CONTROLLED VALVE PIN MOVEMENT BASED ON CAVITY SENSOR FEEDBACK

Abstract

Apparatus and method for performing an injection molding cycle in an injection molding apparatus where the apparatus comprises: a manifold, an actuator associated with a respective gate, each gate having a downstream sensor generating a response signal upon sensing a selected condition of the injection fluid material, each gate having an upstream sensor generating a response signal upon sensing the selected condition of the injection fluid material, the upstream and downstream sensors sending response signals to a controller on performance of each successive injection cycle by the apparatus,
the controller comparing a standard amount of elapsed time with a calculated amount of elapsed time and adjusting the velocity or position of each of the actuators such that the amount of time elapsed approaches or matches the standard amount of elapsed time.

Claims

1. A method of performing an injection molding cycle in an injection molding apparatus comprised of: a manifold that receives an injection fluid material, the manifold having or communicating with a delivery channel that delivers the injection fluid mold material under an injection pressure to two or more gates each leading to an associated mold cavity, an actuator associated with each respective gate, each actuator being drivably interconnected to a valve pin drivable upstream and downstream along a path of travel having a selected stroke length that extends between a gate closed position, a selected maximum flow position at which the injection fluid material flows at a maximum rate through the gate into the cavity and one or more selectable intermediate positions between the first position and the maximum flow position, each actuator being controllably drivable to position an interconnected valve pin at the first, one or more selectable intermediate and maximum flow positions over the course of an injection cycle, a downstream sensor that senses a selected physical condition of the injection fluid material at a position within a mold cavity that is downstream of an associated gate, the downstream sensor generating a signal corresponding to the sensed values, the method comprising the steps of: selecting and recording as a standard for a selected one of the gates, the amount of time elapsed between movement of the valve pin associated with the selected one of the gates out of the gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material flowing into the associated mold cavity, performing a subsequent injection cycle for each of the other gates and sensing the selected physical condition of the injection fluid material at the downstream position with the downstream sensor associated with each of the other gates, and, recording the amount of time elapsed between movement of the valve pin associated with each of the other gates out of the gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material flowing into the associated cavities of each of the other gates, comparing the recorded amounts of time elapsed associated with each of the other gates with the standard amount of time elapsed that is associated with the selected one of the gates, adjusting position or velocity of the actuators or valve pins associated with each of the other gates during further subsequent injection cycles such that the amount of time elapsed between movement of the valve pins associated with each of the other gates of their gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material approaches or matches the selected standard amount of elapsed time, wherein the step of recording the amount of time elapsed between movement of the valve pin and the time at which the downstream sensor first senses the selected condition comprises: detecting movement of the valve pin by sensing position of the valve pin with a position sensor, and wherein the step of adjusting position or velocity of the actuator or valve pin so that the amount of time elapsed approaches or matches the selected standard amount of elapsed time comprises: adjusting the position of a distal tip end of the valve pin having a configuration that interacts with an interior surface of a respective gate area to provide a reduced rate of material flow along the path of travel in the one or more selectable intermediate positions.

2. The method of claim 1 wherein the steps of performing and adjusting are carried out automatically by an algorithm executed by a controller interconnected to and controllably driving or adjusting the drive of the actuators.

3. The method of claim 1 wherein the step of selecting and recording comprises recording and establishing a standard profile of position of the actuator or valve pin versus time for the selected one of the gates and the step of adjusting can comprise recording and adjusting the position or drive rate of the actuators or valve pins associated with the other gates to approach or match the standard profile of position versus time.

4. The method of claim 1, wherein the actuator is a fluid driven actuator and a fluid driven valve system that regulates the flow of either gas or liquid to the actuator.

5. The method of claim 1, wherein the actuator is a pneumatic actuator and a proportional valve regulates the flow of pneumatic fluid to the actuator.

