The invention relates to a conveyor dishwasher for washing washware, with the conveyor dishwasher having at least one wash zone with at least one wash nozzle for spraying wash liquid onto the washware, at least one pre-rinse zone with at least one pre- rinse nozzle for spraying pre-rinse liquid onto the washware, and at least one final rinse zone with at least one final rinse nozzle for spraying final rinse liquid onto the washware, with at least some of the final rinse liquid which is sprayed in the final rinse zone being reused as pre-rinse liquid, and with a metering device which is associated with the final rinse zone being provided for adding a disinfectant to the final rinse liquid in a metered manner.

The invention also relates to a method for operating a conveyor dishwasher of this kind.

Accordingly, the invention relates, in particular, to a flight-type dishwasher (flight- type warewasher) or a rack-conveyor dishwasher (rack-conveyor warewasher) and to a corresponding method for operating a conveyor dishwasher of this kind.

Conveyor dishwashers (conveyor warewashers) are used in the commercial sector. In contrast to domestic dishwashers, in which the washware to be cleaned remains stationary in the machine during cleaning, in conveyor dishwashers the washware is conveyed through various treatment zones of the machine.

In the case of conveyor dishwashers, the washware, for example tableware, pots, glasses, cutlery and other utensils which are to be cleaned, is conveyed through a plurality of treatment zones, for example pre-wash zone(s), main wash zone(s), post-wash or pre- rinse zone(s), final rinse zone(s) and drying zone(s). A conveyor apparatus which generally has compartments for accommodating washware is used to convey washware in a conveying direction through the conveyor dishwasher. In the case of a flight-type dishwasher, the compartments can be formed by supporting fingers on a conveyor belt of the conveyor apparatus. In the case of rack-conveyor dishwashers, dish racks in which compartments can be formed in order to accommodate the washware to be treated serve as the conveyor apparatus. It is feasible here for the dish racks to be conveyed through the rack-conveyor dishwasher by a conveying device.

Treatment agents, for example detergents, rinse aids and disinfectants, are required for operating a dishwasher. Disinfectants are chemical products with a disinfectant action which can be contained in the detergent or are added separately in a metered manner. In the field of commercial dishwashing by means of conveyor dishwashers, it is known to ensure the hygiene performance of cleaning processes with the aid of thermal disinfection. As an alternative to thermal disinfection, a low-temperature process with chemical disinfection is also known. In this process, the wash and rinse temperatures of the conveyor dishwasher are lowered to, for example, 50 ⁰ C and a corresponding disinfectant is employed for chemical disinfection. The disinfectant is usually metered into the final rinse liquid and must not fall below a minimum concentration. A critical factor for implementation of the so-called low-temperature dishwashing method is reliable and accurate metering of the disinfectant component.

US 4,228,813 B has already disclosed a conveyor dishwasher in which a disinfectant is added in a metered manner in the final rinse zone. The quantity of disinfectant added in a metered manner per unit time is constant and predefined in this case.

EP 0 361 380 A2 discloses a method for cleaning, disinfecting and rinsing washware in commercial conveyor dishwashers. In this prior art, it has been found that surfactants of the final rinse agent can serve not only for final rinsing and drying of the washware without leaving residues, but also for effectively cleaning the washware. In this way, it is possible to reliably eliminate any existing germs and bacteria and achieve an equally good cleaning effect in spite of a reduction in operating temperature and saving on cleaning agent.

Accordingly, in conveyor dishwashers which have been known to date, in which the hygiene performance is provided by means of chemical disinfection, the disinfectant component is metered into the final rinse zone. However, this approach has the disadvantage that inadequate and faulty metering of the disinfectant component, for example on account of failure of components of the metering device, blockages in metering pipes or hoses etc., can immediately lead to a hygienically critical situation.

On the basis of this problem, the object of the present invention is to achieve reliable metering of the disinfectant component in low-temperature dishwashing processes, in order to thus avoid possible hygiene safety risks. A further object of the invention is that of adapting the disinfection performance to the machine capacity.

According to the invention, these objects are achieved by the subject matter of independent patent claim 1. The object relating to the method is achieved by independent patent claim 11.

