Dishwasher requiring no added detergent/rinsing agent/softener

The invention relates to a program-controlled dishwasher that is to be operated with combined preparations.

Program-controlled dishwashers generally have the program steps “pre-wash”, “clean”, “intermediate wash”, “final rinse” and “dry”. The detergents needed for operation of dishwashers increasingly include so-called “2 in 1” or “3 in 1” combined preparations. They generally consist of a detergent substance, a rinse-aid substance (2in 1) and additionally if necessary a softener substance (3 in 1). The combined preparations can be obtained both in the form of a compressed tablet, known as tabs, and in the form of a powder. The user puts the combined preparation into a washing container of the dishwasher before activating the wash program. Depending on the preparation and on the specifications by the manufacturer of the preparation, it is put either into a dosing apparatus of the dishwasher or directly into the washing container, for example in the cutlery basket. The combined preparations with their various active substances are then available, essentially from the start of the wash program, to clean the dirty crockery or objects to be washed placed in the dishwasher and with their additional functions, especially softening and final rinsing.

Although all active substances are added to the cleaning process from the outset, they should start working at different times in the wash program. For example, the active substance “rinse aid” is not required until later, i.e. in the “final rinse” subprogram step. To ensure that the various active substances in the combined preparation each start to work at the relevant time within the wash program, combined preparations essentially make use of two principles:

According to the “retardation” or “dilution” principle the active substances which are required at a later stage of the wash program are included in an especially high concentration in the preparation. It is assumed here that thanks to the active substance adhering to the objects to be washed, the washing container walls and the container lining a sufficient concentration of the active substance, e.g. of the rinse aid, is still present in the rinsing liquid at the time it is required to work in order to achieve the desired cleaning effect.

According to another principle, namely that of “encapsulation”, those active substances which are not to be used until a later time are encapsulated, for example in a wax casing. The casing does not start to gradually dissolve, depending on the temperature and/or pH value, until during execution of the wash program. Thus once the first cleaning stages have finished the encapsulated active substance, e.g. rinse aid, is not available in the program run until a later time, e.g. in the “final rinse” subprogram stage.

The object of the present invention is to specify a dishwasher which uses such combined preparations and is cost-effective to manufacturer.

This object is achieved by a dishwasher having the features of claim 1. The inventive dishwasher is, in accordance with the characterizing features of claim 1, designed to be free from softening systems and/or dosing devices. The dishwasher consequently merely includes a washing container within a housing with its basic functions, a heating unit and a circulating pump for the rinsing water, storage containers for the cutlery, and spraying devices inside the washing container. Thus a dishwasher is specified which can be operated as required and successfully with the commonly encountered combined preparations. By dispensing with softening systems and/or dosing devices the dishwasher can however be manufactured significantly more cheaply and is less prone to operating errors on the part of the user. In addition, the maintenance effort required for such a dishwasher is greatly reduced compared to conventional machines because of its simpler fittings and by dispensing with complex adding and dosing devices.

Domestic appliances are subjected to tests by different institutions in different areas. For example, in the European Union domestic appliances must be subjected to tests designed to produce information about the energy consumption of the respective domestic appliance in relation to its output. The result of the test is documented in a certification mark. For domestic dishwashers connected to a cold water supply, the stipulated test procedure and precise quantities of active agents are laid down, for example, in an EU standard. The standard is initially based on dishwashers with dosing devices and softening systems. If no softening system is present in the dishwasher, the manufacturer must specify a maximum permissible water hardness for the operation of the machine. A separate test for dishwashers without a dosing device is not provided for, nor does it make sense to perform one, since there is a lack of comparability. The test cannot therefore be based on combined preparations. Testing dishwashers for operation with combined preparations as rinse-aid is thus not possible. In addition, in many states of the European Union these preparations only attain a market share of 10 to 15%. In contrast, in Germany they already have a share of around 50%, based on their ease of use. Hence it is desirable to have a device available with which it is possible to test the inventive dishwasher, for example in accordance with an EU standard.

According to an advantageous embodiment of the invention the dishwasher can hence have a display device which indicates the dosing time or if appropriate several dosing times for manual dosing of active substances during the program run. Since the proposed dishwashers do not have a dosing device which ensures the addition of active agents at the requisite time, the addition must be simulated. A separate device could indeed be provided for this in the factory. However, the design effort required for this is not worthwhile for just one test run or a few test runs for each type of machine. Hence the active substances are to be added manually by a tester during the test run. Preferably the inventive dishwasher therefore has means which display the dosing time of active substances. So that the addition can take place at the requisite correct time, the inventive dishwasher has for example a corresponding display device. For the addition of several active substances, for example of a detergent after a pre-wash procedure or of a rinse-aid prior to a drying procedure, it may be necessary to display several dosing times. In what follows, for the purposes of simplification, only one dosing time is assumed, but this should include the possibility of several dosing times.

Indicating a dosing time by means of the display device does not entail any considerable design effort, so that the cost advantage of the dishwasher is not significantly impaired. Thus dishwashers designed to operate with combined products can also be subjected to a test in accordance, for example, with an EU standard. Because of the quantities of active substances laid down therein the inventive dishwashers also contain no more active substances during the cleaning process than stipulated in the standard. Although the quantities stipulated in the standard do not absolutely reproduce the actual circumstances of normal or everyday operation with combined products, comparability is assured.

The water hardness requires separate consideration. Where in conventional dishwashers a softening system is operated, a salt must be added to it from time to time in order to regenerate the active substances of the softening system. In contrast, the combined preparations are based on a different principle. A chemical, e.g. phosphate, is added to them, which in itself exerts a softening effect on the rinsing liquid, e.g. absorbs calcium ions. However, it is not automatically available on the market. Hence either an external water softening system can be made available for testing the dishwasher in accordance, for example, with an EU standard, or a maximum water hardness can be stipulated for the test run in separate instructions from the manufacturer.