JPH074602Y2 - Electrostatic potential detector - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to an electrostatic potential detector that detects a charging potential of a flowing powder or the like without contact.

[Prior art]

For example, in a fluid dryer that heats and drys powder and granules while flowing with hot air, the powder and granules are violently flown by hot air, and contact with each other and the wall surface of the drying tank, friction, peeling, separation, etc. are repeated, In the actual case, static electricity was remarkably generated, and the granular material was charged to a high potential and ignited, causing an explosion accident. However, there is a demand for further miniaturization of the powder and granules, and although there is a tendency for the risk of explosion due to electrification and ignition to increase with the miniaturization, as for the electrostatic detection of the powder or granules that are violently flowing as described above, However, due to adverse effects such as mixing of powder or granules in the detection unit or hot air, or a bad environment, there is only a method of sampling the powder and granules and artificially measuring the potential with a Faraday gauge. Until now, there has been nothing that can be properly detected. Therefore, when drying an object to be dried that contains a flammable organic solvent in a fluid dryer, the flammable gas concentration meter installed in the exhaust section is used to detect and monitor the concentration of the flammable gas. If it exceeds the concentration of, the current situation is to prevent ignition explosion by changing the operating conditions or introducing diluted air etc. to reduce the gas concentration.
There was no proper prevention.

[Problems to be solved by the device]

An object of the present invention is to provide an electrostatic potential detector that can directly and automatically and accurately detect the electrostatic charge state of flowing powder particles or gas in a fluid dryer or the like.

[Means for Solving the Problems]

The electrostatic potential detector according to the present invention has a potential sensor built in a case, the detection head of the potential sensor is exposed in a detection hole provided in the case, and air is blown around the detection hole from the inside of the case. Then, an air curtain forming portion for forming an air curtain is provided.

[Action]

