WO2000042872A1

WO2000042872A1 - A material with variable insulation properties

Info

Publication number: WO2000042872A1
Application number: PCT/GB2000/000179
Authority: WO
Inventors: Paula Louise Forshaw
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1999-01-25
Filing date: 2000-01-24
Publication date: 2000-07-27
Anticipated expiration: 2001-07-25
Also published as: GB9901422D0; AU3066600A; GB2346581A; GB2346581B

Abstract

A variable insulation material (1), comprising from two layers (2 and 4) formed from films (5) of a gas impermeable thermoplastic material with a thickness (17) bonded together at a bond line (10) joining the inner surfaces (11) to form a sheet (8), consisting of a plurality of gas tight interconnecting cells (12) in an un-inflated state (9) or blister shaped cells (15) in the inflated state (13). To allow the variable insulation material (1), to breath the sheet (8) is pierced by an array (7) of perforations (6), interposed between the cells (12). The variable insulation material (1), has use in various garments or equipment where variable insulation properties are desirable.

Description

A MATERIAL WITH VARIABLE INSULATION PROPERTIES

This invention relates to a material with variable insulation properties. Such materials find use in situations where control over the thermal insulation properties is desirable. A particular example is when people work or play in situations where their production of body heat fluctuates considerably and where adjustment of the dissipation of that heat by removal or replacement of articles of clothing is difficult or impossible. For example in an environment that is cold or wet or both to keep the body warm a person might require many layers of clothing whilst inactive. However, an increase in physical activity will generate heat. The nature of such activity will in many cases be such that removal of articles of clothing cannot be attempted. For example removal of clothing may be impeded by reason of equipment being carried or by the impracticality of carrying clothing once it has been removed. The aim of the current invention is to provide a breathable material that also has variable insulation properties.

Clothing has been designed of a type that enables its thermal insulation to be increased or decreased by varying the separation of the between two layers. This is disclosed for example in US patent 3 771 178. Garments made in this way would trap sweat. This would cause discomfort to the wearer. UK Patent GB 2 242 609 B in the name of the applicant addresses this problem. GB 2 242 609 B discloses a garment comprising a plurality of inflatable tubes. The applicant has found that a number of problems arise with this form of construction. They stem from how to apply this construction in an article of clothing that is easy to make and yet is breathable in the un-inflated and in the inflated state. For example the inflatable tubes may consist of a series of cylindrical rubber balloons sewn into say a body warmer. This form of body warmer provides too much insulation in the un-inflated state. Although it does have the advantage that after inflation the insulation doubles. In an alternative from of construction the tubes of GB 2 242 609 B may be formed by coating a core of low melting material with a latex. On removal of the core by melting a tubular dipped latex construction remains. A problem was found with this method in that the dipped latex construction produced had a relatively large wall thickness. Attempts to limit the thickness produced structures that were too fragile for use. Also thick walled dipped latex constructions would produce a material that would be uncomfortable to wear because they would be is too heavy and would be difficult to inflate or deflate. The applicant has also found that in articles made to GB 2 242 609 B that any sweat generated when the thermal insulation is at a maximum (that is when the air spaces between the tubes are fully closed) remains trapped next to the skin by the rubber until such time as the tubes are deflated. The moisture in the sweat detracts from the objective of the invention particularly where it dampens clothing. These problems led the applicant to investigate the use of breathable fabric materials in variable insulation garments. Patent Application GB 2 323 015 A teaches such a solution. Again problems arise with this form of construction. For example articles made to GB 2 323 015 A consist of two layers of fabric that are water vapour permeable. This construction allows sweat vapour to pass through the layer next to the skin. However, this vapour condenses on reaching the colder outer layer, and remains trapped within the inflatable structure. This is undesirable because it causes a reduction in the thermal insulation of the garment.

