EP2010706B1 - Method of removing scum in a drum washing machine, and drum washing machine suitable for this purpose - Google Patents

Description

The invention relates to a method for removing foam in a drum washing machine and a drum washing machine suitable for this purpose. In particular, the invention relates to a method for removing foam in a tub of an electronically controlled drum washing machine, in which certain steps are performed after a main wash and a pumping out of the liquid, and a drum washing machine suitable for this purpose.

In a conventional drum washing machine, high speed is thrown after the main wash and rinse cycles. If a lot of foam is present or occurs during spinning, the drain pump does not promote the foam-lye mixture or at least poor. The spin is therefore not carried out on detection of foam during pumping or stopped in the event of detection of foam during spinning. Early foam detection is thus important in order for efficient measures to be taken to remove the foam.

According to the DE 41 04 151 A1 the foam is destroyed by switching on a heater. In order to destroy the foam in the wider vicinity of the heater, the drum is rotated slowly so that more foam passes to the heater and is destroyed there by supplying heat.

In the DE 43 34 969 A1 a device for the destruction of detergent foam is described, which has a device for generating hot air, which is introduced through a feed line in the tub wall between the tub and the drum.

In addition, methods for removing foam in a tub of a drum type washing machine are known from DE 102 34 472 A1 as well as the DE 198 36 248 A1 known. So describes DE 102 34 472 A1 a method for removing foam in a tub of an electronically controlled drum washing machine as a result of a program step, which is provided for dehydrating the tub, with a Laugenablaufsystem arranged at the bottom of the tub with a drain pump and with a sensor for determining the height of the liquid in the tub , The course of the sensor signal (P) is recorded during the operation of the drain pump, contains a gradient Ap _n / .DELTA.t _n compared to Ap _n-1 / .DELTA.t _n-1, indicating the presence of foam, whereupon one of the Gradient-matched foam treatment measure is initiated.

In the EP 0 278 239 A1 Excessive foaming in the main wash, observed during the heating of wash liquor in the tub, is eliminated by adding a limited amount of cold water and / or by temporarily turning off the liquor heater.

The object of the invention was therefore to provide a method by means of which the foam produced in a washing machine can be combated more effectively than with conventional methods. In addition, it was an object of the invention to provide a drum washing machine suitable for carrying out this method.

According to the invention, these objects are achieved by a method having the features of claim 1 and by a drum washing machine having the features of claim 6. Advantageous embodiments of the invention are listed in the subclaims.

1. a) Abwechselndes Drehen der Trommel mit einer niedrigen Drehzahl U₁ und Stillstehen der Trommel sowie Abpumpen der Flüssigkeit während eines Zeitraums t₁ von 30 Sekunden bis 15 Minuten, vorzugsweise 2 bis 10 Minuten, ganz besonders bevorzugt 2,5 bis 4 Minuten,
2. b) Einlassen von Wasser in einer Menge, die ausreicht, um alle Wasserwege zu bedecken, und Spülen während eines kurzen Zeitraums t₂, wobei eine Niveauregelung über eine sehr kleine Hysterese erfolgt,
3. c) Abpumpen der Flüssigkeit während die Trommel mit einer niedrigen Drehzahl U₂ bewegt wird.

The present invention thus relates to a method for removing foam in a tub of an electronically controlled drum washing machine with a lye drain system arranged at the bottom of the tub with a drain pump, with a sensor for determining the height of a liquid in the tub whose sensor signal during operation of the A drum is recorded, and a drum, wherein after a main wash and a pumping out of the liquid, the following steps are carried out:

1. a) Alternately rotating the drum at a low speed U ₁ and stopping the drum and pumping out the fluid during a period t ₁ of 30 Seconds to 15 minutes, preferably 2 to 10 minutes, most preferably 2.5 to 4 minutes,
2. b) introducing water in an amount sufficient to cover all the waterways, and purging for a short period of time t ₂ , with a level control over a very small hysteresis,
3. c) pumping out the liquid while the drum is being moved at a low speed U ₂ .

The invention also relates to a drum washing machine with a program control for controlling the program flow, a rotatably mounted in a tub drum, a bottom of the tub arranged Laugenablaufsystem with a drain pump, a drive motor for the drum, a heater, a sensor for determining the height of in the tub liquid and switching means for rotating and stopping the drum, wherein the switching means in the case of detection of foam can perform the method described above.

In step a), the speed U _{1 is} preferably from 20 to 60, more preferably between 30 and 50 revolutions per minute.

