WO2012052597A1

WO2012052597A1 - Method in earth drill bit arrangement assembly and a bit arrangement

Info

Publication number: WO2012052597A1
Application number: PCT/FI2010/050809
Authority: WO
Inventors: Veli-Pekka Immonen; Heikki Saariluoma
Original assignee: Laserplus Oy
Priority date: 2010-10-18
Filing date: 2010-10-18
Publication date: 2012-04-26

Abstract

The object of the invention is a method in an earth drill bit arrangement assembly and a bit arrangement. In the method at least the outer bit (3) of an earth drill is connected to a casing shoe (2) functioning as a coupling ring such that the outer bit (3) can be rotated in relation to the casing shoe (2) and can be moved a limited distance in the axial direction in relation to the casing shoe (2). For coupling the outer bit (3) to the casing shoe (2), the outer bit (3) is assembled, in connection with the coupling, from two essentially ring-like parts (3a, 3b) disposed consecutively in the axial direction of the drill.

Description

METHOD IN EARTH DRILL BIT ARRANGEMENT ASSEMBLY AND A BIT ARRANGEMENT

The object of the invention is a method as defined in the preamble of claim 1 in the assembly of an earth drill bit arrangement and an earth drill bit arrangement as defined in the preamble of claim 10.

More precisely, the solution according to the invention relates to the installation of a casing shoe as a coupling ring on top of a ring-like outer bit of an earth drill, said outer bit making a rotating and percussive movement, such that the outer bit can rotate around its center axis and move axially in relation to the casing shoe, which axial movement pulls the protective tube fixed to the rear edge of the casing shoe into the borehole. In the following all directions and comparisons of direction are given starting from the tip of the drill. Thus the part of a piece closer to the tip of the drill is a front part, front edge, front surface or front side, while the part of a piece farther away from the tip of the drill is a rear part, rear edge, rear surface or rear side.

European patent no. EP1144797 Bl presents one method according to prior art and generally in use for installing a casing shoe on top of a ring-like outer bit of an earth drill. Before installation the casing shoe is conical such that the casing shoe can be pushed partly on top of the outer bit at the point of a ring-like groove in the outer surface of the outer bit and past the shoulder forming the groove. After this the casing shoe and the outer bit are pressed into a conically shrinking tool, with which compression is produced, which compression shrinks the larger diameter of the conical casing shoe such that the casing shoe locks inwards at its ring-like shoulder into the ring-like groove in the outer surface of the outer bit. A problem in this solution is that it is necessary to use an expensive compression tool, apart from which as many of these tools are needed as there are different diameter dimensions. Another problem is that a casing shoe must withstand axial impacts and for this reason the material of the casing shoe is hard and difficultly weldable at the worksite. At the worksite a protective tube is welded onto the casing shoe. The hard material also causes problems in the shrinking phase. From United States patent no. US5,839,519 another generally used method is known for installing a casing shoe on top of a ring-like outer bit of an earth drill. In this solution also the outer rim of the outer bit again has a ring-like groove, into which the shoulder that is on the inner rim of the casing shoe and that extends inwards is locked. Before installation the casing shoe consists of two identical halves, which are placed on top of the outer bit and welded fast to each other, into a continuous ring, with two longitudinal welded seams. One problem is the making of the ring from two halves. In this case the assembly phase is laborious and the thermal stresses produced by welding might deform the casing shoe. If the casing ring is out-of- round after welding, the defective shape must be rectified, but it is extremely difficult when the casing ring is already on top of the outer bit.

A common problem to all prior-art joints of the outer bit and the casing shoe of a percussive earth drill is that owing to the hammer action both the outer bit and the casing shoe must be through-hardened. The front part of the outer bit must also be hardened such that the wolfram studs, or corresponding studs that resist wear well, on the front surface of the bit would, in practice, remain in place. A preform for hardening is expensive, in which case a lot of expensive material is wasted in machining. Additionally, a material hardened to be hard is not necessarily tough enough, in which case the torque- transmitting parts of the unnecessarily hardened rear parts of both the outer bit and the casing shoe might break more easily than rear parts made of a tougher material.

The aim of the present invention is to eliminate the above- mentioned drawbacks and achieve an inexpensive and reliable method in the assembly of the bit arrangement of an earth drill as well as an inexpensive, operationally reliable and durable bit arrangement of an earth drill, in which bit arrangement the material selection for the different parts of the bit arrangement could be optimized to be that desired. The method according to the invention is characterized by what is presented in the characterization part of claim 1. Correspondingly, the bit arrangement according to the invention is characterized by what is disclosed in the characterization part of claim 10. Other embodiments of the invention are characterized by what is disclosed in the other claims.

