FIELD

The invention relates to a bucket for an underground mining vehicle and an underground mining vehicle including the bucket. It also extends to a method of digging material in a passage of an underground mine.

This invention relates particularly but not exclusively to a bucket for use with an underground loader, and an underground loader including the bucket. It will therefore be convenient to hereinafter describe it with reference to this example application. However, it is to be clearly understood that it is capable of broader application.

DEFINITION

In this specification, the term ‘comprising’ is intended to denote the inclusion of a stated integer or integers, but not necessarily the exclusion of any other integer, depending on the context in which that term is used. This applies also to variants of that term such as ‘comprise’ or ‘comprises’.

In the specification and claims, the term ‘crowd/rotation oscillations’ shall be understood to mean the actions that are taken by a loader operator when digging into a pile of material with a LHD loader in an underground mine. These actions are the movements that are carried out with the bucket to increase the penetration of the bucket into the material to be loaded.

BACKGROUND

Sub-surface mining or underground mining consists of digging tunnels or shafts in the earth to reach ore deposits under the surface. Ore for processing, and waste rock for disposal is brought to the surface through tunnels and shafts. Different types of sub surface mining are classified by the different type of access shafts used, and the extraction method or technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mining uses diagonally sloping access shafts, and shaft mining utilizes vertical access shafts.

Other methods include shrinkage stope mining, which creates a sloping underground room, long wall mining which involves grinding a long ore surface underground, and room and pillar mining which involves removing ore from rooms while leaving pillars in place to support a roof over the room. Room and pillar mining often develops into retreat mining in which supporting pillars are removed as the miners’ retreat, allowing a roof to cave in and free up more ore for recovery. There are physical constraints on moving equipment around in an underground mine. These constraints are unique to an underground mine and are not encountered in above ground mining operations where there is plenty of space. Therefore, in underground mining operations, special equipment is required to gather and remove broken rock, and then transport and process the broken rock. One type of equipment used in underground mining is an underground loader (an underground LHD (load, haul, dump) loader).

Underground loaders are related to conventional front-end loaders but have been adapted for underground mining applications, with production economy, and safety considerations in mind. They are extremely rugged, highly manoeuvrable, and exceptionally productive. Applicant understands that more than 75% of the world’s underground metal mines use underground loaders for handling the broken rock or muck from blasting operations and for excavating and removing ore.

In underground mines loaders are required to work in confined spaces with minimum clearances to the sides and the top of loader backets. In these confined spaces the crowd and lift functionality of the loader cannot be fully utilized. Some underground loaders have powerful prime movers, advanced drive train technology, heavy planetary axles, four-wheel drive, articulated steering, and ergonomic controls. As discussed above, in an underground mine, the tunnels and stopes are very narrow and confined and the underground loader needs to be able to manoeuvre in a confined underground space. As length is not a limitation in a tunnel or a decline in an underground mine, loaders can be designed with a longer profile. Consequently, underground loaders have a narrower, longer, and lower profile than surface loaders. The longer profile of the loader improves the axial weight distribution and enables the capacity of the bucket to be increased. Further, a two-part construction of a LHD loader with a central articulation point helps the loader to manoeuvre, e.g., turn, in an underground mine.

As with all mining endeavours, there is a focus on the efficient utilization of equipment in underground mining. There are constant pressures to maximize the material throughput achieved with each piece of equipment. One example of a prior art bucket for a LHD loader used in underground mining is shown in Figure 1. One feature of this bucket is that the side walls of the bucket extend parallel to each other and perpendicular to a leading end or front end of the bucket. That is, the side walls and front end have a rectilinear configuration. One difficulty with underground loaders is the challenge of efficiently penetrating rock material to load the bucket efficiently and optimize payloads. The confined environment with restricted space limits the thrusting action that can be made with the bucket into the rock pile. It is very different to an above ground environment where the bucket movement is not restricted in any way. On reviewing the prior art relating to loading buckets of LHD loaders in underground mines, it is apparent that numerous efforts have been made by persons skilled in the art to improve loading or digging performance and that these efforts are ongoing. From this review, it is clear that the problem is widely recognized, and that the benefits of finding a solution to this problem will be great. We discuss some of the prior art developments in the loading of underground loaders below.

CATERPILLAR ^® have published a development which involves making the hydraulics system of the bucket handling arrangement more powerful. To do this, they use large bore lift and tilt cylinders that deliver exceptional strength and performance. They provide high hydraulic flow rates with fast hydraulic cylinder response and powerful lift times. This enables fast cycle times to be achieved when digging.

