Apparatus and method for preparing a coffee beverage

Abstract

Device (1) for preparing a coffee beverage, comprising a brewing unit (2) with a brewing chamber (6) which can be closed by a lid (4), in which coffee powder (8) is compressed after being filled by a piston (14) driven by an electric actuator (10) via a mechanical transmission (12), and the compressed coffee powder is subjected to heated water introduced into the brewing chamber (6) by an electric pump (16), which exits from an outlet of the brewing chamber (6), and with an electronic control device (18) which controls the electric actuator (10) depending on the signals of an associated rotary encoder (20) in such a way as tothat the piston (14) is moved from a filling position (A) for the coffee powder under compression of the coffee powder (8) into a brewing position (B) and from there into an ejection position (C) for the coffee pellet formed by the brewing process in the brewing chamber (6), characterized in that the electronic control device (18) first moves the piston (14) against a stop (22) in the ejection position (C) to calibrate the rotary encoder (20), then moves the piston (14) from this ejection position (C) by a predetermined distance downwards into the filling position (A), the length of which corresponds to a first number of pulses of the rotary encoder (20) stored in an electronic memory (24) of the electronic control device (18), that the electronic control device (18) moves the piston (14) by a second distance upwards into the brewing position (B) after a predetermined filling time,the length of which corresponds to the number of a second number of pulses of the rotary encoder (20) stored in the memory (24), and that the electronic control device (18) moves the piston (14) back from the brewing position (B) by a predetermined third distance to the ejection position (C) after a predetermined brewing duration, in which the pellet is removed from the piston (14) by an ejection mechanism after the lid (4) has been opened.

Description

[0001] The invention relates to a device for preparing a coffee beverage and to a method for preparing a coffee beverage using such a device according to the preamble of claims 1 and 4.

[0002] The hot beverage vending machines used today in public areas, which primarily serve coffee, espresso, and other caffeinated hot beverages, are known to use brewing units with a brewing chamber into which dried coffee grounds are poured. A movable piston is located within the brewing chamber, which compresses the grounds after the chamber is closed with a lid. The compressed grounds are then exposed to hot water to release the flavorings, which are then dispensed into a brewer as a hot beverage via a dispensing unit.

[0003] In this context, it is known from DE 198 55 271 C1 to move the piston accommodated in the brewing chamber using a spindle drive comprising a simple electric motor activated by an electronic control device, the rotational angle of which is not detected during the movement of the piston. The magnitude of the pressure exerted by the piston on the coffee powder during the brewing process is determined purely randomly by the fact that the electric motor is supplied with electrical current by the control device for a fixed period of time to move it from the filling position to the brewing position.Since the travel path and thus the final position of the piston in this case depend crucially on the amount of coffee powder added, the degree of grinding, and the frictional forces in the gearing through which the piston is driven by the motor, the pressure exerted by the piston on the coffee powder during the brewing process is subject to significant fluctuations. However, as the applicant has discovered, the pressure exerted by the piston on the coffee powder during the brewing process has a very significant influence on the taste quality of the coffee beverage. This is due, among other things, to the fact that higher pressure causes more bitter substances to escape from the coffee powder. These bitter substances advantageously make the taste appear considerably fuller for a given coffee variety, brewing method, coffee quantity, and grind, if the pressure generated by the piston assumes a predetermined ideal value.However, if the pressure exerted by the piston on the coffee powder during the brewing process only slightly exceeds a certain threshold value, which depends on the parameters mentioned above, the bitter substances will escape from the coffee powder to an increased extent and adversely affect the taste quality to such an extent that the beverage becomes almost undrinkable.

[0004] Further devices for preparing coffee beverages are known from DE 69 407 479 T2 and DE 20 2004 018 776 U1.

[0005] Accordingly, it is an object of the present invention to provide a device and a method for preparing a coffee beverage, with which the taste quality of a coffee beverage which is brewed in a brewing chamber using a piston acting on the filled coffee powder can be further improved.

[0006] This object is achieved according to the invention by a device and a method having the features of claims 1 and 4.

[0007] Further features of the invention are described in the subclaims.

[0008] The invention is described below with reference to a preferred embodiment of the invention and the accompanying drawings. In the drawings: Fig. 1 a schematic representation of the device according to the invention, in which the piston of the brewing unit has been moved into the ejection position, Fig. 2 the device of Fig. 1, after the piston has been moved to the filling position, Fig. 3 the device of Fig. 1, after closing the lid, Fig. 4 the device of Fig. 1, in which the piston was moved from the filling position to the brewing position while compressing the coffee powder, Fig. 5 the device of Fig. 1 during the brewing process, and Fig. 6 the device of Fig. 1 after opening the lid and moving the piston into the ejection position.

