Anchor bolt

An anchor bolt inserted in a mounting hole includes: a shaft including an expanded diameter portion formed on its distal end, the expanded diameter portion having a tapered outer peripheral surface; a sleeve, into which the shaft is inserted from the proximal end side of the shaft, such that the sleeve covers an outer peripheral surface of the shaft, the sleeve including an expandable portion, which is configured to bend outwardly along the expanded diameter portion when pushed from an insertion complete state of the shaft; and a fitting piece connecting the shaft and the sleeve. A first recessed groove is formed in a peripheral surface of the sleeve. A ring, which contacts an inner peripheral wall of the mounting hole, is fitted in the first recessed groove.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an anchor bolt to be fixed in a mounting hole formed in a concrete wall or the like.

Description of the Related Art

In order to mount some component, structure, or the like on a concrete wall or the like, the following technique is widely used: fix an anchor bolt in a mounting hole formed in the concrete wall surface; and fit the component, structure, or the like to the anchor bolt. The mounting hole includes a thin hole portion and an expanded diameter hole portion. The thin hole portion is open at the wall surface, and the expanded diameter hole portion is formed at the back of the thin hole portion. The anchor bolt has an elongated shape, and includes a shaft. The shaft includes an expanded diameter portion formed on its distal end and a bolt formed on its proximal end. The outer peripheral surface of the expanded diameter portion is tapered such that its shape corresponds to the shape of the expanded diameter hole portion (see Japanese Laid-Open Utility Model Application Publication No. H05-017214). A sleeve is fitted to the outside of the shaft in a frictionally slidable manner. The distal end portion of the sleeve is configured to bend outwardly along the expanded diameter portion of the shaft. The diameter of the thin hole portion is substantially the same as the diameter of the expanded diameter portion of the anchor bolt and the external diameter of the sleeve.

In order to fix the anchor bolt in the mounting hole, the expanded diameter portion is inserted into the hole with the sleeve pulled such that the sleeve is away from the expanded diameter portion. When the expanded diameter portion has reached the expanded diameter hole portion, the sleeve is driven into the concrete wall or the like. The distal end portion of the sleeve moves into the expanded diameter hole portion while bending outwardly along the expanded diameter portion, thereby filling the gap between the expanded diameter portion and the expanded diameter hole portion. As a result, the anchor bolt is fixed in the mounting hole. Some component, structure, or the like is fitted through the bolt of the anchor bolt, and then a nut is fitted to the bolt and rotated thereon. In this manner, the component, structure, or the like can be mounted on the concrete wall or the like.

The outer peripheral surface of the sleeve fitted to the shaft of the anchor bolt is in contact with the inner peripheral surface of the mounting hole. The shaft and the sleeve are frictionally in contact with each other, and the sleeve is fixed to the inner peripheral surface of the mounting hole. Accordingly, when the nut fitted to the bolt of the shaft is rotated, the shaft and the sleeve do not rotate, which allows the nut to be screwed on the bolt smoothly.

However, the friction force between the outer peripheral surface of the sleeve and the inner peripheral surface of the mounting hole varies due to, for example, variation in the internal diameter of the inner peripheral surface of the mounting hole. Therefore, there is a case where when the nut is fitted to the bolt and rotated thereon, the sleeve in contact with the shaft rotates, i.e., the shaft and the sleeve rotate together inside the mounting hole when the nut is rotated, and as a result, the nut cannot be tightened sufficiently. In this case, the nut is rotated while preventing the rotation of the shaft by holding the distal end of the bolt with a wrench. In this case, however, it is necessary to rotate the nut with one hand, and hold the wrench with the other hand, which is troublesome work.

In view of the above, an object of the present invention is to provide an anchor bolt capable of preventing the shaft and the sleeve from rotating together with the nut when the nut is fitted to the bolt and rotated thereon.

