WO2007065773A1

WO2007065773A1 - Heating element particularly for obtaining an electric blanket

Info

Publication number: WO2007065773A1
Application number: PCT/EP2006/068415
Authority: WO
Inventors: Gino Tonello; Mirko Tonello
Original assignee: Gino Tonello; Mirko Tonello
Priority date: 2005-12-07
Filing date: 2006-11-14
Publication date: 2007-06-14
Also published as: ITTV20050193A1

Abstract

A heating element (1), particularly for obtaining an electric blanket, comprising a first sheet (2) and a second sheet (3) which are flexible and between which at least one first coiled electrical cable (4) is interposed, the cable (4) being constituted by a bundle (4a) of carbon fibers surrounded by a first sheath (4b) made of insulating material and connected, at its ends, to a pair of second electrical cables (5) made of a metallic conductor (6); at least one heat-conducting silicone layer (11) is distributed uniformly between the first and second sheets (2,3) and covers approximately completely the at least one first electrical cable (4) and is adapted to improve the heat exchange between the cable (4) and the first and second sheets (2,3).

Description

HEATING ELEMENT PARTICULARLY FOR OBTAINING AN ELECTRIC BLANKET

Technical Field

The present invention relates to a heating element particularly for obtaining an electric blanket.

Background Art

Electric blankets are currently used to preheat tires in car and motorcycle races, gas tanks located in cold regions or buried underground, small spaces such as for example the interior of campers or camping tents, walls and floors of buildings, and other similar applications.

These known types of electric blanket are generally constituted by at least two layers of fabric, between which at least one heating element is interposed; such heating element is typically constituted by two flexible sheets, generally made of heat-resistant fabric, between which electrically heatable means are interposed, such means being usually constituted by a coil which is obtained by means of an electrical cable made of a metallic conductor, which is externally insulated and can be connected at its ends to an electric power source, typically at low voltage.

By supplying power to the coil, the metallic conductor is crossed by current and is heated due to the Joule effect; from the coil, the heat is transmitted, mainly by conduction, to the adjacent flexible sheets, heating them, and then flows toward the outside of the electric blanket, so as to heat the body wrapped therein.

The main drawback of these known types of heating element is that the heat is not transmitted uniformly over the entire surface of the flexible sheets, and therefore the heating element has considerable temperature gradients among its various regions, which can compromise the correct heating of the body to be heated; in particular, the temperature can be very high at the coil, with the risk of damaging the body to be heated.

This drawback is particularly harmful in the case of tires for car or motorcycle races, since heating must be as uniform as possible in order to improve their performance; further, it is observed that the high temperature at the coil can produce on the surface of the tires localized melting which can compromise their performance irreparably.

Disclosure of the Invention

The aim of the present invention is to solve the above-mentioned problems, eliminating the drawbacks of the cited background art, by providing a heating element, particularly for obtaining an electric blanket, which has a substantially uniform operating temperature, so as to be able to achieve the most uniform possible heating of the body to be heated.

Within this aim, an object of the invention is to provide a heating element which allows to heat a given body without the danger of damaging it.

Another object is to provide a heating element which is structurally simple and has low manufacturing costs.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by a heating element, particularly for obtaining an electric blanket, which comprises a first sheet and a second sheet which are flexible and between which at least one first coiled electrical cable is interposed, characterized in that said at least one first electrical cable is constituted by a bundle of carbon fibers surrounded by a first sheath made of insulating material and connected, at its ends, to a pair of second electrical cables made of a metallic conductor, at least one heat- conducting silicone layer being distributed uniformly between said first and second sheets and covering approximately completely said at least one first electrical cable and being adapted to improve the heat exchange between said cable and said first and second sheets.

