EP3036365B1 - Laundry care appliance - Google Patents

Description

The present invention relates to a laundry care device having a detection device for detecting foam in a tub and a method for detecting foam in a laundry care device.

Due to the chemical composition and a misdosing of the detergent by the consumer often results in an excess of foam during a wash cycle in a laundry care device. The excess of foam produced worsens the washing result and can lead to damage to the laundry care device itself. There are already known various methods for detecting a presence of foam in a laundry care appliance.

The publication DE 195 49 044 C1 describes a method for washing laundry in a washing machine with a laundry in a tub by means of a motor control Reversierzyklen reversing and Reversierpausen rotatable laundry drum, in which by pressure measurement, the formation of excessive foam is monitored and at the given pressure conditions in the tub a this State characteristic signal is derived.

The publication DE 10 2011 052 619 A1 relates to a method for determining an over-foam condition in a multi-component laundry treating apparatus for executing a washing program including a tub for holding liquid, a drum enclosing a treatment chamber and rotatably supported in the tub, a pressure sensor fluidly communicating with coupled to the tub and outputs a signal indicating the amount of water in the tub, and a controller that is coupled to the components. The method also includes rotating the drum while the tub contains a foamable liquid, determining a time variation of the signal from the pressure sensor as the drum rotates, determining a skim condition if that variance meets a predetermined threshold, and changing the drum Work program in response to the determination of a Überäum-state.

The publication DE 10 2007 042 968 A1 describes a method for detecting foam in a drum washing machine with a program control for controlling a program sequence, a rotatably mounted in a tub drum, a Water supply system, a liquor drainage system arranged on the tub, a drive motor for the drum and a sensor for determining a signal of a liquid contained in the tub and possibly containing foam.

The publication DE 10 2007 033 492 A1 describes a method for controlling foaming in treating laundry with lather from an aqueous surfactant solution in a program-controlled washing machine having a lye drain system disposed at the bottom of a tub with a leach pump, a rotating drum, and a heater.

The publication EP 0 278 239 A1 describes a method for automatically washing laundry in a tub by using dissolved in water detergents, heating energy and mechanical energy in the form of agitation of a laundry in a washing machine to the tub as a water level sensor at least a plurality of output signals emitting pressure sensor is connected.

The known from the prior art concepts for foam detection are carried out indirectly only via detected pressure values in a moving laundry drum. The pressure measurements on a moving laundry drum may have reduced reliability of the sensed fluid pressures. A moving laundry drum could affect the detection of fluid pressure by its movement.

It is the object underlying the invention to provide a laundry care device in which the generation of foam in a tub, especially in an early washing phase, detected with increased reliability and overblowing can be prevented.

This object is achieved by articles having the features according to the independent claims. Advantageous embodiments of the invention are the subject of the figures, the description and the dependent claims.

According to one aspect of the invention, the object is achieved by a laundry care apparatus having a detecting device for detecting foam in a tub, the pressure detecting means for detecting a first liquid pressure in the tub at a first time and a second fluid pressure to a second time during a stationary laundry drum is provided and a determining device for determining the presence of foam in dependence on the first fluid pressure and the second fluid pressure comprises. The detection of each fluid pressure at a time occurs when the laundry drum is stopped. The first and the second fluid pressure are detected, for example, in one and the same standstill phase of the laundry drum. Further, the sensed first and second fluid pressures may be used without determining a fluid pressure average for determining the presence of foam in the tub.

As a result, for example, the technical advantage is achieved that the detection of foam in the tub carried out with increased reliability and thus overshadowing can be avoided.

The present invention is based on the recognition that, to determine the presence of foam in the tub of the laundry care appliance, the time of reflux of the wash water into the tub when the laundry drum is stopped can be used. If there is no foaming, the lifted and sprayed wash water flows back to the bottom of the tub without delay. This in turn leads to a rapid fluid pressure increase from a first fluid pressure to a second fluid pressure in the tub. If, on the other hand, foam was produced in a washing phase with a moving laundry drum, then the washing water requires a longer time to flow back into the tub when the washing drum is stationary. This leads to a slower fluid pressure increase from a first fluid pressure to a second fluid pressure in the tub.

A laundry care appliance is understood to mean, in particular, a domestic appliance, that is to say a laundry care appliance which is used for the purpose of financial management and serves to treat laundry in household quantities. In particular, the laundry care device is a washing machine or a washer-dryer.

