Abstract:
Disclosed is a cartridge containing one serving of coffee powder for preparing a coffee beverage. The bottom of the cartridge is provided with a passage covered by a gas-tight foil. The foil is manually removed before the cartridge is inserted into the coffee machine. Between the passage and the coffee powder, a filter element is disposed, preventing coffee powder to escape from the cartridge. The passage shall prevent a hydraulic pressure build-up in the cartridge, which would lead to the formation of froth.

Description:
BACKGROUND OF THE INVENTION 
   The present invention refers to a cartridge containing one serving of coffee powder for preparing a coffee beverage. Such cartridges are well known in the art in a plurality of embodiments, whereby particularly cartridges for preparing so-called espresso coffee beverage are in widespread use. The fundamental advantage of such cartridges may be seen in the fact that they are gas-tight, whereby the coffee powder is contained therein without oxygen that would impair the quality of the coffee powder during storage of the cartridge. Thus, the coffee powder contained in such cartridges keeps its freshness for a long time. 
   For brewing the coffee powder contained in the cartridge, either manually operated or semi-automatic as well as fully automatic coffee makers are used. Usually, in a manually operated coffee maker, the cartridge is inserted into a cartridge holder that in turn is inserted into the coffee maker. In the semi-automatic coffee makers, the cartridge is inserted into a cartridge retainer or directly into the brewing chamber of the machine, whereby the brewing chamber is manually closed by means of a central lever mechanism. In a fully automatic coffee maker, however, the cartridge is removed from a cartridge magazine and automatically inserted into the brewing chamber; after the brewing operation, the cartridge is removed from the brewing chamber and discarded into a trash receptacle without any intervention of the operator. 
   All these above mentioned species of coffee maker usually comprise a hollow so-called brewing spike provided with radial outlet openings for injecting brewing water into the cartridge that is also adapted to punch the bottom and the cover, respectively, of the cartridge. Also known are manually operated coffee makers in which the cartridge retainer is provided with a plurality of embossments located on an outlet grate; these embossments break open the cover of the cartridge as soon as brewing water is injected into the cartridge from the opposite side thereof and the cartridge is pressed against the embossments under the influence of the hydraulic overpressure created by the pressurized brewing water. During the subsequent brewing operation, the brewing water is injected into the cartridge by means of the brewing spike, with the result that is flows under pressure through the coffee powder contained in the cartridge and escapes from the cartridge through the opening created by the embossments. 
   Independent of the fact whether it is a manually operated coffee maker or a semi-automatic or a fully automatic machine, the coffee maker is designed and adapted to the cartridge so as to produce a coffee beverage having froth on its surface; that froth usually is considered as a characteristic of a good coffee beverage. 
   Even if great efforts have been taken to ensure that the prepared coffee beverage has durable froth on its surface, in certain countries the desire arises to prepare also conventional coffee in the sense of a filter coffee by means of these coffee makers. In place of the expression “filter coffee”, also the expression “gentle coffee” is used. 
   PRIOR ART 
   The U.S. Patent document 2003/172813 discloses a cartridge of the kind referred to herein. It contains a substance extractable by means of water for preparing a beverage, preferably an espresso coffee. Thereby, a sieve-like member is disposed between the bottom of the cartridge and the substance and/or between the cover of the cartridge and the substance, provided with a plurality of axial apertures. The sieve-like member is provided with stampings directed towards the bottom of the cartridge and the cover of the cartridge, respectively, such that fluid channels are formed between the sieve-like member and the bottom of the cartridge, and the sieve-like member and the cover of the cartridge, respectively. In these channels, the brewing water can be distributed over the cross sectional area of the cartridge, and the prepared beverage can be collected in these channels, respectively. In order to prevent that the sieve-like member is punched upon piercing the cartridge, the sieve-like member comprises a central recess directed towards the interior of the cartridge into which the piercing member can extend once the cover or the bottom of the cartridge have been pierced. Even if such a cartridge is well suitable for preparing espresso coffee, it can hardly be used for preparing normal filter coffee, since the cartridge presents a high flow resistance to the brewing water flowing there trough; the result is a formation of froth. 
