NL1021399C1 - Coffee machine and device for creating its hot water involve first heating structure for heating first water volume in reservoir and through passage for emission of water from reservoir - Google Patents

Abstract

The coffee machine (1,2) and a device for creating its hot water involve a first heating structure (17) for heating a first water volume (16) in the reservoir (13) and a through passage (18) for emission of water from the reservoir. A screen (20) at least partly shuts off a second water volume (21) from the first for limiting heat transfer between the volumes. A second heating structure (22) heats water from the second volume and converts it into steam. The production of steam causes excess pressure in the reservoir, impelling water from the first volume out of the reservoir.

Description

Brief indication: Device for providing hot water for coffee preparation and coffee maker with such a device

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a device for providing hot water for coffee preparation as well as to a coffee maker with such a device.

Devices known from practice for providing hot water for coffee preparation can be divided into three categories.

A first category of such devices is used in coffee makers in which water is sprinkled on the coffee granulate and comprises a so-called bubble pump in the passage that guides water from the reservoir to the coffee granulate. This pump heats the water, whereby steam formation occurs. Due to the volume increase associated with the conversion of water into steam, water is forced into the passage to the coffee granulate. Such devices can be manufactured at a low cost, but a problem is that the first water reaching the coffee granulate generally has a temperature lower than the desired minimum water temperature of approximately 91 ° C, while after a while water is supplied from which the temperature is higher than the maximum temperature of approximately 97 ° C that is desirable for coffee preparation. Furthermore, such a device is sensitive to the deposition of lime from tap water.

A second category of such devices is used in devices in which the water is passed through the coffee granulate under excess pressure, such as espresso machines. Such devices are provided with a heating structure for heating water and a pump for pumping the water under excess pressure to the coffee granulate. Such devices are relatively complex in structure and their manufacture is accordingly expensive.

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A third category of such devices is used in a so-called cafetière in which the water is heated by means of an external heat source, such as a gas flame from a stove. In such devices, the water is contained in a closed reservoir in which a riser pipe extends up to near the bottom and communicates with a chamber for receiving coffee granules. A further channel runs from this chamber, which channel opens above or at least at the top of a holder for collecting coffee extract. In the water reservoir, water is brought to the boil and, as a result of steam formation, water is pressed under pressure from the reservoir to the coffee granulate. Such devices are simple in construction, but a drawback is that the water that is forced through the coffee granulate is warmer than the maximum temperature of approximately 97 ° C that is desirable for preparing coffee.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a device for providing hot water for coffee preparation that can be manufactured at low costs, but with which heated water with an accurately controlled temperature can be dispensed.

This object is achieved according to the present invention by providing a device according to claim 1.

With the device, a second water volume shielded from the first water volume from which water is dispensed for coffee preparation can be heated to a higher temperature than that of the first water volume, in order to realize steam formation, with which water of the first water volume can be withdrawn from the reservoir while having a temperature lower than the temperature of the water of the second water volume and at which temperature of the second water volume effective steam formation is possible. Water of the first water volume can thus be dispensed with a temperature that is independent of the water temperature at which the steaming used for displacing the water occurs.

In addition to preparing coffee by extraction, the invention can also be used to prepare coffee using soluble coffee or coffee concentrate. Here, too, it is desirable that the stated maximum temperature is not exceeded. The invention can furthermore be embodied in a coffee maker according to claim 11, in which a device according to the invention is integrated.

Particular embodiments of the invention are laid down in the dependent claims.

Further aspects, effects and detail of the invention are apparent from the following description of a number of exemplary embodiments, wherein reference is made to the drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic, cut-away view in side view of a first example of a coffee maker and device according to the invention;

FIG. 2 is a schematic, cut-away representation in side view 20 of a second example of a coffee maker and device according to the invention; and

FIG. 3 is a schematic representation in side view of a third example of a coffee maker and device according to the invention.

