Conforming end stops for a plastic zipper

Abstract: A plastic bag comprises first and second opposing panels, a reclosable zipper (22), and a slider (32). The first and second opposing panels (12,14) are fixedly connected to each other along a pair of sides (16) and a bottom bridging the pair of sides. The reclosable zipper extends along a mouth (10) formed opposite the bottom. The zipper (22) includes a first track with a first profile (24) and a second track with a second profile (28). The first and second profiles are releasably engageable to each other. The slider (32) is slidably mounted to the zipper for movement between a closed position and an open position. The first and second profiles (24,28) are engaged to each other while the slider (32) is in the closed position, and the first and second profiles (24,28) are disengaged from each other in response to movement of the slider (32) from the closed position to the open position. To prevent the slider from going past the ends of the zipper and to provide adequate end strength that resists stresses applied to the profiles during normal use of the bag, end stops (36) in the form of flexible segments severed from a flexible plastic strip, fairly rigid segments severed from an extruded clip profile, or softened plastic material, are applied and secured to opposite ends of the zipper.

Description: FIELD OF THE INVENTION The present invention generally relates to reclosable plastic bags and, more particularly, to a reclosable plastic bag including a zipper and conforming end stops made from plastic material molded onto opposite ends of the zipper. BACKGROUND OF THE INVENTION A reclosable plastic bag typically includes first and second opposing panels fixedly connected to each other along a pair of sides and a bottom bridging the pair of sides. The first and second panels are not fixedly connected along a mouth which is formed opposite to the sealed bottom. Rather, the bag is provided with a reclosable zipper extending along the mouth of the plastic bag. The zipper includes a male track and a female track. In reclosable plastic bags of the type disclosed in U.S. Patent No. 5,067,208 utilizing a slider to open the zipper, the male track typically includes a male profile and a first fin extending downward from the male profile. Likewise, the female track in such bags with sliders includes a female profile and a second fin extending downward from the female profile. The first and second fins are thermally fused to the inner surfaces of the respective first and second panels. The male and female tracks are typically free of any plastic material above the male and female profiles in order to permit proper mounting and movement of the slider. The male and female profiles are releasably engageable to each other. When the slider is in a closed position, the male and female profiles are interlocked with each other. In response to moving the slider to an open position, the male and female profiles are disengaged from each other. Once the male and female profiles are disengaged from each other, access to the interior of the bag may be obtained by pulling the first and second panels apart at the mouth. Opposite ends of the zipper are provided with end terminations. The end terminations perform the dual function of stops for the ends of the zipper to prevent the slider from going past the ends of the zipper and, in addition, they hold the male and female profiles together to resist stresses applied to the profiles during normal use of the plastic bag. In U.S. Patent No. 5,067,208, each end termination is in the form of a fairly rigid strap/clip that wraps over the top of the zipper. One end of the strap is provided with a rivet-like member that penetrates through the zipper fins and into a cooperating opening at the other end of the strap. Other types of end terminations are disclosed in U.S. Patent Nos. 5,482,375, 5,448,807, 5,442,837, 5,405,478, 5,161,286, 5,131,121, and 5,088,971. SUMMARY OF THE INVENTION The present invention provides end terminations for a zipper of a reclosable plastic bag. The plastic bag comprises first and second opposing panels fixedly connected to each other along a pair of sides and a bottom bridging the pair of sides. The bag is provided with a reclosable zipper extending along a mouth formed opposite the sealed bottom of the plastic bag. The zipper includes a male track and a female track. The male track includes a male profile and a first depending fin extending downward from the male profile. Likewise, the female track includes a female profile and a second depending fin extending downward from the female profile. If the zipper is formed separately from the panels of the bag, the first and second depending fins are thermally fused to inner surfaces of the respective first and second panels. Alternatively, the