U.S. patent application number 10/032460 was filed with the patent office on 2002-05-02 for magnetic tape cartridge.
This patent application is currently assigned to FUJI PHOTO FILM CO., LTD.. Invention is credited to Hayashi, Yoichi.
Application Number | 20020051314 10/032460 |
Document ID | / |
Family ID | 27330314 |
Filed Date | 2002-05-02 |
United States Patent
Application |
20020051314 |
Kind Code |
A1 |
Hayashi, Yoichi |
May 2, 2002 |
Magnetic tape cartridge
Abstract
A magnetic tape cartridge has a reel which comprises an upper
reel and a lower reel which are plastic moldings, the lower reel
being welded to the upper reel by ultrasonic welding. In the
shoulder of a boss section of the upper reel, a plurality of
recesses are formed in such a manner that the recesses are radially
outwardly extended from the center of rotation of the upper reel,
and on the surface of the lower reel which are confronted with the
recesses, a plurality of welding ribs are formed so as to be
engaged with the bottoms of the recesses.
Inventors: |
Hayashi, Yoichi; (Kanagawa,
JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
FUJI PHOTO FILM CO., LTD.
|
Family ID: |
27330314 |
Appl. No.: |
10/032460 |
Filed: |
January 2, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10032460 |
Jan 2, 2002 |
|
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09134040 |
Aug 14, 1998 |
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Current U.S.
Class: |
360/132 ;
G9B/23.066; G9B/23.067 |
Current CPC
Class: |
G11B 23/08735 20130101;
G11B 23/08728 20130101 |
Class at
Publication: |
360/132 |
International
Class: |
G11B 023/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 14, 1997 |
JP |
P. HEI. 9-219549 |
Aug 14, 1997 |
JP |
P. HEI. 9-219550 |
Aug 14, 1997 |
JP |
P. HEI. 9-219551 |
Claims
What is claimed is:
1. A magnetic tape cartridge having a reel which comprises an upper
reel and a lower reel which are plastic moldings, said lower reel
being welded to said upper reel by ultrasonic welding, in which in
the shoulder of a boss section of said upper reel, a plurality of
recesses are formed in such a manner that said recesses are
radially outwardly extended from the center of rotation of said
upper reel, and on the surface of said lower reel which are
confronted with said recesses, a plurality of welding ribs are
formed so as to be engaged with the bottoms of said recesses.
2. The magnetic tape cartridge according to claim 1, in which the
number of said plurality of recesses are the same as said plurality
of welding ribs in such a manner that said welding ribs are
respectively brought in engagement with said recesses.
3. The magnetic tape cartridge according to claim 2, in which each
of said welding rib is a triangular in cross-section.
4. The magnetic tape cartridge according to claim 2, in which the
number is selected from an add number, and said recesses are
arranged at equal interval.
5. The magnetic tape cartridge according to claim 2, in which each
of said welding rib spirally extends from the center to the outer
periphery of said lower reel.
6. The magnetic tape cartridge according to claim 2, in which each
of said welding rib is constituted by a plurality of segments which
are discontinuously extended in a circumferential direction of the
lower reel.
7. The magnetic tape cartridge according to claim 1, in which on a
shoulder surrounding the recesses of said upper reel, welding
stopper surfaces are provided in such a manner that said welding
stopper surfaces are scattered circumferentially over the whole
width of said shoulder.
8. A magnetic tape cartridge having a reel which comprises an upper
reel and a lower reel which are thermo-plastic resin moldings, said
lower reel being welded to said upper reel by ultrasonic welding
with a welding rib protruded from said lower reel abutted against
the shoulder of a boss section protruded from said upper reel, in
which the surface of said shoulder of said upper reel is
roughened.
9. A magnetic tape cartridge having a reel which comprises an upper
reel and a lower reel which are thermo-plastic resin moldings, said
lower reel being welded to said upper reel by ultrasonic welding
with a welding rib protruded from said lower reel abutted against
the shoulder of a boss section protruded from said upper reel, in
which on a part of an over-flow preventing stopper ring which is
protruded from the outer periphery of said shoulder of said upper,
a barrier is formed which is higher than said part, and on the
surface of said lower ring which is confronted with said stopper
ring, a recess is formed which is labyrinth-engaged with said
barrier.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a magnetic tape cartridge formed
by ultrasonic welding.
