AU2012261724B2 - Stemming truck - Google Patents

Abstract

C:\NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 -28 A vehicle for delivering stemming material, the vehicle including: a chassis including wheels; a stemming hopper supported by the chassis, the stemming hopper being for carrying stemming material in use; and a delivery system including a hopper screw conveyor for conveying stemming material from the stemming hopper, and a delivery screw conveyor for receiving stemming material from the hopper screw conveyor and delivering the stemming material to a desired position. Fig. 1A (. CN 0 LO) C'N (Y))

Description

C:\NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 STEMMING TRUCK Background of the Invention [0001] The present invention relates to a vehicle suitable for delivering stemming material, such as an aggregate, to a desired position such as into a blast hole. Such a vehicle may be conveniently referred to as a stemming truck. Description of the Prior Art [0002] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. [0003] Rock blasting is often used in the mining industry and other related industries to remove rock in a controlled manner, using explosives. Typically, blast holes are drilled in a precisely defined configuration to define a desired blast area, and the blast holes are filled with a controlled amount of explosives, followed by a quantity of stemming materials for helping to confine the blast energy in desired directions rather than upwardly from the opening of the blast hole. [0004] It is often necessary to transport stemming materials from locations remote from a blasting site, and it is also desirable to provide stemming materials into the blast holes in a controlled manner, thus precluding the use of typical bulk material transfer equipment. Accordingly, a dedicated stemming truck may be used to carry stemming materials to a blasting site and to deliver the stemming materials into blast holes. [0005] Conventional stemming trucks have resorted to the use of common open belt conveyor systems for delivering the stemming materials into the blast holes. However, it is difficult to precisely control the amount of material delivered by a belt conveyor due to inherent variabilities in transfer rates. Furthermore, delivered stemming materials are exposed to the environment during delivery which allows significant dust to be generated, which is undesirable from health and safety, and environmental perspectives.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 -2 [0006] Additional dust suppression measures have been proposed for inclusion on stemming trucks. These may involve spraying water directly onto spraying material as it is delivered on the conveyor belts. [0007] For example, Australian Innovation Patent No. 2008100869 discloses a vehicle having a stemming unit including at least one stemming hopper for carrying stemming material, a hopper belt conveyor to transport stemming material from the stemming hopper and a delivery belt conveyor to deliver stemming material from the hopper belt conveyor and a water unit water unit having at least one water tank for carrying water and at least one pump for pumping water from the water tank wherein at least one spray nozzle is fluidly connected to the at least one pump to pump water from the water tank onto at least one of the hopper belt conveyor or delivery belt conveyor. [0008] However, such an arrangement results in the need for further dust suppression equipment to be provided on the stemming truck, which may lead to a reduced stemming material carrying capacity, along with additional maintenance concerns. Summary of the Present Invention [0009] In a first broad form the present invention seeks to provide a vehicle for delivering stemming material, the vehicle including: a) a chassis including wheels; b) a stemming hopper supported by the chassis, the stemming hopper being for carrying stemming material in use; and, c) a delivery system including: i) a hopper screw conveyor for conveying stemming material from the stemming hopper; and, ii) a delivery screw conveyor for receiving stemming material from the hopper screw conveyor and delivering the stemming material to a desired position. [0010] Typically the delivery screw conveyor is pivotally movable relative to the chassis to allow stemming material to be delivered to different positions relative to the vehicle chassis.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 -3 [0011] Typically the delivery screw conveyor is pivotally moveable between a stowed position in which the delivery screw conveyor does not substantially protrude from the vehicle, and a deployed position in which the delivery screw conveyor extends substantially outwardly from the vehicle. [0012] Typically the delivery system includes an actuator for controllably moving the delivery screw conveyor. [0013] Typically the actuator is a hydraulic cylinder. [0014] Typically the delivery screw conveyor is pivotally connected to the chassis at a receiving end opposite to a delivery end of the delivery screw conveyor. [0015] Typically the delivery screw conveyor is configured to receive the stemming material from the hopper screw conveyor at a position that is substantially co-located with the pivoted connection. [0016] Typically the hopper screw conveyor is for conveying stemming material from a first end of the stemming hopper towards a second end of the stemming hopper, the stemming hopper being inclined from the first end to the second end. [0017] Typically the incline of the stemming hopper causes contents of the stemming hopper to collect at the first end. [0018] Typically the chassis includes a cabin mounted at one end of the chassis, and wherein the first end of the stemming hopper is positioned at the opposite end of the chassis, such that the hopper screw conveyor is for conveying stemming materials toward the cabin. [0019] Typically the hopper screw conveyor conveys the stemming material to a position that is elevated relative to the delivery screw conveyor. [0020] Typically the hopper screw conveyor is provided in a trough connected along a lower portion of the stemming hopper. [0021] Typically each screw conveyor includes a drive for driving the respective screw conveyor.