A DOOR LOCKING MEANS FOR A WASHING AND/OR DRYING MACHINE FOR LAUNDRY

Abstract: A door locking means for a washing and/or drying machine for laundry, adapted to keep the door locked during the washing or drying cycle se­ lected and to unlock the door after the end of the cycle or if the door is prematurely opened during the washing or drying cycle. The means comprises a bimetallic element (5) associated both with a pin (12) interacting with the lock (13) of the door, and with an electric contact (8) connected before the general switch (4) of the machine and adapted to be closed on a conventional-type optical or acoustic warning means (11) adapted to signal the locked or unlocked state of the door. The bimetallic element (5) is furthermore provided with an electric contact (1) adapted to be closed on the electric components of the ma­ chine and to be activated by the element simultaneously with the other electric contact (8). In this way the warning means (11) is switched on and off when the contact (7) of the bimetallic element (5) is closed and open, respectively, in the particular locked or unlocked state of the door, thereby preventing any incorrect activation of the door.

Description: The present invention relates to a door locking means for a washing and/or drying machine for laundry, that is adapted to signal to the user the locked door state when the machine is in operation or out of operation. Current washing and/or drying machines for laundry are provided with a door locking means adapted to keep the door locked for the entire duration of the washing and/or drying cycle selected, thereby preventing the door from being opened accidentally during the run of the cycle, which could damage the user due to the elevated temperature within the machine and/or the rotation of the drum. Door locking means of various kinds are known which comprise an electromechanical actuator, such as a bimetallic element, a relay or a similar element, subject to the programmer-timer of the machine and provided with a pin interacting with the lock of the door, said actuator being adapted to be driven into two different operating positions by said programmer-timer, namely a first position in which the actuator is idle and moves the pin into a position of rest in which the latter does not interfere with the lock of the door, thereby allowing the door to be opened or closed, and a second position in which the actuator is activated and moves the pin into a working position in which the latter interferes with the lock, thereby preventing the door from being moved. Such locking means furthermore comprise a conventional delay element associated with the electromechanical actuator and calibrated to activate the latter after a predetermined delay time following the end of the last spinning and/or drying phase of the selected cycle, allowing the door of the machine to be opened when the drum has stopped and therefore eliminating any danger of injury for the user in contact with the drum. In particular, the operating states in which the door is locked or unlocked are signaled by means of a suitable warning means of the optical type (e.g. a warning light) or the acoustic type (e.g. a buzzer) connected with the electromechanical actuator within the electric circuit of the locking means, the warning means being adapted to be switched on and off by the general switch or by that of the programmer-timer of the machine when the door is locked and unlocked respectively. The locking means of this design, although they operate reliably and ensure efficient signaling of the locked or unlocked door states during the run of the washing and/or drying cycles selected, are not capable of correctly signaling such states in cases in which the user interrupts the cycle before the end of the cycle, for example to be able to introduce laundry into the drum or withdraw it therefrom. During this operation, which is performed by opening the general switch or that of the programmer-timer of the machine the door is still locked by the action of the aforesaid delay element, whereas the warning means is switched off and thus provides a false signal for the operating state of the door. In this state the door can be opened incorrectly by the user, resulting in the possibility of damage to the lock and/or the door. A control circuit for a washing machine is disclosed in the publication DE-A-30 03 895. In particulary it contains a microprocessor controlling the rotation number of the motor. The signals given by the microprocessor are also used for the drive of a door-closing mechanism which protects the operator during the washing procedure. Document GB-A-2 128 283 is concerned with a safety locking device for delate opening of a washing machine which uses a heated bimetal-contact driving the opening mechanism. The invention is based on the problem of eliminating the above mentioned disadvantage by using a locking means adapted to signal the operating state of the door correctly, even in the case of any interruptions of the washing and/or drying cycle for the reasons specified above. This locking means is realized with the constructional features substantially described in the adjoined claims of this patent. The invention will be better understood from the following description intended solely as a nonrestrictive example, with reference to the single adjoined figure showing the block diagram of the present locking means. Referring to this figure it shows the electric circuit components of a means for locking the door of a washing and/or drying machine for laundry, adapted to prevent the door from being opened during the run of each washing and/or drying cycle selected in order to avoid injury to the user due to the elevated temperature within the machine and/or the rotation of the drum of the machine. This locking means comprises substantially a conventional programmer-timer 1 for controlling the switch-on and switch-off of the various electric components (not shown) of the machine during the run of the washing and/or drying cycle, said programmer-timer 1 being connected in parallel with main conductors 2 and 3 of the electric circuit of the machine, which are in turn fed by the electric mains via general switch 4 of the machine. The means in question also comprises a conventional bimetallic element 5 associated with a positive temperature coefficient resistor (PTC) and connected before programmer-timer 1 and disposed in parallel to main conductors 2 and 3, via an electric contact 6 adapted to be activated by said programmer-timer, said bimetallic element being provided with an electric contact 7 of the normally open type, whose closing (when the PTC is fed) effects the feeding of all the electric components of the machine, and whose opening, which takes place when the PTC is deenergized, occurs after a predetermined delay time, due to the inertia of the bimetallic element. Bimetallic element 5 is furthermore associated both with an electric contact 8 of the normally open type, adapted to be activated simultaneously with the other contact 7 and connected in parallel between main feed conductors 9 and 10, before general switch 4, and to be closed on a suitable warning means such as a warning light 11, an acoustic buzzer or the like situated in the control panel of the machine, and with a pin 12 interacting with lock 13 of the door so as to allow for the latter to be opened or closed when the PTC is deenergized, and to prevent the door from being opened from its closed position when the PTC is alive. The functioning of the present locking means is thus evident. As soon as the desired washing or drying cycle has been selected in accordance with the type and quantity of laundry to be washed or dried by putting programmer-timer 1 in the particular selection position and closing general switch 4, said programmer-timer closes electric contact 6 on the PTC of bimetallic element 5, thereby causing rapid heating and thermal deformation of the element, which closes electric contacts 7 and 8 and moves pin 12 into a position so as to prevent the activation of lock 13 and thus the opening of the door of the machine. Consequently, programmer-timer 1 controls the various electric components of the machine and thus the run of the washing or drying cycle selected due to the closing of electric contact 7, this state being signaled by the lighting up of warning light 11 due to the closing of electric contact 8. As soon as this washing or drying cycle is finished, programmer-timer 1 opens electric contact 6, in which state the PTC of bimetallic element 5 is deenergized and keeps both electric contacts 7 and 8 temporarily closed, and pin 12 in a position so as to lock the door assuming that the predetermined delay time for the opening of contact 7 is not yet past. Consequently, warning light 11 also remains temporarily switched on, thus signaling this state in which the door is temporarily locked, and preventing the user from erroneously activating the lock of the door and possibly damaging the lock and/or the door. Conversely, after the delay time is past during which the PTC of bimetallic element 5 has partially cooled so as to effect the return of electric contact 7 of the element to the initial rest position (open), bimetallic element 5 simultaneously moves also electric contact 8 into the open position, thereby turning off warning light 11 and returning pin 12 to the position in which the door is unlocked, thus signaling this unlocked door state to the user and the possibility of opening the door. Analogously, if it is necessary to open the door during the run of the washing or drying cycle and before the end thereof, for example to be able to introduce laundry into the drum or remove it therefrom, the locking means according to the invention also makes it possible to signal to the user the exact locked or unlocked state of the door of the machine, so as to obtain the same advantages as described above. In this case the washing or drying cycle is momentarily stopped by opening general switch 4 or the (push-pull) switch associated with programmer-timer 1 of the machine and in this state warning light 11 remains temporarily switched on, in the ways described, as long as the door is still locked. As soon as the door is unlocked the warning light is immediately switched off by the opening of electric contact 8, thus signaling this state to the user.

Claims: A door locking means for a washing and/or drying machine for laundry, comprising a programmer-timer (1) which is fed by the electric mains via at least one general switch (4) an controlling the switch-on and switch-off of the various electric components of the machine, and also comprising at least one bimetallic element (5) associated with a conventional PTC and connected with the programmer-timer and being switched on and off via a contact (6) of the programmer-timer (1), the bimetallic element (5) being provided with at least one electric contact (7) which is closed on the electric components when the PTC of the bimetallic element (5) is switched on, and is opened when the PTC of the bimetallic element (5) is deenergized, with a predetermined delay time due to the inertia of the bimetallic element (5), the bimetallic element (5) being also associated with a pin (12) interacting with the lock (13) of the door so as to lock and unlock the door when the electric contact of the bimetallic element is closed and open, respectively, the locking means also comprising at least one conventional-type optical or acoustic warning means (11) to signal the locked or unlocked state of the door, characterized in that the bimetallic element (5) is also associated with at least one further electric contact (8) connected before the general switch (4) and being closed on the warning means (11), the further electric contact (8) being activated by the bimetallic element (5) simultaneously with the electric contact (7) of the element. The locking means of claim 1, characterized in that the electric contact (7) of the bimetallic element (5) and the further electric contact (8) are of the normally open type.

Inventors: MORI, MAURIZIO
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1990
Main classification: D06F37
IPC codes: E05B47, D06F37