Automatic laundry washer of the rotating drum type

Abstract: The invention relates to an automatic laundry washer of the type having a laundering tub in which a drum is rotated by an electric motor (7) at a low speed during a laundering phase, and at a high speed during at least one centrifuging period. For ensuring a complete discharge of foam and lye in the course of a centrifuging period, a pressure switch (4) is adapted to interrupt the centrifuging period and to disconnect the power supply to the program control unit in response to the level within the laundering tub exceeding a predetermined value (L2).

Description: The present invention relates to an automatic laundry washer according to the precharacterizing part of Claim 1. In Italian Patent No. 1187301, filed on 27.11.85 in the name of the present applicant, there is described a laundry washer operable to recirculate the lye collected in a receptacle at the bottom of the laundering tub, returning the lye to the rotating drum so as to soak the laundry contained therein. In the course of the execution of the laundering cycle, the drum is adapted to be rotated at the centrifuging speed for short periodic intervals, in order to extract from the laundry a sufficient amount of the lye as required for the operation of the lye recirculation pump. During these periodic centrifuging intervals, the laundering tub contains not only water, but also detergent, by contrast to what happens during the conventional final spin-drying phase. When these periodic centrifuging intervals exceed a certain duration of for instance three seconds, the centrifuging operation may cause the formation of an excessive amount of foam in the landering tub, which may then escape from the machine, for instance by way of the detergent distributor. The invention described in the above cited patent conveys the teaching of eliminating the disadvantageous formation of an excessive amount of foam by the use of a novel level sensor or pressure switch and an associated circuit for deenergizing the electric motor rotating the drum to thereby interrupt the centrifuging period in response to lye and foam rising above a predetermined level in the course of the centrifuging period. As a result, the high-speed rotation of the drum occurring for determined periods in the course of a laundering phase comes to a halt as soon as the pressure within the laundering tub attains a determined limit value in response to a combination of parameters contributing to the formation of foam, amongst which in particular the dynamic pressure acting on the pressure switch as a result of the increased centrifuging speed of the rotating drum. This laundry washer has been found to be particularly advantageous, since it permit considerable savings of water, detergents and electric energy to be achieved. This laundry washer nevertheless still has a shortcoming which is noted not during the periodic centrifuging phases for the alimentation of the recirculating pump, but rather during the centrifuging phases and simultaneous discharge phases for discharging the liquid from the tub. When the novel pressure switch acts to stop the rotation of the drum in the course of one of these phases, the program control unit continues to run for controlling the selected cycle in the normal manner, so that the discharge pump is stopped after a certain time. During this normally very short interval there is not enough time for the pump to completely discharge all of the lye and foam remaining in the tub, so that these substances are then dissolved in the water of the subsequently charged rinsing bath. The disadvantageous effects of foam and lye remaining in the laundering tub also come about even in the case of normal operation of the discharge pump during the discharge phase, when there are external obstacles to the normal liquid flow due for instance to an excessive length and/or installation height of the discharge hose,, to a strong throttling effect thereof, to the discharge filter being obstructed, or to the fact that the mains voltage is insufficient for properly energizing the discharge pump, so that it is incapable of completely draining the laundering tub. From FR-A-1 212 447 an automatic laundry washer according to the precharacterising part of Claim 1 is known. Within the therein described automatic laundry washer, if the water flung out from the laundry during a spinning period is sufficient to raise the water level in the container above an empty mark, the respective spinning clutch will be disengaged and in addition the timer will be stopped until such time as the pump has had time to reduce the level again. Thereby it is ensured that the full period of spinning will be provided, not taking into account any periods during which the spinning clutch is de-energized. From US-A-4245310 a control unit for dishwashers and laundry washers is known in which a microprocessor monitors the drain operation in order to detect a drain system failure, a long drain situation indicative of partial drain blockage and a plugged drain situation. In the event of a long drain caused by a partial blockage of the drain, the cycle continues to operate but the user is notified that service is required. In the event of a major failure of the drain system, as when the diverter valve fails to operate or the drain is plugged, the micro processor terminates the cycle operation to prevent flooding or damage to the system. It is the object of the present invention to provide an automatic laundry washer with improved user information facilities. This