Coffee machine and method for preparing a coffee drink

Abstract

The invention relates to a coffee machine (1) including a machine unit (2) comprising a brewing piston (4) that is moveably mounted between a starting position (AK) and a brewing position (BK), a piston drive (62), which can be controlled by the control unit (20), for moving the brewing piston (4) from the starting position (AK) into the brewing position (BK), a water preparation unit (60) with a water tank (61), a water pump (62) and a heating unit (63) for generating and outputting pressurised hot brewing water into a brewing chamber (3), as well as comprising a control unit (20) for controlling the coffee machine (1). The coffee machine includes a blocking unit (11) with at least one blocking element (13) for blocking the brewing piston (4) in the brewing position (BK).

Description

[0001] COFFEE MACHINE AND METHOD FOR PREPARING A COFFEE BEVERAGE

[0002] The invention lies in the field of coffee machines and relates to a coffee machine for producing, in particular brewing, a coffee beverage according to the preamble of independent claim 1. Furthermore, the invention also relates to a method for producing, in particular brewing, a coffee beverage.

[0003] There are a variety of different coffee machine systems for preparing or brewing coffee. In addition to the well-known capsule machines, in which the coffee powder is fed into the coffee machine in pre-portioned capsules, there are also systems in which the coffee powder is poured into a coffee chamber in portions for each brewing process. These systems are divided into semi-automatic coffee machines (so-called semi-automatic machines) and fully automatic coffee machines (so-called fully automatic machines).

[0004] Among semi-automatic machines, the so-called portafilter machines are particularly well-known. These are characterized by a manually removable portafilter, which forms the coffee receiving chamber, which is closed off at the bottom by the brewing sieve. Filling the portafilter with coffee grounds and removing the coffee grounds from the portafilter after brewing takes place outside the coffee machine. For this purpose, the portafilter is manually removed from the coffee machine.

[0005] Fully automatic machines differ from semi-automatic machines in that the preparation of the coffee grounds, or filling the coffee chamber with coffee grounds before the brewing process, is a fully automated process integrated within the coffee machine. Furthermore, the coffee grounds are also automatically ejected into an integrated container in the coffee machine after the brewing process. Accordingly, fully automatic machines do not have a removable portafilter.

[0006] In fully automatic machines, the coffee powder is usually provided via an integrated grinder, which grinds coffee beans freshly from a storage container in the coffee machine for each brewing process.

[0007] In this description, coffee powder refers specifically to ground coffee, i.e., ground coffee. Coffee grounds refers specifically to the residue left after the brewing process, also known as coffee grounds.

[0008] The present invention relates in particular to fully automatic and, more particularly, semi-automatic coffee machines, such as portafilter machines. In these coffee machines, the coffee grounds must be pressed into the coffee chamber before brewing. This process is also called "tamping."

[0009] The pressing of the coffee powder in the coffee chamber is crucial for the subsequent brewing process, e.g. for the preparation of an espresso with crema, and influences the preparation method of the brewed coffee.

[0010] It is well known that the coffee powder is pressed, the so-called "tamping," using a movable brewing piston, which is propelled or moved fully automatically downwards into the coffee chamber via a hand lever or a piston drive. However, each automation step, such as the automatic driving of the brewing piston, requires additional components and units, such as drives. This makes the design of the coffee machine increasingly complex. This leads to higher maintenance requirements and a greater susceptibility to failure. Furthermore, additional components, especially drives, increase the cost of the coffee machine.

[0011] It is now an object of the present invention to propose a coffee machine with a high degree of automation, but with as few drive devices as possible for driving the various units by means of a control device.

[0012] A further object is to propose a coffee machine which enables a defined pressing of the coffee powder controlled by a control device even when the portafilter is filled with different amounts of coffee powder.

[0013] A further objective is to propose a coffee machine in which the movably guided brewing piston is secured against being forced back out of the coffee chamber by the brewing pressure in the brewing chamber during the brewing process. The securing means should, if possible, require no additional drive.

[0014] At least one object is achieved by the features of the independent claims. The dependent claims, the description, and the figures contain particular embodiments and developments of the invention.

[0015] The coffee machine according to the invention contains a machine unit with:

[0016] - a control device for controlling the coffee machine,

[0017] - a brewing piston movably mounted between a starting position and a brewing position, - a piston drive controllable via the control device for moving the brewing piston from the starting position to the brewing position, and with

[0018] - a water treatment device with a water tank, a water pump and a heating unit for generating and delivering hot brewing water under pressure into a brewing chamber.

[0019] The brewing piston is mounted so that it can move, particularly along its piston axis, i.e. axially.

[0020] The invention is characterized in that the coffee machine includes a locking device with at least one locking body for locking the brewing piston in the brewing position. The locking mechanism serves, in particular, to prevent axial movement of the brewing piston from the brewing position toward the starting position.

[0021] The brewing piston is, in particular, part of a brewing unit formed in the machine unit and has a piston plunger. The piston plunger is arranged on the brewing side. The piston plunger is, in particular, connected to a piston shaft, which is, in particular, housed in a piston shaft housing. The piston shaft housing is, in particular, part of the brewing unit in the machine unit.

[0022] The brewing unit forms a brewing group, in particular together with the coffee receiving chamber and a brewing sieve or together with a portafilter device.

[0023] The brewing piston serves, in particular, to press (tamp) the coffee powder previously filled into a coffee receiving chamber before the brewing process, as well as to close the coffee receiving chamber and form a closed brewing chamber for the subsequent brewing process. The coffee receiving chamber, or the coffee receptacle forming the coffee receiving chamber, is arranged in a stationary or immobile manner within the machine unit, particularly during the brewing process. The same applies accordingly to the portafilter device if the coffee machine is a portafilter machine.

[0024] The piston plunger can be used to feed brewing water into the brewing chamber.

[0025] The piston drive can include an electric motor. The brewing piston can be driven by the electric motor via a drive spindle.

[0026] The piston drive can also comprise a hydraulic drive, by means of which a hydraulic fluid, such as water, is used to build up hydraulic pressure in a pressure chamber in the brewing unit, which can push, propel, or move the brewing piston into the brewing position. The hydraulic pressure can be generated by a pump. The hydraulic pressure can be, for example, between 2 and 3 bar.

