GB2516626A

GB2516626A - Percussive Drill Bit

Info

Publication number: GB2516626A
Application number: GB1313324.4A
Authority: GB
Inventors: Pietro Guerriero; Glyn Stuart Vickers; Steven Michael Harper
Original assignee: Padley and Venables Ltd
Current assignee: Padley and Venables Ltd
Priority date: 2013-07-25
Filing date: 2013-07-25
Publication date: 2015-02-04
Anticipated expiration: 2033-07-25
Also published as: GB201313324D0; GB2516626B

Abstract

A percussive drill bit (101) has a steel body (102) with tungsten carbide buttons (103, 104) mounted therein. The steel body has a longitudinal rotational axis (105) having a bit face radius 202. In addition, a gauge surface 107 surrounds the bit face and is inclined at a gauge angel. Face buttons 204, 205, 206 are mounted in the bit face substantially equally displaced around a circumference having a radius that is less than the bit face radius. For each face button eg 205, a first gauge button 207 is located in said gauge surface displaced in a clockwise direction and a second gauge 208 button is located in the gauge surface displaced in a counter clockwise direction, so as to define a wing with wing edges 209, 210. A primary flushing flute 108 cuts into the gage surface between each of the first gauge button and the second gage button to an extent such as to reach the bit face radius. The bit includes a drop centre hole 211 and flushing holes 213, 214, 215 located between the wing edges.

Description

Percussive Drill Bit

CROSS REFERENCE TO RELATED APPLICATIONS

This application represents the first application for a patent directed towards the invention and the subject mailer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a percussive drill bit apparatus, of the type comprising a steel body and a plurality of tungsten carbide buttons mounted therein. The present invention also relates to a method of producing a percussive drill bit.

2. Description of the Related Art

It is known to produce percussive drill bits having a steel body and a plurality of tungsten carbide buttons mounted therein. Drill bits of this type are used for drilling rock during the process of quarrying or during the is process of mining, for example. Hard rock quarries are worked from top to bottom in a series of layers, known as benches. The drill rig drills blast holes into a quarry bench and a series of holes may be drilled along a bench typically between one metre and two metre apart. The holes are typically ten metre to fifteen metre deep and are filled with explosive.

The life of a bit is measured in terms of its total drilling distance, so each drill bit is expected to drill more than one hole. In very hard rock, a total dritling distance of three hundred and fifty metre would be expected. In addition to making attempts to extend drilling distance, when used in the field, operatives are also concerned with the rate of penetration and the rate of which debris can be removed.

Experiments have shown that the rate of penetration and the quality of penetration are affected by the rate of debris removal. Thus, when operating at high speeds, the rate of debris removal can be a limiting constraint.

Furthermore, if difficulties are encountered in terms of removing debris, energy will be wasted by creating powder instead of fragmented rocks, and overall efficiency will be reduced. A problem therefore exists in terms of increasing the rate of debris removal without introducing any other detrimental effects to the overall operation.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided an apparatus of the aforesaid type, as set out in claim 1.

According to a second aspect of the present invention, there is provided a method of producing a drill bit of the aforesaid type as set out in claim 13.

The invention will now be described by way of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a percussive drill bit; Figure 2 shows an alternative view of the drill bit identified in Figure 1; Figure 3 shows an enlarged view of the drill bit shown in Figure 2; Figure 4 shows a drill bit drilling into rock; Figure 5 details a flushing hole; Figure 6 shows a percussive drill about to drill a hole; Figure 7 shows a percussive drill having drilled a hole; Figure 8 details a method of producing a percussive drill bit; and Figure 9 shows a drill bit manufactured in accordance with the method detailed in Figure 8.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Figure 1 A percussive drill bit 101 is shown in Figure 1, suitable for top hammer drilling as used for quarrying and mining etc. The drill bit has a steel body 102 and a plurality of tungsten carbide buttons 103, 104 etc mounted into the steel body 102.

The steel body 102 has a longitudinal rotational axis 105, with a substantially circular bit face 106 (detailed in Figure 2) normal or perpendicular to said longitudinal axis 105. The bit face 106 has a defined bit face radius, from which extends a gauge surface 107, inclined at a gauge angle with respect to the bit face 106.

