JP3288201B2 - Powder supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder supply apparatus for supplying a powder coating paint to a coating gun and performing powder coating, and more particularly to a powder supply apparatus for controlling the flow rate of powder. The present invention relates to a powder supply device provided with means for measuring a change.

[0002]

2. Description of the Related Art In the case of automated powder coating, in order to obtain a uniform coating film and to make effective use of the coating material, it is necessary to always use
A certain amount of paint needs to be supplied. In order to control the powder flow rate for supplying a constant paint, various flow rate measurement methods have been proposed, and the present applicant has also proposed a powder flow rate measurement method based on the principle of powder density measurement and a device therefor. . According to this, various measuring means such as light transmittance, ultrasonic wave transmittance, and capacitance have been proposed as powder density measuring means.
Compared with other flow rate measurement methods that detect pressure differences, etc., the powder flow rate can be measured with a very simple mechanism, the production cost is low, and the powder flow rate measurement is easy to maintain and change colors A method and an apparatus thereof can be used (see Japanese Patent Application Laid-Open No. 7-35591).

[0003]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 7-355 is disclosed.
In No. 91, in particular, the capacitance measuring means for measuring the flow rate of the powder as a change in the capacitance between a pair of measurement electrodes is extremely simple and can be suitably used,
Depending on the structure and mounting condition of the electrode used, it is susceptible to changes in ambient temperature, the capacitance may fluctuate, and the fluctuations in measured values due to the position where the powder passes are not small. .

Accordingly, the present invention employs the above-mentioned preferable capacitance measuring means, and particularly improves the electrode structure so that the fluctuation of the capacitance is small and the measured value depends on the position where the powder passes. It is an object of the present invention to provide a powder supply device capable of measuring a powder flow rate more accurately and supplying a fixed amount of powder.

[0005]

According to the present invention, there is provided, according to the present invention, a powder having an air blowing nozzle and a capacitance measuring means in a transfer pipe connected between a tank and an injector. A supply device, wherein the capacitance measuring means is:
It has a pair of parallel strip-shaped measurement electrodes spirally formed along the outer circumference of the measurement tube and a guard electrode formed between the electrodes, and is connected between the tank and the injector. A powder supply device having an air blowing nozzle and a capacitance measuring means in a transfer pipe, wherein the capacitance measuring means is a pair of parallel belt-shaped spirals formed along the outer circumference of the measurement pipe. A control means having an electrode for measurement and a guard electrode formed between the electrodes, receiving a signal input from the capacitance measuring means and outputting a control signal, and a flow rate for controlling a powder supply amount by the control signal An adjusting means is provided.

[0006]

The transfer pipe connected between the tank and the injector is provided with an air blowing nozzle and a capacitance measuring means, and a predetermined amount of a detection fluid is blown into the transfer pipe from the air blowing nozzle to provide a downstream electrostatic capacity. The measuring means measures the flow rate of the powder as a change in capacitance between the pair of measuring electrodes. At this time, since the pair of measurement electrodes are spirally formed along the outer circumference of the measurement tube, members constituting the measurement tube are uniformly subjected to thermal deformation due to a change in ambient temperature, and an actual error in the measured value is caused. Is small and the change is proportional to the change in heat, so that not only the compensation is easy, but also the fluctuation of the measured value due to the position through which the powder passes is small. Based on this measured value, the injector driving air amount can be adjusted and a constant amount of powder can be supplied.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a powder supply device 1 of the present invention
Compressed air, which is a powder detection fluid, is blown into a transfer pipe 4 between an injector 3 for feeding powder at a pressure required for a powder supply tank 2 and a next process portion B such as a coating gun (not shown). It is mainly constituted by providing the nozzle 5 and the capacitance measuring means 6. Reference numeral 7 denotes a valve means such as a pinch valve which is provided on the upstream transfer pipe of the air blowing nozzle 5 and starts or stops the supply of the powder.

