JPH10253638A - Method and apparatus for detecting liquid level in liquid dispenser apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid level detection method in a liquid dispenser apparatus which is simple in structure and control. SOLUTION: A liquid dispenser apparatus has a cylindrical nozzle 1 having a liquid suction discharge opening 1c at a lower end, a nozzle-driving device 2 moving the nozzle 1 up and down, a pressure-supplying device 3 supplying a positive and a negative pressures into the nozzle 1, and a conduit 4 connecting the nozzle 1 with the pressure-supplying device 3. When the nozzle 1 descends to a liquid level in the apparatus, a difference between a pressure in the nozzle 1 and conduit 4 communicating with the nozzle 1 and an atmospheric pressure is detected. If the differential pressure is larger than a predetermined value, it is detected that the liquid suction discharge opening 1c of the nozzle 1 reaches the liquid level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level detecting method and a liquid level detecting apparatus in a liquid dispensing apparatus used for, for example, an automatic biochemical analyzer.

[0002]

2. Description of the Related Art In an automatic biochemical analyzer such as an automatic immunoassay apparatus for automatically measuring components contained in a liquid (sample) such as serum or urine by an immune reaction, a liquid is transferred to a container such as a sample tube. From the injection container) to a reaction detection container or other container (dispensing container), and further, dispenses a liquid (reagent) from a container such as a reagent bottle (container to be dispensed) selected according to the analysis item. For dispensing, a liquid dispensing device is used.

[0003] The liquid dispensing apparatus is provided with a nozzle which can be moved in the horizontal and vertical directions by a suitable driving means. The nozzle includes a tubular nozzle base and a nozzle tip detachably attached to a lower end thereof. At the lower end of the nozzle tip, a liquid inlet / outlet is provided.
The upper end of the nozzle base is connected to a syringe pump that supplies positive and negative pressure into the nozzle via a suitable conduit having a solenoid valve or the like. Then, at a predetermined horizontal position (suction position) above the dispensing container, the nozzle is lowered, and the liquid suction / discharge port is stopped in a state of being contained in the liquid in the dispensing container, and the nozzle is stopped. The liquid is sucked into the nozzle by supplying a negative pressure into the nozzle, the nozzle is raised to above the container to be dispensed, and moved to a predetermined horizontal position (discharge position) above the dispensing container or the like. The nozzle is lowered to a position where the liquid inlet / outlet faces the mouth of the dispensing container, and a positive pressure is supplied into the nozzle,
The liquid sucked into the nozzle is discharged into the dispensing container, and the nozzle is raised to above the dispensing container and moved to the above-described suction position. The liquid in the dispensing container is dispensed to each dispensing container.

In such a dispensing apparatus, if the tip of the nozzle enters the liquid too deeply, the liquid tends to adhere to the outer peripheral surface of the tip of the nozzle, and a large amount of sample adheres to the outer peripheral surface of the tip of the nozzle. Then, it is necessary to frequently replenish the container to be dispensed with liquid, and at the time of dispensing, the dispensed amount varies only due to the variation in the penetration depth of the nozzle, and the attached liquid drips. Therefore, the dispensed amount may be changed, which may adversely affect the accuracy of the biochemical analysis.
In addition, when the liquid is very dirty on the outer peripheral surface of the tip of the nozzle, and when dispensing without replacing the nozzle, the tip of the nozzle cannot be completely washed, and the next liquid is not dispensed. There is a risk that this dirt may be mixed during the injection. Conversely, if the depth of penetration of the nozzle tip into the liquid is smaller than the predetermined amount, air may be sucked in and the dispensed amount may fluctuate, leading to a decrease in analysis accuracy.

Therefore, in order to perform accurate dispensing,
It is necessary to accurately detect the liquid level in the container to be dispensed, and to make the nozzle enter the desired amount of liquid.

Various methods have been proposed for detecting the liquid level in the container to be dispensed. There are two types, one for detecting the position (height) of the liquid surface, and the other for detecting that the tip has reached the liquid surface by lowering the nozzle.

As an example of the former, for example, there is a method of detecting the position of the liquid level using a float. However, in this case, floats are required by the number of containers to be dispensed, and automation is also difficult.

