Abstract:
A heating system has been incorporated into the commercial space fixture of a plastic chair mat to provide a space-saving heating system. The material for the plastic mat is chosen based on its thermal and electrical properties to provide necessary safety and support convenience for occupied rolling office chairs. Materials include vinyl, acrylic, and polyethylene. The heating elements are placed into the body of the plastic material, which is connected to conventional electrical elements, such as power source, GFIs, thermostats, and safety shut offs, outside the plastic mat. Other more complicated electronics, such as an anti-static mechanism, may be included as needed by the environment.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application 60/445,514 filed Feb. 8, 2003, entitled REDUCED VOLUME COMMERCIAL SPACE HEATING SYSTEM AND METHOD FOR MANUFACTURING SAME, which is hereby incorporated by reference in its entirety for all purposes. 

   BACKGROUND 
   The temperature in office and commercial spaces is generally controlled by central systems in discrete locations. Often, workers are unable to get comfortable because they cannot control HVAC system settings. Commercial heating systems are also unpredictable in extreme weather and are often operated minimally during “off-hours.” In order to facilitate comfort and productivity, commercial entities may provide or allow workers to provide their own electric or gas space heaters. However, although the cost of such heaters is small, their safety is uncertain, especially when they include electrical heating coils exposed to the air and the body is made of cheap meltable plastic material. More expensive space heaters include ceramic models that provide more safety but still present space and energy efficiency problems in the office. Furthermore, small heaters must be placed in proximity to a worker to provide heat and may represent a fire hazard. Large heaters that may be placed at a safe distance may be noisy, dry the already parched winter air, and take up valuable commercial space. Space heaters are often equipped with blowers in order to direct the heat produced by the elements. One of the solutions for improving the footprint used by space heaters has been addressed by the COZY FOOT WARMER™ and related products sold by many different retailers. These products include a soft rubber mat that includes a heating element running through it that can be plugged into a standard outlet. As such, these devices are useful for providing heat akin to a space heater without taking up vertical space. A variation of the COZY FOOT WARMER™ allows the device to be mounted vertically. 
   Many workers in commercial spaces currently use chairmats. Such mats provide both safety and convenience for personnel in rolling and/or steno chairs which are generally used to more effectively navigate workspaces. On hard flooring such as cement the mats keep chairs from rolling too quickly and out of control, and also prevent unpleasant noise. On soft flooring these mats allow the worker to move more easily where otherwise the chair wheels get stuck or stalled in carpeting, impeding free motion. The mats also prevent chair wheels from catching on carpets, power cords, files, etc. As such, the mats reduce wear and tear on carpeting or other flooring. These mats are usually made of plastic materials, such as vinyl, acrylic, or other plastics that are flexible and strong. In addition, many of these chairmats have anti-slip mechanisms for the particular environment of their intended use. They may include “spikes” that adhere to carpeting or an alternate type of material if the mat is to placed on another type of surface like concrete, wood, vinyl, etc. 
   Electrical heating elements have been placed in blankets, chairs, mattresses and other items of furniture for some time. Placing such heating elements in an office chair or other piece of furniture made of wood, cloth, or a soft plastic is impractical and unsafe, because the presence of heating coils around foam and fabric increases cost and safety concerns that may not be acceptable for workplace standards. 
   SUMMARY 
   The present invention combines the commercial space fixture of a plastic chair mat with a heating system in order to provide a safe, personalized, and unobtrusive space-saving heating system for workers in an office or commercial setting. The resulting “reverse electric blanket effect” exploits the most basic of thermal properties, that of heat rising, to the advantage of the worker sitting directly above such as heating system. 
   The present invention addresses the above-stated problems and creates an economical solution for commercial entities by providing an appropriate plastic rolling mat or chair mat with heating elements integrated into the body of the mat. The plastic mat is a fixture in most commercial spaces, providing necessary safety, comfort and convenience for rolling office chairs while preserving floor surfaces. 
   The heating elements allow heat to rise directly into the space where the heat is needed, reducing the need for costly HVAC heat and providing much more safety than electric or gas space heaters. The plastic material intended for use in the present invention has thermal properties that make its safety well within workplace standards while still providing heat. Further, the plastic is water-resistant (spills), and generally weather-resistant so it can be used in shop areas that must avoid the presence of heating coils found in conventional space heaters. 
