Patent ID: 7432431

Claim:
A speed detecting apparatus for a keyboard musical instrument comprising: a pivotable key; a hammer pivotably supported by a fulcrum and configured to pivotally move in association with a pivotal movement of said key; a shutter integrally attached to said hammer; a plurality of detectors arranged along a pivotal movement path of said shutter, each having a light emitter and a light receiver for receiving light emitted from said light emitter, arranged on one and the other sides of the pivotal movement path of said shutter, said detectors having detection points on respective light paths of the light from said light emitters, and arranged such that said detection points are positioned on an arc centered at the fulcrum of said hammer; a board on which said plurality of detectors are mounted, wherein each of said plurality of detectors is placed in a respective case and wherein at least one of the cases is spaced from the board by a spacer such that at least two of said plurality of detectors are spaced from said board by different distances from said board; and hammer speed detecting means for detecting a pivot speed of said hammer in accordance with timings at which said shutter opens and closes the light paths of the light from said light emitters of said plurality of detectors when said hammer pivotally moves.