JP3075229U - Casing bit - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention is capable of alleviating the residual heat distortion which occurs when a tip is silver-braded to a shank constituting a casing bit, and has excellent durability and strength. It is another object of the present invention to provide an insert blade type casing bit. SOLUTION: A large number of excavating blades 3 provided for a tip part 2 of a casing steel pipe 1 used for foundation work for civil engineering.
Wherein the casing bit 11 is composed of a tip 12 forming a cutting edge portion and a shank 16 holding the tip 12. 3
In the insert-type casing bit whose surface is silver-braded, the tip 12 is divided into two in the width direction of the tip 12, and the divided tip 12 is divided into a small piece 13 and a large piece 14. , And the large piece 14 constituting the chip 12 is the tip 1 of the chip 12.
5 is included.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a casing bit, and more particularly, to a double-edged casing bit capable of mitigating residual thermal distortion in a tip that is silver-braded to a shank constituting the casing bit.

[0002]

[Prior art]

 As is well known, as one of the methods of excavation work in civil engineering foundation work, a large number of excavating blades are arranged at the tip of a casing steel pipe, and the casing steel pipe on which the large number of excavating blades are arranged is turned. Excavation work has been widely carried out, and a large number of excavating blades arranged at the tip of the casing steel pipe have to be replaced each time in accordance with wear or breakage of the cutting edge due to excavation. It consists of a holder integrally attached to the tip of the casing steel pipe, and a casing bit detachably attached to the holder.

[0003] The casing bit is made of a cemented carbide tip forming a cutting edge portion, and a steel shank for holding the tip and attaching it to a holder. The casing bit is divided into two types: a beveled blade type where the two surfaces of the chip are silver-brazed to the shank, and an insert blade type where the three surfaces of the chip are silver-braded to the shank. In such civil engineering foundation work, a cutting edge type casing bit with a large tip holding force is widely used.

[0004] The thermal expansion coefficient of the steel material, which is the material of the shank forming the casing bit, is about twice the thermal expansion coefficient of the cemented carbide, which is the material of the chip. On the other hand, after the soldering of the chip with silver, the shrinkage of the shank causes large thermal strain to remain on the chip, resulting in a problem that the strength of the chip is impaired and the durability is reduced. Various methods have been used to alleviate this residual thermal strain.

[0005] As a method of alleviating the residual thermal strain, a method of sandwiching a copper plate, a copper wire, a copper net, or the like between a chip and a shank by silver brazing (sandwich), or a chip made of cemented carbide is used. Divided into several parts to relieve the tensile stress on the cemented carbide chip surface, or by forming grooves etc. on the surface where the steel material shank and the cemented carbide chip contact There is a method of reducing the shrinkage force of the steel, and a method of using a special steel material having a coefficient of thermal expansion close to that of a cemented carbide as a material of the shank.

[0006]

[Problems to be solved by the invention]

 According to the above-mentioned conventional technique, the residual of thermal distortion caused when silver is brazed to the shank constituting the casing bit can be reduced, but the cemented carbide chip is divided into several pieces. The method requires that the chips have a certain amount of mass in order to be able to withstand the large excavating forces in civil engineering foundation work, and as a result, there is a problem that the chips cannot be divided into many parts. In addition, the method of forming a groove or the like on the surface where the steel shank and the cemented carbide tip are in contact cannot be applied unless the shank has sufficient margin, and the thermal expansion Special steel materials with a rate close to that of cemented carbide have the disadvantage that they are not practical because they are expensive. How to put silver rows across the copper net or the like is widely used.

However, in the insert-type casing bit, since the three surfaces of the tip are silver-braded, the brazing area is smaller than that of the blade-type casing bit in which the two surfaces of the tip are silver-braded. As a result, the residual thermal strain increases, and the thermal strain remaining on the chip after silver brazing is reduced not only in the chip cross-sectional direction (vertical direction) but also in the direction perpendicular to the cross-section (chip direction). (The width direction), and the total thermal strain of these remains in the chip as a whole. A silver plate is placed between the chip and the shank with a copper plate, copper wire, copper mesh, etc. However, even with the method of attaching, there was a problem that the residual thermal strain could not be sufficiently reduced.

