Piston coffee machine with a brewing unit, and method for controlling the temperature of a brewing bushing of such a brewing unit

Abstract

A brewing unit (1) of a piston coffee machine, wherein the brewing unit (1) having a brewing-unit slide (2) is designed as a brewing chamber with a brewing bushing (3), wherein the brewing bushing (3) comprises a brewing space (4) for ground coffee (KM), having a shower head (8), a tamper (9), a connection (10) for brewing water, and a connection (11) for the finished coffee beverage extracted from the ground coffee, produced by the brewing bushing (3). The brewing bushing (3) is arranged in a continuous stepped bore (BO) of the brewing-unit slide (2), wherein the bore (BO) has a holding region (BOH) for the brewing bushing (3) and a flow region (BOS). A method is provided for heating a brewing bushing (3) of a brewing unit (1) of a piston coffee machine.

Description

[0001] Piston coffee machine with a brewing unit, and method for tempering a brewing socket of such a brewing unit

[0002] The invention relates to a piston coffee machine with a brewing unit according to the preamble of claim 1. The invention also relates to a method for tempering a brewing sleeve of such a brewing unit.

[0003] Piston coffee machines with a brewing unit are available in various designs. Within the brewing unit of a piston coffee machine, coffee powder is ground into a brewing chamber and then pressed into a coffee cake. Heated water is then passed through the cake under pressure to extract flavors from the coffee powder. After a product-specific amount of water has passed through, the moistened coffee powder is pressed out, and the coffee cake (grounds) is deposited into the grounds container.

[0004] A typical brewing chamber of a brewing unit is circular and has a diameter of approximately 45mm. The hot water is introduced into the brewing chamber on one side through a piston unit called a douchette, where it is atomized as evenly as possible to coat all parts of the coffee cake. On the other side, the extracted coffee is dispensed through a plunger, which forms another piston unit. The extracted coffee is often passed through a spring-loaded oscillating component (crema valve), which allows only a small opening to create the typical crema on the coffee.

[0005] To prevent very fine particles from being dispensed into a coffee cup, there is often a fine sieve on the plunger.

[0006] A drive motor creates relative movement between the ram and the douchette, allowing the distance between them to be adjusted. Defined pressing forces can then be set using different motor torques.

[0007] All piston coffee machines have in common that the coffee grounds are compressed by a piston movement in a cylindrical brewing chamber, and then hot water is passed through them. A boiler typically heats the water to 92°C to achieve effective coffee extraction. During this extraction phase, heat loss occurs, partly due to convection to the surrounding components. Heat loss also occurs in the water pipes and in the brewing unit itself.

[0008] Another important factor is the transfer of energy to the coffee powder, which is usually at room temperature. The larger the sample weight, the lower the mixing temperature for a constant amount of water.

[0009] Target beverage temperatures of more than 80°C therefore often require significant design effort to minimize temperature losses. Small water quantities of less than 50ml, which are common in espresso products, pose a particular challenge.

[0010] To compensate for these heat losses, it is possible to increase the temperatures of the boiler or instantaneous water heater to up to 96°C. However, beyond this temperature range, unwanted steam gradually builds up in the energy generator. Therefore, this compensation method cannot compensate for all energy losses in a coffee machine.

[0011] Brewing groups in high-quality portafilter machines are typically heated indirectly via a hot water circuit connected to the boiler. This heat transfer leads to high energy losses, as it must occur almost continuously due to the inertia of the system. This method has also been used in high-quality piston coffee machines, but has not become a permanent fixture due to the aforementioned disadvantage.

[0012] Similar brewing group designs are equipped with electronic heating mats. These make temperature control difficult and also require a long start-up time or constant heating of the brewing group. Another disadvantage of this method is that coffee grounds permanently stick to the brewing group ("crusting").

[0013] In the catering industry, it is common practice to preheat cups using a cup warmer to prevent the beverage from cooling down further. Furthermore, the pipes and brewing group in a piston coffee machine are actively rinsed with hot water to reduce the amount of heat released into the environment during the subsequent brewing process. Since the rinsing and brewing processes must be carried out one after the other, this procedure is very time-consuming. Many brewing cylinders are constructed in several parts, with the actual brewing process taking place in an inlay, which is often made of stainless steel for hygienic reasons. The disadvantage of this is the high thermal conductivity of the metal, which absorbs a lot of heat energy from the brewing water in a short space of time. For better thermal insulation, external guide components are made of plastic. There are also versions with plastic inlays and complete, thicker-walled plastic brewing groups.

