Coffee machine brewing unit

Abstract

The brewing unit (1) of a piston-type coffee machine is configured as a spindle-type brewing unit, comprising a brewing slider (2) as a brewing chamber, two piston units as a shower screen (9) and a plunger (10), a drive motor, and at least one transmission. The brewing unit (1) has a double spindle assembly with an outer spindle (3) and an inner spindle (7), the outer spindle (3) being connected to the inner spindle (7) via at least one transmission. The brewing slider (2) is movable from a first end position to an intermediate position, then to a second end position, and can return to the first end position again. The outer spindle (3) has a moving thread (3d) that engages with an outer spindle nut (13) arranged in the brewing slider (2). The moving screw thread (3d) of the outer spindle (3) is not engaged with the outer spindle nut (13) in the first end position of the brew slider (2), and even if the outer spindle (3) rotates further, the speed of the brew slider (2) is zero and the brew slider (2) is fixed by the holding device (HR) in the first end position, and the moving screw thread (3d) of the outer spindle (3) remains engaged with the outer spindle nut (13) in the second end position of the brew slider (2), and the drive motor is switched off. A piston coffee machine is equipped with such a brewing unit (1).

Description

[Technical Field]

[0001] The present invention relates to a brewing unit for a piston coffee machine according to the preamble of claim 1, as well as to a piston coffee machine equipped with such a brewing unit.

[0002] Brewing units for piston coffee machines are known in a variety of configurations. Inside the brewing unit of a piston coffee machine, coffee powder is ground into a brewing chamber and then pressed to form a coffee cake. Heated water is then guided under high pressure through the cake, thereby extracting flavor from the powder. After a product-specific amount of water has flowed through, the moist coffee powder is pushed out and the coffee cake (grounds) is released into a grounds container.

[0003] Various drive concepts exist for directing the plunger, shower screen and extraction chamber into the required relative positions.

[0004] EP 2907427 describes a nonlinear transmission section that achieves a compromise between high pressing forces and simultaneously short movement cycles. To reach the various positions, the functional elements are moved with large pitches. When compressing the coffee powder, the drive motor is slowed down by a significantly smaller pitch, which allows for the transmission of large forces through the same guide.

[0005] German Patent Application Publication No. 102019119103 relates to a brewing unit for a piston-type coffee machine. The brewing unit is configured as a spindle brewing unit with a brewing slider as a brewing chamber, two piston units as shower screens and plungers, a drive motor, and at least one transmission. The brewing unit has a double spindle assembly with an outer spindle and an inner spindle. The brewing slider is movable from a first end position to an intermediate position, then to a second end position, and back again. The outer spindle has a moving thread that engages with an outer spindle nut axially fixed in the brewing slider. The moving thread of the outer spindle does not engage with the outer spindle nut in the first and second end positions of the brewing slider, so that the speed of the brewing slider is zero even if the outer spindle continues to rotate. The piston-type coffee machine is described.

[0006] Although these configurations have proven effective, there is a constant need for improvement in terms of cost reduction in components, functional groups, assembly time and maintenance.

[0007] The object of the present invention is therefore to advantageously further improve the brewing unit of a piston coffee machine in order to provide an improved brewing unit and an improved piston coffee machine.

[0008] This problem is solved according to the invention by a brewing unit with the features of claim 1 and a piston coffee machine with the features of claim 10.

[0009] The brewing unit according to the invention for a piston coffee machine is configured as a spindle-type brewing unit with a brewing slider as a brewing chamber, two piston units as shower screens and plungers, a drive motor and at least one transmission, the brewing unit has a double spindle assembly with an outer spindle and an inner spindle, the outer spindle is connected to the inner spindle via at least one transmission, the brewing slider is movable from a first end position to an intermediate position and then to a second end position, and then back to the intermediate position. and return to a first end position, the outer spindle having a moving thread which engages with an outer spindle nut arranged in the extraction slider, the extraction unit being characterized in that the moving thread of the outer spindle is not engaged with the outer spindle nut in the first end position of the extraction slider, and even if the outer spindle rotates further, the speed of the extraction slider is zero, the extraction slider is fixed in the first end position by the holding device, the moving thread of the outer spindle remains engaged with the outer spindle nut in the second end position of the extraction slider, and the drive motor is switched off.

[0010] The advantage here is that, although this allows for simple rest positions of the extraction slider in each end position, the outer spindle, which is driven by the drive motor, can still drive the inner spindle via a transmission and thus position the inner spindle and thus the shower screen - no separate motor is required.

[0011] The piston coffee machine according to the invention has a brewing unit as described above and has the advantage of being compact.

[0012] In one embodiment, the extractor slide has a first feed transmission with an outer spindle nut and a retaining device, which provides an advantageously simple and compact design.

[0013] In another configuration, the outer spindle nut is arranged with an axial clearance in the receiving section of the extractor slider, the first end face / contact surface (13d) of the outer spindle nut is in contact with the first pressure surface of the receiving section in the first end position, the second end face / contact surface of the outer spindle nut is separated from the second pressure surface of the receiving section by a clearance, and when the running thread of the outer spindle and the outer spindle nut are engaged, the second end face / contact surface of the outer spindle nut is in contact with the second pressure surface of the receiving section, and a clearance is arranged between the first end face / contact surface of the outer spindle nut and the first pressure surface of the receiving section. The advantage of this configuration is that it allows the extractor slider to be screwed in without load, thereby improving the so-called "screw-in process."

[0014] In yet another configuration, it is specified that at least one contact surface of the threaded region of the internal thread of the outer spindle nut is segmented by segments that are arranged spaced apart around the at least one contact surface of the outer spindle nut, surrounding the internal thread, and each have a spring effect and protrude from the respective contact surface of the outer spindle nut, thereby advantageously avoiding tilting between the outer spindle nut and the running thread of the outer spindle during the screwing process.

[0015] In another embodiment, the inner spindle is connected to a movable shower screen or a movable plunger and is connected to a drive via a second feed transmission, the plunger or shower screen is stationary, the movable extractor slider is guided longitudinally by the outer spindle and at least one guide rod, the shower screen or plunger is guided longitudinally inside the extractor slider, and the extractor slider and the shower screen or plunger can move in a common direction of movement at different speeds. This advantageously results in a simple and inexpensive construction, and advantageously allows for very high movement speeds.

[0016] In another configuration, if the connection between the outer spindle and the extractor slider is eliminated via the first feed transmission in the area of ​​the reversal clearance of the outer spindle nut with respect to the extractor slider, the shower screen is connected to the extractor slider by a controllably actuated entraining device in order to transmit the movement of the shower screen to the extractor slider, which advantageously allows for a simple connection.

[0017] In this case, it is further advantageous if the controllable entrainment device is configured as a controllable tappet device, since a compact design is possible.

