Patent Description:
The invention has been developed with particular reference to electrical heater devices that are to be associated or integrated in vehicle components, such as heaters for tanks or reservoirs, heaters for filters, heaters for fluid ducts, heaters for batteries, heaters for substances that are subject to freezing or that vary their characteristics as a function of temperature, or again heaters used for heating aeriforms, such as air for environments or air subject to forced circulation on the surface of the aforesaid heaters.

The invention finds preferred application in the sector of components of tanks or ducts that are to come into contact with a liquid, for example a liquid necessary for operation of an internal-combustion engine or operation of a system for the treatment or reduction of exhaust gases of an internal-combustion engine, including Water-Injection or Anti-Detonant Injection systems. The heater devices according to the invention may in any case also find application in contexts different from the preferential ones referred to above.

<CIT> discloses an electrical heater device of the type referred to, which comprises a plurality of heating elements integrated in a component of a motor-vehicle tank. Each heating element includes a heating body made of a polymeric material having a PTC effect, set between two parallel electrodes and in contact therewith. The electrodes are in the form of a metal foil, are substantially the same as one another, and are possibly provided with holes, and substantially coat the two opposite major faces of the heating body, which has the shape of a substantially parallelepipedal layer.

This type of structure of the heating element is efficient from the standpoint of heat emission, thanks to the fact that the wide parallel surfaces of the laminar electrodes coat practically entirely the opposite surfaces of the mass of material with PTC effect: in this way, the uniformity and the intensity of the electric current between the electrodes themselves are guaranteed, and hence a good heating power.

It has, however, been found that, in particular over the long term, heater devices may be affected by problems linked to deformation (for example, expansion and contraction) of the PTC-effect material and/or of the corresponding metal electrodes, due to the cycles of heating and cooling. Such deformations may lead to relative movements between the parts made of different materials, with possible risks of delamination or peeling of the electrodes off the corresponding faces of the heating body made of the material with PTC effect, with consequent decay of the operating characteristics of the device.

<CIT>, upon which the preamble of claim1 is based, discloses a PTC electric heating assembly and an electric heating device. The PTC electric heating assembly comprises two electrode plates and a PTC heating module disposed between the two electrode plates, and comprising an insulation fixing frame and a plurality of PTC heating elements, the insulation fixing frame defining a plurality of fixing units and the PTC heating elements being disposed into the fixing units.

<CIT> discloses an electrical heater which comprises a fabric prepared from at least one of the electrodes and another elongate element of substantially higher resistance. The heater preferably comprises a PTC element, e.g. of a conductive polymer, to render the heater self-regulating. The PTC element may be in the form of a fiber forming part of the fabric, or a layer surrounding one of the electrodes, or a laminar element in which the fabric is embedded.

<CIT> discloses a conductive polymer PTC compositions having improved properties, especially at voltages of <NUM> volts or more, if they are very highly cross-linked by means of irradiation, for example to a dosage of at least <NUM> Mrads, preferably at least <NUM> Mrads, e.g. <NUM> to <NUM> Mrads. The cross-linked compositions are particularly useful in circuit protection devices and layered heaters.

In view of what has been set forth above, the present invention has basically the aim of overcoming or at least limiting the aforesaid drawback of the prior art, by means of an electrical heater device built in a way that is as a whole simple, inexpensive, and reliable. The above and other aims still, which will emerge clearly hereinafter, are achieved according to the present invention by an electrical heater device, a motor-vehicle component, and a method for obtaining an electrical heater device that have 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 objects 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" within 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 within this description may be combined in any adequate way in one or more embodiments, even different from the ones represented. The reference numbers and spatial references (such as "upper", "lower", "top", "bottom", etc.) used herein are provided merely 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" is to be understood as including mixtures, compositions, or combinations (for example, multilayer structures) of a number of different materials. In the present description and in the attached claims, the term "meshed structure" or "net structure" is understood as indicating a structure formed by the criss-crossing or interweaving of substantially filiform elements, preferably threads or wires, for example like a net, a mesh, a weave, etc..

With initial reference to <FIG>, designated as a whole by <NUM> is a heater device according to possible embodiments of the invention. In what follows, it is to be assumed that the device <NUM> belongs to a system on board a motor vehicle, for example a system for heating a stream of air or for heating a liquid that is contained in a tank or reservoir, or that passes through a duct.

The device <NUM> comprises a casing body <NUM>, which encloses at least partially at least one heating element, designated as a whole by <NUM> in <FIG>. The casing body <NUM> is preferentially provided with an electrical connector <NUM> for connection to an electric power source.

In various embodiments, the casing body of the heater device according to the invention is made up of two or more parts fixed to one another, whereas in other embodiments the casing body is formed at least in part via overmoulding of material on at least one heating element of the device. The casing body may be of a hermetic type, i.e., devised for enclosing in a fluid-tight way the heating element or elements of the device.

In various embodiments, the heater device forming the subject of the invention is configured as a stand-alone component, in which case its casing body is preferentially configured for installation and/or fixing in a more complex system, for example, the heating system of a motor-vehicle. In other embodiments, the device forming the subject of the invention is instead integrated in a component prearranged for performing also functions different from heating of a generic medium, in which case at least part of a body of the component can be exploited for providing at least in part also the casing body of the heater device. In other applications still, the device does not need a casing body of its own, for example when a corresponding heating element is exposed directly in a given environment for heating it.

In the case exemplified in <FIG>, the device <NUM> is configured as a stand-alone component, and its casing body <NUM> consists of three parts <NUM><NUM>, <NUM><NUM>, and <NUM><NUM>, for example made of electrically insulating thermoplastic material, which can be fixed to one another, preferably in a sealed way, for example via gluing or welding or hooking, in order to enclose within it at least part of the heating element <NUM>.

Once again with reference to the case exemplified in <FIG>, the casing part designated by <NUM><NUM> has a substantially boxlike structure, which defines a seat <NUM> for housing the heating element <NUM> completely or mostly inside it. In the case exemplified, the casing part <NUM><NUM> has a flange-shaped front portion <NUM>, provided with a slit 5a through which the element <NUM> can be inserted in a transverse direction in the seat <NUM>, so that two electrical-connection terminals 12a, which belong or are connected to respective electrodes of the heating element <NUM> (just one of which is visible in <FIG>, designated by <NUM><NUM>), project at the front beyond the portion <NUM>. Fixed at the front to the front portion <NUM> is the casing part designated by <NUM><NUM>, which defines a connector body <NUM> configured for receiving within it the terminals 12a and thereby providing the connector <NUM> of <FIG>. In the example represented, the casing part <NUM><NUM> further comprises a flange-shaped portion <NUM>, designed to close the slit 5a.

