Note: Descriptions are shown in the official language in which they were submitted.
"~896
'rhi5 appllc~tion i5 a division of appliccltion serlal No.
369,577 filed January 28, 1981.
BACKGROUND OF THE INVENTION
The invention relates to a fluid ~ransfer mechanism
for picking up, transferriny and dispensing fluid volumes
and more particularly this invention concerns aspira-tiny a
fluid volume in a first posi.tion, rotat.ing the aspirated
fluid to a second position and dispensing the fluid volume
in the second position.
Fluid transfer and dispensing mechanisms each
operate to dispense amounts of fluid in a desired locat~on;
however, prior art devices do not have the capability tQ picl~
up or aspirate a precise fluid c~uantity in a first position,
move tl~e fluid clu~mtl-ty to a second position at a high.rate
of speed and with a ~ery precise positioning oE the fluid
pick up and dispensing probe in the vertical and horizontal
positions. Further, many of the prior art devices were
developed to pump a dedicated fl.uid through the dispenser,
such as xeagents in chemical analyzing systems or to pick up
multiple volumes in a fluid probe separated by air or other
fluids. If the flexibility is desired to pick up and dispense
different fluid quantit:ies from different sources and mix
them with other fluids then the dedicated or in line systems
are not capable of being utili~ed since the~ either are
physically connected only to one fluid or would run the risk
of carry-over and contamination between fluids.
In some chemical analy2ing sys~ems sample flui.ds
related to a particular patient are programmed for one or
more analytical tests such as measuring the chemical
reaction resultin~ from the addition of one or more reagents
from a reagent supply. One disadvantage in prior art devices
is caused by dedicated reagent positions ancl typ.ically a
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~15~89~
dedicated reagent dispensing mechanism for each position.
Generally the array of cuvettes or xeaction vessels is
segmented or aivided into the number of positions xequired
by the dedicated reagent positions. For example/ lQ0
cuvette positions with 10 .reagent positions results in
samples from only 10 patients being tested in the system
without regard to the number of tests conducted on the.
sample from each patient~
Patient No. 1 might require only one test, but
all ten positions have to be allotted for that patient~s
sample in the device since each of the reagent positions
is dedicated. Each of the nine empty positions may.not be
utilized so that the 100 position machine only is effective
as a ten patient or sample machine. If this problem is
15 - doubled by including 10 second reagents, then the 100
- position machine would be divided in half again such that
samples from only five patients could be analyzed on the
machine at one time. This results in a great increase in
- elapsed time for a given through put as well as a corresponding
decrease in the efficiency of.the system. It would be
.
desirable to provide a fluid transfer mechanism which may
- pLck up~ move and dispense.samples and reagents from one or
more positions to increase the flexibility of the systèm so
that each cuvette may include a sample and reagent fluid
without regard to the number of tests or reagen-ts in the
system.
;,
~l B96
SUMMARY OF TEIE INVI~NTION
The above and other disadvantages of priar art
fluid aspirating, transferring and dispensing syste~s and
techniques are overcome in accordance with the present
invention by providing a fluid transfer mechanis~ h~vin~ an
arm carrying a fluid probe on its distal end rotated about
a fixed axis and precisely positionable in any vertical or
horizontal position desired~ The probe may include a.level
sensing mechanism for sensing when the probe contacts a
fluid surface,an oscillating mechanism to oscillate the probe
in a fluid vessel to stir the fluids in contact therewith as
well as a control for accelerating and deaccelera-ting the
rotational movement of the arm to avoid spillage from the
fluid probe.
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~ iL51i~96
BRIEF DESCRIPTION OF THE DRAWINGS
-
Figure 1 is a partial perspectiVe view of the
fluid transfer mechanism of the invention and a partial
perspective view of a chemical analyzer;
Figure 2 is a side plan view partially in section
of one embodiment of the transfer mechanism;
Figure 3 is an enlarged side plan view partially
in section of one embodiment of fluid probe of the ~echanism;
Figure 4 is a top view taken along the line 4-4
in Figure 2;
Figure 5 i5 a side sectional view of the arm of
the transfer mechanism taken along the iine 5-5 of Figure 2;
Figure 6 is an explode~ perspective view of the
transfer arm and probe of Figure 2;
Figure 7 is a side plan view partially sectional
..
of a`second embodiment of the transfer mechanism; and
- Figure 8 is a partial block and diagrammatical
view of one control system of the fluid transfer mechanism.