[0018] In a further embodiment, it is provided that the controllable tappet device has a hydraulic, pneumatic or mechanical tappet drive, which advantageously results in a simple drive means.

[0019] In this case, a further configuration specifies that the tappet drive is connected to a hydraulically, pneumatically or mechanically actuable shower screen seal of the shower screen, which advantageously allows for simple control of the tappet drive.

[0020] In one configuration, the holding device comprises a permanent magnet, an electrically controllable electromagnet, or a mechanical locking device, with permanent magnets and electromagnets advantageously being high quality, inexpensive components, and mechanical locking devices offering the advantage of a simple configuration without electrical installation.

[0021] The invention will be explained in more detail below on the basis of examples and variants with reference to the drawings, which are used only to illustrate the invention and are not limiting, and the individual features described can be transferred to other variants within the scope of general knowledge. [Brief explanation of the drawings]

[0022] [Figure 1]1 shows a schematic perspective view of an embodiment of a brewing unit according to the invention for a coffee machine in a first position; FIG. [Figure 2] 2 is another schematic view of the brewing unit of FIG. 1 in a first position; FIG. [Figure 3] 2 is another schematic view of the brewing unit of FIG. 1 in a first position; FIG. [Figure 4] 2 is a schematic view of the extraction unit of FIG. 1 in a second position; [Figure 5] 2 is another schematic view of the brewing unit of FIG. 1 in a second position. [Figure 6] 2 is another schematic view of the brewing unit of FIG. 1 in a second position. [Figure 7] 2 is a schematic view of the extraction unit of FIG. 1 in a third position; [Figure 8] FIG. 2 is another schematic view of the brewing unit of FIG. 1 in a third position. [Figure 9] FIG. 2 is another schematic view of the brewing unit of FIG. 1 in a third position. [Figure 10] 2 is a schematic view of the extraction unit of FIG. 1 in the entrainment position. [Figure 11] FIG. 2 is another schematic view of the extraction unit of FIG. 1 in the entrainment position. [Figure 12] 2 is a schematic view of the extraction unit of FIG. 1 in a fourth position. [Figure 13] FIG. 2 is another schematic view of the brewing unit of FIG. 1 in a fourth position. [Figure 14] FIG. 2 is another schematic view of the brewing unit of FIG. 1 in a fourth position. [Figure 15] 2 is a schematic view of the extraction unit of FIG. 1 in an end position. [Figure 16] 2 is another schematic view of the extraction unit of FIG. 1 in an end position. [Figure 17] FIG. 3 is a schematic cross-sectional view taken along line XVII in FIG. 2. [Figure 18] FIG. 2 is a schematic enlarged cross-sectional view of a tappet device. [Figure 19]FIG. 2 is a schematic cross-sectional view of an outer spindle nut. [Figure 20] FIG. 2 is a schematic cross-sectional view of an outer spindle nut. [Figure 21] 2 is a schematic view of the drive side of the extraction unit according to FIG. 1; [Figure 22] FIG. 22 is a schematic cross-sectional view taken along line XXII in FIG. 21. [Figure 23] FIG. 23 is a schematic cross-sectional view taken along line XXIII in FIG. 21. [Figure 24] FIG. 24 is a schematic cross-sectional view taken along line XXIV in FIG. 21. [Figure 25] 10 is a schematic diagram showing a variant of the outer spindle nut. FIG. [Figure 26] 10 is a schematic diagram showing a variant of the outer spindle nut. FIG. [Figure 27] 10 is a schematic diagram showing a variant of the outer spindle nut. FIG. [Figure 28] FIG. 28 is a schematic side view of a brewing unit with an outer spindle nut according to the variant of FIGS. 25 to 27. [Figure 29] 10 is a schematic cross-sectional view of a variant of the outer spindle nut in the installed state.

[0023] In the figure, the coordinates x, y, z are shown for orientation purposes.

[0024] Figure 1 shows a schematic perspective view of an embodiment of a brewing unit 1 according to the invention for a piston coffee machine. Figure 2 shows a schematic plan view of the brewing unit 1 in the xy plane of Figure 1, looking from above. Figure 3 shows a schematic longitudinal section of the brewing unit 1 of Figures 1 and 2 in the xz plane.

[0025] The embodiment described here is a horizontal brewing unit 1. This configuration can also be used for a vertical brewing unit 1 or any other type of tilted brewing unit. The brewing unit 1 is a spindle brewing unit.

[0026] The brewing unit 1 comprises in this case an brewing slider 2, also called brewing chamber, an outer spindle 3, at least one guide rod 4 (two guide rods 4 in the shown example), a first base plate, herein called drive plate 5, and a second base plate, herein called plunger plate 6, an inner spindle 7, two piston units, i.e. the so-called shower screen 9 and plunger 10, and at least one drive motor, not shown.

[0027] This system allows the required relative positions between the plunger 10, shower screen 9 and brewing slider 2 of the brewing unit 1 for a piston coffee machine (not shown) to be realized by means of a double spindle assembly and a drive.

[0028] The drive motor causes a relative movement between the plunger 10 and the shower screen 9 in the x-direction, which allows the spacing between them to be varied. This allows a defined pressing force to be adjusted via a variable motor torque. At the same time, the brewing slider 2 is also moved. This allows a filling position for the coffee powder to be achieved, a sealed brewing chamber to be formed, and finally, the brewed coffee cake to be discharged.

[0029] In this case, the shower screen 9 and the extraction slider 2 are moved in the x direction to various positions, and the plunger 10 is now attached to the plunger plate 6 in a stationary position.

[0030] The double spindle assembly comprises an outer spindle 3 and an inner spindle 7. The outer spindle 3 moves the extraction slider 2 and the inner spindle 7 moves the shower screen 9.

[0031] The outer spindle 3 is connected to the extraction slider 2 via a first feed transmission 12, which will be explained in more detail below.

[0032] Furthermore, the extractor slider 2 is entrained by the shower screen 9 via an entrainment device to overcome the so-called reversal clearance. The controllable entrainment device is configured as a controllable tappet device 22, which will be explained in more detail below.

[0033] Inside this reversal clearance (see clearance 32 in Figure 24), which has a certain dimension in the x-direction, the extractor slider 2 is not engaged with the outer spindle. In this case, the connection between the outer spindle 3 and the extractor slider 2 by the first feed transmission 12 is released. If this connection is released in the region of the first end position and the reversal clearance, the extractor slider 2 is connected to the shower screen 9 via a tappet device 22 in order to transmit the movement of the shower screen 9 to the extractor slider 2 in the absence of a connection between the outer spindle 3 and the extractor slider 2. This will be explained further below.

