Process for the manufacture of low tension sparking plugs

Claim 1

A SPARK PLUG ASSEMBLY OF THE LOW VOLTAGE SURFACE DISCHARGE TYPE COMPRISING, A CENTER ELECTRODE, AN OUTER ELECTRODE COAXIAL WITH THE CENTER ELECTRODE AND SPACED THEREFROM FORMING AN ANNULAR SPACE BETWEEN BOTH ELECTRODES, THE ELECTRODES HAVING CO-PLANAR DISCHARGE END FACES, A SOLID MASS OF ELECTRICALLY NON-CONDUCTIVE SEALING MATERIAL DISPOSED BETWEEN SAID FACES SURROUNDING THE CENTER ELECTRODE AND COMPLETELY FILLING THE SPACE BETWEEN THE CENTER AND OUTER ELECRODE TO FORM A DISCHARGE SURFACE BETWEEN SAID END FACES PRODUCED BY HEATING A COMPOSITION OF COMPACTED PULVERULENT MATERIAL IN AN INERT ATMOSPHERE SUFFICIENTLY TO MELT IT ANS SUBSEQUENTLY COOLING IT, SOLID MASS CONSISTING OF LEAD OXIDE WHICH COMPRISES SUBSTANTIALLY FROM 50 TO 90 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, AND AT LEAST ONE OTHER CONSTITUENT OF THE GROUP CONSISTING OF BORIC ANHYDRIDE WHICH COMPRISES SUBSTANTIALLY 5 TO 30 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, SILICA WHICH COMPRISES UP TO 20 PERCENT, BY WEIGHT OF THE SEALING MATERIAL, TITANIUM OXIDE WHICH COMPRISES UP TO 10 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, ALIMINA WHICH COMPRISES UP TO 20 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, ZINC OXIDE WHICH COMPRISES UP TO 10 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, AND ALKALINE OXIDES WHICH COMPRISE UP TO 2 PERCENT, BY WEIGHT, OF THE SEALING MATERIAL, AND THE AMOUNTS OF SAID LEAD OXIDE, BORIC ANHYDRIDE, SILICA TITANIUM OXIDE, ALUMINA, ZINC OXIDE, ALKALINE OXIDES TOTALING 100 PERCENT.