Abstract:
A capsule ( 1 ) comprising •a side wall ( 2   a ), a bottom wall ( 2   b ), a mouth opening ( 2   c ) and a flange-like rim ( 2   d ) extending outwardly, and •an upper wall ( 3 ) attached to the flange-like rim ( 2   d ) and/or to the side wall ( 2   a ) and at least partially covering the mouth opening ( 2   c ) •the upper wall ( 3 ) comprising a central liquid inlet ( 6 ) for injection of liquid in the capsule and a peripheral portion of wall ( 3   a ) comprising outlet apertures ( 5 ) for beverage to leave the capsule and •an annular engagement portion ( 10 ) located at least between the peripheral portion ( 3   a ) and the inlet ( 6 ) and arranged to form an inwardly protruding inlet flange ( 7 ) by a predefined design or by deformation upon introduction of a dedicated injection member ( 20 ) of a beverage preparation device through the inlet ( 6 ); such inlet flange ( 7 ) providing a liquid-tight sealing interaction with the outer surface of the injection member ( 20 ).

Description:
FIELD OF THE INVENTION  
       [0001]    The present invention relates to the field of beverage preparation using capsules by way of centrifugation. More particularly, the invention relates to a capsule with a sealing means for effectively sealing an inlet side of a capsule during the injection of liquid by means of a dedicated perforation member of a beverage preparation device. 
       BACKGROUND OF THE INVENTION  
       [0002]    Capsules containing beverage ingredients and designed for producing a beverage in a beverage preparation device upon liquid injection into the capsules and by rotating the capsules around a central axis in the device are known in the prior art. 
         [0003]    The principle consists in preparing a beverage by passing a liquid through beverage ingredients contained in the capsule using centrifugal forces. Thereby, liquid is usually injected in a central inlet area of the capsule before and/or during rotation of the capsule in order to make the liquid interact with the ingredients in the capsule, thus forming a beverage such as coffee, ground coffee, tea, or the like. The resulting beverage is then allowed to exit the capsule by means of at least one outlet aperture provided at a portion arranged radially outwards with respect to the central inlet area of the capsule. 
         [0004]    A capsule for preparing a beverage or liquid food and a system using centrifugal forces is for example described in WO2008/148604. The capsule is formed of a body containing a substance such as coffee powder which is closed by a membrane. The membrane is perforated by an injection member of a beverage preparation device in the central part of the membrane for injection of liquid and is simultaneously perforated in the peripheral part of the membrane by smaller piercing members for extraction of the beverage. 
         [0005]    The above-indicated prior art suffers the disadvantage that injection liquid may bypass the substance contained in the capsule at the injection side of the capsule. In particular, when injection liquid fills the capsule, liquid may leak out from the central inlet of the capsule and thereby be centrifuged on the outside of the upper surface of the capsule which may affect the quality of the produced beverage. 
         [0006]    WO2010/063644 relates to a capsule for preparing a beverage using centrifugal forces, the capsule comprising a tightness-producing layer provided at least at a central portion of the inlet wall of the capsule in order to obtain sealing of the capsule during beverage preparation. Thereby, the tightness-producing layer is preferably of resilient or soft material comparatively thicker than the same material in a peripheral outlet portion of the capsule. 
         [0007]    This solution however suffers the drawback that a relatively high piercing force is to be applied to enable piercing of the tightness-producing layer. Furthermore, buckling of the membrane at the inlet side of the capsule may occur which may affect the sealing properties of the capsule. 
         [0008]    Therefore, a capsule comprising enhanced sealing properties is sought-after which overcomes the above-identified problems and which enables the provision of a liquid-tight seal of the inlet side of the capsule during beverage preparation. 
         [0009]    These objects are achieved by means of the features of the independent claims. The depending claims develop further the central idea of the present invention. 
