JP2003287011A - Screws with head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To assure cutting property of a drill portion and corrosion resistance of a head portion at the same time, in a drill screw. <P>SOLUTION: A head 3 is configured of an inner head 8 formed integrally with a shaft 2 and an outer head 9 covering the head 8. The inner head 8 and the outer head 9 are held in a way they cannot rotate relatively by being fitted with a cross hole 10 and a cross projection 12, and in a way they do not come off by caulking of an inner flange 13. The shaft 2 is made of, for example, carbon steel allowing hardening, and the cutting property of a drill portion is improved. The outer head 9 is made of, for example, austenitic stainless steel, assuring high corrosion resistance. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to headed screws such as drill screws and tapping screws.

[0002]

2. Description of the Related Art A drill screw having a drill portion formed at the tip of a shaft is widely used in buildings and the like because it does not require a pre-drilled hole in a work and has a high work efficiency in fastening work.

This drill screw is required to have good machinability with respect to the work in order to further improve workability, reduce the burden on the worker, and form an ideal female screw on the work to increase the fastening strength. To be On the other hand, the material should be as soft as possible from the viewpoint of workability of the drill part and the thread. Therefore, in order to secure both workability and machinability, hardness is generally increased by quenching.

On the other hand, when the head is exposed to a corrosive environment such as a drill screw for fixing a roofing material, ensuring corrosion resistance is also a major factor. Regarding this point of corrosion resistance,
Generally, the material is stainless steel.
From the viewpoint of this corrosion resistance, austenitic stainless steel is particularly excellent.

However, austenitic stainless steel has a problem that high hardness cannot be obtained even by quenching, and it is difficult to achieve both machinability and corrosion resistance.

Regarding this point, conventionally, the drill part and the other parts are made of different materials, and the drill part is made of a material such as carbon steel that can obtain high hardness by quenching, while the other parts are made of austenite. As a stainless steel product, the two are integrated by welding or fitting, etc.The entire drill screw is made of carbon steel or martensitic stainless steel, especially while ensuring the hardness of the drill part, the head is covered with a cap made of a stainless steel plate, the drill Measures have been taken such that the entire screw is made of a material whose hardness is prioritized, and the corrosion resistance is enhanced by applying a surface treatment such as plating or soaking.

[0007]

The above-mentioned method is
The process of welding the drill portion to the shaft is troublesome, and since the heat treatment has to be carried out after the welding is performed in advance, there is a problem that the heat resistance lowers the corrosion resistance of the shaft portion and the head.

In the method of covering the head with the cap as described above, there is a possibility that rainwater may enter between the cap and the head or that electrolytic corrosion may be induced. Another problem is that it can be applied only to a square head such as a hexagonal head, and cannot be applied to a cross-headed head, a frayed head, or a drill screw having a hexagonal head.

Further, the method of applying the surface treatment is as follows:
Due to uneven processing of the surface layer and deterioration of the surface layer over time,
There is a problem that there is a limit to ensuring the corrosion resistance.

An object of the present invention is to improve the present situation.

[0011]

In order to solve the above-mentioned problems, the present invention according to claim 1 is provided with a shaft portion and a head provided at one end portion thereof, and a screw having threads formed on the shaft. The head is composed of an inner head integrally formed with the shaft and an outer head enclosing the inner head.

The invention of claim 2 is applied to a drill screw in which a drill portion is integrally formed at the other end (tip) of the shaft.
In this drill screw, the shaft is made of a material that achieves high hardness by quenching, while the outer head is made of a material with high rust resistance, and the drill part, screw threads and inner head are formed on the shaft. After further hardening, the outer head is wrapped around the inner head by crimping the outer head onto the inner head.

[0013] Claim 3 shows an example of a material particularly suitable for a drill screw. In the present invention, the outer head is made of austenitic stainless steel, and the main body including the shaft, the drill portion and the inner head is made of carbon. Steel or matensite stainless steel (eg SUS410 stainless steel)
Made of.

