EP2053959B2 - Method for assessing and guaranteeing the thermal hygiene effect in a multi-tank dishwasher - Google Patents

Description

The invention relates to a method for assessing and ensuring the thermal hygiene effect on items to be washed in a dishwasher during the cleaning process.

Technical field

In addition to single-chamber dishwashers, multi-tank dishwashers are also used in commercial settings today to clean dishes. In these dishwashers, the items to be cleaned are transported through the various zones by means of a conveyor system. Multi-tank dishwashers generally comprise at least one wash zone, at least one final rinse zone, and optionally a drying zone. Multi-tank dishwashers, in which the items to be cleaned pass through various treatment zones, are generally designed as belt conveyor or rack conveyor machines. What both designs have in common is that the items to be cleaned are continuously transported through the individual treatment zones by the conveyor system. The individual treatment zones are usually designed as chambers with openings in the direction of transport of the conveyor system, through which the items to be cleaned are transported by the conveyor system.

State of the art

At the start of operation of a multi-tank dishwasher, the rinse water storage tank of the wash zone is filled with fresh water and heated to the preset rinse tank temperature. Detergent is then added to the rinse water. The same applies if multiple wash zones are arranged in series. Typically, the wash zone has a rinse water circulation pump, which draws rinse water from the rinse water storage tank and sprays it onto the dishes via a spray system assigned to the wash zone to remove any dirt adhering to the dishes. The rinse water then flows back into the rinse water storage tank along with the rinsed-off dirt.

A sieve system filters the rinsed dirt out of the rinse water.

In the final rinse zone, detergent and dirt residues loose on the dishes are rinsed away using hot fresh water sprayed by a suitable spray system. In some models of multi-chamber dishwashers, the final rinse water is collected in a pumped rinse tank after the first use and sprayed over the dishes again using a pump and another spray system. This process step takes place before the dishes are rinsed with fresh water. Some of the fresh water or final rinse water is then fed to the rinse water storage tank to dilute the dirt particles present there. The dishes to be cleaned are then transported to the optional drying zone, where the dishes are dried.

The cleaning result is determined by the following process factors: detergent concentration, contact time of the items to be cleaned from the first contact with the rinse water in the first rinse zone until they leave the final rinse zone, the mechanics of the spray systems or the spray jets in the rinse zones, and the temperatures in the individual rinse zones. Methods for recording the process parameters detergent concentration, contact of the items to be cleaned with the rinse water in the first rinse zone until they leave the final rinse zone, and the mechanics in the rinse zone. The detergent concentration is usually recorded via the conductivity of the rinse liquid. The contact time results from the transport speed of the conveyor system, and the washing mechanics are determined by the pressure of the circulation pump and the design of the spray system nozzles in the respective rinse zone. The temperature of the rinse water in the individual treatment zones is recorded using temperature sensors. Due to the cooling of the rinse water after it has left the spray nozzles of the spray system, the temperature reached on the surface of the items to be cleaned is not identical to the rinse water temperature. However, the temperature reached on the surface of the item to be cleaned in the individual treatment zones, as well as the time over which these temperatures act on the item to be cleaned, are crucial for reducing germs on the surface. The effect of a certain temperature on the surface of the item to be cleaned over a certain period of time is or can be referred to as the heat equivalent.

The relationship between temperature and time on germ reduction is, among other things, the basis for regulations and standards designed to ensure the cleaning effectiveness of dishwashers. Based on tests conducted on multi-tank dishwashers with the aim of defining the process parameters at which safe hygienic treatment of the wash ware is achieved, DIN 10510 C.3, a procedure for Germany, was adopted. This procedure provides recommendations regarding temperature, detergent concentration, and the duration between the first contact of the ware to be cleaned with the rinse liquid from the first rinse zone until it leaves the final rinse zone. This duration should then be used to operate this multi-chamber dishwasher in the individual process zones in order to achieve the required germ reduction during customer operation. This standard is based on the germ reduction of defined soiled test specimens after the cleaning process using contact tests. The test germ or organism used in this test is E. faecium ATCC 6057.

The hygiene safety testing of multi-tank dishwashers at the end user's site is carried out using contact test and the determination of the bacterial count in the rinse water of the last rinse tank. However, the disadvantage is that testing the bacterial reduction on-site at the customer's site according to this standard is very costly. Another disadvantage of this standard is the fact that the same bacterial reduction could also be achieved with a shorter contact time, for example, but at higher temperatures in the individual treatment zones. However, this standard does not permit this.

In the USA, the relationship between temperature and time on germ reduction is described by the NSF3 standard procedure. This specification is based on the germ reduction of tuberculosis bacteria determined from experiments through the exposure to a certain temperature over time. The effect of the temperature over time is referred to as the "heat equivalent." The number of heat equivalents achieved per second at which temperature is recorded in a table in this procedure. Based on this table, a minimum temperature is defined for the rinse water in the wash zone and the rinse zone, which the dishwasher must achieve in order to achieve the germ reduction required by this standard. For the dishwasher manufacturer, this means that these temperatures must be factory-set in the control system of the respective dishwasher, and that these temperatures are actually maintained during operation of the multi-tank dishwasher at the customer's premises. must be. When testing a dishwasher according to this method, a temperature sensor is attached to a plate. The plate is then placed in a specified position in the conveyor system of the multi-tank dishwasher and transported through the individual process zones of the multi-tank dishwasher. The temperatures during the cleaning process are recorded. From the temperature curve during the transport of the washware through the multi-tank dishwasher, the heat equivalents acting on the plate throughout the entire cleaning process are determined using the table mentioned above. This test must be carried out for three different plate positions in a dish rack or conveyor belt. To meet the required germ reduction, this regulation stipulates that at least 3600 heat equivalents must be achieved in each plate position. The advantage of this method is that it can be carried out on-site at the customer with relatively little effort to check the proper functioning of the multi-tank dishwasher with regard to thermal sanitization. A further advantage is that the result is available immediately after the measurement, allowing immediate confirmation of the quality of the cleaning process.

