Erasing disk surface by direct current applied on a helical trajectory to minimize erase time
View Patent ↗A method of erasing a disk by applying a direct current to a transducer while the transducer is moved in a selected manner relative to the rotating disk. The rotating disk in conjunction with the erasing transducer moving in a first direction in a substantially continuous and smooth manner yields a helical shaped erased path on the disk. Such helical erasure of the disk is faster than conventional erasure method that erases the disk by erasing in concentric circular paths. To erase in circular paths, the transducer needs to be positioned on that circular path, and positioning of the transducer involves a repositioning time that can be significant. The helical erasure method substantially eliminates the repositioning time since the path of the transducer is substantially continuous and smooth. The reduction in erasure time by use of helical erasure method is substantial when compared to the total erasure time.
1. A method of erasing a portion of a disk surface of a disk drive having magnetically recorded components recorded thereon, the method comprising:
rotating a disk about an axis of rotation;
moving a transducer across the disk surface such that the transducer travels over a continuous overlapping path of the portion of the disk surface so as to substantially cover the portion of the disk surface wherein the transducer is moved such that the combined rotational motion of the disk and the movement of the transducer results in the continuous overlapping path having a plurality of circumferential components of continuously varying radial distances from the axis of rotation wherein adjacent circumferential components overlap each other; and
applying a signal to the transducer while the transducer is travelling over the continuous overlapping path such that the magnetically recorded data located in the portion of the disk surface are erased.
2. The method of claim 1 , wherein moving the transducer comprises moving the transducer so as to define a continuous overlapping path over a first portion of the disk surface so that the path extends over a plurality of circumferential servo tracks at a plurality of radial positions in a first portion of the disk surface.
3. The method of claim 2 , wherein applying a signal to the transducer comprises applying a signal to the transducer while the transducer is travelling over the continuous overlapping path such that the plurality of circumferential servo tracks are erased without requiring the transducer to be aligned with the plurality of radial positions of the plurality of circumferential servo tracks.
4. The method of claim 3 , wherein moving the transducer comprises utilizing a push rod to move the transducer in a direction that has a component directed radially with respect to the axis of rotation of the disk.
5. The method of claim 1 , wherein moving the transducer comprises moving an actuator arm of the disk drive having a read/write head positioned thereon.
6. The method of claim 5 , wherein applying the signal to the transducer comprises applying an erase signal to the read/write head of the actuator arm of the disk drive.
7. The method of claim 1 , wherein the continuous overlapping path is a helical path having a plurality of loops of a first width each with a continuously varying radius wherein the radial movement of the actuator is selected such that the outer and inner edges of the plurality of loops of the helical path overlap.
8. The method of claim 7 , wherein the inner and outer edges of the plurality of loops of the helical path overlap a thickness equal to approximately 5 percent of the thickness of the loops of the helical path.
9. A method of erasing a plurality of circumferential servo tracks at a plurality of radial positions on a disk of a hard disk drive, the method comprising:
rotating the disk about an axis of rotation;
moving a transducer having a first width in a first direction having a radial component such that the transducer defines a continuous overlapping path over a first portion of the disk surface wherein the continuous overlapping path has a continuously varying radial component such that the path extends over the plurality of circumferential servo tracks in the first portion of the disk surface;
applying a signal to the transducer while the transducer is travelling over the continuous overlapping path such that the plurality of circumferential servo tracks in the first portion of the disk surface are erased without requiring the transducer to be aligned with the plurality of radial positions of the plurality of circumferential servo tracks.
10. The method of claim 9 , wherein the transducer is moved in a first direction at a constant rate.
11. The method of claim 10 , wherein the first direction has a component that is directed radially inward.
12. The method of claim 9 , wherein the continuous overlapping path is a helical path having a plurality of loops each with first width and a continuously varying radius wherein the radial movement of the actuator is selected such that the outer and inner edges of the plurality of loops of the helical path overlap.
13. The method of claim 12 , wherein the inner and outer edges of the plurality of loops of the helical path overlap a thickness equal to approximately 5 percent of the thickness of the loops of the helical path.
14. The method of claim 13 , wherein the continuously overlapping path has a width that is selected to be approximately 65% of the width of the plurality of servo track.
15. The method of claim 9 , further comprising erasing a second portion of the disk surface by positioning the second portion in a substantially constant magnetic field.
16. The method of claim 15 , wherein the second portion is located radially outward from the axis of rotation and the first portion is located radially inward such that the substantially constant magnetic field is separated form the axis of rotation during erasure of the plurality of circumferential servo tracks.
17. The method of claim 9 , wherein moving the transducer comprises moving an actuator arm of the disk drive having a read/write head positioned thereon.
18. The method of claim 17 , wherein applying the signal to the transducer comprises applying an erase signal to the read/write head of the actuator of the disk drive.