WO2012084809A1

WO2012084809A1 - Slot control unit for a spindle brewing unit of a fully automatic coffee maker

Info

Publication number: WO2012084809A1
Application number: PCT/EP2011/073221
Authority: WO
Inventors: Rudolf Beck; Florian Hoeck; Robert Strobl
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2010-12-22
Filing date: 2011-12-19
Publication date: 2012-06-28
Also published as: EP2654527A1; DE102010063930A1

Abstract

The invention relates to a fully automatic coffee maker, in particular for household purposes, for preparing a plurality of different coffee beverages, comprising a displaceable brewing chamber (10), which has an opening (38) to be filled with ground coffee (16), a displaceable T-piston (14) for ejecting the ground coffee (16) from the brewing chamber (10), and a movable wiper (48) for removing coffee residue formed of the ground coffee (16) from the T-piston (14), and further comprising a slot (20; 22), which during operation controls the movement of at least the T-piston (14). According to the invention, the slot has a first path (I, I') and a second path (II, II') at least in some sections.

Description

Gate control for spindle brewing unit

a coffee machine

The invention relates to a coffee machine, especially for household purposes, for preparing a plurality of different coffee drinks, with a displaceable brewing chamber having an opening for filling with ground coffee, with a displaceable T-flask for ejecting ground coffee in the brewing chamber, and with a movable scraper for removing coffee residue formed from the ground coffee from the T-piston, and with a gate that controls the movement of at least the T-piston during operation.

From DE 198 41 880 B4 a coffee machine is known which has a Spindelbrüheinheit, a displaceable T-piston and a movable scraper, wherein both the T-piston and the scraper with a single drive, the spindle are connected. For controlled movement of the T-piston and the wiper a backdrop is provided.

It is an object of the invention to provide a coffee machine, in which the brewing unit takes less space to complete.

This object is achieved in that the backdrop for guiding at least the T-piston at least partially has a first path and a second path. A backdrop stone regularly intervenes in a backdrop. Under the path of the backdrop is to understand their full trajectory, which it offers the sliding block, so they leads along their path. The Kulissenstein runs in the operation in its backdrop-guided movement along the entire path of the slide track in a first direction, his way, to one end, where he reverses, in a second direction, the opposite direction or his way back, to the other end to run the scenery path. There, he also turns around and runs again along his way, etc. His way out causes a forward movement, his return is associated with a return movement, for example, the T-piston or the scraper. The scenes serve to control movement processes for the preparation of a coffee beverage. Thus, it is a control circuit. The scenery is in the brewing unit usually perpendicular, namely parallel to the course of the spindle. The outward and return movement, for example, the T-piston is thus assigned to a certain altitude of the sliding block in the backdrop.

According to the invention, the guide for guiding at least the T-piston at least partially on a first way and a second way. Thus, the sliding block in operation can successively pass through the first and the second way. Advantageously, the first and the second path associated with different states of motion of at least the T-piston, for example, the first way a back and a return movement and the second way a rest position. The movement states assigned to the sections of the scenery or trajectory are therefore no longer in a flow direction linearly behind each other, but spatially next to each other, as it were designed as alternative routes. This allows a decoupling of different states of movement of the T-piston and / or the scraper, depending on the position in the first or second path and / or operating state. This solves the invention of the idea that all the states of motion associated sections of a backdrop in series behind or over each other must be arranged. Rather, the invention succeeds in decoupling the control of the states of motion from an altitude of the sliding block within the backdrop. This allows shorter scenes for basically the same movement processes and conditions within the brewing unit. The decoupling of the states of motion allows a shortening of the scenery or its trajectory, since different states of motion of the T-piston and the wiper can now be assigned to the two different, for example, adjacent paths. Thus, fully automatic coffee machines can be realized with smaller dimensions, in particular with a reduced height.

The sliding blocks can go through the backdrop in an alternating direction between two endpoints of the scenery, for example, during a preparation process of a coffee beverage in which the brewing chamber is filled with ground coffee, then the brewing chamber is closed, a coffee beverage is prepared, then the brewing chamber is opened again and the coffee trester is removed from the movable scraper by the T-piston. The scenery can also be used as a ring track with z. B. highly oval configuration may be formed, which is composed of two ring sections at their end or reversal points. Here, therefore, by the design as a ring path a motion free movement of the sliding blocks without reversing direction or without changing the direction of the sliding blocks at endpoints possible. If the scenery offers several ways that at least partially cover, there is at least one turn in the scenery, which leads the Kulissenstein in one way or the other. In order to steer the sliding block in the desired way, steering means may be provided. The branch may be associated with a steering means which ensures that the sliding block takes a certain, selected path. In this case, the steering means directly by contact on the sliding block, or contactless, z. B. by means of a magnet, such as an electromagnet act. The steering means may be arranged outside the scenery and z. B. on a compound of the T-piston or the scraper act to ensure that the sliding block as desired selects the first or second way. The steering means and their storage are designed so that they do not deform or give in contact with the sliding block itself. Additionally or alternatively, the steering means may be associated with a stop which prevents further movement of the steering means and absorbs the force acting on the steering means. For this purpose, the stopper may have a contact surface, which is designed so that almost complete area with a portion of the steering means can come into contact. In this case, the stop itself is designed such that it undergoes no deformation due to the impact of the sliding block.

It is preferably provided that the slide for directional selection has a switch as a steering means. By turning the turnout it is ensured that the sliding block is steered in the desired way. A switch connects a feed path with two outlets. The switch may have a switch blade which can be adjusted between two positions to direct a sliding block in the feed path in one of the two outlets targeted. The switch tongue can be adjusted for this purpose z. B. contactless, z. B. electromagnetically, or mechanically, for. B. by a direct connection with an actuator. Thus, by controlling such an electromagnet or actuator sector, the switch can be controlled. The soft tongue of the switch can be adjusted by passing through a sliding block, ie the sliding block meets when driving on a switch blade of the switch and pushes it from the first position to the second position, without the switch blade must be controlled. Thus, there is an alternating change between the two positions as a function of passing through the sliding block. In a preferred embodiment it is provided that the switch has a resiliently biased switch blade. Thus, this switch corresponds to a return fall soft, which is ensured by the resiliently biased tongue that it jumps back after passing through a sliding block in a starting position and directs upon impact of a sliding block from another direction this in the desired way. Alternatively, a re-dividing the switch tongue can be effected automatically by a spring, by gravity, which acts on the guide member, a corresponding stop for a sliding block leaving the switch or a stop on the brewing unit.

The switch tongue can be designed as an elastically deformable component, which can be brought by elastic deformation in one of the two positions. For this purpose, the switch tongue can be designed as a resilient metal tongue. In a further, preferred embodiment it is provided that the switch tongue has a rotatable guide element. The guide element is designed such that the guide element can be rotated from a first position to a second position by the impact of a sliding block and thus releases a path of the switch for the passage of the sliding block. The return parts of the rotatable guide element can automatically be effected by a spring, by the force of gravity acting on the guide element, a corresponding stop for a sliding block leaving the switch or a stop on the brewing unit. For example, during a downward movement, a sliding block may strike an inclined, upper surface of the rotatable guide element. In the further course, a sliding block is deflected by the oblique, upper surface. In an upward movement, however, meets the sliding block on a lower, sloping surface and the rotatable guide element can now perform a rotation and avoid the sliding block and release the way. The provision of the guide element can be done by gravity, a spring element or by another sliding block or stop on the brewing unit.

In a further, preferred embodiment it is provided that the switch tongue has a linearly and transversely to the direction of movement of the sliding block in the scenery displaceable guide element. Thus, the switch has a guide element displaceable along a displacement axis, which is movable between two end positions, wherein in a first end position a sliding block is guided in the first path and in a second end position in the second path. For example, a horizontal movement of the linearly displaceable guide element is prevented by a stop in a downward movement of a sliding block. During an upward movement, the sliding block hits a running slope, which pushes the linearly displaceable guide element horizontally to the side. At the same time, a further upwardly arranged second bevel slides into the slide track, which then ensures the return by the impact of the sliding block. The provision can also be done by spring force or gravity.

The scenery can be used to control various moving elements of a coffee machine with a single drive. It is preferably provided that the T-piston is assigned a first link and the scraper a second link. It can provide different scenes for the vertical or horizontal movement of the T-piston and the scraper, the use of two different scenes allows decoupling of the movement processes of the T-piston and the scraper, and thus a greater variability in the determination of the time sequence the movement processes.

In principle, the first path and the second path of the scenery may have the same length of path. According to an advantageous embodiment of the invention, the first path and the second path have a different path length. So z. B. the longer of the two paths, for example, the way of the scenery, be associated with a movement process, while the shorter of the two paths, ie the way back, corresponds to a rest state. Thus, z. B. the T-piston and / or the scraper inactive when the respective sliding block passes through the return paths and active only when passing through the longer way through by the sliding blocks, for example, deflect a lever for actuating the T-piston or the ejector. During the return journey, however, other preparation processes without participation of the T-piston or the ejector in the brewing unit can take place, so that control possibilities result, through which time and installation space can be saved.

A particularly simple construction results if the first path of the first link has a path length which is equal to the path length of the first path of the second link. In a first direction of movement, a path with the same path length is then provided for the T-piston and the wiper. At the same time can be done when passing through these first paths of the scenes no actuation of the T-piston and the scraper. This can be the case, for example, if after filling the brewing chamber and the T-piston in the Direction are moved towards a brewing head, that are raised to close the brewing chamber.

The second paths of the first backdrop and the second backdrop, however, may have different path lengths. In this case, the second path of the first link may have a path length which is greater than the path length of the second path of the second link, but for example, have a common end point. In this case, the second path of the first link is assigned to the T-piston and the second path of the second link to the scraper. This ensures that the scraper, which is needed to remove the coffee ester, is reliably activated at a later time than the T-piston, namely only after complete extension of the coffee residue from the brewing chamber. On the other hand, the scraper at the same time merges with the T-piston in its rest position.

Thus, the first and the second way can be adapted to the operation, for. B. to the duration of the movement processes and / or rest periods. If two sliding blocks, which engage in each case a backdrop, synchronously go through the scenes, depending on the position reached the sliding blocks different movements of the T-piston and the scraper can run with a time delay. It is also possible that two sliding blocks engage in a single link, but they pass through each other at a distance, so that they are in different positions in the backdrop at all times. This includes that z. B. the first sliding block can still be located in the first path section, while the second sliding block is due to its distance in the second path section of the scenery.

In the following, the invention will be explained with reference to a drawing. Show it:

FIG. 1 shows a schematic representation of a brewing unit of a coffee machine,

2 shows a schematic representation of an embodiment of a backdrop according to the invention with a sliding block in a first position,

3 shows a schematic representation of an exemplary embodiment of a scenery according to the invention with a sliding block in a second position, FIG. FIG. 4 shows a schematic representation of a first and a second link according to the invention,

FIG. 5: representation of scenes with a first exemplary embodiment of a switch,

Figure 6: representation of a second embodiment with a further variant of a switch, and

Figure 7: another embodiment of a backdrop according to the invention with a further variant of a switch.

FIG. 1 shows, in a highly schematic sectional view, a brewing unit 18 arranged in a housing section 36 of a coffee machine. The brewing unit 18 comprises a cylindrical brewing chamber 10, in which ground coffee or coffee powder 16 can be received. The brewing chamber 10 can be moved vertically along a displacement axis A via a spindle 46, so that it can be moved upwards in the direction of a likewise cylindrical brewing head 12 and in the opposite direction. By the upward movement, an upper-side opening 38 of the brewing chamber can be closed with the brewing head 12. A compression or compression of the coffee powder 16 in the brewing chamber 10 is achieved by the brewing chamber 10 is moved further along the displacement axis A upwards. In the brewing chamber 10, a T-piston 14 is mounted on the bottom side, which is also coupled to the spindle 46 as a drive and which is vertically movable within the brewing chamber 10. In addition to the opening 38, a horizontally movable scraper 48 is arranged, which in turn moves the spindle 46 as a drive.

The brewing unit 18 is shown in a filling position in which the brewing chamber 10 can be filled with coffee powder 16. After the subsequent pressing of the coffee powder 16 is an infusion of brewing water in the brewing chamber 10 to leach the coffee powder 16 and prepare a coffee beverage. In the brewing chamber 10, a pomace cake of the leached coffee powder 16 remains.

After the brewing process, the brewing chamber 10 is opened and vented. For this purpose, the brewing chamber 10 is lowered again until the opening 38 is released. In a next step, the T-piston 14 is raised relative to the brewing chamber 10, so that the pomace of the coffee Feepulvers 16 is pushed upwards out of the interior of the brewing chamber 10 through its opening 38. In a further step, the coffee trester is stripped horizontally by the scraper 48 from the surface of the T-piston 14.

