JP2016176582A - Self-boring screw for alc board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-boring screw for ALC board capable of suppressing the occurrence of initial loosening due to depression of ALC.SOLUTION: A head part 4 is fundamentally set as an inverted truncated cone shape, and annular protrusions 6 which is annularly extended in a circumferential direction around a screw shaft as a center on a lateral surface of the head part 4 and is protruded in a radial direction is provided. It is prevented that, as in such a case of the conventional screw that the head part assumes an inverted truncated cone shape, a stress is concentrated to a ridge part of the head part, ALC is depressed and, thereby, initial loosening occurs. Further, (1) a stress which actuates from the head part 4 to ALC can be also dispersed to directions other than the shaft direction and (2) the annular protrusions 6 are provided so that ALC powder cut and generated by the head part 4 is hardly discharged to an external part, the head part 4 is brought into contact with the ALC board in such a state that the ALC powder is closely packed by air bubbles of ALC and, thereby, also the occurrence of initial loosening due to depression of ALC is suppressed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an ALC (Lightweight Aerated Concrete) board, which is screwed on itself and screwed in a sinking hole with its own screw head to fix the ALC board with the head. It relates to a drill screw.

  ALC is a brittle material that contains air bubbles inside and has a structure that is easily destroyed by pressure. Conventionally, as an ALC board self-drilling screw for fixing such an ALC board, what is indicated by patent documents 1 and 2, for example is known.

  The self-drilling screw for an ALC board disclosed in Patent Document 1 has an inverted truncated pyramid shape, and the ALC board is cut off at the ridgeline portion and sinks while digging. At the same time, the ALC cutting waste is discharged from the gap between the head of the inverted truncated pyramid shape and the bottom surface of the hole formed in the ALC (having an inverted truncated cone shape).

  The self-drilling screw for ALC board disclosed in Patent Document 2 also has a head that basically forms an inverted truncated pyramid shape, and performs the same function as the screw of Patent Document 1. However, this screw also has the purpose of sinking while removing the base coating film in order to prevent the base coating film from rolling up during the fastening operation of the ALC board with the base coating. Has a flange-like portion projecting radially from the inverted truncated pyramid-like portion.

Japanese Patent Laid-Open No. 10-37925 Japanese Patent Laying-Open No. 2015-25509

  In the screw disclosed in Patent Documents 1 and 2, since the head has an inverted truncated pyramid shape, the screw head and the bottom surface of the ALC hole formed by cutting after the fastening are the head Since there is a line contact at the ridge line of the inverted truncated pyramid, stress concentrates there, and there is a problem that initial loosening is likely to occur due to the depression of ALC. When the density of ALC is high, the effect is small, but ALC tends to be lighter and the density tends to become smaller in the future. Therefore, the occurrence of the initial slack is expected to become a bigger problem in the future.

  ALC boards are also used on the outer walls of buildings that are expected to have a lifespan of 50 years or more. When mounting ALC boards, initial looseness of 1 mm or less (falling of ALC boards) can also cause large looseness over the long term. There is a risk of inviting.

  Note that the screw of Patent Document 2 also has a flange-like portion protruding in the radial direction from the inverted truncated pyramid-shaped portion at the top of the head as described above, and not only the ridge line of the inverted truncated pyramid portion but also the flange The surface perpendicular to the screw axis on the back of the shape portion is also in contact with the ALC board. Therefore, although the stress concentration at the ridgeline is somewhat relieved, it is still impossible to sufficiently prevent the occurrence of initial loosening due to the depression of the ALC.

  The present invention has been made in view of such a conventional situation, and it is an object of the present invention to provide a self-drilling screw for an ALC board that can suppress the occurrence of initial loosening due to the depression of the ALC.

  Still other objects of the present invention will become apparent from the following description.

A self-drilling screw for an ALC board according to the present invention is:
The shaft,
A male thread portion provided on the outer periphery of the shaft portion;
A head portion provided at the rear end portion of the shaft portion, basically having an inverted truncated cone shape;
It has at least one annular projection that is provided on the side surface of the head portion, extends in a ring shape in the circumferential direction around the axis of the shaft portion, and protrudes in the radial direction. .

  In the self-drilling screw for an ALC board of the present invention, the head basically has an inverted truncated cone shape, that is, a dish shape including a trumpet shape (excluding a square dish type), so the conventional head has an inverted pyramid shape. As in the case of a self-drilling screw for an ALC board having a trapezoidal shape, stress is concentrated on the ridgeline of the head, and the initial slack is not caused by the ALC being depressed.

  Further, if the head has a shape in which the seating surface is a plane perpendicular to the screw axis, such as a pan head, the stress acting on the ALC from the head cannot be dispersed in directions other than the axial direction. However, in the self-drilling screw for an ALC board according to the present invention, since the head basically has an inverted truncated cone shape, the stress acting on the ALC from the head can be dispersed in directions other than the axial direction. This also makes it possible to suppress the occurrence of ALC depression and, in turn, initial slack.

