Patent Publication Number: US-2007102243-A1

Title: Modular heated platform

Description:
FIELD OF THE INVENTION  
      The present invention relates to a heating device and use thereof. More particularly, the present invention relates to a platform provided with a heated surface that minimizes ice formation on the platform. A walkway can be assembled from a plurality of interlocking modular platforms.  
     BACKGROUND OF THE INVENTION  
      Typically, external flooring surfaces such as sidewalks and stair treads exposed to cold weather accumulate ice in on the exposed surface upon which people walk. This makes walking dangerous, and often requires the ice to be removed at the expense of the property owner. The cost of ice removal is particularly high for the owners of public facilities having significant amounts of external flooring such as sidewalks, courtyards, external vending spaces, parking lots, and the like.  
      Of particular relevance to the present invention, sidewalks are commonly encountered by pedestrians walking in icy conditions. Conventional heated sidewalks typically include tubular passages embedded within the concrete poured to initially create the sidewalk. Steam is transported through the tubular passages to generate the thermal energy required to heat the exposed walking surface of the sidewalk. The thermal energy from the steam is conducted from within the concrete to the exposed walking surface, thereby raising the temperature of the walking surface above the freezing point of water.  
      The conventional steam-heated sidewalks, however, require a constant supply of steam to minimize the formation of ice on the walking surface of the sidewalk. This is particularly true during prolonged periods of cold weather. But since sidewalks are somewhat permanent structures, repairing and/or replacing the steam-heating system when a disruption of steam delivery occurs is time consuming, labor intensive and expensive.  
      Accordingly, there is a need in the art for heated flooring that can minimize the accumulation of ice on an external walking surface and that overcomes the limitations of the prior art.  
     SUMMARY OF THE INVENTION  
      According to one aspect, the present invention provides a platform to be arranged adjacent to another platform to collectively form a heated walkway that minimizes the formation of ice on a surface of the walkway that is exposed to a sub-freezing environment. The platform includes a tread with an outermost surface to be exposed to the sub-freezing environment for providing traction for pedestrians walking on the platform, and a heating element for generating thermal energy to be transmitted to the tread for minimizing the formation of ice on the outermost surface. A fastener can be used to couple the platform to a compatible feature of an adjacent platform to collectively form a walkway, and an electrical conductor for delivers electric energy to the heating element and from an external energy source to an adjacent platform.  
      According to another aspect, the present invention provides a heated walkway for minimizing the formation of ice on a surface of the walkway to be exposed to a sub-freezing environment and upon which pedestrians can walk. The walkway includes a first platform and second a second platform. The first platform comprises a first heating element for generating thermal energy to be transmitted to the surface of the walkway for minimizing the formation of ice on the surface, and a fastener for coupling the first platform to the second platform to maintain the position of the first platform relative to the second platform. The first platform also includes an electrical conductor for delivering electric energy to the first heating element and conducting electric energy between an external energy source and the second platform. The second platform includes a second heating element for generating thermal energy to be transmitted to the surface of the walkway for minimizing the formation of ice on the surface, and a second fastener that is compatible with the first fastener. Similar to the first platform, the second platform also includes an electrical conductor for delivering electric energy to the second heating element and conducting electric energy between the first platform and a third platform. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which:  
       FIG. 1  is a top view of a platform in accordance with an embodiment of the present invention;  
       FIG. 2  is a bottom view of a platform in accordance with an embodiment of the present invention;  
       FIG. 3  is a top view of a walkway comprising a plurality of platforms in accordance with an embodiment of the present invention;  
       FIG. 4  is a cross-sectional view of the platform shown in  FIG. 1  taken along line  4 - 4 ; and  
       FIG. 5  is a schematic illustration of a resistive heating element in accordance with an embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS  
      Certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention, which is set forth in the appended claims. Any relative language used herein, such as an “outermost surface,” is to be interpreted in view of the those relationships as shown in the drawings. Further, in the drawings, certain features may be shown in somewhat schematic form.  
       FIG. 1  is a top view of a heated platform  10  in accordance with an embodiment of the present invention. The platform  10  can be arranged adjacent to one or more other platforms  10  to collectively form a heated walkway that minimizes the formation of ice on a surface of the walkway that is exposed to a sub-freezing environment, as described in detail below. The term “walkway” is used herein to refer to any surface upon which pedestrians can walk, such as sidewalks, stairs, ramps, parking lots, driveways, and the like.  
