JPH1096735A - Aerial discharge type dispensing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dispensing device capable of providing high dispensing accuracy even in the case of discharging a minute quantity of sample in air and shortening a dispensing time. SOLUTION: The suction and discharge force of a sample is generated by a syringe pump 15, and the suction and discharge force is transmitted to a nozzle 1 sucking and discharging the sample through washing liquid. A pump controlling means supplies a drive signal prescribing a pump driving speed to the syringe pump 15, and at discharging the sample, it drives the syringe pump 15 following to a rectangular pump driving speed characteristic having steep speed change in the first transition and the last transition. At sucking the sample, an air layer is formed between the washing liquid and the sample.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aerial discharge type dispensing apparatus, and more particularly to a dispensing apparatus for discharging a sample in a nozzle while holding the nozzle in the air with respect to a test container.

[0002]

2. Description of the Related Art Conventionally, in a sample test, a sample such as a sample or a reagent is sequentially dispensed into a test container such as a test tube.
In this sample test, a dispensing device is used to dispense a predetermined amount of a sample into a test container. In the dispensing device,
A dispensing pump is connected to the nozzle, and the sample in the nozzle is discharged to the test container by driving the dispensing pump.

[0003] In a conventional general sample test, a reagent is first dispensed into a test container, and then a sample is dispensed. A dispenser type dispensing device is used for dispensing the reagent. In this device, the reagent is continuously supplied from a pipe connected to the nozzle, and the supplied reagent is discharged from the tip of the nozzle.
When dispensing a sample, the position of the liquid surface of the reagent is detected, a nozzle is inserted to a depth of about several mm from the liquid surface, and after discharging a predetermined amount of the sample, the nozzle is pulled up. Here, in order to avoid cross contamination between samples, a disposable type device, that is, a device in which a nozzle is replaced for each sample is used. A method in which the nozzle is immersed in a liquid and the liquid is discharged as in the above-described sample dispensing is called a submerged discharge method.

[0004]

[Problems to be solved by the invention]

(1) In recent years, along with the diversification of sample tests, there has been an unprecedented demand for a dispensing device. One of such requirements is to dispense a sample such as a specimen with a high dispensing accuracy (the accuracy of the dispensed amount; hereinafter the same) from a state in which nothing is contained in the test container. Can be in this case,
It is necessary to employ an air ejection method, that is, a method of ejecting a sample while the nozzle tip is in the air. However, the conventional air discharge method cannot meet the demand for high dispensing accuracy as described below.

A problem when improving the dispensing accuracy in the air discharge method is that a sample remains on the outside of the nozzle tip at the end of discharge. This sample residue is generated due to the surface tension generated at the tip of the nozzle. When the sample residue is large, it becomes a liquid ball. Since the remaining amount of the sample is not constant, the dispensed amount differs depending on the remaining amount of the sample, and the dispensing accuracy is reduced. In particular, when the dispensed volume is 10
In the case of a very small amount of about 1 μl or less, the sample remaining amount is large relative to the dispensed amount, so that the dispensing accuracy is significantly reduced. In the above-described submerged discharge method, no sample remains because the nozzle is immersed in the liquid. Therefore, even when the dispensed amount is very small, high dispensing accuracy can be obtained.

Here, in order to prevent the occurrence of liquid residue during air discharge, it has been proposed to make the discharge port close to the wall surface of the test container during dispensing. In this method, since the liquid ball at the tip of the nozzle comes into contact with the container wall surface, the liquid ball adheres to the wall surface side, thereby preventing the sample from remaining. However, in this case, the dispensed amount changes according to the contact angle between the tip of the nozzle and the container wall surface, and as a result, sufficient dispensing accuracy cannot be obtained. Further, it is necessary to finely control the positional relationship between the tip of the nozzle and the wall surface of the container, and the time required for dispensing becomes long.

(2) Further, conventionally, there has been a demand for speeding up by reducing the time required for dispensing. However, in the conventional submerged discharge method, as described above, control for adjusting the positional relationship between the nozzle and the liquid surface is required, and a control time corresponding to this control is required.

An object of the present invention is to solve the above-mentioned problems, to obtain a high dispensing accuracy even when a minute amount of sample is discharged in the air, and to shorten the dispensing time. Dispensing device is provided.

[0009]

An aerial discharge type dispensing apparatus according to the present invention comprises a nozzle for sucking and discharging a sample, the nozzle being moved, and the nozzle being held in the air with respect to a test container when discharging the sample. A dispensing pump for generating a suction / discharge force of the sample, transmitting the suction / discharge force to the nozzle via a transmission medium, and supplying a drive signal defining a pump driving speed to the dispensing pump. And pump control means for driving the dispensing pump in accordance with a rectangular pump driving speed characteristic having a sharp speed change at rising and falling at the time of discharging the sample.

