Flexible bags – With means to maintain the bag mouth in an open configuration
Reexamination Certificate
1999-08-04
2001-04-24
Pascua, Jes F. (Department: 3727)
Flexible bags
With means to maintain the bag mouth in an open configuration
C383S107000, C220S495110
Reexamination Certificate
active
06220753
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
BACKGROUND
1. Field of the Invention
The invention relates to generally tubular bags, or liners, made of flexible plastic film and used to line a rigid or semi-rigid receptacle such as a waste bin or other collection receptacle. More particularly, the invention relates to a bag having one or more pleats fixed at points around the mouth portion of the bag to reduce the circumference of the mouth of the bag relative to that of the body portion of the bag. When the bag is placed into a supporting receptacle, such as a waste or recycling bin for example, the reduced mouth portion of the pleated bag may be fitted onto the rim of the receptacle and the top portion of the bag will then more securely engage with the receptacle. The bag is thereby more securely held to the support and the mouth portion of the bag is more securely held in an open state. The invention further relates, in certain embodiments thereof, to a reduced mouth pleated bag which is configured to have one or more stress and strain modifying tabs positioned around the mouth portion of the bag. Each tab is intended to reduce the possibility of tearing of the bag at and near the conjunction of a seam and mouth portion of the bag during installation and service of the bag.
2. Description of Prior Art
A bag used as a liner is typically supported by a rigid or semi-rigid structure such as a waste bin or other collection receptacle. When in service, it is usually convenient that the mouth portion of the bag stay open in order to allow the articles to be passed conveniently and unhindered into or out of the bag. Owing to the flexible, pliant nature of a plastic film, a plastic bag is generally not self supporting, nor is the mouth portion of a bag able to reliably remain in an open state on its own. Therefore, it is common to both support the bag, and at the same time keep the mouth portion of the bag open, by folding the top portion of the bag over the rim of a corresponding mouth or opening in the supporting structure. Unfortunately, this method of supporting the bag and bag mouth is often attended with a tendency for the top portion of the bag to slide or fall off, or otherwise disengage from, the supporting structure. When the top portion of a bag slips from its support in such manner, the bag may then cease to accomplish one or more of the functions for which it was intended.
1. NECKDOWN BAGS
The present invention relates to a category of bag or liner having retaining means which rely primarily on the circumference of the mouth portion of the bag being less than that of the body of the bag. Hereinafter, bags or liners utilizing this retaining means will be referred to as “neckdown” bags. For a bag used as a liner, it is usually convenient and economical that the bag have a body that is larger in circumference than that of a supporting structure or receptacle into which the bag is placed. However, in this case the top portion of the bag, when folded over a rim or lip of the supporting structure, may yield a loose fit at best, and therefore offer little additional support for the bag. A reduced circumference mouth portion of a neckdown bag greatly aids in supporting the bag on all manner of supporting structures, especially if the reduced circumference portion is approximately equal or less than that of the supporting structure. In this case the reduced mouth portion can more readily engage the support and thereby provide additional support for the bag whilst the larger circumference body portion of the bag can remain adequately sized to fit the receptacle.
Some neckdown bags or liners utilize one or more elastic members, or bands, permanently engaged with, or bonded to the bag, and sized so that the elastic member will elastically stretch around and grip a supporting structure. Such constructions are disclosed for example in Eby et al (U.S. Pat. No. 4,509,570), Cortese (U.S. Pat. No. 4,953,704), and Perkins (U.S. Pat. No. 4,747,701). Perkins in U.S. Pat. No. 4,747,701 asserts that in some “liner bags”, the slight elasticity of the plastic itself will aid in holding the bag in place, that some bags will stretch to a small extent so that they are held tightly when folded over the rim of a receptacle. It is further asserted that the elasticity of the typical liner bag is relatively low and the bags will often tear when pulled too hard. These perceived drawbacks of a typical liner bag film force the design of the bag disclosed to require an “elastic band” or head member to be permanently attached to the bag body. Typical materials disclosed for the elastic band are “elastomers” such as “latex” (a rubber elastomer) and “DUREFLEX tm PT6100S” (of Deerfield Urethane, Inc.) an aromatic polyether polyurethane film which is a thermoplastic elastomer. An elastomer film exhibits a rubber-like elastic deformation response, that is, it can greatly elongate upon the application of a relatively weak stretching force, and upon removal of this stretching force, the film quickly recovers substantially its original shape and size, mimicking the familiar action of a rubber band being stretched and then released. The elastic band is required to be bonded to a relatively inelastic bag body in order to achieve a functional self gripping neckdown liner. As the attached elastic band is required to perform the self retaining action, the elastic band, not the bag body, is made to have the neck down feature. It is apparent that such a bag design, while functional, is complicated by having the liner made of two distinct members, the relatively stiff bag body, and the elastic band or head member. The two members are required to be intimately attached along a common edge, leading to a necessary complexity in the bag structure and in the manufacture of such a liner bag.
It is known that a bag having a reduced size mouth relative to the body of the bag can be constructed by joining together portions along the top of the bag to form a pleated neckdown bag having reduced circumference mouth portion relative that of the bag body. Imazeki et al (U.S. Pat. No. 4,919,546) discloses such a method to obtain a neckdown bag, as does Perkins in U.S. Pat. No. 4,747,701 already cited above. Disadvantages are apparent in Imazeki et al in that the bag supporting function relies strictly on the principle that the bag body material is “non-elastic”, or inelastic, and thereby can bear no stretching either on installation of the bag to its support, or while the bag is being supported. The “non-elastic” limitation requires the use of a specially engineered hoop-like support to be designed and then installed in a specified way so as to avoid any stretching of the bag, thereby affording a purely kinematic constraint to secure the liner to the support. The need for the hoop support greatly limits the types of support receptacles that can be used with the bag and increases the complexity and cost of such a system.
Kaczerwaski (U.S. Pat. No. 4,611,350) discloses a closed bottom “sack” of thermoplastic film comprising at least one cold stretched, circumferential band portion of diameter that is reduced from the original diameter of the sack. The band of reduced diameter is obtained by cold stretching the film so as to procure, through a permanent material “necking-down” phenomenon, a circumferential band of reduced diameter in the region adjacent to the bag mouth opening (the “necking-down” term used to describe the phenomenon disclosed in Kaczerwaski is a term of art in the science of materials and is not to be confused with the similar “neckdown” term used herein to refer to a particular construction of a bag). The reduced band region of the bag can be positioned relative to the bag mouth so as to accommodate a more secure, gripping overfold region when the bag is employed as a waste container liner. The method disclosed is limited to materials that will neck-down when cold stretched. Another drawback to this method is that there is a limit to the degree of reduction of bag diameter that can be achieved with the method d
Huff Richard L.
Pascua Jes F.
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