JPS6144194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pit drilling bit used in reverse circulation construction methods, earth auger construction methods, and the like.

Drilling bits used in this type of construction method include so-called blade bits such as three-wing bits and four-wing bits, and roller bits with roller cutters, and the present invention is directed to blade bits.

As is well known, three-winged and four-winged bits are (1) ones with a flat cutter attached, and (2) conical cutters in which the cutter alone can rotate freely due to the excavation resistance of the earth and sand as the bit rotates. (3) A type with a flat cutter and a conical cutter attached. The bit in (1) is for general soil, and the bit in (2) is for general soil.
The bit in (3) is used for hard ground, and the bit in (3) can be used for excavating from general soil to hard ground.

By the way, it was most common for foundation piles to be embedded in the gravel layer of general soil with an N value of 50 or more, but in recent years, with the increase in the size of buildings, foundation piles have been embedded in the hard ground below the general soil or in the hard ground. It has become necessary to excavate and root deep into the underlying rock layer. Therefore,
When excavating a single foundation pile hole, it is necessary to use the bits (1) to (3) above depending on the hardness of the stratum to be excavated.

However, in the case of most foundation piles, the concrete strength of the pile body is approximately 300 kg/cm ² , so it is necessary to excavate the hole for the pile into a soft rock layer with approximately the same compressive strength as the concrete strength. It was found to be sufficient, and a single bit was used to excavate everything from ordinary soil to soft rock layers. As described above, the following bits have been conventionally used as bits capable of excavating from ordinary soil to soft rock layers.

(a) Bits mentioned in (3) above, that is, bits that are a combination of a conical cutter and a flat cutter.

(b) A bit that combines a flat cutter and a special flat cutter.

Fig. 1 shows an excavation bit that is a combination of the conical cutter and flat cutter described in (a) above, where 1 is an earth removal pipe, 2 is a rotary blade, and 3 and 4 are respectively attached to the lower end of the inclined surface of the rotary blade 2. A fixed flat cutter and a conical cutter. This excavation bit forms an indentation with a conical cutter 4, and then excavates with a conical cutter 4 and a flat cutter 3, and when the excavation layer is of ordinary soil, the depth of penetration of each cutter is Because of the large size, most of the earth and sand was excavated with flat cutter 3.
When the excavated layer becomes a hard ground layer (including a soft rock layer), as shown in FIG. We will continue to excavate depending on the situation.

In this drilling bit, as shown in FIG.
Although the carbide chips 3a and 4a are brazed to each other, the height of the carbide chips 3a and 4a is limited as will be described later, so it has not been possible to increase the depth H of the indentations. That is, if the difference in height between the cutters 3 and 4 is increased so that the depth H of the indentation 6 is increased, the cutter body 4b, which is the base material of the conical cutter 4, will be scraped by earth and sand and worn out early. Put it away. Also,
If an attempt is made to form a deep indentation by increasing the length of the carbide tip 4a of the conical cutter 4, the carbide tip is likely to break due to the large thrusting force during excavation. As described above, in the past, the depth of the indentation 6 made by the conical cutter 4 could not be increased (H=about 2 mm), so there was almost no effect of loosening the soft rock between the indentations 6. In addition, since the indentation 6 is shallow, the digging load on the flat cutter 3 increases, and the flat cutter 3
The cutter body 3b and carbide tip 3a were severely worn. Furthermore, since the indentation is shallow, both the conical and flat stub groups have a surface pressure equivalent to the compressive strength of the soft rock, especially when excavating with stakes on the surface layer of soft rock and when excavating the center of soft rock. That is, a large bit load had to be applied, and a large excavation torque was also required.

FIG. 3 shows the bit in (b) above, that is, an excavation bit in which a flat cutter 3 and a special flat cutter 7 whose tips are formed into a protruding shape are attached to the rotary blade 2. As shown in the figure, grooves are excavated using a special flat cutter 7, and spaces between the grooves are excavated using a flat cutter 3. However, this drilling bit also has the same drawbacks as the bit (a) above, as well as the following drawbacks. That is,
Even if an attempt is made to dig a deep groove by strengthening the special flat cutter 7, the cutter body and the carbide tip of the special flat cutter 7 will wear out due to secondary crushing caused by the cutting debris in the groove. Therefore, the special flat cutter 7
It is not possible to increase the depth of the groove due to the
Similar to the drilling bit shown in the figure, a large bit load and large drilling torque were required.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and is for use in vertical hole excavation, which allows deep trenches to be excavated when excavating soft rock, and which can be excavated with the minimum necessary excavation torque and bit load. The purpose is to provide bits.

