US3515849A

US3515849A - Electrical heating system

Info

Publication number: US3515849A
Application number: US635966A
Authority: US
Inventors: Friedrich Chr Math
Original assignee: KAUFFER AND CO GmbH
Current assignee: KAUFFER AND CO GmbH
Priority date: 1966-04-29
Filing date: 1967-05-01
Publication date: 1970-06-02
Anticipated expiration: 1987-06-02
Also published as: GB1189161A; NL141352B; LU53512A1; NO121684B; BE697775A; DE1299784B; NL6706030A; DK127260B

Description

- June 2; 1970 F. CHR. MATH ELECTRICAL HEATING SYSTEM Filed May 1, 1967 m CS United States Patent Office Patented June 2, 1970 3,515,849 ELECTRICAL HEATING SYSTEM Friedrich Chr. Math, Kronberg, Taunus, Germany, assignor to Kaulfer & Co. G.m.b.H., Mainz, Germany Filed May 1, 1967, Ser. No. 635,966 1 Claims priority, application Germany, Apr. 29, 1966,

Int. Cl. 1165b 1/00 Us. Cl. 219-213 I 6 Claims ABSTRACT OF THE DISCLOSURE Background of the invention Electrically heatable floors are known in various modifications, since the heating of the room through the floor by means of electrical energy provides for various advantages. One essential difiiculty encountered in electrical floor heating is to obtain a substantially uniform temperature over the whole area of the floor.

Nearly all building materials used for the construction of floors, such as for instance parquet, xylotith, polyvinylchloride, and so on, have a relatively low heat conductivity. Therefore, the portions of the floor located directly over the heating wire embedded therein will be localized heated to a much higher temperature than portions adjacent thereto so that the floor surface will be divided into overheated and relatively cold surface portions. While this difliculty may be overcome by installing theheating wires closely adjacent to each other, such an arrangement has the disadvantage in that it requires a large amount of heating wire material and considerable labor for installing the same so that such a system becomes too expensive in most cases.

An additional difliculty in the construction of electrically heatable floors or the like is that after extensive use and wear of the floor, the heating wires which are necessarily to be installed closely adjacent to the floor surface will become exposed and may cause that electrical shocks may be imparted to a person walking over the floor.

A further difficulty encountered in the construction of electrically heated floors is that when the heating elements of the heating system are embedded in hardenable floor material during installation, the floor material will shrink during hardening thereof, while the heating elements will not shrink, so that during the hardening of the floor material considerable tension will be created between the floor material and the heating elements which may lead to crack formation in the floor material or to {damage of the heating elements. Up to now it was not possible to eliminate the tension thus created, and it has been only tried to reduce the tension by using a floor material having a small as possible shrinkage factor.

It is an object of the present invention to provide an electrical heating system for floors or the like which avoids the above-mentioned disadvantages of electrical heating systems of this type known in the art.

It is an additional object of the present invention to to provide an electrical heating system for floors or the like which can be easily manufactured and installed in the floor and which will stand up perfectly under extended use.

Summary of the invention With these objects in view, the electrical heating system according to the present invention, which is adapted to be embedded in a floor and the like, mainly comprises electrical heating means distributed over a given area and arranged substantially in a plane, and grid means extending over the area and connected to the electrical heating means but electrically insulated therefrom for protecting the latter and for dissipating the heat developed thereby.

The grid means is preferably formed from metal and preferably the grid means is in the form of an electrically yieldable metal grid in form of a wire netting or in form of perforated or punched metal sheets.

In this arrangement the portions of the metal grid which are closely adjacent to the heating elements of the heating means will dissipate the heat developed thereby to assure a substantially uniform distribution of the heat over the whole surface of the floor in which the electrical heating system is embedded.

The metal grid, which when the heating system is installed will extend at least in part above the electrical heating means, will also properly protect the latter since during wear of the floor surface the metal grid will be first exposed so that the heating elements located beneath the metal grid will still be properly protected. Exposure of the metal grid will also indicate that repair of the floor surface is required.

In addition, the metal grid may be grounded to protect any person walking on the floor from shocks, even if the insulation of the heating elements should be damaged.

The electrical heating means of the heating system according to the present invention preferably comprise a plurality of elongated heating elements arranged spaced from each other substantially in a plane and a pair of conductors respectively connecting opposite ends of adjacent heating elements to each other. The heating elements are preferably flexible and to a certain extent also stretchable, for instance each of the heating elements may comprise a woven band including a heating wire forming the weft thread of the band and warp threads of insulating material and insulating means covering the band, whereas the grid means connected to the thus constructed heating means is, as mentioned before, and elastically yieldable metal grid. If such a constructed heating system is embedded in floor material which shrinks during hardening, evidently creation of tensions in the floor due to the shrinkage of the floor material will be avoided and crack formation in the floor or damage to the electrical heating system due to shrinkage of the floor material will not occur.

In a preferred form, the grid means is in form of a wire netting, the wires of which are intertwined with the elongated heating elements and the conductors forming the electrical heating system. An electrical heating system of such a construction can be easily manufactured with automatic machines known in the art in form of an elongated or endless mat adapted to be cut in portions of desired length in situ so that the whole system may be easily and quickly installed with semi-skilled labor.