   In one embodiment of the system, the heating elements are arranged so that heat is generated on the periphery of the mat, providing heat to the worker&#39;s space, but not directly below the worker. The shape of the mat is easily configured through multiple conventional plastic manufacturing techniques. 
   Furthermore, the mat heating system is economical on many levels because it provides reduced energy costs and allows workers to more easily control their own comfort while taking advantage of the already existing configuration of office spaces. 
   The plastic material intended for use in the mat heating system is chosen for its appropriate electrical and thermal properties, providing the necessary degree of safety appropriate for commercial spaces, including garages where a space heater with exposed coils or flame may not be appropriate. The choice of materials for manufacture and use in the chairmat is also dependent on other end-use considerations such as cost, purpose, and manufacturing technique. In one alternate embodiment newer plastic materials can be chosen for the heating system that do not require electrical elements but provide heat based on the thermal and conductive properties of the mat material because the entire mat acts as a single electrical element. The cost of manufacturing using such materials is may soon become practical for commercial viability. The heating system may include optional anti-slip mechanisms such as “spikes” or rubber bottoms, depending on their intended setting. 
   The electrical heating and control system of the present invention is made up of components known to those skilled in the art. Particular components, such as thermocouples, thermostats, or GFIs may be added in embodiments that need added features of control and safety, but they also may add to the cost and complexity of manufacturing the system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  depicts an embodiment of the reduced-volume heating system. 
       FIG. 2  shows an alternate embodiment of the invention. 
       FIG. 3  is a cross-section of an embodiment of the invention and is representative of a manufacturing process for the invention. 
       FIG. 4  is a diagram of a cross-section of an alternate embodiment of the invention and is representative of a different manufacturing process. 
       FIG. 5  depicts an alternate arrangement of the heating element. 
       FIG. 6  depicts an alternate embodiment of the invention with additional protection and insulation of the heating elements. 
       FIG. 7  is a block diagram of the electrical components of the present invention. 
       FIG. 8  shows an alternate embodiment of the present invention, that uses a conductive composite material in the mat as the heating element. 
       FIG. 9A  depicts an example of  FIG. 3 ; a sample injection mold manufacturing process for the heating system. 
       FIG. 9B  depicts an example of  FIG. 4 ; in which the sheet is manufactured in two separate parts. 
       FIG. 10  depicts an alternate embodiment of the invention that folds. 
       FIG. 11  shows an embodiment of the invention with a pressure sensor. 
       FIG. 12  shows an embodiment of the invention with a presence detection system. 
       FIG. 13  shows the heating system including an environmental conditions detection system. 
       FIG. 14  shows an embodiment of the heating for multiple users. 
       FIG. 15  shows a combination industrial/commercial setting using the present invention in a wireless environmental feedback system. 
       FIG. 16  illustrates the heating system with an optional anti slip device in the form of spikes. 
       FIG. 17  illustrates the heating system with an optional anti slip layer. 
       FIG. 18A  shows the heating system in an embodiment with an anti static system 
       FIG. 18B  illustrates an alternate embodiment with an anti static system and an insulating layer. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As can be appreciated by those skilled in the art, the present invention could have several different embodiments, all of which would have various benefits based on the consumer&#39;s manufacturing process, end-use requirements, pricing, and safety criteria. 
   Referring now to  FIG. 1 , a preferred embodiment of the invention is shown. A heating system  10  includes a sheet or mat of appropriate plastic material  20  in a desired thickness for use as a rolling chair mat in a commercial space. Enclosed in the plastic material  20  is a single electrical heating element  30  that includes a heating coil or wire  32  and optional insulating material in the form a sleeve or air (or gas) pocket  34 . The heating system  10  includes an electrical supply system  40 , which includes an electrical plug or other standard power connection  41 . The electrical supply system  40  may be connected directly to the heating element  30  or connected to the heating element  30  through a transformer or converter  42  and/or a safety interface  44 . In some embodiments, the electrical plug  41  will include a ground prong  45 , but in alternate embodiments grounding may be provided in other ways. 
