WO2009152048A1

WO2009152048A1 - Conveyor dishwasher, in particular commercial rack conveyor dishwasher, and method for operating it

Info

Publication number: WO2009152048A1
Application number: PCT/US2009/046390
Authority: WO
Inventors: Dietrich Berner; Harald Disch; Markus Heidt
Original assignee: Premark Feg L.L.C.
Priority date: 2008-06-13
Filing date: 2009-06-05
Publication date: 2009-12-17
Also published as: DE102008028304A1

Abstract

A conveyor dishwasher (100, 200), in particular a commercial conveyor dishwasher in the form of a rack conveyor dishwasher, which has at least one wash zone (10, 20, 30) and a final rinse zone (40) and which also has a pre-cleaning station (70) which is arranged outside the at least one wash zone (10, 20, 30) and is designed to pre -clean wash ware by means of pre-cleaning liquid before the wash ware is transported through the individual treatment zones of the conveyor dishwasher (100, 200) with the aid of a conveyor apparatus. In order to save, in particular, fresh water during operation of the conveyor dishwasher (100, 200), the invention provides for the waste water from the wash tank (12, 22, 32) of at least one wash zone (10, 20, 30) to be used in the pre-cleaning station (70) as pre-cleaning liquid. The invention also relates to a method for operating a conveyor dishwasher (100, 200) of this type.

Description

Conveyor dishwasher, in particular commercial rack conveyor dishwasher, and method for operating it

The invention relates to a conveyor dishwasher method and apparatus and, more particularly, a method for operating a conveyor dishwasher using a pre-cleaning station and a conveyor dishwasher having a pre-cleaning station.

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

EP 0 808 894 Bl discloses a method for cleaning wash ware which includes the steps of pre-cleaning by spraying the wash ware with a pre-cleaning solution, main cleaning and post- rinsing. At least one alkali component and at least one complexing agent are added in a metered manner to the pre- cleaning solution. The document does not state whether the method relates to a box-type dishwasher (warewasher) or a conveyor dishwasher (warewasher) .

Commercial dishwashers (warewashers) usually operate in two main process steps, namely firstly washing with wash liquid and then final rinsing with heated fresh water to which rinse aid is generally added in a metered manner. In the case of conveyor dishwashers, the wash ware, for example dishes, pots, glasses, cutlery and other utensils to be cleaned, is transported through a plurality of treatment zones, for example a pre-wash zone or zones, main-wash zone or zones, post -wash zone or zones, rinse zone or zones and drying zone or zones. The treatment zones in each case have associated spray nozzles by means of which liquid is sprayed onto the wash ware that is conveyed through the respective treatment zones by a conveyor apparatus. Each wash zone (pre-wash zone, main-wash zone, post-wash zone) has an associated tank in which sprayed liquid is accommodated, and/or in which liquid is provided for the spray nozzles of the relevant wash zone.

A conveyor dishwasher (warewasher) of this type is known, for example, from DE 196 44 438 Al. The known conveyor dishwasher contains, in series in the conveying direction of the wash ware, a pre-clearing zone (pre-cleaning zone) with pre- clearing nozzles (pre-cleaning nozzles) for removing coarse particles of dirt from the wash ware, at least one wash zone with wash nozzles for spraying wash liquid onto the wash ware, a pre-rinse zone with pre-rinse nozzles, and a final rinse zone with final rinse nozzles. The final rinse nozzles spray final rinse liquid, in particular fresh water, onto the wash ware. The sprayed final rinse liquid enters a pre-rinse tank from which it is transported to the second pre-rinse nozzles and to the first pre-rinse nozzles by means of a pump line. The pre-rinse liquid sprayed by the second pre-rinse nozzles flows back into the pre-rinse tank. The pre-rinse liquid sprayed by the first pre-rinse nozzles is conducted into the wash tank of the last wash zone by a baffle plate. By virtue of a liquid cascade system, liquid can flow against the conveying direction of the wash ware from the pre-rinse tank to the last wash tank and from this wash tank further as far as a tank which captures the liquid sprayed by the pre- clearing nozzles (pre-cleaning nozzles) in the pre-clearing zone (pre-cleaning zone) .

Conveyor dishwashers may be rack conveyor dishwashers (warewashers) or flight-type dishwashers (warewashers) . The fresh water consumption of conveyor dishwashers is, in particular, dependent on how much fresh water is required for initially filling the conveyor dishwasher and the amount of fresh water consumed for final rinsing during operation of the conveyor dishwasher. The final rinse liquid used for final rinsing should be of the quality of drinking water in microbiological terms. Therefore, all or at least some of the water for final rinsing in a conveyor dishwasher is normally taken from the public fresh water supply system. Furthermore, it is important for consumption of detergent and rinse aid to be as low as possible for the purpose of cost-effective and environmentally- friendly operation of a conveyor dishwasher.

