Injection molding flow control apparatus and method

A method for controlling the rate of flow of a fluid material during a sequentially gated molding process wherein a fluid mold material is delivered through first and second gates into a common mold cavity, the method comprising:

• controlling delivery of the fluid material through the first gate into the cavity beginning at a first time;
• controlling delivery of the fluid material through the second gate beginning at a second time subsequent to the first time such that the fluid material has entered the cavity through the first gate and approached the second gate prior to the second time;
• wherein the step of controlling delivery through the second gate comprises an actuator interconnected to a valve pin having a tip end, the actuator moving the valve pin upstream along a path of travel between a downstream gate closed position and one or more intermediate upstream gate open positions, the downstream gate closed position being a position wherein the tip end of the valve pin obstructs the second gate to prevent fluid material from flowing into the mold cavity, the one or more intermediate upstream gate open positions being predetermined positions between the downstream gate closed position and an end of stroke position upstream of the one or more intermediate upstream gate open positions, wherein the second gate is partially open when the valve pin is in the one or more intermediate upstream gate open positions and the second gate is more fully open when the valve pin is in the end of stroke position;
• controlling, via an controller interconnected to the actuator, movement of the actuator at least in part according to instructions that instruct the actuator to move the valve pin:
• upstream at one or more selected intermediate velocities for one or more selected lengths of time over the course of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions;
• upstream at a higher upstream velocity than the one or more selected intermediate velocities upon expiration of the one or more selected lengths of time.

An apparatus for controlling the rate of flow of a fluid material during a sequentially gated molding process wherein a fluid mold material is delivered through first and second gates into a common mold cavity, the apparatus comprising:

• a first valve controlling delivery of the fluid material through the first gate into the cavity beginning at a first time;
• a second valve controlling delivery of the fluid material through the second gate beginning at a second time subsequent to the first time such that the fluid material has entered the cavity through the first gate and approached the second gate prior to the second time;
• the second valve comprising an actuator interconnected to a valve pin having a tip end, the actuator moving the valve pin upstream along a path of travel between a downstream gate closed position and one or more intermediate upstream gate open positions, the downstream gate closed position being a position wherein the tip end of the valve pin obstructs the second gate to prevent fluid material from flowing into the mold cavity, the one or more intermediate upstream gate open positions being predetermined positions between the downstream gate closed position and an end of stroke position upstream of the one or more intermediate upstream gate open positions, wherein the second gate is partially open when the valve pin is in the one or more intermediate upstream gate open positions and the second gate is more fully open when the valve pin is in the end of stroke position;
• a controller interconnected to the actuator that controls movement of the actuator at least in part according to instructions that instruct the actuator to move the valve pin:
• upstream at one or more selected intermediate velocities for one or more selected lengths of time over the course of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions;
• upstream at a higher upstream velocity than the one or more selected intermediate velocities upon expiration of the one or more selected lengths of time,
• wherein the tip end of the valve pin and the gate are adapted to cooperate with each other to restrict rate of flow of the fluid material through the gate over the course of the path of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions, and
• wherein the valve pin is withdrawn at a reduced velocity over more than about 50% of the path of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions.

An apparatus for controlling the rate of flow of a fluid material during a sequentially gated molding process wherein a fluid mold material is delivered through first and second gates into a common mold cavity, the apparatus comprising:

• a first valve controlling delivery of the fluid material through the first gate into the cavity beginning at a first time;
• a second valve controlling delivery of the fluid material through the second gate beginning at a second time subsequent to the first time such that the fluid material has entered the cavity through the first gate and approached the second gate prior to the second time;
• the second valve comprising an actuator interconnected to a valve pin having a tip end, the actuator moving the valve pin upstream along a path of travel between a downstream gate closed position and one or more intermediate upstream gate open positions, the downstream gate closed position being a position wherein the tip end of the valve pin obstructs the second gate to prevent fluid material from flowing into the mold cavity, the one or more intermediate upstream gate open positions being predetermined positions between the downstream gate closed position and an end of stroke position upstream of the one or more intermediate upstream gate open positions, wherein the second gate is partially open when the valve pin is in the one or more intermediate upstream gate open positions and the second gate is more fully open when the valve pin is in the end of stroke position;
• a controller interconnected to the actuator that controls movement of the actuator at least in part according to instructions that instruct the actuator to move the valve pin:
• upstream at one or more selected intermediate velocities for one or more selected lengths of time over the course of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions;
• upstream at a higher upstream velocity than the one or more selected intermediate velocities upon expiration of the one or more selected lengths of time,
• wherein the path of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions is between about 1 and about 8 mm.

An apparatus for controlling the rate of flow of a fluid material during a sequentially gated molding process wherein a fluid mold material is delivered through first and second gates into a common mold cavity, the apparatus comprising:

• a first valve controlling delivery of the fluid material through the first gate into the cavity beginning at a first time;
• a second valve controlling delivery of the fluid material through the second gate beginning at a second time subsequent to the first time such that the fluid material has entered the cavity through the first gate and approached the second gate prior to the second time;
• the second valve comprising an actuator interconnected to a valve pin having a tip end, the actuator moving the valve pin upstream along a path of travel through a nozzle between a downstream gate closed position and one or more intermediate upstream gate open positions, the downstream gate closed position being a position wherein the tip end of the valve pin has a cylindrical or tapered configuration and the gate has a complementary cylindrical or tapered surface that mates with the cylindrical or tapered configuration of the tip end surface to close the second gate into a gate closed position,
• the one or more intermediate upstream gate open positions being predetermined positions between the downstream gate closed position and an end of stroke position upstream of the one or more intermediate upstream gate open positions, wherein a flow restriction gap is formed between outer surfaces of the valve pin of the second gate and inner surfaces of the nozzle such that flow of fluid material through the second gate is restricted when the valve pin is in the one or more intermediate upstream gate open positions;
• the second gate being more fully open when the valve pin is in the end of stroke position;
• a controller interconnected to the actuator that controls movement of the actuator at least in part according to instructions that instruct the actuator to move the valve pin:
• upstream at one or more selected intermediate velocities for one or more selected lengths of time over the course of travel of the valve pin from the downstream gate closed position to the one or more intermediate upstream gate open positions;
• upstream at a higher upstream velocity than the one or more selected intermediate velocities upon expiration of the one or more selected lengths of time. positions.