To achieve this objective, the pit drilling bit of the present invention includes a rotatable earth removal pipe, a plurality of rotary blades radially attached to the lower part of the earth removal pipe with dihedral angles and rake angles, and a rotating a plurality of cutters attached at different radial positions from the center of rotation of the blade, the cutter consisting of a main cutter and an auxiliary cutter, the main cutter being a cutting cutter, and fixed to the rotary blade. The cutter body is made of a metal cutter, and a carbide tip is fitted into a fitting groove provided in the cutter body and brazed. The cutting edge of the carbide tip is made slightly higher and its width is slightly larger than the width of the cutter body, so that the lower end cutting edge and both side edges of the carbide tip protrude slightly from the cutter body, and the cutting edge of the carbide tip is the cutting edge of the adjacent auxiliary cutter. The upper end of the carbide tip is located at a height approximately equal to at least the lower end of the cutting edge of the auxiliary cutter, and the groove is first excavated with the main cutter, and the portion between the grooves is It is characterized by being configured to be excavated with an auxiliary cutter.

The details of the present invention will be explained below with reference to the drawings.
FIG. 4 is a front view of a four-winged bit which is an embodiment of the present invention, and FIG. 5 is a view taken along the - arrow in FIG. In the figure, 11 is an earth removal pipe, 12 is four rotary blades provided radially on the earth removal pipe 11, and each rotor blade 12
are fixed to the lower part of the earth discharge pipe 11 with angular phases different from each other by 90 degrees, and with a dihedral angle α and a rake angle. A head cutter 13 is fixed to the lower end of the earth removal pipe 11, and has a hole in the center so that a lump of excavated earth and sand can be guided smoothly into the earth removal pipe 11.
14 is a reinforcing plate fixed to the upper part of the rotary blade 12 and the earth removal pipe 11.

A plurality of main cutters 15 and auxiliary cutters 16 are fixed to the lower end of the inclined surface of the rotary blade 12 at appropriate intervals. The main cutter 15 is arranged so that its cutting edge is located below the cutting edge of the auxiliary cutter 16 so that it can excavate a groove in advance of the auxiliary cutter 16. In addition, the auxiliary cutter 16 is connected to the main cutter 1.
It is arranged so that it can excavate between the excavation grooves made by No. 5.

To explain in detail the arrangement relationship between the main cutter 15 and the auxiliary cutter 16, as shown in FIG. Both katsutas are arranged alternately. And the auxiliary cutter 16 is the main cutter 15.
There are two placed between them.

Next, the detailed structure of the main cutter 15 and the auxiliary cutter 16 will be explained with reference to FIGS. 6, 7, and 8. The main cutter 15 is configured as a cutting cutter consisting of a cutter body 15a fixed to the rotary blade 12 and a carbide tip 15b brazed to the cutter body 15a. The cutter body 15a
Essentially, it is sufficient to include one carbide tip 15b, but the illustration shows an example including three carbide tips 15b as a preferred example. Each carbide tip 15b is fitted into a fitting groove formed on the lower surface of the cutter body 15a at appropriate intervals in the direction of movement of the cutter body 15a, and is brazed to the cutter body 15a. The height of the carbide tip 15b fitted into this fitting groove is slightly higher than the depth of the fitting groove of the cutter body 15a, so that its lower end protrudes slightly below the lower end of the cutter main body 15a. It is located below the cutting edge of the auxiliary cutter 16 adjacent to the auxiliary cutter 16, and the upper end of the carbide tip 15b is at least at a height approximately equal to the lower end of the cutting edge of the auxiliary cutter 16. Also, carbide tip 15b
The width between both sides of the tip is formed to be somewhat larger than the width of the cutter body 15a, and both side edges of the tip protrude from both sides of the cutter body 15a. Also,
The side surfaces of the cutter main body 15a and the carbide tip 15b on the side of the rotation center of the rotor blade are formed into an inclined surface 17 with a notch so that the upper part approaches the rotation center side. Furthermore, the position of the cutting edge of each carbide tip 15b is sequentially made to have a different height by ΔH ₁ and ΔH ₂ in the direction of movement of the cutter body 15a.

