METHOD OF PRODUCTION OF FABRIC BAGS OR CONTAINERS USING HEAT FUSED SEAMS

Abstract

A method of producing flexible polypropylene fabric bags with heat fused seams comprising providing fabric pieces, wherein each fabric piece has a coated side and an uncoated side; positioning fabric pieces so that a coated side of one fabric piece faces a coated side of another fabric piece; selecting an area of fabric to be joined for forming a seam or joint; applying heat to the area to be joined that is less than the melting point of the fabrics, for forming one or more seams or joints and wherein the heat fused seams or joints of a resulting polypropylene bag retains at least 85% of the fabric strength without using sewing machines.

Claims

1-24. (canceled)

25. A method of forming a flexible plastic fabric bulk bag with heat sealed joints, comprising the steps of: a) providing a first folded bag portion having a first pair of outer left edges and a first pair of outer right edges, each of the first pair of outer left edges being a fold wherein a first left side panel of the first folded bag portion is drawn inward and each of the first pair of outer right edges being a fold wherein a first right side panel of the first folded bag portion is drawn inward; b) providing a second folded bag portion having a second pair of outer left edges and a second pair of outer right edges, each of the second pair of outer left edges being a fold wherein a second left side panel of the second folded bag portion is drawn inward and each of the second pair of outer right edges being a fold wherein a second right side panel of the second folded bag portion is drawn inward; c) overlapping the first and second folded bag portions to define an overlapped area, wherein in the overlapped area interior surfaces of the first folded bag portion are in contact with exterior surfaces of the second folded bag portion, and wherein exterior surfaces of the first folded bag portion are in contact with one another, and interior surfaces of the second folded bag portion are in contact with one another; (d) applying heat and pressure to the overlapped area to form a bag joint between the interior surfaces of the first folded bag portion and exterior surfaces of the second folded bag portion that are in contact; and wherein a bag joint is not formed between at least some exterior surfaces of the first folded bag portion that are in contact with other exterior surfaces of the first folded bag portion and under heat and pressure and a bond is not formed between at least some interior surfaces of the second folded bag portion that are in contact with other interior surfaces of the second folded bag portion and under heat and pressure so that the bag can expand to an open configuration when filled with bulk material.

26. The method of claim 25 wherein the flexible plastic fabric is polypropylene.

27. The method of claim 25 wherein the flexible plastic fabric polyethylene.

28. The method of claim 25 wherein the bag joint is formed between an interior surface coating of the first folded bag portion and an exterior surface coating of the second folded bag portion.

29. The method of claim 28 wherein the interior surface coating is different from the exterior surface coating.

30. The method of claim 28 wherein the first folded bag portion is a bottom portion and the second folded bag portion is a body portion.

31. The method of claim 25 wherein the first folded bag portion is a top portion and the second folded bag portion is a body portion.

32. The method of claim 25 wherein the first folded bag portion is a top portion and the second folded bag portion is a top spout.

33. The method of claim 25 wherein the first folded bag portion is a bottom portion and the second folded bag portion is a discharge tube.

34. The method of claim 25 wherein the bulk bag can hold 2,000 to 4,400 pounds of bulk material.

35. The method of claim 28 wherein the heat sealed joint is a bottom load bearing joint.

36. The method of claim 25 wherein the bag joint retains at least 85% to 100% of the fabric strength.

37. A method of forming a flexible plastic fabric bulk bag, comprising the steps of: a) providing a folded first bag portion having a first open end; b) providing a folded second bag portion having a second open end; c) overlapping the first and second open ends of the folded first bag portion and folded second bag portion to define an overlapped configuration, and wherein in the overlapped configuration, there are a pair of outer left edges and a pair of outer right edges, each of the pair of outer left edges being a fold wherein a left side panel of the folded first bag portion and a left side panel of the folded second bag portion are drawn inward, and each of the pair of outer right edges being a fold wherein a right side panel of the folded first bag portion and a right side panel of the folded second container portion are drawn inward; d) applying heat and pressure to the overlapped folded first container portion and the overlapped folded second container portion to form a bag joint between surfaces of the folded first container portion and surfaces of the folded second container portion that are in contact; and e) wherein a bag joint is not formed between at least a substantial portion of folded first container portion surfaces that are in contact with each other and is not formed between at least a substantial portion of folded second bag portion surfaces that are in contact with each other so that the bulk bag can expand to an open configuration after the bond between the surfaces of the folded first container portion and the surfaces of the folded second bag portion that are in contact is formed.