[0014] EP 2 497 396 B1 describes a coffee machine with at least one brewing device, wherein the coffee machine has, in addition to the at least one brewing device, at least one steam connection and / or at least one hot water connection, wherein the at least one steam connection and / or the at least one hot water connection is connected to at least one heating element by means of at least one line for supplying a fluid, wherein the at least one brewing device is connected to at least one further heating element by means of at least one line for supplying a fluid. At least one circuit is routed through the at least one brewing device, and at least one pump is arranged in the at least one circuit routed through the at least one brewing device.

[0015] DE 36 27 277 C2 relates to a continuous-flow heater, in particular for an electric coffee maker, comprising a water pipe and a connecting hose made of a rubber-elastic material attached thereto, wherein an end section of the water pipe serving as a connecting sleeve overlaps longitudinally with an end section of the hose that is elastically deformed for fastening. In such a continuous-flow heater, the hoses are reliably fastened with a simple design. An additional connecting sleeve in the form of a pipe section extends over at least part of the overlap length, wherein the end section of the hose is clamped sealingly between the two connecting sleeves by plastic deformation of at least one of the two connecting sleeves. The additional connecting sleeve is inserted into the end section of the hose, and the end section of the water pipe is plastically deformed.

[0016] EP 2 188 568 B1 discloses a compact, high-pressure spiral flow-through heating unit for electrical devices for preparing hot beverages. The heating unit comprises a tubular support with at least one electrical heating conductor structure using thick-film technology on its outer surface and an outwardly facing flange extending circumferentially at each of its two ends; a core element arranged in the tubular support with at least one web extending spirally around the outer surface of the core element, wherein two adjacent web flanks form a flow groove with the outer surface, which is essentially sealed to the outside by the inner surface of the tubular support to form a flow channel; a first and a second end piece, each with a connection communicating with the flow channel, wherein the end pieces are each firmly connected to the core element at their end of the tubular support;and wherein the unit consisting of the end pieces and the core element consists of at least two parts which are engaged with each other by means of at least one snap connection and are mechanically clamped in such a way that seals arranged between the tubular support and the respective end pieces are subjected to a sufficient pressure so that the seals are water- and vapor-tight.

[0017] DE 10 2015 000491 A1 describes an improved brewing group for coffee / espresso machines. Brewing groups are generally designed in such a way that they do not significantly negatively influence the brewing temperature of the water, because the water is brought to the target temperature as precisely as possible before the brewing group (by a boiler, heat exchanger, or thermoblock). One example is the E61 brewing group, which is brought to approximately the temperature of the brewing water that will later flow through it using water from the heat exchanger. The brewing group is used to significantly influence and control the brewing temperature and, as an additional benefit, to delay / dampen the pressure increase caused by the pump. This is achieved, on the one hand, by making the brewing water-carrying channel through the brewing group as long as possible.In addition, the contact surface of the water and the residence time of the water in the channel are significantly increased by the measures described below, which leads to the water completely or almost completely adopting the temperature of the brewing group. A change in the brewing group temperature logically leads to a change in the brewing temperature. This measure also means that the pressure builds up comparatively more slowly, which has a positive effect on the extraction. A screw-like body with the same diameter, if possible over the entire length of the channel, is inserted into the brewing group channel. A helix (multiple helix) with the same diameter, if possible over the entire length of the channel, is inserted into the brewing group channel. The brewing group channel is replaced by many capillaries.

[0018] Document DE 20 2009 000 075 U1 describes a brewing unit for a coffee machine, comprising a brewing cylinder driven by a spindle drive for movement along the longitudinal axis of the brewing unit. This spindle drive has a threaded spindle arranged parallel to and spaced from the longitudinal axis of the brewing cylinder, the threads of which mesh with an output element associated with the brewing cylinder for moving the latter. It also has a guide rod arranged parallel to and spaced from the threaded spindle, with a guide sleeve associated with and displaceable on the brewing cylinder. In addition to its guide sleeve, the brewing cylinder carries at least one guide element on its outer surface, which is supported on the guide rod only in sections with respect to its circumference.

[0019] These designs have proven successful, but there is a constant need for improvements in the pursuit of cost savings in components, functional groups, assembly times and maintenance.

[0020] The invention therefore has the object of creating an improved brewing unit of a piston coffee machine.

[0021] A further object is to provide a method for heating a brewing bushing of such a brewing unit.

[0022] The invention solves this problem by a brewing unit having the feature of claim 1 and by a method having the feature of claim 13.

[0023] One idea of ​​the invention is to flow a tempered fluid around a brewing socket of a brewing unit for preheating.

[0024] A brewing unit of a piston coffee machine according to the invention, wherein the brewing unit is designed with a brewing carriage as a brewing chamber with a brewing sleeve, wherein the brewing sleeve comprises a brewing chamber for ground coffee with a douchette, a plunger, a connection for brewing water, and a connection for the finished coffee beverage produced from the brewing sleeve, which flows out of the brewing sleeve and is extracted from the ground coffee. The brewing sleeve is arranged in a continuous, stepped bore of the brewing carriage, wherein the bore has a holding area for the brewing sleeve and a flow area.

