| 摘要 |
A power-driven voicing tool simultaneously inserts into and withdraws from the felt of a piano hammer, needles to raise a nap thereon. A row of four needles is driven by two circularly moved cam surfaces on the ends of an assembly rotatable by a variable speed electric motor through a flexible drive cable. One cam surface lies outside the other and drives the external needles of the row of needles; the other drives the internal needles. The slopes of the two cam surfaces are different and one-hundred-and eighty degrees out-of-phase with each other and effect different movements in adjacent needles, one needle moving outward while the other moves inward. A process of inserting a needle while withdrawing an adjacent needle in the felt of the piano hammer, is practiced.
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