U.S. patent number RE29,880 [Application Number 05/881,842] was granted by the patent office on 1979-01-16 for apparatus for use in investigating specimens.
This patent grant is currently assigned to The Secretary of State for Social Services in Her Britannic Majesty's. Invention is credited to Ian D. Duff.
United States Patent |
RE29,880 |
Duff |
January 16, 1979 |
Apparatus for use in investigating specimens
Abstract
The apparatus comprises a turntable carrying, in a circular
array centered n a central rotational axis of the turntable, a
plurality of vials extending below the underside of the turntable.
A stepper motor imparts stepwise rotational motion to the turntable
so that during dwell periods of the turntable, specimens in the
vials can be investigated optically. Air in a space below the
turntable and bounded laterally and at the bottom by an enclosure
is circulated by a rotating vane, and a thermistor, responsive to
the temperature in the region of the vials, controls a heater in
the space below the turntable so as to maintain the temperature of
the vials substantially at a predetermined value. In order to
dispense liquids into the vessels at predetermined temperatures,
the apparatus additionally includes a liquid dispenser mounted
adjacent the turntable and comprising a tubular body with an
electric heating coil and a dispensing device which dispenses
liquid from the outlet of the tubular body in predetermined
quantities, the heating coil being supplied with the necessary
quantity of power to maintain the temperature of the dispensed
liquid substantially at a predetermined value. Preferably, the
apparatus is used for analyzing blood specimens.
Inventors: |
Duff; Ian D. (Ossining,
NY) |
Assignee: |
The Secretary of State for Social
Services in Her Britannic Majesty's (London,
GB2)
|
Family
ID: |
27258406 |
Appl.
No.: |
05/881,842 |
Filed: |
February 27, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
714677 |
Aug 11, 1976 |
04054416 |
Oct 18, 1977 |
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Foreign Application Priority Data
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Aug 20, 1975 [GB] |
|
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34676/75 |
Jun 11, 1975 [GB] |
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25118/75 |
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Current U.S.
Class: |
422/64; 219/413;
219/428; 219/530; 236/3; 237/3; 392/473; 392/480; 422/109 |
Current CPC
Class: |
B01J
4/02 (20130101); B01L 3/0293 (20130101); B01L
7/02 (20130101); G01N 35/02 (20130101); G01N
35/025 (20130101); G01N 21/00 (20130101); G01N
2035/00425 (20130101); G01N 2035/00386 (20130101) |
Current International
Class: |
B01J
4/02 (20060101); B01L 11/00 (20060101); B01L
7/02 (20060101); B01L 7/00 (20060101); G01N
33/483 (20060101); G01N 21/00 (20060101); G01N
35/02 (20060101); G01N 35/00 (20060101); F27D
011/00 (); B01L 007/02 (); B01L 009/06 (); G01N
001/10 () |
Field of
Search: |
;23/259,253,292
;219/413,428,530 ;236/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Serwin; R.E.
Attorney, Agent or Firm: Reed, Smith, Shaw & McClay
Claims
I claim:
1. Apparatus for use in investigating liquid specimens comprising a
substantially horizontal turntable having a central rotational axis
and being adapted to support a plurality of vessels for liquid
specimens in a circular array centered on the said rotational axis
such that the vessels extend below the underside thereof; means for
stepwise rotation of the turntable for specimen investigation
during dwell periods; an enclosure disposed beneath the turntable
to define a space bounded laterally and at the bottom of said
enclosure and upwardly by the turntable and into which the vessels
extend when positioned in the turntable; temperature changing means
for changing the temperature of air in said space; air circulating
means disposed in said space and arranged to circulate air between
the temperature changing means and the vessels wholly within said
space; a control device for the air temperature changing means
arranged to maintain the temperature of the vessels substantially
at a predetermined value; and a liquid dispenser mounted adjacent
the turntable for dispensing liquid specimens into different
vessels in the turntable during respective dwell periods thereof,
the dispenser comprising a tubular body of a high thermal
conductivity having an inlet through which liquid may enter said
tubular body, and an outlet which comprises a dispensing tip of
high thermal conductivity through which liquid may leave the
tubular body, said tubular body also including a cavity adjacent
said outlet, the dispenser being provided with means for charging
the tubular body with liquid by way of said inlet and for
dispensing predetermined quantities of such liquid, said tubular
body including an electric heating coil, wound around substantially
its length and a thermistor positioned in said cavity to control
said heating coil to maintain the temperature of the liquid being
dispensed substantially at a predetermined value.