[0002] FIG. 1 shows a conventional magnetic tape cartridge.
[0003] In FIG. 1, reference numeral 1 designates the magnetic tape
cartridge. The magnetic tape cartridge 1 is constructed as follows:
A magnetic tape 20 is wound on a reel 3 which is formed by
combining upper and lower reels 4 and 4 together by ultrasonic
welding. The reel 3 is rotatably accommodated in a cartridge casing
which is formed by combining upper and lower cartridges 2a and 2b
together with screws 19.
[0004] The upper reel 4 is made of polycarbonate resin containing
glass fibers. The upper reel 4 has an upper flange 4a, and a recess
at the center which has a boss section 4x extended towards the
center. The upper flange 4a has a gear 4y on its outer cylindrical
surface.
[0005] The aforementioned recess has a cylindrical rib, in which a
ring-shaped bearing 6 is press-fitted. And a spring plug 7 is
fixedly press-fitted in the central hole formed in the bearing. A
reel spring 8 is mounted on the spring plug 7, to push downwardly
the aforementioned reel 3 and hold the reel 3 rotatably.
[0006] The lower reel 5 is made of polycarbonate resin, and has a
lower flange 5a which has a hole at the center around which an
ultrasonic welding rib 5b is formed. The lower reel 5 is combined
with the shoulder of the aforementioned boss section 4b.
[0007] When the cartridge is not in use, the reel 3 is locked by
reel brakes 50 and 51 so that it may not be turned unintentionally
which are suitably urged by braking torsion springs 12. When the
magnetic tape cartridge 1 is not in use, the magnetic tape 20 has
been completely wound on the reel 3, and the leader tape 21
connected to the end of the magnetic tape is locked to the end of a
hook 18 which is provided near the side wall of the cartridge.
[0008] The opening through which the magnetic tape 20 is pulled out
is designed as follows: That is, a lid 30, which is swingable in a
cartridge plane, is provided while being suitably urged by a
torsion spring 15. When the cartridge is not in use, the lid 30 is
locked by a locking member 40 (which is suitably urged by a
compression spring 16) so that it may not be swung. On the side
which is opposite to the side where the lid 13 is provided, the
cartridge has a write protect 17.
[0009] The aforementioned leader tape 21 is engaged with an
engaging means adapted to lead the magnetic tape 20 in the tape
path of the recording and reproducing device. The leader tape 21 is
fastened to the magnetic tape 20, for instance, by splicing.
[0010] In the above-described magnetic tape cartridge 1, the upper
and lower reels 4 and 5 are combined together by ultrasonic welding
as follows. As was described before, the annular rib 5, which is
formed along the annular edge of the circular opening formed at the
center of the lower flange 5a, is engaged with the shoulder of the
lower portion of the boss section 4b. Under this condition, while a
predetermined pressure is applied to the upper and lower reels,
those reels are subjected to ultrasonic excitation, so that the rib
5b is molten to combine the upper and lower reels 4 and 5
together.
[0011] In this welding operation, the upper reel 4 is set below the
lower reel. More specifically, the upper reel 4 is fixedly set, and
the lower reel 5 is placed on the upper reel 4 from above. Under
this condition, the upper reel 4 is subjected to ultrasonic
pressure excitation. As the rib 5b is molten, the surface of the
lower reel 5 is brought into contact with the shoulder of the upper
reel. From this fact, it is determined that the welding operation
has been accomplished.
[0012] FIG. 2 shows the conventional ultrasonic welding portions of
the aforementioned reel 3. The boss section 4b of the upper reel 4
comprises a shoulder 4c, and a protrusion 4d which is extended from
the shoulder 4c and is smaller in diameter than the shoulder 4c.
Along the outer annular edge of the shoulder 4c, a stopper ring 4e
is integrally provided which is slightly higher in level. That is,
the upper reel 4 is in the form of a shallow-bottomed container as
a whole. In addition, between the stopper ring 4e and the
protrusion 4d, turn-preventing stoppers 4f are provided in such a
manner that they are diametrically opposite to each other, and are
flush with each other.
