COMMERCIAL DISHWASHING MACHINE AND METHOD FOR OPERATING SUCH A DISHWASHING MACHINE

Description

[0001] The present invention relates to a commercial dishwasher and a method for operating such a commercial dishwasher. Such commercial dishwashers comprise a washing chamber into which dishes to be washed can be placed, and a dispensing device for dispensing one or more different treatment liquids.

[0002] Commercial dishwashers can, for example, be so-called program machines, which only have one washing chamber, or belt / basket transport machines, which have one or sometimes even several washing chambers.

[0003] Such dishwashers comprise a tank, sometimes several tanks, for holding treatment liquid, which can be transported from the tank to one or more dispensers for dispensing the treatment liquid into the washing chamber, whereby wash pumps are usually used to transport and convey the treatment liquid from the tank to the dispensers.

[0004] The treatment fluid is usually produced by feeding raw water or treated (softened, demineralized) water into the tank, for example via a connecting pipe, while additional cleaning agent is added via a dosing pump so that the desired concentration is achieved.

[0005] The dosing of liquid detergent in commercial dishwashers can be carried out by different types of dosing pumps, but so-called peristaltic pumps are frequently used because these are usually cost-effective and can pump larger quantities of detergent, which is particularly important for commercial dishwashers that have to process a high throughput and large quantities of dishes to be cleaned.

[0006] However, such dosing pumps, especially the peristaltic pumps mentioned above, are subject to a certain degree of wear, so their flow rate decreases over time. In peristaltic pumps, the tubing that is squeezed inside the pumps is particularly subject to wear, and this wear has a noticeable impact on their flow rate.

[0007] To compensate for this lower flow rate, the dosing pumps must be operated for increasingly longer periods of time, the longer and more intensively they are operated, otherwise increasingly smaller dosage quantities of detergent are supplied, which leads to a treatment liquid with too low a concentration of detergent, which in turn negatively affects the cleaning of the dishes.

[0008] In order to ensure sufficient dosing of cleaning agents, the fact is used that the concentration of a cleaning agent in the raw water or in the treatment liquid influences the electrical conductivity of the treatment liquid and that the electrical conductivity increases with increasing concentration of cleaning agent.

[0009] In the prior art, a conductivity sensor is therefore installed in the tank, which continuously measures the conductivity of the treatment liquid, wherein a control device is provided which causes a dosage of cleaning agent when the conductivity of the treatment liquid is below a predetermined value or falls below this predetermined value.

[0010] From US 2018 / 199790 A1 a method for dosing a chemical substance into a dishwasher is known, in which a first amount of the chemical substance is added, the conductivity is measured and stored, and subsequently a further amount of the chemical substance is added until a desired conductivity is reached.

[0011] Furthermore, from US 2003 / 0127110 A1 a commercial dishwasher is known which also includes a sensor which measures the electrical conductivity of the water inside the dishwasher and which comprises a control device.

[0012] US 2004 / 0236522 A1 also discloses a dishwasher in which the conductivity of a chemical solution used is monitored. Finally, DE 10 2017 114 665 A1 discloses a dosing device for the metered delivery of media, which can be used in washing machines or dishwashers.

[0013] Based on the above-mentioned prior art, it is an object of the present invention to provide an improved commercial dishwasher and a method for operating such a dishwasher.

[0014] This object is achieved by a commercial dishwasher according to claim 1 and a method according to claim 13. Claims 2 to 12 relate to particularly preferred embodiments of the dishwasher according to the invention, claim 14 relates to a particularly preferred embodiment of the method according to the invention.

[0015] A commercial dishwasher according to the invention comprises a washing chamber in which at least one dispensing device for dispensing a treatment liquid is arranged. The dishwasher according to the invention further comprises: a tank for receiving the treatment liquid, a first supply device for supplying raw water into the tank, a storage container for a cleaning agent, a second supply device with a metering pump, in particular a peristaltic pump, for supplying cleaning agent from the storage container into the tank, a third supply device with a washing pump for supplying treatment liquid from the tank to the at least one dispensing device, a conductivity sensor for determining the conductivity of the treatment liquid

[0016] The dishwasher according to the invention further comprises a control device which is designed such that, when the dishwasher is put into operation, it is able to recognise whether it is a first-time start-up or a subsequent start-up and / or the dishwasher comprises a control device and an input device via which a user can input that it is a first-time start-up or a subsequent start-up, wherein the control device comprises a memory device.

