Patent Application
20100133729
1. Field of the Invention
The present invention is related to the field of container manufacturing. In particular the present invention relates to the method and apparatus for manufacturing wide mouth containers.
2. Description of the Related Technology
Plastic containers are frequently used due to their durability and lightweight nature. Polyethylene terephthalate (PET) is used to construct many of today's containers. PET containers are lightweight, inexpensive, recyclable and manufacturable in large quantities.
PET containers are used for a variety of products, such as beverages. Often these liquid products, such as juices and isotonics, are placed into the containers while the liquid product is at an elevated temperature, typically between 68° C.-96° C. (155° F.-205° F.) and usually about 85° C. (185° F.). When packaged in this manner, the hot temperature of the liquid is used to sterilize the container at the time of filling. This process is known as hot-filling. The containers that are designed to withstand the process are known as hot-fill containers. The formed containers can also be filled with other liquids or materials at temperatures below the hot fill range.
A variety of methods can be used to manufacture PET containers. One such method is called the “two-step” process. The “two-step” process first involves forming a plastic “preform” for use in the blow molding process.
A plastic preform is typically a tubular shaped object that comprises a finish, a neck and body. An exemplary preform 10 is shown in
After the preform 10 is formed in the two-step process it is then transferred, along with other preforms, to a blow molding machine. The preform is then positioned between two open blow mold halves. The blow mold halves close about the preform and cooperate to provide a cavity into which the preform is blown to form a container. After molding, the mold halves open to release the container. The two-step blow molding process is used in order to manufacture large amounts of containers using the preforms.
Another type of blow molding process is a single-step blow molding process. The single-step blow molding process, in contrast to the two-step blow molding process discussed above, involves forming the preform and the finished container without the need to cool the preform fully to form the preform. The single-step process incorporates the preform injection molding and stretch-blow-molding process steps in the same machine. The sequence is basically the same, except that there is less cooling and reheating of the preform. The preform is injection-molded in a parison mold, removed from the mold at maximum temperature, transferred directly through one or more temperature conditioning stations to achieve the proper blowing temperature, and then transferred at the blowing temperature to a blow mold where the preform is blown into the finished bottle.
Both the single-step and the two-step processes have certain advantages and disadvantages. Among the advantages of a two-step process is that efficient and effective use can be made of both the preform, or parison, forming and blowing stations which need not be integrated. The preform may be molded at a central location and shipped to several plants for blowing and filling. Preforms for a large container take up only 11 cubic inches of shipping space, less than 5 percent of the volume occupied by the finished bottle. Preforms may thus be produced at one location by an experienced custom molder and supplied to a beverage bottler in another location who may operate the blow-molding machine without prior knowledge of melt processing of plastic. However, substantial thermal energy is lost during the total operation, since the preform after formation is cooled down during storage and then reheated at the time of blowing. Moreover, the preforms from storage must be fed to the blowing station, thereby duplicating handling and decreasing potential overall efficiencies.
The single-step process eliminates heat loss and duplicate handling. About 50 percent less energy per bottle is consumed during the reheating portion of the process. In addition, in the single-step process, a continuous mechanical grip is maintained on the neck of each bottle from the preform molding stage to the stretch-blow-molding stages This means that there is no need to release and regrip the bottle, eliminating a possible source of distortion and disfiguration due to contact between the preform and other bodies. In addition, the process maintains the preform temperature very high and achieves a more uniform temperature throughout the wall thickness of the preform, permitting low-pressure blowing with accurate dimensional control reducing processing costs and improving product quality. However, the advantages of the single-step process are mitigated since; the systems are not as rapid as sometimes desired in commercial manufacture.
The two processes described above can be used to make either narrow mouth or wide mouth containers. Wide mouth containers are containers that when finished have an opening that is larger than 48 mms. Typically plastic wide mouth containers are used as jars and have a variety of different implementations that narrow mouth containers.
When constructing the wide mouth containers using a single-step process, problems arise due to the creation of excess flash material in the mold and the limited amount of cavities that can be formed in the mold when making the wide mouth containers. When the opening within the mold is designed for use with wide mouth containers, only a limited number of cavities can be formed in the mold as opposed to when a narrow mouth container is formed using the single-step process. This is due to the spatial requirements of the wide mouth containers when the openings are arranged in the mold and the increased requirement of pressure needed in order to close the mold. This can result in the usage of different machinery in order to create narrow mouth and wide mouth containers.
The difference between the usage of narrow mouth container molds and wide mouth container molds are illustrated in
Furthermore, the wide mouth containers require a higher amount of tonnage, or pressure, in order to keep the mold 70 closed and when closed it may be closed in an inefficient manner. This results in excess flash that requires additional steps in order to remove the flash.
Therefore there is a need in the field to develop a single-step process that can be used to form wide mouth containers without sacrificing the amount of cavities in the mold, or requiring increased tonnage or pressure in order to close the mold.
An object of the present invention is a method for making a wide mouth container using a single-step process.
Another object of the invention is a method for making a wide-mouth container using a single-step blow molding apparatus that utilizes a mold having an increased number of cavities.
