Syringe pump abstract
A pressure sensor is connected to an intermediate portion of an
air pipe that connects a syringe pump to a spotting nozzle of a
spot fixing device. The syringe pump consists of a syringe and a
plunger that slides up and down in the syringe, for sucking and
discharging a liquid through the spotting nozzle. While moving the
plunger in the same work range as in the actual sucking discharging
operation, internal pressure of the syringe pump is measured by
the pressure sensor, and derivative values of the measure pressure
are obtained by differentiation. The derivative values are compared
with threshold values, to detect disorder of the syringe pump, such
as leakage caused by insufficient air-tightness of the syringe to
the plunger or some defect in the plunger.
Syringe pump claims
1. A method of detecting disorder of a syringe pump comprising
a cylindrical syringe and a plunger sliding inside said syringe,
said method comprising steps of: connecting an open pipe system
to a vent port of said syringe; measuring pressure in said open
pipe system while moving said plunger relative to said syringe;
obtaining derivative values of the measured pressure; and judging
disorder of said syringe pump based on said pressure derivative
values.
2. A method of detecting disorder of a syringe pump as claimed
in claim 1 wherein pressure of said open pipe system is measured
while moving said plunger relative to said syringe in a working
range used in an actual operation of said syringe pump.
3. A method of detecting disorder of a syringe pump as claimed
in claim 1 wherein disorder of said syringe pump is judged by comparing
said pressure derivative values with predetermined threshold values.
4. A method of detecting disorder of a syringe pump comprising
a cylindrical syringe and a plunger sliding inside said syringe,
said syringe pump being connected to a spot fixing nozzle to supply
sucking and discharging pressure to said spot fixing nozzle for
causing said spot fixing nozzle to suck and discharge a liquid through
its tip or through a nozzle tip attached to the tip of said spot
fixing nozzle, to fix a spot of said liquid on a sampling material,
said method comprising steps of: connecting a pressure sensor to
a pressure system that is connected between said spot fixing nozzle
and said syringe pump; obtaining pressure derivative values by differentiating
pressure signals output from said pressure sensor while said plunger
is being moved relative to said syringe; and judging disorder of
said syringe pump based on said pressure derivative values.
5. A method of detecting disorder of a syringe pump as claimed
in claim 4 wherein said pressure sensor outputs the pressure signal
while said plunger is being moved relative to said syringe, with
the tip of said spot fixing nozzle open.
6. A method of detecting disorder of a syringe pump as claimed
in claim 4 wherein said pressure sensor outputs the pressure signal
while said plunger is being moved relative to said syringe in a
working range used in an actual operation of said syringe pump.
7. A method of detecting disorder of a syringe pump as claimed
in claim 4 wherein disorder of said syringe pump is judged by comparing
said pressure derivative values with predetermined threshold values.
8. A liquid sucking discharging device comprising: a syringe pump
comprising a cylindrical syringe and a plunger sliding inside said
syringe; an open pipe system connected to a vent port of said syringe;
a pressure sensor for measuring pressure in said open pipe system;
a differentiation device for differentiating pressure signals output
from said pressure sensor; and a judging device for judging disorder
of said syringe pump base on pressure derivative values obtained
by said differentiation device.
9. A liquid sucking discharging device as claimed in claim 8 wherein
said open pipe system comprises a nozzle that sucks and discharges
a liquid, and a pipe connecting said nozzle to the vent port of
said syringe pump.
10. A liquid sucking discharging device as claimed in claim 8
wherein said pressure sensor detects the pressure in said open pipe
system while said plunger is being moved relative to said syringe
in a working range used in an actual operation of said syringe pump,
with the tip of said nozzle open.
11. A liquid sucking discharging device as claimed in claim 8
wherein said judging device judges disorder of said syringe pump
by comparing said pressure derivative values with predetermined
threshold values.
12. A liquid sucking discharging device comprising: a spot fixing
nozzle that sucks and discharges a liquid through its tip or through
a nozzle tip attached to the tip of said spot fixing nozzle, to
fix a spot of said liquid on a sampling material; a syringe pump
connected to said spot fixing nozzle to supply sucking and discharging
pressure to said spot fixing nozzle, said syringe pump comprising
a cylindrical syringe and a plunger sliding inside said syringe;
a pressure sensor connected to a pressure system that is connected
between said spot fixing nozzle and said syringe pump; a differentiation
device for differentiating pressure signals output from said pressure
sensor, to obtain pressure derivative values; a judging device for
judging disorder of said syringe pump base on said pressure derivative
values.
13. A liquid sucking discharging device as claimed in claim 12
wherein said pressure sensor outputs the pressure signals while
said plunger is being moved relative to said syringe in a working
range used in an actual operation of said syringe pump, with the
tip of said spot fixing nozzle open.
