| 摘要 |
A body sleeve (4) obtained by widening of a pipe is arranged on a mandrel on which spaced spirals (7) of a resistance wire (6) are wound. By heating the body sleeve (4), it is fixed onto the winding. An electric current circulating in the resistance wire causes the thermoplastic to melt and flow around the spirals for enclosing the latter completely by expansion. Further, the material forms projecting sections (8, 9) next to the winding. Hence, the spirals (7) are protected against accidentals shocks and the recessed end parts (5) of the inner wall which have been deformed inwards during manufacture require no further forming. |