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 -4 [0022] Typically each drive is a hydraulic motor. [0023] Typically each drive is separately controllable. [0024] Typically the delivery system further includes a delivery chute for directing stemming materials being delivered, the delivery chute being connected to a delivery end of the delivery screw conveyor. [0025] Typically the delivery system includes a release mechanism for allowing the selective release of contents of the stemming hopper from the vehicle without the contents being conveyed by the hopper screw conveyor. [0026] Typically the release mechanism is selectively moveable between a closed position for retaining contents within the stemming hopper, and an open position for releasing contents from the stemming hopper. [0027] Typically the release mechanism is provided near a lowermost portion of the stemming hopper. Brief Description of the Drawings [0028] An example of the present invention will now be described with reference to the accompanying drawings, in which: [0029] Figure 1A is a schematic perspective view of an example of a stemming truck with the truck cabin removed for clarity; [0030] Figure 1B is a schematic side view of the stemming truck of Figure 1A; [0031] Figure IC is a schematic top view of the stemming truck of Figure 1A; [0032] Figure ID is a schematic rear view of the stemming truck of Figure 1A; [0033] Figure 2A is a schematic top view of an example of a hopper screw conveyor; [0034] Figure 2B is a schematic side view of the hopper screw conveyor of Figure 2A; [0035] Figure 2C is a schematic front end view of the hopper screw conveyor of Figure 2A; C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 -5 [0036] Figure 2D is a schematic cross section view of the hopper screw conveyor of Figure 2A taken at plane A-A; [0037] Figure 2E is a schematic rear end view of the hopper screw conveyor of Figure 2A; [0038] Figure 3A is a schematic top view of an example of a delivery screw conveyor; [0039] Figure 3B is a schematic side view of the delivery screw conveyor of Figure 3A; [0040] Figure 3C is a schematic front end view of the delivery screw conveyor of Figure 3A; [0041] Figure 3D is a schematic cross section view of a trough of the delivery screw conveyor of Figure 3A taken at plane B-B; [0042] Figure 3E is a schematic rear end view of the delivery screw conveyor of Figure 4A; [0043] Figure 4A is a schematic top view of an example of a hopper and associated support framework; [0044] Figure 4B is a schematic side view of the hopper and structural framework of Figure 4A; [0045] Figure 4C is a schematic cross section view of the structural framework of Figure 4A taken at place C-C; [0046] Figure 4D is a schematic cross section view of the structural framework of Figure 4A taken at place D-D; and, [0047] Figure 4E is a schematic cross section view of the structural framework of Figure 4A taken at place E-E. Detailed Description of the Preferred Embodiments [0048] An example of a vehicle suitable for delivering stemming material, henceforth referred to as a stemming truck, will now be described with reference to Figures 1A to ID. As will be appreciated by those skilled in the art, stemming material may include any C:\NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 -6 materials suitable for use in blast hole stemming applications, including gravel or other aggregate materials. [0049] Figure 1A shows a body portion of a stemming truck 100, having a chassis 110 upon which equipment for enabling the delivery of stemming material is mounted. The chassis 110 may be of a typical truck chassis construction, including a structural framework supporting a cabin 120 (hidden for clarity in Figure 1 but visible in Figures lB to ID), wheels 111, and a power train (not shown). It will be also appreciated that the body portion of the stemming truck 100 may alternatively be provided in a trailer type configuration such that the chassis 110 can be coupled to a prime mover. [0050] The stemming truck 100 includes a stemming hopper 130 supported by the chassis 110, and a delivery system including a hopper screw conveyor 140 and a delivery screw conveyor 150. [0051] The stemming hopper 130 is for carrying stemming material in use, and will typically be configured to allow stemming material to be conveniently supplied thereto. In this example, the stemming hopper 130 is constructed to have an open top to allow stemming material to be supplied into the stemming hopper 130 using a front end loader or the like. A ladder 122 may optionally be provided to allow access to the stemming hopper 130 by an operator, which may be desirable for cleaning, maintenance or inspection purposes. [0052] Any equipment suitable for transferring stemming material from a source, such as an aggregate stock pile, into the stemming hopper 130 can be used, and the stemming hopper 130 may include adaptations to suit the equipment being used. For instance, the stemming hopper 130 may include an upper opening having a size generally corresponding to a bucket of a front end loader. [0053] The hopper screw conveyor 140 is for conveying stemming material from the stemming hopper 130, and the delivery screw conveyor 150 is for receiving stemming material from the hopper screw conveyor 140 and delivering the stemming material to a desired position. Accordingly, stemming material supplied into the stemming hopper 130 can be delivered, via the hopper screw conveyor 140 and delivery screw conveyor 150, into a blast hole or any other desired position.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 -7 [0054] The use of screw conveyors in delivering stemming material from the stemming hopper 130 provides clear advantages over prior stemming truck arrangements, particularly those which utilise open belt conveyor arrangements. [0055] For example, screw conveyors offer improved control over the rate of stemming material being delivered from the hopper, compared to belt conveyors. [0056] Given that screw conveyors typically have a known cross section area for the material being conveyed, the volumetric transfer rate of screw conveyors is directly proportional to the rate of rotation and thus a desired quantity of stemming material can be delivered with a high degree of accuracy by operating the screw conveyors for a predetermined amount of time. [0057] Whilst belt conveyors have transfer rates that are proportional to belt speed, the transfer rate is also highly dependent on the cross sectional area of the material being conveyed. The cross sectional area of conveyed material can vary significantly on an open belt, due to different granular materials having different angles of repose (i.e. steepest natural slope angle for a pile of material), and/or due to the rate at which material is actually supplied onto the belt (which can be highly variable if relatively unsophisticated mechanisms are used to release materials from a hopper onto the belt under the influence of gravity). [0058] It will thus be appreciated that the use of screw conveyors in the manner described above can avoid the inherent variability of belt conveyors to provide a more accurate delivery solution. [0059] In view of this improved accuracy of delivery, it will also be appreciated that it will be possible to meter the quantity of stemming material delivered with good precision. For instance, quantity metering can be provided in a straightforward manner by counting the number of rotations of one of the screw conveyors 140, 150 and, from this, calculating the quantity of stemming material transferred given the known transfer rate properties of the screw conveyor. This allows the precise quantity of stemming material delivered into the blast hole to be recorded.