Manifold system having flow control using extended valve pin

Details Manifold system having flow control using extended valve pin Manifold system having flow control using extended valve pin

2000-01-05

2001-07-03

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...

C425S564000, C425S570000

Reexamination Certificate

active

06254377

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to injection of pressurized materials through a manifold, such as injection molding of plastic melt in a hot runner system. More specifically, this invention relates to an improved injection molding hot runner system in which the rate of melt flow is controlled through the gate during an injection molding cycle.
DESCRIPTION OF THE RELATED ART
U.S. Pat. No. 5,556,582 discloses a multi-gate single cavity system in which the rate of melt flow through the individual gates is controlled independently via a control system according to specific target process conditions. This system enables the weld line of the part (the section of the part in which the melt from one gate meets the melt from another gate) to be selectively located. It also enables the shape of the weld line to be altered to form a stronger bond.
The '582 patent discloses controlling the rate of melt flow with a tapered valve pin at the gate to the mold cavity. It also discloses placing a pressure transducer inside the mold cavity. Placing the pressure transducer inside the mold cavity can result in the pressure transducer sensing pressure spikes which can occur when the valve pin is closed. A pressure spike sensed by the transducer can cause an unintended response from the control system, and result in a less precise control of the melt flow than desired.
The control system disclosed in the '582 patent uses the variables of valve pin position and cavity pressure to determine what position the valve pin should be in. Thus, the algorithm performed by the control system in the '582 patent utilizes two variables to control the rate of melt flow into the cavity.
SUMMARY OF THE INVENTION
An injection molding apparatus is provided in which the rate of material flow during the injection cycle is controlled. According to one preferred embodiment, an injection molding apparatus is provided that includes a manifold having an inlet for receiving material from an injection molding machine, at least one injection nozzle coupled to the manifold, an actuator, and a valve pin adapted to reciprocate through the manifold and the injection nozzle, the valve pin having a first end coupled to the actuator, a second end that closes the gate in a forward position, and a control surface intermediate said first and second ends for adjusting a rate of material flow during an injection cycle.


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