   The patent document EP 0,326,685 discloses a container, called a brewing chamber, adapted to be disposed of after use, which is collapsible and to the bottom of which a filter bag containing ground coffee or tea is glued. Preferably, the container is made of paper, carton or a similar material. The bottom of the container is provided with an outlet opening located below the filter bag through which the prepared beverage can flow out. In a preferred embodiment of the container, the outlet opening is covered at the outside with a removable foil. Such a container may be usable in a conventional filter coffee machine, but not in an espresso coffee machine. 
   OBJECTS OF THE INVENTION 
   It is an object of the present invention to provide a cartridge containing one serving of coffee powder for preparing a coffee beverage which can be used in a conventional espresso coffee machine to prepare a normal coffee beverage not having froth on its surface and corresponding in taste to a normal filter coffee. 
   SUMMARY OF THE INVENTION 
   To meet this and other objects, the present invention provides a cartridge containing one serving of coffee powder for preparing a coffee beverage, comprising a cartridge body having a bottom portion and a cover portion, the bottom portion of the cartridge body having a passage covered by a gas-tight foil member, and a filter element located inside the cartridge body between the coffee powder and the passage in the bottom portion of the cartridge body. 
   By providing at least the bottom portion of the cartridge with a passage constituted by an aperture, adapted to avoid a hydraulic pressure build-up in the interior of the cartridge during brewing and extracting the coffee powder, the fundamental prerequisite is realized to use such a cartridge in a conventional espresso machine for preparing a coffee beverage corresponding in appearance and taste to a normal filter coffee. The passage ensures that the pressurized brewing water fed into the cartridge cannot create a substantial pressure build-up in the interior of the cartridge. Thus, the brewing water can flow through the cartridge and, thereby, through the coffee powder contained therein without any substantial resistance, thereby avoiding the formation of froth. 
   In order to prevent the coffee powder contained in the cartridge from escaping the cartridge through the afore mentioned passage and from being flushed out by the brewing water, a filter element is arranged between the passage and the coffee powder contained in the cartridge. In order to ensure that the coffee powder contained in the cartridge keeps well during an extended period of time in spite of the passage provided in the cartridge, the passage is covered by a gas-tight foil. The latter one is either manually removable or designed such that it can be easily pierced by a punching member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, embodiments of the cartridge according to the invention will be further described, with reference to the accompanying drawings, in which: 
       FIG. 1  shows the elements of a coffee powder cartridge according to the invention in an exploded view; 
       FIG. 2  shows a longitudinal sectional view of a first embodiment of a coffee powder cartridge according to the invention; 
       FIG. 3  shows a longitudinal sectional view of a second embodiment of a coffee powder cartridge according to the invention; and 
       FIG. 4  shows an enlarged portion of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The coffee powder cartridge according to  FIG. 1  comprises a cup-like shaped lower portion  1 , a lower filter element  2 , an upper distribution member  3  and a cartridge cover member  4 . The coffee powder to be received in the lower portion  1  of the cartridge between the filter element  2  and the distribution member  3  is not shown in  FIG. 1 . The filter element  2  and the distribution member  3  are dimensionally stable and have essentially disc-like shape; preferably, they are manufactured by a deep drawing process. 
   The upper region of the lower portion  1  of the cartridge, slightly conically widening towards it top, is provided with a enlarged portion  5 , establishing an annular shoulder  5   a  at the inside of the cartridge, serving for supporting the upper distribution member  3 . At the top, the cup-shaped portion  1  of the cartridge comprises a circumferential edge portion  6  to which a cover  4  is fixed, preferably welded. As schematically indicated in  FIG. 1  by dashed lines, the bottom  7  of the cup-shaped portion  1  of the cartridge is provided with a round aperture  20  for forming a passage  22 , which is covered by a foil  21 . The foil  21  comprises a flap L, laterally protruding from the cup-shaped portion  1  of the cartridge, facilitating a manual removal of the foil  21 . The cup-shaped portion  1  of the cartridge, the cover  4  as well as the foil  21  consist of a gas-tight multi-layer composite material, whereby the lower portion  1 , as compared to the cover  4  and the foil  21 , is relatively stiff, dimensionally stable, elastic and ductile. 
   After the aperture  20  having been covered by the foil  21 , and after the cover having been welded to the circumferential edge portion  6  of the cup-shaped portion  1  of the cartridge, the cartridge and, thereby, its content are air-tightly sealed. All these foil materials used for manufacturing the lower portion  1  of the cartridge, the cover  4  and the foil  21  preferably comprise at least one gas-tight layer as well as a layer of a thermoplastic polymer. Layers of thermoplastic polymer are easily welded to each other, for instance under the influence of heat or ultrasound. 