2. Apparatus according to claim 1, wherein the tubular body
consists of copper and the heating coil is surrounded by a heat
insulative jacket.
3. Apparatus according to claim 1, wherein the dispensing tip is
removable to enable replacement thereof.
4. Apparatus according to claim 1, wherein the said means for
charging the tubular body with liquid and for dispensing the liquid
in predetermined quantities comprises a first pump operative to
draw a first liquid into the dispenser when the dispensing tip is
immersed in such first liquid, by removing a portion of a second
liquid filling the dispenser so as to fill the dispenser only
partially with such first liquid and also operative to dispense the
first liquid in the dispenser into a vessel in position on the
turntable, and a second pump operative to dispense such second
liquid in the dispenser into the vessel following dispensing of the
first liquid.
5. Apparatus for use in investigating liquid specimens, comprising
a substantially horizontal turntable having a central rotational
axis and being adapted to support a plurality of specimen vessels
in a circular array centered on the said turntable; means for
stepwise rotating the turntable so the specimens may be
investigated during dwell periods; an enclosure disposed beneath
the turntable and having an internal surface symmetrical with the
rotational axis to define a space bounded laterally and at the
bottom by said enclosure and upwardly by said turntable; a baffle
plate disposed within the enclosure to provide between said plate
and the turntable a first space into which said vessels extend when
supported by the turntable, and between the said plate and the base
of the said enclosure a second space, the outer edge of the baffle
plate being separated by an air gap from the peripheral wall of
said enclosure, said baffle plate having a central hole for air to
circulate between the said first and second spaces through said air
gap and said central hole; a rotary vane disposed in the said first
space and mounted with its axis of rotation coincident with that of
the turntable, said vane having at least one cutout portion to
permit relative rotational movement between the turntable with the
vessels in position thereon and the vane, said vane having a shape
conforming substantially to the vertical cross-section of said
first space so that the vane sweeps out a volume substantially
equal to that of the said first space during rotation; air
temperature changing means disposed in said second space; a control
device for the air temperature changing means arranged to maintain
the temperature of the vessels substantially at a predetermined
value; and a liquid dispenser mounted adjacent the turntable for
dispensing liquid specimens into different vessels in the turntable
during respective dwell periods thereof, said dispenser comprising
a tubular body of high thermal conductivity and having an inlet
through which liquid may enter the tubular body and an outelt which
comprises a dispensing tip of high thermal conductivity through
which liquid may leave the tubular body, said tubular body
including a cavity adjacent said outlet; said dispenser being
provided with means for charging the tubular body with liquid by
way of said inlet and for dispensing prodetermined quantities of
such liquid, said tubular body includes an electric heating coil
wound around substantially its length, and a thermistor positioned
in said cavity to control operation of the heating coil to maintain
the temperature of the liquid being dispensed substntially at a
predetermined value.
6. Apparatus for use in investigating liquid specimens, comprising
a substantially horizontal turntable having a central rotational
axis and being adapted to support a plurality of specimen vessels
in a circular array centered on the said rotational axis such that
the vessels extend below the turntable; means for stepwise rotating
the turntable for investigating specimens; during dwell periods of
the turntable an enclosure disposed beneath the turntable and
having an internal surface symmetrical with the rotational axis to
define a space bounded laterally and at the bottom by the enclosure
and upwardly by the turntable; a baffle plate disposed within the
enclosure to provide between said plate and the turntable a first
space into which the vessels extend when supported by the
turntable, and between said plate and the base of said enclosure a
second space, the outer edge of the baffle plate being separated by
an air gap from the peripheral wall of said enclosure and the
baffle plate being formed with a central hole so that air can
circulate between the said first and second spaces by way of the
air gap and said central hole; a rotary vane disposed in the said
first space and mounted with its axis of rotation coincident with
that of the turntable, said vane having at least one cut-out
portion to permit relative movement between the turntable with the
vessels in position thereon and the vane, said vane having a shape
conforming substantially to the vertical cross-sectional of said
first space so that the vane sweeps a volume substantially equal to
that of the said first space during rotation; and air heater
disposed in said second space; a control device for the air heater
including a thermistor mounted to be responsive to the temperature
in the region of the vessel, the control device being arranged to
control operation of the air heater to maintain the temperature of
the vessels substantially at a predetermined value; fan means in
said enclosure arranged to be driven independently of the vane to
maintain sufficient circulation of air within said space bounded by
the said enclosure and the turntable to prevent the air heater from
overheating; and a liquid specimens into different vessels in the
turntable during respective dwell periods thereof, said dispenser
comprising a tubular body of high thermal conductivity and having
an inlet through which liquid may enter, and an outlet which
comprises a dispensing tip of high thermal conductivity through
which liquid may leave the tubular body, said tubular body
including a cavity adjacent to the outlet, said dispenser having
means for charging the tubular body with liquid by way of said
inlet and for dispensing predetermined quantities of such liquid,
said tubular body including an electric heating coil wound around
substantially its length, and a thermistor positioned in said
cavity to control the heating coil to maintain the temperature of
the liquid being dispensed substantially at a predetermined value.
