Patent Application
20200187307
The present invention relates to electrical heating devices, in particular devices based upon the use of materials distinguished by an electrical resistance with positive temperature coefficient (PTC), namely, ones having a PTC effect, preferably materials comprising at least one polymer.
The invention has been developed with particular reference to electrical heating devices designed to be associated to, or integrated in, vehicle components, such as heaters for tanks, heaters for filters, heaters for batteries or electrical accumulators, heaters for substances subject to freezing, heaters for devices or substances that change their properties or characteristics as the temperature varies, or again heaters used for heating aeriform fluids, such as air for environments or air subject to forced circulation on the surface of such heaters.
The invention finds a preferred application in the sector of components or tanks designed to be in contact with, or contain, a fuel, or water, or a liquid that contains water, or a liquid additive, or a reducing agent, in particular a liquid necessary for operation of an internal-combustion engine and/or for operation of a system for treatment of exhaust gases of an internal-combustion engine, including ADI (Anti-Detonant Injection) systems. The heating devices according to the invention can in any case be applied also in sectors other than the preferential ones referred to above.
Exhaust-gas-emission systems of some types of vehicles must be devised with a view to reducing the release of nitrogen oxides (NOx) into the atmosphere. A system particularly widespread for this purpose is based upon the process known as SCR (Selective Catalytic Reduction), which enables reduction of nitrogen oxides of the gases by means of injection of a reducing agent into the exhaust line. These treatment systems presuppose that the reducing agent is dosed and injected into the flow of the exhaust gases in order to convert nitrogen oxide (NOx) into nitrogen (N2) and water (H2O). For this purpose, the vehicle is equipped with a tank containing the reducing agent, associated to which are suitable means for carrying out dosed injection of the agent itself into the SCR system.
The reducing agent is typically constituted by urea in aqueous solution, which is liable to freeze when the tank is exposed to low temperatures (indicatively temperatures lower than −11° C.). For this reason, the tank must be equipped with a heating device so that, in the case of freezing, the liquid agent can be liquefied and then injected into the exhaust line. The heating device is in general mounted inside the tank, or else integrated in, or associated to, a component of the tank that is sealingly mounted in an opening of the tank itself. The heating device is in general of the type that bases its own operation on the use of a material having a PTC effect, this material possibly being a ceramic-based or else a polymer-based material.
In general, known heating devices comprise a plurality of heating elements, each having an electrical resistor formed by a solid mass of the material with PTC effect, typically a mass of ceramic material shaped like a small disk. In some solutions, each heating element comprises a PTC resistor set between two respective metal electrodes, and the electrodes of the various heating elements are connected together, for example in parallel and/or in series with one another, for the purposes of electrical supply. In other solutions, a plurality of PTC resistors are arranged between two electrodes in common, typically in the form of metal plates or disks. In applications of this type, the heating device is generally without a casing of its own, and the body that houses it—for example, the body of a component of the tank or of a functional module associated to the tank—must be shaped for defining seats or housings for the various parts of the heating device (see, for example, EP 2 650 497 A1).
Heating devices of this type in general have a small extension in a radial direction, since they have to be positioned in the vicinity of the bottom wall of the tank, at or in the proximity of an opening for outlet or delivery of the reducing agent. This positioning is basically dictated by the need to render rapidly available a certain amount of the reducing agent, even in the case of freezing of the latter. Proper operation of the system for treatment of exhaust gases presupposes in fact dosing and injection of the reducing agent into the exhaust gases substantially immediately after engine ignition.
For this reason, the emission of heat allowed by the heating device occurs in a relatively concentrated area, i.e., in the vicinity of the outlet of the tank, with a consequent reduced contribution to melting of the frozen part of the reducing agent that, inside the tank, is located relatively far from the outlet of the tank itself. Certainly, the size of the heating device could be increased in a radial direction in order to heat an area substantially corresponding to the entire bottom wall of the tank. However, in addition to complicating further construction and mounting of the heating device, and of the component on which the device is mounted, such an approach would lead to a considerable increase in electric power consumption, such an increase being typically proportional to the area of the heater and/or to the heated area. Similar problems may also be encountered in heating devices used in other sectors.
Provision of heating devices equipped with a casing of their own in general entails problems linked to deformations (for example, expansion and contraction) of the PTC-effect material and/or of the corresponding metal electrodes due to the heating and cooling cycles. Such deformations lead to relative movements between the parts made of different materials, including the material or materials of the casing, with possible risks of failure. This problem is particularly felt in the case of laminar electrodes that cover the opposite surfaces of the mass of PTC-effect material practically entirely.
For this reason, it is advisable to provide a casing that covers the heating element (the PTC-effect material with the corresponding electrodes), but that is distinct from or independent of the latter (see, by way of simple, CN202455551U), at times with suitable empty spaces that will enable also relative movements to counter the aforementioned deformations. In the case of heaters with a sealed casing, however, the presence of air in these empty spaces reduces propagation of the heat generated given that the air operates as thermal insulator and is itself subject to variations in volume that depend upon the temperature, and this may cause anomalies in operation of the device.
The object of the present invention is basically to eliminate one or more of the drawbacks referred to above. In this context, an object of the invention is to provide an electrical heating device that is as a whole simple and economically advantageous to produce, as well as being able to heat relatively extensive areas, but at the same time enabling a limited electric-power consumption. An auxiliary aim of the invention is to provide an electrical heating device having a corresponding casing body that is simple and inexpensive to produce and reliable.
One or more of the above aims, and other aims still, which will emerge clearly hereinafter, are achieved, according to the present invention, by an electrical heating device, a motor-vehicle component, and a method for obtaining an electrical heating device that present the characteristics specified in the annexed claims. The claims form an integral part of the technical teaching provided herein in relation to the invention.
The characteristics, advantages, and further aims of the present invention will emerge clearly from the ensuing detailed description, with reference to the annexed drawings, which are provided purely by way of non-limiting example and in which:
Reference to “an embodiment” or “one embodiment” in the framework of the present description is intended to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as “in an embodiment” or “in one embodiment” and the like that may be present in various points of this description do not necessarily refer to one and the same embodiment. Moreover, particular conformations, structures, or characteristics defined in this description may be combined in any adequate way in one or more embodiments, which may even be different from the ones represented. The reference numbers and spatial references (such as “upper”, “lower” “top”, “bottom”, “up”, “down”, etc.) provided herein are used only for convenience and hence do not define the sphere of protection or the scope of the embodiments. In the present description and in the attached claims, the generic term “material” must be understood as comprising also mixtures, compositions, or combinations (for example, multilayer films) of a number of different materials.
