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

Abstract: A door locking means for washing or drying machines for laundry, com­ prising an electromechanical actuator (5) associated with a pin (6) inter­ acting with the lock (7) of the door to lock or unlock it, and comprising an electric contact (31) connected within the electric circuit of the elec­ tromechanical actuator (5) and adapted to feed or deenergize the latter. The locking means also comprises a plurality of electronic compara­ tors (1, 2, 3) provided respectively with first inputs (8, 9, 10) and with second inputs (14, 15, 16) adapted to be fed with voltages respectively proportional to the effective values and to predetermined reference values of characteristic quantities of the machine (temperature, washing bath level and rotating speed of the drum). In accordance with the comparison between the voltages, the comparators (1, 2, 3) thus control a logical NOR gate (4) connected thereafter, which in turn effects the opening or closing of the electric contact (31) and thus the unlocking or locking of the door of the machine via a transistor (26) and an electromagnet (29) or similar elements. The locking means in question thus allows the door to be opened during or after each cycle of the machine in states that are safe for the user.

Description: The present invention relates to a door locking means for a washing or drying machine for laundry, that is adapted to permit opening of the locked door at the end of, or during, each selected washing or drying cycle in accordance with the attainment of predetermined safe operating conditions within the machine. Current washing 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 or drying cycle selected, thereby preventing the door from being opened accidentally during the run of the cycle, which could harm 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 f.e. from the documents DE 2029941 and DE 2163449 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 acitvated 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 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. This delay time can be relatively long (in the range of about 30 to 50 seconds), particularly when the drum of the washing machine is loaded with considerable amounts of laundry and is driven at high spinning speeds, so that it requires a longer period of time to stop after the end of the last spinning phase of the cycle. In such cases, rather long delay times are annoying for the user, who could moreover erroneously activate the lock of the door of the machine before the end of these times, thereby possibly breaking the lock or the door in question. Furthermore, if one must open the door of the machine during the run of the particular cycle and before the end thereof, for example to be able to introduce laundry into the drum or withdraw it therefrom, when the door would be unlocked by the action of the delay element only at the end of the specified delay time, when the drum has practically stopped, the conventional locking means would nevertheless ensure the opening of the door independently of the temperature states and the washing bath level present within the machine. Consequently, these locking means are not capable of checking the temperature states and the washing bath level present within the machine and thus guaranteeing effective safety of the machine by preventing the door from being opened when these temperatures and levels could cause situations dangerous for the persons (scalding, etc.) and harmful for the surroundings (overflowing, etc.). It would thus be favorable, and is the object of the present invention, to eliminate the stated disadvantages by using a door locking means for washing or drying machines for laundry that is realized in such a way as to guarantee the opening of the door in question in states of absolute safety during or after the run of the particular washing or drying cycle selected in the machine. This locking means is in particular designed to measure the states of the temperature and washing bath levels within the machine and to allow the lock of the machine door to be unlocked, and thus the door to be opened, only when the levels are below predetermined minimum values, so as to ensure effective safety for the user. The locking means in question is realized with the features substantially described with reference to the claims of the present patent. The invention will be better understood from the following description intended only as a nonrestrictive example and with reference to the single adjoined figure showing the block diagram of the present locking means. Referring to this figure, which schematically shows the door locking means for washing or drying machines for laundry, adapted to keep the door locked during the run of the particular washing or drying cycle selected in order to prevent harm to the user in contact with the internal parts at elevated temperature or with the rotating drum, one can see that this means substantially comprises three electronic comparators 1, 2, 3 of the conventional type, a logical NOR gate 4 connected operatively following the comparators in the way and for the purposes as described below, and an electromechanical actuator 5 to be activated by NOR gate 4 and associated with a pin 6 interacting with lock 7 of the machine door to keep the door (when it is closed) in the locked position, or release it. Electronic comparators 1, 2, 3 are in particular respectively provided to perform a comparison between the effective value and a predetermined reference value of the temperature and the load level of the washing bath within the tank of the washing machine, and of the rotating speed of the drum of the machine, and are also provided to effect the locking or unlocking of lock 7 of the door in accordance with the result of this comparison. For this purpose, comparators 1, 2, 3 are provided respectively with first inputs 8, 9, 10 which are subjected to voltages proportional to the effective values of the quantities to be controlled, via respective measuring transducers 11, 12, 13 of the conventional type connected to respective probes (not shown) provided within the machine to detect the quantities, and with respective second inputs 14, 15, 16 which are subjected to reference voltages of predetermined fixed values proportional to the final values to be obtained for the particular quantities to be controlled and selected in such a way as to attain safe operating states in the machine. Merely by way of example, the values of the reference voltages of inputs 14, 15, 16 of corresponding comparators 1, 2, 3 are selected to effect, respectively, a maximum temperature of 40°C and a washing bath level in the tank that is lower than the edge of the access opening of the machine, so that the door can be opened without any danger of the user being burned and the washing bath overflowing to the outside, and a maximum rotating speed of the drum of 53 rpm, this drum rotating speed not being dangerous for the user. This drum rotating speed can in particular be advantageously obtained by measuring the voltage generated by a tacho generator connected to the electric motor of the machine, this voltage therefore being proportional to the speed of the motor. Finally, comparators 1, 2, 3 are provided respectively with outputs 17, 18, 19 connected with corresponding inputs 20, 21, 22 of logical NOR gate 4, while logical NOR gate 4 is provided with an output 23 connected via a limiting resistor 24 with base 25 of a transistor 26 having emitter 27 connected to ground and collector 28 connected with d.c. voltage Vcc of predetermined value, via an electromagnet 29 disposed in parallel with a diode 30. In its turn, electromagnet 29 interacts with an electric contact 31 of the normally closed type that is connected within the electric circuit of the machine, in series with electromechanical actuator 5 (which may consist of a bimetallic element, a relay or a similar element), and is influenced by the logical level of output 23 of NOR gate 4 in such a way that it is excited only in the presence of logical level 1 in output 23, in the state in which the predetermined values of temperature, washing bath level and drum rotating speed have been reached, thereby effecting the opening of electric contact 31 and thus allowing the door to be unlocked and opened. The functioning of the inventive locking means is thus evident. As soon as the particular washing cycle of the washing machine has been selected and started, in which state the voltages generated via measuring transducers 11, 12, 13 and applied to first inputs 8, 9, 10 of comparators 1, 2, 3, said voltages corresponding to the effective values measured for temperature, washing bath level in the tank and drum rotating speed, are lower than the predetermined reference voltages applied to second inputs 14, 15, 16 of the comparators, comparator outputs 17, 18, 19 and corresponding inputs 20, 21, 22 of logical NOR gate 4 assume logical level 1. Consequently, output 23 of NOR gate 4 assumes logical level 0, thereby keeping transistor 26 inhibited and electromagnet 29 deenergized, which therefore keeps electric contact 31 closed and thus electromechanical actuator 5 fed. In these states the latter keeps pin 6 in the position blocking lock 7 of the machine door, thus preventing any accidental opening of the door. Subsequently, during the run of the selected cycle and in the operational states of the machine, in which the effective values of temperature, washing bath level and drum rotating speed are usually higher than the predetermined reference values, and the corresponding voltages applied to inputs 8, 9, 10 of comparators 1, 2, 3 are also higher than the predetermined reference values applied to the other comparator inputs 14, 15, 16, the comparators in question and logical NOR gate 4 always remain at the aforesaid logical level, so that the NOR gate always keeps electric contact 31 closed and thus the machine door locked. To allow the machine door to be opened at the end of the washing cycle or during the run thereof when it is necessary e.g. to introduce laundry into the drum or extract it therefrom, the present locking means permits this operation only if all the values of temperature, washing bath level and drum rotating speed have reached the predetermined reference values, even in different time periods. Thus, as long as at least one of the quantities in question has a value higher than the predetermined reference value, in which case the corresponding input of NOR gate 4 remains at logical level 1, output 23 of the NOR gate also remains at logical level 0, thereby keeping electric contact 31 constantly closed and thus the machine door locked. Conversely, as soon as all the specified quantities have reached the predetermined reference values, even in different time periods - upon cooling, emptying of the washing bath in the tank and slowing or stopping of the drum rotating speed -, when it is possible to approach the door and all internal parts of the machine safely, all outputs 17, 18, 19 of comparators 1, 2, 3 and thus also all corresponding inputs 20, 21, 22 of NOR gate 4 assume logical level 0. Consequently, output 23 of the NOR gate is switched to logical level 1, switching on transistor 26 which feeds electromagnet 29 with voltage Vcc, which in turn effects the opening of electric contact 31 and thus the switch-off of electromechanical actuator 5. In these states, the latter allows the return of pin 6 to the unlocked position, thus permitting the activation of lock 7 and the opening of the machine door. The present locking means is equally suitable for installation in drying machines for laundry. In this case one provides only electronic comparators 1 and 3 for controlling the temperature of the drying air and the drum rotating speed, eliminates comparator 2 in view of the lack of a washing bath inside the drum of the machine, and connects these comparators with the electric components of the circuit which are identical to those described. Likewise, according to the invention it is also possible to replace the electric components (limiting resistor 24, transistor 26, electromagnet 29, diode 30) provided for controlling electromechanical actuator 5 by other electric components of different types known per se and performing the same function. It is also possible to combine all the measuring transducers, the comparators and the logical NOR gate in a microprocessor 32 of the conventional type (shown by hatching), which is connected with the measuring probes for the various quantities as well as with the electromechanical actuator and with the electric components for driving the latter, without going beyond the scope of protection of the present invention.

