US 20070102438 A1
A closure for covering an opening of a container. The closure includes an inverted U-shaped peripheral channel for receiving the rim of a container therein. A tear strip is formed with the skirt of the closure via a tear line that circumscribes the skirt. A breakaway pull tab having an inner surface with U-shaped ribs, the combination of the surface and ribs being such as to provide a concavity which assists in gripping the tab to pull the strip away. Linear vertical ribs may be provided on the outer surface to provide further assistance in the gripping function. The skirt includes a recessed area underlying the pull tab for providing access to the pull tab. An alternative embodiment uses a zig-zag structure of strengthening ribs in the skirt to reduce the amount of material necessary to provide the undercut. This reduces the probability of warpage in the closure structure.
1. A molded plastic closure for an open top, industrial container of the type having an undercut top rim and wherein said enclosure comprises:
a central deck portion;
an inverted, U-shaped channel portion peripherally of said deck portion to receive and lock onto said undercut top rim;
said channel portion comprising substantially parallel and concentric, but radially spaced, inner and outer walls, said outer wall defining an inwardly extending locking flange for cooperation with said undercut rim;
said outer wall being integrally formed with an outwardly flaring skirt having an annular lower end portion; and
a substantially continuous pattern of V-shaped ribs formed around and on the inside of said skirt, each V-shaped rib being integral with and extending from said flange to said lower end portion to increase the strength of at least said skirt
2. A molded plastic closure as defined in claim 28 wherein said V-shaped ribs are arranged in circumferential groups with openings between said groups.
This application is a continuation of U.S. application Ser. No. 10/752,756 filed under attorney docket no. LTC-114-A on Jan. 7, 2004, currently pending and claims priority thereto. The content of the U.S. patent Ser. No. 10/752,756 is incorporated herein by reference.
This invention relates to plastic container/closure combinations and more particularly to an improved closure structure.
Injection molded plastic containers and lock-on closures are in popular use for packaging a wide variety of products in quantities of one to six gallons. Examples include asphalt sealant, paint, drywall putty and food products. The “lock-on” feature is typically provided by an undercut in the closure which snaps around a peripheral edge flange in the open top of the container. The hoop strength of the closure is such that means must be designed into the closure to facilitate its removal. The two most common such means include (1) tear strips which are removed to reduce the force of the locking mechanism and (2) windows or apertures in the closure skirt which permit the skirt to be fractured at several circumferentially spaced locations. These mechanisms can also be used in combination.
Prior art tear strips can be difficult for a user to access and to grip as the tab is broken away and the tear strip is removed from the outer periphery of the closure. To solve this problem, some prior art closures have been designed to provide a tab that protrudes outwardly from the skirt of the closure for easier access. However, this method prevents efficient stacking of closures for storage.
Efforts to design strength into the closure generally involve adding thickness to the closure skirt. This approach uses additional plastic material, adds weight and can give rise to warpage problems in critical areas of the closure.
The present invention provides an improved closure for an open top container which solves the problems found in the prior art. The closure includes an integral skirted rim which receives the upper edge of the container therein. In one form, a tear strip is formed with and in the skirt but can be separated therefrom via a tear line that extends around the skirt. An essentially flush pull tab is positioned on the end of the strip directly over a recess in the skirt wall which provides room to grasp the tab.
In the preferred embodiment of the tear strip aspect of the invention, the pull tab includes an inner gripping surface having ribs formed therein in such a way as to form a concavity which adds to the effectiveness of the grip. An outer surface of the pull tab includes one or more substantially linear ribs protruding in a substantially vertical arrangement therefrom. The combination of ribs and the recessed grip area provides a more secure grip for tearing the pull tab away from a frangible connection. Once the pull tab has been broken away, the ribs provide a gripping feature to facilitate the removal of the tear strip from the closure skirt. The recessed area further includes an opening formed in the skirt wall around the perimeter of the pull tab. The opening forms an arrow shaped element indicating the direction for pulling and removing the tear strip from the skirt.
Another aspect of the invention involves the design of a zig-zag rib structure into the interior of the closure to reduce material, add strength, and minimize warpage.
Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.
The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:
Both embodiments of the invention are shown with cylindrical designs. It is to be understood that the improvements disclosed herein can also be used with non-cylindrical designs including oval, square and rectangular.
In the present embodiment, the outer wall of the container 12 is configured to provide an undercut 52 which provides the primary lock between the closure 10 and container 12 in conventional fashion both before and after removal of the tear strip.
A circumferential rib 53 may be formed in the container wall below the undercut 52 to protrude into the interior groove formed by the tear lid 22 to provide a second, supplemental lock which is operable only until such time as the tear strip 20 is removed. A second rib 55 may be formed on the container 12 to immediately underlie the closure skirt 18 to impede access to the lower edge of the skirt with a tool or one's fingers before the tear strip is removed.
Those skilled in the art will appreciate that the tear strip 20 is not limited to use with double lock closures but may also be used with single lock closures simply to reduce the hoop strength of the closure skirt 18 to facilitate post-tearing removal of the closure 12. In this regard, windows or apertures 58 are provided at 45 degree intervals around the skirt 18 to facilitate lifting and bending of the skirt 18 after removal of the strip 20.
The pull tab 24 includes a concave inner surface 62 best seen in
Referring now more particularly to
The closure 10 includes a plurality of stiffening ribs 54 located on the underside thereof (best seen in
In operation, when the closure 10 and container 12 are first attached to one another during manufacturing, the closure 10 cannot readily be manually separated from the container 12, thus ensuring safe storage of the contents of the container 12. The closure 10 is tamper resistant and tamper-evident because the closure 10 cannot normally be opened until the tear strip 20 has been removed from the skirt 18. To remove the closure 10, a user must pull the pull tab 24 away from the skirt 18 and break the pull tab 24 from the skirt 18 along a frangible portion 32 of the skirt. The U-shaped ribs 30 located on the inner surface of the pull tab 24 provides gripping to facilitate breakage from the frangible area 32. The pull tab 24 is more easily accessed because recessed area 28 is provided to allow the user's fingers to reach behind the pull tab 24. The recessed area 28 allows access to the inner surface where the user's fingers can grip the U-shaped ribs 30 and pull the pull tab 24 apart from the skirt 18 along frangible area 32. Once the pull tab has been broken away, the user then pulls the pull tab 24 in the direction of the arrow 37 using the linear vertical gripping ribs 34 on the outer surface of the pull tab 24. The pull tab 24 stays connected to the tear strip 20 as the tear strip is being removed from the skirt 18 along tear line 22. Once the tear strip 20 has been completely removed from the skirt 18, the closure 10 can then be removed from the container 12. The closure 10 can also be reattached to the container 12 in a tightly sealed arrangement using the inverted U-shaped channel 48 to position the O-ring 50 seal.
Referring now to
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.