Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1999-12-22
2002-08-27
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, C425S555000, C425S575000, C425S589000, C425S593000
Reexamination Certificate
active
06440351
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a molding die drive unit for advancing and retracting at least a part of a die to change a volume of a cavity provided in the die for compressing or expanding (enlarging volume) a resin in the die during injection molding, injection compression molding, press molding, large blow gas-injection molding, multi-layered molding, foam molding thereof, and expansion molding of glass-fiber containing resin; a molding unit incorporating the molding die drive unit; and a molding method using the molding unit.
BACKGROUND ART
In injection compression molding, molten resin is loaded inside a die closed with a predetermined compression margin retained and, subsequently, a compression force is applied to the molten resin filled in the die by clamping the die for rendering shape.
According to the injection compression molding, since the molding process can be conducted by a low resin injection pressure and in-mold pressure can be made uniform, warp and distortion are not caused to the molding product, thus being capable of obtaining molding products having good shape even with small thickness and causing less damage to a surface member during surface member integrating molding.
A molding machine used for the injection compression molding generally has a clamp unit for advancing a movable die provided to the molding machine movably toward a stationary die fixed to the molding machine, and a compression unit for compressing the molten resin filled inside the die.
As shown in Japanese Patent Publication Laid-Open No. Sho 57-95429 and Japanese Patent Publication Laid-Open No. Sho 60-122128, a conventional compression unit has a movable portion for increasing and decreasing a volume of a die cavity inside the die and a pin abutted to the movable portion through which the movable portion is advanced to reduce the volume of the cavity so that the molten resin filled inside the die is compressed.
For advancing the movable portion, a pair of slant member having mutually touching slant surfaces slanting relative to advancing direction of the movable portion is disposed along an advancing direction thereof and one of the slant members is moved in a direction orthogonal with the advancing direction of the movable portion to generate compression force.
Since injection compression molding is impossible for an ordinary die having no movable portion thereinside, such compression unit lacks general-purpose properties.
In order to solve the above problems, the Applicant of the present application has proposed a compression unit
75
having unitized mechanism for pressing a movable die
71
toward a stationary die
72
being capable of attaching and detaching between the movable die
71
and a clamp unit
74
(Japanese Patent Publication Laid-Open No. Hei 7-164500).
The compression unit
75
has a pair of slant member
77
and
78
disposed along the compressing direction both having a slant surface
76
slanting toward compressing direction. In the slant members, the slant member
78
on the clamp unit
74
side is advanced toward the slant member
77
by a cylinder unit
79
to generate compression force.
According to the compression unit
75
, the entire thickness can be made relatively small as compared to the unit described in the Japanese Patent Publication Laid-Open No. Sho 57-95429 etc., which can be attached to an ordinary injection molding machine together with the die, thereby enabling injection compression molding even with an ordinary die having no movable portion installed therein so that general purpose properties of the molding machine can be improved.
However, since the above compression unit
75
converts drive force direction of the cylinder unit
79
by slidably moving the slant surfaces
76
of the relatively moving slant members
77
and
78
, friction loss is increased, which result in low mechanical efficiency (50 to 70%) of the unit.
Further, in a molding method accompanying retraction of the movable die during molding process such as the foam molding which requires foaming of foaming agent by enlarging the volume of the cavity during injection or after injection, since the slide resistance of the slant members
77
and
78
is increased by the pressure of the resin injected into the die and since frictional force between the slant members
77
and
78
is static friction, large strength is required for initiating retraction of the slant member
78
for resisting against the static friction.
On the other hand, when the slant member starts moving, the frictional force between the slant members
77
and
78
changes from the static friction into dynamic friction and the slide resistance rapidly decreases.
Accordingly, moving speed is not stabilized and smooth relative movement of the slant members
77
and
78
is difficult, so that minute adjustment of the moving speed and position of the movable die are impossible, proving not suitable for molding method accompanying retraction of the movable die during molding process.
Further, since the pair of the slant members
77
and
78
are linearly disposed along the compressing direction, there is natural limit for reducing the thickness of the compressing unit.
An object of the present invention is to provide a molding die drive unit being capable of compressing and expanding the molten resin injected into the die and having reduced thickness and superior mechanical efficiency, a molding unit installed with the molding die drive unit and molding method using the molding unit.
DISCLOSURE OF THE INVENTION
The present invention is a unitized die driving unit detachably attached to any one of the stationary die and the movable die that intends to achieve the above object by providing a main cylinder used for pressurization and a plurality of sub cylinder unit used for pressurization and high-speed movement around the main cylinder unit.
More specifically, a molding die drive unit according to the present invention is for forming a cavity between a stationary die and a movable die for molten resin to be loaded, the molding die drive unit being detachably attached to either the stationary die or the movable die for moving a part of or entirety of at least one of the stationary die and the movable die to be advanced and retracted relative to the cavity. The molding die drive unit is characterized in having: a large-diameter main cylinder unit; and a plurality of small-diameter sub cylinder unit disposed around the main cylinder unit being spaced apart with each other.
In the present invention, the molding die drive unit advances and retracts a part of entirety of the stationary die or the movable die, or, a part of the stationary die or the movable die relative to the cavity. Advancement or retraction of the part of the stationary die or the movable die refers to advancement and retraction of a slide die when the dies are constructed of die body and the slide die disposed slidably relative to the die body.
According to the present invention, the molten resin is injected into the cavity after closing the stationary die and the movable die. After a predetermined time after initiating injection of the molten resin, the main cylinder unit and the sub cylinder unit are driven to advance and retract at least a part of the stationary die and the movable die relative to the cavity to compress or expand (volume enlargement) the molten resin in the cavity for rendering shape.
Small-diameter sub cylinder unit is used for advancing and retracting at least a part of the stationary die or the movable die to a predetermined position. In other words, hydraulic fluid (hydraulic pressure) is supplied from an external hydraulic source to the sub cylinder. At this time, by allowing circulation of the hydraulic fluid to the main cylinder unit, the main cylinder unit advances and retracts in accordance with advancement and retraction of the sub cylinder unit.
On the other hand, for pressurizing the molten resin in the cavity, not only the sub cylinder unit is advanced but also the large-diameter main cylinder unit is adva
Abe Tomokazu
Matsui Tsuneo
Saito Yoshiaki
Tamura Shigeki
Flynn ,Thiel, Boutell & Tanis, P.C.
Heitbrink Jill L.
Idemitsu Petrochemical Co. Ltd.
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