Claims
- 1. A plastic film sheet for use in forming a reclosable container, comprising in combination: a thin plastic film having mating interlocking
- profiles on the surface thereof; a line of tear perforations extending along the
- film parallel to the profiles and penetrating the film;
- and a sealing frangible cap strip overlaid on the area of the perforations providing an impervious seal preventing the passage of air and moisture through the perforations, said strip being of a strength less than the film so that the film will tear along the perforations and the cap strip will separate along its length with the tearing of the film.
- 2. A plastic film sheet for use in forming a reclosable container constructed in accordance with claim 1:
- wherein the frangible cap strip is laid over the area of perforations on the same surface as the mating interlocking profiles.
- 3. A plastic film sheet for use in forming a reclosable container constructed in accordance with claim 1:
- wherein the frangible cap strip is laid over the film surface on the side opposite the location of the mating interlocking profiles.
- 4. A plastic film sheet for use in forming a reclosable container constructed in accordance with claim 1:
- wherein said line of tear perforations is spaced equidistant between the profiles.
- 5. A plastic film sheet for use in forming a reclosable container constructed in accordance with claim 1:
- wherein the line of tear perforations is positioned closer to one profile than to the other.
- 6. A plastic film sheet for use in forming reclosable containers, comprising in combination:
- a thin plastic film having a first pair of mating interlocking profiles extending parallel to a lateral edge thereof;
- a second pair of mating interlocking profiles positioned along an opposite lateral edge spaced therefrom a distance substantially equal to the spacing of the first pair of profiles from the first edge;
- a first and second line of tear perforations extending parallel to the profiles with one line extending between the first pair of profiles and the other line extending between the second pair of profiles;
- and first and second sealing frangible cap strips overlaid respectively on each of the lines of tear perforations providing an impervious seal preventing the passage of air and moisture through the perforations, said strips being of a strength less than the film so that the film would tear along the perforations and the cap strip will separate with the tearing of the film.
- 7. A plastic film sheet for use in forming reclosable containers constructed in accordance with claim 6:
- wherein each line of tear perforations is located equidistant between the mating profiles.
- 8. A plastic film sheet for use in forming reclosable containers constructed in accordance with claim 6:
- wherein each line of tear perforations is located closer to one of its pair of profiles than to the other.
- 9. A plastic film sheet for use in forming reclosable containers constructed in accordance with claim 6:
- wherein each line of tear perforations is located closer to the profile adjacent the edge of the sheet.
- 10. The method of making a plastic film sheet for use in forming a reclosable container comprising the steps:
- providing a sheet of thin plastic container film;
- forming a line of perforations longitudinally along the sheet and penetrating the sheet;
- and adhering a cap layer of frangible sealing material to the surface of the sheet sealing the perforations with the cap layer having a tear strength less than the film sheet so that the film sheet will tear along the perforations while tearing the sealing material.
- 11. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 10:
- wherein the cap layer is adhered with a heat bond over the container film.
- 12. The method of making a plastic film sheet for use in forming a reclosable container comprising the steps:
- feeding a continuous sheet of thin plastic container film along a path;
- forming film penetrating perforations in said film as it is fed along a path to provide a continuous tear line therealong;
- continuously feeding a cap strip layer of sealing material onto the surface of the film aligned with the line of perforations to cover and seal the perforations with the cap strip having a tear strength less than the film sheet.
- 13. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 12:
- wherein the cap strip is formed by heat extruding the cap layer onto the film so that the cap strip will be tacky and will heat bond onto the surface of the film.
- 14. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 12:
- including feeding a shaped interlocking profile onto the film and bonding the profile to the film in a predetermined position relative to the line of perforation.
- 15. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 14:
- including feeding a second profile complementary shaped to the first profile onto the film and bonding it thereto in a spaced predetermined position relative to the first profile and in a location straddling and on the opposite side of the line of perforation.
- 16. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 14:
- wherein the profile is formed by a plastic extrusion head and the profile is supplied onto the film while warm and tacky so that it will adhere to the surface thereof.
- 17. The method of making a plastic film sheet for use in forming a reclosable container in accordance with the steps of claim 15:
- including feeding said profiles from extrusion heads onto the film while the plastic is warm and tacky and will adhere to the surface of the film.
- 18. The method of making a plastic film sheet for use in forming a reclosable container comprising the steps:
- providing a thin plastic film having mating interlocking profiles on the surface thereof;
- forming a line of tear perforations extending along the film parallel to the profiles and penetrating the film;
- and applying a sealing frangible cap strip overlaid on the area of the perforations providing an impervious seal preventing the passage of air and moisture through the perforations, and strip being of a strength less than the film so that the film will tear along the perforations and the cap strip will separate along its length with the tearing on the film.
- 19. The method of making a plastic film sheet for use in forming a reclosable container comprising the steps:
- providing a thin plastic film having a first pair of mating interlocking profiles extending parallel to a lateral edge thereof;
- said film having a second pair of mating interlocking profiles positioned along an opposite lateral edge spaced from a distance substantially equal to the spacing of the first pair of profiles from the first edge;
- forming first and second lines of tear perforations in the film extending parallel to the profiles with one line extending between the first pair of profiles and the other line extending between the second pair of profiles;
- and applying and adhering to the film first and second frangible cap strips overlaid respectively on each of the lines of tear perforations providing an impervious seal preventing the passage of air and moisture through the perforations, said strips being of a strength less than the film so that the film would tear along the perforations and the cap strip will separate with the tearing of the film.
