US3513297A - Heat radiating articles - Google Patents

Description

May 19, 1970 J. P. JORDAN HEAT RADIATING ARTICLES 2 Sheets-Sheet 1 Filed May 31, 19C? FIG.

INVENTOR JOHN PAUL JORDAN ATTORNE S May 19, 1970 Filed May 31, 1967 FIG.

J. P. JORDAN 3,513,297

HEAT RADIATING ARTICLES 2 Sheets-Sheet 2 '20) FIG. 6

INVENTOR JOHN PAUL JORDAN ATTORNEYS United States Patent O 3,513,297 HEAT RADIATING ARTICLES John Paul Jordan, Highland Park, N.J., assignor to Gulton Industries Inc., Metuchen, N..I., a corporation of New Jersey Filed May 31, 1967, Ser. No. 642,534 Int. Cl. Hb 3/34; H01c 3/04; D03d 15/00 US. Cl. 219545 26 Claims ABSTRACT OF THE DISCLOSURE Heat-radiating fabrics are described containing filaments of a plastic electrical resistance material which has a nonlinear positive temperature coetficient of resistance. The filaments are self-regulating and automatically vary their local resistivity according to the heat load in local areas and thereby adjust themselves automatically to limit their temperature in such local areas. The filaments have their maximum dielectric loss factor in the temperature range where maximum generation of heat is desirable.

BACKGROUND OF THE INVENTION I Field of the invention This invention relates to heat-radiating articles of manufacture, a portion of which comprises a fabric material containing electrical resistance filaments capable of providing heat when connected to an electric circuit.

Description of the prior art In the application of heating to homes, there are numerous locations within the home where heat-radiating articles can be used. Currently available electrical heating elements, if used under or in a rug or carpet, or in venetian blinds, curtains, blankets, upholstery, etc., have a hazard that excessively high spot temperatures can be reached if for any reason normal thermal radiation is blocked. Such occurrences could be caused by bunching of curtains, raising of venetian blinds, placement of furniture, toys, etc. on the floor or against the heating element.

Another problem frequently encountered with the use of normal electrical heating means for the home is that high voltages are used, which present an obvious hazard. To permit the use of low voltages (about 20 volts) with normally available heating elements involves the use of heavy wires and multiple connections in order to obtain adequate electric currents. Such means would cause ridges in rugs, objectionable bunching in such applications as curtains, etc., and generally impair the pleasing and decorative appearance of articles in which heating elements are incorporated.

Other disadvantages associated with a thermal floor covering or other heat-radiating article is that cleaning, repair, and maintenance of the heating unit is frequently required and such units require special devices such as thermostats for controlling temperature.

Summary of the invention Accordingly, one aspect of the present invention is to provide heat-radiating fabrics for home furnishings, wearing apparel, etc., which contain filamentary strands of an electrical resistance material which is homogeneous in nature and inherently self-limiting in its maximum temperature when connected by means of electrodes to an electrical circuit due to its non-linear positive temperature coefiicient of resistance.

A still further aspect of the invention is to provide heat-radiating fabrics which eliminate or reduce operational hazards of the prior art.

3,513,297 Patented May 19, 1970 Another aspect of the present invention is to provide heat-radiating fabrics which contain filamentary strands of an electrical resistance material and electrodes woven into the fabric by conventional weaving means.

A further aspect of this invention is to provide elec trical resistance filaments formed primarily of a resistive substance and a non-conductive carrier, the electrical resistance filaments having a positive temperature coeificient which is greater than the temperature coefficient of the resistive substance, and the non-conductive carrier material having a specific electrical resistance and thermal coeflicient of expansion, both much greater than those of the resistive substance.

Other aspects and advantages of the present invention will become apparent from the detailed description that follows and the accompanying drawing wherein:

FIG. 1 is a diagrammatic perspective view of a heatradiating fabric illustrative of one embodiment of this invention;

FIG. 2 is a fragmentary cross-sectional view of FIG. 1 taken on the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view of FIG. 1 taken on the line 3-3 of FIG. 1;

FIG. 4 is a diagrammatic top plan view of the heatradiating fabric of FIG. 1 showing the electrical circuit thereof;

FIG. 5 is a diagrammatic illustration and electrical circuit layout of an alternative arrangement of a heat radiating fabric and its connection to an electric current source;

FIG. 6 is a diagrammatic illustration and electrical circuit layout of another such arrangement; and

FIG. 7 is a diagrammatic illustration and electrical circuit layout of still another such arrangement.