     FIG. 1  also depicts optional heat controls  50  that may be connected in-between the plug  41  and the transformer/converter  42  or between the transformer  42  and the heating element  30 . As can be appreciated by those skilled in the art, the heat control  50  may be included in particular embodiments, but it may increase the complexity and price of the system. The control  50  includes an optional thermostat  52  and an optional emergency shut-off  54 .  FIG. 16  shows the optional feature of the present heating system  10  with a “spiked” bottom  17  that may prevent slippage on certain types of carpeting by penetrating the surface of the carpet. As can be appreciated by those skilled in the art, the manufacture of a vinyl (or alternate material) sheet with the heating elements is not made significantly more complicated by the inclusion of a “spiked” or “cleated” bottom.  FIG. 17  depicts a second alternate optional anti slippage feature in which the bottom of the heating system  10  has a rubber anti slip layer  18 . The anti-slip layer  18  may also be made of other types of material, such as alternate types of plastic that would be appropriate for an intended surface of use. Thus, the anti slip material  18  may be seen as similar to using different types of casters on a rolling chair to accommodate a floor surface. 
     FIG. 2 . depicts an alternate embodiment of the invention in which one or more thermocouples  60   a ,  60   b , . . . are included in the body of the plastic material  20 . The one or more thermocouples  60   a ,  60   b , . . . , can monitor the temperature of the plastic material  20  at critical junctures  62 , where the electricity to the heating elements  30  can be shut off by the emergency shut off  54  in the control  50  or by an optional regulator  70  in case the plastic material gets too hot. 
   Referring now to  FIG. 3 , a cross-section of the heating system  10  is shown. In this embodiment, one possible manufacturing process for the system can be more easily understood. As can be appreciated by those skilled in the art of plastics manufacturing, the heating system  10  can be implemented by placing the heating element  30  (and other components) into the single piece of plastic material  20 . The body of the plastic material  20  includes a hypothetical space or bond  25  that is either created by the volume heating coil  32  and the insulating material  34  or by the adhesion in the plastic material  20  to the element  30 . One example of a manufacturing process of this embodiment is the well-known process of plastic mold injection manufacturing, in which the precursor (melted) of the plastic material  20  is shot into a mold that includes the electrical heating elements  30  and other components intended for inside the plastic mat  20  which are already properly placed in the mold. This is illustrated by  FIG. 9 , but is not necessary for understanding the invention because it may be manufactured in other ways. 
   Referring now to  FIG. 4 , a cross-section of an alternate embodiment of the heating system  10  is shown. In this case, the plastic material  20  includes two (or more) sections, A  22  and B  24 . Either section A  22  or section B  24  can be molded, stamped, shaped, or otherwise manufactured to appropriately accommodate the heating element  30  and other components ( 60   a ,  60   b ) at an open end. In this example, section B  24  is manufactured such that at the top, the heating elements  30  can be easily placed into the hollowed plastic areas or bonds  25   a ,  25   b , . . . . The heating elements  30  and other components  60   a  are placed into the top of section B  24  after it is prepared. Section B  24  is then assembled, glued, heat-welded, chemically welded, or otherwise appropriately attached to section A  22  at the boundary  27 . Thus, this embodiment may have some manufacturing advantages over the embodiment depicted in  FIG. 3  because the heating elements  30  are not necessarily subjected to, nor must they withstand, the conditions of a plastics manufacturing process. 
   The range in choices of materials suitable for the manufacture of the plastic mat  20  in the claimed invention can be appreciated by those skilled in the art of plastics manufacturing. References that include discussion of the suitability of particular plastic materials for certain purposes in the present invention include polymer and plastic science textbooks such as the  Textbook of Polymer Science , 3 rd    ed  by Fred Billmeyer Jr., John-Wiley &amp; Sons, and appropriate industrial literature, such as that available from the Society of Manufacturing Engineers on manufacturing,  Working with Vinyl, Working with Polyethyelene, Working with Acrylic , and  Working with Polystyrene , etc. Bill Fry, 1999. The relevant portions of these references, as they are needed to practice the invention, are herein incorporated by reference for such purposes. 
