GB2112320A - Thermally insulating laminate - Google Patents

Abstract

A system for the construction of thermally insulating appliances employs a plurality, for example fifteen, of very thin membranes 10 of aluminised polyester sheet material such as Melinex (Trade Mark) disposed in a layered arrangement and sealed to form separate compartments 12 between respective layers. A valve means 11 gives access to the compartments for inflation fractionally above ambient pressure so that the membranes are spaced apart by about 10 millimetres. The system can provide appliances capable of insulating against extreme low temperatures, for example survival bags for use in diving bells, and also capable of deflation and folding to advantageously small bulk for stowage. <IMAGE>

Description

SPECIFICATION Thermally insulating appliances This invention relates to a system of construction for thermally insulating appliances.

The invention is particularly concerned with such appliances which are flexible or which comprise flexible panels.

According to the present invention, there is provided a system of construction for thermally insulating appliances, in which a plurality of gasimpervious flexible membranes are disposed in a layered arrangement and sealed together to form separate compartments between respective layers, and there is provided valve means operable to give access to said compartments for inflation thereof and to close the compartments so that they are mutually separate.

Preferably, the membranes are of a material treated so that it has reduced thermal emissivity.

Preferably, the membranes are of a polyester sheet material having a surface deposit of a reflective material such as aluminium.

Preferably, the membranes are of a heatweldable sheet material.

Preferably, the disposition of the membranes in said layered arrangement is such that upon inflation of the compartments the membranes tend to adopt an even spacing of the order of ten millimetres.

The number of membranes will be determined by having regard to the degree of thermal insulation required.

It is envisaged that as many as fifteen membranes may be used.

Transmission of heat through the inflated appliance by conduction is of a generally low order, related mainly to the thermal conductivity of the gas used for inflation of the appliance.

Transmission of heat through the inflated appliance by convection is also of a low order due to the choice of inter-membrane spacing.

Transmission of heat through the inflated appliance by thermal radiation is minimised by means of reducing thermal emissivity as aforesaid.

Prior to inflation of an appliance constructed in accordance with the present invention, a principal factor determining the size to which the appliance may be reduced for packaging is the thickness of the material of the membranes. Useful membranes of the order of ten microns thickness are available. Accordingly, the present invention enables the provision of an appliance capable of relatively high thermally insulating performance and also capable of being packaged to a relatively low stowage volume.

The principal insulator in an appliance according to the present invention in gas.

Therefore, with the availability of relatively inexpensive plastics sheet materials, an appliance in accordance with the present invention enables the provision of convenient and relatively high thermally insulating performance at relatively low cost.

Since the membranes are sealed together to form separate compartments, puncture or failure of one membrane or a few membranes will not necessarily cause complete failure of the appliance.

Further, according to the present invention, there is provided an appliance constructed in accordance with the aforesaid system.

Incidents involving the loss of life in sub-sea environments have demonstrated the need for emergency survival systems for divers in diving bells in the event of loss of heating supply. A number of systems have been proposed in response to this need, consisting of a large insulated bag similar to a sleeping bag, and a device for preheating breathing gas. Generally, although these proposed systems have been found to be effective in terms of the survival capability which they provide, it has been found that in the confined space of a diving bell, the size of the survival bag causes problems of stowage when the bag is not is use.

The present invention seeks to obviate or mitigate the aforesaid problems and, further, provides a survival bag constructed in accordance with the aforesaid system.

In the construction of an appliance in accordance with the present invention, particularly such as a survival bag, a problem arises from the fact that when the appliance is inflated any 'outer surfaces having roundness will require a different area of membrane than the corresponding 'inner' surfaces.

Further, according to the present invention, there is provided an appliance constructed as aforesaid and comprising a panel in which the membranes are together folded to form at least one double fold, the intended innermost membrane being fixed to itself at said fold and the remaining membranes being free to pay out differentially from said fold upon inflation of the appliance.

Examples of appliances embodying the present invention will now be described with reference to the accompanying drawings in which.~ Figure 1 is an exploded view in sectional elevation of part of an appliance in accordance with the present invention; Figure 2 is an assembled view corresponding with Fig. 1 with the appliance inflated; and Figure 3 is a cross-section through part of a panel of an appliance, showing two double folds.

A variety of thermally insulating appliances may be constructed in accordance with the system of the present invention, for example simple covers for reducing heat loss from generally large flat areas such as sports pitches or attic floors, smaller such covers for maintaining warmth in persons, emergency survival bags for use by persons in extreme environments, emergency drapes for retaining refrigeration, and so on; in effect, for all applications requiring effective control of thermal transfer by means of an appliance capable of being packed to a small stowage volume, and preferably inexpensive to manufacture.

All such appliances will comprise a plurality of gas-impervious flexible membranes disposed in a layered arrangement and sealed together to form separate compartments between respective layers, and valve means operable to give access to these compartments for inflation thereof and to close the compartments so that they are mutually separate. The design of such appliances is preferably such that the layered arrangement is minimally interrupted by transverse joining of the membranes, thus to minimise paths for thermal transfer solely by conduction. To this end, it is envisaged that ideally there would be only a single compartment between mutually adjacent membranes in a simple appliance in the form of a cover, sealing together of the membranes being only along the edges of the appliance.

