DE19629239C2 - Device for the automatic preparation of coffee - Google Patents

Description

The invention relates to a method for automatic Preparation of coffee according to the generic term of the An saying 1 and a coffee machine to carry out procedure.

It has been known for a long time that one and one different types of coffee in the same coffee machine can prepare fairy. Such a coffee machine was formerly called "Solomatic-Espresso" distributed by the applicant and was suitable for prepare either espresso or freshly brewed coffee Depending on whether espresso or freshly brewed coffee should be prepared, the ground coffee was un differently pressed together and the brewed water fed with different pressure. A full one was always independent coffee preparation not possible with this machine.

For the automatic preparation of coffee is from the DE 20 53 466 A known a coffee machine in which Ground coffee in a brewing cylinder with a vertical axis filled and with one into the top of the brewing flask set piston is pressed. Because lower end of the Brewing cylinder is formed by a filter Piston closed so that through holes in the above Hot water introduced into the flask of ground coffee flows through and the filtrate is discharged below. The The contact pressure of the upper piston is fixed. However, the coffee produced in this way does not fully correspond constantly the demands made by the customer - that The goal is consistent quality.

DE 33 16 157 C2 is a coffee machine ben type known, depending on whether espresso or filter coffee to be made, with or without Contact pressure is worked. With this arrangement or in this process, however, is the reproducer Availability of the brewing result is problematic.

The invention has for its object a Ver drive and a coffee machine for automatic closing Preparation of coffee and / or espresso at the beginning mentioned type to the extent that in a achieved an improved brewing result becomes.

This task is accomplished by the in the patent claims Chen specified features solved.

An essential point of the invention is that the contact pressure as such is not constant but a completely different parameter, namely the Water flow rate that default represents value that is essentially constant (from Brüh process for brewing) is held. Surprise consequently, this measure results in an essential one much more constant and therefore on average also special this brewing result than was previously possible.

The contact pressure is preferably reduced, if the flow rate during a brewing process below a predetermined target value (and vice versa).

These adjustments are now preferred made such that corrections (in the sense of a Regulation) only from brewing process to brewing process be made, so not during a individual brewing process. The corrections are made here in such small steps that noticeable Changes happen, excessive "control vibration gen "from setting to setting but ver be avoided. In this way, changes succeed the "environmental conditions", e.g. B. ground coffee or its consistency (humidity, temperature, etc.) to compensate, so that the brewing results opti times will.

It is preferable to set one (at the manufacturer) Setting a basic value for the contact pressure at first brewing process from a contact pressure generator supply device generate maximum contact pressure print one. At the next brewing process, the on pressure then reduced. This ensures that the customer never has the maximum contact pressure occurs, the contact pressure generating device thus cannot be overloaded.

In a particularly preferred embodiment of the method according to the invention flow openings of the filter depending on the liquid cross-section pressure set. This means tet that the filter openings when brewing Espresso have different cross-sections than the broth hen of coffee. This adjustability of filter openings gene is known per se from EP 0 388 975 A1. Hereby further optimization of the brewing results is possible Lich, because the filter openings are very different Brewing conditions are customizable.

It is with the coffee machine according to the invention important that a flow rate measurement be direction is provided so that the contact pressure in Ab dependence on the water flow rate is set. The advantages of this type of scheme have already been explained above. The flow rate digkeitsmeßeinrichtung could now be a separate Flow rate meter, however it is an advantage if the metering device is used is, which is anyway with such beverage vending machine ten must be present. Preferably a pre direction according to DE 37 11 076 C1 used. With Ver Using such a device, the Ab stood the generated pulses from each other or de Ren frequency the basis for the flow rate form measurement. But it is also possible to or falling below the flow rate Setpoint based on an overshoot or undershoot ner predetermined period of time to determine which need is done to reduce the preset coffee volume give.

