JPH0138540B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-speed rotary atomizer for electrostatic coating, and more specifically, the present invention relates to a high-speed rotary atomizer for electrostatic coating, and more specifically, even when the rotary body is rotated at a high speed, the paint atomization discharges over the entire circumference of the rotary body. The present invention relates to a high-speed rotating atomizer for electrostatic coating, which is capable of uniformly and evenly distributing liquid paint and forming an atomization pattern (painting pattern) that is free from bias and is substantially close to a perfect circle.

Conventionally, as a method of electrostatically atomizing liquid paint, paint is supplied inside a rotating body, the supplied paint is spread in a thin film along the inner peripheral surface of the rotating body, and this paint is applied to the rotating body. A method of atomizing and discharging from a tip provided on a circumferential edge is known.

In this electrostatic atomizing means, when the rotational speed of the rotating body is low, such as several hundred to several thousand revolutions per minute, the paint is uniformly and evenly distributed toward the atomizing tip of the rotating body. Even if the paint can be supplied in the form of a thin film, if the rotation speed of the rotating body is set to a high speed such as 10,000 revolutions per minute, the paint will be uniformly applied from one paint supply position to the entire circumferential surface of the rotating body. This has the disadvantage that it becomes difficult to spread, and as a result, the atomized pattern formed tends to be uneven or deviate considerably from a perfect circle.

Therefore, increasing the rotation speed of the rotating body is
Increases the amount of paint atomized per unit time, thereby increasing the amount of coating processing, and also enables the use of high viscosity paints with as little solvent as possible as liquid paints. From this point of view, this is highly desirable.

Therefore, an object of the present invention is to uniformly and uniformly distribute and supply paint over the entire circumference of the paint atomization discharge edge of the rotor even when the rotor is rotated at high speed, thereby To provide a rotary atomizer for electrostatic coating which can form a substantially perfect circular atomization pattern without unevenness or bias.

Another object of the present invention is that uniform distribution of liquid paint can be achieved with a relatively simple configuration, and the paint dispensing mechanism will not be clogged even if the painting operation is stopped or foreign matter gets mixed into the paint. To provide a rotary atomizer for electrostatic coating which is easy to clean and maintain, and also easy to manufacture.

According to the invention, there is provided a rotating outer body having a circumferential tip for atomizing and discharging a liquid paint and a conical inner peripheral surface for guiding the paint in the form of a thin film to the tip; A high-speed rotary atomizer for electrostatic coating, which comprises a rotating inner body assembled inside a rotating inner body, wherein the outer body is formed of an inner circumferential surface substantially parallel to the rotation axis direction for storing liquid paint. An annular paint flow path is formed continuously with the paint reservoir, and the outer body wall forming the paint flow path has knurled grooves for uniformly dispersing the paint. is formed, and the peak of the knurled groove protrudes beyond the peripheral surface of the outer body forming the paint reservoir, and the paint flows from the paint reservoir through the paint flow path and the conical inner peripheral surface of the outer body. A high-speed rotary atomizing device is provided, characterized in that liquid paint is supplied to a circumferential tip of an external body and atomized and discharged.

The invention will be described in detail below with reference to the accompanying drawings.

In FIGS. 1 and 2 showing the overall arrangement of the electrostatic coating device, the coating device main body 1 is mounted on a bracket 3 at the tip of an electrically insulating support rod 2 that is movable up and down by a suitable lifting device (not shown). It is provided so as to be rotatable around the fulcrum 4.

The coating device main body 1 includes an air motor 6 housed inside a housing 5, and an atomizing device (atomizing rotary body) 8 is mounted on the tip of a rotating shaft 7 of the air motor 6 like a nut 9. It is fixed by suitable fastening means. This coating device main body 1 also includes:
An air supply port 10 for driving and rotating the air motor 6 at high speed and an exhaust port 11 for discharging this air are provided. Further, the coating device main body 1 is provided with a liquid paint supply port 12, and the liquid paint is supplied through a paint supply pipe 13 extending from the supply port 12 through the interior of the main body 1 to the rotating body 8. It is designed to be supplied into the atomizing rotating body 8. Furthermore, the coating apparatus main body 1 is provided with a high voltage cable connection terminal 14, and although not shown, the high voltage from the high voltage generator passes through the cable to the coating apparatus main body 1, and is therefore atomized. The voltage is applied to the rotating body 8. On the rotating body mounting side of the housing 5, a large number of jet holes 15 for shaping air, that is, pattern adjustment air, are arranged in an annular manner and are connected to an air supply port 16.

