Abstract:
The present invention proposes a device for preparing a nutritional composition by supplying water to ingredients provided to the device comprising a pump ( 2 ) being connected to an integrated or external water supply ( 1 ), a water discharge head ( 4 ) designed for providing water to a cartridge containing ingredients (7) for interaction between water and the ingredients in the cartridge ( 7 ), wherein the pump ( 2 ) and the water discharge head (74) are in water communication via a water flowpath ( 50 ), whereby the pump can supply water under pressure through the water flowpath, a rigid filter assembly ( 20 ) comprising at least one antimicrobial filter membrane ( 30 ) and filter enclosing means ( 40   a,    40   b ), wherein the filter assembly ( 20 ) and the filter enclosing means ( 40   a,    40   b ) are complementary configured such that the filter assembly (20) is insertable into the filter enclosing means ( 40   a,    40   b ) across the water flowpath ( 50 ) in a fluid tight manner before the water discharge head ( 4 ), and is removable from the filter enclosing means ( 40   a,    40   b ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a filter for a device for providing a ready-to-drink nutritional composition such as an infant formula. More particularly, the present invention relates to an exchangeable filter card which is removably insertable into a device in order to improve the hygiene level and ease the maintenance of the device. 
         [0002]    Infant formulas have been developed as a substitute for human breast milk in order to provide required nutrients to infants. In general the infant formulas are either based on cow or soy milk and may be provided in different forms such as powder or concentrated liquid form. 
         [0003]    Each of the different forms in which infant formulas may be provided has their own advantages. For instance, although the infant formula provided in a powder form has a relative high nutritional quality, the preparation thereof may be regarded as inconvenient and time consuming, since water which has been boiled in advanced and allowed to cool has to be poured into a sterilised drinking vessel containing the powder in order to prepare a liquid infant formula. The same inconvenient preparation process exists for infant formulas in concentrated liquid form. 
         [0004]    If prepared and consumed in this manner, powdered infant formulas provide a safe and nutritionally good substitute for mother&#39;s milk. However, primarily due to the inconvenient preparation, many parents or caregivers do not prepare the formulas properly and hence expose the infant to risks of infection or other risks. For instance, if water is not properly sterilized prior to use or if the final preparation is prepared too long in advance, there can be a risk of transmitting pathogens to the infant. Usually, water sources in developed countries are safe but this may not be the case everywhere. 
         [0005]    In further development, infant formulas in ready-to-feed single serve portions have been introduced which overcome the inconvenience of the preparation of the infant formula. However, these ready-to-feed products are more costly than infant formulas stored in bulk and they often suffer the disadvantage that once the portion is opened, it has to be consumed immediately to avoid the risk of contamination with bacteria. Moreover, even the single serve portion infant formulas are reconstituted with water. Hence, there is a risk that the water may not necessarily be properly sanitized and that the single serve baby bottles are prepared in advance in bulk and stored. 
         [0006]    The immune defences of infants and young children are generally not fully developed and, as a result, these populations are particularly vulnerable to both bacterial and viral infections. For example, they may be prone to infections in circumstances where the immune system of a healthy adult would resist infection or they may suffer more serious consequences as a result of infection than would a healthy adult. Similar difficulties may arise in populations where the immune system is compromised such as the elderly. The consequence of this is that devices that prepare nutritional compositions which are perfectly safe for healthy adults may not be able to produce products which meet the increased safety standards required for products to be consumed by subjects having immature or compromised immune systems. 
         [0007]    Therefore, a method or an apparatus is sought-after which enables a provision of nutritional composition for instance an infant formula in a convenient and safe manner. 
         [0008]    WO2006/077259 discloses a method for preparing a single serving of a nutritional composition comprising introducing liquid such as water into a cartridge containing a unit dose of the composition in concentrated form. Thereby, the water is treated prior to the introduction into the cartridge in order to remove pathogens from the water. This treatment may be for instance a pre-heating, a filtering or an irradiation of the water with ultra-violet light. 
         [0009]    A device which teaches the principle of treating water by means of a filter used for the preparation of nutritional compositions in a dispenser from cartridges is disclosed in co-pending European patent application No. 06117801.8 filed 25 Jul. 2006 entitled “Dispenser for preparing a nutritional composition”. Accordingly, a convenient solution for treating the water can be provided in order to ensure that the water is free of pathogens. However, the filter in the disclosed device is incorporated in the water discharge means. 
         [0010]    In order to ensure a high standard of safety with regard to the removal of any pathogens which may be contained in a liquid used for the preparation of a nutritional composition, the provided filter of such a device may have to be changed repeatedly. Therefore, an improved filter system is sought-after which enables exchangeability and/or maintenance of the filter to provide the necessary level of hygiene and food safety. 
         [0011]    US20070199888 relates to a water filter for a coffee machine that has tabs to be attached to the brew basket of a machine. However, this water filter is simply slidably engaged below a brewing basket which receives water at atmospheric pressure. The filter is said to have a thickness of several millimetres. However, this filter is not intended to remove pathogens to treat water. 
         [0012]    WO01/50875A1 relates to a drip coffee brewer comprising a liquid reservoir connected to a heater and a liquid outlet positioned above a supporting device holding a filter assembly. The filter assembly is designed to remove pathogens. The filter is configured with a reservoir to be able to receive dripping water which accumulates against the filter. Such system is so designed to slowly filter water at atmospheric pressure by a principle of percolation. Furthermore, the filter assembly requires a complex filtering structure including an adsorbent supporting web substrate having a surface fused to a mixture of adsorbent particles and binder particles. 
         [0013]    The present invention seeks to address the above described problems. The invention also aims at other objects and particularly the solution of other problems as will appear in the rest of the present description. 
         [0014]    In particular, the invention aims at providing a solution for supplying water, free of undesired micro-organisms in a device for preparing a nutritional composition, at a certain pressure (above atmospheric) and flow rate for an effective interaction with the ingredients. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0015]    In a first aspect, the present invention proposes a device for preparing a nutritional composition by supplying water to ingredients provided to the device,
       said device comprising a device for putting the fluid under pressure, e.g. a pump, being connected to an integrated or external water supply,   a water discharge head for providing water to a cartridge containing ingredients for interaction between water and the ingredients in the cartridge, wherein the pump and the water discharge head are in water communication via a water flowpath, whereby the pump can supply water at pressure above atmospheric through the water flowpath,   a rigid filter assembly comprising at least one antimicrobial filter membrane and filter enclosing means, wherein the filter assembly and the filter enclosing means are complementary configured such that the filter assembly is insertable into the filter enclosing means across the water flowpath in a fluid tight manner before the water discharge head, and is removable from the filter enclosing means.       