[0017] According to the invention, the dishwasher and the control device are designed in such a way that at least during initial commissioning, the electrical conductivity of the raw water and both during initial commissioning and subsequent commissioning, the electrical conductivities of the raw water and the treatment liquid are measured after a cleaning agent has been added to the raw water by means of the conductivity sensor, wherein the control device determines a correction factor KA on the basis of these measured values ​​and on the basis of a comparison of these measured values ​​at each commissioning, which correction factor is related to or dependent on a delivery rate of the dosing pump decreasing over the service life.

[0018] Since, in such a dishwasher, the electrical conductivity of the raw water is measured at least during initial startup, and the electrical conductivity of the treatment liquid is measured both during initial startup and subsequent startup, where constant and controlled conditions generally prevail, and the electrical conductivities are compared during one or more subsequent startups with the corresponding measured values ​​during initial startup, the control device can use these values ​​to draw conclusions about the aging or wear of the dosing pump and about the declining flow rate of the dosing pump. From this, the control device can calculate a correction factor that is kept constant between two startups.

[0019] During normal operation following commissioning, the dosing pump, especially the peristaltic pump, can therefore be controlled purely on a time-based basis, depending solely on the amount of raw water supplied, the desired concentration of the detergent, and the aforementioned correction factor. Continuous measurement of the electrical conductivity of the treatment liquid is not required, nor is it necessary for the control system to constantly react to the changing measured conductivity values. This allows the dishwasher to adapt to the changed condition or wear of the dosing pump between commissioning cycles.

[0020] A change in the flow rate of the dosing pump between two start-ups is deliberately accepted, since the changes in the flow rate between two start-ups are usually very small and can be neglected, whereby for commercial dishwashers it is usually assumed that start-up occurs about once a day.

[0021] The dosing is adapted in a simple and very reliable manner to the increasing wear of the dosing pump, especially a peristaltic pump.

[0022] Such a control system for a commercial dishwasher also has other decisive advantages: the conductivity of the treatment liquid is not only influenced by the concentration of the detergent, but also by other factors, in particular by increased dirt ingress into the treatment liquid, a change in the raw water quality, defects in the dosing system or by incorrect operation, which sometimes occur during normal operation of the dishwasher.

[0023] If one of the factors, such as the amount of dirt being added, changes during the operation of the dishwasher, a conductivity sensor would detect a change in conductivity and subsequently change the dosage of detergent, even though the concentration of the detergent may be correct.

[0024] This would not only lead to an undesirably high or low concentration of cleaning agent, i.e. to an incorrect concentration, which will sometimes be significantly higher than a deviation in concentration due to the above-mentioned slight change or increase in wear between two commissionings, which would either worsen the cleaning result or lead to an unnecessarily high consumption of cleaning agent, but it would also lead to the dosing pump being switched on and off more frequently, which in turn increases wear.

[0025] The present invention thus provides a simpler and more cost-effective method and a corresponding dishwasher that nevertheless ensures the desired accuracy with regard to the concentration of the cleaning agent in the treatment liquid and in some cases even exceeds the accuracy of significantly more complicated and complex, as well as more expensive and more susceptible systems. In particular, a method and a dishwasher according to the invention are not susceptible to a significantly changing dirt load during the washing operation, as is often the case with commercial dishwashers, and maintains the desired concentration essentially at a constant or consistent level, without major fluctuations, regardless of a changing dirt load during normal operation or washing operation of the dishwasher.

