Apparatus and method for making plastic containers

Claim 1

IN A MOLDING MECHANISM FOR FORMING PLASTIC ARTICLES, SUCH AS DRINKING CUPS AND THE LIKE, FROM FOAMABLE PLASTIC MATERIAL, A BASE, A FRAME SUPPORTED ON THE BASE, MOLD PARTS THEREON DEFINING A CUP-SHAPED MOLDING CAVITY INCLUDING A CAVITY ELEMENT AND A CORE ELEMENT, A SOURCE OF SUPPLY ON THE FRAME ADAPTED TO SUPPLY FOAMABLE PLASTIC MATERIAL TO THE CAVITY, A SUPPLY PASSAE BETWEEN THE SOURCE OF SUPPLY AND THE CAVITY COMMUNICATING WITH THE CAVITY GENERALLY IN THE CENTER OF THE SMALL END OF THE CUP AS DEFINED BY THE CAVITY , A VALVE FOR CONTROLLING THE SUPPLY PASSAGE INCLUDING A MOVABLE PLUNGER GENERALLY ALIGNED WITH THE AXIS OF THE CAVITY AND HAVING A DIAMETER LESS THAN THE DIAMETER OF THE BOTTOM OF THE CUP, THE PLUNGER BEING MOVABLE BETWEEN A WITHDRAWN POSITION TO ALLOW FOAMABLE MATERIAL TO FLOW THROUGH THE SUPPLY PASSAGE INTO THE CAVITY AND AN EXTENDED POSITION IN WHICH THE PLUNGER CLOSES THE SUPPLY PASSAGE AND THE FACE OF THE PLUNGER COMPLETES THE BOTTOM OF THE CUP AS DEFINED BY THE CAVITY, MEANS FOR CREATING AN AIR PRESSURE DIFFERENTIAL THROUGH THE CAVITY TO CONVEY THE BEADS FROM THE SUPPLY PASSAGE TO THE TOP EDGE OF THE CUP AS DEFINED BY THE CAVITY, INCLUDING MEANS FOR APPLYING A POSITIVE AIR PRESSURE TO THE SUPPLY PASAGE FOR BLOWING THE PREFOAMED BEADS INTO THE MOLDING CAVITY, AND MEANS FOR HEATING THE CAVITY TO FOAM AND UNITE THE FOAMABLE MATERIAL INTO A FINISHED ARTICLE.