In an advantageous embodiment, the laundry care device comprises a calibration device for determining a calibration parameter prior to detecting the first and the second fluid pressure. A calibration can be carried out, for example, during a pre-wash in which the detergent is not yet contained in the wash water. Furthermore, the calibration parameters may depend on the amount of laundry loaded into the laundry care appliance; because the absorption behavior different textiles may vary. If a pre-wash is not performed, calibration parameters may also be predetermined at the factory for different amounts of laundry or may be determined by a pre-wash done earlier.

As a result, the technical advantage is achieved, for example, that the detection of the presence of foam can be carried out in each case adapted to the amount of laundry located in the laundry care appliance with increased reliability.

In a further advantageous embodiment, the calibration device is designed to detect a first reference liquid pressure at a first calibration time and a second reference liquid pressure at a second calibration time with surfactant-free wash water. The calibration device may be provided as a separate device or as part of the detection device. The first and second reference liquid pressures are detected while the laundry drum is stopped. The first and second reference liquid pressures at first and second calibration times, respectively, are detected in a manner analogous to the first and second liquid pressures at first and second times, respectively, for determining the presence of foam in surfactant-containing wash water. By acquiring a first reference liquid pressure at a first calibration time and a second reference liquid pressure at a second calibration time, different calibration parameters may be formed.

Thereby, for example, the technical advantage is achieved that a direct comparison between the first and second reference liquid pressures and the first and second calibration times with the first and second liquid pressures and the first and second times is possible and allow conclusions about the presence of foam.

In a further advantageous embodiment, the calibration device is designed to determine one of the calibration parameters a, Δtk0 as a function of the first reference fluid pressure at the first calibration time and the second reference pressure at the second calibration time. To determine the presence of foam, one or two different calibration parameters a, Δtk0 can be determined.

Thereby, for example, the technical advantage is achieved that the determination of the presence of foam can be performed on the basis of the calibration parameter (s). A comparison of the detected fluid pressures or times directly below each other is not required.

In a further advantageous embodiment, the calibration device is designed to determine one of the calibration parameters as a pressure ratio from the second reference fluid pressure to the first reference fluid pressure. The calibration parameter a designed as a pressure ratio has a value between 1 and 1.5, preferably between 1.3 and 1.4.

Thereby, for example, the technical advantage is achieved that the determination of the presence of foam can be performed on the basis of detected relative pressure ratios. A comparison of absolutely recorded fluid pressures with each other is not required.

In a further advantageous embodiment, the calibration device is designed to determine one of the calibration parameters as a time difference Δtk0 between the second calibration time and the first calibration time. The time difference between the second calibration time and the first calibration time indicates the time required for the first reference liquid pressure to increase to the second reference liquid pressure when there is no foaming.

Thereby, for example, the technical advantage is achieved that the determination of the presence of foam can be performed on the basis of detected time differences. A comparison of recorded times with each other is not required, making a comparison easier.

In a further advantageous embodiment, the detection device is designed to determine a time difference between a first time and a second time at which the second fluid pressure exceeds the first fluid pressure by a predetermined determination value. The determined time difference corresponds to the time required when the first fluid pressure detected when the laundry drum is stopped rises to the second sensed fluid pressure. After the expiry of the specific time difference is the second fluid pressure of the predetermined Determination value recorded. As a result, the pressure rise curve in the surfactant-containing phase becomes comparable to the pressure rise curve during a prewash phase.

Thereby, for example, the technical advantage is achieved that can be performed to determine the presence of foam based on a comparison between the detected time difference and the calibration parameter.

In a further advantageous embodiment, the detection device is designed to determine the determination value on the basis of the calibration parameter a. The second fluid pressure is detected when it is a-times as high as the first fluid pressure. The determination value based on the calibration parameter a thus corresponds to the product of the first fluid pressure multiplied by the calibration parameter a.

Thereby, for example, the technical advantage is achieved that for determining the presence of foam at a given pressure increase from a first to a second fluid pressure on the basis of a comparison between the detected time difference and the calibration parameter can be performed.

In a further advantageous embodiment, the detection device is designed to compare the time difference Δt with a calibration time difference Δt0 for determining the presence of foam. For this purpose, the time can be determined from the detection of a first fluid pressure, which is required until reaching a second fluid pressure, in particular the second fluid pressure increased by the determination value.

