Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B3/00—Ohmic-resistance heating
  • H05B3/68—Heating arrangements specially adapted for cooking plates or analogous hot-plates
  • H05B3/74—Non-metallic plates, e.g. vitroceramic, ceramic or glassceramic hobs, also including power or control circuits

Definitions

• the invention relates to a heating plate based on compressed inorganic, highly dispersed thermal insulation material, hardener and heating element operated by means of electric current.
• the heating element is glued to the base plate, but mostly mechanically, for example by means of clamps or retaining pins and the like, attached to the base plate.
• a number of further steps for assembling the heating element are therefore required in addition to the production of the base plate.
• the object of the invention was to present a heating plate, in the production of which additional assembly operations for applying the heating element can be largely avoided. Furthermore, it was an object of the invention to present a hot plate with high thermal insulation values.
• the invention relates to a heating plate based on pressed inorganic, highly disperse thermal insulation material, hardener and heating element operated by means of electric current, which is characterized in that the heating element is at least partially pressed into the inorganic highly disperse thermal insulation material.
• the proportion of hardener in the mixture provided for the press-in layer is preferably at least 1.5% by weight.
• the press-in layer has a different composition, in particular with regard to its opacifying agent and hardener content, than the actual thermal insulation layer of the heating plate.
• electrically insulating, heat-conducting substances are added to the press-fit layer.
• rock powders such as granite powder, quartz powder or low-alkali precipitated silica.
• the particle sizes are preferably in the range of 0.01-1 mm.
• finely divided metal oxide which is used both for the actual thermal insulation layer and for the press-in layer of the heating plate, are pyrogenic silicas including arc silicas, low-alkali precipitated silicas, analogously produced aluminum oxide, titanium dioxide and zirconium dioxide.
• the finely divided metal oxides have specific surfaces of 50-700 m 2 / g, preferably 70-400 m 2 / g.
• the primary particle sizes are preferably in the range of 2-50 nm.
• Ilmenite, titanium dioxide, silicon carbide, iron-II-iron-III mixed oxide, chromium dioxide, zirconium oxide, manganese dioxide and iron oxide are suitable as opacifiers.
• the opacifiers advantageously have an absorption maximum in the infrared range between 1.5 and 10 ⁇ m and particle sizes between 1 and 10 ⁇ m.
• fiber material examples include glass wool, rock wool, Schlakken wool, ceramic fibers, such as those obtained from melts of aluminum oxide and / or silicon oxide, asbestos fibers and others.
• the hardeners used are, for example, the borides of aluminum, titanium, zirconium, calcium, silicides, such as calcium silicide and calcium aluminum silicide, but especially boron carbide.
• borides are used as hardeners, it is preferred to add basic oxides, in particular magnesium oxide, calcium oxide or barium oxide, in amounts of 1.5 to 10 times the hardener content.
• the mixtures are obtained by simply mixing the components in the desired composition.
• so-called agglomerated mixtures in particular based on pyrogenic silica, can also be used. This is done in such a way that the opacifying agent already in the production process of the silica, in which the silica is still in the form of the primary particles, is continuously added in the desired mixing ratio.
• heating elements operated by means of electric current all heating elements can be used within the scope of the invention which have already been used for heating plates.
• heating spirals or heating coils made of resistance wire are to be mentioned.
• the heating elements are at least partially or completely pressed into the press-fit layer.
• Heating coils are usually pressed in at least 1/3 of their coil diameter.
• the pressed-in part of the heating coil is completely surrounded by the heating plate material, so that an anchoring is created which can no longer be released without being destroyed.
• the arrangement of the heating coil on the heating plate is in itself arbitrary. For example, it can take a spiral or zigzag shape.
• the power connections of the Schutile can be at any point, e.g. B. diametrically opposite, adjacent or on the edge or in the middle.
• the heating plate according to the invention is produced by pressing the highly dispersed thermal insulation material together with the heating element which has already been preformed in the desired manner and then curing by heating to 500-800 ° C.
• the press-in layer can have a different composition than the actual insulating layer. Accordingly, different mixtures are optionally pressed together.
• the quantity ratio of these emulsions is chosen in accordance with the desired construction height. In general, the height of the press-fit layer corresponds approximately to the press-in depth of the heating element.
• the pressures are in the range of about 1 - 1.5 N / mm 2 .
• the press-in depth for the heating element can be set, for example, using a suitably shaped press tool.
• This pressing tool has depressions that simultaneously represent the geometric shape of the heating element.
• the pressing-in depth of the heating element corresponds to the height at which the heating element protrudes beyond the pressing tool. If a complete pressing of the heating element is desired, the pressing tool is advantageously flat.
• the heating element can be held in the geometric shape, for example, by electromagnetic forces.
• the press-in layer has a different composition than the actual insulating layer
• the compression and compression is preferably carried out with the application of negative pressure. Degassing can also begin or start before compression or compression.
• the heating plate according to the invention can be produced in any desired shape, for example square, rectangular, round, oval and the like. It can also be shaped with a raised edge.
• heating plate according to the invention can also be equipped with devices which are customary for heating plates, such as protective shells made of metal or plastic, electrical connections, security elements such as overtemperature switches and the like.
• the heating plate according to the invention has excellent thermal insulation properties in the insulating layer. It can therefore be manufactured in the relatively low construction heights. It is particularly suitable as a heater for glass ceramic hot plates and the like.
• the die is then closed with the upper punch and evacuated.
• a final pressure of 1, 2 N / mm 2 By compressing the mixture at a final pressure of 1, 2 N / mm 2, a molded body having a height of 17 mm and a density of 300 kg / m 3.
• the heating coil is embedded in the heating plate halfway up.
• the workpiece is annealed at 750 ° C for 1 hour for curing.
• a heating plate is obtained in which the heating coil is fully pressed in. Due to the composition of the press-in layer, a heating plate with excellent IR radiation properties is obtained.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Surface Heating Bodies (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6146058

Family Applications (1)

Country Status (2)

Cited By (1)

Families Citing this family (1)

Citations (8)

• 1981
  • 1981-11-10 DE DE19813144661 patent/DE3144661A1/de not_active Withdrawn
• 1982
  • 1982-11-09 EP EP19820110294 patent/EP0079076A1/fr not_active Withdrawn

Patent Citations (8)

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