METHOD AND ARRANGEMENT FOR SEALING PAPER BAGS

Abstract: Method and arrangement for sealing paper bags, consisting of a flattened tube (12) having one or more holes (17, 18) included in one tube layer (12A) so that portions of the second tube layer (12B) located to the rear are exposed for sealing the bag by folding over the tube ends so that the exposed portions of the second tube layer (12B) are brought into contact with the outside of the tube through the holes and, by means of a glue, are fastened to this. Simultaneously with the tube (12) which is produced in the form of an endless web being cut off transversely so as to be sealed on either side of the cut, glue is applied o-n either side of the line of the cut (19) and the tube ends formed by cutting off are folded over to both sides so as to glue the folded over portions together during the sealing of one bag at its lower end and one bag at its top end. An arrangement for carrying out the method comprises a guided holder (29) which can move to and from across the paper tube (12) which has been flattened by clamping jaws (15, 16), which holder carries knife devices (26) together with a glue applicator (22), whereby the holder (29) is provided with bent over guide plates (30A) and depression devices (47) for pressing the paper down against the guide plates. The arrangement makes it possible in one simultaneous working operation to cut the paper tube (12), apply glue on either side of the cut line and to fold over and seal the folded over portions by means of gluing.

Description: METHOD AND ARRANGEMENT FOR SEALING PAPER BAGS The present invention relates to a method and an arrangement for sealing paper bags consisting of a flattened tube which is folded over and glued at both ends . The invention is of special application for the packaging of potatoes in paper bags so that, in a man¬ ner which is advantageous and economic from the produc- tion viewpoint, it will be possible to replace the plastic bags which are usually employed at present for packaging of potatoes by paper bags which are considered to better maintain the quality of the packed potatoes. However, it should be stressed that the invention is not restricted to the sealing of paper bags for potatoes, but can be employed during the packing of any other pro¬ ducts whatsoever. The sealing of a flattened paper tube by folding and gluing it at both ends is carried out using current methods normally in such a way that the two layers of the folded over end section are glued to each other and furthermore after folding are glued to the outside of the tube as a whole, which signifies that the sealing operation becomes complicated. It is also possible to provide the paper tube with tabs which are shaped in a certain manner so that sealing can take place with only a single layer of glue. The method i.s also known of ob¬ taining a seal by means of only a single layer of glue when sealing the free apertures of finished paper bags, by arranging holes in one layer of paper in the paper bag which, when the free end of the bags is folded over, are brought into contact with patches of glue applied to the outside of the bag centrally with respect to the folded over holes so that the layer of paper located underneath the said holes is during folding glue against the outside of the bag. However, for efficient packaging of products it is desirable and essential that the paper tube be formed continuously from a flat web of paper simultaneously with the packaging process. None of the above-mentioned known methods have so far proved capable of complying with this requirement in a satisfactory manner and so far, for sealing separate bag packagings made from flattened endless tube it has not proved possible to derive any sealing method or sealing arrangement which is economically justifiable. To remedy this in accordance with the invention a method and arrangement has been developed for sealing paper bags of the type specified in the introduction hav¬ ing the characteristics indicated by the following patent claims, whereby sealing can be integrated in a simple manner with the operations performed during the filling and sealing of bags which are produced continuously from a paper web in conjunction with packaging. The invention will be described in greater detail in the following by reference to the appended . drawings in which FIG 1 is a schematic vertical projection view of a packaging plant for carrying out the method in accordance with the invention, FIG 2 is a cross sectional view on a larger scale through the paper tube along the line 11-11 in FIG 1 , FIG 3 is a fragmental sectional .view through the paper tube on a larger scale along the line 111-111 in FIG 1 , FIG 4 is a view corresponding to that in FIG 3 after the paper tube has been folded over for sealing, FIG 5 is a view corresponding to that in FIG 4 after the fold has been pressed together, FIG 6 is a schematic vertical projection view of a preferred embodiment of a packaging plant for carry- ing out the method in accordance with the inven¬ tion, FIG 7 shows on a larger scale a vertical projection view of a combined cutting off and sealing arrange- ment forming part of the plant, FIG 8 is a side projection view of the cutting off and sealing arrangement illustrated in FIG 7, FIG 9 is a fragmeπtal cross sectional view taken as marked by IV - IV in FIG 8, FIG 10 is a cross sectional view marked as V - V in . FIG 8, FIG 11 is a cross sectional view as marked by VI - VI in FIG 8, FIG 