Abstract:
A heater including an electrically insulative panel having a decorative image on a first side and a resistive heating layer on the second side. The resistive heating layer is preferably a graphite containing sol gel material. The invention can also include a surface or support for supporting an article such as a towel or piece of clothing adjacent to the heated surface to heat and/or dry the article.

Description:
This invention relates to heaters, and in particular to a radiant heater. There are many types of space heaters that can be used to heat a particular room or area. Included among the variety of available space heaters are various convection heaters that usually include a burner and a fan for circulating the heated air, and which can be powered by electricity or fossil fuel. Other designs include radiant heaters. Among the radiant heaters are electrical heaters that heat liquid within a vessel, which in turn heats the surface of the vessel, which in turn radiates heat into the surrounding space. Another known radiant heater design consists of a resistive heating coil mounted in a reflective dish. As the coil is heated the reflective dish disperses and reflects the radiant heat from the coil into the surrounding space. This type of heater is useful in directing the radiant heat to a particular area or in a particular direction. 
   Each of these known types of heaters will provide heat with more or less efficiency, but each must be placed on the floor or on a counter in the space, preventing that space from being used for other purposes. In addition, the heaters are not particularly attractive. They can be ornamented in different ways, but are still utilitarian in appearance. 
   A need therefore remains for a heater that can be conveniently placed within a room and efficiently heat the room, while contributing to the overall decor of the room. 
   SUMMARY OF THE INVENTION 
   This invention meets the need for an efficient, attractive space heater by providing a flat panel radiant heater that includes a first layer of a resistive thick film disposed on an insulating panel. In one preferred embodiment the insulating panel is a flat panel of mica. A resistive film is disposed on one surface of the insulative mica panel and is connected to an electrical source by conductive traces along opposite sides of the resistive film that serve as buses. The decorative image on the opposite surface of the insulating panel is in the form of a painting or print for example, permitting the heater to serve as a decoration in the room. In one embodiment the decorative image is in the form of paint applied directly to the mica panel. In another embodiment the decorative image is in the form of a print or painting that is adhered to the mica panel. It can be readily seen that essentially any decorative image could be applied to the mica panel, and that a heater according to the invention is thereby suitable for use in literally any type or style of room or other space. 
   These and other features of the invention will be described below in greater detail by reference to the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of a heater according to the invention. 
       FIG. 2  is a cross-sectional view along line A—A in FIG.  1 . 
       FIG. 3  is a rear view of the heater shown in FIG.  1 . 
       FIG. 4  is a front view of a second embodiment of the invention which includes a cooling mechanism to limit the surface temperature of the heater. 
       FIG. 5  is a bottom partial cutaway view of the cooling mechanism shown in FIG.  4 . 
   

   DETAILED DESCRIPTION 
   Turning now to  FIGS. 1-3  a preferred embodiment of the invention is shown generally at  10 . Heater  10  includes a central insulative panel  12 , a decorative image  14  on one side of insulative panel  12 , a frame  16  around image  14 , and a resistive heating film  18  on the opposite side of insulative panel  12 . Image  14  can be any form of image on most any substrate, and in one preferred embodiment is glued to insulative panel  12 . Resistive heating film  18  on the opposite side of insulative panel  12  is bordered along two edges by buses  20  and  22  that connect to a power supply line  24 . Power supply line  24  includes a terminal  26  that connects to a power supply such as the electrical system in a home or other building. 
   Heater  10  operates by passing electricity from a power supply through power supply line  24  to bus  20 , through resistive heating film  18 , and into bus  22 . The flow of current heats resistive heating film  18 , which heats insulative panel  12 . Heat from insulative panel  12  in turn heats image  14 . The heated outer surface of image  14  radiates heat from the heater to the surroundings. 
   Insulative panel  12  is preferably formed of a mica material such as Cogemicanite 505, a mica sheet material manufactured by COGEBI, Inc. of Dover, N.H. This material is a mica laminated sheet of muscovite or phlogopite, and which has high temperature resistance, high electrical resistance, and to which the image can be glued and which will bond with the resistive heating film  18  as described below. Other insulative materials having suitable insulative and forming characteristics could be used in place of Cogemicanite 505, as the invention is not intended to be limited to a particular material. Image  14  in form of a print or painting for example, is mounted on insulative panel  12  using an appropriate adhesive that is suitable for a temperature range of up to 250 F. 
   Resistive heating film is preferably a thick resistive film such as a graphite based sol gel manufactured by Datec Corporation of Milton, Ontario, Canada. The sol gel is preferably screen printed or sprayed onto insulative panel  12  as a liquid, and cured at 300 C. It is then stable in air up to a temperature of about 350. 
   In the preferred embodiment, buses  20  and  22  are preferably formed of silver and are positioned along the left and right edges of the resistive film before curing, and are bonded to the sol gel during curing. Buses  20  and  22  are formed by applying a curable silver-containing emulsion such as DuPont No. 7713. The buses could also be formed of other conductive metals such as aluminum or copper applied in ways familiar to those of skill in the art. 
   In other embodiments resistive heating film  18  is a thin resistive film of SnO2 measuring 1 micron or less in thickness, and which can be deposited by known deposition methods. In practice, however, the thin films are more expensive to apply, and for that reason are not the preferred embodiments of the invention. 
   In the preferred embodiment the power of the heater is determined by the thickness of the film and the voltage and current applied to the buses. In one example, a sheet of the mica material described above was coated with the Datec graphite-based sol gel and cured at 300. Buses were bonded to the sol gel during curing as described above. The bus-to-bus resistance was measured at 48 ohms. A voltage of 120 volts was applied, which provided a power output of 280 watts. The surface temperature of the picture rose to 185 Fahrenheit. The heater was mounted on the wall in a room measuring 10 feet by 14 feet by 8 feet. The outside air temperature was about 32, and an adjacent room was at 60. The heater heated and maintained the room at about 70. 
   In another embodiment the surface temperature of the heater can be maintained at a predetermined temperature by the use of a fan or other air moving device to direct a stream of air across the heated outer surface. In one embodiment shown in  FIG. 4  an air moving device  410  is mounted along an upper edge  412  of the heater  10 . Air moving device  410  directs a flow of ambient air across the surface of the heater to limit the surface temperature of the surface. Turning to  FIG. 5 , air moving device  410  includes a hollow housing  414 , a plurality of distribution holes  416  in the lower surface of housing  414 , an open end  420 , and a fan  418  that draws air in through open end  420  and forces it out through distribution holes  416  across the outer surface of the heater. Fan is of any suitable design and is preferably electrically powered. 
   In yet another embodiment of the invention, the heater can be formed in a shape to support and warm articles (e.g. towels) as an alternative to or in addition to heating the surrounding space. Numerous designs can be envisioned that would provide either a flat surface on which the article can be placed, or that would provide a “bar” on which to hang the article to place it adjacent to the heated surface of a heater. 
   While the invention has been described by reference to the preferred embodiments described above, those of skill in the art will recognize that numerous modifications in arrangement and details are possible without departing from the scope of the following claims.