AU2009290128B2

AU2009290128B2 - Pilot bit

Info

Publication number: AU2009290128B2
Application number: AU2009290128A
Authority: AU
Inventors: Maurice Desmond Boakes
Original assignee: Taca Int Pty Ltd
Current assignee: Taca International Pty Ltd
Priority date: 2008-09-04
Filing date: 2009-09-03
Publication date: 2016-03-10
Anticipated expiration: 2029-09-03
Also published as: NZ592774A; AU2009290128A1; WO2010025500A1

Abstract

There is disclosed a pilot bit (20) for an earth excavating device ( 10) comprising an elongate body (25) having a proximal end (27) adapted for coupling to a rotating shall (11) of the earth excavating device (10) and a distal end (23). A plurality of blades (21) extend radially from and being substantially equidislantly spaced about the elongate body (25) such that each blade (21) extends in a spiral at least partially along a length of the elongate body (25). At least one of the blades (21) has a plurality of cutting faces (24, 26, 28) formed therein at predetermined distances along a length thereof. Each cutting face having a cutting edge (24a, 26a, 28a) that extends substantially perpendicular to a longitudinal axis of the elongate body (25) so as to define a plurality of cutting planes.

Description

WO 2010/025500 PCT/AU2009/001137 PILOT BIT CROSS-REFERENCE. TO k lIA D APPLICATIONS The present invention claims priority from Australian Provisional Patent Appication No 2008904590 filed on 4 September 2008, the contents of which is incorporated herein by , reference. FTELD OF INVENTION This invention relates generally to an earth excavation device, such as an carth boring device, and in particular, to a pilot bit for an earth boring device. BACKGROUND OF THE INVENTION -1. Earth boring or excavation devices, such as augers, generally comprise a rotating shaft having a cutting head mounted at a distal end thereof that acts to bore into the carth. .The shaft typically comprises a spiral vane that extends behind the cutting head to convey dislodged or loosened earth away from a cutting head to the soil surface. Typically the shaft is hand or power driven, depending upon the specific application and 15 the purpose of the excavation. The cutting head of a conventional auger generally comprises shank plates or cutting blades forcutting through and boring into die carth. A pilot bit is also typically attached to the cuttingg head so as to provide initial contact with the earth to initiate the hole such that it is sufficient to admit the following larger portions of the auger cutting head. Pilot 20 bits also auction to guide the auger and keep it boring in the desired direction. In this regard, pilot bits may assume a variety of configurations depending upon the type of carth being excavated. Known pilot bits typically comprise a first end portion for coupling to the rotating shaft of the cutting head of the auger and a second end portion having blades or cutting teeth 25 formed thereon for breaking the earth. The number of blades and/or cutting teeth provided on the pilot bit significantly influences the drilling rate of the pilot bit, as overcrowded bits impede the flow of earth being removed from the blades. Hence, whilst a pilot bit with a number of blades and cutting teeth may cut through the earth more easily, if there is not sufficient capability to remove the loosened earth from the 30 cutting blades, the drilling rate will be poor. .Similarly pilot bits having a number of teeth or cutting blades may experience significant forces during use resulting in the need for continual replacement und/or repair of the bits, particularly when used to excavate rock and other hard material.

