Filter

A filter comprising a filter case the interior of which is divided by a separator into upper and lower filtration chambers, a compact filter material of a cylindrical shape disposed in said upper filtration chamber so as to define on both outer and inner sides thereof a non-purification chamber communicating with upper suction ports formed at the upper part of said filter case and a purification chamber communicating with a drain pipe disposed on the upper surface of said filter case and having a large capacity, and a coarse filter material housed in said lower filtration chamber and serving also as a weight, said lower filtration chamber communicating with said purification chamber through passage ports formed in said separator while communicating with lower suction ports formed in a bottom surface of said filter case, said purification chamber communicating with an air feed port connected to an air pump.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a filter of water for keeping aquarium fishes 
such as goldfishes, tropical fishes, saltwater fishes, and the like. 
2. Description of the Prior Art 
A conventional filter used inside a water tank for keeping goldfishes, 
tropical fishes, and the like blows air into water by an air pump or the 
like to generate a water flow, and filtrates the water in the tank by 
feeding the water flow as a whole through a filter material. If the flow 
velocity of the water passing through the filter material is too great, 
however, aerobic bacteria that decompose organic matters such as 
chlorella, residual bait and droppings of fishes, and the like, can not be 
propagated, so that the water quality would be deteriorated. If the flow 
velocity is reduced, on the other hand, oxygen can not sufficiently be 
supplied into the water, and an air pump for supplying oxygen must be used 
additionally. If the filter material gets clogged, the water flow becomes 
weak and will invite the insufficiency of oxygen in the water. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a compact and 
highly efficient filter having a construction in which the interior of a 
filtration case disposed inside a water tank is vertically divided into 
upper and lower filtration chambers, a compact filter material having a 
relatively large filtration area is disposed inside the upper filtration 
chamber while a coarse filter material is disposed in the lower filtration 
chamber so that the flow velocity of water passing through the compact 
filter material is made relatively small in order to promote the 
propagation of aerobic microorganisms including bacteria such as chlorella 
on the filter material and thus to improve the purification efficiency of 
contaminated water inside the water tank, and a sufficiently large 
filtration capacity can be obtained by the two filter materials disposed 
in the upper and lower filtration chambers even if the capacity of the 
filter case capacity is reduced. 
The filter in accordance with the present invention to accomplish the 
object described above has a construction in which the interior of a 
filter case is divided by a separator into upper and lower filtration 
chambers, a compact filter material has a cylindrical shape and is 
disposed inside the upper filtration chamber so as to define the chamber 
into an outside non-purification chamber communicating with an upper 
suction port disposed at the upper part of the filter case and an inside 
purification chamber communicating with a discharge pipe disposed on the 
upper surface of the filter case and having a large capacity, the lower 
filtration chamber communicates with the purification chamber through 
passage ports formed in the separator, the lower filtration chamber 
communicates with lower suction ports formed in the bottom surface of the 
filter case, the coarse filter material serving also as a weight is placed 
inside the lower filtration chamber, and an air feed port connected to an 
air pump is connected to the purification chamber. 
With the construction described above, the contaminated water inside the 
water tank is divided into two flows, that are introduced into the upper 
and lower filtration chambers from the upper and lower suction ports, and 
can be filtrated by the compact filter material and the coarse filter 
material disposed in these filtration chambers, respectively. Therfore, a 
compact filter having a high filtration efficiency can be obtained by 
relatively increasing the total filtration area of the two filter 
materials, even if the capacity of the filter case is reduced. 
The velocity of flow of the contaminated water that passes through the 
compact filter material inside the upper filtration chamber is much 
smaller than that of flow of the contaminated water passing through the 
coarse filter material having low flow resistance inside the lower 
filtration chamber, so that aerobic microorganisms including bacteria such 
as chlorella, that will not grow if the flow velocity is great, can be 
vigorously propagated, decomposing organic matters attaching to the 
compact filter material such as the residual bait and dropping of fishes, 
preventing clogging of the filter material and further improving the 
purification capacity. 
Since the lower suction port is disposed on the bottom surface of the 
filter case, the water inside the water tank can be introduced into the 
lower filtration chamber from the lower suction port through the gaps 
between pebbles that are spread on the bottom surface. This arrangement 
makes it possible to provide air permeability to the pebbles on the bottom 
surface of the water tank, to propagate the aerobic bacteria to let them 
purify the contaminated water, to restrict the propagation of aerophobic 
bacteria that exert adverse influences upon the growth of the aquarium 
fishes, and to keep the water quality at a suitable level. 