In FIGS. 3 and 4 showing an enlarged view of this atomizing rotary body 8, this rotary body 8 is composed of a metal rotary outer body 17 (hereinafter simply referred to as the outer body) and a metal rotary inner body fitted together. 18 (hereinafter simply referred to as the internal body), the inner circumferential surface 1 is for guiding the liquid paint toward the tip in the form of a thin film.
9, and a circumferential tip 2 for atomizing and discharging the paint.
0. Furthermore, an annular paint reservoir 21 is formed in the rotating body 8 to temporarily store the paint supplied from the paint supply pipe 13 described above and to uniformly supply the paint over the entire circumference of the inner peripheral surface 19. The paint reservoir 21 and the inner circumferential surface 19 are communicated via a small annular slit-shaped flow path 22 between the outer body 17 and the inner body 18.

As is clear from FIG. 3, the paint reservoir 21 is formed from an inner circumferential surface that is substantially parallel to the rotational axis direction of the outer body 17.

If this inner circumferential surface is inclined, for example, in the same direction as the inner circumferential surface 19, the paint reservoir 21 will be unsatisfactory in its function of temporarily storing paint; If it is inclined in the direction, the problem arises that paint accumulates in the paint reservoir 21.

A high voltage is applied to the atomizing rotary body 8 via the cable connection terminal 14, and the air motor 6 is driven by the air supplied through the air supply port 10. is driven and rotated at a high speed, for example 8,000 to 30,000 rpm.
The liquid paint is supplied to the paint reservoir 21 inside the rotating body 8 through the paint supply port 12 and the paint supply pipe 13, and is further supplied in the form of a thin film over the entire circumferential surface 19 of the rotary body through the annular flow path 22. be done. Inner peripheral surface 1
The paint on the atomizing rotor 9 flows approximately axially forward through the atomizing rotary body, and is atomized and discharged from the circumferential tip 20 described above.

An important feature of the present invention is that by providing the knurled grooves 24 over the entire outer circumferential surface 23 of the annular flow path 22, the knurled grooves 24 distribute the paint uniformly over the entire annular flow path 22. It acts as a distribution smoothing mechanism to smooth the film thickness,
As a result, even when rotating a rotating body at high speed,
This is based on the fact that it is possible to supply the paint uniformly and evenly distributed over the entire circumference of the paint atomization discharge edge 20 of the rotating body.

This knurled groove 24 is connected to the paint reservoir 21.
The ridge portion protrudes from the inner circumferential surface of the outer body 17 that forms the paint reservoir 21 and is parallel to the rotational axis direction.

First, the paint supplied into the rotation 8 from the paint supply pipe 13 fills the paint reservoir 21, and then overflows to the inner circumferential surface 19 via the annular flow path 22.
When the rotational speed of the rotating body is high, the annular flow path 2
Non-uniformity in overflow from tip 20 tends to lead to non-uniformity in atomization from tip 20. That is, when the rotational speed of the rotating body is relatively low, (a) the annular flow path 2
Since the centrifugal force acting on the paint in the portion 2 is small, and therefore the outflow speed of the paint is relatively low, a sufficient amount of paint is stored around the entire circumference of the paint reservoir 21, and as a result, the annular flow path 22 is filled with a sufficient amount of paint. (b) Even if the overflow of paint from the annular flow path 22 occurs unevenly, the paint overflowing onto the inner peripheral surface 19 will flow along the inner peripheral surface 19. Tip 2 after rolling around
Since the paint is emitted from zero, the flow of the paint is made uniform on the inner circumferential surface 19, and for this reason, there was almost no phenomenon in which the atomization pattern became uneven.

On the other hand, when the rotational speed of the rotating body 8 is high, such as 10,000 revolutions per minute, (A) the annular flow path 2
Since the centrifugal force acting on the paint in the part 2 is large and the paint flow rate in this part is also high, the paint flows annularly before a sufficient amount of paint is stored around the entire circumference of the paint reservoir 21. (B) When the rotating body rotates at high speed, the flow from the annular flow path 22 becomes uneven.
The paint overflowing onto the inner circumferential surface 19 from the inner circumferential surface 19 hardly flows along the inner circumferential surface 19 and flows straight toward the tip in the radial direction or rotational axis direction. For reasons such as the fact that a uniform flow of paint cannot be expected, the non-uniformity of the overflow in the annular flow path 22 immediately manifests itself as unevenness or disturbance in the atomization pattern. The non-uniformity of the overflow or the disturbance of the atomization pattern is caused by the fact that the amount of outflow or discharge gradually increases from the paint supply position from the pipe 13 in the direction of rotation of the rotating body until this amount reaches the maximum. It generally shows a tendency to gradually decrease after that.