[0034] The extractor slider 2 is moved from a stop position, which is a first end position of the extractor slider 2, to an intermediate position, then to a second end position and back again to the first end position, in which case the shower screen 9 is moved to various positions relative to the extractor slider 2 and the plunger 10.

[0035] The stopping positions of the extraction slider 2 are shown in FIGS.

[0036] The intermediate position of the extraction slider 2 is also called the grounds disposal position and is shown in FIGS.

[0037] Finally, FIGS. 15 and 16 show the second end position of the extraction slider 2.

[0038] The shower screen 9 is always located in the extractor slider 2 inside the extractor cylinder 20 of the extractor slider 2 and can assume various relative positions to the extractor slider 2. These relative positions are obtained independently of each other by the movement of the shower screen 9 by the inner spindle 7 and the movement of the extractor slider 2, which can be adjusted by the outer spindle 3.

[0039] The plunger 10 can in this case be located outside or inside the extraction slider 2. The plunger 10 is in this case arranged stationary, so that the relative position / movement of the extraction slider 2 and the shower screen 9 with respect to the plunger 10 is possible by means of the inner spindle 7 (shower screen 9) and the outer spindle 3 (extraction slider 2). It is also conceivable that the plunger 10 can be adjustable.

[0040] The shower screen 9 (or plunger 10) and the extraction slider 2 always have a common direction of travel but different speeds (speed difference), which results in the required relative position between these two components.

[0041] However, an exception is the stop position of the extractor slider 2 (Figs. 1 to 9), in which the extractor slider 2 is fixed to the plunger plate 6 by the retaining device HR (see Figs. 19 and 22) and is not engaged with the outer spindle. In this case, an independent adjustment movement of the shower screen 9 relative to the extractor slider 2 is possible.

[0042] To simplify the illustration of these travel directions, in each figure, a movement direction BR, which comprises two opposite movement directions BR1 and BR2 along the x-axis, is indicated by a single double-headed arrow.

[0043] This allows the brewing unit 1 to be moved to the following positions:

[0044] 1 to 3 show the closed position (first position). The filling position (second position) is shown in FIGS. 7 to 9 show the extraction position (third position). The entraining position is shown in FIGS. The grounds disposal position (fourth position), also called the open position, is shown in Figures 12 to 14. 15 and 16 show the end positions or terminal positions.

[0045] These positions are described in more detail below.

[0046] The outer spindle 3 with the outer spindle axis 3a, the guide rod 4 with the guide axis 4a, and the inner spindle 7 with the inner spindle axis 7a are arranged parallel to one another, and the directions of movement BR1 and BR2 extend parallel to these axes 3a, 4a, and 7a.

[0047] The drive plate 5 and the plunger plate 6 of the brewing unit 1 comprise in this case rectangular plates arranged parallel to one another and perpendicular to the axes 3a, 4a, 7a.

[0048] 1, a further plate 8 is mounted parallel to the drive plate 5, which forms a holder for a drive motor (not shown) and a transmission (e.g., toothed belt and / or gears) that is a drive 14, indicated only by the reference numeral. The transmission, not shown, connects the rotational movement of the inner spindle 7 with that of the outer spindle 3. Plate 8, shown in FIG. 21, forms a holder for a housing 15a of a second feed transmission 15 and for a media connection (not described in detail).

[0049] The outer spindle 3 is supported at its drive end 3b on the drive plate 5. The other end of the outer spindle is supported as a bearing end 3c on the plunger plate 6. The outer spindle 3 has an external thread as a moving thread 3d which cooperates with the first feed transmission 12 of the extraction slider 2.

[0050] A plunger 10 is attached to the plunger plate 6. The plunger 10, shower screen 9, extractor slider 2 and inner spindle 7 are arranged coaxially with respect to the extractor slider axis 2a, which in this case extends within the inner spindle axis 7a.

[0051] The outer spindle 3 and the guide rod 4 connect the drive plate 5 and the plunger plate 6 to each other. The guide rod 4 is concealed from the outside over its entire length by side walls 11, 11a. In this case, each side wall 11 is connected to or integral with the respective lower side wall 11a at its underside. The lower side wall 11a is bent inward relative to the respective upper side wall 11.

[0052] FIG. 17 shows a schematic cross-sectional view along line XVII in FIG.

[0053] The inner spindle 7 is engaged with a second feed transmission device 15. The second feed transmission device 15 includes a casing 15a, a cover 16 with a slot 16a (see FIG. 17), an inner spindle nut 17 with an internal thread 17b, and bearings 18, 18a, and 18b.

[0054] One end of the casing 15a is attached to the drive plate 5 via a plate 8. The other end of the casing 15a is closed by a cover 16. Inside the casing 15a, an inner spindle nut 17 is supported by bearings 18, 18a, and 18b. The bearing 18 is a thrust bearing and is supported by a collar 17a of the inner spindle 17. The bearings 18a and 18b are formed as radial bearings or radial ball bearings.

[0055] The collar 17a of the inner spindle nut 17 is located at one end of the inner spindle nut 17 near the cover 16 and faces the plunger plate 6. The other end of the inner spindle nut 17 extends through the drive plate 5 to the plate 8 and cooperates with the outer spindle 3 via a transmission.

[0056] The inner spindle nut 17 has a through hole 17c, which is formed with an internal thread 17b on the part facing the cover 16, and this internal thread engages with the spindle end 7c of the external thread (moving thread 7b) of the inner spindle 7. The internal thread 17b of the inner spindle nut 17 and the external thread (moving thread 7b) of the inner spindle 7 correspond to each other.

[0057] The inner spindle 7 is further provided with flats 7e on both sides (best visible in Figure 17), which, together with the elongated holes 16a in the cover 16 (see Figure 17), form anti-rotation elements for the inner spindle 7. This ensures that the inner spindle 7 is arranged in an anti-rotation manner. The inner spindle nut 17 can be rotated about the inner spindle axis 7a by the drive device 14, and via the moving threads 7b / 17b, causes a linear movement of the stationary inner spindle 7 and thus the shower screen 9.

[0058] The flat 7e can be provided, for example, directly on the external thread 7b of the inner spindle 7, so that the feeding function and the anti-rotation function are geometrically connected in parallel. Alternatively, the external thread (moving thread 7b) and the flat 7e can be arranged one after the other. This does not change the external thread (moving thread 7b), but extends the shape of the inner spindle 7 by the maximum travel of the shower screen 9.

[0059] The inner spindle 7 includes an inner spindle axis 7a, a moving screw thread 7b, a first spindle end 7c, a second spindle end 7d, and a flat portion 7e. Furthermore, the inner spindle 7 has a thread end 7f of the moving screw thread 7b, which faces the plunger plate 6 and abuts a collar 7g. The collar 7g cooperates with the cover 16 to form a stop and thus an end position for the shower screen 9 in the movement direction BR1 toward the drive plate 5 (see FIG. 6). In this case, the spindle end 7c extends outward through the portion of the through-hole 17c that does not have the internal thread 17b, through the drive plate 5, and through the opening in the plate 8 (FIG. 6).