However, a disadvantage when operating a dishwasher is that the temperatures of the rinsing water in the individual treatment zones must be used to determine the heat equivalents acting on the dishes during the rinsing process, rather than the heat equivalents actually applied to the items being washed.

In the area of washer-disinfectors, prEN ISO 15883-1 describes a method which also uses the relationship between germ reduction and temperature over time to assess the hygiene effect. This relationship is referred to as the _A0 value and is also written down in tabular form or calculated using a mathematical formula. The _A0 value is described in more detail in Annex A of this standard and is defined as the time equivalent in seconds at 80°C at which a given disinfection effect is exerted. It corresponds analogously to the heat equivalents of the NSF3 standard, but based on a different test germ. The test organism used in this method is Enterococcus Faetium. Here, too, a minimum _A0 value to be achieved is specified for each point in the washing chamber of the washer-disinfector. However, this method has not yet been used to assess commercial dishwashers in Europe.

The procedures and standards described above for ensuring cleaning results with regard to thermal hygienization in a multi-tank dishwasher all have the disadvantage that the process parameters during operation of the dishwasher are fixed. This applies in particular to the temperatures in the wash and final rinse zones. If multiple programs or transport speeds are selectable, the multi-tank dishwasher must be designed for the worst-case scenario. This generally means the fastest transport speed. The fact that there is no known permanently built-in process for the heat equivalents actually acting on the washware for the operation of the multi-tank dishwasher, which is linked to the control system of the multi-chamber dishwasher and controls the washing process, results in the disadvantage that the multi-tank dishwasher cannot be optimally adapted to the actual washing process or washing program with regard to the heat equivalents. A further disadvantage of the currently known state of the art is that the heat equivalents actually transferred to the washware are not recorded, but it is assumed that the required germ reduction is achieved with the process parameters specified according to the standard or method.

WO 97/29789 A1 discloses a monitoring method of sterilization processes.

EP 1 196 650 B1 refers to a method for monitoring a washing process. An independent wireless monitoring device is mounted on a conveyor belt of an industrial dishwasher and moved with it. The measured data is recorded in a monitoring unit. This device could record the temperatures at the individual washing zones and evaluate them at a later time. The heat equivalents transferred to the items being cleaned could then be determined based on the measured temperature values. The difference to temperature recording according to the NSF3 standard method is that the temperature recording is wireless. EP 1 196 650 B1 However, with regard to the measured process temperature, the known device is used, similar to the test procedure according to the NSF3 standard, only to control the process temperatures, is not evaluated by the dishwasher control system and is therefore not used to directly control the process parameters of the multi-tank dishwasher.

Out of DE 196 08 036 C5 It is clear that the dependence of the rinse water quantity on the transport speed of the conveyor system of the multi-tank dishwasher is directly related. A dependence of the rinse water quantity and the actual The heat equivalent transferred to the wash ware is calculated according to DE 196 08 036 C5 not discussed in detail.

Description of the invention

The object of the present invention is to provide a method for detecting the heat equivalents transferred to the material to be cleaned in order to eliminate the above-mentioned disadvantages of the solutions according to the prior art and at the same time to increase the process reliability with regard to the thermal hygiene effect.

According to the invention, this object is achieved by the features of patent claim 1.

1. a) Es erfolgt eine Erfassung der Temperatur innerhalb mindestens einer der Behandlungszonen durch den Sensor,
2. b) danach erfolgt die Ermittlung des in mindestens einer der Behandlungszonen auf das zu reinigende Spülgut erfolgten Wärmeeintrags anhand der gemäß Verfahrensschritt a) ermittelten Temperatur,
3. c) anschließend erfolgt ein Vergleich des in der mindestens einen Behandlungszone erfolgten Wärmeeintrags mit einem vorgegebenen Wärmeeintrag und
4. d) abhängig vom Resultat des gemäß Verfahrensschritt c) durchgeführten Vergleiches der Wärmeeinträge wird die Transportgeschwindigkeit des Spülguts durch die Mehrtankspülmaschine oder eine Temperatur ϑ mindestens eines sich auf die Wärmeeinträge auswirkenden Verfahrensparameters als Stellgröße in einem Regelkreis für mindestens eine der Behandlungszonen variiert,

wobei bei der Temperaturerfassung durch mindestens einen stationär angeordneten Sensor eine Prognose des Wärmeeintrags auf Basis einer Extrapolation der Temperaturwerte einer in Transportrichtung des Spülgutes gesehen nachfolgenden Behandlungszone erfolgt.Following the solution proposed by the invention, a method for assessing and ensuring the thermal hygiene effect in a multi-tank dishwasher is proposed, in which at least one sensor is arranged that transmits the temperature within at least one treatment zone to a machine control system, in particular the control system of the multi-tank dishwasher. The following method steps are performed:

1. a) The temperature within at least one of the treatment zones is recorded by the sensor,
2. b) the heat input to the items to be cleaned in at least one of the treatment zones is then determined on the basis of the temperature determined in process step a),
3. c) the heat input in at least one treatment zone is then compared with a predetermined heat input and
4. d) depending on the result of the comparison of the heat inputs carried out according to process step c), the transport speed of the wash ware through the multi-tank dishwasher or a temperature ϑ of at least one process parameter affecting the heat inputs is varied as a control variable in a control loop for at least one of the treatment zones,

wherein, when the temperature is detected by at least one stationary sensor, a forecast of the heat input is made on the basis of an extrapolation of the temperature values of a subsequent treatment zone seen in the transport direction of the items to be washed.

