Patent Application
20100176118
This invention relates generally to an electrical heating film and a method for producing the same. The heating film is formed as a continuous vacuum deposited metal coating having a specified resistance which may be modified by virtue of mechanical reduction. The electric heating film is used to distribute heat onto a surface.
Electric heating films are typically used in applications where space is limited, when a heat output is needed across a surface, where rapid thermal response is desired, or in ultra-clean applications where moisture or other contaminants can migrate. There are various prior art devices which use electric heating film in various applications, for instance the use of electric heating films are disclosed in U.S. Pat. No. 4,990,744 for under-floor heating, U.S. Pat. No. 6,204,480 for window tinting or glazing, U.S. Pat. No. 5,990,449 for mirror deicing or defogging, U.S. Pat. No. 6,686,562 for vehicle heated seating, U.S. Publication No. 2002/0040900 for heating containers, and the like. An electric heating film generally comprises of a dielectric (a non-conducting substance, i.e. an insulator), having a substrate applied thereto, and a resistive material. The substrate is first applied to the dielectric material (discussed in further detail below) and provides an electrical isolation between the substrate and the electrically-live resistive material. The resistive material is applied to the dielectric material in a predetermined pattern and provides a resistive heater circuit. The electric heating film also includes leads that connect the resistive heater circuit to a power source to provide current through the substrate and dielectric material as a source of heat. Accordingly, electric heating films are highly customizable for a variety of heating applications.
Of the many applications where electric heating films may be used, an under-floor heating system is most common. Under-floor heating systems have become more and more prevalent because energy conservation has shifted from an after-thought to an initial design requirement for home designers and builders. Under-floor heating is a form of central heating system that utilizes heat conduction and radiant heat for indoor climate control. Under-floor heating systems are preferred over radiators because under-floor heating systems are not within view, are not noisy, and do not distribute dust from the duct work into the environment. Heat from an under-floor heating system can be provided by circulating heated water or other fluid through tubes or by electric cable, resistance wire, or film. The invisible waves of thermal radiation rise from below the flooring and warm up any object they come in contact with (which radiate that captured heat in turn). A conventional forced-air heating system, in contrast, blows air out of the registers at approximately 120° C. which then rises to the top of the room where it quickly sheds heat and drops back down as it cools. Thus the air in the room becomes uncomfortably stratified. Those jarring ups and downs in room temperature in a conventional forced-air heating system are absent with under-floor heating systems, whereby the warm air rises, but it does so evenly over the entire floor so that the coolest air stays up at the ceiling. In a hot water under-floor systems warm water is circulated through pipes that are laid into the floor (usually a solid concrete subfloor). The disadvantages associated with hot water under-floor systems include downward conductive heat loss to the soil or concrete underneath the piping, insulation and vapor barriers restrictions, expansion of joints in concrete and tiled surfaces, crack formation, floor build up due to the height of the piping, expense to install, noise due to bubbling, frequent maintenance, leakage, and water hammer.
Electric under-floor heating systems using electric cable or film is a preferred alternative. Electric under-floor heating systems are extremely effective as a primary heat source in small spaces because they have low installation costs and are easy to install. Likewise, they are very effective as a supplemental heat source in larger spaces. Known electrical cable or film under-floor heating systems typically vary the spacing of the resistive circuit pattern, as discussed above, such that where the spacing is smaller and the trace of the resistive circuit pattern is closer, the watt density is higher, for a series circuit configuration. For instance, U.S. Pat. No. 4,990,744 discloses an under-floor covering heating system having solid conductor resistance heating wires in a serpentine manner for heating the substrate. Conversely, the larger the spacing between the traces of the resistive circuit pattern, the lower the watt density in those regions. In other known electrical heaters, as disclosed in U.S. Publication No. 2007/0023419, the width of the trace of the resistive circuit pattern is varied along its length in order to vary the watt density, wherein the wider the trace the lower the watt density and the narrower the trace the higher the watt density for a series circuit configuration. However, due to the uneven cable spacing in these resistive circuit patterns, cold and hot spots are common. Furthermore, many electric under-floor heating systems use carbon film (as a substrate). For instance, U.S. Publication No. 2002/0040900 discloses the use of carbon film which is either printed directly on a dielectric film or carried within a cloth layer that is attached to the dielectric film. The drawbacks associated with the carbon film include unpredictable wattage output. As carbon is a semiconductor its physical properties vary widely at temperatures above 50° C.