In addition, CATERPILLAR ^® has also published their development of more powerful engines for underground loaders. A more powerful engine will increase the lugging force while the loader is digging and traversing steep grades. Further, electronic engine management systems have also been developed to monitor sensor inputs and operator actions, and based on this they optimize the engine performance.

Further, CATERPILLAR ^® have also published the development of a Z-bar loader linkage geometry (associated with the loader arms) that generates an increased breakout force and an increased rack back angle. This development, by improving the ability of the loader arms to manoeuvre the bucket, enables more efficient bucket loading to be achieved.

Additionally, CATERPILLAR ^® have published some of their developments for improving the pilot or operator controls to enable a loader operator to better control the bucket. For example, they have provided a low effort joystick implement control with simultaneous lift and tilt functions to improve operating efficiency. This is designed to ease the task of the operator to manipulate the bucket with the controls, but it does not fundamentally improve the operation of the bucket when considered on its own.

Further, CATERPILLAR ^® have also published their development of a nitrogen filled accumulator in the hydraulic lift circuit to act as a shock absorber for the bucket and lift arms. This damps the lift arm and bucket response over rough ground reducing fore and aft pitch and improving cycle times and load retention. This results in a smoother ride enabling operators to load the bucket and then transfer the load more quickly.

However, the limitation of these developments discussed above is that they need to be implemented on new underground loaders. They cannot be implemented on existing underground loaders, and they do not relate to the bucket design. Therefore, the implementation of any of these solutions in an underground mine will involve significant capital expenditure and be expensive. They do not provide a basic solution that can be implemented at minimal cost.

In addition to the efforts directed at redesigning aspects of the underground loader to improve digging ability, other efforts have been directed towards redesigning the bucket that is used in underground loaders to improve performance and/or reduce wear.

For example, Goldmont Engineering (www.qoldmont.com.au) have published that they have utilized different grades of HARDOX ^® wear plate and STRENX ^® performance steel to try and reduce wear of the buckets. They make the following statements about their OUTCAST™ bucket.

The OUTCAST™ bucket is stronger yet lighter and forms a smoother profiler with less resistance when digging. It has much lower wear rates than conventional buckets thanks to its unique shape and the use of SSAB’s steels. The bucket is about 25% lighter than a conventional R2900 loader bucket with the same volume. It is designed to reduce friction inside the bucket and on its outer sides, reduce damage from impact loading and reduce hang up in the bucket. While the bucket primarily reduces wear rates, Goldmont Engineering also claim that the bucket reduces resistance where the lip engages the dirt.

Additionally, further work has been done by some manufacturers, to customize the shape of the lip, at the entrance to the mouth of the bucket, to improve the digging efficiency. In addition, KOMATSU ^® has published some developments in the design of underground buckets. The KOMATSU ^® KVX underground bucket incorporates steel wear parts onto high wear areas of the buckets. These parts include front protectors, wear bars, heel shrouds, wear buttons, and chocky parts. The idea is to provide a bucket that has a hardness and toughness to address the impacts and high wear encountered in use while still providing a light bucket that can carry a large payload.

However, despite the efforts by these companies, there is still a need to improve the efficiency of loading buckets with rock material on existing underground loaders. This efficiency plays a significant role in the overall productivity of loading and moving rock material in underground operations.

In addition to the limitations of prior art equipment and the efforts to address these, it is also recognized that operating a bucket in a confined underground environment is a difficult and arduous task. Mine operators acknowledge that loading efficiencies and outcomes generally depend on the skill of an individual operator. Applicant understands that with current equipment more experienced operators generally achieve better outcomes and it would therefore be advantageous if this activity could be made less dependent on an operator’s skill. That way similar outcomes could be achieved by operators with different levels of experience.

The reference to prior art in the background above is not and should not be taken as an acknowledgment or any form of suggestion that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

SUMMARY OF THE INVENTION

Applicant recognizes that prior art buckets with parallel side walls (perpendicular to the front of the bucket) have limitations in underground mines where there is a confined space with minimal clearance on the sides and top of the bucket. The capability of the bucket to penetrate the material is limited in the cramped conditions of an underground tunnel. This limits the degree to which the bucket can be filled up with each load.

Another shortcoming of the underground environment is the high structural wear that occurs over the entire side wall of the bucket during its working life.

Applicant consequently recognizes that it would be beneficial to improve the performance of buckets used on mining vehicles in underground mining. According to one aspect of the invention there is provided a bucket for use on a mining vehicle, e.g., underground mining vehicle, the bucket comprising: a main wall having two sides; and side walls mounted on each side of the main wall, wherein the side walls taper inward in a rearward direction.

The side walls may extend from a leading end to a rear end.

The main wall and the side walls together may define an interior space and form a mouth at a leading end of the side walls.

