Anti-friction and non-oscillating spool for belt driven cartridge

A tape spool including two flanges interconnected by a hub providing a cylindrical tape winding surface is adapted for mounting on and rotation around a cylindrical pin extending from one of two spaced, parallel walls of a data cartridge by providing a bore extending through the hub and one of the flanges which closely but freely fits said pin, and a bearing protrusion extending from the other of the flanges into the bore wherein the extension of the pin from its cartridge wall is greater than the length of the bore to the bearing protrusion so that the spool is suspended above the wall for free rotation about the pin. Oscillation of the spool on the pin may be prevented by also providing a wear-button protrusion extending from the other of the flanges opposite and coaxial with the bore and a spring which extends from the remaining cartridge wall to contact the wear-button protrusion and force the spool into contact with the pin.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention concerns an improved tape spool for a two-spool tape 
cartridge in which a flexible, elastic drive belt contacts the tape on the 
tape spools and whereby movement of the belt causes movement of the tape 
between the spools. 
2. Description of the Prior Art 
The belt driven tape cartridge of U.S. Pat. No. 3,692,255, issued to Von 
Behren and assigned to the assignee of the present invention, has been 
very successfully utilized to interface with computers where rapid 
acceleration and deceleration of the tape are required. In the cartridge 
there disclosed, a magnetic recording tape is convolutely wound on two 
tape spools and is bidirectionally driven between the spools by an endless 
flexible belt in frictional contact with the tape on both spools. 
When the cartridge of the Von Behren patent was first marketed in 1972, its 
magnetic recording tape had a width of 1/4 inch (6.35 mm), a thickness of 
1 mil (0.025 mm), and was driven at 30 inches (762 mm) per second. Data 
were originally recorded on the tape at a density of 1600 flux reversals 
per inch (63 per mm). Current cartridges come in a variety of sizes and 
the recording tapes range in width from 0.150 inches (3.81 mm) to 0.250 
inches (6.35 mm), may be as thin as 0.6 mil (0.015 mm), may be driven at 
90 or more inches (2286 mm) per second, and data is recorded at densities 
of 10,000 flux reversals per inch (394 per mm) or more. In addition, data 
are recorded on a plurality of independent, parallel tracks, which may 
number in excess of 32, spaced across the width of the magnetic recording 
tape. 
Although no problems were encountered when the cartridge was first 
introduced, the higher tape speeds, recording densities, and track 
densities have created a need for reduced rotational friction in the tape 
spools and improved spool positioning during winding and unwinding of the 
magnetic tape. 
SUMMARY OF THE INVENTION 
The present invention discloses a tape spool for use in a data cartridge 
which includes an anti-friction bearing and means for retaining the spool 
at a predetermined axial position with respect to the cartridge. 
Particularly, the tape spool is adapted for mounting on and rotation 
around a cylindrical pin extending a predetermined distance from one of 
the cartridge walls, and includes two flanges interconnected by a hub 
providing a cylindrical tape winding surface, a bore extending through the 
hub and one of the flanges and closely but freely fitting the pin, a 
bearing protrusion, which may be hemispherical, extending from the other 
of the flanges into the bore, wherein the extension of the pin from the 
cartridge wall is greater than the length of the hub bore to the bearing 
protrusion so that the spool is suspended above the cartridge wall for 
free rotation about the pin. Frictional contact between the cartridge and 
the spool is limited to the hemispherical protrusion of the flange and the 
end of the pin, and thus is very low. 
The improved tape spool of the invention may also include a wear-button 
protrusion extending from the other of the flanges opposite and coaxial 
with the hub bore which may be contacted by a spring connected to an inner 
wall of the cartridge, which spring resiliently biases the spool into 
contact with the pin and resists axial movement of the spool. Thus the 
spool is maintained at a predetermined position relative to the tape 
cartridge and the magnetic tape, resulting in uniform winding of the 
magnetic tape upon the spool.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1 and 2 illustrate a data cartridge 10 of the type described in U.S. 
Pat. No. 3,692,255 (Von Behren) which includes a thin base plate 12, 
usually of aluminum, and a clear or translucent polymeric cover 14, which, 
when assembled, define a thin, generally rectangular enclosure. Enclosed 
within the data cartridge 10 are a pair of tape spools 16 and 18, three 
tape wrap pins 20, 22 and 24, a pair of tape guides 26 and 28, a length of 
magnetic recording tape 30, a driving belt 32, a pair of belt guide 
rollers 34 and 36, and a belt driving roller 38. 
The tape spools 16 and 18 are supported by the cartridge base plate 12 for 
free rotation about spaced parallel axes. The magnetic recording tape 30 
is convolutely wound on the tape spools 16 and 18 in opposite directions 
about their axes. A tape 30 guide path between the tape spools 16 and 18 
is defined by the three tape wrap pins 20, 22 and 24 and the two tape 
guides 26 and 28. 
The cartridge 10 is formed with a cutaway portion 40 along the tape path 
which provides access to the magnetic tape 30 by a magnetic transducer 42. 