WO 20101025500 PCT/AU2009/001137 heree is a need to provide a pilot bit for an earth excavating device that provides For improved drilling rates and reduced wear. The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general s knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding or the inventive-step of the present invention of which the identification of pertinent prior art proposals is butL one part. STATEMENT OF IN VKNTION io Accordingly, in one aspect of (he invention there is provided a pilot bit for an earth excavating device comprising: an elongate body having a proximal end adapted for coupling to a rotating shaft of the earth excavating device and a distal end; and a plurality of blades extending radially from and being substantially equidistantly 15 spaced about the elongate body such that cach blade extends in a spiral at least partially along a length of the elongate body; wherein, at least one of said blades has a plurality of cutting faces formed therein at predetermined distances along a length thereof, each cutting face having a cutting edge that extends substantially perpendicular to a longitudinal axis of the 20 elongate body so as to defne a plurality of cutting planes, In one embodiment, cach blade has a plurality of cutting faces formed therein at corresponding predetermined distances along a length thereof such that the corresponding cutting edges of the blades define the plurality of cutting planes. The cutting edges of adjacent cutting faces formed in the blade may be each-laterally 2s displaced from the longitudinal axis of the elongate body. In a preferred form, the cutting edges of adjacent cutting faces formed in the blade may be each laterally displaced from the longitudinal axis of the elongate body such that they do not substantially overlap. 1he cutting edges of cutting faces located towards the distal end of the body may be laterally displaced closer to the longitudinal axis of the elongate 30 body than the cutting edges of cutting faces located towards the proximal end of the elongate body. The distal end o f the elongate body may comprise a spike member. The spike member may have a substantially triangular wedge shape terminating at a pointed end. 11h spike member may further comprise one or more angular cutting edges configured to 2 WO 2010/025500 PCT/AU2009/001137 remove earth as the elongate body rotates. The proximal end of the body may have an internal recess formed therein for receiving at least a.portion of the rotating shaft of the earth excavating device to facilitate coupling thereto. One or more holes may be provided through the proximal end of the a body to receive one or more fasteners to facilitate removable coupling with the rotating shaft and the body. The proximal end of the body may comprise at least two shoulder portions, each shoulder portion may have a cutting edge that extends substantially perpendicular to a longitudinal axis of the elongate body so as to define a further cutting plane. The ia cutting edges of the shoulder portions may be each laterally displaced from the longitudinal axis of the elongate body so as to project beyond the cutting edges of the blades. In a preferred form, the cutting edges of the shoulder portions may be each laterally displaced from the longitudinal axis of the elongate body such that they do not substantially overlap with the cutting edges of the blades. .BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understood from the following non-limiting description of preferred embodiments, in which: Figure 1 is a side view of an auger assembly employing a pilot bit in accordance with one embodiment of the present invention; 20 Figure 2 is a perspective view of the pilot bit of Figure 1; and Figure 3 shows a bottom view of the pilot bit of Figure 1; Figure 4 shows a side view of the pilot bit of Figure 1; Figure 5 shows an end view of the pilot bit of Figure 1; and Figure 6 shows a top view of the pilot bit of Figure 1. 25 DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figure 1, an auger assembly in accordance with one embodiment of the present invention is shown. The assembly 10 comprises an auger 12 having a pilot bit 20 attached to a distal end thereof. The auger assembly 10 may be mounted to a vehicle, such as a tractor or earth moving vehicle, having an auger drive system for 30 rotating the auger assembly 10 and for applying a downward force to the auger assembly 10 to facilitate boring into the earth. 3 WO 2010/025500 PCT/AU2009/001137 'The auger 12 includes a shall 11 that is typically driven by the auger drive system to rotate about its longitudinal axis. The shaft 11 has a pair of flutes 13 that are arranged in a double helix or spiral configuration about the shaft to function as flighti ng. The flutes 13 define two paths for earth, loosened by thc action of the auger assembly 10, to s flow as the shaft 11 is rotated to penetrate into the carth. 