Coffee machine and method for calculating grinding time of coffee grinder incorporated in said coffee machine

Abstract

A coffee machine (1) comprises: a coffee grinder (6) of coffee; a brewing cylinder (3) which can be moved in a translation direction (T) and which presents a brewing chamber (4); an ejection piston (22) accommodated in the brewing cylinder (3) in a sliding manner along the translation direction (T); a closing piston (21) of the brewing chamber (4); a controller (20) having, in its memory, an algorithm for calculating the grinding time of the grinder (6), the controller (20) being programmed to calculate the weight thereof from a measurement of the height of the dried used coffee grinding charge (7), to which the calculation algorithm is fed a value of the calculated weight, and updating the grinding time of the grinder (6) for a subsequent dispensing cycle.

Description

[0001] Specification

[0002] The present invention relates to a coffee machine and a method for calculating a grinding time of a coffee grinder incorporated in the coffee machine.

[0003] It is known that the correct execution of the dosing cycle involves loading the correct amount of ground coffee into the brewing chamber.

[0004] For the same grinding time, the amount of ground coffee dispensed depends on the flow rate of the grinder, which can vary over time due to component wear.

[0005] Some known espresso machines have algorithms for updating the grinding flow rate of the coffee grinder so that, knowing the actual grinding flow rate, the grinder can be operated for the time required to dispense the exact amount of ground coffee required for a selected recipe.

[0006] Some espresso machines are able to calculate the amount of ground coffee in the brewing chamber by obtaining the value of a calculated variable from a pressing step of loading the ground coffee that must precede the brewing step.

[0007] Obviously, this calculation method cannot be used in coffee machines that also dispense brewed drip or American coffee, because in this case there is no pressing step upstream of the brewing step.

[0008] Therefore, there is a need to provide a coffee machine that can accurately control the amount of ground coffee dispensed into the brewing chamber, regardless of whether an espresso or drip coffee or American coffee brewing cycle is selected.

[0009] Therefore, the technical task of the present invention is to develop a coffee machine and a method for calculating a grinding time of a coffee grinder incorporated in the coffee machine, which will eliminate the technical deficiencies existing in the prior art.

[0010] In the context of this technical task, an object of the present invention is to implement a coffee machine that can accurately execute a dosing cycle according to the specifications of a coffee recipe selected by a user.

[0011] According to the technical task of the present invention and these and other purposes, it is achieved by a coffee machine, which includes: a coffee grinder; a brewing cylinder that can move along a translation direction and presents a brewing chamber configured to receive the ground coffee charge dispensed from the grinder; an ejection piston that can move along the brewing chamber to discharge the used ground coffee charge; a closing piston of the brewing chamber, wherein the closing piston can move in the opposite direction and under the action of an elastic device along the translation direction; a controller that has an algorithm for calculating the grinding time of the grinder in its memory, and the controller is programmed to drive a dispensing cycle, which sequentially provides: a closing step of the brewing chamber, wherein the brewing cylinder moves towards the closing piston; a brewing step, wherein the brewing cylinder stops; and a drying step, wherein the brewing cylinder further moves towards the closing piston to compress the used ground coffee charge against the closing piston and discharge the liquid contained therein into a discharge pipe equipped with a discharge valve. The coffee machine is characterized by the fact that it includes detection means for detecting the height of the dried used ground coffee charge present in the brewing chamber, and the controller is programmed to calculate the weight of the dried used ground coffee charge based on the detected value of the height, feed the calculated value of the weight to the calculation algorithm to update the grinding time of the grinder, and use the updated grinding time for subsequent dispensing cycles.

[0012] In a preferred embodiment of the present invention, the detection means includes a sensor for the threshold position of the closing piston and a sensor for the current position of the brewing cylinder, and the controller is programmed for:

[0013] - moving the brewing cylinder together with the empty brewing chamber towards the closing piston until a predefined position occupied by the brewing cylinder is identified when the closing piston, pushed by the ejection piston and resisted by the elastic device, reaches the threshold position;

[0014] - for each dispensing cycle, performing the brewing step at a given brewing position of the brewing cylinder, and performing the drying step by moving the brewing cylinder towards the closing piston until it reaches a final position corresponding to the detection of the threshold position of the closing piston;

[0015] - calculating the height of the dried used ground coffee charge based on the difference between the predefined position and the final position.

[0016] The controller is programmed to determine the brewing position according to the beverage selection made by the user if the selection refers to drip coffee or American coffee.

[0017] On the other hand, if espresso is selected, the controller is programmed to determine the brewing position based on the position occupied by the brewing cylinder when the closing piston reaches the threshold position during the pressing step of the ground coffee charge before the brewing step, where the pressing step involves the movement of the brewing cylinder towards the closing piston after the closing step.