.
: ' ,' ' ' ' .
L896
DESCRIPTION OF T~IE PREFERRED EMBODIME~TS
Referring now to Figure 1, a fluid trans.fer
mechanism constructed in accordance with the invention is
deslgnated gener~lly by the reference charac-ter 10~ Three
of the transfer mechanismsl0, 10' and 10" are illustrated
in operation with a chemicai reaction analyzer 12. The
analyzer 12 may include a ~ample supply 14 and a reagen-t
supply 16. The transfer mechanism 10 may be utilized with
any type of analyzing or mi~ing system in which it is
desirable to utilize the capabilities of the mechanism 10
as described hereinafter. For ease of descrip~ion of the
operations of the mechanism 10 and the flexibility inherent
therein, one particular analyzer 12 will be described.
The analyzer 12 includes a cuvette rotor 18 which
includes a plurality of cuvettes or cuvette cavities 20.
The sample aliquots are picked up or aspirated by the
mechanism 10 from the sample supply 14 and moved to and
dispensed in the cuvettes 20. The sample aliquots are mixed
with reagent aliquots wh.ich are picked up and dispensed by
the mechanism 10' from the supply 16 for a first reagen-t~
A second reagent may be added to the cuvettes 20 by the
t~ird mechanism 10" from the supply 16 or from a different
supply (not shown). The sample supply 14 may include
samples, stats, controls and blanks which are picked up
from the sample supply 14 in a predetermined order and
which then are analyzed by the analyzer 12 in the cuvettes 20.
The cuvettes 20 preferably are a renewable supply by being
- cleaned in the analyzer 12 before arriving again at the
sample dispensing position of the mechanism 10.
.
896
The s~mple supply,l4 has a plurality of ca,~it,ies 22
in which the samples', blanks, stats, and controls may be
placed and may include one or more pick up positions on an
arc defined by a fluid probe 24. The cavities 22 may be
moved to the pick up positions by rotating the supply 14.
The probe 24 is rotated on an arm 26 about a sha.~t 28.
The arm 26 is shown with the probe 24 in the dispensing
- position inserted into one of the cuvettes 20 in the rotor 1~
The fluid picked up from the supply 14 will be dispensed
10 ' and may be mixed by a motor 30 oscillatin~ the probe 24 back
and forth inside the cuvette 20. The mechanism 10' operates
in a similar manner to pick up a fluid from.one of a plurality~
of reagent containers 32 in the supply 16. The mechanis~
10" may pick up a second reagent quantity from the containers
32 or from another supply or row of containers (,not shown).
The probe 24 is rotated about the shaft 28 and is
- vertically driven up and down on the shaft 23 to pick up and
dispense the fluid ~uantities. The types of supplies as
well as the cuvette array 20 are merely illustrative and the
mechanisms 10, 10' and 10" could pick up and dispense fluids
from any position on an arc defined by the axis of the shaft
28.- The fluids each may be different upon each operation of
- .
the-mechanism 10 and it is very important that carry-over
and contamination lS eliminated since the fluids are related
.to tests upon the body fluids of a particular patient.
The operational positions of the mechanism 10
during each cycle will be as follows, describing the position
of the probe 24 for simplicity. The probe 24 will be in a
rest position such as above a probe washer 34 in which the
probe is washed both internally and externally and dried at
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S~l896
the end of each cycle i.n preparation for the nex-t cycle.
