JP4167078B2 - Remaining amount detection device by back pressure detection - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides stable automatic detection when the remaining amount of liquid such as paint placed in a container is discharged by supplying a small pressure to a detection tube inserted in the liquid and detecting its back pressure. It is related with the apparatus which can utilize a detection signal as an alarm or a control signal secondary.
[0002]
[Prior art]
Many methods are known for detecting the remaining amount in a container to be stored when supplying a liquid and managing the amount of use or grasping the replenishment timing. . However, paints have many problems such as the inability to confirm the level due to color adhesion, and the fact that many of them contain volatile and flammable solvents, and thus the electrical detection device cannot be used.
[0003]
A method using various level sensors with explosion-proof use, a method for measuring changes due to weight, a method for detecting position changes due to float etc. with a magnet sensor, and detecting the load resistance of blades rotating in the liquid There have been proposed replacement methods, but each has its own problems.
[0004]
In this type of remaining amount detection, safety should be considered first from the danger of paint ignition and explosion, and the use of control using air or the like is conceivable as the method. In other words, the pressure is proportional to the depth from the liquid surface with respect to the depth, and when inserting a tube into the liquid and pushing out the gas from the opening, the pressure corresponding to the depth of the liquid is required. In other words, the depth of the liquid, that is, the remaining amount can be detected by the pressure for pushing out the gas. This method is used in the fields of storage tanks, fuel tanks such as oil, and storage tanks for chemicals, etc., but it has various liquid properties, and the stability of detection for paints containing many organic solvents, Due to problems such as the solvent resistance of the apparatus, there were some problems in using it in the field of painting.
[0005]
[Problems to be solved by the invention]
In order to carry out this method when the liquid to be handled mainly contains a volatile solvent such as paint, unlike a storage tank with a certain physical property, which is a relatively large tank, a compressed gas with a low pressure corresponding to the back pressure of the liquid is used. A pressure control valve for stably feeding the pressure is necessary, and a pressure sensor for detecting a fine pressure is indispensable. However, it is good to continue supplying compressed air or inert gas for detection, but when stopping detection for a long time, such as when not in operation, the supply of detection gas should be stopped from the viewpoint of energy saving. Therefore, there is a risk that the solvent in the paint will evaporate and flow backward from the detection pipe inserted in the liquid, and the packing such as the pressure adjusting valve or the pressure receiving member may be eroded, and stable detection cannot be maintained. There's a problem.
[0006]
Also, in the case of paints, not only oil and moisture in the paint but also impurities such as fine dust invade will cause poor finish after painting and lead to defective finished product itself. It is required as a very important matter.
[0007]
In the case of a paint container used for painting, usually there are about 10 liters to 80 liters, and a minute pressure is required for liquid level detection, so that stable detection must be maintained. That is, a differential pressure gauge operated by a minute pressure must be protected from the back flow of the solvent, and a check valve structure which is not affected by the minute pressure is required. Further, when a shut-off means is used to prevent backflow, it is necessary to prevent the overpressure state to the fine pressure detector due to the supply pressure and protect the fine pressure detector from the risk of damage.
[0008]
From a practical point of view, it is important to obtain a detector that can be used safely at an easy cost, and a detector with excellent handling properties that can easily check the remaining amount, especially at the lower limit level, is required. Yes. In addition, the specific gravity and viscosity of paints vary widely, solving problems such as adhesion to the wall of the gas supply pipe for detection, and performing safe and reliable liquid level detection. Obtaining is an issue.
[0009]
[Means for Solving the Problems]
The present invention arranges a detection pipe having an opening toward the bottom surface in a liquid container, connects a means for supplying back pressure detection gas to the detection pipe and continuously supplies a trace amount of gas. A device for detecting a discharge pressure of the gas by connecting a differential pressure detector to the passage, and detecting a remaining amount of liquid corresponding to the discharge pressure, which is closed only by the gravity of the valve body on the detection pipe side of the supply passage. A check valve or a switching valve having a passage that opens the supply passage side to the atmosphere when the supply passage and the detection pipe side passage are shut off is provided.
[0010]
Gravity by a lightweight material is used as a check valve that prevents backflow from the detection pipe side to the supply passage side and operates at a pressure lower than the minimum detection pressure. This prevents the solvent generated from the container side from entering the differential pressure detector or the like. Similarly, when the supply passage and the detection pipe side passage are shut off , a switching valve that can be switched so that the pressure on the supply passage side is discharged to the outside is used to prevent intrusion into the pressure detector and The risk that the pressure is applied to the differential pressure detector and the fine pressure detector is damaged is avoided.
[0011]
As for the gas that is inserted into a liquid such as paint and is always supplied, it is desirable that clean air that has passed through a precision filter is supplied. This prevents impurities from being mixed into the paint and enables use without causing deterioration of the quality of the painted surface. In particular, it can be used for high-grade painting and precision equipment painting.