[0060] The extractor slider 2 has a substantially hollow cylindrical casing with a circular cross section and an extractor slider axis 2a, in which a extractor cylinder 19 with an extractor chamber 25, also of circular cross section, is arranged coaxially with the extractor slider axis 2a.

[0061] The brewing cylinder 19 has a first end face 19a facing the plunger plate 6. The brewing cylinder 19 is provided with an opposite second end face 19b facing the drive plate 5.

[0062] The extraction cylinder 19 is provided with an opening 19c in its circumferential wall, which opening communicates with the filling opening 2c in the casing of the extraction slider 2. In the region of the first end face 19a of the extraction cylinder 19, in the circumferential direction, in the end region of the casing of the extraction slider 2, a seal 19d is arranged, which seals the extraction cylinder 19 against the casing of the extraction slider 2.

[0063] The extraction chamber 25 of the extraction cylinder 19 of the extraction slider 2 accommodates the shower screen 9 and the plunger 10 in a predetermined position of the extraction unit 1, which will be described in more detail below. The shower screen 9 and the plunger 10 are guided within the extraction chamber 19 so as to be slidable in the directions of movement BR1 and BR2 relative to the extraction cylinder 19. When both the shower screen 9 and the plunger 10 are located within the extraction chamber 25 in a predetermined position of the extraction unit 1, the shower screen and the plunger face each other at various distances.

[0064] The extraction slider 2 cooperates with the plunger 10 in such a way that the extraction cylinder 19 of the extraction slider 2 is moved above the plunger 10 at an opening provided in a first end face of the extraction cylinder, the extraction chamber 19 being sealed by a plunger seal 10a on the side facing the plunger plate 6. The plunger seal 10a is an adjustable seal, for example a hydraulically actuable and deactuable seal.

[0065] The extraction slider 2 is slidably guided in both directions of movement BR1 and BR2 via a guide rod 4 between a drive plate 5 and a plunger plate 6.

[0066] The outer spindle 3 extends through a first feed transmission 12. The feed transmission 12 is arranged in a receiving portion 2c on the outer surface of the extraction slider 2 and has an outer spindle nut 13 (Fig. 19). The outer spindle nut 13 is provided with an internal thread 13b that corresponds to the external thread (moving thread 3d) of the outer spindle 3.

[0067] The moving thread 3d of the outer spindle 3 engages with the internal thread 13b of the outer spindle nut 13, but in the rest position of the extraction slider 2 (Figures 1 to 11), the moving thread 3d does not engage with the outer spindle nut 13. This will be explained in more detail below in connection with Figures 19 and 22 to 24.

[0068] The movement mechanism of the brewing unit 1 is based on two threaded spindle drives, namely an outer spindle 3 and an inner spindle 7. The moving thread 3d of the outer spindle 3 and the moving thread 7b of the inner spindle 7 have different thread pitches.

[0069] The outer spindle 3 is synchronized with the inner spindle 7 via a transmission between the drive plate 5 and the plate 8 .

[0070] The transmission is in this case configured as a traction means transmission with a toothed belt (see FIG. 21). The transmission can also be configured with gears or in combination with a toothed belt. The transmission can also be multi-stage.

[0071] The outer spindle 3 is, for example, a drive shaft of the extraction unit 1, and causes the extraction slider 2 to move linearly via an outer spindle nut 13 that is attached to the extraction slider 2 in its accommodation portion 2c so as not to rotate.

[0072] The transmission connection simultaneously causes a rotational movement of the inner spindle nut 17, which is engaged with the moving thread 7b of the inner spindle 7. This causes a linear movement of the shower screen 9, which is attached to the second spindle end 7d of the inner spindle 7. The rotation prevention member of the inner spindle 7 via the flat part 7e, which cooperates with the elongated hole 16a in the cover 16, prevents the shower screen 9 and the inner spindle 7 from rotating together about their own axis (the inner spindle axis 7a), but only moves in the axial movement directions BR1, BR2.

[0073] The moving thread 7b of the inner spindle 7 has a smaller pitch than the moving thread 3d of the outer spindle 3. For this reason, the movement speed of the extraction slider 2 is several times faster with the inner spindle 7 than with the shower screen 9. Advantageously, the pitch of the inner spindle 7 is selected such that the inner spindle is self-locking during the extraction process.

[0074] The shower screen 9 and the plunger 10 are arranged in the extraction unit 1 so that their end faces face each other.

[0075] The shower screen 9 is rigidly connected to the inner spindle 7 and has an adjustable shower screen seal 9a extending circumferentially on its outer surface. The shower screen seal 9a is an adjustable seal, for example a hydraulically actuable and deactuable seal.

[0076] The shower screen 9 and the shower screen sleeve 20 are slidably guided in the directions of movement BR1 and BR2 by the inner spindle 7 in the extraction chamber 25 of the extraction cylinder 19. The shower screen 9 is introduced into the extraction cylinder 19 through an opening provided in the second end face 19b of the extraction cylinder 19.

[0077] Furthermore, a shower screen sleeve 20 with a bottom surface 20a is attached to the shower screen 9 on the side facing the drive plate 5, and an inner chamber 21 of this shower screen sleeve extends over a section of the inner spindle 7 in the direction towards the drive plate 5. An end section 20b of the shower screen sleeve 20 has an opening that leads into the inner chamber 21, the inner diameter of which corresponds to the outer diameter of the casing 15a of the second feed transmission device 15.

[0078] A tappet device 22 having a tappet 23 is arranged on the outer surface of the shower screen sleeve 20. The tappet 23 can be moved radially from a first position to a second position and vice versa by a tappet drive device 24. The tappet drive device 24 is configured so that the tappet 23 is connected to the hydraulic seal 9a of the shower screen via hydraulic lines 24a, 24c (see FIG. 6). In this case, a first line 24a is connected to the tappet device 22 and is arranged in a line section 20c on the bottom surface 20a of the shower screen sleeve 20, where they are integrally formed. The first line 24a is connected to a second line 24c in the body of the shower screen 9 via a line connector 24b. The line connector 24b is sealed to both the bottom surface 20a of the shower screen sleeve 20 and the body of the shower screen 9 via a seal 24d. The second conduit 24c communicates with the hydraulic shower screen seal 9a.

[0079] In the tappet's first position, the upper edge of the tappet 23 is located below or flush with the outer surface of the shower screen sleeve 20 (FIG. 6).

[0080] When the shower screen seal 9a is activated, for example by an increase in pressure of a hydraulic medium (which may be compressed air), the tappet 23 is moved radially outward from its first position (see Figures 6, 9, 14, 16) to its second position (see Figures 3 and 11) and protrudes from the outer surface of the shower screen sleeve 20.

