Water reservoir for beverage machine

Abstract

A water reservoir (30) for a beverage machine has a housing having a base (32) and a side wall (34) forming a water chamber. An outlet structure (36) is formed on the base, the outlet structure having an inner wall (50) upright from the base, wherein the inner volume of the inner wall leads to an outlet of the water reservoir. An outer wall structure (52) extends around the inner wall, and the space between the inner wall and the outer wall structure forms a connection interface for connecting a water treatment unit. The lowest area (70) of the inner wall defines a minimum liquid level in the reservoir. When the liquid is at the lowest liquid level, the water surface extends uninterruptedly between the outer side of the inner wall and the inner side of the side wall.

Description

Technical Field

[0001] The present invention relates to a water reservoir for a beverage machine, such as a coffee machine or an espresso machine. Background Art

[0002] Unless connected to a fixed water connection, beverage machines such as coffee and espresso machines require a water reservoir from which water can be drawn for the brewing process.

[0003] The user fills the reservoir before use and prepares coffee or similar beverages until the reservoir is empty. Typically, such beverage machines have appropriate mechanisms to respond appropriately when the water reservoir is empty. This is necessary, for example, to prevent damage to system components when running dry, but also for user convenience. For example, it is undesirable to have an unresponsive system that continues to pump and make noise while there is no water to complete the beverage preparation.

[0004] Sensors for water level or flow rate are often used to detect and prevent this condition. An important aspect, especially for flow sensors, is to have a clear and sudden stop in the flow of water from the reservoir. The flow of liquid from an almost empty reservoir should not continue for a long period of time (multiple seconds) in the form of small volume drips, but rather the flow should suddenly stop completely when a lower level is reached. This allows the system controller to detect the no-flow condition and prevent a surge in the now partially filled pipe from the water reservoir.

[0005] Nowadays, coffee machines are usually designed to cooperate with optional filter cartridges (i.e., water filter and decalcification unit), which are placed in the water reservoir. The cartridge is mounted on the base of the water reservoir, for which the base is provided with a connection interface, and the cartridge has a corresponding connection interface to cooperate with the base.

[0006] The incorporation of a connection interface for the filter cartridge changes the way water leaves the reservoir when the reservoir is nearly empty. As a result, it is more difficult to maintain a well-defined stable water-air interface, and water will tend to creep through the small geometric features of the connection interface, resulting in intermittent flow.

[0007] Thus, there is the problem of a non-discrete transition between water from the reservoir and an empty reservoir, thus potentially prolonging the empty pumping time and possibly damaging components. Summary of the invention

[0008] The invention is defined by the claims.

[0009] According to an example according to one aspect of the present invention, there is provided a water reservoir for a beverage machine, the water reservoir comprising:

[0010] a housing having a base and side walls forming a water chamber; and

[0011] an outlet structure formed on the base,

[0012] The export structure includes:

[0013] an inner wall upstanding from the base, wherein an interior volume defined by the inner wall opens to an outlet of the water reservoir;

[0014] an outer wall structure extending around the inner wall and standing upright from the base, wherein a space between the inner wall and the outer wall structure forms a connection interface for connecting a water treatment unit,

[0015] Wherein a lowest region of the inner wall defines a lowest liquid level in the reservoir, and wherein water flows across the lowest region to the outlet, and wherein when the liquid is at the lowest level, the water surface extends uninterruptedly between an outer side of the inner wall and an inner side of the side wall.

[0016] This means that when the liquid level reaches the lowest level, the water occupies the full area around the inner wall of the reservoir.Therefore, there is a large surface area flowing towards the inner wall and over the lowest area of ​​the inner wall, resulting in a large flow rather than a trickle caused by flow restriction.

[0017] The inner wall is preferably tubular, meaning that it has a constant cross-sectional shape (which may be circular or any other closed shape) and a length extending upwardly from the base.

[0018] By "uninterrupted" is meant that there are no significant barriers protruding through the water surface, for example forming an enclosed space that could form a water bridge. The flow over the lowest area is a radially inward flow of the water area extending from the inner wall all the way to the side wall of the water reservoir. Therefore, the water surface may instead be considered to be "substantially uninterrupted" because any protrusions of the water surface past the outside of the inner wall have no significant effect on the flow conditions over the lowest area of ​​the inner wall.

