AU2012299228B2

AU2012299228B2 - Dishwasher and method for automatically cleaning a dishwasher

Info

Publication number: AU2012299228B2
Application number: AU2012299228A
Authority: AU
Inventors: Harry Braun; Harald Disch; Markus Heidt; Norbert Litterst
Original assignee: Premark FEG LLC
Current assignee: Premark FEG LLC
Priority date: 2011-08-19
Filing date: 2012-08-14
Publication date: 2015-05-21
Anticipated expiration: 2032-08-14
Also published as: EP2744385B1; CN103841873B; DE102011081246A1; EP2744385A1; WO2013028392A1; DE102011081246B4; AU2012299228A1; CN103841873A

Abstract

A box-type dishwasher has a treatment chamber or a conveyor- type dishwasher has at least one treatment zone. A wash system of the treatment chamber or the treatment zonehas a wash tank for wash liquid, a plurality of spray nozzles, in at least one wash tube, for spraying wash liquid onto the washware, and a wash pump, connected to the at least one wash tube by a line system, for supplying wash liquid from the wash tank to the spray nozzles. The at least one wash tube has a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher when the central cleaning opening is opend for flow.

Description

DISHWASHER AND METHOD FOR AUTOMATICALLY CLEANING A DISHWASHER Description The invention relates to a dishwasher, in particular commercial dishwasher or utensil washer, which is in the form of a box-type dishwasher or a conveyor-type dishwasher, and also to a method for automatically cleaning a dishwasher of this kind. The following discussion of the background to the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application. Throughout the description and claims of this specification the word "comprise" and variations of that word, such as "comprises" and "comprising", are not intended to exclude other additives, components, integers or steps. The invention is particularly directed at a dishwasher which has a wash system, wherein the wash system has the following: a wash tank for accommodating wash liquid, a plurality of spray nozzles, which are formed in at least one wash tube, for spraying wash liquid onto the washware which is to be cleaned, and a wash pump, which is connected to the at least one wash tube by means of a line system, for supplying wash liquid from the wash tank to the spray nozzles which are formed in the at least one wash tube, wherein the spray nozzles are arranged and formed relative to the wash tank in such a way that at least some of the wash liquid which is sprayed by the spray nozzles flows back into the wash tank. 1 Box-type dishwashers are dishwashers which can be manually loaded and unloaded. Box-type dishwashers (also called "box type warewashers" or "batch dishwashers") may be hood-type dishwashers ("hood-type warewashers") or front-loader dishwashers ("front-loader warewashers") . Front-loader dishwashers may be under-counter machines, top-counter machines or free-standing front-loader dishwashers. A dishwasher which is in the form of a box-type dishwasher usually has a treatment chamber for cleaning washware. The treatment chamber generally has arranged beneath it a wash tank in which liquid from the treatment chamber can flow back due to the force of gravity. The wash tank contains wash la WO 2013/028392 PCT/US2012/050697 liquid which is usually water to which detergent may be added if required. A dishwasher which is in the form of a box-type dishwasher also has a wash system with a wash pump, a line system which is connected to the wash pump, and with a plurality of spray nozzles which are formed in at least one wash arm. The wash liquid contained in the wash tank can be conveyed from the wash pump to the spray nozzles via the line system and be sprayed onto the washware to be cleaned through the spray nozzles in the treatment chamber. The sprayed wash liquid then flows back into the wash tank. Conveyor-type dishwashers ("conveyor warewashers") are, in particular, flight-type dishwashers ("flight-type warewashers") or rack-conveyor dishwashers ("rack- conveyor warewashers") . Conveyor-type dishwashers are usually used in the commercial field. In contrast to box-type dishwashers, in which the washware to be cleaned remains stationary in the machine during the cleaning process, the washware is transported through various treatment zones of the conveyor type dishwasher in the case of conveyor-type dishwashers. A conveyor-type dishwasher usually has at least one prewash zone and at least one main-wash zone which is arranged downstream of the prewash zone or zones as seen in the transportation direction of the washware. As seen in the transportation direction, at least one post-wash zone and at least one final-rinse zone, which is downstream of the post wash zone, are generally arranged downstream of the main-wash zone or zones. As seen in the transportation direction, the washware, which is either accommodated directly on the conveyor belt or is retained by racks, usually runs, in the transportation direction, through an inlet tunnel, the following prewash zone or zones, main-wash zone or zones, post-wash zone or zones, final-rinse zone or zones and a drying zone, into an outlet section. 2 WO 2013/028392 PCT/US2012/050697 The abovementioned wash zones of the conveyor-type dishwasher each have an associated wash system which has a wash pump and a line system which is connected to the wash pump, via which liquid is supplied to the spray nozzles of the wash zone. The wash liquid which is supplied to the spray nozzles is sprayed onto the washware, which is transported through the respective wash zones by a transportation apparatus of the conveyor-type dishwasher, in the respective wash zone. Each wash zone has an associated tank in which sprayed liquid is accommodated and/or in which liquid for the spray nozzles of the relevant zones is provided. In the case of the conveyor-type dishwashers which are usually known from the prior art, final-rinse liquid in the form of fresh water, which may be pure or mixed with further additives, for example rinse aid, is sprayed onto the washware via the spray nozzles of the final-rinse zone. At least some of the final-rinse liquid sprayed is transported from zone to zone, counter to the transportation direction of the washware, via a cascade system. The sprayed final-rinse liquid is collected in a tank (post wash tank) of the post-wash zone, from which it is conveyed to the spray nozzles (post-wash nozzles) of the post-wash zone via the wash pump of the wash system which is part of the post-wash zone. In the post-wash zone, wash liquid is rinsed off from the washware. The liquid which accumulates in the process flows into the wash tank of the at least one main-wash zone which is arranged upstream of the post-wash zone as seen in the transportation direction of the washware. Here, the liquid is usually provided with a detergent and is sprayed onto the washware by a pump system (wash pump), which is part of the wash system of the main-wash zone, via the nozzles (wash nozzles) of the main-wash zone. If no further main-wash zones are provided, the liquid then flows from the wash tank of the main-wash zone into the prewash tank of the 3 WO 2013/028392 PCT/US2012/050697 prewash zone. The liquid in the prewash tank is sprayed onto the washware via a pump system, which is part of the wash system of the prewash zone, via the prewash nozzle of