U.S. patent number 3,568,735 [Application Number 04/740,289] was granted by the patent office on 1971-03-09 for laboratory microtitration dispensing apparatus.
This patent grant is currently assigned to Cooke Engineering Company. Invention is credited to Jesse F. Lancaster.
United States Patent |
3,568,735 |
Lancaster |
March 9, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
LABORATORY MICROTITRATION DISPENSING APPARATUS
Abstract
Laboratory dispensing apparatus including a base, a liquid
reservoir and well assembly mounted rearward the base, and a
microtitration plate carrier device mounted on the base for
horizontal movement between a forward retracted position and a
rearward operative position overlying a portion of the well. A
novel vertically movable dispensing assembly is positioned above
the base in operative alignment with the portion of the liquid well
so that with the carrier in the forward retracted position the
dispensed assembly may withdraw microquantities of liquid from the
well and then dispense the same into the microtitration plate wells
when the carrier is moved to the rearward position. The dispensing
unit includes a novel pump piston actuator assembly and pneumatic
control system which enable microquantities of liquid to be
simultaneously and accurately picked up and dispensed from the
dispensing needles or pipettes.
Inventors: |
Lancaster; Jesse F. (Great
Falls, VA) |
Assignee: |
Cooke Engineering Company
(Alexandria, VA)
|
Family
ID: |
24975866 |
Appl.
No.: |
04/740,289 |
Filed: |
June 26, 1968 |
Current U.S.
Class: |
141/238; 422/501;
141/242; 222/263; 422/923 |
Current CPC
Class: |
B01L
3/0217 (20130101); G01N 35/1074 (20130101) |
Current International
Class: |
B01L
3/02 (20060101); G01N 35/10 (20060101); B65b
003/30 (); B01j 004/02 () |
Field of
Search: |
;23/259 ;73/425.6
;103/50 ;141/21,25,20.5,115,129,130,181,234,237,238,242
;222/255,263,275,334 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Geiger; Laverne D.
Assistant Examiner: Earls; Edward J.
Claims
I claim:
1. Dispensing apparatus comprising a base, liquid reservoir means
comprising a portion of said base, carrier means mounted on said
base for horizontal movement between a first nondispensing position
at one side of said liquid reservoir means and a second dispensing
position in which said carrier means overlies a portion of said
liquid reservoir means, liquid receptacle means supported on said
carrier means, pickup and dispensing means mounted on said base in
operative alignment above said portion of said reservoir means,
means for moving said pickup and dispensing means vertically
relative to said base, whereby, when said carrier means is in said
first position, said pickup and dispensing means may be lowered to
a first position to withdraw liquid from said portion of said
reservoir means, then raised to permit said carrier means to be
placed in said second position, and then lowered to a second
position to dispense the withdrawn liquid into said receptacle
means.
2. Dispensing apparatus as in claim 1, said pickup and dispensing
means comprising a plurality of dispensing needles and means
operative to simultaneously withdraw microquantities of liquid from
said reservoir into said needles and then simultaneously dispense
the same into said receptacle means.
3. Dispensing apparatus as in claim 2, said liquid receptacle means
comprising a microtitration plate having a plurality of wells
corresponding in number to the number of said dispensing needles,
means on said carrier means for positioning said microtitration
plate to ensure that said needles and wells are operatively aligned
when said carrier means is moved to said second position.
4. Dispensing apparatus as in claim 2, said pickup and dispensing
means comprising manifold means having a centered main air
passageway intersected by a plurality of side-by-side related
angularly directed passageways each of which is intersected by a
plurality of generally right angularly related passageways, head
means connected to said manifold and having a plurality of
apertures aligned with said vertical passageways but separated
therefrom by flexible diaphragm means, an actuator assembly mounted
in each of said apertures and including piston means normally
biased to maintain said flexible diaphragm means out of its
respective one of said apertures, means connecting a dispensing
needle to each of said actuator assemblies, and means for supplying
air to and exhausting air from said manifold passageways whereby
the differential pressure on opposite sides of said diaphragm means
expands said diaphragm means into each of said plurality of
apertures and activates each said actuator assembly to
simultaneously pick up from said reservoir means into and
thereafter simultaneously dispense from said needles predetermined
volumes of liquid.