[0019] The outlet is connected, for example, to a delivery tube that delivers water to a beverage making section of a beverage machine, such as a coffee brewing section of a coffee machine. The water reservoir outlet structure prevents undesired non-discrete water flow when the water reservoir is empty, while enabling the use of a special connection shape to accommodate a water treatment unit, such as a filter cartridge. In particular, the inner wall is the last barrier through which water flows from the entire surface area of ​​the water chamber surrounding the inner wall to reach the outlet.

[0020] The lowest area of ​​the inner wall may be no more than 2 mm below the height of the outer wall structure. Thus, the inner wall may be up to 2 mm lower than the outer wall structure, because the meniscus formed at the contact between the water and the inner wall creates a raised height of the water surface, which may then reach above the outer wall structure. Thus, the lowest possible height of the inner wall (relative to the outer wall structure) may take into account the meniscus formed by the water at the inner wall. By keeping the height of the inner wall as low as possible, the amount of water remaining in the water chamber after it is functionally empty is kept to a minimum.

[0021] The lowest area of ​​the inner wall may be flush with the height of the outer wall structure or higher than the height of the outer wall structure.

[0022] By positioning the inner wall so that its lowest region is at least as high as the maximum height of the outer wall structure, the inner wall is at a sufficient height to maintain the water level above any barrier formed by the outer wall structure even without taking the meniscus into account.

[0023] In all cases, the design is to prevent any small cavities defined by the outer wall structure (or other parts of the outlet structure, such as between the outer wall structure and the inner wall) which might otherwise produce intermittent flow to the discharge opening.

[0024] This prevents water bridges from playing a role in the flow to the discharge opening by ensuring that gravity can pull the liquid away from the edge.

[0025] The outlet may comprise a discharge opening formed at the base within the inner volume of the inner wall. Thus, water flows downwardly from the inner volume of the inner wall through the discharge outlet.

[0026] Alternatively, the outlet may comprise a discharge opening formed at the side wall, wherein the passage is between the inner volume of the inner wall and the discharge opening. Thus, water flows laterally out of the inner volume of the inner wall towards the discharge outlet at the side of the water reservoir.

[0027] The lowest region of the inner wall for example comprises a rim of equal height (ie a horizontal rim) which extends around the discharge opening for at least 60 degrees, such as at least 90 degrees, such as at least 135 degrees.

[0028] By having a rim at the lowest point rather than a single depression or notch, a large surface area of ​​water can flow over the rim so that when the reservoir is empty there can be a quick transition between flow and no flow over the rim.

[0029] The radially inner edge of the lowest region of the inner wall has, for example, a radius of curvature of less than 1 mm.

[0030] This sharp curvature improves the disconnection of the water flow by enhancing its capillary instability. A small radius of curvature means that flow disturbances will more easily lead to disconnection of the flow.

[0031] The inner and outer wall structures are, for example, circular (in a horizontal plane) and concentric with each other. The space between them defines a connection interface for the water treatment unit.

[0032] The thickness of the inner wall at the base may be greater than the thickness at the top. This reduces the internal volume enclosed by the inner wall and therefore reduces the amount of liquid that needs to flow through the outlet after the flow over the inner wall has ceased.

[0033] The present invention also provides a beverage machine, which comprises:

[0034] a water reservoir as defined above;

[0035] a beverage making section to which water is supplied from a water reservoir; and

[0036] A flow sensor is used to sense the flow between the water reservoir and the beverage making area.

[0037] The design of the water reservoir makes the flow sensor more sensitive in detecting when the water reservoir becomes empty.

[0038] The outlet pipe is for example located between the outlet of the water reservoir and the beverage making section, and the flow sensor is installed along the outlet pipe. It is for example installed between the water reservoir and the water pump.

[0039] The beverage machine comprises, for example, a coffee machine, and the beverage making section is a coffee brewing section.

[0040] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] For a better understanding of the invention, and in order to more clearly show how the invention may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0042] Figure 1A and Figure 1B An example of a known beverage machine to which the present invention may be applied is shown;

[0043] Figure 2 There is shown in schematic form a water reservoir that may be used in the espresso machine of FIG. 1 ;

[0044] Figure 3 A known example of an outlet structure is shown;

[0045] Figure 4 The flow of water to the discharge outlet is shown;

[0046] Figure 5 A plan view of the outlet structure is shown;

[0047] Figure 6 shows an outlet structure according to the present invention;

[0048] Figure 7 Shows Figure 6 A side view of the outlet structure;

[0049] Figure 8 The flow of water to the discharge outlet is shown;

[0050] Fig. 9 Shows water flowing over a rounded edge;

[0051] Fig.10 shows how the capillary effect allows the lowering of the inner wall;

