MILK FOAMING DEVICE USING PRESSURIZED GAS AND METHOD FOR PRODUCING MILK FOAM - Patent application

Abstract

The invention relates to a milk frothing device 1, a beverage supplying device 100 equipped with the milk foaming device 1 and a method for producing milk foam. In particular in the coffee beverage industry, there is a need to produce a variety of different milk modifications, such as fine-pore milk foam or coarse-pore milk foam, based on different milk starting products. To do so, a variety of different equipment is often required. According to the invention, by applying compressed air to the milk at the outlet side A of the pumping device 2 a wide range of different milk modifications can be produced.

Description

[Technical field]

[0001] The present invention relates to a milk frothing device, a beverage dispensing device and a method for producing foamed milk (milk foam) according to the preamble of claim 1. Milk is understood to mean animal milk products, i.e. the glandular secretions of female animals of the Mammalia class, as well as vegetable milk products and comparable products, such as soy milk or almond milk. [Background technology]

[0002] To produce hot and cold milk or mixed milk drinks such as cappuccino or latte macchiato, milk is not only processed in liquid form but also in foamed form. Milk is usually foamed by mechanically stirring the milk in a stirrer, by adding steam to the milk and / or by adding air to a stream of milk flowing through a Venturi nozzle. To produce a wide range of milk and mixed milk drinks, it is necessary to provide different milk modifications, e.g. milk in cold or hot form, as well as in foamed or non-foamed form, and it is therefore sometimes desirable to be able to control and selectively adjust the foam properties (water content, foam bubble size, density, etc.) as well as the temperature of the milk modification in order to affect the aesthetics and the tactile and taste sensations.

[0003] The milk foam may be part of a mixed milk drink, as in the case of a latte macchiato, or it may form a crown of foam on top of the drink, as in the case of a cappuccino. A distinction can be made, for example, between firm, dense coarse-pore foam and fine-pore milk foam. Coarse-pore milk foam is produced as a single layer, and after a certain resting time in the cup, the coarse-pore milk foam transforms into a two-layer milk foam consisting of a lower liquid layer of hot milk and a layer of firm milk foam on top. This coarse-pore milk foam can be used to make, for example, a latte macchiato. However, this firm coarse-pore foam is not suitable for creating decorations in the milk foam on a cappuccino (latte art). For this purpose, a more liquid and creamy fine-pore milk foam consisting of ultra-fine air bubbles, also known as microfoam, can be used. This microfoam is preferably single-layered and has a silky, shiny surface that contains extremely small air bubbles that are evenly distributed in the foam and are difficult to see with the naked eye. When this microfoam is poured onto the surface of coffee with crema (espresso), it causes a partial mixing of the crema and the milk foam, which results in the discolouration of the white milk foam by the dark crema of the coffee, thus making it possible to paint pictures on the foamy surface (latte art).

[0004] It is known to influence the foam properties during the production of foam in a device for foaming a foamable liquid such as milk. It is also known to subsequently change the consistency of the produced foam. The modification of the foam properties can be achieved, for example, in an automatic coffee machine by means of a post-treatment device, as described in EP 2798988 B1. Here, the milk is passed under a preselected pressure through a labyrinth of passages surrounded by baffles in order to standardize the air bubbles of the foam and thus to make the foam consistency uniform. By adjusting the pressure ratio in the post-treatment device, the consistency of the milk foam can also be changed from fine foam, i.e. foam with very small air bubbles, to coarse foam, i.e. foam with large air bubbles, and also from loose to firm creaminess.

[0005] Therefore, certain foam characteristics using this known after-treatment device can only be achieved by adjusting the pressure ratio (i.e. by higher pressure in the steam supply line) without modifications to the after-treatment device, which may be disadvantageous in terms of water dilution and / or overheating of the foam (coagulation of milk proteins).

[0006] Furthermore, many different dairy products are offered, such as low-fat milk, lactose-free milk, as well as vegetable milk substitutes, such as soy milk and almond milk. These milk starting materials for producing milk foam have different processing properties (fat content, foaming ability, heatability, viscosity, etc.) and therefore it may be necessary to adapt the production parameters for supplying the milk foam to the milk starting material in order to produce milk foam with consistent or comparable properties.

[0007] EP 3 763 258 A1 shows the mixing of the air-milk mixture after enriching the milk with air via a Venturi nozzle in a swirl chamber. The foamed milk can then be tempered via a flow heater. A drawback is that the foam properties can only be controlled to a limited extent. In particular, with the device shown in EP 3 763 258 A1 it is not possible to produce different types of foam, such as fine- and coarse-pored foams.

[0008] EP 2 156 771 A1 teaches combining a gas flow, in particular an air flow, with a milk flow for frothing milk and introducing them together into the inlet side of a pump, in particular a gear pump, so that the gas-milk mixture is frothed into milk foam as they pass through the gear pump. The milk foam can then be heated at the outlet side of the pump by adding steam. With this known milk frothing device, both cold and hot milk froth can be produced, whereby cleaning of the device using steam is easily possible. However, the introduction of a milk and gas mixture at the inlet side of the pump can lead to disturbances in the pump action, in particular slippage of the gear pump, which is preferably used as the pump, and a rattling output of the milk foam at the outlet side of the pump. Also, the pump is highly susceptible to wear due to cavitation. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent No. 2798988(B1) [Patent Document 2] European Patent Application Publication No. 3763258(A1) [Patent Document 3] European Patent Application Publication No. 2156771(A1) Summary of the Invention [Problem to be solved by the invention]

[0010] Against this background, the present invention seeks the object of providing a milk foaming device, a beverage supplying device with such a milk foaming device and a method for producing milk foam, which can produce milk foam with adjustable properties and which can be dispensed one after the other at a constant volumetric flow rate without malfunction. It should also be possible to produce different types of milk modifications such as cold or hot milk as well as cold or hot milk foam, preferably with production parameters adapted to different milk starting products (cow's milk, lactose-free milk, almond milk, hemp milk, soy milk, kangaroo milk, etc.), with a freely adjustable volumetric flow rate. At the same time, a high level of functional integration with small size and few parts, a long lifespan and low maintenance requirements should be achieved. [Means for solving the problem]

[0011] These tasks are solved by a milk frothing device having the features of claim 1, by a beverage dispensing device having the features according to claim 16 and by a method having the features of claim 21.

