FI98042C - The sole structure of a footwear - Google Patents

Abstract

A footwear sole construction has an insulating layer (1) with poor heat conductivity but good permeability to heat radiation, the insulating layer (1) and a reflective layer (4) attached thereto being placed between the inner lining or the like and the wear sole. The reflective surface (4a) of the reflective layer is attached directly to the material of the insulating layer (1), e.g. by attaching a metal foil to the insulating layer (1) by vacuum evaporation.

Description

98042 5

The sole structure of the footwear

The invention relates to a sole structure for footwear as set out in the preamble of appended claim 1.

The soles of the footwear are made of a porous plastic containing air, which has poor thermal conductivity and therefore acts as an insulator. The structure of the insulation is so dense that convection, i.e. in this case the flow of air through the insulation, is prevented. Such material is most commonly foamed polyurethane, EVA (ethyl vinyl acetate) foam or latex foam. Another commonly used solution is to "lighten" the thick bottom structure by forming platforms on the surface of the sole against the foot, between which a material and weight-saving air pocket is left, which is at the same time a heat-insulating structure.

Due to the cellular structure of the plastic used, the share of thermal radiation in the heat transfer increases because thermal radiation can easily pass through the gas pore or air pocket, even though the conduction and convection are small. To prevent heat loss due to thermal radiation, a reflective layer, most typically a thin metal film, for example a shiny aluminum foil, may be glued to the surface of the insulating layer.

The shiny metal surface reflects well the heat radiation coming through the insulating layer and should thus prevent the transfer of heat by radiation.

In current solutions, the reflective layer is attached to the insulating layer by gluing. Although the adhesive layer is thin (0.02-0.03 mm) and transparent, for example to the naked eye, it can affect the thermal insulation properties. Namely, many materials used as adhesives absorb heat radiation well in the wavelength range of 8 to 15 μm, and the amount absorbed can easily exceed up to 80%. Also, the radiation reflected back from the reflecting surface of the reflective layer is absorbed when returning to the adhesive layer, so that even a thin adhesive layer can absorb 35 to more than 95% of the thermal radiation. Thus, the thermal radiation returned to the insulating layer can remain very small. The problem then is that the materials of the reflective layer also conduct heat well, so that when heat is transferred from the adhesive layer to the reflective layer, heat 2 9804? just moves out due to the good thermal conductivity of the reflective layer, for example to the adhesive layer on the other side of the reflective layer.

5 These problems occur both in cases where it is desired to protect the foot in the footwear from a cold environment or a hot environment below the sole. In the former case, heat transfer from the inside of the footwear should be prevented and in the latter case from the outside of the footwear to the inside of the footwear. The metal foil glued to the insulating structure 10 does not function as designed to reflect thermal radiation.

British application GB-A-2137866 discloses in detail. wherein the surface facing the inner base is a polyester coated with a metal foil, and between the outermost metal surface and the inner base there is further perforated a spacer layer more than 1 mm thick, which is a polyethylene. Jalan puoiena oieva poiyestenkenos ^ PET; behaves like an adhesive layer, conducting heat well and the openness of the spacer layer facing the inner sole exposes the metal surface to mechanical damage and heat can be partially transferred by convection through the openings, especially in the case of a loose insole which moves during use. British patent GB-1539631 also mentions a polyester film, which thus has poor adhesive properties. Aluminum coating is referred to in this publication as a moisture barrier.

The object of the invention is to eliminate the above-mentioned drawbacks and to present a base structure with improved thermal insulation properties, which is most commonly a pin bottom used between the inner lining and the tread. To achieve this purpose, the base structure is mainly characterized by what is set forth in the characterizing part of the appended claim 1. The reflecting surface of the reflective layer is attached directly to: the material of the insulating layer without an intervening absorbent adhesive layer. The importance of this structure has not been noted before, but it can be shown that the advantage achieved by it in connection with the insulating layers 35 which transmit heat radiation is clearly noticeable.

The invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 98042 illustrates a conventional structure and its phenomena in cross section, Fig. 2 illustrates a structure according to the invention and its phenomena in cross section, and Fig. 3 shows the location of a structure according to the invention.

10 In Fig. 1, reference numeral 1 generally denotes an insulating layer intended to prevent heat transfer mainly by conduction. The insulation layers preferably used in the structure according to the invention will be returned later. Attached to this layer by means of an adhesive layer 2 is a reflective layer 3, the material of which is such that its surface reflects more than 90%, preferably more than 95%, of the incoming heat radiation in the wavelength range 8-15. Such materials include metals, and the most commonly used material is aluminum. On the other side, the reflective layer 3 can be attached to yet another structure by means of an adhesive layer 2. In addition, the heat transfer phenomena described above are schematically illustrated by arrows, of which arrow 6 indicates incoming heat radiation, arrow 7 reflects reflected heat radiation, arrows 8 absorb absorbed heat radiation, and arrows 9 indicate heat transfer between layers.

Figure 2 shows a structure according to the invention, in which, as in Figure 1, the thickness of the layers is exaggerated for the sake of clarity. The insulating layer 1 is generally a plastic material which is highly permeable to thermal radiation but poorly conductive to heat, which is characterized by the permeability of thermal radiation in the wavelength range 8-30 15 pm 40-90% with the layer thickness used. Preferably, the material is a cellular polyolefin having a cellular structure by orientation. Most preferably, films with a thickness of up to 0.1 mm, and most commonly in the range of 0.025 to 0.06 mm, with a closed cell structure obtained by the cavitation technique are suitable. One suitable film material is polypropylene, and a commercial OPP film known from other contexts, for example, is suitable for this purpose. A reflective layer 4 is directly attached to the surface of the insulating layer 1, whereby the reflective surface 4a important for thermal insulation is in direct contact with the material of the insulating layer 1 4 98042. Such adhesion without adhesive to the insulating layer can be obtained, for example, by vacuum vaporizing the material of the reflective layer 4 on the surface of the insulating layer 1, and this can be achieved by a known metal vacuum vapor deposition technique for metallizing plastic materials. The thermal radiation from the structure (arrow 6) is reflected almost completely (arrow 7) from the reflecting surface 4a because there is no heat absorbing material between the insulating layer 1 and the reflective layer 4, and only the portion (arrow 8) determined by the material properties of the reflective layer 4 is absorbed and dissipated. For example, the emission factor of a vacuum vaporized aluminum film at 20 ° C is 0.04, corresponding to a reflectivity of 96%.

The thickness of the reflection layer 4 is most preferably at most 50 nm, which in the vacuum evaporation technique already means a thick layer, corresponding in the case of aluminum 15 to a basis weight of 0.15 g / m 2.

The above-mentioned layers form the minimum conditions for the functionality of the invention. If it is desired to retain heat in the inner part of the footwear, the insulating layer 1 is on the inner lining side in the pin sole and the reflective layer 4a 20 is towards the inner lining, respectively. If, on the other hand, it is desired to protect the foot from a hot environment, for example when the footwear is intended for walking on hot surfaces, the insulating layer 1 is on the sole of the sole and the reflective surface 4a of the reflective layer towards the sole. At the same time, however, Figure 2 shows a 2-sided structure according to the invention, with which heat transfer can be prevented from both sides. In this case, the structure has a second insulating layer 1 and a reflective layer 4 directly attached thereto, which are mirror-symmetrical with respect to the first layered structure so that the reflective layers 4 are located in the middle of the structure and their heat reflecting reflective surfaces 4a are directed in opposite directions. These layered structures comprising the insulating layer 1 and the reflective layer 4 can be attached to each other by attaching the reflective layers 4 to their free surfaces together, for example by means of an interposed adhesive layer 2, which has no detrimental effect at this point. Also in the case of a 2-sided structure, only a small part of the thermal radiation coming through one insulating layer 1 is transmitted through the reflective layers 4 and the adhesive layer 2 and radiates to the second insulating layer (arrow 10). Figure 2 further shows how the insulating layers 1 of s 98042 are connected to other base structure 5, for example to an ordinary pin base material, at their outer surfaces, and there may also be an adhesive joint at this point.

