JPH08271302A - Electromagnetic flow meter - Google Patents

Abstract

(57) [Summary] [Purpose] Prevents dew condensation in the electrode housing and ensures good electrical insulation between the electrode and the measuring tube. [Structure] The outer end of the electrode 4 is covered with an insulating cap 31. The front end of the insulating cap 31 is pressed against the extension 3A of the lining material 3 by the compression coil spring 30 to seal between the extension 3A and the insulation cap 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flowmeter for electrically measuring the flow rate of a conductive fluid flowing in a measuring pipe, and more particularly to prevent deterioration of electrical insulation between the measuring pipe and electrodes due to dew condensation. The present invention relates to an electrode seal structure of.

[0002]

2. Description of the Related Art There are various possible applications for using an electromagnetic flow meter. For example, in a case where a cooling water circulation pipe for air conditioning of a building is buried vertically and horizontally in a building, the amount of this cooling water is controlled by an electromagnetic wave. May be measured with a flow meter. In such a case, the temperature of the cooling water is lower than the temperature of the outside air in the building, so the temperature in the vicinity of the measuring pipe of the electromagnetic flow meter becomes low. On the other hand, the portion of the electromagnetic flowmeter that comes into contact with the outside air is close to the outside air temperature. Therefore, the dew condensation inside the electromagnetic flowmeter, especially near the electrodes becomes a problem. That is, when the outside air that has entered the electromagnetic flowmeter touches a cold measuring tube or an electrode or a spring that presses the electrode against the measuring tube in the electrode housing, the water contained in the outside air becomes supersaturated. Condensation forms and adheres to measuring tubes and electrodes. As a result, the distance between the measuring tube and the electrode is substantially shortened, and the insulation resistance between the measuring tube and the electrode is reduced. Originally, since the current generated by the electromagnetic induction phenomenon is a weak current, if the insulation resistance between the electrode and the measuring tube decreases, the output decreases and the flow rate cannot be measured accurately. Also, in the worst case,
The measuring tube and the electrode may be short-circuited.

Therefore, conventionally, as a method of solving such a problem, an electrode is covered with an insulating cap to ensure insulation between the electrode and the measuring tube, or an inner surface of a spring receiving member which covers the electrode housing is insulated. The coating is applied to ensure insulation between the electrode and the measuring tube, or to prevent outside air itself from entering the electrode housing as shown in FIG. Here, 1 is a measuring tube, 2 is a case,
3 is a lining material that covers the inner peripheral surface of the measuring tube 1, 4 is an electrode,
Reference numeral 5 is a boss portion as an electrode housing portion surrounding the electrode 4, 7 is a lead wire, 8 is a packing, 9 is a cover, and 10 is a crimp terminal. The cover 9 has an O-ring 1 in the opening 5a of the boss 5.
The boss portion 5 is airtightly closed by being screwed via 1 to prevent outside air from entering the boss portion 5.

[0004]

However, all of the above-mentioned conventional methods have problems. That is, neither securing insulation by the insulating cap nor securing insulation by insulating coating prevents the invasion of outside air into the electrode storage part, so it is not possible to completely prevent the occurrence of dew condensation and seal the electrode. Since it is not done, it is difficult to secure the insulation between the electrode and the measuring tube.

On the other hand, in the seal structure of the electrode accommodating portion shown in FIG. 7, the outside air itself can be prevented from entering, but there is a structural problem. That is, since it is necessary to insert the lead wire 7 into the hole 12 formed in the boss portion 5,
The work for that is troublesome. In particular, since it is necessary to form the hole 12 obliquely, the processing is also troublesome, and if the wall thickness of the boss portion 5 is thin, the hole 12 cannot be formed obliquely and a thick boss portion is formed. There is a need.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to reliably seal an electrode with a simple structure and to provide a space between the electrode and the measuring tube. An object of the present invention is to provide an electromagnetic flowmeter capable of ensuring good electrical insulation of the electromagnetic flowmeter. Further, the object of the present invention is to reliably prevent the invasion of outside air into the electrode housing portion with a simple structure, to prevent dew condensation in the electrode housing portion, between the electrode and the measuring tube. An object of the present invention is to provide an electromagnetic flow meter capable of ensuring good electrical insulation.

