JPH03524B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to improvements in a tapping screw and a rolling die thereof. Specifically, the present invention relates to improvements in concrete tapping screws and rolling dies suitable for fixing other components such as angles and channel members to concrete structures.

<Prior Art> Today, tapping screws are often used instead of expansion anchors as anchors for structures such as concrete.

For example, the double threaded anchor bolt proposed in Japanese Patent Publication No. 53-43625 is an example of this type of tapping screw for concrete.
This anchor bolt includes a guide screw and a tapping screw having two different diameters on the outer periphery of a shaft portion having a sharp pointed head. Guide screws help ensure proper rotation of the anchor bolt relative to the pre-machined pilot hole. The tapping screw has an outer diameter that gradually decreases from the lower part of the neck of the shaft to the tip, and is provided with a notch of about 90 degrees. This allows for reliable installation using only a spiral screw thread without damaging the wall of the pre-drilled hole in the concrete structure, and also effectively removes concrete shavings scraped off during installation. This serves to prevent relaxation.

<Problem to be solved by the invention> However, when a large amount of concrete shavings (often in the form of powder) is generated, it gets clogged between the prepared hole and the shaft. However, there is a problem in that the torque required for tapping and tightening increases. Concrete shavings generated at the tip of the screw are an obstacle to tapping. This tendency is particularly noticeable in the case of tapping screws that do not have a type in which the outside diameter of the tapping screw is gradually reduced, such as the anchor bolt of Japanese Patent Publication No. 53-43625. There is a risk of damaging it.

On the other hand, for self-drilling tapping screws that drill a pilot hole by themselves, it has been proposed that the cutting groove in the drilled part at the tip is extended to the part where the tapping thread is formed (particularly Publication No. 41-20009). However, the tapping thread of this screw is formed on the tip side of the tapered shaft portion. Therefore, the root diameter of the tapping thread is set smaller than the root diameter of the tightening thread. This is because this screw was invented for the purpose of being used on relatively thin metal plates, etc., and the tapping part enlarges the pilot hole that it has formed with the drill part at the tip while tapping. This is how it was done. As a result, when this screw is used as a tapping screw for a pre-drilled hole in concrete, the following problem occurs.

First, the pre-drilled pilot hole usually has an inner diameter approximately equal to the root diameter of the tightening screw thread, and therefore is larger than the root diameter of the tapping portion. Therefore,
During tapping, the valley portion does not come into contact with the wall surface of the prepared hole, and only the top of the tapping twist engages with the wall surface to cut the female thread. the result,
Tapping is performed in an indeterminate state without any guide, and good tapping cannot be expected.

Second, although much of the concrete shavings can be discharged from the cutting groove, it is inevitable that some of it will reach the fastening thread. At this time, in this screw, since the diameter of the trough of the tightening thread is larger than that of the tapping thread, there is no space between the trough and the wall of the pilot hole. As a result, it is not possible to completely eliminate the possibility that shavings become stuck between the hole and the wall surface of the prepared hole.

Thirdly, the tapping portion on the tip side of the shaft portion and the drill portion at the tip thereof do not effectively engage with the wall surface of the prepared hole. As a result, the length of the portion that can actually exert the fastening force becomes shorter.

Therefore, it is an object of the first invention of the present application to perform tapping on a prepared hole drilled in a concrete structure using only the rotational movement of an ordinary tightening tool, and to achieve a reliable tightening and holding effect. Our goal is to provide a self-tapping screw. especially,
To provide a tapping screw that reliably disposes of concrete shavings generated during tapping, reduces the torque required for tapping and tightening, and does not cause damage to the wall surface of a pilot hole drilled in concrete.

A second object of the invention of the present application is to provide a die used for manufacturing the above-mentioned novel tapping screw. Furthermore, in order to simplify the manufacturing process, we are trying to provide a die that can process the entire shaft of a screw in one rolling operation.

<Means for Solving the Problems> Therefore, in order to achieve the above object, the first invention of the present application includes a head for receiving a tightening tool, a shaft extending from the head, and a shaft extending from the head. A thread for tightening is formed on the outer periphery of the shank, a thread for tapping is formed on the outer periphery of the distal end of the shaft, and the distal end of the shank has a tapered tip whose diameter decreases toward the distal end. In a tapping screw, in which a plurality of shavings receiving grooves extending approximately vertically are formed in the tapered tip part, and these receiving grooves reach the part where the thread for tapping is formed, the shank part A bulge is formed between the distal end side of the portion where the fastening screw thread is formed and the proximal end side of the tapered tip part, and the diameter of this bulge is larger than the root diameter of the fastening screw. The plurality of receiving grooves are set to be smaller than the outer diameter, and the plurality of receiving grooves reach this bulging part, the area between these grooves is used as a land, and a screw thread for tapping is formed at least on the outer periphery of the land in the bulging part. To provide a tapping screw characterized by:

Here, the shavings receiving groove is not necessarily limited to one that extends only in the vertical direction, but also includes one that extends in the vertical direction while drawing a spiral shape or a curve. Further, the thread may be formed in one thread or in plural threads, and the diameter of the thread may be changed.

