WO2007039517A1

WO2007039517A1 - Process for applying a heating circuit to a fabric, fabric equipped with heating circuit and heating blanket comprising said fabric

Info

Publication number: WO2007039517A1
Application number: PCT/EP2006/066743
Authority: WO
Inventors: Giacomo Manenti; Davide Manenti
Original assignee: Suntech S.R.L.
Priority date: 2005-09-26
Filing date: 2006-09-26
Publication date: 2007-04-12
Also published as: ITMI20051781A1

Abstract

Process for applying a heating circuit to a fabric comprising: - applying a conductive material to a fabric, producing at least one pair of electrical collectors (1, 1'); - applying a resistive material (2) so as to connect said pair of collectors. Fabric comprising said circuit and heating blanket comprising said fabric.

Description

PROCESS FOR APPLYING A HEATING CIRCUIT TO A FABRIC, FABRIC EQUIPPED WITH HEATING CIRCUIT AND HEATING BLANKET COMPRISING SAID FABRIC

FIELD OF THE INVENTION The present invention relates to a process to produce a heating circuit on a fabric, the fabric provided with said circuit and a heating blanket comprising said fabric. PRIOR ART

Heating blankets supplied with an electrical current, for example to heat the bed during sleep, are present on the market. They are positioned, for example, on top of the mattress and their purpose is to maintain a suitable temperature, of around 30⁰C, during sleep. These blankets generally have two layers of fabric, suitably stitched inside which is a heating element made of copper wire or another material, suitably insulated, provided with adequate flexibility. This heating element is supplied at the normal network voltage (220 or 110 V, according to the country) and a thermostat and an electronic safety system are provided to prevent all risks of fire and electrocution.

The production process of these heating blankets is somewhat costly and automation of operations is somewhat difficult, due to insertion and stitching of the heating element. A further cost is represented by the necessary control system, in view of the voltage applied. Notwithstanding the high level of safety attained by available products, the use of network voltage can also discourage the user from using the product.

Therefore, it would be desirable to produce the fabric equipped with heating circuit with an inexpensive and automated process. Moreover, it would be desirable to be able to produce said circuit so that it can be supplied with a low voltage current (i.e. 12 or 24 V), to offer safe use without requiring complex insulation and safety systems. This would also allow the use, if desired, of direct current, to avoid exposure to alternating electromagnetic fields. Moreover, it would be desirable for the circuit not to have a negative influence on the qualities of flexibility and lightness of the fabric. Finally, it would be desirable to be able to produce a heating circuit with self-regulating properties, to improve the safety also in the presence of a thermostat and to be able to forgo the use of this thermostat, if desired, possibly replacing it with a simple timer. SUMMARY

The aforesaid problems have now been solved according to a first embodiment of the invention, by means of a process for applying a heating circuit to a fabric, comprising:

- applying a conductive material to a fabric, producing at least one pair of electrical collectors;

- applying a resistive material so as to connect said pair of collectors. This resistive material is a conductive material equipped with adequate resistivity to transform electrical energy into heat. According to a preferred embodiment this is ink with PTC (positive temperature coefficient) characteristics, as defined in the patent application WO 03105530, and marketed, for example, by Coates

Electrographics (division of Sun Chemical Inc.) According to a possible embodiment, application of the conductive material requires the application of a suitable adhesive to the fabric, to allow bonding of a sheet of conductive material. The production of collectors implies removal of conductive material according to any known technique for the production of printed circuits. According to another possible embodiment, the resistive material is a PTC ink and is applied directly to the fabric and the conductive material is applied thereon, exploiting the adhesive properties of the ink.

LIST OF FIGURES

The present invention will now be illustrated by the detailed description of preferred, although non exclusive, embodiments, provided purely by way of example, with the aid of the accompanying figures, wherein:

Figure 1 represents the diagram of the collectors produced on a fabric in a process according to the present invention;

Figure 2 represents the diagram of a heating circuit applied to a fabric in a process according to the present invention;

Figure 3 schematically represents a heating blanket according to the present invention;