The flexible wire netting will not only prevent crack formation due to shrinkage of the floor material, but the embedded wire netting will also increase the strength of the floor and reduce the danger of crack formation in the latter due to sinking of the floor foundation.

Especially advantageous results are obtained if, according to the present invention, a pretension is applied to' the heating means and to the grid means of the electricalheating system before the latter is embedded into hardenable building material forming the floor and the pretension is maintained during hardening of the floor material.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

Brief description of the drawing FIG. 1 is a top view of the electrical heating system according to the present invention;

FIG. 2. is a cross section taken along the line II-II of FIG. 1; and

FIG. 3 is an enlarged partial view of one heating element with part of the insulation cut away.

Description of the preferred embodiments Referring now to the drawing, and more specifically to FIG. 1 of the same, it will be seen that the electrical heating system according to the present invention may comprise electrical heating means extending over a given area and arranged substantially in a plane and including heating elements 3 arranged spaced from and substantially parallel to each other and connected at opposite ends by current supply conductors 2 extending normal to the heating elements, and grid means which may comprise a wiring netting 1, the wires of which are intertwined or interwoven with the heating elements 3 and the conductors 2 to form with the latter a flexible heating mat. Such a mat may be produced by automatic or semi-automatic machines in form of a more or less endless band which is then cut in situ to the required length.

Instead of a wire mesh as shown in FIG. 1, the grid means or the metal grid may also be formed from a perforated or grid-like stamped metal sheet extending over the electrical heating means 2, 3 and connected thereto in any convenient manner to form therewith a flexible mat.

FIG. 2 shows a cross section taken along the line 11-11 of FIG. 1 with the wire mesh 1 omitted.

The heating elements 3 are constructed to be not only flexible but preferably also stretchable to a certain extent and they may comprise, as shown in FIG. 3, a heating wire 4 interwoven as a weft thread with warp threadsS of insulating stretchable material to form therewith a flexible and stretchable band which is surrounded by an inner layer 6 of electrically insulating material of high heat conductivity, for instance silicone, which in turn is surrounded by an outer insulating layer 7 of an appropriate plastic material of relatively great mechanical strength. The cross section of the heating element 3 is preferably substantially oval as shown in FIG. 2. The current supply conductor 2 may be constructed in a similar manner, of course with the cross section of the wire chosen in such a way so as to be able to carry the necessary current. The wires of the current supply conductors 2 are permanently and electrically connected to the heating wires 4 of the heating elements 3 at the junction of heating elements and conductors and each junction is insulated in a permanent and water-tight manner.

As mentioned above the electrical heating mat shown in FIG. 1 may be produced in a more or less endless band to be cut in situ to the desired length. During installing of the electrical heating system according to the present invention a pretension is preferablyapplied in a known manner to the mat composed of the

elements

1, 2 and 3 and this heating mat is then embedded in hardenable building material forming a floor or the like and the pretension is maintained until the material hardens, whereby the strength of the floor will be increased by the heating mat installed therein. Ground wires maybe connected to the wire mesh 1 so that the latter maybe properly grounded.

It will be understood that each o f the elements de scribed above, or two or more together, may also find a useful application in other types of electrical heating systems differing from the types described above. I I

While the invention has been illustrated and described as embodied in an electrical heating systemincludin'g' electrical heating means and a flexible metal grid con- .nected thereto to form a flexible electrical heatingmat therewith, it is not intended to be limited to the details shown, since various modification and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can be applying current knowledge readily adapt it for various applications without omitting features that, from the standopint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. An electrical heating system adapted to be em bedded in a floor and the like, comprising, in combina tion electrical heating means distributed over a given area substantially in a plane and including a plurality of main elongated heating elements arranged spaced from each other and each comprising a narrow flat band'form'ed from a plurality of warp threads of insulating material all of which extend longitudinally of the respective heating elements, a weft thread constituted by a heating wire arranged in a wavy form and extending only transverse to the elongation of the band intertwined with said warp threads, a layer of silicone material covering said band, and a layer of insulating material covering said-layer of silicone material; a pair of elongated conducted elements serving as conductors for said main elongated heating elements and extending transverse to the latter and 'respectively in the region of opposite ends thereof and respectively connecting said opposite ends to each other; and grid means extending over said given area and intertwined with said main elongated heating elementsand said elongated conductor elements so as to contact'the same over a relatively great area thereof, said grid means serving for protecting said elements and for dissipating heat therefrom.

2. An electrical heating system as definedin claim 1, wherein said main heating elements extend substantially parallel to each other and said conductor elements extend substantially normal to said main heating elements. h

3. An electrical heating system as defined in claim 1, wherein said grid means is formed from metal.

4. An electrical heating system as defined in claim 1, wherein said conductor elements are permanently connected in a water tight and heat resistant manner to said main heating elements.

5. An electrical heating system as defined in claim 1, wherein said grid means comprises a Wire netting, the wires of which are intertwined with said main heating elements and said conductor elements.

6. An electrical heating system as defined in claim 5, wherein the wires of said wire netting extend transverse to said elongated heating elements.

References Cited UNITED STATES PATENTS 6 Crump 338-208 X Sutter 219-345 Logan et a1. 338-214 X Price 219-549 X Custer, 219-345 Leipold et al. 338-208 X Frungel 219-213 Shrimplin et al 219-213 Beery 219-213 X Williams 219-213 Graham et a1 219-345 X US. Cl. X.R.