| 摘要 |
1396502 Seaming non-metallic sheet material DRG PACKAGING Ltd 22 June 1972 [24 June 1971] 29761/71 Heading B5K [Also in Division B8] Prior to heat sealing together two surfaces coated with a heat sealable medium, these surfaces are exposed to a jet of hot air for a sufficient period and at a sufficiently high temperature to evaporate or dissipate greasy contaminents on the surfaces but not sufficient to fully activate the heat sealable medium. A heat-insulated housing 10 contains five electrical cartridge heaters 14 and a sixth similar, but longer, heater 16. An air inlet 18 leads to a transverse manifold passage 22 connected to helical conduits 24 passing around each heater 14 and a helical conduit 26 passing around the heater 16. The conduits 24 open into a chamber 28 leading to a nozzle 30 having an upstanding part 32 with apertures 34 on both sides thereof. The conduit 26 leads to a narrower nozzle 36. A water-cooled anvil 38 is mounted behind the part 32. An infinitely variable-bleeder valve 42 is provided to alter the pressure difference between the air supplied to the conducts 24 and that supplied to the conduit 26. In operation, a heat sealable coating on a carton flap 46 and a carton body 44 is exposed to very hot air, e.g. at 480-500‹ C., as it passes the nozzle 36 to evaporate or dissipate greasy contaminents on the surfaces to be heat sealed. As the flap 46 passes between the part 32 and the anvil 38, cooler air, e.g. at 350‹ C., activates the heat sealable coating. As the carton emerges from the end of the nozzle 30, the flap 46 is ploughed against the body 44 to effect the seal. |
