JPH0330849A - Bell-type rotary spray apparatus - Google Patents

Abstract

PURPOSE:To form a uniform coating film by arranging blades for generation of air flow at an outer periphery side of a rotary atomizing head. CONSTITUTION:A negative pressure zone 17 is formed in front of a discharge end rim 12E of an atomizing head 11 due to an air pumping phenomenon when the rotary atomizing head 11 is rotated at a high speed. If coating material is sprayed from the discharge end rim 12E of a main body 12 of the atomizing head in this condition, a spray pattern 18 of the coating material from the discharge end rim 12E is drawn into the negative pressure zone 17 owing to the difference between the positive pressure of air flow 16 generated by blades 15 and the negative pressure caused by the air pumping phenomenon. Fine and coarse particles are mixed together by the drawing, fly along an electrostatic field and are coated onto an object 7. It is possible to obtain a coating film of a good finish with this apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bell-shaped rotary spraying device suitable for use in an electrostatic coating device.

[Conventional technology]

In general, electrostatic coating equipment using a bell-shaped rotary atomizer is
A bell-shaped rotary atomizing head is rotated at high speed and a high voltage is applied between it and the object to be coated, and paint is supplied to the paint smoothing surface of the rotary atomizing head and atomized by rotation, and the atomized electrostatic charge is generated. Paint particles are caused to fly and coat the object to be coated along an electrostatic field formed between the object and the object located in front of the axial direction.

As electrostatic coating apparatuses using such a bell-shaped rotary spraying apparatus, those shown in FIGS. 8 to 11 are conventionally known.

First, in FIG. 8, reference numeral 1 denotes a casing that forms the main body of the coating device, and inside the casing 1 there are built-in an air motor, an air bearing, a paint valve, etc. (all not shown) that rotate the rotating shaft 2 at high speed. , a high voltage is applied to the casing 1 via a high voltage cable.

The aforementioned bell-shaped rotary atomizing head 3 is attached to the tip side of the rotary shaft 2, and a paint supply pipe 4 for supplying paint to the rotary atomizing head 3 is attached to the rotary shaft 2. It is inserted. 5 is a rotating atomizing head 3 as shown by the dotted line in the figure.
One end of the shaping air ring 5 is fixed to the casing 1, and the other end is arranged so as to surround the outer periphery of the rotating atomizing head 3. In the figure, 7 indicates the object to be coated suspended from the conveyor.

In the electrostatic coating device configured as described above, by applying a high voltage to the casing 1, the rotating shaft 2 and the rotating atomizing head 3 are charged to a high voltage, and an electrostatic field is formed between the rotating shaft 2 and the rotating atomizing head 3. do. At the same time, the rotary shaft 2 and rotary atomizing head 3 are rotated at high speed by the air motor inside the casing 1.

In this state, by opening the paint valve, paint is supplied to the rotary atomizing head 3 via the paint supply pipe 4, spread along the paint smoothing surface, and then from the discharge edge 3A. Sprayed as charged paint particles.

At this time, since the rotary atomizing head 3 is rotating at high speed, the paint particles tend to be blown away in the radial direction from the discharge edge 3A by centrifugal force. However, since the shaping air 6 is ejected from the shaping air ring 5, the charged paint particles are formed into a pattern so as to be sprayed forward by the shaping air 6, as shown by the solid line arrow 8 in FIG. The paint forms a spray pattern in the indicated direction, flies along the electrostatic field, and coats the object 7 to be coated. Note that since the pattern is formed by the shaping air 6, the object to be coated 7
The coating pattern on the surface is a circular pattern as shown in FIG.

[Problem to be solved by the invention]

However, when the paint particles are sprayed from the discharge edge of the rotary atomizing head 3, the particle size of the paint particles is non-uniform. As a result, a large centrifugal force acts on large diameter paint particles, that is, rough paint particles, and they tend to be blown far away, and a small centrifugal force acts on small diameter paint particles, that is, they tend to be blown far away. It won't happen.

In this way, when the rotary atomizing head 3 rotates at high speed, a difference occurs in the centrifugal force acting on the paint particles depending on the particle size of the paint particles. Therefore, as shown in FIGS. 8 and 9, when looking at the coating pattern of the object to be coated 7, fine paint particles 8 are coated at the center of the axis of the rotary atomizing head 3, and rough paint particles are coated at the peripheral portions. The particles 9 will be coated.

