FR2623961A1 - Heating film with variable power per unit length - Google Patents

Abstract

The invention relates to electrical heating films in strips, intended for producing heating surfaces such as heating ceilings or floors or for incorporation in heating appliances. The invention consists in that they include, between two insulating films, flat resistors in the form of strips of conductive material or which are obtained from a film coated on one of its sides with a previously stabilised conductive layer 2, 3 based on carbon black, and which are arranged transversely with respect to the length of the insulating films and are connected electrically at each of their ends to longitudinal electrical supply strips 4, 5 made of copper for example, these resistors being more or less separated from one another so that the completed heating film has a predetermined variable calorifc power per unit length which thereby meets variable mechanical and thermal requirements.

Description

"Heating film with variable linear power
The present invention relates to electric heating films in all their fields of application.

We will quote
- the interposition between thermal insulation and protective facing, as for example for the production of heating surfaces in the building,
- incorporation in heaters.

 The heating films are generally composed of two plastic films ensuring the maintenance and electrical insulation of the resistors and conductors arranged between them.

There are two families
The first consists of a resistive circuit printed with a tin base, of sufficient length taking into account the low resistivity of this metal, connected at its ends and on demand, to cold connection devices.

 For the second family, a surface coated or impregnated with carbon is fed. two side electrodes. The carbon part, subjected to a potential difference, heats over its entire surface. From a mother reel of such a film, more or less long heating elements can be obtained on request.

 The calorific power is the product of the linear power predetermined by the length of the element.

 The manufacture of such heating films and their use poses problems not only for adaptation to the implementation but also for obtaining the linear powers usually sought.

 The linear power of the carbon film is a function of the thickness of the carbon layer.

Its calibration, for the usually exploitable power range (heat requirements and temperature resistance of the insulating films) must be extremely precise.

 Furthermore, this carbon layer does not see its ohmic value really determined until after a few weeks of "maturation" during which the arrangements of the carbon particles stabilize.

 It is difficult to obtain linear powers suitable for all application cases.

 The generally adopted solution is, for printed circuit films, to produce heating elements of different lengths, widths, linear powers and supply voltages. Thus, for the realization of the heating ceiling of a typical example, it is planned to install 29 elements, 17 of which are different from each other, in 3 different widths, 2 different linear powers and 2 voltages, certain elements being supplied in series.

 For carbon-coated heating films, the implementation involves the production of more or less long elements, of different linear power, chosen from the films available.

 Furthermore, the tolerance allowed, for the linear power of the heating films, is + 5 - 10% of the nominal power, which makes the desired thermal result random.

Their implementation must therefore meet
- on the one hand to the calorific needs of equipped premises. For the same construction, these heat requirements are variable from one room to another and variable in the same room.

 - on the other hand to an adaptation case by case, to each type of construction whose ceilings or other constituent elements are generally screened.

 The implementation uncertainties are thus at the origin either of poor thermal efficiency, or of poor comfort for the user, or even of economic penalty.

 As we are going to show, the present invention provides a solution both in terms of obtaining precise calorific powers and in responding to thermal and mechanical problems of implementation, taking into account variable needs.

 According to the invention, one begins by producing a thin film preferably carbonaceous.

 This film can be made of synthetic material, for example from the family of polyesters, of great length and common width. It is coated with a carbon layer according to the usual methods of coating, bonding with a solvent or any other process, on one of its faces.

 It can also be the support for any other conductive material which can constitute an electrical resistance, deposited and fixed by any means.

 The electro-resistant layer is calibrated in thickness according to the usual methods.

 Coils of coated film are thus obtained which are left to stabilize (in the case of a carbonaceous layer).

 One of the important aspects of the invention is that it is no longer necessary, as will be seen later, to constitute manufacturing batches of very different powers. In practice we can be satisfied with a single value.

 These coils are then cut into longitudinal strips, of great length, at the desired width.

 These strips are used to produce the heating film with variable linear power proper, object of the present invention.

This heating film is produced by juxtaposition / bonding according to lamination methods
- a lower insulating support film, for example polyester or polyethylene / polyester complex from a reel of great length and the desired width
- elements of electro-resistant strips described above, arranged transversely to the long length of the support film, more or less spaced apart according to their own unit power and the final power sought for the finished heating film
- two conductors consisting, for example, of thin copper strips, each arranged at one end of the elements of electro-resistant strip, therefore perpendicular to the latter
- a second upper insulating film of the same type as the lower insulating support film.

