DD218124A1 - METHOD FOR CHARACTERIZING TENSIDE-BASED SOLUTIONS IN WASHING MACHINES - Google Patents

Abstract

The invention relates to a method for characterizing surfactant-containing solutions in automatic dishwashers and dishwashers. The aim of the invention is to reduce the information content of the measured variables, such. As Grenzflaechenspannung or electrical Leitfaehigkeit to expand with regard to the evaluation of the effectiveness of the washing and / or Spuelprozesses. The essence of the invention is that a part of the washing and / or Flülflotte is removed from the container and fed to a mixing chamber and measuring cell, in which the washing and / or Spuelprozess characterizing sensors are arranged, which are in communication with a processor which in turn drives a detergent dosing device. The field of application of the invention are above all washing machines and dishwashers, in particular for the household. Fig. 2

Description

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Method for characterizing surfactant-containing solutions in washing appliances Field of application of the invention

The invention relates to a method for characterizing surfactant-containing solutions in washing and dishwashing machines. Characteristic of the hitherto known technical solutions

Automatic washing machines and automatic dishwashers are known in which finished detergent mixtures of solid and / or liquid form are added to the dispensing chambers provided for this purpose before the start of the washing or rinsing process. The user manually sets a washing program via a switch. The controller causes the execution of a wash and / or rinse program with the program start. The choice of program depends on the type of fiber and the degree of soiling of the laundry. Temperature, duration, level and number of wash cycles of the wash program are controlled without feedback to the actual process parameters. From ignorance'der the true process parameters and to ensure a satisfactory washing result, all commercially available heavy duty detergents are often overdosed. The result is an ineffective washing and an enormous increase in environmental impact in recent years. , , '. ·, · · ".

From DE-OS 2017859 a method for monitoring and controlling the program, in particular the water inlet and / or the cleaning or detergent addition in automatic washing and dishwashing machines is known. The surface tension, the water hardness, the electrical conductivity and the pH of the washing and rinsing liquor are measured and suitably evaluated. A control unit can intervene in the program sequence and water level, water change and dosage of cleaning and rinsing agents are controlled! The disadvantage here is that all previously known physochemical sensors for characterizing the washing process show drift phenomena, so that larger errors can occur in the electronic evaluation.

Object of the invention

The aim of the invention is to make the washing and rinsing process in washing equipment more effective and to avoid errors in the electronic evaluation by eliminating the drift phenomena of the physicochemical sensors for characterizing the washing and / or rinsing fleets and thus by an optimal cleaning or Detergent addition to minimize the burden on the environment. , ' . .,

Explanation of the essence of the invention

The technical problem to be solved by the invention is to provide a method for characterizing especially surfactant-containing solutions in washing machines. ,

According to the invention the object is achieved in that an extension of the information content of the previously known technical solutions and measurement by automatic sampling during the washing and / or rinsing process by a subsequent dilution cycle, a Meßdatenerfassung, Meßdatenverarbeitung and feedback to the process. The dilution principle produces a discontinuous or continuous concentration profile. Depending on this concentration profile, the measured variables characterizing the washing and / or rinsing process, in particular the surface and / or interfacial tension, are measured. ^; ,

The metrological advantage of the inventive solution is that only Relativmeßwerte be accumulated during the process. The reference is made by the degree of dilution of the actual critical micelle concentration during the course of the process itself. .. '. ·.,

Long-term drifting of the sensors are meaningless. Problems that inevitably arise in absolute measuring methods are eliminated and the sensors intended for use can be in a wide tolerance range. The latter thus includes a cheap item as a sensor, which can be replaced inexpensively by the user himself when wearing. The surfactant concentration of the detergent solution is about 4 χ 10 ² ~ .mol / l. The location of the critical micelle formation concentration is dependent on the conductivity of the solution. The measuring cell is equipped with a conductivity sensor which, on the one hand, provides additional information on the course of the washing process, in particular for assessing the effectiveness of the rinsing process, and on the other hand, in combination with the measurement of the surface tension, allows the critical process micelle concentration to be reduced to a standard state. normalize. The temperature influence on the measured variables is largely eliminated by the measuring cell upstream and combined with the fresh water supply heat exchanger and can be electronically compensated. In addition to controlling the washing process, the solution according to the invention allows the process to be controlled so that a subsequent dosing of the corresponding washing substances takes place and the process can be extended to all upstream and / or downstream processes, such as, for example, rinsing.

