Magnetic tape cassette molding apparatus

Details Magnetic tape cassette molding apparatus Magnetic tape cassette molding apparatus

2001-06-07

2002-11-05

Heitbrink, Tim (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With product ejector

C264S334000, C425S577000

Reexamination Certificate

active

06474978

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for molding a magnetic tape cassette such as a video tape cassette and the like, and more particularly, for molding guide walls of a brake member, in the magnetic tape cassette, which prevents a magnetic tape from loosening. In addition, the present invention relates to an apparatus in which the above-mentioned molding method is operable.
2. Description of the Related Art
Conventionally, there are known various types of magnetic tape cassettes that can be used in a video deck. As an example of the magnetic tape cassettes, there are relatively small-sized magnetic tape cassettes used in a digital video cassette (DVC).
FIG. 4
is an exploded view of a general magnetic tape cassette
30
that is structured in the following manner. A pair of reels
32
a
and
32
b
is rotatably disposed on a lower half-case
31
(hereinafter referred to as “lower half”). Around the two reels
32
a
and
32
b
, a magnetic tape T (not shown in
FIG. 4
) is wound. The magnetic tape T is guided by two tape guides
33
a
and
33
b
located at the right and left sides of the front end of the cassette
30
. The two tape guides
33
a
and
33
b
allow the magnetic tape to pass through an opening
34
formed on the front end side of the lower half
31
. As shown in
FIG. 4
, teeth
35
a
and
35
b
are formed along the entire peripheral edges of the lower flanges
32
L
a
and
32
L
b
of the two reels
32
a
and
32
b.
As also shown in
FIG. 4
, a brake member
38
is provided between the two reels
32
a
and
32
b
in a space
36
located on the rear side of the lower half
31
. The brake member
38
prevents the magnetic tape T from loosening when the magnetic tape cassette
30
is not loaded in a video deck (not shown), but is instead located in a storage place or is being carried.
A pair of securing pawls
37
a
and
37
b
is provided near the front end of the brake member
38
. The securing pawls
37
a
and
37
b
form a lock member to lock the rotation of the reels
32
a
and
32
b
together with the brake member
38
. In addition, a compression spring (brake spring)
39
is provided at the rear end of the brake member
38
in the lower half-case
31
. The compression spring is used to urge the brake member
38
towards the front side of the lower half-case
31
.
As shown in
FIG. 4
, an upper half-case
40
(hereinafter referred to as “upper half”) cooperates with the lower half
31
to form the magnetic tape cassette
30
. The upper half
40
includes a lid for covering the opening in the front end portion of the lower half
31
. The lid is composed of an outer lid
41
, an upper lid
42
, and an inner lid
43
. The opening can be freely opened and closed using these lids.
The outer lid
41
of the upper half
40
includes a side plate
44
having a projecting lock pin
45
. Correspondingly, a lid lock
47
, which is rotatably mounted on one side plate
46
of the lower half
31
, locks the outer lid
41
of the upper half
40
by engaging with the lock pin
45
. A plate spring
48
urges the lid lock
47
toward the locking side thereof.
As shown in
FIG. 4
, a rotary shaft
44
b
projects from an inner side of the side plate
44
of the outer lid
41
. A lid spring
49
, which is mounted on the rotary shaft
44
b
, is used to open and close the outer lid
41
. In
FIG. 4
, reference numerals of components other than main components of the magnetic tape cassette
30
are omitted, since descriptions thereof are not believed to be essential for an understanding of the general cassette
30
.
FIG. 5
shows a conventional lock device for locking the rotation of the reels
32
a
and
32
b
of the general magnetic tape cassette
30
described above with reference to FIG.
4
. In the conventional lock device, the brake member
38
is urged in the forward direction, which is the direction in which the compression spring
39
(brake spring) is compressed. The compression spring
39
is supported along the floor surface
31
a
of the lower half
31
shown in
FIG. 4
, and has one end engaged with the floor surface
31
a
and the other end engaged with the rear end of the brake member
38
. The compression spring
39
urges the brake member
38
in the forward direction when the cassette
30
is not loaded in a video deck. An insertion hole
51
is formed substantially in the central portion of the bottom surface
38
a
of the brake member
38
. A lock release pin of the video deck (not shown) is inserted into the insertion hole
51
of the brake member
38
when the magnetic tape cassette
30
is loaded in a video deck, thereby allowing the reels
32
a
and
32
b
to rotate.
A pair of guide walls
52
a
and
52
b
is provided on the left and right positions of the insertion hole
51
, and slidingly guides movement of the brake member
38
. Facing brake member removal-prevention projections
53
a
and
53
b
are provided on the upper ends of the two guide walls
52
a
and
52
b
so as to prevent the brake member
38
from being removed from the cassette
30
.
As described above, the two guide walls
52
a
and
52
b
are conventionally provided on the left and right sides of the brake member
38
. The two guide walls
52
a
and
52
b
are located to the left and right of the insertion hole
51
because it is necessary to facilitate the removal of molds employed in a resin injection-molding method.
FIG. 6
is a cross-sectional view of a metal mold
120
used for explaining the conventional molding method. The metal mold
120
is used to mold the lower half
31
of the cassette
30
, and is composed of an upper mold UM and a lower mold LM. The lower mold LM has a component mold CM for molding inner surfaces of the guide walls
52
a
and
52
b
. As shown in
FIGS. 5 and 6
, if the two guide walls
52
a
and
52
b
are erected on the lower half
31
and are disposed adjacent to the insertion hole
51
, the component mold CM may be easily removed in the direction L
6
after completion of the injection-molding.
However, the location of the pair of guide walls
52
a
and
52
b
has drawbacks in that the brake member removal-prevention projections
53
a
and
53
b
, which are provided on the upper ends of the guide walls
52
a
and
52
b
, do not sufficiently hold the brake member
38
. In other words, the pair of guide walls
52
a
and
52
b
holds only the substantially central portion of the brake member
38
. As a result, the brake member
38
can fly out or slip off from the two guide walls
52
a
and
52
b
due to the urging force of the compression spring
39
in the assembled magnetic tape cassette.
In view of the above-described drawback, it is preferable to support the brake member
38
using two or more pairs of guide walls respectively with brake member removal-prevention projections that are the similar to those identified with reference numerals
53
a
and
53
b
. For example, as shown in
FIG. 2
, if two pairs of guide walls have brake member removal-prevention projections, the brake member
38
can be supported in both the front and rear end portions. However, such an arrangement requires that the two pairs of guide walls should be located far from the is insertion hole
51
.
Moreover, the conventional apparatus and methods cannot be used to injection-mold such a two-pair structure because the component mold CM exists between the two guide walls
52
a
and
52
b
. As described above, the component mold CM is conventionally removed from the insertion hole
51
in the direction L
6
, as shown in FIG.
6
. Therefore, the component mold CM cannot be removed because the brake member removal-prevention projections
53
a
and
53
b
mutually overhang and prevent the component mold CM from being removed in the direction L
6
.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the above-mentioned drawbacks found in the conventional magnetic tape cassette molding method and apparatus. That is, it is an object of the present invention to provide a magnetic tape cassette molding method that

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