Brief description of the Drawings

Further characteristics and advantages of the invention will become better apparent from the following detailed description of a particular but not exclusive embodiment thereof, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figures 1 to 4 are schematic views of steps of the production of a heating element according to the invention;

Figures 5 to 7 are schematic views of steps of the method for connecting the first electrical cable made of carbon fiber to a second electrical cable made of a metallic conductor of a heating element according to the invention;

Figure 8 is a perspective view of another embodiment of a heating element according to the invention.

Ways of carrying out the Invention

It is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer.

With reference to the figures, the reference numeral 1 generally designates a heating element particularly for obtaining an electric blanket, not shown in the accompanying figures.

The heating element 1 comprises a first sheet and a second sheet, which are flexible, are designated respectively by the reference numerals 2 and 3, and are advantageously made of a heat-resistant material, such as for example a fabric made of polyester fiber or pile, or the material known by the trade-name Kevlar.

As an alternative, as shown in Figure 8, the first and/or second sheets can be made of silicone loaded with copper or magnesium powder, so as to achieve an increase in the heat capacity of the heating element 1 ; in the example shown in Figure 8, only the first sheet 2 is made of silicone loaded with copper or magnesium powder, while the second sheet 3 is made of a fabric, for example polyester fiber or pile.

At least one first coiled electrical cable 4 is interposed between the first sheet 2 and the second sheet 3 and is constituted advantageously by a bundle 4a of carbon fibers and is surrounded by a first sheath 4b made of insulating material, such as for example a silicone resin.

The first electrical cable 4 is connected, at its two ends, to two second electrical cables 5, which are made of a metallic conductor 6, for example copper, which is wrapped in a second sheath 7 made of insulating material; in the example shown in the accompany figures, only one of the two second electrical cables 5 is shown.

The two second electrical cables 5 protrude from either the first or the second sheet in order to allow the connection of the first electrical cable 4 to an electric power source, not shown in the accompanying figures.

Advantageously, as shown in Figures 5, 6 and 7, the first and second sheaths are partially removed at a first end and at a second end respectively of the first and second electrical cables; the second sheath 7 is advantageously removed by an extent which is longer than the first sheath 4b.

The free portion of the metallic conductor 6 provided at the second end of the second electrical cable 5 is wound in a spiral so as to cover approximately completely the first end 4c of the first conductor 4, forming at least one noose 8 which winds around the first sheath 4b, so as to constitute a means for coupling thereto.

The second end of the second electrical cable 5, which surrounds approximately completely the first end 4c of the first electrical cable 4, in turn is covered approximately completely by at least one covering element, such as for example tin 9, which can be advantageously covered by a heat- shrinking sheath 10 made of electrically insulating material.

Advantageously, at least one layer 11 of heat-conducting silicone is arranged between the first sheet and the second sheet and is adapted to improve the heat exchange between the first electrical cable 4 and the first and second sheets and covers approximately completely the first electrical cable 4. Advantageously but not necessarily, in the regions comprised between the various turns of the coil formed by the first electrical cable 4 it is possible to provide a stitched seam 12, which connects the first and second sheets to each other, preventing their accidental separation.

Operation is therefore as follows: after arranging the first electrical cable 4, connected beforehand to the second electrical cables 5, on the first sheet 2, the layer 11 of heat-conducting silicone is distributed in the liquid state so as to cover the first sheet 2 and the first electrical cable 4 and then said sheet and cable are covered by the second sheet 3.

Once it has hardened, possibly with the aid of appropriate hot pressing and blowing, the layer 11 rigidly couples the first and second sheets and the first electrical cable 4.

Any stitched seams 12 help to keep mutually coupled the first and second sheets, preventing their accidental separation.

The heating element 1 can then be enclosed between two or more layers of fabric or other material in order to obtain for example an electric blanket.

By supplying power to the first electrical cable 4, said cable is crossed by an electric current and is heated; the heat generated by the first electrical cable 4 is then transmitted to the first and second sheets, heat conduction being improved due to the presence of the layer 11 of heat- conducting silicone.

Thanks to the presence of the layer 11, heat is transferred in a relatively short time from the first electrical cable 4 to the first and second sheets, thus preventing the first electrical cable 4 from overheating and damaging the body to be heated.