[0013] On the other hand, the rib 5b of the lower reel 5 has cuts
5d at angular intervals of 90.degree.. When, with the central hole
of the lower reel engaged with the protrusion 4d of the upper reel,
the lower reel is turned, the cuts 5d are engaged with the
turn-preventing stoppers. When, under this condition, the reel is
subjected to pressure excitation, the rib 5b is molten. The molten
portion of the rib 5b, being absorbed in the shallow-bottomed
annular groove, is spread uniformly. As a result, the surface of
the lower flange 5a is brought into contact with the upper surface
of the stopper ring. Thus, the welding operation has been
accomplished.
[0014] In the above-described conventional magnetic tape cartridge,
the lower flange 5a and the stopper ring 4e are almost in line
contact with each other; that is, they are considerably small in
contact area. Hence, it is difficult to weld the upper and lower
reels together in such a manner that they are high in parallelism.
This fact results in a so-called surface play.
[0015] In the case where the tape is wound on the reel, the tape
winding operation is carried out with the upper flange 4a and the
boss section 4b of the upper reel as a reference. In this case,
since the upper flange 4a and the boss section 4b are formed as one
unit by injection molding, the tape can be wound on the reel with
high accuracy. However, in the case where the tape winding
operation is carried out basing on the lower reel 5 and the boss
section which suffer from the surface play, it is difficult to
achieve the tape winding operation with high accuracy.
[0016] If, with the reel, the welding area is increased in the
direction of diameter, the width of the stopper ring 4e should be
increased. However, in this case, the molten portion flows out of
the shallow-bottomed groove; that is, the resultant product is
unacceptable. In addition, the welding area is not large enough;
that is, the upper and lower reel are not satisfactorily welded
together.
[0017] In the case of the conventional reel shown in FIG. 2, the
lower reel 5 is prevented from turning as follows: That is, in
order to prevent the lower reel 5 from turning, after the lower
reel 5 is set on the upper reel 4, the lower reel must be turned at
most 90.degree.. Accordingly, it is impossible to subject the upper
and lower reels to ultrasonic work immediately after the lower reel
is set on the upper reel. Furthermore, a metal mold for forming the
turn-preventing stoppers 4f and the cuts 5d is intricate in
configuration. Therefore, there is a strong demand for the
provision of turn-preventing means which replaces the
turn-preventing stoppers 4f and the cuts 5d.
[0018] Furthermore, in the conventional magnetic tape cartridge, as
shown in FIG. 3(a) the rib 5a is molten starting from its end by
pressure excitation, and the molten resin spreads gradually in the
shallow-bottomed groove according to the pressure.
[0019] However, in practice, as indicated by a group of dots in
FIG. 3(b), owing to the pressure which is applied simultaneously
when the melting operation starts a part of the molten resin
sometimes flows over the stopper ring 4a to the outer periphery of
the boss section 4b. The molten resin thus caused to over-flow is
solidified as cooled, thus sticking onto the outer periphery.
Hence, when the tape is wound on the reel, the winding center is
shifted from the true center; that is, the resultant product is
unacceptable.
SUMMARY OF THE INVENTION
[0020] Accordingly, an object of the invention is to provide a
magnetic tape cartridge in which the above-described difficulties
accompanying a conventional magnetic tape cartridge have been
eliminated.
[0021] Accordingly, a first object of the invention is to provide a
magnetic tape cartridge having a reel which is high in weldability,
and is so shaped that it is increased in the area of a stopper
surface during welding, whereby the upper and lower reels are
sufficiently high in parallelism.
[0022] The first object of the invention has been achieved by the
provision of a magnetic tape cartridge having a reel which
comprises an upper reel and a lower reel which are plastic
moldings, the lower reel being welded to the upper reel by
ultrasonic welding;
[0023] in which, according to the invention,
[0024] in the shoulder of a boss section of the upper reel, a
plurality of recesses are formed in such a manner that the recesses
are radially outwardly extended from the center of rotation of the
upper reel, and
[0025] on the surface of the lower reel which are confronted with
the recesses, a plurality of welding ribs are formed so as to be
engaged with the bottoms of the recesses.
[0026] Furthermore, the first object has been achieved by the
provision of a magnetic tape cartridge having a reel which
comprises an upper reel and a lower reel which are plastic molding,
the lower reel being welded to the upper reel by ultrasonic
welding;
[0027] in which, according to the invention,
[0028] on a shoulder surrounding the recesses of the upper reel,
welding stopper surfaces are provided in such a manner that the
welding stopper surfaces are scattered circumferentially over the
whole width of the shoulder.