[0052] Fig.11 Shows that there is Figure 6 A cross-sectional view of a bottom area of ​​a water reservoir of an outlet structure;

[0053] Fig.12 Shown with Fig.11 a cross-sectional view of the bottom region of the same water reservoir with the water filter cartridge assembled to the outlet structure;

[0054] Fig.13 Shown is a basic design of the outlet structure on the left and a modified design on the right;

[0055] Fig.14 Another example of a water reservoir is shown in perspective view;

[0056] Fig.15 The plan view shows Fig.14 design; and

[0057] Fig.16 Shows Fig.14 Another perspective of the design. DETAILED DESCRIPTION

[0058] The present invention will be described with reference to the accompanying drawings.

[0059] It should be understood that the detailed description and specific examples, although indicating exemplary embodiments of the device, system and method, are for illustrative purposes only and are not intended to limit the scope of the invention. These and other features, aspects and advantages of the device, system and method of the present invention will become better understood from the following description, the appended claims and the accompanying drawings. It should be understood that the drawings are only schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the drawings to represent the same or similar components.

[0060] The present invention provides a water reservoir for a beverage machine, the water reservoir having a housing having a base and side walls forming a water chamber. An outlet structure is formed on the base, the outlet structure having an inner wall upright from the base, wherein the inner volume of the inner wall leads to an outlet of the water reservoir. An outer wall structure extends around the inner wall, and the space between the inner wall and the outer wall structure forms a connection interface for connecting a water treatment unit. The lowest area of ​​the inner wall defines the lowest liquid level in the reservoir. When the liquid is at the lowest level, the water extends uninterruptedly between the outer side of the inner wall and the inner side of the side wall.

[0061] Figure 1A and Figure 1B One example of a beverage machine 10 to which the present invention may be applied is shown. Figure 1A A perspective view is shown, and Figure 1B A view from the front is shown. In this example, the beverage machine is a bean-to-cup espresso machine, which includes a body 12, which houses a water reservoir, a water heater, a reservoir for receiving coffee beans, an internal grinding mechanism for producing coffee grounds, a brewing chamber or brewing group for receiving coffee grounds, and a pumping system for pumping heated water through the coffee grounds. The machine also includes a coffee output 14 located above a drip tray 16 and a user interface 18 for receiving user selections, wherein the brewed coffee is output from the coffee output 14. The operation of the machine to produce a coffee beverage is completely conventional, and the general operation of the coffee machine will not be described further. In addition, the coffee machine shown is only an example of the type of coffee machine to which the present invention can be applied, or in fact more generally a beverage machine.

[0062] The present invention particularly relates to water reservoirs for use in beverage machines.

[0063] Figure 2 A known water reservoir 30 that can be used in the espresso machine of Figure 1 is shown in schematic form. The water reservoir 30 includes a housing having a base 32 and a side 34 forming a water chamber. The side 34 defines a closed shape such as a rectangle. The water reservoir can be removed from the body 12 of the beverage machine for filling and cleaning.

[0064] An outlet structure 36 is formed at the base 32, leading to an outlet of the water reservoir. In this example, the outlet is a discharge opening 38 in the base. The outlet structure 36 is designed to both provide an outlet flow from the water reservoir 30 and enable connection of a water treatment unit 40, which may be a filter and / or a decalcification unit.

[0065] Figure 3A known example of an outlet structure 36 is shown. It includes a tubular inner wall 50 that defines an internal volume leading to the water reservoir outlet. More specifically, the inner wall 50 extends around the discharge opening 38. The inner wall is upright from the base 32. An outer wall 52 extends around the inner wall 50 and also upright from the base. The space 54 between the inner wall and the outer wall forms a connection interface for connecting a water treatment unit, such as a water filter cartridge. The inner wall 50 has an inclined top that facilitates the assembly of the water treatment unit on the outlet structure 36.

[0066] The known outlet structure is intended to empty the water reservoir as much as possible. For this purpose, the outer wall 52 has a notch 56 so that the water level in the reservoir can drop to the bottom of the notch 56. The lowest part of the inner wall 50 is, for example, flush with the bottom height of the notch 56. The notch 56 can also play a role in guiding the correct connection of the water filter cartridge.

[0067] Figure 4 For explaining the water flow to the discharge opening 38: It shows in dotted lines the water surface 60 when the water has reached the top of the outer wall 52. Capillary effects can be seen (both between the top of the outer wall 52 at the notch 56 and away from the notch). Due to these capillary effects, water bridges are formed, and since these water bridges are above the lowest water level (i.e. the bottom of the notch 56), they will affect the final flow to the discharge outlet 38.

