Patent Grant
12185434
This application is the U.S. national phase of International Application No. PCT/IB2019/057516 filed 6 Sep. 2019, which designated the U.S. and claims priority to IT patent application Ser. No. 10/201,8000008700 filed 18 Sep. 2018, the entire contents of each of which are hereby incorporated by reference.
The present invention relates to electric heater devices and to the corresponding methodologies of production, and more in particular to devices based upon the use of polymer-based materials, i.e., materials comprising at least one polymer, distinguished by an electrical resistance with positive temperature coefficient, i.e., ones having a PTC effect.
The invention has been developed with particular reference to the production of electric heater devices that are to be associated to, or integrated in, vehicles components, such as heaters for tanks, 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 of 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 used in a vehicle, such as liquids necessary for operation of internal-combustion engines or operation of systems for treatment or reduction of exhaust gases of internal-combustion engines, including water-injection or anti-detonant-injection systems.
The semifinished product and the heater devices according to the invention may in any case also be applied in contexts different from the preferential ones referred to above.
Production of electric heater devices that use a plurality of heating bodies made of a material having a PTC effect is widespread, given the functional characteristics of these materials. In some cases, the heater device includes a single heating body made of material having a PTC effect with opposite surfaces having a relatively wide area, associated to which are two electrodes of accordingly large dimensions, constituted by metal plates. In other cases, the heater device includes, instead, a plurality of heating bodies of relatively small dimensions, with respective electrodes connected to electrical-connection bodies. Alongside the more traditional ceramic-based materials there have in recent times appeared PTC-effect polymeric materials, which can be obtained more easily in various shapes and can be moulded directly between corresponding electrodes. Notwithstanding this, the production of heater devices that integrate a number of heating bodies made of PTC-effect polymeric material is still generally complicated, and the same may be said as regards integration of the aforesaid heater devices in more complex functional components.
For instance, a typical problem in the sector of motor-vehicle components is represented by the variability of the conformation of the tanks, typically shaped in a different way according to the type of vehicle so as to be able to exploit as far as possible the volumes available. Consequently, in this sector, PTC-effect heater devices are typically provided that are substantially rigid and specifically shaped to adapt to the corresponding tank.
For instance, WO2017077447 A describes a heater device designed for integration in a component of a vehicle tank, in particular a component having a generally cylindrical shape. The device comprises a plurality of heating bodies made of a PTC-effect polymeric material, each of which is set between a first electrode and a second electrode, with the first and second electrodes associated to the various heating bodies that are connected to a first electrical-connection body and a second electrical-connection body, respectively. The PTC-effect polymeric material that is necessary for formation of each heating body is overmoulded between facing surfaces of the first and second electrodes, and then an electrically insulating plastic material is overmoulded on the electrodes, with the corresponding heating bodies set in between, and on the connection bodies.
The first electrodes with their corresponding connection body, on one side, and the second electrodes with their corresponding connection body, on the other side, can be defined in a single piece, via operations of blanking starting from respective plane metal plates. The two blanked plane pieces are set in parallel positions in a mould, via which the PCT-effect polymeric material is moulded only between the facing surfaces of the electrodes defined by each plane piece. In this way, a substantially plane semifinished product is obtained, which is then subjected to bending operations, in areas of junction between the electrodes and the corresponding connection bodies, in such a way that the semifinished product itself will assume an approximately cylindrical configuration. The plastic material that forms the casing body, here corresponding to the body of the tank component, is then overmoulded on the semifinished product.
A further typical problem of known heaters of the aforesaid type is constituted by detachment of the PTC-effect polymeric material from the corresponding metal electrodes, with consequent operating faults, where the aforesaid drawback may be a consequence of the different degrees of expansion and contraction of the different materials, such as a polymer and a metal, during the cycles of heating and subsequent cooling, in particular during operation and/or as a result of environmental conditions. This drawback may be more easily noted in heaters of large dimensions, such as heaters for vehicle tanks, where consequently the phenomena of expansion of the materials are accentuated, in particular in the directions of width and length of the heater device (this on account of the fact that in this case the expansions “add” together, for example causing dimensional variations that are very accentuated in the peripheral areas or in the end areas opposite to the areas of fixing or mechanical constraint of the device).
A further related problem is represented by the mechanical stresses that are set up between the heating bodies and the corresponding casing, in particular in the presence of different expansions or dimensional variations due to cycles of heating and subsequent cooling.
As may be noted, the modalities of production of the heater device and/or its integration in a different component are relatively laborious and can give rise to malfunctioning. It will moreover be appreciated that, since the device is designed for integration in components that have a specific geometry, it is necessary to produce and store various versions of the device, for the purposes of their integration on other components that present different geometries.