       OBJECT AND SUMMARY OF THE INVENTION  
       [0010]    In a first aspect, the present invention relates to a
       capsule for containing beverage ingredients for producing a beverage in a beverage preparation device upon liquid injection into the capsule and by rotating the capsule around its central axis in the device for forcing liquid through the beverage ingredients in the capsule causing beverage to leave the capsule at the periphery of the capsule, the capsule comprising   a side wall, a bottom wall, a mouth opening and a flange-like rim extending outwardly, and   an upper wall attached to the flange-like rim and/or to the side wall and at least partially covering the mouth opening,   the upper wall comprising a central liquid inlet for injection of liquid in the capsule and a peripheral portion of wall comprising outlet apertures for beverage to leave the capsule and,   an annular engagement portion located at least between the peripheral portion and the inlet and arranged to form an inwardly protruding inlet flange, by a predefined design or by deformation upon introduction of a dedicated injection member of a beverage preparation device through the central inlet; such inwardly protruding flange providing a liquid-tight sealing interaction with the outer surface of the injection member.       
 
         [0016]    The capsule may be filled with a predetermined amount of beverage ingredients at the manufacturing site, i.e., be “prefilled” (and thus sold at least partially filled with beverage ingredients) and/or may be filled with a desired amount of beverage ingredients by the consumer. 
         [0017]    According to the invention, an annular inwardly protruding flange is formed about the central liquid inlet. Thereby, the annular engagement portion according to the invention is either present as a preformed flange or may be formed upon engagement with a dedicated perforating injection member. 
         [0018]    The central liquid inlet of the upper wall is preferably geometrically designed to facilitate the opening of the capsule. Therefore, the liquid inlet comprises a portion of wall of reduced thickness. The wall portion of reduced thickness can a relatively thin openable central portion of wall when compared to the thickness of at least the peripheral portion of the upper wall, or can be a mere opening formed in the centre of the liquid inlet. 
         [0019]    As “flange” within the context of this invention, an annular sealing collar or equivalent is understood which provides a liquid-tight sealing engagement at the circumference of the liquid injection member. 
         [0020]    Hence, by contrast to a provided material layer of constant thickness which is prone to crack respectively tear at least partially in the boundaries enclosing an intruding piercing member, a constant liquid-tight sealing engagement is provided about the circumference of the piercing member without the need for a large-volume sealing member provided at the inlet site of the capsule. 
         [0021]    According to the invention, the force necessary for introduction of an injection member into the capsule is reduced while at the same time effective sealing of the inlet site of the capsule is obtained. In addition, a buckling of the upper wall of the capsule, in direction inwards the capsule, may effectively be prevented. Moreover, an annular support is provided for the injection member during liquid injection and/or rotation of the capsule around its central axis. 
         [0022]    Within the context of the present invention, the term “perforating injection member” encompasses any kind of perforating or non-perforating intruding member of a dedicated beverage preparation device enabling to feed liquid into the capsule from an external supply of liquid. According to a preferred embodiment of the invention, the term “perforating injection member” relates to a piercing member of elongated shape comprising one or more liquid supplying outlets at its free end. 
         [0023]    Preferably, peripheral outlet openings or apertures are positioned relatively closer to the sidewall of the capsule than to the central inlet, and the upper wall is free of openings in the intermediate zone between such openings and the central inlet. This outlet configuration for the capsule enables to ensure a proper flow of the centrifuged liquid through the beverage ingredients in the capsule and in particular avoids privileged flow-path by-passing the ingredients, e.g., coffee bed. 
         [0024]    In a preferred embodiment of the invention, the inwardly protruding flange forms, alone or in combination with a portion of reduced thickness of the central inlet, a flexible sealing lip designed to exert a radial inwardly directed force onto an annular portion of the perforating injection member. 
         [0025]    The annular engagement portion protrudes from the upper peripheral portion or is formed in recess from the peripheral portion of the upper wall of the capsule. 
         [0026]    The annular engagement portion preferably differs geometrically from the peripheral portion of the upper wall. Thereby, the geometrical difference may be a different material thickness and/or a different cross-sectional shape. 
         [0027]    The annular engagement portion is preferably integrally formed with the upper wall. Thereby, the engagement portion is preferably bent or tapered toward the inside centre of the capsule. 