[0068] The formation of these water bridges depends on the distance between structures, such as the spacing between the inner and outer walls. Any water bridges that form can change the emptying characteristics because they can hold small liquid streams to the outlet for longer.

[0069] Figure 5 Shows Figure 3 and Figure 4 3. A plan view of a known outlet structure of FIG. 3. It can be seen that the outlet structure 36 comprises a plurality of wall segments 50, 52 of varying heights and shapes attached to the base of the water reservoir. Thus, when water is drawn from the reservoir and the water-air interface encounters these wall segments, the main liquid flow path towards the discharge outlet 38 is cut off. The resulting flow must pass through the notch 56 which has a reduced flow area and therefore increased flow resistance, resulting in a reduced flow velocity. As shown in FIG. Figure 3 As can probably be best seen in FIG. 1 , the inner wall 50 also has only one narrow portion that is low enough for water to flow through. This is the last barrier for water to flow through. Again, this means that when the reservoir approaches its empty state, only a small surface area of ​​water is able to flow (on the narrowest portion of the inner wall 50) toward the outlet 38.

[0070] The way in which the surface area for water flow decreases as the reservoir empties depends on the arrangement and shape of the various wall segments. When the water level in the container is slightly above the last barrier, the lowest point of the inner wall 50, there is no path for the remaining water in the container to flow to the outlet except at the narrow lowest point of the inner wall 50.

[0071] When the water level reaches the lower edge of the last barrier defined by the inner wall 50, the final reduction in flow may take considerable time because there is still a considerable amount of liquid in the reservoir at the water level above the lowest edge of the barrier 50. If the notch 56 is small, the flow rate is low and it takes considerable time for the water level to reach the lower edge of the inner wall 50 and stop.

[0072] The time taken (t_end) is measured as the area of ​​water remaining in the reservoir (A_reservoir) divided by the minimum width of the water flow (w):

[0073] t_end∝A_reservoir / w

[0074] The minimum width w is the width dimension in the plane of the water surface (ie horizontal) through which water can flow towards the discharge opening.

[0075] Therefore, in order to reduce this time to an acceptable level (about one second or less), the width of the water flow must be made as large as possible. Therefore, instead of providing flow through the notch, the flow should preferably flow over a larger flat barrier (such as a dam).

[0076] Figures 6 to 8 An example of an outlet structure according to the invention is shown. The same reference numerals as in the previous figures are used.

[0077] The outlet structure 36 also includes an inner wall 50 leading to the outlet. In this example, the inner wall 50 extends around the discharge opening 38. The inner wall is, for example, tubular (e.g., having a circular cross-section or other cross-sectional shape) and stands upright from the base. The outer wall (which will be more generally referred to as "outer wall structure 52") extends around the inner wall 50 and also stands upright from the base. In this example, the outer wall structure also includes a tubular wall, such as a cylinder. The space 54 between the inner wall and the outer wall structure forms a connection interface for connecting a water treatment unit, such as a water filter cartridge. The inner wall 50 has an inclined top, which helps to install the water treatment unit on the outlet structure.

[0078] The function of the outer wall structure is to form the connection interface of the water treatment unit. The outer wall "structure" can be such as Figure 6 A continuous wall as shown, or it may be an interrupted wall (e.g. a set of struts) surrounding the inner wall.

[0079] The inner wall 50 has a lowest area 70. The height of the lowest area 70 is designed to be:

[0080] Just below the highest effective point of the outer wall structure 52; or

[0081] flush with the highest significant point; or

[0082] (like Figure 7 As shown) is higher than the highest effective point of the outer wall structure 52.

[0083] The "highest effective point" refers to the height of the barrier created by the outer wall structure 52. There may be higher areas of the outer wall structure above this barrier height, but if these higher areas do not create any enclosed cavities where water bridges or flow restrictions may occur, they do not make any functional difference to the flow conditions and therefore they do not define the "highest effective" point of the outer wall structure.

[0084] The lowest region 70 may be just below the outer wall structure 52 (described above), for example up to 2 mm. Fig.10 Explain why this is possible.

[0085] The purpose of keeping the lowest area 70 as low as possible is to minimize the volume of water remaining in the reservoir when the reservoir is functionally empty, ie when no more water is flowing to the outlet.