[0026] Preferably, the dishwasher is designed such that during initial commissioning and / or during subsequent commissioning and / or during normal operation of the dishwasher, the amount of additional raw water required to be fed into the tank (in order to compensate for the water or treatment liquid consumption) is determined, in particular measured or input or is predetermined by the volume of the tank, and depending on this amount of raw water fed in, cleaning agent is fed by means of the dosing pump, wherein the feed amount is controlled over the length of a period over which the dosing pump is operated, wherein the length of the period is determined by the control device taking into account the correction factor KA.Preferably, during normal operation of the dishwasher, the electrical conductivity of the treatment liquid is not measured or at least not passed on to the control device or at least not processed by the control device in order to control the dosing pump, in particular the operating time or switch-on time of the dosing pump or the switching on and off of the dosing pump.

[0027] In a particularly preferred embodiment, the dishwasher further comprises a temperature sensor designed to measure the temperature of the raw water and / or the treatment liquid, wherein the temperatures and / or temperature differences are taken into account by the control device when determining the correction factor KA. In this way, the control becomes even more precise because the electrical conductivity depends on the temperature of the measured liquids, in particular the temperature of the raw water and the temperature of the treatment liquid. Particularly in cases where the temperature differs between two measurements, for example, a different temperature was present during initial commissioning than during subsequent commissioning, the temperature differences can be taken into account and the desired concentration can be set more precisely.In a preferred embodiment, the temperature changes or temperature differences can also be taken into account during normal operation in order to adjust the dosing quantities even more precisely.

[0028] In a further embodiment, the conductivity of the raw water is measured during a subsequent commissioning, preferably during all subsequent commissionings, and fed to the control device to determine the correction factor. In a simple embodiment, this measurement is omitted, particularly if it is assumed that the quality of the raw water will not change and thus the conductivity of the raw water will remain constant over time. However, an additional measurement of the conductivity of the raw water during a subsequent commissioning increases accuracy, particularly if there are fluctuations in the quality of the raw water. Such a measurement also compensates for possible temperature differences in the measurements, in addition to or instead of a calculated compensation or a calculated adjustment or correction if a temperature sensor is present, as explained above.

[0029] Particularly preferred and detailed embodiments of a dishwasher according to the invention are described in claims 5-11, which particularly detail preferred procedures, measurements and calculations which enable particularly reliable results and particularly reliable and simple control of the dishwasher.

[0030] During initial commissioning, the electrical conductivity LR of the raw water is determined using the conductivity sensor. Detergent is then added to the tank by operating the dosing pump to generate the treatment fluid. The dosing pump is operated at a constant output, which is usually specified by the pump itself—usually a fixed output level, as is particularly the case with peristaltic pumps, which are preferred—over a specific period of time. The amount of detergent to be dosed is therefore controlled exclusively on a time-based basis, i.e., by the duration for which the dosing pump, in particular the peristaltic pump, is operated.

[0031] This period tx, with x=o, i.e. the period to during initial commissioning, is determined on the basis of a nominal flow rate PN of the dosing pump, the quantity of raw water fed into the tank, which is in particular measured or entered, or the volume V of the tank and a target concentration, whereby the period tx = to thus determined is subsequently stored.

[0032] The nominal flow rate PN of the dosing pump can be a specification of the dosing pump, but it can also be a starting value for the dosing pump's performance, which is determined or assumed. This value is preferably also stored in the control device or the associated storage device. This flow rate is the starting value from which the subsequent operation of the dishwasher is based.

[0033] For subsequent commissionings, the tank is filled with raw water in a similar manner, cleaning agent is added, and the electrical conductivity of the treatment liquid is subsequently measured. To supply the cleaning agent, the dosing pump is operated for a period tx, with x≥1. This results in a period t1 for the first subsequent commissioning after the initial commissioning, a period t2 for the second subsequent commissioning, and so on. The index 0 or x=0 therefore represents the initial commissioning, which is divided into the indices 1, 2, 3, 4, ... or x=1, x=2, x=3, etc. for subsequent commissionings.

[0034] To determine the length of the period tx, therefore t1 for the first subsequent commissioning, the period of the previous commissioning tx-1, in this case and for the first subsequent commissioning therefore to, is multiplied by the correction factor KAx-1 determined during the previous commissioning, in this case KAo. Since the correction factor KAo was set to 1 during the initial commissioning, the period t1 for the first subsequent commissioning corresponds to the period of the initial commissioning to.

