Patent Publication Number: US-9888739-B2

Title: Thermal footwear

Description:
BACKGROUND 
     There are many people who suffer from having cold feet in winter, and others who suffer from having feet which are too warm and/or sweat during the summer. Many of these people attempt to treat such discomfort with a multiplicity of shoes designed for the different environments: warmer shoes for colder days and cooler shoes for warmer days. This has the potential to lead to excessive waste; for example, younger children often need shoes for one particular season and then grow out of them before they have a chance to wear them next season, leading to those shoes being discarded. 
     Additionally, there are health benefits to properly protecting feet, which may include properly regulating their temperature. Warming feet during the winter, for example, may help blood circulation and prevent or help recovery from colds or the flu. Overly warm feet in the summer can create a favorable environment for fungi or other microbes to grow in a warm and humid shoe. Footwear with insufficient cushioning can lead not only to pain in the feet, but also lower back pain, spinal stenosis, and some spinal cord problems. Various orthotics, including specially-designed footwear and inserts, exist to combat several of these conditions, but none satisfactorily deal with all of them. 
     SUMMARY 
     An article and system for regulating temperature in footwear may be described. Thermal footwear may include a power generation layer, a thermocell layer, and an accessory layer. The power generation layer may be constructed of an actuator material; for example, a dielectric elastomer, which may generate an electric current when compressed or decompressed, may be used. The thermocell layer may be configured to either warm or cool a user&#39;s foot, and may be reversible by being removably coupled to the power generation layer. The accessory layer may include other components; for example, an integrated circuit chip for power transmission to an external device may be included. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Advantages of embodiments of the present invention will be apparent from the following detailed description of the exemplary embodiments. The following detailed description should be considered in conjunction with the accompanying figures in which: 
       Exemplary  FIG. 1  shows a thermal footwear shoe with power generation and thermocell layering. 
       Exemplary  FIG. 2  shows a cross-section of a thermal footwear shoe with power generation and thermocell layering. 
       Exemplary  FIG. 2 a    shows a 3-D detail of the P-N junctions which may be used in thermal footwear. 
       Exemplary  FIG. 2 b    shows a schematic diagram of a thermocell. 
       Exemplary  FIG. 2 c    shows a cross-section of a dielectric elastomer multi-layering. 
       Exemplary  FIG. 3  shows a 3-D rendering of power generation and thermocell layering for thermal footwear. 
       Exemplary  FIG. 4  shows an integrated chip for power transmission external of the thermal footwear. 
       Exemplary  FIG. 4 a    shows an alternative embodiment of an integrated chip for power transmission. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the invention are disclosed in the following description and related drawings directed to specific embodiments of the invention. Alternate embodiments may be devised without departing from the spirit or the scope of the invention. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. Further, to facilitate an understanding of the description, discussion of several terms used herein follows. 
     As used herein, the word “exemplary” means “serving as an example, instance or illustration.” The embodiments described herein are not limiting, but rather are exemplary only. It should be understood that the described embodiment are not necessarily to be construed as preferred or advantageous over other embodiments. Moreover, the terms “embodiments of the invention”, “embodiments” or “invention” do not require that all embodiments of the invention include the discussed feature, advantage or mode of operation. 
     Dielectric elastomers (DEs) are special polymeric materials that, when deformed by an external mechanical force, produce, when paired with the appropriate electronics, an electric current. As the shape of the elastomer changes, the effective capacitance of the device under the external force deformation also changes, and, hence, electrical power can be obtained. This may allow users to generate a quantity of electrical power through the use of mechanical work, which may include a user simply walking from one point to another, raising and lowering their feet as they go. A floor, or, conversely, the sole of a shoe layered with dielectric elastomeric materials may deform if the user places the weight of their foot on a patch of the floor or the sole of the shoe, and may resume its original shape once the user has lifted their foot off of the ground; this deformation-restoration action may generate electrical power that may be harnessed by a device connected to the floor or the shoe. 
     The concept of dielectric elastomers was historically first discovered around 1775 by the French physicist Nicolas-Philippe Ledru. Among other achievements, Ledru discovered that a substance or a material can be deformed or altered in volume, length or width by an electric current. In particular, Ledru noticed that mercury, in a temperature column, would rise if current was applied. Then, in 1776, Italian Alessandro Volta explained the volume changes in a Leyden jar when an electric current passed through it, and was the first to give the right interpretation of this phenomenon. Later, in 1880, German physicist Wilhelm Conrad Röntgen described how a rubber substance would increase in length if current was applied to it. This was the birth of the so-called actuators and electroactive polymers of today&#39;s understanding. More recently, researchers such as Ron Pelrine and R. D. Kornbluh have contributed to the field, allowing for the efficient generation of power with high-density DE material through compression and decompression. 