5. Dispensing apparatus as in claim 4, said head means apertures
each comprising a plurality of cylindrical sections of respectively
greater diameter from the bottom to the top of said dispensing head
means, each said actuator assembly includes a chuck having a
tubular stem extending downwardly through the bottom section of
said aperture, an enlarged hollow head portion located within the
top section thereof, spring means positioned within an intermediate
section for biasing said head portion upwardly into sealing
engagement with said diaphragm means, said piston means being
slidably mounted within said chuck and comprising a rod within said
tubular stem and a piston head of lesser axial length within said
enlarged hollow head portion, and spring means mounted between said
chuck head end wall and said piston head biasing said piston head
into engagement with said diaphragm means, whereby when said
diaphragm means is displaced in response to the air pressure in
said manifold said piston means is moved to dispense fluid from
said needle.
6. Dispensing apparatus as in claim 4, said air supply means
comprising an air pressure source, pressure regulating means
connected to said source and regulating the pressure of air
supplied to solenoid operated air valve means, conduit means
connecting said air valve means to said manifold main passageway,
flow restrainer means located in said conduit means and controlling
the flow rate of air therethrough, and switch means operative to
pass electrical current to said solenoid operated air valve means
to open said valve means and pass air through said flow restrainer
means to said manifold main passageway.
7. Dispensing apparatus as in claim 6, said valve means comprising
vent means operative when said valve is closed to exhaust said
manifold passageways and said conduit means to atmosphere.
8. Dispensing apparatus as in claim 2, said pickup and dispensing
means comprising manifold means, a pipette head unit for supporting
said dispensing needles, flexible diaphragm means operatively
positioned between said manifold means and pipette head unit, said
manifold means having air passage means leading to one side of said
diaphragm means, and a pneumatic supply system connected to said
air passage means for actuating said diaphragm means to
simultaneously pick up predetermined quantities of liquid from said
reservoir means into said needles and thereafter simultaneously
dispense the quantities of liquid from said needles.
9. Dispensing apparatus as in claim 1, said liquid reservoir means
comprising a trough positioned underneath said pickup and
dispensing means, a liquid supply tank remote from and
communicating with said trough through a well and connecting
channel, outlet means on said tank controlling the flow of liquid
therefrom to said well to maintain the liquid level in said trough
at a substantially constant level.
10. Dispensing apparatus as in claim 9, said trough including a
plurality of partitions having aligned circular side recesses, the
opposing recesses of adjacent partitions defining a plurality of
needle pockets which function to eliminate adherent liquid from the
external surfaces of said dispensing needles when said needles are
raised out of said trough.
11. Dispensing apparatus as in claim 1, wherein said base comprises
a rectangular platelike member having an upstanding support post
disposed at the opposite side of said liquid reservoir means and
said means for moving said pickup and dispensing means comprises a
control gear housing carried by said post in vertically upwardly
spaced relation to said platelike member and mounting a vertically
movable rack gear carrying at its lower end a bracket fixedly
mounting said pickup and dispensing means and pinion gear and shaft
means including a handle member for selectively rotating said
pinion gear and shaft means in a direction to first drive said rack
gear to position said pickup and dispensing means in said first
position, then in an opposite direction to its raised position, and
finally in said first direction to said second position, said first
and second positions being predetermined by dependent stop rods
carried by said pickup and dispensing means for end abutting
engagement respectively with said portion of said base in said
first position and with the top wall of said liquid receptacle
means in said second position.
Description
BACKGROUND OF THE INVENTION
This invention is related generally to laboratory analyzing and
titrating apparatus and more particularly to a sampling and
dispensing apparatus capable of precisely and simultaneously
withdrawing into a plurality of needles or pipettes predetermined
reproducible microquantities of liquid such as a diluent, from a
liquid source and delivering the same to a plurality of
corresponding wells of a microtitration plate.
In the laboratory, quite often it is necessary to perform
analytical and/or experimental tests or procedures on large number
of laboratory specimens, the procedures frequently involving the
measuring and dispensing of microquantities of liquid in the nature
of 0.025 milliliters. It is, of course, desirable that such
procedures be performed within a minimum amount of time and with
exactitude and precision to eliminate error.
In the past, laboratory tests of this nature have generally been
performed manually and individually and have required a great deal
of time and effected inaccurate and undependable results. An
operator simply could not time after time reproduce with accuracy
the microquantitative liquid measurements necessary for these
tests, nor could he perform an adequate number of tests within a
reasonable period of time.
