Injection molding machine with multichannel wave screw

An injection molding apparatus comprising:

• a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said scew including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising an outwardly extending conveying flight defining a helical passage, an outwardly extending barrier flight disposed intermediate said conveying flight to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight defining wave crests which are displaced helically from each other, a substantial portion of each channel situated between successive wave crests in the channel being of substantially constant depth, the barrier flight adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel containing an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight being thinner than that of the conveying flight so that the shear energy imparted to molten material flowing over the barrier flight is low.

An injection molding apparatus comprising:

• a barrel having an inner wall and inlet and outlet openings, a rotatable and reciprocable screw disposed in said barrel, means for rotating said screw about its axis and advancing said screw axially in said barrel toward the outlet opening, said screw including a section for enhancing substantially complete melting and mixing of resinous material plasticated by it comprising outwardly extending conveying flight means defining a helical passage, outwardly extending barrier flight means disposed intermediate said conveying flight means to divide the helical passage into flow channels extending side by side helically along said screw section, each of the flow channels having a depth which varies cyclically through a plurality of cycles along the helical length of such channel, the minimum depth portions of the flow channels on opposite sides of said barrier flight means defining wave crests which are displaced helically from each other, and the barrier flight means adjacent each wave crest being undercut to provide sufficient clearance between its outermost surface and the barrel inner wall to permit the flow thereover of molten resinous material from the channel having an area of decreasing depth to an adjacent area of the other channel, the outer width of said barrier flight means being thinner than that of said conveying flight means and being less than eight percent of the screw pitch, so that the shear energy imparted to molten material flowing over said barrier flight means is low.