     The power generation of the DE is governed by the equation: P eq =∈ 0 ∈ r  V 2 /Z 2 . Solving for V 2 , V 2 =Z 2 P eq /∈ 0 ∈ r , where P eq  is the equivalent electromechanical pressure, V is the voltage and ∈ 0  is the vacuum permittivity, ∈ r  is the dielectric constant of the material, and Z is the thickness of the elastomer material. (The equivalent electromechanical pressure P eq  is twice the electrostatic pressure P el ). 
     Electricity may be used to power a thermocell. In 1805 Jean Charles Athanase Peltier discovered the so-called “Peltier effect” with regards to using different metals and materials in conducting an electrical current. Peltier found that when using different materials—e.g. copper and iron-constantan—in one and the same direct current circuit, at one welding junction between the two materials a drop in temperature was recorded and at another a rise in temperature was recorded. The location of the lowered/raised temperature depended on the direction of the current. This effect was then used in building first-generation refrigerators. 
     According to at least one exemplary embodiment, an article and system for regulating temperature in footwear may be described. Thermal footwear may include a power generation layer, a thermocell layer, and an accessory layer. The power generation layer may be constructed of an actuator material—for example, a dielectric elastomer—which may generate an electric current when compressed or decompressed. The thermocell layer may be configured to either warm or cool a user&#39;s foot, and may be reversible by being removably coupled to power generation layer. The accessory layer may include other components; for example, an integrated circuit chip for power transmission to an external device may be included. 
     Referring to exemplary  FIG. 1 , an article of thermal footwear  100  may include a thermocell layer  200 , a power generation layer  300 , and an accessory layer  400 . Footwear  100  may be any type of suitable footwear. Only a standard lace-up sneaker is shown in exemplary  FIG. 1  for simplicity, but footwear  100  may also be a more formal shoe, a child&#39;s shoe, a sandal, flip-flops, a boot, or any other footwear, as desired. 
     Exemplary  FIG. 2  shows a cross-section of the sole of a piece of footwear  100 , showing the thermocell layer  200 , power generation layer  300 , and accessory layer  400 . Thermocell layer  200  may include two different conductors  202  and  203 . Conductors  202 ,  203  may be constructed of any suitable material, for example two different compositions of carbon nanotubes. Conductors  202 ,  203  may be separated by insulator  204 . One or more junction boxes  209  may provide for an electric current to pass through thermocell layer  200 . A junction box  209  may have sockets into which electrodes  201  may be inserted. Electrodes  201  may be affixed to baseplate  208 , and baseplate  208  may be affixed to and be electrically coupled to power generation layer  300 . Electrodes  201  may be inserted into sockets in junction box  209  to create a connection. Electrodes  201  may be shaped and sized such that electrodes  201  only fit approximately half-way through the sockets, but remain in sufficient contact with junction box  209  to create a secure N-P junction. 
     Now referring to exemplary  FIG. 2 a   , further detail for the arrangement of junction boxes  209 , electrodes  201 , and baseplate  208  may be shown. Each junction box  209  may include at least two sockets  209   n ,  209   p  into which two electrodes  201  may fit. Electrodes  201 , junction box  209 , and sockets  209   n ,  209   p  may be configured to create an N-P junction when current is passed through the elements. 
     Now referring to exemplary  FIG. 2 b   , a schematic diagram of thermocell layer  200  may be shown. Thermocell layer  200  may be powered by a power source  207 . Power source  207  may be power generation layer  300 , a battery, a combination of the two, or as desired. As described previously, passing a current through two different conductors  202  and  203  may create temperature changes at the junctions between the materials per the Peltier effect. Such temperature changes can include, but are not limited to, an increase in the local temperature at a junction between a first conductor  202  and a second conductor  203  and a decrease in temperature at an alternate junction between conductors  202 ,  203 . 
     Using the Peltier effect in thermocell layer  200  may provide footwear  100  with both cooling and heating characteristics. The amount of cooling and heating provided by the thermocell layer may be controlled to desirable levels; for example, the amount of cooling and heating provided may depend on the construction of footwear  100 , the choice of materials, or the amount of electrical power provided to the thermocell layer  200 . For example, carbon nanotube thermocells, which may have efficiencies between 8-14%, may be suitable for general use under common winter conditions in North America and northern Europe. These thermocells may generate an amount of heat sufficient to warm feet under these common winter conditions in these locales, but generate insufficient heat to pose a risk of overheating or of burning the sole of the footwear  100  during normal use conditions. Other thermocell designs may be specifically tailored for use under other conditions, and produce levels of heating or cooling appropriate for those conditions. For example, a thermocell design may be specifically tailored for use by deep-sea fishermen, and may be constructed to have a higher efficiency than that disclosed above; another design may be specifically tailored for use by Antarctic researchers and have a higher efficiency still. 
