GB2534370A

GB2534370A - A cutting element for a drill bit

Info

Publication number: GB2534370A
Application number: GB1500909.5A
Authority: GB
Inventors: Woolen Neil; Baker Adam
Original assignee: Halco Rock Tools Ltd
Current assignee: Halco Drilling International Ltd
Priority date: 2015-01-20
Filing date: 2015-01-20
Publication date: 2016-07-27
Also published as: GB201500909D0

Abstract

A cutting element 5 for a drill bit (fig 1, 1), the cutting element 5 having a distal end 9 and a proximal end 11, said cutting element 5 having a hollow 17 to reduce material cost. The cavity 17 extends from the proximal end 11 and partially through the cutting element. The proximal end 11 may be flat 13, conical or dimpled to allow it to be seated in a recess formed in the face (fig 1, 7) of a drill bit head (fig 1, 3). The distal end 9, the cutting edge, may be dome-shaped 15, ballistic-shaped, hemispherical or parabolic in shape. The cutting element 5 may be a single superabrasive material moulding or may be formed from two materials where the outer layer is a superabrasive material. The hollow 17 may extend half way through the length of the cutting element 5 and the diameter may vary as there may be an undercut (fig 6, 25). The cutting element may also have a conduit 23 extending from the distal end of the hollow 19 to the cutting edge 9 or the drill bit (fig 1, 1) may have a passageway through the drill bit face (fig 1, 7) to act as an anti-airlock hole.

Description

A CUTTING ELEMENT FOR A DRILL BIT

The present invention relates to a cutting element for a drill bit and more particularly to an improved cutting element for a deep hole boring drill bit.

Down-the-hole drilling or DTH drilling is a type of drilling often used in the drilling of hard rock. The term "down-the-hole" refers to the fact that the percussion mechanism may follow the drill bit down into the hole which is being drilled. Typically, the percussion mechanism, known as the hammer, is located directly behind the drill bit. Drill pipes are connected to the hammer and these provide pneumatic force to the hammer. As the hole gets deeper, the drill pipes are fed down the hole.

The hammer incorporates a pneumatically operated piston by means of which 20 successive blows are struck on the upper end of the drill bit shank to cause the lower, operative end or head of the drill bit to break away material from the lower end of the bore hole.

In order to break away hard material, for example hard rock, prior art DTH drills comprise what are referred to in the art as drill bits of a "cross bit" design. The cross bit design comprises four chiselled lengths of carbide, for example tungsten carbide, that are brazed into the head of the drill bit. However, the cross bit design poses several disadvantages. Firstly, the cross bit design yields an unequal distribution of cutting power due to majority of the cross bit being centrally located on the head of the drill bit. Secondly, the cross bits must be brazed into the head of the drill bit and the stress of the brazing process on the head of the drill bit limits its lifespan.

Many of these shortcomings were addressed by the introduction of what are referred to in the art as "button bits". Button bits, for example carbide inserts, are cutting elements on a drill bit and, like the cross bit design, are located on the head of the drill bit.

Button bits are typically pressed into recesses formed in the head of the drill bit to establish, for example, an interference fit. Attaching the button bits in this way helps to reduce a large portion of the stress that the drill bit would otherwise incur during the brazing process, and in turn results in improved retention of the button bit. Further, the button bits provide improved distribution of cutting power by making available more cutting power near the outer portion of the drill bit. While button bits are now the design of choice for use in most DTH drills, they still suffer from various drawbacks.

One of the main disadvantages of button bits is the expense involved in their production and use. Button bits typically comprise a solid carbide substrate material and an outer layer of a superabrasive material, such as diamond, polycrystalline diamond (PCD) or diamond-enhanced carbide (DEC). In order to maintain the effectiveness of the drill bit, button bits may need to be replaced frequently due to wear on the button bit caused by the constant contact with hard material. This becomes particularly important in down-thehole drilling of hard rock, which wears the material of the button bits down at a much faster rate.

The term "superabrasive material" as used in this description and in the claims is meant to embrace materials comprising abrasive particles, for example diamond particles, which are useful for drilling, cutting or grinding hard materials. Examples of superabrasive materials include diamond, polycrystalline diamond (PCD), cubic boron nitride, diamond-enhanced carbide (DEC) and combinations thereof, however other types of superabrasive materials are known and will be recognized by one of skill in the art.

The cutting elements of the present invention overcome the problems associated with the expense involved in producing and using button bits for a drill, more specifically button bits for a DTH drill. By manufacturing a button bit having a hollow, the amount of material used to produce the button bit is reduced; this significantly reduces costs, while surprisingly still maintaining the overall structure and function of the button bit.

