JPH08210336A - Tampering preventing screw - Google Patents

Abstract

PURPOSE: To provide a screw of head shape incapable of being returned by a screw driver. CONSTITUTION: A tamper preventing screw forms an engaging part 12 at each position equally-divided in the radial direction from the center of a head part 10, an engaging wall 14 is formed on the rotational side in the screw-in direction of the engaging part 12, and an inclined surface 16 of taper shape is formed from the outer circumferential edge 17 of a seat face 13 of the head part 10 toward the center of an apex face 11 on the rotational side in the screw-out direction. The inclined surface 16 is formed so as to be gradually higher than the seat face 13 between the mutually adjacent engaging walls 14 on the rotational side on the screw-out direction. Even when the head part is held by a set of cutting pliers or pliers to be turned, the tool is slipped and the head part can not be held, and the screw can not be screwed out. No erected parts are present across the screw head part, and perfect tamper preventing effect can be expected. In addition, even if higher tightening force is applied during the screw-in, the engaging wall is not broken, and the stable and high tightening force is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw in which a head having a larger diameter is formed on a leg portion having a thread, and a screwdriver tool is engaged with the head and screwed into a work. The present invention relates to a tamper-proof screw having a head that engages with a screwdriver when screwed into a work and does not engage with the screwdriver when screwing back.

[0002]

2. Description of the Related Art Generally, a screw which is rotated by a driving tool only in a screwing direction can be effectively rotated only in one direction, and once screwed in, a screwdriver which cannot be taken out by a normal screwdriver cannot be tampered with. It is called a screw. This type of screw is widely used to prevent the device from being disassembled and the cover lid removed by a third party. However, most of the screws of this type are provided with engaging walls that can be engaged with a screwdriver tool when screwing the screw into a workpiece in a radially opposed position, that is, a so-called shape. In the direction, i.e. in the screw-reverse direction opposite to the screw-in direction, the screw head is provided with a guide surface for disengaging the tool from the head when screwed back. Therefore, once the screw is screwed in, it is impossible to remove it by the return rotation of the screwdriver.

However, even in the case of practical use even in the known type of this kind, especially when screwing with a power tool, the operation is not easy and the tool and the screw cannot be sufficiently engaged, and the tool The tip of the wrench came off the head of the screw and scratched the work, so a reliable screwing operation could not be obtained.

In order to eliminate such drawbacks, a screw 100 as shown in FIGS. 4 and 5 is currently being used. This is a dome-shaped head portion 110 having a leg portion 120 of a screw 100, and a cutout portion 112 is provided along a portion facing in a radial direction, and an end wall of the cutout portion 112 is arranged in a direction to be rotated during screwing. It's over. The end wall, that is, the abutting surface 114 is on a surface that crosses the center line of the leg portion 120, and the bottom surface 116 of the cutout portion 112 has a flat bottom portion that is parallel to the seat surface 113 of the head portion 110. The bottom surface 116 extends rearward from the contact surface 114 in the direction opposite to the screwing direction. Accordingly, the rotation in the screwing direction is transmitted from the screwing tool to the contact surface 114, and the rotation in the returning direction is not transmitted to the head 110 of the screw 100.

[0005]

However, in the screw having such a structure, if the outer peripheral edge of the head of the screw has a certain thickness, the head of the screw is pinched with pliers or pliers and turned. It is possible to expect a perfect anti-tamper effect. In addition, since the cut-off part of the head of this screw is formed with a constant width on the bottom surface in the center direction of the head, a nearly upright surface is formed between the bottom surface and the end surface of the head so as to face each other. Therefore, this part can be sandwiched by pliers or pliers, and it is impossible to completely prevent the screw returning work. In addition, since it is driven by two surfaces facing each other, if the tip of a normal one-shaped screwdriver is improved, the screw can be rotated in the return direction and the posture of the screw becomes unstable when screwing in, and a stable screw There are problems such as the inability to transmit the tightening torque.

A first object of the present invention is to solve the above problems and to provide a head shape of a screw that cannot be returned by a ready-made screwdriver, and a second object is to provide a screw head shape.
To provide a head shape capable of reliably transmitting rotation from a screwdriver in a screwing operation.

[0007]

SUMMARY OF THE INVENTION A first object of the present invention is to:
Head 10 having engaging portion 12 for rotational drive and screw thread 21
In the screw 1 including the leg portion 20 in which the
The engaging portion 12 is formed at a position that is divided into three equal parts in the radial direction from the center of 0, and the engaging wall 14 is formed on the screwing direction rotating side of the leg portion 20 of the engaging portion 12 to rotate in the screw returning direction. From the outer peripheral edge 17 of the seat surface 13 of the head 10 to the top surface 1 of the head 10
This is achieved by forming a tapered slope 16 towards the center of 1. The second purpose is to make the taper-shaped slopes 16 adjacent to each other the engaging portions 12 on the rotation side in the screw return direction.
It is achieved by gradually increasing the height from the seat surface 13 between the engaging wall 14 and the engaging wall 14.

