WO2006106387A1

WO2006106387A1 - Lightweight electrical heating panel

Info

Publication number: WO2006106387A1
Application number: PCT/IB2006/000483
Authority: WO
Inventors: Roberto Bertato; Andris Raiskums; Giorgio Annen; Sergey Semenikhin; Gioviano Facco
Original assignee: INNOVAZIONI Srl
Current assignee: INNOVAZIONI Srl
Priority date: 2005-04-08
Filing date: 2006-02-14
Publication date: 2006-10-12
Anticipated expiration: 2007-10-08
Also published as: ITVA20050023A1

Abstract

An electrical heating panel for space hearing has a weight for unit of area of less than 3 Kg/m2. It consists of comprising a flat laminated body composed of an electrically conductive carbon layer with copper foil current distributors/collectors along opposite sides of the carbon layer sandwiched between two dielectric layers of thermosetting resin. Two contacts with the respective copper foil distributors/collectors are formed through the thickness of one of the sealing layers of thermosetting resin for connection to the mains. The panel assumes a substantially uniform temperature constituting a heat source of ample area without localized hot spots. It may be tailored to size support a decoration and be hanged on a wall as a picture, bent into a lampshade, sunk in the pavement.

Description

"LIGHTWEIGHT ELECTRICAL HEATING PANEL"

The present invention relates in general to space heating appliances and more in particular to electrical heating appliances for domestic or alike use.

Commercially available electrical heaters whether of radiant or of radiant- convective type, generally employ heating elements, typically filaments of a nickel chromium alloy or other metallic or nonmetallic material of relatively high resistivity that is normally brought to incandescence by the heat developed by Joule effect.

In case of radiant apparatuses, the heat is radiated in the space by parabolic reflectors to determine a certain direction of the energy flux. In case of convective or radiant/convective appliances, the heating elements are often contained inside a heat exchange structure through or in contact with which the ambient air circulates either forced by an air blower or by natural convention. In the latter case, the heating elements are often immersed in a heat transfer fluid, typically an oil, that convectively recirculates in a common heat exchanger body. The apparatus generally mounted on caster wheels diffuses heat in the room by convective circulation of the ambient air and partly by radiation from the hot outer surface of the heat exchanger structure.

Normally, electrical heating appliances are relatively heavy and/or encumbering.

Moreover, the whole heating power is spatially concentrated in a spot (the heating element of the apparatus) such that inside a room they constitute a substantially localized heat source and distribution of heat in the room is limited by the directivity in case of radiant apparatuses and/or by convective movement of the ambient air.

These characteristics make difficult to obtain a most comfortable uniformity of temperature in the room, moreover, a pronounced convective movement of the ambient air can be fastidious and tends to give a feeling of cool even though the air in the room has reached a quite comfortable temperature.

These inconveniences and limitations of known electrical space heaters are surprisingly overcome by the novel electrical heating panel of outstanding lightness and thinness making it suitable of being hanged on a wall or fitted in a lightweight frame that provides a heat source of uniform temperature over the whole area of the panel, the dimensions of which may be tailored to needs.

Basically, the panel of the present invention does not rely, as the known appliances do, on the presence of physically localized heating elements, that therefore constitute spots sources at relatively high temperature, such that the locally generated heat must be diffused by reflectors and/or by heat exchangers to distribute it in the space being heated.

The extreme lightness, thinness and homogenous constitution of the heating panel of the present invention permit to size it and position it in the most appropriate location according to needs. These characteristics coupled to the fundamental characteristic of providing a heat source of uniform temperature over its whole area permit to establish an optimal distribution of the heat introduced in the ambient room, for example by subdividing the total heat input on a plurality of panels easily positionable in the room in a way to produce the most satisfying spatial arrangement of heat sources, while minimizing the intensity of radiant fluxes and/or discomforting localizations and/or intensity of convective air movements in the room.

Basically, the electrical heating panel of the present invention is composed of a flat laminated body comprising:

- a first dielectric layer of a thermosetting resin; - an electrically conductive carbon layer over at least a portion of the surface of said first dielectric layer;

- at least two current distributors (collectors) of copper foil, each overlapping the edge of the electrically conductive carbon layer, along about a respective half of the perimeter of the conductive layer;

- a second dielectric layer of a thermosetting resin covering said conductive carbon layer and said perimetral current distributors (collectors) of copper foil; - at least two electrical contacts, for example of an eutectic tin-lead alloy, respectively with said two perimetral current distributors (collectors) formed through respective openings of said second dielectric layer of thermosetting resin;

- means of electrical connection to the mains of said two contacts optionally including a control thermostat of the temperature of the panel.

