GB2354971A

GB2354971A - A bag featuring longitudinally reinforcing folds

Info

Publication number: GB2354971A
Application number: GB9923730A
Authority: GB
Inventors: Peter John Whitlock; Philip Gordon Haddow; James Goodwin
Original assignee: Molins Ltd
Current assignee: Mpac Group PLC
Priority date: 1999-10-07
Filing date: 1999-10-07
Publication date: 2001-04-11
Also published as: GB2357991A; GB0001037D0; GB9923730D0

Abstract

A bag and the apparatus and method for forming the bag, the bag being formed using a web 256 of packaging material featuring one or more longitudinal folds 284, spaced apart transversely across the web, which are stiffened by joining together laterally spaced portions of the fold and forming the web into a tube. The bag may be closed at one end region by a transversely extending seal and can have a plurality of sides. The folds may have reinforcing elements attached to them, disposed between the laterally spaced portions. The reinforcing folds may be disposed inwardly of the external surface of the tube. The reinforcing portion may be joined to an inner surface of the bag. The fold forming means may comprise elongate elements 292 which act with a surface defining convex depressions, to define ridges on a surface of the web. The folds may have a generally V-shaped cross-section. The laterally spaced portions of the folds may be joined together by heat-sealing and the heat may be applied directly to the surface portions of the web which are to be joined. The heat sealing may be achieved using a stream of hot gas directed between the laterally spaced portions which may then be pressed together to form the reinforcing folds.

Description

2354971 MB/3859-P Bag Making The invention relates to making bags.

A limiting factor in the use of bags in the packaging industry, is the lack of stiffness inherent in the packaging films, or webs, from which bags are made. This reduces the scope for producing large bags, particularly for packaging liquids, and can result in bags which have poor shape and are unable to support themselves resulting in the need to provide additional packaging for display purposes.

One approach has been to make bags with longitudinally extending stiffening ribs. EP-A-0627355 discloses an apparatus for making a bag with edge seams arranged to stiffen the bag and thereby provide improved dimensional and shape stability. The apparatus includes a forming shoulder which is arranged to cause a web of packaging material to wrap around a forming tube which defines a plurality of longitudinally extending edges corresponding to the number of sides of the bag. Each edge has a spreading element projecting radially therefrom which elements bend respective portions of the web outwardly of the forming tube. Those portions pass between respective pairs of heated rollers which form continuous seals extending in the lengthwise direction of the bag.

The invention provides a bag made of a flexible packaging material, said bag having a generally tubular configuration body portion which is closed at one end region by a transversely extending seal and at least one reinforcing portion which extends in a lengthwise direction of said body portion, the or each said reinforcing portion at least comprising a fold in said body portion which is disposed inwardly thereof and opposed portions of which are joined to stiffen said fold.

The invention includes a bag made of a web of flexible packaging material, said bag,having a plurality of sides which define a tube having a corresponding number of edges, which tube is closed at one end by a transversely extending seal, and at least one reinforcing portion disposed inwardly of said tube and extending in a lengthwise direction of a said edge, said reinforcing portion being defined by a fold in said tube opposed portions of which are joined together.

The invention also includes a method of making bags, said method including providing a plurality of folds in a web of packaging material, said folds being spaced apart in a transverse direction of said web and extending in a lengthwise direction of said web, stiffening each said fold by joining together laterally spaced portions of the 2 UB/3859-P fold, and forming said web into a tube such that said stiffened folds extend in a lengthwise direction of said tube and are disposed inwardly of an external surface of said tube.

The invention also includes apparatus for use in making bags, said apparatus including fold forming means for forming a plurality of folds extending in a lengthwise direction of a web of packaging material and spaced apart in a transverse direction of said web, means for stiffening each said fold by securing together laterally spaced portions of the fold, and tube-forming means disposed downstream of said stiffening means for forming said web into a tube, the arrangement being such that said stiffened folds are disposed inwardly of said tube.

The invention also includes a method of making bags, said method including providing a plurality of folds in a web of packaging material, said folds being spaced apart in a transverse direction of said web and extending in a lengthwise direction of said web, stiffening each said fold by joining together laterally spaced portions of the fold, and forming said web into a tube such that said stiffened folds extend in a lengthwise direction of said tube.

Advantageously, said fold-providing step includes forming said folds such that each projects from said web in a first direction and causing said folds to project from said web in a second direction generally opposite to said first direction.

