SK153899A3 - Electrical heating cable and method for producing thereof - Google Patents

Abstract

An electric heating cable comprises a core with a heating conductor wound on it, and additional high conductivity conductors which reduce the resistance over defined areas. An electric heating cable with sections of varying resistance, comprises a heating conductor wound on a core, with a resistance which is reduced over defined areas by additional high conductivity conductors. The heating areas are formed between the conductors. The additional conductors (3) extend along the core and are pressed against it. The core and the additional conductors form a self supporting unit.

Description

Electric heating cable, method of its manufacture and use for the production of heating mats

Technical field

The present invention relates to an electric heating cable with just alternating sections extending along the cable and having different resistance characteristics, in which a heating conductor is wound on the central cord of the core, the resistance of which is reduced in defined sections by additional conductors with higher electrical conductivity. of which just two wires of defined length consecutively in the cable form a supply or cold conductor of a heating element lying therebetween, and these cable heating elements can be cut to length in the area of the auxiliary conductors.

BACKGROUND OF THE INVENTION

An electrical cable of the kind mentioned is known from Japanese publication JP 09 260 040 A (Patent Abstracts of Japan). A large number of thin copper wires are applied to the wound heating conductor at defined intervals as a supply conductor, these wires being held on the heating conductor spiral by means of an additional polyester fiber measure. Notwithstanding this additional manufacturing complexity, there is a risk that in the manufacture of the heating cable, but also in the installation of each length-cut heating element, low bending angles by cracking the polyester fiber or at least releasing it, for example during the length cutting process the connection conductor - heater - the cord of the core and the prescribed pressure on the contact between the heating element and the supply conductor are in question.

Also known is an electric resistance heating cable (US-PS 3,646,322 / DE-OS 21 05 572), the heating wire of which is provided in sections with a metal sheath having a relatively low resistance per unit length. In this way, areas of different operating temperatures can be produced in the cable, which is obviously useful when such cables are used in coiled heating locations, in refrigerator defrosters, in coffee machines, and the like. In any case, cutting to the length of the individual heating elements from the core strand is not carried out.

Starting from this prior art, the invention aims to provide a simple, cost-effective solution for the production of resistive heating elements which can be further processed without difficulty as flexible elements, i.e., in particular, they can be mounted. In particular, the connecting sleeves applied between the heating conductor and the cold conductor can be avoided, especially in the case of high bending stress, the prescribed contact pressure between the heating conductor and the cold conductor can be guaranteed.

SUMMARY OF THE INVENTION

This object is achieved according to the invention by an electric heating cable with alternating sections extending along the cable and having different resistance characteristics, in which a heating conductor is wound on the central cord of the core, whose resistance value is reduced in defined sections by additional conductors with higher electrical conductivity. conductors, of which just two wires of defined length, consecutively in the cable, form the supply or cold conductor of the heating element lying between them, and that these heating elements of the cable can be cut to length in the auxiliary conductor section. The wires extend along the cord of the core and are pushed against the cord of the core by the heating conductor which is in contact with and pressurized against it, the cord of the core, the auxiliary conductors and the wound heating conductor forming a separate unit.

As a result, any kind of connecting sleeve between the heating and cold or supply conductors is eliminated as application parts, which are the cause of the mechanical forces and thus often cause damage to the sleeve and / or the cable itself.

The measures proposed by the invention provide the required contact pressure between the heating conductors and the auxiliary conductors when cutting to length and even under increased bending stresses during assembly. This contributes substantially to increasing the operational reliability of the cable of the type mentioned.

By dropping the sleeves, the corresponding fasteners, which lead to increased transient resistance and, in the case of incorrect assembly, even overheating and burning of the line, are also omitted. However, it is also possible to take into account various materials, copper-nickel or chromium-nickel alloys on the one hand, and also copper on the other hand, in the technique of connecting heating and cold or lead wires. The special care required for the assembly and the assembly of the connection itself are no longer required.

Particular advantages arise in a further embodiment of the invention that the additional conductor is a longitudinally extending copper or aluminum conductor. This wire, which is integrated into the cable and which is in contact with the continuous heating cable over its total length, is not applied outwards, so the overall cable diameter can be kept small, thus contributing to further increase the flexibility. The heating conductor and the cold conductor pass practically without the seam connection sleeve to one another. The auxiliary conductor (cold conductor) according to the invention, guided under the heating conductor spiral, as well as the heating conductor, is preferably closed by a high-temperature, thermoplastic-resistant, thermoplastic sheath which both share, leads to further compactness in the cable construction.

The core core itself consists of a high temperature resistant material, for example, the heating conductor may be wound on an approximately 1 - 1.5 mm thick glass silk core. Here, it is advantageous that the core is compressible, the additional conductors can also be compressed, which leads to a reduction in the outer diameter in this feed region.