A primary flushing flute 108 cuts into the gauge surface 107 between a first gauge button 109 and a second gauge button 110. The primary flushing flute cuts into the gauge surface to such an extent that it reaches the bitface radius.

Figure 2 An alternative view of the drill bit of Figure 1 is shown in Figure 2, looking directly at the bit face 106, that is looking down longitudinal axis 105.

The bit face is substantially circular, defining a bit face circumference 201 at a bit face radius 202 from the centre, that is from the position of the rotational axis 105. A gauge surface 107 surrounds the circular bit face, inclined at an angle, as shown in Figure 1.

A plurality of face buttons are mounted in the bit face, substantially equally displaced around a circumference having a radius 203 that is less than the bit face radius 202.

It is known that drilling characteristics can be improved by placing the face buttons as far out as possible from the rotational centre. However, in this embodiment, the radial length has been reduced, as shown at 203, so as to allow the primary flushing flutes 108 to cut into the gauge surface 107 to an extent such as to reach the bit face radius 202. As shown in Figure 2, the result of this configuration is that the gauge surface no longer remains continuous around the circumference given that, at the position of greatest extent (that is at the centre) of the primary flushing flutes 108, substantially all of the gauge surface has been removed so as to allow the primary flushing flute to reach the extent of the bit face radius 202.

In the embodiment, three face buttons are mounted on the face surface, identified as button 204, button 205 and button 206. For each face button, such as button 205, a first gauge button 207 is located in the gauge surface, displaced in a clockwise direction. A second gauge button 208 is located in the gauge surface displaced in a counter clockwise direction.

Thus, in combination, each group of three buttons is supported by a portion of the steel body so as to define a wing, with wing edges 209 and 210. Thus, in this embodiment, three wings are defined each comprising a face button, a first gauge button and a second gage button. Furthermore, a primary flushing flute 108 is cut between each of said first face buttons and said second face buttons, to extents that reach the face radius.

In an embodiment, the drill bit includes a drop centre hole 211 to improve stability while drilling, as detailed in Figure 4.

While drilling is being performed, it is also necessary for a flushing medium to be inserted down the inside of the drill, so as to remove debris produced by the drilling operation. For maximum efficiency, an optimal level of fragmentation should occur, producing fragments having a size ranging between one millimetre and two millimetre, so as to be small enough to be returned by the flushing medium while at the same time not being unnecessarily small, resulting in a waste of energy. As speeds increase, a greater degree of flushing is required and the present embodiment, with improved primary flushing flutes, facilitates efficient drilling at higher speeds.

The drill bit also includes flushing holes, which, in this embodiment, consist of a flushing hole 212, a flushing hole 213 and a flushing hole 214.

The flushing holes (212, 213, 214) are located between wing edges. In the embodiment, three wings are present, therefore there are three flushing holes and the three flushing holes 212 to 214 are displaced from the drop centre hole 211 by a substantially similar radial distance 215.

Figure 3 An enlarged view of flushing hole 203 is shown in Figure 3. In this embodiment, a substantially straight (that is non-rounded) first face channel 301 extends between flushing hole 213 and the drop centre hole 211.

In an embodiment, secondary flushing flutes are created, including secondary flushing flute 302. In an embodiment, each secondary flushing flute is circumferentially located between wing edges. Thus, in this example, secondary flushing flute 302 is located between wing edge 303 and wing edge 304, cut into the gauge surface 107. The secondary flushing holes line up with a flushing hole, that is to say they are located on the same radius, as a flushing hole. Thus, secondary flushing flute 302 is substantially at the same angle as flushing hole 213.

In an embodiment, a substantially straight second face channel 305 extends between each flushing hole 213 and its radially aligned secondary flushing flute 302.

The first channel 301 is defined by a first edge 306 and a second edge 307. Where edge 306 meets edge 307, an obtuse angIe 308 is defined.

These obtuse angles, including angle 308, occur substantially at the radius of the flushing hole 213.

