Patent Publication Number: US-2021161357-A1

Title: System for monitoring the operation of a commercial dishwasher, dishwasher and method for monitoring the operation of a dishwasher

Description:
TECHNICAL FIELD 
     The present invention relates in general to the field of industrial dishwashers. Specifically, the invention relates to a system for monitoring the operation of a commercial dishwasher, which is implemented in the form of an automatic machine or as a conveyor dishwasher, and to a corresponding dishwasher having such a monitoring system and a method for monitoring the operation of a dishwasher. 
     BACKGROUND 
     Automatic machines of the type considered here are known as box-type dishwashers, which can be manually loaded and unloaded. The machines can be rack conveyor pass-through dishwashers, also known as cover-type dishwashers, or front-loaders. Front-loaders can be under-counter built-in machines, counter-top machines or freestanding dishwashing machines with front loading. 
     A programmable box-type dishwasher usually has a treatment chamber for cleaning washware. Under the treatment chamber a washing tank is normally arranged, in which liquid from the treatment chamber can flow back under gravity. The washing tank contains wash liquid, which is usually water, to which cleaning agent can be added or has been added, as appropriate. 
     A box-type dishwasher also comprises a washing system with a washing pump, a pipe system connected to the washing pump, and washer jets. The wash liquid located in the wash tank can be conveyed by the washing pump via the pipe system to the washer jets and sprayed by means of the washer nozzles in the treatment chamber onto the washware to be treated. The sprayed wash liquid then flows back into the washing tank. 
     Conveyor dishwashers of the type discussed here, which are also referred to as multi-tank dishwashers, are in particular belt conveyor dishwashers or rack conveyor dishwashers. Conveyor dishwashers are usually used in the commercial sector. In contrast to programmable box-type dishwashers, in which the washware to be treated remains stationary in the dishwasher during the cleaning process, in conveyor dishwashers the washware is conveyed through different treatment zones of the conveyor dishwasher. 
     As the treatment zones, a conveyor dishwasher normally has at least one pre-wash zone as well as at least one main washing zone, which is arranged after the at least one pre-wash zone, viewed in the conveying direction of the washware. After the at least one main washing zone, viewed in the conveying direction, there is normally arranged at least one post-wash zone (which may also be referred to as the pumped final rinse zone) and at least one fresh-water final rinse zone downstream of the post-wash zone. 
     Viewed in the conveying direction, the washware, held either directly on the conveyor belt or carried in racks, usually passes in the conveying direction through an inlet tunnel, the immediately following at least one pre-wash zone, at least one main washing zone, at least one post-wash zone, a fresh-water final rinse zone, a drying zone and into an outlet path. 
     The above-mentioned washing zones of the conveyor dishwasher are each assigned a washing system, which has a washer pump and a pipe system connected to the washer pump, through which liquid is fed to the spray jets of the washing zone. In each washing zone the wash liquid fed to the spray jets is sprayed onto the washware, which is conveyed through the respective washing zones by a conveyor device of the conveyor dishwasher. Each washing zone has a tank assigned to it, in which sprayed liquid is collected and/or in which liquid is provided for the spray jets of the particular zone. 
     In the conveyor dishwashers commonly known from the prior art, final rinse liquid in the form of fresh water, which can be pure or mixed with other additives such as rinse aid, is sprayed on to the washware through the spray jets of the final rinse zone. At least part of the sprayed final rinse liquid is conveyed via a cascade system against the conveying direction of the washware from treatment zone to treatment zone of the dishwasher. 
     The sprayed final rinse liquid is collected in a tank of the post-wash zone or pumped final rinse zone, from which it is conveyed via the washer pump of the washing system belonging to the post-wash zone/pumped final rinse zone to the spray nozzles of the post-wash zone/pumped final rinse zone. 
     In the post-wash zone/pumped final rinse zone, wash liquid is rinsed off the washware. The incoming liquid flows into the wash tank of the at least one main washing zone, which viewed in the conveying direction of the washware is upstream of the pumped final rinse zone. Here, a cleaning agent is usually added to the liquid and sprayed onto the washware via the nozzles of the main washing zone by means of a pump system belonging to the washing system of the main washing zone. 
     From the washing tank of the main washing zone the liquid then flows—if no further main washing zone is provided—into the pre-wash tank of the pre-wash zone. The liquid in the pre-wash tank is sprayed via a pump system belonging to the washing system of the pre-wash zone through the pre-wash nozzles of the pre-wash zone onto the washware, in order to remove coarse dirt from the washware. 
     Regardless of whether the dishwasher is implemented as a box-type dishwasher or as a conveyor dishwasher, several standards and/or guidelines must be observed when operating the dishwasher. These standards or directives define in particular the requirements relating to the hygiene performance of cleaning processes and their procedure qualifications. 
     So, for example, with regard to the territory of the United States the requirements related to the hygiene performance are defined in the American directive/standard NSF-ANSI-3-10. More details can be found in the document “NSF/ANSI 3-2010 Commercial Warewashing Equipment” by NSF International Standard/American National Standard, to which explicit reference is made herein, and which is hereafter also referred to as “NSF Directive” (the version applicable is the one which is valid on the date of filing). 