Description
This invention relates to apparatus for use in investigating
specimens.
U.S. patent application Ser. No. 695,032, filed on June 11, 1976,
in the name of Roger Abraham Bunce, relates to apparatus for use in
investigating specimens, comprising a substantially horizontal
turntable having a central rotational axis and being adapted to
support, in a circular array centered on the said rotational axis,
a plurality of vessels, each for containing a specimen to be
investigated, the apparatus further comprising means for advancing
the turntable stepwise about the said rotational axis so that,
during dwell periods of the turntable, specimens may be
investigated, the turntable being adapted to support the vessels in
such manner that they extend downwardly below the underside of the
turntable.
The aforesaid U.S. Patent Application is concerned with the problem
of obtaining high accuracy of analysis of specimens in the vessels
of such apparatus, and recognises that a contributory factor to
achieving the desired high accuracy is ensuring that the
temperature of the vessels is maintained at a predetermined value
to within close limits. To this end, in the specimen investigation
apparatus of the aforesaid application there is a space bounded,
laterally and at the bottom, by an enclosure and limited upwardly
by the turntable so that when the vessels are in position,
supported by the turntable, they extend into the said space, and
wherein there are means provided for changing the temperature of
air in said space and means positioned within said space and
arranged to circulate air between the temperature changing means
and the vessels wholly within said space, the temperaure changing
means being provided with a control device for maintaining the
temperature of the said vessels substantially at a predetermined
value. Hereinafter, such apparatus will be termed "apparatus as
specified".
The present invention represents an improvement in apparatus as
specified and is concerned with taking further measures to control
closely the temperature of the specimens provided in the
vessels.
According to the invention, there is provided apparatus as
specified, comprising a liquid dispenser mounted adjacent the
turntable and operable to dispense liquid into a vessel when in
position on the turntable, the dispenser comprising a tubular body
having an inlet, for receiving liquid to be dispensed, and an
outlet comprising a dispensing tip for dispensing the received
liquid, the dispenser being provided with means for dispensing the
liquid in predetermined quantities and the dispenser also
comprising temperature control means which is so arranged that, in
use, the temperature of the liquid being dispensed is maintained
substantially at a predetermined value.
Preferably, the temperature control means comprise a heating coil,
wound around the tubular body to extend substantially over its
length, and a thermistor, positioned is a cavity in a portion of
the tubular body alongside the dispensing tip and arranged to
control operation of the heating coil. Generally, the tubular body
consists of copper and the heating coil is surrounded by a heat
insulative jacket. The dispensing tip may be removable to enable
replacement thereof.
In a preferred construction for the means for dispensing the liquid
in predetermined quantities, it comprises a first pump operative to
draw a first liquid into the dispenser, when the dispensing tip
thereof is immersed in such first liquid, by removing a portion of
a second liquid filling the dispenser when the apparatus is in use
so as to fill the dispenser only partially with such first liquid
and also operative to dispense the first liquid in the dispenser
into a vessel in position on the turntable, and a second pump
operative to dispense such second liquid in the dispenser into the
vessel following dispensing of the first liquid.