SUMMARY OF THE INVENTION

The present invention is an anchor bolt to be inserted in a mounting hole formed in a wall surface. The anchor bolt includes: a shaft elongated and extending along its axis, the shaft including an expanded diameter portion formed on its distal end and a bolt formed on its proximal end, the expanded diameter portion having a tapered outer peripheral surface that expands outwardly when seen in an insertion direction into the mounting hole; and a hollow sleeve that covers and is in contact with an outer peripheral surface of the shaft, the sleeve including an expandable portion formed at its distal end, the expandable portion being configured to bend outwardly to be in an expanded state. A state where the sleeve covers the shaft such that the expandable portion is in an unexpanded state is a first state of the shaft and the sleeve. When the sleeve is further pushed into the mounting hole in the insertion direction from a state where the shaft and the sleeve in the first state are inserted in the mounting hole such that the distal end of the shaft is in contact with a bottom of the mounting hole, the expandable portion bends outwardly along the expanded diameter portion to be in the expanded state. A first recessed groove is formed in an outer peripheral surface of the sleeve. A ring that comes into contact with an inner peripheral wall of the mounting hole is fitted in the first recessed groove.

A through-hole that allows the first recessed groove and a hollow portion of the sleeve to be in communication with each other is formed in the sleeve. A second recessed groove is formed in the outer peripheral surface of the shaft at a position that corresponds to a position of the through-hole in the first state. A fitting piece is formed on the ring, the fitting piece extending such that the fitting piece passes through the through-hole to reach the second recessed groove in the first state. The fitting piece serves as a connector that connects the shaft and the sleeve in the first state.

Since the ring fitted in the first recessed groove comes into contact with the inner peripheral wall of the mounting hole, by inserting the sleeve into the mounting hole in a state where the shaft is inserted in the sleeve, rotation of the sleeve is prevented by the friction force exerted between the ring and the inner peripheral wall. Even if the sleeve is further pushed in the insertion direction from the state where the distal end of the shaft is in contact with the bottom of the mounting hole, the shaft is still fixed to the sleeve in the rotation direction since the shaft and the sleeve are frictionally in contact with each other.

That is, the ring prevents the sleeve from rotating relative to the mounting hole, and the friction prevents the shaft and the sleeve from rotating relative to each other. This makes it possible to prevent the shaft and the sleeve from rotating together with a nut when the nut is fitted to the shaft and rotated thereon.

In the state where the sleeve covers the shaft, the sleeve and the shaft are connected together by the fitting piece of the ring made of an elastic material. In this connected state, the sleeve is further pushed in the insertion direction, and thereby the ring fitted in the first recessed groove is also pushed in together with the sleeve. Part of the fitting piece is removed from the second recessed groove and moves onto the outer peripheral surface of the shaft. The fitting piece that has moved onto the outer peripheral surface of the shaft is partly sandwiched and deformed between the outer peripheral surface of the sleeve and the inner peripheral wall of the mounting hole. Here, the ring is sandwiched and held between the inner peripheral wall of the mounting hole and the outer peripheral surface of the shaft, i.e., in a tension rod-like state. As a result, rotation of the sleeve relative to the mounting hole and rotation of the shaft are prevented. This makes it possible to prevent the shaft and the sleeve from rotating together with a nut when the nut is fitted to the shaft and rotated thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an anchor bolt according to one embodiment of the present invention is described with reference to the drawings. In the drawings, the same or corresponding elements are denoted by the same reference signs, and repeating the same descriptions is avoided below.

FIG. 1is a partially cutaway sectional view of an anchor bolt1according to the present embodiment. Similar to the anchor bolt described above in Description of the Related Art, the anchor bolt1is to be fixed in a mounting hole drilled in a concrete wall surface. The anchor bolt1includes a shaft2and a hollow sleeve3. The shaft2is elongated and extends along its axis L. The shaft2includes an expanded diameter portion20formed on its distal end and a bolt21formed on its proximal end. The shaft2is inserted into the hollow sleeve3from the proximal end side, i.e., the bolt21side, of the shaft2, such that the hollow sleeve3covers and is in contact with the outer peripheral surface of the shaft2. The hollow sleeve3includes expandable portions31provided at its distal end. The expandable portions31are configured to bend outwardly along the expanded diameter portion20, i.e., configured to be in an expanded state.