38. The method of claim 37 wherein the bag joint is formed between an interior surface coating of the folded first bag portion and an exterior surface coating of the folded second bag portion.

39. The method of claim 38 wherein the interior surface coating is different from the exterior surface coating.

40. The method of claim 38 wherein the folded first bag portion is a bottom portion and the folded second bag portion is a body portion.

41. The method of claim 25 wherein the folded first bag portion is a top portion and the folded second bag portion is a body portion.

42. The method of claim 25 wherein the bulk bag can hold 2,000 to 4,400 pounds of bulk material.

43. The method of claim 25 wherein the bag joint retains at least 85% to 100% of the fabric strength.

44. A method of forming a heat sealed bulk bag of the type that can hold 2,000 to 4,400 pounds of bulk material, comprising the following steps: (a) providing a first folded bag portion having a first coating on at least an exterior surface of the first folded bag portion; (b) providing a second folded bag portion having a second coating that is different from the first coating on at least an interior surface of the second folded bag portion; (c) overlapping the first and second folded bag portions to define an overlapped area, wherein in the overlapped area some interior surfaces of the second folded bag portion are in contact with some exterior surfaces of the first folded bag portion such that the first coating and the second coating are in contact, and wherein some exterior surfaces of the second folded bag portion are in contact with one another, and some interior surfaces of the first folded bag portion are in contact with one another; and (d) applying heat and pressure to the overlapped area to form a bond between the first coating and the second coating that are in contact and a bag joint that has the following directly adjacent layers: (i) first folded bag portion fabric, (ii) first coating, (iii) second coating, (iv) second folded bag portion fabric; and wherein bag joints are not formed between said exterior surfaces of the second folded bag portion that are in contact and bag joints are not formed between said interior surfaces of the first folded bag portion that are in contact, so that when heat sealing of the bag joint is completed the bag is expandable to an open configuration.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0113] For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein:

[0114] FIGS. 1-2 are charts showing comparative data from test results on prior art seams for bulk bag construction using standard sewing seam methods on both weft and warp direction yarns of the fabric;

[0115] FIG. 3 illustrates a simple sewn seam of the prior art;

[0116] FIG. 4 illustrates a pre-hemmed sewn seam of the prior art;

[0117] FIG. 5 illustrates a prior art pre-hemmed sewn seam of a bag in a filled position;

[0118] FIG. 6 is a chart showing test results of a fusion heat seam bulk bag of the present invention;

[0119] FIG. 7 is a perspective view of a bulk bag of the present invention with heat fusion seams;

[0120] FIGS. 8-9 are prior art views of a sewn seam bag, and of the sewing process of the prior art;

[0121] FIG. 10 illustrates the position of a prior art seam as sewn;

[0122] FIG. 11 illustrates the position of a prior art sewn seam when a bag is full;

[0123] FIG. 12 illustrates a heat fusion seam of an embodiment of the present invention;

[0124] FIG. 13 illustrates use of a heat seal bar in an embodiment of the heat fusion seal method of the present invention;

[0125] FIG. 14 illustrates a fill or discharge spout of an embodiment of a heat fusion seal bag of the present invention;

[0126] FIG. 15 illustrates a top or bottom panel of an embodiment of a heat fusion seal bag of the present invention;

[0127] FIG. 16 illustrates a tubular body panel of an embodiment of a heat fusion seal bag of the present invention;

[0128] FIG. 17 illustrates an end view of a folded fill or discharge spout of an embodiment of a heat fusion seal bag of the present invention;

[0129] FIG. 18 illustrates an end view of a folded top or bottom panel of an embodiment of a heat fusion seal bag of the present invention;

[0130] FIG. 19 illustrates an end view of a folded bag body of an embodiment of a heat fusion seal bag of the present invention;

[0131] FIG. 20 illustrates a side view of a folded top or bottom panel of an embodiment of a heat fusion seal bag of the present invention;

[0132] FIG. 21 illustrates an overall view of embodiment of a heat fusion sealed bag of the present invention;

[0133] FIG. 22 illustrates layering of fabrics in an embodiment of the heat fusion seal method of the present invention.

