Patent ID: 8226867

Claim:
A method for the production of caps having a heat shrinkable skirt comprising: (a) extruding a thermoplastic material to form a tube having a first diameter D 0 , a first thickness E 0 , and a first cross-sectional area S 0 ; (b) drawing the tube in an axial direction, the axially drawn tube having a second diameter D 1 less than the first diameter D 0 , a second thickness E 1 less than the first thickness E 0 , and a second cross-sectional area S 1 , the ratio of the first cross-sectional area to the second cross-sectional area between about 2 and 10; (c) providing a cooling assembly and cooling the drawn tube in the cooling assembly; (d) providing a radial expansion assembly having an annular vacuum chamber and increasing the diameter of the drawn tube in the radial expansion chamber to form a radially-expanded tube having a third diameter D 2 greater than the first and second diameters; (e) passing the radially-expanded tube through an axial tension assembly; (f) segmenting the radially-expanded tube into portions of desired length; (g) forming a cap blank by heat shrinking one of the portion on a mandrel; and (h) providing a head on the cap blank to form a cap having a head and a skirt.