In accordance with the present invention, heat-radiating fabrics are provided which have application in home furnishings such as carpets, rugs, curtains, upholstery, blankets, tapestries, blinds, shades, etc., as well as in heated clothing such as socks, gloves, robes, suits, etc. These heat-radiating fabrics have heating filaments therein formed from an electrical resistance composition which will be hereinafter described.

As used herein the term fabric is intended to include any material or article of manufacture comprising at least in part filaments or fibers, no matter how constructed and regardless of the kind of filament or fiber from which it is made. It includes, but is not limited to fabrics made by weaving, knitting, braiding, etc. The term filament means a single continuous strand of indefinite length as Well as a plurality of strands which have been joined together by twisting or in another manner.

The electrical resistance filaments used herein are formed of an electrical resistance material having the following essential components: (1) one or more resistive substances, and (2) a non-conductive carrier in which the resistive substance is homogeneously distributed. In addition if desired, there may be included in the electrical resistance composition at least one of the following: (a) an insulating material, and (b) an oil having a very low dielectric loss factor which increases only slightly, if at all, with an increase in temperature.

The resistive substance may be one having either a negative or positive temperature coefficient. Any electrically conductive material substantially unaffected by air or moisture or by temperatures of up to about 300 C. is suitable. The use of a moisture free resistive substance will avoid difficulties such as formation of bubbles and holes when the electrical resistance material is processed into a heating filament. Representative examples of resistive substances include carbon materials such as graphite, carbon black and lamp black; metal particles such as metal powders of copper, iron, zinc, magnesium, etc. or particles of heating-wire alloys such as coustantan and nickeline, or alloys such as Monel metal and Phosphor bronze. If desired, the resistive substance may be a mixture of two or more resistive materials, such as a mixture of graphite with carbon black, etc.

The non-conductive carrier material in which the resistive substance is distributed may be selected from any one of the following classes of plastic materials:

(a) polymers of substituted and unsubstituted alphaolefins such as polyethylene, polypropylene, polyisobutylene, polystyrene, etc.;

(b) copolymers obtained by polymerizing two different alpha-olefins such as those listed in (a);

(c) halogenated polymers and copolymers, such as for example, polyvinyl chloride, copolymers of vinyl chloride with vinyl acetate, styrene, propylene, etc.; polymeric halogenated hydrocarbons, e.g. polymers of tetrafluoroethylene etc.;

((1) polyesters, preferably unsaturated polyesters. These polyesters are plastic materials derived from the polymerization of esters in the presence of a peroxide which acts as a hardener. These esters are obtained by reacting an unsaturated dicarboxylic acid with a divalent alcohol. Examples of suitable polyesters are Palatal P5 and Palatal P6;

(e) polyamides, e.g. Versamid (a condensation product of dimerized and trimerized unsaturated fatty acids; in particular linolic acid with polyamides);

(f) other materials such as polyacrylonitrile, polymeric vinyl amines and phenol waxes.

The polyolefins are the preferred non-conductive plastic carriers. However, any non-conductive carrier is suitable which has (1) its highest or a substantial dielectric loss factor in the temperature range where substantial or maximum generation of heat is desirable (that is, up to the selected maximum operating temperature) and a dielectric loss factor that remains substantially constant or decreases beyond the selected operating temperature, and (2) a softening point substantially higher than the maximum operating temperature of the heating element.

The insulating material that may be included in the electrical resistance composition in addition to the resistive material and the carrier material should have the characteristic that its specific electrical resistance and its coefficient of thermal expansion are both higher than the specific electrical resistance and the coefiicient of thermal expansion of the resistive substance. The insulating material preferably should have a specific electrical resistance greater than 10 ohm-cm, and also preferably has a specific electrical resistance of at least 10 times that of the resistive substance. The selection of insulating materials is not critical so long as they meet the criteria mentioned above. The insulating materials which may be employed may be either liquid, solid or tacky materials. Liquid insulating materials which have been found particularly suitable are electrical insulating oils including the following:

(a) Lubricating oils (a distillation product from crude oil, tar, or lignite products which are used for motors and machines). These oils preferably have a flame point of at least 200 C. Examples of such lubricating oils are Mobil Vactra Oil No. 2, No. 3 and No. 4. These oils have a viscosity (centistoke) ranging from 37 to 99 at 50 C.

(b) Transformer oils (a chemically neutral mineral oil which is normally used as insulating filling for electrical transformers) such as, for example, Univolt oils.

(0) Silicone oils (linear-polymeric methyl silicone) e.g. methyl polysiloxane. Preferably the silicone oil has a viscosity at 100 F. ranging from 100 to 20,000 centistokes.

(d) Paraffin oils (a petroleum fraction).

