JPS63171658A - Rotary atomizing head for electrostatic painting - Google Patents

Abstract

PURPOSE:To atomize a paint for electrostatic painting in the form of fine particles having uniform sizes, by inclining the side walls on the rear side of guide grooves in the rotating direction thereof more steeply than the inclination of the side walls on the front side of the rotating direction. CONSTITUTION:A rotary atomizing head 7 is connected to a high-voltage generator to form an electrostatic field between side head and a material to be coated. The rotary atomizing head 7 is rotated at a high speed. The liquid paint dropped from a paint supplying pipe 14 into an inside chamber 4 is supplied from a supply port 5 by centrifugal force to the inside peripheral face of the rotary atomizing head 7 from which the paint spreads in the form of a thin film and arrives at a steeply inclined part 10. The centrifugal force in said part is increased and accelerated by which the paint is finely divided in flow along the many guide grooves 12 and is released as fine liquid yarn from the apertures of the respective guide grooves 12. The released liquid is pulverized by the centrifugal force and electrostatic effect and is deposited on the material to be coated. The side walls 12a of the rear side of the respective guide grooves 12 in the rotating direction thereof are more steeply inclined than the inclination of the side walls 12b on the rear side of the rotating direction in this constitution. The flow of the paint over the side walls 12a is prevented when the paint divided in flow in the respective guide grooves 12 is pressed to the side walls by the centrifugal force. The release of the paint from a front end edge 11 in the state of the thin film is thus averted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotary atomizing head for electrostatic coating, which discharges a liquid paint in the form of a mist from its tip edge under the action of centrifugal force and an electrostatic field.

Problems to be Solved by the Prior Art and the Invention Conventionally, such rotary atomizing heads for electrostatic coating have a cup-shaped or dish-shaped inner circumferential surface that gradually increases in diameter toward the tip edge, and A large number of guiding grooves are formed around the entire circumference near the leading edge of the peripheral surface, and the liquid paint supplied to the inner peripheral surface of this rotary atomizing head, which rotates at high speed, forms a thin film due to centrifugal force. The liquid flows to the tip edge of the inner circumferential surface, and by dividing into each guide groove formed on the inner circumferential surface of the tip edge, the liquid flows as silky liquid threads from the openings of each guide groove around the entire circumference of the tip edge. The paint is discharged and atomized by the action of centrifugal force and electrostatic field, and the liquid paint is discharged in the form of threads of uniform size through the many guide grooves on the inner periphery of the tip of the atomizing head. It has the effect of being atomized as fine particles and forming a smooth coating film.

When the amount of liquid paint supplied is large, or when the rotational speed of the atomizing head is low, the paint diverted to each guide groove may run over the rear side wall of the guide groove in the direction of rotation.
The paint is ejected from the entire circumference of the tip in a thin film, and the size of the nized paint particles becomes uneven, resulting in a rough painted surface, or the paint particles envelop air. It has the disadvantage that pinholes are created on the painted surface when it is applied.

Means for Solving the Problems As a means for solving the above-mentioned problems, the present invention has a configuration in which the slope of the side wall on the rear side in the direction of rotation of the guide groove is made steeper than the slope of the side wall on the front side in the direction of rotation. .

Functions and Effects of the Invention Since the rotary atomizing head for electrostatic coating of the present invention has the above structure,
Even when the amount of liquid paint supplied is large or the rotation speed of the atomizing head is low, the paint that has been diverted into each guide groove is prevented from overcoming the rear side wall in the direction of rotation of the guide groove, and each guide at the tip edge The paint is ejected as liquid threads only from the tips of the grooves, and is thereby atomized into fine particles of uniform size.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a rotating shaft that is driven to rotate at high speed by a prime mover (not shown) such as an air motor built into the gun body, and at its tip there is a deep-spreading annular inner space 4 that opens at the rear. A mounting body 3 having A cup-shaped rotating atomizing head 7 on the diameter part 6
are tightly fitted and fixed together.

