PURPOSE: To prevent failure of a blade junction by decreasing a response amplitude according to an impact driving torque, for which a main plate is empowered to display a damping effect by mounting a reinforcement diametral smaller than outside diameter of the main plate on the side wall of the main plate.
CONSTITUTION: A disclike reinforcement 10 diametral smaller than outside diameter of a mani plate 1 is mounted on side wall 1a of the main plate 1 and fixed on a boss 4a of a rotary shaft 4 together with the main plate 1. This way of arrangement may invite an impact driving torque at start-up to induce oscillations on the main plate 1, however, the reinforcement 10 has been mounted on the main plate 1 and a natural oscillation is different between the two, therefore the reinforcement 10 becomes still at a frequency wherein the main plate 1 oscillates and the main plate 1 becomes still, on the contrary, at a frequency wherein the reinforcement 10 oscillates. A damping effect may result from a mutual contact of the main plate 1 and the reinforcement 10, and the main plate 1 oscillates less consequently, thus preventing a fatigue wear on a junction 9 of the main plate 1 and a blade 3.
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FUJISAWA FUMIO
TAKAHASHI RIKUROU
SHIIKI KAZUAKI
