AU783965B2 - A plate drill bit with laid back wings - Google Patents

Description

AUSTRALIA

Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: I :f Applicant: Sandvik-AB In_-e\_c-vrck o -rj '\B Inventor(s): Steven Lee Weaver Michael Andrew McLean David Alexander McCloskey Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: A PLATE DRILL BIT WITH LAID BACK WINGS Our Ref: POF Code: 665943 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 1 N URN%85943' onplee foms210302 doc 2 A PLATE DRILL BIT WITH LAID BACK WINGS Field of the Invention The present invention relates to a drill bit for use in rock bolting. The invention has been designed especially but not exclusively for use as part of a self drilling rock bolt and the invention is herein described in that context.

However, it is to be appreciated that the invention has broader application and may be used in other applications such as more conventional rock drilling operations including a drill rod.

Backgqround of the Invention A reference herein to a patent document or other matter which is given as prior art is not to be taken as an admission that that document or matter was, in Australia, known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

Rock bolts are commonly employed in the underground mining industry to support the walls of rock excavations against fragmentation or collapse. The *i normal procedure for installing such a bolt involves drilling a pilot hole into the rock wall using a drill rod incorporating a drill bit on its distal end, and inserting 20 the bolt therein. The bolt is typically fixed within the hole using a settable glue, such as a resin or mortar cement. Alternatively, the bolt may include means to directly interlock with the surface of the pilot hole, such as a thread or an expanding sleeve.

A wide variety of rock bolts exist. One particular form is tubular and has a central bore formed lengthwise through the bolt. Advantageously, the central bore provides a conduit for the introduction of water during insertion of the bolt into the pilot hole. Water is employed to flush away rock segments, finings and dust, to reduce frictional resistance between the bolt and the rock, and to prevent excessive temperature generation. The central bore also provides a conduit for the injection of cement mortar or resin into the pilot opening to secure the bolt therein.

The above described methods of installing a rock bolt employ a two stage process, in which the pilot hole is first drilled, before the bolt is inserted U WCNPatW U43*043 t 2a and subsequently secured in the pilot hole by the appropriate means. The type of rock bolt therefore has no drilling capability.

*o o e S ECPpasB430oE43 *Ma r- 1M aoc -3- Rock bolts having a drilling capability, and thereby referred to as "self drilling rock bolts", have previously been developed, but such bolts are not in common use in the mining industry. This is because to date the cost of such self drilling rock bolts has been prohibitive, despite their installation advantages.

This is due primarily because the drill bit is only used once in a self drilling rock bolt whereas in a conventional drilling technique using a drill rod, the drill bits can be re-used.

Prior art drill bits are expensive because the bit body is cast and as they are subjected to very high wear, it is normal for the drill bit to include a hardened tip which is typically formed from tungsten carbide. Whilst it is economical to use such drill bits in drill rods where the bits can be re-used, they are too expensive to use in self drilling rock bolt applications.

.o ~It is an aim of the present invention to provide a drill bit which is less costly to manufacture than prior art arrangements, thereby making it ideally suited for use in self drilling rock bolts.

Summary of the Invention According to the present invention there is provided a drill bit having an axis of 20 rotation, and including a drill bit body, a drill tip, said drill bit body being formed from plate material and including a body portion, a tongue and a wing, said body portion including opposite major faces and having a centre plane which extends between said faces with said axis of rotation extending generally in said centre plane, said tongue extending from a lower region of said body portion to form a trailing edge of said bit, said tongue being arranged to enable the bit to be attached to a drive element, and said wing extending from an upper region of said body portion and being angled away from said centre plane, wherein said drill tip is mounted on a leading face of said wing.

An advantage of the present invention is that the drill bit body formed from plate material is significantly cheaper than a cast body. In addition, providing an arrangement where the wing is angled away from the centre plane of the body portion provides an arrangement which is very inexpensive to N: URK\65943,AP CS 2 A pt~e drit bd wah La bc kmp doc -4manufacture yet still enables the drill tip to be appropriately orientated for efficient drilling Preferably, the drill bit includes at least a pair of wings.

The wings are preferably angled away from the central plane in opposite directions thereof. In a particularly preferred form, the leading face of the wings is angled back so as to provide a negative rake to the drill tip mounted thereon.

Preferably, the drill tip includes a cutting edge which is substantially coincident with the central plane of the drill bit body.

Preferably, the wings define there between a channel. The channel is preferably substantially u-shaped.

