| 摘要 |
1,027,528. Flat plastics bags. E. KUGLER. Jan. 28, 1964, No. 3603/64. Heading B8K. [Also in Divisions B4 and B5] A process for heat sealing and/or severing a preselected zone 20, 21 or 22 of a thermal treatable material 10 comprises printing on the preselected zone 20, 21 or 22 a layer of a thermal emitting responsive compound 18 and exposing the compound 18 to a discrete environmental condition whereby the compound 18 will respond by emitting a predetermined quantity of thermal energy. Bags 71, open at one end, are produced from a continuously advancing web 10 of heat sealable material, e.g. polyethylene, having a longitudinal fold 11 forming overlying walls 13, 14. Advertising matter may be printed on one or both walls 13, 14. The web 10 is passed over a backing roller 15 to contact an impression printing roller 16 immersed in a bath of ink compound 18 which must be electrically conductive, e.g. saturated with a relatively fine silver powder. The roller 16 prints a series of curved lines 20, a continuous line 21 parallel to the fold 11 and small circular areas 22. At station A, freely rotatable rollers 30, 31 press the walls 13, 14 into contact and a magnetic field is generated by an induction coil 40 connected to a high frequency oscillator 41 through a control 42. The magnetic field causes eddy currents to be induced in the line 21 and by adjustment of the control 42 sufficient thermal energy is released in the line 21 to bond the walls 13, 14 to form a seal line 23. At stations B and C, by adjustment of controls 52 and 62, respectively, induction coils 50, 60 cause eddy currents to be generated in the areas 22 and lines 20 to form circular cut-outs 25 in the wall 14 only and side seals 26, 27. The bags 71 are removed by a conveyer 70. In a modification, the ink contains silver azide and the elements 40, 50, 60 each represent source of ultra-violet light and/or gamma rays which cause the silver azide to disintegrate and release thermal energy. In a further modification, the ink is relatively dark, preferably black. The elements 40, 50, 60 each comprise a high intensity source of monochromatic light absorbed by the dark areas which generate thermal energy. |
