| 摘要 |
<p>Pyrex pipe having a profiled inner wall is made by moving the tube along its longitudinal axis and feeding it through a heating zone to soften it locally, during which the two parts of the pipe on either side of the softened part may have different speeds, these parts being rotated in relation to each other about the longitudinal axis, whilst in the tube at least one thread of equal length to that of the tube is produced.</p> |
