WO2005017291A1

WO2005017291A1 - Inflatable structural arrangement

Info

Publication number: WO2005017291A1
Application number: PCT/GB2004/003471
Authority: WO
Inventors: Frank Hampl
Original assignee: Pre Con Structures Limited
Priority date: 2003-08-15
Filing date: 2004-08-12
Publication date: 2005-02-24
Also published as: GB2421742B; GB0319312D0; GB0602691D0; GB2421742A

Abstract

A dome shaped structure (10) comprising a framework of elongate inflatable members (12) in a skin (14). The skin (14) defines second inflatable members between the first inflatable members, which second members are held at below ambient pressure. A pressure distributor (18) provides above ambient pressure in the elongate members (12) and below ambient pressure in the second inflatable members.

Description

INFLATABLE STRUCTURAL ARRANGEMENT

This invention concerns structural arrangements and also methods of forming a structure.

According to the present invention there is provided a structural arrangement, the arrangement comprising a first endless inflatable member which defines the periphery of the arrangement and which can be inflated at above ambient pressure, a skin extending from the first inflatable member to define a second inflatable member the interior of which second inflatable member can be caused to be at below ambient pressure.

The invention also provides a structural arrangement, the arrangement comprising a first endless inflatable member which defines the periphery of the arrangement and which is inflated at above ambient pressure, and a skin extending from generally opposite sides of the first inflatable member to define a second inflatable member the interior of the second inflatable member being at below ambient pressure.

The first inflatable member may be at an above ambient pressure of greater than 0.5 atmosphere, and it is desirably at an above ambient pressure of between 0.5 and 1.5 atmosphere. The second inflatable member may be at a below ambient pressure of less than -0.25 atmosphere, and may be at a below ambient pressure of between -0.25 and -1.0 atmosphere.

One or more third inflatable members may be provided which can be inflated at above ambient pressure, and which third member or members connectively extend from the first inflatable member. A plurality of third inflatable members may be provided which define a framework. The skin preferably encloses the third inflatable members to define further second inflatable members extending therebetween. The skin preferably also encloses the first inflatable member.

The structural arrangement may be a regular shape in plan view, and may be circular, square or rectangular.

Some or all of the third inflatable members may extend from the first inflatable member to a substantially central hub of the arrangement.

The arrangement may be in the form of a structure, which may comprise a shelter or building. The structure may be circular in plan view. The structure may include a floor. The floor may include inflatable members. Solid support members may be provided in the floor, and such members may extend through the floor. A solid cover may be provided on the floor, which cover may include the support members. Fourth inflatable members which can be inflated at above ambient pressure may be provided in the floor.

The floor may include a network of inflatable ribs, perhaps with the fourth inflatable members extending therebetween. The arrangement may include ancillary connections provided therein, including any for a power supply, air conditioning, communications, water supply or sewage.

The inflatable members are preferably made of a substantially non- stretch flexible material, and may be made of any of fabric reinforced plastic film, Mylar, Kevlar PTFE, carbon fibre, rubberised fabrics, or micro-meteorite penetration-inhibiting skin materials such as neoprene coated nylon. The structural arrangement may be in the form of panels.

Connections of a material with a relatively low thermal and/or acoustic conductivity may be provided between the first and second inflatable members, and between the second and third inflatable members.

Each panel may be linked to adjacent panels by a link, which link is desirably of a material of a relatively low thermal and/or acoustic conductivity. Respective first inflatable members on adjacent panels may lie substantially adjacent each other, with the links extending between the second inflatable members on each panel.

Each panel may include a plurality of alternate second and third inflatable members. A substantially rigid skin may be provided on the panel covering the edges of the first, second and third inflatable members. Cavities may be provided in the skin which cavities can be caused to be at below ambient pressure. The arrangement may include a pressure distributor which connects to the first and second inflatable members to provide thereto respectively above and below ambient pressure. The pressure distributor may connect to the third member or members. The pressure distributor may include above and below ambient pressure chambers. The pressure distributor may include means for returning the chambers and hence the whole of the arrangement, to ambient pressure. The pressure distributor may include latching valves, which can be locked open to release pressure.