For a better understanding of the invention, and to show how the
same may be carried into effect, reference will now be made, by way
of example, to the accompanying drawings, in which:
FIG. 1 shows a vertical sectional view of one form of specimen
investigation apparatus in the form of an automatic blood analysing
machine,
FIG. 1a is a sectional view of the machine taken along the line
A--A of FIG. 1,
FIG. 1b shows a horizontal sectional view of the machine taken on
the line B--B of FIG. 1 with a cover of the machine removed,
FIG. 2 is a vertical sectional view through a dispenser
incorporated in the blood analysing machine, and
FIG. 3 illustrates diagrammatically an arrangement whereby a
predetermined quantity of a serum or reagent, followed by a
predetermined quantity of diluent, is dispensed through the
dispenser of FIG. 2.
The machine illustrated in FIGS. 1, 1a and 1b is used for
colorimetric, light scattering and fluorimetric evaluation of
reactions between samples of blood and reagent(s), and comprises a
stationary frame 1 which carries a hollow vertical trunnion 2.
Extending coaxially inside the trunnion 2 is a hollow rotatable
shaft 3 which is connected at its upper end by a pulley and belt
arrangement and a gearbox 13 to an electric motor 4 mounted on the
frame 1. The trunnion 2 is surrounded coaxially by a further
rotatable shaft 5 which carries a horizontal turntable 6 at its
lower end and is connected at its upper end by a further pulley and
belt arrangement to a second electric motor 14, which is a stepping
motor.
The turntable 6, which is covered by a stationary cover 17, is
circular, its centre being on the common axis of the trunnion 2 and
the shafts 3 and 5, and has about its periphery a plurality of
equally spaced vials. These vials are removably fitted into notches
in the turntable.
The lower part of the frame 1 is in the form of a cylindrical
enclosure 52 having an inwardly projecting annular flange on the
radially innermost portion of which the cover 7 is positioned. Each
vial extends downwardly from the level of the turntable into the
space bounded laterally and at the bottom by the enclosure and
limited upwardly by the turntable 6. As can be seen in FIGS. 1 and
1a, the diameter of the turntable is slightly greater than the
diameter of the opening in the top of the enclosure 52 and the
turntable is arranged within the enclosure at a very small spacing
below the flange of the enclosure. In this way, the transport of
air between the exterior of the enclosure and its interior and vice
versa is minimal.
The shaft 3 is connected at its lower end, which is below the table
6, to a horizontal arm 7 which extends radially with respect to the
shaft 3. The shaft 3 is also connected to a counterbalance 18 for
the arm 7. The arm 7 carries two fibre optic light guides 8 and 9.
The light guide 8 has an input end at the upper end of the shaft 3
and extends vertically downwards coaxially within the shaft 3. At
the lower end of the shaft 3 the guide 8 extends therefrom radially
outwardly along the arm 7 and has an output end at a position along
the arm which is inward of the periphery of the table 6. The output
end of the guide 8 defines a slit-form output aperture. The guide 9
has an input end which is mounted on the arm 7 outward of the
periphery of the table and aligned with the end of the guide 8. The
input end of the guide 9 defines a slit-form input aperture. The
guide 9 extends from the periphery of the table radially inwards
along the arm 7 and has an output end which is directed vertically
downwards along the axis of the shaft 3. FIG. 1b shows how the
light guide 8 is looped between its radial and axial portions in
order to avoid imposing excessive curvature on the guide. The
arrangement of the guide 9 (not shown in FIG. 1b) is the same.
Above the upper end of the shaft 3 is a lamp 10 arranged to direct
light vertically downwards into a circular input aperture defined
by the input end of the light guide 8. Between the lamp 10 and the
input aperture may be mounted a filter or grating unit for
selecting the wavelength of light entering the input aperture and
thereby enabling different reactions to be evaluated. Radially
outwardly of the output end of the guide 8 is an optical system
comprising a correction slit (not shown), converging lens 11 and a
further correction slit (not shown), for focusing light delivered
by the guide 8 on liquid in a vial. The optical system is clamped
to a horizontal slideway, formed in the arm 7, to facilitate
adjustment. Light which is transmitted by the liquid is received by
the guide 9 at its input end and is delivered to its output end
from which it is directed vertically downwards, along the axis of
the shaft 3, to a photomultiplier 12.
