Phonograph tone arm control system
AssigneeMasterson Engineering Inc.
InventorEarl E. Masterson
Life of this patent
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Abstract
A multi-function phonograph tone arm control system for a low-friction air bearing supported linear-travelling tone arm system is disclosed. Positive horizontal linear positioning is accomplished by means of an electromagnetic force producing system in which opposing linear forces may be balanced at any point along the path of straight-line travel of the tone arm to position the tone at any desired location. A separate electromagnetic force producing system is utilized to control the vertical pivoting of the tone arm including the pressure of the stylus on a phonograph record. A further motion damping means is provided to stabilize the motion of the tone arm and prevent any unwanted vibration of the tone arm. A means for automatically shutting off the system at the end of a record is also provided.
Claims36
An apparatus for reproducing sound recordings from phonograph records comprising:
- a tone arm supported on low-friction bearing system defining a substantially linear path along which said tone arm enjoys free essentially frictionless linear travel, said tone arm also being free to pivot vertically in an essentially frictionless manner;
- a pickup carried by said tone arm such that linear travel of said tone arm products a corresponding linear radial displacement of said pickup relative to a phonograph record to be played and vertical pivoting of said tone arm produces corresponding essentially vertical displacement of said pickup;
- position control means for controlling the linear position of said tone arm, including positioning electromagnetic force producing means for applying a force to said tone arm in either direction along said linear path and positioning force modulating means for balancing said electromagnetic force in a manner which allows reproducible positive positioning of said tone arm at any point along said path wherein said electromagnetic force producing means comprises:
- a pair of spaced magnetic field producing means defining a gap therebetween,
- coil means disposed in said gap along and parallel to the path of said tone arm, said coil means having an increasing electromagnetic interaction with said magnetic field producing means toward each of the two ends of said path and wherein the linear travel of said tone arm produces a relative motion between said coil means and said magnetic field producing means
- wherein said positioning force modulating means comprises:
- adjustable current distribution means for proportioning electric current in said coil means such that the opposing linear forces produced thereby can be balanced at any point along said path to repeatably position said tone arm wherever desired
- pivot control means for controlling the vertical pivoting of said tone arm comprising:
- pivoting electromagnetic force producing means for applying a force to said tone arm to produce a vertical pivot thereof;
- pivoting force modulating means for controlling said vertical pivot including the pressure of said stylus on said record;
- means for supplying electrical current to said position and pivot control means.
An apparatus for reproducing sound recordings from phonograph records comprising:
- a tone arm supported on an essentially frictionless bearing system defining a substantially linear, horizontal path along which said tone arm enjoys free, essentially frictionless linear travel, said tone arms also being free to pivot vertically in an essentially frictionless manner;
- a pickup carried by said tone arm such that linear travel of said tone arm produces a corresponding linear radial displacement of said pickup relative to a phonograph record to be played and vertical pivoting of said tone arm produces corresponding essentially vertical displacement of said pickup;
- position control means for controlling the horizontal linear position of said tone arm, said position control means further comprising:
- a pair of spaced magnetic field producing means defining a gap therebetween;
- first and second coil means disposed in said gap along and parallel to said path of said tone arm wherein each of said coils has an increasing turn density toward a different one of the two ends of said path and wherein the linear travel of said tone arm produces a relative motion between said first and second coils and said magnetic field producing means;
- adjustable current dividing means for proportioning an electric current between said first and said second coils such that the opposing linear forces produced by said first and said second coils associated with said magnetic field producing means can be balanced at any point along said path to repeatably position said tone arm wherever desired;
- pivot control means for controlling the vertical pivoting of said tone arm comprising:
- pivot coil means disposed in said gap between said spaced magnetic field producing means along and parallel to said path of said tone arm;
- and
- means for modulating an electric current in said pivot coil means;
- and
- means for supplying an electric current to said position and pivot control means.
Dependencies are inferred from the claim text.