| 摘要 |
The known mode of operation, in which a non-circular hollow profile strand in the thermoplastic state is stretched in the transverse direction with the aid of a pressurised gas enclosed in the hollow space (10) of the hollow profile strand (8), during passage through a calibrating device (13-20) the free cross-section of which increases in the direction of travel of the strand in the extent of the desired stretching, is improved according to the invention in that a lubricant (24) of at least 5000 cP is introduced between the hollow profile strand and the inner wall of the calibrating device under operating conditions. A uniform sliding of the strand in the calibrating device is thereby ensured. In addition, the strand can be simultaneously stretched in the longitudinal direction by taking it off, by means of a take-off device (31/32), from the calibrating device at a higher rate than it enters the calibrating device. After it has achieved a final cross-section, the hollow profile strand is cooled to below the softening temperature. <IMAGE> |