[0086] Notch 56 is still there Figure 6 The notch does not affect the flow from the reservoir as it is below the minimum water level, but it can be part of the connection interface of the water filter cartridge.

[0087] The above-mentioned height design of the lowest area 70 prevents water bridges from being formed by capillary effects, which can sustain small liquid streams for a long time. When placed closely together, the wall segments of the outlet structure tend to retain and trap liquid volumes that form bridges between larger liquid volumes in the reservoir, as described above. These trapped volumes allow small water streams to continue due to gravity.

[0088] exist Figures 6 to 8 In the design of , the last edge of the wall segment on which water flows before reaching the discharge opening (i.e., the lowest area 70 of the inner wall 50) produces a higher water level than any other flow-restricting wall segment. Therefore, any amount of water retained by capillary effect is below the lowest water level in the reservoir.

[0089] This means that when the liquid is at its lowest level (see Figure 8 ), the water extends uninterruptedly between the outside of the inner wall 70 of the reservoir and the inside of the sidewalls. Thus, the entire surface area of ​​the water in the reservoir (except for the area of ​​the inner wall 50 itself) flows through the lowest portion 70 until the water reaches the lowest water level and the outlet flow stops.

[0090] The lowest region 70 comprises a rim of equal height (i.e. a horizontal dam-like portion) extending at least 60 degrees around the inner wall 50, i.e. in this example around the discharge opening (when viewed in top plan view), for example at least 90 degrees, for example at least 135 degrees. Figure 6 and Figure 7 The example has an edge of approximately 180 degrees. This creates an opening of large width (as described above) over which water can flow until the reservoir approaches its empty state (ie when the water level reaches the lowest portion 70).

[0091] Figure 8 For explaining the water flow to the discharge outlet 38, the water surface 80 is shown when the water reaches the minimum level. Capillary effects are avoided.

[0092] Another aspect is to improve the interruption of the water flow by enhancing its capillary instability. This is achieved by making the last edge over which the water flows as sharp as possible. If the edge has a small radius of curvature, in particular less than 1 mm, flow disturbances will more easily lead to the interruption of the water flow.

[0093] Fig. 9 The flow of water past a rounded edge of radius R is shown. If there is a sharp edge, the flow can break up in a more abrupt manner. In particular, in the phase when the water level approaches the edge, the flow rate decreases and surface tension (capillary) effects become more dominant. Surface tension tends to pull the liquid together, thus narrowing the flow over the edge. In order to interrupt the flow and stop it from flowing, it needs to become unstable.

[0094] If the stream moves over a smooth edge (large radius of curvature), it tends to be fairly stable. If the edge is sharp (small radius of curvature), the stream will experience greater local stresses because the change in direction is more abrupt. Once the stream is unstable and interrupted, the remaining body of water will contract to minimize its surface area. The location of the contact line (indicating where the water-air interface meets the solid wall) will depend on the contact angle. If the edge has a large radius of curvature, some of the water may "hang" or "pin" on the side of the wall near the outlet. The sharper the edge, the less this will be the case. Therefore, the inner edge of the lowest region 70 is preferably a sharp edge with as small a radius as possible (such as Fig.10 ). Alternatively, the edges may be chamfered rather than rounded.

[0095] exist Figures 6 to 8In the design of FIG. 5 , the lowest area 70 of the inner wall 50 is shown as being slightly higher than the highest point of the outer wall structure 52. Alternatively, as described above, the height of the lowest area 70 may be just below the outer wall structure 52, for example up to about 2 mm. In this case, when the lowest liquid level is reached, the water in the reservoir may still extend uninterruptedly between the outer side of the inner wall and the inner side of the side wall due to the capillary effect. This is Fig.10 The height d1 of the lowest area 70 of the inner wall is lower than the highest part of the outer wall structure 52, i.e. the barrier formed by the outer wall structure 52. It can be seen that the water forms a meniscus on the inner wall 50, which results in the total water level still being above the outer wall structure 52. This distance d1 is, for example, at most 2 mm, for example at most 1 mm.

[0096] Fig.11 A cross-sectional view of the bottom region of a water reservoir having the above-described outlet structure is shown.

[0097] Fig.12 Shown with Fig.11 A cross-sectional view of the bottom area of ​​the same water reservoir with a water filter cartridge 40 fitted to the outlet structure.

[0098] The water filter cartridge modifies the flow to the drain outlet 38 so that when the filter cartridge is installed, the above-described flow conditions do not apply.

[0099] An optional additional improvement includes minimizing the dead space within the inner wall 50 around the outlet opening 38 to prevent water from accumulating in that space and dripping down into the opening 38 over a prolonged period of time.

