Electric heating – Heating devices – With heating unit structure
Reexamination Certificate
1999-12-22
2001-07-17
Walberg, Teresa (Department: 3742)
Electric heating
Heating devices
With heating unit structure
C392S457000, C392S489000, C392S503000, C219S481000, C219S523000
Reexamination Certificate
active
06262401
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to heating elements utilized within water heaters.
Over time, electric water heater elements tend to develop scale (calcium carbonate). This scale is a poor heat conductor. The high heat flux at the heating element combined with the poor thermal conductivity of the scale film tends to cause the heating element to overheat, which can lead to failure. Also, the growth of scale on the element may physically deform the element and cause failure. Finally, as scale grows thick it tends to flake off the element and into the heated water.
A water heater element which minimizes or prevents scale growth or formation would be desirable.
SUMMARY OF THE INVENTION
The present invention provides a self-cleaning water heater element. The water heater element is plated with a noble metal, such as gold, having low surface roughness. It has been found that plating a water heater element with gold having a low surface roughness dramatically effects the ability of the water heater element to inhibit scale formation. If the gold surface is too rough, the heating element will not adequately inhibit scale formation. However, if the gold surface is sufficiently smooth, scale formation is inhibited.
The existence of a gold-plated heating element has been documented, for example in an article indicating that Tefal has incorporated a gold-plated heating element into cordless kettles as a means of reducing scale. Generally, kettles have much smaller heating elements than water heaters. Also, kettles typically are not utilized as frequently as water heaters and are not exposed to continuous water contact. Further, kettles run on lower wattage than water heaters, and water heaters are capable of heating a much larger volume of water (that is, gallons rather than cups).
One embodiment of the present invention is a self-cleaning water heater element comprising a water heater element, and a layer of gold at least partially coating the water heater element.
The invention also provides a process for the preparation of a self-cleaning water heater element. The process comprises providing a water heater element, and electroplating a layer of gold onto the water heater element.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawing.
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Appliance, Article Regarding Confortechnologies(1 page).
“Surface Cleaning, Finishing, and Coating”,Metals Handbook Ninth Edition, vol. 5, pp. 199-206 (1982).
Hughes Dennis R.
Knoeppel Ray O.
AOS Holding Company
Dahbour Fadi H.
Michael & Best & Friedrich LLP
Walberg Teresa
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