Pressure sensors may be provided in the first, second and/or third inflatable members. The arrangement may include reflation means arranged to automatically periodically bring the first, second and/or third inflatable members back to respective required above and below ambient pressures.

The reflation means may be operable in response to pressures detected by the sensors. The reflation means may be integrally provided in the arrangement, and could be solar powered. The arrangement may include pressure release valves which open when respective required above and below ambient pressures are attained, to prevent excess high or low pressures building up. The arrangement may be modular with a plurality of units which can be connected together as required. Attachment means may be provided on the units, which attachment means may provide a snap fit. The units may have a polygonal configuration to permit required shaped arrangements to be made. The inflatable members may be arranged in cells such that if a member in a cell is damaged the required above or below ambient pressure will only change in that cell.

The arrangement may be in the form of any of terrestrial or submarine structures, vehicle bodies, boat hulls, housings, storage structures, relief shelters, life-rafts, flight pressure suits.

The first inflatable material may be coated with a settable or curable material.

The invention also provides a method of forming a structure, the method including using an arrangement according to any of the preceding twenty four paragraphs, inflating the first elongate member to a required pressure, connecting the second elongate member or members to a source of below ambient pressure to bring the pressure in the second elongate members to a required below ambient pressure. The third elongate member or members are preferably inflated.

Preferably following inflation, the first, second and/or third inflatable members are covered in a curable or settable coating material, which material is caused to cure or set.

Alternatively or in addition, the first, second and/or third inflatable members may be filled with a curable or settable filling material, which material is caused to cure or set.

Following curing or setting of the curable or settable material, the above ambient pressure in the first and/or third inflatable members may be released. The settable coating material may be any of resin impregnated composite materials, glass reinforced plastics, fibre glass paints, thermoplastic or ceramic based coating compounds.

The filling material may comprise two pack expanding foam forming material such as polyurethane, or solids forming ceramics, pumice, analogues, concrete or gypsum.

Where heat is required for curing or setting, a warm fluid may be passed into the first and/or third inflatable members.

The first and/or third inflatable members may be inflated with air. Alternatively the first inflated members could be filled with a different fluid such as water, which may be sea water. Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a diagrammatic part cut away perspective view of a structure according to the invention;

Fig. 2 is a diagrammatic cross sectional side view of the structure of Fig. 1 ;

Fig. 3 is a diagrammatic view from above of the base of the structure of Fig. 1 ; Fig. 4 is a diagrammatic sectional view from above of a component according to the invention;

Fig. 5 is a cross sectional view through the component of Fig. 4; Fig. 6 is a similar view to Fig. 5 but of an alternative component;

Fig. 7 is a diagrammatic sectional view through part of a structure according to the invention; Figs. 8 - 13 are diagrammatic cross sectional views of alternative structural panels according to the invention;

Fig. 14 is a diagrammatic front view of an article according to the invention;

Fig. 15 is a diagrammatic cross sectional view of a further component according to the invention;

Fig. 16 is a similar view to Fig. 15 of a yet further component according to the invention; Fig. 17 is a cross sectional view through part of another component according to the invention;

Fig. 18 is a diagrammatic cross sectional view of a modular component according to the invention;

Fig. 19 shows a structure made from a number of components as shown in Fig. 18; Fig. 20 is a diagrammatic cross sectional view through a container according to the invention;

Fig. 21 is a diagrammatic cross sectional view through a further component usable in a method according to the invention;

Fig. 22 is a diagrammatic perspective view through a still further component usable in the invention; and

Fig. 23 is a more detailed side view through part of the component of Fig. 22.

Figs. 1 -3 show a dome shaped structure 10 made according to the invention. The structure comprises a framework of elongate inflatable members 12, and a skin 14 either side of the framework to define compartments 16 between the elongate members 12 of the framework. The elongate members 12 and compartments 16 are all connected to an upper terminus 17. The elongate members 12 and compartments 16 are also connected to a pressure distributor 18 located in an aperture 19 at the centre of the floor 20.

In the floor 20 a rigid cover 22 is provided with a plurality of downwardly extending rigid support members 24. A plurality of inflated bags 26 are provided between elongate members 28 in the floor 20 of the structure

10. The structure 10 is held down by ground engaging stakes 30 extending through spaced openings in a flange 32. Fig. 2 also shows an alternative solid floor 34 provided by a rigid member 36. In this instance the stake 30 engages through an opening in an internal flange 38.