         [0028]    Moreover, the annular engagement portion may be essentially funnel-shaped directed towards the interior of the capsule. The term “funnel-shaped” encompasses any geometrical shape of the annular engagement portion having essentially tapered circumferential walls such as a cone shape. Thereby, the annular engagement portion may comprise—when seen in sectional side view—a radial component in particular at a transition portion between the upper wall and the annular engagement portion. 
         [0029]    The annular engagement portion may be tapered with respect to a centre axis of the capsule about an angle of between 10 and 70 degrees, more preferably between 20 and 60 degrees, even more preferably between 40 and 55 degrees. 
         [0030]    In an embodiment, the annular engagement portion comprises a minimum inner diameter that is configured to be smaller than an outer diameter of the perforating injection member of the beverage preparation device. Thereby, the inner diameter of the annular engagement portion may be constant or decreasing towards the centre axis of the capsule. 
         [0031]    The annular engagement portion may as well be formed of a material which is plastically and/or elastically deformable upon introduction of the dedicated injection member through the inlet. Thus, when a perforating injection member is introduced to the engagement portion having an inner diameter smaller than the outer diameter of the perforating engagement portion, the annular engagement portion may be plastically and/or elastically deformed radially outwardly and/or axially directed towards the centre of the capsule to form a liquid-tight sealing engagement with the injection member. 
         [0032]    The annular engagement portion is preferably arranged between the liquid inlet and the peripheral portion of the upper wall. The annular engagement portion may as well be arranged to at least partially overlap with the liquid inlet. 
         [0033]    The annular engagement portion is preferably integrally formed with the portion of reduced thickness of the liquid inlet of the upper wall of the capsule. 
         [0034]    The wall portion of reduced thickness of the liquid inlet of the capsule preferably has a thickness of less than 500 microns. More preferably, the portion of reduced thickness has a thickness lower than 400 microns. Thereby, the annular engagement portion has a preferred thickness of more than 400 microns. 
         [0035]    The wall portion of reduced thickness may be designed to be elastically and/or plastically deformable. Thereby, the wall portion of reduced thickness has an elongation at yield of at least 10%, preferably at least 50%, most preferably at least 100% by reference to standard ISO 527-3:1995. 
         [0036]    The wall portion of reduced thickness is preferably a centre portion of the liquid inlet which is of circular shape when seen in top view onto the capsule. Thereby, said wall portion is easily perforable or tearable by means of the injection member of a dedicated beverage preparation device. 
         [0037]    The wall portion of reduced thickness may as well be a ring-shaped or arc-shaped portion when seen in top view onto the capsule. 
         [0038]    The thickness of said wall portion is preferably constant and/or arranged to diminish towards the centre of the capsule when seen in sectional side view. 
         [0039]    In another preferred mode, the annular engagement portion arranged radially inside of the peripheral portion of the upper wall is arranged to at least partially overlap the central inlet of the upper wall. 
         [0040]    The engagement portion may as well be designed to fully cover the liquid inlet which may be a wall portion of reduced thickness or an opening in the upper wall. 
         [0041]    Thereby, the engagement portion can be of different material than the upper wall. In particular, the annular engagement portion can be preferably formed of softer and/or more resilient material than the upper wall. 
         [0042]    Moreover, the annular engagement portion may be designed to interact with the upper wall upon introduction of the perforating injection member in order to form the inwardly protruding inlet flange. 
         [0043]    The upper wall of the capsule is preferably made of a material or materials chosen amongst plastic(s), biodegradable plastic(s), bio-based polymer(s), aluminum, cellulose-based material(s) such as paper and combinations thereof made from plastic or biodegradable plastic. Moreover, the upper wall may as well be of any other biodegradable material. 
         [0044]    In a particular preferred embodiment, the liquid inlet and/or the engagement portion of the upper wall is at least partially made from a material that softens and/or expands in presence of hot water in order to increase the liquid-tight sealing engagement between the upper wall and the perforating injection member by supplied liquid in the capsule. 
         [0045]    According to such an embodiment, enhanced sealing upon interaction of the material with hot liquid is obtained without the need for providing a preformed large-volume sealing member. 
         [0046]    In a further aspect, the present invention relates to a beverage preparation system comprising a capsule according to any of the preceding claims and a beverage preparation device comprising a liquid injections means connected to a liquid reservoir of the device and designed for supplying liquid to the capsule. 
