Brewing unit of coffee machine

Abstract

The invention relates to a brewing unit (1) of a piston coffee machine, the brewing unit (1) being designed as a screw-type brewing unit having a brewing carriage (2) as a brewing chamber, two piston units as a spray head (9) and a punch (10), a drive motor and at least one transmission, the brewing unit (1) having a twin-screw assembly with an outer screw (3) and an inner screw (7), wherein the outer screw (3) is coupled to the inner screw (7) via the at least one transmission mechanism, and wherein the brewing carriage (2) can be displaced from a first end position into an intermediate position, then into a second end position, and again into the first end position, and wherein the outer screw (3) has a movement thread (3d), the movement thread engages with an outer screw nut (13) arranged in the brewing slide (2). Wherein, in a first end position of the brewing carriage (2), the movement thread (3d) of the outer screw (3) is disengaged from the outer screw nut (13), the speed of the brewing carriage (2) is zero even if the outer screw (3) continues to rotate, the brewing carriage (2) is fastened in the first end position by means of a retaining device (HR), and in a second end position of the brewing carriage (2), the movement thread (3d) of the outer screw (3) is disengaged from the outer screw nut (13). The movement thread (3d) of the outer screw (3) remains in engagement with the outer screw nut (13) and the drive motor is switched off. The piston coffee machine is equipped with such a brewing device (1).

Description

Technical Field

[0001] The invention relates to a brewing unit of a piston coffee machine according to the preamble of claim 1 and to a piston coffee machine having such a brewing unit. Background Art

[0002] Brewing units for piston coffee machines are known in many embodiments. In the brewing unit of a piston coffee machine, coffee powder is ground into a brewing chamber and then pressed into a coffee cake. Subsequently, water heated under overpressure is guided through the cake in order to thereby extract flavor substances from the powder. After a product-specific amount of water has flowed through, the moistened coffee powder is pressed out and the coffee cake (grounds) is discharged into a grounds container.

[0003] There are different drive concepts for moving the ram, douchet and brewing chamber into the necessary relative positions.

[0004] Document EP2907427B1 describes a nonlinear transmission section, by which a compromise is achieved between high pressing forces and simultaneously short movement cycles. To reach different positions, the functional element is moved at a large gradient. When the coffee powder is compacted, the drive motor is decelerated at a significantly smaller gradient in order to transmit high forces using the same guide.

[0005] Document DE102019119103A1 relates to a brewing unit of a piston coffee machine. The brewing unit is configured as a screw brewing unit, which has a brewing slide as a brewing chamber, two piston units as a spray head and a punch, a drive motor and at least one transmission mechanism. The brewing unit has a twin screw assembly with an outer screw and an inner screw. The brewing slide can be displaced from a first end position to an intermediate position, then to a second end position and back to the first end position again, wherein the outer screw has a moving thread that engages with an outer screw nut axially fixed in the brewing slide. In the first end position and the second end position of the brewing slide, the moving thread of the outer screw is disengaged from the outer screw nut, and even if the outer screw continues to rotate, the speed of the brewing slide is zero. A piston coffee machine is provided.

[0006] These implementations have proven to be effective, but there is still a need for continuous improvement in terms of components, functional groups, installation time and cost savings in maintenance. Summary of the invention

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

[0008] The invention achieves this object by a brewing unit having the features of claim 1 and by a piston coffee machine having the features of claim 10 .

[0009] The invention relates to a brewing unit of a piston coffee machine, wherein the brewing unit is designed as a screw brewing unit, wherein the screw brewing unit has a brewing slide as a brewing chamber, two piston units as spray heads and plungers, a drive motor and at least one transmission mechanism, wherein the brewing unit has a twin-screw assembly with an outer screw and an inner screw, wherein the outer screw is coupled to the inner screw via the at least one transmission mechanism, wherein the brewing slide can be displaced from a first end position into an intermediate position, then into a second end position and back into the first end position again. The brewing slide is provided with a second end position, wherein the outer screw has a movement thread which engages with an outer screw nut arranged in the brewing slide, characterized in that in a first end position of the brewing slide the movement thread of the outer screw is disengaged from the outer screw nut, wherein the speed of the brewing slide is zero even if the outer screw continues to rotate, wherein the brewing slide is secured in the first end position by means of a holding device, and in a second end position of the brewing slide the movement thread of the outer screw remains engaged with the outer screw nut and the drive motor is switched off.

[0010] An advantage here is that the rest position of the brewing slide can be easily achieved in the corresponding end position, wherein, although the outer screw is driven by the drive motor, the inner screw continues to be driven via the transmission mechanism in order to position the inner screw and thus the spray head. No additional motor is required.

[0011] The piston coffee machine according to the invention has a brewing unit as described above, wherein the advantage lies in a compact structure.

[0012] In one embodiment, the brewing slide has a first feed drive with an outer spindle nut and a retaining device. This results in an advantageously simple and compact structure.

[0013] In another embodiment, it is provided that the external screw nut is arranged in the receiving portion of the brewing slide with axial play, wherein in a first end position, a first end side / contact side (13d) of the external screw nut is in contact with a first pressure side of the receiving portion, wherein a second end side / contact side of the external screw nut and a second pressure side of the receiving portion are separated by the play, and wherein, when the movement thread of the external screw and the external screw nut are engaged, the second end side / contact side of the external screw nut and the second pressure side of the receiving portion are in contact, and the play is arranged between the first end side / contact side of the external screw nut and the first pressure side of the receiving portion. The advantage of this embodiment is that the so-called "screwing-in process" is improved, since a load-free screwing-in of the brewing slide is achieved in this way.

[0014] Yet another embodiment provides that at least one contact side of the threaded region of the internal thread of the external screw nut is divided into segments, wherein the segments are arranged at a distance from one another around the internal thread at the circumference of at least one contact side of the external screw nut, each having a spring action, and protruding from the corresponding contact side of the external screw nut. In this way, jamming between the external screw nut and the moving thread of the external screw during the screwing-in process is advantageously avoided.

[0015] In another embodiment, the inner screw is connected to a displaceable spray head or a displaceable punch and is coupled to the drive via a second feed drive, and the punch or the spray head is arranged in a fixed position, wherein the displaceable brewing slide is guided longitudinally displaceably by means of the outer screw and at least one guide rod, and the spray head or the punch is guided longitudinally displaceably in the brewing slide, wherein the brewing slide and the spray head or the punch can be displaced at different speeds in a common direction of movement. This results in an advantageously simple and cost-effective construction. In addition, very high displacement speeds can advantageously be achieved.

[0016] In another embodiment, the spray head is coupled to the brewing slide by means of an active, controllable driver in order to transmit the movement of the spray head to the brewing slide, when the coupling between the outer screw and the brewing slide is canceled via the first feed drive and in the region of the backlash of the outer screw nut relative to the brewing slide. This advantageously makes it possible to achieve a simple coupling.

