US 3749886 A
An electrically conductive sheet of flexible material includes conductive particles and channel-shaped electrodes are provided on opposite ends and are connected by lead wires to a power source. A flexible insulating envelope is bonded to and protects the conductive sheet. Holes may be provided in the conductive sheet to facilitate bonding between the protective cover and the conductive sheet. The conductive particles may be carbon and the sheet may be formed from fibrous material or rubber. The protective sheet may be molded from plastic or rubber having a very low carbon content.
Description (OCR text may contain errors)
United States Patent [1 1 Michaelsen ELECTRICAL HEATING PAD  Inventor: Dwight W. Michaelsen, Columbus,
 Assignee: Dale Electronics, Inc., Columbus,
22 Filed: Dec. 6, 1971 2 11 Appl. No.: 204,860
521 U.S. 01...; 219/s 28', 2197541, 2'19/543,
219/549, 338/212  Int. Cl. 1105b 3/36  Field of Search 219/211, 212, 213,
 References Cited UNITED STATES PATENTS 2,458,184 1/1949 Marick 219/543 X 3,344,385 9/1967 Bartos et a1 338/212 3,535,494 10/1970 Armbruster.. 219/528 3,558,858 1/1971 Luger, Jr. 219/528 3,627,981 12/1971 Kuhn 219/549 X 3,697,728 10/1972 Stirzenbecher 219/548 2,473,183 6/1949 Watson 219/543 2,688,070
8/1954 Freedlander 219/528 [451 July 31, 1973 Glicksman 219/528 X 3,281,579 10/1966- 3,367,851 2/1968 Filreis et al. 204/2 3,283,284 11/1966 Eisler 338/212 2,938,992 5/1960 Crump 219/528 3,385,959 5/1968 Ames et 219/549 2,559,077 7/1951 Johnson et a1..... 219/543 2,952,761 9/1960 Smith-Johannsen.. 219/541 3,359,524 12/1967 Gallacher et a1. 219/528 X Primary Examiner-,-Volodymyr Y. Mayewsky Attorney- Zar1ey, McKeejtitThomte 1 I [5 7 ABSTRACT An electrically conductive sheet of flexible material includesconductive particles and channel-shaped electrodes are provided on opposite ends and are connected by lead wires to a power source. A flexible'insulating envelope is bonded to and protects the conductive sheet. Holes may be provided in the conductive sheet to facilitate bonding between the protective cover and the conductive sheet. The conductive particles may be carbon and the sheet may be formed from fibrous material or rubbeLThe protective sheet may be moldedfrom plastic or rubber having a very low carbon content.
1 Claim, 2 Drawing Figures ELECTRICAL HEATING PAD Portable heaters are commonly used in and out of doors. Inside they may be used for a desk top warmer, desk foot warmer, foot stool warmer or for heating pads. Winter conditions outside make them desirale for windshield deicers, seat warmers and cat and dog house warmers.
One of the most important uses is for maintaining a battery at the optimum temperature level to maximize the battery power available for starting engines.
The heating pad of this invention contains no wires or ribbons and will not develop hot spots and burn out: There is basically nothingto breakfandcanKbecome partially damaged and still function. Theelectrical properties remain unchanged by the unit being exposed to dampness and then redrying. Further, repeated flexing has little effect on the electrical properties. The conductive element has uniform conductivity from point to point over the element regardless of the direction of current flow. Also, very important is the fact that the heater unit can be produced more inexpensively than a conventional wire-wound heater unit.
The heater unit of this invention includes a sheet of conductive material which is highly flexible and has channel-shaped electrodes at opposite ends connected to lead lines adapted to be connected to a power source.
This invention consists in the construction, arrangements and combination of the various parts of the device, whereby the-objects contemplated-are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated inthe accompanying ally in FIG. 1 by the reference numeral 10. The heatingv pad includes a flexible electrically conductive sheet 12. Suitable materials include rubber having carbon particles impregnated therein in sufficient quantities to make the sheet electrically conductive. Temsheet produced by Armstrong Cork Company, Lancaster, Pennsylvania, is also acceptable. A channel-shaped electrode 14 is secured to the opposite ends of'the sheet 12 and bonded in place by any suitable means such as the staples l6, seen in FIG. 2. The electrodes 14 are preferably brass.
An electrical lead line 16 includes one line 18 connected to one electrode while the other line 20 is connected to the opposite electrode 14. A rivet and solder connection 22 is used for connecting the lead line wires I envelope 24 of insulating material such as rubber hav-' ing no carbon or very little carbon. A flexible plastic may also be used. The conductive sheet 12 is com-- pletely sealed within the protective envelope 24 by a molding or vulcani zing process. Openings 26 are pro-.
vided in the sheet 12 to further facilitate the bonding of the envelope material to the conductive resistance sheet 12. I
I I It is seen in FIG-2 that'the electrodesl4-are inwardly, j.
spaced from the outer adjacent edges of the envelope 24 and thus provide extra protection at the ends of the heating pad and in particularly provide flexible support for the electrical lead line 16 to minimize stress and strain at the electrodes 14.
It is seen that the use of synthetic natural rubber or plastic in the envelope 24 provides resistance and protection against the action of solvents, acids, and moisture making the heating pad very suitable for industrial applications including the warming of batteries. "It is further seen that there is essentially nothing to break in this heatingpad as there are no wires or ribbons to break. Further, the" carbon impregnated resistance sheet of the battery heater of this invention can be produced more economically than a wound-wire battery' heater.
I claim: Q 1. An electrical heating pad comprising,
an electrically conductive sheet of flexible material an envelope of electrically insulative flexible material molded onto and enclosing said sheet, said envelope having a size larger than said sheet so that said.
sheet is completely enclosed therein, t said conductive sheet having a plurality of openings formed therein which receive the flexible material said conductive sheet being stapled together. i 4
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