GB2085699A

GB2085699A - Heating foil as a heating system for buildings

Info

Publication number: GB2085699A
Application number: GB8128755A
Authority: GB
Original assignee: Jung & Lindig Bleiind
Current assignee: Jung & Lindig Bleiind
Priority date: 1980-10-10
Filing date: 1981-09-23
Publication date: 1982-04-28
Also published as: FR2492208A1; SE8105233L; FI812752L; FI69539B; NO153949B; SE451779B; FR2492208B3; NO813013L; DK388881A; GB2085699B; NO153949C; FI69539C

Abstract

The invention relates to a heating foil as a heating system for buildings. The heating conductor of the heating foil is formed by a narrow layer of an antimony-alloyed hard lead core (15) with a tin coating (17, 17a) on either side and has at least one heating conductor path formed in sandwich-like manner from a narrow layer (20) of tin- lead-antimony alloy or a low melting point lead-bismuth alloy and a further equally narrow layer (25) located thereon and formed by an antimony-alloyed hard lead core with a tin coating on the free side of the first layer and on the free side of the further layer. The depth of the layer (20) is equivalent to 10 to 100% of the total thickness of the heating conductor and the tin coatings in each case <IMAGE> based on the weight of the hard lead core. The first layer of this sandwich-like conductor path functions as a safety device, since it will melt and thus interrupt the current supply at a temperature sufficiently low to avoid the danger of setting fire to, for example, a wooden building incorporating the heating system. <IMAGE>

Description

SPECIFICATION Heating foil as a heating system for buildings The invention relates to a heating foil as a heating system for buildings and which comprises a current path-like heating conductor concealed between two polyethylene and polyester foils. The heating conductor has a clearly defined resistivity value per length.

For the heating of buildings, particularly wooden buildings, churches and chapels a heating system is known in which a heating foil is used comprising a lead-tin alloy with small amounts of other metal additives and which is rolled out to a thickness between 10 and 20 . This heating foil is cut out in meander-shaped manner and is firstly concealed between polyethylene foils and then between polyester foils. The polyethylene foil is used for heat sealing and the polyester foil for giving the complete component a certain mechanical stability. The size of the cut-out meander-shaped heating foil is selected in such a way that there can be a capacity of 500 Watt for a length of e.g. 700mm.Essential characteristics of the metal foil which are used are its electrical resistance necessary to be able to use the foil as a heating conductor and the alloy melting point of 183"C. This low melting point provides the necessary security of obtaining a destruction of the element and consequently an interruption to the power supply even at temperatures below 200 C in dwellings and in particular in conjunction with the use of wood and paper, so that ignition of the latter is impossible.

For the production of such heating foils a metal foil is employed essentially corresponding to the composition of the eutectic in the lead-tin system, i.e. 61.9% tin and 38.1% lead. It is standard practice to add 0.5 to 1% antimony, which is insignificant for the melting point level but stabilizes the rolling characteristics of the alloy.

Due to the high tin content, such heating foils are relatively expensive and as the world's tin supplies are limited and in any case tin prices are very high, the assembly and installation of heating systems using such heating foils have the disadvantage of high costs.

In addition, a heating foil is known as a heating system for buildings which comprises current pathlike heating conductors with a clearly defined resistivity value per length sealed between two polyethylene and polyester foils which have a narrow coating of a tin-lead-antimony alloy consisting 08%+1.2% of 61.5%+176% tin,37.7%+17% lead and 0.8%+0-0.5% antimony. The heating conductor is formed in sandwich-like manner from a narrow coating of the tin - lead - antimony alloy and a further, equally nar row coating located thereon constituted by a hard lead lead core alloyed with 2% -1,5% antimony with a tin coating on both sides.The further coating represents 64% of the total thickness of the heating conductor and the tin coatings in each case 1%+2.5%, based -0.5%' on the hard lead core -ieadrcore(GermanPatent 2-,70S,472L Compared with the known heating systems with a heating foil formed from a lead-tin alloy, the problem of the present invention is to provide a heating foil for such heating systems in which the width of the safety element is reduced to at least one heating conductor path, whilst retaining the electrical characteristics in such a way that such heating systems can be produced in a highly economic manner.

