WO2005022954A1

WO2005022954A1 - Heating panel

Info

Publication number: WO2005022954A1
Application number: PCT/GB2004/003703
Authority: WO
Inventors: Gerald Kingsbury
Original assignee: H K Wentworth Limited
Priority date: 2003-08-30
Filing date: 2004-08-31
Publication date: 2005-03-10
Also published as: CN2775517Y; GB0320387D0

Abstract

A radiant panel heater for providing radiant heat comprises asubstrate layer, an electrically resistive layer andan electrically insulating layer. The heater comprises a pair ofelectrodes locatedtopass an electrical current across the electrically resistive layerandmeans for connecting the electrodes to a source of electrical power. The substrate layeris alayerofmica; the electrically resistive layer is a layer of a thermoconductive paint which has been applied to the substrate layer and the electrically insulating layer is a layer ofmica and is translucent to radiation emitted by the electrically resistive layer when an electrical current is passed between the electrodes.

Description

Title: Heating Panel

The present invention relates to an improved radiant panel heater.

It is known from GB 2244 194 Al to provide a radiant panel heater incorporating a heating element in the form of a film of electrically resistive material deposited on an insulating substrate, the electrically resistive film being in turn covered by a further insulating layer.

While the heater described and claimed in this patent, and other known radiant heaters, are described as >radiant= panel heaters, they are only radiant heaters to a limited extent. The major part of the heat, which they generate is produced by heating air which is then circulated, producing a convection current circulating the heated air. Because of the thickness of the insulating layers, they cannot be described as true radiant heaters where the major part of the heat generated is produced by radiation.

They are therefore not true radiant heaters in the sense that the sun is a radiant heater, producing radiation.

It is a disadvantage of the known radiant panel heaters that they are not true radiant heaters. It is a further disadvantage of known panel heaters that they are bulky items which may not be suitable in some locations or may impose unacceptable constraints on interior design or internal arrangements. IT is a further disadvantage of the known panel heaters that they are expensive to produce. It is an object of the present invention to produce a radiant panel heater in which the above disadvantages are reduced or substantially obviated.

The present invention provides a radiant panel heater for providing radiant heat, which heater comprises a substrate layer, an electrically resistive layer and an electrically insulating layer, characterised in that the heater comprises a pair of electrodes located to pass an electrical current across the electrically resistive layer and means for connecting the electrodes to a source of electrical power, and in that the substrate layer is a layer of mica and in that the electrically resistive layer is a layer of a thermoconductive paint which has been applied to the substrate layer and in that the electrically insulating layer is a layer of mica which is translucent to radiation emitted by the electrically resistive layer when an electrical current is passed between the electrodes.

hi a preferred embodiment of the radiant panel heater according to the invention, the substrate layer is a layer of mica, which has been impregnated with silicone.

h a further preferred embodiment of the radiant panel heater according to the invention, the electrically insulating layer is a layer of mica, which has been impregnated with silicone.

The radiant panel heater according to the invention is preferably substantially rectangular in shape, with the electrodes extending along opposite sides of the substantially rectangular electrically resistive layer.

hi a further preferred embodiment of the radiant panel heater according to the invention, the electrically resistive layer is applied to the substrate layer in two discrete areas, with an insulating gap arranged therebetween.

The electrodes are preferably in the form of a silver paint applied to the substrate.

In an alternative embodiment of the radiant panel heater according to the invention, an additional electrically insulating layer is applied to the first electrically resistive layer, and a second electrically resistive layer is applied to this electrically insulating layer and is itself covered with an electrically insulating layer. The heater preferably includes earthing means.

The radiant panel heater according to the invention is preferably adapted for mounting on a wall, floor, ceiling or similar surface or for mounting within a housing, for example a freestanding housing.

The substrate layer and/or the electrically insulating layer are preferably approximately 0.3mm in thickness. The electrically resistive layer is preferably approximately 100 micron in thickness. The present invention further provides a heating system which comprises a radiant panel heater for providing radiant heat, which heater comprises a substrate layer, an electrically resistive layer and an electrically insulating layer, characterised in that the heater comprises a pair of electrodes located to pass an electrical current across the electrically resistive layer and means for connecting the electrodes to a source of electrical power, and in that the substrate layer is a layer of mica, and in that the electrically resistive layer is a layer of a thermoconductive paint which has been applied to the substrate layer and in that the electrically insulating layer is a layer of mica and is translucent to radiation emitted by the electrically resistive layer when an electrical current is passed between the electrodes, in combination with a power supply.

The heating system according to the invention includes a power supply, which power supply may be a mains voltage supply or means for supplying any other voltage, for example a voltage of less than 50 volts.

The heating system according to the invention preferably further comprises a thermostat for regulating the supply of electricity to the panel heater in response to a measured temperature.

