Filter unit

A filter unit for air purification attached to an outside of an air outlet of a work chamber so as to be connected to said work chamber for purifying air discharged from said work chamber comprising:

• a rectangular cylindrical body having a first wall portion provided with an air inlet portion through which the air discharged from said exhaust port is introduced and a second wall portion formed so as to cross said first wall portion and provided with an air discharge port portion through which the introduced air is discharged;
• a filter member provided in said cylindrical body and for filtering said introduced air, wherein said filter member is provided with its air discharge surface at said air discharge port portion so as to constitute an outer wall surface of said air discharge port portion and to discharge said filtered air;
• an annular seal member surrounding an outer periphery portion of said air inlet portion so as to oppose said work chamber of said first wall portion;
• and
• an opening/closing member provided with a plurality of flexible sheets extended inward from an outer peripheral edge portion of said air inlet portion and closing said air inlet portion capable of opening/closing the same,
• wherein, when the filter unit is connected to said work chamber, an extending portion provided outward from said air outlet of said work chamber pushes and bends said plurality of flexible sheets and is inserted into the air inlet portion, so that said plurality of flexible sheets abut an outer periphery portion of said extending portion, and so that said seal member abuts an outer wall portion of said work chamber in an airtight manner.