Woven plastic fiber cloth having fused stiffening areas

Abstract

 A cloth-like material (20) formed from woven plastic fibers includes a surface region (30) of bonded together fibers. The region adds stiffness to the material thereby improving its utility in, for example, self-standing handles for large plastic bags. In one embodiment, the surface region is formed by pressing a hot iron against a surface of the material. The plastic fibers partially melt, and a slight depression is formed in the material having side and bottom walls formed from fused material from fibers adjoining the depression walls. The stiffened material can be attached as a stiffening rib to the surface of a flexible sheet, e.g., a sheet also formed from woven plastic fibers. In another embodiment, the surface region is formed by means of a rib of hardened, fused plastic.

Description

Background of the Invention:

[0001] This invention relates to cloth-like materials comprising woven plastic fibers, and particularly to means for adding stiffness to portions of articles made of such materials.

[0002] It is known to weave plastic fibers into exceptionally strong sheets of cloth-like materials. Such sheets are used, for example, in place of burlap or canvass, and provide exceptionally strong and lightweight bags, commonly known as bulk bags or super sacks. The woven plastic sheets are generally flexible and, on occasion, require additional means for providing stiffening. An example of such occasion, with which the present invention has particular utility, is in the loop handles of relatively large plastic bags. By "relatively large" is meant that, when filled, the bags are so heavy as to require transporting by mechanical means, e.g., fork lift trucks.

[0003] In such transporting operations, the prongs of the fork lift truck are inserted through loop handles attached to the upper ends of the bags. Preferably, for cost reasons, the bag handles are made of the identical material of the bags, i.e., woven plastic fibers, and owing to the flexibility of the material, the loop handles tend to fold over under their own weight. A problem thus caused is that threading the fork lift prongs through the folded over handles requires assistance, either by the fork lift operator who must dismount from the fork lift, or by a helper. In either case, manpower is wasted.

[0004] It is known to provide handles which include means, e.g., plastic rods or double layers of material and the like, for stiffening the handles to the point where they are self-standing when the bags are vertically oriented. While these various means are mechanically satisfactory, they increase costs and thus preferably avoided.

Summary of the Invention:

[0005] In cloth-like materials, formed from woven plastic fibers, stiffness is increased by rigidly bonding together adjacent fibers of the material, e.g., by means of a surface region of fused together fibers. The fused region is formed by heating a surface portion of the material for at least partially melting and fusing together surface portions of adjacent fibers. The fused material restrains relative movement between the fused together fibers thereby stiffening the material. In looped handles for bags, fused regions in the form of elongated strips are formed directly in the loop legs or are attached thereto in the form of ribs.

Description of the Drawing:

[0006] The drawings are schematic and not drawn to scale.

Fig. 1 is a side elevation of a filled plastic bag having self-standing plastic handles in accordance with this invention;

Fig. 2 is an enlarged view of a portion of one of the handles shown in Fig. 1;

Fig. 3 is a cross-section taken along line 3-3 of Fig. 2;

Fig. 4 is an end view of a strip of woven plastic material being heated by a hot iron for providing a fused region in the material;

Fig. 5 is an end view of a strip of woven plastic fiber material having a woven plastic rib attached thereto; and

Fig. 6 is a view similar to Fig. 5 but showing a stiffening rib of a solid plastic material.

Description of Preferred Embodiments of the Invention:

[0007] By way of example, the invention is described in connection with improvements in the plastic handles of plastic bags. The term "plastic" is used herein in conformity with conventional usage and refers to various organic materials in common use.

[0008] Fig. 1 shows a side a side elevation of a plastic bag 10 having a generally square cross-section and which, except as hereinafter described, is known and commercially available. The bag 10 has a closeable bottom end 12 and an open end 14 that is sealable. The material of the bag 10 is a "cloth" woven from individual plastic fibers. As such, the bag 10 can be identical to known burlap or canvas bags except that it is made from plastic. The plastic bag material, although exceptionally strong, is quite flexible and normally will not stand on its own. As shown in Fig. 1, the bag is substantially completely filled with some material to be transported and the bag, when so filled, stands vertically.

[0009] For lifting and transporting the bag 10, four handles 20 are provided, one each at each bag corner at the upper end of the bag. Two handles 20 are visible in Fig. 1.