[0013]
Further, when it is desired to easily check the remaining amount in the container, it is possible to provide a display device having a display function for converting the back pressure into the remaining amount in place of the differential pressure detector or in the passage. By using a generally used fine pressure gauge, the indicator can check the remaining amount in a container in a hidden place or a remote place. On the other hand, the display can be safely detected by using a mechanical detector, and can be handled easily at a low cost. It is important that the remaining amount can be easily checked for the lower limit value. In the present invention, the pointer is rotated by the pressure output in proportion to the remaining amount of liquid, and the analog indicating the remaining amount of liquid in proportion to the rotation angle of the pointer. By using a display with the display board as a background display of the pointer, it can be easily confirmed visually.
[0014]
In addition, the detection level that varies depending on the specific gravity of the paint to be detected can be easily changed by replacing the detector. However, by changing the display level, the remaining amount can be adjusted to the conversion display according to the specific gravity and can be correctly confirmed.
[0015]
Furthermore, the installation of the detection pipe to be inserted into the paint container is not limited to the paint container. By making the fixing means for installation flexible, it can be easily attached to and removed from the container to be detected or the suction pipe of the paint pump. Can be used.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a main configuration for carrying out the present invention. In a paint container 1, atmospheric pressure is applied to the paint contained in an open container. A container is not limited to a size-shape material, but can respond to various containers. The detection pipe 2 for detecting the remaining amount is in the form of a pipe having an opening 25 at the lower end, and the opening is positioned close to the bottom surface of the container 1. A supply passage 4 for detection is connected to the detection pipe 2, and is supplied from a compressed air source 3 through a filter 5 and a pressure reducing valve 6.
[0017]
The filter 5 is provided for cleaning so that impurities, generally moisture, oil, etc. are not sent into the paint, and the cleanliness is determined by the degree of demand for the liquid to be handled. The pressure reducing valve 6 is required to be a regulating valve that can be stably supplied at a pressure slightly higher than the maximum back pressure in consideration of the specific gravity of the liquid to be detected. The low pressure regulating valve for stably supplying the minimum pressure of the regulating valve corresponding to the differential pressure gauge of high pressure is high in cost and cannot be used practically. In this example, it is 10 to 15 kilopascals.
[0018]
If the specific gravity of the liquid is 1, if the depth of 50 cm is full, it is about 5 kilopascals, and it is only necessary to supply pressure for pushing air from the opening 25 of the detection pipe 2 against this back pressure. The flow rate of the compressed air from the pressure reducing valve 6 is adjusted by the throttle valve 7 and sent to the detection pipe 2. The throttle valve 7 only needs to have an amount sufficient to fill the supply passage with a pressure corresponding to the back pressure. If the amount is too large, the flow will flow and the back pressure cannot be measured accurately. It suffices if the bubbles are intermittently emitted from the normal opening 25. In this example, bubbles are generated at intervals of about 1 second.
[0019]
The thickness and material of the detection pipe 2 are not particularly limited, but a dimension that can stably discharge bubbles is selected depending on the viscosity of the liquid to be detected. In the case of a paint, it is preferable to use a material having a low detergency due to a fluororesin pipe or a coat and having a good cleaning property. The detection pipe 2 is fixed to the container 1 by appropriate fixing means, and the opening 25 is located at the lower limit position E of the liquid. By providing a one-touch joint for pipes in the fixing means and making it easy to remove, it is possible to facilitate handling such as cleaning of dirt with paint.
[0020]
The supply passage 4 is connected by a pipe to a differential pressure gauge 11 in the control device 10 placed outside the danger range of the handling liquid. In the case of the embodiment, the differential pressure gauge 11 detects a difference between the supply pressure and the atmospheric pressure, and a pressure sensor for taking out an output signal is used.
[0021]
In the simplest case, the detected pressure of the pressure sensor is output as an output signal by the comparison calculation means 12 in the control device 10, and the alarm 14 is activated in response to the output signal, or the lamp 15 is turned on and the remaining amount is at the lower limit. You can be informed. Further, the calculation result can be displayed as the remaining amount in a timely manner by the output value of the pressure sensor. Further, according to the output value, it is possible to start the replenishment of the liquid to the container 1 with the signal for starting replenishment as the external output signal 16 at the lower limit value, and similarly stop the replenishment at the upper limit value. The use of a switch directly operated by differential pressure detection instead of the comparison calculation means 12 makes it possible to manage the required remaining amount, particularly the lower limit or upper limit liquid level. That is, in terms of practical cost, a mechanical micro differential pressure switch or micro pressure switch is used, and the upper and lower limits can be managed with an inexpensive configuration.
