Boring or penetrating the earth – Bit or bit element – Cutting edge self-renewable during operation
Patent
1993-03-12
1994-04-12
Novosad, Stephen J.
Boring or penetrating the earth
Bit or bit element
Cutting edge self-renewable during operation
175430, 175432, 175434, E21B 1046, E21B 1062, E21B 1056
Patent
active
053017625
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns an oil or mining drilling too. The base may be a base mounted in the body of the tool, or on a tungsten carbide matrix.
A tool of this kind is disclosed in U.S. Pat. No. US-A-4 844 185. However, the use of a tool of this kind in the difficult conditions prevailing in oil or mine drilling can destroy the cutting edges, by normal wear, by impact subsequent to excess loads, or again, by excessive heating.
When the cutting edges become worn, the surface area in contact with the rock to be drilled is appreciably reduced. To preserve a certain level of effectiveness, greater force must be applied to the tool; there then arises, however, the risk of causing fracture of the cutting edges, as a result of excess load. The fracture is often clean and runs in quite random directions, which may be either advantageous or, to the contrary, harmful. The fracture is advantageously oriented when it originates in the area located just behind the polycrystalline diamond-impregnated layer, in relation to the direction of advance of the cutting edge, and when it forms an acute clearance angle with the surface of the rock formation.
Furthermore, the increased force applied to the tool may cause partial destruction or loss of the cutting edges, through heating.
Patent Nos. U.S. application No. 4 277 106 and GB-A-2055411 disclose a tool fitted with cutting edges comprising hard areas alternating with areas of lesser hardness.
Patent No. EP-A-0 363 313 describes a tool incorporating areas of fracture formed on elements which, by breaking off, allow enlargement of openings for the circulation of a liquid lubricant.
However, none of these patents allows solution of the aforementioned problem, which is that of the fracture of the cutting edges along surfaces whose orientations are advantageous. The present invention is intended to surmount these difficulties by proposing self-sharpening cutting edges, i.e., they can be broken off along surfaces having advantageous orientations, every time that the force applied to the tool exceeds a given threshold.
To this end, the invention relates to a drilling tool of the type specified above and characterized by the fact that the cutting edge and/or its base has formed on it zones of least resistance, such as grooves, which may initiate successive fractures forming an acute angle of clearance with the rock formation to be drilled.
The clearance angle is preferably between 25.degree. and 55.degree..
Other features and advantages of the invention will emerge from the following description, provided with reference to the attached drawings in which:
FIG. 1 is a perspective view of a conventional drilling tool;
FIG. 2 is a perspective view of a cutting edge attached to a base, the groves being formed on both of these elements;
FIGS. 3 to 6 illustrate successive phases of the process for sharpening the cutting edge and base in FIG. 2;
FIGS. 7 to 11 are raised views of several variants of groove formation on the cutting edge and the base.
With reference to FIG. 1, the tool 10 incorporates a steel body 12 supporting, on its lateral wall, a multiplicity of cutting edges 14 arranged in several rows. The tool ends in a threaded portion 16 designed to connect with the rotation-drive casing (not illustrated).
As shown in FIG. 2, each cutting edge 14 is mounted in one end of a substantially cylindrical base 18, whose other end is itself mounted on the body 12. The cutting edge is shaped like a circular plate and comprises a first polycrystalline, diamond-impregnated layer 22, which is fastened, using an appropriate bonding agent, to a second layer 24 made of tungsten carbide.
A number of grooves 26, which can be parallel to each other, are imprinted on the lateral wall of the cutting edge 14 and of the base 18. Each groove comprises two arms (of which one only is visible in FIG. 2), which extend downward from the cutting edge 14 to the base symmetrically in relation to the intermediary plane of the cutting edge, and which meet on the back of the base. Each groove thus delimits a
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Novosad Stephen J.
Total
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