the prewash zone in order to remove coarse dirt from the washware. Irrespective of whether the dishwasher is in the form of a box-type dishwasher or a conveyor-type dishwasher, the dishwashers under consideration here and, in particular, commercial dishwashers therefore usually comprise at least one wash system which has a wash pump which ensures a virtually constant water circulation rate for the duration of a wash process in the treatment chamber (in the case of box type dishwashers) or in the respective treatment zone (in the case of conveyor-type dishwashers). The respective wash pumps of the wash systems are switched on and switched off by a control device (machine controller) which is part of the dishwasher. Each wash system generally also has an associated screen system in order to separate out solid particles of dirt from the wash liquid which is sprayed onto the washware to be cleaned via the spray nozzles. Screen systems of this kind are preferably designed in such a way that they can be manually removed from the dishwasher, for example in order to be cleaned. The dishwasher is and has to be cleaned at the end of each working day. This involves a large number of working steps which have to be performed manually. In order to clean, for example, a conveyor-type dishwasher, the wash arms and the screen systems of the individual wash systems first have to be removed. Since a conveyor-type dishwasher generally has a plurality of wash zones which are arranged one behind the other, and therefore a corresponding plurality of wash systems, these working steps have to be carried out several times. 4 WO 2013/028392 PCT/US2012/050697 The uninstalled screen systems are then manually spray-washed with hot water and additionally manually scrubbed depending on the degree of soiling. In the case of the uninstalled wash arms, the cleaning end caps which are usually arranged at the end of the wash arms are first removed, so that each individual wash tube of a wash arm can be flushed with water. Finally, the wash arm is completely cleaned, that is to say spray-washed and manually scrubbed. The final-rinse arms are likewise spray-washed with water and possibly manually scrubbed. Final-rinse arms are generally not provided with cleaning end caps since no dirt is expected to be found inside the final-rinse tubes. The loading zone of a conveyor-type dishwasher, which is the treatment zone which is soiled to the greatest extent, is spray-washed with hot water and sometimes (if necessary) manually cleaned with a cleaning cloth and possibly with the aid of a detergent solution during the cleaning process. Once the individual treatment zones of the conveyor-type dishwasher have been completely emptied, each zone is purged with hot water and sometimes (if necessary) manually cleaned with a cleaning cloth and possibly with the aid of a detergent solution. The inspection doors, which can be designed as sliding doors or swing doors, also form part of the interior cleaning system. The unloading zone of the conveyor-type dishwasher is only briefly spray-washed with water since it is generally least soiled. The entire cleaning operation for a conveyor-type dishwasher takes between 30 and 40 minutes depending on the size of the machine, with the quantity of fresh water used for cleaning the machine being between 400 and 600 liters. After the interior of the conveyor-type dishwasher has been cleaned and after the previously uninstalled wash system 5 components have been cleaned, the individual parts of the wash systems have to be correctly re-installed into the conveyor-type dishwasher. It is therefore desirable to provide a dishwasher in which the cleaning operation which has to be carried out at the end of a working day can be made more efficient. It is particularly desirable to specify a dishwasher in which at least some of the working steps which are required for cleaning the dishwasher are carried out automatically in order to thus save on personnel and at the same time to be able to reduce the resources (water, energy, chemicals) used for cleaning purposes. It is also desirable to provide a corresponding method for automatically cleaning a dishwasher. According to one aspect of the invention, there is provided a dishwasher, which is in the form of a box-type dishwasher having a treatment chamber or in the form of a conveyor-type dishwasher having at least one treatment zone and has a wash system which is associated with the treatment chamber or the at least one treatment zone, wherein the wash system has the following: - a wash tank for accommodating wash liquid; - a plurality of spray nozzles, which are formed in at least one wash tube, for spraying wash liquid onto the washware which is to be cleaned, wherein the spray nozzles are arranged and formed relative to the wash tank in such a way that at least some of the wash liquid which is sprayed by the spray nozzles flows back into the wash tank; and - a wash pump, which is connected to the at least one wash tube by means of a line system, for supplying wash liquid from the wash tank to the spray nozzles which are formed in the at least one wash tube, wherein 6 the at least one wash tube has a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher. According to another aspect of the present invention there is provided a method for automatically cleaning a dishwasher, which is in the form of a box-type dishwasher or conveyor type dishwasher and has at least one wash system, wherein the wash system has the following: - a wash tank for accommodating wash liquid; - a plurality of spray nozzles, which are formed in at least one wash tube, for spraying wash liquid onto the washware which is to be cleaned, wherein the spray nozzles are arranged and formed relative to the wash tank in such a way that at least some of the wash liquid which is sprayed by the spray nozzles flows back into the wash tank; and - a wash pump, which is connected to the at least one wash tube by means of a line system, for supplying wash liquid from the wash tank to the spray nozzles which are formed in the at least one wash tube, wherein the at least one wash tube has a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher, and wherein the method exhibits the following method steps: a) the central cleaning opening of the at least one wash tube is opened in a cleaning mode of the dishwasher; and b) the wash pump, which is connected to the at least one wash tube, is actuated in such a way that wash liquid is supplied to the spray nozzles, which are formed in the at least one wash tube, from the wash tank, wherein at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening. 