[0017] It is also advantageous here if the controllable entrainment device is designed as a controllable tappet device, since this allows a compact design.

[0018] Yet another embodiment provides that the controllable tappet device has a hydraulic, pneumatic or mechanical tappet drive, thereby achieving an advantageously simple drive possibility.

[0019] In yet another embodiment, it is provided that the tappet drive is connected to a spray head seal of the spray head that can be activated hydraulically, pneumatically or mechanically. In this way, an advantageously simple control of the tappet drive is achieved.

[0020] In one embodiment, the holding device has a permanent magnet, an electrically controllable electromagnet or a mechanical locking structure. Permanent magnets and electromagnets are cost-effective, high-quality components, wherein the mechanical locking structure provides a simple structure without electrical installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is described in more detail below based on embodiments and variants with reference to the accompanying drawings. These drawings are only used to explain the present invention in more detail and do not limit the present invention. The described individual features can also be transferred to other implementation variants within the scope of the ordinary skill in the art. Among them:

[0022] Figure 1 a schematic perspective view showing an embodiment of a brewing unit according to the invention of a coffee machine in a first position;

[0023] Figure 2-3 Show according to Figure 1 Different schematic diagrams of a brewing unit in a first position;

[0024] Figure 4-6 Show according to Figure 1 Different schematic diagrams of a brewing unit in a second position;

[0025] Figure 7-9 Show according to Figure 1 Different schematic diagrams of the brewing unit in a third position;

[0026] Figure 10-11 Show according to Figure 1 Different schematic diagrams of the brewing unit in the driven position;

[0027] Figure 12-14 Show according to Figure 1 Different schematic diagrams of the brewing unit in a fourth position;

[0028] Figure 15-16 Show according to Figure 1 Different schematic diagrams of the brewing unit in the terminal position;

[0029] Fig.17 Shown along Figure 2A schematic cross-sectional view of line XVII in FIG.

[0030] Fig.18 A schematic enlarged cross-sectional view showing a tappet arrangement;

[0031] Figure 19-20 A schematic cross-sectional view showing an external screw nut;

[0032] Fig.21 Show according to Figure 1 A schematic diagram of a driving side of a brewing unit;

[0033] Figure 22-24 Shown along Fig.21 A schematic cross-sectional view of the line XXII-XXIII-XXIV in FIG.

[0034] Figure 25-27 : A schematic diagram of a variant of an external screw nut;

[0035] Fig.28 Shown with basis Figure 25-27 A schematic side view of a brewing unit with a variant of an outer screw nut; and

[0036] Fig.29 A schematic sectional view shows a variant of an external spindle nut in the installed state. DETAILED DESCRIPTION

[0037] In the figures the coordinates x, y, z are given for orientation.

[0038] exist Figure 1 A schematic perspective view of an embodiment of a brewing unit 1 of a piston coffee machine according to the invention is shown in FIG. Figure 2 Shown according to Figure 1 Schematic top view of the upper side of the brewing unit 1 in the xy plane. Figure 3 It is shown in Figure 1 to Figure 2 Schematic longitudinal section of the brewing unit 1 in the xz plane.

[0039] The embodiment shown here is a horizontal brewing unit 1. This embodiment can also be applied to a vertical brewing unit 1 or a brewing unit with any other inclination angle. The brewing unit 1 is a screw brewing unit.

[0040] Here, the brewing unit 1 comprises a brewing slide 2, which is also referred to as a brewing chamber, an outer screw 3, at least one guide rod 4, in the example shown two guide rods 4, a first bottom plate, which is referred to as a drive plate 5, and a second bottom plate, which is referred to as a punch plate 6, an inner screw 7, two piston units, a so-called spray head 9 and a punch 10, and at least one drive motor (not shown).

[0041] This system provides the possibility of achieving the required relative positions between the plunger 10 , the spray head 9 and the brewing slide 2 of the brewing unit 1 for a piston coffee machine (not shown) by means of a twin screw assembly and a drive.

[0042] Via the drive motor, a relative movement occurs between the punch 10 and the spray head 9 in the x direction, so that the distance between them can be changed. Then, a defined extrusion force can be adjusted by different motor torques. At the same time, the brewing slide 2 also moves. This makes it possible to achieve a filling position for coffee powder, provide a sealed brewing chamber space, and finally eject the extruded coffee cake.

[0043] In this case, the spray head 9 and the brewing slide 2 are moved in the x-direction into different positions, wherein the punch 10 is fixedly fastened to the punch plate 6 in this position.

[0044] The twin screw assembly comprises an outer screw 3 and an inner screw 7. The outer screw 3 displaces the brewing slide 2, and the inner screw 7 displaces the spray head 9.

[0045] The outer screw 3 is coupled to the brewing slide 2 via a first feed drive 12. This is described in more detail below.

[0046] Furthermore, in order to overcome the so-called backlash, the brewing slide 2 is driven by the spray head 9 by means of a drive mechanism. The controllable drive mechanism is designed as a controllable tappet mechanism 22 and is explained in more detail below.

[0047] Within this backlash having a specific dimension in the x-direction (see Fig.24 The brewing slide 2 is disengaged from the outer screw 3 by the first feed drive 12. The coupling between the outer screw 3 and the brewing slide 2 is canceled in the first end position and in the region of the backlash, and if there is no coupling between the outer screw 3 and the brewing slide 2, the brewing slide 2 is coupled to the spray head 9 via the tappet device 22 in order to transmit the movement of the spray head 9 to the brewing slide 2. This is explained in more detail below.

[0048] The brewing slide 2 is displaced from the parking position (which is the first end position of the brewing slide 2) to the intermediate position, then to the second end position, and then back to the first end position. Here, the spray head 9 is moved to a different position relative to the brewing slide 2 and the plunger 10.

[0049] The parking position of the brewing slide 2 is Figures 1 to 3 Shown in.

[0050] The middle position of the brewing slide 2 is also called the dregs ejection position and is Figure 12 to Figure 14 Shown in.

[0051] at last, Fig.15 and Fig.16 The second end position of the brewing slide 2 is shown.

[0052] The spray head 9 is always arranged in the brewing slide 2 within the brewing cylinder 20 of the brewing slide 2 and can assume different relative positions relative to the brewing slide 2. These relative positions are achieved independently of one another by the movement of the spray head 9 caused by the inner screw 7 and by the movement of the brewing slide 2 which can be displaced by the outer screw 3.

[0053] The punch 10 can be located outside or inside the brewing slide 2. Since the punch 10 is arranged in a fixed position, the relative position / relative movement of the brewing slide 2 and the spray head 9 relative to the punch 10 is realized by the inner screw 7 (spray head 9) and the outer screw 3 (brew slide 2). It is also conceivable that the punch 10 can be displaceable.

