Patent Publication Number: US-2015083163-A1

Title: Dishwasher with treatment-fluid generator, and method of operating such a dishwasher

Description:
The present application relates in particular to a commercial dishwasher for crockery or utensils and which is designed as a box-type dishwasher or as a conveyor dishwasher. 
     Accordingly, the application relates to a dishwasher having at least one wash tank, for accommodating a treatment fluid, and at least one final-rinse system, for supplying a final-rinse fluid. Such dishwashers are known from the prior art. Thus, in the case of the conventional dishwashers, the treatment fluid located in the wash tank is applied to the washware via spray nozzles. For generating the treatment fluid, it is customary, in particular in the context of commercial dishwashers, to use highly alkaline wash agent. Use is likewise made of final-rinse agents in order to assist in the self-drying of the crockery, to remove residues of wash agent and to accentuate the shine of the crockery. For this reason, a wide variety of products are available on the market from innumerable manufacturers and distributors of wash chemicals, these products, in some cases, being sold at very high prices. 
     High outlay in respect of transportation is also involved, since these chemicals have to be constantly supplied to the user of the dishwasher. 
     On the basis of the problem set out above, a dishwasher is provided which generates at least a main component of the treatment fluid itself. The dishwasher may also have reduced running costs. 
     Accordingly, the dishwasher is characterized in that it has a treatment-fluid generator with at least one electrolysis device. The treatment-fluid generator here is, and/or can be, connected to the wash tank and is designed to supply an alkaline solution in the wash tank of the dishwasher by electrolysis. 
     The advantages of the subject dishwasher may include: for example, the treatment-fluid generator makes it possible to dispense with at least some of the numerous chemicals for generating the treatment fluid. In particular the treatment-fluid generator requires just a fresh-water connection in order to supply a highly alkaline treatment fluid in the wash tank of the dishwasher. This alkaline solution produced by electrolysis has a cleaning action which is at least equivalent to the conventional chemicals. Furthermore, the electrolysis uses up only a very small amount of chemicals, for which reason the present dishwasher is particularly advantageous to operate. Furthermore, the treatment-fluid generator makes it possible to dispense with many of the chemical substances, as a result of which outlay in respect of transportation and ease of use are increased. 
     Thus, in a first realization of the dishwasher, provision is made for the final-rinse system to have a storage container, for accommodating a final-rinse concentrate, and a multiplicity of final-rinse nozzles, for spraying washware with a final-rinse fluid. Accordingly, the storage container is, or can be, connected to the wash tank such that optionally the final-rinse concentrate can be metered into the wash tank. According to this variant, the final-rinse concentrate located in the storage container can be used not just for generating a final-rinse liquid, which is used by the final-rinse nozzles for spraying the washware; rather, at the same time, the final-rinse concentrate can be metered, in the form of a wash additive, into the alkaline solution located in the wash tank, in order to generate a particularly effective treatment fluid. This is advantageous in particular when the alkaline solution generated by the treatment-fluid generator provides insufficient dishwashing results and has to be regenerated. In this case, this embodiment does not require additional chemicals to be fed to the wash tank, since use can be made of the final-rinse concentrate which is present anyway in the final-rinse system. 
     The final-rinse concentrate here may contain, for example, specific substances from the complex-former groups of substances, for reducing the water hardness and for assisting cleaning, surface-active substances, for stabilizing emulsions and dispersions, and anti-foaming agents, and possibly also corrosion inhibitors. 
     The surface-active substances for stabilizing emulsions and dispersions are preferably surfactants which are known from dishwashing technology and can be gathered, for example, from US Patent Publication No.20100108942 A1, paragraphs [0104] to [0132]. Of course, the surface-active substances of the final-rinse concentrate are not restricted to the aforementioned groups of substances. 