A radiant panel heater and a heating system incorporating a radiant panel heater will now be described with reference to the accompanying drawings, in which:

Figure 1 is a plan view of a panel heater, with the electrically insulating layer removed and Figure 2 is a diagram of a heating system incorporating a radiant panel heater.

As can be seen from Figure 1 , a heater shown generally at 10 comprises a flat mica panel 2, on which are provided a positive electrode 4 and a negative electrode 6.

The area between the electrodes 4 and 6 is printed with two separate areas 8, 12 of thin even coating of thermoconductive paint. The space 14 between the areas 8 and 12 is uncoated. The thermoconductive paint is applied to the areas 8 and 12 by a printing process, to ensure a thin even coating of the paint. Suitable paints include the thermoconductive paints described and claimed in the applicant=s co-pending UK patent application No. ##### (Applicants ref: P02034UK) of even date herewith.

The panel shown in the accompanying figure is covered on its painted side with a thin sheet of mica, to provide electrical insulation but to allow the transmission of radiant heat.

In use, the panel heater is connected to an electrical power supply and a voltage is applied across the electrodes. Current flows as shown by the arrows in the figure, and radiant heat is generated.

A panel heater as shown in Figure 1 of the accompanying drawings may be manufactured by the following method.

Board preparation

A sheet of mica was taken, and sanded lightly with a 150 grit or finer sandpaper. The boards were masked up, so that areas, which were not to be covered in the thermoconductive paint remained clear. The masking tape was rolled flat so that there were no lumps and bumps.

Mixture preparation

The mixture was made up in accordance with the mixing instructions described in the applicants co-pending application of even date herewith.

To prepare the conductive composition, 50.2 g of Finnfix (sodium carboxymethylcellulose) and 78.3g of Suparex KS (sodium salt of naphthalene sulphonic acid / formaldehyde condensate) were weighed out into an empty 5 litre lacquered container. 1553.8g of water (deionised) was weighed out into a separate container and added in four stages to the Suparex KS in the first contamer and mixing was commenced. 2238.0 g of potassium silicate was weighed out into a further separate container and then emptied into the container containing the water, Finnfix and Suparex KS. The contents of the container were mixed for a further 15 minutes, until all of the solids were dissolved.

65.4 g of Branwell graphite and 1014.4 g of Timrex KS10 graphite (Timrex is a trade mark of Timcal SA) were weighed out into a separate container, mixed together and then added in five approximately equal aliquots to the solution in the 5 litre container.

The contents of the container were mixed for a further 30 minutes, the container being cooled if necessary to ensure that the container did not warm up too much. Care was also taken to ensure that the contents of the container had been totally mixed.

To prepare the non-conductive composition, 175. Og of Suparex KS was weighed out into an empty 12.5 litre plastic container.2610g ofwater (deionised) was weighed out into a separate container and added in five stages to the Suparex KS in the first container and mixing was coinmenced.

3480g of potassium silicate was weighed out into a further separate container and then emptied into the container containing the water and Suparex KS. The contents of the container were mixed for a further 15 minutes, until all of the solids were dissolved.

2750g of talc (talc OXO MM) were weighed out into a separate container and then added in six approximately equal aliquots to the solution in the 12.5 litre container.

985 g of atta gel were weighed out into a separate container and then added in six approximately equal aliquots to the solution in the 12.5 litre container.

The contents of the contamer were mixed for a further 30 nώiutes, the container being cooled if necessary to ensure that the container did not warm up too much. Care was also taken to ensure that the contents of the container had been totally mixed.

350g per board was decanted into a suitable vessel, to transfer on to the mica sheet. 40C, 240V boards are made up of 144g of the conductive mixture, and 256 g of the non- conductive mixture.

80C, 240V boards are made up of 168g of the conductive mixture, and 232 g of the non- conductive mixture.

40C, 48V boards are made up of 344g of the conductive mixture, and 56 g of the non- conductive mixture.

Preparation for application

The mica sheet was fitted to a jig ensuring that the jig fitted to the board in the centre of the board, and did not impinge on any of the critical surfaces. The board was sucked down on the jig, and a scraper was run over the board ensuring that the masking tape was flat enough. Any areas of the masking tape which appeared to create a problem were replaced. The scraper was placed at one end of the board.

Mixture application

The prepared 350g of conductive paint was added to the mica sheet, and the scraper was swiped across the board going from one end to the other. Any conductive paint was cleaned from the jig and scraper, using water and a cloth. Care was taken not to use anything metallic on the jig. The board was removed to a suitable board-drying frame and allowed to dry. The jig was checked to ensure that it was ready for the next mica sheet.

Drying

The mica sheet may take a few hours to dry on the drying rack. It must be ensured that the conductive paint is dry before proceeding on to the next step.