Subsequently, the scraper 48 returns to its normal position, and the T-piston 14 is again moved away along the displacement axis A from the brewing head 12 until it reaches the starting position shown in Figure 1 again.

Reference is now additionally made to FIGS. 2 and 3. There, the schematic structure of two juxtaposed, in principle similar scenes for controlling the movement of the T-piston 14 on the one hand and the scraper 48 on the other hand is shown, of the two scenes for the sake of simplicity, only one gate 20 is exemplified. Furthermore, Figures 2 and 3 show a schematic sectional view of the link 20 at two cutting lines A - A and B - B with a continuous sliding block 24, which are coupled to the T-piston 14 and the scraper 48.

The scenery 20 is from a sliding block 24 coming from above (see arrow in Figure 2). The gate 20 has a first, upper branch, at which the gate 20 branches into a first path I and a second path II. This is followed by a second, under the heading, where the two paths I, II are brought together again. In this case, the second path II is formed by a bulge 26.

In order to steer the sliding block 24 coming from above into the desired second path II, a switch 30 is provided. It has a guide element 34 which can be displaced along a displacement axis. It carries an upper contact surface 42 which is formed so that the coming from above sliding block 24 is directed into the second path II. The guide member 34 experiences by the impact of the sliding block 24 no deformation, because it is designed to be stiff. In addition, a stop with a contact surface is provided, which limits the movement of the guide element 34. The guide element 34 occurs in the deflected state over the entire surface with the contact surface in contact. Thus, a force acting on the guide member 34 is received by the contact surface of the stopper 34. Subsequently, the sliding block 24 passes through the second path II until it meets the second, lower branch and a path in the direction of a bottom dead center (not shown) continues. After reaching the bottom dead center, the sliding block 24 begins to pass through the slide 20 from bottom to top (see FIG. 3). The link 20 is designed such that a guide block 24 coming from below is guided without engagement of guide or steering means along the first path I, Γ.

On its way up the sliding block 24 meets an adjusting element 46, which has a bevel 48 projecting in the first path I of the scenes 20. The on-running bevel 48 is resiliently biased by a spring element 50, so that the run-up slope 48 can be urged by impact of the sliding block 24 from the first path I, namely from the backdrop or drawing plane in the direction of view. The run-up slope 48 and the spring element 50 are as a component, for. B. in one piece and / or material, formed. After passing the sliding block 24, the ramp 48 returns to its original position.

The guide element 34 with its upper contact surface 42 is coupled to the spring element 48 such that by passing and displacing the ramp 48 through the sliding block 24, the guide member 34 is skewed perpendicular to the plane of the drawing, the upper contact surface 42 is no longer in the first path I stands and thus clears the way for the sliding block 24.

Subsequently, the sliding block 24 continues to move upwards until it passes the upper branch. Since then the sliding block 24 is no longer in contact with the ramp 48, the guide element 34 is moved back into the initial position shown in Figure 2 by the spring force of the spring 50.

Reference is now additionally made to FIG. 4. The two illustrated scenes 20, 22 allow the use of a single drive for the brewing unit, namely both for the vertical process of the brewing chamber 10, as well as for the partially independent vertical movement of the T-piston 14 and the horizontal movement of the scraper 48th The scenes 20, 22 each have a first, straight path I, Γ and a second, angled path II, ΙΓ, which is formed by a respective bulge 26. Thus, the second path II, ΙΓ the backdrop 20, 22 has a longer path than the first path I, Γ. The cou- lissenstein 24 passes through the gate 20, 22 coming from above initially through the branch of the second path II, ΙΓ

By forming the first path I, Γ and the second path II, ΙΓ with diverging gradients decoupling various motions each of the T-piston 14 and / or the scraper 48 in the preparation of a coffee beverage depending on the relative position with respect to the spindle possible , For different states of movement of the T-piston 14 and the scraper 48 can now be assigned to the first path I, Γ and the second path II, ΙΓ. The movement states or operations associated sections of the scenes 20, 22 are arranged side by side as alternative ways I, Γ, II, ΙΓ. Thus, the decoupling of the movement processes allows a shortening of the scenes 20, 22, which can be used to realize coffee machines with smaller dimensions, in particular with a reduced height. Two sliding blocks 24, which are in engagement with two corresponding scenes 20, 22, go through the scenes 20, 22 due to their coupling with the drive synchronously, but can be different in time depending on the position of the sliding blocks 24 different movements of the T-piston 14 and of the scraper 48 effect.

