JPH0554802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an apparatus for undercutting the inner depth of a prepared hole for planting an expansion anchor in a concrete wall surface.

BACKGROUND TECHNOLOGY When planting an expansion anchor in a prepared hole in a concrete wall, in order to facilitate expansion of the anchor and obtain high pull-out strength (holding force), the inside of the prepared hole should be It is known to undercut the back into a truncated conical shape (see, for example, Japanese Patent Laid-Open No. 1-150008).

Problems to be Solved by the Invention However, unless such an undercut is provided at a predetermined position deep inside the pilot hole, the intended purpose cannot be fully achieved.
All of the cutting equipment used to construct this undercut was incomplete and had the problem of low work efficiency.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a pilot hole undercut device for an expansion anchor that can form such an undercut accurately, extremely easily, and efficiently.

Means for Solving the Problems In order to achieve the above object, the prepared hole undercut device of the present invention comprises: a cylindrical body; a radially cylindrical bit connected to the tip of the cylindrical body; A stopper is attached to the outer periphery of the cylindrical body so as to be rotatable and displaceable in the axial direction, and the stopper is fitted into the through hole of the cylindrical body in a slidable but non-rotatable state, and is press-fitted into the tapered hole of the cylindrical bit. and a push-in rod, the cylindrical bit being inserted into a pilot hole provided in the mounting surface, and the push-in rod rotating with the stopper in contact with the mounting surface and supporting the cylindrical body. The cylindrical bit is expanded by being press-fitted into the tapered hole.

The cylindrical bit has a plurality of expansion legs formed by providing a plurality of grooves extending in the axial direction from the end surface, and a blade such as a diamond tip is fixed to the outer surface of the expansion legs.

The stopper is rotatably attached to a support body displaceably displaceable in the axial direction of the cylindrical body via a bearing, and is attached to the opening of the prepared hole. Preferably, it has a fitting cylindrical guide.

Further, the pushing rod is biased rearward by a spring means interposed between the pushing rod and the cylindrical body, and has a rear end connected to a shank protruding from the cylindrical body, and is pushed into the shank. It is effective to employ a configuration that includes a stopper for confirming the position and a connecting portion for the electric rotary tool.

Effect With the above configuration, when the cylindrical bit is inserted into the pilot hole provided on the mounting surface of the concrete wall, the stopper comes into contact with the mounting surface, the stopper limits the insertion length of the cylindrical bit, and the tip The blade body is positioned at a predetermined position deep inside the prepared hole, and the cylindrical body is supported on the mounting surface via the stopper.

Next, when the rear end of the pushing rod is connected to an electric rotating tool and rotated, the tip end is press-fitted into the tapered hole of the cylindrical bit, thereby expanding the expansion leg in the radial direction and expanding the cylindrical bit. A shaped bit and a cylindrical body are rotated together with the push rod. Due to this expansion action and rotational movement, the blade crushes and widens the wall surface of the prepared hole, thereby cutting a truncated conical undercut portion.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

Fig. 1 shows a prepared hole undercut device according to the present invention, in which 1 is a cylindrical body, 2 is a cylindrical bit, and three grooves 3 extending in the axial direction from the tip surface are provided, and three expansion grooves are provided. A leg 4 is formed, and a blade body 5 is formed by welding a diamond chip to the outer surface of the extended leg 4. The cylindrical bit 2 is disposed coaxially at the tip of the cylindrical body 1 and connected to a connecting nut 6.
They are removably connected and can be replaced. The tip of the hole 2a communicating with the through hole 1a of the cylindrical body 1 is formed into a tapered hole 2a with a tapered end.

7 is a stopper that limits the insertion length of the cylindrical bit 2 into the pilot hole; 8 is a support that holds the stopper 7; it is slidably fitted on the outside of the cylindrical body 1, is movable in the axial direction; It can be fixed to the cylindrical body 1 at any position using a set screw 9. The stopper 7 is rotatably assembled to the support 8 via a bearing 10, and is rotatably attached around the axis of the cylindrical body 1. Further, a cylindrical guide 11 that fits into the opening of the prepared hole is connected to the stopper 7.

Reference numeral 12 denotes a push-in rod, which is slidably inserted into the through hole 1a from the rear end of the cylindrical body 1, and the tip portion 12
a is inserted through the hole 2a of the cylindrical bit 2 to form the tapered hole 2.
It is designed to be press-fitted into b. A shank 13 protruding from the cylindrical body 1 is connected to the rear end of the pushing rod 12, and the shank 13 is provided with a stopper 14 for confirming the pushing position and a connecting portion 15 for the electric rotary tool 20. There is. Further, a pin 16 that penetrates in the diametrical direction is fixedly protruded near the connection point between the shank 13 and the push-in rod 12. The protrusions at both ends of the pin 16 are slidably engaged with engagement grooves 17 extending in the axial direction from the rear end surface of the cylindrical body 1, while a presser nut 18 is screwed into the rear end of the cylindrical body 1. The sliding range of the push rod 12 relative to the cylindrical body 1 is limited by the engagement grooves 17, 17, and the push rod 14 cannot rotate relative to the cylindrical body 1. The rotational force generated by the cylindrical body 1 is transmitted to the cylindrical body 1 via the pin 16.

On the other hand, a coil spring 19 is fitted into a large diameter hole 1b formed at the rear of the through hole 1a of the cylindrical body 1, and the push rod 12 is urged toward the rear of the cylindrical body 1 by the coil spring 19. ing.

4 to 7 show the construction sequence of the expansion anchor using the undercut device configured as described above.

First, the insertion length K of the cylindrical bit 2 into the pilot hole 26 previously formed in the concrete wall 25 is determined by adjusting the mounting position of the stopper 7 with respect to the cylindrical body 1.
is set equal to the implantation length L of the expansion anchor 30 (see FIG. 6) to be implanted in the prepared hole 26. When the cylindrical bit 2 is inserted into the prepared hole 26, the insertion length is limited by the stopper 7 that comes into contact with the mounting surface 25a, and the blade 5 at the tip is placed at a predetermined location deep inside the prepared hole 26 where undercutting is to be made. While being positioned, the cylindrical main body 1 is supported by the mounting surface 25a via the stopper 7. At the same time, the cylindrical guide 11 is fitted into the opening of the pilot hole 26 to prevent center runout of the cylindrical body 1.

Next, the connecting portion 15 of the shank 13 is interlocked and connected to the electric rotary tool 20, and when the push rod 12 is rotated by the electric rotary tool 20, it is connected to the cylindrical body 1 and its tip via the pin 16. The cylindrical bit 2 also rotates together.

Push rod 1 while maintaining this rotational state.
2 is pushed against the coil spring 19 and its tip is press-fitted into the tapered hole 2b of the cylindrical bit 2, each of the expansion legs 4 is expanded in the radial direction, and due to the interaction between this expansion action and the rotational movement. Then, the blade 5 crushes and widens the wall surface 27 of the prepared hole 26. When the push rod 12 is pushed in to a position where the position confirmation stopper 14 abuts the holding nut 18, a predetermined truncated conical undercut portion 28 is cut as shown in FIG. At this time, either visually confirm the position of the position confirmation stopper 14 or if the stopper 14
You can easily know when the undercut work has been completed by audibly confirming the metallic sound that occurs when the undercut is in contact with the undercut.

When the undercut portion 28 is formed in this way, the application of rotational force to the shank 13 is stopped, and the push rod 12 and the shank 13 are pulled back to their original positions shown in FIG. 4 by the coil spring 19. , pull out the cylindrical bit 2 from the pilot hole 26.

Next, as shown in FIG. 6, the expansion anchor 30 is inserted into the pilot hole 26, and the driving pin 32 is pressurized to press fit into the anchor body 31. As shown in FIG. The open leg portions 33 are expanded in the radial direction and engage with the undercut portions 28. The engagement of the open leg portion 33 with the undercut portion 28 ensures that the anchor body 31 is retained in the wall surface 27 of the pilot hole 26, thereby providing high pull-out strength (holding force). Moreover, due to the presence of the undercut portion 28, the expansion resistance of the open leg portion 33 is reduced, so the driving pin 3
The open leg portions 33 can be easily expanded with a light pressure applied to the openings 2.

In the above embodiment, the pin-driving type expansion anchor 30 has been described, but it goes without saying that the present invention can also be applied to other types of expansion anchors.

Effects of the Invention As explained above, according to the pilot hole undercutting device of the present invention, the undercut portion can be precisely, extremely easily and efficiently machined at a predetermined position deep inside the pilot hole drilled in concrete. be able to. Furthermore, the completion of the cutting work can be visually or aurally confirmed, which is convenient for the work.

Furthermore, since the device of the present invention can be installed simply by applying rotational force to the shank using an electric rotating tool,
Compared to devices such as electric hammer drills that must apply axial striking force and rotational force, undercutting can be done extremely quietly and efficiently.
This is particularly advantageous when installing on existing buildings.

[Brief explanation of the drawing]

FIG. 1 is a partially vertical front view of a prepared hole undercut device according to the present invention, FIG. 2 is an end view of a cylindrical bit, FIG. 3 is an enlarged view taken along line 3-3 in FIG. 1, and FIG. 4 to 7 are construction explanatory drawings showing examples of the same use. 1... Cylindrical body, 2... Cylindrical bit, 1a...
Through hole, 2b...Tapered hole, 4...Expansion leg, 5...
...Blade body, 6...Connection nut, 7...Stopper, 8
... Support body, 10 ... Bearing, 11 ... Cylindrical guide, 12 ... Push rod, 13 ... Shank,
14... Stopper for checking the pushing position, 15... Connecting portion, 19... Coil spring.

Claims (1)

[Claims] 1. A cylindrical body 1; a radially expandable cylindrical bit 2 connected to the tip of the cylindrical body 1; a stopper 7 displaceably attached; a push rod 12 that is slidably but non-rotatably fitted into the through hole 1a of the cylindrical body 1 and press-fitted into the tapered hole 2b of the cylindrical bit 2; The cylindrical bit 2 is inserted into a prepared hole provided on the mounting surface, and the push rod 12 is rotated while the stopper 7 is in contact with the mounting surface and supports the cylindrical body 1. A prepared hole undercut device for an expansion anchor, characterized in that the cylindrical bit 2 is expanded by being press-fitted into the tapered hole 2b. 2 The cylindrical bit 2 has a plurality of expansion legs 4 formed by providing a plurality of grooves 3 extending in the axial direction from the end surface, and a blade 5 such as a diamond chip is fixed to the outer surface of the expansion legs 4. A pilot hole undercut device for an expansion anchor according to claim 1, characterized in that: 3 The stopper 7 is rotatably attached to the support 8 which is displaceably displaceable in the axial direction to the cylindrical body 1 via a bearing 10, and is attached to the cylindrical body 1 so as to be rotatable around the axis of the cylindrical body 1. The device for undercutting a prepared hole of an expansion anchor according to claim 1, further comprising a cylindrical guide (11) that fits into the opening. 4 The pushing rod 12 is biased rearward by a spring means 19 interposed between the pushing rod 12 and the cylindrical body 1, and a shank 13 protruding from the cylindrical body 1 is connected to the rear end. A pilot hole undercut for an expansion anchor according to any one of claims 1 to 3, wherein the shank 13 is provided with a stopper 14 for confirming the pushing position and a connecting part 15 for an electric rotating tool. Device.