JPH04171067A - Spray gun - Google Patents

Abstract

PURPOSE:To enhance the fine pulverization of paint without lowering coating efficiency by jetting atomizing auxiliary air from the atomizing auxiliary air jet orifice provided in the front end surface of a needle under a pressure equal to or higher than the pressure of the atomizing main air jetted from an atomizing main air jet orifice. CONSTITUTION:A needle valve 20 for opening and closing a paint flow path 15 by the contact and separation of a needle 18 with and from a valve seat 16 is provided in the paint flow path 15 communicating with the paint jet orifice 19 of a nozzle 10 having the pain jet orifice 19 and the atomizing main air jet orifice 13 so opened as to surround the paint jet orifice 19 formed in the front surface thereof in such a way that the front end of the needle 18 faces to the paint jet orifice 19. By opening the front end of the atomizing auxiliary air flow path 22 formed in the needle 18 in the front end surface of the needle 18, an atomizing auxiliary air jet orifice 24 is formed. Atomizing auxiliary air is jetted from the jet orifice 24 under a pressure equal to or higher than the pressure of the atomizing main air jetted from the atomizing main air jet orifice 13. As a result, the fine pulverization of paint is enhanced without lowering coating efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improving the atomization properties of spray guns, primarily spray guns for painting that operate with low-pressure, large-volume air.

BACKGROUND TECHNOLOGY When performing air spray painting, paint is generally atomized by mixing a liquid paint stream ejected from a paint outlet of a nozzle with an atomizing air stream ejected from an atomizing air outlet. It is designed to be applied to the object to be coated.

In conventional air spray painting, the atomizing air flow is
It was sprayed at a relatively high pressure of ~3 kg4/am1, but the high pressure of the atomizing air increased the speed of the atomized paint flow, resulting in a large amount of paint particles bouncing off the painted surface. At the same time, due to the expansion of the atomizing air ejected into the atmosphere from the atomizing air outlet, the amount of paint fine particles scattered from the atomized paint flow toward the object to be painted increases, causing the paint to adhere to the painted surface. Not only is the coating efficiency low due to the small amount, there is also the drawback that the rebounded paint particles and the scattered paint particles become suspended and pollute the environment.

For this reason, in recent years, atomizing air has been reduced to 1 kgr/am'
A method is adopted in which a large amount of paint particles are ejected at the following low pressure. According to this method, the velocity of paint particles is lowered, so it is possible to reduce the amount of paint particles bouncing off the painted surface, and it is also possible to Since the expansion of the air flow is reduced, the scattering of paint particles can also be reduced.

Problems to be Solved by the Invention However, although lowering the pressure of the atomizing air can improve the coating efficiency and suppress environmental pollution as described above, it also reduces the atomization of the ejected liquid paint. It causes a decrease in sex. Therefore, a new problem has arisen in that coating particles with large particle sizes adhere to the painted surface, thereby deteriorating the smoothness of the coating film on the painted surface.

The present invention has been devised in view of the above-mentioned circumstances, and is capable of performing spray coating that improves the atomization of the paint without reducing the efficiency of coating and the control of environmental pollution. It provides a spray gun for painting.

Means for Solving the Problems As a means for solving the above-mentioned problems, the spray gun of the present invention has a paint spout and an atomizing main air spout that opens to surround the paint spout on the front surface. In the paint flow path that communicates with the paint spout of the nozzle, there is a needle valve that opens and closes the paint flow path by moving the needle toward and away from the valve seat.
The front end of the needle is provided so as to face the paint jetting port, and the front end of the auxiliary atomizing air flow path formed in the needle is opened at the front end surface of the needle, thereby forming an auxiliary atomizing air jetting port. The auxiliary atomizing air is ejected from the atomizing auxiliary air outlet at a pressure equal to or higher than that of the atomizing main air ejected from the atomizing main air outlet.

Functions and Effects of the Invention The spray gun of the present invention has the above configuration, and when performing spray painting, a large amount of low-pressure main air for atomization is ejected from the main air outlet for atomization, and an auxiliary air injection for atomization is also performed. Auxiliary air for atomization is blown out from the outlet. When liquid paint is ejected from the paint ejection port in this state, an auxiliary atomizing air jet flow flows inside the liquid paint flow, and a main atomization air jet flow is blown outside the liquid paint flow.

Then, the liquid paint flow is atomized by the main atomization air jet flow and the atomization auxiliary air jet flow, but at this time, the atomization auxiliary air jet flow is formed inside the liquid paint flow. This increases the contact area of the liquid paint stream with the air jet per unit volume. That is, since the atomization energy due to the air jet flow applied to the liquid paint flow per unit volume increases, atomization is significantly promoted. As a result, the liquid paint becomes fine particles with an extremely small particle size, and is atomized well.

The atomized paint stream is directed toward the workpiece at a low velocity by mixing with a low-pressure main atomizing air jet flowing in bulk on the outside. For this reason, when the atomized paint flow reaches the painted surface of the object to be painted, the amount of paint rebounding is slightly suppressed, and the coating rate of the paint on the painted surface is high. The amount of paint particles produced is extremely small.

Furthermore, the atomized paint stream is attracted by the atomizing auxiliary air jet flowing at high speed inside the atomized paint stream, which suppresses the scattering of paint particles to the surroundings and hits the object to be coated. The amount of paint that is not applied and is wasted or floating around is extremely small.

As described above, according to the present invention, it is possible to effectively atomize the paint, improve the coating efficiency, and suppress environmental pollution.

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

In the figure, l is a gun body formed with a paint supply hole 2 that opens at the center of the front end surface and an air inlet chamber 3 that opens annularly around the gun body. A supply source is connected, and low pressure air of 1 kgf/am'' or less is supplied to the air inflow chamber 3 from an air supply source (not shown).

