Coffee grinder and method for grinding coffee beans

Abstract

The present application discloses a coffee grinder for grinding coffee beans and forming a certain dose of ground coffee directly in a filter basket, wherein the ground coffee has a bottom layer of ground coffee and an adjacent layer of ground coffee, the bottom layer of ground coffee has a first average particle size, and the adjacent layer of ground coffee has a second average particle size, and the coffee grinder comprises: a grinding part for grinding coffee beans; an electric motor for rotating at least one grinding part relative to another grinding part; and a device configured to change the rotation speed of the electric motor between a first speed and a second speed during the process of grinding coffee beans for forming a dose, wherein the second average particle size is smaller than the first average particle size and the first speed is greater than the second speed, or the second average particle size is larger than the first average particle size and the first speed is lower than the second speed.

Description

Technical Field

[0001] The present invention relates to a machine for grinding coffee beans. The machine for grinding coffee beans may be a separate machine or may be included in a machine for producing coffee-based beverages. Such machines are also referred to as "coffee grinders", "coffee grinders" or "mills" for short. More particularly, the present invention relates to a coffee grinder arranged to provide a dose of suitably layered ground coffee. Background Art

[0002] As is known, for preparing espresso, a quantity (usually called a "dose") of ground coffee is used. The dose may be a single dose, a double dose or a multi-dose. The dose of ground coffee is loaded into a filter basket, which is usually in the shape of a cup, which is open at the top and has micro-holes at its bottom. Usually, the dose of coffee is pressed inside the filter basket so as to form a coffee powder disc. The filter is in turn supported by a mobile filter (portafilter) which is arranged to be removably engaged inside a dispensing unit of an espresso machine. Espresso is obtained by passing hot water under pressure through the coffee powder disc.

[0003] Coffee powder is obtained using a coffee grinder. In known coffee grinders, the coffee beans are ground by passing them through a grinding member. Grinding members of flat, conical or cylindrical type are known. Usually, the grinding member of a coffee grinder comprises a stationary member and a member that rotates relative to the stationary member. For example, in a coffee grinder with conical grinders, one grinder is stationary and the other grinder is rotated by a motor. Some coffee grinders make it possible to change the distance between the grinders in order to change the particle size of the coffee powder.

[0004] US2016 / 220067A1 discloses a variable speed coffee grinder.

[0005] EP 2 810 592 A1 discloses a coffee grinder particularly for automatic coffee machines.

[0006] WO 2017 / 055433 A1 discloses a coffee grinder with variable speed.

[0007] DE 35 03 011 A1 discloses a device for setting the grinding body spacing of a particle mill.

[0008] CN107692874A discloses a rotation speed regulating speed of a grinding device. Summary of the invention

[0009] The applicant has conducted experiments related to ground coffee powder. For the purposes of the present invention, ground coffee powder is considered to be formed essentially of particles or granules having a theoretical characteristic size. This theoretical characteristic size will also be referred to as the term "equivalent diameter" hereinafter in this specification. Moreover, the abbreviated term "ground product" may be used as an alternative to the more complete term "ground coffee powder" or other similar expressions.

[0010] The Applicant has realised that all known coffee grinders, regardless of the manufacturer or type of grinding element or special mechanism used, produce a ground product containing particles that vary greatly in size from each other. The range of equivalent diameters covers three orders of magnitude, from a few micrometres to more than a millimetre.

[0011] A relatively large number of particles can be expressed as a special distribution called a "particle size distribution" or "particle size curve", which has a similar Figure 1 The development curve shown in (independent of the coffee grinder used).

[0012] A curve representing a particle size distribution is called a bimodal distribution. The high peak (on the right) is called the "first mode" and the low peak (on the left) is called the "second mode".

[0013] As mentioned above, the purpose of ground coffee is to be used in an espresso machine to dispense a coffee beverage.

[0014] Obviously, a particle size with a greater number of fine particles results in a smaller water flow, and therefore a "shorter" coffee in the same dispense time (compared to a particle size with a greater number of large particles).

[0015] Typically, each bartender adjusts his / her coffee grinder appropriately to obtain the particle size that, in his / her opinion, produces the best beverage.

[0016] Regardless of whether the machine has a flat grinder, a conical grinder or a cylindrical grinder, the smaller the distance between the grinding parts, the greater the number of fine particles and the smaller the number of large particles. The greater the distance between the grinding parts, the opposite will be true (i.e. the smaller the number of fine particles and the greater the number of large particles).