[0012] The milk frothing device according to the invention comprises a pumping device having an inlet side and an outlet side for conveying milk from the inlet side to the outlet side. A milk supply line can be connected to the inlet side, so that in particular cooled milk from a storage container can be introduced into the pumping device and can be delivered via the outlet side. The outlet side can be connected to a milk distribution line for dispensing milk foam. The milk frothing device is characterized in that a gas inlet is arranged at the outlet side of the pumping device for introducing a pressurized gas for foaming the milk. Pressurized gases such as air, nitrogen, oxygen, carbon dioxide or mixtures thereof compatible with foodstuffs, e.g. nitrous oxide (N2O), are used as pressurized gas.

[0013] The term "pressurized gas" does not include hot steam, typically provided by a steam generator, e.g., a boiler. Nor does the term "pressurized gas" include wet steam, i.e., gas having a water content that exceeds the saturation limit of the gas for water.

[0014] In the context of the present invention, pressurized gas means in particular essentially anhydrous pressurized gas, i.e. a pressurized gas or gas mixture under pressure whose water content has not been deliberately increased. An example of an essentially anhydrous pressurized gas within the meaning of the present invention is compressed air which contains a certain proportion of water in the form of natural humidity.

[0015] The milk is mixed with the pressurized gas at the outlet side of the high pressure side of the pumping device. Adding pressurized gas to the milk at the outlet side ensures that the function of the pumping device is not adversely affected by the pressurized gas, in particular slippage or free rotation of the pumping device is prevented, and a uniform delivery of the milk foam at the outlet side is possible. Furthermore, the delivery speed of the milk and thus the delivery volume of the pumping device can be adjusted independently of the foam properties. By supplying the pressurized gas at different delivery pressures and thus different amounts of pressurized gas at different delivery speeds, both fine-pore milk foam and coarse-pore milk foam can be produced. It is also possible to use the milk foaming device as a delivery pump for milk without introducing pressurized gas and without producing milk foam. Other delivery means, in particular separate delivery means for producing different milk foams, or the use of different milk foaming devices is therefore not necessary.

[0016] The inlet side and the outlet side should be understood as essentially synonymous with the low pressure side and the high pressure side of the pumping device. "At the outlet side" should therefore be understood as "assigned to the high pressure side". The gas inlet for introducing pressurized gas can be located at the outlet side, inside or outside the housing of the pumping device.

[0017] Further features and advantageous embodiments of the invention are evident from the dependent claims and the following description.

[0018] Preferably, the milk frothing device does not have a gas inlet at the inlet side of the pumping device for introducing pressurized gas for frothing the milk. Embodiments in which milk is frothed by introducing pressurized gas at the inlet side of the pumping device are not encompassed by this embodiment of the invention.

[0019] In an advantageous embodiment, the pumping device of the milk frothing device comprises at least one housing, and a mechanically movable conveying means is arranged in a conveying chamber in the housing. At least one first access opening and at least one second access opening and at least one first outlet opening are provided in the housing. The first access opening is arranged on the inlet side upstream, i.e. in front of the conveying means in the milk flow direction, and forms an inlet for introducing milk into the housing of the pumping device. The outlet opening is arranged on the outlet side downstream, i.e. behind the delivery means in the milk flow direction, and forms an outlet from the delivery chamber for dispensing the milk foam. The second access opening is arranged on the outlet side, preferably in the region of the conveying means. Pressurized gas is introduced into the conveying chamber via the second access opening for foaming the milk. The second access opening forms a gas inlet.

[0020] Pressurized gas is preferably delivered to the outlet side in the housing, in particular in the conveying chamber of the pumping device, so that the foam-forming mixing effect of the pressurized gas delivery can be advantageously used to foam the milk, as well as the turbulence effect generated by the delivery means, and thus the delivery pressure of the pressurized gas can be kept relatively low, since the kinetic energy for frothing the milk does not have to be exclusively pressure-related.

[0021] The pumping device is preferably a pumping device with mechanical conveying means. Continuously operating (e.g. gear pumps) or cyclically operating (e.g. piston pumps, membrane pumps) positive displacement pumps can be used as pumping devices.

[0022] The pumping device is preferably designed as a gear pump, in particular as an external gear pump or as an internal gear pump. Gear pumps comprise two gear wheels which mesh with each other and are arranged to rotate around two parallel rotation axes, the teeth of the gear wheels providing a limited delivery volume when engaged. Gear pumps have a small moment of inertia and high control dynamics. Due to their fast response behavior, high delivery pressures can be achieved even with small delivery volumes of milk (shots). This means that the desired pressure difference at the outlet side of the delivery chamber can be obtained almost instantly, i.e. without a pressure build-up phase. This reduces the amount of waste with insufficient quality. It is also possible to use other pump types such as gear ring pumps, membrane pumps or piston pumps.

[0023] Expedient configurations of the second access opening in the region of the pump supply means of the pumping device include both configurations in which the second access opening has no mechanical contact with the pump supply means of the pumping device, for example by arranging the tip diameter of the conveying means designed as a gear wheel radially outwards, or configurations in which the second access opening has mechanical contact with the conveying means of the pumping device, for example by an access opening arranged radially between the root diameter and the tip diameter of the conveying means in the form of a gear wheel of a gear pump, i.e. in such a way that the access opening is cylindrically covered and uncovered by moving the conveying element of the pumping device. By cylindrically releasing the access opening, a pulsating pressurization of the gas is possible. The pump supply means of the pumping device and the second access opening thereby form a stutter valve without the need for additional components.

[0024] It can be useful if the outlet opening is equipped with or designed as a nozzle and / or a throttle valve, in which case the pressure in the delivery chamber on the outlet side can be adjusted in a controlled manner.