In this way, the central part where the fine paint particles 8 are coated is the first
The state is as shown in the enlarged view in Figure 0, and the film thickness that hides the base of the object to be coated 7 (hidden film thickness) becomes uniform, and the surface finish, which is called gloss, becomes good. On the other hand, the surrounding area to which the rough paint particles 9 have been applied is in a state as shown in the enlarged view in Fig. 11, which not only results in a masking film thickness (but also has a poor surface finish and makes it difficult to obtain a good paint film). Although shaping air 6 is ejected from the shaping air ring 5, the air pressure of the shaping air 6 has a small forward pattern forming effect on rough paint particles. This results in a coating pattern as shown in the figure.

In addition, in the electrostatic coating device, the paint particles fly along the electrostatic field and are applied to the object 7 to be coated, so they can be applied to the object 7 using only the attraction force due to the electrostatic field (electric lines of force). It just collides with the painted surface of 7.

For this reason, the collision speed of the paint particles is small (as shown in Figures 10 and 11, the paint particles are coated in a spherical shape, and in the case of particularly rough particles, gaps are created between the paint particles. There is a problem.

Furthermore, FIG. 12 shows an enlarged view of a state in which paint is sprayed as a liquid system 10 from the discharge edge 3A of the rotary atomizing head 3, and the liquid system 10 includes paint particles 10A, IOB,
...In the process of becoming ION and being atomized, it is atomized only by the centrifugal force of the rotating atomizing head 3. Therefore, the atomized paint particles 10A to ION from the liquid system 10
There is also the problem that particles of large and small sizes are mixed and the particle sizes are not uniform.

The present invention was developed in view of the problems of the prior art, and it not only provides a uniform coating film with good hiding properties, but also uses air pressure to apply impact force and make the particle size uniform. It is an object of the present invention to provide a bell-shaped rotary atomizing device.

[Means to solve the problem]

In order to achieve the above object, the feature of the configuration adopted by the present invention is that an air flow that flows in the axial direction from the discharge edge of the rotary atomizing head toward the object to be coated is formed on the outer peripheral surface side of the rotary atomizing head. This is due to the fact that the blades that generate the electricity are arranged in rows.

[Effect]

When the rotating atomizing head is rotated at high speed, a negative pressure area is generated on the front side of the rotating atomizing head due to the air bombing phenomenon.
As mentioned above, fine paint particles and coarse paint particles are drawn into the negative pressure area by the air pressure of the air flow generated from the blades arranged on the outer peripheral surface of the rotating atomizing head and flowing in the axial direction. mixed. Then, the mixed paint particles are applied by colliding with the object to be coated by air pressure. Furthermore, since the air flow generated from the blades pumps up the liquid system and promotes atomization, it is possible to make the particle size uniform.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to FIGS. 1 to 7. Note that the same components as those in the prior art described above are given the same reference numerals, and their explanations will be omitted.

First, FIGS. 1 to 5 show a first embodiment of the present invention.

First, in FIGS. 1 and 2, 11 is a bell-shaped rotating atomizing head used in this embodiment, 12 is an atomizing head main body forming the main body of the rotating atomizing head 11; outer peripheral surface 1
2A has a cylindrical or cup shape. On the other hand, on the inner circumferential surface side of the atomizing head main body 12, a rim 1 provided in the middle in the axial direction
The negative side in the axial direction across 2B becomes the mounting part 12C of the rotary shaft 2 having a female thread, and the other side in the axial direction becomes the paint smoothing surface 12D that expands in a morning glory shape, and the tip of the smoothing surface 12D becomes the discharge edge 12E. , and a hub member mounting groove 12F is formed in the middle of the smoothed surface 12D. The atomizing head main body 12 is connected to the rotating shaft 2 through the female thread of the mounting portion 12G.
In this attached state, the tip of the paint supply tube 4 extends to a position slightly protruding from the rim 12B. In addition, the discharge edge 12E
A 7-shaped groove may be formed on the inner circumferential side over the entire circumference.

Reference numeral 13 indicates a hub member formed into a substantially disk shape and fitted into the hub member attachment groove 12F of the atomizing head main body 12, and one side of the hub member 13 is supplied with paint from the paint supply pipe 4. The paint supply surface has a convex conical shape, and the other side is a flat surface 13B. 14° 14, . . . are paint outflow holes that are formed in large numbers around the entire circumference of the hub member 13, and each of the paint outflow holes 14 is in contact with the smoothed surface 12D, and is located at the front and back of the smoothed surface 12D. It is designed to communicate.

Note that the above-described configuration is not particularly different from that of the prior art.

However, 15,15. ... are eight blades provided on the outer circumferential surface 12A side of the atomizing head main body 12 at a position slightly recessed from the discharge edge 12E, and in the case of this embodiment, each blade 15 is arranged at a 45° angle They are arranged at intervals and at an angle of 45° to the axis of the atomizing head main body 12. When the rotary atomizing head 11 is rotated at high speed in the direction of arrow A in FIG. 3, an axial air flow 16 directed toward the object 7 is generated. Here, the blades 15 of this embodiment are constituted by rectangular bodies slightly protruding from the outer circumferential surface 12A of the atomizing head main body 12 and arranged obliquely and at equal intervals. The shape is such that it does not create a large resistance to air flow and can generate an air flow 16 with the required air pressure.

