Tone arm
OwnerWilliam H. Firebaughinventor
Life of this patent
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Abstract
A tone arm for a phonograph pickup having a bifilar flexible ligament suspension for vertical and lateral displacement. The suspension takes the place of the more usual pivots, and employs a pair of thin flexible ligaments or fibers in a skewed convergent torsional bifilar configuration. The lower ends of the two ligaments are attached to a basal element, which may be shaped as a disc, connected to and lying below the arm itself. The flexibility of the ligaments confers freedom to the arm for angular displacement in the vertical and horizontal planes, but the skew prevents linear displacement along the direction of its length. The basal element is preferably immersed in a container of viscous liquid to damp movement of the arm.
Claims9
A phonograph tone arm apparatus for playing disc records, comprising:
- an arm member adapted to carry a phonograph pickup cartridge at its outer end portion,
- a basal element disposed below a rear portion of said arm and means rigidly connecting said basal element and arm;
- and
- a pair of flexible suspension ligaments disposed spacedly about a vertical axis and connected to spaced basal points on said basal element and extending generally upward to upper attachment points on stationary upper supports, said ligaments forming a skewed convergent bifilar suspension,
- torsional deflection of said suspension conferring freedom to said arm for angular displacement in a horizontal plane about said axis,
- said upper attachment points lying on a line non-parallel to a line joining said basal points and defining a skew angle therewith,
- the flexibility of said ligaments conferring freedom to said arm for angular displacement in a vertical plane about an axis passing substantially through said base points.
Dependencies are inferred from the claim text.