The above-mentioned double-sided protection can also be obtained by a structure in which a reflective layer 4 is attached to both sides of the same insulating layer 1, with each side of the insulating layer having a directly reflective surface 4a ready to face thermal radiation through the insulating layer 1 without absorbent material. The adhesive joint is also located elsewhere than between the reflective surface and the insulating layer.

Figure 3 shows a cross-section of the footwear in which the sole structure is located. The structure is most preferably a layered structure 15 located close to the inside of the footwear, in the example of Figure 3 a pin sole 11 to which the upper 12 is attached by methods generally known in the footwear industry. The foot, to which the finished upper part is connected by the priming method, is denoted by reference numeral 13 and the infill between the pin base 11 and the foot 13 by reference numeral 14. The entity formed by one or more insulating layers 20 1 and whereby they are supported and protected by its support layers.

The invention is further illustrated by the following two examples, which are not intended to limit its scope.

Example 1,

The effect of the adhesive layer on heat reflectivity was measured with a long-wave 30 camera. The experiment included three samples with the order of the layers from top to bottom: Sample 1: OPP film - vacuum vaporized aluminum layer - adhesive layer - OPP film.

Sample 2: OPP film - adhesive layer - vacuum vaporized aluminum layer - 35 OPP film.

Sample 3: OPP film - adhesive layer - OPP film.

6 98042 OPP film is a biaxially oriented polypropylene film. The samples were above room temperature (23 ° C) of the surface parallel to, and on the other side of the samples was in warm water (36 ° C) filled in the water tank heat-radiation source and on the other side a heat camera to measure the thermal-source by five and a sample surface temperatures. The surface temperature of Sample 1 was found to be 27 ° C and the surface temperature of Samples 2 and 3 was both 25 ° C and the surface temperature below 23 ° C. Based on the measurement, the adhesive layer between the OPP film and the aluminum surface inhibited the heat reflective effect of aluminum with the same reflectivity as the sample without the alu-10 mine layer.

Example 2.

For the experiments, various stencil bases were prepared as samples. The base materials were common commercial pinch base materials. An element according to the invention was laminated to some of the samples. The warmth of the different solutions was measured with a device in which the sample to be measured was pressed against a level of aluminum in a cold weather room (-10 ° C) with a purpose-built heating element. The heating element was heated at constant power and the temperature from the surface of the sample was measured after a settling time of two hours. The higher the insulation, the higher the measured temperature. In the experiment, the stack base with the element according to the invention was 2 degrees warmer than the corresponding structure without the element (8.9 ° C versus 10.8 ° C). A structure without an reflective layer, otherwise element-like and thick, laminated to a corresponding stacked base structure, improved the insulation, but clearly weaker than that provided with the reflective layer.

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Claims (5)

A sole structure in a footwear, the sole structure comprising an insulation layer (1) which is placed between an inner liner or the like and a wear bottom, which conducts heat weakly but permits good heat emission, and a reflection layer attached to the insulation layer ( 4), characterized in that the reflection surface (4a) of the reflection layer (4) is fixed directly to the uniform surface of the insulation layer (1), which layer has in the layer thickness used a transmittance of heat emission of 40-90% within the range of 8- 15 pm. 2. Sole structure according to claim, characterized in that it has two reflecting surfaces (4a) directly attached to the radiation of heat coming from opposite directions through the insulating layer (4a). Sole structure according to claim 1 or 2, characterized in that the reflection surface (4) is a metal film attached to the insulation layer (1) by vacuum extension. 20 A sole structure according to any of claims 1-3, characterized in that it is a tie sole (11). 5. A sole structure according to any one of claims 1-4, characterized in that the insulation layer (1) is an oriented cellular plastic film with closed cells. > 1 «From fllltl IliH '·