Fast acting reduced velocity pin control

Abstract

Apparatus and method for performing an injection molding cycle using the apparatus where the apparatus comprises: a manifold, a pneumatic actuator driven by a pneumatic valve assembly, the actuator driving a valve pin between a gate closed position and a maximum injection fluid flow position, the pneumatic valve assembly having a spool supported within a cylinder driven by a drive device that is supported solely by and translates together with the spool, a controller that instructs the pneumatic valve assembly to cause the actuator to drive the valve pin either upstream or downstream to selected positions or at selected velocities during the course of a single injection cycle based on a feedback signal indicative of position of the pin or actuator or pressure of an injection fluid material.

What is claimed is: 
     
         1 . A method for molding a plastic part, the method comprising:
 providing a valve gated nozzle including a valve stem movable between an open position and a closed position;   wherein the valve gated nozzle includes a pneumatic valve that controls rate of delivery of a pressurized gas from a source to and from gas drive chambers of a pneumatic actuator that is interconnected to the valve stem to controllably drive the valve stem upstream and downstream between the open and closed positions,   the pneumatic valve comprising a housing and a spool controllably and translationally drivable within the housing to selectively open and close fluid delivery ports a selected degree to control flow of pressurized gas to and from the drive chambers of the pneumatic actuator,   the pneumatic valve including a drive member mounted to the spool, the drive member being controllably energizable to cause the spool to controllably slide along a back and forth path of lateral travel, the drive member being translationally movable along the back and forth path of lateral travel together with the spool and being supported during movement solely by mounting to the spool,   the method further comprising:   moving the valve stem via controlled drive of the spool at a first speed for a first portion between the open position and the closed position; and   moving the valve stem via controlled drive of the spool at a second speed less than a maximum speed for at least a final 2 mm between the open position and the closed position.   
     
     
         2 . An apparatus for molding a plastic part, the apparatus comprising:
 a valve gated nozzle including a valve stem movable between an open position and a closed position;   wherein the valve gated nozzle includes a pneumatic valve that controls rate of delivery of a pressurized gas from a source to and from gas drive chambers of a pneumatic actuator that is interconnected to the valve stem to controllably drive the valve stem upstream and downstream between the open and closed positions,   the pneumatic valve comprising a housing and a spool controllably and translationally drivable within the housing to selectively open and close fluid delivery ports a selected degree to control flow of pressurized gas to and from the drive chambers of the pneumatic actuator,   the pneumatic valve including a drive member mounted to the spool, the drive member being controllably energizable to cause the spool to controllably slide along a back and forth path of lateral travel, the drive member being translationally movable along the back and forth path of lateral travel together with the spool and being supported during movement solely by mounting to the spool,   a controller including a program having instructions that:   instruct the valve stem to move at a first speed for a first portion between the open position and the closed position; and   instruct the valve stem to move at a second speed less than a maximum speed for at least a final 2 mm between the open position and the closed position.   
     
     
         3 . An injection molding apparatus for controlling velocity or volume of delivery of an injection fluid material through a gate to a cavity of a mold, the apparatus comprising:
 a pneumatically driven actuator comprising a fluid sealed chamber in which a piston is mounted, the piston being interconnected to a valve pin having a tip end,   the piston forming first and second drive chambers within the fluid sealed chamber, each drive chamber having respective fluid flow ports, the piston and valve pin being drivable along a reciprocal path of axial travel having a stroke length that extends on a downstream cycle between a fully upstream gate open position where unrestricted flow of injection fluid material is enabled through a gate to a mold and a fully downstream gate closed position where the valve pin stops flow of the injection material through the gate to the mold,   a source of pressurized gas that generates gas flow at a selected maximum pressure or flow rate,   a gas metering mechanism comprised of housing and a spool controllably and translationally drivable within the housing by a drive member mounted to the spool to selectively open and close fluid flow ports a selected degree to control flow of pressurized gas to and from the drive chambers of the pneumatic actuator,   the gas metering mechanism being disposed between the source and one or the other or both of the fluid flow ports of the drive chambers, the gas metering mechanism being controllably movable to one or more selectable positions that vary rate of flow or pressure of the pressurized gas through one or the other of the fluid flow ports to one or more corresponding reduced pressures or reduced flow rates of the pressurized gas that are less than the maximum pressure or flow rate,   a controller that includes programmable instructions that:   automatically controllably position the gas metering mechanism such that the piston or valve pin is driven at a high or maximum velocity during the course of at least a selected portion of the stroke length on the downstream cycle from the fully upstream gate open position to the fully downstream gate closed position and then subsequently at some predetermined time or position of the pin that occurs during the same downstream cycle automatically direct drive of the piston or pin downstream to a fully gate closed position at a reduced velocity relative to the high or maximum velocity,   wherein the gate and the pin are adapted such that the velocity of flow of injection fluid material through the gate is restricted and reduced relative to a maximum velocity over a path of travel of at least 2 mm between the tip end of the pin and the gate.   
     
