JPH0246886B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a liquid used to measure the position of a liquid level in a waterway or tank, or to measure the position of a liquid level upstream of a weir in a weir-type flowmeter. Regarding the structure of the position detector. In particular, the present invention relates to a structure in which the position of a liquid level is detected by a float, and an electric signal converter such as a potentiometer, which is placed isolated from a fluid space by a partition wall, is connected and operated by a magnetic coupling.

A conventionally well-known magnetic joint has a cylindrical partition wall arranged vertically, a float attached to the outside of the partition wall so as to be able to swing freely, and an operating rod of an electric signal converter such as a potentiometer inserted into the inside of the partition wall. A ring-shaped magnet is fixed to the control rod, and a cylindrical magnet is fixed to the operating rod, and these are placed facing each other with a partition wall in between. Since the magnets are attracted to each other by magnetic force, when the float moves up and down, the operating rod inside the partition wall also moves up and down at the same time.

In this case, the inner and outer magnets magnetically attract each other and come into pressure contact with the bulkhead, and when they are displaced, sliding frictional resistance acts between them and the bulkhead, so the displacement of the float and operating rod is caused by the liquid level. It will be later than that. Therefore, when the liquid level rises, the detected liquid level becomes lower than the actual level, and when it falls, the detected liquid level becomes higher than the actual level, causing hysteresis in the measurement. For this reason, measurement accuracy deteriorates when detecting minute changes in the liquid level. If the magnetic force of the magnet is weakened, the sliding resistance will be reduced, but at the same time, the connection between the float and the operating rod will become unstable.
It cannot be made weaker than necessary.

Prior Art Therefore, in order to weaken the frictional resistance between the magnet and the partition wall, the present applicant previously proposed rotating the float in Japanese Patent Application No. 220176/1982. This reduces frictional resistance by rolling the magnet rather than sliding it along the partition wall, that is, by utilizing rolling resistance, which is much weaker than sliding resistance.

Problems to be Solved by the Present Invention In the case of the above technique, blades are attached to the outer periphery of the float, and the liquid to be measured is guided so as to hit the blades, so that the liquid to be measured itself rotates the float. Therefore, since it uses the kinetic energy of the flow of the liquid to be measured, it has the advantage of not requiring special energy to rotate the float, but it has the disadvantage that the float cannot be rotated if the flow rate is low. It was hot.

The technical problem of the present invention is to make the magnet roll against the partition wall without using the kinetic energy of the liquid.

Means for Solving the Problems The technical means of the present invention taken to solve the above-mentioned technical problems are as follows: (a) A float is placed on the outside of the cylindrical partition wall, and an operating rod of an electric signal converter is placed inside the cylindrical partition wall. (b) A ring-shaped magnet is attached to the float, a cylindrical magnet is attached to the operating rod so that they face each other across the partition wall, and (c) a cylindrical intervening tube is rotatably arranged between both magnets. (b) The intervening cylinder is rotated by an electric motor,
It is something.

Here, the intervening tube is formed by forming a partition wall intervening between the float and the magnet attached to the operating rod into a cylindrical shape, airtightly bearing it using packing, and arranging it so as to be rotatable. Can be used as a bulkhead member. Alternatively, a cylindrical intervening tube may be rotatably disposed inside the partition member by bearing it.

Effects The effects of the above technical means are as follows.
Like a potentiometer, the operating rod of an electrical signal converter moves back and forth in one motion, but does not rotate. The float is also prevented from rotating due to the viscous resistance of the surrounding liquid. Therefore, when the cylindrical intervening cylinder is rotated by an electric motor, the cylindrical magnet attached to the operating rod rolls relative to the intervening cylinder. The annular magnet attached to the float also rolls relative to the cylindrical partition member. Therefore, there is no sliding friction resistance between the magnet and the intervening tube or partition member, but
Only rolling friction resistance, which is much weaker than this, works. Therefore, the hysteresis of the measured liquid level becomes extremely small.

Example An example showing a specific example of the above technical means will be described.

Example 1 (See Figure 1) This example is applied to a weir type flowmeter. A lid 2 is attached to the main body 1 with bolts (not shown) to constitute a casing of the measuring instrument. A substantially cylindrical space is formed inside the casing, and a cylindrical dam 10 is attached thereto. An inlet 8 communicates with the inside of the weir 10 through a cylindrical screen 22. A V-shaped opening, that is, a weir 11, is formed in the peripheral wall of the weir tube 10, and a communication hole 1 is formed in the upper part of the aperture 11.
Open 2. The inside and outside of the weir tube 10 communicate through the weir 11 and the communication hole 12, and the outside space communicates with the outlet 9 through a rising passage.

A cylindrical partition member 1 is located approximately in the center of the weir tube 10.
3 is placed vertically through the lid 2. The lower end of the partition member 13 is integrally closed, and the weir tube 10
It is rotatably fitted into a bearing 21 attached to the lower plate of. A packing 15 is interposed between the lid 2 and the lid 2 to rotatably support the lid 2 in an airtight manner.