[0081] In the second position, the tappet 23 protrudes into the opening 19c of the extraction cylinder 19. This allows the movement of the shower screen 9 by the inner spindle 7 to be transmitted to the extraction cylinder 19 when the outer spindle nut 13 is not engaged with the moving thread 3d of the outer spindle 3.

[0082] This occurs when the outer spindle nut 13 of the extraction cylinder 19 disengages from the moving thread of the outer spindle 3 during movement in the movement direction BR2 towards the plunger plate 6. The tappet 23 of the tappet device 22 is then actuated together with the seal 9a of the shower screen 9 and protrudes into the opening 19c of the extraction cylinder 19, abutting against the wall of the opening 19c facing the plunger plate 6 and transmitting the movement of the shower screen 9 to the extraction cylinder 2 until the first end face 9a of the extraction cylinder or extraction cylinder 19 is located above the plunger 10 in the rest position, and the member of the holding device HR abuts against the inner surface 6a of the plunger plate 6 (see Figures 19 and 22).

[0083] FIG. 18 shows a schematic enlarged cross-sectional view of the tappet device 22.

[0084] The tappet device 22 includes a tappet 23 with a tappet drive device 24, a tappet holder 26, and seals 27, 27a.

[0085] The tappet 23 is a cylindrical component having a tappet axis 23, a tappet body 23b, an intermediate section 23c, and two collars 23d and 23e. The tappet body 23b has a conical chamfer at its upper end and is connected at its lower end to the intermediate section 23c via a first collar 23d, the free end of which terminates in a second collar 23e. The outer diameter of the tappet body 23b is slightly larger than that of the intermediate section 23c. The outer diameters of the collars 23d and 23e are the same as or larger than that of the tappet body 23b.

[0086] The tappet holder 26 is cylindrical and has a collar 26a extending in the circumferential direction at its upper end. A through opening 26b is formed in the center of the collar 26a, and the inner diameter of the through opening 26b corresponds to the outer diameter of the tappet body 23b. A hollow cylindrical guide body 26c extends downward from the collar 26a and includes a mounting portion 26d and an inner chamber 26e. The inner chamber 26e is cylindrical. The inner diameter of the inner chamber corresponds to the outer diameter of the collars 23c, 23d of the tappet 23. The inner chamber 26e is open downward.

[0087] The tappet 23 is inserted into the tappet holder 26 so that the tappet body 23b extends outward through the through opening 26b and the collars 23d, 23e are arranged in the inner chamber 26e, where the tappet 23 is slidably guided within the tappet holder 26. The tappet 23 and the tappet holder 26 are arranged coaxially with respect to the tappet axis 23a.

[0088] A seal 27a, such as an O-ring, is disposed between the collars 23d and 23e to seal the tappet 23 against the inner wall of the inner chamber 26e of the tappet holder 26.

[0089] The tappet holder 26 including the tappet 23 is arranged by means of a collar 26a of the tappet holder 26 in the receiving part 20e of the shower screen sleeve 20. In this case, a seal 27, for example an O-ring, is located between the underside of the collar 26a of the tappet holder 26 and a step in the receiving part 20. In this case, the tappet holder 26 is screwed by means of a mounting section 26d of the tappet holder, for example an external thread, into the corresponding internal thread of the receiving part 20.

[0090] The housing portion 20 is connected at its lower surface to communicate with the first conduit 24a of the tappet drive device 24, and in this case, the inner chamber 26e communicates with the first conduit 24a of the tappet drive device 24.

[0091] In Figure 18, the tappet 23 is shown in its second position, protruding into the opening 19c of the extraction cylinder 19. In this second position of the tappet 23, the tappet drive 24 is under pressure by the hydraulic medium and exerts a force directed upwards (in this case in the z direction) on the lower collar 23e of the tappet 23. This force pushes the tappet 23 upwards and presses the upper collar 23d of the tappet 23 against the underside of the collar 26a of the tappet holder 26. This limits the second position of the tappet 23.

[0092] 18 shows the upper end of the tappet 23 in contact with the chamfer of the opening 19c of the extraction cylinder 19. The chamfer serves to push the tappet 23 back into its first position in the tappet holder 26 when the shower screen 9 together with the shower screen sleeve 20 moves in the x direction towards the drive side. In this case, the tappet drive 24 is switched to a pressureless state. This is necessary to entrain the extractor slider 2 from its rest position when the outer spindle nut 13 of the extractor slider 2 again engages with the moving thread 3d of the outer spindle 3. This is because, as already mentioned above, the moving thread 3d of the outer spindle 3 and the moving thread 7b of the inner spindle 7 have different pitches.

[0093] Alternatively, a permanent spring support of the tappet 23 is conceivable, which leads to a forced entrainment (screw-in) of the extractor slider 2. In this case, three operating states are possible in principle: 1) Engagement state of the tappet 23 (forced engagement) 2) The spring load state of the tappet 23 (sliding friction inside the extraction cylinder 19) 3) Disengagement of the tappet 23 (e.g., during the pressing and extraction processes) An example of a spring support may be a compression spring or a profile that generates the appropriate spring force that is incorporated directly into the injection molding of the clean reservoir.

[0094] In another alternative, the tappet 23 can be configured as a spring-loaded pressure element. It contacts the chamfer of the opening 19c of the brew cylinder 19, transmitting a force from the shower screen 9 to the brew cylinder 19. This briefly synchronizes their movements, ultimately threading the outer spindle nut 13 onto the moving thread 3d of the outer spindle 3. When the brew cylinder 19 overtakes the shower screen 9 due to the feed of the moving thread 3d of the outer spindle 3, the spring-loaded tappet 23 subsequently leaves the interior of the brew cylinder 19 and slides along its inner wall until it is again pushed by the spring force into the filling opening 2b at its rest position. This design requires low-wear friction pairs and contact surfaces, allowing for multiple spring load cycles. A particularly simple design is achieved, without complex seals for the hydraulic passages 24a, 24b, 24c of the tappet 23.

[0095] Figure 19 shows a schematic longitudinal section through the outer spindle nut 13 and the retaining device HR of the first feed transmission 12 of the extractor slider 2 in the rest position of the extractor slider 2. Figure 20 shows a cross section along the line XX in Figure 19.

[0096] The outer spindle nut 13 has a figure-eight shaped cross section with a retaining section 13a and a thread section with an internal thread 13b (Fig. 20), which corresponds to the external thread 3d of the outer spindle 3.

[0097] The outer spindle nut 13 is arranged in the receiving portion 2c on the outer surface of the extraction slider 2 in the area facing the plunger plate 6 (see also Figures 1, 2, 4, 5, 7, 8, 10, 12, 13, 15).

