JPH10206209A - Liquid level-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure easily a center liquid level distance from an uppermost point on a center axis of a cylindrical tank to a point on a liquid level, by a wind-type liquid level- measuring instrument set close to an edge part of the tank. SOLUTION: The apparatus measures a distance to a liquid level of a cylindrical tank set in an inclined state with the use of a wind-type liquid level-measuring instrument 20. A chord length-measuring instrument 8 measures a length of a chord of a circle of an upper end of the tank, and a tank diameter-calculating means calculates a radius of the tank with the use of the length of the chord measured by the instrument 8 and a length of a perpendicular line at the circle of the upper end of the tank from a middle point of the chord. An angle detector 9 detects an inclination angle of the tank. The liquid level-measuring instrument 20 draws out a wire 22, drops a liquid level detector 30 coupled to a leading end of the wire onto the liquid level, and measures the distance to the liquid level. A center liquid level distance on a center axis of the tank is calculated from the liquid level distance measured by the measuring instrument 20, a predetermined distance on the radius from a base point of the wire of the measuring instrument 20 to the circle of the upper end of the tank, the inclination angle of the tank detected by the angle detector 9, and the radius of the circle of the upper end of the tank calculated by the diameter-calculating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level measuring device for measuring a distance to a liquid level of a cylindrical tank installed at an angle by using a winding type detector.

[0002]

2. Description of the Related Art As a large liquid container, a cylindrical tank is widely used in various fields. This type of cylindrical tank usually has a horizontal bottom and a liquid discharge port is provided at the lower side, so that the discharge port side is slightly lower to allow the liquid of the contents to flow to the end, and vice versa. Install the tank at an angle so that the side is higher.

[0003]

When measuring the distance to the liquid level of such a tank, a winding type liquid level measuring device is generally used. In this liquid level measuring device, a float or an electric liquid level detector is attached to the end of the wire wound on the winder, and the float or the liquid level detector is dropped on the liquid level from above the tank. The length of the wire fed out at that time is measured by a counter, and measured to obtain the distance to the liquid surface.

However, in order to accurately measure the distance to the liquid surface of a cylindrical tank that is installed at an angle, as shown in FIG. 1 or FIG. It is necessary to measure the distance between the surfaces.

[0005] However, when measuring the liquid levels of a large number of large cylindrical tanks installed in factories or the like sequentially using a general-purpose, portable liquid level measuring instrument, the measuring instruments can be easily attached to the cylindrical tank. Since it is difficult to accurately install the tank at the center, a measuring instrument was installed near the side wall of the tank to measure the liquid level distance at an arbitrary point other than the center of the tank.

[0006] For this reason, there are many errors (variations) in such measured values of the liquid level, and it is necessary to accurately measure the distance to the liquid level without installing a measuring instrument on the center axis of the cylindrical tank. There has been a demand for a liquid level measuring device that can perform the measurement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned point, and has been developed in such a manner that the center liquid level distance from the uppermost point on the central axis of the cylindrical tank to a point on the liquid surface is set closer to the edge of the tank. It is an object of the present invention to provide a liquid level measuring device and a measuring method thereof which can be easily measured by a preparatory liquid level measuring device.

[0008]

