Abstract:
A zipper closure for a reclosable bag has a male profile and a female profile, the male profile being snappingly engagable within the female profile to close the zipper closure. One of the male and female profiles includes a collapsible element which forms a hermetic seal between the male and female profiles when the male profile is engaged within the female profile.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the packaging art, and, more particularly, to the art of reclosable plastic bags or packages having extruded zippers. In particular, the present invention relates to extruded zippers having two mutually interlocking members, at least one of which is partially collapsible so as to form a tight seal when interlocked with the other. 
     2. Description of the Prior Art 
     Reclosable bags used, for example, for storing household foodstuffs are typically made of polyethylene. As shown in U.S. Pat. No. 3,416,199 to Imamura, which is commonly assigned with the present invention, a reclosable bag may be formed of two opposed walls and having a mouth equipped with fastener profiles. These profiles include a male profile attached to one wall and a female profile attached to the other wall. The profiles are shaped so that, when they are aligned and pressed together into an engaging relationship, they form a continuous closure for the bag. The bag may be opened by pulling the walls apart at the mouth, thereby separating the male and female profiles from one another. 
     The prior art is replete with different shapes and arrangements for the male and female profiles. In many cases, the profiles are designed to provide relatively high resistance to opening from inside the package, while rendering the package relatively easy to open from the outside. 
     Because the male and female profiles must be shaped so as to be readily interlocked with one another, they may not form an entirely airtight closure. For this reason, peel seals are used in the reclosable plastic packages used for the retail sale of foodstuffs to ensure that the packages remain hermetically sealed prior to sale. Moreover, the peel seals can also serve a tamper-evident function by whitening or otherwise discoloring when being opened, thereby providing a means by which a prospective purchaser could be alerted to the possibility that the package had been opened prior to purchase. 
     Following purchase, there may still be a need to form a hermetic seal after the initial opening of the package to preserve the freshness of any contents remaining in the package. The present invention is an extruded zipper having male and female profiles which provide such a seal. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a zipper closure, and a reclosable bag which incorporates the zipper closure. 
     The zipper closure comprises a male profile and a female profile, the male profile being snappingly engagable within the female profile. In accordance with the present invention, one of the male and female profiles includes a collapsible element which forms a hermetic seal when the male profile is engaged within the female profile. 
     The present invention will now be described in more complete detail, with frequent reference being made to the drawings identified below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a reclosable bag having the zipper closure of the present invention; 
         FIG. 2  is a cross-sectional view taken as indicated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the zipper closure of the present invention; 
         FIG. 4  is a cross-sectional view of an alternate embodiment of the zipper closure; and 
         FIGS. 5A and 5B  are cross-sectional views of another embodiment of the zipper closure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and specifically to  FIGS. 1 and 2 , a reclosable bag  10  having the extruded zipper  12  of the present invention includes front and rear walls  14 , 16  seamed along three edges thereby forming an enclosure with an opening or mouth  18  along the top or fourth edge  20 . 
     The bag  10  is preferably made of thermoplastic material, such as polyethylene, by extrusion. Attached to the internal faces of walls  14 , 16  near mouth  18  are male and female profiles  22 , 24 , respectively, of zipper  12 , which extends continuously across the width of the bag  10 . The zipper  12 , comprising male and female profiles  22 , 24 , serves to close the mouth  18  of the bag  10  when the male and female profiles  22 , 24  are interlocked with one another. The male and female profiles  22 , 24  are extruded from a polymeric resin material, such as polyethylene, and attached to the front and rear walls  16 , 18  at some stage in the process by which bags  10  are manufactured. 
     Although male and female profiles  22 , 24  are shown in  FIG. 2  to be separate from and attached to front and rear walls  14 , 16 , respectively, it should be understood that they may be integrally formed therewith by coextrusion. Specifically, male profile  22  may be coextruded with rear wall  16 , while female profile  24  may be coextruded with front wall  14 . Moreover, the front and rear walls  14 , 16  may be part of a single sheet which is folded along the bottom  26  and sealed along the sides  28 . Each of these variations may be used without departing from the scope of the present invention as defined in the appended claims. 
     Referring, now, more specifically to  FIG. 2 , the male profile  22  includes a base or web  30  and a projecting element or bulb  32  of substantially cylindrical cross-section. The bulb  32  has a hollow core  34 , which allows the bulb  32  to collapse somewhat when compressed, and to return essentially to its original shape when compression is removed. 
     The female profile  24  has a groove  36  which is also of substantially cylindrical cross section. In accordance with the present invention, the cross section of the bulb  32  of the male profile  22  is the same size as or slightly larger than the cross section of the groove  36  of the female profile  24 . As a consequence, when the bulb  32  is pushed into groove  36 , the bulb  32  collapses because of its hollow core  34 . Once inside the groove  36 , however, the bulb  32  tends to return to its original shape, making intimate contact with the walls of the groove  36 , and thereby making a hermetic seal for the bag  10 . 
       FIG. 3  is a cross-sectional view of zipper  20 , shown, for the sake of clarity, unattached to front and rear walls  14 , 16  and with male and female profiles  22 , 24  separated from one another. 
       FIG. 4  is a cross-sectional view, analogous to that presented in  FIG. 3 , of an alternate embodiment of the zipper. As such, zipper  40  comprises male and female profiles  42 , 44 . Male profile  42  differs from that shown in  FIG. 3  by virtue of the fact that bulb  46  has a diamond-shaped cross section which may be easier to insert into groove  48  of female profile  44  than bulb  32 . 
       FIGS. 5A and 5B  show still another alternate embodiment of the zipper. As such, zipper  50  comprises male and female profiles  52 , 54 , shown separated from one another in  FIG. 5A , but joined together in  FIG. 5B . 
     As above, male profile  52  includes a projecting element or bulb  56 , although, in this embodiment, it lacks a hollow core. Female profile  54  again has a groove  58 , although it is somewhat larger in cross section than the bulb  56 , but has edges  64  which snap around the bulb  56 . 
     Within the groove  58 , however, is a projecting element or bulb  60  having a hollow core  62 . When the male profile  52  is joined to the female profile  54  by inserting the bulb  56  into the groove  58  and snappingly engaging it therein, bulb  56  compresses bulb  60  which, because of its hollow core  62 , flattens to make intimate contact therewith, and thereby to make a hermetic seal for the bag  10 . 
     Obviously, numerous modifications may be made to this invention without departing from its scope as defined in the appended claims.