U.S. patent number 3,751,173 [Application Number 05/283,308] was granted by the patent office on 1973-08-07 for flowthrough cuvette.
This patent grant is currently assigned to Micromedic Systems, Inc.. Invention is credited to Georges Revillet, Manuel C. Sanz.
United States Patent |
3,751,173 |
Sanz , et al. |
August 7, 1973 |
FLOWTHROUGH CUVETTE
Abstract
The invention relates to optical cuvettes of the throughflow
type and to the production thereof. The cuvette comprises a
stratified block composed of at least three layers which together
define a space constituting a doubly-bent continuous passage with a
central elongated cavity communicating with two transverse
branch-channels extending to the cuvette surface. An intermediate
layer consists of a pair of transparent plates having oppositely
arranged inner edges which are shaped in accordance with the path
of said passage and are rounded off between the central cavity and
the transverse channels, to provide streamline flow in the passage.
Two lateral layers consist of plates which respectively close off
the passage on either side thereof, between the shaped inner edges
of said pair. The invention further provides a manufacturing method
wherein two plate-edges are shaped in accordance with the profile
of the doubly-bent passage and are oppositely arranged at a given
distance to form an intermediate layer on to which two lateral
plates are then mounted to close off the passage on either side
thereof.
Inventors: |
Sanz; Manuel C. (Grand Lancy,
CH), Revillet; Georges (Onex, CH) |
Assignee: |
Micromedic Systems, Inc.
(Philadelphia, PA)
|
Family
ID: |
23085421 |
Appl.
No.: |
05/283,308 |
Filed: |
August 24, 1972 |
Current U.S.
Class: |
356/246 |
Current CPC
Class: |
G01N
21/05 (20130101); G01N 2021/054 (20130101) |
Current International
Class: |
G01N
21/03 (20060101); G01N 21/05 (20060101); G01n
001/10 () |
Field of
Search: |
;356/180,181,244,246
;23/292 ;250/218 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sikes; William L.
Claims
We claim:
1. An optical cuvette of the throughflow type having therein at
least one doubly-bent continuous passage composed of a central
elongated cavity for enclosing a liquid sample and of two
transverse branch-channels respectively extending between the ends
of the cavity and the cuvette surface to allow admission and
discharge of said sample, the cuvette being at least partially
transparent to allow a light beam for effecting optical measurement
to pass through the cuvette and thereby to longitudinally traverse
the elongated cavity containing the sample, wherein the cuvette
comprises a stratified block composed of at least three layers
arranged in juxtaposition so as to define together a space
constituting the said passage, an intermediate layer of said three
layers being composed of a pair of transparent plates lying in a
common plane at a predetermined distance from each other, each
plate of said pair being provided with an inner edge which is
shaped in accordance with the doubly-bent path of said passage and
which has a gradual transition between said cavity and said
transverse channels whereby to allow streamline flow along said
passage, and two lateral layers being formed by two corresponding
plates whereof the inner surfaces respectively define said passage
on either side thereof, between said shaped inner edges of said
pair of plates of the intermediate layer.
2. An optical cuvette according to claim 1, wherein the transverse
branch-channels extend in opposite directions from the ends of the
central cavity so that the passage extends according to a generally
S-shaped path opening on opposite sides of the stratified
block.
3. An optical cuvette according to claim 2, wherein the inner edges
of the pair of plates forming the intermediate layer are generally
S-shaped and have a rounded-off edge-portion situated in the region
of transition between the cavity and the transverse
branch-channels, the plates of said pair being arranged in spaced
head-to-tail relationship in the intermediate layer.
4. An optical cuvette according to claim 3, wherein at least one of
the inner edges is so shaped as to provide at least one enlarged
portion in said cavity.