In order to achieve the above-mentioned object, a liquid level measuring apparatus according to the present invention uses a winding type liquid level measuring device for measuring a distance to a liquid level of a cylindrical tank installed at an angle. A liquid level measuring device to be used for measurement, which is attached to an upper end of a cylindrical tank, is disposed on an inclined center line on a plane of the tank, and has a main body having an abutting portion corresponding to an edge of the tank. A mounting frame having a string portion mounted on the upper circumference of the tank at both ends so as to form an arbitrary string on the upper end circle of the tank; and the strings on the main body of the mounting frame. A take-up type liquid level measuring device that is mounted swingably on a shaft parallel to the tip of the wire and lowers the liquid level detector connected to the tip of the wire onto the liquid surface to measure the distance to the liquid surface The liquid level measurement device is provided from a state horizontal to the upper end circle of the tank to a state horizontal to the vertical. Rotating, a tilt angle detecting means for detecting a tilt angle of the tank, a chord length measuring means provided on the chord portion, for measuring an arbitrary chord length of the tank top circle, and a chord length measuring means. Measured chord length, tank diameter calculation means for calculating the radius of the tank from the midpoint of the chord using the length of the perpendicular to the top circle of the tank, the liquid level distance measured by the liquid level measuring device, and the liquid level The predetermined distance on the radius from the base point of the wire of the measuring instrument to the top circle of the tank, the inclination angle of the tank detected by the inclination angle detection means, and the radius of the top circle of the tank calculated by the tank diameter calculation means, And a liquid surface distance calculating means for calculating a central liquid surface distance on the central axis.

[0009]

[Function / Effect] In the liquid level measuring apparatus having such a configuration, when measuring the liquid level distance of the tank, first, the mounting frame composed of the main body and the chord is placed on the tank to be measured. Is placed on the inclined center line, the contact portion is placed on the edge of the tank, and the chord is placed on the tank top circle. In this state, the chord length measuring means measures the chord length of the tank top circle,
The tank diameter calculating means calculates the radius of the tank using the chord length measured by the chord length measuring means and the length of the perpendicular from the midpoint of the chord to the top circle of the tank.

The tilt angle detecting means detects the tilt angle of the tank by rotating the liquid level measuring device from a state horizontal to the upper end circle of the tank to a state vertical to the vertical. Then, the liquid level measuring device pulls out the wire, lowers the liquid level detector connected to the wire tip on the liquid level, and measures the distance to the liquid level.

Thereafter, the liquid level distance calculating means calculates the liquid level distance measured by the liquid level measuring instrument, a predetermined distance on the radius from the base point of the wire of the liquid level measuring instrument to the upper end circle of the tank, and the inclination angle detecting means. The center liquid level distance on the center axis of the tank is calculated from the detected tank inclination angle and the radius of the upper end circle of the tank calculated by the tank diameter calculation means.

As described above, even in the case of a large inclined cylindrical tank, the mounting frame of the liquid level measuring device and the liquid level measuring device thereabove are installed near the upper edge of the tank, and the edge of the tank is The distance to the liquid level is measured at the near position, and the distance can be accurately calculated on the central axis of the tank using the distance. For this reason, the liquid level measurement device is manufactured as a general-purpose and portable type, and only by installing the device near the edge on the tank to be measured, it is possible to use a large-sized cylindrical tank whose inclination angle is unknown and whose inner and outer diameters are unknown. Even if there is, the liquid level distance can be efficiently and accurately measured by a simple operation.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS. 1 to 3, this liquid level measuring device is used to measure a distance to a liquid surface of a cylindrical tank installed at an angle, and a mounting frame 1 attached to an upper end of the cylindrical tank T on an inclined side. And a take-up type liquid level measuring device 30 attached to the center of the mounting frame 1 so as to be swingable in an inclined direction.

The mounting frame 1 is formed in a substantially T-shape in plan view, and has a main body 2 to which a liquid level measuring device 30 is attached, and a string fixed on the main body 2 at right angles to a plane circle of the tank T. And a long straight chord portion 3 that is arranged so as to form a string. A contact portion 4 is provided at the tip of the main body 2 so as to contact the edge of the upper end of the tank T. The distance a from the contact point B with the tank T to the center point C of the chord 3 is formed as a known value. Have been.