Detergent is added to the fresh water in the wash zones of the conveyor dishwasher. The detergent renders the water alkaline. The alkalinity and food residues should be completely removed from the wash ware in the pre-rinse zones and at the latest in the final rinse zone, so that no visible residues remain on the wash ware. The residues represent a visible problem, particularly when cleaning glasses.

Accordingly, the main object of final rinsing with final rinse liquid is to remove the liquor from the wash ware. To this end, final rinse liquid in the form of fresh water, which may be pure or have further additives, for example rinse aid, added, is sprayed by means of final rinse spray nozzles onto the wash ware conveyed through the final rinse zone. Some of the sprayed final rinse liquid is usually conveyed counter to the conveying direction of the wash ware from treatment zone to treatment zone of the conveyor dishwasher by means of a cascade system. The remainder is conducted via a valve and a bypass line directly into a wash tank which is associated with the wash zone. Accordingly, the final rinse liquid which flows either via a cascade system or a bypass line into the wash tank during final rinsing also serves to regenerate the wash liquid in the wash tank.

Rack conveyor dishwashers are almost without exception provided with a feed table and a delivery table. In many cases, the feed table is in the form of a pre-cleaning station and is used for precleaning the wash ware by generally manual rinsing-off and/or by manual removal of dirt from the wash ware, specifically before the wash ware is conveyed through the respective treatment zones of the conveyor dishwasher with the aid of a conveyor apparatus (conveyor) . Pre-cleaning by pre-rinsing is normally performed manually. Pre-rinsing in the course of pre-cleaning is generally carried out using on-site cold or preheated fresh water. In some cases, additional cleaning chemicals are also used for pre-rinsing purposes. The delivery table is used for drying and unloading, for example, the dish racks if these are used for conveying the wash ware through the respective treatment zones of the conveyor dishwasher.

Tests carried out within the framework of the invention have shown that approximately two to three litres of fresh water, which may be pure or have additives, for example detergent, added, are typically used for pre-cleaning wash ware, depending on the type of wash ware and the degree to which it is soiled.

The object of the invention is provide a method for operating a rack conveyor dishwasher with which the consumption of resources, and in particular the consumption of fresh water, energy and cleaning chemicals, can be reduced, without adversely affecting the cleaning result of the rack conveyor dishwasher. A further object of the invention is to provide a rack conveyor dishwasher which ensures optimum or effective cleaning of wash ware even during operation with a reduced quantity of fresh water, energy and cleaning chemicals.

Accordingly, the invention relates to a method for operating a conveyor dishwasher, in particular a commercial conveyor dishwasher in the form of a rack conveyor dishwasher, which has at least one wash zone and a final rinse zone through which wash ware is transported with the aid of a conveyor apparatus, with final rinse liquid, which is sprayed in the final rinse zone by final rinse nozzles, and wash liquid, which is sprayed in the wash zone by wash nozzles, flowing into a wash tank, from which the wash liquid can be recirculated to the wash nozzles by means of a wash pump, and with a pre-cleaning station also being provided which is designed to pre-clean the wash ware by means of pre-cleaning liquid before the wash ware is transported through the individual treatment zones with the aid of the conveyor apparatus, with the method being characterized in that the waste water from the wash tank is used as pre-cleaning liquid.

By virtue of the invention, the waste water of the wash tank of the conveyor dishwasher is used to automatically and preferably manually pre-clean or pre-clear wash ware before the wash ware is placed onto the conveyor apparatus of the conveyor dishwasher and in this way fed to the respective treatment zones of the conveyor dishwasher. As a result, the said two to three litres of fresh water, for example, can be saved per cleaning cycle of wash ware. In many cases where preheated fresh water and/or additional cleaning chemicals are/is used in the prior art, the costs of these additional operating means can likewise be saved according to the invention.

Furthermore, the invention can significantly improve the efficiency of pre-cleaning by using the warm wash liquid as pre-cleaning liquid. The wash liquid is a wash liquor which has a temperature of, for example, between 50⁰C and 70⁰C and a pH of greater than 9 and usually greater than 10. As a result, less dirt remains on the wash ware after pre-cleaning in the pre-cleaning station and accordingly less dirt is carried into the treatment zones of the conveyor dishwasher.

The pre-cleaning liquid is sprayed onto the wash ware in the pre-cleaning station, preferably by spray nozzles, for example by means of a manually guided spray head.

Further features of the method according to the invention are contained in the subclaims. According to a particular embodiment, provision is made for on-site fresh water to be automatically fed to the pre- cleaning station as pre-cleaning liquid if the available quantity of wash tank waste water is not sufficient for pre- cleaning purposes.

According to a further preferred embodiment of the invention, provision is made for the wash tank waste water to first be conducted out of the wash tank into a reservoir container, before then being fed from this reservoir container to the pre-cleaning station by means of a pump.

According to another alternative embodiment of the invention, provision is made for the wash tank waste water to be transported directly from the wash tank to the pre-cleaning station by means of a pump.