   The filter element  2 , having essentially dish-like shape, is provided with a circumferential edge portion  11  and comprises a plurality of stampings  9  having essentially the shape of annular segments and protruding above the bottom of the filter element  2  downwards. Once the filter element  2  is inserted into the cup-shaped portion  1 , the stampings  9  rest on the bottom of the portion  1  of the cartridge. Thus, between the stampings  9  and the bottom of the portion  1  of the cartridge, collection channels  17  are formed that extend, with reference to a central vertical axis, radially outwards and circularly around the central axis. In the areas between the stampings  9 , in the region of the channels  17 , the filter element  2  is provided with a plurality of apertures  8 . In the center of the filter element  2 , a central, cone-shaped recess  10  is provided that is directed towards the interior of the cartridge. 
   The upper distribution member  3  also comprises a plurality of stampings  13  having essentially the shape of annular segments and protruding above the top of the distribution member  3  upwards. Between the stampings  13 , at the top of the distribution member  3 , fluid channels  18  are formed that extend, with reference to a central vertical axis, radially outwards and circularly around the central axis. In the areas between the stampings  13 , in the region of the channels  18 , the distribution member  3  is provided with a plurality of apertures  14 . In the center of the distribution member  3 , a central, cone-shaped recess  15  is provided that is directed towards the interior of the cartridge. Along its periphery, the distribution member  3  is provided with an annular surface portion  19 , slightly elevated with respect to the fluid channels  18 , and being essentially flush with the stampings  13 . The edge of the annular surface portion  19  comprises an annular portion  16  extending downwards from the surface portion  19 . 
   Upon inserting the upper distribution member  3  into the cup-shaped lower portion  1  of the cartridge, the distribution member  3  rests with its portion  16  on the shoulder  5   a  of the enlarged portion  5  of the cartridge portion  1 . During feeding brewing water into the cartridge for preparing a coffee beverage, the distribution member  3  particularly serves for evenly distributing the brewing water over the entire cross section of the cartridge, while the lower filter element  2  particularly prevents any coffee powder particles from escaping from the cartridge. Additionally, the upper distribution member  3  also serves as a filter, while the lower filter element  2  also serves to collect and centrally discharge the prepared coffee beverage. 
   In order to arrive at an optimal distribution of the brewing water over the entire cross sectional area of the cartridge and, thereby, at an even soaking of the coffee powder contained in the cartridge, both the apertures  14  provided in the distribution member  3  and the apertures  8  in the filter element  2  are evenly distributed over the respective surface of the member  3  and element  2 , respectively. The entire summed cross sectional area of the apertures  14  provided in the distribution member  3  amounts to at least 3%, preferably to 5% of the total cartridge cross sectional area. The same relationship is also true for the lower filter element  2 . By this design, it is ensured that the brewing water flows through the distribution member  3  into the interior of the cartridge without any substantial resistance, and that the prepared coffee beverage can flow through the lower filter element  2  out of the cartridge without any substantial resistance, as well. Moreover, the aperture  20  in the bottom  7  of the cartridge ensures that neither at the beginning nor during the brewing operation a hydraulic pressure build-up can take place. By this design, the formation of froth in the finished coffee beverage can be reliably avoided. 
   Nevertheless, the size of the apertures  8 ,  14  in the filter and distribution elements  2 ,  3  should not be chosen so large that coffee powder can escape from the cartridge. To this end, the diameter of a single aperture  8 ,  14  is made somewhat smaller than the statistic mean value of the diameter of a single particle of the coffee powder. In order not to confront the brewing water with a high flow resistance when it flows through the coffee powder contained in the cartridge, the coffee powder is relatively coarsely ground. The arithmetic mean value of one particle of the coffee powder amounts to between 400 and 600 μm in the present example. 
   Preferably, the foil  21  has a color that is different from the color of the cartridge. The color of the foil  21  can be selected, for example, to determine the content of the cartridge. In other words, depending on the amount of coffee contained in the cartridge, the blend of the coffee, or the degree of grinding, a different color is selected for the foil. 
