fig1 and fig2 show a dishwasher 2 in the form of a programmable machine for commercial use , with a detecting device 4 for sensing at least one operating condition which requires self - cleaning of the dishwasher 22 , the detecting device 4 emitting a signal on this basis . the detecting device 4 is connected for signal transmission to an indicating device 6 , here by electrical lines 26 . on the basis of this signal , the indicating device 6 outputs for a user an optical and acoustic signal , which informs the user of the requirement for self - cleaning of the dishwasher 2 . the dishwasher 2 also has a control device 8 for executing a self - cleaning program . the indicating device 6 in fig1 and fig2 has a lamp 10 , which is identified by an explanatory text 12 ( for instance “ self - cleaning ”) or a corresponding pictogram . the indicating device 6 also has a buzzer 14 , which is activated by the signal of the detecting device 4 . furthermore , the indicating device 6 of the dishwasher 2 has a display 16 , which can show a message 18 in plain text , for example “ self - cleaning required ” as an additional optical signal . fig3 schematically shows , in a synoptic representation , an embodiment of the detecting device 4 in detail . the embodiment represented in fig3 serves for explaining a large number of possible ways of forming a detecting device , only a single one of which , or a combination of two of the possibilities represented , is preferably realized in practice . the detecting device 4 has a real - time clock 20 and a memory 22 , which stores a point in time of the last self - cleaning operation . the real - time clock 20 is connected to a time - memory device 24 by lines 26 for the transmission of a time signal . the control device 8 is connected for signal transmission to the time - memory device 24 , in order to transmit a signal which signals the execution of the self - cleaning program to the time - memory device 24 , which on this basis stores in the memory 22 a current time signal and consequently the point in time of the last self - cleaning operation . the real - time clock 20 is also connected for signal transmission to a calculating device 28 , in order for a time signal to be transmitted to the calculating device 28 , which calculates from the point in time of the last self - cleaning operation and the time signal of the real - time clock 20 a duration which has elapsed since the last self - cleaning operation . a time comparator 30 is connected for signal transmission to a memory 32 , in which a duration threshold value is stored . the time comparator 30 is also connected for signal transmission to the calculating device 28 , in order for the duration which has elapsed since the last self - cleaning operation to be recorded . the time comparator 30 compares this with the duration threshold value and emits the signal when the duration which has elapsed since the last self - cleaning operation is equal to or greater than the duration threshold value . the detecting device 4 in fig3 also has an elapsed - hour meter 34 and an elapsed - hour resetter 36 , connected to the latter for signal transmission . the control device 8 is connected for signal transmission to the elapsed - hour resetter 36 , in order to transmit a signal which signals the execution of the self - cleaning program to the elapsed - hour resetter 36 , which resets the elapsed - hour meter 34 on this basis . the elapsed - hour meter 34 and a memory 38 for storing an elapsed - hour threshold value are connected for signal transmission to an elapsed - hour comparator 40 , in order for a meter reading of the elapsed - hour meter 34 or of the elapsed - hour threshold value to be transmitted . the elapsed - hour comparator 40 compares the meter reading with the elapsed - hour threshold value and emits the signal when the meter reading is equal to or greater than the elapsed - hour threshold value . furthermore , the detecting device 4 has a cycle meter 42 , for counting washing program cycles , and a cycle resetter 44 . the control device 8 is connected for signal transmission to the cycle resetter 44 , in order to transmit a signal which signals the execution of the self - cleaning program to the cycle resetter 44 , which resets the cycle meter 42 on this basis . the cycle meter 42 and a memory 46 for storing a cycle threshold value are connected for signal transmission to a cycle comparator 48 , in order for a meter reading of the cycle meter 42 or the cycle threshold value to be transmitted . the cycle comparator 48 compares the meter reading with a cycle threshold value and emits the signal when the meter reading is equal to or greater than the cycle threshold value . finally , the detecting device 4 comprises a sensor 50 or alternatively a sensor 52 ( represented by dotted lines ) for sensing a degree of contamination of the dishwasher 2 , which sensors are connected for signal transmission to a contamination comparator 54 , in order for a current value of a variable characterizing the degree of contamination of the relevant sensor 50 , 52 to be respectively transmitted . the detecting device 4 also has a memory 56 for storing a contamination threshold value which is adapted to the sensor 50 , 52 , which memory is connected for signal transmission to the contamination comparator 54 , in order for the contamination threshold value to be transmitted . the contamination comparator 54 compares the current value of the degree of contamination of the sensor 50 , 52 with the contamination threshold value and emits the signal when the current value of the degree of contamination of the sensor 50 , 52 is equal to or greater than the contamination threshold value . signal outputs of the time comparator 30 , of the elapsed - hour comparator 40 , of the cycle comparator 48 and of the contamination comparator 54 , which supply the signal of the relevant comparator 30 , 40 , 48 , 54 , are connected to a logic device 62 , which picks up the signals of the comparators 30 , 40 , 48 , 54 , subjects them to logic operations and feeds them to a common output 64 of the detecting device 4 . in fig3 , the logic device 62 is formed by an or gate , which carries out an or operation on the signals of the individual comparators 30 , 40 , 48 , 54 . in an embodiment of the dishwasher 2 represented in fig4 , a detecting device 4 is connected for signal transmission to a control device 8 , here by