     According to the NSF Directive, in commercial dishwashers it is required that a thermal disinfection is performed during the cleaning process, where no chemical disinfection is provided. With regard to the thermal process of “Hot Water Sanitizing” defined in the NSF Directive, minimum temperatures are required in the washing and rinsing zones of the commercial dishwasher. 
     But also when operating commercial dishwashers outside of the sovereign territory of the United States, requirements with regard to hygiene performance must also be taken into account. For example, in this connection, the applicable standard for the territory of the Federal Republic of Germany is DIN standard 10510. 
     Apart from this, particular requirements related to the hygiene performance of cleaning processes and their process qualifications must be observed and adhered to, in particular for commercial dishwashers which are used in sculleries of hospitals, nursing homes, schools or nursery schools, i.e. in areas in which the operator of the dishwasher is obliged to maintain certain hygiene regulations, which are normally also legally prescribed. 
     Compliance with these hygiene regulations is currently inspected and documented with a so-called “Thermo-Label Sticker”. These are irreversible temperature measuring strips, i.e. temperature measuring strips with an irreversible color change. These measuring strips are glued to the surface of the washware. As the appropriately prepared item of washware passes through the cleaning process in the dishwasher to be monitored, an irreversible color change of the temperature measuring strip takes place if the surface temperature is a pre-specified minimum temperature for a pre-defined minimum period of time. For the purposes of documentation, the temperature measuring strip is removed from the washware after completion of the process and stuck onto a log sheet. 
     The currently used approach to monitoring the hygiene-relevant temperatures of a commercial dishwasher has several disadvantages, however. In particular, it should be mentioned in this context that the temperature measuring strips currently on the market do not really indicate the quantity of heat that is actually supplied to the washware during a process run. In addition, while the “Thermo-Label Sticker” certificate is widely used in the industry to monitor the hygiene-relevant temperatures, in fact this approach is not recognized, in particular by the NSF. 
     SUMMARY 
     On the basis of this problem statement, the object of the present invention is to specify an appropriate improved system for monitoring the operation of a commercial dishwasher. 
     This object is achieved according to the invention by a monitoring system with the features of the independent claim  1  or by a dishwasher having such a monitoring system. 
     The monitoring system according to the invention is particularly suitable for monitoring the operation of a commercial dishwasher, which is embodied as a box-type dishwasher (single-tank dishwasher) or as a conveyor dishwasher (multi-tank dishwasher). 
     The monitoring system has at least one temperature sensor which is designed to record a temperature profile with respect to time, wherein said temperature profile with respect to time corresponds to the temperature profile to which an item of washware is subjected when it is treated in the dishwasher. 
     In addition, the monitoring system comprises at least one evaluation device which is designed to receive and to evaluate the temperature profile recorded by the at least one temperature sensor. In particular, the evaluation device is designed to ascertain a value of a notional unit of quantity of heat from the temperature profile recorded by the temperature sensor. 
     The benefits that can be achieved with the present invention are clear: in contrast to the commonly used temperature measuring strips (“Thermo-Label Stickers”) the monitoring system according to the invention provides a reproducible and accurate statement of the compliance or non-compliance with hygiene relevant temperatures in the operation of a dishwasher. 
     In particular, the at least one temperature sensor of the monitoring system is characterized in that the temperature profile to which an item of washware is subjected when it is treated in the dishwasher is recorded in a time-resolved manner. The system according to the invention thus provides—compared to a temperature measuring strip—significantly more information regarding the hygiene-relevant temperatures used during the operation of the dishwasher. Using the solution according to the invention it is possible, in particular, to monitor the temperatures during the washing process and the final rinse process separately. 
     In addition, the monitoring system according to the invention is characterized in that using this monitoring system, any given dishwasher, in particular a commercial one, can be continuously and efficiently monitored with regard to its hygiene-relevant temperatures. The implementation of the monitoring system in a dishwasher to be monitored is particularly simple and in particular, does not require any manual or complicated work to perform a single measurement. 
     The at least one temperature sensor is preferably designed to work in a dynamic range between at least 40° C. to at least 90° C. and preferably between at least 61.7° C. (corresponding to 143° F.) and 73.9° C. (corresponding to 165° F.). This temperature range is used in accordance with the NSF directive to assign appropriate HUE values. 
     The abbreviation “HUE” stands for “Heat Unit Equivalent” and in accordance with the NSF directive is the unit of measure for the quantity of heat that is applied to the washware while it is washed and rinsed. 
     As already stated above, in accordance with the NSF, in a thermally disinfecting cleaning process (hot-water sanitization) a defined thermal energy input into the washware must take place. This can be described as a function of temperature (item of washware) and contact time and is defined within the NSF by a notional heat quantity unit (HUE values). 
     In this method, maintaining a specific temperature (between 62° C. and 74° C.) over a period of 1 second counts towards one defined HUE value. In order to achieve a safe cleaning result in accordance with NSF hygiene specifications, at least 3,600 HUE values must be obtained during the washing and final rinse process. 
     Since according to the invention the evaluation device of the monitoring system is designed to ascertain a value of a notional heat quantity unit from the temperature profile recorded by the temperature sensor, the monitoring system according to the invention is suitable in particular for the constant and/or continuous monitoring of the hygiene-relevant temperatures specified in the NSF guideline for a dishwasher in accordance with NSF-ANSI 3. 
