JPH069320Y2 - Electromagnetic flowmeter earth ring - Google Patents

Description

TECHNICAL FIELD The present invention relates to a structure of an earth ring of an electromagnetic flowmeter.

2. Description of the Related Art As is well known, an electromagnetic flowmeter measures the flow rate of a conductive fluid flowing in a measuring tube by using Faraday's law of electromagnetic induction. That is, a coil for generating a magnetic field orthogonal to the flow is arranged in the measuring tube, and a minute electromotive force generated in a conductive fluid flowing in the magnetic field is insulated from the inner surface of the measuring tube orthogonal to the flow and the magnetic field. It is output via a pair of electrodes provided, and the micro electromotive force between the electrodes is measured with reference to the potential of the earth ring pressed against the end face of the measuring tube. Therefore, the potential of the earth ring must be reliable and stable.

FIG. 2 (a) is a main part configuration diagram showing an example of a conventional technique in which an earth ring is pressure-welded. In the figure, 1 is a measuring tube of an electromagnetic flow meter made of non-magnetic metal such as stainless steel. A main part 10 on the outer circumference of the measuring tube 1 is composed of a coil that generates a parallel magnetic field orthogonal to the tube axis OO ′, a yoke that forms a return path of the magnetic field, and the magnetic field and the tube axis OO ′. Orthogonal measuring tube 1
A pair of opposing electrodes 4 insulated by a resin lining 2 which is in close contact with the wall surface of the measuring tube 1 is embedded in the wall surface of the. The electromagnetic flowmeter described above is sandwiched by the flange 71 of the flow tube 7 at the flange 11 of the measuring tube 1 at the end. The earth ring 5 is press-fitted between the flange 11 and the flow tube flange 71.
Is led out to the outside by a conductor 54 and is connected to the outer circumference of the flange portion 11 by a screw 6 via a washer 61, so that the measuring tube 1 is reliably held at the ground potential. The earth ring 5 is made of a stainless steel annular plate in the case of an ordinary conductive fluid, and has an inner peripheral surface having a dimension substantially equal to that of the lining 2 and in contact with the fluid to be measured. However, when the fluid to be treated is strongly corrosive acid-alkali, etc., stainless steel is corroded, and the corroded surface increases contact resistance and loses the function as an earth ring. An earth ring having an electrode structure for contacting liquid is used. An example thereof is shown in FIGS. 2 (b), (c) and (d), (e). One of them is shown in the figure (b), and the figure (c) is a sectional view taken along the line P-P of the figure (b). In the figure, 51a,
51b is an annulus such as PTFE or PTA, and one of the annuli 51
Strip-shaped ground plates 52a and 52b made of platinum and having a thickness of about 0.1 mm are adhered on the diameter of a by a resin adhesive or the like. 51
The a and 51b are in close contact with each other with the earth plates 52a and 52b sandwiched therebetween and are integrated. The ground plates 52a and 52b project outside from the outer circumferences 511 of the resin rings 51a and 51b, respectively, and have the conductor wire 54 welded to them, so that the ground plates 52a and 52b slightly project from the inner circumference 512 and come into contact with the liquid to be received. 2 (d) and 2 (e) show another example, and similarly,
(E) figure is a QQ arrow sectional view in (d) figure, but the difference from (b) figure is the inner circumference 512 of the resin ring 51a.
That is, the earth ring 53 is provided on the circumference of the above to contact the liquid over the entire circumference of the inner peripheral surface to reduce the contact resistance.

Problems of Prior Art Since the above-mentioned earth ring 5 uses an expensive platinum plate, the shape and dimensions are selected so as to reduce the area of the platinum plate, but the thickness of platinum is about 0.1 mm and the resin ring 51a, 5
Even if pressure is applied through the adhesive in 1b, the thermal expansions of the resin and platinum differ by more than one order of magnitude, so there is a small gap between the resin and ground plate due to creep and repeated fatigue in a place where temperature changes are large. There was a problem that the corrosive liquid oozes out to the outside.

Means for Solving Problems The present invention has been made to solve the problems shown in the above-mentioned prior art, and is inexpensive without using the expensive platinum plate in the prior art, and the earth ring The main component of the earth ring is a conductive material made of a platinum powder mixed resin having a coefficient of expansion similar to that of the resin annular plate, and the conductive ring embedded portion of the resin annular plate of the earth ring is embedded as a recess groove. After that, the first annular plate having the platinum groove mixed resin bonded to the concave groove so as to be a flat surface, the conductive noble metal powder mixed resin and the noble metal powder mixed resin are electrically connected to each other in the outer peripheral concave part, and the metal plate is provided outside the outer periphery. And the second annular plate, which is a flat surface by embedding, is made into an integral structure by bringing the respective conductive resin portions into surface contact.