BACKGROUND OF THE INVENTION
This application is a continuation-in-part of U.S. Ser. No. 150,229, Filed Jan. 29, 1988, now U.S. Pat. No. 4,846,585, Boeckmann et al, and of its divisional application, U.S. Ser. No. 306,101, Filed Feb. 6, 1989, Boeckmann et al, now abandoned.
The present invention relates to improvements in plastic bags and fasteners therefor, particularly to a method and mechanism for making a reclosable plastic film bag and for making plastic film material for making a bag with a hermetically sealing tear strip at the top which is removable for use of the bag.
In the manufacture of plastic film bags, reclosable rib and groove profile elements have been provided which permit a bag to be opened and reclosed. Where the bags are used for containing products such as foodstuffs, flaps above the rib and groove elements have been joined to hermetically seal the bag until such time when it is purchased and opened for use. To facilitate opening, parallel lines of tear perforations have been placed above the rib and groove profiles so that a strip can be torn from the top to free the flaps and permit opening the bag by pulling the rib and groove elements apart. The addition of perforations to allow tearing a strip off the top has been known in U.S. Pat. Nos. such as 3,172,443, 3,226,787, 3,473,589 and 4,589,145.
Such perforations destroy the hermetic seal of the bag and permit the passage of air. While the rib and groove elements below the perforations may be joined to close and seal the bag, these elements may inadvertently become separated during handling, storage and merchandising so that air can enter the bag via the perforation holes. Further, the rib and groove elements per se may not be sufficiently airtight. The need for airtight integrity is especially so where the contents of the bag must be protected against air, such as where a bag contains foodstuffs, and laminated films are required. The addition of such perforations creates a problem because the rib and groove elements below said perforations may not, as indicated, be sufficiently airtight, though they present the best method of tearing off the top of the bag for access to the rib and groove elements. Other means of providing tear strips have been attempted, but these are not as satisfactory as the relatively simple expedient of perforating the film of the flaps at the bag top. Such perforations can be added by perforation equipment which operates rapidly and satisfactorily.
An important element in the manufacture of reclosable bags of the type above described is the preparation or manufacture of the plastic film for the bags. In making such film, it is necessary to provide a single layer of multiple layer film and to have on the surface of the film profile elements which are accurately and carefully shaped so as to be able to interlock to each other. The profile elements are continuous in structure and are well adapted to being made by an extrusion process. The addition of structural requirements such as the provision of perforations and means for sealing the perforations creates a further manufacturing obligation which must be performed to complete an adequate film for the manufacture of bags.
It is accordingly an object of the present invention to provide a bag structure and method of making the structure where the bag has reclosable rib and groove elements at the top, the flaps are joined to each other so as to provide a hermetic seal, perforations are included to be able to readily tear a strip off the top and yet the perforations do not admit air so as to jeopardize the hermetic seal of the bag.
A further object of the invention is to provide an improved bag structure which provides a reopenable bag which is positively sealed up to the time that the customer or user purchases the bag and tears a strip off the top.
A further object of the invention is to provide an improved simplified bag structure which can be inexpensively made and which provides for a sealed bag which has a reopenable feature.
A further object of the invention is to provide an improved method wherein a plastic film material for making bags is prepared which has reclosable profile elements on the surface and which also has perforations to provide a tear strip for the finished bag where the perforations are temporarily sealed and the method of manufacture enables accomplishment of the complete preparation of the film in a single expedient sequence of steps.
A further object of the invention is to provide an improved apparatus for the preparation of a bag film wherein the completed film has reclosable profiles on the surface, has perforations for a tear strip in a finished bag and a removable seal over the perforations.
The invention provides for a plastic film bag having confronting side walls sealed at their edges with a pressure interlocking reopenable rib and groove element extending along the top. Above the rib and groove elements are flaps which are doubled so as to be continuous and form a hermetically sealed bag. Alternately, such flaps can also be sealed together. The top can be ripped open by tearing a strip off the bag, and this is simply and economically provided for by parallel lines of perforation to provide a tear strip at the top that can be torn off the bag. In accordance with the invention, a perforation sealing means is attached to the film so that the perforations continue to perform their function of permitting a strip to be readily torn off the top but do not impair the hermetic integrity of the bag allowing it to be stored, handled and merchandised, assuring the purchaser that the contents continue to be protected and hermetically sealed. The bag in addition to providing a bag sealed up to the time that the user wishes to open it, provides a bag that is reclosable for use until the contents are fully removed.
A further feature of the invention resides in the manufacture of film for the bags wherein a web of film is continuously fed forwardly, plastic profiles are positioned onto the surface of the film by being extruded and attached in their tacky molten form. A row of tear perforations is positioned in the film in the same pass through mechanism which attaches the profiles, and a perforation seal strip is laid over the perforations essentially simultaneously with the attachment of the profiles.
Other objects, advantages and features will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:
US Referenced Citations (1)
| Number |
Name |
Date |
Kind |
|
3827472 |
Uramoto |
Aug 1974 |
|
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 1010738 |
Nov 1965 |
GBX |
Continuation in Parts (1)
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Number |
Date |
Country |
| Parent |
150229 |
Jan 1988 |
|
Patent Grant
5023122