[0018] The drying step may be formed by a single step defined by the continuous movement of the brewing cylinder, or it may be formed by two or more sub-steps involving the movement of the brewing cylinder separated by waiting periods.

[0019] Typically, the drying step involves a first drying sub-step and a second drying sub-step separated by a waiting period, where each drying sub-step involves moving the brewing cylinder towards the closing piston to an end position corresponding to the detection of the threshold position of the closing piston.

[0020] In a preferred embodiment of the present invention, the controller is programmed to update the grinding time by means of the calculation algorithm only when the closing piston has not reached the threshold position at the start positions of the first drying sub-step and the second drying sub-step.

[0021] In a preferred embodiment of the present invention, the elastic means is pre-tensioned such that the closing piston can reach the threshold position when a pressure between 1 bar and 3 bar acts on the closing piston from the interior of the brewing chamber.

[0022] In a preferred embodiment of the present invention, the ejection piston has a telescopic rod hinged to a fixed pin.

[0023] The present invention also discloses a method for calculating the grinding time of a coffee grinder incorporated in a coffee machine, the coffee machine comprising: a brewing cylinder which is movable along a translation direction and presents a brewing chamber configured to receive a ground coffee charge dispensed from said coffee grinder for performing a brewing cycle; a ejection piston which slides along said brewing chamber for discharging the used ground coffee charge; a closing piston of said brewing chamber, wherein said closing piston is movable in the opposite direction and by the action of an elastic means along said translation direction; a controller which presents in a memory an algorithm for calculating the grinding time of said grinder, said controller being programmed to drive a dispensing cycle which sequentially comprises: a closing step of the brewing chamber, wherein the brewing cylinder moves towards the closing piston; a brewing step, wherein the brewing cylinder stops; and a drying step, wherein the brewing cylinder further moves towards the closing piston for compressing the used coffee charge against the closing piston and discharging the liquid contained therein into an outlet pipe equipped with an outlet valve, the method being characterized by the fact that the height of the dried used coffee charge is detected, the weight of the dried used coffee charge is calculated based on the detected value of said height, and the calculated value of said weight is fed to said calculation algorithm to update the grinding time of said grinder for subsequent dispensing cycles.

[0024] By the description of a preferred but non-exclusive implementation manner of the coffee machine according to the present invention, further features and advantages of the present invention will become more apparent, which implementation manner is illustrated in the accompanying drawings by way of illustration and not limitation, in which:

[0025] Figure 1 A general diagram of the hydraulic circuit of the coffee machine is shown;

[0026] Figures 2 to 14a The sequence of steps in the coffee dispensing cycle is shown;

[0027] Figure 14b Details of the scraper are shown;

[0028] Figures 15a to 15e The sequence of creating the brewing chamber and releasing the upper part of the ejection piston rod from below is shown, in which the construction details A, B and C are also enlarged;

[0029] Figure 16 The principle of calculating the amount of coffee in the brewing chamber during three different correctly executed dispensing cycles is shown;

[0030] Figure 17a and Figure 17bAnother embodiment of the present invention is shown, in which the closing piston occupies a threshold position and an upper end position, and in which the threshold position sensor of the closing piston is still formed by a microswitch, but this time assisted by an additional microswitch which only serves as a safety switch for detecting the upper end position of the closing piston;

[0031] Figure 18a 、 Figure 18b Another way of implementing a two-position closing piston position sensor is shown, in which the closing piston position sensor is formed by a potentiometric linear position sensor;

[0032] Figure 19a 、 Figure 19b A way of implementing a two-position closing piston position sensor is shown, in which the closing piston position sensor is formed by an inductive linear position sensor.

[0033] Referring to the above-mentioned drawings, a coffee machine with the general reference numeral 1 is shown.

[0034] The coffee machine 1 includes a frame having a housing 2 for a brewing cylinder 3, which defines a brewing chamber 4 adapted to receive ground coffee charge 5 directly from a grinder 6. The brewing cylinder 3 has a reversible movement in a vertical plane, which includes a translation in an inclined T direction.

[0035] As will be seen, the movement of the brewing cylinder 3 also includes a rotation to a position for receiving fresh ground coffee charge 5 and discharging the used ground coffee charge 7 and a further movement in the vertical direction.

[0036] The horizontal rotation axis of the brewing cylinder 3 is indicated by R in the figure.

[0037] Therefore, as will be seen, the coffee machine 1 has special means for guiding the movement of the brewing cylinder 3.

