Patent GB-1379717-A (GB)
Title: Machine for cutting and welding a thermoplastics web
IPC: B29C65/18
Filed: 1973-07-12
Abstract: 1379717 Seaming non-metallic sheet material K STIEGLER [trading as FELIX STIEGLER MASCHINENFABRIK] 12 July 1973 [20 July 1972] 33196/73 Heading B5K A machine for simultaneously cutting and welding a longitudinally folded thermoplastics web to form bags comprises a heated welding die 4, Fig. 1, carried by a die holder 5 and which, in use, extends across the web and is movable relatively to a support 2 by a transmission which, with the holder 5, constitutes a unit adjustable by a first setting device 74, 81, 82, 84, the first setting device having an abutment 75, 86 which keeps the unit in operative condition, there being provided a second setting device 62, 63, 67 by which the unit is movable from operative to inoperative position in which latter position the die 4 no longer contacts the support 2 during any part of its stroke. The support 2, Fig. 1, comprises a roller rotatable by a pinion 3 to move the thermoplastic web to be cut and welded into bags stepwise. The holder 5 comprises a cross beam whose ends 9 are displaceable upwardly against pressure springs 7 in two vertically movable slides 6 which are mounted between four rollers 13, Fig. 3. Each slide 6 is releasably connected to an eccentric transmission 14 comprising a circular cam disc 15 eccentrically mounted on a driving shaft 16 driven by a gear 17 from the main shaft of the machine. In the operative position of the machine, a cam follower roll 18 rotatably mounted between the arms of a fork 21 attached to each slide 6 is pressed against the cam 15 by springs 22, 23. Piston-rods 27 of pistons 26 in double-acting cylinders 24 carry abutments 28 which co-operate with abutments 29 on the forks 21. In the operative position of Fig. 1, the pistons 26 are held in their lowermost positions by a force greater than the maximum tension produced by the springs 22, 23. During heating of the die 4 or in an emergency, the die 4 is lifted away from the support 2 and is disconnected from the transmission 14 by raising the pistons 26 and thus the slides 6 through the co-operation of the abutments 28, 29. When the die 4 is lowered again, a limit switch 34 is closed by one of the abutments 28 so that the support 2 and the shaft 16 are driven again. The shaft 16 is mounted on arms 35, Figs. 3 and 4, pivoted on pins 46 and each having a slot 37 in which is seated a pin 38 eccentrically fixed to a disc 36 eccentrically fixed to a shaft 39 parallel to the shaft 16. Rotation of the shaft 39 causes up-and-down movement of the transmission 14 and the slides 6. The first setting device comprises an arm 74 Figs. 1, 5 and 6, having a slot 75 in which is seated a bolt 76 supported by parallel arms 77, 78 of a clamp 79 non-rotatably connected to the shaft 39. An eccentric pin 81 is seated in a bore 80 in the arm 74 and is attached to a shaft 82 rotatable by a handle 84. A shock absorber 85 having a buffer 86 permanently bearing against the bolt 76 is fixed to the arm 74 to absorb vibrations. Alteration of the uppermost position of the die 4 is effected by turning the handle 84 so that the pin 81 displaces the arm 74 and thus the bolt 76 turns the arms 77, 78 and hence the shaft 39. Rotation of the shaft 39 causes the pins 38 to pivot the arms 35 about the pins 46 to raise or lower the transmission 14 and thus to increase or reduce the stroke of the die 4 and the welding period. The second setting device comprises a pneumatic cylinder 62, Figs. 1, 3 and 4, pivotable about a pin 64 on a fixed bracket 65. One arm 67 of a clamp 68 is inserted between the two arms of a fork 66 adjustably mounted on the piston-rod 63, the clamp 68 being pivoted to the fork 66 by a pin 69. The clamp 68 is non- rotatably connected to the shaft 39. When the rod 63 is moved out of the cylinder 62, the clamp 68 and the shaft 39 are rotated counter-clockwise so that the pins 38 pivot the arms 35 about the pins 46 so that the shaft 16 is raised above the position determined by the first setting device without the setting of this device being altered and without disconnecting the transmission 14. The drive of the welding machine is described, Fig. 7 (not shown), and electric and pneumatic control circuits for the second setting device are described, Figs. 8 and 9 (both not shown).