Also suitable as insulating materials are soft pasty materials such as natural or synthetic waxes and lubricating greases. Examples of waxes which may be employed include beeswax, carnauba wax, Castorwax, etc. Also suitable are petroleum waxes, such as parafiin hydrocarbons and microcrystalline waxes. The lubricating greases which may be employed include homogeneous mixtures of a motor lubricating oil with a metal soap, such as obtained from the reaction of a metal hydroxide with a fatty acid. An example of such a metal soap is the lithium soap of l2-hydroxy stearic acid.

The insulating material may also be a solid substance which is easily meltable below the operating temperature of the electrical resistance material. An example of such a material is acetyl cellulose sold under the trademark Cellon. It is also possible to use as the insulating material a solid material such as glass powder, finely divided bentonite, flint, etc.

There may additionally be included in the electrical resistance composition an oil which is characterized by having a low viscosity and a particularly low dielectric loss factor (low dielectric constant and low dissipation factor) which increases only very slightly, if at all, with an increase in temperature. Typical oils which meet this requirement are oils having a dielectric constant (at cycles) below about 2.3 at C., a dielectric dissipation factor below about .001 at 60 C., a maximum viscosity (centistokes) of about 5500 at 20 C. and 500 at 50 C., and which may be primarily composed of to 69% paraffin fraction, about 22 to 28% naphthene fraction and about 5 to 12% aromatic fraction.

There is a relatively wide range of proportions in which the above enumerated materials may be present in the electrical resistance composition. The resistive substance either alone or in combination with the low-dielectricloss-factor oil described above is preferably used in the electrical resistance composition in an amount between about 60 to 110 percent by weight of the non-conductive carrier. When using the low-dielectric-loss-factor oil, which is not essential to the composition, the oil may be present in an amount between about 0.5 to about 20 percent by weight of the resistive substance, and is preferably between about 5 and 110% by weight of the resistive substance. When it is desired to include an insulating material in the liquid or pasty state (at room temperature) in the electrical resistance composition, such a material may be present in an amount between about 7 and 25% by weight of the resistive substance, whereas when the insulating material is a solid such as glass powder, it is employed preferably in an amount between 50 and percent by weight of the resistive substance. The reason for employing a greater quantity of the insulating material when solid than when liquid or pasty is that the solid material does not have a thermal coefficient of expansion as great as that of the liquid or pasty material, and this factor is compensated for by employing more of the solid insulating material.

The various electrical resistance compositions described above, which are extruded into filaments as will later be described, may be prepared in a number of ways. If the electrical resistance composition is to comprise only a resistive substance and a non-conductive carrier, the resistive substance, which preferably exists in finely divided form (e.g. a granular powder) is first mechanically premixed with the non-conductive plastic carrier material (e.g. polypropylene which may be in powder or pellet form. The resistive granular powder particles preferably have a size of about 0.01 mm., but it is possible to employ a granular powder having a particle size between 0.002 and 0.1 mm. The non-conductive carrier-material particles may have an even wider size range. The premixture of resistive substance and non-conductive plastic carrier is heated until 'a homogeneous product is obtained which can no longer be separated. For this operation a dispersion kneader, heated mixing rolls or the like may be used. If mixing rolls are used for homogenizing the materials, the temperature of the rolls is adjusted in accordance with the type of non-conductive plastic carrier material used. The resulting homogeneous mixture of resistive substance and non-conductive plastic is pelletized and then extruded into filaments.

If an electrical resistance composition is desired in which there is incorporated an oil having a low dielectricloss factor, the resistive substance and oil may be mixed in a high-speed fluid mixer for about to minutes at a temperature between about 60 C. and 70 C. This mixing results in the greatest possible dispersion of the oil with the resistive substance. This mixture is then mixed with the non-conductive carrier material as previously described and extruded into filaments as indicated.

If an insulating material is to be included in the electrical resistance composition the following process is suitable. The resistive substance in finely divided form and having a particle size preferably within the range previously described is admixed with the selected insulating material (e.g., lubricating oil). Thorough mixing is desirable in order to obtain a homogeneous combination of the resistive substance and the insulating material. In this combination the individual grains of the resisitive substance are largely surrounded or enveloped by the particles of the insulating material. If the insulating material is liquid, a doughy substance is produced by the mixing of the resistive substance with this material, so that the individual particles of the resistive substance are enveloped by the insulating material. If the resistive substance employed is a porous carbon such as carbon black, and is mixed with a liquid insulating material, the liquid material penetrates into the individual porous carbon particles. The envelopment or surrounding of the individual particles of the resistive substance by the insulating material is not complete, as otherwise no flow of electric current would be possible. Therefore, in the mixture obtained by combining the resistive substance with the insulating material there is obtained a partial contact of the individual resistive particles of the resistive substance with one another throughout the mixture. This partial contact is sufficient for the current to flow through the individual particles.