 One of the important aspects of the invention is that the electro-resistant film can be produced in a power range of the order of twice the usual power. The thickness of the coating is therefore greater and easier to adjust. The cutting into strips makes it possible to continuously control the value of the resistance between two points whose spacing can correspond to the width of the active part of the heating film produced according to the invention.

 Furthermore, it is also easy to cut strips of different widths to obtain greater powers or finer adjustments of the power of the heating film.

 Finally, it becomes possible to use batches of electro-resistant films whose power would be out of tolerance by adjusting the width of the strips or their spacing.

 Another important aspect of the invention is its adaptability to all the cases of implementation.

 In fact, it becomes possible to produce a heating film having, on request, more or less heating parts, non-heating parts, but nevertheless comprising the lateral conductors allowing either fixing or overlapping of parts which should not be heated, or else the electrical connection to the network, as well as parts comprising neither electro-resistant bands nor conductors, and thus obtaining a very long heating film comprising all the heating elements of an installation. The realization, the manufacturing control, the marking are easily programmable from initial data such as customer, thermal study, implantation study, etc ...

 It also becomes possible, from the heating film which is the subject of the invention, to continuously produce heating coatings in coils comprising, in addition to the film, a flexible decorative coating and, in opposition, a thermal insulator. These heating coatings, arranged in parallel strips can all be electrically connected, at one end, for example by plugging into a specialized profile. Such an embodiment is in practice impossible to achieve with films at constant linear power except to have films of thermal values very different from each other and to bear a significant economic and technical handicap.

 The non-conductive parts, that is to say having neither side electrodes nor carbon bands are themselves electrically insulated when cutting a heating element, which avoids electrical isolation operations on construction sites.

 The parts comprising only the side electrodes can be cut or precut to allow either the obtaining of "plugs" for electrical connection at the end of a heating element, or a reduction in the resistance to bending, or the passage of foreign elements through the heating system. They ensure the continuity of the electrical supply to the different heating parts. Their arrangement means that, without taking into account very low pressure drops over very long lengths, the electrodes provide an electrical supply "in parallel" to all the transverse electro-resistant bands.

 Another important aspect of the invention is that if an electro-resistant strip has a fault which may be a cut, for example, this only affects the strip itself with the sole consequence of a minimum loss of power. This is to be contrasted with what happens when a continuous carbon-coated heating film is damaged for any reason. In this case, we observe the appearance of small sparks which have the consequence, due to the resulting heating, of the progressive elongation from the initial cut to the total cut of the resistance, thus affecting the whole heating surface.

Other advantages and characteristics of the invention will emerge from the description which follows, by way of nonlimiting examples, and with reference to the attached drawings in which
- Fig. 1 is a cross-sectional view of the heating film which is the subject of the invention.

 - Fig. 2 is a view in longitudinal section of said heating film.

 - Fig. 3 is a table showing a sequence for preparing the heating film.

 - Fig. 4 / table showing a response of an element of heating film to the heat losses of a room.

 - Figs. 5a and 5b are also tables explaining responses to heat losses.

 - Fig. 6 is a plan view of a heating element produced according to the invention.

 - Fig. 7 is a plan view of a modular heating element produced according to the invention.

 - Fig. 8 is a schematic cross section showing a heating element disposed between a thermal insulating mat and a facing plate.

 - Fig. 9 is a schematic longitudinal section of a modular type heating element secured on one of its faces to thermal insulation mats.

 - Fig. 10 is a schematic section of a modular type heating element disposed between ceiling tiles placed on exposed framework and adjacent thermal insulation mats.

 - Fig. lt is an exploded perspective view of a heating film facing assembly and flexible thermal insulation on a reel.

 Fig. 1 shows a cross section of the heating film object of the invention essentially comprising a lower support film 1 on which is disposed an electro-resistant strip composed of a film 2 coated with a conductive layer 3 represented by a bold line, two flat conductors for example copper in contact with the conductive face of the ends of the electro-resistant strip 2,3 and an upper insulating film 6.

 For clarity, the adhesives ensuring the cohesion of the assembly are not shown and the elements are shown separate and out of proportion. In reality, they are precisely subject to each other.

