ll Z~ '8 HE~OD OF MARIN~ RECLOBABLB PL~TIC ~A~B ON A FORM FILL AND BEAL
MAC~INB
Backaround of the Invention The present invention relates to improvements in the method of manufacturing reclosable plastic bags and more particularly to a method which permits such bags to be formed as they are fed over a filling spout of a filling machine whereby the bags are formed and simultaneously filled with a product.
The art of making reclosable plastic bags provided with mating profiles which form a zipper to render the bags reclosable is well defined in prior patents. Such patents are discussed, for example in V.S. Patents 4,894,975 and 4,709,533. ~he last mentioned patent further describes a method and apparatus which permits the bags to be formed in situ about the filling spout:of a filling machine. In accordance with the disclosed method the lateral edges of a film are brought together and the surfaces adjacent the edges are joined together in a fin seal to form the sealed top of a bag. Zipper strips are brought to the inside of the film between the filling spout and the fin seal to provide a reclosable closure between the fin seal and the contents of the bag.
The method disclosed in the above referenced patent 4,709,533 results in bags in which the zipper is initially disposed within the finished bag. This method as well as other systems proposed in the past either had the zipper inside the tube, (i.e. between the tube and the filling spout) or positioned between the free edges of the tube. These systems required fairly complex arrangements of guides and sealing bars, which tended to cr~ate additional potential prohl~C during the manufacturing process. Hence it became desireable to simplify as much as possible the method of attaching the zipper to the film.
Furthermore, the customer of the packaged product had to first ~ 2~6~ ,8 cut open the bag before the zipper became evident. As a result much of the eye appeal and hence value added of the zippered packaging could be lost on a customer of the product packaged within the bag. In addition, since the zipper was initially within the package its subsequent operation could be interfered with by the contents of the package, particularly when the contents are in a powder form.
~ummarv of the Invention L0 In view of the above it is a principal object of the presen invention to provide an improved method of forming reclosable plastic bags in situ at a form, fill and seal machine in which the zipper is initially disposed on the outside of the bag.
A further object is to provide such a method wherein the bag I
so produced completely seals the product packaged therein.
A still further object is to provide such a method wherein a security seal is provided on the final package so as to provide ready evidence of tampering with the package or its contents.
Still another object is to provide such a zippered package wherein the zipper is protected from the contents of the package prior to and after the package is opened.
In accordance with the present invention a method is provided for forming a reclosable plastic bag in situ at a form, fill and seal machine by continuously feeding a film of plastic material and forming it into a tube about a filling spout of the machine. A plastic zipper strip having first and second interlocking members is fed parallel to the tube and attached to the outside of the film on the surface opposite to that directed towards the f~lling spout. The interlock;ng ~ rs are preferably disposed on strips provided with a web on at least one side of each interlocking member with the webs being attached to Il z~r~ a the film. The film between the zipper and pouring spout may be pleated 60 as to provide a pouring spout or a gasket for the final bag.
Brief Descrl~tion of the Draw~ nas In the accompanying drawings:
Fig. 1 is a simplified perspective view of a form fill and ' seal operation in accordance with the present invention:
Fig. 2 ls a plan view of a typical bag formed in accordance L0 with the form fill and seal operation of the present invention:
Fig. 3 is an enlarged cross sectional view of the top of th bag shown in Fig. 2 taken along reference lines 3-3;
Fig. 4 is a simplified perspective view of a form fill and seal operation in accordance with the present invention depicting a different type of zipper being utilized;
Fig. 5 is a fragmentary enlarged cross sectional view of Fig. 4 taken along reference lines 5-5;
Fig. 6 is a fragmentary perspective view of the zippered tube formed on the equipment depicted in Fig. 4:
Fig. 7 is an enlarged, exaggerated sectional view of a reclosable bag formed in accordance with the present invention depicting a tube construction which provides for a pouring spout or gasket; appearing with Figs. 2 and 3;
Fig. 8 is a view similar to Fig. 7 but with the interlocking members of the zipper open; and Fig. 9 is a fragmentary sectional view of a portion of a package formed utilizing the zipper shown in Fig. 5 and depicting a tube construction that provides for a pouring spout or a gasket; and Fig. 10 is a variation of Fig. 9.
Z~ s,~8 Detailed De9cription of the Preferre~ Embodiment Reference ls now made to the drawings and to Fig. 1 in particular wherein the filling spout 10 of a conventional vertical form fill and seal machine 12 is depicted. In a usual manner a continuous supply of a film 14 is brought from a supply roll about suitable guides to be wrapped into a tube 16 about the filling spout 10. To this end a longitudinal seal 18 and a pair of transverse or cross seals 20, 22 are formed as the tube 16 0 passes over the filling spout 10 so as to seal the sides and seam the film into a final package 24 as shown in Fig. 2. Thus, as the film 14 passes around the filling spout 10 the lateral edges of the film are overlapped and a longitudinal seam 18 is formed by heat sealing bar 26 so as to transform the film into a tube 16. The tube is flattened and a downstream cross seam 20 is - formed by heat sealing bars 28 sealing the bottom of the tube and the tube is then filled with product as it continues to move downstream. After the filling operation is completed the tube is collapsed and an upstream cross seam 22 is formed by the heat sealing bars thereby completing the package about the product.
