US 20030219177 A1
A bag for vacuum packaging, comprising an inner layer, made of sealable material, and an outer layer that is substantially impermeable to gases, and at least one sheet element, which is positioned at least partially proximate to the opening of the bag so as to keep at least one portion of the inner layer spaced from at least one portion of at least one face of the at least one sheet element, in order to form air suction channels.
1. A bag for vacuum packaging, comprising: an opening; an inner layer made of sealable material; an outer layer that is substantially impermeable to gases; air suction channels; and at least one sheet element, which is positioned at least partially proximate to the opening of said bag so as to keep at least one portion of said inner layer spaced from at least one portion of at least one face of said at least one sheet element in order to form said air suction channels.
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 The present invention relates to a bag for vacuum packaging, particularly suitable for the food sector.
 Vacuum packaging machines of the so-called “external suction” type are commercially available which in a first step produce vacuum inside bags, generally made of synthetic material, by aspirating the air from the inside of the bags, and in a second step seal the opening of the bags so as to prevent the subsequent return of air into the bags.
 Usually, bags used in this sector are constituted by two substantially rectangular walls that are heat-sealed at three of their four sides.
 Each wall is constituted by two layers, an inner one made of sealable material generally suitable for food use, such as polyethylene, polythene or polypropylene, and an outer one, which is substantially impermeable to gases: some polymers, including polyester or polyamide, for example, have been found to be suitable for the purpose. The two layers, the inner one and the outer one, are connected one another.
 When using bags of this type with external suction devices, it has been found that long before all the air that they contain has been aspirated, the walls of the bag make contact with each other, adhering to each other proximate to the nozzle, or more generally at the suction region, of the suction pump; accordingly, the pump is prevented from extracting all the air contained in the bags.
 Various solutions have been proposed in order to solve this problem. In one of these solutions, the user deforms the walls of the bag proximate to the suction nozzle (by forming folds, for example) in order to form suction channels.
 It is evident that although this solution allows to reduce the drawback noted above it is very awkward and moreover does not give assurance of fully evacuating the air from the inside of the bag.
 A different attempt to solve the problem described above (reference should be made in this regard to U.S. Pat. No. 2,778,173, U.S. Pat. No. Re. 34,928 and EP 0 216 327 B1) consists in acting on the shape of at least one of the inner layers by adding or removing material, so as to obtain protrusions and/or recesses capable of making evacuation channels available to the air.
 In this manner, even if the two walls adhere one another, the presence of such channels ensures that the pump can fully aspirate the air from the inside of the bag.
 Even this solution, though providing a considerable improvement of the suction conditions, is not devoid of drawbacks.
 First of all, the protrusions, which are formed at at least one of the inner layers, allow to obtain suction channels but do not allow to perform, at the end of the suction step, optimum sealing of the two walls: accordingly, the seal produced is often not efficient.
 Furthermore, if only the face of the inner layer that is directed inward is deformed, leaving flat the face meant to couple to the outer layer, material (polyethylene in particular) is wasted without thereby obtaining any advantage in terms of gas tightness (tightness is ensured by the thickness of the outer layer) or in terms of sealability.
 On the other hand, the provision of incisions on the inner surface of the bag to form said channels can reduce the thickness of the layer made of a material that is impermeable to gases, with a consequent decrease of its tightness.
 If instead one uses an inner layer that is deformed so as to have, for example, protrusions at the face meant to be directed inward and respective recesses on the opposite face, air bubbles form between said inner layer and the outer layer and, since the inner layer is made of a material that is permeable to gases, migrate over i time into the bag, consequently compromising its tightness.
 The aim of the present invention is to eliminate or at least drastically reduce the drawbacks noted above in known types of vacuum packaging bag.
 Within this aim, an object of the present invention is to provide a bag, particularly for vacuum packaging,, that ensures total evacuation of the air.
 Another object of the present invention is to provide a bag for vacuum packaging that is capable of ensuring perfect sealability, so as to ensure its perfect tightness over time.
 Another object of the invention is to provide a bag for vacuum packaging that is capable of ensuring, over time, a gas tightness and particularly a tightness against the inflow of air that is comparable to that of bags used with chamber-type machines.
 Another object of the present invention is to provide a bag for vacuum packaging that allows to extract air at a substantially faster rate than the bags currently in use.
 Another object of the present invention is to provide a bag for vacuum packaging that has a low production cost, in order to be advantageous also from the economical standpoint.
 This aim and these and other objects which will become better apparent hereinafter are achieved by a bag for vacuum packaging, comprising an inner surface made of sealable material and an outer surface that is substantially impermeable to gases characterized in that it comprises at least one inner sheet element, which is positioned at least partially proximate to the opening of said bag and is adapted to keep at least one portion of said inner surface spaced from at least one portion of at least one face of said at least one sheet element in order to form air suction channels.
