Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE FOR CRYSTALLIZING A MOUTH ON A POLYESTER CONTAINER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for
crystallizing a threaded area provided on the mouth of a
polyester container.
2. Description of Related Art
A conventional polyester container usually has a
threaded area at the mouth portion thereof, and because
the threaded area is made from an amorphous polymer, it
is easily deformed under a high temperature or a high
pressure. Therefore, the temperature of a liquid filling
in the container has to be lowered in order to keep the
threaded area from being deformed. But, a lowered
temperature for the filling liquid and the air therein
frequently results in a contamination of germs. To overcome
the deficiency, a prior art has been disclosed a way to
treat the mouth portion by means of crystallization so as
to intensify the heat resistance and the pressure
resistance thereof. The treatment is widely utilized in
the field of hot filling product.
The treatment of crystallization applied in the prior
art is that the polyester polymer is crystallized by heat
to improve the physical property and the mechanical
property thereof . Nevertheless, it can be understood that
no thermal deformation generated in the process of
crystallization is a key factor to keep the dimension of
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the mouth portion unchanged. Therefore, the method and the
technique involved in the treatment substantially affect
the quality of the container.
Presently, SIDEL COMPANY in FRANCE, ELECTRICA FORM
COMPANY in U.S.A., and NISSEI COMPANY in Japan have
manufactured crystallization machines for the threaded
mouth on a polyester container. There is a common feature
of the machines that they basically provide a single
external heating system to focus on the threaded portion
of the mouth. In addition, there are two methods are adopted
in the machines to process the mouth. One is called "insert
crystallization" and the other is called "insert free
crystallization".
The "insert crystallization" provides a better
stability in dimension, but it is hard to eject from the
insert. If an unhardened container blank is ejected from
the insert at a high temperature, the polymer is almost
in a state of visco-elastic body and it is easily deformed
during ejecting. In order to avoid the shortcoming, the
"insertfree crystallization"isdeveloped afterwards.But,
it is not easy for the "insert free crystallization" to
control the dimension of the mouth properly without the
insert. Therefore, the technique offered by the "insert
free crystallization" is not so ideal either. A detail
explanation for these two methods will be further described
hereinafter.
Referring to Figs. 5, 6, 7, and 8, a threaded mouth
portion 10 on a container blank is detachably fitted to
a adapter post 11 on a crystallizing machine. A radiation
heat source 12 is provided around the threaded mouth portion
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externally. The thread on the mouth has a shape of
different thickness of tl, t2, and t3, and it leads to a
lot of dead corners, which are unable to receive the
radiation heat equally. Thus, a lot of cold spots 14 are
5 formed on the threaded mouth unavoidably. It can be
understood that different thickness can result in an
irregular contraction or expansion of volume for the
polymer in the process of crystallization. Therefore, a
thermal stress is induced at the mouth of the container
10 such that the threaded portion of the mouth is deformed
disadvantageously. Furthermore, it can be clear from a
crystallization curve C and a temperature curve to that
there are cold spots 14 in the crystallization zone A3.
Even if it is at the best crystallized point A4, cold spots
14 still exist. Hence, the insert crystallization is hard
to overcome the disadvantage of a deformed mouth induced
by a thermal stress.
Based on the principle described above, a deformation
W occurs while the mouth is crystallized completely. In
order to eliminate the deformation W, the insert free
crystallization is introduced to resolve the problem. Due
to no fixing post 11 provided, the method of insert free
crystallization is difficult to keep the radial dimension
of the mouth on a container blank correctly. Hence, it is
hard for the insert free crystallization to carry out the
quality control of the mouth and a greater error in
dimension may generate undesirably.
SUMMARY OF THE INVENTION
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The present invention resides in that a second heat
source is provided in the crystallization machine such that
the heat from the second heat source flows along the adapter
post and is transmitted to the inner smooth surface of the
mouth on the container blank evenly to eliminate cold points .
In the mean time, the second heat source allows the mouth
to keep a softer inner side thereof while the outer side
thereof is crystallized. That is, the inner side of the
mouth keeps at a certain temperature to reduce a radial
thermal stress resulting from contraction due to
crystallization such that an easy release of the blank can
be reached without deformation.
An object of the present invention is to provide a
device for crystallizing a mouth on a polyester container
, which can offer additional heat evenly to the mouth of
a container blank at the inner side thereof so as to
eliminate cold spots for preventing the mouth from
deformation.
Another object of the present invention is to provide
a device for crystallizing a mouth on a polyester container,
with which the mouth can have a soft inner part and a hard
outer part so as to be released easily.
The present invention can be more fully understood
by reference to the following description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a semi-plan view of the mouth on a container
to illustrate a preferred embodiment of the present
invention.
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Fig. 2 is diagrammatic view of Fig. 1 to illustrate
a crystallized curve thereof.
Fig. 3 is a diagrammatic view of the preferred
embodiment of the present invention.
5 Fig. 4 is a diagrammatic view of a crystallization
machine attaching a plurality of device of the present
invention.
Fig. 5 is a semi-sectional view of a mouth of a
container with an insert to illustrate a conventional
method of crystallization.
Fig. 6 is a semi-sectional view of a mouth of a
container.
Fig. 7 is a semi-plan view of the mouth on a container
to illustrate a crystallized curve thereon.
Fig. 8 is a semi-plan view of the mouth on a container
to illustrate a deformation thereon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in Fig. 1, 2, 3, and 4, due to providing a
second heat source, the threaded mouth 10 forms a hardened
zone A1 and a soft zone A2. The soft zone A2 is hardened
gradually and the time curve T illustrates the hardened
time needed for the zone A1 and zone A2. The adapter post
20 has mounted a heat conductor 21 at an end thereof and
the heat conductor 21 receives the radiation heat from a
second heat source 22. Then, the heat received by the
conductor 21 transmits along the post and toward the other
end of the post 20. The mouth on a container blank 13 fitting
with the post 20 is softened thermally by the heat and forms
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the soft zone A2. The heat in the zone A2 can move toward
zone A1 to eliminate the cold spots, which are arisen from
the heat of the first heat source 12 reaching these spots
difficultly. Therefore, it is advantageous for the
container blank 13 to release from the fixing post easily
and it is preventable for the container blank 13 from being
deformed during releasing.
In addition, when the mouth of the container blank 13
is completely crystallized, the first heat source 12 is
stopped transmitting the heat to the mouth but the second
heat source 21 still supplies the heat to the fixing post
through the conductor 21. Therefore, the post 20
maintains at a certain temperature and it can reduce the
radial force generated on the contracted mouth in the
15 process of crystallization to press the post 20 so as to
minimize the radial shear force during the container blank
13 is releasing.
While the invention has been described with reference
to the preferred embodiment, it is to be understood that
20 modifications or variations may be easily made without
departing from the spirit of the invention, which is defined
by the appended claims.
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