14. A liquid sucking discharging device as claimed in claim 8
wherein said judging device judges disorder of said syringe pump
by comparing said pressure derivative values with predetermined
threshold values.
15. A biochemical analyzer comprising: a spot fixing nozzle that
sucks and discharges a liquid through its tip or through a nozzle
tip attached to the tip of said spot fixing nozzle, to fix a spot
of said liquid on a sampling material; a syringe pump connected
to said spot fixing nozzle to supply sucking and discharging pressure
to said spot fixing nozzle, said syringe pump comprising a cylindrical
syringe and a plunger sliding inside said syringe; a measuring device
that projects measuring light onto said sampling material to measure
light reflected from or transmitted through said sampling material,
and makes quantitative analysis based on the results of measurement;
a pressure sensor connected to a pressure system that is connected
between said spot fixing nozzle and said syringe pump; a differentiation
device for differentiating pressure signals output from said pressure
sensor, to obtain pressure derivative values; a judging device for
judging disorder of said syringe pump base on said pressure derivative
values.
16. A biochemical analyzer as claimed in claim 15 wherein said
pressure sensor outputs the pressure signals while said plunger
is being moved relative to said syringe in a working range used
in an actual operation of said syringe pump, with the tip of said
spot fixing nozzle open, and said judging device judges disorder
of said syringe pump by comparing said pressure derivative values
with predetermined threshold values.
17. A biochemical analyzer as claimed in claim 16 further comprising
a warning device that goes off a warning when said syringe pump
is judged to be disordered.
Syringe pump description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of detecting disorder
of a syringe pump, a liquid sucking discharging device and a biochemical
analyzer. More particularly, the present invention relates to a
liquid sucking discharging device, a biochemical analyzer, and a
method of detecting disorder or malfunction of a syringe pump that
is used in the liquid sucking discharging device for fixing a spot
of a specimen such as blood or urine on a sampling material such
as a dry type analyzing element or an electrolyte slide.
BACKGROUND ARTS
[0002] Medical institutions and laboratories have recently been
demanded to analyze an enormous number of specimens. For quantitative
analysis of chemical components and the like as contained in the
specimens, it becomes popular to use biochemical analyzers that
carry out the quantitative analysis through colorimetry using dry
type chemical analyzing elements, and/or potentiometry using electrolyte
slides, or called dry type ion selection electrode filmstrips, because
the dry type analyzing elements and the electrolyte slides permit
the quantitative analysis of a particular chemical component or
a particular formed component of a specimen just by fixing a spot
of the specimen on them. For example, a desktop type biochemical
analyzer has been brought into the market under a trade name Fuji
Drychem 3500 that is produced by the present applicant.
[0003] The calorimetric biochemical analyzer fixes a spot of a
specimen on a dry type analyzing element and then keeps the dry
type analyzing element at a constant temperature for a given time
in an incubator, to induce a color reaction or pigment producing
reaction. Thereafter, the dry type analyzing element is illuminated
with a measuring illumination light containing a light component
of a predetermined wavelength, to measure optical densities of the
analyzing element. A density value of a biochemical material can
be determined based on the measured optical densities. On the other
hand, a potentiometeric biochemical analyzer does not measure optical
densities, but determines a density value of a material by potentiometeric
quantitative analysis on ion activity of a particular ion contained
in the specimen fixed on a pair of electrodes consisting of two
dry ion selection electrodes of the same kind.
[0004] In either method, the biochemical analyzer uses a liquid
sucking discharging device for fixing a spot of a specimen on a
sampling material, like the dry type analyzing element or the electrolyte
slide. The liquid sucking discharging device is provided with a
spotting nozzle and a sucking discharging pump for supplying the
spotting nozzle with a sucking pressure and a discharging pressure.
The specimen is generally a liquid and contained in a sampling cup
when placed in the biochemical analyzer. The spotting nozzle is
movable vertically and horizontally and, if necessary, a single-use
nozzle tip is fitted on a tip of the spotting nozzle. The spotting
nozzle sucks the specimen from the sampling cup and then moves to
a dripping position above the sampling material, to discharge the
specimen a given amount to fix it as a spot on the sampling material.
As a sucking discharging pump constituting the liquid sucking discharging
device, a syringe pump is known, which consists of a syringe and
a plunger sliding in the syringe.
[0005] In the above described biochemical analyzer, if any leak
is caused by some defect such as insufficient sealing or air-tightness
of the pressure system of the liquid sucking discharging device,
the device cannot normally suck and discharge the specimen, which
comes up with a malfunction and lowers the accuracy of measurement.
