Abstract:
A sachet for preparation of a beverage. The sachet has a compact roast and ground coffee cake having first and second cake opposed surfaces extending between to a peripheral cake edge. The first opposed surface is substantially convex and configured for ensuring leaktightness in an extraction chamber that is configured for injecting water and extracting the coffee. The peripheral edge has a peripheral surface that is generally normal to the opposed surfaces. An outer sheet of a flexible material is impermeable to oxygen and water vapor and contains and impermeably seals the cake therein.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This is a continuation of U.S. patent appplication Ser. No. 08/178,326, filed Jan. 11, 1994, the content of which is hereby incorporated herein by reference thereto. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a sealed flexible sachet containing at least one powder substance for the preparation of a beverage, including substances compacted into a cake by extraction under pressure and the manufacture of the sachet.  
           [0003]    The use of pre-metered and pre-packaged portions of ground coffee for the preparation of espresso-type coffee has the advantage that it facilitates the coffee preparation operations while ensuring that the qualify of the product is relatively consistent.  
           [0004]    These portions are currently provided in three main forms. According to a first version, the pre-packaged portions disclosed in Patent Specifications. Swiss Patent No. 636 311, U.S. Pat. No. 5,012,629 and European patent appplication Publication No. 272 432 are formed by two sheets of filter paper sealed over their periphery and filled with ground coffee. This solution has the drawback that an oxygen-barrier outer packaging is required to prevent any oxidation of the product during storage, entailing additional costs and a supplementary operation for the consumer who has to remove it before the desired coffee can be extracted.  
           [0005]    According to a second version, disclosed in Patent Appplication WO 92/07775, the portion is formed by a sealed capsule opening into its extraction device under the action of the introduction of the extraction fluid, after deformation and then perforation by pointed members.  
           [0006]    This capsule, formed by a sealed envelope forming a lateral wall and two walls, one of which forms the base of the cartridge and the other of which closes the opposite end of the cartridge, has the drawback that it makes use of different packaging materials, some of which have to be thick enough to make them semi-rigid, and can be used only in one direction, i.e., with the cap surface upwards in an extraction device which is completely adapted to the capsule and to its arrangement.  
           [0007]    According to a third version, U.S. Pat. No. 3,607,297 discloses sachets for the preparation of a beverage in the form of a strip having filling cavities and a flat cap on the upper surface. According to this patent, these sachets are adapted for gravity flow and have to be perforated on both surfaced by toothed plates, one of which is pushed by a spring.  
         SUMMARY OF THE INVENTION  
         [0008]    The invention relates to a sachet for preparation of a beverage. A preferred embodiment of the sachet includes a compact roast and ground coffee cake with first and second cake opposed surfaces that extend within and preferably to a peripheral cake edge. The first opposed surface, and preferably also the second opposed surface, is substantially convex and configured for ensuring leaktightness in an extraction chamber that is configured for injecting water into the sachet and extracting the coffee. The peripheral edge has a peripheral surface the is generally normal to the opposed surfaces and is preferably cylindrical. The cake preferably has a lenticular shape. An outer sheet of a flexible material that is impermeable to oxygen and water vapor contains and impermeably seals the cake therein.  
           [0009]    The preferred outer sheet has a sheet surface adjacent the first opposed surface and has a convex shape. The outer sheet can include first and second sheets disposed adjacent the first and second opposed surfaces, respectively. Preferably, the first and second sheets extend beyond the peripheral cake edge and are sealed together to enclose the cake therebetween and to form a sealed edge that substantially defines a plane through the sachet. The sachet can be substantially symmetrical with respect to the plane. Preferably, cake has a volume less than the internal volume of the sachet so that there is free space between the cake and the first and second sheets of less than 20% of the sachet internal volume and sufficient to allow the coffee to expand during extraction.  