According to the present invention, when the sample is discharged, the dispensing pump is driven according to the rectangular pump driving speed characteristic, and accordingly, the rising and falling of the sample discharging speed becomes steep. The ejection speed can be set high even when the dispensed amount is very small, and the ejection of the sample is suddenly stopped at the end of the ejection. As a result, the amount of liquid remaining at the opening at the tip of the nozzle is improved, and the amount of liquid remaining outside the opening decreases. Therefore, high dispensing accuracy can be obtained even when the dispensed amount is very small.

Further, in the submerged discharge type dispensing apparatus conventionally used when the dispensed amount is very small, it is necessary to control the positional relationship between the liquid level and the nozzle. However, in the present invention, such control is not required, and the time required for dispensing is reduced by simplifying the control. As a result, the number of dispensing processes per unit time increases.

In one embodiment of the present invention, the transmission medium is a liquid, and when a sample is sucked, an air layer is formed between the liquid and the sample. By using liquid as the transmission medium,
The transmission of the suction / discharge force generated in the dispensing pump becomes faster. Therefore, the responsiveness of the nozzle discharge speed to the rectangular pump drive speed characteristics is increased, and the liquid drainage effect at the nozzle tip is enhanced. Also, by forming an air layer between the liquid of the transmission medium and the sample, mixing of the liquid and the sample is prevented.

In one embodiment of the present invention, the transmission medium is a cleaning liquid, and after the discharge of the sample is finished, the inside of the nozzle is cleaned by discharging the cleaning liquid. As described above, by using the cleaning liquid as the transmission medium, the inside of the nozzle can be easily cleaned after the discharge of the sample is completed. Therefore, even when a non-disposable type nozzle (a type in which the nozzle is not replaced every time dispensing and is different from a disposable type in which the nozzle is disposable) is employed, contamination between samples can be reliably prevented.

Further, in one aspect of the present invention, the dispensing pump has a syringe mechanism in which a piston driven by a motor is inserted, and the pump control means transmits the drive signal to the motor as the drive signal. A pulse signal having a rate according to the pump driving speed characteristic is supplied. In this configuration, the pump control means supplies a high-rate pulse signal at the start of discharge, and suddenly stops supplying the pulse signal at the end of discharge. When the motor drives the piston in response to this signal supply, the driving speed of the piston rises sharply and falls sharply.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air discharge type dispensing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a dispensing apparatus according to this embodiment. This device is provided on a base (not shown),
The sample is sucked into the nozzle from the dispensing source test tube placed on the base, and the nozzle is moved to the dispensing destination test tube to discharge the sample.

In FIG. 1, a nozzle 1 is a non-disposable type nozzle made of stainless steel. Nozzle 1
Has a sample holding section 3 having an inner diameter of about 2 mm, and a suction section 5 having an inner diameter of about 0.5 mm and a length of about 6 mm at the tip. Then, the sample holding unit 3 and the suction unit 5 are connected to a conical tapered portion 7.
It is connected by. In the nozzle 1, a sample for dispensing can be sucked up to several hundred μl. Nozzle 1 is XYZ
By the robot 10, a sample suction position, a sample discharge position,
Move to nozzle cleaning position. The nozzle 1 is communicated with the switching valve 11 by a polymer tube 13. The inner diameter of the tube 13 is about 2 mm.

The switching valve 11 is further connected to the syringe pump 15 by a tube 17, and is connected to the washing liquid tank 19 by a tube 21. The tube 17 and the tube 21 are both made of polymer and have an inner diameter of about 2 mm. The switching valve 11 performs a switching operation by being driven by a valve motor 12.
Then, the nozzle 1 communicates with the syringe pump 15, and the syringe pump 15 communicates with the cleaning liquid tank 19. In addition, you may use an electromagnetic valve as a switching valve.

The syringe pump 15 is a cylindrical syringe 2
3, a piston 25 is inserted into the syringe 23, and a syringe chamber 27 is formed by the syringe 23 and the piston 25.
Are formed. The syringe 23 is connected to the tube 17 at an opening 29 on the end face. The piston 25 is connected to the syringe 23 by the pump motor 31.
It is driven to reciprocate within. In the syringe room 27,
A cleaning liquid is injected as described below. When the piston 25 moves in the direction of the opening 29, the cleaning liquid is pushed out of the opening 29, and when the piston 25 moves in the direction opposite to the opening 29, the cleaning liquid is sucked. Hereinafter, the former piston movement is referred to as push-out movement, and the latter piston movement is referred to as retracting movement.