In order to let the spotting nozzle suck and discharge a given amount
of liquid with accuracy, it is necessary to detect leakage in the
pressure system. According to Japanese Laid-open Patent Application
No. 2000-258437 a pressure sensor is connected to a pressure system
for a spotting nozzle of a biochemical analyzer. On detecting pressure,
a tip of a spotting nozzle is closed, and a plunger of a sucking
discharging pump is stopped at several points during an operation
to apply a sucking pressure and a discharging pressure. The pressure
sensor measures the pressure at the time points when the plunger
stops.
[0006] A liquid dispensing apparatus disclosed in Japanese Laid-open
Patent Application No. 2002-350453 sucks and discharges a test
liquid, to judge that the dispensing apparatus is normal when a
liquid level of the discharged test liquid is within a tolerance
range around a normal liquid level. If the liquid level of the discharged
test liquid is out of the tolerance range, the dispensing apparatus
is judged to be in trouble such as leakage.
[0007] Meanwhile, as disclosed in the above mentioned Japanese
Laid-open Patent Application No. 2000-258437 it is usual to detect
the trouble like the leakage based on variations in pressure measured
as detection signals from the pressure sensor. Since it is hard
to detect a small pressure variation from the detection signal,
Japanese Laid-open Patent Application No. Hei 8-114605 suggests
a sampling method wherein pressure derivative values are calculated
by differentiating detection signals from a pressure sensor, and
are compared with a reference value, so as to detect even a small
variation in pressure.
[0008] However, according to the leak detection method disclosed
in the above Japanese Laid-open Patent Application No. 2000-258437
the pressure is measured while the tip of the spotting nozzle is
closed, so the leak detection is carried out under different conditions
from where actual sucking discharging operation is carried out.
Besides, since the pressure is detected while the plunger stops,
it is impossible to detect the leakage that may occur while the
plunger is moving for the sucking discharging operation. Furthermore,
Japanese Laid-open Patent Application No. 2000-258437 merely discloses
the leakage caused by insufficient sealing of the syringe to the
plunger, but does not consider such leakage as caused by some malfunction
of the plunger itself.
[0009] On the other hand, according to the method disclosed in
the above mentioned Japanese Laid-open Patent Application No. 2002-350453
it is necessary to suck and discharge the test liquid for the sake
of detecting the leakage. This method is inefficient and costly
because it uses the test liquid. Also the method disclosed in the
above mentioned Japanese Laid-open Patent Application No. Hei 8-114605
has a problem that it cannot detect leakage of a syringe because
the pressure is measured while a tip of the nozzle is brought into
contact with the liquid, to determine the liquid surface based on
the derivative value calculated from the pressure detection signal.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, a primary object of the present
invention is to provide a method of detecting malfunctions of a
syringe pump of a liquid sucking discharging device, the liquid
sucking discharging device, and a biochemical analyzer using the
liquid sucking discharging device, which can detect malfunctions
of the liquid sucking discharging device caused by some disorder
in a syringe or a plunger of the syringe pump.
[0011] To achieve the above and other objects in a method of detecting
disorder of a syringe pump comprising a cylindrical syringe and
a plunger sliding inside the syringe, the present invention suggests
comprising steps of connecting an open pipe system to a vent port
of the syringe; measuring pressure in the open pipe system while
moving the plunger relative to the syringe; obtaining derivative
values of the measured pressure; and judging disorder of the syringe
pump based on the pressure derivative values.
[0012] It is preferable to measure the pressure of the open pipe
system while moving the plunger relative to the syringe in a working
range used in an actual operation of the syringe pump.
[0013] According to a preferred embodiment, disorder of the syringe
pump is judged by comparing the pressure derivative values with
predetermined threshold values.
[0014] In order to detect disorder of a syringe pump that is connected
to a spot fixing nozzle to supply sucking and discharging pressure
to the spot fixing nozzle for causing the spot fixing nozzle to
suck and discharge a liquid through its tip or through a nozzle
tip attached to the tip of the spot fixing nozzle, to fix a spot
of the liquid on a sampling material, the method of the present
invention comprises steps of connecting a pressure sensor to a pressure
system that is connected between the spot fixing nozzle and the
syringe pump; obtaining pressure derivative values by differentiating
pressure signals output from the pressure sensor while the plunger
is being moved relative to the syringe; and judging disorder of
the syringe pump based on the pressure derivative values.
[0015] It is preferable to open the tip of the spot fixing nozzle
while pressure sensor outputs the pressure signal. It is also preferable
to move the plunger relative to the syringe in a working range used
in an actual operation of the syringe pump, when to obtain the pressure
signals from the pressure sensor.
