JP2002061484A - Outer bit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems that a tip is excessively chipped and worn and that the height of protrusion of the tip in the direction of the outer diameter from a bit shank can not be enlarged as a conventional hard cylindrical tip planted in an outer bit can not be enlarged in tip diameter to the wall thickness of the bit shank in the case of drilling double pipes in the ground by a boring machine. SOLUTION: The relationship between the tip diameter (d) of the hard cylindrical tip 51 planted in the excavating face of the outer bit 50 and the wall thickness (t) of the bit shank is that t=0.8d-1.2d. The relationship between the longitudinal size (L) of the embedded part of the tip 51 and the tip diameter (d) is that L=0.35d-0.6d. The height (h) of protrusion of the tip 51 which forms the concentric circle of the maximum outer diameter of the outer bit 50 from the bit shank 52 is 0.8-2 mm. The tip 51 is fixed to the bit shank 52 by brazing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer bit of an inner bit and an outer bit used for excavating a ground with a double pipe using a boring machine. It is effective for

[0002]

2. Description of the Related Art Conventional outer bits include those shown in FIGS.

FIG. 6 shows that the chip 11 has a high speed (HS).
FIG. 8 shows a tip 31 of a chisel type outer bit 30, and FIG. 9 shows a tip (41) of a roof (R) type outer bit 40, which is selectively used depending on the hardness of the ground to be excavated. Note that FIG.
Is not a rigid cylinder, but is shown for reference.

FIG. 5 shows an example of a rigid cylindrical tip.
(A) shows a spike (S) type, (b) shows a high speed (HS) type, (c) shows a button (B) type,
A chisel type chip 31 shown in FIG. 8 is also a kind thereof, and is formed of a cemented carbide.

The outer bit shown in FIGS. 6 and 8 and the spiked type outer bit (not shown) differ only in the shape of the chip. Therefore, as a conventional example, the high-speed type shown in FIG. 6 will be described.

FIG. 6 shows a bit diameter of 137 mm (nominal size).
And the excavation diameter is about 137φ, and the tip diameter (d) is 1
Since the bit shank thickness (t) is 1 mm and the bit shank thickness (t) is 16 mm, t / d = 16/11 ≒ 1.45, and the relationship between the longitudinal dimension (L) of the embedded portion of the chip and the chip diameter (d) is L ≒. 1d
Met. The protruding height (h) of the tip 11 forming a concentric circle of the outermost diameter of the outer bit from the bit shank was small.

FIG. 7 is an explanatory view of a chip in which a high-speed chip having a dimension conventionally used is arranged in the same bit shank as FIG. 1 of the present invention. When the bit diameter is 137 mm, the bit shank thickness ( t) is 14.5 mm and the chip diameter is 12 mm, so that t / d = 1.2 and L
= 1d. In this case, the protruding height (h) of the tip 21, which forms the outermost concentric circle of the outer bit from the bit shank 22, was 0.739 mm. Conventionally, the bit diameter is 230φ or less and the thickness (t) of the bit shank is 14 to 2
In a 0 mm outer bit, a commonly used tip diameter was 10 to 12 mmφ. The relation between the longitudinal dimension (L) of the embedded portion of the chip and the chip diameter (d) is L = 0.9d.
~ 1.3d.

[0008] The projecting height (h) of the outermost diameter concentric tip from the bit shank is less than 0.8 mm. The implantation of the tip in the shank (embedding fixation) was press-fitting or brazing.

In the conventional outer bit, the tip diameter (d) is smaller than the thickness (t) of the bit shank. Therefore, the strength (h) can be designed only as small as less than 0.8 mm. Not only the shank outer diameter was severely worn but also the slight wear of the tip increased the drilling torque.

[0010] In addition, the chip often breaks when it hits hard ground. On the other hand, when the chip diameter is increased, the chip strength can be improved. However, since the embedded portion of the chip is long, if the chip is inclined, it protrudes toward the inner diameter side, which causes inconvenience in use. Therefore, the chip diameter cannot be increased by design.

[0011]

The problem to be solved by the present invention is that the conventional hard cylindrical tip used for the outer bit cannot make the tip diameter (d) much larger than the bit shank thickness (t). Therefore, the chip is severely chipped and worn, and the height (h) of the chip protruding from the bit shank in the outer diameter direction cannot be increased.

[0012]

According to the outer bit of the present invention, the relationship between the tip diameter (d) of the hard cylindrical tip implanted on the excavation surface and the bit shank thickness (t) is t = 0.
8d to 1.2d, the relationship between the longitudinal dimension (L) of the embedded portion of the chip and the chip diameter (d) is L = 0.35d to 0.6d, and the chip is implanted in the bit shank by brazing. ing. In this case, the protruding height (h) of the outermost outer diameter of the outer bit from the outer diameter of the bit shank of a concentric circle.
Is 0.8 mm to 2 mm.

By making the longitudinal dimension of the embedded portion of the chip shorter than before, the tip diameter (d) with respect to the bit shank thickness (t) can be increased, and the strength is improved.
Therefore, the protruding height (h) from the bit shank can be increased.