6a The advantages which can be achieved by the solution according to the invention may include: since the at least one wash tube of the wash system has an associated central cleaning opening which is open in the cleaning mode of the dishwasher, so that at least some of the wash liquid which is supplied to the wash tube by the wash pump can flow back into the wash tank via the central cleaning opening, the result is that the wash arm (wash tube with the spray nozzles correspondingly formed therein) no longer have to be removed 6b WO 2013/028392 PCT/US2012/050697 from the dishwasher for the purpose of cleaning the dishwasher. Instead, the at least one wash arm remains in the wash zone during the cleaning process and is automatically flushed. As a result, the process of removing the individual wash arms, which process usually has to be implemented manually and is time-consuming, and of manually cleaning said individual wash arms outside the dishwasher in a state in which they are uninstalled is dispensed with. Provision is made, according to the invention, for the at least one wash tube of the wash system, in which the plurality of spray nozzles are formed to have a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash arm by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher. For the purpose of cleaning the dishwasher, the central cleaning opening of the at least one wash tube is, in this case, opened and then the wash pump, which is connected to the at least one wash tube, is actuated in such a way that wash liquid is supplied to the spray nozzles, which are formed in the at least one wash tube, from the wash tank, wherein at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening. It is advantageous in respect of the dishwasher according to the invention when the wash system has a plurality of wash tubes which together form a set of wash arms, wherein the plurality of wash tubes is connected to the wash pump by means of a preferably common line system, and wherein the abovementioned central cleaning opening is associated with the entire set of wash arms and is formed in such a way that at least some of the wash liquid which is supplied to the plurality of wash tubes by the wash pump flows back into the wash tank via this common central cleaning opening in a cleaning mode of the dishwasher. 7 WO 2013/028392 PCT/US2012/050697 In a preferred embodiment of the solution according to the invention, a closure element, which can be manually operated or can be automatically actuated, is associated with the central cleaning opening for the purpose of selectively opening the central cleaning opening in a cleaning mode of the dishwasher and for the purpose of selectively closing the central cleaning opening in a washing mode of the dishwasher. It is also feasible in this case for the closure element to be designed as a valve which can be automatically actuated by means of a control device. As an alternative to this, it goes without saying that it is also feasible for the closure element to be in the form of a valve which can be manually operated or in the form of a closure which can be manually removed from the central cleaning opening. The solution according to the invention is distinguished not only by virtue of the individual wash arms remaining in their mounted state and being automatically flushed in the cleaning mode of the dishwasher, but also by virtue of an intelligent monitoring means with which a check is made before or during the course of the automatic cleaning program to determine whether the central cleaning opening is open. To this end, provision is made, in a preferred development of the solution according to the invention, of a control device for actuating the wash pump in a washing mode of the dishwasher in such a way that wash liquid is at least temporarily supplied to the spray nozzles by means of the line system. In addition to this, a sensor device, which is connected to the control device, is provided, said sensor device being used for detecting a hydrostatic pressure profile of the wash liquid in the line system or a volumetric-flow profile of the wash liquid in the line system, wherein the control device is designed for comparing the detected pressure profile or the detected volumetric-flow profile with a predefined pressure profile or, respectively, 8 WO 2013/028392 PCT/US2012/050697 with a predefined volumetric-flow profile. If it is established with the aid of the control device that the detected pressure profile or the detected volumetric-flow profile is continuously below the pressure profile which is predefined during a washing mode or above the predefined volumetric-flow profile, the control device will draw the conclusion that the central cleaning opening is open, and therefore the cleaning mode of the dishwasher can be carried out or continued. If it is determined with the aid of the control device that said central cleaning opening is not in this state, a corresponding fault message is preferably output by means of an acoustic and/or optical interface. In the case of the solution according to the invention - as in the case of conventional cleaning of dishwashers - it is still necessary for a screen system which forms part of the wash system to be manually removed from the dishwasher before the cleaning process is started. In respect of the screen system which can be manually removed from the dishwasher, provision is made in a preferred embodiment of the solution according to the invention for a detector device, which is connected to a control device, to be associated with this screen system, said detector device being used for automatically detecting whether the screen system is in its state in which it is installed in the dishwasher. It is feasible in this case, for example, for this detector device to have an optically, capacitively or inductively operating sensor, in particular a Hall sensor, and/or a switch, in particular a reed switch. In a preferred development of the last-mentioned embodiment, provision is made for the control device of the dishwasher to be designed to actuate the wash pump in a washing mode of the dishwasher only when the detector device detects that the screen system is in its state in which it is installed in the dishwasher, wherein the control device is further preferably designed in such a way that the wash pump is actuated in a 9 WO 2013/028392 PCT/US2012/050697 cleaning mode of the dishwasher only when the detector device detects that the screen system is no longer in the state in which it is installed in the dishwasher. In order to be able to automatically clean the interior of the dishwasher, a cleaning system is provided which has at least one interior cleaning nozzle which is arranged in the treatment chamber (in the case of box-type dishwashers) or in the respective treatment zone (in the case of conveyor-type dishwashers) and can be connected to a fresh-water connection of the dishwasher by means of a fresh-water line system. This at least one interior cleaning nozzle is preferably designed to spray the relevant treatment zone or the treatment chamber with fresh water from the inside in a cleaning mode of the dishwasher, wherein the interior cleaning nozzle is, for example, in the form of an all-round spray nozzle. Exemplary embodiments of the solution according to the invention will be described in greater detail below with reference to the appended drawings, in which: fig. 1 schematically shows a dishwasher, which is designed in the form of a conveyor-type dishwasher, according to one exemplary embodiment of the invention; fig. 2 schematically shows a dishwasher, which is designed in the form of a conveyor-type dishwasher, according to a further exemplary embodiment of the invention; fig. 3a schematically shows the design of a wash system for a dishwasher, which is in the form of a conveyor type dishwasher or in the form of a box-type dishwasher, in the washing mode of the dishwasher; 10 WO 2013/028392 PCT/US2012/050697 fig. 3b shows the wash system shown in fig. 3a in the cleaning mode of