[0035] During subsequent commissioning, the correction factor and thus the time period tx increases due to increasing wear.

[0036] With regard to the electrical conductivity of the raw water LR, one embodiment prefers to use the electrical conductivity determined during initial commissioning. This is generally possible because the raw water often has a consistent quality.

[0037] In another embodiment, however, it is also possible, particularly during subsequent commissioning, to redetermine the electrical conductivity of the raw water LRx each time and then use the newly determined electrical conductivity of the raw water for further calculations. In this case, the LR value is replaced in the calculations by the new, adjusted, or corrected LR value (alternatively also called LRx). This also allows changes in the raw water to be detected, and the dishwasher can react accordingly. Changes in the raw water can occur if the water source changes intentionally or unintentionally by the user.

[0038] In a further preferred embodiment, the dishwasher and the control device are designed such that, when determining the electrical conductivities L of the raw water and / or the treatment liquid, the temperatures T determined by the temperature sensor and a temperature constant and / or cell constant Z of a conductivity sensor are taken into account. The temperature constant takes into account, in particular, the change in the electrical conductivity of the liquid to be measured as a function of temperature. This temperature constant can be used uniformly for all measurements; however, it is also possible to use a different temperature constant for measuring the raw water than for measuring the treatment liquid.

[0039] The cell constant refers to a property of the conductivity sensor. When calibrating a specific sensor, for example, with a calibrated solution of known conductivity, the cell constant can be adjusted accordingly, making the measurements more accurate. This does not change the precision of the measurements; the consistency of the measurements, and thus also the consistency of the control, is maintained at a high level in both cases, with or without calibration and with or without special adjustment of the cell constant.

[0040] According to a further inventive aspect independent of the above-mentioned embodiments, a dishwasher with a washing chamber in which at least one dispensing device for dispensing a treatment liquid is arranged is also provided, which comprises the following: a tank for receiving the treatment liquid, a first supply device for supplying raw water into the tank, a storage container for a cleaning agent, a second supply device with a metering pump, in particular a peristaltic pump, for supplying cleaning agent from the storage container into the tank, a third supply device with a washing pump for supplying treatment liquid from the tank to the at least one dispensing device, and a conductivity sensor for determining the conductivity of the treatment liquid, characterized in that the third supply device comprises a line or a feed which connects the tank to the at least one dispensing device, wherein the washing pump is provided within this line or this feed, or in parts thereof, and between the tank and the dispensing device, wherein further the conductivity sensor is also provided within this line or this feed, or in parts thereof, and between the washing pump and the dispensing device or between the feed and the washing pump.

[0041] This positioning of the conductivity sensor has the advantage that the conductivity sensor's electrodes are constantly flushed, sometimes with a high flow rate, preventing them from becoming contaminated and thus providing more accurate and reliable results. Furthermore, the service life of the conductivity sensor is significantly increased compared to state-of-the-art devices in which the conductivity sensor is located in the tank itself. This positioning also promotes more precise measurements due to the separation from the cleaner supply and the heating system.

[0042] Such an independently inventive positioning of the conductivity sensor can be chosen both in a dishwasher as described above and in dishwashers as described in connection with the prior art, which regularly or essentially continuously measure the conductivity of the treatment liquid. Since these dishwashers are even more dependent on regular and correct conductivity measurements, even during normal operation of the dishwasher and between uses, such an inventive positioning of the conductivity sensor is of particular importance in such dishwashers.

[0043] In a particular embodiment of the dishwasher, it comprises a display device capable of displaying measured values ​​from sensors of the dishwasher, in particular measured values ​​from a conductivity sensor or a temperature sensor, or capable of displaying values ​​and results calculated or determined by the control device, or information entered by the user, or other states and data of the dishwasher. This enables the user to monitor the operating status of the dishwasher at any time and, if desired, make changes.