Furthermore, the coarse filter material placed inside the lower filtration 
chamber also serves as a weight when the filter is placed inside the water 
tank, so that a separate weight need not be disposed, contributing to the 
reduction of size of the filter. 
Since the purification chamber of the upper filtration chamber has a 
relatively large capacity, the air jetted into the purification chamber 
from the air feed port connected to the air pump does not form large 
discontinuous bubbles, but rises as small continuous bubbles inside the 
purification chamber and is discharged from the discharge pipe into the 
water tank. Such fine bubbles do not deteriorate the appearance of the 
water tank, and a continuous rising water flow can be generated inside the 
lower flow chamber. 
It is another object of the present invention to provide a filter having a 
construction in which the peripheral wall of a compact cylindrical filter 
material is formed as a corrugated wall consisting of long wave portions 
having a large wave height and extending radially in the circumferentially 
spaced manner, and short wave portions formed continuously between 
adjacent long wave portions and having a short wave height, this 
configuration serving markedly to increase the filtration capacity without 
increasing the outer diameter of the filter material. 
It is still another object of the present invention to provide a filter in 
which sludge attaching to the outer surface of the compact filter material 
can be automatically removed without the necessity of manual work. 
These and other objects, features and advantages of the present invention 
will become more apparent from the following description of preferred 
embodiments thereof to be taken in conjunction with the accompanying 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinafter, preferred embodiments of the present invention will be 
described with reference to the accompanying drawings. 
Referring initially to FIG. 1 which illustrates a first embodiment of the 
present invention, a filter 2 is shown disposed inside a water tank 1. A 
filter case 3 of this filter 2 consists of a square case main body 11 
including an upwardly projecting drain pipe 9 formed integrally at the 
center of its upper surface 11a and a large number of suction ports 10 
bored on the surface 11a around the drain pipe 9, and a lid 14 fitted 
removably to the lower open end of the case main body. A large number of 
suction ports 16 are bored radially on the bottom 15 of the lid 14, and a 
short cylindrical air feed port 17 having its upper end open projects 
integrally from the center of the bottom 15 of the lid 14. As can be best 
seen from FIG. 2, a large number of air passage grooves 18 having a 
corrugated cross-section are bored over the entire circumference on the 
inner peripheral surface of the air feed port 17. A cap 19 is fitted to 
the upper open end of the air feed port 17 so as to define air passage 
gaps between them by the air passage grooves 18. The hollow interior of 
the air feed port 17 is connected to the inner end of an air feed passage 
22 that is formed integrally and protrusively on the bottom 15 of the lid 
14, and the outer end of the air feed passage 22 is open to the side 
surface 13 of the lid 14. A plurality of support ribs 23 are formed 
equidistantly and integrally in the circumferential direction on the outer 
peripheral surface of the air feed port 17. 
A frame member 6 is disposed inside the filter case 3. A drain port 24 is 
formed at the center of the frame member 6. The frame member 6 consists of 
a ceiling plate 25 having a star-like outer shape as a whole and a bottom 
plate 27 connected to the ceiling plate 25 by a plurality of connecting 
rods 26. The bottom plate 27 is equipped at its center with an open 
portion 28 which is fitted to the outer peripheral surface of the air feed 
port 17 that projects integrally from the center of the lid 14. A large 
number of passage holes 29 are bored around the open portion 28. A 
plurality of engagement protuberances 31 extending downward are formed 
equidistantly around the drain port 24 on the lower surface of the ceiling 
plate 25, and engagement protuberances 32 are also formed on the upper 
surface of the bottom plate 27 so as to correspond to the engagement 
protuberances 31, respectively. 
The frame member 6 comes into abutment with the upper end surface of the 
side surface 13 of the lid 14 and with the upper end surface of the 
support ribs 23 around the outer circumference of the air feed port 17 at 
both outer and inner peripheral portions of the bottom plate 27, and is 
supported by the latter. The bottom plate 27 has substantially the same 
outer shape as the polygonal inner circumference of the square cylindrical 
side surface 11b of the case main body 11, and divides the interior of the 
filter case 3 into an upper filtration chamber 4 cummunicating with the 
suction ports on the upper surface 11a of the case main body 11, and a 
lower filtration chamber 5 communicating with the suction ports 16 on the 
bottom surface 15 of the lid 14, thereby forming a separator of the 
present invention. 
