GB2172925A

GB2172925A - Rigid structures

Info

Publication number: GB2172925A
Application number: GB08507767A
Authority: GB
Inventors: David John Bally
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-03-26
Filing date: 1985-03-26
Publication date: 1986-10-01
Also published as: GB2172925B; GB8507767D0

Abstract

A rigid structure 1, (25 Figure 4), such as a temporary shelter or storage tank, comprises a wall (2) defining its shape, the wall 2 being formed of flexible material and including cavities 4 in which rigid plastics foam 5 is located. The structure 1, is formed by introducing into the cavities 4 foaming materials which react to form the foam 5, which is conveniently a polyurethane foam, expansion of the materials into the foam 5 inflating the structure into the shape defined by the wall 2, with the foam 5 then solidifying to maintain the shape of the structure 1, and to provide structural rigidity. The wall 2 may have one or more inlets (13 Figure 2) and be included in a kit for forming the structure with a container (18 Figure 2) for storing foaming materials and having outlets (19 Figure 2) for connection to the inlets (13). <IMAGE>

Description

SPECIFICATION Rigid structures This invention relates to rigid structures, and to a kit for forming them.

There is a need for rigid structures, such as temporary shelters and storage tanks, which are cheap to make, and are easy to transport and erect.

According to a first aspect of my invention, a rigid structure comprises a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities, and rigid plastics foam located in the cavities, the structure being formed by introducing into the cavities foaming materials which react to form the foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, and the foam then solidifying to maintain the shape and provide structural rigidity.

The components of such a rigid structure are relatively cheap, and the structure can be transported easily in its uninflated form, and then erected on site.

The wall is preferably formed by inner and outer skins of flexible material, with the cavities defined between them. The inner and outer skins may comprise separate sheets of flexible material of the required shape, which are locally connected to each other so that the cavities are formed between them.

In one embodiment the inner and outer skins are polyethylene sheets locally connected by heat welding. Depending on the use for which the structure is intended, other flexible materials may be used to form the wall, with any suitable method of making the local connections.

The wall includes at least one inlet through which the foaming materials are introduced to the cavities. The or each inlet preferably has a one-way valve to prevent escape of the foaming materials.

The arrangement and shape of the cavities, and the location of the inlet or inlets are chosen to assist in ensuring that the structure inflates correctly.

The rigid plastics foam is preferably a polyurethane foam, whose composition is chosen to provide the various properties which are required. The basic requirement is for the foam to provide sufficient rigidity for the structure, although it is preferable for the foam to have a low density as well.

Further, the foam as it forms must be able to inflate the structure properly. Normally, the foaming materials will be introduced under pressure. It is therefore necessary for the foaming materials to flow relatively rapidly to fill up the cavities, and for them to expand to form the foam by an appropriate amount and at a suitable rate to inflate the structure. Clearly, the expansion should not start too soon, nor should the expansion generate too much pressure, as this might damage the wall. The foam must solidify fairly rapidly to ensure that the structure becomes rigid quickly. Lastly, the heat generated by the reaction must not be too great, so that damage to the wall is prevented. As these various properties are affected by the ambient temperature, the composition of the foam must also be chosen to suit the range of ambient temperatures which are expected at the site.

Polyurethane foams having these various properties are known. The foaming materials may be stored in mixed form, and include a fluorocarbon which acts as a propellant when the materials are dispensed under pressure, and then vaporises in the heat of the reaction to produce gases which foam the materials. Alternatively the components of the foaming materials may be stored separately, and mixed only as they are introduced to the cavities.

The use of a polyurethane foam gives the structure good thermal and acoustic insulating properties. Further, the foam can be pigmented so that an appropriate colour for each structure can be chosen.

My invention can be used to form many types of rigid structure. However a particularly advantageous application is in survival tents, where the portability and thermal insulation properties are useful. It is also advantageous for storage tanks, particularly tanks for use in remote areas, where the cost of transporting a normal rigid tank may be prohibitive. When the structure is erected, the foaming materials may be introduced as required from a large store.

Alternatively, the correct amount of foaming materials for a particular structure may be supplied with each wall, so that the structure comes as a complete kit. This is particularly convenient where the structure is a survival tent.

According to a further aspect of my invention, a kit for forming a rigid structure comprises a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities and at least one inlet, and container means for storing foaming materials under pressure, the container having corresponding outlets for connection to the inlets, the structure being formed by introducing the foaming materials into the cavities, the materials reacting to form a rigid plastics foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, the foam then solidifying to maintain the shape and provide structural rigidity.

Some embodiments of both aspects of my invention are illustrated in the accompanying drawings, of which: Figure 1 is a perspective view of a survival tent with a part broken away; Figure 2 is a developed plan view of the wall of the tent shown in Figure 1; Figure 3 is similar to Figure 2, but shows a wall of a further survival tent; and Figure 4 is a perspective view of a storage tank.

Figure 1 shows a rigid structure 1 which is designed as a survivial tent for use in very cold climates. The structure 1 has a wall 2 defining its shape, the wall 2 being formed of flexible materials 3 and including cavities 4 in which rigid plastics foam 5 is located. The structure 1 is formed by introducing into the cavities 4 foaming materials which react to form the foam 5, the expansion of the materials into the foam 5 inflating the structure 1, and the foam 5 then solidifying to maintain the shape, and provide structural rigidity.

The wall 2 defines a semicylindrical shape including a rectangular base 6 and semicircular end flaps 7, 8. The wall 2 is formed by inner and outer skins 9,10 respectively, each skin comprising a sheet of transparent polyethylene (1000 gauge) of the shape shown in Figure 2. The two sheets are heat welded to each other at their peripherai edges. They are also locally connected to each other by continuous heat welds 11 and discontinous heat welds 12. The welds 11 define the cavities 4 between the skins 9,10, and radiate from a point 13 at which the foaming materials are introduced into the cavities 4. The arrangement is such that the foaming materials do not travel more than about 4 m from the point 13, which ensures that the structure 1 inflates properly. The end flap 7 is separated from the point 13 by one of the welds 11, so that it is not inflated by the foam.The welds 12 define the base 6, but do not interfere with the flow of foaming materials in the cavities 4. The edges 14,14' of the wall 2 are heat welded together, as are the edges 15,15'. A zip fastener 16 is inserted to connect the edges 17,17', so that the end flap 7 forms a transparant door.

The foaming materials are stored under pressure in a container 18, which stores sufficient material to inflate the tent 1. The container 18 has an outlet 19 connected through a one-way valve (not shown) to an inlet in the wall 2 at the point 13, and also includes means 20 for releasing the foaming materials into the cavaties 4. The foam is a pigmented polyurethane foam, whose composition is chosen to provide the various properties required, as discussed above. The foam must also be formulated to ensure that it has the required properties at the low ambient temperatures for which the structure is designed.

The form of the container 18 will depend on the particular components of the foaming materials, and the method of propelling them which is to be used. In Figures 1 and 2, the foaming materials are stored in mixed form in the container 18, and include a propellant. However, the container 18 may have separate compartments to store the components, which are mixed only on release of the materials.

The uninflated wall 2 and the container 18 comprise a kit for forming a rigid structure in accordance with the further aspect of my invention. As a kit for a survival tent, it is compact and portable, and when inflated forms a rigid structure whch has good thermal insulation properties, due to the polyurethane foam. The construction described will, if the foam is pigmented with a bright colour, result in a tent which is easily seen, but which also has a transparent door, enabling the occupants to see out.

Figure 3 shows a developed plan view of a wall 2 for a larger, hemispherical survival tent 21. The general construction and method of inflation is similar to that shown in Figure 2, and corresponding reference numerals have been applied to corresponding parts. The skins 9, 10 comprise a circular base 22, and several petals 23 defining the hemispherical portion. The skins are welded together at their peripheral edge, and are locally connected by continuous welds 11 radiating from the centre of the base 22 to form the cavities 4 and by discontinuous welds 12 which define the base 22. One petal 22 forms a transparent door flap 24, which is connected to adjacent petals by zip fasteners 16. Adjacent edges of the remaining petals are welded to each other. The container 18 of foaming materials is located at the centre of the base 22. Again, the tent 21 is formed from a portable kit.

In a modification (not shown) a larger structure may be formed from a kit in which the container has more than one outlet for connection to corresponding inlets in the wall 2.

Figure 4 shows a further rigid structure, this time a storage tank 25. Again the general construction and method of inflation of the tank are the same as for Figures 1 to 3, and corresponding reference numerals have been applied to corresponding parts.

The wall 2 defines a cylindrical tank with a circular base 26. The inner and outer skins 9, 10 are again of sheet polyethylene material, each skin being cylindrical in shape. The skins 9, 10 are heat welded to each other at their upper and lower edges 27, 28, and at two intermediate points 29, 30. The heat weld at the lower edge 28 also joins the base 26 to the skins 9, 10. Three separate annular cavities 4 are therefore formed between the skins 9, 10. Each annular cavity 4 has its own inlet 31 through which foaming materials are introduced into the cavity.

The inlets 31 are not shown in detail, but include a one-way valve preventing escape of the foaming materials. To inflate the structure the cavities 4 are filled with foaming materials one after the other, starting with the lowest cavity. They are each filled with a measured amount of foaming material, which may be provided by a separate container, or from a larger store of materials. Once each cavity is filled the one-way valve prevents escape of the foam. When the tank is rigid, the wall 2 can be drilled for insertion of attachments such as taps.

In a modification (not shown) each annular cavity 4 may be formed as a separate item, and any required number of these are joined together by a suitable method to form a storage tank.

In either case, my invention provides an easy and cheap way of making rigid storage tanks, which can easily be transported in their uninflated form, and then erected on site. Other large structures may also be formed in this way.

Claims

CLAIMS 1. A rigid structure comprising a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities, and rigid plastics foam located in the cavities, the structure being formed by introducing into the cavities foaming materials which react to form the foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, and the foam then solidifying to maintain the shape and provide structural rigidity. 2. A rigid structure as claimed in claim 1, in which the wall is formed by inner and outer skins of flexible material, with the cavities defined between them. 3. A rigid structure as claimed in claim 2, in which the inner and outer skins comprise separate sheets of flexible material of the required shape, which are locally connected to each other so that cavities are formed between them. 4. A rigid structure as claimed in any preceding claim, in which the wall includes at least one inlet through which the foaming materials are introduced into the cavities. 5. A rigid structure as claimed in any preceding claim, in which the rigid plastics foam is a polyurethane foam. 6. A kit for forming a rigid structure comprising a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities and at least one inlet, and container means for storing foaming materials under pressure, the container having corresponding outlets for connection to the inlets, the structure being formed by introducing the foaming materials into the cavities, the materials reacting to form a rigid plastics foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, the foam then solidifying to maintain the shape and provide structural rigidity. Amendments to the claims have been filed, and have the following effect: (a) Claims 4-6 above have been textually amended. (b) New or textually amended claims have been filed as follows: Claims 4-19

1. A rigid structure comprising a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities, and rigid plastics foam located in the cavities, the structure being formed by introducing into the cavities foaming materials which react to form the foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, and the foam then solidifying to maintain the shape and provide structural rigidity.

2. A rigid structure as claimed in claim 1, in which the wall is formed by inner and outer skins of flexible material, with the cavities defined between them.

3. A rigid structure as claimed in claim 2, in which the inner and outer skins comprise separate sheets of flexible material of the required shape, which are locally connected to each other so that cavities are formed between them.

4. A rigid structure as claimed in any preceding claim, in which the flexible material is polyethylene sheet.

5. A rigid structure as claimed in any preceding claim, in which the wall includes at least one inlet through which the foaming materials are introduced into the cavities.

6. A rigid structure as claimed in claim 5, in which each inlet has a one-way valve to prevent escape of foaming materials.

7. A rigid structure as claimed in any preceding claim, in which the rigid plastics foam is a polyurethane foam.

8. A kit for forming a rigid structure comprising a wall defining the shape of the structure, the wall being formed by flexible material, and including cavities and at least one inlet, and container means for storing foaming materials under pressure, the container having corresponding outlets for connection to the inlets, the structure being formed by introducing the foaming materials into the cavities, the materials reacting to form a rigid plastics foam, expansion of the materials into the foam inflating the structure into the shape defined by the wall, the foam then solidifying to maintain the shape and provide structural frigidity.

9. A kit as claimed in claim 8, in which the wall is formed by inner and outer skins of flexible material, with the cavities defined between them.

10. A kit as claimed in claim 9, in which the inner and outer skins comprise separate sheets of flexible material of the required shape, which are locally connected to each other so that cavities are formed between them.

11. A kit as claimed in any of claims 8 to 10, in which the flexible material is polyethylene sheet.

12. A kit as claimed in any of claims 8 to 11, in which each inlet has a one-way valve to prevent escape of foaming materials.

13. A kit as claimed in any of claims 8 to 12, in which the rigid plastics foam is a polyurethane foam, and the foaming materials are stored in mixed form in the container and include a propellant.

14. A kit as claimed in any of claims 8 to 12, in which the rigid plastics foam is a polyurethane foam, and the foaming materials are stored in separate compartments in the container.

15. A rigid structure substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

16. A rigid structure substantially as described herein with reference to and as illustrated in Figure 3 of the accompanying drawings.

17. A rigid structure substantially as described herein with reference to and as illustrated in Figure 4 of the accompanying drawings.

18. A kit for forming a rigid structure substantially as described herein with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

19. A kit for forming a rigid structure substantially as described herein with reference to and as illustrated in Figure 3 of the accompanying drawings.