   In considering the manufacture and operation of the present invention, the following properties of the plastic material  20  chosen for the mat should be considered:
     The melting temperature should be in excess of the junction temperature where the heating element  32  or insulation of the wire  34  is in contact with the plastic material  20 , and should not be greater than a threshold temperature, which is 85 degrees F. in one embodiment. The melting temperature should be at least twice that contact temperature. Thermal resistivity is another property that should be considered in the choice of material.   The thermal conductivity (of which one formula for calculating is: [10**−4(10 to −4th power) cal-cm/(s-cm**2 (squared)×Degrees C.))] of the plastic mat  20  should be relatively high for plastics. As can be appreciated by those skilled in the art, without a reasonable high thermal conductivity, the plastic mat  20  could potentially become soft at the point of the heating wire element  30  and not radiate to either side, creating warm areas only along the heating element  30 .   The tensile strength, compressive strength [lb/(in. **2 (inch squared)], and flexural strength [lb/(in. **2 (inch squared)] must be appropriately chosen in order to support a chair caster or chair foot with a person (up to at least 100 kg) in the chair. The plastic material  20  should be chosen not to break under such conditions because that would potentially interrupt the continuity of the heating element  30 . A crack would allow foreign matter to enter and compromise the electric element  30  and element-to-plastic bond  25  or plastic-to-plastic boundary  27 .   

   The coefficient of linear expansion [10**6 (10 to sixth power)in./(inch*degrees C.)] for both the plastic  20  and the heating element  30  should be consistent with each other such that the heater/chairmat  10  would not expand when heated tearing or displacing the heating coil  32 . Likewise, the heating element coil  32  should not expand/contract within the mat  20  to causing itself to break or to disturb the material/element bond  25 . 
   The dielectric strength (V/mil) of the plastic material  20  must effectively electrically insulate the mat from the heating element  30  so the elements are not electrically shorted to each other. 
   Two additional properties that should be considered are that the mat cannot get warm enough to melt or cause chair casters to soften or score the mat, and any dirt or rocks on the mat cannot become embedded in the mat material, easy cleaning is necessary. Furthermore, the chairmat must be reasonably flexible to the extent the above properties can be incorporated. A more flexible mat would be preferable. 
     FIG. 5  shows an alternate arrangement of heating elements  30  in the plastic material  20 . In this alternate embodiment, the heating coils  32  are placed in an alternate arrangement, such as the periphery of the mat, so that the heat does not directly rise to the worker. Also, in this configuration, the heating coils  32  do not lie in the area of the plastic material  20  that most under the pressure of chair wheels, which would generally be at the center. This area is defined for purposes of the invention as a high stress area on the surface of the mat. 
     FIG. 6  depicts another embodiment of the invention in which an alternate arrangement of plastic material  20  is configured such that it has one or more protective covers in the areas in the locations  28   a ,  28   b , . . . , where the heating element  30  is present. Thus it may be possible to reduce the compression, risk of breakage, etc. on the plastic material  20  at the location of the heating element  30 .  FIG. 6  shows an increase in the depth of the plastic material  20  where the element  30  is present, but other protective devices, such as material substitution, may be employed resulting in a similar effect. 
     FIG. 7  shows a block electrical diagram of an embodiment of the electrical system  200  of the heating system  10  of the present invention. Those skilled in the art will be aware that the electrical system  200  could have different implementations that do not depart from the invention, but may be based on particular needs or criteria of the apparatus embodying the invention. The criteria could include safety features, optional control features, manufacturing costs, intended end-use, etc. The electrical elements of the system  200  include at least a power supply system  40 , a heating element  30 , and an interface  225 . Optionally, one or more thermocouples  60   a ,  60   b , . . . are monitored by a heat control unit  50  that usually includes a thermostat  52  and may also optionally trip an emergency shutoff  54  that shuts down the electrical flow if a critical temperature is reached. Individual components of the electrical system would also be chosen based on the requirements mentioned above. In a preferred embodiment, the heating element  30  includes a nichrome wire. 
   The power may be controlled or regulated by a converter  210  in which standard AC current input through the electrical plug  41  is converted to 12 V DC or other appropriately limited voltage (and/or current). Optionally, a Ground Fault Circuit Interrupter (GFI)  220  may be included as a separate device or incorporated structurally into the converter  210 . As such, the GFI substantially improves the safety of the device, even if it already includes the standard ground prong  45  in the electrical plug  41 . As can be appreciated, other grounding devices may also be appropriate. 
