Abstract:
Device ( 1 ) for the preparation of coffee, wherein a water/coffee powder mixture is introduced into a cylindrical space ( 10 ). The cylindrical peripheral wall ( 15 ) is made as a vertical screen and by rotation/centrifugation the prepared beverage is forced through the filter to the outside, whilst granular coffee material remains behind. The top part ( 17 ) and the bottom part ( 19 ) of the holder ( 16 ) are made such they can be moved with respect to the cylinder wall. The motor ( 26 ) for rotation is above or below the top part or, alternatively, bottom part. Furthermore, there is a construction for producing the displacement of the top part or bottom part of the holder with the same motor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the National Stage of International Application No. PCT/NL2005/000300, filed Apr. 22, 2005, the contents of which is incorporated by reference herein. 
     FIELD OF THE INVENTION 
     The present invention relates to a device for preparing coffee beverage, comprising a holder that can be rotated about an essentially vertical axis, with a motor for driving said holder, which holder comprises a rotary bottom part and a peripheral wall part extending around it, wherein said peripheral wall part is made as a filter for retaining coffee and allowing the beverage prepared to pass through, wherein said part of said peripheral wall part that is made as a filter extends essentially parallel to said axis of rotation, and a top part and wherein said top part or bottom part can be moved linearly in the direction of said axis of rotation along said peripheral wall part made as a filter and provided with removal means for removing powder from said filter, there being arranged a stationary collection chamber for used powder and a discharge adjoining said filter for the prepared beverage. 
     More particularly the present invention relates to a device wherein a mixture consisting of brewed coffee and coffee powder is separated with centrifugal force. Such a mixture is obtained by bringing hot water and coffee powder together for a defined time. The water is then forced through a screen, on which screen powder material is present. In the prior art devices operating with centrifugal force are proposed where the powder material is forced onto the screen by the centrifugal force and the water is then forced through the powder material. 
     BACKGROUND OF THE INVENTION 
     Such a device is disclosed in GB 1 506 074. In this publication a rotary holder part is described, the rotation of which is achieved with a motor, which is not shown and which is connected via a V-belt to a pulley located beneath the bottom part. The rotation shaft is of hollow construction and a shaft can move up and down inside it under the influence of a magnet fitted outside it in order to be able to open the holder part to remove or supply coffee. 
     This is a complex construction that takes up a great deal of space and moreover is not easy to clean. As a result of the use of a magnet the problem arises that either there is insufficient force for opening the holder or opening takes place with an appreciable jolt. 
     In the British patent specification, after the water has been propelled through the rotating filter with the powder layer thereon it is fed into a coffee collection chamber and from there directly to a discharge, from which a cup of coffee can be drawn off. The collection chamber downstream of the filter is many times larger than the volume of a single cup of coffee. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to increase the yield from the coffee powder and to improve the taste of the beverage to be prepared. 
     This aim is realised with a device as described above in that an outlet from said cylinder with a smaller flow surface area than the free flow surface area of said filter is arranged between said filter and said discharge. 
     As a result of the presence of an outlet with a small opening compared with the free cross-sectional surface area of the filter, an increase in the pressure of the water is produced. That is to say the prepared beverage that issues from the filter is not able to drain away into the discharge unimpeded. As a result the residence time of the water in the filter and thus in the coffee powder in contact with the filter is increased, as a result of which there is more time to transfer the taste/aroma of the coffee powder to the water and to prepare an optimum beverage. The volume between the filter and the outlet is many times smaller than the minimum portion between the beverage, so that this phenomenon occurs under all conditions. 
     According to a further advantageous embodiment of the invention the free cross-sectional surface area of the outlet is approximately 2000× smaller than the free cross-sectional surface area of the filter. According to a further preferred embodiment the total cross-sectional surface area of the outlet is 2-20 mm 2  and in particular approximately 5-12 mm 2 . 
     According to a further advantageous embodiment of the invention the cylinder is made such that it extends vertically and the outlet for the prepared beverage is arranged at the top, which further increases the residence time of the prepared beverage in the cylinder. 
     By means of the present invention it is possible to force water through the powder and the filter at an appreciable pressure (depending on the rotational velocity of the cylinder). 
     More particularly, according to the present invention it is possible to influence this pressure by changing the speed of revolution of the cylinder. Thus, it is possible to obtain pressures of 5 bar and above at high speeds of revolution, as a result of which espresso can be prepared in a simple manner. 