         [0047]    In a further aspect, the present invention relates to a kit for producing a beverage in a beverage preparation device comprising:
       a rotational-symmetric capsule body for being filled with beverage ingredients, the capsule body comprising a side wall, a bottom wall, a mouth opening and a flange-like rim extending outwardly, and   an upper wall formed by a lid member which is designed to be mechanically associated to the capsule body by the consumer, preferably without using tools, in order to close off the mouth opening of the body and essentially avoid the leakage of any ingredients filled into the capsule body,
           wherein the upper wall comprising a central liquid inlet for injection of liquid in the capsule and a peripheral portion comprising outlet apertures for beverage to leave the capsule and   an annular engagement portion located at least between the peripheral portion and the inlet and arranged to form by a predefined design an inwardly protruding inlet flange or to form an inwardly protruding inlet flange by deformation upon introduction of a dedicated injection member of a beverage preparation device through the inlet;   
           such inlet flange providing a sealing interaction with the outer surface of the injection member.       
 
         [0053]    In the context of the invention, the term “without using tools” means that the user may associate the capsule body and the upper wall or lid member of the kit essentially without the help of any additional means which are to be provided to the kit such as a mechanical press or a specific association tool. For example, the lid member and body may be provided with complementary press-fitting means allowing a rapid manual connection. 
         [0054]    According to the invention, in particular due to the fact that the upper wall or lid member may be provided separately to the preferably rotational-symmetric capsule body, the sealing properties of the capsule may be adapted to a specific liquid injection means. 
         [0055]    In particular, upper walls or lid members comprising liquid inlets and/or annular engagement portions of different geometric shapes and/or hardness respectively resilience may thus be provided to the capsule body in order to enable an adjustment of the sealing properties thereof. 
         [0056]    A further advantage of such a capsule kit resides in the fact that a user may provide his preferred beverage ingredient to the capsule. Furthermore, the filling level, respectively the volume of a beverage ingredient to be provided to the capsule interior can be individually chosen in order to meet particular taste preferences of the user. 
         [0057]    In addition, upper walls or lid members having peripheral outlet apertures of different amounts and/or geometries may be provided with the kit according to the invention. 
         [0058]    Thereby, due to the independently applicable upper walls or lid members having different outlet apertures, a user may be enabled to adjust the extraction properties of the capsule in relation to at least the different filling levels and/or granulate characteristics of a beverage ingredient to be provided to the capsule. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES  
         [0059]    Further features, advantages and objects of the present invention will become apparent to the skilled person when reading the following detailed description of embodiments of the present invention, when taken in conjunction with the figures of the enclosed drawings. 
           [0060]      FIG. 1   a  to  1   c  relate to a first preferred embodiment according to the present invention in sectional side view, wherein the liquid inlet comprises a central portion of reduced thickness surrounded by a preformed inlet flange. 
           [0061]      FIG. 2   a  to  2   c  relate to another preferred embodiment according to the present invention in sectional side view, wherein the portion of reduced thickness is ring-shaped and surrounded by a preformed inlet flange. 
           [0062]      FIG. 3   a  to  3   c  relate to another preferred embodiment according to the present invention in sectional side view, wherein the annular engagement comprises a reinforcement structure. 
           [0063]      FIG. 4   a  to  4   c  relate to another preferred embodiment according to the present invention in sectional side view, wherein the liquid inlet comprises a central opening. 
           [0064]      FIG. 5   a  to  5   c  relate to another preferred embodiment according to the present invention, in which the annular engagement portion is covering a central opening of the upper wall and is designed to form an inwardly protruding inlet flange during cause of interaction with a dedicated injection member. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0065]      FIG. 1   a  shows a sectional side view of a capsule  1  according to a preferred embodiment of the invention. The capsule  1  comprises a body  2  having a side wall  2   a,  a bottom portion  2   b  and an annular flange-like rim  2   d  which surrounds an aperture respectively mouth opening  2   c  of the body. 