[0025] It is also advantageous if the second access opening is equipped with a nozzle and / or a throttle valve or is designed as a nozzle and / or a throttle valve. By means of a suitably selected nozzle shape, for example when passing through the nozzle, the hydrostatic component of the pressure of the pressurized gas applied to the access opening can be advantageously converted into a dynamic pressure component. In that way, the pressurized gas can be introduced into the milk with a large differential velocity and thus an excellent mixing can be achieved. The nozzle or throttle valve can be formed integrally in the housing of the pumping device as the opening. However, the nozzle and the throttle valve are advantageously exchangeable separate parts that are inserted into the housing, for example bushing inserts. By using exchangeable bushing inserts, it is also possible to subsequently adapt the milk frothing device to changed production parameters.

[0026] In order to achieve the best possible homogenization of the milk foam, especially with air bubbles of uniform bubble size homogeneously distributed in the milk foam, the second access opening (gas inlet) is preferably located immediately close to the gear wheel meshing on the outlet side of the gear pump. By locating the second access opening as close as possible to the gear wheel, the pressurized gas can be displaced by reducing the delivery volume of the gear wheel and thus accelerated in the direction of milk flow, i.e. towards the outlet opening.

[0027] The pressurized gas is preferably introduced into the milk flow perpendicular or tangential to the milk flow direction. It is also possible to introduce the pressurized gas against the flow direction or in a mixed form, for example at an angle. Introduction against the milk flow direction is advantageous when high turbulence and good mixing between the pressurized gas delivered through the second access opening and the milk is desired to produce a high foam quality.

[0028] In an advantageous embodiment, the pumping device may comprise more than two access openings, in particular several gas inlets. The access openings forming the gas inlets may be advantageously arranged opposite one another and facing one another in the housing of the pumping device. Alternatively or additionally, it is also possible to arrange several access openings next to one another or one above the other. By using several gas inlets, the foaming rate and therefore the milk foam throughput can be increased, while the size of the pumping device can be kept approximately the same.

[0029] The first access opening and the outlet opening can be arranged parallel, in particular coaxially. However, it is advantageous if the outlet opening is arranged parallel and offset relative to the access opening. By doing so, a baffle effect is obtained which has a positive influence on the mixing and therefore on the foaming of the milk.

[0030] The housing of the pumping device advantageously comprises a bottom side, preferably flat, a top side, preferably flat, extending parallel to the bottom side at a certain distance, and at least one side wall, preferably arranged at right angles to the bottom side. The side wall may be circumferential, in particular cylindrical. However, the housing can also be designed as a polygon with several side walls, in particular as a cube with four side walls at right angles to each other. The side wall defines a conveying chamber. The first access opening and the outlet opening are advantageously arranged in the center of the circumferential side wall, respectively at mutually opposite points, i.e. on the two mutually opposite side walls. The second access opening is preferably arranged on the top side and / or on the bottom side of the housing. The conveying means is preferably mounted rotatably around an axis of rotation extending between the top side and the bottom side.

[0031] The access openings and / or the outlet openings are advantageously respectively immersed in fluid passages arranged in the housing, whereby the individual fluid passages can form a different cross section compared to the opening cross section of the access openings or the outlet openings. The milk supply line can be connected to the first fluid passage, the milk distribution line can be connected to the third fluid passage and the pressurized gas line can be connected to the second fluid passage. These lines are advantageously designed as hose connections, which have corresponding quick coupling elements for connection to the fluid passages.

[0032] Advantageously, a check valve is arranged at least in the second fluid passage. This check valve can prevent milk from flowing back into the pressurized gas line. It is also possible for check valves to be arranged in the first and in the third fluid passage. This offers the advantage of a high level of functional integration and thus inter alia shorter connections, i.e. hose paths, for example for the milk supply line and the milk distribution line are possible.

[0033] In an advantageous embodiment, the second fluid passage has a further opening, which has another adjacent passage for forming a branch. Water or a cleaning liquid for cleaning purposes can be fed into the housing via the additional passage. This water or cleaning liquid can be used, for example, to clean the delivery chamber on the outlet side or the fluid lines connected to the delivery chamber.

[0034] The second opening access can have an opening diameter of up to 10 mm, preferably up to 5 mm, or particularly preferably up to 0.05 mm. A larger orifice diameter allows for a larger mass flow rate, but requires a correspondingly stronger pressurized gas source. A smaller diameter allows for a larger pressure difference when delivering the pressurized gas into the delivery chamber, and also allows for better foaming.

[0035] When several access openings are used to form more than two gas inlets, it is also possible to design these gas inlets using different diameters. The access openings can be fluidly connected in parallel and pressurized gas can be supplied to them either collectively or individually via electronically controlled valves. By individually controlling different access openings with different opening diameters, the same milk foaming device can be used to produce a wider range of different milk foams, in particular milk foams with significantly larger and significantly smaller pore sizes.

[0036] Furthermore, it is advantageous if the first access opening has a first opening diameter and the outlet opening has a third opening diameter, the third opening diameter being smaller than the first opening diameter. In this way, the back pressure on the outlet side of the delivery chamber can be particularly easily increased. This has an advantageous effect on foam formation.

[0037] In order to provide pressurized gas via the pressurized gas inlet, in an advantageous embodiment the pressurized gas inlet can be connected to or is connected to a compressor for generating pressurized gas under pressure. By compressor is meant a compressor machine which compresses gas by mechanical work. It is also possible to use another source of pressurized gas instead of a compressor, in particular a pressurized gas cylinder, such as a pressure bottle. By using a compressed gas cylinder the supply of pressurized gas can be simplified, but in return it requires regular replacement of the pressurized gas cylinder.

[0038] In one embodiment, the pressurized gas can be supplied under an almost constant absolute delivery pressure, preferably at least 3 bar, in particular in the range from 4 bar to 10 bar, particularly preferably at least 6 bar. Delivery pressures that remain constant over time are technically particularly easy to achieve. However, especially in the case of low milk flows, even pressures of 1 bar or less may be sufficient, for example for producing microfoam.