     
         4 . The apparatus of  claim 3  wherein the instructions automatically controllably direct the valve pin to be driven at the reduced velocity over a path of travel of at least 2 mm between the tip end of the pin and the gate. 
     
     
         5 . The apparatus of  claim 3  wherein the controller automatically positions the gas metering mechanism at a position that effects a high or maximum flow rate or pressure of the pressurized gas that drives the valve pin at the high or maximum pin velocity and automatically positions the gas metering mechanism at a position that effects a reduced flow rate or pressure of the pressurized gas that drives the valve pin at the reduced pin velocity during the course of at least the selected portion of the stroke length on the downstream cycle from the fully upstream gate open position to the fully downstream gate closed position. 
     
     
         6 . A method for controlling velocity or volume of delivery of an injection fluid material through a gate to a cavity of a mold in an injection molding apparatus wherein the apparatus comprises:
 a pneumatically driven actuator comprising a fluid sealed chamber in which a piston is mounted, the piston being interconnected to a valve pin having a tip end,   the piston forming first and second drive chambers within the fluid sealed chamber, each drive chamber having respective fluid flow ports, the piston and valve pin being drivable along a reciprocal path of axial travel having a stroke length that extends on a downstream cycle between a fully upstream gate open position where unrestricted flow of injection fluid material is enabled through a gate to a mold and a fully downstream gate closed position where the valve pin stops flow of the injection material through the gate to the mold,   a source of pressurized gas that generates gas flow at a selected maximum pressure or flow rate,   a gas metering mechanism comprised of housing and a spool controllably and translationally drivable within the housing by a drive member mounted to the spool to selectively open and close fluid flow ports a selected degree to control flow of pressurized gas to and from the drive chambers of the pneumatic actuator, the gas metering mechanism being disposed between the source and one or the other or both of the fluid flow ports of the drive chambers, the gas metering mechanism being controllably movable to one or more selectable positions that vary rate of flow or pressure of the pressurized gas through one or the other of the fluid flow ports to one or more corresponding reduced pressures or reduced flow rates of the pressurized gas that are less than the maximum pressure or flow rate,   the method comprising:   automatically controllably positioning the gas metering mechanism such that the piston or valve pin is driven at a high or maximum velocity during the course of at least a selected portion of the stroke length on the downstream cycle from the fully upstream gate open position to the fully downstream gate closed position and then subsequently at some predetermined time or position of the pin that occurs during the same downstream cycle automatically driving the piston or pin downstream to a fully gate closed position at a reduced velocity relative to the high or maximum velocity, and   adapting the gate and the pin such that the velocity of flow of injection fluid material through the gate is restricted and reduced relative to a maximum velocity over a path of travel of at least 2 mm between the tip end of the pin and the gate.   
     
     
         7 . The method of  claim 6  further comprising driving the valve pin at the reduced velocity over a path of travel of at least 2 mm between the tip end of the pin and the gate. 
     
     
         8 . The method of  claim 6  further comprising automatically positioning the gas metering mechanism at a position that effects a high or maximum flow rate or pressure of the pressurized gas that drives the valve pin at the high or maximum pin velocity and automatically positioning the gas metering mechanism at a position that effects a reduced flow rate or pressure of the pressurized gas that drives the valve pin at the reduced pin velocity during the course of at least the selected portion of the stroke length on the downstream cycle from the fully upstream gate open position to the fully downstream gate closed position.