[0038] The coffee machine 1 has a hydraulic circuit, which includes a pump 8 for supplying the brewing water flow to the brewing chamber 4 of the brewing cylinder 3 and a boiler 9 responsible for heating the brewing water flow.

[0039] As Figure 1 shown, the hydraulic circuit of the coffee machine 1 further includes: a brewing water source 10, which can be in the form of a reservoir (as shown in the figure) or a connection to the main water pipeline; a flow meter 11, which is usually positioned upstream of the supply pump 8; a conduit 12 for supplying the brewing water to the brewing chamber 4 of the brewing cylinder 3; a conduit 13 for distributing the brewed coffee into a cup 14; and a discharge pipe 15, which is equipped with a discharge valve 19.

[0040] The hydraulic circuit also includes a shut-off valve 16 downstream of the brewing cylinder 3 and a bypass 17 of the shut-off valve 16, which bypass is equipped with a foaming valve 18 having a preset opening.

[0041] All the active elements of the hydraulic circuit are connected to the electronic controller 20 of the coffee machine 1.

[0042] The brewing chamber 4 has a cylindrical side wall 4a, a lower base 4b and an open upper access port 4c.

[0043] A closing piston 21 is positioned above the brewing cylinder 3 to close and open the brewing chamber 4.

[0044] The closing piston 21 is axially movable along a fixed guiding support 21a in the translation direction T of the brewing cylinder 3.

[0045] More precisely, the closing piston 21 is movable contrarily and by the action of an elastic means.

[0046] The elastic means can be formed, for example, by a helical spring 27, in particular a cylindrical spring 27 interposed between the fixed guiding support 21a and the closing piston 21 and having an axis parallel to the axis of the closing piston 21.

[0047] The supply conduit 12 is hydraulically connected to the closing piston 21, which is configured to be suitable for injecting brewing water into a sprinkler in the brewing chamber 4.

[0048] On the other hand, the distribution conduit 13 is hydraulically connected to the brewing cylinder 3, which has a special outlet 28 for the brewed coffee.

[0049] The brewing cylinder 3 supports a firing piston 22 that slides inside the brewing chamber 4 along the axis of the brewing cylinder 3.

[0050] The firing piston 22 has a peripheral seal 23 that is radially sealed to the side wall 4a of the brewing chamber 4.

[0051] The firing piston 22 also has a rod 24 that extends below the brewing cylinder 3.

[0052] The piston rod 24 of the firing piston 22 has a telescopic structure, which includes an upper part 24a integral with the firing piston 22 and a lower part 24b having an end located outside the brewing cylinder 3 hinged to a fixed horizontal pin 25.

[0053] The horizontal pin 25 defines the axis of rotation R of the brewing cylinder 3.

[0054] The upper part 24a of the piston rod 24 integral with the firing piston 22 has a hollow structure to accommodate the lower part 24b of the piston rod 24.

[0055] The piston rod 24 of the ejection piston 22 has a plug 33 which has a variable axial configuration for the engagement and disengagement between the upper part 24a and the lower part 24b of the piston rod 24.

[0056] The plug 33 has an axially elastic structure.

[0057] In particular, the plug 33 is received along the diametrical through hole 37 of the lower part 24b of the rod 24 and consists of two terminals 33a connected by a spring 33b.

[0058] The plug 33 can be actuated by a special actuator 34 integral with the upper part 24a of the rod 24.

[0059] Specifically, the actuator 34 can operate on the terminals 33a protruding from the diametrical hole 37 of the lower part 24b of the rod 24 to retract them into the diametrical hole 37 itself.

[0060] The actuator 34 can thus be straddled by the plug 33 during the vertical movement of the upper part 24a of the rod 24.

[0061] The actuator 34 is positioned on the inner surface of the upper part 24a of the rod 24, while on the outer surface of the upper part 24a of the rod 24 there is a stop 35 to intercept the flange 36 protruding downward from the brewing cylinder 3.

[0062] The ejection piston 22 slides coaxially into the brewing cylinder 3 which, in turn, is coaxial with the closing piston 21 when it performs a translational movement along the T direction, which, in turn, can slide coaxially with the brewing cylinder 3 in the opposite direction and by the action of the elastic means 27.

[0063] The brewing cylinder 3 is rigidly supported by a bracket 26 and is particularly guided along a forced trajectory in a known and thus not depicted manner so that the brewing cylinder 3 performs its rotational-translational movement.

[0064] In a known and thus not described in detail manner, the moving means of the brewing cylinder 3 include an electric motor and a transmission device interposed between the electric motor and the bracket 26.