A second invention of the present application provides a die for rolling the above-mentioned tapping screw. The upper part of the die is provided with a thread forming part, the lower part of the die is provided with a tapping part forming part, and the thread forming part has a large number of thread forming grooves formed on a flat surface.
A plurality of convex portions for forming shavings receiving grooves are formed in the tapping portion forming portion, and these convex portions protrude from the flat surface of the thread forming portion and are arranged in parallel, and there is a The concave portion is a concave portion for forming a land, and an inclined concave portion that gradually projects toward the convex portion is provided below the concave portion for forming a land, and a tapping screw thread for forming a screw thread for tapping is provided below the concave portion for forming a land. The present invention provides a rolling die for tapping screws in which a forming groove is provided at least in a concave portion of a tapping portion forming portion.

<Function> Accordingly, in the tapping screw of the present invention, concrete shavings generated by tapping are allowed to escape into the shavings receiving groove and are collected there. As a result, there is no possibility that a large amount of shavings will become stuck between the screw thread and the wall surface of the concrete prepared hole. Furthermore, since the tapping screw thread is divided by a plurality of shavings receiving grooves extending substantially vertically, it is advantageous for gradually scraping away the wall surface of the concrete prepared hole. Furthermore, since a thread for tapping is formed on the land of the large-diameter bulge, this land comes into contact with the wall surface of the prepared hole during tapping, and serves as a guide during tapping, ensuring accurate tapping and It also acts as a guide when tightening screws, achieving smooth tightening. In addition, since the diameter of the trough of the tightening screw is smaller than the diameter of the bulge, a space is formed between this trough and the wall surface of the pilot hole due to the difference in diameter. becomes. Therefore, even if some of the shavings reach the tightening screw portion, they are received within this space, thereby preventing the shavings from clogging. Furthermore, since the tapping thread is formed in the large diameter bulge, the thread in this portion can also engage with the wall surface of the pilot hole. Therefore, the length of the part that can actually exert the fastening force can be increased,
Fastening force can be increased.

Further, the thread forming groove of the rolling die of the present invention forms a thread shaft portion, the convex portion at the bottom of the die forms a shavings receiving groove, the recess forms a land, and the recess forms a tapping thread forming groove. The tapping threads are each formed by rolling in the same process.

<Example> Embodiments of the present invention will be described below based on the figures.

FIG. 1 shows the entirety of an embodiment of a tapping screw, which includes a head 3 having a cross recess 2 for receiving a tightening tool, and a shaft 4 extending from the head. has. This shaft part 4
has a substantially constant diameter, and a thread 7 is formed on its outer periphery. Furthermore, this tapping screw has a bulge having a larger diameter than the shaft portion 4. This bulge is formed with a thread 10 for tapping, which will be described later, and performs a tapping action. Therefore, this embodiment will be described below as the tapping section 5. This tapping portion 5 is provided at the tip of the above-mentioned shaft portion 4, and a tip tapered portion 6 whose diameter is reduced is formed at the tip.

As shown in the enlarged view of FIG. 2 and the explanatory view of FIG. 3, a pair of shavings receiving grooves 8 are formed at the tip of the shaft portion 4. This shavings receiving groove 8 starts from the tip tapered part 6 and ends in the tapping part 5.
The areas between these receiving grooves 8, 8 are lands 9, 9. These lands 9, 9 have a screw thread 1 for tapping, which is continuous with the thread 7.
0 is wound around the receiving groove 8 while being divided. This tapping thread 10 is wound two or three times around the land 9 in the tapping part 5, and the terminal end 11 of this thread 10 ends at the land 9 in the tip tapered part 6. This land 9 has a second diameter, and its diameter decreases as it moves away from the cutting edge 14 of the receiving groove 8, which will be described later. Along with this, the second thread 10 for tapping is also provided.

Here, referring to the diameter of this tapping screw, the diameter a of the land 9 portion of the tapping portion 5 is slightly larger than the diameter b of the shaft portion 4. The diameter of thread 7 is land 9.
is larger than the diameter a of the screw thread 10 for tapping.
It is slightly larger than or almost equal to the diameter of the mountain. The diameter of the thread 10 for tapping decreases as it approaches the end 11 of the thread 10, until the thread 10 disappears. The concrete structure 2 has a diameter c that is approximately equal to the diameter a of the land 9 in the tapping portion 5.
If used for the pilot hole 22 of 1, the land 9 will serve as a guide during tapping and screw tightening.
Ensures smooth screw rotation. Moreover, land 9
Since the land 9 is not entirely engaged with the pilot hole, it is possible to prevent an increase in rotational torque and generation of large frictional heat.