way of example by electrical lines 26 , in order for the signal of the detecting device 4 to be transmitted to the control device 8 . the control device 8 is designed for picking up the signal and executing the self - cleaning program on this basis . the execution of the self - cleaning program may take place after a predetermined waiting time , in which for example a user can remove dishes from the machine , or after completion of a washing program that is possibly in progress . the detecting device 4 is also connected to an indicating device 6 , which outputs for a user a signal indicating the execution of the self - cleaning program . the embodiment of a dishwasher 2 represented in fig1 and fig2 has an operating element 66 for manually starting the self - cleaning program controlled by the control device 8 . in the self - cleaning program , firstly self - cleaning liquid 84 is supplied . for this purpose , the dishwasher 2 has a supply section 68 for accommodating a self - cleaning agent 70 . the supply section 68 is formed by a tank screen 72 , which is arranged over a tank 74 . the screen openings in the tank screen 72 are adapted for accommodating the self - cleaning agent 70 in tablet form . the control device 8 is connected via electrical lines 26 to a controllable valve 76 as a clean - water inlet 77 , which is arranged in a clean - water line 78 , and controls said valve for filling the tank 74 with clean water 80 . arranged in the tank 74 is a circulating pump 82 . after filling the tank 74 , the control device 8 controls the circulating pump 82 , connected to it for control , in order to circulate the clean water 80 in such a way that , with the self - cleaning agent 70 arranged on the tank screen 72 , it forms the self - cleaning liquid 84 . this is represented in fig2 , some of the self - cleaning agent 70 ( here in tablet form ) already having dissolved . the control device 8 is also designed to control the circulating pump 82 after formation of the self - cleaning liquid 84 for further circulating the self - cleaning liquid 84 in the dishwasher 2 and for cleaning parts of the same . the parts to be cleaned comprise the washing system 58 , in particular a spray arm 86 and a pipeline 88 for feeding liquids to the spray arm 86 , and also the inside wall 60 of the dishwasher 2 . for pumping away liquid located in the tank 74 , a pump 90 is provided and connected to the control device 8 for control purposes ( not represented ). the control device 8 controls the pump 90 after the self - cleaning operation to pump away the self - cleaning liquid 84 , out of the dishwasher 2 . the tank 74 is also intended for accommodating washing liquid 92 up to a predetermined level 94 , the supply section 68 lying above the predetermined level 94 in the tank 74 . as represented in fig1 , the tank screen 72 is arranged above the predetermined level 94 of the washing liquid 92 . the dishwasher 2 represented in fig1 and 2 has as a controllable inlet 96 for washing liquid 92 the controllable valve 76 in the clean - water line 78 and a controllable valve 98 in a dishwashing agent feed line 100 . the control device 8 is designed for supplying washing liquid 92 in the tank 74 , to control the valve 76 in the clean - water line 78 and thereby feed clean water 80 into the tank 74 and to control the valve 78 in the dishwashing agent feed line 100 , for metering dishwashing agent 102 out of a dishwashing agent reservoir 104 to the clean water 80 . the washing programs executed by the control device 8 are designed such that , at the end of a washing program in which items to be washed 106 are treated with the washing liquid 92 in a basket 108 , at least some of the washing liquid 92 remains in the dishwasher 2 , in order to save water and energy . provided for pumping away the washing liquid 92 is the pump 90 , with which the self - cleaning liquid 84 is also pumped away from the tank 74 . if a self - cleaning operation is required , the user waits until the end of the washing program and then places the self - cleaning agent 70 on the tank screen 72 . this situation is represented in fig1 . the control device 8 of the dishwasher 2 represented in fig1 and fig2 is designed to control the pump 90 when the operating element 66 is actuated to pump away all the washing liquid 92 before the self - cleaning liquid 84 is supplied , and to subsequently control the self - cleaning program . the control device 8 is also designed to control the controllable inlet 26 for washing liquid 92 , in order to fill the tank 74 up to the predetermined level 94 with washing liquid 92 once the self - cleaning liquid 84 has been pumped away . a preferred embodiment of a self - cleaning program includes the following steps : 0 . the self - cleaning agent ( tablet / powder / liquid ) is supplied in a metered manner . 1 . the washing liquid is pumped away from the tank 74 . 2 . the dishwasher 2 is filled with clean water 80 , without dishwashing agent 102 being supplied in a metered manner . 3 . the clean water 80 is circulated through the washing system 58 , which also serves for cleaning items to be washed 106 . in this case , the self - cleaning agent dissolves ( along with the clean water , the self - cleaning liquid forms ) and cleans the interior space of the machine and also the washing system 58 . 4 . the self - cleaning liquid is pumped away . 5 . the dishwasher 2 is filled as in “ normal operation ”, with dishwashing agent 102 being supplied in a metered manner . the invention is not restricted to the embodiments shown by way of example in the drawings and explained above . rather , the invention is obtained by overall consideration by a person skilled in the art of the claims , the description and the embodiments that are provided by way of example .
a dishwasher has a detecting device for sensing at least one condition indicative of need for self - cleaning of the dishwasher . the detecting device emits a signal in this respect , for example , to an indicating device or to a control device . the control device is designed for executing a self - cleaning program , for controlling : a ) a device for supplying self - cleaning liquid , b ) a circulating pump for circulating the self - cleaning liquid in the dishwasher , for cleaning parts of the same , and c ) a device for emptying the self - cleaning liquid from the dishwasher following the self - cleaning operation according to step b ).