[0016] A liquid sucking discharging device of the present invention
comprises a syringe pump comprising a cylindrical syringe and a
plunger sliding inside the syringe; an open pipe system connected
to a vent port of the syringe; a pressure sensor for measuring pressure
in the open pipe system; a differentiation device for differentiating
pressure signals output from the pressure sensor; and a judging
device for judging disorder of the syringe pump base on pressure
derivative values obtained by the differentiation device.
[0017] The open pipe system comprises a nozzle that sucks and discharges
a liquid, and a pipe connecting the nozzle to the vent port of the
syringe pump.
[0018] The nozzle can be a spot fixing nozzle that sucks and discharges
a liquid through its tip or through a nozzle tip attached to the
tip of the spot fixing nozzle, to fix a spot of the liquid on a
sampling material. In that case, the pressure sensor is connected
to a pressure system that is connected between the spot fixing nozzle
and the syringe pump. It is preferable to output the pressure signal
while the plunger is being moved relative to the syringe in a working
range used in an actual operation of the syringe pump, with the
tip of the spot fixing nozzle open.
[0019] A preferable biochemical analyzer is produced by use of
the liquid sucking discharging device of the present invention.
[0020] The method of the present invention makes sure to detect
any small variations in pressure based on the pressure derivative
values with high accuracy, so that any malfunctions of the liquid
sucking discharging device caused by some disorder in the syringe
or the plunger of the syringe pump may be detected without fail.
[0021] Because the disorder of the syringe pump is detected based
the pressure that is measured while moving the plunger of the syringe
pump in the same work range as in the actual sucking discharging
operation, and with the tip of the spotting nozzle open, like in
the actual operation, it becomes possible to detect such disorders
or malfunctions that can occur during the actual sucking discharging
operation.
[0022] By comparing the pressure derivative values with a threshold
value that is predetermined to detect the defective sealing of the
syringe, and a second threshold value that is predetermined to detect
the defect in the plunger such as leaning of the plunger or insufficient
roundness of the plunger, it becomes possible to detect the leakage
in the respective cases with reliability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other objects and advantages will be more
apparent from the following detailed description of the preferred
embodiments when read in connection with the accompanied drawings,
wherein like reference numerals designate like or corresponding
parts throughout the several views, and wherein:
[0024] FIG. 1 is a schematic diagram illustrating a biochemical
analyzer according to an embodiment of the present invention;
[0025] FIG. 2 is a perspective diagram illustrating essential parts
of a spot fixing device of the biochemical analyzer of FIG. 1;
[0026] FIG. 3 is a sectional diagram illustrating the spot fixing
device as subjected to leak detection;
[0027] FIG. 4 is a perspective diagram illustrating the spot fixing
device as subjected to leak detection;
[0028] FIG. 5 is a graph illustrating detection results in a normal
condition of the spot fixing device;
[0029] FIG. 6 is a graph illustrating detection results in an abnormal
condition where leakage is caused by defective sealing of a syringe
of a syringe pump of the spot fixing device; and
[0030] FIG. 7 is a graph illustrating detection results in an abnormal
condition where leakage is caused by a defect in a plunger of the
syringe pump of the spot fixing device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] In FIG. 1 a biochemical analyzer 10 is provided with a
main cartridge holder 11 holding a plural number of cartridges 3
each of which contains a dry type analyzing element 1 made of a
dry type analyzing film chip, an incubator 12 disposed on one side
of the main cartridge holder 11 an element carrier 13 for carrying
the dry type analyzing element 1 from the main cartridge holder
11 to the incubator 12 a specimen holder 14 for holding sampling
cups 31 containing specimens, for example, urine or serum, a first
spot fixing device 15 for spotting the specimen as held in the specimen
holder 14 onto the dry type analyzing element 1 while the dry type
analyzing element 1 is carried by the element carrier 13 to the
incubator 12 and a measuring device 16 disposed blow the incubator
12. The incubator 12 keeps the dry type analyzing element 1 at a
constant temperature for a given time, to induce a color reaction
of the specimen spotted on the dry type analyzing element 1. Thereafter,
the measuring device 16 projects light onto the dry type analyzing
element 1 to measure optical density of the specimen based on light
reflected from or transmitted through the dry type analyzing element
1. Quantitative analysis is carried out based on the optical density.
The main cartridge holder 11 the incubator 12 the element carrier
13 the specimen holder 14 the first spot fixing device 15 and
the measuring device 16 constitute a colorimetric system or general
measuring system.
