Zipper strip

Abstract: A zipper tape (10) with a narrow band of untreated surface on the leading edges (20,22) of the flanges that permits the tack sealing of the flanges together by noncontinuous sealing bars (30). This prevents the leading edges (20,22) of the flanges from curling or flipping up thereby reducing the tendency of a leading edge of a zipper (10) from jamming as the web moves over the collar of a form fill and seal (FFS) apparatus.

Description: The present invention pertains to the transverse application of zipper strips to films or webs. The application of a zipper to a film or web is demonstrated, for example, in US-A-4909017. However, in a "pinch and pull" configuration, such as is disclosed in US-A-6065872, there has been a tendency for the leading edge of the zipper to jam as the web moves over the collar of a form fill and seal (FFS) device (as shown for example in US-A-6151868). It is therefore an object of the present invention to reduce the tendency for a leading edge of a zipper to jam as the web moves over the collar in a form fill and seal (FFS) device. Accordingly, in a first aspect, the invention consists in a zipper tape comprising: a first zipper half facing a second zipper half, said first zipper half having a leading edge and a trailing edge facing a respective leading edge and a respective trailing edge of said second zipper half; said first zipper half and said second zipper half having portions treated with heat resistant coating; and said leading edge of said first zipper half and said leading edge of said second zipper half being free of heat resistant coating. In a further aspect, the invention consists in a plastic bag comprising: a first wall and a second wall, said first wall sealed to said second wall to form a mouth, said mouth including a zipper tape according to the first aspect sealed to said first wall and said second wall for selectively opening and closing said mouth. By removing the heat resistant coating from the leading edge of the base web and likewise from portions of the four legs of a flange zipper strip in a pinch, grip and pull configuration of a form fill and seal (FFS) device the tendency of the leading edge to jam is reduced. Further, a serrated seal bar is used in the web direction to seal down the leading edge to keep the fourth or top edge of the flange from curling or flipping up, without sealing into the bag. The serrated seal is both a carrier seal and a tack seal that breaks open when the package is opened for use. Particular embodiments of the present invention will now be described with reference to the accompanying drawings; in which:- Figure 1 is a perspective view of the web and how, according to the present invention, the zipper tape is attached to the web, Figure 2 is a detailed perspective drawing of the tack sealing of the zipper tape to the web, as shown in Figure 1, Figure 3 illustrates a typical opening style of the bag resulting from the present invention, Figure 4 is a cross-sectional view of the zipper tape section according to the present invention, Figure 5 is a cross-sectional view of the zipper tape section sealed to the web according to the present invention, Figure 6 is a plan view of the zipper tape, showing the cut lines and the spacing of the clear areas and the areas with a heat resistant coating, according to a first aspect of the present invention, Figure 7 is a cross-sectional view of a zipper resulting from the zipper tape as cut according to the first aspect of the present invention, Figure 8 is plan view of the zipper tape, showing the cut lines and the spacing of the clear areas and the areas with a heat resistant coating, according to a second aspect of the present invention, and Figure 9 is a cross-sectional view of a zipper resulting from the zipper tape as cut according to the second aspect of the present invention. Referring now to the drawings in detail wherein like numerals indicate like elements throughout the several views, one sees that Figure 1 is a perspective view of the web 100 and how the zipper tape 10 is attached thereto. Web 100 is a planar sheet and travels in the direction indicated in Figure 1, generally toward a form fill and seal (FFS) apparatus (not shown). Figure 2 shows the zipper tape 10 in more detail. Zipper tape 10 includes two halves 12, 14 in a four-flange configuration with respective interlocking zipper profiles 16, 18 (also see Figures 4 and 5), and is oriented transverse to the direction of travel of the web 100. As shown in Figure 4, the leading edges 20, 22 of halves 12, 14 are clear of heat resistant coating and are adjacent to portions 24, 26 of halves 12, 14 which have a heat resistant coating on the inwardly facing sides. Heat resistant coating 27, 28 is likewise on the inwardly facing sides of halves 12, 14 of the portion 29 of zipper tape 10 trailing zipper profiles 16, 18. As shown in Figure 1, tack sealing bar 102 is transversely oriented with respect to the direction of travel of web 100 and includes downwardly facing tack sealing ribs 104 periodically spaced along lower surface 106 of tack sealing bar 102. Tack sealing ribs 104 are oriented parallel to the direction of travel of web 100 and form tack seals 30 (see Figure 2) between leading edges 20, 22 of zipper tape 10 and web 100. These tack seals are likewise carrier seals, but typically break when the bag 200 (see Figure 3) is opened. The web 100 is cut, folded into sides 110, 112 and sealed to both halves 12, 14 of zipper tape 10 in an FFS device such as that shown in US-A-6151868, and as shown in Figure 5, top bag seal 114 is formed by sealing side 110 to side 112. This results in the bag 200 as illustrated in Figure 3, which further illustrates a typical opening style of bag 200 wherein seal 114 forms a mouth, the mouth including the zipper tape 10. A first embodiment of zipper tape 10 is illustrated in Figures 6 and 7. Fold cut line 50 separates half 12 from half 14, whereas slitter cut lines 52, 54 separate halves 12, 14 from the zipper tape 10 of preceding or succeeding zippers. Leading edge 22, which is a clear area free of heat resistant coating, is formed immediately adjacent to slitter cut line 52. Likewise, leading edge 20, which is a clear area free of heat resistant coating is formed immediately adjacent to slitter cut line 54. Areas 56, 58, which include the heat resistant coating, are formed adjacent to leading edges 22, 20, respectively. Clear areas 60, 62, which are free of heat resistant coating, are formed adjacent to areas 56, 58. Areas 64, 66 which include the heat resistant coating are formed adjacent to areas 60, 62, and beside each other on opposite sides of fold cut line 50. As can be seen from Figure 7, when halves 12, 14 are separated and faced towards each other, leading edges 20, 22 are adjacent each other, areas 56, 58 face each other, areas 62, 60 face each other and areas 64, 66 face each other. Additionally, seal 70, which may be a peel seal, is formed between portions of areas 62 and 60 and zipper profiles 16, 18 are formed on a portion of areas 62, 60 respectively, and engage each other. A second embodiment of zipper tape 10 with a similar configuration is shown in Figures 8 and 9 without the seal 70 and with different proportions to the various areas. This configuration reduces the tendency of the leading edge of the zipper to jam as the web moves over the collar of a form fill and seal apparatus (not shown).