12 is a cross sectional view as shown by VII - VII in FIG 8, and FIG 13 provides a cross sectional view marked by VIII - VIII in FIG 8. FIG 1 illustrates a flat paper web 10 which is drawn from a stock roll , not shown, to a forming arrange- ment 11 in which the flat paper web is shaped to form a tube 12 and is glued together at the outer edges which are made to overlap ' in a longitudinal seam 13. The shaped tube is filled with the product to be packaged, e g potatoes, through a supply tube 14, whereby the tube 12 is kept closed by being pressed flat by means of a pair of opposing jaws 15. There is a further pair of similar jaws 16 located at a distance below these jaws, which operate synchronously with the jaws 15. Between the upper jaws 15 and the lo ' wer jaws 16 sealing of a bag which is being filled is brought about at the bottom end of this bag and of a second bag 12' , which has been filled previously, at the top end of this latter bag. Two pairs of oval holes 17 and 18 situated some distance from each other along the length of the web are punched into the paper web, this punching taking place whilst the web is flat, and this can be done using known punching tools. When the web is then formed into a flattened tube 12 the apertures are in one layer of the tube, that nearest the observer in FIG 1 and desig¬ nated as 12A in FIG 2, whilst the second layer 12B has no such apertures. It is the intention that the flattened -tube should be cut off by means of a cut along the dash-dotted line 19 in FIG 1 inbetween the jaws 15 and 16 and also inbe- tween the one pair of apertures 17 and the second pair of apertures 18 so that the two end portions of the flattened tube formed by cutting will then be folded over along the dash-dotted line 20 and the dash-dotted line 21, respectively. Before cutting takes place, or in an operation which occurs at the same time as cutting, the two nozzles 23 of a glue applicator 22 are moved across the flattened tube 12 so as to apply two patches of glue 24 above the apertures 17 and two patches of glue 25 below the apertures 18, whereby the glue can be of the hot melt type. The glue patches 24 are placed at mainly the same centre to centre distance from the fold line 20 as the apertures 17 and the same applies to the position of the glue patches 25 and the apertures 18 relative to the fold line 21; in this connection see also FIG 3. To cut the flattened tube along the line 19 a knife device 26 is fed crosswise to the fl-attened tube, the knife device being designed so as to simultaneously fold over the lower end portion of the upper part of the tube along the line 20, and the upper end portion of the lower part of the tube along the line 21. As a result the aper¬ tures 17 are located in the middle of the glue patches 24 as shown in FIG 4, and the situation is analogous as regards the apertures 18 and the glue patches 25. In a stage which follows or takes place simultaneously with cutting included in the method in accordance with the invention the pressure device 27 is passed transversely across the flattened tube so that the layer 12B is glued firmly to the outside of the tube with the glue patches 24 through the apertures 17, as shown in FIG 5, and simi¬ lar gluing takes place with respect to the fold around the line 21. It can thus be seen that by employing the method the tube is reliably sealed, sealing taking place simul- taneously at the base of one bag and at the filling end of a bag which has been previously filled and had its base sealed. When the jaws 16 open the filled and sealed bag 12' is released downwards and subsequently the jaws 15 can be employed for pulling the web to repeat the process with respect to the upper end of the bag which had pre¬ viously been filled and had its bottom sealed, and a following bag which is going to be filled. The procedure in accordance with the invention has been described above in connection with an embodiment shown in highly schematic form in FIG 1 - 5. FIG 6 - 13 illustrate a preferred embodiment of the invention which will be described in the following with reference to these diagrams, whereby the same reference numerals as in FIG 1 - 5 have been employed as far as possible. Hence FIG 6 illustrates a vertical projection view of a preferred embodiment of an arrangement for carrying out the method in accordance with the invention. The diagram shows a paper tube 12 which like the embodiment shown in FIG 1 - 5 is formed from a flat paper web which is glued at the outer edges which have been made to over¬ lap, in a lengthwise seam 13. As with the embodiment in FIG 1 the paper tube is filled with the product to be packed, the tube 12 being kept closed by being pressed flat by a pair of opposing jaws 15. At some distance below these jaws a further pair of similar jaws 16 is arranged which operate synchronously with the jaws 15. Between the upper jaws 15 and the lower jaws. 16 sealing of a bag which is being filled is carried out, at the 5 lower end of this bag, and of a second bag 12', filled previously, at the upper end of this latter bag. In the flat paper web which is then formed into a paper tube a number of rows of elongated holes 17 are punched, where by the holes in each series of holes extend transverse 10 to the lengthwise direction of the paper web, the dist¬ ance between the series of holes being matched to suit the size of the desired packing. Hence it is the inten¬ tion that the flattened tube 12 will be cut off by means of a cut along the dot-dashed