[0027] According to a further development of the invention, the water pump of the water treatment device is part of the piston drive or forms the piston drive.

[0028] By building up a (piston) water pressure acting on the brewing piston through the water pump, the brewing piston can be moved from the starting position to the brewing position.

[0029] In this configuration, the water pump of the water treatment system has a dual function: firstly, it pumps brewing water into the brewing chamber, and secondly, it pumps (piston) water into a pressure chamber in the brewing unit to propel the brewing piston. Piston water refers to the water pumped into the piston water line to build up piston water pressure to move the brewing piston.

[0030] The locking device can now be actuated, in particular, via the piston drive. The locking device can also be actuated by the hydraulic drive, in particular by the water pump of the water treatment system.

[0031] By building up a water pressure acting on the locking device, in particular piston water pressure, the at least one locking body of the locking device can be moved into a locking position.

[0032] The at least one locking body of the locking device can be displaced into a locking position, in particular indirectly by the piston water pressure.

[0033] The locking device is in particular a locking mechanism.

[0034] The locking device includes, in particular, an actuating element movable parallel to the piston axis of the brewing piston. The at least one locking body can be moved toward the brewing piston by or via the actuating element into a locking position.

[0035] The actuating element can be moved parallel to the piston axis of the brewing piston, in particular by hydraulic pressure, in particular fluid pressure or piston fluid pressure, such as water pressure or piston water pressure.

[0036] The coffee machine is now particularly designed such that, to initiate a brewing process, the piston drive first moves the brewing piston into a brewing position and, once the brewing position is reached, actuates the locking device, locking the brewing piston, in a second step. A coffee machine designed as a portafilter machine is particularly designed such that, to initiate a brewing process, the piston drive first moves the brewing piston into a brewing position by pressing the coffee powder and applying a pressing force. Upon reaching a maximum pressing force and assuming the brewing position, actuates the locking device, locking the brewing piston, in a second step.

[0037] According to a further development of the invention, the piston skirt housing is movably mounted along the piston axis. This interacts with the actuating element of the locking device.

[0038] The piston shaft housing and the brewing piston are particularly designed and interact in such a way that the piston drive drives the brewing piston in the first step in the axial direction towards the brewing chamber into the brewing position and then moves the piston shaft housing in the second step in the opposite, axial direction by actuating the locking device.

[0039] The axially movable piston shaft housing, together with the axially movable brewing piston, forms a pressure chamber.

[0040] The piston shaft housing and the brewing piston are now particularly designed and interact in such a way that a hydraulic pressure generated in the pressure chamber, in particular (piston) water pressure, drives or moves the brewing piston in the axial direction, in particular downwards, toward the brewing chamber into the brewing position and then moves the piston shaft housing in the opposite axial direction, in particular upwards, upon actuation of the locking device. The movement or displacement of the brewing piston and the piston shaft housing each occur in particular counter to the restoring force of restoring means, which exert a restoring force on the brewing piston or the piston shaft housing.

[0041] In particular, the piston shaft housing is only moved when the brewing piston has reached the brewing position and the hydraulic pressure in the pressure chamber continues to rise. This means that the hydraulic pressure required to move the piston shaft housing is greater than the hydraulic pressure required to move the brewing piston into the brewing position.

[0042] The pressure chamber is located in particular in an upper section of the brewing unit and especially above the brewing piston.

[0043] The brewing piston delimits in particular a lower section of the pressure chamber, such that the piston pressure in the pressure chamber is able to push or move the brewing piston axially downwards towards the coffee receiving space.

[0044] The piston shaft housing delimits in particular an upper section of the pressure chamber such that the piston pressure in the pressure chamber is able to push or move the piston shaft housing in the opposite direction axially upwards away from the coffee receiving space.

[0045] The piston skirt housing is mounted, in particular, for displacement along a longitudinal or vertical guide. The longitudinal guide can be provided, for example, via at least one connecting screw with, in particular, a threadless guide section. The at least one return spring is arranged, in particular, on the connecting screw.

[0046] The piston skirt housing is coupled to the actuating element, or connected to it, in such a way that the actuating element can be displaced axially, in particular upwards, together with the piston skirt housing to assume an actuating position. The actuating element can also, in principle, be part of the piston skirt housing.

[0047] The axial movement of the actuating element moves the locking body into a locking position, locking the brewing piston. To assume the locking position, the locking body moves, in particular, transversely to the piston axis or radially toward the brewing piston and engages, in particular, in a recess on the brewing piston.

[0048] According to a further development of the invention, the locking of the brewing piston can be achieved in different axial positions of the brewing piston and consequently in different axial brewing positions of the brewing piston. This is achieved, for example, by arranging at least two or more consecutive recesses on the brewing piston in the axial direction.

[0049] The movement of the piston shaft housing is comparatively small, especially compared to the movement of the brewing piston, since the movement only serves to actuate the locking body.

[0050] The piston shaft of the brewing piston is guided, in particular, by a piston shaft guide tube. The piston shaft is guided, in particular, from the piston shaft housing through the piston shaft guide tube into a piston plunger guide housing, in which the piston plunger is arranged. The piston shaft guide tube thus connects, in particular, the piston shaft housing to the piston plunger guide housing.

[0051] The piston skirt housing and the piston skirt guide tube are in particular arranged stationary, i.e. immovably, in the machine unit.

[0052] The piston skirt guide tube can have at least one radial opening, in particular a plurality of radial openings arranged particularly evenly around the circumference of the piston skirt guide tube. The at least one locking body is in particular a spherical body guided in a radial opening of the piston skirt guide tube, which, in the locking position, engages in a recess formed as a depression on the piston skirt. The depression on the piston skirt can be an annular circumferential depression. The actuating element is in particular an annular body that surrounds the piston skirt guide tube.

[0053] The brewing piston can interact with return means, in particular with a return spring, by means of which the brewing piston can be moved back or reset from the brewing position to the starting position after the hydraulic pressure, in particular (piston) water pressure, in the pressure chamber has been released. The return means are arranged in particular in the piston shaft housing.

