Method of and system for injecting a fluid into a plastified mass in an extruder

A method of operating an extruder system having:

• an extruder having a barrel and an extruder worm therein,
• a source of an additive fluid under pressure,
• a conduit connected to said source and opening into said barrel,
• a closable upstream valve in said conduit between said source and said barrel,
• a closable downstream valve in said conduit between said upstream valve and said barrel, and
• a pressurizable fluid reservoir in said conduit between said valves,
• said method comprising the steps of:
• rotating said extruder in said barrel to plastify a resin therein;
• alternatively opening and closing said valves, whereby when said upstream valve is open and said downstream valve is closed said additive fluid flows into and pressurizes said reservoir and when said upstream valve is closed and said downstream valve is open the pressurized additive fluid in said reservoir flows into said barrel;
• detecting the rotation rate of said worm in said barrel;
• and
• pressurizing said reservoir at a level generally proportional to the detected worm rotation rate, whereby as said worm rotates rapidly to greatly pressurize a resin therein said reservoir is pressurized correspondingly with great pressure.