Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1998-07-24
2001-09-11
Dye, Rena L. (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C360S133000
Reexamination Certificate
active
06287654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a molding mold for molding resin material and, more particularly, to an improvement of a gate portion of the molding mold in an open type hot-runner system, and further to a molding method using the molding mold, an injection molding apparatus to which the molding mold is added, and a product molded by the molding mold.
2. Description of the Prior Art
FIG. 8A
is a plan view showing a half shell of a floppy disk molded by a molding mold adopting an open type hot-runner system in the prior art. The half shell
51
includes recessed portions
52
,
53
formed in a fitting portion
51
a
for fitting a shutter plate. The recessed portions
52
,
53
are formed so that a gate residual (a protruded portion) , if produced upon mold releasing, may not protrude from a surface
54
of the shutter plate fitting portion
51
a.
When actually molded, however, a gate residual portion (resin residual)
55
produced, as illustrated in
FIG. 8B
, extends from the recessed portion
52
and protrudes from the surface
54
, resulting in causing high gate. A gate diameter of a gate portion, through which molten resin flows into a cavity, was 0.7 mm.
If a size of a product increases, it is required that the gate diameter of the molding mold be enlarged in order to flow the sufficient molten resin into the cavity of the mold. As the gate diameter becomes larger, the gate residual is stretched higher, and hence a tendency of occurrence of the high gate increases. Further, when speeding up a molding cycle, the molten resin in the gate portion is not well solidified, and therefore similarly the gate residual portion tends to increase in height.
When the gate residual portion
55
protrudes from the surface
54
of the shutter plate fitting portion
51
a,
there must be a trouble in fitting the shutter plate, which therefore needs a step of removing the protruded portion from the surface of the gate residual portion
55
by a post-process. As a result of an increased number of steps, the productivity declines.
Further, if the resin residual is attached to the gate portion, a flow of the molten resin is hindered, and consequently the cavity is not sufficiently supplied with the resin, with the result that a short shot tends to occur.
For preventing the above high gate, the gate diameter is, it can be considered, reduced down to, e.g. 0.5 mm. If reduced so, however, the short shot might easily occur.
The Japanese Patent Laid-Open Publication No. 5-293857 discloses a nozzle for the hot-runner of a thermoplastic resin mold constructed by, as shown in
FIG. 2
therein, connecting a nozzle tip resin passage
2
a
of a hot-runner
2
of the thermoplastic resin mold to a straight pipe resin passage
5
a
of a spool
5
on a downstream side of the passage
2
a
by use of an eccentric gate
4
, thereby preventing string stretch (resin residual) from occurring in the product.
The above publication shows no counter measure to the high gate and the short shot as shown in FIG.
8
B.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a molding mold capable of preventing high gate and short shot.
It is another object of the present invention to provide a molding method using the molding mold capable of preventing the high gate and the short shot, an injection molding apparatus including the molding mold, and a molded product produced from the molding mold.
The present invention was contrived to obviate the problems pertaining to the high gate and the short shot which are caused when molding a product by use of the molding mold, wherein the present inventor as a result of having absorbed in the researches discovered such an approach to those problems that a plurality of passages are provided in a gate portion through which molten resin flows into a cavity of a molding mold.
According to the first aspect of the invention, a molding mold according to the present invention is provides with a plurality of molds for forming a cavity having a configuration corresponding to a shape of a molded product, and a gate portion, contiguous to the cavity, throughwhichamolten resin flows into the cavity, wherein the gate portion includes a plurality of passages. The number of the passages is, e.g., two.
The molding mold is provided with a plurality of the gate portions. The molding mold is further provided with a gate chip member. The gate chip member includes the gate portion.
Further, the gate portion is so disposed as to protrude into the cavity. With the construction, the surface of the molded product is formed with an impression owing to the gate portion. A plurality of gate residuals corresponding to the plurality of passages are formed within the impression and do not protrude from the impression. The molding mold is further provided with a runner portion, and the runner portion is heated. A hot-runner system can be thereby constructed.
The molding mold further includes a shunting portion, provided between the plurality of passages or between the two passages, for making a flow of the molten resin diverge toward the passages. The shunting portion includes a conical protruded portion or a protruded portion which lies in a diametrical direction of the gate portion.
According to the second aspect of the invention, a molding method of the present invention executes a molding process by use of the molding mold described above.
According to the third aspect of the invention, an injection molding apparatus of the present invention is provided with the molding mold described above, and a resin supply heating unit for pressurizing and supplying the molten resin to the molding mold. The resin supply heating unit includes a heating portion for heating and melting a resin material, a resin material supplying portion for supplying the heating portion with the resin material, and a pressurizing portion for pressurizing the molten resin within the heating portion and supplying the molding mold with the molten resin.
According to the fourth aspect of the invention, a molded product of the present invention is molded by the molding mold described above. In the molded product, a molding surface thereof has an impression formed by the gate portion. A plurality of gate residuals corresponding to the plurality of passages are formed within the impression, and the plurality of gate residuals do not protrude from the impression. For instance, the molded product is a half shell of a floppy disk, and two gate residuals are formed within the impression.
The molded product is provided with a recessed portion formed on the molded surface upon molding, and a plurality of protruded portions formed within the recessed portion. The height of the protruded portions is less than the depth of the recessed portion.
REFERENCES:
patent: 4781879 (1988-11-01), Oishi
patent: 5161081 (1992-11-01), Machida et al.
patent: 5305172 (1994-04-01), Sugiaski et al.
patent: 5307229 (1994-04-01), Sata
patent: 5699905 (1997-12-01), Hara
patent: 57-169518 (1982-10-01), None
patent: 5-237879 (1993-09-01), None
patent: 5-293857 (1993-11-01), None
patent: 6-285919 (1994-10-01), None
Darby & Darby
Dye Rena L.
TDK Corporation
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