GB944425A - Method of and apparatus for making valve bags - Google Patents

Abstract

944,425. Valve bags. METAL BOX CO. Ltd. Feb. 17, 1961 [March 3, 1960], No. 7577/60. Heading B5D. [Also in Division B8] In a method of making valve bags from thermoplastics material a multiple valve unit consisting of a series of valve members is interposed between longitudinal edge portions of a V folded bag body-forming web and secured by the transverse heat seals. The valve members include side seams 9 and mouth strips F which remain free to assist opening for filling which takes place through an aperture 23 of the valve exit 11. In one form of apparatus a tubular web 1 is fed from one of two rolls 26 through smoothing rollers 27, splicer 28, used to splice the web ends when a roll is exhausted, past knives 5 which slit the tube at 7 to form two V-folded webs. One web 13 is passed round pins 29, 30, so that it is horizontally offset from the other wider web 14. The webs then pass, through intermittently rotatable rollers 3, round dance rollers 31, 32, and through tension rolls 33 and nip rolls 34 to a press 35 where cutters and heaters form an undulating heat seal between the two layers of the web 13 and sever a waste portion 12. The portion 12 is removed by rolls 37, 38. The remainder of the web 13 is then fed back above the press past a guillotine 36, which cuts off peaks 10 of the undulations, over guide rollers 39, 40 and around a guide pin 16 so as to be fed between the longitudinal edges of the body forming web 14, the web 14 being opened by a peg 22. Seal resistant elements 21 are inserted through the valve mouths and heat sealers mounted on the press 35 form the bag side seams 19, 20 and end seals adjacent the inlet 23. The webs 13, 14 are drawn through the press by means of a reciprocating slide 45 carrying grippers 41-44. In another embodiment (Fig. 1) the tubular web 1 is moved continuously through the machine. It is split at 6, 7 by knives 4, 5 to form a V folded web 14 and two superimposed webs 13. The webs 13 are sealed together by undulating heat seals 9 and waste portions 12 are removed. The remaining portion of the webs 13 which forms the valve unit is passed round pins 16, 17 so as to be inserted in the V folded web 14. Seal resistant elements 21 are inserted through the bag mouths and side seams 19 are formed, these operations being carried out by members which move with the webs while operating. The chain of bags produced may be cut into single bags by cutter 25 or means may be provided to perforate the bags along each heat seal 19 and either a pair of tearing rollers which separate the individual bags from the web be provided or the perforated chain may be rolled or fan-folded for storage until required for use. As a further alternative the method may be carried out manually. Also in any of the above embodiments a pair of overlying webs may be used instead of a tube, a bag bottom forming seal being made in this case.