The mixing of the resistive substance with the insulating material may be carried out in a Henschal mixer or the like. The time required for obtaining a homogeneous mixture is obviously dependent on the amount of material being admixed and the nature of the materials. The temperature employed during the mixing of the resistive substance and the insulating material is selected in accordance with the particular insultaing material being employed.

The homogeneous mixture obtained by combining the resistive substance with the insulating material is then dispersed in the non-conductive carrier material (e.g., polypropylene). This carrier acts primarily as a mechanical support for the resulting electrical resistance material. The introduction of the mixture consisting of the resistive substance and the insulating material into the non-conductive carrier material is achieved according to techniques well known in the art, and is determined by the nature of the carrier and the homogeneous mixture. For example, the non-conductive carrier may be blended with the homogeneous mixture (resistive substance plus insulating material, if used) in a Banbury mixer or the like at temperatures well above the melting temperature of the plastic carrier. The resulting product may be pelletized and extruded to produce filaments, or may be directly extruded.

The mixing of the non-conductive plastic carrier with the homogeneous mixture of resistive substance and insulating material may also be performed by dissolving the plastic in a solvent having dissolving power for the particular plastic being used but inert relative to the homogeneous mixture. Among solvents which are suitable for this purpose are xylene, toluene, benzene, cyclohexane, heptane, dioxane, chloroform, acetone, methylethylketone, tetrahydrofuran and like solvents. The dissolved plastic is added to the homogeneous mixture and homogenized in a fast vibrating 'ball mill or the like.

Any conventional monofilament extrusion equipment may be employed to obtain the filaments. The die may be a straight manifold type, the die opening being a series of small round openings which commonly face downward. After the filaments leave the die, they are run through a quench tank containing water and then taken upon rolls. The diameter of the filaments is preferably in the range from about 6 to 60 mils.

If desired, the monofilaments may be drawn down to a diameter of about 1 mil according to techniques known in the art and subsequently joined together by twisting or the like to produce multifilaments which may be incorporated into the fabric material of this invention.

The electrical resistance composition described herein when extruded into filaments and incorporated into fabrics have been found to give excellent performance up to about 20 watts of heat dissipation per square foot.

The following examples are illustrative electrical resistance compositions extruded into filamentary strands in accordance with the present invention.

EXAMPLE 1 A mixture of parts by weight of resistive substance comprising 70 parts by weight of 10 micron flake graphite (available from the Dixon CO.) and 30 parts by weight of carbon black (available from the Columbia Carbon Co. under the trademark Statex B) is blended with 10 parts by weight of a lubricating oil Vactra No. 2 (available from Mobil Oil Co.) in a Henschal mixer for 15 minutes at 60 C. The resulting powder is blended with polypropylene (EL Rex 11815) in a Banbury mixer for twenty minutes at a temperature of 380 F. in the proportion of 65 percent by weight polypropylene and 35 percent by weight of the blend of the resistive substance and lubricating oil. The resulting homogeneous admixture is pelletized and then extruded at a temperature of 360 F. into strands 8 mils in diameter.

The resulting filament has a room temperature resistance of about 45,000 ohms per inch.

EXAMPLE 2 The same procedure and materials are used as described in Example 1, except that 50 percent by Weight of the resistive substance lubricating oil blend is combined with 50 percent by weight of polypropylene. The resulting filament has resistance of about 20,000 ohms per inch.

A desirable power dissipation for the heat-radiating fabrics of this invention is about 5 watts per square foot. Thus, for -volt applications, with filaments 24 inches long, the filament density would be 65 strands per inch using the 45,000-ohm filaments of Example 1. For 24- volt applications, if the filaments are 12 inches long, the filament density would be about 173 stnands per inch using the 20,000-ohm filaments of Example 2. Using the filaments obtained according to Example 2, and having a llength of 6 inches, requires about 43 filaments per inc Obviously the number of filaments per inch may be varied in accordance with the dissipation power desired, and using shorter lengths reduces the number of strands per inch necessary to obtain the desired dissipation power.

