MILK FROTHER AND COFFEE MACHINES

Description

[0001] The invention relates to a milk frother for frothing milk for a coffee machine, with an adjusting device by means of which an adjustment of a milk flow to be supplied to the milk frother is possible, as well as to a coffee machine with a corresponding milk frother.

[0002] A milk frother for a coffee machine is known, for example, from EP 2 695 558 A1.

[0003] For some time now, conventional coffee machines have been equipped with milk frothers, which can be used to froth milk into foam. The milk frother typically froths milk by blending a mixture of air, milk, and steam, which is used as the propellant to propel the air-milk mixture through a jet pump in the milk frother. The steam also serves to heat the air-milk mixture to a foaming temperature.

[0004] The main advantages of automatic coffee machines are their quick preparation and the various settings available for each cup regarding coffee intensity and temperature. Another advantage is the automatic production of mixed drinks, i.e. coffee with warm milk or milk foam, or even milk foam as a separate drink. All that is required is an additional container of milk and connected to the system. The milk usually does not have its own heating circuit and is therefore heated by the steam generated in the coffee machine. Milk foam is created by switching on an air stream, so that drinks such as cappuccino and latte macchiato can be made at the touch of a button. The consistency and temperature increase experienced by the milk foam due to the steam are usually predetermined by predefined parameters.

[0005] A disadvantage of conventional milk frothers is that the temperature of the finished milk foam also depends on the temperature of the milk used. This can vary, for example, from a normal refrigerator temperature for milk that has just been taken out of the refrigerator to a normal room temperature for milk that has been out of the refrigerator for a long time. Accordingly, with a constant temperature increase due to the steam, the foam temperature or the temperature of the finished milk foam varies by 20° C in extreme cases. Up to now, this could only be countered by considerable recording and adjustment work using controlled valves, as known, for example, from EP 4 062 808 A2. Recording the temperature of the milk used, i.e. of the milk flow being fed in, is particularly complex.

[0006] The object of the present invention is therefore to provide an improved or at least alternative milk frother which in particular overcomes the disadvantages known from the prior art.

[0007] This problem is solved according to the invention by the subject matter of independent claims 1 and 10. Preferred embodiments are the subject matter of the dependent claims.

[0008] The present invention is based on the general idea of providing, for the first time, a structurally simple and intuitively operated adjustment device which automatically adapts to the temperature of the milk used, i.e. of the milk flow to be supplied. In this way, the required foam temperature or the temperature of the finished milk foam, or also the target temperature, can be constantly achieved, regardless of how long the milk has been taken from the refrigerator. The milk frother or coffee maker according to the invention comprises for this purpose an adjustment device via which an adjustment of a milk flow to be fed to the milk frother is possible, which is characterized in that the adjustment device comprises at least one element which changes shape depending on the temperature. The invention thus departs from the principle of recording the temperature separately as a measured value and controlling an electronically controllable valve accordingly.Rather, the element that changes its shape depending on the temperature can be used to directly influence the setting of the adjustment device based on the temperature of the milk flow to be fed in. The adjustment device can therefore adjust itself accordingly without the need for complex recording and control or any action from an operator, and yet a constant foam temperature can still be achieved. A steam flow for heating the milk to a target temperature of the finished milk foam can, for example, be designed for milk that is at room temperature. When using milk straight from the refrigerator, i.e. at a significantly lower temperature, the element that changes its shape depending on the temperature can influence the setting of the adjustment device in such a way that the flow of milk fed into the milk frother is reduced.With an unchanged steam flow, the same amount of energy from the steam is available to heat a comparatively smaller amount of milk. This allows the colder milk to experience a greater temperature increase with the steam flow unchanged, and the temperature of the finished milk foam can still reach the target temperature.

[0009] A temperature-dependent shape-changing element is known as such for applications at comparatively high temperatures and can be realized, for example, with a shape memory material. A shape memory material can be, for example, a shape memory alloy - also called memory metal - or a shape memory polymer. However, with appropriate shaping, a temperature-related linear expansion of a component should also be understood as a changed shape. The invention makes use of the knowledge that with appropriate shaping, a component made of metal and a component made of a plastic such as a conventional PE or PP can have significantly different linear expansions, even in the range of normal room temperature and below. With appropriate arrangement of the two components, e.g.When a PE beam is clamped in a metal holder, the varying linear expansion can result in a significant change in shape even within the temperature range mentioned. This temperature-dependent change in shape can be advantageously used to influence the setting of the milk flow to be fed to the milk frother using the adjustment device according to the invention.

[0010] In an advantageous development of the inventive solution, the temperature-dependent shape-changing element is designed to change its shape reversibly. This allows the advantages of the inventive solution to be utilized not only with disposable products, but preferably over the entire service life of a durable milk frother or coffee machine.

[0011] In a further advantageous development, the temperature-dependent shape-changing element is provided by arranging a flexible milk line adjacent to two components with different thermal expansion coefficients, in particular between the two components. This means that the temperature-dependent shape-changing element can be easily mounted on the flexible milk line and does not have to come into direct contact with the milk. The temperature-dependent shape-changing element can therefore also have components that are not specifically designated for food contact. A flexible milk line is understood here in particular to mean a milk line with a flexible section. The entire milk line can be flexible, or just a section in the area of the temperature-dependent shape-changing element.

