Underwater solids collecting apparatus
The present invention is concerned with underwater solids collecting techniques and more particularly to underwater solids collecting apparatus. One application of the techniques and apparatus of the invention is a means for raising high density solids such as gravel in bulk from the bed of a river or a seabed, particularly in depths beyond the range of normal dredging apparatus. A further application of the techniques and apparatus of the invention is a means for establishing an underwater anchorage such as for a surface vessel or for any other structure such as a well-head. 
     According to the present invention an underwater solids collecting apparatus includes a substantially hollow structure submersible in a volume of liquid and having at least one intake passageway located in the lower region of the structure, the apparatus also including collection means whereby in operation liquid from the lower strata of the volume of liquid on or adjacent the bed of the liquid may be induced into the interior of the structure through the intake passageways with sufficient momentum to carry into the interior solid matter from the bed of the liquid. 
     Preferably the collecting means includes a vent passageway located in the upper region of the structure and through which liquid may be extracted from within the interior of the structure by suction means. 
     In one arrangement of the invention for the collection and harvesting of underwater solids the substantially hollow structure is in the form of a diving bell with the intake passageways extending from the lower region of the structure like peripheral legs, the structure being provided with a hopper like collecting area into which solids induced into the interior of the structure through the intake passageways may be collected. 
     The structure might also include an air inlet passageway through which air under pressure may be fed into the interior of the structure to act in conjunction with the vent passageway as an air-lift pump for the extraction of air/water from within the interior of the structure. With the vent passageway closed the pressurising air may with advantage be used to pressurise the structure to provide buoyancy whereby the structure will rise to the surface of the liquid. 
     In an alternative arrangement of the invention for establishing a means of anchorage in the bed of the liquid the substantially hollow structure includes a lower platform region with the intake passageways arranged in the base of the platform such that solids induced into the structure by the collecting means fill or substantially fill the interior of the platform region and cause it to become at least partially buried in the bed material. 
     In order that the present invention may be more fully understood two embodiments thereof will now be described by way of example only with reference to the accompanying drawings which illustrate vertical sections through the apparatus of the invention. FIGS. 1, 2, 3 and 4 show the apparatus of the invention as applied to the collection and harvesting of underwater solids and FIGS. 5, 6, 7 and 8 show an apparatus of the invention as applied to the establishment of an underwater anchorage. 
    
    
     FIG. 1 shows the empty underwater solids collecting apparatus on the surface, 
     FIG. 2 shows the underwater solids collecting apparatus submerged and resting on the liquid bed, 
     FIG. 3 shows the submerged underwater solids collecting apparatus loaded, and 
     FIG. 4 shows the refloated loaded underwater solids collecting apparatus. 
     FIG. 5 shows the anchoring apparatus on the surface, 
     FIG. 6 shows the flooded anchoring apparatus submerged and resting on the liquid bed, 
     FIG. 7 shows the submerged anchoring apparatus being evacuated of water, which is being replaced by material from the liquid bed, and 
     FIG. 8 shows the anchoring apparatus partially buried in the liquid bed thereby providing a secure anchorage. 
    
    
     Referring firstly to FIGS. 1, 2, 3 and 4 the underwater solids collecting apparatus 1 floats on the surface of the liquid as shown in FIG. 1, until it is located above the site from which solids are to be recovered. The apparatus 1, which resembles the shape of an enclosed diving bell, is then flooded and sinks to the liquid bed, as shown in FIG. 2. Air, at a pressure appropriate to the depth, is pumped into the upper part of the apparatus via an inlet passageway 2 in such a manner that it passes out through a vent extraction passageway 3 in the upper part of the apparatus to form an air-lift pump whereby liquid from within the apparatus 1 is caused to rise up through the vent passageway 3 and thereby induce liquid into the vessel through open intake passageways 4 located in the lower part of the apparatus 1. The momentum of the liquid entering through the intake passageways 4 is arranged to be sufficient to carry over solids from the bed of the liquid, with which the external portions of the intake passageways 4 are in contact or adjacent to, and these solids settle out into a hopper portion 5 of the apparatus 1, excess liquid being passed out through the vent passageway 3. As shown in FIGS. 1-4, the lower ends of intake passageways 4 are positioned below the closed bottom of hopper portion 5, while the upper ends of said passageways are above the solids collecting area provided by hopper 5. With this arrangement of the intake passageways, when the flow of liquid and suspended bed material upwardly through the passageways reaches the upper ends of said passageways, the momentum of said flow is reduced so that the bed material drops into the collecting area of hopper 5 while the liquid continues upwardly to the vent passageway 3. When the hopper 5 is loaded with solids as shown in FIG. 3, the vent passageway 3 is closed and air is continued to be pumped into the apparatus 1, driving out liquid through the intake passageways 4 until the apparatus 1 becomes buoyant and rises to the surface of the liquid as shown in FIG. 4. 
