Bottles and jars – Sidewall structure
Reexamination Certificate
1999-07-14
2001-05-29
Weaver, Sue A. (Department: 3727)
Bottles and jars
Sidewall structure
C215S042000, C215S044000, C264S521000, C264S903000
Reexamination Certificate
active
06237791
ABSTRACT:
FIELD OF INVENTION
This invention relates, in general, to new and useful improvements in plastic containers, and more particularly to a polyester wide mouth container wherein the entire container is biaxially oriented and may be heat set from an injection molded preform using a stretch blow molding process to provide the strength necessary in the packaging of hot ingredients, with provision for post forming features of the container.
BACKGROUND OF THE INVENTION
Wide mouth plastic containers for hot ingredients, in particular containers made of polyethylene terephthalate (PET), are commercially available. These PET containers typically are formed from a wide mouth preform using conventional blow molding techniques. The wide mouth container formed by such a the conventional blow molding process, results in a container having a neck of insufficient strength and thickness in comparison with the rest of the container. This is because with conventional blow molding techniques preforms that have threads already formed in the preform are used. In such preforms, if they are to be utilized substantially in their entirety, as is now customary in bottle forming, the diameters of the mouth of the preform must match that of the resultant container and the blow molding of the preform will result in insufficient biaxial orientation of the container particularly in the container body wall adjacent the open mouth.
A heat setting process helps to alleviate potential shrinkage and distortion, however, the finish of a conventionally blown wide mouth container is not exposed to this heat setting process.
It has also been proposed (U.S. Pat. No. 4,576,843) to create a wide mouth container using a preform with a small diameter preform as is customarily utilized in the blow molding of bottles with the preform being of a materially lesser length than that of the resultant container. Here there is formed an intermediate article of manufacture which has a portion in the form of an accommodation element which permits the necessary biaxial orientation of the thermoplastic material throughout the container, the accommodation element being severed from the container and becoming reusable scrap. This technology results in preforms having a flanged portion where the resultant trimming typically takes place. The trimming results in a wide mouth container biaxially oriented throughout with a flange as its neck portion. This flange is used to attach a lid for holding the contents within the container. The present technology does not provide a hot fillable wide mouth container which resists shrinkage and distortion at hot fill temperatures greater than 160° F.
An object of this invention is to provide a wide mouth container blow molded from a small diameter preform (as opposed to a parison used in extrusion blow molding), as is customarily utilized in the stretch blow molding of bottles, wherein the entire container, including the neck finish, is biaxially oriented and heat set to give thermal stability to the entire container.
Another object is to provide a method of post forming (i.e. post formation of the container by blow molding) neck finish features of the container.
Another object is to provide a wide mouth container having a screw thread formed during the blowing operation.
Another object is to increase the geometric strength of the container by curling the edges of the finished container, so that the container is better able to with-stand distortion and shrinkage. This acts as a safety lip for drinking from the container and a means of providing a “snap” cap when made without blown threads.
SUMMARY DESCRIPTION OF THE INVENTION
The present invention utilizes the stretch blow molding of a preform to produce a heat set biaxially oriented container which cannot be produced by the blow molding from an extruded parison which does not produce biaxial orientation or heat setting.
According to the invention there is provided a method of forming a wide mouth blow molded biaxially oriented heat set thermoplastic container comprising the steps of i) stretch blow molding from a preform, an intermediate article comprising the container with the mouth of the container terminating in an accommodation element having a neck that supports the preform in a mold; ii) removing the intermediate article of manufacture from the mold and severing the accommodation element to produce the biaxially oriented container, and iii) subsequently heating the material of the container adjacent the open mouth until workable and then post forming by rolling the material adjacent the open mouth to form a curled perimeter defining the open mouth.
According to the invention there is provided a method of forming a wide mouth blow molded biaxially oriented heat set thermoplastic container comprising the steps of i) stretch blow molding from a preform, an intermediate article comprising the container with the mouth of the container terminating in an accommodation element having a neck that supports the preform in a mold; ii) heat setting the intermediate article including the entire container in the mold, and iii) removing the intermediate article of manufacture from the mold and severing the accommodation element to produce the biaxially oriented heat set container.
Also according to the invention there is provided a method of forming a wide mouth blow molded thermoplastic container having a screw thread formed adjacent the mouth comprising the steps of i) supporting a preform in a blow mold by a preform neck finish, the mold having a cavity defining the outer shape of the container including the thread; ii) without exceeding about 300° F., heating the thread forming portion of the cavity to from about 25° F. to about 100° F. above the temperature of the remainder of the cavity; iii) stretching the preform longitudinally using an extendable stretch rod; iv) blowing the preform to form an intermediate article comprising the container, having blow molded threads connected to the neck finish by an accommodation element, and v) following removal of the intermediate article from the mold, severing the container from the accommodation element.
Also according to the invention there is provided a container when made by the methods of the invention.
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patent
Beck Martin H.
Caldicott Robert J.
Rollend George F.
Davis & Bujold P.L.L.C.
DTL Technology Limited Partnership
Weaver Sue A.
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