Figures 4, 5 and 6 represent the diagram of a system for connection of a blanket according to the present invention with an electrical energy source. DETAILED DESCRIPTION OF AN EMBODIMENT The process according to an embodiment of the invention includes applying a layer of suitable adhesive to a fabric (this term also includes woven and non- woven fabrics). The adhesive is of an appropriate type to make the fabric bond to the sheet of conductive material. Said conductive material can be metallic, such as copper or aluminium. A material particularly preferred is aluminium, preferably a sheet of aluminium from 0.5 to 500 μm. Bonding can be hot or cold according to the adhesive used, which can be thermosetting, thermoplastic or the like. The method for deposition of the adhesive, which may be of known type (i.e. spraying, printing or roller spreading) varies according to the type of adhesive used. A sheet of plastic material, which is heated with deposition of the sheet of conductive material, can also be positioned. Some examples of adhesives of various types which can be used are: hot melt film marketed by the company VEGAM code HM- PU-25B (polyurethane film); glue produced by Sun Chemical code REMCO- TOP520013 (two-component); Henkel glue (silicone) code 5145/5145. Deposition can advantageously take place on a continuous fabric. According to a suitable system, a reel is foreseen of fabric to which the circuit is applied. The adhesive, and subsequently the conductive material unwound from a second reel, can be applied to the continuously unwound fabric. Fabric and sheet are pressed together by one or more rollers, heated if required. The fabric can be rewound for further processing, or be subjected to other processing phases immediately after the conductive material has been applied. The adhesive, if in the form of a sheet of plastic material, can also be unwound continuously from a reel. In the subsequent steps the collectors are produced. Protective ink of a suitable type, which can be chosen from various products available for printed circuit technology, is deposited on the portions of sheet of conductive material applied to the fabric which will form the collectors and subsequently chemical etching, for example using solutions of fluoroboric acid, is performed to remove excess material. The fabric used must obviously be resistant to the reagent used. The protective ink is then removed in a suitable way, for example using basic solutions (Solvay soda) or similar compounds. Figure 1 shows the pair of collectors applied to the fabric according to a possible embodiment of the invention. The individual collectors 1 and V are present, provided with respective fingers 3, 3' and ends 6 and 6' for connection to an external power supply. Forming of the collectors is followed by application of the resistive material, in order to connect the collectors suitably. If, as preferred, the resistive material is a conductive ink, in particular with PTC characteristics (such as PTC 100), it can be applied with known techniques, such as relief and intaglio printing, also directly on the rotary production line described above. The resistive material connects the two connectors and forms the element which produces heat if a current runs through it. Figure 2 shows an example of the possible arrangement of the resistive material; a series of traces 2 (in grey) are shown deposited on the fingers of the collectors. It is clear that each portion of this trace which connects the finger of one collector with the finger of an opposed connector will form a heating resistor. The diagram of the figures can be varied, both as regards the geometry of the collectors and as regards the arrangement of the resistive material which, for example, instead of being arranged in traces can involve the entire surface of the circuit. The PTC ink imparts self-regulating properties of the temperature.

Application of the resistive material can be followed by application, for example by hot rolling, of an insulating film.

If desired, an operation can also be performed to perforate the layer of adhesive in the areas not involved by the other conductive and resistive materials, to offer the fabric qualities of breathability.

The diagram in Figure 2 represents a complete circuit, which as mentioned, can be produced with an automated process starting from a reel of fabric, which is cut into a plurality of portions each containing a complete circuit (or several circuits if desired). Alternatively, the conductive material can be applied to the fabric in a different way, such as by sputtering or in the form of conductive ink, by means of screen printing deposition, directly on the fabric or subsequent to application of an adhesive or primer. In this case, the collectors can be formed with the deposition process of the conductive material, without the need for subsequent chemical etching, which can be an advantage if specific fabrics are use. According to a possible alternative, the resistive material, in the form of an ink, preferably with PTC characteristics, can be applied to the fabric before the conductive material. In this case, the resistive material can also act as adhesive, and must be applied to the entire surface involved by the circuit, or at least to the surface involved by the collectors and the connection surface between the collectors able to form the heating resistors.

In the event that adhesive is applied, if using an application technique such as a printing technique, which allows this, it is possible for it to be applied only to those parts of the fabric which are to be covered by the collectors, and not to the parts where the conductive material is to be removed. In this way maximum breathability and lightness is imparted to the product.

