TEXT OF THE DESCRIPTION

Technical field.

The present invention relates to a door-lock for household appliances, such as washing machines, dryers, washer-dryer machines and the like.

Description of the prior art

A door-lock for household appliances typically includes :

- a housing having an opening for the insertion of a hook carried by the door of the appliance,

- a cam rotatable relative to the housing about an axis of rotation between a retaining position and a release position, wherein in the retaining position the cam is adapted to lock the hook in a closed-door position,

- a locking slider cooperating with the cam and movable between a release position and a locking position, wherein in the release position the cam is free to rotate around said axis of rotation and wherein in the locking position the slider locks the cam in the retaining position, and

- an actuator including a locking pin adapted to lock the locking slider in the locking position.

The locking slider may have a linear movement, as disclosed, for instance, in WO2013181289, or a rotating movement as disclosed in DE 20 2015 100 627.

When the load of laundry inside the machine is compressed, a high force pushes the door of the machine towards the outside. This force is transferred to the locking pin of the actuator. A high load acting on the appliance door requires a great force to move the locking pin from the locked position to the unlocked position.

One drawback of the prior art solutions is that the arrangement and interaction of the components of the door- lock does not reduce the hook force enough to enable unlocking of door lock mechanism in some circumstances, for instance when the laundry acts on the door with relatively high force (e.g. more than 250 N) at the end of a washing cycle.

Also, the arrangement of parts of the locking mechanisms in prior art door-locks is such that the locking pin (moved by the actuator, e.g. a solenoid) moves perpendicularly to the main slider, whose position depends on the position of the appliance door. In such arrangements, there is friction where the pin and the main slider are in mechanical contact, therefore significant force is needed to move pin from the locking position to the unlocking position.

If, in certain circumstances, the actuator of the locking mechanism is unable to move the locking pin toward the unlocking position, the door remains locked and the user cannot remove the load from the machine. This situation may require a service call to unlock the door-lock and open the door.

Object and summary

The object of the present invention is to provide a door-lock for household appliances which can overcome these drawbacks .

According to the present invention, this object is achieved by a door-lock having the characteristics forming the subject of Claim 1.

The claims form an integral part of the teaching provided in relation to the invention.

Brief description of the drawings

Characteristics and advantages of the present invention will become clear in the course of the detailed description which follows, given purely by way of non-limiting example, with reference to the accompanying drawings, in which:

- Figure 1 is an exploded perspective view of a door- lock according to the present invention with some components removed for better clarity,

- Figure 2 is a perspective view of some parts of the door-lock indicated by the arrow II in Figure 1,

- Figure 3 is a plan view according to the arrow III of

Figure 2,

- Figure 4 is a partially sectioned perspective view according to the arrows IV of Figure 3,

- Figure 5 is an exploded perspective view of a door- lock with some components removed, and

- Figures 6 and 7 are plan views of the part indicated by the arrow VI in figure 5 in a locked and unlocked position, respectively.

It will be appreciated that, for clarity and simplicity of illustration, the various Figures may not be drawn to the same scale .

Detailed description

With reference to Figures 1 and 5, numeral 10 indicates a door-lock for household appliances according to the present invention. The door-lock 10 comprises a locking unit 12 and an electrical control unit 14. The locking unit 12 and the electric control unit 14 may be two independent units separated from one another. The locking unit 12 and the electric control unit 14 comprise respective housings 16, 18 having respective covers 16', 18'. Alternatively, the locking unit 12 and the electric control unit 14 may be integrated in a single housing.

With reference to Figures 1-4 the locking unit 12 comprises a cam 20 rotatable relative to the housing 16 about a first axis A. The cam 20 is rotatable about the first axis A between a retaining position and a release position. The cam 20 is associated to a spring 42 having a bi-stable function. The spring 42 cooperates with the cam 20 through a transmission mechanism which will be described in the following. When the door of appliance is in the open position the spring 42 pushes the cam 20 to the release position. When the door of appliance is closed, the spring 42 pushes the cam 20 to the retaining position.

The cam 20 has a hooking portion 22 which is intended to engage a hook 24 (schematically represented by a cylindrical pin) carried by a door (not shown) of a household appliance . In operation, during the closing of the door the hook 24 penetrates inside the housing 16 through an opening of the housing 16 and engages the cam 20 when it is in the release position. When the door is closed the hook 24 rotates the cam 20 around the first axis A from the release position toward the retention position and after a rotation of the cam 20 of a certain angle the spring 42 pushes the cam 20 with the hook 24 engaged therein to the retaining position.

The locking unit 12 of the door-lock 10 comprises an auxiliary slider 26 which is movable relative to the housing 16 along a first linear direction B orthogonal to the first axis A. The auxiliary slider 26 has a face 28 which abuts against a back portion of the cam 20. The back portion of the cam 20 may have a roller 30 against which abuts the face 28 of the auxiliary slider 26. The roller 30 is rotatable on a pin 32 having an axis M parallel to the first axis A.

The locking unit 12 of the door-lock 10 comprises a lever 34 rotatable relative to the housing 16 about a second axis C orthogonal to the first axis A. The lever 34 has a first end 36 and a second end 38, located on opposite sides with respect to the second axis C. The first end 36 of the lever 34 is pressed elastically against the auxiliary slider 26.

The locking unit 12 comprises a main slider 40 which is movable relative to the housing 16 along a second liner direction D, in a first direction D' and a second direction D". As shown in Figure 4, the spring 42 is set between the main slider 40 and the housing 16 and biases elastically the main slider 40 in the first direction D' . The spring 42 pushes the main slider 40 in abutment against the second end 38 of the lever 34. The main slider 40 is connected to the cam 20 through the lever 34 and the auxiliary slider 26. Therefore, the position of the main slider 40 along the second linear direction D" is directly connected to the position of the cam 20 about the first axis A. When the cam 20 is in the retaining position (closed-door position) the main slider 40 is in a locking position.

The locking unit 12 comprises a locking pin 44 for locking the main slider 40 in the locking position. The locking pin 44 is articulated to the housing 16 about a third axis E parallel to the second axis C.

The locking unit 12 comprises a force-reducing mechanism 46 interconnected between the main slider 40 and the locking pin 44, which reduces the locking force which the main slider 40 transmits to the locking pin 44.

As shown in Figures 1 and 3, the force-reducing mechanism 46 comprises a rack 48 fixed to or integrally formed with the main slider 40. The force-reducing mechanism 46 comprises a double gear wheel 50 rotatable with respect to the housing 16 about a fourth axis F parallel to the third axis E. The double gear wheel 50 comprises a smaller gear wheel 52 and a larger gear wheel 54, coaxially fixed to each other, preferably formed in one piece. The smaller gear wheel 52 meshes with the rack 48 of the main slider 40.

The force-reducing mechanism 46 comprises a locking wheel 56 rotatable with respect to the housing 16 about a fifth axis G parallel to the fourth axis F. The locking wheel 56 comprises a third gear wheel 58. The third gear wheel 58 is fixed or integral with the locking wheel 56 and meshes with the larger gear wheel 54 of the double gear wheel 50. The third gear wheel 58 is smaller than the larger gear wheel

54.

As shown in Figures 6 and 7, the locking wheel 56 has a step 60 which can be engaged by a tooth 62 of the locking pin 44. When the tooth 62 of the locking pin 44 engages the step 60 of the locking wheel 56, the locking wheel 56 is prevented from rotating in the clockwise direction indicated by the arrow H in Figures 6 and 7. As a consequence, since the main slider 40 is connected to locking wheel 56 through rack 48 and gear wheels 52, 54 and 58, when the tooth 62 of the locking pin 44 engages the step 60 of the locking wheel 56 the main slider 40 is prevented from moving in the second direction D" .

With reference to Figures 5-7, the electric control unit 14 of the door-lock 10 comprises an actuator 64 housed in the housing 18. The actuator 64 has a shaft 66 which is movable in a third linear direction L. A connecting element 68 is fixed to the shaft 66 of the actuator 64. The shaft 66 of the actuator 64 and the connecting element 68 are movable along the third linear direction L between two stable positions, namely an unlocking position shown in figure 6 and a locking position shown in Figure 7. The third linear direction L along which the connecting element 68 is movable is orthogonal to the third axis E about which the locking pin 44 is articulated.

The actuator 64 may be a solenoid electromagnetic actuator, for instance as disclosed in DE 10 2014 226 049 of the same Applicant. The actuator 64 may be powered with directional current pulses, namely a locking pulse which moves the shaft 66 and the connecting element 68 from the unlocking position to the locking position and an unlocking pulse which moves the shaft 66 and the connecting element 68 from the locking position to the unlocking position. A compression spring 70 may be set between the housing 16 and the connecting element 68, for biasing the connecting element 68 toward the locking position.