The shaft2and the sleeve3are both made of metal. The internal diameter of a hollow portion37of the sleeve3is substantially equal to the diameter of the shaft2. The expanded diameter portion20has a tapered outer peripheral surface that expands outwardly when seen in an insertion direction into the mounting hole. The maximum diameter of the expanded diameter portion20is substantially equal to the external diameter of the sleeve3.

The expandable portions31are provided on the distal end of a sleeve body30of the sleeve3via a thin-wall connecting portion32, such that the expandable portions31are arranged in a circumferential direction. Adjoining expandable portions31are spaced apart from each other by a slit33, which extends along the axis L.

A recess34is formed in the outer peripheral surface of the sleeve3. By hitting the bottom of the recess34to the inside in a state where the shaft2is inserted in the sleeve3, plastic deformation of the bottom of the recess34occurs such that it bites into the peripheral surface of the shaft2(seeFIG. 4). As a result, the sleeve3and the shaft2are connected together, which allows them to rotate integrally about the axis L. That is, the bottom of the recess34serves as the “connector” of the present invention. When the sleeve3and the shaft2are connected together in this manner, the distal ends of the expandable portions31are positioned at the proximal end of the expanded diameter portion20, and the expandable portions31are not expanded. This state is hereinafter called a “first state”.

A first recessed groove35away from the recess34is formed in the peripheral surface of the sleeve3. A metal ring4, which comes into contact with the inner peripheral wall of the mounting hole, is fitted in the first recessed groove35.

FIG. 2is a sectional view of a mounting hole8drilled in a concrete wall surface85. The mounting hole8includes: a thin hole portion80, which is open at the wall surface85; and an expanded diameter hole portion81formed at the back of the thin hole portion80. The diameter D of the thin hole portion80is slightly greater than the maximum diameter of the expanded diameter portion20and the external diameter of the sleeve3. Accordingly, when the sleeve3and the shaft2are connected together, the expanded diameter portion20and the sleeve3can be inserted into the thin hole portion80.

The diameter D1of the ring4is slightly greater than the diameter D of the thin hole portion80. The shape of the expanded diameter hole portion81corresponds to the shape of the expanded diameter portion20of the shaft2. The maximum diameter D2of the expanded diameter hole portion81is substantially equal to a size that is obtained by adding the thickness of the expandable portion31to both sides of the maximum-diameter part of the expanded diameter portion20. The shape of the mounting hole8is the same as that of a conventional mounting hole, and the method of forming the mounting hole8is well known. Therefore, descriptions of the shape of the mounting hole8and the mounting hole forming method are omitted herein.

FIG. 3is an enlarged sectional view of the ring4and the first recessed groove35. A gap S is formed between the inner periphery of the ring4and the bottom of the first recessed groove35, and the ring4is elastically deformable inwardly by the gap S.

Mounting Anchor Bolt in Mounting Hole

The steps of assembling the anchor bolt1and mounting the anchor bolt1in the mounting hole8are as follows. First, the shaft2is inserted into the sleeve3until the distal ends of the expandable portions31are positioned at the proximal end of the expanded diameter portion20(i.e., until the first state is achieved). Then, the bottom of the recess34is hit to the inside, such that it bites into the peripheral surface of the shaft2, and thereby the sleeve3and the shaft2are connected together. In this manner, the anchor bolt1is completed as shown inFIG. 4.

