Electric resistance heating devices – Heating devices – Radiant heater
Reexamination Certificate
1999-01-06
2002-03-05
Jeffery, John A. (Department: 3742)
Electric resistance heating devices
Heating devices
Radiant heater
C219S213000, C219S542000, C219S552000, C219S544000, C219S549000, C392S480000, C338S284000, C338S289000, C338S293000, C338S295000, C338S210000, C338S280000
Reexamination Certificate
active
06353707
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to the area of electric heating elements. More particularly, the present invention relates to electric heating elements for use in heating residential and non-residential premises, specifically via construction panels and components such as walls and floors, etc., or different industrial or agricultural installations.
BACKGROUND OF THE INVENTION
Previously known heating elements based on applying a thin metal coating to a resistor ribbon are disclosed in U.S. Pat. No. 4,839,500. The thin metal coating can be made of several different metals, such as tungsten, tantalum, molybdenum, titanium, or platinum. The coating can be formed by chemical processes including the following: vapor-phase deposition method, sputtering method, vapor deposition method (U.S. Pat. No.5,331,134). A number of patents also disclose the use of metal oxides in making the thin metal coating, e.g., a tin oxide coating (U.S. Pat. Nos. 4,889,974; 5,304,783; 5,616,266).
Other known types of heating elements are built using film printing technique as set forth in U.S. Pat. No. 5,068,517. The heating element is based on a silver-palladium alloy (AgPd) or a mixture of the silver-palladium alloy (AgPd) and ruthenium oxide (RuO
2
). The cover layer has a thickness of 10 mm. The heating elements of that type have relatively small overall dimensions. According to the patent specifications, the heating element is 270 mm long by 15-25 mm wide.
A number of problems are typically encountered in the practical use of such heating elements in heating installations. There is a need to use special subtle chemical technologies for applying a thin coating. It has been found particularly problematic to apply an even coating throughout the entire surface of the element. Moreover, such thin coatings have a short life. Also, the coatings are also made from expensive metals. In addition, the heaters thus manufactured are limited in size and power.
Another known type of heating device is based on a heating element made of metal foil as disclosed in U.S. Pat. No. 4,797,537; U.S. Pat. No. 4,889,973; EP 0227624 A1; EP 0175662 A1. All of these patents disclose metal foil-based heating devices manufactured by etching or punching. The etching method is applicable only in manufacturing heating elements of limited size. Heaters utilizing such elements are applicable, on the whole, in localized heating in determinate places. These heaters have good results for creating temperature zones of limited size within relatively small, confined spaces. Since the etching agent is not washed away after the etching process, the metal remains brittle and easily destructible, limiting the life-span of the heating element. Elements made using the punching method are similarly limited in size and can be used for small-capacity heaters only. Both methods also entail additional expenses with respect to heating material.
Another known type of heater utilizes a foil made of a highly conductive material, namely, aluminum (WO 9603013 A1, WO 05/22236, U.S. Pat. No. 4,574,186). The specific electric resistance of aluminum is lower than the specific resistance of the resistor alloy by a factor of 40 to 50. Therefore, the thickness of the foil is smaller (microns), and the foil is short lived.
A number of patents have been issued for methods of strengthening existing heating elements (U.S. Pat. No. 4,650,960), and of reinforcing them (U.S. Pat. No. 4,363,947) regardless of the technology used. The latter patent proposes a technology for strengthening a heating element (U.S. Pat. No. 4,025,863) by soldering reinforcing elements thereto. The problem, however, is that the use of a foil of lead-tin antimony alloy having a melting point of 180° C. is proposed for the method in question. Lead, in addition to being an environmental pollutant, is very expensive.
All of the above described heating devices have a limited scope of practical application and a limited size and shape. In addition, the prior art heating devices are too complicated to make and require rare and expensive materials. Another problem is their limited lifespan.
The present invention, therefore, aims to allow the manufacture of more versatile two- and three-dimensional heating elements with larger effective heating surfaces (or practically unlimited shapes and sizes), with the added benefit of an increased life-span. All these goals can be attained using the proposed new electric heating element, intended for incorporation into different construction panels and materials for reliable electric heating.
SUMMARY OF THE INVENTION
An electric heating device in accordance with the present invention comprises a resistor ribbon, a plurality of sections of electroconductive coating attached to the resistor ribbon at preset intervals, and connector contacts coupled to the resistor ribbon for enabling connection of a power source to the resistor ribbon. Because of its thinness, the ribbon is naturally flexible.
Preferably, the flexible resistor ribbon has a high specific impedance. Also, where the flexible resistor ribbon has a width, each of the sections of the electroconductive coating are at least coextensive with the flexible resistor ribbon across the width thereof. It is generally contemplated that the sections of electroconductive coating, which are spaced from one another along the length of the ribbon, each have a length which is greater than the width of the ribbon. Thus, where the flexible resistor ribbon is folded back on itself at bend points located only at the sections of the electroconductive coating, the flexible resistor ribbon is mechanically reinforced at all the bend points by the sections of the electroconductive coating and electrical current is shunted across the bend points via the sections of the electroconductive coating, thereby eliminating overheating at the bend points.
The electroconductive coating of the spaced coating sections is generally the only layer of electroconductive coating which is applied to the resistor ribbon. The sections of coating in accordance with the present invention are spaced from each other by predetermined intervals or distances. These intervals or distances are determined by the expected use of the ribbon, and more particularly, by the expected locations of bending of the ribbon to conform to the size and shape of a preselected substrate.
The specific impedance of the resistor ribbon preferably adheres to the following formula R1/R2>2, where R1 is the specific impedance of the flexible resistor ribbon and R2 is a specific impedance of the electroconductive coating.
Where the heating device has a rated operational current I
element
and the electroconductive coating has a maximum admissible current I
max
, a ratio between the rated operational current I
element
and the maximum admissible current I
max
adhering to the formula:
I
element
/I
max
<{fraction (1/2.)}
In accordance with another feature of the present invention, the heating device further comprises a substrate, for example, a flat base to which the flexible resistor ribbon is attached. The base may be rigid or flexible and made of any of a variety of fire-resistant or fireproof materials including, without limitation, linoleum, PVC, plastic, fiberglass, or ceramic tile. In this form, the heating device is suitable for incorporation into a building as a floor, wall or ceiling panel.
Layers of electric insulation are advantageously attached to the base so as to sandwich the flexible resistor ribbon. Where the resistor ribbon is bent back on itself, for example, to form a snaking configuration, a strip of two-sided adhesive tape may be attached to the layers of electric insulation and to the ribbon at multiple spaced points in order to counteract differential thermal expansion of the various components of the heating device.
In a specific configuration of the heating device, a plate is connected to the base parallel thereto. The flexible resistor ribbon is mounted on a back side of the plate between the plate and the base. The heating devic
Loktev Irina
Papirov Igor
Ceramitech, Inc.
Coleman Henry D.
Jeffery John A.
Sapone William J.
Sudol R. Neil
LandOfFree
Electric heating ribbon with multiple coating sections... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electric heating ribbon with multiple coating sections..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric heating ribbon with multiple coating sections... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2887308