[0029] According to the invention, during ultrasonic welding, the
molten ribs form flows of resin only in the recesses, so that the
welding operation is achieved with an amount of welding resin
corresponding to the number and area of recesses.
[0030] Furthermore, with the whole surface of the shoulder
surrounding the recesses of the upper reel as the stopper surface,
the welding surface spreads radially outwardly, so that the surface
contact of the upper and lower reels which have been welded
together are high in parallelism.
[0031] In the invention, the welding ribs may be extended radially
outwardly from the peripheral edge of the central hole of the lower
reel, or they may be curved spirally from the peripheral edge of
the central hole, or they may be protruded in such a manner that
they are coaxial with the peripheral edge of the central hole.
[0032] A second object of the invention is to provide a magnetic
tape cartridge in which the above-described difficulties
accompanying a conventional magnetic tape cartridge have been
eliminated, and in which, immediately after the lower reel is set
on the upper reel, those reels can be subjected to ultrasonic
welding as they are (without turning the lower reel), and a reel
metal mold is simple in construction.
[0033] The second object has been achieved by the provision of a
magnetic tape cartridge having a reel which comprises an upper reel
and a lower reel which are thermo-plastic resin moldings, the lower
reel being welded to the upper reel by ultrasonic welding with a
welding rib protruded from the lower reel abutted against the
shoulder of a boss section protruded from the upper reel,
[0034] in which, according to the invention,
[0035] the surface of the shoulder of the upper reel is
roughened.
[0036] According to the invention, the lower reel is set on the
upper reel, and under this condition, those reels are pressurized.
As a result, the welding rib is pushed against the roughened
surface to provide a frictional force which prevents the reels from
turning circumferentially. This makes it possible to subject the
reels to ultrasonic welding. The surface roughing metal molding is
not intricate in structure when compared with the conventional
one.
[0037] A third object of the invention is to provide a magnetic
tape cartridge in which the above-described difficulties
accompanying a conventional magnetic tape cartridge have been
eliminated, and which has a reel in which, when the reel is
manufactured, the molten resin is prevented from flowing over the
outer periphery of the boss section to prevent the formation of an
unsatisfactory product thereby to improve the product yield.
[0038] The third object of the invention has been achieved by the
provision of a magnetic tape cartridge having a reel which
comprises an upper reel and a lower reel which are thermoplastic
resin moldings, the lower reel being welded to the upper reel by
ultrasonic welding with a welding rib protruded from the lower reel
abutted against the shoulder of a boss section protruded from the
upper reel,
[0039] in which, according to the invention,
[0040] the surface of the shoulder of the upper reel is
roughened.
[0041] In the invention, even if, during ultrasonic welding, the
molten resin tends to flow over the outer periphery in response to
a pressurizing force applied thereto, the over-flow of the molten
resin is stopped because the gap provided the walls are
narrowed.
[0042] The nature, utility and principle of the invention will be
more clearly understood from the following detailed description and
the appended claims when read in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0043] In the accompanying drawings:
[0044] FIG. 1 is an exploded perspective view of a conventional
magnetic tape cartridge;
[0045] FIG. 2 is an exploded perspective view, with parts cut away,
showing an example of the ultrasonic welding section in the
conventional magnetic tape cartridge;
[0046] FIGS. 3(a) and 3(b) are diagrams for a description of the
ultrasonic welding operation in the conventional magnetic tape
cartridge;
[0047] FIG. 4 is an exploded perspective view, with parts cut away,
showing an example of a magnetic tape cartridge, which constitutes
a first embodiment of the invention;
[0048] FIG. 5 is a plan view, with parts cut away, showing the
assembly of an upper reel and a lower reel in the first embodiment
of the invention;
[0049] FIGS. 6(a) and 6(b) are sectional diagrams for a description
of the welding operation of the upper and lower reels;
[0050] FIG. 7 is an exploded perspective view, with parts cut away,
showing another example of a magnetic tape cartridge, which
constitutes a second embodiment of the invention;
[0051] FIG. 8 is a plan view, with parts cut away, showing the
assembly of an upper reel and a lower reel in the second embodiment
of the invention;
[0052] FIG. 9 is a plan view, with parts cut away, showing the
assembly of upper and lower reels in another example of the
magnetic tape cartridge, which constitutes a third embodiment of
the invention;
[0053] FIG. 10 is an exploded perspective view, with parts cut
away, showing upper and lower reels in another example of the
magnetic tape cartridge, which constitutes a fourth embodiment of
the invention;
[0054] FIG. 11 is a sectional half-view showing essential
components of the fourth embodiment of the invention;
[0055] FIG. 12 is an exploded perspective view, with parts cut
away, showing upper and lower reels in another example of the
magnetic tape cartridge, which constitutes a fifth embodiment of
the invention;
[0056] FIG. 13 is an exploded perspective view, with parts cut
away, showing upper and lower reels in another example of the
magnetic tape cartridge, which constitutes a sixth embodiment of
the invention; and
[0057] FIGS. 14(a)-14(c) are sectional half-views for a description
of the welding operation of the upper and lower reels in the sixth
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0058] Preferred embodiments of the invention will be described
with reference to the accompanying drawings.
