Method for production of a hollow body by extrusion and blowing of a thermoplastic resin
AssigneeEurofeu Societe Anonyme
InventorMichel Lahouati
Life of this patent
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Abstract
A method for production of a hollow body by extrusion and blowing of a thermoplastic resin, includes the steps of filling a quantity of resin into an accumulator (1) which has an accumulation chamber (12) with an open end, placing a blowing mould (24) with an internal cavity (36) and a constricting section (37) in communication with the open end, axially displacing a core (10, 11) across the constriction point of the internal cavity such as to cover a projecting part of the core with a layer of resin (38), continuing the axial displacement of the core in the internal cavity (36) to axially extend the layer of resin (38) and applying a fluid pressure to the internal surface of the resin layer through the core to obtain a hollow body.
Claims15
A method of manufacturing a biaxially oriented hollow body (50) by the extrusion blow molding of a thermoplastic resin, comprising the steps consisting in:
- bringing said resin (35) into a malleable state;
- filling an accumulator (1) with a predetermined quantity of said resin, said accumulator comprising an accumulation chamber (12) defined between a central core (7) and an outer wall (3) having an end opening (6);
- regulating the temperature of the resin in said accumulator from both faces of the accumulation chamber;
- placing (22) a blowing mold (24) with an internal cavity (36) having an open constriction (37) in communication with said end opening;
- axially displacing (32) a moveable mandrel (10, 11) from said central core through said accumulation chamber, said end opening and said constriction of the internal cavity, so as to coat a portion of the mandrel projecting from said central core with a layer of resin (38);
- continuing (32) the axial displacement of the moveable mandrel in said internal cavity (36) at least as far as an intermediate level between said open constriction and an opposite end wall (42) of said internal cavity, simultaneously pushing (30) said predetermined quantity of resin out of said accumulation chamber with an output speed that is lower than the displacement speed of the mandrel, in order to stretch said layer of resin (38) axially;
- applying (43) fluid pressure to said inner surface of the layer of resin through said mandrel in order to stretch said layer of resin transversely as far as the walls of said internal cavity and obtain a biaxially oriented hollow body (50) having a neck corresponding to the constriction of the internal cavity;
- and
- letting said hollow body cool (47) down to a rigid state, retracting (45) said mandrel and ejecting (49) said hollow body from the blowing mold.
Dependencies are inferred from the claim text.