DISHWASHING MACHINE WITH SELF-CLEANING PUMP PROTECTION FILTER

Abstract: A dishwashing machine has a tub (3), a fine-mesh filter (7) disposed in the tub upstream of a circulation pump (5), and a coarse-mesh filter (8) seated within the fine-mesh filter up­ stream of a water discharge pump (9). The coarse-mesh filter is susceptible to clogging by coarse impurities of relatively soft consistency, necessitating frequent removal and cleaning of the filter. According to the invention, spray jet means is pro­ vided for directing a jet of water coaxially onto the coarse­ mesh filter for cleaning it by the disintegration of soft matter collected therein. The spray jet means may take the form of an additional opening (10) in the bottom side of a rotatable irriga­ tion arm, or of a jet nozzle (12) fixedly mounted in a horizontal position and cooperating with a deflector (13) for directing the water jet (11) issueing from the jet nozzle onto the coarse-­ mesh filter.

Description: Description The present invention relates to a dishwashing machine provided with a discharge pump protection filter adapted to be automatically cleaned durign operation of the machine. Known dishwashing machines usually have a water collection well at the bottom of a washing tub, with the inlet of a water circulation pump and the inlet of a water discharge pump connected to said well. The water collection well houses a fine-mesh recirculation filter disposed in the flowpath of the water aspirated by the circulation pump. The fine-mesh filter is formed with an opening directly connecting the interior of the tub with the inlet of the discharge pump. Disposed in this opening is a coarse mesh filter, referred to as a discharge pump protection filter and having as its main purpose the retention of coarse impurities, such as bits of china or glass, bones and the like which might otherwise obstruct or even damage the impeller of the discharge pump. The corase-mesh pump protection filter will of course also retain shreds and bits of softer materials, such as paper shreds, breadcrumbs, fatty matter and the like, which may in the long run obstruct the filter, as part of the water aspirated by the circulation pump also passes therethrough. The usually dismountable coarse-mesh filter has therefore to be cleaned at relatively short intervals. Already known from Italian Patent 952,947 is a diswashing machine provided with stationary jet nozzles for automatically cleaning the fine-mesh and coarse-mesh filters. These jet nozzles are designed to produce jets of water substantially perpendicular to the axis of the coarse-mesh fil ter in proximity to the inlet side of the filteritself (where the tangential water jet has practically no effect at all), and in an intermediate zone, where the coarse-mesh filter is surrounded by the fine-mesh filter which disperses the water jet so as to render it ineffective with regard to the coarse-mesh filter. Also known, for instance from US Patent 3,810,480 are dishwashing machines provided with rotating jet nozzles directed perpendicularly to the fine-mesh filter in countercurrent to the flow of the water aspirated by the circulation pump. This construction does not provide a solution for the problem of automatically cleaning the discharge pump protection filter From European Patent Application No. 0068974 there is further known a dishwashing machine provided with rotating jet nozzles directed obliquely onto the surface of the fine-mesh recirculation filter so as to concentrate and to convey to the interior of the coarse-mesh discharge pump protection filter any particulate impurities collecting on the recirculation filter. In view of their inclined positions, the rotating jet nozzles have no cleaning effect on the coarse-mesh filter, resulting in the latter being all the more readily clogged by the impurities. It is an object of the present invention to provide a dishwashing machine of simple construction and reliable operation, which is provided with a discharge pump protection filter arranged to be automatically and efficiently cleaned at the end at least of each dishwashing cycle. This object is attained by a dishwashing machine comprising a washing tub provided with a fine-mesh filter disposed in the flowpath of water aspirated by a circulation pump and formed with an opening directly connecting the interior of said tub with the water intake of a discharge pump, and a coarse-mesh filter seted in said opening. According to the invention, a dishwashing of this type is essentially characterized by comprising spray jet means adapted to direct at least one water jet against said coarse-mesh filter in a substantially coaxial direction therewith for effecting the cleaning thereof. The spray jet means preferably comprise at least one additional opening formed in at least one rotatable arm provided for irrigating the dishes. In this manner, operation of the circulation pump automatically results in the disintegration of impurities collected in the discharge pump protection filter, which is usually disposed in a relatively quiescent zone of the washing tub. The coarse-mesh filter is thus always kept sufficiently clean, its maintenance being limited to the infrequent necessity of removing coarse and relatively indestructible impurities, such as bits of china or glass, bones and the like, from the filter. The characteristics and advantages of the invention will become more clearly evident from the following description, given by way of example with reference to the accompanying drawings, wherein: fig. 1 and 2 show diagrammatic representations of dish washing machines in two functionally equivalent embodiments of the invention. With reference to the drawings, a dishwashing machine comprises a washing tub 3 (only partially shown), the bottom of which is formed as a well 4 for collecting the dishwashing and rinsing water. Disposed in communication with well 4 is a circulation pump 5 supplying at least one rotatable arm 6 for irrigating the dishes and the like to be washed (not shown) in a per se known manner. Washing tub 3 contains a fine-mesh filter 7 disposed in the flowpath of the water collecting in well 4 after having been sprayed onto the dishes, and to be aspirated again by circulation pump 5. Fine-mesh filter 6 is of a known configuration, having a frustoconical portion for the insertion of a removable coarse-mesh filter 8 of corrsponding shape disposed substantially in the flowpath of water from well 4 to a discharge pump 9. Coars-mesh filter 8 acts in a known manner as a discharge pump protection filter. According to the invention. the dishwashing machine includes spray Jet means arranged to direct at least one water jet onto filter 8 in a substantially coaxial direction thereof for automatically cleaning the filter by disintegrating low-consistency impurities collected therein. In a preferred embodiment, the water jet may be produced by providing an additional opening 10 at the bottom side of rotatable irrigation arm 6 (fig. 1). In this case the water jet 11 is effective to clean filter 8 in an intermittent manner. In an alternative embodiment, water jet 11 may be produced by a stationary jet nozzle 12 (fig. 2) connected to the outlet of circulation pump 5, preferably on a horizontal axis and associated with a deflector 13 for directing the water jet towards the pump protection filter 8. Deflector 13 may of course be mounted at any position considered most favourable. Also, water jet 11 may be produced in any equivalent manner. In any case, and in contrast to known arrangements, the discharge pump protection filter 8 will always have been efficiently cleaned at the edn of each operating cycle of the dishwashing machine.

Claims: Dishwashing Machine with Self-Cleaning Pump Protection Filter Patent Claims 1. A dishwashing machine comprising a washing tub provided with a fine-mesh filter disposed in the flowpath of water aspirated by a circulation pump and formed with an opening directly connecting the interior of said tub with the water intake of a discharge pump, and a coarse-mesh filter seated in said opening, characterized by comprising spray jet means adapted to direct at least one water jet (11) against said coarse-mesh filter (8) in a substantially coaxial direction therewith for effecting the cleaning thereof. 2. A dishwashing machine according to claim 1, wherein said circulation pump feeds at least one rotatable spray arm for spraying the dishes, characterized in that said spray jet means comprise at least one additional opening (10) formed in said rotatable arm (6). 3. A diswashing machine according to claim 1, characterized in that said spray jet measn comprise at least one stationary jet nozzle (12) connected to the outlet of said circulation pump (5). 4. A dishwashing machine according to claim 3, wherein the axis of said stationary jet nozzle extends substantially transversely of the axis of said coarse-mesh filter, characterized by comprising a deflector (13) adapted to direct the water jet exiting from said stationary jet nozzle (12) towards said coarse-mesh filter (8).

Inventors: MILOCCO, CLAUDIO
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1984
Main classification: A47L15
IPC codes: A47L15