     In particular, for this preferably constant and continuous monitoring of the dishwasher no additional effort is required on the part of the operator of the dishwasher, because after the one-off implementation of the monitoring system in the dishwasher to be monitored all further steps are preferably fully automated. 
     In an advantageous way the evaluation device of the monitoring system is also designed to extract a temperature value from the temperature profile recorded by the at least one temperature sensor at pre-defined or pre-definable measurement points, and from the extracted temperature value to determine an equivalent value of a quantity of heat according to a pre-defined or pre-definable mapping. 
     For example, it is suitable in this context if for every second of the time-temperature profile recorded by the at least one temperature sensor the corresponding temperature value is determined, and this determined or extracted temperature value is then converted into an equivalent value of a quantity of heat. 
     Of course, the temporal resolution of the temperature sensor or the temporal resolution in the evaluation of the temperature profile recorded by the temperature sensor can also be chosen to be finer or coarser as required. 
     It is also conceivable if the corresponding measurement points are selected only in certain temporal areas of the recorded temperature profile and the corresponding temperature values at the selected measuring points are extracted and used to determine the equivalent value of the quantity of heat. Thus, for example, it is conceivable that a corresponding equivalent value of the quantity of heat is determined only during a washing process (pre-wash process and/or main washing process) and/or only during a final rinse process (pumped final rinse process and/or fresh-water final rinse process). 
     An example of a pre-defined or pre-definable mapping for determining an equivalent value of the quantity of heat of an extracted temperature value is given in the table shown in  FIG. 1 . This mapping corresponds to the HUE values in accordance with NSF at appropriate temperature values (measured in Fahrenheit). 
     Of course, other mappings for determining an equivalent value of the quantity of heat are also possible. 
     In a further refinement of the last mentioned embodiment, the evaluation device of the monitoring system is designed to determine the value of the notional heat quantity unit by forming a sum of the equivalent values of the quantity of heat from measurement points of the temperature profile. 
     In other words, if corresponding temperature values were extracted for a plurality of measurement points during the washing and/or rinsing process and the extracted temperature values were converted into equivalent values of quantities of heat according to the pre-defined or pre-definable mapping, then by means of the evaluation device the notional heat quantity unit can be formed by adding the assigned equivalent values of the quantity of heat. 
     In this way, it is possible to monitor very efficiently and preferably continuously, whether the hygiene-relevant temperatures of the dishwasher in accordance with NSF/ANSI 3 are complied with. 
     In accordance with one advantageous implementation of the monitoring system the evaluation device is designed to compare the measured value for the notional unit of quantity of heat with a predetermined setpoint value or setpoint value range, and to issue an appropriate warning and/or notification if the measured value for the notional unit of quantity of heat undershoots and/or exceeds the setpoint value or setpoint value range. 
     For example, the warning and/or notification from the evaluation device of the monitoring system can be output to a control device of the dishwasher, which then changes, preferably automatically or at least optionally automatically, corresponding treatment parameters in the dishwasher and/or outputs a notification or alert to the operator of the dishwasher on a display. 
     In this context, it is of course also conceivable, however, if the evaluation device itself has an appropriate display, via which the warning and/or notification can be output to the operator of the dishwasher. 
     In an advantageous way the monitoring system according to the invention works fully automatically. In this context, it is appropriate if the monitoring system additionally has at least one read/write unit, in order to transmit data and/or commands preferably wirelessly between the at least one temperature sensor of the monitoring system and the evaluation device. 
     For example, the at least one read/write unit can be designed to initiate, i.e. to trigger, the at least one temperature sensor and/or the recording of the time-temperature profile by the at least one temperature sensor at the beginning of a treatment cycle of the dishwasher. 
     Alternatively or in addition, it is conceivable if the at least one read/write unit is designed, after completion of at least one processing cycle of the dishwasher or a complete pass (in the case of a conveyor dishwasher), to read out the temperature data recorded by the at least one temperature sensor during the processing cycle or during the pass, which correspond to the time-temperature profile, from the at least one temperature sensor. 
     To transfer data and/or commands between the at least one temperature sensor and the evaluation device of the monitoring system, various communication protocols or transmission technologies are suitable. In particular, it is advantageous if the transmission takes place wirelessly, for example, using RFID technology, Bluetooth, WiFi, NFC, radio or other wireless transmission techniques. 
     The at least one temperature sensor is preferably designed not only to record the time profile of the temperature, but also to store it temporarily. To this end, the at least one temperature sensor preferably comprises a corresponding storage medium. 
     In accordance with embodiments of the monitoring system according to the invention, the at least one read/write unit is designed to read out, preferably automatically after the end of the recording of n whole-number temperature profiles, the temperature profiles and/or the data corresponding to the temperature profiles from the at least one temperature sensor, where n  1 . 
     Different embodiments are conceivable for the implementation of the at least one temperature sensor. For example, the at least one temperature sensor can be mounted on a measurement body and/or item of washware, or integrated in a measurement body and/or item of washware. To monitor the hygiene-relevant temperatures in the dishwasher, the measurement body or item of washware (as well as the other items of washware to be treated) must be guided in the at least one treatment chamber of the dishwasher or through the treatment zones of the dishwasher. 