In use the elongate members 12, 28 are inflated above atmospheric pressure to provide a rigid framework. The elongate members 12, 28 can be inflated for instance to an above atmospheric pressure of 1 atmosphere. The inflated bags 26 when provided are inflated. The compartments 16 formed between the elongate members and by the two skins 14 are connected to a source of below ambient pressure, thereby causing below ambient pressure in the compartment 16. A below ambient pressure in the compartment 16 of for instance -0.5 atmosphere may be produced. This therefore provides a rigid structure, with the compartments below ambient pressure providing significant thermal and acoustic insulation. The structure can however initially be transported and supplied "flat pack" and then inflated to the required shape.

If required ancillary connections could be provided in the structure 10 during construction. Such communications could include wiring for power transmission and communication, as well as a water supply and sewerage. The inflatable member 12A which defines the outer perimeter of the floor 20 constitutes the first inflatable member. The other inflatable members 12 constitute the third inflatable members, whilst the compartments 16 are the second inflatable members. Figs. 4 and 5 show a pressure distributor 18 comprising a circular cross section casing with an above ambient pressure chamber 34 on one side and a below ambient pressure chamber 36 on the other side. The chambers 34, 36 connect via valves 38 to a plurality of radial outlets 40 which connect to the respective elongate members 12, 28 or compartments 16 to provide above or below ambient pressure as required. Pressure relief valves 42 are provided in each of the outlets. Inlets 44 are provided to each of the chambers with non return valves 46. A cover 48 is held on by a screw threaded member 50, such that release of the member 50 and thus raising of the cover 48 will cause the whole system to return to ambient pressure.

Where inflated bags 26 are provided, these could be connected to the chamber 34, or a further above ambient pressure chamber could be provided to inflate the bags 26.

Fig. 6 shows a pressure distributor 52 where the above ambient pressure chamber 54 is located above the below ambient pressure chamber 56, but otherwise operates in a similar way to the pressure distributor 18.

Sensors may be provided in the various elongate members 12, 28 compartments 16, and bags 26 to detect whether a required pressure is has been achieved. If not a signal can be sent to the pressure distributor 18 to connect at least the respective compartments 16, elongate members 12, 28, or bags 26 to the respective chamber 34, 36. Alternatively, the compartments 16 elongate members 12, 28, or bags 26 may periodically be connected to the chambers 34, 36 to ensure that the correct pressure is provided therein. Fig. 7 diagrammatically illustrates how three above ambient pressure compartments 58 are connected in series with a one way inlet valve 60 and one way valves 62 extending sequentially between the compartments. A pressure relief valve 64 is provided in the end most compartment 58 to ensure that the above ambient pressure remains at a required level.

Figs. 8 - 13 show various possible panel structures according to the invention. In Fig. 8 a flexible continuous skin 66 is provided enclosing a plurality of spaced inflatable ribs 68, defining cavities 70 between the ribs 68.

The ribs 68 can be inflated to a required above ambient pressure, whilst air can be sucked from the cavities 70 to cause a below ambient pressure, to provide a profile as illustrated. To continue with the good thermal and acoustic insulation provided by the below ambient pressure cavities 70, a piece of material 72 with a low thermal/acoustic conductivity can be provided extending across the top and bottom of the ribs 68. In the arrangement shown in Fig. 9 the ribs 74 are separated from a skin 76 by projections 78 on each side of the ribs 74, which projections 78 have a low thermal/acoustic conductivity.

Fig. 10 shows an alternative structure where elongate cavities 80 are defined in a sandwich arrangement between elongate inflatable members 82, and elongate links 84 are provided extending between the cavities 80 between respective pairs of inflatable members 82. The links 84 are of low thermal/acoustic conductivity.

