Apparatus for injection and compression molding

A horizontal injection and compression molding apparatus having a compression molding device and an injection device, said compression molding device comprising:

• a stationary die plate holding a stationary die arranged vertically,
• a movable die plate holding a movable die, whereby a mold cavity is defined by the stationary die and the movable die,
• means for rapidly extending and retracting the movable die in a generally horizontal direction relative to the stationary die to cause the movable die plate to reach a predetermined position while approaching the stationary die plate, the movable die being separated from the stationary die by a predetermined distance when the movable die plate is at said predetermined position so that the mold cavity is open to atmospheric pressure,
• at least one tie bar,
• means for locking the movable die plate to the at least one tie bar at a position where the movable die has approached the stationary die, and
• die fastening means for fastening the dies while the movable die plate is locked to the at least one tie bar;
• and
• wherein said injection device comprises:
• a heating cylinder having a molten resin outlet,
• a flow control valve connected to the molten resin outlet of the heating cylinder, and
• a control device for (a) opening the flow control valve, after the movable die plate has approached the stationary die plate sufficiently so as to be at least substantially at said predetermined position, so as to initiate the feeding of the molten plastic material from the heating cylinder into the mold cavity when the stationary die and the movable die are separated from each other by at least substantially said predetermined distance and the mold cavity is open to atmospheric pressure, whereby the molten plastic material can be injected into the mold cavity at a low injection pressure, (b) determining when a predetermined quantity of molten plastic material has been fed into the mold cavity open to atmospheric pressure, (c) moving the movable die plate from said predetermined position towards the stationary die plate after said predetermined quantity of molten plastic material has been fed into the mold cavity open to atmospheric pressure, to thereby compress the molten plastic material in the mold cavity, and (d) actuating said flow control valve to its closed position when the mass of molten plastic material injected into the mold cavity is equal to that of an article to be molded.

A horizontal injection and compression molding apparatus comprising:

• a stationary die plate holding a stationary die arranged vertically,
• a movable die plate holding a movable die, whereby a mold cavity is defined by the stationary die and the movable die,
• means for rapidly extending and retracting the movable die in a generally horizontal direction relative to the stationary die to cause the movable die plate to reach a predetermined position while approaching the stationary die plate, the movable die being separated from the stationary die by a predetermined distance when the movable die plate is at said predetermined position so that the mold cavity is open to atmospheric pressure,
• at least one tie bar,
• means for locking the movable die plate to the at least one tie bar at a position where the movable die has approached the stationary die,
• die fastening means for fastening the dies while the movable die plate is locked to the at least one tie bar,
• a distance sensor for detecting a distance between the movable die plate and the stationary die plate and providing a signal representative thereof,
• a heating cylinder having a molten resin outlet,
• a flow control valve connected to the molten resin outlet of the heating cylinder, and
• a control device for (a) opening the flow control valve in response to a signal from the distance sensor indicating that the movable die plate has approached the stationary die plate so that the movable die and the stationary die are separated from each other by said predetermined distance, so as to initiate the feeding of the molten plastic material from the heating cylinder to the mold cavity when the stationary die and the movable die are separated from each other by at least substantially said predetermined distance and the mold cavity is open to atmospheric pressure, whereby the molten plastic material can be injected into the mold cavity at a low injection pressure, (b) determining when the mass of molten plastic material injected into the mold cavity is equal to that of an article to be molded, and (c) actuating said flow control valve to its closed position when the mass of molten plastic material injected into the mold cavity is equal to that of an article to be molded.