EP4387390A1

EP4387390A1 - Method for producing electric heating elements ans plants implementing the aforesaid method

Info

Publication number: EP4387390A1
Application number: EP23216603.3A
Authority: EP
Inventors: Piermatteo D'AMICO
Original assignee: Rosso24 Srl
Current assignee: Rosso24 Srl
Priority date: 2022-12-15
Filing date: 2023-12-14
Publication date: 2024-06-19

Abstract

A method for producing electric heating elements (1) comprising a substrate (2, 2a) provided with one or more electrically conductive elements (3) that heat said substrate (2, 2a) when the electrically conductive elements (3) are crossed by an electric current, the method comprising a first step in which the electrically conductive elements (3) are applied to the substrate (2, 2a), a second step in which the electrically conductive elements (3) are sintered, a third step in which at least one dielectric protective layer (4) is laid on the sintered electrically conductive elements (3), and a fourth step in which the dielectric protective layer (4) is polymerized. In particular, the electrically conductive elements (3) comprise an electrically conductive substance that is laid on the substrate (2, 2a) by means of dispensing means (6) that are associated with movement means moving the dispensing means (6) according to two or more directions with respect to said substrate (2, 2a) to configure the electrically conductive elements (3) according to a geometry with one or more continuous strips (8).

Description

The present invention relates to a method for producing electric heating elements, as well as to plants which produce electric heating elements by implementing the aforesaid method.
As it is known, electric heating elements are marketed which comprise a flexible laminar substrate of very limited thickness, generally less than a millimeter, on which conductive laminar elements are applied.
Preferably but not necessarily the laminar substrate is formed by a continuous flexible film made of polyethylene wound into a roll, but in other embodiments the polyethylene may be replaced by a composite fabric made of glass fiber, carbon fiber, Kevlar fiber or other materials.
With regard, instead, to the conductive laminar elements, they are formed by conductive strips and bands or they may be obtained with conductive inks or pastes based on silver, copper, carbon, carbon nanotubes, graphene and the like.
Constructively, as in the prior art, the electric heating elements now described, which are also called heating films or radiant films, for example, are made through the flexographic/screen printing method which uses rotary cylinders to apply two copper bands parallel to each other on the edges of the laminar substrate, and a plurality of carbon fiber strips, spaced apart from each other and arranged transversally to the copper bands on the surface thereof.
The copper bands extend as at the length of the laminar substrate and each end of each carbon fiber strip is connected to a corresponding copper band so that, when the copper bands are crossed by the electric current, they power the carbon fiber strips which heat up due to the Joule effect.
The heat produced is therefore transmitted by contact to the object or to the surface to which the electric heating element will be applied.
If the electric heating element thus obtained and formed precisely by the laminar substrate with the conductive laminar elements is applied to a wall or to the floor or ceiling of an environment, this is heated by radiation.
Operatively, the electric heating elements, according to the prior art described, are produced on flexographic/screen printing lines where a flexible laminar substrate is continuously unwound from a roll and laid flat, while special cylinders lay the conductive laminar elements formed by copper bands and carbon fiber strips thereon.
After laying the conductive laminar elements, the carbon fiber strips are sintered in a drying oven and, after sintering, a protective film is laid over the conductive laminar elements which is polymerized so as to make it adhere to the copper bands and to the carbon fiber strips to protect them from damage.
After the polymerization, the flexible laminar substrate, which has thus been transformed into an electric heating element by applying the conductive laminar elements, is once again wound into a roll and is ready to be delivered to the customer for use.
Electric heating elements, otherwise also referred to with the term "electric heating films", are widely used in many applications, for example, to heat domestic and industrial environments, to heat and protect substances contained in containers from freezing, to protect industrial equipment from cold, to defrost glass and for a variety of other different applications where it is necessary to heat objects, environments and surfaces.
The limited thickness thereof also makes them particularly adapted to be applied to items and surfaces to be heated without the application thereof appreciably modifying the size and aesthetics of such items and surfaces.
Furthermore, when the electric heating elements are applied to walls, ceilings and floors delimiting environments, the heating occurs by radiation which, as known, doesn't advantageously generate air circulation in the environment and consequent dust movement. Due to the simplicity of application and the high durability thereof, there is a growing market interest in the use of electric heating films in multiple sectors of use, and the production method which uses the flexographic/screen printing method described is now consolidated since many years.
However, the flexographic/screen printing method implemented during production in the prior art has a series of recognized limitations and drawbacks.
First of all, a recognized limitation of the method of the prior art under examination herein consists of the fact that the technology used by the flexographic/screen printing method offers on the market only fixed power electric heating films wound in rolls of indefinite length and in only three width variants, in particular 30, 50 and 100 cm, since, due to the high cost of manufacturing flexographic/screen printing rollers, customizing the width and length measurements of the rolls would bring high costs which would unlikely be accepted and absorbed by the market.
Consequently, at present, the production method of the known type described only produces electric heating films rewound into rolls and with standard sizes and powers which are not always capable of satisfying the needs of the user.
Another limitation consists in the fact that such known production method is not capable of providing the market with electric heating films made on non-flat, rigid and even three-dimensional substrates.
In addition, a further limitation of the current production method consists in the fact that, for producing electric heating films, only substrates may be used which are capable of resisting, without deforming, the sintering temperatures of the carbon fiber and the polymerization temperatures of the protective film protecting it.