In view of what has been set forth above, the present invention has basically the aim of simplifying production of electric heater devices that use PTC-effect polymeric materials, and/or integration thereof in more complex components, such as tanks and/or devices for tanks, in particular for vehicles.
The above and other aims still, which will emerge clearly hereinafter, are achieved according to the present invention by a semifinished product of an electric heater device, a corresponding production method, and an electric heater 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.
In brief, the invention relates to a semifinished product of a heater device, the structure of which basically comprises at least two connection bodies that extend substantially parallel to one another in a length direction and that are flexible or easily deformable at least in the aforesaid direction, and a plurality of heating bodies that include at least one polymeric material having a PTC effect.
Preferentially, the heating bodies are substantially rigid, or have in any case a lower flexibility or capacity of deformation as compared to the connection bodies. The heating bodies are set at a distance from one another in the length direction and generally extend in a direction transverse thereto.
Preferably, the connection bodies provide areas of articulation or of at least partial bending or deformation between the heating bodies, for example to be able to vary the angular arrangement between the heating bodies themselves, in particular during steps of production of electric heater devices or other components that include at least one semifinished product according to the invention, or to be able to vary the distance between the heating bodies, in particular in the presence of expansions and contractions during temperature variations.
The parts of the connection bodies that extend between two heating bodies can also provide compensation areas, useful for preventing mechanical stresses, with consequent risk of detachment, between the connection bodies and the heating bodies, thereby reducing the risk of decrease in electrical contact or increase in electrical resistance between the heating bodies and the connection bodies. Preferably, the aforesaid compensation areas of the connection bodies that extend between the heating bodies also make it possible to avoid mechanical stresses between the heating elements and the corresponding casing, potentially caused by different degrees of expansion or different dimensional variations due to thermal cycles.
The material having a PTC effect is a polymer-based material that is in electrical contact with the at least two connection bodies, preferably in two opposite end regions of the corresponding heating body, with the at least two connection bodies which each comprise a longitudinal element, that extends in the length direction of the semifinished product and has a width appreciably smaller than the width of the heating bodies. Each of the two connection bodies comprises electrical- and mechanical-connection parts, which have a mesh structure that is at least partially embedded or englobed in the polymer-based material of a respective heating body.
Thanks to the characteristics referred to, the semifinished product can possibly be produced so as to present a large length, even in the region of several metres, and conveniently rolled up or folded on itself for storage purposes. When necessary, the semifinished product can be unrolled and sections or lengths of the desired size can be cut therefrom, according to the requirements of production of heater devices or components that integrate them. This operation is eased by the reduced width of the connection bodies at least in their intermediate parts, i.e., the parts thereof which extends between two successive heating bodies. The intrinsic flexibility or deformability of the semifinished product, also eased by the reduced width of the connection bodies in the intermediate parts thereof that extend between two successive heating bodies, enables its convenient integration and/or its adaptation in a plurality of different types of heater devices and components in general, which may even have geometrical shapes that are very different from one another, such as integration and/or adaptation to the shapes of different tanks for vehicles.
Production of the heating bodies using a PTC-effect polymeric material simplifies production of the semifinished product in so far as such bodies can be formed via simple operations of injection moulding.
Use of mesh structures at least partially embedded in the PTC-effect material, for electrical and mechanical connection of the heating bodies, ensures a reliable electrical and mechanical connection, at the same time countering risks of separation or detachment between the parts in question and/or from a casing of the device, in particular when the semifinished product is being manipulated, for example rolled up or folded on itself and then unrolled or subjected to deformation in the production stage. The mesh structure, distinguished by solids and voids, also eases the bending or deformation capability of the semifinished product, as well as cutting thereof into sections or lengths, when the mesh structure of the connection bodies is also used for connecting the heating bodies to one another.
Further aims, characteristics, and advantages 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”, “one embodiment”, or “various embodiments” and the like, in the framework of the present description is intended to indicate that at least one detail, configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as “in an embodiment”, “in one embodiment”, “in various embodiments”, and the like, that may be present in various points of the present 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, 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 also mixtures, compositions, or combinations of a number of different materials (for example, multilayer structures or composite materials).
In the present description and in the attached claims, the term “mesh structure” is intended to indicate a structure distinguished by an alternation of solids and voids, for example like a net, a sieve, a woven fabric, a braid, etc; the aforesaid structure may be formed by the criss-crossing or interweaving of a plurality of substantially filiform elements, such as threads or wires, or else obtained by processing of a single starting element, for example a metal strap that is blanked and/or shaped and/or stretched for bestowing thereon a meshed shape.