In the example, the seat <NUM> can be closed via the casing part designated by <NUM><NUM>, which basically functions as lid for the aforesaid seat, and is fixed peripherally to the casing part <NUM><NUM>.

Illustrated in exploded view in <FIG> is a possible embodiment of a heating element <NUM>. In this figure, designated by <NUM> is the heating body of the element <NUM>, which is made at least in part of a material having a PTC effect, i.e., a material distinguished by an electrical resistance with positive temperature coefficient, and is arranged so as to be in contact with the two electrodes designated as a whole by <NUM><NUM> and <NUM><NUM>.

In preferred embodiments, the material constituting the body <NUM>, designated by 11a, is a polymer-based material (i.e., a material comprising at least one polymer), preferably 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 preferred embodiments, the material 11a of the heating body <NUM> 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 one other of the immiscible polymers is polyoxymethylene (POM). The electrically conductive filler is preferentially constituted by particles having micrometric or nanometric dimensions, preferably comprised between <NUM> and <NUM>, very preferably between <NUM> and <NUM>, possibly aggregated to form chains or branched aggregates with dimensions of between <NUM> and <NUM>. Preferential materials for the electrically conductive filler are carbon materials, such as carbon black, or graphene, or carbon nanotubes, or mixtures thereof.

HDPE and POM are preferentially in relative percentages of between <NUM>% and <NUM>% of their sum in weight. Preferentially, the electrically conductive filler is confined or mostly confined in the HDPE, in a weight percentage of between <NUM>% and <NUM>%, preferably between <NUM>% and <NUM>% of the sum of the weigths of HDPE and 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 POM, which also in this case can be carried out preferentially via extrusion.

The high melting point of POM makes it possible to keep the two phases, HDPE and POM, better separated, reducing the possibility of migration of the electrically conductive 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 POM as compared to other known polymers likewise makes it possible to obtain a more stable final structure: the PTC effect of the composite material limits self-heating to a maximum temperature of approximately <NUM>. POM moreover presents a high crystallinity, indicatively between <NUM>% and <NUM>%: this means that, in the preferential co-continuous composite proposed, it is more unlikely for migrations of filler from the HDPE to the POM to occur, thereby preventing the loss of performance of the material with PTC effect, 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 <NUM>% and <NUM>%: in this way, a high concentration of the conductive filler in the amorphous domains is obtained, with corresponding high electrical conductivity.

With reference, for example, to <FIG>, according to an aspect of the invention, at least one of the electrodes <NUM><NUM> and <NUM><NUM> comprises a meshed structure or a net structure, designated by <NUM>, which is embedded or englobed at least partially in the heating body <NUM>, i.e., in the material 11a that constitutes it.

As will emerge more clearly hereinafter, the at least partial embedding of the meshed structure <NUM> may be obtained by getting, via mechanical pressure and/or heating, the structure <NUM> to penetrate into the heating body <NUM>, at a face of the latter, or else by overmoulding at least part of the heating body <NUM> on the meshed structure <NUM>, or on the corresponding electrode <NUM>.

It should be noted, in this regard, that in <FIG> the meshed structure <NUM> belonging to the electrode <NUM><NUM> is represented, for reasons of greater clarity, practically entirely in view, i.e., as if it were resting on the heating body <NUM>. However, as has been said, the aforesaid structure <NUM> is at least partially embedded in the material 11a of the body <NUM>, preferably in such a way that - between the openings defined between the various meshes of the structure - part of the material 11a is present. On the other hand, it is also possible to embed the meshed structure <NUM> of an electrode practically completely in the material 11a, as is, for example, represented schematically in <FIG>.

It is preferable for the meshed structure <NUM> to extend substantially parallel to a major face of the heating body <NUM>, with the aforesaid structure <NUM> that defines an area substantially corresponding to that of the major face of the body <NUM>, or in any case an area corresponding to a prevalent part thereof. In this way, the heating body <NUM> is set between the wide surfaces of the structures <NUM> of the two electrodes <NUM><NUM> and <NUM><NUM>, ensuring a good uniformity and a good intensity of the electrical supply current passing between the electrodes themselves.

The meshed structure <NUM> hence extends in a length direction L and in a width direction W and is preferably substantially two-dimensional, i.e., of minimal thickness, substantially like a sheet structure.

In various preferred embodiments, the structure <NUM> is constituted by a fabric formed at least in part with threads of electrically conductive material, preferably metal material. Preferred metals are, for example, selected from among stainless steel, copper, aluminium, brass, bronze, nickel-chrome-based alloys, or iron-chrome-based alloys. The electrically conductive fabric may be obtained via interweaving or criss-crossing of threads using any known technique; for example, the type of weave may be selected from the following:.

Preferentially, the threads that provide the electrically conductive fabric have a reduced nominal diameter (i.e., prior to weaving), indicatively of between <NUM> and <NUM>, for the reasons clarified hereinafter. The mesh opening of the fabric, i.e., the space between two adjacent and parallel threads of the structure, is preferably comprised between <NUM> and <NUM>.

It should be noted that in <FIG> and <FIG>, the meshed structures <NUM> are represented in partial and schematic form, in order to highlight - in particular in <FIG> - the criss-crossing or interweaving of the weft threads and the warp threads, designated by 16a and 16b, respectively.

The fact that the meshed structure <NUM> is at least partially embedded in the material with PTC effect 11a prevents the risk of the corresponding electrode <NUM> separating from or peeling off the heating body <NUM>, which is a problem typical of the prior art, even in the presence of possible deformations of the material <NUM> and/or of the structure <NUM> due to the heating and cooling cycles. The fact that the meshed structure <NUM> is in any case relatively dense and extensive in any case ensures a considerable distribution and intensity of the current between the electrodes <NUM>.

As may be appreciated, the peripheral profile of the meshed structure <NUM> of an electrode <NUM> may, for example, be easily obtained via elementary operations of cutting or dinking of an electrically conductive sheet or web of fabric or mesh. The aforesaid peripheral profile does not necessarily have to be quadrangular, as exemplified so far in the figures.

According to another aspect of the invention, the at least one electrode <NUM><NUM> or <NUM><NUM> comprises, in addition to the meshed structure <NUM>, also at least one electrical-distribution element, such as the ones designated by <NUM> in <FIG> and <FIG>, which is fixed to the meshed structure <NUM> and extends in at least one of the length direction L and the width direction W of the structure <NUM> itself.

The element <NUM> is shaped so as to distribute the electric current on the threads 16a, 16b or similar filiform elements that form the meshed structure <NUM>, in particular in order to prevent undesirable concentrations of electric current on a few threads, which could even cause melting of the threads themselves. For this purpose, in various embodiments, the distribution element <NUM> has at least one portion that extends substantially throughout the whole width W and/or at least one portion that extends substantially throughout the whole length L of the structure <NUM>. However, at least one portion of the distribution element could also extend through only a part of the width W and/or of the length L of the structure <NUM>, preferably for at least one half or one third of the width W and/or of the length L of the structure <NUM>.

