DE1912216A1 - Electric heating element - Google Patents

Description

Ktmp & Korn Pattntanwalt · '

Cologne, Lindenthal J 21 P

20-22

Applicant: Johnson, Matthey & Co. Limited 78, Hatton Garden, London E. Co 1 England

Electric heating element

Coiled ones are mainly used as electrical heating elements Resistance wires application, however, are two essential have technical disadvantages: On the one hand, such resistance elements must be relatively large; their heat dissipation per surface elness is therefore low. Secondly, the nichrome alloys commonly used, which are used for resistance wire, have a strong teniperature coefficient of the resistor, so that when the cold heating element is switched on, a very large starting current compared to the operating current is pulled "

It has been proposed to use a "tin oxide layer" vapor-deposited on a non-conductive base However, ten can only be applied using the tapping technique furthermore it is only possible to produce relatively thin layers. If too much tin oxide is evaporated, the material will crystallize the end. Tin oxide heating elements in layer form can be used with

009832/1208

Manufacture small dimensions, however, their heat dissipation is Technically unsatisfactory per unit area also that the vapor deposition of such layers is generally very is expensive. Another disadvantage of vapor-deposited tin oxide layers is that microscopic unevenness of the substrate Maintain protruding through the layer uncovered.

The invention is based on the object of an electrical To create a heating element, which can be heated to very high temperatures, a high heat output per unit area has, is easy to manufacture and whose temperature coefficient of resistance is much smaller than that of known heating elements.

The invention solves the problem in that the resistor material is a mixture of finely divided ruthenium oxide and glass, in which mixture the ruthenium oxide makes up 10 to 80 wt.% And the glass 90 to 20 wt having up to 65 wt. ~% ruthenium oxide and 54-55 GeWo- # glass ,,

The claims 2 to 8 give particularly useful Ausgestal = services of the invention,

The in the present case to solve the underlying the invention » resistance materials used in an older application by the applicant (official file number P 16 40 561.I) used to solve another problem. In that earlier application, a resistance material is described which can be burned onto a non-conductive substrate is suitable for the production of a resistance element »Here

0098 3 2/1209

a mixture of 10 to 80% by weight of finely divided ruthenium oxide and 90% by weight of finely divided alas is used. In one embodiment, the ruthenium oxide is wholly or z. T. by a »material which is obtained by heating ruthenium oxide and one or more oxides of one or more of the metals of group V of the periodic table, this mixture optionally up to 10 wt .- # of one or has several oxides of one or more metals of groups I and XI of the periodic table.

The earlier application also describes a resistance compound in which up to 50% by weight of the ruthenium oxide can pass through Silver is replaced. The earlier application also describes a resistor material in which no more than 59 wt .- ^ of the mixture with the oxides of the metals of group V and optionally of groups X or Xi are replaced by silver. Zweokm & ßlg is used as the oxide of the metal from group V, nlobpentoxide.

The optionally to be used silver can according to the older Registration in the form of the metal or the oxide or a mixture of metal and oxide.

The resistance materials suitable for solving the problem on which the earlier application is based can - according to the present invention - for solving the above-mentioned problem be used.

The heat-resistant pad that may be used can be a be ceramic material, e.g. alumina ceramic, aluminum oxide, Silicon oxide, porcelain, silicon oxide

009832/1209

any heat-resistant pad to be used can be «in be ceramic material, z * a "alumina ceramic" aluminum oxide, Silioium oxide, porcelain, aluminum porcelain, glass (e.g. Pyrtx). One can also use mica, steatite or other known carriers Using materials «which are commonly used in the electrical or electronic industry for such purposes« One can The forest restoration mass also on lattice or net-like components

^ in a more load-bearing form, e.g. from the radiators in the case of gas feuerungen'lst. Such sieves or nets can also be used as air flow heaters »z. B. in hair token devices or heaters for rooms. The resistor material can be applied in the form of inks «pastes or powders by screen printing» spraying, dipping, off-sefc printing or other known coating processes. After application and drying, the resisting mass is fired at a suitable temperature, e.g. B. can be between 550 and 850 ^° C. The firing temperature depends, among other things, on the composition of the substrate. This firing serves to remove the corresponding organic solvents and to solidify the coating in Filrafonn. The shape and the OrUSe of the resistive layers is chosen according to the intended use. You can apply stripes, tape patterns or surfaces of other shapes. The layer can also be used as a continuous coating train, e.g. B. when applied to documents "which have the shape of a cylinder"

It is useful to have terminals at the ends of the pattern '"Resistance material attached» that a silver-containing Ink or some other material is applied so that lead wires can be soldered or clamped to the actual electrical resistor. You can also use appropriate

009832 / 12Q9

Use caps to make connections.

Let us describe an example: An alumina ceramic plate 5 cm long and 2.5 cm wide and ο.62 mm thick has connections which were made by burning silver ink at the appropriate temperature so that adhesion could be achieved . Then a pattern of the resistance compound according to the invention is applied in the form of a liquid by a screen printing process and then the whole thing was fired * in order to transform the liquid applied resistance compound into a kind of glaze. The resistance element produced in this way can emit the considerable heat output of 800 watts when 240 volts are applied to the terminals. Any desired heating effect between 30 and 800 watts can be achieved by appropriate design and selection of the correct length and width of the figure forming the resistor made of resistor material.

The values given are only to be regarded as examples; the Resistance mass used according to the invention can deliver even higher powers. The power output is essential limited by the thermal conductivity of the base.