According to the invention, this problelll is solved by a heating foil as a heating system for buildings of the type described hereinbefore, wherein the heating conductor comprises a narrow layer of a hard lead core alloyed with 2%+1 5 antimony having a tin coating on both sides and at least one heating conductor path formed in sandwich-like manner from a narrow layer of a tin - lead - antimony alloy constituted by 61.5%+17 tin, 37.7% 6 lead and - 6 ~ 17 0.8%+1.2 antimony, as well as a further, equally nar row layer located therein formed from a hard lead core alloyed with 2% -1.5 antimony having a tin coating on the free side of the first layer and on the free side of the further layer, the layer representing 10 to 100% of the total thickness of the heating con ductor and the tin coatings representing in each case 1%+2.5 t based on the hard lead core.

-0.5 The problem of the invention is also solved in that the heating conductor is formed by a narrow layer of a hard lead core alloyed with 2% -1.5 antimony hav ing a tin coating on either side and has at least one heating conductor path formed in sandwich-like manner from a narrow layer of a low melting point lead-bismuth alloy of 37%+10 bismuth and - +10 -10 lead and a further, equally narrow layer located thereon of a hard lead core alloyed with 2%+ 4 antimony with a tin coating on the free side of the first layer and on the free side of the further layer, the layer representing 10 to 100% of the total thickness of the heating conductor and the tin coatings form ing in each case 1% +2.5 based on the hard lead -0.5 core.

The percentages are based on the weight of the hard lead core.

Further advantageous embodiments of the inven tion can be gathered from the subclaim.

The heating foil constructed according to the invention and partly constituted by a sandwich foil fulfils the conditions of the known heating elements.

However, in the present case, the tin content of the heating foil is reduced to a minimum, which leads to considerable cost savings. Compared with the total width of the heating conductor of the known heating foil, in the case of the present foil at least one heating conductor path is constructed as a safety or protective element.

It has surprisinggly bern foond that that a heatingfoil constructed in this way haslihe fntlowing propertltes: a) The resistance of this partial sandwich foil is the same as that of the sandwich heating foil formed by an alloy of 61.5 tin, 37.7% lead and 0.8% antimony.

b) The protective nature ofthe heating foil is maintained through the melting of the heating conductor path containing the tin -lead - antimony alloy.

The present heating foil replaces the relatively expensive system of the known heating foil by a foil partly formed by a tin - lead - antimony alloy and partly by a lead-antimony alloy or partly by a leadbismuth alloy and partly by a lead-antimony alloy.

Thus, the principle of the present invention goes beyond that of the known proposal and replaces the 60/40 foil used over the entire heating conductor width by a narrow portion comprising at least one heating conductor path.

The heating foil is produced in the following manner. A foil cut out in meander-like manner is selected which has a length of 1m and strip widths for the heating conductor paths of 5mm and gaps of 3mm. It is possible for the same to contain twelve heating conductor paths of the basic antimony-lead alloy, four following heating conductor paths as safety paths from the sandwich alloy from the layer of tin lead - antimony alloy or lead-bismuth alloy and the further layer from the antimony-alloyed hard lead core and from eleven further following heating conductor paths from the basic antimony-lead alloy, said heating conductor paths forming the current paths of the heating foils. Thus, there are in all 27 strips. The total width of the element is 213mm.With an alloy of 61.5% tin, 37.7% lead and 0.8% antimony having a thickness of 13" the resistance of such an element is 63.6 Ohm. The weight per unit area of this foil is 112 g/m2.

A known sandwich heating foil (German Patent 2,705,472) having a comparable resistance has a thickness of 17 it The thickness of the hard lead foil is 10.8ill and the thickness of the tin - lead - antimony alloy 6.2p. The electrical resistance of this foil is 63.5 Ohm. The weight per unit area is 172 git2.

