JPH0441288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a microflow injection device that utilizes the quantitative nature of droplets dripping from the tip of a capillary, and maintains a constant pressure difference with the source of the injected liquid regardless of the pressure of the injected liquid. This pressure difference is used as a condition for the injection liquid to drip as droplets, and the injection amount is measured from the number of droplets dropped.

Conventionally, when a minute flow rate of liquid is injected into a liquid to be injected at a predetermined pressure, a mechanical element such as a gear pump or a plunger pump is used. However, recent advances in biochemistry have made it necessary to inject extremely small flows of liquid, and with conventional methods, it is difficult to stably inject micro flows due to limitations in processing accuracy. It became extremely expensive due to the need for higher processing precision.

The present invention was made in view of the above problems.
The volume of the droplet dripping from the tip of the dripping tube made of a thin tube is constant over a wide range of continuous dropping interval time, and the amount of the injected liquid is measured as a droplet. To provide a microflow injection device that automatically adjusts the pressure of the injected liquid according to the pressure of the injected liquid even if the pressure of the injected liquid changes so that the condition is such that the injected liquid always drips as droplets. This is the purpose. The purpose of this invention is to provide an extremely small continuous liquid injection device by converting the discontinuous flow of droplets into a continuous flow, which will be described below with reference to the drawings. Reference numeral 1 denotes a liquid to be injected, which is moved through a conduit 6 by a transfer means (not shown). A pressure chamber 2 is provided in a part of the conduit 6.
are arranged. In order to reduce the influence of dynamic pressure, the pressure guiding chamber 2 is installed outside the pipeline with a pressure introduction hole 3 provided in a part of the pipeline. Static pressure is conducted from the pressure chamber 2 via a conduit 4 to a source 5 of injection liquid. The injection liquid 8 is supplied from a storage tank (not shown) through a valve 9 supply pipe 10 with a valve 13 disposed on a drip pipe 12 communicating with a measuring container 11 and a valve 14 communicating with a preliminary chamber 15 closed. Once a predetermined amount of the injection liquid has been supplied, the valve 9 is closed and the supply of the injection liquid is stopped. 7 prevents the injected liquid 1 and the injected liquid 8 from mixing in the injected liquid source 5, and the pressure difference between these liquids allows the injected liquid to flow out from the drip tube 12, which will be described later, to maintain the state of droplets. It is a piston that limits the required water head and is freely slidable in the vertical direction within the injection liquid source 5. In order to adjust the initial pressure of the injection liquid sent earlier, a portion of the injection liquid sent to the injection liquid source 5 is transferred to the preliminary chamber 15 by opening the valve 14 disposed below the injection liquid source 5. to be discharged. The preliminary chamber 15 is simply an empty room, and the discharge valve 1 can be installed as needed.
6 to introduce outside pressure or drain the remaining injection liquid. This operation allows the piston 7 to be maintained in the injection liquid source 5 in equilibrium with the source of the liquid to be injected. The measurement container 11 is a hollow sealed container except that a drip tube 12 is opened at the top and an injection tube 20 is opened at the bottom. Further, the dropped liquid 18 is detected by a detector 21 and measured by a measuring device 17. The other end of the injection tube 20 opens into the liquid to be injected 1.

