Assembly for preparing coffee

0001The invention relates to an assembly for preparing a desired quantity of coffee corresponding too one or two cups of coffee and provided with a water container for receiving water and an insert filter holder for receiving ground coffee, wherein the water container is positioned on top of the insert filter holder and is provided with at least one outflow opening which opens above the insert filter holder, the insert filter holder comprises a filter forming a barrier to the ground coffee and a passage for coffee extract, so that, in use, water flows from the water container to the insert filter holder via the outflow opening, and the coffee extract flows from the insert filter holder via the filter. Such an assembly is known from US 4,069,571.

0002Recent research has proved that thereis a need for preparing a relatively small quantity of coffee which is for instance sufficient for filling one or two cups or a mug. Typically, a user has a conventional domestic coffee maker at his disposal which is suitable for preparing four or more cups of coffee. Such a coffee maker typically consists of a water reservoir to be filled with cold water, a metering and heating device, a coffee pot, a filter holder suitable for being placed on the coffee pot and a hotplate on which the coffee pot can be placed.

0003In use, a paper filter ('filter bag') is placed in the filter holder. After this, the filter holder, i.e. the paper filter, is filled with for instance five spoonfuls of ground coffee and the water reservoir is filled with the quantity of water corresponding thereto. Then, the apparatus is switched on and water is passed from the water reservoir to a heating element, after which the heated water is poured on top of the coffee bed contained in the filter holder. In the coffee bed, a coffee extract is formed which flows, via the paper filter and an aperture in the filter holder, towards the coffee pot. In this manner, all the water from the water reservoir is gradually converted into a coffee extract.

0004However, a problem arises when a small quantity of coffee, such as for instance two cups, is to be prepared. In that case, one or two spoonfuls of ground coffee are introduced into the filter holder. Also, the water reservoir is filled with a quantity of water corresponding to the above-mentioned two cups. Although the amount of ground coffee in the filter holder and the quantity of water in the water reservoir are adapted to each other in the proper ratio, the coffee extract proves not to have the desired quality. For instance, the coffee-making efficiency of one cup proves to be about 23%, and the coffee-making efficiency of two cups proves to be about 25%. Such efficiencies are particularly low and result in a coffee extract that is weak and of poor flavor. One object of the invention is to meet this problem. It is a further object of the invention to provide an assembly which can also be used for preparing said quantity of coffee by other means than an existing multiple coffee maker.

0005The invention meets this problem and, accordingly, has as a characteristic feature that the assembly is of substantially conical design, wherein the outer diameter of the assembly decreases at least substantially from the top downwards, so that the outward shape of the assembly is adapted to be placed in the tapering filter holder of a multicup coffee maker for preparing coffee by means of an existing multicup coffeemaker wherein the water container further comprises a temperature-sensitive closing valve where said valve closes the outflow opening when the water container is filled with water having a temperature lower than a predetermined value and which releases the outflow opening when the water container is filled with water having a temperature higher than or equal to the predetermined value, so that, in use, hot water is fed to the insert filter holder when the water container is filled with water having a temperature higher than or equal to said predetermined value, so that the assembly is also suitable for preparing coffee by means of a microwave oven.

0006According to the invention, the assembly is suitable for being placed in the filter holder of the coffee maker. This involves the insert filter holder being filled with, for instance, two spoonfuls of coffee when it is the intention to prepare two cups of coffee. The water reservoir of the coffee maker is filled again with a quantity of water corresponding to two cups of coffee. According to the invention, it has been found that presently, the coffee-making efficiency can be improved by more than 3% (up to, for instance, 26-27%) to obtain a coffee-extract of a good flavor.