[0007]

In order to achieve the above object, the present invention provides an electrode accommodating portion that surrounds an electrode mounting hole on the outer peripheral surface, and the inner peripheral surface and the peripheral surface of the electrode mounting hole are made of a lining material. A covered measuring tube, an electrode provided in the electrode mounting hole, a spring elastically mounted in the electrode housing to press the electrode against the measuring tube, and a rear end of the electrode that closes the electrode housing. A spring receiving member having a through hole projecting to the outside, and an insulating cap fitted to the electrode and electrically insulating the electrode from the measuring tube and the spring,
The lining material is provided with an extension portion that covers an inner bottom portion of the electrode housing portion, and a seal is provided between the extension portion and a front end portion of the insulating cap. Further, according to the present invention, an electrode accommodating portion that surrounds the electrode mounting hole is provided on the outer peripheral surface, the inner peripheral surface and the peripheral surface of the electrode mounting hole are covered by a lining material, and the electrode mounting hole is provided. An electrode, a spring elastically mounted in the electrode housing to press the electrode against the measuring tube, a spring receiving member having a through hole for closing the electrode housing and projecting the rear end of the electrode to the outside, An insulating cap that is fitted to the electrode and electrically insulates the electrode from the measurement tube and the spring is provided, and the lining material is provided with an extension portion that covers the inner bottom portion of the electrode storage portion, and the extension portion and the spring receiving member. It is characterized in that the gap between the through hole of the spring receiving member and the electrode is sealed based on the sealing between the front end.

[0008]

In the present invention, the insulating cap covers the electrode, and the extended portion of the lining material covers the inner bottom portion of the electrode housing to electrically insulate the electrode from the measuring tube. Since the front end portion of the insulating cap and the extended portion of the lining material are sealed, even if dew condensation occurs in the electrode housing, water droplets do not enter the inside of the insulating cap. Since the space between the spring receiving member and the extension of the lining material is sealed, outside air does not enter the electrode housing through the gap between the electrode housing and the spring receiving member. Since the gap between the through hole of the spring receiving member and the electrode is sealed, outside air does not enter the electrode housing portion.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a front view showing an embodiment of an electromagnetic flowmeter according to the first invention, and FIG. 2 is a half sectional view of the electromagnetic flowmeter. The same components as those described in the related art are designated by the same reference numerals and the description thereof will be omitted. In these figures, the electromagnetic flow meter 20 is provided with a measuring tube 1 which is formed of a non-magnetic material such as stainless steel and has pipe connection flanges 1a and 1b integrally formed at both ends.
On the outer wall of the measuring tube 1, a pair of exciting coils 23 that form a magnetic flux φ orthogonal to the flow direction of the fluid to be measured 22, that is, the axis of the measuring tube 1, are arranged so as to face each other vertically. The exciting coil 23 is located between the inner core 24 and the outer core 25 that form a magnetic circuit, and is wound around the core 26.

Further, a pair of electrodes 4 having an axis in a direction orthogonal to the magnetic flux φ generated by the exciting coil 23 are provided so as to penetrate through the centers of both sides of the measuring tube 1 in the axial direction.
The inner end faces the inside of the measuring tube 1 and forms a liquid contact surface. Therefore, the electrode 4 and the exciting coil 23 are out of phase with each other by 90 ° in the circumferential direction of the measuring tube 1. In addition, the inner peripheral surface of the measuring tube 1, the inner peripheral surface of the electrode mounting hole 27 to which the electrode 4 is mounted, and both end surfaces are provided with a lining material 3 such as a fluororesin or neoprene in order to have electrical insulation and corrosion resistance. ing. Further, an electrode housing portion 28 for housing the electrode 4 is provided on the outer peripheral surface of the measuring tube 1. The electrode accommodating portion 28 is composed of a concave portion communicating with the electrode mounting hole 27, and the inner bottom portion thereof is covered by the extension portion 3A of the lining material 3 in order to enhance the sealing property of the measuring tube 1.

The electrode 4 integrally has a flange portion 4a, and the front end portion from the flange portion 4a is the electrode mounting hole 2
7, the rear end portion including the flange portion 4a is covered with an insulating cap 31 formed into a tubular body. The flange portion 4a is in close contact with the extension portion 3A of the lining material 3 that covers the inner bottom surface of the electrode housing portion 28 via an O-ring 29, and is pressed by a compression coil spring 30 mounted in the electrode housing portion 28. ing. The compression coil spring 30 presses the front end of the insulating cap 31 against the extension 3A. The opening of the electrode housing portion 28 is closed by a spring receiving member 32 of the compression coil spring 30. The spring receiving member 32 is formed in a tubular body and has an external thread formed on the outer peripheral surface thereof, and the external thread portion is screwed into a female thread formed on the inner peripheral surface of the electrode housing portion 28.

