Patent Publication Number: US-6216426-B1

Title: Leaktight chamber, method of manufacture and of packaging liquid in these chambers

Description:
This is a continuation of co-pending PCT Application Ser. No. PCT/IB97/01584, filed on Dec. 19, 1997, entitled LEAKTIGHT CHAMBER, METHOD OF MANUFACTURE AND OF PACKAGING LIQUID IN THESE CHAMBERS, the disclosure of which in its entirety is incorporated by reference thereto herein. 
    
    
     CROSS REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a bag for packaging liquid formed using a film of plastic, comprising a leaktight chamber for the liquid and a pocket, adjacent to this chamber, in which a pipe for withdrawing the liquid is housed, means being provided to give access to the inside of the said pocket, an opening being formed through part of the wall of this pocket, adjacent to the said chamber, to allow the said withdrawing pipe to enter the said chamber in a leaktight fashion. This invention also relates to a method for the manufacture of bags and for packaging liquid continuously in these bags. 
     2. Description of the Prior Art 
     There has already been proposed, especially in WO 95/23742, a bag for packaging liquid comprising an incorporated valve for controlling the outlet of liquid and which can be manufactured continuously from a film of thermoplastic. It has been proposed that a drinking straw be associated with this bag to allow the liquid to be accessed through the valve that consists of a passage formed between two layers of film which normally touch and which open when the drinking straw is inserted. Thus, when the drinking straw is withdrawn at least partially from the passage that forms the valve, this passage closes back up and the liquid can no longer get out. The drawback with this system lies in the fact that by withdrawing the drinking straw, this straw makes liquid in the passage of the valve come out, gradually soiling the outside of the bag. 
     Clearly it is not easy to make an effective seal in this kind of bag, even less so when this bag is equipped with a valve of the aforementioned type. The edges of the passage delimiting the valve are made by welding together films of thermoplastic. Now, by welding these films together, the structure of the substance of the film is locally altered and the film becomes amorphous and loses some of its elasticity, so detracting from the quality of seal that can be formed. The use of an element added on to the inlet end of this valve-forming passage is also precluded. This clearly demonstrates the complexity of the problem to be solved, it being necessary for the solution to be appropriate to the very low cost price that can be tolerated for a bag of this type. Other problems associated with this design of bag, and the solutions to which are combined and re-used in the present invention, have already been provided by the inventor of the present invention and have been covered by other protections. These in particular include the question of incorporating a drinking straw into the bag, and the tamper-proofing of this bag for obvious health and safety reasons. 
     By contrast, the problems associated with sealing and with a certain method of manufacture and of packaging the liquid continuously had hitherto not yet been dealt with satisfactorily. One of these problems is associated with incorporating a drinking straw into a closed pocket of the packaging in a manufacturing process that uses a material in the form of continuous strip. 
     BRIEF SUMMARY OF THE INVENTION 
     The object of the present invention is specifically to provide a solution to the problem of sealing, and to that of manufacturing bags and packaging liquid continuously in such bags, allowing in particular the use of known designs of machine even if these machines need after all to be converted substantially so that they can be adapted to the manufacture and packaging of these bags. 
     Thus the subject of the present invention is first of all a bag for packaging liquid of the aforementioned type as defined in Claim  1 . This tubular element of decreasing section is obtained by stretching out a plastic film and thus allows the film to maintain its elasticity which guarantees effective sealing. What is more, this is a very simple solution perfectly suited to the product for which it is intended. 
     As a preference, the wall of the pocket containing the said withdrawing pipe is secured to a tab cut from one layer of film intended to form the leaktight chamber. This tab makes it possible to guarantee that the access to the drinking straw which acts as a pipe for dispensing the liquid has not been tampered with. 
     Advantageously, the opening formed at the end of the tubular element forming the seal communicates with one end of a passage forming a valve between this opening and the inside of the leaktight chamber, the pocket of the bag being formed between a first layer of film forming one of the walls of the said passage and a second layer of film which is appreciably narrower than the first layer and secured to the tab for opening the pocket. Thanks to this arrangement, a saving of one thickness of film is made because one of the walls of the pocket is formed by one of the films of the valve passage. This saving in thickness has an advantage when the strip of part-finished bags has to be wound onto a reel to be sent to a liquid-packaging unit. The added thickness consisting of two thicknesses of film forming the walls of the pocket can thus be reduced by half, also reducing the difference in thickness from one edge of the reel of part-finished bags to the other. 
