JPS6325821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an improvement in a powder electrostatic coating method for tubes.

(Prior Art) For example, when forming a phosphor film on the inner surface of a fluorescent lamp bulb, a method is known in which the phosphor is electrostatically coated on the inner surface of the bulb in powder form. However, in the conventional powder electrostatic coating method, a paint gun is placed at one end of the bulb, the bulb is grounded or at an opposite potential to the gun, and a charged phosphor is ejected from the gun. is electrostatically deposited on the inner surface of the valve.

(Problems to be Solved by the Invention) In such a conventional powder electrostatic coating method, when the injected charged powder enters the bulb, it is immediately attracted to the electric charge on the inner surface of the bulb and deposits, so the bulb is damaged. An imbalance in the deposited film thickness occurs in the longitudinal direction. Therefore, a method was proposed in which the nozzle of the gun is made elongated and inserted into the bulb, and electrostatic painting is performed in the same manner as described above while the gun is moved back and forth. However, this method requires a special mechanism to move the gun forward and backward.
In addition to complicating manufacturing equipment, the painting process requires a long time, reducing productivity.

[Structure of the invention]

(Means for Solving the Problems) The present invention is an electrostatic coating method that uniformly adheres powder to the inner surface of a tube bulb. Charged powder having approximately the same potential as the bulb is sent into the tube bulb and suspended. let me,
In this method, after stopping the feeding, the potential of the bulb is set to 0 potential or a potential opposite to that of the charged powder, and the charged powder floating inside the bulb is electrically attached to the inner surface of the bulb.

(Function) The charged powder sent into the bulb has almost the same potential as the bulb, so it is electrically repelled and cannot be deposited, so it floats in the air. Furthermore, since the charged powders have the same potential, they do not electrically repel and agglomerate. In this way, if the charged powder is uniformly suspended in the valve and the feeding is stopped and the valve is set to 0 potential or the opposite potential to the powder, the charged powder will be electrically attracted to the inner surface of the valve. At this point, it loses its charge and is deposited. In this way, the uniformly suspended powder is deposited over time, so that it is deposited with a uniform thickness on the inner surface of the valve.

(Example) Hereinafter, the details of the present invention will be explained by referring to the illustrated example. First, both ends of the phosphor lamp bulb 1 are supported by the end plates 2 and 3, and both ends of the bulb 1 are closed. A nozzle 5 of an electrostatic coating gun 4 passes through one end plate 2 and faces into the valve 1, and the other end plate 3 is provided with a hole 3a for air leakage. The gun 4 is connected to one end of the painting power supply 6, for example, to a terminal, and the outer surface of the valve 1 is connected to the terminal of the power supply 6 through a contact 7a of a changeover switch 7, and to the terminal of the power supply 6 through a contact 7b. It is designed so that it can be switched and connected to the terminal.

First, the movable contact 7c of the changeover switch 6 is connected to the contact 7a, and if necessary, the valve 1 is rotated about its axis. Then, the power source 6 is activated to inject fluorescent powder 8, 8, . . . from the nozzle 5 of the gun 4. Then, the powders 8, 8, .
The air is injected into the hole 3a and the air leaks out from the hole 3a. However, since the inner surface of the bulb 1 is also electrically charged, the powders 8, 8... are electrically repelled by the inner surface of the bulb 1 and cannot be deposited, and furthermore, the powders 8, 8... are also electrically charged because they have the same charge. The powders 8, 8, . . . are not able to coagulate because of the repulsion, and therefore, the powders 8, 8, .

In this state, the injection of the powder 8 is stopped, and the movable contact 7c of the changeover switch 7 is switched to the contact 7b. Then, the inner surface of the valve 1 is charged and charged powders 8, 8
... are electrically attracted to each other, and the powders 8, 8 ... are deposited on the inner surface of the bulb 1, where they lose their charge and form a phosphor film.

The phosphor coating formed in this manner has extremely uniform adhesion density on each part of the inner surface of the bulb 1, and has high adhesion strength, forming a high-quality phosphor coating.

In particular, as mentioned above, during painting, the charged powder 8 is ejected from the nozzle 5 while rotating the bulb 1 around its axis.
When injected, the settling of the powder 8 is slowed down and its distribution within the bulb 1 becomes uniform, so that a more uniform phosphor coating can be obtained due to the reverse potential of the next bulb 1.

Note that the contact 7b of the changeover switch 7 may be connected to the terminal of the power source 6 via the ground. Further, the potential relationship between the gun 4 and the valve 1 may be reversed from that of the above embodiment. Furthermore, when the charged powder 8 is injected into the bulb 1, applying ultrasonic waves to the bulb 1 prevents the powder 8 from sinking and forms a uniform film.

Although the above-mentioned embodiment described a method for forming a phosphor coating in a fluorescent lamp, the present invention is not limited thereto, and can also be applied to, for example, forming a diffused coating in a diffused light bulb.

〔Effect of the invention〕

In this way, the powder electrostatic coating method of the present invention feeds charged powder having almost the same potential as the bulb into a tube bulb, suspends it, and after stopping feeding, changes the bulb potential to 0 or 0. Since the charged powder floating inside the bulb is electrically attached to the inner surface of the bulb by setting the electrical potential opposite to that of the charged powder, a uniform coating film can be obtained with a simple device.

[Brief explanation of the drawing]

The figure is an explanatory diagram of an embodiment of the powder electrostatic coating method of the present invention. 1...Valve, 4...Gun for powder electrostatic coating, 5
... Nozzle, 6 ... Power supply for painting, 7 ... Changeover switch.

Claims (1)

[Claims] 1 Charged powder having approximately the same potential as the bulb is fed into a tube bulb and suspended, and after stopping the feeding, the potential of the bulb is set to 0 potential or a potential opposite to that of the charged powder. A powder electrostatic coating method characterized in that the charged powder suspended in the bulb is electrically attached to the inner surface of the bulb. 2. The charged powder is sent into the valve by injecting it into the valve by placing an electrostatic powder coating gun facing the opening surface of the tube valve and setting the gun at approximately the same potential as the valve. The powder electrostatic coating method according to scope 1. 3. The powder electrostatic coating method according to claim 1 or 2, characterized in that the bulb is rotated around its axis during coating.