[0008]

When screwing in, the screwdriver having a tip shape adapted to the shape of the head 10 is engaged with the head 10 of the screw 1. Thereafter, when the screwdriver is rotated, the tool engages with the engagement wall 14 of the head 10 and the screw 1 rotates, so that the leg 20 is screwed into the work. On the other hand, screw 1
When the screwdriver tool is rotated in the return direction in order to return the head, the tip of the screwdriver tool slides along the tapered slope 16 of the head 10 and slips, and the return rotation is not transmitted to the screw 1. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIGS. 1 and 2, reference numeral 1 denotes a screw having a head 10 which is entirely dome-shaped, and a head 20 of the screw 1 is integrally formed with a leg 20 having a thread 21 formed therein. ing. Engaging portions 12 are arranged on the head 10 at positions radially divided from the center of the top surface 11 of the head 10 toward the outer circumference. An engagement wall 14 that is substantially upright from the seat surface 13 is formed on the engagement portion 12 in the screwing direction side, and a base portion 15 of the engagement wall 14 has a tapered sloped surface that forms a bottom surface continuous with the engagement wall 14. 16
Are formed. As the engagement wall 14 reaches the center of the head 10, the dome-shaped head surface and the base 1
The height from the seat surface 13 of the head 10 is gradually increased on the side opposite to the screwing direction, that is, on the return direction side. The slope 16 also rises toward the engaging wall 14 provided adjacent to the return direction side, and immediately before the engaging wall 14, the slope 16 has a dome shape of the head 10.

As shown in FIG. 3, the cross section taken along the line AA of FIG. 2 shows that the outer peripheral edge 17 of the portion along the engagement wall 14 is thin on the seating surface side of the head 10, It is linear between the top surface 11 and the top surface 11. On the other hand, in the cross section on the opposite side of the top surface 11, the outer peripheral edge 17 of the head portion 10 forms a part of a dome-shaped curved surface, and a linear slope 16 is provided between the top surface 11 and the dome-shaped curved surface. Has become.

Therefore, when the screw 1 is screwed into a work (not shown), the tip of a screwdriver (not shown) is shaped so as to match the shape of the head 10 of the screw 1, and this is Align with the engagement wall 14 of the head 10. After that, when the screwdriver is rotated in the screwing direction, the screwing force is transmitted to the engagement wall 14, and the screw 1 is screwed into the work. At this time, since the engagement wall 14 is formed at a position which is divided into three equal parts in the radial direction from the center, the head 10 of the screw 1 is formed.
The center of the screwdriver and the center of the screwdriver tool can be exactly coincided with each other when they are engaged with each other, so that the screwing force can be reliably transmitted.

On the other hand, when the screwdriver is rotated in the direction in which the screw 1 is returned, the tip of the screwdriver is moved along the tapered slope 16 and the screwdriver slips and spins idly. Not transmitted to screw 1.

[0013]

As is apparent from the embodiments described above, the present invention provides a screw 1 having a head 10 having an engaging portion 12 for rotational driving and a leg 20 having a thread 21. The engaging portion 12 is formed at a position that is divided into three equal parts in the radial direction from the center of the portion 10, and the engaging wall 14 is formed on the rotation side of the leg portion 20 of the engaging portion 12 in the screwing direction. From the outer peripheral edge 17 of the seat surface 13 of the head 10 to the rotation side, the head 1
Since the taper-shaped slope 16 is formed toward the center of the top surface 11 of 0, only the minimum necessary thickness is formed on the outer peripheral edge of the screw head. Even if you try to pinch it with pliers etc. and turn it, you cannot slip and slip the head of the screw, and you cannot loosen the screw. In addition, since the head of this screw does not have a relatively upright portion with the center of the screw sandwiched, other than the outer peripheral edge, it cannot be pinched with pliers or pliers, and the screw return work can be completely prevented. Yes, you can expect a perfect anti-tamper effect. Furthermore, since the screwing force is applied to the screw at the position where the head is divided into three parts, the engaging part of the screw head and the tip of the screwdriver do not deviate from the center of the screw when screwing in, and it is stable. The screw tightening torque can be transmitted to the screw.

Moreover, the tapered sloped surface 16 is formed so that the sloped surface 16 is gradually raised from the seat surface 13 between the adjacent engagement walls 14 of the engagement parts 12 on the rotation side in the screw return direction. Even if a high screw tightening force is applied to the engagement wall at the time of screwing, the engagement wall is not damaged, and a unique effect such that a high-strength fastening force is stably obtained can be obtained.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a perspective view showing a conventional example of the present invention.

FIG. 5 is a plan view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw 10 Head 11 Top surface 12 Engagement portion 13 Seating surface 14 Engagement wall 15 Base 16 Slope 17 Outer peripheral edge 20 Leg 21 Thread

Claims (2)

[Claims] 1. A head 1 having an engaging portion 12 for rotational driving.
0 and the leg portion 20 having the thread 21 formed therein, the engaging portion 12 is formed at a position radially divided from the center of the head portion 10, and the leg of the engaging portion 12 is formed. Part 2
The engaging wall 14 is formed on the rotation side in the screwing direction of 0, and the tapered slope 1 from the outer peripheral edge 17 of the seat surface 13 of the head 10 to the center of the top surface 11 of the head 10 on the rotation side in the screw returning direction.
Tamper-proof screw characterized in that 6 is formed. 2. The taper-shaped inclined surface is formed so as to be gradually higher than the seat surface 13 between the adjacent inclined wall and the engaging wall 14 of the engaging portion 12 on the rotation side in the screw return direction. Tamper-proof screw according to claim 1.