The contact pressure could now be generated by a force supply specification of the contact pressure generating device can be set. With an electromotive type this could drive current consumption, for example of the power-generating electric motor. In particular to determine a maximum contact pressure value this is also preferably the decisive measurement be worth. To correctly repeat a previous one made contact pressure as well as its enlargement however, reduction is preferably a way used measuring device, which is the path of a Brewing piston in the brewing cylinder (for pressing the coffee feemehls). Here it is assumed that the amount of ground coffee is constant.

Preferably, the brewing cylinder comprises an in considerable fixed brewing sleeve, in its lower Area provided a piston which can be raised by a motor is, the flow openings for introducing the heated Has water. This piston is used for ejection a filter cake from the brewing sleeve. That the broth Piston-forming filter is inserted into the brewing sleeve from above retracted with the help of the pressure printer supply device.

A filter is preferably used, the  Flow cross-sections adjustable sen, for which needles are preferably provided wel depending on the depth of insertion into the openings Define large flow areas. In addition to the Advantages of better adaptation mentioned at the beginning the filter parameters to the respective brewing process there is also the advantage that a certain Self-cleaning of the filter openings takes place. The Self-adjustment of the opening cross sections is then particularly easy if the needles are opposite the opening are held by spring force such that they with increased liquid pressure, the opening cross-section decrease compared to a lower liquid pressure. This also ensures that when Brewing espresso the necessary back pressure is produced and the ground coffee is safely retained becomes. When brewing (filter) coffee, what is under one lower (but still noticeable) contact pressure and with a lower (but still noticeable chen) water pressure happens, the opening cross sections enlarged accordingly.

The following is a preferred embodiment the invention explained in more detail with reference to figures. Here show:

Fig. 1 is a schematic representation of an embodiment of the inventive coffee machine;

Fig. 2 is a partially sectioned side view of an imple mentation form of the coffee machine;

FIGS. 3 and 4 the embodiment shown in FIG. 2 in various further working positions;

Figure 5 is a partial section through the infusion piston of the coffee machine according to Figures 2 to 4..;

FIG. 6 is a view from the direction of arrow VI from FIG. 5;

FIGS. 7 and 8, the coffee machine of FIGS. 2 to 6 further in two positions of use for brewing coffee.

In the following description, for the same che and equivalent parts have the same reference numerals used.

In the embodiment of the invention shown in FIG. 1, a brewing device 20 of the coffee machine comprises a brewing cylinder 30 , the end of which is closed by a piston 32 and whose upper end can be closed by a filter 21 . For brewing coffee or espresso, ground coffee 1 is located in the space formed by the brewing cylinder 30 , the piston 32 and the filter 21 . Through the Kaf feemehl, hot water is delivered through the piston 32 , which flows through the openings 25 of the filter 21 after flowing through the ground coffee 1 and is filled through a discharge line 19 into a cup.

The water comes from a Wasserzufuhreinrich device 10 with a water supply 11 and a pressure reducer / check valve 12 to a pump 13 , which cher a reflux pressure reducer 14 is connected in parallel.

From the pump 13 , the water enters a heating device 15 and from this with increased "brewing" temperature through a control valve 16 into the brewing device 20th The flow rate of the water is measured in a flow rate measuring device 40 which is connected in front of the pump 13 in this embodiment of the invention.

The reflux pressure reducer 14 is set to a pressure of about 8 bar, so that when the pump 13 is operated, its output pressure is set to this value, since water flows back through the back pressure reducer 14 to the pump inlet at increased pressure. The pump 13 has a "leakage current" in such a way that it can be flowed through at standstill without significant pressure losses, so that when the pump 13 is stopped and the valve 16 is open, water flows through the coffee grounds 1 , the pressure of which is essentially that of the pressure reducer. / Check valve 12 corresponds to certain pressure (below 2 bar).

The valve 16 and the pump 13 are controlled by a controller 50 , the output signals of the flow rate measuring device 40 are supplied. Furthermore, the controller 50 controls an electric motor 22 which can move the filter 21 of the brewing device 20 by means of a spindle drive 23 such that it either moves into the brewing cylinder 30 or is lifted out of it. The current supplied to the motor 22 by the controller 50 is measured by means of a current sensor 52 and is essentially proportional to the force with which the filter 21 presses on the ground coffee 1 . The path s, by which the filter 21 is moved into or out of the brewing bush 30 , is scanned by means of a path measuring device 53 (as a motor or spindle pressure angle) and communicated to the controller 50 .