     The solution according to the invention relates not only to the previously described monitoring system but also to a dishwasher with such a monitoring system for preferably continuously monitoring the operation of the dishwasher. The dishwasher is in particular a commercial dishwasher, which is embodied as a conveyor dishwasher or as a box-type dishwasher and has at least one treatment chamber (box-type dishwasher) or at least one treatment zone (conveyor dishwasher), in which wash liquid and/or final rinse liquid is at least temporarily sprayed onto washware to be treated. 
     If the dishwasher according to the invention is embodied as a conveyor dishwasher and comprises a corresponding conveyor device for conveying washware through the at least one treatment zone of the dishwasher, it is advantageous if the at least one temperature sensor of the monitoring system is or can be connected to the conveyor device in such a way, or is integrated in the conveyor device in such a way, that as the washware is conveyed the at least one temperature sensor is also conveyed through the at least one treatment zone of the dishwasher. In this way, the at least one temperature sensor is exposed to the same temperatures as the rest of the washware to be treated in the dishwasher. 
     In the case of a dishwasher embodied as a conveyor dishwasher, it is also advantageous if an inlet region is provided in front of the at least one treatment zone, as viewed in the conveying direction of the washware, in which at least one read/write unit of the monitoring system is arranged, in order then to initiate the at least one temperature sensor accordingly as soon as the latter passes the read/write unit at the inlet region of the dishwasher. 
     In this context, it is also possible for the at least one treatment chamber, or the at least one treatment zone of the dishwasher, to be designed to treat the washware to be treated in a state in which the washware is held in a dish rack. In this case, the at least one temperature sensor of the monitoring system is or can be connected to the dish rack or can be integrated in the dish rack, in order thus to expose the at least one temperature sensor to the temperature profile to which an item of washware placed in the dish rack undergoes or is exposed to during its treatment in the dishwasher. 
     In accordance with advantageous refinements it is provided that the dishwasher according to the invention also has a control device, by means of which a temperature of the at least one treatment chamber, or of wash liquid and/or final rinse liquid to be sprayed in the at least one treatment zone of the dishwasher, is or can be adjusted. 
     Alternatively or additionally, the control system of the dishwasher can also be used for adjusting an action time of the washware to be treated in the at least one treatment chamber or treatment zone, for example by extending or shortening a program run time (in the case of programmable box-type machines) or by changing a conveying speed (in conveyor dishwashers). 
     In this context, it is also advantageous if the control device of the dishwasher is also designed to preferably automatically adjust, in particular to regulate, the temperature of the wash and/or final rinse liquid to be sprayed in the at least one treatment chamber or treatment zone and/or the action time of the washware to be treated in the at least one treatment chamber or treatment zone depending on a value of the notional quantity of heat ascertained using the evaluation device. This is preferably carried out in such a way that it is automatically ensured that the applicable hygiene-relevant temperatures are always observed. 
     Alternatively or in addition, in particular the control device should be designed to store and/or document the value of the notional quantity of heat ascertained during operation of the dishwasher for each cycle or unit of time, in particular for documentation reasons. 
     The invention also relates to a method for monitoring the operation of a commercial dishwasher, in particular a dishwasher according to any one of claims  9  to  14 , wherein a temperature profile with respect to time is recorded during operation of the dishwasher, the said temperature profile with respect to time corresponding to the temperature profile with respect to time to which an item of washware is subjected when it is treated in the dishwasher, and wherein a value of a notional unit of quantity of heat is ascertained from the recorded temperature profile. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following text by referring to the accompanying drawings, an exemplary embodiment of the dishwasher according to the invention will be described in more detail. 
       Shown are: 
         FIG. 1  an example mapping for determining an equivalent value of the quantity of heat at a corresponding temperature value; 
         FIG. 2  a schematic graphical representation for explaining the relationship between time and temperature to obtain 3,600 HUE values during a treatment in a dishwasher; and 
         FIG. 3  a schematic representation of an exemplary embodiment of the dishwasher according to the invention with integrated monitoring system. 
     
    
    
     DETAILED DESCRIPTION 
     Before an exemplary embodiment of the present invention is described with reference to the schematic diagram according to  FIG. 3 , the hygiene-relevant temperatures to be monitored with the monitoring system will be discussed in more detail, namely using the example of the NSF requirements. 
     The thermal process of “hot-water sanitization” defined in the NSF describes a method in which a minimum number of 3,600 heat units (HUE units) should be measured on the surfaces of the washware. In this method described in the NSF, temperature sensors are mounted on three dinner plates. These three plates are washed according to the method described in the NSF and the temperature on them is recorded during the entire program cycle. Heat units are counted per unit of time in seconds according to the temperature profile and added. At the end of the process, in accordance with the NSF, 3,600 NSF-values should have been obtained. 
       FIG. 1  shows a mapping from the temperature (in Fahrenheit) to the corresponding HUE-values in accordance with the NSF directive. 
     For example, if the temperature of 150° F. (corresponding to 65.6° C.) is measured at a measurement point, this corresponds to an HUE-value of 6.5. 
     Each temperature recorded per unit of time in seconds is assigned a corresponding HUE-value and the HUE-values accumulated during the entire processing sequence are then added. If a certain number of HUE values, such as 3,600 HUE values, are achieved at the end, the hygiene-relevant temperatures in the dishwasher are compliant with NSF/ANSI 3. 
