EP0976359B1

EP0976359B1 - Device for fine filtering the washing liquid in a dishwasher

Info

Publication number: EP0976359B1
Application number: EP19980830456
Authority: EP
Inventors: Silvano Fumagalli
Original assignee: Candy SpA
Current assignee: Candy SpA
Priority date: 1998-07-28
Filing date: 1998-07-28
Publication date: 2004-11-03
Anticipated expiration: 2018-07-28
Also published as: DE69827378D1; DE69827378T2; EP0976359A1

Description

The present invention relates to a device for fine filtering the washing liquid in a dishwasher, comprising a wash compartment to contain the objects to be washed, a pump for re-circulating the liquid by collecting it from the bottom of the wash compartment and admitting it into the latter by means of a plurality of nozzles, a drainage pump to drain the liquid out of the wash compartment at the end of the washing and/or rinsing cycle, the said bottom of the wash compartment including a primary grille and a perforated vessel in order to allow the liquid to pass through to the said re-circulation pump but retain the large particles of dirt removed from the objects to be washed.
A device for filtering the washing liquid in a dishwasher according to the preamble of claims is known for example from EP-A-0 454 640.
Within the context of the following description, washing liquid means any solution with detergent which can be used in a dishwasher during the actual washing stages, as well as the water used during the rinsing stages which follow and which are interspersed with the washing stages.
As is known, in dishwashers of the above-described type, various operating cycles are provided to be selected by the user according to the amount of food residues present on the dishes, this definition including plates, glasses, cutlery, pans and kitchen utensils.
The dirtier the dishes and the more efficient the cycle selected to remove this dirt, the dirtier the washing liquid which is recycled.
This is because, owing to the size of their holes, the primary grille and the perforated vessel at the bottom of the wash compartment can retain only the largest particles of dirt. The other particles, on the other hand, pass into the recycling pump and, although they are finely broken up and pulverized, they continue to be recycled inside the wash compartment.
These particles are thus deposited not only on the dishes, leaving undesirable marks, but also on the walls of the wash compartment and of the recycling units, eventually forming blockages.
In order to eliminate this disadvantage, it has been proposed to use a high number of rinsing stages. However, such a measure has not succeeded in removing the fine particles of food residues to an acceptable degree and they sometimes remain stubbornly stuck to the areas of contact between the dishes in the wash compartment, even though these areas are small.
Inter alia, an increase in the number of rinsing stages involves a considerable increase in the consumption of water, contrary to current requirements which demand reductions in consumption.
The object of the present invention is to provide a filtering device which permits elimination as far as possible of all the residues and dirt from the washing liquid during recycling of the latter.
This object is achieved by means of the device according to the following claims.
The invention will now be described in greater detail, with reference to a preferred embodiment thereof illustrated by way of non-limiting example in the attached drawings, in which:
Figure 1 shows a schematic view in vertical cross-section of a dishwasher fitted with the filtering device according to the invention;
Figure 2 shows a schematic view in cross-section of the filtering device in Figure 1, in the stage in which the filtering surfaces are counter-washed; and
Figure 3 shows a schematic partial view from above of the machine in Figures 1 and 2.
With reference to the aforementioned figures, 1 indicates the wash compartment of a conventional dishwasher, equipped with at least two drawers 2 and 3 to accommodate the dishes to be washed and at least two impellers 4 and 5, each of which is provided with nozzles, indicated schematically as 6, in order to spray the washing or rinsing liquid-according to the stage of the cycle - against the objects to be washed.
The impellers 4 and 5 are conventionally mounted such that they are free to rotate on respective support columns 7 and 8.
The bottom 9 of the wash compartment 1 is provided with a primary grille 10, in the centre of which there is a perforated vessel 11 which can be extracted manually.
The grille 10 and the vessel 11 each have holes which permit the washing or rinsing liquid to pass but retain the large particles of food residues which are removed from the objects during the washing stage.
Positioned below the primary grille 10, the device according to the invention comprises a first chamber 12 which, via the annular aperture 13, communicates with a second chamber 14 located concentrically to the vessel 11.
This chamber 14 has a cylindrical wall 15 whose inner surface is covered by a filtering element 16 containing holes which are relatively small compared with those of the primary grille 10.
This latter filtering element 16 is such that it blocks the passage of very fine particles of dirt which would otherwise remain in suspension in the washing water, but still permits adequate passage of the flow of water.
For this purpose, the overall area of the through holes in the filtering element 16 is essentially the same as the total area of the holes in the primary grille 10.
In addition, the overall surface area of the filtering element 16 is essentially half the size of the surface area of the said primary grille.
Around the second chamber 14, the device comprises a third chamber 17, which extends axially as far as the wall 18 which constitutes the bottom of the first chamber 12, with which wall it is connected in a sealed manner.
In the example illustrated, the connection is provided by means of an annular seal 19 which is inserted between a collar 20, which is integral with the wall 18, and an opposing collar 21, which is integral with the wall 22 constituting the periphery of the chamber 17.
The third chamber 17 is connected, via the aperture 23, to the suction duct 24 of the re-circulation pump 25, the delivery unit of which (not shown) supplies the nozzles 6 on the impellers 4 and 5 in a known and conventional manner.
The bottom 26 of the second chamber 14 is provided with a passage 27 which puts the chamber into communication with the suction duct 28 of the drainage pump 29, the delivery unit 30 of which discharges into the drains.
The bottom 26 is also provided with a nozzle 31 which is permanently connected to the water supply coming from the water mains by means of an on/off solenoid valve 32 which is controlled by the operating cycle of the dishwasher.
In the embodiment shown, the nozzle 31 is positioned on the bottom 26, in a position co-axial to the chamber 14 and to the vessel 11, so as to convey its jet against the filtering cylindrical surface 16 of the chamber 14 and against the said vessel.
For safety reasons, in order to ensure operation of the pump 25 even if the filtering surfaces 16 of the second chamber 14 become totally blocked, the wall 18, which constitutes the bottom of the first chamber 12, contains calibrated holes 33 which keep the said chamber 12 constantly in communication with the third chamber 17 so that part, even if only a small part, of the water circulating reaches the pump 25 directly.
According to the above description, whereas during the washing cycle the large particles of food residues removed from the objects being washed are retained by the primary grille 10 and collected in the vessel 11, the remaining particles, which are broken up and pulverized during the various passages from the wash compartment 1 to the nozzles 6 under the action of the pump 25, are retained by the filtering elements 16 found on the inside surface of the cylindrical wall 15 of the second chamber 14.
The path of the washing liquid during the recycling is illustrated by the arrows in Figure 1.
When the recycling stage has been completed, the discharge pump 29 can be activated, discharging the amount of liquid present in the wash compartment 1. During this stage, the liquid is also forced to pass from the chamber 17 into the second chamber 14, passing through the filtering elements 16 in the opposite direction to that of re-circulation, thereby cleaning the filtering elements 16.
Advantageously, during the said discharge stage, by means of an appropriate command given by the cycle to the solenoid valve 32, clean water can be admitted via the nozzle 31 into the second chamber 14.
The jet of clean water from the nozzle 31 contributes to the washing in counter-current of the filtering elements 16, and also of the vessel 11.
The path of the liquid flow during the drainage and filter washing stage is illustrated by the arrows shown in Figure 2.
Thus, according to the invention, it is possible to carry out the washing and rinsing cycles in a dishwasher with liquids circulating which are substantially free from particles of dirt in suspension since the latter are retained by the fine filtering elements 16 of the second collection chamber 14 which can be washed in counter-current during the drainage stage.

Claims

Device for fine filtering the washing liquid in a dishwasher, comprising a wash compartment (1) to contain the objects to be washed, a pump (25) for re-circulating the liquid by collecting it from the bottom (9) of the wash compartment (1) and admitting it into the latter by means of a plurality of nozzles (6), a drainage pump (29) to drain the liquid out of the wash compartment at the end of the washing and/or rinsing cycle, the bottom (9) of the wash compartment (1) including a primary grille (10) and a perforated vessel (11) in order to allow the liquid to pass through the re-circulation pump but retain the large particles of dirt removed from the objects to be washed, said device comprising, for the collection of the liquid from the bottom (9) of the wash compartment (1), a first chamber (12) positioned below the primary grille (10) and at least partially surrounding the perforated vessel (11), a second chamber (14) which communicates freely with said first chamber (12) , a third chamber (17) which communicates on one hand with the said second chamber (14), and on the other hand with the suction duct (24) of the said re-circulation pump (25) characterized in that said second chamber (14) contains filtering elements (16) designed to retain fine particles of dirt, the third chamber (17) communicating with the second chamber (14) around said filtering elements (16), and in that said second chamber (14) is also in communication with the suction duct (28) of the said drainage pump (29) via apertures (27) without filtering elements.
Device according to Claim 1, characterized in that the overall area of the holes for the passage of the liquid through the said filtering element (16) is essentially the same as the overall area of the holes in the said primary grille (10), the overall surface area of the said filtering element (16) being essentially half the overall size of the surface area of the said primary grille (10).
Device according to Claims 1 and 2, characterized in that the said second chamber (14) is cylindrical and is at least partially positioned concentrically to the said perforated vessel (11), the filtering elements (16) being located inside the chamber (14), on the cylindrical wall (15) of the latter.
Device according to Claims 1 and 3, characterized in that the said third chamber (17) is positioned like a ring around the said second chamber (14), around the cylindrical wall (15) containing the said filtering elements (16).
Device according to Claims 1 to 4, characterized in that the said first chamber (12) contains calibrated passages (33) which open directly inside the said third chamber (17).
Device according to Claims 1 to 5, characterized in that the said second chamber (14) is provided with a nozzle (31) which is connected to the water mains in order to admit clean water for washing the said filtering elements (16), in conjunction with operation of the said drainage pump (29).