[0017] Typically, a bartender adjusts the grind setting whenever the coffee beans loaded into the hopper prior to grinding change. A change in coffee may be due to using a different brand or different packaging of the same brand.

[0018] An objective identified by the applicant is to reduce the sensitivity of the coffee grinder to variations in the coffee to be ground.

[0019] Another object identified by the Applicant is that of providing a coffee grinder capable of suitably modifying the organoleptic properties of the espresso obtained by grinding the product.

[0020] According to the applicant, the above objects are achieved by a coffee grinder capable of changing the particle size profile when grinding a dose of coffee.

[0021] US2016 / 220067A1 discusses at

[0019] that a coffee grinder with a variable speed motor is capable of grinding fine ground coffee more accurately and consistently at a lower speed than a conventional high-speed grinder. Different methods of brewing coffee (e.g., espresso) require that the coffee beans be cut into uniformly distributed, consistent particles. Existing coffee grinders that rotate at high speeds tend to crush the coffee beans rather than cut them, especially when the motor is started, resulting in inconsistent particle sizes.

[0022] US2016 / 220067A1 discloses a coffee grinder using a variable speed motor whose speed and starting torque characteristics can be adjusted by a programmable controller to accommodate various coffee preparation methods or coffee bean types while maintaining the ability to grind at high speeds when precision is not required.

[0023] Contrary to said teaching, the object of the present invention is to provide a dose of ground coffee with different layers having different average sizes directly in the filter basket.

[0024] According to a first aspect, there is provided a coffee grinder for grinding coffee beans and forming a dose of ground coffee in a filter basket, wherein the ground coffee has a bottom layer of ground coffee and an adjacent layer of ground coffee, the bottom layer of ground coffee having a first average particle size and the adjacent layer of ground coffee having a second average particle size, the coffee grinder comprising:

[0025] - Grinding part, used for grinding coffee beans;

[0026] - an electric motor for rotating at least one grinding element relative to the other grinding element; and

[0027] - means arranged to vary the rotational speed of the electric motor between a first speed and a second speed during the grinding of the coffee beans for forming a dose,

[0028] in,

[0029] The second average particle size is smaller than the first average particle size, and the first speed is greater than the second speed, or

[0030] The second average particle size is larger than the first average particle size, and the first speed is lower than the second speed.

[0031] An adjacent layer is a layer adjacent to and on top of the first layer. The first layer is produced first (so that the ground coffee is substantially located at the bottom of the filter basket) and the adjacent layer is produced directly after the first layer so that the respective ground coffee rests on the first layer. One or more layers can be provided on the adjacent layer, wherein the one or more layers have ground coffee particles having an average size that is different from the average size of the ground coffee in the adjacent layer.

[0032] According to an embodiment, the coffee grinder further comprises a rotation counter for counting the number of rotations of the grinding part relative to the other grinding part, wherein the speed changing device is configured to change the speed from a first speed to a second speed according to a set number of relative rotations of the grinding part and the other grinding part.

[0033] The set number of relative rotations can be any number (whole number or fractional number). Preferably, the set number of relative rotations is calculated as a function of the total set time to grind a dose or a function of the total number of rotations used to grind a dose. Also preferably, the set number of relative rotations is calculated as a function of the total number of layers in a dose.

[0034] It should be noted that the first speed is the speed that the motor reaches after a threshold number of rotations, which is counted from the start of the motor. The number of rotations can be set to any number between about 0.5 and about 3.0 (e.g., about 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0).

[0035] For example, when the threshold number of rotations is set to 1.0, the total number of rotations is set to 5, and the total number of layers is 2, the set number of relative rotations may be 2. In other words, a first speed is reached in the first rotation, the first speed is maintained for two revolutions, and then a second speed is maintained for the remaining two revolutions. However, grinding can also be set so that the number of rotations for the first layer is different from the number of rotations for the first layer. More than two layers can be provided.

[0036] According to an embodiment, the coffee grinder further comprises a timer, wherein the speed changing device is arranged to change the speed from the first speed to the second speed according to a set time period counted from the start of the electric motor.

[0037] The set time period can be calculated as a function of the total set time for grinding a dose. It is also preferred that the set time period can be calculated as a function of the total number of layers in the dose.