The drill bit body is preferably pressed or stamped from a sheet of metal plate. The metal plate is preferably Bisalloy 360. Another alternative material for the metal plate is XK9258S. The plate preferably has a thickness of approximately 6mm.

S• 15 The drill tips are preferably tungsten carbide drill tips that are brazed to wings of the drill bit body. The leading face may be substantially planar or in an alternative form includes a seat on which the drill tips are located. The seat may be made in any form such as by a separate milling process or by a pressing or forging operation. A preferred material for the drill tips is WC-Co sinter, 6-8 Co with 2-5 gm WC grain size.

The tongue is preferably arranged to be received in an aperture in a leading end of a drive element, such as a drill rod or a rock bolt (in a self drill rock bolt application). The tongue is preferably shaped so that in can be firmly located within the aperture and transmit rotational and thrust forces from the rock bolt to the drill bit. The tongue may include a wedge shaped portion which is arranged to be received in a correspondingly shaped portion of the aperture.

In another form the tongue may include a threaded portion which is arranged to engage in a threaded portion of the aperture in the drive element.

Brief Description of the Drawings Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: NAuRNW85g43.Ap. Cawe 2-A ptea drID bd fth tat bac gs doc Figure 1 is a perspective view of a drill bit in accordance with an embodiment of the invention.

Figure 2 is a side view of the drill bit shown in Figure 1.

Figure 3 illustrates the leading end of a rock bolt which is arranged to receive a drill bit of the type shown in Figures 1 and 2.

Figure 4 is a perspective view of a drill bit in accordance with a second embodiment of the invention.

Figure 5 illustrates the leading end of a rock bolt which is arranged to receive the drill bit shown in Figure 4.

Detailed Description of the Preferred Embodiments S. Figure 1 illustrates a drill bit 10 for a self drilling rock bolt. The drill bit includes a drill bit body 12 which is formed from plate material. The drill bit body S• °12 includes a tongue 14 formed at one end thereof and a pair of wings 16a, 16b S 15 formed at the opposite end thereof. The wings 16a, 16b extend from the drill bit S. body 12 and are angled away from a central plane thereof. As illustrated in Figure 2, the respective wings 16a, 16b are angled away from the central plane in opposite directions.

Mounted on a leading face 18 of each of the wings 16a, 16b is a drill tip 20. The drill tip 20 is essentially a strip tip which is shaped so that the drill tip includes a cutting edge 22 which is substantially coincident with the central plane of the drill bit body 12. This positioning of the cutting edge 22 of each of the drill tips 20 provides optimal cutting characteristics for the drill bit However it is to be appreciated that the cutting angle may be positive or negative depending on the amount the wings are laid back.

As clearly illustrated in Figure 1, each of the wings 16a, 16b define therebetween a channel 24. The channel 24 is preferably substantially ushaped and is provided to eliminate the dead centre.

The drill bit body 12 as formed prior to folding of the wings 16a, 16b includes a pair of first side surfaces which are angled at about 5 100 to the vertical. When the wings 16a, 16b are folded, each first side surface becomes two surfaces 26a, 26b. The angle of the lower side surface 26b provides a N:URNU68543%CAP cas 2 A ptoe dn5 bd wah lad back wVSrgsdoC -6cutting clearance which prevents the bit 10 rubbing against the hole as it is being cut.

The tongue 14 of the drill bit 10 is integral with the drill bit body 12 and is arranged to be received in an aperture 50 located in a leading end 52 of a rock bolt 54. The leading end 52 of such a rock bolt 54 is illustrated in Figure 3. As shown in this Figure the aperture 50 is wedge-shaped so as to receive the correspondingly shaped end portion 14a of the tongue 14. The tongue 14 and aperture 50 are shaped so that they can be readily connected together in such a manner that any rotation and thrust of the rock bolt 54 will be transferred to the drill bit The drill bit 10 which includes the drill bit body 12, wings 16a, 16b and integral tongue 14 is designed so that it can be readily pressed, stamped or otherwise formed from a sheet of metal plate. A suitable material for this 0 purpose is a Bisalloy 360 or XK9258S. It will, however, be appreciated that 15 different materials could be used and the selection of the required material will S. depend on a number of factors, such as the nature of the material that the drill bit 10 is required to penetrate and the required life of the drill bit 10. The metal plate would ideally have a thickness of approximately 6 mm. It will, however, be appreciated that different thickness metal plates could be used.

The drill tips 20 are preferably tungsten carbide drill tips that are brazed to the leading face 18 of each wing 16a, 16b. A preferred material for the drill tips 20 is WC-Co sinter, 6 8% Co with 2 5 pm WC grain size.