DETAILED DESCRIPTION

Fig. 1 shows an example of a coffee maker according to the invention with an example of a device for providing hot water according to the invention integrated therein. The 10? - 4 - coffee maker has a housing with a lower part 1 and an upper part 2, which is pivotable about an axis 3 relative to the lower part 1. Between these two sections there is an extraction chamber 4, in which coffee granulate 5 can be placed, whether or not in a sachet 6 or 5 made of filter material. At the bottom, the extraction chamber 4 is bounded by a coffee granulate holder in the form of a filter holder 7 with one or more perforations for passage of coffee extract. The filter holder 7 is sealed off along its peripheral edge by gaskets 8, 9 relative to the two housing parts 1, 2. Below the filter holder 7 there is a funnel part 10 of the lower part 1 of the housing. This funnel portion 10 has a coffee dispensing passage 11 for guiding coffee extract to a holder 12, which coffee dispensing passage 11 communicates with the filter holder 7 and is located downstream thereof.

When the upper housing part 2 is pivoted upwards from the lower housing part 1, the extraction chamber is accessible for removing spent coffee granules 5 and placing new coffee granules 5 therein for preparing new coffee extract. The upper housing part 2 can be clamped against the lower housing part 1 in the position shown by operating a closure 38. Of course, other arrangements can also be used for sealed sealing of the extraction chamber 4, such as bayonet closures and closures with closing catches which are known per se in the field of coffee makers.

To provide hot water for coffee preparation, a water reservoir 13 is provided with a filling opening 14 which is closed by means of a stopper 15 protruding from the upper housing part 2 when the upper housing part 2 is in the closed position shown.

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Below the water reservoir 13 there is a first heating structure in the form of a first heating element 17 for heating a first water volume 16 in the water reservoir 13.

For dispensing water from the water reservoir 13, a water passage is provided in the form of a supply channel 18 communicating with the water reservoir 13.

The water reservoir 13 is closed in the operating condition shown, so that an overpressure relative to the environment can be built up therein for pushing water from the first water volume 16 into the water reservoir 13 via the dispensing channel 18. The dispensing channel 18 opens into the extraction chamber 4, wherein the mouth of the dispensing channel is designed as a spray head 19 for uniformly distributing supplied water over the coffee granulate 5.

In the water reservoir 13 there is a shield 20 for shielding a second water volume 21 from the first water volume 16 for limiting heat transfer between the first and the second water volume 16 and 20.

In the space for receiving the second water volume 21, which is shielded from the space for receiving the first water volume 16, there is a second heating structure in the form of a heating element 22 for heating the second water volume 21. The heating element 22 has a power in relation to the size of the screened space for receiving the second water volume 21 such that the second water volume can thereby be heated to a temperature higher than the temperature of the first water volume and water of the second water volume can be steamed be converted without heating the first water volume 16 or a substantial portion of the first water volume 16 to the boiling point.

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The supply channel 18 for supplying water from the water reservoir 13 to the coffee granulate has an inlet 23 low in the space for receiving the first water volume 16, so that overpressure in the reservoir 13 caused by steam formation of water from the first volume 16 via the supply channel 18 penetrates the reservoir 13. The water from the reservoir is thus forced into and through the extraction chamber 4 downstream of and communicating with the supply channel 18.

The water reservoir 13, the supply channel 18 and the filter holder 7 connect tightly to each other for urging water under pressure from the water reservoir 13 to the filter holder 7.

According to this example, the heating elements 17, 22 are electric heating elements which connect to a supply circuit 24 which is adapted to control the second heating element 22 separately from the first heating element 17. The supply circuit 24 is equipped with a temperature sensor 25 which is temperature sensitive of the first water volume 16. The feed circuit 24 is further adapted to cause activation of the second heating structure 22 in response to detection by the temperature sensor 25 of a water temperature above a certain temperature. For this purpose, according to this example, the second heating element 22 is connected in series with the temperature sensor 25 which is designed as a temperature-dependent resistor, the electrical resistance of which drops sharply when the desired temperature is reached, whereby the power supplied to the second heating element can be easily obtained. can be arranged.

The first heating element 17 is connected in parallel with the second heating element 22 and the temperature sensor 25 and the supply circuit can be switched on and off by means of an on / off switch 26.

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The temperature sensor 25 is further connected to a control unit 37 of a blow-off valve 35 in a blow-off passage 36 for releasing pressure created by heating water through the heating element 17. According to this example, the control unit is connected in series for this purpose with the temperature sensor 25.