The side walls may taper inward at an angle of 2 to 10 degrees towards each other.

In some example embodiments, the side walls may taper inward at an angle of 2 to 7 degrees, e.g., 2 to 4 degrees. The angle of taper needs to be at least 2 degrees to meaningfully reduce the wear and improve loading of the bucket. However, if the walls taper inward at an angle that exceeds 10 degrees, the taper will significantly reduce the volume of the bucket which is counterproductive. For this reason, the angle of taper may be limited to 10 degrees.

The main wall may comprise a lower floor portion extending from the front end towards the rear end and an upper portion extending up from the lower floor portion and over the lower floor portion back to the leading end.

The lower floor portion may be substantially planar, and the side walls may extend substantially perpendicular upward away from the lower floor portion while also tapering inward as they extend in a rearward direction. That is, while the side walls extend up vertically from the lower floor portion, they taper inward towards each other in a rearward direction. The mouth of the bucket may face forwardly (and not upwardly) when loading.

The bucket may have a width extending from one side wall to the other side wall, and the bucket may have a height.

The height may be measured in a straight line from the lower wall portion at a bottom of the mouth, to the upper portion of the main wall at a top of the mouth.

Another way of measuring a height of the bucket may be to measure the vertical height from a support surface on which the bucket is resting to the highest point on the upper portion of the main wall, e.g., at the mouth. While two different methods of measuring the height of the bucket yielding different height measurements are provided, it is not intended that both methods be used. Rather, either method for measuring the height of the bucket could be used.

The bucket may be elongated in a direction of width such that the width of the bucket is greater than the height of the bucket. In particular, the bucket may have a width that is at least 20% greater than its height. In some forms, the bucket may be at least 25% wider than it is high, or even 40% wider.

The bucket may have a height from 1 .5 to 2.5 m. In some example forms, the bucket may have a height of 1 .8 to 2.4 m.

The interior space of the bucket may have a capacity of 0.8 to 12 m ³ . In some example non-limiting forms, the interior space of the bucket may have a capacity of 3 to 10 m ³ .

The bucket may include bucket manoeuvring formations on the upper portion of the main wall towards the rear end of the bucket that interact with the arms on the loader to manoeuvre the bucket in operational use. These bucket manoeuvring formations may include ears that are operatively connected to the arms on a loader.

The main wall may include a recess portion forming a recess for receiving the bucket manoeuvring formations therein to reduce the extent to which the bucket manoeuvring formations project out of the main wall. This assists with manoeuvrability of the bucket in the cramped conditions encountered in an underground mine.

The recess portion in the main wall may encroach on the interior space of the bucket thereby reducing its capacity.

The recess portion may be substantially centrally positioned on the main wall and may have substantially square walls forming a box, e.g., an internal box.

In some example forms of the invention but not all forms of the invention, the bucket may be a linerless bucket. That is, the bucket does not include removable liners that contact the rock material and can be replaced when the liners are worn through.

Further, in some example forms of the invention but not all forms of the invention, the linerless bucket may be formed from steel and the main wall and the side walls may be formed from different thicknesses of steel. Further, in these example forms, the main wall may have different zones, and the different zones of the main wall may be formed with different thicknesses of steel.

Yet further, the side walls may have different zones, and the different zones of the side walls may be formed with different thicknesses of steel.

The bucket may include GET (ground engaging teeth) formations removably mounted on the main wall and the side walls of the bucket. The GET formations may be positioned around the mouth of the bucket recognizing that this is a high wear area. The bucket may also include GET formations rearward of the mouth, e.g., blocks mounted at spaced intervals along the intersection of the lower wall portion with the side walls, extending rearward from the mouth.

The bucket may include any one or more of the features, or combination of features, of the bucket or loader bucket defined in any other aspect of the invention.

According to another aspect of the invention there is provided a loader bucket for an underground loader used in underground mining, the loader bucket comprising: a main wall having two sides; and a side wall mounted on each side of the main wall, wherein the side walls extend rearward from a leading end to a rear end, and each side wall tapers inward in a rearward direction at an angle of 2 to 10 degrees.

Each side wall may taper inward at an angle of 2 to 6 degrees, e.g., preferably 2 to 4 degrees.

The main wall may comprise a lower floor portion extending from the leading end towards the rear end and an upper portion extending up from the lower floor portion and back over the lower floor portion to the leading end.

The lower floor portion may be substantially planar, and the side walls may extend substantially perpendicular upward away from the lower floor portion while also tapering inward as they extend in a rearward direction. Put another way, the side walls extend vertically upward while also tapering inward in a rearward direction and the tapering can be seen when the bucket is viewed in a plan view.