     As an alternative, this pocket may however be formed in the fold of a film folded on itself. As a preference, this fold may lie adjacent to one end of the passage controlling the flow of the liquid and the tubular element forming the seal may extend over part of this passage. 
     Another subject of this invention is a method for the manufacture of bags and for the packaging of liquid continuously in these bags according to claim  9 . One of the advantages of this method is that it allows the bags to be filled and the straws to be inserted laterally, one of the longitudinal edges of the material in strip form intended to form one of the edges of these bags remaining open until the time of filling. Thus the drinking straw can be inserted laterally along the axis of the seal and of the valve passage when there is this passage, and a liquid-supply pipe can be slipped between the walls of the bag, along its edge that coincides with the longitudinal edge of the material in strip form. This longitudinal edge is welded up as the material in strip form progresses, just before filling. 
     Advantageously, the method takes place in two separate phases, one consisting in forming a continuous strip of part-finished bags, and the second consisting in forming the tubular seal, in inserting the withdrawing pipe therein and in packaging the liquid in the chamber. The advantage of this method of production is that it allows the part-finished bags to be manufactured and the liquid to be packaged in two separate production units, the packager of the product not necessarily being called upon to solve the problems involved in the manufacture of a bag of this kind. 
     Thus the packager of liquid into the packaging can then use the part-finished bags thus produced just like simple sheets or films used for packaging liquid in sachets, bags or cartons, carrying out the packaging using conventional machinery, so that in order to package the liquid he wishes to sell in the bags according to the invention, especially bags with valves, all the liquid packager needs to do is replace the customary sheet materials or simple extruded films with the part-finished bags according to the present invention. 
     One of the main advantages of the chamber that is the subject of the invention is that there is a film seal over the valve passage and this means that by piercing this film seal, not by cutting it, but by a point deformation of the film seal towards the valve passage until it bursts, an annular seal which is slightly conical is obtained and guarantees elastic clamping of the drinking straw, giving a seal that makes it possible to prevent any liquid in the valve passage from escaping. 
     In addition, the two faces of the chamber which come from the same sheet folded onto itself do not become offset from one another, which means that the same is true of the printed wording on the two faces of this chamber. 
     Thanks to the packaging method according to the invention, the pocket which is intended to house the bent-over part of the drinking straw which lies outside the valve passage is produced after the drinking straw has been inserted into the entry to this passage, which means that the drinking straw does not pull on the lateral welds of the pocket. 
     Other advantages and other alternative forms will become clear during the description which will follow, given with the aid of the appended drawing which illustrates, very diagrammatically and by way of an example, one embodiment and one alternative form of the chamber that is the subject of this invention, and the corresponding ways of implementing the manufacturing and packaging methods that are subjects of this invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a plan view, illustrating a first phase of the manufacturing method; 
     FIG. 2 is a sectional view of FIG. 1; 
     FIG. 3 is a plan view illustrating a second phase of this method; 
     FIG. 4 is a sectional view of FIG. 3; 
     FIG. 5 is a plan view illustrating a third phase of this method; 
     FIG. 6 is a sectional view of FIG. 5; 
     FIG. 7 is a plan view illustrating a fourth phase of this method; 
     FIG. 8 is a sectional view of FIG. 7; 
     FIG. 9 is a plan view illustrating a fifth phase of this method; 
     FIG. 10 is a sectional view of FIG. 9; 
     FIG. 11 is a plan view illustrating a sixth phase of this method; 
     FIG. 12 is a sectional view of FIG. 11; 
     FIG. 13 is a plan view illustrating a seventh phase of this method; 
     FIG. 14 is a sectional view of FIG. 13; 
     FIG. 15 is a plan view of the finished bag; 
     FIG. 16 is a sectional view of FIG. 15; 
     FIG. 17 is a plan view of the fourth phase of a second embodiment of the method for manufacturing and packaging liquid in a bag according to a second embodiment that is a subject of the present invention; 
     FIG. 18 is a sectional view of FIG. 17; 
     FIG. 19 is a plan view of the fifth phase of this method; 
     FIG. 20 is a sectional view of FIG. 19; 
     FIG. 21 is a plan view of a later phase of this method; 
     FIG. 22 is a sectional view of FIG. 21; 
     FIG. 23 is a plan view of the first phase of the process of packaging liquid in the bag according to the second embodiment; 
     FIG. 24 is a sectional view of FIG.  23 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2 depict three superimposed sheets  1 ,  2 ,  3  of material in sheet form, the third sheet of which is appreciably narrower than the first two. The first sheet  1 , which is intended to form the wall of a leaktight chamber, in this example a bag for packaging a liquid, especially a drink, preferably consists of a multi-layer plastic sheet like those conventionally used for packaging food products. The various layers of these multi-layer sheets may be formed of different plastics or of the same plastic, allowing them to be recycled. Of course, the bag that is the subject of the present invention is not restricted to the packaging of drinks, but can also be used for any kind of liquid. 
     The second sheet  2  is a film of extruded plastic, especially polyethylene, as is the third sheet  3 . It should, moreover, be emphasized here that even though the sheets  2  and  3  have been depicted as initially being two separate sheets, they could also start out as a common sheet, folded about an axis which is longitudinal to that of this sheet in strip form, in order then to form the two sheets  2  and  3  of different widths depicted in FIGS. 1 and 2. 
     As another alternative, the sheets  2  and  3  could come from a tubular film, with a slightly raised pressure inside, the superimposed layers being obtained by progressively flattening the tube and gradually folding a portion of this tube longitudinally inwards. In this way, four superimposed layers are obtained, two of which are narrower than the other two, the layers being all joined together, as illustrated by FIG. 8, but without needing to be welded together. 
     These three layers  1 ,  2 ,  3  of different widths, at least as regards one of them, are first of all aligned so as to make their left-hand edges coincide. 
     The first manufacturing step of the method consists, in this example, in cutting a tab  4  from the first sheet  1  intended to form the wall of the bag. This tab  4  remains attached to the sheet  1  by one end. The cutting tools are symbolized by the rectangles  5  and  6  in FIG.  2 . During this same step, the sheet  3  can be pierced in the middle of its width to form a hole  7  for the passage of a drinking straw. The tools for making this hole  7  are symbolized by a conical punch  8  and a die  9  in FIG.  2 . The way in which this hole  7  is made is important. This does not involve cutting this hole  7 , but in stretching out the film at a point using the punch  8  in the housing formed in the die  9  until the film  3  bursts. Thus the material of the film surrounding the opening  7  is deformed by flowing, forming a sort of small conical tube  7   a  (FIG. 15) at the bottom of which there is the hole  7 . Thus when the drinking straw  21  (FIG. 15) is inserted into the hole  7  from the same side of the film  3  as the punch  8  pierced this hole  7 , this hole being sized to have a diameter very slightly smaller than that of the drinking straw  21 , the tubular part  7   a  produced during the piercing of this hole  7  grips the drinking straw  21  and forms a seal around it. 
     As an alternative, it can be envisaged for a roundel of the same plastic as this film  3  to be welded to the film  3  at the place where the hole  7  is to be pierced, so as to reinforce the tubular part surrounding the hole  7 . 
     The next operation, illustrated in FIGS. 3 and 4, consists in welding the three sheets  1 ,  2 ,  3  together in the part where the tab  4  has been cut. The weld  10  obtained covers the entire tab  4 , but it leaves an unwelded region  10   a  superimposed with the free end  4   a  of the tab  4 . Thanks to this weld  10 , it will be possible to tear the three sheets of film  1 ,  2 ,  3  using the tab  4  as will be explained later. 
     From the manufacturing method standpoint, this weld  10  is of particular interest. What it actually does is that it allows the three sheets of film  1 ,  2 ,  3  to be bonded together in such a way that there can be no more relative movement between them. Now, it is known that plastics are liable to creep when tension has been exerted on them. These sheets also experience significant dimensional variations as a result of variations in temperature, and as a result of variations in moisture content. When working, as is the case here, with a material in strip form which may have a length of as much as several hundred metres, these variations can eventually result in significant offsets. By bonding the films together at the beginning of the manufacturing method, it can be guaranteed that the operations carried out subsequently on the various sheets will be carried out in relative positions which will no longer be able to vary in inconvenient proportions. 
     The next step, illustrated in FIGS. 5 and 6, consists in folding the sheets  2  and  3  over onto themselves in the direction of the width of the strips about two longitudinal axes of folding to form two parallel folds  2   a ,  3   a . By folding these sheets  2 ,  3  onto themselves, the longitudinal edges of these sheets  2  and  3  are aligned on the left-hand longitudinal edge, which also corresponds to one of the edges of the sheet  1  forming the wall of the bag. Because of the difference in width of the sheets  2  and  3  in strip form, these folded-over sheets  2 ,  3  will be superimposed only in that part of the width of these strips which is adjacent to the superimposed edges of these strips. The sheet  1 , for its part, is separated from the sheet  2  in order to allow access to the latter. 
