PURPOSE: To reduce the cost of fuel by rotating a freely openable/closeable chuck for gripping and raising a part of a round fan rib before the treatment on a feed-in device, and also, dropping down the treated round fan rib onto a feed-out device in the periphery of its rotation axis by an operation of a rotary means, and executing a flame treatment to the surface of the round fan rib which is rotating by a burner.

CONSTITUTION: A double round fan rib A is fed in at an interval of ten seconds by a feed-in device 1, therefore, an undulating means 11 is operated by allowing the timing to coincide therewith, a movable frame 8 is laid down in the periphery of an undulation axis 9, and a chuck 3 in a holding position 3A is switched to a gripping position 3B. Subsequently, in a state that the chuck 3 is fitted to a projection C of the round fan rib A, the chuck 3 is closed, and next, by operating the undulating means 11 to an erect side, the chuck 3 is returned to the original position 3A. Thereafter, by rotating an inversion arm 5 to 90 degrees of the lower side of an inversion device 6, the chuck 3 is switched to an upward rotating position 3C, and also, the chuck 3, that is, the round fan rib A is rotated at a high speed by a rotary means 7. A little later than it, an ignited burner 12 is switched to a flame treatment position 12A from a holding position 12B by a switching means 14, and for a prescribed time, a first face (surface) side of the round fan rib is treated.