JP2002106280A - Outer bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an outer bit which solve problems such as heavy abrasion in the outer bit and large torque in excavation caused by inferior discharge of cuttings when excavating a double-pipe in a boring work. SOLUTION: A plurality of cuttings collecting grooves 32 having the relation among the groove depth L2, the groove width L2, and the shank wall thickness t, L1=1t-2.5t and L2=1t-3t are disposed in the side of an excavation face 31a of a bit shank 31. The center line of the groove width is inclined by a prescribed angle α in the rotation direction A of the shank inner wall 31b and the groove bottom 32b is inclined by a prescribed angle β rearward of the axis O of the groove bottom 32b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer bit used for excavating a double pipe in the ground by a boring machine.

[0002]

2. Description of the Related Art In double pipe drilling, a drilling liquid is usually sent from an inner pipe to a drilling surface at a tip, and an inner bit (not shown) is used.
And the drill bit excavated by the outer bit are discharged to the ground together with the drilling liquid through the gap between the inner and outer pipes, and the conventional outer bit is as shown in FIGS.

FIG. 4B shows a longitudinal section of FIG.
2A shows a cross section taken along the line DD of FIG. 1A, and a plurality of excavation grooves 12 are provided on the excavation surface 11 of the outer bit 10 at right angles to the rotation direction of the outer bit 10. A shallow U-shaped groove 13 was provided inside 10.

FIG. 3 shows an outer bit 20 designed so that the outer bit and the excavated surface can be more efficiently discharged by the outer bit than the outer bit shown in FIG.
Are provided with a plurality of cutting waste intake grooves 22 inclined in the rotation direction A of the outer bit 20, and a spiral groove 25 inclined in the rotation direction for taking in the cutting waste of the outer diameter portion 24 outside the outer bit 20. Are disposed so as to communicate with every other digging waste intake groove 22.

[0005]

However, among the conventional outer bits, the one shown in FIG.
The excavated chips generated in the outer diameter portion 14 are compacted rearward of the bit without being taken into the excavated chip intake groove 12 at the tip of the inner bit 10. In addition, the cutting waste intake groove 12 at the tip
Is perpendicular to the rotation direction, so that the incorporation of cuttings into the gap between the inner bit (not shown) and the outer bit 10 was insufficient. Therefore, resistance to torque and feeding occurs, which is inconvenient for excavation, and is a major cause of abrasion of the tip of the outer bit 10 and the outer diameter portion 14 of the bit shank 15.

A conventional outer bit 20 shown in FIG.
In other words, the cutting waste generated in the outer diameter part 24 of the bit shank 26 passes through the spiral groove 25 of the outer diameter part 24, and the cutting waste intake groove 2 inclined in the rotation direction A at the tip of the outer bit 20.
2, the spiral groove 25 has no effect of reducing the torque resistance of the outer diameter portion 24 of the bit shank 26, and the spiral groove 25 can be narrow and shallow. Therefore, there is a disadvantage that clogging is easily caused.

As described above, in the case of the conventional outer bit, when the bit shank wears quickly, a wear prevention treatment such as hard material overlaying must be performed, which is uneconomical. In particular, when applied to a gravel layer having a relatively small gravel diameter and a low gravel compressive strength, wear was remarkable.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide an outer bit capable of reducing wear of a bit shank and reducing torque during excavation.

[0009]

In order to achieve the above-mentioned object, an outer bit for excavating a double pipe according to the present invention has a groove depth (L1) and a groove width (L) on the side of a bit shank on which a drill is formed.
The relationship between 2) and the shank thickness (t) is L1 =
A plurality of cutting waste intake grooves having 1t to 2.5t and L2 = 1t to 3t are provided, and the center line of the groove width is inclined at a predetermined angle in the rotation direction of the outer bit with respect to the radius line of the circle from the shank inner wall. At the same time, the groove bottom is configured to be inclined at a predetermined angle rearward of the axis.

[0010] Dirt generated on the outer diameter of the bit shank is easily taken in from the outer diameter of the bit shank having a depth of 1 t to 2.5 t and a width of 1 t to 3 t, and follows the groove inclined in the rotation direction. And is pushed into the ground along the gap between the inner bit and the outer bit by the groove bottom inclined in the axial direction.

Preferably, the inclination angle (α) of the cutting waste intake groove in the rotation direction is 15 degrees to 30 degrees.

