Molding method for magnetic tape cassette

A method for image-transfer molding half portions of a casing body of a magnetic tape cassette in which no portions of an image transfer film are left in the cassette holes. The image transfer film includes a base layer, a peeling layer, a protective layer, an ink layer, and an adhesive layer. A band of the image transfer film is pinched between dies for molding said half portion, with the adhesive layer positioned so as to abut an outer surface of the molded half portion. A pair of pins is placed in the dies in a position where a hole is to be formed in the half portion, with an end of one of the pins having a peripheral edge portion projecting in a direction parallel to the longitudinal axis of the pin and forming a recess receiving the end of the other of said pins with a portion of the image transfer film sandwiched therebetween. The ends of the pins cooperate to sever the image transfer film along the peripheral edge except for the base layer so that the base layer can be peeled away leaving no portions of the image transfer film in the holes.

BACKGROUND OF THE INVENTION 
The present invention relates to a magnetic tape cassette, and particularly 
to a method for image-transfer molding the half portions of the casing 
body of a magnetic tape cassette. 
In a magnetic tape cassette, hubs on which a magnetic tape is wound are 
supported in a casing body composed of upper and lower half portions, 
which are usually manufactured by the injection molding of a plastic. 
After the injection molding process, paper or the like on which is printed 
a prescribed design is adhered to the outside surface of each of the upper 
and the lower portions, or the design is directly printed on the outside 
surface. Thus, the manufacture of each of the upper and the lower half 
portions requires separate steps of injection molding and attachment of 
the paper or the like or printing of the design. For this reason, the 
manufacturing process is generally complicated. 
A method for image-transfer injection molding in which a prescribed design 
is printed on the outside surface of each of the upper and lower half 
portions of the casing body of a magnetic tape cassette at the same time 
as the injection molding of the half portion has been developed, as 
disclosed in the Japanese Unexamined Published Utility Model Applications 
Nos. 113281/88 and 118782/88. Such a method will be described with 
reference to FIGS. 5 and 6. 
For the injection molding process, two dies 1 and 2 are set so that the 
recesses 3 and 4 thereof constitute a cavity whose form corresponds to 
that of the upper or lower half portion, and a molten plastic or the like 
is injected into the cavity through a runner 1b. For image transfer, an 
image transfer film 20 having a prescribed design in the form of an ink 
layer is pinched between the dies 1 and 2 so that the film is pushed onto 
the inside surface of the recess 4 of the die 2 when the molten plastic or 
the like is injected into the cavity through the runner 1b. At the time of 
injection, the molten plastic comes into contact with the adhesive layer 
18 of the image transfer film 20, which is composed of a base film 6, a 
peeling layer 7, a protective layer 8, the ink layer 9 and the adhesive 
layer, as shown in FIG. 7, so that the protective layer and the ink layer 
are joined to the surface of the injected material by the adhesive layer. 
After the upper or lower half portion solidifies and is extracted from the 
dies 1 and 2, the base film 6 can be easily peeled off the upper or lower 
half portion because of the presence of the peeling layer 7 so that the 
ink layer 9 coated with the protective layer 8 is left on the outside 
surface of the half portion. The design of the ink layer 9 is thus 
transferred to the outside surface of the half portion. For the injection 
molding process, a pair of nearly cylindrical pins 35 and 36 are fitted in 
the dies 1 and 2 to provide the half portion of the cassette casing body 
with a hole such as a reference hole, a capstan hole and a screw hole. The 
pins 35 and 36 project into the cavity and have their tips in contact with 
each other to form the hole which extends in the direction of thickness of 
the half portion. 
However, when the image transfer film 20 is pinched between the dies 1 and 
2 as shown in FIG. 5, the film is also pinched between the tips of the 
pins 35 and 36. For this reason, when the base film 6 is peeled off the 
half portion after the latter has been removed from the dies 1 and 2, an 
image transfer layer 12, which is composed of the protective layer 8, the 
ink layer 9 and the adhesive layer 18, and which belongs to part of the 
image transfer film 20 and is pinched between the pins 35 and 36, is left 
in the hole as an unnecessary film coupled to the image transfer layer of 
the other part of the image transfer film stuck to the outside surface of 
the half portion. Even if the image transfer layer 12 left as an 
unnecessary film is pierced together with the base film 6 by a sharp-edged 
pin, as disclosed in Japanese Unexamined Published Utility Model 
Application No. 113281/88, it is difficult to completely remove the image 
transfer layer along the inside surface of the hole. Thus, the method of 
image-transfer injection molding requires a step of completely removing 
the image transfer layer 12 following injection molding. This, too, is a 
problem. 