Automatic laboratory devices have been developed in an attempt to
overcome these problems, but such devices have generally been very
complex structurally and prohibitively costly. Additionally, they
have not operated entirely satisfactorily to minimize time while
providing extreme accuracy. Typical prior-art systems are those
described in U.S. Pat. Nos. 3,188,181 3,261,208; 3,264,800; and
3,327,535.
SUMMARY OF THE INVENTION
It is a primary object of this invention to provide a novel compact
laboratory dispensing machine which simultaneously withdraws from a
liquid reservoir into each of a plurality of needles or pipettes a
predetermined reproducible microquantity of liquid, e.g., a drop of
0.025 milliliter, and simultaneously dispenses the same into
corresponding specimen containers or wells of a microtitration
plate.
Another object resides in the provision of a compact laboratory
dispensing machine in which a liquid supply source is readily
mounted as part of the machine and the microtitration plate is
movably mounted to permit the pipettes to first withdraw precise
microquantities of liquid from the supply source and then dispense
the same into the corresponding microtitration plate wells.
Still another object is to provide a laboratory dispensing machine
capable of serially diluting precise microquantities of antigens by
serially transferring and mixing the antigen with diluent in
successive rows of wells of a microtitration plate.
A further object is to provide a novel pickup and dispenser unit
including a plurality of pipettes or needles having associated
actuator assemblies of novel construction to permit the
simultaneous pickup and discharge of precise reproducible
microquantities of liquid from the needles. A still further object
is to provide a novel simplified pneumatic control system for
activating the actuator assemblies to control the pickup and
dispensing of fluid from the plurality of pipettes and for
accurately and precisely determining the exact microquantities of
fluid to be dispensed.
Still another object resides in the provision of simple compact
laboratory machine which includes a novel hand manipulatable
vertically movable pickup and dispensing unit having a plurality of
pipettes, a liquid reservoir and well assembly mounted on the base
underneath the pipettes, and a movable microtitration plate carrier
member slidable between forward and rearward positions and in the
rearward position being located vertically above the well with the
microtitration plate wells aligned with corresponding pipettes.
This arrangement permits the dispensing unit to first pick up
liquid from the well when the carrier is in the forward position
and then to dispense the liquid into the titration plate wells when
the carrier is moved to its rearward position underneath the
pipettes.
Further objects and advantages will become apparent from the
following detailed description of a preferred embodiment and the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the laboratory dispensing apparatus
of the invention with the various parts shown in the retracted
inoperative position;
FIG. 2 is a front elevational view of the apparatus of FIG. 1;
FIG. 3 is a side elevational view of the apparatus of FIG. 1;
FIG. 4 is a top plan view of the apparatus of FIG. 1;
FIG. 5 is a fragmentary elevation section taken along line 5-5 of
FIG. 4 and illustrating the pickup and dispenser assembly in its
lower position in which it picks up liquid from the liquid
well;
FIG. 6 is a fragmentary elevation section taken along line 6-6 of
FIG. 4 illustrating the microtitration plate in its operative
position in which the pickup and dispenser assembly is lowered with
the dispensing needles positioned within the wells of the titration
plate;
FIG. 7 is an enlarged fragmentary sectional view illustrating a
pump piston actuator assembly within the pickup and dispenser head
plate with the piston actuator assembly in its normal retracted
position;
FIG. 8 is a view similar to FIG. 7 but showing the piston actuator
assembly in its operative dispensing position;
FIG. 9 is an exploded sectional view of the piston actuator
assembly illustrated in FIGS. 7 and 8;
FIG. 10 is an exploded perspective view of the reciprocating plate
carrier and the microtitration plate locator positioned on the
carrier;
FIG. 11 is a perspective view of the reservoir and well base;
FIG. 12 is a perspective view of a modified well for the reservoir
and well base;
FIG. 13 is a sectional view taken along line 13--13 of FIG. 12;
FIG. 14 is a front elevational view partially broken away
illustrating the air control assembly used with the pickup and
dispensing apparatus of the invention;
FIG. 15 is a top plan view of FIG. 14 but partially broken
away;
FIG. 16 is a sectional view of a flow restrainer orifice used in
the control assembly of FIGS. 14 and 15;
FIG. 17 is a schematic diagram of the overall air control system
incorporated within the pickup and dispensing unit of the
invention;
FIG. 18 is a perspective view of a modified pickup and dispenser
assembly including only a single row of dispensing needles
particularly useful in serial dilution processes; and
FIG. 19 is a perspective view of a single pickup and dispensing
needle or syringe incorporating the novel piston actuator assembly
shown in FIGS. 7--9.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings, the laboratory pickup and dispensing
apparatus of the invention comprises a rectangular base 20 having
corner mounting pads 21, a pickup and dispenser assembly 22 mounted
above base 20 by vertical post 24, control gear housing 26, gear
rack 28 mounted within housing 26 and driven by pinion 30, and
L-bracket 32 secured to the threaded bottom end of rack 28 by nut
34 and to the rear of dispensing assembly 22 by screws 36. The
pickup and dispensing assembly is moved vertically relative to base
20 by rotating handle 38 which rotates pinion 30 to drive rack
28.