Thereby, for example, the technical advantage is achieved that can be performed to determine the presence of foam based on a comparison between the detected time difference and the calibration parameter.

In a further advantageous embodiment, the detection device is designed to determine the second fluid pressure p2 after detection of the first fluid pressure p1 and expiration of the time difference Δtk0. If the second fluid pressure detected after the time difference Δtk0 determined as the calibration parameter is less than the second reference fluid pressure pk2, foaming occurs. During the time difference .DELTA.tk0 less washing water can flow back into the tub due to the foaming, as in the absence of foaming. A comparison of the second reference liquid pressure pk2 with the detected after the time difference .DELTA.tk0 second fluid pressure p2 therefore allows to determine the presence of foam.

As a result, the technical advantage is achieved, for example, that the presence of foaming can be carried out by comparing the detected second liquid pressure with surfactant-containing and the detected reference liquid pressure with surfactant-free washing water.

In a further advantageous embodiment, the detection device is designed to determine the detection of foam as a function of a pressure ratio from the second fluid pressure p2 to the first fluid pressure p1. If a value is determined from the pressure ratio of the second fluid pressure p2 to the first fluid pressure p1, which deviates from a predetermined pressure ratio, this determines the presence of foam.

As a result, for example, the technical advantage is achieved that the presence of foam can be determined by comparing two pressure conditions.

In a further advantageous embodiment, the detection device is designed to compare the pressure ratio with the calibration parameter a for determining the presence of foam. From the pressure ratio of the second fluid pressure p2 to the first fluid pressure p1, a value smaller than the predetermined calibration parameter a, i. p2 / p1 <a, this determines the presence of foam.

As a result, the technical advantage is achieved, for example, that the presence of foam can be determined from a comparison between the pressure ratio from the calibration step with the pressure ratio from a washing phase.

In a further advantageous embodiment, the detection device is designed to perform a detection of the first fluid pressure and the second fluid pressure in surfactant-containing wash water in the tub. For this purpose, the detection device is connected to a pressure detection device or comprises a pressure detection device. The pressure detection device is preferably arranged in a lower region of the tub, so that a pressure increase from a first fluid pressure to an increased second fluid pressure can be detected. A determination device is further connected to the detection device and the pressure detection device or integrated in one of these. The detection of the first and second fluid pressure in surfactant-containing wash water allows conclusions about the presence of foam.

As a result, for example, the technical advantage is achieved that the presence of foam can be determined by measuring the liquid pressure or the liquid pressure after a time difference in surfactant-containing water, without having to determine a concentration of the dissolved detergent in the wash water.

According to a further aspect of the invention, the object is achieved by a method for detecting foam in a laundry care apparatus, comprising the steps of detecting a first liquid pressure in a tub at a first time and a second fluid pressure at a second time during a stationary laundry drum; and determining the presence of foam in response to the first fluid pressure and the second fluid pressure.

The detection of the first and second fluid pressure occurs during one and the same phase in which the laundry drum is stopped. A first and second fluid pressure can be detected in several phases in which the laundry drum is stationary, in particular following a washing phase in which the laundry drum is moved and foam is generated. When the washing drum is stationary, no vibrations of the pressure detection unit can occur, which could influence or even distort the measurement result of the detected fluid pressure.

As a result, the technical advantage is achieved, for example, that when the laundry drum is stopped, the detection of the liquid pressure with increased reliability is possible.

In a further advantageous embodiment, the method comprises a calibration step for determining a calibration parameter before the detection of the first and the second fluid pressure. The calibration parameter may be determined in surfactant-free wash water by a pressure ratio of a first reference liquid pressure pk1 and a second reference liquid pressure pk2 as a pressure ratio a = pk2 / pk1. The calibration parameter .DELTA.tk0 can also be used as a time difference .DELTA.tk0 between a second calibration time tk2 and a first calibration time tk1 be determined.

As a result, the technical advantage is achieved, for example, that a calibration before each wash in surfactant-containing wash water is possible if this is carried out during a pre-wash with surfactant-free wash water.

Embodiments of the invention are illustrated in the drawings and will be described in more detail below.

