GB2354503A

GB2354503A - Conveyor screen

Info

Publication number: GB2354503A
Application number: GB9922501A
Authority: GB
Inventors: John Robert Crompton; Keith Aubrey Dykes
Original assignee: Dosco Overseas Engineering Ltd
Current assignee: Dosco Overseas Engineering Ltd
Priority date: 1999-09-24
Filing date: 1999-09-24
Publication date: 2001-03-28
Also published as: GB9922501D0; ZA200000214B

Abstract

A conveyor screen suitable for won materials in sub-sea mining operations, for example diamond mining, comprises a taut flexible chain supporting a plurality of elongate flight bars 32 that extend perpendicular to the chain and that are regularly spaced apart from one another wherein, won material dropped onto the conveyor of less than a certain predetermined size falls through the gaps between the flight bars 32 and material of a larger size is dropped off the end of the conveyor 31. The chain may be a drive chain that is endless and wrapped around a pair of sprockets 34, 36 to drive the conveyor. The conveyor may include a baffle 52 for directing the smaller won material to a pump 61 for conveying to a surface ship. The conveyor advantageously reduces jams caused by oversized mineral pieces. The conveyor may include additional features such as water jets 63, 64 and a jam clearance door 56 that assist in the function of reducing jams. A submersible vehicle supporting the conveyor is also disclosed.

Description

2354503 IMPROVEMENTS IN OR RELATING TO CONVEYORS This invention concerns

improvements in or relating to conveyors. In particular the invention concerns a conveyor especially, but not exclusively, suitable for use in sub-sea mining operations. The invention also relates to a submersible vehicle, such as sub-sea mining apparatus, including a conveyor as defined herein.

Valuable minerals such as diamonds are known to be present in certain lo sub-sea locations. One notable location is off the western coast of southern Africa, in the region of the mouth of the Orange River.

There have been various attempts at designing machines suitable for mining diamonds in this and similar locations. One particular example is described in Namibian Patent Application No. 95/0063 filed on 30 August 1995.

Namibian Patent Application No. 95/0063 discloses an underwater mining machine having a sea bed engaging crawler base adapted to propel the machine at least in a forward direction; a forward by projecting cutter head connected to the crawler base, for cutting bedrock material in ftont of the machine; and gathering means for gathering material cut by the cutter head.

The apparatus of Namibian Patent Application No. 95/0063 is designed to be lowered from a surface ship onto the sea bed. The mining machine remains connected to the surface ship by means of a number of support lines such as steel cables; and also by one or more air lift or water pump tubes that convey minerals mined by the mining machine (referred to herein as "won minerals") from the mining machine to the ship for further processing.

The mining machine includes cutter heads that break the bedrock material into pieces of varying sizes. Clearly there is a need for grading of the resulting won mineral pieces before conveying of valuable won mineral pieces to the ship via the air lift tubes, otherwise large mineral pieces, that are of no commercial value, and that may well block the air lift tubes or other parts of the mining machine, may become entrained in the material conveyed to the ship.

In the arrangement of Namibian Patent Application No. 95/0063 the grading of won minerals occurs in an oscillating grille that functions to separate different sizes of material. The grille includes a plurality of parallel, horizontally extending, oscillating bars spaced from one another at substantially fixed distances selected such as to permit material of a desired size to drop through the processing grille into a process hopper.

The processing grille functions also as a conveyor, whereby mineral pieces that are too large to pass between the bars during operation of the grille are conveyed essentially by the scraper chain conveyor and are discharged from the mining machine onto the sea bed, as the mining machine moves.

The bars are oscillated by a series of cams.

The apparatus of Namibian Patent Application No. 95/0063 has proved reasonably successful under full size model trials. However there is a tendency for the oscillating grille to become blocked with mineral material in use. This occurs e.g. when pieces of rock become jammed between the above-mentioned bars and the scraper conveyor. When this happens the 2 oscillating grille may become completely blocked.

In order to reduce this problem, the spaces between the oscillating bars are maintained at a comparatively wide setting. This reduces the incidence of blockages of the oscillating grille, but means that the air lift tubes convey a significant quantity of valueless mineral material to the ship. Energy is wasted in conveying such material to the ship and subsequently discharging it from the ship to the sea bed once again.

lo Also, of course, the passage of large mineral pieces through the oscillating grille can lead to blockages and jams elsewhere in the subsea mining apparatus, for example in the path between the oscillating grille and the entrance to the air lift tubes.

