JPS58104656A - Rotary atomizing type electrostatic painting apparatus - Google Patents

Abstract

PURPOSE:To attain to enhance paint depositing efficiency, by arranging plural air injecting orifices of an air injecting apparatus provided behind a spray head on circles with different diameters around the rotary axial line of the spray head to properly maintain the expanse of a paint spray angle. CONSTITUTION:A paint is supplied in the ring like space 6 of a spray head 3 rotating at a high speed from the nozzle orifice of a paint jet nozzle 7 and flowed out on a cup like inner peripheral surface 5 by rotary centrifugal force to be injected as paint spray from the leading end peripheral part 21 of the spray head while spreaded in a thin liquid film. On the other hand, air is injected from each air injecting ports 15, 16 as shown by arrows A, B by the rotation of the spray head 3. In this case, the advancing direction C of injected paint particles is deflected to the direction shown by an arrow D by the injected air stream A and the flowing direction thereof is further deflected to a direction shown by an arrow E by the injected air stream B. Therefore, the scattering of paint particles by injected air can be controlled and paint depositing efficiency is enhanced.

Description

[Detailed description of the invention] The present invention relates to a rotary atomization electrostatic coating device.

Conventionally, for example, as a coating device for painting vehicle dee, a cup-shaped spray head is fixed to the rotating shaft of the coating device, and a negative voltage is applied to the spray head while the inside of the rotating cup-shaped spray head is heated. Supplying paint onto the surrounding surface, ejecting negatively charged fine paint particles from a cup-shaped spray head, and attracting them onto an electrically grounded surface to be saponified by electric force,
A rotary atomization electrostatic coating device is known that uses this method to coat a surface to be coated. When painting with such a spray I@ paint, in order to achieve a clean painted surface, it is sufficient to increase the circumferential speed of the spray head, that is, the rotational speed, and thereby reduce the particle size of the spray paint. However, when the rotational speed of the spray head is increased, a negative pressure is created in the center of the spray head, so that surrounding air is sucked into the center of the spray head from the front opening of the spray head. This air then flows radially outward due to centrifugal force, then flows along the cup-shaped inner circumferential surface and flows out radially outward from the distal end portion of the cup-shaped inner circumferential surface at a high velocity. As the air flows radially outward from the periphery of the tip of the inner circumferential surface of the cup, the spray paint also scatters outward in the radial direction from the periphery of the tip of the inner periphery of the cup, riding this air flow. As a result, there is a problem in that the amount of a* retouching paint dissipated into the surrounding atmosphere increases, resulting in a decrease in coating efficiency. In order to solve this problem, compressed air is ejected from the back of the spray an toward the front along the outer circumferential surface of the spray m, and this compressed air flow causes the spray head to blow out from the slitted edge of the tip of the bonito-shaped inner circumference of the spray head. A rotary atomizing electrostatic coating device is known in which the flow direction of the airflow flowing outward in the radial direction is deflected forward to narrow the spread angle of the paint spray, thereby improving the coating efficiency. In this rotary atomizing electrostatic coating device, as the U rotation number of the spray head increases, the spread angle of the paint spray increases accordingly, so in order to maintain this spread angle at an appropriate spread angle, the flow rate of the ejected air flow must be must be accelerated. However, if the velocity of the ejected air stream is increased, the velocity of the air stream that bounces off after colliding with the surface to be coated or flows along the surface to be coated also increases, causing paint particles to be
Since the force of transporting the paint particles by the air flow is stronger than the electric force attracted towards IjJ, there is a problem that the paint particles are scattered with the air flow, thus reducing the coating efficiency.

The present invention is a blowout! To provide a rotary atomizing electrostatic coating device capable of narrowing the spread angle of paint spray while ensuring high coating efficiency even when the rotational speed of one head is increased.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to the drawings, a spray head 3 is fixed by a nut 4 to the tip of a rotating shaft 2 which is rotatably supported in a rotary atomizing electrostatic coating.