     By this means, solids may be collected in bulk from the seabed or the bed of a river into an apparatus using only a small compressed air power input, the apparatus being raised to the surface by means of buoyancy. Only one power supply -- compressed air -- is required, and this can be supplied to the apparatus through flexible pipework. Wear of parts is small since the solids only move rapidly relative to boundary surfaces through the intake passageways from the bed of the liquid to the hopper contained within the apparatus. The loaded refloated apparatus can be detached from the compressed air supply and taken to an offloading station without interrupting the raising of the solids using the next empty apparatus, once it in turn has been connected to the compressed air supply. The shape and size of the apparatus is not limited to the form shown in the accompanying drawings, which illustrate only the principle of the collecting cycle. The apparatus could be left at one point on the bed of liquid until loaded or it could be moved about the bed whilst loading, according to the nature of the deposits. Air is only one example of the pumping means by which solids are induced into the vessel. A jet pump, or a centrifugal pump, could also be employed for this purpose, and, in this case, a liquid supply for the jet pump and a supply of electricity for the centrifugal pump would be needed in addition to the air supply required to give the apparatus buoyancy. 
     Referring now to FIGS. 5, 6, 7 and 8 the underwater anchoring apparatus in the form of a hollow structure 10 floats on the surface of the liquid as shown in FIG. 5 until it is located above the site where it is to be anchored. The hollow structure 10 is then flooded and sinks to the liquid bed as shown in FIG. 6. The liquid contained within the structure is then expelled in any one or more of a number of ways; for example, by connecting the interior of the structure to the suction pipe of a pump, either submerged or mounted above the surface of the liquid, or by a water jet ejector, or by an air-lift pump. 
     As shown in FIG. 7 the liquid within the hollow structure 10 is expelled through a pipe 13 connected to a submerged pump 15 whereby liquid is induced into the structure through open intake passageways 14 located in the lower region of a platform-like lower portion of the structure 10. The momentum of the liquid entering through the intake passageways 14 is arranged to be sufficient to carry over solids from the liquid bed, with which the external portions of the intake passageways 14 are in contact or are adjacent to, into the interior of the structure 10. The velocity within the structure 10 is arranged to be sufficiently low for heavy solids to settle out of suspension once they have entered the structure through the intake passageways 14. This action continues with the platform-like lower portion of the structure 10 gradually filling with material from the liquid bed and at the same time being buried deeper in the liquid bed to form a firm anchorage. If the means for expelling the liquid from the interior of the structure is able to handle solids then the process can continue after the structure 10 is full of solid material from the liquid bed, excess solid material passing out through the pipe 13 and the pump 15 and settling on top of the structure which continues to bury itself, thereby increasing the effectiveness of the structure as an anchorage. 
     One advantage of using this method to establish an anchoring point is that comparatively little material need be used to construct the structure, the majority of the mass of the anchoring device being provided by the material dredged up from the liquid bed. The actual size of the anchorage may vary enormously as the artisan skilled in the art will readily appreciate. At one extreme the anchorage might for example be used to provide a secure mooring for a small boat while at the other extreme the anchorage might constitute for example the whole or a substantial part of an oil rig platform.