Therefore, the present invention solves the above-mentioned problems, and can alleviate the residual thermal strain that occurs when a tip is silver-blanked to a shank constituting a casing bit, An object of the present invention is to provide a cutting edge type casing bit capable of obtaining excellent durability and strength.

[0009]

[Means for solving the problem]

 In order to achieve the above object, the present invention has the following technical means. That is, a casing bit 11 constituting a large number of excavating blades 3 provided for a tip end portion 2 of a casing steel pipe 1 used for foundation work for civil engineering, wherein the casing bit 11 is a tip 12 forming a cutting edge portion. And a shank 16 for holding the tip 12. Further, in the insert bit type casing bit in which three surfaces of the tip 12 are silver-brazed to the shank 16, the tip 12 is The chip 12 is divided into two in the width direction of the chip 12, and the chip 12 divided into two is composed of a small piece 13 and a large piece 14, and the large piece 14 constituting the chip 12 is the largest of the chip 12. This is a casing bit including the tip portion 15.

Further, when the width of the small piece 13 and the width of the large piece 14 of the small piece 13 and the large piece 14 constituting the chip 12 divided into two are defined as A and B, respectively, the width dimension ratio A: B is 1: 1: 7 to 1: 1.5.

The present invention comprises the above technical means, and by dividing the chip 12 constituting the casing bit 11 into two parts, it is possible to alleviate the residual thermal strain in the width direction after the chip 12 is soldered to silver. As a result, the residual thermal distortion in the entire chip 12 is reduced, so that the residual thermal distortion in the chip 12 constituting the casing bit 11 can be reduced.

Further, the tip 12 divided into two parts is composed of the small piece 13 and the large piece 14, and the tip 14 of the tip 12 is included in the large piece 14, so that the largest tip is formed during excavation. The large piece 14 is positioned around the tip portion 15 of the tip 12 to which the excavating force is applied, and has a size necessary to obtain a sufficient mass effect, that is, to withstand the excavating force during excavation. Thus, the casing bit 11 having excellent durability and strength can be obtained.

In addition, by setting the width ratio A: B of the width A of the small piece 13 and the width B of the large piece 14 constituting the chip 12 to be in the range of 1: 7 to 1: 1.5, The thermal strain remaining on the large piece 14 constituting the tip 12 can be reduced to a level that does not hinder practical use, and at the same time, the size and strength necessary to withstand the large excavation force generated during excavation can be provided, and the thermal strain can be increased. It is possible to achieve both the reduction of the residue of steel and the improvement of durability and strength.

[0014]

[Embodiment of the invention]

 Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, a large number of excavating blades 3 arranged on the distal end portion 2 of the casing steel pipe 1 used for foundation work for civil engineering are attached to the distal end portion 2 of the casing steel pipe 1 by welding. The holder 4 includes a holder 4 formed integrally with the distal end portion 2 of the casing steel pipe 1, and a casing bit 11 which is detachably attached to the holder 4 by mounting bolts 6.

As shown in FIGS. 2 and 3, the casing bit 11 includes a cemented carbide tip 12 forming a cutting edge portion, and a steel shank for attaching and detaching to and from the holder 4. The chip 12 is inserted into a groove-shaped chip insertion portion 17 formed along the width direction of the shank 16 and is soldered with silver. Constitutes an insert blade type casing bit 11 to which silver is brazed.

A fitting groove 18 and a bolt hole 19 are formed in the shank 16, and the fitting groove 18 is fitted into the fitting portion 5 formed in the holder 4. Thereafter, the mounting bolt 6 is inserted into the bolt hole 19 and tightened, whereby the casing bit 11 is attached to the holder 4. Conversely, to remove the casing bit 11 from the holder 4, the mounting bolt 6 is loosened. This is performed by pulling out from the bolt hole 19.

Further, the chip 12 which is inserted into the chip insertion portion 17 formed on the shank 16 and is soldered with silver is divided into a small piece 13 and a large piece 14 in the width direction of the chip 12. The large piece 14 of the chip 12 is formed on the side of the chip 12 where the foremost end portion 15 is located.