     Using the present invention it is possible to produce a very well prepared beverage within a very short time. More particularly, very intensive contact with the coffee can be achieved within a few seconds. As a result, at high speed minimum amounts of coffee can suffice, whilst a beverage is prepared that meets the most stringent requirements. 
     According to a particular variant embodiment of the invention the motor of the device has a drive shaft that is coincident with the axis. 
     According to the present invention a motor located alongside the actual brewing unit is no longer provided, but this motor is positioned in line with the axis. The motor can be arranged either above or below the brewing unit, depending on the design thereof. 
     According to a particular embodiment of the invention displacement of the bottom part or top part in the longitudinal direction of the axis is achieved with the same rotary motor. As a result the magnet construction known from the state of the art can be dispensed with. Such a drive can, for example, comprise a screw spindle construction in combination with a nut. Such a nut can be made in the form of a simple pin that engages in the screw spindle. 
     With the present invention it is possible, in principle, to produce both the mutual displacement of the bottom/top part with respect to peripheral wall part and the rotary movement of the holder consisting of peripheral wall part and bottom part (including top part) using a single rotary motor. 
     The peripheral wall part is preferably provided with a conically widening part in the direction of flow of the water downstream of the screen. This part widens conically towards an outlet positioned at a high level in such a way that when it does not rotate water is not able to escape from the holder formed by peripheral wall part and bottom part, but on rotation the water, i.e. the prepared coffee, moves obliquely upwards and can be discharged through the outlet. 
     The water/powder mixture can be introduced in the holder delimited by bottom part and peripheral wall part in any manner known in the art. However, according to an advantageous embodiment of the invention the top part is provided with slit-shaped openings through which this mixture is able to enter. 
     The present invention comprises a particularly simple construction with particularly few components that can be made compact and is self-cleaning to a high degree. As a result maintenance is not necessary and high reliability in operation is obtained. According to the invention it is possible to work both “downwards” and “upwards”. In this first case the coffee will be discharged downwards and in the second case upwards when it is removed. 
     According to the present invention the peripheral wall part acting as a screen is arranged essentially parallel to the axis of rotation. In practice this will preferably be essentially vertical. During preparation of the coffee a closed chamber is formed by the peripheral wall part, the bottom part and the top part. According to the present invention the top part is made such that it can move and is able to skim along the filter wall. The peripheral edge of the top part is provided with cleaning means, as a result of which residual coffee material is pushed downwards or upwards in a guaranteed manner. This is achieved in that, according to a particular embodiment of the invention, the removal means for the used coffee material comprise scraper means that engage on the peripheral wall part and more particularly are deformable to some extent. Discharge of used coffee material can take place in some way or other known in the art. However, according to an advantageous embodiment the bottom part or, alternatively, top part is made such that it can move. In the position where there is no engagement with the peripheral wall part there is a gap between the peripheral wall part and the bottom part and by, for example, rotation of the bottom part coffee material present thereon can be propelled outwards and discharged. It has been found that optimum preparation of coffee can take place as a result of the vertical positioning of the screen. Water is forced/thrown at optimum speed against the screen and moves outwards through the coffee material located here. 
     According to a further advantageous embodiment of the invention the top part and bottom part are rigidly connected to one another. Preferably an internal threaded part is included in said connection, which part is in engagement with a pin-shaped part provided with external screw thread that is driven in rotation. As a result the mutual displacement of top part and bottom part with respect to the peripheral wall part as described above can be achieved with a drive motor. By also providing this construction with stops it is possible to make provision for the straight-line movement to be converted at the end of the mutual displacement of top part/bottom part with respect to peripheral wall part into a rotary movement where the peripheral wall part also rotates. 
     According to a further particular variant of the invention the removal means comprise further scraper means for cleaning the collection chamber. That is to say used powder material propelled outwards is removed from the wall of the collection chamber in a mechanical manner. As a result the device can be kept continuously clean in a simple manner and manual maintenance is not necessary. 
     More particularly, these further scraper means are constructed as a fan. This fan is so designed that it generates a blowing action that drives the powder in the correct direction into the collection chamber for used powder, as a result of which the discharge thereof is further promoted. 
     According to a further variant of the invention cylinder, top part, bottom part and the components contained therein are constructed as a unit that can be removed from the motor. This unit can easily be cleaned, for example in a dishwasher. 