The liquid level measuring device 30 is provided on the main body 2 with the chord 3
Is pivotally supported by a shaft 10 parallel to the shaft. The liquid level measuring device 30 has a level 11 for leveling and a level adjuster 1.
2 can be mounted, and the screw of the level adjuster 12 can be turned to adjust the level gauge 30 to a horizontal state. Axis 10
Is mounted with an angle detector 9 composed of a potentiometer or the like. The angle detector 9 is such that the liquid level measuring device 30 is a tank T
The horizontal adjuster 12 detects an angle during rotation from a state parallel to the upper end to a horizontal state, thereby detecting an inclination angle θ of the tank T and outputting a signal thereof.

A pair of chord length measuring claws 5 and 6 are mounted on the chord portion 3 so as to be movable in synchronization with each other in the left and right direction. The chord length is measured at two points (points A and D) at the upper end of. That is, pulleys 13 and 14 are pivotally supported at both ends of the chord portion 3, and a pulley 15 is pivotally supported at the center.
One wire 7 is wound around 3, 14, and 15, a string length measuring claw 5 is connected to one side wire 7, and a string length measuring claw 6 is connected to the other side wire 7.

Thus, the pair of chord length measuring claws 5, 6 are
By manually moving one of the claws, the pulley 15 is relatively moved to both sides so that the distance from the center point C is the same. The center pulley 15 is fixed to the axis of a rotary type chord length measuring device 8 composed of a multi-rotation type potentiometer or the like. The chord length measuring device 8 is rotated by the wire 7 running in accordance with the movement (position) of the chord length measuring claws 5 and 6, and the distance between the chord length measuring claws 5 and 6 (the distance between the points A and D). A signal indicating 2b) is output.

As shown in FIG. 4, a liquid level measuring device 20 installed on the main body 2 of the mounting frame 1 has a built-in winding drum 23 in which a wire 22 is wound in a case 21, and
The liquid level detector 30 connected to the tip of the wire 22 is lowered above the liquid level in the tank T from the opening 21a provided at the bottom of the tank, and the distance from the upper end of the tank to the liquid level is determined by the distance of the pulled wire 22. This is the structure for measuring.

A winding motor 26 is mounted on the shaft of the winding drum 23.
Are connected, and the drum 23 is driven by the winding motor 26. The wire 22 is a pulley 27 for a rotary encoder.
Is multiplied and paid out. On the circumference of the pulley 27, a magnetic pole portion, an opening portion, a reflection portion, and the like are provided at regular intervals, and a rotary encoder 24 including a magnetic sensor, an optical sensor, and the like is provided in opposition thereto. A signal corresponding to the length of the wire 22 is output from the encoder 24.

A storage section for storing the liquid level detector 30 is formed above the opening 21a in the case 21, and a rising end detection such as a limit switch for detecting the rising end of the liquid level detector 30 is formed in the storage section. A vessel 25 is provided. Also, case 21
A light receiving element 29 for receiving an optical signal sent from the detector 30 at the time of detecting the liquid level is attached to the bottom of the bottom.

The liquid level detector 30 is formed in a substantially cylindrical weight, and has a main electrode 33 provided at the center of the bottom of the case, an auxiliary electrode 31 provided around the main electrode 33, and a liquid level detection optical signal transmitted at the upper part. A light projecting element 32 for mounting is mounted. Detector 3
A power supply circuit and a detection circuit (not shown) are built in 0.
The detection circuit, when the bottom of the liquid level detector 30 reaches the liquid level,
Based on the change in the resistance between the main electrode 33 and the auxiliary electrode 31,
The light emitting element 32 is configured to emit light. The power supply circuit usually contains a battery, but a secondary battery, a capacitor, and a charging circuit may be provided to charge the secondary battery and the capacitor when the power supply circuit is in the storage portion of the case 21.

As shown in FIG. 5, the control circuit of the liquid level measuring device 20 is mainly composed of a microcomputer and includes a CPU 40, a ROM 41, a RAM 42, and an input / output circuit 43. The chord length measuring device 8, the angle detector 9,
The light receiving element 29, the rotary encoder 24, the rising end detector 25, the winding motor 26, the display 23 for displaying measured values and the like, and switches (not shown) are connected to the input / output circuit 43.