[0054] The spray head 9 (or the plunger 10 ) and the brewing slide 2 always have a common direction of movement, but at different speeds (speed difference), in order to thereby achieve the desired relative position between the two components.

[0055] However, the parking position ( Figures 1 to 9 ) is an exception. In the parking position, the brewing slide 2 is fastened to the punch plate 6 by means of the holding device HR (see Fig.19 and Fig. 22 ) and disengages from the outer screw. Then, the independent displacement movement of the spray head 9 relative to the brewing slide 2 is achieved.

[0056] In order to facilitate the presentation of these movement directions, a double-arrow movement direction BR is indicated in each figure, with two movement directions BR1 and BR2 in opposite directions along the x-axis.

[0057] In this way, the brewing unit 1 can be displaced into the following positions:

[0058] Figures 1 to 3 The closed position (first position) is shown.

[0059] exist Figures 4 to 6 The filling position (second position) is shown in .

[0060] Figures 7 to 9 The brew position (third position) is shown.

[0061] exist Figure 10 to Figure 11 The entrained position is shown in .

[0062] exist Figure 12 to Figure 14 The slag ejection position (fourth position) is shown in FIG. , which is also referred to as the open position.

[0063] Fig.15 and Fig.16 The end positions or end settings are shown.

[0064] These locations are explained in more detail below.

[0065] The outer screw 3 with the outer screw axis 3a, the guide spindle 4 with the guide axis 4a and the inner screw 7 with the inner screw axis 7a are arranged parallel to one another. The movement directions BR1 and BR2 run parallel to these axes 3a, 4a, 7a.

[0066] Here, the drive plate 5 and the punch plate 6 of the brewing unit 1 are rectangular plates which are arranged parallel to each other and at right angles to the axes 3a, 4a, 7a.

[0067] exist Figure 1 In the figure, a further plate 8 is fixed parallel to the drive plate 5, which is arranged on the left side of the drive plate 5 and forms a support for a drive motor (not shown) (which is only indicated by the reference numeral "drive device 14") and a transmission mechanism (for example a toothed belt and / or gears). The transmission mechanism (not shown) couples the rotational movement of the inner screw 7 and the outer screw 3. The plate 8 is Fig.21 A housing 15 a for the second feed gear 15 and a support for a media connection (not described in detail) are shown and form the housing 15 a for the second feed gear 15 .

[0068] The external screw 3 is supported with a drive end 3b on the drive plate 5. The other end of the external screw is supported as a bearing end 3c on the punch plate 6. The external screw 3 has an external thread as a movement thread 3d, which interacts with the first feed drive 12 of the brewing slide 2.

[0069] The punch 10 is fixedly supported on the punch plate 6. The punch 10, the spray head 9, the brewing slide 2 and the inner screw 7 are arranged coaxially with the brewing slide axis 2a. Here, the brewing slide axis 2a extends on the inner screw axis 7a.

[0070] The outer screw 3 and the guide rod 4 connect the drive plate 5 and the punch plate 6 to each other. The guide rod 4 is covered outwardly with a side wall 11, 11a over its entire length. Here, the corresponding side wall 11 is connected or integrally connected to the corresponding lower side wall 11a at the bottom. The lower side wall 11a is bent inwardly relative to the corresponding upper side wall 11.

[0071] Fig.17 Shown along Figure 2 Schematic cross-sectional view along line XVII in FIG.

[0072] The inner screw 7 is engaged with the second feed transmission mechanism 15. The second feed transmission mechanism 15 includes a housing 15a, a cover member 16 with a long hole 16a (see Fig.17 ), an internal screw nut 17 with an internal thread 17b and bearings 18, 18a, 18b.

[0073] The housing 15a is fixed to the drive plate 5 at one end via the plate 8. The other end of the housing 15a is closed by a cover 16. The inner screw nut 17 is supported inside the housing 15a by bearings 18, 18a, 18b. The bearing 18 is an axial bearing and is supported at the flange 17a of the inner screw 17. The bearings 18a and 18b are designed as radial bearings or deep groove ball bearings.

[0074] The flange 17a of the inner screw nut 17 is located at one end of the inner screw nut 17 close to the cover 16 and faces the punch plate 6. The other end of the inner screw nut 17 extends through the drive plate 5 to the plate 8 and interacts with the outer screw 3 through the transmission mechanism.

[0075] The internal screw nut 17 has a through hole 17c, which is configured with an internal thread 17b in a portion facing the cover member 16, and the internal thread engages with the screw end 7c of the external thread (movement thread 7b) of the internal screw 7. The internal thread 17b of the internal screw nut 17 and the external thread (movement thread 7b) of the internal screw 7 correspond to each other.

[0076] In addition, the inner screw 7 is also provided with flattened portions 7e on both sides (at Fig.17 The flattened portion is aligned with the elongated hole 16a of the cover 16 (see Fig.17 ) together form a rotation-proof structure of the inner screw 7. In this way, the inner screw 7 is arranged rotationally. The inner screw nut 17 can be rotated around the inner screw axis 7a by means of the drive device 14 and causes the fixed inner screw 7 to perform linear movement via the movement thread 7b / 17b and thus causes the spray head 9 to perform linear movement.

[0077] The flattened portion 7e can be directly placed on the outer thread 7b of the inner screw 7, for example, so that the feeding function and the anti-rotation function are switched to the geometric structure in parallel. Alternatively, the outer thread (movement thread 7b) and the flattened portion 7e can be arranged in sequence. This can avoid changing the outer thread (movement thread 7b), but the outer shape of the inner screw 7 is lengthened by the maximum stroke of the spray head 9.

[0078] The inner screw 7 includes an inner screw axis 7a, a moving thread 7b, a first screw end 7c, a second screw end 7d and a flattened portion 7e. In addition, the inner screw 7 also has a thread end 7f of the moving thread 7b, which faces the punch plate 6 and is adjacent to the convex ring 7g. The convex ring 7g interacts with the cover 16 to form a stop portion and thereby forms the terminal position of the spray head 9 in the moving direction BR1 toward the drive plate 5 (see Figure 6 Here, the screw end 7c extends outward through the opening of the drive plate 5 and the plate 8 through the portion of the through hole 17c without the internal thread 17b ( Figure 6 ).

[0079] The brewing slide 2 has a substantially hollow cylindrical housing with a circular cross section and a brewing slide axis 2a. In the housing, a brewing cylinder 19 with a brewing space 25 (which also has a circular cross section) is arranged coaxially with the brewing slide axis 2a.

[0080] The brewing cylinder 19 has a first end side 19 a facing the punch plate 6 . In contrast, the brewing cylinder 19 is provided with a second end side 19 b facing the drive plate 5 .

[0081] In the brewing column 19, an opening 19c is introduced into its surrounding wall, which opening communicates with a filling opening 2c of the housing of the brewing slide 2. In the region of a first end side 19a of the brewing column 19, in an end region of the housing of the brewing slide 2, a seal 19d is arranged circumferentially, which seals the brewing column 19 relative to the housing of the brewing slide 2.

[0082] The brewing chamber 25 of the brewing column 19 of the brewing slide 2 receives the spray head 9 and the plunger 10 in specific positions of the brewing unit 1, which are described in more detail below. The spray head 9 and the plunger 10 are guided movably in the brewing chamber 19 in the movement directions BR1 and BR2 relative to the brewing column 19. When both the spray head 9 and the plunger 10 are located in the brewing chamber 25 in specific positions of the brewing unit 1, they are spaced apart from each other at different distances.

[0083] The brewing slide 2 and the punch 10 interact in such a way that the brewing cylinder 19 of the brewing slide 2 moves with its opening belonging to the first end side 19a onto the punch 10, wherein the brewing chamber 19 is then sealed with a punch seal 10a on its side facing the punch plate 6. The punch seal 10a is a displaceable seal, for example a seal that can be activated and deactivated hydraulically.

[0084] The brewing carriage 2 is guided via guide rods 4 between a drive plate 5 and a punch plate 6 so as to be displaceable in two movement directions BR1 and BR2 .

[0085] The outer screw 3 extends through the first feed drive 12. The feed drive 12 is arranged in a receiving portion 2c on the outside of the brewing slide 2 and has an outer screw nut 13 ( Fig.19 The external screw nut 13 is provided with an internal thread 13b, which corresponds to the external thread (movement thread 3d) of the external screw 3.

[0086] The moving thread 3d of the external screw 3 is engaged with the internal thread 13b of the external screw nut 13, but the moving thread 3d is in the static position ( Figures 1 to 11 ) is disengaged from the outer screw nut 13. This is also combined with Fig.19 as well as Figures 22 to 24 Provide a detailed explanation.

[0087] The movement mechanism of the brewing unit 1 is based on two screw drives, namely on an outer screw 3 and an inner screw 7. The movement thread 3d of the outer screw 3 and the movement thread 7b of the inner screw 7 have different thread pitches.

[0088] The outer screw 3 and the inner screw 7 are synchronized with each other via a transmission mechanism between the drive plate 5 and the plate 8 .

[0089] The transmission is designed as a traction means transmission with a toothed belt (see Fig.21 ). It is also possible that the transmission mechanism can be constructed with a gear or in combination with a gear. In addition, the transmission mechanism can also be multi-stage.

[0090] For example, the outer screw 3 is the drive shaft of the brewing unit 1 and ensures a linear movement of the brewing slide 2 via an outer screw nut 13 which is mounted in a rotationally fixed manner on the brewing slide 2 in its receptacle 2 c.

[0091] At the same time, the coupling by means of the transmission mechanism also ensures the rotational movement of the inner screw nut 17, which engages with the moving thread 7b of the inner screw 7. As a result, the spray head 9 fixed at the second screw end 7d of the inner screw 7 performs linear movement. The anti-rotation of the inner screw 7 through the interaction between the flattened portion 7e and the long hole 16a in the cover 16 ensures that the spray head 9 and the inner screw 7 do not rotate together around their own axis (the inner screw axis 7a), but only move axially in the movement direction BR1, BR2.

[0092] The moving thread 7b of the inner screw 7 has a smaller pitch than the moving thread 3d of the outer screw 3. For this reason, the movement speed of the brewing slide 2 is many times greater than the movement speed of the spray head 9 and the inner screw 7. Advantageously, the pitch of the inner screw 7 is selected so that it has a self-locking effect during the brewing process.

[0093] The spray head 9 and the punch 10 are arranged in the brewing unit 1 in such a way that their end sides face each other.

[0094] The spray head 9 is fixedly connected to the inner screw 7 and has a displaceable spray head seal 9a surrounding the outer side thereof. The spray head seal 9a is a displaceable seal, for example a seal which can be activated and deactivated hydraulically.

[0095] The spray head 9 and the spray head sleeve 20 can be moved in the brewing space 25 and into the brewing space 25 of the brewing column 19 by means of the inner screw 7 in the movement directions BR1 and BR2. The spray head 9 is introduced into the brewing column 19 through an opening of the brewing column 19 belonging to the second end side 19b.

[0096] In addition, a nozzle sleeve 20 with a bottom 20a is arranged on the side of the nozzle 9 facing the drive plate 5, and the nozzle sleeve extends with an inner space 21 through a section of the inner screw 7 toward the drive plate 5. The end section 20b of the nozzle sleeve 20 has an opening leading to the inner space 21, and the inner diameter of the inner space corresponds to the outer diameter of the housing 15a of the second feed transmission mechanism 15.

[0097] The tappet device 22 is arranged on the outside of the spray head sleeve 20 and has a tappet 23. The tappet 23 can be displaced in the radial direction from a first position to a second position and back to the first position by means of a tappet drive 24. The tappet drive 24 is designed so that the tappet 23 is connected to the hydraulic seal 9a of the spray head via hydraulic lines 24a, 24c (see Figure 6). Here, the first pipeline 24a is connected to the tappet device 22 and is arranged in the pipeline section 20c of the bottom 20a of the nozzle sleeve 20, and here: the pipeline section that is formed into the bottom of the nozzle sleeve. The first pipeline 24a is connected to the second pipeline 24c in the nozzle 9 body through the pipeline connector 24b. The pipeline connector 24b is sealed both relative to the bottom 20a of the nozzle sleeve 20 and relative to the body of the nozzle 9 through the seal 24d. The second pipeline 24c is connected to the hydraulic nozzle seal 9a.

[0098] In the first position of the tappet, the upper edge of the tappet 23 is located below the outer side of the nozzle sleeve 20 or flush with the outer side of the nozzle sleeve ( Figure 6 ).

[0099] When the nozzle seal 9a is activated, for example by increasing the pressure of the hydraulic medium (the hydraulic medium may also be compressed air), the tappet 23 moves from its first position (see Figure 6 , 9 , 14, 16) radially outwardly displaced to its second position (see Figure 3 and Fig.11 ) and protrudes from the outside of the nozzle sleeve 20.

[0100] In its second position, the tappet 23 projects into the opening 19c of the brewing column 19. In this way, when the outer screw nut 13 is disengaged from the movement thread 3d of the outer screw 3, the movement of the spray head 9 can be transmitted to the brewing column 19 by means of the inner screw 7.

[0101] This is the case when the outer screw nut 13 of the brewing cylinder 19 is disengaged from the movement thread of the outer screw 3 when it moves in the movement direction BR2 in the direction of the punch plate 6. Then, the tappet 23 of the tappet device 22 is activated together with the seal 9a of the spray head 9, protrudes into the opening 19c of the brewing cylinder 19, comes into contact with the wall of the opening 19c facing the punch plate 6, and transmits the movement of the spray head 9 to the brewing cylinder 2 until the first end face 9a of the brewing cylinder or brewing cylinder 19 is located above the punch 10 in its rest position, wherein the element of the holding device HR comes into contact with the inner side 6a of the punch plate 6 (see Fig.19 and Fig. 22 ).

[0102] exist Fig.18 2 shows a schematically enlarged sectional view of the tappet arrangement 22 .

[0103] The tappet device 22 comprises a tappet 23 with a tappet drive 24 , a tappet holder 26 and seals 27 , 27 a.

[0104] The tappet 23 is a columnar member having a tappet axis 23a, a tappet body 23b, an intermediate section 23c and two convex rings 23d, 23e. The tappet body 23b is provided with a conical chamfer at its upper end and is connected to the intermediate section 23c at its lower end by a first convex ring 23d, and the free end of the intermediate section ends with a second convex ring 23e. The outer diameter of the tappet body 23b is slightly larger than the outer diameter of the intermediate section 23c. The outer diameters of the convex rings 23d, 23e are the same in size and larger than the outer diameter of the tappet body 23b.

[0105] The tappet holder 26 is cylindrical and is provided with a circumferential flange 26a at its upper end. A through opening 26b is formed in the middle of the flange 26a, and its inner diameter corresponds to the outer diameter of the tappet body 23b. A hollow cylindrical guide body 26c with a fixing section 26d and an inner space 26e is adjacent to the flange 26a downward. The inner space 26e is cylindrical, and the inner diameter of the inner space corresponds to the outer diameter of the convex rings 23c, 23d of the tappet 23. The inner space 26e is open downward.

[0106] The tappet 23 is inserted into the tappet holder 26 in such a way that the tappet body 23b extends outward through the through opening 26b and the collars 23d, 23e are arranged in the inner space 26e. Here, the tappet 23 is guided movably in the tappet holder 26. The tappet 23 and the tappet holder 26 are arranged coaxially with the tappet axis 23a.

[0107] A seal 27 a , such as an O-ring, is arranged between the protruding rings 23 d and 23 e and seals the tappet 23 with respect to the inner wall of the inner space 26 e of the tappet holder 26 .

[0108] The tappet holder 26 with the tappet 23 is arranged in the receiving portion 20e of the nozzle sleeve 20 with the flange 26a of the tappet holder 26. Here, a seal 27, for example an O-ring, is located between the underside of the flange 26a of the tappet holder 26 and the recessed portion of the receiving portion 20. The tappet holder 26 is screwed into the corresponding internal thread of the receiving portion 20 with its fixing section 26d, for example with an external thread.

[0109] The receptacle 20 is connected at its underside in a communicating manner to a first line 24 a of the tappet drive 24 , wherein the interior space 26 e is in communication with the first line 24 a of the tappet drive 24 .

[0110] exist Fig.18In the figure, the tappet 23 is shown in its second position protruding into the opening 19c of the brewing column 19. In this second position of the tappet 23, the tappet drive 24 is put under pressure by means of a hydraulic medium and exerts a force directed upwards (here in the z direction) on the lower collar 23e of the tappet 23. This force presses the tappet 23 upwards and presses the upper collar 23d of the tappet 23 against the underside of the flange 26a of the tappet holder 26. The second position of the tappet 23 is thus defined.

[0111] Fig.18 The upper end of the tappet 23 is shown in contact with the chamfer of the opening 19c of the brewing cylinder 19. The chamfer has the task of pushing the tappet 23 back into its first position, into the tappet holder 26, when the spray head 9 together with the spray head sleeve 20 is moved in the x direction toward the drive side. In this case, the tappet drive 24 is switched to a pressure-free state. This is necessary when the brewing slide 2 is driven from the rest position of the brewing slide 2, when the outer screw nut 13 of the brewing slide 2 is again engaged with the movement thread 3d of the outer screw 3. The reason for this is that, as already explained above, the movement thread 3d of the outer screw 3 and the movement thread 7b of the inner screw 7 have different pitches.

[0112] Alternatively, it is conceivable to permanently load the tappet 23 with elasticity, which results in a forced entrainment of the brewing slide 2 (single-screw design). In principle, there are three operating states:

[0113] 1) The tappet 23 is in engagement (forced drive)

[0114] 2) The push rod 23 is elastically compressed (sliding friction is generated in the brewing column 19)

[0115] 3) The tappet 23 is not engaged (e.g. during the extrusion process and brewing process)

[0116] Embodiments of the spring-loaded structure may be compression springs or contours directly integrated into the injection-molded part of the cleaning reservoir, which contours bring about a suitable spring force.

[0117] In another alternative, the tappet 23 can be designed as an elastic pressure piece. When it comes into contact with the chamfer of the opening 19c of the brewing cylinder 19, the driving force of the spray head 9 is transmitted to the brewing cylinder 19. As a result, the two movements are synchronized for a short time and the outer screw nut 13 is finally screwed into the movement thread 3d of the outer screw 3. As soon as the brewing cylinder 19 has been advanced beyond the spray head 9 by the movement thread 3d of the outer screw 3, the tappet 23 is elastically compressed and then slides along the inner wall of the brewing cylinder 19 until it leaves the interior of the brewing cylinder 19 and is pressed out again into its rest position into the filling opening 2b by the spring force. The challenge of this design is to select friction partners and contact surfaces that are low in wear and that have to withstand a large number of elastic compression cycles. This results in a particularly simple design without complex sealing of the hydraulic paths 24a, 24b, 24c of the tappet 23.

[0118] Fig.19 1 is a schematic longitudinal section through the outer spindle nut 13 of the first feed drive 12 of the brewing slide 2 and the holding device HR in the rest position of the brewing slide 2 . Fig. 20 It is along Fig.19 Cross-sectional view of line XX.

[0119] The external screw nut 13 has an 8-shaped cross section, which has a retaining section 13a and a threaded section with an internal thread 13b ( Fig. 20 ). The internal thread 13b corresponds to the external thread 3d of the external screw 3.

[0120] The outer spindle nut 13 is arranged in a receptacle 2c on the outside of the brewing slide 2 in the area facing the punch plate 6 (see also Figure 1 ,2,4,5,7,8,10,12,13,15).

[0121] In addition, the external screw nut 13 is constructed with two opposite coaxial receiving parts 13c, which are arranged in the holding section 13a and belong to the holding device HR. The central axis of the receiving part 13c extends parallel to the external screw axis 3a or the central axis of the internal thread 13b. The two receiving parts 13c are separated by a surrounding shoulder 13f. The shoulder 13 has a through hole.

[0122] The outer screw nut 13 has end sides or contact sides 13d and 13e. The first end side or contact side 13d faces the punch plate 6 and the first pressure side 2d of the receiving portion 2c. The second end side or contact side 13e faces the drive plate 5 and the second pressure side 2e of the receiving portion 2c.

[0123] The external screw 3 extends through the through hole 2 f of the brewing slide 2 and the internal thread 13 b of the external screw nut 3 .

[0124] The holding device HR here comprises a guide pin 28 , a sleeve 29 , 29 a , a compression spring 30 and a magnetic element 31 .

[0125] The guide pin 28 is arranged parallel to the outer screw axis 3a in the sleeve 29 , 29a and has a head 28a at its end facing the drive plate 5 , the outer diameter of which corresponds to the outer diameter of the sleeve 29a , wherein the longitudinal axis of the guide pin 28 forms a pin axis 28b .

[0126] The sleeves 29, 29a are inserted into the receptacle 13c of the retaining section 13a of the outer spindle nut 13 in such a way that they rest with their respective ends arranged in the receptacle 13c against the circumferential shoulder 13f. The shoulder 13f forms an axial stop for the two sleeves 29, 29a. The guide pin 28 extends through the through-holes of the two sleeves 29, 29a and the circumferential shoulder 13f.

[0127] The sleeves 29, 29a protrude axially from the receiving portion 13c with their other ends, wherein the sleeve 29 together with the head 28a of the guide pin 28 protrudes into the through hole 2g of the brewing slide 2 in the direction of the punch plate 6. The other sleeve 29a protrudes into the other through hole 2h of the brewing slide 2 in the direction of 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 movement guide for the sleeve 29a and the head 28a.

[0128] The compression spring 30 is arranged around the sleeve 29a between the retaining section 13a of the outer spindle nut 13 and the second pressure side 2e of the receptacle 2c of the brewing slide 2. One end of the compression spring 30 is attached to the outer spindle nut 13, wherein the other end of the compression spring 30 is in contact with the second pressure side 2e of the receptacle 2c of the brewing slide 2.

[0129] The magnetic element 31 is fixedly connected, for example, screwed, to the end of the guide pin 28 facing the punch plate 6. The end of the magnetic element 31 facing the outer screw nut 13 contacts the end of the sleeve 29 protruding toward the punch plate 6. The end of the sleeve 29a facing the drive plate 5 contacts the head 28a of the guide pin 28. Here, the sleeves 29 and 29a are clamped or fixedly arranged together between the head 28a of the guide pin 28 and the magnetic element 31, and are also fixed in the axial direction with the retaining section 13a of the outer screw nut 13 by means of the surrounding shoulder 13f.

[0130] The magnetic element 31 is columnar and is arranged to be movably guided in the through hole 2g of the brewing slide 2. The inner diameter of the through hole 2g corresponds to the outer diameter of the magnetic element 31.

[0131] In the brewing slide 2 Fig.19 In the rest position shown in FIG. 1 , the internal thread 13b of the external screw nut 13 and the moving thread 3d of the external screw 3 are out of engagement. This state is also referred to as the "unscrewed state". The contact surface 13d of the external screw nut 13 facing the punch plate 6 abuts against the first pressure side 2d of the receiving portion 2c of the brewing slide 2.

[0132] The magnetic element 31 of the holding device HR is in contact with the inner side 6a of the punch plate 6, which is made of a metal that can be attracted by magnets, such as steel. In this way, the holding device HR secures the outer screw nut 13 and thus the brewing slide 2 in its rest position. In this case, the spring force of the compression spring 30 additionally acts and presses the outer screw nut 13 against the first pressure side 2d of the receptacle 2c of the brewing slide 2 in the direction of the punch plate 6.

[0133] exist Fig. 20 Furthermore, one of the two guide holes 2 i for the guide rod 4 of the brewing slide 2 is shown.

[0134] Fig.21 Shown according to Figure 1 Schematic diagram of the drive side of the brewing unit 1, together with the following Figure 22 to Figure 24 The cutting line.

[0135] Figures 22 to 24 Shown along Fig.21 Schematic cross-sectional view along line XXI-XXIII-XXIV in FIG.

[0136] exist Fig. 22 The rest position of the brewing slide 2 is shown in FIG.

[0137] The brewing slide 2 has a first end side 2j, which faces the drive plate 5. The opposite second end side 2k of the brewing slide 2 faces the punch plate 6 and contacts the inner side 6a of the punch plate 4 as a stop in the rest position of the brewing slide 2.

[0138] In the rest position of the brewing slide 2, the first end side 13d of the outer spindle nut 13 abuts against the first pressure side 2d of the receptacle 2c of the brewing slide 2, which faces the punch plate 6. A spacing is formed as a gap 32 between the second end side 13e of the outer spindle nut 13, which faces the drive plate 5, and the associated second pressure side 2e, which faces the drive plate 5. The gap 32 is also referred to as "backlash" and is approximately 5 mm in the example shown. This state is also referred to as "backlash open".

[0139] Here, the external screw nut 13 is in the “unscrewed” state and is approximately 2 mm away from the thread end of the moving thread 3 d of the external screw 3 .

[0140] In this illustrated rest position or in its first end position, the brewing slide 2 is in the position given above:

[0141] - closed position (first position, Figure 1-3 )

[0142] -Filling position (second position, Figure 4-6 )

[0143] - Brewing position (third position, Figure 7-9 )

[0144] In the closed position of the brewing unit 1 (see Figure 1-3 ), the brewing slide 2 is in the rest position and the spray head 9 together with the spray head sleeve 20 is completely retracted into the brewing column 19 of the brewing slide 2. The spray head 9 and the punch 10 are arranged closely adjacent to each other or in contact. The opening 19c of the brewing column 19 below the filling opening 2b is closed by the spray head sleeve 20. The tappet 23 is in its second position and rests on the edge of the opening 19c facing the punch plate 6.

[0145] To assume the filling position of the brewing unit 1, the tappet drive 24 is first deactivated by reducing the pressure, and the seal 9a of the spray head 9 is also deactivated. The spray head 9 and the spray head sleeve 20 connected thereto are moved by means of the inner screw 7 in the movement direction BR1 toward the drive plate 5. In the process, the tappet 23 passes through the chamfer of the opening 19c (see Fig.18 ) back to its first position. Then, the spray head 9 is in the filling position at the end of the brewing cylinder 19 facing the drive plate 5. The spray head sleeve 20 here covers the housing 15a of the second feed drive 15 over the largest part with its end section 20b. The opening 19c leading to the filling opening 2b is free and coffee powder can be filled into the brewing space 25 between the spray head 9 and the punch 10 ( Figure 6 ).

[0146] Then, the spray head 9 is retracted into the brewing column 19 again to compress the coffee powder in the brewing space 25 and occupy the brewing position. By repeatedly moving to the filling position and the brewing position, the coffee powder can be further filled and then further compressed ( Fig. 9 ).