As the tank 2, a so-called fluidized bed tank provided with a fluid supply pipe 8 and a perforated plate 9 is suitably used. Fluid air A is blown from a pressure source (not shown), and powder F is stored in the tank 2. It is kept in a fluid state. The transport pipe 4 constituting the powder passage is connected to the tank 2, and the driving air is blown into the injector 3 from the pressurized air source 10 with the pinch valve 7 opened, so that the powder F is sucked from the tank 2. Is transported. Reference numeral 11 denotes a flow rate adjusting means such as a motor valve for adjusting the amount of driving air to the injector 3, and reference numeral 12 denotes a pipe to the injector 3.

The blowing nozzle 5 is provided via a flow rate setting means 13 for adjusting the blowing amount of the compressed air. The blowing nozzle 5 is capable of constantly blowing a predetermined amount of air from an air source (not shown) into the conveying pipe. it can. As described in the above-mentioned JP-A-7-35591, the powder flow rate in the transport pipe 4 is determined by the flow rate of the detection fluid blown from the blowing nozzle 5 and the transport pipe 4.
The product can be determined as the product of the densities in the inside, and by measuring the density as a change in the capacitance, the measurement of the powder flow rate by the capacitance measuring means 6 described later is ensured.

As shown in FIG. 2, the capacitance measuring means 6 comprises a pair of parallel measuring electrodes 15 and 16 having a narrower band than the electrodes 15 and 16 with the electrodes 15 and 16 interposed therebetween. Along with the guard electrode 17, it is formed so as to be spirally wound along the outer circumference of the measuring tube 14 also serving as the transport tube 4. Each of the electrodes 15, 16, and 17 is formed by printing or attaching a copper foil or the like to the surface of the measurement tube 14. The measuring tube 14 may be a cylindrical insulating tube, for example, a ceramic material such as glass, quartz glass, or alumina, or an insulator made of various plastics. The inner surface of the measuring tube 14 is desirably subjected to Teflon processing to a thickness of about 0.1 to 0.2 mm in order to prevent powder adhesion.

As described above, the pair of measurement electrodes 15 and 16
Is spirally formed along the outer periphery of the measuring tube 14, so that the variation of the measured value due to the position where the powder conveyed in the measuring tube 14 passes is extremely small, and the members constituting the measuring tube 14 are formed. And the actual error of the measured value is small, and the control means 20 described later can reliably supply a constant amount of powder based on the measured value of the powder flow rate.

The guard electrode end 17a of the measuring tube 14
An outer cylinder 19 is provided on 17b via a sealing material 18.
The outer cylinder 19 serving as a shield is made of aluminum, copper, conductive glass, or the like, and seals a space between the outer cylinder 19 and the measuring tube 14 to prevent invasion of moisture and the like, and to reduce the amount of change in capacitance. Measurement errors can be reduced as much as possible.

Next, the control means 20 controls the capacitance measuring means 6
And outputs a control signal 22 in response to the input signal 21 from the control circuit 21. The control signal 22 includes an amplifier 23, a correction circuit 24, a controller 25, and the like. That is, the signals from the measuring electrodes 15 and 16 of the capacitance measuring means 6 to which the AC voltage (not shown) is applied are amplified by the amplifier 23 while the input signal 21 output through the switching circuit, the synchronous detection circuit and the like is amplified and corrected. Circuit 24
In the correction circuit 24, the input signal 21 is corrected in accordance with an on / off signal 26 of a coating gun or the like, for example, a zero point correction is performed, and is output to the controller 25.

The zero-point correction is intended to reduce the influence of powder adhering to the measuring tube 14 during powder supply to a level that does not adversely affect practical use. The measured value during operation is corrected using the measured value as the correction reference value.

The amplifier 23 is not limited to the one shown in the figure, and the amplifier 23 can be further provided after the correction circuit 24. Preferably, a cable for transmitting the input signal 21 to the control means 20 is shielded, and a power supply voltage is applied to the shield and the outer cylinder 19 or an output voltage of the amplifier 23 is connected. It suppresses irregular impedance between the shield and the shield, and enables more accurate flow rate measurement.