According to a further preferred embodiment of the invention, provision is made for the wash tank waste water to be filtered before it is reused in the pre-cleaning station.

The invention also relates to a conveyor dishwasher, in particular a commercial rack conveyor dishwasher, which has the following: at least one wash zone with wash nozzles and a final rinse zone with final rinse nozzles; a conveyor apparatus for transporting wash ware through the individual treatment zones; a wash tank in which wash liquid, which is sprayed by the wash nozzles, and final rinse liquid, which is sprayed by the final rinse nozzles, flow and from which wash liquid can be recirculated back by means of a wash pump; and a pre-cleaning station, which is arranged and formed outside the wash zone, for manually pre-cleaning wash ware by means of pre-cleaning liquid before the wash ware is transported through the individual treatment zones with the aid of the conveyor apparatus, with the conveyor dishwasher being characterized in that a waste water transfer system from the wash tank to the pre-cleaning station is further provided for automatically removing wash tank waste water from the wash tank and for feeding the removed wash tank waste water to the pre-cleaning station as pre-cleaning liquid.

The invention is described below, using preferred embodiments as examples, with reference to the appended drawings, in which

Fig. 1 schematically shows a commercial conveyor dishwasher according to the invention; and

Fig. 2 schematically shows a further embodiment of a commercial conveyor dishwasher according to the present invention.

The dishwashers 100 and 200 according to the invention and illustrated in Figs 1 and 2 are commercial dishwashers (warewashers) which are in the form of rack conveyor dishwashers (warewashers) . They contain a control device 2 for controlling the respective treatment programmes in the treatment zones 10, 20, 30, 40, 50 and for setting the process parameters associated with the treatment programmes.

The conveyor dishwashers 100, 200 according to Figs 1 and 2 are each provided with dish racks for conveying wash ware (not illustrated in the drawings) through the conveyor dishwasher 100, 200 in conveying direction T.

The dish racks, which are populated with the wash ware (not illustrated in the drawings) , are placed on a conveyor apparatus 3. The conveyor apparatus 3 may be continuously driven by a preferably electric drive (not illustrated in Figs 1 and 2) , so that the dish racks placed on the conveyor apparatus 3 are transported through the various treatment zones 10, 20, 30, 40, 50 with the wash ware inserted therein. The dish racks with the wash ware, for example dishes, cutlery, pots, pans and/or trays, inserted therein are usually manually placed on the conveyor apparatus 3 in the region of an inlet 4 to the housing that normally encloses the internal spryy zones within the machine. In accordance with the conveying direction T indicated by the arrow in the drawings, the dish racks containing the wash ware are then conveyed from the inlet 4 into an inlet tunnel 5.

The dishwashers 100, 200 according to the illustrated embodiments each have at least one wash zone, for example, as illustrated in Fig. 1 and Fig. 2, a pre-wash zone 10, a main- wash zone 20 and a post -wash zone 30. The main-wash zone 20 is arranged downstream of the pre-wash zone 10 and the post- wash zone 30 is arranged downstream of the main-wash zone 20, as seen in the conveying direction T.

In the dishwashers 100, 200 illustrated in the drawings, a final rinse zone 40 is arranged downstream of the at least one wash zone (pre-wash zone 10, main-wash zone 20 and post- wash zone 30) , as seen in the conveying direction T.

The wash ware held by dish racks is conveyed from the inlet tunnel 5, through the following wash zones 10, 20 and 30, to the final rinse zone 40 in the conveying direction T. From there, the wash ware runs through a drying zone 50, which is connected downstream of the final rinse zone 40, into a delivery section 60. The delivery section 60 is used for post -drying the wash ware and for unloading, for example, the dish racks if these are used to convey the wash ware through the respective treatment zones 10, 20, 30, 40, 50 of the conveyor dishwasher 100, 200.

The treatment zones 10, 20, 30, 40 of the conveyor dishwasher 100, 200 each have associated spray nozzles 11, 21, 31, 41, 41' by means of which liquid is sprayed onto the wash ware which, together with the dish racks placed on the conveyor apparatus 3, is conveyed from the at least one wash zone 10,

20, 30 to the at least one final rinse zone 40 in conveying direction T.

If - as illustrated in Figs 1 and 2 - a plurality of wash zones 10, 20, 30 are arranged in series, the post-wash zone 30 shown in Figs 1 and 2 is the last wash zone in conveying direction T. Each wash zone 10, 20, 30 has an associated wash tank 12, 22, 32 in which sprayed liquid is accommodated and/or in which liquid is provided for the spray nozzles 11,

21, 31 of the relevant wash zones 10, 20, 30.

In the conveyor dishwashers 100, 200 illustrated in the drawings, final rinse liquid in the form of fresh water which may be pure or have further additives, for example rinse aid, added, is sprayed onto the wash ware (not illustrated) by means of the spray nozzles 41, 41' of the final rinse zone 40 which are arranged above and below the conveyor apparatus 3 and laterally. Some of the sprayed final rinse liquid is conveyed from zone to zone counter to the conveying direction T of the wash ware by means of a cascade system. The remainder is conducted via a valve Vl and a bypass line 6 directly into the pre-wash tank 12 which is associated with the pre-wash zone 10.

