Clothes washing maschine with an innovative-type filter monitoring arrangement

Abstract: The invention relates to an innovative-type monitoring arrangement for the filter of a washing machine so as to ensure that the user is warned of the opportunity of cleaning the filter only when an actual need for this arises. The solution uses functional elements that are normally used in washing machines, such as an analogue pressure switch (13) and an electronic control circuit (14). The parameter that is considered in this connection is the variation of the pressure before and after the priming of the drain pump (12) of the machine.

Description: The present invention refers to a household-type clothes washing machine which is provided with a filter arrangement installed in the water circulation circuit of the machine to separate lint, dirt particles and and possible foreign matters from the washing water. Such a filter arrangement is usually provided upstream of the water draim pump of the machine in view of both protecting the pump itself and preventing particular matters from being unduly discharged from the machine. In modern clothes washing machines in which the washing water is recirculated, the filter is preferably provided in the washing water recirculation circuit of the machine, upstream of the recirculation pump. In all these cases, the filter has the purpose ofensuring a correct operation of the machine. However, for it to perform its duty in a really effective manner, it must be cleaned periodically. In practice, it quite often occurs that the user starts by controlling the filter at rather frequent intervals, but, since he/she obviously finds it to be sufficiently clean most of the time, tends to do this at increasingly less frequent intervals and eventually fails to remember about it completely, thereby putting the good performance capability of the washing machine in jeopardy. Various types of arrangements have therefore been studied and developed in view of automatically informing the user on the actual conditions of the filter, so as to alert him/her of the need for the same filter to be cleaned. EP-A-28067 teaches to use a timer to monitor a pressure switch which is rated on the minimum water level in the wash tub of the machine. When the time needed by the liquor in the tub to lower down to said minum level during water discharge exceeds a pre-determined value, this means that the filter is clogged and an indicator light therefore illuminates to alert the user. EP-A-245870 teaches to use a sensor connected in series with a resistor that heats up to higher than usual temperature values when the filter is clogged, thereby causing means to be switched on to indicate the occurrence of such a condition. A number of other solutions might be cited here, such as for instance the one that uses photodiodes to detect the passage of light through the filter (patent EP-A-443361). Anyway, all such prior-art solutions require the addition of component parts that unavoidably contribute to the complication of both the overall construction and the operation of the machine. A controlling device is known from US 4,711,103: the controlling device includes level control means which comprise two pressure switches for controlling the water level, and an additional pressure switch which is intended to sensitively react to pressure variations occurring in the hose; the purpose of this pressure switch is to constantly sense the pressure of the wash liquor flowing through the hose upstream of the filtering element, thereby to indirectly check the efficiency conditions of the filtering element itself. One problem of this controlling device is due to the fact that the pressure switch which should check the condition of the filtering element detects any pressure variation in the hose at any time of the cycle. Thus, owing to this indetermination about the time when the detection is made, the pressure variation can depend by a different operational condition of the machine not necessarily related to the operating condition of the filter. Therefore the indication given by the controlling device as to the operating condition of the filter can not be accurate. It therefore is a purpose of the present invention to provide a continuous monitoring arrangement for the filter in a clothes washing machine, so as to enable the user to be automatically alerted when the filter reaches such a degree of clogging as to actually require cleaning. Such an aim is reached by making use of the existing analogue pressure switch of the machine and appropriately associating it with the electronic control circuit of the same machine so as this is recited in the appended claim 1 and further detailed in the subsequent sub-claims. As a result, the solution according to the present invention is actually simpler, more realiable and cheaper than the prior-art ones. Features, characteristics and advantages of the solution according to the present invention will anyway be more readily understood from the description which is given below by way of non-limiting example with reference to the accompanying drawings, in which: Figure 1 is a simplified schematic view of a clothes washing machine with the various means and arrangements needed to implement the solution according to the present invention; Figures 2 and 3 are diagrammatical views of the pressure curves in the cases of clean and clogged filter, respectively, in a first embodiment of the present invention; Figure 4 is a simplified schematic view of a clothes washing machine with an arrangement for the recirculation of the washing liquor and the various means and arrangements needed to implement the solution according to the present invention; Figures 5 and 6 are diagrammatical views of the pressure curves in the cases of clean and clogged filter, respectively, in a second embodiment of the present invention. A first embodiment of the present invention is illustrated with reference to a clothes washing machine of a traditional type (Figure 1), comprising essentially a wash tub 10, a filter 11 for the washing liquor, a drain pump 12 for the washing liquor, a pressure switch 13 controlling the level of the liquor in the wash tub, and an electronic control circuit 14 for governing the operational functions of the machine. The component parts of the machine which are involved in the implementation of the present invention are the analogue-type pressure switch 13 and the drain pump 12. The parameter that is used to detect the clogged filter condition and, therefore, to alert the user of the need for the same filter to be cleaned, is the pressure variation in the pressure switch between an instant in which the drain pump is at a standstill, ie. not operating, and a subsequent instant in which the drain pump is primed. As illustrated in Figure 2, when the pump is at a standstill the pressure (A) in the water circuit of the machine is static and stabilized. When the pump starts priming, the pressure drops sharply (B) and, after a short period during which it oscillates, keeps decreasing until the water discharge operation is concluded. This occurs when the filter is normally clean. In the case of a clogged filter (Figure 3), on the contrary, the pressure (B') drops only slightly when the drain pump starts priming, while the subsequent oscillations may even give rise to pressure peaks that are higher than the static pressure prevailing when the same pump is not operating. Such a behaviour has been verified experimentally and it may quite easily be explained with the difficulty encountered by the water in its effort to flow through the filter. The pressure reading, or sensing, is preferably made in the last water discharge phase of a complete washing cycle, although it will be appreciated that it may be arranged to occur in any water discharge phase carried out by the machine. After the water has been filled in for the last rinse operation, the drum holding the washload is driven to rotate at slow speed for a period of approx. 4 minutes. This is followed by a pause (eg. of 20 seconds), during which the pressure in the water circuit of the machine is allowed to stabilize at the level (A) indicated in Figure 2. The drain pump then starts to prime and, as usual, the machine is emptied before the final spin-extraction phase is started. The reading of the pressure in the water circuit of the machine is carried out for a very short initial time (for instance 7/10 of second) after the priming of the drain pump and the variation in the values of water pressure delivered by the analogue pressure switch is analyzed with the following logic sequence: a) reading of the pressure after 20 seconds of pause; b) reading of the maximum pressure drop at the priming of the drain pump. If the pressure after the priming of the drain pump has a lower value than that of the stabilized pressure in the 20 seconds preceding the discharge operation, then the filter may be considered as being clean. If the pressure after the priming of the drain pump has a value which is equal or even higher than that of the stabilized pressure in the 20 seconds preceding the discharge operation, then the filter may be considered as being clogged. In this case the electronic control circuit of the machine would therefore deliver a signal, which may be of any known type, ie, acoustical, optical, combined acoustical and optical, etc., to correspondingly alert the user. A second embodiment of the present invention will now be described with reference to a recirculating-type clothes washing machine (Figure 4) comprising a circuit 15 for recirculating the water in the wash tub of the machine, a filter 16 and a recirculation pump 17 being included in said water recirculating circuit. In this particular case, the reading of the pressure variation is preferably made through the recirculation pump 17, since it is the effectiveness of the washing process that must be here privileged over the effectiveness of the water discharge operation. In fact, the filter 16 included in the water recirculating circuit 15 has a filtering surface which is reduced with respect to the one of the filter installed in the drain system of the machine, so that it is more quickly prone to clogging. The manner in which the readings and the related comparisons are made here is substantially similar to the one described above. After the water has been filled in for the last rinse operation, the drum holding the washload is driven to rotate at slow speed for a period of approx. 4 minutes. Then the machine is stopped (eg. for a period of 20 seconds). After that, the recirculation pump is started again and allowed to operate for approx. 10 seconds, while the variation in the pressure is observed for an initial time of approx. 1 second for due comparison with the value of the static pressure prevailing in the preceding pause period. If the pressure drop (D) at the priming of the recirculation pump (Figure 5) has a value which is equal to or even higher by 10% than that of the stabilized pressure (A) prevailing in the pause period, then the filter may be considered as being clean. If the pressure drop (D') at the priming of the recirculation pump (Figure 6) has a value which is lower by 10% than that of the stabilized pressure (A) prevailing in the preceding pause period, then the filter may be considered as being clogged, so that, as this has been described in connection with the first embodiment, an appropriate signal would be delivered to alert the user of the irregular condition. It can be readily noticed, therefore, that the invention enables the user to be automatically and timely informed of the filter being clogged and requiring cleaning, without any need arising for additional component parts to be used in the machine to achieve such an aim, but making on the contrary simply use, albeit in a rational and innovative manner, of some of the component parts which normally exist in the same machine. Various further improvements and variants are of course possible, ie. may be implemented without departing from the scope of the present invention. For example, by making again use of the analogue pressure switch and the control circuit of the clothes washing machine it is possible for the user to be given also an indication of a possible obstruction of the drain pump. In fact, by applying the same afore described concept, it is for instance possible for the drain pump to be stopped for approx. 20 seconds in anyone of the operating phases of the machine and the stabilized pressure detected after such a pause to be compared with the pressure detected after approx. 15 seconds from the moment in which the drain pump is restarted. Should the pressure detected after the drain pump has been restarted be lower than the pressure detected after the pause, the drain pump may be considered to be operating correctly; should on the contrary the pressure detected after the drain pump has been restarted be equal to or even higher than the pressure detected after the pause, the drain pump has to be considered as obstructed.