the dishwasher; fig. 4 schematically shows the design of a further wash system for a dishwasher, which is in the form of a conveyor-type dishwasher or in the form of a box type dishwasher, in the cleaning mode of the dishwasher; fig. 5a schematically shows a first embodiment of a set of wash arms which can be used in the solution according to the invention; and fig. 5b schematically shows a further embodiment of a set of wash arms which can be used in the solution according to the invention. Fig. 1 shows a schematic longitudinal section through a conveyor-type dishwasher 50 as an example of the solution according to the invention. The conveyor-type dishwasher 50 according to the illustration in fig. 1 has a prewash zone 51 and a main-wash zone 52 which is arranged downstream of the prewash zone 51 as seen in the transportation direction T of the washware (not illustrated in fig. 1). As seen in the transportation direction T, a post-wash zone 53 and a final rinse zone 54, which is downstream of the post-wash zone 53, are arranged downstream of the main-wash zone 52 in the case of the conveyor-type dishwasher 50 illustrated in fig. 1. As seen in the transportation direction T, the washware, which is either accommodated directly on the conveyor belt 58 or is retained by racks, runs, in the transportation direction T, through an inlet tunnel 55, the following prewash zone 51, the main-wash zone 52, the post-wash zone 53, the final-rinse zone 54 and through a drying zone 56, into an outlet section 57. 11 WO 2013/028392 PCT/US2012/050697 The abovementioned treatment zones 51, 52, 53, 54 of the conveyor-type dishwasher 50 each have associated spray nozzles 13-1, 13-2, 13-3, 134, 13-5 via which liquid is sprayed onto the washware which is transported through the respective treatment zones 51, 52, 53, 54 by the conveyor belt 58. The spray nozzles 13-1, 13-2 of the wash system 10 1, 10-2 which is associated with the prewash zone 51 and the main-wash zone 52 are in each case formed in an upper and a lower wash tube 15-1, 15-2, and therefore corresponding wash arms are used in these treatment zones. It is feasible here for the wash systems 10-1, 10-2, 10-3 used to have a plurality of wash tubes 15-1, 15-2 which form a set of wash arms, wherein the plurality of wash tubes is connected to the corresponding wash pump 11-1, 11-2, 11-3 by means of a preferably common line system 12-1, 12-2, 12-3. At least each wash zone (prewash zone 51, main-wash zone 52, post-wash zone 53) has an associated tank (wash tank 14-1, 14-2, 14-3) in which sprayed liquid is accommodated, and/or in which liquid is provided for the spray nozzles 13-1, 13-2, 13-3 of the relevant zones 51, 52, 53. The prewash zone 51, the main-wash zone 52 and the post-wash zone 53 of the conveyor-type dishwasher 50 according to the embodiment illustrated in fig. 1 each have a wash system 10 1, 10-2, 10-3. Each wash system 10-1, 10-2, 10-3 is made up of a wash tank 14-1, 14-2, 14-3, a wash pump 11-1, 11-2, 11 3, a line system 12-1, 12-2, 12-3 which is connected to the wash pump 11-1, 11-2, 11-3, and the spray nozzles 13-1, 13-2, 13-3 which are connected to the line system 12-1, 12-2, 12-3. Also provided is a control device 20 which serves (amongst other things) to actuate the respective wash pumps 11-1, 11 2, 11-3 of the wash systems 10-1, 10-2, 10-3 in a suitable manner during a washing or cleaning process for the purpose of supplying liquid to the spray nozzles 13-1, 13-2, 13-3 of the nozzle system, which forms part of the respective wash 12 WO 2013/028392 PCT/US2012/050697 system 10-1, 10-2, 10-3, at least temporarily by means of the associated line system 12-1, 12-2, 12-3. Specifically, in the case of the conveyor-type dishwasher 50 illustrated in fig. 1, final-rinse liquid in the form of fresh water which can be mixed with further additives, for example rinse aid, is sprayed onto the washware (not illustrated in fig. 1) via the spray nozzles 13-4, which are arranged above and below the conveyor belt 58, of the final rinse zone 54. As illustrated in fig. 1, laterally arranged spray nozzles 13-5 are also provided in the final-rinse zone 54. Some of the sprayed final-rinse liquid is transported from zone to zone, counter to the transportation direction T of the washware, via a cascade system. The remainder is conducted directly into the prewash tank 14-1 via a valve 59 and a bypass line 60. The sprayed final-rinse liquid is collected in the tank (post-wash tank 14-3) of the post-wash zone 53, from which it is conveyed to the spray nozzles 13-3 (post-wash nozzles) of the post-wash zone 53 via the wash pump 11-3 which is part of the wash system 10-3 of the post-wash zone 53. In the post wash zone 53, wash liquid is rinsed off from the washware. The liquid which accumulates in the process flows into the wash tank 14-2 of the main-wash zone 52, is usually provided with a detergent and is sprayed onto the washware with the aid of a wash pump 11-2, which is part of the wash system 10 2 of the main-wash zone 52, via the spray nozzles 13-2 (wash nozzles) of the wash system 10-2 which is part of the main wash zone 52. The liquid then flows from the wash tank 14-2 of the main wash zone 52 into the prewash tank 14-1 of the prewash zone 51. The liquid in the prewash tank 14-1 is sprayed onto the washware by means of a wash pump 11-1, which is part of the wash system 10-1 of the prewash zone 51, via the spray nozzles 13-1 (prewash nozzles) of the wash system 10-1, which 13 WO 2013/028392 PCT/US2012/050697 is part of the prewash zone 51, in order to remove coarse dirt from the washware. Each wash system 10-1, 10-2, 10-3 of the conveyor-type dishwasher 50 according to fig. 1 has a sensor device 30 which is connected to the control device 20. The sensor devices 30 serve to detect a profile of the hydrostatic pressure of the liquid (wash liquid) which is conveyed in the respective line system 12-1, 12-2, 12-3 of the associated wash system 10-1, 10-2, 10-3, with the aid of the associated wash pump 11-1, 11-2, 11-3, to the corresponding spray nozzles 13-1, 13-2, 13-3. The detected pressure profile is then compared with a predefined desired pressure profile which is stored in a memory device which is part of the control device 20. In the case of the conveyor-type dishwasher 50 according to fig. 1, each wash system 10-1, 10-2, 10-3 also has an associated waste-water line 2-1, 2-2, 2-3 which is or can be connected to the tank (prewash tank 14-1, main-wash tank 14 2, post-wash tank 14-3) which forms part of the corresponding treatment zone by means of a valve 3-1, 3-2, 3-3 and issues into a main waste-water line 1. Since the corresponding valves 3-1, 3-2, 3-3 can be opened, the corresponding tanks 14-1, 14-2, 14-3 can be emptied, for example, in the cleaning mode of the conveyor-type dishwasher 50. The prewash zone 51, the main-wash zone 52 and the post-wash zone 53 each also have an associated cleaning system in the embodiment illustrated in fig. 1. Each cleaning system has at least one interior cleaning nozzle which is arranged in the relevant treatment zone and can be connected to a fresh-water connection of the conveyor-type dishwasher 50 by means of a fresh-water line system. Specifically, an interior cleaning nozzle 4-1 which is in the form of an all-round spray nozzle is arranged in the prewash zone 51 in the embodiment illustrated in fig. 