[0134] FIG. 23 illustrates layering of fabrics in an embodiment of the heat fusion seal method of the present invention.

[0135] FIG. 24 illustrates a sample of a heat fusion seam of the present invention wherein the fabric of the wall is doubled;

[0136] FIG. 25 illustrates an overall view of a fusion heat sealed fabric bag of the present invention; and

[0137] FIG. 26 illustrates an isolated view of a heat fusion seal of the present invention wherein the edges of the fabric at the point of the seal are overlapped.

DETAILED DESCRIPTION OF THE INVENTION

[0138] In the method of the present invention, what is provided is a heat sealing method that does not substantially damage the strength of the polypropylene fabric yet still gets a final joint strength equal to or exceeding the strength of the current sewing methods. During testing, products produced using the method of the present invention have achieved joint strengths of 90 to 102% of the strength of the polypropylene fabrics which is considerably above the joint strengths of seams achieved through sewing.

[0139] In an embodiment of the present invention, the invention will aid and enable the automation of bulk bag production, thus freeing up the location of factories around the world. Due to the improved joint strength, this invention will enable the use of thinner materials to accomplish the lifting of similar weights.

[0140] In an embodiment of the present invention, a suitable coating, for example VERSIFY™ 3000, a product produced by The Dow Chemical Company is applied to the polypropylene fabrics or similar fabrics, and provides up to 240 lbs of hold or grip per lineal inch (4,286 kilogram/meter) (to the polypropylene fabric from a heat seal of 1½ inches (3.81 cm) across the joint area. In another embodiment, a coating, for example VERSIFY™ 3000, a product produced by The Dow Chemical Company is applied to the polypropylene fabrics or similar fabrics, and provides up to 200 lbs of hold or grip per lineal inch (3,572 kilogram/meter). In a preferred embodiment, the coating has a melting point which is lower than the melting point of the fabrics being joined together. The method of heat sealing is an improvement over the known art in the woven fabrics industry today.

[0141] A suitable coating may be a propylene plastomer and elastomer, for example Versify™ 3000. The coating may contain for example 50% to 90% polypropylene based polymer and 10%-50% polyethylene, by weight.

[0142] In a coating to be used in a preferred method of the present invention for heat joining polypropylene fabric, one can use 10-99%, preferably 20-95%, more preferably 30-95%, and most preferably 75-90% propylene plastomers, elastomers, or combinations thereof;

[0143] one can use 0-5% additives for color, anti-static, or other purposes (these do not materially affect the performance of the coating, and are typically minimized as they are more expensive than the propylene and polyethylene);

[0144] the balance is preferably polyethylene plastomers, elastomers, or combinations thereof.

[0145] Preferably, the propylene plastomers, elastomers, or combinations thereof have a density of 0.915 to 0.80 grams per cc, and more preferably 0.905 to 0.80 grams per cc. Preferably, the polyethylene plastomers, elastomers, or combinations thereof have a density of 0.91 to 0.925 grams per cc. Typically, one should use at least 5% low density polyethylene to make the coating run, and preferably at least 10%.

Example

[0146] In a preferred embodiment of the present invention, the fabrics are only being heated to the melting point of the coating which is lower than the melting point of the fabrics being joined together. In a preferred embodiment of the present invention, the joining temperatures are at least 5 degrees less than the melting point of the polypropylene fabrics to be joined. Different polypropylene fabrics will have different melting points, and in an embodiment of the method of the present invention, the joining temperatures are at least 5 degrees less than the melting point of the particular polypropylene fabrics to be joined. An example polypropylene fabric may have a melting point of 320 degrees Fahrenheit (176.7 degrees Celsius), and thus in an embodiment of the present invention, the coating will be heated to 315 degrees Fahrenheit (157.22 degrees Celsius). By using a lower heat than the polypropylene fabrics, the method of the present invention does not damage or reduce the strength of the fabric as typically happens when using the prior art high heat formulas for heat welding. Further, in an embodiment of the present invention, the clamping pressure used to make the seal is designed to be low enough (for example 7 psi (48 kilopascal)) to leave the coating largely in place and the materials to be joined, largely separated by the coatings. Clamping pressures may also be lower, for example under 2 psi (13.8 kilopascal). Typically in the prior art heat sealing methods, the clamping process is designed to purposefully melt and push aside any coatings on the fabric and join the fabric yarns directly. When any part of the fabric yarns are heated to and past their melting point and that is combined with high pressure (for example 20 psi (137.9 kilopascal)), the yarns are thinned out, weakened and partially crystallized.

