Abstract: An air ring comprises a circular plenum in fluid communication with a source of pressurized air. An upper and lower annular lips are in fluid communication with the plenum through upper and lower channels and are arranged to supply air to the blown film bubble. A plurality of vanes are disposed in the upper channel and extend radially inwardly from the plenum to the upper annular lip. The vanes divide the upper channel into a plurality of radially extending channel segments. Each vane has a selected length and a distal end proximal the upper annular lip, the distal end being spaced from the upper annular lip no greater than about 20% of the length of the vanes. A powered plunger extends between the vanes of each of the channel segments to vary the cross-sectional area of the channel segments.

Abstract: A melt distribution block for feeding melt through an extrusion die to an extrusion passage. The melt distribution block has a generally annular body with inner, outer, front and rear faces. The front and rear faces include a series of flow divider channels therein extending generally radially inwardly from an inlet and terminating in a plurality of feed spirals. The feed spirals curve radially inwardly from the flow divider channels to encircle the inner face and narrow toward a radially inwardly disposed end. The feed spirals on the front and rear spaces curve in respectively opposite directions. An inlet port extends into the outer face and fluidly communicates with the inlet of the flow divider channels. A melt distribution die includes an axially stacked array of melt distribution blocks interspersed with separator blocks extending radially about a centrally disposed mandrel to define an extrusion and passage therebetween.