[0098] Furthermore, the outer spindle nut 13 is formed with two coaxial opposite receiving sections 13c, which are arranged in the holding section 13a and belong to the holding device HR. The central axes of the receiving sections 13c run parallel to the outer spindle axis 3a or the central axis of the internal thread 13b. The two receiving sections 13c are separated by an annular shoulder 13f, which has a through-hole.

[0099] The outer spindle nut 13 has end faces or contact faces 13d and 13e. The first end face / contact face 13d faces the plunger plate 6 and the first pressing face 2d of the receiving part 2c. The second end face / contact face 13e faces the drive plate 5 and the second pressing face 2e of the receiving part 2c.

[0100] The outer spindle 3 extends through the through hole 2f of the extraction slider 2 and the internal thread 13b of the outer spindle nut 3.

[0101] The holding device HR in this case comprises a guide pin 28 , a sleeve 29 , 29 a , a compression spring 30 and a magnetic element 31 .

[0102] The guide pin 28 is arranged parallel to the outer spindle axis 3a in the sleeve 29, 29a and has a head 28a at the end facing the drive plate 5, the outer diameter of which corresponds to the outer diameter of the sleeve 29a, the longitudinal axis of the guide pin 28 forming the pin axis 28b.

[0103] The sleeves 29, 29a are inserted into the receiving section 13c of the retaining section 13a of the outer spindle nut 13 so that their ends located in the receiving section 13c each rest against an annular shoulder 13f, which forms an axial stop for the sleeves 29, 29a. The guide pin 28 in this case extends through the through-holes of the sleeves 29, 29a and the annular shoulder 13f.

[0104] The sleeves 29, 29a each project axially at their other ends out of the receiving section 13c, with the sleeve 29 projecting axially into a through hole 2g of the extraction slider 2 together with the head 28a of the guide pin 28 in the direction towards the plunger plate 6. The other sleeve 29a projects axially into another through hole 2h of the extraction slider 2 in the direction towards the drive plate 5. The inner diameter of the through hole 2h corresponds to the outer diameter of the sleeve 29a and the outer diameter of the head 28a of the guide pin 28. The through hole 2h thus forms a sliding guide for the sleeve 29a and the head 28a.

[0105] A compression spring 30 is arranged around the sleeve 29a between the retaining section 13a of the outer spindle nut 13 and the second pressure surface 2e of the receiving part 2c of the extractor slider 2. In this case, one end of the compression spring 30 is attached to the outer spindle nut 13, and the other end of the compression spring 30 is in contact with the second pressure surface 2e of the receiving part 2c of the extractor slider 2.

[0106] The magnet element 31 is firmly connected, for example screwed, to the end of the guide pin 28 facing the plunger plate 6. The end of the magnet element 31 facing the outer spindle nut 13 contacts the end of the sleeve 29 protruding towards the plunger plate 6. The end of the sleeve 29a facing the drive plate 5 contacts the head 28a of the guide pin 28. In this case, the sleeves 29 and 29a are clamped or firmly arranged together between the head 28a of the guide pin 28 and the magnet element 31 and are further axially fixed to the retaining section 13a of the outer spindle nut 13 by means of an annular shoulder 13f.

[0107] The magnet element 31 is cylindrical and is arranged so as to be slidably guided within the through hole 2g of the extraction slider 2. The inner diameter of the through hole 2g corresponds to the outer diameter of the magnet element 31.

[0108] In the rest position of the extractor slider 2 shown in Figure 19, the internal thread 13b of the outer spindle nut 13 is not engaged with the running thread 3d of the outer spindle 3. This state is also called the "unthreaded state". The contact surface 13d of the outer spindle nut 13 facing the plunger plate 6 abuts against the first pressure surface 2d of the receiving part 2c of the extractor slider 2.

[0109] The magnetic element 31 of the holding device HR is in contact with the inner surface 6a of the plunger plate 6, which is made of a magnetically attractable metal, for example steel. In this way, the holding device HR fixes the outer spindle nut 13 and thus the extractor slider 2 in its rest position. The spring force of the compression spring 30 then acts additionally, pressing the outer spindle nut 13 in the direction of the plunger plate 6 against the first pressure surface 2d of the receiving part 2c of the extractor slider 2.

[0110] FIG. 20 also shows one of the two guide holes 2i for the guide rod 4 of the extraction slider 2.

[0111] FIG. 21 shows a schematic view of the drive side of the brewing unit 1 according to FIG. 1 with cutting lines for the subsequent FIGS. 22 to 24.

[0112] 22 to 24 are schematic cross-sectional views taken along line XXII-XXIII-XXIV in FIG.

[0113] In FIG. 22 the extraction slider 2 is shown in its rest position.

[0114] The extractor slider 2 has a first end face 2j facing the drive plate 5. The opposite second end face 2k of the extractor slider 2 faces the plunger plate 6 and contacts the inner surface 6a of the plunger plate 4 as a stop when the extractor slider 2 is at rest.

[0115] When the extractor slider 2 is in its rest position, the first end face 13d of the outer spindle nut 13 abuts against the first pressure surface 2d of the receiving part 2c of the extractor slider 2, which faces the plunger plate 6. A clearance 32 is formed between the second end face 13e of the outer spindle nut 13, which faces the drive plate 5, and the corresponding second pressure surface 2e, which also faces the drive plate 5. The clearance 32 is also called the "reverse clearance" and is approximately 5 mm in the illustrated example. This state is also referred to as "the reversal clearance is open."

[0116] In this case the outer spindle nut 13 is "not threaded" and in this case is about 2 mm away from the end of the running thread 3d of the outer spindle 3.

[0117] The extraction slider 2 is in a first end position, in the rest position shown here or in the position described above: - Closed position (first position, Figures 1 to 3) - Filling position (second position, Figures 4 to 6) - Extraction position (third position, Figures 7 to 9).

[0118] In the closed position of the brewing unit 1 (see Figures 1 to 3), the brewing slider 2 is in its rest position and the shower screen 9 together with the shower screen sleeve 20 is completely inserted into the brewing cylinder 19 of the brewing slider 2. The shower screen 9 and the plunger 10 are closely arranged or in contact with each other. An opening 19c in the brewing cylinder 19 below the filling opening 2b is closed by the shower screen sleeve 20. The tappet 23 is in its second position and abuts against the edge of the opening 19c facing the plunger plate 6.