1, it being possible for said interior 14 WO 2013/028392 PCT/US2012/050697 cleaning nozzle to be connected to a main fresh-water connection 5 of the conveyor-type dishwasher 50 by means of the fresh-water line system which is denoted by reference numeral "5-1". In the embodiment illustrated in fig. 1, an interior cleaning nozzle 4-2 which is likewise in the form of an all-round spray nozzle is arranged in the main-wash zone 52, it being possible for said interior cleaning nozzle to be connected to the main fresh-water connection 5 by means of the fresh-water line system 5-2, while the interior cleaning nozzle 4-3 which is in the form of an all-round spray nozzle can be connected to the abovementioned main fresh-water connection 5 of the conveyor-type dishwasher 50 by means of the fresh-water line system 5-3 in the post-wash zone 53. An interior cleaning nozzle 4-4 which is in the form of an all-round spray nozzle is also provided at the outlet of the final-rinse zone 54, it being possible for said interior cleaning nozzle to be connected to the main fresh-water connection 5 by means of the fresh-water line system 5-4. The respective treatment zones of the conveyor-type dishwasher 50 illustrated by way of example in fig. 1 are separated from one another by means of curtains 7, wherein these curtains 7 serve to prevent liquid from overflowing, in particular in the washing mode of the conveyor-type dishwasher 50. Corresponding curtains 7 are also provided at the inlet and at the outlet of the conveyor-type dishwasher 50 in order to prevent vapor escaping from the conveyor-type dishwasher 50. The wash tubes 15-1, 15-2 which are arranged in the corresponding wash zones (prewash zone 51, main-wash zone 52) are in each case provided with a central cleaning opening which will be described in greater detail below with reference to the illustrations in figures 3 to 5. 15 WO 2013/028392 PCT/US2012/050697 The abovementioned interior cleaning nozzles 4-1, 4-2, 4-3 and 4-4 serve to rinse off the inner wall of the corresponding treatment chambers and the separating curtains 7 with fresh water in the cleaning mode of the conveyor-type dishwasher 50. It goes without saying that the invention is not restricted to a dishwasher in which only one single interior cleaning nozzle, in particular which is in the form of an all-round spray nozzle, can be used for each of the treatment zones. As illustrated in fig. 2 for example, it is equally feasible to provide a plurality of interior cleaning nozzles for each treatment zone, wherein these interior cleaning nozzles can be provided in corresponding spray arms. Fig. 3a shows a schematic view of the design of a wash system for a conveyor-type dishwasher according to the invention or a dishwasher according to the invention which is in the form of a box-type dishwasher in a washing mode of the dishwasher. As already indicated, each wash system, which is associated with a treatment zone in the case of a conveyor-type dishwasher and which is associated with the treatment chamber in the case of a dishwasher which is in the form of a box type dishwasher, comprises a wash tank 14-1, 14-2, 14-3 and a line system 12-1, 12-2, 12-3 which is connected to the wash tank 14-1, 14-2, 14-3 by means of a wash pump 11-1, 11-2, 11 3 in order to supply wash liquid which is stored in the wash tank 14-1, 14-2, 14-3, at least to a wash tube 15-1, 15-2 which is arranged in the corresponding treatment zone or treatment chamber. A plurality of spray nozzles 13-1, 13-2 are formed in the at least one wash tube 15-1, 15-2 for the purpose of spraying the wash liquid which is supplied by means of the wash pump 11-1, 11-2, 11-3. The spray nozzles 13-1, 13-2 are arranged and formed relative to the wash tank 14-1, 14-2, 14-3 in such a way that at least some of the wash 16 WO 2013/028392 PCT/US2012/050697 liquid which is sprayed by the spray nozzles flows back into the wash tank. In the embodiment illustrated in fig. 3a, the upper wash tube 15-1 and the lower wash tube 15-2 of the wash system 10-1, 10-2 each have a central cleaning opening 8-1, 8-2 which is closed in the washing mode of the dishwasher 50, so that the wash liquid which is supplied to the corresponding wash tube 15-1, 15-2 by the wash pump 11-1, 11-2 is discharged by means of the plurality of spray nozzles 13-1, 13-2 which are formed in the wash tube 15-1, 15-2 and is sprayed onto the washware (not illustrated in fig. 3a) . The wash liquid sprayed then flows back into the wash tank 14-1, 14-2 due to the force of gravity. In the case of the embodiment illustrated in fig. 3a, a screen system 17 is associated with the wash system 10 1, 10-2 for the purpose of separating out solid particles of dirt from the wash liquid which is sprayed onto the washware, which is to be cleaned, by means of the spray nozzles 13-1, 13-2. The screen system 17 is arranged above the wash tank 14-1, 14-2 in the washing mode. The wash system 10-1, 10-2 illustrated in fig. 3a also has a detector device 18 which is connected to the control device 20 of the dishwasher 50 and automatically detects whether the screen system 17 is in its state in which it is correctly installed. The detector device 18 can have, for example, an optically, capacitively or inductively operating sensor, in particular a Hall sensor, and/or a switch, in particular a reed switch. The control device 20 of the dishwasher 50 is preferably designed in such a way that the corresponding wash pumps 11 1, 11-2 are actuated in a washing mode of the dishwasher 50 only when the detector device 18 detects that the screen system 17 is in its state in which it is installed in the dishwasher 50. Secondly, the control device 20 is designed in such a way that the corresponding wash pump 11-1, 11-2 is 17 WO 2013/028392 PCT/US2012/050697 actuated in a cleaning mode of the dishwasher 50 only when the detector device 18 detects that the screen system 17 is not in its state in which it is installed in the dishwasher 50, that is to say has been manually removed from the dishwasher 50. In the embodiment illustrated in figs 3a and 3b, a sensor device 30 which is connected to the control device 20 is also used and detects a hydrostatic pressure profile of the wash liquid in the line system 12-1, 12-2, 12-3. The hydrostatic pressure profile which is detected by the sensor device 30 is then compared with a prespecified pressure profile in the control device 20. The control device 20 is preferably designed to output a fault message by means of an optical and/or acoustic interface (not illustrated in the drawings) when the detected pressure profile is continuously below the prespecified pressure profile in a washing mode of the dishwasher 50. It can then specifically be assumed that the central cleaning openings 8-1, 8-2 of the wash tubes 15-1, 15-2 are not closed or at least are not correctly closed. The embodiment illustrated in fig. 3a also shows a cleaning system which has an interior cleaning nozzle 4-1, 4-2 which is connected to a fresh-water pump 16 by means of a fresh water line system 5-1, 5-2. Fresh water is correspondingly supplied to the interior cleaning nozzle 4-1, 4-2 in the cleaning mode of the dishwasher 50 in order to spray-wash the inner walls of the treatment zone or of the treatment chamber with fresh water from the inside and also to spray-wash the wash tubes present in the treatment