[0059] First Embodiment
[0060] An example of a magnetic tape cartridge, which constitutes a
first embodiment of the invention, will be described with reference
to FIGS. 4 through 6. In the magnetic tape cartridge, the first
embodiment, its reel is fundamental equal in configuration to the
one in the above-described conventional magnetic tape cartridge;
and in FIGS. 4 through 6 parts corresponding functionally to those
already described with reference to FIGS. 1 through 3 (the
conventional magnetic tape cartridge) are therefore designated by
the same reference numerals or characters.
[0061] As shown in FIG. 4, the shoulder 4c of an upper reel 4 has a
protrusion 4d, and has nine (9) recesses 100 in such a manner that
the recesses 100 are extended radially outwardly from the outer
cylindrical surface of the protrusion 4d. Each of the recesses 100
is deeper than the conventional one, and an add number of recesses
100 are arranged at equal interval to prevent the mold from
bending.
[0062] On the other hand, a plurality of welding ribs 102, the
number of which is equal to that of the aforementioned recesses
100, are arranged along the peripheral edge of the central hole of
the lower reel 5 at equal intervals.
[0063] Each of the welding ribs 102 is triangular extending
downwardly from the lower flange 5a, and it is equal in volume to
each of the recesses 100.
[0064] Therefore, in the gaps between the recesses 100, the whole
width W of the shoulder 4c can be utilized as a stopper surface. As
shown in FIG. 6(a), when the lower reel 5 is slightly turned about
the upper reel 4 with the lower reel 5 engaged with the upper reel
4, the protrusions 102 are fixedly fitted in the recesses 100,
respectively. Hence, the upper and lower reels can be subjected to
ultrasonic welding.
[0065] Accordingly, under this condition, an ultrasonic horn is
pushed against the whole periphery of the opening of the lower reel
5 as indicated by the arrow; that is, the upper and lower reels are
subjected to ultrasonic excitation under a predetermined
pressurizing force F. As a result, the welding ribs 102 are molten
in the recesses 100, thus filling the recesses 100. Finally, as
shown in FIG. 6(b), the lower flange 5a abuts against the whole
surface of the shoulder 4c. Thus, the lower reel 5 is positioned
with respect to the upper reel 4.
[0066] In this case, with respect to the contact area in the
direction of diameter, the whole width W of the shoulder can be
utilized. Therefore, the upper and lower reels are maintained high
in parallelism. The welding area is smaller than that of the
conventional magnetic tape cartridge; however, the welding depth is
larger, and the number of welding parts is plural. Hence, the
welding strength is equal to that of the conventional magnetic tape
cartridge. Furthermore, because of the increase in welding area,
the difference between the load during the welding operation and
that after the welding operation is great, which makes it possible
to readily achieve the detection of the completion of the welding
operation with a sensor or the like.
[0067] Second Embodiment
[0068] Another example of the magnetic tape cartridge, a second
embodiment of the invention, will be described with reference to
FIGS. 7 and 8. As is seen from those figures, the number and
interval of the recesses 100 of the upper reel 4 are equal to those
in the above-described first embodiment. However, it should be
noted that the welding ribs 104 of the lower reel 5 are extended
spirally from the periphery of the central opening. This structure
positively prevents the lower reel from turning about upper reel
when compared with that of the first embodiment.