Application of silver conductive paint and electrodes

Silver paint was applied around three sides of the conductive paint panel to spread the current. A template was placed over the board, and the silver paint applied using a brush. For the higher current panels it was necessary to give the paint a second coat, (this applied to the 80C, and the 48V panels). The paint was allowed to dry completely. The masking tape was removed. A piece of copper tape (5 cm long) was placed on top of the silver conductive paint. The electrical continuity of the board was checked. The resistance should be in the order of 240 ohms for a 240V panel at 40C 12.5 ohms for a 48V panel at 40C 100 ohms for a 240V panel at 80C

Finishing of the board

A second mica sheet was matched to the first mica panel, drilling holes in the panel where the copper tape is located on the conductive paint covered mica sheet. A silicone sealant was applied around the panel where the masking tape had been sited, ensuring a continuity of the silicone sealant

The second mica sheet was placed on top of the conductive paint covered mica sheet, aligning the holes to the copper tape and pressing down firmly on the silicone sealant. Some solder was melted on to the visible copper tape.

Testing of the panel.

A 2-core wire was soldered on to the electrodes of the panel, ensuring continuity through the plug. Resistance should be of the order of the values given above. The necessary voltage was applied across the panel, and the board was tested in 18 places.

The panel heater shown in Figure 1 of the accompanying drawings can be incorporated in a heating system as shown in the system diagram of Figure 2.

As can be seen in Figure 2, a heating system includes a heating panel 20 according to Figure 1, which panel includes an earth layer 22 and a phase layer 24. The control circuitry for the panel 20 comprises a conventional consumer board 26 and a conventional thermostat 28. The consumer board 26 is protected by a residual current device 30 and fuse 32 and is adapted for connection to the mains electricity supply.

The live output from the consumer board 26 is connected via the fuse 32 to the thermostat 28. A thermistor 34 is located in the proximity of the heating panel 20.

In operation, the thermostat 28 is adapted to control the electrical supply to the heating panel 20 in response to temperature dependent signals received from the thermistor 34.

Symbols used in Figure 2 and not defined above are as defined in the following table:

Claims

1. A radiant panel heater for providing radiant heat, which heater comprises a substrate layer, an electrically resistive layer and an electrically insulating layer, characterised in that the heater comprises a pair of electrodes located to pass an electrical current across the electrically resistive layer and means for connecting the electrodes to a source of electrical power, and in that the substrate layer is a layer of mica and in that the electrically resistive layer is a layer of a thermoconductive paint which has been applied to the substrate layer and in that the electrically insulating layer is a layer of mica and is translucent to radiation emitted by the electrically resistive layer when an electrical current is passed between the electrodes.

2. A radiant panel heater according to claim 1 wherein the substrate layer is a layer of mica, which has been impregnated with silicone.

3. A radiant panel heater according claim 1 or claim 2 4 wherein the electrically insulating layer is a layer of mica, which has been impregnated with silicone.

4. A radiant panel heater according to any of claims 1 to 3 which is substantially rectangular in shape and in which the electrodes extend along opposite sides of the substantially rectangular electrically resistive layer.

5. A radiant panel heater according to any of claims 1 to 4 wherein the electrically resistive layer has been applied to the substrate layer in two discrete areas, with an insulating gap arranged therebetween.

6. A radiant panel heater according to any of claims 1 to 5 wherein the electrodes are in the form of a silver paint applied to the substrate.

7. A radiant panel heater according to any of claims 1 to 6 which comprises a second electrically resistive layer applied to the first electrically resistive layer, between the first electrically resistive layer and the electrically insulating layer, which second electrically resistive layer includes means for earthing the heater.

8. A radiant panel heater according to any of claims 1 to 7 which is adapted for mounting on a wall, floor, ceiling or similar surface.

9. A radiant panel heater according to any of claims 1 to 8 which is adapted for mounting within a housing.

10. A radiant panel heater according to any of claims 1 to 9 wherein the substrate layer and/or the electrically insulating layer is approximately 0.3mm in thickness.

11. A radiant panel heater according to any of claims 1 to 10 wherein the electrically resistive layer is approximately 100 micron in thickness.

12. A radiant panel heater substantially as herein described and with reference to the accompanying drawings.

13. A heating system which comprises a radiant panel heater according to any of claims 1 to 14 in combination with a power supply.

14. A heating system according to claim 13 in which the power supply is adapted to supply mains voltage.

15. A heating system according to claim 13 in which the power supply is adapted to supply a voltage of less than 50 volts.

16. A heating system according to any of claims 13 to 15, which further comprises a thermostat for regulating the supply of electricity to the panel heater in response to a measured temperature.

17. A heating system substantially as herein described and with reference to the accompanying drawings.