EP2010706A1

EP2010706A1 - Method of removing scum in a drum washing machine, and drum washing machine suitable for this purpose

Info

Publication number: EP2010706A1
Application number: EP07729355A
Authority: EP
Inventors: Meike Hempel
Original assignee: BSH Bosch und Siemens Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2006-06-12
Filing date: 2007-05-22
Publication date: 2009-01-07
Anticipated expiration: 2027-05-22
Also published as: CN101466884A; US20100154829A1; RU2008148162A; WO2007144248A1; PL2010706T3; RU2439227C2; DE102006027197A1; CN101466884B; EP2010706B1; US8152932B2

Abstract

Method of removing scum in a tub (1) of an electronically controlled drum washing machine, having a detergent-solution runoff system which is arranged on the base of the tub (1) and has a detergent-solution pump, having a sensor (15) for determining the level of liquid located in the tub (1), the signal from this sensor being recorded during operation of the detergent-solution pump, and having a drum (2), wherein, following a main washing cycle and an operation for pumping out the liquid, the following steps are carried out: a) alternating rotation of the drum at a low speed U1 and standstill of the drum and also pumping out the liquid over a period t1 of 30 seconds to 15 minutes, b) letting in a quantity of water which is sufficient to cover all water channels, and rinsing over a short period (t2), the level being regulated with a very small hysteresis, c) pumping out the liquid as the drum is moving at a low speed U2; and drum washing machine which is suitable for this purpose.

Description

Process for removing foam in one

Drum washing machine and suitable for this

drum washing machine

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 carried out 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 in the case of a detection of foam during pumping or stopped in the event of a detection of foam during the Schleudems. Early foam detection is thus important in order for efficient measures to be taken to remove the foam.

According to DE 41 04 151 A1, the foam is destroyed by switching on a heating device. 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 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 supply line in the tub wall between the tub and the drum.

In addition, methods for removing foam in a tub of a drum washing machine from DE 102 34 472 A1 and DE 198 36 248 A1 are known. Thus, DE 102 34 472 A1 describes 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 dewatering the tub, with a arranged at the bottom of the tub lye drain system with a drain pump and a sensor for determining the height of the liquid in the tub. The course of the sensor signal (P) recorded during the operation of the leach pump contains a gradient Δp _n / Δt _n compared to Δp _n -i / Δt _n -i, which indicates the presence of foam, then one on the Gradient-matched foam treatment measure is initiated.

In EP 0 278 239 A1, excessive foam formation in the main wash, which can be observed during the heating of wash liquor in the tub, is eliminated by adding a limited amount of cold water and / or by temporarily switching off the liquor heating.

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.

The present invention is thus a method for removing foam in a tub of an electronically controlled drum washing machine with a lye outlet arranged at the bottom of the tub with a drain pump, with a sensor for determining the height of a liquid in the tub, the 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:

a) alternately rotating the drum at a low speed U ₁ and stopping the drum and pumping out the fluid for a period ti of 30 Seconds to 15 minutes, preferably 2 to 10 minutes, most preferably 2.5 to 4 minutes,

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,

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 switch-on time (hereinafter abbreviated to "ED") is preferably 2 to 30%, particularly 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 the Turning and Stopping the Drum The duty cycle is usually expressed 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. - A -

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 there sitting foam plug 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. For the purpose of the invention, "hysteresis" 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 According to the invention, it is preferable for this pressure difference (hysteresis) to be in the range from 10 to 150 Pa, more is preferably from 20 to 100 Pa and most preferably in the range from 30 to 70 Pa. In a hysteresis which is very small according to the invention, it was surprisingly found that an effective foam dilution results without re-impacting (foam formation) Foam in the water causes the pressure to drop, and the small hysteresis helps to draw water frequently, so that there is always the greatest 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 15 400 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.

