High-voltage detection device for powder spray

Abstract

To provide a high-voltage detection device for powder spray that is capable of detecting high voltage of multiple discharge wires arranged in close proximity within a confined place serving as a powder spraying closed space.SOLUTION: A high-voltage detection device 10 for powder spray comprises: detection means 40 which includes a spraying unit that has a powder storage tank, a spraying roller, and discharge wires and a scattering-prevention unit that is arranged immediately below the spraying unit, forms a spraying closed space between rollers, and has two scattering-prevention rollers arranged with a gap relative to a spraying target and forcibly rotated and discharge wires, and which detects high voltage applied to the discharge wires of the powder spray; and signal processing means 50 which is connected to the detection means, and determines a live-wire state of the discharge wires. The detection means faces the discharge wires, and surrounds portions other than a detection surface of a detection electrode having a length equal to a diameter of the discharge wire with an electric field shielding part. The signal processing means sets a gain that can be detected at a close distance from the discharge wires in an amplification part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high voltage detection device for powder sprays that detects the high voltage applied to powder sprayers (also called powder spraying devices) that spray powder onto the surfaces of plastic films, rubber sheets, etc. in order to prevent adhesion (blocking) between wound laminates, plastic films, rubber sheets, etc., and to improve slip properties in subsequent processes. [Background technology]

[0002] There is a powder sprayer that scatters powder to prevent blocking and improve slipperiness (see Patent Document 1). Figure 9 is an explanatory diagram of the discharge wire of a conventional powder sprayer. The powder sprayer 1 has a spray unit 20 located at the top center, and two anti-scattering units 30 located diagonally below the spray unit 20, in other words, on the left and right sides (upstream and downstream of the conveyance direction of the printing device) in a cross-sectional view of the roller. The spray roller 24 rotates along the conveyance direction of the printing device, the upstream anti-scattering roller 32 rotates in the opposite direction to the conveyance direction, and the downstream anti-scattering roller 32 rotates along the conveyance direction. The space surrounded by these three rollers forms the closed spraying space 13. Within the closed spraying space 13, powder adhering to the surface of the spray roller 24 is scattered by electrical discharge. The anti-scattering roller 32 also releases powder adhering to its surface by electrical discharge. The spray roller 24 and the anti-scattering roller 32 are located close to each other, with discharge wires 26 and 34 generating electrical discharges on their surfaces. The discharge wire 26 of the spray roller 24 is located at the lowest end of the roller within the closed spraying space 13. The lowest end of the spreading roller 24 is located above the closed spreading space 13, from which powder adhering to the roller can be released and spread evenly throughout the space. The discharge wire 34 of the anti-scattering roller 32 is located slightly below the horizontal line passing through the axis of the roller within the closed spreading space 13. In this position, the discharge can be performed without affecting the powder adhering to the roller of the spreading roller 24 or interfering with the object to be spread below. These discharge wires 26, 34 are not in contact with the roller but are spaced a few millimeters, specifically 1 mm, apart. The discharge wires 26, 34 are flexible wires with conductors coated with insulators. They are connected to a high-voltage transformer and a commercial power source via a plug-type cable, and are subjected to a voltage of 7 kV boosted by the high-voltage transformer. The powder carried downward by the spray roller 24 is liberated by the discharge from the discharge wire 26. At this time, the powder adhering to the scatter prevention roller 32 is liberated by the discharge from the discharge wire 34, allowing the powder to be sprayed onto the top surface of the target object, such as a plastic film or rubber sheet, moving below the scatter prevention roller 32.

[0003] When performing maintenance on a powder sprayer, the plugs on the cables connecting to the high-voltage transformer are removed from the sockets on the spray unit and anti-scatter unit to ensure work safety. When maintenance is complete, the plug is inserted into the socket. Previously, there have been many cases where the plug was forgotten to be inserted after maintenance. When a powder sprayer is operated without applying high voltage to the discharge wire, the powder carried downward by the rotation of the spray roller and anti-scatter roller clumps together and adheres to the surface of the target object. Because the target object is transported at high speed below the sprayer, clumps of powder adhere over long distances, resulting in significant product loss and requiring maintenance work on the powder sprayer, which requires a long shutdown of the powder sprayer. Other causes of high voltage not being generated include deterioration of the high-voltage transformer and the discharge wire. For this reason, some kind of detection device is needed to detect the high voltage applied to the discharge wire.