The electrically conductive carbon layer may be for example a conductive aggregate of resin and of fibers and/or particles of graphite and/or of so-called glassy carbon, a material obtained through a thermal carbonization under controlled atmosphere of a woven or nonwoven fabric of a precursor material, for example of polyester fibers. Alternatively, the conducting layer may be a woven cloth of carbon fibers that is sandwiched and practically completely encapsulated between the two layers of thermosetting resin.

Essentially, the conductive carbon layer has an homogeneous electrical conductivity in the plane of the layer, independently of the direction of current lines. In practice, it may be considered free of identifiable privileged current paths.

In this way, by distributing the current through elongated copper foil edge distributors (collectors), that is with power supply rails of a material having an electrical conductivity of many orders or magnitude greater than that of the carbon layer contacting the carbon layer along two opposite sides thereof or even along almost entire respective halves of the perimeter of the conductive layer, a practically uniform current distribution (density of current) is produced over the whole surface area of the conductive carbon layer. The heat generated by Joule effect in the conductive layer is uniformly generated over the whole area of the panel (i.e. the resin encapsulated carbon layer) that assumes a temperature that is practically uniform over its surface, substantially without any "hot spot".

This condition reveals itself extremely advantageous and comfortable by determining a heat transmission by radiant effect from a source surface of relatively extended dimensions, heated at a temperature not excessively high, generally between 50 and 7O⁰C, though it may reach up to a maximum allowable temperature, for example of about 85⁰C, without causing any degradation of the component materials (resins).

Moreover, the unlimited freedom of sizing and of spatially arranging a plurality of panels in an extremely easy and practical manner, permit to optimize the space heating for maximum comfort, for example for a person seated at a table or work desk, in the relax area of an ample living room, etc..

Another important feature of the heating panel of the present invention is that it outstandingly lends itself to be decorated with quality images of any king such to constitute an element of interior furnishing or decoration of unsuspectable effectiveness.

The outer surface of the thermosetting resin layer on one or on the opposite face or even of both, may in fact be serigraphically printed with any design, figure, photograph and the like. Alternatively, an artwork or a serigraphic reproduction on common cloth, for example of a famous painting or of any other image, may be permanently bonded onto the thermosetting resin layer during or at the end of the fabrication process of the heating panel.

Moreover, the heating panel of this invention may be provided with a lightweight frame for hanging it to onto a wall, for example of polycarbonate, in which case it is highly preferable that the frame defines a gap spacing between the rear of the heating panel and the wall, open at the bottom and at the top, in order to favor circulation of air by convention through the space between the heating panel and the wall onto which it is hanged.

In case of a heating panel hung on a wall, in order to enhance radiation of heat toward the space to be warmed and reduce radiation toward the supporting wall, the front of the panel, normally the surface of the first layer of resin facing toward the space to be heated, may be blackened by incorporating soot, metal oxides or metal powders of high specific surface area in order to confer to the front face of the panel a high radiant capacity. On the contrary, the rear surface of the panel facing the wall on which the panel is hanged, may be provided with a specular metallic coating to reduce radiation of heat toward the wall.

The first layer of thermosetting resin may have a thickness generally comprised between 0.4 and 0.8 mm, the conductive carbon layer may have a thickness generally comprised between 0.2 and 0.6 mm and the second layer of thermosetting resin may have a thickness generally comprised between 0.4 and 0.6 mm, for a weight per unit of area of less than 3 Kg/m².

The different aspects and advantages of the panel of the present invention will become even more evident from the following description of few embodiments and by referring to the attached drawings, wherein:

Figure 1 is a plan view of the heating panel of the present invention; Figure 2 is a partial cross section on the plane A of Figure 1 ;

Figure 3 shows a heating panel provided with a frame and with an electrical supply cord, hanged on a wall;

Figure 4 shows a heating panel installed in a supporting frame;

Figure 5 is a schematic view of a yacht furnished with heating panels distributed in the interior of the boat.