[0039] In an advantageous embodiment, the pressurized gas is provided under a supply pressure (feed pressure) which is e.g. 0%, preferably 15%, 30% or 50% more than the pressure at the outlet side of the milk frothing device when no pressurized gas is supplied. In particular, a relative feed pressure at least 30% higher than the dynamic pressure of the milk flow at the outlet side ensures a homogeneous distribution of the pressurized gas flow in the milk flow, which has the further advantage that the foam pattern of the milk foam can be varied depending on the pressure difference present. If the pumping device operates with a variable delivery rate, this also requires additional control efforts of the pressurized gas source.

[0040] It is advantageous if the milk frothing device is equipped with a pressure regulating device (control device) in order to be able in particular to regulate the amount of pressurized gas supplied and / or the dynamic pressure of the pressurized gas supplied.

[0041] In one embodiment, the pressure regulating device may comprise, for example, an electromagnetically controllable proportional valve disposed between the compressor and the gas inlet, providing simple actuation and precise control of the pressurized gas delivery pressure.

[0042] Alternatively or additionally, the pressure regulating device may comprise a shutoff valve (also a stutter valve) that opens and closes at a high cycle rate, the shutoff valve being disposed between the compressor and the gas inlet. The shutoff valve is opened and closed at a very large number of cycles according to the principle of pulse width modulation, so that intermediate delivery pressures of the pressurized gas can be achieved. Furthermore, because it is opened and closed at a very large number of cycles, very fine adjustment of the amount of pressurized air provided into the pumping device is possible.

[0043] The pressure regulating device may alternatively or additionally include a discharge valve for discharging the pressurized gas provided by the compressor. The discharge valve is disposed in the pressurized gas line. The provision of the discharge valve allows for a wider bandwidth of the delivered air volume compared to a control device using a fast switching shutoff valve.

[0044] It is also possible for the compressor itself to have a short response and to be designed to be controllable, so that the pressure regulating device is connected directly to the compressor in such a way that the compressor can be activated, deactivated and / or its output regulated as required, in which case the compressor is essentially connected directly to the gas inlet.

[0045] Combinations of the listed variations of the pressure regulating device are also possible.

[0046] The compressor can furthermore be designed with or equipped with a buffer tank to form a gas pressure storage vessel, via which pressurized air can be fed into the pumping device, even if the compressor is not operated at the same time. Such a temporary decoupling of the pressurized gas generation and use of pressurized gas allows the use of a compressor with a lower pressurized gas output but with a higher efficiency. Furthermore, noise emissions during milk foam production can be avoided.

[0047] The invention further relates to a beverage dispensing device, in particular for coffee and coffee-mixed drinks, which comprises a milk foaming device as described above.

[0048] The beverage supply device comprises a dispensing device for dispensing milk in a foamed and / or non-foamed and / or heated and / or non-heated state, the dispensing device for dispensing milk being preferably exclusively connected to the outlet side of the milk frothing device via a milk dispensing line.

[0049] The milk frothing device can therefore provide different types of milk for every beverage of the beverage dispensing device, so that it is no longer necessary to use different milk frothing devices to produce different milk modifications such as liquid cold milk with different textures (coarse pores, fine pores, ...), liquid hot milk, cold milk foam or hot milk foam.

[0050] To provide heated milk or heated milk foam, a heating device is advantageously arranged in the milk distribution line. The heating device is preferably designed as a continuous flow heater, in particular an electric continuous flow heater, preferably as a thin film heater. By such a design, the milk can be heated without mixing with a heat transfer fluid such as hot steam. Thus, adverse changes in the foam quality due to mixing with a heat transfer fluid such as steam for heating, which would result for example in water dilution of the milk foam, can be avoided.

[0051] The heating device can also be designed as a steam injector for feeding hot steam, in particular water steam, into the milk distribution line, the steam injector being coupled to or comprising a steam source. It is also possible to envisage a combination of milk heating by continuous heating and steam input.

[0052] The invention also relates to a method for producing foamed milk, in which milk, arranged in a housing of a pumping device, is exposed to pressurized gas, in particular pressurized air, by introducing pressurized gas into the milk on the high pressure side in the region of a movable conveying means, such as the teeth of a gear pump, for conveying milk from the low pressure side of the pumping device to the high pressure side of the pumping device.

[0053] The pressurized gas may be an at least substantially anhydrous pressurized gas or gas mixture having a temperature below 100° C., preferably below 80° C., in particular below 40° C. If the temperature of the pressurized gas is low, for example below 30° C., the cold milk supplied and foamed with the pressurized gas is at least substantially not heated and therefore cold milk foam can also be produced. However, if milk has to be heated, hot pressurized gas can also be used, in particular to heat the milk, but essentially anhydrous gas has a low heat capacity, which requires a great technical effort to heat the milk.

[0054] The pressurized gas may be pressurized air produced by a compressor from drawn in atmospheric air, but it is also possible to use nitrogen or carbon dioxide, for example from a pressure vessel, as pressurized gas.

[0055] Pressurized gas has a pressure significantly greater than atmospheric pressure.

[0056] In an advantageous variant of the process, the pressurized gas can be added to the milk in a pulsating manner. Due to the pulsation, the turbulence effect during introduction into the pumping device and therefore the foam formation rate can be high. A higher milk flow rate is therefore possible with a constant foam quality and therefore a larger volumetric flow of the produced milk foam. A continuous, i.e. non-pulsating introduction of the pressurized gas is possible.

[0057] The pulsation can be achieved, for example, by means of a stutter valve. However, it is also possible to achieve the pulsation by dynamically controlling the compressor that supplies the pressurized gas. A combination of a stutter valve and a coordinated control of the compressor is also possible.

[0058] A stutter valve is a fast switching valve (shutter valve) with which intermediate pressures can be achieved by superimposing a high pressure pulse with a low pressure pulse. The shutter valve is for example controlled electromagnetically. Dynamic control of the compressor means in particular a variable speed control of the compressor, providing the desired pressure almost in real time.

[0059] However, it is also possible to supply the pressurized gas through an access opening arranged in such a way that it can be cylindrically covered and uncovered again by moving a conveying element of the pumping device, for example by arranging the access opening radially between the root diameter and the tip diameter of the gear wheel of the gear pump.

[0060] A pressure sensor may usefully be provided in the pressurized gas supply line, the second fluid passageway or in the outlet region of the delivery chamber.

