U.S. patent number 3,688,191 [Application Number 05/071,160] was granted by the patent office on 1972-08-29 for electronic particle study apparatus with fluid circulating system.
This patent grant is currently assigned to Coulter Electronics, Inc.. Invention is credited to William A. Claps.
United States Patent |
3,688,191 |
Claps |
August 29, 1972 |
ELECTRONIC PARTICLE STUDY APPARATUS WITH FLUID CIRCULATING
SYSTEM
Abstract
Electronic particle study apparatus for studying particles,
particularly those whose density and size make difficult
maintenance of a dispersion in a fluid medium and which permits
total sample recovery. A pair of chambers is provided through which
a continuously filtered electrolyte flows. The chambers are
separated by a Coulter type scanning aperture means and drip
chamber means is provided for electrically isolating one of said
chambers. A recirculating system for supplying filtered electrolyte
to the chambers including storage means, recirculating means, pump
means and filter means, for moving of the electrolyte into and out
of the chambers and for collecting the particulate sample.
Inventors: |
Claps; William A. (Hialeah,
FL) |
Assignee: |
Coulter Electronics, Inc.
(Hialeah, FL)
|
Family
ID: |
22099647 |
Appl.
No.: |
05/071,160 |
Filed: |
September 10, 1970 |
Current U.S.
Class: |
324/71.1 |
Current CPC
Class: |
G01N
15/12 (20130101) |
Current International
Class: |
G01N
15/10 (20060101); G01N 15/12 (20060101); G01a
027/08 () |
Field of
Search: |
;324/71,71CP
;204/195 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rolinec; Rudolph V.
Assistant Examiner: Carter; David M.
Claims
1. A system for the study of physical characteristics of particles
not capable of retention in a fluid suspension comprising:
an electronic particle study apparatus including first and second
vessels, scanning aperture means between said vessels to establish
the sole communication path therebetween, each vessel having a
fluid body electrically insulated one from the other except through
the scanning aperture means, means establishing an electric current
through the scanning aperture means and detecting means for
detecting signals generated by the passage of particles through the
scanning aperture means from one vessel to the other;
a fluid electrolyte supply system including a source of fluid
electrolyte, for continuously supplying fluid electrolyte from the
source of fluid electrolyte to one of the vessels,
a fluid recirculating system for conducting fluid electrolyte from
the other of the vessels to the source of fluid electrolyte,
drip chamber means interposed between said other of the vessels and
said fluid recirculating system electrically to isolate the vessels
from said fluid supply and recirculating systems;
pump means for moving fluid electrolyte through said fluid supply
and recirculating systems, and
collector means interposed within one of said fluid supply and
recirculating systems for complete recovery of the total
particles
2. The system as claimed in claim 1 in which the first and second
vessels comprise a pair of open-ended, superposed tubular members
of insulating material and holder means interposed sealably between
the tubular members, and said holder means including, a conical
central portion having an opening in the center thereof and
aperture carrying means sealingly engaged to said central portion
within said opening and sealing means establishing a sealed
juncture between both said vessels and said holder
3. The system as claimed in claim 1 in which the collector means
comprises
4. The system as claimed in claim 1 and agitator means in said
first vessel
5. The system as claimed in claim 2 in which there is a third
vessel of tubular configuration, block means for supporting said
third vessel concentrically arranged relative to the second vessel,
means establishing a sealed engagement of said block means with the
second and third vessels, said block means having at least a pair
of axial passages therethrough communicating between said second
and third vessels, said block means having a recess formed therein
and opening to said third vessel and conical abutment means formed
within said recess, the apex of said abutment means arranged
coaxial with said third vessel and with the passageways opening at
the base thereof whereby fluid passing through said passageways
travels along the abutment to the apex so that said drip chamber is
defined by said block means and the interior of said third vessel,
conduit means leading from said drip chamber to said fluid
electrolyte recirculating system, and valve means interposed in
said last
6. The system as claimed in claim 2 in which there is a third
vessel of tubular configuration, means for supporting said third
vessel concentrically arranged relative to the second vessel and
sealing means for establishing a sealed engagement between said
first and second vessels and said holder means and valve means
between said fluid supply and fluid
7. The system as claimed in claim 2 in which there is a third
vessel, means for sealably supporting said second and third vessels
coaxially superposed one relative to the other and a separator
sealably disposed between the second and third vessels, at least a
pair of axial passageways formed in said separator to establish the
only path for communication between the second and third vessels,
said separator having a conical formation arranged concentric with
said third vessel and said passageways opening to the base of said
formation, the apex of said formation disposed within said third
vessel coaxial therewith and conduit means at the base of said
third vessel leading from the interior thereof to said fluid
recirculating system, and valve means interposed within said last
mentioned conduit
8. The system as claimed in claim 5 in which there is a vacuum trap
interposed between said drip chamber and said fluid recirculating
system
9. The system as claimed in claim 5 in which there is a cleaning
probe means coupled between said third vessel and a movable member
capable of being placed in communication with the interior of the
first vessel and valve means disposed between said third vessel and
said movable member.
