| 摘要 |
<p>A removable core 14 for a shrinkable tubular sheath 12 comprises a tubular wall 24 formed from a plurality of helically wrapped, overlapping, laminated layers of a continuous web 34 and a helical weakened line 56 in said wall. A method for producing such a removable core comprises extruding from a die 32 an advancing web 34 of heated plastic material; taking up said advancing web on a plurality of helically skewed forming rollers 44a-44e disposed within a cylindrical envelope; helically wrapping said advancing web around said forming rollers into a tube having a wall formed of a plurality of overlapping layers of said web while advancing said tube along said forming rollers; forming with the help of a pressure roller 48 a lamination bond between the layers of the web; forming with a knife blade 52 a weakened helical groove 56 in said wall; cooling said tube with an air jet 59; and cutting said tube into desired lengths. In alternate embodiments, the helical weakened line is formed by the extrusion die as a continuous, longitudinal notch in the web, or by a notching tool. <IMAGE></p> |
