PURPOSE: To adjust a vane easily to a desired position by allowing relative movement between two links among links interconnected to vary the predetermined positional relation between the wane and a driver as required.

CONSTITUTION: When a vane 21 is jammed under operating state of an air sweep mechanism, a motor drives a reciprocal link 37 continuously but a pin 28 is kept in stationary state. When the vane 21 is set manually at a specified position, the motor 32 is stopped to keep the vane 21 in stationary state. When the wane 21 is driven manually, a gang bar 24 is driven to slide the pin 28 in an elongated space between the reciprocal link 37 and a press bar 41. According to the mechanism, the wane 21 can be adjusted easily to a desired fixed position.