 The lower 1 and upper 6 films may be made of insulating synthetic material, for example from the family of polyesters, or polyethylene-polyester complexes, the polyethylene faces then being arranged towards the inside of the heating film and thus being able to be welded together and other components of the hot press heating film. In this case, the use of adhesive is not necessary except possibly to keep in place the carbon bands, during manufacture, and to ensure good electrical contact between them and the conductors. For the latter function, provision is made for the use of an electrically conductive adhesive described below.

 The electro-resistant strip may itself consist of a thin film 2, for example of polyester or polyethylene-polyester complex on which a conductive layer 3 of sufficiently high ohmic value has been deposited by any bonding process.

 The conductive layer 3 is preferably based on carbon but can also result from any deposition of metals, metalloids or other conductive or semi-conductive substances. The use of a conductive film of sufficient mechanical strength, allowing it to be cut into strips and its positioning on the support film 1, directly or by transfer, is also possible, thus making the film 2 useless, without the character of the invention be changed.

 The resistance value of each transverse electro-resistant strip 2,3 can be measured before or after its installation on the support film 1, and before installation of the lateral conductors 4,5. This. value can be taken into account to modify the spacing of the electro-resistant bands, during installation, and adjust the final power.

 The lateral conductors 4,5 preferably consist of thin strips of copper, without this being limiting to the invention. They are placed longitudinally with respect to the long length of the heating film, each at one of the ends of the transverse electro-resistant strips 2,3. Connected to an electrical power source, they communicate to the latter by contact or conductive bonding, the potential difference necessary for their heating by the Joule effect.

 In manufacturing, the conductors 4 and 5 can either be arranged on the assembly already made up of the elements 1 and 2.3 or be arranged on the upper insulating film 6, the sub-assemblies 1,2,3 and 4,5,6 being then calendered and glued to form the finished heating film.

 the conductors 4,5 may be continuous over the entire length of a reel of heating film. They can also be discontinuous as will be shown later (Fig. 6 and 7).

 As mentioned above, the conductors 4,5 can be glued to the ends of the electro-resistant strips so as to ensure good electrical contact. In a preferred but nonlimiting embodiment, the adhesive is based on polyurethanes and comprises a charge of conductive particles of suitable hardness and particle size. By hot pressure, which may be that of final calendering, the conductive particles are crushed between each conductor 4.5 and each corresponding end of the electrically conductive strips and constitute as many conductive "bridges".

Simultaneously the glue is expelled between the conductive particles, and assumes its adhesive function.

 Fig. 2 shows a longitudinal section of the heating film object of the invention and its main constituent elements. The transverse electro-resistant bands 2,3 are spaced apart.

Their spacing is substantially equivalent to their width, in a preferred but non-limiting configuration.

In this case, the linear power of the heating film is of the order of 50% of the sum of the power of the electro-resistant bands. The latter can be more or less separated from each other so as to obtain the desired power.

 These spacings can therefore vary the final linear power from the maximum power, and in this case the electro-resistant bands are almost contiguous, at zero power. In the latter case there is no transverse band.

 In practice, electro-resistant bands of sufficiently large power are chosen so that, spaced apart from one another by their width, it is possible to obtain, for the finished heating film, a calorific power considered as nominal or usual. By bringing them together, a heating film is obtained, the power of which can go up to twice the so-called nominal power for particular cases of use.

 The spacing between the electro-resistant bands can obey a fixed law or be variable. In fixed law, the lower support film 1 is moved on the device for applying electro-resistant bands according to a predetermined pitch. As the support film 1 advances step by step, an electro-resistant strip is applied, transverse or not.

 The variable spacing can allow a less brutal variation of the final linear power or its more precise adjustment taking into account ohmic measurements which can be carried out on the electro-resistant bands, as they are laid, which measurements can be integrated into the manufacturing process by intervening on the control of the support film 1.

 The transverse strips 2,3 may also be of identical or different width and arranged on the support film 1 by one or more successive laying devices.

 In a nonlimiting and simplified embodiment of the heating film which is the subject of the invention, not shown, the insulating support film, unwound from its reel1 passes over a cylinder of suitable diameter, pierced with small orifices and closed at its two ends. An axial air intake makes it possible to establish a vacuum inside said cylinder. A mechanism rotates the cylinder on its axis, either step by step or proportionally. The support film is held on part of the surface of the cylinder by the depression created inside it and accompanies its rotation.