         [0066]    Within the aperture or opening  2   c  of the capsule  1 , an upper wall  3  is inserted to, at least preferably partially, close off the mouth opening  2   c,  thereby enclosing beverage ingredients (not shown) within the body  2  of the capsule  1 . 
         [0067]    Accordingly, the side wall  2   a,  the bottom portion  2   b  and the upper wall  3  of the capsule  1  enclose a compartment for containing beverage ingredients such as ground coffee or the like. 
         [0068]    It is to be noted that the flange-like rim  2   d  of the capsule  1  may as well be formed by the upper wall  3  or be constituted at least partially by the upper wall  3  and/or the body  2  of the capsule  1 . 
         [0069]    The capsule  1  can be rotationally symmetric around a central axis respectively a symmetric axis Z. Thus, the capsule  1  is designed to be used in a dedicated beverage preparation device arranged for driving the capsule in centrifugation around axis Z to generate centrifugal forces in order to prepare the beverage from supplied liquid and from the ingredients contained in the capsule  1 . For this purpose, the upper wall  3  comprises a central liquid inlet  6  and peripheral outlet openings respectively apertures  5  which are preferably arranged at a peripheral portion  3   a  of the upper wall  3 . 
         [0070]    In general, the peripheral outlet openings or apertures  5  are positioned relatively closer to the sidewall  2   a  than to the central axis Z in order to allow the brewed liquid which is ejected by the centrifugal forces in the compartment to leave the capsule  1 . The openings  5  are also sufficiently small so that the ingredient particles, e.g., coffee particles, are essentially prevented from leaving the compartment. For this, each opening  5  has a transversal dimension, e.g., an average diameter, which is smaller than the mean volumetric diameter of the particles (D 4, 3 ). Possibly, small particles such as coffee fines may still traverse the capsule  1 , nevertheless without affecting the quality of the brewed beverage. 
         [0071]    The outlet openings  5  can also be formed of a band of porous material such as filter paper or a woven or non-woven fabric closing one or more windows of the upper wall  3 . 
         [0072]    The upper wall  3  is preferably connected to the inner side wall of the body  2  of the capsule  1  and/or to the flange-like rim portion  2   d.    
         [0073]    Moreover, the upper wall  3  is preferably recessed inwardly from the annular flange-like rim portion  2   d,  thereby forming a recess  9  in the upper wall of the capsule. Accordingly, a support member  23  surrounding a dedicated injection member  20  of a beverage preparation device to be used in conjunction with the capsule  1  may be introduced in said recess  9  to possibly enter into contact with the upper wall  3 . 
         [0074]    Moreover, a relief structure  24  of the support member  23  is provided which is normally designed to perforate or break an (optional) top membrane sealed onto the flange-like rim  2   d  (not shown). The relief structure  24 , which may be a series of pyramids or needle-shaped members, protrudes from the surface of the support member  23 . The relief structure can thus enter the recess  9  of the capsule  1  while perforating the top membrane, if necessary, but without perforating the upper wall  3 . 
         [0075]    The sealing or top membrane is preferably welded to the flange-like rim  2   d  of the body. In an alternative, the capsule does not comprise such protective membrane, in which case, the capsule can be hermetically contained in an external, e.g., flexible, secondary package. The package may be gastight and may contain protective gas such as nitrogen and/or CO2. 
         [0076]    The upper wall  3  is preferably essentially disc-shaped. The upper wall preferably comprises an upwardly-oriented annular peripheral portion  3   b  which facilitates the insertion of the wall  3  in the body  2  and the sealing onto the inner surface of the body  2 . The upper wall  3  may as well be of convex or concave shape. 
         [0077]    The upper wall  3  may however as well be provided as a separate part attachable to the body  2  of the capsule  1  to allow filling of the capsule with beverage ingredients. In particular, a capsule kit may be provided to the consumer which comprises the body  2  and a lid member constituting the upper wall  3  and which is designed to be connected to the inside of the side wall  2   a  and/or to the rim  2   d  preferably without using tools. The upper wall  3  may be entirely detachable or be partially linked to it such as via a hinge. 