[0065] Advantageously, the coffee machine 1 provides detection means for detecting the height H of the dried used coffee charge 7 present in the brewing chamber 4.

[0066] The detection means include a sensor 29 of the threshold position of the closing piston 21 and a sensor of the current position of the brewing cylinder 3.

[0067] The sensor 29 is configured to detect the threshold position of the closing piston 21 relative to the fixed guide support 21a.

[0068] For example, as Figure 3 、 Figure 17a 、 Figure 17bAs shown, the sensor 29 can be a microswitch, which is fixed to the fixed guide support 21a and actuated by a probe 30 integral with the closing piston 21. Figure 17a 、 Figure 17b The solution illustrated differs from the solution employed in Figure 3 only in the fact that, in addition to the threshold position sensor 29 of the closing piston 21, which is always formed by a microswitch, another microswitch 29' is provided, which only serves as a safety device for detecting the upper end position of the closing piston 21.

[0069] The threshold position sensor 29 of the closing piston 21 can alternatively be a linear position sensor, which is preferably fixed to the fixed guide support 21a.

[0070] Figure 18a 、 Figure 18b One way of implementing such a linear position sensor (in this case a potentiometric type) is shown.

[0071] The potentiometric linear position sensor 29 measures the resistance of a variable length resistive track (not shown) between a fixed reference point and a movable reference point, which is identified by a slider (not shown) rotating integrally with a rotatable shaft 29a. A pinion 29b engaged with a rack 29c is coaxially attached to the rotatable shaft, and the rack is in turn integral with the closing piston 21. Due to the engagement between the pinion 29b and the rack 29c, the current linear position of the closing piston 21 is uniquely associated with the current angular position of the shaft 29a, the current angular position of which is in turn uniquely associated with the current angular position of the slider, and the current angular position of the slider is ultimately uniquely associated with the current length of the resistor being measured.

[0072] Figure 19a 、 Figure 19b One way of implementing such a linear position sensor (in this case an inductive type) is shown.

[0073] The inductive linear position sensor 29 measures the change in inductive coupling between a first movable magnetic element 29d attached to the closing piston 21 and a second fixed magnetic element 29e (e.g., the fixed guide support 21a).

[0074] The elastic device 27 is pre-tensioned to allow the closing piston 21 to reach the threshold position when a pressure preferably between 1 bar and 3 bar acts on the closing piston 21 from inside the brewing chamber 4.

[0075] The current position sensor of the brewing cylinder 3 (not shown) can be formed, for example, by an encoder associated with the electric drive motor of the carriage 26, by means of which the angular position of the shaft of the electric motor can be bi-univocally related to the linear position of the carriage 26 and thus to the linear position of the brewing cylinder 3.

[0076] The operation of the coffee machine 1 is basically as follows.

[0077] The controller 20 is programmed to drive a dispensing cycle that sequentially includes: a closing step of the brewing chamber 4, in which the brewing cylinder 3 moves towards the closing piston 21; a brewing step, in which the brewing cylinder 3 stops; and a drying step, in which the brewing cylinder 3 further moves towards the closing piston 21.

[0078] In the drying step of the used ground coffee charge 7, the brewing cylinder 3 undergoes an upward movement in the T direction to compress the used coffee charge 7 against the closing piston 21 and discharge the liquid it contains.

[0079] A more detailed operation of the coffee machine 1 is as follows.

[0080] The brewing cylinder 3 is initially at its lower end A, where the axis of the brewing cylinder is vertically oriented below the hopper 31 for loading the ground coffee charge 5 dispensed from the coffee grinder 6.

[0081] The ejection piston 22 is in the extended position towards the open top 4c of the brewing chamber 4 ( Figure 2 ).

[0082] The user selects a product, which can be espresso or drip coffee, by pressing a special control button (not shown), and the coffee machine 1 starts the corresponding dispensing cycle.

[0083] The electric motor drives the brewing cylinder 3, which in its guided movement first performs a vertical upward movement, while the ejection piston 22 first remains stationary to recreate the brewing chamber 4 and allow it to be filled ( Figure 3 ).

[0084] The ejection piston 22 initially remains stationary because the upper part 24a of its rod 24 engages with the lower part 24b of its rod 24: Figures 15a to 15c It is shown that the plug 33 blocks the actuator 34, thus preventing the upper part 24a of the rod 24 of the ejection piston 22 from rising.

[0085] However, at a specific point, the lower base 3a of the brewing cylinder 3 contacts the rear side 22a of the ejection piston 22 and pulls the upper part 24a of the piston rod 24 upwards with sufficient force to cause the retraction of the plug 33 by the actuator 34 and the subsequent crossing of the plug 33 by the actuator 34 (from bottom to top) ( Figures 15c to 15e ).