     Depending on the washware which is to be treated and on the degree of soiling thereof, increased foam formation may occur, in certain circumstances, during operation of the dishwasher. In such cases, it is particularly advantageous if the final-rinse concentrate contains an anti-foaming agent. The anti-foaming agents, also referred to as foam inhibitors or foam dampers, are preferably biodegradable anti-foaming agents which are food-safe. The anti-foaming agents here may be any which are known from the prior art, e.g. natural fats, oils or fatty alcohols. 
     According to one aspect, the storage container is, or can be, connected directly to the wash tank, and therefore it is an option for the final-rinse concentrate to be metered directly into the wash tank. As an alternative, or in addition, the final-rinse system may have at least one boiler, which has a fresh-water connection and is, or can be, connected to the final-rinse tank for the supply of a final-rinse fluid, wherein said boiler is, or can be, connected to the wash tank such that it is an option for the final-rinse fluid (fresh water+final-rinse concentrate) generated in the boiler to be metered out of the boiler into the wash tank. Accordingly, the final-rinse concentrate used as wash additive either can be metered directly out of the storage container into the wash tank or can be directed, in the form of final-rinse fluid, from the boiler into the wash tank. In the case of the final-rinse concentrate being introduced directly into the wash tank, the final-rinse concentrate is particularly straightforward to meter. In contrast, if the final-rinse concentrate is introduced indirectly via the boiler of the final-rinse system, it may prove to be advantageous that conventional dishwashers can be retrofitted in a straightforward manner. A further metering pump may possibly also have to be provided for this purpose. 
     According to a further embodiment, the treatment-fluid generator has a first metering pump, for controlled metering of the alkaline solution into the wash tank. The final-rinse system also has a second metering pump, for controlled metering of the final-rinse concentrate and/or of the final-rinse fluid into the wash tank. The metering pumps may thus be used to supply the desired treatment fluid as a combination of the alkaline solution and of the final-rinse concentrate, or of the final-rinse fluid, in the wash tank. 
     In specific terms, the metering pumps may be set here so as to achieve a treatment fluid with a pH value of at least 9, and preferably at least 10, in the wash tank. This is made possible, in particular, by a control device which is, or can be, connected to the first and second metering pumps and is designed to activate the first and second metering pumps. It is thus possible to generate, via the control device, any desired mixing ratio between the final-rinse concentrate and the alkaline solution of the treatment-fluid generator. 
     In order for it to be possible to generate a feedback signal for the control device, the wash tank may have at least one sensor means for measuring the pH value of the treatment fluid located in the wash tank. Accordingly, the sensor means is likewise connected to the control device, and therefore the latter can draw conclusions as to the pH value of the treatment fluid. It is thus possible for the pH value of the treatment fluid to be regulated continuously by the control device, with the aid of the two metering pumps, throughout the dishwashing operation. Of course, it is likewise conceivable for the sensor means also to be designed to sense precisely the active-substance fractions within the treatment fluid. It would thus be possible for the control device to obtain, for example, information relating to the quantity of complex formers currently located in the treatment fluid. 
     According to a further aspect, the treatment-fluid generator is designed to supply an alkaline solution with a pH value of 10 to 14, in particular of 11.5 to 13. For this purpose, the electrolysis device can operate, for example, in accordance with the principle of producing an aqueous alkali-hydroxide solution. An alkaline solution with such a high pH value of 10 to 14 has a particularly high-level cleaning action. 
