Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTIOM
Field of the Invention
This invention relates to disposable filter units.
Prior Art Relating to the Disc]osure
Automatically operated analytic instruments for
processing substances 5uch as blood serum require that the
blood serum be filtererd to avoid clogging of the instrument
with coagulated material and other solids. Therefore, indi-
vidual quantities of blood to be analyzed are poured into
disposable filter units and the filtrate is collected in sam-
ple cups for further processing. U.S. Patent No. 3,508,736
describes a disposable filter unit having a downwardly depen-
ding cap which fits around the top portion of a sample cup,
making it hard to determine the level of filtered blood serum
in the cup. Since the interior surface of the cap friction-
ally engages and seals against the outside surface of the
sample cup, small holes are provided directly through the
wall of the cap for letting air escape from the cup as it is
filled. ~ disadvantage of that type of cap is that it will
only fit a specimen cup having a certain outside diameter.
The outside diameters of sample cups produced by different
manufacturers vary considerably, even if their inside diam-
eters are the same. The end result is that different sizes
of filtration units are required to be manufactured and
stoc]~ed for each sample cup type. Obviously, this is ineffi-
cient and expensive. Prior disposable filtration units have
a relatively small discharge hole at the bottom of the column
so that the filter material, such as thin sheets of filter
paper, is adequately supported by the column.
Many other biological substances are first filtered
prior to beinq analyzed or processed in containers such as
1 ~62 ~
test tubes or the like. The filtering equipment is sometimes
complicated and expensive. For example, a hollow cylindrical
collection tube has a filter located at its lower end and a
seal positioned around the outside of its lower end. The
seal slides alon~ the inside surfce of a larger cylindrical
test tube containing the fluid substance to be filtered. As
the collection tube is pushed down into the larger test tube,
pressure on the confined fluid forces fluid up through the
filter and up into the collection tube. The filtered fluid
is then transferred from the collection tube to a test tube
or the like for analysis or further processing. Obviously,
this apparatus is expensive to manufacture, requires an oper-
ator's time, and involves transferring fluids to an interme-
diate container, that is, the collection tube, increasing the
possibility of contamination. Pressurization of the fluid
being filtered may force undesired substances through the
filter media.
SUMM~RY OF THE INVENTIOII
To overcome these and other deficiencies of the
prior art, it is an object of this invention to provide an
improved, inexpensively fabricated, disposable filtration
unit.
It is another object of this invention to provide a
disposable blood filtration unit which permits air to easily
escape from a sample cup being filled.
It is another object of this invention to provide
one embodiment of an improved disposable filtration unit
which accommodates a range of sample cups having varying
dimensions and which permits air to easily escape and the
fluid level in a specimen cup to be easily seen.
l5~
It is another object of this invention to provide
another embodiment of a filtration unit having a eap portion
which is spaced Erom the sample cup to provide passages for
the escape of air from the specimen cup.
It is another object of the invention to provide a
filtration unit which includes a support for a filter so that
a larger discharge area is available.
In accordance with these and other objects of the
invention, an improved disposable filtration unit is provided
which provides a frictional interfit between a filtration
column and a sample cup. The filtration column is spaced
from the sample cup to provide passages for the escape of air
from the sample cup as it is filled b~ filtrate discharged
from the column. One embodiment of the invention utilizes
external wedge-shaped projections at the lower end of the
filtration column which frictionally engage a sample cup and
accommodate a range of cup or test tube sizes. A second em-
bodiment of the invention uses an end cap integral with the
filtration column wherein a plurality of projections space
the cap from the top edge and sides of a sample cup, provid-
ing escape passages for air as the sample cup is filled.
spider structure i5 positioned across the filtration column
for supporting a filter media to increase the effective dis-
charge area of the filtration unit.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
Fig. 1 is an exploded isometric view of one embodi-
ment of a disposable filtration unit and a sample cup;
Fig. 2 is an assembled isometric vie~ of the one
embodiment of a disposable filtration unit interfitting with
the sample cupr
Fig. 3 is a sectional view of the filtration unit
and sample cup taken along section line 3-3 of Fig. 2-
Fig. 4 is a partially cut-away, sectional view
taken along section line 4-4 of Fig. 3;
Fi~. 5 is an exploded isometric view of a second
embodiment of a filtration column having a downwardly depend-
in~ cap;
Fig. 6 is an assembled isometric view of the second
embodiment of the filtration column and specimen cup as shown
in Fig. 5;
Fig. 7 is a section view of the assembly of Fig. 6
taken along section line 7-7; and
Fig. 8 is a section view of the assembly of Fig. 6
taken along section line 8-8.