object is solved by the subject matter of Claim 1. According to the present invention, the automatic laundry washer comprises automatic time measuring and comparing means for measuring the duration of at least one discharge interval during which a discharge pump is in operation and the program control unit and the motor are deactivated, and for comparing the measured interval to a predetermined time period stored in said automatic comparing means, and for generating externally perceivable signals when said measured time exceeds said predetermined time period. At least one externally perceivable signal is generated in response to the first discharge interval which exceeds the mentioned predetermined time period and this externally perceivable signal is cancelled in response to at least one subsequent discharge interval being shorter than a corresponding predetermined time period. The cancellation of said externally perceivable signal may occur only when the second discharge interval is shorter than the predetermined time period, irrespective of the characteristics of subsequent intervals. Further, a second externally perceivable signal may be generated, possibly by modifying the first signal, in response to at least one discharge interval which succeeds the above mentioned first discharge interval and which is of longer duration than the corresponding predetermined time period. The characteristics and advantages of the invention will become more clearly evident from the following description, given by way of a non-limiting example with reference to the accompanying drawings, wherein: fig. 1 shows the operation manner of a motor used for rotating the drum in a laundry washer according to the invention, in the first discharge phase after the laundering phase, and under conditions of reduced efficiency of the discharge components, fig. 2 shows the similar operating manner of a similar laundry washer, under the same conditions as above, but without the provisions of the invention, fig. 3 shows a diagram of a preferred embodiment of a control circuit for the program control unit of the laundry washer according to the invention, fig. 4 shows a diagrammatic illustration of determined critical levels and the arrangement of pressure switches in the laundry washer according to the invention, fig. 5 shows a block diagram of an electronic circuit in an improved modification, and fig. 6 shows a flow chart of the control operation performed by the circuit illustrated in fig. 5. The construction of the mechanical and hydraulic components of the laundry washer according to the invention is of a per se known type, for instance as described in the above quoted Patent No. 1187301, and is therefore not shown for the sake of simplicity. The functional characteristics of the laundry washer are likewise as generally known. The present invention is specifically applicable to the laundering tub emptying operation, particularly at the time between two successive phases of a laundering cycle. During one of these discharge phases the foam produced by the high-speed rotation of the drum is limited to a predetermined level L1 in the tub by the action of a pressure switch 11 operable to terminate the centrifuging phase by interrupting the power supply to the motor rotating the drum when the pressure in the tub attains a corresponding value. Subsequent to this instant, the operation of the discharge pump continues for a short period, during which rapid changes of the liquid level and the pressure within the tub give rise to a rapid sequence of high-speed rotation pulses of the drum. At the end of this period as measured by the timer, the laundering cycle proceeds in the normal manner as determined by the characteristics of the program control unit and the electric circuit. The actually employed programs provide that the operating time of the discharge pump is sufficient for completely emptying the laundering tub when the conditions of the charge, of the laundry washer in general and of the power supply are at the normal state, which is not, however, always the case, as indicated above. It is evident that the foam is not completely exhausted and discharged due to its consistency, which causes it to settle rather slowly and to collect at the bottom of the tub. In addition it is to be observed that the foam still contained in the laundry is retained therein, because even a sequence of short high-speed rotation periods, as described for instance in the above quoted Italian patent or in German Patent Application DE 3638498, will not always ensure that the laundering cycle is continued in the normal manner only after all of the foam has been discharged from the bottom of the tub, and also from the laundry. It can thus be generally stated that the presently known laundering cycles provide that the centrifuging phase is carried out in an intermittent manner under the control of the pressure switch, and is therefore dependent on the level of the lye contained in the tub. In any case the centrifuging phase is terminated in response to a specific signal supplied by the program control unit independently of the amount of foam still contained in the tub. According to the invention, and by way of contrast, there is provided a second level L2 for the control not only of the operation of the motor 7 for the high-speed rotation of the drum, but also of the operation of the motor 6 which controls the advance of the program control unit. By suitable calibration and positioning of pressure switch 4 this second level L2 is adjusted to be substantially lower than the first level L1, to which the above described pressure switch 11 is responsive, and lies preferably below the lower end of the tub, so that, when the liquid in the tub is higher than the second level L2, the pressure switch 4 acts to interrupt the high-speed rotation and the advance of the program control unit, while only the discharge pump remains in operation for a sufficient time to lower the liquid in the tub to below the second level L2. At this instant the pressure switch 4 acts to reinstall the power supply to the motor for high-speed rotation of the drum and to the program control unit, which results in the further appearance of liquid and foam, and a corresponding rise of the liquid level and the pressure. This causes the pressure switch 4 to act again in the above described manner, so that the described operations are cyclically repeated. It is evident that this permits the level to which the pressure switch 4 is responsive to be adjusted in such a way that the discharge pump is enabled to completely discharge all of the liquid contained in the tub in a short time, because the operation of the pump is not interrupted by the program control unit. It is also evident that this sequence of cyclical operations can be terminated at a determined instant; this instant can be determined in various manners, for instance after a certain number of high-speed rotation and discharge phases, or after the high-speed rotation has been going on for a certain time without intervention of the pressure switch 4. Shown in fig. 2 is a laboratory test recording of the operating characteristics of a typical domestic laundry washer without application of the present invention, during the centrifuging and discharge phase under conditions of an excessive amount of detergent or of hampered discharge operation. Indicated on the lefthand ordinate of the diagram is the rotational speed of the drum as a function of the time from the start of the discharge operation, while on the righthand ordinate there is indicated the total liquid volume (in litres) discharged at the end of the discharge phase. It is noted that the drum is rotated in successive pulses (P, Q, R, S) practically without any interval between one pulse and the next (the bases of the pulses are in fact contiguous). The overall time spent for the centrifuging operations substantially corresponds to the time measured by the program control unit due to the latter's continuous operation. In the example under consideration, this time continues to the instant at which the fourth pulse S is interrupted, i. e. 120 seconds. In the course of this period, the pressure switch 11 operates four times, at the instances designated 5, 6, 7 and 8. At each of these instances the actuation of the drum is interrupted and again reinstalled immediately thereafter by the subsequent reset pulse of the pressure switch 11. Fig. 1 represents the result of exactly the same kind of a test as described above, with the same laundry washer, under the same conditions, and in the same charging state. The only difference consists in that the present invention has been applied, in accordance for example with the diagram of fig. 3. The difference between the two diagrams of figs. 1 and 2 is fully evident, and its significance readily understandable to one skilled in the art, so that a more detailed explanation is scarcely required. It shall merely be pointed out that the intervals F, G, H and I between one pulse and the next one are representative of periods during which the discharge pump continues to operate while the high-speed rotation of the drum and the operation of the program control unit are interrupted, and that the overall duration of pulses A, B, C and D is equal to the overall duration of pulses P, Q, R and S in fig. 2, because in both cases the high-speed rotation pulses are determined in response to the actual lowering of the liquid contained in the laundering tub to below the second level L2. The result of all this is evident from the respective graphs, showing the discharged liquid volumes to amount to 15 litres in the case of fig. 1, and to about half this volume in the case of fig. 2. The invention thus provides in fact a laundry washer capable of automatically controlling the operating time of the discharge pump as a function of the amount of liquid actually contained in the laundering tub, and does thereby solve the problems arising from too short discharge periods with the resultant remaining of lye in the tub, and the inverse problem of excessively long discharge periods rigidly determined by the program control unit, resulting in useless prolongation of the operating cycle and premature wear of the motor rotating the drum and of the machine as a whole due to the unnecessary prolongation of the high-speed rotation periods. Fig. 3 shows only certain functional and control elements required for the understanding of the present invention. The laundry washer comprises a program control unit having a motor indicated at 6 and including for instance a timer with a number of cam discs adapted to rotate at different speeds for actuating respective electric contacts to control the combined operations of the various functional components. Prior to the initiation of a discharge phase following a laundering phase, pressure switch 11, which is also used as the foam-suppressing switch according to Italian Patent No. 1187301, is in the operative state shown in fig. 3, because the level of foam and lye in the laundering tub lies above the predetermined level L1. At this time the switch 8 controlling the power supply to the discharge pumpe 5 is open, and the switch 10 is closed, whereas the supplementary pressure switch 4 controlling the discharge operation is open, because the level L1 is considerably above the level L2 to which the pressure switch is responsive. For initiation of the discharge phase, the timer acts to close switch 8, causing discharge pump to be continuously energized, to open switch 9 so as to interrupt the power supply to drum motor 7 and timer motor 6, and to close switch 10 in preparation of the resumption of the power supply to motors 6 and 7 via pressure switch 4. After discharge pump 5 has discharged a sufficient amount of liquid for lowering the level to the value L2, pressure switch 4 operates to close the power supply circuit to motors 6 and 7 in cooperation with the already closed switch 10, causing motors 6 and 7 to rotate the drum and to advance the timer, respectively, until the high-speed rotation of the drum causes the liquid level to again rise above L2, whereupon pressure switch 4 again acts to interrupt the power supply to motors 6 and 7. These steps are repeated until the overall activation time of timer motor 6 equals the rated activation time of the timer. At this instant the timer is advanced by a step so as to resume the control of the subsequent phases of the programmed cycle. The described laundry washer may obviously modified in various manners within the purview of the invention. Motor 7 may for instance be of any type suitable for the given purpose, and the program control unit may be different from what has been described. The high-speed rotation period, or periods, may be interposed at any time during the operating cycle of the machine under the control of the program control unit. An additional advantage of the invention consists in that it now possible to timely and automatically inform the user of the progress of the discharge operation, based on the intervals between successive centrifuging phases in the course of a discharge operation. It is in fact evident that, when there is any malfunction or obstacle preventing the discharge system from efficiently discharging the liquid from the tub, e.g. a clogged filter, obstructed discharge hose or any of the other reasons discussed above, the automatic result is a corresponding prolongation of the time required for the discharge operation, and since according to the invention the discharge time includes the intervals between successive centrifuging phases, the observation of these times permits any irregular function of the discharge system to be immediately detected. A useful improvement of the present invention is therefore the provision of a system capable of automatically monitoring the discharge intervals between successive centrifuging pulses and of comparing the thus detected intervals to predetermined reference intervals. Laboratory tests carried out under widely different conditions simulating various causes for the reduction of the efficiency of the discharge system have shown, that amongst the numerous possibilities of comparison, the most significant of these comparisons are directed to the first and also to the last intervals between successive centrifuging pulses, for informing the user of the occurrence of problems, and of the kind of a problem, so as to permit him to take timely action. If in fact the first discharge intervals are unusually long, i.e. longer than a predetermined time T1, this may indicate the existence of difficulties with regard to various components or conditions affecting the discharge operation, or the fact that these components or conditions lie within the norm, and that the prolongation of the discharge intervals is due to abnormal conditions of a temporary nature which are going to disappear in the subsequent phases, for instance the formation of excessive amounts of foam. The measuring of the first discharge intervals can thus immediately inform the user that "something is wrong", although this information would have to be confirmed in the course of subsequent discharge phases. If finally the duration of the last discharge interval between centrifuging pulses is then compared to a predetermined reference time T2, which may be equal to or shorter than the first reference time T1, indicates the persistence of an abnormal condition, the previously given warning is confirmed to inform the user of a real and permanent cause. The techniques of measuring variable time intervals and comparing them to fixed reference times, and of the generation of a signal indicative of the result of such comparison are generally known in the art and need not be explained. What has been explained above with reference to the automatic indication of abnormal operating conditions during discharge phases can be realized in a particularly efficient manner by means of integrated electronic circuits as shown by way of example in fig. 5. In this figure, reference numeral 31 indicates an electric mains power supply, 32 is a rectifier or DC power supply, 33 is a single-chip ROM microprocessor, 35 and 36 are voltage attenuation and tuning resistors, 37 is a terminal for detecting the operating voltage of the discharge pump, 38 is a chopper for converting this voltage to a square waveform, LA1 and LA2 are two lamps or external signalling devices, and 39 and 40 are two amplifyers for energizing LA1 and LA2, respectively. The illustrated circuit functions in the following manner: The voltage supplied to the discharge pump is detected at 37 and applied to the input of chopper 