Fig. 11 shows an arrangement where a plurality of spaced ribs 86 are provided defining cavities 88 therebetween which can be caused to be at lower ambient pressure. A rigid casing 90 is provided over the ribs 86 and cavities 88, with the casing 90 being in the form of linked components 92, such that separate components cover the ribs at the cavities, with links between the components 92 of low thermal and acoustic conductivity. Fig. 12 show an arrangement where a rigid casing 96 is provided in a number of pieces, with each piece being connected to another piece adjacent a rib 98, and being connected by a link 100 of low thermal/acoustic conductors. Chambers 102 may be provided in the casing 96 opposite cavities 104 formed between the ribs 98, and which chambers 102 can also have below ambient pressure caused therein. Fig. 13 shows an arrangement with a plurality of ribs 106 and cavities

108 therebetween, with separate coverings 110, 112 for the ribs 106 and cavities 108, which coverings 110, 112 can be sealed or cemented together. Fig. 14 shows an alternative use for structures according to the invention. Here pressure linked panels 114 formed from a plurality of ribs held at above ambient pressure, interposed with cavities held at below ambient pressure are provided in a flight pressure suit 116. This can insulate a wearer from temperature extremes, and also reduce blood flow away from the brain, and fluid could be pulsed through the panels.

Fig. 15 shows a further structure according to the invention. Here a sandwich is provided of cells which can be held at above ambient pressure with a filling of compartments 120 which can be held at below ambient pressure. A narrow cell 122 connecting between opposite above ambient pressure cells 118 extends through each below ambient pressure compartment 120. An inlet valve 124 into a one of the above ambient pressure cells 118 is shown which can connect either into an adjacent above ambient pressure cell 118 or through the transversely extending cell 122 across to the opposite above ambient cell 118. Both opposite cells 118 have non return valves 126 connecting into adjacent cells 118, The arrangement will extend in a loop or otherwise to a pressure relief valve 128 as shown, to maintain the pressure below a required maximum. Interconnecting non return valves 130 are also provided in the below ambient pressure compartment 120.

Fig. 16 shows a similar arrangement but with only a single set of above ambient pressure cells 132, such that the transversely extending above ambient pressure cells 134 extend to the edge of the below ambient pressure compartments 136. A pressure relief valve 138 and non return valves 140 in the below ambient pressure are illustrated, as well as an inlet valve 142, pressure relief valve 142, and non return valves 146 in the above ambient pressure ceils 132, 134.

Fig. 17 is a cross sectional view through an inflatable member 148 according to the invention which illustrates how these can be used to provide a curved shape. The member 148 shown in Fig. 17 has a significantly thicker lower wall 150 than upper wall 152 and when inflated will tend to curve about its lower wall 150 as the upper wall 152 stretches. Fig. 18 shows part of two interconnected modular elements 154, 156 according to the invention. The elements 154, 156 comprise a sandwich of inflatable members 158 to be inflated at above ambient pressure with a filling of an inflatable member 160 to be inflated at below ambient pressure located therebetween. A connection arrangement 162 is provided such that valves 164 extend between the respective inflatable members 158, 160 on each element 154, 156. A snap fit connection 166 is also provided as shown. Such elements 154, 156 can be provided in a required polygonal formation. Fig. 19 shows a structure 168 made up of a plurality of such elements 154, 156, each having a triangular configuration.

Fig. 20 shows a container 170 made from a structure according to the present invention. The container 170 can be supplied flat and inflated as required to hold substances such as water and the like. The container has a skin formed of an inner and outer inflatable elements 172, 174 which can be inflated at above atmospheric pressure, and a chamber 176 defined therebetween which can be held at below atmospheric pressure. Inlet and outlet valves 178, 180 extending into the above ambient pressure elements 172, 174, and 182, 184 inlet and outlet valves into the chamber 176 are provided. A lid 186 is provided in the upper part of the container.

If required containers and/or structures according to the invention can be retained in their required profile such that it is no longer necessary to provide respective above and below ambient pressure thereto. A settable or curable component coating can be provided on the outside of the respective inflatable elements. A coating could include glass reinforced plastics, a thermoplastic material or fibre glass paint etc. Where heat is required to cure the coating then a warm fluid could be passed through the inflatable members. An alternative or additional approach is to fill the above ambient pressure inflatable members a settable or curable material such as a foamed material which may be in a two pack form, such as polyurethane.

Alternatively a solids formed ceramic, pumice analogue, concrete or gypsum could be used.