The electrical-distribution element <NUM> is preferentially fixed to the face of the meshed structure <NUM> opposite to the body <NUM>, in order to not hinder the structure itself from being embedded in the material with PTC effect 11a. The electrical-distribution element <NUM> could also be fixed to the face of the meshed structure <NUM> facing the body <NUM>, and in this case also part of the distribution element <NUM> could be embedded in the structure of the material with PTC effect 11a.

With a view to improving further the distribution of the electric current, in various preferential embodiments at least one portion of the electrical-distribution element <NUM> extends substantially at or in the proximity of an edge of the meshed structure <NUM>.

With reference, for example, to <FIG>, it may be noted how the elements <NUM> represented have at least one portion 14a that extends in a direction transverse to the structure <NUM> (i.e., in the direction W), as well as at least one portion 14b that extends in the longitudinal direction with respect to the structure <NUM> (i.e., in the direction L), with these two portions that are preferably substantially at right angles with respect to one another (different angles are, however, possible). In various embodiments, such as the ones represented, branching off from the portion 14a are moreover further portions 14c that extend in the longitudinal direction L, preferably generally parallel to the portion 14b and preferably substantially distributed in the transverse direction W.

The electrical-distribution elements can thus have a substantially comb-like conformation, with teeth or fingers of different length (as in the case of the aforesaid <FIG>) or else teeth or fingers of the same length. In any case, as it can be seen, the area of overlapping between a distrubution element, or of all the distribution portions thereof, and the corresponding meshed structure, is smaller than the area of the latter; in particular, as shown in the figures, the overlapping area is appreciabily smaller than the area of the corresponding meshed structure, preferably the overlapping area being at least smaller than one half or one third of the area of the corresponding meshed structure.

In various preferred embodiments, the electrical-distribution element <NUM> has at least one electrical-connection portion, which, when the device is in the assembled condition, is designed to project beyond a peripheral edge of the meshed structure <NUM> or of the heating body <NUM> in order to be accessible for the purposes of electrical connection. In the case exemplified, the aforesaid projecting portion is designated in the figures by 12a, in so far as it corresponds to the terminals referred to previously. Advantageously, then, the electrical-distribution element can define directly an electrical-connection terminal 12a of the corresponding electrode <NUM>.

Also from <FIG> it can be inferred how the total area of the distributio portion 14a or of the distribution portions 14a-14b; 14a-14c of an element <NUM>, which is designed to be overlapped to a corresponding meshed structure, amounts to a limited fraction of the area of the meshed structure. As a mere example, by referring to the cases of parts a), b), c) e d) of <FIG>, the overlapping area may be of less than <NUM>%, less than <NUM>%, less than <NUM>% or less than <NUM>% of the area of the corresponding meshed structure, respectively.

In various embodiments, the distribution element <NUM> is shaped so as to be connected to a substantial or prevalent part of the threads 16a and/or of the threads 16b that provide the meshed structure <NUM>, preferably with at least one transverse portion (such as the portion 14a) connected to at least one third or at least one half of the threads 16a and/or with at least one longitudinal portion (such as the portion 14b) connected to at least one third or at least one half of the threads 16b.

In various embodiments, the distribution element <NUM> is shaped so as to be connected to a number of threads 16a and/or threads 16b such that the sum of the sections of these threads is such as to allow the electric current necessary for operation of the device <NUM> and/or of a heating element <NUM> to circulate without any damage or anomalies.

Represented merely by way of example in <FIG> are some possible configurations of electrical-distribution elements <NUM> that can be used in heater devices according to the invention. The configurations exemplified do not have an exhaustive nature, since innumerable configurations suited to the purpose are possible.

Illustrated in part A) of <FIG> is a simpler shape of the element <NUM>, which has a distribution portion 14a that is to extend in the direction of the width W of a meshed structure <NUM> (or else, obviously, in the direction of the length L of the aforesaid structure), as well as the portion that constitutes the terminal 12a, here generally orthogonal to the portion 14a.

Illustrated in part B) of <FIG> is a prevalently L-shaped element <NUM>, i.e., one that includes both a distribution portion 14a that is to extend in the width direction (or length direction) of a structure <NUM> and a distribution portion 14b that is to extend in the length direction (or, respectively, width direction) of the same structure <NUM>; also in this case, extending from one of the two aforementioned portions 14a and 14b substantially orthogonal to one another (here the portion 14a) is the connection portion that constitutes the terminal 12a.

Illustrated in part C) of <FIG> is an element <NUM> with a substantially comb-like shape, i.e., including both a distribution portion 14a that is to extend in the direction of width (or length) of a structure <NUM> and a plurality of distribution portions 14b, 14c, which are substantially parallel to one another and have the same length and are to extend in the direction of length (or, respectively, width) of the same structure <NUM>; in this case, extending from the portion 14a is the connection portion that constitutes the terminal 12a.

Illustrated in part D) of <FIG> is an element <NUM>, which has also a substantially comb-like shape, but with series of teeth or fingers that are substantially parallel but of different lengths. In the example, there are provided both a distribution portion 14a that is to extend in the direction of width (or length) of a structure <NUM> and four pairs of fingers 14b, 14c<NUM>, 14c<NUM>, and 14c<NUM> that are to extend in the direction of length (or, respectively, width) of the same structure <NUM>, where, for example, the fingers of each pair substantially have the same length but a length different from that of the fingers of the other pairs, and where each finger of one pair is set between two fingers of other two different pairs; also in this case, extending from the portion 14a is the connection portion that constitutes the terminal 12a.

In various preferred embodiments, the electrical-distribution element <NUM> is formed by a strap or foil of electrically conductive material. Hence, preferentially, also the distribution element <NUM> is substantially two-dimensional, i.e., it has a very small thickness, preferably of between <NUM> and <NUM>.

The strap that constitutes the element <NUM> is preferentially made of a metal material compatible with that of the meshed structure <NUM>, in particular compatible in view of a weld being made between the structure <NUM> and the element <NUM>; in this perspective, for example, the metal material constituting the aforesaid strap may, for example, be selected from among: stainless steel, copper, aluminium, brass, bronze, nickel-chrome-based alloys or iron-chrome-based alloys.

The strap that constitutes the element <NUM> may possibly be coated at least in part with a different material, preferably a second electrically conductive material and/or a protective material. In this perspective, the terminal 12a may be coated at least in part with tin, for example to facilitate welding of an electrical thread, or else coated at least in part with gold or some other noble metal, for example to improve the electrical contact with the terminal of an external connector; at least an outer part of the strap not in contact with the meshed structure could also be coated with a protective and/or electrically insulating material.

