Boring or penetrating the earth – Bit or bit element – Bit with leading portion forming smaller diameter initial bore
Patent
1992-10-13
1994-02-08
Bui, Thuy M.
Boring or penetrating the earth
Bit or bit element
Bit with leading portion forming smaller diameter initial bore
E21B 1000
Patent
active
052842169
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a down-the-hole drill tool, said drill tool being adapted to drill a hole in advance of a trailing casing tube, said drill tool including a central pilot bit, a reamer means and a guide means for guiding said drill tool and said casing tube relative to one another, and a shaft that is adapted to be connected to a down-the-hole hammer. The invention also relates to a guide means and a one-piece unit being parts of the drill tool according to the present invention.
In known drill tools of the above-mentioned type the thread connection, e.g. between the guide means and the portion supporting the reamer, is the weak point Therefore it is an aim of the present invention to present a structural design of a drill tool of the type in question that avoids thread connections in portions of the drill tool that is subjected to high bending forces Also there is always a loss of energy in thread connections transferring impact energy.
BRIEF DESCRIPTION OF THE DRAWINGS
Below three embodiments of the drill tool according to the invention will be described, reference being made to the accompanying drawings where FIG. 0 discloses a schematic view of a prior art drill tool; FIG. 1 discloses a schematic, partly sectioned, view of an embodiment of the drill tool according to the invention, said FIG. 1A is an exploded view of the reamer and the guide body per se; FIG. 2 discloses a side view of the base member; FIG. 3 discloses a side view of the base member along III--III in FIG. 2; FIG. 4 discloses a section along IV--IV in FIG. 2; FIG. 5 discloses a view along V--V in FIG. 1A; FIG. 6 discloses a schematic, partly sectioned, side view of an alternative embodiment of the drill tool according to the present invention, FIG. 6A is an exploded view of the parts making up the guide body of FIG. 6; FIG. 7 discloses side view of the base member along VII--VII in FIG. 6; FIG. 8 discloses a schematic, partly sectioned, side view of a further alternative embodiment of the drill tool according to the invention; FIG. 9 discloses a schematic, partly sectioned, side view of a further alternative embodiment of the drill tool according to the invention, FIG. 10 discloses a further alternative embodiment of the drill tool according to the invention, and FIG. 11 is a side elevational view of a prior art drill tool.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The prior art drill tool according to FIG. 0 includes guide body I having a shaft II integral with said guide body I and intended to be coupled to a DTH hammer. A pilot bit III is coupled to the guide body I by means of an externally threaded spigot IV that is received in an internally threaded bore V in the guide body I. A reamer VI is rotatably supported by an intermediate portion of the pilot bit III. The guide body I includes a downwardly facing shoulder VII which pushes a casing VIII downward.
The most frequent damage appearing on said prior art tool is a thread fracture on the upper part of the spigot IV. Therefore, as stated above the aim of the present invention is to delete said thread coupling between the shaft II and the pilot bit III.
The embodiment according to the present invention of the drill tool according to FIG. 1 includes a base member 10 disclosed separately in FIGS. 2 to 4. Said base member 10 comprises a shaft 11 and a pilot bit 12, said shaft 11 and pilot bit 12 constituting an integral unit.
The shaft 11 includes a bearing portion 13 that supports a reamer 14 having a varying wall thickness along its circumference. Said reamer 14 is rotatable a limited angle relative to the shaft 11. In FIG. 1 the reamer 14 is disclosed in its working position, i.e. the reamer 14 will generate a hole diameter that allows a casing tube 15 to advance downwards together with the drill tool. By rotating the drill tool in a direction opposite to its working direction the reamer 14 will rotate a limited angle relative to the bearing radially retracted portion 13 and assume a position that makes it possible to pull
REFERENCES:
patent: 3367430 (1968-02-01), Rowley
patent: 3416616 (1968-12-01), Ahlgren
patent: 4440244 (1984-04-01), Wiredal
patent: 4618010 (1986-10-01), Falgout, Sr. et al.
patent: 4763737 (1988-08-01), Hellnick
Asberg Bengt
Brungs Anders
Hedlund Jan-Gunnar
Jansson Kjell-Ove
Bui Thuy M.
Sandvik AB
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