         [0078]    The upper wall  3  of the capsule  1  is preferably made of the same material as the capsule body  2 . For such as for example, the material can be chosen amongst plastic(s)s, or biodegradable plastic(s), bio-based polymer(s), cellulose-based material(s) such as paper and combinations thereof. 
         [0079]      FIG. 1   b  relates to an enlarged sectional side view showing the upper wall  3  of the capsule  1  being placed into receiving means of a dedicated beverage preparation device. Thereby, at least a liquid injection member  20  of the device is selectively movable with respect to the upper wall  3  such as to be able to open, preferably pierce the capsule  1 . In particular, the injection member  20  is movable in a direction along the centre axis Z of the capsule  1 . 
         [0080]    As can be seen in  FIG. 1   b,  the injection member  20  is preferably equipped with opening means  20   a  such as for example a slanted cutting edge or a tapered (e.g., rounded) tip. 
         [0081]    The central liquid inlet  6  of the capsule  1  is preferably surrounded by outlet channels respectively apertures  5  arranged at a peripheral portion  3   a  of the upper wall  3 . The central liquid inlet  6  is provided at the centre axis Z of the capsule. 
         [0082]    As illustrated in  FIG. 1   b,  the upper wall  3  comprises an annular engagement portion  10  which is preferably an integral part of the upper wall  3 . Thereby, the annular engagement portion  10  forms an inwardly directed inlet flange  7  that extends in axial direction of the rotational axis Z of the capsule  1  beyond the lower face of the upper wall  3 . 
         [0083]    In particular, the inlet flange  7  formed by the engagement portion  10  initially protrudes to a height h 1  from the upper surface of the upper wall  3  into the interior of the capsule  1 , wherein the height h 1  is greater than the thickness of the peripheral portion of the upper wall  3   b.  Thereby, height h 1  is measured in a direction parallel to the centre axis Z from the upper surface of the peripheral portion of the upper wall  3   b.    
         [0084]    The thickness t 2  of the inwardly directed annular engagement portion  10  is preferably thinner than the thickness t 3  of the peripheral portion of the upper wall  3   b.  However, the thickness t 2  may as well be equal to the thickness t 3  of the peripheral portion of the upper wall  3   b.  The thickness t 2  may be of constant thickness. Alternatively, the thickness t 2  may decrease towards the central axis Z. 
         [0085]    The liquid inlet  6  comprises a portion of reduced thickness  6   a  which constitutes an openable centre portion of the inlet  6  and which is preferably integrally formed with the annular engagement portion  10 . In particular, the openable central portion  6   a  is preferably connected to an inner portion of the annular engagement portion  10  having an inner diameter d 1 , as demarcated by the transition line, which is smaller than the outer diameter d 2  of the injection member  20  of the beverage preparation device. 
         [0086]    The central portion  6   a  may be formed as an inverted cone of obtuse angle-shaped. In an alternative embodiment, the centre portion  6   a  may as well be of convex shape or concave shape. The shape may be a portion of sphere for instance. 
         [0087]    In a particular preferred embodiment, the central portion  6   a,  the annular portion  10  and/or the upper wall  3  (outside the central liquid inlet  6 ) may be made from a material that softens and/or expands in volume in presence of hot water in order to increase the liquid-tight sealing engagement between the upper wall  3  and the perforating injection member  20 . 
         [0088]      FIG. 1   c  relates to the injection member  20  being further lowered with respect to the capsule  1  in order to fully open the liquid inlet  6  of the capsule  1 . Accordingly, the injection member  20  opens, preferably pierces, the central portion  6   a.  Thereby, the openable central portion  6   a  is preferably designed to be opened or ruptured in its centre through which the symmetric axis Z extends. Moreover, the central portion  6   a  is designed to be yielded to the circumference of the injection member  20  when being pierced by the injection member  20 , in order to provide an inwardly orientated extension  7   a  to the annular inlet flange  7 . 
         [0089]    Due to the inner diameter d 1  of the flange  7  being less than the outer diameter d 2  of the injection member  20 , the flange  7  is preferably at least partially yielded in direction towards the interior of the capsule, resulting in a height h 1 ′ of the flange  7  upon respectively after introduction of the injection member  20 , wherein said height h 1 ′ is greater than the originally height h 1 . 
