| 摘要 |
PURPOSE:To protect a shaft sealing portion by interposing forcibly an air layer between the shaft sealing portion and liquid. CONSTITUTION:Since a shaft sealing device 5 an a space portion 12 tends to have negaive pressure in driving a pump, the external air is taken in a space portion 12 from a vent pipe 13. As a result, the space portion 12 maintains always pressure approximately equal to the atmosphere, and an air layer is always formed above liquid surface in the pump in the stoppage of the pump irrespective of liquid amount in the pump so that the shaft sealing device 5 is prevented from direct contact with liquid by this air layer. |
