JP2006266476A - Tapping bolt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tapping bolt screwable into a concrete product. <P>SOLUTION: A male screw 4 is formed around an outer peripheral of a shaft part 1 with a tapered part at its tip end and angle of screw thread 4a of the male screw 4 is gradually increased from the tip end of the shaft part to a screw thread 4a at a rear end so that a female screw is formed by the screw thread 4a at a following side even if an incomplete female screw is formed as the screw thread 4a at a precedent side is worn at the time of screwing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tapping bolt screwed into a concrete product such as ALC.

  Conventionally, bolting appropriate articles (attachment objects) to concrete products made of ALC (cellular concrete products), mortar, asphalt, bricks, reinforced concrete, etc. There is still no bolt that can be screwed in directly.

  Therefore, when bolting an object to be attached, conventionally, an anchor composed of a cylindrical body having an axial slit and a tapered nut incorporated in the cylindrical body was used, and the anchor was formed on a concrete product. By inserting the nut into the lower hole and tightening the bolt screwed into the nut, the nut is moved in the axial direction to expand the diameter of the cylinder, and the outer periphery of the cylinder is press-fitted to the inner periphery of the lower hole to It has been common to fix the nut and tighten the bolt to the nut.

  By the way, there is a problem that fixing of an attachment object using an anchor is expensive, and there is a possibility that the anchor may come out of the pilot hole when the bolt is strongly tightened, and the attachment object cannot be firmly fixed. .

  Here, since a generally known bolt has a configuration in which a V-shaped valley bottom is formed between adjacent threads of a male screw, such a bolt is screwed into a prepared hole formed in a concrete product. Then, an extremely large frictional resistance acts on the screw thread, and the frictional resistance becomes a rotational resistance at the time of tightening, so that a very large rotational torque is required for tightening, sometimes causing seizure and locking. .

  In addition, a tapping screw that can be screwed in while forming a female screw on the inner periphery of the pilot hole is conventionally known, but the object into which the tapping screw is screwed is a product made of metal or synthetic resin. When it is screwed into concrete products, the male screw is worn away and a complete female screw cannot be formed, and the drawing strength is extremely low, so that the object to be attached cannot be stably attached.

  It is an object of the present invention to provide a tapping bolt for a concrete product that can be directly screwed into the concrete product.

  In order to solve the above-described problems, in the present invention, a male screw having a triangular thread shape is provided on the outer periphery of a shaft portion having a tapered portion at the tip, with a space between adjacent screw threads. A configuration is adopted in which the angle of the crest is gradually increased from the thread located at the front end of the shaft portion to the thread located at the rear end.

  Here, the thread of the male screw may have a larger angle for each thread from the front end to the rear end of the shaft. Alternatively, the thread of the male thread may be grouped into a plurality of threads and The angle of the thread may be the same, and the angle of the thread may be gradually increased toward the nth group from the first group located at the tip of the shaft to the rear end of the shaft.

  When the tapping bolt having the above structure is screwed, if the concrete product is made of ALC, it may be screwed directly into the ALC, or a pilot hole may be formed in the ALC and screwed into the pilot hole. Good.

  For concrete products with higher hardness than ALC, a pilot hole is formed in the concrete product and screwed.

  Here, if a slit is formed on the outer periphery of the shaft portion so as to extend in the axial direction from the tip thereof and divide the thread in the circumferential direction, chips generated when the male screw is screwed can be accommodated in the slit. Therefore, the rotational resistance can be reduced, and the shaft portion is reduced in diameter when the rotational resistance is increased, so that smooth screwing can be achieved.

  The width and depth of the slit are appropriately determined according to the outer diameter of the shaft portion and the hardness of the concrete product, and the depth is opened at a position facing the outer periphery of the shaft portion, and a forked piece at the tip portion of the shaft portion. May be formed. The slit may be a straight line parallel to the axis or may be a spiral.

  In the tapping bolt according to the present invention, when a plurality of grooves that divide at least a plurality of threads in the circumferential direction from the thread at the end of the shaft portion are formed in the male thread in the circumferential direction, the plurality of divided threads are screwed in The edge of the leading end surface in the rotation direction of the metal acts as a cutting blade, and the chips generated by the cutting of the cutting blade can be accommodated in the groove. And can be screwed in smoothly.

  As described above, the thread angle of the male thread is gradually increased from the front end of the shaft to the rear end, so that when the screw is screwed into the concrete product, the screw thread on the front side of the shaft is in contact with the concrete product. Even if the internal thread cut into the concrete product due to abrasion is incomplete, the subsequent thread penetrates along the internal thread cut by the preceding thread, so the subsequent thread As a result, a complete female screw is cut, and the tapping bolt can be reliably screwed into the concrete product.