The rotating shaft 2 is connected to a high voltage generator (not shown) that generates a negative high voltage of -60 kV to -120 kV.
Therefore, a negative high voltage is applied to the spray @3 via the rotating shaft 2. As shown in the drawings, the spray WA3 has a circular inner peripheral surface 5 and an annular space 6 formed around the rotating shaft 2, and a nozzle 8 of the paint spray nozzle 7 is disposed within this annular space 6. Furthermore, a large number of paint outlet holes 10 are formed at the innermost part of the inner wall surface 9 of the spray head which defines the annular space 5 and extends all around the inner wall surface 9 of the spray head. An air blowing device 14 consisting of a small-diameter disc-shaped intermediate member 11 and a pair of large-diameter disc-shaped end plates 12, 13 is fixed to the end of the housing '1. Large diameter disc-shaped end plate 1
3, a first air outlet group consisting of a large number of air outlets 15 and a second air outlet group consisting of a large number of air outlets 16 are formed. Each air outlet 15 constituting the vine 1 air outlet group is arranged on a concentric circle with a radius r centered on the rotation axis of the rotating shaft 2, and each air outlet 16 forming the second air outlet group As can be seen from the drawing, the radius r is slightly larger than the radius of the rear end 3 of the spray head 3, and the radius R is smaller than the radius r. It's also quite large. Small diameter disc-shaped intermediate member 1
1, an annular air passage 17 is formed in each air outlet 1.
5 directly into this annular air passage 17. On the other hand, the large diameter r
An annular air passage 18 is also formed within the disk-shaped end plate 12;
Each air outlet 16 communicates within this annular air passage 18. The annular air passage 17.18 has a main air supply hole 19.20.
The blades shown in the figure are connected to a source of compressed air through the air outlet 15 and 16, so that air is ejected forward from each air outlet 15 and 16 as indicated by arrows A and B, respectively. - The paint is supplied from the nozzle opening 8 of the paint injection nozzle 7 into the fR-shaped space 6 of the spray head 3 rotating at high speed. The paint then flows out onto the cup-shaped inner circumferential surface 5 of the spray head 3 through the paint outlet hole 10 due to the centrifugal force generated by the rotation of the spray head 3. Next, this paint spreads as a thin liquid film on the inner circumferential surface 5 and advances toward the tip peripheral edge 21 of the spray head 3, and is ejected from the tip peripheral edge 21 as a paint spray. On the other hand, as described above, a high negative voltage is applied to the spray head 3, so that the paint particles are negatively charged. Since the surface to be painted is normally at zero potential, the paint particles are attracted toward the surface by electric force, thereby coating the surface.

On the other hand, when the jet w1113 is rotated, the air flows into the direction indicated by the arrow A.
, B are injected from each air outlet 15,16. Paint particles ejected from the tip peripheral edge 21 of the spray head 3 tend to move in the direction of arrow C due to centrifugal force, but the flow direction of the paint particles is deflected as shown by the arrow by the jetted air streamer. The paint particles whose flow direction has been deflected are then deflected in the flow direction as shown by the arrow E by the ejected air flow B. By the time the f11 heavy particles reach the region of the ejected air flow B, the flow velocity of the paint particles has decreased considerably, and therefore the flow direction of the paint particles has been changed to the ejected air flow B.
easily deflected by Air outlet 15.1
If air is ejected from only one of the two, it will be difficult to obtain the optimum spray bottom angle unless the air ejection speed is increased. By performing this in two steps at radially distant points, it is possible to slow down the air jet speed and obtain the optimum spray bottom angle. Note that a third air outlet group or more air outlet groups may be provided radially outward of the air outlet ports 16 constituting the second air outlet group.

As described above, according to the present invention□, it is possible to narrow the spread angle of paint spray without increasing the flow velocity of the ejected air flow◎Therefore, it is possible to suppress the scattering of paint particles by the ejected air, thereby increasing the coating efficiency. can be improved.

The figure is a side cross-sectional view of a rotary atomization Ikl coating apparatus according to the present invention.

2... Rotating shaft, 3... Spraying rod, 7... Paint injection nozzle, 10... Paint outflow hole, 14... Air blowing device, 15° 16... Air blowing port.

patent applicant Toyota Motor Corporation patent application agent Patent attorney Akira Aoki Patent attorney: Kazuyuki Nishidate :1゜ Patent attorney'□Kyosuke Nakayama Patent attorney Akira Yamaguchi

Claims (1)

[Claims] The paint is supplied onto the inner peripheral surface of a rotating cup-shaped spray head, and the paint spray is discharged from the periphery of the tip of the cup-shaped inner peripheral surface of the spray head, and an air blowing device is provided behind the spray head. In a rotary atomizing electrostatic coating device in which air is jetted forward from an air blowing device around the outer peripheral surface of a spray head,
A rotary atomizing electrostatic device in which the air jetting ports of the air jetting device are arranged on circles of different diameters centered on the rotational axis of the spray head, and air is jetted forward from each air jetting port. Painting equipment.