Filter cartridge with reuseable framework

A filter cartridge comprising a framework and a surrounding envelope of filter material. The framework is reusable and provided with a rough, granular surface texture to provide increase surface area available for the propagation of aerobic bacteria. The envelope is disposable. Thus, biological filtration of the water provided by the aerobic bacteria is not interrupted upon replacement of the filter material. A second filter medium may be disposed within the envelope. The envelope is held in place by a pair of flaps which sandwich an edge of the filter material.

BACKGROUND OF THE INVENTION 
The invention relates to the field of filters and in particular to the 
field of aquarium filters and filtering equipment. 
In the art of home aquariums, it is known to use a filter system which 
continuously circulates the water through a filter medium and returns it 
to the aquarium. One type of aquarium filter system is of the external 
type and uses a small container mounted on the side of the aquarium which 
holds the filter medium. The water from the aquarium is drawn through 
filter material in the container by means of a water pump and then 
returned to the aquarium. The filter medium is usually in the form of 
particles of activated carbon or charcoal and a fluffy mass of synthetic 
resin fibers. 
An external tyoe of filter is shown in U.S. Pat. Nos. 3,513,978 to 
Newsteder and 3,525,435 to Conner. 
The Newsteder device uses two separate compartments, each filled with a 
different filtering substance (i.e, fibrous filtering material and 
charcoal). The water flows through the fibrous material to the charcoal, 
through the charcoal and is then returned to the aquarium. In this type of 
filter, however, the compartment holding the charcoal must have very 
restricted openings to prevent the flow from washing away any charcoal 
dust or particles into the aquarium. 
The Conner filter uses a perforated top with a depending filter bag that is 
filled with charcoal. The flow of the water is down through the top, out 
through the bag walls and returns to the tank. The Conner filter is wholly 
disposable. However, it allows waste particles to contaminate the charcoal 
as there is no filtration prior to its passage through the charcoal. 
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 from the container and air is pumped down into 
the air lift from an external air pump. The air pumped into the air tube 
flows up through the air lift causing a suction to draw water into the 
container, pass it through the filter medium and up through the air lift 
along with the air bubbles. 
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 activated carbon or charcoal provides a 
chemical filtration of the contaminated water. At the same time bacteria 
in the form of accumulated sludge and slime act upon the waste material 
dissolved in the water, thus providing biological filtration. 
The most effective water purification is achieved when bacterial 
propagation is at a high point. However, at this point prior art filter 
cartridges usually become subject to clogging and must therefore be 
removed and replaced. The newly replaced filter cartridge is free of 
bacteria while the old filter cartridge with bacteria is discarded. 
Because the entire filter cartridge is discarded, the filter itself loses 
the biological filtering effects of micro-organisms. These organisms are 
natural filters because their life functions convert many of the harmful 
toxic wastes into harmless nitrates. In existing filter cartridges the 
entire cartridge is sealed and is completely replaced when it becomes 
clogged. Any bacterial organisms which may have grown within the filter 
cartridge are therefore discarded with the cartridge itself. This creates 
a void in filtering ability until the organisms re-establish themselves in 
the replaced filter cartridge. Additionally, since the filter cartridge is 
entirely sealed, the amount of carbon particles or other type of filtering 
material in the cartridge cannot be individually adjusted by the aquarium 
user himself. 
SUMMARY OF THE INVENTION 
The filter cartridge of the invention provides a reusable frame which is 
inserted inside a disposable filter bag or envelope that can be filled 
with filtration material. The framework is conducive to settlement, growth 
and propagation growth of micro-organisms. The reuse of the framework 
without destroying the bacteria provides the filter system with 
uninterrupted biological filtering action. 
The frame is constructed with laterally projecting separators. The 
separators extend across the filter cartridge. They have a narrow 
dimension transverse to the flow of the aquarium water thereacross so as 
to cause only minor constriction of the flow. The separators have a broad 
dimension parallel to the direction of flow, and serve to space apart the 
walls of the filter bag in which the frame is contained. The surface of 
the frame is textued to provide increased available surface area, 
supporting the growth of organisms active in biological filtration. 