line 19 centrally through 15 the holes 17 in a series of holes. The sealing of the top ends of the filled bag 12' and the lower end of the bag 12 which is being filled is brought about by folding over the cut, flattened tube ends in opposite directions until they rest against the remainder of the flattened 20 tube and gluing them against the tube by means of a line of glue applied to the flattened paper tube on the side of the respective fold -line 21 which is opposite in re¬ lation to the cut line. The cutting off of the flattened paper tube 12, application of the lines of glue, folding 25 over and compression of the glued connection is brought about in accordance with the preferred embodiment by means of a combined cutting off and sealing arrangement 28 which will be described in greater detail with re¬ ference to FIGS 6 - 13. 30 As shown in these diagrams the combined cutting off and sealing arrangement 28 comprises a holder 29 which is transverse to the flattened paper tube 12, parallel with the pairs of clamping jaws 15, 16 and displaceable between these, which supports the cutting devices 26A, 35. 26B, the glue applicator 22, the guide plates 30A, 30B, OMPI 30C and the pressure devices 27A, 27B. The holder 29 is mounted on an extended rod 31 which at its end which faces away from the clamping jaws 15, 16 is provided with two guide blocks 32, parallel with each other, which can be moved inside two parallel guides 33 ar¬ ranged essentially in the same plane as the flattened paper tube so as to permit guided movement of the rod 31 and by this means also holder 29 transverse to the flattened paper tube 12 along the entire length of holder 29. The displacement movement of holder 29 is brought about by means of a variable-length force de- vide, e g a telescopic cylinder 34. At its opposite end the rod 31 is provided with two fork-like arms 3-5A, 35B each of which carries the interacting, rotating knives 26A, 26B. One rotatable knife 26B is provided with a ■ worm gearwheel 36 which engages with a worm drive 37 mounted in a sleeve which, by means of the fastening device 29, is fastened to the rod 31. The worm drive 37 and hence the rotatable knife 26B is driven in rotary fashion via a shaft 40 by a drive motor 41 (FIG 6) which is mounted on the holder 29 at the free end portion of the rod 31. A glue applicator 22 is mounted on the rod 31 a short distance to the rear of the knives 26A, 26B. Under- neath the glue applicator 22 is provided with two nozz¬ les 42 so arranged that when the arrangement for cutting off and closing the flattened paper tube is functioning they will place a line of glue on each side of the line of the cut at a sideways distance therefrom such that the layer of paper located at the rear of the respective half of holes 17 will during folding over of the cut flattened paper tube come to rest against the respective line of gl ue . On the rod 31 there are also guide plates 30A, 30B, 30C which are essentially parallel with the flattened paper tube 12 and designed to form a support and guide surface for the end portions of the paper tube 12 which have been freed by being cut off, and designed so that during the movement of the arrangement transverse to 5 the flattened paper tube, they bring about folding of the said free ends of the paper tube. The forward guide plate 30A starts directly at the rear of the knives 26A and 26B and there forms a slitghtly curved guide surface so as to ensure that the cut off end portions of the 10 flattened paper tube, during the cutting movement of the arrangement, are guided in against the surface of the guide plate 30A which faces the glue applicator 22. As shown particularly by FIGS 9 - 13 the edges of the guide plate 30A which are located along the line of the cut 15 are bent away from the line of the cut with an increas¬ ing degree of bend and an increasing bending distance in relation to the line of cut. On each side of the line of cut the bend is provided with a hopper-like portion 43 which changes subsequently into the guide plate 30A 20 which is bent through 180° and which after this bend forms an upper guide plate 30B parallel with guide plate 30A. In the area where the hopper-like portion 43 makes a transition into the upper guide plate 30B the guide * plate 30A is cut off transversely, and a metal tongue 25 44 is swivel -mounted at the cut-off end of guide plate 30A. The metal tongue 44 can be swivelled upwards to make contact with its free edge against the underside of the upper guide plate 30B and is maintained in light contact with the latter by means of a spring 45 fastened 30 to the free edge of the tongue, the other end of the spring being fastened in a fitting 46 which projects upwards from the rod 31 through an aperture in the upper guide plate 30B. The upper guide plate 30B extends for a further distance beyond the metal tongue 44, the dist- 35. ance corresponding to the maximum width of the flattened paper tube 12 which is to be cut and sealed with the arrangement. The upper guide plate 30B is subsequently bent over transverse to its length and then changes after the bend into the-ilower guide;.plate 30C which ex- tends parallel with the guide plates 30A and 30B in a direction back towards the front end of the arrangement which carries the knives. Hence the lower guide plate 30C extends incunderneath the guide plate 30A, parallel with this, and with a gap between the plates which, with a certain tolerance, corresponds to the thickness of the free edges of the