Patent ID: 6799367
Filing Date: 2004-10-05
Classification: H01T,Y10T

Abstract:
The method for manufacturing a spark plug which has a center electrode and a ground electrode to cause a spark discharge and has an electric resistor interposed between the center electrode and a stem equipped with a terminal, said manufacturing method comprising:stuffing an electric resistive powder material in an inner hollow space of each insulator into which said center electrode and said stem are installed; mounting a plurality of insulators each accommodating said electric resistive powder material on a tray; conveying said tray carrying said plurality of insulators into a furnace; thermally processing all of said plurality of insulators mounted on said tray in said furnace; conveying said tray mounting said thermally processed plurality of insulators out of said furnace through an opening of said furnace; and inserting said stem in said inner hollow space of each insulator, wherein a windbreak is provided at a predetermined side of said tray that is close to said opening of said furnace when the tray is placed in said furnace, thereby preventing said thermally processed plurality of insulators from being directly cooled by the flow of air entering via said opening into said furnace, and said windbreak shields thermally processed plurality of insulators located close to said opening of said furnace at least at a portion thereof corresponding to said electric resistor from the flow of air entering into said furnace via said opening, thereby preventing the thermally processed insulators located close to said opening from being unevenly cooled by the air entering into said furnace via said opening when said tray mounting said thermally processed plurality of insulators are conveyed out of said furnace.