The mining machine of Namibian Patent Application No. 96/0063 includes no effective means for clearing such blockages.

It would be desirable to eliminate or at least ameliorate the problems described hereinabove.

Claims

According to a first aspect of the invention there is provided a conveyor

as defined in Claim 1.

The use of a moveable conveyor having flight bars whose spacing is 25 substantially constant during use minimises the risk of mineral pieces becoming jammed between the flight bars.

Consequently the spaces between the flight bars may be set at a sufficiently small size that only mineral pieces that are likely to be of commercial benefit pass through the conveyor. Consequently a reduced 3 quantity of won mineral material is conveyed to the ship. The won material that is conveyed is generally of a higher commercial value than hitherto.

Further, advantageous features of the invention are defined in Claims 2 to 22.

The invention also relates to a submersible vehicle supporting or enclosing a conveyor as defined herein.

There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which:

Figure I is a plan view from above of an underwater InIng machine incorporating a conveyor according to the invention; Figures 2 and 3 are, respectively, front and rear elevational views of the machine of Figure 1; Figure 4 is a side elevational view of a conveyor according to the invention; Figure 5 is a view on arrows 5-5 of Figure 4; Figure 6 shows the underside of the conveyor chain of Figure 4; Figure 7 shows the conveyor chain of Figures 4 to 6 wrapped around a sprocket; and Figure 8 is a cross-sectional view of a sprocket and block assembly forming part of the invention.

Referring to the drawings there is shown a submersible vehicle in the form of an underwater mining machine 10.

4 Machine 10 is generally as disclosed in Namibian Patent Application No.

95/0063.

Underwater mining machine 10 includes a sea bed-engaging crawler base 11 that supports a pair a laterally spaced tracks 12a,12b (Figure 3). The tracks are so-called marinised caterpillar tracks. These tracks engage the sea bed and may be powered to cause controlled movement of the underwater mining machine 10.

io For a more detailed description of the operation of the underwater mining machine 10, we direct the reader's attention to Namibian Patent Application No. 95/0063. For the purposes of the present disclosure it is sufficient to state that the underwater mining machine 10 is controllably moveable about the sea bed by virtue of operation of the tracks 12. The tracks 12 may be braked and driven in order to slew the underwater mining machine 10 as desired.

Respective left and right-hand cutting booms 13,14 are pivotably mounted at the front end of the underwater mining machine 10. Each cutting boom possesses three degrees of freedom and is controllably moveable under the influence of hydraulic actuators such as the actuators 16 visible in Figures 1 and 2.

Figure 1 shows in exemplary fashion, in chain lines, some possible movements of the cutter heads 17,18, pivotably secured to the respective cutter booms 13,14, in use of the underwater mining machine 10.

When the underwater mining machine 10 is moving on the sea bed, the hydraulic actuators 16, and further actuators (not visible in the figures) may be operated to bring the cutter heads 17,18 to a desired position for cutting of the bedrock.

As disclosed in Namibian Patent Application No. 95/0063, each cutter head 17,18 includes a plurality of picks that are rotatable under control of 5 a cutter head motor to cut the bedrock.

The underwater mining machine 10 also includes a gathering apron 19 that is secured at the front end of the machine 10. Apron 19 is a gently inclined plate having rotatably secured thereon on its upper surface on io either side of underwater mining machine 10 a rotatable star wheel 20, 21.

The shape of each star wheel 20,21 and its location is such that, on rotation, the star wheels drive material cut by the cutter heads 17,18 towards an elevator 23. Elevator 23 is as shown constituted by two pairs of endless chains 24 that are mounted about respective drive sprockets at either end of the loop defined by the chains.

At least the upper surface of the loop defined by the chains 24 is inclined upwardly from the gathering apron 19.

The upper surface defined by each pair of chains 24 has secured thereon a series of elevator or lifting bars 25.

It will thus be seen that when the star wheels 21 rotate and the chains 24 are driven about the sprockets referred to above, the elevator bars 25 repeatedly convey won minerals upwardly on the elevator indicated generally by 23.

When won minerals thus conveyed reach the top of elevator 23 (i.e. the point at which the upper end of the endless chains 24 commence a descent 6 as they travel around the drive sprockets) won minerals fall off the top of the elevator 23 onto a conveyor 30 according to the invention.

