Patent ID: 7479049
Filing Date: 2009-01-20
Classification: C03B,H01J,Y02P

Abstract:
1. A manufacturing method of an arc tube including a flat-spiral glass tube, the flat-spiral glass tube being made up of: a central portion; a first end portion; a second end portion; a first flat-spiral portion formed between the central portion and the first end portion; and a second flat-spiral portion formed between the central portion and the second end portion, the flat-spiral glass tube being made of a glass tube including a central-portion scheduled portion, a first-end-portion scheduled portion, a second-end-portion scheduled portion, a first-flat-spiral-portion scheduled portion, and a second-flat-spiral-portion scheduled portion, the manufacturing method comprising: a first step of forming the glass tube into a substantially circular cone shape, by holding the central-portion scheduled portion of the glass tube in softened state to a vertex of a jig having a substantially circular cone shape, and winding to a conical surface of the jig at least the first-flat-spiral-portion scheduled portion and the second-flat-spiral-portion scheduled portion; a second step of flattening the glass tube formed in the substantially circular cone shape into a substantially disc shape so that part of a tubular axis of the glass tube, which corresponds to the first-flat-spiral-portion scheduled portion and the second-flat-spiral-portion scheduled portion, is substantially included in a plane; a third step of, after the second step, providing the first end portion and the second end portion with a corresponding electrode; and a fourth step of, after the third step, a) bending a portion of the first flat-spiral portion including the first end portion so that the first end portion approaches the second flat-spiral portion, and b) bending a portion of the second flat-spiral portion including the second end portion so that the second end portion approaches the first flat-spiral portion, wherein a distance Gb a distance Ge after the fourth step, a distance Ge