The cleaning liquid tank 19 stores a cleaning liquid. This cleaning liquid is used for the switching operation of the switching valve 11,
When the syringe pump 15 is driven, it is supplied to the entire dispensing apparatus.

FIG. 2 is a block diagram showing a configuration of a control system for driving the nozzle 1, the switching valve 11, and the syringe pump 15. In the figure, a control unit 35 is mainly composed of a computer,
In 5, setting conditions such as the dispensing amount, the number of dispensing processes, and the arrangement of test tubes are input. Further, the control unit 35 is connected to a liquid level detector 39 that detects a liquid level position of the sample in the test tube. The control unit 35 drives the XYZ robot 10, the valve motor 12, and the pump motor 31 by outputting a drive signal according to the input setting conditions.

Next, the operation of the air discharge type dispensing apparatus will be described by dividing into "dispensing (suction)", "dispensing (discharging)" and "washing". FIG. 3 is an enlarged view of the nozzle 1,
The dispensing operation of the present apparatus is shown in chronological order. In addition,
Here, the case where the sample to be dispensed is a specimen (for example, serum) and the dispensed volume is 3 μl will be described. However, in the present apparatus, a wide range of dispensing amount from a very small amount of several μl to several hundred μl can be set.

[Dispensing (suction)] In this case, the sample is sucked into the nozzle 1 from the dispensing source test tube placed on the base.
At the start of suction, the nozzle 1 is moved by the XYZ robot 10 above the dispensing source test tube. Switching valve 1
1 is switched so that the nozzle 1 communicates with the syringe pump 15. Then, the piston 25 of the syringe pump 15 is at a predetermined start position in the syringe. The syringe chamber 27, the tubes 17, 13 and the nozzle 1 are filled with a cleaning liquid. At this time, the cleaning liquid is filled up to the tip of the nozzle 1 as shown in FIG.

First, the piston 25 is pulled and moved in a state where the nozzle port 9 is not inserted into the sample in the test tube. The volume of the syringe chamber 27 increases in response to the movement of the piston 25, and the amount of cleaning liquid corresponding to the change in the volume moves from the nozzle 1 to the syringe pump 15. By the movement of the cleaning liquid, air is sucked from the nozzle port 9 as shown in FIG. The amount of air suction is about 30 μl.

Next, the nozzle 1 is moved downward and inserted into the sample. At this time, the liquid level detector 39 in FIG. 2 detects the liquid level position of the sample and inputs the same to the control unit 35. Control unit 35
Controls the XYZ robot 10 based on the position of the liquid level. And the XYZ robot 10 is about 1 mm from the liquid level.
Insert the nozzle 1 to a depth of about
Hold.

Next, the piston 25 is further retracted and moved. The cleaning liquid moves toward the syringe pump 15 in accordance with the movement of the piston, and the portion of the air previously sucked has a negative pressure. Then, the sample is sucked from the nozzle port 9 by the action of the negative pressure. The suction amount of the sample is 13 μl.
This suction amount is an amount obtained by adding 10 μl of the excess amount to 3 μl of the dispensed amount. Here, if 3 μl, which is equal to the dispensed amount, is aspirated, the required dispensed amount cannot be obtained due to factors such as the sample remaining on the inner wall during ejection. Therefore, in order to aspirate an extra sample, 10 μl is set as the amount of excess.

After completion of the suction, the nozzle 1 is pulled up from the test tube. FIG. 3C shows a state after the end of the suction. The air sucked before the sample suction forms an air layer between the cleaning liquid and the sample. This air layer has a function of preventing the cleaning liquid and the sample from mixing. The volume of the air layer is set to about 30 μl as described above. Since the air layer is set to be small, when a discharge force is generated in the syringe pump 15 described below,
The transmission of this ejection force to the sample is fast. Therefore, the response of the sample ejection to the piston movement is high.

[Dispensing (Discharge)] In this case, the sample sucked by the nozzle 1 is discharged to the test tube of the dispensing destination. The XYZ robot moves the nozzle 1 to the dispensing test tube, inserts the tip of the nozzle 1 into the test tube, and holds the nozzle 1 with the nozzle port 9 in the air. Then, the piston 25 of the syringe pump 15 is driven by the pump motor 31 and pushes out. By this pushing movement, the volume of the syringe chamber 27 is reduced corresponding to the dispensed amount. As a result, the washing liquid corresponding to the dispensed amount moves toward the nozzle 1 and the sample is discharged from the nozzle port 9 into the test tube.

