Patent Application
20120228183
1. Field of the Invention
This invention relates to blow molded plastic containers, and in particular to containers that require enhanced top load strength characteristics, especially in the region about the finish portion.
2. Description of the Related Technology
Many products that were previously packaged using glass containers are now being supplied in plastic containers. Polyethylene terephthalate (PET) thermoplastic resins are polyester materials that provide clarity and transparency that are comparable to glass. PET possesses the processing characteristics, chemical and solvent resistance and high strength and impact resistance that are required for packaging products such as juices, soft drinks and water. PET containers are lightweight, inexpensive, and recyclable and can be economically manufactured in large quantities. They will not shatter and create potentially dangerous shards when dropped, as a glass container may.
PET containers have conventionally been manufactured using the stretch blow molding process. This involves the use of a pre-molded PET preform having a threaded portion and a closed distal end. The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container. As the preform is inflated, it elongates and stretches, taking on the shape of the mold cavity. The polymer solidifies upon contacting the cooler surface of the mold, and the finished hollow container is subsequently ejected from the mold.
Another well-known process for fabricating plastic containers is the extrusion blow molding process, in which a continuously extruded hot plastic tube or parison is captured within a mold and inflated against the inner surfaces of the mold to form a container blank. In such systems, the mold is typically designed to travel at the speed at which the extruded parison is moving when it closes on the parison so that the process can operate on a continuous basis. There are several different types of extrusion blow molding machines, including shuttle molds that are designed to travel in a linear motion and extrusion blow molding wheels that travel in a rotary or circular motion.
Extrusion blow molding is typically used to form plastic containers, such as motor oil containers, from nontransparent materials such as polyolefin or polyethylene. In the past, it was not typical to use extrusion blow molding to fabricate PET containers, because no commercially available PET material provided the required melt strength for extrusion blowmolding in addition to being compatible with standard PET recycling processes. More recently, however, extrudable PET (EPET) materials have been made commercially available that can be processed at temperatures and conditions similar to standard PET and that provide the required melt strength for extrusion blow molding. Such materials have higher melt temperatures than the polyethylene or polyolefin materials that are typically used with extrusion blowmolding. A limited number of PET containers that are fabricated using extrusion blow molding have now been commercially introduced.
Despite the advantages of plastic materials such as PET, glass containers are still prevalent for certain products, particularly those that require a substantial amount of column or top load strength so that the structural integrity of the container is not compromised when the containers are stacked in boxes or pallets and subjected to substantial vertical compressive forces. In many plastic container designs, the neck and shoulder portions are the weakest link in terms of the column strength of the container. The column strength of the container may also be reduced in container designs that have a main body portion with a broad upper surface adjacent to the finish portion of the container that does not slope sharply downward. In such container designs, downward force applied to the finish portion may cause the upper surface of the container to deflect downwardly and possibly buckle.
In order to minimize material costs, it is desirable to make the sidewall of these container portions, as with the rest of the container, as thin as possible. However, such lightweighting comes at the expense of container strength, and in particular column strength.
In the packaging of certain types of beverages, a rinsing agent is applied to the inner surfaces of the container, which must be drained from the container prior to filling the container with product. Any structural reinforcement that is provided to the upper portions of the container ideally should not interfere with efficient drainage of the rinsing agent from the container.
A need exists for a PET container that can be manufactured using an extrusion blow molding process that exhibits superior column strength, particularly in the upper regions of the container that are adjacent to the finish portion, and that does not adversely impact drainage from the container.
Accordingly, it is an object of the invention to provide a PET container that can be manufactured using an extrusion blow molding process that exhibits superior column strength, particularly in the upper regions of the container that are adjacent to the finish portion, and that does not adversely impact drainage from the container.
In order to achieve the above and other objects of the invention, a blow molded plastic container according to a first aspect of the invention includes a main body portion having a central longitudinal axis and an upper surface, and a finish portion that is unitary with the main body portion. The finish portion extends upwardly from the upper surface. The container further advantageously includes a reinforcing strut that is defined in the upper surface adjacent to the finish portion.
A blow molded plastic container according to a second aspect of the invention includes a main body portion having a central longitudinal axis and an upper surface; a finish portion that is unitary with the main body portion and extends upwardly from the upper surface; and a drainage channel defined in the upper surface, the drainage channel being in communication with the finish portion.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.
Referring now to the drawings, wherein like reference numerals designate corresponding structure throughout the views, and referring in particular to
The container 10 in the preferred embodiment is fabricated from an extrudable polyethylene terephthalate (EPET) material using an extrusion blow molding process. Most preferably, container 10 is fabricated from Invista Polyclear® EBM PET 5505 extrudable polyethylene terephthalate (EPET) material.
The main body portion 12 of the container 10 includes an upper surface 20 from which a finish portion 22 extends upwardly. Referring to
A reinforcing strut 24 is advantageously defined in the upper surface 20 adjacent to the finish portion 22. In the preferred embodiment, the reinforcing strut 24 is positioned on the same side of the finish portion 22 that faces the central longitudinal axis 18.
Preferably, the reinforcing strut 24 is integrally formed with the rest of the main body portion 12 and is defined from and forms part of the thin sidewall 13. In other words, the reinforcing strut 24 has a thin sidewall throughout. The reinforcing strut 24 is also preferably unitary with part of the finish portion 22. The reinforcing strut 24 is preferably constructed to create a downwardly sloping inner channel 40, best shown in
As is best shown in
The reinforcing strut 24 preferably defines a top surface 26 and a pair of tapered side surfaces 30, 32 that are tapered inwardly and upwardly so as to cause the upper surface 26 to have a width that is less than a base width of the reinforcing strut 24, which is where it merges into the adjacent portion 28 of the upper surface 20. Fillets are preferably provided to create a smooth transition between the respective side surfaces 30, 32 and the adjacent portion 28 of the upper surface 20. Convex radii are preferably provided to create a smooth transition between the respective side surfaces 30, 32 and the upper surface 26. In transverse cross-section, as shown in
The height of the reinforcing strut 24 varies along its length in the preferred embodiment. As
Referring again to
Looking to
Referring to
The presence of the reinforcing strut 24 substantially improves the top load strength of the container 10, particularly in the portion of the upper surface 20 that is adjacent to the finish portion 22.
It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