[0038] Preferably, a threshold time is considered. The threshold time is the time from when the motor is started to when the first speed is reached. The threshold time can be a portion of the total time to grind a dose. According to an embodiment, the threshold time can be between about 1 / 7 and about 1 / 4 of the total time to grind a dose. For example, the threshold time can be between about 1 / 6 and about 1 / 5 of the total time to grind a dose. When the total time is about 6 seconds, the threshold time can be between about 1 second and about 1.2 seconds.

[0039] For example, when the total time is 6 seconds, the threshold time is 1 second, and the total number of layers is 2, the change from the first speed to the second speed can be made after 3.5 seconds from the start of the motor.

[0040] According to an embodiment, the coffee grinder further comprises a weighing component for calculating the mass of the dose of ground coffee, wherein the speed variation device is arranged to vary the speed from the first speed to the second speed depending on the mass of the first part of the dose of coffee ground at the first speed.

[0041] Also in this example, it is preferred to take into account a threshold value and calculate the mass of the coffee dose after a threshold time or a threshold number of rotations. The threshold time can be a fraction of the total time used to grind a dose, as described above. The threshold number of rotations can be a fraction of the total number of rotations used to grind a dose, as described above.

[0042] The speed change device can be arranged to change the speed of the electric motor stepwise or continuously.

[0043] According to an embodiment, the coffee grinder further comprises an interface for selecting a speed profile for grinding a dose of coffee.

[0044] According to an embodiment, the coffee grinder further comprises an encoder for detecting the rotation speed of the electric motor.

[0045] According to a second aspect, the present invention provides a method for grinding coffee beans in order to obtain a dose of ground coffee in a filter basket, the ground coffee having a bottom layer of ground coffee and an adjacent layer of ground coffee, the bottom layer of ground coffee having a first average particle size and the adjacent layer of ground coffee having a second average particle size, the method comprising:

[0046] (a) providing a grinding part for grinding coffee beans;

[0047] (b) providing an electric motor for rotating one grinding component relative to the other grinding component; and

[0048] (c) during the grinding process, causing the at least one grinding component to rotate at a first speed relative to the other grinding component and then to rotate at a second speed,

[0049] in

[0050] The second average particle size is smaller than the first average particle size, and the first speed is greater than the second speed; or

[0051] The second average particle size is larger than the first average particle size, and the first speed is lower than the second speed.

[0052] According to an embodiment, the present invention further includes: counting the number of rotations of the grinding member relative to the other grinding member; and changing the speed from the first speed to the second speed according to the set number of relative rotations of the grinding member and the other grinding member.

[0053] According to an embodiment, the present invention further comprises changing the speed from the first speed to the second speed according to a set time period calculated from the start of the electric motor.

[0054] According to an embodiment, the invention further comprises changing the speed from the first speed to the second speed depending on the mass of the first part of the coffee dose ground at the first speed.

[0055] The speed change from the first starting speed to the second speed can be performed continuously or stepwise.

[0056] According to an embodiment, instead of a device arranged to cause the rotation speed of the electric motor to vary between a first speed and a second speed during the grinding of coffee beans to form a dose, an actuator arranged to cause the distance between one grinding part and another grinding part to vary during the grinding of coffee beans to obtain the dose of ground coffee can be provided.

[0057] The actuator may be arranged to vary the distance between the grinders continuously or stepwise during grinding of the coffee beans to obtain the dose of ground coffee.

[0058] The distance between the grinders can be varied during grinding of a dose from a first distance to at least a second distance, wherein the first distance is smaller than the second distance, so as to obtain at least a first portion of a dose of ground coffee having a first particle size and a second portion of a dose of ground coffee having a second particle size.

[0059] Preferably, the coffee grinder may further comprise an interface for selecting a speed profile or a distance profile for grinding a dose of coffee.

[0060] Preferably, the coffee grinder may further comprise an encoder for detecting the rotation speed of the electric motor.

[0061] According to another aspect, instead of varying the rotation speed of the electric motor during grinding of the coffee beans in order to obtain the dose of ground coffee, the distance between the grinding members is varied during grinding of the coffee beans in order to obtain the dose of ground coffee.

[0062] During the grinding of the coffee beans to obtain the dose of ground coffee, the distance between the grinders may be varied continuously or stepwise.

