JPS60251947A - Rotary atomization head for electrostatic painting - Google Patents

Abstract

PURPOSE:To well divide even a high viscosity paint into fine particles, in a cup shaped rotary atomization head, by providing a gentle oblique surface and a steep oblique surface from the supply side of the inner peripheral surface of said atomization head in a continuous state and providing a large number of small projections at a specific angle in the edge peripheral direction of the most forward end of said atomization head. CONSTITUTION:A rotary shaft is driven in such a state that a high potential electrostatic field is formed between an article to be painted and a rotary atomization head to supply a liquid paint. The paint spreading over the entire inner peripheral surface of the rotary atomization head 1 and sprayed to a gentle oblique surface 3 from a supply aperture by centrifugal force is spread to the peripheral direction while flowed to the leading end side at a low speed to be formed into a uniform thin film and when said paint film reaches a steep oblique surface 4, it is flowed to the leading end side at a high speed by a fanwise acute angle taper and reaches the leading end edge 2 while the thickness thereof becomes further thin. Small triangular projections are arranged to the leading end edge over the entire periphery thereof at equal pitches and the paint is blocked by barrier wall surfaces 6 obliquely opposed to the steep oblique surface 4 and formed into fine threads from the groove between said barrier wall surfaces 6 to be discharged radially.

Description

Detailed Description of the Invention The present invention is attached to a high-speed rotating shaft, and the liquid paint supplied to the inner peripheral edge is made into a thin film by centrifugal force and sent to the leading edge. Regarding the cup-shaped rotary atomizer head for electrostatic coating, which atomizes particles and releases them by the action of an electrostatic field formed by the electrostatic field, and applies the coating to the object to be coated by electrostatic attraction, it is particularly important to avoid air bubbles in the particles. This invention relates to a rotating atomizing head that can uniformly atomize particles without enveloping them.

The cup-shaped rotating atomizing head has a gently sloping inner circumferential surface that gradually expands in diameter toward the sharp edge, and uses this slope to form a thin film of liquid paint and send air to the tip. However, if the liquid paint is simply a ring-shaped sharp edge, the liquid paint will be released into the air as a film, which will break into small pieces and become granular due to surface tension, causing Not only are particles of various sizes generated depending on the size of the film pieces torn, but also there is a drawback that when the film pieces become granular, they enclose air, which adheres to the object to be coated and form pinholes. For this reason, JP-A-5G-
As described in 7C1g52, a large number of small triangular protrusions are arranged in the circumferential direction of the tip edge, each small protrusion is bent inward to form a barrier, and the tip is formed along the inner peripheral surface. The film-like liquid paint that reaches the edges is blocked by small protrusions and guided into the grooves between them, and the liquid paint is made into thin threads and released into the air, making the particle size uniform and preventing air from being trapped. However, with high viscosity paint, the paint film that reaches the tip edge becomes thicker and is ejected from the grooves between the protrusions in the form of relatively thick threads. This has the disadvantage that it tends to cause envelopment and the painted surface becomes rough.

It is an object of the present invention to provide a rotary atomizing head for electrostatic coating which can eliminate such drawbacks and atomize even highly viscous paints.

Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings.

The rotary atomizing head 1 of this embodiment has a cup shape with one end of a cylinder open, and the inner circumferential surface near the open end has a gentle taper that gradually increases in diameter toward the tip edge 2. The surface 3 is connected to a steeply sloped surface 4 which is tapered at a steeper angle than the gently sloped surface 3, and the tip edge 2 has small triangular protrusions 5 arranged at equal pitches over the entire circumference. A barrier surface 6 is formed on the inner circumferential surface of each small protrusion 5 so as to diagonally face the steeply sloped surface 4 .

This rotary atomizing head 1 is fitted externally into a mounting hole 7 in which a hollow hole 8 is formed from the back and is fixed integrally, and is fitted onto the tip of a rotating shaft 11 driven at high speed by a prime mover such as an air motor. The inner peripheral surface 9 of the hollow hole 8 of the mounting body 7 is tapered to widen toward the tip, and the beginning of the gently sloped surface 3 of the rotating atomizing head 1 is attached to the tip of the inner peripheral surface 9 of the hollow hole 8 of the mounting body 7. Several supply holes 10 are provided through the cutout 8, and a paint supply pipe 13 is inserted into the hollow hole 8 from the back side thereof.

