Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2002-09-10
2004-03-02
Paik, Sang (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
Reexamination Certificate
active
06700100
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to safety devices used in cooking or other activities involving hot surfaces, and in particular it relates to safety devices which alert someone that the surface of a stove or other appliance or device is too hot to touch. The present invention also relates to detachable heat alert safety devices for any hot surface.
BACKGROUND OF THE INVENTION
With respect to stoves and related appliances, various kinds of stoves—electric, gas, smooth cooktop using glass or metal tops—and toaster ovens are well known to be used for heating food. In addition, “mobile stove-type appliances” such as hot plates and warming trays are well known to be used for heating food. Each of these kinds of stoves and “mobile stove-type appliances” present a safety problem since the heating elements of the stove are hot during the cooking process and remain hot well afterwards. During the cooking process, the safety problem caused by touching the heating element is mitigated somewhat by visual inspection of the stove. With a gas, electric or smooth top stove, for example, the presence of a pot or other utensil on top of the stove might alert someone to the fact that the stove appears to be in use for cooking and therefore too hot to touch. Even the presence of a pot or other utensil is not a reliable clue, however, since people tend to leave tea kettles on their stove perpetually. When the cooking process has ended, however, it is generally impossible to detect that the heating elements of the stove remains hot and would burn the skin of anyone who touched them. There is no visual or other clue that the stove is hot.
To some degree, adults have developed an inherent caution when approaching stoves because of their experience and knowledge in dealing with such safety problems. This inherent caution, however, does not obviate the need for a device that warns the adult when touching the stove would be dangerous. Moreover, children, and particularly young children, usually have not developed such a watchfulness and there has long been a need for a device that can prevent burn accidents to children who may inadvertently touch a stove that is hot, especially when the stove remains hot well after the cooking process has ended.
Furthermore, the reduction in the size of modern kitchens has led the occupants of modern apartments to make use of the stove as an extension of the counter top adjacent the stove as a resting places for large items that have been carried into the kitchen area. An example of such items is heavy bags of groceries brought into the kitchen. There is an urge to set the bags down on the nearest flat surfaces, which may be the top of a stove adjacent a counter top. This is particularly true for those stoves that are smooth on top, such as smooth cooktops. In general, the top surfaces of modern kitchen stoves are increasingly flat, especially the top surfaces of smooth cooktops. These factors have only increased the danger to adults when the top surfaces of stoves are used as a resting place for packages, such as groceries brought into the kitchen.
Smooth cooktop stoves presently are also dangerous if touched on their top surface when they are still hot, even after use. These smooth cooktop stoves, or “smoothtops” as they are sometimes called, utilize as the heating element separate areas on the top surface of the stove (at the same location that gas stove would have burners) which are made of glass. Under each area, usually circular, is a strong light source, such as a halogen lights. The light source projects the light upward to the surface area of the smoothtop's heating element—the glass area on the top surface of the stove. Since the glass area is coated on its bottom with a dark coating, when the light strikes it, the heat from the strong light is absorbed by the glass area and these glass surfaces form each heating element of the stove.
Another variation of the smooth cooktop is the use of a “ribbon heating element” where the smooth glass surface is heated by a coiled electric circuit called a “ribbon element” just underneath it instead of by a halogen light source. The heat is transmitted directly upward so that only the heat element itself gets hot and the rest of the cooktop surface remains cool. In some cases, the ribbon heating element also has another feature whereby the heating element is made of two concentric circles so that the option exists of two sizes of the heating element to match the two different sizes of the pans that need to be heated. This new technology does not solve the problem of warning adults and children that the heating element should not be touched when the cooking process has ended. If anything, it generates the additional hazard that someone can be lulled into touching the heating element after thinking the heating element is cool since the surface right adjacent to it is indeed cool.
Some of these problems have been addressed in earlier patents, through use of thermochromic inserts or overlays. Thermochromic materials are those such as some liquid crystals which change color when passing through a given temperature range, and are now familiar from use in inexpensive items, like temperature indicating refrigerator magnets or stick-on aquarium thermometers.
These devices however still suffer from some drawbacks. Flat appliable thermometers tend to be made of plastic, and would melt or be destroyed at the temperatures reached by a kitchen oven. Higher temperature chemical temperature indicating systems are known, such as the semiconductor cadmium sulfide, but must either be included as inserts in original equipment manufacturing, or fired on as a vitreous ceramic. Materials which are both capable of resisting high temperature and are transparent, or which are themselves thermochromic, are brittle, and so unsuitable for forming in thin flat removable displays, which makes it difficult to attach these materials to an existing surface, the way refrigerator magnet thermometer is attachable.
In an additional drawback of the prior art, flat indicators, embedded in or applied to a flat surface, are necessarily only usefully visible through a limited viewing angle. It is readily shown through trigonometry that if an observer is offset an angle &agr; from the vertical or normal to a surface, which offset is also referred to as the angle of incidence, the apparent area of objects on the surface will be reduced by a factor of cos(&agr;): A′=Acos(&agr;). For example, if an observer is offset 60° from the vertical, i.e., at a 60 degree angle of incidence, viewing a surface from 30° to the surface itself, the apparent size of objects on the surface is reduced by cos(60)=½. For an observer at an angle of incidence of 80° the apparent size has shrunk to less than 18% of the actual size; and at 85° apparent size is less than 9% of actual. An angle of incidence approaching 90° from the vertical is known as a grazing angle. At grazing angles a flat indicator on the surface clearly approaches zero apparent area, and is completely invisible to the observer.
A second problem that arises from looking at something at an angle of the line of sight is specular reflection. Specular or mirror reflection is the reflection of light rays hitting a flat surface with a reflected ray having an angle of incidence equal to that of the incident ray. For most surfaces specular reflectance increases with angle of incidence, so that more ambient light is reflected to a viewer at larger angles of incidence of the line of sight. This effect wipes out the contrast of a display, so that the display cannot be read at large angles, even if the apparent area of the display were otherwise large enough. Depending on the type of materials used, the loss in visibility at a given display angle may be worse than that predicted by apparent area alone. Liquid crystals for example show a contrast with background notably affected by viewing angle, and readability of a liquid crystal display may be degraded at lower angles of incidence t
Horowitz Steven
Paik Sang
LandOfFree
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