Abstract:
The invention relates to an apparatus for warming feet. The invention includes a flexible and compressible insole that can be removable or integral to boots, shoes, or other footwear. The entire apparatus is battery powered allowing it to be portable and lightweight enough to be comfortable. The battery can be mounted in many possible locations including but not limited to on the footwear, in the footwear, or on the user&#39;s lower leg.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority to and incorporates by reference in its entirety U.S. Provisional Application No. 60,696,527 filed Jul. 6, 2005, titled “HEATED SHOE INSOLE”. 
     
    
     TECHNICAL FIELD  
       [0002]     The following relates to an apparatus and method for providing heating in shoe insoles.  
       BACKGROUND  
       [0003]     In cold environmental conditions, the extremities, such as toes, are particularly susceptible to losing body temperature and becoming uncomfortably cold. To provide insulation from cold temperatures, shoe uppers typically are made of leather or cloth, shoe soles are made of leather or rubber materials, and shoe insoles and liners include padding and other materials. The insulating properties of these materials helps to retain heat from blood circulation through the foot. For example, hunting boots or snow boots are designed with thick rubber soles and a significant amount of padding to help retain body heat while shoveling, hiking, or performing other activities during freezing weather conditions.  
         [0004]     In some circumstances, it is beneficial or necessary to supplement the human body&#39;s natural capabilities of temperature regulation by providing a heat source within a shoe or boot. For example, while snow boots or hiking boots may be effective for keeping a person comfortable outside in sub-freezing conditions for several minutes, a person&#39;s body temperature may begin to fall after several hours outdoors and the insulation in the boot may no longer be adequate. Once a person&#39;s feet become cold, there is a risk of numbness, frostbite, or even hypothermia. For persons with poor blood circulation, it may be beneficial to include heating mechanisms within shoes or boots even if the person does not intend to remain in a cold environment for a long period of time.  
         [0005]     Known mechanisms exist for applying heat within a shoe or boot. As one example, chemical hot packs can be inserted into socks or shoes to help retain heat and adequate body temperature within the shoe or boot. These packs create heat through a chemical reaction that can last up to several hours in some applications. The chemical heat pack must be replaced with a new one for each usage. Other known heating mechanisms use electrical wiring within a sock or shoe or boot to apply resistive heat through the wiring. These conventional electrical heating mechanisms are somewhat vulnerable to failure, however, because a puncture or disconnect at a single point within the wiring can completely disable the electrical circuit that generates the heat. Further, such electrical heaters commonly are powered by nickel cadmium batteries, which are toxic.  
       SUMMARY  
       [0006]     A shoe insole apparatus is disclosed that includes a flexible semiconductive heater element adapted for insertion within a shoe to be in proximate contact with at least a portion of a foot when the shoe is worn. The apparatus also includes a battery in electrical communication with the heater element. The heater element provides warm to a portion of a wearer&#39;s food upon receiving current from the battery.  
         [0007]     The shoe insole may also include a sole. The shoe&#39;s space for receiving a foot is above the sole.  
         [0008]     The apparatus may be a warming slipper that includes a footpad with a heater element. The slipper also includes a toe cup that curls over the footpad to cover less than half of the footpad. A battery provides electricity to the heater element for the slipper.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     Additional embodiments will be more apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout, and in which:  
         [0010]      FIG. 1A  is an illustration of a heated insole within a shoe according to an exemplary embodiment of the present invention;  
         [0011]      FIG. 1B  is an illustration of the shoe in  FIG. 1A  in a side-view.  
         [0012]      FIG. 2A  is an illustration of a heated insole within a shoe according to an alternative embodiment of the present invention;  
         [0013]      FIG. 2B  is an illustration of the shoe in  FIG. 2A  in a side-view.  
         [0014]      FIG. 3  is a simplified illustration of a heater assembly that may be utilized within the shoe as illustrated in  FIG. 1 ;  
         [0015]      FIG. 4  is a simplified illustration of a heater-enclosed insole and battery assembly that may be utilized within the shoe as illustrated in  FIG. 1  and may include the heater assembly as illustrated in  FIG. 3 ;  
         [0016]      FIG. 5  is a simplified circuit schematic for an insole circuit according to an exemplary embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]     The invention provides for a battery powered heated shoe insole. The insole may be an integral part of a shoe, slipper, or boot or may be a removable insert. The insole can be sized to fit various styles and sizes of shoes or boots. In some embodiments, the heater portion of the insole includes a cup over the wearer&#39;s toes, providing more heat to the toe area by enclosing it more.  