With regard to the conveyor dishwasher, the invention thus proposes that, in addition to a metering device which is associated with the final rinse zone, a metering device which is associated with the pre-rinse zone is also provided for adding a disinfectant to the pre-rinse liquid in a metered manner. A sensor device is also provided. The sensor device can be designed to detect the concentration of disinfectant in the final rinse liquid which is sprayed in the final rinse zone. As an alternative to this, it is possible for the sensor device to be designed to detect the concentration of disinfectant in the pre-rinse liquid which is sprayed in the pre-rinse zone. Furthermore, the invention provides a control device which is designed to actuate at least one of the metering devices, and preferably the metering device which is associated with the pre-rinse zone, as a function of the concentration of disinfectant which is detected by the sensor device in such a way that disinfectant is added in a metered manner.

In one possible embodiment of the conveyor dishwasher according to the invention, provision is made for the metering device which is associated with the final rinse zone to be designed in such a way that a predefined quantity of disinfectant which is constant per unit time is added in a metered manner to the final rinse liquid, with the sensor device being designed to detect the concentration of disinfectant in the final rinse liquid which is sprayed in the final rinse zone, and with the control device being designed to actuate the metering device which is associated with the pre-rinse zone, as a function of the concentration of disinfectant which is detected by the sensor device, in such a way that disinfectant is added in a metered manner to the pre-rinse liquid.

The advantages which can be achieved with the solution according to the invention are considerable. Accordingly, it is possible for a predefined quantity of disinfectant which is constant per unit time to be added in a metered manner in the final rinse zone of the conveyor dishwasher while, at the same time and depending on requirements, disinfectant is also metered into the pre-rinse zone. Specifically, it is feasible to add a defined quantity of disinfectant to the final rinse liquid in a metered manner in the final rinse zone by means of the metering device. The final rinse liquid which is mixed with the disinfectant is sprayed onto the washware which is to be treated in the final rinse zone and at least some of said liquid is collected again in a pre-rinse tank of the pre-rinse zone. Since this process step consumes some of the disinfectant - depending on the quantity of washware and the degree of soiling - the concentration of the disinfectant in the sprayed final rinse liquid, for example in a pump line system of the pre-rinse zone, is preferably determined by a defined measurement method. If there is a deviation from a defined setpoint value, the concentration of disinfectant is adapted by means of a corresponding control means.

Advantageous developments of the solution according to the invention are indicated in the dependent claims.

The invention is described below with reference to the associated drawings on the basis of a preferred embodiment as an example.

In the drawing

Fig. 1 shows a schematic longitudinal sectional view through a conveyor dishwasher according to the invention.

Fig. 1 shows a conveyor dishwasher 1 having a conveyor apparatus 2 for conveying washware (not illustrated) in a conveying direction T through the conveyor dishwasher 1. The conveyor dishwasher 1 has at least one wash zone, as illustrated in fig. 1 for example, a pre-wash zone 20 and a main-wash zone 30 which is arranged downstream of the pre- wash zone 20 as seen in the conveying direction T.

As seen in the conveying direction T, a post-wash zone or pre-rinse zone 40 is arranged downstream of the at least one wash zone 20, 30, and at least one final rinse zone, for example only a single final rinse zone 50 as illustrated, is arranged downstream of the post- wash zone or pre-rinse zone 40. In the conveyor dishwasher 1 illustrated in fig. 1, the final rinse zone 50 is followed in the conveying direction T of the washware by a drying zone 60.

The respective zones 20, 30, 40, 50, 60 of the conveyor dishwasher 1 can be separated from one another by means of separating curtains 3. In the embodiment of the conveyor dishwasher 1 illustrated in fig. 1, an inlet tunnel 10 itself is also separated from the inlet 9 of the conveyor dishwasher 1 by a separating curtain 3. The provision of the separating curtains 5 prevents wash liquid and final rinse liquid spraying between zones and prevents vapors escaping from the conveyor dishwasher 1.

Said treatment zones 20, 30, 40, 50 of the conveyor dishwasher 1 have associated spray nozzles 21, 22, 31, 32, 41, 42, 43, 51, 52, 53. The spray nozzles 21, 22, 31, 32, 41, 42, 43, 51, 52, 53 serve to spray liquid onto the washware to be treated as the said washware is conveyed through the respective treatment zones 20, 30, 40, 50 by the conveyor apparatus 2. The individual spray systems of the treatment zones 20, 30, 40, 50 ensure that the washware to be treated is sprayed down both from the top and from the bottom.