The general layout of conveyor 30 is best shown in Figure 4.

Conveyor 30 is elongate. It extends from approximately mid-way along the crawler base 11 and terminates in an overhang 31 that protrudes some distance beyond the rear of crawler base 11.

io Conveyor 30 is upwardly inclined along its entire length from the midpoint of crawler base 11 to overhang 3 1.

As shown in Figure 4, conveyor 30 comprises a series of flight bars 32, upstanding from the conveyor 30. Each flight bar 32 of T-section, and is mounted such that the arms of the T shapes defme an outer surface of the conveyor 30.

As best shown in Figures 6 and 7, each flight bar 32 is rigidly secured to a pair of flexible, elongate chains 33 that are tensioned by means of a drive sprocket and tensioning arrangement described in more detail below.

The chains 33 extend parallel to one another as shown in Figure 6.

In the preferred embodiment, the chains are endless; however, in other embodiments, chains of finite length could be employed.

Regardless of the precise arrangement adopted, the chain constitutes a first taut, flexible chain moveable parallel to its elongate axis.

As is visible in Figure 4, the flight bars 32 are regularly spaced apart 7 from one another and secured to the chain 33. Each flight bar 32 extends generally perpendicular to the elongate axis of each chain 33. Thus, on movement of the chain 33 parallel to its elongate axis (in a manner described below), the flight bars 32 move perpendicular to their elongate axes.

In practice the chains are drivable in a manner described below, and each constitutes a support, for at least part of each flight bar remote from the other.

The spaces between the adjacent flight bars 32 are chosen to permit the passage through the conveyor, between the flight bars 32, of won material pieces of less than a predetermined size (i.e. less than the width of the spaces). Won material of a greater size is conveyed by the conveyor to the overhang 31, in a manner described in more detail below.

In preferred embodiments the chains 33 are endless and are formed into a pair of elongate, parallel oval shapes. Each chain 33 is wrapped around a sprocket assembly at each end of the oval. At least one sprocket assembly, and preferably both sprocket assemblies, are driven to cause rotation of the pair of chains 33 around the sprocket assemblies and thereby convey material supported on the flight bars 32.

Sprocket assembly 34, at the lower end of conveyor 30, comprises a pair of toothed sprocket wheels rigidly mounted laterally spaced apart from one another on a rotatable shaft (not visible in the drawings). The shaft is drivable, e.g. under the computer control of the underwater mining machine 10, to impart drive to the chains 33.

The sprocket 36 at the upper end of conveyor 30, adjacent overhang 31, is 8 shown in Figures 7 and 8.

As best seen in Figure 8, sprocket assembly 36 comprises a pair of toothed chain drive sprockets 37,38, for engaging the respective parallel 5 chains 33.

Each chain drive sprocket is rigidly secured about the outer periphery of a shaft 39. The chain drive sprockets 37 and 38 are spaced apart from each other, and lie at the outer lateral extremities of the shaft 39.

It will thus be seen that the chains 33, when engagingly wrapped around the sprockets 37,38, may be driven thereby when shaft 39 is rotated e.g. by a motor (not visible in the drawings) acting under the computer control of the underwater vehicle 10.

The transversely extending part of the shaft 39 between the sprockets 37, 38 is substantially occupied by a series of blocks 40 that are secured to the outer periphery of shaft 39.

The blocks 40 are spaced at intervals about shaft 39 as best seen in Figure 4. In practice the blocks 40 are constituted as members upstanding from an inner cylindrical sleeve 41 that is rigidly secured onto the outer periphery of shaft 39.

The function of the blocks 40 is to interpose between flight bars 32 of the conveyor 30 as the flight bars, secured to the chains 33, pass around the upper sprocket assembly 36. At this time, the curvature of the chains 30 around the sprocket assembly 36 tends to widen the spaces between adjacent flight bars 32. When this happens large diameter pieces of won 30 mineral material may in the absence of the blocks 40 become jammed 9 between the flight bars. This can cause damage to the conveyor 30, or may cause the chains 33 to disengage from the sprockets 37,38.

A further possibility is that large pieces of won minerals thus jammed between the flight bars 32 may in the absence of the blocks 40 be conveyed to the underside of the oval shape defined by the chains 33 and may subsequently fall into the lower part of the conveyor. From there the large pieces of won material may be conveyed to the air lift tubes previously mentioned, where they may either cause jams or at least lead to io unacceptable increases in energy consumption in operation of the apparatus.