Furthermore, it is shown schematically in Fig. 1 that the controller 50 has a setpoint generator 51 which is adjustable from the outside and a setpoint for the flow rate of the brewing water which corresponds to the measured value from the flow rate measuring device 40 .

The brewing device 20 is explained in more detail below with reference to FIG. 2.

The brewing device 20 comprises a frame 28 in which two spindles 29 , 29 'are rotatably mounted. The spindles 29 , 29 'are rotated by gears 18 , 18 ', 18 "from the electric motor 22. On the spindles 29 , 29 'threaded sleeves 17 , 17 ' are mounted which carry a brewing piston 24 so that when the motor rotates 22 , whose angle of rotation (number of revolutions) is measured by the displacement measuring device 53 , the rotation is transmitted via the gears 18 ", 18 and 18 'to the spindles 29 , 29 ', so that the threaded sleeves 17 , 17 'on the spindles 29th , 29 'are moved and the brewing piston 24 is lifted out of the brewing cylinder 30 with its brewing bush 31 or into it. The brewing cylinder 30 with the brewing bush 31 is again fastened in the frame 28 or forms part of this frame, so that the Brewing cylinder 30 is immovable overall.

In the frame 28 , a lifting frame 60 with lifting rods 61 , 61 'and a (lower) crosshead 62 is slidably mounted, which connects the lifting rods 61 , 61 ' to each other. Between the crosshead 62 and the lower part of the frame 28 fastened holding bushes 63 are biased springs 64 , 64 'are used, which press the main 62 of the lifting frame 60 down.

At their upper, the cross head 62 opposite end, the lifting rods 61 , 61 'are connected to one another via an upper cross head 65 , which is arranged such that the threaded sleeves 17 , 17 ', which hold the brewing piston 24 , with their upper ends when moving upwards come with the upper crosshead 65 in impact and can lift the lifting frame 60 upwards.

At the lower end of the frame 28 , a bore is provided which receives a rod 33 , which is connected to the piston 32 which is tightly seated in the brewing bush 31 , and whose lower end is connected to the (lower) crosshead 62 .

If, with the motor 22 switched on and the spindles 29 , 29 'rotating, the threaded sleeves 17 , 17 ' are further raised from the position shown in FIG. 2, the lifting frame 60 and with it the piston 32 are raised further until the position shown in FIG. 4 position shown is reached.

With an opposite rotation come towards the upper ends of the threaded sleeves 17 , 17 'from the upper crosshead 65 , as shown in Fig. 3, so that the lower position shown in Fig. 2 of the piston 32 is maintained.

The brewing piston 24 with its filter 21 is described in more detail below with reference to FIG. 5.

The brewing piston 24 comprises a holding piece 35 which is connected at its upper end to the threaded sleeves 17 , 17 '(preferably in one piece) and which carries a holding plate 36 at its lower end, from which needles 26 are provided. Between the holding plate 36 and the holding piece 35 , a ring-shaped gap is provided, in which seals 37 sit, which can seal the brewing piston 24 against the brewing sleeve 31 .

In the holding plate 36 sits axially displaceably by means of a spring 27 in the direction of the piston 32 Bea proposes a perforated plate forming the filter 21 , in the flow openings 25 of which the BEFE needles 26 on the holding plate 36 are seated. The needles 26 and / or the flow openings 25 are conical and dimensioned relative to one another such that, in the extreme position shown in FIG. 5, in which the needles 26 are pulled far out of the openings 25 , that between the needles 26 and the openings 25 resulting annular gaps have decimal cross sections. If the filter 21 is pushed upward against the force of the spring 27 in the direction of the holding plate 36 , so that the needles 26 penetrate deeper into the flow openings 25 , these gaps narrow.