     In addition to generating the alkaline solution, the treatment-fluid generator of the dishwasher may also be designed to generate an acid solution which has a pH value of 1 to 7, in particular of 2.5 to 6. The chlorine which is generated anyway during the electrolysis can be used, for example, as an acid solution for disinfecting the washware. It is conceivable, for this purpose, for the dishwasher to have a further tank which is formed for accommodating the acid solution, i.e. the disinfectant. The disinfecting operation using the acid solution can take place, for example, immediately prior to, or at the same time as, final rinsing with fresh water, in order to guarantee that all the germs are killed off 
     According to a further embodiment, the dishwasher has a control device which is designed to make a selection between a first operating mode, for washing the washware with treatment fluid at a first temperature, and a second operating mode, for washing the washware with a treatment fluid at a second temperature. The second temperature may be, for example, lower than the first temperature. 
     The control device is preferably designed to initiate an operation for spraying the washware with the acid solution in the second operating mode. It is thus possible to realize the situation where the dishwasher initiates follow-up cleaning (i.e. disinfection) of the washware only when the washware has been cleaned at a lowered temperature. For example, the first temperature may be a dishwashing temperature of approximately 80 degrees Celsius, whereas the second temperature is approximately 60 degrees Celsius or less. Accordingly, the acid solution is used merely during operation at low temperatures, as a result of which it is possible to cut back on energy and time, since disinfection using the acid solution is not absolutely necessary in the hot operating mode. 
     As an alternative to the aforementioned embodiments, the chlorine which is produced during the electrolysis process can also be disposed of by way of an outlet valve. 
     According to a further realization of the dishwasher, the electrolysis device of the treatment-fluid generator is, or can be, connected to a fresh-water connection, and to an additive container, so that a starting solution can be supplied for the electrolysis device. Accordingly, it is possible to generate, in the electrolysis device, a starting solution which has a higher level of conductivity than fresh water. 
     According to a particularly advantageous variant, the dishwasher has a water-treatment device with a salt container for accommodating sodium chloride. The additive container of the treatment-fluid generator here is, or can be, connected to the salt container such that sodium chloride from the salt container of the water-treatment device can be fed to the additive container. 
     It should be mentioned in this connection that, in practice, virtually every conventional dishwasher has a water-treatment device. This is designed to adjust the properties of the fresh water as best as possible to the subsequent dishwashing process. The water-treatment device therefore frequently contains water filters and also a salt container. The salt container serves, in particular, to meter sodium chloride into the fresh water, in order for the water-treatment device to be regenerated if required. 
     According to the aforementioned embodiment, it is thus possible for the additive container of the treatment-fluid generator to be fed with sodium chloride from the salt container which is located in any case in the water-treatment device. Accordingly, there is no need for any further additive to be fed to the dishwasher. As an alternative, it is even conceivable, for this purpose, for the additive container to be designed in as a salt container of the water-treatment device and to be arranged between the fresh-water connection and the electrolysis device such that a common-salt solution can be fed, as starting solution, to the electrolysis device. 
     As already indicated, the additive container may be a salt container which is designed for accommodating sodium chloride and is, or can be, connected to the electrolysis device such that the starting solution results in a common-salt solution with a concentration of 1 to 20 g/l, preferably 3 to 10 g/l, and in particular 5 g/l. In particular the electrolysis of a common-salt solution gives rise to sodium hydroxide, which can be used as an alkaline solution for generating the treatment fluid. Also achieved is a hypochlorous acid, which can be used as an acid solution for disinfecting the washware. In particular, the electrolysis of the common-salt solution proceeds in accordance with the following reaction equations: 
     Cathode reaction: 
       4H 2 O—&gt;2H 3 O+2OH −   Dissociation of the water
 
