JPS5938014B2 - liquid mixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid mixing device particularly suitable as a solvent mixing and delivery device in a high performance liquid chromatograph.

Conventionally, in this type of device, multiple types of liquids are connected to a plunger pump through respective control valves, and the control valves are sequentially opened once for a predetermined time during the suction process of the plunger pump, and the opening time of each valve is controlled. A device was used that mixed each liquid in a ratio approximately determined by the ratio of .

However, this device has the disadvantage that an accurate mixing ratio cannot be obtained due to fluctuations in the operating characteristics of the plunger pump. The object of the present invention is to eliminate the drawbacks of the conventional apparatus described above and to improve the accuracy of the mixing ratio.

That is, according to the present invention, two or more types of liquid supply sources are connected to the plunger pump through respective control valves, and the control valves are opened and closed during the suction process of the plunger pump to supply each liquid to the plunger pump at a predetermined level. In a liquid mixing device that suctions and mixes at a ratio of Ru.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

Reference numeral 1 shown in FIG. 1 is an embodiment of a liquid mixing device of the present invention, which is a device that mixes solvent A and solvent B at a predetermined ratio and sends the mixture to a liquid chromatograph L.

Solvent A and solvent B are connected to a mixer 4 via control valves 2 and 3, respectively, and the mixer 4 is connected to suction ports T and 8 of two plunger pumps 5 and 6.

The two plunger pumps 5 and 6 alternately perform a suction operation and a discharge operation.

The discharge ports 9 and 10 of the plunger pumps 5 and 6 are connected together to a liquid chromato club L.

11 is a programmer which controls the opening and closing of the control valves 2 and 3 and a cam 12 which operates the plunger pumps 5 and 6;
The drive motor 13 is controlled.

FIG. 2 shows the operating characteristics of the plunger pumps 5 and 6, with the solid line representing the operation of the plunger pump 5 and the broken line representing the operation of the plunger pump 6. In both cases, the suction operation occurs above the baseline, and the discharge operation occurs below the baseline. The suction/discharge flow rate characteristics are trapezoidal waveforms. Since the suction volume and discharge volume are equal,
The area of portions C and E above the base line of one trapezoidal wave is equal to the area of portions F and D below. Further, the trapezoidal waves of both plunger pumps 516 are in a temporal relative relationship such that the sum of their output flow rates is constant. This is to ensure that the solvent is supplied to the liquid chromatograph L in a smooth flow.
The control valves 2 and 3 are opened and closed during the suction process of the plunger pumps 5 and 6.

Figure 3 shows an example of the suction process and the opening and closing of the valves, where A shows the suction operation of the plunger pump, the mouth shows the opening and closing timing of valves 2 and 3 of this device 1, and C shows the valves in the conventional device. It shows the timing of opening and closing. At the entrance in FIG. 3, valve 2 is open at G1 to G5, and valve 3 is opened at H1 to H5. In FIG. 3C, one valve is opened at J, and the other valve is opened at K. In both cases, when one valve is open, the other valve is closed. As is clear from FIG. 3 and C, in this device 1, the cycle time t of a series of valve operations in which each control valve 2, 3 is opened and closed once in sequence is the suction operation time T of the plunger pump. The valve operation is repeated 5 cycles during one suction process. In contrast, in the conventional device, the cycle time τ of the valve operation is equal to the suction operation time T of the plunger pump. Now, if it is desired to mix solvent A and solvent B at a ratio of 1:1, control valves 2 and 3 are each opened for an equal amount of time.

In other words, at the entrance of Figure 3, In Figure 3 C, It is said that

Ideally, the trapezoidal waveform that is the suction flow rate waveform of the plunger pump is well-balanced as shown in Figure 3 A, but in reality, the shape of the cam 12 may deviate from the ideal shape, or the check valve may deviate from the ideal shape. It is distorted due to the difference in characteristics between Nos. 14 and 17 and the inertia of the liquid.

This is, for example, as shown in Fig. 3A, b. The amount of solvent sucked into the plunger pump is obtained by integrating the suction waveform of the plunger pump over the opening time of the valve corresponding to the solvent.

Therefore, by integrating the waveforms A and b in Figure 3A with the opening time characteristics in Figure 3A and C, the amounts of both solvents sucked can be compared. Table 1 shows the calculation results when one section of the grid shown in FIG. 3A is taken as 1. As is clear from Table 1, this device 1 has the advantage that it is less prone to errors than the conventional device when the suction flow rate waveform of the plunger pump is distorted.

The main feature of this invention is to perform a series of valve operations in the part that causes strain to disperse the strain to each solvent and maintain the overall balance. Since distortion is caused at the beginning and end, the effect will not be produced unless the cycle time of a series of valve operations is shorter than the time at the beginning or end.

However, in reality, waveform distortion can occur at any part of the trapezoidal wave, so the cycle time is set to 1/2 or less of the plunger pump's suction operation time, and a series of valve operations are performed during one suction process. By performing two or more cycles, the error can be made smaller than before. In general, the effect increases as the number of cycles increases, but if the number of cycles is increased too much, switching of the control valve becomes a new error factor, so it should be kept below an appropriate limit.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the liquid mixing device of the present invention, FIG. 2 is a diagram of the operating characteristics of the plunger pump in the device of FIG. 1, and FIG. C is an enlarged view of the suction operation characteristics of the control valve in the device shown in FIG. 1... Liquid mixing device, 2, 3... Control valve, 5, 6...
... Plunger pump, A, B... Solvent, L... Liquid chromatograph.

Claims (1)

[Claims] 1 Connect two or more liquid supply sources to the plunger pump through respective control valves, and open and close the control valves during the plunger pump suction process to suck each liquid into the plunger pump at a predetermined ratio and mix them. In a type liquid mixing device, a series of valve operations in which each control valve is opened and closed once in sequence is called 1.
A liquid mixing device characterized in that two or more cycles are performed during one suction process.