Impact extrusion process for making collapsible tubes and preform for use therein

Claim 1

IN A PROCESS OF IMPACT EXTRUDING A SOLID POLYMER OF AN OLEFIN HAVING 2 TO 3 CARBON ATOMS TO FORM A HOLLOW TUBE HAVING A HEAD OF REDUCING INTERNAL DIAMETER AND WITH REDUCED TENDENCY TO STRESS CRACK THE IMPROVEMENT COMPRISING IMPACTING A PLUNGER ON A DISC SHAPED BLANK OF A SOLID POLYMER OF AN OLEFIN HAVING 2 TO 3 CARBON ATOMS, SAID DISC-SHAPED BLANK HAVING TOP, MIDDLE AND BOTTOM PORTIONS AND AN OUTER WALL AND AN INNER WALL, SAID INNER WALL DEFINING A CENTRAL CAVITY EXTENDING THROUGH SAID DISCSHAPED BLANK, SAID OUTER WALL AND SAID INNER WALL BLENDING INWARDLY AT THE BOTTOMS THEREOF TO FORM SAID BOTTOM PORTION OF THE DISC-SHAPED BLANK OF DECREASING THICKNESS AS COMPARED WITH SAID MIDDLE PORTION.