| 摘要 |
PROBLEM TO BE SOLVED: To automatically suspend a rubber ball as an impact source, to make the ball freely fall down from a fixed height at a fixed period at all times. SOLUTION: This device is provided with a base member 11, arranged on a floor face 10 with an opening opened in its central part, four guide bars 12 erected in the base member 11 to guide a rubber ball 1, a suspending member 5 formed of a holding member and a winding cord member, and a winding means 13 for winding up the rubber ball 1 suspended by the suspending member 5. A clearance between the each guide bar 12 and the rubber ball 1 is made larger in the lower end part of the guide bar 12 than in its upper end part, and the rubber ball 1 is wound up to a prescribed height by the winding means 13 and made to fall freely onto the floor face 10 facing to the opening of the base member 11.
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