| 摘要 |
The invention relates to a device for manufacturing a preform, wherein a carrier tube is collapsed to a preform, which device comprises a heating element forming a cylindrical envelope, which envelope defines an annular inlet opening and an annular outlet opening at opposite ends of the envelope, a carrier tube being present within the cylindrical envelope, between said openings, the heating element being movable in axial direction with respect to the carrier tube, and means for supplying a non-oxidizing gas to the space between the carrier tube and the envelope.
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