| 摘要 |
1,114,501. Wrapping-machines. INDUSTRIAL DEVELOPMENTS (PACKAGING) Ltd. 10 Aug., 1965 [14 Aug., 1964], No. 33197/64. Heading B8C. [Also in Division B5] In a packaging machine, thermoplastic film 12 is wrapped about articles 10, 11 and simultaneously sealed and severed by a device comprising an anvil 14 and a heating element 30 mounted for rotation about parallel axes, the element 30 also being mounted for radial movement relative to its axis of rotation, driving means to rotate the anvil 14 and the element 30 in unison, and a rotary cam or pressure member driven in unison with the anvil 14 and the element 30 and adapted to engage the element 30 to press it towards the anvil 14 at the point in the cycle where the element 30 and the anvil 14 are facing each other. At a series of wrapping stations (not shown), a sheet of film 12 is laid over a fibrous tray 10 filled with fruit 11 and the edges of the sheet are folded thereunder. The sheet is sealed and severed between adjacent trays 10 and the wrapped trays pass through a heating tunnel (not shown) to shrink the film tightly on the wrapped articles. In the sealing device, the metal anvil 14 projects radially from a roller 13 geared to the machine drive to rotate at the same speed as a feed conveyer (not shown) for trays 10. A layer 17 of polytetrafluoroethylene prevents the film 12 from sticking to the anvil 14. A block 36 of resilient material spring loads the anvil 14 outwardly of the roller 13. The element 30 comprises an electrical resistance wire stretched across a strip 29 of electrical insulation material adhered to a plate 21 normally held retracted by compression springs 27 surrounding screws 26. The plate 21 is slidable radially in a slot 22 in a shroud 19 mounted on a roller 18 rotated at the same angular speed as the roller 13. The wire 30 is kept under tension by springs (31), Fig. 1 (not shown), secured to pivoted posts (32). In the sealing and severing position shown, two rollers 35 on radial arms 34 secured to a roller 33, driven at the same angular speed as the rollers 13, 18, depress two legs 23 (not shown), 24 to press the plate 21 into contact with the anvil 14. Current passes through the wire 30 as it is projected towards the anvil 14. The outer edge of the plate 21 over which the wire 30 is stretched may be coated with polytetrafluoroethylene. Rubber strips 37 are provided on the shroud 19 to hold the film 12 during sealing and severing. Two flat strip sealing wires, one on each side of the circular-section wire 30 may also be provided. |