In this case (see Figure 4), a first link 20 is provided for controlling the scraper, while the second link 22 is provided for controlling the T-piston 14. The first link 20 differs from the second link 22 in that the second path II of the second link for controlling the T-piston 14 has a longer path than the second path ΙΓ of the first link 20 for controlling the scraper 48 in accordance with FIG the action described above, the activation of the scraper 48 and the T-piston 14 to effect. The sliding blocks pass through the first link 20 and the second link 22 at the same speed during an upward movement of the brewing chamber 10 and the T-piston 14 in the direction of the brewing head 12 along the displacement axis A the shorter path I, Γ the respective gate 20, 22nd because no actuation of the scraper 48 or the T-piston 14 is provided in this movement section of the brewing chamber 10 and the T-piston 14.

If, however, after closing the brewing chamber 10 and performing a brewing process, the brewing chamber 10 again by a downward movement in the direction of the displacement axis A, ie for removing the brewing chamber 10 from the brewing head 12 to open the Opening 38, is moved at the same speed, take the sliding blocks 24 the respective longer second path II, wodurch, whereby the relative movements of the T-piston 14 through the gate 22 and the movement of the scraper 48 through the gate 20 are effected. Thus, the sliding blocks 24 pass through the scenes 20, 22 along different paths depending on the direction, ie during an upward movement to close the brewing chamber 10 along the shorter path I, Γ and to open the brewing chamber 10 along the longer path II, II '.

Reference is now additionally made to FIG. 5. Shown is an example of one of the two scenes 20, 22, wherein the following explanations refer to both scenes 20, 22. To guide the sliding blocks 24 in the scenes 20, 22 in this manner, the gate 20, 22 a switch 30 on. In this case, the switch 30 is designed as a back-up switch with a resiliently biased spring tongue 28. This ensures that the spring tongue 28 is in the normal state in a position in which a sliding block 24 comes from above (see Figure 5, see arrow), along the second, longer path II, ΙΓ is directed.

Wrd at a renewed operation of the sliding block 24 again raised by an upward movement of the corresponding components of the coffee machine (see arrow), the sliding block 24 comes from below coming on the resiliently biased spring tongue 28 and pushed it aside, thereby closing one in the way II, ΙΓ leading opening and opens itself a way further along the gate 20, 22. The gate 20, 22 is thus designed so that a coming from below sliding block 24 is automatically guided along the path II, ΙΓ. The movement of the spring tongue 28 is limited by a stop 52. The stopper 52 is formed so stiff that an unwanted deformation of the spring tongue 28, z. B. will prevent bending through the sliding block 24. In addition, the stop 52 is formed as a contact surface against which the spring tongue 28 bears over the entire surface and thus absorbs the force.

Reference is now additionally made to FIG. 6. Shown is an example of one of the two scenes 20, 22, wherein the following explanations refer to both scenes 20, 22. There, another example of a switch 30 is shown. The switch 30 has a guide element 32 rotatably mounted about a pivot point 40. The design and dimensions of the rotatably mounted guide member 32 are chosen so that it an impact of a sliding block 24 is not deformed. In addition, a stop 52 is provided with a contact surface which serves as a full-surface bearing surface for the rotatable guide member 32. Furthermore, the guide element 32 has an oblique upper contact surface 42. The contact surface 42 closes in its rest position, in which the guide member 32 by action of a spring (not shown) is urged, the second path II, Kul the scenes 20, 22 and directs a sliding block 24 along the first path I, Γ, if he coming from above on the inclined, arranged contact surface 42 meets (see arrow). Instead of a spring can also be done by gravity back.

On the other hand, if a sliding block 24 passes through an upward movement along the second path II,,, the sliding block 24 strikes a second, lower contact surface 44. Thus, the sliding block 24 causes a rotational movement of the guide element 32 around the second contact surface 44 Fulcrum 40, with the result that the sliding block 24, the blocking of the second path II, auf by the guide member 32 cancels and further along the path II, ΙΓ can slide upwards (see arrow). If the sliding block 24 is no longer in contact with the second contact surface 44, (not shown) by the spring action of a spring a provision of the guide member 32 is effected in its initial position in which the guide member 32, the second path II, II 'closes.