[0054] The return spring can, in particular, be a compression spring. The piston shaft of the brewing piston can be guided axially by the compression spring.

[0055] The compression spring is in particular designed and arranged in the brewing unit in such a way that it is compressed by the propulsion or movement of the brewing piston towards the brewing position and by expanding it moves the brewing piston back to its starting position.

[0056] According to a further development of the invention, the piston shaft housing cooperates with return means, in particular with at least one return spring, by means of which the piston shaft housing can be moved back from the actuating position to its starting position after the (piston) water pressure has been reduced.

[0057] The at least one return spring can, in particular, be a compression spring. The compression spring is, in particular, designed and arranged in the brewing unit in such a way that it is compressed by an axial movement of the piston shaft housing opposite to the piston movement, and the piston shaft housing is moved back to its original position by the extension of the compression spring.

[0058] If the piston drive is formed by the water pump of the water treatment system, the water pump is in particular:

[0059] - via a supply water pipe for the supply of water with a water tank,

[0060] - via a piston water line for moving the brewing piston with the brewing piston, and

[0061] - hydraulically connected to the brewing chamber via a brewing water line for brewing coffee.

[0062] The control device is particularly designed to switch the water pump between a piston water feed and a brewing water feed.

[0063] In particular, a directional control valve, such as a 3 / 2-way valve, is arranged in the piston water line, which is designed and can be controlled or switched via the control device in such a way that, when the piston water pressure is reduced, piston water flowing back can be discharged via a discharge line, bypassing the water pump.

[0064] The discharge line is, in particular, a return water line through which returning piston water can flow back into the water tank. The return water line can flow back directly into the water tank, or indirectly into the supply water line.

[0065] A check valve is located in the piston water line, particularly between the water pump and a directional control valve, to maintain the built-up piston water pressure. The brewing water line leads, in particular, to the brewing water feed at the piston plunger. A heating unit, such as a thermoblock or instantaneous water heater, is arranged along the brewing water line, which can heat the brewing water flowing through the brewing water line.

[0066] In particular, a directional control valve, such as a 3 / 2-way valve, is arranged in the brewing water line, which is designed and can be controlled or switched via the control device in such a way that residual water flowing back towards the water pump after the brewing process can be drained off via a drain line, e.g. into a drip tray.

[0067] According to a special design variant, the coffee machine is a portafilter machine and contains a portafilter unit with a brewing sieve, also called a portafilter, that can be removed from the machine unit. The portafilter unit forms a coffee receiving space, which, together with the brewing piston or piston plunger advanced into the brewing position, forms the brewing chamber.

[0068] “Removable” means in particular that the portafilter device can be completely separated from the machine unit without any permanent connection to the machine unit.

[0069] The portafilter device includes, in particular, a handle for manually attaching the portafilter device to the machine unit and for manually removing the portafilter device from the machine unit. Attaching and removing the portafilter device is particularly tool-free.

[0070] The coffee receiving space of the portafilter unit can be formed, in particular, by a filter insert with a brewing sieve integrated into the portafilter housing. The coffee receiving space of the portafilter unit can be formed by a filter insert with a brewing sieve permanently installed in the portafilter housing. However, the filter insert can also be removable.

[0071] Since, according to the present invention, the movably mounted brewing piston is driven into the coffee receiving space of the portafilter device to press (tamp) the coffee powder and to close the brewing chamber, no differently sized sieve inserts are necessary for different amounts of coffee powder.

[0072] The portafilter unit can be attached to the machine unit to initiate the brewing process using a quick-release fastener known in the art, such as a bayonet lock, i.e., by attaching and screwing the portafilter unit onto the machine unit. However, the portafilter unit can also be inserted straight into the machine unit using a linear guide device.

[0073] The portafilter unit is removable from the machine unit, especially for removing coffee grounds after a brewing process. The portafilter unit can also be removed from the machine unit for filling the portafilter unit with ground coffee.

[0074] However, it can also be provided that the portafilter unit or the coffee chamber is filled with coffee powder via a grinder integrated into the machine unit or coffee machine. This applies particularly to fully automatic coffee machines.

[0075] This means that the machine unit or coffee machine can contain a device for dispensing, and in particular for producing and dispensing, coffee powder into the coffee receiving space. The invention further relates to a method for brewing coffee using a coffee machine as described above. By definition, a coffee beverage includes all coffee preparation methods that are possible with a portafilter machine. These include, for example, black coffee, espresso, espresso lungo, ristretto, etc. Furthermore, coffee beverages also include methods with added milk, such as cappuccino or latte macchiato. For this purpose, the coffee machine can also contain a milk preparation device, such as a milk frother.

[0076] The coffee machine contains an input device, e.g., with a display, for initiating a brewing process and, in particular, for selecting the coffee preparation method.

[0077] The process is characterized by the fact that, to carry out a brewing process, the brewing piston is propelled by a piston drive toward the coffee receiving chamber filled with coffee powder. Upon reaching the brewing position, the locking device is activated, locking the brewing piston against axial movement away from the brewing chamber. The water pump pumps brewing water into the brewing chamber, building up brewing water pressure, and the brewing process begins.

[0078] If the piston is driven by the water pump of the brewing water treatment device, a piston water pressure acting on the brewing piston is built up by means of the water pump, whereby the brewing piston is driven forward, in particular against the restoring force of a restoring means, in the direction of the coffee receiving space, in particular downwards, into the brewing position.

[0079] The water pump draws the (piston) water required to build up piston water pressure from the water tank via the supply water line and pumps it as piston water into the piston water line. The piston plunger, which engages the coffee chamber, closes the coffee chamber, forming a closed brewing chamber.

[0080] The brewing piston acts as a coffee press or tamper, compressing the coffee grounds in the coffee chamber. The degree of coffee pressure, which significantly influences the coffee preparation method, can be set, particularly via the control unit.

[0081] Based on the corresponding specifications for coffee pressing (measure or degree of coffee pressing), the control device can control the pressing pressure (piston pressure) exerted on the coffee powder via the piston drive or the water pump.

