Note: Descriptions are shown in the official language in which they were submitted.
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l`h~ prescnt invention relates generally to the
field of sample testinc3, and is specifically adapted to
medical studies of body fluid s~mples, particularly blood,
and to testing various parameters of blood such as the
making of hematocrit determinations. More par-ticularly, the
invention reLates to the study of body fluid samples by
evaluating the electrical properties of such samples.
Various methods and apparatus are known for studying
liquid samples. Some involve centrifucation, others utilize
agitation, and -there are still others which depend upon the
e]ectrical characteristics of the sample being tested. In
virtually all of these known techniques, especially those in
the medical field, it is of prime importance to maintain
isolation between samples. Careful scrubbing and the use of
an autoclave between successive tests are generally sufficient
`` to eliminate cross-contamination of samples. Yet the
` possibility of contamination still remains.
A further problem relates to the protection of the
, technician against contracting infectious diseases from the
samples under test. With the known methods and apparatus,
very little protection if afforded.
An example of an apparatus for studying the electrical
` characteristics of blood can be found in U.S. Patent No.
3,922,598, issued to Steuer et al. on November 25, 1975.
This apparatus includes a rod-like probe having two conductive
electrodes at the tip of the probe. A blood sample is
associated with the electrodes of the probe, and an electric
voltage is applied across the blood for the purpose of
hematocrit determinations. Obviously, the probe must be
thoroughly cleaned between tests to ensure accurate test
results.
It is toward the accomplishment of a simplified,
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saf~ and accurate electrical ev.l]uation of liquid samples that
the prc~scnt inv~ntion is directecl.
The preciellt invention rela-tes yenerally to sample
testing by electrical means. Particular use is found for
the invention in the medical field, especially in studying
~t the electrical conductivity of whole blood samples and the
li~e.
Specifically, the present invention takes the form
of a disposable card containing a chamber, or well, and
supporting a pair of electrical contacts in the region of
the well. In use, the well is filled with a test fluid,
such as whole blood, and the disposable card is associated
! with an instrument which passes an electric current through
the test sample to determine its conductance, and hence the
i characteristic under study.
In one embodiment, both electrodes are plated on
the top surface of the card. The first electrode terminates
~ in a button centrally positioned at the bottom of the well.
; The second electrode, also located in the bottom of the
;- 20 well, surrounds the first, interrupted only to permit the
lead of the first electrode to enter the central region of
the well. The opposite ends of the electrode leads terminate
-~: at an edge of the card for connection to conventional printed
circuit terminals.
A second embodiment of the inventive card has a
,- central electrode similar to that of the first embodiment,
but entering the well through the bottom surface of the
card. The other electrode is plated on the top of the card,
and forms a complete ring about the central button electrode
in the well. The electrode leads associate with printed
circuit terminals as previously described.
In a third embodiment, the central electrode takes
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the forrn of ~1 button erltcring tlle well from the bottom
surface of the card, and the other electrode takes the form
of an outcr co!lcelltric r:ing, the lead of which also enters
the well fro~ beneath the card. Connector pins extend
downwardly from both electrodes, under the well, and are
there adapted to mate with appropriate conventional connectors.
These may take the form of female sockets if the card is
received fro~ the top, or resilient spring clips to receive
the card if introduced in the plane of its base.
The inventive sample-receiving cards are disposable,
so that after one sample has been tested, the soiled card is
dispensed with and replaced by a new card for the next
sample. This procedure eliminates the possibility of
cross-contamination of samples, and minimizes the chances of
- the technician contracting disease from the sample.
The cards are packaged in a clean and uncontaminated
condi-tion, are handled by a small finger tab, and therefore
also cure the contamination and cleaning difficulties of
prior art techniques.
The present invention also relates to an instrument
having a special casing design for receiving the intentive
sample cards. This instrument includes a guide and support for
guiding sample cards into the instrument, for supporting the
cards in the instrument and for associating the cards with
appropriate electrical circuitry.
It is accordingly a principal object of the present
invention to provide a mechanism whereby a liquid sample
can be tested by electrical means in an efficient and reliable
manner.
' 30 A more specific object of the present invention is
to provide disposable sample cards for receiving liquid samples
and for determining a characteristic of such samples through
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electrical m~alls.
A further object of the preserlt invention is to
provide a techllique for testing body fluids in a manner
which avoids cross-contamination of samples and which minimizes
the possibility of a technician contracting a disease.
Another syecific object of -the present invention
is to provide disposable sample receptacles for electrical
evaluations of bod~ fluids, such as hematocrit de-terminations.
~ nother object of the present invention is to
provide an instrument particularly suited -to receive the
inventive disposable sample cards.
These and other objects of the present invention,
; as well as many of the attendant advantages thereof, will
become more readily apparent when reference is made to the
following description, taken in conjunction with the accompanying
drawings.
Figure 1 is a perspective view of an inventive
sample card;
~, Figure 2 is a front view of an instrument associated
with the inventive card illustrated in Figure l;
` Figure 3 is a top view, partially broken away, of
the instrument illustrated in Figure 2;
Figure 4 is a top plan view illustrating a second
embodiment of the inventive sample card;
Figure 5 is a cross-section of the inventive card,
, taken along line 5-5 of Figure 4;
Figure 6 is a top plan view of still another
embodiment of the inventive sample card; and
` Figure 7 is a cross-section of the inventive card
taken along line 7-7 of Figure 6, also showing connector
sockets.