One advantage of the solution according to the invention is that expensive bloom material can be saved, because e.g. the rear part of the outer bit, being smaller in diameter, can be made from a smaller bloom than the front part, which is larger in diameter. Another advantage is that different materials can be used in different parts of the outer bit. Thus expensive, hard and wear-resistant material is needed only in the front part of the outer bit and correspondingly the rear part can be made from cheaper material and at the same time the durability of the material can be optimized by making the rear part from tough material, which withstands torque well. Exactly the same can be done in relation to the materials of the casing shoe. The whole casing shoe does not need to be of expensive and hard material, but instead in this case also the rear part can be made of tough and cheaper material. Toughness of the rear parts improves durability and thereby increase the boring depth e.g. when drilling rock. A particular advantage is that when the joining of the rear parts and front parts of the casing shoe and/or of the outer bit to each other is done as laser welding, a reliable and durable end result that does not need secondary treatment is obtained. In addition, the laser welding needed can be performed from also a small gap.

In the following, the invention will be described in greater detail by the aid of some embodiments and by referring to the attached simplified drawings, wherein Fig. 1 presents a partially sectioned side view of a drilling head of one earth drill according to the invention,

Fig. 2 presents a side view of a cross-section of a casing shoe on a drilling head according to Fig. 1,

Fig. 3 presents a side view of a cross-section of the rear part of an outer bit on a drilling head according to Fig. 1,

Fig. 4 presents a side view of a cross-section of the front part of an outer bit on a drilling head according to Fig. 1,

Fig. 5 presents a side view of a cross-section of a casing shoe on a drilling head according to Fig.

1, said casing shoe being connected to the outer bit, and

Fig. 6 presents a side view of a cross-section of another solution according to the invention, wherein the casing shoe is connected to the outer bit. Fig. 1 presents a partially sectioned side view of a drilling head 1 of one earth drill according to the invention, which drilling head comprises at least a ring- like casing shoe 2 functioning as a coupling ring, a ringlike outer bit 3 drilling the outer rim of the hole and a plug-shaped inner bit 4, together with bayonet detent protrusions 4e and stem 5, said inner bit drilling the center of the hole. In addition, Fig, 1 shows the tubular percussion hammer 5a acting on the inner bit 4 and the protective tube 6 fixed with a welded joint 6a to the rear edge of the casing shoe 2.

When the drilling head 1 is assembled, the outer bit 3 is installed inside the casing shoe 2 and the inner bit 4 is fixed to the outer bit 3 by the aid of a bayonet or other corresponding detachable fixing method. In addition, the protective tube 6 is fixed to the rear edge of the casing shoe 2 and the percussion hammer 5a is connected to the rear surface of the inner bit 4 on top of the shaft 5 of the inner bit. The rotational movement of the inner bit 4 transfers torque via the bayonet to the outer bit 3, which thus rotates along with the inner bit 4. In addition, the impact of the hammer 5a acting on the rear surface of the inner bit 4 produces axial movement, which pushes the inner bit 4 forwards and pulls the outer bit 3 and at the same time the protective tube 6, conveyed by the casing shoe 2, forwards in the hole to be drilled.

Fig. 2 presents a cross-section of a casing shoe 2 functioning as a coupling ring. The rear part of the casing shoe 2 is a ring-like stem part 2a of essentially even thickness, the front edge of which comprises a ring-like locking shoulder 2b extending inwards, the rear edge of which locking shoulder comprises a detent surface 2c in the transverse direction with respect to the axial direction of the casing shoe 2 and pointing towards the rear, which detent surface is arranged to receive axial impacts from the outer bit 3. The front edge 2d of the casing shoe 2 is beveled on its inside surface.

Fig. 3 presents the first part, i.e. the coupling part 3a, being the rear part, of the outer bit 3 according to the invention, which part is essentially ring-like in structure. The rear edge of the coupling part 3a comprises a bayonet coupling arrangement, which comprises at least two or more bayonet grooves 3d and bayonet claws 3e, being at regular intervals to each other. In addition, the outer rim of the coupling part 3a has a shoulder 3j , which comprises a detent surface 3c in the transverse direction with respect to the axial direction of the coupling part 3a and pointing towards the front, which detent surface is arranged at least to give axial impacts to the casing shoe 2 by striking the casing shoe 2 pushed by the inner bit 4 in the opposite direction to the detent surface 2c. In front of the detent surface 3c is a ring-like groove 3f for limiting axial movement of the coupling part 3a. The front edge 3h of the coupling part 3a is intended to be fixed to the rear surface 3i of the drilling part 3b presented in Fig. 4. Fig. 4 presents the second part, i.e. the drilling part 3b, being the front part, of the outer bit 3b according to the invention, which part is also essentially ring-like in structure, and to the front surface of which a plurality of wolfram studs, or corresponding boring studs 3g that resist wear well, is fixed. The internal diameter of the drilling part 3b is essentially the same as the internal diameter of the coupling part 3a, but its largest external diameter is larger than the largest external diameter of the coupling part 3a. The drilling part 3b is manufactured from hard metal that is very resistant to wear and is additionally hardened.

