JPS6118635B2 - - 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 include (1) those with a flat cutter attached, and (2) conical cutters in which the cutter itself 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.

Figure 1 shows an excavation bit that is a combination of the conical cutter and flat cutter of (a) above, where 1 is an earth removal pipe, 2 is a rotary blade, and 3 and 4 are attached to the lower end of the inclined surface of the rotary blade 2, respectively. 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 using a flat cutter 3.
When the excavated layer becomes a hard ground layer (including a soft rock layer), as shown in FIG. The excavation will be carried out by

However, in this drilling bit, there is a limit to the depth H of the indentation due to the dimensional constraints of the carbide tips 3a and 4a brazed to the flat cutter 3 and the conical cutter 4, respectively, as shown in FIG. . That is,
Cutters 3 and 4 so that the depth H of the indentation 6 becomes large.
If the height difference between the cutter and the cutter is increased, the cutter main body 4b of the conical cutter 4 will wear out. Furthermore, if an attempt is made to make a deep impression by increasing the length of the carbide tip 4a of the conical cutter 4, the carbide tip will easily break. Therefore, the depth of the indentation 6 made by the conical cutter 4 cannot be increased (H = about 2 mm).
Therefore, it had little effect on loosening the soft rock between the indentations 6, and could only be used for excavation lengths approximately 100 m deep. Furthermore, since the indentations 6 were shallow, the excavation load on the flat cutter 3 was increased, and the cutter body 3b and the carbide tip 3a of the flat cutter 3 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, a drilling bit in which a flat cutter 3 and a special flat cutter 7 having a protruding tip are attached to the rotary blade 2. Similarly, a groove is excavated using the special flat cutter 7, and a flat cutter 3 is inserted between the grooves.
The excavation is done by However, the above-mentioned 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.

Furthermore, in the drilling bits shown in FIGS. 1 and 3, if the surface layer of the soft rock is sloped, there is a risk that the cutter may slip in the direction of the slope, causing the bit to run out or the hole to bend. If such core runout or hole bending occurs, a large torque several times the normal drilling torque will be generated, which will have an adverse effect on the entire drilling equipment.

The present invention was made in view of the above-mentioned drawbacks of the prior art, and it is possible to excavate deep trenches when excavating soft rock layers, and to perform excavation with the minimum necessary excavation torque and bit load. To provide a pit drilling bit which does not cause core runout or hole bending of the bit itself even if the surface layer part is inclined.

To achieve this objective, the pit drilling bit of the present invention includes a rotatable earth removal pipe, a plurality of blades radially attached to the lower part of the earth removal pipe with a dihedral angle and a rake angle, and a plurality of blades attached to the blades. and a plurality of cutters attached at different radial positions from the center of rotation, the cutters are composed of a first main cutter, a second main cutter, and an auxiliary cutter, and the first main cutter is rotated by the revolution of the bit. It is a rotary cutter that can alternately excavate and discharge soil by rotating on its own axis, and the center side of the bit has a working angle for forming an indentation and crushing on the excavation surface, and the side opposite to the side having the working angle. The second main cutter is a rotary cutter that rotates on its axis as the bit revolves and can perform rolling biting, and the center side of the bit forms an indentation on the excavation surface. and has a working angle for crushing, and the side opposite to the working angle has a relief angle that does not cause indentation, and the first main cutter and the second main cutter first form a groove. is excavated, and the portion between the grooves is excavated by the 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 of FIG. 4 with a blank view. 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 rotor blade 12 and the earth removal pipe 11.

A plurality of first main cutters 15, second main cutters 19, and auxiliary cutters 16 are fixed to the lower end of the inclined surface of the rotary blade 12 at appropriate intervals. The first main cutter 15 and the second main cutter 19 are arranged so that their cutting edges are located below the cutting edge of the auxiliary cutter 16 so that they can excavate a groove in advance of the auxiliary cutter 16. Further, the auxiliary cutter 16 is arranged so as to be able to excavate between the grooves excavated by the first main cutter 15 and the second main cutter 19.