       2H 3 O+2 e   − —&gt;H 2 +2H 2 O  Cathode reaction
 
       2H 2 O+2 e   − —&gt;H 2 +2OH −   Overall reaction in the cathode space
 
     Anode reaction: 
       2Cl − —&gt;Cl 2 +2 e   −   Anode reaction
 
       2NaCl—&gt;2Na + +Cl 2 +2 e   −   Overall reaction in the anode space
 
     Overall reaction: 
       2NaCl+2 H 2 O—&gt;2NaOH+Cl 2 +H 2  
 
     In another aspect, a method of operating a dishwasher involves a step for feeding fresh water into a tank of the electrolysis device, whereupon the electrolysis device is operated in order to generate an alkaline solution from the fresh water located in the tank and added salt (NaCl). This takes place in particular by the analyte generated at the anode being divided off from the catholyte generated at the cathode. The catholyte generated at the cathode is then pumped, as an alkaline solution, out of the tank of the electrolysis device into the wash tank of the dishwasher. In order to clean the washware, the latter is sprayed with the alkaline solution located in the wash tank, said solution serving as the treatment fluid. 
     Of course, the method of generation of the alkaline solution allows many of the conventionally used chemicals to be dispensed with. This not only cuts back on costs, but also reduces the outlay in respect of transportation. 
     In addition to the aforementioned steps, prior to the operation of spraying the washware, the method may have a step for supplying a final-rinse concentrate in a storage container of the dishwasher, wherein the final-rinse concentrate is metered, if required, into the alkaline solution located in the wash tank, in order to generate a treatment fluid with even better cleaning properties. The final-rinse concentrate here may have at least one wash additive comprising complex formers and/or surface-active substances and/or anti-foaming agents and/or corrosion inhibitors. Accordingly, these wash additives, which are often present in conventional final-rinse concentrates, need not be provided in the treatment-fluid generator. Rather, the final-rinse system, which is required in any case, can be used in order to feed the wash additive. 
     According to a further realization of the method, an additive for accelerating the dissociation of the fresh water can be added to the fresh water prior to the alkaline solution being generated by the electrolysis device. This additive may be, in particular, sodium chloride, which is metered into the fresh water so as to achieve a common-salt solution with a concentration of 1 to 20 g/l, preferably of 3 to 10 g/l, in particular 5 g/l. It is conceivable, of course, to use any additive which, following the electrolysis, results in an aqueous alkali-hydroxide solution, which can then be used as the treatment fluid. 
     If the additive used is sodium chloride, this can advantageously be removed from a water-treatment device of the dishwasher and metered into the fresh water. This means that the dishwashing salt which is often used anyway in dishwashers can be used not just for water-softening purposes, but also as an additive in order to allow the electrolysis in the treatment-fluid generator. 
     The method may also have a step for generating an acid solution from the fresh water located in the tank of the electrolysis device. The step for generating the acid solution takes place, in particular, at the same time as the step for generating the alkaline solution, that is to say as a further product of the electrolysis within the treatment-fluid generator. The resulting acid solution is applied to the washware preferably following the operation of spraying the washware with the alkaline solution and prior to, or during, final rinsing with fresh water. This allows the washware to be disinfected in a straightforward manner. 
    
    
     
       The dishwasher will be explained in more detail hereinbelow with reference to the embodiments illustrated in the drawings, in which: 
         FIG. 1  shows a schematic illustration of a first embodiment of the dishwasher; 
         FIG. 2  shows a schematic illustration of a second embodiment of the dishwasher; and 
         FIG. 3  shows a schematic illustration of an exemplary embodiment of the treatment-fluid generator. 
     
    
    