In the present description and in the attached claims, the term “semifinished product” is intended to designate an intermediate product or component, which is to undergo further processing and/or can be used in the production of more complex products or articles, even of types very different from one another. In this perspective, for example, a length of a semifinished product according to the invention can be completed with a casing and suitable control means and/or means for connection to an electric power source in order to produce a heater device, or else can be integrated in a different component that may also perform functions other than heating, such as a component of a tank of a vehicle. Even when a length of a semifinished product according to the invention, without any casing, is simply mounted on a different structure (for example, a duct or a tank), it in any case constitutes an intermediate component, which must be further equipped, for example, with means for fixing in position, means for connection to an electric power source, and possible control means.
Represented schematically in
In various embodiments, the structure 1 can be rolled up or folded on itself. In other words, the structure 1 is sufficiently flexible or deformable in its length direction to enable it to be wound on itself to assume a more or less cylindrical shape, in particular to form a roll or the like, or else be folded on itself in opposite directions (i.e., in a zigzag pattern), to form a sort of more or less parallelepipedal stack.
Hence, assume that
The rollable or foldable structure of the semifinished product 1 comprises at least two electrical- and mechanical-connection bodies 2, which include two longitudinal elements made of electrically conductive material, which extend alongside one another in the direction L, preferably substantially parallel to one another, and which—as has been mentioned—are flexible or deformable at least in the aforesaid direction L. The structure of the semifinished product 1 further comprises a plurality of heating bodies 3, each including at least one material having a PTC effect. One such heating body 3 may be seen in greater detail in
In various embodiments, the material constituting the heating body 3 is a polymer-based material (i.e., one comprising at least one polymer), designated by 3a in
HDPE and POM are preferentially in relative percentages comprised between 45% and 55% of their sum in weight. Preferentially, the electrically conductive filler is confined either totally or to a largest extent in the HDPE, in a weight percentage comprised between 10% and 45%, preferably between 16% and 30%, of the sum (100%) of the weight of the HDPE and the weight of the electrically conductive filler. For this purpose, the HDPE and the electrically conductive filler can be mixed together, in particular via extrusion, before subsequent mixing with the 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, HDPE and POM, phases better separated, reducing the possibility of migration of the electrically conductive filler in 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 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 preferential co-continuous composite proposed, it is less likely for there to occur migration of charge from the HDPE to the POM, 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 in the amorphous domains is obtained, with corresponding high electrical conductivity.
The heating bodies 3 of the semifinished product 1 are at a distance from one another in the length direction L and generally extend in a direction transverse thereto. In this way, in two opposite lateral end regions, here with reference to the width direction W, the material 3a of each body 3 can be electrically and mechanically connected to the two connection bodies 2. In various embodiments, such as the one represented, the bodies 3 have a prismatic shape, preferably a substantially parallelepipedal shape, but this does not constitute an essential characteristic of the invention.
As it can be seen in
Each of the two connection bodies 2 comprises respective electrical- and mechanical-connection parts, some of which are designated by 2a, where associated to each heating body 3 are at least one first part 2a, belonging to one connection body 2, and one second part 2a, belonging to the other connection body 2. The aforesaid first and second parts 2a are preferably each associated to an aforesaid lateral end region of the body 3, here at one and the same major face of the body 3.
According to one aspect of the invention, the connection parts 2a include a mesh structure. In various embodiments, such as the one exemplified in
According to one aspect of the invention, the mesh structure of the parts 2a is embedded or englobed at least partially in the corresponding heating body 3, i.e., in the PTC-effect material 3a in the corresponding end region.
At least partial embedding of the mesh structure can be obtained by getting, via mechanical pressure and/or heating (preferably, heating such as to soften or melt at least superficially the PTC-effect material 3a), the structure itself to penetrate into the corresponding heating body 3, on a face of the latter, or else by overmoulding at least part of the material 3a of the heating body 3 on the mesh structure, i.e., on the corresponding electrical- and mechanical-connection part 2a. The embedding operation is simplified by the reduced width of the bodies 2, or in any case by the fact that each embedded part defines an area—when seen in a plan view—which corresponds to a reduced fraction of the area of the corresponding major face of the respective heating body 3.
It is to be noted that in
It is preferable for the connection parts 2a, i.e., their mesh structure, to extend substantially parallel to a major face of the corresponding heating body 3 (as it can be seen, in the case of
In various preferred embodiments, the mesh structure is constituted by a fabric made at least in part of threads or wires of electrically conductive material, preferably metal material. Preferred metals may, for example, be selected from among stainless steel, copper, aluminium, brass, bronze, nickel-chromium-based alloys, or iron-chromium-based alloys. The electrically conductive fabric may be obtained via interweaving or criss-crossing of threads or wires using any known technique. For example, the type of weave can be selected from among the following:
Preferentially, the threads that provide the electrically conductive fabric have a small nominal diameter (i.e., before being woven), roughly comprised between 0.2 mm and 0.02 mm. The mesh opening of the fabric, i.e., the space or voids between two adjacent and parallel threads of the structure, is preferably comprised between 1 mm and 0.05 mm. As already mentioned, on the other hand, the mesh structure could be obtained also by processing an electrically conductive body; for example, a mesh or network structure suitable for the application may be obtained by making through incisions (staggered cuts) in a length of metal strap, which is then deformed or stretched until apertures or voids are obtained, for example substantially shaped like a rhombus or a square.