With initial reference to
In what follows, it is assumed that the above container is a tank that is designed to contain a liquid, such as an additive or a reducing agent, and forms part of a system on board a vehicle, for example a system for reducing emissions of an internal-combustion engine or for treatment of the exhaust gases of an internal-combustion engine, represented as a whole by the block 2. In various embodiments, the system 2 is a treatment system of the SCR type, with injection of a reducing agent into the exhaust-gas line as explained in the introductory part of the present description, which is used for abatement of emissions of nitrogen oxides and particulate matter, in particular in motor vehicles with diesel engines. The aforesaid reducing agent may hence be urea in solution of distilled water, as for example the is commercially known by the name AdBlue™. In other embodiments, the treatment system 2 may be of the type that envisages injection of water directly into an internal-combustion engine, for reducing emissions and/or for preventing phenomena of spontaneous detonation, such as an ADI system. The container 1 (hereinafter referred to for simplicity also just as “tank”) could in any case be used for other purposes and/or in sectors other than the automotive one, and could be designed to contain a different liquid that requires heating, such as a fuel or a washing agent, or some other liquid or substance.
The body of the tank 1 has a bottom wall 1a, where an outlet or opening 1b for the liquid is defined. In various embodiments, the opening 1a may be sized for insertion and/or mounting of at least one further functional device, such as a device comprising sensor means, for example a module of the type known as UDM (Urea-Delivery Module).
In various embodiments, set on the bottom wall 1a of the tank 1 is an electrical heating device according to the invention, designated as a whole by 10. In the example, the heating device is controlled, i.e., electrically supplied, by means of the system 2.
An electrical heating device 10 according to possible embodiments of the invention, for example suitable for the use described with reference to
As will be appreciated for example in
This type of layered structure makes it possible to provide in a simple way a device 10 even having a relatively extensive surface, at the same time with an as a whole very reduced encumbrance in height. In this way, the device 10 can be easily set up against a supporting surface, for example on the bottom wall 1a of the tank 1 of
It should be noted that, in the present description and in the attached claims, the term “layer” used to identify certain components of the heating device 10 according to its preferred embodiments, is not to be understood in a limiting sense. In this perspective, in various embodiments, the components 11-15 described and identified hereinafter as “layers” may have a structure and/or shape and/or thickness other than what has been exemplified, albeit respecting the functions envisaged according to the invention (for example, the components 11 and 12 could be replaced by rigid or overmoulded walls, or by deposited layers of electrically insulating material or material having a high value of electrical resistance; the components 13 and 14 could be replaced by thick plates of electrically conductive material; the component 15 could be replaced by a solid mass of any shape of a material that is at least in part resistive or semiconductor or of the PTC-effect type, or in any case such as to provide a thermistor).
In various embodiments, the device 10 comprises a coating or casing 10a made of electrically insulating material. With reference also to
The two electrode layers 13 and 14 are arranged facing, preferably substantially parallel to one another and with respect to the heating layer 15, with at least one part of the heating layer 15 that is set between the two electrode layers 13 and 14 in contact with these, at respective opposite major faces. This layered structure provides a heating element, designated as a whole by 20 in
In various embodiments, the casing layers 11 and 12, i.e., the two opposite walls of the casing 10a, are set on top of the two electrode layers 13 and 14, respectively. Preferably, the casing layers 11 and 12 have a larger width than the electrode layers 13 and 14, in order to provide peripheral areas of respective contact and/or superposition of the casing layers 11 and 12. In various embodiments, the casing layers 11 and 12 are sealingly joined together in respective peripheral superposition areas, designated by 11b and 12b, for example via gluing or welding, such as thermal welding or laser welding.
In various embodiments, the layers 11, 12, 13, 14, and 15 each have a through opening, the openings being designated, respectively, by 11a, 12a, 13a, 14a, and 15a in
In various embodiments, on the openings 11a-13a a body for providing fluid-tightness or sealing, designated as a whole by 16, is applied, preferably via overmoulding (or possibly via elastic mounting), the body 16 being configured for insulating the device 10 with respect to the outside also at the openings 11a-13a. As will emerge from what follows, the body 16 can also perform the function of protection of some electrical-connection elements of the device 10, and for this purpose the body 16 is preferentially made of electrically insulating material.
In various embodiments, also the body 16 defines a through opening, designated by 16a. The presence of the opening 16a of the body 16 and of the openings 11a-15a of the layers 11-15 is particularly advantageous, for example in applications of the type represented in
The presence of a passage or of an axial opening that traverses the device 10 in the direction of its thickness (i.e., with reference to the example illustrated, the ensemble of the through openings 11a-16a) does not constitute an essential characteristic of the invention. In the same way, also the presence of the body 16 must be understood as optional. A sealing, and/or electrically insulating body applied or overmoulded on the casing 10a can in any case be provided in embodiments in which the electrical-connection terminals of the device 10 are positioned in a different way from the embodiments exemplified herein.
In various embodiments, at least part of the casing 10a, preferably the entire casing 10a, can be provided via moulding or overmoulding of a polymer on the layers 13, 14, and 15. Such a casing can advantageously be shaped for providing one or more further elements, such as at least one of the following: a body of an electrical connector, elements for fixing the device 10 to the tank 1, a passageway for the fluid, at least part of the outlet of the tank 1, a seat for coupling with some other device (such as a UDM), etc.
As will be seen, in the non-limiting examples provided herein, the electrical-connection terminals 13d, 14d of the device 10 project in a substantially axial direction (or vertical direction, as viewed in the figures), but in possible variant embodiments—for example one in which the device is without the aforesaid axial passage—the connection terminals may be located in some other position, for example in the proximity of the outer profile or of the peripheral areas 11b and 12b, or else could project from the casing 10a in a substantially radial direction (or horizontal direction, as viewed in the figures), preferably coated at least in part by a sealing, and/or electrically insulating body, i.e., by a body of an electrical connector.
The casing layers 11 and 12 or, more in general, the casing 10a, are preferentially made of a material chemically resistant to the environment where the device 10 is installed or to the medium that is to be heated, for example the reducing agent contained in the tank 1 of
In preferential embodiments, as has been said, the casing 10a is formed by the two layers 11 and 12, set on top of one another and sealingly joined at least in the respective perimetral regions 11b and 12b, with the heating element 20 set in between, as exemplified in
In various embodiments, the casing layers 11 and 12 are constituted by respective films of polymeric material. Preferred materials are, for example, polypropylene (PP), polyethylene (PE), high-density polyethylene (HDPE), thermoplastic polyurethane (TPU), ethylene vinyl alcohol (EVOH), polyoxymethylene (POM), and thermoplastic elastomer (TPE).