Next, the anchor bolt1is inserted in an insertion direction F into the mounting hole8, which is indicated by one-dot chain lines inFIG. 4. Since the diameter D1of the ring4is slightly greater than the diameter D of the thin hole portion80, the ring4is elastically deformed inwardly by the gap S at a maximum. The anchor bolt1is inserted against the friction exerted between the ring4and the inner peripheral wall of the thin hole portion80. When the distal end face of the expanded diameter portion20comes into contact with the inner back surface of the expanded diameter hole portion81, the shaft2cannot be inserted any more further, and thus the shaft2is in an insertion complete state.

Next, as shown inFIG. 5, an end face3aof the sleeve3is hit by a hammer or the like (not shown) from the outside of the wall surface85, and thereby only the sleeve3is pushed into the expanded diameter hole portion81in the insertion direction F. That is, the sleeve3is pushed into the expanded diameter hole portion81in a manner to disconnect the bottom of the recess34and the peripheral surface of the shaft2from each other. However, even after the bottom of the recess34and the peripheral surface of the shaft2are disconnected from each other, the bottom of the recess34and the peripheral surface of the shaft2are frictionally in contact with each other. Therefore, the shaft2and the sleeve3are still fixed in the rotation direction about the axis L.

The expandable portions31expand by bending outwardly along the outer peripheral surface of the expanded diameter portion20while the thin-wall connecting portion32serves as a supporting point for the expandable portions31. This state is hereinafter called a “second state”. As a result, the gap between the expanded diameter hole portion81and the expanded diameter portion20is filled by the expandable portions31. Owing to the second state, the shaft2is prevented from coming out of the mounting hole8, i.e., the anchor bolt1is prevented from coming out of the mounting hole8. In this state, some component, structure, or the like (not shown) is fitted through the bolt21of the shaft2, and then a nut9indicated by a one-dot chain line inFIG. 5is fitted to the bolt21and rotated thereon. In this manner, the component, structure, or the like can be mounted on the concrete wall surface85.

Since the ring4is in contact with the inner peripheral wall of the mounting hole8, the friction force between the ring4and the inner peripheral wall prevents the sleeve3from rotating. The shaft2, which is connected to the sleeve3owing to the friction force between the shaft2and the bottom of the recess34, is also prevented from rotating about the axis L. Consequently, when the nut9is rotated, the shaft2and the sleeve3can be prevented from rotating together with the nut9. Thus, unlike the conventional art, it is not necessary to hold the distal end of the bolt21with a wrench to prevent the rotation of the shaft2. As a result, the work efficiency when tightening the nut9is improved.

The anchor bolt1according to Embodiment 1 is advantageous over the conventional art in terms of preventing the shaft2and the sleeve3from rotating together with the nut9when the nut9is rotated. However, due to variation in the external diameter of the ring4, the friction force between the ring4and the inner peripheral wall of the mounting hole8is not constant. Specifically, if the friction force is great, the anchor bolt1cannot be easily inserted into the mounting hole8, and there is a case where the anchor bolt1cannot be sufficiently inserted into the mounting hole8to bring the distal end face of the expanded diameter portion20into contact with the inner back surface of the expanded diameter hole portion81. On the other hand, if the friction force is small, there is a risk that the anchor bolt1falls off the mounting hole8before the sleeve3is pushed into the expanded diameter hole portion81. Particularly in a case where the concrete wall surface85is a ceiling wall surface, this risk is increased.

Moreover, although the sleeve3and the shaft2are connected together by utilizing the plastic deformation of the bottom of the recess34, the connecting force between the sleeve3and the shaft2is not constant due to variation in the amount of the plastic deformation. If the connecting force is great, there is a risk that, when the sleeve3is pushed into the expanded diameter hole portion81in a manner to disconnect the sleeve3from the shaft2, the sleeve3cannot be easily pushed in. The inventor of the present invention has come up with the idea of eliminating these problems by connecting the shaft2and the sleeve3together by a ring4made of synthetic resin.