38 operating to convert it to a square waveform signal of reduced voltage, which is then applied to input 34 of microprocessor 33. The latter detects the start of the pulsed signals oscillating at the mains frequency and starts to count the time from the instant of activation of the discharge pump. Depending on the program stored in microprocessor 33, and as a function of the counted time, the microprocessor activates and deactivates the two amplifyers 39 and 40, so that the associated external signalling devices LA1 and LA2 are correspondingly activated and deactivated. The function of microprocessor 33 is represented in fig. 6, wherein "Loop start zero crossing" represents the operation of a timer functioning at the mains frequency of 50 Hz. In this manner, every 20 ms the logic flow proceeds from "Loop start zero crossing" to ascertain whether the machine is disconnected from the electric mains supply, in which case LA1 and LA2 are deactivated and all of the other program variables are reset. As long as there has not been a "Power-up", and the machine has not previously been switched on, the program ensures that the pump is not activated. In the case that the pump has been activated, a count "Pump activated" is started, and when a pre-set time of for instance 3 minutes has been counted, the program proceeds to compare any given rinsing step to the final rinsing operation, in the present example the fourth such operation as indicated by the symbol 4 in the last box in fig. 6. When the duration of any rinsing operation save the fourth and last exceeds the maximum time T1 of three minutes, L1 is activated. And when the fourth and last rinsing operation exceeds this time, L2 is activated, preferably in an intermittent manner. The activations of LA1 and LA2 are mutually exclusive. The signalizations of LA1 (excessive amount of detergent) and of LA2 (for example, clogged filter) only disappear when the user stops the operation of the machine.

Claims: Autommatic laundry washer comprising a laundering tub housing a drum adapted to be rotated by an electric motor for the execution of at least one laundering operation during which the laundry is soaked with lye and the motor rotates at a slow speed, and at least one interval during which the motor rotates at a spin-drying speed, control means (4) adapted to detect the pressure within said laundering tub and to interrupt said high-speed rotation interval in response to said pressure exceeding a predetermined value (L2), a program control unit (6) operable to connect said motor to an electric power supply in accordance with a predetermined sequence, said control means (4) being operable to interrupt the operation of said program control unit (6) contemporaneously with the interruption of said high-speed rotation interval characterized by further comprising automatic time measuring and comparing means for measuring the duration of at least one discharge interval during which a discharge pump (5) is in operation and the program control unit and the motor are deactivated, and for comparing the measured interval to a predetermined time period stored in said automatic comparing means, and for generating externally perceivable signals when said measured time exceeds said predetermined time period, wherein at least one externally perceivable signal is generated in response to the first discharge interval which exceeds said predetermined time period, and cancelled in response to at least one subsequent discharge interval being shorter than a corresponding predetermined time period. Laundry washer according to Claim 1, characterized in that the cancellation of said externally perceivable signal occurs only when the second discharge interval is shorter than a predetermined time period, irrespective of the characteristics of subsequent intervals. Laundry washer according to any of Claims 1 or 2, characterized in that a second externally perceivable signal is generated, possibly by modifying the first signal, in response to at least one discharge interval succeeding said first discharge interval being of longer duration than the corresponding predetermined time period. Automatic laundry washer according to Claims 1, 2 or 3, characterized in that said control means (4) comprises at least one first pressure switch (4) connected in series with a motor of said program control unit (6) and provided with a normally closed electric contact (20) adapted to open in response to the pressure in said laundering tub exceeding said predetermined value (L2). Automatic laundry washer according to Claim 4, characterized in that said predetermined value (level L2) is established at the location of the discharge pipe (5) below the lower end of said tub. Laundry washer according to one of the preceding claims characterized by further comprising a control and external signalization circuit including means (37) for applying an operating voltage for said discharge pump to the input of a wave-former circuit (38) through a voltage reducer means (35, 36), means for applying the square wave formed voltage to the input (34) of an ROM microprocessor circuit (33), and means connecting the output terminals of said microprocessor circuit to the inputs of respective amplifiers (39, 40) operable to energize respective external signal generating means (LA1, LA2).

Inventors: BABUIN PIERO, CIMETTA SILVANO, RUSSO FERANDO, BABUIN, PIERO, CIMETTA, SILVANO, RUSSO, FERANDO
Applicants: ZANUSSI A SPA INDUSTRIE, INDUSTRIE ZANUSSI S.P.A.
Application year: 1990
Main classification: D06F35
IPC codes: D06F35, D06F33