Hot-beverage maker having a hot-water boiler

Abstract

In the case of a hot-beverage maker, in particular a coffee machine, having a hot-water boiler for heating and storing hot water or steam for making coffee beverages, wherein the hot-water boiler has a cold-water feed, also a storage vessel with a heater, and also a hot-water outlet and / or steam outlet, provision is made for the storage vessel (11, 11') to be designed in the form of a pressure vessel in which hot water is stored at a temperature of more than 110° C during operation and the hot-water outlet is connected to a metering valve (40) for the metered mixing of cold water in order for cold water to be mixed with the hot water during the dispensing step, so that mixed water at a temperature of below 100° C is dispensed for beverage-making purposes.

Description

[0001] Hot drink preparation device with hot water boiler

[0002] Description

[0003] The present invention relates to a hot beverage preparation device, in particular a coffee machine, comprising a hot water boiler for heating and storing hot water or hot steam for preparing hot beverages, wherein the hot water boiler has a cold water inlet, a storage vessel with a heater and a hot water or steam outlet.

[0004] Coffee machines often use boilers to store the hot water required for beverage preparation. These boilers store hot water at temperatures below 100 degrees, typically around 90°C. Separate boilers are often provided for hot water and steam. The waste heat inevitably generated by the boilers during hot water production must be dissipated to prevent the machine's interior from overheating. Excessively high temperatures inside a coffee machine can lead to temporary component failure, long-term defects due to premature aging, and fluctuating product quality. Thermal problems can arise, particularly with very compact machines, if there is not enough space to dissipate the generated waste heat to the outside of the machine. Coffee machines often require active cooling using fans to dissipate the waste heat generated during hot water production.

[0005] US9877608B2 discloses a hot beverage preparation device with a boiler in which boiling water at a temperature of over 100°C is stored as a heat transfer medium. A heat exchanger runs through the boiler, through which cold water is passed, which is heated to approximately 93°C. Cold water can then be added to this heated, but not boiling, water to adjust the water temperature. Maintaining hot water as a heat transfer medium at a temperature of over 100°C is very energy-intensive and generates waste heat. Therefore, it is an object of the present invention to provide a hot beverage preparation device that is improved with regard to temperature management and enables a very compact design.

[0006] The problem is solved by the features of claim 1. Advantageous embodiments can be found in the dependent claims.

[0007] In a hot beverage preparation device of the type mentioned above, the invention provides that the hot water is stored at a temperature of over 110°C and, during beverage preparation, is brought to a preparation temperature of below 100°C by adding cold water. For this purpose, the storage vessel of the hot water boiler is designed as a pressure vessel in which the hot water is stored at a temperature of over 100°C during operation, and the hot water outlet is connected to a metering valve for metered cold water addition in order to add cold water to the hot water during dispensing, so that mixed water with a temperature of below 100°C is dispensed for beverage preparation.

[0008] By adding cold water, the amount of hot water available for beverage preparation is increased, or the boiler can be built more compactly while maintaining the same amount of hot water available for beverage preparation.

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

[0010] In particular, it is provided that in order to prepare a freshly brewed coffee beverage, the mixed water can be fed to a brewing group via a brewing valve.

[0011] It is further preferred that the cold water addition be controlled by embodying the dosing valve for cold water addition as a controllable valve, in particular a proportional valve, and by embodying the beverage preparation device with a temperature sensor for determining the mixed water temperature and a control unit for regulating the mixed water temperature by controlling the dosing valve. Thus, the dispensing temperature of the hot water can be regulated to different values ​​depending on the desired beverage. For example, less cold water can be added for espresso coffee and more cold water can be added for tea water for preparing green tea.

[0012] A static mixer, particularly a reversible mixer, can be arranged between the dosing valve and the temperature sensor to mix the cold and hot water streams. This ensures rapid and thorough mixing of the water streams. The mixed water temperature, which is set after mixing, can thus be measured directly downstream of the mixer as a controlled variable. This allows for a particularly compact design.