         [0090]    The central portion  6   a  comprises a thickness t 1  which is preferably lower than the thickness t 2  of the annular engagement portion  10  and/or the thickness t 3  of the peripheral portion of the upper wall  3   b.    
         [0091]    In a possible mode, the thickness t 1  of the centre portion  6   a  decreases towards the centre axis Z of the capsule  1 . Alternatively, the centre portion  6   a  may as well be of constant thickness t 1 . 
         [0092]    After opening of the liquid inlet  6 , liquid is preferably injected into the interior of the capsule  1  by means of a liquid path  20   b  provided within the injection member  20 . Therefore, the beverage preparation device preferably comprises at least a liquid reservoir, a pump and heating means which are connected to the perforating injection member and designed to provide heated and/or pressurized liquid to the interior of the capsule  1 . 
         [0093]    The injection member  20  may be of varying shapes which may deviate from the shown examples. Thereby, in particular the lower portion  20   a  of the injection member  20  is preferably tapered as shown in  FIGS. 1   b  and  1   c.  However, the injection member  20  may as well comprise a rounded tapered tip replacing the cutting edge which may promote the stretching and forming of the sealing lip along the whole peripheral surface of the injection member. 
         [0094]      FIGS. 2   a  to  2   c  relate to another preferred embodiment of the capsule  1  according to the present invention, wherein the liquid inlet  6  comprises an annular engagement portion  10  and a circular respectively ring-shaped portion of reduced thickness  6   a.    
         [0095]    Thereby, the ring-shaped portion  6   a  constitutes a weakened annular portion  6   a  which encloses a central portion  6   b  of the liquid inlet  6  and which is preferably of constant thickness t 1 . The weakened portion  6   a  is arranged at the transition between the circumference of the central portion  6   b  and the annular engaging portion  10 . 
         [0096]    The thickness t 4  of the central portion  6   b  is preferably lower than the thickness t 2  of the annular engagement portion  10  and/or the thickness t 3  of the peripheral portion of the upper wall  3   b.  The weakened portion  6   a  has a thickness t 1  preferably lower than the thickness t 4 . 
         [0097]    As can be seen in  FIG. 2   c , upon introduction of the injection member  20  into the annular engagement portion  10 , the injection member  20  respectively the cutting edge  20   a  opens respectively tears or cuts the recessed portion  6   a  in order to enable the injection member  20  to be introduced into the interior of the capsule  1 . 
         [0098]    Thereby, the annular engagement portion  10  having an inner diameter d 1  which is smaller than the outer diameter d 2  of the injection member  20  is deflected outwardly and thus provides an inwardly directed force exerted onto an annular portion  21  of the injection member  20 . 
         [0099]    The weakened portion  6   a  may comprise an enforced portion  6   d  which is designed to act as hinge means suitable for connecting the centre portion  6   b  to the annular engagement portion  10  after the injection member  20  has been introduced into the interior of the capsule  1 . Hence, the centre portion  6   a  is prevented from falling into the interior of the capsule, thereby negatively affecting the extraction process. 
         [0100]      FIGS. 3   a  to  3   c  relate to another preferred embodiment of the capsule  1  according to the present invention, wherein the annular engagement portion  10  further comprises a reinforcement structure respectively support means  10   a  which are preferably geometrically designed to enable a piercing of the liquid inlet  6  by means of the injection member  20  with an increased resistance to buckling of the upper wall  3 . 
         [0101]    Therefore, the support means  10   a  are circumferentially arranged to the annular engagement portion  10  and protrude to the exterior of the capsule  1  from the upper surface of the preferably disc-shaped upper wall  3 . The thickness t 5  of the support means  10   a  may be equal to or less than the thickness t 3  of the peripheral portion of the upper wall  3   b.  Alternatively, the thickness t 5  may as well be greater than the thickness t 3  of the peripheral portion of the upper wall  3   b.    
         [0102]    An upper surface of the support means  10   a  is preferably arranged in parallel to the preferably essentially disc-shaped upper wall  3 . However, the upper surface of the support means  10   a  may as well be tapered with respect to the symmetric axis Z of the capsule. 