SUMMARY OF THE INVENTION 
The present invention was made in order to solve these problems. 
Accordingly, it is an object of the present invention to provide a 
simplified method for performing the image-transfer injection molding of 
each half portion of a casing body of a magnetic tape cassette through the 
use of an image transfer film. 
In the method provided according to the present invention, image-transfer 
injection molding of each half portion of the casing body of the magnetic 
tape cassette is performed so that at least the image transfer layer of 
the image transfer film is integrally joined to the surface of the half 
portion. The method is characterized in that the peripheral edge of the 
tip of one of several pins, which are fitted in dies so as to form a hole 
in the half portion, projects parallel to the axis of the pin so that a 
recess is provided in the tip of the pin inside the peripheral edge. The 
image transfer layer is torn off by the peripheral edge of the tip of the 
pin along the edge. 
When the image transfer film is pinched between the dies and between the 
tips of the pins, the film is acutely and strongly bent by the projecting 
peripheral edge of the tip of one of the pins so that the part of the 
image transfer layer of the film which is pinched between the tips of the 
pins is torn off from the other part of the layer along the projecting 
peripheral edge. Hence, when the base film of the image transfer film is 
peeled off the half portion after image transfer injection molding, the 
torn-off part of the image transfer layer is peeled off together with the 
base film because it still adheres thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Preferred embodiments of the present invention are hereafter described in 
detail with reference to the attached drawings. 
FIG. 1 is a perspective view of a magnetic tape cassette, the mutually 
coupled upper and lower half portions 10 and 11 of the casing body of 
which are molded by a method of the invention. A pair of hubs 13 on which 
a magnetic tape 15 is wound are-rotatably supported in the casing body of 
the cassette. The upper and the lower half portions 10 and 11 are 
manufactured separately by injection molding. FIG. 2 is a sectional view 
of the cassette taken along a line II--II in FIG. 1. 
The upper and the lower half portions 10 and 11 are composed of bodies 10a 
and 11a made of an injection-molded plastic such as an ABS resin, and 
image transfer layers 12, which are parts of an image transfer film 20 and 
cover the outside surfaces of the bodies, as shown in FIG. 2. It is 
preferable that the image transfer layers 12 cover the edges 10b and 11b 
of the bodies 10a and 11a of the upper and the lower half portions 10 and 
11 as well as the other parts of the bodies to reinforce them. 
The image transfer layer 12 is produced on the outside surface of the body 
.of each of the upper and the lower half portions 10 and 11 simultaneously 
with the injection molding of the body of each of the portions. The 
production of the image transfer layer 12 will now be described. 
Four of each of the upper and the lower half portions 10 and 11 are 
simultaneously manufactured by injection molding using dies 1 and 2 as the 
image transfer film 20 remains pinched between the dies, as shown in FIGS. 
3 and 4. AT that time, the image transfer layer 12 on the outside surface 
of the body of each of the four upper or lower half portions is made up of 
the protective layer 8, ink layer 9 and adhesive layer 18 of the image 
transfer film 20, which is composed of a base film 6, a peeling layer 7, 
the protective layer 8, the ink layer 9 and the adhesive layer 18, as 
shown in FIG. 7. The peeling layer 7, the protective layer 8, the ink 
layer 9 and the adhesive layer 18 are stacked in that order on the inside 
surface of the base film 6, whose outside surface is located opposite that 
of the upper or lower half portion 10 or 11 across the inside surface of 
the base film. The base film 6 is made of a high-molecular material such 
as polyethylene, polyethylene terephthalate, polypropylene is cellulose 
triacetate. The protective layers 8, ink layers 9 and adhesive layers 18 
of the image transfer film 20, which form the image transfer layers 12 on 
the bodies of the four upper or lower half portions 10 or 11 at the time 
of the injection molding of the bodies, are disposed in a pattern 
corresponding to the dies 1 and 2. The image transfer film 20, which is 
shaped as a band, is intermittently and appropriately fed in a direction 
B, as shown in FIG. 4. During injection molding, the film 20 is pinched 
between the die 2 and plate-like holders 21, for example, so that 
appropriate tensile forces A are applied to the film in directions 
indicated in FIG. 4. 