 
         [0019]    With a device according to the present invention, it is possible to enable an interaction between water supplied in the device, more particularly by the pump connected to the water supply, and ingredients contained in the cartridge. Thereby, water is preferably provided to the water discharge head by a water supply disposed upstream, e.g., at an upper side, of a cartridge receiving chamber. Note that the term “water supply” encompasses also any water supply line of the device which is connectable to an outside tap water or reserve of water foreign to the device itself. 
         [0020]    The water in the disclosed invention is inserted in the cartridge through a needle with a preferred flow rate of between 100 to 500 ml/min, e.g., approximately 400 ml/min. This creates a jet with sufficient energy to dissolve the ingredients within the cartridge. The filter membrane of the antimicrobial filter may be chosen dependent on the pressure drop across the membrane within the water flowpath. The lower the pressure drop across the filter, the higher the energy of the jet and therefore the dissolution of the ingredients within the cartridge. 
         [0021]    An outlet is preferably disposed downstream, e.g., at a lower side of the water discharge head. Thus, after the interaction between the water and ingredients in the cartridge, the output of the nutritional composition to be prepared takes place downstream, e.g., at the lower side of the water discharge head thence, enabling a flow of the nutritional liquid composition into a receptacle such as a cup or a vessel which may be placed beneath the cartridge. 
         [0022]    In another preferred embodiment, it may as well be possible to place the filter means downstream of the water discharge head. Hence, the filter may be used for filtering the dissolved infant formula which results from introducing water into the cartridge. Accordingly, any pathogens in the infant formula can be removed. As the resulting liquid flow discharged by the cartridge is not subjected to high pressure, means for enabling a predefined flow rate through the filter may be provided. For example, the surface of the filter may be enlarged or pressure may be exerted on the resulting liquid flow from the cartridge by means of a dedicated pump or the like. 
         [0023]    The rigid filter assembly provided to the water flowpath between the pump and the water discharge head is provided with at least one antimicrobial filter membrane acting as a physical barrier to control the permeability to micro-organisms, in particular, block the passage to bacteria or pathogens potentially present in the supplied water. Hence, a safe preparation of the nutritional composition can be assured. 
         [0024]    In a preferred embodiment, a cartridge containing ingredients for the preparation of a nutritional composition may be provided. The cartridge is received in a cartridge receiving chamber of the device. Said cartridge is preferably a single-use cartridge which contains a dose of nutritional composition to be hydrated (e.g. diluted, dispersed and/or infused with water). Thus, water provided to the cartridge can be used to reconstitute the nutritional composition. The cartridge preferably comprises a water injection face and a delivery face. 
         [0025]    In possible modes of “direct-flow” gastight cartridges, preferably, as described in European patent EP1472156B1, or also eventually in other modes such as in international patent application WO2007131559, a pressure is typically built up within the cartridge during water injection, which causes a lower face (or septum) of the cartridge to open thence, enabling the output of the liquid to be prepared. Since the output of the beverage to be prepared takes place at the lower face of the cartridge with no contact with opening means of the device, the flow of the liquid can be directly poured into the receptacle, e.g. a baby bottle, without contaminating the surfaces of the device. This results in a very hygienic preparation and delivery of the nutritional preparation. 
         [0026]    After the injection of water into the cartridge, the pouring from the cartridge may be delayed in order to provide sufficient time for interaction of the water and the ingredients, e.g., to obtain complete dissolution of the ingredient in water. For the pouring of the beverage to be prepared from the cartridge, opening means such as reliefs which may be arranged against a delivery tearable foil in order to tear the membrane in a controlled manner. These opening means interact with the foil in response to the pressure rise within the cartridge when injecting water. The nutritional composition to be prepared can then flow directly from a dedicated outlet of the cartridge into the receptacle without contacting the device. 
         [0027]    EP1472156B1 discloses various suitable cartridge configurations that may be used in the device of the present invention. 
         [0028]    Thereby, the use of a new single-use cartridge for the preparation of a nutritional serving coupled with the specific “direct flow” features of the cartridge, i.e., including an inside pressure-responsive opening technology within the cartridge and draining the liquid directly from the cartridge into a receiving vessel such as an infant&#39;s bottle both greatly facilitates the preparation of the nutritional product and make it significantly safer with substantially reduced or even eliminated risk of contamination. 
         [0029]    This is particularly advantageous if the apparatus is to be used in a hospital nursery where infant formulas must be prepared not only for healthy infants but also for infants suffering from specific diseases, deficiencies or severe allergies, for example allergies to cows&#39; milk. 
         [0030]    Moreover, the device may be provided with means to regulate the amount and/or temperature of water to be dispensed into the cartridge so that it stops the flow of water when a pre-selected or automatically controlled quantity has been dispensed. Water regulation means may comprise a water pump, and a control unit of the device comprising programs, a cartridge recognition system between the cartridge and device, e.g., barcodes on the cartridges and the like, for properly controlling the physical conditions of water delivered in respect to the type of cartridge. 
         [0031]    The device may further be provided with purging means to empty the cartridge from residual liquid, for example, by flushing the liquid in the cartridge with a gas. Purge means also reduce the risk of contamination by a back-flow of the nutritional composition into the device. A suitable gas is compressed air at a pressure of between 200 mbar and 2 bar, for example 300 mbar which can be pressurized by an air compressor in the device. 
         [0032]    Since the filter assembly is designed to be inserted to or removed from the device, a used filter assembly can be exchanged by a new filter according to user&#39;s instructions or in response, for example, to an alerting signal, such as a led flashing on the device or an indication on an LCD screen. These indications can be triggered when a specific number of servings have been provided or when a specific volume of water has been run through the filter assembly. The change signal may as well be triggered by a sensor measuring the flow rate through the filter or the pressure above and/or below the filter. Alternatively, the filter assembly can be recycled, for example, by carrying out a proper thermal processing of the filter assembly out of the dispenser, e.g., sterilization, according to user&#39;s instructions. Thus, the filter means can be removed effortlessly after a certain pre-defined time for exchange or recycling in order to ensure proper water filtering conditions in the device ensuring a safe water supply to the device. However, the filter may as well be sterilized within the machine by a provided steam generator. 
         [0033]    Preferably, the filter assembly connected to the device comprise a frame for housing at least one antimicrobial filter membrane. Thereby, the antimicrobial filter membrane means a filter that is designed to filter pathogens or undesired micro-organisms such as bacteria, virus, yeast and/or mold or other microparticles, from the water to be filtered. The antimicrobial filter membrane may have a nominal pore size of 0.45 microns or less. A particularly preferred nominal pore size is between 0.01 and 0.45 microns. For filtering bacteria, the nominal pore size can be of between 0.1 to 0.3 microns, most preferably of about 0.2 microns. For filtering virus, the pore size can be reduced as low as 0.05 microns or even lower. A more porous membrane could be selected if a higher flow rate is required when the removable of pathogens is less critical. 
