METHOD OF MANUFACTURING HEADERLESS PRODUCE BAGS WITH INCREASED ADHESION

Abstract

During the manufacturing process the exterior surface of one or both of the sheets of plastic film which form the bags is treated with low temperature corona discharge plasma to raise the level of surface charge magnitude to at least 43 Dyne to increase the adhesion force between the bags. A recess is formed in each of the bags to further increase the adhesion. The increased adhesion causes the mouth of one bag to automatically open as the adjacent bag is removed from the rack. The recess is formed at the same time openings are created in the bags to accept the support rods of a dispensing rack. The bags can have simple edge sides or side gussets and may be provided in a package including a pouch which receives and supports the lower portions of the bags.

Claims

1-21. (canceled)

22. A produce bag comprising first and second plastic sheets joined at the sides and bottom to form a compartment adapted to receive a product, one of said plastic sheets having an exterior surface with a surface charge magnitude of at least 43 Dyne, and at least one of said sheets comprising a recess.

23. The bag of claim 22 wherein the sides of the bag comprise gussets.

24. A dispenser for use with the bag of claim 22 comprising a pouch adapted to receive and support the lower portion of the bag.

25. First and a second aligned produce bags, each of said bags comprising first and second plastic sheets joined at the sides and bottom to form a compartment with an unsealed mouth adapted to receive a product, said first plastic bag having an exterior surface with a surface charge magnitude of at least 43 Dyne which is adjacent said second plastic bag, each of said bags having a recess, such that said exterior surface of said first bag adheres to said second bag with sufficient force to automatically open the mouth of the second bag as the first bag is moved away from the second bag.

26. A dispenser for use with the bags of claim 23 comprising a pouch adapted to receive and support the lower portion of the bags.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS

[0037] To these and to such other objects that may hereinafter appears, the present invention relates to a method of manufacturing a headerless plastic bag with increased adhesion as described in detail in the following specification and recited in the annexed claims, taken together with the accompanying drawings, in which like numerals refer to like parts and in which:

[0038] FIG. 1 is an idealized side view of a production line for fabricating the bags of the present invention;

[0039] FIG. 2 is a perspective view of a plurality of plastic bags fabricated in accordance with method of the present invention as they would appear suspended from a rack.

[0040] FIG. 3 is a perspective view similar to FIG. 2 showing the first bags being removed from the rack.

[0041] FIG. 4 is a perspective view similar to FIG. 3 showing that the mouth second bag automatically opens as the first bag is removed from the rack;

[0042] FIG. 5 is a perspective view of a side-gusseted plastic bag fabricated in accordance with the present invention; and

[0043] FIG. 6 is a perspective view of a plurality of plastic bags fabricated in accordance with the present invention and situated in a bag dispenser having a pouch or pocket.

DETAILED DESCRIPTION OF THE INVENTION

[0044] FIG. 1 schematically illustrates the steps in the manufacturing process of the present invention. Above a work surface 10 are located feed rollers 12 and 14. Each of the rollers 12, 14 dispenses a continuous sheet of thin plastic material such as polyethylene or polypropylene film. The plastic sheets from the rollers are positioned one on top of another above work surface 10 such that the sheets are aligned.

[0045] The aligned sheets pass into a bag forming station which includes a platen 16 containing heating elements. Platen 16 is reciprocated vertically such that it presses the aligned sheets and heat seals the edges and bottom of what will become each plastic bag, generally designated A. The portion of the aligned sheets which will become the top or mouth of the bag is not sealed.

[0046] The bag forming process is conventional and is therefore not illustrated in detail in the figure. Bags A with either simple side edges (illustrated in FIG. 2) or with gusseted sides A′ (shown in FIG. 5) can be formed by this process, as is well known to those of ordinary skill in the art.