'These flow paths act to remove loosened earth away from the boring head 14 and pilot bit 20, during excavation. The distal end or boring head 14 of the auger 12 has a pair of'plates 15 attached thereto. The plates 15 extend from the flutes 13 of the auger 12 and are attached to the flutes 13 to by way of bolts or the like, such that they can be replaced where necessary. The plates 15 may assiunc a variety of forms and may include teeth or the like to aid in cutting the earth as the shall 11 rotates. The plates 15 extend radially from the shaft 11 to ensure that a clearance is cut into the earth to enable passage of the following auger 12. A pilot bit 20 ii accordance with one embodiment of the present invention is configured is to be fitted to the shaft 11 .of the boring head 14 in the manner as shown in Figur 1. Referring to Figure 2, the pilot bit 20 comprises a conical main body 25 having a proximal end 27 that tapers towards a distal cnd 23. As is shown in Figure 3, the proximal end 27 has an internal recess-29 formed in the surface thereof that receives a male portion (not shown) of the shaft I L A pair of holes 20 19 are formed through opposing side walls of the body 25, adjacent the proximal end 27, so as to communicate with the internal recess 29. The holes 19 are aligned so as to receive a bolt 18, or similar fastening member, which passes through a corresponding hole (not shown) formed in the male portion of the shaft 11, to secure the pilot bit 20 to the shaft 11. In this arrangement, should the pilot tip 20 require replacement or repair, it 25 can be readily removed from the shall II by removing the bolt 18, as necessary. It will be appreciated that other mechanisms may also be employed to releasably secure the pilot bit 20 to the boring head 14 of the auger 12 and still fall within the spirit of the present invention. When the pilot bit 20 is secured to the shaft 11 in this manner, the rotational axis of the pilot bit 20 is substantially collinear with the rotational axis of -the 30 shall. 11 The distal end 23 of the pildt bit 20 has a spike member 22 projecting.therefrom. The spike member 22 is in the form of a triangular wedge that tapers to a point 22a. Tic point 22a of the spike member 22 forms a leading tip that provides initial contact with the earth to create an initial hole in the earth. In this regard, prior to excavation, the as spike member 22 is initially brought into contact with the earth being drilled under force, to break the surface of the earth for the commencement of excavation. 4 WO 2010/025500 PCT/AU2009/001137 As the assembly 10 is further urged into the earth by the corresponding drive system, the. spike member 22 is caused to rotate. Rotation of the spike member 22 results in the spike member 22 performing a drilling function. Due to the triangular wedge shape of the spike member 22 the leading edges of the member 22 act to shave away the earth to . provide a hole in the earth of gradually increasing diameter. Rotation of the spike member 22 also functions to centre the pilot bit 20 thereby reducing the likelihood of the pilot bit 20 drifting or laterally shifting under rotational-motion. This is particularly important where the assembly is being used to excavate earth of varying density and hardness, where lateral shifling of the auger is more likely. 10 The main body 25 of the pilot bit 20 has a pair of radially extending blades 21 forced integral therewith. Ithe blades 21 are spaced equidistantly about the longitudinal axis of the main body 25 and extend from adjacent the proximal end 27 to adjacent the base of the spike member 22 in a helical or spiral manner, as shown. bach of the blades 21 have a substantially identical configuration as shown. i1 As is shown more clearly in Figure 4, the extent to which the blades 21 project from the central axis of the body 25 reduces as the blades 21 approach the spike member 22 such that the pilot bit 20 has an overall conical shape. In this regard, the base of the spike member 22 is formed to blend into the body 25 so as to provide a relatively smooth transition between the blades-21 and the spike member 22. 20 A first cutting face 28 is provided in the most distal region of the blades 21, namely that region of the blades 21 immediately adjacent the base of the spike member 22. As is shown more clearly in Figure 6, the first cutting face 28 of the blades 21 has a cutting edge-28a that extends substantially orthogonal to the central longitudinal axis of the main body 25. Tn such an arrangement, the laterally extending first cutting edge 28a 25 projects beyond the central axis of the body 25 a distance greater than the width of the base of the spike member 22. Hence, as the pilot bit 20 rotates and is urged into the earth, the cutting edges 28a of the first cutting faces 28 act to cut away thc.carth in a chisel-like manner to form a hole having a diameter substantially equivalent to the combined distance of lateral projection of the opposing first cutting edges 28h of the 30 blades 21 from the central axis of the body 25. As the first cutting edges 28a of the blades 21 folow behind the spike member 22, the first cutting edges.28a act to form a hole in the earth having a greater diameter than the hole formed by the spike member 22. As the hole formed by the first cutting edges 28a of the blades is only marginally wider in diameter than the hole formed by the rotating 35 spike member 22, the amount of work perfonned by the first cutting edges 28a is reduced. Tn this regard, the first cutting edges 28a define a first.cutting plane of the 5 WO 2010/025500 PCT/AU2009/001137 pilot bit 20. hlie helical or spiral region ot the blades 21 extend away from the first cutting face 28 towards the proximal end 27. Each of the blades 21 have a leading edge formed therein that is disposed in advance of the zone of connection of the blade 21 with the body 25, 5 as is shown in Figure 4. The leading edge of each blade 21 projects beyond.the central axis of the body 25 a distance greater than the most lateral region of first cutting edges 28a, and progressively increases as the blades 21 travel away from the first- cutting edge 28a towards the proximal end 27. in this arrangement, the leading edge of the blades 21 acts to further remove a portion of the earth as the bit 20 rotates by shaving away the earth along the leading edge. The portion of earth removed by the loading edges of the blades 21 is significantly loss that that removed by the