     The following detailed description of the figures provides like or equivalent components with like designations. 
     The illustration according to  FIG. 1  illustrates a first exemplary embodiment of the dishwasher  1 . It should be pointed out that this dishwasher merely has the components which are required for understanding. The dishwasher  1  is, in particular, a commercial dishwasher for crockery or utensils and is designed as a box-type dishwasher. Of course, it is likewise possible for the dishwasher  1  to be designed as a conveyor dishwasher. The modifications in design which are necessary for this purpose are, of course, known to a person skilled in the art. 
     The dishwasher  1  illustrated in  FIG. 1  has a treatment chamber  10  with an associated wash tank  12 . The wash tank  12  serves for accommodating a treatment fluid  20 , which can be delivered to a multiplicity of wash nozzles  16  via a wash pump  14 . The wash nozzles  16  are located, in particular according to the embodiment illustrated, in the upper and lower regions of the treatment chamber  10 . They are connected to the wash tank  12  via a wash line  15 . Since the wash tank  12  is located in the lower region of the treatment chamber  10 , this allows the treatment fluid to be recirculated once the washware has been sprayed. 
     The dishwasher  1  shown also has at least one final-rinse system for supplying a final-rinse fluid. The final-rinse system, in the embodiment illustrated, comprises a storage container  30 , which contains a final-rinse concentrate. As can be seen from  FIG. 1 , the storage container  30  of the final-rinse system is connected to a boiler  40  via a fluid line  32 . The boiler  40  has a fresh-water connection  50 , via which fresh water (e.g. mains water) can be introduced into the boiler  40 . The fresh water located in the boiler  40  is heated by a heating device  41  and mixed with the final-rinse concentrate from the storage container  30 . For this purpose, the final-rinse concentrate is delivered to the boiler  40  from the storage container  30  by way of a metering pump  31 . The final-rinse fluid, produced from a combination of fresh water and final-rinse concentrate, can be delivered to a multiplicity of final-rinse nozzles  18  via a final-rinse pump  43  and the associated final-rinse lines  44 . In a manner similar to the wash nozzles  16 , it is also the case that the final-rinse nozzles  18  are located in the interior of the treatment chamber  10  of the dishwasher  1 . 
     Finally, it can be seen from  FIG. 1  that the dishwasher  1  also has a treatment-fluid generator  100 , which is illustrated merely as a “black box” in the schematic illustration. The treatment-fluid generator  100  has at least one electrolysis device (see  FIG. 3 ) and is, or can be, connected to the wash tank  12  of the dishwasher  1 . The treatment-fluid generator  100  is designed to supply an alkaline solution in the wash tank  12  of the dishwasher  1  by electrolysis. There is therefore no need for the dishwasher  1  to use additional chemicals in order to generate the treatment fluid. 
     The treatment-fluid generator  100  used for this purpose is illustrated schematically in  FIG. 3 . It has at least one fresh-water connection  101 , which is connected to the electrolysis device  109  via a control valve  102 . The fresh water located in the electrolysis device  109  is divided into an alkaline solution and an acid solution by virtue of an electric voltage being applied to appropriate electrodes. The alkaline solution, which forms at the cathode of the electrolysis device  109 , can then be delivered into the wash tank  12  of the dishwasher  1 , via the fluid line  111 , with the aid of a metering pump  110 . 
     It should be noted here that the treatment-fluid generator  100  may be located either within the housing (not illustrated) of the dishwasher  1  or outside the same. It is thus conceivable, for example, for conventional dishwashers to be retrofitted, by the provision of an external treatment-fluid generator. 
     In addition to the fresh-water connection  101  and the electrolysis device  109 , the treatment-fluid generator  100  may have, for example, a filter  103 , a water-treatment element  105  and an additive container  107 . The units  103 ,  105  and  107 , each illustrated as a “black box” in  FIG. 3 , serve, in particular, to influence the composition of the alkaline solution formed by the electrolysis device. It is also possible to use the additive container  107  to supply a starting solution with a higher reaction speed for the electrolysis device  109 . 
     For example, it is possible here for the additive container  107  to be designed as a salt container for accommodating sodium chloride and to be connected, or connectable, to the electrolysis device  109  such that the starting solution located in the electrolysis device  109  results in a common-salt solution with a concentration of 1 to 20 g/l, preferably of 3 to 10 g/1 and in particular 5 g/l. Using common-salt solution as the starting solution for the electrolysis gives rise to the alkaline solution sodium hydroxide (NaOH), which can be fed directly to the wash tank  12  via the discharge line  111 . 
     Also produced is a hypochlorous acid (HClO), which can be used as an acid solution for disinfecting the washware. For this purpose, the acid solution may be connected to the wash nozzles  16  and/or final-rinse nozzles  18  directly for example via a second discharge line  112 . As an alternative, or in addition, it is also possible to provide an outflow line  113 , or the second discharge line  112  may have an outflow line  113 , via which the acid solution can optionally be disposed of (cf.  FIG. 3 ). 