The term "a hollow" as used in this description and in the claims is meant to embrace an indentation in the cutting element, the hollow beginning at the proximal end of the cutting element and extending partially (but not totally) through the cutting element, toward the distal end of the cutting element.

The term "distal end" as used in this description and in the claims is meant to embrace the end of the hollow or the end of the cutting element that is situated away from the point of attachment of the cutting element to the face of the head of the drill bit.

The distal end of the cutting element is not retained within the recess in the face of the head of the drill bit; a portion of the cutting element protrudes from the face, and is thus exposed to the hard material, for example hard rock, earth or worked material, when the drill bit is in use. The distal end of the cutting element may be used, for example, as a cutting edge.

The term "proximal end" as used in this description and in the claims is meant to embrace the end portion of the hollow and the end portion of the cutting element situated nearer to the point of attachment of the cutting element to the face of the head of a drill bit.

The proximal end of the cutting element is retained within the head of the drill bit, seated within the recess and is thus not exposed to the hard material when the drill bit is in use.

In addition to the above advantages, the cutting elements of the present invention provide the advantage of a reduced residual button ejection force when in use in a drill bit.

US Patent No. 8,701,798 discloses a button bit for use in drilling tools, machining equipment, bearing apparatuses and wire-drawing machinery. The button bit has a recess that houses a separate superabrasive cutting element.

The superabrasive cutting element is exposed at the distal end of the button bit through at least one opening in the recess. Thus, unlike the present invention, the recess is not completely closed at its distal end. Rather, the recess must comprise at least two openings, one of which is located at its distal end, in order to expose the superabrasive cutting element housed within. In other words, the button bit must be at least partially open at both the proximal end and the distal end in order for it to function for its intended purpose.

According to the present invention, there is provided a cutting element for a drill bit, the cutting element having a distal end and a proximal end, said cutting element having a hollow, said hollow extending from the proximal end and partially through the cutting element.

Preferably, the cutting element is formed of a single material moulding.

Conveniently, the single material moulding is a material selected from the group consisting of tungsten carbide, silicon carbide, boron nitride, diamond, boron nitride carbide, polycrystalline diamond, polycrystalline cubic boron nitride, diamond-enhanced carbide and combinations thereof.

Advantageously, the cutting element further comprises at least one outer layer.

Preferably, said at least one outer layer is an outer cutting surface comprising a superabrasive material.

Conveniently, the superabrasive material is selected from the group consisting of diamond, polycrystalline diamond (PCD), cubic boron nitride, diamond-enhanced carbide and combinations thereof.

Advantageously, the at least one outer layer is bonded to a substrate.

Preferably, the substrate is a material selected from the group consisting of tungsten carbide, silicon carbide, boron nitride, diamond, boron nitride carbide, polycrystalline diamond, polycrystalline cubic boron nitride, diamond-enhanced carbide and combinations thereof.

Conveniently, the substrate material is tungsten carbide.

Advantageously, the proximal end is substantially flat, conical and/or dimpled.

Preferably, the distal end is substantially dome-shaped, for example substantially ballistic-shaped, substantially semi-ballistic-shaped, substantially hemispherical or substantially parabolic.

Conveniently, the distal end of the cutting element is a cutting edge. Advantageously, the hollow is empty.

Preferably, the hollow contains a non-carbide material.

Conveniently, the hollow is substantially full.

Advantageously, the non-carbide material is a material with high thermal conductivity, adhesive strength and/or compressive strength.

Preferably, the hollow comprises an under-cut at a distal portion of the hollow.

Conveniently, the hollow comprises an under-cut at a most distal end of the hollow.

Advantageously, the cutting element further comprises at least one conduit configured to convey air out of the hollow.

Preferably, the conduit is configured to convey air from the hollow through the distal end of the cutting element.

Conveniently, the cutting element is configured to be located in a recess of a face of a drill bit, said recess being provided with a conduit to convey air out of the hollow.

Advantageously, the length of the hollow is about 50% of the length of the cutting element, and is preferably about 5mm to 30mm.

Preferably, the diameter of the cutting element is about 5mm to 30mm, and is preferably about 16mm.

Conveniently, the diameter of the hollow is about 2mm to 20mm, and is 5 preferably about 7mm.

Advantageously, the cutting element is at least about 5mm in length, and is preferably at least about 26.5mm in length.