[0086] The brewing cylinder 3 is then raised, with the ejection piston 22 accommodated therein being in a retracted position towards the bottom of the thus created brewing chamber 4.

[0087] The grinder releases a ground coffee charge 5, which flows by gravity from the hopper 31 into the brewing chamber 4 ( Figure 4 ).

[0088] The electric motor drives the brewing cylinder 3 again, which in its guided movement now performs a rotation about the R axis, by which the axis of the brewing cylinder 3 is aligned with the axis of the closing piston 21 along the T direction ( Figure 5 ), and performs a subsequent upward movement along the T direction until the brewing cylinder 3 engages with the closing piston 21.

[0089] Then the brewing step begins, in which the discharge valve 19 located on the discharge pipe 15 is closed.

[0090] If the user selects espresso, the shut-off valve 16 is closed and the brewed coffee reaches the valve 18, while if drip coffee or American coffee is selected, the shut-off valve 16 is open and the bypass 17 is not operative.

[0091] The controller 20 activates the supply pump 8 and the brewer 9 to supply a brewing water stream to the brewing cylinder 3.

[0092] At the end of the brewing step, the controller 20 commands the opening of the discharge valve 19 located on the discharge pipe 15 and commands the execution of a drying step ( Figures 7 to 10 ).

[0093] At the end of the drying step of the used ground coffee charge 7, the controller 20 drives the electric motor, which initially moves the brewing cylinder 3 downward in the direction T until it disengages from the closing piston 21 and then returns it to its initial position A.

[0094] Specifically, after a rotation of the brewing cylinder 3 opposite to the initial rotation, which initial rotation is followed by a downward translation along the T axis, the brewing cylinder 3 returns with a vertical axis and performs a further downward vertical translation, in which the ejection piston 22 rises in the brewing chamber 4 and brings the dried used ground coffee charge 7 to the level of the inlet port 4c, where a dedicated scraper 32 automatically operates to remove it.

[0095] The lifting of the ejection piston 22 is due to the fact that during the vertical descent of the brewing cylinder 3, the plug 33 intercepts the actuator 34 and prevents further descent of the upper part 24a of the rod 24 of the ejection piston 22 until a later moment, at which the flange 36 encounters the stop 35 and pulls the stop downward to re-engage the actuator 34, which then passes downward over the plug 33.

[0096] According to a particularly advantageous aspect of the invention, the controller 20 has in its memory an algorithm for calculating the grinding time of the grinder, which algorithm is capable of updating the grinding time of the grinder for performing subsequent dosing cycles.

[0097] The controller is programmed to convert the measured value of the H height of the charge 7 into its weight and to feed the calculated weight value to the calculation algorithm to update the grinding time of the grinder for subsequent dosing cycles.

[0098] Specifically, the controller has in its memory a Pref value of the theoretical reference flow rate of the grinder, and for each Qref reference value of the weight-by-weight amount of ground coffee for each selectable beverage, there is a corresponding Tref reference value of the grinding time taken by the grinder, and the known relationship applies:

[0099] Pref = Qref / Tef

[0100] However, the current flow rate of the grinder can vary over time.

[0101] If the Pj value (Pj ≠ Pref) of the current flow rate of the grinder changes during the j-th grinding cycle, then a different amount of ground coffee (Qj ≠ Qref) is obtained for the same grinding time (Tj = Tref). The machine controller knows the value Pj of the current flow rate of the grinder because once the value Qj of the weight-by-weight amount of ground coffee obtained in a grinding time equal to Tref has been calculated, then Pj = Qj / Tref is obtained.

[0102] Given the value Pj of the current flow rate of the grinder, the value of the grinding time Tk of the subsequent k-th grinding cycle associated with the same selected beverage will be subject to a correction ΔT (where ΔT = Tk - Tref) associated with the change ΔQ (where ΔQ = Qj - Qref).

[0103] Typically, this correction ΔT is inversely proportional to the change ΔQ, in the sense that for an increase in the amount of ground coffee, the algorithm matches a decrease in the grinding time in subsequent grinding cycles, and vice versa, for a decrease in the amount of ground coffee, the algorithm matches an increase in the grinding time in subsequent grinding cycles.

[0104] The height H is the dimension of the dried used coffee charge 7 along the axial direction of the brewing cylinder 3.