Here, too, the gate 20, 22 is designed so that a coming from below sliding block 24 is automatically guided along the way II, ΙΓ.

In Figure 7, the switch 30 is formed by a displaceable along a displacement axis B guide member 34. Shown is an example of one of the two scenes 20, 22, wherein the following explanations refer to both scenes 20, 22. The displaceable guide element 34 has a turnout 28 for guiding a sliding block 24 in a desired path I, Γ, II, ΙΓ, a lower contact surface 44 for displacing the guide member 34 by hitting the sliding block 24 and a run-on slope 48. The displaceable guide element 34 is designed as a component, for. B. in one piece and / or material, formed. Due to the shape of the gate 20, 22 a coming from above guide block 24 is automatically along the first path I, Γ out. The design and dimensions of the displaceable guide element 32 are chosen so that it is not deformed by an impact of a sliding block 24. For this purpose, also a stop 52 with a contact surface is provided which serves as a full-surface bearing surface for the rotatable guide member 32.

If, in contrast, a sliding block 24 passes through the slide 20, 22 from bottom to top, it is automatically guided along the second guide path II, und and strikes the contact surface 44 and opens the second path II, ΙΓ, so that the sliding block 24 can happen (See arrow). He restores the starting position.

Since the foregoing detailed embodiments are exemplary embodiments, they may be readily modified by one skilled in the art to a wide extent without departing from the scope of the invention. In particular, the specific embodiments of the invention may follow in other forms than those described here. Likewise, the invention can be configured in a different form, if this is necessary for space reasons or designerischen reasons. Furthermore, the use of the indefinite article "on" or "one" does not exclude that the characteristics in question may also be present multiple times.

LIST OF REFERENCE NUMBERS

10 brewing chamber

12 brewing head

14 T-pistons

16 ground coffee

18 brewing unit

20 backdrop of the scraper

22 backdrop of the T-piston

24 sliding block

26 bulge

28 switch tongue

30 points

32 guide element

34 guide element

36 housing section

38 opening

40 pivot point

42 upper contact surface

44 lower contact surface

46 adjusting element

48 ramp

50 spring element

52 stop

A displacement axis

B displacement axis

Claims

1. Coffee machine, in particular for household purposes, for preparing a plurality of different coffee drinks, with a displaceable brewing chamber (10) having an opening (38) for filling with ground coffee (16), with a displaceable T-piston (14) for ejection of the ground coffee (16) from the brewing chamber (10), and with a movable scraper (48) for removing coffee residue formed from the ground coffee (16) from the T-piston (14), and with a link (20; 22) in operation, controlling the movement of at least the T-piston (14), characterized in that the link (20; 22) at least in sections has a first path (I; Γ) and a second path (II; ΙΓ).

2. Coffee machine according to claim 1 with engaging in the backdrop sliding blocks, characterized in that the backdrop, the sliding blocks (24) in dependence on their direction of movement the first path (I, Γ) or the second path (II, führt) leads.

3. Coffee machine according to claim 1 or 2, characterized in that the link (20, 22) branched at a branch in the first path and the second path and the directional selection of the first path (I, Γ) or the second path ( II, ΙΓ) has a switch (30).

4. Coffee machine according to claim 3, characterized in that the switch (30) has a resiliently biased switch blade (28).

5. Coffee machine according to claim 4, characterized in that the switch tongue (28) has a rotatable guide element (32).

6. Coffee machine according to claim 5, characterized in that the switch tongue (28) has a linearly displaceable guide element (34).

7. Coffee machine according to one of claims 1 to 6, characterized in that the T-piston (14) has a first link (22) and the scraper (48) is associated with a second link (20)

8. Coffee machine according to one of claims 1 to 7, characterized in that the first path (I, Γ) and the second path (II, ΙΓ) have a different path length.

9. Coffee machine according to claim 8, characterized in that a path length of the first path (I, Γ) of the first link (22) is equal to the path length of the first path (I) of the second link (20).

10. Coffee machine according to claim 8 or 9, characterized in that the path length of the second path (II) of the first link (22) is greater than the path length of the second path (ΙΓ) of the second link (20).