Signals and indicators – Indicators – Element wear type
Utility Patent
1998-10-30
2001-01-02
Bennett, G. Bradley (Department: 2859)
Signals and indicators
Indicators
Element wear type
C175S039000
Utility Patent
active
06167833
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to rotary drilling tools such as drilling bits for drilling sub-surface formations although the invention is not limited to such and may find application in other types of rotary drilling tools used above ground.
2. Description of Related Art
As is well known, a drill bit for drilling sub-surface formations can comprise a steel core around which the main part of the bit body, providing its leading face, is formed such as by a powder metallurgy process. In this process the steel core is located in an appropriately shaped mould which is then packed with particulate matrix-forming material which may be powdered tungsten carbide. Pieces of suitable copper or other alloy are then placed above the packed particulate material and the whole assembly is placed in a furnace so that the alloy fuses and infiltrates downwardly through the carbide particles so as to form, upon cooling, a solid body of infiltrated matrix material in the shape of the mould. The abrasive particles with which the matrix material is impregnated commonly comprise superhard materials such as diamond particles.
Other types of rotary drill bits are also comprised of a bit body for attaching to a source of rotary movement such as a power-operated chuck, and having leading edges for cutting, abrading or reaming of a relatively hard material.
Whatever the construction of the rotary drill bit, a problem with such is that due to their construction the measurement of wear on the external surface is inherently difficult to determine so that as the bit is used and then re-used the risk of failure due to wear becomes progressively greater. Since the failure of a drill bit must be avoided at all costs it is often preferred to discard such drill bits at a relatively early stage rather than take the risk of failure even though the drill bit may, in reality, still be well within acceptable limits in terms of wear so that it is discarded unnecessarily.
It is an object of the present invention to provide a wear indicator for rotary drilling tools such as drilling bits, core bits, reamers and undereamers, etc. in which the aforementioned disadvantages are obviated and by which the rate of wear can be easily and conveniently determined by visual inspection of the tool.
SUMMARY OF THE INVENTION
According to a first aspect of the invention there is provided a rotary drilling tool comprising a bit body having a leading surface for cutting, abrading or reaming a hole in a target substrate material such as a sub-surface formation, wherein at least part of the bit body and/or leading surface comprises or includes one or more discrete areas of a visually distinct material to that from which the drilling tool is mainly composed, the visually distinct material being arranged or configured at or adjacent the surface of the bit such that progressive wear of the bit and hence the or each visually distinct material provides a visual indication of surface wear.
Preferably, the relatively visually distinct material is embedded in outer surface portions of the bit in a graduated manner so as to indicate the level of wear thereof, such as in a step formation with the exposure of each step indicating the progression of wear in the bit.
Alternatively, the visually distinct material may be wedge-shaped with the apex of the wedge pointing outwards relative to the axis of rotation of the drill bit so that initially the thin end of the wedge is at or adjacent the surface of the drill bit and as where progresses the worn edge of the wedge becomes progressively thicker larger or longer, thereby indicating the extent of wear. In a further alternative construction the wedge shaped visually distinct material may point inwardly relative to the axis of rotation of the drill bit so that as wear progresses the worn edge becomes progressively thinner, shorter or smaller.
Advantageously, where the visually distinct material is embedded into one or more outer surface portions of the bit the size and shape thereof may correspond with the depth of wear so that if, for example, the visually distinct material is wedge shaped with the wedge subtending an angle of 45°, the increasing length of the worn end of the wedge corresponds to the wear depth of the drill bit.
Since the primary purpose of the invention according to the first aspect is to make the assessment of wear in a drilling tool very simple by reference solely to the visual indication of wear on the or each discrete areas of visually distinct material, it will be apparent that any suitable material can be used for this purpose, provided it is visually distinct from the material from which the drilling tool is mainly composed and, by way of example only, such visually distinct material may be stainless steel, brass, aluminium, tungsten, graphite, ceramic, etc.
According to a second aspect of the invention there is provided a method of indicating wear on the outer surface of a rotary drilling tool, such as a drill bit, the method including the steps of providing one or more areas of a visually distinct material to that from which the drilling tool is mainly composed, the visually distinct material being arranged or configured at or adjacent the surface of the bit, and as wear proceeds measuring the amount of visually distinct material visible at the surface of the tool to thereby indicate the amount of surface wear.
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Translated Abstract of SU 618525, Titled “Diamond drill bit—has wear indicator as insert dissimilar from die in properties and colour, placed radially, with length equal to die endface” issued Jul. 21, 1979, obtained from DialogIP through Dwewent World Patents Index.
Caraway Douglas Bruce
Nguyen David Martin
Patton Douglas Alan
Watts Tony Martin
Bennett G. Bradley
Camco International Inc.
Daly Jeffrey E.
Verbitsky Gail
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