The controller 25 compares the measured value corrected by the correction circuit 24 with the set target value 27 of the supply amount, and takes out the difference as a control signal 22. This control signal 2
2 controls the flow rate adjusting means 11 such as a motor valve to adjust the amount of driving air to the injector 3 so that a certain amount of powder can be reliably supplied to a coating gun or the like (not shown) in the direction of arrow B. it can. Although not shown, the control signal 22 is provided in the upstream conveying pipe of the air blowing nozzle 5 separately from or together with the adjustment of the driving air amount to the injector 3. The amount of powder supply may be controlled by adjusting the opening of the valve means 7 such as a pinch valve, and similarly, a suitable powder supply can be achieved.

Next, another embodiment of the present invention will be described. FIG.
4 and 4 show an example in which the air blowing nozzle 5 and the valve means 7 are incorporated in a single holder 30.
Has a substantially cylindrical shape in which a small-diameter portion 32 inserted into the tank 2 and a large-diameter portion 33 protruding out of the tank 2 are formed with a step portion 31 formed substantially at the center in the longitudinal direction as a holder. A powder passage 34 is formed inside 30, and the valve means 7 is integrated into the upstream of the powder passage 34, and the air blowing nozzle 5 is integrated into the downstream of the powder passage 34. Valve means 7
As in the previous embodiment, a pinch valve is suitably used, and the powder passage 34 is opened and closed by introducing compressed air C from an air source (not shown) into a fluid passage 35 formed in the holder 30. . A powder detection fluid is introduced by blowing a predetermined amount of air into the air blowing nozzle 5 via the flow rate setting means 13. Note that the rear end portion 34a of the powder passage 34 is connected to the transport pipe 4, the capacitance measuring means 6, and the like described in the above embodiment, and constitutes a powder supply device of the present invention.

The holder 30 can be fixed to the side wall 2b of the tank 2 by an adhesive or welding, or can be detachably provided by a screw member or the like. Further, by screwing the outer peripheral surface of the tube 5 a forming the air blowing nozzle 5 and forming the inner peripheral surface of the holder 30 so as to screw with the tube 5 a, the air blowing nozzle 5 is attached to the holder 30. It is desirable to be provided detachably. As described above, by incorporating the air blowing nozzle 5 and the valve means 7 in the single holder 30, it is possible to easily replace the nozzle 5 which is particularly in contact with the powder flow and is easily worn.

FIG. 5 shows still another embodiment of the present invention, in which a powder container, for example, a paint box delivered from a paint maker or the like can be directly used as a tank. is there. In FIG. 5, a paint box 2a as a tank is placed on a carrier 41 to which a vibrator 40 is attached. A powder take-out pipe 42 having an inner / outer double pipe having a powder passage 42a at the center and a fluid passage 42b at the periphery is supported by the carrier 41 via a support column 43, and extends inside the paint box 2a. It is provided almost vertically so as to be present. The valve means 7 is connected to the rear end 42c of the powder take-out pipe 42, and the compressed air blowing nozzle 5, the capacitance measuring means 6, the injector 3 and the like are provided in the same manner as in the previous embodiment. A powder supply device is formed. The paint box 2a is placed on the loading platform 41 in an inclined state.
It is preferable that the powder F can be efficiently taken out even when the amount of the powder in a is small.

In the powder supply device of the present invention thus formed, the paint box 2a is vibrated by the vibrator 40, and a small amount of powder is supplied from the fluid supply port 42d to the vicinity of the powder suction port 42e via the fluid path 42b. Air is blown and blown to locally fluidize the powder in the paint box 2a. Next, when the driving air is blown into the injector 3 with the pinch valve 7 open, the powder F is sucked from the paint box 2a into the powder passage 42a, and a certain amount of powder Can be supplied. In this example,
As described above, there is an advantage that the paint box delivered from a paint maker or the like can be used as it is as a tank, and the powder does not constantly flow, so that there is little deterioration of the powder and a small amount of flowing air is required.

[0021]

As described above, according to the present invention, with a very simple structure, the fluctuation of the measured value due to the change in the ambient temperature, the fluctuation of the measured value due to the position of the powder passing through the measuring tube,
Furthermore, the influence of the powder adhering to the measuring tube is reduced to a level that does not cause a practical problem, the flow rate of the powder can be measured more accurately, and a certain amount of powder can be reliably supplied. . Further, the present invention is a powder supply device which is low in production cost and easy in maintenance and color change especially in powder coating.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a powder supply device of the present invention.