[0004] Conventionally, techniques for detecting a high voltage applied to a conductor are disclosed in Patent Documents 2 and 3. The technologies disclosed in Patent Documents 2 and 3 have a detection distance of approximately 1 m (Patent Document 2) and a predetermined distance (a distance of several meters is generally required to prevent electric shock accidents), and the detection range directionality is 180 degrees (Patent Document 2) and omnidirectional (Patent Document 3). In addition, the technologies disclosed in Patent Documents 2 and 3 assume that the device is attached to the human body, and that the floating capacitances generated between the detection target, the detection means, the human body, and the earth form a capacitor that is grounded (earthed). Therefore, the device does not include an earth terminal. The spray spray that is the target of high voltage detection in this invention is a special location where three discharge wires are arranged at close range (several tens of mm) at the vertices of a triangle in a cross section perpendicular to the longitudinal direction, in a narrow, enclosed space where the powder is sprayed. For this reason, the device configurations described in Patent Documents 2 and 3 cannot be applied because they cannot detect multiple discharge wires individually. Furthermore, it is not possible to position a person in close proximity to the discharge line that applies high voltage, and without an earth terminal, it is not possible to protect the circuit for detecting high voltage from high voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3773191 [Patent Document 2] Japanese Patent Application Publication No. 17372 / 1983 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-203961 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem that the present invention aims to solve is, in view of the problems of the above-mentioned conventional technology, to provide a high voltage detection device for powder spray that can detect the high voltage of multiple discharge wires that are close to each other in a narrow, closed space where powder is sprayed. [Means for solving the problem]

[0007] As a first means for solving the above problems, the present invention provides a spraying unit having a powder storage tank, a spraying roller, and a discharge wire; and a scattering prevention unit having two scattering prevention rollers and discharge wires that are arranged downstream and upstream of the spraying unit to form a closed spraying space between the rollers and are arranged with a gap from the object to be sprayed and are forced to rotate, wherein the three discharge wires are close to each other at the vertices of a triangle in a cross section perpendicular to the longitudinal direction, and detection means that is close to the discharge wires of the powder spray and detects the high voltage applied to the discharge wires. a signal processing means connected to the detecting means for processing the detected high voltage and determining the live line state of the discharge line; The object of the present invention is to provide a high voltage detection device for powder sprays, characterized in that the detection means faces the discharge wire, and the detection electrode has a length approximately the same as the diameter of the discharge wire, and is surrounded by an electric field shielding section except for the detection surface, and the signal processing means has an amplifier section set to a gain that allows detection at close range from the discharge wire. According to the first means, it is possible to individually detect the live state of a plurality of discharge wires arranged close to each other in a narrow space. Furthermore, even if an error occurs in the installation position each time the discharge wire is replaced, it is possible to detect the high voltage of the opposing discharge wire without the detection electrode coming into contact with the discharge wire.

[0008] As a second means for solving the above problem, the present invention provides a high voltage detection device for powder sprays, characterized in that, in the first means, the signal processing means is provided with a lightning protection section on the detection means side. According to the second means, if a discharge causes insulation breakdown (which can occur due to deterioration over time caused by current passing through the discharge wire, a decrease in insulation due to the adhesion of powder or the like adhering to the surface of the discharge wire, interference with the object being sprayed, or damage when the discharge wire is replaced) and leakage occurs to the detection electrode, malfunctions, noise, and the power supply voltage can become unstable. However, since the lightning protection section is configured so that power escapes directly to the ground from the earth terminal, the signal processing means can be protected.

