Patent Description:
As is known, the final result of the brewing is influenced by a variety of parameters, depending or not on the user's preferences.

For example, the final particle size of ground coffee powder is one of the most important variables in determining the final result.

The final particle size of the coffee powder heavily influences the hydraulic conditions of the percolation, determining the pressure drop of the percolation water and consequently the flow rate provided by the pump and the thermal behaviour of the boiler.

A finer grinding leads to a greater extraction of the substances contained in the coffee, producing a stronger and more full-bodied drink and with the production of a lot of cream, while a coarser grinding is more suitable for the preparation of a less extracted coffee with less cream.

The definition of the correct dose of ground coffee at a given particle size in accordance with the user's taste is made difficult by the variability of many other parameters depending on the type of coffee used, in particular by the batch, the brand, the roasting, its moisture content, and on the other side by the grinder, in particular by the grinding system, the mechanical adjustment once it has been broken in, the wear of the grinders, and the quantity of coffee introduced.

<CIT> discloses a time-based grinder control method, in which the quantity of ground coffee is set by the user via an interface. The controller of the grinder varies the activation time of the grinder as a function of the setting of the particle size of the coffee powder selected by the user. <CIT> discloses a device for grinding coffee beans comprising a controller, wherein the controller is configured to acquire the current value of the number of turns of the motor or the grinder such that when a pre-determined threshold value is achieved, the motor is stopped.

The disadvantage of these methods is that they do not take into account a multiplicity of ancillary conditions which can affect the final result.

The technical task of the present invention is therefore to make a device for grinding coffee and its control method which make it possible to eliminate the cited technical drawbacks of the prior art.

As part of this technical task, an object of the invention is to provide a correct quantity of ground coffee taking into account both user-selectable preferences and ancillary conditions which cannot be determined by the user.

The technical task, as well as these and other objects, are obtained according to the present invention by a grinding device for grinding coffee beans, comprising a hopper for the coffee beans, grinders, an interface for the user for selecting the quantity of ground coffee in a range of values of selectable quantities of coffee powder, an electric motor supplied by mains electricity voltage for driving the grinders, characterised in that it comprises measuring means for measuring the mains electricity voltage and an electronic controller configured to:.

The present invention also relates to a method for controlling a grinding device for grinding coffee beans having grinders drivable by an electric motor supplied by a mains electricity voltage, characterised in that it comprises the following steps:.

Advantageously the association, for each quantity of ground coffee selectable by a user, of the grinding times with the corresponding values of the mains electricity voltage is experimentally determinable.

The association can be determined experimentally and be represented by a mathematical law or by a table which, for each value of ground coffee quantity selectable by a user, establishes a two-way correspondence between grinding time and mains electricity voltage.

Therefore, the present invention allows to compensate for the temporal variations in mains supply voltage due to the variability of the load of the electricity distribution mains which, for example, can vary significantly between day and night when many industrial plants are stopped.

Dispensing the correct quantity of ground coffee obtained by modifying the grinding time as the mains supply voltage changes improves the user experience, since they can taste a coffee with organoleptic properties corresponding to their choices.

The quantity of ground coffee selectable by the user is linked to several parameters, including the origin of the coffee, the roasting degree of the coffee beans, the particle size of the ground coffee, the mechanical and/or electrical tolerances of the grinding device.

Taking all these parameters into account, the user selects the quantity of ground coffee and the electronic controller, once the selection made by the user has been acquired, determines the grinding time based on the detected mains supply voltage. Further features and advantages of the invention will more fully emerge from the description of a preferred but not exclusive embodiment of the device and relative control method according to the invention, illustrated by way of non-limiting example in the accompanying figures of the drawings, in which:.

The coffee bean grinding device <NUM> can be of the stand-alone type or, as shown in <FIG>, can be integrated in a coffee machine <NUM>.

The grinding device <NUM> comprises in a known manner an electronic controller <NUM>, an interface <NUM> with the user for selecting the quantity of ground coffee in a range of selectable coffee powder quantity values, a coffee bean loading hopper <NUM>, grinders <NUM>, <NUM> which receive the coffee beans from the loading hopper <NUM>, and an electric motor <NUM> powered by a mains electricity voltage for driving the grinders <NUM>, <NUM>. The electric motor <NUM> can be a typical universal motor or a direct current motor, but could be a different type of motor.

