one end of a screw shaft 2, and three cutouts 4 on which the rotating tool 10 described below engages on the upper surface of the head 3.
And one conical recess 5.

The cutting portion 4 is formed by an engaging surface 6 with which the rotating tool 10 engages only in the tightening direction, and an inclined guide surface 7 extending from the lower edge of the engaging surface 6 to the upper surface in a circular upward direction. In the direction opposite to the tightening direction, that is, in the loosening direction, the rotating tool 10 is separated from the cutout 4 by the cam action of the inclined guide surface 7 and comes off the head 3.
The engagement surface with which the rotating tool 10 engages only in the tightening direction is provided along a plane including the axis of the screw shaft 2.

On the other hand, the conical concave portion 5 is provided at the center of the top surface of the head portion 3 so as to extend in the axial direction.
Locating hole and biting surface. The biting surface 8 is formed by the tapered inner peripheral surface of the conical recess 5.

FIG. 4 shows a rotary tool 1 used to tighten the anti-removal screw 1 according to the present invention constructed as described above.
0 is shown. The rotating tool 10 has three engaging claws 12 protruding from a peripheral portion of a distal end surface of a cylindrical main body 11 to be engaged with the cutout portion 4 of the head 3, and is in close contact with the conical recess 5 at a central portion. A taper pin 13 that fits into the projection is provided. The engaging claw 12 has an abutting surface 14 that abuts and engages with the engaging surface 6 of the cutout 4 along a plane including the axis of the columnar main body 11. A flank 15 is formed on the side and is inclined in the circumferential direction and inward.

In order to tighten the removal prevention screw 1 using the rotating tool 10, the tapered pin 13 is fitted with the conical recess 5 of the head 3, and the fixed portion is fixed. And the abutting surface 14 of the engaging claw 13 and the cutout 4
Is brought into contact with the engaging surface 6. When a tightening torque is applied by the rotating tool 10 in this state, the removal prevention screw 1 is tightened via the engagement surface 6. At this time, since the tapered pin 13 is in close contact with the conical recess 5 of the head 3 and is in a biting state, there is no possibility that the rotating tool 10 comes off the head 3 unexpectedly. When the removal prevention screw 1 is tightened to a predetermined position, the rotation of the rotary tool 10 is stopped, and then the rotation of the rotary tool 10 is slightly loosened. By the action, the rotating tool 10 is pushed up in the axial direction, the tapered pin 13 is separated from the conical recess 5, and the rotating tool 10 is
Get off.

Note that the removal preventing screw 1
When tightening, the cylinder 1 for tightening torque control shown in FIG.
6, a cylindrical main body 11 of the rotary tool 10 as shown in FIG.
When the turning prevention tool 1 is tightened to a predetermined position by the rotating tool 10, the end face of the cylindrical body 16 comes into contact with the surface of the member to be fastened, and the tightening torque is regulated. Can be controlled to be constant, which is more effective.

FIGS. 7 to 10 show another embodiment of the anti-removal screw 21 according to the present invention. The detachment prevention screw 21 is different from that of the embodiment shown in FIGS. 1 to 3 only in the shape of the engagement means of the turning tool provided on the head 3, so that the same components are not provided. The same reference numerals are given and the description is omitted.

A pair of arc-shaped grooves 22 extending in the circumferential direction are provided on the upper surface of the head 3 so as to face each other in the radial direction. The arc-shaped groove 22 is disposed concentrically with the axis of the screw shaft 2, and the bottom surface thereof is a central flat surface 23 and the central flat surface 23.
Inclined guide surface 2 continuing to both sides of the head and extending to the upper surface of the head 3
4 and 24. And the central flat surface 23
A protruding piece 25 in the form of a pin is provided so as to protrude, and a rotating tool 30 described later is engaged with the protruding piece 25 only in the tightening direction. The protruding piece 25 is designed to be broken or deformed by a fixed tightening torque applied by a rotating tool 30 which is engaged with the protruding piece 25 and tightened. The projecting piece 25 can be formed integrally with the head 3 by forging. Further, a projecting piece 25 manufactured separately may be implanted and protruded from the central bottom surface 23 of the head 3.