There is also a method of detecting the position of the liquid surface using electrodes. However, also in this case, there is a problem that the electrodes are required by the number of containers to be dispensed, and furthermore, the electrodes come into contact with the liquid, so that dirt is mixed into the liquid.

There is also a method of detecting the position of the liquid surface using a photoelectric switch. However, also in this case, as many photoelectric switches as the number of containers to be dispensed are required. Moreover, the dispensing container is limited to a transparent one, and in the case of a transparent liquid, it is generally difficult to detect the liquid level. Furthermore, since the photoelectric switch detects the liquid level from the outside of the container, it cannot be used if the containers are dense.

There is also a method of detecting the position of the liquid surface from a change in the capacitance at the liquid surface. However, also in this case, there is a problem that the number of sensors for measuring the capacitance is required as many as the number of containers to be dispensed, and that the sample comes into contact with the liquid surface when the sensors touch the liquid surface. There is also a method of providing a capacitance type sensor on the nozzle side, but this is a factor of contamination, and it is not possible to dimension a small-diameter container.

Further, there is an apparatus which detects a relative distance between a nozzle and a liquid surface using ultrasonic waves. In this case, it is only necessary to provide an ultrasonic sensor on the nozzle side. However, if the liquid to be dispensed is an organic solvent or the like, ultrasonic waves are irregularly reflected on the vapor layer above the liquid surface, which causes a measurement error. There is.

As an example of the latter, see, for example,
As described in Japanese Patent No. 3960, for example, there is a method of lowering the nozzle while supplying a negative pressure into the nozzle by a syringe pump, and detecting that the nozzle has reached the liquid level by a change in the pressure in the nozzle.

In this case, it is only necessary to provide a pressure sensor on the nozzle side. However, it is necessary to continue to supply a negative pressure into the nozzle by operating the syringe pump until the nozzle reaches the liquid level. It is. In addition, for detecting the liquid level, a negative pressure can be supplied into the nozzle using a syringe pump for suctioning and discharging the liquid, but in this case, after the nozzle reaches the liquid level, the nozzle is further discharged. It is necessary to supply a negative pressure to the inside to suck the liquid, and to accurately suck a desired amount of the liquid, control of the syringe pump is troublesome. Further, at the moment when the liquid level is detected, a small amount of liquid is sucked, and the suction amount becomes inaccurate. Aspiration of liquid,
If a pump for supplying a negative pressure when the nozzle descends is provided separately from the syringe pump for discharging, such a problem does not occur, but in that case, an extra pump is required.

There is also a method in which the nozzle is lowered while supplying a positive pressure into the nozzle to detect that the nozzle has reached the liquid level due to a change in the pressure in the nozzle. In this case, too, the liquid surface is wavy. There is a problem that the detection of the liquid level becomes inaccurate, or the bubbles in the liquid surface are sucked, and the dispensed amount becomes inaccurate.

[0015]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a liquid level detecting method and a liquid level detecting apparatus in a liquid dispensing apparatus having a simple structure and control.

[0016]

A liquid level detecting method in a liquid dispensing apparatus according to the present invention comprises a cylindrical nozzle having a liquid suction / discharge port at a lower end, a nozzle driving means for raising / lowering the nozzle, and a nozzle inside the nozzle. Pressure supply means for supplying a positive pressure and a negative pressure to the liquid supply device, and a pipe connecting the nozzle and the pressure supply means, when the nozzle is descending toward the liquid level, the nozzle And the pressure difference between the pressure in the pipeline communicating with it and the atmospheric pressure,
When the pressure difference becomes larger than a predetermined value, it is detected that the liquid inlet / outlet of the nozzle has reached the liquid level.

When the liquid suction / discharge port at the lower end of the nozzle reaches the liquid level, the liquid penetrates into the nozzle by capillary action, thereby causing a slight change in the internal volume of the air layer in the nozzle and the conduit communicating therewith. Then, the internal pressure slightly changes. Therefore, by detecting that the pressure difference between the pressure in the nozzle and the pipeline and the atmospheric pressure has become larger than a predetermined value, it is possible to detect that the liquid inlet / outlet of the nozzle has reached the liquid level. .

Since the nozzle is simply inserted into the container, the liquid level can be detected even if the small-diameter containers to be dispensed are densely packed.

