NEW ZEALAND PATENTS ACT, 1953
No.: 244970 Date: 30 October 1992
COMPLETE SPECIFICATION
"Underwater Structural Element, Structure & Method of Making Same"
I, CONRAD SIDARTA HOPMAN, a Dutch citizen of 23 Avenue Michelange, Noumea, New Caledonia do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement:-
-2- fc Al* 'V ■' ;This invention relates to the provision of underwater structural elements, underwater structures and a method of making the same. ;In the past, it has been known to support above water structures through the use of rigid foundations to rigidly support the above water structure. However, in some instances, it is not necessary to rigidly support such a structure and, in these cases, it may be preferable to provide a flexible foundation which can move with water currents or flexibly resist such currents rather than trying to supply a rigid foundation which must resist the currents and wave forces. ;Some flexible underwater foundations are also known which involve the provision of an impermeable flexible bag or other inflatable structure which may then be inflated by pumps or the like. However, once the underwater structure is placed at great depth, the pressure required to inflate such a structure against the water pressure at that depth may require expensive pumping and other apparatus. ;Herein after "enclosed bag" is taken to mean containers of various shapes preferably produced from flexible or semi-flexible material. ;The present invention is directed to providing an underwater structural element, an underwater structure whether constructed from several structural elements or constructed as a whole and method of making the same which uses the water pressure at the depth at which the structural element, structure is placed plus an increase in pressure through osmosis to ensure that the foundation structure is always at a greater pressure than the surrounding water without the need for any pumping apparatus. ;Accordingly, the invention may broadly be said to consist in an underwater structure comprising: ;an enclosed bag made from an impermeable membrane; ;at least one panel or area of said bag including a semipermeable membrane to allow the transfer of water through said panel or area; and a content within said bag, said content capable, in use, of creating an osmotic pressure through the semipermeable membrane. ;Preferably said content is of a molality greater than that of or$ ;Preferably said content includes common salt. ;-3- ;Accordingly, the invention may broadly be said to consist in a method of manufacture of an underwater structure comprising: ;placing a content within a bag made from an impermeable membrane except for at least one panel or area made from a semipermeable membrane; ;placing said bag with said content into the water and, in use, allowing pressure equalisation through the semipermeable membrane between the interior of the bag and the surrounding water plus an increase in pressure within the bag due to the osmotic pressure created by the differential between the molality of the content in the liquid within the bag to the concentration outside the bag. ;Preferably the content is common salt. ;The invention consists in the foregoing and also envisages constructions of which the following gives examples. ;The invention may now be described with reference to the following drawings in which: ;Figure 1 is a drawing of underwater structure in accordance with the invention; ;Figure 2 is a drawing of an individual element of the underwater structure as depicted in Figure 1; and ;Figure 3 is a wall type structure made up of structural elements according to the present invention as illustrated in Figure 2. ;Referring to the drawings, the invention comprises an enclosed bag or bags 10 made from an impermeable membrane 2 with at least one panel or area made from a semipermeable membrane 3. ;Within the bag is a content other than water such as salt 4. ;The cell may contain: ;when being transported, eg on barges, structures composed of osmotic pressure cells will be folded up. The cells will be empty except, perhaps, for a little air, some salt and antifouling. Or the salt and antifouling may be added later. But a large underwater pipe may be towed into place from the factory by inflating sj osmotic pressure cells with air and/or water. If the ends are sealed of structure formed by the cells can be used as a container; ;0 ;when in place, osmotic pressure cells will certainly contain water which is saltier than the surrounding ocean. This water will probably be ordinary sea water, and the salt, ordinary NaCl. However, it may turn out that over time this produces slimy green stuff within the cells which fouls membranes etc. If this is so, it may be better to fill the cells initially with clean fresh water. If the cells are to be flexible, the brine within them may be topped off with small quantities of gases and/or oils as explained. ;Provided the concentration of the salt 4 throughout the water within the bag 10 when immersed is higher than in the water surrounding the bag, an osmotic pressure will be developed such that the bag will always be at greater pressure than the surrounding water. ;It is necessary that the semipermeable membrane allows for the passage of water through the membrane but not the content. ;The selection of the semipermeable membrane and the content depends on the situation