5. A method of manufacturing an optical cuvette of the through-flow
type having at least one doubly-bent continuous passage composed of
a central elongated cavity and of two transverse branch-channels
respectively extending between the ends of the cavity and the
cuvette surface, the cuvette being at least partially transparent
so as to allow a light beam to pass through the cuvette and thereby
to longitudinally traverse the elongated cavity, said method
comprising:
shaping at least one transparent plate so as to obtain at least one
pair of edges corresonding to the desired double-bent path of said
passage and providing a gradual transition between said central
cavity and said transverse channels;
arranging said edges in spaced relationship facing each other to
form a first pair of wall portions partially defining said passage
so as to provide a central cavity of predetermined length;
and sealingly mounting two lateral plates so as to close-off either
side of the space lying between said spaced edges, whereby to form
a complementary pair of wall portions defining said passage
together with said first pair of wall portions.
6. The method defined in claim 5, wherein said pair of edges are
formed by cutting out of the transparent plate a space
corresponding to the desired doubly-bent longitudinal profile of
the passage, and rounding off said edges so as to provide a gradual
transition in the bent portions thereof between the central cavity
and the transverse branch-channels of said passage.
7. The method defined in claim 6, wherein the said space cut out of
the transparent plate has a generally S-shaped profile and the
edges defining said space are rounded off so that the transverse
channels gradually merge into the central cavity of the
passage.
8. An optical flow-through cuvette comprising a body means, said
body means having at least one internal layer, said layer including
a pair of transparent plates in a common plane and spaced from one
another, the spacing of said plates providing three generally
linear passages in successive communiccation with one another, the
first and last passages being substantially parallel to one another
and smoothly merging with the middle passage, the middle passage
being located at an angle to said first and last parallel passages
whereby fluids flowing through said passages will not cavitate and
an accurate optical measurement may be taken.
9. A cuvette as in claim 8 wherein the merger of said first passage
with said middle passage provides a curved surface which is a
mirror image of the merger of said last passage with said middle
passage.
10. A cuvette as in claim 8 wherein the sides of said passages in
said transparent layer are equidistant from the centers
thereof.
11. A cuvette as in claim 8 wherein said body means comprises two
layers on opposite sides of said transparent layer.
12. A cuvette as in claim 8 wherein said middle passage is longer
than said first and last passages.
13. A cuvette as in claim 8 wherein said middle passage has a
central axis adapted to be horizontal when the cuvette is used,
said middle passage having a top and bottom side in said
transparent layer, the bottom side of said passage being parallel
to said axis and the top side being inclined relative thereto.
14. A cuvette as in claim 13 wherein said middle passage is longer
than said first and last passages.
15. An optical flow-through cuvette comprising a body consisting of
three planar layers, the outer layers being non-transparent, the
inner layer including a pair of identically configured transparent
members, said members being juxtapositioned to form said inner
layer and having three surfaces internal to said outer layers, said
members being spaced from one another to form three generally
linear passages in successive open communication with one another
and opposite edges of said cuvette, the first and last passages
being disposed at identical but opposite angles to the ends of said
middle passages, said middle passage being adapted to be horizontal
when a fluid is passed through said passages and an optical
measurement can be taken linearly of said middle passage.
16. The cuvette of claim 15 wherein said first and last passages
are disposed at right angles to said middle passages.
17. A cuvette as in claim 16 wherein said middle passage has a
larger cross-sectional area than said first and last passages.
18. A cuvette as in claim 15 wherein the merger of said first and
last passages with said middle passage having larger
cross-sectional areas than said middle passage.
19. A cuvette as in claim 15 wherein said middle passage has a
larger cross-sectional area at its intersection with said first
passage than it does at its intersection with said last
passage.
20. A cuvette as in claim 19 wherein said middle passage is adapted
to be horizontal and defines an upper wall and a bottom wall, said
bottom wall being parallel with the horizontal and said top wall
diverging away from the horizontal from the last passage to said
first passage.