The fact that the mesh structure is at least partially embedded in the PTC-effect material 3a prevents the risks of separation or detachment of the connection parts 2a from the corresponding heating body 3, and notwithstanding this enables possible deformation of the material 3a and/or of the mesh structure due to the heating and cooling cycles. The fact that the mesh structure is in any case relatively dense and extensive ensures, however, a considerable current distribution and intensity.
As may be appreciated, the peripheral profile of the mesh structure that forms a connection body 2 may, for example, be easily obtained via elementary operations of cutting or dinking of a sheet or web of electrically conductive fabric or netting, or else the peripheral profile may be obtained via the aforesaid weaving processes. As will be seen, the aforesaid peripheral profile does not necessarily have to be quadrangular, as so far exemplified in the figures.
Using suitable equipment, the areas of the bodies 2 corresponding to the connection parts 2a are pressed or forcefully pushed, after prior possible heating, on the aforesaid face of each body 3, causing penetration therein of the corresponding portions of the mesh structure. For this purpose, in preferential embodiments, the manufacturing equipment used is configured for heating the bodies 3 in order to cause a modest softening thereof that facilitates penetration of the PTC-effect polymeric material into the openings of the mesh structures corresponding to the parts 2a; next, in particular after cooling of the bodies 3 (if heating thereof is envisaged), the pressure or thrust is interrupted and the semifinished product thus obtained can be removed from the equipment. As has been mentioned, this operation is eased by the reduced width of the connection parts 2a, i.e., of the corresponding bodies 2.
The semifinished product 1 may present in the form visible in the detail of
The equipment used for the aforesaid purpose may be of any known conception, provided that it performs the functions described above. For instance, the equipment could be configured like a press, with a stationary element defining a plurality of seats for positioning of the bodies 3 and 2, with the bodies 2 locally set on top of the bodies 3, and a moving element that is designed to exert the necessary mechanical pressure on the bodies 2 at the parts 2a. In such a case, the stationary element could also be configured for heating the heating bodies 3, as mentioned above. In addition or as an alternative to the equipment may be configured for heating the connection bodies 2.
According to other embodiments, the equipment could also be configured as continuous-production machine, for example, one in which the two bodies 2 are supplied, starting from respective rolls or folded webs, at input to a workstation where the bodies 3 are loaded individually in order to be heated and then pressed against the bodies 2; at output from the aforesaid workstation the semifinished product 1 obtained is then rolled up or else folded on itself, for the purpose of storage.
As has been mentioned, the heating bodies 3 are substantially stiff, or have in any case a lower flexibility or capacity for deformation than the connection bodies 2, so that the semifinished product 1 has, in its length direction L, an alternation of stiffer portions and less stiff portions. In this way, the stretches of the connection bodies 2 that extend between two successive heating bodies 3 provide in effect areas of articulation, or deformation, or compensation of the semifinished product 1. The aforesaid areas make it, for example, possible to vary the angular arrangement between the heating bodies themselves (see, for example, the lengths of semifinished product designated by 1′ in
In various embodiments, the areas of the connection bodies 2 in an intermediate position between the heating bodies 3 are coated at least partially by protective layers, made, for example, of material having a PTC effect, or else by an electrically and thermally conductive material, for example a conductive adhesive or a conductive coating layer, or else by an electrically insulating material, such as an insulating polymer.
In preferential embodiments of this type, at least some of such intermediate areas of the bodies 2 are in any case at least partially exposed; i.e., they envisage openings or passages that may be useful for the purposes of electrical connection of the semifinished product 1. Illustrated in
In embodiments of this sort, the protective layers 3b may coat just one side of the mesh structure of the bodies 2, so that the opposite side can be made to penetrate more easily into the bodies 3, at their electrical- and mechanical-connection parts 2a. Of course, the protective layers 3b could also be overmoulded on the bodies 2, or else be applied thereto after coupling thereof to the bodies 3.
From
The coating layers 3b preferentially have a comparatively small thickness as compared to the heating bodies 3. A small thickness of the coating layers 3b, and a reduced width thereof, in any case guarantees the necessary flexibility or deformability of the areas of the bodies 2 intermediate between the bodies 3 in order to enable rolling up or folding of the semifinished product 1, in particular for the purpose of storage, and/or to enable shaping of the semifinished product 1, for example to adapt it to different contexts of installation. The small thickness of the coating layers 3b, and the reduced width thereof, in any case guarantees the necessary flexibility or deformability of the areas of the bodies 2 intermediate between the bodies 3 in order to enable also an appropriate compensation in regard to any possible expansion or contraction during temperature variations.