The cutaway portion 40 is normally closed by a spring-loaded door 44 which 
is opened as shown upon insertion of the data cartridge 10 into a tape 
recorder (not shown). A second opening 46 is provided in the cartridge 
cover 14 to provide access to the belt driving roller 38 by a drive roller 
48 driven by a reversible motor 50. The magnetic transducer 42, the drive 
roller 48, and the reversible motor 50 are illustrated in phantom lines as 
they form a portion of the tape recorder rather than the data cartridge 
10. The cartridge belt driving roller 38 is provided with a reduced 
diameter 51 to prevent contact between the driving belt 32 and the 
magnetic recording tape 30. The driving belt 32 is thin, continuous, 
flexible and elastic. It has a uniform cross-sectional area and it extends 
around the belt driving roller 38 and the belt guide rollers 34 and 36, 
contacting the tape 30 on the tape spools 16 and 18. 
The length of the belt 32 is less than the length of the path along which 
it extends so that when the belt 32 is stretched into position it will 
have an installed tension or pretension. The angle of wrap of the driving 
belt 32 at the tape spools 16 and 18 is at least 60 degrees and provides 
the necessary contact between the belt 32 and the tape 30 wound on the 
tape spools 16 and 18 to assure frictional driving of the tape 30 and the 
tape spools 16 and 18. 
Rotation of the belt driving roller 38 in a counterclockwise direction (as 
viewed in FIG. 1) by the drive roller 48 causes the belt 32 to traverse 
its path in a counterclockwise direction and the tape 30 to move from the 
tape spool 18 to the tape spool 16, the tape spool 18 serving as a supply 
spool and the tape spool 16 serving as a take-up spool. Opposite rotation 
of the driving roller 38 by the drive roller 48 will cause tape to be 
supplied by the tape spool 16 and convolutely wound upon the tape spool 
18. A predetermined frictional coupling between the belt guide rollers 34 
and 36 and their respective support shafts applies a predetermined drag to 
the belt 32 as it passes around the guide belt rollers 34 and 36, thereby 
increasing the tension of the belt 32 as it passes around each of the 
guide rollers 34 and 36. This increased tension in the belt 32 increases 
the length of the belt 32 according to its elasticity and thereby the 
speed at which the belt 32 passes around the spool 18 is increased 
compared to that at which it passes around the spool 16. This increased 
speed causes tension in the tape 30 as well as the ability to take up any 
slack developed in the tape 30 between the tape spools 16 and 18 as is 
more fully taught in U.S. Pat. No. 3,692,255. 
The improved tape spool 16 or 18 of the present invention is best 
illustrated in FIG. 2 and includes an upper flange 52 and a lower flange 
54 interconnected by a hub 56 providing a cylindrical tape winding surface 
58. The spool 16 or 18 is preferably molded of plastic with the hub 56 and 
lower flange 54 molded as a single unit and the upper flange 52 molded 
separately and attached to the hub 56 either by an adhesive or welding. 
The spool 16 or 18 is mounted to the cartridge 10 on and for rotation 
around a pin 60 which is press-fitted into a hole 62 in the cartridge 
plate 12 to extend a predetermined distance above the plate 12. The spool 
16 or 18 is journaled for free rotation around the pin 60 by means of a 
bore 64 provided in the hub 56, which bore is sized to closely but freely 
fit the diameter of the pin 60. 
To reduce rotative friction of the spool 16 of 18 about the pin 60, the 
upper flange 52 is provided with a bearing protuberance 66 which extends 
into the hub bore 64 and contacts the pin 60. The bearing protuberance 66 
is preferably frusto-conical or hemispherical in shape and preferably has 
a rounded surface 68 which reduces the area of contact between the 
protuberance 66 and the pin 60. It will be recognized, however, that the 
protuberance 66 could simply be a cylindrical projection which contacts 
the pin 60 at a flat surface or the pin 60 could simply contact the flange 
52. It is desirable, however, to include the bulk of material provided by 
the protuberance 66, rather than simply allowing the pin 60 to contact the 
flat, lower surface of the upper flange 52, because the upper flange 52 is 
molded of a polymer and may be somewhat abraded or frictionally heated by 
contact with the pin 60. The relatively large bulk of material provided by 
the protuberance 66 minimizes any damaging effects caused by such heating 
and the rounded shape of its surface 68 further minimizes heat caused by 
friction and reduces abrasion caused by the pin 60. 
In order to further reduce friction and abrasion generated between the pin 
60 and the bearing protuberance 66, the terminal surface 70 of the pin 60 
may likewise be rounded rather than flat as illustrated. The length of the 
pin 60, from the surface of the cartridge plate 12 to its terminal end 70, 
is selected to be slightly greater than the length of the hub bore 64 from 
the flange 54 to the protuberance 66 so that the spool 16 or 18 is 
suspended by contact between the pin 60 and the protuberance 66 such that 
the lower flange 54 rotates free of contact with the cartridge plate 12. 