0007The invention is inter alia based on the insight that for preparing one or two cups of coffee by means of a conventional coffee maker, the height of the coffee bed in the filter holder is too low. Moreover, the amount of water fed to the relatively thin coffee bed per unit of time is too large. The unduly great flow of water on the one hand and the relatively low coffee bed on the other result in the above-mentioned low coffee-making efficiency. As according to the invention, an insert filter is used that can have a smaller dimension than the filter holder, a higher coffee bed can be obtained at the same amount of ground coffee. On the other hand, the outflow opening of the water container determines the magnitude of the flow of water and is for instance dimensioned so that the flow of water decreases by a factor 2.5 relative to the flow of water generated by the coffee maker itself. The combination of these two measures results in the improved efficiency.

0008According to the invention the assembly, is also suitable for preparing coffee in a microwave oven. For this purpose, the water container further comprises the temperature-sensitive closing valve. If it is desired to make coffee by means of a microwave oven, the insert filter holder is first filled with the desired amount of ground coffee. The water container is filled with the desired quantity of water. Then, the water container is positioned on the insert filter holder and the thus obtained assembly is placed on a coffee extract container, such as for instance a mug. The coffee extract container and the assembly are placed in the microwave oven and the microwave oven is switched on, so that the water in the water container will be heated. If the water in the water container reaches a temperature higher than the predetermined temperature, the temperature-sensitive valve will release the passage of the water container so that hot water is fed from the water container to the ground coffee in the insert filter holder. The magnitude of the flow of water is again determined by the outflow opening of the water container. The hot water will be poured onto the coffee bed, whereupon the coffee extract can form itself to subsequently flow to the coffee extract container via the insert filter holder. After for instance two minutes, all the water from the water container has flown, via the insert filter holder, to the coffee extract container in the form of coffee extract, and the microwave oven can be switched off. The coffee is now ready for consumption.

0009It is observed that US Patent 4,069,751 describes an assembly likewise provided with a water container and a filter holder. However, because of its outward shape, the assembly is not suitable for being placed in a tapering filter holder of an existing multicup coffee maker. Further it is observed that US 4,104,957 discloses an assembly for preparing coffee in a microwave oven. However the assembly is designed for preparing quantities of coffee larger than one or two cups. Furthermore it is not suitable to be positioned in an existing tapering filter holder of a multicup coffee maker.

0010Presently, the invention will be specified with reference to the accompanying drawings. In these drawings: <ul id="ul0001" list-style="none" compact="compact"><li>Fig. 1 is a top plan view of an insert filter holder of an assembly according to the invention;</li><li>Fig. 2 shows a first side elevation of the insert filter holder of Fig. 1;</li><li>Fig. 3 shows a second side elevation of the insert filter holder of Fig. 1;</li><li>Fig. 4 is a top plan view of a possible embodiment of a water container of an assembly according to the invention;</li><li>Fig. 5 shows a cross section of the water container according to Fig. 4;</li><li>Fig. 6 shows the assembly comprising the insert filter holder of Figs. 1-3 and the water container of Figs. 4 and 5;</li><li>Fig. 7 shows a filter holder of a conventional coffee maker;</li><li>Fig. 8 shows a conventional coffee maker comprising the filter holder according to Fig. 7 and the assembly according to Fig. 6;</li><li>Fig. 9 shows a possible embodiment of an annular adapter of an assembly according to the invention;</li><li>Fig. 10 is a top plan view of the annular adapter according to Fig. 9;</li><li>Fig. 11 shows an assembly consisting of the insert filter holder according to Fig. 1, the water container according to Fig. 4 and the adapter according to Fig. 9, which assembly is placed on a mug;</li><li>Fig. 12 shows an assembly arranged for filling the insert filter holder with ground coffee;</li><li>Fig. 13 is a top plan view of an alternative embodiment of an insert filter holder according to the invention;</li><li>Fig. 14 is a first view of the insert filter holder according to Fig. 13; and</li><li>Fig. 15 is a second view of the insert filter holder according to Fig. 13.</li></ul>

0011In Figs. 1-3, reference numeral 1 designates an insert filter holder of an assembly according to the invention. The insert filter holder 1 comprises a bottom part 2 and obliquely vertical sidewalls 4 extending from the bottom part 2. The outer diameter of the insert filter holder 1 increases from the bottom upwards, so that the insert filter holder is of conical design. A portion 6 of the sidewall is provided with fine-mesh through-flow openings. This portion 6 thus forms a filter that forms a barrier to ground coffee and a passage for the fluid extract of the coffee. The portion 6 is popularly known as a 'gold filter' and is of metal construction. In this example, the remaining portion of the insert filter holder is made of plastic.