A sample carrier plate 40 having side flanges 42 (FIG. 4) is
slidably mounted within longitudinal recesses 44 in guide rails 46
and 47 which are spaced above base plate 20 by spacers 48. As shown
in FIG. 2, spacers 48 are internally threaded to receive a top
screw 50 which secures the rails to the spacers and bottom screw 52
which holds the spacers to base 20. Carrier 40 has a knob 54 by
which an operator may slide the plate from its forward retracted
position shown in FIGS. 1 and 5 to its rearward operational
position underneath the dispensing assembly as shown in FIG. 6.
The carrier plate 40 may support a plurality of separate vials or
tubes or may suitably support a transparent microtitration plate
140 having a plurality of wells 142 and being generally constructed
similar to the microtitration plates disclosed in U.S. Pat. No.
3,356,462. When the latter is used, carrier 40 is provided with a
titration plate locator and guide assembly shown in FIG. 10
including a rectangular plate 144 fixed to carrier 40 by rivets
146, the upper projecting ends of which serve as locator pins
received within the cutout corners 148 of hollowed locator 150 on
which the titration plate 140 rests as shown in FIGS. 5 and 6. The
sides of the titration plate overlap the sides of locator 150 with
the base of the wells 142 resting on the bottom of locator 150.
This locator assembly enables an operator to readily replace one
titration plate for another and ensures that the wells 142 of the
titration plate will be accurately aligned with their respective
corresponding needles 128 during a dispensing operation.
Also mounted on base 20 is a liquid or reagent reservoir well plate
56 (FIG. 11) positioned on the base by an end recess 58 which
engages guide pin 60 secured to the base and by a locking pin 62
which passes through guide rail 47 into a hole 64 in well plate 56.
Well plate 56 mounts a liquid reservoir tank 66 connected by
cylindrical recess 72 and channel 68 to a supply well 70 located
underneath dispenser assembly 22. Tank 66 is an inverted
cylindrical container disposed within cylindrical recess 72 in well
plate 56 with its mouth aperture 74 defined by protuberant plug 76
opening into counterbore 78 communicating through channel 68 with
trough 70. The reservoir maintains the liquid in trough 70 at a
constant level and also prevents undesirable liquid overflow in
well-known manner through the vacuum formed when plug 76 becomes
fully immersed to prevent air from bubbling upwardly through mouth
aperture 74.
With particular reference to FIGS. 5 and 6, the pickup and
dispenser assembly 22 includes an air manifold comprising a
rectangular body member 80 having a central main longitudinally
directed passageway 82 intersected by a plurality of transverse or
cross passageways 84 plugged at opposite ends 86. Passageways 84
also are intersected by vertical downward passageways 88. A conduit
fitting 90 threadedly engages one end of passageway 82 and receives
an air conduit 92 to deliver air into manifold 80 from a suitable
regulated air source and exhaust air therefrom in a manner to be
described.
Connected to the bottom of manifold 80 by screws 94 is a
rectangular dispenser head plate or member 96 having a top
rectangular recess 98 receiving a thin flexible diaphragm 100 which
separates a plurality of stepped circular apertures 102 from
aligned manifold passageways 88.
As shown in detail in FIGS. 7--9, stepped aperture 102 comprises
increasingly diametered circular sections 104, 106, 108,
respectively and houses a needle piston actuator assembly 109
including a piston sleeve 110 having an end tapered tubular stem
112 which passes through aperture section 104 and a circular hollow
head or skirt portion 114 received within section 108 and biased
upwardly into sealing engagement with diaphragm 100 by spring 116
positioned within section 106.