  Further, the provision of the annular protrusion makes it difficult for the ALC powder generated by cutting by the head to be discharged from the upper part of the head to the outside, and the powder that has not been discharged accumulates in the bubble part of the ALC. Since the inverted frustoconical head comes into contact with the ALC board in a state where the bubbles are tightly packed in bubbles, this can also suppress the occurrence of initial loosening due to the depression of the ALC.

  According to the self-drilling screw for an ALC board of the present invention, when the ALC board is attached, it is possible to obtain excellent effects such as suppressing initial loosening that may cause long-term loosening.

It is a front view which shows Example 1 of the self-drilling screw for ALC boards by this invention. It is an enlarged plan view which shows the self-drilling screw for ALC boards of the said Example 1. FIG. It is an expansion perspective view which shows the head of the self-drilling screw for ALC boards of the said Example 1. FIG. It is an enlarged front view which shows the head of the self-drilling screw for ALC boards of the said Example 1. FIG. It is sectional drawing in the VV line | wire of FIG. It is sectional drawing in the VI-VI line of FIG. It is sectional drawing which shows the state which the fastening of the ALC board by the self-drilling screw for ALC boards of the said Example 1 was completed. It is an expanded sectional view which shows Example 2 of the self-drilling screw for ALC boards by this invention.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  1 to 7 show a first embodiment of a self-drilling screw for an ALC board according to the present invention. The self-drilling screw for ALC board 1 includes a shaft portion 2 and one of the rear end sides of the shaft portion 2. The male screw part 3 provided on the outer periphery of the part excluding the part, the head part 4 provided at the rear end part of the shaft part 2, and a square hole for driving the screw provided in the head part 4 It has a recess 5 integrally. In addition, the said recess 5 is good also as other shapes, such as a hexagon hole and a cross hole.

  The head 4 basically has an inverted truncated cone shape, and the apex angle α (see FIG. 5) of the inverted truncated cone formed by the head 4 is 90 degrees. Two annular protrusions 6 are provided on the side surface of the head 4. These annular protrusions 6 extend annularly in the circumferential direction around the axis of the shaft portion 2 (the axis of the self-drilling screw 1), and protrude in the radial direction. These two annular protrusions 6 have different outer diameters and are stepped.

  Four non-annular cutting projections 8 for cutting the ALC board 7 (see FIG. 7) are provided at 90 ° intervals on the side of the head 4 closer to the shaft portion 2 than the annular projection 6. Yes. When viewed in the axial direction, the position of each cutting projection 8 is the same as the phase of the position of the radially outermost portion of the recess 5 (in the present embodiment, the four vertices of the square hole).

  FIG. 7 shows a state in which the fastening of the ALC board 7 by the ALC board self-drilling screw 1 of the present embodiment is completed. In this example, the ALC board 7 is attached to the wooden material member 9 of the building frame (not shown) by the ALC board self-drilling screw 1 (however, the ALC board self-drilling screw of the present invention is The ALC board may be fastened and is not limited to the one used in the fastening structure as shown in FIG. Next, with reference to this FIG. 7, the effect of this self-drilling screw 1 for ALC boards is demonstrated.

  When the ALC board self-drilling screw 1 is screwed into the ALC board 7 using the recess 5, the shaft portion 2 enters the ALC board 7 and further the wood material member 9. At this time, the screw 1 forms a female screw on the ALC board 7 and the wood material member 9 by the male screw part 3 itself.

  Next, when the head 4 reaches the ALC board 7, the head 4, particularly the cutting protrusion 8 of the head 4 cuts the ALC board 7, and forms a hole 10 in the ALC board 7 (that is, performing the ditching). Go). Then, the fastening of the ALC board 7 is completed when the head 4 with a predetermined depth sinks as shown in FIG.

  In this self-drilling screw 1 for ALC board, since the head 4 basically has an inverted truncated cone shape, as in the case of the conventional ALC board self-drilling screw having an inverted truncated pyramid shape. As a result, stress is concentrated on the ridgeline of the head and the ALC is depressed, so that an initial slack of 1 mm or less does not occur.

  In a conventional self-drilling screw for an ALC board having an inverted truncated pyramid shape, the head and the bottom of the inverted frustoconical hole formed in the ALC are formed by making the head such a shape. It has been said that the ALC cutting waste is easily discharged to the outside from the gap between the two, and thereby the effect of good ALC cutting is obtained. However, once a weak cordless screwdriver was used for screw fastening work, this was certainly the case, but now, an impact-type cordless screwdriver with a powerful output has come to be used. In addition, since the density of ALC tends to be small as described above, the necessity of improving the machinability by discharging the cutting waste to the outside has disappeared. Therefore, even if the head 4 is basically shaped like an inverted truncated cone as in the present invention, there is no particular disadvantage in cutting performance. On the other hand, if the density of ALC becomes smaller and smaller in the future, in the conventional self-drilling screw for an ALC board with an inverted truncated pyramid shape, the ALC is more likely to sink due to the stress concentration at the ridgeline of the inverted truncated pyramid. It is considered that initial loosening is more likely to occur.