The invention also providing a drill bit comprising at least one cutting element, and preferably a plurality of cutting elements, according to the present invention.

Preferably, the drill bit comprises at least one recess for holding at least one respective cutting element or cutting elements, for example in an interference fit, a pressure fit or a press fit.

Conveniently, the hollow of the cutting element does not extend to or beyond the face of the drill bit post-fitment.

Advantageously, the at least one recess having at least one conduit configured to convey air from the hollow and through the drill bit.

The invention also includes a deep hole boring drill having a drill bit comprising a cutting element according to the present invention.

Embodiments of the invention are described below with reference to the accompanying drawings in which: Figure 1 is a side perspective view of a conventional down-the-hole hammer drill bit comprising a plurality of cutting elements according to the present invention; Figure 2 is a side perspective view of a cutting element according to the present invention; Figure 3 is a cross section of a further embodiment of a cutting element according to the present invention; Figure 4 is a cross section of a further embodiment of a cutting element according to the present invention; Figure 5 is a cross section of a further embodiment of a cutting element according to the present invention; Figure 6 is a cross section of a further embodiment of a cutting element according to the present invention; and Figure 7 is a side perspective view of a cutting element assembly according to the present invention.

Referring firstly to figure 1, there is illustrated a down-the-hole drill bit 1 in which the drill bit head 3 comprises a number of cutting elements 5 according to the present invention. The cutting elements 5 may be pressed into recesses in the face 7 of the drill bit head 3 to form, for example, an interference fit. It is also possible to attach the cutting elements by means of a brazing process.

Figure 2 shows an enlarged view of a cutting element 5 according to an embodiment of the present invention. The cutting element 5 comprises a proximal end 11 and a distal end 9, and may have a substantially flat surface 13 at the proximal end 11. The cutting element may also have a conical and/or dimpled proximal end 11.

The proximal end 11 may comprise a substantially flat surface 13 to allow for the proximal end 11 of the cutting element 5 to lay flush against the bottom of the recess formed in the head 7 of the drill bit 3 when the cutting element 5 has been fully inserted into a corresponding recess formed in the face 7.

According to an embodiment of the present invention, the cutting element 5 may be of a dome-shape 15 at the distal end 9, such that the distal end 9 of the cutting element 5 resembles, for example, a bullet. The distal end 9 of the cutting element may be ballistic-shaped, semi-ballistic-shaped, hemispherical or parabolic.

The term "dome-shaped" as used in this description and in the claims is meant to embrace shapes such as ballistic-shaped, semi-ballistic-shaped, hemispherical or parabolic, and thus may include substantially round shapes or partially pointed shapes, for example a bullet-shape.

The distal end 9 of the cutting element 5 may be a cutting edge for purposes of breaking away hard material, such as hard rock, when the drill bit is in use.

The cutting element 5 may be made from a single material moulding, such as tungsten carbide, but may also be made from two materials that are arranged as substrate and surface features. If the cutting element 5 comprises at least two materials, the outer layer may be made of a superabrasive material for purposes of cutting and breaking away hard material. Examples of suitable superabrasive materials include, but are not limited to, diamond, polycrystalline diamond (PCD), cubic boron nitride, diamond-enhanced carbide (DEC) and combinations thereof. Other types of superabrasive material are known and will be appreciated by one of skill in the art.

The inner material moulding, i.e. the material underneath the outer layer, may be a substrate material such as tungsten carbide. For example, a superabrasive material such as PCD is typically manufactured on a carbide substrate material.

Suitable substrate materials include, but are not limited to, tungsten carbide, silicon carbide, boron nitride, diamond, boron nitride carbide, polycrystalline diamond, polycrystalline cubic boron nitride and combinations thereof.

Figure 3 illustrates a cross section of an embodiment of a cutting element 5 according to the present invention. It is to be appreciated that the embodiment depicted and discussed below is just one possible embodiment of the invention and that the invention is only limited by the language of the attached claims.

The cutting element 5 comprises a proximal end 11 and a distal end 9. The proximal end 11 may comprise a substantially flat surface 13 to allow for the proximal end 11 of the cutting element 5 to lay flush against the bottom of the recess formed in the head 7 of the drill bit 3 when the cutting element 5 has been fully inserted into a corresponding recess formed in the face 7. The distal end 9 may be dome-shaped 15, for example hemi-spherical.

The cutting element 5 is provided with a hollow 17 at the proximal end 11, thus allowing air to enter into the cutting element 5 upon inserting the cutting element 5 into a recess in the face 7 of the head of the drill bit 3.