The sandwich part of the heating foil has a thickness of 17,. The four safety paths have a thickness of 10p of the almost eutectic tin - lead - antimony alloy and 7 cm of the lead-antimony basic alloy. The complete sandwich partofthe heating foil then has a resistance of 64.6 Ohm and a weight per unit area of 183 gI.

The following example illustrates the invention: Chemical analysis: For the heating conductor of the known tin - lead antimony alloy 61.5% tin 37.7% lead 0.8% antimony.

The sandwich foil according to Patent 2,705,472 has an analysis of 78.1% lead 20.3% tin 1.6% antimony.

The sandwich part of the heating foil has an analysis of 92.8% lead 52%tiro t-an*ny.

If the following prices are used as a basis for the metal components, lead DM 1.20/kg tin DM 23/kg antimony DM 5/kg then with a composition of the known heating foil constituted by an alloy of 61.5% tin, 37.7% lead and 0.8% antimony for 100kg the total costs are 37.7 kg lead DM 45.24 61.5 kgtin DM 1,414.50 0.8 kg antimony DM 4.00 DM 1,463.74 In the case of the known sandwich heating foil a 53.6% higher square metre weight is assumed. The following figures are obtained for the same purpose: 120 kg lead DM 153.95 31.2 kg tin DM 717.16 2.5 kg antimony DM 12.29 DM 873.40 Thus, material cost savings of DM 590.34 or 40.3% are obtained.

The partial sandwich heating foil requires a 63.4% higher square metre weight than the known heating foil, i.e.: 151.6 kg lead DM 181.92 8.7 kg tin DM 200.10 2.9 kg antimony DM 14.50 DM 396.52 Compared with the known heating foil, this leads to a saving of DM 1,067.22 or 72.9% and compared with the sandwich heating foil according to German Patent 2,705,472 a saving of DM 476.88 or 54.6%.

It is obvious that such a heating foil can be rolled down again to the old thickness of 13eel in the same way as the known heating foil from the tin - lead antimony alloy. However, this would lead to a corresponding increase in the resistance, so that the same heating capacity can be housed in a correspondingly smaller area. This leads to a further advantage when using the heating foil according to the invention.

The invention is described in greater detail hereinafter with reference to non-limitative embodiments and the attached drawings, wherein show: Fig 1 a plan view of a heating system comprising a meander-shaped heating foil.

Fig 2 a portion of a single heating conductor path with the antimony-alloyed hard lead core in a diagrammatic larger-scale view.

Fig 3 a vertical section along line Ill-Ill of Fig 7.

Fig 4 a portion of a single heating conductor path of the heating foil with the two layers of the tin - lead - antimony alloy or the lead-bismuth alloy on one side and the antimony-alloyed hard lead core on the other in a larger-scale diagrammatic view.

Fig 5 is a vertical section along line V-V of Fig 1.

Fig 6 a heating foil with twelve heating conductor paths with the antimony-alloyed hard lead core, with four heating conductor paths from the sandwich alloy and eleven heating conductor paths with the antimony-aXoyed hard lead core in a ptan view.

Ascanbe seen in Figs t and f heatingfwl-IO-O partly comprises a layer 15 of an antimony-alloyed hard lead core 16 and partly comprises two sandwich-like layers 20,25. Layers 15,20,25 are concealed between plastic foils 30, 31, each of which is formed by an outer polyester foil 30a, 31 a and an inner polyethylene foil 30b, 31 b (Figs 2 and 4). The foil forming the heating foil is cut out in meandershaped manner, as can be gathered from Figs 1 and 6. Heating foil 100 has a plurality of heating conductor paths 110,120 (Fig 1).

Each heating conductor path 110 is formed by a narrow layer 15 of antimony-alloyed hard lead core 16 with a tin coating 17, 17a on either side. At least one heating conductor path 120 of heating foil 100 is formed in sandwich-like manner from a narrow layer 20 of a tin - lead - antimony alloy of 61.5% tin, 37.7% lead and 0.8% antimony or a low melting point lead-bismuth alloy of 37%+100 bismuth and -10 f10 lead and a further equally narrow layer 25 -10 located thereon of an antimony-alloyed hard lead core 26. The two layers 20, 25 joined together in sandwich-like manner are provided on both sides and the outside with in each case a tin coating 27, 27a. Layers 20 or 20a represent 10 to 100% of the total thickness of the heating conductor.The hard lead cores 16 or 26 are alloyed with 2% antimony.