zipper may be integrally formed with the panels of the bag. A slider is slidably mounted to the zipper for movement between a closed position and an open position. The male and female profiles are engaged to each other while the slider is in the closed position. The male and female profiles are disengaged from each other in response to movement of the slider to the open position. To prevent the slider from going past the ends of the zipper and to provide adequate end strength that resists stresses applied to the profiles during normal use of the bag, plastic end stops are molded onto the opposite ends of the zipper. Each plastic stop end is made from the melted plastic material that is injected through chilled anvils, that in turn, mold the injected plastic material about the profiles at the end of the zipper. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: FIG. 1a is an enlarged isometric view of a mouth portion of reclosable plastic bag in accordance with an embodiment of the present invention. FIGS. 1b, 1c, and 1d are isometric views illustrating the method of forming end stops on the bag mouth portion in FIG 1a. While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the invention as defined by the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Turning now to the drawings, in which like reference numerals designate like parts, FIG. 1a depicts a mouth portion 10 of a reclosable plastic bag in accordance with a first embodiment of the present invention. As shown in FIGS. 1a and 1b, the plastic bag comprises first and second opposing panels 12 and 14 fixedly connected to each other along a pair of sides 16 (only one shown in FIG. 1a) and a bottom (not shown) bridging the pair of sides 16. The bag is provided with a reclosable zipper 22 extending along the mouth portion 10 formed opposite the sealed bottom of the plastic bag. The zipper 22 includes a male track and a female track. The male track includes a male profile 24 and a first depending fin or flange 26 extending downward from the male profile 24. Likewise, the female track includes a female profile 28 and a second depending fin or flange 30 extending downward from the female profile 28. If the zipper 22 is formed separately from the panels 12 and 14 of the bag, the first and second fins 26 and 30 are thermally fused to inner surfaces of the respective first and second panels 12 and 14. Alternatively, the zipper 22 may be integrally formed with the panels 12 and 14 such that the first fin 26 is integrally formed with the first panel 12 and the second fin 30 is integrally formed with the second panel 14. To assist in opening the plastic bag, a slider 32 is slidably mounted to the zipper 22 for movement between a closed position and an open position. In the closed position of the slider 32, the male and female profiles 24 and 28 are interlocked with each other. Movement of the slider 32 from the closed position toward the open position (see FIG. 1a) disengages the male and female profiles 24 and 28 from each other and allows a user to gain access td the interior of the plastic bag. Further details concerning the construction and operation of the zipper 22 and slider 32 may be obtained from U.S. Patent No. 5,067,208 to Herrington, Jr. et al. To prevent the slider 32 from going past the ends of the zipper 22 and to provide adequate end strength that resists stresses applied to the profiles 24 and 28 during normal use of the bag, end stops 36 in the form of plastic ribbon segments (only one shown in FIG. 1a) are molded onto the opposite ends of the zipper 22. The end stops 52 project outwardly from the profiles 24 and 28 and are engageable with the slider 32 to prevent it from moving past the ends of the zipper 22. An end stop assembly station for applying the end stops 52 is illustrated in FIGS. 1b to 1d. In this embodiment the end stops 52 are added to the ends of the zipper 22 in melted form and then solidified. The end stops 52 project outwardly from the profiles 24 and 28 and are engageable with the slider 32 to prevent it from moving past the ends of the zipper 22. Each plastic end stop 52 is made from melted plastic material 53 that migrates from or is injected from a supply tube 54 through one of a pair of chilled anvils 56a and 56b. In the illustrated embodiment, the supply tube 54 delivers the melted plastic material to the inner surface of the anvil 56a. As best shown in FIG. 1c, when the anvils 56a and 56b are closed around a continuous zipper 22', the melted plastic material is forced about the profiles 24 and 28 by a conventional back pressure device (not shown) coupled to the supply tube 54. The chilled anvils 56a and 56b mold and solidify the injected plastic material. As shown in FIG. 1d, the inner surfaces of the anvils 56a and 56b preferably form respective channels 58 for conveying the