Process for the manufacture of hollow articles from thermoplastic resin blanks by cold extrusion

Claim 1

A PROCESS FOR THE MANUFACTURE OF HOLLOW ARTICLES OF A SYNTHETIC RESIN OF THE CLASS CONSISTING OF POLYVINYL AND POLYETHYLENE RESINS BY COLD EXTRUSION STARTING FROM DISCSHAPED BLANKS, COMPRISING INSERTING A DISC BETWEEN TWO OPPOSITELY LYING CO-AXIAL PLUNGERS HAVING DIFFERENT DIAMETERS AND SLIDABLY MOUNTED IN A PAIR OR CORRESPONDING CYLINDERS FIRMLY ATTACHED TOGETHER AND FORMING AN ANNULAS STEP AT THEIR MEETING PLANE; SAID CYLINDERS BEING SLIDABLY TOGETHER IN THE DIRECTION OF THE SMALLER DIAMETER PLUNGER; EXERCISING A PRESSURE, ON THE SMALLER DIAMETER PLUNGER, WHICH IS SUFFICIENT TO SQUEEZE SAID MATERIAL AND CAUSE IT TO FLOW RADIALLY, WHILE IN A SOLIF CONDITION, AND REACT IN AXIAL DIRECTION AGAINST SAID ANNULAR STEP, WHEREBY SAID CYLINDERS ARE SHIFTED BY THE PRESSURE OF THE SQUEEZED MATERIAL IN THE DIRECTION OF SAID SMALLER DIAMETER PLUNGER BY THE SQUEEZED MATERIAL WHICH THUS FILLS AN ANNULAR SPACE FORMED AS A CONSEQUENCE OF SAID SHIFTING BETWEEN THAT PART OF THE LAST NAMED PLUNGER WHICH COMES TO LIE INSIDE SAID LARGER DIAMETER CYLINDER AND THE CORRESPONDING WIDER BORE END OF SAID CYLINDER, THE HOLLOW, ARTICLE THUS PRODUCED BEING CONSTITUTED BY THE SYNTHETIC RESIN FILLING SAID ANNULAR GAP AND THE SPACE BETWEEN THE TWO PLUNGER ENDS.