Coffee maker with hot water boiler

Abstract

In a hot beverage preparation apparatus, particularly a coffee maker, having a hot water boiler for heating and storing hot water or hot steam for preparing a hot beverage, the hot water boiler is configured as a pressure vessel in a hot beverage preparation apparatus having a cold water inlet, a reservoir with a heater, and a hot water and / or steam outlet, in which hot water is stored at a temperature above 110°C during operation, and the hot water outlet is connected to a distribution valve (40) for distributing and mixing cold water with the hot water when released, so that mixed water at a temperature below 100°C is released for beverage preparation.

Description

[Technical Field]

[0001] The present invention relates to a hot beverage preparation device, in particular a coffee maker, having a hot water boiler for heating and storing hot water or hot steam for preparing hot beverages, the hot water boiler having a cold water inlet, a reservoir with a heater, and a hot water or steam outlet. [Background technology]

[0002] To store the hot water needed for beverage preparation in coffee makers, a boiler is often used, typically storing hot water at a temperature below 100°C, typically around 90°C. Separate boilers are often used for hot water and steam. The boiler's waste heat, inevitably generated when producing hot water, must be vented to prevent the device from becoming too hot inside. High temperatures inside the coffee maker can lead to temporary component failure, long-term failure due to premature deterioration, and inconsistent product quality. Thermal problems can occur, especially in very compact devices, if there is insufficient space to vent the generated waste heat to the outside of the device. In many cases, coffee makers must be actively cooled using a fan to vent the waste heat generated when preparing hot water. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 9,877,608 Summary of the Invention

[0004] US Patent No. 9,877,608 discloses a hot beverage preparation device having a boiler that stores boiling water at a temperature above 100°C as a heat transfer medium. A heat exchanger extends within the boiler, through which cold water passes, heating it to approximately 93°C. The heated, but not boiling, water can then be mixed with cold water to adjust the water temperature. The behavior of hot water as a heat transfer medium at temperatures above 100°C is very energy-intensive and generates waste heat. [Problem to be solved by the invention]

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a hot beverage preparation device which has improved temperature management and allows for a very compact construction. [Means for solving the problem]

[0006] This problem is solved by the features of claim 1. Advantageous embodiments result from the dependent claims.

[0007] In a hot beverage preparation device of the type mentioned at the beginning, hot water is stored at a temperature above 110°C and, during beverage preparation, is mixed with cold water to bring the preparation temperature below 100°C. For this purpose, the hot water boiler reservoir is configured as a pressure vessel in which, during operation, hot water is stored at a temperature above 100°C, the hot water outlet is connected to a distribution valve for mixing the dispensed cold water, and, upon discharge, the hot water is mixed with the cold water to discharge mixed water below 100°C for beverage preparation.

[0008] The mixing of cold water increases the amount of hot water available for beverage preparation, or the boiler may have a more compact design for the same amount of hot water available for beverage preparation.

[0009] The storage temperature may be selected above 110°C, preferably in the range of 110°C to 180°C, more preferably in the range of 120°C to 140°C.

[0010] In particular, for preparing freshly brewed coffee drinks, it is possible to supply premixed water via the brewing valves of the brewing group.

[0011] Furthermore, it is preferred that the dispensing valve for mixing the cold water is configured as an adjustable valve, in particular a proportional valve, and that the beverage preparation device has a temperature sensor for determining the mixed water temperature and a control device for adjusting the mixed water temperature by controlling the dispensing valve, so that the mixing of the cold water is performed in a regulated manner. This allows the hot water discharge temperature to be adjusted to different values ​​depending on the desired beverage. For example, it is possible to mix less cold water for espresso coffee and more cold water for tea water for preparing green tea.

[0012] A static mixer, in particular a spiral mixer, for mixing the cold and hot water streams can be arranged between the distribution valve and the temperature sensor. The mixer ensures that the water streams are mixed quickly and thoroughly. This allows the temperature of the resulting mixed water to be measured immediately after mixing as a control variable. This allows for a particularly compact design.

[0013] In a preferred embodiment of the invention, the reservoir is at least partially equipped with vacuum insulation or surrounded by vacuum insulation. Higher reservoir temperatures lead to significantly higher heat rejection in conventional hot water boilers. However, vacuum insulation significantly reduces this, so that even at higher reservoir temperatures, the device can be constructed compactly and the permissible operating temperature within the device is not exceeded.