The shaft 3 is also connected at its lower end to a vane 57
arranged within the space bounded by the enclosure and turntable
and spaced angularly from the arm 7, about the vertical axis of
rotation of the shaft 3, by 90.degree.. The vane consists
essentially of two rectangular plates which are arranged so that
the longer and shorter edges of the rectangular faces of the plates
are respectively radially and axially disposed relative to the
shaft 3. The vane is formed with cut-out portions 63 which are
slightly larger than, but conform approximately to the shape of,
the vials. This enables the vane 57 to be rotated with its upper
edge close to the underside of the turntable while at the same time
ensuring that rotation of the vane is not impeded by the vials. In
addition, the overall length end-to-end is only slightly less than
the internal diameter of the peripheral wall of the enclosure.
Arranged beneath the vane of radial supporting plates 61 and with a
small spacing from the vane is a horizontal annular plate 58 whose
central opening 59 is coaxial with the shafts 5 and 6 and whose
greater diameter is less than the length of the vane 4 from
end-to-end in order to leave an annular air gap 62 between the
outer edge of the annular plate 58 and the peripheral wall of the
enclosure. Electric heaters 60, arranged in the form of concentric
rings, are positioned in the space between the base of the
enclosure and the plate 8 and extend through openings in the
supporting plates 61. A thermistor (not shown), positioned within
the enclosure close to the vials and responsive to the temperature
within the space limited by the plate 58, turntable 6 and
peripheral wall of the enclosure, is arranged to control the power
supplied to the heaters 10 and thereby regulate the quantity of
heat generated by the heaters so as to maintain the temperature
within the space, and thereby that of the vials, at a predetermined
value.
Dispensing means are provided on the flange of the enclosure 52
adjacent the periphery of the turntable 6 whereby, at a first
station, a predetermined quantity of blood, together with a
predetermined quantity of diluent, is dispensed into a vial when
the turntable is at rest between stepwise rotational advancements
and, at a second station, when the turntable is again at rest,
predetermined quantities of reagent and diluent are dispensed into
a vial containing blood and diluent, from the first station. For
this purpose a dispenser 100, to be described in detail hereinbelow
with reference to FIG. 2, is provided at each station. The
dispenser is mounted on a support member 101 and is vertically
displaceable to allow itself to be raised clear of the vial so that
the turntable can undergo its stepwise rotational advancement. The
support member 101 can be swung to one side to guide the probe over
a container of blood or reagent. The dispenser is lowered into the
container and a measured quantity of blood or reagent is drawn in.
When the turntable next comes to rest, the dispenser is returned to
its lowered position in another vial and the measured quantity is
dispensed, followed by a measured quantity of diluent, into the
vial.
When the blood analysing machine is in operation, the turntable 6
is rotated stepwise by the motor 14 past the dispensing means,
whereat a sample of blood and a quantity of reagent (and possibly
also diluent and/or dye) is placed in a different vial, as has just
been explained, during each dwell period of the turntable 6 between
successive stepwise rotational advancements of the table. At the
same time, the motor 14 is caused to rotate the shaft 3 through at
least one revolution during each dwell period, thus causing the arm
7 to rotate so that the light beam from the light guide 8 scans the
vials in succession and the light transmitted by the liquids in the
vials is received by the light guide 9 and passed to the
photomultiplier 12 which provides an output voltage, the magnitude
of which depends upon the intensity of light received by the guide
9. At the same time as the vials are scanned in succession, the
vane 57 rotates with the arm 7 and in doing so it sweeps out the
space limited by the plate 58, the turntable 6 and the peripheral
wall of the enclosure and causes the air in this space to rotate.
Owing to centrifugal force, the air passes around the individual
vials in the radially outward direction, downwardly through the
annular air gap 62 between the plate 58 and peripheral wall of the
enclosure, radially inwardly to pass around the electrical heaters
10, and then upwardly and radially outwardly again. At the same
time, the air cirulates about the vertical axis of the vane 57.
Thus a circulating air pattern is set up as indicated in FIGS. 1
and 1a. The thermistor ensures that the vials, and thus the
specimens, are maintained at a predetermined temperature to within
close limits.
