| 摘要 |
Four straight main wings are arranged in rhombic form capable of vertex or corner angle variation and with opposed upper and lower vertices or corners penetrated by a vertical centre shaft. The upper corner of the rhomb is held at a fixed position with respect to the shaft. The lower corner of the rhomb is constituted by a slidable ring slidable along the shaft. A ring stopper is provided on the shaft at a lower position for providing a lower limit position of the slidable ring. Auxiliary wings are each provided on and project from each of the main wings, and are made of a flexible material.
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