Further, the inclination angle (β) of the cutting waste intake groove in the rearward direction of the axis is preferably 10 to 50 degrees.

[0013]

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

FIG. 1 shows an embodiment of the present invention.
Excavation surface 31a of bit shank 31 of outer bit 30
On the side, there are provided three cutting dust intake grooves 32 which divide the circumference into three equal parts, and the center line of the groove width is the rotation direction A of the outer bit 30 with respect to the radial line 33 of the circle from the inner wall 31b of the shank.
And the groove bottom 32b is inclined 45 degrees (β) in the rear direction of the axis O.

In the figure, the bit diameter is 137 mm, the shank thickness t is 14.5, the groove depth L1 is 25 mm,
The width L2 of the groove is 25 mm.

The digging waste intake groove 32 is set to a plurality of two or more pits depending on the bit diameter and the digging ground.

In the case of the present invention, L1 =
Values of 1t to 2.5t and L2 = 1t to 3t are preferred.

Further, the angles α and β are each 15 degrees or more.
30 degrees and 10 degrees to 50 degrees are preferable in design and construction.

FIG. 2 is a schematic view showing the flow of cuttings by the outer bit 30. The cuttings generated in the outer diameter portion 31c of the bit shank 31 are cut out from the groove 32a of the outer diameter portion 31c in the direction indicated by the arrow B in the arrow B direction. 32, and are taken into the gap 34 between the inner bit 40 and the outer bit 30 from the tip of the outer bit 30 in the direction of arrow C, respectively.

Since the cutting waste intake groove 32 has inclination angles α and β in the rotation direction and the rear direction in the axial direction, the slime of the cutting waste flows into the rear of the gap 34 (toward the ground) with little resistance.

[0021]

According to the present invention described in detail above, the following effects can be obtained.

(1) Dirt generated at the outer diameter portion of the bit shank is taken into the gap between the inner bit and the outer bit without being compacted behind the outer bit, and is discharged to the ground through a flow path between the inner and outer pipes. You.

(2) Since the cutting waste is smoothly collected, the outer bit tip and the annular portion having the outer diameter are secured.
Does not promote wear of the outer bit and the outer tube connected to it. Therefore, the time required for the outer bit and the outer tube to reach the wear life is long, which is economical and has a low environmental load.

(3) Since the groove of the outer bit according to the present invention is formed with a sufficient size with respect to the excavated area, the groove is not clogged with the cutting waste, and the operation can be continued without interruption.

(4) Since the drill bit is forcibly taken in by turning and advancing the bit, excavation for a certain period of time is possible even if the water supply hole of the inner bit is blocked.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams of an outer bit illustrating an embodiment of the present invention, wherein FIG. 1A is a plan view and FIG.

FIGS. 2A and 2B are schematic diagrams showing the flow of cuttings by the outer bit of the present invention, wherein FIG. 2A shows a plane and FIG. 2B shows a half longitudinal section.

FIGS. 3A and 3B are views of an outer bit in which a spiral groove is provided in an outer diameter portion, where FIG. 3A is a plan view and FIG.

4A and 4B are diagrams of an outer bit generally used in the related art, where FIG. 4A is a plan view, FIG. 4B is a longitudinal section, and FIG. 4C is a sectional view taken along line DD of FIG.

[Explanation of symbols]

 Reference Signs List 30 outer bit 31 bit shank 31a excavated surface 31b inner wall 31c outer diameter portion 32 cutting waste intake groove 32a groove hole 32b groove bottom 33 radius line A rotation direction O axis center

Claims (3)

[Claims] In the outer bit for double pipe excavation, the relationship between the groove depth (L1) and the groove width (L2) and the shank wall thickness (t) on the excavation surface side of the bit shank is L1 = A plurality of digging waste intake grooves in which 1t to 2.5t and L2 = 1t to 3t are provided, and the center line of the groove width is:
An outer bit which is inclined at a predetermined angle in a rotation direction of the outer bit with respect to a radial line of a circle from a shank inner wall, and a groove bottom is inclined at a predetermined angle rearward of the axis. 2. The outer bit according to claim 1, wherein an inclination angle (α) of the cutting waste intake groove in a rotation direction is 15 degrees to 30 degrees. 3. The outer bit according to claim 1, wherein an inclination angle (β) of the cutting waste intake groove in a rearward direction of the axis is 10 degrees to 50 degrees.