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Postiion Calibration Tool for Magnetic Moving Tape Drive Heads

IP.com Disclosure Number: IPCOM000113690D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 6 page(s) / 204K

Publishing Venue

IBM

Related People

Barenboim, M: AUTHOR [+3]

Abstract

The need existed for a tool capable of calibrating to extremely close tolerances the position and movement of the Read/Write (R/W) heads of 1/2-inch tape drives used with the IBM 3490 cartridge. In prior art, all drives for this type of cartridge used stationary R/W heads with 18 or 36 pairs of elements. This severely limited the track recording density that could be achieved, leaving a significant amount of unused tape area on each cartridge.

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Postiion Calibration Tool for Magnetic Moving Tape Drive Heads

      The need existed for a tool capable of calibrating to extremely
close tolerances the position and movement of the Read/Write (R/W)
heads of 1/2-inch tape drives used with the IBM 3490 cartridge.  In
prior art, all drives for this type of cartridge used stationary R/W
heads with 18 or 36 pairs of elements.  This severely limited the
track recording density that could be achieved, leaving a significant
amount of unused tape area on each cartridge.

      In an improved design, the magnetic tape drive head is built
into an actuator that steps the head into several additional
positions.  The moving head design permits greatly increases the
track density of the tape, but requires that the R/W heads be
positioned with extreme accuracy in a submicron environment.  To
position the head/guide assembly (HGA), an encoder, called the
independent position sensor (IPS), outputs a signal that indicates
the displacement of the HGA from a fixed reference point.

The Position Calibration Tool (PCT) disclosed herein provides a means
to calibrate the IPS by:
  o  Establishing the position of the fixed guide as a basic
reference
     position;
  o  Finding the physical stops of the actuator to use as the
physical
     "home position";
  o  Tracking the HGA as it moves to prescribed locations using a
     laser triangulator controller.

      The triangulator provides a reference for the signals from the
IPS, indicating its displacement from the basic reference position.

The design of the PCT also incorporates means of:
  o  Making indirect measurements of various selected positions of
the
     R/W element pairs in reference to the tape fixed guide,
     reflecting their relationship within 50 microns.

      This arrangement also provides clamps to hold the HGA, an XY
slide assembly, fixed guide and beam targets laser triangulator, and
travel stops.
  o  Attaching a target to the tape fixed guide so that it accurately
     rests against it as it is pushed by the HGA's compliant guide,

      This permits the reflective target to represent the location of
the fixed guides with repeatable accuracy.
  o  Attaching a target to the HGA load beam so that it registers on
     three pads coplanar with the head modules to determine its
     orientation, then rests on the side of the upper pad to
determine
     its longitudinal placement.

      Three spring-loaded plungers provide retention and insure
contact with all four pads, particularly the one determining the
longitudinal placement of the beam or head.  This permits the
reflective target to represent the location of the R/W head elements
with repeatable accuracy.
  o  Clamping the upper HGA tab quickly with a spring-loaded hook
     without exposing the head to damage.

      Tool Description - Fig. 1 shows the magnetic tape drive's HGA 1
with its base mount 2 an...