| 摘要 |
1382343 Seaming mon-metallic sheet material FMC CORP 5 Jan 1972 [20 Jan 1971] 430/72 Heading B5K Overlapping portions 14a, 14b of a loop 14 of thermoplastic strapping tensioned about an article are friction welded and the tensioned loop is severed from a supply of strapping at the seal without leaving a tab or a free end of strap extending beyond the seal on the outside of the loop. A strapping tool comprises a tensioning mechanism in the form of a wheel 10 operated by a lever 12. During tensioning, a pivoted dog 16 holds one end of the strapping stationary. A sealing head 18 includes a strap engaging part 26 comprising a resilient pad or a metal having a spiked, serrated or roughened surface and which is secured to a base 22 of a cylindrical portion 24. The drive shaft 28 of a motor 30 has an eccentric sleeve 32 secured thereto and extends into the portion 24. A needle bearing 34 is provided between the portion 24 and the sleeve 32. A compression spring 28 acts between the motor 30 and a collar 36 loosely surrounding the portion 24 and provided with balls 40 resting on the base 22. A shifter yoke 44 is articulated to the collar 36 by pins 46, 48. Operation of a lever 52 is effective to hold the yoke 44 up to or lower it to release the collar 36 so that the spring 38 compresses the portions 14a, 14b between the part 26 and a stationary polyurethane pad 50. Alternatively, the pad 50 may be yieldingly mounted. The pad 50 is longer than the part 26 and a portion thereof underlies a saw-toothed blade 54 secured to the collar 36. In use, when the lever 52 is operated to lower the yoke 44 the portions 14a, 14b are compressed and the motor 30 is started to cause a point on the longitudinal centre line of the portion 14a to orbit about a point on the longitudinal centre line of the portion 14b to effect welding. Simultaneously, the blade 54 cuts through the portion 14a but not the portion 14b since there is no relative movement between the blade and the portion 14b. In an alternative embodiment (not shown), instead of the frictional heat being produced by an orbit movement, the portion 14a is longitudinally reciprocated relative to the portion 14b. In this case, the cutting blade 56, Fig. 4, is provided with teeth 58 extending at an angle such that a front comer 60 of one tooth overalps with the rear corner 62 of an adjacent tooth in a plane 64 perpendular to the blade. |