[0105] In order to detect the height H of the ground coffee charge 7, a preparatory operation is required, which can be carried out once, periodically, or before the start of each dispensing cycle, in which the controller 20 moves the brewing cylinder 3 (initially stopped at its lower end corresponding to position A) together with the empty brewing chamber 4 towards the closing piston 21 until a predetermined position B occupied by the brewing cylinder 3 is identified, which predetermined position B corresponds to the closing piston 21 being pushed by the ejection piston 22 and reaching a threshold position against the elastic means 27.

[0106] The predetermined position B and the lower end position A can be uniquely identified by the brewing cylinder position sensor 3.

[0107] The controller 20 performs a brewing step at the position C of the brewing cylinder 3 in each dispensing cycle, which position C is determined as will be seen later, and performs a drying step by moving the brewing cylinder 3 towards the closing piston 21 until it reaches an end position D' corresponding to the detection of the threshold position of the closing piston 21.

[0108] The brewing position C of the brewing cylinder 3 and this end position D' can also be uniquely identified by the brewing cylinder 3 position sensor.

[0109] At this time, the controller 20 calculates the height H of the ground coffee charge 7 based on the difference between the predetermined position B and the end position D' of the brewing cylinder 3.

[0110] Taking into account the geometry of the brewing chamber 4, the controller 20 calculates the volume of the ground coffee charge 7 based on the height H.

[0111] Taking into account the density of the ground coffee, the controller 20 calculates the weight of the ground coffee charge 7 based on the volume.

[0112] The calculation algorithm fed with the calculated weight value corrects the grinding time for subsequent dispensing cycles in which the same beverage is required.

[0113] The brewing position C of the brewing cylinder 3 is determined differently depending on whether a compression step of the ground coffee charge is required before the brewing step for the selected beverage.

[0114] If not, especially if the user selects drip coffee or American coffee, the controller 20 automatically associates the choice made by the user with the brewing position C of the brewing cylinder 3 that has been stored.

[0115] The brewing position C of the brewing cylinder 3 must ensure a water film on the ground coffee charge 5 during the brewing step.

[0116] On the other hand, if the selected beverage (usually espresso) requires a pressing step of the ground coffee charge before the brewing step, the controller 20 determines the brewing position C of the brewing cylinder 3 based on the position occupied by the brewing cylinder 3 when the closing piston 21 reaches the threshold position during the pressing step of the ground coffee charge before the brewing step.

[0117] The pressing step involves the movement of the brewing cylinder 3 towards the closing piston 21.

[0118] Once the position of the brewing cylinder 3 corresponding to the closing piston 21 reaching the threshold position has been identified, the controller 20 automatically determines the brewing position of the brewing cylinder 3, which is lower than the identified position by a predetermined amount to ensure the presence of a water film on the pressed ground coffee charge 5 during the pressing step.

[0119] For higher drying efficiency, the drying step preferably includes a first sub-step and at least a second sub-step separated by a waiting period.

[0120] Each drying sub-step involves moving the brewing cylinder 3 towards the pressing piston 21 to an end position D, D' corresponding to the detection of the threshold position of the closing piston 21.

[0121] The controller 20 only feeds the calculation algorithm to update the grinding time when the closing piston 21 has not reached the threshold position at the start positions of the first sub-drying step and the second sub-drying step.

[0122] More precisely, the drying during the regular operating distribution cycle is as follows.

[0123] Initially, at the end of the brewing step, the closing piston 21 is below the threshold position, which means that the pressure inside the brewing chamber 4 is correctly below the pressure between 1 bar and 3 bar required to cause the closing piston 21 to exert a thrust in the opening direction greater than the elastic thrust exerted by the elastic means 27 in the closing direction.

[0124] The first sub-step of the drying step is carried out as follows.

[0125] The electric motor moves the brewing cylinder 3 upwards.

[0126] Thus, the ejection piston 22 held in the retracted position in the brewing chamber 4 presses the used ground coffee charge 7 against the closing piston 21, which retracts (rises) against the action of the elastic means 27 until it reaches the threshold position, which once detected by the threshold sensor 29 causes the electric motor to stop and thus the brewing cylinder 3 to stop.

[0127] At this point, the first sub-step of the drying step ends with the brewing cylinder in the temporary end position D recognized by the brewing cylinder position sensor 3, and the controller 20 anticipates a waiting period of a few seconds in order to start discharging the liquid contained in the used ground coffee charge 7 being dried.

[0128] The discharge of the liquid causes a volume contraction of the used ground coffee charge 7 being dried, which makes the closing piston 21 advance (downward) due to the thrust of the elastic means 27 to a position below the threshold position.

[0129] At this point, the controller 20 executes a second sub-drying step identical to the first sub-drying step, but the brewing cylinder reaches the final end position D' above the temporary end position D recognized by the brewing cylinder position sensor 3.

