Improved injection mold apparatus for the production of substantially cup-shaped and sleeve-shaped thermoplastic containers

Claim 1

An injection mold assembly for the production of molded articles, especially thin-walled cup-shaped or sleeve-shaped containers formed of thermoplastic material, comprising a female mold portion, a cooperating male mold portion including a longitudinally extending opening for receiving locking means therein, said locking means movably positioned within said longitudinally extending opening for selectively locking both of said mold portions when the injection mold assembly is closed, said movable locking means comprising a substantially ram-like locking element having an outer surface which engages the inner surface of said longitudinally extending opening to provide lateral support for said male mold portion, said female mold portion being provided with recess means for receiving said ramlike locking element, a double-acting piston and cylinder arrangement provided for said ram-like locking element in order to positively control said ram-like locking element in such a manner that during the entire initial phase of injection molding at which time the greatest injection molding pressure arises said ram-like locking element is displaced in axial direction into said recess means so as to lock both of said mold portions relative to one another and only during a subsequent phase during which the injection molding terminates at a lower injection molding pressure are said mold portions unlocked by axially displacing said ram-like locking element in a direction away from said recess means.