[0044] In a particularly preferred embodiment, the control device is designed such that it generates a warning signal when the correction factor KA or KAx exceeds a predetermined or adjustable value, wherein the dishwasher preferably comprises a display device which outputs an optical or an acoustic signal when the predetermined or adjustable value of the correction factor KA or KAx is exceeded.

[0045] An increase in the correction factor value indicates increased wear and / or reduced flow rate of the dosing pump, due to wear or other reasons. Reaching a predetermined or adjustable value indicates that maintenance and / or replacement of wearing parts, such as replacing the hoses that are squeezed in the peristaltic pumps, should be considered. An indicator provides the user with an early notification or warning, allowing them to be informed in a timely manner about the wear status of the dishwasher, and in particular of the dosing pump, and to organize appropriate maintenance steps, including the procurement of parts.

[0046] In another preferred embodiment, the dishwasher also includes an input device by means of which manual settings can be made. This allows the user to easily and at any time adjust the operation and control of the dishwasher according to their preferences, possibly also taking the displayed values ​​into account.

[0047] The invention further relates to a method for operating such a commercial dishwasher, wherein with regard to the advantages and special aspects, reference is made to the above explanations in order to avoid repetition.

[0048] Further features and advantages of the dishwasher according to the invention and the method according to the invention will become even clearer with reference to the following figures: Fig. 1 shows schematically a structure of an embodiment of a dishwasher according to the invention, and Fig. 2 schematically shows a flow chart according to an embodiment of the present invention.

[0049] Fig. 1 schematically shows the structure of an embodiment of a dishwasher 10 according to the invention, which comprises a washing chamber 20 with a plurality of dispensing devices 110 for dispensing treatment liquid into the washing chamber 20. In this embodiment, two upper dispensing devices and two lower dispensing devices are provided, which are arranged rotatably. A washing basket 120 for receiving dishes to be cleaned is schematically shown between the upper and lower dispensing devices 110.

[0050] The dishwasher 10 comprises a tank 200 with a heater 210 for holding a treatment liquid. The tank 200 can be filled with raw water via a first supply device 250.

[0051] Furthermore, the dishwasher 10 comprises a storage container 300 for a cleaning agent, which can be dosed from the storage container 300 into the tank via a second feed device 330 with a dosing pump 320, here a peristaltic pump.

[0052] The dishwasher 10 further comprises a third supply device 230 with a wash pump 220, via which treatment liquid from the tank 200 can be supplied to the dispensing devices 110.

[0053] Within the third supply device 230 and downstream of the wash pump 220, a conductivity sensor 240 is provided, which can measure the conductivity of the treatment liquid. The conductivity sensor 240 is connected to a control device 500 so that the measured values ​​of the conductivity sensor 240 can be forwarded to the control device 500. The control device 500 includes a memory so that the measurement results of the conductivity sensor 240 or other data information can be stored.

[0054] The dishwasher further comprises an input device 800, via which a user can enter data and information. For example, a user can explicitly enter that an initial start-up should occur after starting the dishwasher, or can also specify that this is a subsequent start-up. The control device can also be designed, for example, such that it always assumes that a new start-up is a subsequent start-up, as long as there is no explicit external input from a user that it is an initial start-up, or the control device detects this automatically, for example because it has detected that the dosing pump has been replaced.

[0055] In a particular embodiment, the dishwasher also includes a display device 820. The display device is capable of showing the user certain modes or operating data of the dishwasher, or even certain measured values.

[0056] This gives the user a good overview of the operating status of the dishwasher and, if necessary or desired, he can also enter changes via the input device 800, for example a manual correction factor, as described above.

[0057] Furthermore, the dishwasher 10 comprises a drain line 630 in which a drain pump 600 is provided so that treatment liquid, in particular contaminated treatment liquid, can be removed from the tank 200 and disposed of.

[0058] The embodiment of the dishwasher 10 also includes a boiler 400 with a heater 410 for receiving a rinse liquid. The rinse liquid can be fed to the dispensing devices 110 via a further supply device 430, in which a rinse pump 420 is provided.

[0059] The boiler 400 is fed by a supply device 440 for supplying raw water, wherein a storage container 450 for rinse aid is also provided, which is added by means of a dosing pump 460.

[0060] Fig. 2 shows, in schematic form, a flow chart according to the present invention: Step S is the start-up of the dishwasher; in step B, the control device detects whether this is a first-time start-up (or a system reset). As explained above, the user can also enter, for example, that this is a first-time start-up.

[0061] If so, steps N are to fill the tank with raw water, measure the electrical conductivity of the raw water using the conductivity sensor, add cleaning agent, measure the electrical conductivity of the resulting treatment liquid, calculate the difference in electrical conductivities and save the data.

[0062] In a further step, the correction value KAo is set to 1, as described above.

[0063] If not, as steps X the tank is filled with raw water, in this embodiment the electrical conductivity of the raw water is also measured using the conductivity sensor (although in another embodiment the measurement of the electrical conductivity of the raw water is omitted at this point and the value already measured during initial commissioning can be used), cleaning agent is added, the electrical conductivity of the resulting treatment liquid is measured, the difference in the electrical conductivities is calculated and the data is saved.

[0064] In a subsequent step, a new correction factor KAx is calculated as described above.

[0065] Based on the calculations and the current correction factor, the normal operation of the dishwasher is now initiated, and the control device controls the dishwasher, in particular the dosing of the detergent by controlling the duration of operation of the dosing pump, on the basis of the determined values, in particular the determined correction factor KAx.

Claims

1. A commercial dishwasher (10) with a washing chamber (20) in which at least one dispensing device for dispensing a treatment liquid is arranged, wherein the dishwasher (10) further comprises: - a tank (200) for receiving the treatment liquid, - a first supply device (250) for supplying raw water into the tank (200), - a reservoir (300) for a cleaning agent, - a second supply device (330) with a dosing pump (320), in particular a peristaltic pump, for supplying cleaning agent from the reservoir (300) into the tank (200), - a third supply device with a washing pump (220) for supplying treatment liquid from the tank (200) to the at least one dispensing device, and - a conductivity sensor (240) for determining the conductivity of the treatment liquid, wherein the dishwasher (10) comprises a control device, which is designed such that it is able to recognize, during a start up of the dishwasher (10), whether this is an initial start-up or a subsequent start up, and / or the dishwasher (10) comprises a control device and an input device (800), via which a user may enter that this is an initial start-up or a subsequent start up, wherein the control device comprises a memory device, wherein the dishwasher (10) and the control device are designed such that at least during an initial start-up, the electrical conductivity of the raw water is measured by means of the conductivity sensor (240), and during both an initial start-up and also during a subsequent start up, the electrical conductivity of the treatment fluid is measured after supplying a cleaning agent into the raw water by means of the conductivity sensor (240), wherein the control device determines, on the basis of these measured values and on the basis of a comparison of these measured values during each start up, a correction factor KA, which is linked to a decreasing flow rate of the dosing pump (320) over the service life.

2. The dishwasher (10) according to claim 1, characterized in that the dishwasher (10) is designed such that, during an initial start-up and / or during a subsequent start up and / or during normal operation of the dishwasher (10), the volume of the raw water supplied into the tank (200) is determined, in particular is measured or entered, or is determined by the volume of the tank (200), and, depending on this volume of supplied raw water, cleaning agent is supplied by means of the dosing pump (320), wherein the supply volume is controlled via the length of time, during which the dosing pump (320) is operated, wherein the length of time is determined by the control device taking the correction factor KA into account.

3. The dishwasher (10) according to claim 1 or 2, wherein the dishwasher (10) further comprises a temperature sensor, which is designed such that it can measure the temperature of the raw water and / or of the treatment liquid, wherein the control device is designed such that the temperatures and / or the temperature differences are taken into account during the determination of the conductivity and / or during the determination of the correction factor KA, and / or characterized in that during a subsequent start up, preferably during all subsequent start ups, the conductivity of the raw water is also measured and is supplied to the control device for determining or changing the correction factor.

