Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a bottle-shaped container of
synthetic resin and, more particularly, to a tubular parison Eor molding
a bottle-shaped container of biaxially oriented synthetic resin.
A bottle formed from synthetic resin such as, for example,
saturated polyester has advantages such as no oozing of detrimental sub-
stances such as solvents or the like and no production of toxic gas when
incinerated after disposal of the bottle. The bottle is generally biaxially
oriented and molded to enhance i~ts mechanical strength of its material.
It is convenient in molding a biaxially oriented bottle to provide a
prernoulded tubular parison (or cold parison) of synthetic resin with a
bottom at one end and with an upper opening at the other end by an
injection molding process to heat the tubular parison at a temperature adapted
for the orientation, and to then biaxially orient it in a blowing mold.
It is necessary in providing a biaxially oriented bottle having
superior strength from the tubular parison to substantially equalize the
thickness of the portion to be oriented of the tubular parison. If the
tubular parison is thick along one side wall and thin along the other sLde
wall, the bottle produced from the tubular parison thus formed is also
similarly formed having an irregular thickness profile, to thus cause the
bottle to lose its strength.
Accordingly, it is a primary object of this invention to
provide a tubular parison for molding a bottle-shaped container of biaxially
oriented synthetic resin which eliminates the aforementioned disadvantages of
the convention tubular parison.
It is another object of this invention to provide a tubular
parison for molding a bottle-shaped container of biaxially oriented synthetic
resin which does not displace the center axis of the core from the center
line of the cavity of injection molds so as to prevent irregular thickness
t~
at the parison body wall.
It is still another object of this invention to provide a
tubular parison for molding a bottle-shaped container of biaxially oriented
synthetic resin which incorporates superior mechanical strength with
uniform thickness of the body wall.
Thus by one aspect of this invention there is provided a
tubular parison of synthetic resin for use in molding a biaxially oriented
cylindrical bottle-shaped container having a bottom wall and an upper
opening and with a gate run retained at the center of the bottom wall
surface comprising: an inner bottom wall surface ~ormed perpendicularly
with respect to the longitudinal axis thereof and having a diameter larger
than the diameter of the gate run.
Fig. 1 is an elevational sectional view of the conventional
tubular parison;
Fig. 2 is a partial elevational sectional view of injection
molds for molding the conventional parison shown in Fig. l;
Fig. 3 is an elevational sectional view of the tubular parison
molded according to this invention;
Fig. 4 is a partial elevational sectional view of injection
molds for molding the parison of this invention shown in Fi~. 3;
Fig. 5 is a view similar to Fig. 3 but showing another
preferred embodiment of the tubular parison of this invention;
Fig. 6 is a view similar to Fig. ~ but showing the molds for
molding the parison shown in Fig. 5; and
Fig. 7 is a sectional view o~ another example of the molds
for molding the parison of this invention.
Referring now to the drawings, a conventional tubular parison 1
is shown in Fig. 1 and is formed with a recess spherical profile 3 on the
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inner surface of the bottom wall 2 thereof. This parison 1 incorporates
a body 4 of cylindrical shape, a neck portion 5 with threads 6 formed
thereon, and a gate run 7 retained at the center of the bottom wall 2 as
formed at its injectlon molding process. As further shown in Fig. 2,
the tubular parison 1 is molded by inserting a core 10 into a cavity 9
formed at the injection molding molds 8, 8 and injecting molten resin
material through a gate 11 opened at the center of the bottom of the
cavity 9. The core lO is formed at its bottom end with projected spherical
profile 12 corresponding to the recess spherical profile on the inner
surface of the bottom wall of the tubular parison. Accordingly, the
molten resin material thus injected into the cavity is press-fitted along
the outer surface of the core as it is, and is thusfilled in the cavity
between the molds 8, 8 and the core 10. If the center line of the cavity 9
of the molds 8, 3 does not coincide with the center axis of the core 10
at this time, the thickness of the tubular parison body wall becomes irreg-
ular. If the gate 11 is not disposed at the center line thereof along the
extension line of the center axis of the core 10, the core 10 tends to
incline at the center axis thereof with respect to the center line of the
cavity 9 due to the injecting pressure of the molten resin mater:ial since
the core 10 is long to thereby cause the tubular parison to be molded with
irregular thickness at the body wall. Now with reference to Fig. 3 showing one
preferredembodiment of the tubular parison 21 constructed according to this
invention, wherein like reference numerals designate the same parts in
the following views, the bottom wall 22 of the tubular parison 21 is formed
or molded perpendicularly with respect to the longitudinal axis of the
parison 21 at the inner surface thereof. The orthogonal surface 23 on the
inner surface of the bottom ~all 22 of the parison 21 with respect to the
longitudinal axis of the parison 21 is formed larger indiameter than the
gate run 27 on the outer bottom wall surface of the parison 21.
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As shown in ~ig. 3, the outer surface profile at the lower
portion of the parison body 24 may be formed in projected spherical shape,
or may also be, as shown in Fig. 5, formed in inverted tapered shape
with the bottom outer diameter formed smaller than the upper body diameter.
In order to form or mold the tubular parison thus shaped, the
core 30 is, as illustrated in Figs. 4 , 6 and 7, formed at the bottom
surface thereof with a horizontal surface 32 with respect to the longi-
tudinal center axis of the core 30 in such a manner that the horizontal
bottom surface 32 thereof is larger in diameter than the gate 31 of
the molds 28.
When the molds 28 and core 30 are thus for~ed, the molten
resin material lnjected through the gate 31 into the cavity 29 of the
molds 28 makes contact with the horizontal bottom surface 32 of the core
30, and then spreads peripherally outwardly along the horizontal bottom
surface 32 to thus fill in the cavity 29.
It should be understood from the foregoing description that
since the tubular parison of this invention is mol~ed perpendicu:Larly :Erom
the inner bottom wall surface with respect to the longitud:Lnal ax:i.s of the
parison in such a manner that the orthogonal surface 23 thereof is formed
larger in diameter than the gate run 27 on the outer bottom wall surface
thereof, the molten resin material injected through the gate into the
cavity 29 immediately makes contact with the horizontal bottom surface 32,
and then spreads peripherally outwardly along the horizontal surEace ~o
thus fill in the cavity with the result that the core i5 not urged
i,rregularly in one direction by the injecting pressure of the -molten resin
material to cause the core to be displaced axially from the center line of
the cavity of the molds as occurred at the conventional parison so that
the formed parison does not have an irregular thickness at the parison body
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wall. It should also be appreciated that the tubular parison thus
biaxially oriented into a bottle-shaped container can be blow-molded into
superior bottle-shaped container product having high and uniform mechanical
strength at the body wall with uniform thickness thereat.