The bell-shaped rotary atomizing device according to this embodiment is constructed as described above, but the basic operation when constructed as an electrostatic coating device as shown in FIG. 3 using the rotary atomizing head 11 is similar to that of the prior art. Since there is nothing different from the original, the explanation will be omitted.

However, the rotary atomizing head 11 of this embodiment has eight blades 15 arranged in a row on the outer circumferential surface 12A side of the atomizing head main body 12 at a position slightly recessed from the discharge edge 12E. Head 1
An axial air flow 1 toward the workpiece 7 due to the high speed rotation of 1
It is configured to generate 6. On the other hand, the rotating atomizing head 11
When rotated at high speed, a third
As shown by the dotted line in the figure, a negative pressure region 17 is generated due to the air bombing phenomenon. Furthermore, what is the air bombing phenomenon?
When the rotary atomizing head 11 is rotated at high speed, the air in front of the discharge edge 12E is blown away in the radial direction by centrifugal force, resulting in a negative pressure phenomenon, and in order to compensate for this negative pressure phenomenon, air is moved toward the discharge edge 12H. This refers to a backflow phenomenon that replenishes air from the front.

In this state, when paint is sprayed from the discharge edge 12E of the atomizing head main body 12, this spray pattern 18 is formed by the blade 15.
Due to the pressure difference between the air pressure of the air flow 16 due to the air pumping phenomenon and the negative pressure region 17 due to the air bombing phenomenon, the discharge edge 12
The paint spray pattern 18 from E is rolled up in the negative pressure region 17, and this paint spray pattern 18 becomes a spiral as shown in FIG.

As a result, the paint particles sprayed from the rotary atomizing head 11 are
The fine particles and coarse particles are mixed by the entrainment action described above to form mixed paint particles. Then, the mixed paint particles fly along the electrostatic field and are applied to the object 7 to be coated. Therefore, in this embodiment, as shown in FIG. 3 or 4, the object 7 is coated with a mixture of fine particles 19 and coarse particles 20, and the entire surface of the object 7 is coated. It is possible to make the thickness of the hiding film uniform over the entire area, and also to improve the surface finish.

Furthermore, since the blades 15 can generate an axial air flow 16 with the required air pressure, this air pressure can be used to increase the flight speed of the paint particles, thereby increasing the speed of the paint particles toward the object 7. Collision speed can be increased. As a result, the paint particles are applied to the object to be coated 7 in a manner that they are struck, and even the rough paint particles 20 are applied in a flattened state, as shown in an enlarged view in FIG. This can be prevented and a high-quality coating surface can be obtained.

Furthermore, although FIG. 5 shows an enlarged view of the state in which paint is sprayed as a liquid system 21 from the atomizing head main body 12, in this embodiment, an axial air flow 16 is generated by the blades 15. Therefore, this air flow 16 pumps up the liquid system 21 to promote atomization. As a result, the centrifugal force of the atomizing head main body 12 and the air flow 16 cooperate, and the liquid system 21
Paint particles 21A, 21B, ... 21 atomized from
N has a uniform particle size and can improve coating quality.

Furthermore, in the prior art, if the shaping air 6 is not ejected from the shaping air nozzle 5, the pattern when the paint is applied to the object 7 will be donut-shaped (ring-shaped) and a cavity will be formed in the center. However, in this embodiment, a coating pattern without a cavity in the center can be obtained without using shaping air.

Next, FIGS. 6 and 7 show a second embodiment of the present invention. Note that the same components as those in the first embodiment are indicated by a dash (
') and the explanation thereof will be omitted.

However, in the atomizing head main body 12' according to this embodiment,
7. The blades 15'15', . . . provided on the outer peripheral surface side.
The reason is that 48 pieces are arranged in a row at 5° intervals and at an angle of 45° with respect to the axis.

Although the present embodiment is configured as described above, its operation and effect are the same as those of the first embodiment.

Here, the above-mentioned 1. When the rotary atomizing head 11,11' according to the second embodiment and the rotary atomizing head 3 of the prior art without blades are rotated at high speed, the flow velocity of the air flow at a position 1 cm away from the discharge edge ( The results of measuring m/5ec) are shown in the table below.

Table Comparison of flow velocity As can be seen from the above table, when the rotary atomizing head 3 according to the prior art was rotated at 45,000 rpm, the flow rate was 6 m/min.
The one in which only an air flow rate of sec was obtained was the first one. In the rotary atomizing head 11 and 11' according to the second embodiment, each
2m/sec.