         [0034]    For the use with the present device, a polymer membrane such as e.g. a superposed hydrophilic PES (polyethersulphone) membrane produced by Pall Corporation Switzerland or any other thin filter membrane e.g. made from a polymer having comparable specifications can be used (e.g. Millipore membranes). Antimicrobial filter membranes made from plastic materials are preferred. Preferably the thickness is less than 2 μm, more preferred less than 1 μm. Preferably the filter assembly comprises one or more of these thin membranes. Preferably the anti-microbial effect is achieved by filtration and not e.g. by adsorption produced e.g. by activated carbon. This has the effect that the filter can be more easily regenerated (in comparison to activated carbon). 
         [0035]    By use of such a filter, the risk of contamination of the nutritional composition to be prepared can be significantly minimized. 
         [0036]    The thin antimicrobial filter membrane(s) being physically sensitive and not easy to manipulate, the filter assembly preferably comprises water permeable backing means positioned, preferably adjacent, to support the antimicrobial filter membrane(s). Such backing means may for example be least one perforated wall which is abutting the filter membrane and extends across the direction of the flow path at the downstream side of the filter assembly, in order to support at least partially the surface of the filter membrane. Thus, breaking and/or deflection of the filter assembly when water is passed through it can effectively be prevented. Most preferably, a second perforated wall is placed adjacent the membrane and extends across the direction of the flowpath to further support the membrane at the upstream side of the filter assembly. The perforated walls may be formed of several ridges or a grid for example. 
         [0037]    Moreover, in case the filter is blocked, the differential pressure across the filter membrane can go from about 0.1 bar up to 10 bars. In such a case, the backing means can provide a protection for the filter membrane in order to prevent rupture of the membrane. The backing means also provide a protection for the membrane when it is manipulated and inserted in the device. 
         [0038]    In order to ensure fluid tightness between the filter assembly and the water path of the device, sealing means are provided at the interface of the filter assembly and device. Preferably, the sealing means are located around the filtering section of the filter assembly and/or the outlet and inlet of the channels. The sealing means may be part of the water communication channels of the dispensing device and/or part of the filter assembly. A possible material for the seal is Santopren or Thermolast K. Preferably, a lip-seal is provided which enables a water-tight assembly of the filter and the device at high pressures. 
         [0039]    The device further comprises a steam generator connected to the fluid communication path in order to sanitize the filter assembly and the other surfaces of contact with water such as the tubing, the water discharge head and the cartridge receiving chamber of the device. The filter is therefore manufactured and assembled in such a manner to resist steaming, up to, for example, 120° C. Therefore, according material is selected, e.g. PP for the rigid frame of the filter assembly and Santopren for the seal. 
         [0040]    The filter assembly for the device can be preferably inserted to or removed from an aperture disposed in an easy accessible position. The aperture is preferably disposed on one face of the device, e.g., the top face of the device. Thus, the exchangeability of the filter assembly is significantly enhanced since any user may carry out an exchange of the filter assembly. 
         [0041]    Multiple use of the same filter membrane should be prevented as the filter does not have the same properties after being used during a long time. Therefore, an element may be mounted on the filter assembly and/or on the device to prevent multiple use of the same filter membrane. Each filter membrane may for instance be individually marked with a barcode and remembered by the device. Another possible solution is to have an element on the filter assembly that breaks when the filter is removed and prevents a new insertion mechanically or by a sensor in the device. 
         [0042]    When the filter assembly is fully inserted to a corresponding aperture of the device, the filter assembly may be locked by locking means provided at the filter assembly and/or the device. For example, a snap fit may be provided at the filter assembly which may interact with a protruding or recessed element provided in vicinity of the aperture of the device when the filter assembly is fully inserted into the aperture. When a user intends to remove the filter assembly from the device, the snap fit can be released by the user and hence, the filter assembly can be removed from the aperture of the device. The filter assembly may as well be locked within the aperture by means of friction which is exerted onto the filter assembly by the adjacent faces at the inside of the aperture when the filter assembly is connected to the device. Frictional forces may as well be exerted by the sealing means of the filter assembly and the corresponding faces within the aperture being adjacent to the sealing means when the filter is inserted into the aperture. When inserting the filter assembly into the aperture, the user has to apply a certain force in order to overcome the frictional forces and hence fully insert the filter assembly into the aperture. The same applies to the removal of the filter assembly from the aperture. Accordingly, locking of the filter card within the device is achieved and the filter assembly can be connected to the device in a stable and safe manner. 
         [0043]    In another preferred embodiment, the closing mechanism comprises at least two enclosing members to enclose the filter assembly which are relatively moveable to each other. Accordingly, when the filter is provided to the corresponding aperture at the device, the closing mechanism is to be operated by a user in order to enable a relative motion of the enclosing members and hence enclose the filter assembly situated within the aperture. Thus, as the enclosing members are approached, a filter assembly situated between the enclosing members can be effectively enclosed. Accordingly, the filter assembly can be hold at a fixed and stable position during operation of the device. For this purpose, a lever may be provided at the housing of the device which is connected to at least one of the enclosing members. Thus, by operation of the lever, a user may enclose and/or release the filter assembly between the enclosing members. Of course, the enclosing of the filter assembly may be operated automatically. Therefore, a button may be provided at the housing of the device which enables an operation of a dedicated motor which permits a relative motion of at least one enclosing member to enclose and/or release the filter assembly within the aperture. 
         [0044]    In addition, a proximity sensor may be provided at the bottom of the aperture in order to detect a presence of the filter assembly. Thereby, the proximity sensor is connected to the pump of the device. Thus, the operation of the pump is preferably only possible when the proximity sensor detects a presence of the filter assembly. Accordingly, a safe operation of the system is enabled as the device can only be operated when the filter assembly is fully inserted into the aperture of the device. 
         [0045]    The nutritional composition to be prepared by the device according to the present invention may be any composition which by nature is very sensitive to contamination by pathogens. Examples of preferred nutritional compositions for use in the method of the present invention are infant formulas, growing up milks and liquid infant cereals. The ingredients of the composition are not critical to the method of the present invention and other food powder or liquid concentrate may be used. Examples of different types of infant formula that may be used in the method of the present invention include whey protein dominant formulas, formulas containing a mixture of whey and casein, formulas based on other proteins such as soy, formulas in which the protein component is partially or extensively hydrolyzed etc. The nutritional composition is preferably stored in a gastight single-use cartridge provided to the chamber, in powder form or concentrated liquid form. 
