Note: Descriptions are shown in the official language in which they were submitted.
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ON-LINE SAMPLING DEVICE FOR IR MILK ANALYSIS
Background of the invention
Field of invention
This invention is generally concerned with liquid analysis and in particular
with
a sampling device for spectrometric analysis of emulsions and suspensions.
Related art
Spectrophotometry is largely used for electro-optical analysis of emulsions
and suspensions as it is economical in manufacture and accurate in results.
Spectrophotometric analysis is generally used for measurement of fat, protein,
lactose, or solids present in milk, as well as bacteria (e.g. e-coli) or
somatic cells.
Typically, a representative analysis sample, which normally should not
comprise
more than 50 ml of milk, is flown into an optical measurement cell and
irradiated with
a reference beam and a measurement beam at differing wavelengths. The received
signals are indicative of uncorrected concentrations. Sampling results are
compared
with stored data taken through calibration runs under similar conditions.
Scaling and
correction circuits are then used for compensating the effects on each reading
caused by other constituents. The corrected signals are finally provided in
percentage by weight, or weight over volume.
Miik analysis can be carried out by infrared (IR) spectroscopy using for
example a through-flow type detector connected to a IR spectrometer analyzer.
Light emitted by the IR radiation unit goes to a representative analysis
sample, or
probe and comes back from the probe. The reflected beam is analyzed and
converted in numeric data. IR spectroscopy can gather data on a continuous
basis
and can perform a complete multi component analysis in a matter of seconds.
The quality of milk is dictated by its constituents, in particular the fat
content.
Obtaining a representative analysis sample and determining the fat content
require
long and exact procedures, especially when the milk has been standing for a
period
of time, since a large portion of fat separates and deposits on the upper
surface of
the milk.
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It is to be noted that, performing the IR analysis in the main flow using an
on-
line sampling device, may provide inaccurate results and adverse effects. For
example, expected values for total production of a cow differ between around
5kg
and 30 kg. During milking, the flow can fluctuate between around 0.1 and 1.2
kg/minute, and this adds to the difficulty of extracting a proportion sample
for volume
calculations. Similarly, the fat content in milk increases towards the end of
milking,
and obtaining a representative analysis sample becomes problematic. An adverse
effect of using measurements in the main flow (during milking), is due to the
under
pressure prevailing at the milking unit placed on the udder which is
influenced by the
measuring apparatus creating a vacuum drop. This results in an incomplete milk
extraction causing udder irritation and/or inflamation.
On the other hand, the information contained in a representative analysis
sample may lead to inaccurate readings if the sample is not homogenous, or
"flowing". Air pockets, concentration gradients, or turbulence have a direct
impact
on readings. Such gas inclusion may be due to turbulence when air is mixed
with
liquid, or to small drop in pressure when some liquid sample is vaporized to
create
bubbles. The changes in milk concentration and the presence of bubbles in milk
is
one of the problems associated with liquid chromatography, as the injection of
a
probe containing bubbles or gas into the chromatographic column is conducive
to
erroneous results, as it provides for inaccurate flow measurement and/or noise
generation in the IR measuring unit.
Freshly milked milk is a foaming liquid which does not have a clearly defined
surface. Particularly during milking, the air content of the fresh milk
produces a
significant foam volume and thus, variations in flow density.
Circulation systems such as agitators, have to be provided to increase the
quality and the accuracy of the on-line sampling devices.
To determine the correction factors, the content of the entrained air has to
be
constantly measured, e.g. using gas chromatography, for subsequently weighing
the
samples according to a predetermined formula. This is a time consuming method
and also generally inaccurate due to fluctuations in the air bubble content
during
milking.
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The quality of milk is constantly monitored by state agencies. Diary control
agents request samples from farmers tanks which are labeled and sent to a
district
laboratory. Typically, the results are returned from the laboratory about one
week
after the analysis and evaluated by the diary control agent about two weeks
following sample collection at the farm. The above procedure provides for
undesirable delays as the dairymen need at the cowsite results for efficient
herd
management.
It is a need for a sampling device which is easy to manufacture and operate,
and provides suitable sampling for a spectroscopic measuring unit performing
in-flow
testing of emulsions and suspensions.
Summary of the Invention
It is an object of the present invention to overcome the disadvantages of the
prior art associated with spectrometric analysis of emulsions and suspensions.
The invention provides an on-line sampling device capable of extracting a
proportion sample of substantially bubble-free liquid suitable for IR
spectrometry
analysis.
According to one aspect of the invention, a proportion sampling device is
provided. The sampling device comprises a sampling chamber with a vertical
axis
including a dome-shaped upper section with an intake conduit arranged along
the
vertical axis for receiving a main flow of liquid, a funnel-shaped lower
section for
discharging by gravity liquid from the sampling chamber, and connecting means
for
joining the upper section and the lower section together and forming the
sampling
chamber. A frustroconical deflector is attached to the upper section and has a
?5 bottom wall defined in a horizontal plane and an inclined wall connecting
the bottom
wall with a rim, such that the main flow is first reversed about 180°
when contacting
the bottom wall and uniformly redirected upwards along the inclined wall.