Next, the operation of this embodiment will be explained. The rotating atomizing head 1 is directed toward the object to be coated, and is connected to a high voltage generator (not shown) via the rotating shaft 11 to form a high potential electrostatic field between the rotating shaft 11 and the object to be coated. When the liquid paint is dripped from the paint supply pipe 13 onto the inner circumferential surface 9 of the attaching body 7 while rotating the rotary atomizing head 1 together with the attaching body 7 at a high speed by the drive of the , the dropped paint spreads over the entire circumference of the inner circumferential surface 9 due to centrifugal force and flows toward the tip side from the supply hole 10 to the rotating atomizing head 1.
is sprayed onto the gently sloped surface 3. Since this gently inclined surface 3 has a gentle taper that widens towards the end, the supply hole 1
The paint sprayed from zero spreads in the circumferential direction while flowing toward the tip at low speed due to centrifugal force, forming a uniform thin film.
When reaching the steeply sloped surface 4, this surface is tapered at a steep angle and widens at the tip, so the flow flows toward the tip at a higher velocity than on the gently sloped surface 3, and as a result, the film thickness becomes even thinner and the flow reaches the tip. It reaches the edge 2, is blocked by the barrier surface 6 of the small protrusion 5, becomes a thin thread from the groove between them, is emitted radially by centrifugal force and electrostatic attraction, and becomes fine particles due to surface tension, and is affected by the electrostatic field. It is attracted to the object to be coated and coated.

As specifically explained in the above embodiments, the rotary atomizing head for electrostatic coating of the present invention has a cup shape with a tapered inner peripheral surface whose diameter gradually increases toward the tip edge,
In a rotary atomizing head for electrostatic coating, the liquid paint supplied to the inner peripheral surface becomes a thin film due to centrifugal force, reaches the tip edge, and is discharged from the tip edge toward the object to be coated, The inner peripheral surface has a gently sloped surface on the liquid paint supply side and a steeply sloped surface reaching the tip edge, and a large number of small protrusions are arranged at regular intervals in the circumferential direction of the tip edge. The gist is that a barrier surface is formed on the inner circumferential surface of the small protrusion, facing the steeply inclined surface at a certain angle, and the paint supplied to the inner circumferential surface is applied to the gently inclined surface at a low speed toward the tip side. As it flows, it spreads in the circumferential direction to form a thin film with a uniform thickness, and then the flow velocity is increased on the steeply sloped surface, so even if the viscosity of the paint is high, the film becomes thinner, and this spreads over the inner peripheral surface of the small protrusion. The threads of paint released radially from the grooves between the small protrusions become extremely thin, as they are blocked by the barrier surface and branched.
As a result, the particle size of the paint granulated due to surface tension is small, and since small-sized particles are difficult to envelop air, it is possible to form a smooth coating film.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the tip thereof, and FIG. 3 is an enlarged perspective view of the same. Rotating atomizing head 2: Tip edge 3: Gently inclined surface 4: Steeply inclined surface 5: Small protrusion 6: Barrier surface 10: Supply hole 13: Paint supply pipe Applicant: Asahi Okuma Sangyo Co., Ltd. Agent Patent attorney Noguchi Hiroshi - 1μm January

Claims (1)

[Claims] It has a cup shape with a tapered inner circumferential surface that gradually expands in diameter toward the tip edge, and the liquid paint supplied to the inner circumferential surface becomes a thin film due to centrifugal force and reaches the tip edge,
In the rotary atomizing head for electrostatic coating, the atomizer head is configured to discharge water from the tip edge toward the object to be coated, and the inner circumferential surface connects a gently sloped surface on the liquid paint supply side with a steeply sloped surface that reaches the tip edge. A large number of small protrusions are arranged at regular intervals in the circumferential direction of the tip edge, and a barrier surface is formed on the inner circumferential surface of the small protrusions, facing the steeply inclined surface at a constant angle. Characteristic rotating atomizer head for electrostatic painting