Patent GB-1234754-A (GB)
Title: Improvements in or relating to strapping machines
Inventor: SIMPSON LIONEL BRUCE
IPC: B65B13/32
Filed: 1967-02-21
Abstract: 1,234,754. Seaming non-metallic sheet material. BRITISH ROPES Ltd. 20 May, 1968 [21 Feb., 1967], No. 8299/67. Heading B5K. [Also in Division F2] A strapping machine for heat sealing thermoplastic strapping comprises means for supporting two portions of strapping in overlapping relationship, means for advancing a heater 25a in a path transverse to the length of the strapping between the overlapping portions so as to heat them to welding temperature and for withdrawing the heater 25a along the transverse path, and means for pressing the strapping under comparatively light pressure against the heater prior to withdrawal thereof and for pressing the heated overlapping portions together, after withdrawal of the heater, to effect a weld. Strapping from a spool passes, from its free end, between a serrated under-surface wedge 3 and a base 1, Figs. 2 and 3, to be gripped therebetween, through a heat sealing device, Fig. 4, around the package to be strapped, between the wedge 3 and a knurled roller 2 and again through the heat sealing device to the spool. A lever 5 is moved to and fro and carries a spring- loaded pawl 5b acting on a ratchet wheel 2b to drive the roller 2, A pawl (5a), Fig. 1 (not shown), allows rotation of the ratchet 2b in one direction only so as to tighten the strapping around the package. The heat sealing device is operated to seal the overlapping end portions of the strapping and to sever the strapping from the spool. The lever 3 is moved to the right of Fig. 3 to engage an arm 4b, Fig. 2, to swing an arm 4, Fig. 3, so that a tongue 4a thereon moves the wedge against the action of a spring- loaded plunger 3a to release the strapping. The heat sealing mechanism, Fig. 4, comprises a fixed pad 34b over which the overlapped strapping passes and which is situated adjacent the tensioning device. In use, a lever 7 is pulled to the position shown in Fig. 4 to rotate a spindle 8 having a disc 10 fixed thereto. A pin 11  on the disc 10 rotates a pawl 12 loaded by a spring 12b and rotatably and slidably mounted on the spindle 8. A part 12c of the pawl 12 moves a slide 13 to the right of Fig. 4 against a spring 14 until a spring-loaded latch 16 engages a tooth 17 on the slide. When the latch 16 is about to engage the tooth 17 a pin (23), Fig. 5 (not shown), on a cut-away disc (22) on the spindle 8 engages a lever (19), Fig. 6 (not shown), having a pin (18) thereon spring-loaded against a step (20) on a quadrant (21), see also Fig. 4, to swing the lever (19) so that the pin (18) enters a recess (24) in the quadrant (21) to allow the quadrant to swing down a short distance. This movement of the quadrant allows a pin 29, Figs. 4 and 7 (the latter not shown), on a lever 27 straddling a pin (28) on a slide 25 connected to the slide 13 by a tension spring 26, to move past a thickened part (30) of the quadrant (21) so that the slide 25 is moved rapidly to the right of Fig. 4 by the spring 26. A continuously electrically-heated blade 25a on the slide 25 is thus moved between the overlapping portions of strapping on the pad 34b. Preferably, the blade 25a comprises windings of resistance wire on mica and has a steel sheath. The downward movement of the quadrant 21 also causes a pin 31 thereon engaging a radial rod 33a on a plunger 33 to allow a spring 32 to move the plunger downwardly for a short distance so that a pressure pad 34a thereon lightly engages the strapping. The final part of the movement of the slide 25 causes a pin (28), Fig. 7 (not shown), to engage the lever (19), Fig. 6 (not shown), to swing it so that the pin (18) clears the recess (24) to allow the quadrant (21) to swing further down so that the pin 31 frees the plunger 33 to allow it to move downwardly, this movement being slowed down by a dashpot arrangement comprising a space 37 having a small bleed hole 37a to atmosphere. The plunger 33 contains a spring-loaded piston 35 carrying the pad 34a which now bears resiliently against the strapping. The blade 25a has an upstanding side edge which cuts through the strapping between the overlap and the spool. Half-way through the downstroke of the plunger 33, it trips the latch 16 to release the slide 13 so that the spring 14 returns the slide 13 together with the slide 25 and the blade 25a. The plunger 33 directly engages the pad 34a to force it under the direct action of the spring 32 against the strapping. The lever 7 is moved to the right of Fig. 4 so that the disc (22) engages the quadrant (21) and returns all the parts to their original positions.