  Also, by making the angle of the thread on the trailing side larger than the angle of the thread on the leading side, the thread on the trailing side penetrates while cutting the flank on both sides of the female thread formed by the thread on the leading side. To do. For this reason, the engagement force between the female screw and the succeeding screw thread is strong, and even if the leading screw thread of the male screw wears out and does not engage with the screw, it is sufficient by the plurality of succeeding screw threads. The pulling strength can be obtained, and the object to be attached can be firmly attached.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of a tapping bolt according to the present invention. As shown in the figure, the shaft portion 1 has a tapered portion 2 at the front end, and a screw shaft portion 3 is provided at the rear end portion.

  On the outer periphery of the shaft portion 1, a male screw 4 is formed by rolling from the front end to the rear end, and after the screw formation, heat treatment is performed to increase the hardness. The external thread 4 has a triangular thread 4a, a space is formed between adjacent threads 4a, and the valley bottom 4b is straight.

Here, the thread 4a from the distal end side of the shaft portion 1 and the first thread _{a 1} to the n threads _{a n,} the angle theta ₁ to the first thread _{a 1} through n-th thread _{a n} When theta _n, the angle theta ₁ to theta _n of the threads is gradually increased in accordance extending from the first thread a ₁ to a n threads a _n.

In the embodiment, the angle theta ₁ of the first thread a ₁ as 60 °, toward the first n threads a _n increased by 1 °, and the angle theta _n of the n threads a _n and 90 ° but the angle theta ₁ of the first thread a _1, the angle theta _n of the angular difference and the n threads a _n adjacent threads 4a is not limited to this, and suitably determined depending on the hardness of the concrete products . Further, the pitch P of the thread 4a is constant, and the pitch P is also appropriately determined according to the concrete product.

  The tapping bolt shown in the first embodiment has the above structure. When the concrete product is screwed into a concrete product, if the concrete product is a concrete product with a relatively low hardness such as ALC, the tapping bolt may be screwed directly into the concrete product. Alternatively, a pilot hole having a diameter substantially the same as the valley diameter of the tapping bolt may be formed in the concrete product and screwed into the pilot hole. On the other hand, in the case of a concrete product with high hardness, a pilot hole is formed and screwed. At the time of screwing, two nuts 5 are screwed into the screw shaft portion 3, and the surface pressure of the abutting surface of the nut 5 is increased by relative rotation of the nut 5 to fix the two nuts 5 to the screw shaft portion 3. Then, a wrench is engaged with the nut 5 to apply a rotational torque in the tightening direction to the tapping bolt.

  Now, when the tapping bolt is screwed into the prepared hole formed in the concrete product, the inner periphery of the prepared hole is cut by the male screw 4 to form the female screw. At this time, the thread on the leading side of the tip of the shaft portion 1 is easily worn by contact with the inner periphery of the lower hole, and an incomplete female screw is formed on the inner periphery of the lower hole due to the wear. Since the thread a penetrates along the female thread formed by the preceding thread 4a, a complete female thread is formed by cutting with the succeeding thread 4a. At this time, since the angle of the trailing screw 4a is gradually larger than that of the leading screw thread 4a, the trailing screw thread 4a cuts both side flank of the female screw formed by the leading screw thread 4a. While invading. For this reason, the engagement force between the female screw and the succeeding screw thread 4a is strong, and even if the preceding screw thread 4a is worn and does not engage with the screw, the plural screw threads 4a on the succeeding side do not. Sufficient pulling strength can be obtained, and a firm screwed-in state can be obtained.

  FIG. 2 shows a second embodiment of a tapping bolt according to the present invention. This embodiment is different from the first embodiment in that a flange 6 is provided at the rear end of the shaft portion 1 and the screw shaft portion 3 is provided on the flange 6. For this reason, the same parts as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  When the flange 6 is formed at the rear end of the shaft portion 1 as in the tapping bolt shown in the second embodiment, the tightening amount of the tapping bolt can be limited by the flange 6.

FIG. 3 shows a third embodiment of the tapping bolt according to the present invention. In this embodiment, grouped first group G ₁ through n-th group (not shown) the threads 4a of the external thread 4 formed on the outer periphery of the shaft portion 1 to each of a plurality of threads, a plurality of the same group angle theta ₁ of the thread _4a, theta _{2 ...} theta _n was the same, the threads 4a toward the first group G ₁ to the n groups leading to the rear end portion of the shaft portion 1 which is positioned on the distal end side of the shaft portion 1 The angles θ ₁ , θ ₂ ... Θ _n are gradually increased.