To explain in detail the arrangement relationship between the first main cutter 15, the second main cutter 19, and the auxiliary cutter 16, as shown in FIG. The second main cutter 19 is closer to the center of the rotary blade 12 than the first main cutter 15 is, and the auxiliary cutter 16 is closer to the small diameter part than the first main cutter 15 and the second main cutter 19 is closer to the center of the rotary blade 12. It is located between. Two auxiliary cutters 16 are arranged between the first main cutter 15 and the second main cutter 19.

Next, the first main cutter 15 and the second main cutter 1
9 and the auxiliary cutter 16 will be explained in detail with reference to FIGS. 6 to 10. 1st main cutter 15
is a rotary cutter that can alternately excavate and remove earth by rotating with the revolution of the bit, and includes a bracket 15a fixed to the rotary blade 12 and a bracket 15a
It consists of a disk 15d supported via a bearing 15c on a shaft 15b fixed to a shaft 15b, and blades 15e and grooves 15f alternately formed on the outer periphery of the disk 15d.

The tip of each of the blades 15e has an indentation action angle θ on the side facing toward the center of the bit, and a clearance angle (inward from the cutting point 15g of the cutting edge) that prevents the indentation action on the side facing the side. angle) β. Further, each blade 15e is made of carburized hardened steel or cemented carbide with good wear resistance.

The second main cutter 19 is a rotating cutter that can rotate and perform rolling biting due to the revolution of the bit.
A bracket 19a is fixed to the rotary blade 12, and a bearing 19c is attached to a shaft 19b fixed to the bracket 19a.
It is composed of a disk 19d supported via a blade 19d, and a blade 19e formed on the outer periphery of the disk 19d.

The tip of the blade 19e has a working angle θ for forming an indentation on the excavation surface and crushing it on the side facing the center of the bit, and has a working angle θ on the side opposite to the side having the working angle θ. It has a clearance angle β (an angle that enters inside the excavation point 19f of the cutting edge 19) that does not cause an indentation effect. The blade 19e is made of carburized hardened steel or cemented carbide, which has good wear resistance.

On the other hand, the auxiliary cutter 16 includes a cutter main body 16a,
The cutter body 16a is configured as a conical cutter, and a carbide tip 16b is press-fitted or 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 tips of the blade 15e of the first main cutter 15 and the blade 19e of the second main cutter 19 are bent as shown in FIG. It comes into contact with the excavated surface having an inclination angle α before the auxiliary cutter 16 does. The rotation (revolution) of the rotary blade 12 causes the first main cutter 15 and the second main cutter 19 to rotate, that is, the disk 15d in the first main cutter 15 moves toward the bracket 15.
Each blade 15e excavates the excavation surface by rotating about the axis 15b of a. Further, the disk 19d of the second main cutter 19 rotates about the shaft 19b of the bracket 19a, and the blade 19e bites into the excavated surface and crushes it. Then, when excavation is performed by the first main cutter 15. Since each blade 15e of the main cutter 15 has an indentation angle θ on the side surface on the bit center side, the cutting edge bites into the excavated surface and the indentation effect is good. Further, since the side surface of each blade 15e facing the above-mentioned side surface has a clearance angle β that does not cause an indentation effect, the bite of the excavation surface in the excavation radial direction is also good.

When excavation is performed by the second main cutter 19,
The blade 19e has an indentation action angle θ on the side surface on the center side of the bit, and since the blade 19e is continuous, the indentation action and crushing effect due to the indentation action angle θ are even better. Further, since the blade 19e also has a relief angle β like the blade 15e of the first main cutter 15, the cutting surface can be easily bitten in the radial direction of the excavation.
In addition, as shown in Fig. 18, as the distance (radius) R between the bit center O and the cutter becomes smaller, the relief angle β becomes larger, so the amount of slippage of the cutter increases, and the indentation and crushing effects become even greater. becomes. Therefore, the excavation efficiency is further improved by the excavation action by the first main cutter 15 and the crushing and biting action by the second main cutter 19.

Next, the first main cutter 15 excavates a deep groove (groove depth H') while alternately excavating and discharging soil using its blade 15e and the groove 15f between the blades, and the second main cutter 19 excavates a deep groove (groove depth H') using its blade 15e and the groove 15f between the blades. 19e, a deep groove is excavated while performing indentation action and crushing action.