[0069] Third Embodiment
[0070] Another example of the magnetic tape cartridge, a third
embodiment of the invention, will be described with reference to
FIG. 9. In the third embodiment, in the shoulder 4c, the number of
recesses 106 is only five (5); however, they are spread
circumferentially. On the other hand, in the lower reel 5, welding
ribs 108 are protruded at equal intervals in correspondence to the
recesses 106 in such a manner that they 108 are coaxial with the
periphery of the central hole.
[0071] In the third embodiment, the welding area is larger than
that in the above-described embodiments, while the stopper area is
smaller. Therefore, the length of the stopper surface as viewed in
the direction of diameter is substantially equal to that in the
above-described embodiment. Hence, the upper and lower reels are
maintained high in parallelism.
[0072] As is apparent from the above description, in the magnetic
tape cartridge of the invention, the reel welding characteristic is
maintained high, and during the welding operation the area of the
stopper surface is sufficiently spread: Hence, the upper and lower
reels are sufficiently high in parallelism. This feature prevents
the lowering of production yield which may be caused by surface
play.
[0073] Fourth Embodiment
[0074] Another example of the magnetic tape cartridge, a fourth
embodiment of the invention, will be described with reference to
FIGS. 10 and 11. In the fourth embodiment, the reel configuration
is fundamentally equal to that in the prior art. Therefore, in
FIGS. 10 and 11, parts corresponding functionally to those already
described with reference to FIGS. 1 through 3 are therefore
designated by the same reference numerals or characters.
[0075] Similarly as in the case of the conventional magnetic tape
cartridge, an over-flow preventing stopper ring 4e is formed around
the periphery of the shoulder 4c of the upper reel 4. On the inner
periphery of the stopper ring 4e, a barrier 200 (higher than the
stopper ring 4e) is formed in such a manner that it is protruded
from the stopper ring 4e.
[0076] Between the stopper ring 4e and the protrusion 4d, a groove
202 is formed coaxial with the stopper ring in such a manner that
it is deeper. The inner bottom surface of the groove 202, as shown
in FIG. 11, is a roughened surface 204.
[0077] On the other hand, the welding rib 5b of the lower reel 5
has welding section 206 on the end which is substantially
triangular in section and engaged with the aforementioned deep
groove 202. And the outer periphery of the welding rib 5b has a
recess 208 in such a manner that the former is coaxial with the
latter, and the recess 208 is labyrinth-engaged with the
aforementioned barrier 200.
[0078] Hence, when the lower reel 5 is set on the upper reel 4,
those reels are labyrinth-engaged with each other, and the end of
the welding section 206 is abutted against the roughened surface
204, thus providing a frictional force which prevent the
circumferential movement of the reels. Hence, the reels can be
subjected to the welding operation immediately. The relative
surface roughness of the roughened surface 204 to provide the
frictional force is preferably 5 to 100 .mu.m in Rz (ten-point
average roughness), more preferably 8 to 70 .mu.m, and most
preferably 10 to 50 .mu.m.
[0079] In the following process, the upper and lower reels are
subjected to ultrasonic excitation while being pressurizing with
the ultrasonic horn. As a result, the welding section 206 abutted
against the deep groove 202 is molten beginning with its end, and
the deep groove 202 is also partially molten. The molten resin
flows to spread in the deep groove 202, and tends to flow over the
deep groove 202. However, the amount of over-flow is relatively
small because the distance between the shoulder of the welding rib
5b and the edge of the deep groove 202.
[0080] As the process advances, the molten resin caused to flow
over the deep groove 202 tends to pass through the gap between the
barrier 200 and the recess 208; however, since the gap is further
reduced, the molten resin is detained in the gap between the
barrier 202 and the welding rib 5b, and between the welding rib 5b
and the periphery of the protrusion. Under this condition, the
pressure torque variation is detected, and the ultrasonic work is
accomplished. After the work, the molten material is solidified by
cooling, so that the upper and lower reels 4 and 5 are provided as
one unit.
[0081] Fifth Embodiment
[0082] Another example of the magnetic tape cartridge, a fifth
embodiment of the invention, will be described with reference to
FIG. 12.
