Patent ID: 7980834

Claim:
A method for furnishing liquid color at elevated pressure for injection thereof directly into the barrel housing of an extruder screw or an injection molding ram, comprising: a) allowing a chamber to fill with liquid color entering the chamber at a first pressure through an inlet; b) closing the inlet; c) energizing a solenoid to move a piston of an air cylinder-piston combination in a direction to contact and advance a free-floating pumping piston along a cylindrical part of the chamber into liquid color occupying the chamber thereby displacing the liquid color at pressure increased from the first pressure out of the chamber via an outlet leading to a barrel housing of an extruder screw or an injection molding ram; d) de-energizing the solenoid so as to permit spring bias to withdraw the piston of the air cylinder-piston combination away from the free-floating pumping piston and thereby permit new liquid color entering the chamber to urge the free-floating pumping piston away from the liquid color displacement position and towards the piston of the air cylinder-piston combination.