DK2733249T3

DK2733249T3 - Washing machine with detergent storage containers

Info

Publication number: DK2733249T3
Application number: DK14000594.3T
Authority: DK
Inventors: Markus Zwimpfer
Original assignee: V-Zug Ag
Priority date: 2014-02-20
Filing date: 2014-02-20
Publication date: 2017-02-06
Also published as: EP2733249B1; PL2733249T3; EP2733249A3; SI2733249T1; EP2733249A2

Description

Field of the invention

The invention relates to a washing machine with at least a storage container arranged inside a drawer, for receiving at least a detergent in a quantity which is sufficient for multiple washing cycles. The washing machine further has an extracting device for automatically extracting the detergents from the at least one storage container.

Background A washing machine of this type is disclosed in DE 3403628. The device has a drawer inside which two storage containers for liquid detergent are located. In order to remove the detergents from the storage containers, a relatively complex rinsing mechanism is provided, which is fixedly integrated in the drawer. Such a rinsing mechanism is complex with regard to manufacturing and difficult to clean. US 2012/0152290 also describes such a washing machine and shows furthermore a mixing chamber for mixing water and detergent. The detergent is transported from the storage chambers via hoses, a pump and further hoses to the mixing chamber. EP 2 251 481 also describes a washing machine with a mixing chamber. The detergent is guided from the storage chambers via valves and via connecting hoses to pumps, and from the pumps via further hoses into the mixing chamber. A washing machine according to the preamble of claim 1 is also known from DE 10 2009 027 875 A1.

Description of the invention

It is the objective of the present invention to provide a washing machine of the type mentioned at the beginning, which is simple with regard to manufacturing and maintenance.

This objective is reached by the washing machine according to claim 1. According to it, the extraction device, by means of which the detergents can be extracted from the storage containers, has an adapter unit which is mounted from the top onto the storage container in a usage position. The adapter unit has at least a suction pipe for sucking the detergent and at least a filling level sensor for detecting the filling level in the storage container. The suction pipe and the filling level sensor protrude from the top into the storage container in the usage position of the adapter unit.

This construction concentrates the complex components (namely the suction pipe or the suction pipes, respectively and the filling level sensor or the filling level sensors, respectively) in one unit which can be put on the at least one storage container in a simple way. Compared with this, the construction of the drawer can remain simple.

When the drawer has multiple storage containers, the adapter unit preferably has multiple suction pipes and multiple filling level sensors, such that detergent can be extracted from the each storage container with only one adapter unit and each storage container can be monitored.

Advantageously, each filling level sensor has at least one, advantageously two, electrodes. This electrode or electrodes, respectively, protrudes or protrude, respectively, from the top into the respective storage container. Such a filling level sensor allows determining the presence of detergent by means of an electric resistance measurement or impedance measurement. The design as electrode(s) protruding into the storage container from the top is particularly suitable for a solution in case of which the adapter unit can be put on the storage containers from the top.

In a further preferred embodiment, the adapter unit has a first coupling part. Additionally, a second coupling part is provided as component of the washing machine, wherein on the one hand both coupling parts can be coupled to one another in order to form at least an extraction pipe for detergent from the storage container or containers, respectively, and on the other hand to form at least a signal line for the filling level sensor or sensors, respectively. Thus, the fluidic and electric connections between the drawer and the rest of the washing machine can be created with only one coupling .

According to the invention, each storage container has a drain valve by means of which an opening in a floor of the storage container can be opened or closed, respectively. The detergent can be discharged from the storage container by means of the drain valve.

Furthermore, the washing machine can have an arrest for limiting the pull-out movement of the drawer in a maximum pull-out position. In this way it is possible to avoid pulling out the drawer inadvertently and too far. In this case, the device is advantageously formed such that the adapter unit is inaccessible in the maximum pull-out position. "Inaccessible" means that a non-destructive removal of the adapter unit from or inserting it into the usage position is not possible in the maximum pull-out position. The washing machine advantageously has a tool for opening the arrest. This tool may be coupled to the arrest in order to subsequently free the arrest.