first cutting edges 28a, due to the gradual increase in the projection of the blades 21 from the central axis of the body 25 with respect to the lateral projection of the first cutting edges 28a. As is apparent from the Figures, the thickness of the blades 21 also increases as the blades 21 travel f-oNm the 15 first cutting edges 28a. As well as performing a cutting function, the helical nature of the blades 21 functions to provide a path for removal of the loosened earth away from first cutting edges 28a and the leading edges of the blades 21. A second cutting face 26 is formed in the blades 21 at a point intermediate the distal end 20 23 and the proximal -end 27 of the body 25. As is shown in Figure 6, the second cutting face 26 has a laterally extending cutting edge 26a that extends substantially orthogonal to the central longitudinal axis of the main body 25. As is more clearly shown in Figure 6, the second cutting edges 26a are configured such that they are located beyond the lateral projection of the first cutting edges 28a. In this arrangement, as the pilot bit 20 25 rotates and penetratos into the earth, the second cutting edges 26a come into contact with tie carth to progressively increase the diameter of the hole being excavated in the earth. The second cutting edges 26a define a second cutting plane of the pilot bit 20 that cuts a hole having a wider diameter to the hole cut by the preceding portion of the bit 20. 3o As is shown in Figure 3, the second cutting edges 26a form a hole in the earth having a diameter 'x' of between around 70 90 mm, preferably around 81 mn. The proximal end of the body 25 has a pair of opposed cutting shoulders 24 formed therein. l'he cutting shoulders 24 define the widest portion of the pilot bit 20, spanning a distance 'y' of between around 85mm - 125mm, preferably around 105 mm. The 35 cutting shoulders 24 each have a cutting edge 24a that extends substantially orthogonal to the central longitudinal axis of the main body 25. Cutting edges 24a are configured 6 WO 2010/025500 PCT/AU2009/001137 it) contact the carth as the pilot bit 20 rotates, thereby excavating a greater diameter of' earth than the preceding bit 20. As shown in Figure 6, the cutting shoulders 24 are configured such that the cutting edges 24a arc located beyond the lateral projection of the second cutting edges 28a. In this arrangement, the cutting shoulders 24 define a s third cutting plane of the pilot bit 20 that forms a bole having a wider diameter to that cut by the preceding portion of the pilot bit 20. In this regard, the pilot bit 20 provides at least a three stage cutting process for excavating a hole in the earth for providing a passage for the auger 12. 'lie first cutting edges 28a, second cutting edges 26a, and the cutting shoulders 24 of i the pilot bit 20 each work together to loosen and remove the earth in. three distinct steps or stages. The leading edges of the blades 21 are also able to perform an earth cutting function as well as a removal function to aid in penetration of the pilot bit 20 into the earth. It will be appreciated that the spike member 22 also provides another stage of earth removal. Due to the progressive stages of earth removal to form a hole of a 1s particular diameter, the amount of work performed by the pilot bit 20 to form such a hole in the carth is reduced, particularly in comparison to a pilot bit having a single cutting plane. Similarly, the forces experienced by the various cutting edges of the pilot bit 20 are diminished due to the progressive citing arrangement, reducing the need to continually replace and/or repair the pilot bit 20. It has been found that the pilot bit 20 20 of the present invention is able to more aggressively penetrate into the earth to provide improved boring rates and better control of the overall process. As shown in Figure 1, the blades 21 of the pilot bit 20 are arranged to have an attack angle 0 of betwcn 1200- 160u. The attack angle e is the angle farmed between the rotational axis of the blades 21. and the work surface, defining the helix angle of the 2s blades 21. lt has been found that such an atack angle also provides for more aggressive penetration of the pilot bit through the earth, thereby greatly increasing drilling rates of the auger 12. Whilst not shown in the Figures, the spike member 22, first and second cutting edges 28, 26, cutting shoulders 24 and blades 21 may be provided with one or more tiles to aid 30 in earth removal. The tiles may be welded or otherwise attached to the surface of the body 25 of the pilot hit 20 and may be in the form of conventional tungsten tiles. Similarly, the surfaces of the pilot bit 20 may include granules of tungsten welded therein so asto be integrally formed with the body 25 to facilitate improved penetration of the pilot bit 20 into the earth during use. 35 Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is 7 WO 2010/025500 PCT/AU2009/001137 expressly stated or the context requires otherwise. That is, the word comprisec" and its derivatives will be taken to indicate the inclusion oflnot only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires s otherwise. It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention; Throughout the specification and claims the word "comprise" and its derivatives are io intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to indicate the inclusion of not only the listed components. steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires 1s otherwise. Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower ate to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the auger uppermost. 20 It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention. 8

