EP2263512B2

EP2263512B2 - Hood-type industrial dishwasher with improved filter assembly

Info

Publication number: EP2263512B2
Application number: EP09425235.0A
Authority: EP
Inventors: Ezio Gobbi; Damiano Piazza
Original assignee: Bonferraro SpA
Current assignee: Bonferraro SpA
Priority date: 2009-06-17
Filing date: 2009-06-17
Publication date: 2019-01-09
Anticipated expiration: 2029-06-17
Also published as: EP2263512A1; EP2263512B1; PL2263512T3; PL2263512T5

Description

The present invention relates to industrial dishwashers, and in particular to a hood-type dishwasher with an improved filter assembly aimed at a more effective and efficient washing of the dishes.
It is known that industrial dishwashers used in professional fields (restaurants, bars, etc.) are capable of washing dishes within extremely reduced times, thanks to some constructional features that make them different from domestic dishwashers in various respects. In particular, thanks to the presence of two distinct wash and rinse circuits each having its own sprinklers, the wash water is sprayed onto the dishes by a wash pump and during the rinse a portion of this water is replaced by rinse water pre-heated in a heater and fed to the rinse circuit by a suitable rinse pump.
However, most often the same manufacturers of those machines advise the users to rinse the dishes prior to washing them, with a clear waste of water and time, because if the dishes are introduced into the machine as they are removed from the table (apart from disposing of the largest residues) the wash results are often poor. In fact, these machines are provided with filter devices substantially intended only to prevent damages to the wash and drain circuits of the machine, because in case some residues such as nutshells, toothpicks, mollusc shells or the like end up in the pumps they can block them and/or clog the water ejection nozzles.
In practice these machines have a single removable filter, introduced in the flat filter arranged at the bottom of the wash tank, with holes having a diameter equal to or smaller than the holes of said flat filter. Such a filter can be removed also when the collecting sump is filled with water, so as to clean it between a wash cycle and the following cycle. Prior art filters, therefore, rather than contributing to keep as clean as possible the wash liquor, which is not changed between a cycle and the following one but for a partial restoring during the rinse phase with clean water, retain almost completely the dirt that by building up cycle after cycle pollutes the wash liquor ever more and makes difficult for the water to pass through the filter. An example of such a machine is disclosed in EP 2087830 .
In such a condition and without the manual pre-wash, the dirt residues present on the dishes build up cycle after cycle resulting in a wash liquor so dirty as to require its frequent total replacement, with an evident waste of water, time and power. As a matter of fact, very little attention has been given until now to the importance of maintaining a sufficiently clean "wash bath" in order to improve the wash quality and consequently reduce the importance of the rinse and decrease consumptions.
It is clear that in order to achieve a good wash effectiveness it is necessary that the filter assembly succeeds in retaining the potentially harmful dirt particles without clogging. For this reason, it is essential to manufacture a filter assembly having a correct balance between the requirements of filtering and not being clogged, i.e. capable of letting through for evacuation by the drain pump all those residues that by building up increase the water dirtiness in addition to progressively clogging the filters, typically rice grains, bits of meat or vegetables, bread crumbs and the like.
In prior art hood-type dishwashers the filter devices have the drawback of not striking this balance of requirements, whereby they do not allow to achieve a desirable high wash effectiveness.
Therefore the object of the present invention is to provide a hood-type dishwasher with an improved filter assembly which overcomes said drawback.
This object is achieved by means of a hood-type industrial dishwasher having the features of claim 1. Other advantageous features are disclosed in the dependent claims.
The main advantage of the dishwasher according to the present invention is that of having a filter assembly that achieves a high filtering without clogging problems, since it is capable of retaining all those residues that could actually cause damage to the machine while letting through all those residues that could cause the clogging, so as to validly contribute to a good wash effectiveness of the dishwasher.
A second advantage of the above-mentioned filter assembly is that it is divided in two parts so as to maintain the possibility of removing the top filter for large residues also when the sump is full, while the wash and drain circuit remains protected by the bottom filter so as to limit the risk that during the removal of the top filter other dirt residues present along the edge of the flat filter and having a size greater than that allowed fall into the sump and end up blocking the pumps or clogging the nozzles.
Another advantage of the present dishwasher is that the improved filter assembly is made up of few simple parts, which positively affects its cost and the ease in assembling and disassembling it.
These and other advantages and characteristics of the dishwasher according to the present invention will be clear to those skilled in the art from the following detailed description of an embodiment thereof, with reference to the annexed drawings wherein:

Fig.1 is a perspective exploded view, in longitudinal section, showing the tank bottom of a dishwasher provided with the present filter assembly;
Fig.2 is a view similar to the preceding one with the filter assembly in the assembled state;
Fig.3 is a diagrammatic exploded view, in cross-section, of the above-mentioned tank bottom region;
Fig.4 is a diagrammatic front view, in cross-section, of the dishwasher during its normal operation; and
Fig.5 is a diagrammatic front view, in cross-section, of the bottom portion of the dishwasher during the removal of the top filter.

With reference to figures 1 to 3, there is seen that the filter assembly of a dishwasher according to the present invention includes a first top filtering element 1, introduced from above into a central opening 2a of a concave-shaped flat filter 2 that acts as a lid of the collecting sump 3 formed in the tank bottom 4. A second bottom filtering element 5 is similarly introduced from above into a central opening 3a at the bottom of the sump 3, said opening 3a being concentric with said opening 2a in the flat filter 2, and a manifold 6 is secured under opening 3a for the connection to the wash and drain pumps.
Preferably, the correct positioning of the bottom filtering element 5 is detected by a suitable sensor that authorizes the operation of the dishwasher. An example of such a sensor, illustrated only in Figs.1 and 2, consists of a reed switch 7 arranged in manifold 6 so as to detect the presence of a magnet 8 located in the bottom filtering element 5.
The flat filter 2 consists of a perforated stainless steel sheet, with holes having a diameter indicatively between 1,5 and 2,5 mm, which has the function of letting through most (about 75-85%) of the flow rate of the wash pump, and of receiving in its central opening 2a the first filtering element 1 that is made up of two coaxial bodies 1a, 1b joined at their bases through connecting ribs that leave a circular passage 9 whose width "w" ranges from 4 to 6 mm, preferably 5 mm.
More specifically, the inner body 1a is a closed cylinder but for openings on the top side and the outer body 1b is slightly frustoconical and has a top peripheral rim 10 for fitting into opening 2a, a diametral crossbar 11 for its handling, as well as a side wall with vertical passage slots having a width indicatively between 1 and 1,5 mm, preferably 1,2 mm. The connecting ribs defining the circular passage 9 are formed with a pitch in the range from 10 to 16 mm, preferably between 12 and 14 mm.
The second filtering element 5 is made up of three coaxial bodies 5a, 5b and 5c of different diameter joined through a circular ring 5d provided with openings. More specifically, the inner body 5a is a solid cylinder extending above ring 5d and has an inlet 12 at the top with an inward tapering; the outer body 5b, slightly frustoconical, also extends solid above ring 5d but is much shorter than cylinder 5a and has a top peripheral rim 13 for fitting into opening 3a of sump 3; and finally the intermediate body 5c is a solid cylinder extending below ring 5d. Both the latter and rim 13 are provided with passage slots having a size equal to or greater than the passage holes of the flat filter 2, indicatively 2,5 mm wide, yet such as to retain the residues having a size that could clog the wash nozzles or block the wash pump.
As better illustrated in Fig. 4, when rim 13 of the bottom filtering element 5 is fitted in opening 3a the bottom edge of the intermediate cylinder 5c results located inside manifold 6 between the top connection 6a to pipe WP leading to the wash pump and the bottom connection 6b to pipe DP leading to the drain pump. Furthermore, when rim 10 of the top filtering element 1 is fitted in opening 2a the tapered inlet 12 of the bottom filtering element 5 is adjacent to the bottom end of the top filtering element 1 that has a corresponding outlet 14 tapered inwards so as to achieve a substantially continuous conduit between the two filtering elements 1 and 5.
During the operation of the machine the largest residues having a size greater than the holes of the flat filter 2 are collected within the top filtering element 1, and among these the residues having such a size as to pass through the circular passage 9 reach the discharge region of manifold 6 through the central portion of the bottom filtering element 5. Said residues, once they are gathered there, will be discharged through pipe DP upon activation of the drain pump at the end of each wash cycle. On the contrary, the smaller residues passing through the flat filter 2, body 1b, ring 5d and rim 13 remain in the wash liquor without significantly polluting it nor contributing to the clogging of the filter assembly.
The largest residues retained within the top filtering element 1, having a size such that they can not be discharged through the drain pump, even when the machine is in the operating condition (i.e. with sump 3 full of water) can be removed by the operator by removing only element 1 for cleaning, as shown in Fig.5. During this operation there is the risk that large residues possibly present along the edge of opening 2a fall into sump 3 but even if they did fall therein they would be retained, as previously explained, by ring 5d and rim 13 of the bottom filtering element 5 which, at the end of the use of the machine when sump 3 is empty, can be in turn removed from opening 3a and thoroughly washed.
It should also be noted that the tapered shape of inlet 12 coupling with the similarly tapered outlet 14 has the function not only of assuring a good coupling between the two filtering elements, but also to increase the horizontal distance "d" between the edge of inlet 12 and the edge of opening 2a so as to limit the risk that during the removal of the top filtering element 1 large residues present along the edge of opening 2a fall and reach the discharge region by entering the central cylinder 5 a.
Thanks to the above-illustrated features, all the residues that pass through the filter assembly can smoothly be evacuated by the drain pump, through pipe DP, that removes them from the discharge region of manifold 6 located under the filter assembly, whereas the other residues that could cause troubles are retained.
It is clear that the above-described and illustrated embodiment of the dishwasher according to the invention is just an example susceptible of various modifications. In particular, the filtering elements 1 and 5 could even be without radial symmetry and openings 2a, 3a could be not concentric as long as the filter assembly forms a smooth path for the passage of residues of suitable size towards the drain pump.

