Abstract:
A package for containing sterile packed items is formed from the joining of a first sheet of material and a second sheet of material. The package formed comprises a cavity for containing at least one item, a first group of sealing elements and a second set of sealing elements. The two groups of sealing elements have relative size(s), shape(s) and placement(s) to provide a desired level of seal and mechanical cohesion while reducing fiber tear out that could contaminate the contained items.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is related to co-pending provisional application serial No. 60/437,496, filed Dec. 30, 2002, which is incorporated herein by reference for any and all purposes. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates to packaging, and, more particularly, to packaging for sterilized products, such as surgical instruments and the like, formed in part from non-paper products, such as olefins.  
         BACKGROUND  
         [0003]    Certain items, such as surgical instruments, syringes, catheters, and the like, are routinely sterilized and packed (sterile-packed) at the manufacturer primarily to provide convenience of use. Sterile-packed items are available for immediate use upon removal from the packaging (i.e., no sterilization is required following removal but prior to use). Additionally, use of pre-sterilization provides a measure of protection against re-use of the packaged items. If the sterilization step occurred with the end user, there could be a greater incidence of users re-sterilizing and reusing certain products.  
           [0004]    After the items are secured within the packaging, the packaging is subjected to a sterilization process. Sterilization can occur in one of a number of ways, including via application of heat (steam), gases, and combinations thereof. While historically most sterilization has been carried out through the application of heat (e.g., steam), elevated temperature can have deleterious affects on both the constituent components of the packaging, as well as on the item(s) contained therein. For example, many medicines and surgical instruments are adversely affected when exposed to elevated temperatures.  
           [0005]    When heat is to be avoided, sterilization is accomplished most often via the introduction of a gas, for example a germicidal gas. To accomplish sterilization via such gas, the packages to be sterilized are placed in an enclosed container and the air within the packages is replaced to some degree by a germicidal gas. The gas is commonly introduced into the container by alternate application of a partial vacuum and the use of super-atmospheric pressure.  
           [0006]    Once the gas is introduced, a process of gas exchange occurs between the environment external to packages and the environment within the packages. One or more materials used for the packaging are selected for gas permeability characteristics, allowing the gas exchange to occur through the packaging material. The introduction of such gas not only eliminates the level of microorganisms then-existing within the packages, but the quantities of residual gas retained within the packages provide adequate protection against renewed bacterial contamination within the packages until the packages are used or consumed, assuming the package is adequately sealed.  
           [0007]    It is now known to join a strip of paper and a strip of plastic foil sheeting together, preferably by sealing, to form a container exhibiting an acceptable level of seal to contain sterile- packed items. Using prior art methods, there is a minimum width (typically approximately  5  millimeters) of joined edges (i.e., perimeter regions of the package formed) of the sheeting materials required to produce a sufficient seal. A tight seal is formed by pressing together the edges of the sheeting material, with optional application of heat.  
           [0008]    There exists a balancing of competing interests when forming a seal. On the one hand, the strength of the seal should be sufficient to retain the sterilized interior environment of the package. At the same time, the strength of seal should not be so great that opening the package requires tools or extraordinary effort. Ideally, when access to the sterile-packed items is desired the user should be able to peel the strips of materials apart to reveal the packaged items. If needed, a tab or similar region of material can be used to facilitate this process.  
           [0009]    Another factor that must be considered in peeling the sheets of materials apart to open the sterile package is whether fibers from one or both materials will be dislodged during the peeling. A seal that is too tight can cause fibers associated with the material(s) to be ripped out as the sheets are being separated. Once dislodged, the loose fibers can fall inside the package and compromise the sterility/use of any items contained therein. For example, loose fibers coming into contact with surgical instruments can cause inflammation in patients upon whom such instruments are used. Therefore, ideally the bond or seal between the strip paper and the strip of foil sheeting is made such that while ease of “peelability” is retained, no loose fibers result during peeling.  
           [0010]    There are a number of disadvantages associated with use of paper and paper-like materials for packaging used for sterile-packed items. For example, use of traditional agents, such as glue and the like, to increase the cohesion of the fiber-bond of strip paper (thereby reducing the occurrence of loose fibers upon peeling) precludes the level of gas permeability needed for sterilization. Likewise, use of materials likely to enhance gas permeability can also increase the chance that loose fibers will be produced upon peeling.  