Yet another object of the invention is a one-step blow molding system that can be utilized to fabricate both narrow mouth and wide mouth containers.
Still yet another object of the invention is a method for making wide mouth containers in a single-single step machine that uses a mold with openings adapted for the receipt of narrow mouth blow molding apparatus injectors.
Yet another object of the invention is a single-step blow molding apparatus that uses a mold that forms a moil.
An aspect of the present invention can be a single step blow molding system comprising: a single step blow molding apparatus: a mold comprising a moil forming portion, a wide mouth container finish forming portion located below the moil forming portion and a body forming portion located below the moil forming portion; and wherein the mold is adapted to receive a narrow mouth blow molding apparatus injector.
Another aspect of the invention can be a method for manufacturing wide mouth containers comprising: providing a mold comprising a moil forming portion, a wide mouth container finish forming portion located below the moil forming portion, and a body forming portion located below the finish forming portion; forming a preform in a one step blow molding apparatus, wherein the preform is located in the mold within an opening adapted to receive a narrow mouth container preform; forming a wide mouth container comprising a body, a wide mouth container finish, a moil and a body; and removing the moil.
Another aspect of the invention can be a mold for use in a single-step blow molding process comprising: an opening having a diameter less than 48 mm, a moil forming portion; a wide mouth container finish forming portion located below the moil forming portion; a body forming portion located below the finish forming portion; and wherein the opening is adapted to receive a single-step blow molding apparatus.
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.
One method of making a wide mouth container is through the use of a two-step process, which is described in U.S. Pat. No. 6,228,317 to Smith et al., the contents of which are herein incorporated by reference. As previously discussed, in the two-step process a preform 10 is formed at some earlier point in a separate manufacturing apparatus and then the preform 10 is shipped to a separate apparatus that is then used to blow mold the container that is intended to be formed. Referring to
Referring to
The formed container 30 may be prepared from a monolayer plastic material, such as a polyamide, for example, nylon; a polyolefin such as polyethylene, for example, low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, a polyester, for example, polyethylene terephthalate (PET), polyethylene naphtalate (PEN), or others, which may also include additives to vary the physical or chemical properties of the material. For example, some plastic resins may be modified to improve the oxygen permeability. Alternatively, the container may be prepared from a multilayer plastic material. The layers may be any plastic material, including virgin, recycled and reground material. The layers may include plastics or other materials with additives to improve physical properties of the container. In addition to the above-mentioned materials, other materials often used in multilayer plastic containers include, for example, ethylvinyl alcohol (EVOH) and tie layers or binders to hold together materials that are subject to delamination when used in adjacent layers. A coating may be applied over the monolayer or multilayer material, for example to introduce oxygen barrier properties. In an exemplary embodiment, the present container is prepared from PET.
The blow molded containers 30 may then be filled, with either a cold fill or alternatively, hot-filled, Plastic blow-molded containers, particularly those molded of PET, are utilized in hot-fill applications. Hot-filling involves filling the finished container 30 with a liquid product heated to a temperature in excess of 180° F. (i.e., 82° C.), capped immediately after filling, and then allowed to cool to ambient temperatures.
FIGS 8-10 illustrate how a wide mouth container is formed in a two-step process by using preform and a mold having a moil forming portion. While the usage of the types of molds shown in
The mold 40 has a body forming portion 45 that is used to form the body of the finished container. A wide mouth container finish forming portion 48 is formed above the body forming portion 45. The wide mouth container finish forming portion 48 is used to form the finish of the formed container. By having the wide mouth container finish forming portion 48 not directly exposed To the exterior, less force is required in order to close the mold halves for the blow molding process. The wide mouth container finish portion 48 is located below the moil forming portion 42. The moil forming portion 42 is located above the body forming portion 45 and below the opening 43. The moil forming portion 42 forms the moil of the container and is ultimately discarded or recycled. The wide mouth container finish forming portion 48 has a diameter that can form a container having a diameter that is greater than 48 mm.
The blow molding apparatus 90 is also able to be used with narrow mouth containers as well as wide mouth containers because the openings 43 are adapted to receive the narrow mouth blow molding apparatus 91. Therefore the openings 43 have diameters that are sized to be less than 48 mm. The usage of the openings 43 enables spatial arrangement of the cavities 46 in order to increase the number of cavities 46 used as opposed to the number of cavities used in standard single-step wide mouth container blow molding apparatuses. Single-step blow molding apparatuses are known in the field and details of their operation are not described herein. Any portion of the mold can blow narrow neck containers, while the other side is blowing large neck containers with the same preforms.
In the example shown in
As discussed previously, the usage of the single-step method for the formation of wide mouth containers results in a system that is able to employ the usage of more cavities per a mold and lower tooling and operation costs. This overcomes the problems found in existing single-step processes used to form wide mouth containers.
The mold 80 is able to form both narrow mouth and wide mouth containers in the same processing operation in the same mold 80. This enables production of at least two different types of containers using the same mold. It should be understood that more than two different types of containers can be formed.
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.