The hollow 17 extends partially through the cutting element 5, with the distal end 19 of the hollow 17 located, for example, in a location about halfway through the length of the cutting element 5. The hollow 17 may be about 5- 30mm in length. For purposes of shear strength, it is possible that the hollow does not extend to or beyond the face of the drill bit after the cutting element has been fit into a recess formed in the face 7 of the head of the drill bit.

The diameter of the hollow 17 may also vary, depending upon the diameter of 10 the cutting element. The cutting element 5 may have a diameter of at least 5mm. The hollow 17 may have a diameter of at least 2mm.

A cutting element 5 having a hollow 17, as in the present invention, provides significant material saving, and thus reduced manufacturing costs. Prior art cutting elements, i.e. prior art button bits, are formed as completely solid pieces. No hollow exists within the cutting element, and thus no material is saved in their production. The present inventors have discovered that providing a cutting element 5 with a hollow 17 not only provides significant material saving and thus reduced costs, but also provides for better cutting element retention once the cutting element 5 has been inserted into a recess formed in the face 7 of the head of the drill bit 3 for use in, for example, down-the-hole drilling.

Further, without being bound to any particular theory, the hollow 17 may also allow for increased strain prior to cracking or failure.

Figure 4 illustrates cross sectional view of an embodiment of a cutting element 5 of the present invention. The cutting element illustrated in figure 4 comprises a distal end 9, a proximal end 11 and a hollow 17. The hollow 17 may extend slightly past the mid-point of the cutting element 5 and comprises a proximal end 11 and a distal end 9. The cutting element 5 may also comprise a dome-shaped distal end 15 and a substantially flat surface 13 at the proximal end 11.

The cutting element 5 may also comprise a conduit 23 extending from the distal end 19 of the hollow 17 through to the distal end 9 of the cutting element 5 for purposes of acting as a small anti-airlock hole; however the hollow 17 may remain fully closed its distal end 19, in which case the face 7 of the head of the drill bit 3 may have a conduit 23 instead.

The term "conduit" as used in this description and in the claims is defined as a passageway or channel for conveying air out of the hollow. The conduit is configured to function as an anti-airlock hole for eliminating residual pressure within the hollow. The conduit may be located in the cutting element, such that the conduit extends from the distal end of the hollow through to the distal end of the cutting element. The conduit may also extend from the face of the head of the drill bit in contact with the proximal end of the hollow and through at least part of the head of the drill bit, i.e. the conduit may extend in the direction opposite the hollow.

Another embodiment of the present invention is shown in figure 5. The cutting element 5 comprises a hollow 17 having a proximal end 21 and a distal end 19. However, in this particular embodiment, the hollow 17 further comprises an under-cut 25 at its distal end 19. The under-cut 25 provides retaining geometry once the cutting element 5 has been inserted into a recess formed in the face 7 of the head of the drill bit 3. The under-cut 25 may be located in a distal portion of the hollow 17, for example at the most distal end 19.

The distal end 9 of the cutting element 5 may be dome-shaped and the proximal end 11 of the cutting element 5 may have a substantially flat surface.

Figure 6 illustrates a cross section of a further embodiment of a cutting element 5 according to the present invention. The cutting element 5 comprises an under-cut 25 located at the distal end 19 of the hollow 17. As shown in figure 5, the under-cut 25 and hollow 17 may be symmetrical. The under-cut is not limited to any particular shape, but may be substantially rectangular, as depicted in figures 5 and 6.

The cutting element 5 may also comprise a conduit 23 extending from the distal end 19 of the hollow 17 through to the distal end 9 of the cutting element 5 for purposes of acting as an anti-airlock hole; however the hollow 17 may also be fully closed its distal end 19, in which case the face 7 of the head of the drill bit 3 may comprise a conduit 23 instead.

Figure 7 illustrates an embodiment of the cutting element 5 according to the present invention after having been inserted into a recess formed in the face 7 of the head of a drill bit 3. Upon the insertion of the cutting element 5 into the recess, majority of the cutting element 5 is retained within the head of the drill bit 3, while a portion of the distal end 13 protrudes from the head of the drill bit 3. The distal end 9 of the cutting element 5 protrudes from the head of the drill bit 3 such that the dome-shaped end portion 15 acts as a cutting edge for breaking away material, for example hard rock.

As shown in figure 7, the substantially flat portion 13 located at the proximal end 11 of the cutting element 5 is flush against the bottom of the recess formed in the head 7 of the drill bit 3. The hollow 17 becomes closed off once the cutting element 5 has been fully inserted into the recess, such that the face 7 of the head of the drill bit 3 covers the opening of the hollow 17.

