JP3521361B2 - Flow measurement device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow measuring device,
In particular, the present invention relates to a flow rate measuring device suitable for measuring a minute flow rate, such as a flow rate measurement of a liquid chromatograph sample. 2. Description of the Related Art As a flow rate measuring device, there is known a flow rate measuring device which measures the speed of a divided body which moves with the flow of a fluid in a flow path (cylinder) to measure the flow rate (Japanese Patent Application Laid-Open No. Sho. 60
-133319, etc.). FIG. 4 shows an example of a flow rate measuring device using a rod-shaped member, that is, a free piston, as the dividing body. This flow rate measuring device comprises a cylinder 10 installed in a substantially horizontal direction, a free piston 11 which moves with the movement of a fluid flowing through the cylinder 10, and a sensor 12 for measuring the moving time of the free piston 11. ,
13, both ends of the cylinder 10 are connected to a pipe having switching valves 14 and 15 for switching the flow direction of the fluid. When the flow rate of a fluid is measured by this flow rate measuring device, for example, as shown in FIG.
If 1 is on the right side of the cylinder 10, the switching valve 14,
15 is operated to flow the fluid as shown by the solid line in FIG. As a result, the free piston 11 moves from right to left in the figure with the flow of the fluid, so that measurement starts when the right end of the free piston 11 passes through the right sensor 12. Then, when the left end of the free piston 11 is detected by the left sensor 13, the measurement is terminated, and the flow rate is calculated from the obtained measurement time and the capacity of the cylinder 10. In the next measurement, the switching valves 14 and 15 are switched,
The fluid flows through the pipe shown by the broken line in FIG.
1 is moved from left to right in the figure. That is, the left end of the free piston 11 is
Measurement is started after passing, and the measurement ends when the right sensor 12 detects the right end of the free piston 11,
Similarly, the flow rate is calculated. Further, the sensors 12, 1
3 detects the free piston 11 and the switching valves 14 and 15
The flow rate can be continuously measured by linking the switching with the above. [0006] However, in the above-described system, if the sensors 12 and 13 fail to operate during measurement and the flow path is not reversed, the free piston 1 is not used.
1 is the position of the cylinder 10
Since the fluid outlet of the cylinder 10 is closed by the free piston 11, the pressure on the liquid inflow side rises, and there is a possibility that the piping or the like may be damaged. When air bubbles are generated in the pipe,
Since the volume of the fluid in the flow rate measuring device fluctuates due to the expansion and contraction of the air bubbles and a measurement error occurs, the air bubbles must be quickly discharged. However, if the air bubbles adhere to the end of the free piston 11, Is moved together with the free piston 11, so that it is difficult to discharge it. Therefore, the present invention can release fluid even if the free piston closes the end on the fluid outlet side of the cylinder due to malfunction of the sensor or the like, thereby preventing damage to piping and the like. When air bubbles are generated in the piping,
It is an object of the present invention to provide a flow measurement device capable of rapidly discharging bubbles. [0009] In order to achieve the above object, a flow measuring device of the present invention comprises a cylinder installed in a substantially horizontal direction, a free piston movably provided in the cylinder, Two sets of sensors for detecting the free piston moving with the flow of fluid in the cylinder;
A flow measuring device, comprising: a switching valve for switching a flow direction of a fluid in a cylinder; and a pipe, and measuring a flow time of a fluid by measuring a moving time of a free piston moving between the two sets of sensors. Ten
While forming to the diameter and length that can obtain a good liquid tightness,
The relief port of the central portion above the flow body of the cylinder is provided, the two sets of sensors, the relief port of the fluid
In the symmetric position with respect to the center,
Provided at wide intervals, each sensor and the fluid
The distance from the relief port to the length of the free piston 2
It is characterized by being set shorter . According to the above construction, the fluid escape port is provided.
The free piston is between the two sets of sensors.
When the piston is closed by the free piston,
Ton moves past the sensor to the end of the cylinder
When the flow rate is released , the normal flow rate measurement can be performed in the same manner as in the related art in a state where the escape port is closed by the free piston. If the free piston moves to the end on the fluid outlet side of the cylinder without operating the sensor, the escape port is opened by the movement of the free piston, and the fluid is discharged from this port to the outside of the cylinder. be able to. Further, when bubbles are detected in the cylinder during use or when bubbles are discharged before the measurement is started,
By moving the free piston to the end on the fluid outlet side to open the escape port, bubbles can be discharged to the outside of the cylinder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to one embodiment shown in FIGS. The flow measuring device shown in this embodiment includes a cylinder 1 installed in a substantially horizontal direction,
It comprises a free piston 2 that moves with the movement of the fluid flowing in the cylinder 1 and two sets of left and right sensors 3 and 4 for measuring the movement time of the free piston 2. Both ends of the cylinder 1 are conventional. Switching valves 5 and 6 similar to