The operation of this device for providing hot water for brewing coffee is as follows. When the on / off switch 26 is closed, the first heating element 17 is supplied with current, whereby the first water volume 16 is heated. Thereby also some heat transfer to the second water volume 21 will occur and current can also flow through the second heating element 22, whereby, in particular, the second water volume 21 is heated, but the temperature 1 of the second water volume 21 does not exceed that of the first water volume 21. water volume 16. Pressure that arises in the reservoir 13 as long as the first water volume 16 has not yet reached the required minimum temperature for preparing coffee is discharged via the open blow-off valve 35. The valve 35 thus prevents water from being fed to the coffee granulate 5 before the the required temperature has reached 20.

When the first water volume 16 has reached the target temperature, which temperature is below a temperature at which substantial steam formation forces water out of the reservoir 13, the resistance of the temperature sensor 25 decreases, so that the power supplied by the second heating element 22 increases. Furthermore, in response to the increased voltage across the operating unit 37 of the blow-off valve 35, the blow-off valve 35 is closed, so that pressure loss through the blow-off passage 36 is prevented. The increase in the power supplied by the second heating element 22 is such that water of the second water volume 21 is converted into steam and water of the first volume 16 is forced by force 10213 9 9-8 by the pressure increase associated with steam formation in the reservoir 13 via the supply channel 18 from the reservoir to and through the extraction chamber 4. The discharged water then has the intended temperature lower than the temperature at that moment of the water of the second volume 21 which is partially converted into steam.

The water temperature for preparing coffee is preferably 91 to 97 ° C.

According to this example, the first and the second heating structure are designed as mutually separate heating elements 17, 22, as a result of which the supply of power to the first and the second water volume 16, 21 can be regulated independently of each other to a great extent and reliably. However, it is also possible that both heating structures form part of a single heating element. It can be provided, for example, that this heating element in relation to the spaces shielded from each other for receiving the first and the second water volume is positioned such that steam formation occurs in the second water volume while the temperature of the first water volume is too low to cause substantial steam formation. Thereby, as well as in combination with the previously described example, the temperature of the first water volume can be thermostatically controlled. It is also possible to control the electrical power supplied to different zones of a heating element entirely or to a certain extent separately, for example by connecting power supplies to the heating element at suitable places. Furthermore, instead of electric heating, heating by other means such as burners can also be used, wherein the heat transfer to the first and the second water volume is regulated such that steaming occurs in the second water volume while the temperature in the first water volume from which water is released , is too low for that.

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According to the example shown in Fig. 1, the second heating element 22 is located in the reservoir 13. This offers the advantage that for heating the second water volume 21, which is protected to a certain extent from the first water volume 16, no separate reservoir is required in which water is heated.

The shield 20 is open upwards, through which steam can escape from the shielded, second water volume 21 without displacing water therefrom. As a result, relatively little space is required for the second water volume 21.

The shield 20 is further closed below the opening at the top, whereby a water circulation is prevented around the shield. This would lead to an intensive heat transfer, making the temperature of the first water volume more difficult to control.

In order to prevent excessive heat transfer from the second water volume 21 to the first water volume 16, it is furthermore advantageous that the shield 21 completely shields the second heating element in the lateral direction. Although the shield 21 does not extend to the highest possible level of the first water volume 16 in the reservoir 20, and steam thus formed rises through a portion of the first water volume 16, the resulting heating of the required water volume remains limited. Moreover, this effect decreases as the water level in the reservoir drops to closer to the inlet 23 of the supply channel 18.

Fig. 2 shows a second example of a coffee maker according to the invention with integrated therein a second example of a device for providing hot water according to the invention. This coffee maker also has a housing with a lower part 51 and an upper part 52. However, the upper part 51 and the lower part are connected to each other by means of a threaded connection 53. / "> f? ·

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i t i. <'5 «-' ··" - 10- linked. The parts can be removed from each other by unscrewing them from each other.

Between these two sections 51, 52 there is an extraction chamber 54, in which coffee granulate 5 can be placed, whether or not in a sachet 56 or the like from 5 liner material. At the bottom, the extraction chamber 54 is bounded by a water distribution bed 69 with a downward-reaching water supply channel 68. At the top, the extraction chamber 54 is bounded by a perforated filter holder 57. The water distribution bed and the filter holder 7 are along their peripheral edge by 10 gaskets 58, 59 sealingly sealed with respect to the two housing parts 51, 52. Above the filter holder 57 there is a lifting channel 60 with outlets 61 for directing coffee extract to a collecting reservoir 62.