It will appear evident that also the peripheral profile of the distribution element <NUM> of an electrode <NUM> may, for example, be easily obtained via elementary operations of blanking or dinking (and possible deformation) of a sheet or strip of electrically conductive metal.

In preferential embodiments, the mechanical connection or fixing between the meshed structure <NUM> and a corresponding electrical-distribution element <NUM> of an electrode <NUM> is obtained via welding, preferably welding without added weld material.

In various preferential embodiments, the welding operation carried out between the two parts in question is resistance welding, i.e., a method of autogenous pressure welding in which the material is heated via an electrical resistance. Such a technique is exemplified in <FIG>, where designated by E1 and E2 are two metal electrodes of a welding apparatus.

Represented schematically in part A) of <FIG> is an initial condition, in which the two welding electrodes E1 and E2 are at a first distance apart, which enables insertion between them of the structure <NUM> and of the element <NUM> simply laid on top of one another. Part B) of <FIG> exemplifies, instead, a subsequent step in which the two welding electrodes E1 and E2 are brought up to one another so as to press mechanically the structure <NUM> on the surface of the element <NUM> in contact with the structure <NUM> itself, i.e., at the corresponding overlapping areas. Simultaneously with application of the mechanical pressure, between the electrodes E1 and E2 an electric current is made to flow having an intensity such as to generate, by the Joule effect, a heat sufficient to cause partial melting of the threads 16a, 16b and/or of the strap of the element <NUM> and hence mutual welding (the heat generated at the area of the aforesaid threads and strap will be substantially proportional to the current intensity and to the electrical resistance of the parts to be joined). Part C) of <FIG> illustrates the subsequent step in which the welding electrodes E1 and E2 are moved away from one another, to enable removal of the electrode <NUM><NUM>, with the structure <NUM> and the element <NUM> now welded together.

Welding of the distribution element <NUM> on the meshed structure <NUM> typically also causes a deformation of the threads of the aforesaid structure, which is, however, substantially circumscribed to the areas of overlapping between the element <NUM> and the structure <NUM>. With reference to the welding technique exemplified above, the degree of the deformation of the threads at the overlapping welded areas will be substantially a function of the welding heat generated and/or of the mechanical pressure between the parts. From <FIG>, and in particular from the corresponding detail of <FIG>, it may be noted how at the welding areas 17a the shape of the threads of the meshed structure <NUM> differs from that of the non-overlapping areas 17b not involved in the welding process. This circumstance may be better appreciated from the further detail represented in <FIG>, where there may be noted the different shape of the threads 16a, 16b at the welding areas 17a, where the aforesaid threads are squeezed, with partial melting, and in the areas 17b not involved in the welding process, where the threads substantially maintain the initial nominal diameter and/or shape.

<FIG> exemplifies, via a view similar to that of <FIG>, the case of a more intense welding carried out between the structure <NUM> and the element <NUM>, i.e., with a greater generation of heat and/or a higher mechanical pressure at the areas to be welded 17a, and hence with a consequent more marked melting and/or deformation of the threads 16a, 16b, which in these areas 17a come to form a substantially flat grid.

In various embodiments, such as the ones so far exemplified, both of the electrodes <NUM><NUM> and <NUM><NUM> each comprise at least one corresponding meshed structure <NUM> and at least one corresponding electrical-distribution element <NUM>, the two electrodes being preferably substantially the same as one another, to the advantage of standardisation of production. The electrodes <NUM><NUM> and <NUM><NUM> may be integrated in the heating body <NUM> at opposite faces of the body <NUM>, preferably opposite major faces that are substantially parallel to one another, in order to bring about a circulation of the electric current in a plane perpendicular to the aforesaid faces, i.e., through the thickness of the body <NUM>. According to other embodiments, however, the electrodes may be located at one and the same face of the body <NUM>. Moreover, as has been said, it is preferable for the electrodes <NUM><NUM> and <NUM><NUM>, or at least the respective meshed structures <NUM> to extend substantially parallel to a corresponding face of the body <NUM>.

Arrangements of the above type are particularly advantageous when the distribution elements <NUM> of the two electrodes <NUM><NUM> and <NUM><NUM> have respective electrical-connection portions 12a, which can hence be set in a position close to one another to provide an electrical connector, such as the connector <NUM>.

Hence, in various embodiments, at least part of the heating body <NUM> is set between the two electrodes <NUM><NUM> and <NUM><NUM>, preferably a part having a substantially constant thickness. The body <NUM> can have perimetral dimensions substantially similar to those of the electrodes, or of their structures <NUM>, but not excluded is the case of a part of the body <NUM> that projects beyond the edges of the structures <NUM>, or else that is recessed with respect thereto.

To return to <FIG>, in the case exemplified the heating body <NUM> is preferably a body overmoulded at least in part on the electrodes <NUM><NUM> and <NUM><NUM>. In applications of this type, the two electrodes in question are inserted in a mould, into which the polymeric material with PTC effect 11a is injected in the molten state. In order to facilitate the aforesaid production step, in particular during injection of the polymer and/or during previous handling of the semi-finished product, between the two electrodes there can be interposed a spacer body and/or positioning body, in particular configured for ensuring proper relative positioning of the electrodes, in particular in the mould.

Exemplified in <FIG> is a possible embodiment of a such a spacer body, designated by <NUM>, which may be made of an electrically insulating material, or else may itself be made of a material having an electric resistance or a PTC effect, which, for example, is also a polymer-based material. In the example, the spacer body <NUM> is shaped basically to define a meshed framework, with a sort of peripheral frame 15a extending within which are a series of longitudinal elements 15b and a series of transverse elements 15c, preferably coplanar with respect to one another. In the case where the elements 15b and 15c have a height (thickness) smaller than that of the frame 15a, it is possible to provide reliefs 15d at the areas of criss-crossing between the aforesaid elements 15b and 15c in order to compensate for the difference in height. Some reliefs 15d could also be shaped as engagement means so as to engage with at least one electrode <NUM><NUM> and/or <NUM><NUM>, for example in openings of the structure <NUM>.

In the example, the outer side of the peripheral frame 15a of the spacer body <NUM> is designed not to be coated by the material 11a of the heating body <NUM> so as to constitute a peripheral edge of at least one part of the heating element <NUM> (see in this connection <FIG>). It will be appreciated in any case that also a spacer body could be completely embedded in the overmoulded material 11a, as, for example, in the case of <FIG>, where also the meshed structures of the electrodes are completely embedded in the material 11a of the heating body <NUM>. It will moreover be appreciated that the shape of the spacer body used may be different from the one exemplified, provided that its functions remain the same.

A heater device according to the invention may comprise a plurality of heating elements and/or, as already mentioned, may be integrated in a component that performs also functions different from, or additional to, heating of a generic medium.