In the present invention, the knurled groove 24 provided on the outer circumferential surface 23 of the annular flow path 22 has a V-shaped flow regulating orifice 25 (i.e., trough) and an inverted V-shaped weir 26 (i.e., peak). By being arranged alternately, it acts as a weir to allow a small amount of paint to overflow from a part of the paint reservoir 21, but prevents a large amount of paint from flowing out. It is recognized that the adjustment function is performed simultaneously, and the liquid level in the paint reservoir 21 is made smooth and uniform, and the flow rate is made uniform over the entire circumference.

Moreover, according to the present invention, the effect of uniformly distributing the paint on the inner circumferential surface of the rotating body is achieved with a simple structure of providing knurled grooves on the outer circumferential surface of the annular flow path, and the manufacturing thereof is also easy. In addition to being easy to use, it also has the advantage that no clogging occurs even if the painting operation is stopped or foreign matter gets mixed into the paint, and cleaning and maintenance are also easy.

The knurled groove provided on the outer circumferential surface of the annular flow path is
As shown in the embodiments of the accompanying drawings, serrations are particularly desirable in view of the aforementioned effects. The pitch of this knurled groove is 0.1 to 3 mm, especially
It is preferred for the purposes of the invention that the groove depth is in the range 0.2 to 1.5 mm, and the groove depth is in the range 0.1 to 3 mm, especially 0.2 to 1.5 mm. Of course, the knurled grooves can have any shape as long as they are regularly provided in large numbers over the entire outer peripheral surface of the annular flow path, such as trapezoidal waves, gear shapes, rectangular waves, U-shaped notches, etc. can take any shape.

It should also be understood that the rotating body 8 may have any shape other than the deeply constricted cup shown in the drawings, such as a shallow cup shape or a flat dish shape.

The atomizing device for electrostatic coating of the present invention has a rotating atomizing body.
It is used for painting by rotating at a high speed of 5,000 to 50,000 rpm, especially 8,000 to 30,000 rpm.
In addition, the voltage applied to the atomizing rotor is 20 to 160KV,
In particular, it can be selected appropriately from the range of 40 to 120KV.

The paint to be used may be any of those conventionally used for this type of electrostatic coating, such as organic solvent paints such as epoxy paints, phenolic paints, melamine paints, and acrylic paints, or water-based paints, especially solvents. It can be advantageously applied to high viscosity paints in which a small amount of is used, for example, paints with a viscosity of 30 seconds or more (75 centipoise or more) using a #4 food cup.

The amount of paint discharged, that is, the amount of paint to be processed, varies considerably depending on the diameter of the open edge of the rotating body, the dimensions of the notch, etc., but according to the present invention, the paint having the above-mentioned viscosity is used, and the outside diameter of the edge is is 700 c.c./ using a rotating body of 60 mm.
It was confirmed that even when electrostatically atomizing paint up to 50% of paint, the atomization pattern (paint pattern) had no unevenness or turbulence and had a nearly perfect circular shape.

[Brief explanation of drawings]

Figure 1 is a partial cross-sectional plan view of the entire electrostatic coating apparatus, Figure 2 is a side cross-sectional view of the apparatus in Figure 1, and Figure 3 is a partial cross-sectional plan view of the entire electrostatic coating apparatus.
The figure is a side sectional view of the atomizing cup, and FIG. 4 is a front view of the cup of FIG. 3. Reference number 1 is the coating equipment body, 6 is the motor, 8
13 is a rotating body, 13 is a paint supply pipe, 14 is a high voltage cable connection terminal, 19 is an inner peripheral surface, 20 is a circumferential tip, 21 is a paint reservoir, 22 is an annular flow path, 23 is an inner peripheral surface, 24 is a A knurled groove, 25 an orifice, and 26 a weir.

Claims (1)

[Scope of Claims] 1. A rotary outer body having a circumferential tip for atomizing and discharging liquid paint and a conical inner peripheral surface for guiding the paint to the tip in the form of a thin film; A high-speed rotary atomizer for electrostatic coating comprising a rotating inner body assembled inside a body, the outer body storing liquid paint formed by an inner circumferential surface substantially parallel to the rotation axis direction. The paint reservoir is equipped with a paint reservoir, and an annular paint channel is formed continuously with the paint reservoir, and the external body wall that forms the paint channel has knurling holes for uniformly dispersing the paint. A groove is formed, and the crest of the knurled groove protrudes beyond the peripheral surface of the outer body forming the paint reservoir, and the paint flows from the paint reservoir through the paint flow path and the conical inner peripheral surface of the outer body. A high-speed rotating atomizer, characterized in that liquid paint is supplied to a circumferential tip of an external body and atomized and discharged.