Patent Description:
A door lock has the purpose of ensuring that the door of a domestic appliance is locked in the closed position and can only be opened when sufficient time has lapsed after the end of an operating cycle.

In many cases, in addition to the locking function, the door locking device should also be provided with a door sensing switch. The function of the door sensing switch is to prevent the start of the domestic appliance (e.g. the start of a washing cycle) when the door is open and in some special circumstances which are described in one of the IEC standards for domestic appliances.

A number of solutions are known for sensing the closed position of the door and for closing a door sensing switch when the door is closed.

<CIT> discloses an electromagnetic door lock for locking the door of a domestic appliance, comprising a door sensing device including a door sensing pin cooperating with a bistable switch which snaps from an open position to a closed position when the door sensing pin moves from an extracted position to a retracted position.

The bistable switch includes metal contact strips, attached to or integrally formed with the terminals used to electrically connect the door lock to the control unit of appliance. These metal components are usually provided with contact rivets, which can be attached, for example by riveting, onto metal components or can be formed by a contact material welded to the metal components.

Because of the geometry of the parts which constitute the switches and because of the characteristics of the materials applied, the door locks according to the prior art have the following drawbacks:.

The object of the present invention is to provide an electromagnetic door lock with an integrated door sensing switch which overcomes the above drawbacks.

In accordance with the present invention, this object is achieved by an electromagnetic door lock having the features of claim <NUM>.

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

Embodiments of the present invention will now be described in detail with reference to the annexed drawings, given purely by way of non-limiting example, in which:.

It should be noted that in the drawings some components have been removed to show more clearly the relevant aspects of the embodiments.

With reference to the drawings, the reference number <NUM> indicates an electromagnetic door lock for locking the door of a domestic appliance, in particular a washing machine. The door lock <NUM> comprises a rotating cam <NUM>, which rotates about a first axis A between an open-door position (<FIG>) and closed-door position (<FIG>). The rotating cam <NUM> cooperates with a hook <NUM> fixed to a door (not shown) of a domestic appliance. The hook <NUM> engages the rotating cam <NUM> in the open-door position of <FIG> and, during closure of the door, causes the rotating cam <NUM> to rotate about the first axis A to the closed-door position shown in <FIG>. In the closed-door position the rotating cam <NUM> is engaged with the hook <NUM> and holds the door of the appliance in a closed position.

The door lock <NUM> comprises a locking device <NUM> arranged to lock the rotating cam <NUM> in the closed-door position. The locking device <NUM> comprises a main lever <NUM> rotatable about a second axis B and a rocker arm <NUM> rotatable about a third axis C. The rocker arm <NUM> has a surface <NUM> in contact with the rotating cam <NUM>. The main lever <NUM> cooperates with the rocker arm <NUM> and biases the rocker arm <NUM> in contact with the rotating cam <NUM>.

The locking device <NUM> includes an electromagnetic actuator <NUM>. With reference to <FIG> and <FIG>, the electromagnetic actuator <NUM> has a solenoid core <NUM> movable between a retracted position (<FIG>) and an extended position (<FIG>). A cam element <NUM> is attached at the distal end of the solenoid core <NUM>. A locking pin <NUM> cooperates with the cam element <NUM> and moves between an unlocking position (<FIG>) corresponding to the retracted position of the solenoid core <NUM> and a locking position (<FIG>) corresponding to the extended position of the solenoid core <NUM>.

When the locking pin <NUM> is in the locking position it engages a surface <NUM> of the main lever <NUM> and prevents a rotation of the main lever in an anticlockwise direction. An attempt to open the door, e.g. by the user of appliance, causes the main lever <NUM> to rotate in counterclockwise direction, as indicated by the arrow D in <FIG>. The locking pin <NUM> prevents a rotation of main lever <NUM>, so it is impossible to open the door. Therefore, in this condition the rotating cam <NUM> is locked in the closed-door position.

With reference to <FIG>, <FIG> and <FIG>, the door lock <NUM> comprises a door sensing device <NUM>. The door sensing device <NUM> includes a door sensing element <NUM> movable between a first position (<FIG>) and a second position (<FIG> and <FIG>) corresponding, respectively, to the open-door position and to the closed-door position of the rotating cam <NUM>. The door sensing device <NUM> may include a door sensing lever <NUM> which may be rotatable about an axis E and a door sensing slider <NUM> connected to the door sensing lever <NUM> and to the door sensing element <NUM>.

As shown in <FIG> and <FIG>, the rotating cam <NUM> is in contact with the door sensing lever <NUM>. The rotation of the rotating cam <NUM> from the open-door position to the closed-door position causes a rotation of the door sensing lever <NUM> about the axis E, which in turn causes - through the door sensing sider <NUM> - a movement of the door sensing element <NUM> from the first position to the second position. The movement of the door sensing element <NUM> from the first position to the second position may be a rotation about an axis F.

With reference to <FIG>, <FIG> and <FIG>, the door lock <NUM> comprises a first contactless proximity sensor <NUM> which detects the second position of the door sensing element <NUM>.

According to the invention, the door lock <NUM> comprises a second contactless proximity sensor <NUM> which detects the locking position of the locking pin <NUM>.

The first or the second contactless proximity sensor <NUM>, <NUM> may be carried by a stationary support <NUM>, for instance a printed circuit board. The first or second contactless proximity sensor <NUM>, <NUM> cooperates with at least one respective actuating element <NUM>, <NUM> carried by the door sensing element <NUM> or by the locking pin <NUM>.

The first and the second contactless proximity sensor <NUM>, <NUM> replace the electromechanical switches of the prior art solutions. The first and the second contactless proximity sensor <NUM>, <NUM> may be magnetic sensors, like Hall sensors, magnetoresistive (MR) sensor, optical sensors and the like.

The description of the exemplary embodiment and the accompanying drawings are based on magnetic sensors, but the invention is not limited to them. In one or more embodiments, sensors based on other principles can be implemented to sense the relative positions of movable and non-movable parts in the door lock <NUM>.

In case of sensors based on magnetic principle of operation, the actuating elements <NUM>, <NUM> are preferably made of magnetic or magnetizable material, for example permanent magnets, but may also be made of other materials suitable for detection by the contactless proximity sensors <NUM>, <NUM>. The magnets can be fixed to the respective supports, for example door sensing element <NUM> or locking pin <NUM>, by snap-fixation, gluing, over-molding or other suitable processes.

Preferably, the contactless proximity sensors <NUM>, <NUM> are carried by a stationary support <NUM>, e.g. a printed circuit board, as shown in the drawings, which can contain also other electronic or electromechanical elements needed for the operation of the sensors <NUM>, <NUM>. The part carrying the sensors <NUM>, <NUM> can contain other electronic elements needed for its operation and preferably contains connections to connect electrical signals to the control unit of appliance. The sensors <NUM> and <NUM> can be carried by a single printed circuit board <NUM> (as shown in the described embodiment) or by two separate printed circuit boards, depending on the applications.

The basic principle of operation is the same for all pairs sensors/actuating elements in the door lock <NUM>. In case of sensors based on magnetic principle of operation, the magnetic field of the magnets <NUM>, <NUM> is detected by a sensing surface of the respective sensor <NUM>, <NUM>. Because of this influence, the output of the sensor changes its state. Depending on the type of sensors and respective electronic elements, the output of the sensors can be digital or analogue. In case of digital output, the output of each sensor <NUM>, <NUM> has two discrete values in case of presence or absence of a magnet <NUM>, <NUM>.

The shape of the magnets <NUM>, <NUM> can be rectangular, tubular or the like. In the positions when the magnetic fields of the magnets <NUM>, <NUM> influences the sensing area of the respective sensors <NUM>, <NUM> the areas of the magnets <NUM>, <NUM> which generate magnetic field and the sensing areas of the sensors <NUM>, <NUM> are in close proximity and positioned so that the sensing areas of the sensors <NUM>, <NUM> is preferably parallel to the respective surfaces of the magnets <NUM>, <NUM> which generate the magnetic fields.

The sensors <NUM>, <NUM> are preferably carried by a part of door lock <NUM> which does not move during the operation of door lock, while the magnets <NUM>, <NUM> are preferably carried by parts which are movable during the operation of door lock <NUM>, for example movable linearly or rotatable or a combination of both. This description is not limiting as depending on specific execution of door lock <NUM>. For instance, the relative position of the sensors and magnets may be inverse, so the sensors may be carried by movable parts and the magnets by non-movable parts.