Embodiment FIG. 1 is a schematic explanatory view of a grounding ring of an electromagnetic flowmeter according to the present invention, which includes a first annular plate 21 shown in FIG.
(C) The second annular plate 31 shown in the figure is the main constituent element. The first and second annular plates 21 and 31 are resin plates made of polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalcoethylene copolymer (PFA), or the like. The first annular plate 21 shown in (a) is a plan view, and (b) is shown.
The figure shows a sectional view taken along the line XX in FIG. Note that (b)
The thickness of the figure and the later-described figure (d) are exaggerated for the sake of explanation. On one surface A of the first annular plate 21, a concave portion 27a is formed on the inner circumference.
27b, which is a recess of the same depth, which radially extends from the recess 27a in the outer peripheral direction, is provided. The fine particles of platinum and the PTFE, PF are provided in the recesses 27a, 27b of each one.
A conductive resin ring 22 and a branch conductive plate 23 are respectively formed by mixing a resin powder such as A and applying it as a paste of a highly viscous conductive resin with a solution such as volatile alcohol or benzene and a resin adhesive. To do. The height of the conductive resin ring 22 and the branch guide plate 23 after coating is set to be slightly higher than the same plane as the first annular plate 21. It should be noted that the branch guide plate 23 may be provided in plural, and for example, 24, 28, 29, etc. may be provided. In the same manner, the recess 35 is formed on the outer circumference of the one surface A of the second annular plate 31. The depth of the concave portion 35 is set to be approximately the same as that of the grooves 27a and 27b in FIG. 3A, but the concave portion 35 corresponding to the branch conducting plate 23 and the other branch conducting plate 24 of the first annular plate 31 has terminals. Board 3
Grooves having a depth corresponding to the plate thickness of the conductive plates 3, 34 are further provided. After the terminal plates 33, 34 are pressed into the grooves and fitted, the recesses 35 are coated with the paste 27A, 27b of the first annular plate 31 of a conductive resin paste to the extent that the surface A is flat. The first and second annular plates 21 and 31 described above are arranged so that the surfaces A are in contact with each other.
3, 24 and the terminal plates 33, 34 are overlapped with each other so as to form the same ring and heat-treated at 380 to 400 ° C. or the like, and the conductive resin is pressure-contacted so as to become the same body as the ring plate. ，
24, the branch guide plate 23, the external conductive resin ring 32, and the terminal plates 33 and 34 are integrated conductors as shown in the cross section in FIG. Plate 33,
It is possible to bring the electromagnetic flowmeter measuring pipe 1 to the ground potential from 34 through the lead wire 54 (not shown).

Effects As described above, according to the earth ring of the electromagnetic flowmeter of the present invention, the mixture of the resin powder and the precious metal powder such as platinum is heat-treated to be integrated with the annular plate, and only the necessary local parts are made conductive. Since the amount of noble metal is small and the materials are almost the same, the physical properties of the conductive part and the annular plate substrate are the same, so it is possible to provide a cheap and stable earth ring. .

[Brief description of drawings]

FIG. 1 shows an outline of the earth ring of the electromagnetic flowmeter of the present invention. (A) is a first annular plate, (b) is (a).
Sectional view taken along the line XX in the figure, (c) the second annular plate, (d)
The figure is a cross-sectional view taken along the line YY of the figure (c), and the figure (e) is a cross section when combined and integrated. FIG. 2 shows a conventional technique, and FIG. 2 (a) is an example of mounting an earth ring, and (b) and (c).
Figures and (d) and (e) show an example of a conventional earth ring. 1 ... Measuring tube, 2 ... Lining, 4 ... Electrode, 5 ... Earth ring, 7 ... Flow tube, 21 ... First annular plate, 31 ... Second annular plate, 22 ... Conductive resin ring, 23, 24, 28 , 29 ... Branch conductive plate, 32 ... External conductive resin ring, 33, 34 ... Terminal plate.

Claims (1)

[Scope of utility model registration request] 1. A non-magnetic measuring tube having an insulated inner surface sandwiched by a flow tube through which a fluid flows through an earth ring, and a pair of electrodes arranged to face each other on the diameter of the measuring tube. And a magnetic field generating means for applying a magnetic field in a direction orthogonal to the line connecting the measuring tube axis and the electrodes, and the flow rate is calculated from the flow rate signal output between the pair of electrodes with reference to the potential of the earth ring. In the electromagnetic flowmeter seeking, the earth ring has a pair of circular plates made of a resin insulating material as a substrate, and the substrate has an inner surface of an inner peripheral portion and a radial shape extending from the inner peripheral portion to the outer peripheral portion. A first annular plate having a flat surface in which a conductive noble metal powder mixed resin is embedded in the recess, a conductive noble metal powder mixed resin in the outer peripheral recess of the inner surface, and a conductive noble metal powder mixed resin conducting to the outside of the outer periphery. Second with a metal plate extending to form a flat surface
An earth ring for an electromagnetic flowmeter, which is an annular plate, wherein the inner surface of the first annular plate and the inner surface of the second annular plate are intimately integrated with each other, and the metal plate serves as a ground terminal.