In step a), the duty cycle (hereinafter abbreviated to "ED") is preferably 2 to 30%, more preferably 5 to 15%. The duty cycle ED is a measure of the time proportion of the rotation of the drum relative to the total time for turning and, the standstill of the drum. The duty cycle is usually given in%, where 50% means that the drum moves halfway over a certain period of time and stops halfway, for example, moving 30 seconds and resting for 30 seconds.

In step a), the drum is preferably rotated at a frequency of 1 to 5, more preferably 2 to 4 revolutions per minute.

It is preferred that the pump is shut down at drum standstill. The rotation of the drum is preferably carried out in both directions, that is, reversing.

If in step b) a quantity of water is introduced which is sufficient to cover all waterways, this means that the water intake takes place to a safe, high level above all waterways. By waterways are meant the ways in which water enters the tub. This can be done exclusively via a dispenser, whereby detergent is also flushed into the tub, and / or directly into the tub.

The remaining foam is rinsed in this way with plenty of water from the waterways and diluted. Preferably, this water is used at a temperature which is below the temperature of the wash liquor in the tub during the main wash, as this causes the wash liquor is cooled. The waterways are flushed free, which prevents that sitting there Schaumpfropfen in a subsequent rinse in the dispenser - and possibly from the washing machine - are pressed. The cooling of the wash liquor also prevents the stabilization of the foam.

In step b), the terms "water entrainment" and "purge" are closely inseparable, as will be understood from the description of step b).

According to the invention, in step b) a level control takes place via a very small hysteresis. "Hysteresis" within the meaning of the invention is the pressure difference between the pressure at the upper switching point for the water supply and the pressure at the lower switching point for the water supply. In the present invention, it is preferable that this pressure difference (hysteresis) is in the range of 10 to 150 Pa, more preferably 20 to 100 Pa, and most preferably in the range of 30 to 70 Pa. In a very small hysteresis according to the invention, it was surprisingly found that an effective foam dilution results without re-impacting (foaming). It has been found that the solution of the foam in the water causes a decrease in the pressure; The small hysteresis supports frequent water drawing, so that there is always the largest possible amount of water for diluting the detergent concentration in the washing machine.

The period t ₂ is preferably from 1 to 5 minutes, more preferably from 1 to 3 minutes.

The pumping out of the liquid in step c) takes place while the drum is being moved at a low rotational speed U ₂ . The values of the rotational speed U ₂ are preferably in the preferred range specified for the rotational speed U ₁ , wherein the rotational speeds U ₁ and U ₂ can be selected independently of one another.

The slight movement of the drum in step c) prevents the foam from laying like a blanket on the laundry. Instead, the foam is circulated and transported away better.

It is preferred that between step a) and step b) with a speed U _{3 of} the drum below 500 revolutions / minute, preferably at a speed below 400 revolutions / minute, most preferably at a speed in the range of 100 to 200 Revolutions per minute over a short period t _{3 is} thrown (step d)). The time period t ₃ is preferably from 30 seconds to 5 minutes, more preferably from 1 to 2 minutes.

It has surprisingly been found that the foam is not re-pitched during this spinning or pushed out of the tub. Instead, the destabilized foam is smashed and restructured or compacted.

In a particularly preferred embodiment of the method, subsequent to step d), ie between steps d) and c),
(e) alternately rotating the drum at a low speed U ₅ and stopping the drum, and pumping out the fluid for a period t ₄ of 30 seconds to 15 minutes, preferably 2 to 10 minutes, most preferably 2.5 to 4 Minutes (step e)).

In step e), the values of the rotational speed U _{5 are} preferably in the preferred range specified for the rotational speed U ₁ , wherein the rotational speeds U ₁ and U ₅ can be selected independently of one another.

In the method, preferably after step c), a regular dishwashing (spinning before a rinse cycle) is carried out, in which foam can be detected again. In this case, centrifuging is preferably stopped when foam is detected, and the process according to the invention is carried out with steps a) to c) and optionally steps d) and e).

It has surprisingly been found that the process according to the invention results in efficient "dripping" of the foam. The water runs down the walls of the membranes of the bubbles and runs off through the holes in the drum. It is believed that the foam becomes unstable due to the ever-thinner bubble walls. Due to the movement of the drum thus the foam is smashed. The burst bubbles then release further liquid which can flow off in the rest phase following the movement of the drum.

In the method according to the invention, in step a) and optionally in step e), an alternating rotation and standstill of the drum takes place. The pumping out of the liquid is preferably carried out at intervals, whereby the water can accumulate between the pumping steps. During the movement and standstill phases of the drum, the pump can be turned on. Preferably, however, the pump is switched off between the pumping steps.