The following examples are illustrative of other electrical resistance compositions which may be extruded into filaments in the manner described in the previous EXAMPLE 3 Oil having low dissipation factordos s -(Edclis- 7 Cable Oil K065 without added resin; this oil has viscosity of 500 centistokes at 50 C.; a molecular weight of 670; a dielectnic constant of 2.26 at 60 C. and a dielectric dissipation factor of 0.001 at 60 C.) 10.00 Polypropylene (Hostalen PPH availavle from Farbwerke Hochst) 100.00

EXAMPLE 4 Parts by weight Mixture of graphite and carbon black (70:30,

same as in Example 1) 100.00 Polypropylene (same as in Example 3) 100.00

'EXAMPLE 5 Parts by weight Graphite (same as in Example 1) 85.00 Oil (same as in Example 3) 5.00 Polyethylene (Lupolen 1812 Ea-vailable from Badische Anilin-Soda Fa-brik CO.) 100.00

EXAMPLE 6 Parts by weight Graphite (same as in Example 1) 90.00 Lubricating oil (same as in Example 1) 10.00 Polystyrene (475 KHavailable from Badische Anilin-Soda Fa-brik C0.) 120.00

EXAMPLE 7 Parts by weight Graphite (same as in Example 1) 65.00 Lamp Black (Corax Lavailable from Degussa Co.) 35.00 Lubricating oil (same as in Example 3) 10.00 Polyester (Palatal P5-available from Badische Anilin-Soda P abrik Co.) 130.00

EXAMPLE 8 Parts by weight Graphite (same as in Example 1) 80.00 Iron powder 20.00 Beeswax 15.00 Polyamide (Versamid-available from Schermg A.G.) 150.00

EXAMPLE 9 Parts by weight Graphite (same as in Example 1) 75.00 Lamp black (same as in Example 7) 15.00 Beeswax (same as in Example 8) 10.00 Polystyrene (same as in Example 6) 200.00

EXAMPLE 10 Parts by weight Graphite (same as in Example 1) 33.00 Iron powder (same as in Example 8) 9.00 Methyl silicone oil (M1000available from Wacker Chemie) 5.00 Polyamide (same as Example 8) 57.00

EXAMPLE 11 Parts by wei ht Graphlte same as in Example 1) 100%00 Methyl sillcone oil (same as in Example 10) 20.00 Polyvinyl chloride (Vinnol P l00 available from Wackcr Chemie) 120.00

EXAMPLE 12 Graphite (same as in Example 1) 10 0.00 Lamp black (same as in Example 8) 10.00 Acetyl cellulose (Cellonavailable from Dynamit Nobel A.G.) 10.00 Polyisobutylene (Oppanol B-available from Badische Anilin-Soda Fabrik) 150.00

The heat-radiating articles of this invention are preferably composed at least in part of natural or synthetic fibers, the selection of which depends on the end use contemplated for the fabric. Illustrative of fibers for making fabrics include: nylons, e.g. polycaprolactam, polyhexamethylene adipamide, polyhexamethylene sebacamide, as well as other polyamides; polyesters, e.g. polyethylene terephthalate; celluloses, e.g. cotton, viscose rayon, cellulose acetate, alginate, cuprammonium rayon, etc.; acrylics, e.g. copoly'mers of acrylonitrile with vinyl acetate or acrylic esters; polyolefines, e.g. polypropylene, polythylene, etc.; proteins, e.g. wool, casein, zein, etc.; vinyls, e.g. polyvinyl alcohol, polyvinyl acetate, polyvinylchloride; fluorocarbons, e.g. polytetrafiuoroethylene; polyurethanes, e.g. Lycra, etc.

The manner of incorporating the electrical resistance filaments into fabrics will now be described with reference to the drawings.

Referring first to FIGS. l-2, in FIG. 1 there is shown a diagrammatic perspective view of a carpet 10 comprising a woven pile fabric 11 and a backing 12 secured to the pile fabric 11 by adhesive, or the like.

The pile fabric 11 comprises a plurality of warp threads 13 and a plurality of weft threads 14 woven by known weaving means, as illustrated in FIGS. 2 and 3. The pile or nap 24 of the pile fabric 11 may be formed in any conventional manner, but as shown, comprises a plurality of fiber threads 25 which may be secured to the warp in any conventional manner such as. by frictional engagement between the adjacent warp and weft threads or by knotting. A plurality of plastic filamentary electrical resistance elements 15, whose composition and manufacture have been described in the above examples, may be woven into pile fabric either as warp or weft threads in one direction only. The filamentary electrical resistance elements are illustrated in FIG. 1 as being woven into the fabric as weft threads. The manner of such filamentary electrical resistance elements per inch of woven fabric may be varied as heretofore described, to obtain desired power dissipation values. The filamentary electrical resistance elements are connected with an electric current source 16 by means of terminal leads 17 and 18 and electrodes 19 and 20. Each of electrodes 19 and 20 may comprise fine copper wire or the like and may be woven into the fabrics, either as warp or weft threads depending upon the direction the filamentary electrical resistance elements are woven into the fabric.