The groove is excavated by rotating the disk 15d of the first main cutter 15 and the disk 19d of the second main cutter 19 several times. When the excavation surface is soft rock, by digging the deep groove, large cracks are created in the soft rock around the groove, and the soft rock between the grooves is loosened. Next, supplementary cutter 1
6 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 way, the first main cutter 15, the second main cutter 19, and the auxiliary cutter 16 continue to excavate, thereby forming a pit in the soft rock layer.

Also, when the excavated layer is of general soil quality, a groove is excavated by the first main cutter 15 and the second main cutter 19, and the area around the groove is loosened, and then the part between the grooves is excavated by the auxiliary cutter 16. .

Therefore, in the excavation bit according to the present invention, the first main cutter 15 is configured as a rotary cutter that alternately excavates and removes soil, and the second main cutter 19
are configured as rotary cutters that perform indentation and crushing, and their cutting edges are positioned below the cutting edges of the auxiliary cutter 16, making it possible to excavate deep grooves. In addition, since each blade 15e of the first main cutter 15 digs into the excavation surface one after another as the cutter rotates (rotates), there is little wear on each blade 15e. Moreover, since excavation is performed intermittently by each blade 15e, the frictional heat of the cutting edge during digging is cooled when it is not in contact with the excavated surface, and deterioration of the blade is prevented. Furthermore, since the excavated earth and sand are discharged through the grooves 15f between the blades 15e, the earth removal efficiency is improved, and damage to the cutter 15 due to secondary and tertiary crushing of the residual earth and sand is prevented. The second main cutter 19 has a lower circumferential speed than the first main cutter 15 (it is located inside the main cutter) and is closer to the suction port, so there is no problem with frictional heat and earth removal performance.

Then, the first main cutter 15 and the second main cutter 1
Supplementary cutter 1 is created by excavating a deep groove according to 9.
The excavation burden on the auxiliary cutter 1 is reduced.
6 wear is reduced and the life of the cutter is extended. In addition, the auxiliary cutter 16 is connected to the first main cutter 15 and the second main cutter 1.
Since only the loosened part between the deep trenches excavated by step 9 is excavated, the excavation resistance is reduced.Especially when excavating mainly in soft rock, the excavation resistance is reduced, so the bit load and excavation torque are smaller than before. It is possible to excavate at Furthermore, the first main cutter 15
A deep groove is excavated by the second main cutter 19, and the excavation is performed sequentially using the groove as a guide, so even if the surface of the excavated layer is sloped, the cutter will not slip and cause core runout or hole bending, and the excavation will be carried out smoothly. It can also prevent the vibration of time.

11 and 12 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. 3, it consists 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, the same functions and effects as the drilling bit shown in FIGS. 4 and 5 can be achieved.

14 and 15 also show other embodiments of the present invention, and the difference from FIGS. 4 and 5 is 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. 16, the conical cutter 16
is arranged to excavate between the grooves excavated by the first main cutter 15 and the second main cutter 19 before the flat cutter 18, and the flat cutter 18 is connected to the excavation surface excavated by the conical cutter 16 and the main cutter. It is arranged so as to excavate between it and the groove excavated by the cutter.

According to this embodiment, two types of auxiliary cutters, namely the conical cutter 16 and the flat cutter 18, are used to excavate between the grooves excavated by the first main cutter 15 and the second main cutter 19. The excavation resistance of the shaped 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. Also, the number of first and second main cutters arranged on a concentric circle at a position with a larger radius from the center of rotation is greater than the number of first and second main cutters arranged on a concentric circle inside thereof. By increasing the number, it is possible to eliminate uneven life due to differences in circumferential speed.

Furthermore, in the embodiment described above, the first and second
We have shown an example in which the main cutter, a rotary cutter, has a clearance angle on the side surface of each blade to prevent indentation.
As shown in Fig. 17 and Fig. 18, the rotary cutter 1
By changing the mounting positions of 5 and 19, the clearance angle β may be provided on the side opposite to the side having the indentation action angle. That is, when each blade 15e, 19e of the rotary cutters 15, 19 rotates, the blade 15
The rotary cutter 1 is set so that the excavation point M of e, 19e has a clearance angle β with respect to the tangent L direction of the circular arc locus N drawn by the excavation point M by the rotation of the bit.
5, 19 may be attached. In the figure, R is the excavation radius, J is the rotation direction of the bit, and G is the rotary cutter 1.
5,19 excavation range, K is rotary cutter 15,1
9 shows the direction of rotation.

