Patent ID: 8348661

Claim:
A check valve ( 36 , 136 ) for a screw ( 24 ), comprising: a retainer tip ( 54 , 154 ), operable to be attached to a distal end of a screw shaft ( 52 , 152 ), the retainer tip ( 54 , 154 ) defining at least one melt channel ( 30 ), the at least one melt channel ( 30 ) being defined as a plurality of flutes ( 58 , 158 ) longitudinally aligned on an exterior surface of the retainer tip ( 54 , 154 ); a first ring ( 60 ), coaxially mounted to and rotationally-coupled with the retainer tip ( 54 , 154 ), the first ring ( 60 ) being a crenellated ring ( 60 , 160 ); a second ring ( 66 ), coaxially and slidably mounted relative to the retainer tip ( 54 , 154 ), and operable to rotate relative to the retainer tip ( 54 , 154 ); and wherein the second ring ( 66 ) is operable to reversibly move relative to the retainer tip ( 54 , 154 ) between an open position which permits melt to flow through the check valve ( 36 , 136 ) and a closed position which prevents backflow of the melt, and the first ring ( 60 ) includes a plurality of teeth ( 62 , 162 ) which are sized as to fit within the plurality of flutes ( 58 , 158 ) on the retainer tip ( 54 , 154 ).