The general arrangement of the resistance elements 15 and conductive elements 19, 20 in one form may be as shown in FIG. 4, from which the normal carpet warp and weft threads have been omitted for clarity. Here, the resistance elements 15 run horizontally of the figure, preferably but not necessarily equally spaced, and at each end contact the vertically running conductive elements 1'9, 20 which act as distributor electrodes or current headers to feed current to the resistance elements 15 in parallel. It will be understood that the diameter, resistivity and number of filamentary resistance elements per inch are chosen in relation to the applied voltage, to produce the desired power dissipation for the heating purpose at hand.

The conductive elements 19, 20 may be sewed rather than woven in place, or alternatively may be formed of foil strip suitably adhered to the edges of the fabric to maintain contact with the resistance elements 15', or may be a conductive strip painted or deposited on the fabric edges in contact with the resistance elements 15 or formed in other ways suitable for connecting the resistance elements 15 to source 16.

In some fabrics, the spacing between conductive ele ments 19, 20 (when at the fabric edges) may be longer than desired. An alternative arrangement is shown in FIG. 5, in which subsidiary conductive elements 21, 22 extend horizontally from each main element 19 or 20 toward the other, either terminating before reaching the opposite main element, or crossing it in spaced insulated relation, as at 119, 120, for example. In this case the resistance elements run vertically in the figure, in electrical contact with the conductive sub-elements 21, 22 as they cross. Thus, the spacing between adjacent conductive sub-elements 21, 22 determines the effective length of resistance element 15 across which the source 16 voltage is applied, permitting any desired effective length, independent of the fabric width.

Another arrangement is shown in FIG. 6 in which a plurality of conductive elements extend vertically in the figure, alternate ones such as 19, 19a being connected together at one end to one terminal 17 and the intermediate ones, such as 20, 20a, being connected together and to the other terminal 18. In this way also, the effective length of the horizontally extending resistance elements 15 may be selected as desired, by suitably choosing the spacing between adjacent conductive elements. It will be understood that any desired number and spacing of conductive elements may be used as circumstances dictate.

When the conductive elements are spaced at a substantial distance from each other, e.g. more than about 12 inches, it may be desirable to weave into the fabric intermediate floating elements 23 which are not connected with the current supplying elements 19, 210, 21, 22. These floating elements 23 which may be spaced apart at any desired distance, are woven in the pile fabric of the carpet either parallel or at right angles to conductive elements 19, 20, so long as they are at an angle (preferably a right angle) to the resistance elements 15. For example, FIG. 7 shows an arrangement similar to FIG. 4, but with added floating conductive elements 23, interposed between the conductive elements 19, 20 and parallel there-With. Floating elements 23 are not directly connected to the current supplying elements 19, 20, except through the resistance elements 15.

The desirability of using floating elements 23, arises from the special property of the resistance elements 15, that when heat dissipation from a local area of an element 15 is impaired, this material substantially increases its resistivity, which may block current flowing in the elements 15 and reduce heat dissipation from other areas through which the same elements extend, even though spaced from the blocked area. If this should happen, then floating elements 23 would distribute current to such other areas, notwithstanding that the resistivity of some elements 15 may be increased in the blocked area.

Such floating conductive elements may be used with any configuration of resistance and conductive elements, but should be kept out of direct contact with the currentsupplying conductive elements, which may be accomplished by any techniques well known in the art.

Other modifications in the construction of the heat radiating articles are possible. For example, the conductive elements may be secured to the pile fabric by stitching, cementing or other means rather than being woven inte the fabric. Similarly, the filamentary resistance elements need not necessarily be woven into the fabric, but may be secured thereto by other suitable means such as cementing, stitching, etc. Also the conformation of the conductive elements is not critical, except to the extent that they should be pliable if the heat radiating article is itself pliable.

In any of the above forms of the invention, where two conductive elements are joined, their electrical connection may be made by spot-Welding or soldering, or in many cases merely by their contact with one another, since their contact resistance will be low relative to the resistance of the resistance elements fed thereby.

Since both the filamentary electrical resistance elements described herein and the electrically conductive elements may be woven into a fabric by conventional techniques, heat-radiating draperies and other articles may be manufactured which maintain their decorative appearance because both the heating elements and the conductive elements are an integral part of the fabric. In addition, the filamentary electrical resistance elements may be incorporated into knitted or non-woven fabrics to provide heat-radiating articles such as socks, gloves, and other wearing apparel.

