Conveyor dishwasher and operating method for same

A conveyor dishwasher includes a storage tank for holding sprayed final rinse liquid and a controllable liquid transfer device for transferring liquid from the storage tank to at least one wash zone as a function of a liquid demand in at least one of the wash zones.

TECHNICAL FIELD

The invention relates to a conveyor dishwasher and an operating method for same.

BACKGROUND

Conveyor dishwashers (such as a belt conveyor dishwashing machine or flight-type dishwasher) are used in the commercial area. An exemplary conveyor dishwasher is known from European Patent 0 838 190 B1. In contrast with household dishwashers in which the wash ware to be cleaned remains stationary in the machine during the cleaning process with conveyor type dishwashers the wash ware is conveyed through various zones of the conveyor dishwasher. Each zone is provided with a tank which holds the liquid sprayed in the respective zone. The conveyor dishwasher includes in particular at least one zone designed as a wash zone in which the wash ware is cleaned to remove impurities, e.g., food residues.

With known conveyor dishwashers, two factors often contribute to the total water consumption: first, the initial filling of the conveyor dishwasher in which fresh water is added to the tank of the at least one wash zone and, secondly, the final rinse during operation of the conveyor dishwasher. The final rinse liquid supplied for the final rinse runs according to the cascade principle through the entire machine. The water is kept fresh in the tanks, i.e., the concentration of impurities is kept low by constant dilution. Another effect of this supply of liquid into the tanks is that exactly as much liquid is displaced out of the tanks, i.e., enters the drain, as is supplied to the tanks.

SUMMARY

In an aspect, a conveyor dishwasher for cleaning wash wares includes a conveyor device for conveying the wash wares in a direction of conveyance through at least two zones of the conveyor dishwasher, at least one zone of which is a wash zone having spray nozzles. A tank and a pumping device are provided for recirculating wash liquid from the tank to the spray nozzles and spraying the wash liquid through the spray nozzles onto the wash wares. At least one zone is a final rinse zone including spray nozzles for spraying final rinse liquid onto the wash wares. A storage tank gathers sprayed final rinse liquid and a liquid transfer device is used for transferring liquid from the storage tank to the wash zone, which thereby forms a target zone. A control unit is configured for automatic operation of the liquid transfer device depending on the liquid demand in the wash zone.

In another aspect, a method for operating a conveyor dishwasher is provided. The method includes providing the conveyor dishwasher with a final rinse zone for spraying final rinse liquid onto the wash ware and a wash zone for spraying wash liquid onto the wash ware. Wash liquid is sprayed onto the wash ware in the wash zone. Final rinse liquid is sprayed onto the wash ware. The final rinse liquid is collected in a storage tank. The final rinse liquid is supplied to the wash zone as a function of demand for liquid.

Advantageously, a supply of final rinse liquid may be available in the storage tank, the tank may be filled with the final rinse liquid from the storage tank when liquid is entrained. This can reduce fresh water consumption.

The initial filling of the conveyor dishwasher may be performed using final rinse liquid from the storage tank. This can reduce the demand for fresh water.

This invention is explained in greater detail below with reference to the drawings on the basis of preferred embodiments as examples. The definitions and explanations given above also apply to the following description of the drawings and vice-versa.

DETAILED DESCRPTION

The conveyor dishwasher2shown inFIG. 1for washing wash ware4contains a conveyor device6for conveying the wash ware4in a direction8of conveyance through at least two zones of the conveyor dishwasher2. In the embodiment shown here, the conveyor device6is a belt-type conveyor device. As an alternative, the conveyor device6may be a rack conveyor device.

The term “wash ware4” includes, as examples, dishes, glasses, cutlery, pots, containers, boxes, trays, etc. The term “cleaning” includes, as examples, pre-wash, wash, post-wash, final rinse, etc. The term “washing” refers to cleaning the wash ware4with the wash liquid to remove impurities from the wash ware4. The term “final rinse” refers to the treatment of the wash ware4with final rinse liquid to remove wash liquid in particular from the wash ware4. Final rinse liquid may be, for example, pure water or water to which a rinse aid has been added.

The conveyor dishwasher2illustrated inFIG. 1includes a front wash zone10, as seen in the direction8of conveyance of the wash ware4, a rear wash zone12, a post-wash zone14and a final rinse zone16. The post-wash zone14is also referred to as the pre-rinse zone. The front wash zone10, the rear wash zone12and the post-wash zone14each have a tank18,20,22, spray nozzles24,26,28and a pump mechanism30,32,34for recirculating liquid from the respective tank18,20,22to the spray nozzles24,26,28of the respective zone10,12,14and thereby spraying the liquid out of the respective tank18,20,22onto the wash ware4. The final rinse liquid is preferably used for the first time in the final rinse zone16. In the post-wash zone14, final rinse liquid that has already been used is reused as post-wash liquid. In one embodiment, it is recirculated.

