EP1096052A2

EP1096052A2 - Method for controlling the lint filter in an automatic clothes washing machine

Info

Publication number: EP1096052A2
Application number: EP00120377A
Authority: EP
Inventors: Valentino Peressi; Piero Babuin
Original assignee: Electrolux Zanussi Elettrodomestici SpA; Electrolux Zanussi SpA
Current assignee: Electrolux Zanussi Elettrodomestici SpA; Electrolux Zanussi SpA
Priority date: 1999-10-28
Filing date: 2000-09-18
Publication date: 2001-05-02
Also published as: IT1311716B1; ITPN990081A0; ITPN990081A1; EP1096052A3

Abstract

In a clothes washing machine that comprises a washing tub (4) containing a drum (5), and is adapted to carry out a rinse cycle with water at a level (L3), as well as a water discharge phase down to a minimum level (L0), the method calls for:

during the discharge phase (t1-t4), the time interval (T) to be measured, which elapses from an instant (t2), in which the water in the tub lowers to a level (L2) corresponding to the bottom of the drum (5), to a subsequent instant (t3), in which the water decreases down to a level (L1); and
when the so measured interval (T) is detected to be longer than a given threshold value (Tr), a signal to be generated which is indicative of a clogged state of the lint filter (7).

Description

The present invention refers to a method that is capable of being used in an automatic clothes washing machine to the purpose of controlling the lint filter thereof in such a manner as to be able to detect a possible clogged state of the same filter and alert the user of the existence of such a condition.
The lint filter in clothes washing machines is generally known to be arranged in the water discharge circuit of the machine, where it is able to retain part of the soil removed from the clothes. At the longer term, owing to its limestone contents, such a soil tends to become solid, thereby giving rise to occlusions, ie. clogged states that may well reduce the flow rate of the water being let off down said water discharge circuit of the machine.
Such a condition causes the performance capabilities of the concerned washing machine to undergo a gradual deterioration, down to the point at which the lint filter becomes substantially fully clogged, thereby reaching a condition that may even lead to the operating cycle of the machine to be stopped, ie. prevented from going on regularly.
As a result, the lint filter usually needs to be checked and cleaned periodically. In practice, however, users tend to perform such cleaning operations quite seldom, ie. not so often as actually required.
Clothes washing machines are known in the art to be provided with an alarm system which is actuated when, during a phase in which water is discharged from the washing tub thereof, the latter fails to be emptied within a pre-determined, relatively long time interval, that may for instance amount to 10 minutes. However, such a solution is based on a too generic detection criterion that is not directly indicative of an actual clogged condition of the lint filter, since the so detected irregularity can in fact be determined by a number of different causes, such as in particular a failure or defective state of the discharge pump of the machine.
It therefore is a main purpose of the present invention to provide a method for controlling the lint filter in an automatic clothes washing machine in such a manner as to be able to detect and signal a possible condition of substantial clogging of the lint filter in a preventive way, ie. well in advance of the filter itself reaching such a clogged condition as to practically cause the operating cycle of the machine to be interrupted.
A further purpose of the present invention is to provide a method of the above cited kind, which makes it possible for a possible clogged condition of the lint filter to be detected in a simple and reliable manner, regardless of the operating variables of the machine, while discriminating such a clogged condition of the lint filter from other possible irregular conditions of the machine.
According to the present invention, these aims are reached in method for controlling the lint filter in an automatic clothes washing machine having the characteristics as recited in the appended claims.
Anyway, features and advantages of the present invention can be more readily understood from the description that is given below by way of non-limiting example with reference to the accompanying drawing, in which:

Figure 1 is a basic schematical view of a clothes washing machine adapted to implement the method according to the present invention; and
Figure 2 is a diagrammatical view of the variations in the water level L during significant phases of the method according to the present invention.