According to possible embodiments, the layers 11 and 12 in turn have a multilayer structure; i.e., they are themselves constituted by a plurality of layers of different materials, which possibly have different technical characteristics (for example, in terms of thermal conductivity, electrical insulation, barrier properties in regard to the external environment, flexibility, etc.): for example, the layers 11 and/or 12 may comprise two or more layers, each made of one and the same material, preferably chosen from the ones referred to above (PP, PE, HDPE, TPU, EVOH, POM, TPE), or else may comprise combinations of two or more layers of different materials, preferably chosen from the ones referred to above (PP, PE, HDPE, TPU, EVOH, POM, TPE); in the case of a multilayer structure, the layers 11 and/or 12 may also include at least one metal layer to provide a barrier to the penetration of liquid, and/or vapour, and/or gas.
In general, the layers 11 and 12 may each have a thickness of between 0.1 mm and 2 mm, in particular when they are in the form of films.
In possible variant embodiments, instead of being obtained using films 11, 12 of polymeric material, the casing 10a may be obtained using protective layers consisting of resins, coatings, or other substances deposited or overmoulded at least in part on the electrode layers 13, 14 and/or on the heating layer 15: in these cases, the thickness of the layers 11, 12 (or of the walls that perform their function) may, for example, be up to 3 or 4 mm.
It will be appreciated that, in various preferential embodiments, the casing 10a is very simple and inexpensive to produce in so far as the casing layers 11 and 12 may, for example, be obtained via simple operations of blanking or dinking, starting from webs or films of the material of interest. The layers 11, 12 thus obtained can be laid on the two opposite major faces of the heated element 20, for example via lamination. As has been said, when necessary, the layers 11 and 12 can be sealingly joined along their peripheral superposition areas 11b and 12b, for example via welding or gluing (they may, however, be joined via moulding, also in a single piece). The body 16 may possibly be overmoulded on the semifinished product thus obtained.
In various embodiments, the layers 11 and 12 are arranged so as to adhere in part to the electrode layers 13, 14 and in part to the heating layer 15, in particular, at edges or parts of the latter that project from the electrode layers, or else directly at the opposite major faces of the heating layer 15 when, as will be seen, the electrode layers 13-14 are englobed in the material of the layer 15 itself. Consequently, in various embodiments, a polymeric material of the casing 10a of the device 10 is directly in contact with at least part of the material of the heating layer 15, in particular when the heating layer itself comprises a polymeric material, preferably a polymer of the casing 10a and a polymer of the heating layer 15, that are compatible with one another or are such as to form bonds with one another, such as chemical and/or structural bonds between the polymeric chains: thanks to this characteristic, the adhesion or fixing of the casing on the heating element, including the electrode layers and heating layer, is improved.
The electrode layers 13 and 14 are preferentially, but not necessarily, made of one and the same electrically conductive material, such as a metal material (for example, selected from among stainless steel, brass, bronze, aluminium, or alloys thereof) or an electrically conductive polymeric material. In various embodiments, at least one of the electrode layers 13 and 14 is formed by a material in sheet or laminar form, or a meshed material, or again a fabric material (including electrically conductive non-woven fabrics). One or both of the electrode layers 13 and 14 may possibly be obtained also by depositing an electrically conductive material directly on the heating layer 15 or on the casing layers 11 and 12, on a respective face, for example using silk-screen techniques or else overmoulding or co-moulding techniques. Of course, it is also possible to use or combine different materials and types of electrode (for example, one electrode layer may be obtained starting from a metal lamina, and the other electrode layer may be obtained starting from an electrically conductive fabric). Also the electrode layers 13 and 14 may possibly have a multilayer structure.
In general, the electrode layers 13 and 14 can each have a thickness of from a few microns (for example, in the case of a deposition process) up to 3 mm (for example, in the case of a blanking or photo-etching process). It will be appreciated that, by virtue of their preferably small thickness, the electrode layers 13, 14 may also be relatively flexible or deformable. Also the electrode layers 13 and 14 may, for example, be obtained via simple blanking or dinking operations, starting from sheets, or webs, or laminas, or films, or pieces of the material of interest or else, as has been said, using known deposition techniques.
In preferred embodiments, the heating layer 15 is made of a material having a PTC effect. In various embodiments, the material constituting the layer 15 is a polymer-based material (i.e., comprising at least one polymer), for example a composite material having a matrix formed by a polymer or by a mixture of a number of polymers and by a corresponding filler, for example an electrically conductive filler and/or a thermally conductive filler.
In various embodiments, the material of the layer 15 is a co-continuous polymeric composite with PTC effect, having a matrix that comprises at least two immiscible polymers and at least one electrically conductive filler in the matrix. In preferred embodiments of this type, at least one of the immiscible polymers is high-density polyethylene (HDPE) and at least another one of the immiscible polymers is polyoxymethylene (POM). The electrically conductive filler is preferentially constituted by particles having micrometric or nanometric dimensions, preferably comprised between 10 nm and 20 μm, very preferably between 50 nm and 200 nm, possibly aggregated to form chains or branched aggregates of dimensions comprised between 1 μm and 20 μm. Preferential materials for the electrically conductive filler are carbonaceous materials, such as carbon black, or graphene, or carbon nanotubes, or mixtures thereof.
The HDPE and the POM are preferentially in relative percentages of between 45% and 55% of the sum of their weights. Preferentially, the electrically conductive filler is confined or mostly confined in the HDPE, in a weight percentage of between 10 wt % and 45 wt %, preferably between 16 wt % and 30 wt %, taking to be 100 the sum of the weights of the HDPE and of the electrically conductive filler. For this purpose, the HDPE and the electrically conductive filler can be mixed together, in particular via extrusion, prior to subsequent mixing with the POM, which also in this case can be obtained preferentially via extrusion.
The high melting point of the POM enables, during extrusion of the composite, the two HDPE-POM phases to be kept better separated, reducing the possibility of migration of the carbonaceous filler into the POM (contributing to this effect is the fact that the filler is preferentially previously mixed with just the HDPE). The higher melting point of the POM as compared to other known polymers likewise enables a more stable final structure to be obtained: the PTC effect of the composite material limits self-heating to a maximum temperature of approximately 120° C. POM moreover has a high crystallinity, roughly comprised between 70% and 80%: this means that, in the proposed preferential co-continuous composite, any migration of filler from the HDPE to the POM is more unlikely to occur, thereby preventing loss of performance of the PTC-effect material, for example due to heating and passage of electric current. The higher crystallinity of POM also renders the composite particularly resistant from the chemical standpoint and bestows high stability thereon. On the other hand, the crystallinity of HDPE is typically comprised between 60% and 90%: in this way, a high concentration of the conductive filler is obtained in the amorphous domains, with corresponding high electrical conductivity.