The side walls and the main wall may define an interior space. The leading end of the side walls and the main wall may form a mouth, e.g., through which rock material can enter the interior space. The mouth may face forwardly in use, e.g., when loading. That is the mouth may face substantially parallel to a support surface on which an associated loader is mounted.

The loader bucket may have a width that is greater than its height as described in the previous aspect of the invention, e.g., a width that is at least 20% greater than its height.

The bucket may have bucket manoeuvring formations or control plates on the upper portion of the main wall towards the rear end of the bucket.

The main wall may include a recess portion forming a recess for receiving the bucket manoeuvring formations to reduce the extent to which the bucket manoeuvring formations project out of the main wall.

The recess portion in the main wall may encroach on the interior space of the bucket thereby reducing its capacity. In particular, the recess portion in the main wall may be substantially centrally positioned on the main wall and may have substantially square walls forming a box.

Further, the loader bucket may include any one or more of the features or combination of features of a bucket as defined in any other aspect of the invention.

According to another aspect of the invention there is provided a mining vehicle including a vehicle body and a bucket operatively mounted on the vehicle body, wherein the bucket is in accordance with any other aspect of the invention.

The mining vehicle may be a loader, e.g., an underground loader used in underground mining operations.

The bucket may be a loader bucket configured for use on the underground loader.

The underground loader may include bucket support arms projecting forward from the vehicle body and the loader bucket may be mounted on the bucket support arms.

The bucket may include externally facing bucket manoeuvring formations on the main wall of the loader bucket, and the bucket support arms may be operatively connected to the loader bucket by means of the externally facing bucket manoeuvring formations.

The underground loader may include ground engaging formations in the form of wheels for displacing the loader over a support surface, e.g., a floor of a passage in an underground mine. Further, the bucket may also include any one or more of the optional features, or combination of features, of a bucket as defined in any other aspect of the invention.

Further, the loader may include any one or more of the features of a loader or mining vehicle as defined in any other aspect of the invention.

According to yet another aspect of the invention there is provided an underground loader for use in underground mining, the underground loader comprising: a loader body having wheels for travelling over a support surface, wherein the loader body comprises a forward body section and a rear body section which sections are able to articulate relative to each other to enable the loader body to manoeuvre in an underground passage; two bucket support arms that are operatively mounted on the forward body section; and a bucket in accordance with any one of the other aspects of the invention, that is operatively mounted on the bucket support arms.

The rear body section may include an operator’s zone for an operator and a drive unit.

The forward and rear body sections may articulate relative to each other by means of a hinge.

The bucket may also include any one or more of the optional features or combination of features of a bucket as defined in any other aspect of the invention.

Further, the loader may include any one or more of the features of a loader or mining vehicle as defined in any other aspect of the invention.

According to yet another aspect of the invention there is provided a method of loading broken rock into a bucket of an underground loader in an underground passage of a mine, the method including: providing an underground loader in the underground passage having a bucket as defined in any other aspect of the invention, inserting the bucket into a pile of broken rock material a plurality of times to load some of the broken rock, e.g., a payload of broken rock, into the bucket, displacing the loader to a discharge location, and discharging the broken rock at the discharge location. Inserting the bucket into a pile of broken rock may include urging the bucket into the broken rock, and then oscillating the bucket to insert the bucket deeper into the broken rock.

In turn, oscillating the bucket may include performing crowd/rotation oscillations with the bucket to urge it deeper into the broken rock.

The underground loader may include bucket support arms, and the method may include raising the bucket carrying the broken rock, e.g., a pay load of broken rock, with the arms up to a height spaced above the support surface prior to said displacing the underground loader. Further, discharging the broken rock may comprise tipping the broken rock into a dump truck. Instead, discharging the broken rock may comprise tipping the broken rock onto a conveyor.

The bucket may include any one or more of the features, or combination of features, of a bucket defined in any other aspect of the invention. Further, the underground loader may include any one or more of the features of a loader as defined in any other aspect of the invention.