In the cascade system, the final rinse liquid sprayed by the final rinse nozzles 41, 41' flows from the final rinse zone 40 into the post-wash tank 32 associated with the post-wash zone 30 due to the force of gravity. The final rinse liquid sprayed in the final rinse zone 40 and captured by the final wash tank 32 is then transported to the spray nozzles (post- wash nozzles 31) of the post-wash zone 30 with the aid of a post -wash pump 33.

Wash liquid is rinsed-off from the wash ware in the post-wash zone 30. The liquid (post-wash liquid) produced in the process flows into the main-wash tank 22 associated with the main-wash zone 20 due to the force of gravity. A discharge element 34, for example a discharge base or a guide plate, is preferably provided for this purpose, the said discharge element conducting the post -wash liquid sprayed by the post- wash nozzles 31 into the main-wash tank 22. According to another embodiment (not shown) , the discharge element 34 may be dispensed with if the main-wash tank 22 extends as far as beneath the post-wash nozzles 31 of the post-wash zone 30.

The liquid accommodated by the main-wash tank 22 of the main- wash zone 20 is usually provided with a detergent and sprayed onto the wash ware by means of the wash nozzles (main-wash nozzles 21) of the main-wash zone 20 with the aid of a main- wash pump 23 and a wash liquid line system 24. The wash liquid sprayed by the main wash nozzles 21 flows back into the main-wash tank 22 due to the force of gravity. As a result, the main-wash tank 22, the main-wash pump 23, the wash liquid line system 24 and the main-wash nozzles 21 together form a wash liquid circuit.

The main-wash tank 22 is fluidically connected to the pre- wash tank 12 associated with the pre-wash zone 10 via an overflow line 25. The wash liquid sprayed in the main-wash zone 20 enters the pre-wash tank 12 via this overflow line 25 when there is a sufficient quantity of wash liquid in the main-wash tank 22.

The liquid accommodated in the pre-wash tank 12 of the pre- wash zone 10 is then sprayed onto the wash ware by means of the wash nozzles (pre-wash nozzles 11) of the pre-wash zone 10 with the aid of a pre-wash pump 13 and a pre-wash liquid line system 14, in order to remove coarse particles of dirt from the wash ware. The wash liquid sprayed by the pre-wash nozzles 11 flows back into the pre-wash tank 12 due to the force of gravity. As a result, the pre-wash tank 12, the pre- wash pump 13, the pre-wash liquid line system 14 and the pre- wash nozzles 11 together form a pre-wash liquid circuit. The pre-wash tank 12 is provided with an overflow line 15 which is used to feed the excess quantity of liquid to a waste water system if a liquid level in the pre-wash tank 12 is exceeded.

The individual nozzles (final rinse nozzles 41 and wash nozzles 11, 21, 31) provided in the treatment zones 10, 20, 30, 40 ensure that the wash ware is sprayed both from the top and from the bottom. However, it goes without saying that it is also feasible for lateral spray nozzles to additionally be provided in the respective treatment zones 10, 20, 30, 40. In the illustrated embodiments, such lateral spray nozzles 41' are already provided, for example, in the final rinse zone 40.

The final rinse liquid may be fresh water or fresh water which is mixed with rinse aid. The liquid sprayed in the main-wash zone 20 and in the pre-wash zone 10 preferably contains detergent which is added, for example, to the liquid accommodated in the main-wash tank 22 of the main-wash zone 20 with the aid of a detergent metering apparatus (not shown in the drawings) in a metered manner.

In the illustrated embodiments of the conveyor dishwashers 100, 200 according to the invention, the pre-wash zones 10 and the main-wash zones 20 are in each case separated from one another by means of separating curtains 7. In addition - as indicated in the drawings - the inlet tunnel 5 itself can be separated from the inlet 4 by means of a separating curtain 7. It is likewise preferred to provide a separating curtain 7 between the final rinse zone 40 and the drying zone 50. The provision of the separating curtains 7 prevents final rinse liquid, wash liquid and pre-wash liquid splashing over and prevents moisture escaping from the conveyor dishwasher 100, 200. The abovementioned drying zone 50 follows the final -rinse zone 40 in the conveying direction T. The wash ware is dried with dry and heated air in the drying zone 50, in order to blow off and/or dry up the moisture located on the wash ware. In order to keep the moisture content of the air in a range which is suitable for drying, it is feasible, for example, to feed external room air to the drying zone 50 via an opening, for example through the outlet opening for the wash ware.

