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
2001-04-24
2003-07-01
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
C264S040300, C264S040700, C425S149000, C425S564000, C425S572000
Reexamination Certificate
active
06585505
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to automatic control of plastic flow through injection nozzles in a molding machine. More particularly the invention relates to proportional control of plastic flow via proportional control of the actuator mechanism for a valve for a nozzle particularly where two or more nozzles are mounted on a hotrunner for injection into one or more mold cavities. The proportional control is achieved via the use of one or more sensors which senses a selected condition of the plastic flow through a manifold, nozzle or into a mold and the use of the recorded condition in conjunction with a selected nozzle design, hotrunner/manifold design, actuator design, actuator drive mechanism and/or flow control mechanism. Proportional control of melt flow typically refers to control of the rate of melt flow according to an algorithm utilizing a value defined by a sensed condition as a variable.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided an apparatus and method for proportionally controlling the rate of melt flow through a melt flow path in an injection molding machine, in particular controlling the melt flow through two nozzles.
More particularly, there is provided in an injection molding machine having first and second nozzles for delivering melt material from a common manifold to one or more mold cavities, an apparatus for controlling delivery of the melt material from the nozzles to the one or more mold cavities, each nozzle having an exit aperture communicating with a gate of a cavity of a mold and being associated with an actuator interconnected to a melt flow controller, the apparatus comprising:
a sensor for sensing a selected condition of the melt material through at least one of the nozzles; and,
an actuator controller interconnected to each actuator, each actuator controller comprising a computer interconnected to a sensor for receiving a signal representative of the selected condition sensed by the sensor, the computer including an algorithm utilizing a value corresponding to a signal received from the sensor as a variable for controlling operation of an actuator for the at least one nozzle.
At least one of the nozzles most preferably has a seal surface disposed on a tip end of the nozzle which is engaged and in compressed contact with a complementary surface surrounding the gate of a cavity of a mold, the engaged surfaces forming a seal against leakage of the melt material around the nozzle and maintaining the pressure of the melt against loss of pressure due to leakage. The at least one nozzle is typically expandable upon heating to a predetermined operating temperature, the nozzle being mounted relative to the surface surrounding the gate such that the seal surface disposed on the tip end of the nozzle is moved into compressed contact with the complementary surface surrounding the gate upon heating of the nozzle to the predetermined operating temperature. The complementary mating surfaces of the nozzle and the gate area of the mold are typically radially disposed relative to the axis of the exit aperture of the nozzle, although the mating surfaces may also be disposed longitudinally or axially.
The tip end of the nozzle may comprise a single unitary piece or, in another embodiment, an outer unitary piece formed of a first material and an inner unitary piece formed of a second material, the first material being substantially less heat conductive than the second material. The complementary mating surfaces of the nozzle and the gate area of the mold are typically radially disposed relative to the axis of the exit aperture of the nozzle, although the mating surfaces may also be disposed longitudinally or axially.
At least one of the nozzles may have a tip end having a central portion having a central bore in alignment with a gate and an outer circumferential flange portion surrounding the gate and the central portion of the tip end of the at least one nozzle.
The melt flow controller of the apparatus typically comprises a pin which is controllably slidable via interconnection to an actuator along a reciprocal path of movement within the bore of a nozzle, or the controller typically comprises a rotary valve having a rotatable flow channel connecting an input flow channel to the exit aperture of at least one of the nozzles, the rotatable channel being interconnected to the actuator and controllably rotatable via the actuator to selectively vary the rate of flow of plastic melt through the rotatable flow channel to the exit aperture according to the degree of rotation of the rotary valve. The rotary valve typically comprises a cylinder rotatably mounted within a housing the cylinder having a bore rotatably communicable with a pair of bores in the housing.
One or more actuators may comprise a piston mounted within a fluid sealed housing, the piston having a stem extending outside the fluid sealed housing, the valve pin having a head wherein the stem is readily detachably interconnected to the head of the valve pin outside the fluid sealed housing.
One or more actuators may comprise an electrically driven motor, the motor being mechanically interconnected to either a valve pin disposed in a bore of one of the nozzles such that the valve pin is reciprocally drivable within the bore of the nozzle by the motor, or a rotary valve for rotatable drive of a rotatable component having a fluid flow bore, the motor being electrically interconnected to the algorithm, the algorithm controlling the drive of the motor.
Each actuator for each of the first and second nozzles may be fluid driven wherein each actuator is commonly supplied with an actuator drive fluid flowing through a manifold which commonly delivers fluid to each of the nozzles.
The actuator controller for a fluid driven actuator typically comprises a solenoid having a piston controllably movable between selected positions for selectively delivering a pressurized actuator drive fluid to one or the other of at least two chambers of the actuator
The actuator controller for a fluid driven actuator may include a drive fluid valve which receives pressurized drive fluid from a source, the drive fluid valve having one or more fluid ports sealably communicating with one or more complementary fluid drive chambers disposed within the fluid driven actuator, the drive fluid valve being controllably driven to selectively distribute received pressurized fluid through the one or more fluid ports to the one or more complementary fluid drive chambers of the actuator. The drive fluid valve typically comprises a sealed housing and a plunger movable within the sealed housing to positions along a path wherein the one or more fluid ports are open to communication, partially open to communication, or closed from communication with the one or complementary fluid drive chambers by the plunger, the plunger being controllably movable to any position along the path between the open and closed positions such that flow of the drive fluid to a drive fluid chamber is controllably variable to a selected rate. The plunger typically comprises a slidably movable rod having interference projections which are selectively slidable by movement of the rod over the fluid ports to open, partially open to any desired degree, or close the fluid ports.
In another embodiment, at least one gate of a mold may be an edge gate extending radially outward through a mold cavity plate, at least one of the nozzles having a bore having a first portion having an inlet for the plastic melt which is not in alignment with the edge gate and a second portion extending radially outward from the first portion terminating in the exit aperture being in alignment with the edge gate. In such an embodiment the nozzle may have an exit end comprising a center nozzle member and a circumferential nozzle member surrounding the center nozzle member, the exit aperture extending through the center nozzle member in alignment with one of the gates, the circumferential nozzle member surrounding the one gate, wherein a groove is formed be
Kazmer David
Moss Mark D.
Heitbrink Tim
Kudirka & Jobse LLP
Synventive Molding Solutions, Inc.
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