The operation of the above device will be explained. The conditions for liquid to fall from a thin tube as droplets are mainly as follows:
When energy is applied to the liquid that exceeds the equilibrium condition between the surface tension acting on the circumference of the capillary and the weight of the droplet, that is, the water head from the opening of the capillary exceeds the above condition. When this critical head is exceeded, the time interval between droplets falling decreases.
Furthermore, when the falling stream of droplets reaches a head that exceeds the droplet formation time that satisfies the above equilibrium condition, the droplets fall as a continuous flow. In this way, there is a predetermined range in the size of the water head at which liquid drops as droplets. The piston 7 in the injection liquid source 5 selectively provides the above-mentioned water head, which is determined by the diameter of the dripping tube made of a thin tube, the surface tension, the droplet dropping time interval, etc. On the other hand, since the injection liquid is injected by overcoming the water head obtained by subtracting the water head from the liquid to be injected 1 and the piston 7, the pressure at the time of injection is high and the piston 7 contacts the upper surface of the injection liquid source 5. The injection liquid supply from the storage tank is shut off by the valve 9, and the preliminary chamber 1 is
By discharging a portion of the injected liquid at point 5, the piston 7 is separated from the upper surface of the injected liquid source, and the pressure is balanced with the injected liquid 1. Since the pressure inside the measuring container 11 is also open to the liquid to be injected via the injection pipe, the pressure is in equilibrium with the liquid to be injected 1, so that the pressure conditions for dropping the liquid through the dripping tube 12 can be configured. Under such pressure equilibrium conditions, the pressure in the space within the measurement container changes as the droplets drop, so in order to satisfy this equilibrium condition, a volume of liquid equal to the droplet is inserted into the injection tube 20. is injected into the injected liquid through the injected liquid. These responses occur extremely quickly and instantaneously when the measurement container is made smaller to reduce the space capacity, since the friction elements of the injection tube and the drip tube are delay elements caused only by liquid viscosity.

In the above example, the constant pressure difference for forming droplets was determined by the pressure difference due to the weight of the piston, but it is also possible to control the pressure of the injection liquid by separately providing injection and measuring the pressure of the liquid to be injected.

According to the "Volume of a Drop of Water" stated in the Metrology Research Institute Report Vol. 1.28, No. 1 published by the Ministry of International Trade and Industry's Metrology Research Institute in January 1974, the volume of a water droplet dripping from the tip of a dripping tube is The data shows that the time interval between continuous drops is almost constant within a predetermined range, although it varies depending on the diameter of the tip. Furthermore, since the time interval between drops varies depending on the water head, by keeping the water head constant, a constant flow rate of the injection liquid can be dropped, and the same amount of injection liquid can be injected. The amount of the injected liquid can be measured by placing the droplets facing each other, for example, and counting them by electrical conduction as the droplets pass between them, or by detecting and measuring the passage of light, changes in capacitance, thermal changes, etc. It is determined by

In addition, the diameter of the injection tube 20 is made smaller than the dripping tube 12 that opens into the metering chamber, and the diameter is reduced to a diameter that satisfies the condition of continuity for the amount of liquid dripped from the dripping tube 12, thereby reducing discontinuous flow due to dripping. Converts to continuous flow for even injection. If a discontinuous flow is converted into an equivalent continuous flow in this way, and the dropping time interval of the discontinuous flow is constant, the flow rate of the continuous flow can also be grasped by time-dividing this time interval.

Furthermore, a flow meter is installed at the source of the injected flow, and the flow rate of the injected liquid is controlled so that the flow rate signal transmitted from this flow meter and the number of dripped liquids in the dripping stream become a predetermined ratio. Quantitative mixing is possible. Since the volume of the dripping liquid depends on the diameter of the dropping tube, when changing the injection mixing ratio, the diameter of the dropping tube may be changed or a plurality of dropping tubes may be arranged in parallel.

As described above, according to the present invention, the volume of the droplet dripping from the capillary can be increased by controlling the pressure difference with the injection fluid source to become the condition for dropping the droplet, regardless of the pressure of the fluid to be injected. This micro-flow injection device, which uses the simple principle that the dripping time interval is constant within a predetermined range, can be applied to a wide range of pressure conditions, making it possible to inject micro-flows at an unprecedented cost and accuracy. The economic effects are extremely large.

[Brief explanation of drawings]

The figure is a configuration diagram of a microflow injection device according to the present invention. 2... Pressure chamber, 4... Conduit, 7... Piston,
11...Measurement container, 12...Dripping tube, 20...Injection tube, 21...Detector.

Claims (1)

[Claims] 1 A conduit that guides static pressure from a conduit through which the liquid to be injected flows, an injection liquid source that communicates with the conduit, and which isolates the injection liquid source from the liquid to be injected and is slidable in the vertical direction within the injection liquid source. a piston, a dripping tube that communicates with the injection liquid source, a measuring device that detects droplets dripping from the dripping tube, and an injection tube that communicates the injection liquid dripped from the dripping tube into the pipe line. A microflow injection device characterized by: