Patent Publication Number: US-6334711-B1

Title: Liquid-tight container and process for conditioning a liquid in said container

Description:
This application claims is a continuation of application number PCT/IB96/01214, filed Nov. 13, 1996. 
    
    
     The present invention relates to a leaktight container for packaging a liquid, including a sheet fixed to the internal face of a wall of the container by a leaktight connection surrounding a region of this sheet thus isolating it from the inside of the container, the breaking of this sheet in the said region thus isolated allowing access to the inside of the container. 
     Such leaktight containers with more or less solid flexible walls, pierced with an opening which is sealed by a membrane fixed against its internal face, and used for the packaging of liquid are already known. To access the inside of the container, all that is required is for the membrane to be pierced. In general, when the liquid is a drink, the membrane is pierced using a drinking straw which is then used for sucking up the liquid. When the container is a flexible-walled bag in particular, the pressure required to pierce the membrane is transmitted to the wall of the bag, thus temporarily increasing the pressure on its liquid contents at the moment it is being opened, this meaning that the pressurized liquid can come out of the bag. 
     DE-A1-41 15 000 discloses a tubular bag in which the border parts adjacent to the longitudinal edges overlap, each of these edges being welded to the adjacent face. An opening is made in the border part of the underlying longitudinal edge, while a tab, which is offset with respect to the opening, is cut in the border part of the longitudinal edge covering this underlying part. A transverse weld extends between the two welded longitudinal edges. This transverse weld passes between the opening and the tab, so that a leaktight barrier isolates this opening from the cut out tab. To open the bag, it is merely necessary to pull on this tab so as to tear that portion of the wall of the bag which covers the opening. 
     To access the opening, the transverse weld which separates the opening from the tab must first of all be broken by pulling this tab. This breaking of this transverse weld requires substantial effort. It is also difficult to control. This means that there is a risk of it&#39;s either causing the tab to break, or of the longitudinal welds becoming torn, causing the bag to fall apart. Independently of these risks, the leaktight overlap region in which the opening is located, situated between the longitudinal welds, the transverse weld and a weld sealing one end of the bag, is in communication with the inside of the bag. This means that liquid can enter this region. As the bag is being opened, this liquid may run out over the external face of the bag and dirty it. 
     Leaktight bags are also known which have a valve, at least part of which is situated inside the bag and is formed between two flexible sheets passing through part of the bag and fixed in leaktight fashion between the edges of the bag. These sheets are joined together along two lines which do not converge so that by moving the said sheets away from one another a passage is formed between these lines, allowing a fluid to pass from the inside to the outside of the bag, the flexible sheets being intended to be pressed one against the other as soon as a force for parting them is no longer applied to them, thus preventing the said fluid from coming out of the bag. 
     Such bags are known and have been described in WO 985/23742, in FR 2 711 115 or in FR 1 338 549 in particular. 
     The valve of these leaktight bags is normally formed by a passage which is open at both of its ends which means that it offers the user no guarantee regarding use of this bag prior to its purchase. Aside from the fact that the purchaser therefore has no guarantee that the bag still contains the initially packaged amount of product, neither does he have any guarantee regarding the conditions of hygiene of the product thus packaged. 
     To overcome this drawback, it has been proposed to seal one of the ends of the passage using an attached cap, thus requiring another component to be added to the packaging. 
     To work effectively, the passage forming the valve between the two flexible sheets has to be long enough to provide an effective seal. In the solutions proposed hitherto, the length of the passage has been increased by forming a passage which is at an angle to the major axis of the bag, which means that the length of this passage is increased without a proportionate increase in the length of the flexible sheets extending into the bag. All the same, the surface area of flexible sheet used is substantially greater than the surface area occupied by the passage. 
     In addition to optimum usage of the sheet material forming the valve, one of the objects of the present invention is optimum usage of the volume of the bag. In bags of the state of the art, the top of the bag is left open to allow for filling. The fill level cannot be very high in such cases otherwise the liquid overflows from the bag when the top edge is welded up. This means that the extent to which the liquid fills the bag is not very high. Of course it is possible to fill the bag through the passage of the valve, but liquid would remain in this passage, and this would not be acceptable as the passage has to remain perfectly clean until it is first used. 
     The object of the present invention is to overcome, at least in part, the aforementioned drawbacks. 
     To this end, the subject of the present invention is a leaktight container in which a tab, intended for opening the said container, is formed in the portion of its wall adjacent to a region of the sheet fixed to the inside of the container, surrounded by a leaktight connection attaching this sheet to the wall of the container, one end of this tab being free and acting as a means for holding, while another part of this tab is fixed to the said sheet, thus allowing the said sheet to be broken by pulling on the tab and thus gaining access to the inside of the container. 