[0013] In a preferred embodiment of the invention, the storage vessel is at least partially provided with or surrounded by vacuum insulation. Due to the higher storage temperature, the waste heat of conventional hot water boilers increases significantly. However, vacuum insulation significantly reduces the waste heat, allowing the device to be built compactly despite the higher storage temperature, and the permissible operating temperature inside the device is not exceeded.

[0014] By using vacuum insulation, the heat loss of the hot water boiler can be significantly reduced compared to normally insulated boilers. The low waste heat has a positive effect on the quality, shelf life, and grinding properties of fresh coffee beans, which are typically stored at the top of the appliance and are therefore particularly exposed to rising waste heat. Due to the reduced waste heat, active cooling or ventilation of the appliance can be omitted, or at least the cooling capacity can be significantly reduced. The lower waste heat of the vacuum-insulated hot water boiler reduces the appliance's energy consumption, thus improving energy efficiency and reducing operating costs and CO2 emissions.

[0015] Although the use of a vacuum-insulated boiler offers particular advantages due to the higher storage temperature, a standard, conventionally insulated hot water boiler can also be used. In the simplest case, the outer wall of the boiler's storage vessel can simply be double-walled, at least in some areas, so that the double-walled area of ​​the outer wall encloses an evacuated space. The boiler is thus compact and generates little waste heat.

[0016] Alternatively, for vacuum insulation, the storage vessel can be placed in a double-walled outer shell, at least in part, whose double-walled section encloses an evacuated space. This allows the use of a conventional boiler, which can be removed from the vacuum-insulated outer shell for repair or replacement in the event of a defect.

[0017] In both cases, it is possible to equip the double-walled storage vessel or the double-walled outer shell with a non-vacuum-insulated lid, through which the boiler's electrical and / or hydraulic connections are routed. This allows for simple installation without the need to laboriously penetrate the vacuum shell. The non-vacuum-insulated lid can, for example, be provided with conventional thermal insulation made of insulating material.

[0018] Within the scope of the invention, a hot water boiler is also considered to be a boiler for the provision and storage of steam, which, during normal operation, contains a pressurized steam volume and a hot water volume that has not yet evaporated under the prevailing temperature and pressure conditions. A hot water boiler within the scope of the invention can also serve to simultaneously provide hot water and steam and be equipped with both a hot water outlet and a steam outlet.

[0019] The boiler's heater can expediently be designed as a heating coil arranged within the storage vessel. This leads to a particularly compact boiler design. In particular, the heater can be designed as a coiled tubular heater, with the heating coil running within a coiled heating tube, which is preferably filled with magnesium oxide powder for electrical insulation of the heating coil. It is within the scope of the invention to provide not just one vacuum-insulated hot water boiler, but rather several hot water boilers, of which, for example, one is provided for steam generation and another for hot water generation, and both are each provided with or surrounded by vacuum insulation. The use of more than two hot water boilers, for example to enable two beverages to be dispensed in parallel, can also be provided.

[0020] Further advantages and embodiments of the invention will become apparent from the following description of embodiments with reference to the figures.

[0021] It shows:

[0022] Figure 1 shows a first embodiment of a vacuum-insulated hot water boiler,

[0023] Figure 2 shows an embodiment of a hot water boiler inserted into a vacuum-insulated outer shell,

[0024] Figure 3 shows a water flow diagram of a hot beverage preparation device with two vacuum-insulated hot water boilers, one for providing hot water and one for providing steam,

[0025] Figure 4 shows the time course of the hot water temperature within the hot water boiler in a diagram illustrating the recording of the cooling curve for assessing the quality of the vacuum insulation and

[0026] Figure 5 is a water flow diagram of a hot beverage preparation device in a further embodiment in which a static mixer is additionally provided for mixing cold water supplied via a mixing valve with hot water taken from the hot water boiler.

[0027] A hot water boiler 10 used in a hot beverage preparation device, such as a coffee machine, is shown in section in Figure 1. The hot water boiler 10 comprises a storage vessel 11, which is double-walled in the lower region and has an inner outer wall 11a and an outer outer wall 11b. Between them is a gap 12, which is evacuated so that the outer walls 11a, 11b have vacuum insulation. In the upper region, the hot water boiler 10 is provided with a single-walled cover 13, through which electrical and hydraulic feedthroughs run. Inside the storage vessel 10 is a coiled tubular heating element 14. This has two electrical connections 14a, 14b, which are led to the outside through corresponding feedthroughs in the cover 13. In addition, the hot water boiler has several free feedthroughs 15, 16, 17.These allow the connection of supply and discharge lines, as well as measuring devices such as a pressure gauge or a thermometer. In the lower area, there is an evacuation valve 18, through which the gap 12 between the inner and outer walls 11a, 11b is evacuated.