BRIEF DESCRIPTION OF DRAWINGS

A bucket for an underground loader and an underground loader (LHD loader) in accordance with this disclosure may manifest itself in a variety of forms. It will be convenient to hereinafter describe several embodiments of the disclosure in detail with reference to the accompanying drawings. The purpose of providing this detailed description is to instruct persons having an interest in the subject matter of the invention how to carry the disclosure into practical effect. However, it is to be clearly understood that the specific nature of this detailed description does not supersede the generality of the preceding broad description. In the drawings:

Figure 1 is a top plan view of a bucket for an underground loader known in the prior art;

Figure 2 is a top plan view of a bucket for an underground loader in accordance with one embodiment of the invention;

Figure 3 is a front perspective view of the bucket of Figure 2; Figure 4 is a rear perspective view of the bucket of Figure 2;

Figure 5 is a schematic drawing showing an underground loader fitted with a bucket in accordance with this invention;

Figure 6 is a schematic sequence of drawings comparing the digging performance of a prior art underground loader bucket with an underground loader bucket in accordance with this invention;

Figure 7 is a schematic graph comparing the digging performance of the Figure 1 prior art loader bucket and the loader bucket of Figure 2 in accordance with this invention;

Figure 8 is a schematic drawing depicting the comparative wear rates of respectively the prior art loader bucket of Figure 1 and the loader bucket of Figure 2 in accordance with one embodiment of the invention;

Figure 9 is a schematic drawing with a table providing a quantitative measure of the different wear rates in six different zones on the side wall of respectively the Figure 1 and Figure 2 loader buckets;

Figure 10 is a schematic plan view showing how the prior art bucket of Figure 1 and the bucket according to the invention of Figure 2 is driven forward into a pile of broken rock material to load up the bucket with material; and

Figure 11 is a schematic plan view of the loader of Figure 6 showing the line of sight from an operator’s position to the wide leading ends of the side walls.

DETAILED DESCRIPTION

Figure 1 refers to a bucket for an underground loader used in underground mining that is known in the prior art. The bucket has a main wall and side walls on each side of the main wall which together form a front and rear end of the bucket. The side walls extend parallel to each other along their length and perpendicular to the front and rear ends. The side walls of the bucket extending perpendicular to the front is shown clearly in Figure 1 .

Figures 2 to 4 illustrate a bucket for an underground loader used in underground mining in accordance with one embodiment of the invention. In the drawings, the bucket will be referred to generally by the reference numeral 10. The bucket 10 has a main wall 12 extending across a width of the bucket 10 and left and right side walls, 20 and 22, on each side of the main wall 12 defining an interior space and forming a mouth 24. The side walls 20 and 22 taper inward in a direction from a front or leading end to a rear or a rear end at an angle in a range of 2 to 10 degrees as shown in the plan view shown in Figure 2. In the illustrated embodiment, the side walls taper in at an angle of 2 to 7 degrees. In some example forms, the taper angle may be 2 to 6 degrees, 2 to 5 degrees, 2 to 4 degrees or even 2 to 3.5 degrees. Yet further in other example forms, the taper angle may be 1.5 to 7 degrees, 1 .5 to 6 degrees, 1 .5 to 5 degrees, 1.5 to 4 degrees or even 1.5 to 3.5 degrees The main wall 12 transitions from a lower floor portion 14 to an upper wall portion 16. The lower floor portion 14 forms a substantially planar bottom of the bucket 10. T owards the rear end, the lower floor portion 14 transitions into the upper portion 16 which initially extends upwardly forming the rear end of the bucket 10 and then turns forwardly across the lower floor portion 14, spaced above the lower floor portion 14, back to the front or leading end of the bucket 10.

The side walls 20, 22 extend substantially perpendicular upward away from the lower floor portion 14. That is, the side walls 20, 22 taper inwards from the sides of the bucket 10 while still being vertically extending. The mouth 24 of the bucket 10 faces forwardly when loading and not upwardly. The bucket 10 has bucket manoeuvring formations 30 on the upper wall portion of the main wall 12 of the bucket 10 towards its rear end. The formations 30 are on an exterior surface of the main wall 12 facing away from the interior space thereof. These bucket manoeuvring formations 30 include control plates/ears that interact with bucket support arms on a loader to facilitate control and manoeuvring the bucket 10 as will be described in more detail below.

The main wall 12 includes a recess portion 62 forming a recess for receiving the bucket manoeuvring formations 30 to reduce the extent to which the bucket manoeuvring formations 30 project rearward out of the main wall 12. This assists with manoeuvrability of the bucket 10 in a cramped passage of an underground mine. An external view of the main wall recess can be seen in Figure 3.

As illustrated in Figures 3 and 4, the recess portion 62 in the main wall 12 encroaches on the interior space of the bucket 10 thereby reducing its capacity. When viewed from the interior space, the recess portion 62 is substantially centrally positioned on the main wall 12 within the interior space and has square walls forming a box 64.

The bucket also includes GET (ground engaging teeth) formations 40 that are removably mounted on the bucket. The GET formations 40 are mounted primarily around the mouth 24, and help the bucket 10 to penetrate the rock material and also resist wear from the rock material. As the structure and function of GET formations 40 would be known to the person skilled in the art, they will not be described in greater detail in this description.