The CPU 40 takes in the liquid level detection signal and the output signal of the encoder 24 based on the program data stored in the ROM 41 in advance, calculates the distance x to the liquid level, and further calculates the radius r and the inclination θ of the tank T. Is calculated from the distance x, the radius r, the inclination θ, and the known distance a, and the distance y (the distance from the upper end on the central axis of the tank to the liquid surface) is calculated. Processing such as displaying a measured value on the display unit 23 is performed. In the ROM 41,
In order to correct the calculated distance data, a correction coefficient corresponding to the distance data is stored in advance as table data or the like. The correction coefficient is calculated in advance from an actually measured value and stored in accordance with, for example, slippage of the pulley and the wire and elongation of the wire.

Next, the operation of the liquid level measuring apparatus having the above configuration will be described. As shown in FIGS. 1 and 2, the mounting frame 1 of the measuring device is applied to the edge of the tank T to be measured, the abutment 4 of the main body 2 is applied to the edge of the tank, and the chord 3 is placed on the tank. The apparatus is placed with the both-chord length measuring claws 5 and 6 of the chord portion 3 abutting against the edge of the tank T. The main body 2 is arranged such that its center line coincides with the center line L of the tank T in the inclined direction. In this state, the chord length measuring device 8 generates a signal indicating the length of the chord AD in accordance with the positions of the chord length measuring claws 5 and 6, and the CPU 40 determines that a point A corresponding to half the length of the chord AD corresponds to a point C. The data of the distance b to is taken.

Next, while looking at the level 11,
2 is operated to change the attitude of the liquid level measuring device 20 from a state along the upper end of the tank T to a horizontal state (horizontal with respect to the vertical). At this time, a signal indicating the inclination angle θ of the tank T is output from the angle detector 9, and the CPU 40 takes in the angle data θ.

When the operation switch for starting the measurement is turned on,
As shown in the flowchart of FIG. 6, the CPU 40 first determines in step 100 whether or not the liquid level detector 30 is at the rising end. If the rising end detector 25 has detected the rising end, then, in step 110, the winding motor 26 is driven to the lower side, and in step 120, the taking in of data from the encoder 24 is started.

Thus, the winding drum 23 is driven to rotate in the wire feeding direction, and the liquid level detector 30 at the tip of the wire 22 descends in the tank by its own weight. At this time, the pulley 27 is driven to rotate in accordance with the feeding of the wire 22, a signal indicating the rotation angle is output from the encoder 24, the signal is taken into the CPU 40, and in step 130, the current wire length, that is, the liquid The distance to the surface detector 30 is calculated, and the distance is displayed on the display 23 in step 140. Such processing is repeated every predetermined time (several hundred milliseconds), and the display distance is incremented.

When the lower part of the liquid level detector 30 reaches the liquid level, the resistance between the main electrode 33 and the auxiliary electrode 31 changes due to the liquid, and the liquid level detection circuit detects the arrival of the liquid level. The light emitting element 32 provided on the upper side performs the light emitting operation.

At this time, the light receiving element 29 on the measuring instrument body side
Receives a light signal indicating liquid level detection from the light emitting element 32 and sends the received light signal (liquid level detection signal) to the CPU 40. When the liquid level detection signal is input, the CPU 40 determines that the liquid level has been detected and proceeds to step 170, where the winding motor 2
6 is stopped immediately, and the lowering of the liquid level detector 30 is stopped. Then, in step 180, the distance data at that point is corrected to calculate the distance x to the liquid level.

Next, the CPU 40 determines in step 185 that
The radius r of the tank T is calculated using the known distance a and the measured half distance b of the chord. As shown in FIG. 7, in the triangle ABC and the triangle OAB, c ² = a ² + b ² , t
Since the equations of anβ = b / a and cosβ = c / 2r hold, the radius r of the tank is calculated from these three equations.

