LAUNDRY DRYER OR COMBINED WASHER-DRYER WITH SENSOR ELECTRODES FOR SENSING THE RESIDUAL MOISTURE OF THE LAUNDRY

Abstract: In a laundry dryer or combined washer-dryer of the­ rotating-drum type having a charging opening (2) closed by a door (3) having a transparent window (4), at least a pair of sensor electrodes (6, 7) are provided on the interior surface of said window (4) in the form of metallized areas separated from one another by a nonmetallized surface area (8). The thickness of said metallized areas is of the order of a few microns, so that said electrodes may extend over the entire interior surface of the window without sub­ stantially detracting from the transparency thereof.

Description: D e s c r i i,e. tion The present invention relates to automatic laundry dryers or combined washer-dryers particularly of the rotating-drum type for domestic use, comprising a charging opening with a transparent closure door or window. More particularly, the invention refers to a laundry dryer or combined washer-dryer of the type including a system for controlling the residual moisture of the laundry and for automatically stopping the machine as soon as the laundry therein has attained a predetermined degree of dryness. Normally these systems are of the electronic controll type, their operation being based on the method of measuring the conductance between two sensing electrodes disposed in contact with the laundry. The wet or moist laundry constitutes a connecting bridge between the two electrodes, the conductance of which diminishes with the progress of the drying operation. The control system senses, umplifies and measures the electric current flowing between th two electrodes. As the conductance between the two electrodes diminishes below a certain value, the control system becomes operative to index the program unit of the machine so as to stop the latter. In certain cases the sensor electrodes are located in the interior of the rotating drum, so that their connection to the remainder of the control system requires the employ of sliding contacts which are, as generally known, sub ject to rapid wear, resulting in insufficient reliability. The connections of this type may by accomplished through the bearings carrying the drum, in which case, however, the rather weak currents flowing through this type of connection are frequently subjected to variations falsifying the result of the measuring of the conductance of the laundry. Tot avoid these disadvantages, it is generally preferred to attach the sensor electrodes to the interior surface of the closure window which, particularly in the case of a combined washer-dryer, is preferably transparent for permitting observation of the interior of the drum during the successive operating pahses of the machine. This solution does not require the employ of sliding contacts, but is inconvenient in so far as the sensor electrodes reduce the transparency of the closure window. On the other hand, a reduction of the surface area of the sensor electrodes, which are usually in the form of metal disks or the like, would result in a corresponding reduction of the contact points between the laundry and the electrodes, so that a correct reading of the residual moisture of the laundry is not reliably ensured. A first object of the invention is therefore the provision of a laundry dryer or combined washer-dryer of the type having a transparent closure window and equipped with a system for controlling the residual moisture of the laundry, comprising sensor electrodes lending themselves to economical manufacture on an industrial scale and ensuring a large surface for contact with the laundry while being adapted to be located on the interior surface of the transparent closure window A further object of the invention is the provision of an assembly of the above stated type, in which the sensor electrodes are attached to the interior surface of the closure window without detracting from the transparent properties thereof. These and other objects of the invention are attained by a laundry dryer or combined washer-dryer of the rotating drum type, comprising a charging opening with a transparent closure window, and means for controlling the residual moisture of the laundry, said means including sensor electrodes disposed on said closure window, the invention being characterized in that said sensor electrodes comprise metallized areas on the interior surface of said window. The metallized areas may be formed by the employ of per se known techniques so as to have a reduced thickness rendering them substantially transparent. Further characteristics and advantages of the invention will become evident from the following description of an exemplary embodiment with reference to the accompanying drawings, wherein: fig. 1 shows a diagrammatic perspective view of a laundry dryer or combined washer-dryer in an embodiment of the invention, and fig. 2 shows an enlarged view of a detail of the interior surface of a closure window of the apparatus of fig. 1. The apparatus shown in fig, 1 is a laundry dryer or combined washer-dryer 1 of the rotating-drum type, having a forward facing charging opening 2 adapted to be closed by a door 3 provided with a window 4. Applied to the interior surface of window 4 is a metal lized layer 5, formed for instance of aluminum, comprising at least two areas 6, 7 separated from one another by a non-metallized and thus non-conductive area 8 on the interior surface of window 4. The two areas 6 and 7 constitute a pair of sensor electrodes connected in a per se known manner to a system for controlling the residual moisture of the laundry A system of this type is generally known and needs therefore not be described. The sensor electrodes may be readily applied to the interior surface of window 4 by employing any well-known metallizing technique permitting the electrode 6, 7 to be formed with an extremely reduced thickness in the order of a few microns. This results in the surface of window 4 covered with the metallized layer 5 relaining substantially transparent as specified as an object of the invention. This arrangement also enables the entire interior surface of the Window 4 to be employed for the formation of the electrodes 6, 7 without any restrictions as to their shapes and dimensions. The sensor electrodes 6, 7 may thus be formed in the interdigitating configuration shwon as an example in fig.2. The laundry dryer or combined washer-dryer according to the invention thus presents, on the interior surface of window 4, a pair of sensor electrodes 6, 7 having a sufficiently large contact surface for the laundry, so that the residual moisture thereof can be measured with a high degree of reliability. The described laundry dryer or combined washer-dryer may of course be modified in any suitable manner within-the scope of the invention as defined in the claims appended hereto.

Claims: Laundry Dryer or Combined Washer-Dryer With Sensor Electrodes for Sensing the Residual Moisture of the Laundry P a t e n t C l a i m s Patent Claims 1. Laundry dryer or combined washer-dryer of the rotating-drum type, comprising a charging opening with a transparent closure window, and means for controlling the residual moisture of the laundry, said means including sensor electrodes disposed on said closure window, characterized in that said sensor electrodes comprise metallized areas (6, 7) on the interior surface of said window (4). 2. Laundry dryer or combined washer-dryer according to claim 1, characterized in that said metallized areas (6, 7) are substantially transparent, having a thickness in the order of a few microns.

Inventors: DURAZZANI, PIETRO, FRUCCO, GIUSEPPE
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1982
Main classification: D06F58
IPC codes: D06F58, G01N27