As it is easy to understand, this excludes the possibility of using a plurality of materials available on the market as substrates.
Another limitation of the prior art under examination is associated with the variations in the expressed power which, by means of the flexographic method, are not easily obtainable due to the difficulty of such technology in laying high quantities of resistive material.
A limitation also consists in the fact that the flexographic/screen printing method does not allow to manufacture in a cost-effective manner electric heating films in small series or single pieces, differentiated by size and materials.
Moreover, it is a drawback of the flexographic/screen printing method of the prior art the poor precision with which the carbon fiber is laid onto the substrate, leading to reductions in the power output that may reach up to 15% of the nominal value indicated by the manufacturer. Consequently, there is a lower quality of the product that is offered on the market and which, in some cases, may not be accepted by the user.
Furthermore, as a further drawback, since the electric heating films made using the known flexographic/screen printing method are capable of delivering only rather limited power, if they are used for environmental heating, to reach the power required by the manufacturer, the installer is often forced to use a greater quantity of film.
However, this entails the need to also increase the number of cables going to the energy distribution network, with the drawback that doing so increases electrical losses and also risk of accidents caused by accidental contacts due to possible deficiencies in the insulations.
Further and last but not least drawbacks and limitations of the currently implemented flexographic/screen printing method are to be found in the large size of the flexographic/screen printing lines, which reach and exceed lengths of thirty meters and more, and in the high maintenance costs due to the multiplicity of operating units which make up each flexographic/screen printing line.
The prior document, published as US2018/310366 A1 , simply describes a system for laying a conductive track in which the plant lacks a system for affixing a dielectric protective layer, as well as, consequently, a system for polymerizing such dielectric layer.
Furthermore, in the aforesaid prior document, the laying of the conductive paste (whose viscosity has values which however do not exceed a certain limit) occurs by screen printing or by using a piezoelectric ink jet, on laminar glass substrates which remain stationary at the workstation.
In addition, in US2018/310366 A1 , the conductive paste, or more precisely the conductive mixture, laid on the substrate is sintered in an oven during a rather long time, between 30 minutes and 2 hours.
The prior document published as US2014/197159 A1 describes, however, an induction system for sintering conductive pastes and inks; therefore, this prior document only covers a small fraction of what the actual object of the current invention is.
In addition, prior document published as WO2021/231435 A1 purely describes a component for controlling the positive temperature coefficient (also known by the acronym PTC): the object of such prior document, therefore, remains somewhat far from the technical field of the present invention, as it's neither a method nor a plant manufacturing thermo-radiant electric elements.
The present invention intends to overcome the drawbacks and limitations just complained of the known method for manufacturing electric heating elements and, in particular, electric heating elements using the flexographic/screen printing system.
In particular, it is a first purpose of the invention to create a method which allows the manufacturing of electric heating elements using substrates of any type, flexible or rigid, of any size, of any material and of any shape.
It is another purpose of the invention to provide a method for manufacturing electric heating elements which, with respect to the known flexographic/screen printing method, allows the resistive strips to be laid with micrometric precision onto the flexible substrate forming the electric heating element.
It is a further purpose that the method of the invention allows to manufacture electric heating elements in which the deviation between the nominal power declared by the manufacturer and the real power is lower than the deviation found in the electric heating elements made using the flexographic/screen printing method.
It is another purpose that the method of the invention allows to manufacture electric heating elements of greater power with respect to electric heating elements with the same surface area manufactured with the flexographic/screen printing method.
It is a further purpose that, with the method of the invention, it is possible to manufacture electric heating elements using plants much smaller in size and comprising a smaller number of operating units with respect to the known plants that are used to manufacture electric heating elements with the flexographic/screen printing method.
It's a last but not least purpose that the plants using the invention method have significantly lower construction, maintenance and energy consumption costs compared to the plants used to manufacture electric heating elements with flexographic/screen printing method.
The purposes listed are achieved by the method for manufacturing electric heating elements as in the accompanying claim 1, to which reference is made and which is not indicated in this section for the sake of brevity of description.
Further detailed technical features of the method of the invention and of the plants implementing it are described in the dependent claims.
The aforesaid claims, hereinafter specifically and concretely defined, are intended as an integral part of the present description.
Advantageously, by using the method of the invention it is possible to manufacture electric heating elements of any type, power, length and shape, and having substrates made of any material.
Again advantageously, by using the method of the invention, the laying of the conductive laminar elements on the substrate occurs with greater precision and regularity with respect to the prior art that uses the flexographic/screen printing method.
This has the advantage of minimizing the deviation of the value of the actual heating power supplied with respect to the rated or nominal power, to the advantage, with respect to the known flexographic/screen printing method, of the quality of the product offered on the market.
In a further advantageous manner, the method of the invention is applied using plants having shorter lengths, consisting of a smaller number of operating units and requiring less maintenance with respect to the plants used to manufacture electric heating elements with the known flexographic/screen printing method.
The objects and advantages listed above, and others which will eventually be described in more detail below, are achieved by the method for producing electric heating elements and by plants implementing it, which are both the object of the invention, and which are described below with reference to the accompanying drawings in which:

figures 1 to 8 show the method of the invention in a diagrammatic and illustrative manner;
figure 9 shows an embodiment of the plant of the invention which implements the method shown in figures 1 to 8;
figure 10 shows another embodiment of the plant of the invention which implements the method shown in figures 1 to 8;
figure 11 shows a further embodiment of the plant of the invention which implements the method shown in figures 1 to 8;
figure 12 shows another embodiment of the plant of the invention which implements the method shown in figures 1 to 8.

The method for producing electric heating elements, as object of the invention, is described below with reference to figures 1 to 8 which diagrammatically show the different operating steps.
With reference to the aforesaid figures, the method of the invention makes electric heating elements 1, each of which comprises a substrate 2, 2a provided with electrically conductive elements 3 that heat the substrate 2, 2a when the electrically conductive elements 3 are crossed by an electric current.
The method comprises a first step in which the substrate 2, 2a is arranged in the working position shown in figures 1 and 2 where the conductive elements 3 are applied thereto.
This is followed by a second step shown in figures 3 and 4 in which the electrically conductive elements 3 are sintered, and therefore a third step shown in Figures 5 and 6 in which at least one dielectric protective layer 4 is laid on the sintered electrically conductive elements 3 (at this point, otherwise indicated with 3').
Finally, as shown in Figures 7 and 8, a fourth step occurs that consists in polymerizing the laid dielectric protective layer 4, which is thus indicated with 4'.
According to the invention, the first step of the method comprises the operation of laying on the substrate 2, 2a at least one electrically conductive substance belonging to the electrically conductive elements 3 by means of dispensing means 6 associated with movement means, not shown in figures 1-8, which move the dispensing means 6 according to two or more directions with respect to the substrate 2, 2a to configure the electrically conductive elements 3 according to a geometry with one or more continuous strips (or tracks) 8.
Therefore, contrarily to what described in the prior art document US2018/310366 A1 , the method of the invention involves a step of affixing a dielectric protective layer 4 and a subsequent step of polymerizing such protective layer 4, as well as that the operation for laying the electrically conductive substance (that forms the electrically conductive elements 3) onto the substrate 2, 2a occurs using a piezoelectric system combined with a Venturi system, instead of a simple piezoelectric ink jet.
Another significant difference with respect to what is described in US2018/310366 concerns the fact that the laying of the electrically conductive substance occurs on a substrate 2, 2a which may be of any type (rigid or flexible) while, above all, it is in motion, to the full advantage of a greater efficiency associated with the method of the invention.
By means of the method of the invention, it is possible to apply electrically conductive substances (pastes) to the substrate 2, 2a with almost no limit in viscosity values, exceeding 50,000 mPa.s (milliPascal-seconds).
In particular, the electrically conductive substance forming the continuous strips (or tracks) 8 is laid by means of high-speed ejection and adheres to the substrate 2, 2a by virtue of the adhesive components thereof.
The dispensing means 6 used are devices of a known type available on the market which are not described below and which may be divided into two categories, in particular:

dispensing means 6a that lay the electrically conductive substance for dispensing without contact the dispensing means 6a with the substrate 2, 2a
or
dispensing means 6b that lay the electrically conductive substance for dispensing with contact the dispensing means 6b with the substrate 2, 2a

The following belong to the category of means for dispensing 6a without contact:

micro nozzle dispensing means of a known type, which are powered by an electronically controlled pressurized system and are capable of dispensing the exact quantity of a plurality of different inks/pastes of different viscosities, which form the electrically conductive substance forming the electrically conductive elements 3;
dispensing means with volumetric valves, also of a known type, which are electronically controlled and which allow electrically conductive pastes of different densities to be laid with high precision, thus ensuring a coherent and constant laying;
jet dispensing means, also of a known type, which allow for a constant and precise laying of the electrically conductive substance.

The following belongs to the category of dispensing means 6b dispensing with contact:

ball-shaped dispensing means of a known type, which transfer the electrically conductive paste or ink by rolling an inked sphere onto the substrate 2, 2a,
pad dispensing means that transfer the electrically conductive paste or ink by sliding an inked pad onto the substrate 2, 2a,
nozzle dispensing means that transfer the electrically conductive paste or ink by sliding onto the substrate 2, 2a a nozzle fed with the electrically conductive paste or ink.