zone or in the treatment chamber with fresh water from the outside. The wash system 10-1, 10-2 described above with reference to the illustration in fig. 3a is illustrated in a cleaning mode of the dishwasher 50 in fig. 3b. 18 WO 2013/028392 PCT/US2012/050697 In order to prepare the dishwasher 50 for the cleaning mode, it is necessary to first manually remove the screen system 17. The central cleaning openings 8-1, 8-2 of the wash tubes 15-1, 15-2 are then opened and wash liquid is supplied to the wash tubes 15-1, 15-2 with the aid of the wash pump 11-1, 11 2. The central cleaning openings 8-1, 8-2 are formed in such a way that at least some of the wash liquid which is supplied to the wash tubes 15-1, 15-2 by the wash pump 11-1, 11-2 flows back into the wash tank 14-1, 14-2 by means of the central cleaning openings 8-1, 8-2 in a cleaning mode of the dishwasher 50. A closure element 9-1, 9-2, which can be manually operated or can be automatically actuated, is associated with each central cleaning opening 8-1, 8-2 for the purpose of selectively opening the central cleaning opening 8-1, 8-2 in a cleaning mode of the dishwasher 50 and for the purpose of selectively closing the central cleaning opening 8-1, 8-2 in a washing mode of the dishwasher 50. It is feasible, for example, for the closure element 9-1, 9-2 used to be a valve which can be automatically actuated by means of the control device 20. As an alternative to this, it goes without saying that it is also possible for the closure element 9-1, 9-2 used to be a valve which can be manually operated or a closure which can be manually removed from the central cleaning opening 8-1, 8-2. In one embodiment, the central cleaning opening may be formed at the distal end of the wash tube that faces downwardly. Therefore, wash liquid is recirculated with the open cleaning openings 8-1, 8-2 in the cleaning mode of the dishwasher 50. As a result, the wash tubes 15-1, 15-2 are flushed and the insides of the wash tubes 15-1, 15-2 are cleaned. Waste-water outlet valves (valves 3-1, 3-2, 3-3 in fig. 1) are then opened for the purpose of emptying the corresponding wash tanks 14-1, 14-2, 14-3 into a waste-water system. The 19 WO 2013/028392 PCT/US2012/050697 interior cleaning nozzles 4-1, 4-2, 4-3, 4-4 (fig. 1) are actuated after a prespecified time. In this case, the wash arms are also cleaned from the outside, as are the wash tanks 14-1, 14-2, 14-3 of the individual wash zones 51, 52, 53 or of the treatment chamber. The waste-water outlet valves (in fig 1: valves 3-1, 3-2, 3 3) are open until the wash liquid and the additional fresh water which is used for cleaning purposes has completely drained away. Finally, the screen systems 17 are replaced in the machine 50 and the central cleaning openings 8-1, 8-2 are closed again. Fig. 4 schematically shows the design of a further wash system 10-1, 10-2 for a dishwasher 50, which is in the form of a conveyor-type dishwasher or in the form of a box-type dishwasher, in the cleaning mode of the machine. The embodiment illustrated in fig. 4 corresponds substantially to the embodiment shown in fig. 3b, with the exception that, in the embodiment illustrated in fig. 4, the cleaning system has an interior cleaning nozzle 4-1, 4-2 which is not connected to a fresh-water pump but rather to a central fresh-water connection 5 by means of a fresh-water line system 5-1, 5-2. Fig. 5a schematically shows a first embodiment of a set of wash arms which can be used in the case of the solution according to the invention and which is preferably used when the wash system 10-1, 10-2 has a plurality of wash tubes 15 1, 15-2. The plurality of wash tubes 15-1, 15-2 can be connected to a wash pump by means of a preferably common line system. A central cleaning opening 8-1, 8-2 is used for the set of wash arms, said central cleaning opening being formed in such a way that at least some of the wash liquid which is supplied to the plurality of wash tubes 15-1, 15-2 by the wash pump flows back into the wash tank by means of the central cleaning opening 8-1, 8-2 in a cleaning mode of the dishwasher 50. In the embodiment illustrated in fig. 5a, the 20 WO 2013/028392 PCT/US2012/050697 central cleaning opening 8-1, 8-2 is angled downward or upward in the state in which the set of wash arms are installed. Fig. 5b schematically shows a further embodiment of a set of wash arms which can be used in the case of the solution according to the invention. In contrast to the embodiment illustrated in fig. 5a, in this case the central cleaning opening 8-1, 8-2 is arranged laterally in the state in which the set of wash arms is installed. The invention is not restricted to the exemplary embodiments described above with reference to the drawings, but rather is made up of a combination of all the features disclosed in said exemplary embodiments. It is particularly preferred when the wash system 10-1, 10-2, 10-3 of the dishwasher which is in the form of a box-type dishwasher or in the form of a conveyor-type dishwasher has a plurality of wash tubes 15-1, 15-2 which form a set of wash arms, wherein the plurality of wash tubes 15-1, 15-2 is connected to the associated wash pump 11-1, 11-2, 11-3 by means of a preferably common line system 12-1, 12-2, 12-3, and wherein the central cleaning opening 8-1, 8-2 is formed in such a way that at least some of the wash liquid which is supplied to the plurality of wash tubes 15-1, 15-2 by the wash pump 11-1, 11-2, 11-3 flows back into the wash tank 14 1, 14-2, 14-3 via the central cleaning opening 8-1, 8-2 in a cleaning mode of the dishwasher. In a feasible embodiment of the dishwasher according to the invention, said dishwasher has a control device 20 for actuating the corresponding wash pump or pumps 11-1, 11-2, 11-3. The dishwasher can also have a sensor device 30, which is connected to the control device 20, for detecting a hydrostatic pressure profile of the wash liquid in the line system 12-1, 12-2, 12-3 and for comparing the detected 21 WO 2013/028392 PCT/US2012/050697 pressure profile with a predefined pressure profile. In this case, the control device 20 is preferably designed to output a fault message by means of an optical and/or acoustic interface if the detected pressure profile is continuously below the predefined pressure profile in a washing mode of the dishwasher. If, in contrast, a closure element 9-1, 9-2 in the form of a valve which can be actuated by means of the control device 20 is associated with the central cleaning opening 8-1, 8-2, it is feasible for the control device 20 to be designed to automatically close the valve if the detected pressure profile is continuously below the predefined pressure profile in a washing mode of the dishwasher. Finally, it is preferred when the control device 20 is designed to actuate the wash pump or pumps 11-1, 11-2, 11-3 in a washing mode of the dishwasher only when a detector device 18 detects that the screen system 17, which forms part of the corresponding wash system 10-1, 10-2, 10-3, is in its state in which it is installed in the dishwasher. Secondly, the control device 20 is intended to be designed in such a way that it actuates the wash pump or pumps 11-1, 11-2, 11-3 in a cleaning mode of the dishwasher only when the detector device 18 detects that the screen system 17 is not in its state in which it is installed in the dishwasher. 22