The probe 24 is first rota-ted to the proper pick up position
above one of the cavities 22, driven downwardl~ .into the
cavity until it reaches the f].uid, aspirates the precise
: 5 aliquot of fluid des.ired, driven back up to the rotation
position above the supply 14, rotated to a dispensing
position above one of the cuvettes 20, driven downwardly into
the cuvette 20, dispenses the aspirated fluld aliquot,
oscillates to mix the fluids in the cuvette 20, driven
upwardly to its rotating position, rotated to a position above
the probe washer 34, driven down into the probe washer 34
wherein it is washed and dried of all previous fluids and
then returned to its rest position above the probe washer 34. .
In one chemical. anal~zer 12, utilizing the above cycler the
lS cuvettes 20 are stepped by the rotor 18 one position in the
direction "A" each six seconds and hence each of the
mechanisms 10, 10' and 10" performs each of the above
movements in less than six seconds. It can be seen that it
is extremely critical that each of the positions, both
vertical and rotational, precisely and quickly must be
attained by the probe 24.
A first embodiment of the transfer mechanism 10
and fluid probe 24 is illustrated-in Figures 2 through 6
Referring to Figure 2, the probe 24 is shown illustrated
inserted in one of the cuvettes 20 in the rotor 1~. The
probe 24 is oscillated back and forth as shown by the
arrow "B" to mix the fluids in the cuvette 20. The probe
24 is driven up and down along the axis of the shaft 2B
as shown by the arrow "C" to remove and insert the probe
~0 into the cavities 22, cuvettes 20 and the probe washer 34.
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:
~51896
The mechanism 10 may be mounted to any conyenien-t surface
such ~S a baseplate 36 of the an~lyzer 12~
The arm 26 is mounted to the shaft 28 and is driven
horizontally by a motor 88 and vertically by a motor 40.
The motors 38 and 40, preferably are stepper motors to
provide a very precise movement and alignment of the probe 24.
In one example, the motox 38 moves the probe 24 alon~ the
horizontal arc two thousandths of an inch for each drive
pulse it receives, while the motor 40 moves the probe 2~
along the shaft 28 six thousandths of an inch for each pulse
it receives. Further, the pulses may be applied to one or
both of the motors 38 and 40 at an increasing and decreasing
frequency to accelerate the probe 24 at the start o-f the
movement to reach a high speed of movement and then
deaccelerate so that the arm 26 does not stop suddenly ana
vibrate the probe 24 to spill fluids from the probe~ This
also is expedient, because of the number of motions the-arm
has to make in a very short period of time, plus the
precision necessary for each of the locations of the probe 24.
To provide the speed and precision movements of
the probe 24, the shaft 28 is a high helix screw having the
pitch designed to provide the high speed movement necessary
for the arm and probe movement. Only a portion 42 of the
high helix screw thread is shown in detail; however~ it
will be understood that the threaded portion 42 extends
from the uppermost potion of the shaft 28 to the l~wermost
portion of the shaft to which the arm 26 will be drivenO
The arm 26 is mounted to the shaf-t 28 by a hi~h helix nut
44 of opposite confi~uration to the threads 42, which is
engaged in a passageway 46 in the arm 26. The motors 3~
.9 _
96
and 40 may he mounted to a plate 4%, which is below the
baseplate 36 and may be moun-ted thereto or may be mounted
to another ~urface,
The motor 38 includes a drive shaft 50 extending
through an aperture or opening 52 in the plate 48 and has
a pulley 54 mounted thereon. The pulley 54 has a drive belt
engaged around one end. .The belt 56 is engaged at the
opposite end around a drive pulley 58 mounted to a hub 60..
The hub 60 is rotatingly mounted by a pair of bearings 62
and 64 around a sc~ew drive shaft 66. The screw drive shaft
66 is pinned or or otherwise secured to a lower end 68 of
the high helix screw 28 at one end and-is pinned or other-
. .
wise secured at its opposite end to a drive shaft 70 of the
motor 40.
The hub 60 also includes a guide rod 72 mounted
or secured -therein by a screw or other retaining device 74.
The opposite end of the guide rod 72 is secured in an upper
.
bearing retainer 76 by a screw or other securing device 78.