10. The system as claimed in claim 8 and means sealably but
releasably
11. The system as claimed in claim 10 wherein said last mentioned
means
12. The system as claimed in claim 10 wherein said first vessel is
covered and a positive displacement pump is disposed between the
vessel and said
13. The system as claimed in claim 10 wherein the first vessel is
covered and a positive displacement pump is interposed between the
first vessel and said fluid supply system and a sample aspirator is
interposed between
14. The system as claimed in claim 13 in which said cover of the
first vessel comprises a tap from an exterior source of particles
and only a
15. The system as claimed in claim 14 wherein said tap has a
chamber communicating to said source by way of a pipe having inlet
and outlet ports and a delivery port therebetween communicating to
said chamber, and aperture means interposed between said chamber
and the interior of the
16. The system as claimed in claim 10 where the fluid supply system
includes a source of filtered air under pressure and first and
second conduit means arranged respectively between said source of
filtered air and the second vessel, and said source of filtered air
and said fluid
17. The system as claimed in claim 16 in which said fluid supply
system includes ported storage means for storing fluid electrolyte,
fluid inlet means leading from the second vessel to said storage
means, air inlet means leading from said source of filtered air to
said storage means and fluid outlet means leading from said storage
means to said pump means and a fluid reservoir interposed between
said pump means and the first vessel, and said collector means
comprises a filter interposed between said first vessel and said
fluid reservoir, the relative levels within said fluid
18. An electronic particle study apparatus for use in monitoring
particles of nature incapable of being retained in fluid suspension
and recovery of the said particles comprising;
means defining first and second chambers having first and second
fluid bodies respectively therein,
scanning aperture means disposed between said first and second
chambers defining the only path of communication between said fluid
bodies,
electrical circuit means for establishing an electrical path
through said aperture means whereby signals are generated by the
passage of particles through said aperture means,
signal monitoring means capable of receiving said signals,
fresh fluid circulation means for introducing fresh filtered fluid
to one of said chambers and including, a source of fresh fluid,
first conduit means leading from said source to said one chamber,
pump means interposed in said first conduit means between said
source and said one chamber, filter means interposed in said first
conduit means between said pump means and said one chamber and
fluid flow control valve means in said conduit means,
fluid return means for returning fluid from said other chamber to
said source and including second conduit means leading from said
other chamber to said source, trap means interposed in said second
conduit means and a regulated vacuum supply coupled to said trap
means, and second fluid flow control valve means fluid flow in said
second conduit means, and
a drip chamber interposed between the other of the chambers and the
fluid return means electrically isolating said other chamber from
said fluid
19. The apparatus as claimed in claim 18 in which said drip chamber
comprises an open top vessel sealably engaged with said second
chamber and having a drain at the lower portion thereof, cover
means disposed between the open top and the second chamber, said
cover means including at least one axial passageway formed
therethrough, a tapered formation extending into said vessel, the
apex thereof being coaxial with said vessel and the passageway
opening to the base of said formation whereby fluid leaving the
second vessel by way of said passageway travels along said tapered
formation to the apex for release into said vessel in the form of
discrete
20. The apparatus as claimed in claim 19 in which said drip chamber
is placed between said second chamber and said trip means and third
fluid
21. The apparatus as claimed in claim 18 and a source of filtered
air, fourth conduit means between said source of filtered air and
said drip chamber and fourth fluid flow control valve means