[0014] By using vacuum insulation, it is possible to significantly reduce the heat loss of a hot water boiler compared to a normally insulated boiler. Less heat rejection has a positive effect on the quality, shelf life, and grind of fresh coffee beans, which are typically stored at the top of the unit and are therefore particularly exposed to elevated heat rejection. By reducing heat rejection, it is possible to eliminate active cooling or ventilation of the unit, or at least significantly reduce the cooling capacity. The lower heat rejection of a vacuum-insulated hot water boiler reduces the unit's energy consumption, thereby improving energy efficiency and further reducing operating costs and carbon dioxide emissions.

[0015] Although the use of vacuum insulated boilers carries special advantages due to the higher storage temperatures, it is also possible to use normal, conventionally insulated hot water boilers.

[0016] In the simplest case, the outer wall of the boiler reservoir is simply designed to be at least partially double-walled, so that the double-walled area of ​​the outer wall encloses the evacuated space, thereby resulting in a compact boiler with low heat rejection.

[0017] Alternatively, the reservoir can be at least partially inserted into a double-walled outer casing for vacuum insulation, the double-walled region of the outer casing enclosing the evacuated space, thus allowing the use of a conventional boiler, which can be removed from the vacuum-insulated outer casing for repair or replacement in the event of a failure.

[0018] In both cases, the double-walled reservoir or the double-walled outer casing can be provided with a non-vacuum insulated lid through which the boiler's electrical and / or hydraulic connectors can pass. This allows for a simple feed-through without the need for complex penetrations into the vacuum casing. The non-vacuum insulated lid can be provided with insulation, for example, consisting of insulation material in a conventional manner.

[0019] Within the scope of the present invention, a boiler for supplying and storing steam is also considered to be a hot water boiler, which during normal operation contains a quantity of steam under pressure and a quantity of hot water that is not evaporated under the current temperature and pressure conditions. Also, a hot water boiler within the scope of the present invention may be used to supply hot water and steam simultaneously and may be provided with both a hot water outlet and a steam outlet.

[0020] The heater of the boiler is preferably configured as a heating coil arranged inside the reservoir, which leads to a particularly compact construction of the boiler. In particular, it is possible to configure the heater as a spiral tubular heater, by extending the heating coil inside a spiral heating tube, which is preferably filled with magnesium oxide powder for electrical insulation of the heating coil.

[0021] It is within the scope of the present invention to provide not just one vacuum insulated hot water boiler, but several, for example one for steam production and another for hot water production, both of which are provided with vacuum insulation or both of which are surrounded by vacuum insulation. It is also possible to use more than one hot water boiler, for example to allow for the parallel production of two beverages. [Brief explanation of the drawings]

[0022] Further advantages and embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the drawings. [Figure 1] 1 is a first embodiment of a vacuum insulated hot water boiler. [Figure 2] 1 is an example embodiment of a hot water boiler inserted into a vacuum insulated outer casing. [Figure 3] 1 shows a water flow diagram of a hot beverage preparation apparatus having two vacuum insulated hot water boilers, one for supplying hot water and one for supplying steam. [Figure 4] 1 is a diagram of the hot water temperature in a hot water boiler over time, illustrating the recording of a cooling curve for assessing the quality of vacuum insulation. [Figure 5] 10 is a water flow diagram of another example embodiment of a hot beverage preparation machine further comprising a static mixer for mixing cold water supplied via a mixing valve with hot water taken from a hot water boiler. DETAILED DESCRIPTION OF THE INVENTION

[0023] A hot water boiler 10, used in a hot beverage preparation device such as a coffee maker, is shown in cross section in FIG. 1. The hot water boiler 10 has a double-walled reservoir 11 in its lower region, with an inner and outer wall 11a and 11b. A clearance space 12 is provided between the two walls, which are evacuated, providing vacuum insulation for the outer walls 11a and 11b. In its upper region, the hot water boiler 10 has a single-walled lid 13 through which electrical and / or hydraulic connectors extend. A spiral tubular heater 14 is located inside the reservoir 11. The tubular heater has two electrical connectors 14a and 14b that are routed to the outside through corresponding feedthroughs in the lid 13. The hot water boiler also has several open feedthroughs 15, 16, and 17, through which supply and discharge pipes and measuring devices, such as pressure and thermometers, can be connected. A vacuum valve 18 was disposed in the lower region, and the gap space 12 between the inner and outer walls 11a, 11b was evacuated via the vacuum valve.

