JPS61283370A - Method and apparatus for controlling paint spray width of painting spray gun - Google Patents

Abstract

PURPOSE:To always keep constant the spray width of the paint to an article to be painted, by automatically controlling the jet pressure of compressed air from a painting spray gun according to the change in the injection amount of a paint. CONSTITUTION:When a number-of-rotation control apparatus 26 is operated to alter the number of rotation of a speed variable motor 21 proportional to a paint emitting amount in order to alter the thickness of a paint film during painting, the number of rotations thereof are inputted to a paint spray width control apparatus 27. Hereupon, the value calculated according to a calculation formula for calculating set pressure from the number of rotations of the speed variable motor 21 preliminarily programmed in the control apparatus 27 is inputted to a second pressure control valve 24 and the set pressure of the pressure control valve 24 is automatically altered on the basis of said calculated value. Therefore, the pressure of compressed air injected from an air jet orifice 17 for controlling a paint spray width changes according to a paint emitting amount and the spray width on an article (a) to be painted is automatically kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applied to a paint spray gun that flattens the cross-sectional shape of a paint stream by blowing pressurized air from both sides of the paint stream ejected from a nozzle. The present invention relates to a method and apparatus for automatically controlling the spray width of paint according to the amount of paint ejected.

Conventional technology For example, when painting an object by hanging it on a conveyor and transporting it horizontally, a spray gun is attached to a lifting drive device installed near the conveyor and moves it up and down reciprocatingly. is the lifting speed of the spray gun, Gs is the transport speed of the conveyor, and Gr is the reciprocating lifting length of the spray gun. It is necessary to determine the spray width Pw in the horizontal direction so as to satisfy the following equation.

The spraying width Pt+ of this paint is determined by jetting pressurized air to both the upper and lower sides of the paint nozzle of the spray gun, directing the paint flow ejected from the paint nozzle, and flattening the cross-sectional shape of the paint flow in the horizontal direction. Although the ejection pressure can be changed by providing a nozzle and adjusting the ejection pressure, in conventional spray guns, the ejection pressure is manually changed by setting the pressure of a pressure regulating valve.

Problems to be Solved by the Invention However, the spray width Pw of paint varies slightly depending on line conditions such as the amount of paint ejected. Then, the spray width P-
In such cases, it is difficult to manually accurately adjust the pressure of the pressurized air that is sprayed onto the paint stream to keep the spray width Pir constant. It required a lot of skill.

Means for Solving the Problems The inventor of the present invention conducted various experiments regarding the various conditions such as the amount of paint ejected for air atomizing electrostatic spray guns, and found that the spray width Pw of the paint, the amount of paint ejected, etc. It was confirmed that the following relationship holds between the various conditions.

Pv: Paint jet width (mm) d: Paint jet amount (g/m1n) p: Air jet pressure for spray width control (kg/cTI) m
:@Other air injection pressure (kg/CIJ)
0.782. +=1.05. kz=0.30, 3=
0.045, k, = o, 601', and the index k of the paint ejection amount d is set to another index λ, 3. However, this trend is similar for other types of air atomizing electrostatic spray guns.

Similarly, in non-electrostatic spray guns, the paint spray width Pv is greatly influenced by the paint ejection amount d.
It was confirmed that the paint spray width Pw expanded and contracted approximately in proportion to the amount of paint sprayed.

The present invention was completed based on the above-mentioned experiments and analysis results, and one method invention is to blow pressurized air from both sides of a paint flow jetted from a nozzle to form a cross-sectional shape of the paint flow. The jetting pressure of the pressurized air of the painting spray gun for flattening the paint is automatically controlled in accordance with the change in the jetting amount of the paint. In a painting spray gun equipped with an air nozzle for ejecting pressurized air in the direction of a paint stream ejected from the nozzle, a pressure regulating valve is interposed in the pressurized air supply line, and the amount of ejected paint is varied. A control device is provided for automatically changing the set pressure of the pressure regulating valve in response to the above.

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

In FIG. 1, ■ is a conveyor that suspends the object to be coated by hangers 2 and conveys it horizontally, and an air-electrostatic spray gun 5 is attached to the lifting arm 4 of the lifting drive device 3 installed near the conveyor. is attached to the object A to be painted, and the object A to be painted is transported at a constant speed in the horizontal direction.
By reciprocating the spray gun 5 up and down, the spray gun 5 draws a zigzag path relative to the object to be painted, and sprays the paint with a constant spray width in the horizontal direction, so that the object to be painted is The coating is designed to have a uniform thickness. As shown in FIG. 2, the head of the spray gun 5 has a paint nozzle 7 and an air nozzle 8 fixed to the tip of the gun body 6 with a hub nut 9, and an air cylinder (not shown) provided at the rear end of the gun body 6. An on-off valve 1 that opens and closes by advancing and retracting a valve rod 10 connected to a piston rod.
1 is interposed in a paint pressure passage 12 formed at the center of the gun body 6 and the paint nozzle 7, and an electrode 14 for applying an electrostatic voltage protrudes from a paint spout 13 at the tip of the paint nozzle 7. An annular atomizing air outlet 15 surrounding the paint outlet 13 is formed at the center of the gun body 6 and the first air pressure feeding passage 1 formed in the paint nozzle 7 .
6, and there are paint spout ports 1 on both the upper and lower sides of the air nozzle 8.
A pair of air outlets 17 and 17 for controlling the paint spray width are formed in the gun body, and the second air outlet is formed in the gun body.
It has a structure in which it communicates with the air pressure feeding passage 18.

