Receptacles – Sidewall structure – Contoured sidewall
Reexamination Certificate
2002-05-13
2003-10-07
Pollard, Steven (Department: 3727)
Receptacles
Sidewall structure
Contoured sidewall
C220S675000, C206S315900, C215S382000
Reexamination Certificate
active
06629623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
A present invention relates to a pressure wide-mouth container made of a synthetic resin and a method of manufacturing the pressure wide-mouth container. More particularly, the present invention relates to a container which is used to store tennis balls under pressure. To seal the container, a flange portion is projected from the periphery of a wide mouth of the container having a diameter almost equal to that of the cylindrical body portion thereof. A lid made of metal is tightened against a flange portion, with the lid doubly covering the flange portion.
2. Description of the Related Art
As a container containing an object such as tennis balls desired to be stored under pressure, a metal can made of a metal material has been used. In recent years, instead of the metal can, there is the wide use of a container made of a synthetic resin manufactured by blow-molding a synthetic resin such as polyethylene terephthalate or the like.
In using a container made of a synthetic resin, such as a pressure container for storing tennis balls or the like under pressure, similarly to the metal can, it is necessary to put the object in the container under pressure, close the container by tightening the metal lid against the flange portion projecting from the edge of the opening of the container, with the flange portion being doubly covered with the lid, and sealing the inside of the container under pressure.
A container made of the synthetic resin is much less expensive than a metal can in material cost. However, since a container made of a synthetic resin is produced by using a biaxial drawing and blow molding operation, it is difficult to provide the container with the flange portion which can meet the high strength requirement of withstanding the pressure to be applied thereto from the lid which is doubly tightened against the flange portion.
In order to solve the above-described problem, a container manufactured by the process shown in
FIGS. 8A through 8D
is proposed in Examined Japanese Patent Publication No. 6-22859. According to the container, as shown in
FIG. 8A
, there is formed by injection molding a parison
1
having a closed bottom surface
1
a
, an opening
1
b
at its top, and a cylindrical body portion
1
c
long and small in its diameter. Then, as shown in
FIG. 8B
, the parison
1
which is a molded product of a primary process is transferred to a blow molding die
2
to draw it in a biaxial direction (X and Y-directions) to obtain a molded product
3
of a secondary process, as shown in FIG.
8
C. The semi-finished product
3
is cut along a line L to remove an umbrella-shaped part
1
d
formed at the upper end thereof. A container
4
shown in
FIG. 8D
is a final product.
The container
4
formed by blow molding has a cylindrical body portion
4
a
; a wide mouth
4
b
open at one end of the body portion
4
a
and having a diameter substantially equal to that of the body portion
4
a
; a flange portion
4
c
projecting radially from the periphery of the wide mouth
4
b
; and a bottom portion
4
d
formed at the other end of the body portion
4
a
. After tennis balls are put in the container
4
from the flange portion
4
c
, a lid
5
is tightened against the flange portion
4
c
, with the lid
5
doubly covering the flange portion
4
c
, as shown in
FIG. 9
to seal the interior of the container
4
. In this manner, tennis balls are stored in the container
4
under pressure.
In the method shown in
FIG. 8
, for manufacturing a container having the flange portion
4
c
against which the lid
5
is doubly tightened, the semi-finished (secondary) product
3
shown in
FIG. 8C
is formed by molding. Then, it is necessary to perform the additional process step of cutting off the unnecessary umbrella-shaped part
1
d
formed at the upper end of the body portion
4
a
. Thus, the method shown in
FIG. 8
has comparatively many process steps.
In addition to the above-described problem, if the degree of the size accuracy of he flange portion
4
c
is low, a gap is generated between the flange portion
4
c
and the lid
5
which is doubly tightened against the flange portion
4
c
. Thus, the container
4
has a low degree of sealing performance. To prevent this, it is necessary to allow the flange portion
4
c
to have a high degree of size accuracy in the cutting operation. To this end, it is necessary to use a particular cutting tool having a high degree of cutting accuracy such as a ring-shaped cutter and perform the cutting step at high accuracy. Consequently,the method shown in
FIG. 8
causes the manufacturing cost to be high and the manufacturing time to be extended.
Moreover, to form the flange portion
4
c
with a high size accuracy, it is necessary to minimize the variation of the thickness thereof. However, to allow the thickness thereof to be uniform in the biaxial drawing and blow molding operations, stability in the molding technique and molding condition and the operation stability of the molding machine are demanded. However, it is not always easy to keep these factors stable. In particular, the flange portion
4
c
requires a thickness of less than 1 mm. Thus, defective products are likely to be produced in the blow molding process. Actually, many defective articles are produced.
Furthermore, in the process of the formation of the flange portion
4
c
, the umbrella-shaped portion
1
d
formed at the upper end of the body portion
4
a
is cut off and discarded. That is, a part of the material is wasted. It is conceivable that the umbrella-shaped portion
1
d
can be recycled by mixing it with a resinous material. However, in this case, it is necessary to pulverize the umbrella-shaped portion id before mixing it with the resinous material with a pulverizing machine. Further, there is a limitation in the mixing percentage in consideration of the stability in the molding of the mixed materials. Thus, it is difficult to recycle the umbrella-shaped portion
1
d.
Furthermore, when the container is used to accommodate tennis balls, the container is exposed to a high temperature atmosphere of the trunk of a vehicle or the like for a long time. Because the flange portion
4
c
is thinly formed by blow molding, it can become deformed by heat. As a result, gaps can be formed between the flange portion
4
c
and the lid
5
permitting air to leak out from the interior of the container
4
. Thus, it is impossible to hold the interior of the container under pressure and hence hold the tennis balls therein at a predetermined internal pressure.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problem. Thus, it is an object of the present invention to provide a pressure wide-mouth container made of a synthetic resin and material and having a flange portion against which a lid is tightened, with the lid doubly covering the flange portion and which has a precise dimensional accuracy and a high degree of strength to seal the interior of he container under pressure.
It is another object of the present invention to manufacture a container in a minimum number of process steps and without generating waste.
In order to achieve this object, there is provided a pressure wide-mouth container made of a synthetic resin and having a cylindrical body portion, a flange portion projecting from the-periphery of the wide mouth formed at one end of the body portion; and a bottom portion closing the other end of the body portion. Advantageously, the flange portion and a peripheral portion of the wide mouth are formed by injection molding and not drawn after the injection molding is carried out. The body portion except for the peripheral portion of the wide mouth and the bottom portion are formed by injection molding and drawn by blow molding to be performed after the injection molding is carried out. The bottom portion is drawn at a lower drawing ratio than the body portion.
As described above, the flange portion and the peripheral portion of the wide mouth continuous with the flange portion are formed
Fujisawa Koichi
Nakamura Yoshinobu
Tawara Masamichi
Pollard Steven
Sumitomo Rubber Industries Ltd.
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