When the housing portions 51, 52 are unscrewed from each other and the filter holder 57 is detached from the lower housing portion, the extraction chamber 54 is accessible for removing spent coffee granules 55 and placing new coffee granules 55 therein for preparing new coffee granules. extract. By screwing together the housing parts 51, 52, the upper housing part 52 is clamped against the lower housing part 1.

The water reservoir 63 has an open top side which, in the position of use shown, is sealed air-tightly by the upper housing part 51 so that an overpressure with respect to the environment can be built up therein. The water reservoir 63 is accessible for filling the reservoir 63 when the upper housing portion 51 is unscrewed and when the water distribution bed 69 has been removed from the water reservoir 63.

Below the water reservoir 63 there is a first heating structure in the form of a first heating element 67 for heating mainly a first water volume 66 in the water reservoir 63. The dispensing channel 68 opens into the extraction chamber 54, the water distribution bed 69 for distributing supplied water evenly over coffee granulate 55 ensures.

In the water reservoir 63 there is a shield in the form of a sleeve 70 which is vertical and is raised from the bottom of the water reservoir for shielding a second water volume 71 in the sleeve 70 from the first water volume 66 for limiting heat transfer between the first and the second water volume 66 and 70.

A second heating element 72 is provided in the sleeve 70 for heating the second water volume 71. The heating element 72 has such a power in relation to the size of the shielded space for receiving the second water volume 71 that the second water volume is thereby 71 can be heated to a temperature higher than the temperature of the first water volume and water of the second water volume 71 can be converted to steam without at least a substantial part of the first water volume 66 being heated to the boiling point.

The feed channel 68 for supplying water from the water reservoir 63 to the coffee granulate 55 has an inlet 73 in a lower portion of the space for receiving the first water volume 66, so that overpressure in the reservoir 63 caused by steam formation of water from the first volume 66 from the reservoir 63 via the supply channel 68. The water from the reservoir is thus forced into and through the extraction chamber 54 downstream of and communicating with the feed channel 68.

The water reservoir 63, the supply channel 68 and the extraction chamber 54 connect to each other in a sealed manner for urging water under pressure from the water reservoir 63 to and through the extraction chamber 54.

The power supply circuit 74 which is adapted to control the second heating element 72 separately from the first

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Heating element 67 is designed in substantially the same way as the supply circuit according to Fig. 1. The temperature sensor 75 as well as the blow-off valve 85 for closing the blow-off passage 86 and the operating unit 87 for operating the blow-off valve 85 are according to this example mounted against a side wall 63 of the reservoir 63.

To prepare coffee, the first water volume 66 is first heated. Thereby some heat transfer to the second water volume 71 will also occur and current can also flow through the second heating element 72, whereby in particular the second water volume 71 is heated, but the temperature of the second water volume 71 does not exceed that of the first water volume 66.

When the first water volume 66 has reached the target temperature, which temperature is below a temperature at which substantial steam formation penetrates water from the reservoir 63, the resistance of the temperature sensor 75 drops, so that the power supplied by the second heating element 72 increases. This increase in the power output is such that water from the second water volume 71 is converted into steam and water from the first volume 66 rises up through the pressure increase in the reservoir 63 associated with steam formation via the supply channel 68 from the reservoir 63 to and is pressed through the extraction chamber 54. The discharged water is thereby colder than the water of the second volume 71, which is partially converted into steam. This produces coffee extract which flows out via the riser pipe 60 and the outlets 61 into the reservoir 62 for collecting coffee extract 25. Because the water forced through the coffee granulate 55 has a lower temperature than the temperature required to cause sufficient steam formation, better quality coffee extract is obtained than when water of a temperature is needed to form steam therefrom to and from is pressed through the coffee granulate 55.