[0010] As shown in Fig. 1, the handles 20 project vertically upwardly from the bag upper end 14 and, as such, are "self-standing." The self-standing handles form open loops, hence a fork lift operator can readily thread the leading ends of the fork lift prongs through the handle loops without dismounting from the fork lift and without assistance from a helper.

[0011] An enlarged view of one leg 22 of the loop handles 20 is shown in Fig. 2. As previously noted, the handle comprises an elongated strip of a woven plastic material. The details of the woven pattern are of no particular importance. Preferably, however, as is conventional, a relatively tight weave is present, with much contact between adjacent fibers. As indicated in the circle of Fig. 2 and in the cross-sectional view of Fig. 3, the woven material includes diagonal "threads" 24, held together by transverse threads 26. Other patterns of woven fibers are known and can be used.

[0012] As indicated in Figs. 2 and 3, elongated "stiffened" zones or areas 30 are provided along the vertical leg portions 22 of the handle loop. As shown, the stiffened areas 30 terminate on the vertical leg portions 32 and do not extend the full length of the handle. The stiffening provided by the areas 30 is sufficient to maintain the handles 20 in vertical orientation as shown in Fig. 1.

[0013] The "stiffened" areas are regions where adjacent, separate fibers are bonded together for reducing the amount of relative movement between the bound together fibers. This can be accomplished, for example, by applying a glue within the areas 30, which glue hardens to form a rigid area of glued together fibers.

[0014] Preferably, and more economically, the "glue" bonding together the fibers in the areas 30 is a fused material of the fibers themselves. By "fused" is meant that heat is applied to the fibers for at least partially liquefying them, with the molten material formed from adjacent fibers merging into a continuous molten mass.

[0015] One means for accomplishing this is shown in Fig. 4. An elongated heated bar 40 of metal covered with a plastic non-adhering material, such as Teflon coated glass cloth, is pressed against the surface 42 at the end of an elongated strip 44 of the woven plastic material. The bar 40 can be heated by placing it in an oven, although, preferably, an electric "iron" is used.

[0016] The temperature of the bar, e.g. 170 degrees C for use with plastic fibers of polypropylene, is sufficient to cause melting of the plastic fibers contacted by the bar. Pressure is applied against the bar 40, either externally or by virtue of the weight of the bar 40, such that the bar tends to sink into the surface 42 of the material 44 as the fibers 24 and 26 thereof begin to melt. As shown in Fig. 4, a continuous layer 46 of molten plastic is formed beneath the bar 40 but, preferably, not entirely through the thickness of the material 44. As mentioned, the weave of the strip material is relatively tight and, owing both to the surface tension of the molten layer 46 and the close fitting underlying fibers, the molten plastic (relatively viscous) does not flow through the underlying fibers. Rather, a depression 30 (Fig. 3) is formed in the strip surface 42, with the side and bottom walls of the depression comprising a solid layer 48 of plastic.

[0017] Because the layer 48 is of the same material as the underlying fibers and is in intimate contact therewith while in molten form, the continuous layer 48 serves as a relatively stiff plate firmly glued to the adjoining fibers, thereby reducing the freedom of movement of the glued fibers relative to one another and to the stiff layer 48. The fused layer 48 thus sufficiently stiffens the strip for maintaining the looped handles 20 in vertical orientation, as shown in Fig. 1, when the bag 10 is substantially full.

[0018] Preferably, as shown in Fig. 3, only a relatively thin layer 48 of fused material is produced. That is, only a relatively small quantity of fiber (e.g., 10%) is liquefied for preserving the basic woven characteristic of the strip material. While the layer 48 does have some strength, its principal purpose is to serve as a glue for restraining relative movement between adjacent fibers, and it is the intact woven fibers which provide strength of the handle material.

[0019] Fig. 5 shows an embodiment where the strength of the plastic fabric or cloth is critical. In this embodiment, a rib 60 comprising a narrow strip of the woven plastic material is secured, as by stitching or stapling, to the surface of a sheet 62 of woven plastic material or, indeed, to any number of different types of materials, e.g., burlap or canvass and the like. The presence of the rib 60 itself provides added stiffness to the underlying sheet and, in accordance with this invention, a surface 64 of the rib 60 is provided with a fused, stiffening region 66 formed as hereinbefore described. An advantage of this embodiment is that the addition of a fused stiffening region 66, in the added rib 60, provides no weakening of the underlying sheet 62.

