Throughout the specification, unless the context requires otherwise, the word "comprise"or variations such as"comprises"or"comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Background Art The increasing depth and mining rates in new and developing open pit mining operations has led to the consideration of alternative options to the conventional diesel truck haulage for the removal of ore and waste out of open pits. To date, the alternatives comprise the partial electrification of the haulage trucks, using overhead conductors, or the in-pit crushing of ore and waste followed by incline conveying. A further variation on in-pit crushing and conveying has been the consideration of high angle conveyors.

Any type of trucking operation out of a pit results in considerable operating and maintenance manpower, high road maintenance, dust control problems, safety issues and particularly, in tight conical pits, the problem of congestion. The likelihood of serious production delays due to a truck breakdown is a reality. The wide truck haul roads to accommodate two large mine trucks passing in opposite direction of travel, mean the overall slope of the pit wall has to be flatter than if there was only a narrow road for equipment access only. The flatter the pit wall slope, the greater the amount of waste material that has to be removed to gain access to the ore, i. e. a higher strip ratio results. This can make a very significant difference to the economies of large deep pits. Trucks do, however, have great flexibility and are needed at the operating faces to collect rock from any type of face shovel or excavator to transport the material to an in-pit crusher or to a pit side loading station, if either of these options was introduced.

The type of crusher suitable for crushing hard rock at run-of-pit size and with crushing rates of say 4000 tonnes per hour, at present means selection of a large gyratory type of crusher. These installations are up to 1000 tonnes in weight and although claimed as transportable, relocation is both expensive and time consuming and in practice is only practical every 5 years or so. As total pit life is normally only 10 to 15 years, it means much of the material excavated still has to be trucked up to the crusher. Other major disadvantages of the in-pit crushing/conveying systems include: High initial installation cost and subsequent relocation cost of the hard rock crusher and conveyors.

Possibility of high wear on a series of very large and long conveyor belts, particularly by dense and very sharp rocks, resulting in high maintenance and belt replacement costs.

Susceptibility of in-pit crushers and conveyors to damage from basting.

. High operating costs caused by crushing all the waste.

Batching of ore and waste crushing and conveying with resulting pit scheduling problems.

Redesign of the pit layout necessary to accommodate the conveyors. This results in a greater strip ratio and overpass or underpass systems to allow conveyors to cross haul roads, or diversion of the haul roads.

Disclosure of Invention Accordingly, it is an object of the present invention to provide an alternative pit haulage system which is essentially more efficient and economical than present types of pit extraction systems in operation. Current designs of slope haulage systems, in the main, cannot handle the size of material generated by large open pit mining, nor at the rates required.

It is a preferred object of the present invention to provide a pit haulage system which is capable of being automated.

In accordance with one aspect of the present invention, there is provided a haulage system for pit mining comprising:- a head station disposed at the outer peripheral surface of a pit including a headframe having sheave means mounted thereto and a discharge station; a loading station disposed within said pit; a track extending between said discharge station and said loading station having a surface at a prescribed inclination; a steerable haulage conveyance for: receiving material excavated from said pit at said loading station, conveying said material to said discharge station along said track, and discharging said material therefrom at said discharge station; and hauling means comprising a winder fixedly disposed near said head station, and rope means attached between said winder and said conveyance via said sheave means to haul said conveyance along said track in accordance with the operation of said winder.

Preferably, said conveyance is supported for trundling along said track by wheels incorporating resilient tyres and a heavy duty suspension system.

Preferably, the sheave means is mounted at the apex of said headframe, sufficiently spaced from said winder to provide the required fleet angles of said rope means onto said winder.

Preferably, said discharge station includes a tipping station integral with said headframe at the head of said track comprising a head opening, above which a said conveyance may repose for discharging the load thereof into said head opening, a head receival hopper having a head discharge opening at the base thereof and being capable of holding the contents of said conveyance, said head receival hopper being located beneath said head opening for receiving the contents of said conveyance discharged into said head opening, and a truck loading bay disposed beneath said head discharge opening at which a series of successive surface haul trucks may be disposed for loading via said head discharge opening and subsequent surface haulage.

Preferably, said loading station comprises a pit opening, above which a pit truck may repose for discharging the load thereof into said pit opening, a pit receival hopper having a pit discharge opening at the base thereof and being capable of holding the contents of said conveyance, said pit receival hopper being located beneath said pit opening for receiving the contents of said conveyance discharged into said pit opening, and a conveyance loading bay disposed beneath said pit discharge opening at which said conveyance may be disposed for loading via said pit discharge opening and subsequent hauling along said track.