associated with said
22. The apparatus as claimed in claim 18 and a fluid transfer
system coupled between said drip chamber and cleaning probe means
selectively introduced and withdrawn from said first chamber
establishing flow
23. The apparatus as claimed in claim 18 and secondary fluid
conduit means leading between the source of fresh fluid and said
trap means and a positive displacement pump disposed in said
secondary fluid conduit means for leading fluid from the trap means
to said fresh fluid source for
24. In an electronic particle study apparatus of the type including
first and second vessels, a scanning aperture means between said
vessels to establish the sole communication path therebetween, each
vessel having a fluid body electrically insulated one from the
other except through the aperture means, means establishing an
electric current through the aperture, means for detecting signals
generated by passage of particles through the aperture from one
vessel to the other, a suspension of particles in a fluid
electrolyte medium being passed from a source of said suspension
through said aperture means from the first vessel to the second
vessel; the improvement comprising:
a fluid electrolyte supply system including a source of fluid
electrolyte, for continuously supplying fluid electrolyte from the
source thereof to one of the vessels,
a fluid electrolyte recirculating system for recirculating fluid
electrolyte from the other of the vessels to the source of fluid
electrolyte, a drip chamber interposed between said other of the
vessels and said fluid recirculating system isolating the vessels
electrically from said fluid supply and recirculating systems;
pump means operable to move fluid electrolyte through said fluid
supply and recirculating systems, and
means interposed within one of said fluid supply and recirculating
systems for complete recovery of the total particles examined.
Description
FIELD OF THE INVENTION
This invention relates generally to electronic particle study
apparatus and more particularly provides means whereby particulate
samples of size and density incapable of being retained in
suspension may be studied utilizing the Coulter principle yet with
substantially total sample recovery.
RELATION TO EARLIER PATENTS
This invention is an improvement on the electronic particle study
apparatus described in U.S. Pat. No. 3,395,343 granted to Morgan et
al. and assigned to Coulter Electronics Inc., the assignee of the
instant application.
BACKGROUND OF THE INVENTION
The Coulter principle of particle study asserts that a particle,
suspended in a fluid medium, passing through a microscopic aperture
changes an electrical characteristic of the fluid within the
aperture by an amount functionally related to the size of the
particle. Accordingly, a suspension of particles to be studied is
prepared and placed in a first vessel and second vessel having a
small aperture in the side wall thereof is immersed into the first
vessel to place the aperture within the suspension. Fluid is
withdrawn from the second vessel, drawing the suspension from the
first vessel through the aperture. Electrodes of non-corrosive
metal are suspended in the fluid of both vessels and external leads
pass from these respective electrodes to a detecting device, such
as the input of a counting means. An electric current is caused to
flow between the electrodes through the respective bodies of fluid
and through the aperture. Each time the particle is drawn through
the aperture there will be detectable change in a measured
electrical characteristic of the aperture which will produce an
electrical signal transmitted through the detector and amplified so
that it can be measured and counted.
The second vessel referred to above has come to be known generally
as the Coulter aperture tube and carries the aperture. The typical
aperture tube is constructed generally as shown in Coulter et al.
U.S. Pat. No. 2,985,839, wherein the Coulter aperture is formed by
drilling a minute hole in a thin wafer of vitreous material such as
sapphire and cementing or fusing the wafer to a side wall of a tube
over a relatively large orifice previously formed in a tube. The
aperture is positioned to facilitate flow of this suspension from
one vessel to the other through the aperture without adverse
statistical effects caused by drawing from a settled portion of the
first vessel.