Next, at step 190, the inclination angle θ of the tank detected by the angle detector 9, the distance x to the liquid surface measured by the measuring device 30, the radius r of the tank, and the known distance a are used. , The distance y (appropriate liquid level distance) from the upper end of the tank on the central axis S of the tank T to the liquid level is calculated and displayed on the display 23.

As shown in FIG. 8, the center liquid surface distance y is from point O to point G, and y = y ₁ + y _2. Therefore, in the triangle EFG, y ₂ = x / cos θ and the triangle OC ₂ E, y ₁ = (r−a ₂ ) / tan θ,
It is a ₂ = a-a _1. Therefore, the center liquid level distance y can be calculated from these three equations. Incidentally, a ₁ is the known distance between the base point C ₂ of the wire chord center point C and the liquid level measuring device 20, a ₂ is the known distance between the base point C ₂ from a point B on the arc (FIG. 1).

Then, in step 200, the winding motor 2
6 is driven to the winding side, and the wire 2 is
2 and the liquid level detector 30 is raised, and step 21 is performed.
0, when the liquid level detector 30 rises to the storage portion of the measuring instrument main body and the rising end detector 25 detects the rising end, the process proceeds from step 210 to step 220, where the winding motor 2
The ascending operation by 6 is stopped, and the liquid level measurement of this time is completed.

As described above, even in the case of an inclined cylindrical tank, the distance x to the liquid level at a position near the edge of the tank can be obtained simply by installing the liquid level measuring device at the upper end near the side wall of the tank.
And using the distance x, an accurate center liquid level distance y
That is, the liquid level distance on the central axis S of the tank can be calculated. For this reason, the liquid level measuring device can be manufactured as a general-purpose and portable type, and even if it is a large cylindrical tank installed in a factory or the like and having an unknown inclination angle and an unknown inner or outer diameter, the liquid level can be measured. The distance can be measured efficiently and accurately with a simple operation.

The present invention is not limited to the above embodiment, but can be implemented in the following embodiments.

1. In the above description, the contact portion 4 is provided outside the tank T.
The outer diameter of the tank was measured by measuring the outer dimensions of the tank by applying the string length measuring claws 5 and 6, but the inner diameter may be measured and the inner diameter calculated.

2. Further, although the mounting frame 1 is installed below the inclined center line L of the upper end circle of the inclined tank, it can be installed above the inclined center line L. In that case, the distance y ₂ calculated from the measured liquid level distance x, to become larger than the center liquid level distance obtaining, determined from the distance y ₂ by subtracting the distance y _1.

3. In the above embodiment, the liquid level detector electrically detects the liquid level, and the detection signal is transmitted to the measuring instrument main body by spatial light transmission, but the detection signal is wirelessly transmitted or the detection signal is wired along a wire. You may transmit by the electric wire which carried out.

4. The above liquid level detector electrically detects the liquid level, but connects the float to the tip of the wire, draws out the wire, and when the float reaches the liquid level, detects the change in the tension of the wire and draws out the wire. May be configured as a liquid level detector having a structure for stopping the operation.

5. In the above embodiment, the base point position of the wire of the liquid level measuring device 20 is provided at a position a ₁ away from the chord center point C, but the base point position of the wire of the liquid level measuring device 20 is adjusted to the chord center point C. For example, a ₁ = 0 and a ₂ = a, and a ₂ = a−a used in calculating the liquid level distance y described above.
The expression of ₁ becomes unnecessary.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an installation state of a liquid level measuring device according to an embodiment of the present invention.

FIG. 2 is a plan view of the liquid level measuring device.

FIG. 3 is a rear view of the measuring device.

FIG. 4 is a cross-sectional view of the liquid level measuring device 20.

FIG. 5 is a block diagram of a control circuit of the liquid level measuring device.

FIG. 6 is a flowchart showing the operation of the control circuit.

FIG. 7 is an explanatory diagram for obtaining a radius r of a tank T.