Within method step c), following the method proposed according to the invention, it is determined whether the heat input into at least one of the treatment zones corresponds to the predetermined heat input, exceeds the predetermined heat input or falls below the predetermined heat input.

Depending on the result of this comparison and, if applicable, other parameters relevant to the washing result, if the specified heat input is exceeded, for example, the transport speed of the wash ware, which serves as a manipulated variable for the control loop, is increased so that the wash ware transported through the relevant treatment zone of the multi-tank dishwasher is transported through the zone more quickly. As an alternative to increasing the transport speed through the relevant treatment zone of the multi-tank dishwasher, if the specified heat input is exceeded, the temperature can be reduced in at least one heated zone of the treatment zones or the temperature in a subsequent treatment zone can be reduced in order to compensate for the increased heat input in the previous treatment zone. In addition, the temperature in a treatment zone already passed through by the wash ware can also be reduced, which enables energy savings with regard to heating at least one treatment zone and enables predictive operation of the multi-tank dishwasher, which is highly energy-efficient.

If, however, it is determined that the specified heat input is not reached due to the heat input in at least one of the treatment zones, the machine control system can reduce the transport speed of the wash ware through at least one of the relevant treatment zones. On the other hand, if the above criterion is met, i.e., if the actual heat input falls below the specified heat input, it is also possible to stop the wash ware from passing through the treatment zone of the multi-tank dishwasher and/or to indicate this condition on the display of the multi-tank dishwasher so that the operator of the multi-tank dishwasher is aware of it and can initiate appropriate measures. It is also possible, despite the heat input in at least one of the treatment zones of the multi-tank dishwasher falling below the specified heat input, to simply register this condition and take no action. but to ensure continuous monitoring of the heat input in the respective heated treatment zones of the multi-tank dishwasher. Continuous monitoring of the heat input in the heated treatment zones can also be carried out if it is determined that the specified heat input has been exceeded by the actual heat input.

The temperature in the individual treatment zones of the multi-tank dishwasher is recorded by stationary sensors assigned to each zone and transmitted to the machine control system, where the actual heat input in the treatment zones is calculated. The decisive factor is that the stationary sensor transmits the temperatures individually recorded in at least one treatment zone to the machine control system of the multi-tank dishwasher. When calculating the actual heat input in one or more of the treatment zones passed through or still to be passed through, the machine control system can calculate the heat input depending on the transport path covered by the washware in the respective treatment zone, taking into account the transport speed.

In the machine control system, the actual heat input in the relevant treatment zone can be determined based on the temperature values determined by the stationary sensor, also depending on the residence time of the items to be washed in the respective treatment zone.

To ensure hygiene, the multi-tank dishwasher's control system stores the specified heat inputs into the overall multi-tank dishwasher system, e.g., based on heat equivalents (HUE) of the NSF3 standard, the _A0 values of EN 15883-1 Annex 1, or an arbitrarily defined relationship between temperature ϑ and corresponding heat equivalents. These data stored in the machine control system and the resulting specified heat inputs into the washware are compared with the heat input actually occurring in at least one of the treatment zones of the multi-tank dishwasher and actually acting on the washware.

In a further embodiment of the method proposed according to the invention for assessing and ensuring the thermal hygiene effect in a multi-tank dishwasher, if the specified heat input is not reached by the actual heat input Heat input can temporarily set the transport speed of the wash ware through one of the treatment zones to 0, i.e., the transport of the wash ware through the multi-tank dishwasher can be stopped. This results in a longer dwell time of the wash ware in at least one of the treatment zones of the multi-tank dishwasher, so that the actual heat input increases.

In practical implementation of the method proposed according to the invention, depending on the result of the comparison between the actual heat input and the respectively predetermined heat input in at least one, preferably several, of the treatment zones of the multi-tank dishwasher, a fresh water flow supplied, for example, in a fresh water final rinse zone can be varied with regard to its volume flow, i.e. increased or decreased, or the temperature of the amount of water introduced into the fresh water final rinse zone can be varied in order to influence the actual heat input. In an analogous manner, in practical implementation of the method proposed according to the invention, the volume flow circulated within a pump final rinse zone of a multi-tank dishwasher can also be increased or decreased. In at least one wash zone of the multi-tank dishwasher upstream of the fresh water final rinse zone or the pump final rinse zone, the heating output of the heating elements installed, for example, in the tanks assigned to the wash zones can be varied depending on the result of the comparison between the actual heat input and the predetermined heat input. In the drying zone of the multi-tank dishwasher, which is usually located downstream of the fresh water final rinse zone or the pumped final rinse zone, the temperature of the drying air blown onto the washware can be varied, i.e. its temperature can be raised or lowered, in order to vary, i.e. increase or decrease, the heat input actually occurring there. Furthermore, following the method proposed according to the invention, additional heat can be input into at least one of the treatment zones of the multi-tank dishwasher by means of an infrared radiator, which is preferably arranged downstream of a drying zone as seen in or in the transport direction of the washware. This provides a further possibility of influencing heat input into the overall multi-tank dishwasher system, even when the treatment zones upstream of the drying zone, which the washware has already passed through, have been passed through. As an alternative to the additional heat input via an infrared radiator, electromagnetic radiation can be applied to the washware, or microwave or short- or long-wave irradiation of the washware can be carried out.

Based on the temperature data available in the machine control system of the multi-tank dishwasher, which is transmitted to it via the sensor permanently assigned to at least one treatment zone, the temperature can be adjusted in a treatment zone already passed by the washware, and a forecast of the heat input can be made based on an extrapolation of the temperature values of a subsequent treatment zone in the direction of transport of the washware. If the temperature is recorded in at least one of the treatment zones using one of these permanently assigned sensors, a temperature can be determined in at least one of the treatment zones, or a change can be made to a temperature gradient present in a heated one of the treatment zones.

Advantageously, the temperature can be adjusted in a treatment zone already passed by the wash ware and a forecast of the heat input can be made on the basis of an extrapolation of the temperature values of subsequent treatment zones seen in the direction of transport of the wash ware.

The method proposed according to the invention advantageously enables a multi-tank dishwasher to actively monitor the hygiene of the items to be cleaned and, for example, to initiate suitable measures, such as the aforementioned reduction or increase in the transport speed of a conveyor system, in the event of irregularities during washing operation, such as the introduction of items to be cleaned with different heat capacities and the associated change in energy requirements, or the introduction of cold water by the machine control system. Furthermore, the method proposed according to the invention can easily demonstrate flawless functioning of the multi-tank dishwasher with regard to thermal hygiene during operation at the end user of the multi-tank dishwasher, without, for example, actively introducing bacterial strains specified in the aforementioned standards into the multi-tank dishwasher.

The method proposed according to the invention further allows the hygiene effect to be ensured during operation of the multi-tank dishwasher at the operator's premises.

drawing

The invention is described in more detail below with reference to the drawing.

Figur 1

einen Ausschnitt eines Durchlaufspülautomaten mit einer Spülzone, einer Pumpenklarspülzone sowie einer Frischwasserklarspülzone und nicht erfindungsgemäßen kabellosen Sensoren,

Figur 2

einen Ausschnitt eines Durchlaufspülautomaten mit den einzelnen Behandlungszonen jeweils zugeordneten Sensoren, die erfindungsgemäß ortsfest installiert sind.

It shows:

Figure 1

a section of a continuous-flow dishwasher with a rinsing zone, a pump rinse zone and a fresh water rinse zone and wireless sensors not according to the invention,

Figure 2

a section of a continuous flow dishwashing machine with sensors assigned to the individual treatment zones, which are installed in a fixed location according to the invention.

Examples of implementation

According to the illustration Figure 1 1 shows a continuous-flow dishwasher 1 in which goods 32 to be cleaned are transported in the transport direction 2 through various treatment zones of the continuous-flow dishwasher 1 and which does not serve to carry out a method according to the invention. A conveyor device 3, which in the illustration according to Figure 1 is designed as an endless conveyor belt, transports the goods 32 to be cleaned through the various treatment zones of the continuous-flow dishwasher 1. Seen in the transport direction 2 of the goods 32 to be cleaned, these first pass through a rinsing zone 4.

Within the rinsing zone 4 are a first rinsing system 5 and a second rinsing system 6. From these, cleaning fluid 7 emerges in the form of jets. The first rinsing system 5 and the second rinsing system 6 are supplied with cleaning fluid via a first pump 8. The first pump 8 is housed within a rinsing zone tank 9, which is assigned to the rinsing zone 4. A pump housing 10 is located in the upper area of the first pump 8; the rinsing zone tank 9 is covered by a tank cover strainer 11. The rinsing zone tank 9 assigned to the rinsing zone 4 contains a heated or unheated water supply.

The rinsing zone 4 is separated by a separating curtain 13 from the pumped rinsing zone 14, which adjoins it—as seen in the transport direction 2 of the material 32 to be cleaned. The rinsing zone tank 9 is separated by a partition wall 12 from the tank located below the pumped rinsing zone 14 or the fresh water rinsing zone 18.

In the representation according to Figure 1 , which does not show an embodiment according to the invention, the item 32 to be cleaned leaving the rinsing zone 4 runs into a pumped rinse zone 14 after passing through the separating curtain 13. The pumped rinse zone 14 is fed via a second pump 15. The cleaning fluid 7 emerging from a first spray pipe 16 and a second spray pipe 17 in the pumped rinse zone 14 wets the item 32 to be cleaned from the top and bottom. The spray pipes 16 and 17 arranged in the pumped rinse zone 14 are held on a bent pipe, so that an offset of the first spray pipe 16 compared to the second spray pipe 17 of the pumped rinse zone 14 is achieved.

The same applies to a fresh water rinsing zone 18, which can be arranged downstream of the pumped rinsing zone 14. The fresh water rinsing zone 18 comprises an upper spray pipe 20 and a lower spray pipe 21. The two spray pipes 20 and 21 are also arranged offset from one another according to the spray pipe path 19 - as seen in the transport direction 2 of the material to be cleaned. The fresh water volume exiting the upper spray pipe 20 and the lower spray pipe 21 wets the material 32 to be cleaned from its top and bottom.

The fresh water rinsing zone 18 is followed by a heat recovery device 23, which contains an exhaust air fan 24, by means of which exhaust air is extracted from the continuous-flow dishwasher 1. A drying zone 25 adjoins the heat recovery device 23, as seen in the transport direction 2 of the items 32 to be cleaned. The drying zone 25 comprises a fan 26, to which a sensor 27 is assigned.