For the purposes of this description reference hereinafter shall be
made to a structure termed a "Coulter scanning aperture means." In
Coulter U.S. Pat. No. 2,656,508, the said "scanning aperture"
comprises an opening of microscopic proportion formed in a wall of
a fluid holding vessel through which aperture particles are passed.
The aperture may also be provided as in Coulter et al. U.S. Pat.
No. 2,98,830, wherein the microscopic dimension aperture is
provided in a wafer of generally heat resistant vitreous material
and a larger orifice is formed in the wall of the vessel, the
orifice being of predetermined contour, and the wafer carrying the
microscopic dimension aperture is secured to the vessel wall with
the orifice and aperture aligned. This structure shall be
hereinafter referred to in this application as "Coulter scanning
aperture means," which term is used to describe that portion of a
wall which carries the aperture, as well as the aperture itself
whereat the effects measured actually occur.
In the earlier U.S. Pat. Nos. 2,656,508 and 2,985,830 which
describe embodiments presently commercially available under the
registered trademark "Coulter Counter," manufactured by Coulter
Electronics Inc. of Hialeah, Fla., particles capable of being
studied are many and varied but all share a common characteristic
and that is, all are capable of being suspended in a fluid medium
of conductivity different from that of the particles to be
measured.
Since the particles in sample suspension are carried through the
aperture into the relatively small volume aperture tube of the
Coulter apparatus and into the fluid system, the particles counted
inside normally are lost and never recovered, being removed from
time to time with continued removal of the fluid from the interior
of the Coulter aperture tube by, for example, a vacuum source. Many
of the particles to be studied re valuable and must be recovered.
These include extremely pure metals, gold, radioactive materials
such as uranium isotopes, and the like. Many particles are products
in a continuing research program and also require recovery for
further processing, testing and studying. Thus means for obtaining
total recovery of the sample are desirable. Another problem
involved, particularly with the use of relatively heavy particles
which soon settle out of any suspension, is that the previously
available Coulter aperture tubes are immersed in the sample
containing vessel with the aperture spaced from the bottom of the
sample containing vessel. Thus it was not possible to complete the
sizing and counting of all the particles in this sample.
Statistical sampling was difficult particularly where heavier
particles are concerned since these particles tend to separate from
the suspension and, due to gravational forces, collect near the
bottom of the sample holding vessel spaced from the vicinity of the
aperture. Difficulty occurred in maintaining agitation since the
level in the vessel concerned would decrease.
In U.S. Pat. No. 3,395,343, a vessel construction for use with an
electronic particle study apparatus of the Coulter type was
provided wherein the vessel comprised a pair of beaker like vessels
of insulating material arranged nested one within the other and
having the rims thereof in sealed relationship to define an
enclosed chamber. The inner one of the vessels function as a sample
chamber and carried a precise microscopic dimension aperture in the
bottom wall thereof. The enclosed vessel functioned as the second
vessel of the Coulter apparatus so that the sample was introduced
into the inner vessel and drawn through the aperture, into the
enclosed second vessel. Means leading to a vacuum source for
drawing the sample suspension from the inner vessel to the enclosed
chamber were so arranged relative to the aperture means that the
heavy particles would be retained within the enclosed chamber to be
later recovered as a residium subsequent to such
determinations.
One of the problems involved in utilization of the previous vessel
construction was that with a decreasing level in the inner vessel,
portions of the sample did not pass through the aperture. Necessary
agitation scattered many particles about the vessel, as well. Hence
counting and study in its entirety of a particulate sample not
capable of being retained in a suspension was not possible.
Further, it is still possible for some of the sample to be lost
with the heavier portions being retained.
Accordingly the principal object of this invention is to provide an
electronic particle analyzing apparatus for utilization in the
study and analysis of relatively heavy particles for total sample
recovery.
Another object of this invention is to provide, in an electronic
particle analyzing apparatus, means to prevent the sample
containing chamber or vessel from being depleted of a fluid by
continuouly replacing electrolyte therein with clean filtered
electrolyte to avoid the absence of an electrolyte path between the
scanning aperture means and measuring electrodes.