As shown in FIG. 2, the sheet-like compact filter material 7 is fixed to 
and supported by the frame member 6 as its inner peripheral surface is 
engaged with the connecting rods 26 while its outer peripheral surface is 
engaged alternately with the engagement protuberances 31 and 32 that are 
formed so as to oppose one another on the ceiling plate 25 and bottom 
plate 27, respectively. In other words, the sheet-like filter material 7 
is disposed in the upper filtration chamber 4 while being bent in a 
corrugated form and being wound in the cylindrical form. A 
non-purification chamber 37 communicating with the upper suction ports 10 
on the upper surface 11a of the case main body 11 and a purification 
chamber 33 which communicates with the drain pipe 9 projecting from the 
upper surface 11a of the case main body 11 via the drain port 24 of the 
ceiling plate 25 and has a relatively large capacity are defined outside 
and inside the filter material 7, respectively. 
The purification chamber 33 communicates with the lower filtration chamber 
5 defined by the bottom plate 27 and the inner surface of the lid 14, via 
a large number of passage ports 29 bored in the bottom plate 27 of the 
frame member 6, and also with the air feed port 17 via the air passage 
grooves 18. 
A coarse filter material consisting of pebbles or the like is stored in the 
lower filtration chamber 5, and serves also as a weight to prevent 
floating of the filter 2 when the filter 2 is placed inside the water tank 
1. 
One of the ends of a connector 34 is removably fitted to the outer end of 
the air feed passage 22 communicating with the air feed port 17, which 
outer end opens to the side surface 13 of the lid 14, and the other end of 
the air feed passage 22 is connected to an air pump 36 via an air feed 
pipe 35. 
Next, the operation of this embodiment will be described. 
When the air pump 36 is actuated after the filter 2 having the construction 
described above is placed on the bottom of the water tank 1, the air is 
fed to the air feed port 17 through the air feed pipe 35, the connector 34 
and the air feed passage 22, and is from thence jetted in a bubble form 
into the purification chamber 33 of the upper filtration chamber 4 through 
the air feed grooves 18 on the inner peripheral surface of the air feed 
port 17. The jet air rises as an air stream inside the purification 
chamber 33 and along with it, the water inside the purification chamber 33 
also rises, so that the water is discharged into the water tank 1 through 
the discharge port 24 and the drain pipe 9. As a result, the suction force 
acts upon the purification chamber 33, and part of the contaminated water 
inside the water tank 1 is sucked into the non-purification chamber 37 
from the suction ports 10 on the upper surface of the filter case 3 as 
represented by arrow in FIG. 1 and passes through the compact filter 
material 7. The purified water then flows into the purification chamber 
33. The other part of the contaminated water in the tank 1 passes through 
the spacings between the pebbles spread on the bottom surface of the water 
tank 1 and is sucked into the lower filtration chamber 5 through the 
suction ports 16 bored in the lid 14 of the filter case 3. After the 
contaminated water passes through the coarse filter material placed in the 
lower filtration chamber 5 and is purified by it, the resulting purified 
water flows into the purification chamber 33 of the upper filtration 
chamber 4 through the through-holes 29 on the bottom plate 27 of the frame 
member 6. The water inside the purification chamber 33, that has been 
purified after passing through the filter materials 7 and 8, flows into 
the drain pipe 9 through the discharge port 24 opening at the ceiling 
plate 25 together with the air that is introduced into the purification 
chamber 33 from the air feed port 17 through the air feed grooves 18, 
which water is thereafter returned to the water tank 1 as the purified 
water. 
The compact filter material 7 inside the upper filtration chamber 4 has 
higher flow resistance of water than the coarse filter material 8 inside 
the lower filtration chamber 5, so that the velocity of the contaminated 
water flowing through the compact filter material 7 becomes relatively 
low. Accordingly, the water promotes the propagation of aerobic 
microorganisms including useful bacteria such as chlorella, that are 
otherwise difficult to grow if the velocity of water flow is high, and 
these microorganisms decompose organic matters attaching to the filter 
material 7 such as the residual bait and droppings of fish, preventing 
clogging of the filter material 7. Moreover, the bacteria such as 
chlorella can be used as living bait for the aquarium fishes. 