Illustrated in <FIG> are various embodiments that are suited to implementing both of the aforesaid characteristics. These figures exemplify how, in various embodiments, the heater device, or a heating element thereof, can have a generally arched shape, unlike the embodiments illustrated previously, where the device <NUM> and the heating element <NUM> are generally straight or planar. Even just a single part of a heating element (the heating body or an electrode thereof) may be at least in part planar, or else at least in part arched, or else be in part planar and in part arched.

With reference in particular to <FIG>, designated as a whole by <NUM> is a motor-vehicle component, and in particular a component of a tank for containing a generic liquid substance. The component <NUM> may, for example, form part of a system of the type known as Water-Injection or Anti-Detonant Injection (ADI), in which case the liquid in question is water that is to be injected into a cylinder of an internal-combustion engine. Alternatively, the component <NUM> could form part of a so-called Selective-Catalytic-Reduction (SCR) system, in which case the liquid in question is an aqueous solution containing urea that is to be injected into the exhaust line in order to reduce nitrogen oxides.

As mentioned in the introductory part of the present description, on the other hand, the component <NUM> could be of some other type, for example a component for housing or installing a fuel filter of an internal-combustion engine.

In the case exemplified, the component has a substantially cup-shaped body, in which there may be identified a generally tubular upper part, designated by <NUM>', in so far as it is basically provided by a heater device according to the invention, and a lower base <NUM>, having a lower box-shaped portion <NUM> provided with an inlet <NUM> and an outlet <NUM> for the liquid, and preferably provided with an electrical connector <NUM>'. The upper part <NUM>' could, however, also have some other shape, possibly provided with openings, for example made up of a number of arched walls set at a distance from one another in order to provide at least one intermediate opening.

The box-shaped portion <NUM> is preferentially provided with a lower lid (not shown) to enable positioning inside it of functional elements, such as electrical circuit parts. In the example, the body of the base <NUM> also has a flange portion, designated by <NUM>, which could also serve for fixing the component <NUM> to some other part of a vehicle, such as for fixing or welding of the component <NUM> to a tank.

The component <NUM> illustrated likewise integrates a further functional component, for example a sensor, such as a level sensor, denoted as a whole by LS, which constitutes in any case an optional element of the component <NUM>; for this purpose, the device <NUM>' and/or the base <NUM> can be appropriately shaped and/or provided with at least one opening or seat for housing the aforementioned further functional component.

As may be appreciated, following upon joining in a sealed way of the device <NUM>' to the base <NUM>, the body as a whole of the component <NUM> is formed, which defines a volume - denoted by T in <FIG> - designed to contain the liquid, or in any case designed to define an internal area in which the liquid can be heated more easily.

<FIG> is a partially exploded view of a component <NUM>, of the type in which the heater device <NUM>' and the base <NUM> are configured as parts distinct from one another and fixed together in a sealed way. As may be noted, the heater device <NUM>' has a casing body of its own, designated by <NUM>', having a substantially tubular shape, which may, for example, be made of an electrically insulating material (for example, a polymeric material) overmoulded on a plurality of heating elements, as clarified hereinafter. As may be noted, projecting from the casing body <NUM>', here at a lower edge thereof, are terminals 12a for electrical connection of the heater device, which are to be electrically connected to an electrical circuit present in the base <NUM>, which includes respective terminals (not shown) of the connector <NUM>'. In the figures just two terminals 12a are shown, but the device <NUM> may comprise more than two, as exemplified hereinafter.

Once again from <FIG> it may be noted how, in the example, at the upper face of the base <NUM> an inlet port 33a and an outlet port 34a for the liquid are defined, which are in fluid communication with the inlet <NUM> and the outlet <NUM>, respectively. Illustrated moreover in <FIG> is a seat <NUM> for positioning and electrical connection of the further functional component, such as the level sensor LS of <FIG>, and it may likewise be noted how, within the flange portion <NUM> of the base <NUM> a substantially annular seat 35a is defined, for fixing in a sealed way the lower edge of the casing body <NUM>' of the heater device <NUM>'. The body of the base <NUM> may be obtained at least in part via moulding of polymeric material, for example the same material used for producing the casing body <NUM>'.

<FIG> exemplifies a possible step of overmoulding of the casing body <NUM>' of the heater device <NUM>' of <FIG>. In the example, the heater device is designed to integrate three heating elements <NUM> having a generally arched shape, which are preferably, but not necessarily, substantially the same as one another. In the example, the mould part designated by M1 has a base part (without any reference number), rising from which is a shape <NUM> designed to define the inner peripheral surface of the casing body <NUM>' of the heater device. In the aforesaid base part, in a peripheral position with respect to the shape <NUM>, seats <NUM> are defined, into which there may be inserted the terminals 12a of the heating elements <NUM>, which are positioned on the mould part in the proximity of one another to form an arc of a circle. The mould part M2 defines a hollow impression (not visible), designed to define the outer peripheral surface of the casing body <NUM>' of <FIG>, as well as its top edge.

As may be appreciated, after positioning of the heating elements <NUM> on the mould part M1, as in <FIG>, the two mould parts are closed on one another so as to delimit a hollow shaped volume having a shape corresponding (complementary) to that of the casing body <NUM>', and injected into the aforesaid hollow volume is the polymeric material designed to form the aforesaid casing body. After the time necessary for solidification and cooling, the mould parts M1 and M2 can be opened again, and the device <NUM>' including the casing body <NUM>' can be extracted, as represented in <FIG>.

As an alternative to what has been exemplified with reference to <FIG> and <FIG>, at least part of the base <NUM> and of the casing <NUM>' of the heater device <NUM>' may also be configured in a single piece, in particular a piece obtained by overmoulding the necessary polymeric material on the heating elements <NUM>. Such a case is exemplified schematically in <FIG>, where designated by M3 and M4 are two corresponding mould parts. In this case, the mould part M3 has an impression <NUM> designed to define part of the outer profile of the base <NUM> and its inner profile (as has been mentioned, the base <NUM> can have a lower opening that is to be closed by a lid applied subsequently). Defined within the impression <NUM> are seats <NUM> for the terminals 12a of the heating elements <NUM>, as described with reference to <FIG>.

The mould part M4 instead defines an impression <NUM>, visible only partially, designed to define the remaining part of the outer profile of the base <NUM>, as well as the casing body <NUM>' of the heater device <NUM>' (within the aforesaid impression there will then be provided also a shape of a type similar to the one designated by <NUM> in <FIG>).

Hence, also in this case, after positioning of the heating elements <NUM> on the mould part M3, as in <FIG>, the two mould parts M3 and M4 are closed on one another so as to delimit a hollow shaped volume, injected into which is the polymeric material that is to form the body defining both the base <NUM> and the casing body <NUM>'. Also in this case, after the time required for solidification and cooling, the mould parts M3 and M4 can be re-opened and the corresponding semi-finished product of the component <NUM> can be extracted, as represented in <FIG>.