The tin coatings 17, 17a and 27, 27a in each case represent 1%, based on the hard lead core.

Layer 20 is preferably formed from a tin-lead alloy with a melting point below 200"C. Layers 15 and 25 of the sandwich foil comprise hard lead cores 16 or 26, in each case in the form of a foil.

There can be a random number of heating conductor paths 20 formed from sandwich foil with the two layers 20, 25. However, as compared with the heating conductor paths 110 at least one heating conductor path 20 of the heating foil must comprise the sandwich foil with the two layers 20, 25, because said heating conductor path 120 forms the safety or protective element for the heating foil.

However, it is also possible to use several heating conductor paths from a sandwich foil with layers 20 and 25, in the manner shown in Fig 6. In this embodiment of a heating foil, there are twelve heating con ductorpathsll0a,110b,110c,110d,110e,110f, 110g, 110h, 110i, 110j, 110k, 1101 constructed in the same way as heating conductor path 110. These heating conductor paths 110a to 1101 are followed by four heating conductor paths 120a, 120b, 120c, 120d formed from the sandwich alloy and which corresponds to the heating conductor paths 120. These heating conductor paths 120a to 120d are in turn followed by eleven heating conductor paths 11 or, 1100,110p,110q,110r,110s,110t,110u,110v,110w, 110x, which are constructed in the same way as heating conductor paths 11 Oa to 1101, so that the heating conductor of Fig 6 has 27 heating conductor paths.

The aforementioned alloyed percentages are percentages by weight.

Claims

1. A heating foil as a heating system for buildings, comprising a current path-like heating conductor having a cleaFly defined specific resistivity value per length and concealed between two polyethylene and polyester foils, wherein the heating conductor comprises a narrow layer of a hard lead core alloyed +4 with 2% ~ 1.5 antimony having a tin coating on both sides and at least one heating conductor path formed in sandwich-like manner from a narrow layer +17 of atin-lead-antimonyalloyconstituted by61.5%~16 tin, 37 6 lead and 0.8%+o 5 antimony, as -17 -0.5 well as a further, equally narrow layer located therein formed from a hard lead core alloyed with +4 2%+145 antimony having a tin coating on the free side of the first layer and on the free side of the further layer, the layer representing 10 to 100% of the total thickness of the heating conductor and the tin tin coatings representing in each case 1 %+0 5, based on the hard lead core.

2. A heating foil as a heating system for buildings, comprising a current path-like heating conductor with a clearly defined resistivity value per length concealed behind two polyethylene and polyester foils, wherein the heating conductor is formed by a +4 narrow layer of a hard lead core alloyed with 2%~14 .5 antimony having a tin coating on either side and has at least one heating conductor path formed in sandwich-like manner from a narrow layer of a low melting point lead-bismuth alloy of 37+10 bismuth and 63%+10 lead and a further, equally nar -10 row layer located thereon of a hard lead core alloyed with with 2%~1.5 antimony with a tin coating on the free side of the first layer and on the free side of the further layer, the layer representinng 10 to 100% of the total thickness of the heating conductor and the = 2.5 tin coatings forming in each case 1 %-0.5, based on the hard lead core.

3. A heating foil according to claim 1, wherein the two layers of the sandwich foil have the same electrical resistance.

4. A heating foil according to either of the claims 1 and 3, wherein the tin - lead - antimony alloying layer is constructed as a foil with a thickness of 5 to 30 micrometers.

5. A heating foil according to claim 2, wherein the two layers of the sandwich foils have the same electrical resistance.

6. A heating foil according to claims 2 and 5, wherein the lead-bismuth alloying layer is con structed as a foil with a thickness of 5 to 30 mic rometers.

7. A heating foil as a heating system for build ings, substantially as hereinbefore described with reference to the accompanying drawings.