Figure 4 As previously described with reference to Figure 2, the drill bit includes a drop centre hole 211 to improve stability while drilling. It has been suggested that the presence of this hole 211 may reduce drilling speed.

However, this advantage is not as great as the advantage gained from having the hole present. The percussive nature of the drill results in each carbide button tip, such as gauge tip 207 and face tip 205, crushing the rock at the position where the button makes contact. Rotation then occurs, in anticipation of the next strike. When this rotation occurs, solid rock is present at the interface. A portion 401 of this rock enters the hollow drop centre, before yielding on the next cycle or so of rock crushing. However, the presence of portion 401 helps to stabilise the bit and prevent deviation.

Figure 5 As shown in Figure 5, drill bit 101 is hollow, with its internal surface 501 being threaded in order to receive a hollow drilling rod. To achieve debris removal, a flushing medium is directed down the drilling rod, indicated by arrow 502, to be directed towards the cutting surfaces via the flushing holes, including flushing hole 503. On land, the flushing medium tends to be air and underground the flushing medium tends to be water, in order to reduce airborne dust. In operation, the flushing medium picks up fragmented rock and returns it via the flushing flutes up the cut hole around the gap 402 (Figure 4) between the wall edge 403 and the drilling rod, in a direction indicated by arrow 404.

Figure 6 A percussive drill 601 is shown in Figure 6. The drill bit 101 has been attached to a drill rod 602 and a carousel 603 stores up to seven additional drill rods that, in use, are coupled together to extend the hole down to a depth of fifteen metre.

Figure 7 After reaching the desired depth, the drill is retracted, removing the drilling rods one by one and returning them to their carousel 603. During the drilling operation, spoil will have been removed by spoil extraction device 701, minimising dust creation. The resulting hole 702 is then available for receiving explosives.

The process of top hammer drilling does not generate large quantities of spoil but the spoil must be removed to facilitate the drilling operation; although it is likely that not all of the spoil will be removed. Efficient spoil removal facilitates an improvement in overall efficiency, thereby reducing overall energy consumption when conducting the drilling processes.

Extension drilling rods are connected together by couplings. To provide sufficient strength, the overall diameter of the couplings are greater than the thread diameter of the rod. The fragmented rock must be transported past these couplings, so the bit diameter must be greater than the coupling diameter.

With insufficient flushing, broken fragments lie at the bottom of the hole until they have been broken small enough to allow them to be blown out. This situation causes a reduction in the drilling rate and excessive wear on the bit. The collection of dust at the bottom of the hole, through this inefficient fragment removal, results in some of the dust remaining in the hole such that it may be necessary to drill by an additional ten percent in order to achieve a hole of the required depth; with ten percent of the hole being effectively filled back in by dust that has not been removed. Thus, further inefficiencies occur if the fragments are not removed in an optimised way.

Figure 8 & Figure 9 A method of producing a percussive drill bit is illustrated in Figure 8.

At step 801, a substantially cylindrical steel component is machined; the component having a longitudinal rotational axis 105, as shown in Figure 9.

The machining operation produces a substantially circular bit face 902, normal to axis 901, having a bit face radius, as shown in Figure 2. In addition, a gauge surface 903 is machined surrounding the bit face 902 and inclined at a gage angel.

At step 802, flushing holes 904 are formed that extend through an internal conduit 503, so as to receive flushing medium from the surface.

At step 803 the primary flushing flutes 905 are cut into the gauge surface 903, to an extent that substantially reaches the bit face radius and illustrated at 905.

A plurality of primary flushing flutes may be cut, each to an extent that substantially reaches the bit face radius. In the embodiment shown in Figure 9, three primary flushing flutes are cut into the gauge surface to an extent that substantially reaches the bit face radius.

At step 804 a drop centre is formed to improve stability while drilling.

At step 805, secondary flutes and channels are formed. In an embodiment, the secondary flushing flutes are formed at the radius of each flushing hole.

In an embodiment, second face channels are formed between each of the flushing holes and a radially aligned secondary flushing flute. In this way, each first face channel edge may form an obtuse angIe 307 with a respective second face channel edge around the position of a flushing hole 213.

