| 摘要 |
<p>PURPOSE:To prevent cracks of a glass tube by always keeping a gap between the glass tube end and the large diameter part of each electrode by a method wherein the the side surface of the large diameter part of each electrode on the glass tube side is provided with a plurality of projections coming into contact with the glass tube end with small areas. CONSTITUTION:Metallic wires, produced by coating Fe-Ni alloys easy of fitting to glass with Cu, processed by heating are used for a pair of electrodes 21a, 21b of the titled device. The side-end surfaces of electrode large diameter parts 22a, 22b corresponding to the projecting direction of small diameter projections 23a, 23b of these electrodes 21a, 21b are provided with four conical small projections 24a-24d and 25a-25d, respectively. These small projections 24a-24d, 25a-25d are integrally formed with an electrode-forming die provided with recesses corresponding to the projections shapes. Then, the cracks of the glass tube 26 are prevented by always keeping a gap between the end of the glass tube 26 and each of the electrode large diameter parts 22a, 22b.</p> |