[0009] As in Fig. 1-6, the device 1 according to the invention for preparing a coffee beverage comprises a brewing unit 2 which has a brewing chamber 6 which can be closed by a lid 4 which can be moved, for example, by means of the curved paths indicated schematically in dashed lines and pins arranged laterally on the lid and guided in the curved paths by means of an actuator (not shown in detail), in order to open or close the brewing chamber 6.

[0010] In the brewing chamber 6, a piston 14 is movable up and down by an electric actuator 10 via a mechanical gear 12 in order to compress coffee powder 8 filled into the brewing chamber 6. During the brewing process, heated water, which is introduced into the brewing chamber 6 by an electric pump 16, flows through the ground coffee. This water then exits as a coffee beverage from an outlet (not shown in more detail) of the brewing chamber 6. The movement of the piston 14 is controlled by an electronic control device 18, which is connected to the actuator 10 for driving the piston 14 and which, in addition, preferably also controls the other components, such as the pump 16 for conveying the heated water into the brewing chamber 6, as well as the boiler (not shown in more detail), or the grinder, etc.

[0011] The electronic control device 18 controls the electric actuator 10 in dependence on the signals of a rotary angle sensor 20 assigned to it in such a way that the piston 14 moves from a filling position A ( Fig. 3) for the coffee powder 8 under compression of the coffee powder 8 into a brewing position B ( Fig. 5) and from there into an ejection position C ( Fig. 7) for the coffee pressed pellet formed by the brewing process in the brewing chamber 6. The device according to the invention is characterized in that the electronic control device 18 initially moves the piston 14 against a stop 22 in the ejection position C to calibrate the rotary encoder 20 ( Fig. 1). From this ejection position C, the piston 14 is then moved a predetermined distance in the downward direction into the filling position A, the length of which corresponds to a first number of pulses from the rotary angle sensor 20 stored in an electronic memory 24 of the electronic control device 18. After a predetermined filling time, during which the grinder (not shown in detail) is activated and the coffee powder is filled from above into the open brewing chamber 6, the electronic control device 18 moves the piston 14, after the lid 4 has been closed, a second distance in the upward direction into the brewing position B, the length of which corresponds to a second number of pulses from the rotary angle sensor 20 stored in the memory 24. After the electronic control device 18 has received the corresponding second number of pulses from the rotary angle sensor 20.wherein in the present application the term "pulse" is intended to include any type of pulse-shaped electronic signals, such as in particular digital input and output signals, the control device 18 moves the piston 14 after a predetermined brewing time from the brewing position B by a predetermined third distance into the ejection position C, in which the pressed product is removed from the piston 14 by an ejection mechanism (not shown in detail) after the lid 4 has been opened.

[0012] The invention provides the advantage that the calibration of the rotary encoder 20 takes place in a state in which the lid is open and no pressure load acts on the piston 14. This allows the errors during the calibration process caused by frictional forces to be kept as low as possible, which in turn leads to the positioning error when moving the piston 14 into the brewing position B while compressing the coffee powder 8 being reduced, and the piston can be moved into the brewing position with significantly greater accuracy. This increased accuracy when moving the piston 14 into the brewing position while compressing the coffee powder opens up the possibility of reproducibly adjusting the pressure that the piston exerts on the coffee powder during the brewing process with extremely high accuracy.

[0013] Due to the derivation of the travel of the piston 14 when moving into the brewing position B from the pulses of the previously calibrated rotary angle sensor 20 alone, this results in the advantage, compared to purely time-controlled positioning or positioning via the absorbed motor current of the electric actuator 10, that the reached end position for the brewing process is almost independent of the frictional forces occurring.

[0014] Compared to a similarly conceivable measurement of the pressure force of the piston on the coffee powder 8 by a pressure sensor, for example a piezoelectric pressure sensor, the solution according to the invention has the advantage that the determined pressure force does not depend on the temperature prevailing in the area of ​​the sensor, which in this case acts between the piston and the drive element, but solely on the number of pulses generated by the rotary encoder 20 and fed to the control device 18. Since the number of pulses generated by the rotary encoder is not influenced by the temperature, which can vary considerably in the area of ​​the brewing chamber 6 and also below the piston 14 between the filling of the brewing chamber and the brewing process due to the hot water introduced, the pressure exerted by the piston 14 on the coffee powder 8 is subject to almost no temperature influences during the brewing process.

