Patent GB-1496312-A (GB)
Title: Welding and cutting device for packaging machines
IPC: B65B51/30
Filed: 1976-01-15
Abstract: 1496312 Seaming non-metallic sheet material SITMA INTERNATIONAL SA 15 Jan 1976 [17 Jan 1975] 01582/76 Heading B5K [Also in Division B8] A device for welding and severing thermoplastic film in a packaging machine in which articles to be packaged are fed in succession by a conveyer belt 1 and wrapped in a continuous tubular thermoplastic film, comprises a welding tool 11 and a counter-welding tool 12 mounted on a carriage 6 reciprocable horizontally in the direction of movement of the belt 1, the arrangement being such that, in use, the tools 11, 12 lie on opposite sides of the film and each tool 11, 12 is reciprocable between a rest position and a welding and severing position of mutual engagement, and means (9), Figs. 4 and 5 (both not shown), so deflecting the belt 1 to avoid it passing through the gap between the tools 11, 12. As shown in Fig. 1, the carriage 6 is guided in guides 5 and comprises idler rollers 8, (9), 10 to guide the belt 1. Preferably, the tool 11 comprises an electrically heated wire. The carriage 6 is reciprocable horizontally by a motor 13 through a reducing gear 14, a chain 15, and a shaft 16 carrying an eccentric 17 connected through a clevis 18 to a lever 19 fixed to a shaft 20 connected to the carriage 6 by pairs of levers 23, 24. Adjustment of the amplitude of the stroke of the carriage 6 is effected by adjustment of a slider 22 carried by the clevis 18 on a screw 21 carried by the lever 19. The tool 11 is reciprocable vertically by a pneumatic ram 25 through a crank 26 connected to a shaft 27 having secured thereto two cranks 28 connected to the tool 11 by links 29 having springs 30 inserted therein. The tool 12 is reciprocable vertically from the shaft 27 by eccentrically mounted boxes 36 in which are inserted followers 35 on cranks 34 secured to a shaft 33 having integral therewith cranks 32 connected by rods 49, 31 to the tool 12. The stroke of the tool 12 is adjustable by adjusting the position of the followers 35 in the boxes 36 by altering the position of the shaft 27 by a screw 37 and a crank 38. If the shaft 27 and the followers 35 are coaxial, the tool 12 remains stationary, relative to the carriage 6, immediately below the film, Fig. 4 (not shown). Any adjustment of the screw 37 causes the shaft 33 to oscillate and the tool 12 to oscillate between its rest position and a raised position, Fig. 5 (not shown). Due to the superposition of the horizontal movement of the carriage 6 and the vertical movement of the tools 11, 12, these tools each move along a path of elliptical outline. The downstroke of the tool 11 is started by the engagement of a part 40 on the shaft 16 with a microswitch 41, Figs. 1 and 3, mounted on a lever 42 pivoted to the shaft 16. The lever 42 is connected through a rod 43 to a lever 44 the position of which is a function of the speed of the motor 13, a speed-position transducer 45 being provided. The actuation speed of the ram 25 is controlled according to the position of the lever 44 through a rod 46, a lever 47 and a flow regulator 48. An alternative mechanism for the adjustment of the engagement position of the tools is described, Figs. 7 and 8 (both not shown).