Further object of this invention is to provide a continuous flow
type of electronic particle studying apparatus for handling of
heavier particles in which one of the vessels is electrically
isolated from the fluid moving system.
A still further object of this invention is to provide means
whereby all of the particulate matter of a sample may be recovered
subsequent to its analysis by way of the Coulter type electronic
particle analyzing apparatus.
A still further object of this invention is to improve the
statistical sampling in a Coulter type electronic particle
analyzing apparatus.
A still further object of this invention is to provide means for
speeding the passage of particles through the vessels and aperture
of the Coulter type electronic particle analyzing apparatus.
A still further object of this invention is to provide apparatus of
the character described which will accept particles in the form of
dry powders, and for plurries.
A still further object of this invention is to provide a Coulter
type apparatus which conserves electrolyte by filtering and
recycling it.
ABSTRACT OF THE INVENTION
The invention is concerned with the counting and sizing of
particles particularly those whose density and size make difficult
dispersion in a liquid medium and to monitor, in its entirely, a
particulate sample with recovery of the total sample subsequent to
the testing.
The invention here provides apparatus wherein the original
electrolyte is continuously fed with clean filtered electrolyte.
The particulate matter to be measured is placed in the upstream
chamber where it is immediately diluted. The extent of the dilution
is immaterial since all of the particles are to be counted
eventually. Since there is an electrolytic path existing between
the upstream chamber and the clean electrolyte system, the said
upstream chamber preferably is maintained at ground potential so
that the downstream electrode, that is the electrode in the
downstream chamber is other than ground, necessitating an
electrical isolation of that chamber, this being provided by a drip
chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the apparatus according to the
invention in diagrammatic form.
FIG. 2 is a diagrammatic sectional schematic representation of the
apparatus according to the invention.
FIG. 3 is an elevational section of the chamber portions of the
apparatus diagrammatically illustrated in FIGS. 1 and 2.
FIG. 4 is a diagrammatic sectional schematic representation of a
modified embodiment of the invention.
FIG. 5 is a plan view of the drip chamber portion of the apparatus
according to the invention.
FIG. 6 is a diagrammatic sectional schematic representation of
another modified embodiment of the invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, wherein the examining apparatus
shall be designated generally by reference character 10 while the
electrolyte supply system shall be generally designated by
reference character 100. A successful arrangement of the apparatus
and system may be provided by mounting the examining apparatus on
the front side of a panel and the electrolyte supply system upon
the opposite side of the panel with the conduit means therebetween
passing through suitable openings in the panel, the panel itself
not being shown in the illustrations.
Looking now at FIG. 2 and in particular to the examining apparatus
10, a pair of chambers 12 and 14 are defined by cylindrical vessels
16 and 18. Open top vessel 16 is provided with a bottom flange 19
while vessel 18 is provided top and bottom flanges 21 and 23. A
conical aperture holder 26 is disposed between the vessels 16 and
18 and has a tapered bottom opening 28 into which a collar 30 is
sealingly engaged. The collar carries a central passageway having a
narrow diameter portion which shall be referred to as an orifice
32. The upper wall surface 34 of the collar 30 is flattened and
mounts fused thereon, a wafer 36 in which a microscopic dimension
aperture 38 is formed. The wafer is mounted on the said surface 34
so that the aperture and orifice are coaxial. Reference may be made
to U.S. Pat. No. 2,985,830 for details of the wafer, etc. Thus we
have the Coulter scanning aperture means. The holder 26 for the
Coulter scanning aperture means is provided with a flange 40 as the
upper edge of the holder 26. Mounting or support blocks 42 and 44
are provided and preferably are formed of plastic electrical
insulating material, such as for example, polypropylene. The pair
of blocks 42 and 44 are joined together by means of screw type
clamp means 46. (FIG. 3) Gaskets 48 and 50 make a sealed connection
between the blocks 42 and 44 and vessel 18. A screwed on clamp 52
is secured to block 42 and an adjusting screw 54 is thereby engaged
with the block 42 with the end 53 of the clamp arm 52' engaged on
the flange 19 with gaskets 56 and 58 interposed between the flanges
19 and 21 and between flange 21 and block 42.