Figure 4 illustrates an alternative form of the drill bit 100. The drill bit 100 is substantially identical to that illustrated in Figures 1 and 2 with the exception that the tongue 114 includes a threaded arrangement 102 on either side of the tongue 114. The threaded arrangement 102 is arranged to be received within a threaded aperture 150 formed in the leading end 152 of a rock bolt 154. The leading end 152 of such a rock bolt 154 is shown in Figure The configuration of the wings 16a, 16b is such that there is clearance of the drill bit body 12 behind each cutting tip 20. This clearance can be achieved during the pressing/stamping process used to form the drill bit 10. No extra processing of the drill bit 10 is subsequently required. Consequently, the drill bit N URNW5943T.AP Case 2 A plate dnfl bM wah tai back wums doe -7can be produced relatively inexpensively while still providing satisfactory cutting characteristics. A further advantage is that the cutting edge of each drill tip 20 is positioned close to the central plane of the drill bit body 12.

Drill bits made in accordance with an embodiment of the invention are advantageous because the drill bit body 12 is readily formed from a sheet of plate material and because the drill tips 20 are simply brazed or otherwise attached to the wings 16a, 16b. The wings 16a, 16b are manufactured as part of the initial forming step and thus no separate machining of the side surfaces 26 is required. Accordingly, the manufacturing process for such a drill bit 10 is relatively simple and thus the cost of producing such a drill bit 10 is reduced when compared to prior production costs.

It will also be appreciated that the drill bits 10 can be readily secured to the leading end of a rock bolt.

"The embodiments have been described by way of example only and modifications within the spirit and scope of the invention are envisaged.

NAJRN85g43CAP Ce 2 -A ptlm drh im back wpdoc

Claims (14)

1. A drill bit having an axis of rotation, and including a drill bit body, a drill tip, said drill bit body being formed from plate material and including a body portion, a tongue and a wing, said body portion including opposite major faces and having a centre plane which extends between said faces with said axis of rotation extending generally in said centre plane, said tongue extending from a lower region of said body portion to form a trailing edge of said bit, said tongue being arranged to enable the bit to be attached to a drive element, and said wing extending from an upper region of said body portion and being angled away from said centre plane, wherein said drill tip is mounted on a leading face :o of said wing.

2. A drill bit according to claim 1, wherein said drill bit body includes a pair of said wings, said pair of wings being angularly spaced relative to the axis of rotation and being angled away from the centre plane in opposite directions, wherein each of said pair of wings includes a said drill tip mounted on its respective leading face.

3 A drill bit according to claim 2, wherein each of the wings are radially spaced from the axis of rotation so as to thereby define a channel along said axis. 20

4. A drill bit according to either claim 1 or 2, wherein the leading face of the .i or each wing is angled back so that the drill tip mounted on that face has a negative rake.

A drill bit according to any preceding claim, wherein the or each drill tip includes a cutting edge which is substantially coincident with the centre plane of the drill bit body.

6. A drill bit according to any preceding claim, wherein the drill bit body is pressed or stamped from metal plate.

7. A drill bit according to any preceding claim, where the or each drill tip is brazed to the leading face of the wing, or a respective one of wings, of the drill bit body.

8. A drill bit according to any preceding claim, wherein the leading face of the wing is substantially planar. N URNM ON5943AP Case 2 A plte drill li wit lad back ings oriC -9-

9. A drill bit according to any one of claims 1 to 7, wherein the leading face of the or each wing includes a seat on which a said drill tip is operative to be mounted.

A drill bit according to any preceding claim, wherein the tongue is arranged to be received in an aperture in a leading end of the drive element so that rotational and thrust forces are operative to be transmitted from said drive element to said drill bit.

11. A drill bit according to claim 10, wherein the tongue is wedged shaped and is arranged to be received in a correspondingly shaped portion of the aperture.

12. A drill bit according to claim 10, wherein the tongue includes a threaded portion which is arranged to engage a corresponding thread in the aperture of the drive arrangement.

13. A self drilling rock bolt including a drill bit according to any one of the preceding claims mounted at a leading end thereof.

14. A drill bit substantially as herein described with reference to the accompanying drawings. A self drilling rock bolt substantially as herein described with reference to the accompanying drawings. DATED: 28 March, 2002 /4PHILLIPS ORMONDE FITZPATRICK a SEC ttorneys for: SASE0-Ag 1 3,. N URN85943CAP Case 2 A "a drU bt wft lad back wngs.doc