Obviously, the choice of the best type of dispersing means 6a or dispensing means 6b to use is up to the user or the manufacturer, on the basis of the production needs thereof.
All the methods for laying the electrically conductive elements 3 and the relevant dispensing means 6a, 6b that have been described above allow a multiplicity of different electrically conductive inks or pastes to be applied to the substrate 2, 2a with greater precision with respect to the prior art which uses the flexographic/screen printing method.
Thereby, it is possible to achieve a better control of the quality of the electrically conductive substance that is laid to form the electrically conductive elements 3 and this improves the quality of the electric heating elements 1 produced.
Furthermore, the possibility of precisely dosing the quantity of electrically conductive substance that is applied onto the substrate 2, 2a allows the manufacturing of electrically conductive elements 3 with greater powers with respect to the electrically conductive elements with the same surface area made with the flexographic/screen printing method of the prior art.
Finally, the purpose is also achieved of manufacturing electric heating elements 1 in which the deviation between the nominal power declared by the manufacturer and the actual power supplied is lower than the deviation found in electric heating elements of the same surface area made with the known flexographic/screen printing method.
After laying the electrically conductive substance forming the electrically conductive elements 3 onto the substrate 2, 2a, the method comprises the execution of the second step that is described with reference to figures 3 and 4 and involves sintering the electrically conductive elements 3 by administering heat using a moving pulsed light source 5.
The pulsed light source 5 and the use thereof for heating and therefore for carrying out the sintering are known.
Preferably but not necessarily, a pulsed light source 5 emitting high frequency pulsed light is used.
The emission power of the pulsed light may be varied so that the thermal energy that the light beam transfers onto the electrically conductive elements 3 is sufficient to achieve the sintering thereof and the high frequency of the pulsation ensures that the thermal energy transfer time is sufficiently rapid so as not to damage the underlying substrate 2, 2a whatever the nature thereof is.
This also achieves the object of manufacturing electrically conductive elements 3 by laying the electrically conductive substances on substrates 2, 2a made of any material, not exclusively rigid and thickened.
Therefore, the sintering provided for by the method of the invention is carried out with a system of moving pulsed light sources (or lamps) that follow the electrical circuit just laid onto the substrate 2, 2a and forming the electrically conductive elements 3 in an arc of time between 2-3 minutes, significantly lower with respect to the times indicated by the prior art document US2018/310366 A1 already highlighted above.
Alternatively to the pulsed light source, it's possible to use a source of infrared rays through emissive ceramic elements arranged so as to follow the tracks of the circuit and sinter only the latter, thus getting the same advantages, compared to the prior art, highlighted above.
Following the sintering operation, the method of the invention comprises the execution of the third step that is described with reference to Figures 5 and 6 and involves applying a dielectric protective layer 4 onto the sintered electrically conductive elements 3 by means of moving spraying means 9 that comprise spraying nozzles of a known type which, depending on the manner of spraying the dielectric protective layer 4, operate in the absence of air, or with high pressure air or with low pressure air.
The application of this dielectric protective layer 4, which essentially comprises a protective film of stretchable and peelable paint, prevents the electrically conductive elements 3 from being damaged during application activities.
For this purpose, preferably but not necessarily, the laying of the protective layer 4 may also affect the entire surface of the substrate 2, 2a.
Finally, the method is completed by a fourth step that is described with reference to figures 7 and 8 and involves carrying out the polymerization of the dielectric protective layer 4 which, preferably but not necessarily, is carried out by means of at least one UV light source of a known type, numbered with 10, which is also moving.
All the operations that are carried out during each of the steps forming the method of the invention and having been described involve movements of the dispensing means 6a, 6b of the electrically conductive substance, of the pulsed light source 5 (or of the infrared ray source), of the spraying means 9 and of the UV light source indicated with 10 with respect to the substrate 2, 2a by means of movement means which preferably, as it will also be mentioned below, are robotic means and are not provided for in the prior document US2018/310366 A1 .
The method of the invention is implemented by means of plants that may be configured in various manners.
A plant of the invention is diagrammatically shown in figure 9 where it is overall indicated with number 100 and where it is observed that it comprises a work surface 101 that supports a plurality of substrates 2 each of which is an element with a defined width and length, and means 101c, 101d for advancing the work surface 101 towards a plurality of workstations 102.
The workstations comprise a first workstation 102a that in turn comprises means 103 for moving the dispensing means 6 which lay, onto each substrate 2, the electrically conductive substance that forms the electrically conductive elements 3, and a second workstation 102b comprising means for moving 104 the pulsed light source 5 that sinters the electrically conductive substance.
There is then a third workstation 102c that comprises means 105 for moving the spraying means 9 that apply the dielectric protective layer 4 onto the sintered electrically conductive substance 3, and a fourth workstation 102d that comprises a fixed portal 106 with which a UV light source 10 is associated which, when moving, polymerizes the dielectric protective layer 4 onto the sintered electrically conductive substance.
Furthermore, in relation to the work surface 101, it comprises a conveyor belt 101a for advancing the substrates 2 through the workstations 102a, 102b, 102c, 102d, and the advancement means in turn comprise a winding roller 101c and an unwinding roller 101d, of which at least the winding roller 101c is motorized, which are each supported at a respective end of the base 101 b of the plant 100.
Another plant implementing the method of the invention is shown in Figure 10 where it is overall indicated with 200; it is observed that it comprises a work surface 201 that supports the substrate 2a comprising a continuous flexible laminar element with a defined width and an indefinite length, and means 201c, 201d for advancing the substrate 2a towards a plurality of workstations 202.
The workstations include a first workstation 202a which in turn comprises means 203 for moving the dispensing means 6 that lay, onto each substrate 2a, the electrically conductive substance that forms the electrically conductive elements 3, and a second workstation 202b comprising means 204 for moving the pulsed light source 5 that sinters the electrically conductive substance.
A third workstation 202c comprising means 205 for moving the spraying means 9 that apply the dielectric protective layer 4 onto the sintered electrically conductive substance, and a fourth workstation 202d comprising a fixed portal 206 with which a UV light source 10 is associated which polymerizes the dielectric protective layer 4 onto the sintered electrically conductive substance are also present.
With regard to the advancement means 201c, 201d of the continuous flexible laminar element with an indefinite length and a defined width forming the substrate 2a, they include a winding roller 201c and an unwinding roller 201d (of which at least the winding roller 201c is motorized) supporting the substrate 2a wound in rolls 211c, 211d.
The rollers 201c and 201d are each supported at a respective end of the base 101b of the plant 200 and advance the substrate 2a through the workstations 202a, 202b, 202c, 202d.
A further plant implementing the method of the current invention, overall indicated with 300, is shown in figure 11 where it is observed that it comprises a work surface 301 that supports a plurality of substrates 2, each of which is an element with a defined width and a defined length, and means 301c, 301d for advancing the work surface 301 through a plurality of workstations 302.
The workstations 302 include a first workstation 302a comprising, in turn, an electrically conductive ink jet printer 303 in which both the dispensing means 303a of the electrically conductive ink forming the electrically conductive elements 3 and the pulsed light source 5 sintering the electrically conductive ink are integrated.
Furthermore, a second workstation 302b, comprising means 304 for moving the spraying means 9 for applying the dielectric protective layer 4 on the sintered electrically conductive ink, and a third workstation 302c comprising means 305 for moving the UV light source 10 for polymerizing the dielectric protective layer 4 arranged on the sintered electrically conductive ink are comprised.
In relation to the work surface 301, it comprises a conveyor belt 301a for advancing the substrates 2 through the workstations 302a, 302b, 302c, and the advancement means comprise a winding roller 301c and an unwinding roller 301d, of which at least the winding roller 301c is motorized, which are each supported at a respective end of the base 301b of said plant 300.
Another plant implementing the method of the invention is shown in figure 12 where it is overall indicated with 400 and where it is observed that it comprises a work surface 401 that supports a plurality of substrates 2 each of which is an element with a defined width and length, and means 401c, 401d for advancing the work surface 341 towards a single workstation 402.
The workstation 402 includes an electrically conductive ink jet printer 403 in which the following is integrated:

means 6 for dispensing the electrically conductive ink that forms the electrically conductive elements 3;
the pulsed light source 5 that sinters the electrically conductive ink;
spraying means 9 for applying the dielectric protective layer 4 at least on the sintered electrically conductive ink;
the UV light source indicated with 10 for polymerizing the dielectric protective layer 4 arranged at least on the sintered electrically conductive ink.

In relation to the work surface 401, it comprises a conveyor belt 401a for advancing the substrates 2 through the single workstation 402e, while the advancement means comprise a winding roller 401c and an unwinding roller 401d, of which at least the winding roller 401c is motorized, which are each supported at a respective end of the base 401b of the plant 400.
In the plants 100, 200 and 300 of the invention, the movement means are robotic means that, based on the operations to be carried out and on the choice of the plant manufacturer or of the user, may be of the anthropomorphic type, of the Cartesian type or of the collaborative type (cobots).
With regard to the substrates, the substrate 2 is a flexible or rigid laminar element with a defined width and length but it may also be a three-dimensional body made of any material.
For its part, instead, the substrate 2a is a flexible laminar element with a defined width and an indefinite length wound in a roll.
However, each of the plants described is mechanically designed to treat any type of substrate, in particular even three-dimensional substrates.
Obviously, the configurations of the plants that have been described are only some of the possible configurations which are capable of implementing the method of the invention.
For example, a configuration of a plant that has not been described may provide one or more of the movement means be associated with multiple operating groups in combination with one another, such as, for example, the dispensing means 6 of the electrically conductive substance, in combination with the pulsed light source 5 for sintering the electrically conductive substance after it has been applied to the substrate 2.
Furthermore, in each plant of the invention, the work surface may be provided with a conveyor belt and/or advancement means comprising a winding roller and an unwinding roller for advancing towards the workstations of a continuous flexible substrate with a defined width and an indefinite length, which is wound in a roll.
Alternative embodiments may also be provided, not shown in the following drawings, in which the plant of the invention may be provided with robotic means for loading, unloading and transferring the substrates between the workstations.
With regard then to the means for moving the dispensing means 6, the pulsed light source 5, the spraying means 9 and the UV light source indicated with 10, as mentioned, they are preferably but not necessarily robotic means of the anthropomorphic, Cartesian or collaborative type, which may be variably combined with one another according to operational needs.
Although it has not been shown in the figures, for each plant there is, on board the machine or in a remote position, a command-and-control station that comprises IT means which in turn comprise:

memory means in which an IT product is stored;
at least one microprocessor configured to run the aforesaid IT product
where the aforesaid IT product, when working, is configured to perform the following operations:
- activating the advancement means to advance the respective work surface 101, 201, 301, 401 and the substrates 2, 2a by means of the workstations and during advancement:
- activating the dispensing means 6 to lay the electrically conductive substance forming the electrically conductive elements 3 on each substrate 2, 2a;
- activating the pulsed light source 5 to sinter the laid electrically conductive substance 3;
- activating the spraying means 9 to apply the dielectric protective layer 4 on the laid and sintered electrically conductive substance 3;
- activating the UV light source indicated with 10 to polymerize the dielectric protective layer 4;
- activating, if present upstream and/or downstream of the plant, automatic means for loading the substrates 2, 2a and/or unloading the electric heating elements produced.