The compact filter material 7 placed in the upper filtration chamber 4 is 
more likely to get clogged than the coarse filter material 8 stored in the 
lower filtration chamber 5. However, since the water inside the water tank 
1 always flows into the purification chamber 33 of the upper filtration 
chamber 4 through the coarse filter material 8 having relatively low flow 
resistance inside the lower filtration chamber 5, the suction force always 
acts upon the purification chamber 33 and hence, the water inside the 
non-purification chamber 37 of the upper filtration chamber 4 is sucked 
into the purification chamber 33 through the compact filter material 7. 
Therefore, the flow of water from the non-purification chamber 37 to the 
purification chamber 33 never stops, and the excellent filtrating 
operation by the compact filter material 7 can be kept for an extended 
period of time. 
FIGS. 4 through 6 illustrate a second embodiment of the present invention, 
in which like reference numerals are employed to identify like 
constituents as in the first embodiment. 
As can be best seen from FIG. 5, the sheet-like compact filter material 7 
in this embodiment is fixed to and supported by the frame member 6 and its 
inner peripheral surface is supported by the connecting rods 26 while its 
outer peripheral surface is alternately engaged with the engagement 
protuberances 31a, 31b and 32a, 32b that are formed on the ceiling plate 
25 and the bottom plate 27 so as to oppose one another, respectively. In 
other words, the sheet-like filter material 7 is formed to have a 
corrugated peripheral wall that is bent in the radial direction. The 
corrugated peripheral wall consists of long wave portions 7a of a large 
wave height which extend radially in the circumferentially spaced manner 
and short wave portions 7b of a short wave height formed continuously 
between the adjacent long wave portions 7a, 7a. 
A hollow air jet cylinder 20 made of an air permeable material such as a 
foamed synthetic resin and having its upper end closed is fitted to the 
cap 19, and the hollow interior of this air jet cylinder 20 communicates 
with the air feed port 17 through a passage port 21 formed on the cap 19. 
A connector 34' is rotatably fitted to the bottom surface of the air feed 
port 17, and is connected to an air pump, not shown, via the air feed pipe 
35. 
A plurality of engagement protuberances 31a and 31b are formed integrally 
and protrusively on the lower surface of the ceiling plate 25 in inner and 
outer two circular lines in the concentric arrangement so as to extend 
downward and equidistantly around the drain port 24. Likewise, a plurality 
of engagement protuberances 32a and 32b are integrally formed on the upper 
surface of the bottom plate 27 in such a manner as to correspond to the 
engagement protuberances 31a and 31b, respectively. 
The frame member 6 comes into abutment with and is supported by the upper 
edge surface of the side surface 13 of the lid 14 and a step-like shoulder 
17a of the outer circumference of the air feed port 17, at the inner and 
outer peripheral portions of the bottom plate 27. 
The operation of this second embodiment will be described. As described 
above, the cylindrical filter material 7 disposed in the upper filtration 
chamber 4 formed inside the filter case is formed to have a corrugated 
peripheral wall that is bent in the radial direction, and this corrugated 
peripheral wall consists of the long wave portions 7a of a large wave 
height which extend radially in the circumferentially spaced manner, and 
the short wave portions 7b of a small wave height formed between the long 
wave portions 7a, 7a so as to continue them. With this arrangement, the 
filtration area of the filter material 7 can be remarkably increased 
because all the radially inner-most parts of the corrugated wall need not 
be arranged in a high density on substantially the same circumference as 
in the prior art device in which the height of the wave portions of the 
filter material is substantially the same. Since the sufficient spacings 
can be defined between the inner-most parts of the adjacent long wave 
portions 7a of the filter material, the flow of fluid from the peripheral 
portion of the purification chamber 33 toward the center of the 
purification chamber 33 defined inside the filter material 7 is never 
inhibited, and the entire surface of the filter material 7 can be 
effectively utilized to improve the filtration efficiency. Accordingly, 
the filtration capacity can be easily increased without increasing the 
outer peripheral diameter of the filter material 7 which is disposed 
cylindrically. 
FIG. 7 illustrates a third embodiment of the present invention. A large 
number of engagement protuberances 38, 39 and 40 are formed on the ceiling 
plate (not shown) and bottom plate 27 of the frame member 6 in at least 
three concentric circles having mutually different diameters with their 
phases being appropriately deviated in the circumferential direction. The 
sheet-like filter material 7' is engaged with the connecting rods 26 and 
alternately with the engagement protuberances 38, 39 and 40, and is 
thereby fixed and held in place. In this case, the short wave portions 7b' 
consisting of three short waves are formed between the mutually adjacent 
long wave portions 7a', 7' having a large height, and the short wave 
7b.sub.1 ' at the center has a greater wave height than those of the short 
wave portions 7b.sub.2 ', 7b.sub.2 ' on both sides. 