The warm and moisture- laden air in the drying zone 50 is then drawn-off from the drying zone 50 via a further opening, for example with the aid of a fan 51. It is advantageous here if the exhaust -air stream from the drying zone 50 passes a heat- recovery device 8 in which, for example, a condenser can be provided. The heat -recovery device 8 is used to recover at least some of the thermal energy contained in the exhaust air.

If, before initial starting of the conveyor dishwasher 100, 200, the tanks 12, 22, 32 associated with the individual wash zones 10, 20, 30 are empty or insufficiently filled, the said tanks first have to be filled with fresh water via a fresh water line 16, 26, 91 and/or by spraying final rinse liquid in the final rinse zone 40. The quantity of wash liquid available to the wash liquid circuit and the pre-wash liquid circuit in each case can be monitored and signalled to the control device 2 with the aid of a wash tank level sensor 27 provided in the wash tank 22 and with the aid of a pre-wash tank level sensor 17 provided in the pre-wash tank 12.

In order to fill the tanks 12, 22, 32 associated with the individual wash zones 10, 20, 30, for example before initial starting of the conveyor dishwasher 100, 200, and to spray final rinse liquid in the final rinse zone 40, the conveyor dishwashers 100 and 200 according to Figs 1 and 2 are in each case provided with a fresh water connection 90.1 which can be connected to a fresh water supply system. The fresh water connection 90.1 can be connected to the intake end of the final rinse pump 43 which belongs to the final rinse zone 40 via a fresh water feed valve V2, which can be controlled by the control device 2, and preferably via a fresh water container 42. Rinse aid can be added to the fresh water in a metered manner, for example in the water heater 9.

In order to heat up the final rinse liquid to be fed to the final rinse zone 40 from the fresh water connection 90.1 and/or from the fresh water container 42, a water heater 9 (boiler) is provided, as illustrated in the drawings, through which at least some of the final rinse liquid is conducted. If rinse aid has not yet been added to the fresh water in a metered manner in the fresh water container 42, this may be done in the water heater 9.

As indicated in the drawings, it is feasible for at least some of the final rinse liquid to be conducted through the heat-recovery device 8 before this portion of final rinse liquid enters the water heater 9. In this way, it is possible to utilize the heat (thermal energy) of the exhaust air discharged from the drying zone 50.

The conveyor dishwashers 100 and 200 according to Figs 1 and 2 also each have a fresh water line 91 which can be connected to a further fresh water connection 90.2 via a fresh water feed valve V6 which can be controlled by the control device 2. A fresh water branch line 26 can be connected to the fresh water line 91 via a valve V5, in order to feed fresh water to the main-wash tank 22 as required. A further fresh water branch line 16 is provided and can be connected to the fresh water line 91 via a valve V4 , in order to feed fresh water to the pre-wash tank 12 as required.

The conveyor dishwashers 100 and 200 according to the illustrated embodiments are each provided with a pre-cleaning station 70 which is arranged upstream of the inlet tunnel 5 as seen in the conveying direction T (e.g., external of the machine housing that encloses the aforesaid spray zones 10, 20, 30 and 40) . The pre-cleaning station 70 is used to pre- clean the wash ware which is to be fed to the respective treatment zones 10, 20, 30, 40, 50 with the aid of the dish racks placed on the conveyor apparatus 3 with pre-cleaning liquid in advance, that is to say before the dish racks containing the wash ware are placed on the conveyor apparatus 3 or possibly before the wash ware is placed into the dish racks and then transported through the respective treatment zones 10, 20, 30, 40, 50 of the conveyor dishwasher 100, 200.

To this end, the wash ware can be manually cleaned of dirt and rinsed-off with the pre-cleaning liquid in the pre- cleaning station 70. For this purpose, the pre-cleaning station 70 contains a dirty or soiled water tank 72, a spray head 73 which can be either mechanically positioned or preferably manually held and has at least one and preferably a large number of spray nozzles 71 for spraying the pre- cleaning liquid onto the wash ware to be pre-cleaned. The spray head 73 is preferably located above the soiled water tank 72, so that the pre-cleaning liquid sprayed by means of the spray nozzles 71 can flow back into the soiled water tank 72 due to the force of gravity. Accordingly, the soiled water tank 72 accommodates the sprayed pre-cleaning liquid and the dirt removed from the wash ware in the pre-cleaning station 70.

The soiled water tank 72 is provided with a soiled water outlet 74 for draining soiled water from the soiled water tank 72. The soiled water outlet 74 can be provided with a screen (not illustrated in the drawings) for capturing particles of dirt.

According to the invention, a waste water transfer system 101, 201 is provided from the wash tank 12, 22, 32 of a wash zone 10, 20, 30 of the conveyor dishwasher 100, 200 to the spray head 73 of the precleaning station 70.

In the embodiments of the conveyor dishwasher 100, 200 illustrated in the drawings, the waste water transfer system 101, 201 is arranged between the pre-wash tank 12 and the spray head 73 of the pre-cleaning station 70. However, it goes without saying that it is also feasible to provide the waste water transfer system 101, 201, for example, between the main-wash tank 22 or the post-wash tank 32 and the precleaning station 70.