In accordance with another aspect of the present invention, there is provided a discharge gate for a discharge opening of a hopper containing frangible material, the discharge opening having an upper end and a lower end, the gate comprising:- a closure pivotally mounted to an upper end of the discharge opening; a plurality of fingers inwardly projecting from said closure to engage and overlie the lower end of the discharge opening when said closure occludes same; and closure operating means to controlledly move said closure between an occluding position and an open position in a uniform manner; wherein said fingers are spaced apart to define a progressively increasing opening between said closure and the discharge opening to permit initially finer fractions of the frangible material to discharge therethrough, with increasingly larger fractions of material being able to discharge through said fingers, as said closure operating means moves said closure closer towards said open position, said fingers retaining the larger fractions of material within the hopper until the opening between said closure and the discharge opening is sufficiently large to permit the same to discharge therethrough.

In accordance with a further aspect of the present invention there is provided a method for conveying material excavated from within a pit mine to the outer peripheral surface of the mine, including: loading a wheeled conveyance disposed within the pit with excavated material from within the pit at a loading station; hauling said conveyance containing the material along an inclined track extending radially of the pit; discharging the material from the conveyance at the top of said track outside of the pit at a head station; and returning the conveyance to the loading station along said track.

Brief Description of Drawings The invention will be better understood in the light of the following description of one specific embodiment thereof. The description is made with reference to the accompanying drawings, wherein: Fig. 1 is a section through a side of the pit at which the head station, skip track and loading station are disposed; Fig 2 is a schematic plan view of the chassis of a skip showing the range of movement of the independently steerable wheel pairs; Fig. 3 is a side elevation of a skip disposed along the track with its rear door disposed in the closed position; Fig. 4 is a sectional end elevation of Fig. 3 taken along section 4-4 and showing the rails for the self-tracking system but not the self-tracking assembly; Fig 5 is a schematic cross-sectional side elevation of Fig 4, taken along section 5-5 but showing the self-tracking assembly with the wheels removed and the rear door disposed in the open position; Fig. 6 is a schematic end elevation taken along the entire cross-section of the track and showing a pair of skips adjacent to each other along the track; Fig. 7 is an end elevation of a pit loading station showing a pair of pit trucks disposed at a pair of loading bays for discharging excavated material from the pit into the loading station for independently loading a pair of skips; Fig. 8 is a cross-sectional side elevation of the loading station taken along section 8-8 of Fig 7; Fig. 9 is a plan view of the loading station taken along view 9-9 of Fig 7, without the trucks disposed at the loading bays; Fig. 10 is a larger scale elevation of the loading station taken from the opposite side to Fig 8, showing the perspective of the loading station with respect to the side of the pit; Fig. 11 is an end elevation of Fig 10.

Fig. 12 is a plan view of Fig 11, without the truck disposed at the loading bay; Fig. 13 is a side elevation of the head station; Fig. 14 is a plan view of Fig 13; Fig. 15 is a detailed side elevation of a discharge station showing a skip disposed at one of the discharge bays in the discharge position for discharging excavated material from the pit conveyed thereto by the skip; Fig. 16 is a similar view to Fig 15, but showing the skip in the chairing position; Fig 17 is a similar view to Fig 16, but showing the skip in the removal position; Fig. 18 is a detailed plan view of Fig 17; Fig. 19 is an end view of Fig 17; Fig. 20 is an end view of Fig 15; Fig. 21 is a section end elevation of a storage hopper arrangement showing a pair of discharge gates disposed over a pair of discharge openings of the hopper; Fig. 22 is a side view of Fig 21; Fig. 23 is a view of the discharge gate of Fig 21 looking in direction A showing the closure and fingers in the occluded position; and Fig. 24 is a similar view to Fig 23, but showing the closure and fingers in the open position.

Mode (s) for Carrying Out the Invention The haulage system described in the embodiment delivers run-of-pit ore and waste from a selected position near the working levels in the developing pit which are close to the elevation of the loading stations, for subsequent haulage to the surface. It is in fact a very large inclined haulage system which enables certain advantageous features to be incorporated into the design thereof because of its size, which in smaller types of haulage systems, could not be realised. Thus, the system is based on the handling of very large tonnages in pit mining situations, for example tonnages in the vicinity of 30 to 40 megatonnes per annum, with very large individual rocks up to 20 tonnes in weight.