[0014]

According to the present invention, since the main body portion having the inner head and the outer head can be made of different materials, the main body portion is made of a material with emphasis on workability and hardness. As the outer head is made of a material that emphasizes corrosion resistance, the main body portion and the outer head can be made of a material according to the required function. Thereby, various performances required for screws can be secured.

As described above, the drill screw is often required to have workability, machinability and corrosion resistance. However, by constructing as in claim 2, it is not possible to secure a single material for the drill screw. It can hold various functions. Therefore, it can be said that the present invention is particularly suitable for a drill screw.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

(1). First Embodiment (FIGS. 1 to 3) FIGS. 1 to 3 show the first embodiment. This embodiment is applied to a drill screw, FIG. 1 is a front view in a state in which it is in a horizontal direction, FIG. 2A is a longitudinal sectional view, and FIG. 2B is a sectional view taken along line BB of FIG. 3 is a separation view showing the processing steps.

The drill screw comprises a shaft (shaft portion) 2, a head (head portion) 3 provided at one end of the shaft 2, and a drill portion 4 integrally provided at the other end of the shaft. Has a thread (male thread)
5 is formed. In this embodiment, the unthreaded portion remains on the side of the shaft 2 close to the head 3, but it goes without saying that the thread 5 may be formed up to the bottom of the neck. Also, the thread 5
There is also a drill screw in a mode in which there is a non-threaded portion between the and the drill portion 4. Reference numerals 6 and 7 in FIG. 1 denote works.

The drill portion 4 is formed by forging (cold heading), and the screw thread 5 is formed by rolling. Of course, both can be machined by cutting. Further, the shape of the drill portion can be variously embodied.

The head 3 is composed of an inner head 8 that is integrally provided at the other end of the shaft 2 and an outer head 3 that wraps the inner head 8. The shaft 2, the inner head 8 and the drill portion 4 make up the main body portion 1. It is configured. The inner head 8 is circular when viewed in the axial direction, and has a cross hole 10 formed on the top surface as an example of a rotation stopping means. Also, the bearing surface 8a of the inner head 8
Is formed in a tapered shape that is inclined toward the side opposite to the shaft 2.

A space 9 into which the inner head 8 is inserted is formed in the outer head 9, and a cruciform protrusion 12 that fits in a cross hole 10 of the inner head 8 is formed on the bottom surface of the space 9. There is. The inner head 8 is used as a retaining means.
An inward flange 13 is integrally formed on the seat surface of the above so as to overlap from the outside. That is, the inward flange 13 is caulked to the inner head 8.

A circular outward flange 14 is integrally provided on the outer head 9. In the present embodiment, the portion of the inward flange 13 is recessed toward the top surface side of the outward flange 14, but both flanges 13 and 14 may be flat surfaces that extend in series.

As the material of the main body 1, for example, carbon steel such as SWCH22A specified in JIS or martensitic stainless steel also specified in JIS as SUS410 is used to obtain high hardness by quenching. It is made of iron-based material that can be used. On the other hand, the outer head 9 is made of a material having high corrosion resistance such as austenitic stainless steel, and is not heat-treated.

As a manufacturing process of this drill screw, first,
The inner head 8, the drill portion 4, and the screw thread 5 are processed on the main body 1, and then heat treatment such as quenching and annealing is performed on this. On the other hand, the outer head 9 is formed with a tubular portion 15 as an intermediate form which becomes the inward flange 13.

Then, with the outer head 9 fitted into the inner head 8 and the cross hole 10 and the cross-shaped projection 12 fitted together, the tubular portion 15 is bent radially inward to form the inward flange 13. The outer head 9 is attached to the inner head 8 such that it cannot rotate and cannot be removed.

As described above, the corrosion resistance of the outer head 9 can be remarkably improved while maintaining the high cutting property of the drill portion 4. Therefore, it is particularly suitable as a drill screw used in places where the head is exposed to wind and rain, such as fastening roofing materials and fastening outer wall materials.