[0032] The biochemical analyzer 10 is further provided with an
electrolyte slide storage 21 storing electrolyte cartridges 4 containing
electrolyte slides 2 as dry type analyzing elements for potentiometry,
a second element carrier 22 for carrying the electrolyte dry type
analyzing element 2 from the electrolyte cartridge 4 to a spot fixing
position, a second spot fixing device 23 for spotting the specimen
as held in the specimen holder 14 onto the electrolyte dry type
analyzing element 2 a third spot fixing device 24 for spotting
a referential fluid as held in a referential fluid container 32
onto the electrolyte dry type analyzing element 2 and a potentiometer
25 disposed in front of the spot fixing position for the electrolyte
dry type analyzing element 2 for measuring a potential difference
while keeping the electrolyte dry type analyzing elements 2 at a
constant temperature for a given time. The electrolyte slide storage
21 the second element carrier 22 the second spot fixing device
23 the third spot fixing device 24 and the potentiometer 25 constitute
a potentiometry system. Besides the first and second spot fixing
devices 15 and 23 a tip supplier 26 is disposed, which has a tip
rack 39 holding nozzle tips 38 in a sequence, wherein the nozzle
tips 38 are formed as pipettes and are attached to tips of spotting
nozzles 36 and 37 of the spot fixing devices 15 and 23.
[0033] The specimen holder 14 is provided with a rotary specimen
table 30 which is loaded with a plural number of sampling cups
31 arranged in circles around its rotary center, so that the sampling
cups 31 are placed in turn at a supply position.
[0034] The tip supplier 26 drives a diluting container 40 which
is provided with an array of recesses to serve as cups, to slide
in a lateral direction in addition to the tip rack 39. The movement
of the tip supplier 26 is controlled such that the nozzle tip 38
or the recess of the diluting container 40 is placed underneath
the nozzle 36 or 37 as they are placed above the tip supplier 26.
[0035] The first spot fixing device 15 has the spotting nozzle
36 at a tip of a sampling arm 42 that is mounted to be able to turn
about and move up and down. The spotting nozzle 36 sucks the specimen
from the sampling cup 31 on the rotary specimen table 30 moves
to a spot fixing position to drip and fix a spot of the specimen
on the dry type analyzing element 1 that is held on a carriage member
13a of the element carrier 13. A diluting fluid holder 44 is located
beside the rotary specimen table 30 permitting diluting the specimen
in the diluting container 40 before dripping it on the dry type
analyzing element 1 according to measurement items. The structure
of the sampling arm 42 will be concretely described later. After
each spot fixing, the nozzle tip 38 is changed and thrown away in
a not-shown disposal box.
[0036] The second spot fixing device 23 also has a sampling arm
46 like the sampling arm 42 which is mounted to be able to turn
about and move up and down, and has at its tip the spotting nozzle
37 that sucks and discharges the specimen, and the nozzle tip 38
is attached to a tip of each spot fixing nozzle 37 to suck the
specimen from the sampling cup 31 on the rotary specimen table 30
and move to the spot fixing position to drip and fix a spot of the
specimen on the electrolyte dry type analyzing element 2.
[0037] The third spot fixing device 24 also has an arm 48 that
is mounted to be able to turn about and move up and down. The arm
48 holds at its one end a spotting nozzle 51 that sucks the referential
fluid from the referential fluid container 32 and drips it to fix
a spot of the referential fluid on the electrolyte dry type analyzing
element 2. The potentiometer 25 measures a potential difference
between the specimen and the referential fluid on the electrolyte
dry analysis elements 2. After being used, the electrolyte dry analysis
elements 2 are thrown away in a not-shown disposal box.
[0038] The first spot fixing device 15 is configured as shown in
detail in FIG. 2. The first spot fixing device 15 is constituted
of the spotting nozzle 36 the sampling arm 42 a spline shaft 62
a belt wheel 63 a belt 65 a first motor 64 a flange 66 a belt
67 a second motor 68 an air pipe 69 a syringe pump 70 a transmission
member 73 a drive gear 74 and a third motor 76.
[0039] The sampling arm 42 holds at its first end the spotting
nozzle 36 to be movable up and down. The spline shaft 62 is oriented
vertical, supporting the sampling arm 42 at its second end to keep
it horizontally. The belt wheel 63 is provided with a hook that
is engaged in a groove 62a formed in a peripheral wall of the spline
shaft 62 along its axial direction, so that the belt wheel 63 is
fixed in a rotational direction but is movable in the axial direction
relative to the spline shaft 62. One end of the belt 65 is suspended
around the belt wheel 63. The first motor 64 drives the belt 65
to move in a direction of an arrow A, to rotate the belt wheel 63
in a given direction by a given amount. The flange 66 is mounted
to a bottom end of the spline shaft 62 and the belt 67 is affixed
to a side wall of the flange 66 by a screw. The belt 67 is moved
by the second motor 68 in a direction of an arrow B, to move the
spline shaft 62 a given amount up or down.