Note that even if the pilot hole 22 of the concrete structure 21 is incomplete, it can be cut by the receiving groove 8 and corrected to a pilot hole of an appropriate diameter. That is, the receiving groove 8 is
Consisting of a cutting surface 12 and a drag surface 13, the cutting surface 12
The pilot hole can be cut by the cutting edge 14 of. However, the names of the cutting surface 12 and the cutting edge 14 are borrowed from the names of the drill, and in the present invention,
The receiving groove 8 does not necessarily have to perform a cutting function. Further, in the embodiment, the tip of the tip tapered portion 6 is pointed and has a substantially drill shape, but the tip does not necessarily have to be sharp, and may be in the shape of an inverted truncated cone without a sharp tip. .

Further, the tapping thread 10 is divided by the receiving groove 8, and its end face 15 projects from the cutting edge 14 of the receiving groove 8. This end surface 15 is preferably along the vertical plane B passing through the axis of the screw, but
It is not limited to this, and may be at an angle with respect to the vertical plane B. By dividing the tapping thread 10 by the receiving groove 8, a large number of end surfaces 15 are formed...
... engages with the wall surface of the pilot hole 22 and scrapes the wall surface, thereby forming a female thread in the pilot hole 22. In addition, since the screw thread 10 for tapping has a second hole,
During this tapping, only the end face 15 and the thread 10 in its vicinity engage with the wall surface of the prepared hole 22, and the other portions of the thread 10 do not engage, thereby reducing the rotational torque required for tapping. Can be done. In addition, the other part of the screw thread 10 for tapping, where the second hole is taken out, is
It provides appropriate strength to the end face 15 and its vicinity and functions to support them.

Concrete shavings generated when the tapping screw thread 10 scrapes the wall surface of the pilot hole 22 of the concrete structure 21 is removed from the receiving groove 8.
stored inside. This receiving groove 8 has a tapered tip portion 6.
It is formed from the center to the axis of the tapping 5, and has a considerable capacity and can store a large amount of concrete shavings. Incidentally, if the receiving groove 8 extends in the vertical direction while drawing a spiral as in the embodiment, the shavings are efficiently discharged through the receiving groove 8. A portion of the discharged shavings is carried to the outside of the pilot hole 22, but a portion is deposited in the space between the wall surface of the pilot hole 22 and the shaft portion 4, increasing the reliability of the tapping screw installation. useful for. Note that this space depends on the difference in diameter between the pilot hole 22 and the shaft portion 4, but in this embodiment, as described above, the diameter a of the land 9 portion in the tapping portion 5 is set to the diameter b of the shaft portion 4. Because it was made a little larger than that, due to the difference between the two,
Space will be secured.

4 to 6 show dies for rolling the aforementioned tapping screws. However, since FIG. 6 is an enlarged perspective view looking down from above the die,
It is shown upside down compared to the plan view of FIG.

The upper part of the die is provided with a thread forming part 101, and the lower part of the die is provided with a tapping part forming part 102.

The thread forming portion 101 has a large number of thread forming grooves 104 arranged in parallel on a flat surface 103 at a predetermined lead angle.

A large number of convex portions 105 for forming shavings receiving grooves are arranged in parallel in the tapping portion forming portion 102, and concave portions 106 between the convex portions 105 serve as concave portions for forming lands.

To form this convex portion 105, a bank portion 107 protruding in a trapezoidal shape from the flat surface 103 at the bottom of the die must be formed.
This bank portion 107 may be formed in advance and processed by grinding, electrical discharge machining, or the like.

The convex portion 105 and the concave portion 106 extend obliquely at a larger lead angle than the thread forming groove 104.
As shown in FIG. 5, the recess 105 is a substantially parallel recess 10 extending slightly deeper than the flat surface 103.
8 and the top 10 of the bank part 107 from the bottom of the die.
9 and an inclined recess 110 that rises toward the direction 9.

The approximately parallel recess 108 has a tapping thread forming groove 1 extending from the thread forming groove 104 at the same lead angle.
11 is formed. The tapping thread forming groove 111 has approximately the same size and depth as the thread forming groove 104, but as shown in FIG. 5, it gradually becomes shallower and disappears as it goes downwards in the die.

The convex portion 105 includes a substantially parallel convex portion 112 that protrudes from the flat surface 103 and extends at approximately the same height, and an inclined convex portion 113 that further rises near the bank portion 107.
It consists of. This inclined convex part 113 and the above-mentioned inclined recessed part 110 cooperate to form the tip tapered part 6,
In particular, the inclined convex portion 113 forms the receiving groove 8 in the tapered tip portion 6 . The substantially parallel convex portion 112 is composed of a cutting surface forming surface 114 and a drag surface forming surface 115, and the boundary between the cutting surface forming surface 114 and the convex portion 106 becomes a cutting edge forming line 116.

