SANDWICH STRUCTURE

Abstract: A sandwich structure, in particular one for sleeping bags. The invention aims to eliminate the drawbacks of sleeping bags of prior art: to remove the cold bridges and allergy detriments and to achieve a warm, light sleeping bag structure usable for spending the night even in arctic conditions. The aims of the invention are achieved by means of a thermally insulating sandwich structure comprising an outer layer (1) advantageously made of non-moisture binding polyamide, an inner layer (7) advantageously made of breathing viscose-polyamide or polyester fibre, and between these an air-containing filling, advantageously made of Quallofil fibre, disposed between a reflecting material (8, 8') and a light, binding layer (2) advantageously consisting of non-woven material. As taught by the invention, the heat-reflecting material (8, 8') is perforated and disposed in stepped layers to reflect inward substantially all the heat radiated from within.

Description: SANDWICH STRUCTURE The present invention concerns a sandwich structure, in particular one for sleeping bags. The aim of the invention is to eliminate the cold bridges encountered in bags of prior art and to enable a person to spend the night in extremely cold circumtances. It is believed as a rule that the warmth of a sleeping bag is directly related to the amount and quality of its stuffing. This is no doubt valid when a distinction is being made between winter bags and summer bags. On the basis of the stuffing no more specific division can be made. The stuffing material most commonly used in winter sleeping bags consists of various polyester waddings and/or down. The warmth of a sleeping bag is based on the air present in the stuffing, not on the thickness of the stuffing. The warmth of a sleeping bag depends on how much the sleeping bag is able to store of that heat which the person within the bag releases. Heat is dissipated from the bag in two ways: by conduction and by radiation. In the simplest sleeping bags, the bag is formed of a material in which between two fabrics by quilting has been disposed a stuffing containing air. Not much air remains enclosed in a structure of this type, and it is not very warm. It is also a fact that cold bridges are established at the quilting points, through which the heat escapes. With a view to increasing the warmth, the structure just mentioned has been improved by adding a separate fabric thereupon. By a design like this the cold bridges have been partly eliminated, and the warmth improved somewhat. In one design, for eliminating the cold bridges there were disposed on upon the other two quilted layers in such a way that the cold- bridges constituted by the points of quilting were staggered. Although in this way the warmth of the bags could be improved, not enough air remains in the structure, and the bag is not sufficiently warm e.g. for use in wintertime conditions. Attempts have also been made to eliminate the thermal radi¬ ation by adding a layer of a reflective material, and this has been found to improve the thermal values, yet a bag of this kind is not warm enough in view of the very coldest wintertime conditions. In oreder to achieve sufficient warmth, down has also been used for stuffing, but this solution is not well consistent with nature conservation, nor can it be used by allergic persons, and it is incon¬ venient to maintain because most often it has to be sent to the manufacturer to be washed, thus causing extra costs. Down has a high moisture absorption capacity, and therefore in humid conditions and in the event of major temperature changes the thermal insulation of a down stuffing is substantially impaired. The invention aims to minimize the conduction of heat making use of the air that has been stored in the sandwich structures. The heat that is dissipated by radiation is minimized by the aid of reflecting layers. The features which are characteristic of the invention are readable in the characteristic features part of claim 1. In the following, the invention and the advantages thereby gainable are described more in detail with reference to the attached drawings, wherein: Pig. 1 presents the cross-section of a sleeping bag material of prior art; OMP EET Pig. 2 presents the structure of the preceding figure, with a top fabric added thereto; Pig. 3 presents a structure known in the art, having two quilted layers; Pig. 4 displays the cross-section of a structure according to Pig. 3 > to which a reflecting surface has been added; Pig. 5 presents the cross-section of a structure according to the invention; Pig. 6 shows the temperature graphs in experiments carried out with the bag of the invention in an arctic chamber; Pig. 7 gives the list of the symbols employed in Pig. 6. In the structure of prior art depicted in Pig. 1, two fabrics 1, 2 have been quilted together with a stuffing 3, e.g. polyester wadding, between them. At the quilting points 4, a cold bridge is formed, through which the heat is con¬ ducted out. In Pig. 2 there has to the preceding structure been added a top fabric, an outer layer 5- In the structure of Pig. 3 there are two quilted layers 6,6' and in these, in order to prevent the escape of heat, the cold bridges 4,4' have been staggered with reference to each other. In the solution of prior art of Pig. 4, a reflecting surface 7 has been added, close to the sleeping person. In the structure of the invention, Pig. 5, the outermost layer consists of an outer layer 5 which is moisture- repelling and gives protection against the wind, and this layer is separate from the rest of the structures of this sleeping bag. Within the outer layer 5 reimain the sandwich structures 6,6', which comprise a stuffing 3,3' containing SUBSTITUTE SHEET air and disposed between them a perforated reflecting layer 8,8' and a light, binding layer 2,2'. Closest to the sleeping person in the bag is a light, binding inner fabric 2'. The reflecting layers 8,8' are disposed on the outer surface of the sandwich structures 6,6', to reflect inward. The outer layer 5 consists of a material which is breathing in spite of its tightness, preferably of polyamide, whereby on outermost thermos-structure is obtained. The reflecting layers 8,8* have been perforated, whereby the structure is breathing. The sandwich structures 6,6' remaining inside have been staggered with reference to each other, whereby the thermal radiation, part of which owing to the perforation passes through the innermost reflecting layer 8', is reflected into the interior of the bag by the outer reflecting layer 8. Since the innermost reflecting layer 8' has been disposed to be at a