While the nozzle is being lowered, there is no need to supply pressure (positive pressure or negative pressure) into the nozzle. Therefore, in addition to the pressure supply means for sucking and discharging the liquid, a pressure supply means is provided. There is no need to provide, and after the nozzle reaches the liquid level, the nozzle is immersed in a predetermined amount of liquid, and then the pressure supply means is operated, so that the desired amount of liquid can be accurately suctioned. Control of the means is easy.

Even if the ambient temperature changes, the pressure difference between the pressure in the nozzle and the pipe communicating with the nozzle and the atmospheric pressure does not change. Further, even if vibration is applied to the nozzle or the pipeline when the nozzle is descending, the internal volumes of the nozzle and the pipeline do not change, so that the pressure in the nozzle or the pipeline does not change.
Therefore, the liquid level can always be accurately detected.

Therefore, according to the method of the present invention, it is possible to always accurately detect that the nozzle has reached the liquid level and to accurately detect the liquid level, and the configuration and control therefor are simple. .

For example, before the detection of the differential pressure, a gas such as air or nitrogen is supplied into the nozzle and the conduit communicating therewith, so that the residual vapor pressure in the nozzle and the conduit is eliminated.

This eliminates the residual steam pressure in the nozzle and the pipeline, so that the differential pressure can be accurately detected.
Therefore, the liquid level can be accurately detected.

The liquid level detecting device in the liquid dispensing apparatus according to the present invention includes a cylindrical nozzle having a liquid suction / discharge port at a lower end, a nozzle driving means for raising / lowering the nozzle, and a pressure for supplying a positive pressure and a negative pressure to the nozzle. In a liquid dispensing apparatus including a supply unit, and a pipe connecting the nozzle and the pressure supply unit, a differential pressure between the pressure in the nozzle connected to the pipe and the pipe in the pipe connected to the nozzle and the atmospheric pressure is provided. A differential pressure detecting means for detecting, and a judging means for detecting that the liquid inlet / outlet of the nozzle has reached the liquid level when the differential pressure becomes larger than a predetermined value are provided. .

According to the apparatus of the present invention, it is possible to always accurately detect that the nozzle has reached the liquid level and to accurately detect the liquid level for the same reason as in the liquid level detecting method described above. It is possible, and the configuration and control are simple.

For example, a gas supply means for supplying a gas such as air or nitrogen is provided in the nozzle connected to the pipe and the pipe communicating with the nozzle.

In this way, before the detection of the differential pressure, the gas can be supplied into the nozzle and the pipeline communicating therewith, so that the residual vapor pressure in the nozzle and the pipeline can be eliminated, and therefore, The liquid pressure can be accurately detected by accurately detecting the differential pressure.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a main part of a liquid dispensing apparatus, and FIGS. 2 and 3 show a part of the apparatus in detail.

As shown in FIG. 1, the pipetting device comprises a vertical cylindrical nozzle (1), a nozzle driving device (2), and a pressure supply device (3).
Pipe (4) connecting the nozzle (1) and the pressure supply device (3)
, And a liquid level detecting device (5).

The nozzle (1) is, as shown in detail in FIG.
A cylindrical nozzle base (1a) extending vertically up and down, and a cylindrical disposable nozzle tip (1
b). The nozzle tip (1b) is automatically replaced by a tip replacement device (not shown). Chips
The lower part of (1b) is tapered, and the lower end is a liquid inlet / outlet (hereinafter abbreviated as “inlet / outlet”) (1c). The inner diameter of the nozzle tip (1b) is preferably 0.3 to 1.5 mm,
In this example, it is 0.8 mm. The nozzle tip (1b)
Preferably, at least the inner peripheral surface of the lower end portion and the inner and outer peripheral surfaces is coated with a non-adhesive resin such as a fluororesin such as an ethylene tetrafluoride resin or a silicon resin (silicone resin).

The nozzle driving device (2) constitutes nozzle driving means for moving the nozzle (1) horizontally and moving it up and down, the details of which are shown in FIG.