[0130] At the end of the second drying sub-step, the controller 20 calculates the weight of the dried ground coffee charge 7 in the manner already described and feeds the calculated weight value to the calculation algorithm to update the drying time for the next dispensing cycle of the same type of beverage.

[0131] As described above, the position sensor of the brewing cylinder 3 (in particular the encoder of the electric motor) is used to calculate the height H of the dried ground coffee charge 7.

[0132] In Figure 16 as an example, the controller 20 estimates the following height H (measured in the number of encoder pulses):

[0133] First dispensing cycle:

[0134] H = B - D' = 2800 - 2400 = 400

[0135] Second dispensing cycle:

[0136] H = B - D' = 2800 - 2600 = 200

[0137] Third dispensing cycle:

[0138] H = B - D' = 2800 - 2300 = 300

[0139] In an incorrectly operating dispensing cycle, it is possible that before the start of the first drying sub-step, the closing piston 21 is not below its threshold position.

[0140] In this case, the drying step can be carried out by subjecting the brewing cylinder 3 to an upward stroke of a predetermined or otherwise determined entity, but the controller 20 does not calculate the weight of the dried ground coffee charge 7, and the calculation algorithm is not used to update the grinding time for the next dispensing cycle of the same type of beverage; instead, the controller 20 reduces the grinding time for the next dispensing cycle of the same type of beverage by a predetermined amount in order to quickly regularize the subsequent dispensing cycles of the same type of beverage.

[0141] In an incorrectly operating dispensing cycle, it is also possible that, before the start of the second drying sub-step, the closing piston 21 does not return to a position below its threshold position.

[0142] Also in this case, the drying can be ended by subjecting the brewing cylinder 3 to an upward stroke of a predetermined entity or an upward stroke determined in some other way, but the controller 20 does not calculate the weight of the dried used ground coffee charge 7, and the calculation algorithm does not update the grinding time for the next dispensing cycle of the same type of beverage; on the other hand, the controller 20 reduces the grinding time for the next dispensing cycle of the same type of beverage by a predetermined amount.

[0143] The coffee machine and the method of coffee preparation thus conceived are susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept; furthermore, all details can be replaced by technically equivalent elements.

[0144] In the implementation, depending on requirements and the state of the art, the materials and dimensions used can be any materials and dimensions.

Claims

1. A coffee machine (1), the coffee machine comprising: a coffee grinder (6); a brewing cylinder (3) that is movable along a translation direction (T) and presents a brewing chamber (4) configured to receive a ground coffee charge (5) dispensed from the grinder (6); a ejection piston (22) that is movable along the brewing chamber (4) for discharging the used ground coffee charge (7); a closing piston (21) of the brewing chamber (4), wherein the closing piston (21) is movable in the opposite direction and by the action of an elastic means (27) along the translation direction (T); a controller (20) that has in its memory an algorithm for calculating the grinding time of the grinder (6), the controller (20) being programmed to drive a dispensing cycle that sequentially provides: a closing step of the brewing chamber (4), wherein the brewing cylinder (3) moves towards the closing piston (21); a brewing step, wherein the brewing cylinder (3) stops; and a drying step, wherein the brewing cylinder (3) further moves towards the closing piston (21) for compressing the used ground coffee charge (7) against the closing piston (21) and discharging the liquid contained therein into a discharge pipe (15) equipped with a discharge valve (19), the coffee machine being characterized by the fact that it comprises detection means for detecting the height (H) of the dried used ground coffee charge (7) present in the brewing chamber (4), and the controller (20) is programmed to calculate the weight of the dried used ground coffee charge (7) based on the detected value of the height (H), feed the calculated value of the weight to the calculation algorithm to update the grinding time of the grinder (6), and use the updated grinding time for subsequent dispensing cycles.

2. The coffee machine (1) according to claim 1, characterized in by the fact that the algorithm calculates a flow rate deviation between a current value (Pj) of the grinder flow rate and a reference value (Pref) of the grinder flow rate based on the calculated weight, and updates the grinding time by correlating the grinding time with the deviation.

3. The coffee machine (1) according to any one of the preceding claims, characterized in by the fact that the detection means comprises a sensor (29) of the threshold position of the closing piston (21) and a current position sensor of the brewing cylinder (3), and the controller (20) is programmed for: - moving the brewing cylinder (3) together with the empty brewing chamber (4) towards the closing piston (21) until a predefined position (B) occupied by the brewing cylinder (3) when the closing piston (21) reaches the threshold position caused by being pushed by the ejection piston (22) and resisted by the elastic means (27) is identified; - for each dispensing cycle, at a given brewing position (C) of the brewing cylinder (3) The brewing step is performed at this location, and the drying step is performed by moving the brewing cylinder (3) towards the closing piston (21) until it reaches an end position (D') corresponding to the detection of the threshold position of the closing piston (21); - The height of the dried used ground coffee charge (7) is calculated based on the difference between the predefined position (B) and the end position (D').

