Method and apparatus for securing a reel in a cartridge

A plug inserted into the access opening of a tape cartridge to prevent movement of the reel inside the cartridge. Damage to the tape media is thus prevented by contact of the reel with the tape media. The plug may also be used to seal the access opening and eliminate environmental contamination which would otherwise enter therethrough.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to the field of special receptacles or packages. More 
particularly, the invention relates to the field of receptacles or 
packages for holding a machine readable recording medium. In still greater 
particularly the invention relates to the field of magnetic tape 
cartridges including a reel movably mounted in the cartridge. By way of 
further characterization, but not by way of limitation thereto, the 
invention is a plug for insertion into the access opening in a cartridge 
to eliminate reel movement and the resultant tape damage encountered 
during shipping and handling of the cartridge. 
2. Description of the Related Art 
Magnetic tape cartridges have been employed for a number of years as a way 
to conveniently and efficiently store and handle magnetic recording media. 
Previously, magnetic tape had been contained on large reels which were 
cumbersome to handle and which required significant labor to place onto 
and remove from tape reading and writing devices. In order to overcome 
this problem, International Business Machines of Armonk, N.Y. introduced 
the 3480 style tape cartridge. The 3480 style cartridge enabled more 
efficient handling of magnetic recording media and the reading of 
information stored thereon and the 3480 has gained wide acceptance. The 
external dimensions and architecture of the 3480 type magnetic cartridge 
are an industry standard. 
Referring to FIG. 1, a 3480 style cartridge consists of a substantially 
rectangular exterior housing including an upper shell portion 11 which may 
be made of plastic or other suitable material. A lower shell portion 12 
retains a single reel of magnetic tape between it and upper shell 11 with 
a leader block 13 affixed to one end of the magnetic tape 21. Leader block 
13 is exposed through an opening in the housing of the cartridge to allow 
a tape drive (not shown) to retrieve tape 21 from the cartridge. 
Referring to FIG. 2, an exploded view of the tape cartridge illustrates the 
components contained therein. A spring 14 is retained in the center of 
portion 11 by guide 15. A break button 16 includes a plurality of teeth 17 
to engage similar teeth (not shown) on the backside of reel 18. Reel 18 
includes teeth 19 to engage a drive clutch on a tape drive (not shown) in 
order to rotate reel 18 and thereby allow magnetic media 21 to move over 
the reading and recording heads in the tape drive as is known to one 
skilled in the art. Lower portion 12 includes an access opening 22 to 
allow the drive clutch in the tape drive to engage teeth 19 on reel 18. 
Spring 14 allows reel 18 to move essentially longitudinally or axially 
against the spring bias between upper portion 11 and lower portion 12 to 
allow teeth 19 on reel 18 to align with the drive clutch in the tape 
drive. 
While movement of reel 18 between upper portion 11 and lower portion 12 is 
necessary during normal operation in a tape drive, it has been found that 
such movement presents problems during handling outside the tape drive. In 
particular, the movement of reel 18 may damage magnetic media 21 which is 
wound thereon. Referring to FIG. 3, a side view of the cartridge is shown. 
If the cartridge is dropped or otherwise severely jostled, axial or 
tilting movement of reel 18 may result in reel contact with upper portion 
11 or lower portion 12 resulting in the contact of the reel 18 with tape 
21. Reel 18 is shown contacting upper portion 11 at 22 and lower portion 
12 at 23. These contact points deflect flanged portions 24 of reel 18. In 
general flanged portions are rather thin and deflect somewhat easily. 
Deflection of flanged portions 24 results in contact between magnetic 
media 21 and flanged portions 24 at 25. Deflected flange portion 24 is 
shown in broken lines in FIG. 3. Because the current design preference 
among tape manufacturers is to develop media that is thinner, that media 
is more easily damaged. Besides damage at the outside edge of the media, 
winding phenomena which results in the uneven or staggered wrap (i.e. 
packslip, popped strand) of the media onto the reel, renders the tape 
vulnerable to damage. Thus, for example, in the 3480 type magnetic tape 
cartridge, damage to the magnetic tape may result in incorrect data track 
writing or reading by the read and write heads in the tape drive. That is, 
because the edge of the tape has been creased, errors in reading or 
writing on these edges may occur. 
There are solutions to the problem of tape damage. One solution would be to 
strengthen flange portions 24 on reel 18. This may protect the tape from 
damage because the flanged portions would be prevented from deflecting. 
Strengthening could be done by adding ribs to the flanged portions or by 
changing the material used to construct the flanged portions. This 
solution would require expensive and time intensive tool and design 
changes and would not address the millions of tape cartridges in use 
today. Of course, greater flange separation would also alleviate the 
problem but this would also require significant cartridge design changes. 
Another possible solution would be to wrap less tape media 21 onto reel 
18. The contact points 25 on tape media 21 would thus be farther away from 
the points 22 and 23 at which flanges 24 contact the upper 11 and lower 12 
portions of the cartridge housing. However, by putting less tape on a 
reel, the capacity of the cartridge to store data is reduced and the 
system performance is reduced by a factor which depends upon the number of 
cartridges in the library. Thus, this solution is unacceptable to cost and 
capacity conscious users.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 4, lower portion 12 of a tape cartridge is shown. The 
outside edge of reel 18 is shown as a broken line with teeth 19 and a hub 
portion 26 of reel 18 shown in access opening 22. Center portion 20 of 
break button 16 is visible through an opening 27 in hub 26. Hub portion 26 
is moveable into and out of access opening 22 by exerting pressure against 
hub portion 26. That is, spring 14 provides light compression of reel 18 
against lower portion 12. Because reel 18 is moveable, any impacts or 
jarring of the cartridge results in the impact of flanges on reel 18 
against upper and lower portions 11 and 12 of the cartridge as described 
above. 
Referring to FIG. 5, the present invention is shown. A plug 28 is provided 
which generally conforms to the configuration of access opening 22. In the 
preferred embodiment plug 28 is of a substantially circular configuration 
and is made of plastic or other elastomeric material. Plug 28 includes a 
plurality of lip portions 29 which are outwardly biased such that, when 
plug 28 is fully inserted into access opening 22 these lip portions 29 
extend over lower portion 12 around access opening 22 (snap fit) to hold 
plug 28 securely in place. A grasping ring 31 on plug 28 allows a user to 
remove plug 28 from access opening 22. 
Referring to FIG. 6, plug 28 is shown inserted into access opening 22 in 
lower portion 12 such that lip portions 29 extend over lower portion 12 
around access opening 22. With plug 28 in place against hub 26, reel 18 is 
biased against spring 14 and upper portion 11. Thus, with plug 28 in 
place, longitudinal or axial movement of reel 18 due to mechanical 
vibration of the cartridge is eliminated or substantially reduced. Damage 
to the magnetic tape 21 from contact with the flanges of reel 18 is thus 
minimized. When it is desired to place the cartridge into use, an operator 
may remove plug 28 by pulling grasping ring 31 away from the cartridge. 
Referring to FIG. 7, an alternate embodiment of plug 28 is shown in which 
plug 28 is a solid piece of elastomeric material and lip portion 32 may 
extend around the entire circumference of plug 28. A grasping handle 33 
allows the operator to insert and remove plug 28 into and out of access 
opening 22. As with the first embodiment, plug 28 restrains reel 18 
against spring 14 and upper portion 11 of the cartridge. Movement of reel 
18 with respect to the cartridge would otherwise cause pressure changes 
within the cartridge resulting in aspiration of contamination into the 
cartridge thus degrading performance and reducing the useful life of the 
cartridge. However, in this embodiment, plug 28 is a solid piece of 
material, resulting in the substantial sealing of the interior of the 
cartridge from environmental contamination which would otherwise enter the 
cartridge through access opening 22. Sealing of access opening 22 during 
shipping and handling eliminates this source of contamination as well as 
preventing movement of the reel with respect to the cartridge. 
With the present invention, both mechanical vibration and environmental 
contamination may be minimized as causes of poor tape performance or 
failure. While the invention has been disclosed with respect to a 
preferred embodiment thereof, it is not to be so limited as the invention 
is defined by the appended claims. For example, while the invention has 
been disclosed with respect to a 3480 type of magnetic tape cartridge, it 
may be advantageously used with other types of media and cartridges. A VHS 
type of video cartridge may make use of one or two plugs of the present 
invention to eliminate mechanical vibration and environmental 
contamination. An alternative design for a dual reel cartridge would be to 
join the two plugs by a strip of material to allow both plugs to be 
removed in tandem. These joined plugs would also ensure that the plugs did 
not become separated and would allow for convenient use. Similarly, other 
types of tape cartridges such as helical scan magnetic tape cartridges and 
the D3 cartridge offered by a number of vendors such as, for example, 
Matsushita Electric Industry Corp. may employ the present invention.