| 摘要 |
PURPOSE:To prevent dust from adhering to shaft by fastening a shield pipe surrounding the shaft provided with a block valve for an exhaust gas back flow channel, to the inner surface of the valve body forming an exhaust gas back flow channel. CONSTITUTION:A shield pipe 19 is fastened to the inside of a valve body 15. The shield pipe 19 covers the surface of a shaft 19 to the end of which a valve 13 is installed. The exhaust gas sucked from the clearance between an oriffice 14 and the valve 13 branches into two flows-one circulating the outside of the shield pipe 19 and the other directly flowing. After the flow branch, the two flows join again at an outlet 17. As the pressure of the shield pipe 19 exceeds the pressure in a corner part C of the valve body 15 and the portion A of the outlet 17, the exhaust gas can not enter the shield pipe 19. The upper end 13a of the valve 13 is enlarged and turned to the lower surface of the shield pipe 19 so that the exhaust gas may be scaled off and settled to stick to the inner wall of the valve body 15. |