[0061] The invention will now be described, by way of example only, with reference to embodiments thereof as illustrated in the accompanying drawings. [Brief description of the drawings]

[0062] [Figure 1] Schematic diagram of a beverage supply device according to the invention, comprising a milk foaming device according to the invention. [Diagram 2] FIG. 2 is a cross-sectional view of a milk frothing device according to the invention; [Figure 3A] FIG. 1 is a first perspective view of a milk frothing device according to the invention; [Figure 3B] FIG. 3B is another perspective view of the milk frothing device according to the invention from FIG. 3A. [Figure 4] 2 is a schematic diagram of a beverage supply device according to the invention with a milk foaming device according to the invention similar to FIG. 1 with a modified pressure regulating device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0063] FIG. 1 shows a schematic representation of a beverage dispensing device 100 for dispensing cold and hot beverages based on coffee and milk, comprising a milk system.

[0064] The milk system of the beverage supply device 100 comprises a milk container 105, a milk frothing device 1 with a pumping device 2 having an inlet side E and an outlet side A, and a distribution device 101. The pumping device 2 is connected to the milk container 105 at the inlet side E via a milk supply line M1 and to the distribution device 101 at the outlet side A via a milk distribution line M2. At the outlet side A, the pumping device 2 is also connected to a compressor 10 via a pressurized gas line DL, which draws in and compresses atmospheric air through a filter element, here called air source 106. Compressed air (pressurized air) is fed into the pumping device 2 via the pressurized gas line DL and the gas inlet 3. A proportional valve V, which can be electromagnetically controlled by a control unit 104, is also arranged between the compressor 10 and the pumping device 2. The milk supply line M1 is connected via a branch to a water connection 107 via a water line WL. A heating device 102 in the form of a continuous flow heater 102' is also arranged in the milk distribution line M2 for tempering and heating the milk or milk foam.

[0065] Backflow obstacles in the form of check valves RSV1, RSV2 and RSV4 are present in the milk supply line M1, the pressurized gas line DL and the water line WL to prevent backflow or improper delivery of liquid.

[0066] The pumping device 2 comprises a housing 4 which contains a conveying chamber 16 in which a conveying element 5 is arranged. The conveying element 5 divides the conveying chamber 16 into an inlet feed chamber 17 and an outlet mixing chamber 9.

[0067] The beverage dispensing device 100 can be operated in four different operating modes, namely a first mode for dispensing cold liquid milk, a second mode for dispensing tempered liquid milk, a third mode for dispensing cold milk foam and a fourth mode for dispensing hot milk foam, the milk or milk foam being in each case dispensed via the dispensing device 101 into a beverage container, for example into a cup placed under the outlet of the dispensing device 101. Furthermore, the beverage dispensing device 100 has a cleaning mode. The beverage dispensing device 100 is controlled by the electronic control unit 104 to set the operating and cleaning modes as follows:

[0068] First operating mode (cold milk) In the first mode, chilled milk is sucked from the milk container 105 via the first access opening O1 in the housing 4 into the feed chamber 17 of the pumping device 2, here designed as an external gear pump, conveyed into the mixing chamber 9 via the conveying element 5 and pumped through the outlet-side outlet opening O3 through the throttling element DS into the milk distribution line M2, so that when the pumping device 2 is activated, chilled milk flows out of the distribution device 101. The flow heater 102' is switched off in this mode. The milk distribution line M2 can furthermore have a bypass line (bypass), through which milk is passed in the first operating mode in order to avoid the milk passing through the flow heater 102' and thus heating of the milk by residual heat from the flow heater 102'. The control unit 104 activates only the pumping device 2 in this mode.

[0069] Second mode (warm milk) In the second mode, warm milk will be dispensed via the dispensing device 101. The second operating mode differs from the first in that the control unit 104 activates the flow heater 102' immediately before or simultaneously with the activation of the pumping device, so that the milk is heated while flowing through the flow heater 102'. In this operating mode, the heating capacity of the flow heater as well as the delivery capacity of the pumping device 2 to affect the milk flow rate can be adjusted by the control unit 104 depending on the desired target temperature of the milk.

[0070] 3rd mode (cold milk foam) In the third operating mode, cold coarse-pore milk foam is dispensed from the dispensing device 101 floating on the beverage surface. The flow heater 102' is switched off or bypassed by a bypass line, as in the first operating mode. The control unit 104 simultaneously activates the pumping device 2 and the compressor 10 to produce the cold foam. The compressor 10 provides pressurized air, for example at a pressure of 6 bar. The pressurized air is then blown into the mixing chamber 9 via a second access opening O2 at the outlet side A (high pressure side) of the pumping device 2, and foams the milk therein. The second access opening O2 corresponds to a gas inlet for introducing pressurized gas from the pressurized gas line DL. In this case, the delivery volume of the pumping device 2 is selected such that milk accumulates under a pressure of, for example, 4 bar on the outlet side A in front of the throttling element DS, which is arranged downstream of the outlet opening O3. The foamed milk is then homogenized as it passes through the throttling element DS.

[0071] Fine regulation of the amount of pressurized air provided is achieved via a valve V arranged in the pressurized air line DL (between the compressor 10 and the access opening O2). In one possible embodiment, the valve V is a proportional valve of the pressure regulating device 103, which is electromagnetically controlled via the control unit 104. Instead of a proportional valve it is also possible to use a stutter valve, which is controlled in a fast repetitive manner in the manner of pulse width modulation, i.e. by clocking the valve open and close at a fast rate. By opening and closing the valve in a fast alternating manner the amount and pressure of pressurized air can be very finely controlled. Furthermore, a pulsating pressure is applied to the milk in the mixing chamber, which is advantageous for milk foam formation.

[0072] Further control of the amount of pressurized gas introduced into the milk can be achieved by adjusting the pumping power of the pumping device 2 in such a way that, for example, the pumping power of the pumping device 2 is set to a higher power for producing fine-pored milk foam having a high density than for producing coarse-pored milk foam having a low density.