[0028] Figure 2 also shows a partially sectioned view of a second embodiment of a vacuum-insulated hot water boiler 10. The hot water boiler 10 comprises a storage vessel 1T, which is of conventional single-wall design. A coiled tubular heating element 14 is arranged in the storage vessel, which has two electrical connections 14a, 14b, which are led to the outside through bushings arranged in the upper region of the storage vessel 1T. Additional bushings, of which only one bushing 15 is visible in Figure 2, serve to connect supply and discharge lines, as well as measuring instruments, if required.

[0029] The storage vessel 11' is located within a vacuum-insulated outer shell 20, the lower region of which is double-walled with an inner outer wall 21a and an outer outer wall 21b. In between there is a gap 22 which has been evacuated via an evacuation valve 28. In the upper region, the outer shell 20 is closed by means of a non-vacuum-insulated cover 23, through which the electrical and hydraulic feedthroughs run. The cover 23 can be insulated in a conventional manner with insulating material (e.g. needle felt made of synthetic fibers, silicone foam, glass wool, or the like). The cover 23 can be opened for assembly or disassembly of the water boiler 10 or for its repair, so that the hot water boiler 10 can be serviced and replaced without the vacuum-insulated outer shell 20.

[0030] Figure 3 shows a so-called water flow diagram of a coffee machine with two hot water boilers 10a, 10b, both of which are provided with or surrounded by vacuum insulation, as previously explained. Hot water boiler 10a serves to prepare and store hot water for beverage preparation, and hot water boiler 10b serves to prepare and store steam for frothing milk and contains a volume of water and a volume of steam that are in thermal equilibrium.

[0031] At a water inlet, which is connected on the inlet side to the connection of a water supply or a water tank, there is an assembly 30 with a water filter 31, a shut-off valve 32, two check valves 33 connected in series, a water pump 34 and a temperature sensor 35. From the water pump 34, cold water flows via a flow meter 36 and another check valve 37 to the inlet of the boiler 10a.

[0032] In the hot water boiler 10a, the water is heated to a storage temperature of 120°C to 140°C. The temperature in the hot water boiler 10a can be determined via a temperature sensor 39 and regulated by controlling the heater 14 of the hot water boiler 10a. A pressure relief valve 38 at the boiler inlet directs water from the hot water boiler 10a to an outlet in the event of excess pressure. The hot water outlet of the boiler 10a leads to two valve blocks 41, 42. Between the inlet and outlet of the hot water boiler 10a is a proportional valve 40, with which hot water from the hot water boiler 10a can be mixed with cold water. The water temperature of the mixed water can be measured via a temperature sensor 44 and adjusted by accordingly controlling the proportional valve 40.

[0033] Mixing of the hot water and the cold water supplied via the proportional valve 40 can take place in the hose line downstream of the junction of the cold and hot water. To achieve the fastest possible mixing of the two water streams, a static mixer 43, such as a reversible mixer, can also be arranged to thoroughly mix the two water streams. This is shown schematically in Figure 5. A reversible mixer is a static mixer in which several 180° spirals are arranged one behind the other in a tubular housing, each offset by 90° to each other. In addition, the successive spirals each rotate in opposite directions. Each spiral divides the flow of liquid into two partial streams. These are in turn divided into two partial streams at each transition to the next spiral and each merged with partial streams from the previous spiral.In this way, the liquid flow is mixed.