         [0018]     In accordance with the following, a heater assembly is provided in the insole or footpad of a shoe, boot, or slipper that provides electrical heating. Preferably, the heating is done by using one or more flexible, semiconductive, electrically resistive heating elements powered by a rechargeable battery pack. This heater assembly is preferred because it withstands the stresses that can break and disconnect an electrical wire-based heater and efficiently provides long-lasting heating capability with reduced power requirements. Further, the rechargeable battery enables frequent use and re-use without having to replace the heating assembly.  
         [0019]      FIGS. 1A and 1B  illustrate a heated insole within a shoe according to an exemplary embodiment of the present invention. Insole  10  (shown with crossed-lines) is located within the boot  14 , above the sole  12 , such that it will directly contact the bottom portion of a sock when a foot is placed within the shoe. As can be seen, the insole  10  is substantially flat inside the shoe, extending from substantially along the toe area to substantially along the heel. In some embodiments, the insole  10  may be placed atop an existing insole as an insert that can be removed when the application of heat within the shoe is unnecessary or undesirable. In the exemplary embodiment illustrated in  FIG. 1B , the insole includes wiring  18  that traces beneath the stitching and within a seam along the rear of the boot, toward where the heel and the back of the ankle fit within the rearmost section of the boot. The electrical wiring connects the heater  16  (illustrated as the darkened area at the front of the insole in the toe area of the shoe) in the insole  10  to a power source  19 . As shown in  FIG. 1B , the power source  19  is a battery pack that attaches to the upper rear section of the boot above the ankle. In other embodiments, the battery pack attaches directly to the ankle or leg of the wearer by use of a strap.  
         [0020]     Although the embodiment depicted in  FIGS. 1A and 1B  is of a work boot, the insole  10  may be utilized in a boot for duty (for military or police use) or for leisure (such as a ski boot, an ice skating boot, a hiking boot, or cowboy boot), a shoe, or a slipper. Of course, the shoe upper may be leather, canvas, or any other material and the sole may be rubber, leather, or any other material, but for safety purposes, the shoe preferably should be constructed of materials, or those materials should be treated such that they are not flammable. If the power source  19  is to be affixed to the boot  30 , it may instead be affixed within the boot. The power source may be removable for re-charging, or there may be terminals that can be exposed to connect the power source to an AC outlet or another charging source to re-charge the power source.  
         [0021]      FIGS. 2A and 2B  depict an alternative embodiment for the heated insole. As can be seen, the insole  20  includes the substantially flat portion shown in  FIGS. 1A and 1B , but additionally includes a front covering section  22  that substantially encloses the toes of the foot when inserted into a shoe. Although the front covering section is identified separately from the flat portion of the insole, the two may be of the same material and may be part of the same continuous fabric or sheet. As in  FIGS. 1A and 1B , the insole is connected via an electrical wire  24  to a power source  26 . In  FIG. 2B , the wiring  24  can be stitched within the seam at the rear of the shoe.  
         [0022]     As a further alternative, the insole  20  and integrated covering  22 , depicted in  FIG. 2A , may be further integrated with a slipper-type shoe to be worn indoors. In this embodiment, the fabric covering of the insole  20  and toe covering  22 , to be described in further detail below, can be sewn or otherwise affixed to a sole for contact with flooring as a user walks in the slipper. The wiring  24  and power source  26  may be attached to the user&#39;s ankle via a strap, or in a further embodiment, the power source may be located within the sole of the slipper itself. An advantage to placing the power source in the sole is to avoid any exposure of the wiring  24 .  