Description
There are various types of optical cuvettes commonly used for
holding a liquid specimen or sample intended to undergo optical
measurement, for example by means of a spectrophotometer. To this
end, the known optical cuvettes generally consists of a transparent
body made for instance of glass or quartz and comprising a
cylindrical cavity for receiving the specimen. This cavity extends
inside the cuvette over a given distance constituting the "optical
path" travelled by the light beam passing through the sample during
the optical measuring operation. The two ends of the cavity are
delimited by transparent zones of the cuvette wall, which zones
constitute inlet and outlet windows for the said beam.
This cavity communicates with the outside of the cuvette via two
transverse channels which are respectively connected to the two
ends of the cavity and enable the sample to be inserted in the
cavity and to be removed therefrom after the measurement has been
effected. The cylindrical cavity thus forms a central elongated
limb of a doubly-bent continuous passage.
One type of commonly used optical cuvette consists of a quartz or
glass tube, which is bent at two places to from the said passage.
The central cavity of this passage is thus delimited at its ends by
curved portions of the wall of the twice-elbowed tube forming the
cuvette. Consequently, the said inlet and outlet windows for the
measuring beam are also curved, thus causing light deviation, and
hence a risk of notably affecting the accuracy of the optical
measurement. Further, this mode of production, which consists in
bending a tube, does not make it possible to determine in a very
accurate reproducible manner the length of the said optical path
for the beam of light passing through the liquid specimen. Now,
even a relatively small variation of this length, between different
cuvettes, is liable to cause notable measurement errors.
In a variant of the above-described known optical cuvette, the said
windows are flattened to obviate the cited drawbacks. To this end,
the twice-elbowed tube is softened by heating and two flat plates
are pressed against the curved windows to flatten them and to
adjust the distance between them. Such indirect deformation of the
internal surface of the windows, by acting on their outside faces,
does not however make it possible fully to obviate the
above-mentioned drawbacks of the type of cuvette under
consideration.
In a second variant of this type of known cuvette, the
twice-elbowed tube is cut out so as to remove the said curved
portions defining the two ends of the cavity and two flat
transparent plates are fixed in their stead so as to form flat
windows. This cutting operation obviously requires a very high
degree of accuracy so as to set in a precise manner the distance
between the said plates and hence the optical path of the beam. The
cuvette according to this second variant does nonetheless enable
the above-mentioned drawbacks to be obviated to a large extent,
provided this accuracy is ensured. However, it has another drawback
due to the fact that the said plates are disposed transversely to
the central cavity and thus form corners, approximately at right
angles, at the two ends of this cavity, such corners forming
stagnant zones in which a residue of the liquid tends to remain
after discharge of the sample. Such a residue from one sample to
the next can however notably affect the accuracy of the optical
measurement.
Besides the above-mentioned drawbacks, the production of this type
of known cuvette, as well as of the two described variants, gives
rise to problems which become more and more difficult to solve as
the size of the cuvette decreases. Thus, it has not been possible
so far to produce cuvettes as described having the very small
dimensions needed to perform optical measurements on liquid
micro-specimens.
Another known cuvette, which is intended for micro-samples,
comprises a block traversed by a capillary bore forming the central
measuring cavity and transparent plaquettes mounted at the ends of
this cavity to form the previously mentioned windows for the entry
and exit of the light beam serving to effect the optical
measurement. Two lateral bores are moreover provided in the block
so as to connect the two ends of said central cavity with the
exterior and to thus form a doubly-bent passage with the central
bore. This type of capillary cuvette allows the length of the
optical path of the light beam traversing the cuvette to be fixed
quite accurately. However, the doubly-bent passage, delimited by
the walls of said bores, likewise has right-angled corners and
sudden changes of direction at both ends of the bore forming the
central cavity. This results in the previously mentioned drawback
of stagnanant zones leading to sample residues which can render the
measurements inaccurate from one sample to the next.