Fig. 5 presents one solution according to the invention for connecting the outer bit 3 to the casing shoe 2. Since the internal diameter of the detent surface 2c of the locking shoulder 2b in the casing shoe 2 is smaller than the external diameter of the detent surface 3c of the coupling ring 3a and the largest external diameter of the drilling part 3b, the whole outer bit 3 cannot be made to fit inside the casing shoe 2 past the locking shoulder 2b. In the solution according to the invention the outer bit 3 is made from two consecutive and concentric ring-like parts, i.e. from the coupling ring 3a and from the drilling part 3b to be fixed to the front side of it.

The coupling to the casing shoe 2 is performed e.g. such that the coupling ring 3a is pushed from the rear into the casing shoe 2 such that the front edge 3h of the coupling ring 3a extends past locking protrusion 2b and to outside the front edge 2d of the casing shoe 2. After this the rear surface 3i of the drilling part 3b is positioned concentrically with the front surface 3h of the coupling ring 3a and the surfaces are pressed against each other. The joining is then performed e.g. as laser welding from the gap 8 between the casing shoe 2 and the drilling part 3b, which gap remains sufficiently large owing to the dimensioning. The coupling can be done by welding also from inside the outer bit 3. In Fig. 5 the coupling ring 3a and the drilling part 3b are joined together with a laser- welded seam 7.

Fig. 6 presents a second solution according to the invention for connecting the outer bit 3 to the casing shoe 2. In this solution both the casing shoe 2 and the outer bit 3 are made from two consecutive and concentric ringlike parts. If the procedure is now that the parts of the casing shoe are first joined to each other, then the joint of the outer bit 3 is made, as described above in the case according to Fig. 5.

If, on the other hand, the parts of the outer bit 3 are first joined together, the joining can take place outside the casing shoe 2, but such that the detached locking shoulder ring 2b of the casing shoe 2 is placed ready on top of the coupling ring 3a and in front of the countersurface 3c. In this case the coupling ring 3a is pushed in the axial direction partly through the locking shoulder 2b, until the front edge 3h of the coupling ring 3a comes out from the front edge 2d of the locking shoulder 2b of the casing shoe 2. After this the joint 7 of the outer bit 3 itself is made by laser welding from the same parts as in the case according to Fig. 5. When the parts 3a and 3b of the outer bit 3 are welded together, the stem part 2a of the casing shoe 2 can be joined with the locking shoulder 2b. In this case the stem part 2a of the casing shoe is first placed on top of the coupling ring 3a of the outer bit 3 and centered with the locking shoulder 2b, and also the rear surface of the locking shoulder 2b and the front surface of the stem part 2a are pressed against each other and the parts are welded fast to each other with a laser-welded seam 9.

In the joining, the joining sequence can also be different. When the locking shoulder 2b of the casing shoe 2 is on top of the coupling ring 3a of the outer bit 3, it is also possible to proceed so that the parts 2a and 2b of the casing shoe 2 are welded together first and only after this are the parts 3a and 3b of the outer bit 3 welded. It is common to all the manufacturing methods that different materials to each other can be used in the different parts of the outer bit 3 and/or of the casing shoe 2. In this case expensive, hard and wear-resistant material is needed only in the drilling part 3b of the outer bit 3 and correspondingly the coupling part 3a can be made from cheaper material and at the same time the durability of the material can be optimized by making the coupling part 3a from tough material, which withstands torque well. Exactly the same can be done in relation to the materials of the casing shoe 2. The whole casing shoe 2 does not need to be of expensive and hard material, but instead in this case the stem part 2a can be made of tough, better-weldable and cheaper material than a ring-like locking shoulder 2b made of hard material and that is to be hardened.

It is obvious to the person skilled in the art that different embodiments of the invention are not only limited to the examples described above, but that they may be varied within the scope of the claims presented below. Thus, for example, also other welding methods can be used instead of laser welding, e.g. conventional welding, friction welding, electronic beam welding, et cetera.