     If the starting material is a single tubular film, as mentioned earlier by way of an alternative, then the next step is to make a fold parallel to the axis of the tube as has already been explained as regards this alternative form. 
     During the step illustrated in FIGS. 7 and 8, two non-converging weld lines  11  are made in that part of the folded-over sheet  2  which is not superimposed with the sheet  3 . These weld lines  11  form the edges of a passage  12 , between the two folded-over films of the sheet  2 , which passage is intended to form the valve  12   a  controlling the dispensing of the liquid packaged in the bag. At the same time, the two longitudinal edges of the folded-over parts of the sheets of film  2  and  3  are fixed together by a longitudinal weld  13 . As illustrated in FIG. 8, a separator  14  is inserted between the two folded-over parts of the sheet  3  to keep a longitudinal opening to allow ready access to the inside of the pocket  15  formed between the two films of the folded-over sheet  3 . The tools used to weld together the edges  11  of the passage  12  are symbolized in FIG. 8 by two rectangles  16  and  17 . 
     FIGS. 9 and 10 show the cut-out  18  of the two superimposed films that come from folding the sheet  2 , which is carried out using two tools symbolized by the rectangles  19  and  20  in FIG.  10 . This cut-out has the shape of a U, the two parallel legs of which are non-symmetric. The transverse leg of this cut-out  18  is close to the end of the passage  12  adjacent to the fold in the sheet  2 . This cut-out  18  is intended to make the passage  12  communicate with the inside of the bag. The non-symmetry of the parallel legs of this cut-out  18 , which extend one on either side of that part of the passage  12  that forms the valve  12   a  is intended to make it work better, in association with the non-symmetric narrowings of the section of the passage  12 . 
     This stage corresponds to the end of manufacture of the part-finished bag. What this means is that up until this stage in the manufacture, the part-finished bag obtained can be rewound so that it can be transported to another manufacturer so that the liquid can be packaged into the future bags that this manufacturer will finish off by packaging the liquid, as will be explained. Of course, this is merely one possibility to which the invention is obviously not restricted. Indeed, the packaging may be carried out in line following on from the steps in the manufacturing method which have been described hitherto. 
     FIGS. 11 and 12 depict the insertion of the drinking straw  21  between the two folded-over portions of film of sheet  3 , until it enters the first part of the passage  12  through the opening  7  formed at the end of the tubular seal  7   a  discussed earlier. Note that in an alternative form, the hole  7  could be made using the drinking straw  21  itself or using a separate tool, just before the drinking straw  21  is inserted rather than during the manufacture of the part-finished bag as was described earlier. In this alternative form, the hole  7  could also be started off during the manufacture of the part-finished bag, to make piercing with the drinking straw  21  easier. As illustrated in these figures, the end of the straw  21  has an annular bulge  21   a  the purpose of which is to offer resistance when the straw  21  is withdrawn from the passage  12  and when this bulge reaches the opening  7 . As illustrated in FIGS.  11  and  12 , grippers  22  arranged on either side of the drinking straw  21  are used to hold the part-finished bags while the drinking straw  21  is being inserted. 
     As an alternative, the annular bulge  21   a  of the drinking straw  21  may advantageously be replaced by a deformation of the end of the drinking straw which is turned down outwards over a certain length, advantageously a few mm, as one does with a sock. This turning-down can easily be achieved in the hot state. The turned-down part forms an annular space in which the tubular seal  7   a  can engage when an attempt at withdrawing the drinking straw  21  from this seal is made, thus forming an end stop. 
     The last step before the liquid is packaged consists in connecting that end of the passage  12  which is adjacent to the fold  3   a  of the third sheet of film  3  to the longitudinal edge where all the longitudinal edges of the sheets  1 ,  2  and  3  are superimposed by two parallel welds  24 ,  25 . The second longitudinal edge of the first sheet  1  intended to form the wall of the bag  30  will also be fixed along this longitudinal edge, when the liquid is packaged, as will be seen below. These two welds  24  and  25  divide the pocket  15  formed between the two adjacent films of the folded-over sheet  3  into three compartments  31 ,  32 ,  33 , the last,  33 , of which contains the bent-over part of the drinking straw  21 . These welds  24  and  25  join together the two folded-over sheets  2  and  3  with the sheet  1  not yet folded over, that is to say that once the bag  30  is finished, the two folded-over sheets  2 ,  3  will be bonded to one and the same internal face of this bag  30 . 