A different type of known cuvette is the so-called "thin-layer
cuvette," wherein the liquid is admitted between two transparent
plates mounted at a slight distance from each other and forming the
said windows for entry and exit of the light beam. The use of this
type of cuvette is however limited to effecting measurements on
opaque liquids, such as non-diluted blood, due to the fact that the
optic path through the thin liquid layer is very short.
The object of the present invention is to produce an optical
cuvette of the throughflow type, which is relatively easy to
manufacture in a reproducible manner and which, in addition,
enables the above-mentioned drawbacks of the known cuvettes to be
obviated.
The invention provides an optical cuvette of the throughflow type
having therein at least one double-bent continuous passage composed
of a central elongated cavity for enclosing a liquid sample and of
two transverse branch-channels extending between the ends of the
cavity and the cuvette surface to allow admission and discharge of
said sample, the cuvette being at least partially transparent so as
to allow a light beam for effecting optical measurement to pass
through the cuvette and thereby to longitudinally traverse the
elongated cavity containing the sample.
The cuvette according to the invention comprises a stratified block
composed of at least three layers arranged in juxtaposition so as
to define together a space constituting the said passage, an
intermediate layer of said three layers being composed of a pair of
transparent plates lying in a common plane at a predetermined
distance from each other, each plate of said pair being provided
with an inner edge which is shaped in accordance with the
doubly-bent path of said passage and which has a gradual transition
between said cavity and said transverse channels whereby to allow
streamline flow along said passage, and two lateral layers being
formed by two corresponding plates whereof the inner surfaces
respectively define said passage on either side thereof, between
said shaped inner edges of said pair of plates of the intermediate
layer.
The invention also provides a method of manufacturing an optical
cuvette of the throughflow type having at least one doubly-bent
continuous passage composed of a central elongated cavity and of
transverse branch-channels respectively extending between the ends
of the cavity and the cuvette surface, the cuvette being at least
partially transparent so as to allow a light beam to pass through
the cuvette and thereby to longitudinally traverse the elongated
cavity, said method comprising:
shaping at least one transparent plate so as to obtain at least one
pair of edges corresponding to the desired double-bent path of said
passage and providing a gradual transition between said central
cavity and said transverse channels;
arranging said edges in spaced relationship facing each other to
form a first pair of wall portions partially defining said passage
so as to provide central cavity of predetermined length;
and sealingly mounting two lateral plates so as to close-off either
side of the space lying between said spaced edges, whereby to form
a complementary pair of wall portions defining said passage
together with said first pair of wall portions.
The accompanying drawings represent, schematically and by way of
example, various optical cuvettes embodying the features of the
invention and also illustrate a method of manufacturing an optical
cuvette in accordance with the invention, as well as a variant of
this method.
FIG. 1 shows in perspective, partly borken away, an optical cuvette
according to a first form of embodiment.
FIG. 2 is a front view of the cuvette according to FIG. 1, with an
outer plate removed.
FIGS. 3a to 3d show, in section, four variants of the cuvette
according to FIG. 1.
FIG. 4 respesents, in longitudinal section, a double cuvette
according to a second form of embodiment.
FIGS. 5a to 5b schematically illustrate two steps of the
manufacturing method.
FIGS. 6a and 6b schematically illustrate two steps of a variant of
the manufacturing method.
FIGS. 7 and 8 respectively show a longitudinal and a transverse
sectional view of a third form of embodiment.
The cuvette represented in FIGS. 1 and 2 consists of a stratified
block 1, made up of three layers. Two small rectangular plates 2a
and 2b form the outer layers of this block 1 and a pair of similar
plates 3a and 3b having the general form of the letter L are
arranged in spaced head to foot relationship in the plane so as
together to form its intermediate layer.
As will be seen in FIG. 1, an elongated cavity 4 extends inside the
block 1 along the mean longitudinal axis 0-0 representing the
optical path and the ends of this cavity respectively communicate
with two channels 5 and 6 which extend on opposite sides of this
axis 0-0 and at right angles to the latter, as far as the opposite
faces A and B of the block 1 (see FIG. 2). As may moreover be seen
in FIG. 1, this cavity 4 and these channels 5 and 6 thus constitute
a continuous doubly-bent passage which extends through the block 1,
in the intermediate layer of the latter.