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 [0060] Furthermore, screw conveyors have other advantages over belt conveyors in that they are able to convey materials at higher incline angles (since screw conveyors are not subject to the same limitations caused by the angle of repose of a material), and, in suitable configurations, can convey materials having substantial water content without significant reduction in transfer rate. [0061] Screw conveyors are typically provided with an enclosed construction, which prevents exposure to moving internal components of the screw conveyor in use. Accordingly, an operator will be able to work around an enclosed screw conveyor with minimal risk of coming into contact with moving parts, thus helping to ensure safer operation. In contrast, belt conveyors usually have an open construction where numerous moving parts are exposed to thereby create safety hazards. For instance, exposed rollers in belt conveyors create pinch points which may entrap the clothing or appendages of operators. [0062] Finally, since screw conveyors typically have an enclosed construction, there is a reduced opportunity for dust to be released as the stemming materials are being delivered from the stemming truck 100, compared to open belt conveyor arrangements. Dust resulting from the movement of the stemming material can be effectively contained within screw conveyors whilst the stemming material is conveyed from the stemming hopper 130 to the desired position. Dust may only have an opportunity to escape when the stemming material is briefly exposed to the environment as it is delivered from the delivery end of the delivery conveyor 150, into a blast hole or the like. It is noted that even further measures can be taken to reduce the release of dust into the environment, as will be described further below. [0063] Optionally, the delivery system of the stemming truck 100 may also include a delivery chute 160 for directing stemming materials being delivered. The delivery chute 160 can be connected to a delivery end 151 of the delivery screw conveyor 150, so that the stemming materials conveyed by the delivery screw conveyor 150 can be transferred into the blast hole with even further improved precision. [0064] In one example, the delivery chute 160 may include a shroud (not shown) configured to interface with a blast hole to ensure the stemming materials are directed into the stemming hole without spillage. The shroud may also be configured to effectively surround the flow of C:\NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 -9 stemming materials into the hole and thus even further prevent the escape of dust into the environment. [0065] The configuration of the example of the stemming truck 100 can be better appreciated with reference to the detailed side, top and rear view drawings of Figures lB to ID. [0066] As can be best seen in Figures lB and IC, the truck cabin 120 is provided at a forward end of the stemming truck 100. The cabin 120 provides seating and controls for a driver and also houses the engine and other power train components. [0067] The structural framework of the chassis 110 extends rearwardly from the cabin 120 and provides supporting structure for the equipment of the stemming truck 100. A rollover protection structure 112 extends upwardly from the chassis and protrudes above the cabin 120 to provide improved protection against inward collapse of the cabin 120 in the event of the stemming truck 100 rolling over. [0068] It will be appreciated that the main equipment enabling the functionality of delivering stemming material are the stemming hopper 130 and delivery system including the hopper screw conveyor 140 and delivery screw conveyor 150. Preferred features of this equipment will now be described. [0069] A substantial portion of the stemming truck 100 is occupied by the stemming hopper 130. It is in fact desirable to maximise the size of the stemming hopper 130, subject to practical delivery system considerations, in order to maximise the capacity of the stemming truck 100 for carrying stemming materials. It has been found that the arrangement of screw conveyors 140, 150 of the delivery system as depicted in the preferred embodiment allows for efficient utilization of available space on the stemming truck 100. [0070] Preferably, the delivery screw conveyor 150 is pivotally movable relative to the chassis 110. This allows stemming material to be delivered to different positions relative to the vehicle chassis 110. In this example, and as best appreciated with reference to Figure 2B, the delivery screw conveyor 150 is pivotally moveable between a stowed position (shown as 150' in Figure IC), in which the delivery screw conveyor 150 does not substantially protrude from the stemming truck 100, and a deployed position (as normally shown in the Figures) in C:\NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 10 which the delivery screw conveyor 150 extends substantially outwardly from the stemming truck 100. [0071] In this particular example, the delivery screw conveyor 150 is capable of pivoting throughout a range of 700 between a deployed position where the delivery screw conveyor 150 extends substantially perpendicularly from a longitudinal centreline of the stemming truck 100, and a stowed position where the delivery screw conveyor 150 is effectively contained within the lateral extremities of stemming truck 100 (i.e. the stowed delivery screw conveyor 150 does not protrude outwardly past the stemming hopper 130 and chassis 100 when viewed from above). [0072] It will be appreciated that this pivotally moveable configuration of the delivery screw conveyor 150 allows the stemming truck 100 to be driven normally whilst the delivery screw conveyor 150 is stowed, but then once the stemming truck 100 is at a location at which delivery of stemming materials is required, the delivery screw conveyor 150 can be deployed to a desired position located outboard from the truck. [0073] Such an outboard delivery position allows a driver of the stemming truck 100 to drive the stemming truck 100 alongside a blast hole (or row of blast holes) and stop the truck in a position that allows delivery directly into the blast hole. The delivery screw conveyor 150 may be deployed before the stemming truck 100 is finally positioned alongside a blast hole, so that the driver can directly observe the position of the delivery end 151 of the delivery screw conveyor 150 through a side window or side mirror of the cabin 120. This enables the driver to position the delivery end 151 relative to the blast hole without necessarily requiring guidance from another operator. [0074] It will be appreciated that alternative designs of the stemming truck can use different pivoting angle ranges, depending on the configuration of equipment provided on the stemming truck and operational requirements. In particular, it is not essential that the deployed position extends substantially perpendicularly from the truck. For instance, it may be desirable to provide a delivery screw conveyor 150 where the deployed position extends at an angle forwardly and outwardly from the stemming truck 100.