     The present invention also relates to a method for the preparation of coffee by applying a layer of coffee powder to a filter, rotating the filter when supplying water and moving said water by centrifugal force through said powder and said filter, wherein downstream of said filter the flow of the prepared beverage is impeded in order to build up a pressure gradient. More particularly, the pressure of the water that moves through the coffee powder is controlled by regulating the centrifugal effect and the taste of the coffee can be influenced depending thereon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below with reference to an illustrative embodiment shown in the drawing. In the drawing: 
         FIG. 1  shows, partially in section, a side view of a device according to the present invention in the position for the preparation of coffee. 
         FIG. 2  shows a cross-section along the line II-II; 
         FIG. 3  shows a cross-section along the line III-III in  FIG. 1 ; 
         FIG. 4  shows a device according to  FIG. 1  in the position when/after cleaning the device; 
         FIG. 5  shows a variant of the device according to the invention in a position corresponding to  FIG. 1 ; 
         FIG. 6  shows the construction according to  FIG. 5  in the state corresponding to  FIG. 4 ; and 
         FIG. 7  shows a detail of the construction shown in  FIGS. 5 and 6 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the figures the device according to the present invention is indicated in its entirety by  1 . This forms part of a larger coffee machine. Only parts of interest for the present invention are shown in the figures. There is a stationary housing  2  provided with a discharge  3  for brewed coffee. This discharge  3  is part of an annular channel  4 . 
     There is an inlet for a coffee/water mixture, which is indicated by  5 . Water is introduced via pipe  6 . This water will be heated water. Coffee is introduced via inlet  8 , which, for example, is constructed as a screw conveyor  8 . This mixture moves via stationary inlet  5  downwards as a result of gravity and passes into annular channel  9 . There is a holder that is fitted such that it can rotate. This consists of a cylinder  10  with a top wall  11 . A piston  16  consisting of a top surface or top wall  17  and a bottom wall or bottom surface  19  is fitted in the cylinder  10 . 
     In  FIG. 2  the top wall  11  of the cylinder is shown in cross-section. It can be seen from this figure that there are slits  12  which, as can be seen from  FIG. 1 , adjoin the annular channel  9 . 
     A cross-section of the top surface  17  of the piston  16  is shown in  FIG. 3 . It can be seen from this figure that there are slits  18  that are in line with slits  12 . As can be seen from  FIG. 1 , a further annular channel  33  is delimited between the top surface  17  and the top wall  11  of the cylinder. 
     That is to say, the powder/water mixture in the annular channel is able to move through the slits  12  and  18  and passes into the space delimited between cylinder  10  and piston  16 . Cylinder  10  consists of a wall  13  that widens conically from bottom to top and opens into an annular outlet  14  that emerges in the annular channel  4 . The cylinder is furthermore provided with an essentially vertical screen wall  15 . 
     The piston  16  consists of the abovementioned top surface  17  that is provided close to the periphery with a brush or skimmer lip  21 . The bottom surface  19  is provided with a seal  20  that engages on the underside of the cylinder  10 , as can be seen from  FIG. 1 . 
     Top surface  17  and bottom surface  19  are connected by a sleeve  22 . This is partially provided with an internal screw thread  23  that engages on the external screw thread of a spindle  24  that is connected to a shaft  25  of a motor  26 . Spindle and shaft are essentially located on the axis  30 . The spindle  24  is provided with a stop  29  at the bottom. 
     At the bottom of the housing there is a discharge  31 . 
     The device described above functions as follows. 
     Starting from the position shown in  FIG. 1 , hot water is introduced through inlet  6  and coffee powder via inlet  7 . This passes via annular channel  9  and the slits  12 ,  18  into the closed space delimited by the top surface  17 , the bottom surface  19  and the screen wall  15 . During or after introduction the motor is rotated in a direction such that sleeve  22  is pulled upwards by spindle  24 . However, because the bottom surface  19  engages on cylinder  16 , via seal  20  further upward movement is not possible and on rotation of the spindle  24 , and thus sleeve  22 , cylinder  10  will also be rotated. As a result of this rotation a centrifugal force is exerted on the mixture that is inside the space described above and coffee material will be propelled against the screen  15  and water, i.e. brewed coffee, will then be forced outwards through it and flow obliquely upwards via the walls  13  and via outlet  14  and annular channel  4  emerge into outlet  3  for tapping off coffee. Because the cross-sectional surface area of outlet  14  is many times smaller than the cross-sectional surface area of the filter  15  pressure build-up of water will occur at the filter  15 . This pressure build-up is dependent on the flow rate of the water, that is to say at a higher rotational velocity of the cylinder  10  water will be forced through the powder at a higher pressure. The taste of the coffee can be improved i.e. influenced by this means. 