     As already indicated, dishwashers usually already have a water-treatment device with a salt container, in order to reduce, for example, the hardness of the fresh water. Accordingly, it is also conceivable, according to a variant which is not illustrated, for the fresh-water connection  101 , the control valve  102 , the filter  103 , the water-treatment element  105  and the additive container  107  of the treatment-fluid generator  100  to be formed by the water-treatment installation which is present in any case. In specific terms, it is particularly advantageous here to use the salt container as additive container  107  and to connect the same, consequently, to the electrolysis unit  109  of the treatment-fluid generator  100 . As an alternative, it is also possible for the additive container  107  to be connected, or connectable, to the salt container of the water-treatment device via a delivery line, in order to feed sodium chloride as additive. 
     The dishwasher  1  also has a control device (not illustrated) which is, or can be, connected to the metering pump  110  and is designed to activate the metering pump  110  so as to achieve a treatment fluid with a pH value of at least  10  in the wash tank. 
     As already indicated, the final-rinse system has a storage container  30  for accommodating a final-rinse concentrate, wherein the final-rinse concentrate is used to supply the multiplicity of final-rinse nozzles  16  with the final-rinse fluid  42  generated in the boiler  40 . At the same time, it is possible for the storage container  30  to be connected, or connectable, to the wash tank  12  such that it is an option for the final-rinse concentrate and/or the final-rinse fluid to be metered out of the final-rinse system into the wash tank  12 . 
     According to the embodiment illustrated in  FIG. 1 , this takes place, in particular, by way of a direct connection between the storage container  30  and the wash tank  12 . For this purpose, the storage container  30  has a second fluid line  36 , which is connected directly to the wash tank  12 . A metering pump  38  is located within the second fluid line  36 , and can likewise be operated via the aforementioned control device (not illustrated). This makes it an option for the final-rinse concentrate located in the storage container  30  to be fed to the wash tank  12  of the dishwasher  1 . Accordingly, the treatment fluid  20  located in the wash tank  12  is a combination of the final-rinse concentrate and of the alkaline solution from the treatment-fluid generator  100 . 
     The final-rinse concentrate functions as a wash additive comprising complex formers and/or surface-active substances and/or anti-foaming agents and/or corrosion inhibitors. Reference is also made in this connection to the aforementioned exemplary embodiments of the wash additives. 
     In respect of the second exemplary embodiment of the dishwasher  1 , this exemplary embodiment being illustrated in  FIG. 2 , it should be mentioned that provision may also be made, as an alternative, for the final-rinse fluid generated in the boiler  40  to be introduced into the wash tank  12  via a second discharge line  46  of the boiler  40 . Accordingly, according to the second embodiment, the final-rinse concentrate is not supplied directly into the wash tank  12 ; rather, the final-rinse fluid  42  consisting of the final-rinse concentrate and the fresh water is metered into the treatment fluid  20 . A metering pump  48  is once again provided for this purpose, and this one can likewise be controlled via the control unit (not illustrated). According to this embodiment, the treatment fluid  20  is a combination of the alkaline solution and the final-rinse fluid supplied in the boiler  40 . 
     In summary, all that remains to be said is that the control device of the dishwasher  1  is connected to the respective metering pumps  31 ,  38 ,  48  and  110 , and is designed to activate the same, so as to achieve a treatment fluid  20  with a pH value of at least  9 , and preferably at least  10 , in the wash tank  12 . This provides a treatment fluid  20  with an optimum cleaning behavior. The wash tank  12  may also have at least one sensor means (not illustrated in the drawings) for measuring the pH value of the treatment fluid located in the wash tank  12 . This sensor means is, of course, likewise connected to the control device, in order to allow conclusions to be drawn as to the pH value of the treatment fluid  20 . Should the pH value be below a predetermined desired value of, for example, at least 9, then the control device will feed alkaline solution from the treatment-fluid generator  100  repeatedly to the wash tank  12 . 
     The treatment-fluid generator is also designed to supply an alkaline solution with a pH value of 10 to 14, in particular 11.5 to 13. In contrast, the acid solution supplied by the treatment-fluid generator  100  should have a pH value of 1 to 7, in particular 2.5 to 6. 
     According to a further embodiment, the control device also has the task of making a selection between a first operating mode, for washing the washware with treatment fluid  20  at a first temperature, and a second operating mode, for washing the washware with treatment fluid  20  at a second temperature. The second temperature here is preferably lower than the first temperature, wherein the control device is designed to initiate an operation for spraying the washware with the acid solution in the second, colder operating mode. The second operating mode is based on the finding that the dishwashing result with the alkaline solution from the treatment-fluid generator  100  at low temperatures is not always sufficient. For this reason, the acid solution, which is generated anyway, is applied as disinfectant once the washware has been cleaned. If the treatment fluid has a first, higher temperature of approximately 80 degrees Celsius, then subsequent disinfection of the washware is not absolutely necessary. In this case, the control device is designed to operate the dishwasher in a first operating mode, which does not provide for the follow-up cleaning with the acid solution. 
     The present application is not restricted to the features and combinations illustrated in the drawings. In particular it should be pointed out that the dishwasher need not be designed, as illustrated in the figures, as a box-type dishwasher. It may, of course, also be designed as a conveyor dishwasher.