Advantageously, said laterally spaced portions are joined together by heat sealing by directing heat between said laterally spaced portions such that said heat is applied directly to surface portions of said web which are to be joined. As compared with the apparatus disclosed in EP-A-0627355 in which heat has to be transferred through the web to the surfaces to be joined, this provides the advantages that less heat is required, damage to the web by overheating is reduced and multi-layer materials, which may have poor heat transfer properties, can be used.

The web may be formed into said tube such that said folds project inwardly of an external surface of said tube. This provides the possibility of making a bag in which the stiffening ribs are inside the bag so that a more attractive exterior shape can be obtained.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the drawings, in which:

Figure 1 is a schematic view of the upstream end of a bag making apparatus; 3 MB/3859-P Figure 2 is a section on line II-11 in Figure 1; Figure 3 is a continuation of Figure 1 showing a downstream end of the apparatus; Figure 4 is a transverse cross-section view of the forming tube of the apparatus shown in Figure 3; Figure 5 is a side elevation of a V-forming device of the apparatus shown in Figure 1; and Figure 6 is a perspective view of a bag made on the apparatus shown in Figures 1 to 5.

Referring to Figures 1 to 5, a bag making apparatus 200 includes a reel stand 252 for mounting a reel 254 of a flexible plastics web. The web 56 is fed from the reel 254 to a bow-forming device 258 via guide bars 260, 262. The bow-forming device 258 extends across the web perpendicular to the lengthwise direction of the web and includes an arcuate forming surface 264. The device 258 is positioned above the web (as viewed in the drawing) and the forming device is arranged to press against a central portion of the web causing the web to bow about its centreline. As an alternative to a fixed member, the bow-forming device could comprise a crowned roller.

A V-forming device 268 is positioned downstream of the bow-forming device 258 and in a different horizontal plane. The V-forming device 268 has an arcuate surface 270 which faces in the opposite direction to the forming surface 264. The V forming device also has a substantially planar surface 272 disposed perpendicular to the arcuate surfaces 264, 270. The surface 272 defines, or has fixed to it, four V-section ridges 274 (Figure 5), which serve to form correspondingly shaped ridges 276 in the top surface (as viewed in the drawing) of the web 256. The ridges are arranged to converge in the downstream direction of the surface 272. The forming surface 270 has four V shaped grooves 278, which are aligned with the downstream ends of the respective ridges and extend in parallel spaced apart relationship over the full length 280 of the forming surface 270. Rotatable discs, or other suitable guiding members (not shown), corresponding to the discs 82 shown in Figure 3, may be provided for pressing the web into the grooves to convert the ridges 276 into grooves 284 in the top surface.

Downstream of the V-forming device 268, there is a sealing station 290. The sealing station includes four nozzles 292. The nozzles 292 are in the form of elongate elements with a tapering cross-section arranged to allow the nozzles to protrude into the grooves 284. As shown in Figure 9, each nozzle has a plurality of orifices 294 defined 4 MB/3859-P in the portion of the nozzle which is received in the respective groove 284. The nozzles are connected by suitable pipe work 296, or any other suitable form of conduit, such as a manifold, to a hot air source 298.

Downstream of each nozzle 292, there is a respective pair of contrarotating rollers 300. The pairs rollers 300 are arranged such that the respective grooves 284 pass between the rollers as the web is fed through the sealing station 290.

Downstream of the rollers 300, there is a turning device 300 which is arranged to turn the web through 180 and feed it back over the reel stand 252 towards a guide roller which guides the web onto a forming shoulder 332. The turning device comprises two guide rollers 302, 304 which is disposed in parallel spaced apart relationship one above the other. The forming shoulder is arranged to guide the web so that it wraps itself around a vertically oriented forming tube 334, which in cross- section may be rectangular (Figure 4) or circular. The arrangement of the forming shoulder and forming tube is such that the web adopts a generally tubular configuration with the lengthwise extending edges 256a, 256b of the web in overlapping relationship. The forming tube 334 has a lengthwise extending groove 335 at each comer region thereof.

A backseal unit 336 is provided adjacent the forming tube 334 to seal the regions of the web 256 adjacent the edges 256a, 256b to one another to form a continuous backseal 402 (Figure 12) and thereby secure the web in the form of a tube.