With reference to Figures 1 and 2, the heating panel 1 is composed of a multilayered laminated body comprising a first dielectric layer 2 of thermosetting resin, for example of polyester, that may incorporate or not reinforcing fibers such as for example glass fibers.

The layer is substantially flat and in the shown example has a rectangular area.

Optionally, the outer surface of the first layer 2 of thermosetting resin may be blackened by loading it with a black pigment for favoring the radiant capacity of the panel toward. the space or object to be warmed.

A thin layer of soot carbon black or other black pigment of powdered large specific surface area metals or oxides may either be incorporated in the resin while still in fluid state prior to being powered or distributed onto the bottom surface of a mold or of a platen or may be distributed uniformly over the surface before applying thereon the fluid resin.

Alternatively, a textile fabric eventually decorated may be disposed over the surface of the platen in order to embed or permanently bond it to the thermosetting resin layer 2.

Over this first dielectric layer of thermosetting resin is formed or placed an electrically conductive carbon layer 3 of an area marginally reduced compared to the area of the base layer 2 of thermosetting resin such to end short of reaching of the perimetral edge of the thermosetting resin base layer 2.

In the plan view of Figure 1, the profile of the conductive carbon layer 3 is indicated by a broken line perimeter.

Along opposite sides and partially even along part of the bottom side of the perimeter of the conductive carbon layer 3 are disposed two strips or ribbons of thin copper foil, respectively 4 and 5, the profiles of which are indicated in the layout view of Figure 1, with broken lines.

The two ribbons may be cut from thin copper foil of thickness that may generally be comprised between 0.2 and 0.4 mm. The copper laminae 4 and 5, that will constitute respectively a current distributor and a current collector, overlap perimetral edge portions of the conductive carbon layer 3 such to electrically contact the carbon layer 3 at least along two opposite sides and, as shown in the example, even for part of the bottom side of the rectangular perimeter, as may be observed in the plan view of Figure 1.

The conductive carbon layer 3 and the current distributors (collectors) 4 and 5 of copper foil are thereafter covered with a second layer of thermosetting resin, for example a polyester, that joins itself along the entire perimeter of the panel to the polyester base layer 2 that was previously formed, thus completely sealing and isolating between the two dielectric layers of polyester 2 and 6 the conductive layer 3 and the current distributors (collectors) 4 and 5.

In case the panel is destined to be hung on a wall, the surface of the thermosetting resin layer 3, is preferably provided with a mirror-like metallic coating, for example by flash metallization or by coupling onto the surface of the resin layer 3 aluminum foil. In this way, back radiation of heat toward the supporting wall can be sensibly reduced favoring radiation of heat toward the space to be heated.

By forming two holes through the dielectric covering layer 6, the underlying copper foils 4 and 5 are exposed and the contact openings can be filled with an eutectic tin-lead alloy that solders itself to the copper constituting the two electrical contacts 7 and 8.

Within a minuscule box of isolating material 9, for example a polycarbonate, to the contacts 7 and 8 may be soldered wires of electrical connection to the mains.

The electrical connections to the two contacts 7 and 8 are not illustrated in the drawings, being of immediate recognition that they may be arranged in any of innumerable ways.

Preferably, within the connection box 9, a safety thermostat may be installed for controlling the temperature reached by the panel that will intervene to open a contact or both contacts of electrical power supply, if, by any accidental reason or because of inadvertent connection of the panel to mains of a voltage higher than the specified voltage, the temperature reaches a preestablished maximum tolerable level. This will prevent accidental overheating of the panel that could damage or degrade the conductive carbon layer 3 and/or the dielectric layers of thermosetting resin 2 and 6.

Of course, in the box 9 or along the cord may also be optionally installed an on/off power switch of the heating panel.

The resistivity of the conductive layer 3 is designed such to permit to power the heating panel directly at the mains voltage, establishing, in the design phase of the conductive layer a nominal electrical power input compatible with the heat dissipation capacity by radiation of the panel and for a minor proportion by convective heat exchange with the ambient air, such to ensure under normal use of the space heating panel that the maximum temperature that can be reached by the panel remains below the maximum tolerable temperature.

Of course, the panel may be designed to be used for any supply voltage of an AC or of a DC electrical power source.

