Helical scan recording with a self-acting negative air bearing

• US 6,151,191 A
• Filed: 07/06/1999
• Issued: 11/21/2000
• Est. Priority Date: 03/11/1997
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Hinteregger, Hans F, Muftu, Sinan
• Primary Examiner(s): Tupper, Robert S.
• Application Number:
  US09/347,978
• Time in Patent Office: 504 Days
• Field of Search: 360/107, 360/130.23, 360/130.24
• US Class Current: 360/271.1
• CPC Class Codes: G11B 15/62 Maintaining desired spacing between record carrier and head
• CPC Class Codes: G11B 5/00821 using stationary heads

Abstract

A flat head and a tape transport arrangement impart a wrap angle to the tape at the upstream corner of the head. The wrap angle, corner sharpness and tape stiffness are sufficient to cause a moving tape to form a hollow bump at the upstream corner, thereby creating a hollow into which entrained air can expand, causing a subambient pressure within and downstream of the bump. This pressure keeps the tape in contact with the head. It is created without the need for a groove or complex pressure relief slot(s). No contact pressure arises at the signal exchange site due to media wrap. The highest contact pressures are developed at a wrapped upstream corner. For a tape drive, traveling in both forward and reverse, the wrap can be at both the upstream and downstream (which is the "reverse upstream") corners. Heads that are not flat can also be used, if the wrap angle relative to a main surface is sufficient and not too large. The wrapped head can also be used with rotating media, such as disks (floppy and hard) and rotating heads, such as helical wound heads for video recording. Multiple flat tape bearing surfaces can be separated by grooves and/or angles. Each flat can carry heads along one or more gap lines. Multiple adjacent narrow tracks can thus be written for extreme high track density recording.

Claims

1. A helical scan head assembly for use with magnetic tape that is wrapped helically around a rotating drum of said head assembly, and moves, relative to a stationary reference in the same direction that said drum is rotating, but at a slower speed, so that, from the perspective of the rotating drum, the tape is observed to be moving along a circumferential machine dimension from an upstream direction to a downstream direction, said head assembly comprising:

a. a first circular cylindrical drum that is rotatable around an axis;

b. fixed to said rotatable drum, a head, having a signal exchange surface that comprises;

i. a signal exchange site;

ii. an upstream corner upstream of said signal exchange site; and

iii an upstream signal exchange surface, defined by an upstream main signal exchange surface curve, located along said machine dimension between said upstream corner and said signal exchange site, which signal exchange surface meets said upstream corner at a main slope discontinuity and has an upstream main tangent τ

_main at said main slope discontinuity; and

said head being located at a radial position and said upstream corner being sufficiently sharp and said upstream main tangent being such that, if any said tape is wrapped helically around said drum and contacts said head and said drum is rotating relative to said tape, then;

i. an upstream portion of said tape contacts said upstream corner;

ii. a portion of said tape that is downstream and adjacent to said upstream corner contacting portion, is spaced away from said signal exchange surface adjacent to and downstream from said main slope discontinuity, forming a hollow bump between said tape and said signal exchange surface; and

iii. a portion of said tape downstream from and adjacent said hollow bump contacts said signal exchange surface along the full extent from said bump to and including said signal exchange site.

2. The head assembly of claim 1, said signal exchange surface comprising a flat surface that is inclined at a non-zero angle φ

relative to a tangent to the circumference of said drum along a radius that passes through said surface.

3. The head assembly of claim 1, said signal exchange surface comprising a flat surface that is substantially parallel to a tangent to the circumference of said drum along a radius that passes through said surface.

4. The head assembly of claim 1, said signal exchange surface comprising a non-flat, curved surface.

5. The head assembly of claim 1, further comprising a drive for rotating said drum and a transport for moving said tape.

6. The head assembly of claim 1, further comprising signal amplification and processing circuitry.

7. The head assembly of claim 1 said upstream corner comprising a corner surface that meets said main upstream signal exchange surface at said main slope discontinuity, said corner surface having a main corner tangent τ

_corner, at said main slope discontinuity and having a side corner tangent τ

_side, at a side slope discontinuity that is spaced upstream from said main slope discontinuity.

8. The head assembly of claim 7, said first head support being located such that a wrap angle θ

from said upstream main tangent τ

_main to a point along said tape path upstream of said upstream corner and downstream of any portion of said tape that contacts the circumference of said drum is overwrapped past an angle α

between said upstream main tangent τ

_main and said side corner tangent τ

_side.

9. The head assembly of claim 7 said head being located radially of said drum such that a wrap angle θ

from said upstream main tangent τ

_main to a point along said media path upstream of said upstream corner and downstream of any portion of said tape that contacts the circumference of said drum is between 0.25 and 5.5°

.

10. A helical scan head assembly for use with magnetic tape that is wrapped helically around a rotating drum of said head assembly, and moves, relative to a stationary reference in the same direction that said drum is rotating, but at a slower speed, so that, from the perspective of the rotating drum, the tape is observed to be moving along a circumferential machine dimension from an upstream direction to a downstream direction, said head assembly comprising:

a. a first circular cylindrical drum that is rotatable around an axis;

b. fixed to said rotatable drum, a head, having a signal exchange surface that comprises;

i. a signal exchange site;

ii. an upstream corner upstream of said signal exchange site; and

iii an upstream signal exchange surface, defined by an upstream main signal exchange surface curve, located along said machine dimension between said upstream corner and said signal exchange site, which signal exchange surface meets said upstream corner at a main slope discontinuity and has an upstream main tangent τ

_main at said main slope discontinuity; and

c. said head being located at a radial position and said upstream corner comprising a corner surface that meets said main upstream signal exchange surface at said main slope discontinuity, said corner surface having a main corner tangent τ

_corner, at said main slope discontinuity and having a side corner tangent τ

_side, at a side slope discontinuity that is spaced upstream from said main slope discontinuity such that, if any said tape is wrapped helically around said drum and contacts said head and said drum is rotating relative to said tape, then a wrap angle θ

from said upstream main tangent τ

_main to a point along said media path upstream of said upstream corner and downstream of any portion of said tape that contacts the circumference of said drum is between 0.25 and 5.5°

.