Field of the invention

The present invention relates to a control circuit for actuating a door locking device for household appliances.

So-called locking devices for locking the door of a household appliance, typically a washing machine, which comprise a device for detecting a closing condition of a household appliance door, a device for locking and possibly unlocking the household appliance door and a device for detecting the locking condition of such a door, are known and commonly used in the field of household appliances.

The device for detecting the closing condition determines whether the household appliance door is closed.

The closing condition of the door causes the closing of a switch, so that the electronics of the machine can detect that the door is actually in the closing position.

The closing condition of the door is a precondition for the door to be locked.

The locking device of the household appliance door can be actuated in order to lock the closed door if the door is in the closing condition, and thus take it to a condition in which the door cannot be opened.

The fact that the door is locked in addition to being closed is detected by the detecting device of the locking condition.

The detecting device of the door closing condition thus provides a signal, which confirms that the door is closed. This signal transmits the fact that the door is closed and can thus be locked to a door locking control.

In turn, the detecting device of the door locking condition provides a signal, which confirms that the door is locked. This signal transmits the fact that the door can no longer be opened to the control electronics and that the household appliance can be actuated as a consequence.

Prior art

To date, the arrangement of a control which checks the closing condition of the door and allows to lock it, also detecting the locking condition of the door in order to prevent an actuation of the household appliance until such a locking condition of the door is detected, is the minimum requirement asked by household appliance safety standards.

Various solutions have thus been developed over the years to make devices which allow the mentioned dual function: to check closing with consequent possibility of actuating the lock and to check the correct locking condition.

As a representative example of the prior art, reference is made to prior patent EP1834027, which describes a device based on a three-wire circuit as innovative. According to EP1834027, the invention it describes relates to a door locking device which comprises the function of checking the closing of the door and of locking it as mentioned above, and is based on a circuit which comprises only three connecting contacts, according to the diagram shown in appended figure 1 , which reproduces figure 8 of patent EP1834027.

The same prior patent illustrates that the prior art, shown for example in figure 4, reproduced in figure 2 here, comprises examples of devices adapted to perform the same technical function described for the door lock which use no fewer than six connecting contacts to the control circuit of the household appliance.

The prior art shown in figure 3 (corresponding to figure 9 of patent EP1834027) relates instead to a known door locking device of the simpler type which thermoelectric actuators have three connecting contacts I, II and III, as shown in Figure 3. Unlike the ones considered here, these door locks do not have any device for determining whether the household appliance door is closed or not. Figure 3 diagrammatically shows an electric diagram for locking a door of known type with thermoelectric actuator, indicated as TA, in form of an actuator element indicated as PTC, and a device indicated as DV to detect a locking condition.

In order to obtain the locking of the door with electromagnetic actuator or thermomagnetic actuator, it was necessary to provide numerous connection devices on household appliance side, in particular three-contact connections on one side and six-contact connections on the other side, with this type of circuit. The three-contact connection shown in Figure 3 alone not being suitable to check the door closing condition and the door locking condition at the same time. The technical solution which is the object of patent EP1834027, based on the circuit shown in Figure 1 here, thus belongs to this prior art.

Such a solution includes the presence of a door contact switch 10, a locking contact switch 46 and an actuator 24, as electric switching diagram.

The door contact switch 10 and the actuator 24 are electrically connected in series between the connecting contact 20 and the second connecting contact 34.

In parallel to this switching in series, the locking contact switch 46 is connected between the first connecting contact 20 and the third connecting contact 56.

The door contact switch 10 is open until the door of the household appliance is closed.

Activation of the actuator 24 by supplying electric power through the first and the second connecting contacts 20 and 34 is therefore not possible.

The door contact switch 10 is closed if the household appliance door is closed. Thus, the first and the second connections 30 and 32 of the actuator are electrically connected to the first and the second connecting contacts 20 and 34. In this condition, the actuator 24 may by controlled by supplying energy by means of the first and the second connecting contacts 20 and 34, for example in form of pulse actuation.

The activation of the actuator 24 for locking the household appliance door causes a closing of the locking contact switch 46. This situation is indicated by a dashed line in the diagram in Figure 1 .

The closed locking contact switch 46 produces an electric connection between the first 20 and the third 56 connecting contacts in response to the locking.

An electric connection between the first and the third connecting contacts 20 and 56 confirms that the door is locked and that the household appliance may be started to the control electronics of the household appliance.

The first connecting contact 20 is generally connected to ground.

The second connecting contact 34 is generally connected with an electric connection to a household appliance control in order to be able to supply the control signals (e.g. pulse signals) to the actuator 34. The first connecting contact 56 is preferably connected to a connection of a household appliance which has a predetermined potential, different from ground. The current passes between the first and the second connecting contacts 20 and 56 if the locking contact switch 46 is closed. This passage of current confirms the locking condition of the household appliance.

Summary of the invention

It is the main task of the present invention to provide a simplified door locking device, based on a circuit which includes a reduced number of connecting contacts to the machine.

In particular, it is mentioned that devices with from 6 to 5 contacts came to replace devices with 3 contacts in the sector over the years by virtue of the range of products introduced on the market also by the applicant itself during the 1970s and 1980s.

It is the object of the present invention to provide a configuration of an operating circuit for a door locking device of the type adapted to detect the closing condition and the locking condition of a household appliance door which is characterized in that it has only two connecting contacts to the machine electronics.

The present invention thus belongs to a prior art of currently known solutions which include at least the presence of three connecting contacts of the actuating circuit of the door locking device to the control electronics of the household appliance offering a technical solution which allows to reduce the connecting contacts of the device to the electronics of the household appliance to only two. The advantages in terms of simplification of the device, and consequently of dimensions and production costs, are apparent.

It is sufficient to provide as reference indicator the fact that such door locking devices are required by the market for a total price lower than 1 Euro/piece to understand that any, however minor, simplification of the same can be highly appreciated from the production and market point of view in a perspective of containing production costs, and reflects also in containing the wiring costs needed aboard the machine for connecting the device. Furthermore, a device with only two contacts is more compact and thus less cumbersome in an assembly perspective of the household appliance.

This purpose and the other objects which will be more apparent following a detailed description of the present invention given here by means of illustrative, non-limitative example, are reached by a locking device of a household appliance door having a first and a second connecting contacts with the household appliance, the device comprising:

- a door closing switch, arranged on said first contact;

- an actuator, arranged electrically in series with said door closing switch; - a door locking switch, arranged electrically in series between said actuator and said second contact;

- a resistance, arranged between said actuator and said second connecting contact, and electrically in parallel to said door locking switch.

Brief description of the figures

Further features and advantages of the present invention will be more apparent in the following detailed description provided by way of non-limitative example and illustrated in the accompanying figures, in which:

figures from 1 to 3 show examples of door locking circuits of the known type of the prior art;

figure 4 shows an electric circuit of the locking device according to the present invention in an operating condition in which the door is open;

figure 5 shows the same diagram in figure 4 in an operating condition in which the door is closed but not locked;

figure 6 shows the same diagram in figure 5 in an operating condition in which the door is closed and locked.

Detailed description of the invention

With particular reference to figure 4, the device 1 according to the present invention comprises only two connecting contacts to the household appliance, in particular a first contact 10 and a second contact 20.

Following the electric circuit diagram shown in figure 4 starting from said first connecting contact indicated by 10, the device 1 comprises a closing switch 30 of the door and an actuator 40, arranged electrically in series with said closing switch 30 on said first contact.

Continuing to follow the circuit starting from the first contact 10, the device 1 according to the present invention further comprises a door locking switch 50 arranged electrically in series between said actuator and said second contact 20. The device 1 according to the present invention further comprises a resistance 60 arranged between said actuator 40 and said second connecting contact 20, said resistance 60 being arranged electrically in parallel to said door locking switch 50. In the described general diagram, said actuator 40 may preferably consist of a solenoid valve, and in such a case the device will be supplied with alternating current. Alternatively, said actuator 40 may consist of an element made of memory-shape material, e.g. a wire, and in such a case the actuator may be actuated by supplying the circuit with direct current.

With regards to the resistance 60, if the circuit includes a solenoid as actuator 40, said resistance may consist of a PTC, i.e. a ceramic element arranged to "protect" the solenoid, as known to a person skilled in the art.

If instead the circuit includes a memory-shape wire or other element as actuator 40, the PTC may not be provided and any electric resistance may be provided in its place.

The locking device described above operates as follows.

When the door of the household appliance is open, the circuit of the device 1 is in the configuration of figure 4, in which both switches, i.e. the door closing switch 30 and the door locking switch 50, are open.

In this configuration, the control electronics of the household appliance detects the open door condition deriving from the opening of the closing switch 30 at the terminals of the first 10 and of the second 20 connecting contacts.

When the user manually closes the door of the household appliance, the closing switch 30 is closed and the control electronics thus detects an electric resistance given by the sum of the resistances determined by the presence of the actuator 40 and of the resistance 60, as shown in figure 5, between the first 10 and the second 20 connecting contacts. At this point, the control electronics sends an electric signal capable of actuating the actuator 40 which closes the locking switch 50, as shown in figure 6.

The control electronics of the household appliance exclusively detects a difference of potential associated to the presence of the actuator 40 only at this point between the first 10 and the second connecting contacts 20 and can thus check the door closing and locking condition.

In order to obtain the opening of the locking switch 50 at the end of the operating cycle of the household appliance it is sufficient to provide a new pulse to the solenoid which, from the condition in figure 6, may reopen the locking switch 50 thus returning the circuit in the configuration in figure 5.

We have thus shown that the door locking device according to the present invention reaches the suggested purpose and objects.

In particular, we have shown that the door locking device according to the present invention allows to reduce the connecting contacts of the device itself to the household appliance to only two.

In addition to the apparent advantages in the overall dimensions of the device itself, this simpler, more compact configuration also provides considerable advantages in terms of cost-effectiveness deriving both from the lower production costs of the device itself and from the lower number of wires which need to be arranged in the household appliance.

Many changes may be made by a person skilled in the art without departing from the scope of protection of the present invention.

The scope of protection of the claims, therefore, must not be limited to the illustration or preferred embodiments described by way of example, but rather the claims must include all the features of patentable novelty inferable from the present invention, including all the features that would be treated as equivalent by a person skilled in the art.