Short description of the drawings

Further embodiments, advantages and applications of the invention result from the dependent claims and the now following description by means of the figure. It is shown in:

Fig. 1 a schematic view of the most relevant components of a washing machine in the present context,

Fig. 2 the storage drawer in its maximum pull-out position,

Fig. 3 the storage drawer in removed state,

Fig. 4 an explosion view of the storage drawer,

Fig. 5 the adapter unit in its usage position,

Fig. 6 a section through the storage drawer with the adapter unit in its usage position along the line VI-VI of Fig. 5,

Fig. 7 and 8 two views of the adapter unit,

Fig. 9 a view of the opened adapter unit,

Fig. 10 a view of the storage drawer from the top with removed cover,

Fig. 11 the arrest as seen from the interior of the device,

Fig. 12 a view of the washing machine with opened mixing drawer,

Fig. 13 the view of Fig. 12 with the mixing drawer eguipped for liguid detergent, and

Fig. 14 a view of the actuation tool.

Way(s) of carrying out the invention

Definitions : "Detergents" are understood as washing agents of any type, by means of which laundry is treated, e.g. colour detergent, boil detergent, fabric softener or textile finisher. The detergents used in the storage drawer are liquid or at least free-flowing detergents.

The terms "top", "bottom", "on", "below", "above" etc. are understood as related to the gravitational force with respect to the orientation of the components of the washing machine as intended. "Front side" of the washing machine is understood as the vertical side of the washing machine which is normally facing the user and "rear side" is the side opposed to the front side.

Basic construction:

Fig. 1 shows the most important components of a washing machine in the present context. The device comprises, inside a stationary housing 1, a vat 2 of known type for receiving a drum (not shown) inside which the laundry is washed. A fresh water valve 4 controls the fresh water supply to a mixing chamber 5. The mixing chamber may be formed, as known, by a mixing drawer which is adapted to mix detergent with water. Such a mixing drawer, which may also be adapted to receive individual portions of detergent, will be described in more detail further down.

Furthermore, a storage drawer 6 is provided, which is normally called "drawer 6" in the following. At least two storage containers 7, 8 are arranged in this drawer 6, which serve to receive detergents. Different or same detergents may be stored in the storage containers. The detergents are free flowing, particularly liquid. An adapter unit 9 is arranged on the storage containers 7, 8, which primarily has two tasks. On the one hand, it serves to extract detergent from the storage containers 7, 8 and on the other hand it is equipped with filling level sensors which measure the filling level inside the storage containers 7, 8. The construction of the adapter unit 9 is described in more detail further down.

Furthermore, two transport pipes 11a, lib are provided for transporting detergent from the storage containers 7, 8 to the mixing chamber 5. At least the end of each transport pipe 11a, lib, which is attributed to the adapter unit 9, is formed by a flexible hose 12a, 12b which is capable of following the normal pull-out motion of the drawer 6. Transport pumps 13a, 13b are provided in the transport pipes 11a, lib in order to suck the detergents out of the storage containers 7, 8 and transport them to the mixing chamber 5. The transport pumps 13a, 13b are preferably arranged in a stationary way, i.e. they are stationary with respect to the housing 1 and don't follow the pull-out motion of the drawer 6.

The openings of the transport pipes 11a, lib into the mixing chamber are each provided with a valve 14a, 14b which prevent in closed state entry of air from the mixing chamber into the transport pipes 11a, lib. Preferably, these valves 14a, 14b are formed as nonreturn valves which open when the respective transport pipe 13a, 13b is operated and automatically close after switching off the transport pump again. The valves 14a, 14b prevent that the detergent in the transport pipes 11a, lib dries out or coagulates.

If the openings of the transport pipes 11a, lib on the side of the mixing chamber are arranged lower than the storage containers 7, 8, the valves 14a, 14b may be formed in such a way that they open only in case of a certain overpressure in the respective transport pipe. This certain overpressure is chosen higher than the hydrostatic pressure exerted by the detergent on the respective valve when the transport pump is switched off. In this way, emptying the storage containers due to the "siphon" principle can be avoided.

Furthermore, Fig. 1 shows a controller 15 which controls the operation of the device. Particularly, it also controls the transport pumps 13a, 13b and it evaluates the signals of the filling level sensors of the adapter unit 9.

Storage container:

The structure of the storage drawer or the drawer 6, respectively, results from Fig. 2-4 and 10.

The storage drawer or the drawer 6, respectively, is preferably arranged in an upper area of the housing 1 and opens towards the front side. Fig. 2 shows it in its maximum pull-out position, i.e. in the position in which the user normally pulls it out to a maximum, e.g. for filling the storage container.