The air exiting from the blower 26 is blown via outlet nozzles 28 onto the upper side of the material to be cleaned. In the illustration according to Figure 1 Two outlet nozzles 28 are assigned to the blower 26, which are arranged one behind the other as seen in the transport direction 2 of the goods 32 to be cleaned. The drying zone 25 is shielded from an outlet section 30 of the continuous-flow dishwasher 1 by a further separating curtain 33. In the area of the outlet section 30 of the continuous-flow dishwasher 1 as shown in Figure 1 The dried and partially cooled, now cleaned material 32 can be removed from the conveyor device 3 designed as a conveyor belt. The conveyor device 3 designed as a conveyor belt is driven by a drive 31, which can be arranged at the end of the outlet section 30. According to the illustration Figure 1 , which does not show an embodiment according to the invention, it can also be seen that wireless sensors 40 not according to the invention can be attached to individual holding devices 33 of the conveyor device 3. The mounting position of the wireless sensor 40 in the upper region of holding devices 33 for the material 32 to be cleaned ensures that the temperature value detected by the sensor 40, which is transmitted via a signal 35 to a receiving part 34 of the controller 36, corresponds to the temperature of the material 32 to be cleaned held in the conveyor device 3. Alternatively, the wireless sensor 40 for detecting and transmitting the temperature signal 35 can also be mounted on a transport element of the circulating conveyor device 3, which is preferably designed as a conveyor belt. According to the Figure 1 In the non-inventive embodiment variant shown, the wireless sensor 40 is transported with the conveyor device 3 together with the items 32 to be cleaned through the individual treatment zones 4, 14, 18 and 25 of the continuous-flow dishwasher 1. The temperatures recorded in this process can be transmitted to the controller 36 either permanently at the end of each individual treatment zone 4, 14, 18, 25 or at the end of the entire process path. This controller calculates the heat equivalents transferred to the items 32 to be cleaned during the washing process and, if necessary, corrects, for example, the transport speed of the conveyor device 3 in the transport direction 2, the temperature of the final rinse water which is applied to the items 32 to be cleaned in the pumped final rinse zone 14 or in the fresh water final rinse zone 18, or other process parameters.

Figure 2 To illustrate an embodiment of the invention, shows a conveyor-type dishwasher with permanently installed sensors assigned to the individual treatment zones.

By means of the method proposed according to the invention and the correspondingly designed continuous-flow dishwasher 1, it is possible to always achieve an optimal transport speed of the conveyor device 3 during continuous transport of the goods 32 to be cleaned through the continuous-flow dishwasher 1 in its individual treatment zones 4, 14, 18, 25, depending on the process steps taking place there.

In the various treatment zones 4, 14, 18, 25 of the continuous-flow dishwasher 1, there are preferably fixed sensors 50, 51, 52, 53, which are arranged in the various treatment zones. The respective installation positions of the sensors 50, 51, 52, 53 are shown as examples; depending on the other general conditions, the positions of the respective sensors 50, 51, 52, 53 are selected such that the values determined by them Temperatures correspond to the temperatures which the items 32 to be cleaned have when passing through the various treatment zones 4, 14, 18, 25 within the conveyor dishwasher 1. The sensors 50, 51, 52 and 53 exchange measurement data with the controller 36 of the conveyor dishwasher 1. The controller 36, which is assigned to the conveyor dishwasher 1, can either be an internal controller, i.e. arranged within the conveyor dishwasher 1, or an external controller 36, i.e. located outside the conveyor dishwasher 1. The controller 36 comprises a microprocessor (CPU) 45 and a data memory 46. All functions relating to the program steps running in the conveyor dishwasher 1, i.e. also the process running within the conveyor dishwasher 1 for assessing the hygiene effect, are controlled via a main control line. The controller 36 further comprises a measurement data acquisition unit 47, via which the temperature values recorded by the at least one stationary sensor 50, 51, 52, 53 are recorded and stored in a data memory 46. The stationary sensors 50, 51, 52 and 53 are connected to the Figure 2 The line shown is connected to the control unit 36, via which the individual process steps of the continuous-flow dishwasher 1 are controlled.

In addition, the controller 36 controls the electrical power supply of pumps 8 and 15 via a power regulator, which can be connected upstream of each of them. A power regulator can also be connected upstream of the fresh water pump, i.e., the second pump 15, via which the electrical power supply of the fresh water pump can be controlled. The same applies to a power regulator, via which the power supply of a heating element for the rinse solution can be controlled, as well as to another power regulator, which controls the power supply of a heating element in a possibly provided continuous-flow heater or boiler for heating the final rinse water.

The controller 36 stores the values for the heat equivalents within the data memory 46 provided therein, which are relevant either according to the NSF3 standard or according to the A ₀ value method for determining or classifying the hygienic performance of a conveyor-type dishwasher 1. For example, the following A ₀ values can be stored in the data memory 46 of the controller 36, in accordance with the prEN ISO 15883 standard expected in Europe:

The A ₀ value shown in the table above is defined as the time equivalent in seconds during which a disinfection effect is exerted. The A ₀ value of a moist heat disinfection process indicates the killing of germs, specified as a time equivalent in seconds at a temperature transferred by the process to the product, such as the item 32 to be cleaned.

A permanently installed sensor 50, 51, 52, 53, which is used in a respective treatment zone 4, 14, 18, 25 of a conveyor dishwasher 1, can be calibrated to the temperature sensor used within the NSF3 standard test procedure or within the A ₀ test procedure in such a way that the same heat equivalents as in the NSF3 standard procedure or in the A ₀ test procedure can be determined via the control 36 within the conveyor dishwasher 1. The heat equivalents currently achieved within a program step are determined by means of the sensors 50, 51, 52, 53 according to the invention mounted within the respective treatment zone 4, 14, 18, 25 or the sensors 40 not according to the invention mounted on the continuous transport device and the control 36 and are compared with the table values stored in the data memory 46, for example in the case of prEN ISO 15883-1 the values stored there. If the values for the heat equivalents achieved within the respective treatment zone 4, 14, 18, 25 of the continuous-flow dishwasher 1, determined by the sensors 50, 51, 52, 53 according to the invention, mounted within the respective treatment zone 4, 14, 18, 25, or by the sensors 40 not according to the invention, mounted on the conveying device through which the washing product passes, are too low, the controller 36 can either increase the temperature of the rinsing solution stored in the rinsing solution tank, or the controller 36 can increase the temperature of the fresh water supplied within the final rinse zone 18 via the final rinse systems 20, 21 arranged there. For this purpose, the controller 36 controls the corresponding power regulators assigned to the respective pumps 8, 15. Furthermore, it is possible to vary the transport speed of the items 32 to be cleaned in the transport direction 2 through the continuous-flow dishwasher 1 via the control system 36, depending on the heat equivalent values calculated in the control system 36. If the values for the heat equivalents required according to the aforementioned standards are not achieved, the drive of the conveyor device 3 can be influenced, for example, via the control system 36, so that it runs more slowly and thus transports the items 32 to be cleaned at a lower speed through the individual treatment zones of the continuous-flow dishwasher 1, so that the exposure time of the heat equivalents is extended, which ultimately contributes to ensuring or increasing the temperature acting on the items 32 to be cleaned or being cleaned.

