Patent ID: 8123194

Claim:
An on-off valve comprising: a valve body that is provided within an evacuation pipe, the evacuation pipe being connected between a process chamber and an evacuation apparatus, the evacuation apparatus evacuating the process chamber of a process gas or active species and has two openings that allow the process chamber and the evacuation apparatus to be in pressure communication with each other, the valve body including a cylindrically or spherically curved inner surface away from the two openings; a closure element located inside the valve body and adapted to close one of the two openings; a seal member provided in the closure element and adapted to seal the one of the two openings when the closure element closes the one of the two openings; a protection seal member provided in the closure element to surround the seal member; a linear motion driver that linearly moves the closure element; a retreat portion provided in the cylindrically or spherically curved inner surface of the valve body; and a pivotal motion driver adapted to pivot the closure element between a first position corresponding to the one of the two openings and a second position corresponding to the retreat portion; wherein the closure element is positioned in the second position by the linear motion driver and the pivotal motion driver, thereby allowing the process gas or active species to flow through the inner space of the valve body from the process chamber to the evacuation apparatus, at least when a process using the process gas or the active species is carried out in the process chamber, and wherein the linear motion driver linearly moves the closure element that has been positioned in the second position, thereby contacting the closure element to the retreat portion, so that the seal member is closed inside the protection seal member and thus not directly exposed to the gases and/or active species from the process chamber, without contacting the cylindrically or spherically curved inner surface of the valve body while the protection seal member contacts the retreat portion.