Fig. 21 shows a device 188 according to the invention for filling an inflatable member 190 with a two part foam. The device 188 comprises a collar 192 mountable around a port 194 in the inflatable member 190. A tube 196 extends from the collar part way into a container 198 divided into two compartments by an internal membrane 200, with the two parts of the foam component on either side of the membrane 200. A thread is provided on the collar 192 and also the tube 196. As the tube 196 is rotated into the inflatable member 190 this firstly breaks a seal into the interior of the inflatable member 190. A further thread 202 on the tube is then uncovered by removing a strip 203, and the container 198 can then be screwed onto the tube 196 which breaks a seal into the first compartment and subsequently breaks the membrane 200 causing the two materials to mix and enter the inflatable member 190. Once the material has entered the inflatable member 190 the container 198 can be snapped of about a weakness 204 in the tube 196 leaving the collar 192 around the remainder of the tube 196 with a plug 206 therearound. Once the settable/curable material in the inflatable member 190 has cured or set, or during the filling process then the above ambient pressure can be released leaving a permanent structure.

Figs. 22 and 23 show a latching valve 210 usable to release pressure in the system for example when being in a flat pack condition before erection. The valve 210 comprises a housing 212 and a closure mechanism 214 such as a coil spring which has not been shown in detail. The valve 210 includes a seal mount 216 from which a piston and cylinder arrangement 218 extends. The arrangement 218 comprises a cylinder 220 and a piston 222 slidably movable therein. A peg 224 on the cylinder 220 engages in a profiled groove 226 on the piston 222.

The groove 226 comprises a first left hand vertical section 228 which extends through a right hand bend into an inclined section 230. This curves at an apex 232 with a relatively steep lower curve 231 and gentle upper curve

233 into a second vertically extending section 234, the lower end of which is level with the top end of the first vertical section 228.

In use, an appropriate compressor would be connected to a common inlet valve of a pressure distributor with the common outlet valve connected to a pressure considerably above ambient. As the compressor is switched on and pressure beneath the seal mount 216 exceeds ambient, the piston 222 moves upwardly in the cylinder 220 and also rotates by virtue of the profile of the groove 226, until the peg 224 overreaches the apex 232. When the compressor is switched off the cylinder 220 will drop relative to the piston 222 but only until the peg 224 reaches the bottom end of the second vertical section 234. The valve 210 will now operate as a pressure release valve and be suitable for packaging and transportation of the structure. When it is required to inflate the structure a compressor or gas supply is connected to the inlet valve of the pressure distributor causing the cylinder 220 to rise relative to the piston 222. This lifts the peg 224 to the apex 232. When the pressure is turned off this time the peg will return to the end of the first vertical section 228 causing the valve 210 to close.

There are thus described a number of structures and structural arrangements which provide for considerable advantages. These arrangements can be provided flat packed but can be readily inflated for use.

Where required the inflatable member can be solidified either internally, externally or both to leave a permanent structure. The structures are extremely rigid for two reasons: the above ambient inflated elongated members comprising a frame, and pressure contrast between ambient pressure and compartmental underpressure which places the skins under stress about the frame. The structures are relatively light and can be readily transported without occupying much space. The arrangements can be modular to provide required sizes and shapes of structure. The structures also provide a very good thermal and acoustic insulation which is advantageous in a number of situations. Structures made in this way are also generally earthquake resistant and flood resistant, and will float if appropriately designed integral floors are included Various other modifications may be made without departing from the scope of the invention. For instance a wide range of different structures or uses of structures are possible with the present invention. The structures can take many different forms as required, and different materials may be used. Features in the structures such as doorways can be defined by inflatable members. Alternatively such features may be defined by rigid components, and rigid components may be used elsewhere in the structures to provide support. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A structural arrangement, the arrangement comprising a first endless inflatable member which defines the periphery of the arrangement and which can be inflated at above ambient pressure, a skin extending from the first inflatable member to define a second inflatable member the interior of which second inflatable member can be caused to be at below ambient pressure.

2. A structural arrangement, the arrangement comprising a first endless inflatable member which defines the periphery of the arrangement and which is inflated at above ambient pressure, and a skin extending from generally opposite sides of the first inflatable member to define a second inflatable member the interior of the second inflatable member being at below ambient pressure.

