EP0787848B1

EP0787848B1 - Method for determining quantity and/or type of fabric introduced in a laundry washing machine

Info

Publication number: EP0787848B1
Application number: EP97101794A
Authority: EP
Inventors: Valerio Aisa
Original assignee: Wrap SpA
Current assignee: Wrap SpA
Priority date: 1996-02-05
Filing date: 1997-02-05
Publication date: 2002-05-08
Anticipated expiration: 2017-02-05
Also published as: DE69712380T2; ES2177838T3; EP0787848A1; ITTO960076A1; IT1284371B1; ITTO960076A0; DE69712380D1

Description

The present invention refers to a method to determine the quantity of clothes and the type of fabric introduced in a laundry washer, and a laundry washer implementing such a method.
As known, the knowledge of the fabric type and the quantity of clothes introduced in a laundry washer are of a substantial importance in order to select best washing program. Said information may be transmitted to the laundry washer control-system directly by the user, through appropriate means (such as keyboards with display, indexed knobs, keys, etc.), or can be automatically obtained by the control system itself, when the latter is technologically appropriate to this purpose (e.g. including an electronic microprocessor control system).
In the latter case, the measure of the quantity of clothes and the type of fabric can be performed either directly or indirectly.
A direct measurement method appears stricter but difficult to implement, as some sophisticated and expensive sensors are required, whereas an indirect measurement method better complies with the low-cost and moderate accuracy requirements as demanded by a commercial laundry washer.
Some methods of indirect measurement of the fabric type and the quantity of clothes introduced in a laundry washer are known, which are based on the software elaboration of data information being generated by proper settings of the process of water inlet inside the laundry washer.
Said methods are based on the physical capacity of fabrics to absorb water, according to a procedure based on their quantity and fibre type.
In particular, due to the specific geometric configuration of the European laundry washing machines, it is known from experimental results that a fabric type considerably affects the water initial absorption speed inside the washing tub, whereas the total quantity of water being absorbed under saturation conditions is a function of both the quantity of clothes and fabric type (i.e. sponge-cloth, cotton. synthetics, silk, wool, etc.).
For a detailed description of this phenomenon, see for instance EP-A-0 649 932.
German patent application DE-A-4.122.307 discloses an indirect measurement method as mentioned above. According to said method, the control system of a laundry washer elaborates the data information supplied by an electromechanical level sensor (pressure switch) during the initial phases of a washing cycle; such data information relate to the water level restoring process in the washing tub of the laundry washer.
For a better understanding, the method disclosed in the above German patent application DE-A-4.122.307 will now be briefly described and commented. To this purpose Fig. 1 shows the main figure of said application DE-A4.122.307; said Fig. 1 shows a diagram indicating the water level in a laundry washer tub as a function of time.
The axis of ordinates (time) show some phases of water inlet into the machine tub, indicated by t1 and tk, and some phases of water absorption by the laundry, indicated by ts.
According to the above method, during a first phase t1, a quantity of water preset by the manufacturer is introduced through a proper solenoid valve into the machine tub, while the drum is at standstill; upon reaching the preset working level NA (i.e. the "full" level), the pressure switch trips causing said water inlet solenoid valve to close.
At the end of this phase, the laundry will absorb water, still with the drum at standstill, causing a water level decrease from the working level NA down to the pressure-switch NE insertion level (i.e. the "empty" level). This second phase occurs during a time interval ts1, whose duration provides a measurement of the water absorption capacity by the laundry and consequently by the type of laundry.
Upon reaching the level NE, the pressure switch reacts, so causing the water inlet solenoid valve to open; therefore, during the subsequent time interval tk, water will be topped up in the washing tub to reach the working level NA; upon reaching it the pressure-switch will react again, causing said solenoid valve to close.
During the subsequent time interval ts2, there will be a second water absorption by the laundry, causing a new water level decrease down to the pressure-switch insertion level NE.
As it can be noticed, this involves a number of water top-up and absorption cycles, with the absorption times gradually increasing due to a progressive laundry saturation; the pressure-switch setting cycles will end when the laundry is saturated with the washing liquid. According to the above German application, the number of top-ups, or the sum of top-up times tk, represents a measurement of the quantity of clothes introduced into the laundry washer.
The method described above has two main problems :

the determination of the fabric type based on the measurement of water absorption initial speed is considerably affected by the wide tolerance values featuring laundry-washer pressure-switches; therefore, according to the method suggested in DE-A-4.122.307 the measurement result is often unreliable;
the quantity of clothes is determined only after concluding the water supply process; the ensuing delay (10 to 15 minutes) does not allow to optimize the initial washing actions as provided by a treating program.