[0063] The distance between the grinders can vary from a first distance to at least a second distance during grinding of a dose, wherein the first distance is smaller than the second distance, so as to obtain at least a first portion of a dose of ground coffee having a first particle size and a second portion of a dose of ground coffee having a second particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The following is a detailed description of the present invention, which is provided by way of non-limiting examples and is to be read with reference to the accompanying drawings, in which:

[0065] - Figure 1 is a graph showing an example of a particle size distribution expressed on a logarithmic scale;

[0066] - Figure 2a A schematic diagram showing a dose of ground coffee with a standard particle size distribution obtained in a filter basket inserted inside a movable filter;

[0067] - Figure 2b A schematic diagram showing a dose of ground coffee obtained in a filter basket inserted inside a movable filter and having a particle size distribution varied according to the invention;

[0068] - Figure 3 shows a graph on a linear scale of two particle size distributions obtained at two different milling speeds;

[0069] - Figure 4 is a graph of two particle size distributions on a linear scale, a first particle size distribution being obtained at a constant speed and a second particle size distribution being obtained by combining milled products produced by two different speeds;

[0070] - Figure 5 is a schematic diagram of a coffee grinder according to an embodiment of the present invention; and

[0071] - Figure 6 is based on Figure 5 View of some parts of the machine. DETAILED DESCRIPTION

[0072] As briefly described above Figure 1is a graph showing an example of the particle size distribution of a dose of ground coffee. A curve showing the particle size distribution is called a bimodal distribution. The high peak (on the right, associated with larger sized particles) is called the "first mode", while the low peak (on the left, associated with smaller sized particles) is called the "second mode".

[0073] Applicants have conducted research and surprisingly found that it is possible to modify the particle size curve to increase the relative position of the first mode (in Figure 1 In other words, increasing the amplitude of the first mode reduces the need to adjust the particle size when the coffee in the hopper changes.

[0074] The applicant has conducted further research and surprisingly found that arranging the ground product in a suitable manner inside the filter basket can further reduce this sensitivity. In particular, it has been shown that better performance is obtained by arranging larger particles at the bottom and finer particles at the top.

[0075] Applicants have recognised that a coffee grinder that is able to change the particle size profile during the course of grinding a dose can reduce the sensitivity of the coffee grinder and achieve two objectives.

[0076] According to a first embodiment of the invention, the coffee grinder comprises grinding members whose distance is adjustable and varies during the grinding of a dose. Preferably, the distance between the grinding members can be electrically adjusted by an actuator (e.g. an electric motor or a linear actuator, such as a piston 8) and a suitable control circuit.

[0077] With the coffee grinder according to the first embodiment, it is possible to carry out the grinding of a dose D by varying (stepwise or continuously) the distance between the grinding members (during the grinding of a dose) so as to obtain a ground product having a first wider modality. In practice it has been found that when the distance between the grinders decreases, the first modality moves towards finer particles, whereas when the distance increases, the first modality moves towards larger particles.

[0078] Thus, for example, a coffee grinder that produces a first portion of a dose of powder using a greater distance between the grinders, and a smaller distance between the grinders to produce the remaining portion, will generally produce a ground product having a first modality with a wider bell shape. Thus, in general, starting with a certain distance between the grinders, and reducing that distance during the course of grinding a dose, will result in a ground product having a first modality with a wider bell shape.

[0079] The variation of the distance between the grinders during the grinding of a dose F can be continuous or stepwise. With the coffee grinder according to the first embodiment, it is also possible to provide, for example, a first layer of ground product using a greater distance (in order to obtain larger particles) and a second layer using a smaller distance (in order to obtain finer particles). Obviously, it is possible to obtain more than two layers, or, as described above, a continuous variation (single, double or multiple) by continuously varying the distance between the grinders during the grinding of a dose D.

[0080] The dose D shown in the figure is obtained by grinding the coffee beans without changing the distance between the grinders. Figure 2a In the process, the distribution of the ground product inside the filter is random and not controlled.

[0081] exist Figure 2b In the coffee machine according to the invention, the distribution inside the filter is suitably controlled. In particular, the bottom layer is characterized by larger particles on average, while the top layer is characterized by smaller particles on average. The bottom layer is obtained by keeping the grinder at a greater distance than the distance at which the grinder is located in the second part of the dose grinding operation, in which the top layer with finer particles on average is obtained.

[0082] According to another embodiment of the invention, the coffee grinder is arranged to vary the particle size during grinding of a dose by varying the relative rotation speed of the grinding parts. The expression "relative rotation" is understood to mean the rotation of one part relative to the other. Typically, one grinding part remains stationary while the other grinding part rotates.