The user interface <NUM> can comprise various types of selectors, e.g., knobs and/or levers and/or buttons, e.g., virtual buttons made using "touch screen" technology. In <FIG>, the interface <NUM> includes at least a first selector <NUM> and a second selector <NUM>. As will be seen below, the first selector <NUM> discriminates whether the dispensing is of only one or two doses of ground coffee, and the second selector <NUM> indicates the quantity of ground coffee requested by the user.

The grinders <NUM>, <NUM> can be driven in relative rotation by the electric motor <NUM>.

In particular, the grinder <NUM> includes a rotating grinder <NUM> and a non-rotating grinder <NUM> coaxial with respect to an axis <NUM> and delimiting a gap <NUM>, which determines the particle size, where the grinding is performed.

The grinding device typically further comprises means for adjusting the particle size of the ground coffee configured to change the distance between the grinders <NUM>, <NUM> and possibly also a sensor for detecting the distance between the grinders in communication with the electronic controller. Such a sensor for detecting the distance between the grinders can also not be included.

The particle size adjustment means comprises an adjustment ring <NUM> which can be driven to move the non-rotating grinder <NUM> parallel to the axis <NUM> so as to be able to change the width of the gap <NUM>.

A grinding device with a construction different from that described above obviously falls within the scope of the invention, as long as it falls within the scope of the appended claims.

The coffee machine <NUM> in a known manner comprises a brewing water supply pump <NUM> connected in suction to a tank <NUM> or directly to the water mains, with a brewing water heating boiler <NUM>, and with a brewer <NUM>.

In the illustrated case in which the grinding device <NUM> is integrated in the coffee machine <NUM>, it is possible to include a single electronic controller <NUM> and a single user interface <NUM> for both.

The coffee machine <NUM> can be automatic with direct dispensing of the quantity of ground coffee into the brewer or, as illustrated in <FIG>, manual with dispensing of the quantity of ground coffee into a filter 18a, 18b of a filter holder <NUM> which can be gripped by a handle <NUM> to be coupled by hand to the head of the brewer <NUM>.

The filter holder <NUM> is configured to interchangeably house a single-dose filter 18a of ground coffee or a double-dose filter 18b of ground coffee.

Advantageously, the grinding device <NUM> comprises means <NUM> for measuring the mains electricity voltage which powers the electric motor <NUM>, whether universal or in direct current or other types.

The means for measuring <NUM> the mains electricity voltage can be made by a dedicated electronic circuit in communication with the electronic controller <NUM>.

The electronic controller <NUM> is configured to: associate, for each value of a selectable quantity of ground coffee, a series of grinding time values with a series of corresponding mains electricity voltage values; acquire a value of a quantity of ground coffee selected by the user via the interface <NUM>; detect a mains electricity voltage value by the measuring means <NUM>; for the acquired value of a quantity of ground coffee selected by the user, set the grinding time value corresponding to the detected mains electricity voltage value; and drive the grinders <NUM>, <NUM> for the set grinding time.

More precisely, the electronic controller <NUM> is configured to detect the mains electricity voltage before the grinders are driven.

For example, when the user performs the selection and imparts the grinding command via the interface <NUM>, the measuring means <NUM> measures the mains electricity voltage and communicates it to the electronic controller <NUM> before the latter can start the grinding.

Alternatively, the measurement of the electrical voltage can be updated at regular time intervals and the last measurement acquired by the measuring means <NUM> is communicated to the electronic controller <NUM> before the latter can start the grinding. The electronic controller <NUM> advantageously stores in its memory mathematical laws and/or tables, determined experimentally, which represent the association, for each quantity of selectable ground coffee, of the grinding time values with the corresponding values of the mains electricity voltage.

The association defines an inverse correlation between the grinding time values and the corresponding mains electricity voltage values.

The fine selection by the user of the quantity of ground coffee is linked to various parameters including the particle size of the ground coffee, the origin of the coffee, the roasting degree of the coffee beans, the mechanical and/or electrical tolerances of the grinding device.

The fine selection of the quantity of ground coffee is performed with the second selector <NUM>.

With the same choice of the aforesaid parameters represented by the final selection made with the second selector <NUM>, the user has the possibility, always through the interface <NUM>, to choose with the first selector <NUM> among a first coarse quantity of ground coffee if he/she uses the filter 18a with a single dose of ground coffee for the brewing and a second coarse quantity of ground coffee if he uses the filter 18b with a double dose of ground coffee for the brewing.

Ultimately, the first selector <NUM> of the interface is used for the coarse selection of the quantity of ground coffee according to the type of filter which the user decides to use, while the second selector <NUM> is used for the fine selection of the quantity of ground coffee according to the aforesaid parameters.

To clarify how the grinding time is associated with the mains voltage, we refer to <FIG> which shows four mathematical functions, determined experimentally. Each function yij which refers to a specific quantity of selected ground coffee matches the grinding time to the mains electricity voltage.

The mathematical functions can be polynomial functions of degree n.

For example but not necessarily, the mathematical functions shown in <FIG> are of the second degree, and therefore describe parables.

Therefore: the function y<NUM> determines the grinding time when the mains voltage varies, for the minimum value of the quantity of selectable ground coffee in the single-dose filter 18a; the function y<NUM> determines the grinding time when the mains voltage varies for the minimum value of the quantity of selectable ground coffee in the double-dose filter 18b; the function y1N determines the grinding time when the mains voltage varies, for the maximum value of the quantity of selectable ground coffee in the single-dose filter 18a; and the function y2N determines the grinding time when the mains voltage varies, for the maximum value of the quantity of selectable ground coffee in the double-dose filter 18b.

As a rule, each quantity value of selectable ground coffee "ij" corresponds to a function yij.

Therefore, there are N functions yij for when the single-dose filter 18a is used and other N functions yij for when the double-dose filter 18b is used.

However, it is alternatively possible to adopt a simplified logic which consists in determining only y<NUM> , y<NUM>, y1N, y2N, i.e., determining the function yij only for the minimum and maximum value of the quantity of ground coffee and envisaging, for each mains voltage value, a predetermined relationship, for example linear, between the value of the selected quantity of ground coffee and the grinding time value; this is both when using the single-dose filter 18a of ground coffee (i =<NUM>) and when using the double-dose filter 18b of ground coffee (i =<NUM>).

In practice, through the interface <NUM>, the user selects the type of filter with the first selector <NUM> and the precise value of the quantity of ground coffee with the second selector <NUM>.

The electronic controller <NUM> acquires the value of the quantity of ground coffee selected by the user and the value of the mains electricity voltage.

The electronic controller <NUM> selects the mathematical function or the table combined with the request processed by the user, and based on the electricity voltage value detected, uses the mathematical function or the table selected to calculate the grinding time and sets the value of the grinding time thus calculated for driving the grinders <NUM>, <NUM>.

The coffee been grinding device and its relative control method thus conceived are susceptible to numerous modifications and variants within the scope of the appended claims. Moreover, all details may be replaced with other technically equivalent elements within the scope of the appended claims.

Claim 1:
A grinding device (<NUM>) for grinding coffee beans, comprising a hopper (<NUM>) for the coffee beans, grinders (<NUM>, <NUM>), an interface (<NUM>) for the user for selecting the quantity of ground coffee in a range of values of selectable quantities of coffee powder, and an electric motor (<NUM>) supplied by mains electricity voltage for driving said grinders (<NUM>, <NUM>), characterised in that it comprises measuring means (<NUM>) for measuring the mains electricity voltage and an electronic controller (<NUM>) configured to:
- associate, for each value of a selectable quantity of ground coffee, a series of grinding time values with a series of corresponding values of the mains electricity voltage;
- acquire a value of a quantity of ground coffee selected by the user via said interface (<NUM>);
- detect by said measuring means (<NUM>) a mains electricity voltage value;
- for the acquired value of a quantity of ground coffee selected by the user, set the grinding time value corresponding to the detected mains electricity voltage value; and
- drive the grinders (<NUM>, <NUM>) for the set grinding time value.