         [0046]    A ready-to-drink nutritional composition may also be prepared according to the method of the present invention using more than one cartridge to prepare a single serving. This permits a degree of flexibility in the compositions that is prepared. For example, a range of cartridges containing different supplements may be manufactured and consumers may be provided with instructions as to how to combine these to prepare a personalized composition suited to the particular needs of the recipient. 
         [0047]    In a second aspect, the invention proposes a filter card for being connected to a device for preparing a nutritional composition, said filter card comprising a frame for holding in position at least one antimicrobial filter membrane and at least one rigid water permeable backing member for supporting the filter membrane. The backing member may be placed adjacent or close to the filter membrane. The backing member may be perforated with small holes but of a diameter sufficiently large to minimize the pressure drop at the member. 
         [0048]    With a filter card according to the present invention, the required water filtering function for the device can be provided in a more convenient and safer way. In particular, the exchange of the filter means by a filter card can be operated by any user. Moreover, the rigidity of the frame of the card makes it easy to manipulate and to protect the fragile and not inherently form stable membrane(s), as well as to ensure the correct positioning of the card in the device. 
         [0049]    Moreover, the perforated backing member(s) disposed adjacent to the antimicrobial filter membrane(s) supports the filter membrane to maintain its integrity under the pressure of water (e.g., avoid it to tear, collapse, deflect or crease). Thereby, the perforations have preferably a wider diameter than the pores of the filter membrane (e.g. 0.6 mm). Hence, water passing through the filter card is not deflected by the backing members and the filter membrane can be subjected to a high liquid flow rate without the risk of deflection and/or breaking of the filter membrane. 
         [0050]    Preferably, the frame of the filter card is made of rigid plastic and/or metal material. 
         [0051]    The filter membrane is a preferably flat membrane which has a nominal pore size between 0.01 and 0.45 microns, most preferably between 0.1 and 0.3 microns, as already described. Hence, pathogens present in the water to be used for the preparation of the nutritional composition can effectively be blocked in the membrane. It can be noted that the membrane is asymmetrically designed in such a manner that it may comprise a varying pore section in the flow direction through the membrane thus determining an inlet filtering side and an outlet filtering side for the membrane. In particular, the pore widens from inlet side toward the outlet side. 
         [0052]    In another preferred embodiment, at least one antimicrobial filter membrane is sandwiched between at least two perforated backing members. Thereby, the perforations of the backing members can be aligned such that water which is conducted through the perforations is not deflected. Moreover, the perforations have preferably a wider diameter than the pores of the filter membrane. Hence, water passing through the filter card is not deflected by the backing members. Thereby, the flow resistance generated by the perforations of the backing members can be regarded as lower than the flow resistance of the pores of the membrane(s). 
         [0053]    However, it may as well be possible to provide an embodiment of the filter card, wherein two or more perforated backing members of aligned perforations are situated at each side of the filter membrane. The upstream backing member thereof which are disposed adjacent to a first filter membrane have preferably perforations of smaller diameter than a downstream backing members. Therefore, the outer backing members are designed such that no water is deflected when being passed through the filter card. The downstream backing member may support a second filter membrane. Accordingly, it is possible to provide a filter card which can sustain a high pressure drop across the filter card when being connected to a water flowpath. Preferably, the pressure drop within the water flowpath across the filter means is below 1 bar. 
         [0054]    Furthermore, the filter card preferably comprises sealing means for ensuring water tightness of the filter when being connected to the device, in particular, for avoiding any water to by-pass the filter card. Hence, when water is passed through the filter card, the sealing means prevent a leakage of the water flowpaths into which the filter card is inserted. 
         [0055]    Moreover, the perforated backing members of the filter card may be designed such that they can be supported by support members of the device to which the filter card is connected. For instance, support areas may be provided at the surface of the backing members. Thus, support members connected to the device may be designed to abut on said support areas in order to provide additional support for the filter card against deflection and/or breaking. Hence, a stable and fixed position of the filter card within the water flowpath can be assured. 
         [0056]    Preferably, the filter card further comprises guiding means which are connected to the frame of the filter card. The guiding means can be asymmetrical such that the filter card is insertable in the device by only one predetermined side. The guiding means may be a protrusion or, alternatively a groove, at only one side of the frame which fits in a corresponding groove or, alternatively protrusion, in the aperture of the device into which the filter card may be inserted. This asymmetrical card configuration ensures that the user is effectively prevented from inserting the filter card in the wrong way. Since as described, the filter membrane(s) may be designed asymmetrically, it is important to respect a correct insertion side of the card. 
         [0057]    Furthermore, the filter card may be equipped with locking means in order to ensure a safe and stable connection between the filter card and the device the filter card is connected to. For example, a snap fit may be provided at the filter card which may interact with a protruding or recessed element provided in vicinity of an aperture at the device when the filter card is fully inserted into the aperture. Thus, when a user intends to remove the filter card from the device, the snap fit can be released by the user and hence, the filter assembly can be removed from the aperture of the device. 
         [0058]    Moreover, it is important to ensure that the water to be filtered is flowing through the filter membrane(s) and will not bypass it by its outer edge. Therefore, sealing means are provided between the backing means and the filter membrane. Such sealing means may comprise plastic sealing material which is provided to the outer edge of the filter membrane by an overmoulding process. Alternatively, an o-ring may be provided within the assembly to prevent the water from by-passing the filter membrane. In case an o-ring is used, the filter membrane should be mono-directional in order to prevent a radial water flow trough the membrane and bi-pass it by capillarity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0059]    Further features, advantages and objects of the present invention will become apparent for the skilled person when reading the following detailed description of embodiments of the present invention, when taking in conjunction with the figures of the enclosed drawings. 
           [0060]      FIG. 1  shows a schematic drawing of a preferred embodiment of the device according to the present invention for preparing the nutritional composition. 
           [0061]      FIG. 2  shows a perspective view of a preferred embodiment of the filter card according to the present invention. 
           [0062]      FIG. 3  shows an exploded assembly drawing of a preferred embodiment of the filter card being connected to the water flowpath. 
           [0063]      FIG. 4  shows a sectional drawing of a preferred embodiment of the filter card being connected to the water flowpath. 
           [0064]      FIG. 5   a  shows a preferred embodiment of a backing member in top view. 
           [0065]      FIG. 5   b  shows a sectional drawing of a preferred embodiment of a backing member according to line A-A shown in  FIG. 5   a.    
           [0066]      FIG. 6  shows a sectional drawing of a preferred embodiment of the filter card being equipped with a filter membrane sandwiched between two backing members. 
           [0067]      FIG. 7  shows a sectional drawing of another preferred embodiment of the filter card being equipped with an o-ring. 