Represented schematically in <FIG> are three heating elements <NUM> having an arched configuration, for example of a type suitable for production of the heater device <NUM>'. In the example, each element <NUM> includes the respective two electrodes, each formed by at least one meshed structure <NUM> and at least one electrical-distribution element <NUM>, shaped for defining a respective terminal 12a, here projecting downwards. Visible in <FIG> is just one part of the structure <NUM>, i.e., the part welded to the element <NUM>, the remaining part of the structure being or embedded in the material with PTC effect 11a of the heating body <NUM>. The electrodes are preferably arranged so that the respective distribution elements <NUM> are located substantially at opposite longitudinal edges of the corresponding heating element <NUM>; this does not constitute in any case an essential characteristic.

A meshed structure <NUM> and a corresponding electrical-distribution element <NUM> are illustrated schematically in <FIG>. As may be noted, the structure <NUM> has an arched shape and the element <NUM> consists of a single portion, which here extends in the length direction L of the structure <NUM> in order to be fixed at or in the proximity of a longitudinal edge thereof. The length of the element <NUM> is greater than that of the structure <NUM>, so that a terminal portion of the element <NUM> provides the corresponding terminal 12a. The join between the two parts <NUM> and <NUM> may be of a welded type, for example as described previously with reference to <FIG>. It should be noted that in <FIG>, as in the subsequent figures, the meshed structure <NUM> is represented only schematically, with very wide mesh openings, to enable a more immediate understanding.

As mentioned previously, at least part of the meshed structure <NUM> may be force-fitted in the heating body <NUM> at a face of the latter, i.e., by getting the structure <NUM> to penetrate into the body <NUM>.

A possible technique, in this connection, is exemplified in <FIG>, where designated by M5 and M6 are two moving elements, at least one of which is movable with respect to the other, of a pressing apparatus. Each moving element can define a respective seat <NUM> (here only the seat of the moving element M5 is visible) designed to receive a corresponding part of an arched electrode <NUM><NUM> or <NUM><NUM>, respectively, and a corresponding part of a pre-formed heating body <NUM>. The body <NUM> may be in this case obtained via operations of blanking or dinking starting from a sheet or web of the PTC-effect polymer, which is then heat-formed in order to bestow thereon the necessary arched configuration, or else the body <NUM> may be directly injection-moulded in the arched form.

The electrodes are set between the moving elements M5 and M6, exploiting the corresponding seats <NUM>, and then the moving elements themselves are forced on one another, so that the meshed structures are forcefully pressed or pushed against the opposite major faces of the body <NUM>, causing the structures to penetrate into the faces. For this purpose, in preferential embodiments, at least one of the moving elements M5 and/or M6, or the corresponding pressing apparatus, is configured for heating the body <NUM> in order to cause a modest softening thereof, that facilitates penetration of the structures into the material 11a. Then, in particular after cooling of the body <NUM> if heating thereof is envisaged, the two moving elements M5 and M6 are moved away from each other, and the heating element <NUM> thus obtained can be extracted from the apparatus, as exemplified in <FIG>. The heating element <NUM> may be in the form represented in <FIG>, with the threads of the structures <NUM> completely embedded in the material 11a (possibly except for those welded to the respective distribution elements <NUM>), or else the threads may be partially exposed, if they are not completely embedded in the material 11a.

In applications of this type, the body <NUM> is preferentially pre-formed so as to present, at an edge, at least one area of smaller thickness (11b, <FIG>) for positioning of the element <NUM>, so that the outer surface of the latter will substantially be flush with the surface of the face of the body <NUM> in which the threads of the structure <NUM> are embedded.

The seats <NUM> of the moving elements M5 and M6 will preferentially include a portion designed to receive the portion 12a of the element <NUM> projecting from the structure <NUM>.

Of course, the apparatus described with reference to <FIG> and <FIG> may have a shape different from the one exemplified, provided that its functions remain the same. For instance, just one of the two moving elements M5 and M6 could include a seat <NUM> designed to receive both of the electrodes <NUM><NUM> and <NUM><NUM> with the pre-formed body <NUM> set in between, with the other moving element that includes a part in relief designed to exert the mechanical pressure where necessary, when the two moving elements are pressed against one another.

It will be appreciated that what has been described with reference to <FIG> may be applied also to the case of straight or plane heating elements, for example as in <FIG>, of course with a different shape of the moving elements M5 and M6 and of the corresponding impressions <NUM>.

Of course, also in the case of heating elements that are at least in part arched, the polymeric material with PTC effect 11a can be overmoulded at least in part on the electrodes <NUM><NUM> and <NUM><NUM>, for example as described previously with reference to the heating elements of <FIG>. Such a case is represented schematically in <FIG>, where designated by M7 and M8 are two mould parts for injection of the material 11a that is to form the heating body <NUM>, where each mould part includes a respective impression that is to define a corresponding part of the profile of an arched heating element <NUM>.

Also in this case, as described previously, it is preferable to provide a spacer and/or positioning body (here designated by <NUM>') that is to be interposed between the electrodes <NUM><NUM> and <NUM><NUM> when these are inserted into the mould, for example in the impression <NUM> of the mould part M7 visible in <FIG>. In the case illustrated in <FIG>, the body <NUM>', which may be made of electrically insulating material or else of a resistive material with PTC effect, has a substantially comb-like shape, arched according to the shape of the electrodes <NUM><NUM> and <NUM><NUM>, but obviously this shape is to be understood as being provided merely by way of example.

<FIG> shows schematically the result of the operation of setting the electrodes <NUM><NUM> and <NUM><NUM> on top of one another, with the spacer body <NUM>' that keeps them at the right distance apart and the fingers of the body <NUM>' that here extend in the longitudinal direction of the electrodes themselves, i.e., substantially parallel to the electrical-distribution elements <NUM>. <FIG> illustrates, instead, the step of insertion of the ensemble or "sandwich" formed by the electrodes <NUM><NUM> and <NUM><NUM> and the spacer body <NUM>' between the parts M7-M8, after closing of which the polymeric material 11a that is to form the heating body <NUM> is injected into the mould. <FIG> exemplifies the subsequent step of re-opening of the mould and extraction of the heating element, after the time necessary for solidification and cooling of the injected material. Also in this case, the element <NUM> may present with the threads of the structures <NUM> completely embedded in the material 11a (possibly except for the ones welded to the respective distribution elements <NUM>), or else the aforesaid threads may be partially exposed if the moulding operation does not envisage complete covering thereof by the material 11a.