In FIG. 2, a horizontal ball screw (7) driven by a horizontal driving motor (6), and a horizontal ball screw (7) moved in a horizontal direction by the rotation of the ball screw (7) are mounted on a frame of a device (not shown). A moving member (8) is provided. Pinion (9) and pinion on moving member (8)
(9) An elevating member (11) having a rack (10) that engages therewith is mounted. A spline shaft (12) rotatably supported by the frame in parallel with the ball screw (7) is passed through a ball spline sleeve (not shown) attached to the center of the pinion (9), and the pinion (9) and the spline The shafts (12) do not rotate with respect to each other, but can move relative to each other in the axial direction. Then, the elevating drive motor (13) is used to drive the spline shaft (12).
The lifting member (11) is moved by rotating the
Go up and down along (8). The nozzle base (1a) is a lifting member (11)
Is passed through a linear motion ball bearing (not shown) provided on the inner periphery of the guide block (14) fixed to the
It is biased downward by 5). The spring (15) is for absorbing an impact when the nozzle tip (1b) is mounted on the nozzle base (1a) .Nozzle (1) is usually provided with the spring (15).
As a result, the flange portion of the nozzle base (1a) is held at a fixed lower end position where it is pressed against the upper surface of the guide block (14).

The pressure supply device (3) constitutes a pressure supply means for supplying a positive pressure and a negative pressure into the nozzle (1), the details of which are shown in FIG.

In FIG. 3, 2 (F)
Syringe pumps (16), (17), a vertical ball screw (19), which is rotationally driven by an electric motor (18) for raising and lowering, and a vertical guide rod (20) ascending and descending by rotating the ball screw (19) A lifting member (21) is provided. Each pump (16) (17)
Is a syringe (16a) (17) fixed vertically to the frame (F).
a), and piston rods (16b) (17b) inserted into the syringes (16a) (17a) from below, and the upper end of each syringe (16a) (17a) is connected to the air intake / discharge ports (16c) (17c). Has become. The lower end of each piston rod (16b) (17b) is moved up and down by the connecting member (22).
The piston rods (16b) and (17b) are connected to the respective syringes by moving the elevating member (22) up and down a predetermined range.
(16a) Move up and down a predetermined stroke with respect to (17a). The two pumps (16) and (17) are used by being appropriately switched according to the amount of the dispensed amount. For example, the inside diameter of the syringe (16a) of the first syringe pump (16) is 2.30 mm, and the second syringe (17)
It is 7.28 mm. Also two pumps (16)
(17) The stroke of piston rod (16b) (17b) is 60mm
(With full stroke).

FIG. 1 shows the structure of the pipeline (4) and the liquid level detecting device (5). Line (4) has three solenoid valves (V
1) (V2) and (V3) are provided. The liquid level detector (5)
The liquid level is detected by detecting that the suction and discharge port (1c) at the lower end of (1) has reached the liquid level, and two solenoid valves (V
4) (V5) and a slight differential pressure sensor (23) are provided.

The above five valves (V1) to (V5) are all diaphragm type direct acting three-port two-position valves. In the drawings, for the sake of convenience, a diaphragm-type direct acting three-port valve is referred to as J
It is represented by using the channel symbol of the pneumatic 3-port solenoid valve of ISB8374. Exit port in drawing (A)
, Inlet port (P) and exhaust port (R) are COM (common) port of diaphragm type direct acting 3 port valve, NC
It corresponds to a (normally closed) port and a NO (normally open) port, respectively. For each of the valves (V1) to (V5), the non-energized state is referred to as an off state, and the energized state is referred to as an on state. In the off state of each of the valves (V1) to (V5), the outlet port (A) (COM port) communicates with the exhaust port (R) (NO port), and the outlet port (A) and the inlet port (P). (N
(C port) is shut off. In the ON state, the outlet port (A) communicates with the inlet port (P), and the outlet port
(A) and the exhaust port (R) are shut off.

The fine differential pressure sensor (23) constitutes a differential pressure detecting means for detecting a differential pressure between the pressure in the nozzle (1) and the pipe (4) communicating therewith and the atmospheric pressure. The sensor (23) detects a pressure difference between a positive pressure port (hereinafter abbreviated as “+ port”) (23a) and a negative pressure port (hereinafter abbreviated as “−port”) (23b), Display the detected value (digital value) on display (24)
And output to the control device (25). The fine differential pressure sensor (23) preferably has a full scale of 30 mmH ₂ O or more and a resolution of ₂ mmH ₂ O or less. As the small differential pressure sensor (23), for example, a semiconductor diffusion type small differential pressure sensor SCXL004DN manufactured by Krone Co., Ltd. can be used. The full scale of this sensor is 100mmH ₂
O, resolution is 1 mmH ₂ O, reproducibility is ± ₂ mmH ₂ O
The overload withstand voltage is 250 mmH ₂ O.

