Injection molding flow control apparatus and method

1. A method of performing an injection molding cycle in an injection molding apparatus comprising a manifold that receives an injection fluid, the manifold distributing injection fluid to a fluid delivery channel that delivers the injection fluid under an injection pressure to a gate of a mold cavity and a valve pin having an axis and a tip end, the valve pin being slidably mounted for movement along the axis within the fluid delivery channel, the method comprising:

drivably interconnecting the valve pin to an electric motor driven by a source of electrical power or energy in an arrangement wherein the electric motor drives the valve pin along the axis and drives the tip end of the valve pin between a first position where the tip end of the valve pin obstructs the gate to prevent the injection fluid from flowing into the cavity, a second position upstream of the first position wherein the tip end of the valve pin restricts flow of the injection fluid along at least a portion of the length of the drive path extending between the first position and the second position, and a third maximum upstream position where the injection fluid material flows freely without restriction from the tip end of the pin through the first gate, the electric motor being electrically operable to drive the valve pin at one or more intermediate rates of upstream and downstream travel extending between zero and a maximum rate of upstream travel and a maximum rate of downstream travel, controllably operating the electric motor to begin driving the downstream travel of the valve pin at one or more intermediate rates of downstream travel that are less than the maximum rate of downstream travel when the valve pin is disposed at the third maximum upstream position during the course of an injection cycle to drive the tip end of the valve pin downstream from the third position to the first position at the one or more intermediate rates of downstream travel.

2. The method of claim 1 further comprising:

beginning the injection molding cycle from the first position,

controllably operating the motor to drive the valve pin at one or more of the intermediate upstream rates of travel over the length of the path of upstream travel between the first position and the second position,

sensing the position of the valve pin to determine when the tip end of the valve pin has reached the second position during the course of upstream travel,

controllably operating the motor to drive the valve pin upstream from the second position to the maximum upstream position at one or more high upstream rates of travel that are greater than the intermediate upstream rates of travel.

3. The method of claim 2 wherein the motor is controllably operated to drive the valve pin upstream from the second position to the maximum upstream position at the maximum rate of upstream travel.

4. An injection molding apparatus comprising:

a manifold that receives an injection fluid, the manifold distributing injection fluid to a fluid delivery channel that delivers the injection fluid under an injection pressure to a gate of a mold cavity and a valve pin having an axis and a tip end, the valve pin being slidably mounted for movement along the axis within the fluid delivery channel,

an electric motor driven by a source of electrical power or energy in an arrangement wherein the electric motor drives the valve pin along the axis and drives the tip end of the valve pin between a first position where the tip end of the valve pin obstructs the gate to prevent the injection fluid from flowing into the cavity, a second position upstream of the first position wherein the tip end of the valve pin restricts flow of the injection fluid along at least a portion of the length of the drive path extending between the first position and the second position, and a third maximum upstream position where the injection fluid material flows freely without restriction from the tip end of the pin through the first gate, the electric motor being electrically operable to drive the valve pin at one or more intermediate rates of downstream travel extending between zero and a maximum rate of downstream travel,

a controller including instructions for beginning an injection cycle with the tip end of the valve pin disposed in the first position,

the controller including instructions for controllably operating the electric motor to drive the valve pin from the first position to the third maximum upstream position,

the controller including instructions for controllably operating the motor to begin driving the downstream travel of the valve pin at the one or more intermediate rates of downstream travel that are less than the maximum rate of downstream travel when the valve pin is disposed at the third maximum upstream position during the course of an injection cycle to drive the tip end of the valve pin downstream from the third position to the first position at the one or more intermediate rates of downstream travel.

5. The apparatus of claim 4 wherein the controller includes instructions for controllably operating the motor to drive the valve pin at one or more intermediate downstream rates of upstream travel that are less than a maximum rate of upstream travel over a selected length of upstream travel between the maximum upstream position and the first position beginning when the tip end of the valve pin is disposed in the first position.

6. The apparatus of claim 4 including a position sensor that senses axial position of the valve pin and sends a signal indicative of the sensed position to the controller, the controller including instructions to operate the electric motor to drive the valve pin at the one or more intermediate downstream rates of travel upon sensing the position of the valve pin in the third maximum upstream position.