[0025] One advantage here is that the holding area for the brewing sleeve completely encloses it, creating a secure hold. The flow area is separated from it, allowing a tempered fluid to flow around it as a tempering medium in a confined space. A tempered fluid can be, for example, hot, warm, or cold water, hot, warm, or cool steam, or gas.

[0026] A major advantage over the state of the art is that a significantly higher temperature level of the dispensed beverage can be achieved, especially for products with a small amount of water.

[0027] A method according to the invention for tempering a brewing socket of a brewing unit of a piston coffee machine has the following method steps: (VS1) selecting a desired beverage temperature of the coffee as a setpoint, detecting a current temperature of the coffee before dispensing using a temperature sensor; (VS2) comparing the detected temperature of the coffee with previously stored reference values; and (VS3) regulating the beverage temperature of the coffee to the desired setpoint based on the comparison with the reference values ​​by adjusting the amount and exposure time of a tempering medium, which flows from a medium source through a space around a flow region of the brewing socket and then into an outlet immediately before and / or during the extraction phase of the coffee.

[0028] One advantage is that it allows for a regulated outlet temperature of the coffee.

[0029] It's advantageous if the tempered fluid is already created in the coffee machine from a medium source. Of course, a separate boiler can also be provided for this purpose. For a hot fluid, a hot water heater can be used, which can also generate steam, for example. Cold water for temperature reduction can be drawn from a water main or from suitable water reservoirs, for example.

[0030] A further advantage is that the tempered fluid flows freely into a drain as a tempering medium without additional conveying means, such as pump(s).

[0031] Further advantageous embodiments can be found in the remaining subclaims.

[0032] In one embodiment, the flow area of ​​the brewing carriage has an inner diameter that is larger than an inner diameter of the holding area of ​​the brewing carriage, with a circumferential gap defined as an annular cavity in the flow area between an outer diameter of the brewing sleeve and the inner diameter of the brewing carriage. This results in a space-saving design and efficient heating of the flow area of ​​the brewing sleeve, since the gap surrounding the brewing sleeve has a certain degree of thermal insulation from the outside due to the material of the brewing carriage.

[0033] In another design, the intermediate space communicates with at least two radially opposite connections, namely an inlet connection and an outlet connection. This allows for short paths for the temperature control medium, along which only insignificant heat energy loss can occur.

[0034] For this purpose, it is advantageous for the intermediate space to be connected to a medium source supplying a tempered fluid via the inlet connection, and for the intermediate space to be connected to a drain via the outlet connection. This results in time efficiency, for example, due to parallel operation between the steam and water boilers and separate lines.

[0035] In one embodiment, the tempered fluid is hot water or steam. This is advantageous because, for example, an existing hot water heater can be used.

[0036] Another design provides for the tempered fluid to be cold water or a cooled gas, such as air or nitrogen. This allows the brewed coffee to be easily cooled.

[0037] In another embodiment, at least one valve is arranged in series between the inlet connection and the medium source. This provides an advantageous option for controlling the heating of the brewing sleeve. For this purpose, the valve can be a solenoid valve, for example.

[0038] If the at least one valve is connected to a control device and controlled by the control device, this is advantageous because this enables remote control of the heating of the brewing socket.

[0039] Another embodiment provides for the brewing unit to have at least one temperature sensor that detects the coffee temperature (K). This allows for easy and cost-effective detection of the coffee temperature using a space-saving, cost-effective component.

[0040] In yet another embodiment, the brewing unit has at least one temperature sensor that detects the temperature of the flow section of the brewing sleeve. This is advantageous because it allows not only control of the coffee temperature, but also regulation.

[0041] In yet another embodiment, the brewing sleeve is a thin-walled stainless steel sleeve and is axially fixed in the brewing carriage in the holding area of ​​the bore of the brewing carriage. This advantageously minimizes the thermal resistance of the brewing sleeve in the flow area, enabling efficient heat transfer from the temperature control medium in the intermediate space into the brewing sleeve. Furthermore, the brewing sleeve is advantageously stable, allowing it to be secured in the holding area.

[0042] A further advantage is that a large heat transfer effect of the brewing unit is possible due to high or low temperatures of the tempered fluid.

[0043] A further embodiment provides for the brewing unit of the coffee machine to be arranged such that the brewing unit's longitudinal axis is positioned horizontally, vertically, or at an angle greater than 0° and less than 90° between an imaginary horizontal and an imaginary vertical. This advantageously achieves a high degree of adaptability to different configurations.