The filter cartridge further provides an internal structure for the filter 
bag or envelope. In this way the water may be circulated through the 
filtration material from one side of the envelope, through the interior 
space of the envelope and out the second side. The first wall of the 
filter envelope filters out large contaminants before reaching the 
filtration material, such as carbon, which is disposed within the 
envelope. This prevents clogging and, therefore, early failure of the 
carbon. The second wall of the envelope prevents carbon dust, which may be 
picked up by the flow, from being carried out of the filter into the 
aquarium. 
The wall of the filter envelope is comprised of a water permeable filter 
membrane structure. The membrane is formed of an open web of closely 
spaced or randomly disposed fibrous or filamentary material which forms a 
matrix and provides numerous interstices or pores defining water passages. 
Passage of the water through the interstices in the membrane structure 
causes mechanical filtration of the water by retaining the solid waste and 
contaminants. 
The roughened, textured, or etched surface of the framework provides a 
matte finish which increases surface area for the growth of organisms 
active in biological filtration. This, in combination with the presence of 
oxygenated water, provides an environment conducive to bacterial 
propagation. Such aerobic bacteria which propagate cause purification of 
the contaminated water by acting upon, digesting or converting the toxic 
materials accumulating in the filler and those dissolved in the water into 
products which are harmless to aquatic life in the aquarium. 
The filter cartridge can be inserted in an external or an internal filter 
such as a corner or bottom filter. The soft filter envelope covering the 
rigid or semi-rigid frame creates a better seal along its edges when slid 
into position in the filter box itself. This eliminates the need for 
perfect measurements for the sealing area and also prevents breaking or 
scratching the wall of the filter box. 
Additionally, the filter cartridge can be used as a filtering device by 
itself by causing a flow of the aquarium water through the filter 
cartridge.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 2, 3 and 4, there is shown the filter cartridge 1 of the 
invention. The cartridge includes the frame 2 and a filter envelope 3. 
Charcoal or other filtration material 13 can be placed into the envelope. 
Filter envelope 3 is formed of any suitable filter material and may be 
constructed of synthetic resin fibers in a random or non-woven pattern. 
The envelope has a front wall and back wall which are joined on three of 
the four perimeter edges of each. 
The frame 2 can be molded plastic. It includes a perimeter defining a frame 
formed by top portion 4, bottom portion 5 and side portions 6. Two flaps 7 
are hingeably attached to the top edge of top portion 4. In the preferred 
embodiment the flaps 7 are integrally molded with the frame and provided 
with plastic living hinges 8, that is portions of plastic which are 
flexible and resist fatigue failure. However, the flaps may be attached in 
any known manner. 
Traversing the interior of the peripheral frame are a plurality of 
separators 9. The separators extend laterally beyond the front and back of 
the frame surface in the direction of flow of the water being filtered 
when the cartridge is in use. In FIGS. 2-5, the separators are shown as 
vertical flanges which have a narrow thickness in the direction parallel 
to the top portion 4 and bottom portion 5. This minimizes the surface area 
which is transverse to the flow of the water being filtered when the 
cartridge is in use. The separators 9 have a width which is one-half to 
three-quarters of an inch for an envelope which is about four inches by 
six inches. The width is measured in a direction perpendicular to the 
plane of the perimeter defining frame; that is, parallel to the direction 
of flow when the cartridge is in use. There are similar flanges or 
separators 10 extending from side portions 6 of the frame. 