4. The commercial dishwasher (10) according to one of the preceding claims, wherein the control device is designed such that, during start up of the dishwasher (10), in the case that the control device recognizes and / or it is entered via the input device (800), that this is an initial start-up, the following steps are carried out: - filling the tank (200) with raw water, wherein the volume VN of the raw water supplied into the tank (200) during the start up is determined, in particular is measured or entered, or is predetermined by the volume of the tank (200), - measuring and storing the electrical conductivity LR of the raw water by means of the conductivity sensor (240), - supplying cleaning agent into the tank (200) by operating the dosing pump (320) for a time tx, where x=0, to generate the treatment liquid, wherein the time tx, where x=0, is determined by the control device on the basis of a nominal flow rate PN of the dosing pump (320), the volume of raw water VN filled into the tank (200), and a predetermined or adjustable target concentration CSOLL, and storing the time tx, where x=0, - measuring and storing the electrical conductivity LN of the treatment liquid, - determining and storing the difference ΔLN of the electrical conductivities, wherein ΔLN=LN-LR, - setting and storing a correction factor KAx, where x=0, to the value 1, wherein the control device is designed such that during start up of the dishwasher (10), in the case that the control device recognizes that this is a subsequent start up, and / or no entry is carried out via the input device (800) that this is an initial start-up, and / or an entry is carried out via the input device (800) that this is a subsequent start up, the following steps are carried out: - filling the tank (200) with raw water, wherein the volume Vx of the raw water supplied into the tank (200) during the start up is determined, in particular is measured or entered, or is predetermined by the volume of the tank (200), - supplying cleaning agent into the tank (200) by operating the dosing pump (320) for a time tx to generate the treatment liquid, wherein the time tx, where x≥1, is determined by the control device by multiplying the stored time tx-1 by the stored correction factor KAx-1 and depending on the volume of raw water supplied into the tank (200), where t x = t 0 × K A x − 1 × Vx VN - measuring and storing the electrical conductivity Lx of the treatment liquid, - determining and storing the difference ΔLx of the electrical conductivities, wherein ΔLx=Lx-LR, - setting and storing a new correction factor KAx, wherein the correction factor KAx is determined according to the following formula: K A x = K A x − 1 × Δ LN Δ L x 5. The dishwasher (10) according to claim 4, characterized in that the control device is designed such that, during start up of the dishwasher (10), in the case that this is a subsequent start up, that after the step of filling the tank (200) with raw water, the following step is carried out: - renewed measuring and storing of the electrical conductivity LR of the raw water by means of the conductivity sensor (240), - wherein, during the step of determining and storing the difference ΔLx of the electrical conductivity, the electrical conductivity LR of the raw water, determined again during the subsequent start up, is taken into account, where ΔLx=Lx-LR.

6. The dishwasher (10) according to claim 4 or 5, characterized in that the time tx, for which the cleaning agent is supplied, additionally taking a manual correction factor KMx into account, which can preferably be entered or selected by a user or a technician via an input device (800) of the dishwasher (10), is determined and subsequently stored according to the following formula: t x = t 0 × K A x − 1 × K M x 7. The dishwasher (10) according to one of claims 4 to 6, characterized in that, during a normal operation of the dishwasher (10), the volume VFÜLL of the raw water supplied into the tank (200) during the normal operation is determined, in particular is measured or entered, and, depending on this volume of the supplied raw water, cleaning agent is supplied by means of the dosing pump (320), which is operated for a time tdx, wherein the time tdx is determined by the control device on the basis of the volume VFÜLL of the supplied raw water, the target concentration CSOLL, the nominal flow rate PN of the dosing pump (320), and the correction factor KAx, according to the following formula: t d x = VF Ü LL x CSOLL x K A x PN 8. The dishwasher (10) according to one of claims 4 to 6, characterized in that during a normal operation of the dishwasher (10), the volume VFÜLL of raw water supplied into the tank (200) during the normal operation is determined, in particular is measured or entered, and, depending on this volume of supplied raw water, cleaning agent is supplied by means of the dosing pump (320), which is operated for a time tdx, wherein the time tdx is determined by the control device on the basis of the volume VFÜLL of the supplied raw water, the target concentration CSOLL, the nominal flow rate PN of the dosing pump (320), the correction factor KAx, and a manual correction factor KMx, which can preferably be entered or selected by a user or a technician via an input device (800) of the dishwasher (10), according to the following formula: td x = VF Ü LL × CSOLL × KA x × KM x PN 9. The dishwasher (10) according to one of the preceding claims, characterized in that it further comprises a temperature sensor for determining the temperature of the raw water and / or of the treatment liquid, further preferably characterized in that the temperatures of the raw water and / or of the treatment liquid, determined by the temperature sensor, are taken into account as correction factor KA during the determination of the electrical conductivity of the raw water and / or of the treatment liquid and / or during a comparison of the determined electrical conductivities.