Claims: A zipper tape (10) comprising: a first zipper half (12) facing a second zipper half (14), said first zipper half (12) having a leading edge (20) and a trailing edge (62), facing a respective leading edge (22) and a respective trailing edge (62) of said second zipper half (14); said first zipper half (12) and said second zipper half (14) having portions (56,58,64,66) treated with heat resistant coating (27,28); and said leading edge (20) of said first zipper half (12) and said leading edge (22) of said second zipper half (14) being free of heat resistant coating. The zipper tape (10) of claim 1, wherein a central area (62) of said first zipper half (12) faces a central area (60) of said second zipper half (14), said central areas each having a respective interlocking profile (16,18) secured thereto or formed therein, said interlocking profiles (16,18) being interlockable with each other. The zipper tape (10) of claim 1 or claim 2, wherein said trailing edges of said first zipper half (12) and said second zipper half (14) are treated with said heat resistant coating (27,28). The zipper tape (10) of any one of the preceding claims, further including a peel-seal (70) between said first zipper half (12) and said second zipper half (14) adjacent to said respective interlocking profiles (16,18). The zipper tape (10) of any one of the preceding claims, wherein said leading edges (20,22) are at least intermittently sealed to a web (100). A plastic bag (200) comprising: a first wall (110) and a second wall (112), said first wall sealed to said second wall to form a mouth, said mouth including a zipper tape (10) according to any one of the preceding claims, sealed to said first wall and said second wall to allow selective opening and closing said mouth. The plastic bag (200) of claim 6, wherein said leading edges (20,22) are at least intermittently sealed to at least one of said first (110) or second (112) walls.

Inventors: LINTON BASIL C, LINTON, BASIL C.
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 2001
Main classification: B65D33
IPC codes: B65D33, A44B19