Milacron Inc.

Uniloy Milacron Usa, Inc.

Norman L Steffens

M Barr Klaus

A two-stage, electrically-powered injection unit for an injection molding machine includes an extruder for plasticating material, and a separate melt accumulator to receive the plasticated material. The accumulator includes an injection plunger that is slidably positioned to inject the plasticated material from the accumulator into a mold. The plunger is rotated and translated by an electrically-driven linear actuator, such as a roller screw mechanism. The plunger extends outwardly of the accumulator barrel at the commencement of an injection stroke and is peripherally supported by a bushing at the outer end of the accumulator barrel. The outwardly-extending portion of the plunger can also be supported by a movable intermediate support member to minimize lateral deflection of the plunger and enable a longer injection stroke to be employed. The injection pressure imposed upon the plasticated material can be varied from a relatively low initial injection pressure, to minimize lateral deflection of the plunger, to a relatively higher injection pressure as the length of the portion of the plunger that extends outwardly of the accumulator barrel decreases.

Method for electrically operated plastics injection

A two-stage, electrically-powered injection unit for an injection molding machine is disclosed. The injection unit includes an extruder for plasticating material, and a separate melt accumulator to receive the plasticated material. The accumulator includes an injection plunger that is slidably positioned to inject the plasticated material from the accumulator into a mold. The plunger is rotated and translated by an electrically-driven linear actuator, such as a roller screw mechanism. The plunger extends outwardly of the accumulator barrel at the commencement of an injection stroke and is peripherally supported by a bushing at the outer end of the accumulator barrel. The outwardly-extending portion of the plunger can also be supported by a movable intermediate support member to minimize lateral deflection of the plunger and enable a longer injection stroke to be employed. The injection pressure imposed upon the plasticated material can be varied from a relatively low initial injection pressure, to minimize plunger lateral deflection, to a relatively higher injection pressure as the length of the portion of the plunger that extends outwardly of the accumulator barrel decreases.

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Loveland, OH, United States of America

Norman L Steffens