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 11 [0075] In one alternative example, the delivery screw conveyor 150 can be configured to pivot from a stowed position (similar to that described above) to a deployed position wherein the delivery end 151 is positioned substantially alongside the cabin 120. Accordingly, the pivoting range extends forwardly beyond the substantially perpendicular angle depicted in Figure IC. Positioning the delivery end 151 alongside the cabin 120 allows a driver to conveniently obtain a view of the stemming material delivery position through a side window of the cabin 120 without requiring the driver to use side mirrors or look rearwardly from the side window. This can allow further improved positioning accuracy. [0076] The delivery screw conveyor 150 is pivotally connected to the chassis 100 at a receiving end 152 opposite to the delivery end 151. In this example, the pivot connection is provided by a pivot assembly 153 suitably mounted to the chassis 100. The mounting to the chassis will typically include a pivot bearing selected to support the weight of the screw conveyor 150 and stemming materials that can be conveyed within. [0077] The delivery screw conveyor 150 will preferably be configured to receive the stemming material from the hopper screw conveyor 140 at a position that is substantially co located with the pivot connection, such that stemming material is received at the same position independently of the pivoted position of the delivery screw conveyor 150. [0078] In preferred forms, the delivery system includes an actuator for controllably moving the delivery screw conveyor 150 between the stowed and deployed positions. In this example, the actuator is in the form of a hydraulic cylinder 154, which is pivotally connected to an attachment structure 155 provided on the chassis 110 at a first end and pivotally connected to the delivery screw conveyor 150 at an attachment point 156 at a second end. Extension of a rod of the hydraulic cylinder 154 causes the delivery screw conveyor 150 to pivot about its connection to the chassis 110 to thereby controllably move the delivery screw conveyor 150. [0079] In one embodiment, the hydraulic cylinder 154 can be controlled by the driver from the cabin 120, allowing the positioning of the stemming truck 100 and its delivery screw conveyor 150 to be controlled by the driver without requiring an additional operator.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 12 [0080] Since the positioning of the delivery screw conveyor 150 can be controlled between the stowed and deployed positions, this allows finer adjustment of the final delivery position. Consider the case where the stemming truck 100 is driven alongside a blast hole, but the delivery end 151 of the delivery screw conveyor 150 is positioned too far outboard to allow stemming material to be delivered into the blast hole without spillage. If no adjustment was allowed from the deployed position, it would be necessary to completely reposition the stemming truck 100 further away from the blast hole. In most circumstances this would required several steered forwarding and reversing manoeuvres of the stemming truck 100, or in extreme circumstances, the driver may need to drive the stemming truck 100 away from the blast hole entirely to allow a new approach to the blast with a different heading direction. However, the present arrangement allows the delivery screw conveyor 150 to be pivoted from the deployed position so that the delivery end 150 can deliver stemming material at a position closer to the stemming truck 100. Accordingly, the only manoeuvre required will be to drive the stemming truck 100 by a small distance without steering to bring the delivery end 150 into alignment with the blast hole. It will be appreciated that this will aid the driver in easily positioning the stemming truck 100 for the delivery of stemming material into a blast hole. [0081] The hopper screw conveyor 140 is for conveying stemming material from a first end 131 of the stemming hopper 130 towards a second end 132 of the stemming hopper 130. The stemming hopper 130 may be inclined from a first end 141 to a second end 132. Preferably, the incline of the stemming hopper 130 causes contents of the stemming hopper 130 to collect at the first end 131, under the influence of gravity. This allows operation of the stemming truck 100 for delivering stemming material to effectively proceed as the stemming hopper 130 approaches an empty state, and also allows collection of other materials such as water, for convenient release as required (as will be described further below). [0082] A cap 137 is provided in the stemming hopper 130, which extends longitudinally along the centreline of the stemming truck 100 and is positioned above the hopper screw conveyor 140. As can be seen in Figure ID, the cap 137 has an angled cross section and substantially covers the hopper screw conveyor 140 from above. The cap 137 is supported C:\NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 13 from the stemming hopper 130 in such a way as to provide gaps which allow stemming material to enter the hopper screw conveyor 140 in use. [0083] One purpose of the cap 137 is to bear the weight of the stemming material positioned above the hopper screw conveyor 140 in the stemming hopper 130. If the cap 137 were absent, the weight of the stemming material would bear upon the screw blade of the hopper screw conveyor 140 and thus provide a significant load on the hopper screw conveyor 140. However, by providing the cap 137, loading on the hopper screw conveyor 140 is reduced. [0084] It will be appreciated that the cap 137 also serves to substantially enclose the moving parts of the hopper screw conveyor 140 such that these are not exposed when the stemming hopper 130 is not filled with stemming material. [0085] In this example, the hopper screw conveyor 140 extends along a lower portion of the stemming hopper 130 with an incline between first and second ends 141, 142 of the hopper screw conveyor 140 corresponding to that between the first end 131 and the second end 132 of the stemming hopper 130. Accordingly, the hopper screw conveyor 140 conveys stemming material upwardly along the incline of the stemming hopper 130. The hopper screw conveyor 140 conveys the stemming material to a position that is elevated relative to the delivery screw conveyor 150, such that stemming material is allowed to fall from the hopper screw conveyor 140 at the second end 132 of the stemming hopper and into the delivery screw conveyor 150 at the receiving end 152. [0086] A transfer chute 143 may be provided between the second end 142 of the hopper screw conveyor 140 and the receiving end 152 of the delivery screw conveyor 150. The transfer chute 143 contains the stemming material to ensure there is no spillage as it is transferred between screw conveyors and also ensure that there is little opportunity for dust to escape from the stemming material as it falls. [0087] As can be seen in Figures lB and IC, the first end 131 of the stemming hopper 130 is positioned at the opposite end of the chassis 110 from the cabin 120, such that the hopper screw conveyor 140 is for conveying stemming materials toward the cabin 120. The hopper screw conveyor 140 thus conveys the stemming