A pair of vacuum belts 338 are positioned on opposite sides of the forming tube 334 to draw the web over the forming tube towards a transverse sealing station 340. The vacuum belts 338 are preferably assisted by a drive to the reel stand (not shown) which cooperates with the belts to feed the web 256 through the apparatus 200.

The transverse sealing station 340 comprises reciprocating sealing jaws 346 which are arranged to seal the web transversely. The sealing jaws may be entirely conventional and carry a severing device 360 which cuts through the web as the seal is being formed.

Just upstream of the sealing jaws, there are two gusset plates which are arranged to cooperate with the sealing jaws to form the bag 400 with a socalled block bottom. Block bottom bags and the arrangement of the sealing jaws and gusset plates to form a block bottom are well known to those skilled in the art and will therefore not be described in any further detail herein.

A product feed device 340 is positioned above the forming tube and arranged to drop predetermined amounts of product down the inside of the forming tube 334.

MB/3859-P Suitable product feed devices are commonly used with vertical form, fill and seat packaging machinery and will be familiar to those skilled in the art. Accordingly, no further description of such devices will be provided herein.

The apparatus 200 includes a control system 366 (Figure 10) which is arranged to synchronise the operation of the various parts of the apparatus and may include a PLC.

In use, the web 256 is fed from the reel 254 to the bow-forming device 258 via the guide bars 260, 262. As it passes under the bow-forming device, the web is caused to bow so that widthwise, it adopts the shape of the arcuate surface 264. The bowed web then turns through 90 and flows onto the upright surface 272 of the V- forming device 268. As the web flows over the surface 272, four generally V-shaped ridges 276 are formed. The ridges project from the top surface (as viewed in the drawing) of the web.

At the downstream end of the surface 272, the web again turns through 90 and passes over the surface 270. As the web passes over the surface 270, the material defining the ridges 276 is drawn down into the grooves defined in the surface 270 thereby inverting the ridges 276 such that they define a corresponding number of V shaped grooves 284 in the top surface of the web. The grooves 284 extend in the lengthwise direction of the web and are disposed in parallel spaced apart relationship.

As the web passes the nozzles 292, hot air is directed into the grooves against the surface portions 256g of the top surface of the web which define the inward facing surfaces of the grooves. The hot air heats the surfaces 256g to a temperature at which they will heat seal to one another and as grooves pass between the respective pairs of rollers 300, the surfaces 256g are pressed against one another thereby forming spaced apart stiffening ribs 404 extending in the lengthwise direction of the web and projecting downwardly, as viewed in the drawing.

The ribbed web is then fed over the guide rollers 302,304a which turn the web through 180' such that the ribs project upwardly (as viewed in the drawing). The web is then fed over the forming shoulder 332 and into a space defined between the downstream edge of the forming shoulder and the periphery of the forming tube 334.

This causes the web to form into a tube having a rectangular crosssection corresponding to that of the forming tube, with longitudinal edges 256a, 256b of web in overlapping relationship and the ribs 404 projecting inwardly of the tubular web and received in the respective grooves 335. As the web thus formed passes between the 6 NO/3859-P backseal unit 336 and the forming tube 334, the overlapped edges 256a, 256b are sealed together to form a continuous backseal 402.

The web the passes between the sealing jaws 346 which move together at predetermined intervals to form transverse seals at bag length intervals. The product feed device 340 drops product down the forming tube in synchronisation with the operation of the sealing jaws so that each bag formed contains the required amount of product.

Each time the jaws make a transverse seal, the severing device 360 operates to cut through and along the length of the seal so that each seal made forms the top seal 406 of a newly completed bag, which falls away when the jaws open, and the bottom seal 408 of the next bag to be formed. In a conventional manner, the gusset plates 342 reciprocate in synchronisation with the sealing jaws 346 and the drop of the product so that when the sealing jaws engage the web, a block bottom is formed and when the sealing jaws are retracted, product can drop into the newly formed bag.

It is envisaged that the web feed will be intermittent, the web being drawn forward in bag length increments and then held stationary to permit the forming of the transverse seals. The operation of the nozzles can be synchronised with the web feed so that the heat transmitted to the web is reduced when the web is stationary. Alternatively, the apparatus could be modified so as to include an accumulator so that the web feed through the sealing station 290 can be continuous. Accumulators are devices well known to those skilled in the art and accordingly will not be described in any detail herein. Although an intermittent transverse sealing process is presently preferred, it is envisaged that for certain applications it may be possible to apply sufficient heat to seal through the various layers of the web by means of a continuous rotary D- motion sealing arrangement which will be known to those skilled in the art.