The bearing retainer 76 includes a bearing 80 re~ained in a
slot or recess 82. An upper end 84 of the helix 28 is
rotatingly engaged in the bearing 80. The guide rod 72
.. . . . . . .
maintains the angular position o~ the arm 26 by a bearing
86 mounted in the passageway 88 in the arm 26. The bearing
86 such as a ball bushing surrounds the guide rod 72
allowing the arm 26 to move easily up and down the rod 72,
while accurately positioning the arm 26 and probe 24.
When the motor 40 is operated the screw shaft 28
is rotated driving the arm 26 and hence the probe 24 upwardly
or downwardly by the drive nut 44. The bottom of the guide
rod 72 is mounted in the hub 60, so that when the mo-tor 38
is operated and the drive belt 56 rotates the hub 60, the
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1~51l~6
guide rod 72 accuratel~ ~ill position the probe 24 as the
hub 60 is rota-ted~ The motor 40 may be opera-ted in tandem
with the motor 38 to maintain the position of -the arm 26 on
the shaft 28 if the positioning o~ the arm 26 on the shaft 28
is critical. If the arm 26 may be allowed to move slightly
up and down as the arm is rotated by the motor 3~, then the
motor 40 need not be activated. Then as the hub 60 rotates
around the sha~t 28 the arm 26 will be dxiven slightly
upwardly or downwardly on the shaft 28, since the nut 44 will
be rotated on the threads 42 as the arm 26 is rotated by the
guide rod 72.
The upw~rd position of the arm 26 and the probe 24
may be ascertained by an optical reader 90 carried on th,e
arm 26 which may be a conventional U or C shaped light switch,
which will generate a signal when the light path be-tween the
arms is interrupted by a tàb 92 depending from the upper
bearing retainer 76 (best illustrated in Figure 4~. The
lower position of the arm 26 and'the probe 24 may be
.
ascertained by a second optical switch 94 carried on the
arm 26 below the switch 90 which is activa-ted by a, tab 96
mounted on the rod 72. ~he tabs 92 and 96 may be fixed or
adjustable as desired to set the uppermost position as well
as the lowermost position of the arm 26 and the probe 24.
The position de~ined by the tab 92 will be the
~5 ~ppermost position in which the probe 24 is removed from
any of the vessels or cavities into which it may be placed
so that it may be rotated without damage to the probe 24.
The lowermost position de~ined by the tab 96 may be the
lowermost position into which the probe 24 is lnserted
such as the desired spacing above the bottom oE the cuvette
20 or in the probe washer 34. To provide the mechanism 10
with flexibility other tabs and readers could be utilized to
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~5189~
define other posi~ions, which readers could be ~ounted
adjacent the reader g4 and have tabs extendin~ vertically
upwards parallel to the rod 72 and moun~ed to the rod 72
or hub 60.
The angular position of the arm 26 i5 determined
by the horizontal drive motor 38 and may be verified by a
code wheel 98 which is secured to a depending flange lOD of
the hub 60 by a lower bearing holder 102~ The code wheel 98
rotates with the hub 60 and the an~ular position oE the
code wheel 98 and hence the arm 26 and the probe 24 may be
sensed by an optical reader 104 mounted to the plate ~8 by
a mounting block 106. The code wheel 98 may be utilized to
determine the angular position of the probe 24 or it just
may be utilized as a check to verify the position which has
been determined by the number of drive pulses fed to the
motor 40. Since each of the motors 38 and 40 preferably
are stepper motors and are driven a precise distance for
- each drive pulse supplied thereto, the vertical and
,.~. . ........................................ .
rotationa-l position of the probe 24 may be determined
:20 merely by the number of pulses fed to the motors 38 and 40.
Tabs 92 and 96 and the code wheel 98 then just may be
utilized to verify the position determlned by the drive
- motors.
The probe 24 is best illustrated in Figures 2 and
3 and includes a central passageway 108 which extends the
: length of the probe and opens at the top in a bore 110 into
which may be f.itted a fluid fitting 112 to which is connected
: a conventional fluid tubing 114. The passageway 108
preferably is formed in a non reactive plastic material
and extends to and opens through a bo-ttom end 116 which is
the fiuid aspirating and dispensing portion of the probe 24.