DETAILED DESCRIPTIO~ OF THE PREFERRFD EMBODIMENTS
__ _ __ ___ _
Referring to Figs. 1 and 2, the lower end of a fil-
tration column 10 fits within the mouth of a typical sample
cup 12. Note that the filtration column 10 also fits within
the mouth of a variety of containers r such as test tubes, and
the invention is not restricted to use with the sample cup
12, which is exemplary. A plurality of wedge-shaped projec-
tions 14, having angled external surfaces 15 which angle
downwardly and inwardly along the lower outside surface of
the filtration column 10, wedge-fit within a range of sample
cup sizes. The filtration column 10 is an elongated cylin-
drical body inexpensively formed from a molded plastic ma-
terial. The wedges 14 longitudinally extend along the outer
surface of the cylindrical filtration column and are inte-
grally molded with the column. As shown in Fig. 3, the sam-
ple cup has a circular rim 20 formed around the mouth opening
at the top of the cup~ Below the rim 20 of the sample cup 12
1 16~153
is formed a radially extending, annular flan~e 21 which may
serve as a locating member for placement of the cup in an an-
alytic machine. The flange 21 a:Lso serves as a fill indica-
tor for the cup, The surfaces 16 of the wedges 14 engage the
interior surfaces 22 of the rim 20 and frictionally join the
filtration column 10 to the sample cup 12. A variety of cup
sizes having different mouth diameters are accommodated by
the variable configuration of the wedge faces 16 formed on
the column. Thus, one size of the filtration column 10 is
used with a range of sample cup sizes having different mouth
sizes. Note that what has been said for the sample cup also
applies to other containers, such as test tubes and the like.
The wedge portions 14 not only frictionally inter-
fit with the sample cup 12, but also space the filtration
column 10 away from the interior surface of the rim of sample
cup 12 so that air passages are provided between the lower
external surface of the filtration unit 10 and the interior
surface 22 of the sample cup rim 20. These passages permit
air to escape from the sample cup as the sample cup is filled
with filtrate.
As shown in Fig. 4, a transversely positioned par-
tition 23 extends across the bore of the column's interior
away from the lower end of the column 10 and provides a cham-
ber above the partition for holding the substance to be fil-
tered. A central aperture 24 is formed in the partition 23and the aperture 24 is spanned by a spider structure 26 hav-
ing a plurality of radially extending arms 28. The top sur-
face oE the spider 26 is coplanar with the interior surface
of the partition 23, providing surfaces against which a sheet
of fi]ter paper 30 lies as shown in Figs. 3 and 4. The spi-
der 26 provides a relatively large discharge area for the
filtration column 10 while providing support for the filter
paper overlying the discharge opening defined by the aperture
24. The arms 28 of the spider 26 define a plurality ~f pass-
ages ~or filtrate, which is gravity fed through the filter
530. A downwardly depending, cylindrical discharge nozzle
portion 32 is formed adjacent the ends of the spider arms 28
and directs the filtrate into the interior of the sample cup.
In operationr the filtration column 10 is joined to
a sample cup 12 or some other container, such as a test tube,
10by coaxially placing the lower end of the filtration column
10 within the rim 20 of the sample cup 12 or container. The
filtration column 10 is pushed downwardly toward the sample
cup 12 so that the faces 16 of the wedqes 14 engage the cup
rim 20 along its interior surface 22. The filtration column
1510 is pushed until the wedge faces 16 are in tight frictional
engagement with the interior surface 22 of the sample cup 12.