The explanation of the manner in which the filamentary electrical resistance elements are believed to function is fully described in the copending applications of Hummel et al., Ser. No. 578,133, filed Sept. 9, 1966 and of Philipp, Ser. No. 603,761, filed Dec. 22, 1966.

While certain preferred embodiments of the invention have been described herein, it is to be understood that the invention is not limited thereto, but is defined by the appended claims.

What is claimed is:

1. A heat radiating article of manufacture comprising a fabric portion made up at least in part of a plurality of plastic filamentary electrical resistance elements and electrically conductive means forming part of said fabric portion for electrically connecting said filamentary electrical resistance elements with an electrical current source, said filamentary electrical resistance elements extended along said fabric in one direction only and said filamentary electrical resistance elements during the passage of current therethrough automatically increasing and decreasing the resistance of individual regions of said filamentary elements in accordance with the dissipation of heat from said individual regions.

2. A heat radiating article according to claim 1 wherein said electrically conductive means comprise at least two opposed spaced conductive elements in electrical contact relationship with said filamentary electrical resistance elements.

3. A heat radiating article according to claim 2 wherein said conductive elements extend along said fabric portion at substantially right angles to the direction of said filamentary electrical resistance elements.

4. A heat radiating article of manufacture comprising a fabric portion at least in part made up of a plurality of plastic filamentary electrical resistance elements, and electrically conductive means forming part of said fabric portion for electrically connecting said filamentary electrical resistance elements with an electrical current source, wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and (b) a plurality of intermediate conductive elements located between said terminal portions and substantially parallel therewith, alternate ones of said intermediate elements being in electrical contact relationship with the same terminal portion, said intermediate elements intersecting and being in electrical contact relationship with said plastic filamentary electrical resistance elements at their points of intersection.

5. A heat radiating article according to claim 4 wherein'said filamentary electrical resistance elements extend along said fabric portion in one direction only.

6. A heat radiating article according te claim 5 wherein said terminal portions and said intermediate conductive elements are woven in said fabric portion and wherein said fabric portion is a woven fabric.

7. A heat radiating article according to claim 6 wherein said filamentary electrical resistance elements and said conductive elements are woven in said fabric such that they are substantially at right angles to each other.

8. A heat radiating article of manufacture comprising a fabric portion at least in part made up of a plurality of plastic filamentary electrical resistance elements, and electrically conductive means forming part of said fabric portion for electrically connecting said filamentary electrical resistance elements with an electric current source, wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and (b) a plurality of intermediate conductive elements located between said terminal portions and substantially parallel therewith, said intermediate conductive elements being at substantially right angles to said plastic filamentary electrical resistance elements and in electrical contact relationship with said plastic filamentary electrical resistance elements at their point of intersection and said conductive elements being out of electrical contact with respect to said terminal portions.

9. A heat radiating article according to claim 8 wherein said filamentary electrical resistance elements extend along said fabric portion in one direction only and said intermediate conductive elements and said filamentary electrical resistance elements are woven in said fabric portion.

10. A heat radiating article of manufacture comprising a fabric portion at least in part made up of a plurality of plastic filamentary electrical resistance elements, and electrically conductive means forming part of said fabric portion for electrically connecting said filamentary electrical resistance elements with an electrical current source, wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and (b) a plurality of intermediate conductive elements substantially at right angles to said terminal portions and to said plastic filamentary electrical resistance elements and wherein alternate ones of said intermediate conductive elements are in electrical contact relationship with the same terminal portion.

11. A heat radiating article according to claim 10 wherein said filamentary electrical resistance elements extend along said fabric portion in one direction only and wherein said terminal portions, said intermediate conductive elements and said filamentary electrical resistance elements are woven in said fabric portion.

12. A heat radiating article of manufacture which comprises a fabric portion made up at least in part of a plurality of plastic filamentary electrical resistance elements extending along said fabric in one direction only, and electrically conductive means forming part of said fabric portion electrically connecting said filamentary electrical resistance elements with an electrical current source, said filamentary electrical resistance elements comprising: a. resistive substance and a non-conductive plastic carrier, said non-conductive carrier having a specific electrical resistance and coetficient of thermal expansion, respectively, greater than that of said resistive substance, said resistive substance being uniformly distributed in said filamentary electrical resistance elements, said filamentary electrical resistance elements having a positive temperature coefiicient of resistance, and said filamentary electrical resistance elements during the passage of current therethrough automatically increasing and decreasing the resistance of individual regions of said filamentary elements in accordance with the dissipation of heat from said individual regions.