The embodiment is directed towards a haulage system 11 disposed at one side of an open pit mine 13 and a method for conveying material excavated from within the pit mine to the outer peripheral surface thereof using the haulage system.

The haulage system generally comprises a head station 15, a discharge station in the form of a tipping station 16, a pit loading station 17, a track 19, a pair of steerable conveyances in the form of skips 21, and hauling means. The hauling means comprises a double drum winder 23, two sets of sheave means in the form of headsheaves 25 and a pair of rope means, one for each skip, each rope means comprising a pair of wire ropes 27.

In the present embodiment, the pair of skips 21 operate in balance. That is, each skip 21 is connected to one end of the pair of wire ropes 27, and the other end of each rope is connected to, and is wound opposingly around, corresponding drums 107 of the winder 23, as best shown in Figs 13 and 14 of the drawings.

Each drum 107 is a double split drum, that is, it is divided into two halves, with one of the two ropes 27 of each pair of rope means connected for winding around one half or split of the drum, and the other of the two ropes connected for winding around the other half or split of the same drum. Both ropes of the one rope means are wound around their double split drum in the same direction, but opposite to the direction of winding of the ropes of the other rope means about the other double split drum. The winder 23, wire ropes 27, and the skips 21 are arranged in such a manner that when the winder is operated, the drums rotate in the same direction, whilst one coils the rope thereon and the other uncoils the rope therefrom. When the winder is wound to one extreme, one of the skips 21 is disposed at the tipping station 16 for discharging its load and the other skip is disposed at the pit loading station 17 for loading, and when the winder is wound to the other extreme, the position of the skips is reversed. In this manner, the winder 23 is always under a consistent load from a fully laden skip and an empty skip during winding between its extremities, in either direction.

Each skip 21 is supported for trundling along the track 19 by wheels 29 incorporating resilient tyres 31, whereby each skip has a capacity equal to a large pit haulage truck. In the present embodiment, the tyres of each skip are pneumatic. The skips 21 are hoisted in balance along the track 19 by way of the hauling means, which shall be described in more detail later. A pit haul truck 33 of equal capacity to a skip 21 is intended to tip directly into a receival hopper 35 at the loading station 17.

Now the details of the various components of the haulage system shall be described in more detail.

Having regard to Fig. 1 of the accompanying drawings, a typical initial installation of the automatic haulage system is shown in a pit 13, where the hauling commences from about 150 metres vertical.

The track 19 along which the skips 21 trundle between the head station 15 and the loading station 17 is cut down the side wall 13a of the pit 13 at a gradient to correspond to the final pit wall slope. The grade from top to bottom is up to 45° to the horizontal, but can vary to follow changes in pit wall slope selected according to the stability of the ground and the pit wall 13a.

The track 19 is divided into two discrete skip tracks 19a and 19b, adjacent to each other in parallel, spaced relationship, one for each skip 21. The width of the track 19 need only be about 30 metres in total as the skips in the present embodiment are provided with very accurate automatic steering.

As shown in Fig 6 each skip track 19a and 19b includes a pair of wheel tracks 37 along which the tyres 31 of the corresponding skip 21 run.

The surface of the wheel tracks 37 is reasonably smooth to ensure good tyre life, so smooth wall blasting techniques can be employed for producing the final cuts.

The skip tracks 19a and 19b would normally be excavated progressively as the benches 14 are formed while the pit is being deepened. If necessary a working platform 39 on the skip 21 can be used for man access for final skip track preparation, such as removal of any individual protruding rocks.

On poor ground, fibrecrete or bitumen can be used for the wheel tracks 37. As there is no traction applied through the wheels 29, the wheels effectively act as rollers and consolidate the track surface rather than cause deterioration.

The design of the track 19 is such as to lead to minimum additional rock removal beyond the pit wall outline, so that the track surface can run just below the intersection of the bottom of each bench wall 14 and berm.

Rollers 41 are set along the track 19 to support the moving ropes 27 at an elevated position relative to the track.

The area for the initial loading station 17 is at the bottom of the pit 13, as developed at that point in time. A flat area 43 is provided either side of the loading station 17 for the pit haul trucks 33 to manoeuvre and back up for tipping.