materials in a forward direction relative to C:\NRPortbI\DCC\SEH\4810308 I.DOC- 13/12/2012 - 14 the forward driving direction of the stemming truck 100. This results in a generally forward placement of the delivery screw conveyor 150. [0088] Although it is possible to configure the stemming truck 100 so as to have the stemming hopper 130 inclined in the opposite direction and thus have the hopper screw conveyor 140 convey stemming materials rearwardly to a delivery screw conveyor 150 with a rear placement on the stemming truck 100, there are advantages to having a forward delivery screw conveyor 150 placement as depicted in the preferred embodiment. [0089] For instance, having the delivery screw conveyor 150 placed forwardly on the stemming truck 100 means that the delivery position can be more easily observed by the driver through a side window or side mirror, thus facilitating positioning of the stemming truck 100 and delivery screw conveyor 150 by the driver only. Adjustment of the delivery position in the event that the stemming truck 100 is positioned too close to a blast hole can be easily achieved through a pivoting of the delivery screw conveyor 150 and driving the stemming truck 100 a small distance forward to account for the rearward component of the delivery screw conveyor 150 pivoting action. [0090] Other advantages are provided due to this arrangement having the first end 131 of the stemming hopper 130, in which contents are allowed to collect, positioned at the rear extremity of the stemming truck 100. For instance, this may allow a release mechanism 180 to be provided for allowing the selective release of contents of the stemming hopper 130 from the stemming truck 100 without the contents being conveyed by the hopper screw conveyor 140. The release mechanism 180 is most suitably provided near a lowermost portion of the stemming hopper 130, so that collected water, or stemming materials, may be conveniently released. It is preferable for this release to be from the rear of the stemming truck 100, particularly if significant quantities of materials are to be released, so as to allow the stemming truck 100 to be able to drive away from the released materials in a forward direction without the need to drive over them. This also allows convenient inspection of materials being released. [0091] In this example, the release mechanism 180 is selectively moveable between a closed position for retaining contents within the stemming hopper 130, and an open position for C:\NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 15 releasing contents from the stemming hopper 130. Although this movement might be manually effected, it is preferably provided using an actuator, such as a hydraulic cylinder. Further details of the release mechanism 180 will be provided below. [0092] It should be noted that, in the preferred embodiment, the stemming hopper 130 overhangs the chassis 100 in a rearward direction. This can allow a stemming hopper 130 to be provided which has greater length than the length of extension of the chassis 100 behind the cabin 120. [0093] A rear end assembly 170 is provided which extends rearwardly from the chassis 100 to provide support for the first end 131 of the stemming hopper 130, but this may have a different configuration compared to the chassis 100. For example, the rear end assembly 170 may have an opening which registers with an opening of the release mechanism 180 to allow released materials to fall from the stemming hopper 130 unobstructed. [0094] Another advantage of the forward placement of the delivery screw conveyor 150, which will become more apparent in further discussion below, is that this can also better allow the stemming truck 100 to also be used in towing further equipment on a trailer from a rearwardly mounted towing point (not shown). [0095] It will be appreciated that other equipment can be provided as part of the stemming truck 100, whether this forms part of the delivery system or provides peripheral functions. As shown in Figure IB, a hydraulic tank 191, a cooling system 192 and a valve bank 193 are mounted onto the chassis, and these provide elements of the hydraulic system used to power and control the screw conveyors and other actuators on the stemming truck 100. [0096] Each screw conveyor includes a drive for driving the respective screw conveyor. Specifically, the hopper screw conveyor 140 is driven by hopper screw drive 144 as can be best seen in Figure IB, and the delivery screw conveyor 150 is driven by delivery screw drive 157 as can be best seen in Figure IC. Preferably, each drive is separately controllable, which in the case of hydraulic drives may be achieved through having the drives 144, 157 on different hydraulic lines controlled by different valves.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 16 [0097] Further details of a preferred example of the hopper screw conveyor 140 will now be described with reference to Figures 2A to 2E. [0098] The hopper screw conveyor 140 generally includes a helical screw blade 210 (depicted schematically for convenience) installed on a shaft 220. These screw conveyor components are provided in a trough 230. In this example, the screw blade 210 has an outer diameter of 400mm with a screw pitch of 400mm, and the trough 230 is sized accordingly. It will be appreciated that the screw conveyor parameters will be selected to suit the particular conveying requirements including incline angle, stemming material composition and other requirements that will be apparent to those skilled in the art. [0099] The trough 230 includes flanges 231, 232, 233 connected along an upper portion thereof (relative to the installed configuration of the hopper screw conveyor 140 on the stemming truck 100). The trough 230 thus has an open top bounded on three sides by the flanges 231, 232, 233. A cross section view of the screw blade 210 and trough 230 can be seen in Figure 2D. [0100] The flanges 231, 232, 233 allow the trough 230 and thus the hopper screw conveyor 140 to be installed along a lower portion of the stemming hopper 130 by fastening to corresponding flanges 411, 412, 413 of the stemming hopper 130 (as can be seen in Figure 4A). When the hopper screw conveyor 140 is installed in this way, the trough 230 is in communication with the internal volume of the stemming hopper 130 and thus stemming material carried by the stemming hopper 130 is allowed to enter the trough 230 and is thus brought into contact with the screw blade 210. [0101] The shaft 220 is driven by hopper screw drive 144 (best seen in Figure IB) provided at the second end 142 of the hopper screw conveyor 140. Driving of the shaft 220 thus causes the screw blade 210 to rotate and allows stemming material to be conveyed along the hopper screw conveyor 140 from the first end 141 to the second end 142. The hopper screw drive 144 is preferably a hydraulic motor and may be connected to the shaft 220 via an internal gearbox. A sealing housing 240 may be provided extending from the trough 230 at the second end 142 of the hopper screw conveyor 140 to suit the gearbox of the hopper screw drive 144.