[0040] The air pipe 69 is mounted in the sampling arm 42 with
one end 69a connected to one end 36a of the spotting nozzle 36
which protrudes toward the first end of the sampling arm 42. The
air pipe 69 extends outside from a position near the second end
of the sampling arm 42. A second end 69c of the air pipe 69 is connected
to a vent port 71b of the syringe pump 70 through a connection rod
71c, as shown in FIG. 3.
[0041] The syringe pump 70 consists of a syringe that is shaped
into a cylindrical body and is connected to the second end 69c of
the air pipe 69 and a plunger 72 that is fitted in the syringe
71 to be movable up and down and has male helicoids 72a formed around
its external peripheral portion that protrudes out of the syringe
71. The syringe 71 also has a groove 71a formed in its internal
periphery along a circumferential direction, and a sealing member
77 is fitted in the groove 71a to keep air-tightness between the
syringe pump 70 and the syringe 71. The transmission member 73 has
female helicoids 73a formed around its internal periphery, to mesh
with the male helicoids 72a of the plunger 72. The transmission
member 73 has a gear 73b formed around its external periphery, and
the gear 73b gears into the drive gear 74 that is fixedly mounted
to a rotary shaft 76a of the third motor 76.
[0042] As the third motor 76 rotates, the rotational movement is
transmitted through the transmission member 73 to the plunger 72
to drive the plunger 72 to move up or down by a given amount according
to leads of the male and female helicoids 72a and 74a. As a result,
an internal volume of the syringe 71 changes to send the air into
or suck the air from the air pipe 69 through the second end 69c,
so that a pressure is supplied to a pipe system consisting of the
nozzle tip 38 the spotting nozzle 36 and the air pipe 69.
[0043] The first to third motors 64 68 and 76 of the first spot
fixing device 15 are connected to a controller 78 that controls
the motors 64 68 and 76 according to predetermined sequence programs.
[0044] First, the controller 78 outputs a motor drive signal to
the first motor 64 causing the sampling arm 42 to rotate in a direction
of an arrow C (see FIG. 2) by the driving power of the first motor
64 that rotates according to the motor drive signal, so as to position
the spotting nozzle 36 and the nozzle tip 38 above the sampling
cup 31 that contains a specimen 80.
[0045] Next, the controller 78 drives the third motor 76 in a forward
direction to move the plunger 72 upward. Thereby the air is sent
from the syringe 71 into the air pipe 69 so the pipe system is
positively pressured. Simultaneously, the controller 78 drives the
second motor 68 to rotate in a direction to move the sampling arm
42 downward at a given speed. When the sampling arm 42 moves down
to bring a tip of the nozzle tip 38 into contact with a liquid surface
of the specimen 80 in the sampling cup 31 a not-shown liquid surface
detection unit detects it, so the controller 78 stops driving the
second motor 68 to stop downward movement of the sampling arm 42.
Simultaneously, the controller 78 stops driving the third motor
76 to stop upward movement of the plunger 72 and thus stop sending
the air from the syringe 71 into the air pipe 69.
[0046] Thereafter, the controller 78 drives the third motor 76
to rotate reversely to move the plunger 72 downward by a given amount.
Thereby, the specimen 80 is sucked by a predetermined amount into
the nozzle tip 38. Then, the controller 78 outputs drive signals
sequentially to the respective motors 64 68 and 76 to move the
sampling arm 42 upward and rotate it by a given angle and then move
it downward, so that the specimen 80 sucked in the nozzle tip 38
is discharged from the nozzle tip 38 and is fixed as a spot on the
dry type analyzing element 1. According to the present embodiment,
the specimen is discharged 5 ml to 100 ml at a time. The second
and third spot fixing devices 23 and 24 have the same structure
as the first spot fixing device 15.
[0047] According to the present embodiment, the spot fixing devices
15 23 and 24 are subjected to a leak test before the biochemical
analyzer 10 is shipped as a product. Now the leak test will be described
with respect the spot fixing device 15 as shown in FIGS. 3 and
4 and the same applies to the other spot fixing devices 23 and
24. For the leak test, the spotting nozzle 36 is connected to the
syringe pump 70 through the air pipe 69 and the air pipe 69 is
connected at its intermediate position to a pressure sensor 81 through
a three-way pipe 79. The syringe pump 70 is also connected to the
transmission member 73 the drive gear 74 and the third motor 76
in the same way as described above with respect to the first spot
fixing device 15. The pressure sensor 81 and the third motor 76
are connected to a leak detection controller 85.