If the values specified according to the NSF3 standard or according to prEN ISO 15883-1 for the heat equivalents entered in the respective treatment zones 4, 14, 18, 25 of the conveyor-type dishwasher 1 are reached, the items 32 to be cleaned are transported to the next treatment zone 4, 14, 18, 25. The determined values for the heat equivalents can be displayed on a display 48.

A further advantage that can be achieved with the method proposed according to the invention for assessing and ensuring the hygiene effect, which is implemented on a conveyor-type dishwasher 1, is that the conveyor-type dishwasher 1 actively monitors the hygiene of the items 32 to be cleaned. Irregularities in the washing operation, such as the introduction of a larger quantity of cold water into, for example, the rinse solution tank and a resulting drop in temperature within the washing zone 4, can be compensated for by suitable countermeasures initiated via the controller 36. For example, the controller 36 can be used to extend the final rinse process on the one hand, or to increase the temperature of the rinse solution tank by appropriately controlling a power regulator assigned to the heating element of the rinse solution tank in order to counteract the temperature drop caused by the cold water introduction. Furthermore, as already mentioned above, it is possible to vary the transport speed of the conveyor belt through the individual treatment zones 4, 14, 18, 25 of the continuous-flow dishwasher 1 based on the values for the heat equivalents determined in the controller 36, which are based on the temperatures detected by the wireless sensors 40 not according to the invention or by the stationary sensors 50, 51, 52, 53 according to the invention. Using the method proposed according to the invention, it is possible to record the respective heat equivalents achieved at each process step within the continuous-flow dishwasher 1, regardless of irregularities, before the start of each process step, and to evaluate them according to the specifications of the NSF3 regulation or the prEN ISO 15883-1 standard, and to control the process parameters of the continuous-flow dishwasher 1 accordingly. The achieved values for the calculated heat equivalents can be displayed on the display 48. The user of the continuous flow dishwasher 1 is thus given the opportunity to monitor and control the thermal hygiene effect during each process step.

The method proposed according to the invention can preferably be carried out at the Figure 2 implement the multi-tank dishwasher shown, designed as a continuous-flow dishwasher, which has at least one cleaning zone, a pump rinsing zone, a fresh water rinsing zone and, if appropriate, a drying zone.

The above in connection with the Figures 1 and 2 The continuous-flow dishwasher 1 shown has a machine control system that has at least one microprocessor 45, a data memory 46, a measurement data acquisition device 47, and a display 48. The temperatures within the at least one treatment zone 4, 14, 18, 25 are transmitted to the machine control system 36 via the sensors 27 or the wireless sensors 40 not according to the invention or the stationary sensors 50, 51, 52, and 53 according to the invention. The temperatures within at least one of the treatment zones 4, 14, 18, 25 are previously detected by the wireless sensors 40 not according to the invention or the stationary sensors 50, 51, and 53 according to the invention, and the heat input to the items 32 to be cleaned in at least one of the treatment zones 4, 14, 18, 25 is determined in the machine control system 36 based on the previously determined temperature. In the machine control system 36, a comparison of the heat input occurring in at least one treatment zone 4, 14, 18, 25 with a predetermined heat input is then carried out. Depending on the result of this comparison of the heat inputs, either a variation in the transport speed of the wash ware 32 through the continuous-flow dishwasher 1 or a variation in the temperature ϑ of at least one of the process parameters affecting the heat input can be carried out as a manipulated variable in a control loop for at least one of the treatment zones 4, 14, 18, 25.

Depending on the result of the comparison, whether the heat input into at least one of the treatment zones 4, 14, 18, 25 corresponds to the specified heat input, it can be determined that the specified heat input was exceeded, undershot or exactly met.

If the specified heat input is exceeded, the transport speed of the wash ware 32 can be increased or the temperature can be reduced in the relevant treatment zone 4, 14, 18, 25. If this is a heated treatment zone 4, 14, 18, 25, then, for example, in the case of a cleaning zone, a heating element installed in a tank can have its heating output reduced or the temperature can be reduced in a subsequent treatment zone - viewed in the conveying direction of the wash ware 32 through the treatment zones 4, 14, 18, 25. It is also possible to reduce the temperature in a treatment zone already passed through by the wash ware 32. of the treatment zones 4, 14, 18, 25 in order to optimize the required heating power to be supplied to the entire system of continuous-flow dishwasher 1.

