Process and apparatus for applying a primer

A primer is thinly and uniformly applied by supplying a primer and a spraying air to a spray gun, in which an amount of the primer to be supplied to the spray gun is controlled, and a solvent for the primer is supplied to the spraying air to be supplied to the spray gun.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process and an apparatus for supplying a primer 
and spraying air to a spray gun to spray the primer. 
2. Description of Related Art 
Previously, in the manufacture of a polymer insulator, for example, a 
primer (priming agent such as an adhesive) is applied onto an outer 
surface of a rod-shaped FRP core as a workpiece, and then a shed made of 
silicone rubber or the like is molded thereon. When applying the primer on 
the outer surface of FRP core, it is known to apply the primer through use 
of an airless spray gun or to apply the primer through a spray gun under 
an operation of a worker. 
However, when of applying the primer by using conventional airless spray 
gun, several problems arise. 
For instance, in order to apply the primer thinly and uniformly, it becomes 
necessary to decrease the amount of the primer sprayed. However, airless 
spray guns supplying such a small spraying amount are not commercially 
available. 
Moreover, inknown airless spray guns, the spraying amount can be decreased 
by decreasing a spraying pressure. However the spraying state is not 
stable and hence the primer can not be applied thinly and uniformly. 
Additionally, the primer tends to deposit around nozzle portion of the 
spray gun thereby stopping the spraying. 
In order to avoid the deposition of the primer around the nozzle portion of 
the spray gun, it is necessary to use a large-scale installation for 
isolating the whole of the spraying apparatus from the atmosphere. 
On the other hand, there are also problems associated with applying primer 
by using a conventional spray gun. 
Even though the spraying amount smaller than that of the airless spray gun, 
the spraying amount is still relatively large in commercially available 
spray guns. 
Even though the spraying amount can be decreased by lowering the spraying 
pressure and the pressure applied to a liquid surface of the primer, the 
spraying state will not be stable. Thus, In addition, spraying still stops 
because the primer still deposits around the nozzle portion of the spray 
gun the primer can not be applied thinly and uniformly. 
In order to avoid the deposition of the primer around the nozzle portion of 
the spray gun, it is therefore still necessary to use a large-scale 
installation for isolating the whole of the spraying apparatus from an 
atmosphere. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the invention to solve the aforementioned 
problems of the conventional technique. It is also an object to provide a 
process for applying a primer in which the spraying can stably be carried 
out even at a small spraying amount, and wherein deposition of the primer 
around the nozzle portion of the spray gun is substantially eliminated. 
According to a first aspect of the invention, there is the provision of a 
process for applying a primer by supplying a spray gun with a primer and a 
spraying air. The process is characterized in that an amount of the primer 
to be supplied to the spray gun is controlled. Moreover a solvent for the 
primer is supplied to the spraying air supplied to the spray gun. 
According to a second aspect of the invention, there is the provision of an 
apparatus for applying a primer, which comprises a spray gun, a primer 
container for storing a primer to be supplied to the spray gun, and a high 
pressure generating device for supplying a spraying air to the spray gun, 
characterized in that means for controlling an amount of the primer to be 
supplied to the spray gun is disposed between the spray gun and the primer 
container, and means for supplying a solvent for the primer to the 
spraying air is disposed between the spray gun and the high pressure 
generating device. 
According to the invention, the stable spraying can be attained even at a 
small spraying amount by controlling the amount of the primer to be 
supplied to the spray gun and hence the primer can be applied thinly and 
uniformly, while the deposition of the primer around the nozzle portion of 
the spray gun can be prevented by supplying the solvent for the primer to 
the spraying air to be supplied to the spray gun.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 is a schematic view illustrating an embodiment of the structure of 
the primer applying apparatus according to the present invention. As shown 
in FIG. 1, the primer applying apparatus according to the invention 
comprises a spray gun 1, a primer container 2 for storing a primer to be 
supplied to the spray gun 1, a primer supplying pipe 3 connecting the 
spray gun 1 to the primer container 2, a compressor 4 as a high pressure 
generating device for supplying a spraying air to the spray gun 1, a 
spraying air supplying pipe 5 connecting the spray gun 1 to the compressor 
4, and regulators 6-1 and 6-2 disposed in the spraying air supplying pipe 
5. 