 Another device transversely deposits the elements of electro-resistant tape 2,3 on the support film 1 when the cylinder is stopped and when it has received the command. These strips may be partially or completely coated with adhesive beforehand on their nonconductive contact face with the support film 1. Conversely, the support film 1 may itself be previously coated with adhesive.

 The conductors 4 and 5 are then laid by another device, either on the conductive ends of the electro-resistant strips already placed on the support film 1, the assembly then being glued / calendered with the insulating film 6, or glued on the insulating film 6 thus constituting the sub-assembly 4,5,6 this then being glued / calendered with the sub-assembly 1,2,3.

 Other devices allow all the other Sections like those of marking, control, cuts, etc ...

 the finished heating film can be wound or cut into heating elements. It can be combined with additional elements.

 Fig. 3 is a table showing a simplified set of manufacturing sequences.

The col. Has described in a simplified and nonlimiting manner a certain number of operations transmitted by pulses according to the col. B to the various manufacturing devices.
In C we see schematically 2 heating elements obtained.

 Fig. 4 is a curve showing a nonlimiting example of adaptation of the linear power of a heating film element object of the invention to the thermal needs of a room. The heating element is considered to be. incorporated into a part of the heated ceiling.

 On the abscissa the length of the element. On the ordinate, the power in watts.

 The dashed curve a expresses the heating needs. Curve b in full shows a response to these needs by a bare heating element according to the invention. The zero power parts are those which correspond to the beginning and the end of the heating element, and to the possible cutouts for the passage, for example, of lighting cables.

 The dotted curve c is the response to the needs of the curve a after weighting resulting from the installation of the facing.

 Figs. 5a and 5b are explanatory of the possible and non-limiting responses by several heating film elements which are the subject of the invention, arranged for example on the ceiling or on the floor and are interpreted in relation to each other.

 Fig. 5a shows the outer wall of a room, pierced with a window e. The curve f expresses the heat losses near this wall. Curve g shows a response to these losses.

The fatty parts of the curve g can be considered as the power, near the wall d, either of the active end of the heating elements arranged perpendicularly to it, or of a heating element arranged parallel to the wall d.

 Fig. 5b shows a heat loss curve f '. The curve g 'shows in its fatty parts the different power ranges either of a heating element arranged perpendicular to the window e' or the power levels of different heating elements arranged in strips parallel to the window e '.

 Figs. 5a and 5b therefore show in a simplified and nonlimiting manner the possibility of both thermal and mechanical response to the thermal needs of a room in accordance with its construction characteristics, by the heating film with variable linear power object of the invention.

 Fig. 6 is a schematic plan view of a heating element 7 produced according to the invention.

 the heating pads include the transverse bands 2,3 more or less spaced from each other. Non-heating parts include cutouts ll which may have various shapes. At the right end of the figure, the conductors 4.5 are flush with the ends of 8 and 9 and allow the electrical connection of the element 7 to the electric power source.

At the left end, the conductors 4,5 are interrupted before the heating element 10 is cut. At this point the support films 1 and 6 (Fig. 2) are glued together and provide electrical insulation for the cut.

 Fig. 7 shows a schematic plan view of a heating element 12 produced according to the invention comprising heating pads separated from one another by transverse cutouts 13 regularly spaced from one another. This arrangement makes it possible to have a modular system adapted to certain applications.

 Although the heating pads are shown in this figure as being of equal power and in limited number, they can be of different powers and in variable number, according to the needs.

 Each module is supplied in parallel by the conductors 4; 5 at substantially the same electrical voltage.

 As in the case of FIG. 6, the conductors 4.5 are flush with 8.9 and allow the electrical connection of the line of modules.

 Fig. 8 is a diagrammatic cross section out of proportion showing a heating element 14 disposed between a thermal insulating mat 15 and a facing plate 16, in a configuration for producing a heating surface. The heating element 14, produced according to the invention, being able to be of type 7 (Fig. 6) or 12 (Fig. 7) being connected to an electrical supply (not shown), it heats by Joule effect. The thermal insulation mattress 15 is opposed to thermal losses. The facing plate 16, itself heated by the heating element 14, by conduction, dissipates its heat mainly by radiation towards the room to be heated.