           [0010]    In one embodiment, the sheet material is plastically prestretched for reducing or avoiding folds therein due to volume expansion of the cake. Preferably, the outer sheet comprises a multilayer structure that includes an outer layer, which can be made of plastic, an inner layer made of a plastic, and an central layer made of an aluminum material and disposed between the outer and inner layers. An embodiment has the outer layer made of PET, PE, PP, PA, or PS, and the inner layer made of PE, PP, or OPP. A preferred sheet has an inner layer of OPP, a central layer of aluminum, and an outer layer PET.  
           [0011]    The construction of the outer sheet is preferably configured for maintaining a leaktightness about piercing members in the extraction chamber that pierce the sachet during extraction of the coffee. Preferably the plasticity of the outer sheet is selected for controlling and reducing the size of tears therein when pressurized against raised portions of the extraction chamber. In one embodiment, the outer sheet comprises a tongue configured for facilitating positioning in the extraction chamber.  
         DETAILED DESCRIPTION OF THE INVENTION  
         [0012]    The aim of the present invention is to provide a sealed flexible sachet containing ground roast coffee and adapted to be extracted under pressure for the preparation of a beverage, this sachet requiring no outer packaging and the extraction system being adapted solely to the sachet and not to the arrangement of a sachet, as it is fully adapted to be extracted in one or other direction.  
           [0013]    The present invention also aims to limit to a minimum the quantity of material needed for the packaging of a portion.  
           [0014]    The invention provides a flexible sachet in the form of an individual portion formed by thin sheets of circular, oval, or polygonal shape, which provide between one another a space for the powder substance and which are sealed over their periphery so that the sachet is substantially symmetrical with respect to its plane of sealing. The material used for the flexible sheets is impermeable to oxygen and water vapour.  
           [0015]    The sheets used to form the sachet may be identical, but as a variant, for reasons relating to manufacture, the two flexible sheets may, however, differ slightly from one another as regards shape and/or material without thereby impairing the symmetry required for extraction.  
           [0016]    The sheets used to form the sachet may be identical, but as a variant, for reasons relating to manufacture, the two flexible sheets may, however, differ slightly from one another as regards shape and/or material without thereby impairing the symmetry required for extraction.  
           [0017]    The invention also includes embodiments wherein the powder substance is in a form of a compacted cake of powder substance wherein one or more pieces of the compacted caked substance is/are contained between the sheets.  
           [0018]    The invention also relates to the method of manufacture of the sachet described above, in which two flexible sheets which are impermeable to oxygen and water vapour, are deformed in a symmetrical manner by moulding or by stretching, a metered quantity of powder substance is placed on one of the deformed flexible sheets and the two sheets are sealed over their periphery.  
           [0019]    The method and the device used for the extraction of sachets of the invention may advantageously be of the type disclosed in European Patent Applications EP 92107548.7 or EP 92112364. The upper surface of the sachet is firstly opened by one or a plurality of perforating members provided under the upper surface of the device, and the lower surface is opened by local breakages following its deformation against raised and hollow portions which are not cutting or perforating disposed on the lower surface of the device, solely under the effect of the pressure increase during the injection of the extraction fluid. There is consequently no need to open the sachet in advance or to remove a portion of material therefrom prior to its use. After use, the sachet may be readily removed with a minimum of waste.  
           [0020]    Therefore, since the sachet of the present invention is symmetrical, the user may insert it into the extraction system without paying attention to the direction of introduction. Moreover, the sachet is ready for immediate use and requires no prior preparation before insertion into the extraction system.  
           [0021]    However, when the extraction device available is only partial with respect to the device described above, i.e., it does not comprise the means for opening one or other of the two surfaces, for instance a device of the type of conventional espresso machines, openings may be provided, just prior to positioning in this partial extraction device, in one and/or the other surface of the sachet, allowing the passage of the extraction fluid.  
           [0022]    The inner diameter of the sachet is preferably between 25 and 70 mm and the sealed edge has a width of 3 to 15 mm. Once filled, the sachet preferably has a thickness of between 5 and 20 mm at its centre. The quantity of powder substance which it contains may vary between 5 and 20 g depending on its use.  
