PROGRAM CONTROL DEVICE FOR A LAUNDRY WASHING MACHINE

Abstract: A program control device for a laundry washing machine comprising a tub, a rotatable drum mounted in the tub and a liquid collecting receptacle communicating with lower and upper portions of the tub via a conduit and an electric recirculation pump (5). The device comprises two pressure switches (1, 2) adapted respectively to determine a minimum liquid level and a maximum liquid level in the tub irrespective of the amount and the liquid absorption capacity of the laundry contained in the drum to thereby permit the execution of "intense" and "gentle" laundry washing programs. The "intense" washing programs, in particular, may be executed by admitting reduced amount of liquid to the tub both for the washing operations proper and for the rinsing operations, with the resultant reduction of the liquid and electric power consumption of the machine.

Description: The invention relates to a program control device for a laundry washing machine of the type in which washing of the laundry is carried out by spraying a washing liquid onto the laundry. Described in Italian Patent Application 45725-A/84, filed on 20-11-84 by the present applicant, is a laundry washing machine of the type defined above, comprising a laundering tub, a drum for containing the laundry and mounted for rotation within the tub, and a washing liquid collecting receptacle disposed at a level below tub and communicating therewith, this collecting receptacle being designed to contain at least one filtering element, and electric heater element and a temperature sensor acting respectively to filter the washing liquid, to heat it, and to monitor its temperature. The collecting receptacle is connected to the discharge conduit of the machine via a conventional discharge pump, and to the laundering tub via an electric recirculation pump and a recirculation conduit. The machine under discussion is further provided with pressure switches of different settings for controlling the operation of the machine according to "intense" and "gentle" laundry washing programs at a normal washing liquid level in the tub and with the electric recirculation pump inoperative for the full duration of these programs, and according to "intense" laundry washing programs with a reduced washing liquid level in the tub and operation of the electric recirculation pump during determined periods in the course of these programs to thereby repeatedly recirculate the washing liquid from the collecting receptacle to the tub via the recirculation conduit, and to spray it directly onto the laundry. Thanks to the provision of such "intense" laundry washing programs with reduced liquid levels in the tub, the respective level being determined in response to the amount of laundry charged into the drum, the described laundry washing machine is capable of attaining noticeably reduced consumption of water, detergents and electric energy as compared to the respective consumption attainable with washing programs at normal liquid levels in the tub. The execution of these "intense" washing programs in followed by conventional rinsing stages during which the electric recirculation pump is inoperative and the tub is filled with a liquid to a substantially constant level irrespective of the absorption capacity and the amount of the laundry charged into the drum, this level being higher than the above mentioned reduced levels. Although in practice this liquid level is on the one hand adequate for efficiently rinsing delicate synthetic fabrics and/or woolens, it is on the other hand sometimes excessively high for efficiently rinsing fabrics made of cotton and/or synthetic fabrics resistant to high temperatures which could be efficiently rinsed with reduced quantities of liquid in the tub. It would be desirable, and is therefore an object of the present invention, to enable a laundry washing machine of the washing liquid recirculation type to carry out "intense" and "gentle" washing programs in the course of which the washing and rinsing operations can be carried out with optimized consumptions of water and electric energy of the machine, with the aid of a program control device composed of a reduced number of electric components as compared to the number of components in the program control device of the washing machine described above. In particular, these "intense" washing programs include the execution of washing and rinsing operations during which the amount of liquid admitted to the tub should be adequate to the amount of laundry contained in the drum, and to the liquid absorption capacity of the laundry. These and other objects are attained according to the invention by the provision of a program control device for a laundry washing machine comprising a tub, a drum mounted for rotation in the tub, and a liquid collecting receptacle communicating with lower and upper portions of the tub via a conduit and an electric recirculation pump, wherein said program control device comprises at least a first and a second pressure switch or similar level control element adjusted to respectively determine a minimum and a maximum liquid filling level in said tub irrespective of the amount and the liquid absorption capacity of the laundry contained in the drum. The program control device under consideration is characterized in that the electric recirculation pump is adapted in a first operative phase during the washing operation to be actuated via one of said first and second pressure switches in the "full" position, and by the intermediary of selector means, and in a second operation phase during the rinsing operations via a current supply circuit adapted to be closed by the operation of change-over switch means. The characteristics of the invention will become more clearly evident from the following description, given by way of example with reference to the accompanying drawing illustrating an electric circuit diagram of the program control device according to the invention. This program control device finds application in a laundry washing machine (not shown) provided with a washing liquid recirculation system of the type described in Italian Patent Application No. 45725-A/84, filed on 20-11-1984 by the present applicant. This washing machine comprises a tub, a drum mounted in the tub for rotation by means of a conventional electric motor, and a washing liquid collecting receptacle communicating with lower and upper portions via a conduit and an electric recirculation pump operable to repeatedly recirculate the washing liquid from the collecting receptacle to the tub during the various washing programs of the machine. The collecting receptacle is also provided with at least one heater element (not shown) and temperature monitoring means in the form for instance of a (likewise not shown) conventional thermostat sensor operable respectively to heat the washing liquid contained in the collecting receptacle und to monitor its temperature. The laundry washing machine under consideration is further provided with a program control device designed to permit the execution of "intense" and "gentle" washing programs with normal or reduced washing liquid filling levels in the tub, similar to the programs conventionally executed by a laundry washing machine of the type defined above. In the present case, however, the "intense" washing programs include the execution of a number of rinsing operations with operative sequences different from those of conventional programs, as will become evident from the following description. The program control device according to the invention as diagrammatically shown in the accompanying drawing comprises two pressure switches 1 and 2 or similar level control elements set respectively to determine a minimum and a maximum liquid filling level in the tub of the machine irrespective of the amount and liquid absorption capacity of the laundry charged into the drum. The device further includes a solenoid valve 3 for the admission of the liquid to the tub, a conventional discharge pump 4, an electric recirculation pump 5, a heater element 6, thermostatic control means 7 associated to a conventional "thermostop" device (not shown), and an electric motor 8 for rotating the drum. In particular, pressure switches 1 and 2 are provided with respective movable contacts 9 and 10 adapted to be selectively connected to a main current supply conductor 11 of the program control device via a movable contact 12 operable by a cam of the control device. Movable contact 12 is connected to main supply conductor 11 and operable to selectively engage one of two fixed contacts 13 and 14 connected respectively to movable contacts 9 and 10 of pressure switches 1 and 2, respectively. Movable contact 9 of pressure switch 1 is operable to engage a fixed contact 15 in the "empty" state of the tub, in which the latter is empty or filled to a level below the one to which pressure switch 1 is set, or a fixed contact 16 in the "full" state of the tub, in which the latter is filled at least to the level to which pressure switch 1 is set. Fixed contacts 15 and 16 of pressure switch 1 are on their part connected via respective conductors 17 and 18 to further movable contacts 19 and 20 associated to specific cams of the program control device and displaceable between two operative positions. In particular, movable contact 19 is operable to selectively close on solenoid valve 3 itself connected to the other main current supply conductor 21 of the program control device, or on an electric conductor 22 connected to a conventional electronic control unit 23 itself connected via further electric conductors 24 to electric motor 8 for controlling its operation at variable speeds of rotation and in opposite directions of rotation during execution of the various washing programs of the machine. Movable contact 20 on its part is adapted to close on a series circuit including heater element 6 and temperature control means 7 and connected to the other main conductor 21 mentioned above. Movable contact 10 of pressure switch 2 is operable to selectively close on fixed contacts 26 or 27 connected respectively to conductor 17 and to electric recirculation pump 5 itself connected between conductor 18 and main supply conductor 21. In particular, movable contact 10 is operable to close on fixed contact 26 in the "empty" state of the tub, in which the latter is empty or filled to a liquid level below that to which pressure switch 2 is set, or on fixed contact 27 in the "full" state of the tub, in which the latter is filled to the set maximum level. The present program control device additionally includes further movable contacts 28, 29, 30 and 31 each of which is associated to a respective cam of the program control device. In particular, movable contact 28 is connected to main supply conductor 11 and selectively operable to close a circuit including discharge pump 4 and connected to main conductor 21, or to close on a conductor 32 connected to solenoid valve 3. Movable contact 29 is likewise connected to main supply conductor 11 and operable to close on a conductor 33 for the energization of a motor 34 of the program control device, motor 34 being connected to the other main conductor 21 and operable to rotate the cams associated to the various movable contacts. Movable contact 30 is operable to close on a conductor 35 interconnected between conductors 18 and 33, while movable contact 31 is operable to selectively close on one of fixed contacts 36 or 37 themselves adapted to be connected to conductor 22 and electronic control unit 23 by means of a change-over switch 38 associated to a fast actuation cam of the program control device. Movable contact 31 and change-over switch 38 serve the purpose of determining the operation of motor 8 via electronic control unit 23 at two different frequencies, namely, in a rapid sequence by closing movable contact 31 and change-over switch 38 on conductor 37, and a slow sequence by closing movable contact 31 and change-over switch 38 on conductor 36. The present program control device permits the execution of "intense" and "gentle" washing programs to be described as follows: In particular, for the execution of "intense" washing programs for laundering cotton fabrics or high-temperature resistant synthetic fabrics, the tub is filled with liquid to a minimum level as determined by the setting of pressure switch 1 irrespective of the amount of laundry charged into the drum and its liquid absorption capacity. To the purpose of executing this program, the present program control device initially operates to close movable contact 12 on fixed contact 13 and movable contact 19 on solenoid valve 3, while all of the other movable contacts 20, 28, 29, 30, 31 remain in their open state. This operation results in the selection of pressure switch 1, the movable contact 9 of which is initially closed on fixed contact 15 in the "empty" state of the tub. The admission of liquid to the tub is thus initiated with recirculation pump 5, heater element 6 and motor 8 remaining in their deenergized state, until the tub is filled with the liquid up to the preset minimum level. At this time movable contact 9 is caused to close on fixed contact 16 for interrupting the admission of liquid to the tub by deenergizing solenoid valve 3, and for energizing recirculation pump 5. As a result the liquid is recirculated to the tub and sprayed onto the laundry to be progressively absorbed thereby, causing the level of the liquid to be gradually lowered to a level below that to which pressure switch 1 has been set, as a result of which movable contact 9 closes again on fixed contact 15, so that a further amount of the liquid is admitted to the tub. Thanks to this repeated switching of its movable contact 9 between its two operative positions, pressure switch 1 is thus capable of accurately metering the amount of liquid admitted to the tub, irrespective of the amount and liquid absorption capacity of the laundry charged into the drum, to thereby permit such "intense" washing programs to be executed with limited liquid consumption. After attaining the operative condition in which the laundry is completely saturated with the liquid, and movable contact 9 therefore remains closed on fixed contact 16 in the "full" position of pressure switch 1, so that recirculation pump 5 is maintained in its energized state, the program control device operates to close movable contact 20 for energizing heater element 6 and the associated temperatore sensor means 7, and to energize motor 8 through electronic control unit 23 by closing movable contact 29 on conductor 33 and movable contact 31 of change-over switch 38 on one of conductors 36 or 37. In this manner the laundry is efficiently laundered by heating the washing liquid to the temperature determined by the setting of thermostatic control means 7, recirculating the liquid to the tub and spraying it onto the laundry, and rotating the drum at predetermined intervals in opposite directions in a slow or fast sequence. During these operations motor 34 of the program control device remains continually energized for rotating the various cams of the device to thereby successively operate the movable contacts of the device in a sequence to be described in the following. On termination of the washing operation, the program control device operates to open movable contacts 20 and 31 as well as change-over switch 38, and to close movable contact 28 on solenoid valve 3 by way of conductor 32. This causes the heating of the washing liquid to be terminated and the rotation of the drum in alternating directions to be stopped, while recirculation pump 5 remains energized by pressure switch 1 in its "full" position. Under these conditions a further amount of cold liquid is admitted to the tub to thereby partially cool the still rather hot washing liquid and laundry for avoiding the formation of undesirable creases in the laundry before initiation of the successive rinsing operations. This cooling effect is accelerated by the recirculation of the hot and cold liquid to the tub by the opertion of recirculation pump 5, resulting in thorough mixing of the two liquid bodies and in the at least partial dilution of the lye contained in the laundry. This operation is carried out with a reduced energy consumption of the machine due to the fact that the motor for rotating the drum remains inoperative. The program control device subsequently operates to close movable contact 19 on electronic control unit 23 by way of conductor 22, and to close movable contact 28 on discharge pump 4. This causes the partially cooled washing liquid to be discharged from the tub. As soon as the liquid level in the tub has thus been lowered below the predetermined minimum level, movable contact 9 of pressure switch 1 closes on fixed contact 15 to thereby energise electronic control unit 23 for starting the operation of motor 8 at a higher spin-drying speed in a single direction and for intervals of short duration. This spin-drying operation is maintained for a sufficient duration to efficiently wring the laundry during the discharge phase, so that practically all of the liquid contained in the laundry is discharged from the machine prior to the subsequent rinsing operations. The program control device then operates to open movable contact 28 and to close movable contacts 19 and 30 on solenoid valve 3 and conductor 35, respectively, while retaining the remaining movable contacts in their previous operative positions. This causes the discharge operation to be terminated and further cold liquid to be admitted to the tub, with simultaneous operation of recirculation pump 5 thanks to the closed state of the two series-connected movable contacts 29 and 30, to thereby execute the rinsing operation. In this manner the liquid admitted to the tub is simultaneously recirculated and sprayed onto the laundry to be progressively absorbed thereby. When the liquid admitted in this manner attains the predetermined minimum level in the tub, movable contact 9 of pressure switch 1 closes on fixed contact 16, so that solenoid valve 3 is deenergized to thereby interrupt the admission of further liquid to the tub. During these operations recirculation pump 5 remains always energized, initially via the main current supply circuit, and subsequently via pressure switch 1 in its "full" position. As a result, the liquid recirculated to the tub continues to be absorbed by the laundry, causing the liquid level in the tub to be lowered to below the minimum level determined by the setting of pressure switch 1, whereupon movable contact 9 of pressure switch 1 again closes on fixed contact 15. Even during the operations for rinsing cotton fabrics and/or high-temperature resistant synthetic fabrics, the repeated switching of movable contact 9 between fixed contacts 15 and 16 of pressure switch 1 thus permits the amount of the liquid admitted to the drum to be accurately metered irrespective of the amount and liquid absorption capacity of the laundry contained in the drum. At the end of the liquid admission step of each rinsing operation, movable contact 9 of pressure switch 1 remains in the "full" position, while the program control device maintains the remaining movable contacts in their previous operative positions, with the exception of movable contact 31 of change-over switch 38, which is alternately closed on conductors 36 and 37 for causing the drum to be rotated at higher or lower speeds and in alternating directions. Each rinsing operation carried out in the above described manner is terminated by opening movable contact 30 and closing movable contacts 28 and 19 on discharge pump 4 and electronic control unit 23, respectively, so that the liquid is discharged from the tub while recirculation pump 5 remains inoperative to thereby avoid the undesirable continued soaking of the laundry. Subsequent switching of pressure switch 1 to its "empty" position then initiates the sequence of spin-drying steps of variable duration for accelerating the discharge of the liquid from the tub. With a given amount of liquid to be discharged from the tub, these spin-drying steps permit the time required for discharging the rinsing liquid from the drum to be noticeably reduced. The "gentle" washing programs for washing delicate synthetic fabrics and/or woolens are on their part executed with the same operative sequence as the "intense" washing programs described above by using in this case pressure switch 2 instead of pressure switch 1, to which purpose movable contact 12 is closed on fixed contact 14, while all of the other movable contacts of the program control device remain in the previously specified positions. After termination of these "gentle" washing programs proper, the required number of rinsing operations is executed with the maximum liquid level in the tub as determined by the setting of pressure switch 2 and required by the nature of the laundry contained in the drum. The operative sequence of these rinsing operations is the same as described above, except that the liquid is admitted to the drum in a single step, and not in successive steps, so that in this case it is not possible to accurately meter the amount of liquid admitted to the tub in compliance with the amount and the liquid absorption capacity of the laundry contained in the drum. The advantages obtainable by the program control device according to the invention are thus evident from the above. This device does in fact permit the efficient execution of "intense" and "gentle" laundry washing programs with the lowest possible water consumption due to the provision, in the case of "intense" washing programs, of washing and rinsing operations in which the amount of water admitted to the tub is accurately metered with regard to the amount and liquid absorption capacity of the laundry charged into the drum. Thanks to the reduction of the amounts of water admitted to the tub during the rinsing operations, the duration of these rinsing operations is reduced, as is the power required for rotating the drum, resulting in a corresponding reduction of the electric power consumption of the machine. The described program control device is finally composed of a smaller number of electric components as compared to known program control devices for washing machines. The device additionally permits rapid cooling of the washing liquid on termination of the washing operation and before the initiation of the rinsing operations as required for safety reasons.

Claims: 1. A program control device for a laundry washing machine comprising a tub, a rotatable drum mounted in said tub, and a liquid collecting receptacle communicating with lower and upper portions of said tub via a conduit and an electric recirculation pump, said device comprising at least a first and a second pressure switch or similar level control means set respectively to determine a minimum liquid admission level and a maximum liquid admission level in said tub irrespective of the amount and liquid absorption capacity of the laundry charged into said drum, characterized in that during a first operative phase during the washing operation, said electric recirculation pump (5) is energized via one of said first and second pressure switches (1, 2) in its "full" position by the operation of selector means (12), and in a second operative phase via a current supply circuit adapted to be closed by the operation of selectively operable switch means (29, 30). 2. A program control device according to claim 1, characterized in that selector means comprises a movable contact (12) of the device adapted to selectively close on respective movable contacts (9, 10) of said first and second pressure switches (1,2), and said selectively operable switch means comprise further movable contacts (29,30) of the device connected in series with one another and with said electric recirculation pump (5). 3. A program control device according to the preceding claims, for a laundry washing machine additionally comprising at least a liquid admission solenoid valve and a pump for the discharge of liquid from said tub, characterized in that said solenoid valve (3) and said discharge pump (8) are adapted to be selectively connected to the electric power supply of the program control device via a change-over switch means (28) of the device. 4. A program control device according to claim 3, characterized in that there is provided further change-over switch means (19) connected to the respective movable contact (9, 10) of said first and/or second pressure switch (1, 2) in the "empty" position thereof, and adapted to be selectively connected to said solenoid valve (3) or to said motor (8).

Inventors: FRUCCO, GIUSEPPE, SACCONATO, EMANUELE
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1988
Main classification: D06F33
IPC codes: D06F33, D06F39