Thus far a tape spool 16 and 18 has been described which will be effective 
to greatly reduce friction between the spool 16 or 18 and the pin 60 as 
the spool 16 or 18 rotates in use. If it could be assured that the data 
cartridge 10 would only be used at low tape speeds and that the cartridge 
10 would always be oriented in an upright position such that the pin 60 
were vertical, the bearing protuberance 66 would be all that was required 
for adequate performance since gravity could be relied upon to maintain 
the bearing protuberance 66 in contact with the pin 60 and prevent the 
spool 16 or 18 from lifting with respect to the cartridge plate 12 and 
oscillating on the pin 60 as tape 30 was being wound or removed. However, 
high speed rotation of the spools 16 and 18 may cause lifting or 
oscillation of the spool 16 or 18 relative to the pin 60 and imperfect 
convolute winding of the tape 30 upon the spool 16 or 18. Such movement of 
the spool 16 or 18 may cause damage to the edges of the tape 30 by contact 
with the flanges 52 or 54 and may be detrimental to tape guidance 
throughout the cartridge 10. In addition, the data cartridge 10 may be 
oriented in use in a position other than that shown in FIG. 2, in which 
case gravity would not assist in maintaining the protuberance 66 in 
contact with the pin 60. 
To minimize lifting and oscillation of the spool 16 or 18 relative to the 
pin 60, the upper flange 52 is further provided with a wear-button 
protuberance 72 extending from the flange 52 opposite and coaxial with the 
hub bore 64. The cartridge cover 14 is provided with a spring 74 which 
contacts the wear-button protuberance 74 and urges the bearing 
protuberance 66 into contact with the pin 60. Although it might be 
possible to eliminate the spring 74 and allow the wear-button protuberance 
74 to bear directly against the cover 14, such an arrangement would be 
difficult to achieve because tolerances would have to be controlled 
tightly and either a lack of contact between the cover 14 and the spool 16 
or 18 or excessive pressure between the cover 14 and the spool 16 or 18 
would likely exist. The spring 74 is, therefore, provided to provide 
resiliency and a limited amount of travel to compensate for tolerance 
variations in the length of the pin 60 and the manufacture of the upper 
flange 52. 
The wear-button protuberance 72 is provided to prevent contact between the 
upper flange 52 and the cartridge cover 14 or the spring 74. The preferred 
shape of the wear-button protuberance 72 is frusto-conical or 
hemispherical and either shape preferably includes a rounded outer surface 
76 to minimize the area of contact between the protuberance 72 and the 
spring 74. 
The preferred type of spring 74 is illustrated in FIGS. 1 and 2 and 
consists of double-cantilever spring arms 78 and 80 extending between a 
central, circular spool-contacting area 82 and diametrically opposed areas 
84 and 86 of a spring mounted ring 88, which ring 88 is suitably attached 
to the cartridge cover 14. 
The spring arms 78 and 80 are preferably wound in a flat helix to increase 
the length of the arms 78 and 80 and thus the resilient travel of the 
spring 74. 
FIG. 3 illustrates an alternate embodiment of a tape spool 90 according to 
the present invention in which a bearing protuberance 92 and wear-button 
protuberance 94 are provided as opposite sides of a spherical ball 96 
which is press-fitted, adhesively attached, or welded to a collar 98 which 
is in turn attached to the upper flange 100 of the spool 90 by an 
adhesive, welding or press-fitting. The sphere 96 and collar 98 may also 
be machined or molded as an integral unit of metal or plastic or the 
collar 98 may be eliminated and the sphere 96 pressed or otherwise 
attached to the upper flange 100 by means of a hole in the flange 100 
closely fitting the sphere. 
Although the arrangement of FIG. 3 requires a greater number of separate 
pieces and greater assembly than does the arrangement of FIG. 2, the 
arrangement illustrated by FIG. 3 may be advantageous in that the sphere 
96 which provides the bearing and wear-button protuberances 92 and 94 need 
not be of the same material used to produce the upper flange 100. Thus the 
sphere 96 may be manufactured of a highly abrasion-resistant material, 
such as metal, acetal resin or polycarbonate, while the upper flange 100 
is manufactured of a softer but more economical material such as 
acrylonitrilebutadiene-styrene copolymer or high-impact polystyrene. FIG. 
3 also illustrates an alternative to the spring 74 of FIG. 2 by providing 
a straight leaf spring 102 which includes a mounting portion 104 and 
spring arms 106 (only one is shown) which extend from opposite ends of the 
mounting portion 104 to contact each of the spools 16 and 18. The mounting 
portion 104 of the spring 102 may be attached to the cartridge cover 108 
by any suitable method, but preferably is riveted thereto. It will be 
recognized that the leaf spring 102 of FIG. 3 could be used in conjunction 
with the spool 18 of FIGS. 1 and 2. 
Either of the alternate embodiments described herein is effective to 
greatly reduce friction between the rotating spool and its mounting pin 
and also to prevent oscillation of the spool relative to the pin. Although 
only two embodiments have been illustrated, it will be apparent to those 
skilled in the art that many modifications are possible. All of such 
modifications which fall within the spirit and scope of the appended 
claims are intended to be included in the present invention.