involved, however, for the support of a structure in sea water, common salt at a concentration greater than that of sea water will create the necessary osmotic pressure. ;The semipermeable membrane would then be chosen to allow the passage of water through the membrane so that the ordinary water pressure created by placing the bag at depth can be equalised through the membrane and yet the osmotic pressure due to the non-passage of the salt through the membrane will always allow the underwater structure to be at a greater pressure than the surrounding sea water and, therefore, the bag will be inflated. ;These structural elements whether singular or a group joined together so as to form a structure such as a wall or pipe may be transported on barges substantially empty of water and folded up. The substantially empty structural element may contain some air, some salt and/or antifouling. In other forms of the invention an underwater pipe formed from at least one structural element may be towed into place by means of deflating one or more of structural elements with air and/or water. L of the invention the ends of the structure may be sealed off in order 1 ;container. ;• k a 7« ;-5- ;When in place the construction elements are filled or partially filled with water, preferably sea water. In either case the salt content of the water is adjusted so that the require osmotic pressure is achieved. ;Whatever content is chosen, the semipermeable membrane must be chosen to stop the transfer of this content from the interior of the bag to the surrounding water. ;Of course, a large number of different materials may be used as the content. Some of these may be gases or compressible liquids such as oil. Said gases or compressible liquids increase die elasticity of said cells ;A safety valves can be incorporated in the wall of the container to allow excess pressure to be released during storms or other conditions of high stress. ;A stopper may be incorporated in the wall of the container to allow water and other contents to be injected into the cell or released from it during construction and maintenance. ;In the manufacture of an underwater structure, apparatus as described previously may be placed in the sea water and lowered or allowed to sink to the depth required. Pressure equalisation can occur through the semipermeable membrane 3 to equalise ordinary water pressures regardless of the depth to which the bag is placed and then the osmotic transfer can ensure that the bag is inflated to a greater pressure to provide the structural support. In this manner, no pumping or other apparatus is required to inflate the bag at any depth. Furthermore, the pressure provided by the osmotic transfer can be accurately calculated and the structural strength of the bag can, therefore, be calculated regardless of the depth to which it is placed. Also, the structural integrity of the bag must only be sufficient to contain the pressure differential caused by the osmotic pressure as the pressures inside and outside of the bag will only be different by this differential as the bag is lowered or raised in the water. ;Thus, it can be seen that the invention provides an underwater structural element and/or structure and method of providing the same which can provide a flexible structure at any depth without the need of inflation apparatus such like to generate great pressures to overcome the inward water presshfes at that depth. ;$ -V f' ;* -J . n
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Furthermore, the same bag can be used at any depth and always provide the same stiffness or resistance to change of form.
WHAT I CLAIM IS:
1. An underwater structural element comprising:
an enclosed bag made from an impermeable membrane;
at least one panel or area of said bag including a semipermeable membrane to allow the transfer of water through said panel or area; and a content within said bag, said content capable, in use, of creating an osmotic pressure through the semipermeable membrane.
2. An underwater structural element as claimed in Claim 1 wherein said content is of a molality greater than that of ordinary sea water.
3. An underwater structural element as claimed in either Claims 1 or 2 wherein said content includes common salt.
4. An underwater structure constructed from one or more structural elements as claimed in any one of Claims 1 to 3.
. An underwater structure as claimed in Claim 4 wherein said underwater structure comprises a pipe.
6. An underwater structure as claimed in Claim 4 wherein said underwater structure comprises a wall.
7. An underwater structure as claimed in claim 4 wherein said underwater structure comprises a wave lens.
8. A method of manufacture of an underwater structural element comprising: placing a content within a bag made from an impermeable membrane except for at least one panel or area made from a semipermeable membrane;
placing said bag with said content into the water and, in use, allowing pressure equalisation through the semipermeable membrane between the interior of the bag and the surrounding water plus an increase in pressure within the bag due to the osmotic pressure created by the differential between the molality of the content in the liquid within the bag to the concentration outside the bag.
9. A method of manufacture of an underwater structural element as c
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