FIGS. 8 through 11 illustrate a fourth embodiment of the present invention, 
wherein like reference numerals are used to identify like constituents as 
in the foregoing embodiments. 
A half split type cylindrical cover 45 is integrally fixed to the side 
portion 11b of the case main body 11 of the filter case 3 and extends in 
the vertical direction, thereby forming a pure fluid chamber 46 on the 
external side of the case main body 11. This pure fluid chamber 46 is 
defined over the entire length of the filter material 7 in its axial 
direction, and a separator 47 is interposed between the pure fluid chamber 
46 and the non-purification chamber 37. As shown in FIG. 11 which is an 
enlarged view, a plurality of first nozzles 48 and a plurality of second 
nozzles 49 are alternately formed in the vertical direction on this 
separator 47. The first nozzles 48 are directed towards one side of the 
circumferential direction of the frame member 6 (clockwise in FIG. 9) with 
respect to the radial direction of the frame member 6, while the second 
nozzles 49 are open in the radial direction of the frame member 6. A 
connection tube 51 such as a vinyl tube is connected to the pure fluid 
chamber 46 via a connector 50. This connection tube 51 is connected to a 
pure fluid feed source 52 such as a water tap or the like. 
Referring to FIG. 12, a half split type cylindrical cover 54 is integrally 
fitted to the side portion 11b of the case main body 11 at a position 
thereof offset relative to the adjacent purified chamber 46 in the 
circumferential direction of the frame member 6 (clockwise in FIG. 9). 
This discharge chamber 53 extends over the entire axial length of the 
filter material 7 and is connected to the non-purification chamber 37. A 
connection pipe 56 such as a vinyl tube is connected to this discharge 
chamber 53 via a connector 55, and the connection pipe 56 is in turn 
connected to a suction pump 57. 
A plurality of legs 41 engage with the lid 14. Each leg 41 is formed by 
connecting a pair of leg bases 42a, 42b, that are spaced apart 
progressively from each other as they separate outward from the lid 14 in 
the radial direction, at their inner positions in the radial direction of 
the lid 14. An engagement protuberance 43 formed at the base of each leg 
41 engage with the suction port 16 at the radially innermost position of 
the lid 14. A plurality of support beds 44, that are recessed inward in 
the radial direction, are disposed at a plurality of positions in the 
circumferential direction of the lid 14 at its side portion 13. 
The operation of this fourth embodiment will be described. Although the 
filter material 7 can keep its excellent filtration efficiency for an 
extended period of time, the gradual decrease of filtration efficiency 
cannot be avoided because sludge attaches to the outer surface of the 
filter material 7 in the course of use of the filter for a long period. 
After filtration is made for a long period, therefore, the operation of 
the air pump is temporarily stopped to stop filtration, the suction pump 
57 is actuated and at the same time, pure water such as tap-water is 
supplied into the pure fluid feed chamber 46 from the pure fluid feed 
source 52. Then, the pure water is jetted from the first and second 
nozzles 48 and 49 towards the filter material 7. The pure water jetted 
from the first nozzle 48 impinges against the corrugated peripheral wall 
of the filter material 7 and removes the sludge, and at the same time, 
applies a force of rotation to the filter material 7 and to the frame 
member 6 in one of the circumferential directions (clockwise in FIG. 2). 
Accordingly, the filter material 7 as well as the frame member 6 rotate, 
and the jet pure water from the first and second nozzles 48 and 49 is 
sequentially sprayed to the corrugated peripheral wall of the filter 
material 7 in its circumferential direction. In this instance, the second 
nozzles 49 jet the pure water so that it can reach the deep spacings 
between the short wave portions 7b and the long wave portions 7a. In this 
manner, the entire outer surface of the filter material 7 is cleaned by 
the first and second nozzles 48 and 49, and the removed sludge flows in 
one of the circumferential direction inside the non-purification chamber 
37 with the rotation of the filter material 7, and is thereafter 
discharged from the discharge chamber 52 by the sucking operation of the 
suction pump 57. Accordingly, the filter material 7 can be cleaned 
automatically without the necessity of disassembling the filter case 3 and 
removing the filter material 7 out from the case. Thus, the necessity of 
the disassembly of the filter case 3 that has been required in the prior 
art device is eliminated, and the filter of the present invention is 
extremely convenient.