If, as is often required, the heating cable has to be provided with a protective conductor, it is applied in the form of a wire strand, wire netting or the corresponding tape to the packaging common to the heating and cold conductors. This protective conductor also serves to shield the electromagnetic radiation. With or without a protective conductor, the core of the cable is closed with an outer sheath, which is marked at the points where the individual heating elements are to be cut to length. Since the length of the additional conductor according to the invention integrated into the cable is e.g. 7 to 21 m, depending on the length of the cold wire required, it is expedient to modify the marking at the beginning and end of the additional conductor. The marking can be of any kind, can be visibly applied to the surface of the conductor, but can be integrated into the protective sheath, for example by means of additional materials which can be detected, as the cable passes through the sensor device and is signaled to cut off the cable end to a length that corresponds to the heating element.

It is not important in the invention that contacting the lateral cold conductor can be made at the ends of the heating element, which arise by cutting to length from the heating cable. It is much more important for the invention to have a cold conductor and a heating conductor already integrated in the heating cable, so that, after cutting to length, only the free ends of the cold conductors need to be connected appropriately to a suitable current / voltage source.

The present invention also allows the respective length of the heating elements integrated in the heating cable to be chosen differently, i.e. according to the desired heating output. Thus, the length of the heating zones determined by the effect of the heating elements can be, for example, 6, 10 or 18 m, and the length of the corresponding cold conductors already integrated in the heating cable can be 0.5 to 30 m, depending on the connection possibilities.

The method for producing a heating cable according to the invention with integrated heating elements of any length, which can be cut to length, can be carried out continuously. Thus, when wrapping a thin insulating heating sheath, the twine of the core, e.g. on the basis of glass silk, a heating conductor (with one or more wires), for example based on chromium-nickel, conducts an additional conductor (cold conductor) of the same predetermined length at predetermined locations along the core strand. The core cord, the heating conductor and the cold conductor form the core after the wrapping. the core cord and the auxiliary conductors guided therewith, the unit, the threads of the heating conductor are practically short-circuited by the supply conductor. This unit, in which the contact pressure between the heating conductor and the auxiliary conductors is carried out by a self-wound heating conductor, is an independent functional system. This also means that the unit can first be rolled up to the sheathing device for the manufacturing process, and can then be unfolded again so as to avoid contact problems between the conductor and the additional conductors. Following e.g. of a fluoropolymer, e.g. in extruded form when processed from the melt, or e.g. in the form of a strip, when it is, as in the case of polytetraflorethylene, a polymer that cannot be processed from the melt, fixes the heating conductor and the cold conductor along the predetermined section.

It is particularly advantageous to use heating elements cut to length from the heating cable according to the invention for the production of heating mats. Due to their high flexibility, their co-guided cold conductor and the safe contact between the heating and cold conductors, these heaters are particularly well suited for automatic processing in the manufacture of so-called thin-bed heating mats with a maximum thickness of approximately 5 mm.

Heating elements cut to length from the electric heating cable, self-supporting support mats, e.g. If such a carrier mat consists of ropes impregnated with artificial means, only stabilizing a predetermined shape of the heating conductor, approximately as a meander, but also, for example, of a mortar bed, when the heating mat is stored there, e.g. for floor or wall heating of living rooms.

In the meander course of the heating element on the support mat, it is particularly advantageous if only a rectilinear portion of the heating element is fixed to the support mat by sewing or similar measures. By distributing the support mat and guiding the fastened parts of the heating element around the non-fastened parts, any shaped surfaces can be lined with the heating mat.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail with reference to Figures 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

For the central cord 1 of the heating cable core, as shown in FIG. 1, winds a heating conductor / heating wire 2 which is of one or more wires. Core 1, e.g. With small dimensions of 1 - 1.5 mm, it can be made of glass silk to guarantee high flexibility in the unimpregnated state. As a rule, the heating conductor 2 will be a resistance wire of copper, a nickel-nickel alloy or a chrome-nickel alloy. An additional conductor 3, here a copper wire with a cross-section of 1 mm ² and a defined length, also tin-plated or nickel-plated, is placed in the heating cable, which is practically manufactured as an endless wire, located below the heating conductor 2 and the threads therein. contact, practically shortened along its length. The conductor 3, which is located in such a now low-ohmic part of the heating cable, is to be used immediately as a supply or cold conductor after cutting to the length of the individual elements from the cable. For example, it may be up to 25 m in length, the respective length being determined by the later use of the length-cut heating element as well as the position of the voltage source in the respective object.

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The external dimensions of the heating and cold lines are almost the same, thus eliminating the sleeve-like reinforcement in the supply area. Furthermore, the unrestricted flexibility of the heating elements according to the invention cut lengthwise from the heating cable is advantageous.

