Patent ID: 7618571

Claim:
An extrusion head for blow moulding of hollow bodies comprising: a) a body defining within it a substantially cylindrical chamber; b) a force plug having a substantially cylindrical shape and set axially within said cylindrical chamber of the body so as to define a cylindrical gap between the outer side surface of the force plug and the inner side surface of the body, through which the molten plastic material fed by an extruder can flow; c) a die opening set at the bottom end of the body; and d) a bottom part of the force plug set within said die opening so as to define an annular gap communicating with said cylindrical gap for exit of the tubular parison from said extrusion head, e) said extrusion head further comprising: i) a plunger supporting at the bottom an ovalizing insert having a substantially annular shape and comprising an asymmetrical bottom edge presenting portions with convex profile and portions with concave profile, said plunger being slidably mounted axially within a chamber formed in said bottom part of the force plug and open downwards, so that said plunger can pass from a retracted, resting, position, in which the bottom edge of the ovalizing insert is within said chamber of the bottom part of the force plug, to an extracted, working, position, in which the bottom edge of said ovalizing insert projects at the bottom with respect to the bottom edge of said bottom part of the force plug.