[0044] In one embodiment of the method, in process step VS3, the desired coffee beverage temperature is controlled by adjusting the amount and exposure time of the temperature control medium by controlling a valve via a control device. This enables a controlled coffee outlet temperature.

[0045] In a further embodiment of the method, in the process step VS1, selecting, a current temperature of the flow area of ​​the brewing sleeve is additionally detected using a temperature sensor. In the second process step VS2, the detected temperature of the flow area of ​​the brewing sleeve is additionally compared with previously stored reference values. This results in an energy-efficient method, since, for example, the heating of the brewing sleeve can advantageously only take place immediately before and during the product dispensing. Furthermore, the coffee temperature can advantageously be controlled more precisely using the detected temperature values ​​of the brewing sleeve.

[0046] In another embodiment of the method, in process step VS3 Control, the control of the valve by the control device is influenced by a timer. This provides the advantage of additional control options.

[0047] A further embodiment of the method provides for monitoring the temperature profile of the dispensed coffee based on the recorded values ​​to determine whether the temperature is increasing, maintaining its current level, or decreasing. This allows the control device to predict the necessary switching signals for the valve. This can advantageously increase the efficiency of heating the brewing socket.

[0048] A further advantage is that no coffee powder / flour adhesion (encrustations) on / in the brewing socket is possible due to the gentle and easily adjustable temperature control of the brewing socket.

[0049] In addition, the extraction intensity and the coffee taste are beneficially influenced.

[0050] In addition, a further advantage is achieved by reducing contamination caused by condensing water vapor on the brewing chamber (in the brewing socket).

[0051] A further embodiment of the method provides for the tempering medium to flow through a condensation unit after leaving the flow area of ​​the brewing sleeve before flowing into the drain. This results in a favorable flow pattern.

[0052] It is advantageous if the temperature control medium is a fluid, e.g., water, steam, gas, etc. In the case of steam or gas, this can reach higher temperatures than water, thus enabling advantageous heat transfer to the brewing sleeve due to the higher temperature difference.

[0053] Alternatively, the brewing sleeve can be flushed with water or nitrogen, for example, to achieve a targeted reduction in beverage temperature. The operating principle of the invention offers the following advantages over non-temperature-controlled brewing units for coffee machines:

[0054] • Significantly increased temperature level for products with a small amount of water, such as espresso drinks

[0055] • Controlled outlet temperature possible (time control e.g. of a steam valve)

[0056] • Heating of the coffee grounds in the brewing socket possible

[0057] • Time efficiency due to parallel operation between steam and water boiler

[0058] • Energy-efficient process, as temperature control only takes place immediately before and during product delivery

[0059] • Large heat transfer effect of the brewing unit in case of heating due to high steam temperatures and in case of temperature reduction a high cooling effect, e.g. with cold water (circuit) or cooled gas, e.g. nitrogen.

[0060] • No coffee powder build-up (crusting) on ​​the brewing socket due to the gentle and easily adjustable temperature control of the inlay

[0061] • Influence on the extraction intensity and thus on the coffee taste

[0062] • Reduction of contamination by condensing water vapor on / in the brewing chamber

[0063] The invention is described in more detail below using an exemplary embodiment with reference to the drawings. The figures serve only to explain the invention in more detail and are not limiting. Individual features described can also be applied to further embodiments within the scope of general technical knowledge. They show:

[0064] Figure 1: a schematic sectional view of an embodiment of a brewing unit according to the invention of a piston coffee machine in an open position;

[0065] Figures 2-3: schematic sectional views of the embodiment according to Figure 1 in a brewing position;

[0066] Figure 4: a schematic sectional view of the embodiment according to Figures 2-3 with an exemplary temperature control; and Figure 5 is a schematic flow diagram of an embodiment of a method according to the invention.

[0067] Fig. 1 shows a schematic sectional view of an embodiment of a brewing unit 1 according to the invention of a piston coffee machine in an open position.

[0068] An example of a piston coffee machine not shown here is described in detail in the document DE 10 2019 119 103 A1.

[0069] The brewing unit 1 here comprises a brewing carriage 2 with two end faces 2a and 2b, in which a brewing bushing 3 is inserted in the axial direction of an axis 1a.

[0070] The brewing bushing 3 is arranged in the form of a thin-walled stainless steel bushing in the brewing carriage 2 in a through bore BO of the brewing carriage 2.

[0071] In this embodiment, the brewing carriage 2 is designed as a carrier made of high-performance plastic.

[0072] The bore BO is formed into the brewing carriage 2 as a stepped bore BO with a holding area BOH and a flow area BOS. The axial length of the holding area BOH is approximately 1.3 times the axial length of the flow area BOS in the example shown. Of course, other ratios are also possible.