Is connected to the piping having The cylinder 1 is made of transparent glass, and a fluid escape port 7 is formed above the center. The free piston 2 is made of ceramic, is movable in the cylinder 1, and has a diameter and a length that can obtain sufficient liquid tightness. The sensors 3 and 4 are, for example, optical sensors each including a light emitting unit and a light receiving unit, and are provided at symmetrical positions around the port 7 at intervals wider than the length of the free piston 2, and The distance from each port 7 is set shorter than the length of the free piston 2. That is, the length of the free piston 2 and the positional relationship between the positions of the sensors 3 and 4 and the port 7 are such that when both ends 2a and 2b of the free piston 2 are located between the sensors 3 and 4, 2 closes the port 7, and when the right end 2a or the left end 2b of the free piston 2 moves toward one end of the cylinder 1 beyond one of the sensors 3 and 4, the port is moved with the movement of the free piston 2. 7 is set to be openable. The switching valves 5 and 6 are provided on the inflow side pipe A and the outflow side pipe B of the flow rate measuring device, respectively.
The flow path shown by the solid line in FIG. 1 and the flow path shown by the broken line are switched, and the flow direction of the fluid in the cylinder 1 is switched accordingly. When the flow rate is measured by using the flow rate measuring device having the above-described structure, first, as shown in FIG. 1, the switching valves 5 and 6 are switched to the flow paths shown by solid lines to flow the fluid to be measured. Accordingly, the free piston 2 in the cylinder 1 moves from right to left by being pushed by the fluid, so that the measurement is started when the right end 2a of the free piston 2 passes the right sensor 3. As shown in FIG. 2, when the left sensor 2 detects the left end 2b of the free piston 2, the measurement is terminated, and the time obtained by the measurement and the previously measured cylinder 1 To calculate the flow rate of the fluid. At this time, the port 7 is connected to the free piston 2
As a result, no fluid flows out of the port 7. Although a small gap is formed between the cylinder 1 and the free piston 2 to allow the free piston 2 to move, sufficient fluid tightness is ensured. The free piston 2 is pushed to the liquid outflow side without entering the gap, and the fluid on the outflow side is pushed by the free piston 2 and flows out. Further, the switching valves 5 and 6 are connected to the sensors 3 and 4
And the flow path is sequentially switched between the solid line side and the broken line side in FIG. 1 to continuously measure the flow rate. If the free piston 2 moves to the end of the cylinder 1 beyond the sensors 3 and 4 when the sensors 3 and 4 do not operate or an abnormality occurs in the control system, for example, as shown in FIG. As described above, when the free piston 2 moves too much, the port 7 is opened along with the movement of the free piston 2, so that the fluid flowing from the right side of the cylinder 1 can flow out of the port 7. As a result, the pressure on the liquid inflow side does not increase, and damage to the cylinder 1 and the piping system can be prevented. As described above, since the free piston 2 itself has the function of opening and closing the port 7, there is no need to provide a complicated control system or the like, and reliable operation can be obtained with a simple configuration. Further, when measuring a large flow rate, the free piston 2 is moved to the cylinder 1 by the time the flow path is reversed.
May move excessively to the end side of the port, but since the port 7 is opened with the movement of the free piston 2, the fluid is supplied to the port 7 as in the case where the sensors 3 and 4 do not operate.
Can be drained from If bubbles are discharged before measurement or bubbles are found during use, the free piston 2 is moved to the fluid outflow side and the port 7 is opened, so that the bubbles are removed from the port 7. Can be discharged. In this embodiment, the pipe from the port is connected to the outflow pipe, but an independent pipe system may be formed to discharge the fluid. Also, the port is
By disposing in the vertical direction at the center of the cylinder, the discharge of air bubbles can be performed extremely easily. As described above, the flow rate measuring apparatus according to the present invention is an apparatus for measuring a flow rate by measuring a moving time of a free piston moving in a cylinder. A fluid relief port, which is closed by the free piston when the free piston is between the two sets of sensors and opened when the free piston moves past the sensors to the end of the cylinder. With this configuration, even if the free piston moves to the outlet end of the cylinder, the fluid can be discharged through the port, and the pressure on the inflow side can be prevented from rising, thereby preventing damage to the piping system and the like. Further, since the port is provided above the cylinder, the air bubbles in the pipe can be quickly discharged, and an accurate measurement value can always be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing one embodiment of a flow rate measuring device according to the present invention, and showing a state at the start of measurement. FIG. 2 is an explanatory diagram showing a state at the time of completion of measurement. FIG. 3 is an explanatory diagram showing a state in which a port is open. FIG. 4 is an explanatory diagram showing an example of a conventional flow measurement device. [Description of Signs] 1 ... Cylinder, 2 ... Free piston, 3,4 ... Sensor, 5,6 ... Switching valve, 7 ... Relief port, A ... Inflow side piping, B ... Outflow side piping

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01F 3/14 G01F 1/00-1/30 G01F 1/34-1/54 G01F 3/00-9/02 G01F 25 / 00

Claims (1)

(57) [Claim 1] A cylinder installed in a substantially horizontal direction, a free piston movably provided in the cylinder, and the free piston moving in accordance with the flow of fluid in the cylinder , A switching valve for switching the flow direction of the fluid in the cylinder, and a pipe, and the flow rate of the fluid is measured by measuring the travel time of the free piston moving between the two sets of sensors. In the flow measuring device, the free piston does not have sufficient liquid tightness.
And forming the diameter and length is provided with a relief port of the central portion above the flow of the cylinder, the two sets of Se
Sensor in a symmetrical position about the fluid escape port.
Provided at intervals greater than the length of the free piston,
And each sensor and the fluid escape port
The flow rate measuring device is characterized in that the distance is set shorter than the length of the free piston 2 .