The drawer 6 forms the two storage containers 7, 8. As Fig. 4 and 10 indicate, these storage containers are formed as vats, i.e. they have closed side walls 21 -23 and a floor 24, and they are opened towards the top. The storage containers 7, 8 are closed by a removable cover 25 during "normal operation", which prevents the detergent from drying out or coagulating inside the storage containers.

Two flaps 26a, 26b are provided in the cover 25, which can be opened in a pull-out state of the drawer, e.g. in order to fill the storage containers 7, 8 .

Furthermore, Fig. 2 and 3 show the adapter unit 9. The cover 25 covers this adapter unit 9 in its usage position (which is shown in Fig. 3).

The drawer 6 has two lateral side areas which are formed by the outer side walls 21, 22, as well as a bottom area formed by the floor 24. These areas extend along the pull-out direction 28 of the drawer 6, which is shown in Fig. 2. The front area 29 as well as the rear wall area 30 (Fig. 3) of the drawer 6 extend perpendicularly to this direction.

Adapter unit:

The adapter unit 9 is shown in detail in Fig. 5 - 9. It has a housing made of plastic which is preferably manufactured as one-piece injection moulding component. The housing has a cover 32 which is connected to a housing base 34 via a flexible bridge 33 forming a hinge. The cover 32 can be attached on the housing base 34 by clamp connectors 35.

Two suction pipes 36, 37, which are immersed in the storage container 7 or 8, respectively, in the usage position of the adapter unit 9, are arranged on the underside of the adapter unit 9. Furthermore, two electrode pairs 38a, 38b, 39a, 39b are arranged on the underside of the adapter unit 9, which form two filling level sensors 38, 39 and which are also immersed from the top in the storage container 7 or 8, respectively, in the usage position. A horizontal pipe section 40 or 41, respectively, follows each suction pipe 36, 37 inside the adapter unit 9 (Fig. 9), which leads to a pipe coupling 42 or 43, respectively, on an outer side of the adapter unit 9.

Each electrode pair 38a, 38b, 39a, 39b comprises two electrode rods 45 which protrude downwards and have a blank metal surface, such that an electric contact with the detergent is made possible inside the storage container. The electrode rods 45 protrude in usage position of the adapter unit 9 at least up to the lower guarter of the storage container 7 or 8, respectively, such that the electric contact is only lost in case of a relatively low level of the detergent. In this way, it is possible to determine by a resistance measurement between the electrode rods 45, if the respective detergent has to be added. This may be shown to the user by the controller 15 on a display of the device .

As indicated in Fig. 9, cable shoes 46 are attached on the upper ends of the electrode rods 45, from which cables or wires lead to an electric connector 47 which is arranged between the two pipe couplings 42, 43.

The two pipe couplings 42, 43 and the connector 47 arranged between them form a "first coupling part" 50. The latter can be coupled to a "second coupling part" 51 which is shown schematically in Fig. 3 and 4. The second coupling part 51 forms the counterparts to the pipe couplings 42, 43 and to the connector 47. The hoses 12a, 12b as well as the flexible electric inbound pipes 12c towards the filling level sensors 38, 39 are attached on the second coupling part 51, which are schematically indicated in Fig. 3 and 4 as a hose bundle and cable bundle 52.

As can be seen in Fig. 3, the first coupling part 50 is located at the adapter unit 9, which is in usage position, in the side area 21 of drawer 6. This has - as compared with an arrangement in the rear wall area 30 - the advantage that the coupling parts 50, 51 become reachable by the user when the drawer 6 is opened wide enough, however without having to remove the drawer completely out of the machine. More about this aspect is described in more detail further down in the section "Arrest".

The first coupling part 50 comes to lie at the adapter unit 9, which is in usage position, in an area 54 of the side area 21 of the drawer 6, which is shifted backwards with respect to the drawer interior, see Fig. 3 and 4. This ensures that the two coupling parts 50, 51, which are connected to one another, don't protrude on the sides. The shifted back area 54 extends along the bottom edge of the drawer 6 up to the rear wall area 30 of the drawer and forms in this way space for the hose bundle and cable bundle 52.

Each of the coupling parts 50, 51 forms a contiguous body with at least two pipe couplings 42, 43 and at least an electric connector 47, such that each electric and fluidic contact can be created or interrupted, respectively, with only one move of the hand.

