Patent ID: 7578228

Claim:
An air balance structure for a linear drive device, comprising: a stationary member; a movable member having an inner space opened downward, a portion of said stationary member being inserted into the inner space of said movable member such that said movable member is linearly movable in a vertical direction, to form an air balance chamber containing air in the inner space of the movable member which is not occupied by the inserted portion of said stationary member; and an air bearing provided between an outer surface of said stationary member and an inner surface of said movable member confronting each other, for bearing said movable member with respect to said stationary member and also sealing the air in the air balance chamber, wherein weight of said movable member is balanced by a force due to the air in the air balance chamber pressurized only by exhausted air from the air bearing, and the air balance chamber is provided with an exhaust port that communicates with means for adjusting a flow of the air from the exhaust port so that the force due to the air exhausted air from the air bearing is adjusted.