[0100] Fig.13 A known design is shown on the left, and a modified design is shown on the right, wherein the inner wall 50 has a thickness at the base greater than the thickness at the top. Thus, the cylindrical chamber surrounded by the inner wall 50 becomes conical to reduce the volume.

[0101] The above example has the outlet 38 in the base of the reservoir within the space enclosed by the inner wall 50 .

[0102] like Fig.14 As shown in the perspective view of FIG. , the outlet may also be located in the side wall of the reservoir. Fig.15 shows a plan view, and Fig.16 Another perspective view is shown. In this case, the outlet comprises a discharge opening 82 formed at the side wall 34 with a passage 80 between the inner volume enclosed by the inner wall 50 and the discharge opening 82 .

[0103] In all examples, the outlet structure of the reservoir may thus combine several features to achieve a sudden stop of the water flow by promoting the interruption of the liquid flow between the reservoir and the outlet. The different features may be achieved individually or in combination. Features are: a sufficiently wide flow area (i.e. a large flat edge in the (horizontal) plane of the lowest water level), the final wall edge over which the water flows (before reaching the outlet) is just below, horizontal with, or above the other wall edges of the outlet structure, or the final wall edge over which the water flows (before reaching the outlet) has a small radius of curvature.

[0104] The invention is applicable to any beverage machine having a water reservoir supplying water to the beverage making section.

[0105] By studying the drawings, the disclosure and the appended claims, those skilled in the art can understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

[0106] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0107] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A water reservoir (30) for a beverage machine, comprising: a housing having a base (32) and side walls (34) forming a water chamber; as well as an outlet structure (36) formed on the base, The outlet structure (36) comprises: an inner wall (50) upstanding from the base, wherein an interior volume defined by the inner wall opens to an outlet of the water reservoir; an outer wall structure (52) extending around the inner wall and standing upright from the base, wherein the space between the inner wall and the outer wall structure forms a connection interface for connecting a water treatment unit, wherein a lowest region (70) of the inner wall defines a lowest liquid level in the reservoir, and wherein water flows across the lowest region to the outlet, and wherein when the liquid is at the lowest level, the water surface extends uninterruptedly between the outer side of the inner wall and the inner side of the side wall.

2. The water reservoir according to claim 1, wherein the lowest area (70) of the inner wall is no more than 2 mm below the height of the outer wall structure (52), and the height of the outer wall structure (52) is the barrier height of the outer wall structure (52).

3. The water reservoir according to claim 1, wherein the lowest area (70) of the inner wall is flush with or higher than the height of the outer wall structure (52), and the height of the outer wall structure (52) is the barrier height of the outer wall structure (52).

4. A water reservoir according to any one of claims 1 to 3, wherein the outlet comprises a discharge opening (38) formed at the base within the internal volume defined by the inner wall.

5. A water reservoir according to any one of claims 1 to 3, wherein the outlet comprises a discharge opening (82) formed at the side wall, with a passage (80) between the inner volume defined by the inner wall and the discharge opening.

6. The water reservoir of claim 4, wherein the lowermost region (70) of the inner wall comprises a rim of uniform height extending at least 60 degrees around the discharge opening.

7. The water reservoir of claim 4, wherein the lowermost region (70) of the inner wall comprises a rim of uniform height extending at least 90 degrees around the discharge opening.

8. The water reservoir of claim 4, wherein the lowermost region (70) of the inner wall comprises a rim of uniform height extending at least 135 degrees around the discharge opening.

9. A water reservoir according to any one of claims 1 to 3, wherein the radially inner edge of the lowermost region (70) of the inner wall (52) has a radius of curvature of less than 1 mm.

10. A water reservoir according to any one of claims 1 to 3, wherein the inner and outer wall structures (50, 52) are circular and concentric with each other.

11. The water reservoir according to any one of claims 1 to 3, wherein the inner wall (50) has a greater thickness at the base than at the top.

12. A beverage machine, comprising: The water reservoir according to any one of claims 1 to 11, a beverage making section to which water is supplied from the water reservoir; and A flow sensor is used to sense the flow between the water reservoir and the beverage making section.

13. The beverage machine of claim 12, comprising an outlet tube between the outlet of the water reservoir and the beverage making section, wherein the flow sensor is mounted along the outlet tube.

14. A beverage machine according to claim 12 or 13, comprising a coffee machine, wherein the beverage making section is a coffee brewing section.

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