Abstract: To evacuate a vacuum chamber without stirring up particles in the chamber or associated piping, a pneumatically-actuated vacuum valve is used between the chamber and the vacuum pump. The valve controls evacuation in two stages: in the first stage, the valve partially opens, and a skirt with leak vents in it is brought into play so that air is drawn slowly through the leak vents to gradually achieve a vacuum of a few Torr without stirring up particles; in the second stage, the valve fully opens, and the remaining air in the chamber can be drawn out efficiently, utilizing the large diameter of the valve fully, without risk of stirring up particles. The actuation of the valve is controlled by a timer, which dictates how long the valve stays in the partially-open state before switching to the fully-open state.

Abstract: A body is engaged with a sleeve by a direct sealing coupling. The sleeve has a flange at one end acting as a belleville spring. The flange has a sleeve sealing surface and a rear annular projection. The body has a body sealing surface at one end. The sleeve sealing surface has a conical angle and comes in contact with the body sealing surface by a female nut, a female thread of which is engaged with a male thread of the body, thereby applying fastening force onto the rear annular projection to form sealing between the body and the sleeve.