The lower extreme position, that is, the maximum opening cross sections are defined by an adjusting screw 38 , via which the filter 21 is secured in the holding plate 36 .

The existing between the needles 26 and the Durchflußöff openings 25 annular gaps are in fluid-tight connection with a flow chamber 39 , which in turn is in tight connection with the discharge line 19 Ver. Thus, liquid which passes through the flow openings 25 constricted by the needles 26 passes through the flow space 39 into the delivery line 19 .

In FIGS. 2 and 4, a Abräumschieber is further indicated 34 with a dash-dotted line, which is so constructed and arranged that a highly elevated by the piston 32 filter cake 2 (see Fig. 4) (not shown) from From räumschieber 34 in a Sammelbe container can be transported. The clearing slide 34 is moved by an actuating device (not shown) which is controlled by the controller 50 or is only controlled mechanically.

Hereinafter, with reference to Figs. Explained 2 to 4 takes place as the basic setting of the machine and thereafter as espresso or coffee to be brewed.

The first basic setting specifies a maximum compression pressure. This specification takes place by means of a maximum current specification potentiometer 54 in the controller 50 , the value of which takes place with the output value of the maximum value generator 52 , which samples the current which is supplied to the motor 22 . This current is proportional to the force with which the ground coffee 1 is compressed. Now a sufficient amount of ground coffee is poured in to brew espresso. The brewing piston 24 is lowered into the brewing cylinder 30 until the preset maximum current in the maximum current potentiometer 54 is reached, that is to say the ground coffee is compressed with the maximum force. Now the piston path s associated with this maximum pressing force is scanned via the sensor 53 and stored in the controller 50 . A brewing process then begins, in which the pump 13 is operated and the valve 16 is opened. The heater 15 is always on standby. The pressure of the coming from the water supply 11 through the check valve with pressure reducer 12 What sers is increased by the pump 13 to about 8 bar, this pressure being set in the pressure reducer 14 . If the pressure generated by the pump 13 exceeds this value, the water flows from the pressure-side outlet of the pump 13 via the reflux pressure reducing valve 14 to the input of the pump 13 .

The water is heated in the heating device 15 and passes through the piston 32 into the ground coffee 1 and through it through the filter 21 or its flow openings 25 into the discharge line 19 . The position of the brewing piston 24 in the brewing bush 31 shown for this process is shown in FIG. 3.

The flow rate of the water is scanned with the flow rate measuring device 40 . A corresponding measured value is fed to the control 50 . Now it is determined whether the measured flow rate is greater or less than a setpoint, which is preset in the controller 50 by means of a setpoint generator 51 . In the first brewing process, in which the maximum contact pressure is set, this cannot be the case by definition. In such a first brewing process, the press force is set to a maximum, so it can only become smaller. As a result, the flow rate is minimal during the first brewing process, i.e. lower than the flow rate at which an optimal brewing result is achieved (pre-set value). Accordingly, for the next brewing process, a default value for the travel measurement value (travel measurement device 53 ) is set, which is somewhat lower. Accordingly, in a next brewing process, the filter 21 or the brewing piston 24 is moved a little less far into the brewing bush 31 with the same amount of coffee. As a result, the coffee contact pressure is reduced, so that the flow rate increases during the next brewing process. This is kept for all further ren brewing processes until the Durchflußge speed is higher than the preset value. Thereafter, the path by which the brewing piston 24 is inserted into the brewing bush 31 is increased again by a certain small amount until the flow rate becomes lower again than the preset value in the case of a further brewing process, so that the travel setting is always around an "optimum point "sways back and forth. If the user wants the coffee to be stronger, he reduces the flow rate by means of the setpoint generator 51 . The machine then adjusts itself automatically, using the flow rate as a setting parameter - and this has proven to be particularly important in practice - the parameter that most directly describes the properties of the coffee itself or the coffee powder co-recorded.