The heating cable 2 and the conductor 3 are fixed with a cover 4, e.g. of a fluoropolymer. Above it is a protective conductor 5, which at the same time shows the shielding of the cable, e.g. in the way of braiding. The protective conductor 5 is covered by an outer sheath 6. For special applications, the protective conductor 5 can also be omitted. The outer sheath 6 has a marking 1 at the positions of the additional conductor 3, which guarantees a targeted distribution of the heating cable for the purpose of cutting to the length of the individual heating elements. The length of these heating elements is correspondingly predetermined by the selected marking distance 11 on the heating cable.

The heating elements cut to length with an integrated supply conductor 3 can be further processed according to a predetermined length. An advantageous possibility is that such heating elements can be mounted in the meander shape on the support and such heating mats can be used for surface heating. If, as a support, e.g. This mat also serves as a stabilizing pad of a heating element which is highly flexible according to the invention and at the same time serves as protection during transport, storage and processing.

Such a heating mat is shown in FIG. 3. On a carrier mat 8 made of plastic-impregnated glass silk rope 9, the heating element 10 is cut to length from the heating cable according to the invention, fixed by sewing with a fastening thread 11, for example of glass silk, polyamide or the like. The meander-like heating element 10 is expediently secured exclusively in the directly extending sections of the meander, while the connecting tubes 12 are not attached to the support mat.

If the support mat 8 is now divided by a cut along the dotted line 13, as shown in FIG. 3, the upper part of the support mat 8 can be folded down, including the heating element 10 disposed thereon. In this way, any shaped surfaces, e.g. in a residential building, completely lined with heating mats according to the invention. It is thus possible to heat all surfaces.

Claims (15)

PATENT CLAIMS An electric heating cable with alternating sections extending along the cable and having different resistance characteristics, in which a heating conductor is wound on the central core of the core, the resistance of which is reduced in defined sections by means of auxiliary conductors of higher electrical conductivity. just two wires of defined length consecutively in the cable form the supply or cold conductor of the heating element lying between them, and that the heating elements of the cable can be cut to length in the section of the auxiliary conductors, characterized in that the auxiliary conductors (3) extend along the cord (1) of the core and are printed by means of a heating conductor (2) which is in contact with and loaded by pressure against the cord (1) of the core, the cord (1) of the core, additional conductors (3) and wound the heating conductor (2) forms a self-supporting unit. Heating cable according to claim 1, characterized in that the additional conductors (3) are longitudinally extending copper or aluminum conductors, also in tinned or nickel-plated form. Heating cable according to one of Claims 1 or 2, characterized in that the central cord (1) of the core consists of a material resistant to high temperatures. Heating cable according to one of Claims 1 to 3, characterized in that the heating conductor (2) and the auxiliary conductors (3) are surrounded by a heat-resistant, high-temperature-resistant floroplastic sheath (4). Heating cable according to claim 4, characterized in that the sheath (4) consists of an extruded floroplast. The heating cable according to claim 4, characterized in that the envelope (4) consists of a fluoroplastic strip produced by extrusion of the paste and subsequent rolling, wound and finally sintered. Heating cable according to claim 4, characterized in that the common sheath (4) is surrounded by a protective conductor (shielding) (5). Heating cable according to claim 7, characterized in that the protective conductor (5) is surrounded by an outer sheath (6) which has a marking (7) at designated points cut to length of the individual heating elements (10). Heating cable according to one of Claims 1 to 8, characterized in that the respective length of the auxiliary conductors (3) is 0.5 to 30 m in the longitudinal direction of the cable. Heating cable according to one of Claims 1 to 9, characterized in that the respective length of the heating elements (10) in the cable varies according to the required heating output. Method for producing a heating cable according to claim 1, characterized in that additional conductors (3) are placed at the predetermined locations of the central core strand (1) and, when wrapping the core strand (1) with the heating conductor (2), Wrap that the heating conductor (2) and the auxiliary conductors (3) are wrapped together as a unit with insulating material (4) and after applying the protective conductor / shield (5) to the common packaging (4) the outer sheath (6) and the additional section The conductors (3) located inside the cable are marked (7). Use of the heating elements (10) cut to length from the heating cable according to one of claims 1 to 11, for the manufacture of heating mats, in particular for the production of maximum 5 mm thick thin-layer heating mats without sleeve. A heating mat according to claim 12, characterized in that the heating elements (10) cut to length from the electric heating cable are sewn onto a self-supporting support mat (8). The heating mat according to claim 13, characterized in that the support mat (8) is a glass silk mat with individual ropes (9) impregnated with plastic. A heating mat according to claim 13 or 14, with a meandering course of the heating element on the support mat, characterized in that only a rectilinear portion of the heating element (10) is fixed to the heating mat (8) by sewing.