           [0068]      FIG. 8  shows an exploded assembly of another preferred embodiment of the filter card wherein the backing members are formed as an integral part of the filter card frame. 
           [0069]      FIG. 9  shows a preferred embodiment of an enclosing mechanism designed to secure the position of the filter card within the dedicated aperture of the device. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0070]      FIG. 1  shows a schematic drawing of a preferred embodiment of a device according to the present invention. The device comprises a water supply  1  connected to a water pump  2 . The output of the pump is connected to a heater  3  which preferably comprises a coiled stainless-steel pipe in a die cast aluminium thermoblock (not shown). Power is supplied to the thermoblock sufficient to heat the water to the desired temperature as it passes though the pipe. The output of the heater is connected to a filter  5  which is connected to the discharge or injection head  4  of the device. Said discharge head  4  comprises a chamber  9  for housing a cartridge  7 . The term “cartridge” refers, in the general concept of the invention, to a single-use package such as pod, capsule or sachet of various packaging materials containing nutritional ingredients. 
         [0071]    The term “pump” means any technical means that can transport a liquid at a sufficient positive pressure from the water supply to the injection head. This means can be a pressure pump such as a piston pump, a diaphragm pump, a peristaltic pump, a gear pump, a centrifugal pump, a progressive cavity pump, a hand pump and the like. 
         [0072]    Furthermore, flow control means  2   a  are provided preferably between the pump  2  and the heater  3  of the device. Moreover, temperature control means  3   a  are provided preferably between the heater  3  and the discharge head  4 . Hence, the temperature and the flow of a liquid within the device can be controlled and adjusted. 
         [0073]    In addition, an air pump  6  is connected to discharge head  4  in order to enable the flushing of any residua within a cartridge  7  into a receptacle disposed beneath the cartridge  7 . 
         [0074]    The cartridge  7  which is shown only schematically contains approximately 10 ml of ingredients. The ingredients are preferably provided in a powdered or in a liquid concentrated form within the cartridge  7 . The preparation of a 100-ml single serving of a nutritional beverage such as infant formula with the device according to the present invention will now be described. 
         [0075]    The cartridge  7  is located in the cartridge receiving chamber  9  of the discharge head  4  such that an injection element (not shown) protruding into the chamber  9  punctures a membrane sealing the cartridge  7 . Flow control means  2   a  and temperature control means  3   a  are set such that a desired quantity of water at the desired temperature is provided to the cartridge. Thereby, water is preferably pumped at a pressure of about 0.2 bar from a water tank  1  (or a water supply line from outside) to the heater  3  where it is heated to a preferred temperature between 25 and 40° C. The heated water is then passed through the filter  5  to the chamber  9  of the discharge head  4  at a preferred pressure between  2  and  7  bar and dispensed from there into a cartridge  7  which contains a unit dose of a nutritional composition such as an infant formula. When the pressure in cartridge  7  reaches a predetermined value which is preferably 2.5 bars, the cartridge opens and the reconstituted infant formula is dispensed directly from the cartridge into a suitable receptacle such as a baby bottle (not shown). The air pump  6  is then operated to flush any remaining liquid out of the cartridge and into the receptacle. 
         [0076]    In addition, a steam generator  8  is connected to the discharge head  4  and to the filter  5 . In operation, the chamber  9  of the discharge head  4  and the filter  5  may be sterilised as often as desired by passing steam from the steam generator through the discharge head  4  and the filter  5 . 
         [0077]      FIG. 2  shows a preferred embodiment of a filter card  20  according to the present invention. The filter card  20  comprises a frame  21  designed for housing a filter membrane (shown in  FIG. 3 ) and at least one rigid perforated backing member  24 . The frame  21  are preferably of rigid plastic or metal material equipped with a semicircular ending  21   a  which is the ending to be first introduced into an aperture such as a slot provided at a device and designed to receive the filter card  20 . Due to the semicircular ending  21   a,  the filter card  20  can easily be inserted into a provided slot of the device, even if a user inserts the filter card  20  in a slanted way or offset the central axis of the aperture. 
         [0078]    Furthermore, the filter card  20  comprises guiding means  22  in order to prevent a user from inserting the filter card  20  into a provided slot in an incorrect side. Preferably, the guiding means  22  is at least one protruding ridge provided at one of the edges of the filter card  20  and designed to be received by a corresponding groove  22   a  (shown in  FIG. 3 ) provided at the aperture of the device, the filter card  20  is designed to be inserted to. Preferably, the guiding means  22  are an integral part of the frame  21 . 
         [0079]    As shown in  FIG. 3 , the frame  21  comprises a preferably circular aperture  23  for housing the filter membrane  30  and at least one perforated backing member  24 . More preferably, at least one filter membrane  30  is placed or sandwiched between at least two backing members  24  which are situated in parallel and in close contact to the filter membrane  30 . Furthermore, the backing members  24  are perforated in order to enable a flow of fluid through the filter membrane  30  and thus through the filter card  20 . The diameter of the perforations of the backing members  24  is preferably wider than the nominal pore size of the provided filter membrane  30 . Thus, the flow resistance of the backing members  24  does not influence the overall flow resistance of the filter card  20  in a negative way. Moreover, in the case when two or more perforated backing members  24  are provided to the filter card  20 , the arrangement of the backing members  24  is adjusted such that the perforations of the backing members are aligned. Hence, water which is passed through the filter card  20  is not deflected. 
         [0080]    The backing members  24  are preferably designed to be supported by support members  25   a  (shown in  FIG. 3 ) of the device to which the filter card  20  is intended to be connected. Said support members  25   a  may for instance be ridges or the like designed to abut on the backing members when the filter card  20  is connected to the device. Therefore, the surface of the backing members  24  comprises support areas  25  onto which the support members  25   a  may abut. The support areas  25  are preferably uniformly distributed over the surface of the backing member  24 . The support areas  25  do not comprise any perforations such that the support members  25   a  abutting on the support areas  25  do not deflect any water passed through the perforations of the backing members  24 . Accordingly, the support areas  25  of the backing members  24  abutting on given support members  25   a  enable a stable position of the filter card  20  when being connected to a device for preparing a nutritional composition. The risk of deflection or breaking of the filter card  20  or particularly of the filter membrane  30  when water at high pressure is passed through the perforations of the backing members  24  can thus effectively be minimized. 
         [0081]    Furthermore, the protection of the filter membrane  30  against deflection or breaking when water is passed through the filter card  20  may be enhanced by providing one perforated backing member  24  of sufficient rigidity to each side of the filter membrane  30 . Thereby, the outer ones of said backing members  24  on each side of the filter membrane  30  have a wider diameter than the inner ones of the backing members  24  which are disposed in close contact to the filter membrane  30 . Hence, liquid which is passed through the backing members  24  and through the filter membrane  30  is not deflected by the outer ones of the backing members  24 . Furthermore, to enable a flow of water through the filter membrane  30  and the backing members  24 , the perforations of all backing members  24  disposed on either side of the filter membrane  30  are arranged such that they are aligned. 
