| 摘要 |
<p>The flipper is used for underwater swimming, and comprises a flat surface, widening outwards from the foot end, and having a thickened reinforcing rib (3, 4) down each side. The flat surface also has a central channel, its open side on the flipper top face. This channel stabilises the flipper and acts as a guide for the water expelled by the flexible valve flaps (7, 8). These are positioned, one each side of the channel, to the rear of the flipper. Each flap opens and closed an aperture (13, 14) to permit free flow (A, B) of the water on the non-working stroke.</p> |