[0022]
Depending on the liquid to be handled, these control devices 10 are installed in a place away from the danger area by piping, and it becomes easy to ensure safety. In other words, when dealing with volatile organic solvents such as paint, it is necessary to avoid the installation of electrical control equipment or to use a complete explosion-proof specification because of the danger of solvent vapor ignition and explosion. Safety can be ensured at low cost by using the control device 10 placed outside the danger zone through the tube piping.
[0023]
A check valve 8 is provided between the supply passage 4 and the detection pipe 2 so that the solvent vapor entering the detection pipe 2 does not flow backward. The check valve 8 is desirably a valve having such a low resistance that the pressure of the supplied air does not substantially affect the detection of the back pressure.
[0024]
In the detection apparatus of the present invention, the detection pipe 2 is inserted into the liquid, and therefore air supply is stopped from the viewpoint of energy saving when measurement is not required. For this reason, there is a possibility that the solvent in the paint evaporates due to the stop for a long time, and the supply passage 4 flows back to the differential pressure gauge 11 for detection or the pressure reducing valve 6 for supply. The check valve 8 prevents the intrusion of the solvent into these devices, and is configured to protect a normally used packing or rubber pressure receiving member and maintain stable use.
[0025]
Except for expensive special specifications, rubber is generally used for these pressure-receiving members. Especially, a device targeting a fine pressure applied to the present invention requires high flexibility that is sensitive to reaction, Often vulnerable to solvents. Therefore, by providing a check valve, a switching valve for blocking the backflow, and the like as shown in the embodiments described later, it is possible to reliably and inexpensively.
[0026]
2 and 3 show specific embodiments. In this example, the detection pipe 2 is fixed by a clip 21 to a suction pipe 20 of a pump (not shown) that sucks the paint and sends it to a device to be used. The position of the opening is determined such that a necessary lower limit level E is determined and can be easily fixed in accordance with the position.
[0027]
The supply passage 4 for supplying the detection gas is connected to the detection pipe 2 by a connection tube 19 through a check valve 8 and a switching valve 9. On the other hand, the supply passage 4 is connected to the differential pressure gauge 11 by a detection tube 17. As shown in FIG. 4, the check valve 8 uses a ball valve, and the ball 81 is made of light resin so that it can be opened with a slight air pressure. The check valve 8 makes a back flow from the detection pipe 2 side to the supply passage 4 and the differential pressure gauge 11 side. To prevent. If the ball has a weight of 1 g with respect to a passage area of 1 cm 2, the operation can be performed with about 0.1 kilopascal, that is, with a liquid level difference of 1 cm or less. As described with reference to FIG. 1, the detection air is adjusted in flow rate by the throttle valve 7 through the air filter 5 and the pressure reducing valve 6, and sent to the inlet side of the check valve 8, and simultaneously through the detection tube 17. The back pressure in the pipe is detected by communicating with the pressure gauge 11.
[0028]
The switching valve 9 provided on the outlet side of the check valve 8 may be provided in place of the check valve 8, but is connected in series to increase the safety of the device. At the time of normal detection, the detection pipe side and the supply passage side communicate with each other. When the detection is stopped, the communication is interrupted. At this time, the supply gas from the pressure reducing valve 6 is subjected to the total pressure on the differential pressure detector. The pressure sensor that detects the minute pressure will be damaged. For this reason, the switching valve is provided with a passage in which the supply side opens to the atmosphere side 22 at the same time when the knob 23 is switched to shut off to the detection pipe side.
[0029]
With the above configuration, the supply air is maintained in the supply passage 4 at a pressure corresponding to the hydraulic pressure (back pressure) at the height at which the supply air has entered the liquid. I will escape from 25. Therefore, as shown in FIG. 1, if the pressure indicator 18 such as a pressure gauge is connected to a part of the supply passage 4, the remaining amount can be directly known.
[0030]
The pressure indicator 18 is used to display the pressure output by transmitting to the rotating pointer using the deformation of the bent pipe that receives the pressure represented by the Bourdon tube. Normally, it is a scale display, but the display board itself has an analog display portion that increases in proportion to the rotation angle of the pointer as shown in FIG. 5 so that it can be easily judged visually. In this type of apparatus, the lower limit can be easily determined and the remaining amount level can be easily determined between the upper limit and the effect that can be confirmed by a display method that can be determined at a glance.
[0031]
As another problem, the pressure is an indication of the liquid pressure, and if the specific gravity of the liquid is 1, it is equivalent to the water column and can be known as the liquid surface height up to the lower limit. Since the pressure when the container is full is different and there is a possibility that the user will misunderstand it, it is necessary to replace or convert the display. In such a case, as shown in the example shown in FIG. 5, the display scale of the pressure indicator 18 can be changed according to the specific gravity of the liquid to be used.
