JPH0318507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of spraying in airless spray operation.

Originally, airless spray is a type of spraying from an airless nozzle using the pressure of the liquid itself, without relying on the power of air, and the spraying is continuous. It was a principle.

However, as a practical matter of work, if you want to obtain a relatively thin coating film, or if the line speed during coating has to be slow due to the work process before and after it, Naturally, the amount of liquid ejected must be suppressed to be small. In this case, particularly in the case of highly viscous liquids, significant problems occurred and difficult problems were encountered. (1) In order to reduce the flow rate, a nozzle with a small diameter is used, but in this case, the orifice of the airless spray nozzle may be damaged by gel-like substances or foreign matter that are likely to be present in the liquid. It may get clogged. This not only impedes productivity but also reduces the quality of the products to be coated, which is a fatal blow.

(2) It is difficult to manufacture an airless nozzle that reduces the flow rate and widens the pattern width.

For example, if you use a commonly used cat's eye type airless nozzle and use white lacquer as the liquid with a viscosity of Zahn Cup #2 for 20 to 25 seconds, you can spray it over a distance of 250 mm. The pattern width is limited to about 50 mm, and it is difficult to make it more stable than that, and even if it were possible, the defective rate of the coating would be high, and the cost for a good product would be relatively high. Therefore, it is difficult to obtain a wide pattern at low flow rates.

(3) When a nozzle with a relatively low flow rate is used, a phenomenon called "tail" tends to occur at both ends of the airless spray pattern. This phenomenon is more likely to occur as the viscosity of the liquid is higher and the condensation power of the liquid is stronger, and furthermore, the width of the pattern becomes extremely narrow. This phenomenon increases the fluid pressure,
Even if the amount is 100Kg/cm2 or ^more , it is often difficult to repair. Even if the problem were to be fixed, the high pressure would cause the atomized particles to move too fast, resulting in a lot of bouncing back, resulting in an extremely low coating efficiency. Furthermore, in the state where the above-mentioned "tail" occurs, the thickness distribution of the coating film is uneven, and it is difficult to obtain a high-quality coated product.

For the three reasons mentioned above, in order to obtain a thin coating film or to match low line speeds, it is not possible to suppress the amount of liquid sprayed below a certain limit, and it is unavoidable to spray more than necessary. I was wasting it by applying a thick layer of unnecessary liquid. When it was necessary to avoid thick coatings, methods such as air spraying, which had low coating efficiency, were used.

The present invention uses an airless spray nozzle with a higher flow rate to spray liquid when it is desired to obtain a relatively thin coating film on the surface of the object to be coated, or when it is desired to obtain an appropriate coating film at low line speed. By intermittent airless spraying, the total amount of liquid applied is reduced, thereby completing the application work in the above case, and at the same time reducing the amount of liquid consumed. With the goal.

Next, the gist of the present invention will be described. By opening and closing the liquid on-off valve in the airless spray gun intermittently, the liquid is spouted out intermittently,
Since the amount of liquid ejected during the total time of the interruption can be suppressed, the overall result is a relatively thin coating film on the object to be coated, or a relatively thin coating film on the object to be coated at low line speed. provides the desired and appropriate coating film.

Before explaining the present invention, an overview of the airless spray experimental equipment used in the experiments of the present invention will be described. Please refer to FIG. The airless spray gun 2 consists of a liquid discharge section A and an air operating section B that operates a valve 3 that opens and closes the liquid, and the air operating section is connected to an air solenoid valve 18 by an air pipe 11. There is. The electromagnetic valve is connected to a timer 19. Further, the electromagnetic valve is connected to a compressed air tank 22 through a piping 21 for operation air.

Next, the operation of the above experimental device will be explained. The electric signal emitted from the timer 19 is transmitted to the electromagnetic valve 1.
8 to open it. Released compressed air P
passes through the pipe 11, enters the air operation section B of the airless spray gun, pushes up the piston 7, and opens the liquid on-off valve 3 connected to the piston. The liquid L is pressurized on the back side of the liquid on-off valve through the pressure pump 10, and when the on-off valve is opened, it is airlessly sprayed (S) from the airless nozzle 1 and runs below the airless nozzle 1. The object to be coated 0 on the conveyor 30 is coated. Then, when the set time comes, the electric signal from the timer 19 is cut off, and according to the above-mentioned path,
The opposite operation occurs, cutting off the spray of liquid from the airless sprayer. And again, the intermittent spray is repeated according to the set timer.

In the present invention, intermittent airless spraying is repeatedly performed through the operating path as described above, but these times are extremely short, on the order of milliseconds (ms). That is, many intermittent airless sprays are performed on one object or surface to be coated. Although these short-term interruptions were performed using a timer in the above experiment, they may actually be performed by transmitting pulse signals from a computer or the like.

Although there are countless possible temporal combinations of pulse signals, the following five patterns will be selected from among these. See Figure 2A.

Pattern A...The ON-OFF time of one cycle is ON<OFF. In the example shown, ON (10ms)
<OFF (30ms).

Pattern B...ON time > OFF time. In the example
ON (30ms) > OFF (10ms) Pattern C...ON time = OFF time. In the example
ON (30ms) = OFF (30ms) Pattern D: A series of relatively short ON-OFFs is set as one group, and these similar groups are continued into a series with OFF. In the example diagram, ON (30ms) - OFF (40m
Let the group consisting of multiple members of s) be GPa, and let many groups of the same type GPa′, GPa″, GPa
, ... is continued in the series with OFF (260ms).

Pattern E...ON- according to the application speed
The OFF time and the number of pulses can be changed as appropriate. In the example diagram, ON−OFF=
30ms-30ms, 10ms-30ms, 30ms-20
Each group GPb, according to ms etc.
It is a combination of GPc, GPd, etc.

As described above, according to the continuous airless spray method of the present invention, liquids, such as liquid paints, oils, chemicals, etc., and thermoplastic melts, such as hot melt adhesives and wax, are applied to the object to be coated in a relatively thin coating film. It is also possible to apply an appropriate amount of coating film to the object to be coated at relatively low line speeds, avoiding unnecessary overcoating as in conventional methods, and contributing to reducing the consumption of these liquids. It is something to do.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of the airless spray device used in the experiment of the present invention, and Fig. 2 is a diagram of five types of intermittent spray patterns of the airless spray according to the present invention.Explanation of main symbols: 1...Airless spray nozzle; 3...Liquid on/off valve, 7...Liquid on/off valve operation piston, 9...Liquid flow rate adjustment valve, 10...Liquid pressure pump, 11...Operation air piping, 18...Solenoid valve, 19... ...Timer, 22...Compressed air tank, A...Liquid discharge section, B...Liquid discharge valve operating section.

Claims (1)

[Claims] 1. Electricity or operation air is applied to a single or multiple objects running on a line according to a pre-installed program from a separate control device and computer, or a pulse signal transmitter, etc. pulse signal,
An airless spray method, which is applied to an airless spray gun via an electromagnet or an air operation device, and intermittently sprays a liquid or melt from an airless spray nozzle on the gun according to the pulse signal. How to spray. 2. In response to the relative speed movement of the object to be coated or the airless spray gun and airless spray nozzle,
2. The airless spraying method according to claim 1, wherein the airless spray gun and its airless spray nozzle intermittently eject liquid or molten material in response to a pulse signal corresponding to the change.