If the comparison carried out in the machine control system 36 shows that the specified heat input is not achieved by the heat input actually applied to the wash ware 32, the transport speed of the wash ware 32 through at least one of the treatment zones 4, 14, 18, 25 can be reduced via the machine control system 36. To achieve this, the speed of the drive driving the conveyor device 3 can be reduced. Furthermore, the transport of the wash ware 32 through the treatment zones 4, 14, 18, 25 in the conveying direction 3 can also be stopped via the machine control system 36 and resumed after a dwell time has elapsed. As an alternative to interrupting the continuous flow of wash ware 32 through the treatment zones 4, 14, 18, 25 of the conveyor dishwasher 1, this circumstance can also be simply displayed on the display 48 of the machine control system 36. Even if the specified heat input is exceeded by the heat input actually applied to the items to be washed 32 in at least one of the treatment zones 4, 14, 18, 25, this circumstance can only be displayed via the display 48, whereby the operator(s) of the continuous-flow dishwasher 1 are free to intervene via the machine control 36 and initiate countermeasures.

While the continuous flow dishwasher according to Figure 1 If the sensor 40 is not transported in the conveying direction 3 through the continuous dishwashing machine 1 with the items 32 to be cleaned, the sensor 27 assigned to the drying zone 25 is installed in a fixed location. The same applies to the Figure 2 illustrated embodiment of the continuous-flow dishwasher 1, where the sensors 50, 51, 52 and 53 are assigned to the respective treatment zones in a stationary manner according to the invention. Figure 1 During the transport of the wash ware 32 in the conveying direction 3 through the continuous-flow dishwasher 1, the temperature values ϑ _1...n in the respective treatment zones 4, 14, 18, 25 can be detected by means of the sensor 40 which is not according to the invention and which is moved along with the wash ware 32, and after transmission to the machine control 36, the actual heat input in the respective treatment zones 4, 14, 18, 25 can be calculated. In the case of the Figure 2 illustrated embodiment with inventive stationary sensors 50, 51, 52 and 53, the heat input in the treatment zones 4, 14, 18, 25 is calculated taking into account the transport path of the wash ware 32 in the conveying direction 3 covered in the respective treatment zone and the prevailing speed of the conveying device 3. The heat input into at least one of the treatment zones 4, 14, 18, 25 can also be carried out depending on the residence time of the items to be cleaned 32 in the respective treatment zone 4, 14, 18, 25, for example by setting the restart time after a stop in the transport of the items to be cleaned 32 in the transport direction 2 through the continuous-flow dishwasher 1.

In the machine control 36, the specified heat inputs are stored either based on the heat equivalents (HUE) of the NSF3 standard or the A ₀ values of EN 15883-1 Annex 1 or an arbitrarily defined relationship between the temperature ϑ and the corresponding heat equivalents.

As already explained above, if the heat input actually occurring in at least one of the treatment zones falls below the specified heat input, the transport speed of the material to be cleaned 32 in transport direction 2 through one of the treatment zones 4, 14, 18, 25 can be temporarily set to 0. To practically implement a variation in the heat input, the fresh water flow supplied to the fresh water final rinse zone 18 can be varied with regard to the volume flow or with regard to the temperature of the fresh water 22 to be introduced into the fresh water final rinse zone 18. Within the pump final rinse zone 14, the volume flow circulated there can also be increased or decreased to vary the temperature. In one or more wash zones 4 of the conveyor-type dishwasher 1, heating elements arranged in tanks 9 can be varied with regard to their heating output in order to vary the actual heat inputs in the wash zones 4. Within the drying zone 25, the temperature of the air used to dry the material 32 to be cleaned can be changed depending on the comparison of the predetermined heat input with the actual heat input.

In a further advantageous embodiment of the method proposed according to the invention, the Figure 2 The continuous-flow dishwasher 1 shown can be provided with an infrared radiator arranged behind the drying zone 25, an emitter emitting electromagnetic radiation or a microwave system or a short- or long-wave emitting device in order to create a further possibility, after passing through all treatment zones 4, 14, 18 and 25, of treating the items 32 to be cleaned, which have already passed through the aforementioned treatment zones, again with regard to the heat input acting on the items 32 to be washed.

If the sensor is a sensor 40 which is not in accordance with the invention and which moves with the machine control system 36, it can be used to adjust the temperature in a treatment zone 4, 14, 18, 25 which has already been passed through by the items 32 to be cleaned and/or to predict the heat input on the basis of an extrapolation of the temperature values of a treatment zone 4, 14, 18, 25 which follows in the direction of transport of the items 32, which enables the continuous-flow dishwasher 1 to be operated in an energy-optimized manner.

In the case of temperature detection by means of a sensor 40 not according to the invention which is moved through the treatment zones 4, 14, 18, 25, a correction of the temperature in a transport zone or a correction of the temperature in at least one tank 9 assigned to a treatment zone can be carried out.

Are the sensors 50, 51, 52, 53 as in Figure 2 However, if the sensors 40, 50, 51, 52, 53 are shown as being permanently assigned to the treatment zones 4, 14, 18, 25 according to the invention, the temperature is determined directly in the treatment zone or a change in a temperature gradient present in a heatable one of the treatment zones 4, 14, 18, 25 can be achieved. With stationary sensors 40, 50, 51, 52, 53 according to the invention, the temperature can be adjusted in a treatment zone 4, 14, 18, 25 already passed through by the items 32 to be cleaned, and a forecast of the heat input can be made based on an extrapolation of the temperature values of the subsequent treatment zones 4, 14, 18, 25 as seen in the transport direction 2 of the items 32. <u>List of reference symbols</u> 1 Continuous-flow dishwasher 34 Recipient 2 Transport direction of goods to be cleaned 35 Temperature signal, wireless 3 conveyor system 36 steering 4 Flushing zone 38 Basket 5 first flushing system 40 wireless sensor 6 second flushing system 7 Cleaning fluid 42 Run-off area 8 first pump 43 drain line 9 Rinse zone tank 10 Pump housing 45 Microprocessor (CPU) 11 Tank cover strainer 46 Data storage 12 partition 47 Measurement data acquisition device 13 Partition curtain 48 Display 14 Pump rinse zone 15 second pump 50 Sensor flush zone 16 first spray tube 51 Sensor pump rinse zone 17 second spray tube 52 Sensor fresh water rinse zone 18 Fresh water rinse zone 53 Drying zone sensor 19 Spray pipe course 20 upper spray tube 21 lower spray tube 22 Fresh water jet 23 Heat recovery system 24 Exhaust fan 25 Drying zone 26 fan 27 sensor 28 Outlet nozzle 29 Outlet opening 30 Run-off section 31 drive 32 goods to be cleaned 33 Holding devices