Preferably, before carrying out the method according to the invention, an examination is made for the presence of foam ("foam detection"). Which type of sensors are used for foam detection is unimportant for the measures to be carried out in the case of a foam signal ("foam signal").

• Schaumdetektion beim Abpumpen bei Stillstand der Trommel mittels Auswertung der Gradienten im Druckverlauf bei einem Sensor (z.B. einem Gebergehäuse, das im Allgemeinen einen Luftschlauch enthält, in dem durch Zusammendrücken von Luft die Menge an vorhandenem Wasser bestimmt werden kann).
• Schaumerkennung mittels eines im Schleudern detektierten Druckniveaus im Gebergehäuse

In general, a foam detection is used when pumping the wash liquor and when rinsing. Preferably, one of the following measures is taken:

• Foam detection when pumping down when the drum is stopped by evaluating the gradients in the pressure curve in a sensor (eg a sensor housing, which generally contains an air hose in which the amount of water present can be determined by compressing air).
• Foam detection by means of a pressure level detected in the encoder housing during spin

The foam detection can also be carried out via a conductivity measurement with two electrodes in the lower region of the tub.

In addition, a foam detection during spin by means of an evaluation of the target / actual speed difference is possible. In the foam detection by evaluation of the target / actual speed difference use is made of the fact that the foam can brake a rotating drum, whereby there is a difference between the target and the actual speed. In this case, the association between a specific foam concentration and the target / actual difference is generally stored in a data memory of the drum washing machine.

Upon detection of foam during spinning, the spinning is stopped and the process of the invention is carried out.

In addition to steps a) to f), further foam control measures can be taken in the process according to the invention. For example, in the rinse a pressure level can be released that does not allow foam (a foam mat) can be pushed out of the Einspülschale (washing the detergent). Releasing a pressure level in this case means that the sensor is given a certain pressure value until it is filled water is filled into the tub. This method is preferred in the presence of foam. If no foam is present, a certain predetermined amount of water is generally filled.

Another measure to combat foam is that the duty cycle ED is reduced.

As a further measure for the suppression of foam, a substance for inhibiting the foam can be added automatically during the performance of the method according to the invention. This is particularly useful if facilities for automatic dosing of detergents in a drum washing machine are present anyway.

Figur 1

ist eine schematische Darstellung der vorliegend relevanten Teile einer Trommelwaschmaschine, in der ein Verfahren zur Beseitigung von Schaum durchgeführt werden kann.

Figur 2

ist eine graphische Darstellung eines typischen Ausschnittes aus dem zeitlichen Verlauf von Drehzahl, Wasserzulauf, Druck und Temperatur während eines Waschvorgangs für den Fall der Detektion von Schaum bei einem herkömmlichen Verfahren.

Figur 3

ist eine graphische Darstellung eines Ausschnittes aus dem zeitlichen Verlauf von Drehzahl, Wasserzulauf, Druck und Temperatur während eines Waschvorgangs im Falle von Schaum bei einer Ausführungsform des Verfahrens.

An embodiment of the invention will be described below with reference to the FIGS. 1 to 3 illustrated in more detail.

FIG. 1

FIG. 12 is a schematic representation of the presently relevant parts of a drum type washing machine in which a method of removing foam can be performed.

FIG. 2

is a graphical representation of a typical section of the time course of speed, water supply, pressure and temperature during a washing process in the case of the detection of foam in a conventional method.

FIG. 3

is a graphical representation of a section of the time course of speed, water inlet, pressure and temperature during a washing process in the case of foam in one embodiment of the method.

FIG. 1 Fig. 12 is a schematic representation of the presently relevant parts of an embodiment for a drum type washing machine in which the foam removing method to be described below can be performed. Other embodiments are conceivable. The drum washing machine of in FIG. 1 embodiment shown has a tub 1, in which a drum 2 is rotatably mounted and driven by the drive motor 14. According to recent findings for the ergonomics in dealing with such drum washing machines, the rotation axis 3 of the drum 2 from the horizontal by a small angle (eg 13 °) directed forwardly upwards, so that the user of the drum washing machine easier access and insight into the interior of the drum washing machine Drum 2 has. By this arrangement, in conjunction with specially shaped Wäschemitnehmern 4 and 5 Schöpfeinrichtungen for the wash liquor 6 on the inner surface of the drum shell also also an intensification of the flow of the laundry 7 with wash liquor and a reduction of the so-called free liquor achieved which the amount of wash liquor in the tub 1, which can no longer be absorbed by the saturated laundry (substantially below the lowest point of the laundry drum 2).