     Another subject of this invention is a leaktight bag of the aforementioned type, fitted with a valve. To this end, a second flexible sheet is joined to the first sheet, which is also flexible, along two connection lines which do not converge extending between two distant parts of the joined-together edges of the walls of the container to form a passage between these sheets in the part extending between the connection lines, at least one of the said sheets having a cut between the said non-converging connection lines, some distance from the said leaktight connection between the said first sheet and the wall of the container so as to make the said passage communicate with the inside of the container, the parts of these sheets situated between the said connection lines being intended to be pressed one against the other as soon as a force for parting them is no longer applied to them, thus preventing the said fluid from coming out of the container after an opening has been made in the said first sheet using the said tab. 
     Another subject of the invention is a bag or a leaktight container of the aforementioned type, fitted with a valve, in which bag or container a second passage is formed between the said flexible sheets and has an outer end adjacent to one edge of the said bag and the other end in communication with the inside of this bag. 
     Another subject of this invention is a method for packaging a liquid in a bag or container including the said second passage, according to which method the bag together with the two passages is formed, at least the outer end of the said second passage adjacent to the edge of the said bag is left open, the said liquid is introduced through this second passage and the said outer end of the second passage is sealed. 
     Among the many advantages of the container which forms the subject of the present invention, in the case of a valveless container, apart from the fact that it overcomes the risk of liquid under pressure leaking out as this container is being opened, the solution proposed does not add any additional components to the leaktight container as compared with the known solutions, the tab being formed by a portion of the wall of the container. This solution therefore does not lead to an increase in production costs. Furthermore, existing production lines can continue to be used with only very slight modifications affording an advantage which is not insignificant from the product standpoint. 
     In the container with a valve, the valve is protected from any attempts at tampering. Hygienic conditions are perfectly guaranteed right up to the first time that the bag is used. The number of components forming the bag and the valve are reduced as far as possible, no attached element being needed to tamperproof the valve. The area of sheet needed to produce the passage and the fillable volume of the bag is optimized. 
     Other advantages will emerge from reading the description which follows, given with the aid of the appended drawing which illustrates, diagrammatically and by way of example, one embodiment and various alternative forms of the leaktight container which forms the subject of this invention. 
    
    
     FIG. 1 is an elevation illustrating the various stages in the process for manufacturing this leaktight container. 
     FIG. 2 is a plan view on II—II of FIG.  1 . 
     FIG. 3 is a plan view on III—III of FIG.  1 . 
     FIG. 4 is a plan view on IV—IV of FIG.  1 . 
     FIG. 5 is a plan view on V—V of FIG.  1 . 
     FIG. 6 is a plan view on VI—VI of FIG.  1 . 
     FIG. 7 is a plan view on VII—VII of FIG.  1 . 
     FIG. 8 is a section on VIII—VIII of FIG.  7 . 
     FIG. 9 is a section on IX—IX of FIG.  7 . 
     FIGS. 10,  11  and  12  are perspective views of a leaktight bag illustrating three stages in its use. 
     FIGS. 13 to  15  are perspective views of an alternative form, illustrating three stages in its use. 
     FIGS. 16 to  19  illustrate various phases in the production of an alternative form of the container forming the subject of the invention. 
     FIG. 20 is a perspective view of another alternative form, in the sealed position. 
     FIG. 21 is a view similar to FIG. 20, in the open position. 
     FIG. 22 is a section on XXII—XXII of FIG.  20 . 
     FIG. 23 is a section on XXIII—XXIII of FIG.  21 . 
     FIG. 24 is a part elevation of an alternative form of the manufacturing process of FIG.  1 . 
     FIG. 25 is a section illustrating the successive stages in the manufacturing process of FIG. 24, on a—a, b—b, c—c, d—d, e—e and f—f. 
    
    
     FIG. 1 illustrates four endless strips  1 ,  2 ,  3 ,  4  of monolayer or multilayer thermoplastic film, such as polystyrene, polypropylene, polyethylene or polyamide, which are used to manufacture the leaktight bag which is the subject of the invention. The strips  1  and  4 , which are wider, are intended to form the walls of the bag, while the narrow strips  2  and  3  are used to produce the valve. As a preference, the thickness of the film of the strips  2  and  3 , which is of the order of 40 μm, is less than that of the film of the strips  1  and  4 , which is of the order of 100 μm, so as to make the strips  2  and  3  more flexible, to make it easier for the valve to close. 