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 17 [0102] As can be seen in Figure IB, the second end 142 of the hopper screw conveyor 140 extends beyond the second end 132 of the stemming hopper 130. A lid 250 is attached to the portion of the trough 230 protruding forward from the stemming hopper 130, and an end flange 234 is attached to the trough 230 and lid 250 to seal the second end 142 of the hopper screw conveyor 140 and provide a mounting point for the hopper screw drive 144 and sealing housing 240. [0103] A circular cutout 235 is provided in the lower portion of the trough 230 near the second end 142. This cutout 235 allows the stemming material being conveyed by the hopper screw conveyor 140 to be supplied to the delivery screw conveyor 150. The transfer chute 143 is installed at the cutout 235 to direct the flow of stemming material being received by the delivery screw conveyor 150, and to prevent the release of dust, as described above. The direction of travel of conveyed stemming material is indicated by a series of arrows in Figure 2B. [0104] The release mechanism 180 is provided near the first end 141 of the hopper screw conveyor 140. As can be best seen in Figures 2B and 2E, the lower portion of the trough 230 does not extend completely to the first end 141, but is instead replaced by sidewalls 183, 184 and end wall 189 connected to the trough 230 and a slide gate 181 which is normally in a closed position that retains stemming materials but can be moved into an open position which allows stemming materials and other contents of stemming hopper 130 to be released through a release opening 260. An end plate 187 is fixed to the side walls 183, 184 to seal the first end 141 of the hopper screw conveyor 140. [0105] In this example, the slide gate 181 is supported in slide supports 188, 189 and is actuated by a hydraulic cylinder 182, which is fixed to the trough 230 at attachment point 185 and to the slide gate 181 at attachment point 186. In Figure 2B, the hydraulic cylinder 182 is depicted in a compressed state corresponding to the slide gate 181 being in the open position; although the slide gate 181 and attachment point 186 in the closed position are also depicted to allow the range of motion of the release mechanism 180 components to be appreciated. [0106] An example of the delivery screw conveyor 150 is shown in Figures 3A to 3E, and preferred features thereof will now be described.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 18 [0107] It will be appreciated that the delivery screw conveyor 150 has a generally similar construction to the hopper screw conveyor 140, in that the delivery screw conveyor 150 includes a helical screw blade 310 installed on a shaft 320, which are provided in a trough 330. In this example, the screw blade 310 is of a similar configuration as that of the hopper screw conveyor 140, having a 400 mm outer diameter and a 400 mm pitch. [0108] The shaft 320 of the delivery screw conveyor 150 is driven by a delivery screw drive 157 (best seen in Figure IC) provided at the receiving end 152 of the delivery screw conveyor 150. Driving of the shaft 320 causes the screw blade 310 to rotate and allows stemming material to be conveyed along the delivery screw conveyor 150 from the receiving end 152 to the delivery end 151. As for the hopper screw drive 144, the delivery screw drive 157 is also preferably a hydraulic motor and may be connected to the shaft 320 via an internal gearbox. A sealing housing 340 may be provided extending from the trough 330 at the receiving end 152 to suit the gearbox of the delivery screw drive 157. [0109] The trough 330 includes side flanges 331, 332 (as seen in the cross section view of Figure 3D), however, in the case of the delivery screw conveyor 150, a lid 333 is fastened to the flanges 331, 332 to close the trough 330. A receiving opening 350 is provided in the lid 333, through which stemming materials may be received by the delivery screw conveyor 150, via the transfer chute 143 of the hopper screw conveyor 140. [0110] An end flange 334 is attached to the trough 330 and lid 333 to seal the receiving end 152 of the delivery screw conveyor 150 and provide a mounting point for the delivery screw drive 157 and sealing housing 340. The attachment point 156 for attachment of the hydraulic cylinder 154 is also mounted on the trough 330 at a position allowing the desired pivoting range. [0111] The lower portion of the trough 330 does not extend all the way to the delivery end 151 of the delivery screw conveyor 150, in a similar manner to the provisions for the release mechanism 180 on the hopper screw conveyor 140. In this case, sidewalls 335, 336, end wall 337 and end plate 338 are attached to the trough 330 to provide a delivery opening 360 at the delivery end 151 of the delivery screw conveyor 150, through which stemming material can be delivered.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 19 [0112] Accordingly, stemming materials are received in use through the receiving opening 350, and are conveyed from the receiving end 152 to the delivery end 151 and delivered via the delivery opening 360. The direction of travel of conveyed stemming material is indicated by a series of arrows in Figure 3B. The delivery chute 160 can be attached to the sidewalls 335, 336 and end wall 337 to allow the delivered stemming materials to be more accurately directed into a blast hole. [0113] The pivot assembly 153 includes a pivot bearing 371 which is connected to a mounting beam 372 which facilitates mounting to the chassis 110 structure. The pivot bearing 371 is also connected to a U-shaped pivot bracket 373 which has upwardly extending arms for attachment to the trough 230, as can be seen in the end view of Figure 3C. As can be seen in Figure 3B, the receiving opening 350 is substantially co-located with the pivoting axis of the pivot assembly 153. [0114] Details of a preferred construction of the stemming hopper 130 and structural framework 190, by which it is mounted to the chassis 110, are shown in Figures 4A to 4E, and will now be described. [0115] As discussed above, the stemming hopper 130 is configured for carrying stemming material and thus defines an internal volume of a suitable size and has an upper opening for receiving stemming material, from suitable equipment such as a front end loader. In this example, the opening is defined along the entire length of the stemming hopper 130 between the first and second ends 131, 132, and between side walls 133, 134. [0116] Lower side wall panels 135, 136 extend downwardly and inwardly from the side walls 133, 134 toward the inclined lower portion of the stemming hopper 130, which includes attachment flanges 411, 412, 413 to which the flanges 231, 232, 233 of the hopper screw conveyor 140 are connected to thereby install the hopper screw conveyor 140 to the stemming hopper 130. In this example, the lower portion of the stemming hopper 130 is inclined at an angle of 6' to the horizontal, although it will be appreciated that this angle may be varied to accommodate other design requirements including relative placement of equipment on the stemming truck, for example. A lid flange 414 is provided at the second end 132 to allow attachment of the lid 250 of the hopper screw conveyor 140.