0012The vertical sidewalls 4 have their upper ends provided with an annular edge 8. For the sake of completeness, it is further observed that Fig. 2 shows the side elevation of the insert filter holder in the direction P₁ of Fig. 1 and Fig. 3 shows the side elevation of the insert filter holder in the direction P₂ of Fig. 1.

0013The assembly according to the invention further comprises a water container 10, as shown in Figs. 4 and 5. The water container 10 comprises a more or less flat bottom 12 in which, in this example, one outflow opening 14 is provided. Extending obliquely upwards from the edge of the annular flat bottom 12 is a conical sidewall 16, the arrangement being such that the outer diameter of the water reservoir increases from the bottom upwards. The water container 10 further has its bottom side provided with a bayonet catch 18 capable of cooperating with the annular edge 8 of the insert filter holder 1, the arrangement being such that the water container 10 can be positioned on the insert filter holder and be connected therewith so as to be detachable, as shown in Fig. 6.

0014The assembly of Fig. 6 can be used for preparing for instance one or two cups of coffee by means of a conventional, domestic coffee maker, as shown in Fig. 8. The coffee maker 20 according to Fig. 8 comprises a water reservoir 22 that can be filled with cold water. The water reservoir 22 comprises a transparent, vertical sidewall 24 provided with a graduation 26. The graduation 26 shows to what level the water reservoir 22 should be filled for preparing four, six, eight, ten or twelve cups of coffee. The coffee maker 20 further comprises a schematically shown heating element 28 which heats water from the water reservoir 22 and feeds it to a horizontal conduit 30. The horizontal conduit 30 comprises, adjacent a free end thereof, an outflow opening 32. The coffee maker further comprises a hotplate 34 on which, in this example, a coffee pot 36 is placed. Placed on the coffee pot 36 is a conventional filter holder 38.

0015If it is desired to prepare one or two cups of coffee in a conventional manner, one proceeds as follows. First, a quantity of water equal to the contents of two cups is introduced into the water reservoir 22. Further, a paper filter (filter bag) 40 is inserted into the filter holder 38. The paper filter 40 is filled with an amount of ground coffee. The ratio between the amount of ground coffee and the quantity of water is equal to the ratio between the amount of ground coffee and the quantity of water that would be used if, for instance, 10 cups of coffee were made. As shown in Fig. 7, the coffee bed 42 formed by the ground coffee on the bottom of the paper filter 40 has only a slight height h. When, subsequently, the filter holder with the paper filter 40 and the coffee bed 42 is placed on the coffee pot 36 and the coffee maker 20 is switched on, the entire quantity of water from the water reservoir 22 is within a short time heated and poured, via the tube 13 and the outflow opening 32, onto the coffee bed 42. There is thus formed in the coffee bed 42 a coffee extract which can leave the filter holder 38 via an opening 44 in the filter holder 38 to subsequently flow into the coffee pot 36. Experiments have shown that the coffee extract present in the coffee pot 36 is of poor flavor and experienced as weak. The coffee-making efficiency proves to be to the order of from 22 to 25%.