[0015] In the preferred embodiment of the device 1 according to the invention, the electric actuator 10 is a DC electric motor, which, via a gear 12a attached to its drive shaft 10a, drives a spindle drive 12b for a threaded spindle 12c, to which the piston 14 is coupled. The rotary encoder 20 comprises a perforated disk or slotted disk 20a, which is rotationally fixedly coupled to the drive shaft 10a of the electric motor and which - as shown in the Fig. 1 to 6 - is preferably arranged on the end of the drive shaft 10a opposite the gear 12a.

[0016] In the preferred embodiment of the invention, the rotary encoder 20 can be moved when the piston is moved from the position shown in Fig. 1 shown initialization position, or ejection position C to the maximum travel distance in the Fig.For example, the filling position A shown in Figure 2 can generate 680 pulses. A travel of 1 mm of the piston 14 corresponds to 15 pulses, for example. It is understood that the number of pulses per millimeter of travel can also be selected differently by appropriately reducing the gear ratio of the gearbox 12 or the spindle drive.

[0017] According to a further idea underlying the invention, the device 1 according to the invention has input means 26 connected to the electronic control device 18, in particular a first electrical switch, which is preferably designed as a touch-sensitive switch or a touch-sensitive sensor field, by the actuation of which the value for the number of pulses assigned to the second path in the memory 24 can be gradually increased or decreased in order to increase or decrease the pressure which the piston 14 exerts on the coffee powder 8 in the brewing position B.

[0018] The functioning of the device 1 according to the invention is explained in more detail below using the method for preparing a coffee beverage in which the device 1 described above is used.

[0019] The process according to the invention is characterized by the following process steps: a) Entering a desired coffee type, coffee strength and a taste parameter associated with the coffee type, and b) increasing or decreasing a value stored in the memory 24 for the second number of pulses generated by the rotary encoder 20 when the piston 14 moves the second distance from the filling position A to the brewing position B, depending on the entered taste parameter, c) Filling a quantity of coffee powder 8 corresponding to the type and strength of coffee into the brewing chamber 6, d) moving the cover 4 into the closed position, e) moving the piston 14 from the filling position A while compressing the coffee powder by the second distance in the direction of the ejection position C until the rotary encoder 14 has generated the second number of pulses increased or decreased depending on the taste parameter, f) activating the pump 16 for a predetermined period of time to introduce a predetermined amount of hot water into the brewing chamber 6 and deactivating the pump, g) Opening the cover 4 and moving the piston 14 into the ejection position C, and h) Remove the coffee pellet from the piston.

[0020] In the method described above, it is particularly advantageous if, after deactivating the pump 16 for re-pressing the coffee pressed part, the piston 14 is moved from the brewing position B by a fourth distance in the direction of the ejection position C into a re-pressing position (not shown in detail), until the rotary encoder 14 has generated a number of pulses corresponding to the fourth distance and stored in the memory 24. Re-pressing the coffee powder 8, which has previously been subjected to hot water, has the advantage that a dry coffee powder pressed part is produced which, in the ejection position A, can be easily pushed off the piston 14 by a slider or the like, which can also be attached to the lid 4, without watery residues remaining on the piston, which would adversely affect the taste of the coffee beverage during a subsequent brewing process.

[0021] Furthermore, it may be advantageous if, in the method according to the invention, after deactivating the pump 16 and before opening the lid 4, a valve arranged in the water supply line to the brewing chamber 6, not shown in detail in the illustrations, is opened in order to divert the brewing pressure generated in the brewing chamber 6 during the brewing process from the brewing chamber 6 before opening the lid 4.

[0022] According to a further concept underlying the invention, the value stored in the memory 24 for the second number of pulses can additionally be increased or decreased depending on the coffee strength entered and stored in the memory 24, such that with an increase in the amount of coffee powder 8 filled into the brewing chamber 6, the second number of pulses is reduced and the second path is shortened accordingly. This takes into account the fact that there is no increase in the pressure exerted by the piston 14 on the coffee powder 8 due to the increased coffee volume in the brewing position B, which would lead to the escape of additional bitter substances, but that the position of the piston 14 in the brewing position is corrected accordingly in order to maintain the original preset pressure value, or the pressure value corrected via the input means 26, despite the increased volume of coffee powder 8.