[0083] Figure 3 The effect of the mill rotation speed on the particle size is shown. In particular, Figure 3 Two particle size curves obtained by maintaining a constant distance between the mills and by varying the rotation speed are shown. Figure 1 different, Figure 3 The curves in are on a linear scale in order to highlight the differences in the first mode.

[0084] It can be seen that at lower speeds, the first mode moves to the left and its relative magnitude (preponderance over the second mode) decreases.

[0085] At higher speeds, the first mode moves to the right and increases its relative amount.

[0086] The speed variation is preferably obtained by a suitable electronic speed regulator for the electric motor. Many devices of this type (which vary according to the type of motor used) are available on the market. According to an embodiment of the invention, the coffee grinder comprises a three-phase asynchronous electric motor and an inverter or any known frequency regulator for speed control.

[0087] According to an embodiment of the invention, the coffee grinder performs the grinding of a dose at a variable speed (stepwise and / or continuous) in order to obtain a dose of ground product having a first modality that is wider than normal.

[0088] In fact, according to what has been said above, when the rotation speed decreases, the first mode moves to the left, and when the rotation speed increases, the first mode moves to the right. Thus, for example, a coffee grinder according to the invention can be arranged to provide a portion of the powder dose at a higher speed and another portion of the powder dose at a lower speed. Overall the dose thus obtained will include a ground product with a wider bell shape of the first mode.

[0089] Figure 4 is a graph showing a comparison of two particle size curves. In particular, the graph shows a first particle size curve (dashed line) obtained at a single speed and a second particle size curve obtained at two speeds. The particle size curve obtained by combining powders obtained by performing two grinding operations at different speeds shows a greater dispersion (greater standard deviation) than the curve obtained at a constant speed (which curve produces the same total head loss).

[0090] According to the invention, it is preferred that, for example, a first layer (bottom layer) of ground product can be produced at a higher speed in order to obtain larger particles, and a second layer (top layer) can be produced at a lower speed in order to obtain finer particles. Figure 3 The particles belonging to the solid curve shown in will be deposited in the first layer, while the particles belonging to the dashed curve will be deposited in the second layer. Obviously, more than two layers can be obtained, or also a continuous variation can be obtained by continuously varying the speed.

[0091] According to the applicant, the increase in the amplitude of the bell-shaped shape corresponding to the first mode modifies the sensory aspects of the beverage. As is known, in fact, for the same dispensing time and flow rate, the particle size distribution determines the amount of beverage dispensed. In fact, the coffee powder causes a "head loss" or "pressure drop", which determines the flow rate of the beverage.

[0092] According to the present invention, it is possible to exceed the limitations of known coffee grinders and produce more particle size curves at the same head loss. For example, Figure 4 The two curves shown in are characterized by two different amplitudes of the bell shape of the first mode.

[0093] This means that although Figure 4 The two curves shown in result in the same steeping time, but the different size of the particles results in different contact areas between water and coffee grounds and therefore different solubility.

[0094] The choice of particle layering changes the total load loss. Arrange in reverse order Figure 3 The two curves shown in will result in two different head losses and thus in two different beverages. The wetting pattern of the coffee grounds inside the filter also results in different drainage during the extraction cycle.

[0095] Figure 5 The main components of a coffee grinder 1 according to an embodiment of the invention are shown in a very schematic form: 2 represents an electric motor for relative rotation of the grinder 3 or for moving the grinder 3; 4 represents an inverter for controlling the speed of the motor; 5 represents a control unit; and 6 represents an encoder (optional) for detecting the speed.

[0096] Figure 5 Also shown in schematic form is the path followed by the coffee to be ground up to the filter basket FT housed in the active filter PF.

[0097] According to an embodiment, the speed / distance of the grinder can be changed by the bartender via a suitable interface 7 ( Figure 6 ). The interface 7 can include, for example, a button (or buttons) for selecting a predetermined rotation speed, a predetermined distance between the grinders, a rotation speed profile, and a distance profile between the grinders. The interface may alternatively include a rotatable knob for selecting (continuously or stepwise) a plurality of rotation speeds (or distances between the grinders), or a touch screen for selecting from a plurality of available options / speeds. The interface 7 is connected to an inverter 4 (directly or through other means, such as a CPU 5), which is used to change the power frequency of the motor and thus the speed of the motor. Preferably, an option of selecting a rotation speed from the rotation speeds provided by the manufacturer or a user-selected speed can be provided. Preferably, a memory for storing rotation speed values ​​and / or speed profiles can be provided for grinding a dose (single, double or multiple) not at a constant speed, but at two (or more) different speeds or at a continuously varying speed.