This continuous passage 5 - 4 - 6 has a rectangular cross-section
with a first pair of opposite sides respectively defined by the
internal edges of the intermediate pair of plates 3a and 3b and a
second pair of opposite sides respectively defined by the outer
plates 2a and 2b. Thus, as will be observed from FIG. 1, the inner
edges of the plates 3a and 3b comprise three consecutive surfaces
7a, 8a, 9a and 7b, 8b, 9b, respectively, which form pairs of
opposite surfaces, i.e. 7a and 7b, 8a and 8b, 9a and 9b, which
pairs define two opposite sides of the channel 5, of the cavity 4
and of the channel 6, respectively.
These surfaces 7a, 8a, 9a and 7b, 8b, 9b are machined and polished,
before the plates 3a and 3b are mounted in the block 1, so as to
properly round the angles respectively formed between the
successive surfaces 7a and 8a, 8a and 9a, 7b and 8b, and 8b and 9b.
This rounding of the said angles enables any abrupt deviation along
the said doubly-bent passage 5 - 4 - 6 to be eliminated by
producing a gradual transition between the cavity 4, on the one
hand, and the channels 5 and 6, on the other hand, thus eliminating
any stagnant zone during the flow of liquid through this
double-bent passage.
It thus becomes possible completely to discharge from the described
cuvette each liquid sample that has served for the desired optical
measurement. This discharge can be done by inserting into the
cuvette another liquid thereby to force all of the liquid of said
sample out of the cavity 4, without leaving any residue thereof in
this cavity. In most cases, this other liquid may be the liquid
sample which is to be subjected to the next optical
measurement.
The structure of the described cuvette, in the form of a stratified
block made up of four plates 2a, 2b, 3a and 3b, thus enables the
cavity 4, as well as the channels 5 and 6, to be defined by the
surfaces 7a, 8a, 9a and 7b, 8b, 9b which are readily accessible and
which can thus be machined and polished without difficulty before
assembling the cuvette. This not only enables the said passage to
be given an outline which is favourable for complete discharge of
each sample, but also to delimit the cavity 4 at its ends by
windows having a flat polished surface and arranged at a precise
predetermined distance from each other.
The plates 3a and 3b forming the intermediate layer are made of a
transparent material, e.g. glass, quartz, or a plastics material
such as acrylic resin. This material is selected in dependence on
the wavelength of the light intended to perform the required
optical measurement, such that this material be transparent to the
light having this wavelength. The side plates 2a and 2b are made of
the same material as the intermediate plates 3a and 3b. Since the
side plates 2a and 2b are not intended to be passed through by the
light used to perform the optical measurement, in particular in a
spectrophotometer, these plates are preferably blackened to reduce
lateral light diffusion.
The assembly of the cuvette can be achieved in any suitable manner.
In this instance, the plates 3a and 3b may be assembled with the
side plates 2a and 2b by heat bonding causing localized fusion of
the adjacent surfaces of these plates.
The described cuvette is particularly suitable for optical
measurements in a spectrophotometer and the mean axis 0-0 will then
coincide with the optical axis of the spectrophotometer light
beam.
The described form of embodiment can obviously be modified in
various ways, with a view to adapting it better to the particular
use to which the cuvette is to be put in each case.
Thus, for example, the channels 5 and 6 may be ground conically,
after assembly of the described cuvette, to facilitate connection
of these channels to a feed tube and to a discharge tube for the
samples. This conical grinding, illustrated in dash-dotted lines in
FIG. 2, may form an angle of 5.degree. in relation to the
respective axes of the channels 5 and 6.
Further, it is not necessary for the stratified block constituting
the cuvette to be rectangular, as described. Thus, the side plates
2a, 2b and the intermediate plates 3a and 3b may have different
outlines like those shown by way of example in FIGS. 3a to 3d.