[0082] The coffee pressing can be controlled on the basis of stored default values ​​or on the basis of default values ​​entered or selected via the input device on the machine unit.

[0083] The pressure exerted by the brewing piston on the coffee powder is lower than the brewing water pressure exerted on the brewing piston in the opposite direction during the brewing process by the brewing water in the brewing chamber.

[0084] Therefore, according to the invention, the brewing piston is locked in the brewing position against any axial movement opposite to the direction of advance of the brewing piston. Thanks to this locking mechanism, the piston drive only needs to apply the lower pressing force required to press the coffee during the brewing process, rather than the higher force that counteracts the brewing water pressure.

[0085] According to the locking device described above, after the

[0086] Once the brewing piston has reached the brewing position, an actuating element is moved or displaced by the piston water pressure in an axial direction opposite to the direction of advance of the brewing piston, in particular upwards. The movement of the actuating element displaces at least one locking body radially toward the brewing piston, in particular toward the piston shaft, into a locking position, thereby locking the brewing piston. "Radial" also means, in particular, perpendicular to the piston axis.

[0087] In the locking position, the at least locking body engages in a recess on the brewing piston, in particular on the piston shaft.

[0088] For the axial movement of the actuating element, in particular the movably mounted piston shaft housing, to which the actuating element is coupled or connected, is moved or displaced by the piston water pressure in the pressure chamber against the restoring force of the restoring means in an axial direction opposite to the propulsion direction of the brewing piston, in particular upwards, into the actuating position.

[0089] As mentioned, the piston water pressure is maintained during the brewing process, whereby the actuating element or the piston shaft housing with the actuating element remains in the actuating position and thus the locking body remains in the locking position.

[0090] The locking device according to the invention has the advantage that, in portafilter machines, the brewing pistons are only locked after the coffee powder has been pressed or compressed (tamped) into the portafilter device. Since the amount of coffee powder and, accordingly, the brewing position of the brewing piston along the brewing piston axis can vary depending on the preparation method, the water pump draws water from the water tank via the supply water line and pumps this as brewing water into the brewing water line.

[0091] For this purpose, the water pump is switched from the piston water supply to the brewing water supply. This is also done via the control unit. Thanks to the check valve in the piston water line, the built-up piston water pressure is maintained in the piston water line despite switching to the brewing water supply.

[0092] The piston water pressure is only released after the brewing process has been completed in order to release the locking mechanism and move the brewing piston back to its original position.

[0093] At the end of the brewing process, the water pump stops supplying brewing water, and the brewing water pressure is reduced accordingly. By switching the directional control valve on the brewing water line, any remaining water in the brewing water line is drained, e.g., into a drip tray.

[0094] Furthermore, to reduce the piston water pressure for the purpose of releasing the locking mechanism and resetting the brewing piston, the directional control valve in the piston water line is switched via the control device, so that the piston water is drained via the drain water line. The piston water is returned to the water tank, in particular, via the drain water line designed as a return water line.

[0095] As the piston water pressure decreases, the actuating element or the piston shaft housing with the actuating element moves back from the actuating position to its original position due to the restoring force of the return means. This allows the brewing piston to be released from its locking position by the at least one locking body, and the brewing piston can be moved back to its original position via the return means. The locking is released passively, as the returning brewing piston pushes the at least one locking body back into a space created by the returning actuating element.

[0096] The individual units or devices, such as the water pump, valves, piston drive, or grinder, are controlled primarily via the control unit. Control commands can be transmitted to the control unit via the input device.

[0097] As already mentioned above, the piston drive, in particular, is also controlled by the control unit. The degree of coffee pressing, for example, can be set via the input device or via presets. The control unit then controls the pressure exerted on the coffee powder (piston pressure) via the piston drive based on the corresponding specifications for the coffee pressing (degree of coffee pressing).

[0098] The coffee machine according to the invention is characterized by the following advantages:

[0099] - Individual adjustment of the coffee pressure thanks to the brewing piston which can be driven into the coffee receiving space or into the brewing chamber via the control device using a piston drive;

[0100] - thanks to the locking mechanism, the brewing piston does not retreat during the brewing process despite lower piston pressure;

[0101] - The brewing piston is locked using an existing drive.

[0102] The advantages of portafilter machines are in particular: - thanks to the movable brewing piston, which allows individual coffee pressing even when the coffee chamber is filled with different amounts of coffee powder, portafilter inserts of different sizes are no longer necessary;

[0103] - thanks to the movable brewing piston, there is no need to tighten the portafilter device against a (fixed) stamp on the machine unit for the coffee pressing.

[0104] The subject matter of the invention is explained in more detail below using specific embodiments illustrated in the accompanying figures. Each of these figures schematically shows:

[0105] Figure 1a: perspective view of a first embodiment of an arrangement of brewing unit and grinder as well as of linear guide device and portafilter device of a portafilter machine, obliquely from the front;

[0106] Figure 1b: Cross section through the arrangement according to Figure 1a;

[0107] Figure 1c: further perspective view of the arrangement according to Figure 1a from an angle behind;

[0108] Figure 2: perspective view of the portafilter device from above;

[0109] Figure 3: perspective view of the linear guide device according to Figure 1a without portafilter device, obliquely from below;

[0110] Figure 4: schematic view of a portafilter machine with an arrangement according to

[0111] Figure 1a to 1c;

[0112] Figure 5 : perspective view of the grinder according to Figures 1 a to 1 c, obliquely from below.

[0113] According to a first embodiment according to Figures 1a to 1c, the coffee machine 1 contains a brewing unit 10 and a device for producing and dispensing coffee powder 30 with a conical grinder 31. A holding and guiding device 40 with a linear guide device 41 is arranged below the brewing unit 10 and the device 30. The linear guide device 41 contains two guide rails 42a, 42b arranged at a distance from one another and running parallel to one another, each of which contains a guide slot 44 for the sliding reception of guide strips 55 on a portafilter device 50.

[0114] Furthermore, the coffee machine 1 comprises a portafilter device 50 with a portafilter housing 54 and a handle body 53 for holding the portafilter device 50. On the outside of the portafilter housing 54, two guide rails 55 are arranged, extending laterally and parallel to one another on both sides of a receiving opening 56, for insertion into the guide slots 44 of the guide rails 42a, 42b.