As is clear from Figure 4, the T-shaped flight bars are upstanding from the chains 33. The upper surfaces 44 of the respective flight bars define a conveyor surface on the upper run of the conveyor as shown in Figure 4.

As is also visible in Figure 4, the gaps between adjacent edges 43 of the transverse parts of the T-shapes are of generally the same width when the conveyor is flat, i.e. in portions of the conveyor that are not wrapped around the sprockets.

Figures 4 and 7 show that the upper surface 44 of each T-shape is generally triangular, in particular a truncated triangle shape, and is so orientated that material contacting the apex of a said upper surface 44 tends to move under gravity from the apex towards one of the gaps between edges 43. Thus won minerals conveyed by the conveyor tend to be shaken or otherwise moved towards the gaps, through which won mineral pieces of less than a predetermined size pass.

The lower or return run 30b of the conveyor 30 passes through a tuimel open at either end and defined by a baffle 46 that is of generally triangular cross-section.

The apex of the triangle of baffle 46 overlies the lower run 30b of the conveyor 36. As is clear from Figure 5, won minerals passing between the gaps between adjacent edges 43 on the upper run 30a of conveyor 30 fall onto the triangular surface of baffle 46 and pass under gravity to either side thereof, without falling onto lower conveyor run 30b which would otherwise become jammed with won mineral material.

Won mineral material passing to either side of baffle 46 falls into respective left and right-hand troughs 47,49 that are defined between the side walls of the baffle 46 and side walls 50 of a housing 51 that at least partially encloses the conveyor 30.

The floor 52 of housing 51 is inclined at approximately the same angle as the conveyor 30. Thus won mineral materials tend to pass under gravity downwardly along the floor 52 in the troughs 47,49 towards the left-hand end of the housing 50 as shown in Figure 4.

The right-hand, upper end of each trough 47,49 has secured therein at the level of floor 52 a respective water jet 53,55 that may be operated under control of the underwater rnining machine's computer control to provide jets of water that blow won mineral materials towards the lower left-hand end of the housing 51 as shown in Figure 4.

At the lower, left-hand end of housing 51, floor 52 includes an openable door 56 that is pivotably secured at its upper, right-hand end by means of a pivot 57 secured on the underside of housing 52. As is shown by solid and chain lines in Figure 4, door 56 is moveable between closed and open positions. When in the closed position the upper surface of door 56 forms a continuation of floor 52; when open the door 52 permits clearing of jams of mineral material from the vicinity of lower, left-hand end of housing 51.

A hydraulic actuator is connected between a point on door 56 that is spaced outwardly from pivot 57, and a further location that is fixed relative to housing 51. Consequently door 56 may be controllably opened and closed. In preferred embodiments hydraulic actuator 58 operates io under control of the underwater mining machine's computer control system.

When submerged under water, housing 50 fills with sea water, i.e. a compressible fluid that assists in transportation of won mineral material in the vicinity of the conveyor 30.

The lower, left-hand end of housing 51 terminates in an opening 60 in communication with a centrifugal pump 61 of per se known design. The outlet 61 of pump 61 is connected to e.g. an air lift tube, whereby won mineral materials in the vicinity of opening 60 may be pumped to e.g. a surface ship for cleaning, grading, sizing and other processes.

Centrifugal pump 61 may be supplied with power by tile underwater mining machine's power supply. Pump 61 may operate under control of the machine's computer control system.

In addition to the water jets 53,55 for moving won mineral materials along the floor 52, the conveyor also includes fluid jets (i.e. water jets) 63 that direct jets of compressible fluid, i.e. water, downwardly onto the upper, conveying surface of upper run 30a of conveyor 30. The water 12 jets 63 tend to blow the smaller sizes of won mineral materials downwardly through the gaps between adjacent edges 43. The water jets are operable under control of the underwater mining machine's computer control system.

A further water jet 64 is located to blow a jet of water upwardly into the housing 51 in the vicinity of -door 56. This water jet 64 may be employed, under control of the underwater mining machine's computer control system, to clear jams that are not severe enough to necessitate io opening of the door 56.