At step 806, a heat treatment operation is performed in order to increase the hardness of the external surface of the bit, while retaining the original strength of the material for the majority of its body.

At step 807, holes are drilled into the face and into the gauge surface for receiving tungsten carbide buttons. Thereafter, at step 808, tungsten carbide buttons are inserted into the holes, while the receiving metal is hot, so as to create an interference fit and place the carbide buttons in a state of compression.

Claims

Claims What we claim is: 1. A percussive drill bit apparatus, comprising a steel body and a plurality of tungsten carbide buttons mounted therein, wherein: said steel body has a longitudinal rotational axis, a substantially circular bit face normal to said axis having a bit-face radius, and a gauge surface surrounding said bit face inclined at a gauge angle with respect to said bit face; a plurality of face buttons are mounted in said bit face, substantially equally displaced around a circumference having a radius less than said bit-face radius; for each said face button, a first gauge button is located in said gauge surface displaced in a clockwise direction and a second gauge button is located in said gauge surface displaced in a counter-clockwise direction so as to define a wing with wing edges; and a primary flushing flute cuts into said gauge surface between each said first gauge button and said second gauge button to an extent such as to reach said bit face radius.
2. The apparatus of claim 1, wherein: said primary flushing flute reaches the bit face radius at substantially the circumferential position of a face button; and said face button is displaced away from said bit face radius so as to provide a portion of said bit face present between the face button and the primary flushing flute.
3. The apparatus of claim I or claim 2, wherein: three wings are defined, each comprising a face button, a first gauge button and a second gauge button; and a primary flushing flute is cut between each said first face button and said second face button to extents such as to reach said bit face radius.
4. The apparatus of any of claims 1 to 3, further comprising a drop-centre hole to improve stability while drilling.
5. The apparatus of claim 4, further comprising a flushing hole in said bit face, located between wing edges.
6. The apparatus of claim 5, comprising three wings and three flushing holes, wherein said flushing holes are displaced from said drop centre holes by a substantially similar radial distance.
7. The apparatus of claim 5 or claim 6, wherein a substantially straight first face channel extends between each said flushing hole and said drop-centre hole.
8. The apparatus of any of claims I to 6, further comprising a secondary flushing flutes, wherein each said secondary flushing flute is circumferentially located between said wing edges and is substantially on the radius of a flushing hole.
9. The apparatus of claim 8, wherein a substantially straight second face channel extends between each said flushing hole and its radially aligned secondary flushing flute.
10. The apparatus of claim 9, wherein each first face channel edge defines an obtuse angle with a respective second face channel edge around flushing hole.
11. A percussive drill configured to drill rock for a process of quarrying or mining, comprising a plurality of drill rods and a drill bit apparatus as claimed in any of claims ito 10.
12. A method of mining or quarrying using the compressive drill of claim ii.
13. A method of producing a percussive drill bit, comprising the steps of: machining a substantially cylindrical steel component with a longitudinal rotational axis, a substantially circular bit face normal to said axis having a bit face radius, and a gauge surface surrounding said bit face and inclined at a gauge angle; forming flushing holes and an internal flushing conduit; and cutting a primary flushing flute into said gauge surface to an extent that substantially reaches said bit face radius.
14. The method of claim 13, wherein a plurality of primary flushing flutes are cut to an extent that substantially reaches said bit face radius.
15. The method of claim 14, wherein three primary flushing flutes are cut into the gauge surface to an extent that substantially reaches said bit face radius.
16. The method of any of claims 13 to 15, including the forming of a drop centre hole to improve stability while drilling.
17. The method of claim 16, further comprising the step of forming a substantially straight first channel between each flushing hole and said drop centre hole.
18. The method of claim 17, further comprising the step of forming secondary flushing flutes at the radius of each flushing hole.
19. The method of claim 18, further comprising the step of forming second face channels between each of said flushing holes and a radially aligned secondary flushing flute.
