Mold for compression molding a resin article

Details Mold for compression molding a resin article Mold for compression molding a resin article

1994-02-02

2001-09-25

Heitbrink, Jill L. (Department: 1732)

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

C264S328110, C425S546000

Reexamination Certificate

active

06294121

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mold for compression molding a resin article. More particularly, the present invention relates to a mold for compression molding a resin into a molded resin article, which mold can produce a molded resin article while preventing squeeze-out of the resin melt from the mold and leaving no air in the mold cavity during molding.
2. Description of the Related Art
As a method for compression molding a resin into a molded article, there is known a method comprising supplying a resin melt to a cavity formed in a mold consisting of male and female mold portions and closing the male and female mold portions to mold the resin.
In the conventional method, the upper (female) and lower (male) molds
21
and
22
are once opened and then closed to mate with each other in the vertical direction V as shown in
FIG. 1A
, whereby a cavity
23
is formed therebetween and the resin melt
24
is compressed. Therefore, a dimensional accuracy of the molds
21
and
22
is strictly defined. In particular, a mold edge
21
a
of the upper mold
21
and a mold edge
22
a
of the lower mold
22
are so designed that no gap is formed in the horizontal direction H or the length L′ of the mated part is made unnecessarily long (see.
FIG. 1B
) whereby the excess resin melt is squeezed out from the end of the edges
21
a
and
22
a
so that, as shown in
FIG. 2B
, the molded article
25
has an irregular shape.
However, if the size accuracy is too strict or the length L′ is too long, air
26
can be trapped in the cavity
23
as shown in
FIG. 1B
, so that, as shown in
FIG. 2A
, the molded article
27
has an underfilld part
28
.
In addition, the edges
21
a
and
22
a
may engage each other and may be damaged.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a mold for compression molding a resin article, which can prevent squeeze-out of a resin melt and also prevent the formation of air pockets in the mold cavity during molding.
Accordingly to the present invention, there is provided a mold for compression molding a resin article, which mold consists of male and female mold portions, wherein, at the time of complete mold closing, the length L in the mold closing direction of a mated parts formed between the outermost wall of said male mold portion and the innermost wall of said female mold portion satisfies the equation:
(
t
1
−t
0
+10)mm≧
L
≧(
t
1
−t
0
)mm
wherein t
1
is a distance (mm) in the mold closing direction at an arbitrary point between the male and female molds when the resin melt first reaches the horizontally mating edge of the male mold, and t
0
is a distance (mm) in the mold closing direction between the same points on the male and female molds as those used for measuring t
1
when the mold closing is complete and wherein the horizontal distance of a mating gap between the outermost wall surface of said male mold and the innermost wall surface of said female mold is from 0.02 to 0.1 mm.


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patent: 4309379 (1982-01-01), Dannels et al.
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patent: 2-052709 (1990-02-01), None
Design of Plastic Moulds and Dies, by Laszlo Sors and Imre Balazs, from “Studies in Polymer Science”, vol. 3, p. 17.
“Duroplaste”, Kunststoff Handbuch 10, by Professor Dr. Wilbrand Woebcken, p. 301.
“Plastics Engineering”, vol. XL No. 10, Oct. 1984, pp. 36 and 37.

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