In addition to the selection of a suitable substrate to be applied to the dielectric material there are drawbacks regarding the application of the substrate to the dielectric material. Electric heating films typically use a “thick”, “thin”, or “thermally sprayed” method of applying a substrate to a dielectric material. Of primary concern are the heating films for “thin” heaters, which are typically formed using a deposition processes such as ion plating disclosed in U.S. Pat. No. 4,707,586, sputtering (vacuum deposition) disclosed in U.S. Pat. No. 4,952,783, chemical vapor deposition disclosed in U.S. Pat. No. 5,780,820, arc plasma spraying disclosed in U.S. Publication No. 2001/0003336, among others. Unfortunately, using these techniques yields a resistance which is not very accurate and requires use of propriety methods during the deposition process in order to reduce the variation of resistance across the electric heating film, specifically with a vacuum deposition process. For example, resistance across a vacuum deposited metal on a dielectric layer has a significant variance. Controlling desired resistance across the electric heating film can greatly improve to provide more accurate and efficient resistance but requires the use of expensive proprietary methods such as controlling the time of exposure of the film to the vacuum deposition source, controlling the power that is used to heat source, controlling the pressure level in the chamber, and controlling the distance from the source to the film have been implemented. Unfortunately, these techniques are extremely expensive and time-consuming.
While these prior art devices may be suitable for the particular purpose to which they address, these prior art devices would not be suitable for the purposes of the present invention as heretofore described. What is needed is an electric heating film and method of producing the same using a continuous coating of vacuum deposited metal on a dielectric film base and obtaining a desired resistance across the electric heating film using mechanical reduction.
An electric heating film and a method of producing the same that includes an electrically insulative and thermally conductive first polymeric film layer having a top surface and bottom surface, an electrically insulative and thermally conductive second polymeric protective film layer, a metalized surface, and conductive bus electrodes. The top surface of the first polymeric film layer includes a continuous vacuum deposited metal coating layer and a pair of conductive bus electrodes, e.g. copper strips, which includes leads that extend from the first polymeric film layer for connection to a power source. The conductive bus electrodes are conductively adhered to the metalized surface to distribute an electrical current into the vacuum deposited metalized layer and provide a heating element across the vacuum deposited metalized layer. The second polymeric protective film layer is provided as a protective layer atop of the top surface of the first polymeric film layer forming an electric heating film. It is contemplated that more than one second polymeric protective film layers may enclose the top and bottom surface of the first polymeric film layer to form an electric heating film.
The electric heating film is then mechanically reduced to vary the electrical resistance across the electric heating film. The mechanical reduction includes providing a plurality of perforations across the second polymeric protective film layer, thereby decreasing the surface area of the metalized surface and thus obtaining a specified resistance across the metalized surface.
Accordingly, it is an objective of the present invention to provide an electric heating film and a method of producing the same using continuous coating of vacuum deposited metal on the first polymeric film layer and using mechanical reduction, i.e. perforation, across the electric heating film to obtain a desired resistance.
It is a further objective of the present invention to provide an electric heating film and a method of producing the same capable of providing a heating element in interior space, such as ceiling, flooring, and wall panels. The electric heating film may be used as a primary or supplemental heating means within the interior space.
It is a further objective of the present invention to provide an electric heating film and a method of producing the same capable of a heating solution in exterior surfaces, such as driveways, pathways, and sidewalks. The electrical heating film is particularly useful in continuously removing snow from the exterior surface so ice does not form. The heating solution does not allow ice to form on the exterior surface eliminating the need to use a shovel, snow blower, or chemical treatment. Furthermore, by not allowing ice to form on the exterior surface the electric heating film provides a safer walk way.
It is a further objective of the present invention to provide an electric heating film and a method of producing the same capable of reducing heat loss, specifically, helpful in inflated military tent structures.
It is an additional objective of the present invention to provide an electric heating film and a method of producing the same using a mechanical reduction to precisely control electrical resistance across the heating element by perforating the second polymeric layer, which encloses the first polymeric layer having a vacuum deposited metal coating and copper strips to distribute current to the vacuum deposited metal. Perforations may be formed by a punch or roll method to reduce the amount of surface area of the vacuum deposited metal coating on the electric heating film.
It is an additional objective of the present invention to provide an electric heating film and a method of producing the same to be used as an under-floor heating device for indoor climate control. The electric heating film would have a precision power rating (watts/square foot) due to mechanical reduction.
It is also an objective of the present invention to provide an electric heating film and a method of producing the same with continuous heating over an entire surface eliminating hot and cold spots ever-present in other under-floor heating systems.
It is also an objective of the present invention to provide an electric heating film and a method of producing the same having a metalized surface on a dielectric layer, whereby the metalized surface is a continuous, non-interrupted, non-pattern, and non masking vacuum deposited metal coat. The continuous vacuum deposited metal coat greatly simplifies the production process, makes the production process more reliable, and eliminates the expensive masking process.
It is a further additional objective of the present invention to provide an electric heating film and a method of producing the same that is safe, reliable, cost effective to produce, easy to install, flexible, and maintenance free. Furthermore, the electric heating film and a method of producing the same can be produced easily and efficiently in large numbers.
It is a further additional objective of the present invention to provide an electric heating film and a method of producing the same contemplated for alternative uses such as heated towel rack, heated wall and ceiling panels, moisture remover for damp areas such as closets or the like, heated vehicle seats, compact clothes dryers, agricultural seed growth accelerator, heated clothing, industrial drum heater, and heater for air systems to eliminate noise and pollution.
It is also a further objective of the present invention to provide an electric heating film and a method of producing the same having perforations on the metallic surface thereby allowing the film to be more readily anchored to thin-set tile grout.
It is also a further objective of the present invention to provide an electric heating film and a method of producing the same which may be attached to the underside of a ceiling joist to provide uniform warmth from the evenly heated ceiling surface.
It is yet further an objective of the present invention to provide an electric heating film and a method of producing the same attachable behind a mirror to automatically defog the mirror.
It is yet further an objective of the present invention to provide an electric heating film and a method of producing the same which offers a distribution of heat about a drum to prevent the contents thereof from freezing or to maintain at operating temperatures.
It is yet also a further objective of the present invention to provide an electric heating film and a method of producing the same to maintain a suitable environment for ectothermic animals (reptiles), which require them get their body heat from external sources.
It is yet also a further objective of the present invention to provide an electric heating film and a method of producing the same which is a highly effective direct acting radiant heating system capable of replacing traditional convector radiators by providing a primary source of heating, or alternatively a secondary source of heating to warm a cool floor and provide background heat.
It is also a further objective of the present invention to provide an electric heating film and a method of producing the same to be used in the agricultural field to extend growing and germination periods in cold climates.
Other objectives and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
Detailed embodiments of the instant invention are disclosed herein, however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representation basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.
Referring now to
A substrate in the form of a metalized surface 20 is applied to the top surface 14 of the first polymeric layer 12. The metalized surface 20 is deposited onto the top surface 14 using a continuous vacuum metal coating. The metalized surface 20 adheres to the entire top surface 14 of the first polymeric film 12. It is preferred that the edges 18 surrounding the periphery of the first polymeric layer 12 are not subject to the vacuum deposited metal coating. The continuous vacuum deposition manufacturing process is capable of producing thin metalized film surfaces that are very uniform, electrically conductive, and which adhere well to dielectric materials. The vacuum deposition manufacturing process produces a thin metalized film surface 20 having an approximate thickness of 0.0000002 inches or 50 Angstroms. Furthermore, the metal contemplated for use in the vacuum deposition coating is nichrome, nickel, tin and silver, or the equivalent.
A resistive material comprising of a pair of parallel spaced conductive buss electrode bars 30 are conductively adhered to the metalized surface 20. The electrical buss bars 30 are used to allow a powering current to be delivered to the metalized surface 20 to heat the metalized surface 20 for various applications. The electrical buss bars are preferably constructed of copper strips; however, aluminum strips provide a suitable alternative. The electrical buss bars 30 generate a voltage across the metalized surface 20 when energized by a power source coupled to a pair of electrical connectors which may include conductive strips and conductive leads, not shown. It is contemplated that the pair of electrical buss bars 30 need not be spaced parallel to each other. Depending on the application and construction of the electric heating film 1, the pair of electrical buss bars 30 spacing may be positioned ubiquitously about the metalized surface 20.
The electric heating film 1 further includes at least one outer protective second dielectric layer 40 having a top surface 42 and a bottom surface 44. The second dielectric layer 40 is an electrically insulative and thermally conductive polymeric layer. The second dielectric layer 40 provides an outer protective layer against scratching, moisture intrusion, etching, and destruction of the metalized surface 20 on the top surface 14 of the first polymeric layer 12. Various embodiments with the second dielectric layer are contemplated and described herein. As shown in
The second polymeric layer 40 is preferably constructed of biaxially-oriented polyethylene terephthlate (boPET) such as commercially available under MYLAR®. However, other dielectric material selections, such as plastics, thermoplastics, and the like, are contemplated without departing from the scope of the invention. Due to the polymeric material selection of MYLAR®, the electric heating film 1 is limited to a maximum temperature of approximately 110° C. However, if elastomers, such as silicone rubber or the like, or synthetic fiber, such as commercially available as KEVLAR®, were to be used; then high temperatures for the electric heating film may be achieved in excess of 250° C.
As shown in
If concerns arise regarding Ground Fault Interruption (GFI) the second dielectric layer 40 may be provided with an additional outer protective layer 60 comprising of a thickly-metalized film which is grounded to meet GFI, as shown in
All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference.
It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.
One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.