     The critical 3,600 HUE values can thus be achieved if relatively high temperatures are used for a relatively short time during the washing and/or rinsing process, or if relatively low temperatures are used for a relatively long time. This relationship of time and temperature in order to achieve the required 3,600 HUE-values is shown in  FIG. 2 . 
     In the following text, by referring to the drawing in  FIG. 3  an exemplary embodiment of the conveyor dishwasher according to the invention will be described in more detail. Although this embodiment involves a conveyor dishwasher, it should be noted that this is not to be regarded as restrictive. Instead, the monitoring system according to the invention can also be used in a programmable box-type dishwasher, in particular a commercial dishwasher. 
     Specifically,  FIG. 3  schematically illustrates a conveyor dishwasher  2  with a conveyor device  4  for conveying washware, not depicted, in a conveying direction  8  through the conveyor dishwasher  2 . The conveyor dishwasher  2  has at least one washing zone, for example as shown in  FIG. 3 , a pre-wash zone  12  and a main wash zone  14 , which seen in the conveying direction  8  is arranged after the pre-wash zone  12 . 
     As seen in the conveying direction  8 , after the at least one wash zone  12 ,  14  a post-wash zone  16  (or pumped final rinse zone) and after the post-wash zone  16  at least one final rinse zone (or fresh water final rinse zone) is arranged, for example only one single final rinse zone  18  as shown. In the conveyor dishwasher  2  shown in  FIG. 3  the final rinse zone  18  is followed in the conveying direction  8  of the washware by a drying zone  40 . The respective zones  12 ,  14 ,  16 ,  18 ,  40  of the conveyor dishwasher  2  can be separated via partition curtains  47 . In the embodiment shown in  FIG. 3  the inlet tunnel  10  itself is also separated from the inlet  11  by a partition curtain  47 . The provision of the partition curtains  47  prevents excess spraying of wash liquid and final rinse liquid and the escape of steam from the conveyor dishwasher  2 . 
     The above-mentioned treatment zones  12 ,  14 ,  16 ,  18  of the conveyor dishwasher  2  are assigned spray nozzles  20 ,  22 ,  24 ,  26 ,  28 ,  30 . These spray nozzles  20 ,  22 ,  24 ,  26 ,  28 ,  30  are used to spray liquid onto the washware when this is being conveyed by the conveyor device  4  through each of the treatment zones  12 ,  14 ,  16 ,  18 . The individual spray systems of the treatment zones  12 ,  14 ,  16 ,  18  ensure that the washware to be treated is sprayed from both the top and the bottom. 
     In the conveyor dishwasher  2  schematically shown in  FIG. 3 , however, the final rinse zone  18  has not only downwards directed upper spray nozzles  20  and upwards directed lower spray nozzles  22 , but also transversely directed lateral spray nozzles  24  on each side of the conveyor device  4 . The use of lateral spray nozzles  24  allows a precise spraying of the washware surfaces (surfaces of the dishes) with final rinse liquid, even in obscured zones. In particular in a fully loaded conveyor system, i.e. when the dish rack is loaded plate to plate, the use of lateral nozzles  24  in the final rinse zone  18  has a clear advantage with regard to the final rinse result (effective rinsing of cleaner residues off the washware surfaces even in obscured zones), compared to systems in which in the final rinse zone  18  only upper and lower nozzles  20 ,  22  are provided, but no cross-directed lateral spray nozzles  24 . 
     The post-wash zone  16 , main wash zone  14  and pre-wash zone  12  are also assigned tanks (post-wash tank  32 , main wash tank  34 , pre-wash tank  36 ) for collecting sprayed liquid and/or for providing liquid for the spray nozzles  26 ,  28 ,  30  of the relevant treatment zones  14 ,  16 ,  18 . 
     As already indicated, in the conveyor dishwasher  2  shown in  FIG. 3 , final rinse liquid, which is composed of fresh water with added rinse aid, is sprayed onto the washware, not shown, via the spray nozzles  20 ,  22 ,  24  arranged above and below the conveyor device  4  and laterally positioned in the final rinse zone  18 . A part of the sprayed final rinse fluid is conveyed via a cascade system against the transport direction  8  of the washware from treatment zone to treatment zone. The remainder of the final rinse liquid sprayed in the final rinse zone  18  is directed via a valve V 1  and a bypass pipe  38  directly into the pre-wash tank  36  assigned to the pre-wash zone  12 . 
     In the cascade system the final rinse liquid sprayed by the final rinse nozzles  20 ,  22 ,  24  flows under gravity from the final rinse zone  18  into the post-wash tank  32  assigned to the post-wash zone  16 . The final rinse liquid which is sprayed in the final rinse zone  18  and captured by the post-wash tank  32  is then pumped by means of a post-wash pump  45  to the spray nozzles (post-wash nozzles  26 ) of the post-wash zone  16 . 
     In the post-wash zone  16 , wash liquid is rinsed off the washware. The resulting liquid (post-wash liquid) flows under gravity into the main wash tank  34  assigned to the main wash zone  14 . A drainage element  39 , such as a drain floor or a baffle plate, is preferably provided which directs the post-wash liquid sprayed by the washer nozzles  26  into the main wash tank  34 . In accordance with another embodiment, not shown, the drainage element  39  can be omitted if the main wash tank  34  extends below the post-wash nozzles  26  of the post-wash zone  16 . 