[0034] The hot water outlet of the hot water boiler 10a is connected to the two valve blocks 41, 42. Hot water for making tea can be dispensed via valve 41a, and the hot water boiler 10b can be filled for steam preparation via valve 41b. Valve 41c is not occupied in the exemplary embodiment and is available for further optional functions. The inlet of valve 41d is connected to the outlet of valve 41b and also leads to the hot water outlet, so that hot water and steam can be dispensed simultaneously. Hot water can be dispensed via valve 42a at the beverage outlet head 45, which can be used, for example, for instant beverages or for adding to coffee beverages. In addition, the outlet line from the brewing group 52 to the outlet head 45 can be rinsed via valve 42a. Valve 42b is not occupied in the exemplary embodiment and can be used, for example, for the “instant beverages” option.

[0035] A line also leads from the hot water outlet of the hot water boiler 10a to the 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. This can be automatically filled with freshly ground coffee powder via two separate grinders 53a, 53b for different types of coffee. When the brewing valve 51 is open, hot water from the hot water boiler 10a can flow through the brewing group 52 under pressure from the water pump 34. At the outlet of the brewing group 52 is an adjustable backpressure valve 54, which can be used to regulate the flow rate of the freshly brewed coffee beverage. From there, the freshly brewed coffee flows to the outlet head 45 of the coffee machine. Steam is provided via the hot water boiler 10b for heating and, if necessary, frothing milk.A valve block 60 with two parallel valves 60a, 60b can be used to release a steam line 61 leading to a steam lance 62. An air pump 63 and a check valve 64 can be used to add air to the steam during dispensing to froth the milk. Furthermore, a temperature sensor 65 can be provided on the steam lance 62 to measure the temperature of the milk heated or frothed by steam.

[0036] At the steam outlet of the hot water boiler 10b there is also a pressure relief valve 66, a pressure gauge 67 and a temperature sensor 68. The temperature inside the hot water boiler 10b can be monitored via temperature sensors 69 and adjusted by controlling the heater 14 accordingly.

[0037] The vacuum insulation of the hot water boilers 10a, 10b significantly reduces waste heat generated by the heating system, allowing the unit to be designed very compactly without causing thermal problems. Furthermore, the vacuum insulation allows for the hot water to be stored at higher storage temperatures, allowing a larger water volume to be available for dispensing by adding cold water. This allows for either a more compact design of the hot water boiler 10a or the preparation of a larger quantity of hot beverages before reheating the hot water.

[0038] The vacuum in the double-walled area of ​​the vacuum insulation is typically below one millibar, preferably even below one microbar, and more preferably even below 0.1 pbar. Additionally, to maintain the long-term stability of the vacuum, a so-called getter material can be introduced into the vacuum to absorb gases with minimal leaks and during outgassing of materials. A getter, or capture material, is a chemically reactive material designed to maintain a vacuum for as long as possible. At the surface of a getter, gas molecules form a chemical bond with the atoms of the getter material (oxidation), or the gas molecules are held by sorption. In this way, gas molecules are "captured." Metals such as barium, aluminum, or magnesium alloys are suitable as getters; after pumping, they can be heated if necessary to evaporate the getter metal.

[0039] In addition, reflective foils can be inserted into the evacuated gap space 12, 22, which further reduce the waste heat of the hot water boilers 10, 10'.

[0040] As already explained, the vacuum insulation can be part of the hot water boiler and be mechanically connected to it or form a unit, or the vacuum insulation can be designed as a separate component and the hot water boiler can be enclosed within it.

[0041] The recording of a cooling curve, which can be used to assess the quality of the vacuum insulation, is illustrated in the diagram shown in Figure 4, which shows the temporal course of the hot water temperature within the hot water boiler.

[0042] For this purpose, an additional software function is implemented using a controller that can also simultaneously control the heater 14 and regulate the hot water temperature in the hot water boiler 10, 10'. This function determines the insulation quality based on the cooling curve of the hot water boiler 10, 10', which can be measured using the temperature sensor 39, 69. This allows the vacuum insulation to be tested. If excessive cooling is detected, it can be concluded that the vacuum in the vacuum insulation is defective and a corresponding error message can be generated, prompting the vacuum insulation to be replaced or repaired. This information can be retrieved both on the device itself and via remote maintenance.