A cylindrical nozzle tip 4 is provided at the front end of the gun body l.
is screwed onto the opening of the paint supply hole 2, and an air cap 8 with pattern adjusting air outlets 6 opened at two locations on the top and bottom of the front surface is connected to the gun body I by a hub nut 9.
is fixed so as to cover the front surface of the nozzle IO. A nozzle tip 4 is housed in a housing chamber 11 that opens at the rear surface of the air cap 8 and communicates with the air inlet chamber 3, and the front end of the nozzle tip 4 is
It protrudes from the storage chamber 11 concentrically with a circular hole 12 that opens on the front surface of the air cap 8, and the gap between the circular hole 12 and the nozzle tip 4 forms an annular main air outlet 13 for atomization. .

A paint flow path 15 is constituted by the hollow nozzle tip 4 and the paint supply hole 2 of the gun body l, and this paint flow path I
A valve seat 16 is formed within the nozzle tip 5 by providing a stepped portion on the inner periphery of the nozzle tip 4, and a valve body portion 17 corresponding to the valve seat 16 is formed in a long tapered shape at the front end. A needle 18 is inserted into the nozzle tip 4 so as to be freely movable in the front-back direction and with its front end protruding from the opening in the front end surface of the nozzle tip 4.

The valve seat 16 and the needle 18 allow the paint flow path 15
A needle valve 20 is configured inside, and the needle I8 is moved back and forth by a driving means (not shown) such as trigger operation or hydraulic cylinder operation to cause the valve body portion 17 of the needle 18 to approach and separate from the valve seat 16. As a result, the needle valve 20 is opened and closed.

Further, a ring-shaped paint spout 19 is formed in the nozzle tip 4 by a gap between the opening on its front end face and the needle 18, and when the needle valve 20 opens and closes, liquid paint is discharged from the paint spout 19. The gushing of water and its stopping are performed.

Inside the needle 18, a perforation is formed that opens on its front end surface, and this perforation serves as an auxiliary atomization air flow path 22, and the opening on the front end surface serves as an auxiliary atomization air outlet. 24.

The auxiliary air flow path 22 for atomization is connected to an air supply source (not shown) that is different from the air supply source for supplying air to the main air outlet 13 for atomization, and is connected to the auxiliary air outlet for atomization. 24
is supplied with pressurized air of 0.5 to 4 kgf/am', which is the same or higher pressure than the air supplied to the main air outlet 13 for atomization.

When painting with the spray gun configured as described above, low pressure main air 13 for atomization is supplied from the main air outlet 13 for atomization.
At the same time, high-pressure auxiliary atomizing air 242L is ejected from the auxiliary atomizing air outlet 24, and in this state, the liquid paint 19a is ejected from the paint outlet 19.

A main atomizing air jet 13a is blown into the ejected liquid paint flow 192L from the outside in an annular shape, and an auxiliary atomizing air jet 24a flows inside the atomizing air jet 13a, 24a. The liquid paint 19a is atomized by contacting and mixing with the liquid paint 19a. At this time, the liquid paint 19a is blown away by the atomizing auxiliary air jet flow 24 flowing through one part of the liquid paint 19a.
By a, the contact area per unit volume with the air jet flow is increased, and atomization is significantly promoted to form paint particles with extremely small particle diameters, thereby achieving good atomization.

The atomized paint flow 19+1 is pattern-adjusted to have an elliptical cross section by pattern-adjusting air jets 6a, 6a that are blown from above and below, and is then combined with a large amount of low-pressure atomizing main air jets 13a. By mixing, the mixture is directed at a low speed to an object to be coated (not shown).

After the atomized paint stream 19a is ejected from the paint outlet I9, the pressure drop around the atomizing auxiliary air jet 24a flowing at a high speed through the center of the atomized paint stream 19a causes the paint particles to be filled with atomizing auxiliary air. A force is applied to the air jet flow 24a. Therefore, in the atomized paint flow 19a, the paint particles fly to the object to be coated without causing almost any scattering of the paint particles around the outer periphery.

Since the speed of the atomized paint stream 19a is low, the paint particles that have reached the painted surface of the object hardly bounce back on the painted surface, and almost all the paint particles are coated on the painted surface.

As described above, since the scattering of paint particles and the amount of rebound on the painted surface are extremely small until the atomized paint stream 19a reaches the painted surface, the coating efficiency is extremely high.

Furthermore, since the amount of paint particles floating around due to scattering and splashing is extremely small, there is almost no contamination of the working environment.

Further, since the paint is atomized well by the atomizing auxiliary air jet flow 24a, a smooth paint film is formed on the painted surface.

[Brief explanation of drawings]

The attached FIG. 1 is a partial cross-sectional view of one embodiment of the present invention. lO: Nozzle 13: Main air outlet for atomization 13a 2 Main air for atomization 15: Paint flow path 16: Valve seat 18: Needle 19: Paint outlet 20: Two-dollar valve 22: Auxiliary air flow for atomization Route 24: Auxiliary air outlet for atomization 24a
: Auxiliary air for atomization

Claims (1)

[Claims] A needle is inserted into the valve seat of the nozzle, which has a paint outlet and a main air outlet for atomization that opens so as to surround the paint outlet, in the paint flow path that communicates with the paint outlet. In a spray gun having a needle valve that opens and closes the paint flow path by approaching and separating the needle valve, the front end of the needle faces the paint spout, and the spray gun is provided with an atomizing valve formed in the needle on the front end surface of the needle. By opening the front end of the auxiliary air flow path, an auxiliary air outlet for atomization is formed, and from the auxiliary air outlet for atomization, the main air outlet for atomization is blown out. A spray gun characterized by ejecting auxiliary air for atomization at a pressure equal to or higher than that of the main air.