Plastic and nonmetallic article shaping or treating: processes – Flame contact or reshaping by heat decomposition of work
Patent
1986-03-05
1989-02-07
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Flame contact or reshaping by heat decomposition of work
264134, 264292, 264296, 264322, 264512, 264516, 264521, 264532, B29C 3502, B29C 4922, B29C 5526
Patent
active
048030244
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of producing a container from a tubular blank of plastic material capable of being oriented and/or crystallized, in at least two consecutive shaping stages, utilizing mechanical forming elements for stretching the material in the axial direction of the blank and in the circumferential direction of the blank.
PRIOR ART
It is previously known in this art to reshape blanks, which include axially oriented material, into containers. In such a process, the reshaping is effected by means of a blowing process in which the blank is brought into abutment against forming walls whose form (configuration) corresponds to the form of the container which is to be produced. Patent Specification No. GB 2 076 731 describes a technique for the production of a bottle-like container from a blank which includes axially oriented material.
Patent Specification No. GB 2 052 364 discloses a technique in which an axially stretched blank is, by one or more mechanical reshaping stages, reshaped into a container. According to the technique shown in this Patent Specification, a reduction only of the circumference of the container body takes place on reshaping of the blank into the container.
Patent Specification No. GB 2 052 363 describes a technique in which a blank of axially oriented material is reshaped, by a blowing process, into a container. Also according to this patent specification, an axially oriented blank is reshaped into a container.
There are pressing needs within this Art for a container of plastic material which is suitable for high-temperature applications and/or for the storage of liquids under pressure, e.g. the storage of carbonated soft drinks, beer etc. The term high-temperature application is here taken to mean that the containers are used, for example, for pasteurization (at 60.degree.-65.degree. C.) of the contents in the filled and sealed container, for hot-filling, by which is taken to mean that boiling liquid is filled directly into the containers, or for sterilization (at least 121.degree. C.) of the contents of the filled and sealed containers.
Further desires relating to containers of plastic material are that it must be possible to produce containers whose body is of a cross section which is independent of the mouth portion of the container, e.g. the body has a polygonal cross section, while the mouth portion of the container is circular. The circular configuration of the mouth portion of the container is desirable so as to facilitate closure of the container.
So as to reduce unit costs for the containers, it is further necessary that the material distribution in the containers be adapted to meet calculated mechanical stresses in the different parts of the container (mouth portion, container body and bottom). Furthermore, it is also necessary that the material distribution in each region (portion) of the individual container be as uniform as possible, since the thinnest--and thereby the weakest--part in each such region is determinative of those stresses which the container can withstand. Apart from the material distribution, the mechanical strength of the containers is, naturally, also determined by the orientation and/or thermal crystallization of the material.
A further requirement placed on containers of the type contemplated herein, and particularly on containers intended for high-temperature applications, is that the shrinkage which occurs on heating of stretched and oriented material must be eliminated or reduced to acceptable levels.
In the storage of liquids under pressure, it is a matter of the Laws of Physics that when there is inner pressure within the container, its wall material is subjected to a stress which is approximately twice as great in the circumferential direction as in the axial direction. In order to improve the strength of the plastic material, it is known in the art to shape the container by a blowing process, the temperature of the material being adapted to suit the properties of the material being employed in
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patent: 2249775 (1941-07-01), Millspaugh
patent: 3205290 (1965-09-01), Covington, Jr. et al.
patent: 3651202 (1972-03-01), Raabe
patent: 3757718 (1973-09-01), Johnson
patent: 3929959 (1975-12-01), Findlay et al.
patent: 4261948 (1981-04-01), Krishnakumar et al.
McCarthy Neil M.
Petainer S.A.
Silbaugh Jan H.
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