[0047] After leaving the bag forming station, the plastic sheets move to the plasma treatment station where the exterior surface of the top plastic sheet is exposed to low temperature corona discharge plasma to create a surface charge magnitude of at least 43 Dyne. This station includes corona discharge plasma treatment equipment 18 in the form of a high-frequency power generator and a high-voltage transformer. Extending downwardly from equipment 18 is a linear array of sharp tipped stationary ceramic or metal electrodes 20. The electrodes of the array are spaced alone a direction generally perpendicular to the direction of movement of the aligned sheets so as to form a charged region through which the bags pass. A grounded roller 22 is situated under the bags, spaced from and aligned with the electrodes.

[0048] The corona discharge plasma is generated by the application of high voltage to the sharp tips of electrodes 20 which forms plasma at the ends of the electrodes. Spacing the electrodes in a linear array creates a uniform curtain of corona discharge plasma across the sheets which form the bags. As the plastic sheets pass through the air gap between electrodes 18 and the grounded roller 22, the plasma imparts changes in the properties of the exposed plastic surface by increasing the surface energy of the material.

[0049] Although not illustrated in the drawing, it is possible to include a second plasma treatment station, with the electrodes situated below the aligned plastic sheets and the grounded roll above the sheets, so as to treat the exterior surface of the bottom plastic sheet in addition to or instead of the exterior surface of the top plastic sheet. Accordingly, either or both of the exterior surfaces of the aligned plastic sheets of the bags can be treated.

[0050] The treated bags then pass into the cutting station. The cutting station includes a reciprocating knife 24 which cuts the sealed and treated sheets at appropriate locations to separate the individual bags A. The bags then exit the work surface and are moved by a conveyor 26 to a stacking station where the bags accumulate into a pile or stack 28 on a platform at the end of the production line.

[0051] On the platform, stack 28 is situated below a second reciprocating platen 30. The undersurface of platen 30 includes one or more sharp-tipped tools 32 aligned with the upper section of the bags. Tools 32 create aligned openings 36 in all of the bags in the stack. As many tools 32 are required as the number of openings 36 that are necessary. In the drawings, two spaced opening 36 in the upper section of the bags are provided to receive the two support rods of a dispensing rack.

[0052] Platen 30 also has one or more blunt-tipped tools 34 which are shorter and smaller in diameter than tools 32. Tools 34 create one or more sets of aligned rounded recesses 42 in all of the bags in the stack. In the drawings tools, two recesses are formed, one recess As seen in FIG. 1, tools 32 and 34 are aligned such that the holes 42 and recesses 42 are situated

[0053] Each tool 32 punches aligned openings 36 in the all of the bags of the stack each time the platen is moved downwardly. One or more sets of openings 36 can be created at a time. Openings 36 are adapted to receive the support rods 38 of a bag rack 40 such that the stack of bags hang in face-to-face relation from the rack, as illustrated in FIG. 2. The number of openings formed depends upon the number of support rods of the rack on which the bags will be hung. Typically, at least two spaced openings designed to accept two support rods are provided in each bag.

[0054] Tools 34 are provided with blunt ends such that they create aligned recesses or “dimples” 42 in all of the bags in the stack at the same time as platen 30 is pressed into the stack of bags. The blunt ends of the tools 34 are configured such that the bags are not pierced. No openings in the bags are created by this tool, only recesses. As many different tools 34 are provided as the number of recesses which are required in each bag. The number of recesses required is a function of the size of the bags being produced. The larger the bag, the more recesses that are required. The purpose of the recesses 42 is to further increase the adhesion between to bags beyond that which is imparted by the corona discharge plasma treatment.

[0055] The completed stacks of bags 28 are the packaged and shipped to retail establishments. At the retail establishment, the stack of bags A is mounted on a rack 40 by inserting the support rods 38 through openings 36 in the bags, as seen in FIG. 2. Rack 40 may be a floor standing rack or may be designed to rest on a counter.

[0056] As the first bag A1 of the stack 28 is being removed from the rack (FIG. 3), the mouth 44 of the next bag A2 on the rack is automatically opened due to the adhesion between the exterior surface of the first bag and the exterior surface of the second bag (FIG. 4), one or both of which exterior surfaces having been treated with the corona plasma discharge.

