Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1979-07-02
1981-09-15
Pavelko, Thomas P.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
26432816, 264335, 425437, 425556, B29F 114
Patent
active
042897262
ABSTRACT:
Straight walled hollow containers may be molded without taper, according to the present invention. Two mold halves, when brought together define a cavity configured to the outer wall of a hollow plastic container to be injection molded, and also an opening at one end of the cavity to enclose the stem of a core defining the inner wall of the hollow plastic container. When the core is disposed in the cavity, it is centered within the latter. Thereby a space is provied between the inner walls of the mold halves and the outer wall of the core to receive plastic material injected under high pressure through a sprue, also defined by the inner walls of the mold halves. After injection, the plastic is cooled to just below the softening point of the plastic. At this point separation of the mold halves surrounding the outer portion of the core, is commenced and a force is applied to initiate withdrawal of the core from between the mold halves. Simultaneously therewith, air under pressure is injected into the space between the innermost end of the core within the cavity and the adjacent end of the cavity. Thereby, the air under pressure is forced between the core and the surrounding soft molded plastic to act as a bearing or lubricant to enable the core to be completely withdrawn from the cavity without damaging the molded container.
REFERENCES:
patent: 2361026 (1944-10-01), Greene
patent: 2568129 (1951-09-01), Morris
patent: 3183292 (1965-05-01), Dvoracek
patent: 3475786 (1969-11-01), Pearson
patent: 4080147 (1978-03-01), Dumortier
patent: 4187271 (1980-02-01), Rolston
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