Further
on, the main flow is again reversed about 180° after leaving the rim
due to gravity.
Collecting means are formed on the inside wall of the lower section including
a
sampling conduit with one exterior end extending downwardly outside the lower
section and having a collecting spout at the opposite end protruding upwardly
inside
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the upper section. The spout has a slot defined in a plane located under the
plane
of the rim and radially extending towards the inside wall of the upper section
for'
diverting a proportion flow from the main flow of liquid.
The main flow of liquid exiting the rim is a flowing liquid film of constant
thickness and substantially bubble-free. A measurement attachment may be
connected to the sampling conduit for receiving the proportion flow. The
attachment
has an indentation for compacting the proportion flow into a slab of liquid
with no
entrained air and suitable for accurate spectrometric measurements.
The sampling device of the invention is an inexpensive tester, easy to
position and use in any parlor and with any farm milking machine. It provides
at the
cowsite complete milk information extremely valuable for herd management.
Advantageously, the slabs of liquid flown through the indentation of the
measurement attachment, are similar to a microscope slide and provide for an
optimal IR sensing. A representative analysis sample containing homogenous
liquid
may be extracted as well.
The sampling device is described more particularly in its application to fresh
milk, but it can be used with any other foaming liquids (beer, petroleum,
etc.), non-
foaming liquids, emulsions, or suspensions. As well, any light source may be
used
for spectrometric analysis.
The "Summary of the Invention" does not necessarily disclose all the features
essential for defining the invention. The invention may reside in a sub-
combination
of the disclosed features.
Brief Description of the Drawings
The invention will be now explained by way of example only and with
reference to the following drawings.
Figure 1 is a perspective view of the sampling device of the invention;
Figure 2 is an illustration of the upper section of the sampling device of
Figure
0 1 as viewed from the inside;
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Figure 3 is an illustration of the deflector as viewed from the direction of
the
flow;
Figure 4 is a top perspective view of the lower section of the sampling device
of Figure 1 with the deflector illustrated in a working position:
Figure 5 is a top view of the lower section of the sampling device of Figure
1;
Figure 6 is a longitudinal cross section along line 6-6' of Figure 4;
Figure 7 is a perspective view of the IR measurement attachment;
Figure 8 is a longitudinal cross section of the sampling device of Figure 1
connected to a sample flask meter; and
Figure 9 is a longitudinal cross section of the sampling device of Figure 1
connected to a somatic cell count (SCC) flowcell and to an IR sensing unit for
performing on-line multi-component milk analysis.
Similar references are used in different figures to denote similar components.
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Detailed Description of the Preferred Embodiment
The following description is of a preferred embodiment by way of example
only and without limitation to combination of features necessary for carrying
the
invention into effect.
The invention will be now described with reference to Figures 1 to 6. Figure 1
is a perspective view of an on-line sampling device 10 according to the
invention.
Sampling device 10 comprises a dome-shaped upper section 15, also illustrated
in
Figure 2, for receiving liquid (arrow A) through conduit 14 and input port 12,
and a
funnel-shaped lower section 17, also illustrated in Figures 4 to 6, for
collecting the
liquid and discharging same through conduit 14' having an output port 18
(arrow B).
The upper section 15 is joined to the lower section 17 along a mating plane
substantially perpendicular to the AB direction of flow. An upper ring 25 is
formed in
section 15 in a plane perpendicular to the direction of flow. Similarly,
funnel 17 has
a lower ring, shown at 35 in Figure 5, which is formed in a plane
perpendicular to the
direction of flow. Both upper and lower rings 25, 35, have an annular form and
are
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of the same size which is substantially the thickness of the material used to
manufacture the sampling device 10.
Two identical reinforcing collars, 26, 36, are provided around both the upper
and the lower rings 25, 35. Three screws and corresponding paired ears 13,
13',
defined at 120° around the circumference of the upper and the lower
reinforcing
collars 26, 36, are used for connecting the upper section 15 with the lower
section
17.
Paired ears 13, 13', may be larger than the thickness of the reinforcing rings
26, 36, in order to increase their mechanical resistance. In such a case, a
plurality
of indentations 29 will be provided on the perimeter of the upper collar 26 to
match
with the lower collar 36. Indentations 29 and corresponding grooves co-operate
for
allowing upper ring 25 to be in contact and flush with lower ring 35. One or
two
indentations 29 may be of a larger size and when matched with corresponding
notches (not shown) defined on the perimeter of the opposite ring provides for
easy
assembling. An O-ring (not shown) may be provided along the mating plane in-
between sections 15 and 17 for sealing the sampling device 10. When connected,
the upper section 15 and the lower section 17 define a sampling chamber 30.