The first proximity sensor <NUM> provides an information on whether the door of the appliance is open or closed. In some cases it may be required to know also an intermediate position of door, for example door partly open. This position of the door enables constant venting of drum of appliance, for example a washing machine, and can be required in case of automatic door opening of, for example, washing machines. In this case, after the washing cycle, the door of the appliance would be opened for a certain angle automatically or by manual action of user, but the hook <NUM> would still be engaged with rotating cam <NUM>. In this situation door lock <NUM> would be neither in an open door or closed door position but would be in partly open position. In case of analogue output, the sensor enables to sense also intermediate positions of the moving element carrying the magnet <NUM>, <NUM> relatively to sensor, enabling for example the possibility to sense a partially closed-door position, which can be advantageous for example to sense a partially open position of the door needed for venting the drum of the washing machine when it is not operating.

After the start of the cycle of the appliance, for example in case of washing machine a washing cycle, the appliance control unit generates an activating pulse to the electromagnetic actuator <NUM> and as the result solenoid core <NUM> moves to the extended position. As a result, the magnet <NUM> carried by the locking pin <NUM>, reaches its "locked" position and influences the sensing area of the second proximity sensor <NUM> carried by the printed circuit board <NUM>. As a result, the output of the second sensor <NUM> changes as compared to the previous "unlocked" condition and corresponds to a "locked" condition. This information, generated directly by the sensor or through elaboration of the signal by the electronic parts on the printed circuit board <NUM>, is available to control unit of appliance, signaling a "locked" condition of the door lock <NUM>.

In the example not forming part of the invention shown in <FIG>, each sensor <NUM>, <NUM> cooperates with only one magnet <NUM>, <NUM>. <FIG> shows an embodiment according to the invention in which each of the contactless proximity sensors <NUM>, <NUM> cooperates with two magnets <NUM>', <NUM>" and <NUM>', <NUM>". This solution is required in particular due to the following reasons:.

In the embodiment according to the invention of <FIG>, the door sensing element <NUM> and/or the locking pin <NUM> carries a first and a second actuating element <NUM>', <NUM>" or <NUM>', <NUM>". The first and second actuating element <NUM>', <NUM>" or <NUM>', <NUM>" may be magnets with opposite polarities.

In the open door position the sensing area of the sensor <NUM> is influenced by the magnetic field of a first magnet <NUM>', which has a first polarity, for example south. In the closed door position the sensing area of sensor <NUM> is influenced by the magnetic field of a second magnet <NUM>" which has a second polarity, for example north.

In the same way, in the unlocked door position the sensing area of the sensor <NUM> is influenced by the magnetic field of a first magnet <NUM>', which has a first polarity, for example south. In the locked door position the sensing area of sensor <NUM> is influenced by the magnetic field of a second magnet <NUM>", which has a second polarity, for example north.

Claim 1:
An electromagnetic door lock for locking the door of a domestic appliance, comprising:
a rotating cam (<NUM>) rotating about an axis (A) between an open-door position and closed-door position and cooperating with a hook (<NUM>) fixed to a door of a domestic appliance,
- a locking device (<NUM>) which locks the rotating cam (<NUM>) in the closed-door position, the locking device (<NUM>) including an electromagnetic actuator (<NUM>) configured for moving a locking pin (<NUM>) between a locking position and an unlocking position, and
- a door sensing device (<NUM>) including a door sensing element (<NUM>) movable between a first position and a second position corresponding, respectively, to the open-door position and to the closed-door position of the rotating cam (<NUM>),
characterized in that it comprises at least a first contactless proximity sensor (<NUM>) which detects said second position of the door sensing element (<NUM>), and a second contactless proximity sensor (<NUM>) which detects said locking position of the locking pin (<NUM>), wherein said first or second contactless proximity sensor (<NUM>, <NUM>) cooperates with at least one respective actuating element (<NUM>, <NUM>) carried by the door sensing element (<NUM>) or by the locking pin (<NUM>),
wherein said door sensing element (<NUM>) or said locking pin (<NUM>) carries a first and a second actuating element (<NUM>', <NUM>", <NUM>', <NUM>").