The sealing bars 28 simultaneously cut the tube in the upstream seam thereby separating the filled package 24 from the tube and forming the downstream cross seam 20 for the next package. The process is then repeated.
In accordance with the present invention, as the film 14 passes the filling spout 10 a zipper strip 30 is fed from a supply roll (not shown) past appropriate guides 32, 34 to abut the outside of the tube 16. That is the zipper strip 30 is positioned to a~`-t against the surface of t~lbe '' ~ppnsite to the surface directed toward the filling spout 10. The zipper strip 30 .-~
and tube 16 are fed in this abutting condition past a pair of .
sealing bars 36, 38 which seal the zipper strip 30 to the tube along seal lines 40, 42. It should be appreciated that the seal lines 40, 42 may be circumferentially spaced from the longitudinal seal 18 as shown in figure 1, straddle the longitudinal seal or even overlie the longitudinal seal. Thus, since the zipper is on the outside of the tube, it can be easily positioned at any location relative to said tube.
The zipper strip 30 is commonly formed of a thermoplastic material such as polyethylene. Similarly, for many products the film 14 may be polyethylene or a similar thermoplastic and hence the zipper and film may be heat bonded to one another. In other cases a moisture, odor or other barrier layer may be necessary to protect the contents of the package. If a barrier layer is provided on the film which prevents the zipper from being heat sealed to the film, the zipper strip 30 may be provided with stripes of a reactivatable adhesive to form an adhesive bonding with the film. In such cases the seal bars 36, 38 serve to guide the zipper strip against the film and to provide sufficient pressure to effect the adhesive bondinq. Said bars can also be replaced by pressure rollers.
Referring to Fig. 3, it can be seen that the zipper strip 30 comprises a first interlocking member 44 and a second interlocking member 46. The member 46 includes a profile section 48 and an adjacent web section 50 whereas the member 44 includes a mating profile section 52 disposed between web sections 54 and 56. The web sections 50 and 56 are bonded to the tube 16, along seal lines 42 and 40 respectively, providing a hinged attachment for the zipper strip. The web section 54 provides a convenient flange to permit ~e ultimate user to grip in Q-d-- ' to separate the zipper members and provide access to the underlying tube section 58 which must ultimately be ruptured to provide access to I
~he package contents. The existence of a rupture in tube section 58 thus provides evidence of the package having been previously opened or tampered with.
A rod or other means may be provided to form a crease in the tube to provide a pleat or gusset in the final bag in a conventional manner. This can be used to form a tube as shown in Fig. 7 wherein the tube section 58 behind the zipper 30 is pleated. To gain access to the contents of the package, the interlocking members 44, 46 of zipper 30 are separated (as shown 0 in Fig. 8) and the apex 60 of the pleat must be cut or punctured.
The pleat 58 is sufficiently deep so that the material defining the sides 62, 64 of pleat 58 may be pulled between the separated zipper profiles 48 and 52 to provide a funnel which when punctured will facilitate pouring out the contents of the package 24 or when slit will protect the profiles from being clogged by powder type materials. Further, the material of one or both sides 62, 64 may be positioned between the profiles 48, 52 when the zipper is reclosed to provide a sealing membrane between the profiles for better liquid tightness and/or to protect the profiles form powdered materials.
Figs. 4 through 6 show the modifications to the form fill and seal machine 12 and the final package 24 which enable use of a different type of zipper 90. This zipper will extend beyond the edge 92 of the finished package 24 (as shown in Figs. 5 and 6) rather than being positioned on a side of the finished package as shown in Fig. 2. Thus, in Fig. 5 the interlocking zipper .-members 66 and 68 are positioned to straddle an edge of the collapsed tube 16. Zipper member 66 includes a male profile member 70 between eb sections 72 and 74 while z~p~-- member 68 includes a female profile member 76 between webs 78 and 80. In this case one web 72 and 80 of each interlocking member 70 and 76 is secured to the tube 16 on its opposite sides, while the other webs 74 and 78 form gripping flanges to facilitate opening of the package. In Fig. 9, the embodied tube section 82 is pleated below the zipper interlocking member 70 and 76 so as to provide a funnel or sealing membrane as discussed previously. In addition, the zipper of Flg. 9 can have its webs 74 and 78 joined at juncture 83 (as shown in Fig. 10) to provide for an additional tamper evident feature.
Thus, in accordance with the above, the aforementioned O objec are effectLvely attaLned.
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