6. The method of claim 1, wherein the actuators control simultaneous flow of injection fluid material through each one of multiple nozzles into separate mold cavities or the same cavity.

7. The method of claim 1, wherein the downstream sensor is a temperature sensor.

8. The method of claim 1, wherein the downstream sensor is a pressure sensor.

9. The method of claim 1, wherein the actuator is an electrically powered actuator.

10. The method of claim 1, wherein the apparatus includes a controller with a memory and a program with instructions that store and use the standard amount of time elapsed for the subsequent injection cycles, and the controller performs the step of adjusting by automatically adjusting the position or velocity of the actuators or valve pins.

11. The method of claim 1, wherein the controller is a closed loop controller and proportional valve driver that receives position signals from the position sensors to control the position and velocity of the actuators or valve pins.

12. Apparatus for performing an injection molding cycle in an injection molding apparatus, the apparatus comprising: a manifold that receives an injection fluid material, the manifold having or communicating with a delivery channel that delivers the injection fluid mold material under an injection pressure to two or more gates each leading to an associated mold cavity, an actuator associated with each respective gate, each actuator being drivably interconnected to a valve pin drivable upstream and downstream along a path of travel having a selected stroke length that extends between a gate closed position, a selected maximum flow position at which the injection fluid material flows at a maximum rate through the gate into the cavity and one or more selectable intermediate positions between the first position and the maximum flow position, each actuator being controllably drivable to position an interconnected valve pin at the first, one or more selectable intermediate and maximum flow positions over the course of an injection cycle, a downstream sensor that senses a selected physical condition of the injection fluid material at a position within a mold cavity that is downstream of an associated gate, the downstream sensor generating a signal corresponding to the sensed values, a controller including instructions for: selecting and recording as a standard for a selected one of the gates, the amount of time elapsed between movement of the valve pin associated with the selected one of the gates out of the gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material flowing into the associated mold cavity, recording, based on signals received from the downstream sensors of each of the other gates on a subsequent injection cycle upon sensing the selected physical condition of the injection fluid material at the downstream position, the amount of time elapsed between movement of the valve pin associated with each of the other gates out of the gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material flowing into the associated cavities of each of the other gates, comparing the recorded amounts of time elapsed associated with each of the other gates with the standard amount of time elapsed that is associated with the selected one of the gates, adjusting position or velocity of the actuators or valve pins associated with each of the other gates during further subsequent injection cycles such that the amount of time elapsed between movement of the valve pins associated with each of the other gates of their gate closed position and the time at which the downstream sensor first senses the selected condition of the injection fluid material approaches or matches the selected standard amount of elapsed time, wherein the step of recording the amount of time elapsed between movement of the valve pin and the time at which the downstream sensor first senses the selected condition comprises instructions for: detecting movement of the valve pin by sensing position of the valve pin with a position sensor, and wherein the step of adjusting position or velocity of the actuator or valve pin so that the amount of time elapsed approaches or matches the selected standard amount of elapsed time comprises instructions for: adjusting the position of a distal tip end of the valve pin having a configuration that interacts with an interior surface of a respective gate area to provide a reduced rate of material flow along the path of travel in the one or more selectable intermediate positions.

13. The apparatus of claim 12, wherein the actuator is a fluid driven actuator and a fluid driven valve system regulates the flow of either gas or liquid to the actuator.

14. The apparatus of claim 12, wherein the actuator is a pneumatic actuator and a proportional valve regulates the flow of pneumatic fluid to the actuator.

15. The apparatus of claim 12, wherein the actuators control simultaneous flow of injection fluid material through each one of multiple nozzles into separate mold cavities or the same cavity.

16. The apparatus of claim 12, wherein the downstream sensor is a temperature sensor.

17. The apparatus of claim 12, wherein the downstream sensor is a pressure sensor.

18. The apparatus of claim 12, wherein the actuator is an electrically powered actuator.

19. The apparatus of claim 12, wherein the controller has a memory and a program with instructions that store and use the standard amount of time elapsed for the subsequent injection cycles, and the controller performs the step of adjusting by automatically adjusting the position or velocity of the actuators or valve pins.