Claims: A door locking means for washing or drying machines for laundry, comprising a rotating drum, at least one electromechanical actuator (5) associated with a pin (6) interacting with the lock (7) of the door and connected with at least one electric contact (31), the electromechanical actuator (5) locking and unlocking the door when the electric contact (31) is closed or open, respectively, characterized in that it comprises comparator means (1, 2, 3) comparing the measured effective values and predetermined reference values of characteristics quantities of the machine, such as the temperature and the load level of the washing bath as well as the rotating speed of said drum, and control means (4, 26, 29, 30) connected with the comparator means (1, 2, 3) and closing or opening the electric contact (31) in accordance with the results of the comparison. The locking means according to claim 1, characterized in that the comparator means comprise a plurality of electronic comparators (1, 2, 3) provided respectively with first inputs (8, 9, 10) and with second inputs (14, 15, 16) and with outputs (17, 18, 19), the first (8, 9, 10) and second (14, 15, 16) inputs being fed respectively with voltages proportional to the effective values of the particular quantity to be controlled, via corresponding measuring transducers (11, 12, 13) and with voltages proportional to the predetermined reference values of the quantities. The locking means according to claim 2, characterized in that the control means comprise at least one logical NOR gate (4) provided with a plurality of inputs (20, 21, 22) connected with the corresponding outputs (17, 18, 19) of the comparators (1, 2, 3) and with an output (23) connected, via at least one transistor (26) or similar control element, with at least one electromagnet (29) disposed in parallel with a diode (30) and interacting with the electric contact (31) in such a way as to open it only when all the voltages respectively applied to the first (8, 9, 10) and second (14, 15, 16) inputs of the comparators (1, 2, 3) are equal to one another.

Inventors: FRUCCO, GIUSEPPE
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1990
Main classification: D06F37
IPC codes: D06F37