 Fig. 9 is a diagrammatic longitudinal section out of proportion of a heating element 17 of the modular type, similar to element 12 of FIG. 7, subjected on one of its faces to thermal insulation mats 18, for example by gluing.

 As the figure shows, the insulation blankets 18 are discontinuous. Their surface is designed to adjust to suspended ceiling tiles while fitting between the load-bearing profiles.

 By their weight and their shape, they ensure, for this type of implementation on the one hand a good contact of each heating surface of the element 17 with the ceiling tiles, and on the other hand a good peripheral hermeticity s' opposing the loss of calories by hot air leaks.

 Free spaces 19 between the thermal insulation blankets 18 correspond to the non-heating parts 19 comprising transverse cutouts 13 (FIG. 7). The arrangement of FIG. 9 allows folding into an "accordion" that can be used to facilitate packaging.

 Fig. 10 is a schematic section of a modular heating element 17 produced according to the invention and according to the description of FIG. 9 fitted with its thermal insulation mattresses 18, placed on ceiling tiles 20 themselves supported by an inverted T-frame 21. The insulation mattresses 18 fit between the frame profiles, ensuring the contact of the element 17 in its heating zones with the ceiling plate 20 and preventing unwanted losses. The non-heating parts / 19 fold over the frame cross members 21.

 Fig. 11 is a schematic perspective and exploded view of a flexible heating and insulating complex 22 comprising a heating film element 23 produced according to the invention, interposed between a protective and decorative facing 24 and a continuous thermal insulation mat 25.

 In a preferred but nonlimiting embodiment of the invention, the protective and decorative facing 24 is a mineral fiber fabric, the thermal insulation mattress 25 is a semi-rigid felt of glass wool or rock. The latter has transverse slots 26 which allow presentation on a reel. During the implementation of the heating complex, by bonding to a support or by suspension on a carrier system, the slots 26 of the thermal insulation mattress close and ensure the continuity of the thermal insulation.

 The constituent elements of the complex 22 are bonded together. The electrical supply of the strips arranged parallel to each other is carried out at one of their ends comprising access to the lateral electrodes of the heating film produced according to the invention.

Claims (5)

 10) Electric heating film, in strips, for producing heating surfaces or heating devices, characterized in that it comprises, between two insulating films (1,6), for example made of polyester, electrical resistances made up of strips of thin and of appropriate width, obtained from a conductive or semiconductor material or from an Xeket support film, on one of its faces, with a conductive layer (2,3) for example based on black of carbon, which conductive layer having had, beforehand, the possibility of stabilizing in its final electrical characteristics, arranged transversely with respect to the length of the finished heating film, electrically connected, at their ends, to two longitudinal electrical supply conductive strips (4,5), for example made of copper, and spaced apart so as to obtain, on demand, and during manufacture, by their greater or lesser spacing, a power final linear heating variable from zero to a predetermined maximum value, the constituent elements then being glued or welded together in a coherent whole.  20) Heating film according to claim 1 characterized in that the insulating films (1,6) are glued or welded together at locations not occupied either by the longitudinal conductive elements (4,5) or by the transverse electro-resistant strips (2 , 3) thus ensuring electrical insulation both peripheral and intermediate between the electro-resistant strips.  30) Heating element obtained from the heating film according to claims 1 and 2 characterized in that it has at one end, an access (8,9) to the conductive strips (4,5) and at the other end, a electrically insulated part (10) by the combination of the insulating films (1,6) respectively lower and upper, and any intermediate cutouts made in non-heating locations, themselves electrically insulated by the insulating films (1,6) combined.  4) modular heating element obtained from the heating film according to any one of claims 1 to 3 comprising at least two heating pads, of identical or different power comprising at least one transverse electro-resistant strip, separated by a non-heating part which can the object of a transverse cut (13).  50) Modular heating and insulating element according to any one of Claims 1 to 4, characterized in that it comprises at least one modular heating element (17) secured on one of its faces to a continuous or discontinuous thermal insulation blanket .  60) Heating film or heating element according to one of claims 1 to 4 characterized in that it is subject on one of its faces, to a protective or decorative coating and, on its other face, to a thermal insulation mattress .