  Further, when the head 4 is shaped like a pan head or the like so that the seating surface is a plane perpendicular to the screw axis, the stress acting on the ALC from the head 4 cannot be dispersed in directions other than the axial direction. . However, in the self-drilling screw 1 for an ALC board of the present invention, the head 4 basically has an inverted truncated cone shape, so that the stress acting on the ALC from the head 4 is also distributed in directions other than the axial direction. This also makes it possible to suppress the occurrence of ALC depression and, in turn, initial slack.

  Further, the provision of the annular protrusion 6 makes it difficult for the ALC powder produced by cutting by the head 4, particularly the cutting protrusion 8, to be discharged from the upper part of the head 4 to the outside. Since the trapezoidal head 4 comes into contact with the ALC board 7 while the powder is closely packed in the bubbles, this also suppresses the occurrence of initial loosening due to the ALC depression. can do.

  Even if the cutting protrusions 8 are not provided, the head 4 having an inverted truncated cone shape cuts the ALC board 7, and therefore the cutting protrusions 8 are not necessarily provided. However, cutting can be performed more favorably by providing the cutting projections 8.

  Further, since the thickness of the head 4 is the thinnest in the radially outermost portion (in this embodiment, the apex of the square hole) of the bottom of the recess 5, a problem in strength occurs in this portion. There is a fear. In this embodiment, however, the position of the cutting projection 8 is the same as the phase of the position of the radially outermost portion of the recess 5 (in the case of this embodiment, the square vertex). Since the thickness of the screw in the radially outermost portion can be increased, it is possible to prevent a problem in strength.

In this embodiment, the angle α of the inverted truncated cone formed by the head 4 is set to 90 degrees. However, in the present invention, the angle α of the inverted truncated cone is
60 ° ≦ α ≦ 120 ° (1)
It is preferable to select within the range. When α is larger than this range, the effect of dispersing the stress acting on the ALC from the head 4 also in directions other than the axial direction is reduced. On the other hand, when α is smaller than the above range, the height of the head 4 may be excessive.

  FIG. 8 shows a second embodiment of the self-drilling screw for an ALC board according to the present invention. In the present embodiment, only one annular protrusion 6 is provided on the side of the head 4 around the top of the head 4. Other configurations are the same as those in the first embodiment.

  Also in the present embodiment, the same operational effects as those of the first embodiment can be obtained. However, when only one annular protrusion 6 is provided as in this embodiment, the total area of the annular protrusion 6 viewed in the axial direction of the screw 1 can be increased without causing a problem in strength. However, if two or more annular projections 6 having different outer diameters are provided in a stepped manner as in the case of the first embodiment, the annular shape seen in the axial direction of the screw 1 without causing a problem in strength. The total area of the protrusions 6 can be increased, and the outflow of the ALC powder to the outside can be more effectively prevented.

  In Examples 1 and 2, the contour of the tapered seat surface portion of the head 4 is linear when viewed from the side, but the trumpet shape (the contour of the tapered seat surface portion when viewed from the side is an arc shape). Shape).

  As described above, the self-drilling screw for ALC board according to the present invention is useful as a screw used for fastening the ALC board.

DESCRIPTION OF SYMBOLS 1 Self-drilling screw for ALC board 7 2 Shaft part 3 Male screw part 4 Head 5 Recess 6 Annular projection 7 ALC board 8 Cutting projection 9 Wood material member 10 Hole formed in ALC board by self-drilling screw α Reverse made by the head Vertical angle of the truncated cone

Claims (5)

The shaft,
A male thread portion provided on the outer periphery of the shaft portion;
A head portion provided at the rear end portion of the shaft portion, basically having an inverted truncated cone shape;
For an ALC board having at least one annular protrusion provided on a side surface of the head, extending annularly in a circumferential direction around the axis of the shaft and projecting in a radial direction Self-drilling screw.   2. The self-drilling screw for an ALC board according to claim 1, further comprising a cutting projection provided on a side closer to the shaft portion than the annular projection on the side surface of the head to cut the ALC board.   The head further includes a recess for driving the self-drilling screw, and when viewed in the axial direction, the position of the cutting projection is the phase of the position of the radially outermost portion of the recess. The self-drilling screw for an ALC board according to claim 2, wherein the self-drilling screw is the same.   4. The self-drilling screw for an ALC board according to claim 1, wherein 60 ° ≦ α ≦ 120 degrees, where α is a vertex angle of the inverted truncated cone formed by the head. 5. The self-drilling screw for an ALC board according to any one of claims 1 to 4, wherein two or more annular projections having different outer diameters are formed in a stepped manner.

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