Abstract: Disclosed is an evacuation system for use with plastic extrusion dies, in particular a contaminant evacuation system for removal of air borne contaminants generated at the die orifice of a plastics extrusion apparatus. The system includes an annular evacuation chamber and a suction source connected to the evacuation chamber for generating a vacuum in the evacuation chamber. The evacuation chamber has a radially inwardly directed annular air intake opening for placement about the die orifice, and a baffle structure in the evacuation chamber for equalizing suction pressure along the air intake opening and reduce or avoid localized pressure differences around the extruded product, which would lead to deformation of the product.

Abstract: Disclosed is an evacuation system for use with plastic extrusion dies, in particular a contaminant evacuation system for removal of air borne contaminants generated at the die orifice of a plastics extrusion apparatus. The system includes an annular evacuation chamber and a suction source connected to the evacuation chamber for generating a vacuum in the evacuation chamber. The evacuation chamber has a radially inwardly directed annular air intake opening for placement about the die orifice, and a baffle structure in the evacuation chamber for equalizing suction pressure along the air intake opening and reduce or avoid localized pressure differences around the extruded product, which would lead to deformation of the product.

Abstract: The invention relates to an air ring for a blown film process, the air ring comprising: at least one air outlet for directing a stream of air outside the film; at least one component movable through a range of positions for controlling the air stream, said component being moveable to a set position within the range of positions for achieving a film of preselected properties; adjustor means for moving the component to any one of the positions; and output generating means for generating a unique output signal for each of said positions in said range to produce a unique signal representative of the set position. The invention also relates to methods of producing blown film. By providing output generating means to produce an output signal which identifies the positions of the components, component settings are reproducible and may be automated.

Abstract: Apparatus for producing plastic film, of the type in which molten plastic is extruded through an annular die to form a tubular bubble which is expanded by air blown into the bubble, and a collapsing frame for forming the bubble into a flat tube prior to passing the tube through a nip formed between rollers, in which opposed, converging reaches of endless belts are used for the collapsing. The belts have their upstream ends held by a pair of first rollers spaced apart on opposite sides of the bubble, and have their downstream ends held by a pair of nip rollers which hold the belts together to form a nip for the collapsed tube. Pulleys and a belt, or gears, are provided which rotatably interconnect the pinch rollers and ensure that the belts entering the nip travel at the same surface speed.

Abstract: A novel air cooling ring is provided herein for supplying successive streams of cooling air to a surface of a tubular bubble of plastic, after its extrusion from an annular die surface, the annular die surface having a die axis. The air cooling ring includes a ring-shaped plenum chamber which is provided radially-outwardly of the die axis from annular die orifice. The ring shaped plenum chamber has an air inlet, and an air outlet. The ring-shaped plenum chamber also includes an upper lip, which includes such air inlet and the air outlet, and a lower deflector lip. A forming cone extends radially outwardly from the air cooling ring. An annular air passage, which is formed in the forming core, communicates with the air outlet in the ring-shaped plenum chamber. A plurality of axial outlet ports is provided in that annular air passage.

Abstract: An air ring, for supplying successive streams of cooling air to the exterior surface of a tubular bubble of plastic after its extrusion from an annular die, has a primary annular cooling air outlet arranged to be located around and closely adjacent the die orifice, and a secondary annular cooling air outlet located axially downstream of the primary annular air outlet in the direction of travel of the tubular bubble. The primary annular air outlet is formed between an inner lip and an adjacent edge of an intermediate lip, and the secondary annular air outlet is formed between an outer lip and an adjacent edge of the intermediate lip, The lower lip, intermediate lip, and the outer lip are arranged to diverge from the die so as to allow the tubular bubble to expand coaxially with the die at an angle of divergence of at least 60 degrees from the die axis without interfering with any of the lips. Air ring means is also provided for ease of adjustment of cooling air flow rate from the primary cooling outlet.

Abstract: A bubble guide unit according to the present invention comprises two concentric frames, at least one of which rotates relative to the other, through which the film bubble passes. At least four bubble guiding rods are arranged symmetrically to each pivotally engage one frame at one end and to freely engage the other frame near its other end. Freely engage here means that the other end of each rod is free to pivot to some extent as well as to move in the direction of its length beyond the pivoting point and back. This is most easily accomplished by a pivoting ring through which the rod passes or, less elegantly, by a fixed ring having an aperture larger than the rod diameter.