The connecting element 68 is connected to the locking pin 44 by means of a lever 71 having opposite ends articulated respectively to the connecting element 68 and to the locking pin 44 about respective axes parallel to the third axis E. The arrangement of the lever 71 is such that the linear movement of the connecting element 68 along the liner direction L causes the locking pin 44 to oscillate about the third axis E. More specifically, the linear movement of the connecting element 68 along the liner direction L between the unlocking position (Figure 6) to the locking position (Figure 7) causes oscillation of the locking pin 44 about the third axis E between a disengaged position and an engaged position with respect to the locking wheel

56.

Disengagement of the mutually engaged surfaces 60, 62 occurs by the oscillating movement of the locking pin 44, which significantly reduces the friction as compared with prior art solutions wherein the locking pin is movable in a linear direction with respect to a locking element.

The oscillating locking pin 44 may cooperate with a generic locking element (not necessarily with a locking wheel) which directly or indirectly locks the cam 20 in the retaining position.

The electrical control unit 14 of the door-lock 10 may comprise a printed circuit board 72 containing the electric circuit that powers the actuator 64. At least one first sensor (not shown) , for instance a Hall sensor or a magnetoresistive sensor, may be provided on the printed circuit board 72 for detecting at least one first magnet 74 (Figures 1, 2) carried by the main slider 40. The first sensor provides to an electronic control unit of the appliance a signal indicative of the open/closed state of the door. At least one second sensor (not shown) , for instance a Hall sensor or a magneto-resistive sensor, may be provided on the printed circuit board 72 for detecting at least one second magnet 76 (Figure 5) carried by the connecting element 68. The second sensor provides to an electronic control unit of the appliance a signal indicative of the locked/unlocked state of the door. In the example shown in the drawings there are provided a pair of first magnets 74 and a pair of second magnets 76 which cooperate, respectively, with a pair of first sensors and with a pair of second sensors.

When the hook 24 carried by the door of the household appliance moves inside the housing 16 of the door-lock 10 it rotates the cam 20 about the first axis A from the release position to the retaining position. The rotation of the cam 20 about the first axis A from the release position to the retaining position moves the main slider 40 in the second direction D" and compresses the spring 42. The linear movement of the main slider 40 along the second direction D" rotates the wheels 50, 56 and 58 around the respective axes

F, G.

When the hook 24 moves for a specified distance inside the housing 16 of the door-lock 16 the cam 20 begins to pull the hook 24. In such situation, the position of the axis M of the pin 32 of the roller 30 of the cam 20 is below the position of the axis A of the cam 20. In this phase the spring 42 is extending.

When the hook 24 is in the closed-door position the step 60 on the locking wheel 56 is in the position shown in Figure 6, which permits movement of the locking pin 44 to the engagement position.

At this point, the actuator 64 is powered with a locking pulse. The actuator moves the connecting element 68, which oscillates the locking pin 44 to the locking position shown in Figure 7. The interaction between the locking pin 44 and the locking wheel 56 inhibits rotation of the locking wheel 56 in clockwise direction K. Therefore, the main slider 40 cannot move in the second direction D" and the cam 20 remains locked in the retaining position so the door of the appliance cannot be opened. In the locked state of the door-lock the hook 24 can still move deeper inside the housing 16 of the door-lock.

When the control unit sends to the actuator 64 an unlocking pulse, the force of the actuator 64 is bigger than the force of the spring 70 and, through the movement of the shaft 66 of the actuator 64, moves the connecting element 68 towards the unlocking position. The connecting element 68 causes rotation of the locking pin 44 away from the locking wheel 56, which disengages the interaction between the locking pin 44 and the locking wheel 56. Accordingly, the door-lock is unlocked as the cam 20 can rotate to release the hook 24.

The force reducing mechanism 46 reduces the force transferred from the hook 24 of the appliance to the locking pin 44. The reduction of the force transferred to the locking pin 44 enables unlocking of door-lock even in circumstances when the laundry acts on the door with relatively high force (e.g. 250 N) .

The solution according to the present invention therefore enables the release the door-lock even in the most critical conditions, in which door-lock according to the prior art risk to remain locked with the door closed.

As additional advantage, the door-lock 10 may use a solenoid actuator, which is a preferred actuator in such applications, so no change of the control unit of the appliance is needed if the appliance producer uses the door- lock according to the present invention instead of prior art door-locks .

Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to those described and illustrated without departing from the scope of the invention as defined in the following claims.