     FIGS. 15 and 16 depict the finished bag  30 . This bag is finished off during the packaging of the liquid, and the finishing operations consist in folding the sheet  1  longitudinally around the other two sheets  2  and  3  already folded. Next, the sheets  1 ,  2  and  3  are welded together longitudinally by a weld  26  that joins together the longitudinal edges of the six layers of the three folded-over sheets  1 ,  2  and  3  and by another longitudinal weld  27  formed along the adjacent folds of the two folded-over sheets  1  and  2 . A third, transverse, weld  28  is formed between the longitudinal welds  26  and  27 . This weld  28  is intended to form the bottom of the bag  30  which is then filled via the fourth side which is left open for this purpose, after which the bag is closed by a second transverse weld  29 . The bag  30  thus obtained is detached from the material in strip form to which it was attached hitherto by cutting this strip material level with the welds  28  and  29 . 
     As can be seen, the bag  30  has two sealing barriers. One consists of the valve  12   a  formed by the part of the passage  12  situated between that end of this passage  12  adjacent to the cut-out  18  and the non-symmetric restrictions leading to a widened-section part of this passage. Another is formed between the drinking straw  21  and the tubular seal  7   a . 
     To consume the contents of the bag  30 , when this is a drink, all that is required is for the end  4   a  of the tab  4  to be gripped and pulled towards the weld  26 , thus tearing the three superimposed layers which are welded together by the weld  10 , at the welds  24  and  25 , thus giving access to the inside of the compartment  33  containing the bent-over part of the drinking straw  21 . The end of this bent-over part is gripped and is moved towards the outside of the compartment  33 , the drinking straw  21  is then pushed further into the passage  12  in order to part the part of the adjacent films of the sheet  2  forming the valve  12   a , and the liquid is sucked up through the drinking straw  21 . If one does not wish to consume the entire contents of the bag  30 , all that is required is for the drinking straw to be withdrawn to the position illustrated in FIG. 15 so that the valve  12   a  formed in the passage  12  closes back up. As to the liquid in the rest of the passage  12 , it is prevented from coming out thanks to the seal  7   a  which grips the drinking straw  21  around the opening  7  formed through the sheet  3 . As a result of this, the outside of the bag always remains clean and dry. The seal  7   a , in cooperation with the annular bulge  21   a  in the drinking straw  21 , also serves to avoid accidental withdrawal of the drinking straw  21  from the passage  12 . This is why it may be beneficial for the portion of the film  3  forming this seal  7   a  to be locally reinforced, as was mentioned earlier. 
     The closed compartments  31 ,  32  lying one on either side of the compartment  33  containing the bent-over part of the drinking straw  21  are isolated from the main chamber of the bag  30  intended to contain the liquid, which chamber is formed between the two folded-over parts of the sheet  1 . These compartments could be used to accommodate all kinds of articles, objects, treats, offers, games or parts of games, etc., which can be inserted during the operation of packaging the liquid in the main chamber of the bag  30 . 
     In a last alternative form of this first embodiment, it is envisageable to start off with a single sheet or strip folded longitudinally to produce the assembly of the chamber and of the valve that were described earlier, an approach which is not in any way impossible as far as the method according to the present invention is concerned. It should nonetheless be pointed out that to the best of our knowledge at the present time of plastics available on the market, it is preferable for the wall  1  of the bag to be formed from a PE/PET laminate. Now, PET will not weld to itself, which means that it cannot be used for the layers  2  and  3 . Furthermore, sheets formed of just PE to form the walls of the bag do not give very good results as regards the tearing of the tab  4  to open the bag. In the tests carried out, we obtained excellent results as far as forming the wall of the bag was concerned, with PE/PET sheets in which the respective thicknesses were 100 and 12 μm, the thin layer of PET making it possible to obtain a clean cut by the tab  4  at the time of opening. 
     The various steps of the method described earlier will need to be modified a little to suit the methods of manufacture adopted; a step-by-step method of manufacture or a method of manufacture in which the strip or strips advance continuously and in which the operating members on the production line are of the rotary type may be adopted. A method of manufacture of this kind can achieve higher production rates and is therefore potentially more attractive. If a tubular film is being used to produce the folded-over sheets  2  and  3 , as mentioned earlier by way of an alternative, then the tubular element needs to be moving continuously anyway. 
     To make continuous movement possible in all scenarios, it may be necessary, especially for some of the welding operations, to provide a device for accumulating strip in zig zags over rollers suspended elastically on either side of the strip, so that it can even itself out progressively into a line should there be a temporary stoppage of this strip upstream. A device of this kind is not needed if the welding stations are of the “accompanying” type. 