<FIG> is a partially sectioned schematic view of a heating element obtained according to <FIG>, from which it may be noted how also the spacer body <NUM>'is embedded in the material 11a in the space between the two electrodes <NUM><NUM> and <NUM><NUM>.

<FIG> are schematic illustrations of a further possible embodiment of a heating element of a heater device according to the invention. These figures show how the element <NUM> does not necessarily have to be substantially quadrangular or polygonal, it possibly having a peripheral profile partially curved and/or comprising stretches that are curved and stretches that are rectilinear.

<FIG> likewise show how, in various embodiments, an electrical-distribution element <NUM> may present a dimensional-compensation structure, to compensate for the possible dimensional variations, for example with intermediate curves, or else have a substantially wavy development, or distinguished by a sequence of curves and/or stretches that are angled or oriented in opposite directions.

Shapes of this type may prove convenient to enable the distribution element <NUM> to lengthen and/or shorten in order to compensate for possible dimensional variations due to thermal variations, such as expansions and contractions and/or lengthening and shortening in at least one of the directions L and/or W, in particular during heating of the heating body <NUM> made of PTC material 11a.

Preferably, the aforementioned dimensional-compensation structure enables compensation for possible dimensional variations, such as different expansions and contractions between different materials of at least part of the electrodes <NUM><NUM> and <NUM><NUM> and of the heating body <NUM>, in particular between at least the electrical-distribution elements <NUM> made of metal and the body <NUM> made of the polymer-based PTC material 11a.

In the case exemplified, the two elements <NUM> represented both have a distribution portion 14a that extends in the width direction W and a distribution portion 14b that extends in the length direction L, each in the proximity of a respective edge of the corresponding meshed structure <NUM>. Preferentially, but not necessarily, the electrical-connection portions, or the terminals 12a, are defined at the area of joining between the two aforementioned distribution portions 14a and 14b. Obviously, elements <NUM> of this type may have shapes different from what has been represented by way of example, and include even just one distribution portion.

It goes without saying that also in embodiments of the type described with reference to <FIG> the structures <NUM> may be fixed to the corresponding elements <NUM> in the ways already described above, for example via welding, and that likewise the structures <NUM> may be at least partially embedded in the heating body <NUM> in the ways described above, i.e., via mechanical pressure or else via overmoulding of the material 11a. In the example of <FIG>, the two electrodes of a heating element <NUM>, preferably electrodes with a dimensional-compensation structure, are located at respective opposite faces of the corresponding heating body <NUM>, in order to bring about a circulation of the electric current substantially in a way perpendicular to the plane of the corresponding face of the heating body <NUM>.

In various embodiments, two electrodes of a heating element <NUM> are located at one and the same face of the corresponding heating body <NUM> in order to bring about a circulation of the electric current substantially according to a plane parallel to the plane of the corresponding face of the heating body <NUM>. Such a case is exemplified in <FIG>, where it may in fact be noted how the two electrodes <NUM><NUM> and <NUM><NUM>, preferably, but not necessarily, electrodes <NUM><NUM> and <NUM><NUM> comprising a dimensional-compensation structure similar to the one described previously with reference to <FIG>, are both located at one and the same face of the body <NUM>, with the corresponding structures <NUM> that are here only partially embedded in the material 11a. Also the two elements <NUM> exemplified both have a distribution portion 14a that extends inclined in the width direction W, and a distribution portion 14b that extends in the length direction L, each in the proximity of a respective edge of the corresponding meshed structure <NUM>, possibly with a part of each portion 14a that is set directly on top of the material 11a, i.e., without interposition of a corresponding part of the structure <NUM>.

The electrical-connection portions, or the terminals 12a, are here defined at an end of the elements <NUM>, in particular at the end of the portions 14a. Obviously, the elements <NUM> may have shapes different from the one exemplified, and include even just one transverse or longitudinal distribution portion.

Also in embodiments of the type described with reference to <FIG>, the structures <NUM> may be fixed to the corresponding elements <NUM> in the ways already described above, for example via welding, and the structures <NUM> may be at least partially embedded in the heating body <NUM> in the ways described above, i.e., via mechanical pressure or else via overmoulding of the material 11a.

In various embodiments, at least one electrode, or each electrode, of a heating element includes a number of meshed structures <NUM>, which are preferentially electrically connected to one another by way of at least one electrical-distribution element.

An example of this type is represented schematically in <FIG>, where the electrode designated by <NUM> has a first meshed structure <NUM>, with associated to it a corresponding electrical-distribution element <NUM> of the type already represented in part A) of <FIG>, as well as a second meshed structure <NUM><NUM>, which is connected to the first meshed structure <NUM> via a further distribution element <NUM><NUM>, here substantially L-shaped, or having a portion 14a transverse to, and a portion 14b longitudinal with respect to, the second meshed structure <NUM><NUM>. The further distribution element <NUM><NUM> is preferentially fixed, in particular welded, between the two structures <NUM> and <NUM><NUM>, in a position intermediate thereto.

As has been said, in various embodiments, a heater device according to the invention may be integrated in a component that also performs functions different from heating of a generic medium, for example, a component of a tank. For such applications, it is evidently not necessary for the heater device to be of a generally arched type, or present one or more arched heating elements; it may, in fact, present one or more straight or planar heating elements, for example as in the aforementioned <CIT>. Moreover, one or more planar heaters do not necessarily have to be integrated in a tubular part of such a component.

Represented, for example, in <FIG> and <FIG> is a component of the type already designated previously by <NUM>, defined in the base <NUM> of which is a housing <NUM> for a straight or planar heating element <NUM>, here having a peripheral profile shaped so as to present curvatures. Also visible in these figures is a lower lid of the base <NUM> - designated by 32a only in <FIG> - of the type mentioned previously, for closing the box-shaped portion <NUM>. The seat is defined substantially at the transverse wall that defines the containment volume of the component <NUM> (i.e., the bottom wall of the volume designated by T in <FIG>).

<FIG> and <FIG> are likewise useful to illustrate the case of electrodes <NUM><NUM> and <NUM><NUM>, the electrical-distribution element <NUM> of which has a closed or substantially closed, or annular or substantially annular, development. In the example, the distribution elements <NUM> hence have an annular peripheral portion 14d, which is to extend substantially at or in the proximity of the peripheral edge of the corresponding meshed structure <NUM>. This peripheral portion 14a hence extends both in the longitudinal direction and in the transverse direction of the corresponding structure <NUM>. In various embodiments of this type, the element <NUM> may also include one or more intermediate distribution portions, for example portions 14e that converge towards a central area 14f of the element <NUM>. In the example, defined at the aforesaid central area 14f is an opening that is designed to couple with a corresponding positioning element 37a defined within the housing <NUM> of the base <NUM> of the component <NUM>. Within the aforesaid housing <NUM> there may also be defined a seat 37b having a profile substantially complementary to that of the distribution element <NUM> of one of the electrodes, here the electrode <NUM><NUM>, in order to contribute further to proper positioning of the heating element <NUM>.