[0023] According to a further advantageous embodiment of the method according to the invention, the value stored in memory 24 for the second number of pulses can additionally be increased or decreased depending on a value stored in memory 24 for the coffee type, such that for a stronger roasted coffee, the second number of pulses is reduced and the second path is shortened accordingly. This results in the advantage that a corresponding correction of the pressure value can be made for different roasted coffee types, allowing the quality of the coffee beverage produced during the brewing process to be individually adapted to the preferences of the respective user.

[0024] In this context, it can further be provided that the value stored in the memory 24 for the second number of pulses can be stored together with an individual user index as a fixed value in the memory 24 of the electronic control device 18. In this case, it is particularly advantageous if additional input means 26 are provided, via which the stored value can be retrieved for a next brewing process by entering the individual user index in order to move the piston 14 from the filling position A by the second distance into the brewing position B until the rotary encoder 20 has generated the second number of pulses retrieved from the memory 24.

[0025] Furthermore, in order to shorten the dispensing time of the coffee beverage, it is advantageous if the movement of the piston 14 from the ejection position C into the filling position A and / or from the filling position A into an intermediate position located between the brewing position B and the filling position A takes place at a speed which is higher than the speed at which the piston 14 is moved from the intermediate position into the brewing position.

[0026] Finally, according to a further idea underlying the invention, it can be provided that the temporal change in the pulses generated by the rotary angle sensor 20 when the piston 14 moves the second distance from the filling position A to the brewing position B is recorded by the electronic control device 18 and compared with a predetermined threshold value, in particular one previously stored in the memory 24, and that the electronic control device 18 generates a warning signal when the threshold value is undershot, alerting the operator to a lack of coffee in the coffee reservoir. By monitoring the temporal change in the pulses generated by the rotary angle sensor 20 when the piston 14 moves the second distance, which pulses are proportional to the rotation rate of the drive motor, it is possible to detect a lack of coffee beans orIn simple devices without a grinder, the level of coffee powder in the storage container can be detected in the simplest way without an additional fill level sensor in the coffee storage container. This is due to the fact that if the amount of coffee powder filled into the brewing chamber in the filling position A is too low or even missing, no compression-related counterpressure is generated by the coffee powder when the piston 14 moves into the brewing position B. This counterpressure, which, with a correct fill level, leads to the rotation rate detected by the speed sensor 20 decreasing and falling below the threshold value. In other words, the lack of a decrease in the rotation rate is determined by the electronic control device by comparing the rotation rate with a predetermined target value or threshold value, and in this case, a warning signal is generated which alerts the user to a lack of coffee beans or coffee powder in the storage container. List of reference symbols 1 device 2 brewing units 4 lids 6 Brewing chamber 8 coffee powders 10 electric actuator 10a Drive shaft 12 mechanical transmission 12a Gear on drive shaft 12b spindle drive 12c threaded spindle 14 pistons 16 Pump 18 electronic control device 20 rotary encoders 20a Perforated disc or slotted disc 22 stop 24 electronic memory 26 input devices A Filling position of the piston B Brewing position of the piston C Ejection position of the piston