The control device (25) controls the electric motors (6), (13) and (18) and the valves (V1) to (V5) based on the output of the sensor (23) and the like. Processing in the control device (25) is performed using, for example, a microcomputer,
The control device (25) functionally includes a liquid level detection determination unit (26) and a drive control unit (27). The determination unit (26) is a part of the liquid level detection device (5), and outputs the output (differential pressure) of the sensor (23).
Is larger than a predetermined determination value, and constitutes a determination means for detecting that the suction / discharge port (1c) of the nozzle (1) has reached the liquid level. The drive control unit (27) determines the electric motors (6), (13), (18) and the valve (V
1) to (V5) are controlled.

The outlet port (A) of the first valve (V1) is connected to the suction port (16c) of the first syringe pump (16), and the outlet port (A) of the second valve (V2) is connected to the second syringe pump (17). ), And the inlet ports (P) of these valves (V1) (V2) are connected to the exhaust port (R) of the third valve (V3). The exhaust ports (R) of the first and second valves (V1) (V2) are open to the atmosphere. The outlet port (A) of the third valve (V3) is at the nozzle base
It is connected to the upper end of (1a). Then, while the third valve (V3) is off, the first valve (V1) (or the second valve (V2)) is turned on, and the piston rod (16) of the syringe pump (16) (17) is turned on.
b) By lowering (17b), the air in the nozzle (1) is sucked into the syringe (16a) of the first syringe pump (16) (or the syringe (17a) of the second syringe pump (17)). Then, a negative pressure is supplied into the nozzle (1), and conversely, by raising the piston rods (16b) (17b) of the syringe pumps (16) and (17), the syringe (1) of the first syringe pump (16) is raised. 16a) (or the air in the syringe (17a) of the second syringe pump (17)) is discharged into the nozzle (1), and a positive pressure is supplied into the nozzle (1).

The inlet port (P) of the third valve (V3) is connected to the fourth valve (V4)
Of the fourth valve (V4) connected to the outlet port (A) of the
(P) is connected to a nitrogen supply device (28). The nitrogen supply device (28) constitutes inert gas supply means for supplying an inert gas into the nozzle (1) and the pipe (4) communicating therewith. The exhaust port (R) of the fourth valve (V4) is connected to the outlet port (A) of the fifth valve (V5), and the exhaust port (R) of the fifth valve (V5) is connected to the differential pressure sensor (23). Connected to + port (23a).
The inlet port (P) of the fifth valve (V5) and the minus port (23b) of the sensor (23) are open to the atmosphere.

FIGS. 4 to 7 show the switching state of the valves (V1) to (V5) during the dispensing operation. Next, with reference to these drawings, the operation of the dispensing apparatus when dispensing the liquid placed in the dispensed container (30) to another dispensing container (not shown) will be described. This operation repeats a series of operations shown in FIGS. 4 to 7, in which the nozzle (1) is horizontally moved to the suction position above the container (30) by driving the electric motor (6). The explanation starts from the state.

When the nozzle (1) moves to the suction position, the piston rod (1) of the nozzle (1) and the pumps (16) and (17) are moved.
6b) and (17b) have risen to the upper end position of the stroke, and as shown in FIG. 4, only the third valve (V3) is on.
When the third valve (V3) is turned on, the inside of the nozzle (1) communicates with the + port (23a) of the slight differential pressure sensor (23). When the nozzle (1) moves to the suction position,
The motor (6) is stopped, and the nozzle (1) stops at that position.

