| 摘要 |
The pressure relief valve is debris resistant, self-cleaning, and self-actuating in a cryopump. It includes an o-ring carried by a valve member within a valve cylinder. In opening, the valve member moves away from an end port to open vent ports in the side of the valve cylinder while withdrawing the o-ring to a debris free and protected region of the valve. As the valve member is moved into the closed position in response to an atmospherical pressure differential, a wiper ring cleans debris from the inner surface of the valve cylinder. A taper is provided on the inner surface of the cylinder to release compression on the vacuum sealing o-ring upon opening and to compress the o-ring as the valve member moves to the closed position. The wiper ring is expansible in order to provide a wiping action along the entire taper and prevent debris from reaching the o-ring. The end of the valve cylinder opposite to the end port serves as a shock absorber as the valve is opened. An outer connecting flange is provided for connection of an exhaust housing. |