Sampling chamber 30 is surrounded by a substantially continuous inside wall
including the inside wall 37 of the upper section 15, and the inside wall 37'
of the
lower section 17.
A cylinder, or proportion collector 16 is formed in sampling chamber 30.
Proportion collector 16 is attached tangent to the inside wall 37' of funnel
17 for
diverting a secondary flow of a known proportion from the main flow, as it
will be
explained later.
?5 Figure 2 is an illustration of the upper section 15 of the sampling device
of
Figure 1 as viewed from the sampling chamber 30. A deflector 20 is centered
inside
the upper section 15 and attached to the upper section 15 by screws 11
threaded in
ears 24. Preferably, ears 24 are of the same length "L".
In operation, the sampling device 10 is vertically connected to the milking
pipes 50 (see Figure 7), and the liquid flows from the input port 12 to the
output port
18 by gravity, as shown by arrows A and B. The secondary flow diverted by
cylinder
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16 inside the sampling chamber 30 is discharged through an output sample port
19
(arrow C).
Throughout the description the words "upper" and "lower" are used with
respect to the vertical position of the sampling device 10, when in operation.
All parts forming the sampling device 10, may be manufactured by injection
molding from polysulphone plastic made by Amoco Corp. No silicone based mold
release shall be used. The parts shall be free of flash, grease, and other
contaminants. It is also understood, all conduits are slightly conical for
easy
coupling.
Figure 3 is an illustration of the deflector 20 as viewed from the direction
of
the flow, or the upper side. Figure 6 includes a longitudinal cross section of
the
deflector 20 and of the lower section 17 of Figure 4 along line 6-6'.
Deflector 20 has a frustroconical shape with a circular bottom wall 23 for
receiving the main stream of milk along direction "A", an inclined wall 22,
and a rim
21. The bottom wall 23 is defined in a horizontal plane which is parallel to
the plane
of rim 21. Bottom wall 23 is positioned substantially perpendicular to the
direction of
the incoming main flow and has a diameter substantially equal to the interior
diameter of conduit 14. Inclined wall 22 has a predetermined inclination
(~i°) for
placing rim 21 in a plane positioned above the proportion collector 16 inside
the
sampling chamber 30.
Deflector 20 is used for re-directing a portion of the main flow (the
secondary
flow) into the proportion collecting elements 16, 28. The main flow arriving
in the
sampling chamber 30 through input port 12, hits first the bottom wall 23 where
the
flow is reversed about 180°, then flows upwardly along the inclined
wall 22, and is
?5 reversed about 180° for a second time due to gravity, when leaving
the rim 21.
It is known that the main flow contains air pockets and turbulence areas. It
has been discovered that by twice-reversing (Z x 180°) the main flow, a
radially
flowing milk film of constant thickness and substantially bubble-free is
generated.
Accordingly, the proportion collecting elements 16, 28, can divert a probe
containing
0 homogenous liquid.
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As illustrated in Figures 5 and 6, proportion collecting elements include
proportion collector 16 and a collecting spout 28. Collecting spout 28
includes in the
example of Fig. 5 a rectangular crater 38 with a rectangular slot 39. In this
example,
slot 39 is rectangular but any shape like circular, oval, square, rhomboidal,
trapezoidal, may be considered. Crater 38 is carved at the upper end of spout
28
along a radial direction and extending above the mating plane inside upper
section
15. Collecting spout 28 projects above the mating plane with a protrusion
length "h".
In the example of Figures 5 and 6, slot 39 is positioned in a plane
substantially parallel to and slightly under the plane of rim 21, radially
extending
between rim 21 and inside wall 37. Rim 21 is closely spaced and above slot 39
allowing a secondary flow representing a known portion of the twice-reversed
main
flow, to be diverted. The liquid by-passed by proportion collecting elements
16, 28,
(the secondary flow) is discharged through output sample port 19 and may be
later
returned to the main flow.
The inclination (~3°) of the inclined wall 22, the length "L" of ears
24, and the
protrusion length "h", are so chosen so as to provide a known proportion
secondary
flow since it is extracted from a radially flowing liquid film of constant
thickness and
substantially bubble-free. The dimensions of the slot 39 are selected so as to
divert
always a given amount of liquid, e.g. 1.5% of the main flow, irrespective of
the main
flow velocity or accelerations.
Figure 7 is a perspective view of a measurement attachment 45 according to
the invention. Attachment 45 is a cylinder having an inlet 46 which fits into
the
output sample port 19 of the proportion collector 16, and an outlet 48 coupled
to the
main pipe 50 to redirect the secondary flow into the main flow. As mentioned
before, the homogenous and substantially bubble-free secondary flow entering
attachment 45, is forced through indentation 47, 47', formed in a middle
region of
the measurement attachment 45. Indentations 47, 47', are formed on
diametrically
opposite sides of attachment 45. Indentation 47, 47', provides throughout its
passage of length "d", a constant and uniform flow of homogenous liquid
suitable for
IR analysis.
