1. Field of the Invention
The invention relates to a method and to a cleaning apparatus for cleaning washware. Such methods and cleaning apparatuses are used for cleaning washware of all types in various areas of daily life, in hospitals and in the care sector, for cleaning machine parts and other types of washware in industry, and also in various areas of medicine and natural sciences. Without restricting possible further uses, the invention will be described below in particular with reference to dishwashers which are designed to clean dishes, for example glasses, cups, cutlery, plates, trays or other types of articles which can come into direct or indirect contact with food and drink or which can be used for food preparation.
2. Description of the Background Art
Cleaning apparatuses for cleaning various types of washware are known from various areas of daily life, natural sciences and technology, medicine and also other areas. The following description relates, in particular, to dishwashers in which dishes of the type described above are acted on by cleaning liquids of various types as part of a program sequence. This can be performed, in particular, in a cleaning chamber. Various types of dishwashers are known from the prior art. In principle, a distinction is first drawn between single-chamber and multi-chamber dishwashers. The invention described in the text which follows is, in principle, suitable for all types of dishwashers but can be used particularly advantageously for single-chamber dishwashers in which the washware is not transported during the cleaning process. Cleaning programs with one or more cleaning steps can be executed in dishwashers of this type.
A further distinction can be drawn between dishwashers for the domestic sector and dishwashers for commercial use. Whereas the first-mentioned dishwashers are generally equipped with a so-called single-circuit system, in which the same cleaning circuit is used for the actual cleaning process (also called wash process in the text which follows) and a final-washing process, dishwashers for commercial use are generally designed in the form of two-circuit cleaning apparatuses. In two-circuit cleaning apparatuses of this type, a two-circuit washing system is provided, in which at least partly separate washing systems are provided for the wash process and the final-washing process. The present invention can, in principle, again be used for all types of dishwashers, but it is particularly preferably used in commercial dishwashers with two-circuit washing systems.
DE 43 05 020 A1 discloses a domestic dishwasher with a washing program which is made up of several program substeps. The dishwasher comprises a reverse-osmosis device in which the introduced water is converted partly into permeate and partly into concentrate. In this case, the permeate is used as washing liquid in a “rinsing” program substep.
Commercial dishwashers usually have a tank system in which a washing liquor for a wash process is stored. This washing liquor is repeatedly used, without being discarded after a cleaning cycle, to clean washware which has been introduced, in order to clean adhering particles of dirt from said washware. Following the wash process or cleaning process, fresh water which has been heated in a boiler or a flow heater is applied to the washware via an additional rinsing system. This introduced rinse water generally has at least one rinse agent added and is entirely or partly used to regenerate the washing liquor for the wash process. EP 0 133 677 A2 discloses a method and apparatus for demineralizing water for a dishwasher. In this case, water which is used for a third washing step is demineralized by means of reverse osmosis.
Commercial dishwashers with a two-circuit system are mainly used in establishments with a high throughput of washware, for example in restaurants or in canteens in factories, hospitals, offices, schools, care homes or similar facilities. One reason for this is, in particular, that machines of this type are distinguished by very short cycle times, for example cycle times of from less than 60 seconds to a few minutes. In this respect, dishwashers of this type are designed for a high throughput.
In order to achieve a required hygiene effect for washware despite the high throughput, there are two important procedures. One procedure, which is used primarily in European countries, uses fresh water for rinsing, said fresh water having been heated to a high temperature. Temperatures in the region of approximately 85° C. are normally used. This rinse water is enriched with a rinse agent and then a sufficient quantity is sprayed onto the freshly cleaned washware, for example dishes, so that a thermal hygiene effect is produced in addition to a washing-off effect for removing adhering wash liquor. At the end of the cleaning program, the washware is then in a satisfactory state both from a visual and a sensory and hygiene point of view.
In an alternative method which is primarily used in and around North America, for example in the USA, a predominantly thermochemical hygiene effect is aimed at. This is achieved by the rinse water being heated to a comparatively low temperature. For example, temperatures of approximately 49° C. can be used here. However, at the same time, a disinfectant, for example a rinse agent with a proportion of disinfectant, is added to the rinse water. Customary disinfectants of this type are disinfectants based on chlorine which are also called “sanitizers”. The use of such sanitizers, including the required concentrations of sanitizer for correct operation, are described, for example, in the so-called NSF3 standard. One advantage of this second alternative is that the energy consumed for heating the rinse water is considerably lower than in the first-described method. In addition, somewhat shortened program run times result, this occurring primarily on account of the reduced heating times and/or reduced cooling times of the washware. A further important advantage of low-temperature rinsing is that thermally sensitive washware, in particular drinking glasses, are subjected to a lower thermal load and therefore are exposed to a lesser risk of damage. In addition, the washware, for example the glasses, can be reused quickly since shorter cooling times are required for this washware than in the case of the described first method.
However, an important disadvantage of the thermochemical method is that the washware, for example drinking glasses, in many cases have often absorbed the smell of the disinfectant at the end of the program and, for example, an intense odour of chlorine is produced. This distinctive sensory characteristic is highly pronounced and long-lasting in many cases, and therefore the smell and taste of drinks which are later poured into glasses which have been treated in this way can be adversely affected to a great extent.
Both known methods therefore have associated disadvantages. Whereas the high-temperature final-washing process is predominantly associated with disadvantages in terms of energy, the thermochemical final-washing method has a pronounced adverse effect on the environment and sensorily influences the washware.
In addition, the prior art describes numerous washing methods which have the purpose of, in particular, improving the cleaning effect and/or saving washing liquid. U.S. Pat. No. 5,401,421, for example, describes a dishwasher with a reverse-osmosis apparatus. The reverse-osmosis apparatus is used to recondition used washing liquid and feed it back to the washing systems. However, apparatuses of this type do not, in principle, solve the above-described problem of known final-washing processes which either operate in a comparatively energy-inefficient manner or are associated with a strong adverse effect on the environment or on the washware.