JPH0233425B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an airless spray nozzle that pressurizes liquid paint to high pressure and sprays it at high speed through a small jet port to atomize it by friction with air. The present invention relates to a nozzle in which liquid is atomized well over the entire spray pattern.

In airless spray painting, in order to efficiently form a uniform coating film, a lip-shaped flat jet is formed at the tip of the nozzle tip to spray liquid paint in a thin film, which is then atomized by friction with the air. Generally, the ejection port is spread out in a fan shape to reach the object to be coated, but both longitudinal ends of the flat ejection port are close to the inner wall surface and the ejection speed is lower than that at the center due to the influence of the boundary layer. Since the particle size is small, atomization is insufficient, and side streams with coarse particles called tails are generated on both sides of the main stream in the center, which is well atomized, resulting in a defective surface to be coated. For this reason, a method has been proposed in which a small-diameter orifice is installed at the rear of the nozzle tip to restrict the flow of paint, thereby making the flow of paint in the nozzle tip turbulent and making the flow velocity uniform. Because it was formed concentrically with the orifice, the paint passing through the center of the orifice would go straight to the center of the orifice, making it impossible to completely eliminate the tendency for the flow velocity at the center of the orifice to be higher than at both ends. However, with high viscosity paints, the occurrence of tails could not be avoided unless the injection pressure was significantly increased.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such drawbacks and provide a nozzle that can eliminate the tail of even highly viscous paint at a relatively low pressure.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 show a first embodiment of the present invention, in which a nozzle tip 1 is made of a hard material such as cemented carbide or ceramic, and has a flange 2 formed on the outer periphery of the rear end, and a flange 2 at the center of the rear surface. An elongated bell-shaped guide hole 3 is formed near the tip, and by forming a V-shaped groove 4 on the tip surface, a flat lip-shaped jet is formed as shown in Fig. 2. An outlet 5 is formed, and the rear end surface is a planar wall surface 20. The aperture plate 6 is also made of a hard material such as cemented carbide, and has a disk shape with the same diameter as the collar 2 of the nozzle tip 1, and as shown in FIG. A ring groove 7, which is slightly smaller than the diameter of the opening, is recessed on one side, and three orifices 8 penetrating to the other side are formed at equal angular intervals in the center of the groove bottom, and these three orifices 8
The total area of the nozzle tip 1 is slightly larger than the area of the spout 4 of the nozzle tip 1.The nozzle tip 1 is fitted into the small diameter hole 10 of the holder 9, the flange 2 is abutted against the stepped surface 12, and then the aperture plate 6 is fitted. and a synthetic resin bush 13 having a center hole 14, and a large diameter hole 1.
The nozzle tip 1 and the aperture plate 6 are inserted into the holder 9 through the bush 13 by screwing the hub nut 19, which is fitted into the gun body 16 and engaged with the flange 15 protruding from the outer periphery of the rear end of the holder 9, into the gun body 16. The orifice 8 is fixed to the wall 2 of the rear end of the nozzle 1.
It is oriented towards 0.

Then, the liquid paint pressurized to high pressure by the paint pump is released into the gun body 16 by opening the on-off valve 18.
is supplied from the pressure passage 17 into the center hole 14 of the bush 13, and passes through the three orifices 8 to the throttle plate 6.
into the ring groove 7 on the front surface of the ring groove 7.
It flows into the guide hole 3 through the gap between the inner circumferential wall of the nozzle tip 1 and the rear end surface of the nozzle tip 1, and is ejected from the jet port 5 as a thin film, atomized by friction with the air, and spread in a fan shape to form a thin film to be coated. In this embodiment, the liquid paint that has passed through the three orifices 8 reaches the wall surface 20 of the rear end surface of the nozzle tip 1.
The liquid paint in the guide hole 3 changes direction and collides with the inner circumferential wall of the ring groove 7, and flows into the guide hole 3 through the narrow annular gap between the nozzle tip 1 and the end surface of the nozzle tip 1. becomes a completely turbulent flow, and the velocity component toward the jet nozzle 5 is made uniform, and the viscosity is actually reduced due to severe stirring, so the velocity of the liquid paint jetted from the jet nozzle 5 is different between the center and both ends. The liquid paint ejected from both ends is also atomized in the same way as the center part, and tails are prevented from forming.

In the nozzle according to the second embodiment of the present invention shown in FIGS. 4 and 5, a circular concave surface 7a is formed on the front surface of the aperture plate 6a, and three orifices 8a are formed at equal angular intervals on the periphery of the concave surface 7a. Other than that, the structure is the same as that of the first embodiment, and the liquid paint that has passed through the three orifices 8a is transferred to the wall surface 20 of the rear end surface of the nozzle tip 1.
The flow changes direction and flows into the guide hole 3 from the concave surface 7a as a turbulent flow, and as in the first embodiment, it is ejected into the air at approximately the same velocity throughout the ejection port 5. , uniformly atomized.

As specifically explained in the above embodiments, the airless spray nozzle of the present invention sprays pressurized liquid paint from a flat jet nozzle and atomizes it by friction with air. In the airless spray nozzle, a constriction plate having a plurality of orifices formed around the center of the liquid coating passage is interposed near the jetting opening of the liquid paint passage, and a throttle plate having a plurality of orifices formed around the center of the liquid paint passage is provided, and immediately before the orifice on the jetting opening side. The main idea is to form a wall surface against which the liquid paint collides, and the liquid paint that has passed through the orifice does not go straight to the spout, as in the case where one orifice is formed at the center of the pressure passage. After passing through multiple orifices, it violently collides with the wall surface and reaches the jet port while being mixed in a complicated manner, creating a turbulent flow and making the jet speed uniform.Furthermore, the stirring reduces the actual viscosity and flattens it. The liquid paint ejected from the spout is well atomized over the entire width, and tails are prevented from forming.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the first embodiment of the present invention, FIG. 2 is an enlarged front view of the nozzle tip, FIG. 3 is a partially cutaway perspective view of the aperture plate, and FIG. 4 is a sectional view of the second embodiment.
FIG. 5 is a partially cutaway perspective view of the aperture plate. 1: Nozzle tip, 3: Guidance hole, 5: Spout port,
6, 6a: Aperture plate, 8, 8a: Orifice.

Claims (1)

[Claims] 1 Pressurized liquid paint is sprayed through a flat-shaped spout 5
In an air spray nozzle that sprays liquid paint from the air and atomizes it by friction with air, near the spout 5 of the liquid paint pressure feeding passages 3 and 14,
Throttle plates 6, 6a having a plurality of orifices 8, 8a are interposed around the centers of the pressure feeding passages 3, 14, and the liquid paint collides with the orifices 8, 8a immediately before the spout 5 side. An air spray nozzle characterized in that a wall surface 20 is formed.