[0020] While, as explained, it is preferable that only a relatively small portion of the woven fibers be fused, the quantity is not critical, and as much as 80% of the original fibers can be fused depending upon the particular use of the fused plastic material.

[0021] As described, the stiffened area 30 is provided by the application of heat and, preferably, the process is performed by the bag manufacturer while the handles are separate from the bags and in the form of easily handled elongated strips. Thus, the stiffening process can be "automated" using quite simple apparatus. The thus stiffened handle strips are then attached to the bags in known manner, e.g., by stitching.

[0022] Because adding stiffened areas to the handles does involve some expense (minor in comparison with prior known handle stiffening means) an alternative arrangement, particularly in those situations where identical bags are to be sold to different customers, some of whom do not require stiffened handles, is for the user to provide the handle stiffening. When done by the user, the handles are already attached to the bags and the process is somewhat more awkward to perform. Still, owing to the extreme simplicity of the process, involving merely the pressing of a hot iron against the handle material, the option of on-site handle stiffening is quite feasible.

[0023] The invention has been described in connection with polypropylene plastic. Such plastic material does not emit excessive fumes when heated and such fumes as are emitted are not health hazardous. Other known plastic materials can be used. Examples are polyethylene, polyethylene terephthalate ("polyester") and Nylon.

[0024] Additional embodiments of the invention using ribs similar to the rib 60 shown in Fig. 5 are now described.

[0025] In Fig. 6, a rib 70 is provided which is not of woven plastic fibers (as in the rib 60 shown in Fig. 5), but is a solid bead of plastic which is fused to underlying fibers at the surface of the sheet 62 preferably, but not necessarily, of woven plastic fibers. The rib 70 can be placed against the sheet surface and then heated to liquefy it. Alternatively, the rib can be applied from a suitable applicator, e.g., similar to a caulking gun, as a heated, viscous bead which hardens as it cools and adheres to the fibers of the underlying sheet.

[0026] Further, while it is generally preferable to use added ribs or beads of the same composition as the underlying sheet 62, e.g., the foregoing specified "plastic" materials, other commercially available adhesives, e.g., various epoxy cements, can be used to provide a stiffening rib of the type illustrated in Fig. 6.

Claims

1. A cloth-like material formed from woven plastic fibers, the material having a surface region of fused together fibers.

2. A material according to claim 1 having a surface formed from adjacent woven fibers, said surface region comprising a depression in said surface said depression having side and bottom walls formed from fused material from fibers adjoining said depression walls.

3. A material according to claim 1 in the form of an elongated strip having two legs, one ofsaid legs including said surface region extending from an end of said one leg at least partially along the length of said strip.

4. A material according to claim 3 including a bag having a wall, said legs of said strip being attached to said wall and providing a loop handle for said bag.

5. A material according to claim 4 wherein said bag side wall is formed from woven plastic fibers.

6. A material according to claim 1 and including a sheet of flexible material, said material being attached to a surface of said sheet for providing stiffening of said sheet.

7. A method of treating a cloth-like material formed from woven plastic fibers comprising heating a surface region of the material for partially melting and fusing together portions of adjacent fibers of the material.

8. A method according to claim 7 including pressing a hot object against said surface region.

9. A method according to claim 7 wherein said material is in the form of an elongated strip, said surface region is formed along one length of said strip, and including the step of attaching said strip to a wall of a bag.

10. A method according to claim 9 wherein said attaching step is performed prior to or after said heating of said surface region.

11. A method according to claim 7 wherein said material is in the form of an elongated strip, and including the step of attaching said strip as a stiffening rib to a surface of a flexible sheet.

12. A handle comprising a sheet of woven fibers of a plastic material for use with a bag also comprising woven fibers of said plastic material, said handle comprising a region having increased stiffness, said region including adjacent fibers bonded together by a rigid bonding material.

13. A handle according to claim 12 wherein said rigid bonding material comprises a fused mass of said plastic material on a surface of said sheet.

Drawing