13. A heat radiating article of manufacture which comprises a fabric portion at least in part made up of a plurality of plastic filamentary electrical resistance elements, and electrically conductive means forming part of said fabric portion electrically connecting said filamentary electrical resistance elements with an electrical current source, said filamentary electrical resistance elements comprising: a resistive substance and a non-conductive plastic carrier, said non-conductive carrier having a specific electrical resistance and coefiicient of thermal expansion, respectively, greater than that of said resistive substance, said resistive substance being uniformly distributed in said filamentary electrical resistance elements, said filamentary electrical resistance elements having a positive temperature coeflicient of resistance, and said filamentary electrical resistance elements during the passage of current therethrough automatically increasing and decreasing the resistance of individual areas of said filamentary elements in accordance with the dissipation of heat from said individual areas, said filamentary electrical resistance elements including at least one member selected from the class consisting of (1) a low viscosity oil having a low dielectric constant and dissipation factor, said oil being present in said filamentary electrical resistance elements in an amount between about 0.5 to about 20% by weight of the resistive substance, and (2) an insulating material having a specific electrical resistance greater than 10 ohm-cm., said insulating material having a greater coefficient of thermal expansion than said resistive substance and being present in said filamentary electrical resistance elements in an amount between about 7 and about 25% by weight of the resistive substance.

14. A heat radiating article according to claim 13, wherein said non-conductive carrier is characterized in that its dielectric loss factor remains substantially constant or decreases beyond the maximum operating temperature of said filamentary electrical resistance elements.

15. A heat radiating article according to claim 14 wherein said non conductive carrier is a polypropylene.

16. A heat radiating article according to claim 13 wherein said insulating material is selected from the class consisting of lubricating oils, transformer oils, silicone oils and parafiin oils.

17. A heat radiating article according to claim 13 wherein said electrically conductive means comprises at least two opposed spaced conductive elements in electrical contact relationship with said filamentary electrical resistance elements and wherein said conductive elements extend along said fabric portion at substantially right angles to the direction of said filamentary electrical resistance elements.

18. A heat radiating article according to claim 13 wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and (b) a plurality of intermediate conductive elements located between said terminal portion and substantially parallel therewith, at least some of said intermediate elements being in electrical contact relationship with one of said terminal portions, said intermediate elements intersecting and being in electrical contact relationship with said plastic filamentary electrical resistance elements at their points of intersection.

19. A heat radiating article according to claim 18 wherein alternative ones of said intermediate conductive elements are connected to the same terminal portion, and said filamentary electrical resistance elements extend along said fabric portion in one direction only.

20. A heat radiating article according to claim 19 wherein said filamentary electrical resistance elements and said conductive elements are woven in said fabric such that they are at right angles to each other.

21. A heat radiating article according to claim 13 wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and a plurality of intermediate conductive elements located between said terminal portions and substantially parallel therewith, said intermediate conductive elements being at substantially right angles to said plastic filamentary electrical resistance elements and in electrical contact relationship with said plastic filamentary electrical resistance elements at their point of intersection and. said conductive elements being in a non-electrical contact relationship with said terminal portions.

22. A heat radiating article according to claim 21 wherein said filamentary electrical resistance elements extend along said fabric portion in one direction only and said intermediate conductive elements and filamentary electrical resistance elements are Woven in said fabric portion.

23. A heat radiating article according to claim 13 wherein said electrically conductive means comprises (a) two opposed spaced terminal portions adapted to be connected to respective terminals of an electrical current source and (b) a plurality of intermediate conductive elements substantially at right angles to said terminal portions of said plastic filamentary electrical resistance elements and wherein alternative one of said intermediate conductive elements are in electrical contact with the same terminal portion.

24. A heat radiating article according to claim 23 wherein said filamentary electrical resistance elements extend along said fabric portion in one direction only and wherein said terminal portions, said intermediate conductive elements and said filamentary electrical resistance elements are woven in said fabric portion.

25. A heat radiating article according to claim 13 wherein said fabric portion of said heat-radiating article is a woven fabric.

26. A heat-radiating article according to claim 13 wherein said article is a carpet.

References Cited UNITED STATES PATENTS Hall 219-52 Adamson 219-54 Jacob 338-2C Hunter 219-535 I Spier et a1. 219-52 York et al. 219-52 Freedlander 219-52 Lichtenstein 219-52 Asakawa 338-224 I Williams 219-21 Van Eeck 219-52 Morey 338-20 VOLODYMYR Y. MAYEWSKY, Primary Examiner US. Cl. X.R. 219-529, 549; 338-20 8

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