[0119] To position the brewing unit 1 in the filling position, the tappet drive 24 is first deactivated by depressurization, which also deactivates the seal 9a of the shower screen 9. The shower screen 9 and the shower screen sleeve 20 connected to it are moved by the inner spindle 7 in the direction of movement BR1 towards the drive plate 5. The tappet 23 is then returned to its first position by the chamfer of the opening 19c (see FIG. 18). The shower screen 9 is then positioned in the filling position at the end of the brewing cylinder 19 facing the drive plate 5. With its end section 20b, the shower screen sleeve 20 now surrounds a large part of the casing 15a of the second feed transmission 15. The opening 19c leading to the filling opening 2b is free, allowing coffee powder to be filled into the brewing chamber 25 between the shower screen 9 and the plunger 10 (FIG. 6).

[0120] The shower screen 9 is then moved back into the brewing cylinder 19 to compress the coffee powder in the brewing chamber 25 and assume the brewing position. Further filling and subsequent further compression of the coffee powder can be achieved by repeating the approach to the filling position and the brewing position (Figure 9).

[0121] After the extraction process is completed, the grounds disposal position is assumed. For this, the shower screen 9 is moved further into the extraction cylinder 19 in the direction of movement BR2 until the tappet 23 is positioned below the opening 19c of the extraction cylinder 19, thereby assuming the entrainment position shown in FIGS. 10-11. The tappet drive 24 is activated, which also puts the shower screen seal 9a under pressure. The shower screen 9 is then moved in the direction of movement BR1 towards the drive plate 5 by the inner spindle 7. In this case, the tappet 23 in its second position presses against the edge of the opening 19c of the extraction cylinder 19 and exerts a force on this edge in the direction of movement BR1, and thus on the extraction slide 2. At the same time, this is facilitated by the friction of the shower screen seal 9a in the extraction cylinder 19. The holding device HR with the magnetic element 31 moves away from the plunger plate 6, and the reversal clearance (clearance 32) is passed through and overcome. The thread 13b of the outer spindle nut 13 engages with the moving thread 3d of the outer spindle 3 (also known as the "threading process"). The second end face 13e of the outer spindle nut 13, facing the drive plate 5, presses against the second pressure face 2e of the receiving part 2c of the associated brewer slider 2, so that the compression spring 30 of the retaining device HR is preloaded. Adjustment of the brewer slider 2 in the movement direction BR1 is now effected by the outer spindle 3, and the tappet 23 is returned to the first position as described above in connection with FIG. 18. Further movement of the brewing unit 1 results in the grounds disposal position (FIG. 14).

[0122] This is also shown in cross section in Figure 23. There is now a reversal clearance or clearance 32 between the first end face 13d facing the plunger plate 6 and the corresponding first pressure surface 2d of the receiving part 2c of the extraction slider 2. This state is also referred to as "closed reversal clearance".

[0123] In the grounds disposal position, the shower screen 9 is located at the end of the brewing cylinder 19 facing the drive plate 6 and pushes out the coffee cake present in the brewing chamber 25, which then falls into a collection container.

[0124] The brewing slider 2 is in an intermediate position in the grounds disposal position of the brewing unit 1 .

[0125] Further movement of the extraction unit 1 in the direction of movement BR1 towards the drive plate 5 leads to the end positions shown in FIGS. 15-16 and 24.

[0126] In the end position of the brewing unit 1, the brewing slider 2 is located in the second end position of the brewing slider.

[0127] In this end position of the brewing unit 1, which is also the end position of the brewing slider 2, the outer spindle nut 13 is no longer unthreaded from the running thread 3d of the outer spindle 3. The collar 7g of the inner spindle 7, together with the cover 16 of the second feed gear 15, form an end position stop. The drive, e.g., the electric motor, is switched off by a limit switch (not shown) or motor current monitoring.

[0128] This end position is used as a reference for the position of the brewing unit 1 and the position of the brewing slider 2, for example.

[0129] To resume the rest position or the first end position of the extractor slider 2 from the end position, the extractor unit 1 is moved in the direction of movement BR2 towards the plunger plate 6 until the outer spindle nut 13 is unthreaded from the running thread 3d of the outer spindle 3. The tappet 23 is then already moved to its second position by the tappet drive 24. The tappet 23 is now in contact with the edge of the opening 19c facing the plunger plate 6, so that the movement of the shower screen 9 can be transmitted in the direction of movement BR2 towards the plunger plate 6, since after unthreading the outer spindle 3 no longer transmits movement to the outer spindle nut 13 of the extractor slider 2. The extractor slider 2 is therefore moved into the rest position by the movement of the shower screen 9 in the direction of movement BR2, with the magnetic element 31 of the holding device HR fixing the extractor slider 2 to the inner surface 6a of the plunger plate 6 in the rest position.

[0130] Figure 25 shows a schematic perspective view of one variant of the outer spindle nut 13'. A corresponding side view is shown in Figure 26. Figure 27 shows a front view of the contact surface 13e of the variant of the outer spindle nut 13'. Figure 28 shows a schematic side view of a brewing unit 1 with the variant of the outer spindle nut 13' according to Figures 25 to 27. Figure 29 shows a schematic cross-section of the variant of the outer spindle nut 13' in the installed state.

[0131] The modified outer spindle nut 13' has several differences with respect to the outer spindle nut 13 shown in FIG.

[0132] In this variant, the guide pin 28 is formed integrally with the retaining section 13a of the outer spindle nut 13' and has a flat portion 28c on its longitudinal side, protruding from the contact surface 13e of the outer spindle nut 13'.

[0133] A compression spring 30 is arranged on the guide pin 28. In the assembled state (FIG. 29), the compression spring 30 rests at one end on the second end face / contact surface 13e of the outer spindle nut 13′ and at the other end via a disk (not shown) on the pressure surface 2e of the receiving part 2c of the extraction slider 2.

[0134] The second end face / contact surface 13e of the thread area at the thread end of the female thread 13b of the outer spindle nut 13' is segmented by segments 33, which prevents tilting between the outer spindle nut 13' and the running thread 3d of the outer spindle 3 during the screwing process.

[0135] The individual segments 33 each have a spring-elastic effect and are arranged spaced apart from one another around the second end face / contact face 13e of the outer spindle nut 13a, surrounding the female thread 13b, i.e., surrounding the thread end of the female thread 13, and protrude from the second end face / contact face 13e of the outer spindle nut 13'.

[0136] As soon as the head diameter and base diameter of the thread pair (the internal thread 13b of the outer spindle nut 13' and the running thread 3d of the outer spindle 3) show a tendency to jam, the individual segments 33 can spring open, i.e. spring open radially outward. In this embodiment, eight segments 33 are provided, but a different division may also be advantageous. What is important is that the individual segments 33 can spring-displace in the event of tilting. If the design requires unscrewing at both thread ends of the outer spindle 3, segmentation at the contact surfaces 13d, 13e of the both thread ends of the internal thread 13b of the outer spindle nut 13 is also conceivable.

[0137] The invention is not limited to the embodiments described above, but it can be varied within the scope of the claims.