[0083] The fifth embodiment is different from the fourth embodiment
only in that, instead of the roughened surface 204, a roughened
portion 210 is formed which comprises a number of ribs which are
radially outwardly extended. Similarly as in the above-described
embodiment, when the welding portion 206 is engaged with the
roughened portion 210, the lower reel is prevented from turning
with respect to the upper reel. In this connection, it is
preferable that the height of each of the ribs forming the
roughened portion 210 is in a range of from 10 .mu.m to 50
.mu.m.
[0084] As is apparent from the above description, the magnetic tape
cartridge of the invention is advantageous in the following points:
Even if, after the lower reel is set on the upper reel, those reels
are subjected to ultrasonic treatment, the resultant vibration will
never turn the reels. This feature shortens the time required for
ultrasonic treatment, and the metal mold for the magnetic tape
cartridge of the invention is not intricate in construction when
compared with the one for the conventional magnetic tape
cartridge.
[0085] Sixth Embodiment
[0086] Another example of the magnetic tape cartridge, a sixth
embodiment of the invention, will be described with reference to
FIGS. 13 and 14. In the sixth embodiment, the reel is fundamental
equal in configuration to the one in the conventional magnetic tape
cartridge. In FIGS. 13 and 14, parts corresponding functionally to
those already described with reference to the prior art are
therefore designated by the same reference numerals or
characters.
[0087] Similarly as in the case of the conventional magnetic tape
cartridge, an over-flow preventing stopper ring 4e is protruded
from the outer periphery of the shoulder 4c of the upper ring 4.
Inside the stopper ring 4e, a barrier 300 (larger in height than
the former) is protruded in such a manner that it is extended along
the stopper ring 4e. A deeper groove 302 is formed between the
stopper ring 4e and the protrusions 4d in such a manner that the
groove 302 is coaxial with the stopper ring 4e and the protrusion
4d.
[0088] On the other hand, welding portions 304 are extended from
the end of the welding rib 5b of the lower reel 5. The welding
portions 304 are each substantially triangular in section, and are
engaged with the aforementioned deep groove 302. The outer
periphery of the welding rib 5b has a recess 306 which is
labyrinth-engaged with the barrier 300. The recess 306 is arranged
coaxial with the welding rib 5b.
[0089] Hence, as shown in FIG. 14(a), when the lower reel 5 is set
on the upper reel 4, those reels are labyrinth-engaged with each
other.
[0090] Under this condition, as shown in FIG. 14(b), the upper and
lower reels are subjected to ultrasonic excitation while being
pressurizing (the pressurizing force F) with the ultrasonic horn.
As a result, the welding section 104 abutted against the deep
groove 302 is molten beginning with its end, and the deep groove
302 is also partially molten. The molten resin (indicated by a
group of dots in FIG. 14(b)) flows to spread in the deep groove
302, and tends to flow over the deep groove 302. However, the
amount of over-flow is relatively small because the distance
between the shoulder of the welding rib 5b and the edge of the deep
groove 302.
[0091] As the process advances, the molten resin caused to flow
over the deep groove 302, as shown in FIG. 14(c), tends to flow
through the gap between the barrier 300 and the recess 306;
however, since the gap is further reduced, the molten resin is
detained in the gap between the barrier 302 and the welding rib 5b,
and between the welding rib 5b and the periphery of the protrusion
4d. Under this condition, the pressure torque variation is
detected, and the ultrasonic work is accomplished. After the work,
the molten material is solidified by cooling, so that the upper and
lower reels 4 and 5 are provided as one unit.
[0092] In the above-described embodiment, the ultrasonic welding
operation is carried out with the welding portion 304 of the
welding rib 5b abutted against the deep groove 302. This is to
double the labyrinth effect. However, the above-described
construction can be simplified with the same effect. That is,
merely by adding the barrier 300 and the recess 306 to the
structure of the prior art, the over-flow preventing effect can be
obtained.
[0093] As is apparent from the above description, in the magnetic
tape cartridge of the invention, merely by modifying the
configuration of the reel the molten resin can be prevented from
flowing over the outer periphery of the boss section; that is, the
lowering of production yield attributing to the over-flowing of the
molten resin can be positively prevented.
[0094] While there has been described in connection with the
preferred embodiments of the invention, it will be obvious to those
skilled in the art that various changes and modifications may be
made therein without departing from the invention, and it is aimed,
therefore, to cover in the appended claims all such changes and
modifications as fall within the true spirit and scope of the
invention.
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