On the other hand, the auxiliary cutter 16 includes a cutter main body 16a,
The cutter body 16a is configured as a conical cutter with a carbide tip 16b brazed to the tip of the cutter body 16a.

Next, the operation of the drilling bit according to the present invention will be explained.

When a downward pressing force (bit load) is applied to the earth removal pipe 11 while rotating the rotary blade 12, the main cutter 15 precedes the auxiliary cutter 16 and creates a deep groove (groove depth) in the excavation surface, as shown in FIG. H') will be excavated. The groove is excavated by several rotations of the rotary blade 12, and the interpolation cutter 16 is in a state in which it does not excavate the excavated surface. When the excavation surface is soft rock, by digging the deep trench, large cracks are created in the soft rock around the trench, loosening the soft rock between the trenches. When the main cutter 15 excavates a groove having a groove depth H', the auxiliary cutter 16 excavates the loose soft rock between the grooves. The excavated earth and sand are discharged to the ground through the earth discharge pipe 11.

In this case, in the present invention, the main cutter 15
The cutter body 15a is fixed to a rotary blade, and a carbide tip 15b is fitted into a fitting groove provided in the cutter body 15a and brazed. The depth of the fitting groove provided in the main body 15a is made slightly higher and the width thereof is made slightly larger than the width of the cutter main body 15a, so that the cutting edge and both side edges of the lower end of the carbide tip 15b are made to protrude slightly from the cutter main body 15a. Even if the length of the carbide tip 15b is increased, the portion other than the lower cutting edge and both side edges is protected by the cutter body 15a and there is no risk of it breaking, and furthermore, the cutting edge of the carbide tip 15b is adjacent to this. Since it is located below the cutting edge of the auxiliary cutter 16 and the upper end of the carbide tip is located at least at approximately the same height as the lower end of the cutting edge of the auxiliary cutter 16, it is possible to cut deep grooves with the main cutter 15.
Even if H' is excavated, there is no risk that the cutter body 16a of the auxiliary cutter 16 will be scraped by earth and sand.
In this way, as shown in FIG. 6, the deep groove H' can be excavated extremely smoothly and efficiently.

Also, if the excavated layer is of general soil, the main stub 1
5 loosens the grooves around the groove, and then the auxiliary cutter 16 excavates the area between the grooves.

Therefore, with the digging bit according to the present invention, it is possible to dig a trench as deep as, for example, 15 mm. Therefore, the digging load on the auxiliary cutter 16 is reduced, and wear of the auxiliary cutter 16 is reduced, so that the life of the cutter is extended. In addition, since the auxiliary cutter 16 only excavates the loosened part between the deep grooves excavated by the main cutter 15, the digging resistance is reduced, and even when excavating mainly soft rock, the bit load and digging torque are kept to the minimum. It is possible to excavate at

Furthermore, in this embodiment, since the inclined surface 17 is formed by a notch on the side of the rotation center of the rotor blade of the cutter body 15a of the main cutter 15 and the carbide tip 15b, the excavated earth and sand are moved toward the rotation center side during excavation. The soil is pushed out and collected into the opening of the soil discharge pipe 11 using the dihedral angle α of the rotary blades 12. That is,
Good soil removal performance.

9 and 10 show another embodiment of the present invention, which differs from the previous embodiment in that a flat cutter 18 is used as an auxiliary cutter.

To explain in detail, the flat cutter 18 is
As shown in FIG. 1, the cutter body 18a is made up of a cutter body 18a fixed to a rotary blade 12, and a carbide tip 18b brazed to the excavated surface of the cutter body 18a. The flat cutter 18 cuts between the grooves excavated by the main cutter 15.

In this embodiment as well, it is possible to achieve the same functions and effects as the drilling bit shown in FIGS. 4 and 5.

12 and 13 also show other embodiments of the present invention, which differ from FIGS. 4 and 5 in that the auxiliary cutter is composed of a conical cutter 16 and a flat cutter 18. To specifically explain the arrangement relationship of each cutter, as shown in FIG. 14, the conical cutter 16
is arranged to excavate between the grooves excavated by the main cutter 15 before the flat cutter 18, and the flat cutter 18 excavates between the excavated surface excavated by the conical cutter 16 and the groove excavated by the main cutter. arranged to be excavated.

