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(11) | EP 0 858 244 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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| (54) |
Field free electrical floor heating cable Feldfreies elektrisches Kabel zur Bodenheizung Câble electrique chauffant les sols et dépourvu de champ magnétique |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention relates to electrical floor heating cables and in particular to cables generating acceptably small electromagnetic fields. In general the magnetic field is best reduced/eliminated by a concentric shield, as in coaxial cables, but this is not a practical solution with heating cables. The field generation problem can also be somewhat reduced by using two-conductor cables instead of single-conductor cables because the fields generated from the two conductors tend to eliminate each other. The fields from two-conductor cables having a resistance conductor and a return conductor should - however - be further reduced.
[0002] The object of the present invention is to reduce the field generating properties of electrical floor heating cable having a first, near end and a second, far end and comprising within an outer protective sheath a cable core consisting of
- a central resistance conductor,
- a first concentrical sheath of insulation material surrounding the resistance conductor, - as well as
- return conductor means arranged to be interconnected with the resistance conductor in the far end of the cable.
[0003] The main features of the invention appears from the accompanying claims. The problem of eliminating or greatly reducing generation of electromagnetic fields which could be harmful to human beings occupying rooms heated with electrical floor heating cables has been solved by letting the return conductor means consist of at least two separate conductors which are distributed in the cable core. The electromagnetic field is reduced to about 1% of the field experienced from single conductor heating cables, and to some 10% of the fields from normal two conductor cables.
[0004] The prior art document WO 92 08036 A discloses an electrical heating cable comprising within an outer protective sheath a cable core consisting of: a central resitance conductor, a concentrical sheath of insulation material return conductor means arranged to be interconnected with the resistance conductor in a far end of the cable and consisting of at least two separate conductors.
[0005] The present invention is characterised in that the return conductors are embedded in a second insulation sheath arranged over said first sheath.
[0006] Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in conjunction with the drawings, where
Figures 1-4 show four embodiments of the invention.
[0007] In Figure 1 to 4 a resistance conductor 1 is provided with a first concentrial sheath 2 of insulation material such as crosslinked polyethylene. All embodiments have an outer protective sheath 4 of PVC or other suitable material and an earth screen 7 in contact with earth means 6 or 20. The earth screen could be a conventional Al/PE tape in contact with Cu wires 6 or 20. In the near end of the cable the resistance conductor can be substituted with a cold end copper conductor. Return conductors 5;10,11;15,16,17 are embedded in a second common insulation sheath 3 arranged over the resistance conductor sheath 2. The sheath 3 could be a PVC sheath.
[0008] In Figure 1 the return conductor means is divided into three separate conductors 5a, 5b and 5c which are distributed in the cable core. In Figure 2 the return conductors means is constituted by two conductors 10 and 11 arranged 180° apart whereas in Figure 3 there are three conductors 15, 16 and 17 arranged 120° apart. In Figure 4 the return conductors 5 are arranged 90° apart.
1. Electrical floor heating cable having a first, near end and a second, far end and
comprising within an outer protective sheath (4) a cable core consisting of
characterized in that the return conductors are embedded in a second common insulation sheath (3) arranged over the said first sheath (2).
- a central resistance conductor (1),
- a first concentrical sheath of insulation material (2) surrounding the resistance conductor, as well as
- return conductor means (5) arranged to be interconnected with the resistance conductor in the far end of the cable,
the return conductor means consisting of at least two separate conductors which are distributed in the cable core,characterized in that the return conductors are embedded in a second common insulation sheath (3) arranged over the said first sheath (2).
2. Cable according to claim 1, characterized in that the return conductors are arranged in contact with the said first sheath (2).
3. Cable according to claim 1 or 2, characterized in that the return conductors are evently distributed around the said first sheath, such
as two conductors 180° apart or three conductors 120° apart or four conductors 90°
apart.
4. Cable according to claim 1 or 2, characterized in that the return conductors include three conductors arranged 90° apart from each other
and from an earth wire (6).
5. Cable according to claim 1, characterized in that the said second common insulation sheath (3) is provided with a slot (8) for receiving
an earth wire (6) which is in contact with an earth screen (7).
6. Cable according to claim 1, characterized in that it includes a number of earth wires (20) arranged around the said second common insulation
sheath (3) in contact with an earth screen (7).
7. Cable according to claim 6, characterized in that the earth wires (20) are arranged as a group around the said second sheath (3) covering
10 to 25% of the sheath surface.
8. Cable according to claim 1, characterized in that all the elements of the cable are arranged in parallel with the cable axis.
9. Cable according to claim 1, characterized in that in the near end of the cable the resistance conductor is substituted with a cold
end copper conductor.
1. Elektrisches Bodenheizungskabel mit einem ersten nahen Ende und einem zweiten fernen
Ende, das innerhalb eines äußeren Schutzmantels (4) einen Kabelkern einschließt, der
besteht aus
dadurch gekennzeichnet, dass die Rückleiter in einem zweitem gemeinsamen Isoliermantel (3), der über dem ersten Mantel (2) angeordnet ist, eingebettet sind.