In the conveyor dishwasher 1 which is schematically illustrated in fig. 1, the final rinse zone 50 not only has downwardly directed upper final rinse nozzles 51 and upwardly directed final rinse nozzles 52, but also transversely directed lateral spray nozzles 53 on either side of the conveyor apparatus 2. The use of lateral final rinse nozzles 53 permits areas of the washware (areas of the dishes) to be sprayed with final rinse liquid in a targeted manner in shadow zones too. The use of lateral final rinse nozzles 53 in the final rinse zone 50 has a significant advantage in terms of the final rinse result (effective rinsing- off of detergent residues from dish surfaces in shadow zones too) over systems in which only upper and lower final rinse nozzles 51, 52 and no transversely directed lateral final rinse nozzles 53 are provided in the final rinse zone 50, specifically when the conveying system is fully loaded, that is to say with plate-to-plate loading of the dish rack.

The post-wash zone or pre-rinse zone 40, the main-wash zone 30 and the pre-wash zone 20 also have associated tanks (pre-rinse tank 44, main-wash tank 34, pre-wash tank 24) for accommodating sprayed liquid and/or for providing liquid for the spray nozzles 21, 22, 31, 32, 41, 42, 43 of the relevant treatment zones 20, 30, 40.

As already indicated, final rinse liquid, which comprises fresh water with rinse aid which is added in a metered fashion, is sprayed onto the washware (not illustrated) by means of final rinse nozzles 51, 52, 53 which are arranged above and below the conveyor apparatus 2 and on the side in the conveyor dishwasher 1 which is illustrated in fig. 1. A portion of the sprayed final rinse liquid is conveyed from treatment zone to treatment zone via a cascade system in the opposite direction to the conveying direction T of the washware. The remaining portion of the final rinse liquid which is sprayed in the final rinse zone 50 is conducted directly to the pre-wash tank 24, which is associated with the pre- wash zone 20, via a valve Vl and a bypass line 7.

In the cascade system, the final rinse liquid which is sprayed by the final rinse nozzles 51, 52, 53 flows from the final rinse zone 50 into the pre-rinse tank 44 which is associated with the pre-rinse zone 40 due to the force of gravity. The final rinse liquid which is sprayed in the final rinse zone 50 and collected by the pre-rinse tank 44 is then delivered to the spray nozzles of the pre-rinse zone 40 (upper and lower pre-rinse nozzles 41, 42, 43) with the aid of a pre-rinse pump 45.

Wash liquid is rinsed off from the washware in the pre-rinse zone 40. The liquid which is produced in the process flows into the main-wash tank 34, which is associated with the first main-wash zone 30, due to the force of gravity. A discharge element 4, for example a discharge base or a baffle plate, which conducts a portion of the pre-rinse liquid which is sprayed by the pre-rinse nozzles 41, 42, 43 into the main-wash tank 34 is preferably provided for this purpose. According to another embodiment (not shown) of the conveyor dishwasher 1, the outlet element 4 can be dispensed with if the main-wash tank 34 extends as far as beneath the pre-rinse nozzles 41, 42, 43 of the pre-rinse zone 40.

The liquid accommodated by the main-wash tank 34 of the main-wash zone 30 is usually provided with a detergent and sprayed onto the washware by means of the spray nozzles of the main-wash zone 30 (upper and lower main- wash nozzles 31, 32) with the aid of a main- wash pump 35. The wash liquid which is sprayed by the main-wash nozzles 31, 32 then flows back into the main-wash tank 34 due to the force of gravity.

The main-wash tank 34 is fluidically connected to the pre-wash tank 24 which is associated with the pre-wash zone 20 via an overflow line 5. The wash liquid which is sprayed in the main- wash zone 30 enters the pre-wash tank 24 via this overflow line 5 when there is a sufficient quantity of wash liquid in the main-wash tank 34.