[0073] The bore BO of the brewing carriage 2 and the brewing bushing 3 are arranged coaxially with each other to the axis 1a.

[0074] The holding area BOH of the brewing carriage 2 has an inner diameter 2g, which corresponds to an outer diameter 3e of the brewing bushing 3 and forms a firm seat of the brewing bushing 3 in the bore BO of the brewing carriage 2.

[0075] The brewing bushing 3 is also secured to the brewing carriage 2 by an axial securing means 3g in the region of the outer end face 2b of the brewing carriage 2 and an associated first end face 3b of the brewing bushing 3. In contrast to the holding area BOH of the brewing carriage 2, the flow area BOS of the brewing carriage 2 is formed with an inner diameter 2h which is larger than the inner diameter 2g of the holding area BOH. At the same time, the opposite outer diameter 3f of the brewing bushing 3 in the flow area BOS is smaller than the outer diameter 3e of the brewing bushing 3 in the holding area BOH. In this way, a circumferential intermediate space 5 is defined between the outer diameter 3f of the brewing bushing 3 and the inner diameter 2h of the brewing carriage 2.

[0076] The intermediate space 5 is formed as an annular cavity surrounding the flow area BOS at the outer diameter 3f of the brewing sleeve 3. The intermediate space 5 is sealed from the atmosphere by means of sealing elements 3d. The sealing elements 3d can, for example, be O-rings between the outer side of the brewing sleeve 2 and the inner side of the bore BO of the brewing carriage 2 near the first end face 2a of the brewing carriage 2 and in the region of an imaginary boundary between the holding area BOH and the flow area BOS.

[0077] The intermediate space 5 communicates with two radially opposite connections, namely with an inlet connection 6 and with an outlet connection 7.

[0078] The inlet connection 6 is inserted into a radially outwardly projecting flange 2d of the brewing carriage 2. A line section 6a of the inlet connection 6 is connected to a through-opening 2e in the flange 2d. The through-opening 2e extends from the flange 2d through the wall of the brewing carriage 2 and opens into the intermediate space 4.

[0079] The inlet connection 6 serves for a media inlet ME of a tempering medium into the intermediate space 5. This is described in more detail below.

[0080] The outlet connection 7 is inserted here into a radially extending opening in the wall of the brewing carriage 2. Of course, a flange can also be provided for this purpose, as with the inlet connection 6. A line section 7a of the outlet connection 7 is connected to a through opening 2f in the wall of the brewing carriage 2 and opens into the intermediate space 4.

[0081] The outlet connection 7 forms a media outlet MA for the tempering medium from the intermediate space 5, as explained below. The brewing socket 3 has an interior space referred to as the brewing space 4 or brewing chamber.

[0082] An opening 2c is formed radially into the wall of the brewing carriage 2 in the holding area BOH, which opens into a corresponding opening 3c of the brewing sleeve 3. Ground coffee KM is poured into the brewing chamber 4 through the openings 2c, 3c.

[0083] The brewing chamber 4 is closed by a piston unit on each end face. A first piston unit, namely a so-called douchette 8, is inserted from the first end face 3b into the interior 4 of the brewing sleeve 3 and is arranged therein so that it can be displaced longitudinally in the direction of the axis 1a. A seal 8a serves to seal the douchette 8 against the inner wall of the interior 4.

[0084] The second piston unit is referred to as plunger 9 and is inserted from the second end face 3a into the interior 4 of the brewing sleeve 3. Like the douchette 8, it is sealed with a seal 9a against the inner wall of the interior 4. The plunger 9 can be fixed in this closed position. However, it is also possible for the plunger 9 to be movable in the direction of the axis 1a.

[0085] The douchette 8 and the plunger 9 are arranged in the brewing unit 1 in the brewing bushing 3 coaxially to each other and coaxially to the axis 1 a.

[0086] The stamp 9 is equipped with a connection 11.

[0087] Fig. 2 shows a schematic sectional view of the embodiment according to Fig. 1 in a brewing position.

[0088] Fig. 3 shows the brewing position of the brewing unit 1 according to Fig. 2 with functional units for a tempering medium.

[0089] The shower head 8 has a connection 10 for brewing water (BW). The brewing water (BW) is used to prepare a beverage, in this case coffee, using ground coffee (KM).

[0090] The plunger 9 is equipped with a connection 11 for the finished beverage produced from the ground coffee KM, here coffee K, emerging from the brewing sleeve 3. In the brewing position in Fig. 2, 3, ground coffee KM is compressed in the interior 4 of the brewing sleeve 3 by the douchette 8, which is now pushed toward the plunger 9 in the direction of the axis 1a.

[0091] The coffee grounds KM compressed in this way are located in the flow area BOS of the brewing bushing 3, surrounded by the intermediate space 5.