FIG. 4A shows the characteristics of the drive signal output from the control unit 35 to the pump motor 31 during the above-described discharge operation. In the figure, the horizontal axis is time, and the vertical axis is the number of pulses per time (pulse rate). As a feature of the present embodiment, the drive signal has a rectangular characteristic, the pulse rate is high from the start of ejection, and the pulse rate drops sharply at the end of ejection. FIG.
(B) shows a change in the speed of the piston 25 corresponding to the drive signal, in which the horizontal axis is time and the vertical axis is the moving speed. As shown in the figure, the speed characteristic of the piston 25 is also rectangular, corresponding to the characteristics of the drive signal, and has a sharp change in the rise and fall of the speed.

[Washing] FIG. 3D shows a state in which the discharge of the sample has been completed, and a sample having an excess amount remains in the nozzle 1. The XYZ robot 10 moves the nozzle 1 to a cleaning position where a cleaning tank is provided. Then, the piston 25 of the syringe pump 15 is pushed out and moved, and several hundred μ
1 of the cleaning liquid is discharged into the cleaning tank. At this time, the cleaning liquid is also applied to the outside of the nozzle 1 at the same time. Thereby, the inner and outer surfaces of the nozzle 1 are cleaned.

After the washing is completed, the washing liquid is supplied to the syringe pump 15 as appropriate. In this replenishment, the switching valve 11 performs a switching operation, and the syringe pump 15 and the cleaning liquid tank 19 are switched.
To communicate. When the piston 25 retracts, the cleaning liquid in the cleaning tank 19 is supplied to the syringe pump 1.
Move to 5.

Next, the effect of the liquid dispenser according to the present embodiment will be described. In order to prevent liquid droplets or the like from remaining on the outside of the nozzle port 9, it is necessary to improve the liquid shortage at the end of discharge. To this end, it is effective to increase the ejection speed of the sample and to stop the ejection of the sample suddenly.

FIG. 5 shows a drive signal supplied to the pump motor and a change in the speed of the piston corresponding to the drive signal in the conventional general dispensing apparatus in the same manner as in FIG. Have been. As shown in the figure, conventionally, the speed characteristic of the piston is trapezoidal, and the rise and fall of the piston speed are gentle. When this trapezoidal velocity characteristic is applied to the present dispensing apparatus, a sufficient drainage effect cannot be obtained as described below. With the trapezoidal velocity characteristic, a certain amount of sample is discharged even when the piston is accelerated or decelerated. If the dispensed volume is very small, deceleration starts before the piston speed reaches the maximum speed, and the dispensed volume is discharged only during acceleration / deceleration. Therefore, there is no point in setting the maximum sample discharge speed to a high value. For these reasons, it is not possible to set the maximum speed of sample discharge high. Further, the falling of the speed is gentle, and if the conventional trapezoidal speed characteristic is applied, the liquid drainage effect is reduced.

On the other hand, in this embodiment, the characteristic of the driving speed of the piston is rectangular as shown in FIG. Since the rise and fall of the speed are steep, and the sample is hardly ejected at the time of acceleration / deceleration, even if the maximum speed of the sample ejection is set high, the liquid running out does not deteriorate as in the above-described prior art. Therefore, it is possible to set the maximum speed of the sample discharge high. Further, the fall of the speed is set steeply. With such a setting, a large inertial force acts on the discharged sample. Therefore, the liquid is often drained at the end of the discharge, and substantially no liquid residue such as a liquid ball is generated.

FIG. 6 shows a sample discharge speed suitable for obtaining a sufficient liquid drainage effect. That is, if the maximum discharge speed of the sample at the nozzle tip is set to be equal to or higher than the minimum liquid discharge speed in the figure, a sufficient liquid discharge effect can be obtained.
In the present embodiment, the inner diameter of the suction part 5 of the nozzle 1 is 0.5 m
m, the minimum drainage rate is 1012 mm / sec.
c. Therefore, the maximum speed of the piston 25 is set so that the discharge speed is equal to or higher than the minimum liquid drainage speed.

FIG. 7 shows a pressure change of the air layer formed in the nozzle 1 at the time of discharge. In the figure, the horizontal axis is time, and the vertical axis is the pressure of the air layer. As shown in the figure, the pressure rises sharply with the start of discharge and drops sharply at the end of discharge. Here, the dotted line indicates a pressure change when a conventional trapezoidal characteristic is adopted as the velocity characteristic of the piston. In this case, the pressure drop is gradual, so that the liquid runs out poorly. On the other hand, in this embodiment, since the pressure drop is steep, the liquid runs out well.