[0009] As a third means for solving the above problem, the present invention provides a high voltage detection device for powder sprays, characterized in that in the first means, the detection electrode is made of stainless steel containing molybdenum. According to the third means, it is possible to reduce corrosion of the surface of the detection electrode due to ozone generated by partial discharge.

[0010] As a fourth means for solving the above problem, the present invention provides a high voltage detection device for powder sprays, characterized in that, in any one of the first to third means, the signal processing means is configured to be switchable between a low-pass filter and a band-pass filter. According to the fourth means, it is possible to switch between detecting high voltage and corona discharge depending on the needs. [Effects of the Invention]

[0011] According to the present invention, it is possible to individually detect the live state of a plurality of discharge wires that are arranged close to each other in a narrow closed space where powder is scattered. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a high voltage detection device for a powder spray according to the present invention. [Figure 2] FIG. 1 is a plan view of the powder sprayer in its operating position (closed). [Figure 3] 1 is a plan view (1) of the powder sprayer in the maintenance position (open state) and FIG. 2 is a cross-sectional view (2) of (1) taken along the line BB. [Figure 4] FIG. 3 is an enlarged cross-sectional view taken along the line AA in FIG. 2. [Figure 5] 1 is a side view (1) of the detection means of the spray unit and FIG. 2 is a cross-sectional view (2) taken along CC of (1). [Figure 6] 1A and 1B are a plan view (1) and a side view (2) of the detection means of the shatter prevention unit. [Figure 7] FIG. [Figure 8]FIG. 10 is a schematic diagram of a modified high voltage detection device for a powder sprayer. [Figure 9] FIG. 1 is an explanatory diagram of a discharge line of a conventional powder sprayer. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a high voltage detection device for a powder spray according to the present invention will be described in detail below with reference to the drawings.

[0014] [Powder spray 1] First, the powder sprayer to which the present invention is attached will be described below. Figure 2 is a plan view of the powder sprayer in its operating position (closed state). Figure 3 is a plan view (1) of the powder sprayer in its maintenance position (open state) and a cross-sectional view (2) taken along the line BB of (1). Figure 4 is an enlarged cross-sectional view taken along the line AA of Figure 2. Figure 5 is a side view (1) of the detection means of the spraying unit and a cross-sectional view (2) taken along the line CC of (1). Figure 6 is a plan view (1) and a side view (2) of the detection means of the anti-scattering unit.

[0015] As shown in the figure, the powder sprayer 1 comprises a spraying unit 20 having a powder storage tank 22, a spraying roller 24, and a discharge wire 26, two anti-scattering rollers 32 that are arranged downstream and upstream immediately below the spraying unit 20 to form a closed spraying space 13 between the rollers and are arranged with a gap between them and the object to be sprayed and are forced to rotate, and an apparatus stand 12, and sprays powder onto the object to be sprayed that passes below the anti-scattering rollers 32. A discharge wire 34 is attached to each of the two anti-scattering rollers 32, and the spraying unit 20 and the anti-scattering unit 30 consisting of the anti-scattering rollers 32 and the discharge wire 34 can be moved between an operating position where they are close to each other and a maintenance position where they are spaced apart, with space provided in the maintenance position for replacing the discharge wires 26, 34.

[0016] The anti-scattering unit 30 moves horizontally from the device stand 12. Specifically, the two anti-scattering rollers 32 and discharge wires 34 arranged below the spraying unit 20 are divided along a vertical line passing through the axis of the spraying roller 24, in other words, at the center of the device stand 12, and each unit (referred to as an anti-scattering unit 30) is composed of one anti-scattering roller 32 and one discharge wire 34 arranged on a unit stand 36. The single discharge wire 34 attached to the anti-scattering roller 32 of each unit has a fixing screw on one end of the anti-scattering roller 32 and a fastener and a coil spring on the other end. The discharge wire 34 is bent outward at both ends of the anti-scattering roller 32 in a direction intersecting the longitudinal direction (at an obtuse angle in FIG. 3 ) using pulleys 17. Two such anti-scattering units 30 are arranged symmetrically with respect to the spraying unit 20. The discharge wire 34 may be attached linearly without using a pulley. The device stand 12 is provided with a mounting base 14 on which a unit stand 36 can move horizontally.

