Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Feed control of material en route to shaping area
Reexamination Certificate
2003-01-31
2004-08-03
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Feed control of material en route to shaping area
C425S149000
Reexamination Certificate
active
06769896
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 and method are provided in which the rate of material flow during an injection cycle is controlled. According to one preferred embodiment, an injection molding apparatus is provided that includes a manifold, 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 has 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 the rate of material flow during an injection cycle. Retracting the valve pin tends to decrease the rate of material flow during the injection cycle and displacing the valve pin toward the gate tends to increase the rate of material flow during the injection cycle.
According to another preferred embodiment, in an injection molding system having a manifold for injecting material into first and second mold cavities, respectively, and a controller for controlling the flow rate of material injected into the first and second mold cavities during an injection cycle according to first and second target profiles, respectively, wherein the first and second target profiles represent a desired value of first and second sensed conditions related to the flow rate of material injected into the first and second cavities during an injection cycle, respectively, a method is provided for creating at least the first target profile for the first mold cavity. The method includes the steps of shutting off a flow of material into the second cavity, and injecting material into the first cavity to determine what values of the first sensed condition produce an acceptable molded part in the first cavity, the values of the first sensed condition that produce an acceptable molded part constituting the first target profile.
According to another preferred embodiment, in an injection molding system having a manifold for injecting material into first and second mold cavities, respectively, and a controller for controlling the flow rate of material injected into the first and second mold cavities according to first and second target profiles, respectively, wherein each target profile represents a desired value of first and second sensed conditions related to the flow rate of material injected into the first and second cavities during an injection cycle, respectively, a method is provided for creating the first and second target profiles. The method includes the step of simultaneously injecting material into the first and second cavities; and based on the simultaneous injection of material, determining what values of the first sensed condition produce an acceptable molded part in the first mold cavity, the values of the first sensed condition that produce an acceptable molded part constituting the first target profile, and determining what values of the second sensed condition produce an acceptable molded part in the second mold cavity, the values of the second sensed condition that produce an acceptable molded part in the second mold cavity constituting the second target profile.
According to another preferred embodiment, in an injection molding system having a manifold for injecting material through first and second gates into one or more mold cavities, and a controller for controlling the flow rate of material injected through the first and second gates during an injection cycle according to first and second target profiles, respectively, wherein the first and second target profiles represent a desired value of first and second sensed conditions related to the flow rate of material injected through the first and second gates during an injection cycle, respectively, a method is provided for creating at least the first target profile, the method includes the steps of selecting a test first target profile to be executed by the controller, injecting material through the first gate into a cavity according to the test first target profile executed by the controller, and determining whether the material injected produces an acceptable molded part in the cavity.
According to another preferred embodiment, in an injection molding system having a manifold for injecting material through a first gate into a first mold cavity, and a controller for controlling the flow rate of material injected through the first gate during an injection cycle according to a first target pressure profile by comparing a target pressure to an actual pressure during the injection cycle, wherein the first target pressure profile represents a target value of the pressure exerted by the material injected through the first gate during the injection cycle, a method is provided for creating the first target pressure profile. The method includes the steps of selecting a value of a variable corresponding to target injection pressure of the injected material, selecting a value of a variable corresponding to target pack pressure of the injected material, and selecting a value of a variable corresponding to a duration of the injection cycle.
According to another preferred embodiment, in an injection molding system having a manifold for injecting material through a first gate into a first mold cavity, and a controller for controlling the flow rate of material injected through the first gate during an injection cycle according to a first target pressure profile by comparing a target pressure to an actual pressure exerted by the material, a method is provided for creating the first target pressure profile. The method includes selecting pressure values for a plurality of variables corresponding to target pressures at a corresponding plurality of times during the injection cycle, and forming the first target pressure profile according to the pressure values.
According to another preferred embodiment, an injection molding apparatus is provided that includes a manifold for directing material through first and second gates into one or more mold cavities, and a controller to independently control a flow rate of material injected into through the first and second gates during an injection cycle according to a first target profile associated with the material injected through the first gate and a second target profile associated with material injected through the second gate. The first target prof
Doyle Mark
Kazmer David
Moss Mark D.
van Geel Huip
Heitbrink Tim
Kudirka & Jobse LLP
Synventive-Molding Solutions, Inc.
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