[0092] When a liquid or vaporous tempering medium flows through the intermediate space 5, which forms a cavity, a temperature of the brewing chamber, ie the brewing space 4, can be controlled and an energy loss during the extraction phase of the ground coffee KM in the brewing space 4 can be reduced.

[0093] The tempering medium is fed as medium inlet ME from a medium source 12 via the inlet connection 6 into the intermediate space 5.

[0094] The liquid temperature control medium can be a heated or cooled liquid, such as water. A vapor temperature control medium can be steam or a gas (such as nitrogen or air).

[0095] The medium source 12 can be, for example, a boiler, e.g., a hot water generator, which, depending on the temperature supply, also generates steam, e.g., water vapor. The boiler can also be designed, for example, with a heat exchanger, by means of which the temperature control medium in the boiler can be heated or cooled.

[0096] The above-described structure of the brewing unit 1 with the intermediate space 5 between the brewing carriage 2 and the brewing socket 3 enables a direct flow around the interior 4 of the brewing chamber or brewing socket 3 in the flow area BOS of the tempering medium, e.g. of hot water or steam, cooled water or gas, and thereby reduces the energy loss in the beverage, here coffee K, during the extraction phase.

[0097] After the tempering medium has given off its heat to the brewing bushing 3, it is led through the outlet connection 7 as medium outlet MA in the example shown in Fig. 3 into a condensation unit 13.

[0098] The condensation unit 13 extracts heat from the medium outlet MA. In the case of hot liquids, their temperature is lowered. Steam, e.g., water vapor, is also cooled in the condensation unit 13 and condenses into water as the medium condensate MK. The cooled liquid medium condensate KM then flows into an outlet 14, e.g., into a wastewater disposal system, such as a sewer system.

[0099] If the tempering medium is steam, it can advantageously increase the temperature of the flow area BOS of the brewing socket 3 very quickly and effectively due to its high energy density. High-quality piston coffee machines usually incorporate steam and hot water boilers, allowing the heating and brewing processes to take place in parallel and independently of each other.

[0100] Such a separation of the temperature control medium and the brewing water (BW) offers the advantage that the ground coffee (KM) ground into the brewing sleeve (3) is preheated by the temperature control medium in the intermediate chamber (5) before the actual extraction process by means of steam flow, and immediately afterwards is passed through by the hot brewing water (BW). This preheating principle allows beverage temperatures to be increased significantly because less heat energy from the brewing water (BW) is lost in the ground coffee. This principle is particularly effective for beverages with a low water content, such as espresso.

[0101] In the case of cooling, the temperature of the beverage brewed in the brewing socket 3 can be reduced by the tempering medium.

[0102] Fig. 4 shows a schematic sectional view of the embodiment according to Figure 2-3 with an exemplary temperature control.

[0103] The tempering medium generated by the medium source 12 is conveyed as media inlet ME via a valve 15 to the inlet connection 6.

[0104] The valve 15 is, for example, an electromagnetic 2 / 2-way control valve that is actuated by a control device 16. The control device 16 here has a timer 17 and is connected to a first temperature sensor 18 and a second temperature sensor 19.

[0105] The first temperature sensor 18 detects a temperature 3K of the coffee K before the coffee is dispensed. A temperature &BOS of the brewing socket 3 in the flow area BOS is sensed by the second temperature sensor 19.

[0106] A desired beverage temperature of the coffee K can be achieved with repeatable accuracy by detecting the beverage temperature of the coffee K before dispensing from the coffee machine with the first temperature sensor 18 and regulating it by the amount and exposure time of the temperature control medium of the brewing socket 3. The temperature of the temperature control medium of the brewing socket 3 is transmitted by the second temperature sensor 19 to the control device 16.

[0107] In such an exemplary control loop, the controlled variable in this system is the beverage temperature of the coffee K and the control variable is the tempering of the brewing socket 3, i.e. the temperature of the brewing socket 3 in the flow area BOS, and the associated indirect tempering of the ground coffee in the flow area BOS of the brewing socket.

[0108] The level of preheating, ie the temperature control, can be easily achieved by controlling the valve 15 for the steam, ie the medium inlet ME.

[0109] Fig. 5 shows a schematic flow diagram of an embodiment of a method according to the invention for tempering a brewing socket 3 of a brewing unit 1 of a coffee machine.

[0110] In a first process step VS1, a desired beverage temperature, here a temperature $K of the coffee K, is selected as the setpoint.

[0111] Then, the current temperatures $K of the coffee K and &BOS of the flow section BOS of the brewing socket 3 are detected by means of the temperature sensors 18, 19 and transmitted to the control device 16.

[0112] In a second method step VS2, the current value of the temperature $K of the coffee K is compared with a reference value in the control device 16.