   In one embodiment of the invention, the heating element  30  is similar in structure and character to that used in the defrosting of car windows. The electrical properties of the element  30  should allow adequate heat to be produced but also limit the current (in addition to any converter  210 ) and plastic material  20  temperature. The point at which the electrical power connection to the mat occurs is the interface  225  and can include a rubberized plug connection  225  that adds to the safety of the mat but does not add substantially to the cost. Depending on the properties of the material, the spacing and size of the heating elements chosen for the present invention can vary. Furthermore, the thermal and electrical properties of the plastic material  20  will determine whether an appropriate insulating material  34  must be present to insulate the heating element  30  from the plastic material  20  and which such material  34  would be appropriate. Such materials range from vinyl to polyethelene, and may include rubber as well, but would be easily referenced by a handbook on insulating materials known to those skilled in the art. 
   The heating system  10  of the present invention can be adapted for a variety of different geometries, depending on the space in which they are used, including L, T, rectangular, and cross-shaped (and combinations thereof). The manufacturing of the heating system  10  may be adapted to accommodate different shapes of plastic mats, including customized shapes as are needed in the marketplace. 
     FIG. 8  depicts another embodiment of the heating system  80  in which the heating element is the plastic material itself  85  or layered in-between other layers of plastic material  87 . The properties of such material  85  are varied but may include carbon-fiber materials, including resins and carbon-aluminum resins capable of the proper amount of resistance to produce heat. However, other materials may be appropriate, provided that they produce the desired flexibility of the chairmat  10  (too rigid a material would not be appropriate). Some of the electrical, thermal flexural and strength properties of these materials are known by those skilled art and are included in the text  Modern Plastics Handbook , Charles Harper, Ed. (McGraw-Hill, 2000), which is hereby incorporated by reference for understand how to implement such material into a particular embodiment of the invention. There may be more than one electrical contact  88   a ,  88   b , . . . needed to provide the proper power supply to such a material  85  or a continuous or discontinuous insulated electrical band. In another embodiment of the fiber and/or resin based single heating element, there is a layer of such material in between a more traditional non-conductive material like clear vinyl. 
   Other embodiments would include a folding plastic heater chair mat  90  embodiment, depicted in  FIG. 10 , in which a pair of plastic panels  92  and  94 , each with a heating element  30 , are connected by a pair (or more if needed) of (preferably flush) hinges  95  that both act as a conductor and cover the electrical heating element. The addition of mechanical features would add to the cost and reduce the simplicity of the preferred embodiment. 
   The chairmat of the present invention may include electronic sensors or devices that may be appropriate for an industrial or commercial setting, including automatic shutoff and anti static functions thereby consolidating necessary electronics for the economical operation of the heating system and other types of devices. Other relevant features may be included that are appropriate to the particular environment in which the chairmat will be used. Because the chairmat must include at least a few electrical components to operate the heating elements, other types of elements that detect or affect safety and/or economy can be included in the present invention. 
   Referring now to  FIG. 11 , a set of pressure detectors  315  may be included in a strategic part of the heating system sheet for various safety and efficiency purposes. 
   Referring now to  FIG. 12 , an embodiment with a sensor for controlling the operation of the heating system based on a user&#39;s attendance is shown. The heating system includes a sensor system  300  that is electrically connected to the power supply  40  through an external interface or connection  305 . The attendance sensor system  300  may include a pressure sensor  315  on the chair and a timer (not shown) to shut off the heating system when a user is not present. Alternately, there may be a connection  350  to a personal workstation or a static field detector that determines the presence of a user by an alternate method. The attendance sensor system  300  can be connected to the workstation, but is connected to the controller  50  and/or power supply  40  through an internal or external connection  320 . For the sake of efficient manufacturing and implementation, it is contemplated that all the electrical/electronic components of the present invention will be located as near to each other as possible, but as one skilled in art can appreciate, there are desirable alternate configurations. 