[0073] 4th mode (hot milk foam) In the fourth operating mode, hot microporous milk foam is dispensed from the dispensing device 101, which mixes with the crema of a beverage, for example an espresso, located below the outlet of the dispensing device 101. To that end, the control unit 104 activates the pumping device 2 and the compressor 10 and adjusts the valve V, as in the third operating mode. Both the delivery of the pumping device 2 and the pressure of the pressurized air provided by the compressor 10 are selected lower than in the third operating mode. Furthermore, the pressure difference between the pressurized air applied to the access opening O2 and the milk entering the mixing chamber 9 is kept low, so that the pressurized air is introduced into the mixing chamber 9 under an overpressure of about 10-30% of the milk pressure. By doing so, a high proportion of air in the milk can be achieved and a homogeneous foam with extremely fine pores can be produced.

[0074] Additionally, in the fourth mode of operation the flow heater 102 ′ is activated to heat the milk foam prior to dispensing via the dispensing device 101 .

[0075] Cleaning Mode The pumping device 2 and the milk distribution line M2 can be washed with water or a cleaning liquid. To that end, the control unit 104 opens the valve in the water line WL and activates the pumping device 2 so that the pumping device 2 can pump water from the water line WL through the mixing chamber to the milk distribution line M2.

[0076] In order to flush the second access opening O2 for pressurized gas, in a subsequent step of the flushing mode the pumping device 2 is deactivated, whereby the passage of liquid through the pumping device 2 via the inlet side E of the pumping device 2 is blocked by the stationary conveying element 5. Water is pumped under water line pressure through the intersection between the water line WL and the pressurized gas line DL, where the check valve RV4 is located, through the second access opening O2 into the mixing chamber 9 and then discharged through the outlet opening O3 and the milk distribution line M2 through the distribution device 101. The outlet opening O3 and the connecting path of the pressurized air line DL, which are potentially contaminated by milk residues, are thereby flushed.

[0077] Other Operating Modes Further operating modes can be provided: for example it is also possible to provide hot coarse-pore milk foam or cold fine-pore milk foam, since the milk foam is foamed cold and only thereafter, if required, heated via the flow heater 102', so that the foam type (coarse-pore vs. fine-pore) is not or only to a lesser extent dependent on the desired temperature of the milk foam in the dispensing device 101.

[0078] Figure 2 shows a cross section through a pumping device 2 according to the invention, used in the scheme of Figure 1. The pumping device 2 comprises a housing 4 in which a conveying chamber 16 is arranged. The conveying chamber is surrounded by a substantially flat bottom side 6, a top side (not shown) spaced parallel to the bottom side 6 and a cylindrical side wall 8 extending vertically therebetween. Two conveying means 5 in the form of gear wheels are mounted in the conveying chamber 16 around respective parallel rotation axes X1, X2 arranged one behind the other in the plane of the drawing, these two conveying means 5 (gear wheels) meshing with each other (Figure 2, pitch circle diameter d or tip diameter d K ), thereby forming an external gear pump. These two conveying means 5 (gear wheels) are driven by a motor, not shown here, for example an electric motor, whereby different speeds can be set for conveying the milk from the inlet side E to the outlet side A. The motors are electronically controlled for this purpose via a control unit. The motors can be electronically controlled via an electronic control unit 104, which is referred to in FIG. 2.

[0079] The conveying means 5 divides the conveying chamber 16 into an inlet side E with the feed chamber 17 and an outlet side A with the mixing chamber 9. The inlet side E has a single access, namely a first access opening O1, which is formed at approximately half the height H / 2 of the side wall 8 of the feed chamber 17. The first access opening O1 extends vertically through the side wall 8 as a round hole, thus forming a constriction acting as a nozzle. Around the first access opening O1, a connecting socket is arranged integral with the housing 4, which forms a first circular-cylindrical fluid passage L1 with a central axis C1. A connecting piece 11 is inserted in the connecting socket in a fluid-tight manner, via which the pump device 2 can be connected to a fluid line, shown as the milk supply line M1.

[0080] The outlet side A of the pump device 2 has a single outlet in the form of an outlet opening O3, through which the fluid arranged in the mixing chamber 9 can be discharged. The outlet opening O3 is formed in the side wall 8 as a circular-cylindrical transverse hole, into which a third nozzle DS3 with a variable cross-sectional profile is inserted. The third nozzle DS3 forms a throttling element, through which a counter pressure can be built up in the mixing chamber 9 even with low conveying speeds or small conveying volumes. Similar to the first access opening O1, a third connecting socket is formed on the outside of the housing 4, integrally therewith, around the outlet opening O3, the third connecting socket forming a third fluid passage L3 with a central axis C3. A connecting piece 13 is inserted in the third connecting socket and fluidly connects the mixing chamber 9 with the milk distribution line M2 shown in FIG. 1.

[0081] As can be seen from figure 2, the axes C1 and C3 or the access openings O1 and O3 are arranged at the same height in the side wall 8. Different, in particular asymmetrical, arrangements are possible.

[0082] The mixing chamber 9 has a second access opening O2 in the bottom side 6, which in this case extends vertically through the bottom side 6. However, it is also possible that the second access opening O2 is arranged in the bottom side 6 at an inclined angle, preferably an acute angle, preferably against the flow direction, i.e. aligned with the conveying element 5. Such a design can induce a larger turbulence effect (turbulence), which leads to an improved mixing of the pressurized gas with the milk in the mixing chamber 16, if the pressurized gas is introduced via the second inlet opening O2, or an improved cleaning of the mixing chamber 16, if water is introduced via the second inlet opening O2. Instead of being arranged against the flow direction, i.e. perpendicular to the flow direction, it is also possible to align the second access opening with the flow direction, in order to reduce the pressure required to introduce the pressurized gas.

[0083] The second inlet opening O2 (as well as the first outlet opening O3) has a throttling element DS2 inserted in the inlet opening O2. The throttling element DS2 can be used to control the injection pressure and injection rate of the pressurized air and / or water.