By the way, in the case of the prior art in which the head is covered with a thin plate cap, since the strength of the cap is small, a slip phenomenon may occur between the cap and the head when rotating with a wrench, or the cap may be deformed. It cannot be said that there is no such phenomenon, but since the outer head 9 of the present invention is thick, such a phenomenon does not occur.

The inner head 8 and the outer head 9
In order to increase the mounting strength of the inner head 8, it is necessary to secure an outer diameter of the inner head 8 to some extent, and then it is necessary to increase the size of the outer head 9 as well. It is preferable to set the size of the rank one larger than the nominal diameter of 5.

That is, for example, the nominal diameter of the thread 5 is JI.
When the S standard or ISO standard is M6, the outer head 9 is set to a size corresponding to M8, and the nominal size of the outer head 9 is made one rank larger than the nominal size of the thread 5. .

In the case of the prior art in which the head is covered with a cap, the outer shape of the head is increased only by the thickness dimension of the cap, and therefore a dedicated wrench is required instead of using an ordinary sizing wrench. Although there is a risk, setting the size so that the nominal size is different as described above has an advantage that a normal wrench (particularly a box wrench) can be used as it is for work.

When the tubular portion 15 is caulked, the inner circumferential length of the tip of the inward flange 13 is shorter than the outer circumferential length dimension of the tubular portion 15 by bending it inward, so that Will wrinkle.

However, when the inward flange 13 is formed to have a recess (recess) as in the present embodiment, the unevenness due to wrinkles is absorbed by the recess, and the outward flange 14 and the inner flat surface thereof are flattened. The part can be brought into close contact with the work 6. Therefore, it is possible to prevent or remarkably suppress the formation of a gap between the head 4 and the work 6 even though the head 4 is combined by caulking, and the sealing property can be secured. In another embodiment described later, the caulked portion may be absorbed in the recess after caulking as in the first embodiment.

(2). Second Embodiment (FIGS. 4 to 7) FIG. 4 shows the second embodiment. (A) is the figure which looked at the inner head 8 from the axial direction, (B) is a partial front view.

In this embodiment, in addition to forming a cross hole in the inner head 8 as the rotation preventing means, the outer diameter of the inner head 8 is formed in a quadrangle when viewed from the axial direction. Although not shown, the hollow portion 11 of the outer head 9 and the tubular portion 15 also have a square shape that fits into the inner head 8.

(3). Third Embodiment (FIG. 5) FIG. 5 shows a third embodiment. (A) is the figure which looked at the inner head 8 from the axial direction, (B) is a partial front view.

This embodiment is basically the same as the first embodiment, and four engaging grooves 16 are formed at equal intervals on the outer circumference of the inner head 8 as the rotation preventing means.
Although not shown, an engagement protrusion that fits into the engagement groove 16 of the inner head 8 is formed on the inner peripheral surface of the space 11 of the outer head 9 (however, the cylindrical portion 15 of the outer head 9 is , The protrusion is not formed so as to be in close contact with the seat surface of the inner head 8.

When a plurality of detent means (the cross hole 10 and the engaging groove 16) are formed in a state where the inner head 8 is formed in a circular shape as in this embodiment, the cylindrical portion 15 of the outer head 9 is also formed in a circular shape. Therefore, there is an advantage that the attachment strength of the outer head 9 can be improved while maintaining the state where the caulking can be performed uniformly.

The engaging groove 13 of the inner head 8 and the outer head 9
The number of the protrusions is not limited to four, and can be set to an arbitrary number, for example, six at equal intervals along the circumferential direction.

(4). Fourth Embodiment (FIG. 6) FIG. 6 shows a third embodiment. (A) is a front sectional view of the outer head 9, (B) is a view of the inner head 8 seen from the axial direction, and (C) is a partial front view.