- einem zentralen Widerstandsleiter (1),
- einem ersten konzentrischen Mantel aus Isoliermaterial (2), der den Wiederstandsleiter umgibt, sowie
- Rückleitermitteln (5), die so angeordnet sind, dass sie mit dem Widerstandsleiter im fernen Ende des Kabels verbunden sind;
wobei die Rückleitermittel aus mindestens zwei getrennten Leitern, die in dem Kabelkern verteilt sind, bestehen,dadurch gekennzeichnet, dass die Rückleiter in einem zweitem gemeinsamen Isoliermantel (3), der über dem ersten Mantel (2) angeordnet ist, eingebettet sind.
2. Kabel nach Anspruch 1, dadurch gekennzeichnet, dass die Rückleiter in Kontakt mit dem ersten Mantel (2) angeordnet sind.
3. Kabel nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Rückleiter gleichmäßig um den ersten Mantel so verteilt sind, dass zwei Leiter
um 180 ° beabstandet oder drei Leiter um 120 ° beabstandet oder vier Leiter um 90
° beabstandet sind.
4. Kabel nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Rückleiter drei voneinander um 90 ° und von einem Erdleiter (6) beabstandet angeordnete
Leiter aufweisen.
5. Kabel nach Anspruch 1, dadurch gekennzeichnet, dass der zweite gemeinsame Isoliermantel (3) mit einem Schlitz (8) zur Aufnahme eines
Erdleiters (6), der mit einer Erdabschirmung (7) in Kontakt ist, ausgestattet ist.
6. Kabel nach Anspruch 1, dadurch gekennzeichnet, dass es eine Anzahl von um den zweiten gemeinsamen Isoliermantel (3) in Kontakt mit einer
Erdabschirmung (7) angeordnete Erdleiter (20) aufweist.
7. Kabel nach Anspruch 6, dadurch gekennzeichnet, dass die Erdleiter (20) als Gruppe um den zweiten Mantel (3), der 10 bis 25 % der Manteloberfläche
bedeckt, angeordnet sind.
8. Kabel nach Anspruch 1, dadurch gekennzeichnet, dass sämtliche Elemente des Kabels parallel zur Kabelachse angeordnet sind.
9. Kabel nach Anspruch 1, dadurch gekennzeichnet, dass der Widerstandsleiter in dem nahen Ende des Kabels durch einen Kaltend-Kupferleiter
ersetzt ist.
1. Câble de chauffage électrique par le sol doté d'une première extrémité proche et d'une
deuxième extrémité lointaine et comprenant, à l'intérieur d'une gaine protectrice
extérieure (4), une âme de câble constituée :
caractérisé en ce que les conducteurs de retour sont noyés dans une deuxième gaine isolante commune (3) disposée par-dessus ladite première gaine (2).
- d'un conducteur résistant central (1),
- d'une première gaine concentrique de matériau isolant (2) entourant le conducteur résistant, ainsi que
- de moyens formant conducteurs de retour (5) disposés de façon à être interconnectés avec le conducteur résistant au niveau de l'extrémité lointaine du câble,
les moyens formant conducteurs de retour étant constitués d'au moins deux conducteurs distincts répartis dans l'âme de câble,caractérisé en ce que les conducteurs de retour sont noyés dans une deuxième gaine isolante commune (3) disposée par-dessus ladite première gaine (2).
2. Câble selon la revendication 1, caractérisé en ce que les conducteurs de retour sont disposés au contact de ladite première gaine (2).
3. Câble selon la revendication 1 ou 2, caractérisé en ce que les conducteurs de retour sont uniformément répartis autour de ladite première gaine,
comme deux conducteurs espacés de 180° ou trois conducteurs espacés de 120° ou quatre
conducteurs espacés de 90°.
4. Câble selon la revendication 1 ou 2, caractérisé en ce que les conducteurs de retour comportent trois conducteurs séparés les uns des autres
de 90° et d'un fil de terre (6).
5. Câble selon la revendication 1, caractérisé en ce que ladite deuxième gaine isolante commune (3) est pourvue d'une fente (8) destinée à
recevoir un fil de terre (6) qui est au contact d'un blindage de terre (7).
6. Câble selon la revendication 1, caractérisé en ce qu'il comporte un certain nombre de fils de terre (20) disposés autour de ladite deuxième
gaine isolante commune (3) au contact d'un blindage de terre (7).
7. Câble selon la revendication 6, caractérisé en ce que les fils de terre (20) sont disposés en groupe autour de ladite deuxième gaine (3)
en couvrant 10 à 25 % de la surface de la gaine.
8. Câble selon la revendication 1, caractérisé en ce que tous les éléments du câble sont disposés parallèlement à l'axe du câble.
9. Câble selon la revendication 1, caractérisé en ce qu'à l'extrémité proche du câble, le conducteur résistant est remplacé par un conducteur
en cuivre d'extrémité froide.