As described above, the dispensing apparatus according to the present embodiment satisfies an unprecedented demand for dispensing a minute amount of sample by air discharge and obtaining high dispensing accuracy. In order to meet this demand, the characteristic of the driving speed of the piston 25 is set to a rectangular shape as shown in FIG. As a result, liquid shortage at the nozzle port 9 is improved, the generation of liquid residue is prevented, and high dispensing accuracy is obtained.

In particular, in the present embodiment, the syringe pump 1
As a pressure transmission medium from 5 to the nozzle 1, a cleaning liquid which is a liquid is employed. The air layer between the cleaning liquid and the sample is set small. Thus, the amount of air in the pressure transmission path is small. Accordingly, the transmission of the discharge force generated in the syringe pump 15 is fast, and the response of the sample discharge to the piston drive is high. As a result, the syringe pump 15
The rectangular characteristics of the piston drive speed at are reflected directly on the sample ejection speed.

In the present embodiment, the cleaning liquid is injected into the path from the nozzle 1 to the syringe pump 15 as described above. By discharging the cleaning liquid from the nozzle port 9, the inner wall of the nozzle 1 can be easily cleaned. Therefore,
Despite the use of a non-disposable type nozzle, the occurrence of cross contamination between samples is reliably prevented.

Furthermore, in the conventional submerged discharge method, it is necessary to finely control the positional relationship between the nozzle and the liquid surface when discharging the sample. On the other hand, in the present embodiment, the air ejection type is used, and fine control of the position of the nozzle 1 is not required. Therefore, the position control of the nozzle 1 using the XYZ robot 10 is simplified, and the dispensing time is shortened. As a result, the number of processes per unit time can be increased.

Further, in the conventional submerged discharge, high dispensing accuracy is obtained, but it is premised that another sample is injected into the test container before dispensing. However, in the present embodiment, such a prerequisite is unnecessary, and can be used regardless of whether or not another sample has been dispensed in advance. Further, by changing the setting of the piston drive amount, it is possible to set the dispensing amount in a wide range from several μl to several hundred μl, and high dispensing accuracy can be obtained.
Thus, the dispensing apparatus of the present embodiment can be used flexibly for various dispensing conditions.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an aerial discharge type dispensing device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system for driving a nozzle, a switching valve, and a syringe pump of the apparatus of FIG.

FIG. 3 is an enlarged view of a nozzle 1 showing a dispensing operation of the apparatus of FIG. 1 in a time series.

FIG. 4 is an explanatory diagram showing a drive signal supplied to a pump motor and speed characteristics of a piston of a syringe pump corresponding to the drive signal in the apparatus of FIG. 1;

FIG. 5 is an explanatory diagram showing a drive signal supplied to a pump motor and a speed characteristic of a piston of a syringe pump corresponding to the drive signal in a conventional dispensing apparatus.

FIG. 6 is an explanatory diagram showing a sample discharge speed suitable for obtaining a sufficient liquid drainage effect.

FIG. 7 is an explanatory diagram showing a pressure change of an air layer formed in a nozzle at the time of ejection in the apparatus of FIG. 1;

[Description of Signs] 1 nozzle, 3 sample holding section, 5 suction section, 7 taper section, 9 nozzle port, 10 XYZ robot, 11 switching valve, 12 valve motor, 13, 17, 21 tube,
15 syringe pump, 19 cleaning liquid tank, 23 syringe, 25 piston, 27 syringe chamber, 31 pump motor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomoyuki Yoshimura 6-22-1, Mure, Mitaka-shi, Tokyo Aloka Co., Ltd.

Claims (4)

[Claims] A nozzle for sucking and discharging a sample; a nozzle moving means for moving the nozzle and holding the nozzle in the air with respect to a test container when discharging the sample; and generating a suction and discharge force for the sample. A dispensing pump for transmitting the suction / discharge force to the nozzle via a transmission medium; and a drive signal for defining a pump driving speed is supplied to the dispensing pump. An air discharge type dispensing device, comprising: pump control means for driving the dispensing pump in accordance with a rectangular pump driving speed characteristic having a change. 2. The dispenser according to claim 1, wherein the transmission medium is a liquid, and an air layer is formed between the liquid and the sample when the sample is sucked. apparatus. 3. The air-dispensing dispenser according to claim 2, wherein the transmission medium is a cleaning liquid, and after the discharge of the sample is completed, the inside of the nozzle is cleaned by discharging the cleaning liquid. apparatus. 4. The apparatus according to claim 1, wherein the dispensing pump has a syringe mechanism in which a piston driven by a motor is inserted, and the pump control unit is configured to control the driving signal. And supplying a pulse signal having a rate in accordance with the pump drive speed characteristic to the motor.