[0147] After the brewing process is finished, the grounds ejection position is occupied. Figure 10-11As shown in FIG, the injection head 9 is brought into the entrained position by further retracting it into the brewing column 19 in the direction of movement BR2 until the tappet 23 is located below the opening 19c of the brewing column 19. The tappet drive 24 is activated and the injection head seal 9a is also put under pressure. Then, the injection head 9 is moved in the direction of movement BR1 in the direction of the drive plate 5 by means of the inner screw 7. In this case, the tappet 23 in its second position presses against the edge of the opening 19c of the brewing column 19 and exerts a force in the direction of movement BR1 onto it and thus onto the brewing slide 2. At the same time, this is assisted by the friction of the injection head seal 9a in the brewing column 19. The retaining device HR with the magnetic element 31 is disengaged from the punch plate 6u, and the backlash (gap 32) is passed and eliminated. The thread 13b of the outer screw nut 13 engages with the moving thread 3d of the outer screw 3 (also called "screwing process"). The compression spring 30 of the holding device HR is preloaded because the outer screw nut 13 is pressed with its second end side 13e facing the drive plate 5 against the associated second pressure side 2e of the receiving portion 2c of the brewing slide 2. The displacement of the brewing slide 2 in the movement direction BR1 is then taken over by the outer screw 3 and the tappet 23 is moved as described above in conjunction with Fig.18 The brewing unit 1 is moved further to its first position. Fig.14 ).

[0148] This is also Fig.23 The back gap or gap 32 is now located between the first end side 13d facing the punch plate 6 and the associated first pressure side 2d of the receiving portion 2c of the brewing slide 2. This state is also referred to as "back gap closed".

[0149] In the grounds ejection position, the spray head 9 is located at the end of the brewing cylinder 19 facing the punch plate 6 , wherein it has already pressed out the coffee cake located in the brewing space 25 , which then falls into a collecting container.

[0150] In the grounds ejection position of the brewing unit 1 , the brewing slide 2 is in its central position.

[0151] By further moving the brewing unit 1 along the movement direction BR1 toward the driving plate 5, the brewing unit 1 occupies the space according to Figure 15-16 and Fig.24 terminal position.

[0152] In the end position of the brewing unit 1 , the brewing slide 2 is in its second end position.

[0153] In this end position of the brewing unit 1 (which is also the end position of the brewing slide 2), the outer screw nut 13 and the movement thread 3d of the outer screw 3 cannot be screwed out. The collar 7g of the inner screw 7 and the cover 16 of the second feed gear 15 form an end position stop. The drive device, for example an electric motor, is shut off by a limit switch (not shown) or a motor current monitoring device.

[0154] This end position serves, for example, as a reference for the position of the brewing unit 1 and of the brewing slide 2 .

[0155] In order to re-assume the rest position or first end position of the brewing slide 2 from the end position, the brewing unit 1 is moved in the direction of movement BR2 in the direction of the punch plate 6 until the outer spindle nut 13 and the movement thread 3d of the outer spindle 3 are screwed out. In this case, the tappet 23 has previously been moved into its second position by means of the tappet drive 24. The tappet 23 then abuts against the edge of the opening 19c facing the punch plate 6 and can thus transmit the movement of the spray head 9 in the direction of movement BR2 in the direction of the punch plate 6, since after the screwing out, the outer spindle 3 no longer transmits the movement to the outer spindle nut 13 of the brewing slide 2. As a result, the brewing slide 2 is moved into the rest position by the movement of the spray head 9 in the direction of movement BR2, wherein the magnetic element 31 of the holding device HR secures the brewing slide 2 on the inner side 6a of the punch plate 6 in the rest position.

[0156] Fig.25 A schematic perspective view of a variant of an external screw nut 13' is shown. Fig.26 Shown in. Fig. 27 A front view of the contact side 13e of a variant of the external screw nut 13' is shown. Fig.28 The following table shows the Figure 25-27 Schematic side view of a brewing unit 1 with a variant of an outer screw nut 13 ′. Fig.29 is a schematic sectional view of a variant of an external spindle nut 13 ′ in the installed state.

[0157] The variant scheme of the outer screw nut 13 ' and the Fig.19 The outer screw nut 13 has some differences.

[0158] In this variant, the guide pin 28 is formed integrally with the retaining section 13 a of the external spindle nut 13 ′, has a flattened portion 28 c at one longitudinal side, and protrudes from the contact side 13 e of the external spindle nut 13 ′.

[0159] The compression spring 30 is arranged on the guide pin 28. In the installed state ( Fig.29), the compression spring 30 rests with one end against the second end side / contact side 13e of the outer spindle nut 13' and with the other end against the pressure side 2e of the receiving portion 2c of the brewing slide 2 via a disk not shown.

[0160] The second end face / contact side 13e of the threaded region of the thread end of the internal thread 13b of the external screw nut 13' is divided into sections 33 in order to prevent jamming between the external screw nut 13' and the movement thread 3d of the external screw 3 during screwing-in.

[0161] The sections 33 each have an elastic effect, are arranged at intervals from each other around the internal thread 13b, i.e., around the thread end of the internal thread 13, at the circumference of the second end side / contact side 13e of the external screw nut 13a, and protrude from the second end side / contact side 13e of the external screw nut 13'.

[0162] Once the tip circle diameter and the root circle diameter of the threaded mating parts (the internal thread 13b of the external screw nut 13' and the moving thread 3d of the external screw 3) have a tendency to get stuck, a plurality of individual segments 33 can be elastically opened, that is, elastically deformed radially outward. In this embodiment, eight segments 33 are provided, but other division methods can also be reasonable. It is important that the individual segments 33 can be evaded in an elastic manner when getting stuck. If it is necessary to unscrew at the two thread ends of the external screw 3 in this structure, it is conceivable to also divide at the contact sides 13d, 13e of the two thread ends of the internal thread 13b of the external screw nut 13.

[0163] The invention is not limited to the exemplary embodiments given above, but can be modified within the scope of the claims. It is conceivable that the movement functions of the spray head 9 and the punch 10 in the brewing unit 1 can also be interchanged, that is, they can be arranged in a sideways manner.

[0164] Instead of the drive plate 5 and the punch plate 6 , a frame may also be used.

[0165] The magnetic element 31 can also be a controllable electromagnet. Mechanical locking structures in different embodiments are also conceivable, such as releasable snap-lock structures.

[0166] In addition, it is also conceivable that the drive of the spray head 9 can be realized by a drive device that is subjected to spring loading. For this reason, it is necessary to also unscrew it in the second end position. Otherwise, it is then impossible to drive to the filling position.