20. The method of claim 19, wherein each first face channel edge forms an obtuse angle with a respective second face channel edge around the position of a flushing hole.Amendments to the claims have been filed as follows Claims What we claim is: 1. A percussive drill bit apparatus, comprising a steel body and a plurality of tungsten carbide buttons mounted therein, wherein: said steel body has a longitudinal rotational axis, a substantially circular bit face normal to said axis having a bit-face radius, and a gauge surface surrounding said bit face inclined at a gauge angle with respect to said bit face; a plurality of face buttons are mounted in said bit face, substantially equally displaced around a circumference having a radius less than said bit-face radius; for each said face button, a first gauge button is located in said gauge surface displaced in a clockwise direction and a second gauge button is located in said gauge surface displaced in a counter-clockwise direction so as to form a wing defined by a first wing edge and a second wing edge; a substantially straight first face channel extends between a flushing hole in said bit face and a hollow drop-centre hole, said flushing hole located between one of said wing edges and a third wing edge; and : * a primary flushing flute cuts into said gauge surface between each * 20 said first gauge button and said second gauge button to an extent such as to reach a bit face circumference defined by said bit face radius.* S.... * .2. The apparatus of claim 1, wherein: S...said primary flushing flute reaches the bit face radius at substantially the circumferential position of a face button; and said face button is displaced away from said bit face radius so as to provide a portion of said bit face present between the face button and the primary flushing flute.3. The apparatus of claim 1 or claim 2, wherein: three wings are defined, each comprising a face button, a first gauge button and a second gauge button; and a primary flushing flute is cut between each said first gauge button and said second gauge button to extents such as to reach said bit face circumference defined by said bit face radius.4. The apparatus of claim 1, comprising three wings and three flushing holes, wherein said flushing holes are displaced from said drop centre hole by a substantially similar radial distance.5. The apparatus of any of claims 1 to 4, further comprising a plurality of secondary flushing flutes, wherein each said secondary flushing flute is circumferentially located between said wing edges and is substantially on the radius of a flushing hole.6. The apparatus of claim 5, wherein a substantially straight second face channel extends between each said flushing hole and its radially aligned secondary flushing flute. *0e7. The apparatus of claim 6, wherein an edge of each first face channel defines an obtuse angle with a respective second face channel edge e.*ee.* around each said flushing hole. *0*** * .8. A percussive drill configured to drill rock for a process of quarrying or mining, comprising a plurality of drill rods and a drill bit apparatus as claimed in any of claims I to 7.9. A method of mining or quarrying using the compressive drill of claim 8.10. A method of producing a percussive drill bit, comprising the steps of: machining a substantially cylindrical steel component with a longitudinal rotational axis, a substantially circular bit face normal to said axis having a bit face radius, and a gauge surface surrounding said bit face and inclined at a gauge angle; mounting a plurality of face buttons in said bit face; locating a first gauge button and a second gauge button into said gauge surface, such that, for each said face button, said first gauge button is displaced in a clockwise direction and said second gauge button is displaced in a counter-clockwise direction to present a wing defined by a first wing edge and a second wing edge; forming flushing holes between one of said wing edges and a third wing edge and an internal flushing conduit; cutting a primary flushing flute into said gauge surface between each said first gauge button and said second gauge button to an extent that substantially reaches a bit face circumference defined by said bit face radius; forming of a hollow drop centre hole; and forming a substantially straight first channel between each said flushing hole and said drop centre hole. * *11. The method of claim 10, wherein a plurality of primary flushing "en.* flutes are each cut to an extent that substantially reaches a bit face * circumference defined by said bit face radius. C... * . C12. The method of claim 11, wherein three primary flushing flutes are cut into the gauge surface to an extent that substantially reaches said bit face circumference defined by said bit face radius.13. The method of claim 10, further comprising the step of forming secondary flushing flutes at the radius of each flushing hole.14. The method of claim 13, further comprising the step of forming second face channels between each of said flushing holes and a radially aligned secondary flushing flute.15. The method of claim 14, wherein each first face channel includes an edge which forms an obtuse angle with a respective second face channel edge around the position of a flushing hole.16. A percussive drill bit apparatus as described herein with reference to the accompanying Figures.17. A method of producing a percussive drill bit as described herein with reference to the accompanying Figures. S... *. *.* .. *.. * **....: * * * * * S... * * * *5 II1111*5 * *_)