Dual density filter cartridge

Details Dual density filter cartridge Dual density filter cartridge

2001-11-07

2004-02-17

Prince, Fred G. (Department: 1724)

Liquid purification or separation

Structural installation

Closed circulating system

C210S232000, C210S282000, C210S283000, C210S416200, C210S486000, C210S489000

Reexamination Certificate

active

06692637

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to aquarium filters providing improved mechanical water filtration without accelerating the rate of clogging. The present invention also relates to methods of using such filters.
BACKGROUND OF THE INVENTION
Aquarium filter systems which continuously circulate water from an aquarium, through a filter medium and, then, back to the aquarium are well known in the art. One such type of aquarium filter system is represented by the external-type system which employs a small container comprising a filter mounted on the side of the aquarium. The water from the aquarium is drawn by means of a water pump, it flows through filter medium in the container and is then returned to the aquarium. The filter medium is usually in the form of elements of activated carbon or charcoal and fluffy masses of synthetic resin fibers.
Examples of external-type filter systems can be found in U.S. Pat. No. 3,513,978 to Newsteder and U.S. Pat. No. 3,525,435 to Conner, both of which are herein incorporated by reference in their entirety.
The Newsteder system uses two separate compartments, each filled with a different filtering substance (i.e., fibrous filtering material and charcoal respectively). The water flows through the fibrous material and then through the charcoal before going back to the aquarium. In this type of filter, however, the compartment holding the charcoal must have very restricted openings to prevent any charcoal from passing through openings into the aquarium.
The Conner filter uses a perforated top with a dependent filter bag that is filled with charcoal. The flow of the water is down through the top, out through the bag walls and then back into the tank. The Conner filter is wholly disposable. The filter, however, lacks a mechanism for mechanically or physically filtering water prior to passing through the charcoal. Consequently, the filter allows waste particles to enter the interior space of the filter and, thereby, reduce the effectiveness of the charcoal. Specifically, particulate matter can block (or occlude) the surface of adsorbents like charcoal and activated carbon and, thus, reduce their capacity to surface adsorb dissolved gases and toxins.
Another type of aquarium filter is the internal or underwater filter. A container is provided which includes a filter medium such as activated carbon or charcoal and a fluffy mass of synthetic resin fibers. An air lift is provided, extending vertically up from the container, and air is pumped down into the base of the air lift from an external air pump. The air rises which, in turn, induces water flow into the container, such that the water passes through the filter medium and, then returns back to the aquarium.
In aquarium filtration, the filter medium provides various types of filtration activity. As the water flows through a porous wall, mechanical filtration of the water occurs with the walls acting as a sieve, retaining the solid contaminants. The mechanical filtering capability of this “sieve-type” mechanism increases for finer contaminants as the surface area of the porous wall increases and the pore size of the openings or interstices decrease. Increasing the density of the porous wall results in improved trapping of smaller particles. Such increases in the surface area of the porous wall, however, also results in accelerated clogging rates of the porous wall. Therefore, a need exists for filter cartridges providing mechanical filtration using high density (or, high surface area) porous walls to improve the filtration of finer contaminants without a corresponding acceleration in the clogging rate of the filter cartridge as a whole.
The present inventors have discovered that filter cartridges incorporating dual density filters, comprising a low-density (surface area) in-flow porous wall and a high-density (surface area) out-flow porous wall, provide improved mechanical filtration without accelerating clogging.
Accordingly one aspect of the present invention is to provide improved filter cartridges.
A further aspect of the present invention is to provide filter cartridges which improve mechanical filtration without accelerating the clogging of the filter cartridge.
A still further aspect of the present invention is to provide filter cartridges comprising a plurality of filter walls produced from porous materials, with each wall varying in density or surface area such that the density or surface area of the filter walls increases in the direction of water flow.
These and other advantages are accomplished by the present invention as will be further detailed in the following description.
SUMMARY OF THE INVENTION
The present invention relates to water filter articles, comprising:
a.) a first porous filter wall for filtering liquid flowing into the filter article; and
b.) a second porous filter wall for filtering liquid flowing out of the filter article
wherein the density or surface area of the first porous filter wall is less than the density or surface area of the second porous filter wall. Methods of using the disclosed filter are also described.
Frame
The frame is constructed with laterally projecting separators. The separators extend across the filter cartridge and have a narrow dimension transverse to the flow of the aquarium water there across so as to cause only minor restriction to the flow. The separators have a broad dimension parallel to the direction of flow, and can serve to space apart the filter walls. The surface of the frame is also textured to provide increased available surface area. This increased surface area additionally provides a support media for growing organisms active in biological filtration.
The frame also provides an internal structure for the plurality of filter walls described herein. Accordingly, water can be, first, circulated through an in-flow filter wall on one side of the filter cartridge, next, through the interior space of the filter cartridge and, finally, exit through the out-flow filter wall on the opposite side of the filter cartridge. The in-flow filter wall of the filter cartridge captures and retains large contaminants from the water before it reaches any optional chemical filtration material, such as activated carbon, typically disposed within the filter cartridge while the out-flow filter wall filters out smaller contaminants.
Frames suitable for use herein are described in detail in U.S. Pat. No. 5,053,125 to Willinger et al., herein incorporated by reference in its entirety.
Filter Walls
The filter cartridges of the present invention comprise at least two filter walls. The filter walls of the present invention are, preferably, comprised of a water permeable porous, filter membrane material. The density or surface area of the filter membrane material differs from one filter wall to the next, with the first filter wall (or the filter wall receiving incoming water) having a lower density or surface area than the second filter wall. Water exiting the lower density or first filter wall will contain fewer particulates, thus, reducing the surface loading on the carbon and enhancing its effective life. The higher density out-flow or second filter wall, in turn, filters the finer waste particulates as well as prevent carbon from being carried out of the filter by the water flow into the aquarium.
The membrane can be formed of an open web of closely spaced and randomly disposed fibrous or filamentary substances and/or polymeric materials which form a 3-dimensional matrix and provides for numerous interstices or pores defining water passages. Any filter material or substance suitable for forming such matrices, interstices or pores can be used to form the filter walls of the present invention. Passage of the water through the interstices in the membrane material causes mechanical filtration of the water by the filter walls retaining solid waste and other contaminants. Increasing the density or surface area of the porous material increases the mechanical filtration capability of the filter wall for finer particulate contaminants.
Suitable porous membran

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