A pump piston 118 is in the form of a rod 120 received in tubular
stem 112 and a head 122 positioned in skirt 114. A spring 124
located in the upper increased diameter stem section 113 rests on
shoulder 113a and biases piston 118 upwardly to engage head 122
with diaphragm 100.
As shown in FIGS. 7 and 8, a chuck 126 snugly engages the
end-tapered stem 112 and communicates the hollow stem with the
tubular dispenser needle 128 received and supported within its
lower end.
The number of dispenser needles 128 provided in the dispenser
assembly 22 of the invention may be varied as desired or required,
and in the embodiment illustrated there are 96 dispenser needle
assemblies aligned in 8 rows of 12 needles each. The number of
wells 142 in the microtitration plate 140 of course correspond to
the number of dispenser needles provided in assembly 22.
Piston sleeve 110 has its tubular stem 112 and cavitied head
portion 114 accurately machined to close tolerances to cooperate
with similarly machined pump piston 118 to provide for the
displacement of a predetermined exact microquantity of air from the
needle assembly 109 as piston 118 moves from the normal position
shown in FIG. 7 to the dispensing position of FIG. 8. In this
manner, the amount of liquid withdrawn from well 70 by each of the
needles 128 and subsequently dispensed therefrom is accurate and
reproducible through a series of dispensing operations.
Stop rods 130 are threadedly secured to the bottom of diaphragm
plate 96 and, as shown in FIG. 5, cooperate with the circulate top
recesses 65 in well plate 56 to determine the depth of immersion of
needles 128 in the liquid in well 70 and prevent the needle from
contacting the bottom of the well when liquid is withdrawn into the
needles. Similarly, as shown in FIG. 6, when the liquid is
dispensed from the needles into the microtitration plate wells 142,
rods 130 abut the top of the sides of plate 140 to prevent the
needles from contacting the bottom of wells 142.
The air supplied to dispensing manifold 80 through conduit 92 is
controlled by the control assembly 150 illustrated in FIGS. 14--16,
with the overall control function accomplished as shown in the
schematic diagram of FIG. 17. The control assembly 150 includes a
housing 152 and base 154 on which are mounted a pressure regulator
156 which received compressed air from a suitable source 157
through conduit 158 and passes it at a reduced regulated pressure
preferably about 20 psi, to an electrical solenoid operated air
valve 160. Valve 160 has an exhaust outlet 161 to atmosphere which
is normally closed when the valve is open, but which opens when the
valve 160 closes to exhaust the air in manifold 80 and conduit 92
to atmosphere.
The solenoid valve is energized from a terminal board 162 connected
to a suitable socket 164 which receives the plug of an electrical
cord 166 through which the flow of electrical current from a
115-volt AC power source is controlled by a footpedal-operated
switch 170.
A dial pressure gauge 172 connected to reducing valve 156 by
suitable L-shaped piping 174 provides an indication of the pressure
of the air being supplied to solenoid valve 160 and dispenser
manifold 80.
A conduit fitting 176 houses a fixed orifice flow restrainer 178
(FIG. 16) having an orifice 179 which accurately controls the air
flow rate from valve 160 to conduit 92 and manifold passageway 82
so that a predetermined fixed reproducible volume of air is
supplied to the manifold to ensure that accurate and reproducible
microquantities of air may be displaced from each needle assembly
109 and similar quantities of liquid may be picked up by the
needles from well 70 and dispensed therefrom into the
microtitration plate wells 142.
A typical dispensing operation is as follows. Initially, the
respective parts are shown in FIGS. 1--3 with the carrier 40 and
titration plate 140 in the forward retracted position and the
pickup and dispenser assembly 22 in its raised position.
Footpedal switch 170 is then closed to pass electric current to
solenoid terminals 162 to open air valve 160 and pass compressed
air at a controlled rate of flow to manifold passageway 82. The air
then passes through passageways 84 and 88 to the top face of
diaphragm 100 which deforms downwardly into piston sleeve skirt 114
and causes each of the 96 pump piston assemblies to move from its
normal position of FIG. 7 to its depressed position of FIG. 8, this
movement causing a predetermined accurate quantity of air inside
piston sleeve 110, chuck 126, and needle 128 to be displaced
therefrom to atmosphere.