In some example embodiments of the invention, the bucket 10 is formed or fabricated from a steel material which makes direct contact with the broken rock material. That is, the bucket 10 does not have removable liners that make direct contact with the rock material and are replaced when the liners are worn through (hereinafter a linerless bucket).

Further, in an example embodiment, the main wall 12 and the side walls 20, 22 of the bucket 10 can be fabricated from different thicknesses of steel. Additionally, both the lower floor portion 14 and the upper portion 16 of the main wall 12 may comprise different zones undergoing differing levels of wear. These different zones of the main wall 12 may be formed from steel of different thickness and/or hardness. Similarly, the side walls 20, 22 may also have different zones undergoing differing levels of wear and these different zones may be formed from steel of different thickness and/or hardness properties. Typically, the different zones on the side walls 20, 22, are bilaterally symmetrical and are the same on each side wall 20, 22.

Figures 5 and 11 illustrate an underground loader fitted with a bucket like that in Figures 2 to 4. In Figures 5 and 11 , the loader is indicated generally by reference numeral 50.

The loader 50 comprises a loader body 52 having wheels 54, 56 for travelling over the ground having bucket support arms 58 projecting forward from the loader body 52. The loader 50 further includes a bucket 10 operatively mounted on the bucket support arms 58. The bucket 10 is either the same as, or similar to, the bucket described above in the detailed description with reference to Figures 2 to 4.

The loader body 52 comprises a forward body section 72 and a rear body section 74 and the forward and rear body sections 72 and 74 are capable of articulating relative to each other. In the illustrated embodiment, the forward and rear sections 72 and 74 are hinged to each other to permit them to pivot or turn relative to each other to enable the loader 50 to turn. The forward and rear body sections 72, 74 with an intermediate articulation point helps the manoeuvrability of the loader in a confined underground tunnel.

The bucket support arms 58 and the bucket 10 are operatively mounted on the forward body section 72 with two front wheels 54. The bucket 10 is operatively connected to the support arms 58 through the bucket manoeuvring formations 30 on the bucket 10. In use, the bucket 10 is manipulated and controlled by an operator using a series of hydraulic systems of the type known in the art. As the structure and function of these systems would be known to persons skilled in the art, they will not be described in further detail in this description. The rear body section 74 has two rear wheels 56 mounted thereon and includes an operator zone 75, which may be in the form of an operator’s seat, for receiving an operator of the loader. Further, the rear body section 74 includes a drive unit 76 for providing drive to the two rear wheels 56, e.g., in the form of a diesel engine. The loader 50 has a powerful prime mover with advanced drive train technology, heavy planetary axles, four-wheel drive, articulated steering, and ergonomic controls.

The loader 50 has a narrow, long, and low profile making it suitable for underground applications where the height and width of a mining passage are very confined. As the length of a loader 50 is not a limiting factor in their operation in tunnels and declines, LHD loaders can be designed with sufficient length for them to have the functionality required to be fit for purpose. The length of the loader 50 also improves axial weight distribution and enables the bucket capacity to be increased.

An underground loader may have a weight in the range of 17-25 metric tons. These loaders are available in both diesel and electric versions and the engines may be either water-cooled or air-cooled. A diesel version is easily transportable from one location to another and has diesel engines providing 75 to 150 HP.

In some forms, the drive systems of the loaders have hydraulic pumps and hydraulic motors for carrying out the various movements of the loader bucket and also the vehicle traction and steering. The speed of the vehicle may be controlled mechanically, and the transmission may be controlled by a hydrostatic drive. In hydrostatic transmission, the motor drives a variable displacement pump hydraulically connected to a hydro-motor driving the axle via a gearbox. The speed is controlled by changing the displacement volume of the axial pump. The power train consists of a closed-loop hydraulic transmission, parking brakes, two-stage gearbox, and drive lines. Service, emergency, and parking brakes with fire-resistant hydraulic fluids may also be provided. Headlights, audible warning signals, backup alarms, and portable fire extinguishers are also fitted. A safety device may also be provided to shut off the engine if exhaust gases exceed a set temperature.

Figure 11 shows the line of sight from an operator’s position in an operator’s seat to the wide leading ends of the side walls. This shows how the operator can focus on the leading end of the bucket to avoid contacting external structures in a mine passage while driving in a straight line. The bucket is widest at the leading end and tapers inward back from the leading end to the rear end which has a much smaller lateral width. Consequently, the side walls of the bucket spaced back from the leading end are less likely to contact the tunnel walls and other external structures.