In use, the frame is positioned within the filter envelope. A second 
treatment material such as activated carbon or activated charcoal 13 may 
be added to the envelope and the flaps 7 are folded down, sandwiching the 
upper edge 11 of the filter envelope 3 between the flap 7 and top portion 
4. When the assembled cartridge is inserted into a filter assembly, the 
flaps will normally be held down. However, optionally, in order to assure 
that the flaps hold the envelope tightly, a clip 12 can be used. The clip 
is also useful in preventing the escape of filtering material in shipping 
the cartridge pre-assembled. The clip is U-shaped and is snapped over the 
flaps 7 once they have been folded down. The clip biases the flaps toward 
one another thus holding the envelope. It should be understood that other 
suitable biasing means may also be used, such as molding the flaps 7 and 
frame so the flaps are resiliently biased in the sandwiching position. 
The separators hold the opposing front and back walls of the envelope in 
spaced relation. As the watr is forced through the filter, it passes first 
through the front wall, which initially filters the water. It then passes 
through and is treated by the carbon or charcoal 13 or other filtration 
material placed in the envelope. Finally, the water flows through the back 
panel of filter material which causes secondary filtering and prevents the 
passage of charcoal particles to the aquarium. The two-wall filtering 
allows freer water flow, as the filter clogs in parts with waste and 
biological activity. 
The filter cartridge can be used in connection with a filter mechanism such 
as that depicted in FIG. 1. The mechanism is an external filter assembly 
and has a tank 14 which receives the filter cartridge. The filter 
cartridge is slideably received in two opposing grooves 15 in the side 
walls partially defining a clear water chamber 16 in the front and a 
filtering chamber 26 in the rear. Water from the aquarium is pulled into 
the filter tank through pipe 17 by a water pump 18. The pump has an 
impeller 19 and drive motor 20 which are magnetically coupled in any known 
manner. Pipe 17 has a strainer 21 on the intake end so as to prevent 
pulling in fish or other objects which may jam or damage the impeller in 
the pump. The aquarium water is pulled into a receiving chamber 22 which 
is partially separated from filtering chamber 26 by divider 23. Divider 23 
is spaced from back wall 24 of the tank. Water pumped into receiving 
chamber 22 is allowed to flow into the filter chamber 26 behind the filter 
cartridge. The rising water level in the filter chamber 26 between the 
filter cartridge and the back wall and under the force of gravity the 
water to flow through the interstices in the material of the filter 
cartridge. The water passing through the filter cartridge wall is 
mechanically cleaned of contaminants in a sieve-like manner. Once within 
the filter envelope, the water is further cleansed by the carbon within 
the envelope and aerobic bacteria which grow on the frame and surfaces of 
the filter envelope. The water passes through the second wall and is 
subject to secondary filtration thereby. The water passes through the 
envelope wall to the clear water chamber 16. As the water level in this 
chamber rises, it reaches the level of spillway 25 and spills back into 
the aquarium. 
When the filter cartridge becomes clogged with contaminants, it is removed, 
the envelope, the carbon and other filtration material are discarded and a 
new envelope positioned on the frame. New carbon and other filtration 
material is placed within the envelope and the cartridge is replaced in 
grooves 15 and the filtering process continues. 
In addition to mechanical filtration, biological filtration is by far the 
most important type for removal of toxic waste within an aquarium. In 
biological filtration, the aquarium water is conditioned as a result of 
the presence of living organisms, primarily bacteria. The presence of the 
bacteria serves to convert toxic waste into end products which are not 
harmful to the aquatic life. The type of bacteria that serve to convert 
the toxic waste, and especially ammonia, into nitrates which are not 
harmful, are aerobic bacteria. Aerobic nitrifying bacteria have two basic 
requirements in order to propagate: high oxygen concentrations and a place 
to attach themselves. The oxygen is generally provided within the aquarium 
tank by means of a natural interchange at the surface of the water. The 
water flowing back into the aquarium from the filter is aerated and brings 
a fresh supply of oxygen to the aquarium water. 
The bacteria adhere in some degree to almost any surface available to them. 
Such surfaces will naturally include the filter cartridge, especially the 
frame contained within the cartridge. The frame is especially suited for 
the growth of bacteria because it is in the path of the constant flow of 
water laden with dissolved contaminants. Such contaminants include toxic 
ammonia which serves as the nutrient for the growth of the bacteria. 