flattened paper tube which have been cut off and bent over. The lower guide plate 30C extends past the tongue 44 and up to the periphery of one of two compression rollers 27A, 27B which are arranged on each side of the line of cut and which are rotatably mounted on shafts fastened to the rod 31. The rollers 27A, 27B are provided with an elastic peripheral layer and are arranged to make contact with the underside, i e the side facing away from the glue applicator 22, of guide plate 31A. In order to hold the flattened paper tube against the guide plate 30A ' during the folding operation, de¬ pression devices 47 are provided adjacent to the upper surface of guide plate 30A, and in the embodiment shown these consist of a circular bar bent in U-fashion, the free ends of which extend parallel with the upper sur¬ face of the guide plate 30A at a short distance above this and onwards into the vicinity of the supporting edge of metal tongue 44. Apart from holding the paper web against the guide plate, the arms of the depression device 47 must also form a bending edge so as to faci¬ litate the folding over of the free ends of the flat¬ tened paper tube 12. At its opposite end the U-shaped depression device 47 is attached to the upper fork-like arm 35A. OMPI In front of knives 26A and 26B two guide plates 48, arranged in V-fashion, are provided to guide the flattened paper tube 12 accurately into the knives during the introductory stage of the cutting operation. A similar guide plate 49 is provided after knives 26A, 26B to provide guide interaction with the forward por¬ tion of guide plate 30A. The gearwheel 36 is further¬ more covered by a protective casing 50 so as to prevent the sealed edge of the paper tube 12 coming into contact with gearwheel 36 during the return movement of the arrangement. Application of the arrangement illustrated in FIGS 6 - 13 for cutting and sealing a flattened paper web will be described in the following by reference particularly to FIG 6. In the position illustrated in the diagram the paper tube is kept firmly clamped be¬ tween the upper pair of jaws 15 and the lower pair of jaws 16 and with the series of holes 17 placed central¬ ly between the pairs of jaws. Thus, underneath the lower pair of jaws 16 there is a tube-shaped bag 12' which has been filled and with its bottom already sealed, and above the upper pair of jaws 15 the paper tube 12 is being filled with the material destined for packing, e g potatoes. When the cutting off and sealing operations are to be carried out the telescopic cylinder 34 is acti¬ vated, which causes the holder 29 to be moved to the left in the diagram towards the paper tube, which has been flattened between the pairs of jaws 15 and 16. Simul¬ taneously, the drive motor 41 is also activated, which causes the rotatable knife 26B to rotate. During the movement of holder 29 to the left in the diagram, the knives 26A and 26B thus perform a cut along the dash-dot¬ ted line 19 through the paper tube and transversely through the holes 17. When the nozzle 23 of the glue applicator 22 has reached the edge of the flattened 1 1 paper tube during the displacement movement of holder 29, under the influence of control signals from control devices not shown in the diagram, e g photoelectric cells or the like, the glue applicator 22, via the nozzles 26, issues a jet of glue against the flattened paper tube so that during the movement of the holder 29 a line of glue is applied to the flattened paper tube on either side of the cut 19 and beyond the two fold ' lines 21. During the movement of the holder 29 the bent over edges of guide plate 30A cause the cut off ends of the flattened paper tube to be bent upwards and folded through circa 180° whilst at the same time the layer of paper is held downwards against guide plate 30A. Folding takes place around the two free arms of the depression device 47 which ensure that folding takes place along the envisaged fold lines 21 parallel wit'd the cut line. During the continued movement of the hol¬ der the metal tongue 44 is passed underneath the bent over edges of the flattened paper tube so that after a complete stroke movement in the said direction the en¬ tire length of the bent over edges has proceeded past the metal tongue 44, which now under the influence of spring 45 is swivelled up once more to rest against the upper guide plate 30B. The direction of movement of the holder 29 is then reversed, so that the bent over edges pass underneath the metal tongue 44 and inbetween the lower guide plate 30C and the unders-ide of guide plate 30A, also between the compression rollers 27A and 27B, which press the folded over paper webs against each other so as to provide a firm bond by means of the layer of glue. The return movement of the holder 29 continues until its holder has adopted the starting position shown in the diagram. Thus, as a result of the reciprocating displacement movement of the holder 29 the flattened paper tube 12 has been cut off along the line of cut 19, 12 folded over and in an effective but simple manner by means of a layer of glue one bag 12' has been sealed at its upper end and the upper tube portion 12 at its lower end. When the jaws 16 subsequently open, the filled and sealed bag 12' is released downwards and then the jaws 15 can be employed for pulling out the web so as to re¬ peat the process with respect to the upper end of the bag which had previously had its bottom sealed and been filled, and a following bag which is next to be filled.