[0115] The brewing unit 10 and the device 30 with conical grinder 31 are arranged one behind the other along the insertion axis EA, wherein the device 30 with conical grinder 31 is arranged after the brewing unit 10 in the insertion direction ER.

[0116] The portafilter device 50 can be inserted into the machine unit 2 of the coffee machine 1 via the guide rails 55, which engage laterally in the guide slots 44 of the guide rails 42a, 42b. The machine unit 2 corresponds to the coffee machine 1 without the portafilter device 50.

[0117] The portafilter device 50 can be inserted, among other things, into a filling position FS, in which the portafilter device 50 is arranged below the device 30 or the grinder 31. The holding and guiding device 40 forms an end stop 45, which represents an insertion limit and simultaneously ensures the precise positioning of the portafilter device 50 in the filling position FS for filling the portafilter device 50 with coffee powder 22. This means that the portafilter device 50 assumes the filling position FS upon reaching the stop 45.

[0118] The conical grinder 31 contains a multi-part housing 35 in which the grinding cone 32 and the grinding ring 33, which surrounds the grinding cone 32, are arranged. The grinding cone 32 tapers upwards along the cone axis, starting from the cone base. The grinding ring 33 is mounted in the housing 35 via bearings, such as ball bearings, for rotation about the cone axis of the grinding cone 32 and is driven by an electric motor 34. The grinding gap is formed between the grinding ring 33 and the grinding cone 32, into which the coffee beans are fed from above and ground by the grinding ring rotating about the cone axis. The ground coffee powder leaves the grinding gap at the lower end in the area of ​​the cone base and falls downwards due to gravity.

[0119] The grinding cone 32 is rigid, ie, stationary, and is connected to the housing 35 at each of its two cone ends via several connecting webs 36a, 36b. The connecting webs 36a, 36b extend radially outward from the cone axis toward the housing 35 in a star shape.

[0120] At the upper end of the grinding cone, between the connecting webs 36a, several passage openings are formed for the passage of coffee beans in the direction of gravity G downwards into the conical grinder 31 (see Figure 1c).

[0121] At the lower end of the grinding cone, ie at the cone base, a plurality of passage openings are formed between the connecting webs 36b for the passage of coffee powder 22 from the conical grinder 31 in the direction of gravity G downwards into the coffee receiving space 51 of the portafilter device 50 (see Figure 5).

[0122] However, it is not mandatory for the coffee machine to include an integrated grinder as shown in the figures. This is especially true for portafilter machines. For example, the grinder can be arranged or attached to the coffee machine in such a way that a portafilter unit is already filled with ground coffee before it is inserted into the machine unit or before it is attached to the machine unit. Furthermore, it is also possible for the coffee machine not to include a grinder, and for the ground coffee to be drawn from a separate coffee grinder or from a storage tank.

[0123] The portafilter device 50 contains a sieve insert 49 embedded in the portafilter housing 54 with a brewing sieve 52 forming the base of the sieve insert 49. The sieve insert 49 forms the coffee receiving space 51 for receiving the coffee powder 22. This is open at the top. Accordingly, the sieve insert 49 has a receiving opening 56 at the top. This opening lies opposite the brewing sieve 52. The coffee receiving space 51 is cylindrical, but has a circumferential, funnel-shaped extension 57 in the area of ​​the receiving opening 56. In this exemplary embodiment, the sieve insert 49 is firmly connected to the portafilter housing 54 and accordingly cannot be removed. However, the sieve insert 49 can also be removable. Likewise, the sieve insert can be an integral part of the portafilter housing 54.

[0124] Following the filling of the coffee receiving chamber 51 of the portafilter device 50 with coffee powder 22, the portafilter device 50 is retracted into the brewing position BS in a linear countermovement via the linear guide device 41. In the brewing position BS, the portafilter device 50 is located below the brewing unit 10.

[0125] As can be seen in more detail in Figures 2 and 3, the linear guide device 41 and the portafilter device 50 have cooperating locking means 43, 59, which allow precise, self-centering positioning of the portafilter device 50 in the brewing position BS. In the present exemplary embodiment, locking notches 43 are formed in the guide slot 44 of the guide rails 42a, 42b, into which spring-loaded balls 59 arranged on the guide strips 55 of the portafilter device 50 engage. The locking notches 43 each form an inlet ramp in the insertion direction ER and opposite to the insertion direction ER. This is intended to reduce the force required when pushing or pulling the portafilter device 50 out of the locking position, so that the portafilter device 50 can be easily pushed or pulled over the locking position or pulled or pushed out of the locking position again.

[0126] In principle, the portafilter attachment can also be secured using a conventional quick-release fastener, such as a bayonet lock. Likewise, an integrated grinder is not mandatory.

[0127] The brewing unit 10 contains a brewing piston 4 with a piston shaft 5, which is guided in a piston shaft housing 7, and a piston plunger 6 arranged at the lower end, i.e., toward the portafilter device 50, which is guided in a piston plunger guide housing 19. The piston plunger guide housing 19 comprises a piston shaft guide tube 15, through which the piston shaft 5 is guided from the piston shaft housing 7 into the piston plunger guide housing 19. The piston axis KA is perpendicular to the insertion direction ER or insertion plane EE of the portafilter device 50 and accordingly also runs perpendicular to the receiving opening 56 of the portafilter device 50.

[0128] To initiate the brewing process, the brewing piston 4 is moved by a piston drive 21 from its starting position AK in the direction of gravity G downwards toward the coffee receiving chamber 51 of the portafilter device 50. The piston plunger 6 is thereby moved into the coffee receiving chamber 51 and presses or compresses the coffee powder 22. In other words, the so-called "tamping" is performed with the brewing piston 4. Upon reaching the brewing position BK, the advance of the brewing piston 4 is terminated. The coffee receiving chamber 51, closed by the piston plunger 6, now forms a brewing chamber 3.