0016However, when the coffee is prepared by means of the assembly according to Fig. 6, a much better result is obtained. To this end, the insert filter holder is filled with the same amount of ground coffee as shown in Fig. 7. However, this same amount of coffee results in a much higher coffee bed 46, as shown in Fig. 6. The height of the coffee bed is here indicated by h'. Then, the water container 10 is positioned on the insert filter 1 and attached thereto by means of a bayonet catch 18. Of course, another known type of closure can be used as well, such as a screw-thread closure. The assembly of Fig. 6 is then placed in the filter holder 38 as is schematically shown in Fig. 8. In the example, the water reservoir 22 is again filled with a quantity of water corresponding to the volume of two cups. Then, the coffee maker 20 is switched on. After this, the heating element 28 heats the water coming from the water reservoir and feeds this water to the conduit 30. Via the outflow opening 32 of the conduit 30, the hot water ends up in the water container 10. In this manner, all the water contained in the water reservoir is heated and fed to the water container 10 within a relatively brief time. However, the outflow opening 14 of the water container has such dimensions, i.e. such a through-flow area, that the quantity of water that can flow per unit of time, via the outflow opening 14, to the ground coffee located in the insert filter holder, is limited to a predetermined maximum. Generally, this maximum will be less than the quantity of water that is fed to the water container by the multicup coffee maker per unit of time. In this example, the outflow opening 14 has such dimensions that the quantity of hot water fed to the ground coffee per unit of time is smaller by a factor 2.5 than the quantity of water leaving the outflow opening 32 of the conduit 30 per unit of time. As a consequence, the quantity of water fed to the ground coffee is independent of the coffee maker 20, because on the one hand the quantity of water fed to the ground coffee per unit of time has been reduced to a predetermined maximum value, and on the other because the height h' of the coffee bed is determined by the insert filter holder and the amount of ground coffee. Thus, there is presently obtained, by means of the conventional coffee maker, a coffee extract that is of good flavor and not too weak. More in particular, the coffee-making efficiency has increased by some percents to, for instance, 26-27%.

0017It is observed that the assembly of Fig. 6 is adapted to be placed in the tapering filter holder 38. For this purpose, the assembly in this example is of an at least substantially conical design. This has as an advantage that the assembly can readily be positioned in the filter holder, as shown in Fig. 8. Other suitable shapes wherein use is made of, for instance, supporting ribs extending outwards in radial direction of the assembly, are also conceivable. In the present exemplary embodiment, the water container 10 is entirely open at its upper end. This entirely open upper end in fact forms a feed opening. Of course, it is also possible to partly close the upper end of the water container 10 and provide it with a feed opening at its center only.

0018Hereinafter, it will be discussed in what manner the assembly of Fig. 6 can also be used for preparing coffee by means of a microwave oven. For this purpose, the water container further comprises a temperature-sensitive closing valve 50, as shown in Figs. 4 and 5. The closing valve has the property of closing the outflow opening 14 when the water container is filled with water having a temperature below a predetermined value. Further, the closing valve 50 releases the outflow opening 14 when the water container is filled with water having a temperature higher than or equal to the predetermined value. In this example, the closing valve 50 consists of an elongated bimetal connected, adjacent a first end 52, to the bottom 12 of the water container 10. The temperature-sensitive closing valve 50 extends lengthwise at least substantially in horizontal direction. The bimetal of the closing valve is located, adjacent its second end, directly above the outflow opening 14. The bimetal has its bottom side provided with a rubber closing cap 54. When the filter holder is filled with water having a temperature above or equal to the above-mentioned predetermined value, the rubber closing cap 54, slightly spaced above the outflow opening 14, as shown in Fig. 5, will pass the water. When, on the other hand, the water has a temperature below the above-mentioned predetermined value, the bimetal of the temperature-sensitive closing valve 50 will adopt a shape such that the rubber closing cap 54 moves downwards and, consequently, closes the outflow opening, which is schematically shown in dotted lines in Fig. 11.