Passageways 60 and 62 are formed in blocks 42 and 44 respectively
and lead to valve assemblies 64 and 66 respectively. Measuring
electrodes 68 and 70 are introduced into the chambers 12 and 14
respectively, with their lead wires passing through the walls of
vessels 16 and 18 by way of a metalized glass electrodes 72 and 74
respectively. Block 44 has a plurality of axial passageways 76 and
78 formed therein and opening to a recess 8, the annular wall 82
thereof being tapered outwardly. The formation 84 in recess 80 is
conical leading to a central apex 86. An annular groove 88 is
formed in the surface 44' of block 44. The inner wall portion 88'
of groove 88 is notched to receive an 0-ring 90 therein. An open
top vessel 2 of cylindrical configuration is received in the groove
88 and held therein by frictional contact with the 0-ring 90. The
floor 94 of vessel 92 is tapered downwardly toward the axis leading
to a conduit 96 and valve means 98. Conduits 96' and 96" lead to
valve means 98' and 98".
Referring to the electrolyte supply and recirculation system 100, a
storage tank 102 is provided with a filling top opening 104 capped
by suitable cap 106. Conduit 108 opening from the tank 102 near the
bottom thereof leads to a pump 110, the outlet portion 123 thereof
then leading to a filter 114 and then, by conduit 116, to reservoir
118. The reservoir 118 is a closed vessel having the entry from
conduit 116 opening at the bottom of said reservoir and having a
line 120 leading from a location near the top of the reservoir back
to the storage tank 102 to enter same via overflow opening 120'. A
source 122 of filtered air is coupled to the upper portion of
reservoir 118. A line 124 leads from the source 122 to the storage
tank 102 to enter at air inlet port 124'. The conduit 126 leads by
way of valve means 128 to the upstream vessel 16 by way of line
130.
A trap 132 is provided connected to a regulated vacuum supply 134
by way of line 136. The downstream vessel 18 is coupled to the trap
132 by way of the conduit 138, passageway 60 and valve assembly 64.
Valve means 98" is tapped into line 138 by way of line 140.
Valve means 98' is connected to cleaning probe 142 by way of
flexible line 144, which may be formed of rubber or plastic
tubbing. The probe is raised and lowered into and out from the
vessel 16, as will be described hereinafter.
Suitable shielding indicated by broken line representation 146 is
provided to surround all parts of the chamber 14 as to prevent
spurious electrical paths effecting the measurement across the
aperture 38.
Agitation means is provided in the form of a stirrer 146 driven by
motor 148 and having an agitator tip 150 immersed within the first
or upstream chamber 12. The electrodes 68 and 70 are connected to
the detecting, counting and analyzing apparatus, indicated
generally by box 152.
The operation of the invention may be most quickly understood by
following the course of events as a given particulate sample as
treated through the apparatus 10 and utilizing system 100.
Electrolyte is supplied to the storage tank 102 by way of the
opening inlet 104 until the level 154 reaches the air inlet 124'
the overflow inlet 120". Inlet 104 is capped with cap 106. The pump
110 is activated, drawing electrolyte from the storage tank 102 by
way of conduit 108 and forcing it through the filter 114 which
retains all particles larger than a selected size, for example let
us say those having a dimension exceeding 0.45 microns. The
electrolyte then continues its travel by way of line 116 to the
reservoir 118, the purpose of which is to reduce the velocity of
liquid flow past the opening to conduit 126. Electrolyte rises in
the reservoir 118 until the surface 156 thereof rises higher than
the outlet 158 to the line 120, at which time further flow is
returned by way of line 120 and inlet 120' to the storage tank 102.