As described above, by dividing the chip 12 into two parts, it is possible to alleviate the residual thermal strain in the width direction that occurs after the chip 12 is soldered to silver, and as a result, the entire chip 12 Relaxation of residual thermal strain can be realized.

Further, a large piece 14 constituting the tip 12 is formed on the side of the tip 12 where the tip end portion 15 is located, and the tip end portion 15 is included in the large piece 14, so that the largest tip portion is formed during excavation. The periphery of the tip portion 15 of the tip 12 to which the excavation force is applied has a size (necessary for obtaining a mass effect) and strength that can withstand the excavation force at the time of excavation. Damage can be prevented.

When the width of the small piece 13 is A and the width of the large piece 14 is B, the ratio A: B of the small pieces 13 and the large pieces 14 constituting the two divided chips 12 is as follows. , 1: 7 to 1: 1.5 (In the present embodiment, the width ratio A: B of the width A of the small piece 13 to the width A of the large piece 14 is 1: 2.5. (Shown).

When the width ratio A: B of the width A of the small piece 13 and the width B of the large piece 14 constituting the two-divided chip 12 is larger than 1: 7, the small piece 13 becomes small. At the same time, the large piece 14 becomes too large, so that the thermal distortion remaining in the large piece 14 increases. Conversely, the width A of the small piece 13 and the width B of the large piece 14 are increased. When the ratio A: B is smaller than 1: 1.5, the large piece 14 becomes too small, so that the mass effect is reduced and it becomes impossible to endure a large excavation force.

That is, by setting the width ratio A: B of the width A of the small piece 13 and the width B of the large piece 14 constituting the chip 12 in the range of 1: 7 to 1: 1.5, In addition to reducing the thermal strain remaining in the large piece 14 constituting the drill to the extent that it does not hinder practical use, it has the size and strength necessary to withstand the large excavation force generated during excavation. A casing bit 11 which can achieve both improvement in durability and strength can be obtained.

Then, as described above, the chip 12 constituting the casing bit 11 is divided into two into small pieces 13 and large pieces 14 in the width direction, so that the chip 12 remains on the chip 12 that has been soldered to silver on the shank. By reducing the thermal distortion, it is not necessary to insert a copper plate, a copper wire, a copper net, etc. between the chip 12 and the shank 16 when soldering silver, thereby reducing the processing cost of the casing bit 11. can do.

[0024]

[Effect of the invention]

 As described in detail above, according to the present invention, it is possible to alleviate the residual heat distortion that occurs when the chip constituting the casing bit is soldered to the shank with silver, and at the same time, to achieve excellent durability and strength. Can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a casing bit of the present invention.

FIG. 2 is a front view showing the casing bit of the present invention.

FIG. 3 is a view as seen from an arrow P in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing steel pipe 2 End part of casing steel pipe 3 Drilling blade 4 Holder 5 Fitting part 6 Mounting bolt 11 Casing bit 12 Tip 13 Small chip piece 14 Large chip piece 15 Tip of tip part 16 Shank 17 Tip insertion part 18 Fitting Groove 19 Bolt hole A Width of small chip B Width of large chip

Claims (2)

[Utility model registration claims] 1. A large number of excavating blades 3 provided for a tip portion 2 of a casing steel pipe 1 used for foundation work for civil engineering.
Wherein the casing bit 11 is composed of a tip 12 forming a cutting edge portion and a shank 16 holding the tip 12. 3
In the insert-type casing bit having a surface brazed with silver, the tip 12 is divided into two in the width direction of the tip 12, and the two divided tips 12
A casing bit comprising a chip 3 and a large piece 14, wherein the large piece 14 constituting the chip 12 includes a tip portion 15 of the chip 12. 2. When the width of the small piece 13 and the width of the large piece 14 of the small piece 13 and the large piece 14 constituting the chip 12 divided into two are set to B, the width ratio A: B is 1: 1, respectively. 7 ~
2. The casing bit according to claim 1, wherein the ratio is in the range of 1: 1.5.