Claims: CLAIMS 1. Method for sealing paper bags consisting of a flattened tube (12) in which one or several holes are made in one tube layer (12A) , so that portions of the second tube layer (12B) located to the rear are exposed for sealing of the bag by folding over the tube end, so that the exposed portions of the second tube layer (12B) are brought into contact with the outside of the tube through the holes and by means of a glue are bonded to this, c h a r a c t e r i z e d in that simultaneous¬ ly with the tube, which is produced as an endless web using a known method, being cut off transversely in order to be sealed on either side of the cut (19) , the tube ends formed by cutting are folded over to both sides of the cut (19) for gluing together the folded over portions, during the sealing of one bag at its lower end and one bag at its upper end in the specified manner. 2. Method as claimed in claim ^ c h a c ¬ t e r i z e d in that glue is applied on either side of the cut line (19) in one working operation which occurs simultaneously with the cutting off of the tube and the folding over of the tube ends to both sides. 3. Method as claimed in claim 1 , in which the tube (12) is formed from a flat paper web (10), the lengthwise edges of which are glued together (at 13), c h a r a c ¬ t e r i z e d in that the aperture or apertures (17, 18) are punched in the flat paper web before this is shaped to form a tube. 4. Arrangement for carrying out the method in accordance with claims 1 or 2, comprising two pairs of clamping jaws (15, 16) arranged parallel with each other, one pair at a distance from the other and extending trans¬ versely to a flattened paper tube (12) formed as an end¬ less web, for clamping the flattened paper tube between clamping jaws in respective pairs of clamping jaws at two 1 4 different points along the flattened paper tube, to¬ gether with a cutting and sealing arrangement (28) for cutting off the flattened paper tube (12) transverse¬ ly between the said pair of clamping jaws (15, 16) and si ultaneously sealing the paper tube on either side of the cut line (19), c h a r a c t e r i z e d in that the cutting and sealing arrangement (28) includes a holder (29) which is transverse to the flattened paper tube (12), parallel with the said pair of clamping jaws (15, 16) and capable of movement between these, which at its end supports cutting devices (26, 26A, 26B) for cutting off the flattened paper tube during the move¬ ment of the holder (29) transverse to this, and that the holder (29) is provided on either side of the cut line (19) with guide plates (30A, 30B, 30C) which are essentially parallel with the flattened paper tube (12), and whose edge portions located nearest the Tine of cut are bent over in a direction outwards from the line of cut (19) with a degree of bending which increases with increasing distance from the knife devices, the aim being during the movement in the cutting direction of the holder (29) to bend over the cut off ends of the flattened paper tube (12), one end in one direction and the other end in the opposite direction so as to seal the ends of the paper tube by means of the said layer of glue, and in that at each side of the said bent over edge portions of the guide plates (3.0A) means (47) are arranged for holding the paper down against the guide plates (30A), whereby on each side of the line of cut (19) the said means are arranged- in line with the de¬ sired 1 iπe of fold (21 ) . 5. Arrangement as claimed in claim 4, c h a r a c - t e r i z e d in that the said holder (29) furthermore carries a glue applicator (22) arranged, during movement - of the holder in the cutting direction, to apply a layer 15 of glue on either side of the line of cut (19) . 6. Arrangement as claimed in claims 4 or 5, c h a r a c t e r i z e d in that the holder (29) car¬ ries at least two rotatable elastic rollers (27A, 278) arranged so that during movement of the holder (29) transverse to the flattened paper tube each presses against one of the folded over portions of the said flattened paper tube (12) . 7. Arrangement in accordance with any of claims 4 - 6, c h a r a c t e r i z e d in that the said guide plates (30A, 30B, 30C) include, a guide tongue (44) which can swivel between two positions, and arranged so that during movement of the holder (29) in the cutting direction it permits passage past the entire width of the flattened paper tube (12) and which during the re¬ turn movement of the holder is arranged to guide the flattened paper tube (12) past the opposite side of the guide plate (31A) located nearest the cutting devices (26, 26A, 26B), whereby the said elastic rollers (27A, 27B) are arranged to press against the underside of the said gu de plate (30A). OMPI

Inventors: SILVANDERSSON KARL AKE ELVIN
Applicants: KAMEK VERKSTADS AB
Application year: 1982
Main classification: B65B7
IPC codes: B65B51, B65B61