[0129] The piston drive 21 and thus also the piston pressure, which in turn is a measure of the coffee pressure, is controlled by the control device 20. The piston drive 21 can be an electric drive or a hydraulic drive. In the latter case, as explained in more detail below, a hydraulic fluid, such as water, is introduced into a pressure chamber 9 via an inlet 25. A hydraulic drive of the brewing piston 4 can be achieved via the water pump 62 of the brewing water treatment device 60, as explained further below with reference to Figure 4.

[0130] The coffee machine or machine unit 2 further includes a brewing water treatment device 60 with a water tank 61, a water pump 62, and a heating unit 63 for supplying hot brewing water under pressure to the brewing chamber 3 (see also Figure 4). The hot brewing water is fed under pressure into the brewing chamber 3 via a brewing water feed 18 guided by the piston plunger 6.

[0131] The portafilter device 50 contains a coffee outlet opening 58 arranged below the brewing sieve 52. The coffee brewed in the brewing chamber 3 and pressed through the brewing sieve 52 flows downward through this outlet opening, e.g., into a drinking vessel (not shown).

[0132] The brewing piston 4 interacts with a return spring 8. In the present embodiment, this corresponds to a compression spring 8 in the form of a helical spring surrounding the piston shaft 5. The compression spring 8, which is compressed when the brewing piston 4 is advanced toward the portafilter device 50, pushes the brewing piston 4 back to its starting position AK after the brewing process is completed and the piston pressure is released. With a piston drive 21, such as an electric drive, which actively moves the brewing piston 4 back, return means such as return springs are not absolutely necessary.

[0133] The brewing piston 4 further comprises a piston guide sleeve 24, by means of which the brewing piston 4 is axially guided in the piston shaft housing 7. The piston guide sleeve 24 is arranged in the upper end section of the brewing piston 4 towards the pressure chamber 9. According to the present embodiment, the brewing piston 4 is locked in the brewing position BK by a locking device 11 against an axial direction opposite to the advancing direction of the brewing piston 4. The locking device serves, among other things, to relieve the load on the piston drive 21. Thus, the piston pressure exerted by the piston drive 21 on the brewing piston 4 for pressing the coffee powder 22 is significantly lower than the brewing water pressure built up in the brewing chamber 3 by the water pump 62 of the brewing water treatment device 60, which acts as counterpressure on the brewing piston 4.Thanks to the locking of the brewing piston 4 during the brewing process, no counterpressure corresponding to the brewing water pressure needs to be built up by the piston drive 21. However, the locking device 11 is not mandatory. Furthermore, locking can also be achieved by the piston drive 21 itself.

[0134] The embodiment according to Figures 1a to 1c shows a special design of a locking device, which is characterized in that it is also triggered via the piston drive 21.

[0135] In the present case, the piston drive 21 exerts hydraulic pressure on the brewing piston 4 via a hydraulic pump using a hydraulic fluid. For this purpose, a hydraulic fluid is introduced via an inlet 25, such as a piston water inlet, into a pressure chamber 9, which is delimited, among other things, by the movable brewing piston 4. The pressure chamber 9 is not particularly clearly visible in Figure 1b, since it only expands spatially upon the movement of the brewing piston 4 from its starting position AK downwards into the brewing position BK.

[0136] As explained in more detail with reference to Figure 4, the hydraulic pump of the water pump 62 can correspond to the brewing water treatment device 60, and the hydraulic fluid can be water from the water tank 61 of the brewing water treatment device 60. Due to the pressure of the hydraulic fluid (e.g., water) flowing into the pressure chamber 9, the brewing piston 4 moves, against the return force of the return spring 8, from its initial position AK downwards toward the portafilter device 50 into the brewing position BK.

[0137] The pressure chamber 9 is delimited at the top by the piston shaft housing 7. The piston shaft housing 7 is mounted for axial movement relative to the piston rod guide housing 19 and correspondingly relative to the piston shaft guide tube 15 along the connecting screws 23 via two connecting screws 23. The connecting screws 23 accordingly form a guide section, in particular a thread-free guide section, for axially guiding the axially movable piston shaft housing 7. The piston shaft housing 7 is held in an initial position by two compression springs 17 that press the piston shaft housing 7 downward. The compression springs 17 are designed as helical springs and each surround the connecting screws 23.

[0138] Upon reaching the brewing position BK, the axial downward movement of the brewing piston 4 is terminated. The pressure, which continues to rise in the pressure chamber 9, now exerts a corresponding force on the piston shaft housing 7, causing it to move slightly upward, counter to the restoring force of the compression springs 17, in a direction opposite to the piston movement.

[0139] Also connected to the piston skirt housing 7 is an annular actuating element 12 of the locking device 11, which surrounds the piston skirt guide tube 15 and is also moved upwards accordingly. In an upper section, the actuating element 12 forms a radial distance from the piston skirt guide tube 15, creating an annular cavity or gap. In a lower section, the actuating element 12 is in sliding contact with the piston skirt guide tube 15 and rests against it. The upper and lower sections merge into one another via a guide ramp.

[0140] At the level of the actuating element 12, the piston shaft guide tube 15 has radial through-openings 14 in which spherical bodies 13 are movably mounted.

[0141] The piston shaft 4 has a plurality of recesses 16 arranged along the piston axis KA, each of which is annular and in which the ball bodies 13 can engage.

[0142] In the unlocked position, the piston shaft housing 7 and, with it, the actuating element 12 are held in a lower starting position by the restoring force of the compression springs 17. The upper section of the actuating element 12, with its annular cavity or gap, is located at the level of the radial through-openings 14. The spherical bodies 13 are recessed from the radial through-openings 14 and engage in the annular cavity.

[0143] When the brewing piston 4 reaches the brewing position BK, the piston shaft housing 7, together with the actuating element 12, is slightly raised in the axial direction, as mentioned above. As a result, the lower section of the actuating element 12 moves upwards along with the annular gap, whereby the spherical bodies 13 are pushed radially inward into the through-openings 14 by the lower section, which also moves upwards. The guide ramp between the upper and lower sections ensures that the spherical bodies 13 do not wedge themselves against the actuating element 12, but rather move evenly into the through-openings 14.