As is visible in Figure 4, the sprocket assembly 36 at the upper, righthand end of conveyor 30 is mounted at either side by means of a tension adjusting cylinder 66. This is an hydraulic or other actuator of per se known design that may be operated e.g. under control of a control circuit or by means of the computer control system of the underwater mining machine to alter the spacing between the axes of the respective sprocket assemblies 34 and 36, whereby to maintain the desired tautness in the chains 33.

As shown in Figure 6, each alternate link 33a of each chain 33 is formed as a conventional, round chain link.

Each intermediate link 33b is a modified round chain link. The outer 25 portion of each link 33b is as shown in the profile of a round chain link, but the inner portion of each link 33b is formed as a pair of clamp bars 33b' extending inwardly perpendicular to the elongate axis of each chain 33. The pairs of clamp bars 33b' are spaced from one another and each includes a through-going bore that is transverse to the elongate direction of the clamp bars.

13 Thus the stem of each T-shape flight bar may at either end be inserted between a pair of the clamp bars 33b' of a link 33b. At its respective comers the stem of each T-shape of the flight bars 32 includes a throughgoing bore. When the various bores are mutually aligned as indicated in Figure 6, the insertion of a nut and bolt combination as shown in serves to clamp each flight bar 32 rigidly to each alternate link 33b of the pair of chains 33.

lo In use of the apparatus the conveyor 30 is submerged together with the remainder of the underwater mining machine, whereby the housing 51 becomes filled with water and the centrifugal pump 61 suitably primed.

As the underwater mining machine moves about the sea bed, the cutter 15 heads attached to the cutting booms 13,14, cut the bed rock. The star wheels 20 and the gathering apron 19 convey the cut mineral material to the elevator 23, that continuously elevates cut material to a location above the lower, left-hand end of conveyor 30.

Cut material falls from the elevator 23 in the direction of arrow A in Figure 4 onto the upper surface of the top level 30a of conveyor 30.

The sprockets 34,36 rotate in the direction of the arrows B in Figure 4, whereby the chains 33, and hence the conveyor surface defined by the flight bars 32, move in the direction of arrow C to convey the won mineral material upwardly towards the overhang 3 1.

During this process the water jets 63 operate to blow small particles of won mineral material through the gaps between the edges 43, into the troughs 47,49. The general agitation of won mineral material on the 14 conveyor surface 30a also assists in the process of small mineral particles and pieces falling into the troughs 47,49.

Larger pieces of mineral material, such as rocks, are conveyed by the 5 conveyor 30 to the overhang 31 whence they fall, as indicated by arrow D, back to the sea bed at the rear of the underwater mining machine 10.

Won mineral material particles 68 of small size that have passed or been blown through the gaps between the edges 43 move under gravity and io under the influence of water jet 43 towards the lower, left-hand end of housing 51, adjacent centrifugal pump 61. The particles 68 become entrained in the flow pumped by pump 61, and consequently are conveyed to the air lift tubes whence they travel to the surface support ship (not shown in the drawings).

This process takes place continuously while the underwater 9 machine is operating to cut the sea bed.

The apparatus of the invention may include monitoring cameras such as 20 CCDTV cameras, that can convey visible signals of e.g. any jams in the vicinity of centrifugal pump 61. In the event of such jams occurring an operator may operate a control to activate water jet 64 and/or door 57 as necessary, to clear the jam. Alternatively, a transducing mechanism may be employed automatically to operate the water jet 64 and door 56 as necessary on the detection of jams.

It will thus be seen that the conveyor of the invention serves only to convey comparatively small won mineral particles 68 to the vicinity of centrifugal pump 61. Such particles are most likely to contain valuable minerals such as diamonds. They are also comparatively economical to convey to the surface ship, because they can be easily entrained in a stream of water in which the conveyor is immersed. The larger mineral pieces, that may cause jams or be uneconomical to convey to the surface, are discarded by virtue of their falling from the overhang 31 as shown.

All components of the conveyor of the invention may be suitably proofed against the effects of sea water, e.g. using means that are well known to those skilled in the art.