In use, the loader 50 and the bucket 10 may be used to load broken rock or broken rock material indicated generally by numeral 80, from a muck pile in an underground mining passage into the bucket 10. To do this, the bucket 10 is urged to penetrate a pile of broken material with the intention of filling the bucket 10 with as big a payload as possible to operate the loader 50 productively.

The confined space of the underground passage limits the movements that can be made with the bucket 10. The operator can only make small oscillations of the bucket 10, e.g., small to- and fro- movements, or crowd/rotation oscillations, in which the bucket undulates, e.g., moves up and down, to urge the bucket further into the broken rock material to increase the load in the bucket 10.

Once the bucket 10 is loaded up with a payload of broken rock, it is lifted by the loader 50 and carried to a dumping location where it is dumped. In some example applications, the mines may have dump trucks into which the broken rock is dumped at the dumping location and then carried out of the mine. In other example applications, the broken rock may be loaded onto an underground conveyor at the dumping location and conveyed out of the underground passage on the conveyor.

EXAMPLES

The Applicant has measured the digging and/or loading performance of the bucket in accordance with the invention and compared its performance with that of a prior art bucket to demonstrate the efficacy of the Applicant’s invention. The bucket in accordance with the invention is that illustrated in Figures 2 to 4 of the drawings and a bucket in accordance with the prior art is that illustrated in Figure 1. The main differences between the prior art bucket and the bucket in accordance with the invention is the tapered side walls (which taper inward from the front of the bucket to the rear or back of the bucket). The grade of steel used to form the bucket is the same. This analysis tests the performance of the buckets in penetrating a certain load of particulate material.

Analysis of Dig Performance

An analysis of digging performance using EDEM high performance software for simulating bulk and granular materials was carried out. In this analysis, the bucket penetrates the material stockpile until an initial equilibrium is reached. Then the bucket is oscillated (by doing crowd/rotation oscillations) with the digging force kept constant, to further penetrate the stockpile. Finally, the bucket is crowded back to complete the fill. Using the same stockpile and digging conditions, it is possible to compare the digging performance of the two buckets. Since the digging force is constant, a bucket with lower resistance will penetrate the stockpile further leading to an increased fill factor for the bucket.

Key stages of the digging performance analysis are shown in Figure 6 of the accompanying drawings. An improved penetration of a new bucket in accordance with the invention can be seen in both the initial and final dig phases. The mass sensor in the analysis shows the final payload achieved by each bucket at the end of the simulation, with the new bucket design in accordance with the invention achieving an extra 322kg payload.

Further, the graph shown in Figure 7 of the accompanying drawings charts the penetration achieved by the respective buckets as they progress through the various stages of the digging analysis. After the initial digging phase, the loading bucket of Figure 2 in accordance with the invention is shown to have greater penetration compared to the prior art bucket in Figure 1 . This initial digging phase is then followed by four crowd/rotation oscillations of the bucket, which mimic the limited bucket movements that can be carried out in an underground mine to measure the penetration achieved by the respective buckets. After this phase, the new bucket in accordance with the invention shows an even greater penetration over the prior art bucket. This leads to a better fill factor and a greater payload. Analysis of Wear Performance

An analysis of digging performance using EDEM high performance software for simulating bulk and granular materials was carried out. This analysis compared the relative wear rates of the prior art bucket design in Figure 1 against the new bucket design as shown in Figures 2 to 4. It will be appreciated that similar grades of material would been used in the comparative analysis of the respective buckets because the wear rates depend a lot on the grade of steel. Figures 8 and 9 show the predicted wear rates across the side walls of the prior art bucket and the bucket that is the subject of the invention. In this analysis, a full digging and dumping cycle was performed based on the cycle times obtained from a particular site. This cycle was then repeated many times to produce a wear rate plot. This relative wear rate plot was scaled up based on thickness testing data carried out on an existing prior art Austin bucket on site.

The levels of wear on the side walls of respectively, the prior art Austin bucket and the bucket in accordance with the invention, are shown in Figure 8 where the spacing of the lines indicates or provides a measure of the level of the wear. Where the lines are more spaced apart the wear is less severe. By contrast where the lines are more closely packed together, e.g., in a lower region of the side wall, the wear is more severe.

The predicted wear rates of various zones on the side walls after 10,000 hrs of service life are shown in Figure 9. These wear rates have been estimated from thickness testing performed on the prior art bucket and extrapolated based on the EDEM wear analysis. The wear analysis shows that the bucket in Figure 2 produces less drag whilst moving through the material which reduces the wear rates on the side walls. The reduction in wear occurs largely on an outer or outside surface of the side walls 20, 22. Despite the fact that numerous efforts have been directed at improving digging efficiency in the difficult and confined environment of passages in underground mines, the idea of tapering the side walls of the loader bucket inward has not been suggested or taught in the prior art. Flowever, this feature confers the surprising and unexpected effect of improving the digging efficiency of the bucket. Further, it does this at very little additional cost because it does not require any modification of the loader and is implemented purely on the bucket itself. This bucket described above and illustrated in Figures 2 to 4 achieves the following working advantages:

1 . Bucket filling and penetration properties are substantially improved enhancing digging performance. 2. Increased clearance of the side walls of the bucket minimizes wear on the side walls in operation for an increased service life.