The final rinse zone16has spray nozzles36for spraying final rinse liquid onto the wash ware4. The final rinse liquid may be conveyed by a pump mechanism38to the spray nozzles36, as depicted here, for example, or it may be conveyed through corresponding line pressure in the final rinse liquid line. A heat exchanger40and a heating device42, preferably a water heater, are provided for heating the final rinse liquid.

The final rinse liquid discharged from the final rinse nozzles36may be fresh water, for example or fresh water mixed with rinse aid.

The conveyor dishwasher2has a bottom part44where the sprayed final rinse liquid collects. In the embodiment illustrated here, the bottom area44includes an area of the final rinse zone16and the post-wash zone14. A tank opening45may be formed in the bottom area44opening into the tank22of the post-wash zone14, as illustrated inFIG. 1. In this way final rinse liquid sprayed by the spray nozzles36enters the tank22of the post-wash zone14. In this sense, the tank22of the post-wash zone14is a shared tank which is provided for both the final rinse zone16and also the post-wash zone14. The final rinse liquid sprayed by the spray nozzles36of the final rinse zone16is recirculated by the pump mechanism34to the spray nozzles28of the post-wash zone14.

According to this invention the conveyor dishwasher has a storage tank46to hold sprayed final rinse liquid. “Sprayed final rinse liquid” as used herein may be final rinse liquid sprayed by the spray nozzles36of the final rinse zone16or post-wash liquid sprayed by the spray nozzles28of the post-wash zone14. Post-wash liquid is final rinse liquid that has already been used. In any case, “sprayed final rinse liquid” refers to a liquid to which no detergent has been added in order to maintain a predetermined detergent concentration in the final rinse liquid, as is the case with the wash liquid in wash tanks18,20. Of course, the final rinse liquid sprayed onto the wash ware4and running off of the wash ware4contains a nonspecific detergent concentration, but it is lower than the detergent concentration in the wash tanks.

In general, at least one zone in which final rinse liquid is sprayed is connected by fluid flow to the storage tank46. For example, the final rinse zone16may be connected to the storage tank46by flow in such a way that sprayed final rinse liquid enters the storage tank46. Furthermore, the post-wash zone14may be connected by flow to the storage tank46in any desired manner so that sprayed final rinse liquid enters the storage tank46.

In the embodiment depicted here, the bottom part44has a storage tank opening47in the area of the post-wash zone14, said opening being connected by flow to the storage tank46, namely by a line48here. As an alternative to the embodiment depicted here, the line48may be connected to the bottom part44in the area of the final rinse zone. Furthermore, the line48may be connected to the tank22of the post-wash zone14.

In the depicted embodiment, zone walls50are provided, bordering the bottom part44at the side and permitting a liquid level52above the tank opening45and above the storage tank opening47so that liquid can flow out of the tank22and into the storage tank opening44and then can flow out through the line48into the storage tank46. This configuration permits adequate filling of the tank22with final rinse liquid on the one hand, while on the other hand also allowing final rinse liquid to automatically flow over into the storage tank46when the liquid level52is higher than the storage tank opening47.

A controllable liquid transfer device54is provided having a pump mechanism56and a liquid line58for transferring liquid from the storage tank46to the rear wash zone12, which thus forms a target zone. The liquid transfer device54may be formed by any other device which allows controlled transfer of liquid from the storage tank46into the at least one target zone.

The mouth60of the liquid transfer device54is preferably arranged with a distance in height above than tank20of the wash zone12, as illustrated inFIG. 1. The conveyor dishwasher2also contains a control unit62which is designed for automatic operation of the liquid transfer device54as a function of a liquid demand in at least one of the wash zones10,12, e.g., as a function of a liquid demand in the rear wash zone12or in the front wash zone10.

To determine a liquid demand in at least one of the wash zones10,12, a sensor device may be provided.

The front wash zone10includes a sensor device in the form of a turbidity sensor64for detecting a degree of soiling of the liquid in the tank18of the front wash zone10. Furthermore, the rear wash zone12includes a sensor device in the form of a turbidity sensor66for detecting a degree of soiling of the liquid in the tank20of the rear wash zone12. The control unit62is designed for operating the liquid transfer device54when the degree of soiling in the tank20of the rear wash zone12is above a predetermined degree of soiling. By operating the liquid transfer device54, liquid from the storage tank64is supplied to the tank20of the rear wash zone12and thus the degree of soiling, i.e., the concentration of impurities in the tank20of the rear wash zone12is reduced.

