FR2736500A1 - Electric heating element in thermoplastic support - has conductive mesh set in thermoplastic matrix that supports and provides insulation - Google Patents

Abstract

The heater has conductors in the form of a mesh. The conductors are embedded in a thermoplastic matrix. The thermoplastic may be sufficient to provide all necessary electrical insulation, or an electrical insulating material may be used to enclose the plastic. The materials chosen allow operation at temperatures between 280 and 550 [deg] C, depending on the materials and the pressures used during manufacture. The thermoplastic matrix can provide an attachment surface to allow the heater to be fixed to another surface.

Description

Thermoplic matrix heating element
The present invention relates to a heating element, consisting of a conductive element O, associated with a thermoplastic matrix 0, with electrical insulation @.

O + O can be shaped and heat worked to obtain various heating objects or parts. The way can include O, or O can be added after these operations.

Such heating elements comprise, a conductive element O type nonwoven, nonwoven or fiber veil (see appendix A); reinforced with a thermoplastic resin (see appendix B) acting as a matrix, mechanically and heat resistant, giving it cohesion and the possibility of bonding to other parts; insulated by an electrically insulating material (see appendix C), put in from the start or added later.

In some cases, the thermoplastic resin E> can also have the electric insulating function, and eliminate the need for a third product.
These elements can be worked and assembled in different ways, in particular: - By stamping, after softening of the thermoplastic resin O, in the manner of working sheet metals, By molding in a press, in an open or closed mold, with the action of the heat, By vacuum molding, with the action of heat, By molding in an autoclave e By lamination, using a calendering machine or other means e By any other means aimed at softening the thermoplastic resin 9
A suitable cut can then be made.

Different types of heating elements have been proposed, or are currently manufactured and sold.

A first technique consists in using a heating resistance. This technique has various drawbacks:
- The heat diffusion is not always homogeneous.

- The means of mechanical assemblies are often expensive.

- The volume used is important
A second technique consists of producing heat using the induction created by the current.This technique has various drawbacks:
- The heat diffusion is not always homogeneous.

- Means of mechanical assembly can be expensive
- The volume used by the system is important.

- The yield is not optimum.

The third technique consists in obtaining a heating resistor from a plate of a conductive metal.

This plate, often very thin, is placed on a support. The assembly is then cut according to the methods of chemical attack, commonly used for the production of printed circuits. Here, the support ensures the cohesion of the plate once cut.

This technique has the following drawbacks:
- The cost of the assembly (complexing of the conductive metal on its support) can be high and the development of that technically difficult to achieve in large quantities and for high temperature applications.

- The good cohesion of the conductive metal plate on its support is sometimes difficult to obtain.

This poses implementation problems during chemical attack. There is a risk of peeling the conductive metal.

- The chemical etching process requires a quality flatness of the conductive metal / support complex. However, this is difficult to obtain.

The fourth technique consists in obtaining a heating resistance by stamping, or mechanical cutting of a conductive metal plate. This technique has various drawbacks:
- Raised cost of cutting tools, wear of thoseì
- Difficulties in handling the cut elements with the possibility of significant deformation, affecting the homogeneity of the system
The present invention relates to: = The production of a heating element exhibiting a homogeneous heat diffusion and a very good thermal efficiency.

The fibers, nonwoven or nonwoven veil constituting the conductive element can be distributed very homogeneously over a surface.

e The realization of a heating element occupying a very small volume.

, The realization of a heating element, easy to manufacture and easily industrializable, whatever the shapes or elements to be made, and quantities to be produced.

The thermoplastic resin works easily and quickly. Manufacturing cycles can be very short.

e The realization of a heating element, able to work, according to the products used and the desired performances, at high temperatures continuously.

Certain elements mentioned in appendix k, B. and C. have very good temperature characteristics.

e The realization of a heating element without limit or almost on the intensities and tensions necessary for its supply, according to the nature and the thickness of the products used.

The present invention particularly relates to the production of heating devices, with assembly temperatures of the elements between 280 and 5500C depending on the materials and pressures used.

According to the present invention, the heating element comprises at least 3 functions:
- conductive element, heat generator
- Thermoplastic binder and possibly bonding support for the conductive element
- Electrical insulation of the element
According to the present invention, the heating element comprises, * at least 2 products ", more generally" at least 3 products ":
- Non-woven, non-woven or fiber veil, these elements being conductive
- A thermoplastic matrix
- An electrical insulating material
In the case of “at least 2 products”, the thermoplastic resin used combines the functions of thermoplastic matrix and of electrical insulator.

We consider as two distinct products, the conductive element and the thermoplastic matrix, even if these two elements are mixed within the same product. For example, a nonwoven, a nonwoven veil, or a fiber combining a conductive material with a material acting as a thermoplastic matrix.

Appendices k As a fiber, from nonwoven to nonwoven veil, constituting the conductive element O and which can be used according to the invention, mention may be made, by way of examples, of articles made from the following materials (alloys and derivatives included):
- Copper - Carbon - Boron - Tungsten
- Aluminum - Constantan - Nickel
- Silver - Steel - Silicon carbide
The conductive materials may be associated in the fiber, the nonwoven or the nonwoven veil, with other non-conductive materials which will serve as examples of reinforcement, metallization support, support, envelope. , ..