According to the present invention a variable insulation material capable of inflation is provided that consists of a plurality of inter- connecting cells forming a sheet, the sheet being pierced by an array of perforations inteφosed between the cells such that the array of perforations maintains an areal density that is substantially constant whether in an un-inflated or an inflated state. In this context the areal density is the ratio of the total area of the perforations in a representative sample of the variable insulation material to the area of the sample. The advantage of this aspect of the invention is that it provides a material with a cellular arrangement that is easily manufactured into a garment that does not trap excessive body heat during periods of physical activity because any sweat generated by a wearer when the thermal insulation is at a maximum that is in an inflated state or at a minimum that is in the un- inflated state is able to escape through the array of perforations.

According to another aspect of the invention preferably the cells are substantially disc shaped, although other shapes may be used. The advantage of this aspect of the invention is that it allows the sheet in the un-inflated state to lay substantially flat. This has advantages of comfort and easy of tailoring when the material is made in to a garment.

According to another aspect of the invention an inflation means is provided such that the cells in an un-inflated state are expandable by inflation with a gas to form in an inflated state plurality of blister shaped cells. The advantage of this aspect of the invention is that in the un- inflated state the material has low thermal insulation properties and in the inflated state the material has high thermal insulation properties. An further advantage of each of the above aspects of the invention is that the area of the array of perforations in the un-inflated or the inflated state remains substantially constant to allow the sweat created by the wearer to escape without preventing moisture build up which can cause discomfort to the wearer.

According to another aspect of the invention the cells inflate to form blister shaped cells with a thickness that varies between almost 0.0 and 16 mm. The advantage of this aspect of the invention is that it allows the thickness of a layer of gas or air in the cells to be varied. This has the effect of varying the thermal insulating properties of the material within limits that are useful for the manufacture of wearable articles of clothing. It also allows the increase and decrease of the air gap between the fabric layers above and below the blister shaped cells.

According to another aspect of the invention the array of perforations has an areal density of between 0.1 to 0.6. The advantage of this aspect of the invention is that a number of different types of material can be made to the invention. The breathablity properties of a material according to the invention can therefore be varied depending on the end use of the material. For example a sleeping bag made from the material will require less breathability than say salopettes made from the material.

According to another aspect of the invention the disc shape cells have a length chosen from the range 8 to 50 mm, and a width chosen from the range 8 to 40 mm. Those skilled in the art will know that natural convection will occur in gas filled spaces of greater then 8 mm in thickness, although as described below the applicant has made a successful sample of the material with a cell length of 50 mm and a width of 40 mm. The advantage of this aspect of the invention is that a number of different types of material can be made to the invention. The insulation properties of a material according to the invention can therefore be varied depending on the end use of the material. For example a parka made from the material will require less stiffness and higher insulation properties than say a snow boarders suit made from the material.

According to another aspect of the invention the perforations have a diameter chosen from the range 2.0 to 20 mm. As described below the applicant has made a sample of the material with the perforations having a diameter of 15 mm. Those skilled in the art will readily understand the need to scale up or down or tailor to suit the geometric parameters of the material. The diameter of the perforations for example may need to be varied to produce a practical design. The advantage of this aspect of the invention is that a number of different types of material can be made to the invention. A material according to the invention can be tailored to match the end use of the material. Thus the insulation properties and breathability properties can both be varied. To achieve this the diameter of the perforations may be varied to achieve the proportion of perforations in the material.

According to another aspect of the invention the sheet consist of a thin non elastic, thermoplastic film. Preferably a thickness of the film is such that a sample of the material is flat in the un-inflated state and the sample returns to the initial flat state on deflation. Also the elasticity of the film may be chosen such that the film does not permanently stretch as a result of inflation. Preferably the film is air tight and sufficiently durable to function in an article of clothing. The applicant has found that a polythene film with a thickness of 26 microns in thickness fulfils these requirements. Although those skilled in the art will realise that a number of other films may also be used. The first advantage of this aspect of the invention is that the material according to the invention inflates easily under blow to inflate conditions. That is by a wearer inflating the material using only lung pressure. A second advantage of this aspect of the invention is that the material inflates without permanent stretching. This in turn has the advantage that the material collapses into the initial flat un- inflated state on release of the inflation pressure.