These latter figures illustrate moreover some variants for the said
double-bent passage consisting of the cavity 4 and of the channels
5 and 6.
Thus, for example, in the variants illustrated in FIGS. 3c and 3d,
the cavity 4 further comprises at least one zone, 10 and 11, 12
respectively, which is located at a greater distance from the mean
axis 0-0. Microbubbles of gas, which are often present in liquid
specimens, can thus rise in the cavity 4 and accumulate in such a
zone, which is located outside the axial measurement zone as such.
It thus become possible to obviate the errors due to the presence
of these microbubbles in the specimen during the optical measuring
operation.
FIG. 4 shows an optical cuvette of similar structure to that shown
in FIGS. 1 and 2. However, the laminar block 1 is here made up of
five layers and forms a double cuvette comprising two similar
cavities 4 and 4', with their associated channels 5, 6 and 5', 6'.
The block forming this double cuvette comprises plates 2a, 2b and
3a, 3b which define the cavity 4 and the channels 5 and 6, as
already described in relation to FIGS. 1 to 3. To form the second
cavity 4' and associated passages 5' and 6', this block moreover
comprises a further pair of intermediate plates 3a' and 3b',
similar to the plates 3a and 3b described above, as well as a
further side plate 2c similar to the plates 2a and 2b. The central
plate 2b thus serves to define at the same time a part of the
passage 5 - 4 - 6 and of the similar passage 5' - 4' - 6'.
The cavities 4 and 4' of the described double cuvette are thus
arranged in identical manner and can for example be used to
respectively receive a liquid specimen intended to be subjected to
an optical measurement and a standard specimen used for a
comparative measurement. The described double cuvette can thus be
used to advantage to carry out optical measurements in a
spectrophotometer of the well-known double beam type.
FIGS. 5a and 5b illustrate schematically two operations of a method
of manufacturing an optical cuvette such as the one in FIG. 1. As
is apparent from FIG. 5a, a glass or quartz plate 3 is first cut by
means of an ultrasonic cutting tool 13 which has an S-shaped
outline corresponding to that of the desired passage 5 - 4 - 6 so
as to obtain a pair of identically shaped half-plates each
comprising an edge formed by the three surfaces 7a, 8a, 9a and 7b,
8b, 9b, respectively. As will be observed from FIG. 5b, several of
these shaped plates are then placed side by side, and subjected to
a polishing operation by means of a polishing tool 14.
The inner surfaces of the said windows through which the light beam
is intended to pass are then rendered perfectly flat and smooth and
these surfaces may moreover be very accurately situated in all of
the plates thus shaped. dimensions
The cuvette is finally assembled as shown in FIG. 1 by juxtaposing
in spaced head to foot relationship in the same plane, a pair of
shaped and polished plates thus produced, e.g. in a jig having the
initial dimensions of the plate 3, by disposing on opposite sides
of this pair side plates 2a and 2b (see FIG. 1) and by finally heat
bonding the contacting surfaces between each of the plates 2a and
2b, on the one hand, and the plates 3a and 3b, on the other
hand.
FIGS. 6a and 6b illustrate a variant of the described method. As is
apparent from FIG. 6a, use is also made of an ultrasonic cutting
tool 17 having an outline in the form of an S corresponding to the
desired profile of the passage 5 - 4 - 6. However, in this
instance, the plate 3' is wider than the tool 17 so that this plate
3' remains in one piece after the cutting operation and comprises a
central zone cut in the form of an S. As shown in FIG. 6b, a
polishing tool 18 is then used to polish those parts of the
surfaces 7b and 9a, which define the ends of the cavity 4, where
the exit windows for entry and exit of the beam are to be
located.
