| 摘要 |
PURPOSE:To increase the life of a shaft seal and to improve maintenance and economy by providing a gas reservoir for so forming a curtain of laser gas as to block a gap by spraying clean laser gas supplied from a supply unit along the outer periphery of a shaft. CONSTITUTION:A motor is driven to rotate a shaft 21 to rotate a fan, thereby circulating laser gas. Magnetic fluid 22 is collected between the inside of protrusion stripes 15 of pole pieces 13, 14 and the shaft 21 in a magnetic field of a magnet 16 to seal it therewith. On the other hand, clean laser gas 27 supplied to a gas reservoir 24 from the unit through a supply tube 26 is sprayed from a gap 27 provided between the shaft 21 and the reservoir 24 to form a curtain along the outer periphery of the shaft 21 with the sprayed gas 27, thereby preventing powder dusts from invading into a shaft seal 17 from a gap 23 between the shaft 21 and a housing 2. Thus, the life of the seal is increased, and maintenance, economy are improved. |