According to another embodiment of the present invention, the hollow 17 may contain a non-carbide material. For example, the hollow 17 may be substantially full or partially full. The non-carbide material may be a material with high thermal conductivity.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

2.
3.
4.
5.
6.
7.A cutting element for a drill bit, the cutting element having a distal end and a proximal end, said cutting element having a hollow, said hollow extending from the proximal end and partially through the cutting element.

The cutting element of claim 1, wherein the cutting element is formed of a single material moulding.

The cutting element of claim 2, wherein the single material moulding is a material selected from the group consisting of tungsten carbide, silicon carbide, boron nitride, diamond, boron nitride carbide, polycrystalline diamond, polycrystalline cubic boron nitride, diamond-enhanced carbide and combinations thereof.

The cutting element of any one of claims 1 to 3, wherein the cutting element further comprises at least one outer layer.

The cutting element of claim 4, wherein said at least one outer layer is an outer cutting surface comprising a superabrasive material.

The cutting element of claim 5, wherein the superabrasive material is selected from the group consisting of diamond, polycrystalline diamond (PCD), cubic boron nitride, diamond-enhanced carbide and combinations thereof.

The cutting element of any one of claims 4 to 6, wherein the at least one outer layer is bonded to a substrate.
8. The cutting element of claim 7, wherein the substrate is a material selected from the group consisting of tungsten carbide, silicon carbide, boron nitride, diamond, boron nitride carbide, polycrystalline diamond, polycrystalline cubic boron nitride, diamond-enhanced carbide and combinations thereof.
9. The cutting element of claim 8, wherein the substrate material is tungsten carbide.
10.The cutting element of any one of the preceding claims, wherein the proximal end is substantially flat, conical and/or dimpled.
11.The cutting element of any one of the preceding claims, wherein the distal end is substantially dome-shaped, for example substantially ballistic-shaped, substantially semi-ballistic-shaped, substantially hemispherical or substantially parabolic.
12.The cutting element of any one of the preceding claims, wherein the distal end of the cutting element is a cutting edge.
13.The cutting element of any one of the preceding claims, wherein the hollow is empty.
14.The cutting element of any one of claims 1 to 12, wherein the hollow contains a non-carbide material.
15.The cutting element of claim 14, wherein the hollow is substantially full.
16.The cutting element of claim 14 or claim 15, wherein the non-carbide material is a material with high thermal conductivity, adhesive strength and/or compressive strength.
17.The cutting element of any one of the preceding claims, wherein the hollow comprises an under-cut at a distal portion of the hollow.
18.The cutting element of claim 17, wherein the hollow comprises an undercut at a most distal end of the hollow.
19.The cutting element of any one of the preceding claims, wherein the cutting element further comprises at least one conduit configured to convey air out of the hollow.
20.The cutting element of claim 19, wherein the conduit is configured to convey air from the hollow through the distal end of the cutting element.
21.The cutting element of any one of claims 1 to 18, wherein the cutting element is configured to be located in a recess of a face of a drill bit, said recess being provided with a conduit to convey air out of the hollow.
22.The cutting element of any one of the preceding claims, wherein the length of the hollow is about 50% of the length of the cutting element, and is preferably about 5mm to 30mm.
23.The cutting element of any one of the preceding claims, wherein the diameter of the cutting element is about 5mm to 30mm, and is preferably about 16mm.
24.The cutting element of any one of the preceding claims, wherein the diameter of the hollow is about 2mm to 20mm, and is preferably about 7mm.
25.The cutting element of any one of the preceding claims, wherein the cutting element is at least about 5mm in length, and is preferably at least about 26.5mm in length.
26.A drill bit comprising at least one cutting element, and preferably a plurality of cutting elements, according to any one of the preceding claims.
27.The drill bit of claim 26, wherein the drill bit comprises at least one recess for holding at least one respective cutting element or cutting elements, for example in an interference fit, a pressure fit or a press fit.
28.The drill bit of claim 27, wherein the hollow of the cutting element does not extend to or beyond the face of the drill bit post-fitment.
29.The drill bit of claim 27 or 28, said at least one recess having at least one conduit configured to convey air from the hollow and through the drill bit.
30.A deep hole boring drill comprising the drill bit of any one of claims 26 to 29.
31.A cutting element, drill bit or drill substantially as described herein, with reference to Figures 1-7.
32.Any novel feature or combination of features described herein.