Boring bit and boring casing

Abstract

 A boring bit 2 includes a cutter 24 which is in contact with the face of the ground to be bored to substantially conduct crushing of the ground and a shank 20 for holding the cutter 24. The cutter 24 comprises a disk-shaped cutter main body 24A, and journals 24B which are formed integrally with and on the opposite sides of the cutter main body 24A. Only a boring blade 24a projects beyond the distal end of the shank 20. The cutter 24 is rotatable born by the journals 24B. The wear of chip is less in comparison with the prior art chip. Extension of life time of the chip is achieved.

Description

BACKGROUND OF THE INVENTION

a) Field of the Invention

[0001] The present invention relates to a boring bit which is mounted on boring machines such as auger boring machines, all casing boring machines or multiaxial boring machines and in particular to a boring bit and a boring casing using the same for boring mainly hard rock such as large gravel, cobble stone to achieve extension of service life as well as enhancement of the boring efficiency.

b) Description of the Related Art

[0002] Various methods of boring have recently been developed to meet the requirements of reduced noise and vibration on foundation working for civil or building structures. Among them, auger and all casing methods are expected to be feasible. The auger methods are mainly classified into earth auger method in which boring is conducted by rotating in a given direction an auger screw 50 (shown in Fig. 5) on which bits 51 made of cemented carbide are mounted at its tip end; a donut auger method in which a casing 52 on which bits 53 are mounted on its tip end is disposed around the auger screw 50 as shown in Fig. 6 and the auger screw 50 and casing 52 are rotated in opposite directions for penetrating into the ground for boring; and a separate auger method in which the above-mentioned auger screw 50 and the casing 52 are independently rotated depending upon the kind of ground formation.

[0003] However, it is difficult for these methods to bore hard rock layers including large gravel and cobble stone. Accordingly, the above-mentioned all casing method has been developed for boring in particular had rock layers. In this method, soil is discharged with a hummer grab 54 simultaneously with boring with the casing as shown in Fig.7. Currently, this method is dominantly conducted in civil and construction working in urban areas.

[0004] The boring bit 55 which is mounted on the auger screw 50 and casing 52 at the tip end thereof comprises a chip 57 which is buried in a shank 56 as shown in Fig. 8. The bits 55 are mounted on the auger screw 50 or casing 52 at the tip end thereof by means of welding or bolts.

[0005] Development of chips for boring bit 55 having an excellent boring efficiency, a high wear resistance and an extended service life has been made for many years. However, bits which overcome the problems encountered in boring of hard rock layers including large gravel and cobble stone have not yet been put into market as products. The wear of chips is still so high that the chip may have to be exchanged within one or two days. Since development of chips having a remarkably long life can not be currently expected, various shapes of bits such as saddle shape, insertion type or cylindrical shape as shown in Figs. 9(A) to (C) ( quoted from brochure of Toshiba Tungalloy K.K.) for ease of exchange.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to provide a boring bit and a boring bit using the same which has a high wear resistance, extended period of life and increased boring efficiency even if they are used for boring hard rock layer including large gravel and cobble stone.

[0007] In order to achieve the above mentioned object, the present Invention provides a boring bit mounted on a ground boring machine, comprising a cutter which is brought into contact with the face of the ground to be bored for substantially conducting crushing of the groun d and a shank for holding said cutter, said cutter being held at the distal end of said shank so that it is rotatable around its rotation axis.

[0008] In this case, said cutter may be preferably provided within the shank in such a manner that only its boring blade projects outwardly beyond the distal end of the shank.

[0009] Said cutter may preferably comprise a disc-shaped cutter main body and journals which are integrally formed with the opposite sides of the cutter main body.

[0010] The boring bit may further include a blade having a wedge-shaped section, which is integral with the outer periphery of said disc shaped cutter main body.

[0011] The boring blade of said cutter may comprise a plurality of buried blades which are buried in the outer periphery of said disk shaped cutter main body at a given space. Since in the this case, only the blade which is buried in the cutter main body is required to replace if the blade is worn, working efficiency can be enhanced.

[0012] The range in which the present invention can be applied is not particularly limited. Since line cutting is carried out along the cutter locus, the present invention is most preferably applied to a boring casing in which cutting is carried along the circular contour of the tube wall.

[0013] The boring bits which are mounted on ground boring machine such as auger, all casing and multiaxial boring machines always comprise chips which are buried in the tip end of a billet type shank. In the present invention, the cutter at the tip end of a shank in this type of boring bit comprises a rotary blade to provide an extended life time of the bit. In the prior art chip fixed bit, wear of the bit is very high since high shearing forces, bending moments and/or frictional forces are always applied to the chip. In contrast to prior art, the blade is contact with the face of ground to be bored while being rotated due to the fact that the blade is rotatable. Therefore, the wear is remarkably reduced, achieving the enhancement in boring efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 

Fig. 1 is a schematic view showing a manner of boring which is conducted by a full rotation all casing method;

Fig. 2 is a longitudinal sectional view showing a bit of the present invention;

Fig. 3 is an enlarged view showing a blade tip of a rotary cutter 24;

Fig. 4 is an enlarged view showing a blade tip of another rotary cutter 24;

Fig. 5 is a view showing a manner of boring which is conducted by a prior art earth auger method;

Fig. 6 is a view showing a manner of boring which is conducted by a prior art donut auger method;

Fig. 7 is a view showing a manner boring which is conducted by a prior art all casing method;

Fig. 8 is an elevational view showing a prior art boring bit; and

Figs. 9(A) to 9(c) are views showing the manner in which prior art bits are mounted.