     The liquid collected by the main wash tank  34  of the main wash zone  14  usually has a washing chemical added to it in the form of a cleaning agent (detergent), and with the aid of a main wash pump  35  is sprayed onto the washware via the spray nozzles (main wash nozzles  28 ) of the main wash zone  14 . The wash liquid sprayed with the main washer nozzles  28  flows into the main wash tank  34  under gravity. 
     The main wash tank  34  is fluidically connected via an overflow pipe  37  to the pre-wash tank  36  associated to the pre-wash zone  12 . Via this overflow pipe  37 , the wash liquid sprayed in the main wash zone  14  arrives in the pre-wash tank  36  if a sufficient quantity of wash liquid is collected in the main wash tank  34 . 
     The liquid collected in the pre-wash tank  36  of the pre-wash zone  12  is then sprayed onto the washware by means of a pre-wash pump  33  via the spray nozzles (prewash nozzles  30 ) of the pre-wash zone  12 , in order to remove coarse dirt from the washware. The wash liquid sprayed with the pre-wash nozzles  30  flows into the pre-wash tank  36  under gravity. 
     The pre-wash tank  36  is provided with an overflow line  31 , which is used to drain away the excess quantity of liquid to a waste water network, if a maximum fluid level in the pre-wash tank  36  is exceeded. 
     As already indicated, the liquid sprayed in the main wash zone  14  and in the pre-wash zone  12  contains a wash chemical in the form of a cleaning agent (detergent). This wash chemical is added as required to the liquid collected in the main wash tank  34  of the main washing zone  14  by means of a cleaning agent dosing device. 
     The cleaning agent dosing device has a corresponding  51  dosing pump, whose inlet side is flow-connected to a reservoir  52  for wash chemicals. On the pressure side the dosing pump  51  is connected to the main wash tank  34 . The dosing pump  51  of the cleaning agent dosing device is preferably embodied as a controllable dosing pump  51 . For this purpose the dosing pump  51  is connected via a control bus or similar (wired or wireless) control line to the control device  50  of the conveyor dishwasher  2 . 
     As already mentioned, the final rinse zone  18  directly follows the drying zone  40  in the conveying direction  8 . In the drying zone  40  the washware is dried with dry warmed air to blow away or dry off the moisture on the washware. To keep the moisture content of the air within a favorable range for drying, it is possible to supply external air to the drying zone  40 , for example, via an opening, for instance through the outlet opening for the washware. 
     The warm and moist air in the drying zone  40  is then extracted from the drying zone  40 , for example by means of a blower  41 , through a further opening. It is advantageous in this case if the stream of exhaust air from the drying zone  40  passes through a device  42  for heat recovery, in which for example a condenser can be provided. The device  42  for heat recovery is used to recover at least a portion of the heat energy contained in the exhaust air. 
     If before the conveyor dishwasher  2  is first started the tanks assigned to the wash zones  12 ,  14  and  16  (pre-wash tank  36 , main wash tank  34 , post-wash tank  32 ) are empty or only insufficiently filled, these must first be filled via a fresh water pipe  90  and/or by spraying final rinse liquid in the final rinse zone  18 . The fresh water pipe  90  can be connected via a controllable valve V 3  to a fresh water supply network. The quantity of wash liquid available in the main washing zone  14  and in the pre-wash zone  12  can be monitored in each case by means of a level sensor provided in the main wash tank  34  or by means of a level sensor provided in the pre-wash tank  36 , and notified to a control device  50 . 
     The final rinse zone  18 , may—as shown in  FIG. 3 —be assigned a fresh water reservoir  30  for the temporary storage of at least a portion of the fresh water used for the final rinse. The fresh water reservoir  30  is provided, on the one hand, with a fresh water connection which can be connected via a controllable fresh water supply valve V 2  to a fresh water supply network, and on the other hand connected on the inlet side to a final rinse pump  43 . Of course, it is also conceivable to dispense with a fresh water reservoir  30  for temporary storage of at least a portion of the fresh water provided for the final rinse and to connect the fresh water supply valve V 2  directly to the inlet side of the final rinse pump  43 . 
     The pressure side of the final rinse pump  43  is connected via a pipe system to a water heater  9 . The pipe system is embodied in such a way that the liquid pumped by the final rinse pump  43  to the spray nozzles  20 ,  22 ,  24  of the final rinse zone  18  first passes through the device  42  for heat recovery before it reaches the water heater  9 . In this way it is possible to use at least a portion of the thermal energy of the discharged exhaust air for heating up the liquid supplied to the spray nozzles  20 ,  22 ,  24  of the final rinse zone  18 . 
     The fresh water supplied to the final rinse pump  43  either directly from the fresh water supply valve V 2  or from the fresh water reservoir  30  is dosed with rinse aid by means of a rinse aid dosing device. The rinse aid dosing device has a (rinse aid) dosing pump  57  and a rinse aid reservoir  58 . In a particularly preferred manner the rinse aid dosing pump  57  is arranged in such a way that the addition of rinse aid to the fresh water takes place at a position in which the fresh water was not yet been heated. Studies have shown that a much better and more uniform mixing of the rinse aid with the fresh water occurs when the rinse aid is added to unheated fresh water. In particular, the addition of rinse aid should be carried out in fresh water which has a temperature of less than 40° C., and preferably less than 30° C. 