3. The side walls are not parallel to the adjacent mine wall surfaces in transit, and that reduces the risk of damage to the bucket and also external mining structures on the wall of the passage. With regards to working advantage (1 ) above, a bucket as shown in Figures 2 to 4 of the drawings has a lower drag coefficient when it is displaced through broken rock and as a result it penetrates more effectively through the broken rock. Thus, the bucket in Figures 2 to 4 is filled more fully with broken rock to achieve a greater payload when compared with the same actions taken on the prior art bucket. Further, the bucket illustrated in Figures 2 to 4 can be manufactured at minimal additional cost to the straight sided bucket in Figure 1. Tapering the side walls inward at an angle of 2 to 6 degrees adds only a small amount to the cost of manufacture.

Additionally, without being bound by theory, the Applicant believes that the bucket in Figures 2 to 4 is less dependent on an individual operator’s skills to achieve good digging outcomes. That is, the design is more forgiving on operators having limited technical skill than the design in Figure 1 and enables good efficiencies to be achieved with operators having limited experience in the art of manoeuvring the bucket to penetrate into the pile.

In relation to working advantage (2) above, as can be seen from the experimental work illustrated in Figures 8 and 9, the external surfaces of the side walls of the loader bucket, encounter substantial wear in normal operation. Flowever, as shown in this analysis, the outer surfaces of the side walls of the bucket in Figures 2 to 4 encounter significantly less wear than the prior art bucket in Figure 1. This is schematically illustrated in Figure 10 of the drawings which shows two buckets being driven into a pile of broken rock material to fill the bucket. The drawing shows how each tapering side wall reduces contact and abrasion with the rock material behind the leading edges of the side wall. Based on their experimental work, Applicant believes that the bucket of Figures 2 to 4 may reduce wear by approximately 25% on each side wall. In relation to working advantage (3) above, an operator using the bucket of Figures 2 to 4 with tapering walls is less likely to collide with underground walls in a confined space. They are also less likely to collide with external mining structures on the underground walls causing damage to these structures. Applicant recognizes that the natural point of focus when driving any vehicle, is the front of the vehicle in the direction of travel, when they are steering and manoeuvring the vehicle. Correspondingly, a natural point for a driver of an underground loader would also be the front of the loader. Expressed another way, an operator who is operating an underground loader in a tunnel naturally fixes their eyes on the front of the loader. In this environment, the front of the underground loader is the front of the bucket on the front of the underground loader. The bucket is also the widest dimension on the underground loader.

Applicant has found that it is difficult for an operator to keep a watch on the clearance of the side walls along the full length of the bucket which typically might have a length of, for example, 2 to 4 m. That is, it is difficult for the operator to keep an eye on clearance along the full length of the bucket while they are also manoeuvring the loader in a confined passage. Consequently, operators are prone to making contact with tunnel walls and other external structures in this environment.

However, by configuring the bucket with a broad leading end and side walls that taper inward away from the leading end in accordance with this invention, the operator can direct their focus to the leading end or front of the bucket. The additional clearance back from the leading end (because the side walls tapers inward), helps to avoid contact with external structures. This is shown schematically in Figure 11 of the drawings. The tapered walls confer a distinct operational advantage when the operator is performing development work and the loader is travelling in a straight line with the bucket in a neutral position. Therefore, the tapering side walls on the bucket confers a surprising and unexpected working advantage at an operational level that has not previously been taught or suggested by the prior art arrangements for underground loaders.

Without being bound by theory, Applicant believes that where the bucket has parallel side walls, having the same width along their length, like the bucket in Figure 1 , the operator is required to visually observe a far greater and wider field to try and avoid contact in a narrow and confined space. It is therefore more difficult for the operator to avoid contact with the walls in a narrow passage. By contrast, a bucket that is widest at its end (adjacent the mouth) and tapers inward, enables the operator to visually concentrate on the end, and this makes it easier to avoid contact with external structures.

It will of course be realized that the above has been given only by way of illustrative example of the invention and that all such modifications and variations thereto, as would be apparent to persons skilled in the art, are deemed to fall within the broad scope and ambit of the invention as is herein set forth.