This rotary atomizing head 7 has an insertion hole 8 formed in the center of the rear surface, and a gently sloped part 9 whose diameter expands at a gentle angle toward the front on the inner peripheral surface, and from the front edge of this gently sloped part 9. A narrow, steeply sloped part 10 whose diameter expands at a steep angle is connected to the tip edge 11, and this steeply sloped part 10 has a guide groove 12 with a triangular cross section that is perpendicular to the tip edge 11 around the periphery. A large number of guide grooves 12 are formed continuously in the direction, and each guide groove 12 is formed in a cross section perpendicular to the center line of the rotating atomizing head 7 shown enlarged in FIG. The extension of the line indicating the rear side wall 12a in the rotation direction intersects the center line of the rotary atomizing head 7, and is steeper than the opposing side wall 12b on the front side in the rotation direction.

The tip of a paint supply pipe 14 connected to a paint supply device (not shown) is inserted into the interior space 4 of the mounting body 3 through an insertion hole 8 on the rear surface of the rotary atomizing head 7.

In this embodiment, the rotary atomizing head 7 is connected to a high voltage generator (not shown) via the rotary shaft 1 to form a high potential electrostatic field between it and the object to be coated. When the liquid paint is dripped into the inner space 4 of the mounting body 3 from the paint supply pipe 14 while rotating the rotary atomizing head 7 at high speed, the liquid paint is turned into a rotating mist from the supply hole 5 of the mounting body 3 due to centrifugal force. Kato 7
The centrifugal force spreads the film along the gently sloped part 9 and guides it forward, and when it reaches the steeply sloped part 10, the centrifugal force increases and accelerates, forming a large number of guide grooves. 12 and reaches the tip edge 11, and due to centrifugal force, it is released into the air from the opening of each guide groove 12 as a thread of drying fluid, and due to the action of centrifugal force and electrostatic field, it becomes atomized and coated. The paint is applied to the object to be painted, and the paint separated into each guide groove 12 is applied to the side wall 12 on the rear side in the direction of rotation of the rotary atomizing head 7 due to centrifugal force.
However, in this embodiment, since this side wall 12a is steep, the paint pressed against the side wall 12a by centrifugal force is prevented from getting over this side wall 12a, and this prevents the rotation. This prevents paint from being discharged in a thin film form from the entire circumference of the tip edge 11 of the atomizing head 7.

As shown in FIG. 2, the reason why the front side wall 12b of each guide groove 12 in the direction of rotation of the rotary atomizing head 7 is made gentle is that it is not steeply sloped like the rear side wall 12a. This is because, when the groove width is made constant, the cutting edge of the cutter for forming the guide groove 12 becomes thinner and is likely to be damaged.

Further, in this embodiment, the cross-sectional shape of each guide groove 12 is triangular, but in addition, as shown in FIGS. 3(a) and (b), the rotating atomizing head 7 is The side wall on the rear side in the rotation direction may have a trapezoidal or substantially U-shaped cross section with a steeper inclination angle.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of the tip thereof, and FIG. 3 is a sectional view of a modified example of the guide groove. 7: Rotating atomization head 11: Tip edge 12: Guide groove 12a:
Side wall on the rear side in the rotation direction 12b = Side wall on the front side in the rotation direction

Claims (1)

[Claims] The inner circumferential surface has a cup-shaped or dish-shaped shape whose diameter gradually increases toward the tip edge, and a large number of guide grooves are formed radially around the entire circumference on the tip edge of the inner circumferential surface, and the liquid is supplied to the inner circumferential surface. The paint is made into a thin film by centrifugal force, guided to the tip edge, and diverted to the guide grooves, whereby the paint is drawn from the tips of each guide groove by the action of the centrifugal force and the electrostatic field formed between it and the object to be coated. In a rotary atomizing head for electrostatic coating that discharges liquid as thin threads and atomizes the liquid, the slope of the side wall on the rear side in the direction of rotation of the guide groove is made steeper than the slope of the side wall on the front side in the direction of rotation. Characteristic rotating atomizer head for electrostatic painting