           [0023]    The sachet is filled with a powder substance for the preparation of a beverage. This substance is preferably roast and ground coffee, but may also be tea, soluble coffee, a mixture of ground and soluble coffee, chocolate or any other dehydrated food substance.  
           [0024]    The powder substance is compacted conventionally during the manufacturing process.  
           [0025]    The external shape of the sachet is preferably circular, but may also be oval or polygonal with four to ten sides possibly with rounded edges, or may be a combination of these three elements. Its section is preferably substantially in the form of the flattened hexagon, but it may also have a lenticular shape.  
           [0026]    According to a variant, not illustrated, the sachet is provided with at least one lateral tongue facilitating its positioning. This tongue is simply produced when the sachet is cut out.  
           [0027]    According to a first configuration, the sachet is formed by two sheets sealed over their periphery, the seal being provided as a plane surface.  
           [0028]    According to a first production variant, the two sheets are stretched in advance (deformation in the plastic zone) in order to avoid any random folds due to the volume expansion of a material which is originally plane, either by means of compression in a die-piston assembly, or by means of pressurization by a gas of the inner surfaces and/or possibly suction of the outer surfaces in a mould of appropriate shape at a controlled temperature, in which the sheets are kept plane at their periphery.  
           [0029]    According to a second variant, the material is simply pushed back as in the two examples above, but in this case, it is not held at its periphery and then has more or less random folds resulting from the volume expansion of a plane surface.  
           [0030]    According to a second configuration, the two sheets are pre-formed in a systematic and controlled manner and sealing is carried out, after filling with the powder substance, in accordance with a three-dimensional device. The volume expansion of a plane surface, without elastic or plastic stretching, means that the apparent diameter of the material is modified with respect to its real diameter. This excess material has to be compensated by an appropriate geometrical shape in order to avoid any random folds.  
           [0031]    In order to achieve this aim, systematic and controlled moulding takes place in a mould in which, at all locations, the principle of the equality of the apparent deployed diameter and the real diameter is ensured. This is obtained in the mould by creating corrugations of varying height which flare outwards. In the central portion of the sheets of the sachet, deformation is non-existent or small because this involves the reference plane. In contrast, as they develop towards the outer diameter, these corrugations increase in height and become flared. This corrugation depends on the ratio between the diameter of the sachet and the distance between the planes of the sealing zone and that in the central zone of the sachet, i.e., half the height of the sachet.  
           [0032]    The two sheets of the sachet undergo equivalent volume expansion and are positioned during sealing, after filling, so that they are correctly superimposed on one another. The sealing zone of the two sheets thus takes the form of a corrugated circular strip.  
           [0033]    This moulding of the sheets is carried out, either by means of compression in a die-position assembly, or by means of pressurization by a gas of the inner surfaces and/or suction of the outer surfaces. In both cases, the mould has the desired relief.  
           [0034]    According to a third configuration, the sachet may have gussets on one or more sides. The gussets, resulting from folding prior to the sealing of the sheets, make it possible to provide the assembly with a specific volume, while eliminating random folds. The manufacture of the sachets using this latter method may be carried out in a known manner.  
           [0035]    The sheets may be made from a flexible material such as aluminium of thickness of 5 to 40 μm or plastic such as polyethylene-terepthalate (PET) or from polyethylene (PE), polypropylene (PP), polyamide (PA), polystyrene (PS), ethylene and vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC) and polyvinyl alcohol (PVA), and may be single layer sheets or multilayer sheets including paper. The sheets are preferably made from a flexible multilayer material suited to sealing by conventional methods, while protecting the product adequately against oxygen and water vapour. The following combinations of materials are recommended:  
           [0036]    outer layer: PET (normal, woven or nonwoven), PE, PP, PA, PS or paper;  
           [0037]    high-barrier central layer: aluminium of a thickness of 5 to 20 μm, EVOH, PVDC, PET or PVA;  
           [0038]    inner layer: plastic, preferably PE or PP or OPP. The following multi-layer combinations can be envisaged: PET-EVOH-PE or PET-aluminium-PE. The use of biodegradable or hydrosoluble material is also possible as a single layer or in combination with other materials.  