[0024] 2 also shows a partial cross-sectional view of a second embodiment of a vacuum-insulated hot water boiler 10. Here, the hot water boiler 10 comprises a reservoir 11' of conventional single-wall construction. A spiral tubular heater 14 is arranged in the reservoir, and the tubular heater has two electrical connectors 14a, 14b that are routed out through feedthroughs arranged in the upper region of the reservoir 11'. Only one feedthrough 15 is visible in FIG. 2; the other feedthroughs are used to connect supply and discharge pipes and, if necessary, measuring devices.

[0025] The reservoir 11' is housed in a vacuum-insulated outer casing 20. The lower region of the outer casing is double-walled, consisting of an inner outer wall 21a and an outer outer wall 21b. A clearance space 22, which is evacuated via a vacuum valve 28, is located between the two. The upper region of the outer casing 20 is closed with a non-vacuum-insulated lid 23, through which electrical and / or hydraulic connectors extend. The lid 23 can be insulated with conventional insulating materials (e.g., synthetic needle felt, silicone foam, glass wool, etc.). The lid 23 can be opened to install, remove, or repair the water boiler 10, allowing maintenance and replacement of the hot water boiler 10 without the vacuum-insulated outer casing 20.

[0026] 3 shows the so-called water flow system of a coffee maker with two hot water boilers 10a, 10b, both of which are provided with or surrounded by vacuum insulation as described above. Hot water boiler 10a is used to prepare and store hot water for beverage preparation, while hot water boiler 10b is used to prepare and store steam for frothing milk, and contains a quantity of water and a quantity of steam in thermal equilibrium.

[0027] At the water inlet, which is connected at its inlet side to the connector of the water supply or water container, there is arranged a unit 30 having a water filter 31, a shut-off valve 32, two serially connected check valves 33, a water pump 34 and a temperature sensor 35. From the water pump 34, cold water passes through a flow meter 36 and an additional check valve 37 to reach the intake of the boiler 10a.

[0028] In the hot water boiler 10a, water is heated to a storage temperature of 120 to 140°C. The temperature in the hot water boiler 10a can be determined via a temperature sensor 39 and adjusted by controlling the heater 14 of the hot water boiler 10a. In the event of overpressure, a relief valve 38 at the boiler's inlet directs water from the hot water boiler 10a to the outlet. The hot water outlet of the boiler 10a leads to two valve blocks 41, 42. A proportional valve 40 is arranged between the inlet and outlet of the hot water boiler 10a, by means of which cold water can be mixed with the hot water from the hot water boiler 10a. The temperature of the mixed water can be measured via a temperature sensor 44 and set accordingly by appropriately controlling the proportional valve 40.

[0029] Mixing of the hot water with the cold water supplied by the proportional valve 40 can be carried out in a hose line downstream of the junction of the hot and cold water. To ensure the fastest possible mixing of the two water streams, a static mixer 43, such as a spiral mixer, can be provided to thoroughly mix the two water streams. This is shown diagrammatically in FIG. 5. A spiral mixer is a static mixer that includes multiple consecutive 180-degree coils arranged in a cylindrical housing, offset by 90 degrees from each other. Each successive coil rotates in opposite directions. Each coil divides the liquid flow passing through it into two partial streams. At the transition to the next coil, each partial stream is again divided into two partial streams and merges with the partial stream from the previous coil. This achieves mixing of the liquid streams.

[0030] The hot water outlet of the hot water boiler 10a is connected to both valve blocks 41 and 42. Hot water can be released for tea preparation via valve 41a, and the hot water boiler 10b can be filled for steam preparation via valve 41b. In this embodiment, valve 41c is not used and can be used for any other function. The inlet of valve 41d is connected to the outlet of valve 41b, which is also connected to the hot water outlet, allowing hot water and steam to be released simultaneously. Hot water can be released at the beverage delivery head 45 via valve 42a, which can be used to mix, for example, an instant drink or coffee drink. Furthermore, valve 42a can be used to rinse the delivery line from the brewing group 52 to the delivery head 45. In this embodiment, valve 42b is not used and can be used, for example, for the "instant drink" option.