Claims

1. A pilot bit for an carth excavating device comprising: an elongate body having a proximnal end adapted for coupling to a rotating shaft of the earth excavating device and a distal end; and. 6 a plurality of blades extending radially from and being substantially equidistantly spaced about the elongate body such that each blade extends in a spiral at least partially along a length of the elongate body; wherein, at least one of said blades has a plurality of cutting faces formed therein at predetermined distances along a length thereof, each cutting face having a 10 cutting edge that extends substantially perpendicular to a longitudinal axis of the elongate body so as to define a plurality of cutting planes.

2. A pilot bit according to claim 1, Wherein each blade has a plurality of cutting faces formed therein at corresponding predetermined distances along a length thereof such that the corresponding cutting edges' of the blades define the 15 plurality of cutting planes.

3. A pilot bit according to claim I or claim 2, wherein the cutting edges of adjacent cutting fices: formed in the blade are each laterally displaced from the longitudinal axis of the elongate body.

4. A pilot bit according to claim 3, whercin the cutting cdges of adjacent cutting 20 faces formed in the blade are each literally displaced from the longitudinal axis of the elongate body such that they do not substantially overlap.

5. A pilot bit according to claim 3 or claim 4, wherein the cutting edges of cutting faces located towards the distal end are laterally displaced closer to the longitudinal axis of the elongate body than the cutting.cdges of cutting faces 25 located towards the proximal end of the elongate body.

6 A pilot bit according to any one of the preceding claims, whercin the distal end of the elongate body comprises a spike member.

7. A pilot bit according to claim 6, wherein the spike member has a substantially triangular wedge shape terminating at a pointed end. 3o

8. A pilot bit according to claim 7, wherein the spike member comprises one or more angular cutting edges configured to remove earth as the elongate body 9 WO 2010/025500 PCT/AU2009/001137 rotates.

9. A pilot bit according to any one of the preceding claims, wherein the proximal cnd of the body has an intenial recess formed thercin for receiving at least a portion of the rotating shaft of the earth excavating device to facilitate coupling s thereto.

10. A pilot bit according to claim 9, wherein one or more holes are provided through the proximal end of the body to receive one or more fasteners to facilitate removable coupling between the rotating shaft and the body.

11. A pilot bit according to any one of the preceding claims, wherein the proximal 10 end of the body comprises at least two shoulder portions, each shoulder portion having a cutting edge that extends substantially perpendicular to a longitudinal axis of the elongate body so as to define a further cutting plane.

12. A pilot bit according to claim 11, wherein the cutting edges of the shoulder portions are each -laterally displaced from the longitudinal axis of the elongate 1S body so as to project beyond the cutting edges of the blades. 1.3. A pilot bit according to claim 12, wherein the cutting edges of the shoulder portions are each laterally displaced from the longitudinal axis of the elongate body such that they do not substantially overlap with the cutting edges of the blades, 10