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 20 [0117] There is lower opening defined along the lower portion of the stemming hopper 130 between the attachment flanges 411, 412, 413 and lid flange 414. Accordingly, when the hopper screw conveyor 140 is attached to the stemming hopper 130 as shown in Figures 1A to ID, the stemming material in the stemming hopper 130 is able to enter the trough 230 of the hopper screw conveyor 140 via the lower opening, to allow the stemming material to be conveyed when the screw blade 210 is driven. [0118] As mentioned above, the cap 137 is provided within the stemming hopper 130 to act as an upper enclosure portion for the hopper screw conveyor 140 which supports the weight of the stemming material above the hopper screw conveyor 140 in use. The cap 137 is suitably in the form of a gable roof like structure having sloping sides extending from a central upper ridge. The cap 137 may consist of two similar flat sheet members connected together along respective edges at a desired angle, or a single sheet member bent along its centreline at the desired angle. In any event, the cap 137 extends longitudinally substantially along the length of the stemming hopper 130 with the central upper ridge positioned along the centreline of the stemming truck 100. [0119] The cap 137 may be supported from the lower side wall panels 135, 136 of the stemming hopper 130 by a series of brackets 451. The brackets 451 are configured to offset lower edges of the sides from the lower side wall panels 135, 136, to thereby create longitudinally extending gaps between the edges and lower side wall panels 135, 136. [0120] It will be appreciated that the gaps can also extend substantially along the length of the stemming hopper 130 so that stemming material is allowed to enter the hopper screw conveyor 140 substantially along its entire length. However, the gaps may also be configured to only allow stemming material to enter the hopper screw conveyor 140 along a portion of its length, preferably at the lower first end 131 of the stemming hopper 130. In any event, the particular configuration of the gaps between the cap 137 and the lower side wall panels 135, 136 can be selected to allow further control over the rate of stemming material provided to the hopper screw conveyor 140. [0121] In this example, the stemming hopper 130 is mounted onto the chassis 110 using a structural framework 190 including longitudinal beams 421, 422 for connection to the chassis C:\NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 21 110, upon which upright frames 431, 432, 433, 434 are attached. The stemming hopper 130 is in turn attached to the upright frames 431, 432, 433, 434. [0122] The upright frames 431, 432, 433, 434 are of generally similar construction, but further details can be seen in Figures 4C to 4E which respectively correspond to views of planes C-C, D-D and E-E. [0123] The forwardmost upright frame 431 is shown in Figure 4C and is unusual compared to the other frames 432, 433, 434 in that members of the frame are only provided on one side of the stemming truck 100, namely the side opposite to the delivery screw conveyor 150. This allows the delivery screw conveyor 150 to be moved to the stowed position without interference with the structural framework 190 supporting the stemming hopper 130. [0124] Figure 4D shows an intermediate upright frame 432 and is of symmetrical construction. The upright frames 432, 433, 434 other than the forwardmost upright frame 431 each include a pair of substantially vertical members 441, and a pair of outwardly angled members 442, and a horizontal member 443 spanning between the vertical members 441. In this example, the angled members 442 extend at a 30' from the vertical members 441, although the particular configuration of the upright frames 431, 432, 433, 434 will of course be selected depending on the structural requirements for supporting the stemming hopper 130 and other design considerations as will be apparent to those skilled in the art. As mentioned, the forwardmost upright frame 431 omits a vertical member 441 and an angled member 442 on one side. [0125] As can be seen by comparison of Figures 4C, 4D and 4E, the vertical members 441, and outwardly angled members 442 of the upright frames 431, 432, 433, 434 become smaller in size towards the rear first end 131 of the stemming hopper 130. This is to accommodate the incline of the stemming hopper 130. [0126] With reference to Figure 4E, it can be seen that the rear end assembly 170 may be attached to the chassis 110 via attachment plates 171, so as to allow the overhanging extension of the stemming hopper 130 beyond the rear extremity of the chassis 110, as discussed above.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 22 [0127] As mentioned previously, the use of screw conveyors 140, 150 in the delivery system of the stemming truck 100 allows stemming materials to be delivered with a greatly minimised opportunity for dust to be released from the stemming materials as they are conveyed from the stemming hopper 130 and into a blast hole via the delivery screw conveyor 150. This is largely due to the stemming materials being enclosed throughout the path along which the stemming materials are conveyed. [0128] As discussed above, the enclosed construction of the screw conveyors 140, 150 also obstructs access to moving screw conveyor parts resulting in improved operator safety. For instance, it is noted that the screw blade 310 of the delivery screw conveyor 150 is fully enclosed, such that an operator working in the vicinity of the delivery screw conveyor will not be exposed to safety hazards associated with the movement of the screw blade 310 during delivery of stemming material. [0129] Dust may still be generated in the final process of the stemming materials being delivered into the blast hole, and also during loading of stemming materials into the stemming hopper 130. However, the generation of dust can be at least partially suppressed by undertaking further dust suppression measures. [0130] For example, the delivery system of the stemming truck 100 may include dust suppression features such as vacuum dust filtering apparatus for removing dust from the stemming materials as they are delivered. In another example, which does not require further dust suppression equipment to be installed onto the stemming truck, the stemming materials may be treated prior to being loaded into the stemming hopper 130 to provide dust suppression. [0131] The stemming material may be suitably treated in preparation for delivery by pre wetting the stemming material, in order to reduce the likelihood of dust being generated as it is transferred into the stemming truck 100 and subsequently delivered. This can be conveniently performed by spraying the stemming materials with water when the stemming materials are in a stockpile before it is moved by front end loader or the like into the stemming hopper 130.