           [0011]    As a result of the foregoing, and other disadvantages, use of non-paper materials, like polyolefins, for packaging of sterile-packed items is desired because such materials provide superior inner bond strength, superior tear resistance, low fiber release and good porosity, when compared with paper materials. As set forth more completely in U.S. Pat. No. 4,630,729, assigned to Firma Dixie Union Verpackungen, a related company to assignee, the complete disclosure of which is incorporated herein by reference for any and all purposes, it is also known to seal a package consisting of a strip of plastic foil or sheeting, and a strip of paper, whereby the two strips are sealed together at their margins, so as to permit opening of the package by a peeling action, wherein the seal consists of two groups of sealing elements, group 1 (one) of which includes small dimension seals to ensure the integrity of the resulting seal, and group 2 (two) of which includes linear seals with restricted dimensions (width) that are arranged such that they run transverse to the direction of the peel. The arranging of the group 2 (two) seals combines a high degree of mechanical strength with ease of peeling, minimizing fiber tear-out.  
         SUMMARY  
         [0012]    It is the object of the present invention to improve on a package constructed at least in part of one or more olefins, and, more specifically, spunbounded polyolefins, such that, on the one hand, the absolute “sealability” and the mechanical cohesion of the two strips of the package remains in tact under expected conditions, and that, on the other hand, the two strips can nevertheless be easily peeled apart from each other in a manner that minimizes fiber tear-out.  
           [0013]    The present invention provides a package, for example, for use with surgical instruments and other sterile-packed products, comprising one or more olefins (e.g., ethylene), and, more specifically, one or more spunbounded polyolefins (e.g., Tyvek™ 2FS™). The package preferably includes two strips of material that surround at least one cavity formed when the sheets are joined (e.g., via sealing). When sealed together, the sheets preferably include a projection or similar region to facilitate the process of peeling the joined sheets apart. The sealed edges (i.e., the joined region of the margin areas) to be opened include at least two uniformly distributed groups of bonding elements. The first group of sealing elements is comprised of relatively small-dimensioned elements, positioned in at least one direction in the plane of the edge. The second group of sealing elements is comprised of considerably longer lines of elements having limited width, positioned such that the lines run substantially transversely to the expected direction of peel.  
           [0014]    Non-paper materials as a component of sterile-packed packages are favored for at least the following reasons: superior inner bond strength; superior tear resistance; low fiber tear; and improved porosity. Use of such materials substantially decreases any delamination of uncoated polyolefin materials upon opening of a package. Additionally, there is a diminished need for coating such materials, thereby greatly reducing associated costs. Moreover, use of such materials (versus paper products) provides the ability to longitudinally cut through the sealed area, thereby reducing the need for an unsealed area (apron), which in turn allows the package to have a wider seal and/or a larger inner cavity for containment of products.  
           [0015]    The present invention recognizes and takes advantage of the discovery that there is no appreciable additional expenditure over conventional sealing methods and systems to use various sealing elements adopted for joining the two material strips. In this context, the arrangement of the multiple groups of sealing elements is flexible, allowing any desired shape(s) of packages to be produced. For example, the sealing bars and the counter-bearers for these groups can be manufactured as plate-like blanks. From these blanks, the desired forms can be produced. Alternatively, a specific tool for each desired package type and/or size is manufactured.  
           [0016]    The first group of sealing elements is preferably laid out uniformly, each element of which is of relatively small dimension. The combination of uniform coverage with relative size reduces, if not eliminates, tear out of fibers. Separating a seal formed with such elements significantly reduces, if not eliminates, the risk of fiber tear since the forces transmitted from the sealing elements to the fibers are too limited to overcome the cohesion forces of the fibers in the bonded fibers. Additionally, since, generally, the fibers associated with the strip material are considerably longer than the individual dimensions of the sealing elements of the first group, even if portions of a fiber are dislodged, the fiber overall remains attached to the strip material. Alternatively, if portions of the fiber are actually separated from the strip material, they are generally small enough to be retained on the sealing elements that dislodged them. In either case, no fibers are dislodged and released during peeling.  