Thanks to the presence of the layer 11, maximum temperature gradients of less than approximately 2°C have been achieved in steady-state conditions between the first electrical cable 4 and the first and second sheets. By providing, as described earlier, the first and/or second sheets by using silicone loaded with copper or magnesium powder, it is further possible to maintain for a long time (for example even for fifteen minutes), without an electric power supply, the temperature of the heating element 1 at a value close to the one reached when the first electrical cable 4 is supplied with power.

It has thus been shown that the invention has achieved the intended aim and objects, a heating element, particularly for obtaining an electric blanket, having been provided which by virtue of the presence of the layer of heat-conducting silicone has a substantially uniform operating temperature and therefore allows to achieve substantially uniform heating of the body to be heated.

Further, also thanks to the presence of the layer of heat-conducting silicone, transmission of heat from the electrical conductor to the first and second sheets is very quick, and therefore excessive overheating of the metallic conductor is avoided, thus ensuring perfect preservation of the body to be heated.

Moreover, by providing one or both of the first and second sheets by using silicone loaded with copper or magnesium it is possible to maintain for a certain time the temperature of the heating element at a value which is close to the steady-state value even without supplying power to the electrical cable.

Moreover, the production costs of the heating element according to the invention remain low, since it is constituted only by components which are easily available or simple to manufacture and assemble.

The invention is of course susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

The materials used, as well as the dimensions that constitute the individual components of the invention, may of course be more pertinent according to specific requirements. The various means for performing certain different functions need not certainly coexist only in the illustrated embodiment but can be present per se in many embodiments, including ones that are not illustrated.

The characteristics indicated as advantageous, convenient or the like may also be omitted or be replaced with equivalents.

The disclosures in Italian Patent Application No. TV2005A000193 from which this application claims priority are incorporated herein by reference.

Claims

1. A heating element, particularly for obtaining an electric blanket, comprising a first sheet and a second sheet which are flexible and between which at least one first coiled electrical cable is interposed, characterized in that said at least one first electrical cable is constituted by a bundle of carbon fibers surrounded by a first sheath made of insulating material and connected, at its ends, to a pair of second electrical cables made of a metallic conductor, at least one heat-conducting silicone layer being distributed uniformly between said first and second sheets and covering approximately completely said at least one first electrical cable and being adapted to improve the heat exchange between said cable and said first and second sheets.

2. The heating element according to claim 1, characterized in that said first and/or second sheets are made of silicone loaded with copper or magnesium powder.

3. The heating element according to one or more of the preceding claims, characterized in that said layer of heat-conducting silicone is spread in the liquid state so as to cover said first sheet and said first electrical cable, said second sheet being arranged so as to cover said layer of heat- conducting silicone in the liquid state, said layer rigidly coupling, once it has hardened, said first and second sheets and said first electrical cable.

4. The heating element according to one or more of the preceding claims, characterized in that said second electrical cables protrude from said first or second sheet in order to allow the connection of said first electrical cable to an electric power source.

5. The heating element according to one or more of the preceding claims, characterized in that said first and second sheaths are partially removed at a first end and a second end, respectively, of said first and second electrical cables, said second sheath being removed by an extent which is longer than said first sheath, the portion of free metallic conductor provided at said second end of said second electrical cable being wound in a spiral so as to cover approximately completely said first end and forming at least one noose which winds around said first sheath, so as to constitute a means for coupling thereto, said second end being approximately completely coverable by at least one layer of tin or other metal or covering element.

6. The heating element according to claims 1 and 5, characterized in that said layer of tin or other metal or covering element is covered by a heat- shrinking sheath made of electrically insulating material.

7. The heating element according to one or more of the preceding claims, characterized in that in the regions between the various turns of the coil formed by said first electrical cable there is a stitched seam which joins said first and second sheets to each other, preventing accidental separation thereof.