GB1039110A - Improvements in and relating to the heat sealing of plastic film - Google Patents

Abstract

1,039,110. Seaming non-metallic sheet material. INDUSTRIAL DEVELOPMENTS (PACKAGING) Ltd. Dec. 3, 1964, No. 9809/65. Heading B5K. Plastics film 34, 36 is severed and/or sealed by a heated wire 32 having two distinct heating periods with a reduced temperature interval between, the whole sequence of heating, non- heating and second heating taking place whilst the wire 32 is pressed into contact with the film 34, 36. As shown, a metal angle iron 18 on the machine frame supports an anvil 20 comprising a metal strip 22 situated beneath a neoprene strip 24. The strips 22, 24 are covered with a layer 26 of glass cloth impregnated with polytetrafluoroethylene on which the film layers 34, 36 are placed. The wire 32 is mounted on an insulation strip 30 mounted on a metal strip 28. In operation, the strip 28 is lowered to nip the layers 34, 36 against the anvil 20 and a master switch is immediately closed to supply current to the wire 32 via a first time control switch to seal and sever the film. The first time switch opens and this closes a second time switch to stop the current to the wire 32 so that the molten globules of plastic begin to set. The second switch opens and this closes a third time switch to reheat the wire 32 to remelt the globules which are fused together and to the parent material. The second time switch may only reduce the current to the wire 32. The device may be used in a packaging machine to seal two layers of film wrapped around an article, the strip 28 being part of a rectangular frame adapted to seal along at least three edges. Alternatively, the article may be wrapped in a single sheet folded along one edge with two sealing edges provided on a frame.