Accordingly, the frame serves as an excellent location for the propagation 
of organisms which cause biological filtration of the aquarium water. 
The propagation of such bacteria increases with time. In fact, a common 
method of starting biological filtration is to begin with some gravel or 
some filter material from an established aquarium on which the bacteria 
have already propagated. Placing such substances having bacteria on it 
into the aquarium permits the bacteria to propagate as they feed on the 
waste products in the aquarium. 
With prior art filter cartridges, when the cartridge became clogged with 
contaminants, the entire cartridge was removed. Therefore, any build up of 
microorganisms useful in biological filtration was thrown away. Insertion 
of a new, clean filter cartridge which would not have any bacteria 
present, therefore, would recuire that the biologic filtration process 
begin anew on the replaced filter cartridge. 
In the present invention, the reuseable frame insures the presence of the 
microorganisms needed for biological filtration. Any build up of such 
bacteria is retained on the frame itself. The frame can be cleaned in cold 
water which does not destroy the organisms. Placing the frame into a new 
envelope retains the organisms previously propagated and permits continued 
enhancement of the biological filtration process rather than a restarting 
of the process. 
Since a large surface area provides many more aerobic nitrifying bacteria 
with a place for attachment the surface of the framework can be etched, 
sandblasted, or the like, to provide a rough, granular surface texture 
typically referred to as a matte finish. FIG. 6, shows an enlarged section 
of the framework 27 which includes the granular surface texture 28. As 
shown in FIG. 7, the surface includes protrusions 29 and valleys 30 along 
the surface of the frame. Such protrusions and valleys defining the 
roughened texture substantially increase the surface area beyond that 
normally required for structural purposes. However, the bacterial 
organisms use the protrusions and valleys as adhesion areas on which they 
can propagate. In this manner, the amount of surface available for the 
propagation of the organisms is dramatically increased to permit 
enhancement of the biological filtration provided by the filter. 
The frame can be formed by a sandblasting operation in conjunction with a 
molding process. Either the mold itself can be initially sandblasted in 
which case each time the frame is molded it will be produced with a rough 
granular surface. Alternately, a smooth mold can be utilized and the end 
product frame resulting from the mold can be sandblasted to produce the 
granular texture on the surface. Another approach would be to etch the 
rough surface using a chromic acid, or other type of etch material. 
The reusable frame assembly provides additional benefits. Existent 
disposable filter cartridges are completely sealed. They include the 
exterior envelope which contains charcoal or other filter material. The 
user never has an opportunity to verify the type of carbon or charcoal 
utilized or any other type of filtration material that may be in the 
envelope, and is never certain of the quality or amount of such material 
present in the filter. With the present invention the user can open the 
envelope, and verify the presence and type of the activated carbon 
utilized. In fact, the user can add additional carbon or other water 
conditioning materials and can select the type that he desires to use. In 
this way, the filter cartridge can be tailored by the user to the 
individual needs and requirements of his aquarium. The carbon can also be 
removed, which is useful in tanks where diseased fish are being treated 
with medication and where chemical filtration must be stopped while 
continuing the mechanical and biological filtration. 
It should also be appreciated that the present structure provides that the 
frame is internally of and slidable with respect to the envelope. There is 
no permanent attachment between the frame and the filter envelope. As a 
result, there is no wasted portion of the envelope which might be required 
for attachment to a frame. This allows the envelope to be filled with more 
material. 
The separators traversing the perimeter of the frame need not be only 
vertical flanges or blades. Other configurations can also be utilized. By 
way of example, FIG. 8 shows a peripheral frame 31 having a top and bottom 
wall 32, 33 and opposing side walls 34, 35. Flaps 36, 37 are hingedly 
connected at the top 32 to close onto the envelope. Three horizontal 
shelves or trays 38a, 38b, 38c serve as the separators. The trays extend 
laterally beyond the front and back surface of the frame to provide 
adequate spacing of the walls of the envelope when the frame is inserted 
within the envelope. 