Claims

Hood-type industrial dishwasher including a first top filtering element (1) provided with a peripheral rim (10) that is fitted into an opening (2a) of a concave-shaped flat filter (2) suitable to act as a lid for the collecting sump (3) formed in the tank bottom (4), characterized in that it further includes a second bottom filtering element (5) provided with a peripheral rim (13) that is fitted into an opening (3a) formed at the bottom of said collecting sump (3), said second bottom filtering element (5) being partially received within a manifold (6) for the connection to the wash and drain pumps, which is secured under said opening (3a) of the sump (3), said second bottom filtering element (5) being provided at the top with an inward tapered inlet (12) and forming in combination with said first top filtering element (1) provided at the bottom with an inward tapered outlet (14), adjacent to said inward tapered inlet (12) so as to achieve a substantially continuous conduit between the two filtering elements (1, 5), a filter assembly extending substantially continuously between said flat filter (2) and a pipe (DP) leading to the drain pump
Dishwasher according to claim 1, characterized in that said first filtering element (1) is made up of two coaxial bodies (1a, 1 b) joined at their bases through connecting ribs that leave a circular passage (9) whose width (w) ranges from 4 to 6 mm, preferably 5 mm.
Dishwasher according to claim 1 or2, characterized in that the first filtering element (1) includes an inner cylindrical body (1a) closed but for openings on the top side and an outer frustoconical body (1b) with vertical passage slots having a width between 1 and 1,5 mm, preferably 1,2 mm.
Dishwasher according to claim 2 or 3, characterized In that the connecting ribs defining the circular passage (9) are formed with a pitch in the range from 10 to 16 mm, preferably between 12 and 14 mm.
Dishwasher according to any of the preceding claims, characterized in that the second filtering element (5) is made up of three coaxial bodies (5a, 5b, 5c) of different diameter joined through a circular ring (5d) provided with openings.
Dishwasher according to the preceding claim, characterized in that the an inner body (5a) is a solid cylinder extending above the ring (5d), the outer body (5b) is slightly frustoconical, extends solid above the ring (5d) but much less than said inner body (5a) and has the peripheral rim (13) as a top peripheral rim (13) suitable for fitting into the opening (3a) of the sump (3), and the intermediate body (5c) is a solid cylinder extending below the ring (5d), both the latter and said rim (13) being provided with passage slots having a size equal to or greater than the passage holes of the flat filter (2), indicatively 2,5 mm wide, yet such as to retain the residues having a size that could clog the wash nozzles or block the wash pump.
Dishwasher according to the preceding claim, characterized in that the inner cylinder (5a) of the second filtering element (5) has the inward-tapered inlet (12) at the top end and the bottom end of the first filtering element (1) has the corresponding inward-tapered outlet (14) so as to form the substantially continuous conduit between the two filtering elements (1, 5).
Dishwasher according to any of the preceding claims, characterized in that it further includes a sensor suitable to detect the correct positioning of the second filtering element (5).
Dishwasher according to the preceding claim, characterized in that the sensor consists of a reed switch (7) arranged in the manifold (6) so as to detect the presence of a magnet (8) located in the second filtering element (5).
Dishwasher according to any of the preceding claims, characterized in that the flat filter (2) consists of a perforated stainless steel sheet with holes having a diameter between 1,5 and 2,2 mm.
Dishwasher according to any of the preceding claims, characterized in that the opening (2a) in the flat filter (2) is concentric with the opening (3a) in the sump (3) and the two filter elements (1, 5) have a radial symmetry.