Expressed in general, the waste water transfer system 101, 201 is used firstly to automatically remove wash tank waste water from the wash tank 12, 22, 32, which is connected to the waste water transfer system 101, 201, of the corresponding wash zone 10, 20, 30 and secondly to feed the removed wash tank waste water to the external pre-cleaning station 70 as pre-cleaning liquid. Figs 1 and 2 show two preferred embodiments of waste water transfer systems 101, 201 according to the invention, without the invention being restricted to these embodiments.

The conveyor dishwasher 100 according to Fig. 1 is provided with a waste water transfer system 101 which has a transfer line 102a, 102b which connects the wash tank of the pre-wash zone 10 (pre-wash tank 12) from a point beneath the abovementioned wash tank level sensor 17, preferably from the sump 18, to the spray head 73. The waste water transfer system 101 also contains a transfer pump 103 which is used to transport pre-cleaning liquid from the wash tank (pre-wash tank 12) to the spray head 73. The transfer line 102a, 102b has a first transfer line section 102a which connects the delivery end of the transfer pump 103 to the spray head 73 and whose downstream end can form a flow connection with or be disconnected from the spray head 73 via a valve V3. The valve V3 can be located at the end of the first transfer line section 102a or upstream thereof or preferably on the spray head 73.

The intake end of the transfer pump 103 is or can be connected to the pre-wash tank 12 of the pre-wash zone 10, preferably to its sump 18, via a second transfer line section 102b and a further valve (not shown) which may be arranged in the said second transfer line section.

Although not illustrated in Fig. 1, it is feasible, in principle, for the intake end of the transfer pump 103, for example, to be provided with a further fresh water feed line or with a fresh water branch line which leads to the fresh water line 91 via a fresh water feed valve, in order to feed pure fresh water to the spray head 73 of the pre-cleaning station 70 as required. The fresh water feed line (not illustrated in the drawings) which is optionally provided can be connected to the fresh water connection 90.1 or 90.2, for example via a fresh water valve of a fresh water branch line.

In the embodiment of the conveyor dishwasher 100 according to the invention illustrated in Fig. 1, the pre-wash tank 12 can be directly connected to the spray head 73 of the pre- cleaning station 70 with the aid of the waste water transfer system 101, and in particular without intermediate storage of the wash liquid taken from the pre-wash tank 12 as pre- cleaning liquid. The waste water transfer system 101 can be provided with a screen (not illustrated) for capturing particles of dirt, which screen could, for example, be located anywhere along the line 102b, 102a or at either end thereof .

In the embodiment according to Fig. 1, some of the waste water (wash water) produced in the pre-wash tank 12 during operation of the conveyor dishwasher 100 is taken from the pre-wash tank 12 and fed to the spray head 73 as pre-cleaning liquid with the aid of the transfer pump 103 when the valve V3 which connects the downstream end of the first transfer line section 102a to the spray head 73 is actuated. It should be noted here that all the wash liquid must not be taken from the pre-wash tank 12 since at least some of it is required for the washing process in the pre-wash zone 10. The minimum quantity of wash liquid remaining in the pre-wash tank 12 is monitored, for example, by the wash tank level sensor 17 which generates a signal if the liquid level in the pre-wash tank 12 falls to or below the level of the level sensor 17. In order to empty the pre-wash tank 12 as required, a corresponding discharge pump (not illustrated in the drawings) whose intake end preferably is or can be connected to the sump 18 of the pre-wash tank 12 may be provided. The delivery end of the optionally provided discharge pump issues into the on-site waste water system.

When the valve V3 is manually actuated (or, according to another embodiment which is not shown, when the valve V3 is automatically actuated) , the transfer pump 103 is switched on and wash liquid is transported from the pre-wash tank 12 to the spray head 73 as pre-cleaning liquid.

If, during pre-cleaning in the pre-cleaning station 70, more than the maximum permissible quantity of wash liquid defined by the pre-wash tank level sensor 17 is required as pre- cleaning liquid, the control device 2 can automatically open the fresh water valves V4, V6 provided in the fresh water line system 91, for example as a function of the signal from the pre-wash tank level sensor 17, in the embodiment illustrated in Fig. 1, in order to feed fresh water to the pre-wash tank 12 via the fresh water branch line 16.

In addition to this, it is also feasible, in principle, to directly feed fresh water to the waste water transfer system 101 and/or to the spray head 73 automatically via an additional fresh water feed line (not illustrated in Fig. 1) . As a result, the spray head 73 can be supplied with fresh water from the additional fresh water supply line which is optionally provided.

If the liquid level in the pre-wash tank 12 has again risen to the wash tank level sensor 17, feeding of fresh water to the pre-wash tank 12 and/or to the spray had 73 should be stopped in order to save fresh water.