C \NRPortbI\DCC\SEH\4810308_ 1.DOC- 13/12/2012 - 23 [0132] Additives may be mixed with the water to even further enhance the dust suppression. For instance, wetting agents or specialised dust suppressant compositions such as those formulated using citrus oils may be used. In any event, references to the use of water for pre wetting the stemming material should be understood to include water mixed with additives. [0133] Blasting will often be performed at locations which are remote from convenient water sources, and therefore pre-wetting stemming materials by spraying water on stock piles introduces a requirement for water to be transported to the stock piles, which also may not be located near the blast holes. Although a water truck may be used to transport water, the use of a separate truck represents a significant additional equipment requirement and also an additional personnel requirement for a driver to operate the water truck. [0134] In order to reduce the associated additional equipment and personnel requirements, in one example water may be transported to the stock piles for use in spraying the stemming material using a water trailer which can be towed by the stemming truck 100. In such a case the stemming truck 100 would be provided with a towing point (not shown) for allowing the water trailer to be coupled to the stemming truck 100 for towing. [0135] The water trailer may include a water tank, a pump, a sprayer and a self contained power source, such that the water trailer operates independently from the stemming truck 100, and can be deployed remotely from the stemming truck to provide dust suppression at a stock pile whilst the stemming truck 100 is used to deliver stemming materials into blast holes as intended. An illustrative example of such a method of use will now be outlined. [0136] For the purpose of this example, it will be assumed that the stemming truck 100 and water trailer are empty (i.e. no stemming materials are in the stemming hopper 130 and no water is in the water tank of the water trailer), which may be the case at the start of a shift, for instance. [0137] The water trailer is coupled to the towing point of the stemming truck 100 and the stemming truck 100 is driven, towing the water trailer behind it, to a water source, from which the water tank of the water trailer can be filled. The pump provided on the water trailer may also be used in the filling of the water trailer, in the event no pump is provided at the water source.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 24 [0138] With the water trailer full, the stemming truck 100 is then driven to the location of the stemming material stock piles. The water trailer can then be decoupled from the stemming truck 100 at a desired position to enable spraying of the stemming material from the water trailer. It will be appreciated that this will be dependent on the configuration of the sprayer provided on the water trailer. The water trailer may then be left at the stemming material stock piles to spray the stemming material periodically or as otherwise required. For instance, it may be desirable to spray stemming material immediately prior to loading into the stemming truck 100. [0139] In any event, the stemming material will be pre-wet by spraying with water from the water trailer, such that when stemming material is transferred into the stemming truck 100 by a front end loader or similar loading equipment, the pre-wet stemming material will be effectively dust suppressed, and minimal dust will be released as part of the transfer of stemming material. Once the stemming truck 100 has had its stemming hopper 130 loaded with dust suppressed stemming material, the stemming truck 100 can be driven to blast holes where stemming material needs to be delivered, and the stemming truck 100 will be used to deliver the stemming material as described above. [0140] Since the stemming material in the stemming hopper 130 has been pre-wet, the amount of dust released during delivery of the stemming material into blast holes can be significantly reduced or even eliminated. [0141] When pre-wet stemming material is provided into the stemming hopper 130, water may eventually collect in the lower portion of the stemming hopper 130 at the first end 131. Depending on the particular design of the hopper screw conveyor 140, this collected water might not be conveyed upwardly along the incline of the stemming hopper 130, and thus the water will continue to accumulate unless it is released. However, the release mechanism 180 can be used to release collected water as required. [0142] It will be appreciated that the stemming truck 100 can thus be used, in conjunction with a water trailer, to deliver dust-suppressed stemming material into a blast hole. The quantity of delivered stemming material can be accurately controlled, and the pivoting delivery screw conveyor 150 allows more convenient positioning of the stemming truck 100.

C \NRPortbI\DCC\SEH\4810308_ I.DOC- 13/12/2012 - 25 [0143] Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. [0144] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.