JPH034950A - Airless nozzle - Google Patents

Abstract

PURPOSE:To stably form an extremely thin liquid film and to stabilize the size, particle size distribution and spray width of fine particles sprayed under low pressure by forming a jet orifice of a pressure passage for paint of plain plates opposed to the paint passage. CONSTITUTION:When the valve provided to the leading end of a spray gun is opened, paint pressurized to 50kg/cm<2> or less expands the gap between nozzle plates 2, 2' forcibly to open a jet orifice and is injected in an extremely thin liquid film state. The part held between both nozzle plates 2, 2' can be regarded as a part of an extremely thin liquid film and a uniform liquid film becoming the matrix of breakup optimum to fine pulverization can be stably formed under low pressure. Further, the liquid films at both ends of the jet orifice held between both nozzle plates 2, 2' become extremely thin and absorbed at the central part thereof by surface tension and, therefore, no tail phenomenon is generated. When jet pressure is raised, the area of the jet orifice is expanded and a jet amount can be increased.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an airless coating method in which highly pressurized liquid paint is jetted into the air from a spout at high speed and atomized by the frictional force with the air. Regarding nozzles used for.

[Problems to be solved by conventional technology] In airless spray painting, in order to efficiently form a uniform coating film, a pea-sized nozzle tip is sintered and formed from a highly hard material such as WC (tungsten carbide). 60kg/ej~80
kg/c! It is common practice to spray a thin film of slightly pressurized liquid paint, which is atomized by friction with the air and then spread out in a fan shape to reach the object to be painted.
Both ends in the longitudinal direction of the elongated small jet nozzle are close to the low flow velocity part of the wall surface of the tubular paint passage S in the nozzle tip, and the jetting velocity is lower than the central part, so atomization is insufficient.
This method has the disadvantage that side streams with coarse particles called tails are formed on both sides of the main stream in the central part, which is well atomized, and a defective coating film is formed on the surface to be coated. In addition, since airless spray relies on an atomization mechanism in which a thin liquid film is split by air resistance, the shape of the liquid film when spraying liquid paint into a thin film is the basis for splitting into atomization. The size and particle size distribution of the generated fine particles are determined by the state of the thin liquid film. In conventional airless nozzles, the shape, width, thickness, and ejection speed of the liquid film are not stable due to the effects of turbulence in the flow of the paint passage inside the nozzle tip, turbulence in the air flow around the nozzle tip, etc., and the particle size distribution is unstable. Since it is not possible to obtain a uniform particle size due to the scattering of particles, there has been a need to improve the yield in terms of coating quality control of the surface to be coated.

Furthermore, in order to compensate for the above-mentioned drawbacks, a method has been proposed in which multiple small-diameter orifices are installed behind the nozzle tip to restrict the flow of paint, thereby making the flow of paint within the nozzle tip turbulent and making the flow velocity uniform. However, it has not been possible to maintain the thin liquid film, which is the matrix for fragmentation into fine particles, in an optimal state.

Furthermore, there is a method of accelerating atomization by applying high pressure of 100 kg/ej or more to the paint to increase the jetting speed, but this method deteriorates the durability of nozzles, pressurizing devices, etc., increases manufacturing costs, and increases the flight speed of fine particles. There is a problem with deterioration of coating efficiency due to the high speed of coating, which causes it to bounce off the surface to be coated, and stable atomization at low pressure has been desired.

In addition, with conventional airless nozzles, it was not possible to control the amount of ejection and the spray pattern, so F't in manufacturing
For JJ m, it was necessary to prepare nozzles with various spray volumes and spray pattern widths to accommodate various applications, and the cost was high due to the need to secure and process specialized materials suitable for each product.

As for the problem on the user side, since it is not possible to control the spray amount and spray pattern width of conventional airless nozzles, when repeating coating on an airless automatic painting line, the spray amount and spray pattern width deviate from the specified values due to nozzle wear. If
Although the nozzle itself was in usable condition, it had to be replaced with a new one. Furthermore, even when replacing a nozzle with a new one of the same size, it is not possible to absorb fluctuations in the spray amount and spray pattern width due to variations in nozzle quality during manufacturing, and there is a problem in that the coating conditions must be adjusted each time. There has been a strong demand in the industrial coating field to be able to control the jet volume and jet pattern width of airless nozzles.

[Problem to be solved by the invention]

The present invention eliminates these drawbacks, so that 50 kg/c
When spraying liquid paint pressurized to a low pressure under breath in a thin film form from an airless nozzle, it is possible to stably generate an ultra-thin liquid film that serves as a base for atomization. This was done to stabilize the size, particle size distribution, and spray width, as well as to enable control of the spray amount and spray pattern, which was impossible with conventional airless nozzles.

[Means to solve the problem]

The present invention provides an airless spray nozzle in which pressurized liquid paint is injected from a flat-shaped jet nozzle and is atomized by friction with air. The structure is formed by overlapping flat plates facing each other along the .

As a specific means for this, a clamping plate may be attached to the opposing flat plates, and the clamping state may be controlled by the clamping force, and the tension of the opposing flat plates may be adjusted by the clamping plate. It's okay. Furthermore, as a countermeasure against wear of the opposing flat plates, the liquid-contacted portions may be subjected to a surface hardening treatment with high hardness.

[Action of the invention and its effects]

EMBODIMENT OF THE INVENTION Hereinafter, an embodiment in which the present invention is applied to a coating nozzle will be described based on the accompanying drawings.