[0017] [High voltage detection device for powder spray 10] 1 is a schematic diagram of a high-voltage detection device for powder sprays according to the present invention. The high-voltage detection device 10 for powder sprays according to the present invention comprises a spraying unit 20 having a powder storage tank 22, a spraying roller 24, and a discharge wire 26, and a scattering prevention unit 30 disposed downstream and upstream of the spraying unit 20 to form a closed spraying space 13 between the rollers, the scattering prevention unit 30 having two scattering prevention rollers 32 and discharge wires 34 disposed with a gap from the object to be sprayed and forcibly rotated, the three discharge wires 26, 34 being close to each other at the vertices of a triangle in a cross section perpendicular to the longitudinal direction, and the powder is sprayed. The device is equipped with a detection means 40 that is close to the discharge wires 26, 34 of the body spray 1 and detects the high voltage applied to the discharge wires 26, 34, and a signal processing means 50 that is connected to the detection means 40 and processes the detected high voltage to determine the live line state of the discharge wires 26, 34. The detection means 40 faces the discharge wires 26, 34, and a detection electrode 42 that has a length approximately the same as the diameter of the discharge wires 26, 34 is surrounded by an electric field shielding section 44 except for the detection surface, and the signal processing means 50 has an amplifier section 53 set to a gain that allows detection at close range from the discharge wires 26, 34. The discharge wires 26 and 34 have one end connected to the high voltage transformer 2 and the commercial power supply 3, and the other end grounded.

[0018] (Detection means 40) Figure 7 is an explanatory diagram of the detection means. The detection means 40 has a detection electrode 42 and an electric field shielding portion 44. The detection electrode 42 is a rectangular electrode with a length equal to or approximately equal to the diameter of the discharge wires 26, 34, and is located close to the discharge wires 26, 34 at a predetermined distance without contacting them. The detection electrode 42 is made of a metal material such as stainless steel containing molybdenum, for example, SUS316 or SUS316L, to reduce the corrosion of the electrode surface caused by partial discharge. The electrode surface is also polished to prevent deterioration if it comes into contact with the discharge wires 26, 34.

[0019] The electric field shield 44 is an insulating resin member made of a low-permittivity material that covers the detection surface of the detection electrode 42, i.e., the surface other than the surface facing the discharge wire. The electric field shield 44 is recessed to fit the rectangular detection electrode 42, limiting the directivity of the detection surface to a predetermined range so that only the high voltage of the single discharge wire facing the target electrode surface can be detected. In this embodiment, as an example, the distance between the discharge wires 26, 34 and the detection electrode 42 is set to within a few millimeters, specifically within 3 mm. This allows for detection even when the centers of the new discharge wires 26, 34 and the detection electrode 42 are misaligned within a range that does not affect powder spraying. For example, even if the tolerances of the components that make up the powder sprayer are within the allowable values, the center positions may differ when the components are assembled. In addition, the back surface of the electric field shielding portion 44 is grounded (earthed), providing electrostatic shielding and preventing the influence of external electric fields. This prevents erroneous detection by not providing directionality to the back surface of the electric field shielding portion 44.

[0020] (signal processing means 50) The signal processing means 50 is connected to the detection means 40 via a cable 5, and includes, from the detection means 40 side, a lightning protection section 51, a low-pass filter 52, an amplifier section 53, a signal determination section 54, and an output section 55. The lightning protection unit 51 is an earth terminal located closest to the detection unit 40 in the signal processing unit 50, and is configured so that when an abnormal voltage, surge, or leak detected by the detection unit 40 occurs, power is released directly from the earth terminal to the ground. This makes it possible to protect the circuits downstream of the lightning protection unit 51.