It is envisaged that a reinforcing strip could be fed into the grooves 284 at a position upstream of the sealing station 290 and that the height of the strip may correspond to the depth of the grooves in which case the surfaces 256g would be joined together via the reinforcing strip. The reinforcing strip may take the form of a flexible tube in which case, the apparatus may be provided with a suitable device for directing discrete lengths of tubing into the grooves upstream of the sealing station. It will be appreciated that the reinforcing strip should have a length less than that of the bag to avoid having to form the transverse seal through the strip.

7 NM/3859-P In the embodiment, four folds are produced in the web so as to provide four stiffening ribs 404 which project from the comers of a bag 400 having a rectangular cross-section of a bag 400 having a rectangular cross-section. It will be appreciated that the process can readily be modified to produce a number of ribs matching the number of comers of the bag to be produced. Thus for a bag having a triangular cross-section, three folds would be produced to provide three stiffening ribs.

It is also envisaged that the backseal may be formed as a fin seal by conventional means well known to those skilled in the art and that by modifying the lateral positioning of the ribs 404 produced by the folding and joining process described hereinabove, the fin seal could act as a stiffening rib so that a rectangular section bag can be provided with a stiffening rib at each comer by an apparatus which produces and stiffens only three folds in the web.

It is envisaged that the stiffening ribs may be secured to the inner surface of the bag. For this purpose heated rollers or a unit similar to the backseal unit 336 may be positioned opposite each groove 335 to seal the ribs to the inner surface of the bag. A heated roller 390 for sealing a rib 404 to the bag body is indicated by dashed lines in Figure 4.

The apparatus 200 could by used to produce unfilled bags without the top seal 406. Such bags could then, for example, be filled and sealed on a machine such as that disclosed in CH 323793 (Hesser Maschinenfabrik) which includes devices for separating bags from a stack, opening the bag, filling the bag and sealing the bag as the bag is moved progressively around a track carried by a container.

In cases where the bags 400 are filled and sealed by the apparatus 200, it may be desirable to feed the bags to a bag finishing machine such as that disclosed in WO 98/33709 (Molins PLC), the content of which is incorporated herein by reference. Such a machine could be arranged to receive filled and sealed bags 400 directly from the apparatus 200 and shape and seal the top end of the bag to form a so- called block top bag which is a bag form well known to those skilled in the art. For the purposes of shaping and sealing the top end on such a machine, it may be preferable for transverse seal at the top end to be partial, with resealing taking place on the bag finishing machine as disclosed in WO 98/33709. In view of the envisaged difficulty in forming the transverse seals through the stiffening ribs, it may be desirable to carry out further sealing operations on both transverse seals whilst the bag is on this machine.

8 MB/3859-P It will be appreciated that the turning device 300 is only one example of a means for turning the web and the skilled person will have no difficulty in envisaging many other suitable devices and layouts which would not involve feeding the web back over the reel stand. It will also be appreciated that the stiffening ribs may be formed on the web in such a way that it is not necessary to turn the web through 180' in order for the ribs to be on the inside of the tube when it is formed.

9 MB/3859-P

Claims

1. A bag made of a flexible packaging material, said bag having a generally tubular configuration body portion which is closed at one end region by a transversely extending seal and at least one reinforcing portion which extends in a lengthwise direction of said body portion, the or each said reinforcing portion at least comprising a fold in said body portion which is disposed inwardly thereof and opposed portions of which are joined to stiffen said fold.

2. A bag made of a web of flexible packaging material, said bag having a plurality of sides which define a tube having a corresponding number of edges, which tube is closed at one end by a transversely extending seal, and at least one reinforcing portion disposed inwardly of said tube and extending in a lengthwise direction of a said edge, said reinforcing portion being defined by a fold in said tube opposed portions of which are joined together.

3. A bag as claimed in claim 1 or 2, wherein the or at least one said reinforcing portion includes a reinforcing element attached to said fold.

4. A bag as claimed in claim 3, wherein said reinforcing element is disposed between said opposed portions.

5. A bag as claimed in claim 3 or 4, wherein said reinforcing element comprises a flexible tube.

6. A bag as claimed in any one of the preceding claims, wherein the or each said reinforcing portion is secured to an inner surface of said bag.