From FR-A- 2.684.116 a method is also known, for adjusting the water inlet process in a laundry washing machine, in function of the type of laundry, said method providing for:
a) a first water inlet, up to the full level of a pressure switch;
b) a phase of movement of the drum containing the laundry, having a preset duration, for obtaining a lowering of the water level in the washing thank, below the empty level of the pressure switch, due to the absorption by the laundry;
c) a second water inlet, up to the full level of the pressure switch;
d) the measure of the time which has been necessary for passing from the level of step b) to the level of step c), which time is representative of the type of laundry;
e) a timely-controlled supplementary water inlet, in order to reach within the washing tank a level which is always above the full level of the pressure switch, wherein the duration of said supplementary water inlet is determined in function of the time which was measured during step d).
It is the object of the present invention to provide a method allowing indirect determination of the type and the quantity of the clothes introduced in a laundry washer, through which said drawbacks may be removed, and a laundry laundry washing machine implementing such a method.
Said purpose is obtained according to the present invention by a laundry washing machine having the characterizing features of the annexed claim 1, and a method to determine the type of laundry introduced in a laundry washer and a laundry washing machine having the characterizing features of the annexed claim 10; further advantageous embodiment of the invention are then contained in the dependent claims 2-9 and 11-17.
The characteristics and advantages of the present invention will become apparent from the following description and the annexed drawings, supplied only by way of an explanatory but not limiting example, wherein :

Fig. 1 shows a diagram where the water level in the tub of a laundry washer is indicated as a function of time, according to the solution described in the German patent application DE-A-4.122.307;
Fig. 2 shows a diagram where the water level in the tub of a laundry washer is indicated as a function of time, according to the present invention.

As it will be seen, the method according to the present invention allows to overcome the two problems related to the cited known art, due to the fact that it is independent from the characteristics of the level sensor being used and is based on the concept of a "forced restoration" of the water level, as it will be better explained later.
The method according to the present invention develops through the following five phases shown in Fig. 2 by their time intervals indicated with T1, T2, T3, T4 and T5 respectively.

Phase 1

During the first phase, water is supplied into the laundry washer tub for a fixed time T1 as imposed by the machine control system. Based on the known flowrate of the solenoid valve in use, said time T1 allows the introduction in the tub of an appropriate water quantity, which is below the one related to the final working level ("full" level); in particular, said water quantity indicated with "a" in Fig. 2, equals a fraction (eg. 1/2 or 2/3) of the quantity related to the final level and, in any case, is such to allow the laundry to be wetted, without however that the same is fully immersed in the water.
Thus, in occasion of said first partial water inlet, the level sensor of the laundry washer is "by-passed" by the electronic control system of the machine.
Said water inlet takes place while the laundry-washer drum is at standstill.

Phase 2

During the second phase, the laundry-washer drum is constantly rotated at a fixed speed for a preset time T2. During this phase, the water level in the tub gradually decreases due to the water absorption by the clothes.
Time T2 is conveniently selected as a function of the machine geometry, i.e. as a function of the tub and drum characteristics, so as to warrant the required contact between the water supplied in the tub and the fabric contained in the drum.
Therefore, as it will be noticed, also during this second phase the level sensor of the laundry-washer according to the present invention is in fact "by-passed" by the control system.

Phase 3

During the third phase the drum is at standstill and the water inlet in the tub is completed up to the fixed level (indicated with "c" in Fig. 2) related to the "full" condition of the level sensor in the laundry-washer (therefore the "full" level will be detected by the level sensor, which is enabled during this phase).
The machine control system will then execute the counting of time T3, as required for this purpose.
The value of the ratio T3/T1 (multiplied by an appropriate experimental coefficient K, which takes the machine geometry into account) is in relation with the water absorption speed by the fabric inside the laundry-washer drum, thus allowing the machine control system to identify the type of such fabric, on the basis of experimental reference data previously stored in permanent memory means contained in the control circuit itself.

Phase 4

During the fourth phase, the control system will cause the drum to rotate again at a constant speed for a preset time T4 long enough (T4 > T2) to warrant that the water absorption is proportional to both the quantity of clothes and type of fabric (this latter data information being already obtained by the control system at the end of previous Phase 3).
Also the time T4 is adequately selected as a function of the machine geometry without taking into account the characteristics of the level sensor. The only condition being required is that at the end of the fourth phase the level sensor have left the "full" level and is in the socalled "empty" level condition, which is required for completion of the fifth phase.
In order to comply with said condition it will be enough that the hystheresis of the level sensor is equal to a water quantity being not over about a liter of water, a condition which can be easily obtained for any type of level sensor available in trade.
As it can be noticed, also the fourth phase is a phase with a preset time.