      In general, the platform  10  includes a generally rectangular or square base  11  made from a rigid plastic that has favorable thermal properties. The favorable thermal properties include resistance to brittleness and breakage over a wide range of temperatures, as well as suitable insulation to minimize the loss of thermal energy generated by a heating element  22  ( FIG. 4 ) to the ground supporting the platform  10 . Although the illustrative embodiments are described and illustrated in the drawings as square, 4 ft×4 ft platforms, the present invention encompasses all shapes in addition to square, including triangular, pentagonal, hexagonal, trapezoidal, and the like. All of these shapes can be interlocked into a lattice of platforms  10  to establish a generally-uniform walkway without significant spaces between platforms  10 .  
      As shown in  FIG. 1 , the platform includes a tread  14  with an outermost surface  18  ( FIG. 4 ) that will be exposed to a sub-freezing environment during certain times of the year depending on the geographic location. The tread  14  can optionally be removable and replaceable, and can optionally be provided with a texture or other traction-enhancing feature on its outermost surface to provide pedestrians with traction while they are walking on the platform. Examples of suitable traction-enhancing features include grit, contours, and the like. This, in addition to the heat generated by the heating element  22  ( FIGS. 4 and 5 ) serve to minimize the likelihood that pedestrians will lose traction and slip while walking on the platform  10 .  
      Fasteners  26   a,    26   b  extend outwardly from the sides of the platform  10  for coupling the platform  10  to a compatible fastener  26   a,    26   b  of an adjacent platform  10 . Assembling the platforms  10  in this manner allows for the formation of a floor, sidewalk, ramp, stair, or other type of surface as desired. For the embodiment shown in the drawings, particularly  FIGS. 1 and 4 , it can be seen that the fastener  26   a  includes an inclined surface with a protruding rail  29   a  and a similarly-sized impression  32   a.  Likewise, the compatible fastener  26   b  also includes an inclined surface  27   b  with a protruding rail  29   b  and a similarly-sized impression  32   a.  The primary difference between the fasteners  26   a,    26   b  is that the inclined surface  26   a  is complementary to the inclined surface  26   b.  Thus, when two or more platforms  10  are positioned adjacent to each other to form a walkway  36  or other floor-type surface as shown in  FIG. 3 , the inclined surface  27   a  opposes the inclined surface  27   b.  Further, when the walkway is formed, the protruding rail  27   a  is disposed within the compatible impression  32   b  and the protruding rail  27   b  is disposed within the compatible impression  32   a.  Such features promote proper alignment of the plurality of platforms  10  to allow for proper alignment of the conductors of electric energy, shown in  FIG. 2 . Locking pins (not shown) can be inserted through keyhole apertures  39  formed in the fasteners  26   a,    26   b  in each platform  10 , said keyhole apertures  39  being aligned when the platforms  10  are assembled. The locking pins fix the relative position of one platform  10  another platform  10  when aligned to form the walkway  36 .  
      A heating element  22 , such as that shown in  FIG. 5  for example, is provided to the platform  10  to generate thermal energy for minimizing the formation of ice on the platform in a sub-freezing environment. The thermal energy generated by the heating element  22  is transmitted by conduction, convection, radiation, any other mechanism or combination thereof to the outermost surface  18  of the tread. Due to the supply of thermal energy by the heating element, the outermost surface  18  of the tread is maintained at a temperature above the freezing temperature of water, which is approximately 0° C., or 32° F. at sea level.  
      The heating element  22  shown in  FIG. 5  is an electronic resistive heating element, but the present invention encompasses any heat-generating device that can convert electric energy into thermal energy. The resistive heating element  22  includes an array of metallic conductors  42  supported by a flexible, dielectric substrate  45 . Electric energy is supplied to and from the array of conductors  42  by leads  48  that conduct electric energy transported by the power-supply lines  52  ( FIG. 2 ) of the platform  10 . Due to the resistance of the conductors  42 , at least a portion of the electric energy delivered to the conductors  42  is converted into the thermal energy that is eventually transmitted to the outermost surface  18  of the tread  14 .  
      A flexible heating element  22  such as that shown in  FIG. 5  allows for location of the heating element at a variety of locations throughout the platform  10 . The embodiment shown in  FIG. 4  discloses one suitable location for the heating element  22  relative to the other features of the platform  10 . In  FIG. 4 , the heating element  22  is disposed between the tread  14  and the base  11  of the platform  10 . This offers at least two advantages to other locations within or on the platform  10 . First, the tread  14  provides a degree of protection to the heating element  22  from the sub-freezing environment as well as the forces imparted on the platform  10  by pedestrians as they walk on the platform  10 . And second, the base  11  provides thermal insulation between the heating element  22  and the ground supporting the platform  10 . Although suitable thermal insulation can be provided by the base  11  with the heating-element in a variety of locations, one embodiment of the present invention provides for a ratio of:  
                     Overall   ⁢           ⁢   Heat   ⁢           ⁢   Transfer   ⁢           ⁢   Coefficient     ⁢                         of   ⁢           ⁢   the   ⁢           ⁢   Thermall   ⁢           ⁢   PathFrom   ⁢           ⁢   the   ⁢           ⁢   Heating     ⁢                       Elementto   ⁢           ⁢   the   ⁢           ⁢   Outermost   ⁢           ⁢   Surface                     Overall   ⁢           ⁢   Heat   ⁢           ⁢   Transfer   ⁢           ⁢   Coefficient   ⁢           ⁢   of   ⁢           ⁢   the     ⁢                         Thermal   ⁢             ⁢             ⁢   Path   ⁢           ⁢   from   ⁢           ⁢   the   ⁢           ⁢   Heating   ⁢           ⁢   Element   ⁢           ⁢   to     ⁢                       the   ⁢           ⁢   Surface   ⁢           ⁢   Supporting   ⁢           ⁢   the   ⁢           ⁢   Platform             ×   100   ⁢   %     ≤     20   ⁢   %         
 
      Other embodiments include a heating element  22  supported on the outermost surface  18  of the tread  14 , integrating the heating element  22  within the tread  14 , and integrating the heating element  22  directly into the material used to create the base  11  of the platform  10 . For embodiments expose the heating element  22  to the ambient environment, the term “outermost surface” refers to the outermost surface of the heating element, and not the outermost surface of the tread  14 . In any event, the outermost surface  18  is used herein to refer to the surface of the platform  10  that will be exposed to the sub-freezing environment and upon which ice formation can occur.  
      Electric contacts  56  also extend through the fasteners  26   a,    26   b  to facilitate the conduction of electric energy from one platform  10  to another when the to platforms  10  are coupled together to form the walkway  36 . Each contact  56  is made from a conductor of electricity, such as a metal, and conducts electric energy from an external power source and/or another platform  10  to the power-supply lines  52 , shown in  FIG. 2 . Each contact can optionally include a quick-disconnect plug allowing for rapid connection or disconnection of the contacts to an external source of electric energy or another platform  10 .  
      The location of the contacts  56  are uniform such that when the fasteners  26   a,    26   b  overlap when the platforms  10  for a walkway  36 , the contact  56  in a fastener  26   a  of a first platform  10  is in contact with a contact  56  in a fastener  26   b  of a second platform  10 . Thus, when the platforms  10  are assembled to form a walkway  36 , the electric energy supplied by a common external energy source can be conducted to all platforms  10  in the walkway  36  without the need for a dedicated wiring system aside from that provided to each platform  10 . Accordingly, the power-supply lines  52  are electrical conductors that deliver electric energy to the heating element  22  and conduct electric energy from an external energy source to an adjacent platform  10 .  
      To somewhat automate control of the heating-element provided to a platform  10 , a temperature sensor and thermostat (not shown) can optionally be provided to the platform  10 . The temperature sensor can be disposed anywhere within or on the platform  10 , and even remotely from the platform  10  from where it can sense a temperature indicative of whether ice is likely to form on the outermost surface  18  of the tread  14 , where the ambient temperature can be below the freezing temperature of water. For instance, the temperature sensor can be concealed beneath the outermost surface  18  of the tread  14 , between the tread  14  and the heating element  22 , or anywhere else on the platform  10 . Regardless of where the temperature sensor is installed, the temperature measure by the temperature sensor is to be correlated to the temperature of the outermost surface  18 . Other embodiments include the use of an infrared temperature sensor.  
      Operation of a thermostat can automatically respond to changes in the temperature of the outermost surface  18  (either calculated base on an indirect temperature measurement by the temperature sensor or measured directly by the temperature sensor) to activate, deactivate, and prolong or shorten the duration of operation of the heating element  22  as appropriate. If, for example, significant ice accumulation is suspected due to a prolonged period of sub-freezing ambient temperatures, the thermostat can activate and ensure a sufficient duration of activation of the heating element  22  to heat the outermost surface  18 .  
      A temperature sensor can be provided to each platform  10  making up a walkway  36 , a group of platforms forming a region of a walkway  36 , an entire walkway, or any other arrangement. Likewise, a thermostat can be assigned the task of controlling operation of the heating element  22  of each single platform  10  in a walkway  36 , a plurality of platforms  10  in a walkway  36 , or the entire walkway  36 . Thus, each platform  10  in a walkway  36  can be individually controlled, controlled as part of a region of platforms  10 , or controlled as the entire walkway  36 .  
      From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.