The bottom end of the skip track 19 may therefore have to be a short cut into the rock accessed by a flatter cut from the bottom end as shown at Fig. 1. This will subsequently be mined out as lower benches 14 are developed.

It may be considered desirable to leave a barrier of solid or broken rock behind the lowest normal stopping points of the skips 21 to provide protection in case of an overwind, but when this has to be removed for final construction of the track extension, wire ropes stretched across the bottom of the working track can also provide a safety barrier.

The loading station 17 is more clearly shown at Figs. 7,8 and 9 and is of extremely simple and robust design.

The loading station 17 is provided with a main receival hopper 35, comprising a single entry chute 45 and a truncated storage hopper 47 capable of holding 440 tonnes or the same capacity as two truckloads. The bottom of the storage hopper 47 is designed with a rock box to minimise wear and two discharge gates 49 having a closure operable to controlledly discharge material therefrom into a skip.

Each discharge gate 49 is able to discharge approximately half of the live material stored in the storage hopper 47, which is approximately 220 tonnes or the same capacity as one skip load. The discharge gate 49 and closure will be described in more detail later.

The whole loading station 17 is suspended on two trusses 51 which sit on solid rock either side of the opening made by the skip track 19. They are designed to be joined end to end for launching across the opening. Once the first truss is in place, the second is unbolted and slid over the top of the first truss bridging the opening. In this way small cranes only are required at either side, facilitating the installation in an operating pit. The remainder of the loading station is suspended beneath the two trusses 51 and can be quickly and simply installed in modular form. The same procedure in reverse can be used to remove a loading station 17 and relocate it to a lower level as the pit 13 deepens.

As the pit 13 is deepened and the track 19 extended, the loading station 17 can be transferred down to a new position. Each new loading station 17 requires a cut for the track 19 to take the skips 21.

The new location of the loading station 17 can be chosen at an area which provides for access and manoeuvrability of pit haul trucks 33 around and to the top of the loading station.

As shown, trucks 33 can approach the receival hopper opening 53 from either side of the skip track 19.

Some of the impact of rock falling out of a pit truck 33 can be absorbed by a deflection plate 55, which divides the openings of the entry chutes 45 to limit the size of material passing through the openings.

In the present embodiment involving a large pit operation, all pit haul trucks 33 and the haulage system operation is controlled by an automatic winder control system (not shown). The control system includes a single computer and a plurality of radio transceivers for receiving and transmitting information by radio between the computer and all mobile units. This is similar to existing control systems successfully operating at various mines in Australia and hence will not be described in detail.

The automatic winder control system includes detectors for registering which receival hopper 35 of the loading station has been emptied into a skip 21. Means are also provided for illuminating a sign or operating a boom gate, to allow a truck to tip another load when the hopper discharge gate 49 has been proved closed.

In this way, overfilling of the loading station receival hoppers 35 is prevented.

The computer also has means for registering whether a pit truck has been loaded with ore or waste, and directing a receival truck 57 on the surface accordingly.

Final correct positioning of each truck 33,57 at both loading and tipping stations is by radar type proximity control fitted to each truck to automatically apply the brakes. This system has been developed and proven for quarry operations.

The winder control system also includes proving means for proving when a skip is disposed in the correct position for discharge of material into it at the loading station 17, or for discharging material from it at the tipping station 16, at either of the extremities of the winder 23.

When a skip 21 is proved in position at the loading station 17, it is automatically filled by discharging the contents of the storage hopper 47 above the skip, via the appropriate discharge gate 49. The discharge gate 49 is fitted with fingers 59 to allow progressive filling of the skip commencing with the finer size fraction and finally allowing large rocks to be discharged, so protecting the integrity of the skip.

The design of the skips 21 in the present embodiment is shown more clearly at Figs. 2 to 5 of the drawings, whereby each skip has a capacity to hold 220 tonnes of ROM rock tipped directly into them from a 220 tonne pit haul truck 33. The skip 21 is designed for the impact of falling rock, similar to a pit truck accepting falling rock from a large loader bucket.

Each skip 21 has a skip hopper 60 mounted on the chassis 30, formed with an inclined skip hopper floor 61, down which material discharged into the skip is intended to rill, and a rear door 63 against which the material is retained. The rear door 62 includes a flexible resilient sheet, such as rubber, supported by polyethylene ropes (not shown), for confronting and holding the material within the skip hopper 60. This is a very satisfactory means of absorbing the energy from the material being loaded.

