DISHWASHING MACHINE WITH SELF-CLEANING RECIRCULATION FILTER

Abstract: A dishwasher comprising a recirculation filter (7) for re­ taining particulate matter entrained by the circulating water, and nozzle merins (10,12) for directing at least one jet of water onto the surface of the recirculation filter for cleaning it. In known dishwashers a jet of water is directed onto the surface of the recirculation filter at an inclination of about 10 to 25°. Proper cleaning of the filter is not achieved in this manner, as the vertical component of the water jet tends to propel particulate matter into the filter passages. The invention overcomes this shortcoming by the prov­ ision that the water jet is directed onto the surface of the recirculation filter (7) in a substantially tangential direction. The nozzle means may comprise deflector means (13) for def­ lecting a substantially vertical jet in a tangential direction, or suitable shaped branch pipe means (12) on a rotating nozzle carrier arm (6) disposed above the surface of the recirculation filter.

Description: The present invention relates to a dishwashing machine having a recirculaticn filter adapted to be automatically cleaned during operation of the machine. Known dishwashers usually have a water collection sump at the bottom of the washing chamber, with a water recirculation pump and a water discharge pump connected thereto. The water collection sump communicates with the washing chamber through a fine-mesh recirculation filter of a substantially planar configuration adapted to retain particulate matter entrained by the water flowing from the chamber into the collecting sump. The recirculation filter is formed with an opening through which the interior of the washing chamber communicates directly with the intake of the discharge pump. A large-mesh filter inserted into this opening serves the main purpose of retaining large particles which might otherwise obstruct or damage the rotor of the discharge pump. A dishwashing machine known from EU-A-0068974 is provided with rotating jet nozzles directed obliquely onto the surface of the recirculation filter for rinsing retained particulate matter off the recirculation filter and sweeping it into the pump protection filter. In view of their small inclination in the order of 10 to 250, the jet nozzles have experimentally been found to practically lack any efficiency. To the contrary, the vertical components of the rotating jets tends to jam the particulate matter into the passages of the recirculation mesh filter, with the result that the filter is progressively obstructed. It is an object of the present invention to provide a dishwashing machine having a recirculation filter provided with efficient self-cleaning characteristics without requiring particularly complicated auxiliary devices. This object is attained in a dishwasher of the type having a recirculation filter with a substantially planar surface adapted to retain particulate matter, and nozzle means adapted to direct at least one water jet onto the surface. According to the invention the dishwasher is characterized in that said water jet is directed substantially tangentially onto the surface of said recirculation filter. The tangential water jet is preferably of the rotating type, issueing from a rotating nozzle carrier arm disposed above the recirculation filter by way of a branch outlet thereof and/or deflector means. The employ of a water jet substantially devoid of vertical components with respect to the surface of the recirculation filter has been experimentally found to result in that any particulate matter is swept along the surface of the filter without hindrance, so that the filter is automatically cleaned. 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 drawing, the only figure of which shows a diagrammatic partical view of a dishwasher according to the invention. With reference to the figure, a dishwasher comprises a washing chamber 3 (only partially shown), the bottom of which is formed with a sump 4 for collecting the washing and rinsing water. Located in sump 4 is the intake section 2 of a circulation pump 5 for the supply of water to at least one rotating nozzle carrier arm 6 for spraying the water onto the (not shown) dishes to be washed in the known manner. Disposed in washing chamber 3 below nozzle carrier arm 6 is a fine-mesh recirculation filter 7. Filter 7 is disposed in the flow path of the water sprayed onto the dishes and flowing back into sump 4 for being recirculated by pump 5. Filter 7 is formed with a frustoconical portion housing a removable large-mesh filter 8 of a corresponding shape disposed in the flow path of the water from sump 4 to the intake of a discharge pump 9. The dishwasher further comprises nozzle means adapted to direct a jet of water 11 onto the surface of recirculation filter 7 in a direction towards the center of washing chamber 3. According to a characteristic aspect of the invention jet 11 is directed substantially tangentially onto the surface of recirculation filter 7. This effect may preferably be obtained by means of a substantially annular deflector 13 extending adjacent the periphery of filter 7, itself shaped for instance as an annular sheet member concentric with the axis of rotation of nozzle carrier arm 6. In this embodiment nozzle carrier arm 6 has its underside formed with at least one supplementary opening 10 adapted to direct a jet 14 of water onto deflector 13 shaped to deflect the water so as to form tangential jet 11, the latter being preferably aligned in the radial direction of filter 7. As already stated it has been experimentally found that jet 11, being substantially devoid of vertical components, does not cause the passages of filter 7 to be obstructed by the particulate matter it entrains; quite to the contrary, the particulate matter is swept along the surface of the recirculation filter substantially without hindrance and into large-mesh filter 8 to be collected therein prior to being expelled therefrom during a supsequent water discharge cycle. The invention thus attains the stated object of achieving an effective automatic cleaning of recirculation filter 7 which may advantageously be of a simple construction (for example a simple metal sheet or plastic panel), and may be formed with particularly narrow passages to result in improved filtering performance. The described combination results in an improvement of the overall performance of the dishwasher by achieving effective filtering of the total volume of the recirculated water instead of filtering only part of the circulating water as in conventional embodiments. In this contect it is to be noted that the particularly narrow passages of the recirculation filter facilitate the displacement of particulate matter on the surface of the filter, thus contributing to the self-cleaning effect It has been experimentally found that the optimum dimension of the passages of filter 7 lie between 0.2 and 0.3 millimeters. In an alternative embodiment, deflector 13 may be omitted, jet 11 being produced by a branch pipe 12 extending downwards from nozzle carrier arm 6 and being suitably shaped into an "L" configuration as shown in the drawing. The described dishwasher may of course be subjected to various modifications and alterations within the scope of the invention. The jet 11 issueing from supplementary opening 10 may for instance be inclined directly onto filter 7 in the known manner; in this case, however, the recirculation filter would be of substantially conical shape with its surface aligned with respect to jet 11 so that the latter impinges tangentially thereon. Further jet 11 may be produced in any suitable manner to be directed from a central position of filter 7 towards its periphery, or any number of such jets may be produced by a corresponding number of stationary nozzles in place of rotating ones.

Claims: Dishwashing Machine with Self-Cleaning Recirculation Filter Patent Claims: 1. A dishwasher comprising a recirculation filter having a substantially planar surface adapted to retain particulate matter, and nozzle means for directing at least one water jet onto said surface, characterized in that said water jet (11) is directed substantially tangentially onto said surface of said recirculation filter (7). 2. A dishwasher according to claim 1, characterized in that said nozzle means (13) include deflector means (13) supplied with water by at least one rotating nozzle carrier arm (6) disposed above said surface of said recirculation filter (7). 3. A dishwasher according to claim 1, characterized in that said nozzle means comprise at least one branch pipe (12) on a rotating nozzle carrier arm (6) disposed above said surface of said recirculation filter (7). 4. A dishwasher according to claim 2 or 3, characterized in that said tangential jet (11) is aligned in a radial direction with respect to said surface of said recirculation filter (7). 5. A dishwasher according to any of claims 1 to '4, characterized in that said filter (7) is provided with passages having dimensions between 0.2 and 0.3 mm.

Inventors: MILOCCO, CLAUDIO, PUP, GIOVANNI
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1986
Main classification: A47L15
IPC codes: A47L15