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Indentation 47, 47', may be so formed so as to define a bore-like passage.
Preferably, indentation 47, 47', defines a passage having parallel walls for
outputting
slabs of liquid.
As milking an intermittent process, segments, or slabs of liquid similar to a
microscope slide are irregularly flown through attachment 45. The slabs allow
for
optimal optical analysis since they have well defined dimensions, uniform
flowing
velocity, and thickness. In this way, the liquid is analyzed in a standardized
fashion.
Indentation 47, 47', may include connectors for attaching a pair of emitter-
detector and fiber optic cables for exposing the slab of liquid to light of a
specific
wavelength, and to provide the modulated light signal to electronics for
interpretation, as it is known in the art. A continuous beam of light can
detect time of
flowing and the interruptions due to slabs of liquid irregularly flown through
attachment 45, the analyzed data (volume, milk components) may be recorded
such
that the contribution each slab may be accounted for. At the end of the
milking
process, a composite value for each analyzed component contained in the liquid
may be generated. Real time values for these components may be also supplied
during milking as interval, readings.
One or more attachments 45 having one or more pairs of emitters-detectors
may be also used if necessary. As mentioned before, conduits 14, 14', 16, as
well
as inlet 46 and outlet 48 are slightly conical for easy coupling, as known in
the art.
Figure 8 is a longitudinal cross section of the on-line sampling device 10 of
Figure 1 used as a flask type meter 51. A flask 55 is coupled to the output
sample
port 19. "Flask type" means that the measure of the total flow of liquid can
be
determined on-line by capturing a known portion of the main stream in the
calibrated
flask 55. This sample collection technique may provide for a quick in-line
measurement of the main flow volume, mass velocity, and accelerations. A valve
56
may be provided in proportion collector 16 for controlling the collection
time.
Alternatively, the flask may be used to provide a representative sample of
homogenized liquid as required by the DHI (dairy herd improvement) standards.
>0 The total volume of the liquid examined, the mass velocity and flow
accelerations
during milking may be calculated as well,
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Figure 9 is a longitudinal cross section of the on-line sampling device 10 of
Figure 1 connected to a somatic cell count (SCC) flowcell 60, and to the IR
measurement unit 10 for multi-component milk analysis. Multi-component testing
device 52 includes IR port 57, positioned along the length "d" of indentation
47, 47',
of the measurement attachment 45. An IR source (62) and an IR receiver (64)
are
connected to IR port (57). A central processing unit (65) with interface (IF)
68,
receive IR modulated signal from IR receiver (64) and the output of a
spectrometer
(65) for processing and outputting results of display (70). In this way, in-
flow,
continuous IR monitoring is provided and real time data are obtained from a
homogeneous, substantially bubble-free proportion flow. By incorporating the
spectrometer 65, milk components and flow rates may be measured as well.
In the example of Figure 9, the milk is flown through SCC flowcell 60 for
counting the somatic cell and to generate a complete milk analysis. SCC
flowcell 60
is disclosed in US Patent No. 6,031,367 issued on February 29, 2,000 to the
same
applicant and incorporated herein by reference. Flowcell 60 may be used
upstream
or downstream sampling device 10.
The sampling device 10 may be used on-line, during milking and can fit any
farm milking machine. As mentioned before, optimal IR sensing can not be
achieved by performing the analysis in the main stream due to the entrained
air
bubble content . The sampling device according to the invention, uses a
deflector
positioned in such way so as reverse twice the main flow incidence by
180° and to
generate a film of flowing liquid substantially bubble-free. A secondary flow
having a
predetermined quantity of liquid is diverted from the main flow and compacted
in a
measurement device to create slabs of liquid with no entrained air.
Advantageously, these slabs of liquid are similar to a microscope slide and
provide for an optimal iR sensing. Accurate and complete information is
provided by
the in-flow testing device 10 at a reduced time and an affordable price. In
addition,
testing device 52 can provide end of milking information and precise milk
temperature values.
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The complete milk information provided at the cowsite is extremely valuable
for herd management purposes. Representative analysis samples containing
homogenous liquid according to laboratory standards may be easily obtained.
No adverse effects like rancid milk are caused by mechanically forcing the
milk in conduits, nor the milk chemistry is modified as the device prevents
the air to
mix with milk, nor vacuum drops are generated as the device uses gravity for
diverting the proportion flow of liquid.
Numerous modifications, variations, and adaptations may be made to the
particular embodiments of the invention without departing from the scope of
the
invention which is defined in the claims.
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