BEST MODE FOR EMBODYING THE INVENTION

[0015] Referring now to Fig. 1, there is shown a manner of boring which is conducted by a peripheral full rotation all casing method.

[0016] In the entire peripheral rotation all casing method, a casing 1 in which a multiplicity of boring bits 2 (hereinafter referred to as "bit") spaced at given spaces along the periphery of a tube are mounted on the tip end of the tube having an outer diameter corresponding to the inner diameter of a bore to be bored is penetrated into the ground while it is rotated around its central longitudinal axis in a given direction by means of a casing driver (not shown) on the ground and the sand and mud within the tube is discharged by a hummer grab 3 which is suspended by a crane while achieving protection of the bore wall as shown in Fig. 1. The present invention may be preferably applied to the bit 2.

[0017] As shown in Fig. 2, each of the bits 2 mainly comprises a rotary cutter 24 which is in contact with the boring face for substantially crushing it and a shank 20 which is a member for rotatably holding the rotary cutter 24 and for mounting the cutter 24 on the casing 1.

[0018] The shank 20 has a slit groove 21 extending in its longitudinal direction on the base side thereof, which is defined between two opposing bracket pieces 22A and 22B. A bolt hole 22a is formed through two bracket pieces 22A, 22B. The bracket pieces 22A, 22B are fitted into notches 1a which are formed on the inner and outer sides of the tip end portion of the casing 1. Then, the shank 20 is firmly secured to the casing 1 by fastening a bolt (not shown) which is inserted into the bolt hole 22a. Alternatively, the bits 2 may be secured to the tip end of the casing 1 by welding and the like.

[0019] The bit 2 is formed on the distal end side thereof with an opening 23e through which a blade 24a of a rotary cutter 24 extends outwardly. The bit 2 is further formed on more inner side thereof with a bearing space 23 which is in communication with the opening 23c and is also formed in more inner position thereof with a blade space 23b which is in communication with the space 23. The bearing space 23 enables the rotary cutter 24 to be rotatably born.

[0020] The rotary cutter 24 is provided within the shank 20 in such a manner that the boring blade 24a projects externally beyond the distal end of the shank 2. The rotary cutter 24 comprises a cutter main body 24A which is in the form of disc and journals 24B which are formed on and integrally with the both sides of the cutter main body 24A.

[0021] The bearing which defines the bearing space 23 is formed on the inner surface thereof with convex ribs 23a having a semi-circular section extending in a peripheral direction. The journals are formed with recesses 24b having a semi-circular section. Mating of the ribs 23a into the recesses 24b enables the rotary cutter 2 to be rotatably born on the bearing at a less rotational friction. Suitable lubricants such as solid or liquid lubricant may be used.

[0022] The blade structure of the cutter main body 24A of the rotary cutter 24 may include a peripherally extending tip 25 having a wedge-shaped section, which is integrally buried in the outer periphery of the cutter main body 24A as shown in Fig. 3 or may include buried blades 26 having their base portions in holes 24 which are spacedly formed along the outer periphery of the cutter main body 24A as shown in Fig. 4. The chip shape of the buried blade 26 may be semi-spherical as shown in the drawing, chisel-shaped, bulletin-shaped, or double cone-shaped. These chips are changed depending upon the rocks to be bored.

[0023] Although only an embodiment in which one disk shaped cutter main body 24A is provided, that is single type cutter is illustrated, it is to be understood that other cutter structures such as a structure in which two cutter main bodies 24A are provided, that is, a double disk type cutter structure or a structure having two or more cutter blades may be used. Although only one embodiment which is used for the casing 1 for all casing method has been described, it is to be understood that the present invention may be applied to tip bits of an auger screw of auger boring machines, multiaxial boring machines or rod tip bit of a large diameter boring machines.

[0024] As mentioned above in detail, the boring bit of the present invention has a high wear resistance of the chip in comparison with the prior art and achieves the extension of the service life of the bit even if it is used for boring of hard rock layer including large gravel and cobble stone, resulting in an enhanced boring efficiency.

Claims

1. A boring bit mounted on a ground boring machine, comprising a cutter which is brought into contact with the face of the ground to be bored for substantially conducting crushing of the groun d and a shank for holding said cutter, said cutter being held at the distal end of said shank so that it is rotatable around its rotation axis.

2. A boring bit as defined in Claim 1 in which said cutter is provided within the shank in such a manner that only its boring blade projects outwardly beyond the distal end of the shank.

3. A boring bit as defined in Claim 1 or 2 in which said cutter comprises a disc-shaped cutter main body and journals which are integrally formed with the opposite sides of the cutter main body.

4. A boring bit as defined in Claim 3 and further including a blade having a wedge-shaped section, which is integral with the outer periphery of said disc shaped cutter main body.

5. A boring bit as defined in Claim 3 in which the boring blade of said cutter comprises a plurality of buried blades which are buried in the outer periphery of said disk shaped cutter main body at a given space.

6. A boring casing on which a multiplicity of boring bits as defined in any one of Claims 1 to 5 are mounted.

Drawing