To produce a heating blanket, which forms another embodiment of the invention, a portion of fabric to which a circuit as described above has been applied can be stitched to a similar portion not bearing a circuit, so that the circuit remains inside. With the method illustrated above, it is possible to obtain light heating blankets, which can be used without problems of resistance of the circuit, and can even be washed, at least at low temperatures, if the materials are chosen appropriately. Moreover, the use of PTC inks as resistive material imparts qualities of self- regulation, for example, to temperatures of around 30⁰C, so that the thermostat can be eliminated and replaced with a simple timer. Moreover, the structures of the circuit which can be obtained according to the present invention, like the one in Figure 2, allow the use of a low voltage current, preferably from 2.4 to 50 V, for example from 12 to 50 V, also direct if desired, unlike prior art structures in which a single wire acts as heating element. Devices for connection to power supply systems will be suitably provided. As can be seen in Figure 2, the collectors have ends 6, 6' to which devices are connected for the connection to electrical supply systems of the circuit. In the case of a heating blanket, such as the one shown in Figure 3, connection devices (with a transformer or with batteries) can be provided which include a female connector with pins connected to said ends 6 and 6' of the circuit and included in a specific structure 8 which is integral with the blanket 7, accessible from the outside of the blanket, destined to house a male connector, connected to the electric power source 10.

Automatic button systems can also be provided. Soft rubber elements 11 allow the connection device to be connected to the rest of the cover. Figures 4 and 5 show side views of a pin device as described above, with the structure. Figure 6 schematically shows an automatic button 14 connection device, with connection elements 12 and 13 connected respectively to a collector of the heating circuit and to a power cable 15 (only one of the two pairs of connection elements is shown). Other devices can easily be devised by those skilled in the art, also in consideration of the voltage used (the system in Figure 3 is suitable in the case of safe voltage (i.e. 12 or 24 V, so that contact with the pins of the male connector does not create dangers of any kind). A connection device that allows disconnection of the heating blanket from the cables coming from the electrical power supply is preferred to allow the heating blanket to be washed or put away separately.

Claims

1. Process for applying a heating circuit to a fabric comprising:

- applying a conductive material to a fabric, producing at least one pair of electrical collectors (1 , 1 '); - applying a resistive material (2) so as to connect said pair of collectors.

2. Process as claimed in claim 1 , wherein said resistive material is a PTC ink.

3. Process as claimed in claim 1 or 2, comprising applying an adhesive to said fabric and subsequently applying said conductive material in the form of a sheet.

4. Process as claimed in claim 3, comprising applying a protective ink to the part of said sheet corresponding to said collectors, and removing the remaining part by chemical etching.

5. Process as claimed in claim 3 or 4, wherein said adhesive is applied to the fabric only in the areas corresponding to said collectors.

6. Process as claimed in claim 3 or 4, wherein said adhesive is applied to the fabric in the entire area involved by the circuit and is subjected to perforation in the area not involved by said collectors.

7. Process as claimed in any one of the previous claims, wherein said conductive material is in the form of a sheet of aluminium of a thickness ranging from 0.5 to 500 μm.

8. Process as claimed in claim 2, wherein said PTC ink is applied after said collectors have been formed.

9. Process as claimed in claim 2, wherein said PTC ink is applied directly to the fabric and said conductive material is bound by means of said PTC ink.

10. Process as claimed in claim 1 or 2, wherein said conductive material is in the form of a conductive ink, applied directly to the fabric.

11. Process as claimed in any one of the previous claims, wherein said fabric is unwound from a reel, subjected to continuous application of heating circuits, and cut into portions comprising one or more circuits.

12. Process as claimed in any one of the previous claims, wherein said collectors comprise ends (6, 6') for connection to an electrical power source.

13. Fabric provided with heating circuit obtainable by means of a process as claimed in any one of the previous claims.

14. Fabric as claimed in claim 13, wherein said circuit is suitable to be supplied with a voltage from 2.4 to 50V.

15. Heating blanket comprising a fabric as claimed in claim 13 or 14.

16. Heating blanket as claimed in claim 15, comprising two portions of fabric, one of which comprises a heating circuit, stitched together so that said circuit is on the inside.

17. Heating blanket as claimed in claim 15 or 16, comprising a connection device accessible from the outside, with an electrical power source.

18. Heating blanket as claimed in claim 16, wherein the connection is removable.