Method and apparatus for writing servo-tracks on rotating magnetic memory surfaces

An apparatus for writing substantially concentric servo tracks of first and second pre-determined widths of different magnitudes on the servo surface of a movable magnetic storage device, said apparatus comprising:

• a write transducer having a gap width no less than the magnitude of the greater of said first and second pre-determined widths and adapted to be coupled to means for enabling said write transducer to write a series of substantially concentric tracks of width substantially equal to said gap width;
• means for mounting said write transducer for translational movement along a first direction;
• translating means adapted to be secured to said movable magnetic storage device for translating said servo surface past said write transducer in a second direction substantially normal to said first direction;
• and
• drive means coupled to said mounting means for incrementally translating said write transducer along said first direction, said drive means including means for translating said write transducer along said first direction by a first pre-determined incremental amount substantially equal to said first predetermined track width after one of said series of substantially concentric tracks has been written by said write transducer and before the next one of said series of substantially concentric tracks has been written by said write transducer during writing of said servo-tracks of said first pre-determined width, and means for translating said write transducer along said first direction by a second predetermined incremental amount substantially equal to said second pre-determined track width after one of said series of substantially concentric tracks has been written by said write transducer and before the next one of said series of substantially concentric tracks has been written by said write transducer during writing of said servo tracks of said second pre-determined width so that said write transducer erases a portion of pre-determined substantially constant width of each previously written track during writing of a subsequent track to provide a servo track of desired width.

An apparatus for writing a series of substantially concentric servo tracks of pre-determined width on the servo surface of a movable magnetic storage device, said apparatus comprising:

• a write transducer having a gap width greater than said pre-determined width;
• means for translating said servo surface in a first direction past said write transducer;
• means for enabling said write transducer to record a series of substantially concentric tracks of width substantially equal to said gap width;
• and
• means for incrementally translating said write transducer in a direction substantially normal to said first direction by an amount substantially equal to said pre-determined servo track width after recording a previous one of said series of substantially concentric tracks of widths substantially equal to said gap width and before recording of the next one of said series of substantially concentric tracks of width substantially equal to said gap width so that the width of said previous one of said series of substantially concentric tracks is reduced to said predetermined servo track width when the next one of said series of substantially concentric tracks is recorded.

In an information storage device having a rotatable magnetic storage element, a transducer for recording and reproducing information on said magnetic storage element, means for enabling said transducer to record and reproduce said information and a transducer positioning device, the improvement wherein said transducer positioning device comprises:

• a housing;
• a driving shaft rotatably secured in said housing along a first axis;
• an input gear secured to said driving shaft and adapted to be coupled to a mechanical power source;
• an output gear freely rotatably mounted on said driving shaft;
• clutch means for releasably driving said output gear;
• a driven shaft coupled to said transducer and rotatably secured in said housing along a second axis laterally spaced from said first axis and substantially parallel thereto;
• a first gear secured to said driven shaft at a first axial location therealong and having a first pitch;
• a second gear secured to said driven shaft at a second axial location therealong different from said first axial location and having a second pitch different from said first pitch;
• one of said first and second gears being enmeshed with said output gear;
• first and second pawl means each having a gear nib portion adapted to engage a different one of said first and second gears;
• means for normally biasing said first and second pawl means to a first position in which each gear nib portion engages the associated one of said first and second gears;
• and
• control means for selectively disengaging the gear nib portions of said first and second pawl means to enable said driven shaft to be intermittently rotated by incremental amounts dependent upon the pitch of said first and second gear means.