[0012] In a further advantageous development, the temperature-dependent shape-changing element is configured such that, when the temperature of the milk flow to be supplied is less than or equal to 15°C, it reduces the diameter of the flexible milk line relative to a temperature of greater than or equal to 25°C. This ensures that the milk flow to be supplied is throttled even when the milk used has a temperature just below, but significantly below, a normal room temperature of, for example, 20°C to 25°C. This means that, even when the milk flow to be supplied is less than 15°C and the steam flow remains unchanged, the target temperature of the finished milk foam can be achieved without temperature measurement or user adjustment.

[0013] The diameter of the flexible milk line should be understood here in particular as the smallest distance between the inner walls of the flexible milk line perpendicular to a longitudinal direction of the flexible milk line. In simple terms, this could be referred to as the inner diameter of the flexible milk line. However, a reduced diameter should also be understood here in particular if a flexible hose made of a silicone material, for example, is compressed, i.e. if the flow resistance of the flexible milk line increases due to an external influence. If, for example, a flexible hose is almost completely compressed so that almost no fluid can flow through, strictly speaking, the distance between the walls of the hose in the direction of pressure is the smallest and the distance perpendicular to the direction of pressure is the largest. However, this should be understood here in particular as a reduction of the term diameter.

[0014] In a further advantageous development, the element which changes shape depending on the temperature is designed in such a way that it reduces a diameter of the flexible milk line more when the temperature of the milk flow to be supplied is less than or equal to 10°C than when the temperature is 15°C. As a result, the target temperature of the finished milk foam can be achieved without temperature measurement or user adjustment, particularly in a most frequently occurring temperature range of the milk flow to be supplied of less than or equal to 10°C with an unchanged steam flow.

[0015] In a further advantageous development, the temperature-dependent shape-changing element is configured such that, at a temperature of the milk flow to be supplied of less than or equal to 6°C, it reduces the diameter of the flexible milk line more than at 10°C. This allows the aforementioned advantages to be achieved even when, after a milk container that has been standing next to the coffee machine at a high room temperature for a long time has been emptied, new milk is used fresh from a very cold refrigerator. Since no user adjustment is required for this, particularly intuitive handling is also enabled.

[0016] In a further advantageous development, the temperature-dependent shape-changing element comprises a holder and a counterholder that act on a flexible milk line. This not only allows for a particularly simple and effective temperature-dependent shape change, but also enables a simple structure and, at the same time, easy cleaning of all components.

[0017] In a further advantageous development, the counterholder comprises a material with a higher coefficient of thermal expansion than the holder. This allows the counterholder to be easily mounted in the holder and also fixes the flexible milk line in the area affected by the temperature-dependent deformation.

[0018] In a further advantageous development, the counterholder comprises a plastic material, in particular PP or PE, and the holder comprises a metal part or a reinforced plastic material. This provides a particularly cost-effective way to achieve the temperature-dependent deformation for adjusting the adjustment device – and, in the version with a metal part, provides a visually and haptically very appealing option at only a very slightly higher cost.

[0019] The aforementioned problem is solved particularly advantageously by a coffee machine with a milk frother and an adjustment device that includes at least one element that changes shape depending on the temperature. In addition to the aforementioned advantages, the adjustment device can also be used to secure the flexible milk line on the coffee machine.

[0020] Preferred embodiments of the invention are illustrated in the drawings and explained in more detail in the following description, wherein like reference numerals refer to like or similar or functionally identical components. They show, schematically, Fig. 1 shows a milk frother according to the invention with an adjustment device in a coffee machine according to the invention, Fig. 2a shows a schematic sectional view through the adjustment device according to the invention at a temperature of the milk flow to be supplied of 25° C, and Fig. 2b shows a view as in Fig. 2a , but at a temperature of the milk stream to be supplied of 10° C.

[0021] According to the Figure 1 , the milk frother 1, which is installed in a coffee machine 2, has an adjustment device 3. In Figure 1For a better overview, the adjustment device is shown at a distance from the milk frother 1, but it can also be arranged directly on the milk frother 1. The adjustment device 3 can be used to adjust the milk flow to be fed to the milk frother 1. For this purpose, the adjustment device has the Figure 2a and Figure 2bschematically shown in partial section is an element 4 which changes its shape depending on the temperature. The element 4, which changes its shape depending on the temperature, comprises a holder 6 made of metal and a counter-holder 7 made of PE, which act on a flexible milk line 5. In the present example, the flexible milk line 5 is formed by a silicone hose. In the present example, the metal holder 6 is assembled from five individual semi-finished products to form a type of rail, but it can, for example, be bent from a sheet metal part or be made by profile casting. It can also be made from fiber-reinforced plastic, for example, by injection molding or by other known processes. In the present example, the counter-holder 7 is formed as a simple strip made of a PE material, with which the flexible milk line 5 is fixed in the holder 6.