[0144] The spherical bodies 13, which have been pushed back into the radial through-openings 14, now engage on the other side into a recess 16 on the piston shaft 5 and cause the brewing piston 4 to lock in the brewing position BK. The spherical bodies 13 thus act as locking bodies.

[0145] The locking remains in place as long as the hydraulic pressure in the pressure chamber 9 is able to push the piston shaft housing 7 upwards against the restoring force of the compression springs 17.

[0146] After the brewing process is completed, the pressure in the pressure chamber 9 is released, causing the piston shaft housing 7, together with the actuating element 12, to return downward to its original position due to the restoring force of the compression springs 17. The upper section of the actuating element 12, together with the annular gap between the actuating element 12 and the piston shaft guide tube 15, returns to the level of the radial through-openings 14.

[0147] Due to the reduction of pressure in the pressure chamber 9, the restoring force exerted by the compression spring 8 on the brewing piston 4 now predominates again. Due to the pressure force of the compression spring 8 or the brewing piston 4 being moved upwards by the compression spring 8, the spherical bodies 13 are pushed back out of the recess 16 into the radial through-openings 14 and the annular gap located behind them.

[0148] The locking mechanism is released and the brewing piston 4 moves back upwards into the starting position AK due to the restoring force of the compression spring 8.

[0149] Figure 4 shows a special further development of the coffee machine 1, which is characterized in that the brewing piston 4 is driven by the water pump 62 of the brewing water treatment device 60 or propelled into the brewing position BK. The water pump 62 draws the water from a water tank 61 via a supply water line 64. The water pump 62 is connected to the brewing water inlet 18 on the piston piston 6 via a brewing water line 66. A heating unit 63, e.g., a thermoblock or continuous-flow heater, is arranged along the brewing water line 66 for heating the brewing water flowing through the brewing water line 66. The water pump 62 pumps water from the water tank 61 via the brewing water line 66 under pressure into the brewing chamber 3. The brewing water is heated by the heating unit 63 on its way through the brewing water line 66.

[0150] A 3 / 2-way valve 72 is located on the brewing water line 66, which includes a further connection for draining residual water into a collecting container, such as a drip tray, following the brewing process. The 3 / 2-way valve 72 is switched via the control device 20.

[0151] The water pump 62 is further connected to a piston water line 65, via which water is pumped from the water tank 61 into a pressure chamber 9 in the piston shaft housing 7 (see Figure 1b) to drive the brewing piston 4 from the starting position AK into the brewing position BK.

[0152] The piston water line 65 has a check valve 71, which prevents the backflow of water from the pressure chamber 9 into the water pump 62. Furthermore, a 3 / 2-way valve 70 is arranged in the piston water line 65 between the check valve 71 and the pressure chamber 9. A return water line 67 is connected to the 3 / 2-way valve 70, through which piston water can be fed back into the water tank 61. Also located on the piston water line 65 is a pressure gauge 73 for monitoring the pressure in the pressure chamber 9.

[0153] To move the brewing piston 4 from the starting position AK to the brewing position BK, the water pump 62 pumps water from the water tank 61 into the piston water line 65 and builds up a piston pressure predetermined by the control device 20. After the brewing piston 4 has reached its brewing position BK and is locked, the water pump 62 pumps heated water from the water tank 61 through the brewing water line 66 into the brewing chamber 3 and builds up a brewing pressure that is generally higher than the piston pressure.

[0154] The water pump 62 is switched between the piston water line 65 and the brewing water line 66, or between the piston water feed and the brewing water feed, via the control device 20. The check valve 71 in the piston water line 65 prevents a pressure loss in the pressure chamber 9 when the water pump 62 switches from the piston water line 65 to the brewing water line 66.

[0155] At the end of the brewing process, the pressure in the brewing water line 66 is reduced and the 3 / 2 way valve 72 is switched by the control device 20 so that the residual water is drained into a collecting container (not shown).

[0156] Furthermore, the pressure in the piston water line 65 is also reduced and the 3 / 2 way valve 70 is switched so that the piston water is directed back into the water tank 61 via the return water line 67.