20. The apparatus of claim 12, wherein the controller is a closed loop controller and proportional valve driver that receives position signals from the position sensors to control the position and velocity of the actuators or valve pins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0117] The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which:

[0118] FIG. 1 is a schematic of an embodiment of the invention showing an electrically powered actuator interconnected to a valve pin that controls flow through a gate into a mold cavity having a single sensor disposed for detecting injection material downstream of the gate.

[0119] FIG. 2 is a schematic of an embodiment of the invention showing an electrically powered actuator interconnected to a valve pin that controls flow through a gate into a mold cavity having a first sensor disposed at the exit of the gate into a mold cavity and another sensor disposed downstream of the first sensor for detecting injection material downstream of the gate.

[0120] FIG. 3 is a schematic of an embodiment of the invention showing a pneumatically powered system injection molding system comprising a valve pin that controls flow through a gate into a mold cavity having a single sensor disposed for detecting injection material downstream of the gate, the valve pin having a distal tip end that is adapted to interact with the interior surface of the gate area of the apparatus to reduce injection fluid material flow to a reduced rate of flow that is less than the maximum rate of flow of the fluid material when the tip end is not in restriction proximity to the gate area, the valve pin being controllably driven by a remotely controllable, high precision flow control valve interconnected respectively between the flow ports of the upper and lower gas drive chambers of a pneumatic actuator and a master source of pressurized gas, typically air, that drives the system.

[0121] FIG. 4 is a schematic of an embodiment of the invention showing a pneumatically powered system injection molding system comprising a valve pin that controls flow through a gate into a mold cavity having a first sensor disposed at the exit of the gate into a mold cavity and another sensor disposed downstream of the first sensor for detecting injection material downstream of the gate, the valve pin having a distal tip end that is adapted to interact with the interior surface of the gate area of the apparatus to reduce injection fluid material flow to a reduced rate of flow that is less than the maximum rate of flow of the fluid material when the tip end is not in restriction proximity to the gate area, the valve pin being controllably driven by a remotely controllable, high precision flow control valve interconnected respectively between the flow ports of the upper and lower gas drive chambers of a pneumatic actuator and a master source of pressurized gas, typically air, that drives the system.

DETAILED DESCRIPTION

[0122] FIG. 1 shows a system 10 according to the invention comprised of multiple injection valve assemblies 200, 200a each of which comprise an electrically powered actuator 20 having an electric motor rotor 30 that is interconnected to a valve pin 40 that is controllably driven back and forth along an axis A at controlled velocities by controller 100 that contains a programmable processor and interconnected memory that can execute instructions using data input by the user. The valve pin 40 for each valve assembly has a distal tip end 60 that opens and closes a separate gate 50 for each valve assembly and, depending on the precise positioning of the tip end 60 relative to the interior surface of the nozzle that forms the gate 60, regulates the rate of flow of injection fluid material 90 injected from manifold 80 into nozzle passage 95 and ultimately through gate 50 into the mold cavity 70. Thus the controller 100 can, when appropriately programmed regulate the rate or velocity of flow of injection fluid material 90 into cavity 70 by regulating the velocity or positioning of valve pin 65 and its tip end 60 during the course of an injection cycle particularly the withdrawal or upstream velocity of the pin at the beginning of the injection cycle.