According to yet another aspect of the invention the sheet comprises two layers of the thermoplastic film having a bond line joining together an inner surface of each layer of thermoplastic film. The advantage of this aspect of the invention is that layers of polythene or other thermoplastic material are easily joined along the bond line by thermal bonding to define the inter-connecting cells.

According to yet another aspect of the invention in an article made from the material the cells may be linked to an inflation tube and an inflation means. The advantage of this aspect of the invention is that it allows a practicable article of clothing or insulating equipment such as a sleeping bag to be made from the material according to the invention.

According to yet another aspect of the invention an article made from the material may consist of the cells grouped in modules and connected to a separate inflation tube connected to a manifold. The advantage of this aspect of the invention is that it allows a large article of clothing or insulating equipment to be made from the material according to the invention. According to yet another aspect of the invention an article made to the invention has an isolation valve is placed in the inflation tube. This has the advantage that a puncture in one part of the article will not cause the whole article to deflate.

According to yet another aspect of the invention an article made from a material according to the invention the inflation means may be a blow to inflate arrangement or an external power source. That is so that small articles may be inflated by lung pressure. On the other hand articles larger than could be inflated by lung pressure may be inflated by an external power source. The external power source may consist of a hand or foot pump, a power driven compressor or a compressed gas supply such as air or carbon dioxide. According to yet another aspect of the invention an article made from the material according to the invention may consist of a vest type garment or a jacket type garment. The advantage of this aspect of the invention is that practical garments can easily be made from a material according to the invention. The material according to the invention can also be made into other items of outer clothing, underclothing, footwear, headgear or bed-wear such as sleeping bags or duvets that are worn or used in intemperate climatic conditions and are associated with dynamic work tasks or leisure pursuits such that variable insulation and breathability properties may be required. By way of example, some embodiments of the invention will now be described, by reference to the following drawings, of which:

Figure 1 is a plan view of a material according to the invention. Also shown in Figure 1 are two cross sectional views on the line S 1 -S 1 (a) of a material according to the inventions in the un-inflated state and S l-Sl(b) the inflated state.

Figure 2 is a front view of a vest type garment made of a material according to the invention. Figure 3 is a front view of a jacket type garment made of a material according to the invention.

Figure 4 shows views of articles made of a material according to the invention. Referring to Figure 1 a variable insulation material 1, according to the invention is formed from two layers 2 and 4 formed from films 5, of a gas impermeable thermoplastic material with a thickness 17, bonded together by a heat bonding process or other adhesive process at a bond line 10 joining the inner surfaces 11 to form a sheet 8, consisting of a plurality of gas tight inter-connecting cells 12 in an un-inflated state 9 or blister shaped cells 15 in the inflated state 13. To allow the variable insulation material 1 , to breath the sheet 8 is pierced by an array 7 of perforations 6, interposed between the cells 12.

Cross section SI -SI (a) shows the cells 12 in the uninflated state 9. Cross section S l-Sl(b) shows the cells 12 in the in-inflated state 13 as blister shape cells 15 containing a gas 3. The array 7, of perforations 6, are shown inteφosed between the cells 12, 15 in the plan view of Figure 1.