As shown in Fig 3, the rear door 63 is pivotally mounted about an upper horizontal axis and is held closed during travel by an over centre mechanism 65.

When the rear door 63 is closed it is also held by hydraulically operated safety latches (not shown).

At the head tipping station 15, the rear door 63 of the skip is opened by hydraulic cylinders 67 contained on the skip when the skip is proved in position, as shown in Figs 5 and 15. The rear door 63 is pulled away for the discharging rock as the skip 21 empties, so it is not worn by rocks sliding over it.

Standard large pit truck wheels 29 and heavy duty suspensions mounted to a heavy duty chassis 30 are used for both the rear and front wheels of the skips 21. These are readily available in sizes to suit the loading and transporting conditions.

The wheels 29 at each end are steerable via a mechanical steering control using standard hydraulic cylinders 69, and a mechanical and an electronic tracking system. The leading wheels are used for steering in each direction of travel to eliminate steering in the reverse direction by trailing steering wheels.

The hydraulics for the steering control comprise a hydraulic pump driven by a small diesel engine (not shown).

A 24 volt alternator (not shown), also driven by the diesel engine, is provided to charge a battery and supply power for the steering control and the electronic tracking system. Furthermore, a complete hydraulic and electric back-up system is provided on each skip.

Each skip is designed to be self steering. Self steering is provided by a pair of steering arms 71 trailing at each end of the skip following a pair of light guide rails 73 set in the track 19, and by the use of TV cameras (not shown) following the line of the tracks, with one system overviewing the other for increased safety.

The steering arms and rails may be disposed to best suit the layout of the track, where in Fig 4, two equistantly spaced rails are disposed on the wheel tracks 37, whereas in Fig 6, an alternative arrangement is shown where one rail 73a is disposed on the outer wheel track 37a and another rail 73b is disposed centrally between the wheel tracks.

The automatic winder control system is typically set to enable the skips to travel at a speed of approximately 15 to 20 kms per hour depending upon the weight of the load conveyed therein. The speed of the winder control system is also set to achieve the required hoisting rate to suit the pit and crushing operations.

As previously described two wire ropes 27a and 27b are attached to each skip to allow it to be pulled up the side of the pit 13 by the hauling means to repose at the tipping station 16, at which it may discharge its content into a receival hopper 77.

Use of two wire ropes 27a and 27b per skip provide for a far higher standard of safety compared with one rope, and also the size of ropes required are manufactured for hoisting use.

The tipping station 16 is located at the front of the head station 15 to receive a skip 21 thereat for discharging the load of each skip. The tipping station 16 is conceptually similar to a loading station 17, but being arranged to provide for an upper skip discharge bay at which a skip 21 may stop and discharge its contents into the receival hopper 77, and a lower passage way 79 for surface trucks 57 to pass underneath the tipping station and receive the contents of the receival hopper after filling by a skip, and having a marginally different form of receival hopper. The skip discharge bay includes a pair of hinged inclined ramps 81 which are contiguously disposed with the upper end of the track 19, one for each skip track 19a and 19b, to receive a fully laden skip hauled up along the track. An opening 83 is provided in each ramp 81, one in line with each skip track 19a and 19b, respectively. Each opening is centrally disposed with each corresponding skip track. The openings 83 between the skip wheel tracks are large enough to prevent the possibility of any sillage and small enough to allow the wheels of a skip to travel along the ramp adjacent the sides of the corresponding opening.

The receival hopper 77 instead of comprising a single entry chute and storage hopper, generally comprises a pair of entry chutes 87, each communicating with each opening 83 and a pair of storage hoppers 89 to which the chute extends.

Each storage hopper 89 can hold 220 tonnes or the equivalent of the truck and skip size used in the particular pit. The storage hoppers 89 are fitted with rock boxes to absorb the impact of large rocks and to minimise wear.

Each hopper 89 has a discharge gate 91 fitted with fingers 93, as is the case with the discharge gates provided at the loading station 17. When a discharge gate 91 is first opened, the fingers 93 hold back the discharge of very large rocks. The finer fraction forms a bed on the tray of the truck receiving the material, which absorbs the impact of the larger rocks when they are subsequently discharged.