Using the horizontal trays 38a, 38b, and 38c, there is provided the 
additional benefit that any charcoal or activated carbon inserted within 
the envelope will be retained by the trays and will spread the charcoal to 
various levels within the filter envelope. This will avoid the tendency of 
the charcoal to settle at the bottom and will instead provide a 
distribution of the charcoal throughout the height of the filter 
cartridge. 
FIG. 9 shows yet a further arrangement wherein the frame 40 includes a 
separator arrangement having an inner circle 41 surrounded by a concentric 
outer circle 42 and connected by a plurality of webs 43 in the form of 
spokes. The outer circle 42 is spaced from the periphery by means of 
additional webs 44 also in the form of spokes. With the arrangements shown 
in FIG. 9 the charcoal will be retained by the spokes and provide a 
distribution throughout the interior of the envelope. 
In all cases, the separators are thin so as not to impede the flow of water 
through the filter envelope. They also extend laterally forward and behind 
the frame surface to adequately space apart the walls of the filter 
envelope. 
In order to retain closure of the flaps onto the envelope, as shown on FIG. 
10, the upper wall 32 of the frame can include a plurality of laterally 
extending dimples 45. A corresponding plurality of receiving apertures 46 
are provided each of the side flaps 36, 37. As the side walls of the 
envelope 48 are placed between the flaps and the frame, the projecting 
dimples 45 penetrate into the woven material of the envelope to extend 
there through. Closure of the flaps onto the dimples permit the apertures 
46 to engage the dimples thereby securing the envelope in place. This 
prevents the envelope from sliding down off the frame work even if it 
becomes heavy as a result of the weight of the water as well as the 
presence of the charcoal and any sludge and contaminants that may be 
retained within the envelope. 
Preferably the envelope is made of non-woven reticular filter material. As 
shown in FIGS. 11 & 12, a sheet of such non-woven mat filter material 50 
can be formed into a cylinder by wrapping it about its longitudinal axis 
and stitching the two joining longitudinal ends 52 & 54 together with 
stitches 56. The edge portions 58 & 60 beyond the stitching 60 mesh 
together to close the gap formed by the stitches. The meshed portion can 
than be pressed onto the cylinder 50 so that it overlies the stitched part 
56. This gives a doubled over portion at the stitching 56 so there is no 
loss of thickness at that location. The envelope can then be completed by 
squeezing the back of the cylinder 50 together and stitching 64 along the 
bare edge thus formed. In this way the filter envelope can be formed of a 
single sheet of non-woven material. 
As is noted in FIG. 1, the external filter assembly is preferably formed of 
molded plastic material. In order to extract the molded housing from the 
mold using an injection molding process, it is noted that the shape of the 
assembly is downwardly tapered. In a similar manner, the corresponding 
shape of the frame as shown in FIGS. 3, 8, 9, and others is likewise 
downwardly tapered to fit into the sideward grooves provided in the filter 
assembly. 
As best noted in FIG. 3, the envelope 3 need not be made with a 
corresponding tapered shape. The width of the envelope can be made of a 
size approximately corresponding to the narrow tapered end of the frame. 
Because of the construction of the bag of non-woven reticulated material, 
the bag stretches as the frame enters inside the bag. This makes the bag 
fit tightly onto the frame and causes the bag to grip the frame and 
provide a snug fit. At the same time, it is not too tight so that it can 
still be removed for replacement when needed. 
As is noted in the drawings, the lateral side edges of the filter cartridge 
have the envelope as the exterior edge. Since the envelope is formed of a 
non-woven soft material, as the filter cartridge is inserted into the 
grooves 15 provided on the side of the filter assembly shown in FIG. 1, 
the envelope grips the rails within the grooves and gives a tight fit of 
the filter cartridge within the filter assembly. This prevents leakage of 
the contaminated water around the sides of the bag and prevents flow of 
the contaminated water into the clean water chamber. 