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According to this example, the shield 70 between the first and the second water volume 66 and 71 protrudes above the highest operational level of the first water volume 66 in the water reservoir 63. As a result, the steam formed during operation does not rise through the first water volume and the associated heat transfer to the water from the first water volume 66 is prevented. At the top of the shield 70 there is a shield 77 which prevents steam from flowing from the tube 70 directly against the wall of the extraction chamber 54 and causes undesired local heating there.

In the third example of a coffee maker according to the invention shown in Fig. 3, with a third example of a device for providing hot water according to the invention integrated therein, the water is not heated in the water reservoir 113, but

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J in a buffer reservoir 128. This buffer reservoir 128 is accommodated between a supply channel 134 which extends from the water reservoir 113 and a water supply channel 118 which flows into a spray head 119 above the coffee granulate 105 in a filter holder 107. The reservoir 128 has a first chamber 129 for receiving a first volume of water 116 and a second chamber 130 for receiving a second volume of water 121, which second chamber 130 is shielded from the first chamber 129 and is connected thereto via a restriction 131. Upstream of the second In the chamber 130, a one-way valve 132 is accommodated in the supply channel 134, which valve also exerts some counter pressure, so that the water from the reservoir 113 does not flow up under the influence of gravity or only over a small distance beyond the first chamber 129.

Included in the water supply channel 118 is a shut-off valve 135 which is provided with an operating unit 137 for operating the shut-off valve 135.

Below the filter holder 107 there is a holder 112 for collecting coffee extract dripping down from the filter holder 107.

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The supply circuit 124 for the heating elements 117, 122 is adapted to control the second heating element 122 separately from the first heating element 117. The first heating element 117 is arranged and positioned for heating primarily a first water volume 116 in the first chamber 129.

In the first chamber 129 there is furthermore a temperature sensor 125 which is coupled to a switch 133 which switches between a conductor leading to the first heating element 117 and the operating unit 137 of the shut-off valve 135 and a conductor leading to the second heating element 122.

In operation, an amount of water corresponding to the desired amount of coffee extract is first introduced into the reservoir 113. A portion of this water flows through gravity through the supply channel 134 to the buffer reservoir 128 which is lower than the storage reservoir 113. As a result, the first and the second chamber 129, 130 of the buffer reservoir 128 are completely or partially filled. The operating unit 135 leaves the shut-off valve 135 open, so that air can escape from the buffer reservoir 128 during filling with water. When the main switch 126 of the power supply 124 is closed, the first water volume 116 in the first chamber 129 is first heated and the shut-off valve 135 is closed in response to the voltage also applied to the control unit 137. During the heating of the first water volume 116, some heat transfer to the second water volume 121 in the second chamber 130 will generally also occur, and it may also be provided that current flows through the second heating element 122, so that also the second water volume 121 is heated directly, but the temperature of the second water volume 121 preferably does not exceed that of the first water volume 116.

When the first water volume 116 has reached the target temperature 30, which temperature is below a temperature at which substantial steam formation occurs that forces water out of the reservoir 128, in response to a signal from the temperature sensor 125, the switch 133 is converted to the position shown in FIG. As a result, the switching from the supply of the first heating element 117 to the supply of the second heating element 122 is switched over. Moreover, the shut-off valve 135 is opened by the loss of voltage across the operating unit 137 of the shut-off valve 135. The second heating element 122 is dimensioned such that steam formation occurs in the second chamber 130 already a short time after switching on. The steaming is accompanied by expansion or at least a pressure increase, whereby the pressure in the buffer reservoir 128 increases. The one-way valve 132 thereby prevents water or steam from flowing back to the storage reservoir 113. The steam therefore presses the water from the first water volume 116 in the first chamber 129 to the coffee granulate 105 over which it is sprinkled.

The time that the switch 133 remains in the position shown for supplying the second heating element 122 may, for example, be limited in time. It is also possible that after the water 116 has been discharged from the first chamber 129, the pressure in the buffer reservoir 128 drops to such an extent that the temperature sensor 125 detects a temperature drop in response to which the switch 133 is returned to the position in which the first heating element 117 is fed and the cycle described above starts again. An advantage of this method of supplying hot water above the coffee filter is that water is poured onto coffee granulate 105 in "shoots" with controlled temperature, so that a result comparable to manual pouring of the water is obtained.