Fig. 6 shows a section through the drawer 6 (without cover 25) with the adapter unit 9 in its usage position. As can be seen, the adapter unit 9 touches the vertical walls 21 and 23 of the storage containers 7, 8.

The connection between the adapter unit 9 and these walls 21, 23 is such that it forms a - at least in case of a short overflow tight - seal. For this, the adapter unit 9 forms a first sealing part 60 on each wall 21 or 23, respectively, having a groove 61 which is opened towards the wall 21 or 23, respectively. The wall 21 or 23, respectively, forms with its corresponding uppermost end a second sealing part 62 formed as a tongue which engages the groove 61. The thickness of the tongue is advantageously dimensioned such that the groove 61 touches the tongue on both sides in order to create in this way an as tight as possible connection.

Such a seal is advantageously provided at least between the outer side wall 21 and the adapter unit.

In the upper example, the first sealing part 60 forming the groove 61 is arranged on the adapter unit 9 while the second sealing part 62 which forms the tongue is formed by the wall 21 or 23, respectively. The first sealing part may also be formed by the wall 21 or 23, respectively, while the second sealing part is arranged at the adapter unit 9.

As can be seen in the figures, the adapter unit 9 is supported inside the drawer 6 in such a way that it can be removed from its usage position as a whole in one piece by upward movement or inserted in the usage position in opposite direction by a movement from the top to the bottom, respectively.

Drain valves:

Each storage container 7, 8 is equipped with a drain valve 65 for cleaning or removal of the drawer 6, by means of which an opening in the floor of the storage container can be opened or closed, respectively. This allows to remove the detergent, if necessary, in an easy way from the storage containers.

As can best be seen in Fig. 4 and 10, each drain valve has an actuation shaft 66 which protrudes from the floor 24 upwards through the respective storage container 7 or 8, respectively, and which allows the user to handle the valve. In the present embodiment, the actuation shaft 66 can be rotated around its vertical axis in order to open or to close, respectively, the opening.

In the present embodiment, the actuation shafts 66 also form maximum filling level indicators by arranging their head 67 on the maximum filling level of the respective storage container 7 or 8, respectively. For this, the actuation shafts 67 should extend, if possible, up to the uppermost quarter of the height of the storage containers 7, 8.

In order for the actuation shafts 67 to be well visible and capable of being gripped, they are arranged vertically below the flaps 26a, 26b.

Arrest:

As already mentioned, Fig. 2 shows the drawer 6 in its maximum pull-out position. In this position the flaps 26a, 26b are accessible, however not the adapter unit 9.

In the maximum pull-out position the drawer 6 is prevented from being pulled out further by an arrest 70. This arrest 70 is preferably formed in such a way that it can only be removed with a suitable actuation tool, i.e. not by hand by the normal user.

The structure of the arrest 70 is indicated in Fig. 2 and 11, wherein Fig. 11 shows the arrest from the interior of the device. The arrest 70 has a body 71 which can be rotated about an axis which is perpendicular to the front side of the device.

Normally, the body 71 is located in a first position which is shown in Fig. 2 and 11. In this position a nose 72 attached to the body 71 protrudes towards the drawer 6 and prevents it from moving beyond the maximum pull-out position. The body 71 is kept in this first position by the elastic force of a spring element 73.

The body 71 can be brought in its second position by rotating the body 71 against the elastic force of the spring 73 along a rotation direction 74. In this position the nose 72 frees the drawer 6 such that it can be pulled out of the device beyond the maximum pullout position.

In order to turn the body 71, a head 75 (Fig. 2) is arranged on it, which makes possible a positive fit (with respect to the rotation) connection with the actuation tool. For this, e.g. a slit can be provided, as shown in Fig. 2, in the head 75, inside which a tongue of the actuation tool can be inserted.

If the drawer 6 is pulled out further, after freeing the arrest 70, first the adapter unit 9 or the coupling parts 50, 51, respectively, are accessible. In this position the drawer 6 is still guided in the device, i.e. the user can let it go in order to free the coupling parts 50, 51. In order to ensure a secure guiding in this position, the distance A (see Fig. 3) between the first coupling part 50 of the adapter unit 9 located in the usage position and the rear wall area 30 of the drawer 6 should preferably be of at least 10 cm.