     The various operations in manufacturing this bag progress in line on the strips  1  to  4  and are illustrated by FIGS. 2 to  7  in which the width of the bag is drawn in chain line. 
     The first operation is carried out on the sheet  1  and consists in precutting tabs  5  at regular spacings. Each tab  5  is intended to be situated close to one of the corners of the bag. The end of this tab  5  is cut out, while its parallel edges are precut in such a way that before use the tab  5  remains in the plane of the sheet  1 . 
     The second operation (FIG.  3 ), consists of depositing a rectangle  6  of heat-resistant ink or lacquer on the sheet  2 , at regular spacings, corresponding to the spacings between the tabs  5 . 
     The third operation consists of welding the sheets  2  and  3  along two parallel lines  7  and  8  (FIG.  4 ), leaving a passage  10  between them, the flexible walls of which passage are normally touching, but can be moved apart, thus forming the valve which controls the dispensing of the packaged liquid. These welds  7  and  8  narrow at the point where the heat-resistant lacquer  6  is situated. During the same operation, two parallel cuts  9  are made in the welds  7  and  8 , and a transverse cut  9   a  connects the parallel cuts  9 , thus placing the passage  10  in communication with the outside. 
     During the fourth operation (FIG.  5 ), the two strips  2  and  3  are welded to the strip  1  with a weld  11  which extends along the outer edge of the strips  2  and  3  and near to the adjacent edge of the strip  1 . A weld  12  is also produced. The welds  11  and  12  are disposed on both long sides of the rectangle  6  of heat-resistant lacquer deposited on the sheet  2  and the weld  12  cuts across the width of this rectangle  6  so that the sheets  2  and  3  are not welded together at the location of the passage  10 . A weld  13 , in the shape of a rectangle, superimposed on the rectangle  6  of heat-resistant lacquer is also produced so that only the sheets  1  and  2  are welded together at the location of this rectangle  13 . 
     Next, in the next stage, the strips  1 ,  2 ,  3  are covered with the fourth strip  4  and three welds  14   a,    14   b,    14   c,  forming three sides of the leaktight bag  15  are formed, one of them,  14   b,  along one of the edges of the strips  1  and  4 , and the other two,  14   a,    14   c,  transversely to these strips. The fourth side, adjacent to the other edge of the strips  1  and  4 , remains open to allow subsequent filling of the leaktight bag  15 . 
     The last step consists in detaching the leaktight bags from one another between two adjacent welds  14   a,    14   c.    
     The leaktight bag  15  illustrated in FIG. 7 is ready to receive the liquid to be packaged, after which the fourth side will be welded up, enclosing the liquid in a leaktight way. 
     The contents of such a bag cannot be consumed straight from the hermetically-sealed bag after the bag illustrated in FIG. 7 has been filled. This is because there is no opening giving access to the inside of the leaktight bag, which means that this bag is guaranteed tamperproof and any tampering can be verified, and that hygienic packaging conditions are ensured insofar as there is no opening giving access to the inside of the bag. 
     FIGS. 10 to  12  show how it is possible to access the contents of the bag using a drinking straw or some sort of passage  17  allowing the liquid to pass from the inside to the outside. All that is required is for the tab  5  to be lifted and pulled towards the edge  14   c  of the bag  15 . Given that the tab  5  is welded along the weld rectangle  13  to the strip  2  which forms one of the walls of the passage  10 , by pulling it, this wall  2  is torn thus making an opening  16  in the passage  10 . This opening  16  allows a tubular element  17  such as a drinking straw or pouring device to be inserted. This tubular element  17  has to be long enough to emerge from the cut end  9   a  of the passage  10 , thus placing the contents of the leaktight bag in communication with the outside. 
     To interrupt this communication before all the liquid contained in the bag has been used up, all that is required is for the drinking straw  17  to be withdrawn so that its end becomes set back by a certain distance from the cut end  9   a  of the passage  10 . As a preference, as illustrated in FIGS. 7 and 12, the start of the passage  10  has a sudden widening  10   a  intended to allow a folded-back end  17   a  of the drinking straw  17  to be housed and kept in place when one wishes to stop consuming the liquid. The end of the widening  10   a  also forms a stop for the folded over end  17   a  of the drinking straw  17 , preventing this drinking straw from being pushed so far into the passage  10  that it would open the valve formed by this passage  10 . As can be seen in FIGS. 10 to  12 , the edge of the tab  5  attached to the wall  1  of the leaktight bag  15  is adjacent to the weld  14   c,  which means that this weld limits the amount by which the tab  5  can be pulled back. 