     FIG. 2  shows a longitudinal sectional view of the cartridge of  FIG. 1 , whereby the cartridge is filled with coffee powder KP. The coffee powder KP is enclosed between the lower filter element  2  and the upper distribution member  3  in the cartridge. As can be seen from  FIG. 2 , fluid channels  17  are formed by the stampings  9  of the lower filter element  2  resting on the bottom  7  of the cup-shaped lower portion  1  of the cartridge into which the prepared coffee beverage can flow through the apertures  8  provided in the lower filter element  2 . Similarly, by the stampings  13  provided in the distribution member  3 , fluid channels  18  are formed between the distribution member  3  and the cover  4  of the cartridge, by means of which the brewing water is evenly distributed on top of the coffee powder to flow through the apertures  14  for soaking the coffee powder. Due to the fact that both the distribution member  3  and the filter element  2  are dimensionally stable, the channels  17 ,  18  are preserved even if outer forces affect the cover  4  and the bottom  7  of the cartridge. It is understood that the foil  21  is removed from the bottom  7  of the cartridge prior to inserting the latter one into the coffee machine, as is indicated in  FIG. 2  by broken lines. 
   Once the foil  21  is removed, the cartridge can be inserted into the brewing chamber of a coffee machine (not shown). For punching the cartridge, a punching means, e.g. in the form of a piercing sting  23 , is lowered towards the cover  4  of the cartridge and pierces the latter one. Thereby, the piercing sting  23  moves through the cover  4  into the recess  15  provided in the distribution member  3 , thus avoiding any damage to the distribution member  3 . For feeding brewing water  24  into the interior of the cartridge, the piercing sting  23  is provided with a central bore, opening into radial outlet openings. 
   In the present case, it is assumed that the brewing water  24  flows through the cartridge from its top to its bottom. By means of the fluid channels  18 , the brewing water is evenly distributed over the entire cross section of the cartridge. Through the apertures  14  provided in the upper distribution member  3 , the brewing water enters the interior of the cartridge to flow through the coffee powder. Through the apertures  8  in the lower filter element  2 , the prepared coffee beverage enters the space below the filter element  2  and escapes from the cartridge through the passage  22  formed by the aperture  20 ; Therefrom, it is led by not further shown means to a coffee beverage outlet of the coffee machine. 
   By the provision of the previously described distribution member  3  and filter element  2 , it is ensured that the coffee particles contained in the cartridge are homogenously soaked, resulting in an optimal extraction of the entire coffee powder. The stampings  9 ,  13  are distributed such that the respective element  2 ,  3  rests in a two-dimensional way on the bottom  7  of the cartridge and on the cover  4  of the cartridge, respectively. Thereby, it is ensured that the fluid channels  17 ,  18  maintain their shape between element  2  and bottom  7 , and member  3  and cover  4 , respectively, even if external forces affect the cartridge. 
   The diameter of the apertures  8 ,  14  provided in the distribution member  3  and the filter element  2 , respectively, is preferably smaller than the statistic diameter of a single particle of the coffee powder, preferably smaller than x-σ, whereby x is the arithmetic mean value of the diameter and σ is the standard deviation. Thereby, it is ensured that essentially no coffee particles can escape from the cartridge, independent of the size of the opening that is punched into the cover  4  by the piercing sting  23 . 
     FIG. 3  shows a longitudinal sectional view of a second embodiment of a cartridge filled with coffee powder KP, whereby the reference numerals of corresponding parts and elements are the same as used in  FIGS. 1 and 2 , but with the letter “a” added. The essential difference to the embodiment discussed in connection with  FIGS. 1 and 2  consists in the fact that the passage  22   a  constituted by the aperture  20   a  is not covered by a foil from the outside of the cartridge that is manually removable, but by a foil  21   a  located at the inside of the bottom  7   a  of the cartridge and covering the passage  22   a , the foil  21   a  being punched by a piercing sting  35  before the brewing operation starts. The cup-like shaped lower portion  1   a  of the cartridge is provided with a slightly outwardly domed bottom  7   a , surrounded along its outer edge by a circumferential annular edge portion  26 . The diameter of the aperture  20   a  provided in the bottom  7   a  of the cartridge is smaller than the corresponding aperture  20  in the first embodiment. The foil  21   a  for covering the aperture  20   a  is located in the interior of the cartridge between the filter element  2   a  and the bottom  7   a  of the cartridge. 