[0138] It is contemplated that the movement functions of the shower screen 9 and the plunger 10 in the brewing unit 1 may be interchangeable, i.e. they may be arranged in reverse.

[0139] Instead of the drive plate 5 and plunger plate 6, a frame may be used.

[0140] The magnetic element 31 may be a controllable electromagnet.Various configurations of mechanical locking devices are also contemplated, for example releasable locks.

[0141] It is further conceivable that the entrainment of the shower screen 9 can be realized via a spring-loaded entrainment device, which requires that it also be unscrewed in the second end position, as otherwise the filling position is no longer reachable. [Explanation of symbols]

[0142] 1 Extraction unit 2 Extraction slider 2a Extraction slider axis 2b Filling opening 2c Storage section 2d, 2e Pressing surface 2f,2g,2h through hole 2i Guide hole 2j,2k end face 3 outer spindle 3a Outer spindle axis 3b Drive end 3c Bearing end 3D Moving Thread 4 guide rods 2i Guide axis 5 Drive Plate 6 Plunger Plate 5a,6a inner surface 7 Inner Spindle 7a Inner spindle axis 7b Moving thread 7c, 7d Spindle end 7e flat area 7f Thread end 7g Color 8 plates 9. Shower Screen 9a Shower screen seal 10 Plunger 10a Plunger seal 11,11a side wall 12 First feed transmission device 13,13' outer spindle nut 13a Retention category 13b internal thread 13c Storage section 13d,13e Contact surface 13f Shoulder 13g Segment 14 Drive unit 15 Second feed transmission device 15a casing 16 Cover 16a long hole 17 Inner spindle nut 17a Color 17b internal thread 17c through hole 18, 18a, 18b Bearings 19 Extraction cylinder 19a,19b end face 19c aperture 19d seal 20 shower screen sleeves 20a bottom 20b End section 20c pipe division 20d storage section 21 Inner room 22 Tappet device 23 Tappet 23a Tappet axis 23b Tappet body 23c Intermediate division 23d, 23e color 24 Tappet drive unit 24a Pipeline 24b Pipe Connector 24c conduit 24d seal 25 Extraction chamber 25' Disposal Room 26 Tappet holder 26a color 26b Through opening 26c Guide body 26d Installation section 26e Inner room 27,27a Seal 28 Guide pin 28a head 28b Pin axis 28c flat area 29,29a Sleeve 30 compression spring 31 Magnetic element 32 Clearance 33 segments BR,BR1,BR2 Movement direction HR holding device x,y,z coordinates

Claims

1. A brewing unit (1) for a piston coffee machine, said brewing unit (1) being configured as a spindle brewing unit with a brewing slider (2) as a brewing chamber, two piston units as a shower screen (9) and a plunger (10), a drive motor and at least one transmission, said brewing unit (1) having a double spindle assembly with an outer spindle (3) and an inner spindle (7), The outer spindle (3) is connected to the inner spindle (7) via the at least one transmission device, The extraction slider (2) is movable from a first end position to an intermediate position, then to a second end position, and back again to the first end position; The outer spindle (3) has a running thread (3d) which engages with an outer spindle nut (13) located in the extraction slider (2); In the extraction unit (1), the moving thread (3d) of the outer spindle (3) is not engaged with the outer spindle nut (13) in the first end position of the extractor slider (2), and even if the outer spindle (3) rotates further, the speed of the extractor slider (2) is zero and the extractor slider (2) is fixed in the first end position by a holding device (HR), the moving thread (3d) of the outer spindle (3) remains engaged with the outer spindle nut (13) in the second end position of the extractor slider (2), and the drive motor is switched off.

2. 2. The brewing unit (1) according to claim 1, wherein the brewing slider (2) comprises a first feed transmission (12) with the outer spindle nut (13) and the holding device (HR).

3. the outer spindle nut (13) is arranged in the receiving part (2c) of the extraction slider (2) with an axial clearance (32), a first end face / contact surface (13d) of the outer spindle nut (13) contacts a first pressing surface (2d) of the receiving part (2c) in the first end position, and a second end face / contact surface (13e) of the outer spindle nut (13) and a second pressing surface (2e) of the receiving part (2c) are separated by the clearance (32); 3. The brewing unit (1) according to claim 2, wherein when the running thread (3d) of the outer spindle (3) and the outer spindle nut (13) are engaged, the second end face / contact surface (13e) of the outer spindle nut (13) and the second pressing surface (2e) of the receiving part (2c) are in contact, and the clearance (32) is arranged between the first end face / contact surface (13d) of the outer spindle nut (13) and the first pressing surface (2d) of the receiving part (2c).

4. 4. The brewing unit (1) according to claim 3, wherein at least one contact surface (13d, 13e) of the threaded region of the internal thread (13b) of the outer spindle nut (13') is segmented by segments (33), which are arranged spaced apart from one another around the at least one contact surface (13d, 13e) of the outer spindle nut (13a) and surrounding the internal thread (13b), each having a spring effect and protruding from the respective contact surface (13d, 13e) of the outer spindle nut (13').

5. 5. The brewing unit (1) according to claim 1, wherein the inner spindle (7) is connected to the movable shower screen (9) or the movable plunger (10) and is connected to a drive device via a second feed transmission (15), the plunger (10) or the shower screen (9) is arranged stationary, the movable extraction slider (2) is guided by the outer spindle (3) and at least one guide rod (4) so ​​as to be longitudinally slidable, the shower screen (9) or the plunger (10) is guided inside the extraction slider (2) so as to be longitudinally slidable, and the extraction slider (2) and the shower screen (9) or the plunger (10) are movable in a common direction of movement (BR1, BR2) at different speeds.

6. 6. The extraction unit (1) according to claim 1, wherein the shower screen (9) is connected to the extraction slider (2) by a controllably actuated entraining device in order to transmit the movement of the shower screen (9) to the extraction slider (2) when the connection between the outer spindle (3) and the extraction slider (2) is released via the first feed transmission device (12) in the region of the reversal clearance of the outer spindle nut (13) with respect to the extraction slider (2).

7. 7. The brewing unit (1) according to claim 6, wherein the controllable entrainment device is configured as a controllable tappet device (22).

8. 8. The brewing unit (1) according to claim 7, wherein the controllable tappet device (22) comprises a hydraulic, pneumatic or mechanical tappet drive (24).

9. 9. The brewing unit (1) according to claim 8, wherein the tappet drive (24) is connected to a hydraulically, pneumatically or mechanically actuable shower screen seal (9a) of the shower screen (9).

10. 10. Brewing unit (1) according to any one of the preceding claims, wherein the holding device (HR) comprises a permanent magnet, an electrically controllable electromagnet or a mechanical locking device.

11. A piston coffee machine equipped with a brewing unit (1) according to any one of claims 1 to 10.

Images