CA1144727A

CA1144727A - Tubular parison of synthetic resin for molding biaxially oriented bottle-shaped container

Info

Publication number: CA1144727A
Application number: CA000347628A
Authority: CA
Inventors: Akiho Ota; Fumio Negishi
Original assignee: Yoshino Kogyosho Co Ltd
Current assignee: Yoshino Kogyosho Co Ltd
Priority date: 1979-05-01
Filing date: 1980-03-13
Publication date: 1983-04-19
Also published as: GB2048757B; CH636298A5; IT1143079B; IT8048222A0; AU541924B2; NL8001418A; FR2455507B1; FR2455507A1; JPS55146718A; DE3008883A1; GB2048757A; AU5613580A

Abstract

ABSTRACT OF THE DISCLOSURE
A high mechanical strength tubular parison for use in molding a bottle-shaped container of biaxially oriented synthetic resin having walls formed with uniform thickness. The parison is formed by means of a mold having a gate opposite a core having a lower end perpendicular to the longitudinal axis of the parison, and in which the lower end has a larger diameter than the gate.

Description

~4'7~27 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 4'7Z7 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.

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 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A tubular parison of synthetic resin for use in molding a biaxially oriented cylindrical bottle-shaped container having a bottom wall with an inner and outer surface, an open upper end and a gate run retained at the center of the bottom wall outer surface, said bottom wall inner surface being flat and disposed perpendicularly WITH
respect to the longitudinal axis of the parison and having a diameter larger than the diameter of the gate run,

2. A tubular parison according to claim 1, wherein said parison is formed of saturated polyester.

3. A tubular parison according to claim 1, wherein the lower portion thereof is formed in inverted tapered shape with the bottom outer diameter formed smaller than the upper body diameter.

4. A method of forming a parison of synthetic resin comprising providing a mold and core therefore wherein an end surface portion of the core is flat and located opposite a gate used to inject the resin into mold, said flat end portion of the core being larger in diameter than said gate and injecting the resin into the mold directing the same onto said core flat surface and in a direction perpendicular thereto whereby the injected resin strikes the flat surface and is directed thereby radially outwardly into the mold.