When the horizontal movement of the nozzle (1) stops, the electric motor (13) is driven, and the nozzle (1) starts lowering toward the liquid level in the container (30). Nozzle (1) descent speed 3-1
5 mm / sec is preferable, for example, 10 mm / sec
It is. While the nozzle (1) is descending, the judgment unit (26)
Output of nozzle, nozzle (1) and pipeline communicating with it
(4) The differential pressure between the internal pressure and the atmospheric pressure is constantly monitored, and when this differential pressure exceeds the determination value, a liquid level detection signal is output to the drive control unit (27). The drive control unit (27) includes a determination unit (26)
Until the liquid level detection signal is output from the motor, the motor (13) continues to be driven and the nozzle (1) continues to descend.When the liquid level detection signal is output, the motor (13) is stopped and the nozzle (1) is stopped. (1) is stopped. This determination value is appropriately set according to the type of the liquid, the type of the nozzle (1), and the like.
₂ O is set. Until the lower end of the nozzle (1) reaches the liquid level, since the inside of the nozzle (1) is in communication with the atmosphere through the suction and discharge port (1c), the output of the sensor (23) is almost 0, and the determination unit ( No liquid level detection signal is output from 26) and the nozzle
(1) continues to descend.

When the lower end of the nozzle (1) reaches the liquid level, the liquid penetrates into the nozzle (1) through the suction / discharge port (1c) by capillary action, whereby the nozzle (1) and the pipe (4) The inside volume of the air layer inside changes slightly, and the inside pressure changes slightly. For this reason,
When the output of the sensor (23) becomes larger than the judgment value, the judgment unit (2
The liquid level detection signal is output from 6), the motor (13) is stopped, and the lowering of the nozzle (1) stops. When the liquid level is detected in this way and the nozzle (1) stops, the nozzle (1) is immersed in the liquid by the amount of the liquid to be sucked, and suction of the liquid is started. The liquid is, for example, ethyl acetate, DMA
In the case of organic solvent systems such as (dimethylaniline) and DMF (N, N-dimethylformamide), the surface tension and viscosity are low, so the moment the lower end of the nozzle (1) comes into contact with the liquid surface,
The liquid penetrates into the nozzle (1) by capillary action. For this reason, the nozzle (1) can be stopped when the penetration depth of the nozzle (1) from the liquid level (hereinafter, simply referred to as “penetration depth”) is almost 0, and after the stop, the nozzle (1) is placed. It can be immersed in the fixed amount liquid and the suction of the liquid can be started as it is.
When the liquid is an aqueous solution, the liquid penetrates into the nozzle (1) when the head at the penetration depth of the chip (1) overcomes the surface tension at the lower end of the chip (1). Because of this, the nozzle
In (1), the operation is stopped when a predetermined amount of liquid has entered the liquid surface. When the nozzle (1) stops, the penetration depth depends on the liquid and the nozzle (1).
Although it varies depending on the type, the maximum is about several mm. The penetration depth is determined by the type of liquid and nozzle (1) and can be determined in advance.
After (1) has stopped, raise the nozzle (1) by this amount of penetration depth or slightly less than this,
The suction of the liquid may be started by immersing the nozzle (1) in a predetermined amount of the liquid. As described above, by coating a non-adhesive resin on at least the inner peripheral surface of the tip of the nozzle (1), when the type of the liquid or the nozzle (1) is the same,
Experiments have shown that the penetration depth when the nozzle (1) stops is halved compared to when there is no coating. Also, if the outer peripheral surface of the lower end portion of the nozzle (1) is coated, the liquid is less likely to adhere to the outer peripheral surface, and there is little possibility that the adhered liquid drips and the dispensed amount is changed.

As shown in FIG. 5, the liquid is sucked by using one of the first and second valves (V1) and (V2) (in this case, the first valve).
(V1)) is turned on and the third valve (V3) is turned off, and the electric motor (18) is driven to drive the pumps (16) (1).
This is performed by lowering the piston rods (16b) and (17b) of (7) to the lower end position of the stroke. The first valve (V1) turns on,
When the third valve (V3) is switched off, the nozzle
When (1) communicates with the syringe (16a) of the first pump (16) and the piston rod (16b) descends, a negative pressure is supplied into the nozzle (1) to suck the liquid. At this time, the second pump (17) also has a negative pressure in the syringe (17a) due to the lowering of the piston rod (17b). However, the syringe (17a) is in the off state of the second valve (V2). Air communicates with the atmosphere, allowing atmospheric air to flow through the valve (V2)
7a) is only inhaled.