         [0103]      FIGS. 4   a  to  4   c  relate to another preferred embodiment of the capsule according to the present invention, wherein the liquid inlet  6  comprises an annular engagement portion  10  surrounding a central inlet opening  6   a  replacing the portion of reduced thickness of the preceding mode. 
         [0104]    According to this embodiment, the central inlet opening  6   a  is covered by means of an additionally provided central sealing portion  13  which is preferably sealed to an upper surface of the upper wall  3  at least in an annular portion provided between the peripheral portion of the upper wall  3   b  and the engagement portion  10 . 
         [0105]    Thereby, the thickness t 6  of the sealing portion  13  is preferably smaller than the thickness t 3  of the peripheral portion of the upper wall  3   b.    
         [0106]    The central sealing portion  13  may be of equal material or of different material than the annular engagement portion  10  and/or the upper wall  3 . In a particular preferred embodiment, the central sealing portion  13  may be made from a material that softens and/or expand in presence of hot water in order to increase the liquid-tight sealing engagement between the upper wall  3  and the perforating injection member  20 . 
         [0107]    The annular engagement portion  10  forms an inwardly protruding inlet flange and has a lower edge  10   b  of reduced inner diameter d 1  which is smaller than the outer diameter d 2  of the injection member  20 . 
         [0108]      FIGS. 5   a  to  5   c  relate to another preferred embodiment of a capsule according to the present invention, wherein the upper wall  3  comprises an annular engagement portion  10  and a portion of reduced thickness  6   a  which are designed to interact upon introduction of the injection member in order to form an inwardly protruding sealing flange  7 . 
         [0109]    Thereby, the annular engagement portion  10  which is arranged radially inside of the peripheral portion of the upper wall  3   b  at least partially overlaps with the portion of reduced thickness  6   a.    
         [0110]    The portion of reduced thickness  6   a  may be constituted by an opening integrally formed with the upper wall  3  as shown in  FIGS. 5   a  to  5   c.    
         [0111]    A stepped portion  12  of the upper wall  3  which is overlapped respectively covered by the engagement portion  10  delimits the portion of reduced thickness respectively the opening  6   a.  In particular, the stepped portion  12  provides a reduction in thickness which is overlapped by the engagement portion  10 . 
         [0112]    Thereby, the engagement portion  10  is preferably arranged on the upper surface of the upper wall  3   a  or within a provided recess  6   c  circumferentially provided to the opening  6   a  and which is of lower thickness t 7  than the peripheral portion of the upper wall  3   b.    
         [0113]    The engagement portion  10  is preferably of different material than the upper wall  3 . 
         [0114]    The engagement portion  10  is preferably formed of a material which is of softer consistence respectively which is more resilient and/or flexible than the upper wall  3 . 
         [0115]    In a particular preferred embodiment, the engagement portion  10  is made of material that softens and/or expand in presence of hot water in order to increase the liquid-tight sealing engagement between the upper wall  3  and the perforating injection member  20 . For instance, the material may be PLA or starch-based material which softens when contacted by a liquid at a temperature above 80° C. 
         [0116]    The height h 3  of the engagement portion  10  before the interaction with the injection member  20  is preferably equal to or more than the thickness t 3  of the peripheral portion of the upper wall  3   b.    
         [0117]    As shown in  FIG. 5   b , the stepped portion  12  preferably comprises an inner diameter d 3  which is greater than the outer diameter d 2  of the injection member  20 . 
         [0118]    Upon introduction of the injection member  20  into the liquid inlet  6  of the capsule  1 , the stepped portion  12  interacts with the overlapping annular engagement portion  10  which is elastically and/or plastically deformed about the inner diameter d 3  of the stepped portion  12  in order to form an inwardly protruding inlet flange  7  about the circumference of the injection member  20 . 
         [0119]    Thereby, the inlet flange  7  has a height h 3 ′ which is greater than the initial height h 3  of the engagement portion  10 . The height h 3 ′ of the formed inlet flange  7  is preferably constant about the circumference of the injection member  20 .