[0167] Reference numerals list

[0168] 1 Brewing unit

[0169] 2 brewing slides

[0170] 2a Brewing slide axis

[0171] 2b Fill the opening

[0172] 2c Receiving Department

[0173] 2d, 2e pressure side

[0174] 2f, 2g, 2h through hole

[0175] 2i Guide hole

[0176] 2j,2k side

[0177] 3 External screw

[0178] 3a External screw axis

[0179] 3b drive end

[0180] 3c Support end

[0181] 3d motion thread

[0182] 4 Guide rods

[0183] 4a Guide axis

[0184] 5. Driver board

[0185] 6 Punch Plate

[0186] 5a, 6a inner side

[0187] 7 Internal screw

[0188] 7a Internal screw axis

[0189] 7b sports thread

[0190] 7c, 7d screw end

[0191] 7e flattening part

[0192] 7f thread finishing

[0193] 7g convex ring

[0194] 8 boards

[0195] 9 nozzles

[0196] 9a Nozzle seal

[0197] 10 Punch

[0198] 10a punch seal

[0199] 11,11a Side wall

[0200] 12 First feeding transmission mechanism

[0201] 13,13' external screw nut

[0202] 13a Holding section

[0203] 13b internal thread

[0204] 13c Receiving section

[0205] 13d, 13e contact side

[0206] 13f Shoulder

[0207] 13g section

[0208] 14 Drive device

[0209] 15 Second feeding transmission mechanism

[0210] 15a Shell

[0211] 16 Cover

[0212] 16a Long hole

[0213] 17 Internal screw nut

[0214] 17a Flange

[0215] 17b internal thread

[0216] 17c through hole

[0217] 18,18a,18b bearings

[0218] 19 Brewing column

[0219] 19a, 19b side

[0220] 19c opening

[0221] 19d seal

[0222] 20 nozzle sleeve

[0223] 20a bottom

[0224] 20b End section

[0225] 20c pipeline section

[0226] 20d receiving part

[0227] 21Interior Space

[0228] 22 Tappet device

[0229] 23 Tappet

[0230] 23a Tappet axis

[0231] 23b tappet body

[0232] 23c middle section

[0233] 23d,23e convex ring

[0234] 24 Tappet drive device

[0235] 24a pipeline

[0236] 24b pipe connector

[0237] 24c pipeline

[0238] 24d seal

[0239] 25 Brewing Space

[0240] 25' Throwing Space

[0241] 26 Tappet retainer

[0242] 26a Flange

[0243] 26b Through opening

[0244] 26c guide body

[0245] 26d fixed section

[0246] 26e Interior Space

[0247] 27,27a Seals

[0248] 28 guide pins

[0249] 28a Head

[0250] 28b pin axis

[0251] 28c flattening part

[0252] 29,29a sleeve

[0253] 30 Compression spring

[0254] 31 Magnetic components

[0255] 32 Gap

[0256] 33 sections

[0257] BR, BR1, BR2 movement direction

[0258] HR holding device

[0259] x,y,z coordinates

Claims

1. A brewing unit (1) of a piston coffee machine, wherein: The brewing unit (1) is configured as a screw brewing unit, comprising a brewing slide (2) as a brewing chamber, two piston units as a spray head (9) and a punch (10), a drive motor and at least one transmission mechanism, wherein the brewing unit (1) comprises a twin-screw assembly with an outer screw (3) and an inner screw (7). The outer screw (3) is coupled to the inner screw (7) via the at least one transmission mechanism. The brewing slide (2) is displaceable from a first end position to an intermediate position, then to a second end position, and then back to the first end position. The outer screw (3) has a movement thread (3d) which engages with an outer screw nut (13) arranged in the brewing slide (2). It is characterized in that In the first end position of the brewing slide (2), the movement thread (3d) of the external screw (3) is disengaged from the external screw nut (13), wherein the speed of the brewing slide (2) is zero even if the external screw (3) continues to rotate, wherein the brewing slide (2) is secured in the first end position by means of a retaining device (HR), and in the second end position of the brewing slide (2), the movement thread (3d) of the external screw (3) remains engaged with the external screw nut (13), and the drive motor is switched off.

2. The brewing unit (1) according to claim 1, characterized in that The brewing slide (2) has a first feed drive (12) with the outer spindle nut (13) and the holding device (HR).

3. The brewing unit (1) according to claim 2, characterized in that The external screw nut (13) is arranged in a receiving portion (2c) of the brewing slide (2) with an axial play (32), wherein in a first end position, a first end side / contact side (13d) of the external screw nut (13) is in contact with a first pressure side (2d) of the receiving portion (2c), wherein a second end side / contact side (13e) of the external screw nut (13) and a second pressure side (2e) of the receiving portion (2c) are spaced apart by the play (32), and wherein when the movement thread (3d) of the external screw (3) and the external screw nut (13) are engaged, the second end side / contact side (13e) of the external screw nut (13) and the second pressure side (2e) of the receiving portion (2c) are in contact, and the play (32) is arranged between the first end side / contact side (13d) of the external screw nut (13) and the first pressure side (2d) of the receiving portion (2c).

4. The brewing unit (1) according to claim 3, characterized in that At least one contact side (13d, 13e) of the threaded region of the internal thread (13b) of the external screw nut (13') is divided into sections (33), wherein the sections (33) are arranged at intervals from each other around the internal thread (13b) at the circumference of at least one contact side (13d, 13e) of the external screw nut (13a), respectively have an elastic effect, and protrude from the corresponding contact side (13d, 13e) of the external screw nut (13').

5. Brewing unit (1) according to any one of the preceding claims, characterized in that The inner screw (7) is connected to a displaceable spray head (9) or a displaceable punch (10) and is coupled to a drive device via a second feed drive (15), and the punch (10) or the spray head (9) is arranged in a fixed position, wherein the displaceable brewing slide (2) is guided in a longitudinally displaceable manner by means of the outer screw (3) and at least one guide rod (4), and the spray head (9) or the punch (10) is guided in a longitudinally displaceable manner in the brewing slide (2), wherein the brewing slide (2) and the spray head (9) or the punch (10) can be displaced in a common direction of movement (BR1, BR2) at different speeds.

6. Brewing unit (1) according to any one of the preceding claims, characterized in that When the coupling between the outer screw (3) and the brewing slide (2) is released via the first feed drive (12) and in the region of the backlash of the outer screw nut (13) relative to the brewing slide (2), the spray head (9) is coupled to the brewing slide (2) by means of an activated, controllable drive device in order to transmit the movement of the spray head (9) to the brewing slide (2).

7. The brewing unit (1) according to claim 6, characterized in that The controllable entrainment device is designed as a controllable tappet device (22).

8. The brewing unit (1) according to claim 7, characterized in that The controllable tappet device (22) has a hydraulic, pneumatic or mechanical tappet drive (24).

9. The brewing unit (1) according to claim 8, characterized in that The tappet drive (24) is connected to a spray head seal (9a) of the spray head (9) which can be activated hydraulically, pneumatically or mechanically.

10. Brewing unit (1) according to any one of the preceding claims, characterized in that The holding device (HR) has a permanent magnet, an electrically controllable electromagnet or a mechanical locking structure.

11. A piston coffee machine having a brewing unit (1) according to any one of the preceding claims.

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