[0021] The low-pass filter 52 removes high-frequency noise that cannot be processed by the analog IC in the subsequent stage, thereby preventing the analog IC from being damaged by high-frequency noise. The amplifier 53 amplifies the noise-removed detection signal to a level that can be distinguished by the downstream signal determination unit 54. In this embodiment, the amplification factor is adjusted by the resistance value of the semi-fixed resistor. The level is set to a level that can be stably detected at close range from the discharge wires 26 and 34. The signal determination unit 54 applies a preset threshold value and determines whether a high voltage is generated based on whether the detection signal level amplified by the amplifier unit 53 exceeds the threshold value.

[0022] The output unit 55 converts the detection signal determined by the signal determination unit 54 into a non-voltage contact. At this time, the detection signal and the output signal are electrically isolated. This reduces restrictions on the devices and circuits connected downstream of the output unit 55. As an example of this embodiment, by connecting a programmable logic controller (PLC) downstream of the output unit 55, an output signal is transmitted to the input terminal of the PLC when high voltage is detected.

[0023] (Method for detecting high voltage in powder sprays) Next, a method for detecting high voltage in the discharge line of a powder sprayer will be described below. After being attached to a spray unit or a scattering prevention unit, the powder spray high voltage detection device 10 receives power from the unit and becomes ready to measure high voltage. (1) During normal spraying During normal spraying, the power supplies of each unit are properly connected, power is being supplied to each unit, and the power cables and signal lines connecting each unit are not broken. The high-voltage plugs of the discharge wires 26 and 34 are properly connected to the sockets on the main body, and powder is being sprayed. At this time, the high-voltage detection device 10 of the present invention detects high voltage from the discharge wires 26 and 34 using the detection means 40, and the signal determination unit 54 outputs an output signal indicating that the high voltage is above the high-voltage threshold.

[0024] (2) During abnormal spraying Abnormal spraying occurs when the power supplies of each unit are properly connected and power is being supplied to each unit, but powder is sprayed while a portion of the power cable or signal line connecting each unit is disconnected or detached. Specifically, this occurs when the high-voltage plug supplying high voltage to the discharge line is not properly connected to the socket on the main unit and becomes detached, or when the high-voltage transformer or discharge line deteriorates. In this case, the high-voltage detection device 10 of the present invention fails to detect high voltage from the discharge lines 26, 34 using the detection means 40, and the signal determination unit 54 outputs an output signal indicating that the high voltage does not meet the high-voltage threshold.

[0025] (Variation) FIG. 8 is a schematic diagram of a modified high-voltage detection device for powder sprayers. As shown, the modified high-voltage detection device 10A for powder sprayers differs from the device shown in FIG. 1 in the configuration of the signal processing means 50A. The remaining configuration is the same as that shown in FIG. 1, and detailed description thereof will be omitted. The signal processing means 50A employs a filter unit 52A. The filter unit 52A includes a low-pass filter 522 similar to that shown in FIG. 1, and also includes a band-pass filter 523. The band-pass filter 523 can detect partial discharges (corona discharges) by narrowing the frequencies passing through the filter. Specifically, the corona noise generated by corona discharges is treated as a signal source, and a filter is installed to block specific frequency bands contained in the corona noise. Generally, the frequency band of corona noise ranges from 15 kHz to 380 MHz, but the strength of the noise electric field decreases approximately inversely proportional to the frequency. Therefore, the corona noise signal level is narrowed to a range that does not reduce too much and does not exceed the upper operating frequency of the amplifier. The filter section 52A is provided with a changeover switch for switching between a low-pass filter and a band-pass filter. This modified high-voltage detection device 10A for powder sprayers allows the user to select a low-pass filter or a band-pass filter using a selector switch according to the user's needs, enabling measurement of high voltage or corona discharge. Similar to the high-voltage detection method, a threshold is set for detecting corona discharge. Therefore, the high-voltage detection device 10A detects corona discharge from the discharge wires 26 and 34 using the detection means 40, and the signal determination unit 54 outputs an output signal indicating that the corona discharge is above the corona discharge threshold. The advantage of detecting high voltage is that it can determine whether the high-voltage transformer is on or off, whether the cable connecting the high-voltage transformer to the discharge wire is connected, or whether high voltage is being applied to the discharge wire. Specifically, when the high-voltage transformer is on and the cable connecting the high-voltage transformer to the discharge wire is connected, high voltage is applied to the discharge wire, and a high-voltage signal is detected. The benefit of detecting corona discharge is that it not only tells you whether high voltage is being applied to the discharge wire, but also tells you whether electrons ejected by corona discharge are colliding with powder adhering to the surface of the spray roller, causing the powder to peel off from the surface of the spray roller. Specifically, a cable is connected between the high-voltage transformer and the discharge wire. If the output voltage of the high-voltage transformer drops due to aging, corona discharge will not occur even if high voltage is being applied to the discharge wire, resulting in normal spraying and dripping. Therefore, detecting corona discharge helps maintain normal spraying conditions.

