EP0031016B1 - Method of washing laundry - Google Patents

Description

The invention relates to a method for washing laundry in a program-controlled drum washing machine, which is provided with connections for cold and hot domestic water of a household.

Drum washing machines with connections for cold and warm fresh water are known (DE-C-853 151). In principle, the washing processes taking place do not differ from washing processes that are used in drum washing machines that are only equipped with a cold water connection.

A generally prevailing and as yet not seriously doubted view among experts in laundry care about the composition of optimal washing processes is expressed in the so-called Sinner's Circle (compare Dr. K. Lindner in the journal "Soap-Oil-Fate-Waxes" 1964, pages 714 and 715 ), which describes a law between the proportions of the effects of the four factors of time, temperature, mechanics and chemistry on the laundry to be washed in the sense of a constant sum of the individual effects.

Based on this legality as a fact, the laundry care specialist is required to set up a program section for washing normally soiled laundry, in which only fresh or only warm fresh water is used instead of cold so that the total washing time during this program section is approximately as long as for a corresponding program section with only cold fresh water. This is because the time to heat the liquor at a higher initial temperature up to the required washing temperature, e.g. 90 ° C, is shorter, this specialist will compensate for the time lost here by extending the active washing time, which counts from the time the washing temperature is reached to the end of the program section, so that the time factor is not neglected and leads to a disruption of the leads the optimum described by Sinner's circle.

The invention has for its object to develop a washing process mentioned at the outset which further increases the energy-saving effect which can be achieved by a shortened heating phase and which leads to a shortening of the overall duration of a washing program. The results regarding cleaning effect, bleaching intensity and gentle washing should be achieved, if not exceeded, as far as possible compared to those program sections in which only cold fresh water runs in.

According to the invention, this object is achieved in that, in the case of a program section for normally soiled laundry in which hot domestic water is flowing in, in comparison to such a program section in which only cold domestic water is running in, the active washing time after reaching the desired washing temperature of the alkali is only approx. 0 is up to 40%.

In the case of, for example, rinse-aid program sections with a washing temperature at 90 ° C., the heating-up time is approximately 40 minutes when the washing machine is fully loaded. This is usually followed by an active washing time of 20 minutes. The total time of this program section is therefore approx. 1 hour. As explained above, the person skilled in the art would also adhere to this total time for a program section in which hot domestic water is supplied, that is to say which is initiated at a higher starting temperature of approximately 50.degree. In the washing process according to the invention, the heating-up time for this example is only about 20 minutes. Instead of now extending the duration of the active washing time to 40 minutes in order to come back to a total time of approximately 1 hour for the program section “clear wash”, the active washing time is shortened using the method according to the invention. For example, it is now only 0 to 8 minutes (corresponding to 0 to 40% of usually 20 minutes). The total time is now only 25 minutes: a reduction of almost 60%. During this short time, less heat is of course lost through radiation and transition to the environment, so that another energy saving effect can be seen.

Surprisingly, it has also been shown that the results regarding cleaning action, bleaching intensity and gentle laundry care are hardly impaired in the process according to the invention, and the laundry is even better protected than with the washing processes customary hitherto, in which only cold water flows. The laundry protection is even considerably better than a method in which hot water flows in and whose total washing time again takes about 1 hour.

The loss of mechanical action on the laundry in the program section in which warm process water flows in, as a result of a shorter washing time compared to such a program section in which only cold process water runs in, can be at least partially compensated for in an advantageous development of the method according to the invention by intensifying the rhythm of movement. This means that the results regarding cleaning effectiveness and bleaching intensity can be adapted to the respective requirements.

A comparison in a test by the applicant showed that using a commercially available drum washing machine for prewash and subsequent hot wash at 95 ° C with an active washing time of 15 min and an alkali starting temperature of 15 ° C, cleaning effects according to DIN 44983 for WFK dirt fabric of 64 , 2% and with EMPA dirty tissue of 56%, a bleaching intensity of 49.5% and a loss of tear strength of 6.5%. When the method according to the invention was also used for prewashing and subsequent hot washing at 95 ° C. without an active washing time and an alkali starting temperature of approximately 50 ° C., the values for the results listed above were in the same order 63%, 55.4%, 49, 4% and 5.2%. Dar from it can be clearly seen that the method according to the invention has significant economic advantages over the previously known washing methods.

The method according to the invention can be carried out in a drum washing machine which, according to one embodiment of the invention, contains a program control device with a switching stage which, when the desired washing temperature is reached, emits an output signal to the set input of a time control stage for the active washing process, the one of which has a timing signal output with a step forward of the program control unit is connected. The switching stage can be activated by a step-up device and, when the desired washing temperature is reached, starts a timing stage, the output of which changes when the signal changes after a certain time, e.g. 4 min, the activity of this switching stage ends for the active washing process.