Another important point in the brewing process is that, according to the contact pressure and the water pressure, the filter 21 is moved toward the holding plate 36 by compressing the spring 27 in such a way that the needles 26 are inserted into the openings 25 ben. As a result, the annular gaps, which are due to the conicity of the needles 26 and the through-flow openings 25 and their size differences, are narrower. This means that even with a very low contact pressure (for brewing coffee) the water flows through the coffee grounds 1 with a pressure that is not negligible and that the (very fine-grained) coffee grounds are safely retained when brewing espresso. Due to the mobility of the needles 26 in the flow openings 25 , a kind of self-cleaning is still guaranteed.

In short, the ground coffee is poured into the brewing cylinder 30 in the position of the brewing piston 24 shown in FIG. 2; then the brewing piston 24 is inserted into the brewing cylinder 30 , in which the ground coffee 1 is located, namely as deep as is predetermined by the target value determined in the previous brewing process. This position is shown in Fig. 3. After the preset amount of water (corresponding to one or more portions of coffee in accordance with the amount of ground coffee 1 ) has been passed through, the brewing piston 24 is raised to its uppermost position ( FIG. 4), the upper crosshead 65 making contact with the threaded sleeves 17 , 17 'arrives and thus the entire lifting frame 60 is raised by compressing the springs 64 , 64 ', so that the piston 32 is raised via the piston rod 33 into the position shown in FIG. 4, to the extent that its upper surface is essentially flush runs with the upper edge of the brewing sleeve 31 . In this position, the compressed filter cake 2 lies on the piston 32 and is cleared by means of the clearing slide 34 in a substantially exclusively horizontal sliding movement into a waste container (not shown). Then the position shown in FIG. 2 is set again. The next brewing process can now take place.

The brewing of coffee differs from the brewing of espresso in that on the one hand a different type of ground coffee 1 is filled in a different amount and on the other hand the brewing piston 24 is only moved into the brewing sleeve 31 by a smaller amount, as shown in FIG . 7 is shown. The filled Kaf feemehl is only very slightly compressed (if at all), the filter 21 being pressed into its position by the spring 27 , in which the adjusting screw 38 comes into abutment with its seat in the filter plate 36 . As a result, the gaps between the needles 26 and the flow openings 25 are as large as possible. The brewing process is again shown in Fig. 8 Darge.

Another difference from the brewing of espresso is that the pump 13 is not operated. It is now designed in such a way that the water coming from the water supply 11 through the check valve or the pressure reducer 12 with its pressure (below 2 bar) can flow through the pump 13 without significant pressure losses, as is known per se . Otherwise, the machine is set in the same way as when brewing espresso, so that the position of the brewing piston 24 in the brewing sleeve 31 is also regulated via the flow rate.

Reference list

1

Ground coffee

2nd

Filter cake

10th

Water supply device

11

Water supply

12th

Check valve / pressure reducer

13

pump

14

Reflux pressure reducer

15

Heating device

16

Control valve

17th

,

17th

'' Threaded sleeve

18th

,

18th

',

18th

"Gears

19th

Output line

20th

Brewing device

21

filter

22

engine

23

Spindle drive

24th

Brewing flask

25th

Flow opening

26

needle

27

feather

28

frame

29

,

29

'Spindle

30th

Brewing cylinder

31

Brewing sleeve

32

piston

33

pole

34

Clearing slide

35

Holding piece

36

Retaining plate

37

poetry

38

Adjusting screw

39

Flow space

40

Flow rate measuring device

50

control

51

Flow rate setpoint device

52

Maximum value transmitter / current sensor

53

Position measuring device

54

Maximum current potentiometer

60

Lifting frame

61

,

61

'' Lifting rod

62

Crosshead

63

Holding bush

64

,

64

' Feather

65

upper crosshead
s piston travel

Claims (15)

