| 摘要 |
Plastic bags 4 are sealed in the neck region by ballooning of the neck region and exposure of the ballooned neck portions to infra-red radiation emitted by heating units 13, 14, Figure 1, or 37, 38, Figure 2A. The thus heated neck region is then collapsed onto itself to seal upon contact. The mouth region of each bag is held by yieldable members 33, 35 so that air can escape slowly from the interior thereof but cannot re-enter. Shrinking heat is applied to the bag 4 by activation of fan motors 8, 9 and heating elements 10, 11 so that trapped air holds the bag ballooned out. Radiation from units 37, 38, protected by wire screens 39, 40, heats the bag material to its softening point. A heated wire 48 of saw-tooth or sinusoidal shape cuts the bag neck to allow escape of air from the bag and vertically movable clamping bars 45, 46 come together to effect the seal, the units 37, 38 being swung aside. A blade 47 cuts away surplus bag material. The bag may be made of a laminated film of ethylene-vinyl acetate, polyvinylidene chloride and irradiated ethylene-vinyl acetate. <IMAGE> |
