The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of a divergent cooling element with a divergent cooling interface containing a cooling gas deflector spaced adjacent to the molten film tube and providing an expelled cooling gas (i) in a path opposing the flow of the molten film tube toward a first exit gap and (ii) in a path with the flow of the molten film tube toward a second exit gap. A minimum gap between the divergent cooling interface and the molten film tube occurs at the first exit gap and/or the second exit gap. Advantageously, the divergent cooling interface is provided with one or more compound angles to maximize stability and cooling efficiency. Additionally, multiple cooling elements can preferably be arranged in a stackable configuration to achieve higher throughput rates. Operation is characterized by improved film holding forces without the presence of high noise levels or detrimental vibration, flutter, and drag. Additionally, employing simplified single air delivery channels, and a stackable design, significantly reduces complexity and manufacturing costs.

A method for manufacturing a blown plastic film using an extruder, the method comprising extruding a tube of polymer resin; cooling air from a temperature of greater than 55° F. down to a temperature between about 35° F. about 50° F., to produce an intermediate cooled air stream; dehumidifying the intermediate cooled air stream to less than about 15% humidity, to produce a dehumidified intermediate cooled air stream; cooling the dehumidified intermediate cooled air stream to less than 35° F., to produce a super-cooled air stream; and directing the super-cooled air stream at the extruded tube of polymer resin.

The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of one or more enclosures with one or more respective cavities that directly receive a portion of cooling gas emanating from one or more associated cooling elements. Each enclosure includes a port containing a variable exhaust device and optional flow buffer, acting to maintain a pressure differential between the cavity and an adjacent inside volume of the molten film tube, adjustable to optimize molten film tube stability cooling element efficiency and spaced apart dimension between cooling elements. Additionally, at least one cooling element is provided, comprised of a divergent cooling element with a divergent cooling interface containing a cooling gas deflector spaced adjacent to the molten film tube and providing an expelled cooling gas.

The invention relates to a calibrating device and to a method for calibrating a film tube. An elastically deformable element (704) is secured to the sleeve (703) such that a fluid, in particular a gas, preferably air, can be introduced or discharged via a fluid connection such that a specific pressure P1 and/or a specific volume V1 is set in an area (708) enclosed by the sleeve and the elastically deformable element at a given temperature. Annular bodies (706) and (707) are arranged within the area (708), and a surface section of each annular body (706), (707) supports a respective region of the elastically deformable element (704). The elastically deformable element (704) regions which are supported by the annular bodies are located in the inlet region (711) and the outlet region (712) of the calibrating device for the film tube (713).

A system and method for extruding film with a thickened profile section. In some embodiments, the film forms bags with integral zipper profiles. Plastic film is extruded to form a tube. During extrusion, each thickened profile section is radiantly cooled in a preferential manner before thinner sections of the film freeze. A freezing control device includes at least one radiant cooling plate that is operatively aligned with a thickened profile section. The device also includes a cooling fluid recirculation system configured to maintain the plate at a temperature below the temperature of the extruded tube. The plate can be adjustably mounted on a base for positioning the plate at the desired orientation for cooling the thickened profile section of the tube.

A method of producing a blown film with a controlled thickness profile, comprises the steps of: extruding molten plastic through an annular extrusion die; cooling the molten plastic using an annular blower around the extrusion die, positioning one or more sources of supplemental air at one or more desired circumferential positions about the annular extrusion die and adjacent to the extruded molten plastic, the annular blower and the one or more sources of supplemental air being operated to supply cooling air to the molten plastic between the annular extrusion die and the frost line where the molten plastic solidifies; and controlling the one or more sources of supplemental air to form one or more areas of increased thickness along a circumferential thickness profile of the blown film, the one or more areas of increased thickness having a thickness that is greater than an average thickness of the circumferential profile.

An apparatus includes an upper lip positioned with respect to an air flow passage. The upper lip is to direct air flow from the air flow passage around a bubble of blown film. The apparatus further includes a Venturi ring movably mounted with respect to the upper lip and adjustable in position with respect to the upper lip. The Venturi ring is to adjustably lock the bubble of blown film.

A blown-film extrusion apparatus for manufacturing a tubular polymer film comprises an extruder; a solidification ring for solidifying a tubular element produced by the extruder and for forming the film by delivering cooling air on the tubular element at a given cooling height, and a film conveyor for conveying the film upwards. The apparatus also comprises a delivery device for projecting correction air on the tubular element, in order to locally correct the thickness of the film, comprising a distribution chamber; a plurality of air delivery members with delivery channels whose delivery mouths are arranged about said axis of the apparatus for projecting correction air partial streams on respective angular correction positions, between the die and the cooling height; flow control elements between the distribution chamber, and the inlet of respective air delivery members, configured for adjusting the flowrate of the respective correction air stream according to an adjustment signal. According to an aspect of the invention, a plurality of separate radial ducts is provided defining respective delivery channels and spaced apart, at an own end portion, by separation spaces, so that the correction air partial streams, after hitting the tubular element in the respective angular correction positions, can flow away from the tubular element through said separation spaces. According to another aspect of the invention, the distribution chamber is defined by an upper ring and by a lower ring connected to each other by means of tight fixed joints with a first substantially cylindrical wall and with a second substantially cylindrical wall arranged around the first cylindrical wall, wherein possible separate radial ducts of the air delivery members protrude from the first cylindrical wall.

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.

The invention relates to an apparatus for producing tubular films stretched in-line by blow molding with an extruder, a film blowing line, a lay-flat unit, an oscillating haul-off unit, and a stretching line for monoaxially stretching the film laid flat in machine direction. According to the invention, the stretching line is arranged above the extruder between the lay-flat unit and the oscillating haul-off unit.