It should be noted that, thanks to the presence of the heating element <NUM> described, the component <NUM> of <FIG> does not necessarily have to integrate also the heater device designated by <NUM>', even though the presence of both of the heaters <NUM>' and <NUM> is preferable.

Also in embodiments of this type, the structures <NUM> may be fixed to the corresponding elements <NUM> in the ways already described above, for example via welding, and the structures <NUM> may be at least partially embedded in the heating body <NUM> in the ways described above, i.e., via mechanical pressure or else via overmoulding of the material 11a. In the case represented in <FIG>, the structures <NUM> are completely embedded in the material 11a, but this does not constitute an essential characteristic.

Once again with reference to the example illustrated, the electrical-connection portions of the elements <NUM>, or the terminals 12a of the heating element <NUM>, extend in a direction perpendicular to the plane of the element itself, and for this purpose the peripheral portion 14d of the element <NUM> of an electrode - here the element <NUM> of the upper electrode <NUM><NUM> - bends inwards (14d<NUM>, <FIG>) or is in any case shaped so as to enable passage of the terminal 12a of the other electrode. As has been mentioned, in any case, the peripheral portion 14d of an electrode does not necessarily have to be closed on itself, it possibly presenting at least one interruption or discontinuity.

As mentioned previously, the meshed structure <NUM> is preferably formed by the interweaving or criss-crossing of relatively fine filiform elements or threads, preferably having a diameter of between <NUM> and <NUM>. The use of fine threads makes it possible to obtain an efficient fixing of the structures <NUM> to the material 11a, also thanks to their at least partial embedding in the aforesaid material, thus countering the risks of detachment between the parts in question.

For instance, threads having a diameter of less than <NUM> are advantageous for enabling the threads themselves to be embedded by force into the material 11a, preferably by heating the latter, as explained previously, and this also in the case of small mesh openings, for example even of less than <NUM>. Threads having a diameter greater than <NUM> may instead be more convenient to use when the material 11a is overmoulded on the structures <NUM>, and it is necessary to have wider mesh openings to enable passage of the material itself, for example mesh openings even larger than <NUM> (in general, in conductive fabrics that can be used for implementation of the invention, corresponding to threads of larger diameter are wider mesh openings).

A thread of relatively large diameter can advantageously be replaced by a number of threads of smaller diameter. For instance, the cross section of a thread having a diameter of <NUM> substantially corresponds to that of three threads having a diameter of <NUM>: hence, neglecting the skin effect, the passage of electric current that can occur in a thread having a diameter of <NUM> can occur in three threads having a diameter of <NUM>. If, however, the sum of the circumferences of the three threads with a diameter of <NUM> is considered (approximately <NUM>), it will be noted that it is almost equal to twice the circumference (approximately <NUM>) of the single thread having a diameter of <NUM>. It will hence be appreciated that corresponding to the aforesaid larger "overall" circumference of the three finer threads is a larger (almost twice as large) surface of contact between the meshed structure <NUM> and the material with PTC effect 11a, hence with a better electrical contact and a more extensive total mechanical adhesion between the structure and the material.

From the foregoing description, the characteristics of the present invention emerge clearly, as likewise do its advantages. The electrical heater device according to the invention is built in a way that is as a whole simple, inexpensive, and reliable.

The fact that the electrodes of the heating element of the device include at least a meshed structure at least partially embedded in the material with PTC effect counters the risks of the electrodes separating from or peeling off the material, a phenomenon that is, instead, encountered in the prior art. The fact that the meshed structure is relatively extensive and dense, i.e., formed by relatively fine threads, in any case ensures a wide surface of adhesion and contact between the electrodes and the material with PTC effect, with an optimal distribution and intensity of the current flowing between the electrodes themselves. The presence in the electrode of at least one distribution element prevents undesirable concentrations of electric current on just a few threads of the meshed structure, and hence prevents the risk of melting of the threads themselves, a risk that moreover could be potentially greater given that threads of small cross section are preferably used for achieving a better electrical contact with, and a better mechanical adhesion, to the PTC material.

It is clear that numerous variations may be made by the person skilled in the art to the electrical heater device described by way of example, without thereby departing from the scope of the invention as defined in the ensuing claims.

In the embodiments exemplified previously, the meshed structure <NUM> of at least one of the electrodes <NUM><NUM> and <NUM><NUM> is embedded or englobed at least in part directly in the material 11a with PTC effect. In other possible embodiments, the structure <NUM> is instead at least in part embedded or englobed in a further electrically and thermally conductive material that coats at least partially the body <NUM> in electrical contact therewith, for example a conductive adhesive or a conductive coating layer; in these embodiments, the heating body <NUM> includes the aforesaid further material, which can hence be exploited to enable mechanical fixing of at least one of the electrodes <NUM><NUM> and <NUM><NUM> to the heating body itself.

Claim 1:
An electrical heater device (<NUM>; <NUM>') comprising at least one heating element (<NUM>) which includes a first electrode (<NUM><NUM>), a second electrode (<NUM><NUM>) and a heating body (<NUM>) that includes a material having a positive temperature coefficient effect (11a) in electrical contact with the first electrode (<NUM><NUM>) and the second electrode (<NUM><NUM>), wherein
- at least one of the first electrode (<NUM><NUM>) and the second electrode (<NUM><NUM>) comprises a meshed structure (<NUM>; <NUM>, <NUM><NUM>), which extends in a length direction (L) and in a width direction (W) and is in electrical contact with the heating body (<NUM>),
- the at least one of the first electrode (<NUM><NUM>) and the second electrode (<NUM><NUM>) further comprises at least one electrical-distribution element (<NUM>; <NUM>, <NUM><NUM>), preferably including a shaped strap or foil of electrically conductive material, which has at least one distribution portion (14a, 14b) that extends in at least one of the length direction (L) and the width direction (W) of the meshed structure (<NUM>; <NUM><NUM>),
the electrical heating device (<NUM>; <NUM>') being characterized in that:
- the material having a positive temperature coefficient effect (11a) comprises at least a polymer or a polymer-based material,
- the at least one electrical-distribution element (<NUM>; <NUM>, <NUM><NUM>) is fixed to the meshed structure (<NUM>; <NUM><NUM>), and
- the meshed structure (<NUM>; <NUM>, <NUM><NUM>), is at least partially embedded or englobed in said polymer or polymer-based material of the material having a positive temperature coefficient effect (11a) of the heating body (<NUM>), or in a further electrically and thermally conductive material that coats at least partially the heating body (<NUM>) in electrical contact therewith, such as a conductive adhesive or a conductive coating layer.