     When essentially all the water has been forced through the coffee after some time the direction of rotation of motor  26  will be reversed. Because this is an abrupt movement, cylinder  10  will want to continue to rotate as a result of the mass inertia, but sleeve  22  will be moved in the opposite direction. As a result any clamping effect close to seal  20  will be overcome and as cylinder  10  will or will not continue to rotate in the original direction (will gradually brake) piston  16  will move downwards. This movement is continued until the position that is shown in  FIG. 4  is reached. At that point in time further downward movement will not be possible because of the stop  29 . At that point in time the piston  16  will be rotated at fill speed in the other direction and any coffee material on the bottom surface  19  and any coffee material clinging to the top surface  17  will be propelled outwards into discharge  31 . 
     During this downward movement brush lip  21  scrapes along the screen wall. As a result coffee material that is clinging to the screen wall thereof is removed and drops onto bottom surface  19  and is then propelled outwards in the manner described above. Optimum cleaning is provided by this means. 
     Starting from the position shown in  FIG. 4  the direction of rotation of motor  26  is again reversed with controller  27  and as a result of the shock/mass inertia sleeve  22  will come away from stop  29  and the piston  16  will move in the upward direction into the position shown in  FIG. 1 , it being possible to repeat the filling process after engagement of the bottom surface  19  on the cylinder. 
     A variant of the device described above is shown in  FIGS. 5 and 6 , coffee being discharged in the upward direction after use. This variant is indicated in its entirety by  41 . Parts corresponding to what has been described with reference to  FIGS. 1-4  are not described in detail. There is a stationary housing  42  provided with a discharge  43  for brewed coffee. The inlet for coffee/water is indicated by  45 . The metering of coffee is not shown in more detail. As in the embodiment described above there are a bottom part  59  and a top part  57 . These are rigidly coupled to one another. Top part  57  is provided with scraper arms  68 . As can be seen from  FIG. 7 , in addition to a lateral scraper surface  70  these have a fan-shaped part  71  made such that on rotation an air flow is generated in collection chamber  69  in the direction of arrow  72 . The state where the bottom part  59  is in the low position is shown in  FIG. 5 . A motor  56  with shaft  65  that is coincident with axis  70  is arranged beneath it. There is a screw spindle  64  in which there is a pin  63  that is joined to the bottom part  59  and acts as a nut. The groove  58  is open at the end so that any contamination between nut  63  and groove  58  can be discharged. 
     The peripheral wall part is indicated by  55  and at the top consists of a ring  56  beneath which a conical outwardly widening part  53  terminates and between which a number of openings  54  are delimited. Openings  54  emerge into a discharge  43 . A scraper lip  61  that engages in a somewhat deforming manner on the peripheral wall part  55  that is made as a screen is connected to the bottom part  59 . The top part  57  is provided with a seal  60  that interacts with the peripheral wall part  55  in the position shown in  FIG. 6 . There are openings  67  that emerge into a discharge  61  for used coffee material. Any coffee material not removed by scraping can be discharged by this means. 
     In  FIG. 6  the construction according to  FIG. 5  is shown in the open position. The top part  57  has been moved upwards together with the bottom part  59 . By moving bottom part  59  upwards the coffee residues are scraped upwards and on reaching the same level as the ring  56  they are propelled past this and discharged via space  61 . 
     There is a locking construction  75  and by operating this the part of the device located above broken line  76  can be removed from the motor  56 . This removable part can be easily cleaned in a dishwasher or in another way and completely submerged in water or other cleaning liquids. The locking mechanism consists of a construction by means of which coupling of motor shaft  65  and bottom part  59  can be achieved in a simple manner without the risk of errors. Furthermore, the construction is such that in principle operation is not possible if complete locking does not take place. A push-and-turn mechanism is one example thereof. 
     In the manner described above the entire process can be carried out with a single motor. Furthermore, all relevant parts are always cleaned. A particularly high degree of cleaning can be obtained by having the piston rotate at an appreciable speed of revolution. A speed of revolution of 3-4 thousand revolutions per minute is mentioned as an example. However, other values can also be used. The entire process can be carried out in a few seconds and tests have shown that the coffee prepared in this way has a particularly good taste. Moreover, it is possible to choose to have the volume of the holder part smaller than the desired amount of coffee. As a result an optimum thickness can be chosen for the coffee material layer on the peripheral wall part. During the process further water has to be fed in. The volume of the holder can, for example, be one third of the total amount of coffee desired per operation. 
     Following the above variants will be immediately obvious to those skilled in the art. These fall within the scope of the appended claims.