It is further obvious that the fixing of the inner bit to the outer bit can be different to the bayonet fixing presented above. The fixing method can be any detachable fixing whatsoever, owing to which the inner bit can be pulled out of the borehole after the drilling work has ended. It is further obvious that, instead of the bayonet fixing presented above, the fixing of the inner bit to the outer bit can be such that the inner bit can be brought forwards past the outer bit. In this case the outer bit can be left in place and the hole can be drilled further with the inner

Claims

1. Method in an earth drill bit arrangement assembly, in which method at least the outer bit (3) of an earth drill is connected to a casing shoe (2) functioning as a coupling ring such that the outer bit (3) can be rotated in relation to the casing shoe (2) and can be moved a limited distance in the axial direction in relation to the casing shoe (2), characterized in that for coupling the outer bit (3) to the casing shoe (2), the outer bit (3) is assembled, in connection with the coupling, from two essentially ringlike parts (3a, 3b) to be disposed consecutively in the axial direction of the drill.

2. Method according to claim 1, characterized in that, in connection with the coupling, the first part (3a) of the outer bit (3) is pushed in the axial direction at least partly through the locking shoulder (2b) of the casing shoe (2), until the front edge (3h) of the first part comes out from the front edge (2d) of the locking shoulder (2b) and when it comes out the second part (3b) of the outer bit (3) is fixed to the edge (3h) by welding.

3. Method according to claim 1 or 2, characterized in that, in connection with the coupling, the first part (3a) of the outer bit (3) is pushed in the axial direction partly through the casing shoe (2) at least until the front edge (3h) of the first part comes out from the front edge (2d) of the locking shoulder (2b) of the casing shoe (2) and when it comes out the second part (3b) of the outer bit (3) is fixed to the edge (3h) by welding.

4. Method according to claim 1, 2 or 3, characterized in that the joining of the first part (3a) and the second part (3b) of the outer bit (3) is performed as laser welding from the gap (8) between the casing shoe (2) and the second part (3b) of the outer bit (3) .

5. Method according to any of the preceding claims, characterized in that the second part (3b) of the outer bit (3) is made of harder material than the first part (3a) .

6. Method according to any of the preceding claims, characterized in that the first part (3a) of the outer bit (3) is made of tougher material than the second part (3b) of the outer bit (3) .

7. Method according to any of the preceding claims, characterized in that the casing shoe (2) is assembled from two consecutively placed and essentially concentric ringlike parts (2a, 2b) , such that the ring-like part (2b) that is the locking shoulder is first disposed on top of the first part (3a) of the outer bit (3), after which either the parts (3a, 3b) of the outer bit (3) are first welded together and only then the parts (2a, 2b) of the casing shoe (2), or vice versa.

8. Method according to claim 7, characterized in that the second part (2b) of the casing shoe (2) is made of harder material than the first part (2a) .

9 Method according to claim 7 or 8, characterized in that the first part (2a) of the casing shoe (2) is made of tougher and better weldable material than the second part (2b) .

10. Earth drill bit arrangement, which comprises at least an essentially ring-like outer bit (3) of the earth drill, which outer bit is connected to a casing shoe (2) functioning as a coupling ring such that the outer bit (3) can be rotated in relation to the casing shoe (2) and can be moved a limited distance in the axial direction in relation to the casing shoe (2), characterized in that the outer bit (3) is assembled, in connection with the coupling, to the casing shoe (2), from two essentially ring-like parts (3a, 3b) that are consecutive in the axial direction of the drill.

11. Bit arrangement according to claim 10, characterized in that the front edge (3h) of the first part of the outer bit (3) is, in connection with the coupling to the casing shoe

(2) , fixed to the rear surface (3i) of the second part (3b) of the outer bit (3) by welding.

12. Bit arrangement according to claim 10 or 11, characterized in that the joining of the first part (3a) and the second part (3b) of the outer bit (3) is performed as laser welding by welding a seam (7) from the gap (8) between the casing shoe (2) and the second part (3b) of the outer bit (3) .

13. Bit arrangement according to claim 10, 11 or 12, characterized in that the second part (3b) of the outer bit

(3) is made of harder material than the first part (3a).

14. Bit arrangement according to any of claims 10-13 above, characterized in that the first part (3a) of the outer bit (3) is of tougher material than the second part (3b) .

15. Bit arrangement according to any of claims 10-14 above, characterized in that the casing shoe (2) is assembled, in connection with the coupling of the outer bit (3) and the casing shoe (2), from two consecutively placed and essentially concentric ring-like parts (2a, 2b) , of which the second part (2b) , being the locking shoulder, is made of harder material than the first part (2a) , which is the stem part (2a) .

16. Bit arrangement according to claim 15, characterized in that the first part (2a) of the casing shoe (2) is made of tougher and better weldable material than the second part (2b) of the casing shoe (2) .