[0043] Figure 4 shows the temperature curve measured by temperature sensor 39 or 69 of hot water boiler 10b or 10b over time t. After the heater is switched off, the temperature slowly drops to a lower control threshold. Once this threshold is reached, heater 14 is switched on for a heating period H. The temperature thus rises again to an upper control threshold or to the target temperature in the boiler. A predetermined period of time, in this case 60 seconds, is then waited until heater 14 has transferred all of its heating energy to the hot water. The time period Δt within which the temperature has dropped by a predetermined temperature difference Δt of 1 °C in the exemplary embodiment is now measured. This cooling time is a measure of how good the insulating properties of the vacuum insulation are.If the 1° cooling time falls below a minimum value for intact vacuum insulation, an error message is generated and transmitted via data link to a monitoring center, indicating that the vacuum insulation of boiler 10a or 10b is presumably defective and needs to be inspected. This makes it easy to assess the vacuum insulation and determine whether a vacuum defect exists. Of course, the cooling time can also be recorded, for example, as the period between two heating periods H—that is, the time until the temperature has dropped to the lower control threshold and the heater 14 is reactivated.

Claims

Claims 1. Hot beverage preparation device with at least one hot water boiler (10, 10a, 10b) for heating and storing hot water for preparing hot beverages, wherein the hot water boiler (10, 10a, 10b) has a cold water inlet, a storage vessel (11, 11') with a heater (14) and a hot water outlet, characterized in that the storage vessel (11, 11') is designed as a pressure vessel in which hot water is stored at a temperature of over 110°C during operation and the hot water outlet is connected to a metering valve (40) for metered addition of cold water in order to add cold water to the hot water above 110°C during dispensing, so that mixed water with a temperature of below 100°C is dispensed for beverage preparation.

2. Hot beverage preparation device according to claim 1, wherein the storage vessel (11, 1 T) is designed to store hot water during operation at a temperature in a range from 110°C to 180°C, in particular in the range from 120°C to 140°C.

3. Hot beverage preparation device according to one of claims 1 or 2, in which, for the preparation of a freshly brewed coffee beverage, the mixed water can be fed to a brewing group (52) via a brewing valve (51).

4. Hot beverage preparation device according to one of the preceding claims, in which the dosing valve (40) for adding cold water is designed as a controllable valve, in particular a proportional valve, and the hot beverage preparation device has a temperature sensor (44) for determining the mixed water temperature and a control device for regulating the mixed water temperature by controlling the dosing valve (40).

5. Hot beverage preparation device according to one of the preceding claims, in which between the dosing valve (40) and the temperature sensor (44) a static mixer, in particular a reversible mixer, is arranged for mixing the cold and hot water streams. Hot beverage preparation device according to one of the preceding claims, in which the storage vessel (11, 11') is at least partially provided with or surrounded by vacuum insulation (12, 22). Hot beverage preparation device according to claim 6, in which, for vacuum insulation, the outer wall (11a, 11b) of the storage vessel is at least partially double-walled and the double-walled region of the outer wall encloses an evacuated space (12). Hot beverage preparation device according to claim 6, in which, for vacuum insulation, the storage vessel (11') is inserted into an at least partially double-walled outer shell (20), the double-walled region (21a, 21b) of which encloses an evacuated space (22).Hot beverage preparation device according to claim 7 or 8, wherein the double-walled storage vessel (20) or the double-walled outer shell (11a, 11b) has a non-vacuum-insulated lid (13, 23) through which electrical and / or hydraulic connections (14a, 14b, 15, 16, 17) are passed. Hot beverage preparation device according to one of the preceding claims, wherein the heater (14) is designed as a heating coil arranged within the storage vessel (11, 11'). Hot beverage preparation device according to claim 10, wherein the heating coil runs within a coiled heating tube (14), which is preferably filled with magnesium oxide powder for electrical insulation of the heating coil. Hot beverage preparation device according to one of the preceding claims, with a first hot water boiler (10a, 10b) provided for generating hot water and a second hot water boiler (10a, 10b) provided for generating steam, both of which are provided with or surrounded by vacuum insulation (12, 22). Hot beverage preparation device according to claim 7 or 8, wherein a getter material is introduced into the evacuated space (12, 22). Hot beverage preparation device according to claim 7 or 8, wherein a reflective foil is introduced into the evacuated space (12, 22).

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