Patent ID: 7654808

Claim:
An air ring for supplying cooling air to a hot extruded plastic film after the film has been extruded from an annular extrusion die at an elevated temperature, said air ring having: an annular body which in use surrounds the hot tubular plastic film after the film has left the extrusion die, said annular body having an annular plenum chamber to which air is supplied from an external source and which supplies air through an annular passage in the annular body to an annular orifice which in use of the air ring is adjacent to and surrounds the tubular film; a series of separate air passages extending completely around the annular body and communicating with the plenum chamber for receiving cooling air therefrom, each of said separate air passages extending radially inwardly from the plenum chamber to only a single respective separate orifice, wherein in use of the air ring the separate orifices are adjacent to and completely surround the hot tubular film; separate remotely controlled adjustors, each adjustor being associated with a corresponding separate air passage and being positioned entirely outside the plenum chamber and the annular passage to individually control air flow from the plenum chamber to said corresponding separate air passage, each adjustor controlling air flow to only one of said separate orifices, whereby air flow from each separate orifice impinges on a discrete circumferentially extending portion of the tubular film substantially independently of air flow from the other separate orifices.