In various preferential embodiments, the composite that forms the heating layer 15 includes a thermally conductive filler, preferably comprising a material having a value of thermal conductivity higher than 200 W/(m·K) at 25° C. A preferred material in this sense is, for example, boron nitride (NB). Preferentially, with reference to the example HDPE+POM referred to previously, the thermally conductive filler is confined or mostly confined in the POM, in particular in a weight percentage comprised between 5 wt % and 70 wt %, preferably between 15 wt % and 30 wt %, taking to be 100 the sum of the weights of the POM and of the electrically conductive filler, For this purpose, the POM and the thermally conductive filler can be mixed together, in particular via extrusion, prior to mixing with the HDPE, which is possibly pre-mixed with a corresponding electrically conductive filler.
For further details as regards to the preferred polymeric co-composite indicated for providing the heating layer 15, i.e., having a matrix that comprises HDPE and POM, the reader is referred to the Italian patent application No. IT102017000038877, the teachings of which are incorporated herein for reference.
In general, the heating layer 15 can have a thickness of between 0.5 mm and 5 mm. Also in this case, considering its small thickness and its basically polymeric nature, the heating layer 15 may, if need be, present a certain bending capacity.
Also the heating layer 15 may possibly be obtained via simple operations of blanking or dinking, starting from a sheet or web of the starting PTC-effect polymer. However, as already mentioned, according to possible variant embodiments of the invention, the layer 15 can be overmoulded on or co-moulded with the layers 13-15.
In various embodiments, provision of the heating layer 15 by means of a polymer-based material (i.e., a material comprising at least one polymer) is advantageous in order to improve adhesion or fixing between the heating element 20, which integrates the layer 15, and the corresponding casing 10a, when the latter is present. In this perspective, in various embodiments, the material of the layer 15 and the material of the casing are mutually compatible or such as to form bonds, such as chemical or structural or mechanical bonds, or comprise one or more materials or components in common. For instance, with reference to a material of the heating layer 15 that includes HDPE and/or POM, the material of the casing 10a, i.e., of the casing layer 11 and/or layer 12, may itself comprise PE or HDPE and/or POM: in this way, on the parts of casing that are set on top of the heating layer a better adhesion or bonding will be obtained between the corresponding materials, for example between the chains of the polymer that is in common. More in general, the materials of the layer 11 and/or 12 and the material of the layer 15 comprise polymers designed to melt at least in part and bond to one another, for example in the course of a hot lamination or of an overmoulding, and/or designed to bind to one another, for example chemically and/or mechanically (as in the case exemplified previously of the layers 11, 12, and 15 that include PE or HDPE and/or POM).
In preferential embodiments, the electrode layers 13 and 14 have substantially similar overall perimetral dimensions, i.e., the shape and perimetral dimensions of the electrode layer 13 are substantially similar to the shape and perimetral dimensions of the electrode layer 14. More in general, preferentially, the electrode layers 13 and 14 define respective superposition areas that are substantially similar, whereby it is meant that the facing areas of the two electrode layers, with at least part of the heating layer set in between, are substantially similar. It should be noted, for this purpose, that the terms “superposition areas” or “facing areas” are meant to designate a “theoretical” area, i.e., without considering the electrically non-conductive (or substantially electrically insulating) sites described hereinafter.
At least one part of the heating layer 15, preferably a part having a substantially constant thickness, is set between the two electrode layers 13 and 14. Preferentially, also the layer 15 has overall perimetral dimensions substantially similar to those of the electrode layers 13 and 14, but not excluded is the case of a part of the layer 15 that projects beyond the edges of the layers 13, 14 or else that does not reach as far as the aforesaid edges. Moreover, as will be seen, in possible embodiments, the electrode layers 13, 14 are at least in part embedded in the heating layer 15, or else the latter is shaped so as to define recesses for housing the aforesaid layers 13, 14. Hence, in these embodiments, only a part of the layer 15 is effectively set between the layers 13 and 14: in these cases, preferably, part of the material of the casing 10a is directly in contact with part of the material of the heating layer 15.
The casing layers 11 and 12, in the embodiments that envisage them, preferentially have a peripheral profile substantially similar to that of the layers 13-15 (or at least to the profile of the one from among the layers 13-15 that has largest dimensions), but of larger dimensions in order to enable definition of the corresponding superposition areas 11b and 12b for peripheral sealing of the casing 10a.
In
The connection elements 13c and 14c may, for example, be arranged in such a way that a part thereof projects at a corresponding passage close to the through openings 13a and 14a, for instance, a passage constituted by a radial extension of the through openings 13a and 14a. These passages or radial extensions of the openings 13a and 14a are designated by 13a1 and 14a1 in
The connection elements 13c and 14c preferably have a small thickness and are, for example, in the form of a shaped metal lamina, shaped, for instance, as an open ring, with an internal diameter substantially corresponding or close to the diameter of the through opening 13a and 14a of the corresponding electrode layer 13 and 14. In various embodiments, the elements 13c and 14c are substantially designed to provide an electrical-distribution element, which is particularly useful in the case of connection to electrode layers made of fabric or meshwork. In various embodiments, the connection elements 13c and 14c, preferably in the form of a shaped metal lamina, are welded to the respective electrode layers 13 and 14, for example when the latter are in the form of a wire mesh in such a way as to guarantee mutual electrical connection and mechanical fixing.