The liquid which is accommodated in the pre-wash tank 24 of the pre-wash zone 20 is then sprayed onto the washware by means of the spray nozzles of the pre-wash zone (upper and lower pre-wash nozzles 21, 22) with the aid of a pre-wash pump 25 and a line system 26 in order to remove coarse particles of dirt from the washware. The wash liquid which is sprayed by the pre-wash nozzles 21, 22 then flows back into the pre-wash tank 24 due to the force of gravity.

The pre-wash tank 24 is provided with an overflow line 6 which is used to feed the excess quantity of liquid to a waste water system if a liquid level in the pre-wash tank 24 is exceeded.

As already indicated, the liquid which is sprayed in the main- wash zone 30 and in the pre-wash zone 20 preferably contains detergent which is added in a metered fashion with the aid of a detergent metering apparatus (not shown in fig. 1), for example, to the liquid accommodated in the main-wash tank 34 of the main-wash zone 30.

As already mentioned, the final rinse zone 50 is followed by the drying zone 60 in the conveying direction T. In the drying zone 60, the washware is dried using dry and heated air in order to blow off and/or dry up the moisture on the washware. In order to keep the moisture content of the air in a range which is expedient for drying, it is feasible, for example, to supply external room air to the drying zone 60 via an opening, for example through the outlet opening for the washware.

The warm and moisture-laden air in the drying zone 60 is then drawn-off from the drying zone 60 via a further opening, for example with the aid of a fan 61. It is advantageous here if the exhaust-air stream from the drying zone 60 passes a heat recovery device 62 in which, for example, a heat exchanger can be provided. The heat recovery device 62 serves to recover at least some of the thermal energy contained in the exhaust air.

If, before initial starting of the conveyor dishwasher 1, the pre-wash tank 24, the main-wash tank 34 and the pre-rinse tank 44 are empty or insufficiently filled, said tanks first have to be filled with fresh water via a fresh-water line 8 and/or by spraying final rinse liquid in the final rinse zone 50. The fresh-water line 8 can be connected to a fresh-water supply system via an actuable valve V4. The quantity of wash liquid available in the main- wash zone 30 and in the pre-wash zone 20 can in each case be monitored and signalled to a control apparatus (not explicitly illustrated) with the aid of a level sensor which is provided in the main-wash tank 34 and with the aid of a level sensor which is provided in the pre- wash tank 24.

The final rinse zone 50 can - as illustrated in fig. 1 - have an associated fresh-water container 57 for temporarily storing at least a portion of the fresh water which is provided for final rinsing purposes. The fresh-water container 57 is firstly provided with a freshwater connection which can be connected to a fresh-water supply system via an actuable fresh-water feed valve V3, and secondly is connected to the intake end of a final rinse pump 55. However, it is also feasible to dispense with a fresh- water container 57 for temporarily storing at least a portion of the fresh water which is provided for final rinsing purposes and to connect the fresh- water feed valve V3 directly to the intake end of the final rinse pump 55.

The delivery end of the final rinse pump 55 is connected to a water heater 54 (boiler). In this case, the line system is designed in such a way that the liquid which is supplied from the final rinse pump 55 to the final rinse nozzles 51, 52, 53 of the final rinse zone 50 first passes the heat recovery device 62 before reaching the water heater 54. In this way, it is possible to use at least some of the thermal energy from the discharged exhaust air to heat the liquid which is supplied to the final rinse nozzles 51, 52, 53 of the final rinse zone 50.

Rinse aid is added to the fresh water, which is supplied to the final rinse pump 55 either directly from the fresh- water feed valve V3 or from the fresh-water container 57, in a metered manner with the aid of a rinse-aid metering apparatus (not shown in fig. 1). In this case, it is feasible to arrange the rinse-aid metering apparatus in such a way that rinse aid is added to the fresh water in a metered manner in a situation in which the fresh water has not yet been heated. Experiments have shown that the rinse aid mixes significantly better and more uniformly with the fresh water when the rinse aid is supplied to unheated fresh water. Specifically, it is preferred if rinse aid is added in a metered manner to fresh water which is at a temperature of less than 40 ⁰ C, and preferably less than 30 ⁰ C.