[0031] A conduit leads from the hot water outlet of the hot water boiler 10a to a brewing valve 51 in the brewing unit 50. The brewing unit 50 comprises a brewing group 52 with a movable brewing piston that closes a cylindrical brewing chamber. The brewing group can be automatically filled with freshly ground coffee powder via two separate mill sections 53a, 53b for different coffee varieties. When the brewing valve 51 is open, hot water can flow from the hot water boiler 10a through the brewing group 52 under the pressure of the water pump 34. An adjustable backpressure valve 54 is provided at the outlet of the brewing group 52, via which the flow rate of the freshly ground coffee beverage can be adjusted. From there, the freshly ground coffee flows to the dispensing head 45 of the coffee maker.

[0032] Steam for heating and, if necessary, frothing the milk is supplied via a hot water boiler 10b. A steam pipe 61 leading to a steam lance 62 can be opened via a valve block 60 having two parallel-connected valves 60a, 60b. To froth the milk, air can be added during the steam release via an air pump 63 and a check valve 64. Furthermore, the steam lance 62 can be equipped with a temperature sensor 65 for measuring the temperature of the milk heated or frothed by the steam.

[0033] The steam discharge port of the hot water boiler 10b is further provided with a relief valve 66, a pressure gauge 67, and a temperature sensor 68. The temperature inside the hot water boiler 10b can be monitored via a temperature sensor 69, and the temperature can be set by appropriately controlling the heater 14.

[0034] The vacuum insulation of the hot water boilers 10a, 10b significantly reduces heater waste heat, allowing for a very compact design without thermal issues. Furthermore, the vacuum insulation allows for hot water to be stored at a higher storage temperature, allowing for a larger volume of water to be used upon release by mixing with cold water. This allows for either a more compact design of the hot water boiler 10a or for a larger volume of hot beverages to be prepared before new hot water needs to be reheated.

[0035] The vacuum in the vacuum-insulated double-walled region is generally less than 1 millibar, preferably even less than 1 microbar, and even more preferably less than 0.1 μbar. Additionally, to maintain the long-term stability of the vacuum, so-called getter materials can be placed in the vacuum to absorb gases in the event of minute leaks and outgassing of the material. Getters or trapping materials are chemically reactive materials used to maintain the vacuum as long as possible. Gas molecules chemically bond with atoms of the getter material on the getter surface (oxidation) or are fixed by adsorption. In this way, the gas molecules are "trapped." Suitable getters are metals, such as barium, aluminum, or magnesium alloys, which can optionally be heated to evaporate the getter metal after evacuation.

[0036] Additionally, the evacuated interstitial spaces 12, 22 may be fitted with reflective foil to further reduce the heat rejection of the hot water boilers 10, 10'.

[0037] As previously mentioned, the vacuum insulation can be part of the hot water boiler, mechanically connected to or integrated with the hot water boiler, or the vacuum insulation can be constructed as a separate component with the hot water boiler contained within it.

[0038] The detection of a cooling curve that can be used to assess the quality of vacuum insulation is illustrated in the diagram shown in FIG. 4, which shows the change in hot water temperature in a hot water boiler over time.

[0039] For this purpose, an additional software function is implemented in the control device, which can be used simultaneously to control the heater 14 and to regulate the hot water temperature in the hot water boiler 10, 10'. The software function determines the quality of the insulation using the cooling curve of the hot water boiler 10, 10', which can be measured using the temperature sensors 39, 69. This makes it possible to check the vacuum insulation. If premature cooling is detected, it can be determined that the vacuum of the vacuum insulation is defective and an appropriate error message can be generated so that the vacuum insulation can be replaced or repaired. This information can be retrieved either on the device itself or by remote maintenance.

