JPH0314242Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention is used to create an underhole with a diameter larger than the diameter of the pilot hole by cutting the hole wall of a pre-drilled hole when embedding anchor bolts etc. in concrete. This invention relates to an undercut drill for drilling a cut, that is, an enlarged diameter hole.

[Prior art]

In order to plant anchor bolts in concrete, a pilot hole of a specified depth is drilled in the concrete, and the hole wall is cut deep into the pilot hole to create an enlarged diameter hole. The pull-out strength of the anchor bolt after installation is significantly increased.

Therefore, an undercut drill for drilling this enlarged diameter hole has been put into practical use.

6a and 6b show a conventional undercut drill, FIG. 6a is a front view of the undercut drill showing one side in cross section, and FIG. 6b is a line bb of FIG. 6a.
FIG.

This undercut drill has a main body 1 having a shank 2 connected to a drive shaft at the upper end, a hollow part 3 with an open lower end, and a wedge center 4 slidably inserted into the hollow part 3. A stop ring 5 fitted onto the upper end of 4 and the main body 1
are connected by a pin 7 inserted into a vertical hole 6 provided in the circumferential wall of the hollow part 3, and a compression spring 9 is interposed between the stop ring 5 and a cover body 8 fixed to the main body 1, and the wedge center 4 is attached downward. A pair of elastic plate pieces 10 are formed at the bottom of the main body 1 by cutting the main body 1, and a cutting blade 11 made of a carbide chip is provided at the lower end of the plate piece 10. An overhanging jaw 1 whose lower surface is inclined downward at the lower end of the wedge center 4
In the normal state, the compression spring 9 is engaged with the guide groove 13 of the
The cutting blade 11 is positioned at the base of the overhanging jaw 12 under the pressure of Alternatively, the stop ring 5 is brought into contact with the opening of the hole to hold the wedge center 4 in a fixed position relative to the prepared hole, and the main body 1 is pushed into the prepared hole against the compression spring 9 while giving rotation to the main body 1. When the pressing operation is performed as shown in FIG. be.

[Problem that the invention attempts to solve]

By the way, as mentioned above, when providing the cutting blade made of carbide chips at the lower end of the elastic plate formed on the main body, the cutting blade is made to protrude from both the inner and outer surfaces of the plate, and the outer protruding portion is Considering the configuration in which the cutting blade cuts the wall of the prepared hole and the inner protrusion serves as the guide portion that engages with the guide groove of the overhanging jaw, the cutting blade rotates with vibrational vertical movement and cuts the wall of the prepared hole. The problem is that the internal guide part of the cutting blade itself that engages with the guide groove receives the impactful cutting resistance when cutting, and the part that comes into contact with the guide groove is likely to crack and break. There is.

This invention has been developed in view of the above points, and aims to provide an undercut drill that eliminates the direct engagement of the cutting blade with the protruding jaw provided at the lower end of the wedge center, thereby extending the useful life of the cutting blade. purpose.

[Means to solve the problem]

The gist of the present invention to achieve the above object is to provide a main body having a shank connected to a drive shaft at the upper end, and a hollow part with an open lower end,
A wedge center is slidably inserted into the hollow part,
The upper end of the wedge center and a stop ring fitted externally on the main body are connected by a pin inserted through a vertically elongated hole provided in the peripheral wall of the hollow part, and a compression spring is interposed between the main body and the wedge center to urge the wedge center downward, In an undercut drill, a cutting blade made of a carbide tip is provided at the lower end of an elastic plate formed at the bottom of the main body, and the cutting blade is moved onto an overhanging jaw provided at the lower end of the wedge center. The plate has an arcuate cross-section, a cutting edge is provided in a protruding manner on the upper surface of the lower end of the plate, and a guide portion is provided on the protruding jaw corresponding to the lower end of the plate, on which the lower end of the plate engages and slides. There is an undercut drill characterized by having a shape.

[Effect]

When inserted into a pre-drilled hole and holding the wedge center in a fixed position relative to the hole, press the main body into the hole against the compression spring while applying rotation. The lower end of the elastic plate formed at the bottom of the main body slides into engagement with the guide part of the protruding jaw at the lower end of the wedge center, moves downward and extends outward, and is provided in a protruding shape on the lower end of the plate. Cut the wall of the pilot hole with a cutting blade to create an enlarged diameter section.

At this time, the cutting blade and the overhanging jaw are not in a direct engagement relationship, and the impact cutting resistance when the cutting blade cuts the prepared hole wall is caused by the plate that engages with the guide part of the overhanging jaw. Since it is received at the lower end, there is a slight cushioning effect that reduces damage to the cutting edge.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In the following description, parts common or equivalent to those in FIG. 6 will be described with the same reference numerals.

Figures 1a, b, and c show a first embodiment of the present invention, where Figure 1a is a front view of the main parts, Figure 1b is a cross-sectional view taken along the line bb--b of Figure 1a, and Figure 1a is a front view of the main part. c is c- in Figure 1a
It is a sectional view taken along the c line.

In this first embodiment, a pair of elastic plate pieces 10 are formed at the lower part of the main body 1 by cutting the main body 1, and the lower ends 14 of both plate pieces are formed into an arcuate cross-section with an appropriate width. In addition, a cutting blade 11 is provided at the center of the lower end of the plate in a protruding manner on the upper surface of the plate, and the lower end 14 of the plate
Corresponding to this, a guide portion 15 on which the lower end portion 14 of the plate piece engages and slides is formed on the overhanging jaw 12 of the wedge center 4 so as to be inclined downward from the base of the overhanging jaw 12 to the maximum overhanging portion. The guide portion 15 includes an arc surface portion 15a on which the inner surface of the lower end portion 14 of the plate piece slides, and a lower end portion 1 of the plate piece.
The cutting resistance caused by the cutting blade 11 is reduced by the guide portion 15b of the protruding jaw 12.
The contact surface of the lower end portion 14 of the plate piece that comes into contact with the lower end portion 14 of the plate is dispersedly received.