With reference to the above listed Figures, the method according to the present invention can be implemented in a clothes washing machine having a substantially traditional structure, which comprises a washing tub 4 housing a rotating drum 5 adapted to contain the clothes to be washed. The washing tub 4 is connected to a water discharge circuit 6, to which there are associated a pump (not shown) and a lint filter 7.
Again in a traditional manner, the clothes washing machine shall be understood as being provided with a plurality of operational and functional parts controlled by a programme sequence control switch or unit, preferably of the electronic type, for carrying out selectable operating cycles.
In particular, the machine is adapted to carry out at least a rinse phase, in which it lets water into the tub 4 up to a level L3. Said rinse phase is then followed by at least a water discharge phase, in which the water is let off down to a minimum level L0, and may of course be preceded by at least a washing phase performed with water to which detergent has been duly added. In the diagram illustrated in Figure 2, such a water discharge phase is shown to last from an instant t1 through to an instant t4, in which the water in the tub decreases from the level L3 to said minimum level L0, respectively
The present invention is based mainly on the consideration that, with the discharge or drain pump of the machine performing regularly, the time taken for the rinse water to be discharged from the tub 4 is in correlation not only with the extent to which the lint filter 7 is actually clogged, but also with other factors, such as in particular the weight of the clothes, ie. the washload, the distribution of the clothes inside the drum 5, the type of fabrics being handled. During water discharge, in fact, a part of the water contained in the washing tub of the machine is retained by the clothes in a hardly determinable proportion that depends on the above cited number of factors.
On the other hand, as opposite to the washing water, the rinse water is substantially free from detergent, so that the related discharge phase t1 ― t4 is substantially not affected by froth.
According to the present invention, the lint filter 7 can be checked for its actual clogged condition in the following manner.
During the rinse water discharge phase t1 - t4, provisions are made to detect a first instant t2, in which the water in the tub 4 decreases to a first level L2 that is substantially equal to or lower than the one corresponding to the bottom (ie. the lowest point) of the rotating drum 5, as well as a second instant t3, in which the water in the tub 4 further decreases to a second reference level L1, which is obviously lower than said first level L2.
As illustrated in Figure 1, the moment at which the water reaches said levels L2 and L1 can be easily detected through the use of appropriate level sensor means 8, 9, which may for instance be of the pressure-actuated switch type and are adapted to drive a starting input 10 and a switch-off input 11 of a timer 12, respectively.
In particular, the timer 12 is started when the water in the tub 4 decreases to the level L2 and is switched off when the water then decreases down to the level L1. In other words, the timer 12 measures the time interval T that elapses from said first instant t2 to said second instant t3.
It should be noticed that when the level is defined here as being "substantially equal" to the base or bottom of the rotating drum 5, the same is to be understood as being able in practice to be even slightly higher than said base or bottom (eg. 3 to 5 mm), anyway to such an extent as to prevent the water discharge operation from being affected, during the above mentioned measurement time interval T, by the clothes contacting the water being let off. This practically enables the measurement of the time interval T to be substantially cleared from all variables that have no correlation with the clogging extent of the lint filter 7.
In the example being described here, the timer 12 has an output 13, through which it drives a threshold-value comparator 14 with a signal that is indicative of the measured time interval T.
When the measured time interval T is so detected to exceed a pre-determined threshold value Tr, the comparator 14 is adapted to generate, at an output 15, an alarm signal that is indicative of a condition of substantial clogging of the lint filter 7. In a preferred manner, such an alarm signal is adapted to trigger actuator means 3, which in the most elementary embodiment thereof may comprise optical and/or acoustical indicator means through which the user can be warned of the clogged state of the lint filter 7, which therefore should most suitably be cleaned.
Preferably, the threshold value Tr is set in the comparator 14 at such a value (for instance, approx. 10 to 15 seconds) as to ensure that the above cited alarm signal is generated when the clogging state of the lint filter 7 has not yet reached such an extent as to prevent the rinse water discharge phase from being brought to regular conclusion, ie. when said minimum level L0 is eventually reached. In an advantageous manner, therefore, the user is in this way able to take the necessary actions, ie. to clean the filter, when the machine is still capable of operating in a substantially satisfactory manner.
It will of course be appreciated that the above described method can be the subject of a number of modifications without departing from the scope of the present invention.
For instance, the level L1 may be equal to, but preferably it will be slightly higher, for instance by a few millimetres, than the minimum level L0. In any case, the difference between the levels L2 and L1 will preferably be wide enough to allow for an adequately accurate measurement of the time interval T.

Claims

Method for controlling the lint filter in a clothes washing machine of the type which comprises a washing tub accommodating a rotating drum for holding the washload, and is adapted to carry out operating cycles including at least a rinse phase performed with water, which is let into said washing tub up to an operating level (L3), as well as at least a subsequent water discharge phase, in which said water is let off the tub down to a minimum level (L0), characterized in that it comprises following phases:

during said water discharge phase (t1-t4), provisions are made to detect a first instant (t2), in which the water in the tub (4) decreases to a first level (L2) that is substantially equal to or lower than the one corresponding to the bottom of the rotating drum (5), as well as a second instant (t3), in which the water in the tub (4) further decreases to a second reference level (L1), which is lower than said first level (L2);

the time interval (T) that elapses between said first and said second instant (t2, t3) is then measured;

when the so measured time interval (T) is detected to exceed a pre-determined threshold value (Tr), an alarm signal is generated which is indicative of a condition of substantial clogging of the lint filter (7).
Method according to claim 1, characterized in that said alarm signal triggers actuator means (3).
Method according to claim 1, characterized in that said threshold value (Tr) is set at such a value as to ensure that said alarm signal is generated in advance of the filter (7) being capable of reaching such a clogged state as to prevent the rinse water discharge phase from being brought to regular conclusion, when said minimum level (L0) is eventually reached.
Method according to claim 1, characterized in that said second reference level (L1) is slightly higher than said minimum level (L0).
Method according to claim 1, characterized in that said second reference level (L1) is substantially equal to said minimum level (L0).