The various heating bodies 3 of a length of semifinished product can be electrically supplied by applying an electrical potential difference between the at least two connection bodies 2, for example by connecting supply terminals directly to one of the longitudinal ends of the aforesaid bodies 2 (as described hereinafter with reference to
As mentioned previously, provision of connection cables 10 that extend in a direction transverse to the direction L is particularly advantageous when it is necessary to connect together electrically a number of lengths of semifinished product 1 arranged side by side. As an alternative to connection cables 10, provided with an electrically insulating coating 10b of their own, leads of some other form could be provided, such as metal straps, even of a type not provided with an electrically insulating coating of their own (in this case envisaging further electrical insulation elements in the areas where the electrical cables 10 must not come into contact with the connection bodies 2).
In the embodiments so far described, each of the two connection bodies 2 is entirely formed by a single piece or element with mesh structure, for example a strip of electrically conductive fabric or of metal netting. This does not, however, constitute an essential characteristic, in so far as each body 2 could be formed by assembling a number of parts together.
Hence, in the example of
In various preferential embodiments, welding between the two parts in question is resistance welding, i.e., a pressure autogenous welding method in which the material is heated by an electrical resistor.
Overmoulding of the bodies 3 on the corresponding elements 2″ can be obtained in a number of steps and/or with a number of materials, or else the two elements 2″ can be bonded to the corresponding body 3, in particular via an electrically conductive bonding agent that is preferably also thermally conductive. As it can be noticed, in embodiments of this type, the mesh structure of each part 2a of a body 2 is associated to a major face of the heating bodies, and the mesh structure of each part 2a of another body 2 is associated to the other major face of the of the heating bodies 3.
In the case exemplified, the projecting portion of the elements 2″ faces and is welded on the surface of the respective element 2′, as may be clearly noted, for example, in
It will be appreciated that, in embodiments of the type described with reference to
Obtaining of the connection bodies 2 in a number of parts 2′, 2″ may be useful for production purposes, in particular for associating—in a first manufacturing step—the connection parts 2a-2″ to the heating bodies 3, and—in a subsequent manufacturing step—for associating the bodies 3 (i.e., their connection parts 2a-2″) to the longitudinal elements 2′. This may be useful for producing and storing initially the bodies 3 provided with the corresponding connection parts 2a, and thereafter use them according to needs for obtaining semifinished products even distinguished by differentiated spacings between the corresponding heating bodies 3, so as to be enabled to obtain different configurations, with different distributions of heating elements, while maintaining unaltered the manufacturing equipment.
The proposed configuration allows for carrying out a continuous production while keeping the cycle time constant (avoiding machine downtimes or slowing down which might jeopardize the quality of the product), as well as a quality control on the performances of the single heating bodies 3, without compromising a semifinished product 1 as a whole.
By having longitudinal elements 2′ with a smaller width than the body 3, the risk is also avoided of a short-circuit between the same elements 2′, without the need of arranging an insulating element between the two elements 2′. Additionally, provided that the parts 2a have a smaller dimension than that of the bodies 3, the risk is avoided of a short circuit occasioned by the presence of possible scraps between the same parts 2a at a same heating body 3.
In the cases exemplified in
The connection bodies 2 can be formed entirely by a mesh structure, but have a complex peripheral profile, for example substantially comb-shaped, so as to define respective electrical- and mechanical-connection parts 2a that project in a transverse direction. Such a case is represented schematically in
In the case exemplified, the second transverse portions 22 have a part folded back, which is partially embedded or englobed in the polymer-based material of the corresponding heating body 3, in an end region thereof. In such an embodiment, the bodies 2 may initially have a comb-shaped configuration and be arranged parallel, with the transverse portions 22 opposed and aligned with respect to one another. On the two bodies 2 there are then fixed and/or connected the various bodies 3, in particular by moulding or interpenetration, in such a way that the material of each of them englobes at least part of two respective opposite transverse portions 22, and next the longitudinal portions 21 are folded on the bodies 3, for example as emerges from
By folding the portions 21 a reduction is obtained of the overall dimension in the direction W, or alternatively—this the same outer dimensions—a greater heating area is obtained. Furthermore, this comb-like configuration reduces the number of electrical connections (the portions 21 e 22 are in a single piece), so rendering the semifinished product stronger, from the reliability viewpoint.