The line 120 is joined to the reservoir 118 in a downwardly sloping
manner, as shown at 125 so that flow in the line 120 commences very
quickly after the level 156 exceeds the lower edge of the outlet
158.
When the valve means 128 is opened, the electrolyte flows through
conduit 126 and line 130 into the upper chamber 12 defined by
vessel 16. The electrolyte seeks its own level, thus causing the
surface 160 to be at the same elevation as the surface 156 of
reservoir 118.
Thus the upstream chamber 12 is filled with electrolyte and the
lower chamber 14 remains to be filled. In order to fill lower
chamber 14, valve means 64, 98 and 98' are placed in open condition
and valve means 98" is closed. Cleaning probe 142 connected by way
of line 144 is immersed in the electrolyte contained in the upper
chamber 12. The regulated vacuum supply 134 is activated,
evacuating the trap 132. Thus the vacuum is applied to the chamber
14 since valve means 98 and 98' are in open condition to the
cleaning probe 142. Electrolyte is drawn through the cleaning probe
142 and line 144 and by way of valve means 98' and 98 is caused to
rise into the chamber defined interior of vessel 92. The
electrolyte will continue to rise until it encounters the
passageways 76 and 78 through which it passes to enter the chamber
14. The electrolyte keeps rising and eventually enters the
passageway 60. At this time the operator can place valve means 64
in closed condition. Thus we have now filled the chambers 12 and 14
as well as the vessel 10 with electrolyte and, accordingly,
provided them substantially free of air.
At this time, valve means 98' is placed in closed condition and the
cleaning probe 142 is removed from the chamber 12. The valve 98" is
now placed in open condition. Valve 66 is now open so that the
interior of vessel 92 is connected by way of line 162 to the source
of filtered air. With opening of valve 98" and 66, air enters the
interior of vessel 92 forcing the electrolyte therefrom by way of
valve means 98 and 98" and lines 140 and 138 to the trap 132. When
the operator notices the vessel 92 is substantially empty, valve
means 66 is placed in closed condition. Now, with valve means 128
in the open position and valve means 98 and 98" in the open
position, the electrolyte is constantly recirculated into the
chamber 12. The only flow in the chambers is that permitted by
passage through the aperture 38. The electrolyte which passes
through this aperture 38 displaces electrolyte from the chamber 14
and causes dripage through passageways 76 and 78. The system is now
ready for the addition of the particulate sample which will be
studied.
A small sample of the particulate material to be studied, which is
preferably in the form of dry powder so that it may be accurately
weighed, is sprinkled on the surface 160 of the electrolyte in
chamber 12. The agitating means is in operation at the time of the
addition so that the sample powder is directed into suspension in
the electrolyte immediately. The agitation prevents the individual
particles from adhering to the sides of vessel 16, until they can
be passed through the aperture 38. With valve means 128, being in
the open position, clean electrolyte is continuously being fed to
the suspension. As the sample suspension is drawn through the
aperture 38, the sample itself is diluted progressively and the
particle count rate decreases. The decrease is one that is
substantially exponential. When it decreases to a predetermined
level selected by the operator on the basis of the accuracy
desired, the count is terminated. It can be assumed that all the
particles which were added have gone into suspension and have been
counted.
The cleaning probe 142 can be reintroduced into the vessel 16 and
valve means 98" opened until air is drawn thereinto.
There are occasions where the electrolyte might be more valuable
than the particles and in those occasions a positive displacement
pump such as peristaltic pump 164 may be placed in the system 100
as shown in dotted outline in FIG. 2. This pump 164 must be capable
of developing sufficient pressure to overcome that of the other
pumps. If this is supplied the electrolyte is recycled and the
particles are collected in the filter 114. It should be noted that
conduits 98" and line 140 are arranged for gravity feed so as not
to serve as particle traps. It also is important to note that the
entry to passageway 62 from the vessel 92 is located to open at the
highest possible location in the drip chamber defined by interior
of vessel 92 so that all the air in the vessel 92 is removed when
vessel 92 is filled with fluid electrolyte.