10. The dishwasher (10) according to claim 8 or 9, characterized in that the dishwasher (10) and the control device are designed such that, during the determination of the electrical conductivity L of the raw water and / or of the treatment liquid, the temperatures T determined by the temperature sensor and a temperature constant and / or a cell constant Z of a conductivity sensor (240) are taken into account, wherein the electrical conductivities L are calculated according to the following formula: L = Z × 100 100 + σ T × T − 25 o _ C × G where G is the electrical conductivity value measured by the conductivity sensor (240) and σT is a general or a treatment agent specific temperature constant.

11. The dishwasher (10) according to one of the preceding claims, characterized in that the third supply device comprises a line or a feeder, which connects the tank (200) to the at least one dispensing device, wherein the washing pump (220) is provided within this line or feeder and between the tank (200) and the dispensing device, wherein furthermore the conductivity sensor (240) is likewise provided within this line or feeder and either between the washing pump (220) and the dispensing device or between the tank (200) and the washing pump (220), and / or is characterized in that it comprises a display device (820), which is able to display measured values from the sensors of the dishwasher (10), in particular measured values from a conductivity sensor (240) or from a temperature sensor, or is able to display values and results calculated or determined by the control device, or information entered by the user, or other states and data of the dishwasher (10), and / or is characterized in that the control device is designed such that it generates a warning signal when the correction factor KA or KAx exceeds a predetermined or adjustable value, wherein the dishwasher (10) preferably comprises a display device (820), which, upon exceeding the predetermined or adjustable value of the correction factor KA or KAx, outputs an optical or an acoustic signal, and / or is characterized in that manual adjustments, which can be made by means of the input device (800), or can be entered by means of the values and / or corrections and / or correction values, can be used by the control device for controlling the dishwasher (10).

12. The dishwasher (10) according to one of claims 4 to 11, characterized in that the dishwasher (10) is designed such that the target concentration is adjustable after the initial start-up to a value CSOLLx, in which case the correction factor KAx is multiplied by an additional adaptation factor CSOLLx / CSOLL.

13. A method for operating a dishwasher (10) according to one of the preceding claims, characterized in that the dishwasher (10) comprises a control device, which, during start up of the dishwasher (10) recognizes whether this is an initial start-up or a subsequent start up, and / or wherein the dishwasher (10) comprises an input device (800), via which a user can enter that this is an initial start-up or a subsequent start up, wherein both during an initial start-up and also during a subsequent start up, the electrical conductivity of the raw water and of the treatment liquid is measured by means of the conductivity sensor (240) after supplying a cleaning agent into the raw water, wherein the control device determines, on the basis of these measured values and on the basis of a comparison of these measured values during each start up, a correction factor KA, which is linked to a decreasing flow rate of the dosing pump (320) over the service life.

14. The method according to claim 13, characterized in that during an initial start-up and / or during a subsequent start up and / or during a normal operation of the dishwasher (10), the volume of the raw water supplied into the tank (200) is determined, in particular is measured or entered, or is determined by the volume of the tank (200), and, depending on this volume of supplied raw water, cleaning agent is supplied by means of the dosing pump (320), wherein the supply volume is controlled for the length of time, for which the dosing pump (320) is operated, wherein the length of time is determined by the control device while taking the correction factor KA into account.