Although not explicitly illustrated in fig. 1, the conveyor dishwasher 1 preferably has a control apparatus which is designed to be able to actuate the different actuable components of the conveyor dishwasher 1, for example the respective pumps (final rinse pump 55, pre-rinse pump 45, main-wash pump 35, pre-wash pump 25), in accordance with predefined or predefinable process parameters in order to thus be able to adjust the process parameters in the individual treatment zones 20, 30, 40, 50 of the conveyor dishwasher 1.

The requirements relating to the hygiene performance are fulfilled by means of chemical disinfection in the exemplary embodiment of the conveyor dishwasher 1 according to the invention which is schematically illustrated in fig. 1. Specifically, a low- temperature process is used in the conveyor dishwasher 1, in which low-temperature process the liquid (wash liquid, pre-rinse liquid or final rinse liquid) which is sprayed in the individual treatment zones 20, 30, 40 is in each case at a temperature of at most 60 ⁰ C and preferably a temperature of at most 55°C. Chemical disinfection is realized by providing a metering device 70 which is associated with the final rinse zone 50 and serves to add a disinfectant to the final rinse liquid in a metered manner. Specifically, in the conveyor dishwasher 1 which is illustrated in fig. 1 , the metering device 70 which is associated with the final rinse zone 50 is designed in the form of a metering pump, of which the intake end is connected to a disinfectant tank 90. The delivery end of the metering device 70 which is in the form of a metering pump is connected to the final rinse line system 56 via a metering line 71. In this way, a portion of the disinfectant which is stored in the disinfectant tank 90 can be added in a metered manner to the final rinse liquid, before said liquid is sprayed, by means of the final rinse nozzles 51, 52, 53, with the aid of the metering device 70 which is associated with the final rinse zone 50. The final rinse liquid, to which the disinfectant has been added in a metered manner, is then sprayed onto the washware by means of the final rinse nozzles 51, 52, 53.

As already cited above, at least a portion of the final rinse liquid which is sprayed in the final rinse zone 50 is collected in the pre-rinse tank 44 of the pre-rinse zone 40 and supplied to the pre-rinse nozzles 41, 42, 43 with the aid of the pre-rinse pump 45 by means of the pre-rinse line system 46.

Depending on the quantity of washware and the degree of soiling, some of the disinfectant which is added in a metered manner, with the aid of the metering device 70, to the final rinse liquid before said liquid is sprayed is consumed in the above-described process step, in which the final rinse liquid which is admixed with the disinfectant is sprayed onto the washware in the final rinse zone 50.

In order to reliably meter the disinfectant component and, in particular, to avoid potential hygiene safety risks, for example if the metering device 70 which is associated with the final rinse zone 50 fails, in a conveyor dishwasher 1 in which the requirements relating to the hygiene performance are fulfilled with the aid of chemical disinfection, the solution according to the invention provides a further metering device 80 which is provided in addition to the metering device 70 which is associated with the final rinse zone 50. Specifically, in the solution according to the invention, in addition to the metering device 70 which is associated with the final rinse zone 50, a metering device 80 which is associated with the pre-rinse zone 40 is also used, this metering device serving to add a disinfectant to the pre-rinse liquid in a metered manner before the pre-rinse liquid is sprayed onto the washware with the aid of the pre-rinse nozzles 41, 42, 43. In the exemplary embodiment of the conveyor dishwasher 1 which is illustrated in fig 1, the metering device 80 which is associated with the pre-rinse zone 40 is designed in the form of a metering pump, of which the intake-end connection is connected to the abovementioned disinfectant tank 90. The delivery-end connection of the metering pump which is in the form of an additional metering device 80 is connected to the pre-rinse line system 46 via a metering line 81. Specifically, a line system 47 which is arranged parallel to the pre-rinse line system 46 is provided in the embodiment of the conveyor dishwasher 1 according to the invention which is illustrated in fig. 1. This parallel branch 47 of the pre- rinse line system 46 begins in a region in the delivery-end connection of the pre-rinse pump 45 and issues again in the pre-rinse line system 46 in a region upstream of the pre-rinse nozzles 41, 42 of the pre-rinse zone 40.

Secondly, the abovementioned metering line 81 connects the metering device 80, which is associated with the pre-rinse zone 40, to the parallel branch 47 of the pre-rinse line system 46. In this way, it is possible for disinfectant to be added to the pre-rinse liquid in a metered manner, before the pre-rinse liquid is sprayed by means of the pre-rinse nozzles 41, 42, 43 onto the washware which is to be treated in the pre-rinse zone 40, with the aid of the metering device 80 which is associated with the pre-rinse zone 40.