[0113] The temperature &BOS of the flow section BOS of the brewing socket 3 is monitored.

[0114] The temperature &BOS can also be compared with an associated reference value and influence the control device 16 for controlling the valve 15.

[0115] In a third method step VS3, the desired beverage temperature, ie the value of the temperature $K of the dispensed coffee K, is regulated with repeatable accuracy by comparing it with the reference values ​​by adjusting the amount and exposure time of a tempering medium which flows immediately before and / or during the extraction phase of the coffee (K) from a medium source (12) through an intermediate space (5) around a flow area (BOS) of the brewing socket (3) and then into an outlet (14).

[0116] In this case, the valve 15 is opened or closed by the control device 16. This results in a temporary, switchable fluid temperature control of the brewing unit 1 of the piston coffee machine.

[0117] In the embodiment shown here, the opening and closing of the valve 15 by the control device 16 can also be influenced by a timer 17, which, for example, transmits a signal from the control device 16 for the valve 15 to the valve 15 with a time delay.

[0118] Temporary tempering only occurs immediately before / during the extraction phase of the coffee K.

[0119] The control device 16 is also connected to a control system of the coffee machine, to which the brewing unit 1 belongs. This allows for process-controlled tempering of the ground coffee (KM) in the brewing sleeve 3 to occur even before the extraction phase begins. This means that tempering begins using the tempering medium before hot water is introduced through the showerhead 8 into the brewing chamber 4 and into the ground coffee (KM) contained therein.

[0120] In addition, a profile of the temperature $K of the dispensed coffee K can be monitored based on the recorded values ​​to determine whether the temperature $K is increasing or decreasing. From this, the control device 16 can calculate the necessary switching signals for the valve 15 in advance to appropriately incorporate a dead time of the temperature control.

[0121] The following highlights the advantages of the operating principle compared to non-tempered brewing units for coffee machines:

[0122] • Significantly increased temperature level for products with low water quantity

[0123] • Controlled outlet temperature Temperature $K of the dispensed coffee K possible (time control e.g. of a steam valve or valve 15)

[0124] • Heating of the coffee grounds KM in the brewing socket 3 possible • Time efficiency due to the parallel operation between steam and water boiler

[0125] • Energy-efficient process, as temperature control only takes place immediately before and during product delivery

[0126] • Large heat transfer effect of the brewing unit 1 due to high or low temperatures of the tempering medium

[0127] • No coffee powder build-up (crusting) on ​​the brewing socket 3 due to gentle and easily adjustable temperature control of the inlay / brewing socket 3

[0128] • Influence on the extraction intensity and thus on the coffee taste

[0129] • Reduction of contamination by condensing water vapor on the brewing chamber / brewing socket 3

[0130] The invention is not limited by the embodiments given above, but can be modified within the scope of the claims.

[0131] It is conceivable that superheated steam can be used as a tempering medium.

[0132] A further valve can be arranged between the outlet connection 7 and the condensation unit 13.

[0133] Reference symbol

[0134] 1 brewing unit

[0135] 1a Longitudinal axis

[0136] 2 brewing carriages

[0137] 2a, 2b front side

[0138] 2c Opening

[0139] 2d flange

[0140] 2e, 2f passage opening

[0141] 2g, 2h inner diameter

[0142] 3 Brewing socket

[0143] 3a, 3b front side

[0144] 3c Opening

[0145] 3D seal

[0146] 3e, 3f outer diameter

[0147] 3g axial lock

[0148] 4 Brewing chamber

[0149] 5 space

[0150] 6 Inlet connection

[0151] 6a line section

[0152] 7 Outlet connection

[0153] 7a line section

[0154] 8 Shower

[0155] 8a Seal

[0156] 9 stamps

[0157] 9a Seal

[0158] 10, 11 connection

[0159] 12 Medium source

[0160] 13 Condensation unit

[0161] 14 Procedure

[0162] 15 Valve

[0163] 16 Control device

[0164] 17 Time switch

[0165] 18, 19 Temperature sensor

[0166] BO drilling

[0167] BOH holding area

[0168] BOS flow area

[0169] BW Brewing water K Coffee

[0170] KM coffee grounds

[0171] MA medium outlet

[0172] ME medium inlet MK medium condensate

[0173] VS1, VS2, VS3 process step

Claims

Claims 1. Brewing unit (1) of a piston coffee machine, wherein the brewing unit (1) is designed with a brewing carriage (2) as a brewing chamber with a brewing bushing (3), wherein the brewing bushing (3) comprises a brewing chamber (4) for ground coffee (KM) with a shower head (8), a plunger (9), a connection (10) for brewing water (BW) and a connection (11) for the finished coffee beverage (K) extracted from the ground coffee (KM) and produced from the brewing bushing (3), characterized in that the brewing bushing (3) is arranged in a continuous stepped bore (BO) of the brewing carriage (2), wherein the bore (BO) has a holding area (BOH) for the brewing bushing (3) and a flow area (BOS).