Claims (19)

1. Method for assessing and guaranteeing the thermal hygiene efficiency in a multi-tank dishwasher in which there is at least one sensor (40; 50, 51, 52, 53) that transmits the temperature inside at least one treatment zone (4, 14, 18, 25) to a machine control system (36), in particular to the control system of the multi-tank dishwasher, said method comprising the following method steps:

   a) detecting the temperature inside at least one of the treatment zones (4, 14, 18, 25) by means of the sensor (40, 50, 51, 53),

   b) determining the heat input applied to the items to be cleaned in at least one of the treatment zones (4, 14, 18, 25), on the basis of the temperature determined under a),

   c) subsequently comparing the heat input in the at least one treatment zone (4, 14, 18, 25) with a predefined heat input, and

   d) as a function of the result of the comparison of the heat input values according to method step c), varying the transport speed of the items to be cleaned through the multi-tank dishwasher, or varying the temperature 9 of at least one process parameter acting on the heat input values as a control variable in a control loop for at least one of the treatment zones (4, 14, 18, 25),

   wherein, when the temperature is detected by at least one stationary sensor, a prognosis of the heat input is made on the basis of an extrapolation of the temperature values of a downstream treatment zone (4, 14, 18, 25) viewed in the transport direction of the items to be cleaned.
2. Method according to Claim 1, characterized in that, in method step c), it is determined whether the heat input in the at least one treatment zone (4, 14, 18, 25) corresponds to the predefined heat input, exceeds the predefined heat input or is below the predefined heat input.
3. Method according to Claim 2, characterized in that, if the predefined heat input is exceeded, the transport speed of the items to be cleaned is increased as control variable.
4. Method according to Claim 2, characterized in that, if the predefined heat input is exceeded, the temperature in at least one heated zone of the treatment zones (4, 14, 18, 25) is lowered.
5. Method according to Claim 4, characterized in that the temperature in a downstream treatment zone is lowered.
6. Method according to Claim 4, characterized in that the temperature is lowered in a treatment zone of said treatment zones (4, 14, 18, 25) through which the items to be cleaned have already passed.
7. Method according to Claim 2, characterized in that, if the heat input is below the predefined heat input, the transport speed of the items to be cleaned through at least one of the treatment zones (4, 14, 18, 25) is reduced.
8. Method according to Claim 2, characterized in that a discontinue criterion is satisfied, and the passage of the items to be cleaned through the treatment zones (4, 14, 18, 25) of the multi-tank dishwasher is stopped and/or this status is displayed.
9. Method according to Claim 1, characterized in that the temperature of the treatment zones (4, 14, 18, 25) is in each case detected by respective stationary sensors, and the heat input in the treatment zones (4, 14, 18, 25) is calculated as a function of the distance travelled by the items to be cleaned in the zone and as a function of the conveyor belt speed.
10. Method according to Claim 10, characterized in that the heat input in at least one of the treatment zones (4, 14, 18, 25) is calculated as a function of the dwell time of the items to be cleaned in the respective treatment zone (4, 14, 18, 25).
11. Method according to Claim 1, characterized in that the predefined heat input values correspond either to the heat equivalents (HUE) of the NSF3 standard or to the A₀ values of EN 15883-1 Annex A, or any defined relationship between the temperature ϑ and the corresponding heat equivalents.
12. Method according to Claim 2, characterized in that, if the actual heat input is below the predefined heat input, the transport speed of the items to be washed through one of the treatment zones (4, 14, 18, 25) is temporarily set to 0.
13. Method according to Claim 1, characterized in that, as a function of the result of method step c), a fresh water flow delivered in a fresh-water final-rinse zone is varied in terms of its volumetric flow, or the temperature of the water added in the fresh-water final-rinse zone is varied.
14. Method according to Claim 1, characterized in that, as a function of the result according to method step c), the volumetric flow circulated inside a pump-operated final-rinse zone is increased or reduced.
15. Method according to Claim 1, characterized in that, as a function of the result of method step c), the heating power of the heating elements installed in a washing zone of the multi-tank dishwasher is varied.
16. Method according to Claim 1, characterized in that, as a function of the result of method step c), the temperature of the air located inside a drying zone of the treatment zones (4, 14, 18, 25) is varied.
17. Method according to Claim 1, characterized in that, as a function of the result of method step c), additional heat is input into the treatment zones (4, 14, 18, 25) by means of an infrared emitter which, viewed in the transport direction of the items to be cleaned, is preferably arranged downstream of a drying zone.
18. Method according to Claim 1, characterized in that, as a function of the result of method step c), additional heat is input into at least one treatment zone (4, 14, 18, 25) by electromagnetic radiation or by microwaves or by short or long waves.
19. Method according to Claim 1, characterized in that, when the temperature is detected by at least one stationary sensor assigned to a treatment zone (4, 14, 18, 25), the temperature in the at least one treatment zone (4, 14, 18, 25) is determined, or a temperature gradient present in a heated zone of the treatment zones (4, 14, 18, 25) is modified.

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