embodiment

The invention will be explained in more detail with reference to an embodiment. In the accompanying drawings: FIG. 1 shows the dependence of the surface tension Cf on the water with different surfactant content. In Fig. 1 are plotted: The detergent concentration in percent as a function of the surface tension. This representation clearly shows the typical course of a dilution series for a commercially available detergent. The surfactant concentration of the detergent solution is about 4 χ 10 ^-2 mol / l. It can be seen that in practical operation, work is always carried out substantially above the critical micelle concentration. The critical micelle concentration, however, is about one power of ten lower in this example. A curve analogous to FIG. 1 results in a specific 1: 1 dilution. This special dilution series is technically easy to implement and gives a sufficiently accurate picture even with 4 measuring points. From the quantity changes set by mixing, which are proportional to the concentration of the substances dissolved in the washing and / or rinsing liquor and the corresponding measured variables, the value pairs lying above and below the critical micelle concentration are computationally combined as two curves and their common point of intersection determined. The degree of dilution corresponding to the critical micelle concentration (point of intersection of the two curves) is a measure of the washing activity of the wash liquor. If the degree of dilution reaches a certain limit (lower setpoint), feedback to the process takes place. .

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Adding surfactant sets to a specific upper setpoint set before the start of the process.

Fig. 2 shows the block diagram of the measuring and controlled system of the solution according to the invention.

From the container, a small portion of the washing and / or rinsing liquor 1 is removed via the valve V ₁ and through the supply line

fed via a heat exchanger 3 of the mixing chamber and measuring cell 6. ,,

The heat exchanger 3 is flowed through by the fresh water supply line 2. The addition of fresh water into the container

or in the mixing chamber and measuring cell 6 via the control of the valves V ₂ and V ₄ . : °

Via the valve V _{5 of} the mixing chamber and measuring cell 6 from the reservoir 5 in addition a Leitelektrolytflüssigkeit be supplied.

After dilution, a certain degree of dilution is set by pumping down to a specific degree

Volume in the mixing chamber and measuring cell 6 via the valve V ₆ and the discharge 7. '

Finally, the measured value detection and processing via the processor 8, which activates the valve V ₃ for a metered detergent addition from the detergent container 9 and thus causes the feedback to the process.

Claims (4)

1. A method for characterizing surfactant-containing solutions in washing machines, wherein the parameters of the washing or rinsing process is detected and evaluated and intervened via control means in the program flow and water quantity, water change and dosage of cleaning or rinsing agents are affected, characterized in that a part of the washing and / or rinsing liquor (1) is removed via pumps and valves and fed to a mixing chamber and measuring cell (6), in which one or more sensors characterizing the washing and / or rinsing process are arranged, which are connected to a Processor (8) are available, which controls a metered detergent addition from a detergent container (9) and allows a feedback to the washing and / or rinsing process. ί 2. The method according to item 1, characterized in that the removed washing and / or Spülflötte (1) with tap water and / or ion exchange water and / or a suitable, known per se conductive electrolyte is diluted and a measurement of this resulting mixture by means of a or more suitable sensors, at least one of which responds to surfactant concentration and in this dependence undergoes a change in the differential quotient at or near the critical micelle concentration, and an electronic evaluation of the measured values follows, the evaluation result depending on the degree of dilution represents a measure of the over- and / or under-dosage of surfactant with respect to the critical micelle concentration. 3. The method according to item 1, characterized in that the sampling and dilution by mixing and suction to a certain filling level in the mixing chamber and measuring cell (6). -3- 253 968 Invention claims: 4. The method according to item 1 and 2, characterized in that the dilution is carried out by mixing two streams. To this 1 page drawings' i.