           [0017]    The second group of sealing elements of the present invention provides the mechanical cohesion between the two strips of material comprising the package. As a result, the second group of sealing elements is not intended to produce an adequate degree of “sealability,” and can therefore be designed accordingly. The second group of sealing elements comprises elements of a general linear shape having a limited width. This relatively narrow dimension would not be sufficient alone to effectuate a proper seal. The second group of sealing elements also is positioned such that no disadvantageous effects occur upon peeling. The present invention achieves this by positioning the elements of the second group to run substantially transversely to the expected direction of peel. If the linear elements of the second group were aligned to run in the general direction of the peel, such sealing elements would likely tear out rows of fibers or lumps of fibers during peeling. Since the linear elements of the second group are arranged substantially transversely to the expected direction of the peel, only a relatively limited width of the strip is affected by the elements of this group during peeling. Any fibers that are actually dislodged (those that run virtually parallel to the linear elements) are retained by the sealing elements, thus preventing release of such fibers. Fibers that run transversely to the linear elements are, in contrast, only slightly affected, if at all, and are therefore not dislodged.  
           [0018]    Through testing, the present invention recognizes that the most advantageous performance of the linear elements of the second group occurs when the linear elements of the second group of sealing elements do not run exactly at right angles to the direction of peel, but rather form an acute angle with the expected direction of peel. Use of an acute angle results in both a reduction of the tear-out forces during peeling, and a uniformity of peeling operation. 
       
    
    
       [0019]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.  
       DESCRIPTION OF DRAWINGS  
       [0020]    [0020]FIG. 1 is a plan view of a package formed in accordance with the present invention;  
         [0021]    [0021]FIG. 2 is an alternative embodiment of a package formed in accordance with one embodiment of the present invention;  
         [0022]    [0022]FIG. 3 is a sectional view corresponding to the section line III--III of FIG. 2; and  
         [0023]    [0023]FIG. 4 is a magnified plan view of a package formed in accordance with another embodiment of the present invention.  
     
    
       [0024]    Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0025]    Referring now to FIGS. 1 and 3, there is shown a package  10  formed in accordance with one embodiment of the present invention in plan view and in cross section (FIG. 3 is a sectional view corresponding to the section line III--III of FIG. 2), respectively. The package  10  comprises a bottom sheet  20  and a top sheet  30 . A cavity  40  is formed within the bottom sheet  20  to receive one or more items  45  (FIG. 1) to be contained by the package  1   0 . Although a single cavity  40  of a generally rectangular shape is shown and described, it is noted that any number and/or shapes and/or sizes of cavities can be used in connection with the present invention, as desired, and all such combinations thereof are contemplated by the present invention.  
         [0026]    Once one or more items  45  are placed within the cavity  40 , the top sheet  30  covers the items and is bound to the bottom sheet  20  via sealing. In a preferred embodiment, the top sheet  30  is preferably constructed of a non-paper material having sufficient gas permeability characteristics. Examples of such materials include olefins, such as spunbounded polyolefin substrates. One example of an spunbounded polyolefin substrate suitable for use with this embodiment of the present invention is DuPont® Tyvek™ 2FS™ material. Spunbounded polyolefin materials function well as a component material for packages made in accordance with the present invention, but provide different sealing and peeling challenges than those associated with paper and paper-like materials. The present invention package  10  provides sealing and peeling functionality that allows such olefin materials to achieve desired sealing and peeling characteristics, thereby producing a superior package when compared to those made with paper or paper-like materials.  
         [0027]    At a surrounding margin of the package  10 , the bottom sheet  20  and the top sheet  30  are bonded with each other to form a joined region  60 , preferably by sealing, utilizing methods and/or tools known in the industry for forming same. For example, sealing can occur via the application of heat, such as steam, and/or mechanical force. Sealing tools known in the industry can be utilized. Although the application of heat and/or force via known tools is described herein, it is noted that sealing by any suitable means and employing any suitable tools can be used, if desired, and such use is contemplated by the present invention.  
