US 3,942,403 AGranted

Bushing for piano action

AssigneeSteinway & Sons

InventorJoseph J. Pramberger

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Abstract

For use in the pivotal connections of wooden members in a piano action, a bushing formed of a suitable plastic or elastomeric material, such as Teflon, is inserted in bushing holes in each arm of a forked action member for supporting a bearing pin secured to the tongue portion of a mating action member. The bushing has an internal bore of substantially uniform diameter throughout its length, and an outer diameter at the end portions of that portion received in the bushing hole smaller than the outer diameter over the portion thereof mediate the end portions, whereby the bushing can rotate along its axis relative to the bushing hole so as to be self-aligning with the bearing pin received in the internal bore. Because of the "barrel shape" of the bushing, variations in the tolerance on the size of the bushing holes are taken up by compression, causing a slight reduction in the diameter of the internal bore and thereby providing a low-friction essentially line contact between the bushing and the bearing pin. Thus, the bushing is tightly held in the bushing hole, yet the center works freely, despite distortion of the wood parts when subjected to extreme climatic conditions.

A piano action assembly comprising in combination with a bifurcated piano action member having fork arms and a piano having a tongue portion disposed between and in spaced relation to said fork arms to provide opposed surface portions at opposite sides of said tongue portion, a pivotal connection between said tongue portion and said fork arms comprising:

a metal bearing pin traversing and fixedly carried by said tongue portion and projecting from opposite sides of said tongue portion to provide a trunnion end portion at each of said opposite sides,
said trunnion end portions each being journalled in and surrounded by a bushing formed of a resilient, inert elastomeric material seated in a bushing hole in the respective fork arms, which bushing holes are normally aligned but subject to slight misalignment, said bushings each having an internal bore of substantially uniform diameter throughout its length within which the corresponding trunnion end portion of the bearing pin is received with an interference fit and an outer diameter at the end portions of that portion of its length that is seated in the bushing hole less than its outer diameter over a portion thereof mediate said end portions, the mediate portion of said bushing being in press fit with its respective bushing hole,
said bushings each having an integral annular spacing flange at one end thereof, said flanges being disposed in substantially close-fitting surface engagement with the inner surface of its respective fork arm and disposed at opposite sides of said tongue portion between said tongue portion and said fork arms, the surface of the flange which engages the inner surface of the fork arm being inclined outwardly from the surface of the fork arm sufficiently to provide clearance between the flange and the fork arm to allow the bushing to be rotated along its axis about the larger outer diameter portion thereof to effect alignment of the internal bore thereof with the bearing pin whereby the bushings are self-aligning with the bearing pin and with each other regardless of misalignment of the bushing holes in the respective fork arms.

Abstract

Claims3