Patent GB-1460050-A (GB)
Title: Apparatus for making bags from synthetic plastics film
IPC: B31B23/00
Filed: 1974-12-06
Abstract: 1460050 Seaming non-metallic sheet material; making bags T G HUTT 6 Dec 1974 [21 Dec 1973] 52974/74 Headings B5K and B5D A machine for making bags from a continuous heat-sealable synthetic plastics web comprises means for feeding the web to a rotatable roller 12; a cutter sealing member 20 disposed transversely to the direction of feed of the web; a link lever system 28, 29 for displacing, in synchronism with the rotation of the roller 12, the member 20 so that it reciprocates to perform a working stroke in the downstream direction, and a return stroke in the upstream direction, of the feed of the web; cam tracks 26 at opposite ends of the roller 12 and extending in the direction of web feed; means, adapted to operate in synchronism with the link lever system 28, 29, for displacing the cam tracks 26 cyclically away from the roller axis for a working stroke of the member 20; and cam followers R1, R2 on the member 20 adapted to co-operate with the cam tracks 26. The roller 12 is formed with slots 42 into one of which a blade 23 of the member 20 enters, during use, to effect cutting and sealing 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. At each end of the roller 12 a gear 14 coaxial therewith is provided. Each gear 14 engages a change wheel 16 mounted on an adjustable slide 17. The member 20 is supported at both ends of the roller 12 by forks 22 straddling the shaft 18 thereof. Radial movement of the member 20 is controlled by shallow V-shape cam tracks 26 in arms 24 at opposite ends of the roller 12. Each arm 24 is displaceable about a pivot 24À1 by the link lever system 28, 29. A rod L2 is connected to a crank pin 16À1 on the wheel 16 and to an arm 28À1 pivoted at 28À21 to an arm 28À2. A rod 28À3 transmits motion of the arm 28À2 to an arm 29À1 pivoted at 29À11 to a rod 29À2 having lost motion at 29À21. A shoe (not shown) pivoted at 29À22 to the rod 29À2 is securable at varying distances along a path 29À3 of an effort arm 29À4 of a lever 29À5 having a working arm 29À6 connected by a link 29À7 to the arm 24. Rotation of the wheel 16 causes the member 20 to move cyclically in a closed loop 20À1. A lever having an effort arm L1 and a working arm M1 is pivoted at 30. The rod L2 is connected to the arm L1 and a rod M2 is connected to the arm M1 and to one of the forks 22 to ensure that arcuate movement of the member 20 and the forks 22 takes place in unison with the periphery of the roller at the time of seal. In practice, the pivot points 28À11, 29À11 coincide. A lever system 32 compensates automatically for varying distances between the shaft 18 and the axes 17À1 rotatably support the wheel 16 on the slide 17. The slide 17 is connected by a link 32À2 to an arm 32À1 fast with an arm 32À3 pivotable about a fulcrum 33 and connected by a rod 32À4 to a lever arm 32À5 fast with an arm 32À6 connected by a rod 32À7 to the pivot 29À22. The arms 32À5, 32À6 are pivotable about the pivot 30. Any increase in the distance between the shaft 18 and the axis 17À1 causes the pivot 29À22 to move away from the fulcrum 29À51 of the lever 29À5 to lengthen the effective part of the effort arm 29À4. Conversely, any decrease in this distance causes the pivot 29À22 to move towards the fulcrum 29À51. As shown in Figs. 7 and 8, the cam tracks 26 have faces 26À1, 26À2, respectively, engaged by rollers R1, R2 provided on the rods 172 at the ends of the member 20. Each arm 24 is pulled downwardly by a spring 24À2. A lever system 47 is provided to lift the member 20 when required, e.g. for cleaning, and comprises a lever 47À1 having a fulcrum 47À0, a link 47À2 and a lever 47À3 fast with a shaft 47À4 pivotable about the fulcrum 29À51 and fast with the arms 29À6 so that pulling of the lever 47À1 in the direction 47À11 raises the links 29À7 and thus the arms 24 and the member 20. Constructions of the cutter sealing member (20), the roller (12), a bag take-off mechanism (82), and a bag counter (80), Figs. 4-15 (all not shown), identical to those described in Specification 1,459,051, are described and the machine may be used in a bag-making installation identical to that described in that Specification, Figs. 16-18 (all not shown).