7. A method of making bags, said method including providing a plurality of folds in a web of packaging material, said folds being spaced apart in a transverse direction of said web and extending in a lengthwise direction of said web, stiffening each said fold by joining together laterally spaced portions of the fold, and forming said web into a tube such that said stiffened folds extend in a lengthwise direction of said tube and are disposed inwardly of an external surface of said tube.

MB/3859-P

8. A method as claimed in claim 7, including the step of feeding a reinforcing strip between said laterally spaced portions prior to joining said portions together.

9. A method as claimed in claim 8, wherein said reinforcing strip comprises discrete lengths of flexible tubing, each said length being less than a length of said tube.

10. A method as claimed in claim 7, 8 or 9, including securing said stiffened folds to an internal surface of said tube.

11. Apparatus for use in making bags, said apparatus including fold forrning means for forming a plurality of folds extending in a lengthwise direction of a web of packaging material and spaced apart in a transverse direction of said web, means for stiffening each said fold by securing together laterally spaced portions of the fold, and tube-forming means disposed downstream of said stiffening means for forming said web into a tube, the arrangement being such that said stiffened folds are disposed inwardly of said tube.

12. A method of making bags, said method including providing a plurality of folds in a web of packaging material, said folds being spaced apart in a transverse direction of said web and extending in a lengthwise direction of said web, stiffening each said fold by joining together laterally spaced portions of the fold, and forming said web into a tube such that said stiffened folds extend in a lengthwise direction of said tube.

13. A method as claimed in claim 12, wherein said fold-providing step includes causing said web to bow in a direction transverse to said lengthwise direction.

14. A method as claimed in claim 12 or 13, wherein said fold-providing step includes forming said folds such that each projects from said web in a first direction and causing said folds to project from said web in a second direction generally opposite to said first direction.

11 M113/3859-P

15. A method as claimed in claim 14, wherein said folds have a generally V shaped cross-section.

16. A method as claimed in any one claims 12 to 15, wherein said laterally spaced portions are joined together by heat sealing.

17. A method as claimed in claim 16, including directing heat between said laterally spaced portions such that said heat is applied directly to surface portions of said web which are to be joined.

18. A method as claimed in claim 17, including directing a stream of hot gas between said laterally spaced portions.

19. A method as claimed in claim 17 or 18, further including pressing together said laterally spaced portions.

20. A method as claimed in any one of claims 12 to 19, wherein said web is formed into said tube such that said folds project inwardly of an external surface of said tube.

21. Apparatus for use in making bags, said apparatus including fold forming means for forming a plurality of folds extending in a lengthwise direction of a web of packaging material and spaced apart in a transverse direction of said web, means for stiffening each said fold by securing together laterally spaced portions of the fold, and tube-forming means disposed downstream of said stiffening means for forming said web into a tube.

22. Apparatus as claimed in claim 21, wherein said fold forming means includes a bow-forming device arranged to cause said web to bow such that a distance between lengthwise extending edges of said web is reduced.

23. Apparatus as claimed in claim 21 or 22, wherein said fold forming means includes respective projections arranged to form folds which define respective ridges on a surface of said web.

12 MB/3859-P

24. Apparatus as claimed in claim 23, wherein said projections are elongate elements which converge in a downstream direction of the flow forming means.

25. Apparatus as claimed in claim 23 or 24, wherein said projections are arranged such that said ridges are generally V-shaped.

26. Apparatus as claimed in claim 23, 24 or 25, wherein said fold forrning means includes means defining respective depressions associated with said projections such that said ridges become troughs in said surface.

27. Apparatus as claimed in claim 26, wherein said depressions are defined in a convex surface.

28. Apparatus as claimed in any one of claims 21 to 27, wherein said stiffening means includes heat sealing means for securing together said laterally spaced portions.

29. Apparatus as claimed in claim 28, wherein said heat sealing means includes respective heat applying devices arranged to direct heat between said laterally spaced portions such that heat is applied directly to surface portions of said web which are to be secured together.

30. Apparatus as claimed in claim 29, wherein said heat applying devices include a nozzle arranged to direct a hot gas between said laterally spaced portions.

31. Apparatus as claimed in any one of the claims 21 to30, including means for pressing said laterally spaced portions together.