The drum washing machine also has a liquor inlet system comprising a water connection fitting for the domestic water network 8, an electrically controllable valve 9 and a supply line 10 to the tub 1, which may optionally also be guided via a Waschmitteleinspüleinrichtung ("Einspülschale") 11, from which the feed water Can carry detergent portions in the tub 1. In addition, in the tub 1, a heater 13. The valve 9 as well as the heater 13 can be controlled by a control device ("program control") 12 in response to a program flowchart, the to a time program and / or to the achievement of certain measurements of Parameters such as liquor level, liquor temperature, speed of the laundry drum, etc. may be bound within the drum washing machine. 15 means a sensor for measuring the pressure in the tub 1.

FIG. 2 is a graphical representation of a typical section of the time course of speed, water inlet, pressure and temperature in the case of the detection of foam in a previously known method. When the wash liquor is pumped off, the pressure measured at the sensor 15 drops, which leads to foam detection. As the time course of the speed of the drum shows, the first Spülschleudern does not take place. The first rinse is performed with reduced duty cycle ED. Foam is detected again in the first executed spin, whereupon the spin is stopped., The rinse is again performed with reduced duty cycle ED. In the third spin no foam is detected, so that the duty cycle ED is high again in the subsequent rinse.

FIG. 3 is a graphical representation of a section of the time course of speed, water inlet, pressure and temperature in the case of foam in one embodiment of the method presented here. Compared to FIG. 2 is the time course of speed, water supply, pressure and temperature significantly different.

The invention has numerous advantages. The method according to the invention is characterized by a high degree of effectiveness in the case of foam, which is produced during washing and can lead to foaming in the first rinsing cycle. This is thrown only when the foam is sufficiently reduced and the risk of foam leakage from the dispenser is no longer.

Unlike conventional methods, mere dilution of the foam is not necessary. In this conventional method was due to the constant movement and the entry of water into the foam the risk of impact of the foam. The foam was not destabilized but steadily enriched with water. In this way, over several rinses - sometimes until the last rinse - visible foam remained in the drum while the Spülschleurggänge were stopped. The rinsing effect was very bad for this case. The inventive method avoids this.

In the method according to the invention, however, the bubbles are already destroyed before the addition of water. In addition, no new foam is opened, but instead reduces the detergent concentration. Flushing may be carried out, thereby effectively removing the detergent-containing caustic and improving the scavenging effect.

Claims (6)

1. Method of eliminating foam in a solution container (1) of an electronically controlled drum washing machine with a solution drain system, which is arranged at the base of the solution container (1), with a solution pump, with a sensor (15) for determining a height of the liquid present in the solution container (1), the sensor signal of which sensor is recorded during operation of the solution pump, and a drum (2), characterised in that after a main washing process and pumping out of the liquid the following steps are performed:

   a) alternating rotation of the drum at a low rotational speed U₁ and stopping of the drum as well as pumping out of the liquid during a time period t₁ of 30 seconds to 15 minutes,

   b) letting in water in an amount sufficient to cover all water paths and rinsing during a short time period t₂, wherein a level regulation takes place over a very small hysteresis, and

   c) pumping out of the liquid while the drum is moved at a low rotational speed U₂.
2. Method according to claim 1, characterised in that between step a) and step b)

   d) the drum is spun over a short time period t₃ at a rotational speed U₃ below 500 revolutions per minute.
3. Method according to claim 2, characterised in that subsequently to step d)

   e) alternately rotation of the drum at a low rotation speed U₅ and stopping of the drum as well as pumping out of the liquid during a time period t₄ of 30 seconds to 15 minutes are carried out.
4. Method according to any one of claims 1 to 3, characterised in that subsequently to step c) a regular rinsing-spinning is carried out in which foam can be recognised again.
5. Method according to claim 4, characterised in that on recognition of foam the spinning is broken off and the method according to any one of claims 1 to 3 is repeated.
6. Drum washing machine with a program control (12) for controlling the program sequence, a drum (2) rotatably mounted in a solution container (1), a solution drain system, which is arranged at the base of the solution container (1), with a solution pump, a drive motor (14) for the drum, a heating device (13), a sensor (15) for determining the height of the liquid present in the solution container (1) and switching means (9, 12, 14) for rotating and stopping the drum, characterised in that the switching means (9, 12, 14) in the case of detection of foam can perform the method according to any one of claims 1 to 5.

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