CORE DRILL BIT

Field of the Invention

The present invention relates to core drill bits used in the mining and construction industries.

Background of the Invention

Core bits are used to provide core samples. In the mining industry, core samples are used for geological assessment of mineral content. In the construction industry, core samples are used to test structural integrity.

US patent document US 2,326,908 discloses a core drill bit having an axis, the drill bit comprising: a barrel; cutting members detachably fixed to the barrel, the barrel being arranged to engage a drill shaft for driving the drill bit around the axis, the barrel and the cutting members being adjacently located on the axis, and an aperture centered on the axis, the aperture passing completely through both the cutting members and barrel; wherein the cutting members have a cutting face, and a backing face located adjacent the barrel, the faces being spaced apart along the axis, and the cutting face comprising a plurality of cutting teeth or elements, between which passage ways are defined; wherein the cutting members together form cylindrical inner and outer surfaces centered on the axis, the inner surface surrounding the aperture passing through the cutting members; wherein the cutting members together form a plurality of passage ways passing through the inner and outer surfaces and the cutting face; wherein the barrel has cylindrical inner and outer barrel surfaces centered on the axis, the inner barrel surface surrounding the aperture passing through the barrel; wherein the cylindrical aperture passing through the barrel is continuous with the cylindrical aperture passing through the cutting members; wherein the cutting members and barrel are mechanically fixed together by a pair of engaged cooperating elements, each of the pair of elements being located on one of the barrel and cutting member respectively.

Summary of Invention

According to a first aspect of the present invention there is provided a core drill bit according to claim 1. In an embodiment, the cutting member is metallurgically fixed to the barrel.

In an embodiment, the cutting member is fixed to the barrel with an adhesive.

In an embodiment, the backing face comprises a composite having a plurality of diamonds or other super hard constituents. The backing face may comprise a circular flange arranged to engage the barrel.

In an embodiment, the cutting member comprises a plurality of elements in a layered configuration.

In an embodiment, the cutting member and barrel are formed of different materials.

In an embodiment, the cutting member is formed of one or more composite materials. The one or more composite materials may include a metal and a plurality of diamonds.

In an embodiment, the inner and/or outer barrel surfaces may comprise wear resistant matrices.

In an embodiment, the barrel is arranged to stabilize the bit during drilling. The barrel may be longer than the cutting member.

According to a second aspect of the present invention there is provided a method of making the aforementioned drill bit according to the first aspect of the present invention having an axis, the method comprising the steps of:

• providing a cutting member;
• providing a barrel separate to the cutting member, the barrel being arranged to engage a drill shaft for driving the drill bit around the axis;
• locating the barrel adjacent the cutting member on the axis; and
• fixing the barrel to the cutting member.

Brief description of the Figures

In order to achieve a better understanding of the nature of the present invention embodiments will now be described, by way of example only, with reference to the accompanying figures in which:

• Figure 1 shows from above a perspective view of one embodiment of a drill bit according to an aspect of the invention, comprising a cutting member and a barrel;
• Figure 2 shows from below a perspective view of one embodiment of the cutting member of Figure 1;
• Figure 3 shows from above a perspective view of the barrel of Figure 1; and
• Figure 4 shows from above a perspective view of the cutting member of Figure 3.

Detailed Description of embodiments of the invention

Figure 1 shows one embodiment of a drill bit generally indicated by the numeral 10. The drill bit 10 has a central axis 12 around which it is driven. The drill bit 10 has a cutting member 14, in the form of a crown, detachably fixed to a separate barrel 16. The barrel 16 and the cutting member 14 are adjacently located on the axis 12. The cutting member 14 and barrel 16 are formed separately and then fixed together. The barrel 16 is arranged to engage a drill shaft (not shown) for driving the drill bit 10 around the axis 12. Typically the barrel connects to a drill string or possibly a drill chuck. In this embodiment, the drill bit 10 is a core bit, and so the barrel 16 is a barrel for the core bit 10 and the cutting member 14 is a cutting member for the core bit 10.

The cutting member 14 and barrel 16 are mechanically fixed together by a pair of engaged cooperating elements. The cooperating elements are arranged to interfere when the drill bit 10 is driven around the axis 12 providing resistance against separation of the cutting member 14 from the barrel 16. This transfers the drive power from the barrel to the cutting member. The engaging elements, in alternatives not forming part of the invention, comprise a pair of complimentary threads, each of the threads being formed on the cutting member 14 and barrel 16 respectively. Of course, the handedness of the thread is chosen so that the barrel 16 and cutting member 14 do not separate during drilling and rotation around the axis 12 in the desired direction. Because the threads engage each other there is no need for a separate retainer, such as a bolt, to fix the barrel to the cutting member. Some embodiments, however, may include a retainer. In some alternatives, the barrel and cutting member are detachably fixed together by the threads for example, so that they can be separated without destruction of either the barrel or cutting member. According to the present invention, as shown in figures 2 and 3, there are spigots 18 locatable in a corresponding recesses 20, the spigot being located on the barrel 16 and the recesses being located on the cutting member 14 or vice versa. This may not be enough to fix the cutting member and barrel together, and so the spigots 18 may be tapered and securely pressed into the corresponding recesses 20, for example. The cutting member 14 also has a flange 31 that telescopes with a corresponding flange 35 of the barrel 16.