Fig. 1

eine schematische Ansicht eines Wäschepflegegeräts von außen;

Fig. 2

eine schematische Ansicht eines Wäschepflegegeräts von innen:

Fig. 3

ein Diagramm mit einem vollständigen Programmzyklus des erfindungsgemäßen Wäschepflegegeräts;

Fig. 4

einen Ausschnitt aus dem Diagramm nach Fig. 3, der einen Druckanstieg während des Stillstehens der Wäschetrommel ohne Vorliegen von Schaum zeigt; und

Fig. 5

einen Ausschnitt aus dem Diagramm nach Fig. 4, der einen Druckanstieg während des Stillstehens der Wäschetrommel mit Vorliegen von Schaum zeigt.

Show it:

Fig. 1

a schematic view of a laundry care device from the outside;

Fig. 2

a schematic view of a laundry care device from the inside:

Fig. 3

a diagram with a complete program cycle of the laundry care device according to the invention;

Fig. 4

a section of the diagram after Fig. 3 showing an increase in pressure during standstill of the laundry drum without the presence of foam; and

Fig. 5

a section of the diagram after Fig. 4 showing an increase in pressure during standstill of the laundry drum with the presence of foam.

Fig. 1 shows an exterior view of a laundry care device 100. The laundry care device 100 is a washing machine with a menu bar 102 and buttons 104 for operating the menu bar 102. Furthermore, the laundry care device 100 has a door 106 in the form of a circular porthole with a door handle 108.

Fig. 2 shows an interior view of the laundry care device 100. In the interior of the laundry care device 100 is a laundry drum 117, which is surrounded by a tub 115. Along the inner circumference of the laundry drum Wäschemitnehmer 114 are provided to take away the laundry from the wash water 125. By means of a pressure detection device 110, the fluid pressure in the tub 115 can be detected. The pressure detecting device 110 is provided with a in connected to upper portion of the laundry care device arranged detection device 130. The detection device is used to control and monitor the individual process steps during a wash cycle. The detection device 130 is therefore further connected to a drive motor 112, a water supply system 116 and a wash water pump 124 of the laundry care device 100. In addition, a determination device 119 which determines calibration parameters a, Δtk0 is integrated in the detection device 130. The calibration parameters a, Δtk0 can be stored by the detection device 130 after their determination.

Fig. 3 1 shows a course of a complete washing cycle with a prewash cycle in a laundry care appliance 100. The abscissa shows the time 150 and the ordinate the detected liquid pressure 170 in a unit of the pressure 140. Further, with the time 150, the course of the rotational frequency 160 of the laundry drum 117 is shown.

Fig. 4 shows a section Fig. 3 in which the prewash cycle is shown without the presence of foam. During the pre-wash in a laundry care device 100, the laundry to be washed is moistened with wash water 125, in which no detergent is present dissolved. The laundry is thus moistened with surfactant-free wash water 125, while the laundry drum 117 is in motion at the rotational frequency 160. In a phase of the standstill 180 with the washing drum 117 stopped, the rotational frequency 160 of the laundry drum 117 drops to zero. During standstill 180 with the washing drum 117 stopped, a first detected reference pressure pk1 at a first calibration time tk1 rises to an increased second reference pressure pk2 when a second calibration time tk2 is reached. The time difference between the first calibration time tk1 and the second calibration time tk2 is determined as a calibration parameter Δtk0. Another calibration parameter a is determined by determining the reference pressure ratio from the second reference pressure pk2 to the first reference pressure pk1 according to a = pk2 / pk1. By detecting the time difference Δtk0 in which the first reference pressure pk1 increases to a second reference pressure pk2 increased by the calibration parameter a, a pressure change rate can be determined.

Fig. 5 shows another section Fig. 3 in which the detected pressures 170 and the rotational frequency 160 are shown in a washing phase with a moving laundry drum 117 and with a stationary laundry drum 117. With beginning of standstill 180 of the laundry drum 117 is of the connected to the detection device 130 Pressure detection device 110 detects a first fluid pressure p1 at a first time t1. At this time, the laundry drum is at standstill 180 at which the rotational frequency 160 of the laundry drum 117 has dropped to zero. A second fluid pressure p2 is detected at a second time t2. As soon as the laundry care device 100 moves from a phase with the laundry drum 180 stationary to a washing phase with a moved laundry drum 117, the detected liquid pressure 170 in the tub 115 drops down to a liquid pressure due to the washing water raised with the movement of the laundry drum 117.