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89f~
The end 116 and a pair ~f electrical leads 118 and 12~
extend ou-t of a botto~ non conductive sheath 122~ The
sheath 122 is dimensioned to fit within the inner dimensions
of the cuvettes 20, the cavities 22 and the probe washer 34.
The upper ends of the leads 118 and 120 are
coupled to a fluid sensing circuit ~Figure 8) which includes
a power source and a detector to sense when the e~posed
bottom ends of the leads 113 and 120 contact a fluid sur~ace
to provide a level sensor for the mechanism 10~ The bottoms
1~ of the probe 116 and the leads 118 and 120 are spaced so
that the bottom end 116 has a minimal contact with the fluid
in the cavities 22 and 32 and so that there is a mlnimal
- amount of carry-over on the outside of the probe 24 and a
precise aliquot of fluid thus may be aspirated and dispensed
The probe 24 is mounted through an aperture 124
in a slide 126. The slide 126 includes a mounting block
128 formed therewith or fixed thereto which includes a
threaded bore 130 into which is inserted a spring type
plunger 132 which ensures the proper orientation of the
probe 24. The spring plunger 132 allows the probe 24 to
move laterally and vertically if -the probe 24 should be
moved against a solid object to avoid damage to the probe
24 and mechanism 10. The vertical positioning of the
probe 24 is maintained by a spring 134 which is screwed
around a threaded portion 136 of the mounting block 128 on
one end and at the opposi-te end around a threaded portion
138 of the probe 24. Thus, if the probe 24 should be moved
against a solid object in its downward travel the probe 24
will pop up through the aperture 124 to avoid dama~e t~ the
mechanism 10~ Such a malfunction could occur without any
fault of the mechanism 10 since the supply 14 may not move
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~5~9~
the cavities 22 into the pro~er position or the rotor 18 ~ay
not move the c.uVettes 2Q into the proper position o~ one
of the cuyettes 20 could be blocked,
The probe 24 is oscillated back and forth. to ~tir
the fluids in the cuvettes 20.on the slide 126 b~ the motor
30. The operation of the motor 30, construction of the
slide 126 and mounting on the arm 26 is best illustrated in
Figures 5 and 6. The slide 126 includes a pair of ~rooves
140 and 142 in either side of the slide and extending the
length thereof. The top portion of the arm 26 includes a
channel 144 into which the slide 126 fits with lateral
space between the sides of the channel 144 and the grooves
140 and 142. The sides of the channel 144 include a
plurality of bores 146 therethrough, which have a ~irst
outer dimention and a second smaller inner dimenslon opening
- into the channel 144. The bores 146 each have a ball bearing
148 inserted into the first dimension portion thereof and
partially extending into the channel 144 to enga~e ln the
respective grooves 140 and 142. The ball bearings 148 are
maintained in the bores 146 by a pair of spring plates 150
and 152.
: The spring plates 150 and 152 are secured to -the
arm 26 by a plurality of screws 154 inserted through
apertures 156 in the plates 150 and 152 and into threaded
bores 158. The arm 26 includes a base portion 160 in which
is formed the nut passageway 46 and the bearing passageway
88. The base 160 may include grooves or slots 162 in the
sidewalls thereof into which the leads for the wires 118
and 120 and the tubing 114 may be secured. The.slide 126 is
reciprocated in the channel 144 by the mo~or 30 with an
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.;
396
eccentric drive shaft e~tending throu~h an aperture or slot
164 in the plate 126.
A second embodiment of the mechanism 10 includincJ
a probe 24' is illustrated in Figure 7. The mechanism 10
in Figure 7 as well as the probe 24', provides -the same
operations as previously described. Substantially identical
members will be described with the sa~e numbers as
previously utilized in Figures 1 through 6 with a prime to
indicate minor modifications and different numerals are
used for elements which have been substantially or completely
changed.