The air flow pattern achieved within the enclosure is very
effective in reducing temperature fluctuations in the region of the
vials projecting downwardly into the enclosure. In fact, following
investigation, it has not been possible to measure any such
temperature fluctuations but a maximum value of .+-.0.05.degree. C
has been estimated. In a typical form of blood analysing machine,
the thermal time constant of the machine is about 30 seconds and
the maximum input power consumed is about 200 watts.
The photomultiplier 12 is connected to a computer (not shown) which
stores a set of data for each revolution of the shaft 3,
representing the output voltage of the photomultiplier 12 for each
of the vials. When the shaft 3 is rotated at least twice during
each dwell period, the computer uses the several sets of data to
form a mean value for the output voltage of the photomultiplier in
respect of each vial. In practice, it is more convenient to rotate
the motor 4 continuously rather than for it to rotate only during
each dwell period of the turntable 6. Then, the computer is
arranged so as to disregard the data received during each stepwise
rotational advancement of the turntable 6 between successive dwell
periods. Furthermore, the computer 4 is so arranged that if during
each dwell period the shaft 3 rotates through a non-integral number
of revolutions the computer accepts data only for the nearest
integral number of revolutions of the shaft, below the actual
number of revolutions undergone.
In the circumstances, therefore, the illustrated machine is used
for colorimetric analysis of the blood samples. By making a slight
modification, however, the machine may be used for light scattering
of fluorimetric analysis of the blood samples. The modification is
shown in broken lines in FIG. 1 and entails replacing the light
guide 9 by a guide 9' whose input end is vertically below the vial
and perpendicular to the output end of the guide 8 and placing a
colour filter between the output end of the light guide 9' and the
photomultiplier 12. Then the output voltage of the photomultiplier
depends upon the intensity with which light from the guide 8 in a
selected wavelength band, predetermined by the filter, leaves the
vial.
Referring to FIG. 2, the dispenser 100 will now be described. It
comprises an upright tubular body 102 of metal having at its upper
part an inlet connection stub 103 to which a flexible inlet pipe
104 for liquid supplied to the dispenser is connected.
A heating coil 106 is wound around the tubular body to extend
substantially over its length. The heating coil is in turn
surrounded by cylindrical jacket 107 of heat insulative material
which seats at its upper end against an annular shoulder 108 of the
tubular member and of which two opposite annular surfaces 109
engage with a collar 105 formed at the lower end of the tube.
The tubular body 102 is formed in the collar 105 at the lower end
of the tube with a bore which is concentric with the axis of the
tubular body and of slightly larger diameter than the internal
diameter of the body. Into the bore is fitted a replaceable
dispensing tip 110 that may have a stainless steel insert to reduce
the volume of the space provided within the dispensing tip and not
heated. The tip 110 projects downwardly beyond the lower end of the
tubular member and heat insulative jacket 107. The collar 105 is
formed with a cavity to receive a thermistor 111 which is arranged
to control the quantity of current supplied to the electrical
heating coil so as to maintain the dispensed liquid substantially
at a predetermined temperature.
In operation, a dispenser 100 is provided at a first dispensing
station at which a sample of unheated serum together with a
quantity of heated diluent is placed into a single vial during one
dwell period of the turntable between successive stepwise
rotational advancements of the turntable. This is achieved by
sucking into the dispenser filled with diluent a quantity of serum
which is sufficiently small that it is contained entirely within
the dispensing tip, and then dispensing the diluent and serum.
Simultaneously, a second dispenser 100 at a second station places a
quantity of heated reagent together with a quantity of heated
diluent into another vial. The procedure is much the same as in the
case of the first station except that a sufficiently large quantity
of reagent is sucked in to fill the dispensing tip completely and
partially fill the tube so that the reagent becomes heated too. The
position of the latter vial with respect to the first one is chosen
such that the stepwise advancements of the turntable cause each
vial to move from the serum/diluent dispenser to the
reagent/diluent dispenser. To dispense the liquids, each dispenser
100 is displaced downwardly until the dispensing tip 110 is
positioned near to the bottom of the vial and touching one wall of
the vial in order to avoid the formation of droplets at the lower
end of the dispensing tip. After the liquid contents of each tube
assembly have been dispensed, the dispenser is raised to its upper
position in which the dispensing tip is clear of the vial and then
the turntable is indexed by one step, after which the dispenser is
displaced downwardly again into the next vial, and so on.
