Patent GB-1448014-A (GB)
Title: Apparatus for attaching strips to a continuous web
IPC: B31B50/72
Filed: 1973-09-10
Abstract: 1448014 Making bags R J WALKER 10 Sept 1973 [11 Sept 1972] 42524/73 Heading B5D [Also in Division B8] Apparatus for adhesively-attaching metal foil strips 51 to a plastics web 52 to form twisttype closure elements on bags or wrappers formed from the web, comprises a rotating drum 92 to which an adhesive-coated metal foil sheet 86 is continuously-fed by a drive roll 87, a rotatable-driven cutter 93 intermittently contacting the drum to cut strips from the sheet, vacuum parts 12 in the drum to retain the cutstrips, and a pinch roll 94 over which the plastics web is continuously fed coacting with the drum to transfer the strips on to the web, the arrangement being such that after each strip is attached to the web, the spacing between drum and pinch roller increases to release the web from gripping pressure therebetween and relieve any tensions induced in the web due to differences between web feed speed and drum peripheral speeds. The increased spacing may be achieved by providing flats 148 in the drum. Alternatively, Figs. 20- 22 (not shown), the pinch roller may be displaced away from the drum against spring bias by coacting cams and followers 286 and 287. The web is fed from a supply reel 57 by a driven roll 96 and a co-operating counter-roll 97, between the drum and pinch roll, and thence round a pivotable dancer mechanism 98 to a wind-up reel or, as shown, a bag-making machine 61. The drum, cutter, and roll 89 are synchronously and continuously driven by a variable speed motor 102 through a gear transmission 183, Fig. 7 (not shown), the speed of the motor being automatically adjusted to match that of a web-feed mechanism of the bag-making machine by the dancer mechanism. The mechanism pivots under web tension when the web feed speed is mismatched to that demanded by the machine 61 and rotates a pulley 112, Figs. 5A and 5B (not shown), and associated arms 116 and 117 to approximately reset the arm 15 of a potentiometer speed control unit 114 of the motor. The spacing between adjacent strips and/or the centre-to-centre spacing of the strips on the web may be varied by changing the gears 198 or 209 (Fig. 7) in the gear train to respectively vary the foil sheet and plastics web speed. Alternatively, the centre-to-centre strip spacing may be varied by the provision of a differential speed control unit 217 incorporated in the drive between the motor and web drive roll 96 and under the control of a manuallysettable switching unit 213, Figs. 13 and 14 (not shown), whereby the web can be driven at a selectable different average speed to that of the drum. The unit 213 may also be actuated by sensor 245 responsive to repetitive printing matter on the web to maintain the applied strips and printed matter in register. To avoid excessive stress in the web the drive to the web drive roll 96 may be taken through a belt 255, the runs of which pass over spring-biased elements 250<SP>1</SP> and 255<SP>1</SP>, Fig. 27, not shown. If the foil sheet is precoated with a heat-activatable adhesive, both the drum and the drive roll 89 incorporate electrical heating elements 66 and 154, Figs. 16 and 17 (not shown). Alternatively, the sheet may be coated with an adhesive by a roll 256 movable by a solenoid 261 into operative engagement with a roll 251. As shown, two rows of strips are bonded to the web adjacent its edges by two strip applying units 53 and 54 and the resultant web is reled, cut to form wrappers (Figs. 25 and 26), or folded longitudinally by a plough 64 and fed to a bag-making machine 61 which transversely welds and cuts the folded web to form side-welded bags. Lateral deviation of the web through the apparatus is prevented by a web-edge sensor 74 controlling a control mechanism 82 which is actuatable to displace the support frame 78 laterally along rails 79, Fig. 2 (not shown). In a modification Figs. 20-22 (not shown), a precoated foil sheet is slit longitudinally to form a plurality of parallel lengths which are each sheared into strips on a vacuum drum 277 by a cutter roll. The strips are transferred in discrete transverse rows on to a plastics web by a pinch roll 282, which is spring-urged against the drum and is intermittently displaceable away from the drum by cams 286 and 286<SP>1</SP>. This arrangement facilitates the formation of bottom-welded bags (Fig. 24) by forming the web into a tube and transversely-welding and cutting the formed tube, Fig. 19 (not shown).