distance from the sleeping person, lying in the bag cannot become uncomfortable. The reflecting layers 8,8' , together with the light, binding layer 2,2' hold the air-containing stuffing 3.3' in its place. Por heat-binding stuffing, in an advantageous design according to the invention has been used "Quallofil" (Du Pont) fibre with four holes, which has an excellent thermal value and a high degree of filling, that is, the weight per unit volume is substantially lower than for any other fibres in present use. A sleeping bag made of a sandwich structure according to the invention has been tested: 1. by " an examination for determining the thermal lagging capacity according to British standard; 2. with the aid of heatable and dressable "perspiring" CU33TΪTUTE SKEST cylinders heatable to human body temperature; 3. by heat camera studies combined with temperature measurement made with electric pick-ups, in the temperature range from -10 to -20°C; 4. in the arctic chamber, in a measurable environment constructed to approximate arctic conditions as closely as possible. At the Technical Research Centre of Finland, the thermal insulating capacity of different sandwich materials was tested according to the British standard BS 4745:1971 (Thermal resistance of textiles. Single plate method), the thermal resistance R 0 being expressed in Km^/W. The study involved tests with a sleeping bag made of material according to the invention, both in washed and unwashed state. By the invention has been obtained a sandwich material which has better thermal values, according to the measurements made at the Research Centre, than any sandwich structure known in the art. The thermal values of the sandwich structure of the invention were found to be about 170 x 10-2 KE-2/W, while the corresponding value for conventional structures in which known artificial fibre materials have been used as air-binding stuffing, e.g. polyester wadding, is about 90-120 Kπ_2/W. It may be mentioned that the best down sleeping bags subjected to measurement at the Technical Research Centre have a thermal value of 135 Kπ_2/w. Moreover, the thermal values of sleeping bags made using the material of the invention have been found even to improve slightly after having been washed 1 to 3 times. Sleeping bags made of the material of the invention may more over be washed in a washing machine, whereby their mainten- SUBGT-TUTE SHEET ance is facilitated and the operating costs are reduced. The test subjects (three persons), the sleeping bags and the sleeping bases were fitted with pick-ups appropriate for temperature measurement, these pick-ups being placed at points accurately defined in advance; and the subjects slept in the sleeping bags in an arctic chamber. The temperature in the chamber at the start of the test was about -30oc, and the temperature in the closed bag went up close to +30°C in about 10 minutes. During the test the temperature in the arctic chamber was lowered to -62°C. The velocity of the air flow applied was 9-10 m/s. Pig. 6 shows temperature measured in the course of the test, plotted in the form of curves for easier reading. In Pig. 7 are explained the symbols used. The lowermost curve 9 in Pig. 6 represents the changing of the temperature in the arctic chamber, plotted over time. The curves 10,10' and 10'' higher up represent the interior temperatures of the sleeping bags during the test. As can be seen from the graphs in Pig. 6, the temperature in the closed bag stayed substantially throughout the test at about +30°C. The transient downward drops of the curves are due to the subjects being in contact with the exterior of the cold chamber: from time to time they opened their sleeping bag and talked on the telephone with the research workers outside. With the structure of the invention, a sleeping bag is achieved which is appropriate for use as a winter sleeping bag, even in arctic conditions. It was established in heat camera studies at the Technical Research Centre of Finland that by the structure of the invention a sleeping bag is obtained from the surface of which virtually no heat , O PI dissipation takes place. The good thermal insulating capacity of the structure of th invention is a result, aside from the favourable, abundantl air-binding structure of the Quallofil fibre, especially of the "multi-reflexion" effect obtained by the specific way o disposing the perforated heat-reflecting layers. Owing to the disposition of the perforated reflecting layers, substan tially all heat emitted by the person in the bag is re¬ flected back and remains in the bag. Obviously, there may be more than two reflecting layers, but it has been found that excellent results are achieved with two, as the tests at the Research Centre demonstrate. The polyamide fibre, which is advantageously used for the outer surface in the structure of the invention, binds no moisture. In the structure of the invention, only the lining fabric, which advantageously consists of viscose/polyamide fibre (abt. 80/20), transmits outward the skin moisture of the person sleeping in the bag, whereby the use of this bag is more pleasant than that of designs known in prior art. The sandwich structure of the invention may also be applied to purposes other than sleeping bags, e.g. in heat clothing, in which case the structure may be modified in accordance with conditions, within the scope of the claims. SU33TJTUTE SHEET

Claims: CLAIMS 1. A thermally insulating sandwich structure, comprising an outer layer, an inner layer and between them disposed between a reflecting material and a binding layer, an air- containing sandwich structure constituted by a stuffing, characterized in that the heat-reflecting material (8,8') is perforated and disposed in layers separate from each other and from the heat source to reflect back substantially all the radiated heat. 2. A sleeping bag with a sandwich structure according to claim 1 , characterized in that the inner layer under the outer layer (1) comprises two sandwich structures (6,6*) having on their outer surface an inward reflecting material (8,8') and on the inner surface a light, binding layer (2,2'), and that the sandwich structures have been staggered with reference to each other. 3- Sleeping bag according to claim 2, characterized in that the outer layer (1) consists of polyamide and the heat- binding stuffing (3,3') is "Quallofil" (Du Pont) fibre with four holes, and that the light, binding inner layer (2 1 ) is moisture-transmitting, preferably consisting of vicose- polyamide. OMPΓ

Inventors: SOINI MIKKO, SOINI, MIKKO
Applicants: ESPE OY
Application year: 1984
Main classification: A47G
IPC codes: A47G9