[0032]
That is, as an example, FIG. 5A shows the position from the lower limit to the full amount when the specific gravity is 1, and FIG. 5B shows the position up to the full amount when the specific gravity is 1.5. The display plate 22 can be changed by concealing the full position by an adjustment plate 24 that changes and fixes the rotation position according to the specific gravity. In addition, if it is a digital display, it is also possible to display the converted value as the remaining amount level by performing arithmetic processing of the existing technology. These pressure indicators 18 may be installed at remote locations through the detection tube.
[0033]
As already described, the pressure in the supply passage 4 is transmitted to the control device 10 via the detection pipe 17 and acts on the internal pressure sensor, and the output signal activates the buzzer and the lamp. Further, it can be output as another control signal.
[0034]
FIG. 6 shows another example in which the detection pipe 2 is fixed. FIGS. 6A and 6B show a case where the detection pipe 2 is fixed to the vertical suction pipe 20, and FIG. The example fixed to the edge 23 of the paint container 1 is shown. Various mounting positions and mounting methods can be considered depending on the container to be used, but if a simple fixing means is provided on the detection pipe and the fixing means is made variable, it can be used for various containers and can be used more easily. It becomes.
[0035]
【The invention's effect】
As described above, according to the present invention, gas pressure such as air without danger of fire or the like is sent into the liquid, and the back pressure required for the discharge is detected in a stable state to detect the remaining amount of liquid. In particular, there is an effect that the remaining amount detection of a liquid containing a volatile organic solvent such as a paint and having a high risk of ignition of a solvent vapor can be obtained safely and reliably.
[0036]
In addition, it is possible to maintain detection stably by preventing backflow of the solvent so as not to impair the function of the device, and it can be detected simply by inserting the detection pipe into the container or pump suction pipe. Since only the detection pipe can be removed from the fixing means with a single touch, it is easy to use and easy to divert to other containers, including maintenance such as cleaning when dirty. Can be used.
[0037]
In addition, the present invention provides a control device that outputs the detection signal of the differential pressure detector to the alarm means or the control means. For example, if only the lower limit value is managed, an alarm or replenishment is output by outputting when the differential pressure is lost. If the change in the differential pressure is output, the change in the remaining amount can be displayed, and control according to the required value can be performed, allowing automatic liquid management Become.
[0038]
In addition, by providing the detection pipe with a fixing means whose mounting position can be changed, the detection pipe is not limited to the paint container, but the detection pipe can be easily installed at a predetermined position in the container, making it easy to handle, etc. All the big effects can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
FIG. 2 is an external configuration diagram showing the configuration of the present invention in a specific embodiment.
FIG. 3 is a view in the direction of arrow A in FIG. 2;
FIG. 4 is a partial cross-sectional configuration diagram illustrating an example of a check valve and a switching valve.
FIG. 5 is an external view showing an example of a remaining amount display device and showing a difference in full amount display according to specific gravity.
FIGS. 6A and 6B show a method of fixing a detection pipe, A and B show a method of fixing to a suction pipe, and C shows an example of a method of fixing to the edge of a container.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Container 2 Detection pipe 4 Supply path 5 Filter 6 Pressure reducing valve 7 Throttle valve 8 Check valve 9 Switching valve 10 Control device 11 Differential pressure gauge 14 Alarm device 16 External output signal 18 Pressure indicator 20 Suction pipe 21 Clip 25 Opening

Claims (5)

A detection pipe having an opening toward the bottom in the liquid container is arranged, and a means for supplying back pressure detection gas to the detection pipe is connected to continuously supply a trace amount of gas so that bubbles are intermittently exhausted. An apparatus for detecting a discharge pressure of the gas by connecting a differential pressure detector with the atmosphere to the supply passage and detecting a remaining amount of liquid corresponding to the discharge pressure. A remaining amount detection device comprising a check valve that is closed only by the gravity of the valve body or a switching valve having a passage that opens the supply passage side to the atmosphere when the supply passage and the detection pipe side passage are shut off. The remaining amount detection device according to claim 1, wherein the detection liquid is a paint, and the trace gas to be supplied is supplied via a precision dust and oil removal filter and a fine pressure reducing valve. 2. The remaining amount detecting device according to claim 1, wherein the differential pressure detector is a mechanical micro pressure switch, and performs opening / closing output of a valve for supplying operating air to the alarm means or the control means by the detected pressure. 2. A display device according to claim 1, further comprising: an indicator that detects the discharge pressure, rotates the pointer according to the pressure, and displays an amount of remaining liquid using a liquid level analog display board proportional to the rotation angle of the pointer as a background display of the pointer. Remaining amount detection device. The remaining amount detection apparatus according to claim 1, wherein a clip having a variable fixing direction is provided on the detection pipe so that the detection pipe can be attached to and detached from a part of the liquid container.

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