  Since other configurations are the same as those of the first embodiment, the same portions are denoted by the same reference numerals and description thereof is omitted.

  As with the first embodiment, the tapping bolt shown in the third embodiment can be reliably screwed into the concrete product and can have sufficient pulling strength.

  4 and 5 show a fourth embodiment of a tapping bolt according to the present invention. This embodiment is different from the first embodiment in that a slit 7 is provided on the outer periphery of the shaft portion 1 so as to extend from the front end to the rear end and divide the thread 4a in the circumferential direction.

  For this reason, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in the fourth embodiment, when the slit 7 is formed at the tip of the shaft portion 1, chips generated by cutting when the male screw 4 is screwed can be accommodated in the slit 7. Reduction of rotational resistance can be achieved. Moreover, since the diameter of the shaft portion 1 is reduced when the rotational resistance is increased, smooth screwing can be achieved.

  Here, the width and depth of the slit 7 may be appropriately determined according to the outer diameter of the shaft portion 1 and the hardness of the concrete product. As shown in FIG. 5, the depth may reach the center of the shaft 1, or from one outer periphery of the shaft 1 to the other outer periphery of the shaft 1 as shown in FIG. 6. It may penetrate.

  7 and 8 show a fifth embodiment of a tapping bolt according to the present invention. In this embodiment, a plurality of grooves 8 that divide at least a plurality of screw threads 4a in the circumferential direction from a screw thread 4a at the tip of the shaft part of the male screw 4 formed on the outer periphery of the shaft part 1 are formed.

  As described above, when the plurality of grooves 8 are formed, the edge 9 on the leading end surface in the rotation direction when the divided thread 4a ′ divided into a plurality of parts is screwed functions as a cutting blade, and the cutting blade is While entering the concrete while cutting the inner periphery of the hole, the chips generated by the cutting are accommodated in the groove 8, so that the rotational resistance during screwing is small, and the tapping bolt is screwed into the concrete product very smoothly. be able to.

  When the tapping bolt shown in the first to fifth embodiments is screwed into the lower hole formed in the concrete product, a mixed liquid of a molten resin such as epoxy resin and a curing agent is put in the lower hole. When the screwing operation is performed, the mixed liquid serves as a lubricant, so that the tapping bolt can be screwed smoothly.

  Further, since the liquid material enters and solidifies between the male screw 4 and the screw engaging portion of the female screw formed by the male screw 4 or a gap between the lower hole and the tapping bolt, the tapping bolt can be prevented from loosening. In this case, if a resin that expands when solidified is used as the resin, the tapping bolt can be more reliably prevented from loosening.

  In the first embodiment, the screw shaft portion 3 is provided at the rear end of the shaft portion 1, but a head for wrench engagement such as a hexagon head may be formed instead of the screw shaft portion 3, or You may form a square hole in the rear-end surface of the axial part 1. FIG.

  In the first embodiment, the straight shaft portion having the same diameter over the entire length is shown as the shaft portion 1, but it may be a tapered shaft portion having a front end or a rear end as a large diameter end.

The front view of the state which showed 1st Embodiment of the tapping bolt which concerns on this invention, and a part of axial part was abbreviate | omitted The front view which shows 2nd Embodiment of the tapping bolt which concerns on this invention The front view which shows 3rd Embodiment of the tapping bolt which concerns on this invention The front view which shows 4th Embodiment of the tapping bolt which concerns on this invention Sectional view along line VV in FIG. Sectional drawing which shows the other example of a slit Front view showing a fifth embodiment of a tapping bolt according to the present invention. Sectional view along line VIII-VIII in FIG.

Explanation of symbols

1 Shaft 2 Taper 4 Male Thread 4a Thread 7 Slit 8 Groove

Claims (4)

  On the outer periphery of the shaft part with a tapered part at the tip, a male screw with a triangular thread shape is provided with an interval between adjacent screw threads, and the angle of the thread of the male screw is determined from the thread located at the tip of the shaft part. A tapping bolt that gradually increases as it reaches the thread located at the rear end.   The threads of the male thread are grouped into a plurality of threads, the angles of the threads of the same group are the same, and from the first group of threads located at the tip of the shaft to the rear end of the shaft The tapping bolt according to claim 1, wherein the angle of the screw thread is gradually increased toward the nth group of screw threads.   The tapping bolt according to claim 1 or 2, wherein a slit is formed on an outer periphery of the shaft portion so as to extend from the front end to the rear end and divide the screw thread in the circumferential direction.   The tapping bolt according to any one of claims 1 to 3, wherein a plurality of grooves are formed in the male screw to divide at least a plurality of threads into a plurality in the circumferential direction from a thread at the tip of the shaft portion.

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