When the piston rods (16b) and (17b) of the pumps (16) and (17) are lowered to the lower end position and the suction of the liquid is completed, the electric motor
(13) is driven, the nozzle (1) rises to the upper end position,
Next, the electric motor (6) is driven to move the nozzle (1) to the discharge position just above the dispensing container. When the nozzle (1) stops at the discharge position, the electric motor (13) is driven as necessary, and the nozzle (1) descends to a predetermined height. Then, in order to discharge the liquid, the electric motor (18) is driven,
The piston rods (16b) and (17b) of the pumps (16) and (17) rise to the upper end position. As a result, a positive pressure is supplied to the nozzle (1), and the liquid sucked in the nozzle (1) is discharged into the dispensing container. At this time, the second pump (17) also raises the piston rod (17b), thereby causing the syringe (17a)
The inside of the syringe (17a) becomes positive pressure, but only the air in the syringe (17a) is discharged to the atmosphere through the second valve (V2) in the off state.

When the piston rods (16b) and (17b) of the pumps (16) and (17) are raised to the upper end position and the discharge of the liquid is completed, the electric motor (13) is driven, if necessary, and the nozzle (1) is driven. ) Rises to the upper end position, and then the electric motor (6) is driven to move the nozzle (1) to the suction position just above the container (30). 6, 7, and 4 are performed until the nozzle (1) stops at the suction position.

First, as shown in FIG. 6, the first valve (V1) is turned off, and the third and fifth valves (V3) (V5) are turned off.
Is switched on. When the first valve (V1) is turned off, the syringe (16a) of the first pump (16) is shut off from the nozzle (1), and when the third valve (V3) is turned on, the nozzle (1) is turned off. Is connected to the outlet port (A) of the fourth valve (V4),
When the fifth valve (V5) is turned on, the exhaust port (R) of the fourth valve (V4) is communicated with the atmosphere.

Next, as shown in FIG. 7, the fourth valve (V4) is turned on, and a nitrogen purge is performed. 4th valve (V4)
Nitrogen gas at a predetermined pressure is always supplied to the inlet port (P) from the nitrogen supply device (28), but when the valve (V4) is off, the inlet port (P) and the outlet port (A) The nitrogen gas does not flow anywhere. However, when the fourth valve (V4) is turned on, the inlet port (P) and the outlet port (A) communicate with each other, so that nitrogen gas flows through the fourth valve (V4),
It flows through the third valve (V3) and the nozzle (1), and
discharged from c). This nitrogen purge is for eliminating the residual vapor pressure of the organic solvent in the nozzle (1) and the pipe (4) and accurately detecting the above-mentioned differential pressure.
For example, it is performed for a few seconds. At the moment when the fourth valve (V4) is switched on, the inlet port (P)
(R), a small amount of nitrogen gas flows to the outlet port (A) of the fifth valve (V5). However, since the fifth valve (V5) is turned on, this nitrogen gas is supplied to the fifth valve (V5). It is discharged into the atmosphere from the inlet port (P) of V5) and does not flow to the sensor (23). Therefore, the overload pressure does not act on the sensor (23).

When the nitrogen purge has been performed for a predetermined time, the fourth valve (V4) is turned off, the nitrogen supply device (28) is disconnected (the same state as in FIG. 6), and the fifth valve (V4) is further turned off. V5) is turned off, and returns to the state of FIG. Then, in such a state, the pressure difference between the pressure in the nozzle (1) and the pipe (4) and the atmospheric pressure is smaller than a predetermined minute pressure value, that is,
It is confirmed that there is no residual pressure in the nozzle (1) and the pipe (4), and the above operation is repeated. The minute pressure value can be set as appropriate, for example, 0.3 mmH
₂ O.

In the above example, the first syringe pump (16) is used for dispensing, but the second syringe pump (17) is used for dispensing.
When using the first valve (V1), the first valve (V1) is kept off, and the on / off operation of the second valve (V2) is performed instead of the on / off operation of the first valve (V1) in the above description. Good.

In this dispensing apparatus, as described above, the nozzle
Detecting that (1) has reached the liquid level, stop the nozzle (1), inject a predetermined amount of the nozzle (1) into the liquid, and then suction the liquid. Does not penetrate below the liquid level. For this reason, it is possible to minimize the adhesion of the liquid to the outer peripheral surface of the lower end of the nozzle (1), to prevent liquid dripping and fluctuations in the dispensed amount, and to perform accurate dispensing. At the same time, the number of replenishments of the liquid to the container can be reduced. Also, since no air is sucked, the dispensed amount is accurate.