Claims

[1] Device (1) for preparing a coffee beverage, comprising a brewing unit (2) with a brewing chamber (6) which can be closed by a lid (4), in which coffee powder (8) is compressed after filling by a piston (14) driven by an electric actuator (10) via a mechanical gear (12), and the compressed coffee powder is flowed through by heated water which is introduced into the brewing chamber (6) by an electric pump (16) and which emerges from an outlet of the brewing chamber (6), and with an electronic control device (18) which controls the electric actuator (10) in accordance with the signals of a rotary angle sensor (20) assigned to it in such a way thatthat the piston (14) is moved from a filling position (A) for the coffee powder under compression of the coffee powder (8) into a brewing position (B) and from there into an ejection position (C) for the coffee pellet formed by the brewing process in the brewing chamber (6), , characterized bythat the electronic control device (18) first moves the piston (14) against a stop (22) in the ejection position (C) to calibrate the rotary angle sensor (20), then moves the piston (14) from this ejection position (C) by a predetermined distance in the downward direction into the filling position (A), the length of which corresponds to a first number of pulses of the rotary angle sensor (20) stored in an electronic memory (24) of the electronic control device (18), that the electronic control device (18) moves the piston (14) after a predetermined filling time by a second distance in the upward direction into the brewing position (B), the length of which corresponds to a second number of pulses of the rotary angle sensor (20) stored in the memory (24),and that the electronic control device (18) moves the piston (14) after a predetermined brewing time from the brewing position (B) by a predetermined third distance back to the ejection position (C), in which the pressed product is removed from the piston (14) by an ejection mechanism after the lid (4) has been opened. [2] Device according to claim 1, characterized by that the electric actuator (10) is a DC electric motor which, via a gear (12a) fastened to its drive shaft (10a), drives a spindle drive (12b) for a threaded spindle (12c) to which the piston (14) is coupled, and that the rotary angle sensor (20) is a perforated disc or slotted disc which is non-rotatably coupled to the drive shaft (10a) of the electric motor and which is preferably arranged on the end of the drive shaft (10a) opposite the gear (12a). [3] Device according to claim 1 to 2, characterized bythat it has input means (26) connected to the electronic control device (18), in particular a first electrical switch, by the actuation of which the value for the number of pulses assigned to the second path in the memory (24) can be gradually increased or decreased in order to increase or decrease the pressure which the piston (14) exerts on the coffee powder (8) in the brewing position (B). [4] Method for preparing a coffee beverage using a device (1) according to one of the preceding claims, comprising the following method steps, a) Entering a desired coffee type, coffee strength and a taste parameter associated with the coffee type, and b) increasing or decreasing a value stored in the memory (24) for the second number of pulses generated by the rotary encoder (20) when the piston (14) moves the second distance from the filling position (A) to the brewing position (B) depending on the entered taste parameter, c) Filling the amount of coffee powder (8) corresponding to the type and strength of coffee into the brewing chamber (6), d) moving the cover (4) into the closed position, e) moving the piston (14) from the filling position (A) while compressing the coffee powder (8) by the second distance in the direction of the ejection position (C) until the rotary encoder (14) has generated the second number of pulses increased or decreased depending on the taste parameter, f) activating the pump (16) for a predetermined period of time to introduce a predetermined amount of hot water into the brewing chamber (6) and deactivating the pump (16), g) Opening the cover (4) and moving the piston (14) into the ejection position (C), and h) Remove the coffee pellet from the piston (14). [5] Method according to claim 4. characterized by that the piston (14) is moved, after deactivation of the pump (16) for re-pressing the coffee pressed part, from the brewing position (B) by a fourth distance in the direction of the ejection position (C) into a re-pressing position until the rotary angle sensor (14) has generated a number of pulses corresponding to the fourth distance and stored in the memory (24). [6] Method according to claim 4 or 5, characterized by that after deactivating the pump (16) and before opening the lid (4), a valve arranged in the water supply line to the brewing chamber (6) is opened in order to divert the brewing pressure generated in the brewing chamber (6) during the brewing process from the brewing chamber (6) before opening the lid (4). [7] Method according to one of claims 4 to 6, characterized by that the value stored in the memory (24) for the second number of pulses is additionally increased or decreased depending on the coffee strength entered and stored in the memory (24), such that when the amount of coffee powder (8) filled into the brewing chamber (6) is increased, the second number of pulses is reduced and the second path is shortened accordingly. [8] Method according to one of claims 4 to 7, characterized by that the value stored in the memory (24) for the second number of pulses is additionally increased or decreased depending on a value stored in the memory (24) for the type of coffee, such that for a more strongly roasted coffee the second number of pulses is reduced and the second path is shortened accordingly. [9] Method according to one of claims 4 to 8, characterized bythat the value stored in the memory (24) for the second number of pulses can be stored together with an individual user index as a fixed value in the memory (24) of the electronic control device (18), and that input means (26) are provided via which the stored value can be called up for a next brewing process by entering the individual user index in order to move the piston (14) from the filling position (A) by the second distance into the brewing position (B) until the rotary angle sensor (20) has generated the second number of pulses called up from the memory (24). [10] Method according to one of claims 4 to 9, characterized bythat the movement of the piston (14) from the ejection position (C) into the filling position (A) and / or from the filling position (A) into an intermediate position lying between the brewing position (B) and the filling position (A) takes place at a speed which is higher than the speed at which the piston (14) is moved from the intermediate position into the brewing position. [11] Method according to one of claims 4 to 10, characterized by that the temporal change of the pulses generated by the rotary angle sensor (20) when the piston (14) moves the second distance from the filling position (A) to the brewing position (B) is detected by the electronic control device (18) and compared with a predetermined threshold value, in particular stored in the memory (24), and that the electronic control device (18) generates a warning signal when the threshold value is undershot, which alerts the operator to a lack of coffee in the coffee reservoir.

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