The head 75 of the arrest 70 is covered in the closed state of the drawer 6 by the front plate 77 of the drawer 6, see Fig. 2. The front plate 77 forms the front area 29 of the drawer. The head 75 is only accessible when the drawer 6 is pulled out a little.

The mentioned actuation tool may e.g. be a screw driver or a wrench. Preferably, the tool is delivered as part of the washing machine. A corresponding embodiment is shown in Fig. 12 - 14. In this embodiment, the washing machine has additionally to the storage drawer 6 a mixing drawer 80 in order to receive individual portions of detergent and to mix them with water. The mixing drawer 80 forms the above mentioned mixing chamber 5. The mixing drawer 80 contains at least a vat (in the present embodiment three vats 81, 82, 83 for prewash detergent, main wash detergent and tissue finisher), which are dimensioned in such a way that they can receive detergent for a washing cycle and which are entirely emptied during the washing cycle . A first support 84 for a secure reception of the actuation tool 86 is formed inside the mixing drawer 80. This actuation tool 86, which is shown in Fig. 14, has at least a part which can form a positive fit connection (with respect to the rotation) with the head 75 of the arrest 70. In the shown embodiment, e.g. each of the upper edge areas 87 of the actuation tool is suitable for this, which can each be inserted into the slit of the head 75.

If the actuation tool 86 is stored in the first support 84 in its "first position", it doesn't assume a functional task in the mixing drawer 80.

However, additionally a second support 88 is provided inside the mixing drawer 80 in order to store the actuation tool in a "second position". This second position is in the vat 82 for the main wash detergent. When the actuation tool 86 is located in its second position, it forms a permeable side wall for this vat 82. The side wall is permeable because the actuation tool 86 has a recess 89 at its bottom end, which forms a discharge opening for the vat 82 in the second position (see Fig. 14) .

The actuation tool 86 is inserted in its second position when a liquid detergent shall be used in the vat 82 as detergent. It prevents a fast discharge of the liquid detergent after filling, such that the major part of the detergent stays in the vat 82 until the main washing cycle. Only then the vat 82 is rinsed with water. During this, a major part of the detergent flows into the vat of the washing machine in diluted form via the wall formed by the actuation tool 86. After that, the remaining quantity of diluted detergent (which is considerably more fluid than the pure detergent) flows relatively fast through the recess 89.

In this way the actuation tool 86 can on the one hand be used in the mixing drawer 80 and on the other hand it can be used for actuating the arrest 70.

In the embodiment according to Fig. 1, an own transport pipe 11a, lib is shown for each storage container 7, 8. However it is basically conceivable to use a common transport pipe for all storage containers 7, 8 if e.g. a switch is used in the area of the adapter unit 9.

It is possible to also provide more than two storage containers in the drawer 6. In this case the adapter unit 9 is equipped with a corresponding number of suction pipes and filling sensors.

The invention can also be applied for drawers 6 which only have a single storage container.

While in present application preferred embodiments of the invention are described, it is clearly noted that the invention is not limited thereto and may also be executed in other ways within the scope of the now following claims.

Claims

A washing machine with at least one storage container (7, 8) arranged in a drawer (6) for storing at least one detergent in a quantity sufficient for several washes, and with a withdrawal device for automated removal of the detergent by the storage containers (7, 8), the withdrawal device comprising an adapter unit (9) which can be mounted on the storage container (7, 8) from above in a use position and comprising at least one suction pipe (36, 37) and at least one filling level sensor (38, 39) ) and wherein the suction tube (36, 37) and the filling level sensor (38, 39) in the position of use of the adapter unit (9) project from above into the storage container (7, 8), characterized in that a drain valve (7, 8) is arranged in the storage container (7, 8). (65) by which an opening in a bottom (24) of the storage container (7, 8) can be opened and closed.

A washing machine according to claim 1, wherein the drawer (6) comprises a plurality of storage containers (7, 8) and the removal device comprises a plurality of suction pipes (36, 37) and several filling level sensors (38, 39) protruding from above in the operating position of the adapter unit (9). into the storage container (7, 8).

A washing machine according to one of the preceding claims, wherein each filling level sensor (38, 39) comprises at least one, in particular two electrodes (38a, 38b, 39a, 39b), which project from above into a storage container (7, 8).