On the basis of what has been described, it is therefore understood that the method for manufacturing electric heating elements of the invention, and each of the described plants of the invention implementing it, meet the purposes and achieve the advantages yet listed above.
In particular, the purpose of manufacturing a method is met, which allows the manufacturing of electric heating elements using substrates of any type, flexible or rigid, of any size, of any material, of any shape and of any expressed electro-thermal power.
Furthermore, the purpose of laying the electrically conductive elements onto the substrate with a greater precision and with a greater efficiency with respect to the known flexographic/screen printing method is achieved.
The further purpose of manufacturing heating supports in which the deviation between the nominal power declared by the manufacturer and the real power is lower with respect to the deviation found in equivalent heating supports with the same surface area and made with the flexographic/screen printing method is also achieved.
The purpose of manufacturing electric heating elements of greater power with respect to electric heating elements with the same surface area produced with the flexographic/screen printing method is also achieved.
The further purpose that the plants of the invention have lengths and construction, maintenance and energy costs which are much lower with respect to those of the corresponding known plants manufacturing electric heating elements with the flexographic/screen printing method is also achieved.
It is clear that numerous variations may be made to the method and plants of the invention which have been described, still falling within the scope limited by the accompanying claims.
Where the constructional features and techniques mentioned in the following claims are followed by reference signs or numerals, such reference signs were introduced for the sole purpose of increasing the intelligibility of the claims themselves, and therefore have no limiting effect on the interpretation of each element identified, by way of example only, by such reference signs.

Claims

Method for producing electric heating elements (1) comprising a substrate (2, 2a) provided with one or more electrically conductive elements (3) that heat said substrate (2, 2a) when said electrically conductive elements (3) are crossed by an electric current, said method comprising:
- a first step in which said electrically conductive elements (3) are applied to said substrate (2, 2a);

- a second step in which said electrically conductive elements (3) are sintered;

- a third step in which at least one dielectric protective layer (4) is laid on said sintered electrically conductive elements (3);

- a fourth step in which said dielectric protective layer (4) is polymerized,
and being characterized in that said first step comprises the operation of laying on said substrate (2, 2a) at least one electrically conductive substance belonging to said electrically conductive elements (3) by means of dispensing means (6) associated with movement means moving said dispensing means (6) according to two or more directions with respect to said substrate (2, 2a) to configure said elements according to a geometry with one or more continuous strips (8).
Method according to claim 1), characterized in that the sintering of said electrically conductive elements (3) occurs by administering heat by means of at least one moving pulsed light source (5) or infrared ray source.
Method according to claim 1) or 2), characterized in that said dielectric protective layer (4) is applied on said electrically conductive elements (3) by means of moving spraying means (9).
Method according to any of the preceding claims, characterized in that the polymerization of said dielectric protective layer (4) occurs by means of at least one moving UV light source (10).
A plant (100) for producing electric heating elements (1) according to the method of any one of claims 1) to 4), characterized in that the plant comprises:
- a work surface (101) that supports a plurality of substrates (2) of electric heating elements (1), each of said substrates (2) being an element with defined width and length;

- means (101c, 101d) for advancing said work surface (101);

- a plurality of workstations (102) including:
• a first workstation (102a) comprising moving means (103) for said dispensing means (6, 6a, 6b) that lay on each of said substrates (2) said electrically conductive substance forming said electrically conductive elements (3);

• a second workstation (102b) comprising moving means (104) for a pulsed light source (5) that sinters said electrically conductive substance;

• a third workstation (102c) comprising moving means (105) for spraying means (9) that apply said dielectric protective layer (4) onto said sintered electrically conductive substance (3);

• a fourth workstation (102d) comprising a fixed portal (106) with which at least one UV light source (10) is associated, which polymerizes said dielectric protective layer (4) on said sintered electrically conductive substance.
Plant (100) according to claim 5), characterized in that said work surface (101) is a conveyor belt (101a) for advancing said substrates (2) through said workstations (102a, 102b, 102c, 102d), and said advancement means include a motorized winding roller (101c) and an unwinding roller (101d), each of which is supported on a respective end of a base (101b) of said plant (100).
Plant (200) for producing electric heating elements (1) according to the method of any one of claims 1) to 4), characterized in that the plant comprises:
- a work surface (201) that supports said substrate (2a) of electric heating elements (1), said substrate (2a) comprising a continuous flexible laminar element with a defined width and an indefinite length;