The rear end of the electrode 4 is projected from the through hole 33 provided in the spring receiving member 32 to the outside of the electrode accommodating portion 28, and the projecting end is crimped to one end of the signal lead wire 7. The terminal 10 is fixed by a set screw 34. The other end of the lead wire 7 is guided upward together with the lead wire 35 of the exciting coil 23, and is connected to a converter 36 installed on the neck portion 2A of the case 2 that covers the measuring tube 1.

The case 2 is formed in a cylindrical shape and protects the measuring tube 1, the electrode 4, the exciting coil 23 and the like. A cylindrical electrode lead-out portion 38 is integrally projectingly provided on the case 2 so as to correspond to each electrode 4, and an opening thereof is normally airtightly closed by a lid 39. By removing the lid 39 and the spring receiving member 32, the electrode 4 can be easily attached and detached from the outside of the case.

In the electromagnetic flowmeter 20 having such a structure, when the exciting coil 23 is energized to excite it,
A magnetic field is generated across the fluid to be measured 22 flowing in the measuring tube 1 and orthogonal to the flow. When a magnetic field is generated, an electromotive force proportional to the flow velocity is generated in the fluid in a direction orthogonal to both the magnetic field direction and the flow direction due to the electromagnetic induction phenomenon.
This is taken out by a pair of electrodes 4, amplified and signal-processed and then recorded, or transmitted to an indicator to measure the flow rate or average flow rate of the fluid 22 to be measured, or perform constant value control of the flow rate.

In the present invention, the inside of the insulating cap 31 is sealed by pressing the front end of the insulating cap 31 covering the electrode 4 against the extension 3A of the lining material 3 by the compression coil spring 30. , Through hole 3
Even if the moisture in the outside air is condensed by touching the measuring tube 1, the compression coil spring 30, the insulating cap 31 or the spring receiving member 32, in which the outside air that has entered the electrode housing portion 28 from the outside is cold, the water droplets of the outside air will condense into the insulating cap 31. Does not enter the cap from between the front end of the and the extension 3A. Therefore, the insulation between the measuring tube 1 and the electrode 4 does not deteriorate due to the occurrence of dew condensation, and the electromotive force can be reliably detected. Further, in the present invention, the insulating cap 31 is simply attached to the lining material 3.
Since it suffices to press the extension 3A to form a seal structure, the structure is simple and it is not necessary to form a hole for guiding the lead wire 7 to the outside in the electrode housing part 28. Wiring work of the lead wire 7 is easier than the conventional device.

The sealing structure between the extension portion 3A of the lining material 3 and the insulating cap 31 can be various structures, for example, the sealing structure shown in FIGS.

In the embodiment shown in FIG. 3, an elastic member 44 made of an insulating material such as rubber or synthetic resin is coated on the front end surface of the insulating cap 31 pressed against the extension 3A of the lining material 3 by the compression coil spring 30. Thus, the extension 3A and the insulating cap 31 are sealed. Other configurations are the same as those in the above-described embodiment. In such a structure, since the elastic member 44 is pressed against the extension portion 3A, the sealing property between the extension portion 3A and the insulating cap 31 is high, and the water droplets are not covered by the insulating cap 31.
It is possible to more reliably prevent the intrusion.

In the embodiment shown in FIG. 4, a gasket 46 is interposed between the front end of the insulating cap 31 pressed against the extension 3A of the lining material 3 by the compression coil spring 30 and the extension 3A, thereby extending the extension. Part 3
A seal is made between A and the insulating cap 31. Also,
An electrode accommodating portion 45 formed of a cylindrical body is integrally provided on the outer peripheral surface of the measuring tube 1 so as to project.

In the embodiment shown in FIG. 5, an O-ring 47 is interposed between the outer peripheral surface of the front end of the insulating cap 31 and the extension 3A of the lining material 3. Therefore, the extension portion 3A of the lining material 3 covers not only the inner bottom surface of the electrode housing portion 45 but also a part of the inner peripheral surface thereof.
It surrounds the outer peripheral surface of the front end portion of 1. Electrode storage part 45
Are integrally provided on the outer peripheral surface of the measuring pipe 1. In such a structure, it is not necessary to press the front end of the insulating cap 31 against the extension 3A.