         [0023]     The insole of  FIGS. 1 and 2  includes a heater that is intended to fit beneath (in  FIG. 1 ) or around (in  FIG. 2 ) the toes of the foot when worn in a shoe. In this manner, the insole provides localized heat to the toes, where the foot is the most susceptible to losing desired body temperature. Preferably, the heater portion of the insole includes a broad area semiconductor material on its upper surface. This material may be a semiconductive fabric, such as a graphite fabric or a carbonized fabric, or a felt-type material comprised of graphite, carbon, or one or more other semiconductive materials. The fabric or felt is particularly suitable for use in an insole because it is flexible, stretchable, and compressible. The fabric tends to heat quickly when provided with electrical energy from a power source and heats uniformly. If one point within the felt or fabric is damaged, broken, torn or punctured, the electrical circuit is still made such that heat continues to be created to warm the toes of the foot. This stands in marked contrast with a resistance wire heater, which is more vulnerable to failure in this regard.  
         [0024]     The heater may be configured as a circuitous serpentine configuration of a flexible graphite heating element with two electrical contacts. It is noted that, according to various embodiments, the use of a configuration in which the ends of the heating element are in close proximity to each other may be desired, e.g., to facilitate connection to the positive and negative terminals of the power source being used. According to the invention, the particular dimensions and configuration of the heating element being used may be chosen such that specific desired heater resistance requirements are met.  
         [0025]      FIG. 3  illustrates a heater within an insole in accordance with an exemplary embodiment of the present invention. The heater  30  includes metallic contacts  32   a  and  32   b  and dielectric insulation  34 . Two metallic electrodes are included to establish an electrical circuit. Electrical wires  36   a  and  36   b  connect to a power source. The electrical wiring is insulated so as not to expose a user to stray voltage.  
         [0026]      FIG. 4  illustrates an enclosed insole, heater, and power source assembly in accordance with an exemplary embodiment of the present invention. The insole  40  is enclosed in a flame retardant material, along with the heater fabric or felt and other electrical connections as described with reference to  FIG. 3 . At the rear side portion of the insole  40  is attached an enclosed cord  42  that contains electrical wiring to an enclosed battery pack  44  as a power source. An enclosed strap  46  is optionally provided for wrapping the battery pack around an ankle.  
         [0027]      FIG. 5  is a circuit schematic for a heated insole in accordance with an exemplary embodiment of the present invention. Heater  50  is the felt, fabric, or other resistive material that applies heat under or around the toe area in the insole or in-seam of a shoe, as described above. Battery  54  is a power source in accordance with one embodiment of the invention. The battery  54  may be one or more batteries, which are preferably rechargeable to allow for efficient reuse. The battery or batteries may be charged either through a stand-alone charger or by connecting the battery pack to an AC or DC power supply. The overall system voltage may be less than 5 volts. Although nickel cadmium batteries may be used, these are toxic. A preferred implementation uses nickel metal hydride batteries or non-toxic lithium batteries.  
         [0028]     In series with the heater  50  and the battery  54 , an power switch  52  may optionally be provided for disabling the heating and associated power drain without requiring removal of the battery. The power switch may be provided on or near the battery pack, or may be anywhere on the insole or shoe. As opposed to a chemical heat pack, for which the chemical reaction that creates the heat cannot be easily discontinued and restarted, a battery-operated heated insole can be easily turned on and off depending upon the user&#39;s comfort level or change in temperature. This allows a user to temporarily go indoors while continuing to wear the shoe or boot with the heater, without experiencing overheating. Optionally, sensors can also be included (not shown in  FIG. 5 ) to automatically shut-off the heater if the shoe is removed. For example, a pressure activated push switch may be used.  
         [0029]     An optional controller  56  may be placed in parallel with the heater for providing features such as high and low adjustability or other temperature regulation capabilities. Controller  56  can receive input from temperature sensors or motion sensors. The output of controller  56  feeds to a power setting switch  58  to adjust the current supplied to the heater  50 . A user may manipulate a control setting (e.g., a switch, knob, dial, or the like) that controls a field effect transistor (FET) or another suitable type of circuit device, which in turn controls the amount of time that the heating element is being heated versus the amount of time that it is not. The battery  54 , controller  56 , and heater  50  are connected to a common ground  59 .  
         [0030]     To prevent possible burning, a fuse circuit also may be included. A fuse circuit may be any suitable type of fuse circuit that is capable of providing over current protection. For example, the fuse circuit may be designed to melt and open the circuit under abnormally high electric loads.  
         [0031]     From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.