     FIG. 13  shows another optional feature of the present invention, in which a device for detecting an environmental condition  395  is also included. The environmental detection device  395  may be incorporated into the material  20  and may include a chemical, radiological, biological or other type of detector. Depending on the type of detector  395 , an opening to the environment  396  may also be included. A connection  398  to an indicator is also an optional feature in another embodiment. Thus, the heating system with such a feature may be designed for use in particular industrial or commercial environments where detection of harmful conditions is necessary. 
   Referring now to  FIG. 14 , another alternate embodiment in which the heating system  400  is used for an alternate space arrangement of an industrial workspace for multiple workers (the diagram shows an assembly table for seven seated workers) is shown. The arrangement of the components of the invention in the single office chair is adapted for an industrial space but has the same set of components, including a power supply system  430 , optional control  420 , and a heating element  410 . Such a device may be particularly useful in settings where the atmosphere in the industrial space is hard to control or must be kept below a comfortable temperature. Although the invention contemplates a chairmat, similar materials would be appropriate for standing worker as long as the chairmat met appropriate industrial needs. The above-mentioned optional environmental detector may be added as appropriate for the setting. 
     FIG. 15  represents a possible embodiment of the present invention in an industrial/commercial setting with both individual heater chairmats  10  in the “cube farm” and larger versions of the heating system  400  that were shown in  FIG. 14  in the industrial or assembly areas. The individual heating systems may be controlled by a central environmental control program running on a computing device  500  through a simple wireless receiver/controller  525  on the individual heating systems  10  or  400 . The computer device detects and broadcasts appropriate information to each device through a wireless broadcaster  510 , such as an IEEE 802.11 or a similar system. As such, the computing device can track the temperature conditions in individual space, allowing an entity not only to make workers more comfortable but determining where money may be saved by reducing wasteful or irregular energy consumption.  FIG. 15B  illustrates an individual temperature controller  525  on the individual heating systems  10 , which includes the presence detector  300  and a processor  520  that is connected by a bus  522  and has an optional external interface  305 . 
     FIGS. 18A and 18B  show further embodiments of the invention that include the anti static functionality and feature for the office or industrial workspace that take advantage of the fact that an electrical system is already present in the heating system. The inclusion of the anti static function would be appropriate in industrial and commercial workspaces where this feature is needed, such as where electrically sensitive components could be harmed by static electricity.  FIG. 18A  shows a heating system with integrated anti-static function  700 . The vinyl layers  20 ′ and  20 ″ are the “dissipative” layers, but top layer  20 ′ still includes the heating element  30  in order to provide heat for the user. An anti static conductive layer  705  includes a conductive element  710  and an electrical transition device  725 . An integrator/splitter  715  may allow the anti static electrical element to be plugged into the same socket as the power source  40  for the heating elements  30 . However, the integrator/splitter is optional.  FIG. 18B  shows an alternate anti static version of the heating system  750  that has a dissipative layer  735 , and/or an optional electrically insulating layer  740  below the layer  20 ′ that includes the heating elements  30 . In other industrial environments conductive mats may be appropriate as well. 
   Referring now to  FIG. 9A , a sample of a manufacturing method for the heating system is shown. A plastic mold injection system  1001 , as known by those skilled in the art, includes a mold  1000 , that includes a die  1050  of the desired dimensions for the floormat. Electrical elements, such as heating element  30  and optional sensors  60   a ,  60   b , . . . are placed in a desired arrangement  1070  with material appropriate for the process, possibly including the material used in the sheet. Optionally, a protective coating  1090  for the electrical elements  30 ,  60   a , . . . may act as the insulating sleeve  32  as well. In another embodiment represented by  FIG. 9B , the electrical elements are placed into a plastic sheet with a series of pre-configured cut-outs  1101  at one end, that represent the top or bottom half (the bottom half is shown)  24  of the sheet  20 . This allows for easier placement of the electrical elements, but requires the additional step of adding a top layer  22  as described above. Thus, the layer  24  may be manufactured by multiple methods, but it is more easily made by plastic mold injection than the single layer detailed above. 
   The examples provided in the description of the invention are meant to be illustrative and not limiting. Other uses for the heating system are possible without departing from the spirit and scope of the invention. Furthermore, the heating system  10  may also be appropriate for rugged outdoor use where gas or electric space heaters are either inappropriate or ineffective and the rugged plastic material  20  used in the invention is more suitable.