     The alternative form illustrated by FIGS. 13 to  15  consists in adding to that part of the bag  15  which is fitted with the valve, a strip of a more rigid material, such as a strip of thicker material (of the order of 200-250 μm)  18 , such as a thermoplastic film of the same type as that used for the sheets  1  to  4 . This strip  18  has parallel score lines  19  which are obtained by compression. This strip  18  is fixed to the bag by welding it to the tab  5 , itself welded around the rectangle  13  to the sheet  2 , as illustrated in FIGS. 5 to  7 . 
     By pulling on the strip  18 , the tab  5  is first uncovered by strip  18  and then pulled and the wall of the passage  10  is torn, thus opening the valve. The strip  18  is then detached from the tab  5 , the weld between this strip  18  and this tab being chosen to offer lower resistance to pulling than the weld  13  between the tab  5  and the sheet  2 . Once the strip  18  has been detached, it is bent along the score lines  19  to form a pipe which acts either as a drinking straw or as a pouring spout depending on the shape it has, and it is inserted into the opening  16  as before (FIG.  15 ). 
     The alternative form illustrated by FIGS. 16 to  19  shows, in addition to the passage  10  which acts as a valve and as a pipe for dispensing the liquid packaged in the bag, a passage  20  intended only for filling the bag. 
     The operations in manufacturing the bag according to this alternative form are the same as those described in respect of the previous embodiment, which means that these operations will be described more briefly for this alternative form. 
     As before, the opening tab  5  is precut in the sheet  1  used to form one of the walls of the bag. In parallel, a layer of sparing lacquer  6  is deposited on one  2  of the sheets, the one intended to form the valve. As is visible in FIGS. 16 to  19 , the layer of sparing lacquer  6  also extends over some  6   a  of the width of the weld  14   a  forming the perimeter of the bag, and over a certain length of this weld  14   a,  for the reason which will be explained later. 
     Next, the sheets  2  and  3  are welded along the line  7 ,  8  to form the passage  10 , and the cut  9  is made to place this passage in communication with the inside of the bag. As far as the passage  20  is concerned, it is formed between the weld  8  and a weld  21  which extends along the inner edge of the sheets  1  and  2 . 
     Once the passages  10  and  20  have been formed, the sheets  2  and  3  are joined to the sheet  1  using a weld  22  (FIG. 17) which has an opening  22   a  superimposed with the head  5   a  of the tab  5 . This weld, as before, joins the rest of the tab  5  to the wall  1  of the bag, the sparing lacquer  6  preventing the two walls  2  and  3  from being welded together at the location of the passage  10  between them. 
     At this stage (FIG. 18) the sheet  4  is superimposed on the sheets  1 ,  2  and  3  and they are welded edge to edge to form the leaktight bag. During this operation, it is contrived for the welding of the edge of the bag to be superimposed with the region  6   a  covered with sparing lacquer, which has the effect of leaving this part of the bag open. 
     The next operation consists in inserting a folded drinking straw  17  into the passage  10  and in inserting a filling lance  23  into the passage  20 . Once filling is over, the ends of the passages  10  and  20  are sealed by welding the edge of the bag in that part of the width which has been left free by the sparing lacquer  6   a  as illustrated in FIG.  19 . 
     This bag can then be used like the bag described earlier, by tearing back the tab  5  giving access to the drinking straw  17  and to the dispensing passage  10 . 
     Of course, it is also possible not to place a drinking straw in the passage  10 , in which case the outer edge of this passage may be sealed when the edge of the bag is welded up and only that end of the second passage  20  which is adjacent to this edge left open. 
     All the embodiments described hitherto relate to bags with valves. Now, it would seem that the use of a tab also offers a great advantage for containers for packaging liquid which are sealed by a cap welded or bonded around an opening formed through the internal wall of the container. 
     The leaktight container illustrated by FIGS. 20 to  23  is shown empty and includes two sheets  1 ,  32  of monolayer or multilayer plastic such as polystyrene, polypropylene, polyethylene or polyamide, coming from two endless strips of the order of 100 μm thick, welded edge to edge along their entire periphery  33 , then cut transversely in the direction of travel of the strips once the container is finished. A strip  34  made of a material of the same type, but which is preferably thinner, for example of the order of 40 μm is arranged between the sheets  1  and  32  and is fixed against the inner face of the sheet  1 . This sheet  1  has a precut tab  5 , a free end  5   a  of which constitutes an element for holding on to this tab  5 , while the body  5   b  of this tab is welded to the strip  34 . 