As may be noted, in particular in
In the example of
The heating element 20 thus obtained is then equipped with the casing 10a if the presence of the casing is necessary or preferable in view of the application for which the heating device is designed (for example, it is useful for protecting the device from chemically aggressive liquids or agents, whereas, if the device is used for heating a forced flow of air or some types of fuel, the casing may be omitted). Hence, with reference to the examples illustrated so far, the casing layers 11 and 12 are set on top of the two opposite major faces of the heating element 20, for example via lamination, with the terminals 13d and 14d that pass also through the radial extension 12a1 of the opening 12a of the layer 12. The layers 11 and 12 are then joined (sealingly, if this is necessary in view of the application of the device 10) in the respective peripheral superposition areas 11b and 12c. Next, the body 16 is applied to the semifinished product, in particular via overmoulding and/or resin bonding. The body 16, in addition to sealing the layered structure at the through openings 11a-15a, as already mentioned above, is preferentially also shaped for defining a portion 16b (
The heating device according to the invention is configured so as to present areas with diversified emission of heat. In general, the definition “emission of heat” may here be understood as an emission of heat referred to a unit surface or to a surface of predefined area, or else as a power or heating density or else as an emittance, for example, expressed in W/cm2 or W/dm2 or other unit of measurement suitable for the purpose. In this perspective, the phrase “areas with diversified emission of heat” may be understood as referring to areas subject to a different distribution or intensity of heat emission, or to a different power or heating density, or to a different emittance, referred to a unit surface or a predefined surface. The emission of heat may regard each of the electrode layers 13, 14 and/or the heating layer 15 given that the electrode layers can behave as dissipator of the heat emitted by the heating layer, in particular in the case of metal electrodes or electrodes that are in any case thermally conductive.
The solution of providing areas of diversified heat emission is based upon the consideration that, in various applications, it may prove convenient to provide a heating device that enables a different distribution of heat emission to be obtained, such as an higher, or more concentrated, heat emission in at least one first area to be heated, and at the same time a lower, or less concentrated, heat emission also in at least one further area to be heated.
An example of such an application is the preferential one previously mentioned with reference to
Of course, a known heating device could be sized for heating uniformly an area substantially corresponding to that of the entire bottom 1a of the tank 1, but this, in addition to complicating construction of the device, would imply an excessive use of electric power in proportion to the actual needs. Considering that the flow rate of the reducing agent or other liquid at outlet from the tank 1 may be limited, is in fact sufficient to heat and melt the liquid rapidly just in the area close to the outlet 1b, it being possible to heat and melt the liquid more slowly in the other areas of the tank.
According to a different approach, the tank 1 could be equipped with a number of heating devices, of which a first heater with higher thermal emission in a first area in the vicinity of the outlet 1b and at least one second heater in a second area peripheral with respect to the first area, with the second heater distinguished by a lower heat emission, and then by a lower consumption: also in this case, however, construction of the heating system would be as a whole complicated and costly, as likewise its control.
Hence, in accordance with the invention, the differentiated emission of heat by the device 10 is obtained via a particular structuring of at least one from among the electrode layer 13, the electrode layer 14, and the heating layer 15.
According to a first aspect, at least one of the first and second electrode layers 13 and 14 has at least one region in contact with a corresponding region of the heating layer 15, and the region of the layer 13 and/or of the layer 14 and/or of the layer 15 is provided with a plurality of electrically non-conductive sites. The electrically non-conductive sites are prearranged for bringing about an emission of heat by the heating device 10 in the aforesaid region that is different from the emission of heat by the heating device 10 in at least another region of the first electrode layer 13 and/or of the second electrode layer 14 and/or of the heating layer 15, or else that is different from the emission of heat by the heating device 10 at the other one of the first and second electrode layers 13 and 14.
In this way, within each electrode layer 13 and 14 and the heating layer 15 homologous regions may be provided distinguished by a different emission of heat, or else the emission of heat at one electrode layer may be different from the emission of heat at the other electrode layer.
For instance, in the first case mentioned, with a preferably substantially parallel and stacked arrangement of the layers 13-15, in each of the electrode layers 13 and 14 a plurality of regions may be identified in contact with the heating layer, in homologous positions of the two electrode layers, with these regions that are prearranged for diversified emission of heat. With reference, for example, to
In this way, as will emerge more clearly hereinafter, the emission of heat (or heating power density or emittance, measured in W/cm2 or W/dm2) by the heating device 10 in the first region 21 is lower than the emission of heat in the second region 22. Moreover, the emission of heat in the first region 21 of the electrode layer 13 and in the corresponding first region 21 of the second electrode layer 14 is lower than the emission of heat in the second region 22 of the electrode layer 13 itself and in the corresponding second region 22 of the electrode layer 14.
In other embodiments, described hereinafter, the electrode layers and the electrically non-conductive sites may be prearranged in such a way that the emission of heat by one electrode layer is different from the emission of heat by the other electrode layer.
With reference to the case of
Basically, then, the holes are arranged or distributed on at least one electrode layer so as to be absent or in a smaller number in the areas where it is desired to obtain greater heating (i.e., a higher power density), as for example the area close to the outlet 1b of
In the example, the subregion 21a is the one distinguished by the lowest heat emission and is provided with holes 30a with largest cross section, whereas the subregions 21b and 21c are distinguished by respectively increasing heat emissions: this is obtained, in the case of the subregion 21c, by holes 30c that are in a number a little greater than in the subregion 21a, but that have a decidedly smaller cross section than the holes 30a; the subregion 21b has instead holes 30b with an intermediate cross section as compared to the holes 30a and 30c, but in a decidedly higher number.
In more general terms, the greater the ratio between the total area of the holes of a given region (i.e., the sum of the areas of the individual holes) of an electrode layer and the overall or “full” area of the same region (i.e., its theoretical area in the absence of holes), the lower the emission of heat in this region.
The above concept may be clarified with reference to
Of course, the holes provided in the various regions 21 and 22 could also differ for the electrode layer 13 and the electrode layer 14, for example by envisaging in the region 21 of the layer 14 holes that have a shape, and/or size, and/or density different from those of the holes provided in the corresponding region 21 of the layer 14.
With reference, for example, to
Of course, the holes provided in the electrode layer 13 and/or in the electrode layer 14 may be configured in multiple different ways or be combined with one another according to various configurations, according to the production requirements, for example in terms of shape, and/or arrangement, and/or size, and/or density on the electrode layer. For instance, exemplified in
As has been mentioned previously, the electrode layers 13 and 14 may be formed via blanking or dinking, in particular when they are obtained starting from material in the form of a sheet, or web, or plate, for example from a metal sheet or a mesh or an electrically conductive fabric. Obviously, the operation of blanking or dinking will be prearranged so as to obtain also the necessary holes on the electrode layer considered. For instance, operations of blanking or dinking are suitable for providing electrodes according to
In various embodiments, the warp and weft are arranged so as to define regions provided with differently sized holes. In the example illustrated, for instance, the warp and weft are arranged so as to define a sort of frame, with a central region 21 practically corresponding to a single hole 30a of maximum dimensions, and four angular regions 23 in which the warp and weft define holes 30c of minimum dimensions. The regions 22 that extend between the regions 23 are defined by just weft yarns or else just warp yarns, thus obtaining holes 30b of intermediate dimensions with respect to the central hole 30a and the holes 30c. As may be appreciated, heat emission will hence be minimum in the region 21, maximum in the regions 23, and intermediate in the regions 22.