[0123] One or more additional injection valve assemblies 200a each separately associated with a different gate to the same or different mold cavities can be interconnected to and controlled by controller 100. In the embodiment shown in FIGS. 1-4, each individual one of the assemblies 200, 200a inject into a separate mold cavity 70, 70a in which a separate part is formed. In the FIG. 1 embodiment, a single downstream sensor, Sensor 1, is shown positioned for detecting a selected condition of the injection fluid at a selected downstream position 120 within the cavity 70. Similarly, each of the other assemblies 200a have a downstream sensor 1a positioned for sensing a selected condition of injection fluid at a downstream position 120a within cavity 70a. The distance between the exit of gate 50 and downstream sensing position 120 is preselected and is the same or substantially the same as the distance between the downstream sensing position 120a and exit 50a of each of the other injection assemblies 200a. The assemblies 10, 10a can each include a position sensor 130aa that sends a signal 130, 130a indicative of the axial A position of rotor 30 and/or valve pin 65 and tip end 60 of each assembly 10, 10a to the processor or memory of controller 100. The controller 100 includes memory and a program with instructions that store and use as a standard, the predetermined amount of time that it takes injection fluid to flow from gate 50 to the time of detection by Sensor 1 at position 120. The standard time is predetermined either by conducting one or more test cycles at various trial and error withdrawal speeds for pin 65 or profiles of pin 65 position using assembly 10. After conducting such trials and determining the formation of a part formed within cavity 70 that is ideal, the withdrawal speed or position profile of pin 65 for the most preferred part forming trial is selected as a standard. The standard elapsed time or position profile is input to controller 100. Alternatively, the user can simply select a standard elapsed time or pin position profile

[0124] The controller 100 contains instructions that for one or more subsequent injection cycles of assemblies 200a, preferably all subsequent injection cycles, automatically records the time elapsed between the associated valve pins first opening gates 50a and the time that sensor 1a detects the injection fluid at position 120a of assemblies 200a. The controller then compares the automatically recorded elapsed times for assemblies 200a. If the compared recorded elapsed time for any assembly 200a differs from the established standard elapsed time, the controller 100 automatically adjusts the velocity or positioning of the valve pins associated with assemblies 200a to drive the actuators associated with such other assemblies to attempt to achieve a velocity or profile of position of movement of the actuators and valve pins of assemblies 200a that will cause the elapsed time for the assemblies 200a to approach or match the elapsed time for the standard.

[0125] As shown in FIGS. 1-4, there are one or more, typically multiple additional X injection assemblies in any given system.

[0126] The preselected condition of the fluid that the Sensor 1 typically senses is pressure or temperature.

[0127] FIG. 2 shows a system 10 analogous to the system 10 of FIG. 1, the only difference being that the elapsed time on which the control system is based is the time elapsed between the time that an upstream sensor, Sensor 2 (or Sensor 2a) senses a preselected condition of the injection fluid at upstream point 150, 150a, and the time at which the downstream Sensor 1 senses the preselected condition of the injection fluid at point 120, 120a.

[0128] The preselected condition of the fluid that the Sensor 1 and Sensor 2 typically sense is pressure or temperature. Sensor 1 could sense one condition such as pressure and Sensor 2 could sense a different condition such as temperature or the same condition as Sensor 1.

[0129] FIGS. 3 and 4 depict systems in which the actuation systems comprises a fluid driven, as opposed to an electricity driven, actuator 20. A preferred fluid driven valve system 205 comprises a fast acting linear force motor driven proportional valve 205 that regulates the flow of either gas or liquid to the actuator 20, namely either a pneumatic or hydraulic system.

[0130] The system 10 of FIG. 3 operates in the same manner as described with reference to FIG. 1, the difference being that the controller 100 controls the operation of the fluid control valve system 205 and the same or similar fluid control valve system that drives the injection system 200a.

[0131] The system of FIG. 4 operates in the same manner as described with reference to FIG. 2, the difference being that the controller controls the operation of the valve system 205 and the same or similar fluid control valve system that drives the injection system 200a.

[0132] A fast acting fluid control valve system as described in detail in PCT/US2014/31000 and in U.S. Pat. No. 5,960,831, the disclosures of both of which are incorporated herein by reference can be used in the apparatuses described herein particularly where pneumatic valve control systems are preferred for the particular application.