In the fourth embodiment, the shape of the inner head 8 and the shape of the void 11 of the outer head 9 are formed in a hexagonal shape. In this case, the inner head 8 has a size corresponding to the nominal diameter of the screw thread 5, and the outer head 9 is set to a larger nominal size by one rank (or two ranks), so that the conventional drill screw giving priority to machinability. It is also possible to attach the outer head 9 having high corrosion resistance to the.

(5). Fifth Embodiment (FIG. 7) FIG. 6 shows a third embodiment. (A) is a front sectional view of the outer head 9, (B) is a view of the inner head 8 seen from the axial direction, and (C) is a partial front view.

In this embodiment, the shape of the inner head 8 and the shape of the space 11 in the outer head 9 are formed into a square as an example of a regular polygon, and further, the inner head 8 is provided with a square engagement hole 17. A square prismatic protrusion 18 is formed in the void 11 of the outer head 9.

A cross hole 19 into which a cross driver is engaged is formed on the top surface of the outer head 9. Instead of the cross hole 10, a hexagonal hole, a square hole, a star-shaped hole, or a slot is formed. That is, it is also possible to arrange the slot and the cross hole in parallel. As shown by the alternate long and short dash line in (B), the inner head 8
The outer shape and the space 11 of the outer head 9 may be formed in a circular shape.

In this case, the cylindrical portion 15 of the outer head 9 may be formed in a square shape in conformity with the shapes of the inner head 8 and the void 11, but in order to perform the caulking evenly, it is preferable to make it circular. preferable.

The outer head 9 with a cross hole as in the fifth embodiment may be used in the first to fourth embodiments, or the polygonal outer head 9 such as a hexagon may be applied to the fifth embodiment. good. Further, the outer head 9 may be formed in a hexagonal shape such as a hexagon, and an engaging hole such as a cross hole may be formed in this.

(6). Others The present invention can be variously embodied in addition to the above-described embodiments. For example, the shapes of the inner head and the outer head can be variously embodied as needed. Further, the rotation preventing means and the retaining means for the inner head and the outer head can be variously embodied.

Further, the object of application of the present invention is not limited to the drill screw, but can be applied to other types of self-drilling screws such as tapping screws and wood screws, and ordinary screws or bolts.

The combination of materials of the main body and the outer head can be arbitrarily set according to the application. For example, various materials such as gold, silver, copper, brass, aluminum and titanium can be used for the outer head. Needless to say, the screws may be surface-treated.

[Brief description of drawings]

FIG. 1 is a front view of a drill screw in a horizontal state.

FIG. 2A is a longitudinal sectional view, and FIG. 2B is a sectional view taken along line BB of FIG.

FIG. 3 is a separation view showing a processing step.

FIG. 4 is a diagram showing a second embodiment.

FIG. 5 is a diagram showing a third embodiment.

FIG. 6 is a diagram showing a fourth embodiment.

FIG. 7 is a diagram showing a fifth embodiment.

[Simple explanation of symbols]

1 body 2 axes 3 heads 4 drill section 5 screw threads 8 inner head 9 Outer head 10 Cross hole that forms part of the detent means 11 vacant places 12 Cross-shaped projections that form part of the detent means 13 Inward flange 15 Cylindrical part as intermediate form of inward flange

Claims (3)

[Claims] 1. A screw having a shaft portion and a head provided at one end thereof, wherein the shaft has a thread, and the head has an inner head integrally formed with the shaft, Screws with a head consisting of an outer head that wraps this inner head. 2. A drill screw in which a drill portion is integrally formed at the other end (tip) of the shaft, wherein the shaft is made of a material having high hardness by quenching, while the outer head is rustproof. It is made of a high material, and the outer head is wrapped with the outer head by caulking the outer head to the inner head after forming the drill part, the screw thread and the inner head on the shaft and further quenching. A drill screw as an example of the head screw described in Item 1. 3. The outer head is made of austenitic stainless steel, and the main body composed of a shaft, a drill portion, and an inner head is made of carbon steel or matensite stainless steel (for example, SUS410 stainless steel). Screws with heads described in.