Those skilled in the art know that electrical power is utilized to produce heat in dielectric panels (a.k.a., units), for example, glass, ceramic, or glass-ceramic panels, that have an electrically conductive thin-film coating, which typically is non-magnetic, disposed thereon. In the past, film deposition techniques, such as those used in spray coatings, were not precise, which resulted in non-uniform coatings and consequently imprecise heating. Recently, the deposition of, for example, metal oxide coatings has improved through the use of chemical vapor deposition (CVD) processes.
Examples of heated glass applications that have utilized these coatings over the last thirty years are commercial refrigerator and freezer doors in supermarkets, where a tin oxide coating is disposed on one of the interior surfaces of an insulating glass (IG) panel and where an electric current is dissipated in the tin oxide coating to provide heat to raise the glass temperature above the dew point. On such doors, the heat eliminates the formation of condensation so that employees and customers can view the refrigerator/freezer contents after individuals have opened and closed the doors.
Non-uniform coatings and traditional electrical control connection methods, however, result in wasted energy, produce hot and cold spots on the glass, and can result in safety hazards should the glass break and expose the current-carrying film. In order to provide the electrical power to such heated dielectric panels, electrical wires are, typically, directly connected to bus bars that are disposed on the heated dielectric panels or electrical wires are directly connected to metal tabs that are disposed on these bus bars.
Often, electrical wires from, for example, an electrical power source, are routed by pathways, for example, conduit, raceways, and/or door/window sashes and jambs, to the heated dielectric panels. Potentially, direct wiring to the bus bars or the metal tabs can be unyielding and unsafe.
As they apply to building applications (i.e., windows, doors, skylights, and radiant heater panels) in the U.S., the methodologies associated with electrical wiring are established by the National Electrical Code (NEC). Per the NEC, any wiring having voltages greater than 42 volts is designated as class I wiring, which must be protected from accidental damage and must have all interconnections, splices, etc. inside an approved junction box (j-box). Hence, it is not possible to directly run wiring, for purposes of carrying line voltage and usable power, to operable windows and doors, and still comply with NEC requirements.
In addition, most code officials and inspectors require that any installed electrical device must have Underwriter Laboratory (UL) or equivalent approval. UL also will not approve exposed wiring or exposed connectors at 110-250 volts.
One means of interconnecting wiring, which has been used in the past, is to utilize pin connectors with a safety interlock, but there are concerns regarding the long term reliability of such connectors, since corrosion of the connectors can result in electrical arcing at the connectors. Also, if the safety interlock is bypassed or defeated, electrical shock potential can result.
Regarding connectivity to heated glass panels, U.S. Pat. No. 5,852,284 to Teder et al. utilizes a capacitor to electrically couple to a heated glass door/panel, where the coupling is achieved by “adjusting” power from an electric power source by way of the capacitive reactance of an RC (resistor/capacitor) circuit. Then, Teder directly connects the capacitor, whose geometry must be considered when being mounted in the frame/sash of a door/window or in the space between two panes of glass, to the heated glass door/panel. In addition, the value (in farads or portions thereof), plate size, spacing, and dielectric material of the capacitor must be specifically chosen for the glass size and power level.
On the other hand, U.S. Pat. No. 5,529,708 to Palmgren et al. teaches the use of electrical radio frequency energy in the range of 2.5-8 MHz, where a non-magnetic substrate has a magnetic coating disposed thereon, to provide an inductive heater. However, Palmgren is silent on the utilization of non-magnetic coatings that are typically found in heated glass applications and which are discussed herein. Hence, neither Teder nor Palmgren overcome the above stated shortcomings associated with directly connecting a power source to a heated glass panel.
U.S. Pat. No. 5,821,507 to Sasaki et al. provides an electric cooker that utilizes a work coil to generate an inductive flux that heats a metal heating member. An insulator separates the work coil from the metal heating member and a wire mesh is used to support a food item. As illustrated in Sasaki's FIGS. 11 and 13, alternatively, a pot or pan may be used to support the food item, where electrical power is transmitted from a first work coil to an induction coil, which in turn supplies electrical power to a second work coil. The second work coil directly generates eddy currents in the bottom portion of the metal pan, thus heating the food item by way of eddy current loss.
Still, it would be advantageous to seek an indirect electrical connectivity means to wirelessly communicate electrical energy to a heated glass panel assembly that is electrically safe, energy efficient, and meets or exceeds NEC and UL standards.