A sample of a material according to the invention was made from layers 2 and 4 of films 5 of polythene of thickness 21 of 26 microns, and with cells 12 or 15 with a length 20 of 50 mm and width 22 of 40 mm and perforations with a diameter 24 of 15 mm such that the areal density of the array 7 of perforations 6 was 0.15. In the uninflated state 9 the measured thermal insulation properties were 0.42 Togs per cms. Note: 10 Togs equals 1 metre squared kelvins per watt. This low level makes the sample suitable for manufacture into a garment for keeping the body of a wearer cool during physical activity. In the inflated state 13 the measured insulation increased by approximately 3.5 times to 1.52 Togs per cms. The sample was also rated a breathable material. This rating results from testing to BS EN 31092# Skin Model Water Vapour Test. Also referring to Figure 1 , the blisters shaped cells 15 are expandable to a variable thickness 17 by introducing a gas 3 by inflation of through an inflation tube 14 connected to an inflation means 28, or more conveniently through a blow to inflate arrangement 30. The inflation tube 14 is connected through an isolation valve 16 to a manifold 18. This arrangement allows modules 29 of a material according to the invention to be made into articles of clothing 42 or 44 shown in Figure 2.

Referring to Figure 2 this shows a vest type article 42 made in material according to the invention. This has two modules 29 joined at the shoulder by press studs 46 and at the side by adjustable tabs 48.

Referring to Figure 3 this shows a jacket type article 44 made in material according to the invention. This has three modules 29 joined at the shoulder and at the side by press studs 46 and at the front by adjustable straps 50. Referring to Figure 4 this shows a ski-ing boot liner 52, a ski-ing hat 54, a sleeping bag 56 and a duvet 58 made from a varaible insulation material accorting to the invention or having variable insulation panels 60 consisting of variable insulation material according to the invention.

Claims

1. A variable insulation material capable of inflation consisting of a plurality of inter-connecting cells forming a sheet, the sheet being pierced by an array of perforations inteφosed between the cells such that the array of perforations maintains an areal density that is substantially constant whether in an un-inflated or an inflated state.

2. A variable insulation material as claimed in claim 1 wherein the cells are substantially disc shaped.

3. A variable insulation material as claimed in claim 2 wherein the substantially disc shaped cells have a length chosen from the range 10 to 50 mm, and a width chosen from the range 10 to 40 mm.

4. A variable insulation material as claimed in claim 1 or claim 2 or claim 3 having an inflation means wherein the cells in an un inflated state are expandable by inflation with a gas to form in an inflated state plurality of blister shaped cells.

5. A variable insulation material as claimed in any one of the preceding claims wherein the cells in the inflated state form blister shaped cells with a thickness that varies between almost 0.0 and 16 mm.

6. A variable insulation material as claimed in any one of the preceding claims wherein the array of perforations has an areal density of between 0.10 to 0.6.

7. A variable insulation material as claimed in any of the preceding claims wherein the perforations have a diameter chosen from the range 2.0 to 20 mm.

8. A variable insulation material as claimed in any of the preceding claims wherein the sheet consists of a thermoplastic film with a thickness that is suitable for inflating and deflating and that is non- elastic, flat, durable and air tight.

9. A variable insulation material as claimed in any of the preceding claims wherein the sheet comprises two layers of film having a bond line joining together an inner surface of each layer of film.

10. An article made from the material as claimed in any of the preceding claims wherein the cells are linked to an inflation tube and an inflation means.

11. An article as claimed in claim 10 wherein the cells are grouped into a number of modules each connected to a separate inflation tube and connected to a manifold connected to an inflation means.

12. An article as claimed in claim 1 1 wherein an isolation valve is placed in the inflation tube.

13. An article as claimed in claim 10 or 1 1 wherein the inflation means is a blow to inflate arrangement.

14. An article as claimed in claim 10 or 1 1 wherein the inflation means includes an external power source.

15. An article as claimed in any one of claims 10 to claim 14 wherein the article consists of an item of a vest type garment or a jacket type garment.

16. An article as claimed in any one of claims 10 to claim 14 wherein the article consists of an item of outer clothing, underclothing, footwear, headgear or bed-wear such as a sleeping bag or a duvet.

17. A material or an article made from the material as claimed in any one of claims 1 to claim 16 comprising the combination and arrangement of parts substantially as described herein with reference to Figures 1 to 4.