The probe 24' includes a stainless steel pick up
and dispensing probe 166 mounted in a non conductive sleeve
168 by a threaded fitting 170. The probe 166 includes a
bottom tip 172 which has the fluid aspirating and dispens.ing
opening therein and also serves to form one lead of a
capacitive level sensing circuit described in Figuxe 8. The
electrical connection to the probe 166 is made by a block
174 which i5 welded or otherwise electrically connected to
an upper end 176 of the probe 166 and includes an electrical
lead (Figure 8) connected in a conventional manner.
The upper end 176 of the probe 166 will have a
-fluid tubing connected thereto. The sleeve 168 is mounted in
. a slide 126' which is screwed or otherwise secured to a
conventional ball slide 178 (only the slide portion thereof
being illustrated in the Figure) which is mounted on the
arm 26'. The motor 30 again has an eccentric drive shaft
180 engaged in the drive slot 164 in the slide 126'. The
motor 38 rotates a drive pulley 58' by the drive belt 56.
The hub 60' is secured to the pulley 58' and rotates with
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396
the pulle~ 58' around a p~ix of bearings 182 and 184 which
are mounted on a non rotati.ng hub 186 mounted to khe
baseplate 48.
The high helix drive sha~t 28 is mounted ~or
rotation in a pair of bearings 188 and 190 mounted on the
inside of the hub 186. The bearings 182 and 188 are secured
by a cap 192 screwed or otherwise secured -to the hub 186.
The shaft 28 is mounted in the bearings 188 and 190 by its
lower end 68'. The lower end 68' of the shaft 28 is secured
to the drive shaft 70 of the motor 40 by a flexible coupl;ing
194. The coupling 194 is rotationally rigid and axially
flexible with the shaft 28 to eliminate motor vibrations
and binding from the operation of the mechanism 10.
The hub 60' includes a Elange 196 to which is
secured a code skirt 198 which extends partially or totally
around the hub 60' depending upon the maximum angle of
.
rotation through`which the arm 26' will be ro-ta-ted. The
code skirt 198 may be read by an optical reader 200 mounted
.on a.plate 202 on the baseplate 48. The code position
~ 20 reader 200 again may be utilized to verify the number of
:~ drive pulses fed to the motor 40 to ensure that the proper.
position has been reached by the probe 24'. The code also
may be utilized as the primary position control for the
arm 24' if desired.
The arm 26' includes the drive nut 44 engaged on
the high helix screw 28'. The upper end of the high helix
screw 28' is not.engaged in the upper retainer 76'. The
upper retainer 76' still includes the downwardly depending
tab 92 cooperating with the reader 90 carried by the arm 26'.
The guide rod 72' is mounted in the hub 60' and retained in
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~51B96
the retainer 76' and slidingly eng~ged through ~he bea~ing
86 t preEerably a ball bushin~ type oE beaxing, for ease of
movement of the arm 26l up and down the guide 'rod 72'.
A second guide'rod 204 has one end mounted in the
hub 60' and the other end in the retainer 76'~ The ~uide
rod 204 is engaged through a passageway 206 in the arm 26',
- which may or may not include a bearing therein. With the
two parallel guide rods ?2 ~ and 2~4, the upper end of the
shaft 28' might cause the movement of the arm 26' to bind
' if the upper end was retained in the retainer 76'. The
second guide rod 204 furthe.r. ensures that the probe 24' '
is properly aligned and the mechanism lQ has the necessary
life and reliabiIity.
The lowermost position of the arm 26' is shown in
phantom at 208, which is the lowest position of the arm 26'.
The'position 208 may be obtained either by countina the drive
pulses to the motor 40, as previously described, or by one
or more other optical readers mounted on the arm 26'
similar to, but spaced from the reader 90 and corresponding
position tabs mounted on the hub 60' ~not shown).
