Device and method for continuously extruding tubing having different materials

A co-injection extrusion apparatus comprising:

• a first extruder and a first material delivery channel for delivering a first material to a die, a first plunger positioned in the first material delivery channel, the first plunger is provided in a portion of the first material delivery channel positioned proximate the die;
• a second extruder and a second material delivery channel for delivering a second material to the die, a second plunger positioned in the second material delivery channel, the second plunger is provided in a portion of the second material delivery channel positioned proximate the die;
• the first plunger being movable between a first plunger first position in which to the first plunger is extended in the first material delivery channel toward the die, and a first plunger second position in which the first plunger is retracted in the first material delivery channel away from the die, wherein as the first plunger is moved to the extended position, the first material is forced from the portion of the first material delivery channel to the die, and wherein as the first plunger is moved to the retracted position, the flow of the first material from the portion of the first material delivery channel to the die is slowed or stopped;
• the second plunger being movable between a second plunger first position in which to the second plunger is extended in the second material delivery channel toward the die, and a second plunger second position in which the second plunger is retracted in the second material delivery channel away from the die, wherein as the second plunger is moved to the extended position, the second material is forced from the portion of the second material delivery channel to the die, and wherein as the second plunger is moved to the retracted position, the flow of the second material from the portion of the second material delivery channel to the die is slowed or stopped;
• a controller controls the movement of the first plunger between the first plunger first position and the first plunger second position, the controller controls the movement of the second plunger between the second plunger first position and the second plunger second position.

A method of co-extruding material, the method comprising:

• providing first extruded material through a first material delivery channel to a die;
• providing second extruded material through a second material delivery channel to a die;
• controlling the flow of the first extruded material through the first material delivery channel by a first plunger positioned in the first material delivery channel;
• controlling the flow of the second extruded material through the second material delivery channel by a second plunger positioned in the second material delivery channel.