| 摘要 |
A strip is folded longitudinally around a tube to, thereby, establish an assembly of an inner and a concentric outer tube; individual slotted foam strips are placed in transverse orientation onto the strip just prior to folding; they will become spacers with V-shaped notches. Just prior to closing the outer split tube, foam is introduced into the ring space between the tubes which will spread freely through the notches.
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