Exemplified in
With initial reference to
In various preferred embodiments, the casing body of the heater device according to the invention is made up of two or more parts associated to one another, but in other embodiments the casing may be obtained at least in part by overmoulding of material on at least one heating element of the device. The casing body may be of a hermetic type, namely, designed 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 being installed and/or fixed in a more complex system, for example the heating system of a motor vehicle. In other embodiments, the heater device is instead integrated in a component designed for performing also functions different from heating of a generic medium, in which case at least part of a body of the aforesaid component can be exploited to obtain at least in part also the casing body of the heater device.
In the case exemplified in
Preferably, at least part of the casing body of the heater device comprises at least one polymer, such as a high-density polyethylene (HDPE). Preferably, at least part of the aforesaid casing body is made of a material compatible with and/or that can be welded to the material of a different structure (such as a tank or a hydraulic duct), in which the aforesaid body is to be mounted, in particular for the purpose of mutual fixing via welding (for example, vibration welding and/or at least partial remelting of the respective materials).
As may be seen in
In various embodiments, the housing 25 is also shaped for receiving a positioning element 26 for a pair of electrical terminals 27, set in electrical contact with the connection bodies 2 of the length 1. In the case exemplified, the positioning element 24 and the terminals 27 are shaped so as to project in a direction transverse or orthogonal to a plane identified by the length 1, through an opening 28 defined in the casing part 22, where a connector body 24a, configured for receiving inside it part of the terminals 27 and thereby providing the connector 24, is mounted.
In various preferential embodiments, the casing parts 22 and 23 are welded together, for example via vibration welding, while a tool or template compresses them against one another, in particular in the areas around the heating elements 3, thus preventing or reducing the presence of air within the device. In this way, the risk of possible operating faults of the device is prevented or reduced: the presence of a high amount of air within the device could in fact bring about significant expansions during the operating steps of heating of the device. The reduced width of the bodies 2 is also advantageous for these purposes.
Visible in
In an advantageous embodiment, at least one of the two casing parts comprises a polymer added with fillers or particles that are thermally conductive but electrically insulating; i.e., the material of at least part of the casing body could be electrically insulating but thermally conductive (for example, an HDPE added with boron-nitride particles), in particular to improve thermal exchange between the heating bodies 3 and the environment external to the casing body, for example with as compared to the liquid contained in a tank or duct in which the device can be mounted.
In general, preferential thicknesses for the casing parts 22 and 23 can range from 0.1 mm to 2 mm. The combination of parts 22 and 23 of different thicknesses can also be exploited for modulating the flexibility/stiffness of the heater device as a whole, according to the production needs and the requirements of installation of the device itself.
In the cases illustrated in
One or both of the casing parts 22, 23 can advantageously be pre-formed via thermoforming in order to define the housing 25 or a respective part 25a or 25b thereof. On the other hand, if at least one of the two parts 22, 23 is sufficiently thin, in particular in the form of a film of relatively small thickness (for example, 0.35 mm), the shaping of the housing 25 or of the part of housing 25a or 25b in the film can be obtained using a template used for welding together the two casing parts, in particular a template used for purposes of vibration welding. Also one such operation may be eased due to the reduced width of the bodies 2.
The device 20 of
In the version of device 20 represented in
In various embodiments, one or more lengths of semifinished product are located within the casing 21 in a generally bent or curved configuration, as for the lengths designated by 1′ in
It will be appreciated that the casing 21 of a heater device according to the invention may be of a rigid type, for example with its parts moulded with the desired curvature or inclination, in which the length or lengths 1 is/are then enclosed; as an alternative, however, the device 20 could be initially obtained with a rigid and plane casing 21 (for example, as in
The distribution of the electric power and heating capacity of a semifinished product 1 according to the invention, or else of a device that uses it, can be easily varied in the production step in various ways, for example by means of variation of the length dimension of the heating bodies, i.e., the dimension denoted by L1 in
In addition or as an alternative, the distribution of electric power and heating capacity of a semifinished product 1 can be obtained in the production step by varying the distance between the heating bodies 3, i.e., the dimension denoted by S in
Another possibility still for distribution of electric power and heating capacity of the heater device 20 that uses a number of lengths 1 arranged alongside one another is to vary the distance between the lengths themselves, as indicated by the dimension I in
Without prejudice to the fact that the type of embodiment proposed makes it possible to have the maximum flexibility in terms of electric power, practical tests conducted by the present applicant have made it possible to define the following preferential sizings:
Once again preferentially:
In general, the power density at the electrical- and mechanical-connection parts 2a depends upon the specific modalities of coupling between the connection bodies 2 and the heating bodies 3. For instance, connection configurations of the type described with reference to
On the above basis, according to possible embodiments of the invention, it is possible to integrate in a heating device lengths of semifinished product distinguished by different versions of the connection parts 2a, for example first lengths with parts 2a according to
Once again on the above basis, it is also possible to obtain a semifinished product 1 in which at least two different configurations of connection of the parts 2a coexist in order to be able to have sections that guarantee powers that are locally different in their direction of length: for example, between at least two heating bodies 3 connected with parts 2a according to
It is also possible to envisage different connection configurations, for example selected from among the ones described herein, for two opposite end regions of one and the same heating body. For instance, one first of the two connection bodies 2 can be associated to the heating bodies 3 with a configuration of the type illustrated in
As mentioned previously, the mesh structure is preferably formed by the interweaving or criss-crossing of relatively thin elements or parts, for example threads or portions of a netting obtained from machining of a strap. The aforesaid elements or parts preferably have a diameter or other cross-sectional dimension comprised between 0.2 mm and 0.02 mm: this enables an efficient fixing of the mesh structures to the material 3a also thanks to their at least partial embedding in the aforesaid material, thus countering any risk of detachment between the parts in question.