1. A method for the automatic preparation of coffee and / or espresso, whereby heated water with predetermined liquid pressure is guided through coffee powder and the ground coffee compressed with predetermined pressure is retained by a filter, characterized in that the contact pressure is a function of a measured water flow rate is posed. 2. The method according to claim 1, characterized records that the water flow rate measured value compared with a target value and if the setpoint is not reached, the contact pressure reduced, is increased when exceeded. 3. Method according to one of the preceding An sayings, characterized in that the water flow rate measurement at a he Most brewing process determined and the pressure  in a subsequent brewing process Water flow rate measurement ent is set accordingly. 4. The method according to claim 3, characterized records that for setting a basic value for the contact pressure during the first brewing process from a contact pressure generating device maximum contact pressure that can be generated is set becomes. 5. Method according to one of the preceding An sayings, characterized in that the setting contact pressure via a presetting a pressure path of a brewing piston in one Brewing cylinder takes place in which the coffee flour. 6. Method according to one of the preceding An sayings, characterized in that flow openings of the filter depending on the liquid cross-section pressure can be set. 7. Coffee machine for preparing coffee or espresso, comprising a water supply device with a water heating device and a pressure generating device ( 11 , 13 , 14 ) for dispensing heated water with pre-tunable liquid pressure, a brewing device ( 20 ) comprising a filter ( 21 ) and to a pressing pressure generating device ( 22 , 23 ) for compressing ( 21 ) ground coffee ( 1 ) with pre-tunable contact pressure, characterized by a flow rate measuring device for generating a measured value in accordance with a speed at which the heated water through the ground coffee ( 1 ) and the filter ( 21 ) flows and a controller ( 50 ) which is of the type and connected to the contact pressure generating device ( 22 , 23 ) that the contact pressure is set as a function of the flow rate measured value. 8. Coffee machine according to claim 7, characterized in that the controller ( 50 ) has a target value transmitter ( 51 ) and a comparison device for comparing a target value with the flow rate measurement value and is formed such that the contact pressure is reduced when the target value is undershot and is increased when exceeded. 9. Coffee machine according to one of claims 7 or 8, characterized in that the controller ( 50 ) has a memory device and is designed such that the Durchflußgeschwindig keitsmeßwert determined in a first brewing process and the contact pressure in a subsequent brewing process the stored contact pressure is set accordingly. 10. Coffee machine according to one of claims 7 to 9, characterized in that the contact pressure generating device comprises a Wegmeßeinrich device ( 53 ) for measuring the path of a brewing piston ( 24 ) in a brewing cylinder ( 30 ). 11. Coffee machine according to one of claims 9 or 10, characterized in that the contact pressure generating device ( 22 , 23 ) has a maxi malwertgeber ( 52 ), and that the controller ( 50 ) is designed such that for setting a basic value for the contact pressure a maximum contact pressure generated by the contact pressure generating device ( 22 , 23 ) is set. 12. Coffee machine according to one of claims 7 to 11, characterized in that the brewing cylinder ( 30 ) comprises a substantially fixed brewing socket ( 31 ), in the lower region of which a motor-driven piston ( 32 ) for ejecting a filter cake ( 2 ) and in the upper region of which the filter ( 21 ) forming the brewing piston ( 24 ) is arranged such that it can be moved out of the brewing bush ( 31 ), where the contact pressure generating device ( 22 , 23 ) is preferably connected to the filter ( 21 ) and this increases when a filter is produced Contact pressure continues into the brewing sleeve ( 31 ). 13. Coffee machine according to one of claims 7 to 12, characterized in that the filter ( 21 ) has flow openings ( 25 ) with adjustable cross sections and that the controller ( 50 ) is designed such that the cross sections of the flow openings ( 25 ) can be set depending on the liquid pressure. 14. Coffee machine according to claim 13, characterized in that the filter ( 21 ) comprises a sieve with openings ( 25 ) with defined cross sections and needles ( 26 ) which, depending on the insertion depth in the openings ( 25 ), have differently large flow cross sections define. 15. Coffee machine according to claim 14, characterized in that the needles ( 26 ) with respect to the openings ( 25 ) by means of spring force (spring 27 ) are held in such a way that with increased contact pressure / liquid pressure, the opening cross-sections are smaller than with a lower contact pressure. / Fluid pressure.