According to this embodiment, between the grooves excavated by the main cutter 15, two types of auxiliary cutters, namely, the conical cutter 1
6 and the flat cutter 18, the excavation resistance of the conical cutter 16 and the flat cutter 18 becomes extremely small, allowing smooth excavation and further reducing wear on both cutters.

In addition, although each of the above-mentioned embodiments has shown an example of a four-winged bit, it goes without saying that the invention can also be applied to a three-winged bit. In addition, if the number of main cutters arranged on a concentric circle at a position with a large radius from the center of rotation is greater than the number of main cutters arranged on a concentric circle inside the main cutters, the life expectancy due to the difference in circumferential speed can be increased. It is possible to eliminate non-uniformity.

As explained above, the pit drilling bit of the present invention is composed of a main cutter and an auxiliary cutter, the main cutter being a cutting type cutter, a cutter body fixed to a rotor blade, and a cutter body fixed to a rotor blade. The cutting edge of the carbide tip is located below the cutting edge of the adjacent auxiliary cutter, and the upper end of the carbide tip is positioned at least above the cutting edge of the auxiliary cutter adjacent to the carbide tip. Since the height is approximately equal to the lower end of the cutting edge of the auxiliary cutter, and the main cutter excavates a groove first, and the auxiliary cutter excavates between the grooves, it is possible to dig deep grooves with the main cutter. This has the effect that excavation can be performed with the minimum necessary excavation torque and bit load.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an example of a conventional pit drilling bit, Fig. 2 is a diagram of the drilling state of the drilling bit shown in Fig. 1, and Fig. 3 is a front view showing another example of the conventional pit drilling bit. It is a diagram. Fig. 4 is a front view of a four-winged bit which is an embodiment of the pit drilling bit of the present invention, Fig. 5 is a view taken along the line V-V in Fig. 4, and Fig. 6 is a diagram of the four-winged bit in the drilling state. , FIG. 7 is a side view of the main cutter according to the present invention, as seen from the - direction of FIG. 6, FIG. 8 is a sectional view of the main cutter of FIG. Fig. 9 is a front view, Fig. 10 is a view taken along the line X-X in Fig. 9, Fig. 11 is an excavation state diagram, and Fig.
14 to 14 also show a four-winged bit which is another embodiment of the present invention, FIG. 12 is a front view, FIG. 13 is a view taken along the - arrow in FIG. 12, and FIG. 14 is an excavation state diagram. . 11...Earth removal pipe, 12...Rotary blade, 15...Main cutter (cutting type cutter), 15a...Cut body of the main cutter, 15b...Carbide tip of the main cutter,
16...Supplemental cutter (conical cutter), 18...Supplementary cutter (flat cutter).

Claims (1)

[Scope of Claims] 1. A rotatable earth removal pipe, a plurality of rotary blades radially attached to the lower part of the earth removal pipe with a dihedral angle and a rake angle, and the rotor blades have different radial positions from the center of rotation. Equipped with multiple cutters attached in parallel,
The cutter consists of a main cutter and an auxiliary cutter, and the main cutter is a cutting type cutter, and includes a cutter main body fixed to the rotary blade and a cutter cutter that is fitted into a fitting groove provided in the cutter main body and brazed. The carbide tip has a height slightly higher than the depth of the fitting groove provided in the cutter body, and a width slightly larger than the width of the cutter body, and the carbide tip has a height slightly higher than the depth of the fitting groove provided in the cutter body. The cutting edge and both side edges are made to protrude slightly from the cutter body, and the cutting edge of the carbide tip is located below the cutting edge of the adjacent auxiliary cutter, and the upper end of the carbide tip is at least the lower end of the cutting edge of the auxiliary cutter. 1. A vertical hole drilling bit, characterized in that the bits are arranged at substantially the same height, and are configured such that the main cutter excavates a groove first, and the part between the grooves is excavated by an auxiliary cutter. 2. The pit drilling bit according to claim 1, wherein the main cutter has an inclined surface formed by a notch on the surface on the rotation center side of the rotor blade.