Patent GB-1459051-A (GB)
Title: Method of amking bags from synthetic plastics film and apparatus therefor
IPC: B31B23/00
Filed: 1974-12-04
Abstract: 1459051 Seaming non-metallic sheet material; making bags T G HUTT 4 Dec 1974 [12 Dec 1973] 52528/74 Headings B5K and B5D Bags are made from a web 50, comprising at least two layers of heat sealable synthetic plastics film, by feeding the continuously moving web 50 over a cylindrical roller 12 having a plurality of circumferentially spaced slots 42 extending longitudinally in its periphery, the roller 12 being rotated at a speed synchronized to that of the web 50, moving a cutter blade 23 of a cutter sealing member 20 in synchronism with the rotation of the roller 12 to register with and enter one of the slots 42, and then causing the member 20 to move for a period in unison with the roller 12 in an arc about the roller axis, during which period cutting and sealing of the web 50 takes place. In one embodiment, Figs. 1 and 2, the hollow roller 12 is formed with the slots 42 and with perforations 40 connected to suction cavities 44, 46, 48 to draw the web 50 against the surface of the roller 12 as it rotates. The heated blade 23 is energized via leads 25 connected to axially spaced slip rings 67 on a shaft 68 rotated at a speed synchronized with that of a pair of chains 60, or toothed belts, between which a carrier 23.1 for the blade 23 is mounted. Preferably, a series of spaced members 20 is mounted on the chains 60. Rollers 60.1 on the chains 60 engage cam paths 66 along which the blade 23 engages the web 50 in a slot 42. In another embodiment, Fig. 3, the cutter sealing member 20 is driven by a link lever system 70 comprising a crank-wheel 70.2 carrying a crank-pin 70.1 and driven by a toothed wheel 12.2 fast with the roller 12 driven through gearing by a motor 72.5. A rod 70.3 is pivoted to the pin 70.1 and to a strut 70.4 adapted to displace the effort arm of a lever 70.5 pivoted at 70.52. A tie member 70.6 is pivoted to the lever 70.5 and to the member 20. A beam 70.7 is also pivoted to the member 20. The rod 70.3 and the beam 70.7 are pivoted, respectively, to hanging members 70.8, 70.9 hung pivotally from fixed mountings. In operation, the member 20 follows a locus (70.621), Fig. 4 (not shown), to travel with the roller 12 over a small arc for a short period during which cutting and sealing of the web 50 takes place. The web 50 is pressed into contact with the roller 12 by at least one roller 74.3 and may be fed from a supply roll 50.3 or from a printing machine. The member 20, Fig. 5, comprises downwardly-biased shoes 21 on opposite sides of the blade 23 carried by a hollow box carrier 23.1 having ventilating holes 23.11. The shoes 21 have polytetrafluoroethylene coverings 21.1 and, in use, come into contact with the web 50 before the blade 23 and are withdrawn after the blade 23. The carrier 23.1 may have a pair of aligned forks 23.21, Fig. 9, which straddle a shaft 12.13 at opposite ends of the roller 12 to permit displacement of the carrier both arcuately about and radially relative to the roller axis. A take-off mechanism 82 for the sealed bags, Fig. 6, comprises a roller 82.1 having a peripheral speed higher than that of the roller 12 to ensure that two adjacent seals are separated. Stripper members 82.2 project into spaced circumferential grooves 12.11 in the roller 12 to strip bags 50.2 therefrom and guide them, in co-operation with fingers 82.3, between corrugating rollers 82.4, 82.5 to provide corrugations in the bags which then pass to a stacking device 78, Fig. 3. A bag counter 80, Fig. 10, comprises a shaft 80.1 driven from the crank-wheel 70.2, Fig. 3, and having cam faces 80.2 which in turn operate counter mechanism 80.3. The shaft 80.1 drives a worm 80.4 engaging a worm-wheel 80.5 and is adapted to actuate bag removing means when an appropriate number of bags, corresponding to the number of teeth on the wheel 80.5, have been stacked in the device 78, Fig. 3. In a further embodiment, Fig. 12, each slot 42 contains an aluminium heat sink 42.1, insulator blocks 42.2, and electrically heated sealing bars 42.3 connected by conductors 86 to a slip ring 88. Each bar 42.3 has a polytetrafluoroethylene sheet covering 42.4 secured by a flat spring member 42.5 and wires 42.6. The cutter sealing member 20.7 comprises an electrically heated cutter blade 23.12 and electrically heated sealing strips 20.71 covered by polytetrafluoroethylene sheets 20.72 held by wires 20.73 . The arrangement is such that the blade 23.12 is heated to a higher temperature than the strips 20.71.  In another embodiment, Fig. 13, a single sealing strip 20.81 is provided to co-operate with a single sealing bar 12.81 in a slot 42 and may be arranged either against the downstream, as shown, or against the upstream side of the slot 42. In this embodiment, the groove 12.11 is deeper than the slots 42. In a bag making installation, Fig. 16, thermoplastic film 112 is blown in the form of a bubble 124 from an extruder 110, having a die 110.1 and a cooling ring 110.2, and passes between nip rollers 126 through a Corona discharge unit 114 having Corona discharge bars 114.1, 114.2 and idler rolls 114.3, 114.4. The film passes over a roller 130 and into four sets of printing rollers 132.1, ... 132.4. Each set comprises a driven impression roller 134, a stereo cylinder 136 driven by the roller 134, a transfer roller 138, and an inking roller 140 adapted to dip into ink 142 in a tray 144. The printed film passes between draw rollers 118, comprising a driven roller 118.1 and a roller 118.2 biased to roll on the film against the roller 118.1, and into a bag making machine, 10 as previously described. The rollers @ and the roller 118.1 are driven in syn- @ ism and any printing roller set may be taken out of commission by declutching the cylinder 136 from the roller 134. For this purpose, a toothed slide 134.2, Fig. 17, is axially slidable on a splined portion 134.3 fast with the roller 134. To transmit drive to the roller 136, the slide 134.2 is brought into engagement with a portion 134.4 freely rotatable on the roller shaft 134.1 and having teeth 134.5 meshing with teeth 136.1 on the roller 136.