injected plastic material about the profiles 24 and 28. In the illustrated embodiment, each channel 58 has a generally W-shaped cross-section. The amount of plastic material injected through the channels 58 while the anvils are closed about the zipper 22' is preferably sufficient to form a pair of end stops 52 in side-by-side relationship. The end stops 52 are integrally joined along an area 60 of reduced cross-section and serve as end stops on the adjacent ends of two connected bags. At a conventional side sealing station downstream from the end stop assembly station, a side seal is formed between the two connected bags along this area 60 of reduced cross-section such that one of the end stops 52 becomes part of one of the bags and the other of the end stops 52 becomes part of the other of the bags. The location of this side seal to be formed at the side sealing station is indicated by dotted lines and designated by the reference numeral 62 in FIG. 1d. After the injected plastic material is molded about the profiles 24 and 28 and solidified, the reciprocating anvils 56a and 56b shift to the open position (FIG. 1d) and the continuous bag material B is indexed forward in the direction of the arrow M so that the next pair of side-by-side end stops 52 can be applied to the continuous zipper 22' in the manner described above. In the embodiment described above, the end stops are composed of a polymer or copolymer that is preferably compatible with the plastic matorial of the profiles 24 and 28, which are preferably composed of polyethylene. Some possible materials for forming the end stops include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), high density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and copolymers of the foregoing materials.

Claims: A method for applying an end stop (52) for a slider (32) at an end of a reclosable zipper (22) extending along a mouth of a reclosable plastic bag, wherein said zipper including a first track with a first profile (24) and a second track with a second profile (28), said first and second profiles being releasably enngageable to each other and wherein said slider is slidably mounted to said zipper (22) for movement between a closed position and an open position, said first and second profiles being engaged to each other while said slider (32) is in said closed position, said first and second profiles being disengaged from each other in response to movement of said slider from said closed position to said open position, characterised by the steps of: supplying a predetermined amount of melted plastic material (53); guiding said melted plastic material (53) about said end of said zipper (22), and solidifying said melted plastic material about said end of said zipper. The method of Claim 1, wherein said step of supplying said predetermined amount of melted plastic material (53) includes passing said melted plastic material through a supply line (54). The method of Claim 2, wherein said step of guiding said melted plastic material (53) about said end of said zipper (22) includes injecting said melted plastic material (53) from said supply line (54) between said end of said zipper and an anvil (56a, 56b) adjacent to said end of said zipper. The method of Claim 3, wherein said anvil (56a, 56b) includes an inner surface forming a channel receiving said melted plastic material (53). The method of Claim 4, wherein said anvil (56a, 56b) is chilled, and wherein said step of solidifying said melted plastic material (53) includes chilling said melted plastic material with said chilled anvil. A reclosable plastic bag, comprising: first and second opposing panels (12, 14) fixedly connected to each other along a pair of sides (16) and a bottom bridging said pair of sides; a reclosable zipper (22) extending along a mouth formed opposite said bottom, said zipper including a first track with a first profile (24) and a second track with a second profile (28), said first and second profiles being releasably engageable to each other; a slider (32) slidably mounted to said zipper for movement between a closed position and an open position, said first and second profiles being engaged to each other while said slider is in said closed position, said first and second profiles (24, 28) being disengaged from each other in response to movement of said slider (32) from said closed position to said open position; and an end stop (52) formed from a melted plastic material (53) guided about an end of said zipper (22) and solidified about said end of said zipper (22).

Inventors: BRYNIARSKI DAVID A, CATCHMAN VERNON C, DOBRESKI DAVID V, MCMANUS MICHAEL W, BRYNIARSKI, DAVID A., CATCHMAN, VERNON C., DOBRESKI, DAVID V., MCMANUS, MICHAEL W.
Applicants: PACTIV CORP, PACTIV CORPORATION
Application year: 1997
Main classification: A44B19
IPC codes: B29C65, A44B19, B65D33