The plate 3', thus shaped and polished, is then assembled by fusion
bonding, as already described, with two side plates of the same
size to form a stratified block which is wider than the final
cuvette-forming block. The longitudinal edges of the three plates
forming this block are then cut, as indicated by dash-dotted lines
in FIG. 6b, so as to clear the inlet and outlet openings of the
channels 5 and 6 and to give to the stratified block the desired
final dimensions of the cuvette. There is thus produced a cuvette
similar to that illustrated in FIG. 1, but having a cavity 4 with a
profile similar to that shown in FIG. 3c. This variant according to
FIGS. 6a and 6b facilitates the assembly of the stratified
cuvette-forming block by obviating the need for accurately spaced
juxtaposition in head to foot relationship of the plates 3a and 3b
forming the intermediate layer, so as to obtain the exact desired
length of the cavity 4.
It should be noted that the methods described above by way of
example lend themselves to the manufacture on a large scale of
cuvettes according to the various forms of embodiment of the
invention, whilst ensuring very high accuracy and obviating the
previously mentioned drawbacks of the known cuvettes. Indeed, these
method have enabled cuvettes according to FIG. 1 and to FIG. 4 to
be manufactured very accurately and with very small dimensions,
such as are needed to perform optical measurements on liquid
microspecimens, the overall dimensiosn of these cuvettes being at
most of the order of 1 to 2 cm.
The outline of the doubly-bent passage may obviously have various
forms other than those described and may be obtained by other means
than an ultrasonic cutting tool, as described above. This outline
may thus be obtained by any suitable machining means or by
moulding.
FIGS. 7 and 8 represent a further embodiment of a double cuvette
comprising two cavities 4 and 4' having a profile similar to that
of the variant according to FIG. 3c. This profile is defined by two
pairs of plates 3a, 3b and 3a', 3b', which are respectively mounted
between plates 2a, 2b and 2c (see FIG. 8).
However, as may be seen from FIGS. 7 and 8, the same pairs of
plates are turned around by 180.degree. with respect to each other,
around a vertical axis in the present case. An arrangement is thus
obtained, wherein the transverse channels 5 and 5', as well as 6
and 6', respectively extend to diagonally opposite locations on the
same sides of the cuvette. In view of the relatively small width of
the cuvette, this arrangement provides the advantage of
considerably increasing the spacing between the channels which open
on to the same face of the cuvette and of thus facilitating
connection of the channels 5, 5' and 6, 6' to outside conduits, as
described below.
In this embodiment, the cuvette is further provided with a pair of
connecting blocks 19a and 19b made of glass, of plastics material
or of metal, for example. These identical blocks are respectively
mounted on the opposite faces of the cuvette, on to which the
transverse channels 5, 5' and 6, 6' open, this assembly being
achieved by gluing, welding or mechanical fastening for
example.
Each of the blocks 19a and 19b comprises two connecting channels,
20, 20' and 21, 21', respectively, each aligned with one of the
transverse channels 5, 5' and 6, 6' and each having a cross-section
which varies progressively from a rectangular section,
corresponding to that of the opposite transverse channel, up to a
circular section communicating with a conical cavity 22, 22' and
23, 23', respectively, leading to the external surface of the
corresponding block 19a or 19b.
These blocks 19a and 19b serve for the connection of conduits 24,
24' and 25, 25', respectively, and allow admission and discharge of
the liquid samples which are to undergo optical measurement, in the
central cavities 4 and 4' of the cuvette.
In the present instance, each of the conduits 24, 24' and 25, 25'
has an enlarged conical end portion sealingly mounted in the
corresponding cavity 22, 22' and 23, 23', so that its internal
section is situated so as to form a prolongation of the
corresponding connection channel 20, 20' and 21, 21', respectively.
These conduits are moreover mounted by means of shaped clamping
plates 26a and 26b which are respectively fixed on to the opposite
external faces of the blocks 19a and 19b. As may be seen from FIGS.
