Pneumatically driven, pin velocity controlled injection molding apparatus and method

An injection molding apparatus for controlling velocity or volume of delivery of an injection fluid material 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,
• the piston forming first and second drive chambers within the fluid sealed chamber, each drive chamber having respective fluid flow ports piston and valve pin being drivable along a reciprocal path of axial travel having a stroke length that extends between a fully upstream gate open position where injection fluid material is enabled through a gate to a mold and a fully downstream gate closed position where the pin stops flow of 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 interconnected 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,
• wherein the gas metering mechanism comprises one or more shutters or adjustable aperture devices that are mounted on or to or are integral with the actuator and are adjustable to one or more selectable positions that controllably vary the degree of openness of the fluid flow ports,
• wherein the one or more shutters or adjustable aperture devices are interconnected to one or more electric motors which are interconnected to the controller and controllable to selectively adjust the shutters or adjustable aperture devices to the one or more selectable positions that correspond to reduced pressures or reduced flow rates during the course of at least a selected portion of the stroke length from the fully downstream gate closed position to the fully upstream gate open position that correspond to reduced pressures or reduced flow rates during the course of at least a selected portion of the stroke length from the fully downstream gate closed position to the fully upstream gate open position.

A method of controllably adjusting rate of travel or velocity of a pneumatic actuator piston or valve pin associated with the piston during an injection cycle in an injection molding apparatus, wherein the actuator comprises a fluid sealed chamber in which the piston is mounted forming first and second fluid sealed drive chambers having respective first and second fluid flow ports, the piston being interconnected to the valve pin, the piston and valve pin being drivable along a reciprocal path of axial travel having a stroke length that extends between a fully upstream gate open position where injection fluid material is enabled to flow through a gate to a mold cavity and a fully downstream gate closed position where the pin stops flow of injection material through the gate to the mold cavity,

• the method comprising:
• interconnecting a source of pressurized gas that generates gas flow at a selected maximum pressure or flow rate to the fluid flow ports,
• preselecting a start time at which and a duration over the course of which the flow of the pressurized gas from the source is to be metered through the fluid flow ports during the course of the injection cycle,
• metering the flow of pressurized gas from the source through the fluid flow ports at the preselected start time and for the selected duration at a rate of flow or pressure of the pressurized gas that is less than the maximum pressure or flow rate of the source,
• controllably operating a metering mechanism that comprises one or more shutters or adjustable aperture devices that are mounted on or to or are integral with the actuator and are adjustable to one or more selectable positions that controllably vary the degree of openness of the fluid flow ports,
• wherein the one or more shutters or adjustable aperture devices are interconnected to one or more electric motors which are interconnected to the controller and controllable to selectively adjust the shutters or adjustable aperture devices to the one or more selectable positions that correspond to reduced pressures or reduced flow rates during the course of at least a selected portion of the stroke length from the fully downstream gate closed position to the fully upstream gate open position.