Claims

1. A dishwasher, which is in the form of a box-type dishwasher having a treatment chamber or in the form of a conveyor-type dishwasher having at least one treatment zone and has a wash system which is associated with the treatment chamber or the at least one treatment zone, wherein the wash system has the following: - a wash tank for accommodating wash liquid; - a plurality of spray nozzles, which are formed in at least one wash tube, for spraying wash liquid onto the wash ware which is to be cleaned, wherein the spray nozzles are arranged and formed relative to the wash tank in such a way that at least some of the wash liquid which is sprayed by the spray nozzles flows back into the wash tank; and - a wash pump, which is connected to the at least one wash tube by means of a line system, for supplying wash liquid from the wash tank to the spray nozzles which are formed in the at least one wash tube, wherein the at least one wash tube has a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher.

2. The dishwasher as claimed in claim 1, wherein the wash system has a plurality of wash tubes which form a set of wash arms, wherein the plurality of wash tubes is connected to the wash pump by means of a line system, and wherein the central cleaning opening is formed in such a way that at least some of the wash liquid which is supplied to the plurality of wash tubes by the wash pump flows back into the wash tank via the central cleaning opening in a cleaning mode of the dishwasher. 23

3. The dishwasher as claimed in claim 1 or 2, wherein a closure element, which can be manually operated or can be automatically actuated, is associated with the central cleaning opening for the purpose of selectively opening the central cleaning opening in a cleaning mode of the dishwasher and for the purpose of selectively closing the central cleaning opening in a washing mode of the dishwasher.

4. The dishwasher as claimed in any one of claims 1 to 3, wherein the dishwasher also has the following: - a control device for actuating the wash pump in a washing mode of the dishwasher in such a way that wash liquid is at least temporarily supplied to the spray nozzles by means of the line system; and - a sensor device, which is connected to the control device, for detecting a hydrostatic pressure profile of the wash liquid in the line system and for comparing the detected pressure profile with a predefined pressure profile.

5. The dishwasher as claimed in claim 4, wherein the control device is designed to output a fault message by means of an optical and/or acoustic interface if the detected pressure profile is continuously below the predefined pressure profile in a washing mode of the dishwasher.

6. The dishwasher as claimed in claim 4, wherein a closure element in the form of a valve which can be actuated by means of the control device is associated with the central cleaning opening, and wherein the control device is designed to automatically close the valve if the detected pressure profile is continuously below the predefined pressure profile in a washing mode of the dishwasher.