[0084] The second inlet opening O2 is immersed in a second fluid passage L2 formed by a connecting socket, in which a check valve RSV2 and a connecting piece 12 are inserted for connection to the pressurized air line DL shown in Fig. 1. The second fluid passage L2 has a branch with an opening O4 which develops into a fourth fluid passage L4, in which a check valve RSV4 and a connecting piece 12 are inserted for fluid connection to the water line WL shown in Fig. 1. 14 is inserted. Check valves RSV2 and RSV4 prevent fluid in the mixing chamber from flowing back into the pressurized air line DL and water line WL, respectively.

[0085] The connecting piece 12 of the compressed air line DL, the second fluid passage L2 and the second access opening O2 are arranged coaxially with respect to one another, which results in the lowest flow resistance. The connecting piece 14 of the water line WL and the additional opening O4 are arranged at right angles to the second fluid passage L2.

[0086] The opening cross-sections and opening contours of the access openings O1, O2, O3 and the other openings O4 can be changed by exchanging the bushings used in those openings depending on the specified contour, for example the openings can be designed as standard holes into which different bushings with different opening diameters can be inserted depending on the specified contour.

[0087] Figures 3A and 3B show a variant of the milk frothing device 1 from Figure 2 in a perspective view. Here one can clearly see the geometric design of the delivery chamber 16 of the pumping device 2 as a superposition of two circular cylinders with axes corresponding to the rotation axes X1 and X2. The gear wheels and the associated shafts of the gear pump are not shown for the sake of clarity. A drive in the form of a motor, also not shown, is mounted on the top side 7 of the housing 4 of the pump device 2 and drives the shaft of the gear wheels via a reduction gear (not shown). The second gear wheel is indirectly driven via the first gear wheel, which is meshed with the second gear wheel. A tandem drive is also possible. The bushing 15 represents the mounting opening for the check valve RSV2 shown in Figure 2.

[0088] The pump device 2 of Figures 3A and 3B differs from the pump device shown in Figure 2 in the position of the outlet opening O3, which is not located at half the height of the delivery chamber 16 but approximately at the first third of the height H / 3. The outlet opening O3 is therefore offset in parallel to the first inlet opening O1, which is located at half the height (see H / 2 in Figure 2).

[0089] As can be seen in Figure 3A, the second access opening O2 is located immediately adjacent to the side wall 8 of the bottom side 6 of the housing 4, directly opposite the outlet opening O3. A flow of pressurized gas can therefore be applied to the milk as soon as it enters the outlet opening O3, conveyed by the pumping device 2.

[0090] For all other features of the pump device 2 according to FIGS. 3A and 3B, reference is made to the description for the embodiment example of FIG.

[0091] FIG. 4 shows a variant of the milk frothing device 1 in the beverage supply device 100 shown in FIG. 1. The essential difference is that here a pressure regulating device 103 is arranged downstream of the compressor 10 in order to control the amount of pressurized gas introduced into the pumping device 2. Instead of the proportional valve V used in the embodiment example of FIG. 1, a shutoff valve V', which can be switched open or closed, and a discharge valve V'' arranged downstream in the direction of flow and also arranged in a branch of the pressurized gas line Dl are arranged in the pressurized gas line DL. The shutoff valve V' and the discharge valve V'' form the pressure regulating device 103. Via the discharge valve V'', the pressurized gas provided by the compressor 10 can be partially discharged to the atmosphere. In comparison with the use of a proportional valve or a stutter valve arranged directly in the pressurized gas line, as in the embodiment example of FIG. 1, pressurized air can be provided over a wider pressure bandwidth. Thus, for example, a desired mixture ratio of air to milk can be set only via the discharge valve V'', again without having to adjust or change the pumping capacity of the pumping device 2. Thus, via such a pressure regulating device 103 with a discharge valve, it is possible to simultaneously produce both a low density, very coarse pore foam for producing a foam crown on top of the beverage and a very fine pore foam (microfoam) that mixes well with the beverage crema located below the dispensing device 101. The control unit 104 regulates the pumping capacity of the pumping device in this example embodiment only between the on and off positions.

[0092] In the version shown here, the drain valve V'' is designed as a fast acting stutter valve. However, it is also possible for the drain valve V'' to be designed as a proportional valve.

[0093] For essentially identical other details of the beverage supply device, reference is made to the description of the embodiment example of FIG. 1 above.

[0094] The described invention in particular provides a flexible milk foaming device with a high mass flow rate, which is structurally very simple but can be used in beverage supply devices and processes and which can be used to produce milk foam of different consistencies and temperatures with a homogenous composition and which can be dispensed with a uniform volumetric flow, without compromising the pumping function of the pumping device used in the milk foaming device. [Explanation of symbols]

[0095] 1 Milk frothing device 2. Pumping Device 3 Gas inlet 4. Housing 5. Means of transport 6 Bottom side 7 Top side 8 side wall 9 Mixing Chamber 10 Compressor 11 Connecting piece 12 Connecting piece 13 Connecting piece 14 Connecting piece 15 Bushing 16 Transport chamber 17 Feeding chamber 100 Beverage supply device 101 Distribution Device 102 Heating Device 102' Continuous Flow Heater 103 Pressure Regulating Device 104 Control Unit 105 Milk container 106 Air Source 107 Water supply A Exit side C1 axis C2 axis C3 axis DL Pressurized Gas Line d Pitch circle diameter (gear wheel) d K Tip diameter (gear wheel) DS throttle valve DS2 throttle valve DS3 throttle valve E Entrance side H Height L1 fluid passage L2 fluid passage L3 fluid passage L4 fluid passage M1 Milk supply line M2 Milk distribution line O1 opening (first access opening) O2 opening (second access opening) O3 opening (outlet opening) O4 opening (water supply line) RSV1 Check valve RSV2 check valve RSV4 check valve V-Valve V' Valve V'' valve WL Water Line X1 Rotation Axis X2 Rotation Axis

Claims

1. A milk foaming device (1) comprising a pumping device (2) having an inlet side (E) and an outlet side (A) for delivering milk from said inlet side (E) to said outlet side (A), wherein said inlet side (E) can be connected to a milk supply line (M1), and preferably cold milk is introduced into said pumping device (2) via said milk supply line (M1), wherein said outlet side (A) can be connected to a milk distribution line (M2) for distributing the foamed milk, characterized in that in the milk foaming device (1), a gas inlet (3) for introducing a pressurized gas, in particular pressurized air, is arranged at said outlet side (A) of said pumping device (2) for foaming said milk. Milk foaming device (1).