[0098] The control unit 5 therefore transmits the rotational speed for the motor 2 to the inverter 4. The system can operate in open loop, ie without measuring the actual rotational speed of the motor, or in closed loop, ie by detecting the speed of the motor using dedicated means, such as an encoder 6.

Claims

1. A coffee grinder (1) for grinding coffee beans and forming a dose (D) of ground coffee having two layers in a filter basket (FT) in a single continuous grinding cycle, wherein: The ground coffee has a bottom layer of ground coffee and an adjacent layer of ground coffee, the bottom layer of ground coffee has a first average particle size, the adjacent layer of ground coffee has a second average particle size, and the coffee grinder comprises: - a grinding part (3) for grinding coffee beans; - an electric motor (2) for rotating at least one grinding element (3) relative to the other grinding element (3); and - speed variation means (4) arranged to vary the rotation speed of the electric motor (2) between a first speed and a second speed during the grinding of coffee beans for forming a dose (D), The speed changing device changes the relative rotation speed of the grinding parts to change the particle size, so that the second average particle size of the ground coffee in the adjacent layer is smaller than the first average particle size of the ground coffee in the bottom layer, and the first speed is greater than the second speed, or The second average particle size in the adjacent layer of ground coffee is larger than the first average particle size in the bottom layer of ground coffee, and the first speed is lower than the second speed.

2. The coffee grinder (1) according to claim 1, further comprising: A rotation counter for counting the number of rotations of a grinding component (3) relative to another grinding component (3), wherein: The speed changing device (4) is configured to change the speed from a first speed to a second speed according to a set amount of relative rotation of the grinding component (3) and the other grinding component (3).

3. The coffee grinder (1) according to claim 1, further comprising: Timer, where The speed changing device (4) is configured to change the speed from a first speed to a second speed according to a set time period calculated from the start of the electric motor (2).

4. The coffee grinder (1) according to claim 1, further comprising: a weighing means for calculating the mass of said dose of ground coffee, wherein The speed variation device (4) is arranged to vary the speed from a first speed to a second speed depending on the mass of a first portion of a dose of coffee ground at the first speed.

5. The coffee grinder (1) according to any one of claims 1 to 4, wherein: The speed variation device (4) is arranged to vary the speed of the electric motor (2) step by step.

6. The coffee grinder (1) according to any one of claims 1 to 4, wherein: The speed variation device (4) is arranged to continuously vary the speed of the electric motor (2).

7. The coffee grinder (1) according to any one of claims 1 to 4, further comprising: Interface for selecting the speed profile for grinding a dose (D) of coffee.

8. The coffee grinder (1) according to any one of claims 1 to 4, further comprising: The encoder (6) is used to detect the rotation speed of the electric motor (2).

9. A method of grinding coffee beans, the method obtaining in a filter basket (FT) in a single continuous grinding cycle a dose (D) of ground coffee having two layers, the ground coffee having a bottom layer of ground coffee and an adjacent layer of ground coffee, the bottom layer of ground coffee having a first average particle size and the adjacent layer of ground coffee having a second average particle size, the method comprising: (a) providing a grinding part (3) for grinding coffee beans; (b) providing an electric motor (2) for rotating one grinding component (3) relative to the other grinding component (3); and (c) during the grinding process, causing at least one grinding component (3) to rotate at a first speed relative to another grinding component (3), and then to rotate at a second speed, in, The second average particle size in the adjacent layer of ground coffee is smaller than the first average particle size in the bottom layer of ground coffee, and the first speed is greater than the second speed; or The second average particle size in the adjacent layer of ground coffee is larger than the first average particle size in the bottom layer of ground coffee, and the first speed is lower than the second speed.

10. The method according to claim 9, further comprising: Counting the number of rotations of the grinding component (3) relative to the other grinding component (3); And the speed is changed from a first speed to a second speed according to a set amount of relative rotation of the grinding component (3) and the other grinding component (3).

11. The method according to claim 9 or 10, further comprising: The speed is changed from a first speed to a second speed according to a set time period calculated from the start of the electric motor (2).

12. The method according to claim 9 or 10, further comprising: The speed is varied from the first speed to the second speed depending on the mass of the first portion of the dose of coffee ground at the first speed.

13. The method according to claim 9 or 10, wherein: The speed change from the activated first speed to the second speed can be performed continuously or stepwise.

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