2. Brewing unit (1) according to claim 1, characterized in that the flow area (BOS) of the brewing carriage (2) has an inner diameter (2h) which is larger than an inner diameter (2g) of the holding area (BOH) of the brewing carriage (2), wherein between an outer diameter (3f) of the brewing bushing (3) and the inner diameter (2h) of the brewing carriage (2) a circumferential intermediate space (5) is defined as an annular cavity in the flow area (BOS).

3. Brewing unit (1) according to claim 2, characterized in that the intermediate space (5) communicates with at least two radially opposite connections, namely with an inlet connection (6) and with an outlet connection (7).

4. Brewing unit (1) according to claim 3, characterized in that the intermediate space (5) is connected via the inlet connection (6) to a medium source (12) which supplies a tempered fluid, and that the intermediate space (5) is connected via the outlet connection (7) to an outlet (14).

5. Brewing unit (1) according to claim 4, characterized in that the tempered fluid is hot water or steam.

6. Brewing unit (1) according to claim 4 or 5, characterized in that the tempered fluid is cold water or a cooled gas, e.g. air.

7. Brewing unit (1) according to one of claims 3 to 6, characterized in that between the inlet connection (6) and the medium source (12) at least one valve (15) is arranged in series with the inlet connection (6) and the medium source (12).

8. Brewing unit (1) according to claim 7, characterized in that the at least one valve (15) is connected to a control device (16) and is controlled by the control device (16).

9. Brewing unit (1) according to claim 8, characterized in that the brewing unit (1) has at least one temperature sensor (18) which detects a temperature ($K) of the coffee (K).

10. Brewing unit (1) according to one of claims 7 to 9, characterized in that the brewing unit (1) has at least one temperature sensor (19) which detects a temperature (&BOS) of the flow section (BOS) of the brewing bushing (3).

11. Brewing unit (1) according to one of the preceding claims, characterized in that the brewing bushing (3) is a thin-walled stainless steel bushing and is fastened and axially fixed in the brewing carriage (2) in the holding area (BOH) of the bore (BO) of the brewing carriage (2).

12. Brewing unit (1) according to one of the preceding claims, characterized in that the brewing unit (1) of the coffee machine is arranged such that the brewing unit (1) is arranged with its longitudinal axis (1a) horizontally, vertically or at an angle which is greater than 0° and less than 90° between an imaginary horizontal and an imaginary vertical.

13. Method for tempering a brewing bushing (3) of a brewing unit (1) of a piston coffee machine, characterized by the method steps (VS1 ) Selecting a desired beverage temperature ($K) of the coffee (K) as a setpoint, detecting a current temperature ($K) of the coffee (K) before dispensing by means of a temperature sensor (18); (VS2) comparing the detected temperature ($K) of the coffee (K) with previously stored reference values; and (VS3) Regulating the beverage temperature ($K) of the coffee (K) to the desired setpoint based on comparison with the reference values ​​by adjusting the quantity and exposure time of a tempering medium which flows immediately before and / or during the extraction phase of the coffee (K) from a medium source (12) through an intermediate space (5) around a flow area (BOS) of the brewing socket (3) and then into an outlet (14).

14. The method according to claim 13, characterized in that in the method step (VS3) the desired beverage temperature ($K) of the coffee (K) is regulated by adjusting the quantity and exposure time of the tempering medium by controlling a valve (15) by a control device (16).

15. The method according to claim 13 or 14, characterized in that in the method step (VS1) selecting, a current temperature (&BOS) of the flow area (BOS) of the brewing sleeve (3) is additionally detected by means of a temperature sensor (19), wherein in the second method step (VS2) the detected temperature (&BOS) of the flow area (BOS) of the brewing sleeve (3) is additionally compared with previously stored reference values.

16. The method according to claim 14 or 15, characterized in that in the method step (VS3) regulating the control of the valve (15) by the control device (16) is influenced by a timer (17).

17. Method according to one of claims 14 to 16, characterized in that a course of the temperature ($K) of the dispensed coffee (K) is monitored on the basis of the detected values ​​in order to determine whether the temperature ($K) is increasing, is maintained or decreases in order to calculate corresponding necessary switching signals for the valve (15) by the control device (16) in advance.

18. Method according to one of claims 14 to 17, characterized in that the tempering medium after leaving the flow area (BOS) the brewing bushing (3) flows through a condensation unit (13) before flowing into the drain (14).

19. Method according to one of claims 13 to 18, characterized in that the tempering medium is a fluid, e.g. water, steam, gas and the like.

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