[0048] The pressure sensor 81 outputs electric detection signals
representative of pressure values inside the air pipe 69 and sends
them to the leak detection controller 85. The pressure sensor 81
is provided with a piezoelectric element 81a that generates piezoelectricity
corresponding to the internal pressure of the air pipe 69 so the
current generated from the piezoelectric element 81a is output as
the detection signal. The leak detection controller 85 is provided
wit an A/D converter 86 a differentiation circuit 87 and a comparator
circuit 88. The A/D converter 86 digitalizes the analog electric
signal from the pressure sensor 81. The differentiation circuit
87 differentiates the digitalized electric signal, to clearly show
variations in pressure as derivative values of the pressure. The
comparator circuit 88 is fed with a predetermined threshold value
as a reference signal, to judge from the comparison with the threshold
value as to whether any leakage takes place or not. The threshold
value may vary depending upon what kind of leakage should be detected,
using not-shown operational members like a keyboard. The differentiation
circuit 87 and the comparator circuit 88 may be embodied as hardware
devices but may preferably embodied as software programs installed
and executed in the leak detection controller 85. If the comparator
circuit 88 detects a leakage as the pressure derivative value goes
above the threshold value, the leak detection controller 85 lets
an alarm 89 go off. As a device for warning the leakage, a not-shown
display device may display a warning instead of or in addition to
the alarm 89.
[0049] In the leak test of the present embodiment, the plunger
72 of the syringe pump 70 is moved up and down in the same work
range L and at the same speed as for its actual sucking discharging
operation, to output the internal pressure of the air pipe 69 through
the pressure sensor 81 and detect the pressure derivative values
through the differentiation circuit 87. More specifically, the syringe
pump 70 moves from a lowermost position pE as shown by phantom lines
in FIG. 3 where the plunger 72 is pulled out farthest from the
syringe 71 to an uppermost position pS as shown by solid lines
in FIG. 3 where an inner tip of the plunger 72 is pushed up to a
top end of the syringe 71. Continuously to the upward movement,
the plunger 72 is moved from the uppermost position pS down to the
lowermost position pE. The internal pressure is detected during
the reciprocation of the plunger 72. It is to be noted that the
tip of the spotting nozzle 36 is not closed but kept open during
the leak detection.
[0050] As described so far, the spotting nozzle 36 and the air
pipe 69 constitute an open pipe system, and the pressure sensor
81 is connected to the open pipe system through the three-way pipe
79. The open pipe system, the pressure sensor 81 and the leak detection
controller 85 constitute a leak detection unit. The open pipe system,
the pressure sensor 81 and the differentiation circuit of the leak
detection controller 85 are shared with the above-mentioned not-shown
liquid surface detection unit, so as to simplify the apparatus structure.
[0051] FIGS. 5 to 7 show results of the leak test on three cases,
wherein FIG. 5 shows a curve 90 of the internal pressure P and a
curve 91 of the derivative values DP of the pressure in a normal
case without any leakage, FIG. 6 shows curves 92 and 93 of the internal
pressure P and derivative values DP of the pressure in a case where
a leakage occurs due to defective sealing of the syringe 71 to the
plunger 72 and FIG. 7 shows curves 95 and 96 of the pressure P
and derivative values DP of the pressure in a case where a leakage
occurs due to a defection of the plunger 72.
[0052] In these graphs, the horizontal axis represents time T,
and the plunger 72 is located in the lowermost position pE at a
measurement starting time t0. From this point, the third motor 76
starts rotating to move the plunger 72 upward. As the plunger 72
moves upward, the internal pressure P increases gradually and reaches
a maximum value Pmax at a time point t1. From the measurement starting
time t0 to the time point t1 the derivative value DP gradually
decreases, which means that the pressure P fluctuates lesser.
[0053] In the normal condition, the pressure P is kept at the maximum
value Pmax from the time point t1 till the plunger 72 comes to the
uppermost position pS at a time point t2 as shown by the curve
90. While the pressure P is kept unchanged, that is, from the time
point t1 to the time point t2 the derivative value DP is kept at
zero, as shown by the curve 91. From the time point t2 to a time
point t3 the motor 76 stops, so the plunger 72 stays in the uppermost
position pS. During this time period, the pressure P decreases gradually
and comes to zero at the time point t3. At the time point t2 the
derivative value DP becomes negative, and then comes back to zero
at the time point t3. Since the plunger 72 stops in the time period
from t2 to t3 the derivative values DP detected during this time
period are not used for the leak detection.