The membranes in one example, such as an emergency survival bag, are of an aluminised material known as MELINEX (trade mark). The reflective surfaces reduce thermal emissivity, but are not an essential feature of all appliances in accordance with the present invention.

The exterior surfaces of outermost membranes are preferably coated with a protective material. A sprayed coating of a polyurethane is envisaged.

In Figs. 1 and 2, part of an appliance comprises a plurality of MELINEX membranes 10 (four such membranes are shown, but fifteen may be used), and a valve means indicated generally by reference numeral 11 for allowing inflation of compartments 12 between the membranes. The valve means 1 1 consists of a valve core 13, a valve collar 14, a valve cap 15, and a stack of valve washers consisting of alternately arranged rubber washers 16 and bowed (not dished) springy metal washers 17. The valve core 13 has a flange portion 18 for supporting the washer stack, and a hollow stem 19 the lower portion of which has radial gas ports 20 and the upper portion of which is screw threaded for screw engagement with the valve cap 1 5. The rubber washers 16 are fixed to their respective membranes 10 by means of an adhesive in the early stages of construction of the appliance.The assembled valve means 1 1 is shown in Fig. 2 in the closed condition. It will be appreciated that by loosening the valve cap 15, gas introduced through the open end of the hollow stem 19 may reach the compartments 12 by way of the ports 20. The compartments 12 are closed by screwing the valve cap 15 to cause the collar 14 to compress the washer stack.

In the construction of an appliance of complex configuration, and so that the membranes 10 will tend to be evenly spaced upon inflation of the appliance, it will be desirable to provide for a greater quantity of membrane material for 'outer' layers than for 'inner' layers. In Fig. 3, part of a panel 21 of an appliance in accordance with the present invention consists of several layers of membrane material which layers are together folded to form two double folds 22 and 23. The inner side of the panel 21 is lowermost in Fig. 3 and the innermost membrane is fixed to itself at each double fold by means of an adhesive strip 22A or 23A. Although the 'inner' membrane is non-expandable in terms of girth of the appliance.

the remaining membranes upon inflation of the appliance can be paid out from the two double folds thereby to accommodate complex configurations without seriously impairing the need for the membranes to tend to adopt an even spacing in the interest of thermal insulation.

In some applications, for example an emergency survival bag, special provision is made for supporting a person within the bag bearing in mind that an appliance in accordance with the present invention offers no physical support capability since the inflation pressure will be only fractionally above ambient or atmospheric pressure. The gas pressure within each compartment requires to be enough simply to hold the membranes generally evenly spaced. There is no requirement to induce tension in the membranes by means of the inflation.

Claims (13)

1. A system of construction for thermally insulating appliances, in which a plurality of gasimpervious flexible membranes are disposed in a layered arrangement and sealed together to form separate compartments between respective layers, and there is provided valve means operable to give access to said compartments for inflation thereof and to close the compartments so that they are mutually separate.

2. A system of construction according to Claim 1, wherein the membranes are of a material treated so that it has reduced thermal emissivity.

3. A system of construction according to Claim 2, wherein the membranes are of a polyester sheet material having a surface deposit of a reflective material.

4. A system of construction according to any one of Claims 1, 2 and 3, wherein the membranes are of a heat-weldable material.

5. A system of construction according to any one of the preceding claims, wherein the disposition of the membranes in said layered arrangement is such that upon inflation of the compartments the membranes tend to adopt an even spacing of the order of 10 millimetres.

6. A thermally insulating appliance constructed in accordance with the system of construction claimed in any one of the preceding claims.

7. A thermally insulating appliance according to Claim 6, comprising a panel in which the membranes are together folded to form at least one double fold, the intended innermost membrane being fixed to itself at said fold and the remaining membranes being free to pay out differentially from said fold upon inflation of the appliance.

8. A thermally insulating appliance according to Claim 6 or 7, wherein the said valve means co operates with mutually aligned apertures one through each membrane, the valve means comprising a hollow transversely-ported core extending through said apertures and having inner and outer flange or cap elements of which at least one is adjustable on the core to free the membranes so that gas can be introduced therebetween via the valve core and the transverse ports therein and to clamp the membranes thereby to close the valve means and retain gas between the membranes.

9. A system of construction for thermally insulating appliances, substantially as hereinbefore described with reference to the accompanying drawings.

10. A thermally insulating appliance constructed in accordance with the system of construction claimed in Claim 9.

1 A thermally insulating appliance according to Claim 10 having a valve means substantially as hereinbefore described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

12. A thermally insulating appliance according to Claim 10, having a panel folded substantially as hereinbefore described with reference to and as shown in Figure 3 of the accompanying drawings.

13. Any novel feature or novel combination of features disclosed herein.