Claims: Clothes washing machine comprising a wash tub (10), at least a drain pump (12) for discharging the washing water, an electronic pressure switch (13) to control the level of the water in the tub, a filter (11) to separate possible lint and/or foreign matters or substances from the washing water, and an electronic circuit (14) to control the operation of the machine, characterized in that said electronic pressure switch (13) is adapted to supply said electronic circuit (14) with a continuous analogue indication of the pressure prevailing in the water circuit of the machine, said electronic circuit (14) being adapted to compare a value of the stabilized water pressure (A), at an instant when the drain pump is at a standstill, with a value of the water pressure (B) at a subsequent instant immediately after the priming of the drain pump (12), to supply a signal which is indicative of the operating condition of said filter (11), said signal depending on the variation between said pressure values (A) and (B) analyzed by said electronic circuit (14). Clothes washing machine according to claim 1, characterized in that said electronic circuit (14) is adapted to carry out said comparison between said pressure values (A, B) in any water discharge phase of the machine, preferably in the last water discharge phase of a complete washing cycle. Clothes washing machine according to claim 1 or 2, wherein the water circuit of the machine comprises a recirculating circuit (15) for the recirculation of the water in the wash tub, said recirculating circuit including a filter (16) and a recirculating pump (17), characterized in that said comparison of the pressure values (A,D) is carried out in the recirculating circuit (15) when the recirculating pump (17) is at a standstill and after the priming of the same pump.

Inventors: BABUIN PIERO, CIMETTA SILVANO, BABUIN, PIERO, CIMETTA, SILVANO
Applicants: ELECTROLUX ZANUSSI ELETTRODOME, ELECTROLUX ZANUSSI S.P.A.
Application year: 1997
Main classification: D06F39
IPC codes: D06F39