Title: Hydraulic drive for the die closing unit of an injection molding machine

Abstract: A hydraulic drive for the die closing unit of an injection molding machine in which at least one power cylinder and power piston with a coaxially attached auxiliary cylinder opens and closes the molding die by executing the opening and closing travel with a differential piston action in the power cylinder and/or with the auxiliary cylinder, while valve-closable bypass channels in the power piston are kept open. The closing of these channels switches the drive from an accelerated travel mode to a high-pressure die clamping mode. An annular valve plunger cooperates with a valve seat on the power piston to open and close the bypass channels, several alternatives of guiding and hydraulically moving the valve plunger being contemplated.

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Inventors: Hehl, Karl (7291 Lossburg, DT)

Application Number: 546036
Filing Date: 1975-01-31
Publication_date: 1976-02-03
Assignee:
Primary Class(es): 91/517 91/519, 92/146, 425/451.2, 425/590
Other Classes:
US Patent Ref:

3340756	Sep, 1967	Mize	91/411.
3663140	May, 1972	Hehl	425/154.

Other Refs:
Primary Examiner: Geoghegan, Edgar W.
Assistant Examiner:
Attorney: Geiger; Joseph A.