Method of manufacturing lamp and quartz bulb

A method of manufacturing a lamp including a quartz bulb having a chamber formed as a light emitting portion to a longitudinally intermediate portion of the quartz tube and straight tubular sealing portions formed on both ends thereof, in which electrode mounts are inserted from the openings of both ends and the sealing portions are sealed in a state of keeping the inside at a negative pressure, wherein the method includes;

• a) forming a positioning step to the quartz bulb by welding an extension tube having an inner diameter larger than the inner diameter of an opening to at least one of the openings of a body tube where the light emitting portion and the sealing portion are formed, and forming a positioning engagement portion to the electrode mount at a position spaced by a predetermined length from the top end of the electrode,
• b) inserting the electrode mount from the opening on the side formed with the step in a state of sealing the opening on the side opposite to that formed with the positioning step, and temporarily sealing the opening while maintaining the inside at a negative pressure,
• c) standing the quartz bulb and engaging the positioning engagement portion of the electrode mount to the positioning step and, in this state, sealing the sealing portion while transiting a portion to be heated from the light emitting portion to the upper opening of the body tube, and thereby sealing the electrode mount and then
• d) cutting the ends of the quartz bulb containing the electrode mounts sealed therein, thereby removing respective extension tubes to form the quartz bulb to a predetermined length.