Field of the invention

The present invention relates to an electromagnetic door-lock for domestic appliances, in particular for washing machines.

Background of the invention

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.

EP-A-2167717 discloses a locking device for a door of a domestic appliance, wherein a slider is selectively locked in a locking position by a locking element movable between an extracted position and a retracted position. The movement of the locking element is controlled by an electromagnet associated to a movable frame, the movable frame being in contact with the locking element. The movable frame is associated to a push-push retaining device which is configured to retain the frame into a first and a second position, corresponding, respectively, to the extracted and retracted position of the locking element. The push-push retaining mechanism changes the retaining position of the frame each time the electromagnet is energized .

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.

One of the problems of the prior art solutions is that the closing speed of the door sensing switch is directly related to the closing speed of the door. This could be a problem in certain operating conditions of the household appliance .

Object and summary of the invention

The object of the present invention is to provide an electromagnetic door-lock with an integrated door sensing switch, wherein the closing speed of the door sensing switch does not depend on the closing speed of the door.

In accordance with the present invention, this object is achieved by an electromagnetic door-lock having the features of claim 1.

Preferred embodiments of the invention are disclosed in the dependent claims .

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

Brief description of the drawings

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:

- figure 1 is a perspective view of an electromagnetic door-lock according to the present invention,

- figure 2 is an exploded perspective view of the electromagnetic door-lock of figure 1,

- figure 3 is a plan view of the door-lock of figure 1 in the open door position,

- figures 4, 5, 6 and 7 are cross-sections taken along the lines IV-IV, V-V, VI-VI and VII-VII of figure 3,

- figure 8 is a plan view of the door lock of figure 1 in the closed door position, and

- figures 9, 10, 11 and 12 are cross-sections taken along the lines IX-IX, X-X, XI-XI and XII-XII of figure 8.

Detailed description of the invention

With reference to the drawings, an electromagnetic door-lock according to the present invention is indicated by the reference number 10. The door-lock 10 comprises a housing 12 carrying at least two end preferably three fixed electric contacts, indicated respectively N, L and C. The fixed electric contacts N, L, C include respective metal blades engageable by a female connector.

The casing 12 is made of injection-molded plastic material and has a plurality of integral seats designed for receiving the components of the door-lock 10. The housing 12 has an open top which is closed by a cover 14.

The door-lock 10 comprises a main slider 16 which is movable with respect to the housing 12 in the direction indicated by the arrow A between an unlocking position corresponding to the open door position and a locking position corresponding to the closed door position. In the locking position the main slider 16 projects from a lateral side of the housing 12 and in the unlocking position the main slider 16 is retracted with respect to the housing 12.

A hook 18 is fixed to a door (not shown) of a domestic appliance such as a washing machine. In the embodiment shown in the drawings, the hook 18 cooperates with a rotating cam 20 which rotates about an axis 22 between a locking position and a releasing position. When the door is closed, the hook 18 engages the rotating cam 20. When the cam 20 is engaged by the hook 18, the cam 20 rotates from the releasing position to the locking position. A locking slider 24 locks the rotating cam 20 in the locking position. The locking slider 24 is movable in a direction orthogonal to the direction A. The main slider 16 in the locking position abuts against the locking slider 24 and prevents the movement of the locking slider 24 from the locking position to the releasing position. The main slider 16 and the locking slider 24 cooperate with respective springs 26, 28 (figure 2) which bias the main sliders 16 and the locking slider 24 towards the respective locking positions .

In an alternative embodiment, the main slider 16 could be configured for engaging directly the hook 18 and lock the hook 18 in the closed door position.

A locking element 30 is provided for locking the main slider 16 in the locking position. The locking element 30 is movable with respect to the housing 12 in a direction orthogonal to a bottom wall 32 of the housing 12 between a retracted position and an extracted position. In the extracted position of the locking element 30 the main slider 16 is locked in the locking position.

The movement of the locking element 30 between the extracted position and retracted position, and vice versa, is controlled by an electromagnetic actuator 34. The electromagnetic actuator 34 includes an electromagnet 36, a movable frame 38 and a push-push retaining mechanism 40.

The electromagnet 36 includes a winding 42 and a movable magnetic core 44. The winding 42 has a first terminal 46 and a second terminal 48 (figure 2) . The movable frame 38 is connected to the magnetic core 44 and is movable in a direction B between a first and a second position, corresponding to the retracted and extracted positions of the locking element 30.

The push-push retaining mechanism 40 is configured for selectively retaining the frame 38 in the first position or in the second position. The push-push retaining mechanism 40 changes the retaining position of the frame 38 from the first position to the second position, and vice versa, each time the electromagnet 36 is energized. The structure and the operation of the electromagnetic actuator 34, including the construction of the push-push retaining mechanism 40, are disclosed in detail in EP-A-2167717.

The first terminal 46 of the electromagnet 36 is permanently connected to the first fixed electric contact N. The second terminal 48 of the electromagnet 36 is electrically connected to the second electric contact L through a bistable switch 50. The bistable switch 50 comprises a hoop spring 52 fixed to the second electric contact L. The hoop spring 52 has a first movable contact 54 at its free end. The bistable switch 50 also includes a strip spring 56 integral with the hoop spring 52 and having a tooth 58 which engages a tab 60 projecting from the bottom wall 32 of the housing 12 (see figure 2) . The bistable switch 50 also includes a flexible strip 62 opposed to the hoop spring 52 and having at its free end a second movable contact 64 which faces a fixed contact 66 formed on the third electric contact C.

The hoop spring 52 of the bistable switch 50 has an open position and a closed position. In the open position the first movable contact 54 is disconnected from the second terminal 48 of the electromagnet 46. In the closed position the first movable contact 54 abuts on the second terminal 48 and electrically connects the second terminal 48 to the second electric contact L.

The bistable switch 50 is controlled by a door sensing pin 68. As shown in particular in figures 4 and 9, the door sensing pin 68 is movable between an extracted position corresponding to the unlocking position of the main slider 16 and a retracted position corresponding to the locking position of the main slider 16. The lower end of the door sensing pin 68 abuts on a ramp portion 70 of the main slider 16. The upper end of the door sensing pin 68 abuts on a first arm 72 of a rocker lever 74. The rocker lever 74 has a second arm 76 with an end portion 78 which abuts on a contact area 80 of the hoop spring 52. With reference to figure 3 to 7, in the open door position the main slider 16 is in the unlocking position. The door sensing pin 68 is in the extracted position and the rocker lever 74 does not apply pressure on the contact area 80 of the hoop spring 52. In this condition the movable contact 54 is disconnected from the second terminal 48 of the electromagnet 36. The second terminal 48 of the electromagnet 36 is therefore disconnected from the second electric contact L and the electromagnet 36 cannot be energized. The first electric contact N and the second electric contact L are disconnected from each other, which indicates that the door is open.

With reference to figures 8 to 12, in the closed door position the main slider 16 is in the locking position. The door sensing pin 68 is in the retracted position. The rocker lever 74 is rotated by the door sensing pin 68 and applies a pressure on the contact area 80 of the hoop spring 52. When pressure is applied on the contact area 80, the bistable switch 50 instantaneously snaps from the open position to the closed position. The closing speed of the bistable switch 50 is independent from the closing speed of the door .

In the closed position the first movable contact 54 abuts on the second terminal 48 of the electromagnet 36 and connects the second terminal 48 to the second electric contact L. In this condition the first and the second electric contacts N, L are electrically connected to each other through the winding 42 and the bistable switch 50. The electric contacts N, L are electrically connected to each other, which indicates that the door is closed. In this condition, when a voltage is applied between the electric contacts N, L the electromagnet 36 is energized. When the electromagnet 36 is energized, the magnetic core 44 is attracted within the winding 22 and pulls the frame 38 towards the electromagnet 36 in the direction B. The movement of the frame 38 in the direction B changes the retaining position of the push-push retaining mechanism 40. Therefore, each voltage impulse applied to the electromagnet 36 changes the position of the frame 38 from a first position to a second position, and vice versa.

The locking element 30 has a projection 73 which engage a ramp portion 75 of the frame 38. Accordingly, the movement of the frame 38 from the first position to the second position, and vice versa, causes the movement of the locking element 30 from the extracted position to the retracted position, and vice versa.

The locking element 30 has a seat 77 in which is engaged a lateral tab 79 of the flexible strip 62. Therefore, when the locking element 30 is in the retraced position, the second movable contact 64 of the flexible strip 62 is disconnected from the fixed contact 66 of the electric contact C. When the locking element 30 is in the extracted position, the second movable contact 64 is connected to the fixed contact 66 and closes the electrical connection between the electric contacts L and C. The fact that the electric circuit between the electric contacts L and C is closed indicates that the door is locked.

The door-lock according to the present invention is preferably provided with a safety protection against breakage of the hook 18 and/or rotary cam 20. This function is carried out by a safety device which prevents the closure of the electric connection between the fixed electric contacts N and L or between the fixed electric contacts L and C in case of breakage of the hook 18 and/or the rotary cam 20. The safety device comprises an auxiliary slider 81 which is movable with respect to the housing 12 in direction parallel to the direction A. The auxiliary slider 81 is biased by a spring 82 towards an extracted position. The front end 84 of the auxiliary slider 81 abuts against the hook 18 in the closed door position (see figure 10) . In the open door position the front end 84 of the auxiliary slider 81 abuts against the rotary cam 20 (see figure 5) . As shown in figures 5 and 10, the lower end of the safety pin 86 engages a ramp portion 88 of the auxiliary slider 81. When the auxiliary slider 81 abuts against the hook 18 (closed door position of figure 10) the safety pin 86 is in the extracted position. When the auxiliary slider 81 does not abut against the hook 18 (see figure 5) the safety pin 86 is in the retracted position. The safety pin 86 is in the retracted position of figure 5 when the door is open or when there is a breakage of the hook 18 or rotary cam 20. As shown in figure 5, when the safety pin 86 is in the retracted position, the upper end of the safety pin 86 abuts against a lateral tab 90 of the hoop spring 52, thereby preventing the closure of the movable contact 54 against the second terminal 48. When the safety pin 86 is in the extracted position of figure 10 the movable contact 54 is free to move in contact with the second terminal 48.

In an alternative embodiment, the safety pin 86 could be placed in correspondence with the second movable contact 64 of the flexible strip 62. In this case, when the safety pin 86 is in the retracted position it prevents the closure of the second movable contact 64 on the fixed contact 66.

The door-lock according to the present invention has a further preferred feature, consisting in the mutual looking between the frame 38 and the door sensing pin 68. The door sensing pin 68 has a lateral projection 92 at its upper end. The lateral projection 92 cooperates with two steps 94, 96 of the movable frame 38. As shown in figures 4 and 9, when the door sensing pin is in the retracted position (figure 9) the frame 38 locks the door sensing pin 68 in the retracted position and prevents the door sensing pin 68 from moving down when the main slider 16 moves. When the door sensing pin 68 is in the extracted position (figure 4) the door sensing pin 68 locks the frame 38 and prevents movement in the direction B of the frame 38. These features are useful in particular during transport, before the assembly of the door-lock on the domestic appliance.