Patent Application
20070090121
This invention relates to lids for containers and especially to composite type lids formed from a combination of paper and plastic materials.
Containers used for packaging foodstuffs, as well as other products for retail sale, must perform several functions. The container must hold the product, must allow the product to be transported effectively from the manufacturer to the point of sale, and from the point of sale to the consumer, must often serve to dispense and store the product after acquisition by the consumer, and no less importantly, must identify the product and its source and serve as an advertising medium and to promote further sales.
It is desirable that the containers be inexpensive to manufacture, yet durable so as to continue to perform their various functions effectively despite abuse and harsh environments.
The container lid plays an important role in the proper functioning of the container. It is desirable that the lid effectively close the container, and when the container is used to store and dispense the product, it is also desirable that the lid be removable and reclosable many times over the life of the container. Ice cream containers provide a good example of a container used to store and dispense the product held in the container. Ice cream containers are also subject to conditions of freezing, thawing, moisture and repeated opening and closing of the lid, all of which tend to cause deterioration and rapid failure of the container unless it is properly designed and manufactured.
It has been found advantageous to make the lids for such containers as a composite combination of both paper and plastic materials. The designs currently in use comprise an injection molded plastic skirt surrounding a paperboard center. The plastic skirt fits over the end of the container engaging the end and/or sides, thereby sealing the container and providing a means for retaining the lid in the closed position. Plastic is used for the skirt because it is inexpensive, easy to mold, resilient, impervious to freezing, thawing and moisture and relatively rigid. The skirt is the portion of the lid which sees the most abuse during the life of the container, and the above noted qualities of plastic allow the lid to maintain its shape and hold together to continue to effectively close the container despite the adverse environment and repeated handling.
It is not desirable, however, to make the entire lid from plastic. Plastic does not provide a surface capable of receiving the high-quality printed graphics needed for the container to fulfill its function as identifier of the product and its source and as an advertising medium for the product. Paper is the preferred medium for displaying high-quality graphics regarded as necessary to compete in the advertising environment of retail sales. Thus, the paperboard center provides the means for presenting complex, colorful and detailed graphics, such as illustrations of product, company trademarks and trade dress designs, while the plastic skirt provides a durable material impervious to abuse and environmental conditions.
A problem with the composite lid design described above is that the graphics are confined to the paperboard center portion of the lid and do not extend continuously over the plastic skirt. The absence of graphics over portion of the container is unacceptable to many product manufacturers who want a container which can receive printed media over the entire outer surface without interruption. Such continuity is important for the proper presentation of trademarks and trade dress, which are vital to customer recognition of a particular product from among the many competing products displayed side-by-side in a typical retail sales environment. There is clearly a need for a composite lid design combining the robustness and durability of the plastic skirt with the ability to receive high-quality graphics continuously over the entire surface of the lid without interruption.
The invention concerns a lid for a container. The lid comprises a panel and a skirt surrounding the panel. The skirt extends transversely to the plane of the panel and is formed from a plastic resin. The skirt is attached to the panel. A tube surrounds the skirt and is attached thereto. The tube is formed of paperboard. Preferably, the panel is also formed of paperboard but could also be formed of a polymer and may be opaque, translucent or transparent.
Preferably, the tube comprises a spiral wound paperboard tube. Other types of tubes are also feasible and include a tube formed by joining ends of a paperboard substrate using a butt joint, an overlap joint or a scarf or skived joint. The tube may be a simple cylindrical tube or comprise a first portion attached to the skirt and a second portion that projects beyond the skirt and is deformed inwardly toward the panel.
The invention also concerns a method of making a lid for a container having a panel attached to a skirt of plastic resin surrounded by a paperboard tube. The method comprises:
(a) providing a mold;
(b) opening the mold;
(c) positioning the tube within the mold;
(d) closing the mold; and
(e) injecting a plastic resin into the mold to form the skirt surrounding the panel, the skirt adhering to an inwardly facing surface of the tube, the tube and the skirt being oriented transverse to the panel.
The method may also include positioning a paperboard substrate within the mold. The paperboard substrate comprises the panel, and skirt adheres to the panel.
The method may further include engaging a portion of the tube with the mold upon closing of the mold to deform a portion of the tube inwardly toward the panel.
Skirt 14 is attached to the perimeter 16 of panel 12 and is preferably formed from plastic resin. The skirt may have various features molded in, such as the inwardly protruding lip 18 which engages a rolled edge around the rim of a container (not shown) to help secure the lid to the container while still allowing it to be removable. Other features, such as ribs which stiffen the lid and/or facilitate the distribution of resin during the molding process may also be integrally formed with the skirt.
As best shown in detail in
Lids 10 according to the invention may be produced in a cavity and core mold. A process for their production includes positioning a paperboard tube, such as any of tubes 20a-20d within the mold, and positioning a paperboard or plastic central panel within the mold as well. The mold is then closed and plastic resin is injected. The resin adheres to the paperboard tube and the plastic or paperboard central panel and provides structural integrity to the lid thus formed. Adherence of the plastic to the paperboard is ensured by choosing a plastic, such as polystyrene, that naturally adheres to paper upon curing from a molten state, or by coating the paperboard components with a resin or other coating that is compatible with a molten plastic, such as polypropylene, upon injection and curing within the mold. As noted above, the mold may also be used as a tool to shape the paperboard tube, for example, by engaging a portion of the mold with a portion of the tube upon closing of the mold to deform the tube portion into a curved shape, such as the curved portion 28 shown in
Plastic resins that are feasible for lids as described herein include polypropylene, polyethylene, polystyrene to cite several examples.
Lids according to the invention combine dissimilar materials in the form of plastic resin and paperboard to each material's inherent advantage to provide a composite lid that is economical to produce, robust, impervious to harsh environments, and has an outer surface substantially over the entire lid that is capable of receiving a print media for the display of high-quality graphics.
This application claims priority to U.S. Provisional Application No. 60/730,325, filed Oct. 26, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60730325 | Oct 2005 | US |