Because the power supply structure 124 is adapted to deactivate the first heating element 117 in response to activation of the second heating element 122, it is prevented that the first water volume 116 is excessively heated by the action of both elements. 1 Q M '- 16 - heating elements 117, 122. It may also be sufficient for this effect to reduce the power of the first heating structure.

It is noted that within the scope of the present invention as laid down in the claims, many other variants are possible than the examples described above. For example, it is possible to realize premature water delivery in many other ways, such as by blowing off through a small fixed passage or by providing a blower valve that closes above a certain pressure drop or a shut-off valve in the water supply channel that opens over that valve from a certain pressure drop .

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Claims (12)

A device for providing hot water for coffee preparation, comprising: a water reservoir (13; 63; 128) in an environment, which water reservoir (13; 63; 128) is closed in operating condition for building up an overpressure therein relative to of the environment; a first heating structure (17; 67; 117) for heating a first water volume (16; 66; 116) in the water reservoir (13; 63; 128); a water passage (18; 68; 118) communicating with said water reservoir (13; 63; 128) for dispensing water from the water reservoir (13; 63; 128); a shield (20; 70) for at least partially shielding a second water volume (21; 72; 122) from said first water volume (16; 66; 116) for limiting heat transfer between the first and the second water volume (21; 72) 122); and a second heating structure (22; 72; 122) for heating said second water volume (21; 72; 122) to a temperature higher than the temperature of the first water volume (16; 66; 116) and for steam conversion of water of said second water volume (21; 72; 122), wherein the water passage (18; 68; 118) is positioned such that overpressure in the reservoir (13; 63; 128) caused by steam formation of water of said first volume via the water passage (18; 68; 118) penetrates the reservoir (13; 63; 128). 2. Device as claimed in claim 1, further comprising a supply circuit (24; 74; 124) for supplying the first heating structure (17; 67; 117) and the second heating structure (22; 72; 122), which supply circuit (24; 74; 124) comprises a temperature sensor (25; 75; 125) sensitive to temperature of said first water volume (16; 66; 116), wherein the supply circuit (24; 74; 124) is adapted to causing activation or additional activation of the second heating structure (22; 72; 122) in response to detection by the temperature sensor (25; 75; 125) of a water temperature above a certain temperature. Device according to claim 1 or 2, wherein the first and the second heating structure are designed as mutually separate heating elements (17, 22; 67, 72; 117, 122). Device as claimed in any of the foregoing claims, wherein the power supply structure (124) is adapted to at least partially deactivate the first heating structure (117) upon activation or additionally of the second heating structure (17; 67; 117). 5. Device as claimed in any of the foregoing claims, wherein the temperature sensor (25; 75) is a resistance, the electrical resistance of which decreases with the temperature. Device according to any one of the preceding claims, wherein the second heating structure (22; 72; 122) is located in the reservoir (13; 63; 128). The device of claim 6, wherein the shield (20; 70) is open upwards. Device as claimed in any of the foregoing claims, wherein the shield (20; 70) is closed below the opening at the top. 9. Device as claimed in any of the foregoing claims, wherein the shield (20; 70) completely shields the second heating structure (22; 72) in the lateral direction. 10. Device as claimed in any of the foregoing claims, further comprising a shut-off valve (35: 85; 135) communicating with the water reservoir (13; 63; 128) for preventing water discharge via the water passage (18; 68; 118) in a first position ) by expansion of water or water vapor in the water reservoir (13; 63; 128) and for admitting water delivery through the water passage (18; 68; 118) in a second position by steam formation in the water reservoir (13; 63; 128). A coffee maker comprising a device according to any one of the preceding claims, a granulate holder (7; 57; 107) downstream of and communicating with the water passage (18; 68; 118) and a coffee dispensing passage (11; 61) for moving to a coffee extract container (12; 62; 112), which coffee dispensing passage (11; 61) communicates with the granulate container (7; 57; 107) and is located downstream thereof. A coffee maker according to claim 11, wherein the water reservoir (13; 63; 128), the water passage (18; 68; 118) and the granulate holder (7; 57; 107) connect to each other in a sealed manner for overpressure of the water reservoir (13). ; 63; 128) urging water to the granulate holder (7; 57; 107). 15 ί n o i u n c%