4. The coffee machine (1) according to the preceding claim, characterized in that the following fact: the controller (20) is programmed to determine the brewing position (C) based on the selection of the beverage made by the user.

5. The coffee machine (1) according to claim 4, characterized in that, the controller (20) is programmed to determine the brewing position (C) based on the position occupied by the brewing cylinder (3) when the closing piston (21) reaches the threshold position during the pressing step of the ground coffee charge before the brewing step, wherein the pressing step includes the movement of the brewing cylinder (3) towards the closing piston (21) after the closing step.

6. The coffee machine (1) according to any one of claims 3 to 5, characterized in that, the drying step includes a first drying sub-step and at least a second drying sub-step separated by a waiting period, wherein each drying sub-step includes moving the brewing cylinder (3) towards the closing piston (21) to a temporary end position (D) and accordingly moving to a final end position (D') corresponding to the detection of the threshold position of the closing piston (21).

7. The coffee machine (1) according to the preceding claim, characterized in that the following fact: the controller (20) is programmed to update the grinding time by means of the calculation algorithm only when the closing piston (21) has not reached the threshold position at the start positions of the first sub-step drying and the second sub-step drying.

8. The coffee machine (1) according to any one of claims 3 to 6, characterized in that the following fact: the elastic means (27) is pre-tensioned such that the closing piston (21) can reach the threshold position when a pressure between 1 bar and 3 bar acts on the closing piston (21) from the inside of the brewing chamber (4).

9. The coffee machine (1) according to any one of the preceding claims, characterized in that the following fact: the ejection piston (22) has a telescopic rod (24), the telescopic rod includes an upper part (24a) integral with the ejection piston (22) and a lower part (24b) having an end located outside the brewing cylinder (3) hinged to a fixed pin (25).

10. The coffee machine (1) according to the preceding claim, characterized in that, the piston rod (24) of the ejection piston (22) has a plug (33), the plug having a variable axial configuration for the engagement and disengagement between the upper part (24a) and the lower part (24b) of the piston rod (24).

11. The coffee machine (1) according to any one of claims 3 to 10, characterized in that the fact that the sensor (29) of the threshold position of the closing piston (21) comprises at least a first microswitch.

12. The coffee machine (1) according to the previous claim, characterized in that it comprises a second safety microswitch (29') which is configured and arranged to detect the upper end position of the closing piston (21).

13. The coffee machine (1) according to any one of claims 3 to 10, characterized in that the fact that the sensor (29) of the threshold position of the closing piston (21) comprises a linear position sensor.

14. A method for calculating the grinding time of a coffee grinder (6) incorporated in a coffee machine (1), the coffee machine comprising: a brewing cylinder (3) which is movable along a translation direction (T) and presents a brewing chamber (4) configured to receive a ground coffee charge (5) dispensed from the coffee grinder (6) for performing a brewing cycle; an ejection piston (22) which slides along the brewing chamber (4) for discharging the used ground coffee charge (7); a closing piston (21) of the brewing chamber (4), wherein the closing piston (21) is movable in the opposite direction and by the action of an elastic means (27) along the translation direction (T); a controller (20) which presents in a memory an algorithm for calculating the grinding time of the grinder (6), the controller (20) being programmed to drive a dispensing cycle which sequentially comprises: a closing step of the brewing chamber (4), wherein the brewing cylinder (3) moves towards the closing piston (21); a brewing step, wherein the brewing cylinder (3) stops; and a drying step, wherein the brewing cylinder (3) further moves towards the closing piston (21) for compressing the used coffee charge (7) against the closing piston (21) and discharging the liquid contained therein into a discharge pipe (15) equipped with a discharge valve (19), the method being characterized by the fact that the height (H) of the dried used coffee charge (7) is detected, the weight of the dried used coffee charge (7) is calculated based on the detected value of the height (H), and the calculated value of the weight is fed to the calculation algorithm to update the grinding time of the grinder for a subsequent dispensing cycle.

15. The method for calculating the grinding time according to the previous claim, characterized in that, the algorithm calculates a flow rate deviation between a current value (Pj) of the grinder flow rate and a reference value (Pref) of the grinder flow rate based on the calculated weight, and updates the grinding time by correlating the grinding time with the deviation.

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