 Advantageously, said sheet, element is adapted to keep at least one portion of both of its faces spaced from a respective portion of said inner surface.
 According to another aspect, the present invention provides a tubular element for providing said bag, characterized in that it comprises an inner surface made of sealable material and an outer surface that is substantially impermeable to gases and in that it comprises internally at least one sheet element.
 Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of a bag for vacuum packaging according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, wherein:
FIG. 1 is a perspective view of a bag for vacuum packaging according to the invention; and
FIG. 2 is a partial sectional perspective view of a wall of the bag, taken along the line II-II of FIG. 1;
FIG. 3 is an enlarged-scale partial sectional perspective view of a sheet element, taken along the line III-III of FIG. 1;
FIG. 4 is a schematic view of an apparatus adapted to provide a tubular element;
FIG. 5 is a top view of the apparatus of FIG. 4;
FIG. 6 is a schematic view of a device for providing the bag according to the invention;
FIG. 7 is a view of a bag according to the invention that has a reduced length; and
FIG. 8 is a view of a bag according to the invention that is longer than the bag of FIG. 7.
 With reference to the figures, a bag for vacuum packaging according to the invention, generally designated by the reference numeral 1, can be constituted for example by a first wall 2 and by a second wall 3, which substantially have the same shape (in the drawings, the first wall 2 and the second wall 3 are substantially rectangular but can have other shapes as well) and are generally heat-sealed to each other along three sides, so as to form a receptacle, which can be accessed through an opening 1 a and is meant to contain, for example, food products to be preserved in vacuum.
 As an alternative, the bag 1 can be constituted by a monolithic tubular body, not shown in the figures, which is closed at one end, for example by heat-sealing, in order to form the bottom of the bag 1, and is open at the other end, so as to form the opening 1 a.
 The opening 1 a is designed to engage the suction region (nozzle or, optionally, chamber), not shown in the figures, of a pump associated with a vacuum packaging machine of the external suction type.
 The first wall 2 and the second wall 3 have respectively an inner sealable surface or layer, which allows to close hermetically the bag 1 once the air has been aspirated from its interior, and an outer surface or layer that is substantially impermeable to gases and prevents the air from entering the bag 1 and compromising the preservation of any food contained therein.
 In particular, the first wall 2 and the second wall 3 are structured so as to have an inner layer 4, made of sealable material such as for example polypropylene or polythene or polyethylene, which also have the characteristic of being suitable for food use, and an outer layer 5 made of a material that is substantially impermeable to gases.
 Polymeric materials, such as polyester, polyamide or Nylon®, have been found to be particularly suitable to provide said outer layer 5.
 The inner layer 4 and the outer layer 5 are connected and perfectly coupled, so that they do not trap between them bubbles or pockets of air, which over time might migrate through the inner layer 4 and reach the inside of the bag 1.
 According to the invention, the bag 1 is provided internally with at least one sheet element 6, which is arranged at least partially proximate to the opening 1 a.
 Also according to the invention, said sheet element 6 is adapted to keep at least one portion of the inner surface of the bag 1 spaced from at least one of its faces 6 a, or from part of its faces 6 a, so as to form air suction channels 8.
 More particularly, as shown in the drawings, the sheet element 6 can be structured so as to keep both the first wall 2 and the second wall 3 spaced from each other and from the sheet element 6 itself, so as to form said suction channels 8 between said sheet element 6 and the first wall 2 and between said sheet element and the second wall 3.
 Advantageously, the sheet element 6 is capable of preventing the mutual collapse of the first wall 2 and of the second wall 3 by providing protrusions, such as for example, ribs or studs and/or recesses, such as for example slots or cavities, on a portion, or on the entirety, of one or both of its faces 6 a.
 As an alternative, as shown more clearly in FIG. 1, the sheet element 6 has an undulated structure, with an alternation of peaks or convexities and troughs or concavities arranged transversely to the opening 1 a.
 The peaks and troughs, as shown in FIG. 1, may be replaced by corresponding ribs or studs and recesses or slots or cavities in the embodiments mentioned above.
 Conveniently, the sheet element 6, in addition to being rigidly coupled laterally to the edges 1 b of the bag 1, has a plurality of micro-openings 7, which are designed to increase suction by connecting the suction channels delimited by the first wall 2 and by the sheet element 6 to the channels delimited by the second wall 3 and by said sheet element 6 and vice versa.
 In the illustrated embodiment, in order to facilitate the rapid and easy outflow of the air, each one of said micro-openings 7 is frustum-shaped, but nothing prevents them from being cylindrical.
 The sheet element 6 can also be arranged along at least half of the bag 1, so as to also affect part of the region occupied by the products introduced therein.
 This, if the separation action applied by the sheet element 6 fails, prevents the mutual adhesion of the first wall 2 and the second wall 3 in the region between the suction nozzle and the product to be packaged, which would prevent complete evacuation of the air.