           [0039]    In the case in which PET is used, it may take the form of a single layer combining the outer and central layers, particularly if it is filed with a layer of silicon oxide or if it is metallized.  
           [0040]    According to a variant, the themosealing operation is facilitated by the insertion between the two sheets of an intermediate material, such as a food glue or a coating of plastic material. This material can then form a further thickness advantageously used to provide complete leak-tightness during extraction.  
           [0041]    The sachet of the invention preferably contains a compacted cake of the powder substance in the form of one or more pieces, the compacting rate being such that there is a reduction of volume of between 10% and 60% with respect to the non-compacted substance. This compacting is carried out so that the free space between the two flexible sheets and the substance accounts for between 1 and 20% of the total space between the flexible sheets. This free space is needed to allow the coffee to expand sufficiently, during extraction, to allow correct extraction.  
           [0042]    The compacted substance further comprises, on at least one of its surfaces, impressions forming water circulation channels of appropriate shape (for instance crosses, circles) making it possible to improve the pre-moistening of the sachet and its extraction. The shape of these impressions is selected in accordance with the extraction device used.  
           [0043]    The compacted material may also have, on at least one of its surfaces, a concave or convex shape making it possible, where necessary, to modify the compacted state during its positioning in the extraction device.  
           [0044]    This shape is adapted to the arrangement of the extraction chamber and may be advantageously used to ensure a correct leak-tightness of the sachet in the peripheral zone of injection, i.e., between the upper surface of the extraction chamber and the upper sheet of the sachet.  
           [0045]    According to a first embodiment of a manufacturing process, the substance may be compacted after it has been metered out and placed between the sheets of the sachet.  
           [0046]    According to a second preferred embodiment, the substance is compacted and then metered out and placed between the sheets of the sachet. Depending on the shape and size of the pieces of compacted substance, one or several pieces are used to obtain the desired quantity.  
           [0047]    Compacting at an appropriate pressure and into an appropriate shape may also be carried out after closure of the sachet.  
           [0048]    Compacting is carried out in a conventional manner, either by rollers or by a die-piston assembly, the physico-chemical parameters such as pressure, temperature and moisture level of the substance being adapted to the nature of the substance to be compacted.  
           [0049]    According to a particular embodiment, the compacted substance may be partially or completely decompacted after closure of the sachet, for instance by vibration or by any other known mechanical means.  
           [0050]    Net compacting at an appropriate pressure and into an appropriate shape may also be carried out after the closure of the sachet.  
           [0051]    When the powder substance is subject to oxidation, the manufacturing operations can be carried out under the protection of a current of inert, oxygen-free gas, for instance under nitrogen or CO 2 .  
           [0052]    Some plastic materials have the property that they return substantially to their initial shape after temporary deformation. The sachet of the invention makes use of this property, together with an appropriate configuration of its extraction device. The lips of the openings formed by the perforated portions of the sachet consequently close about tapered perforating members such as needles, ensuring the desired leak-tightness about these members during extraction. After extraction, this property also limits discharges from the sachet during its removal, including those portions torn by the extraction system.  
           [0053]    The symmetry of the sachet, in terms of both shape and material, its flexibility and the property mentioned above, make it possible at will to vary the method and the location of water introduction and extraction. Both may be, for instance, concentric, on the same surface or on opposite surfaces, the objective being to cause the water to travel an optimum path.  
           [0054]    The flexibility of the walls of the sachet is also advantageously used to allow, by its deformation without breakage in the extraction device, a reconfiguration of the volume of the coffee which it contains. This controlled deformation is designed to improve the distribution of the flow in the bed of coffee and consequently the quality of extraction.  