Hereinafter, various modes of operation of the laundry-care apparatus 100 will be described on the basis of which the presence of foam can be determined.

In a first operating mode, to determine a calibration value, the laundry drum 117 is stopped after a moistening phase with surfactant-free wash water so that it reaches a phase when the laundry drum 180 is stationary. Upon reaching standstill 180, the pressure detecting means 110 detects a first reference liquid pressure pk1 at a first calibration time tk1. Upon reaching a second reference liquid pressure pk2 corresponding to a reference liquid pressure increased a times at a second calibration time tk2, the calibration parameter a and the time difference required to reach the increased reference liquid pressure are determined as the calibration parameter Δtk0.

In the washing phase with surfactant-containing wash water, this is transferred to a phase with moving laundry drum 117 in a phase with a stationary laundry drum. Upon reaching standstill 180 of the laundry drum 117, a first liquid pressure p1 is determined. When the fluid pressure reaches the second fluid pressure p2 = a * p1 a-fold increased by the calibration parameter after a time, the time difference for reaching the second fluid pressure p2 is detected. To assess whether foam is present, the calibration parameter Δtk0 is compared with the detected time difference Δt. If it is detected that Δt> Δtk0, the presence of foam is detected.

In a second operating mode, to determine a calibration value, the laundry drum 117 is stopped after a moistening phase with surfactant-free wash water so that it reaches a phase when the laundry drum 180 is stationary. Upon reaching standstill 180, the pressure detecting means 110 detects a first reference liquid pressure pk1 at a first calibration time tk1. Upon reaching At a second calibration time tk2, the calibration parameter a and the time difference required to reach the increased reference liquid pressure are determined as a calibration parameter Δtk0 of a second reference liquid pressure pk2 corresponding to a reference liquid pressure increased a times.

In the washing phase with surfactant-containing wash water, this is transferred to a phase with moving laundry drum 117 in a phase with a stationary laundry drum. Upon reaching standstill 180 of the laundry drum 117, a first liquid pressure p1 is determined. After a time difference Δtk0 has elapsed, an increased second fluid pressure p2 is detected. In order to judge whether foam is present, the pressure ratio from the second fluid pressure p2 to the first fluid pressure p1 is determined and compared with the calibration parameter a. If it is detected that p2 / p1 <a, the presence of foam is detected.

In a third mode of operation is in the washing phase with surfactant-containing wash water after a phase with moving laundry drum 117 this transferred to a phase with a stopped laundry drum. A calibration parameter .DELTA.tk0, for which a first reference liquid pressure pk1 rises to a second reference liquid pressure pk2 in the case of surfactant-free washing water, is predetermined in the detection device 130. The second reference liquid pressure pk2 is increased or met by a factor a: p2 = p1 * a.

In the washing phase with surfactant-containing wash water, this is transferred to a phase with moving laundry drum 117 in a phase with a stationary laundry drum. Upon reaching standstill 180 of the laundry drum 117, a first liquid pressure p1 is determined. When the fluid pressure reaches the second fluid pressure p2 = a * p1 a-fold increased by the calibration parameter, the time difference for reaching the second fluid pressure p2 is detected. To assess whether foam is present, the predetermined calibration parameter Δtk0 is compared with the detected time difference Δt. If it is detected that Δt> Δtk0, the presence of foam is detected.

The described operating modes for detecting the presence of foam are carried out with the washing drum stopped and can be performed during an early or a late washing phase of the laundry-care appliance. Determining fluid pressure averages is not for determining the presence of foam required, so that a laundry care device and a method with a simplified monitoring system for detecting the presence of foam is specified.

All features explained and shown in connection with individual embodiments of the invention may be provided in different combinations in the article according to the invention, in order to simultaneously realize their advantageous effects.

The scope of the present invention is given by the claims and is not limited by the features illustrated in the specification or shown in the figures.