The head station 15 comprises a steel structure which forms a headframe 95 mounted on a rock fill pad 97 above the surface level, which is essentially integral with the tipping station 16. Rock fill is available as waste rock from the pit 13. The passage way 79 for the surface trucks 57 passing underneath the tipping station 16 is formed by reinforced concrete retaining walls 99 running through the rock fill pad 97. In this way the height and so the cost of the steel structure can be kept to a minimum.

The head station 15 includes two sets of steel fabricated skip track extensions 101 and two sets of headsheaves 25, one set for each skip and corresponding skip track 19 a and 19b. Each set of skip track extensions 101 comprises a pair of fixed ramps 101 a and 101b which are contiguous with the corresponding hinged inclined ramp 81 associated with the particular skip track thereof, so that a skip may continue along the track up the head frame, if hauled past the upper skip discharge bay of the tipping station 16. The extended skip tracks 86 are disposed to be contiguous with the upper end of the skip tracks 19a and 19b formed along the pit wall track 19. A fixed stop in the form of a pair of crash beams 103, is mounted at the upper distal end of the skip track extensions 101.

The crash beams 103 are designed to be capable of taking the breaking load of the two ropes 27 if a skip 21 strikes one in the event of overtravel.

A plurality of jack catches 105 are set between the skip track extensions 101 immediately adjacent the crash beams 87, so that in the event of overtravel, and immediately before hitting a crash beam, the skip rides up on and over the jack catches, partially lifting it off its wheels 29, and retaining it on the head frame. In the event of both ropes breaking, the skip is held by the jack catches 105 and is prevented from rolling back into the pit.

This protection provides a similar function to jack catches on a conventional mine hoisting system, but is specifically designed to be applicable to very large 220 tonne skips on an incline haulage.

When the skips 21 reach the top of the pit, they pass onto the corresponding inclined ramp 81 of the tipping station 16 as shown in Figs. 13 to 20 of the drawings. The tipping station 16 is high enough to enable surface trucks 57 to be positioned at a loading bay disposed in the passage way 79, beneath the tipping station storage hoppers 89.

The skip is stopped in a discharge position by limit switches connected into the automatic winder control system for commencing discharging. At this discharge position, the rear door safety latches of the skip are released and the rear door 63 is allowed to swing open under the control of the hydraulic cylinders 67. The rear door mechanism is designed so that little wear will occur on the rubber door as the rock discharges by moving the door quickly and clear of discharging rock, as shown in Fig 15.

Notwithstanding this, the automatic winder control system is designed to prevent skip discharge if the storage hopper 89 at the particular skip discharge bay is not proved empty.

When a surface haul truck 57, which also has substantially the same capacity as a skip, is proved in position, the driver of the truck can initiate the hopper discharge gate 91 to open, discharging the contents of the storage hopper 89 into the truck via the gate and fingers 93 to allow progressive filling of the truck commencing with the finer size fraction and finally allowing large rocks to discharge, so protecting the integrity of the truck.

The surface truck 57 can bypass under the tipping station 16 in a single direction and have a return loop around the back of the headframe 95. Accordingly tipping station operations can be fully automatic.

Each of the inclined ramps 81 is hinged about a pivot 111, disposed at the lower end of the ramps, proximate to the main track 19. This hinging is normally locked into the running track position for the skips to pass over as shown in Figs 13,15 and 20.

When it is necessary to interchange a skip 21 for overhaul, or for ease of maintenance, skip engaging members 112 provided in the inclined ramp are operated to engage and chair a skip disposed in a chairing position, which is marginally lower than the discharge position along the track, as shown in Fig 16.

At this chairing position, the ropes attached to the skip may be disconnected, readying the skip for chairing to the horizontal position.

Lowering means in the form of a hydraulic cylinder 113 is provided to lower the hinged ramp 81 with the chaired skip 21 thereon, into the horizontal position, parallel to the ground as shown in Figs 17,18 and 19. The skip can then be towed out under the headframe for transfer to the workshops, and a replacement skip installed. This greatly simplifies skip interchange and provides for safe inspection and maintenance.

Each set of headsheaves 25 includes two headsheaves 25a and 25b, one for each rope 27a and 27b connected to the skips 21. The headsheaves 25 are mounted at the apex of the head frame 95 to guide the ropes 27 from the winder 23 and along the respective skip tracks 19a and 19b to each skip 21.

