| 摘要 |
955,618. Seaming non-metallic sheet material. DU PONT OF CANADA Ltd. Dec. 20, 1961 [May 27, 1961], No. 45629/61. Heading B5K. A process for sealing thermoplastic materials comprises applying heat to the materials in the region thereof to be sealed so as to form a molten pool and moving the material on each side of the seal towards this molten pool to reinforce the seal. In one embodiment, Fig. 3, thermoplastic films 1 are conveyed by bands 4, woven, knitted or non-woven of fibres of nylon, polytetrafluoroethylene, glass or cotton, to heated jaws 2 which close to flatten spring compression bands 3. As the jaws 2 open the bands 3 return to the shape shown so that unmolten film at the edge of the seal is forced into the liquid pool thereof, the molten material sticking to the bands 4 which can be stripped off easily after the seal has solidified. In modifications, heating bands 7 may be situated outside, Fig. 4, or inside, Fig. 5 (not shown), the bands 3 so that when the non- heated jaws 2 are closed and a current impulse is passed through the bands 7 the temperature thereof is raised and the films sealed. When the bands 7 are located inside the bands 3 a covering of polytetrafluorethylene impregnated glass cloth is applied thereto. In an alternative embodiment, Fig. 6, to form a continuous seal, continuously heated jaws 5 are kept pressed together and the bands 3, 4 move continuously therebetween, the bands 3 being flattened between the jaws 5 but returning to their curved shape after leaving the jaws 5. In a further embodiment, Fig. 9, continuously heated bands 8 and the bands 3 pass around driven and idler pulleys 9 and 10 respectively whilst the bands 4 pass around driven and idler pulleys 11 and 12 respectively. In a still further embodiment, Fig. 11, the bands 3, 8 are wrapped around rotating wheels 14 and, on sealing, are flattened owing to the resilience of a silicone rubber layer 15, the bands 3 resuming their original shape at the exit side of the wheels to compress the molten seal. The bands 4 may be omitted in which case the bands 3 are covered with polytetrafluoroethylene, glass fibres or nylon to prevent adhesion of the films thereto. The bands 3 have slotted edges and examples are shown in the Specification. Examples of thermoplastic materials sealed by this method are given. |