   While the cup-like shaped lower portion  1   a  of the cartridge is relatively, stiff, dimensionally stable, elastic and ductile, the foil  21   a  is, as compared thereto, thinner and comprises a lower elasticity, ductility and tear strength. Thereby, it is ensured that the foil  21   a  readily tears apart under the influence of the piercing sting  35 . In order to keep the foil  21   a  relatively thin, it is made of a two layer material. The combination of a layer of aluminum and a layer of thermoplastic polymer has been proven to be particularly advantageous. As a thermoplastic polymer, particularly suitable are polypropylene or polyethylene. By providing a layer of aluminum, a very good gas-tight sealing can be achieved, while the thermoplastic polymer layer enables a welding of the foil to the bottom  7   a  of the cartridge. 
   In the second embodiment, moreover, the cup-like shaped lower portion  1   a  of the cartridge is provided with a circumferential groove  27  located at the inside of the lower portion  1   a , while the edge  11   a  of the filter element  2   a  is provided with a circumferential annular projection  28  engaging the groove  27  to clampingly fix the filter element  2   a  in the interior of the cartridge. 
     FIG. 4  shows an enlarged portion of  FIG. 3 , particularly a portion of the bottom  7   a  of the cartridge, together with the aperture  20   a  provided therein and the foil  21   a  covering the aperture  20   a . In this illustration, it can be clearly seen that both the lower portion  1   a  of the cartridge and the foil  21   a  comprise multiple layers. While the lower portion  1   a  and, thereby, the bottom  7   a  of the cartridge consist of a three-layer composite material, the foil  21   a  comprises two layers. In the material constituting the lower portion  1   a  of the cartridge, the two outer layers  29  and  31  consist of a thermoplastic polymer, while the intermediate layer  30  consists of a gas-tight foil material, for example EVOH (ethylene vinyl alcohol). The lower layer  32  of the foil  21   a , facing the cartridge bottom  7   a , consists of a thermoplastic polymer as well, while the upper layer  33  facing the interior of the cartridge consists of aluminum. Since the layers  31 ,  32  of the cartridge bottom  7   a  and the foil  21   a , respectively, facing each other, both consist of a thermoplastic polymer, these two layers  31 ,  32  can easily be welded to each other. The foil  21   a  has, as compared to the composite material of the cup-like shaped lower portion  1   a  of the cartridge, a relatively low ductility, elasticity and tear strength. 
   The foil  21   a , visible from the outside through the aperture  20   a , preferably has another color than the cartridge itself. After the foil  21   a  and the cover  4  having been welded to the lower portion  1   a  of the cartridge, the cartridge und, thereby, its content are air-tightly sealed. 
   Due to the fact that the foil  21   a  is relatively thin and does not exhibit a high ductility, elasticity or tear strength, it can easily be punched by the piercing sting. Thereby, it is ensured that in a fully automatic espresso coffee machine both conventional coffee powder cartridges, suitable for preparing an espresso coffee having froth on its top, and coffee powder cartridges as hereinbefore discussed, suitable for preparing a normal coffee without froth, can be used. In any case, the foil is designed such that it is punched by a piercing sting even at a relatively low force, while a conventional, one-piece coffee powder cartridge, and particularly its bottom, are designed such that the bottom, in a first phase, is elastically deformed and pierced only under the influence of the pressure of the brewing medium. By such elastic behavior of the bottom of a conventional cartridge, it is ensured that an initial pre-brewing phase takes place. To this end, brewing water is fed into the interior of the cartridge that is still closed at its bottom, thus creating an overpressure in the interior of the cartridge to soak and, if appropriate, swell the coffee powder, before the bottom of the cartridge is punched, whereby the prepared coffee beverage escapes from the cartridge under formation of froth. 
   Whenever, in the foregoing, the expression “espresso coffee machine” has been used, it was to designate generally a coffee machine, having a brewing chamber adapted to receive the coffee powder cartridge and a pump for feeding pressurized water into the cartridge, independently of the fact whether the espresso coffee machine is used for preparing a “small” espresso coffee or a “larger” coffee. Anyway, coffee beverages prepared with an espresso coffee machine have been characterized by the fact that they had froth on the surface. However, by means of the coffee powder cartridge according to the present invention, it is possible to prepare a coffee beverage that does not exhibit any froth and has a taste coming very close to a filter coffee beverage, even using a conventional espresso coffee machine designed for preparing espresso coffee using special espresso cartridges.