 Preferably, the region of the sheet element 6 that is substantially proximate to the opening 1 a and is arranged along the edge of said opening is fixed to the inner surface of the bag 1, by heat-sealing or food-safe adhesive, so that the edge of the sheet element 6 that is proximate to the opening 1 a does not hinder the insertion of the products to be packaged and preserved inside the bag 1.
 Moreover, one face 6 a of the element 6 can be coupled, preferably by means of a food-safe adhesive and/or by heat sealing, to the inner surface of the bag 1 along its entire extension or optionally on part thereof and particularly at a substantially median region thereof, which lies substantially longitudinally with respect to the bag 1, starting from the region proximate to the opening 1 a and up to a region that lies substantially opposite said region.
 Operation of the invention is rather evident from the above description: once the product to be packaged has been inserted in the bag 1, the opening 1 a is coupled to an external suction device, which by way of said suction nozzle or chamber extracts the air contained inside the bag.
 Full extraction of the air is ensured by the fact that notwithstanding the tendency of the first wall 2 and of the second wall 3 to collapse during aspiration, the sheet element ensures that suction channels remain open through which the air can flow out, arriving even from the furthest regions, such as for example the bottom of the bag 1.
 The presence of the micro-openings 7 allows, if some channels are blocked for any reason, to bypass said channels, providing the extracted air with a path to access other channels.
 Advantageously, the user can obtain the bag 1 starting from a tubular element (possibly available in rolls), formed monolithically or constituted by a pair of flat elements that are substantially rectangular and joined at the two opposite long sides.
 According to the invention, a sheet element 6 is arranged and anchored, in the manner described above, inside said tubular element.
 Conveniently, and in the same manner described for the first wall 2 and the second wall 3, the tubular element has a sealable inner surface and an outer surface that is substantially impermeable to gases.
 By cutting, performed by means of any bladed instrument, such as for example scissors, the user can obtain at least one piece of preset length of the tubular element.
 Said piece can be closed and sealed at one end, by using suitable heat-sealing means, so as to obtain the bag 1 according to the invention having the length dimensions required-by the user.
 Therefore, users, according to the requirements or the dimensions of the food to be preserved, can easily have available a short bag 1 or a long bag 1, as shown respectively in FIGS. 7 and 8.
 With particular reference to FIGS. 4, 5 and 6, a preferred method of manufacturing the bag 1 according to the invention and a suitable apparatus for carrying out the method are described briefly and merely by way of example.
 A first continuous lamina 10 and a second continuous lamina 11, each provided with a face made of sealable material and another face made of a material that is substantially impermeable to gases, are mutually coupled on the side of the respective sealable face, with the interposition of a third continuous lamina 13, which is meant to constitute the sheet element 6, by means of a pair of coupling rollers 12.
 Downstream of the set of coupling rollers 12, two opposite heat-sealing rollers heat-seal the first and second laminas at their lateral edges, so as to form in practice said tubular element constituted by two flat elements, which is then gathered in a roll 16 with the possible aid of conveyor rollers 15.
 The resulting tubular element can subsequently feed a device 17 for mass-producing the bags 1 or can be used directly by the user in the manners specified above.
 If the device 17 is used, the roll 16 is unwound and the tubular element is made to advance in the direction indicated by the arrow 100 intermittently by traction rollers 18 toward a feeder roller 19, which is arranged opposite a supporting surface 20.
 Said feeder roller 19 is designed to feed the tubular element to cutting and heat-sealing means 21, which are provided with a blade 22 that lies transversely to the tubular element and can move alternately toward and away from it, so as to cut it and obtain therefrom a piece of preset length.
 Downstream of the blade 22, the cutting and heat-sealing means 21 further have a heat-sealing bar 23, which also lies transversely to the tubular element and can move alternately in the same manner as, and optionally in step with, the blade 22.
 The heat-sealing bar 23 is meant to seal one end of the piece of tubular element obtained by way of the action of the blade 22 and thus complete the forming of the bag 1.
 The bag 1, once formed, is finally removed from the cutting and heat-sealing means 21 by conveyor means 24, for example of the belt type.
 In practice it has been found that the invention has achieved the intended aim and objects.
 As clearly shown by the description given above, in a bag 1 according to the invention both the first wall 2 and the second wall 3 are substantially smooth, have a constant thickness and are therefore capable of being produced by way of a process of extrusion of the layer of sealable material 4 and of the layer of substantially gas-impermeable material 5.
 This ensures not only optimum sealability but also, at the same time, perfect gas-tightness.
 The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.
 The bag, according to the invention may, for example, be used in the medical or chemical field, for packing compositions which require special preservation conditions.
 In practice, the materials used, as well as the dimensions and shapes, may be any according to requirements.
 The disclosures in Italian Patent Application No. VR2002A000059 from which this application claims priority are incorporated herein by reference.