         [0028]    The joined region  60  of the package  10  is bordered by parallel contours  65  and  70 , whereby the contour  65  essentially forms the outer edge of the package  10 , while the contour  70  simultaneously defines the inner edge of the package  10  and the outer edge of cavity  40 . The joined region  60  can have substantially the same width around the perimeter of the package  10 , or can have varying widths along the perimeter of the package  10 , as desired. As shown in FIGS. 1 and 2, embodiments of the present invention can include a joined region  60  that totally surrounds the cavity  40  and that is generally similar in shape and width throughout the package  10 . However, embodiments of the present invention can include a joined region  60  that surrounds less than the entire cavity  40  of the package  10  and/or that is dissimilarly shaped/sized throughout the package  10 , if desired. It is noted that embodiments of the package  10  including a joined region  60  that surrounds less than the entire cavity  40  may be desired where it is preferable for the top sheet  30  to stay attached to the package  10  following peeling.  
         [0029]    Generally, a width of approximately 5 millimeters is sufficient for the width of the joined region  60 . However, varying widths, either uniformly or dispersed over the entire surface of the joined region  60 , can be utilized, if desired. It is noted that utilizing the unique features of the present invention package  10 , widths of less than 5 millimeters for the joined region  60  can be employed, if desired. The use of such reduced widths for the joined region  60  will result in increased space for use in the cavity(ies)  40  of the package  10 .  
         [0030]    Referring again to FIG. 1, the package  10  includes a tab region  80 . The tab region  80  represents an area where the top sheet  30  and the bottom sheet  20  are not bound together. Gripping the tab region  80  allows one to easily initiate the peeling of the top sheet  30  from the bottom sheet  20  to gain access to the item(s) stored within the cavity  40 . It is noted that, depending upon a number of factors, the presence, size and shape of the tab region  80  can vary (e.g., FIG. 2). For example, in some embodiments no tab region  80  may be desired. In such embodiments the very edges of top sheet  30  and bottom sheet  20  could be used to initiate peeling action to separate the sheets and access the item(s) contained within the package  10 . One or more tab regions  80  could also be placed at virtually any point along the package, most likely, but not exclusively, along the perimeter of the package  10 .  
         [0031]    In FIGS. 1 and 2, an expected direction of peel  85  is shown via arrow  90 . This direction represents the direction that peeling optimally occurs. In other words, a user optimally separates the top sheet  30  from the bottom sheet  20  by peeling in the direction of the expected direction of peel  85  (arrow  90 ). This is not to suggest that peeling is restricted to the expected direction of peel  85 , but merely that such direction is optimal and therefore is expected. As detailed below, the expected direction of peel  85  is important to the functionality of the present invention package  10 .  
         [0032]    Now referring to FIG. 4, the package  10  of another embodiment of the present invention includes a first sealing group  100  associated with the joined region  60 . The first sealing group  100  is preferably comprised of first sealing elements  110 , each element of which has relatively small dimensions. Examples of such first sealing elements  110  include small circles, squares, triangles, dots, whether “hollow” or “filled”, and the like. Although representative shapes of the first sealing elements  110  have been described herein, it is noted that any suitable shape, or combination of shapes, could be employed, if desired.  
         [0033]    Additionally, placement of the first sealing elements  110  within the joined region  60  is preferably relatively uniform. As will be explained, such uniform placement aids in the reduction of fiber tear out upon separation of the bottom sheet  20  and the top sheet  30  to access the cavity  40 . Although uniform placement of the first sealing elements  110  is described herein, any suitable placement of the first sealing elements can be employed, if desired. The relative shape, number and placement (including distance between each element) of the first sealing elements  110  are used to provide a tight, but not flat, seal. Flat seals are to be avoided since they transfer large fiber tear out forces.  
         [0034]    The combination of uniform placement and relative size of the first sealing elements  110  reduces, if not eliminates, tear out of fibers associated with the top sheet  30  and/or the bottom sheet  20 . Reduction, if not elimination, of fiber tear-out occurs since the forces transmitted from the first sealing elements  110  to any fibers within the top sheet  30  and/or the bottom sheet  20  are too limited to overcome the cohesion forces of such fibers with the larger material. Additionally, since, generally, fibers associated with strip material are considerably longer than the individual dimensions of the first sealing elements  110 , even if portions of a fiber are dislodged, the fiber overall remains attached to the strip material. Alternatively, if portions of the fiber are actually separated from the strip material, they are generally small enough to be retained on the first sealing elements  110  that dislodged them. In either case, no fibers are dislodged and released during peeling.  