Claims

PATENT CLAIMS Coffee machine (1) comprising a machine unit (2) with: - a control device (20) for controlling the coffee machine (1), - a brewing piston (4) which is movably mounted between a starting position (AK) and a brewing position (BK), - a piston drive (62) controllable via the control device (20) for moving the brewing piston (4) from the starting position (AK) into the brewing position (BK), and with - a water treatment device (60) with a water tank (61), a water pump (62), and a heating unit (63) for generating and dispensing hot brewing water under pressure into a brewing chamber (3), characterized in that the coffee machine includes a locking device (11) with at least one locking body (13) for locking the brewing piston (4) in the brewing position (BK). Coffee machine (1) according to claim 1, characterized in that the locking device (11) can be actuated via the piston drive (62). Coffee machine (1) according to one of claims 1 to 2, characterized in that the piston drive (62) is a hydraulic drive. Coffee machine (1) according to one of claims 1 to 3, characterized in that the piston drive (62) is formed by the water pump (62) of the water treatment device (60). Coffee machine (1) according to one of claims 1 to 4, characterized in that the locking device (11) can be actuated by the water pump (62) of the water treatment device (60). Coffee machine (1) according to one of claims 1 to 5, characterized in that the locking device (11) contains an actuating element (12) movable parallel to the piston axis (KA) of the brewing piston (4), and the at least one locking body (13) can be moved via the actuating element (12) toward the brewing piston (4) into a locking position. Coffee machine (1) according to one of claims 2 to 6, characterized in that the coffee machine (1) is designed such that, to initiate a brewing process, the piston drive (62) moves the brewing piston (4) into a brewing position in a first step and, after reaching the brewing position, actuates the locking device (11) in a second step, locking the brewing piston (4).Coffee machine (1) according to one of claims 2 to 7, characterized in that the coffee machine (1) is designed such that, to initiate a brewing process, the piston drive (62) moves the brewing piston (4) into a brewing position by applying a pressing force to press the coffee powder, and when a maximum pressing force is reached and the brewing position is assumed, the locking device (11) is actuated in a second step to lock the brewing piston (4). Coffee machine (1) according to one of claims 2 to 8, characterized in that the machine unit (1) contains a piston shaft housing (7) which is movably mounted along the piston axis (KA), which cooperates with the actuating element (12) of the locking device (11), wherein the piston... shaft housing (7) and the brewing piston (4) are designed and interact in such a way that the piston drive (62) drives the brewing piston (4) in a first step in the axial direction towards the brewing chamber (3) into the brewing position (BK) and then moves the piston shaft housing (7) in a second step in the opposite, axial direction by actuating the locking device (11).Coffee machine (1) according to one of claims 3 to 9, characterized in that the machine unit (1) contains a piston shaft housing (7) which is movably mounted along the piston axis (KA), which cooperates with the actuating element (12) of the locking device (11), and which together with the brewing piston (4) forms a pressure chamber (9), wherein the piston shaft housing (7) and the brewing piston (4) are designed and cooperate in such a way that a piston fluid pressure, in particular piston water pressure, generated in the pressure chamber (9) drives the brewing piston (4) in the axial direction towards the brewing chamber (3) into the brewing position (BK) and then displaces the piston shaft housing (7) in the opposite, axial direction under actuation of the locking device (11).Coffee machine (1) according to one of claims 1 to 10, characterized in that the at least one locking body (13) is a spherical body (13) guided in a radial opening (14) of a piston shaft guide tube (15), which, in the locking position, engages in a recess (16) on the brewing piston (4). Coffee machine (1) according to one of claims 1 to 11, characterized in that the coffee machine (1) contains a portafilter device (50) which is removable from the machine unit (2) and has a coffee receiving space (51) and a brewing sieve (52), wherein the coffee receiving space (51) of the. The portafilter device (50) forms the brewing chamber (3) together with the brewing piston (4) driven into the brewing position (BK). The coffee machine (1) according to one of claims 3 to 12, characterized in that the brewing piston (4) cooperates with return means (8), in particular with a return spring, by means of which the brewing piston (4) can be moved back from the brewing position (BK) to the starting position (AK) after the piston fluid pressure, in particular the piston water pressure, has been reduced. The coffee machine (1) according to one of claims 10 to 13, characterized in that the piston shaft housing (7) cooperates with return means (17), in particular with at least one return spring, by means of which the piston shaft housing (7) can be moved back to its starting position in the direction of the brewing chamber (3) after the piston fluid pressure, in particular the piston water pressure, has been reduced.Coffee machine (1) according to one of claims 3 to 14, characterized in that the water pump (62) of the water treatment device (60):. - via a supply water line (64) for supplying water to a water tank (61), - via a piston water line (65) for moving the brewing piston (4) with the brewing piston (4) and - is hydraulically connected to the brewing chamber (3) via a brewing water line (66) for brewing coffee. Coffee machine according to claim 15, characterized in that a directional control valve (70) is arranged in the piston water line (65), which is designed and can be controlled via the control device (20) such that When the piston water pressure is reduced, the piston water flowing back can be discharged via a discharge line (67) bypassing the water pump (62).

17. Coffee machine according to claim 16, characterized in that the discharge line (67) is a return water line (67) via which returning piston water can flow back into the supply water line (64) or into the water tank (61).

18. Coffee machine according to one of claims 15 to 17, characterized in that a check valve (71) for maintaining the built-up piston water pressure is arranged in the piston water line (65), in particular between the water pump (62) and a directional control valve (70).

19. Coffee machine according to one of claims 15 to 18, characterized in that the heating unit (63) for heating the brewing water is arranged on the brewing water line (66).

20. Method for brewing coffee with a coffee machine (1) according to one of claims 1 to 19, characterized in that, in order to carry out a brewing process, the brewing piston (4) is driven by means of a piston drive (62) in the direction of the coffee receiving space (51) filled with coffee powder, and when the brewing position (BK) is reached, the locking device (11) is actuated and the brewing piston (4) is locked against an axial movement directed away from the brewing chamber (3), and by means of the water pump (62) brewing water is pumped into the brewing chamber (3) by building up a brewing water pressure and the brewing process is carried out.

21. Method according to claim 20, characterized in that a piston water pressure acting on the brewing piston (4) is built up by means of the water pump (62) and the brewing piston (4) is driven forward by the piston water pressure in the direction of the coffee receiving space (51).

22. Method according to one of claims 20 to 21, characterized in that the brewing piston (4) acts as a coffee press and compresses the coffee powder in the coffee receiving space (51).

23. Method according to one of claims 20 to 22, characterized in that the pressure exerted by the brewing piston (4) on the coffee powder is lower than the brewing water pressure exerted in the opposite direction on the brewing piston (4) during the brewing process.

24. Method according to one of claims 21 to 23, characterized in that the water pump (62) draws water from the water tank (61) via the supply water line (64) to build up a piston water pressure and pumps this as piston water into the piston water line (65).

25. Method according to one of claims 20 to 24, characterized in that the water pump (62) draws water from the water tank (61) via the supply water line (64) to build up a brewing water pressure in the brewing chamber (3) and pumps this as brewing water into the brewing water line (66).

26. Method according to one of claims 21 to 25, characterized in that the piston water pressure generated is maintained until the end of the brewing process and in order to release the locking mechanism and to move the brewing piston (4) back to its starting position (AK) after the brewing process has been completed.

27. Method according to one of claims 21 to 26, characterized in that the reduction of the piston water pressure takes place by discharging piston water via the discharge water line (67).

28. Method according to one of claims 21 to 27, characterized in that the reduction of the piston water pressure takes place by returning piston water via the return water line (67) into the supply water line (64) or the water tank (61).

29. Method according to one of claims 21 to 28, characterized in that in order to reduce the piston water pressure and to discharge or return piston water, the directional control valve (70) is switched via the control device (20).

30. Method according to one of claims 21 to 29, characterized in that at the end of the brewing process the piston water pressure is reduced and as a result the locking device is released and then the brewing piston (4) is moved back into its starting position (AK) via the return means (8).

31. Method according to one of claims 20 to 30, characterized in that the control device (20) switches the water pump (60) between a piston water feed and a brewing water feed.

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