JPS6213607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic flowmeter, and particularly to electrodes thereof.

An example of a conventional capacitive electrode electromagnetic flowmeter is shown in FIG. A detection electrode 3 and a shielding electrode 4 are disposed within the lining 2 provided on the inner wall of the non-magnetic metal tube 1.
is provided. Since these electrodes 3 and 4 are made of metal, if the material of the lining 2 is fluororesin, complete adhesion between the metal electrodes 3 and 4 and the lining 2 is impossible.
Therefore, due to pressure fluctuations or negative pressure of the fluid flowing inside the metal tube 1, a phenomenon occurs in which the lining 2 and the electrodes 3 and 4 come into close contact with each other and then separate from each other. For this reason, the cross-sectional area of the metal tube 1 changes, causing measurement errors, and, especially in the case of capacitive electrodes, friction generates electric charges, which causes noise.

Furthermore, because the thickness of the lining 2 to protect the detection electrode 3 from the measurement fluid cannot be made sufficiently thick due to its structure, there is a risk that if the measurement fluid is corrosive, components in the fluid may penetrate the thin lining 2 and corrode the detection electrode 3. In some cases, expensive noble metals were used as the detection electrode 3.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention aims to provide an electromagnetic flowmeter that eliminates measurement errors and noise and prevents corrosion.

In order to achieve this object, the present invention provides an electromagnetic flowmeter having a lining made of fluororesin on the inner wall of the pipe, in which the electrodes provided in the lining are made of conductive fluororesin, and the lining and electrodes are connected together. It is characterized by being fused.

Here, an embodiment of the present invention will be described with reference to FIG. 2 and subsequent figures. Note that the same parts as in FIG. 1 are given the same reference numerals. FIG. 2 is an example of a capacitive electrode type electromagnetic flowmeter. The lining 2 provided inside the non-magnetic metal tube 1 is made of fluororesin. On the other hand, a detection electrode 3' and a shielding guard electrode 4' are provided within the lining 2, and these electrodes 3' and 4' are made of conductive fluororesin. This conductive fluororesin is made by filling a fluororesin with a conductive material 5 such as graphite or metal powder, so that the entire body has conductivity. In this case, although the conductive fluororesin has lower conductivity than metal, it does not need to have very good conductivity because the input impedance of the converter connected to the electrodes of the electromagnetic flowmeter is high.

In order to bring the detection electrode 3' and guard electrode 4' into close contact with the lining 2, conductive fluororesin films 3a and 4a, which will become the electrodes 3' and 4', are placed inside the lining 2 as shown in FIG. conductive fluororesin film 3a,
When a high frequency wave is applied to 4a, eddy currents are generated in the resin films 3a, 4a, and the conductive fluorine resin films 3a, 4a and the lining 2 are bonded to each other by thermal melting due to self-heating. In this case, it is necessary to heat and bond the hot-melt adhesive surfaces together using a pressing jig 6. In hot melt bonding, it is preferable that the fluororesin of the lining 2 and the fluororesin of the electrodes 3' and 4' be made of the same material having the same melting point, and the adhesive performance will be improved.

FIG. 4 shows an example of a wetted electrode electromagnetic flowmeter in which the electrode 3b contacts the fluid to be measured. In this case as well, the electrode 3b and the lining 2 can be brought into close contact with each other by melt-bonding the electrode 3b using a conductive fluororesin. In this example, reducing measurement errors,
In addition to preventing corrosion, it is also possible to reduce leakage accidents due to poor sealing between the electrode 3b and the lining 2.

As an adhesion method, in addition to the above-mentioned heat-melting bonding using high frequency, heat-melting bonding using Joule heat by directly passing an electric current through the electrode 3b as shown in FIG. 5 may be used.

As explained above in the embodiments, according to the present invention, the electrodes included in the fluororesin lining are made of the same conductive fluororesin, thereby making it possible to fuse the lining and the electrodes. This allows for tighter bonding, thereby eliminating measurement errors and noise due to changes in cross-sectional area, as well as the use of expensive metals that are resistant to corrosion.

[Brief explanation of the drawing]

Figures 1a and 1b are examples of conventional electromagnetic flowmeters, where a is a partially cutaway perspective view and b is a cross-sectional view, and Figures 2a, b to 5 are examples of electromagnetic flowmeters according to the present invention.
FIG. 2a is a sectional view of an example, FIG. 2b is a partially enlarged sectional view of FIG. 2a, FIG. 3 is a sectional view for explaining the bonding method, and FIG. 4 is a sectional view of another example. FIG. 5 is an enlarged sectional view for explaining another example of the bonding method. In the drawing, 1 is a metal tube, 2 is a lining, 3,
3' is a detection electrode, and 4 and 4' are guard electrodes.

Claims (1)

[Claims] 1. An electromagnetic flowmeter having a lining made of fluororesin on the inner wall of the pipe, characterized in that the electrodes provided in the lining are made of conductive fluororesin, and the lining and the electrodes are fused. Electromagnetic flowmeter.