Abstract:
An insulated sole having down feather insulation held captive therein and method of fabrication is described. The sole is formed with open top end cavities in which there is disposed down feathers r mixtures thereof to capture and retain heat. A membrane seals the open top end of the cavities. The insulated sole is used in the fabrication of articles of footwear for use in cold weather climate to resist to the cold emanating from the ground to shield against heat loss from the wearer&#39;s feet.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an insulated sole for use in the fabrication of an article of footwear, and particularly, but not exclusively, to an article of footwear for use during cold weather conditions. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various articles of footwear structures are known for use during cold weather conditions and most of these consists in the insulation of the upper of the article of footwear. The sole structure usually consists of a solid structure and an insulating insole, such as “Thinsulate” a registered trademark of the 3M Corporation, is disposed thereover inside the article of footwear for use as a barrier between the cold sole and the wearer&#39;s feet. This provides minimal resistance against the transfer of the cold emanating from the ground through the sole and to the feet of the wearer person. It is known that a major part of cold feet is caused by the sole of the article of footwear which is not capable of resisting to the cold emanating from the ground and thereby resulting in major heat loss incurring from the wearer&#39;s feet. The risk of frostbite on any exposed skin can have a lasting effect on the sensory nerves of the foot, especially the toes. Keeping a thermal buffer between one&#39;s foot and the frozen ground is very important as a significant amount of body heat can be lost through one&#39;s feet. It would therefore be desirable to create soles that are more thermally efficient to buffer the cold emanating from the ground and provide the wearer person comfort to its feet while maintaining breathability and comfort during cold weather conditions. 
         [0003]    It is known that the sole of a shoe deforms less during cold weather conditions due to an increase in stiffness resulting in that a smaller area of a wearer&#39;s foot is in contact with the shoe insole during impact of the sole of the shoe with the ground surface. This results in more localized pressure on the foot and putting more pressure or impact force on a smaller area of the foot, much like running on a hard surface. It would therefore be desirable to construct an article of footwear with a sole providing more flexibility, better impact absorbing, lightweight and better insulation properties during cold weather conditions. 
         [0004]    Down insulation from duck and goose feathers is known as an excellent insulator due to its superior heat retaining properties. However, down is difficult to handle during manufacturing of products containing down. My U.S. Pat. No. 6,025,041 addresses this problem and resolves it by the construction of down feather sheets in which the down is held captive in a substantially evenly distributed form. It would therefore also be desirable to use down in the construction of the sole of article of footwear to provide insulation therein. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore a feature of the present invention to provide an insulated sole for an article of footwear which provides the above mentioned desires and overcomes some of the problems associated with soles of articles of footwear adapted to be worn during cold weather conditions. 
         [0006]    Another feature of the present invention is to provide an insulated sole having cavities in an inner surface thereof and wherein down insulation is disposed in such cavities and trapped therein to provide a thermal insulating barrier and comfort to the user&#39;s feet. 
         [0007]    Another feature of the present invention is to provide a method of manufacturing an insulated sole for an article of footwear using down insulation or a mixture thereof. 
         [0008]    According to the above features, from a broad aspect, the present invention provides an insulated sole for an article of footwear. The insulated sole has a ground engaging outer surface and an inner surface. A plurality of cavities are formed in the inner surface. Down insulation or a mixture thereof with a material having insulating properties is disposed in each of the cavities and a membrane is disposed over the cavities to trap the down insulation or a mixture thereof therein to provide a thermal insulating barrier. 
         [0009]    According to another broad aspect of the present invention there is provided a method of fabricating an insulated sole for an article of footwear. The method comprises the steps of molding a sole from a moldable material with the sole defining a ground engaging outer surface and an inner surface having a plurality of open top end cavities. The cavities are filled with down insulation or a mixture thereof. A membrane, shaped to the contour of the sole, is secured over the cavities to trap the down insulation or a mixture thereof in the cavities to form a thermally insulating sole. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
           [0011]      FIG. 1  is a partly fragmented perspective view illustrating the construction of the thermally insulated sole of the present invention; 
           [0012]      FIG. 2  is a fragmented cross-section view illustrating the sole construction with down feathers held captive in cavities formed in the sole and the breathability of the down trapped in the cavities; 
           [0013]      FIG. 3  is a further fragmented perspective view illustrating a modification to the construction of the thermally insulated sole of the present invention; 
           [0014]      FIG. 4  is a fragmented top view illustrating a modification of the vertical supports as being vertical support posts, instead of walls; 
           [0015]      FIG. 5  is a simplified side view illustrating a method of fabricating the thermally insulated sole of the present invention; 
           [0016]      FIG. 6  is a fragmented top view illustrating the various steps in the method of fabricating the thermally insulated sole of the present invention, and 
           [0017]      FIG. 7  is a fragmented side view showing a cold weather article of footwear incorporating in its construction the thermally insulated sole of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    Referring now to the drawings, and more particularly to  FIGS. 1 and 2 , there is shown generally at  10  the construction of the thermally insulated sole of the present invention for use in the fabrication of articles of footwear adapted for cold weather conditions to provide thermal comfort to a use&#39;s feet. As shown, a sole  11  is molded from moldable waterproof material such as rubber or suitable moldable plastic, such as polyurethane of proper density with cavities  12  being formed in an inner surface  13 , herein the top inner surface, of the sole. The bottom surface  14  of the sole is formed as a flat surface or with ground engaging ribs, not shown, depending on the use of the article of footwear to which the sole is to be used. 
         [0019]    As shown in  FIGS. 1 to 3 , the cavities  12  are delineated by surrounding vertical support walls  15 . The support walls  15  as herein shown have flat top surfaces extending in a foot support plane and are disposed transverse to one another and are interconnected at their crossings. The vertical support walls  15  may have openings  15 ′ therein for the passage of air between the cavities  12 . An outer contour edge  17  is formed about the sole  11  and its top surface and the top surface of the vertical support walls  15  forms the inner surface  13  of the sole. Cavities  12  are distributed throughout the sole  11  in the heel portion  11 ′, where the cavities  12  are deeper due to the fact that the heel portion  11 ′ is thicker, and in the forward foot portion  11 ″ where the cavities are more shallow. Down insulation  16 , consisting of duck or goosed down or mixtures thereof or mixtures including feathers, or suitable polymer fibers is contained in each of the cavities  12 .  FIG. 1  illustrates the down disposed in only a few of the cavities to better illustrate the construction of the thermally insulated sole, but it is to be understood that the down insulation is disposed in all of the cavities  12 . 
         [0020]      FIG. 4  shows another modification of the vertical supports wherein instead of walls  15  the supports are constituted by spaced apart support posts  45  having a flat top surface  46  lying in a common foot support plane together with the outer contour edge  17 . The down insulation  16  is disposed in the cavity area surrounding the posts  45 . 
         [0021]    The down insulation  16  is held captive in the cavities  12  by a membrane  20 , herein a sealing insole provided with holes  21  therein for breathability of the down to trap heat generated from the feet of a wearer person. The membrane  20  may also be a solid membrane and have thermally conductive fibers or consist of material having thermal conductivity to distribute heat from the user&#39;s feet. It may also contain a layer of down insulation or a mixture thereof as a layer therein. This sealing insole  21  is formed of a suitable material having a certain rigidity to maintain its shape and provide comfort to the wearer&#39;s feet. The membrane  20  is herein glued to the inner surface  13  of the sole  11  by the application of glue  22  on the top surface of the vertical support walls  15  or support posts  45  and the contour top edge  17  of the sole by the use of a roller applicator or other suitable means. 
         [0022]      FIG. 3  illustrates another example of the construction of the thermally insulated sole  10  of the present invention. As herein illustrated, a perforated membrane  20 ′, or a solid membrane shaped to the underfoot and formed of fusible material, is fused over the inner surface  13  of the soles  11  in a further molding step with the holes  21 ′ being pre-formed in the membrane. 
         [0023]    Referring now to  FIGS. 5 and 6 , there is described the method of fabricating the insulated sole  10  of the present invention using the support walls of  FIGS. 1 to 3 . Firstly, the sole  11  is molded in a molding process of a type well known in the art to form the sole  11  with cavities  12  as illustrated in  FIG. 1 . The cavities are rectangular shaped to facilitate mold construction. To disposed the down insulation into the cavities  12 , a down feather sheet  30 , such as the type described in my previously mentioned U.S. Pat. No. 6,025,041, is positioned over the inner surface  13  of the sole  11  and held in contact with the inner surface by a holding plate  31  shaped to clamp the down feather sheet  30  evenly over the inner surface  13  of the sole. A die cutting plate  32  having a pattern of cutting knives  33  is then brought down on the feather sheet  30  to cut down insert pieces  39  shaped to fit in adjacent cavities  12 . A pusher plate  34 , having a pattern of pusher blocks  35 , is then actuated to push the down insert pieces into their adjacent cavities  12 . The sole  11 , now having its cavities  12  filled with down insulation, is moved to another station where the membrane  20  or  20 ′ is secured over the inner surface  13  of the sole  11  by gluing or fusing as above mentioned, to trap the down in the cavities. Because down has excellent shape restoring characteristics, any compression of the down is automatically restored when the compression force is released. 
         [0024]      FIG. 7  illustrates an article of footwear  40  fabricated with the thermally insulated sole  10  of the present invention. As shown, an upper  41  is secured on the sole  10  and is herein insulated with the down insulated sheet of my previous invention. Accordingly, insulation is provided all about the upper of the article of footwear. An upper insole  42  is also shown disposed over the membrane  20  to provide added comfort and insulation, such as the “Thinsulate” insole of the 3M Company. The article of footwear  40  as illustrated substantially completely surrounds a wearer&#39;s feet with thermally insulating down to provide comfort to the user&#39;s feet during cold weather conditions. 
         [0025]    As can be appreciated, the insulated sole of the present invention provides several advantages to the sole. The sole provides a thermal barrier to act as a buffer to cold emanating from the ground. It can also act as a buffer the heat with its ability to cool. The cavities and supports also provides more flexibility, shock absorbing, and light weight. 
         [0026]    It is within the ambit of the present invention to include any obvious modifications of the preferred embodiment described herein, provided such modifications fall within the scope of the appended claims.