Pins 30 and 31 for forming screw holes 32, capstan holes 33, hub holes 14 
and reference holes 34 are fitted in the dies 2 and 1, respectively, so 
that the tips 37 and 38 of the pins are engaged with each other, as shown 
in FIG. 3. The peripheral edge 39 of the tip of each of the pins 30 
projects parallel to the axis of the pin 30 so that a recess is provided 
in the tip inside the peripheral edge; that is, the cross section of the 
peripheral portion of the tip is shaped as a wedge. The peripheral portion 
of the tip of each of the other pins 31 has a chamfer 40 corresponding to 
the peripheral portion of the tip of the pin 30. 
When the image transfer film 20 is pinched between the dies 1 and 2, the 
film is also pinched between the tips of the pins 30 and 31 so that the 
film is acutely bent by the peripheral edge 39 of the tip of the pin 30 
and the chamfer 40 of the tip of the other pin 31. The peripheral portions 
of the tips of the pins 30 and 31 are appropriately shaped so that the 
image transfer film 20 is severed along the peripheral edges 39 of the 
tips of the pins 30, except for the base film 6, when the image transfer 
film is pinched between the tips of the pins 30 and 31. 
When the molten plastic is injected between the dies 1 and 2 through the 
runner of the die to push the image transfer film 20 onto the inside 
surface of the die 2, the molten plastic comes into contact with the 
adhesive layer 18 of the image transfer film so that the adhesive layer 
causes the protective layer 8 and ink layer 9 of the film to adhere to the 
outside of the upper or lower half portion 10 or 11. However, the parts of 
the protective layer 8, the ink layer 9 and the adhesive layer 18 which 
are pinched between the tips of the pins 30 and 31 are severed from the 
other parts of the layers along the peripheral edge 39 of the tip of each 
pin 30 and are peeled off together with the base film 6 when the base film 
is peeled off the outside surface of the body 10a or 11a of the upper or 
lower half portion 10 or 11. Therefore, when the base film is peeled away, 
no parts of the protective layer 8, the ink layer 9 and the adhesive layer 
18, which are pinched between the pins 30 and 31 are left in the screw, 
capstan, hub or reference hole 16. 
The present invention is not limited to the above-described embodiment, but 
may be practiced or embodied in other various ways without departing from 
the spirit or essential character thereof. For example, the peripheral 
portion of the tip of each of the pins 30 can be provided with a chamfer, 
and the peripheral edge of the tip of each of the other pins 31 made to 
protrude so that a recess is provided in the tip inside the peripheral 
edge. The cross section of the projecting peripheral portion of the tip of 
the pin 30 need not be wedge shaped, but may be shaped otherwise as far as 
the parts of the layers pinched between the tips of the pins 30 and 31 are 
severed from the other parts of the layers along the projecting peripheral 
edge of the tip of the pin 30 when the image transfer film is bent when it 
is pinched between the tips of the pins. 
In the magnetic tape cassette molding method provided according to the 
present invention, the peripheral edge of the tip of one of several pins, 
which are fitted in dies so as to form a hole in the half portion of the 
casing body of a magnetic tape cassette, projects parallel to the axis of 
the pin so that a recess is provided in the tip of the pin inside the 
peripheral edge thereof. As a result, when an image transfer film is 
pinched between the dies, the parts of the layers of the film which are 
pinched between the tips of the pins are acutely and strongly bent by the 
tips of the pins so that the parts are severed from the other parts of the 
layers along the projecting peripheral edge of the tip of the pin. For 
that reason, the torn-off parts of the layers are peeled off together with 
the base film of the image transfer film when the base film is peeled from 
the outside surface of the half portion of the cassette casing body. 
Therefore, no parts of the layers which are pinched between the tips of 
the pins at the time of the molding of the half portion of the cassette 
casing body are left in the hole after the molding as an unnecessary film 
coupled to the image transfer layer on the outside surface of the half 
portion. Consequently, no separate step of removing the parts of the 
layers from the half portion following image-transfer molding is needed. 
The manufacture of the half portion is thus simplified to provide a 
cassette of good design at a lower cost.