The cutting member 14 may be metallurgically fixed to the barrel 16 by, for example, low temperature induction brazing, in cases were there are no co-operating elements such as threads, spigots & recesses for example, or to supplement them. A low temperature braze, such as a silver braze, is advantageous because the drill bit can be heated above the melting point of the braze (above 425°C typically) and the cutting member detached from the barrel without overheating and damaging either the barrel or cutting member. A worn out or damaged barrel or cutting member can then be replaced without requiring replacement of the whole drill bit. Alternatively, the drill bit could be reconfigured by replacing the cutting member or barrel as required without requiring a whole new bit. Brazing may prevent inadvertent separation of the cutting member from the barrel, for example if the parts are attached by a thread and the drill bit is spun the wrong way. A drill bit wherein an adhesive, such as a cyanoacrylate based adhesive, is used instead of silver brazing has similar advantages.

As shown in figure 4, the cutting member 14 has cylindrical inner 22 and outer 24 surfaces centered on the axis 12, the inner surface 22 defining an aperture 26 passing through the cutting member 14. The cylindrical aperture 26 receives a core sample as the bit 10 drills into the ground or structure. The inner 22 and/or outer 24 surfaces comprise wear resistant matrices, such as a diamond/tungsten carbide and metal composite, which in some circumstances increases the life of the drill bit.

The cutting member 14 has a cutting face 28 (Fig. 4) and a backing face 30 (Fig. 2). The backing face is located adjacent the barrel 16 when joined to it. The faces 28,30 are spaced apart along the axis 12. The cutting face 28 has a plurality of cutting teeth or elements such as 32,34. The cutting teeth or elements 32,34 are arranged in a turret or crown-like ring formation. The cutting face 28 has a series of concentric hill 42 and valley 44 formations running around the axis 12. The cutting member 14 in this embodiment, is slotted to form a plurality of passage ways such as 46. The slots cut through the inner 22 and outer 24 surfaces and also the cutting face 28 itself. The passageways allow lubricant flow and the transport of drilling detritus or debris therethrough. The lubricant is typically water injected through the bit.

The backing face 30 may comprise a composite having a plurality of relatively large diamonds or other super hard constituents, to resist wear and keep the outer 24 and inner 22 diameters in gauge.

As shown in Figure 3, the barrel 16 has cylindrical inner 36 and outer 38 barrel surfaces centered on the axis 12, the inner barrel surface defining an aperture 40 passing through the barrel 16. The cylindrical aperture 40 is continuous with the aperture 26 passing through the cutting member to form a greater drill bit aperture into which the core sample is received. The inner 36 and/or outer 38 barrel surfaces comprise wear resistant matrices, which in some circumstances increases the life of the drill bit. The barrel is substantially made of a steel, such as a carbon steel. The inner surface of the barrel has a grooved thread such as 48 for joining it to a threaded drill string.

The barrel 16 is arranged to stabilize the bit during drilling. This is achieved, in this embodiment, at least in part by having a barrel 16 longer than the cutting member 14.

To make the drill bit 10, first a cutting member 14 and barrel 16 are provided. The barrel 16 is separate to the cutting member 14. Then, the barrel 16 is located adjacent the cutting member 14 and fixed to it. These last steps are achieved in some embodiments by screwing the barrel 16 and cutting member 14 together. In some other embodiments, they are brazed together. Thus, the barrel and cutting member are separate in that they are formed separately, and not for example, made in the same mold.

In some embodiments a green cutting member is first formed that is later sintered or hot isostatic pressed to form the final member 14. Forming a green cutting member, in this embodiment, includes distributing diamonds in a metallic powder to form a composite material precursor from which the green cutting member is at least in part formed. The composite material precursor is then placed in a cutting member mould, and pressed into it. The composite material precursor is one of a plurality of different composite material precursors which are separately located in the cutting mould to form a cutting member having elements. Typically, the elements are layered like a sandwich.

A layer containing an alloy is placed over the composite material precursor in the mould. The alloy infiltrates and binds the composite during sintering or hot isostatic pressing of the green cutting member. Alternatively, the composite material precursors may include a binder premixed to facilitate self infiltration or self sintering powders may be used to avoid the use of a liquid phase.

The co-operating engagement element of the cutting member, such as a thread or recess, may be formed by the mold or a mold insert or by machining or cutting the green member.

The diamonds may be first encapsulated in a layer of material which is then semi- or fully-sintered. The material may be a metal powder that provides plasticity and in-filling between the diamonds during sintering.

The cutting face 32 itself contains sandwich segments and/or increased wear resistant matrices at the outer and/or inner diameters to prevent premature wear and early bit retrieval.

The cutting member and barrel are thus formed of different materials.

Now that embodiments have been described, it will be appreciated that some embodiments have some of the following advantages:

• The drill bit face is produced without producing waste, a typical by product of machined bits, which is more economical;
• The drill bit face is produced without machining which is labor and cost effective;
• The steel barrel stabilizes the bit during drilling without an intermediate stabilizer;
• The cutting member and barrel can be fabricated of different materials as is appropriate for each part, through completely different processes, for example sintering of a steel barrel which may soften, weaken and decrease the ductility of a carbon steel barrel can be avoided, while the crown may be sintered, resulting in a better bit;
• No expensive and consumable graphite moulds are required which must be destroyed to remove the molded part inside;
• High production capacity is possible;
• The manufacturing process is relatively very fast and cheap.
• The manufacturing process is highly repeatable.

It will be appreciated that numerous variations and/or modifications may be made to the embodiments without departing from the scope of the invention as defined by the appended claims. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.