Winding – tensioning – or guiding – Unwinding and rewinding a machine convertible information... – Cartridge system
Reexamination Certificate
2000-12-06
2003-07-22
Nguyen, John Q. (Department: 3654)
Winding, tensioning, or guiding
Unwinding and rewinding a machine convertible information...
Cartridge system
C360S132000
Reexamination Certificate
active
06595450
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a guide roller for guiding a magnetic tape in the magnetic tape cassette and a method of manufacturing the same.
Conventionally, a magnetic tape cassette is widely used as a storage medium. The magnetic tape cassette is divided into ones for consumer use and ones for industrial use depending on the purpose.
FIG. 20
is an exploded perspective view showing main components of a BETACAM L cassette that is a magnetic tape cassette for commercial use.
As shown in
FIG. 20
, the BETACAM L cassette (hereinafter referred to as “magnetic tape cassette”)
20
generally comprises an upper cassette half
24
and a lower cassette half
22
constituting a cassette case, a pair of tape reels which is rotatably received in the upper and lower cassette halves
24
,
22
and on which a magnetic tape
26
is wound, and a lid
32
for opening and closing the opening formed on the front end side of the upper and lower cassette halves
24
and
22
.
On the lower cassette half
22
, guide rollers
36
and metallic guide pins
38
are mounted at both sides of the opening on the front end side across which a magnetic tape
26
is to be routed. In addition, pads
44
to be in sliding contact with the back side of the magnetic tape
26
is mounted on the lower cassette half
22
. On the upper cassette half
24
, there are provided reel springs
28
for urging the respective tape reels
28
,
30
via the reel holders
46
, and center caps
50
for engaging the reel springs
48
from outside of said cassette half
24
. The upper and lower cassette halves
24
,
22
are fixed together by a plurality of screws
34
.
Among components described above, the guide roller
36
is a cylindrical member formed of a smooth and mechanically strong resin such as POM, and rotatably supported on the lower cassette half
22
by being loosely fitted on the trunnion pin
36
A fixed on the lower cassette half
22
.
FIG. 21
is an enlarged view of the guide roller
36
and the guide pin
38
on the lower cassette half
22
viewed in the direction shown by the arrow B in FIG.
20
. In
FIG. 21
, there is shown a state where the magnetic tape
26
is routed from the tape reel
28
(See
FIG. 20
) over the guide roller
36
and the guide pin
38
. The pad
44
is in sliding contact with the back surface of the magnetic tape
26
between the tape reel
28
and the guide roller
36
and urges the magnetic tape
26
. As a consequent, the magnetic tape
26
comes into contact with the outer periphery of the guide roller
36
. When the magnetic tape cassette
20
is loaded on the recording/replaying apparatus, not shown, and replayed or rewound, the magnetic tape
26
is passed on the outer periphery of the guide roller and then routed out from the cassette case and then travels over the magnetic head of the recording/replaying apparatus.
FIG. 22
is a cross sectional view taken along the line C—C in FIG.
21
. The guide roller
36
is cylindrical in shape and the outer periphery thereof has a uniform diameter.
In the guide roller
36
of the magnetic tape cassette
20
as described above, there are cases where the magnetic tape
26
being in contact with the guide roller
36
is displaced from the normal position upwardly along the axis of said guide roller or downwardly along the same though it is not shown, and thus the magnetic tape
26
does not travel stably. As a consequent, when the magnetic tape
26
is traveling over the magnetic head of the recording/replaying apparatus, the position of the magnetic tape
26
may be displaced with respect to the magnetic head, and thus reading or writing of the record cannot be accomplished properly. This is a problem.
On the other hand, when molding a guide roller
36
described above by injection molding, the parting line PL of the mold is normally defined along the end surface of the molded object. However, it has been a very troublesome work to take an elongated guide roller out of the mold. Though it is also possible to form the guide roller
36
by cutting a bar by machining, it requires a long process time. In addition, since a costly machine such as NC lathe is required for such a cutting work, the processing cost increases to a significant level.
In order to solve this problem, the parting line of the injection mold may be defined along the center portion or along the axis thereof. However, defining the parting line in this way generates molding burr that projects all along the periphery thereof, and thus the secondary process such as cutting work must be made by a machine for deburring, which results in increase in time and effort. This is also a problem.
In addition, since the guide roller
36
shown in
FIG. 22
guides the magnetic tape
26
, it is supported with good rotatability, and thus when the magnetic tape
26
travels at high velocity such as fast forwarding operation or fast rewinding operation, the guide roller
36
rotates at high velocity accordingly. Consequently, at least one of the guide roller
36
and the upper and lower cassette halves
24
,
22
is cut down by friction between the upper and lower end surfaces of the guide roller
36
and the inner surfaces of the upper and lower cassette halves
24
,
22
, and resultant cutting powder may be attached on the magnetic tape
26
and cause a dropout.
It has been shown that when the magnetic tape
26
is running at low velocity for replaying the record, the guide roller also rotates at a low velocity and the upper and lower end surfaces of the guide roller
36
comes into contact with the inner surfaces of the upper and lower cassette halves
24
,
22
, but cutting powder is not generated during low velocity rotation. This is a problem.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problem in the conventional technique.
With such problems in view, the first object of the present invention is to provide a magnetic tape cassette in which the magnetic tape can travel stably so that the magnetic head can accomplish reading and writing of the record on the magnetic tape correctly.
With this problem in view, the second object of the present invention is to provide a guide roller that allows the magnetic tape to travel stably so that reading and writing of the record on the magnetic tape can be accomplished correctly without generating molding burr on the circumferential surface along the parting line, and the method of manufacturing the same.
With the problem described above in view, the third embodiment of the present invention is to provide a guide roller for the magnetic tape cassette in which generation of cutting powder at the contact point between the guide roller and the upper and lower cassette halves is minimized, and the magnetic head can carry out reading and writing of the record on the magnetic tape correctly.
In other words, said first object of the present invention is accomplished by a magnetic tape cassette comprising a pair of tape reels with a magnetic tape wound therearound and a guide roller for transferring said magnetic tape rotatably supported within a cassette case formed by combining the upper cassette half and the lower cassette half so that said magnetic tape is guided by said guide roller and travels at a prescribed position, wherein said guide roller is generally barrel shaped, and a coefficient of curvature T expressed by the expression [1] which represents the extent of curvature of the outer circumferential surface thereof is between 0.001 and 0.01 inclusive.
T
=&Dgr;/(
L&PHgr;
max
) [1]
Wherein &Dgr; represents a difference between the maximum diameter and the minimum diameter of the outer circumferential surface of the guide roller (mm), L represents the axial length of the guide roller, and &PHgr;
max
is a maximum diameter (mm) of the circumferential surface of the guide roller (mm).
The present Inventor has found that the problems described above may be solved by employing a barrel shaped guide roller and defining the extent of curvat
Asano Katsuki
Moriwaki Masayoshi
Nishiyama Shigeru
Fuji Photo Film Co. , Ltd.
Nguyen John Q.
Sughrue & Mion, PLLC
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