Furthermore, a working air supplying pipe 7 connects the spraying air 
supplying pipe 5 between the regulators 6-1 and 6-2 to the spray gun 1, 
and an opening and closing of a needle valve in the spray gun 1 is 
controlled by a pressure of air supplied through the working air supplying 
pipe 7. Moreover, a high pressure air discharged from the compressor 4 is 
supplied to the spraying air supplying pipe 5 and the working air 
supplying pipe 7, respectively, in which an amount of air passing through 
each pipe is controlled by driving the regulators 6-1 and 6-2. 
The aforementioned structure is the same as that of the conventional primer 
applying apparatus. The primer applying apparatus according to the 
invention is entirely different from the conventional primer applying 
apparatus in a point that a tubular pump 8 is disposed in the primer 
supplying pipe 3 connecting the spray gun 1 to the primer container 2 as 
means for controlling an amount of the primer to be supplied to the spray 
gun 1 and a solvent supplying pipe 11 connecting a solvent container 9 for 
storing a solvent to a tubular pump 10 for controlling an amount of the 
solvent to be supplied from the solvent container 9 to the spraying air is 
disposed in the spraying air supplying pipe 5 connecting the spray gun 1 
to the compressor 4 as means for supplying the solvent for the primer to 
the spraying air supplying pipe 5. 
In the primer applying apparatus having the aforementioned structure 
according to the invention, the primer supplied from the primer container 
2 is not only sprayed by the spraying air passing through the spraying air 
supplying pipe 5, but also, even in a negative pressure generated in the 
nozzle portion under an action of the spraying air, the amount of the 
primer passing through the primer supplying pipe 3 from the primer 
container 2 can evenly be decreased by the actuation of the tubular pump 8 
disposed in the primer supplying pipe 3 as compared with that supplied in 
the conventional apparatus. As a result, the stable spraying can be 
conducted even at the spraying amount smaller than that of the 
conventional apparatus. On the other hand, a given amount of a solvent for 
the primer is added to the spraying air by the actuation of the solvent 
container 9 and the tubular pump 10, whereby the deposition of the primer 
existing around the nozzle portion of the spray gun 1 can be prevented. 
The process for the application of the primer according to the invention 
can be conducted by controlling the amount of the primer to be supplied to 
the spray gun 1 through the actuation of the tubular pump 8 disposed in 
the primer supplying pipe 3, and by supplying the solvent for the primer 
to the spraying air to be supplied to the spray gun 1 through the 
supplying means disposed in the spraying air supplying pipe 5 or the 
supplying means comprising the solvent container 9 and the tubular pump 10 
in the primer applying apparatus shown in FIG. 1. 
FIG. 2 shows an embodiment of the spray gun used in the primer applying 
apparatus according to the invention. In the embodiment of FIG. 2, numeral 
21 is a nozzle, numeral 22 a needle valve, numeral 23 a needle packing, 
numeral 24 a spring, numeral 25 a member for adjusting a liquid amount, 
numeral 26 a primer supplying throat, numeral 27 a spraying air supplying 
throat, and numeral 28 a working air supplying throat. In the spray gun 1 
shown in FIG. 2, the opening and closing of the needle valve 22 can be 
controlled by the spring 24 and air supplied through the working air 
supplying pipe 7 and the working air supplying throat 28. Further, air 
supplied through the spraying air supplying pipe 5 and the spraying air 
supplying throat 27 is jetted out from a circumference of the nozzle 21 
outward, and the primer supplied through the primer supplying pipe 3 and 
the primer supplying throat 26 can be sprayed from a tip of the nozzle 21 
accompanied with the jetting. Moreover, the structure of the spray gun 1 
shown in FIG. 2 is the same as that of the conventional spray gun. 
As seen from the above, according to the invention, the amount of the 
primer to be supplied to the spray gun is controlled, so that the stable 
spraying can be attained even at a small spraying amount and hence the 
primer can be applied thinly and uniformly. Further, the solvent for the 
primer is supplied to the spraying air to be supplied to the spray gun, so 
that the deposition of the primer around the nozzle portion of the spray 
gun can be prevented.