As explained above, the pit drilling bit of the present invention is composed of first and second main cutters and an auxiliary cutter, and the first main cutter rotates on its own axis as the bit revolves to alternately excavate and remove soil. The second main cutter is a rotary cutter that can perform indentation and crushing by rotating on its own axis as the bit revolves, and its cutting edge is positioned below the cutting edge of the auxiliary cutter, and the first, First excavate the trench with the second main cutter,
Since I decided to excavate between the grooves with a supplementary cutter,
It is possible to excavate deep trenches with the minimum necessary excavation torque and bit load. Furthermore, even if the surface layer of the soft rock layer is sloped, the bit itself will not run out of core or the hole will bend. The first and second main cutters each have a working angle on the bit center side of the cutting edge for forming an indentation on the excavation surface, and have an indentation effect on the side opposite to the side having the working angle. Since it has a relief angle that does not affect the drilling, it has good grip on the excavated surface and enables efficient excavation of deep grooves with the blade bit.

[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. 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 an excavation of the four-winged bit. FIG. 7 is a side view of the first main cutter according to the present invention, as seen from the - direction of FIG. 6, FIG. 8 is a cross-sectional view of FIG. The second main cutter, the sixth
A side view seen from the - direction in the figure, Figure 10 is the 9th
11 to 13 show a four-winged bit which is another embodiment of the present invention.
Figure 1 is a front view, Figure 12 is a view taken along arrows XII-XII in Figure 11, Figure 13 is an excavation state diagram, and Figures 14 to 1.
Fig. 6 also shows a four-winged bit which is another embodiment of the present invention, Fig. 14 is a front view, Fig. 15 is a view taken along the - arrow in Fig. 14, Fig. 16 is an excavation state diagram, and Fig. 17 is a diagram showing the excavation state.
18 are diagrams showing clearance angles and excavation ranges of the rotary cutter according to the present invention. 11...Earth removal pipe, 12...Rotary blade, 15...First main cutter (rotary type cutter), 15a...Cut body of the first main cutter, 15e...Blade of the first main cutter, 16...Supplementary cutter Katsuta (conical katsuta), 18...
...auxiliary cutter (flat cutter), 19... second main cutter (rotating cutter), 19a... cutter body of the second main cutter, 19e... blade of the second cutter.

Claims (1)

[Claims] 1. A rotatable earth removal pipe, a plurality of blades radially attached to the lower part of the earth removal pipe with a dihedral angle and a rake angle, and the blades have different radial positions from the center of rotation. and a plurality of cutters attached in parallel, the cutters are composed of a first main cutter, a second main cutter, and an auxiliary cutter, and the first main cutter rotates due to the revolution of the bit to alternately excavate and discharge earth. It is a rotary cutter that can be used for cutting, and the center side of the bit has a working angle to form an indentation on the excavation surface and crush it, and the side opposite to the side having the working angle has a relief that does not exert an indentation effect. The second main cutter is a rotary cutter that can perform rolling biting by rotating on its own axis as the bit revolves; The side opposite to the working angle has a clearance angle that does not cause indentation, and a groove is first excavated by the first main cutter and the second main cutter, and the part between the grooves is A vertical hole drilling bit, characterized in that the bit is configured such that the auxiliary cutter excavates the hole. 2. The first main cutter is closer to the outermost end and large diameter part of the wing, and the second main cutter is closer to the center of the wing than the first main cutter, and the second main cutter is closer to the small diameter part than the first main cutter. The pit drilling bit according to claim 1, wherein the cutter is located between the first main cutter and the second main cutter, respectively. 3. The pit drilling bit according to claim 1 or 2, wherein the auxiliary cutter is a conical cutter. 4. The pit drilling bit according to claim 1 or 2, wherein the auxiliary cutter is a flat cutter. 5. The auxiliary cutter consists of a conical cutter and a flat cutter, the conical cutter excavates in advance of the flat cutter, and the flat cutter connects the excavation surface excavated by the conical cutter with the first and second main cutters. 2. The vertical hole drilling bit according to claim 1, wherein the bit is configured to excavate a portion between the bit and the excavated groove.