Patent Application
20150336310
The present invention relates generally to the field of plastic molding. The present invention relates specifically to a system and method of molding a plastic item using more than one mold core during molding.
Many commercial plastic containers are formed by blow-molding a plastic preform within a mold to form a plastic container of the desired size and shape. Typically, the preform is heated to a temperature that allows the material of the plastic to soften, and air is blown into the center of the preform causing the preform to expand into confluence with the cavity of the blow mold. In many conventional systems, the preform used during blow molding is formed by injection molding a single layer of plastic for create the preform. In other conventional systems, a multilayer preform is injection molded using an overmolding process. In the overmolding processes, the preform is formed by injection molding a first layer of plastic around a single mold core. Next, while leaving the single mold core in place, a second layer of plastic is injection molded around the outside of the first layer of plastic. Such systems are typically referred to as over-molding systems because each subsequent injection molded layer is deposited along the outer surface of a preceding layer in the molding process.
One embodiment of the invention relates to a method of injection molding a plastic preform. The method includes providing an injection mold system including an inner surface defining an injection mold cavity. The method includes positioning a first core having an outer surface within the injection mold cavity such that a first space is defined between the inner surface of the injection mold cavity and the outer surface of the first core. The method includes injecting a flowable first plastic material into the first space to form a first preform layer having an outer surface facing the inner surface of the injection mold cavity and an inner surface facing the first core. The method includes solidifying the first preform layer. The method includes removing the first core from the injection mold cavity such that the inner surface of the first perform layer defines a first preform cavity. The method includes positioning a second core having an outer surface within the injection mold cavity and within the first preform cavity such that a second space is defined between the inner surface of the first preform layer and the outer surface of the second core. The method includes injecting a flowable second plastic material into the second space to form a second preform layer having an outer surface contacting the inner surface of the first preform layer and an inner surface facing the second core.
Another embodiment of the invention relates to an injection molding system. The injection molding system includes a mold body having an open end, a closed end and an inner surface defining a mold cavity shaped to form a plastic item. The injection molding system includes a gate extending through the closed end of the mold body. The injection molding system includes a resin injection system coupled to the gate. The gate is moveable between a closed position and an open position in which resin is delivered from the resin injection system through the gate into the mold cavity. The injection molding system includes a first mold core including an outer surface. The injection molding system includes a second mold core including an outer surface. An outer dimension of the outer surface of the first mold core is greater than an outer dimension of the outer surface of the second mold core. The injection molding system includes an actuator configured to move the first mold core into the mold cavity, to remove the first mold core from the mold cavity and to move the second mold core into the mold cavity after removal of the first mold core.
Another embodiment of the invention relates to an injection molded preform. The preform includes an outer layer formed from a first plastic material. The outer layer has an inner surface and an outer surface that defines an exterior sidewall surface of the preform. The preform includes a hole formed in the outer layer extending from the outer surface of the outer layer to the inner surface of the outer layer. The preform includes an inner layer formed from a second plastic material. The inner layer has an inner surface defining an inner surface of the preform and an outer surface. A portion of the inner layer extends through the hole. The second plastic material is a light transmitting material, and the first plastic material is more opaque than the second plastic material.
Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.
This application will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, wherein like reference numerals refer to like elements in which:
Referring generally to the figures, various embodiments of a system and method for forming a multilayer blow-mold preform are shown and described. In other embodiments, the multi-core system described herein may be used for the molding of other plastic items, e.g., vials, thick-walled bottles, tubes, etc. In specific embodiments, the multi-layer plastic components and/or multi-layer plastic preforms discussed herein are molded using a system and process that molds the outermost layer of the preform first and forms each subsequent layer inside of the adjacent outer layer. In specific embodiments, the system and method discussed herein utilize multiple mold cores of differing diameters during preform molding.
To form the first, outermost component or preform layer, a first mold core is positioned in the cavity of the injection mold body, and the resin material of the first preform layer is injected into the space between the outer surface of the first mold core and the mold cavity. Once the resin material of the first layer cools and solidifies, the first mold core is removed from the injection mold cavity. Next, a second mold core that is smaller than the first mold core is positioned within the injection mold cavity and also within the first preform layer. In this position, the resin material of the second preform layer is injected into the space between the outer surface of the second mold core and the inner surface of the first preform layer. Once the material of the second preform layer solidifies, the second mold core is removed and the finished preform is removed from the injection mold.
Thus, the system and process discussed herein forms a multi-layer preform by forming each layer of the preform inside of an outer preform layer. In contrast to conventional overmolding processes, the process described herein allows each layer of the preform to be molded while in direct contact with a mold core. This arrangement is believed to allow each preform layer to be cooled more quickly due to contact with the mold core, in comparison to overmolding techniques where each subsequent layer has a layer of plastic between the newly injected layer and the mold core. Allowing for fast cooling may be advantageous for a variety of reasons including limiting crystallization that is common with PET resin that is cooled slowly. Further it is believed that the system and process discussed herein allows for the formation of preforms having a thicker sidewall with better and more precisely controlled material properties than other conventional preform injection molding systems, such as overmolding systems.
Referring to
System 10 also includes an actuator, shown as mold core actuator 21. Mold core actuator 21 is an actuation device configured to or operable to move mold cores 18 and 20 into and out of mold cavities 14. Mold core actuator 21 is also configured to index mold cores 18 and 20 relative to mold cavities 14 to alternately position mold core 20 into each cavity 14 following removal of mold core 18 into a given cavity to form the two layer perform discussed below. In the embodiment shown, each mold cavity 14 includes an open end 19, and mold core actuator 21 is configured to move mold cores 18 and 20 into and out of mold cavities 14 through open end 19 via operation of mold core actuator 21.
Each mold cavity 14 includes an inner surface 22 that is shaped to create the contours of the outer surface of the preform, and, as will be explained in more detail below, the outer surface of smaller diameter mold cores 20 are shaped to create the contours of the inner surface of the preform formed using injection mold system 10. In some embodiments configured for formation of a blow-mold preform (i.e., a preform intended for use during blow molding to form a blow molded container), inner surface 22 includes an upper portion 23 with contours shaped to form threading 25 and a collar 27 on the outer surface of the molded preform. Injection mold system 10 utilizing mold cavity 14 and mold cores 18 and 20 allows for a preform to be formed with precisely controlled inner and outer diameters, and also allows for a preform having multiple layers and may also allows for formation of preforms that are thicker and/or have superior material properties than preforms formed using overmolding or other conventional molding systems.
Injection mold system 10 includes a resin injection system 24 that is in fluid communication with cavity 14 such that liquid resin is permitted to flow into mold cavity 14 to produce a preform. In one embodiment, resin injection system 24 includes a gate 26 located through the closed end 28 of each mold cavity 14. In general, gate 26 is a mechanical structure that selectively opens and closes to control flow of liquid resin from resin injection system 24 to mold cavity 14. In another embodiment, resin injection system 24 may be a thermal gated system in which the opening into the injection mold cavity remains open and flow of liquid resin into mold cavity 14 is controlled by controlling the temperature and/or pressure of the liquid resin within resin injection system 24.
Referring to
To form outer layer 32, gate 26 opens allowing resin injection system 24 to inject a flowable first plastic material, shown as molten resin A, into the space 34. With gate 26 is the first open position shown in
Outer layer 32 includes a channel 40 extending through outer layer 32 that provides a passageway for a second resin material to be delivered to the interior surface of outer layer 32. In one embodiment, a cylindrical wall is located or inserted into flowable material of outer layer 32 prior to solidification that acts to block the area for channel 40, and following solidification, the cylindrical wall is removed leaving channel 40. In another embodiment, channel 40 is formed following solidification of the material of outer layer 32, for example via mechanical or laser drilling.
Referring specifically to
To form inner layer 42, gate 29 opens allowing resin injection system 24 to inject a flowable second plastic material, shown as molten resin B, into the space 44. With gate 29 is the second open position shown in
Referring back to
As can be seen in
In some embodiments, mold cores 18 and 20 act as passive cooling elements or heat-sinks that remove heat through conduction without active cooling systems, and in such embodiments, mold cores 18 and 20 are formed from a material with high thermal conductivity (e.g., metal). In other embodiments, mold cores 18 and 20 are actively cooled. In one such embodiment, mold cores 18 and 20 have a cooling circuit, such as internal conduits that circulate a cooling fluid that decreases the temperature of the outer surfaces of mold cores 18 and 20 and that provides a means for transferring heat from the injected preform layer. In various embodiments, the cooling device or circuit for mold cores 18 and 20 are configured maintain a mold core surface temperature below 200 degrees Fahrenheit, specifically to between 0 degrees Fahrenheit and 200 degrees Fahrenheit, and more specifically to between 0 degrees Fahrenheit and 100 degrees Fahrenheit.
In addition to forming multilayer preforms with improved cooling characteristics, injection molding system 10 may be used to form a preform with thicker sidewalls than other conventional molding methods. Referring to
Injection molding system 10 may be used to form preforms from a wide variety of plastics, including plastic resins used for the formation of containers. In various embodiments, the layers of preform 30 may be formed from various resin types including polyethylene, polypropylene, or polyethylene terephthalate. In various embodiments, each layer of preform 30 may be formed from the same resin type, and in other embodiments, each layer of preform 30 may be formed from a different resin type. In various embodiments, preform 30 may include more than two layers, and in certain such embodiments, preform 30 may include one or more barrier material layer (e.g., an ethylene vinyl alcohol (“EVOH”) layer, a nylon layer, etc.).
In various embodiments, each layer of preform 30 may be the same or different resin types with different properties or additives. For example in one embodiment, resin A of outer layer 32 includes a coloring additive lending a desired color to preform 30 and to the final blow-molded container formed from preform 30. In various embodiments in which outer layer 32 includes a colorant material, resin B of inner layer 42 is a plastic resin material without a coloring additive, and in another such embodiment, resin B of inner layer 42 is an approved food contacting plastic material, such as a virgin plastic resin material. In such embodiments, resin B of inner layer 42 is a plastic resin having a contaminant level (e.g., a level of unknown material, non-resin materials, toxins, heavy metals, etc.) that is a below a threshold such that the material has been deemed safe as a food contacting surface.
In some embodiments in which outer layer 32 includes a colorant material, resin B of inner layer 42 is a translucent plastic resin material (i.e., a material that transmits visual spectrum light, including transparent materials). In another embodiment, resin A may include a post-consumer recycled resin material, and resin B is an approved food contacting plastic material, such as a virgin plastic resin material. In another embodiment, resin A may include UV blocking additive materials, and resin B is a resin material without UV blocking additive materials. In such embodiments, the use of a resin B that is an approved food contacting resin allows outer layer 32 to be formed from a material without needing to ensure that each material for outer layer 32 is food contact compatible.
It should be understood that while the exemplary embodiments discussed herein relate primarily to system 10 configured to form a two-layer preform for use in the formation of a blow-molded container, in other embodiments, system 10 is configured to form plastic items or preforms with more than two layers (e.g., 3 layers, 4 layers, 5 layers, etc.). In such embodiments, injection molding system 10 includes a mold core assembly having a mold core of progressively smaller diameters to form each layer.
In various embodiments, a method of forming a multi-layer molded plastic item, such as a preform, is provided herein. In various embodiments, the method may utilize or operate system 10 discussed above. The method includes providing an injection mold system including an inner surface defining an injection mold cavity. The method includes positioning a first core having an outer surface within the injection mold cavity such that a first space is defined between the inner surface of the injection mold cavity and the outer surface of the first core. The method includes injecting a flowable first plastic material into the first space to form a first preform layer having an outer surface facing the inner surface of the injection mold cavity and an inner surface facing the first core. The method includes solidifying the first preform layer. The method includes removing the first core from the injection mold cavity such that the inner surface of the first perform layer defines a first preform cavity. The method includes positioning a second core having an outer surface within the injection mold cavity and within the first preform cavity such that a second space is defined between the inner surface of the first preform layer and the outer surface of the second core. The method includes injecting a flowable second plastic material into the second space to form a second preform layer having an outer surface contacting the inner surface of the first preform layer and an inner surface facing the second core.
In various embodiments, the method includes or utilizes one or more of the components of system 10 as discussed herein. In various embodiments, the method includes forming a channel through the first preform layer, and the flowable second plastic material is injected through the channel into the second space to form the second preform layer. In various embodiments, the method includes providing a supply of the first plastic material in fluid communication with the injection mold cavity and providing a supply of the second plastic material in fluid communication with the injection mold cavity. In various embodiments, the method includes moving a gate to a first position in which the flowable first plastic material flows from the supply of the first plastic material, through the gate and into the first space and moving the gate to a second position following removing of the first core and following positioning of the second core. In such embodiments, the gate in the second position allows the flowable second plastic material to flow from the supply of the second plastic material, through the gate, through the channel and into the second space.
In various embodiments, a preform and a container having a transparent portion or widow are provided. In such embodiments, the window provides for viewing of the interior cavity and/or contents of a container through the window. In additional embodiments, systems and methods for forming a preform and container having a transparent portion are provided.
Referring to
Body 102 of preform 100 includes a light transmitting (e.g., transparent, translucent) window portion 110 and includes a more opaque body portion 112 surrounding window portion 110. In various embodiments, window portion 110 is made from a material that is less opaque than surrounding body portion 112. Thus, in some embodiments, body portion 112 may not be completely opaque. However in other embodiments, surrounding body portion 112 may be completely opaque. In various embodiments, both window portion 110 and surrounding body portion 112 are made from the same type of resin (e.g., both are PET) but include different fillers/additives resulting in the different light transmitting properties. In other embodiments, window portion 110 and surrounding body portion 112 may be made from different types of resin. Following formation of a bottle or container from preform 100, the container includes a window formed from the material of preform window portion 110. A window in an otherwise opaque container may be desirable to allow a user to view the amount of contents in the container while still providing substantial protection to the container contents from light.
Referring to
Following removal of the large diameter mold core, a small diameter mold core, such as mold core 20, is placed into outer layer 114, and inner layer 116 is injection molded along the inner surface of outer layer 114 as discussed above. In this embodiment, inner layer 116 is made from a light transmitting material such that the portion of inner layer 116 that fills in hole 118 acts as a window allowing material within the final blow molded container to be viewed through the wall of the container. Thus, at the position of hole 118, inner layer 116 forms both an exterior surface of preform 100, shown as outer surface 124, and an inner surface 126 of preform 100. In certain embodiments, the resin material of inner layer 116 is both translucent and food-contact compatible.
In one embodiment as shown in
It should be understood that the figures illustrate the exemplary embodiments in detail, and it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.
Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only. The construction and arrangements, shown in the various exemplary embodiments, are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the present invention.
While the current application recites particular combinations of features in the claims appended hereto, various embodiments of the invention relate to any combination of any of the features described herein whether or not such combination is currently claimed, and any such combination of features may be claimed in this or future applications. Any of the features, elements, or components of any of the exemplary embodiments discussed above may be used alone or in combination with any of the features, elements, or components of any of the other embodiments discussed above in the implementation of the teachings of the present disclosure.
This application is a continuation of International Patent Application No. PCT/US2015/024023, filed Apr. 2, 2015, which claims priority to and the benefit of U.S. Provisional Patent Application No. 61/976,299, filed Apr. 7, 2014, which are incorporated herein by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 61976299 | Apr 2014 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2015/024023 | Apr 2015 | US |
| Child | 14819177 | US |