With reference first to Figures 1 through 3, the
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first embodililent of the inventive sample card will be described.
The sample c,~rd is shown generalLy at 10, and comprises a
generally planar base portion 12 into which is recessed a
central well 14. The well is preferably sized so as to
accommodate approximately one drop of blood; a well volume
on the order of 0.05 ml. is contemplated. A tab 16 extends
from one edge of the card, and lies generally in the plane
of base 12. Thc sample card 10 may be of many non-conductive
materials, but for purposes of cost, ease of manufacture and
suitability for disposal, a plastic is preferred.
An optional cover 15 is illustrated in Figure 1,
hinged at one surface of base 12. Figure 2 illustrates
cover 15 in its closed orientation. The purpose of cover 15
is to protect the clinician from disease; cover 15 also
avoids loss of the sample.
A button electrode 18 is located in the central
, region of the well 14, and is encircled by an outer electrode
20. As seen bes-t in Figure 3, electrode 20 is generally ~ ~ -
hook-shaped, and is open at 21 to permit the passage of a
lead 22 from button electrode 18. The outer electrode 20 is
equipped with a similar lead 24.
The electrodes 18 and 20 are plated on the top
interior surface of the well 14, and the associated electrode
leads 22 and 24 are similarly plated on the upper surface of
base 12. The respective electrode leads 22 and 24 extend to
the edge of the base 12, as shown at 26 and 28.
An instrument, such as one for determining hematocrit,
is shown generally at 30 in Figures 2 and 3. The instrument
30 has a base 32 and a top 34, and is provided with an
intermediate groove, or track, 36, between the base and
' top. As seen best in Figure 2, the groove 36 is shaped and
dimensioned to accommodate the sample card 10, and includes
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a rec~is 38 comE)atible with the well 14.
The card 10 is held by tab 16 and is introduced to
the instrument 30 by sliding the same into groove 36. When
the card is fully introduced into instrument 30, the res-
pective electrode leads at 26 and 28 mate with spring contacts
40 and 42 of a conventional printed circuit connector device
shown generally at 44.
In operation, the well 14 is filled with a sample
to be tested, such as whole blood, and the card 10, with
sample, is introduced into the instrument 30 by way of
groove 36. Electrical contact is made between the leads on card
10 and the contacts of connector 44, and a current is passed
through the sample. The conductivity of the sample is
determined by measuring sample impedance, through the means
of appropriate and conventional electronics (not shown).
For example, if the instrument 30 were of the type used in
hematocrit determinations, circuitry such as that disclosed
in U.S. Patent No. 3,922,598 could be employed.
With reference now to Figures 4 and 5, the second
embodiment of the inventive sample card will be disclosed.
In this embodiment, the sample card can be seen at 50, and
includes a base 12, well 14 and tab 16 as previously described.
This embodiment differs from the first in that the outer
electrode, shown at 52, is in the form of a closed circle.
The circular electrode 52 is plated on the upper surface
well 14, and is integral with a lead 54 plated on the upper
surface of base 12. The central electrode, illustrated at
56, is also different in this embodiment. Here, the lead 58
of the central electrode 56 is plated on the bottom surface
of well 14 and base 12. As seen best in Figure 5, the
electrode 56 takes the form of a rivet in electrical contact
with lead 58, and passing through the base of well 14 from
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thc bottom into the interior thereof. This arrangement of
central electrode 56 is adapted to enable the outer electrode
to fornl a closed circle.
A third embodiment of the inventive sample card is
shown in Figures 6 and 7 at 60. Here, like the embodiment
described when reference was made to Figures 4 and 5, and
outer electrode forms a closed circle about an inner electrode.
In this embodiment, an inner electrode 64 comprises a
button which passes through the base of the well 14, and an
outer electrode 62 is plated on the upper surface of well 14
and forms a circle about inner electrode 64. A contact
button 66, like button 64, is electrically integral with outer
conductor 62, and passes through the base of the well 14.
Rigid connector pins 68 and 70, integral with
respective buttons 64 and 66, extend from the bottom of the
' well 14, and serve to associate the electrodes of sample
card 60 with the electronics of the instrument 30. Th~se
pins 68 and 70, as shown in Figure 7, are able to mate with
sockets 72 and 74, respectively, if the card 60 is introduced
in the direction of arrow 75. In this case, the top of the
;'- instrument is open to accept the sample card 12. It should
be understood, however, that other instrument-associated
electrical contacts can be used. For example spring-like
connectors could be employed to make contact with respective
pins 68 and 70 if the card 60 were to be slid into the
instrument 30 in a direction perpendicular to that represented
by arrow 75.
Above, specific embodiments of the present invention
` have been described. It should be appreciated, however,
that these embodiments were described for purposes of
illustration only, without any intention of limiting the
v scope of the present invention. Rather, it is the intention
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that the preserlt ~nven~ion be limited only as is defined in
th~ ap~nded claims.
This application is a divisional application
of our cop~nding appli~ation ~o. 281,753 fi1ed 7une 30, 1977.
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