A shutter assembly includes an internal shutter and an external shutter. The internal shutter including a contact member is movable between a first position at which the internal shutter closes the outlet, a third position at which the internal shutter opens the outlet, and a second position between the first position and the third position. The internal shutter at the second position is movable to the third position while closing the outlet. The external shutter is movable between a closed position at which the external shutter closes the outlet and an open position at which the external shutter opens the outlet, and includes an interlocking member to contact the contact member to move the internal shutter. As the external shutter is moved from the closed position to the open position, the internal shutter is moved from the first position to the second position in conjunction with the external shutter.