Patent GB-1039170-A (GB)
Title: Process for cutting and/or welding thin thermoplastic films, and machine for carrying out the process
IPC: B31B19/10
Filed: 1963-10-03
Abstract: 1,039,170. Seaming and cutting non-metallic sheet material. ELECTRONIC GESELLSCHAFT FUR HOCHFREQUENZTECHNIK. Oct. 3, 1963 [Oct. 3, 1962], No. 39048/63. Headings B4B and B5K. In a process for cutting and/or welding a thin thermoplastic film which is taken from a supply and is moved forward lengthwise and intermittently, the leading edge of the film is gripped by a first gripping device 5 in at least two regions disposed with mutual transverse spacing and is moved a predetermined length past a cutting and/or welding beam 6 until the edge is adjacent to a second gripping device 25 which grips the edge at positions between those positions at which it had been gripped by the device 5 whereupon the device 25, with the device 5 open, advances the film by an amount corresponding to the length of film to be manufactured and then the film is cut and/or welded. In the embodiment shown, for producing bags from a flattened thermoplastic synthetic plastic tube, the devices 5, 25 are mounted on carriages 1, 2, respectively, which run on rails 3. The beam 6 comprises a fixed lower part 6a and an upper part 6b movable in a guide 10 and which is reciprocable by the running of a roller 9 thereon on the sloping surface of a rail 8 on the carriage 1. The upper jaw of the device 5 is pivotable by an electromagnet 15 by a lever 12 about a pin 13 against the action of a spring 14. The carriage 1 is moved to the right of Fig. 1 against the action of a spring 20 by applying pressure to member 19 to pivot levers 16, 17 about a fulcrum 18. The device 25 comprises a fixed jaw 25a and a movable jaw 25b movable by arms 27 about pivots 28 by the action of electromagnets 30. A conveyer belt 33 is continuously driven so that the upper run thereof moves to the right of Fig. 1. In use the carriage 1 is stationary and the leading edge of the flattened tube is gripped by the device 5. The carriage 2 moves towards the left of Fig. 1 and in the vicinity of the carriage 1, the electromagnet 30 is energized but the jaws 25a, 25b are held open by the engagement of a pulley on a downward extension 31 on each arm 27 with a fixed wedge-shaped member 32. An abutment 26 provided on the carriage 2 strikes against the member 19 and moves the carriage 1 to the right of Fig. 1 and raises the part 6b so that the device 5 holding the film passes through the gap between the parts 6a, 6b. The projections 25c, Fig. 4, of the gripper 25 pass into the recesses 5c of the gripper 5 and vice versa. The jaws 25a, 25b close due to the pulleys on the extensions 31 leaving the memtiers 32. The carriage 2 reverses and the gripper 5 opens so that the film is withdrawn from the supply. The spring 20 moves the carriage 1 towards its starting position. When the carriage 2 stops, after moving a distance corresponding to the length of the bag to be formed, the beam 6 is actuated to cut and weld the film. After completion of the cutting and welding operation the carriage 1 reaches its starting position and the device 5 is closed. The carriage 2 travels a little further and the device 25 opens so that the bag is deposited on the belt 33. The cycle is repeated. The part 6b of the beam 6 carries a welding beam 42, Fig. 6, and a clamping device 40 comprising spring-loaded members 41. The part 6a carries a plurality of oscillatable cutter blades 43 which turn about bolts 44 when they are rotated from the gap 46, into which they are lowered when not in use, by displacement of a strip 45 and coupling bolts 47 in slots perpendicular to the plane of Fig. 6. In a modification (not shown), the belt 33 is moved intermittently and may be moved only after a certain number of bags have been stacked thereon. The drive of the belt 33 may be effected by way of a magnetic coupling energized and-de-energized by the movement of the carriage 2. In a further modification (not shown), the movable gripper jaws are actuated by small pneumatic or hydraulic cylinders, the operating medium being controlled by adjustable valves displaceable along the track of the carriages 1, 2. Alternatively, programme control devices may be provided.