Further, since the liquid level can be detected simply by inserting the nozzle (1) into the container (30), it can be used even when small-diameter containers are densely packed.

While the nozzle (1) is being lowered,
There is no need to supply pressure (positive pressure or negative pressure) into the nozzle (1), so there is no need to provide pressure supply means in addition to the pressure supply device (3) for sucking and discharging liquid. After the nozzle (1) reaches the liquid level, a predetermined amount of the nozzle (1) is immersed in the liquid, and then the pressure supply device (3) is operated to accurately aspirate the desired amount of liquid. It is easy to control the pressure supply device (3).

Furthermore, even if the ambient temperature changes, the nozzle
The pressure difference between (1) and the pressure in the pipe (4) communicating therewith and the atmospheric pressure does not change. Also, even if vibration is applied to the nozzle (1) or the pipeline (4) when the nozzle (1) is lowered, the internal volumes of the nozzle (1) and the pipeline (4) do not change. The pressure in (1) and in line (4) also does not change. Therefore, the liquid level can always be accurately detected.

Specific configurations such as a liquid dispensing device, a nozzle (1), a nozzle driving device (2), a pressure supply device (3), a pipeline (4) and a liquid level detecting device (5), and dispensing The operation etc.,
The present invention is not limited to the above embodiment, and can be changed as appropriate.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a liquid dispensing apparatus according to an embodiment of the present invention.

FIG. 2 is a partially cutaway exploded perspective view showing a nozzle and a nozzle driving device in an enlarged manner.

FIG. 3 is an enlarged perspective view showing a part of a pressure supply device.

FIG. 4 is a diagram showing a state of a solenoid valve in a certain process of a dispensing operation.

FIG. 5 is a diagram showing a state of a solenoid valve in a different process of the dispensing operation from the above.

FIG. 6 is a diagram showing a state of a solenoid valve in a dispensing operation in a process different from the above.

FIG. 7 is a view showing a state of the solenoid valve in a process different from the above in the dispensing operation.

[Explanation of symbols]

 (1) Nozzle (1c) Liquid inlet / outlet (2) Nozzle driving device (3) Pressure supply device (4) Pipe line (5) Liquid level detecting device (23) Micro differential pressure sensor (26) Liquid level detection judgment section

Claims (4)

[Claims] A cylindrical nozzle having a liquid suction / discharge port at a lower end thereof, a nozzle driving means for raising / lowering the nozzle, a pressure supply means for supplying a positive pressure and a negative pressure into the nozzle, and a connection between the nozzle and the pressure supply means. In a liquid dispensing apparatus provided with a pipe line, when the nozzle is descending toward the liquid surface, the pressure difference between the pressure in the nozzle and the pipe line communicating with the nozzle and the atmospheric pressure is detected, and A liquid level detecting method in a liquid dispensing device, comprising: detecting that a liquid suction / discharge port of a nozzle has reached a liquid level when a differential pressure is larger than a predetermined value. 2. The liquid according to claim 1, wherein a gas is supplied into the nozzle and a pipe communicating with the nozzle before detecting the differential pressure, so that a residual vapor pressure in the nozzle and the pipe is eliminated. Liquid level detection method in the dispensing device. 3. A cylindrical nozzle having a liquid suction / discharge port at a lower end thereof, a nozzle driving means for raising / lowering the nozzle, a pressure supply means for supplying a positive pressure and a negative pressure into the nozzle, and a connection between the nozzle and the pressure supply means. A liquid dispensing apparatus provided with a pipe that communicates with a pipe, a differential pressure detecting means that is connected to the pipe and detects a differential pressure between the pressure in the pipe communicating with the nozzle and atmospheric pressure, and the differential pressure is A liquid level detecting device in a liquid dispensing device, comprising: a determination unit configured to detect that a liquid inlet / outlet port of a nozzle has reached a liquid level when the value exceeds a predetermined value. 4. A liquid level detecting device in a liquid dispensing apparatus according to claim 3, further comprising a gas supply means connected to the pipe and supplying gas into the nozzle and a pipe communicating with the nozzle. .