For instance, threads that have a diameter smaller than 0.1 mm are advantageous for enabling their forced penetration into the material 3a, preferably by heating the latter, as explained previously, and this also in the case of small mesh openings, for example even smaller than 0.05 mm. Threads that have a diameter larger than 0.1 mm may, instead, be more convenient to use when the material 3a is overmoulded on the structures 2a and it is necessary to have available wider mesh openings to enable penetration of the material itself, for example mesh openings even larger than 1 mm (in general, in conductive woven fabrics that can be used for implementation of the invention, corresponding to threads of larger diameter are wider mesh openings).
The section of a thread of relatively large diameter can be advantageously replaced by the section of a number of small threads. For instance, the section of a thread of 0.14 mm of diameter substantially corresponds to that of three threads of 0.08 mm of diameter: hence, neglecting the skin effect, the passage of electric current that can occur in a thread with a diameter of 0.14 mm can occur in three threads with a diameter of 0.08 mm. If, however, the sum of the circumferences of the three threads with a diameter of 0.08 mm is considered (which is approximately 0.77 mm), it will be noted that it is equal almost to twice the circumference (approximately 0.44 mm) of the single thread having a diameter of 0.14 mm. It will hence be appreciated that to the aforesaid larger “overall” circumference of the three finer threads there corresponds a larger surface of contact (almost twice as large) between the mesh structure and the PTC-effect material, hence with a better electrical contact and a better more extensive overall mechanical adhesion between the mesh structure and the PTC-effect material.
In the case exemplified, associated to each of the connection bodies 2 of the length 1—which may for example be of the type described with reference to
It will be appreciated how, also in this case, construction of the heater, or of the component that integrates it, is very simple: the length 1 is cut to the necessary size, and the terminals 27, for example formed by a metal strap, are then associated to it. The ensemble formed by the length 1 and by the terminals 27 can then be assembled in the corresponding casing or set in a mould, configured according to a technique in itself known for keeping or supporting the length 1 in the arched configuration, and, after closing of the mould, the material necessary for formation of the casing body 21 is injected therein.
In various embodiments, the semifinished product according to the invention can include more than two connection bodies. For instance, exemplified in
Solutions of this type can be adopted to vary emission of heat by the heating bodies 3, it being possible to supply electrically only a part of heating body 3 or the entire heating body 3, i.e., it being possible to supply a length 1 with different supply configurations. For instance, by applying a potential difference between the connection bodies 2, substantially the entire PTC-effect material of the bodies 3 will be supplied for the purposes of heat generation; instead, by applying the potential difference between one of the bodies 2 and the body 2i, only a fraction of the aforesaid material will be electrically supplied, here approximately half of each body 3. According to a different example, by supplying simultaneously with the positive polarity the bodies 2 and with the negative polarity the body 21 (or vice versa) it would substantially be possible to double the power of the body 3, in so far as in this way the resistance of the circuit is substantially halved.
The various bodies 2 and 2i are not necessarily all associated to one and the same face of the corresponding heating body: for example, it is possible to associate the two bodies 2 to one face and the body 2i to the opposite face, it being understood that their width will be preferably equal to a fraction of the width of the bodies 3 (here a width which is lower to one third of the width of the bodies 3) in the intermediate stretches comprised between two bodies 3.
Moreover, in the case exemplified the heater device includes three electrical terminals 27, each set in electrical contact with a respective connection body 2 and 2i of the length 1. Also in this case the positioning element 26 for the terminals 27, and the terminals themselves, are shaped so as to project in a direction transverse or orthogonal to a plane identified by the length 1, through an opening 28 defined in the casing part 22, where a connector body 24a, configured for receiving inside it part of the three terminals 27 and thereby providing an electrical connector, is mounted.
