| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for forming a hollow cylinder in a glass tube of a large diameter having high dimension stability.SOLUTION: A hollow cylinder 2 having an outer diameter Dis formed from glass, and the hollow cylinder 2 is softened in a part of a heating region which moves at a relative supply speed Va, while rotating the hollow cylinder 2 around a rotation shaft 6. The softened part is expanded in a diameter direction under action of centrifugal force and/or inner pressure applied in the hollow of the hollow cylinder so that a deformation region 30 is formed, and a tube having an outer diameter Dlarger than an outer diameter Dof the hollow cylinder is contiguously molded, in the method. Expansion of the softened part in the diameter direction is at an expansion speed Vr in the diameter direction depending on a position, and a profile of the expansion speed in the diameter direction along a deformation region 30 has a maximum value Vr,max which is less than twice of a supply speed Va.SELECTED DRAWING: Figure 3 |