In a further advantageous embodiment of the drum washing machine according to the invention, the program control device contains a further switching stage, which on the output side is connected to a changeover input of a clock generator for the movement rhythm. must be switchable when the hot water supply has ended and the desired washing temperature has been reached. As a result, an intensive movement rhythm, e.g. 12 s run and 3 s pause can be selected, which, when the hot water supply has ended and the washing temperature has been reached, is based on a normal movement rhythm, e.g. 7.5 s run and 7.5 s pause.

With a 4 min expiry time between the set signal to the time control stage and its time expiry signal, there was an active washing time, in which experience has shown very good results.

Advantageously, the program control unit can furthermore contain a switching stage which is connected to a switch for a magnetic valve controlling the flow of the hot domestic water or a further switching stage which is connected to a switch for a heating device which heats the washing liquor. Such an embodiment allows, for example, a dependency circuit for the water level and the washing temperature.

The method according to the invention and an automatically operating drum washing machine suitable for carrying out this method are described below on the basis of a diagram shown in FIG. 1 and a block circuit-type circuit arrangement shown in FIG. 2.

The unfilled diagram line in FIG. 1 shows from 0 to 40 minutes, calculated from the beginning of the program section intended for a rinse cycle, the heating phase in a program section in which only cold process water that has an initial temperature of 15 ° C. is supplied. After the continuous heating process has ended, the wash liquor has a temperature of 90 ° C as a prerequisite. This is followed by a 20-minute active washing time, so that this section of the program ends after a total of 60 minutes and ends with the gradual inflow of cold water and cooling of the washing liquor.

In contrast to this, the filled diagram line shows the time course of the temperature in the washing method according to the invention in the program section for normally soiled laundry, in which warm process water flows in. At the beginning there is also cool water in the hot water network, so that the lye temperature quickly increases from around 15 ° C to around 50 ° C until the hot water supply is switched off. There the heating phase begins, the course of which is essentially parallel to the course of heating up cold water. After 20 minutes since the beginning of this program section, the heating-up phase has ended and a washing temperature of 90 ° C has been reached. This is followed by an active washing time of around 15 minutes, so that after a total washing time of 25 minutes within this program section, the clear wash cycle ends.

2 shows a part of a block diagram for a program control device provided according to the invention in an automatically operating drum washing machine, which controls the washing process according to the invention. It contains switching stages 1, 2 and 3, which can activate switching stages 11, 12 and 13 one after the other. The output of the switching stage 11 controls the flip-flop 21 in a position in which it switches on the solenoid valve 30 connected to its output 210. This solenoid valve controls the hot water flow in line 31.

The switching stage 12 controls the bistable flip-flop 22 in a position in which its output 220 switches on the contactor 40 for the caustic heater 41.

The inflow line 31 opens into the tub 50. Furthermore, a water level sensor 51 and a temperature sensor 52 are arranged in the tub, the switches 53 and 54 of which emit suitable signals to the switching stage 13. The switching stage 13 outputs its output signal to the set input of a timing stage 23, one output of which is connected to the sliding input of the advance stages 1 to 3. The output signal of the switching stage 13 is dependent on the signal of the switches 53 and 54.

The switch 53 is also connected to the reset input of the bistable multivibrator 21, which switches off the solenoid valve 30 again when the switch is reset. The switch 54 is also connected to the reset input of the bistable multivibrator 22, which switches off the heating contactor 40 when the switch is reset.

Claims (7)

1. Method for the washing of laundry in a program-controlled drum washing machine which is provided with a respective connection for the cold and for the warm service water mains of a household, characterised thereby, that in a program section for normally polluted laundry, during which warm service water runs in, the active washing time after attainment of the desired washing temperature of the liquor amounts to only about 0 to 40% by comparison with such a program section, during which only cold service water runs in.

2. Method according to claim 1, characterised thereby, that the loss in mechanical action on the laundry during the program section, during which warm service water runs in, in consequence of shorter washing time compared with such a program section, during which only cold service water runs in, is at least partially balanced through intensification of the rhythm of movement.

3. Automatically operating drum washing machine for the performance of the method according to claim 1, characterised thereby that, the program control device (fig. 2) contains a swithing stage (13), which on the attainment of the desired washing temperature delivers an output signal to the setting input of a time control stage (23) for the active washing operation, the one time run-down signal output of which is connected with a stepping switch stage of the program control device.

4. Drum washing machine according to claim 3 for the performance of the method according to claim 2, characterised thereby, that the program control device contains a further switching stage which is switchable at the output side to a changeover input of a pulse generator for the rhythm of movement when the inflow of warm water is terminated and the desired washing temperature is attained.

5. Drum washing machine according to claim 3 or 4, characterised thereby, that the run-down time between the setting signal to the time control stage (23) and its time run-down signal amounts to at most 4 minutes.

6. Drum washing machine according to one of the claims 3 to 5, characterised thereby, that one of the switching stages (11) of the program control device is connected with a switch (21 for a magnetic valve (30) controlling the flow of the warm service water.

7. Drum washing machine according to one of the claims 3 to 6, characterised thereby, that one of the switching stages (12) of the program control device is connected with a switch (22) for a heating equipment (41) heating the washing liquor.

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