The control unit62is also designed for operating the liquid transfer device54when the degree of soiling in the tank18of the front wash zone10exceeds a predetermined degree of soiling. The predetermined degree of soiling of the liquid in the tank20of the rear wash zone12may be equal to the predetermined degree of soiling of the liquid in the tank18of the front wash zone12. Furthermore, the predetermined degree of soiling of the liquid in the tank18of the front wash zone10may be higher than the predetermined degree of soiling of the liquid in the tank20of the rear wash zone12. In the case of a liquid demand in the tank18of the front wash zone10and operation of the liquid transfer device54on this basis, the liquid is supplied in the embodiment depicted here from the storage tank46to the tank20of the rear wash zone12from which liquid can flow via liquid overflow device68, namely an overflow channel here, into the tank18of the front wash zone10to thereby reduce the concentration of impurities in the liquid in the tank18. The liquid from the tank20of the rear wash zone12flows over the overflow channel68into the tank18of the front wash zone10when the liquid level in the tank20of the rear wash zone12is above the outflow level77.

The tank18of the front wash zone10is equipped with an overflow70(drain) through which liquid can flow out of the tank18. When the liquid in the tank18of the front wash zone is above an outflow level79, liquid flows out of the tank18through the overflow70.FIG. 1illustrates such a situation, where the prevailing momentary liquid level in the tanks18,20is above the prevailing outflow level77,79.

At least one of the sensor devices may also be designed in the form of a liquid level sensor for detecting a predetermined level of liquid in the tank of the respective at least one wash zone. In the embodiment depicted here, the rear wash zone12is provided with a level sensor72for detecting a predetermined lower level73of liquid in the tank20of the rear wash zone12. Furthermore, the front wash zone10is provided with a liquid level sensor74for detecting a predetermined lower level75of the liquid in the tank18of the front wash zone10. The predetermined lower level73of the rear wash zone12may be at the same height as the predetermined lower level75of the front wash zone10. Furthermore, the predetermined lower level73of the rear wash zone12may be higher or alternatively lower than the predetermined lower level75of the front wash zone10. The predetermined lower levels73,75are preferably below the respective outflow level77,79of the respective tank20,18. In the embodiment depicted here, the liquid level sensors72,74are designed as level switches, where the predetermined lower level73,75corresponds to the lower switch point of the respective liquid level switch72,74.

Liquid may be supplied out of the storage tank46into the respective target zone over a predetermined period of time, for example. Furthermore, liquid may be supplied from the storage tank46into the respective target zone until a predetermined upper level has been reached or exceeded in the target zone. The predetermined upper level may be for example the upper switch level of the liquid level switch72,74in the respective wash zone10,12. The predetermined upper level of the respective wash tank may be at the same height as the outflow level77,79of the respective wash tank, for example.

In particular, entrainment of liquid by large dishes from the rear zone12into the front zone10can be detected by means of the liquid level sensor72in the tank20of the rear zone12and the tank may be filled accordingly with liquid out of the storage tank46. Such an entrainment of liquid in conveyor dishwashers occurs in particular with large wash ware whereby liquid entrainment occurs in the opposite direction from the direction of conveyance of the wash ware and consists of the fact that liquid which is sprayed onto the wash ware4in a downstream zone in the direction8of conveyance, flows into the preceding zone10on this wash ware4.

There may also be a demand for liquid in the wash zones10,12in the initial filling of the conveyor dishwasher2. Accordingly, the control unit62is preferably designed for operating the liquid transfer device54in the initial filling of the conveyor dishwasher2to supply liquid from the storage tank46to at least one of the wash zones10,12, preferably both wash zones10,12. In this way, the fresh water demand of the conveyor dishwasher2can be reduced because no supply of fresh water is necessary for the initial filling of the wash tanks18,20but instead the final rinse liquid generated in a previous cleaning operation of the conveyer dishwasher is reused for the initial filling of the wash tanks10,12.

To this end, the volume of the storage tank46maybe of such a dimension that it is at least equal to the sum of the individual tank volumes of the wash tanks18,20of the wash zones10,12. Furthermore, depending on the available space, the volume of the storage tank46may be smaller than the sum of the individual tank volumes of the wash tanks18,20.

