Boring or penetrating the earth – Bit or bit element – Impact or percussion type
Patent
1993-09-27
1994-10-25
Neuder, William P.
Boring or penetrating the earth
Bit or bit element
Impact or percussion type
E21B 1038
Patent
active
053580630
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a rock drill bit, preferably a down-the-hole drill bit, said drill bit including a head and a shaft, said head defining a cutting face and carrying a number of hard material button inserts having end portions extending outwardly of said cutting face, means for transporting flushing medium from the free end of the shaft to the cutting face of the head.
In the field of down-the-hole drill bits large volumes of flushing medium, normally compressed air, are used since the flushing medium is also activating the down-the-hole hammer, said hammer demanding large volumes of flushing medium, normally compressed air, to achieve a sufficient penetration rate. Those large volumes provide erosion of the cutting face since the flushing medium has a very high speed when passing the front face of the drill bit. Said erosion creates problems when so much material, usually steel, of the cutting face has been eroded away that the button inserts are lost before they are worn out.
OBJECTS AND SUMMARY
An aim of the present invention is to present a drill bit that has a longer life due to less erosion of the cutting face of said drill bit.
BRIEF DESCRIPTION OF THE DRAWINGS
Below embodiments of the invention will be described, reference being made to the accompanying drawings where
FIG. 1 shows a partly sectioned side elevation of a drill bit according to the present invention;
FIG. 2 shows a top view of a cutting face of a drill bit according to prior art;
FIG. 3 shows a top view of a cutting face of a drill bit according to the present invention;
FIG. 4 shows in section a detail of a branch passage of the drill bit according to FIGS. 1 and 3;
FIG. 5 shows a partly sectioned side elevation of a an alternative embodiment of a drill bit according to the present invention;
FIG. 6 shows a top view of a cutting face of a drill bit according to prior art;
FIG. 7 shows a top view of a cutting face of a drill bit according to the present invention; and
FIG. 8 shows in section a detail of a branch passage of the drill bit according to FIGS. 5 and 7.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In the figures corresponding details have been given the same reference numerals.
The drill bit 10 according to FIG. 1 includes a head 11 and a shaft 12 connected to the head 11. The shaft 12 has a surface 13 at its free end, said surface 13 receiving strikes from a piston of a down-the-hole hammer (not shown).
The head 11 defines a cutting face 14 having a number of hard material button inserts 15 with end portions extending outwardly of said cutting face 14. As can be seen in FIG. 3 the cutting face 14 has a central planar portion 14a and a bevelled portion 14b surrounding said central portion 14a.
A central passage 16 for flushing medium extends from the surface 13 of the shaft 12 well into the head 11 where said central passage 16 terminates. A number of branch passages 17 emanates from the central passage 16 and diverge outwardly to emerge in the cutting face 14. At a certain distance L from the cutting face 14 the cross-sectional area of the branch passages 17 increases in direction towards the cutting face 14. The shape of said increasing cross-sectional area is not critical and it may also vary along the axial direction of said branch passage 17. In the shown embodiment the branch passage 17 has a circular cross-sectional area closest to the central passage 16 while the increasing cross-sectional area is oval. Preferably the cross-sectional area is continuously increasing from the region of the central passage 16 to the region of the cutting face 14.
In FIG. 2 a is shown the cutting face of a down-the-hole drill bit having a branch passage with a constant circular cross-sectional area, i.e. in accordance with prior art. However, in the top view of FIG. 2 the branch passage is slightly oval due to the fact that the branch passage is inclined to the longitudinal center axis of the drill bit.
In FIG. 3 is shown the cutting face 14 of a down-the-hole drill bit 10 according
REFERENCES:
patent: 1577244 (1926-03-01), Brown
patent: 3995707 (1976-12-01), Herke
Asberg Bengt
Hedlund Jan-Gunnar
Neuder William P.
Sandvik AB
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