An embodiment of a control circuit 210 o~ the
mechanism 10 is lllustrated in Figure 8. The control circuit
210 may be a portion of the control of the analyzer 12 or may
be a separate control provided with one or more of the
mechanisms 10 as desired. For purposes oE descrip-tion only,
the control 210 will be described as operating with the
level sensing probe 24' with the sample mechanism 10, the
probe 24' with the mechanism 10' and the probe 24 with
the mechanism 10-l. Generally, the analy~er 12 would be
supplied with substantially identical mechanisms 10, 10'
and 10" and hence only one type of probe 24 or 24'. Further
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L896
as pre~iously described, only one mechanism 10 ~ay ~e
operating With the eontrol 210~
Réferring to the mechanism 10 the level sensing
eircuit inclucles an ose.illator 212 whieh supplies a h.igh
frequency output on a pair of lines 214 and 216. There ~lso
could be a separate oscillator 212 with each of the probes
~4' for the meehanisms 10 and 10~. The line 214 c~uples
the high frequency si~nal through a capaci~.or 218 to the
probe 24' on a line 220 and to a resistor 222. When the
probe 24' has its tip 172 above the fluid surface 224, the
eurrent path i5 through the eapaeitor 218 and resistor 222
to ground. This eurrent level or voltage proportional to
eurrent is sensed by a deteetor 226 over a line 228 eoupled
to the junction of the line 220 and the esistor 222. ~hen
the probe tip 172 reaches the sample fluid sur-Eace 224 in
one of the eavities 22 a second eurrent path is formed
through the capacitor 218, the line 220, the probe 24' and
the fluid in the cavity 22 which has a fluid resistanee
230. The eavity 22 may be formed of a conduetive material
or may have an eleetronie ground elosely associated therewith,
which will aet in the same manner as the circuit described
with respect to the mechanism 10'.
By designing the resistanee 222 to be-of a signif-
icantly different magnitude than the fluid resistance 230~
when the probe tip 172 touches the fluid surface the detector
226 will sense the current ehange and couple a level sensing
signal to the control 210 on a line 232. The-control 21V
may utilize this to control the motor 40 to stop the probe
tip 172 from being immersed further in the fluid
;18~6
or to stop the probe a.precise distance!belo~7 the ~luid
surface 224 as desired. Thus, the probe 24' may be utilized
to aspirate or pick up the sample fluid in the cavity 22
without immersing the probe tip 172 comple-tely in the fluid~
without regard to the ~luid level 224 in the caVity 22.
. The level detec-ting circuit of the mechanism 101
is illustrated with the probe 24' in one of the rea~ent .
containers 32, which typically may be formed of glass or
other conventional non conductive material. In this instance
the high frequency signal, for example about 100 kilohertz,
is coupled on the line 216 through a capacitor 234 to a ~. .
resistor 236 and by a line 238 to the probe 24' and the tip
172. When the probe 24' is above the reagent surface 240,
the current path is through the resistor 236 to ground which is
detected on a line 242 by ~ detector 244. The detector 2~4
may be a separate detector or it could be a portion of the
detector 226. When the probe tip 172 contacts the fluid
surface 240 a second current path is established through the
reagent fluid which has a fluid xesistance 246.
The container 32; however, is made of a non
conductive material such as glass and therefore acts as a
capacitance 248. The containers 32 may be placed in a
metallic well or against a metallic grounded surface in
the reagent supply 16 to complete the circuit pakh. Again,
the impedance value of the resistor 236 is chosen to be
significantly different than the impedance provided by the
fluid resistance 246 and the container capacitance 248.
~hen the current path is established by the probe 172
contacting the fluid surface 240,the detector 244 wlll
detect the current difference and couplea level sensing
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sic~nal on a line 250 to the control 210. Ac~ain, the control
210 may insert the tip 172 as ;Ear below -the surEace 240 as
i-t is desirable for the particular operation. The capacitors
218 and 234 and the AC siynal prevent electrolysis of the Fluids.
The mech~nism 10 1~' i5 illustrated with the level
sensing probe 24 having the elec-trical leads 116 and 118.