Figures 2a, b, and c show a second embodiment of the present invention, with Figure 2a being a front view of the main parts, Figure 2b being a cross-sectional view taken along line bb--b of Figure 2a, and Figure 2a being a front view of the main parts. c is c- in Figure 2a
It is a sectional view taken along the c line.

This second embodiment has three elastic plate pieces 10, whereas the first embodiment has a pair of elastic plate pieces 10, and is similar to the first embodiment from an operational point of view. It is.

Figures 3a, b, and c show a third embodiment of the present invention, with Figure 3a being a front view of the main parts, Figure 3b being a sectional view taken along line bb--3 of Figure 3a, and Figure 3 c is c- in Figure 3a
It is a sectional view taken along the c line.

In this third embodiment, the basic structure in which the lower end portion 14 of the elastic plate piece 10 is engaged with the guide portion 15 of the overhanging jaw 12 is the same as that in the first embodiment, but in this third embodiment, the plate Both side edges 14 of the lower end portion 14 are configured to mesh with the guide portion 15 in the form of a dovetail groove 15c.
When the plate hits a reinforcing bar etc., the lower end 14 of the plate is twisted and lifted up from the guide part 15, and the elastic plate 10
This is to prevent it from breaking.

Figures 4a, b, and c show a fourth embodiment of the present invention, where Figure 4a is a front view of the main part, Figure 4b is a sectional view taken along line bb--b of Figure 4a, and Figure 4a is a front view of the main part. c is c- in Figure 4a
It is a sectional view taken along the c line.

In this fourth embodiment, a piece of elastic plate 1
It has a structure in which a cutting edge 11 is provided for 0, and is similar to the first embodiment from an operational point of view.

Figures 5a and 5b show a fifth embodiment of the present invention, Figure 5a is a front view of the main part, Figure 5b is the b of Figure 5a.
It is a sectional view taken along the -b line.

Like the fourth embodiment, this fifth embodiment also has one piece of elastic plate 10, and in this embodiment,
On the opposite side of the overhanging jaw 12, a planar guide surface 16 is formed in the wedge center 4 in the axial direction.
In terms of operation, this embodiment is similar to the first embodiment.

〔effect〕

In the present invention, the lower end of the elastic plate formed at the bottom of the main body as described above engages and slides with the guide part formed on the protruding jaw of the wedge center, and the impact generated by the cutting blade provided at the lower end of the plate is applied. Since the target cutting resistance is distributed and received on the contact surface of the lower end of the plate that comes into contact with the guide part of the overhanging jaw, it is different from the conventional structure in which the cutting edge and the overhanging jaw are directly engaged. Compared to the conventional drill, it also produces a slight buffering effect, which reduces the chance of breakage of the cutting edge and extends the useful life of the drill, which has extremely large working and economical effects.

[Brief explanation of drawings]

Figures 1a, b, and c show a first embodiment of the present invention, where Figure 1a is a front view of the main parts, Figure 1b is a cross-sectional view taken along the line bb--b of Figure 1a, and Figure 1a is a front view of the main part. c is c- in Figure 1a
A sectional view taken along the line C, and FIGS. 2a, b, and c show a second embodiment of the present invention. FIG. 2a is a front view of the main part, and FIG. 2b
2A is a cross-sectional view taken along the line bb--b of FIG. 2a, FIG. 2c is a sectional view taken along the line c-c of FIG. 2a, and FIGS. Figure 3a is a front view of the main part;
Figure 3b is a sectional view taken along line bb of Figure 3a, Figure 3c
are sectional views taken along line c-c in Figure 3a, Figures 4a, b, and c.
4 shows a fourth embodiment of the present invention, FIG. 4a is a front view of the main part, FIG. 4b is a sectional view taken along the line bb--b of FIG. 4a,
Figure 4c is a sectional view taken along the line CC of Figure 4a, Figures 5a and b show the fifth embodiment of the present invention, Figure 5a is a front view of the main parts, and Figure 5b is a 5a is a sectional view taken along the line b-b, FIGS. 6a and 6b show a conventional undercut drill, FIG. 6a is a front view of the undercut drill with a part removed, and FIG. 6b is a Figure 6 a b-
It is a sectional view taken along the b line. 1...Main body, 2...Shank, 3...Hollow part,
4... Wedge center, 5... Stop spring,
6... Vertical hole, 7... Pin, 8... Cover body, 9
... Compression spring, 10 ... Elastic plate piece, 11 ... Cutting blade, 12 ... Overhanging jaw, 13 ... Guide groove, 14 ...
Lower end of plate piece, 15...guiding section, 16... guiding surface.

Claims (1)

[Scope of utility model registration request] A main body having a shank connected to a drive shaft at the upper end is provided with a hollow part with an open lower end, a wedge center is slidably inserted into the hollow part, and a stop ring is fitted onto the upper end of the wedge center and the main body.
They are connected by a pin inserted through a vertical hole formed in the circumferential wall of the hollow part, and a compression spring is inserted between the main body and the wedge center to force the wedge center downward. An undercut drill is provided with a cutting blade made of a hard tip and is configured to move the cutting blade onto an overhanging jaw provided at the lower end of the wedge center, and the lower end of the plate piece is formed to have an arcuate cross section, and the lower end of the plate piece is 1. An undercut drill, characterized in that a cutting edge is provided in a protruding manner on the upper surface of the undercut drill, and a guide part is formed in the protruding jaw corresponding to the lower end of the plate, with which the lower end of the plate engages and slides.