FIG. 6is an exploded view of the anchor bolt1according to the present embodiment.FIG. 7shows a cutaway sectional view of the sleeve3ofFIG. 6, the view being taken along a plane including a line C-C ofFIG. 6as seen in the direction of the arrows of the line C-C, and also shows the ring4. The mounting hole8, into which the anchor bolt1is to be inserted, is the same as the one shown inFIG. 2.

Similar to Embodiment 1, the anchor bolt1includes the shaft2and the sleeve3. The shaft2includes the expanded diameter portion20formed on its distal end and the bolt21formed on its proximal end. The shaft2is inserted into the sleeve3from the proximal end side of the shaft2. The sleeve3includes the expandable portions31provided at its distal end. The expandable portions31are configured to bend outwardly along the expanded diameter portion20. As shown inFIG. 7, part of the first recessed groove35formed in the peripheral surface of the sleeve3is continuous with a through-hole36, which reaches the hollow portion of the sleeve3. A second recessed groove22, which coincides with the through-hole36in the first state, is formed in the shaft2.

In a state where the shaft2is inserted in the sleeve3such that the through-hole36coincides with the second recessed groove22, the ring4is fitted into the first recessed groove35from the outside of the sleeve3. In the present embodiment, the ring4includes two arc-shaped half ring bodies40, and both the half ring bodies40are made of synthetic resin. Hooks41are provided on both ends of each of the half ring bodies40. The hooks41of both the half ring bodies40are combined together, and thus the half ring bodies40form the ring4. A plurality of recesses42away from each other are formed in the outer surface of each half ring body40. The reason for this will be described below. The two half ring bodies40are fitted into the first recessed groove35from the opposite sides, such that the half ring bodies40sandwich the sleeve3and the hooks41facing each other are combined together. Since each of the half ring bodies40can be separately fitted into the first recessed groove35, the work efficiency when forming the ring4on the sleeve3is improved.

As shown inFIG. 7, a fitting piece43projects inwardly from each half ring body40at its central portion in the lengthwise direction of the arc. In a state where the half ring bodies40are fitted in the first recessed groove35, the fitting pieces43pass through the through-hole36, and the distal ends of the fitting pieces43are fitted in the second recessed groove22of the shaft2. In this manner, the shaft2and the sleeve3are detachably connected together. That is, the half ring bodies40and the ring4serve as the “connector” of the present invention.

FIG. 8is a partially cutaway sectional view of the anchor bolt1in an assembled state according to the present embodiment.FIG. 9shows a cutaway sectional view of the anchor bolt1ofFIG. 8, the view being taken along a plane including a line A-A ofFIG. 8as seen in the direction of the arrows of the line A-A.

The steps of assembling the anchor bolt1are as follows. First, the shaft2is inserted into the sleeve3until the distal ends of the expandable portions31are positioned at the proximal end of the expanded diameter portion20. As a result, as mentioned above, the through-hole36and the second recessed groove22coincide with each other (seeFIG. 8). In this state, the two half ring bodies40are fitted into the first recessed groove35from the opposite sides with respect to the sleeve3. As shown inFIG. 9, in a state where the half ring bodies40are fitted in the first recessed groove35, the fitting pieces43pass through the through-hole36, and the distal ends of the fitting pieces43are fitted in the second recessed groove22of the shaft2. By locking the hooks41of the half ring bodies40together, the ring4is formed, and the shaft2and the sleeve3are detachably connected together. In this state, the external diameter of the ring4is slightly greater than the diameter D of the thin hole portion80.

Next, the anchor bolt1is inserted into the mounting hole8.FIGS. 10A to 10Dare sectional views showing the steps of inserting the anchor bolt1into the mounting hole8. As shown inFIG. 10A, since the external diameter of the ring4is slightly greater than the diameter D of the thin hole portion80, the anchor bolt1is inserted into the mounting hole8against the friction exerted between the ring4and the inner wall of the thin hole portion80. As shown inFIG. 10B, when the distal end face of the expanded diameter portion20of the shaft2comes into contact with the inner back surface of the expanded diameter hole portion81, the shaft2cannot be inserted any more further, and thus the shaft2is in an insertion complete state.