FIG. 6 is a sectional view of an electrode portion showing an embodiment of the second invention. In this embodiment, an electrode accommodating portion 45 made of a cylindrical body is integrally provided on the outer peripheral surface of the measuring tube 1 so as to project. The extension portion 3A of the lining material 3 covers a part of the inner bottom surface and the inner peripheral surface of the electrode housing portion 45, and surrounds the outer peripheral surface of the front end portion of the insulating cap 31. The front end of the spring bearing member 32, that is, the open end is pressed against the end surface of the extension 3A, thereby sealing between the electrode housing portion 45 and the spring bearing member 32. Further, an O-ring 48 seals the gap between the through hole 33 of the spring receiving member 32 and the insulating cap 31. The O-ring 48 is pressed against the opening of the through hole 33 by the crimp terminal 10.

In the electromagnetic flowmeter adopting such a sealing structure, the inside of the electrode accommodating portion 45 can be completely sealed, so that the outside air does not enter the inside of the electrode accommodating portion 45, so that the electrode Condensation does not occur in the storage portion 45, and the insulation between the measuring tube 1 and the electrode 4 can be secured.
In this case, in this embodiment, the rear end of the insulating cap 31 is extended to the rear end of the electrode 4, but it is formed shorter than this and a gap between the through hole 33 and the rear end of the electrode 4 is formed. May be sealed by an O-ring 48.

[0022]

As described above, the electromagnetic flowmeter according to the present invention seals between the insulating cap that covers the electrode and the extended portion of the lining material that covers the inner bottom of the electrode housing.
Even if the outside air enters the electrode housing and touches a cold measuring tube etc. to condense the water contained in the outside air, water droplets will not enter the insulating cap and adhere to the electrode. It is possible to ensure insulation between the electrodes and the electrodes. In addition, the present invention seals the gap between the electrode receiving portion and the spring receiving member and the through hole of the spring receiving member and the electrode, so the airtightness inside the electrode receiving portion is high and the entry of outside air is prevented. Can be prevented. Therefore, it is possible to prevent the occurrence of dew condensation in the electrode housing portion, and it is possible to ensure the insulation between the electrode and the measuring tube.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an electromagnetic flowmeter according to the first invention.

FIG. 2 is a half sectional view of the same electromagnetic flow meter.

FIG. 3 is a sectional view of an electrode part showing another embodiment.

FIG. 4 is a cross-sectional view of an electrode portion showing another embodiment.

FIG. 5 is a cross-sectional view of an electrode portion showing another embodiment.

FIG. 6 is a cross-sectional view of an electrode portion showing an embodiment of an electromagnetic flowmeter according to the second invention.

FIG. 7 is a cross-sectional view of an electrode portion showing a conventional example of an electromagnetic flow meter.

[Explanation of symbols]

1 ... Measuring tube, 2 ... Case, 3 ... Lining material, 3A ... Extension of lining material, 4 ... Electrode, 7 ... Lead wire, 23 ...
Excitation coil, 27 ... Electrode mounting hole, 28 ... Electrode housing, 3
0 ... Compression coil spring, 31 ... Insulation cap, 32 ... Spring receiving member, 33 ... Through hole, 45 ... Electrode housing section, 48 ... O
ring.

Claims (2)

[Claims] 1. A measuring tube having an electrode accommodating portion surrounding an electrode mounting hole on an outer peripheral surface, the inner peripheral surface and a peripheral surface of the electrode mounting hole being covered with a lining material, and the electrode mounting hole. An electrode, a spring elastically mounted in the electrode housing to press the electrode against the measuring tube, a spring receiving member having a through hole for closing the electrode housing and projecting a rear end of the electrode to the outside, and the electrode An insulating cap that is fitted to the electrode to electrically insulate the electrode from the measuring tube and the spring, the lining material is provided with an extension portion that covers the inner bottom portion of the electrode storage portion, and the extension portion and the front end portion of the insulation cap. An electromagnetic flowmeter characterized by having a seal between the and. 2. An electrode housing portion is provided on an outer peripheral surface to surround the electrode mounting hole, the inner peripheral surface and a peripheral surface of the electrode mounting hole are covered with a lining material, and the electrode mounting hole is provided. An electrode, a spring elastically mounted in the electrode housing to press the electrode against the measuring tube, a spring receiving member having a through hole for closing the electrode housing and projecting a rear end of the electrode to the outside, and the electrode An insulating cap for electrically insulating the electrode from the measuring tube and the spring, the lining material being provided with an extension portion for covering the inner bottom portion of the electrode accommodating portion, and the extension portion and the front end of the spring receiving member. An electromagnetic flowmeter characterized in that the gap between the through hole of the spring receiving member and the electrode is sealed based on the fact that the gap is sealed between the electrode.