Hollow thermoplastic products with internally opening grooves - inject and blow mould design ensures constant wall thickness

摘要

Hollow objects of synthetic thermoplastic material are produced by injection/blow moulding with an inwardly opening groove forming a projection on their outer surfaces. After injection and the cooling off of the material to a point at which it can still be deformed, a first plunger sleeve retracts axially to leave a cavity of the width and height of the circumferential groove. This motion generates the axial displacement in the opposite direction a second plunger against the outer face of the plastic container, and simultaneously admits the medium for expanding the vessel wall into the moulding groove. The circumference of the moulding arbor, at each side of the ports for the pressure medium, may have recesses machine to assist in providing extra material for the groove wall. Forms a circular rib, opening internally, without any weakening of the wall thickness. The forced reinforcement ensures a wall thickness in the zone of the groove at least equal to the original.