The winder 23 of the hauling means is more clearly shown at Figs 13 and 14 of the drawings and is designed and constructed along the lines of a standard double drum winder having each drum 107 and 107b divided to take two hoist ropes 27a and 27b per drum. The drums are mounted on a common shaft 108 which is clutched therebetween.

The winder 23 is mounted on a concrete foundation 109 of sufficient mass to prevent the winder lifting up under the extreme condition of rope break. The winder 23 is also sufficiently spaced from the headsheaves 25 to provide the required fleet angles of the ropes onto the drums of the winder, as shown in Fig 14.

The drum diameter and width for use in the present embodiment have been selected to accommodate the large ropes 27 with only a single layer of rope on each drum 107a and 107b. This is possible because of the centre distance of the very wide skips.

A large drum and hence good drum diameter/rope diameter ratio, and single layer winding, will result in a long rope life. For this application each drum 107a and 107b is grooved, is 6.1 metre in diameter and is of sufficient width to accommodate the required rope length on a single layer.

The shaft 108 is clutched to allow for changes in relative skip position for loading from any selected loading station 17 or for removal of both skips 21 to a safe position at the top of the pit during certain firings, if required, and also to allow for rope cuts. The clutch (not shown) is designed for push button control. Each drum 107a and 107b has a standard disc brake and callipers (also not shown).

The winder 23 is designed for fully automatic control which is extremely simple with rubber tyred skips operating at comparatively slow speed.

During periods of rope adjustment, or repositioning of the loading station 17, a push button control box (not shown) is provided to be plugged into a socket near the tipping station 16 at the edge of the pit 13 with a view of operations, and the winder 23 controlled from this console.

The anticipated installed capacity of even the largest winder considered would be 6. OMW which is quite a normal double drum winder size.

The use of two ropes 27a and 27b per skip allows the use of standard hoist ropes and provides greater safety compared with a single rope. Single layer coiling on the winder drum 107a and 107b ensures equal displacement of the two ropes 27 during the wind and hence equal tensions in the two ropes is maintained.

Now describing the discharge gates of the receival hoppers at both the loading station 17 and the tipping station 16, reference is made to Figs 21 to 24.

As shown in the drawings, a receival hopper arrangement is depicted where discharge gates 121 are disposed on opposite sides of a flat bottomed storage hopper 123 which contains frangible material discharged into it via an entry chute.

The discharge gates 121 comprise a closure 125 pivotally mounted about a horizontal axis to the upper end of discharge openings 127 provided at either side of the hopper 123.

Each closure 125 is provided with a plurality of fingers 129 projecting inwardly from the general plane of the closure, substantially orthogonal thereto. In the present embodiment, three fingers 129 are provided on each closure.

These inwardly projecting fingers 129 engage and overlie the lower end of the discharge opening 127 thereof when the closure 125 occludes the opening.

Closure operating means 131 in the form of a linkage and hydraulic ram is pivotally mounted at one end to the side of the hopper 123, above the upper end of the discharge opening 127, and to the back of the closure 125 at the other end.

The hydraulic ram of the closure operating means 131 is operated to controlledly move the closure 125 between an occluding position (shown in full outline) and an open position (shown in dotted outline) in a uniform manner.

The fingers 129 are laterally spaced apart in parallel relationship to each other so that as the closure is partially and progressively opened, they define a progressively increasing opening between the closure 125 and the discharge opening 127, which initially permits finer fractions of the frangible material stored within the hopper to discharge through the fingers. With increased opening of the closure 125, increasingly larger fractions of material are able to discharge through the fingers 129. During this process, the fingers 129 are sufficiently strong to retain the larger fractions of material within the hopper 123 until the opening between the closure 125 and the discharge opening 127 is sufficiently large to permit the largest fractions to discharge from the opening.

This arrangement has the useful effect, as previously described of initially forming a bed of finer fraction material in the skip hopper 60 or the tip tray of a surface haul truck 57, depending on whether the discharge gate 49 or 91 is used, which provides a buffer for the subsequent discharge of heavier and more bulky material form the hopper, which may include boulders or rocks up to 20 tonnes or more.

An important advantage of the system described in the embodiment is that it is capable of accepting any rock lump size that can be handled by the loading equipment in the pit, and by the trucks which still have to be used to deliver material from the working benches of the pit to the loading station of the haulage system, and from the head station to the waste stockpiles of ore to the surface crusher.