         [0082]    Moreover, the filter card  20  comprises sealing means  26  for sealing the filter card  20  when being connected to a water flowpath  50  (shown in  FIG. 3 ). The sealing means  26  are disposed at the aperture  23  of the frame  21 . Preferably, the sealing means  26  is an O-ring or the like suitable for sealing the aperture  23  and thus the filter card  20  when water is passed through it. The sealing means  26  are preferably provided at either side of the filter card  20 . The sealing means  26  may as well be provided at the water flowpath  50  which the filter card  20  is designed to be connected to. As shown in the drawing, the sealing means is preferably a lip-seal. The lip-seal is especially advantageous since pressure exerted onto the lip-seal enhances the sealing effect by pressing the lip against the counter part. Thus, the higher the pressure in the filter chamber, the higher the pressure which presses the lip against the counterpart. Hence, the preferred embodiment according to the figure is able to withstand pressure as high as 16 bars, for instance, without leaking. 
         [0083]    Moreover, the sealing means  26 , the backing members  24  and the filter membrane  30  are designed to be easily removed from the aperture  23  of the filter card  20 . Therefore, fastening means  27  (see  FIG. 2 ) are provided which can be connected to the aperture  23  of the filter card  20 . Thereby, said fastening means  27  preferably enclose the filter membrane  30 , the backing members  24  and the sealing means  26 . The fastening means  27  is preferably a clamping piece or the like, designed to be connected to the aperture  23 . Of course, the fastening means may as well be provided as an integral part of the aperture  23 . Hence, when the filter card  20  is not connected to the designated water flowpath  50 , a user may easily change the filter membrane  30 , the backing members  24  or the sealing means  26 . Accordingly, a repeatedly exchange of the filter membrane  30  may be performed in a convenient way in order to enhance the protection provided by the filter card  20  against pathogens. 
         [0084]      FIG. 3  shows an exploded assembly drawing of a preferred embodiment of the filter card  20  being connected to the water flowpath  50 . Thereby, the two enclosing members  40   a,    40   b  are connected between the water flowpath  50  in order to enable a connection between the water flowpath  50  and the filter card  20 . The two enclosing members  40   a,   40   b  enclose an aperture  42  formed by their surfaces  41   a,   41   b  into which the filter card  20  can be inserted. Thereby, the semicircular ending  21   a  of the filter card  20  abuts on a semicircular recess  21   b  at the bottom of the aperture  42  enclosed by the two enclosing members  40   a,   40   b.    
         [0085]    Furthermore, a linear groove  22   a  is preferably provided at one side of the aperture  42  and, preferably, one of the two enclosing members  40   a,   40   b.  The linear groove  22   a  is designed to receive the ridge  22  formed at one side of the filter card  20 . Thus, the filter card  20  can only be inserted into the aperture formed by the two enclosing members  40   a,   40   b  in the correct side. 
         [0086]    Each of the two enclosing members  40   a,   40   b  comprises a circular recess  51  at its inside which is concentrically arranged and which is connected to the water flowpath  50 . Hence, the diameter of the water flowpath  50  can be adapted to the diameter of the filter membrane  30  provided at the aperture  23  of the filter card  20 . Accordingly, the whole surface of the filter membrane  30  provided at the filter card  20  can be used for filtering water. When water is passed through the water flowpath  50  and thus trough the recesses  51 , the recesses  51  are sealed by the sealing means provided at the frame  21  of the filter card  20 . Of course, the sealing means  26  may as well be provided on the enclosing member around the recesses  51 . 
         [0087]    As can be seen from  FIG. 3 , support members  25   a  are provided within the recesses  51  of the enclosing members  40   a,    40   b.  These support members  25   a  are preferably cylindrical protruding ridges which are abutting on the support areas  25  provided at the perforated backing members  24 , when the filter card  20  is inserted into the aperture  42  enclosed by the two enclosing members  40   a,   40   b.  Thus, deflection and/or breaking of the perforated backing members  24  and thus of the filter membrane  30  can effectively be prevented. 
         [0088]    In order to fully enclose the filter card  20  and fix its position within the aperture  42 , the enclosing members  40   a,    40   b  can be moved relatively to each other. Hence, after the filter card  20  is inserted into the aperture  42 , the two enclosing members  40   a,    40   b  can be approached and the position of the filter card  20  is fixed at a stable position and in a water-tight manner within the aperture  42 . In the same manner, releasing the filter card  20  can be achieved by distancing the two enclosing members  40   a,    40   b  from each other. In order to enable a relative movement of the enclosing members  40   a,    40   b,  at least one of the enclosing members is connected to a closing mechanism (not shown) such as a lever or a motor which can be operated by a user. 
         [0089]    In case the filter card  20  is disconnected from the device by distancing the enclosing members  40   a,    40   b  from each other, the remaining water within the water path  50  and the circular recess  51  upstream of the filter is released in a controlled manner through an opening  51   a  provided at the bottom of the aperture  42 . A collector below the opening  51   a  (not shown) is connected to a drip tray (not shown) so that the fluid can be discharged from the device. 
         [0090]    Furthermore, the aperture  23  of the filter card  20  comprises a circular support  28  for mounting the filter membrane  30  and the perforated backing members  24  thereon. Thereby, the support  28  comprises locating means  29   a,   29   b  for determining the correct position of the filter membrane  30  and the backing members  24  when being mounted at the support  28  of the aperture  23 . The locating means  29   a  provided at the support  28  interlock with locating means  30   a  provided at the filter membrane  30  and thus prevent relative rotation of the backing member and filter membrane and enable a user to correctly mount the filter membrane  30  at the support  28  of the filter card  20 . Preferably, the locating means  29   a  is at least one protruding ridge which fits in at least one correct recess  30   a  provided at the circumference of the filter membrane  30 . The backing members  24  are preferably provided with recesses  24   a  which are equally distributed over the circumference of the backing members  24 . Hence, these recesses  24   a  interlock with corresponding protruding ridges  29   b  which are disposed at the circumference of the support  28  of the filter card  20 . Thereby, the locating means  29   b,   24   a  for the backing members  24  are designed such that the perforations of the backing members  24  on either side of the filter membrane  30  are aligned. Accordingly, a user can effectively be guided to mount the filter membrane  30  and the perforated backing members  24  at the filter card  20  in a correct way. 
         [0091]    In the shown embodiment, two filter membranes  30  are mounted at the support  28  of the filter card  20  which are sandwiched between two perforated holders  24 . It may as well be possible to mount three or more filter membranes  30  to influence the filtration properties of the filter card  20 . 