In addition, since the land 9 is cut second, the recess 106 forming the land is deepest near the cutting edge forming line 116 and gradually becomes shallower as it approaches the drag surface forming surface 115 of the convex portion.

By rolling the wire with the die thus formed, the thread 7 of the shaft portion of the screw, the tapping portion 5, and the tapered tip portion 6 are simultaneously formed.

<Effects of the Invention> As described above, in the case of the tapping screw that is the first invention of the present application, when tapping is performed on a prepared hole drilled in a concrete structure, concrete shavings generated by tapping are removed. Since the shavings escape into the receiving groove and are collected there, there is no risk of a large amount of shavings becoming stuck between the screw thread and the wall surface of the concrete pilot hole. Therefore, there is no risk of shavings getting stuck between the screw and the pilot hole, and the problem of increased torque required for tapping and tightening is also resolved, and the female thread can be screwed without damaging the wall of the pilot hole drilled in concrete. can be formed and tightened.

Moreover, since the thread for tapping is divided by the swarf receiving groove, a large number of end faces thereof are formed. The end face of this tapping screw gradually scrapes away the wall surface of the concrete pilot hole. Therefore, a female thread can be accurately formed without damaging the wall surface of the pilot hole.

A second invention of the present application provides a die capable of rolling the above novel tapping screw. Moreover, according to the die of the present invention, the threaded portion, the tapping portion, and the tapered tip portion can be processed simultaneously in one step.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a tapping screw that is an embodiment of the first invention, Fig. 2 is an enlarged perspective view of the main parts of the same screw, Fig. 3 is a schematic illustration of the bottom surface of the same screw, and Fig. 4 5 is a front view of a rolling die for a tapping screw according to an embodiment of the second invention, FIG. 5 is an enlarged side view of the main part of the die, and FIG. 6 is an enlarged perspective view of the main part of the die. 3... Head, 4... Shaft part, 5... Tapping part, 6... Tapered tip part, 7... Screw thread, 8...
Reception groove, 9... Land, 10... Thread for tapping, 101... Thread forming part, 102... Tapping part forming part, 103... Flat surface, 104...
...Thread forming groove, 105...Convex portion, 106...Concave portion, 111...Tapping thread forming groove.

Claims (1)

[Claims] 1. A head for receiving a tightening tool and a shaft extending from the head, a thread for tightening is formed on the outer periphery of the shaft, and a screw thread is formed on the outer periphery of the tip of the shaft. A thread for tapping is formed, and a tip tapered part is formed at the tip of the shaft part, the diameter of which decreases toward the tip, and a plurality of shavings receiving grooves extending approximately vertically are formed in the tip tapered part. In the case of a tapping screw in which a receiving groove is formed and these receiving grooves reach the part where the thread for tapping is formed, the distal side of the part where the thread for tightening the shaft part is formed and the proximal end of the tapered part of the tip. A bulging portion is formed between the bulging portion and the diameter of the bulging portion is set to be larger than the root diameter of the tightening screw and smaller than its outer diameter, and the plurality of receiving grooves reach this bulging portion. A tapping screw characterized in that a region between these grooves is used as a land, and a thread for tapping is formed on the outer periphery of the land at least in the bulged portion. 2. The tapping screw according to claim 1, wherein the thread formed on the outer periphery of the shaft portion and the tapping thread formed on the land are continuous. 3. Claim 1, characterized in that the thread for tapping is formed from the land in the bulging part to the land in the tapered tip part.
The tapping screw described in item 1 or 2. 4. The tapping screw according to claim 1, 2, or 3, wherein the tip of the tapered portion is sharp and has a substantially drill shape. 5. The tapping screw according to claim 1 or 2, or 3 or 4, wherein at least the land on which the tapping thread is formed is double-bored. 6 A thread forming part is provided at the top of the die,
A tapping part forming part is provided at the bottom of the die, a large number of thread forming grooves are formed on a flat surface in the thread forming part, and a plurality of thread forming grooves are formed in the tapping part forming part for forming shavings receiving grooves. A convex portion is formed,
These convex portions are juxtaposed to protrude from the flat surface of the thread forming portion, and the concave portion between these convex portions is used as a concave portion for forming a land, and below the concave portion for forming a land, A rolling die for a tapping screw, which is provided with an inclined recess that gradually projects toward a convex part, and in which a tapping screw thread forming groove for forming a thread for tapping is provided at least in the recess of the tapping part forming part. 7. The tapping screw rolling die according to claim 6, wherein the concave portion of the tapping portion forming portion is formed deeper than the flat surface and shallower than the thread forming groove.