One of the leads, for instance 118, is coupled to a signal
source 252 which could be identical to the oscillator 212
i desired. In this instance, the line 120 is couple~ to
a detec-tor 254 which will not receive a signal when the
probe ~4 and the ends of the leads 118 and 120 are above the
fluid surface 256. When the leads 118 and 120 contact the
Eluid surEace 2S6 in the reagent container 32, the signal
- from the source 252 on the line 118 will be coupled across
lS the fluid to the lead 120 and will be detected b~ the
detector 254. The detector 254 then couples a level
sensing signal over a line 258 to the control 21Q lndicating
that the tip 116 has reached a known position with respect
to the fluid surface 256, depending on the alignment ~ith
the -leads 118 and 12b.
The other functions of the control 210 are
diagrammatically illustrated for one probe 24. The control
210 will apply the appropriate number of drive pulses to the
motor 38 on a line 260 to rotate the arm and hence the
probe 24 to the proper pick up position. Assuming Eor
example, that this is one o the sample cavities 22 the
control 210 will assume the probe 24 has been rotatecd the
proper distance. The position may be veri:E:ied to see that
the arm 26 and hellce the probe 24 are in the proper positlon
hy reading the position of the code wheel ~8 by the reacler
~` 10~. ~rhe con-trol 210 after determining that the probe 2
-20-
.
~::ILSlB96
is in the proper position above th~ cavity 22 loca~ed in the
pick up position of the mechanism 10, then will provide
drive pulses to the vertical motor 40 over a line 262 -to ,,
drive the probe 24 do~nwardly to the fluid surface.
The level detector will generate a signal when
the probe tip reaches the fluid level which is coupled to
the control 210. The control then will stop the drive
pulses on the line 262 with the prohe tip at or sli~htly
- below the fluid surface. The control 210 will then activate
a fluid-motive source 264 by a line 266. The fluid motive
source 264 may be a syringe drive or other ~luid movincJ
means coupled by appropriate valving to the fluid tubing 114.
The syringe will be driven the appropriate distance to
pick up or aspirate the proper amount of fluid into the
- 15 , probe passageway 108.
The di'mensions of the probes 24 and 24' will be
,chosen so that the sample fluid volume or reagent fluid
volume will be contained en-tirely in the passageway 108 or
probe 166. This substantially eliminates any carry-over
'20 problem when the probes are washed in the probe washer 34.
Once the probe 24 has,aspirated the desired fluid ali~uot,
the control 210 will provide pulses to the motor 40 over the
line 262 to drive it upwardly until the swi-tch 90 is activated
by the tab 92 indicating that the probe 24 and arm 26 are
in the uppermost position. When the arm and hence the probe
24 have reached the uppermost or rotating position the control
210 then will provide the appropriate number of drive pulses
on the line 260 to the motor 38 to rotate the probe 24 to
the dispensing position above the cuvette 20 or other
-21-
.
-
~5~396
reaction vessel located in the dispen$ing position, T~e
angular position again may be verified the code wheel 98.
The probe 24 then is dxiven downwardly to its
lowermost dispensing position, which wi~l be :Eixed b~ a.
switch such as the tab 96 or by the number of drive pul~es
applied to the vertical motor 40. The control 266 then.
indicates to the fluid motive sourcè 264 that the probe 24
is in the dispense position and then the source 264 will
dispense the fluid in the probe 24 and by appropriate valving
also may add an amount of diluent to the sample aliquot in
the cuvette 20. The control 210 will thell activate the
oscillating motor 30 over a line 268 to oscillate the probe
24 back and forth to stir the fluids in the cuvette. 20. The
contxol 210 will deactivate the motor 30 and then drive the
probe 24 to the uppermost position by supplyiny the drive
pulses to the motor 40.
The probe 24 then is rotated by the motor 38 to a
position above the probe washer 34, where it is driven
downwardly by the motor 40 into the probe washer and
externally washed in the probe washer 34. The probe 24 may
be internally washed by coupling a wash f:Luid from the source
264 through the probe passageway 108 or 166. The pxobe then
is driven back up to its uppermost position by the motor 40
where it then is maintained in a ready position :Eor the
next cycle.
-. Many modifications and variations of the present
invention are possible in light of the above teachings~
It is, therefore, to be understood that within the scope of
the appended claims, the invention may be practiced otherwise
than as specifically described.
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