In various embodiments in which at least one electrode layer is formed by a fabric (not necessarily according to the configuration of
As has been said, what has been described and exemplified in the figures with reference to the electrode layer 13 may apply also in relation to the electrode layer 14.
In various embodiments, at least one of the electrode layers 13 and 14, preferably both, is in the form of grid or mesh, for example obtained by making through incisions (staggered cuts) in a length of metal web and then deforming or stretching the lengths until passages 30d (
In a meshed structure of this type, there may hence be made the specific holes 30e provided according to the teachings provided herein, i.e., the electrically non-conductive sites specifically provided for determining the type of heat emission, i.e., ones having a function different from that of the regular series of passages that are typically provided in common meshed structures or in certain fabrics. As may be seen in
In various embodiments, at least one of the electrode layers, preferably both of the layers 13 and 14, is at least partially embedded in the material of the heating layer 15, in such a way that the corresponding casing layer 11 or 12 will adhere directly on at least part of the surface of the heating layer 15, at one of the two opposite major faces of the latter. This solution is particularly advantageous in so far as the layer 15 has its two opposite major faces substantially plane, thereby guaranteeing a better adhesion of the casing layers 11 or 12. In embodiments of this type, as exemplified in
The cross-sectional view of
According to an aspect in itself inventive, the transfer of heat between the electrode layer 13 and/or 14 and the respective casing layer 11 and/or 12 may be improved via the addition of a thermally conductive filler present in the material of the layer 15, for example, in the part 15′ and/or the parts 15″.
The cross-sectional view of
The cross-sectional view of
As an alternative to overmoulding of the layer 15 on the layers 13 and 14, meshed electrode layers may be made to penetrate at least in part into the material of the layer 15 previously moulded in the form of a sheet, in particular by heating the layer 15 and then pressing the electrode layers into it. Such a case is exemplified in
In various embodiments, defined on the two opposite faces of the heating layer 15 are recesses for housing and positioning at least part of the electrode layers, not necessarily electrode layers in the form of a mesh: an example of this type is illustrated in
In various embodiments, even in the absence of the openings 11a-15a and of the body 16 of
For instance, illustrated schematically in
In the case exemplified, in the intermediate area 40 illustrated, also the casing layers 11 and 12 have substantially coaxial or at least partially facing through openings 11d and 12d, respectively, which may, for example, be exploited for fixing the device, or again for enabling passage of a fluid between the two opposite faces of the heating device. In the presence of the openings 11d and 12d, joining between the layers 11 and 12 in the area 40 will preferably be fluid-tight; however, in addition or as an alternative to fixing between the casing layers 11 and 12, tightness in regard to infiltration of liquids or other fluids within the heating device may be obtained via a sealed fixing between the casing layers 11 and the heating layer 15 (at least at its edge 15b), in particular via welding or gluing or overmoulding. In the case of welding or overmoulding, it is preferable to use polymers for the layers 11, 12, and 15 that are to melt at least in part and weld to one another, or polymers that are bind to one another, such as a layer 15 and at least one layer 11 and/or 12 comprising PE or HDPE and/or POM. The presence of the openings 11d and 12d must in any case be understood as optional and hence not indispensable.
As may be appreciated, also in the case of
In various embodiments, the heating layer 15 defines one or more edges, which have a substantially tapered profile, and the casing 10a of the device has one or more portions shaped in a substantially corresponding or complementary way. This characteristic has already been previously highlighted in relation to the intermediate fixing areas 40 of
As may be seen also with reference to
The tapered or inclined peripheral profile of the edges 15c may be bestowed upon the layer 15 in the course of its production, for example in the course of its moulding, as highlighted in
Alternatively, the layer 15 may be initially formed with squared edges or edges of a different shape, for example having sharp corners, as highlighted in
The presence of tapered edges in the layer 15 presents the further advantage of preventing formation of significant empty spaces (air bubbles) between the layers 11, 12 and the peripheral edge 15c of the layer 15, and risks of failure following upon high degrees of expansion during the operating cycles of the device 10, at the same time enabling proper propagation of the heat towards the outside.
Highlighted in part A of
The structure illustrated in part B of
Part C of
As has been mentioned previously, at least one of the electrode layers 13, 14 and/or the heating layer 15 and/or the electrically non-conductive sites may be prearranged in such a way that heat emission is as a whole different from one electrode to another. This measure may be adopted, for example, in applications where it is desired to have a maximum heat emission from a major face of the heating device, corresponding for example to the electrode layer 13, and a lower heat emission from the other major face of the device, corresponding, for example, to the electrode layer 14.
In this perspective, in various embodiments, a first electrode layer, for example the layer 14, has a plurality of electrically non-conductive sites, and the second electrode layer, for example the layer 13, is substantially devoid of electrically non-conductive sites, or else comprises one or more respective electrically non-conductive sites prearranged in such a way that the overall surface of contact between the heating layer 15 and the first electrode layer 14 is smaller than the overall surface of contact between the heating layer 15 and the second electrode layer 13, the emission of heat at the first electrode layer 14 thereby being smaller than the emission of heat at the second electrode layer 13.
Likewise,
In various embodiments, the two electrode layers 13 and 14 may both have a plurality of respective electrically non-conductive sites, where the two pluralities of sites are, however, different one another, for example in terms of shape, and/or size, and/or arrangement, and/or number, and/or density of the corresponding electrically non-conductive sites. For instance,
In the embodiments described previously, the heating device 10 has been exemplified as a stand-alone component, designed for being mounted in a container or on a generic supplied device, such as a tank. It will be appreciated, however, that a heating device according to the invention may also be integrated in, or associated to, devices prearranged to perform functions different from heating or containment or conveying of a generic medium, such as functions of detection, for example, for detecting the level, and/or characteristics, and/or pressure of a substance, or else again functions of management of the aforesaid substance, such as dosing thereof.
In this perspective, in particularly advantageous embodiments, the heating device 10 forming the subject of the invention may be associated or coupled to a functional device used in combination with a container or tank, for example a device comprising a plurality of functional elements, such as a duct for a liquid and/or a pump, and/or sensors, and/or a further heater. Such a functional device may, for example, be a device for a fuel tank, or for managing an additive or a reducing agent used in an internal-combustion engine. Functional devices of this type, for example the ones known as UDM, are frequently mounted in a fluid-tight way at an opening of a tank containing a liquid reducing agent and in general comprise a pump and sensor means for detecting one or more characteristics of the liquid. As already highlighted, given that the liquid, in particular if it comprises water, is liable to freeze when the tank is exposed to low temperatures (indicatively temperatures lower than −11° C.), provision of a heating device according to the invention enables melting of the frozen liquid to be achieved.
Preferably, the electrical-connector body 16b of the heater 10 and the electrical-connector body 50a of the device 50 and/or the respective terminals 13d, 14d, and 50b are arranged in a position where they are close to one another and/or arranged in such a way as to facilitate electrical connection, preferably via a single connector or electrical wiring of the vehicle.
In various inventive embodiments, also the heating layer alone of a device according to the invention may be prearranged for bringing about differentiated heat emission in at least one region thereof. In various embodiments of this type, for example, the heating layer has at least one region set between the respective electrode layers that is provided with electrically non-conductive sites, for example in the form of holes or cavities. This solution may be implemented in addition or as an alternative to the presence of electrically non-conductive sites in one or both of the electrode layers, in order to bring about differentiated heat emission by the heating device.
An inventive implementation of this type is illustrated schematically in
In various embodiments, when the sites 30′ comprise through holes of the layer 15, at least some of the holes 30′ are connected to at least one other hole 30′, by means of voids or connection passages, some of which are designated by 30″ in
The connection passages 30″ may be provided in order to facilitate formation of the holes 30′ in the production stage, for example in the course of an operation of injection moulding of the layer 15, or else when the holes themselves are blanked or dinked from a layer 15 formed previously. The presence of the passages 30″ proves advantageous also in those embodiments in which the holes 30′ and the passages themselves are provided for being occupied by a different material, for example a material that is electrically insulating, and possibly also thermally insulating, or else a second heating material, such as a second resistive or PTC-effect material, in particular of the type having a different heating temperature and/or heat-emission capacity as compared to a first heating or PTC-effect material, as described hereinafter.
It should, however, be noted that, in various embodiments, the holes that constitute electrically non-conductive sites of the layer 15 may be separate holes or holes not connected to one another, i.e., formed even in the absence of connection passages 30″.
Of course, the electrode layer 13 and/or the electrode layer 14 of
In the case exemplified, the second material 300 is shaped so as to provide a shape substantially complementary to that of the array of holes 30′ and of the corresponding connection passages 30″; for example it comprises an array of elements or inserts 300′—here substantially disk-shaped—joined together by means of connection portions 300″—here substantially rectilinear.
The material 300 may be configured as a whole as a single body, as in the case exemplified in the figures, distinct or obtained separately with respect to the heating layer 15 and defining the inserts 300′ and the portions 300″, which is subsequently applied or fitted, preferably with slight interference, on the layer 15, so as to occupy the corresponding holes 30′ and passages 30″. In other embodiments, the material 300 may be applied directly on the layer 15, filling the holes 30′ and the passages 30″ of the layer 15 itself with the material 300: this filling may, for example, be obtained by overmoulding or co-moulding of the material 300 on or with the layer 15, or else by pouring the material 300 (for example, a resin) into the holes 30′ and passages 30″. For this purpose the passages 30″ may advantageously serve to get the second material to flow and distribute between the various holes 30′. However, the passages 30″ could also be totally or in part absent, as explained hereinafter.
Of course, it is also possible to mould first a single body made of the material 300 and, subsequently, overmould thereon or co-mould therewith the material designed to provide the remaining part of the heating layer 15 (i.e., the part defining the holes 30′ and passages 30″).
In the case of a heating layer 15, the sites 30′ of which are constituted by distinct holes (i.e., without the connection passages 30″), the inserts 300′ may be configured as bodies distinct from one another, or else the corresponding material may be moulded or poured into the individual holes 30′ of the layer 15. The embodiment illustrated in
As may be appreciated, operation of a heating device integrating a heating layer 15 of the type illustrated in
In the embodiments exemplified, with a relatively thin heating layer 15, the holes 30′ and possible passages 30′ are preferentially holes and passages formed through the layer 15. In other embodiments, when the heating layer 15 has a sufficient thickness, the holes 30′ and possible passages 30′ may, instead, be configured as blind cavities, i.e., provided with a bottom. Embodiments of this type are exemplified also in the partial cross-sectional views of
It will be appreciated that the solution of providing electrically non-conductive sites in the form of blind cavities or cavities with a bottom may be implemented also in relation to the electrode layers 13 and/or 14, when these layers have a thickness sufficient for the purpose.
According to a different inventive aspect, the heating layer provided in a device according to the invention is prearranged for differentiated heat emission obtained with the use of at least two different materials having a PTC effect, or else two different thermistor materials, distinguished by heating temperatures and/or heat-emission capacity that are different from one another. In solutions of this type, in a heating layer formed prevalently with a first PTC-effect material there made be provided one or more areas or islands made of a second PTC-effect material, distinguished by a heat-emission capacity higher or lower than that of the first material.
For instance, and as previously designated by reference to
A similar effect may be obtained by providing in a PTC-effect material 300 an electrically conductive filler in a different proportion (for example, a lower proportion) with respect to the material of the layer 15, so as to vary or increase its electrical resistance. Yet another possibility is to use a PTC-effect material 300 similar to that of the layer 15 (for example, both materials being HDPE+POM), but distinguished by a higher amount of filler constituted by electrically conductive particles so as to reduce its electrical resistance and thus develop less heat. As has been said, the PTC materials used may differ from one another also for the specific composition of the material of the matrix or of its electrically conductive filler, for example in the sense that the polymer or polymers of a first PTC material may differ from the polymer or polymers of a second PTC material. Similar considerations apply to the materials constituting the possible electrically conductive and/or thermally conductive fillers.
What has been described previously with reference to
From the foregoing description, the characteristics of the present invention emerge clearly, as likewise its advantages. The electrical heating device according to the invention is as a whole simple and inexpensive to produce, and reliable in operation, as well as being able to heat relatively extensive areas, but with limited power consumption, by virtue of the possibility of differentiating heat emission from the device, i.e., of defining one or more regions with high heat emission and one or more other regions with low heat emission. The invention enables a heating device to be obtained having at least two areas with different distribution of the heating power and/or with different electric-power consumption and/or with different temperature, without the use of electronic control circuits and without having to associate the areas to different electrical connections.
