Flexible bags – Wall details – Specified seam structure
Reexamination Certificate
2001-05-10
2003-04-01
Gehman, Bryon P. (Department: 3629)
Flexible bags
Wall details
Specified seam structure
C206S439000, C206S484000
Reexamination Certificate
active
06540401
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to pouch packaging of sterile items, such as surgical instruments, to protect them against contamination by microorganisms. More specifically, it relates to the construction of a side-edge closure seal for a sterile pouch.
BACKGROUND OF THE INVENTION
Packaging for medical instruments such as tear-open bags and peelable pouches that are hermetically sealed are well-known. Pouches are delivered to the packager where items are introduced to the pouches and then sealed closed by a final heat-seal process. The final heat-seal applies heat, dwell and pressure to the thermoplastic material of the pouch, fusing both webs of the pouch material together across the pouch opening. In a specific type of pouch, one side of the pouch includes a semipermeable panel which permits the gas sterilization of the contents after sealing. In both instances, there is concern about the integrity of the seal around the perimeter of the bag sidewall. Of greatest concern are the areas of the seal which are transition points between the heat-seal footprint of the manufacturing seal and the closure seal later applied by the packager.
The occurrence of overlapping heat seals is a consequence of separate sealing operations occurring at different times and places. A first sealing operation occurs during the manufacturing of the pouch in which all side edges are sealed except a length of one edge left unsealed to create an opening for the introduction of the packaged items. The second sealing operation is similar to the first but carried out at the packaging site where the opening in the pouch is sealed closed. In order that the seal be continuous throughout the entire perimeter of the pouch, it is necessary for the two seal footprints (surface area where the opposing pouch sidewalls are fused together) to overlap.
In this pouch construction, the overlap joint is the point of least integrity along the length of the seal due to handling of the pouch at times between the two sealing operations. This occurs due to the type of packaging material used which is easily deformable and has no shape memory. The line along which the first and second seal footprints overlap is at the sides of the bag opening and this area is also the point of highest mechanical stress of the bag material as it is handled making it vulnerable to distortion. Thus an imperfect seal may result along the overlap points of the heat-seal footprints of the two above-described sealing operations because of distortions in the material.
In another type of well-known pouch, there is a problem with seal integrity in the areas of transition between thicknesses of a multi-ply construction having a transverse sidewall seam, for example those having a semipermeable panel to provide preliminary gas sterilization prior to final closure. In this construction, a problem can occur along a transverse edge of an intermediate ply of material fused between two outer plies where the edge of the intermediate ply forms the transition line from a three-ply thickness to a two-ply thickness in final construction. Because of the way in which the pouch is manufactured, this transverse internal edge extends to the outside side edge of the pouch and therefore can possibly create a migration channel for microbes entering the pouch from the outside. Furthermore, in this type of bag the perimeter sealing along the edge of the panel is imperfect because the transition in the overall thickness between the different number of layers causes uneven pressure to be applied during the sealing process and therefore imperfections in the perimeter seal can occur.
SUMMARY OF THE INVENTION
The present invention has been devised in order to satisfy the need in the art described above for greater seal integrity of pouch-type containers for sterilized materials to prevent microbial contamination. The applicant has created a pouch-type container comprising two webs positioned face-to-face having peripheral portions of their bottom and side edges joined by heat fusion thereby forming a pouch having an interior cavity. A mouth of the pouch is created by an unsealed portion of the webs along the top edge. The area of fusion creates a peripheral seal footprint along the bottom and side edges. An interior boundary line lies along the inside of the seal footprint facing the interior cavity and it terminates at two points at the sides of the mouth of the pouch. The two end portions of the boundary line proximate the mouth are provided with a wavy configuration which includes a series of inward facing peaks and valleys. This configuration of the heat seal footprint is created by a heat seal die which has a corresponding wavy edge that creates the peaks and valleys along the above-described portion of the heat seal footprint. The geometry of the peaks and valleys can be radiused or jagged, and when the transverse heat seal closure is applied after materials are inserted into the pouch, the closure seal footprint extends across the top edge and overlaps the wavy end portions of the interior boundary line.
To provide greater seal integrity in a sterilizable pouch having a breather panel, a pouch-type container has been created which comprises two opposing faces composed of heat-fusable sheet materials fused in an area along their side and bottom edges. One of the two opposing faces consists of two webs spliced together along a transverse seam which extends the entire width of the face and overlaps a transverse edge of one of said webs being a breather panel material. The transverse edge of the breather panel web is provided with a wavy configuration including a series of peaks and valleys along its entire length. Preferably the breather panel web is composed of a semipermeable material such as Dupont Tyvek®. Because the above-described problem migration channel occurs along the edge of the breather panel, the resulting shape of the channel is a tortuous path for any migrating microbes and hence contamination is prevented.
It is therefore the main object of the present invention to create enhanced seal performance in web-fused sterile pouches to more reliably prevent contamination from outside of the pouch. This object has been achieved by the above-disclosed invention, a preferred embodiment of which is described in detail in the following drawings and description of preferred embodiments.
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Gehman Bryon P.
Gore Gregory J.
Mangar Industries, Inc.
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