16 CLAIMS 1. A conveyor for won minerals comprising a first, taut, flexible chain moveable parallel to its elongate axis; a plurality of elongate flight bars regularly spaced apart from one another and secured to the chain, each flight bar extending generally perpendicular to the elongate axis of the chain whereby, on movement of the chain parallel to its elongate axis, the flight bars move perpendicular to their elongate axes; and a support, for at least part of each flight bar lo remote from the chain, the spaces between adjacent flight bars being substantially constant in use and permitting the passage through the conveyor of won mineral pieces of less than a predetermined size less than the width of said spaces.
2. A conveyor according to Claim 1 wherein the support for part of each flight bar is a further, taut, flexible chain extending parallel to and spaced laterally from the first taut chain.
3. A conveyor according to Claim 2 wherein each flight bar interconnects the first and further taut chains.
4. A conveyor according to any preceding claim, wherein the or each chain is endless and is wrapped around at least one sprocket for driving the chain to move parallel to its elongate axis.
5. A conveyor according to Claims 2 and 4 including respective said sprockets around which the first and further chains are wrapped, the sprockets being secured spaced from one another on a rotatable shaft, the rotatable shaft including, in the space extending laterally between the sprockets, a series of blocks that each interpose between an adjacent pair 17 of flight bars, whereby the blocks tend to close the gaps, between adjacent flight bars, that widen as the flight bars pass around the sprockets in use of the conveyor.
6. A conveyor according to any preceding claim wherein each flight bar is of generally T-section, with the stem of the T-shape secured to and upstanding from the or each chain, whereby the upper surfaces of the adjacent said T-shapes define a conveyor surface.

lo
7. A conveyor according to Claim 6 wherein the conveyor surface includes a series of gaps between adjacent upper surfaces of the T-shapes, the gaps each being of generally the same width when the conveyor is flat.
8. A conveyor according to Claim 7, wherein in use the upper surface of each T-shape is generally triangular, and is so orientated that material contacting the apex of a said upper surface tends to move under gravity from the apex towards a said gap.
9. A conveyor according to any preceding claim including a baffle, located beneath at least a part of the conveyor, for directing won minerals, that have passed through the spaces between the flight bars, to a preferred location in the housing.
10. A conveyor according to Claim 9, wherein the baffle defines a hollow, elongate chamber open at either end and extending parallel to the elongate axis of the conveyor; and wherein the conveyor is endless, a conveying part of the conveyor extending above the baffle and a return part of the conveyor passing through the chamber defined by the baffle, whereby the baffle prevents won minerals that have passed through the conveying part from engaging the return part in the chamber.

18
11. A conveyor according to Claim 10, wherein the baffle includes at least one panel that is inclined relative to the plane of the conveyor whereby the baffle tends to guide the won minerals to the preferred 5 location.
12. A conveyor according to Claim 9 or any claim dependent therefrom, wherein the housing includes at least one floor that is elongate and inclined in its elongate direction whereby won mineral on the floor lo tends to move to one end of the floor.
13. A conveyor according to Claim 12, wherein at least a conveying part of the conveyor is inclined at generally the same angle as the floor.
14. A conveyor according to Claim 12 or Claim 13 wherein the floor includes a door, at said one end, that is selectively openable and closeable for the purpose of clearing jams of won minerals.
15. A conveyor according to Claim 12 or any claim dependent therefrom, wherein the housing contains a generally incompressible fluid and supports a centrifugal pump located for pumping said fluid at said one end, and won minerals entrained in the fluid, out of the housing to a remote location.
16. A conveyor according to Claim 9 or any claim dependent therefrom, wherein the housing includes one or more fluid jets for moving minerals within the housing.
17. A conveyor according to Claim 16 including a plurality of said fluid jets located for moving minerals off a conveying part of the 19 conveyor.
18. A conveyor according to Claim 16 and Claim 12, including at least one fluid jet located for moving won minerals along the floor.
19. A conveyor according to Claim 16 and Claim 14 including at least one fluid jet located for moving won minerals away from the vicinity of the door.

lo
20. A conveyor according to any preceding claim that is submersible under water such that the conveyor is immersed in water.
21. A conveyor according to Claim 20 and Claim 15 wherein the centrifugal pump is a water pump.
22. A conveyor according to Claim 20 and Claim 16 wherein the fluid jets are water jets.
23. A submersible vehicle supporting or enclosing a conveyor 2o according to any preceding claim.
24. A conveyor generally as herein described, with reference to and/or as illustrated in Figures 1 to 8 of the accompanying drawings.
25. A submersible vehicle generally as herein described, with reference to and/or as illustrated in Figures 1 to 3 of the accompanying drawings.