[0001] 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.
[0002] 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.
[0003] 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.
[0004] The dirtier the dishes and the more efficient the cycle selected to remove this dirt,
the dirtier the washing liquid which is recycled.
[0005] 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] This object is achieved by means of the device according to the following claims.
[0011] 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.
[0012] 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.
[0013] The impellers 4 and 5 are conventionally mounted such that they are free to rotate
on respective support columns 7 and 8.
[0014] 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.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] The path of the washing liquid during the recycling is illustrated by the arrows
in Figure 1.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] The path of the liquid flow during the drainage and filter washing stage is illustrated
by the arrows shown in Figure 2.
[0034] 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.
1. 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 said 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 to the said
re-circulation pump but retain the large particles of dirt removed from the objects
to be washed, characterized in that it comprises, for collection of the liquid from
the bottom (9) of the wash compartment (1), a first chamber (12) positioned below
the said primary grille (10) and at least partially surrounding the said perforated
vessel (11), a second chamber (14) which communicates freely with the said first chamber
(12) and contains filtering elements (16) designed to retain fine particles of dirt,
a third chamber (17) which communicates on one hand with the said second chamber (14),
around the said filtering elements (16) of the latter, and on the other hand with
the suction duct (24) of the said re-circulation pump (25) , the said second chamber
(14) also being in communication with the suction duct (28) of the said drainage pump
(29) via apertures (27) without filtering elements.
2. 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).
3. 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.
4. 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).
5. 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).
6. 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).