| 摘要 |
PURPOSE:To prevent a blowing hole from being clogged and constantly maintain an optimum blowing condition, by a method wherein the pressure of a gas supplied to a fitting part between a threaded part and a masking jig is varied between the time when the jig is inserted and the time when the jig is released. CONSTITUTION:When masks 2, 3 are inserted into a joint base 1, namely, in an inside and outside surface coating period (period A), a low pressure selected from the viewpoint of quality is maintained. When the masks 2, 3 are mechanically released from the joint base 1, a solenoid valve fitted to a blowing air pipe system or the like functions in synchronism with a release-driving system for the masks 2, 3 to automatically change over to a high-pressure air source. Then, high-pressure air is discharged through the blowing holes 21, 31 for a fixed period of time (period B), thereby cleaning the part clogged at the time of coating. In a continuous production, these operations are automatically repeated.
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