One convenient way of supplying the diluent to the dispenser and
causing the serum and reagent to be sucked in and the whole
contents subsequently dispensed is to use the arrangement
illustrated very diagrammatically in FIG. 3 of accompanying
drawings. This comprises a diluent pump 120 having an inlet
supplied through a non-return valve V1 and an outlet with a
non-return valve V2, and a syringe pump 121, these two pumps
discharging into a common output connection 122 supplying the
dispenser 100 by way of the flexible pipe 104. In operation, the
pumps undergo a cycle commencing in the position shown in FIG. 3.
The dispensing tip is positioned in the serum or reagent and the
syringe pump 121 undergoes a half revolution to suck into the
dispenser a measured quantity of serum or reagent, determined by
the stroke of the pump. After the dispensing tip has been
repositioned for dispensing the diluent and serum or reagent, the
syringe pump 121 completes its cycle to dispense the serum or
reagent and this is immediately followed by the diluent pump 120
undergoing a half revolution to dispense the heated diluent in a
predetermined quantity governed by the stroke of the diluent pump.
Finally, the cycle is completed by the diluent pump undergoing
another half revolution to recharge its cylinder with fresh
diluent.
As an example, at the serum dispensing station either 5 .mu.l or 25
.mu.l of serum at ambient temperature is to be mixed with preheated
diluent from the dispenser to give a total volume of 150 .mu.l. The
serum and diluent are dispensed into a vial at the particular
temperature determined by the thermistor controlling the heaters
60. The vial of course has a finite thermal capacity and so will
affect the temperature of the liquid mixture. After one minute the
reagent and diluent are added and it is not until then that an
accurately controlled temperature is required. At this time the
mixture of serum and diluent should be within .+-.0.05.degree. C of
the temperature within the enclosure. It has been shown
experimentally that this condition will be achieved providing that
the diluent at the serum dispensing station is preheated to within
.+-.0.5.degree. C of the required temperature, a requirement that
can be satisfied using a solid copper tubular body in the
dispenser.
At the reagent dispensing station, 50 .mu.l of reagent at 4.0 .+-.
0.5.degree. C is dispensed with 300 .mu.l of preheated diluent from
the dispenser into the vial. The dispenser is required to dispense
every 6 seconds and so it will generally be possible to control the
mean temperature of the dispensed mixture with good precision,
although considerable temperature gradients may be present within
the heated diluent. Experiments suggest that control to within
.+-.0.2.degree. C for the dispensed reagent and diluent (that
includes errors caused by incorrect reagent temperature) should be
possible. This would produce a maximum initial error of
0.15.degree. C in the reaction mixture which would reduce to an
error of 0.1.degree. C within 30 seconds.
In some applications the addition of more than one reagent may be
desirable. In such cases the conditions required at the additional
reagent dispensing station(s) are not as stringent. They depend
upon time of addition and quantity added. It should be noted that
if the addition of further reagent(s) were immediately to follow
dispensing of the first reagent, difficulties may be encountered
since any errors would add directly to those already present, no
time being allowed for correction of errors by the preheated
vials.
Thus, with the blood analysing machine described, the vials are
maintained at a closely controlled temperature and, in addition, so
also are the serum, reagent and diluent when they are dispensed.
Thus, the reactions which take place between the blood and reagent
occur under precisely controlled temperatures, so that the data
obtained from the blood analysing machine assists in highly
accurate analysis of the blood samples.
With reference to FIGS. 1 and 1a, in a modification, a fan 70 is
mounted centrally within the enclosure to extend from the lower
edge of the vane 57 to the bottom of the enclosure. This fan is
driven independently of the rotating arm 7 and vane 57. The purpose
of the fan is to ensure some circulation of air within the
enclosure even when the arm 7 and vane 57 are at rest, so as to
avoid the possibility of the heaters 60 overheating owing to the
thermistor controlling them being situated close to the vials.
Although the use of the arrangement described with reference to
FIG. 3 to supply the dispenser 100 is preferred, it would be
possible to use one dispenser for dispensing the first quantity of
diluent, another for the serum, a third one for the second quantity
of diluent, and a fourth dispenser for the reagent. The means for
supplying each dispenser would then be required merely to supply a
measured quantity of diluent, serum or reagent at the appropriate
intervals of time.
* * * * *