Grooved tape guide

Details Grooved tape guide Grooved tape guide

2002-12-19

2003-12-23

Vidovich, Gregory (Department: 3726)

Roll or roller

With specific roller exterior surface structure

Surface projections, indentations, or slits

C492S033000

Reexamination Certificate

active

06666805

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to tape drives and, more particularly, to flanged tape guides that have a grooved surface to reduce the air bearing between the tape and the surface of the hub.
BACKGROUND OF THE INVENTION
Information is recorded on and read from a moving magnetic tape with a magnetic read/write head positioned next to the tape. The magnetic “head” may be a single head or, as is common, a series of read/write head elements stacked individually or in pairs within the head unit. Data is recorded in tracks on the tape by moving the tape lengthwise past the head. The head elements are selectively activated by electric currents representing the information to be recorded on the tape. The information is read from the tape by moving the tape longitudinally past the head elements so that magnetic flux patterns on the tape create electric signals in the head elements. These signals represent the information stored on the tape.
Data is recorded on and read from each of the parallel tracks on the tape by positioning the head elements at different locations across the tape. That is, head elements are moved from track to track as necessary to either record or read the desired information. Movement of the magnetic head is controlled by an actuator operatively coupled to some type of servo control circuitry. Tape drive head positioning actuators often include a lead screw driven by a stepper motor, a voice coil motor, or a combination of both. The carriage that supports the head is driven by the actuator along a path perpendicular to the direction the tape travels. The head elements are positioned as close to the center of a track as possible based upon the servo information recorded on the tape.
FIG. 1
illustrates generally the configuration of a tape drive
10
typical of those used with single spool tape cartridges. Referring to
FIG. 1
, a magnetic tape
12
is wound on a single supply spool
14
in tape cartridge
16
. Tape cartridge
16
is inserted into tape drive
10
for read and write operations. Tape
12
passes around a first tape guide
18
, over a magnetic read/write head
20
, around a second tape guide
22
to a take up spool
24
. Head
20
is mounted to a carriage and actuator assembly
26
that positions head
20
over the desired track or tracks on tape
12
. Head
20
engages tape
12
as tape
12
moves across the face of head
20
to record data on tape
12
and to read data from tape
12
. Referring to
FIGS. 2 and 3
, roller guide
28
includes disc shaped flanges
30
and an annular hub
32
. Flanges
30
and hub
32
may be machined as a single integral part or as three separate parts bonded together. In either case, flanges
30
function to keep tape
12
at the proper angle as it passes across head
20
. If the tape is presented to the head at too great an angle, then the read and write elements in the head may be misaligned to the data tracks. Flanges
30
are also needed to help keep tape
12
properly packed on take up spool
24
.
As the tape is pulled over the guides, a film of air is created between the outside surface
34
of hub
32
and tape
12
. This film is often referred to as an air bearing. The air bearing allows the tape to move with low friction very rapidly back and forth between flanges
30
. Consequently, high frequency tape movement can occur when the edge of the tape bumps abruptly against flanges
30
. Read/write head positioning systems have difficulty following such high frequency tape movement. It is desirable to reduce this air bearing and thereby increase the friction between the tape and the hub to slow the movement of the tape back and forth between the flanges. Slowing the tape in this manner would allow the head positioning system to better follow the tape as it wanders back and forth between the guide flanges.
U.S. patent application Ser. No. 09/597,882, filed Jun. 20, 2000 titled Irregular Surfaced Tape Guide, describes a tape guide in which grooves are formed in the surface of the hub to reduce the air bearing. The '882 Application discloses a preferred configuration for a ½″ tape in which the grooves are 0.50 mm wide and spaced 1.50 mm on center. It has been discovered that this configuration may not perform as well as desired at higher tape speeds, tape speeds exceeding 4.1 m/s for example, due to instability in the spacing between the tape and the guide surface. At higher speeds, air is drawn in between the tape and the guide land. (The surface area of the guide between grooves is called the “land.”) The tape is so flimsy that flapping occurs with the 1 mm land of the preferred configuration described in the '882 Application. The instability reduces the tracking ability of the guide, allowing the tape to wander back and forth between the guide flanges.
U.S. patent application Ser. No. 09/510,834 filed Feb. 23, 2000 title Improved Tape Guide discloses a tape guide designed to minimize the effect of the tape wandering back and forth between the flanges. The '834 Application describes a tape guide in which the corner geometry between the flanges and the hub prevents the tape from abruptly bumping the flange. The corners are rounded, chamfered or otherwise configured to apply progressively more force to the edge of the tape as the tape moves around the corner from the hub toward the flange. These corner configurations urge the tape more gently away from the flange at a much lower rate of acceleration. Guiding the tape in this manner results in smoother movement of the tape allowing the head positioning system to better follow the tape as it wanders back and forth between the guide flanges. This corner configuration requires flange spacing about 0.04 mm wider than the tape. The added spacing can lead to excessive tape tilt, where the tape passes at an angle across the head. Excessive tilt prevents the head from operating effectively in read-after-write mode. The added spacing also allows for increased debris build-up on the guide.
The present invention was developed to improve grooved tape guides for use in higher tape speed applications.
SUMMARY OF THE INVENTION
The present invention is directed to a tape guide that includes multiple spaced grooves or a spiral groove in the surface of the hub to bleed air from between the surface of the hub and the tape. In one exemplary embodiment of the invention, the distance between adjacent grooves, or turns in the case of a spiral groove, is 2.4 to 3.7 times greater than the width of each groove or turn. The grooves or turns are 0.30 mm to 0.38 mm wide and spaced 0.90 mm to 1.12 mm center to center. The enhanced stability of the narrower and more closely spaced grooves or turns allows for more narrow guide flange spacing. This closer spacing allows narrow flange spacing and reduces debris build-up. The narrowly and more closely spaced grooves or turns means more grooves or turns can be formed on the guide. More grooves or turns means lower contact pressure between the tape and the guide at the edge of the groove and, hence, less tape damage for the same tracking force.
Testing for ½ inch type data storage tapes nominally 12.65 mm wide and 9 &mgr;m thick indicates that the range of enhanced operating space is so small that groove widths of 0.40 mm and spacings of 1.25 mm do not work well. It is believed that the enhanced stability is achieved by keeping a shallow angle between the tape and the guide land as the tape rises from the groove on to the land. By carefully matching this angle with the land width, the tape can span the land without the air pocket alternately filling and then collapsing. By eliminating instability, the guide is able to function adequately at tape speeds up to 5.5 m/s.


REFERENCES:
patent: 3037290 (1962-06-01), Dolby
patent: 3405855 (1968-10-01), Daly et al.
patent: 3559861 (1971-02-01), Knox
patent: 4310863 (1982-01-01), Lelandais
patent: 4427166 (1984-01-01), Oishi et al.
patent: 4466582 (1984-08-01), Shiba
patent: 5088172 (1992-02-01), Daly
patent: 5199168 (1993-04-01), Daly
patent:

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