The filter cartridge of the present assembly was shown in FIG. 1 for use in 
an exterior filter assembly which uses a water pump. The cartridge, 
however, can also be utilized in numerous other types of filter assemblies 
of various configurations, including the internal or underwater filter, as 
shown in FIGS. 13-14. By way of example, there is shown an underwater or 
internal filter 70 including a substantially rectangular tank or housing 
72. The housing 72 includes a front wall 74 having a plurality of holes or 
perforations 76 to permit entry of the water. A pair of side rails or 
U-shaped channels or grooves 78 and positioned laterally on either side of 
the housing. The filter cartridge 80 of a type heretofore described in 
connection with the invention can be slid into the side rails so as to 
separate a front chamber 82 from a rear chamber 84. The front chamber 
receives the contaminated water which then passes through the filter 
cartridge of the invention and then enters into the rear or clear water 
chamber 84 behind the filter cartridge. A removable cover 86 is provided 
on the housing 72 to seal the top of the cartridge and permit entry into 
the housing or tank 72 for removal of the filter cartridge. 
Rearward of the housing 72 is formed an air lift tube 88 which can be 
integral with the housing. A passageway 90 communicates between the clear 
water chamber 84 and the interior 92 of the air lift tube 88. 
An air pipe 94 extends downward into the interior 92 of the air lift tube 
88. An air pump 96 serves to pump air through the air pipe into the air 
lift tube. Typically, an air stone 98 may be placed at the lower end of 
the air pipe proximate the passageway 90 into the clear water chamber. 
During operation, air pumped through the air pipe exits through the air 
stone at the lower end of the air pipe and travels upwardly through the 
air lift tube 88. The flow of air upwardly causes a suction drawing the 
clear water from the clear water chamber 84 along with it upwardly through 
the air lift tube and back into the aquarium. This flow of the clear water 
from the clear water chamber 84 causes a suction which brings the 
contaminated water from the aquarium through the holes 76 in the front 
wall of the housing to thereby provide a continuous flow through the 
filter assembly. 
As before, it is noted that the housing is slightly downwardly tapered as a 
result of the injection molding process. Again, the correspondingly shaped 
taper of the filter cartridge will fit into the housing assembly and the 
presence of the soft envelope will provide a tight fit into the side 
grooves 78 in the housing assembly. 
Although the use of the filter cartridge has been shown in connection with 
external filters utilizing water pumps as well as internal filters using 
air pumps, it will be shown in FIGS. 15 and 16 that the filter cartridge 
itself can provide an entire filter assembly without an entire filter 
unit. As shown, the filter cartridge 100 of the present invention is 
placed vertically across a corner in the aquarium 102 extending diagonally 
between the corner walls 104 and 106. In order to hold the filter 
cartridge in place, side suction cups 108, 110 can be connected. Other 
attachment or securement means could be utilized. In addition, the 
cartridge could simply be stuck into the gravel 112 provided at the bottom 
of the aquarium 114. It should be appreciated, that as the filter 
cartridge gets further clogged it actually sticks tighter and remains more 
securely in place. 
An air tube 116 extends down behind the filter cartridge 100 and an air 
stone 118 may conveniently be placed at the distal end of the air tube 
116. Through the use of an external air pump, air would be pumped through 
the pipe 116 resulting in a flow of air bubbles 120 from the lower end of 
the tube or the air stone 118 if it is utilized. The upward flow of 
bubbles 120 causes a suction behind the filter cartridge 100 to cause the 
water to flow into the front of the cartridge as shown by the arrows 122. 
Thus the cartridge by itself can serve as a filter by inserting it into 
the aquarium and causing a suction behind one wall causing a flow path of 
the aquarium water through the filter cartridge. 
Thus, it is seen that by providing a reusable internal support frame, the 
filter of the invention continues to increase the biological filtration in 
the aquarium. The envelope-frame combination also provides an easy 
maintenance filter with disposable filter material.