It should be appreciated that it will probably be necessary to relocate the loading station at intervals as the pit is progressively deepened. Accordingly, it is a feature of the present system that it can accommodate the use of multiple loading stations in use at any one time, and that it can accommodate relocation of a loading station in a working pit without disruption to operations in the pit.

Other important advantages of the automatic haulage system of the present embodiment are: (1) It handles large size uncrushed ore that normally can only be transported by large loaders and mine trucks. The 220 tonne skips, and the loading stations and skip tipping station, can accept individual rocks weighing up to 20 tonnes. By comparison, conventional skips used in existing incline haulage or vertical shaft systems are in the order of 20 tonnes in capacity and would normally not handle individual rocks weighing more than 0.5 tonnes. Conveying systems can only handle material with maximum lump size very much less than 0.5 tonnes. Thus the haulage system of the present invention is an order of magnitude larger than any previously installed system, and requires the numerous special design features outlined above to accommodate in particular the handling of rocks up to 20 tonnes in weight.

(2) The loading stations are designed as modular structures for relocation in the pit by transport on the mine trucks. Normal loading stations for any incline or vertical hoisting systems are permanent installations and are of fabricated construction taking several weeks to build in any one location.

(3) The skips have pneumatic tyres, are self steering and are designed to run up the rock side of the open pit.

(4) There are two ropes per skip for additional safety and ease of procurement.

(5) The rubber sheet rear door discharge gate on each skip will incur only perpendicular impact of loading rocks and virtually no sliding wear on discharge of the skip.

(6) Because the skips are mounted on very large mine truck pneumatic tyres, a liberal tolerance in the track surface is permissible. Any small ground movement or settlement due to mining operations will not affect the automatic haulage operations.

(7) Likewise as there are no traction force reaction between the tyres and the track, surface treatment of the track surface can be minimal when over competent rock, and there will be little wear (8) The automatic guidance system of the skips allows the introduction of TV cameras for steering.

The automatic haulage system described in the present embodiment has many advantages compared with existing haulage systems for material excavated from a pit. When compared with trucking out of a pit the present embodiment has the following advantages: (1) Large operating cost savings (2) Removal of much of the truck haulage and congestion up haul roads above the loading station horizon (3) Very significant energy cost savings. Because the two skips are in balance, the only work done is lifting the payload itself. A mine truck engine has to lift both the payload and the truck itself out of the pit on each cycle.

(4) The haulage system allows the use of electricity as the sole power source, rather than diesel fuel. Electricity generation is likely to cause significantly less carbon emissions to reduce the greenhouse effect, compared with individual diesel trucks. This will contribute to carbon credits for the country of operation.

(5) Removes the safety hazard associated with drivers operating trucks on long monotonous journeys up and down the pit, where any short period of inattention can have disastrous consequences.

(6) The introduction of an automatic pit haulage system can allow significant reduction in waste removal in certain pits by having steeper pit sides by elimination of double width hauiroads designed at shallow gradients for truck haulage.

(7) Great reduction in truck fleet with corresponding operating and maintenance savings in man power and cost.

(8) Reduction of haul road maintenance and dust creating.

(9) Independent of slippery road conditions in wet weather or icy conditions When compared with in-pit crushing and conveying waste techniques, the present system has the following advantages: (1) Capital cost saving by elimination of large in-pit crushers and the inclined conveyor installation out of the pit (2) Elimination of the operating and maintenance costs associated with crushing all the waste (3) Reduction in pit traffic and congestion which is caused by haulage of material mined at a lower horizon to the crusher; the crusher relocation is not flexible.

(4) Virtual elimination of blast damage to in-pit equipment (5) Obviates problem of batch crushing and conveying ore and waste, or the alternative of trucking ore out of the pit and crushing waste only.

(6) Elimination of conveyors out of the pit which cause greater excavation and in many cases flatter pit sides, together with diversion of haul roads, all of which can significantly increase pit development costs The automatic haulage system of the present invention presents major advantages in efficiency once the vertical depth of the pit is over 150 metres with total ore and waste removal over 15 million tonnes per annum. Indeed, the greater the vertical depth of the pit, the greater are the benefits of adopting the haulage system of the present invention compared with truck haulage.

It should be appreciated that the scope of the present invention is not limited to the specific embodiment described herein. Accordingly, changes and modifications to the embodiment that are in accordance with standard engineering design and which do not depart from the spirit of the invention are considered to fall within the scope of the invention.