FIG. 8 shows the center liquid level distance y from the inclination θ and the radius r of the tank T.
FIG.

[Explanation of symbols]

 Reference Signs List 1-Mounting frame 2-Main body part 3-String part 4-Patch part 5,6-String measuring claw 8-String length measuring instrument 9-Angle detector 20-Liquid level measuring instrument 22-Wire 30-Liquid level detector

Claims (6)

[Claims] 1. A liquid level measuring device for measuring a distance to a liquid surface of a cylindrical tank installed at an inclination using a winding type liquid level measuring device, wherein the liquid level measuring device is attached to an upper end of the cylindrical tank. A main body having a contact portion disposed on an inclined center line on a plane of the tank and corresponding to an edge of the tank, and attached at a right angle to the main body so as to form an arbitrary chord on an upper end circle of the tank; A mounting frame having both ends thereof mounted on a circumference of an upper end of the tank; and a string mounted on a main body of the mounting frame so as to be swingable on an axis parallel to the string, and attached to a tip of a wire. A take-up type liquid level measuring instrument for measuring the distance to the liquid level by lowering the connected liquid level detector on the liquid level; and An inclination angle for detecting the inclination angle of the tank by rotating the liquid level measuring device to a horizontal state. Detecting means, provided on the chord portion, a chord length measuring means for measuring an arbitrary chord length of the tank top circle, a chord length measured by the chord length measuring means, and a midpoint of the chord. Tank diameter calculating means for calculating a radius of the tank using a length of a perpendicular line at the upper end circle of the tank; a liquid level distance measured by the liquid level measuring device; and a tank from a base point of a wire of the liquid level measuring device. From the predetermined distance on the radius to the top circle, the inclination angle of the tank detected by the inclination angle detection means, and the radius of the top circle of the tank calculated by the tank diameter calculation means, the center on the center axis of the tank A liquid level measuring device, comprising: liquid level distance calculating means for calculating a liquid level distance. 2. The apparatus according to claim 1, wherein the chord length measuring means includes a chord length measuring claw movably disposed on both sides of the chord portion and electrically measures a distance between the chord lengths. The liquid level measurement device according to claim 1, wherein the chord length is measured from a distance between the chord length measurement claws when the chord length measurement claws are in contact with an upper end of the tank. 3. The liquid level detector of the liquid level measuring device has an electrode, and detects the liquid level by a change in resistance between the electrodes when the liquid level detector reaches the liquid level. 2. The liquid level measuring device according to 1. 4. The liquid level measuring device according to claim 3, wherein the liquid level detector of the liquid level measuring device has a light projecting element, and transmits the detected liquid level detecting signal to the measuring device main body by spatial light transmission. . 5. The liquid crystal display according to claim 1, wherein the inclination angle detector electrically measures a rotation angle of the liquid level measuring device, a level detects horizontality of the liquid level measuring device, and the liquid level measuring device. The liquid level measuring device on the main body, which is in a state parallel to the upper end circle of the tank, is operated by operating the level adjusting device while looking at the level. The liquid level measuring device according to claim 1, wherein the liquid level measuring device is tilted to a state to detect a tilt angle. 6. A liquid level measuring method for measuring a distance to a liquid level of a cylindrical tank installed at an inclination using a winding type liquid level measuring device, wherein an arbitrary chord of an upper end circle of the tank is provided. Measuring the length of the tank; calculating the radius of the tank from the length of one half of the string and the length of a perpendicular drawn on the top circle from the midpoint of the string; Measuring the angle of inclination with respect to; a step of measuring the liquid surface distance by lowering the liquid surface detector to the liquid surface by pulling out a wire from the liquid surface measuring device installed at the midpoint of the chord or on a perpendicular line thereof, Calculating a center liquid level distance on a center axis of the tank from the calculated radius of the tank, the inclination angle of the tank, and the length of the perpendicular line.