Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Patent
1997-09-11
1999-11-16
Bagnell, David
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
175415, 299100, E21B 1036
Patent
active
059840307
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL BACKGROUND
The present invention relates to a rock drilling tool for percussive drilling comprising a drill bit and a drill tube. The drill bit has a head having a front surface wherefrom a number of front inserts are project and peripheral inserts provided in a peripheral row. The drill bit is provided with a first thread co-operating with a second thread provided on the drill tube. The invention further relates to a drill bit and a method of transferring percussive energy from a rock drilling tool to a bore hole.
It is previously known through U.S. Pat. No. 1,447,855 to provide a so called shoulder abutment at threaded connections between a drill rod and a rock drill bit in equipment for percussive drilling. When loosening the drill bit in the known equipment with a relatively heavy drill bit, there is a risk that the thread entrance on the bit shank will become damaged due to the substantial difference in mass on opposite sides of the shoulder abutment. Furthermore, the known drill bit is provided with chisel edges of hardened steel, which project relatively far in the radial direction. This means that the percussive energy during percussive drilling is forced to deflect towards the radially outer tip of the edge and therefore the effective coefficient of efficiency decreases, thereby resulting in impaired guiding ability and impaired drilling speed. Chisel edges give a relatively slow drilling speed. Furthermore it seems as the known tool can have abutment between the drill rod and bit, both in the radial and axial directions which during drilling create hardening of the material with subsequent crack initiation points.
OBJECTS OF THE INVENTION
An object of the present invention is to provide a method of transferring percussive energy from a rock drilling tool to a drill hole, such as to provide good guidance of the bit, acceptable loads and also a good energy transfer.
Another object of the present invention is to provide a rock drilling tool comprising a rigid connection which does not deflect in spite of difficult angles of attack.
Still another object of the present invention is to provide a rock drilling tool, which has a good, coefficient of efficiency by making the drill bit as light as possible simultaneously as the entrance of the shank is spared, during loosening, due to low bit weight.
Still another object of the present invention is to provide a rock drilling tool, through which connection a good length of life can be achieved simultaneously as the part most frequently changed is easy to handle.
Still another object of the present invention is to provide a rock drilling tool, whose front end of the drill tube does not have a projecting portion and therefore there will be no transport damages.
Still another object of the present invention is to provide an effective rock drill bit.
DESCRIPTION OF THE DRAWING
The objects and advantages of the invention are met by providing a method, a rock drilling tool and a rock drill bit according to the features of the present invention. Below embodiments of the invention will be described in connection with the appended figures.
FIGS. 1 to 4 show a schematical, partly sectioned view of a rock drilling tool according to the invention.
FIG. 5 shows the tool in a top view.
FIGS. 6 and 7 show cross-sections of alternative ends of the female thread.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The rock drilling tool 10 as shown in the figures comprises a rock drill bit 11 and a drill tube 12. The bit 11 has a head 13 provided with a front surface 14, wherefrom a number of front inserts 15 projects, and a peripheral row of peripheral inserts 16, preferably provided with spherical or ballistic working surfaces. The drill bit is provided with a male thread 17, which is provided to cooperate with a female thread 18 on the tube.
The male thread 17, which is provided on a shank 19, is an integral part of the percussive drill bit 11. The drill bit is provided with a shoulder at the inner end of the shank 19, which shoulder has a
REFERENCES:
patent: 1477855 (1923-04-01), Thurston
patent: 4968068 (1990-11-01), Larsson
patent: 5595252 (1997-01-01), O'Hanlon
patent: 5699867 (1997-12-01), Jones
patent: 5794728 (1998-08-01), Palmberg
Beccu Rainer
Larsson Kenneth
Bagnell David
Kang Chi H.
Sandvik AB
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