Composition resistor suitable for spark plugs and method of making the same

Claim 1

A COMPOSITION RESISTOR SUITABLE FOR INCORPORATION IN A SPARK PLUG CONSISTING OF A FUSED MIXTURE CONSISTING ESSENTIALLY OF CARBON BLACK IN A PORPORTION BETWEEN 0.3 AND 2.5% BY WEIGHT A BOROSILICATE GLASS, AN INORGANIC FILLER AND AN ORGANIC BINDER, THE BOROSILICATE GLASS CONSTITUTING THE MAJOR PORTION OF THE COMPOSITION AND THE FILLER BEING METAL OXIDE HAVING A THERMAL EXPANSION COEFFICENT EXCESS OF 5.5 PARTS PER MILLION PER *C AND BEING PRESENT IN A QUANTITY APPROXIMATING THE AMOUNT THEREOF REQUIRED TO RAISE THE AVERAGE THERMAL EXPANSION COEFFICIENT TO A VALUE WITHIN THE TEC RANGE COMMON TO CERAMIC MATERIALS, AND THE ORGANIC BINDER BEING PRESENT IN A PROPORTION OF THE ORDER OF MAGNITUDE OF 6% BY WEIGHT, IN WHICH, FURTHER, SAID GLASS CONSISTS ESSENTIALLY OF BETWEEN 35 AND 65% BY WEIGHT OF SILICON DIOXIDE, BETWEEN 20 AND 55% BY WEIGHT OF BORIC OXIDE, AND BETWEEN 0.5 AND 10% BY WEIGHT OF LITHIUM OXIDE, HAVING AN AGGREAGATE SODIUM OXIDE AND POTASSIUM OXIDE CONTENT, IF ANY, NOT EXCEEDING 2% BY WEIGHT, WITH OR WITHOUT ONE OR MORE OF THE FOLLOWING CONSTITUENTS IN THE FOLLOWING RANGES OF PERCENTAGES BY WEIGHT:

Claim 5

A method of manufacturing a composition resistor suitable for incorporation in a spark plug from materials consisting essentially of carbon black in a proportion between 0.3 and 2.5% by weight, a lithium or lithium-alkaline-earth borosilicate glass in which the aggregate content of sodium oxide and potassium oxiDe does not exceed 2% by weight of the glass, said glass constituting the major portion of the composition, a metal oxide filler having a thermal expansion coefficient in excess of 5.5 parts per million per *C present in a quantity approximating the amount thereof required to raise the average thermal expansion coefficient of the mixture to a value within the TEC range common to ceramic materials, and an organic binder constituting approximately 6% by weight of the materials, said method comprising the steps of: pre-grinding the entire carbon black component of the composition, with a portion amounting to from between 20 and 35% of the remaining portion of the aforesaid materials not including, however, any of the organic binder, including at least 2% by weight of the total amount of glass to be used, wetting the portion of the glass not pre-ground in the previous step with an aqueous solution or emulsion of the organic binder said binder being selected from the group consisting of dextrin, methyl cellulose, polyvinyl alcohol, polyvinyl acetate and wax and mixtures of at least two of the foregoing, and mixing and stirring the pre-ground mixture with the rest of the aforesaid materials including the glass wetted as aforesaid; and filling molds or containers for resistors with the resulting material and fusing the contents by heat.

Claim 6

A method of manufacturing a composition resistor suitable for incorporation in a spark plug from materials consisting essentially of carbon black in a proportion between 0.3 and 2.5% by weight, a lithium or lithium-alkaline-earth borosilicate glass in which the aggregate content of sodium oxide and potassium oxiDe does not exceed 2% by weight of the glass, said glass constituting the major portion of the composition, a metal oxide filler having a thermal expansion coefficient in excess of 5.5 parts per million per *C present in a quantity approximating the amount thereof required to raise the average thermal expansion coefficient of the mixture to a value within the TEC range common to ceramic materials, and an organic binder constituting approximately 6% by weight of the materials, said method comprising the steps of: pre-grinding the entire carbon black component of the composition, with a portion amounting to from between 20 and 35% of the remaining portion of the aforesaid materials not including, however, any of the organic binder, including at least 2% by weight of the total amount of glass to be used, wetting the portion of the glass not pre-ground in the previous step with an aqueous solution or emulsion of the organic binder said binder being selected from the group consisting of dextrin, methyl cellulose, polyvinyl alcohol, polyvinyl acetate and wax and mixtures of at least two of the foregoing, and mixing and stirring the pre-ground mixture with the rest of the aforesaid materials including the glass wetted as aforesaid; and filling molds or containers for resistors with the resulting material and fusing the contents by heat.

Claim 7

A method of preparing material for the manufacture of composition resistors suitable for use in spark plugs from starting materials consisting essentially of carbon black in a proportion between 0.3 and 2.5% by weight, a lithium or lithium-alkaline-earth borosilicate glass in which the aggregate content of sodium oxide and potassium oxide does not exceed 2% by weight of the glass, said glass constituting the major portion of the composition, a metal oxide filler having a thermal expansion coefficient in excess of 5.5 parts per million per *C present in a quantity approximating the amount thereof required to raise the average thermal expansion coefficient of the mixture to a value within the TEC range common to ceramic materials, and an organic binder constituting approximately 6% by weight of the materials, said method consisting essentially of the steps of: grinding together all of the carbon black and between 20 and 35% of the other starting materials except the organic binder; mixing a water dispersion of the binder, said binder being a material selected from the group consisting of dextrin, methyl cellulose, polyvinyl alcohol, polyvinyl acetate and wax and mixtures of at least two of the foregoing, to form a pasty mass; drying the resulting material and granulating it in a granulator to form pourable granules of material.

Claim 8

A method of preparing material for the manufacture of composition resistors suitable for use in spark plugs from starting materials consisting essentially of carbon black in a proportion between 0.3 and 2.5% by weight, a lithium or lithium-alkaline-earth borosilicate glass in which the aggregate content of sodium oxide and potassium oxide does not exceed 2% by weight of the glass, said glass constituting the major portion of the composition, a metal oxide filler having a thermal expansion coefficient in excess of 5.5 parts per million per *C present in a quantity approximating the amount thereof required to raise the average thermal expansion coefficient of the mixture to a value within the TEC range common to ceramic materials, and an organic binder constituting approximately 6% by weight of the materials, said method consisting essentially of the steps of: grinding together all of the carbon black and between 20 and 35% of the other starting materials except the organic binder; mixing a water dispersion of the binder, said binder being a material selected from the group consisting of dextrin, methyl cellulose, polyvinyl alcohol, polyvinyl acetate and wax and mixtures of at least two of the foregoing, to form a pasty mass; drying the resulting material and granulating it in a granulator to form pourable granules of material.