0019The assembly further comprises an annular adapter 56 shown in Figs. 9 and 10. The annular adapter 56 has its outside provided with a cylindrical outer wall 58. Further, the annular adapter 56 comprises a flange 60 extending around the outer wall 58 at about half the height of the adapter. The annular adapter has its inside provided with inner walls 62 which obliquely taper towards each other from the top downwards. Thus, an inner space of conical shape is formed. The annular adapter 56 has its bottom side provided with an opening 64, which is rectangular in the example. For preparing one or two cups of coffee, the insert filter holder is filled with the same amount of coffee as described hereinabove in relation to Fig. 8. Then, the water container 10 is positioned on the insert filter holder 1 again and detachably connected thereto by means of the bayonet catch 18. Because the above-mentioned predetermined value for the temperature is approximately equal to 60°, the temperature-sensitive closing valve 50 will close the outflow opening 14. This implies that the water container 10 can be filled with the same quantity of cold water as described with reference to Fig. 8 in relation to the water reservoir 22. The annular adapter 56 is now placed on a coffee extract container in the form of a mug 66, the arrangement being such that the flange 60 of the adapter rests on the upper rim 68 of the mug 66. Subsequently, the coffee-filled insert filter holder 1 and the water-filled water container 10, already interconnected, are positioned on the adapter, the arrangement being such that the bottom side of the insert filter holder 1 extends into the inner space of the adapter 56. As this inner space of the adapter is of conical design and the bottom side of the insert filter holder 1 is likewise at least substantially conical, the insert filter holder 1 can be inserted into the adapter 56 in a stable manner. Thus, a configuration as shown in Fig. 11 is obtained. Then, the entire assembly is placed in the microwave oven, after which the microwave oven is switched on. Consequently, the temperature of the water contained in the water container will rise. When the temperature of the water is higher than or equal to the predetermined value of about 60°, the temperature-sensitive closing valve 50 will release the outflow opening 14. As a result, water of a proper temperature will be fed to the ground coffee contained in the insert filter holder 1. The quantity of hot water that is fed to the ground coffee per unit of time is again determined by the dimensions of the outflow opening 14 as described hereinabove. After some time, all the water will have been fed to the coffee bed and the coffee extract formed in the coffee bed will leave the insert filter holder via the filter 6. The coffee extract now flows, via the opening 64 of the adapter 56, to the mug 66. At the end of the coffee-making process, the microwave oven is switched off and the mug of coffee can be removed from the microwave oven. After this, the assembly can be used afresh for preparing a new quantity of coffee.

0020For the sake of completeness, it is observed that the invention is by no means limited to the above-described embodiment. For instance, the water container can for instance further comprise, on the inside thereof, supporting means 68 of a shape corresponding to the outside of the insert filter holder 1, as shown, inter alia, in Fig. 5. This provides the possibility of placing the insert filter holder in the water container from the open upper end of the water container, with the supporting means supporting the insert filter holder. This facilitates the filling of the insert filter holder with ground coffee. Fig. 12 is a transparent view of such a filling arrangement. The advantage is that during filling, a user need not hold the insert filter holder and keep it upright.

0021It is also possible that an insert filter holder is used wherein the portion 6 is not constructed as a metal filter, but as an impermeable wall. An example of this is shown in Figs. 13-15. In these Figures, an opening 70 is provided in the bottom part 2, while in the insert filter holder 1, a paper filter bag 72 is placed which, in use, is filled with coffee. For the rest, the alternative embodiment of the insert filter holder according to Figs. 13-15 is used as described hereinabove.

0022Also, it is possible to use the assembly as shown in Fig. 11 outside the microwave oven. In that case, the water container 10 can be manually filled with hot water, for instance from a whistling kettle.

0023In Fig. 10, the opening 64 of the adapter 56 is of rectangular design. This involves a portion of the insert filter holder 1 projecting above the adapter 56, as is clearly shown in Fig. 11. In particular, a portion of the gold filter 6 will likewise project above the adapter 56. As a result, it is possible that, in particular when much ground coffee is received in the insert filter holder, coffee extract passes out through the filter 6 at a position located above the adapter 56. The coffee extract could then possibly end up on the adapter 56. To prevent this, the opening 64 can be shaped so that the insert filter holder 1 and the adapter 56 contact each other only at, for instance, three or four points. This is shown in dotted lines in Fig. 10, by replacing the rectangular opening 64 by an opening having round sides 76. In that case, the filter holder 1 will rest on the corner points 78 of the opening. It is understood that in the case where the coffee extract flows through the filter at a level located above the adapter 56, it can flow through the opening 64 of the adapter 56 without any problem.