〔Example〕

Fig. 1 is a front view of the nozzle of the present invention as seen from the spout side, Fig. 2 is a side view thereof, and Fig. 3 is a bottom view. FIG. 4 shows a longitudinal section taken along the line (A-A') in FIG. 1, and FIG. 5 shows a cross-sectional view taken along the line (B-B') in FIG. The nozzle of the present invention has a cylindrical flange-shaped nozzle body (1
), the nozzle plates (2) (2') made of elastic material face each other and overlap each other, and the sides of the nozzle plate (2) (2'), which are made of elastic material, are overlapped to face each other so as to surround the tip of the funnel. The root part is joined and sealed, and the part where the nozzle plates (2) and (2') corresponding to the wide mouth part of the funnel face each other and overlap forms the spout (0). Further supplies are provided. The spraying of paint is controlled by opening and closing the valve at the tip of the spray gun.

When the valve at the tip of the spray gun is closed, the jet nozzle (0) is closed by the tension of the nozzle plate (2) (2') and the clamping force of the clamping plate (3).

Figures 6 and 7 show when the valve at the tip of the spray gun is open.
As shown in the figure, a pressurized butterfly nut (5) is provided at L, 50 kg/- or less. Further, behind the plunge portion of the nozzle body, there is a packing (7) that presses against and seals the tip valve of a spray gun, etc., and a retaining nut (6) that screws the nozzle body into the tip valve. A spray gun, a paint supply path, a paint pressurizing device, etc. (not shown) are connected to the rear of the gasket to constitute a spray system.

Now, the paint pressurized by the paint pressurizing device passes through the paint supply path, and can be regarded as a part of the valve membrane at the tip of the spray gun, and is uniformly distributed as a matrix for fragmentation that is ideal for atomization. It becomes possible to stably generate a liquid film under low pressure. Moreover, the liquid film at both ends of the jet nozzle sandwiched between the two nozzle plates becomes extremely thin and is absorbed into the center by surface tension, so that no tail phenomenon occurs.

Furthermore, by increasing the ejection pressure, the area of the opening can be expanded and the amount of ejection can be increased. In other words, by controlling the pressure applied to the paint, the amount of ejection can be controlled.

Further, at the same pressure, it is possible to finely adjust the length of the opening of the jet outlet by adjusting the clamping force of the clamping plate using the clamping force adjustment screw. In other words, if the clamping force of the clamping plate is large, the opening length of the jet nozzle becomes short, and the spray pattern width is also narrow. Since film-like ejection under low pressure is possible and the liquid film state grows large, a coating method that does not cause atomization called film coating, which is used for applying resist liquid to PC boards, is also possible.

Furthermore, even if there is foreign matter in the material and the nozzle is clogged, applying force from both sides of the nozzle plate toward the center will open the discharge port and remove the foreign matter. Therefore, foreign matter can be easily discharged.

Furthermore, the nozzle nozzle itself has a valve function and is automatically closed when spraying is stopped, so the paint inside the nozzle will not solidify even if left for a long time.

Further, even when the closing performance of the tip valve of the spray gun is deteriorated and the spray gun is not sharp, there is an effect of preventing the spray gun from becoming uneven.

Furthermore, if the width of the hole positions on both wings of the pressure plate (3) is widened, the installation will sometimes require pressing inward from both sides of the pressure plate.
By bending it and attaching it to the nozzle plate, it is possible to increase the tension on the nozzle plate. As a result, a spacer may be incorporated to limit the amount of pressure between the nozzle plate (2), which has a wide pattern width, and the pressure plate (3) by suppressing the amount of ejection.

It is also known that the size of the particles can be controlled by adjusting the thickness of the liquid film.

Furthermore, by forming a surface hardening layer of WC (tungsten carbide) or the like on the surface of the member in the liquid-contacting part of the nozzle, the abrasion resistance and corrosion resistance of the nozzle can be ensured.

In this example, the nozzle outlet was constructed of opposing flat plates, but the nozzle of this example was formed by flattening a cylindrical or approximately funnel-shaped nozzle material using a press or the like. The same effect as a spout can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a front view of the nozzle of the present invention viewed from the spout side, and FIG. 5 is a cross-sectional view taken along the line (B-B') in FIG. Figure 6 shows the jet when the spout in Figure 1 is open, a front view seen from the outlet side, and Figure 7 is a longitudinal cross-sectional view when the spout (0) in Figure 4 is opened. . 1: Nozzle body 2.2j: Nozzle plate 3: Pressure plate
4: Adjustment screw 5: Butterfly nut 6: Ritini 2 nut)・7
:- Patsukin

Claims (5)

[Claims] (1) In an airless spray nozzle that injects pressurized liquid paint from a flat-shaped jet nozzle and atomizes it by friction with air, the jet nozzle of the paint pressure feeding passage is connected along the paint passage. An airless spray nozzle characterized by being formed by opposing flat plates. (2) The airless spray nozzle as set forth in claim (1), wherein means for compressing the opposing flat plates is provided at the spout to control the compressed state. (3) The airless spray nozzle according to claim (1), wherein the tension of the opposing flat plates is adjusted at the jet nozzle. (4) In the jet nozzle, a surface hardening treatment is applied to the inner side of the opposing flat plate.
Airless spray nozzle described in section 1). (5) The airless spray nozzle as set forth in claim (1), wherein the opposing flat plates in the jet nozzle are formed by flattening a cylindrical or funnel-shaped nozzle material.