Patent GB-1073726-A (GB)
Title: Improvements in or relating to bag making machines
IPC: B65B35/20
Filed: 1964-06-25
Abstract: 1,073,726. Making cross bottom bags with valves. UNION CARBINE CORPORATION. June 25, 1964 [June 26, 1963], No. 26247/64. Heading B5D. [Also in Division B8] Single or multiply thermoplastic tubing is severed transversely and longitudinally (Fig. 2, not shown) and the bottom flaps infolded to form a block-bottom bag. Forming block-bottom closures.-Bag tubing 12 (Fig. 1), which has been lowered over a mandrel 40 is held under tension by clamps 4 and a gripper assembly 30 whilst the tubing is severed transversely by a knife (70, Fig. 27, not shown) and vertically and diagonally by knives (74). Magnetic members (56, Fig. 8, not shown) which have been lowered to engage metallic leaves 44 in the mandrel are then raised so that the leaves 44 are spread, causing side flaps of the bag bottom to be out-folded and the end flaps to be infolded. Rolls (304, Fig. 24, not shown) above the clamping platens (300, 302) of the clamp are moved downwardly in quick succession through openings in the platens to fold under the side flaps. To prevent catching of the two side flaps, one flap is forced upwards against the platen surface by arms (91) and air jets (93). The cutting and heating assembly is then further advanced until the heat sealer (62, Fig. 27, not shown) is beneath the infolded side flaps. A cooled clamping platen (430, Fig. 26c, not shown) is then raised to engage the infolded flaps, and a heat seal bar (412) engaging slots in the platen (430) seals the bottom of the bag. Rolls (21, 23, Fig. 8, not shown) are moved downwards to partially collapse the mandrel leaves 44 and the mandrel assembly 40 is lowered with the tubing until the leaves 44 engage a saddle (78) of the gripper assembly (30). The tubing is held by clamps (803) whilst the mandrel is raised and air injected into the tube (12) to prevent formation of a vacuum. After the top of the bag has been severed by the cutters (60) a wheel (59) presses the top of the bag against a clamping platen (302<SP>1</SP>) of the clamp (28) where it is held by suction. When the bottom of the next bag is being heat sealed the bag 72 is rotated through 90 degrees to a second station where a valve is inserted. Inserting valves.-The top ply of the portion of the bag held against the clamps (28) is raised by suction cups (96, Fig. 12, not shown) and a shuttle assembly (84) inserted between them causing the end tabs to be infolded and the side flaps outfolded. A valve sheet (88) is inserted under an end tab and a heat sealer (92) lowered to seal the end tab and the valve sheet together, the shuttle plate preventing the valve sheet from being sealed to the side walls of the bag. A clamping member (90) is then lowered to hold the edge of the valve sheet against the clamp (28) and the heat sealer (92) and shuttle (86) retracted. The valve web (713) is held in position by a clamp (711) whilst cutting means (94) are swung downwardly so that an electrically heated wire (120) severs the valve sheet. Valves may be inserted at each end of the bag. Alternatively a bottom sheet overlapping both infolded end tabs may be inserted, instead of a valve. Sealing top closures.-As the bag is rotated through a further 90 degrees a silicon-coated rubber platen 130 (Fig. 1) is inserted into the top of the bag over the infolded tab at the valve end and under the infolded tab at the other end. The rolls (304, Fig. 24, not shown) on the clamps 28 are then advanced to fold over the side flaps and a heat sealer lowered to form the top closure. Discharging finished bags.-As the platen 130 is being withdrawn between stations 3 and 4 small air jets are directed between the completed bag closure and the clamping platens to break the bag loose. The clamps are then opened and the finished bag is discharged on to a shoot.