| 摘要 |
655,893. Paper and like bags. ROBINSON, Ltd., E. S. & A., DAVIES, K. W., and WILLS, S. C. F. May 25, 1948, No. 14154. [Class 94(ii)] [Also in Group VIII] A method of making papei bags comprises the application of a stream of hot air or other gas to the outside of a seam in a bag tube which is to be sealed. thereby heating the contacting surfaces of the seam by conduction through the plys of material being sealed. As shown, a web 11 drawn from a reel 12 is formed into a tube having an overlapping longitudinal seam which passes beneath a nozzle 33 discharging a stream of hot air adapted to soften the heat-sealing material comprised in the seam area of the tube The seal is completed by passing the seam between pressure rolls 19 and then under a nozzle 35 which emits a stream of cold air. The sealing of transverse seams is effected by means of a pair of elements 36, 37 which grip the tube and travel with it while applying hot air to it through orifices formed in the elements. The latter are slidably mounted on a frame 48 adapted to be swung about an axle 41 by cranks carried by an axle 43. The element 36 is mounted resiliently, while the element 37 is adapted to be reciprocated by means of an eccentric 54 mounted on the axle 43. After sealing is completed, the tube is severed into bag lengths by cutter rolls 23. Air is passed over heated electrical resistances and issues continuously from the nozzle 33, but is supplied to the elements 36, 37 only when these are in contact with the bag tube. It is stated in fhe Provisional Specification that the sealing may be effected in two stages, the temperature in the first stage being comparatively low and in the second stage higher to complete the sealing. |