On occasion, it may be feasible to apply pressure to the upstream
chamber 16. In FIG. 4, the examining apparatus 10' and supply
system 100' differs from apparatus 10 and system 100 in that the
chamber 12 is closed off at the top to enable pressure to be
applied, here for the purpose of speeding the flow of sample
suspension through the sensing aperture 38. This is useful in order
to provide shorter pulses to match the frequency response of the
amplifiers used in the detecting, counting and analyzing apparatus
152. Also, the apparatus 10' and system 100' uses more electrolyte
so that with a reasonably short sample run, one can measure enough
individual particles to give good statistical representation.
A lid 166 is placed on the vessel 16' and a reversable, positive
displacement pump, such as peristaltic pump 168 is placed in the
line 170 fed by the sample reservoir 172 by way of conduit 174.
Line 170 also carries the electrolyte from reservoir 102', line 170
bottoming within the reservoir 102' at port 176. Reservoir 102'
replaces the storage tank 102 and reservoir 118 of the system 100
and is vented at 178.
Since the reservoir 102' is vented, it is at atmospheric pressure
and the pressure within the chamber 16 will be above atmospheric
pressure by the pressure developed by pump 168. The fluid return
system 96', 98', line 144 and cleaning probe 142 is eliminated.
The pressure within the drip chamber defined by vessel 92' is
either at atmospheric pressure or is evacuated by a regulated
vacuum supply 134 by way of lines 138 and 140 leading from trap
132, controlled by valve means 98" and 98 respectively. The
pressure drop across the drip chamber is so small that practically
all of the pressure appears across the aperture 38, hence
accelerating the flow of electrolyte and sample therethrough. The
flow of electrolyte from the reservoir 102' sucks sample from the
sample reservoir 172 and the mixture of electrolyte and sample is
complete by the time it gets to the chamber 16', where it undergoes
further mixing due to the flow. The pressure developed by the pump
168 is measured by pressure gauge 180 in order to monitor the
operation of the system 100'.
In FIG. 6, another chamber 182 and another aperture 184 have been
added to the apparatus 10' so that the apparatus 10" and system
100" can be utilized to monitor slurry in industrial usage which is
usually tapped off a large line (not shown) and returned thereto.
The peristaltic pump 186 is disposed in the sample line, here
represented by line 188 having inlet 188' and outlet 188". The
newly added chamber 182 and aperture 184 is interposed between the
line 188 and the chamber 12", equilvalent to chambers 12 and 12' of
earlier described apparatus 10 and 10'. The electrolyte fluid is
introduced to the chamber 12" by way of line 170' and peristaltic
pump 168', and is connected back to its source (not shown) by way
of line 170". Most of the electrolyte entering the chamber 182
leaves by way of outlet 188" but the slurry, passing in small
amounts through the aperture 184, enters the chamber 12" and is
mixed with the outflow at 170", thus diluting the particles of the
slurry within the chamber 12". The outflow through 170" being
regulated by differential pressure regulator means 173. The
remaining portions of apparatus 10" are the same as that of
apparatus 10 and 10'. Thus, the apparatus 10" and system 100"
illustrated in FIG. 6 provides a continuously diluted slurry and
the electronic observation of the particles going through the
sensing aperture 38 can be performed at any convenient time. In the
case of slurry study, the dilution could be carried out
continuously.
While the examples of vessels 12, 14 and 92 have been described as
providing flange type sealed connections one to the others, it is
conceivable that such connections be replaced by using concentric
telescoping cylinders in which the seals are provided by an 0-ring,
thickness of which is slightly greater than the difference between
the inside radius of the larger vessel and the outer radius of the
smaller vessel. Referring to FIG. 5, one will note that in addition
to the passageways 76 and 78, the block 44 carries additional like
passageways arranged in circular array about the axis of the recess
80. The passageways 76 and 78 only were described to
diagrammatically illustrate the construction and operation of the
apparatus and system according to the invention. The plural
passageways aid to increase electrolyte flow to the drip chamber
defined by vessel 92.
* * * * *