An air flow rate of 23 m/sec can be obtained, which promotes mixing of paint particles and provides a coating film with uniform thickness and good finish. The same holds true when rotating at 60,000 rpm.

Note that the shape of the blades and the number of blades arranged in a row are not limited to those of the embodiments, and blades of various shapes and numbers can be used. Axial flow vanes having other shapes may be used as long as they can generate an axial air flow.

Further, in each embodiment, the blades are arranged in a row at a position slightly recessed from the discharge edge of the atomizing head main body, but the blades may be arranged in a row adjacent to the discharge edge, or the blades may be arranged in a row adjacent to the discharge edge. They may be arranged in a row at an intermediate position in the axial direction of the head body.

On the other hand, the main body of the atomizing head may be cylindrical or cup-shaped (it also includes those with a conical or hemispherical external shape).

Furthermore, in the embodiment, the rotating shaft is fixed to the attachment part of the atomizing head main body, and the paint supply pipe is inserted into the rotating shaft. However, the rotating shaft is attached to the hub member and is separated from the rotating shaft. Of course, the present invention can also be applied to a bell-shaped rotary atomizing head in which the paint supply pipe disposed on the hub member faces the paint supply surface of the hub member.

〔Effect of the invention〕

The bell-shaped rotary atomizer according to the present invention is as described in detail above (in which vanes are arranged on the outer peripheral surface side of the rotary atomizing head to generate an air flow that flows in the axial direction toward the object to be coated). Because of this structure, it is possible to obtain a coating film in which paint particles of various sizes are mixed in the coating pattern of the object to be coated, resulting in a coating film with a uniform thickness and good finish. In addition, since the air flow can be used to impart collision speed to paint particles, individual paint particles can be deformed into flat shapes and applied, which prevents the formation of gaps between particles. On the other hand, the liquid system sprayed from the discharge edge is easily torn apart by the air flow, and combined with the centrifugal force caused by the high speed rotation of the rotating atomizing head, it is possible to obtain paint particles with a uniform particle size.Furthermore, Since the paint particles are mixed in front of the rotary atomizing head, there are no cavities in the coating pattern, resulting in high-quality coating.

[Brief explanation of drawings]

1 to 5 relate to a first embodiment of a bell-shaped rotary atomizing device according to the present invention, FIG. 1 is a half-sectional view showing the overall structure of a rotary atomizing head according to the present embodiment, and FIG. Fig. 1 is a left side view, Fig. 3 is a block diagram of the electrostatic coating device using the rotating atomizing head shown in Fig. 1, and Fig. 4 is a diagram showing the state in which paint particles are applied to the object to be coated. Figure 5 is an enlarged view of part a in Figure 3, Figure 5 is an enlarged view of part b in Figure 3 showing the spray state of the liquid system from the discharge edge, and Figure 6 is an enlarged view of part b in Figure 3.
7 and 7 relate to a second embodiment of the bell-shaped rotary atomizing device according to the present invention, FIG. 6 is a half-sectional view showing the overall structure of the rotary atomizing head according to the present embodiment, and FIG. The left side view of the figure, Figures 18 to 11 relate to the prior art, Figure 8 is a configuration diagram of an electrostatic coating device using a rotary atomizing head according to the prior art, and Figure 9 is in Figure 8. Fig. 10 is an enlarged view of section C in Fig. 8 showing the state in which fine paint particles are applied to the object to be coated, and Fig. 11 is a plan view showing the coating pattern on the object to be coated. FIG. 12 is an enlarged view of section d in FIG. 8 showing a state in which rough paint particles are applied, and FIG. 12 is an enlarged view of section e in FIG. 8 showing a state in which the liquid system is sprayed from the discharge edge. 11.11'...Rotating atomizing head, 12.12'...Atomizing head body, 12A, 12A'...Outer peripheral surface, 12C9
120'...Mounting part, 12D, 21D'...Paint smoothing surface, 13.13'...Hub member, 14.14'
...Paint outflow hole, 15.15'...Blade.

Claims (1)

[Claims] Equipped with a bell-shaped rotary atomizing head having a cylindrical or cup-like outer peripheral surface and a paint smoothing surface formed on the inner peripheral surface, the rotary atomizing head is supplied with the rotary atomizing head rotated at high speed. In a bell-shaped rotary spraying device configured to spray paint from the discharge edge of the tip onto the object to be coated in front through the paint smoothing surface, the discharge end is disposed on the outer peripheral surface side of the rotary atomizing head. A bell-shaped rotary spraying device characterized by a row of vanes that generate an air flow that flows in the axial direction from the edge toward the object to be coated.