20 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), i. 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 during a period U of 30 seconds to 15 minutes, preferably 2 to 10 minutes, most preferably 2.5 to 4 minutes performed (step e)). 30

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 trickles down the walls of the membranes of the bubbles and runs off through the holes present in the drum Due to the movement of the drum, the foam is thus smashed, and the burst bubbles then release further liquid which can flow out 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, prior to carrying out the method according to the invention, a check 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").

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 at a standstill by evaluating the gradients in the pressure curve in the case of a sensor (for example a sensor housing that is installed in the sensor)

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 spin

encoder housing 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 centrifugation, 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 cycle, a pressure level can be released that does not allow foam (a foam mat) to be pushed out of the dispensing bowl (washing in 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. An embodiment of the invention is illustrated below with reference to Figures 1 to 3 in more detail.

Figure 1 is a schematic representation of the presently relevant parts of a

Drum washing machine in which a process for removing foam can be carried out.

Figure 2 is a graphical representation of a typical portion of the time course of speed, water inlet, pressure and temperature during a wash in the case of the detection of foam in a conventional method.

Figure 3 is a graphical representation of a portion of the time course of speed, water inlet, pressure and temperature during a wash in the case of foam in one embodiment of the method.

Figure 1 is a schematic representation of the presently relevant parts of an embodiment for a drum type washing machine, in which the method for the removal of foam to be described below can be carried out. Other embodiments are conceivable. The drum washing machine of the embodiment shown in Figure 1 comprises 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, which includes 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") 1 1, from the Inlet water can carry detergent portions into the tub 1. In addition, a heating device 13 is located in the tub 1. The valve 9 as well as the heating device 13 can be controlled by a control device ("program control") 12 in accordance with a program schedule which corresponds to a time program and / or may be bound to the achievement of certain measurements of parameters such as liquor level, liquor temperature, laundry drum speed, etc. within the drum washing machine. 15 means a sensor for measuring the pressure in the tub 1.

Figure 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. In the first spin performed foam is detected again, after which the spin is canceled. 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 graphic representation of a section of the time profile of speed, water inlet, pressure and temperature in the case of foam in an embodiment of the method presented here. Compared to Figure 2, the time course of speed, water supply, pressure and temperature is 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 slipping 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

claims

1. A method for removing foam in a tub (1) an electronically controlled drum washing machine with a at the bottom of the tub (1) arranged Laugenablaufsystem with a drain pump, with a sensor (15) for determining a level of the liquid in the tub (1) , whose sensor signal is recorded during operation of the suds pump, and a drum (2), characterized in that after a main wash and a pumping out of the liquid the following steps are carried out:

a) Alternately rotating the drum at a low speed U ₁ and resting the drum and pumping out the liquid for a period tι of 30 seconds to 15 minutes,

c) pumping out the liquid while the drum is being moved at a low speed U ₂ .

2. The method according to claim 1, characterized in that between step a) and step b)

d) is centrifuged at a speed U _{3 of} the drum below 500 revolutions / minute over a short period t ₃ .

3. The method according to claim 2, characterized in that subsequent to step d)

(e) alternately rotating the drum at a low speed U ₅ and a

Stopping the drum and pumping out the liquid during a period L _{1 is} carried out from 30 seconds to 15 minutes.

4. The method according to any one of claims 1 to 3, characterized in that subsequent to step c) there is a regular Spülschleudern in which again foam can be detected.

5. The method according to claim 4, characterized in that upon detection of foam spinning is stopped and the method according to one of claims 1 to 3 is carried out again.

6. drum washing machine with a program control (12) for controlling the program flow, a in a tub (1) rotatably mounted drum (2), at the bottom of the tub (1) arranged Laugenablaufsystem with a drain pump, a drive motor (14) for the drum , a heating device

(13), a sensor (15) for determining the height of the liquid in the tub (1) and switching means (9, 12, 14), for rotating and stopping the drum, characterized in that the switching means (9, 12, 14 ) in case of a

Detection of foam can perform the method according to one of claims 1 to 7.