[0040] In FIG. 4, the temperature curve measured by the temperature sensor 39 or 69 of the hot water boiler 10a or 10b is plotted over time t. After the heater is switched off, the temperature slowly drops to the lower threshold. Once the lower threshold is reached, the heater 14 is switched on for a heating period H. Thus, the temperature rises again to the upper threshold, or the target temperature of the boiler. A predetermined time span, here 60 seconds, is then waited for the heater 14 to provide all of the heating energy to the hot water. The time span Δt is then measured, during which the temperature drops by a predetermined temperature difference ΔT, which in this embodiment is 1°C. The cooling time is an indicator of how good the insulating properties of the vacuum insulation are. If the cooling time of 1°C falls below the minimum value for good vacuum insulation, an error message is generated and a monitoring center is notified via data communication that the vacuum insulation of the boiler 10a or 10b is likely defective and requires inspection. This allows for a simple method of evaluating vacuum insulation and determining whether a vacuum defect has occurred. Naturally, it is also possible to detect both the cooling time, for example the time span between two heating periods H, ie the time it takes for the temperature to fall to the lower threshold value and for the heater 14 to be activated again.

Claims

1. 1. A hot beverage preparation apparatus for preparing hot beverages, comprising at least one hot water boiler (10, 10a, 10b) for heating and storing hot water, said hot water boiler (10, 10a, 10b) having a cold water inlet, a reservoir (11, 11') with a heater (14) and a hot water outlet, The hot beverage preparation device is characterized in that the reservoir (11, 11') is configured as a pressure vessel, and hot water is stored inside the reservoir at a temperature above 110°C during operation, and the hot water outlet is connected to a distribution valve (40) for distributing and mixing cold water with the hot water at a temperature above 110°C when released, so that mixed water at a temperature below 100°C is released for beverage preparation.

2. 2. The hot beverage preparation device according to claim 1, characterized in that the reservoir (11, 11') is configured to store hot water at a temperature in the range of 110°C to 180°C, in particular in the range of 120°C to 140°C, in operation.

3. 3. A hot beverage preparation device according to claim 1 or 2, characterized in that the mixed water can be supplied via a brewing valve (51) of a brewing group (52) for preparing a freshly brewed coffee beverage.

4. 4. The hot beverage preparation device according to claim 1, wherein the dispensing valve (40) for mixing cold water is configured as an adjustable valve, in particular a proportional valve, and the hot beverage preparation device comprises a temperature sensor (44) for determining the mixed water temperature and a control device for adjusting the mixed water temperature by controlling the dispensing valve (40).

5. 5. The hot beverage preparation device according to claim 1, wherein a static mixer, in particular a spiral mixer, for mixing the cold and hot water flows is arranged between the distribution valve (40) and the temperature sensor (44).

6. 6. A hot beverage preparation device according to any one of claims 1 to 5, characterized in that the reservoir (11, 11') is at least partially provided with vacuum insulation (12, 22) or is surrounded by said vacuum insulation.

7. 7. The hot beverage preparation device according to claim 6, characterized in that for vacuum insulation the outer wall (11a, 11b) of the reservoir is at least partially double-walled, the double-walled area of ​​the outer wall enclosing an evacuated space (12).

8. 7. The hot beverage preparation device according to claim 6, characterized in that for vacuum insulation the reservoir (11') is at least partly inserted into a double-walled outer casing (20), the double-walled areas (21a, 21b) of which enclose an evacuated space (22).

9. 9. A hot beverage preparation device according to claim 7 or 8, characterized in that the double-walled reservoir (20) or the double-walled outer casing (11a, 11b) has a non-vacuum insulated lid (13, 23) through which electrical and / or hydraulic connectors (14a, 14b, 15, 16, 17) are guided.

10. 10. Device for preparing hot beverages according to any one of claims 1 to 9, characterized in that the heater (14) is formed as a heating coil arranged inside the reservoir (11, 11').

11. 11. A hot beverage preparation device according to claim 10, characterized in that the heating coil extends in a spiral heating tube (14), which is preferably filled with magnesium oxide powder for electrical insulation of the heating coil.

12. 12. A hot beverage preparation machine according to any one of claims 1 to 11, characterized in that it comprises a first hot water boiler (10a, 10b) for producing hot water and a second hot water boiler (10a, 10b) for producing steam, both of which are provided with or surrounded by vacuum insulation (12, 22).

13. 9. A hot beverage preparation device according to claim 7 or 8, characterized in that a getter material is arranged in the evacuated space (12, 22).

14. 9. A hot beverage preparation device according to claim 7 or 8, characterized in that a reflective foil is arranged in the evacuated space (12, 22).

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