Figs. 3 and 4 show a piece of filter paper 30 positioned
along the top surface of the partition portion 23 of the fil-
tration column 10. The substance to be filtered, for exam-
20ple, blood, is poured into the open top of the chamber formed
in the hollow interior of the filtration column 10 above the
partition 23. The blood flows by gravity through the filter
paper 30, which collects undesired clotted material and other
substances from the blood. The filtrate is discharged from
25the filter paper through a large area nozzle portion 32 of
the column into the interior of the cup 12, where it is col-
lected. The air within the sample cup 12 is displaced by the
filtrate and is forced out of the cup through the air pas-
sages provided between the lower end of the fltration column
3010 and the interior surface 22 of the rim 20 of the sample
cup 12, permitting the air to be easily vented. The spider
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structure 26 permits a relatively large area oE the filter
paper to be used for filtering and provides a large discharge
cross-sectional area for the column~ Note again that a range
of diameters for the sample cup 12 or other container is eas-
ily accommodated by the variable contact surface of the wedge
faces 16 and that air is readily discharged from the sample
cup or other container with this confiquration. The lower
end of the column fits inside the sample cup rim and allows
an operator to easi]y determine the level of filtrate within
the sample cups with respect to the flange 21 formed on the
exterior of a transluscent sample cup 12.
Another Embodiment
Figs. 5 and 6 show another embodiment of the inven-
tion. Another filtration column 50 joins to a sample cup 52
similar to the sample cup 12 described above. The filtration
column 50 is an elongated, hollow cylindrical tube, preferab-
ly inexpensively molded from a plastic material. At the low-
er end of the filtration column 50 is formed an integral de-
pending cap 54 which fits over the rim 55 at the upper end
of the hollow cylindrical sample cup 52, but the cap 54 does
not seal against the cup. The cup 52 has a radially extend-
ing annular flange 56 extending therefrom which serves both
as a locating stop for the cup 52 and as a fill indicator
line for the cup 52.
Referring to Figs. 7 and 8, the cap 54 includes a
cylindrical depending rim 58 which projects downwardly from
the periphery of a flange 60 radially extending from the
bottom 62 of the filtration column 50. A series of longitu-
dinally extending ribs 64 are formed to space the interior of
the cap 54 away from the exterior surface of the top rim 55
of sample cup 52. Depending on the length of the rim 55 of
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the cup, the lower projecting ends 66 of the ribs 64 engage
the upper surface of the flange 56 and space the cap 54 away
from the flange 56. The upper interior surface 68 of the cap
portion 54 has a plurality of elongated, downwardly project-
ing horizontal ribs 70 positioned thereupon which extend fromthe upper ends of the longitudinal ribs 66 toward a downward-
ly depending nozzle portion 71 of the filtration column 50.
Depending on the length of the rim 55 of the cup, the hori-
zontal ribs 70 space the cap 54 away from the top edge of the
rim 55 of the sample cup 52. The longitudinal ribs 64 and
the horizontal ribs 70 t if necessary, space the interior sur-
faces of the cap 54 from the exterior surfaces of the sample
cup 52 and provide air passages between the interior surfaces
of the cap 54 and the underlying portions o~ the sample cup
52. A series of circumferential ribs 65 are formed around
the cylindrical interior surface of the cap. These ribs also
frictionally contact the cup and, during manufacture of the
cup, are used to remove the filtration unit from the die in
which -the filtration unit is molded.
As shown in Figs. 7 and 8, a piece of filter paper
74 overlies the bottom interior surface of the filtration
column 50 and is supported by a spider structure 76 having
radially extending ribs 78. The spider structure 76 extends
across a central aperture 80 formed in the bottom of the fil-
tration column 50 and the filter paper 74 is supported by the
top surfaces of the radially extending rib portions 78 with
the top surfaces of the ribs 78 are flush with the bottom
surface of the column interior. The ribs define a plurality
of discharge ou-let passages for the column 50 and the spider
structure permits a large cross-section discharge area for
the column 50.
~ 16~53
In operation, the cap 54 of the filtration column
50 is placed around the rim 55 of the sample cup 52 as indi-
cated in Fig. 7. Dependent upon the length of the cup rim
55~ the Proiections 66 and/or the horizontal ribs 70 may con-
tact the cup, together with the longitudinal ribs 64. Pas-
sages are thereby provided for air to escape as filtrate
fil].s the interior of the sample cup 52 and forces air out of
the cup and through the passages formed between the interior
surface of the cap and the rim 55 of the sample cup.
While particular embodiments of the invention have
been shown and described, it should be understood that the
invention is not limited thereto since many modifications may
be made. It is therefore contemplated to cover by the pre-
sent application any and all such modifications that fall
within the true spirit and scope of the basic underlying
principles disclosed and claimed herein.