FIGS. 11 to 13 show a rotary tool 30 used for tightening the detachment preventing screw 21 configured as described above. The rotating tool 30 is a cylindrical body 3
Two engaging claws 32 which engage with the arc-shaped groove 22 of the head 3 are protrudingly provided at the peripheral portion of the front end face of the head 3 so as to oppose each other in the radial direction. A tapered pin 33 is provided to protrude.

Using the rotating tool 30, the removal prevention screw 21
In order to tighten, the taper pin 33 is fitted and positioned in the conical concave portion 5 of the head 3, and the engaging claw 32 is inserted into the arc-shaped groove 22 to be engaged with the protruding piece 25. When a tightening torque is applied by the rotating tool 30 in this state, the removal preventing screw 21 is tightened via the protruding piece 25. At this time, since the tapered pin 33 is in close contact with the conical recess 5 of the head 3 and is in a biting state,
There is no possibility that the rotating tool 30 comes off the head 3 unexpectedly.
When the removal prevention screw 21 is tightened with a predetermined tightening torque, the protruding piece 25 is broken or deformed, so that the removal prevention screw 21 is tightened with a constant tightening torque. When the protruding piece 25 is broken or deformed, the engaging claw 32 of the rotating tool 30 is moved to the inclined guide surface 2 of the arc-shaped groove 22.
4 is pushed up by the cam action to come off the arc-shaped groove 22, and at the same time, the tapered pin 33 is separated from the conical recess 5, and the rotary tool 30 comes off the head 3.

[0023]

As described above, according to the present invention,
A conical recess is formed at the center of the top surface of the head of the removal prevention screw to form a locating hole and biting surface for the rotating tool, so that the rotating tool can be easily engaged with the screw head in the correct position. In addition, the rotating tool can be smoothly tightened without the risk of the rotating tool coming off the screw head unexpectedly during the tightening operation. Therefore, this kind of removal preventing screw, which has a difficulty in fastening work, can be fastened extremely efficiently and accurately.

According to the third aspect of the present invention, in addition to the excellent workability as described above, the tightening torque can be made constant, which is more effective in use and handling.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a detachment prevention screw according to the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a cross-sectional view of a main part along line 3-3 in FIG. 2;

FIG. 4 is a perspective view of a rotating tool used for tightening the removal prevention screw shown in FIG. 1;

FIG. 5 is a perspective view of a tightening torque controlling cylinder assembled to the rotating tool.

FIG. 6 is a perspective view showing a state in which the tightening torque controlling cylinder is assembled to a rotating tool.

FIG. 7 is a front view showing another embodiment of the removal prevention screw according to the present invention.

FIG. 8 is a plan view of the same.

9 is a sectional view taken along line 9-9 in FIG.

FIG. 10 is a perspective view of the main part.

FIG. 11 is a front view of a rotating tool used for tightening the removal prevention screw shown in FIG. 7;

FIG. 12 is an end view of the same.

FIG. 13 is a cross-sectional view of a main part showing a tightening operation state in which the rotating tool is engaged with a screw head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Removal prevention screw 2 Screw shaft 3 Head 4 Cutout part 5 Conical recess 6 Engagement surface 7 Inclined guide surface 10 Rotating tool 11 Cylindrical body 12 Engagement claw 13 Taper pin 14 Contact surface 15 Relief surface 16 Tightening torque control Cylinder

Claims (3)

[Claims] 1. A detachable screw having a head at one end of a screw shaft, and having an engaging means on an upper surface of the head for engaging a turning tool only in a tightening direction, A removal prevention screw, wherein a conical recess which forms a biting surface with a positioning hole of the rotary tool is provided at a central portion of a top surface of the portion. 2. The engaging means is formed by a plurality of arc-shaped grooves extending in a circumferential direction, wherein the bottom surface of the arc-shaped groove is a central flat surface and the upper surface of the head is continuous with both sides of the central flat surface. 2. The rotary tool according to claim 1, wherein the rotary tool is formed so as to engage only in a tightening direction with a protrusion protruding from the central flat surface. Screw for removal prevention described. 3. The projecting portion is broken or deformed by a constant tightening torque of the rotating tool for engaging the projecting portion and tightening the screw, and the rotating tool is a cam of the inclined guide surface. The detachment prevention screw according to claim 2, wherein the screw is configured to be detached from the arc-shaped groove by an action.