[0054] From the time point t3 the motor 76 starts rotating reversely
to move the plunger 72 downward. From the time point t3 to a time
point t4 the pressure P decreases gradually, that is, the negative
pressure increases gradually, and the pressure P reaches a minimum
value Pmin, i.e. a maximum negative pressure value, at the time
point t4. From the time point t4 till the plunger 72 comes to the
lowermost position pE at a time point t5 the pressure P is kept
at the minimum value Pmin. When the plunger 72 comes to the lowermost
position pE, one cycle of the leak test is accomplished. As shown
by the curve 91 the derivative value DP becomes negative at the
time point t3 and then increases gradually till the time point
t4. From the time point t4 to the time point t5 the derivative
value DP is kept zero.
[0055] As described so far, if the first spot fixing device 15
is in the normal condition, the pressure P detected by the pressure
sensor 81 little fluctuates in most time during the reciprocation
of the plunger 72 except the time periods immediately after the
plunger 72 starts moving in either direction, so the pressure derivative
value DP is mostly kept zero. In this condition, the first spot
fixing device 15 can suck and discharge a predetermined amount of
liquid exactly. As obvious from the graph of FIG. 5 the pressure
P and the derivative value DP vary with the movement of the plunger
72 in a symmetrical fashion between the time period from t0 to t2
that is, while the plunger 72 moves from the lowermost position
pE up to the uppermost position pS, and the time period from t3
to t5 that is, while the plunger 72 moves from the uppermost position
pS down to the lowermost position pE, although they are positive
on one hand, and are negative on the other hand. So the result of
leak judgment derived from the curves will be substantially same
in both periods. Therefore, FIGS. 6 and 7 show merely the results
of measurement during the upward movement of the plunger 72 i.e.
from the lowermost position pE to the uppermost position pS.
[0056] As shown in FIG. 6 if the sealing of the syringe 71 is
not good, the derivative value DP indicated by the curve 93 fluctuates
greatly at several points as designated by 93a, 93b and 93c, during
the time period from the time point t1 when the pressure P indicated
by the curve 92 reaches the maximum value Pmax to the time point
t2 when the plunger 72 comes to the uppermost position pS. According
to the present embodiment, a threshold value is predetermined for
detecting the leakage due to the defective sealing of the syringe
71 as shown by dashed lines 94 in FIG. 6. The threshold value 94
is fed as a reference signal to the comparator circuit 88 so the
pressure derivative value DP from the differentiation circuit 87
is compared with the threshold value 94. If the pressure derivative
value DP is above the threshold value 94 the leak detection controller
85 judges the sealing member 77 to be defective, and lets the alarm
89 go off.
[0057] If on the other hand the leakage occurs because the plunger
72 is defective, the pressure derivative value DP indicated by the
curve 96 in FIG. 7 varies at regular intervals in a period 96a from
the time point t1 when the pressure P indicated by the curve 92
reaches the maximum value Pmax to the time point t2 when the plunger
72 comes to the uppermost position pS. This variation patterns of
the derivative values DP indicate that the leakage occurs at the
regular intervals because the plunger 72 leans to an axial direction
of the syringe 71 or because the plunger 72 is defective with respect
to roundness. In order to detect the leakage due to the defect in
the plunger 72 a second threshold value 97 is predetermined, as
shown by dashed lines in FIG. 7. The threshold value 97 is fed as
a reference signal to the comparator circuit 88 so the pressure
derivative value DP from the differentiation circuit 87 is compared
with the threshold value 97. If the pressure derivative value DP
is above the threshold value 97 the leak detection controller 85
judges the plunger 72 to be defective.
[0058] As described so far, since the derivative value of the pressure
is used for detecting the leakage, it is possible to detect small
variations in pressure that is measured by the pressure sensor 81
so the leakage can be detected with high accuracy whichever the
leakage is caused by defect in the syringe 71 or the plunger 72
of the syringe pump 70.
[0059] Because the malfunctions of the syringe pump 70 are detected
based on the derivative value of the pressure that is measured by
the pressure sensor 81 while moving the plunger 72 of the syringe
pump 70 in the same work range L as in the actual sucking discharging
operation, it becomes possible to detect such malfunctions without
fail that can occur during the actual sucking discharging operation.
Furthermore, because the leak detection is carried out with the
tip of the spotting nozzle 36 open, the pressure is measured under
proximate conditions to the actual sucking discharging operation,
so it is possible to judge the malfunctions of the syringe pump
70 with reliability.
[0060] Although the leak detection of the syringe pump 70 is carried
out before the shipment of the biochemical analyzer 10 from the
factory in the above described embodiment, it is possible to carry
out the same leak detection as above after the shipment of the biochemical
analyzer 10 before the actual use thereof.
[0061] The present invention is not to be limited to the above
embodiments but, on the contrary, various modifications will be
possible without departing from the scope of claims appended hereto.
|