Abstract:
A flexible package is provided with a shrouded slide fastener closure. Fastener tracks are deformed at each end to provide an end stop to limit slider movement. A stop of reduced area with increased pull off force performance is provided. Features of the end stop include an L-shaped shoulder located above an underlying finger portion comprising an undeformed portion of the fastener tracks. The remainder of the end stop is formed by heating, softening and displacing portions of the fastener track material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to the closure of flexible packages, such as plastic bags, and in particular to fastener closures employing sliders. 
     2. Description of the Related Art 
     With the recent emphasis in providing consumers with bulk quantities of various commodities, such as food products, reclosable packages have become increasingly popular. One of the most popular means of providing reclosability is to employ zippers of various types, particularly zippers which are compatible with flexible packages of plastic film construction. Manufacturers of food products and other commodities are concerned with filling the contents of a flexible package as quickly and economically as possible. It is important that the opening provided by the fastener be made as large as practically possible. Consumers or other end users also prefer large sized openings for easy extraction of products from the package interior. Even with large openings, however, products within the package may interfere with fastener operation when product poured or otherwise dispensed from the package becomes entrained in the fastener components. 
     Other improvements to flexible reclosable packages are being sought. For example, when handling products comprised of numerous small pieces, such as shredded cheese or cereal, for example, it is generally desirable to have the package formed into a pouch which is open at one end, or along one side, so as to allow product to be poured or shaken through the reclosable opening. It is desirable that the product be allowed to freely flow past the reclosable opening. Preferably, the path taken by the product within the package should be made as smooth as possible. 
     Although improvements have been made in the art of plastic welding and joining, manufacturers of consumer products employing high speed production techniques are continually seeking improved package forming methods and equipment. Concern has been focused on the formation of stop members which limit the travel of a sliding closure traveling along fastener tracks. Any reduction in the time needed to form these and other package features can result in substantial cost savings. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a shrouded flexible package with an improved fastener closure. 
     Another object of the present invention is to provide reclosable packages having fastener sliders which are protected during shipment and display, and afterwards, when the package contents are poured out or otherwise extracted. 
     A further object of the present invention is to provide a shrouded reclosable package having improved arrangements for hanging display. 
     Yet another object of the present invention is to provide a shrouded reclosable plastic package having a slider fastener with improved containment of the slider in a manner which also optimizes the size of the bag opening. 
     A further object of the present invention is to provide a shrouded plastic bag having a slider fastener with an improved end or “crush” seal of the fastener tracks. 
     These and other objects of the present invention are attained in a reclosable flexible package which comprises opposed front and rear panels that have sides and are joined together to form an interior and a package opening communicating with the interior. First and second interlockable fastener tracks configurable in an interlocked, closed position and an unlocked open position. A slider that at least partly extends above the fastener tracks and is movable along fastener tracks to configure tracks in interlocked position to close the opening and to configure the fastener tracks in unlocked position to allow access through the opening to the package interior. Fastener tracks that have opposed ends located adjacent opposed sides of front and rear panels. A side seal of pre-selected width joining together one side of front and rear panels; and a stop adjacent side seal formed from an end of fastener tracks comprising an L-shaped shoulder having a portion extending above the fastener tracks and a finger-like portion lying below the shoulder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary front elevational view of a flexible package according to principles of the present invention; 
         FIG. 2  is a fragmentary perspective view of a fastener track assembly according to principles of the present invention; 
         FIG. 3  is a cross-sectional view taken along the line  3 — 3  of  FIG. 2 ; 
         FIG. 4  is a fragmentary perspective view of a fastener track and slider assembly; 
         FIG. 5  is a cross-sectional view taken along the line  5 — 5  of  FIG. 2 ; 
         FIG. 6  is a cross-sectional view taken along the line  6 — 6  of  FIG. 2 ; 
         FIG. 7  shows a portion of  FIG. 2  taken on an enlarged scale; 
         FIG. 8  is a cross-sectional view taken along the line  8 — 8  of  FIG. 7 ; 
         FIG. 9  is a top plan view of the slider component; 
         FIG. 10  is a front elevational view thereof; 
         FIG. 11  is an elevational view from one end thereof; 
         FIG. 12  is an elevational view from the other end thereof; 
         FIG. 13  is a cross-sectional view taken along the line  13 — 13  of  FIG. 1 ; 
         FIG. 14  is a front elevational view of an ultrasonic member for forming portions of the fastener track; 
         FIG. 15  is a cross-sectional view taken along the line  15 — 15  of  FIG. 14 ; and 
         FIG. 16  is a cross-sectional view taken along the line  16 — 16  of FIG.  14 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings and initially to  FIGS. 1 and 13 , a flexible package illustrating principles of the present invention is generally indicated at  10 . Flexible package  10  preferably comprises a plastic bag having front and back panels  12 ,  14  joined together at the left end by a side seal  20  and at the right end by a side seal  22 . Side seal  20  is preferably of conventional conduction heat-sealed construction, having a generally constant width throughout. Panels  12 ,  14  are further joined together at their bottom ends by a bottom seal  24  (see  FIG. 13 ) extending between side seals  20 ,  22 , as is known in the art. Alternatively, the bottom seal can be replaced by a fold line with panels  12 ,  14  being formed from a continuous sheet of plastic material. 
     The upper end of flexible package  10  features a reclosable opening including a slide fastener arrangement with fastener tracks  26 ,  28  and a slider  30 , all preferably of polyolefin material. The slider  30  is slidable along the fastener tracks, causing the fastener tracks to interlock or mate for closure of the flexible package and to unmate or separate to open the flexible package for access to contents in the package interior. 
     The flexible package according to principles of the present invention has found immediate commercial acceptance for use with food products, including perishable food products, such as cheese. Accordingly, it is generally preferred that the flexible package includes an hermetic seal  36  (see  FIG. 13 ) in the form of a peelable seal as taught in commonly assigned U.S. Pat. Nos. 5,014,856; 5,107,658; and 5,050,736, the disclosures of which are incorporated by reference as if fully set forth herein. 
     As mentioned above, flexible package  10  preferably comprises a bag having panels  12 , 14  formed from plastic sheet material. The sheet material can be of a single material type, such as polyolefin materials including polyethylene and polypropylene, but preferably comprises a laminate assembly of several different material types, as is known in the art to provide a barrier to moisture as well as certain gases, such as oxygen or inert fillers of the types used with food products. Other types of laminate films, such as those known in the art to preserve food freshness, may be employed. Where the contents of the flexible package are not perishable or where other considerations may dictate, the panels  12 ,  14  can be constructed without regard to gas or vapor barrier properties. It is generally preferred that the fastener tracks be joined to web-like flanges  72 ,  74  (see  FIG. 3 ) which, in turn, are joined to panels  12 ,  14  as shown in FIG.  13 . 
     Referring now to  FIGS. 9-12 , fastener slider  30  has a top wall  44 , a shorter side wall  46  and a longer side wall  48 , cooperating to define an internal cavity for receiving the fastener tracks  26 ,  28 . As can be seen by comparing the end views of  FIGS. 11 and 12 , a first end  54  of the slider defines a cavity opening  50   a  which is generally rectangular. The opposed end  56  (shown in  FIG. 12 ) defines a cavity opening which is generally arrowhead or A-shaped, as indicated by reference numeral  50   b , conforming to the outline of the interlocked fastener tracks. When the slider  30  of  FIG. 1  is moved to the right, end  56  is at the leading end of the slider and the fastener tracks  26 ,  28  are unlocked, thus opening the flexible package  10 . Conversely, as slider  30  of  FIG. 1  is moved to the left, end  54  is made the leading end, and fastener tracks  26 ,  28  are interlocked to close the flexible package. 
     Referring again to  FIGS. 11 and 12 , a number of features cooperate to maintain slider  30  captive on fastener tracks  26 ,  28 . As can be seen for example in  FIG. 12 , a pair of upwardly facing stepped portions  62  are formed on either side of the slider cavity. Inwardly extending protrusions  64  are located at the other end of the slider. Protrusions  64  and stepped portions  62  engage the bottoms  26   a  and  28   a  (see  FIG. 2 ) of fastener tracks  26 ,  28 , as can be seen for example in FIG.  13 . The engagement of the stepped portions  62  and the protrusions  64  with the bottoms of the fastener tracks prevents the slider from being upwardly dislocated from the fastener tracks. 
     Referring to  FIG. 1 , the ends of the of the fastener tracks are deformed or “crushed” to form stops  68 . Preferably, stops  68  are formed by the application of ultrasonically generated heat and pressure to the ends of fastener tracks  26 ,  28  using ultrasonic horn  300  (see FIGS.  14 - 16 ). It has been found that the use of present day conduction heat sealing techniques does not provide the control needed to attain the intricate, close tolerance design of stop members according to principles of the present invention. Further, it has been found that the use of present day conduction heat sealing techniques immediately adjacent previously formed stop members tends to distort the stop members, oftentimes to an extent rendering the stop members unacceptable from a quality control standpoint. 
     It is generally preferred that the fastener tracks  26 ,  28  be formed off line, that is, at a remote location and brought to the assembly point on a reel or other bulk supply. With reference to  FIG. 2 , for example, skirt or flange portions  72 ,  74  are joined to or otherwise provided with the fastener tracks  26 ,  28 . It is generally preferred that the end stops  68  be provided at a remote location either during fabrication of the fastener tracks, or at a later point in time. As will be seen herein, the end stops  68  are formed by heating and softening, with application of pressure to displace portions of the fastener track material in a carefully defined manner shown for example in FIG.  4 . Referring to  FIG. 4 , end stop  68  includes a generally L-shaped shoulder  200  having an inwardly facing edge  202  located opposite a cut edge  204 . As shown in  FIG. 4 , end stop  68  has a major surface  208  which is recessed or inset from the adjacent major face  28   a  of fastener track  28 . Shoulder  200  includes an end face  212  located adjacent a “fin” portion  214 . With reference to  FIG. 2 , it is generally preferred that a pair of laterally opposed end stops be formed in a single operation and subsequently severed along line  6 — 6 . The severing produces the cut edge  204  described in FIG.  4 . It is important in many commercial applications, that the bottom portions of the fastener tracks remain undeformed. As can be seen in  FIG. 4 , a finger-like portion  220  underlies a major portion of the shoulder  200  and comprises the undeformed bottom portion of the fastener tracks from which shoulder  28  is formed. 
     Turning now to  FIGS. 5-8 , and initially to  FIG. 7 , the dual opposed end stop formation generally designated at  220  has a width W which, in the preferred embodiment, ranges between ⅞ inch to 1-½ inch. With the present invention, the width of end stops  68  (i.e., ½ of dimension W) can be made optimally small to allow maximum opening of the fastener tracks for easy access into the package. The height h of the end stop extending above the top of the fastener tracks ranges between {fraction (1/16)}-⅛ inch and is maximized for the best interference with the slider. The distance R across the bottom of the fastener tracks (see  FIG. 3 ) is important to hold the slider on the tracks and it has been found important in many commercial applications that the full width R is maintained at the end stop. With reference to  FIG. 2 , the cross-section along line  6 — 6  occurs at the cut line which divides the dual end stop formation into respective end stop portions. The cross-sectional dimension or thickness at cross-section  6 — 6  is illustrated in  FIG. 6  with reference to lateral dimension T. Also shown in  FIG. 5  is the angular feature indicated by reference designator λ. This feature comprises an undercut where the upstanding portion of the  FIG. 5  cross-section is joined to the relatively more massive base portion. With reference to  FIG. 8 , the upper fin portion  226  is defined with reference to a beveled surface  228  defined by an angular offset φ. 
     With reference again to  FIG. 2 , an adjacent cross-section along line  5 — 5  is illustrated in FIG.  5 . The width of the end stop at this section is indicated by reference designator S a dimension which preferably is held equal to or slightly greater than the dimension R of the undeformed fastener tracks as indicated in FIG.  3 . With reference to  FIG. 7  a fin-like flattened portion  224  is located between the finger-like extensions  220 . The width of the flattened portion in the preferred embodiment, indicated by reference designator F is {fraction ( 1 / 4 )} inch. At the upper end of the dual end stop formation, a corresponding fin-like portion  226  is provided between the end stops. It should be noted that the fin-like portions  224 ,  226  of reduced thickness are located along the severing line which divides the dual end stop formation into respective, opposed end stops. This reduces wear on the cutting member, and allows a lighter cutting stroke causing less disruption to the fastener track assembly. Further, the substantial reduction in thickness along the cut line provided by portion  224 ,  226  more closely resembles the thickness of the remainder to be cut, namely, the skirt or flange portions  72 ,  74 . This allows a more even cutting across the entire extent of the zipper track assembly. 
     Turning now to  FIGS. 3 and 13 , and initially to  FIG. 3 , the fastener tracks are preferably formed from a sub-assembly generally indicated at  70  in which the fastener tracks  26 ,  28  are provided with corresponding fastener flanges  72 ,  74 . The fastener flanges  72 ,  74  are co-extensive with the fastener tracks  26 ,  28  and take the form of a plastic web to be heat sealed to the panels  12 ,  14 . As can be seen in  FIG. 3 , fastener flange  74  is shorter in height than fastener flange  72 , so as to accommodate the preferred hermetic seal arrangement shown in FIG.  13 . The fastener flanges  72 ,  74  are heat sealed to panels  12 ,  14 . With reference to  FIG. 13 , fastener flange  72  is welded or otherwise mechanically sealed to panel  12  at weld band  78 . As shown at the upper portion of  FIG. 13 , the upper ends of panels  12 ,  14  are joined to the outer outwardly facing surfaces of fastener flanges  72 ,  74  at points intermediate the fastener tracks and peelable seal  36 . Band  36  preferably comprises an hermetic peelable seal formed by the joinder of panel  14  to the inside face  72   a  of fastener flange  72 . Panel  12  is sealed to the opposite outside face of the fastener flange as schematically indicated in FIG.  13 . 
     As indicated in  FIG. 13 , flanges  72 ,  74  are joined to respective panels  12 ,  14 , preferably at their lower ends, so as to prevent product from entering between flange  72  and panel  12 , as well as between flange  74  and panel  14 . In certain applications this may not be a critical requirement. In  FIG. 13 , the upper portion of panel  12  is shown for illustrative purposes as spaced from the lower end of flange  72 . In practice, it is generally preferred that this spacing be eliminated, with panel  12  being in intimate contact with flange  72 . Similarly, any gap between panel  14  and the lower end of fastener flange  74  is preferably eliminated. Although it is most preferred that the peelable seal be formed by joining panel  14  to fastener flange  72 , the peelable seal, preferably an hermetic seal, can be formed between the fastener flanges  72 ,  74  or directly between the panels  12 ,  14 , although these alternative constructions are less preferred than the arrangement shown in FIG.  10 . 
     Turning now to  FIG. 13 , flexible package  10  is shown constructed with the panels  12 ,  14 , side seal  22 , upper enlarged side seal portion  80  and fastener tracks  26 ,  28 , as described above.  FIG. 13  schematically illustrates a preferred commercial fabrication of flexible package  10 . As will be appreciated by those skilled in the art, practical commercial assembly requires recognition of tolerances of the equipment and materials used to construct a viable commercial product. For example, tracks  26 ,  28  are ultimately mechanically coupled to panels  12 ,  14  using conduction heat seal tooling. It is preferred that the upper end of enlarged side seal portion  80  be spaced below the lower ends of the fastener tracks. 
     In one commercial embodiment, flexible package  10  comprises a plastic bag having a width of approximately 6.5 inches from side edge to side edge and a total overall height of approximately 10.75 inches. The fastener tracks  26 ,  28  have a height of approximately 4 millimeters. As shown in the upper left hand corner of  FIG. 7 , the stop projects a distance h above the top edge of the fastener tracks. Although the package opening, fastener tracks and related features are shown at the upper end of the flexible package, the present invention is intended to cover arrangements in which the opening and related structure is provided on the side or bottom of the flexible package. 
     The present invention is also directed to an improved package which includes the features of flexible package  10 , described above and in addition includes a shroud portion such as a shroud portion which extends above a line of weakness formed in panels  12 ,  14 . Preferably, the shroud is made for easy tear-away removal in an intuitive manual operation not requiring special directions. A notch may be formed in edge  18 , located slightly above stop  68 . In order to gain access to the package contents, a user grasps the upper edge of the shroud causing an initially tearing the notch. Tearing continues along a weakening line to a laser score line under the fastener tracks. With continued tearing across the width of the package, the shroud is removed, leaving a package substantially similar to the package described above in FIG.  1 . 
     The drawings and the foregoing descriptions are not intended to represent the only forms of the invention in regard to the details of its construction and manner of operation. Changes in form and in the proportion of parts, as well as the substitution of equivalents, are contemplated as circumstances may suggest or render expedient; and although specific terms have been employed, they are intended in a generic and descriptive sense only and not for the purposes of limitation, the scope of the invention being delineated by the following claims.