A hollow float 18 is arranged outside the partition member 13. Along the central axis of the float 18, the partition member 1
3 is attached, and an annular magnet 20 is fixed to the outer periphery of the cylinder.

On top of the lid 2, a heat insulating plate 3 and supporting members 4 and 5 are attached in a stacked manner, and a potentiometer 7 is fixed.
Cover with cap 6.

The operating rod 14 of the potentiometer 7 is inserted into the partition member 13. At this time, the cylindrical magnet 19 is placed on the hollow float 1 with the partition member 13 in between.
It is attached to the operating rod 14 so as to face the magnet 20 attached to the magnet 8 .

An electric motor 16 is installed in the space provided between the lid 2 and the heat insulating plate 3.
is arranged, and its output shaft is engaged with a gear 17 attached to the partition member 13.

In this embodiment, the cylindrical partition member 13 is also used as an intervening cylinder, which has the advantage of simplifying the structure, but has the inconvenience of having to interpose the packing 15 between it and the lid 2.

The liquid flows into the diaphragm 10 from the inlet 8,
It flows out through weir 11 to outlet 9. Since there is a certain relationship between the flow rate of liquid passing through the weir 11 and the liquid level inside the weir 10, by measuring the liquid level inside the weir 10, the liquid passing through the weir 11 can be measured. The flow rate can be determined.

The liquid level is detected by the float 18, and the operating rod 14 is displaced via the magnetic coupling (magnets 19, 20).
The potentiometer 7 converts it into an electrical signal. Although a meter that receives electrical signals, calculates and displays the flow rate is required, illustration and description thereof will be omitted.

The partition member 13 is constantly rotated by an electric motor 16. For this purpose, the magnets 19 and 20
It will roll relative to 3.

Example 2 (See Figure 2) This example is also applied to a weir-type flowmeter whose structure is basically the same as that in Figure 1, and parts corresponding to those in Figure 1 are given the same reference numbers. , saves explanation.

The cylindrical partition member 13 is hermetically joined to the lid 2, and its lower end is hermetically joined to the member 51.
It is not necessary to mount it rotatably.

A cylindrical intervening tube 50 is arranged along the inner wall of the partition member 13. A gear 17 is fixed to the outer periphery of the upper part,
It engages with the output shaft of the electric motor 16. The intervening cylinder 50 is supported by a bearing member such as a bearing interposed between the lid 2 and the partition member 13, but this is not shown in the drawings as it will be understood by those skilled in the art and would complicate the drawings.

When the electric motor 16 rotates the interposed cylinder 50, the cylinder along the center axis of the float 18 aligns with the partition member 13.
Magnet 1 attached to operating rod 14 in contact with the outer periphery of
9 are in contact with the inner circumferential wall of the intervening cylinder 50 and roll relative to each other.

This embodiment has an advantage over the first embodiment in that it does not require a packing structure, but has the disadvantage that the partition member 13 cannot also be used as the intervening cylinder 50.

Effect of the invention The present invention produces the following unique effects.

Conventional techniques for rotating a float using the kinetic energy of the liquid to be measured require a passage structure that guides the liquid against the float to cause it to rotate, which results in a complex structure and large size. The present invention has a simple structure in which the liquid is introduced into the dam.

In addition, with conventional technology, there is a risk that the float may be shaken by the water flow hitting the blades, or the liquid surface around the float may ripple, resulting in poor liquid level measurement accuracy. In contrast, in the present invention, the float is caused to roll relative to each other by rotating the cylindrical partition member and the intervening tube, and the float itself and the surrounding liquid do not rotate. There is no oscillation or rippling of the liquid level, and the accuracy of liquid level detection is improved.

In order to rotate the operating rod of an electric signal converter using an electric motor, it is necessary to divide the operating rod into upper and lower parts and connect the two with a joint such as a ball spline. It is sufficient to simply use a cylindrical partition member or an intervening tube.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a weir-type flowmeter to which an embodiment of the present invention is applied, and FIG. 2 is a cross-sectional view of a weir-type flowmeter to which another embodiment of the present invention is applied. 7: Potentio meter, 10: Sewer tube, 1
1: Weir, 13: Partition wall member (also serves as intervening tube), 1
4: Operation rod, 16: Electric motor, 18: Float, 1
9: magnet, 20: magnet, 50: intervening tube.

Claims (1)

[Scope of Claims] 1. A float is arranged on the outside of a cylindrical partition, and an operating rod of an electric signal converter is arranged inside, and an annular magnet is placed on the float and a cylindrical magnet is placed on the operating rod, facing each other across the partition. A liquid level detection structure in which a cylindrical intervening cylinder is rotatably arranged between both magnets, and the intervening cylinder is rotated by an electric motor. 2. The liquid level detection structure according to claim 1, wherein the cylindrical partition member is airtightly supported using packing and is rotatably arranged to serve also as an intervening cylinder. 3. The liquid level detection structure according to claim 1, wherein a cylindrical interposed tube is rotatably disposed inside a cylindrical partition member by bearing it.