Abstract: The present invention provides apparatus which operates the door of a chamber that is capable of maintaining pressure within the chamber. The invention includes an improved closure for cooperating to move the door among positions in which it confronts the opening of the chamber, seals the chamber and allows access to the interior of the chamber. The preferred embodiment of the present invention includes a driving member and an operating member which have surfaces which cooperate to move the operating member in two separate directions. Movement of the operating member in the first direction secures the door in its position in which it confronts the chamber opening but in which it cannot seal the chamber. Movement of the operating member in the second direction causes the door to be secured against the perimeter of the chamber opening, thus sealing the chamber against fluid flow from between the perimeter opening and the door.

Abstract: Apparatus secures in its closed position the door of a chamber capable of maintaining pressure within the chamber. The present invention includes apparatus disposed on the chamber for cooperating to move the door to and from its closed position including at least two members, one of which is movable relative to the chamber. The door is in its closed position when the stationary member and the door are separated from each other by a predetermined distance. The movable member can be forced between the door and the stationary member to separate the door and the stationary member from each other by a predetermined distance. Further, the present invention includes apparatus for preventing the door from assuming its closed position until the movable member is forced between the door and the stationary member.