         [0092]    A proximity sensor  54  may be provided at the bottom of the aperture  42  for inserting the filter card  20 . The sensor enables to detect a presence of the filter card  20  within the aperture  42 . The proximity sensor  54  is preferably connected to at least the pump  2  (see  FIG. 1 ) of the device. Thereby, the sensor  54  preferably transmits a signal in response to the presence of the filter card  20  within the aperture  42 . It can thus be ensured that the operation of the pump  2  is only possible when the filter card  20  is fully inserted into the aperture  42 . Therefore, it can be prevented that a user unintendedly operates the device without having the filter card  20  fully inserted into the aperture  42 . 
         [0093]      FIG. 4  shows a preferred embodiment of the enclosing members  40   a,    40   b  enclosing a filter card  20  when being inserted into the aperture  42  and thus being connected to the water flowpath  50 . As can be seen from the figure, the filter membrane  30  is sandwiched between two perforated backing members  24 . The perforations thereof are aligned such that water passed through the filter card  20  is not deflected. 
         [0094]    The water flowpath  50  is connected to a circular recess  51  formed in each of the enclosing members  40   a,   40   b.  Within the circular recess, protruding support members  25   a  are disposed, which are designed to abut on the support areas  25  of the perforated backing members  24  when the filter card  20  is inserted into the aperture  42 . Thereby, the support areas  25  of the backing members  24  do not comprise any perforations. 
         [0095]    As can be seen in  FIG. 4 , a circular recess  51   b  for housing sealing means is provided at both enclosing members  40   a,   40   b.  The circular recess  51   b  is preferably concentric to the circular recess  51  housing the protruding support members  25   a.  The circular recess  51   b  for housing the sealing means  26  is disposed radially outside of the circular recess  51 . Thus, the sealing means  26  housed by the circular recess  51   b  enable an efficient sealing of the aperture  42  when the filter card  20  is provided within the aperture  42  and when water is passed through the filter card  20 . The sealing means  26  is preferably an o-ring or the like. Moreover, the sealing means  26  are preferably exchangeable. Hence, when the sealing means  26  are subjected to deterioration, a user may easily exchange the sealing means  26 . As previously described, the sealing means  26  may as well be provided at the frame  21  of the filter card  20 . 
         [0096]    For ensuring a safe and stable defined position of the filter card  20  when the filter card  20  is fully inserted into the aperture  42 , the two enclosing members  40   a,    40   b  can be brought in tight contact to the filter card  20  by enable a relative movement of the two enclosing members, as already described. Alternatively, locking means  51   a,    51   b  may be provided at the frame  21  of the filter card  20 . As can be seen from  FIG. 4 , the locking means are e.g. a snap fit. Thereby, a protruding ridge  52   a,  preferably provided at the frame  21  of the filter card  20 , interacts with at least one corresponding recess provided at the snap fit member  52   b.  By pressing the member  52   b  in direction of the shown arrow  53   c,  the user may loosen the connection between the filter card  20  and the snap fit member  52   b  and thus, the filter card  20  may be withdrawn from the aperture  42 . The snap fit member  52   b  is preferably an integral part of one of the enclosing members  40   a,   40   b.    
         [0097]    In another preferred embodiment of the filter card  20 , the defined safe and stable position of the filter card  20  within the aperture  42  is ensured by frictional forces (press fitting) between the frame  21  of the filter card  20  and the adjacent faces  42   a,    42   b.  Hence, the fit of the frame  21  within the aperture  42  is chosen such that a user has to apply a certain force onto the filter card  20  in order to fully insert the filter card  20  into the aperture  42 . The same applies for removing the filter card  20  from the aperture  42 . 
         [0098]      FIGS. 5   a  and  5   b  show a preferred embodiment of a backing member  24 . Thereby, the backing member  24  has individual arcuated recesses  53   a  and ridges  53   b  which are formed to enable a perfect fit of two equal backing members  24  in a predefined angular position. Accordingly, the recesses  53   a  and ridges  53   b  of the first backing member  24  interlock with provided ridges  53   b  and recesses  53   a  of the second backing member  24 . Hence, a relative rotation of the backing members  24  can be prevented. Moreover, as the relative angular position of the two backing members  24  is defined by the recesses  53   a  and ridges  53   b,  the perforation of the two backing members  24  can be effectively aligned. As shown in the figure, support areas  25  are provided at the backing member  24  in order to provide a surface onto which the support members  25   a  (see  FIG. 3 ) of the device can abut. 
         [0099]    As can be seen from  FIG. 5   a , the recesses and ridges are preferably arranged symmetrically about the perpendicular axes A 1  and A 2 . Moreover, a semicircular recess  53   c  and a protruding semicircular part  53   d  are formed at opposing endings of the backing member  24 . Hence, when two equal backing members  24  are connected to each other, the semicircular recess  53   c  and protrusion  53   d  of the two backing members  24  interlock with each other and the correct predefined assembly position of the two backing members  24  is obtained. 
         [0100]    Between the two backing members  24 , a filter membrane  30  (not shown) is placed which preferably has an outer diameter which is bigger than the diameter of the portion of the backing member  24  which is perforated. 
         [0101]    As shown in  FIG. 5   b , the protruding recesses  53   a  and ridges  53   b  may vary in their dimensions. For example, the height of the recesses  53   a  and ridges  53   b  may be adjusted to enable a correct fitting of the two backing members  24  when assembled. Moreover, the recesses and ridges may overlap as indicated by reference B in  FIG. 5   a . Thus, a tight and correct fitting of the two backing members can be obtained. 
         [0102]    In manufacturing process of the filter card  20 , the filter membrane  30  is placed on one of the backing members  24 . Then, the second backing member  24  is placed onto the first backing member  24 , wherein their relative position to each other is defined by the arcuated recesses  53   a  and ridges  53   b  provided on their joint face. To secure the assembly, the frame  21  is injected. Thereby, injection ports are preferably provided at the backing members  24  in order to enable plastic material to pass through during the injection process and hence further secure the membrane between the backing members  24 . Moreover, sealing means  26  which may be provided at outer surfaces of the backing members  24  can be placed in provided recesses at the backing members  24  before the injection process. Accordingly, the sealing means  26  can be secured to the backing members  24  by the injection process as well. 
         [0103]      FIG. 6  shows a sectional drawing of a preferred embodiment of a filter card  20 . As can be seen from the figure, the filter membrane  30  is sandwiched between two perforated backing members  24 . The perforation of the backing members  24  is designed such that the diameter of the perforations widens towards the filter membrane  30 , i.e. the diameter of the perforations is bigger at the surface adjacent to the filter membrane  30  than at the outer surface of the backing member  24  being directed towards the water flowpath  50  (see  FIG. 4 ). 