Since an air curtain is formed around the detection head of the potential sensor, flowing powder or gas does not touch the detection head of the potential sensor and is not blown away by the air jet in the direction away from the detection head. The electric potential sensor detects the charged electric potential of powder particles or the like without any trouble.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a state in which an electrostatic potential detector 2 according to the present invention is attached to the outside of a container 1 in which powdery particles or gas is flowing, and a window 3 for detection is provided on the peripheral wall of the container 1. Is provided,
The electrostatic potential detector 2 detects the charging potential of the powdery particles or gas in the container 1 through the window 3 without contact. As shown in FIG. 1 to FIG. 5, the electrostatic potential detector 2 has a rear case 5 in which a rear opening of a metal case 4 is closed, a potential sensor 6 is mounted in the case 4, and a front side of the case 4 is attached. An inner plate 8 and a front outer plate 9 are superposed on and adhered to the wall plate 7 to form the following air curtain forming portion 10. That is, as shown in FIG. 6, the front wall plate 7 of the case 4 is provided with a circular detection hole 11 and an air injection hole 12 immediately above the detection hole 11, and the front outer plate 9 is provided with the air detection hole 12 as shown in FIG. A circular air blowout window 13 is provided in the center plate 8 and a cutout window 14 is provided in the intermediate plate 8 as shown in FIG. The air outlet window 13
Although it is larger than the detection hole 11 and is concentric therewith, it is not so large as to reach the air injection hole 12, whereas the cutout window 14 has a size including the air blowout window 13 and the air injection hole 12. Moreover, the lower peripheral edge 14a has an air blowing window 13
The upper peripheral edge 14b has a semicircular shape corresponding to the lower half of the peripheral edge and has a square arch shape. The front wall plate 7, the middle plate 8 and the front outer plate 9 of the case 4 are provided with screw holes 15 at four corners,
The middle plate 8 and the front outer plate 9 are screwed to the front wall plate 7 through these screw holes 15. On the other hand, an air supply pipe 16 is arranged in the case 4. The base end of the air supply pipe 16 is connected to the air supply joint 17 fixed to the bottom surface of the case 4, and the tip is connected to the air injection hole 12. The air supply joint
When a hose is connected to 17 and air is sent to the air supply pipe 16 from the outside, the air is jetted from the air jet hole 12. In this case, since the air injection hole 12 is located at a position higher than the air blowing window 13 of the front outer plate 9, the air ejected from the air injection hole 12 passes through the cutout window 14 of the middle plate 8 to the inside of the front outer plate 9. It hits the side surface and flows vertically along the cutout window 14 to form an air curtain in front of the detection hole 11, and through the air blowing window 13 through the hole 19 of the packing 18 and the detection window 3 of the drying tank 1 into the drying tank 1. Is injected into. The potential sensor 6 is a conventionally known one in which a vibrator, a detection electrode plate, a field effect transistor, a resistor, etc. are built in the sensor case 20. The potential sensor 6 has a thin gap 21 formed on the inside of the front wall plate 7 of the case 4 and is attached to the mounting metal fitting.
A small circular detection head (detection part) 23 fixed by 22 and protruding from the front surface of the sensor case 20 is provided with an annular gap.
24 is exposed in the detection hole 11. Mounting bracket 22
Is a screw hole provided in the front outer plate 9, the middle plate 8 and the front wall plate 7.
It is screwed through 25. The cable 26 from the potential sensor 6 is pulled out through a cable outlet 27 which is fixed to the bottom of the case 4. A small hole (not shown) for injecting a part of the air into the internal space of the case 4 is provided in the middle of the air supply pipe 16, and the air injected into the internal space is the detection head 23.
Is ejected forward from the annular gap 24 between the detection hole 11 and the detection hole 11. Since the electrostatic potential detector 2 has the above structure,
Air is jetted forward from the annular gap 24 between the detection head 23 and the detection hole 11, and the air jetted from the air jet hole 12 hits the front plate 9 and flows downward, so that the front side of the detection hole 11 is reached. To form an air curtain that is almost vertical to. The air curtain merges with the air from the annular gap 24 while weakening the flow velocity of the air jetted forward from the annular gap 24, spreads into the air blowing window 13 and the window hole 3, and flows into the container 1. Since this inflow pressure is set to be slightly higher than the pressure in the container 1, even if the powder or granules are flowed in the container 1 by hot air, the flowing powder or granules are It does not flow from the container 1 to the outside of the window 3 and directly touch the detection head 23 or enter the case 4. However, although this air from the electrostatic potential detector 2 side flows into the container 1 at a pressure slightly higher than the pressure inside the container 1, it seems that the particles are strongly blown away in the direction away from the detection head 23. It is not very strong, and only prevents it from entering the case 4 through the window hole 3. Further, even if the powder particles are blown away in the direction away from the detection head 23, the powder particles in the container 1 are large in quantity, and the powder particles in the container 1 are in the air blowing window 13 and the window hole 3. Since the electric field according to the electric potential is generated by the charged electric potential of the body, the electric potential sensor 6 can detect the charged electric potential of the granular material in the container 1 without contact and without any trouble. Therefore, when the output of the potential sensor 6 is processed by a control device such as a microcomputer, and the charging potential of the powder or particles rises above a predetermined level, for example, the exhaust path of the container 1 or the gas supply path is controlled by this control device. With automatic control, it is possible to accurately prevent ignition due to an increase in electrostatic potential of powder or particles or gas.

[Effect of device]

According to the present invention, it is possible to directly, automatically, and accurately detect the electrostatic charge state of flowing powder particles or gas without being affected by the flow.

[Brief description of drawings]

FIG. 1 is a sectional view of the electrostatic potential detector according to the present invention in use, FIGS. 2 to 5 are front, side, top and bottom views, and FIGS. 6 to 8 are electrostatic potential detectors. It is a front view of a case of a detector, a front view of a middle board, and a front view of a front outer board. 4 ... Case, 6 ... Potential sensor, 10 ... Air curtain forming part, 23 ... Detection head.

Claims (1)

[Scope of utility model registration request] 1. An air curtain in which a potential sensor is built in a case, a detection head of the potential sensor is made to face a detection hole provided in the case, and air is jetted from the inside of the case around the detection hole. An electrostatic potential detector characterized by comprising an air curtain forming part for forming a.