         [0035]    The package  10  of this embodiment further includes a second sealing group  120  associated with the joined region  60 . The second sealing group  120  is preferably comprised of second sealing elements  130  having a generally linear shape of relatively narrow width (preferably less than 2 mm in width). Examples of such second sealing elements  130  include lines, continuous and broken (e.g., dashes, zig-zags), whether “hollow” or “filled”, and the like. Although representative shapes of the second sealing elements  130  have been described herein, it is noted that any suitable shape, or combination of shapes, could be employed, if desired.  
         [0036]    Referring now to FIGS. 1 and 4, the second sealing group  120  of the present invention provides mechanical cohesion between the top sheet  30  and the bottom sheet  20  comprising the package  10 . As a result, the second sealing group  120  is not intended to produce an adequate degree of “sealability” for the package  10 , and can therefore be designed accordingly. Importantly, the second sealing elements  130  are positioned within the joined region  60  to run substantially transverse with respect to the expected direction of peel  85  (arrow  90 ). If the substantially linear shape(s) of the second sealing elements  130  were aligned to run in the general direction of the expected peel  85  (arrow  90 ), said second sealing elements  130  would likely tear out fibers associate with the top sheet  30  and/or the bottom sheet  20  during peeling. Since the second sealing elements  130  are arranged substantially transversely to the expected direction of the peel  85  (arrow  90 ), only a relatively limited portion of the top sheet  30  and/or bottom sheet  20  is affected by the second sealing elements  130  during peeling. Any fibers that are actually dislodged (e.g., those that run virtually parallel to the second sealing elements  130 ) are retained by the second sealing elements  130 , thus preventing release of such fibers. Fibers that run transversely to the second sealing elements  130  are, in contrast, only slightly affected, if at all, and are therefore not dislodged.  
         [0037]    In a preferred embodiment, the second sealing elements  130  form one or more acute angles with respect to the expected direction of peel  85  (arrow  90 ). Use of one or more acute angles results in both a reduction of the tear-out forces during peeling, and a uniformity of peeling operation. Although substantially transverse orientation of the second sealing elements  130  is described, orientation of the second sealing elements  130  with respect to the expected direction of peel  85  (arrow  90 ) at any one or more acute angles is contemplated by the present invention. As shown in FIGS. 1, 2 and  4 , the second sealing elements  130  can be arranged in repeating or “zig-zag” patterns. Such patterns are described as representative patterns. Any suitable pattern, or combination of patterns, may be utilized, if desired.  
         [0038]    In operation, one of more items  45  to be contained by the package  10  is placed within the cavity  40 . The top sheet  30  is then placed over the bottom sheet  20  and sealing of the two materials is accomplished. Alternatively, the seal item(s) can be sterilized by subjecting the package  10  to known methods of sterilization. Such methods can include the application of thermal energy (e.g., steam) and/or the introduction of one of more gases, as desired. It is noted that the application of thermal energy can have deleterious effects on certain items within the package  10 . As a result, the use of one of the gases (e.g., a germicidal gas) can be employed. In the event one of more gases are used to provided sterilization, the component materials of the package  10  must facilitate gas exchange between the interior and exterior environments of the cavity  40  of the package  10 . For example, a top sheet  30  having gas permeability characteristics can be employed.  
         [0039]    Once access to the item(s) contained within the package  10  is desired, the top sheet  30  and the bottom sheet  20  are separated from each other by a peeling action that is preferably initiated at the optional tab region  80 . Optimally, the top sheet  30  and the bottom sheet  20  are peeled apart in the expected direction of peel  85  (arrow  90 ), such that fiber tear-out forces are reduced, any dislodged fibers are retained, and peeling is uniform. Depending upon the design and placement of the first sealing group  100  and the second sealing group  120 , the top sheet  30  can be removed and discarded apart from the package  10 , or is retained with the package  10  for disposal.  
         [0040]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, an embodiment of the present invention package employing more than two groups of sealing elements could be utilized. Accordingly, other embodiments are within the scope of the following claims.