FIG. 2 is a schematic diagram showing capacitance measuring means of the powder supply device of the present invention.

FIG. 3 is a partially enlarged view showing another embodiment of the powder supply device of the present invention.

FIG. 4 is a sectional view taken along line AA of the embodiment shown in FIG. 3 of the present invention.

FIG. 5 is a partial schematic view showing still another embodiment of the powder supply device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder supply apparatus 2 Tank 2a Paint box 2b Side wall 3 Injector 4 Conveyance pipe 5 Nozzle 6 Capacitance measuring means 7 Valve means 8 Fluid supply pipe 9 Perforated plate 10 Pressure air source 11 Flow control means 12 Piping 13 Flow setting means 14 Measuring tube 15 Measuring electrode 16 Measuring electrode 17 Guard electrode 17a Guard electrode end 17b Guard electrode end 18 Seal material 19 Outer cylinder 20 Control means 21 Input signal 22 Control signal 23 Amplifier 24 Correction circuit 25 Controller 26 ON / OFF Signal 27 Set target value 30 Holder 31 Stepped section 32 Small diameter section 33 Large diameter section 34 Powder passage 34a Rear end 35 Fluid passage 40 Vibrator 41 Carrier 42 Powder extraction tube 42a Powder passage 42b Fluid passage 42c Rear end 42d Fluid Supply port 42e Suction port A Flowing air C Compressed air F Powder

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yutaka Ishikawa 2-13-27 Shinonome, Koto-ku, Tokyo Inside Ionics Technology Center Chichibu Onoda Co., Ltd. (72) Inventor Mitsuyoshi Kumada 2-13-, Shinonome, Koto-ku, Tokyo 27 Chichibu Ono field, Inc. Ionics intra-technology center (56) reference Patent Sho 58-55716 (JP, a) JP Akira 62-76440 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ , DB name) B65G 53/66 B65G 53/26 B05C 19/06 G01F 1/74 G01F 1/56

Claims (12)

(57) [Claims] 1. A powder supply device comprising an air blowing nozzle and a capacitance measuring means in a transfer pipe connected between a tank and an injector, wherein the capacitance measuring means extends along an outer periphery of the measuring pipe. A powder supply device comprising: a pair of parallel strip-shaped measurement electrodes spirally formed; and a guard electrode formed between the electrodes. 2. A powder supply device comprising an air blowing nozzle and a capacitance measuring means on a transfer pipe connected between a tank and an injector, wherein the capacitance measuring means extends along an outer periphery of the measuring pipe. Control means having a pair of parallel strip-shaped measurement electrodes formed in a spiral shape and a guard electrode formed between the electrodes, and receiving an input signal from the capacitance measurement means and outputting a control signal And a flow rate adjusting means for controlling a powder supply amount by a control signal. 3. The powder supply device according to claim 2, wherein the flow rate adjusting means is a flow rate adjusting means for adjusting an injector driving air amount by a control signal. 4. The powder supply device according to claim 2, wherein the flow rate adjusting means is a flow rate adjusting means for adjusting an opening of a valve means provided in the conveying pipe. 5. The powder supply device according to claim 1, wherein the guard electrode is formed in a band shape smaller than the pair of band-shaped measurement electrodes. 6. The powder supply device according to claim 1, wherein an outer cylinder is provided on the measurement tube via a sealing material. 7. The powder supply device according to claim 1, wherein a valve means is provided on an upstream transfer pipe of the air blowing nozzle. 8. The powder supply device according to claim 7, wherein the air blowing nozzle and the valve means are incorporated in a single holder. 9. The tank according to claim 1, wherein the tank is a fluidized bed tank into which a fluid is introduced via a perforated plate.
8. The powder supply device according to any one of 8. 10. The powder supply device according to claim 1, wherein the tank is a paint box placed on a carrier having a vibrator. 11. The powder supply device according to claim 10, wherein the transport pipe is connected to a powder extraction pipe provided to extend inside the paint box. 12. A powder passage in a center portion of the powder discharge tube,
The powder supply device according to claim 11, wherein the powder supply device has a substantially vertical inner / outer double pipe line having a fluid path formed in a peripheral portion.