           [0055]    Moreover, taking account of the method of extraction for which it is designed, the sachet if formed by a combination of materials selected according to an additional criterion of plasticity. The deformability by elongation of its material must be sufficient to allow the shaping described above, but it must also, under the effect of the pressure of the fluid and at the location of the raised portions of the extraction device, break in the form of small tears without its elongation being too great.  
           [0056]    The following description is made with reference to the accompanying drawings, given by way of non-limiting example. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0057]    [0057]FIG. 1 is a diagrammatic representation in section of the sachet of the invention;  
         [0058]    [0058]FIG. 2 is a diagrammatic representation in section of the sachet according to a second embodiment;  
         [0059]    [0059]FIG. 3 is a perspective view of the moulded sheet used for the sachet of FIG. 2;  
         [0060]    [0060]FIG. 4 is a plan view of a sachet according to a third embodiment;  
         [0061]    [0061]FIG. 5 is a diagrammatic representation in section along the line A-A′ of FIG. 4;  
         [0062]    [0062]FIG. 6 is a perspective view of a sheet of the sachet according to a fourth embodiment; and  
         [0063]    [0063]FIG. 7 is a perspective view of the unpackaged compacted coffee. 
     
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0064]    The sachet  1  of circular shape comprises two sheets of flexible material  2  and  3  sealed over their periphery  4  by thermosealing and containing a one-piece of cake of compacted ground roast coffee  5  for the preparation of a beverage. The compacted coffee has concave surfaces  35 , the general shape of its section being a flattened octagon, whereas that of the sachet is hexagonal. The cylindrical edge  38  of the cake is designed to prevent the undesirable presence of grains in the sealing zone.  
         [0065]    In terms of figures, the sachet has a total space between the two sheets of 15 cm 3 , the volume of the compacted coffee is 14 cm 3  and has a compacting rate of 30%.  
         [0066]    The sachet  10  of FIG. 2, obtained from two moulded sheets  6 ,  7 , has corrugations  8 ,  12  and  13  whose amplitude and distance from one another increase from the plane surface  11  towards the sealing edge  9 . In this example, the cake of coffee has a single concave surface  35  and is not exactly symmetrical, but this difference is not connected with the shape of the sachet.  
         [0067]    [0067]FIG. 3 shows a moulded sheet  7  with a flat base  11  and corrugations which become increasingly accentuated as the outer edge is approached. These corrugations have bosses  14  and hollows  15 .  
         [0068]    After placing the ground roast coffee on the base  11 , the sheet  6  is positioned so that the bosses of  6  face the hollows of  7  and vice versa. Thermosealing may then be carried out.  
         [0069]    In FIGS. 4 and 5, the sachet  18  is of square shape with two gussets on the opposite sides. The two sheets  20  and  22  are sealed along the two gussets at  19 ,  23 ,  24 ,  25  and on the edges  26 ,  27  where the two sheets are simply joined. The gussets make it possible to provide the sachet with a specific volume without the appearance of random folds.  
         [0070]    [0070]FIG. 6 shows a sheet  30  having corrugations  31  on the edge and also on the base  32 . Manufacture takes place in the same way as for the sachet of FIG. 2.  
         [0071]    [0071]FIG. 7 shows the compacted substance  36  alone. On at least one surface it has zones  37  for water circulation in the form of channels allowing uniform pre-moistening and extraction.  
       Key to Abbreviations  
       [0072]    PVDC Polyvinylidene chloride  
         [0073]    EVOH Ethylene and vinyl alcohol copolymer  
         [0074]    PP Polypropylene  
         [0075]    PE Polyethylene  
         [0076]    PET Polyester  
         [0077]    PA Polyamide  
         [0078]    PVA Polyvinyl alcohol  
         [0079]    OPP Oriented polypropylene