3. An arrangement according to claim 2, characterised in that the first inflatable member is at an above ambient pressure of greater than 0.5 atmosphere.

4. An arrangement according to claim 3, characterised in that the first inflatable member is at an above ambient pressure of between 0.5 and 1.5 atmosphere.

5. An arrangement according to any of claims 2 to 4, characterised in that the second inflatable member is at a below ambient pressure of less than -

0.25 atmosphere.

6. An arrangement according to claim 5, characterised in that the second inflatable member is at a below ambient pressure of between -0.25 and -1.0 atmosphere.

7. An arrangement according to any of the preceding claims, characterised in that one or more third inflatable members is provided which can be inflated at above ambient pressure.

8. An arrangement according to claim 7, characterised in that the third member or members connectively extend from the first inflatable member.

9. An arrangement according to claims 7 or 8, characterised in that a plurality of third inflatable members are provided which define a framework.

10. An arrangement according to claim 9, characterised in that the skin encloses the third inflatable members to define further second inflatable members extending therebetween.

1 1. An arrangement according to claims 9 or 10, characterised in that some or all of the third inflatable members extend from the first inflatable member to a substantially central hub of the arrangement.

12. An arrangement according to any of the preceding claims, characterised in that the skin encloses the first inflatable member.

13. An arrangement according to any of the preceding claims, characterised in that the structural arrangement is a regular shape in plan view, and may be circular, square or rectangular.

14. An arrangement according to any of the preceding claims, characterised in that the arrangement is in the form of a structure.

15. An arrangement according to claim 14, characterised in that the structure comprises a shelter or building.

16. An arrangement according to claims 14 or 15, characterised in that the structure is circular in plan view.

17. An arrangement according to any of claims 14 to 16, characterised in that the structure includes a floor.

18. An arrangement according to claim 17, characterised in that the floor includes inflatable members.

19. An arrangement according to claim 18, characterised in that fourth inflatable members which can be inflated at above ambient pressure are provided in the floor.

20. An arrangement according to claims 18 or 19, characterised in that the floor includes a network of inflatable ribs.

21. An arrangement according to claim 20 when dependent on claim 19, characterised in that the fourth inflatable members extend between the inflatable ribs.

22. An arrangement according to any of claims 17 to 21 , characterised in that solid support members are provided in the floor.

23. An arrangement according to claim 22, characterised in that the support members extend through the floor.

24. An arrangement according to any of claims 17 to 23, characterised in that a solid cover is provided on the floor.

25. An arrangement according to claim 24 when dependent on claims 22 or 23, characterised in that the cover includes the support members.

26. An arrangement according to any of the preceding claims, characterised in that the arrangement includes ancillary connections provided therein, including any for a power supply, air conditioning, communications, water supply or sewage.

27. An arrangement according to any of the preceding claims, characterised in that the inflatable members are made of a substantially non- stretch flexible material.

28. An arrangement according to claim 27, characterised in that the inflatable members are made of any of fabric reinforced plastic film, Mylar, Kevlar PTFE, carbon fibre, rubberised fabrics, or micro-meteorite penetration- inhibiting skin materials such as neoprene coated nylon.

29. An- arrangement according to any of the preceding claims, characterised in that connections of a material with a relatively low thermal and/or acoustic conductivity are provided between the first and second inflatable members.

30. An arrangement according to claim 7 or any of claims 8 to 29 when dependent on claim 7, characterised in that the connections of a material with a relatively low thermal and/or acoustic conductivity are provided between the second and third inflatable members.

31 . An arrangement according to any of the preceding claims, characterised in that the structural arrangement is in the form of panels.

32. An arrangement according to claim 31 , characterised in that each panel is linked to adjacent panels by a link, which link is of a material of a relatively low thermal and/or acoustic conductivity.

33. An arrangement according to claim 32, characterised in that respective first inflatable members on adjacent panels lie substantially adjacent each other, with the links extending between the second inflatable members on each panel.

34. An arrangement according to any of claims 31 to 33, characterised in that each panel includes a plurality of alternate second and third inflatable members.

35. An arrangement according to claim 34, characterised in that a substantially rigid skin is provided on the panel covering the edges of the first, second and third inflatable members.