Similar to Embodiment 1, in this state, as shown inFIG. 10C, the end face3aof the sleeve3is hit by a hammer or the like (not shown) to push the sleeve3into the expanded diameter hole portion81. Accordingly, the ring4fitted in the first recessed groove35is also pushed in together with the sleeve3. As shown inFIG. 11in an enlarged manner, the fitting pieces43are removed from the second recessed groove22and move onto the peripheral surface of the shaft2. Since the fitting pieces43move onto the peripheral surface of the shaft2, i.e., move in a manner to bulge outwardly, the fitting pieces43are partly sandwiched and deformed between the outer peripheral surface of the sleeve3and the inner peripheral wall of the mounting hole8. The fitting pieces43thus deformed serve as bulging portions44. The elastic force of the bulging portions44pushes the sleeve3to the shaft2. That is, the bulging portions44, which are deformed portions of the fitting pieces43fitted in the sleeve3, fill the gap between the outer peripheral surface of the sleeve3and the inner peripheral wall of the mounting hole8and are frictionally in contact with the inner peripheral wall of the mounting hole8. Here, the ring4is sandwiched and held between the inner peripheral wall of the mounting hole8and the peripheral surface of the shaft2, i.e., in a tension rod-like state. As a result, rotation of the sleeve3relative to the mounting hole8and rotation of the shaft2about the axis L are prevented.

As shown inFIG. 10D, by fitting some component or a structure90through the bolt21of the shaft2and fitting the nut9to the bolt21and rotating the nut9thereon, the component or the structure90can be mounted on the concrete wall surface85.

As described above, according to the anchor bolt1of the present embodiment, when the nut9is fitted to the shaft2and rotated thereon, the shaft2and the sleeve3can be prevented from rotating together with the nut9. Therefore, unlike the conventional art, it is not necessary to hold the distal end of the bolt21with a wrench to prevent the rotation of the shaft2. As a result, the work efficiency when tightening the nut9is improved. The applicant mainly assumes that the anchor bolt1is mounted in the mounting hole8formed in a ceiling wall, and the work efficiency is improved when performing the work of fitting the nut9to the bolt21of the anchor bolt1mounted on the ceiling wall and rotating the nut9on the bolt21.

In the above description, the plurality of recesses42away from each other are formed in the outer surface of each of the half ring bodies40. The reason for this is that the anchor bolt1is mainly assumed to be mounted on the concrete wall surface85. As is well known, there are fine irregularities on the inner peripheral surface of the mounting hole8formed in the concrete wall surface85. The recesses42of the half ring bodies40and the irregularities of the inner peripheral surface of the mounting hole8are fitted together. This consequently makes it possible to, as shown inFIG. 10B, prevent the anchor bolt1from falling off the mounting hole8more assuredly in the insertion complete state of the shaft2. In particular, when mounting the anchor bolt1in the mounting hole8formed in a ceiling wall, the anchor bolt1can be advantageously prevented from falling off the mounting hole8.

The present embodiment assumes that the anchor bolt1is mounted on the concrete wall surface85. However, the anchor bolt1of the present embodiment can be mounted not only on the concrete wall surface85, but also on a different wall surface.

In the above description, the first state is a state where the distal ends of the expandable portions31are positioned at the proximal end of the expanded diameter portion20. However, the first state is not thus limited, but may be a different state, so long as the expandable portions31are in an unexpanded state. The first state may be a state where the distal ends of the expandable portions31are located at a position that is slightly shifted from the proximal end of the expanded diameter portion20in a direction reverse to the insertion direction.

Moreover, the ring may be tubular or cylindrical, and may be formed integrally.

Other Matters

The present invention is useful when applied to an anchor bolt that is to be fixed in a mounting hole formed in a concrete wall or the like.

REFERENCE SIGNS LIST