Liquid color gravimetric metering apparatus and methods

A method for gravimetrically supplying liquid color concentrate from a container thereof directly into the barrel of a plastic resin material molding press or into the barrel of plastic resin material extruder, using a pump, for molding or extrusion of a product exhibiting such color, the method comprising:

• a) continuously measuring weight of a container of liquid color concentrate in the course of pumping liquid color concentrate therefrom directly into the barrel of either a plastic resin material molding press or a plastic resin material extruder;
• b) continuously comparing the measured weight of the container of liquid color concentrate to an expected weight of the container of liquid color concentrate based on a desired usage rate of liquid color concentrate by the molding machine or the extruder for the product being molded or extruded ;
• and
• c) adjusting speed of the pump continuously, in response to the comparison of the measured weight of the container of liquid color concentrate to the expected weight of the container of liquid color concentrate, to supply continuously the desired amount of liquid color concentrate material to the barrel of the plastic resin material molding press or the plastic resin material extruder.

A method for delivering liquid color concentrate from a container directly into the barrel of a plastic resin material molding press or into the barrel of plastic resin material extruder for molding or extrusion of a product exhibiting such color, comprising:

• a) continuously measuring weight of a container of liquid color concentrate in the course of pumping liquid color concentrate therefrom directly into the barrel of either a plastic resin material molding press or a plastic resin material extruder;
• b) pumping liquid color concentrate from the container by displacing a first pusher to close a tube for transporting liquid color concentrate from the container of the barrel of the plastic resin material molding press or the plastic resin material extruder while a second and third pusher are not displaced thereby permitting liquid color concentrate to flow through the tube from the supply to a first position of tube closure, then displacing the second pusher to close the tube and trap liquid color concentrate in the tube between the first position of tube closure and a second position of tube closure, permitting the first pusher to return to its undisplaced position thereby permitting liquid color concentrate to flow through the tube past the first position of tube closure and displacing the third pusher to force at least a portion of the trapped liquid color concentrate through the tube past the first position of tube closure and supplying liquid color concentrate to a plastic resin material processing machine at a predetermined rate according to a selected recipe to produce plastic parts having desired color characteristics;
• c) continuously comparing the measured weight of the container of liquid color concentrate to an expected weight of the container of liquid color concentrate based on a desired usage rate of liquid color concentrate by the molding machine or the extruder for the product being molded or extruded;
• and
• d) continuously adjusting pumping speed, by adjusting frequency of displacement of the pushers in response to the comparison of the measured weight of the container of liquid color concentrate to the expected weight of the container of liquid color concentrate, to supply continuously the desired amount of liquid color concentrate to the barrel of the plastic resin material molding press or the plastic resin material extruder.