Phase 5

During the fifth and last phase the water inlet is completed up to the fixed level related to the appropriate sensor ("full" level) with the drum at standstill and the relevant time T5 required to this purpose is measured.
The value of T5 jointly with the ratio T3/T1 (indicating the fabric type) provides a good evaluation of the quantity of clothes contained in the laundry-washer.
Upon completion of the fifth phase, i.e. after the control system of the machine has determined both the quantity of clothes and the type of fabric, the water inlet process goes on in the usual manner (i.e. normally using the level sensor) till it reaches saturation, according to the inlet procedure which is typical for the type of level sensor being used. Said procedures, as mentioned, are apart from this invention.
As described above, the concept of "forced restoration" is quite clear: in order to determine the fabric type and the quantity of clothes, water top-up phases in the washing tub are not automatically started by the response of a level sensor to the crossing of a preset threshold (as it is according to DE-A-4.122.307), but rather by a control system "forcing" a lock condition of the water inlet solenoid valve for enough time to allow the water level to decrease to the minimum response level (considering the maximum hystheresis) of the level sensor.
Therefore, the advantage of the method being the subject of the present invention will be apparent in respect to the method suggested in DE-A-4.122.307.
In the latter, both the restoration and water absorption phases are always started by the response of the pressure-switch, when crossing preset thresholds (called NA and NE), but the start instant is considerably affected by the sensor physical and manufacturing characteristics (specifically the hystheresis), so that the measurements are often unreliable.
Moreover, according to said German application, the time required to complete the measurement phase may be considerably long, due to the progressive extension of the absorption times tS, as the clothes become gradually saturated with water, and to the non-determinability of the required number of top-up/absorption cycles.
On the contrary, the method being the object of the present invention is fully independent from the characteristics of the level sensor and the total time required is restricted and exclusively a function of the values T3 and T5.
In addition, considering that the type of fabric and the quantity of clothes are determined following the first and second water inlet at working level respectively, it will ensue how according to the present invention the required data information are obtained quite more rapidly.
The method of an indirect measurement of the quantity of clothes and of the fabric type in a laundry washer being the object of the present invention is based on the following conditions, which can be easily complied with:

the solenoid valves used for the water inlet in the laundry-washer tub shall warrant a given constant flowrate, also under variable water pressure conditions;
the laundry washer shall be equipped with an appropriate water level sensor being capable of signalling the control system that a preset fixed level has been reached;
the control system shall be of the electronic type.

The first condition is warranted by the flowrate self-setting characteristics being typical of the solenoid valves presently used for household laundry washers.
The second condition is always verified, being required for the water level control inside the laundry washer. It is independent from the type of the adopted level sensor, which may then be a conventional pressure-switch or an optical sensor (i.e. based on liquid refraction) or still a conductivity sensor or a solid state pressure sensor, etc.
The third condition fully agrees with the control system evolution in the field of household appliances, favoured by the increasing availability of low-cost microcontrollers.
Under these circumstances, an excellent method for compact codification of the data information as required for the method according to the present invention is provided by the control technology based on fuzzy logic, widely used by now in the consumers' application field, in particular in the household appliances field. The evaluation of the quantity and type of clothes will then be executed using experimental data adequately codified in a permanent memory being comprised in the control system, since the latter, as previously mentioned, will be based on a microcontroller.
The characteristics of the present invention are clear from the above description. as well as its advantages are also apparent.

Claims

Laundry washing machine, comprising a washing-tub, a drum within said tub, a level sensor for the washing liquid in said tub, an electronic control circuit, said laundry washer executing more than one liquid inlet in said tub up to a full level of said sensor, followed by a liquid absorption cycle by the laundry, which decreases the liquid level in said tub below an empty level of said sensor, characterized in that means are provided for making the control system to deduce the type of fabric at the end of the first liquid inlet cycle (T1,T2,T3) up to said full level (c) and to deduce the quantity of the fabric at the end of the second liquid inlet cycle (T5) up to said full level.
Laundry washing machine, according to Claim 1, characterized in that said means are provided for controlling, during said first liquid inlet cycle (T1,T2,T3) up to said full level (c), a liquid absorption phase (T2) by the laundry, having a preset duration, which is independent from the signal from said level sensor.
Laundry washing machine, according to Claim 1, characterized in that said means are provided for controlling, before said second liquid inlet cycle (T5) up to said full level (c), a liquid absorption phase (T4) by the laundry, having a preset duration, which is independent from the signal from said level sensor.
Laundry washing machine, according to Claim 2, characterized in that said means are provided for controlling, at the beginning of said first liquid inlet cycle (T1,T2,T3) up to said full level (c), an initial liquid inlet phase (T1) having a preset duration, followed by said liquid absorption phase (T2) by the laundry.
Laundry washing machine, according to the previous Claim, characterized in that said means are provided for controlling. after said liquid absorption phase (T2) by the laundry, a final liquid inlet phase (T3), which ends upon reaching said full level detected by said sensor.
Laundry washing machine, according to Claim 2 or 3, characterized in that the preset duration of said liquid absorption phase (T2,T4) by the laundry is selected as a function of the machine geometry, i.e. as a function of the tub and drum characteristics.
Laundry washing machine, according to Claim 2 or 3, characterized in that said means are provided for controlling the rotation of said drum while said liquid absorption phase (T2,T4) by the laundry is occurring.
Laundry washing machine, according to the previous Claim, characterized in that said control system is programmed for deducing the type of laundry in function of the duration of said final liquid inlet (T3) up to said full level (c).
Laundry washing machine, according to the previous Claim, characterized in that said control system is programmed for deducing the quantity of laundry in function of the duration of said second liquid inlet cycle (T5) and in function of the laundry type.
Method to determine the type of laundry introduced in a laundry washer, which comprises a washing tub, a drum within said tub, a level sensor for the washing liquid and an electronic control circuit, characterized in that it provides in the given sequence:

a first washing liquid inlet phase in said tub, which ends upon reaching a preset water level (a) below the full level of said level sensor, said preset water level (a) being reached through a constant water flowrate for a preset first time interval (T1);

a first liquid absorption phase by the laundry, in particular while the drum is rotating, having a preset duration (T2) which depends upon the laundry-washer geometry;

a second washing liquid inlet phase in said tub, which ends upon reaching the full level (c) of said level sensor;

where the ratio between the duration of said second inlet phase (T3) and said preset first time interval (T1) provides the control system with a measurement of the liquid absorption speed by the laundry contained in the drum, so that said control system is able to identify the laundry type on the basis of data information being stored in proper memory means.
Method according to Claim 10, characterized in that after said second washing liquid inlet phase (T3) in said tub, a second liquid absorption phase by the laundry is provided, specifically while the drum is rotating, having a preset duration (T4) such to warrant a liquid absorption by the laundry which is proportional to the quantity of the laundry itself, where said preset time (T4) is such that at the end of said second absorption phase the liquid level (c) in said tub is lower than the empty level of said level sensor.
Method according to Claim 11, characterized in that after said second liquid absorption phase (T4) by the laundry, a third washing liquid inlet phase in said tub is provided, which ends upon reaching the full level (c) of said level sensor,
where the duration (T5) of said third inlet phase is used by the control system to evaluate the quantity of laundry as a function of its type, on the basis of data information being stored in proper memory means.
Method, according to claim 10, characterized in that the quantity of water (a) supplied during said first washing liquid inlet phase in said tub equals a fraction (eg. 1/2 or 2/3) of the quantity related to the full level (c) of said level sensor and/or is in any case such to allow the laundry to be wetted, without hower that the same is fully immersed in the liquid.
Method, according to claim 10, characterized in that, after said first inlet (T1,T2,T3), it provides in the following sequence:

a liquid absorption phase by the laundry, specifically while the drum is rotating, having a preset duration (T4) such to warrant a liquid absorption by the laundry which is proportional to its quantity, where said preset time (T4) is such that at the end of said absorption phase the liquid level (d) in said tub is below the empty level of said level sensor;

a second washing liquid inlet phase in said tub, which ends upon reaching the full level (c) of said level sensor, said inlet phase being started by the control system at the end of the preset time interval (T4) representing said liquid absorption phase;

where the duration (T5) of said second inlet phase is used by the control system to evaluate, according to the type of fabric, the quantity of laundry on the basis of data information being stored in proper memory means.
Method according to Claim 14, characterized in that said first washing liquid inlet comprises:

a first partial washing liquid inlet phase in said tub, which ends upon reaching a preset water level (a) below the full level of said level sensor, said preset water level (a) being reached through a constant water flowrate during a preset first time interval (T1);

a second partial washing liquid inlet phase (T3) in said tub, which ends upon reaching the full level (c) of said level sensor.
Method according to Claim 15, characterized in that between said first and second partial inlet phase (T1,T3) there is provided a liquid absorption phase by the laundry, specifically while the drum is rotating, having a preset duration (T2), such to warrant that at the end of said liquid absorption phase the liquid level (b) in said tub is below the empty level of said level sensor.
Method according to Claims 15 and 16, characterized in that the ratio between the duration of said second partial inlet phase (T3) and said preset first time interval (T1) provides the control system with the measurement of the liquid absorption speed by the laundry contained in the drum, so that said control system is able to identify the laundry type on the basis of data information being stored in proper memory means.