In the embodiment of the conveyor dishwasher 1 according to the invention which is schematically illustrated in fig. 1, provision is made for both the disinfectant which is to be supplied to the final rinse liquid with the aid of the metering device 70 which is associated with the final rinse zone 50 and also the disinfectant which is to be supplied to the pre-rinse liquid with the aid of the metering device 80 which is associated with the pre- rinse zone 40 to be stored in the common disinfectant tank 90. Accordingly, in the illustrated embodiment of the conveyor dishwasher 1 , the disinfectant which is added to the final rinse liquid in a metered manner in the final rinse zone 50 is identical in terms of the chemical composition and in terms of the concentration to the disinfectant which is added to the pre-rinse liquid in a metered manner.

However, it goes without saying that is also feasible for disinfectant tanks which are designed separately from one another to be associated with the respective metering devices 70, 80. In this way, it is possible for the concentration of the disinfectant which is added in a metered manner by the metering device 80 which is associated with the pre- rinse zone 40 to differ from the concentration of the disinfectant which is added in a metered manner by the metering device 70 which is associated with the final rinse zone 50. In addition or as an alternative to this, it is also feasible for the chemical composition of the disinfectant which is added in a metered manner by the metering device 80 which is associated with the pre-rinse zone 40 to differ from the chemical composition of the disinfectant which is added in a metered manner by the metering device 70 which is associated with the final rinse zone 50.

In principle, it is preferred if the disinfectant which is added in a metered manner by the metering device 80 which is associated with the pre-rinse zone 40 and/or the disinfectant which is added in a metered manner by the metering device 70 which is associated with the final rinse zone 50 contain/contains chlorine dioxide, sodium hypochlorite, ozone, iodine and/or ammonium. However, it goes without saying that other disinfectants can also be used.

Since, in addition to the metering device 70 which is associated with the final rinse zone 50, a metering device 80 which is provided in addition to said metering device 70 and is associated with the pre-rinse zone 40 is provided in the solution according to the invention, it is possible to effectively ensure that, as before, the requirements relating to the hygiene performance are fulfilled in the event of, for example, failure of the metering device 70 which is associated with the final rinse zone 50. In order to additionally allow the disinfection performance to be matched to the machine capacity, a sensor device 95 is provided in the solution according to the invention. This sensor device 95 is arranged and designed so as to detect either the concentration of disinfectant in the final rinse liquid which is sprayed in the final rinse zone 50, or to detect the concentration of disinfectant in the pre-rinse liquid which is sprayed in the pre-rinse zone 40. In the embodiment of the solution according to the invention which is schematically illustrated in fig. 1, the sensor device 95 is used to detect the concentration of disinfectant in the pre-rinse liquid which is sprayed in the pre-rinse zone 40. Specifically, in the illustrated embodiment of the conveyor dishwasher 1 according to the invention, the sensor device 95 has at least one measured-value sensor which detects the concentration of disinfectant in the pre-rinse liquid which is conveyed from the pre- rinse pump 45 to the individual pre-rinse nozzles 41, 42, 43 with the aid of the parallel branch 47. In this way, in the illustrated embodiment of the conveyor dishwasher 1 according to the invention, the concentration of disinfectant in the pre-rinse liquid in the pump line system 46 or in the parallel branch 47 can be detected with the aid of the sensor device 95 or with the aid of the at least one measured-value sensor of the sensor device 95, in order to obtain information about the concentration of disinfectant in the pre-rinse liquid before the pre-rinse liquid is sprayed onto the washware by means of the pre-rinse nozzles 41, 42, 43.

In addition to the sensor device 95, a control device 100 is provided in the solution according to the invention, the values of the detected concentration of disinfectant which are recorded by the sensor device 95 being supplied to said control device. The control device 100 is designed to actuate at least one of the metering devices 70, 80, in the embodiment illustrated in fig. 1 the metering device 80 which is associated with the pre- rinse zone 40, as a function of the concentration of disinfectant which is detected by the sensor device 95 in such a way that disinfectant is added in a metered manner with the aid of this metering device 80.