As shown in FIG. 1, the paint pressure passage 12 of the spray gun 5 is connected via a paint hose to the discharge port of a gear-type paint pressure pump 20, which has a suction pipe inserted into a paint tank 19. The air cylinder that drives the on-off valve 11 of the paint pressure feeding passage 12 is connected to the electromagnetic on-off valve 22, and the first air pressure feeding passage 16 is connected to the first pressure regulating valve 23@
-Through.

Further, the second air pressure feeding passage 18 is connected to the second pressure regulating valve 2.
4 to a pressurized air supply source 25, respectively. Also, a variable speed motor 21 for driving the paint pressure pump 20
The rotation speed is controlled by the rotation speed control device [26], and the rotation speed is input to the paint spray width control device 27, and the output of the control device 27 is input to the second pressure regulating valve 24 to set the set pressure. is adapted to be changed, and the electrode 14 is connected to a high voltage generator 28.

Next, the operation of this embodiment will be explained.

The rotation speed control device 26 appropriately sets the rotation speed of the variable speed motor 21 to drive the paint pressure pump 20, and an amount of liquid paint proportional to the rotation speed is sent to the paint pressure feed passage 12.
The air cylinder is activated by opening the electromagnetic on-off valve 22.
When the valve rod 10 moves back and the on-off valve 11 opens, liquid paint is ejected from the paint spout 13, and pressurized air adjusted to an appropriate pressure by the first pressure regulating valve 23 is sent to the first pneumatic pump. through the passage 16 and ejected from the atomizing air outlet 15;
The liquid paint mixes with this airflow and becomes a mist, creating a high voltage generator! Due to the action of the electrostatic field formed between the electrode 14 and the object to be painted by 28, the atomized liquid paint is attracted to and applied to the object to be painted, and the second pressure regulating valve 24 controls the liquid paint as appropriate. The pressurized air, which has been adjusted to a pressure of The cross-sectional shape of the paint stream is flattened in the horizontal direction, and the spray width is made to a predetermined size to form a coating film of uniform thickness on the object to be painted. 1 to change the thickness of the coating film.
When the rotation speed of the variable speed motor 21 is changed by operating the rotation speed control device 26.

The rotation speed is input to the paint spray width control device 27.

The variable speed motor 2 programmed in advance in this control device @27
The value calculated by the formula for calculating the set pressure from the rotation speed of 1 is input to the second pressure regulating valve 24, and the set pressure of the pressure regulating valve 24 is automatically changed based on that value, and paint spraying is performed. Width control air outlet L7. The pressure of the pressurized air ejected from L7 changes, and when the amount of paint ejected decreases and the spray width becomes narrower, the pressure of the pressurized air ejected from the ejection port 17.17 increases, and vice versa. In addition, when the amount of paint ejected increases and the spraying width becomes wider, the pressure of the pressurized air decreases, so that the spraying width on the object to be painted is kept constant, preventing unpainted areas and excessive overcoating. The occurrence of paint spots is prevented.

In this embodiment, the rotation speed of a gear-type paint pressure pump 20 whose discharge amount is proportional to the rotation speed is controlled by a variable speed motor 21, and the paint discharge amount is detected by the rotation speed, and the paint spray width control device 26 However, if a plunger-type paint pressure pump is used, a flow meter is provided in the paint pressure pipeline to measure the amount of paint discharged and input it to the control device 26.

The present invention can also be applied to non-electrostatic airless spray guns.

Effects of the Invention The present invention has the above-described configuration, and the jetting pressure of the pressurized air that is blown onto the spouting paint stream changes automatically in response to changes in the spouting amount of paint, thereby spraying the paint onto the object to be painted. The width can be kept constant.

Even if the thickness of the coating film is arbitrarily changed, the occurrence of coating spots due to uncoated areas or excessive overcoating is prevented, and uniform coating can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a side view with a block diagram showing an outline of an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of a portion of the spray gun. 1: Conveyor 3: Lifting drive device 5 Varnish spray gun
7: Paint nozzle 8: Air nozzle 11: Open/close valve 13
:Paint spout 14:Electrode 15:Fi air jet
17: Air outlet for controlling paint spray width 20: Paint pressure pump 21: Variable speed motor 22: Open/close valve 23.24:
Pressure regulating valve 26: Rotation speed control device t! 27: Paint spray width control device

Claims (1)

[Scope of Claims] 1. The ejection pressure of the pressurized air of a painting spray gun that flattens the cross-sectional shape of the paint flow by blowing pressurized air from both sides of the paint flow ejected from the nozzle. Method 2 for controlling paint spray width of a paint spray gun, characterized in that automatic control is performed in response to changes in the amount of spray gun A pressure regulating valve is interposed in the pressurized air supply line of the painting spray gun equipped with an air nozzle for ejecting air, and the set pressure of the pressure regulating valve is adjusted in response to changes in the amount of paint ejected. A paint spraying width control device for a painting spray gun, characterized in that it is equipped with a control device that automatically changes the width of the spray gun.