PACKAGING MACHINE

1319104 Extruding blister packaging film POSSIS MACHINE CORP 26 June 1970 [18 July 1969] 31163/70 Heading B5A [Also in Division B8] Articles on a carrier are covered by a film of thermoplastic material extruded from an elongated nozzle which bridges the carrier and which is arched so that its ends are nearer the carrier than its centre. Any tendency of the edges of the film to waver is thus reduced. In the skin packaging machine shown in Figs 2 and 3, articles are fed from a shoot 8 on to a moving paperboard substrate 5 and are thereby advanced into contact with the thermoplastic sheet 5 extruded from the nozzle 11. Subsequent passage over a suction chamber 13 ensures that the sheet is drawn tightly on to the articles and the substrate before the individual packages are separated by a guillotine 15. For the main part of the substrate's travel, it is supported by a fixed table 4, but during passage over the suction chamber 13 the substrate is supported by rollers, Figs. 12 and 13 (not shown), at least some of which are driven to move the substrate through the machine. A pump 19 draws molten thermoplastic material from a melting pot 12 and passes it through a deaerator 20 to a chamber 23 which it leaves through a slit to form the film 5. The table 4 is interrupted beneath the nozzle 11 so that if there is no substrate passing through the apparatus, the thermoplastics material returns to the melting pot. Heaters are provided as appropriate in the nozzle and circulation assembly. In an alternative feed arrangement, Fig. 5 (not shown), the thermoplastic material is fed from a hopper to the nozzle by a screw. The nozzle 11 is formed so that the velocity of the material leaving it is greater at its centre than at its ends by an amount which results in a uniform velocity across the film at its contact with the substrate. Folding of the centre part of the film on the substrate is thus avoided. The velocity differential may be achieved by providing a nozzle slit which is narrower at its centre than at its ends, Fig. 9 (not shown), or which is longer (in the direction of film emergence) at its centre than at its ends, Fig. 10 (not shown). Alternatively, the molten material may be fed to the ends of the chamber 23, the latter being of smaller cross-section at its centre than at its ends, Fig. 11 (not shown). The nozzle is formed by bolting together two components 22. The sheet forming slit may be formed by including an appropriately shaped shim 28, or the components 2