The device 20 of
Also in this case, at least one of the two casing parts 22, 23 defines a housing or seat 25, configured for receiving at least partially a plurality of respective sections or lengths. With reference in particular to
In the case exemplified, the opposite ends of the aforesaid conductors 10 are each connected to a respective connection body of the two lengths designated by 1 in
As mentioned previously, the fact that the semifinished product according to the invention can have a substantially flexible or semi-rigid structure enables it to be wound on itself so as to assume a more or less cylindrical shape, in particular to form a roll or a reel, this being particularly advantageous for the purpose of handling in the production and storage stage. This possibility, as has been seen, is allowed by the areas of articulation provided by the stretches of the connection bodies having reduced width that are located in an intermediate position between the heating bodies.
As already mentioned, the aforementioned structure can also be folded on itself in opposite directions or according to a zigzag pattern, preferably with portions substantially of the same length, to form a sort of more or less parallelepipedal stack of the desired height, which is likewise advantageous for the purpose of handling and storage.
The rolled-up or folded form of the semifinished product, possibly with the aid of a support or container, makes it possible to obtain a feeder designed to be mounted on a machine or an automatic production line, for example for feeding and cutting into lengths the semifinished product in the size required, and implementing other production steps, such as welding of wires or electrical terminals and/or mounting on a support or casing of a heater device.
In
It will be clear to the person skilled in the art that the concepts expressed in relation to the embodiments described with reference to
From the foregoing description, the characteristics of the present invention emerge clearly, as likewise do its advantages. The semifinished product according to the invention, which is simple and economically advantageous to produce, can be obtained in the form of a strip or web that can be produced and advantageously stored in compact form, for example in the form of roll or folded on itself, and then be subsequently cut to the desired length in order to be assembled in various possible forms inside a corresponding protective and supporting casing. The fact that the connection bodies include mesh structures at least partially embedded in the PTC-effect material of the heating bodies ensures a reliable electrical and mechanical connection, at the same time countering any risk of separation or detachment between the parts in question, in particular when the semifinished product is rolled up or folded or has to be bent during the production step, for the purposes of production of a heater device or of its integration or mounting in a different component. The fact that the mesh structure used for the electrical and mechanical connection of the various heating bodies is preferentially relatively extensive and dense ensures a good surface of adhesion and contact between the connection bodies and the PCT-effect material, with an optimal distribution and intensity of electric current. The fact that the heating bodies are relatively stiff and the intermediate portions of the connection bodies have a reduced width and are relatively flexible or deformable, possibly in a plastic way, means that it is possible to have available a structure that can be easily adapted or integrated for different uses or products. As has been seen, the structure in question can in any case be easily rolled up or folded, with evident advantages in terms of reduction of encumbrance and ease of handling of the semifinished product.
The lengths of the semifinished product according to the invention can be easily “modelled” in different shapes in order to allow distribution of the heat in an optimal way according to the shapes of the heating devices or components that are to integrate the aforesaid lengths, it being possible for these devices and components to have geometries that are even very different from one another. This also avoids having to provide dedicated moulds for the PTC-effect material according to the geometry of the application; the moulds for producing the heating bodies according to the invention are on the other hand very simple. Also the casings of devices that integrate lengths of semifinished product according to the invention are convenient to produce and can be used for a wide range of shapes of heater device, for example using thermoforming techniques or, as has been seen, exploiting for modelling the same equipment used in the step of welding between two casing parts.
The portions of the connection bodies that extend in intermediate positions between two heating bodies can function not only as areas of articulation or deformation but also as areas of compensation for recovery of possible dimensional variations, in particular the dimensional variations due to thermal variations (such as expansions or contractions during the operating cycles of heating and subsequent cooling), thus reducing the risks of faults in the semifinished product and/or in the device or component that integrates it. Provided that the aforesaid portions are set at a distance in the width direction, any risks is avoided of accidental electrical contact between the connection bodies, when non-rectilinear shapes are given to the semifinished product, such as arc shapes or circular shapes.
It is clear that numerous variations may be made by the person skilled in the branch to the semifinished product and the electric heater device described by way of example, without thereby departing from the scope of the invention as defined in the ensuing claims.
Without prejudice to the other advantages, the semifinished product according to the invention may be produced also as plane strip or web (i.e., not rolled up or folded), having a length in any case suitable for convenient storage, for example between 1 and 4 m, which can subsequently be cut to the desired length.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102018000008700 | Sep 2018 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2019/057516 | 9/6/2019 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/058797 | 3/26/2020 | WO | A |
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| 1571586 | Jan 2005 | CN |
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| Entry |
|---|
| International Search Report for PCT/IB2019/057516, mailed Dec. 2, 2019, 4 pages. |
| Written Opinion of the ISA for PCT/IB2019/057516, mailed Dec. 2, 2019, 7 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20210385911 A1 | Dec 2021 | US |
