Television – Video display – Cabinet or chassis
Reexamination Certificate
1998-06-30
2001-04-24
Cuomo, Peter M. (Department: 3624)
Television
Video display
Cabinet or chassis
C312S007200, C264S328100
Reexamination Certificate
active
06222594
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to injection molding processes, and more particularly, to a runner apparatus which is incorporated into a part molded by an injection molding process.
BACKGROUND OF THE INVENTION
Materials such as plastics are frequently molded into desired shapes through the use of injection molding equipment having an injection unit and a clamping unit. In a conventional injection molding process, a pellet or powder resin is melted within a heating chamber of the injection unit. The injection unit further includes a hydraulic piston or ram which pushes the melted plastic past a “torpedo” or spreader that spreads the melted plastic. This enables improved thermal contact with the heating chamber and thus improves the flow of the melted plastic. The melted plastic then converges at a nozzle which is connected to a sprue located within the mold. The sprue is connected to a gate by a runner that is formed in the mold through which the melted plastic flows. The gate serves to direct the flow of melted plastic into a mold cavity to thus form a desired part. Additionally, the gate limits backflow of the melted plastic. Further, the clamping unit provides a clamping force to hold the mold together during the injection molding process. In a mold type known as a cold runner mold, the melted plastic left in the runner is allowed to cool and solidify. This material is then later separated from the part and may be recycled for later use.
Projection televisions, such as rear projection televisions, typically include relatively large and/or asymmetric parts which are fabricated using injection molding techniques. Referring to
FIG. 1
, a front portion
12
and a rear mirror cover
14
of a rear projection television
10
fabricated by an injection molding process are shown. It is noted that the front portion
12
may be either a cabinet or a beznet. A mirror
16
is used in such televisions for reflecting an image onto a screen. The mirror
16
includes a first reflection surface
18
and a mounting surface
20
. The mirror cover
14
includes an inner surface
22
having first
24
, second
26
, third
28
and fourth
30
mirror mounting areas which may include either mounting blocks or bosses. The mounting areas
24
,
26
,
28
,
30
are positioned in an upper area of the inner surface
22
. In use, the mounting surface
20
is positioned upon the mounting areas
24
,
26
,
28
,
30
. Upper
32
and lower
34
mirror holders are then used to affix upper and lower horizontal portions, respectively, of the mirror
16
to the mounting areas
24
,
26
,
28
,
30
.
It is desirable that the parts formed by the injection molding process are uniformly and consistently molded. However, this is difficult to achieve due to the uneven filling of polymer within the mold, especially in relatively large and/or asymmetric parts. Several methods have been utilized to increase the flow of melted plastic so as improve part uniformity and consistency. In one method, higher injection pressures and/or clamping forces are used in order to improve polymer homogeneity. However, this necessitates the use of larger capacity injection molding equipment which increases costs. Other techniques include the use of a hot runner system having heated runners and molds having multiple polymer entrance points. However, these techniques also increase costs since molds incorporating these features are substantially more complicated to fabricate.
SUMMARY OF THE INVENTION
A method of forming a part by injection molding is disclosed. The method includes the step of providing injection molding equipment having a sprue for supplying melted plastic. In addition, the method includes the step of providing a mold for forming the part, wherein the mold is adapted for forming a runner integrally with the part and wherein the mold is connected to the sprue. Further, the method includes the step of injecting the melted plastic into the mold so as to form the part and the runner such that the runner is integrally formed with the part.
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawing.
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patent: 5402263 (1995-03-01), Kita et al.
patent: 5580146 (1996-12-01), Maslow
patent: 5629745 (1997-05-01), Naito et al.
patent: 5656307 (1997-08-01), Naito et al.
patent: 5663774 (1997-09-01), Baik
patent: 5669681 (1997-09-01), Ishikawa et al.
patent: 5719548 (1998-02-01), Stirling et al.
patent: 5730512 (1998-03-01), Heirich
patent: 5786933 (1998-07-01), Iwai et al.
patent: 5806970 (1998-09-01), Giorgianni et al.
patent: 6039912 (2000-03-01), Ohira et al.
Corn Roger Gordon
Higgs Jeffrey Warren
Ishikawa Takayasu
Kobayashi Seijiro
Cuomo Peter M.
Mayer Fortkort & Williams
Sony Corporation
Tran Hanh V.
Williams Esq. Karin L.
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