Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
2001-05-31
2002-03-12
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S088000, C210S089000, C210S234000, C210S416300, C210S444000, C062S339000
Reexamination Certificate
active
06355177
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to the art of water filtering systems and, more particularly, to a water filtering system incorporating a replaceable filter cartridge and a replacement reminder arrangement for use in a refrigerator.
2. Discussion of the Invention
Providing water dispensers and automatic ice makers in household refrigerators has become extremely commonplace. In addition, there is a growing trend towards increasing the purity of all consumed water. For at least these reasons, it has heretofore been proposed in the art to incorporate a water purifying system in a refrigerator in order to filter the water supplied to a water dispenser and/or ice maker. Early proposed purifying systems of this type centered around providing a filtering unit between the water supply and the conduit entering the refrigerator. These systems were typically installed by service personnel as aftermarket add-on units. More recently, it has been proposed to incorporate filter assemblies during the overall manufacturing of refrigerators, while utilizing filters which can be fairly, readily accessed for replacement directly by consumers.
In developing an improved water filtering system, many factors need to be considered, including associated manufacturing costs, ease of use, manner of operation and reliability. Although various refrigerator water filtering assemblies are known in the art, many improvements are left to be made to simplify known filtering assemblies while increasing reliability, particularly with respect to the manner and ease in which filter cartridges can be effectively and timely replaced.
To this end, there have been a fair number of proposals concerning different arrangements for determining when a filter cartridge of a water filtering system should be changed. For instance, in the field of refrigerator water filtering systems, it has been proposed to monitor the total time period since a filter cartridge was initially installed and to indicate a need for the filter to be changed after a predetermined period of time elapses. In addition, it is been heretofore proposed to sensing a fluid flow volume associated with a filter assembly in order to indicate the need to change the filter of the assembly. Time based filter changing systems typically do not represent the most efficient replacement indicators since the elapsed time need not be directly related to the actual in-use time of the filter. Arrangements which accumulate the time during which a flow controlled switch is activated are also known, but such arrangements either require a minimum flow rate in which to activate the switch or provide commensurate signals regardless of varying flow rates, such that these arrangements are not generally accurate.
Volumetric based systems typically function to either mechanically sense a filtered flow rate or electronically sense flow based on monitoring a differential pressure across a flow restriction. Although volume based systems may offer some significant benefits over simple time based systems, the cost of known volume based systems are considered to be generally prohibitive. In addition, water filter replacement systems which directly sense flow volumes are prone to failure, particularly given the life expectancy of a modern refrigerator. In any event, based on the above, there exists a need in the art for a cost effective and reliable water filter replacement reminder system for a refrigerator. In addition, there is considered a need for an arrangement to signal when a filter cartridge has been replaced in order to reset the overall indicator arrangement.
SUMMARY OF THE INVENTION
The present invention is directed to a water filter arrangement for a refrigerator and, particularly, to a water filter cartridge replacement system. Preferably, the filter cartridge is mounted in a clearly visible and accessible location for ease of replacement by the consumer. In the most preferred embodiment, the refrigerator is provided with a temperature control housing mounted in an upper rear portion of the fresh food compartment. The control housing covers a portion of a filter mounting head to which the filter cartridge is selectively secured to complete a water circuit for the system.
In accordance with a preferred embodiment of the invention, the filter cartridge includes a housing enclosing a filtering medium and a stem which projects axially from the housing for insertion into a port of the mounting head. At least one mounting lug projects radially outwardly beyond the stem, with the lug being adapted to interengage with a support element of the mounting head upon insertion of the stem into the port and at least partial rotation of the cartridge. Preferably, the lug and support element include cooperating camming surfaces which cause the stem to be drawn into the port upon initial rotation of the cartridge in a first direction. In addition, further camming surfaces are provided between the cartridge and the mounting head which causes the stem to at least partially withdraw from the port upon rotation of the cartridge in an opposite direction. In the most preferred form, the additional camming surfaces do not become interengaged until the lug is disengaged from the support element.
In accordance with another aspect of the invention, the filtering system further includes a plug which can be used in place of the filter cartridge to complete the fluid circuit through the mounting head. Preferably, the plug also incorporates multiple camming surfaces adapted to cooperate with the mounting head structure to enhance the seating and withdrawal of the plug respectively.
In accordance with a further aspect of the invention, a switch assembly is provided to sense the attachment of the filter cartridge or the plug to the mounting head. If either attachment is sensed, water is permitted to flow to a water fountain and/or automatic ice maker. If no attachment is sensed at the mounting head, the flow of water is prevented.
In accordance with a particular aspect of the invention, a system is provided to determine when the water filter needs to be replaced based on sensing actuating time periods for a flow control valve, calculating a flow volume for each actuation period, summing each of the calculated flow volumes to obtain an accumulated flow volume, and comparing the accumulated flow volume with a threshold value. When the accumulated flow volume reaches or exceeds the threshold value, an indicator light or other similar device is activated to signal the need to replace the water filter. The accumulated flow volume value is reset, either manually or automatically, upon replacement of the water filter.
Additional objects, features and advantages of the water filtering system of the invention will become more readily apparent from the following detailed description of a preferred embodiment, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.
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Senner Kurt C.
Wetekamp Robert L.
Diederiks & Whitelaw, PLC.
Maytag Corporation
Prince Fred
Simmons David A.
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