Patent ID: 7748942

Claim:
A load port apparatus comprising: a chamber configured to maintain a higher pressure inside the chamber than a pressure of a space exterior to the chamber; an opening portion defined by a chamber wall of said chamber, said opening portion creating a passage between the chamber and the space exterior to the chamber; and a door comprising a plate configured to rest at a position at which it substantially closes said opening portion, wherein a clearance exists between an outer circumferential surface of said plate and an inner circumferential surface of said opening portion as a boundary surface with which said opening portion is defined by said chamber wall, when said plate rests at a position at which said plate substantially closes said opening portion, and an area of a cross section of said clearance between said plate and said opening portion on a plane flush with an interior side of the chamber is larger than an area of the cross section of said clearance between said plate and said opening portion on a plane flush with an exterior side of the chamber.