| 摘要 |
PURPOSE:To obtain a U-shaped glass tube having a uniform thickness by directly joining two glass tubes to each other with a communicating hole in-between, softening the open ends of the tubes on the communicating hole side by heating, and blocking the ends by pinching so that a glass gob is not produced at the blocked part. CONSTITUTION:Glass tubes 1, 1 are arranged parallel to each other and held by a holder 5. The inner joining parts of the tubes 1, 1 are locally melted by jetting flames from burners 6, 6 so that the flames confront each other and a communicating hole 12 is made by the pressure of air. The open ends of the tubes 1, 1 on the communicating hole side are softened by heating with burners 8, crushed and blocked by a pincher head 15 to form a linear thick part 16 meeting at right angles to the axes of the tubes 1, 1. The thick part 16 is softened by reheating 8 and a split forming die 9 having an inner U-shaped groove 91 is brought into contact with the softened part 16. At the same time, air is blown from the other open ends of the tubs 1, 1 to swell the softened part 16 and its periphery until they are brought into close contact with the inside of the groove 91. Thus, a U-shaped glass tube is formed.
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