As already indicated, the waste water transfer system 101, which is used in the conveyor dishwasher 100 according to Fig. 1, can also contain a filter (not illustrated in Fig. 1) for filtering the wash water used as pre-cleaning liquid.

In the embodiment of the conveyor dishwasher 200 according to the invention illustrated in Fig. 2, a waste water transfer system 201 is provided which once again contains the transfer pump 103, the first transfer line section 102a and the valve V3 which can be arranged in the first transfer line section 102a or at its end or preferably on the spray head 73 and operated manually, in order to form a flow connection between the delivery end of the transfer pump 103 and the spray head 73. However, in contrast to the embodiment illustrated in Fig. 1, the intake end of the transfer pump 103 in the conveyor dishwasher 200 according to Fig. 2 is not be connected directly to the wash tank of the pre-wash zone 10 (pre-wash tank 12) but rather to a reservoir container 202, and preferably to the lower end of the reservoir container 202, via the second transfer line section 102b. Reservoir container 202 may be either internal or external of the machine housing.

In the embodiment according to Fig. 2, the overflow line 15 which originates from the pre-wash tank 12 is used to conduct the liquid accommodated in the pre-wash tank 12 to the reservoir container 202 if the liquid in the pre-wash tank 12 reaches or exceeds a specific, predefined or predefinable level. However, it goes without saying that it is also feasible to provide a discharge pump (not illustrated in Fig. 2) in addition to the overflow line 15, which discharge pump is preferably connected by way of its intake end to the sump 18 of the pre-wash tank 12 and is not connected to an on-site waste water system by way of its delivery end, as is customary, but instead forms a flow connection with the reservoir container 202 via a connection line and preferably via a removable screen, in order to transfer wash liquid from the pre-wash tank 12 to the reservoir container 202 as a function of the liquid level in the pre-wash tank 12, as required.

As already described with reference to Fig. 1, the liquid level in the pre-wash tank 12 is preferably monitored by means of the wash tank level sensor 17.

Although not shown in the illustration according to Fig. 2, the lower end of the reservoir container 202 can be connected to a further discharge pump in order to empty the reservoir container into the on-site waste water system, in particular into the sewerage system, as required.

In addition to or in place of the further discharge pump (not illustrated in Fig. 2) which is preferably connected to the lower end of the reservoir container 202 and is used to empty the reservoir container 202 into the waste water system, it is possible - as illustrated in Fig. 2 - to also provide the reservoir container 202 with a safety overflow 204 by means of which at least some of the liquid accommodated in the reservoir container 202 is fed to the waste water system when a specific liquid level in the reservoir container 202 is exceeded.

In the embodiment according to Fig. 2, the fresh water feed line 91, which leads to the pre-wash tank 12 of the pre-wash zone 10 in the conveyor dishwasher 100 according to Fig. 1, forms a flow connection with the reservoir container 202 via its fresh water feed valve V4 and the fresh water branch line 16. The fresh water feed valve V4 is actuated by the control device 2, specifically preferably as a function of whether the liquid level in the reservoir container 202 has fallen to or below the level of a reservoir container level sensor 203 or is higher than this level .

In the embodiment of the conveyor dishwasher 200 according to the invention illustrated in Fig. 2, all the waste water from the pre-wash tank 12 is taken from the pre-wash tank 12 and conducted into the reservoir container 202. The abovementioned overflow line 15 is used for this purpose. However, it goes without saying that it is also feasible to provide a corresponding discharge pump between the pre-wash tank 12 and the reservoir container 202. The waste water taken from the pre-wash tank 12 is preferably filtered by a filter (strainer) , before it flows into the reservoir container 202. This filter (not shown in Fig. 2) should preferably be of removable design, so that it is easy to clean.

From the reservoir container 202, when the valve V3 is manually actuated (or, according to another embodiment which is not shown, when the valve V3 is automatically actuated) , the transfer pump 103 is switched on and the waste water stored in the reservoir container 202 as pre-cleaning liquid is transported from the reservoir container 202 to the spray head 73. As already mentioned, the reservoir container 202 is provided with the reservoir container level sensor 203 which causes the fresh water feed valves V4, V6 of the fresh water feed line 91 to in each case be opened and as a result causes fresh water to be conducted into the reservoir container 202 only when the liquid level in the reservoir container 202 falls below the lower liquid level limit defined by the reservoir container level sensor 203. The maximum upper liquid level in the reservoir container 202 is defined by its overflow 204. It is also feasible, in principle, for the reservoir container 202 to be emptied by a further discharge pump (not illustrated in Fig. 2) whose intake end is connected to the reservoir container 202.

In the embodiment according to Fig. 2, a filter can be provided at any point in the waste water transfer system 201 in order to filter the wash liquid taken from the pre-wash tank 12 on the way to the reservoir container 202. As an alternative or in addition to this, a filter can also be provided in the path of the pre-cleaning liquid from the reservoir container 202 to the spray head 73.