[0026] According to the high voltage detection device for powder spray of the present invention, it is possible to individually detect the live state of multiple discharge wires that are placed close to each other in a narrow space that becomes the closed space where the powder is sprayed. In this embodiment, the anti-scattering unit 30 has been described as being manually slid horizontally from the mounting base 14, but this configuration is not limiting as long as it can be moved horizontally, and an automatic system using an electric or fluid (air, hydraulic, etc.) drive cylinder may also be used. In this case, if the positioning between the spray roller and the anti-scattering roller is performed during initial setup, even if the anti-scattering unit is moved horizontally for maintenance or discharge wire replacement, when it is returned to the operating position it will maintain the initial position, eliminating the need for re-alignment and allowing the discharge wire replacement work to be completed in a short time. Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications can be made without departing from the spirit and scope of the present invention. Furthermore, the present invention is not limited to the combinations shown in the embodiments, but can be implemented in various combinations. [Explanation of symbols]

[0027] 1 powder spray 2 High-voltage transformers 3 Commercial power supply 10,10A Powder Spray High Voltage Detector 12 Equipment stand 13 Spraying closed space 14 Mounting base 16 fixing holes 17 Pulley 20 Spray Unit 22 Powder storage tank 24 Spreading roller 26 Discharge wire 30 Anti-scattering unit 32 Anti-scattering roller 34 Discharge wire 36 Unit stand 40 Detection means 42 detection electrode 44 Electric field shielding section 50,50A Signal processing means 51 Lightning protection part 52 Low-pass filter 52A filter section 53 Amplification section 54 Signal determination unit 55 Output section 521 Changeover switch 522 Low-pass filter 523 Bandpass Filter

Claims

1. a spraying unit having a powder storage tank, a spraying roller, and a discharge wire; and a scattering prevention unit having two scattering prevention rollers and discharge wires, which are arranged downstream and upstream of the spraying unit to form a closed spraying space between the rollers and are arranged with a gap from the object to be sprayed and are forced to rotate, wherein the three discharge wires are close to each other at the vertices of a triangle in a cross section perpendicular to the longitudinal direction, and a detection means for detecting a high voltage applied to the discharge wires in the vicinity of the discharge wires of the powder sprayer; a signal processing means connected to the detecting means for processing the detected high voltage and determining the live line state of the discharge line; The detection means faces the discharge wire, and the detection electrode has a length approximately the same as the diameter of the discharge wire, and is surrounded by an electric field shielding section except for the detection surface, and the signal processing means has an amplifier section set to a gain that enables detection at close range from the discharge wire.

2. 2. The high voltage detection device for powder sprays according to claim 1, A high voltage detection device for powder sprays, characterized in that the signal processing means has a lightning protection section on the detection means side.

3. 2. The high voltage detection device for powder sprays according to claim 1, A high voltage detection device for powder sprays, characterized in that the detection electrode is made of stainless steel containing molybdenum.

4. 4. A high voltage detection device for powder sprays according to claim 1, wherein the signal processing means is configured to be switchable between a low pass filter and a band pass filter.

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