     Therefore, in the embodiment of the conveyor dishwasher  2  shown in  FIG. 3  the rinse aid dosing takes place between the final rinse pump  43  and the water heater  9  or the device  42  for heat recovery. For this purpose a supply pipe is provided which discharges in the pipe system between the final rinse pump  43  and the device  42  for heat recovery, and which is connectable via the dosing pump  57  to the rinse aid reservoir  58 . 
     Like the dosing pump  51  of the cleaning agent dosing device, the rinse aid dosing pump  57  is preferably also connected via a suitable control bus to the control device  50  of the conveyor dishwasher  2 , so that the rinse aid dosing pump  57  can also be correspondingly activated via the control device  50 . 
     In the conveyor dishwasher  2  shown in  FIG. 3  the above-mentioned control device  50  is only indicated schematically. The control device  50  to automatically adjust a final rinse liquid quantity to be sprayed per unit of time in the final rinse zone  18  and/or for automatically adjusting a wash liquid quantity to be sprayed per unit of time in the main wash zone  14 . Preferably, the control device  50  is designed to control the different controllable components of the conveyor dishwasher  2 , such as the individual pumps and valves, in accordance with a pre-defined or pre-definable program sequence, so as to control the process parameters in the individual treatment zones  12 ,  14 ,  16 ,  18  of the conveyor dishwasher  2 , and in particular to allow the process parameters in the final rinse zone  18  and/or in the main wash zone  14  to be adjusted. 
     Also, the control device  50  is preferably designed to adjust the temperature of the final rinse liquid to be sprayed in the final rinse zone  18  and/or the temperature of the wash liquid to be sprayed in the main wash zone  14 . 
     It is also advantageous if the control device  50  is designed to control the conveyor device  4  to adjust a specific conveying speed of the washware to be treated, and thus the action time of the washware in the individual treatment zones of the dishwasher  2 . 
     The dishwasher  2  represented schematically in  FIG. 3  is characterized by the fact that a monitoring system for monitoring the operation of the dishwasher  2  is provided. Specifically, the purpose of the monitoring system is to monitor continuously during the operation of the dishwasher  2  whether the hygiene-relevant temperatures in the individual treatment zones of the dishwasher  2  are complied with. 
     For this purpose, the monitoring system integrated in the dishwasher  2  has at least one temperature sensor  60  which is designed, or used, to record a temperature profile with respect to time, which corresponds to the temperature profile with respect to which an item of washware is subjected when it is treated in the individual treatment zones of the dishwasher  2 . 
     For example, the at least one temperature sensor  60  of the monitoring system is or can be connected to the conveyor device  4  of the dishwasher  2  in such a way or be integrated in the conveyor device  4  in such a way that as the washware is conveyed the at least one temperature sensor  60  is also conveyed through the at least one treatment zone of the dishwasher  2 . 
     The at least one temperature sensor  60  is assigned a storage unit, in which the time-temperature profile recorded by the temperature sensor  60  is temporarily stored. In this way, it is possible that after the passage of the at least one temperature sensor  60  through the treatment zones, or at least through a portion of the treatment zones, the recorded time-temperature profile can be read out from the storage unit assigned to the temperature sensor  60 . 
     The readout of the data from the temperature sensor  60  is preferably carried out with a read/write unit  61  provided on the outlet tunnel of the conveyor dishwasher  2 . The purpose of this read/write unit  61  is, in particular, to transfer data and/or commands preferably wirelessly between the at least one temperature sensor  60  and at least one evaluation device  62 . In particular, the at least one read/write unit  61  is designed to read out, preferably automatically after the end of the recording of n whole-number temperature profiles, these temperature profiles and/or the data corresponding to the temperature profiles from the temperature sensor  60 , where n  1 . 
     The evaluation device  62  of the monitoring system is designed not only to receive the data of the temperature profile with respect to time recorded by the at least one temperature sensor  60 , but also to evaluate them. For this purpose, the evaluation device  62  is designed (e.g., programmed or otherwise configured) in particular to ascertain a value of a notional unit of quantity of heat from the temperature profile recorded by the temperature sensor  60 . 
     For example, for this purpose the evaluation device  62  is designed to extract a temperature value from the temperature profile recorded by the at least one temperature sensor  60  at pre-defined or pre-definable times (measurement points), and from the extracted temperature value to determine an equivalent value of a quantity of heat according to a pre-defined or pre-definable mapping. An example of such a mapping is shown in  FIG. 1 . 
     In accordance with advantageous implementations, the corresponding temperature value is extracted from the recorded temperature profile once per second and in accordance with the mapping, for example the mapping shown in  FIG. 1 , converted into an equivalent value of a quantity of heat. 
     The evaluation device  62  of the monitoring system is also designed to determine the value of the notional heat quantity unit by forming a sum of the equivalent values of the quantity of heat from measurement points of the temperature profile. In this context, it is conceivable that the determined value of the notional heat quantity unit is compared with a predetermined setpoint value, such as—expressed in terms of the requirements in accordance with NSF—the 3,600 HUE values. At the same time, a warning and/or notification to this effect should be output by the evaluation device  62  if the measured value of the notional heat quantity unit falls below the setpoint value. 
