Patent Description:
It is known that the opening and closing movement of an automatic door requires a safety control to prevent the door from damaging an obstacle (an object or an operator) that could be found in its path. To this end, the presence of the obstacle is typically detected through the increase in the motor torque required to move the door, which has a two-way connection with the motorised device that controls its movement. In practice, the safety control is entrusted only to a sensor that detects the increased absorption due to an obstacle, so as to interrupt/reverse the operation of the motor beyond a certain overload threshold.

However, this type of traditional control is not very safe or convenient, as it depends on adjusting the threshold according to the weight of the door. However, said weight can change significantly if the door is equipped with a support frame for placing lids or pans on the door, or in the case of a refrigerator depending on the amount of bottles or other heavy items placed on the door. This variability in weight implies a risk of malfunctioning of the safety control, because if the threshold is set too low a "false positive" can occur, i.e. a non-existent obstacle is detected, whereas if the threshold is set for the maximum possible door weight there is a risk of not detecting in time an obstacle in the path of the door in a low weight condition.

Other problems can occur in the case of appliances in which the compartment that is closed by the door has a perimeter seal that the door must compress when closing, for example to prevent the escape of water and steam in a dishwasher, or hot air and/or steam in an oven.

A first drawback can arise when the seal becomes stiffer as it ages, requiring a greater push to compress it. In such a case, if the safety control intervention threshold is not raised to take account of this increased push, a "false positive" as mentioned above may occur, with the result that the device is unable to close the door.

A second similar drawback that can occur at the beginning of the opening phase is that the aged seal tends to stick to the door, thus causing an initial overload of the motor. This leads to a risk of "false positive" if the threshold is too low, as an obstacle is detected in the opening process that is not there, with the result that the device is unable to open the door.

On the other hand, adjusting the threshold to suit the aged seal is not easy either, as it is necessary to proceed by trial and error and the threshold may be adjusted so high that it risks damaging an obstacle.

Finally, there are other types of safety control using different means, such as an infrared barrier or a contact-sensitive moving edge, which are however much more expensive and complex to operate. <CIT>discloses an example of an appliance.

The object of the present invention is therefore to provide an appliance having an automatic door which overcomes these drawbacks. This object is achieved by means of an appliance whose door movement device provides an active connection between the motor and the door only in the opening direction, by means of the interposition of an elastic safety element, while the closing is performed by an elastic return element whose actuation speed is limited by a passive connection with the motor or by a damping element. In a preferred embodiment, the device also comprises a door latch which actively assists in compressing the seal in the closing phase and detaching it from the door in the opening phase.

The main advantage of the appliance according to the present invention is therefore that of having a door movement device in which the safety control is obtained through means which do not rely on the current consumption of the motor, so that the safety control is independent of variations in the weight of the door without risk of "false positives" or damage to an obstacle due to an excessively high intervention threshold.

A further significant advantage of this appliance, in its preferred embodiment, is that interventions on the seal are entrusted to the latch, so that ageing of the seal does not affect the correct functioning of the safety control.

Yet another advantage is that the door movement device is extremely simple and therefore reliable and inexpensive, and its operation is very easy to control by the control unit.

These and other advantages and features of the appliance according to the present invention will be evident to those skilled in the art from the following detailed description of an embodiment thereof, with reference to the accompanying drawings in which:.

Referring to <FIG>, it can be seen that a dishwasher according to the present invention traditionally comprises a door <NUM> hinged at the bottom, so as to rotate about a horizontal axis <NUM>. The door <NUM> is provided with a lever <NUM> extending inwards and downwards to act as a connection with the movement device.

More specifically, lever <NUM> carries at its distal end a roller <NUM> having a horizontal axis, and in an intermediate position a horizontal pin <NUM> to which the upper end of a return spring <NUM> is engaged, the lower end of which is engaged to a similar pin fixed on the frame of the dishwasher. In addition, a damper <NUM> is pivoted between the frame and lever <NUM>, preferably in correspondence with roller <NUM> but pin <NUM> could also be used or a further pin could be provided specifically for damper <NUM>.

A linear actuator <NUM> is arranged vertically and has an extendible stem <NUM> with a portion 9a of reduced cross-section, on which a spring <NUM> is threaded. A vertical plate <NUM>, with a substantially inverted L shape, is carried by stem <NUM> through two vertically aligned collars 11a, 11b which are fitted with minimum play on said reduced portion 9a above spring <NUM>, which thus acts as an element for the transmission of the push of actuator <NUM> to plate <NUM>.

It should be noted that stem <NUM> ends with a portion of a cross-section larger than the reduced portion 9a, so that plate <NUM> is constrained to move with stem <NUM> both upwards and downwards. The only relative movement between stem <NUM> and plate <NUM> is due to the compressibility of spring <NUM>, as will be illustrated below.

The plate <NUM> carries a microswitch <NUM> arranged above actuator <NUM> in such a way that its movable element 12a is vertically aligned with stem <NUM>. In addition, plate <NUM> also carries a pushing element <NUM> arranged in a substantially horizontal position at its lower end and shaped as a track for the rolling of roller <NUM>. More specifically, the pushing element <NUM> has in sequence from the inside to the outside a flat horizontal part, a flat downwardly sloping part and a curved part rising upwards until it exceeds the inner horizontal part (inside/outside being defined from the wash tank towards the door).

For reasons of balance and smooth operation of the device, it is preferable to have a lever <NUM> on each side of door <NUM>, with equal and parallel springs <NUM> acting on both sides of the door. On the contrary, for cost reasons, damper <NUM> and actuator <NUM> are provided only on one side of the door, preferably the same side.

Referring now to <FIG>, the simple and effective operation of the safety control during automatic door opening of the dishwasher according to the invention is immediately apparent from the above description.

Starting from the position of <FIG>, corresponding to <FIG>, when door <NUM> encounters an obstacle which stops its opening movement, actuator <NUM> continues to extend stem <NUM> by pushing up plate <NUM> through spring <NUM>, but roller <NUM> does not allow the pushing element <NUM> to rise since lever <NUM> cannot rotate further. Consequently, the push of stem <NUM> results in a compression of spring <NUM> against the lower collar 11b, and this compression stroke allows the top of stem <NUM> to come into contact with the movable element 12a of microswitch <NUM> (<FIG>), which is then activated and can command the stopping or reversal of actuator <NUM>.

<FIG> show different positions of the door and of the elements of the movement device (lever <NUM>, roller <NUM>, spring <NUM>, damper <NUM>, stem <NUM>, plate <NUM>) during the opening stroke, from the closed door of <FIG> to the fully open door of <FIG>. More specifically, it can be seen that spring <NUM> and damper <NUM> rotate counterclockwise around their lower mounting pins to the position in <FIG>, where lever <NUM> is arranged horizontally, and then rotate slightly clockwise in the final stretch of the stroke to <FIG> where lever <NUM> is tilted upwards.

Similarly, roller <NUM> starts from the outer end of the track forming the pushing element <NUM>, descending along the curved part (<FIG>) and then ascending along the sloping part (<FIG>) to reach the inner end at the beginning of the horizontal part (<FIG>), and finally moves back slightly (<FIG>). Note that the shape, size and position of the pushing element <NUM> are related to the position of roller <NUM> with respect to the axis of rotation of door <NUM>, so it is clear that the one depicted is only an exemplary shape that any person skilled in the art can easily modify in case of a different position of roller <NUM> on lever <NUM>.

During the closing of door <NUM>, as shown in <FIG>, stem <NUM> is retracted and brings with it plate <NUM> so that spring <NUM> can recall lever <NUM> with a counterclockwise rotation, the rotation speed being limited by the fact that roller <NUM> continues to rest on the pushing element <NUM>, so it is the retraction speed of stem <NUM> that determines the time necessary for the closing (usually in the order of <NUM>-<NUM> seconds). The safety control during closing is intrinsic in the structure of the movement device, since actuator <NUM> does not act on lever <NUM> which is rotated only by the action of spring <NUM>, which is selected to have a recall force sufficient to close door <NUM> but not such as to cause damage to any obstacle.

Furthermore, in the event that door <NUM> remains open, due to manual intervention by the user or due to an excessive weight on the door, even when stem <NUM> is retracted (as indicated by the continuous line in <FIG>), damper <NUM> nevertheless ensures that the subsequent closing performed when spring <NUM> succeeds in recalling door <NUM> takes place at a limited speed, even if roller <NUM> is not in contact with the pushing element <NUM>.

As mentioned above, in a preferred embodiment illustrated in <FIG>, the appliance is also provided with an "active" latch which provides for the compression phase of a seal, if any, at the end of the closing movement of the door, as well as for the detachment of the door from the seal at the beginning of the opening movement, so that the ageing of the seal does not affect the correct functioning of the safety control.

The latch acts on a horizontal eyelet <NUM>, fixed to the door <NUM>, which is engaged by the free end of an inverted hook <NUM> swinging around a horizontal pin <NUM>, under the action of a connecting rod <NUM> pivoted at the other end of hook <NUM>. The connecting rod <NUM> is pivoted at its opposite end to a crank of a crankshaft <NUM>, which rotates counterclockwise about a horizontal axis <NUM> being driven by a unidirectional motor <NUM>.

The engagement position of <FIG> is preferably confirmed by means of a sensor that detects the presence of door <NUM> when it arrives in the vicinity of the latch in such a position that eyelet <NUM> can be engaged by hook <NUM>, preferably a Reed sensor (not shown) that detects a magnet <NUM> mounted on door <NUM>. A control unit (not shown), once it receives confirmation from the aforementioned position sensor, activates motor <NUM> so that the rotation of crankshaft <NUM> causes the backward movement of the connecting rod <NUM> which rotates hook <NUM> clockwise around the pin <NUM>.

Consequently, hook <NUM> pulls inwards eyelet <NUM> and therefore door <NUM>, which compresses seal <NUM> without the need for a push by actuator <NUM>. A microswitch (not shown) is actuated by hook <NUM> when the fully closed position of door <NUM> is reached in which seal <NUM> is compressed (<FIG>), so as to authorize the start of the washing cycle.

The crankshaft <NUM> is also provided with a cam profile <NUM> that is able to operate a second microswitch <NUM> that is used to detect the position in which hook <NUM> has disengaged from eyelet <NUM> (<FIG>), so as to authorize the activation of actuator <NUM> for the start of the opening phase. Note that in the passage from the locked position of <FIG> to this disengagement position, the central portion of hook <NUM> comes into contact with eyelet <NUM>, pushing it outwards. In this way, door <NUM> is detached from seal <NUM> even before the start of the opening phase, without the need for intervention by actuator <NUM>.

It is clear that the embodiment of the appliance according to the invention described and illustrated above is only an example susceptible to numerous variations. In particular, the exact nature, form and arrangement of the elements could be varied according to specific constructional requirements, for example by using mechanical equivalents of the elements described above such as a different type of sensor/detector than the Reed sensor and microswitches <NUM>, <NUM> (e.g. optical sensors, resistive sensors, etc.), a different type of linear actuator than the one with the extendible stem <NUM> (e.g. rack and pinion, worm screw, etc.), a different type of spring elements than coil springs <NUM>, <NUM> and so on, as long as the general structure of the automatic door actuating device is maintained with the actuator acting in the opening phase through an elastic safety element and the elastic return element acting in the closing phase in cooperation with the actuator and/or the damper.

Similarly, the rotation mechanism of hook <NUM> could also be different from the connecting rod <NUM>+crankshaft <NUM> combination, and the rotation pin <NUM> of hook <NUM> could be vertical if the mechanism is intended to act on an eyelet <NUM> arranged in the vertical plane. Alternatively, hook <NUM> could be reversed and pivot <NUM> located below eyelet <NUM> to engage it from below, in which case motor <NUM> would rotate clockwise.

Claim 1:
An appliance having an automatic hinged door (<NUM>), a motorised device for the movement of said door (<NUM>) and at least one sensor capable of detecting the interference of an obstacle during the movement of the door (<NUM>) and sending a stop/reverse command to said motorised device via a control unit of the appliance, characterized in that said door movement device comprises at least one linear actuator (<NUM>) acting on the door (<NUM>) only during the opening phase and through an elastic safety element allowing a relative movement between said linear actuator (<NUM>) and the door (<NUM>) in case of an obstacle during opening, said interference sensor being capable of detecting said relative movement, whereas the closing phase is performed by at least one elastic return element (<NUM>) arranged between the door (<NUM>) and a fixed part of the appliance, the actuation speed of said elastic return element (<NUM>) being limited by the linear actuator (<NUM>) during its return stroke and/or by at least one damping element (<NUM>) arranged between the door (<NUM>) and a fixed part of the appliance.