Washing machine according to one of the preceding claims, wherein the adapter unit (9) can be removed as a whole in one piece by moving it upwards from the operating position.

Washing machine according to one of the preceding claims, wherein the adapter unit (9) comprises a first coupling part (50) and the washing machine further comprising a second coupling part (51), wherein the first and second coupling parts (50, 51) can be coupled to each other. for forming at least one outlet line for the at least one detergent from the at least one storage container (7, 8) and at least one signal line for the at least one filling level sensor (38, 39).

A washing machine according to claim 5, wherein the drawer (6) comprises two side regions (21, 22) in the side and a lower bottom region (24), which extend along an extension direction (28) of the drawer (6), and the first the coupling part (50) of the adapter unit (9) located in the use position is arranged on one of the side regions (21, 22), and in particular where the first coupling part (50) of the adapter unit (9) which is in the use position is spaced at least 10 cm from a rear wall area (30) of the drawer (6).

Washing machine according to claim 6, wherein the first coupling part (50) of the adapter unit (9) located in the use position lies in an area (54) of the side area (21) which is displaced back relative to the interior of the drawer, and especially where the back-displaced region (54) extends along the side region (21) to a rear wall region (30) of the drawer (6).

Washing machine according to one of claims 5 to 7, wherein each coupling part (50, 51) comprises a continuous body with at least two pipe plugs (42, 43) and at least one electrical plug (47).

Washing machine according to one of the preceding claims, wherein the adapter unit (9) is in the use position on at least one vertical wall (21, 23) of the at least one storage container (7, 8) and with this forms a seal, the seal comprising a first sealing member (60) and a second sealing member (62), wherein the first sealing member (60) is formed by the adapter unit (9) and the second sealing member (62) is formed by the vertical wall (21, 13), or vice versa, and the first sealing member (60) comprises a groove (61) which engages a tongue of the second sealing member (62), and in particular where a width of the groove (61) and a thickness of the tongue are dimensioned in such a way that the groove (61) touches the tongue on both sides.

Washing machine according to one of the preceding claims, wherein the at least one storage container (7, 8) is designed as a vessel, wherein the drawer (6) has at least one lid (25) which covers the vessel from above and the lid (25) covers the adapter unit (9) in the operating position.

A washing machine according to any one of the preceding claims, wherein each drain valve (65) comprises a control shaft (66) which projects through the storage container (7, 8) from the bottom (24), and in particular where the opening can be opened and closed by turning the control shaft (66) about a vertical axis.

A washing machine according to claim 11, wherein the control shaft (66) extends as the maximum filling level indicator up to an upper quarter of the height of the storage container (7, 8).

Washing machine according to one of the preceding claims, with a lock (70) for limiting the pull-out movement of the drawer (6) in a maximum pull-out position.

A washing machine according to claim 13, wherein the adapter unit (9) is not available in the maximum pull-out position of the drawer (6).

A washing machine according to any one of claims 13 or 14, wherein the washing machine further comprises an operating tool (86) which can be coupled to the lock (70) for opening the lock (70).

Washing machine according to claim 15, with a mixing drawer (80) for receiving single portions of detergent and mixing with water, wherein at least a first holder (84) for receiving the operating tool (86) is arranged in the mixing drawer (80).

A washing machine according to claim 16, wherein a first and a second holder (84, 88) are arranged in the mixing drawer (80) for holding the operating tool (86) in a first and second positions, wherein the operating tool (86) forms in the second position. a permeable side wall of a vessel (82) of the mixing tray (80), but does not form such a side wall in the first position.

A washing machine according to any one of claims 13 to 17, wherein the lock (70) comprises a rotatable body (71) which can be rotated against an elastic force from a first to a second position, whereby it releases the drawer (6) in the second position. and wherein a head (75) is disposed on the rotatable body (71), which head is designed for form-fitting connection with an operating tool.

A washing machine according to one of the preceding claims, with at least one mixing chamber (5) for mixing detergent and water and with at least one transport line (11a, 11b) for transporting detergent from the at least one storage container (7, 8) to the mixing chamber, wherein at least a portion of the transport line (11a, 11b) is formed by a hose (12a, 12b) coupled to the adapter unit (9).

A washing machine according to claim 19, wherein a valve (14a, 14b), in particular a check valve, is arranged in the mixing chamber at an outlet of the conveyor line (11a, 11b).