[0014]

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

FIG. 1 is a view of an outer bit showing an embodiment of the present invention, wherein (a) shows a plane and (b) shows a longitudinal section. 2A and 2B are cross sections of FIG. 1, wherein FIG. 2A shows a cross section taken along line AA, FIG. 2B shows a cross section taken along line BB, and FIG. 3A and 3B are explanatory views of the chip implanted in the outer bit of FIG. 1, wherein FIG. 3A is an enlarged view of a cross section taken along line CC of FIG. 1, and FIGS. 3B and 3C are front views of the chip. Of 5
1a shows a wear part.

In the figure, the ratio of the tip diameter (d) to the shank thickness (t) is t / d = 14.5 / 14 ≒ 1.03.
Since the value is smaller than the conventional 1.45 of FIG. 6 and 1.2 of FIG. 7, the tip diameter (d) is smaller than the shank thickness (t).
Is big. In addition, the ratio L / d = 6/14 ≒ 0.43 between the longitudinal dimension (L) of the chip embedded portion and the chip diameter (d) is about 1 in FIG. 6 and 1 in FIG. In comparison, the longitudinal dimension (L) of the chip buried portion is smaller than the chip diameter (d), and therefore, the chip has higher resistance to breaking than the conventional one.

Further, as shown in FIG. 3A, the height (h) of the outer bit 50 protruding from the tip 51 and the bit shank 52 which are concentric with the outermost diameter is 1.185 mm.
(The bit diameter (nominal) is 137 mm), a small value close to 0 in FIG. 6 (h) and 0.739 m in FIG.
It is considerably larger than m.

In FIG. 3 (c), a black portion 51a indicates a worn portion. FIG. 4 shows a commonly used inner bit for reference.

In the present invention, the relationship between the longitudinal dimension (L) of the chip embedded portion and the chip diameter (d) is L = 0.35d or more.
By setting it to 0.6d, the thickness of the bit shank (t)
, The tip diameter (d) can be designed to be larger, and as a result, it has been found that the tip diameter (d) can be made larger than before in the relation of t = 0.8d to 1.2d. Since the longitudinal dimension (L) of the buried portion has become shorter, the chip is implanted into the bit shank by brazing in order to secure the fixing strength to the bit shank.

The inclination (α) of the outermost diameter concentric circle in the outer diameter direction is preferably 20 to 35 degrees in terms of design and excavation resistance (torque feeding force). In the case of, the protruding height (h) from the outer diameter of the bit shank is 0.8
It is possible to take a value larger than the conventional value of up to 2 mm.

Further, since the tip diameter (d) can be increased, the tip protrusion from the bit shank to the excavation surface can be increased.

[0022]

According to the present invention, the following effects can be obtained.

(1) Since the tip diameter is large, the defect strength can be improved by increasing the volume. Therefore, the effect of preventing chipping can be obtained without changing the chip hardness or the shape of the chip.

(2) The projecting height (projecting dimension) from the bit shank in the outer diameter direction is large, and the life of the outer bit until the wear limit is reached is long.

(3) Excavation efficiency is good because the tip protruding height from the bit shank to the excavation surface is large. In addition, clogging between chips due to digging waste is small.

(4) Since the ratio of the volume of the consumable part of the chip to the whole becomes large, the economic efficiency is improved and the environmental load is reduced.

(5) Chips large enough for the shank wall thickness are planted. However, since the planting of the chips is brazing, sufficient mounting strength can be maintained.

[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.

2A and 2B show partial cross sections of FIG. 1, wherein FIG. 2A shows a cross section taken along line AA, FIG. 2B shows a cross section taken along line BB, and FIG. 2C shows a cross section taken along line CC.

3A and 3B are explanatory views of a chip implanted in an outer bit of FIG. 1, wherein FIG. 3A is an enlarged view of a cross section taken along line CC of FIG. 1, and FIGS. 3B and 3C are front views of the chip.

FIG. 4 is a diagram of a commonly used inner bit, in which a spike type tip is used, (a) showing a plane, (b) showing a front surface, and (c) showing a vertical section.

5A and 5B are explanatory diagrams of a hard cylindrical tip, wherein FIG. 5A shows a spike type, FIG. 5B shows a high speed type, and FIG. 5C shows a button type.

6A and 6B are diagrams of a conventional high-speed type outer bit, in which FIG. 6A shows a plane and FIG.

FIGS. 7A and 7B are explanatory views of a chip in a conventional high-speed type outer bit, in which FIG. 7A shows a partial cross section of an outermost diameter chip, and FIGS.

FIG. 8 is a diagram of a conventional chisel type outer bit,
(A) shows a plane, and (b) shows a half cross-sectional front.

FIG. 9 is a diagram of a conventional loop type outer bit;
(A) shows a plane, and (b) shows a half cross-sectional front.

[Explanation of symbols]

 50 Outer bit 51 Tip 52 Bit shank h Projection height from bit shank outer diameter t Bit shank wall thickness d Tip diameter L Longitudinal dimension of buried portion

Claims (2)

[Claims] In a double pipe drilling bit, the relationship between the tip diameter (d) of the hard cylindrical tip implanted on the drilling surface and the bit shank wall thickness (t) is t = 0.8d to 1.d. 2d
Then, the longitudinal dimension (L) of the embedded portion of the chip and the chip diameter (d)
L = 0.35d to 0.6d, and the chip is implanted in the bit shank by brazing. 2. A protruding height (h) of the outermost concentric tip from the bit shank outer diameter is 0.8 mm to 2 mm.
The outer bit according to claim 1, wherein: