FILTER FOR A LAUNDRY WASHING MACHINE

Abstract: A filter for domestic laundry washing machines of the recirculation type comprising a collecting receptacle (5) disposed below the tub (3) and connected thereto by a conduit (6) and a housing (15) for a removable filtering element (14). The collecting receptacle (5) is adapted to contain an electric heater element (12) and to communicate with a top portion of the tub through a conduit (7) and a recirculation pump (8), and with a discharge conduit (10) of the machine through a discharge pump (11). According to the invention the removable filer element (14) is of one-oiece construction comprising a fine-mesh filtering surface (17, 21) disposed upstream of the heater element (12) in the washing liquid recirculation direction, and a coarse-mesh filtering surface (18, 22) disposed upstream of the discharge pump (11) in the washign liquid discharge direction. In this manner, any contaminants deposited on the fine-mesh filtering surface (17, 21) during the recirculation phase are carried away by the washing liquid during each discharge phase.

Description: The invention relates to a filter for laundry washing machines, particularly for domestic laundry washing machines adapted to effect the treatment of the laundry by spraying it with a washing liquid. As described in Italian Patent Application 45715 A/85, filed on 24. 5. 1985 by the present applicant, a laundry washing machine of this type substantially comprises a laundering tub, a drum for containing the laundry, and a collecting receptacle disposed below the tub and connected thereto for collecting the washing liquid not retained by the laundry. The washing liquid collecting receptacle is connected to the discharge conduit of the machine through a conventional discharge pump, and to a spray nozzle arrangement in the tub through a recirculation conduit and pump. Housed within the collecting receptacle are at least one filtering element, an electric heater element, and a thermostatic sensor for respectively filtering and heating the washing liquid and monitoring its temperature. The filtering element has a fine-mesh surface mainly serving for preventing loose fibers entrained by the washing liquid from entering the collecting receptacle and collecting on the electric heater element to thereby impair its efficiency and reliability in the course of time. The fine-mesh filtering element suffers from the disadvantage, however, that it is rapidly clogged, so that it has to be frequently cleaned by the user. With the objective of avoiding such rapid clogging of the filter German Patent 1,191,781 describes a filter for a laundry washing machine in combination with a mechanical device for cleaning its filtering surface. This construction is obviously rather complicated and uneconomical. Known from US Patent 3,727,435 is a fine-mesh filter for a recirculation laundry washing machine, in which the liquid flow passing through the filter during the recirculation phase is reversed during the discharge phase, so that the contaminations collected on the filter during the recirculation phase are removed therefrom during the discharge phase. The solutions offered by both of the above cited patents suffer from the shortcoming that the filter is not removable and that the discharge pump, particularly when not of the self-cleaning type, is not protected from foreign bodies such as buttons, coins and the like possibly entrained by the washing liquid. Numerous filter constructions are known, however, for use in dishwashing machines, in which they provide a fine-filtering effect in the flow direction towards the recirculation conduit, and a coarse-filtering effect towards the discharge conduit. The nature of the impurities and contaminations encountered in a dishwashing machine is different, however, from that of the contaminants encountered in a laundry washing machine. In addition, among the various parts of a filter for a dishwashing machine, the fine-mesh filter component is not readily removable and serves the purpose of preventing the jet nozzles mounted on the rotating spray arms from being obturated, and not that of protecting the surface of the heater elements from foreign bodies being deposited thereon, these heater elements being located in the washing chamber of the dishwashing machine in contrast to the arrangement in the type of laundry washing machines under discussion. In view of the above, it is an object of the invention to provide a filter for a laundry washing machine of the type described above, which should be readily removable and of integral construction while being capable of reliably preventing loose fibers and the like from being deposited on the surface of the resistance heater element without requiring any more frequent cleaning operations on the user's part than a corresponding filter in a conventional immersion-type laundry washing machine. According to the invention, these and other objects are attained by a filter for laundry washing machines, particularly for domestic laundry washing machines of the type comprising a laundering tub, a rotatable drum mounted in the tub, and a washing liquid collecting receptacle disposed below the tub and connected to a lower portion thereof through a flexible conduit and a housing for a removable filter, and to a top portion of the tub through a recirculation conduit and pump, said collecting receptacle being additionally adapted to house an electric heater element and to communicate with a discharge conduit of the machine through a discharge pump, characterized in that the removable filtering element is of integral construction including a fine-mesh filtering surface disposed transversely in the collecting receptacle upstream of the heater element in the direction of the washing liquid recirculation, and a coarse-mesh filtering surface disposed upstream of the discharge pump in the washing liquid discharge direction. The characteristics 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 shows a filter according to a first embodiment of the invention, and fig. 2 shows a filter according to a second embodiment of the invention. With referecne to fig. 1, there is shown the lower part of a laundry washing machine of the recirculation type as described in Italian Patent Application No. 45715 A/85, filed on 24. 5. 1985 by the present applicant. The machine comprises a tub 3, a rotatable drum 4 mounted in tub 3, and a collecting receptacle 5 for collecting the washing liquid not retained by the laundry. Collecting receptacle 5 is connected to a lower portion of tub 3 by a flexible conduit 6, and to an upper portion of tub 3 by a conduit 7, a recirculation pump 8 and a further conduit 9 connecting pump 8 to an upper portion of receptacle 5. Recirculation pump 8 and conduits 7 and 9 serve the purpose of delivering the washing liquid from collecting receptacle 5 to tub 3 for washing the laundry in drum 4 by the spray soaking method as described in the above named patent application. Collecting receptacle 5 is further connected to a discharge conduit 10 of the machine via a discharge pump 11 of the conventional non-self-cleaning type, and dimensioned to house an electric heater element 12, a thermostatic sensor 13 and part of a mesh filter element 14 removably inserted into a housing 15 which is accessible from the exterior of the machine. Filtering element 14 and its associated housing 15 are of a round shape and extend downwards as described for example in Italian Patent Application No. 45713, filed on 5.5.83 by the present applicant. In particular, in the embodiment shown in fig. 1, filtering element 14 is of substantially cylindrical shape and provided with an opening at least adjacent the point at which conduit 6 opens into filter housing 15. The upper end (not shown) of filtering element 14 is connected to a closure cover of filter housing 15, while its lower end extends to a level closely above the bottom wall 16 of collecting receptacle 5. At the side facing towards resistance heater element 12, filtering element 14 has a fine-mesh structure 17, while its surface facing towards discharge conduit 10 is of a coarse-mesh structure 18. During the washing operation the washing liquid passes the fine-mesh surface 17 before entering recirculation conduits 9 and 7, as indicaetd by dotted arrows in fig. 1. As a result, any foreign bodies entrained by the washing liquid, including any loose fibers, will be retained by fine-mesh filtering surface 17. When the operation of the machine is switched over from the washing cycle to the discharge phase, the washing liquid is drawn in by discharge pump 11 and has to pass through coarse-mesh filter surface 18 before entering discharge conduit 10, as indicated by solid-line arrows. During this phase the washing liquid sweeps the inner side of fine-mesh filter surface 17 so as to carry away any loose fibers possibly retained thereon. In the embodiment shown in fig. 2, filtering element 14 has a cylindrical body 22 having a coarse-mesh structure throughout. The lower end of filtering body 22 terminates at the level of the top wall 20 of collecting receptacle 5 and is connected to a fine-mesh partition 21 extending downwards to a level closely above bottom wall 16 of collecting receptacle 5. During the washing phase the washing liquid drained from tub 3 passes initially through coarse-mesh filter body 22 and subsequently through fine-mesh partition 21 before entering recirculation conduits 9 and 7. During the discharge phase any loose fibers retained by filtering partition 21 are carried away by the washing liquid flowing towards discharge conduit 10. The structure of filtering partition 21 as well as that of filtering surface 17 of the embodiment shown in fig. 1 is selected so as to prevent any loose fibers from being entrapped therein, so that they can be readily carried away during the discharge phase. By contrast the coarse-mesh portions 18 and 22 of both embodiments of filtering element 14 permit the passage and discharge of loose fibers, but will reliably retain any foreign bodies which might otherwise damage or obstruct the rotor 19 of discharge pump 11. For the remainder, the removability and one-piece construction of the filter according to the invention facilitate the periodically required cleaning of the two filtering surfaces and the extraction of any foreign bodies possibly entrapped therein. With the described solutions the main object of the invention is achieved in a simple manner by preventing deposits of loose fibers and the like from being formed on the surface of the resistance heater element without requiring frequent cleaning of the filtering device by the user.

Claims: A filter for laundry washing machines, particularly for domestic laundry washing machines of the type comprising a laundering tub, a rotatable drum mounted in said tub, and a washing liquid collecting receptacle disposed below said tub and connected to a lower portion thereof through a flexible conduit and a housing for a removable filter, and to a top portion of said tub through a recirculation conduit and pump, said collecting receptacle being additionally adapted to house an electric heater element and to communicate with a discharge conduit of the machine through a discharge pump, characterized in that said removable filtering element (14) is of integral construction including a fine-mesh filtering surface (17;21) disposed transversely in said collecting receptacle upstream of said heater element (12) in the direction of the washing liquid recirculation, and a coarse-mesh filtering surface (18;22) disposed upstream of said discharge pump (11) in the washing liquid discharge direction. A filter according to claim 1, characterized in that said removable filtering element (14) is of a substantially cylindrical shape extending to a location closely adjacent the bottom wall (16) of said collecting receptacle (5), and composed of a fine-mesh structure (17) in a part facing towards the resistance heater element (12) and the recirculation system (9,8,7),, and of a coarse-mesh structure (18) in a part facing towards the discharge system (11,10). A filter according to claim 1, characterized in that the removable filtering element (14) comprises a cylindrical coarse-mesh body (22) having a lower end terminating at the level of the top wall (20) of said collecting receptacle (5), and a fine-mesh filter partition (21) extending from the lower end of said body to a level closely adjacent the bottom wall (16) of said collecting receptacle (5).

Inventors: BABUIN, PIERO, COLAUTTI, ROBERTO
Applicants: INDUSTRIE ZANUSSI S.P.A.
Application year: 1987
Main classification: D06F39
IPC codes: D06F39