LIST OF REFERENCE NUMBERS

100

Laundry care device

102

menu bar

104

Buttons

106

door

108

door handle

110

Pressure sensing device

112

drive motor

114

laundry agitator

115

tub

116

Water supply system

117

washing drum

119

determiner

120

calibration device

124

Water Pump

125

wash water

130

detector

140

print

150

Time

160

rotational frequency

170

detected fluid pressure

180

Standstill (phase with washing drum stopped)

p1

first fluid pressure

p2

second fluid pressure

tk1

first calibration time

tk2

second calibration time

t1

first time

t2

second time

.delta.t

time difference

Δtk0

calibration parameters

a

calibration parameters

Claims (15)

1. Laundry care appliance (100) having a detector device (130) for detecting foam in a washing liquid tub (115), which comprises a pressure detector device (110) for detecting a first liquid pressure (p1) in the washing liquid tub (115) at a first time instant (t1) and a second liquid pressure (p2) at a second time instant (t2) when a laundry drum (117) is at rest, and a determination apparatus (119) for determining the presence of foam as a function of the first liquid pressure (p1) and the second liquid pressure (p2), characterised in that the pressure detector device (110) is also configured to detect the first liquid pressure (p1) in the washing liquid tub (115) at the first time instant (t1) and the second liquid pressure (p2) at the second time instant (t2) during a liquid pressure rise in the washing liquid tub (115).
2. Laundry care appliance (100) according to claim 1, characterised in that the laundry care appliance (100) comprises a calibration facility (120) for determining a calibration parameter (a, Δt0) prior to detecting the first and the second liquid pressure.
3. Laundry care appliance (100) according to claim 1 or 2, characterised in that the calibration facility (120) is embodied to detect a first reference liquid pressure (pk1) at a first calibration time instant (tk1) and a second reference liquid pressure (pk2) at a second calibration time instant (tk2) with surfactant-free wash liquor.
4. Laundry care appliance (100) according to claim 3, characterised in that the calibration facility (120) is embodied to determine one of the calibration parameters (a, Δtk0) as a function of the first reference liquid pressure (pk1) at the first calibration time instant (tk1) and the second reference pressure (pk2) at the second calibration time instant (tk2).
5. Laundry care appliance (100) according to claim 4, characterised in that the calibration facility (120) is embodied to determine one of the calibration parameters (a) as a pressure ratio from the second reference liquid pressure (pk2) relative to the first reference liquid pressure (pk1).
6. Laundry care appliance (100) according to claim 4, characterised in that the calibration facility (120) is embodied to determine the calibration parameter (Δtk0) as a time difference (Δtk0) between the second calibration time instant (tk2) and the first calibration time instant (tk1).
7. Laundry care appliance (100) according to one of the preceding claims, characterised in that the detector device (130) is embodied to determine a time difference Δt between a first time instant (t1) and a second time instant (t2), at which the second liquid pressure (p2) exceeds the first liquid pressure (p1) by a predetermined determination value.
8. Laundry care appliance (100) according to claim 7, characterised in that the detector device (130) is embodied to determine the determination value on the basis of the calibration parameter (a).
9. Laundry care appliance (100) according to claim 7 or 8, characterised in that the detector device (130) is embodied to compare the time difference (Δt) with a calibration time difference (Δt0) in order to determine the presence of foam.
10. Laundry care appliance (100) according to one of the preceding claims, characterised in that the detector device (130) is embodied to determine the second liquid pressure (p2) after detecting the first liquid pressure (p1) and after the time difference (Δtk0) has elapsed.
11. Laundry care appliance (100) according to claim 10, characterised in that the detector device (130) is embodied to determine the detection of foam as a function of a pressure ratio from the second liquid pressure (p2) relative to the first liquid pressure (p1).
12. Laundry care appliance (100) according to claim 10 or 11, characterised in that the detector device (130) is embodied to compare the pressure ratio with the calibration difference (a) in order to determine the presence of foam.
13. Laundry care appliance (100) according to one of the preceding claims, characterised in that the detector device (130) is embodied to perform a detection of the first liquid pressure and the second liquid pressure in wash liquor which contains surfactant in the washing liquid tub (115).
14. Method for detecting foam in a laundry care appliance, comprising the steps:

    - detecting a first liquid pressure in a washing liquid tub (115) at a first time instant (t1) and a second liquid pressure at a second time instant (t2) while the laundry drum (117) is at rest, and

    - determining the presence of foam as a function of the first liquid pressure and the second liquid pressure
    characterised by the step

    - detecting the first liquid pressure in the washing liquid tub (115) at the first time instant (t1) and the second liquid pressure at the second time instant (t2) during a liquid pressure rise in the washing liquid tub (115).
15. Method according to claim 14, characterised in that the method comprises a calibration step for determining a calibration parameter (a, (Δtk0) prior to detecting the first and the second liquid pressure.

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