Moreover, as in any heating element of a space heating system, the electrical heating panel of the present invention may be controlled by a dedicated control system of the room temperature that will command in a on-off mode the electrical power supply to the panel.

Figure 3 shows an embodiment of the panel of the present invention particularly suited for hanging the panel onto a wall. As depicted, the panel 1 is provided with a frame or with side spacer brackets 10, for example of polycarbonate, that can be hung to hooks fastened to the wall. The frame or side brackets may be shaped in a way to determine a gap space open at the bottom and at the top between the back surface of the panel and the wall in order to favor circulation of air by natural convention as indicated by the curved arrows. The straight arrows projecting normally out of the surface of the panel, represent the fact that the predominant portion of the generated heat is dispersed in the ambient by radiation.

Figure 4 shows an embodiment of the heating panel hung to a lightweight structure 11 , made for example with light polycarbonate tubes, that can be easily moved and oriented inside a room according to need.

The outstanding lightness of about 2 Kg/m², thinness and intrinsic flexibility of the laminated composite constituting the heating panel can be exploited for realizing the heating panel in special shapes having either a technical effect and/or a decorative effect. For example, the laminated panel may be given the shape of a trapezium and be thereafter curved around to form a truncated cone lamp shade that will be electrically powered to act as space heating element.

The laminated panel of the present invention may be incorporated or associated to other structural elements, for example fitted inside the back of an armchair or in a seat to warm it or it may be laid under the pavement, etc..

The ability of lending itself in an outstandingly simpler and effective manner than known electrical heating appliances to be tailored according to need and easily held even in a nonpermanent manner because of its outstanding lightness and ability to become an object of decor or of furnishing, is underlined in Figure 5, wherein it is schematically shown how a certain number of panels, each being sizable according to need, may be distributed inside cabins of a yacht for positioning radiant sources of heat particularly comfortable in distinct cabins of the boat.

Claims

C L A I M S

1. An electrical heating panel having a weight for unit of area of less than 3 Kg/m² comprising a flat laminated body comprising

- a first dielectric layer of a thermosetting resin; - an electrically conductive carbon layer over at least a portion of the surface of said first dielectric layer; at least two current distributors/collectors of copper foil, each overlapping the edge of the electrically conductive carbon layer, along about a respective half of the perimeter of the conductive layer; - a second dielectric layer of a thermosetting resin covering said conductive carbon layer and said perimetral current distributors/collectors of copper foil;

- at least two electrical contacts, respectively with said two perimetral current distributors/collectors formed through respective openings of said second dielectric layer of thermosetting resin; - means of electrical connection to the mains of said two contacts.

2. The panel according to claim 1, wherein said conductive carbon layer is of a material belonging to the group composed of conductive aggregate of a resin and of fibers and/or particles of graphite, glassy carbon, a fabric of carbon fibers.

3. The panel according to claim 1, wherein said first layer of thermosetting resin has a thickness comprised between 0.4 and 0.8 mm, said conductive carbon layer has a thickness comprised between 0.2 and 0.6 mm said second layer of thermosetting resin has a thickness comprised between 0.4 and 0.6 mm.

4. The panel according to claim 1 , having a weight per unit of area of less than 3 Kg/m².

5. The panel according to claim 1, wherein the surface of said first layer of thermosetting resin constitutes the front of the heating panel and at least partially has dark tonality.

6. The heating panel according to claim 5, wherein the first layer of thermosetting resin incorporates powder of a black material belonging to the group composed of powders of high specific surface area of metal or oxide, soot and carbon black.

7. The heating panel according to claim 1, wherein the outer surface of said second layer of thermosetting resin constitutes the rear of the panel and includes a reflecting metal layer coupled to the thermosetting resin of said second layer.

8. The heating panel according to claim 7, wherein said reflecting metal layer is aluminum foil coupled to the thermosetting resin.

9. The panel according to claim 1, wherein said electrical contacts are of eutectic tin-lead alloy.

10. The panel according to claim 1, wherein said electrical connection to the mains of said two contacts includes a limit thermostat of the temperature reached by the panel.

1 1. The panel according to any of the preceding claims, characterized in that it comprises a light weight frame suitable for hanging the panel onto a wall and defining a space open at the bottom and at the top between the rear of the panel and the wall on which it is hanged allowing for a conductive flow of air therebetween.