AsFIG. 1shows, a fresh water supply device76may be provided, so that fresh water can be supplied to the storage tank46. In this case, preferably at least one sensor device is provided for determining a fresh water demand in the storage tank46and the control unit62is designed for operating the fresh water supply device76and therefore supplying fresh water to the storage tank46when there is a demand for fresh water in the storage tank46.

A sensor device for determining a fresh water demand in the storage tank46may be, for example a liquid level sensor78for detecting a predetermined lower level80of the liquid in the storage tank46. The control unit62is in this case designed to operate the fresh water supply device76in predetermined operating states, e.g., in the initial filling of the wash tanks and thereby supply fresh water to the storage tank46when the liquid level in the storage tank is equal to the predetermined lower level80or below the predetermined lower level80. The predetermined lower level80in the embodiment depicted here corresponds to the lower switch point of the liquid level sensor78which is designed as a level sensor. It is possible to provide for a predetermined amount of fresh water to be supplied in operation of the fresh water supply device76. Furthermore, it is possible to provide for fresh water to be supplied until reaching a predetermined upper level81which is detected by a suitable liquid level sensor. In the embodiment depicted here, the predetermined upper level81corresponds to an upper switch point of the level sensor78and is thus also detected by the level sensor78.

A sensor device for determining a fresh water demand in the storage tank46may be, for example, in the form of a turbidity sensor82for detecting a degree of soiling of the liquid in the storage tank46. The control unit62is in this case designed for operating the fresh water supply device76and thereby supplying fresh water to the storage tank46when the degree of soiling of the liquid in the storage tank46is equal to or greater than a predetermined soiling limit.

The storage tank46preferably has an overflow84over which liquid flows out when the liquid level in the storage tank is above a predetermined outflow liquid level86, as illustrated inFIG. 1. An operating state like that depicted inFIG. 1may occur, for example, in a cleaning operating in which the conveyor dishwasher receives more liquid from the final rinse than is necessary for replenishing the wash tanks, depending on the type of wash ware and the degree of soiling. The predetermined upper level81is preferably as high as (as illustrated here) or lower than the predetermined outflow level86.

In the embodiment illustrated here, the liquid transfer device54is the only liquid transfer device for transferring final rinse liquid out of the post-wash zone14or out of the final rinse zone16into one of the wash zones10,12. The baffle87shown inFIG. 1serves to direct liquid that splashes out of the rear wash zone12, arranged in front of the baffle87as seen in direction8of conveyance and sent it back into this wash zone12.

Due to the flow connection of the two wash tanks18,20through the liquid overflow device68, it is sufficient to provide a liquid transfer device54only in the rear wash zone12. As an alternative, it is possible for a liquid transfer device from the storage tank46into the rear wash zone12to be provided as well as a liquid transfer from the storage tank46into the front wash zone10to be provided (not shown), preferably controlled by the control unit62independently of one another. In this case, the flow connection68between the rear wash zone12and the front wash zone10may be omitted.

In the above-described conveyor dishwasher2, sprayed final rinse liquid is advantageously collected in a storage tank, and liquid from the storage tank46is supplied to at least one wash zone as a function of a liquid demand. In this way, replenishing of the liquid in the wash tank, i.e., dilution of the liquid in the wash tanks, is performed only when necessary. Any addition of final rinse liquid or fresh water to the wash tanks requires a corresponding addition of detergent to maintain the desired detergent concentration in the wash tanks. Liquid is supplied to the wash tanks only when needed, and the demand for detergent for operation of the conveyor dishwasher2is reduced. When a great deal of water is entrained by large dishes, liquid can be supplied to the rear wash tank20through the storage tank46. In this way, a fresh water supply to the rear wash tank, as is customary with known dishwashers, becomes superfluous. This reduces the fresh water consumption by the conveyor dishwasher2. The final rinse liquid in the storage tank46may be used for an initial filling of the wash tanks18,20. The fresh water demand by the conveyor dishwasher2is reduced in this way.

Depending on the level distance desired between the predetermined upper level and the predetermined lower level in the respective tank10,12or in the storage tank46, a float switch having a suitable hysteresis range (distance between the upper and lower switch points) may be used for the respective liquid level switches72,74,78. Alternatively, a different number of liquid level sensors having a different function principle may also be used.

The connecting lines have not been shown in the drawings for reasons of simplicity. However, it is self-evident that all the parts of the conveyor dishwasher2(e.g., the control unit62with the liquid transfer device54) that cooperate functionally are connected to one another functionally accordingly.

It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. Accordingly, other embodiments are within the scope of the following claims