Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means between charger and mold to cut off flow of...
Reexamination Certificate
1999-01-20
2001-02-06
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means between charger and mold to cut off flow of...
C425S566000
Reexamination Certificate
active
06183239
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an injection molding apparatus, and more particularly, to an injection molding machine valve gate nozzle having a reciprocal valve pin cyclically movable between valve gate opening and closed positions for controlling the flow of fluid material to a mold cavity.
BACKGROUND OF THE INVENTION
Nozzles commonly are employed in plastic injection molding machines for heating and directing the flow stream, such as molten plastic, through a gate into a mold cavity while maintaining the flow stream at the proper elevated temperature. Nozzles, sometimes referred to as valve gate nozzles, are known which each include a valve pin movable by an actuator for opening and closing the valve gate at the nozzle tip during each cycle of the molding operation Such valve gate nozzles may be employed in single cavity molds, or alternatively, a series of nozzles may be used in multiple cavity molds. The valve pin actuating means for such valve gate nozzles heretofore have been relatively complicated in design and problem prone in operation. They also often are mechanically inefficient and do not permit precision control of valve pin movement.
Since the plastic injection mold apparatus typically is operated at temperatures in the range of 500-700° F., the valve pin actuator cannot contain lubricant, which may leak and contaminate the flow stream. As a result, relative movement of the actuator parts causes wear and erosion over time, which can effect the shut-off position of the valve pin. Periodically it is necessary to recalibrate the position of the valve pin and/or replace the valve pin and actuator, which may require substantial disassembly of the mold apparatus.
Existing valve gate nozzles, furthermore, channel the flow of the melt stream along the valve pin, which can create a build up about the valve pin and impede reliable operating movement. Because of the high operating temperatures, the nozzles and the mold plates incur temperature expansion and contraction, which also can result in undesirable leakage and contamination about the nozzle. In the event of malfunction or leakage, the manifold must be, disassembled, which can cause costly interruptions in mold operation. Repairs to the valve gate nozzles and their actuators also can be time consuming and expensive.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a plastic injection molding apparatus having valve gate nozzles adapted for more efficient and reliable operation.
Another object is to provide a valve gate nozzle as characterized above which has an actuating mechanism that is mechanically efficient and enables precision control of valve pin movement.
A further object is to provide a valve gate nozzle of the foregoing type that is less susceptible to leakage and wear. A related object is to provide a valve gate nozzle that defines a sealed unit adapted to compensate for heat expansion and contraction without leakage.
Still another object is to provide such a valve gate nozzle in which the valve pin can be easily and accurately calibrated to accommodate for wear from a location external to the mold apparatus.
Yet a further object is to provide a valve gate nozzle that is designed for substantially zero maintenance.
Another object is to provide a valve gate nozzle of the above kind which permits easy replacement of the valve pin and/or valve pin actuator without substantial disassembly of the molding machine.
Still another object is to provide a valve gate nozzle in which the movable valve pin is less susceptible to undesirable build up or contamination from the flow stream. A related object is to provide such a valve gate nozzle in which the valve pin is substantially separated from the fluid flow stream.
Another object is to provide a valve gate nozzle of the above type which has a standardized design that permits its usage in single or multiple cavity molding machines without alteration.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
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Fast Heat Inc.
Heitbrink Tim
Leydig , Voit & Mayer, Ltd.
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