2. The milk foaming device (1) according to claim 1, characterized in that said pumping device (2) comprises a housing (4), conveying means (5) arranged in said housing (4), and at least a first access opening and a second access opening (O1, O2) arranged in said housing (4), and at least a first outlet opening (O3), wherein said first access opening (O1) is arranged at the inlet side upstream of said conveying means (5), said first outlet opening (O3) is arranged at the outlet side downstream of said conveying means (5), and said second access opening (O2) is said gas inlet (3) arranged at said outlet side, in particular in the region of said conveying means (5).

3. The milk foaming device (1) according to claim 1 or 2, characterized in that said first outlet opening (O3) and / or said second access opening (O2) comprises a nozzle and / or a throttle valve (DS2, DS3), or is designed as a nozzle and / or a throttle valve (DS2, DS3).

4. The milk foaming device (1) according to claim 1 or 2, characterized in that said pumping device (2) is designed as a gear pump having two gear wheels rotatably arranged around two mutually engaging and parallel rotating axes (X1, X2).

5. The milk foaming device (1) according to claim 4, characterized in that said gas access (3) is arranged in the immediate vicinity of the engagement of the gear wheel at said outlet side (A).

6. The housing (4) comprises a bottom side (6), a top side (7) and at least one side wall (8), the first access opening (O1) and the outlet opening (O3) being arranged in the side wall (8), and / or the second access opening (O2) being arranged in the top side (7) or the bottom side (6) of the enclosure (4). The milk frothing device (1) according to claim 2, characterized in that.

7. Each of the access openings (O1, O2) and / or the outlet opening (O3) is immersed in a respective fluid passage (L1, L2, L3) arranged in the housing (4), the fluid passages (L1, L2, L3) being designed to connect a milk supply line (M1), a milk distribution line (M2) or a pressurized gas line (DL). The milk frothing device (1) according to claim 2, characterized in that.

8. The milk frothing device (1) according to claim 7, characterized in that a check valve (RSV2, RSV4) is arranged in at least one fluid passage (L1, L2, L3).

9. The milk frothing device (1) according to any one of claims 2, 7, 8, characterized in that at least one fluid passage (L2) has another opening (O4) with an adjacent passage (L4) for forming a branch, and water can be introduced into the housing (4) via the other opening (O4).

10. The milk frothing device (1) according to any one of claims 2, 7, 8, characterized in that the second access opening (O2) has an opening diameter of at most 10 mm, preferably at most 5 mm, or particularly preferably at most 0.05 mm.

11. The first access opening (O1) has a first opening diameter, the first outlet opening (O3) has a third opening diameter, The milk frothing device (1) according to any one of claims 2, 7, 8, characterized in that the third opening diameter is smaller than the first opening diameter.

12. The gas inlet (3) can be connected to a compressor (10) for generating pressurized gas, or is connected to the compressor (10). The milk frothing device (1) according to any one of claims 1, 2, 7, 8, characterized in that.

13. The pressurized gas is provided under a supply pressure of at least 4 bar, preferably 6 bar, and / or The pressurized gas is provided under a supply pressure that exceeds 0%, 30%, and even 50% of the pressure at the outlet side (A) of the milk foaming device (1) when no pressurized gas is being supplied. The milk foaming device (1) according to any one of claims 1, 2, 7, and 8, characterized in that.

14. The milk foaming device (1) according to claim 12, characterized in that the compressor (10) comprises a buffer tank.

15. The milk foaming device comprises a pressure regulating device 103, and the pressure regulating device 103 A controllable proportional valve (V) arranged between the compressor (10) and the gas inlet (3), and / or A high-cycle on-off shut-off valve (V') placed between the compressor (10) and the gas inlet (3), and / or A discharge valve (V'') arranged in the pressurized gas line (DL) for discharging the compressed gas provided by the compressor (10) Comprises any one of, and / or The compressor (10) is controllable and is connected substantially directly to the gas inlet (3) The milk foaming device (1) according to claim 12, characterized in that.

16. A beverage preparation device (100), in particular for coffee and coffee-based mixed beverages, comprising the milk foaming device (1) according to any one of claims 1, 2, 7, and 8.

17. The beverage preparation device (100) comprises a dispensing device (101) for dispensing milk in a foamed or non-foamed state in a heated or non-heated state, and the outlet side (A) of the milk forming device (1) is connected to the dispensing device (101) via a milk dispensing line (M2). The beverage preparation device (100) according to claim 16, characterized in that.

18. The beverage preparation device (100) according to claim 16, characterized in that a heating device (102) is arranged in the milk dispensing line (M2).

19. The beverage preparation device (100) according to claim 18, characterized in that the heating device is designed as a continuous flow heater (102').

20. The heating device (102) is designed as a steam injector for feeding hot steam, in particular water steam, into the milk dispensing line (M2), and the steam injector is coupled to a steam source or comprises a steam source. The beverage preparation device (100) according to claim 18, characterized in that.

21. A method for producing foamed milk, wherein milk disposed in a housing (4) of a pumping device (2) is acted upon by a pressurized gas, in particular pressurized air, in the region of a movable conveying means (5) for conveying the milk from the low-pressure side of the pumping device (2) to the high-pressure side of the pumping device (2), and the pressurized gas is introduced into the milk at the high-pressure side.

22. The method according to claim 21, characterized in that the pressurized gas is at least substantially anhydrous pressurized gas or gas mixture, the gas or gas mixture having a temperature of less than 100°C, preferably less than 80°C, in particular less than 40°C, and the pressurized gas being preferably compressed air, compressed nitrogen, compressed oxygen or compressed carbon dioxide, or a mixture thereof, in particular nitrous oxide, and in particular not water vapor or wet steam.

23. The method according to claim 21, characterized in that the pressurized gas is applied to the milk in a pulsating manner.

24. The method according to claim 22, characterized in that the pulsation is brought about by a stutter valve or by a dynamically controlled start-up of a compressor (10).

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