     The read/write unit  61  is preferably provided with an interface to send the data read out from the temperature sensor  60  to the evaluation device  62  or the control device  50  of the dishwasher  2 . 
     As is schematically indicated in  FIG. 3 , viewed in the conveying direction of the washware in front of the first treatment zone of the dishwasher  2  an inlet region  11  is provided, in which a further read/write unit  63  or similar unit, such as an inductively operated unit of the monitoring system, is arranged. This read/write unit  63  can be used to initiate the temperature sensor  60 , as soon as it moves past the region of influence of the read/write unit  63  via the conveyor device  4 . 
     The control device  50  of the dishwasher  2  according to the invention is also preferably designed (e.g., programmed or otherwise configured) so as to adjust the temperature in the at least one wash zone  10 ,  12 ,  14 , and/or at least one final rinse zone  16 ,  18 , or the temperature of the liquid to be sprayed in the at least one washing zone  10 ,  12 ,  14  and/or the at least one final rinse zone  16 ,  18 , and/or the speed at which the washware is conveyed through the treatment zones  10 ,  12 ,  14 ,  16 ,  18 ,  40  of the dishwasher  2 . 
     In this context it is conceivable if the control device  50  preferably automatically adjusts the temperature or the action time/conveying speed, in order to ensure at all times that the hygiene-relevant temperatures in accordance with the current standard or directive are complied with. 
     It is also conceivable that the control device of the dishwasher  2  informs the operator of the dishwasher  2  accordingly, preferably via data transmission (app/cloud). 
     In the following the underlying concept of the invention is summarized once again as follows: 
     During normal operation a temperature sensor  60 , fixed for example to the conveyor belt of the conveyor device  4 , passes through the wash and final rinse zones of the conveyor dishwasher  2 . During the traverse, the temperature is recorded as a function of time. The recording starts when the sensor enters the cleaning tunnel and is stopped on its exit. At the same time, the recorded temperature profile is transferred to the evaluation device  62 , which can be part of the control device  50  of the dishwasher  2  (e.g. via RFID, Bluetooth, WiFi, NFC, radio, etc.), and is converted into the HUE-value obtained in accordance with the NSF/ANSI3 specifications. This may be displayed and documented directly on the evaluation device  62  and/or control device  50  (operating log) or forwarded to a management system. 
     The monitoring system integrated in the dishwasher  2  consists of at least one temperature sensor  60  and at least one read/write unit  61 ,  63  as well as at least one evaluation device  62 . The temperature sensor  60  can be mounted on or integrated in the conveyor belt, the dish rack, a piece of dishware (plate, small bowl, glassware, cutlery, cookware, etc.) or a specific measurement body. The sensor itself is provided with a data store which can record the temperature profile as a function of time. 
     The recording is started as soon as the temperature sensor  60  enters or is inserted into the cleaning tunnel of the machine  2 . In so doing, the “Start” command can be triggered by the write/read unit  63  itself or an additional sensor (e.g. inductive sensor). 
     At the end of the tunnel, the recorded temperature profile is transferred as a data block by a second read/write unit  61  to the machine controller  50  or the evaluation device  62  (e.g. via RFID, Bluetooth, WiFi, NFC, radio, etc.). 
     The machine controller  50  or the evaluation device  62  calculates the HUE-value obtained in accordance with NSF/ANSI3 from the temperature profile, and depending on the result, can output information to operators or to the management system. For example, the HUE-value could be directly displayed and evaluated on a display unit of the machine controller  50  or the evaluation device  62  (green for &gt;3,600 HUE and red for &lt;3,600 HUE). Also, it is conceivable to change the operating state of the machine  2  depending on the HUE value (for example hygiene stop), or to change the operating parameters (e.g. tank temperature, conveyor speed, throughput, etc.). For documentation of the hygiene performance the HUE values can either be stored directly in the operating log of the machine stored or transferred to an external database. 
     Based on this concept, the following variations would be possible: 
     The starting and the reading of the measurement series could also be implemented by only one read/write unit  63 . 
     An immediate, continuous data transfer from the temperature sensor  60  to the machine controller  50  or the evaluation device  62  (e.g. via radio) would also be conceivable. 
     If a temperature sensor  60  mounted on the washware (for example, dishes) or on a specific test specimen is used, readout using an external or separate readout/evaluation unit is also conceivable. This could be located in a control cabinet of the dishwasher  2  or in an additional hand-held device. In this case the starting and the reading of the measurement would also be possible using a smartphone app (via WiFi, Bluetooth, NFC, etc.). 
     If the system is used in stationary machines (cover-type and under-counter machines) the measurement would be started by a read/write unit at the beginning of the wash cycle and evaluated after the completion of the rinse cycle. Of course, the implementation via a smartphone app (via WiFi, Bluetooth, NFC, etc.) would also be feasible here. 
     By means of the method described above the hygiene parameters temperature (HUE-value) prescribed within the NSF/ANSI3 can be implemented and documented costeffectively and automatically. 
     The invention is not limited to the embodiments shown in the drawings, rather it results from a combination of all the features disclosed herein.