     By grasping hold of this end  5   a,  to pull the tab  5  away from the strip  1  from which it is cut, the body  5   b  which is welded to the strip  34  tears this strip as illustrated by FIGS. 21 and 23, leaving an opening  36  which gives access to the inside of the container and therefore allows the liquid packaged therein to be got out. When this liquid is a drink, a drinking straw may be inserted through the opening  36  and the liquid sucked out. When it is an ecologically-friendly refill, for example, the contents may be poured out of the container. 
     Although the essential advantage of the present invention is associated with flexible-walled leaktight containers of the bag type, the invention could also be applied to other types of leaktight containers for packaging liquid. Of course the invention is not in any way limited to the fact that the membrane fixed against the inner face of the wall of the container consists of a strip passing across the length or width of the container, the use of a strip of this type is advantageous because it allows the container according to the invention to be produced continuously from materials in strip form. The entire surface area of the strip  34  need not necessarily be welded to the inner face of the wall  1  of the bag. In actual fact, all that is required is for it to be welded to the body  5   b  of the tab, and for the unwelded portion of the membrane  34  adjacent to the holding end  5   a  of the tab  5  to be isolated from the inside of the bag by a leaktight connection so as to prevent the liquid being able to get out until that part of the membrane  34  which is welded to the body  5   b  of the tab  5  has been torn. 
     FIGS. 24 and 25 illustrate not only an alternative form of the method of FIGS. 1 to  7 , but also an alternative form of the valve formed between the sheets  2  and  3  arranged between the sheets  1  and  4  forming the bag. In this alternative form, the sheet  1  has not been represented, but it is of course there. 
     The first operation carried out in FIG. 24 is illustrated by section a—a of FIG.  25  and corresponds to the weld  7 ′,  8 ′ delimiting the passage  10 ′ of the valve. As may be seen, this passage does not have parallel edges, and the purposes and functions of the variations in cross-section thus given to the passage  10  will be explained later. A transverse weld  42  is formed close to one end of the passage  10 ′ the utility of this weld will be explained later. 
     The next operation consists in making the cut  9 ′,  9 ′ a  intended to make this passage  10 ′ communicate with the outside. This cut  9 ′ has the shape of a U, the two arms of which are of unequal length. As can be seen, this lack of symmetry of the arms of the U-shaped cut  9 ′ coincides with the lack of symmetry of the narrowing at the middle of the passage  10 ′. This lack of symmetry of the passage  10 ′ and of the cut  9 ′ has been shown to improve the sealing of the valve, that is to say of that part of the passage  10 ′ which extends from the asymmetric narrowing of this passage and the cut  9 ′,  9 ′ a.    
     During the operation illustrated by the next section c—c, a drinking straw  17 ′ is inserted into the passage  10 ′. The diameter of this drinking straw is such that it corresponds substantially to the narrowing formed at the entry of the passage  10 ′. This means that the drinking straw seals against the inlet end of the passage  10 ′, which means that liquid which may have flowed between the passage  10 ′ and the drinking straw  17 ′ during the opening of the valve is prevented from leaving this passage  10 ′. It may also be noted that the end of the drinking straw  17 ′ inserted into the passage  10 ′ has a bulge  17 ′ a  which prevents the drinking straw  17 ′ from coming out of the passage  10 ′, this bulge resting against the narrowing situated at the entry to the passage  10 ′. Furthermore, the transverse weld  42  limits the movement of the drinking straw  17 ′ in the passage  10 ′. 
     The operation illustrated by section d—d is carried out in parallel on the sheet  4  forming one of the walls of the bag. It consists in cutting out the tab  5 . 
     Between the operation (c—c) of inserting the drinking straw  17 ′, and the next operation d—d, the sheet  4  joins the other two sheets  2 ,  3  and a non-weldable sheet (not represented) is inserted between the drinking straw and the sheet  3  adjacent to the sheet  4 . This means that the weld  40  made in operation e—e welds together only the sheets  3  and  4  and the opening  40   a  leaves the end  5   a  of the tab  5  free, the rest of this tab being welded to the sheet  4 . 
     The last operation consists in making two spot welds  41  between the welds  7 ′,  8 ′ forming the passage  10 ′ and the wall  4  of the bag as well as two parallel weld lines  43 , the spacing of which corresponds to that of the welds  7 ′,  8 ′ of the passage  10 ′. These welds  43  attach the valve formed by the passage  10 ′ to the opposite edge of the sheets  2 ,  3  and  4 . It  43  thus delimit [sic] the width of the housing accommodating the folded-over part of the drinking straw  17 ′. As for the spot welds  41 , they prevent the sheets  2 ,  3  from following the drinking straw  17 ′ when the bulge  17 ′ a  is brought up against the narrowing situated at the entry to the passage  10 ′, allowing the valve to close.