[0022] In Figure 2aIt is shown that the holder 6 and the counterholder 7 act on the flexible milk line 5 at a temperature of the milk flow to be supplied of 25°C, but its inner diameter remains unchanged and corresponds, so to speak, to the raw state of the flexible milk line 5. The holder 7 is made as a straight, strip-shaped bar made of PE material and is clamped against the flexible milk line 5 during assembly in the holder 6. This causes it to be bent and exerts a force on the flexible milk line 5, which in this case is not yet sufficient to deform the flexible milk line 5. For a target temperature of the finished milk foam of 65°C to 68°C, a temperature increase of 40°C to 43°C is necessary.A steam flow supplied to the milk frother 1 is designed such that the milk is sucked in as a milk flow to be fed to the milk frother 1 via the flexible milk line 5 from a milk container (not shown) by a jet pump (not shown) in the milk frother 1. The milk flow to be fed to the milk frother 1 is limited by the inner diameter of the flexible milk line 5. The steam flow supplied to the milk frother 1 is also designed such that the sucked-in 25°C warm milk experiences a temperature increase of 40°C to 43°C. This achieves the target temperature of the finished milk foam of 65°C to 68°C.

[0023] In Figure 2bIt is shown that the holder 6 and the counterholder 7 act on the flexible milk line 5 at a temperature of 10° C of the milk flow to be supplied in such a way that its inner diameter is reduced in the direction of pressure. This is achieved by the fact that the lower temperature of the milk flow to be supplied in the counterholder 7 made of PE is compensated by its higher thermal expansion coefficient and the Fig. 2 a and b corresponding shape and installation position a significantly more reduced

[0024] Longitudinal extension (in Fig. 2a and 2b essentially from top to bottom) than with the metal holder 6. In other words, the counterholder 7 contracts more strongly in the longitudinal direction than the holder 6. By clamping the counterholder 7 in the holder 6, the shape therefore also changes and the force acting on the flexible milk line 5 increases. As a result, compared to the temperature in the example according to Figure 2aThe shape of the temperature-dependent shape-changing element 4 is changed in such a way that an adjustment, in this case a reduction, of the milk flow to be supplied to the milk frother 1 occurs. Consequently, the supplied milk flow experiences a relatively larger temperature increase due to the constant steam flow, so that a target temperature of 65°C to 68°C for the finished milk foam can be achieved without the need for temperature measurement or user adjustment.

[0025] As in Figure 1 As can be seen, the adjustment device 3 in the coffee machine 2 also serves to fix the flexible milk line 5 on the coffee machine 2. In addition to the advantages already mentioned, this also allows for a reduction in manufacturing costs.

[0026] With the milk frother 1 according to the invention or the coffee machine 2 according to the invention, it is possible for the first time with little effort and intuitive operation to achieve a constant froth temperature or temperature of the finished milk froth regardless of the temperature of the milk used, ie of the milk flow to be supplied. List of reference symbols

[0027] 1Milk frother 2Coffee machine 3Adjustment device 4Temperature-dependent shape-changing element 5Flexible milk line 6Holder 7Counterholder

Claims

1. Milk frother (1) for frothing milk for an automatic coffee machine (2), having an adjustment device (3), by way of which it is possible to adjust a milk stream to be supplied to the milk frother (1), characterised in that the adjustment device (3) comprises at least one element (4) which changes shape depending on temperature.

2. Milk frother according to claim 1, characterised in that the element (4) which changes shape depending on temperature is designed to reversibly change its shape.

3. Milk frother according to claim 1 or 2, characterised in that the element (4) which changes shape depending on temperature is provided so that a flexible milk line (5) is arranged adjacent to two components with different thermal coefficients of linear expansion, in particular between the two components.

4. Milk frother according to one of claims 1 to 3, characterised in that the element (4) which changes shape depending on temperature is designed such that at a temperature of the milk stream to be supplied of less than or equal to 15°C, it reduces a diameter of the flexible milk line (5) relative to a temperature of greater than or equal to 25°C.

5. Milk frother according to one of claims 1 to 4, characterised in that the element (4) which changes shape depending on temperature is designed so that at a temperature of the milk stream to be supplied of less than or equal to 10°C, it reduces a diameter of the flexible milk line (5) more significantly than at 15°C.

6. Milk frother according to one of claims 1 to 5, characterised in that the element (4) which changes shape depending on temperature is designed so that at a temperature of the milk stream to be supplied of less than or equal to 6°C, it reduces a diameter of the flexible milk line (5) more significantly than at 10°C.

7. Milk frother according to one of the preceding claims, characterised in that the element (4) which changes shape depending on temperature comprises a support (6) and a counter support (7), which act on a flexible milk line (5).

8. Milk frother according to claim 7, characterised in that the counter support (7) comprises a material with a higher thermal coefficient of linear expansion than the support (6).

9. Milk frother according to claim 8, characterised in that the counter support (7) comprises a plastic material, in particular a PP or a PE, and the support (6) comprises a metal part or a reinforced plastic material.

10. Automatic coffee machine (2), having a milk frother (1) and an adjustment device (3) according to one of the preceding claims.