         [0104]    As can be seen from  FIG. 6 , the two backing members  24  are interlocking due to provided circular recesses  53   a  and ridges  53   b  on the backing members  24 . The position of the ridges  53   b  is chosen such that the filter membrane  30  is as close as possible to the protruding inner edge  53   c  of the protruding ridges  53   b  and/or recesses  53   a.  Hence, the filter membrane  30  can efficiently be held in place and a tight enclosing of the filter membrane is obtained. 
         [0105]    Moreover, a lip-seal  26  is provided to the outer surfaces of the backing members  24  in order to seal the filter assembly when the filter card  20  is in connection with the water flowpath  50 . 
         [0106]    As already described, the sealing means  26  and the backing members  24  can be effectively connected to the frame  21  of the filter card  20  by means of the injection process during manufacturing of the frame  21 . 
         [0107]      FIG. 7  is a sectional side view of another preferred embodiment of a filter card  20 . In this embodiment, an o-ring  56  is placed in a provided circular recess  61  at one of the backing members  24 . Accordingly, the outer joint face between the filter membrane  30  and the backing members  24  is sealed and water cannot by-pass the filter membrane  30 . Preferably, the recess  61  and hence the o-ring  56  is provided at the backing member  24  which is situated on the upstream side of the filter card  20 . 
         [0108]    Instead of the shown o-ring  56 , plastic material may be provided to the outer edge of the filter membrane  30  such that the plastic material is compressed by the backing members  24  when the filter card  20  is assembled. Such plastic material can e.g. be applied to the filter membrane(s) by means of rubber overmoulding. Accordingly, effective sealing of the filter membrane  30  can be provided such that water passed through the filter card  20  is prevented from by-passing the filter membrane  30  through the joint face of the two backing members  24 . 
         [0109]      FIG. 8  shows an exploded assembly drawing of another preferred embodiment of the filter card. As shown in the figure, the backing means  24  are an integral part of the frame  21  of the filter card  20 . The backing means  24  are relatively large compared to the other embodiments. The backing means  24  may be grids formed in the frame  21 . Thus, dedicated support members  25   a  (see  FIG. 4 ) provided at the device can abut on the grid  24  in order to support a stable position of the filter card  20  when it is inserted into the aperture  42  (see  FIG. 4 ) of the device. 
         [0110]    The frame  21  comprises two parts which can be assembled in order to enclose a filter membrane  30  there between. To enable a correct assembly of the frame  21 , locating means  55   a  are provided. Preferably, the locating means  55   a  are protruding and/or recessed bolts arranged circularly around the grids  24 . Thus, the two parts of the frame  21  can be effectively assembled and a relative motion of the frame parts  21  after the assembly is prevented. 
         [0111]    As shown in  FIG. 8 , at least one filter membrane  30  is sandwiched between the grids  24  and thus can be effectively supported when water is passed trough the filter membrane  30 . The direction of the preferred water flow through the assembly is indicated by arrow  60 . Preferably, two or more filter membranes  30  are situated between the grids  24 . Thereby, the filter membranes  30  are of different pore sizes. More preferably, the filter membrane situated relatively upstream has a wider pore size than the filter membrane(s) situated relatively downstream. For instance, the upstream filter membrane has a nominal pore size of 0.65 μm and the downstream filter membrane has a nominal pore size of 0.22 μm. 
         [0112]    Furthermore, an additional membrane support  24   b  may be provided between the grids  24  in order to further support the filter membrane(s)  30 . Preferably, the support member  24   b  is a circular aluminium grid wherein the openings of the grid have a smaller size than the backing members  24  of the frame  21 . More preferably, the additional support  24   b  is positioned downstream of the filter membrane(s)  30 . In addition, locating means  55   b  are preferably provided at the membrane support  24   b  which interact with the locating means  55   a  provided at the frame  21  in order to hold the support  24   b  at a fixed position relative to the frame  21 . Preferably, the locating means are apertures formed close to the outer edge of the circular support member  24   b.    
         [0113]    In assembly process, the two frame parts  21  can be manufactured e.g. injected as separate pieces. After that, the additional backing member  24   b  may be fixed, e.g. glued, onto one of the backing members  24 . Of course, two backing members  24   b  may be provided at each side of the filter membrane(s)  30 . 
         [0114]      FIG. 9  shows a preferred embodiment of the closing mechanism  70  of the device which is provided in order to enclose the filter card  20  between the two enclosing members  40   a,    40   b.  The closing mechanism is preferably a lever connected to at least one of the enclosing members  40   a,    40   b  which are moveable relative to each other. Alternatively, a dedicated motor which may be operated by a push button can be provided in order to enable a relative movement of the two enclosing members  40   a,    40   b.    
         [0115]    As can be seen from the figure, the two enclosing members  40   a,    40   b  are arranged such that a dedicated aperture  42  for inserting the filter card  20  is formed between them. When the filter card  20  is fully inserted by a user, as shown by the figure, the user may operate the closing mechanism  70  in order to enclose the filter card  20 . Thereby, the closing mechanism  70  transmits mechanical forces in order to move the enclosing member  40   b  towards the other enclosing member  40   a,  as indicated by arrows  80 . Hence, the two enclosing members  40   a,    40   b  are approached and the filter card  20  situated between them is fixed in its position. Accordingly, the filter card  20  can be secured at a stable position in the aperture  42 . Moreover, when the enclosing members  40   a,    40   b  are approached, the sealing means  26  provided at the enclosing members  40   a,    40   b  are pressed against the surface of the filter card  20 , thereby enabling a water-tight sealing of the assembly. 
         [0116]    When a user intends to remove the filter card  20 , the closing mechanism is to be operated in advance in order to separate the two enclosing members  40   a,    40   b.    
         [0117]    Although the present invention has been described with reference to preferred embodiments thereof, many modifications and alternations may be made by a person having ordinary skill in the art without departing from the scope of this invention which is defined by the appended claims. For example the filter membrane may be provided in another embodiment of a filter frame means such that the filter membrane can be exchanged relatively easy by any operator of the device. It may as well be possible to mount more than two filter membranes at the filter card in order to enhance the filtration properties of the filter card. Moreover, other filtration media could be incorporated by the removable filter card which enables a sufficient filtration of water. It may as well be possible to design a filter card having two or more apertures, each of them housing at least one filter membrane and at least one backing member, in order to filter water passed through two or more water flowpaths of a device to which the filter card is connected. Moreover, different embodiments of locating devices for the filter membrane and the backing members may be provided at the frame means of the filter card in order to enable the correct mounting of the filter membrane and the backing members.