7 and 8, tightening springs 27, 27' and 28, 28', which are
respectively mounted in recesses provided for this purpose in the
plates 26a and 26b, each press against the enlarged end of one of
the conduits 24, 24' and 25, 25', via a washer 29, 29' and 30, 30',
respectively. These four conduits are thus connected in a simple
manner to the descirbed double cuvette, via the connecting blocks
19a and 19b having the channels 20, 20' and 21, 21' which provide a
gradual transition of the flow cross-section at the outer end of
the transverse channels 5, 5' and 6, 6' respectively associated
with the central cavities 4, 4' of the passages of the double
cuvette.
The double cuvette described above and shown in FIGS. 7 and 8 is
further equipped with a heating device adapted to maintain the
cuvette, and hence the liquid contained therein, at a desired
temperature. This device comprises an electrical resistance 31
coiled around the cuvette, together with its connecting blocks 19a
and 19b, in a zone extending practically over the whole length of
the central cavities 4 and 4' the cuvette. This resistance is
supplied with current from an electrical source 32 (see FIG. 8)
which is controlled in a well known manner by means of a
thermostatic regulator (not shown) associated with a temperature
measuring member 33 mounted in the middle of the median plate 2b
situated between the two passages 5 - 4 - 6 and 5' - 4' - 6' of the
described double cuvette.
Maintenance of the temperature of the samples at a constant value,
by means of a heating device such as described above by way of
example, is advantageous for various optical measurements, such as
those intended for determining the activity of enzymes; in that
case, the temperature may be maintained at 37.degree. C for
example. Heating of the cuvette may moreover obviously be ensured
by any other conventional means, such as a thermostatically
controlled circuit of heating liquid, arranged in any suitable
manner allowing the samples contained in the cuvette to be
maintained at the desired temperature.
It is understood that all the other cuvettes which have been
described may likewise be equipped with heating means such as are
mentioned and are described above.
When the cuvette is not provided with heating means, it may
nevertheless be useful to equip it with means for measuring the
temperature of the samples in order to be able to take it into
account when effecting the optical measurements.
As appears from the described embodiments and variants, the optical
cuvette according to the invention is of the throughflow type
comprising a traversing passage having a central elongated cavity
through which a light beam is made to travel longitudinally for
effecting optical measurement. Thanks to the particular structure
of the cuvette in the form of a stratified block, it becomes
possible to round off the inlet and the outlet of the said central
cavity, at the places where the latter communicates with the
transverse channels leading to the exterior of the cuvette. As a
matter of fact, this rounding off may be readily carried out before
assembling the cuvette, i.e. before mounting the lateral plates so
as to complete the wall of the traversing passage on either side
thereof. Thanks to this rounding off, it thus become possible to
give the said passage a longitudinal profile which is such as to
ensure optimum liquid flow conditions from which any dead zone is
eliminated. One may thus ensure very effective sweeping of the
central cavity and hence eliminate therefrom any residue of each
specimen once it has undergone the optical measurement. This
important advantage is not only limited to measurements which are
carried out discontinuously on stationary samples, but also applies
to continuous measurements which are effected on liquid specimens
flowing continuously through the central cavity.
Besides the advantages mentioned above, it may be noted that the
cuvette according to the invention does not have the previously
mentioned limitations of conventional cuvettes of the same type. As
a matter of fact, it may be readily manufactured very accurately
and in large series, without its dimensions playing a critical
role; the manufacture of so-called "capillary" cuvettes in
accordance with the invention thus does not present any particular
problem. In addition, the cuvettes may be utilized for effecting
optical measurements on all sorts of liquid samples and, when the
liquids in question are too opaque, they may be readily diluted in
order to obtain more transparent specimens.
It is understood that the desired cuvettes may be used for all
sorts of optical measurements which may be based, for example, on
the absorption or the fluorescent properties of the specimens. In
the latter case, the lateral layers of the cuvette should likewise
be transparent, in order to allow measurement of the fluorescent
properties of the sample, perpendicularly to the axis of the
central cavity.
* * * * *