[0057] Once suspended from the rack, the bags can be easily removed from the rack, one at a time, for use in packaging produce or other food products. Removal of one bag automatically opens the mouth of the succeeding bag because of the adhesion forces between the bags, making the use of the bags easy and dramatically decreasing the amount of bags which are wasted.

[0058] FIG. 5 illustrates a bag A′ fabricated with the process of the present invention which is essentially the same as bag A except for the gusseted sides 50. Bag A′ can be formed and treated by the same equipment and process disclosed above except that the gusseted sides are formed by an additional folding processes known in the art. The bags A′ function in the same manner as the simple edge sided bags A in the sense that the adherence between adjacent bags causes the mouth of the second bag to automatically open as the first bag is removed from the rack.

[0059] FIG. 6 illustrates a dispenser, generally designated B, which includes a pouch or pocket 52 with an open mouth 54. The lower portions of the bags are received in and supported by the pouch.

[0060] Dispenser B is formed of a back 51 and a pouch or pocket 52. The dispenser is made of paper or plastic material which is somewhat more ridged than that of the bags. The dispenser and stack of bags is provided with an exterior wrapper surrounding it can form a package in which the bags can be shipped. When the package is received by the retail establishment, the exterior wrapper is removed and the package hung on a rack 40 as illustrated in FIG. 6.

[0061] Pouch or pocket 52 supports the lower portions of the bags in a pouch and reduces the number of bags which are wasted and end up on the floor. This dispenser is the subject of U.S. Pat. No. 7,314,137, which describes the structure and function of dispenser B in greater detail. In this embodiment, as with the bags which hang freely from the rack, the mouth 44 of the next bag A2 in the stack is opened automatically as the first bag A1 in the stack is removed from the dispenser because of the adhesion forces between the adjacent bags.

[0062] The bags may be formed with one or more than one recess 42 as needed. FIG. 6 shows two recesses 42. However the number of recesses depends upon the size of the bag. Larger bags are provided with additional recesses to further increase the adhesion forces between the bags.

[0063] It will now be appreciated that the present invention relates to a method for manufacturing plastic bags from sheets of plastic film in which a first bag having an exterior surface is formed and a second bag having an exterior surface is formed. An exterior surface of one or both of the bags is treated by exposing the surface to low temperature corona discharge plasma. The bags are aligned, for example being hung from a rack, such that the treated surface of one bag faces the exterior surface of the second bag.

[0064] The exterior surface of one or both of the bags is treated to have a surface charge magnitude of at least 43 Dyne. The surface treatment increases the adhesion between the bag surfaces. Aligned recess are created in the bags. The recesses further increase the adhesion forces between the bags. The adhesion forces cause the mouth of a next bag in the stack to automatically open as the first bag is moved away relative to the next bag, such as being removed from a rack.

[0065] The number of aligned recesses to be created in the aligned plastic bags is based upon the size of the bag. The number of aligned recesses necessary increases as the size of the plastic bags becomes larger. Preferably, the recesses have a substantially round shape.

[0066] Preferably, the aligned recesses in the bags are created at the same time and by the same tool as the rod receiving openings.

[0067] The invention also relates to a headerless produce bag formed of first and second plastic sheets joined at the sides and bottom to create a compartment adapted to receive a product. At least one of the plastic sheets has an exterior surface with a surface charge magnitude of at least 43 Dyne. A least one of the sheets has a recess. The bags may have a simple edge side or have a side gusset. Further, the bags may be packaged within a dispenser having a pouch or pocket adapted to receive and support the lower portions of the bags.

[0068] While only a limited number of preferred embodiments of the present invention have been disclosed for purposes of illustration, it is obvious that many modifications and variations could be made thereto. It is intended to cover all of those modifications and variations which fall within the scope of the present invention, as defined by the following claims.