B. As thermoplastic resins constituting the matrix O and which can be used according to the invention, there may be mentioned, by way of examples, the following materials:
- Polyetherimides (abbreviated PEI)
- Polyether-etherketones (abbreviated PEEK)
- Liquid crystal polymers (abbreviated LCP)
- Polyphenylene sulfides (abbreviated PPS)
- Polyethersulfides (abbreviated PES)
- Polyimide (abbreviated PI)
These materials are generally in the form of films.

They are also found in the form of nonwovens, nonwoven webs, fabrics, or other pasty, liquid forms, ..

C. As electrical insulating materials, constituting the electrical insulator O and which can be used according to
The invention may be mentioned, by way of examples, the following materials:
- Polyirnid
-Teflon
- Perfluoro Alkosy (abbreviated PFA)
- Polyvinylidene Fluoride (abbreviated PUDF) - -Fluoruated Echylene Propylene (abbreviated FEP)
These materials are generally in the form of films.

They are also found in the form of woven fabrics, non-woven veils, fabrics, or other pasty, liquid forms, etc.

Examples
For all the examples cited below, the elements will be assembled according to the techniques mentioned on the first page (stamping, press molding, vacuum molding, autoclave molding, lamination or calendering).

Here is a first example, of an element in accordance with the invention, composed of:
O A non-woven veil composed of nickel and carbon
O A thermoplastic PEEK resin, in the form of a film, a nonwoven or the like, which serves as a bonding agent.

O A Kapton film (polyimide) on both sides of O + O, glued by O
Here is a second example, of an element according to the invention, composed of:
O A non-woven veil composed of nickel and carbon
e A thermoplastic polyimide resin, in the form of a film, which serves as a matrix i 0.

A Kapton film (polyimide) on both sides of O +, glued by O
Here is a third example, of an element according to the invention, composed of:
O A non-woven veil composed of nickel and carbon
e A polyimide film on both sides of O, the thermoplastic side on the O side.

e will be in the form of a layer or tri-layer film, with a thermoplastic side (for the bi
layer) or two sides (for sorting <ouche) and a conventional polyimide on the other side (for bi
layer) or in the middle (for the tri-layer).

Here are the parts that can be made according to the previous examples:
- Domestic appliances, heating appliances (iron soles, ovens, hotplates, etc.)
- Wall radiators (extra-flat panels favoring homogeneous heat distribution,
floors, ceilings, walls, ...)
- Tools, heating equipment for transport (plane, train, automobile, boat ...)
Complementary example
The preceding examples showed the production of heating elements according to the invention.

The following example includes peripheral items. The orientations given in this example, or certain elements mentioned, could serve as a working basis in the production of heating devices such as iron soles, for example. Refer to the attached drawing for a better understanding.

This element in accordance with the invention is composed of the following stack: 1 An aluminum plate, or steel, or other metals, alloys and derivatives Q A film of PEEK thermoplastic resin, used as O's glue on 3 Q A polyimide film , uses as electrical insulation 4 A film of thermoplastic resin PEEK, used as glue of (a) on 5 and matrix of O5 5 A non-woven web composed of nickel and carbon 4 A film of thermoplastic resin PEEK, used as glue of 3 out of 5 and matrix of 5
In certain cases, this element (i) will be optional. This is on the assumption that the first film (3 mentioned above has sufficiently "wet (fi) in order to achieve uniform bonding and to fully fulfill the matrix function.

A polyimide film, used as an electrical insulator Q A PEEK thermoplastic resin film, used as a glue of Ol on 6 Q An aluminum plate, or steel, or other metals, alloys and derivatives
Thermocouples can be incorporated between the elements Q, which sandwich elements 4 and in or on 4 and tlD. These thermocouples will allow the transmission of the information necessary for the thermal regulation of the heating element.

5 will be connected to a power supply which can be adjusted.

The assembly will be done by means of the techniques mentioned above with assembly temperatures of the elements between 280 and 5500C depending on the materials and pressures used.

Press assembly is very suitable.

This example proposes a solution, without however covering all the solutions which the invention allows.

PEEK films could, for example, be replaced by other films or other forms of thermoplastic matrices, just as bi- or tri-folded insulating films could simultaneously provide the thermoplastic matrix and electrical insulation functions. We could also use a fiber, a nonwoven or nonwoven veil, combining a conductive material and a thermoplastic material, to simplify stacking.

Claims (4)

Claims 1) Device for making heating elements, characterized in that it comprises a conductive element O type nonwoven, nonwoven or fiber veil, a thermoplastic matrix and an electrical insulator O. 2) Device for making heating elements, comprising a conductive element O type fleece of nonwoven, nonwoven or fiber, a thermoplastic matrix O and an electrical insulator O characterized in that the invention can be used for the production of devices heating, with element assembly temperatures between 280 and 5500C depending on the materials and pressures used. 3) Device according to claims 1) or 2), characterized in that the thermoplastic matrix O set matrix 0 and can seMr bonding support 8 0. 4) Device according to claims 1) or 2) where the thermoplastic matrix O can, in certain cases, provide the insulation function and thus replace O.