- advancing means (201c, 201d) for said substrate (2a);

- a plurality of workstations (202) comprising:
• a first workstation (202a) comprising moving means (203) for said dispensing means (6, 6a, 6b) that lay on said substrate (2a) said electrically conductive substance forming said electrically conductive elements (3);

• a second workstation (202b) comprising moving means (204) for a pulsed light source (5) that sinters said electrically conductive substance;

• a third workstation (202c) comprising moving means (205) for spraying means (9) that apply said dielectric protective layer (4) onto said sintered electrically conductive substance;

• a fourth workstation (202d) comprising a fixed portal (206) with which at least one UV light source (10) is associated, which polymerizes said dielectric protective layer (4) on said sintered electrically conductive substance.
Plant (200) according to claim 7), characterized in that said advancing means (201c, 201d) for said continuous flexible laminar element forming said substrate (2a) comprise a motorized winding roller (201c) and an unwinding roller (201d) that support said laminar element (2a) wound in rolls (211c, 211d), said rollers (201d, 201d) being supported each at a respective end of a base (101b) of said plant (200), and advance said substrate (2a) through said workstations (202a, 202b, 202c, 202).
Plant (300) for producing electric heating elements (1) according to the method of any one of claims 1) to 4), characterized in that the plant comprises:
- a work surface (301) that supports a plurality of substrates (2) of electric heating elements (1), each of said substrates (2) being an element with a defined width and a defined length;

- means (301c, 301d) for advancing said work surface (301);

- a plurality of workstations (302) comprising:
• a first workstation (302a) comprising an electrically conductive ink jet printer (303) wherein dispensing means (303a) for the electrically conductive ink that forms said electrically conductive elements (3) and a pulsed light source (5) that sinters said electrically conductive ink are integrated;

• a second workstation (302b) comprising moving means (304) for spraying means (9) for applying said dielectric protective layer (4) on said sintered electrically conductive ink;

• a third workstation (302c) comprising moving means (305) for a UV light source (10) for polymerizing said dielectric protective layer (4) arranged on said sintered electrically conductive ink.
Plant (300) according to claim 9), characterized in that said work surface (301) is a conveyor belt (301a) for advancing said substrates (2) through said workstations (302a, 302b, 302c), and said advancement means comprise a motorized winding roller (301c) and an unwinding roller (301d), each of which is supported on a respective end of a base (301b) of said plant (300).
Plant (400) for producing electric heating elements (1) according to the method of any one of claims 1) to 4), characterized in that the plant comprises:
- a work surface (401) that supports a plurality of substrates (2) of electric heating elements (1), each of said substrates (2) being an element with defined width and length;

- means (401c, 401d) for advancing said work surface (401);

- a single workstation (402) comprising an electrically conductive ink jet printer (403) in which the following is integrated:
• dispensing means (6) for the electrically conductive ink that forms said electrically conductive elements (3) and a pulsed light source (5) that sinters said electrically conductive ink;

• spraying means (9) for applying said dielectric protective layer (4) on said sintered electrically conductive ink;

• a UV light source (10) for polymerizing said dielectric protective layer (4) on said sintered electrically conductive ink.
Plant (400) according to claim 11), characterized in that said work surface (401) is a conveyor belt (401a) for advancing said substrates (2) through said single workstation (402), and said advancement means comprise a motorized winding roller (401c) and an unwinding roller (401d) that are each supported on a respective end of the base (401b) of said plant (400).
Plant (100, 200, 300) according to any of claims 5) to 10) characterized in that said movement means are robotic means.
Plant (100, 300, 400) according to any of claims 5), 6), 9), 10), 11), 12), characterized in that said substrate (2) is a flexible laminar element with defined width and length.
Plant (100, 300, 400) according to any of claims 5), 6), 9), 10), 11), 12), characterized in that said substrate (2) is a rigid laminar element with defined width and length.
Plant (100, 300, 400) according to any of claims 5), 6), 9), 10), 11), 12), characterized in that said substrate (2) is a three-dimensional body.