The handle 38 is then rotated to lower assembly 22 and immerse the
tips of needles 128 in the liquid in well 70 as shown in FIG. 5
with the stops 130 determining the depth of immersion of the
needles in the liquid. The foot pedal is then released, closing air
valve 160, and exhausting the compressed air from manifold 80 back
through conduit 92 and flow restrainer 178 to atmosphere through
valve vent 161. When this occurs, diaphragm 100 and piston 118 of
each of the needle assemblies are biased upwardly back to the
position of FIG. 7 causing a predetermined, accurate microquantity
of liquid e.g., 0.025 milliliter, to be drawn into each needle 128
from well 70.
Handle 38 is then rotated in the opposite direction to raise the
pickup and dispenser assembly 22 back to the phantom position of
FIGS. 5 and 6. The operator next slides the carrier plate 40 to its
rearward operative position underneath and aligned with assembly
22, which is then lowered to the dispensing position of FIG. 6. The
foot switch 170 is again actuated to depress the pump piston as in
FIG. 8, thus forcing the liquid from needles 128 into the
corresponding wells 142. The needles are then raised out of the
wells and the foot switch released to exhaust the air from manifold
80 to atmosphere as described above.
It has been found that when a liquid having a relatively low
viscosity is being handled, small quantities of the liquid from
well 70 may adhere to the outside surface of the needles 128, thus
resulting in somewhat inaccurate and uncontrollable amounts of
liquid being withdrawn from the well. To overcome this, the
modified well 70a shown in FIGS. 12 and 13 may be used.
Well 70a is provided with a plurality of partitions 180 having
circular side recesses 182 with the opposing recesses of adjacent
partitions forming needle pockets 184 which are sized to be
sufficiently larger than the diameter of the needles so that the
created surface tension in the pockets pulls the diluent liquid off
the outside of the corresponding needles. For example, in one
operation, with the outside diameter of needles 128 being 0.065
inches, a pocket diameter of one-quarter inch was found to
effectively result in removal of excessive diluent from the needle
exterior surface. In addition, the height of the partitions is such
that the liquid level in the well 70a will not extend over the top
ridges of pockets 184 and with a liquid depth of five thirty-second
inches, a height of three-eighths inch has been satisfactory.
The invention may also be used to serially dilute microquantities
of liquids, such as antigens by using a pickup and dispenser
assembly 222 illustrated in FIG. 18, which is constructed exactly
the same as assembly 22, except that it includes only a single row
of needles 228. Pickup and dispenser head 222 is suitably connected
to the bottom end of rack 28 to that the needles 228 are located at
an intermediate position above base 20 sufficiently forward of rod
24 to permit each of the rows of titration wells 142 to be
successively aligned with the needles as the carrier plate 40 and
titration plate 140 are moved from their forward to their rearward
position. Conduit 292 may be suitably connected to a valved nipple
294 of T-fitting 93 (see FIG. 17) to provide compressed air for the
pickup and dispensing operation.
In a serial dilution process, initially with the carrier plate 40
in the forward inoperative position, the needles 228 are provided
with precise microquantities of antigens to be diluted either from
well 70 or from a separate row of vials or test tubes (not shown).
Similarly, each of the wells 142 is provided with predetermined
amounts of diluent.
Next, plate 40 is moved rearwardly so that the first row of wells
142 aligns with needles 228 which are then lowered to dispense the
antigen into the wells where they become thoroughly mixed with the
diluent by a jet action accomplished by alternately dispensing and
picking up the diluted combined mixture from the wells. Precise
microquantities of this mixture are withdrawn into the needles 228
which are then raised to permit the next row of wells to be aligned
therewith and the diluting and mixing action to again take place.
This procedure is repeated for each successive row of wells so that
the final mixture in each successive row of the series is more
dilute than that in the previous row.
When the last row of wells has been diluted, any quantity of liquid
mixture remaining in the needles 228 is discarded and the needles
subsequently cleaned by alternately picking up and dispensing
distilled water or any other acceptable purging solution from a
suitable source.
It is a that a single, hand portable pickup and dispenser needle or
syringe 250 illustrated in FIG. 19 having the same manifold and
needle assembly structure as that shown in FIGS. 7 and 8 may be
provided for such operations as dilution or dispensing of a single
specimen or transfer of a single sample to a microscope slide for
viewing a precisely metered micro sample of liquid in preparation
for seriological testing or microscopic observation.
The syringe 250 may be connected to a valved nipple 252 of
T-fitting 93 by conduit 254 to supply air for operation of the
syringe.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive, the scope of the invention
being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *