Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Reexamination Certificate
2002-07-02
2004-11-02
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
C134S018000, C134S025200, C134S104100, C134S111000
Reexamination Certificate
active
06811617
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of dishwashers and, more particularly, to a pump and filtration system employed in a dishwasher.
2. Discussion of the Prior Art
In a typical dishwasher, washing fluid is pumped from a sump into upper and lower wash arms such that kitchenware retained on vertically spaced racks within a tub of the dishwasher will be sprayed with the washing fluid for cleaning purposes. The washing fluid is heated, filtered and recirculated. Prior to recirculating the washing fluid, the fluid is directed through one or more filters to remove soil from the fluid, with the soil being collected in a chamber. Periodically, the system will be purged in order to drain the collection chamber of the soil.
In recent years, it has become increasingly common to provide a series of straining or filtering units in connection with an overall dishwasher pumping system such that different sized soil particles are collected at varying locations. For example, a strainer can be employed to retain large soil particles, while a fine filter can be utilized to remove smaller particles. That is, the smaller particles are able to pass through the strainer, which essentially constitutes a first filtering unit, and are caught by the second or fine filter. In connection with the pumping and filtering operation, it is also known to incorporate a mincer or chopper in order to minimize soil particle size, such as just prior to a drainage operation.
Obviously, the ability of the dishwasher to thoroughly clean the kitchenware will depend on a number of factors, including the actual configuration and flow of fluid through the filtering system, as well as the manner in which pumping and draining operations are performed. Although various dishwasher pump and filtration systems are known in the art, there still exists a need for improvements in this field in order to further enhance the overall cleaning functions performed by dishwashers.
SUMMARY OF THE INVENTION
The present invention is directed to a pump and filtration system in a dishwasher. In accordance with a preferred embodiment of the invention, an overall dishwasher pump system includes two separate pumps, one for providing a recirculation flow of washing fluid and the other being utilized during draining or purging operations. Most preferably, all of the washing fluid to be recirculated flows past a radial strainer, through a generally U-shaped inlet trap and then to an impeller of the recirculation pump through a chopper blade and apertured plate arrangement. In this manner, any large particles are prevented from passing through the strainer, while the remainder of the fluid entrained particles are forced through the chopper blade and plate arrangement prior to reaching the impeller of the recirculation pump.
The impeller directs the recirculating fluid radially outwardly, then the fluid is forced to flow through an involute manifold. At the manifold, the recirculating fluid is directed radially inwardly and then up to respective upper and lower wash arms. A flow conduit leading to the upper wash arm is provided with a sampling port which directs a percentage of the fluid flow into a filter chamber. The upper wall or top of the filter chamber is generally defined by one or more fine mesh filter screens that open into the dishwasher tub basin. At one annular position about the filter chamber is provided a collection chamber that leads to a flapper valve and then to a drain port. The drain port is connected to an inlet of the drain pump. With this arrangement, a percentage of the recirculating fluid flow is directed through the sampling port wherein any particles therein will settle in the collection chamber. Fluid in the filter chamber is permitted to flow upwardly through the fine mesh filter screen(s). Periodically, at timed intervals, drainage operations are performed to purge the collection chamber.
In the most preferred form of the invention, an overflow tube, which is in fluid communication with the filter chamber, extends upwardly along the rear wall of the tub basin. When the fine mesh filter becomes clogged, fluid will be forced to flow up the overflow tube. A separate filter is provided within a housing atop the tube in order to prevent soiled fluid from the filter chamber reaching the tub basin through the overflow tube. In this manner, the recirculated fluid can continue to be filtered, even while the fine mesh filter is clogged, until a timed drainage operation is performed.
In further accordance with the most preferred embodiment of the present invention, a filter guard is secured to the housing of the recirculation pump, with the filter guard extending over portions of the fine mesh filter. More specifically, the filter guard is mounted directly above the fine filter and has an outer wall which is angled to protect or shield the fine filter from damage, such as from utensils or the like falling thereon within the tub basin, as well as visually obscuring the fine filter. The filter guard preferably has a curved underside for directing downward sprays from the lower wash arm onto the fine filter in order to backwash the fine filter for cleaning purposes. In addition, the filter guard includes wash out areas for flushing out any trapped food particles.
Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.
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Elick Robert A.
Morrison John Trevor
Thomas Chad M.
Diederiks & Whitelaw PLC
El-Arini Zeinab
Maytag Corporation
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