36. An arrangement according to claim 35, characterised in that cavities are provided in the skin which cavities can be caused to be at below ambient pressure.

37. An arrangement according to any of the preceding claims, characterised in that the arrangement includes a pressure distributor which connects to the first and second inflatable members to provide thereto respectively above and below ambient pressure.

38. An arrangement according to claim 37 when dependent on claim 6, characterised in that the pressure distributor connects to the third member or members.

39. An arrangement according to claims 37 or 38, characterised in that the pressure distributor includes above and below ambient pressure chambers.

40. An arrangement according to claim 39, characterised in that the pressure distributor includes means for returning the chambers and hence the whole of the arrangement, to ambient pressure.

41. An arrangement according to claim 40, characterised in that the pressure distributor includes latching valves, which can be locked open to release pressure.

42. An arrangement according to any of the preceding claims, characterised in that the arrangement includes reflation means arranged to automatically periodically bring the first, second and/or third inflatable members back to respective required above and below ambient pressures.

43. An arrangement according to any of the preceding claims, characterised in that pressure sensors are provided in the first, second and/or third inflatable members.

.

44. An arrangement according to claim 43 when dependent on claim 42, characterised in that the reflation means is operable in response to pressures detected by the sensors.

45. An arrangement according to any of claims 42 to 44, characterised in that the reflation means is integrally provided in the arrangement.

46. An arrangement according to any of claims 42 to 45, characterised in that the reflation means is solar powered.

47. An arrangement according to any of the preceding claims, characterised in that the arrangement includes pressure release valves which open when respective required above and below ambient pressures are - attained, to prevent excess high or low pressures building up.

48. An arrangement according to any of the preceding claims, characterised in that the arrangement is modular with a plurality of units which can be connected together as required.

49. An arrangement according to claim 48, characterised in that attachment means are provided on the units, which attachment means may provide a snap fit.

50. An arrangement according to claims 48 or 49, characterised in that the units have a polygonal configuration to permit required shaped arrangements to be made.

51. An arrangement according to any of the preceding claims, characterised in that the inflatable members are arranged in cells such that if a member in a cell is damaged the required above or below ambient pressure will only change in that cell.

52. An arrangement according to any of the preceding claims, characterised in that the arrangement is in the form of any of terrestrial or submarine structures, vehicle bodies, boat hulls, housings, storage structures, relief shelters, life-rafts, flight pressure suits.

53. An arrangement according to any of the preceding claims, characterised in that the first inflatable material is coated with a settable or curable material.

54. A method of forming a structure, the method including using an arrangement according to any of the preceding claims, inflating the first elongate member to a required pressure, connecting the second elongate member or members to a source of below ambient pressure to bring the pressure in the second elongate members to a required below ambient pressure.

55. A method according to claim 54 when dependent on claim 7, characterised in that the third elongate member or members are inflated.

56. A method according to claims 54 or 55, characterised in that following inflation, the first, second and/or third inflatable members are covered in a curable or settable coating material, which material is caused to cure or set.

57. A method according to any of claims 54 to 56, characterised in that the first, second and/or third inflatable members are filled with a curable or settable filling material, which material is caused to cure or set.

58. A method according to any of claims 54 to 57, characterised in that following curing or setting of the curable or settable material, the above ambient pressure in the first and/or third inflatable members is released.

59. A method according to claim 56 or claims 57 or 58 when dependent on claim 55, characterised in that the settable coating material is any of resin impregnated composite materials, glass reinforced plastics, fibre glass paints, thermoplastic or ceramic based coating compounds.

60. A method according to claim 57 or claims 58 or 59 when dependent on claim 56, characterised in that the filling material comprises two pack expanding foam forming material such as polyurethane, or solids forming ceramics, pumice, analogues, concrete or gypsum.

61. A method according to any of claims 54 to 60, characterised in that where heat is required for curing or setting, a warm fluid is passed into the first and/or third inflatable members.

62. A method according to any of claims 54 to 61 , characterised in that the first and/or third inflatable members are inflated with air.

63. A method according to any of claims 54 to 61 , characterised in that the first and/or third inflatable members are inflated with a fluid other than air, which fluid may be water and may be sea water.