     To allow some of the superimposed sheets and not others to be welded together selectively, separators are inserted into the corresponding parts of the path of the strip or strips of films. In the case of “accompanying” welds, the separators will be moved back and forth in the direction of travel of these strips to allow them to follow the movement of the welding electrodes or of the cutting punches. 
     Given that the bags fitted with valves according to the invention can be produced from one, two or three sheets, one of which may be tubular, it may be preferable to begin the method by folding the sheets so as to bring them, before welding or cutting, into the position illustrated in FIG. 6, after which the cutting and welding operations are begun in the order described earlier. It can, however, be mentioned that the weld  10  superimposed with the tab  4  and around the end  4   a  of this tab  4  may preferably be produced at the same time as the weld  11  of the passage  12  of the valve illustrated in FIG.  7 . 
     As already mentioned earlier, the piercing of the opening to allow the drinking straw  21  to access the passage  12  of the valve in a leaktight fashion, made in the fold  3   a  of the sheet  3 , may be carried out during the operation of packaging the liquid in the bag. 
     The bag according to the second embodiment, the method of manufacture of which is illustrated by FIGS. 17 to  24 , differs from the one described earlier essentially in the fact that the pocket  15  is no longer formed inside a folded-over sheet, as it was earlier, but between a sheet  35  and a sheet  36 , between which the passage  12  of the valve  12   a  is formed by the two non-converging welds  11 . Unlike in the previous embodiment, this passage  12  is preferably not formed of a sheet folded  3  about a longitudinal axis of the strip film, but between two sheets  36 ,  37 . The internal longitudinal edge of the sheet  35  is welded along the line  38  to the sheet  36  forming one of the walls of the passage  12  (FIGS.  17  and  18 ). 
     In this second embodiment, most of the steps of the method are similar to those of the first embodiment, and so to avoid needless repetition, these steps have been neither depicted nor described. 
     Like in the first embodiment, the wall of the bag is preferably formed of a single sheet  1  intended to be folded longitudinally at a later stage. A tab  4  is cut in this sheet  1  (FIGS. 17,  18 ) by cutting tools  39 ,  40 , and this tab  4  is welded to the sheet  35  by a weld  10 , with the exception of its end  4   a  which is in the unwelded region  10   a  (FIGS. 19,  20 ), by welding tools  41 ,  42 . As before, this weld  10  extends right around the tab  4  to isolate it from the liquid inside the bag. 
     Next, the sheet  1  forming the wall of the bag is folded longitudinally in two to make its two edges meet, these edges being aligned with one of the edges of each band of film  35 ,  36  and  37 . This step marks the last step in the method of manufacturing the part-finished bag according to the present invention. There are then two conceivable possibilities: either the strip along which a number of uniformly spaced part-finished bags follow on from one another continues as far as a liquid-packaging unit, or this strip of part-finished bags is wound onto a reel to be transported to a separate packaging unit. 
     FIGS. 23 and 24 illustrate the first step in the packaging process, the other steps will not be described as reference need merely be made back to the previous embodiment in which the subsequent steps relating to the packaging process are the same as for this second embodiment. 
     Whereas in the first embodiment, the tubular seal  7   a  was formed in the folded-over sheet  3 , at the site of its longitudinal fold, in this embodiment, the tubular seal  7   a  is formed by piercing the film  36  forming a wall of the passage  12  and of the pocket  15 , adjacent to the film  35  forming the other wall of this pocket  15 , using a tool  42 . 
     As far as the rest of the operations relating to the insertion of the drinking straw  21 , to the filling with liquid and to the closing of the bag are concerned, as these are similar to those described in relation to the previous embodiment, reference need merely be made back to that part of the description that deals with the packaging of the liquid in this first embodiment. 
     One of the advantages of the manufacturing method of this second embodiment of bag arises out of the fact that the film  1  intended to form the wall of the bag stays flat and does not need to be pulled downwards as it did in the first embodiment, and this allows the material in strip form to be pulled under better conditions. 
     The bag equipped with a valve  12   a  constitutes the preferred embodiment of the invention. However, given the effectiveness of the tubular seal  7   a , this valve could be dispensed with provided that up until the first time it is used, the dispensing pipe  21  of the bag is plugged by a removable seal such as a stopper, then after it has been used for the first time, the bag is either restoppered or always held in a position in which the outlet opening of the dispensing pipe  21  is not below the level of the liquid in the bag.