A heating element made in the manner described can be used for a variety of different heating purposes, z. B. in coffee machines, holding trays, plate heaters, Iron, soldering iron, hot water tank, space heaters with forced and free circulation, glass house heating, etc. etc .. The heating element can be used in the air and above the ground it can also be used to heat aquariums, etc.

009832/1209

One of the invention can also produce heating elements "reach particularly high temperatures and indeed up to UOO ⁰ C. In this case the Widerstandsinasse is condensed into a block or differently shaped body d" h. thus used without a base made of non-conductive material »with corresponding electrical connections being formed on this block or body. In this case, too, the resistance masses or. Use materials that have been specified above and are also described in the earlier application mentioned by the applicant.

* In the single figure of the drawing there is a schematisoh after of the invention formed heating element shown for an electric cooking kettle. It initially has a porcelain base of about 10 by 3.8 cm in length or width with a thickness of about 0.62 to 1.2 mm. On this base 1 is a U-shaped designed layer 2 made of resistance material, the thickness of which is about 0.025 ram »

The electrical conductivity of the covering should be given for the following W consideration in 0ha per unit area, where ° according to the experiments - each unit area is equal to one square inch »If the heating element is to deliver 3000 watts, then the conductivity of the covering is about 1.28 ohms per unit area, ie per square inch «This is only an approximation, since the individual imaginary square units are not arranged in a line, but rather there is a corresponding deviation when the U is bent.

As mentioned * the topping is 0.025 nanometers thick and the topping layer was made from the following resistance mass:

009832/1209

10 % Borslllkat «Qlaa

82 % RuO ₂ ZlIb ₂ O ₅

3 % silver powder

3%% organic carrier (ζ. B. Kthylcelluloae).

This only applies a well-known sieve printing process dl «underlay applied and after firing at 850 to 1000 ° C, the entire underlay was provided with the upper layer thereby ustttllt tones, including that they are in melted Qla "was submerged" The drawing shows that the resistance * aohioht the silver contacts 2 and about at both ends 5 Mi overlaps.

To produce a heating element for the output of 100 watts for a hair dryer, the interior of a cylinder with two inches of interior and 2.5 inches of lungs is covered with a floor stand that has a connection to each. (The hatred is given in inches, since the "BlnheltflKehe" used in experiments measured 1x1 inches). The hollow cylinder is made of porcelain and has a wall thickness of 1.5 ble 3 ms. The conductivity of the material was (according to the above definition) 48 ou per surface element, ie per lead part 9% * fde »known length one number times an inch. The interior is therefore a rectangle five square inches in area. lOOf WJrtt at, 2 ^ 0 ToIt receives »an at about, 60 Ohp and V5 of 60 ajbof ^ Obs per unit area.

Han can dl «« rfU »di * lgsgena * 9eii Hel ^ materiAibii also on low * documents that can be processed easily, e.g. B. Qlinmer raise, so z. B. to manufacture a heating element for an iron.

009832/1209 _{0R (GINAUNSpECTED}

The resistance material can also be made into blocks or bodies. seals, which serve as heating elements after firing.

For example, a cylindrical body made of densified resistance material 3 mm long and 3 mm in diameter emit 400 watts at 12 volts if the following resistor material is used:

77.5

7.5 wt -.% Silver powder
15.0 percent -.% Glass powder.

To produce the material suitable for processing, 3 g of acrylic resin are added to every 100 g of the above mixture, which resin acts as a binder. The mass produced in this way is then fired in air at a temperature which is at least as high as the working temperature of the heating element, i. ho z. B. 850 to 1000 ⁰ C.

Claims

009832/1209

Claims (1)

J 21 P PATENT CLAIMS Electrical heating element, characterized in that the resistance material is a mixture of finely divided ruthenium oxide and glass, in which mixture the ruthenium oxide makes up 10 to 80 wt. ₄ = # and the glass 90 to 20 wt preferably 46 to 65 wt. % ruthenium oxide and 54 to 55 wt.% glass. 2 β heating element according to claim 1, characterized in that the ruthenium oxide is wholly or partially replaced by a material which is obtained by heating ruthenium oxide with one or more oxides of one or more metals of group V of the periodic table, the Mixture optionally - up to 10% by weight of one or more oxides of one or more of the metals of groups I and Tt of the periodic table are added » 2. Heating element according to claim 1 or 2 characterized characterized geke * η η ~ that 50 wt. ~% Or less of Rutheniumoxydes or Oxydraischung by silver in metallic or oxide form metallic and Oxydforsi are replaced or. 4. Heizeleaant according to claim 2 or 5, characterized g e- te e η η <= indicates that the oxide of the metal from group V of the periodic table is a niobium oxide » 009832/1209 5. The method for producing a heating element according to claims 1 to h _f <iaclurnh characterized _s that the finely built-up components of the mixture are mixed with a binder and an evaporable liquid, which is then printed onto a base using a printing process, and the base is also included the layer on top is then fired _o 6ο heating element according to claim 5 »characterized by g e k e η η that the burned base with on it The layer is then dipped in molten glass to produce a coating over the layer. 7 «Electrical heating element according to claim 1 to 4, characterized characterized in that the resistance material is present as a compacted block or body which has two connections for the heating current. 8 «heating element according to claim 7.« thereby g e k e η η ~ draws that the compacted block or body is burned ο 009832/1209