As illustrated in Fig 1, it is preferred if only the metering device 80 which is associated with the pre-rinse zone 40 is actuated with the aid of the control device 100, as a function of the concentration of disinfectant which is detected by the sensor device 95, in such a way that disinfectant is added to the pre-rinse liquid in a metered manner with the aid of this metering device 80, while the metering device 70 which is associated with the final rinse zone 50 is designed in such a way that a predefined quantity of disinfectant which is constant per unit time is added to the final rinse liquid in a metered manner. However, in principle, it is also feasible for the metering device 70 which is associated with the final rinse zone 50 to be actuated with the aid of the control device 100 as a function of a detected concentration of disinfectant, while the metering device 80 which is associated with the pre-rinse zone 40 adds a predefined quantity of disinfectant, which is constant per unit time, to the pre-rinse liquid in a metered manner. Provision is particularly preferably made for the control device 100 to be designed to compare the value of the concentration of disinfectant which is detected by the sensor device 95 with a predefined concentration value, and to actuate at least one of the metering devices 70, 80, the metering device 80 which is associated with the pre-rinse zone 40 in the embodiment of the conveyor dishwasher 1 which is illustrated in fig. 1, as a function of the result of the comparison in such a way that disinfectant is added in a metered manner. Specifically, it is preferred here if the control device 100 is designed to actuate at least one of the metering devices 70, 80, for example the metering device 80 which is associated with the pre-rinse zone 40, in such a way that no disinfectant is added in a metered manner by the metering device 70, 80 if the value of the concentration of disinfectant which is detected by the sensor device 95 is greater than the predefined concentration value. In addition to this, it is advantageous if the control device 100 is designed to actuate one of the metering devices 70, 80, and preferably the metering device 80 which is associated with the pre-rinse zone 40, in such a way that disinfectant is added in a metered manner by the metering device 70, 80 if the value of the concentration of disinfectant which is detected by the sensor device 95 is less than the predefined concentration value.

In principle, it is feasible, in the last-mentioned embodiment, for the control device 100 to be designed to actuate one of the metering devices 70, 80, and preferably the metering device 80 which is associated with the pre-rinse zone 40, in such a way that disinfectant is added in a metered manner by the metering device 70, 80 if the value of the concentration of disinfectant which is detected by the sensor device 95 is less than the predefined concentration value, with the metering device 70, 80 being actuated here in such a way that the quantity of disinfectant which is added in a metered manner per unit time by the metering device 70, 80 is dependent on the difference between the value of the concentration of disinfectant which is detected by the sensor device 95 and the predefined concentration value.

If the value of the concentration of disinfectant which is detected by the sensor device 95 is greater than or equal to the predefined concentration value, it is advantageous if, with the aid of the control device 100, one of the metering devices 70, 80, and preferably the metering device 80 which is associated with the pre-rinse zone 40, is actuated in such a way that the quantity of disinfectant which is added in a metered manner by the metering device 70, 80 per unit time remains unchanged.

The invention is not restricted to the embodiment of the conveyor dishwasher 1 which is shown by way of example in fig. 1, but rather further embodiments can be gathered from an overall expert view of the patent claims and of the present description.

In particular, the invention also relates to a method for operating a conveyor dishwasher 1 , for example for operating a conveyor dishwasher which is described above with reference to the illustration in fig. 1, with the method comprising the following method steps:

i) the metering device 70 which is associated with the final rinse zone 50 is used to add a predefined quantity of disinfectant which is constant per unit time to the final rinse liquid in a metered manner before the final rinse liquid is sprayed by means of the final rinse nozzles 51, 52, 53 in the final rinse zone 50;

ii) the sensor device 95 is preferably used to measure the concentration of disinfectant in the pre-rinse liquid which is sprayed in the pre-rinse zone 40; and

iii) the metering device 80 which is associated with the pre-rinse zone 40 is used to add disinfectant to the pre-rinse liquid in a metered manner as a function of the concentration of disinfectant which is measured by the sensor device 95, specifically before the pre-rinse liquid is sprayed by means of the pre-rinse nozzles 41, 42, 43 in the pre-rinse zone 40.