7. The dishwasher as claimed in any one of claims 1 to 6, wherein the dishwasher also has the following: 24 - a control device for actuating the wash pump in a washing mode of the dishwasher in such a way that wash liquid is at least temporarily supplied to the spray nozzles by means of the line system; and - a sensor device, which is connected to the control device, for detecting a volumetric-flow profile of the wash liquid in the line system and for comparing the detected volumetric-flow profile with a predefined volumetric-flow profile.

8. The dishwasher as claimed in claim 7, wherein the control device is designed to output a fault message by means of an optical and/or acoustic interface if the detected volumetric-flow profile is continuously below the predefined volumetric-flow profile in a washing mode of the dishwasher.

9. The dishwasher as claimed in claim 7, wherein a closure element in the form of a valve which can be actuated by means of the control device is associated with the central cleaning opening, and wherein the control device is designed to automatically close the valve if the detected volumetric-flow profile is continuously below the predefined volumetric-flow profile in a washing mode of the dishwasher.

10. The dishwasher as claimed in one of claims 1 to 9, wherein a screen system which can be manually removed from the dishwasher is provided for the purpose of separating out solid particles of dirt from the wash liquid which is sprayed onto the wash ware, which is to be cleaned, by means of the spray nozzles, wherein a detector device, which is connected to a control device, is also provided for the purpose of automatically detecting whether the screen system is in its state in which it is installed in the dishwasher.

11. The dishwasher as claimed in any one of claims 1 to 10, 25 wherein the dishwasher is in the form of a conveyor-type dishwasher and has at least one wash zone and at least one final-rinse zone, and also has a conveyor apparatus for conveying wash ware through the at least one wash zone and the at least one final-rinse zone, and wherein the wash system is formed in at least one of the at least one wash zones.

12. The dishwasher as claimed in claim 11, wherein a cleaning system is associated with the at least one wash zone and/or the at least one final-rinse zone, the said cleaning system having at least one interior cleaning nozzle which is arranged in the relevant treatment zone and can be connected to a fresh-water connection of the dishwasher or to a fresh-water pump of the dishwasher by means of a fresh water line system.

13. A method for automatically cleaning a dishwasher, which is in the form of a box-type dishwasher or conveyor-type dishwasher and has at least one wash system, wherein the wash system has the following: - a wash tank for accommodating wash liquid; - a plurality of spray nozzles, which are formed in at least one wash tube, for spraying wash liquid onto the wash ware which is to be cleaned, wherein the spray nozzles are arranged and formed relative to the wash tank in such a way that at least some of the wash liquid which is sprayed by the spray nozzles flows back into the wash tank; and - a wash pump, which is connected to the at least one wash tube by means of a line system, for supplying wash liquid from the wash tank to the spray nozzles which are formed in the at least one wash tube, wherein the at least one wash tube has a central cleaning opening which is formed in such a way that at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central 26 cleaning opening in a cleaning mode of the dishwasher, and wherein the method exhibits the following method steps: a) the central cleaning opening of the at least one wash tube is opened in a cleaning mode of the dishwasher; and b) the wash pump, which is connected to the at least one wash tube, is actuated in such a way that wash liquid is supplied to the spray nozzles, which are formed in the at least one wash tube, from the wash tank, wherein at least some of the wash liquid which is supplied to the wash tube by the wash pump flows back into the wash tank via the central cleaning opening.

14. The method as claimed in claim 13, wherein a screen system which can be manually removed from the dishwasher is provided for the purpose of separating out solid particles of dirt from the wash liquid which is sprayed onto the wash ware, which is to be cleaned, by means of the spray nozzles, and wherein the screen system is removed from the dishwasher before method step a).

15. The method as claimed in claim 14, wherein the following method step is also provided: - a detector device is used to automatically detect whether the screen system is in its state in which it is installed in the dishwasher, wherein method step b) is automatically carried out in a cleaning mode of the dishwasher if the detector device detects that the screen system is not in its state in which it is installed in the dishwasher.

16. The method as claimed in any one of claims 13 to 15, wherein, after method step b), the following method step is also provided: c) opening of a waste-water outlet valve, which is associated with the wash tank, for the purpose of emptying the wash tank, 27 wherein the waste-water outlet valve, which is associated with the wash tank, is actuated by means of a control device, and wherein - after the wash liquid has been recirculated for a pre-specified period of time in method step b) - method step c) is automatically carried out.

17. The method as claimed in any one of claims 13 to 16, wherein a hydrostatic pressure profile of the wash liquid in the line system is detected using a sensor device, which is connected to a control device, in a continuous manner or at pre-definable times or in the case of pre-definable events, and wherein the detected pressure profile is compared with a predefined pressure profile using the control device, wherein a fault message is automatically output by the control device by means of an optical and/or acoustic interface if the detected pressure profile is continuously below or continuously above the predefined pressure profile in a washing mode of the dishwasher.

18. The method as claimed in claim 17, wherein a valve, which can be automatically actuated by means of a control device, is associated with the central cleaning opening for the purpose of opening the central cleaning opening in a cleaning mode of the dishwasher and for the purpose of closing the central cleaning opening in a washing mode of the dishwasher, and wherein the valve is automatically closed using the control device in a washing mode of the dishwasher if the detected pressure profile is continuously below the predefined pressure profile.

19. The method as claimed in any one of claims 13 to 16, wherein a volumetric-flow profile of the wash liquid in the line system is detected using a sensor device, which is connected to the control device, in a continuous manner or at pre-definable times or in the case of pre-definable events, and wherein the detected volumetric-flow profile is compared 28 with a predefined volumetric-flow profile using the control device.

20. The method as claimed in claim 19, wherein a valve, which can be automatically actuated by means of a control device, is associated with the central cleaning opening for the purpose of opening the central cleaning opening in a cleaning mode of the dishwasher and for the purpose of closing the central cleaning opening in a washing mode of the dishwasher, and wherein the valve is automatically closed using the control device in a washing mode of the dishwasher if the detected volumetric-flow profile is continuously above the predefined volumetric-flow profile. 29