| 摘要 |
A longitudinal, welded, seam is formed in a tube of flexible material by arranging a flexible strip tube-wise with overlapping longitudinal edges about a shaping mandrel and covering the strip into the working range of heat-welders which operate such that the welding heat is confined within the overlapping zones of the shaped strips. The welders are pref. H. F. welders, the strip being conveyed stepwise i.e. intermittently, towards them. The strip is pref. of plastics material. Two seams, spaced, from and parallel to, each other are formed so that the longitudinally extending pocket results in the region of overlap. |