     Now referring to exemplary  FIG. 2 c   , the power generation layer  300  may include a multilayering of DE materials. Each layer may have an N-P junction  302 ,  304  with DE material  301  sandwiched in between. An insulator  303  may insulate the layers from each other and an elastic cushioning material  305  may provide structural support and elasticity, and may protect the power generation layer  300  through the various stresses which may be encountered in normal usage of footwear  100 . A power generation layer  300  with six layers is shown, but any number of layers may be used, as desired. 
     As a person walks, pressure may be exerted on power generation layer  300 . The applied pressure on the DE material may then generate an electric current as explained above. According to at least one embodiment, multilayering the DE material may be preferred due to increasing the density of power-generating material. Electricity generated by power generation layer  300  may then be conducted to thermocell layer  200 , to accessory layer  400 , or as desired. 
     Now referring to exemplary  FIG. 3 , electrodes  201  of power generation layer  300  may fit into sockets  209   n ,  209   p  of junction boxes  209  in thermocell layer  200 . One or more junction boxes  209  may be used to efficiently transfer electric power from power generation layer  300  to thermocell layer  200 . According to at least one exemplary embodiment, and as shown in exemplary  FIG. 3 , more junction boxes  209  may be disposed toward the front of footwear  100  than toward the rear. More power may be required in the front of footwear  100  in closed shoes—for example, sneakers and boots—as the extremities may lose heat more quickly in colder or wetter environments. 
     The thermocell layer  200  may have a coating on it to protect the DE material and any inner components during use, and may also be removable from power generation layer  300 . For example, the thermocell layer  200  may be coupled to the power generation layer via a tacky adhesive or a snap-attach system, or as desired. This may allow a user to detach and reattach the thermocell layer  200  such that in one attachment configuration thermocell  200  may conduct the supplied current in such a way as to create heat on the top surface. In another attachment configuration—for example, if the thermocell  200  is turned upside-down—the thermocell  200  may conduct the supplied current in such a way as to cool the now-top surface. Additionally, the coating of the thermocell  200  may be colored differently on each side with warmer and cooler colors, or otherwise marked with any desired indicia. For example, the thermocell may be given a coloring of red on one side and blue on the other, which may communicate to the user which side—warming or cooling—is face-up. Alternatively, only one side of the thermocell may be marked, or symbols may be used instead. 
     Thus, footwear  100  may be used in both a winter and summer application by adjusting the thermocell  200 . The thermocell  200  and the power generation layer  300  may additionally be integrated as an insert or add-on technology for use with pre-existing footwear. Either as an insert or as a stand-alone footwear system, the footwear  100  may be capable of both warming and cooling feet but also may provide cushioning comfort to a user in a similar fashion as an orthotic insert. Because the power generation layer  300  may compress and decompress in usage, its relative elasticity may be configured to provide a desired optimal balance of cushioning and temperature regulation via thermocell  200 . 
     Now referring generally to exemplary  FIGS. 4 and 4   a , because DE material has a high potential of power density, according to some embodiments generated power may also be used to recharge small appliances, such as, for example, cell phones and laptops. Exemplary  FIG. 4  shows accessory layer  400  with an integrated circuit chip  401  for wireless power transmission. Chip  401  may be one of any known chips which provide wireless power transmission, which can function, for example, to power or recharge small appliances. Wires  404 ,  405  may connect chip  401  to power generation layer  300 . Exemplary  FIG. 4 a    shows an alternative embodiment with a manual socket  402  for power output. Socket  402  may be, for example, a mini-USB connector. Socket  402  may extend through socket opening  403  and may be configured to connect with one or more electronic components. Accessory layer  400  may additionally include other components as one of ordinary skill in the art would recognize as useful in the use of footwear  100 ; for example, a battery for storing power, a control switch for turning on/off the power generation capabilities, an indicator of power generation such as an LED display, or any other such components that are desired may be used. 
     The foregoing description and accompanying figures illustrate the principles, preferred embodiments and modes of operation of the invention. However, the invention should not be construed as being limited to the particular embodiments discussed above. Additional variations of the embodiments discussed above will be appreciated by those skilled in the art. 
     Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive. Accordingly, it should be appreciated that variations to those embodiments can be made by those skilled in the art without departing from the scope of the invention as defined by the following claims.