The invention is not restricted to the embodiments of the conveyor dishwasher according to the invention shown by way of example in the drawings. Rather, the invention can be gathered from an overall expert view of the patent claims and of the description of the exemplary embodiments.

Claims

Patent claims

1. A method for operating a conveyor dishwasher (100, 200) , which has at least one wash zone (10, 20, 30) and at least one final rinse zone (40) through which wash ware is transported with the aid of a conveyor apparatus (3) , with final rinse liquid, which is sprayed in the final rinse zone (40) by final rinse nozzles (41, 41') , and wash liquid, which is sprayed in the wash zone (10, 20, 30) by wash nozzles (11, 21, 31) , flowing into a wash tank (12, 22, 32) from which the wash liquid can be recirculated to the wash nozzles (11, 21, 31) by means of a wash pump (13, 23, 33) , and with a pre-cleaning station (70) also being provided which is arranged outside the at least one wash zone (10, 20, 30) and is designed to pre-clean the wash ware by means of pre-cleaning liquid before the wash ware is transported through the individual treatment zones with the aid of the conveyor apparatus (3) , characterized in that the waste water from the wash tank (12, 22, 32) is used as pre-cleaning liquid.

2. The method according to claim 1 wherein the conveyor dishwasher is a rack conveyor dishwasher, and the pre-cleaning station is located external of a dishwasher housing that enclosed the at least one wash zone .

3. The method according to Claim 1 or Claim 2, characterized in that the wash tank waste water is conducted directly from the wash tank (12, 22, 32) to the pre-cleaning station (70) by means of a pump (103) .

4. The method according to Claim 1 or Claim 2, characterized in that the wash tank waste water is conducted out of the wash tank (12, 22, 32) , via an overflow (15) , into a reservoir tank (202) , and from there is fed to the pre-cleaning station (70) as pre-cleaning liquid by means of a pump (103) as required.

5. The method according to one of the preceding claims, characterized in that on-site fresh water is automatically fed to the pre-cleaning station (70) if the available quantity of wash tank waste water is not sufficient for pre- cleaning the wash ware.

6. The method according to one of the preceding claims, characterized in that the wash tank waste water is filtered before it is used in the pre-cleaning station (70) as pre- cleaning liquid.

7. A conveyor dishwasher (100, 200) , including: at least one wash zone (10, 20, 30) with wash nozzles (11, 21, 31) and a final rinse zone (40) with final rinse nozzles (41, 41') ; a conveyor apparatus (3) for transporting wash ware through the wash and final rinse zones; a wash tank (12, 22, 32) into which at least some wash liquid, which is sprayed by the wash nozzles (11, 21, 31) , and at least some final rinse liquid, which is sprayed by the final rinse nozzles (41, 41') , flow and from which wash liquid can be recirculated back by means of a wash pump (13, 23, 33) ; and a pre-cleaning station (70) , which is arranged and formed outside the at least one wash zone (10, 20, 30) , for manually pre-cleaning wash ware by means of pre- cleaning liquid before the wash ware is transported through the individual treatment zones with the aid of the conveyor apparatus (3) , characterized in that a waste water transfer system (101, 201) from the wash tank (12, 22, 32) to the pre-cleaning station (70) is provided for automatically removing wash tank waste water from the wash tank (12, 22, 32) and for feeding the removed wash tank waste water to the pre- cleaning station (70) as pre-cleaning liquid.

8. The conveyor dishwasher according to Claim 7 wherein the conveyor dishwasher is in the form of a rack conveyor dishwasher, and the pre-cleaning station is located external of a dishwasher housing that enclosed the at least one wash zone and the final rinse zone .

9. The conveyor dishwasher (100, 200) according to one of Claims 7 or 8, characterized in that a fresh water supply system (16, 91) is provided for automatically feeding on-site fresh water to the pre-cleaning station (70) as pre-cleaning liquid when the pre-cleaning station (70) outputs a requirement signal for pre-cleaning liquid but the available quantity of wash tank waste water has reached or fallen below a predetermined lower value.

10. The conveyor dishwasher (200) according to one of Claims 7 to 9, characterized in that the waste water transfer system (201) has a reservoir container (202) which is designed to accommodate wash tank waste water from the wash tank (12, 22, 32) and from which liquid can be fed to the pre-cleaning station (70) by means of a pump (103) as pre-cleaning liquid.

11. The conveyor dishwasher (100) according to one of Claims 7 to 9, characterized in that the waste water transfer system (101) has a pump (103) in a transfer line (102a, 102b) from the wash tank (12, 22, 32) to the pre-cleaning station (70) , by means of which pump wash tank waste water can be transported directly, without intermediate storage, from the wash tank (12, 22, 32) to the pre-cleaning station (70) as pre-cleaning liquid.

12. Conveyor dishwasher (100, 200) according to one of Claims 7 to 11, characterized in that the waste water transfer system (101, 201) has a filter for filtering the wash tank waste water on the way from the wash tank (12, 22, 32) to the pre-cleaning station (70) .