The protective casing of a heating element of a device according to the invention, when envisaged, is itself simple to produce and reliable, at the same time guaranteeing an increased adhesion, and/or fixing, and/or bonding thereof to the corresponding heating element. The characteristics of adhesion, and/or fixing, and/or bonding of the casing to the corresponding heating element, and in particular adhesion, and/or fixing, and/or bonding of the casing to the heating material, at least in part set between the electrodes, make it possible to improve and guarantee in time contact between the casing and the heater, and/or prevent corresponding detachment, and/or prevent formation of albeit minimal air gaps or voids between the casing and the heater. It is thus possible in this way to prevent an increase in the thermal resistance and/or a reduction in the propagation of heat from the heater to the casing, and hence to the fluid to be heated. Preferably, the protective casing described enables total elimination or in any case reduction of the risk of stagnation of air that might possibly have negative effects.
The protective casing described makes it possible, wherever necessary, to provide a heating device that is more protected from the medium that is to be heated, such as chemically aggressive or corrosive liquids; i.e., it makes it possible to provide a heating device that can be appropriately insulated from the medium to be heated, in particular in order to prevent any contamination of the medium itself by the materials of the heating device.
The intrinsic elasticity of the casing according to various embodiments, and of the heating device as a whole, contributes to reducing the risks of failure due to the thermal cycles of the heating device and to the consequent expansion/contraction of the materials involved.
It is clear that numerous variations may be made by the person skilled in the branch to the electrical heating device described by way of example, without thereby departing from the scope of the invention as defined in the ensuing claims.
In the preferential versions, the electrically non-conductive sites provided in one or both of the electrode layers are constituted by holes prearranged in a specific way for the purposes of the invention. However, in variant embodiments, the aforesaid sites could be obtained in some other way, in particular by providing the specific areas of one or each electrode layer with pads or spots of electrically insulating or substantially insulating material, on the face of the electrode layer that is to be set on top of the heating layer. In this perspective, the phrase “electrically non-conductive sites”, which is present in various points of this description and in the attached claims, is hence to be understood as comprising also substantially electrically insulated or insulating sites, as well as sites with high electrical resistance, i.e., distinguished by an electrical resistance significantly higher than the electrical resistance of the electrode layers 13 and 14 and/or of the heating layer 15 (or, conversely, distinguished by an electrical conductivity lower than the electrical conductivity of the electrode layers 13 and 14 and/or of the heating layer 15). In this perspective, also the phrase “substantially electrically insulating” and the like (used also previously, for example in relation to the material 300) is meant to include the case of materials with high electrical resistance (or low electrical conductivity) as compared to the material of the electrode layers and of the heating layer.
According to the above variants, and with reference, for example, to
The same concept may be implemented also in the case of electrode layers obtained via deposition or fixing of material directly on the heating layer, in which case there will be envisaged deposition of a first electrically insulating or substantially electrically insulating material for formation of the electrically non-conductive sites, and deposition of a second electrically conductive material for formation of the electrode layers. In the same way, the electrically non-conductive sites may be defined in electrode layers made of fabric, using for the warp and weft either electrically conductive wires or strips or electrically insulating or substantially electrically insulating wires or strips, or else wires or strips or fabrics that are electrically conductive but coated locally with electrically insulating or substantially electrically insulating material. It will be appreciated that, by appropriately weaving such wires or strips, it is possible to define in the final fabric both electrically conductive areas and electrically insulating (and possibly also thermally insulating) areas.
It will be appreciated that, also in the case of the overmoulded casing 10a, one or both of the overmoulded walls that form the casing layers 11 and 12 may be locally in contact with the material of the heating layer 15, for example at the through holes (electrically non-conductive sites) of a corresponding electrode layer 13 and/or 14, and/or at the openings between the meshes of a meshed electrode layer, as already mentioned previously, to improve thereby fixing and adhesion of the casing 10a to the heating element 20. Preferentially, the material of the overmoulded casing 10a is in any case in contact with the material of the layer 15 at least at the peripheral edge of the latter. What has been described previously in relation to the use of compatible polymers for providing the layer 15 and the layers 11 and 12 applies, of course, also to the case of an overmoulded casing 10a. The aforesaid characteristics and/or technologies for producing the casing could be combined together in different ways, for example by providing a casing 10a in part obtained using a film or laminate and in part overmoulded, or else a casing 10a in part moulded separately and in part overmoulded.
As has been said, the material 300 used for filling the holes 30′ of the layer 15 (see
In embodiments alternative to the ones so far described, the heating layer 15 could be made of a material other than a polymer-based material, such as a ceramic-based material having a PTC effect. The use of a polymer-based PTC material for the layer 15 is to be deemed preferential, in so far as its capacity for being modelled and/or adapted and/or bent slightly is higher than in the case of a ceramic-based material. This enables, for example, the device to adapt, to a certain extent, during assembly or use, to the possible tolerances or dimensional variations of a tank for vehicles, which is typically made of polymer and is subject to deformations during moulding and/or during use in the various environmental conditions and/or during heating of the fluid. Also handling of the device 10 and its assembly and installation in the final working position proves less critical. The use of a polymer-based PTC material proves even more advantageous from the production standpoint, rendering modelling of the layer 15 and/or its possible overmoulding on the electrode layers 13 and 14 more convenient.
The heating layer 15 may itself present a multilayer structure, i.e., be formed by a plurality of layers of material set on top of one another, such as a number of heating layers (even made of different materials) fixed or bonded to one another, for example via welding, or hot lamination, or co-moulding, or overmoulding, with the various layers that form in any case a single heating layer 15 in contact with the two electrode layers 13 and 14.
At least one part of the polymer-based material of at least one of the casing layers 11 and 12 may be joined, or welded, or bonded to at least one part to the material of at least one of the electrode layers 13 and 14, according to what has already been described, in particular when at least one electrode layer is made of an electrically conductive material having a polymeric base compatible with a polymer of the at least one casing layer. Likewise, at least one part of the electrically conductive polymer-based material of at least one electrode layer may be joined, or welded, or bonded to at least one part of a polymeric material compatible therewith that belongs to the heating layer 15.
According to possible further variant embodiments, the heating device forming the subject of the invention may have a shape different from the one exemplified in the attached figures. In particular, what has been described with reference to adhesion, or joining, or welding, or bonding between at least one of the casing layers or walls 11 and 12 and at least one of the opposite major faces of the heating layer 15 may also refer to a device having a different shape and/or a different arrangement of the electrode layers, for example with a first electrode layer and a second electrode layer arranged in the proximity or at minor opposite faces of a heating layer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102017000048641 | May 2017 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2018/052970 | 4/30/2018 | WO | 00 |