[0147] It is an objective of the present invention to heat fuse fabrics together. In a preferred embodiment of the present invention, fabrics are not being heated up past their melting points, which is useful in preventing degradation of the strength of the fabric. In a preferred embodiment of the present invention, the fabrics are only being heated to the melting point of the coating which is lower than the melting point of the fabrics being joined together. In an embodiment of the present invention, the joining temperatures are at least 5 degrees less than the melting point of the polypropylene fabrics to be joined. Different polypropylene fabrics will have different melting points, and in an embodiment of the method of the present invention, the joining temperatures are at least 5 degrees less than the melting point of the polypropylene fabrics to be joined. (An example polypropylene fabric may have a melting point of 320 degrees Fahrenheit (176.7 degrees Celsius), and thus in an embodiment of the present invention, the coating will be heated to 315 degrees Fahrenheit (157.22 degrees Celsius)). By using a lower heat than the polypropylene fabrics, the method of the present invention does not damage or reduce the strength of the fabric as typically happens when using the prior art high heat formulas for heat welding. Further, in an embodiment of the present invention, the clamping pressure used to make the seal is designed to be low enough (for example 7 psi (48 kilopascal)) to leave the coating largely in place and the materials to be joined, largely separated by the coatings. Clamping pressures may also be lower, for example under 2 psi (13.8 kilopascal). Typically in the prior art heat sealing methods, the clamping process of the prior art is designed to purposefully melt and push aside any coatings on the fabric and join the fabric yarns directly. Naturally, when any part of the fabric yarns are heated to and past their melting point and that is combined with high pressure (for example 20 psi (137.9 kilopascal)), the yarns are thinned out, weakened and partially crystallized.

[0148] In the present invention, using low heat and low pressure, only the coating itself is being joined. This leaves the fabric completely undamaged and unweakened. In fact, the strength of the coating now can add to the overall joint strength rather than being squeezed out in the current methods. With the resulting joint strengths, the present invention enables lifting of higher weights with less material, than can be done with the prior art methods of sewing fabrics together.

[0149] As previously, discussed, in a preferred embodiment, the coating materials have a melting point lower than the fabrics to be joined. In a preferred embodiment, the coating materials in the process may be any suitable material or materials which may be used to successfully carry out the process, and could be selected from a range of coating materials. A suitable coating, for example, may be a propylene plastomer and elastomer, for example VERSIFY™ 3000, a product produced by The Dow Chemical Company. A suitable coating may contain 50% to 90% polypropylene based polymer and 10%-50% polyethylene, by weight. VERSIFY™ is a registered trademark of The Dow Chemical Company for propylene-ethylene copolymers used as raw materials in the manufacture of films, fibers and a wide variety of molded plastic objects; propylene-ethylene copolymers used as raw materials in the manufacture of compounds to make coated fabrics, artificial leather, soft touch grips, shoe stiffeners and flexible roofing membranes.

[0150] In a preferred embodiment of the present invention, the method would utilize a mixture of a minimum of 70% pure VERSIFY™ 3000 and 25% Polyethylene and 5% of additives such as UV protection and colors. Using 100% pure VERSIFY™ 3000, the method of the present invention achieved up to 96% to 102% joint efficiency in a shear joint tensile test, while at 70% VERSIFY™ 3000, 91% to 95% joint efficiency has been obtained in the same test. (The resulting percentages are based on the average strength of the fabric tested. There is generally approximately a 5% variable strength in any section of fabric tested.)

[0151] Turning now to the figures, the charts shown in FIGS. 1-2, illustrate comparative data and results from testing performed on seams made for bulk bag construction using both the standard sewing seam methods on both weft and warp direction yarns of the fabric. They are several ways to make prior art seams in the bulk bag industry. In FIGS. 3-4, the most common seams are depicted.

[0152] FIG. 3 depicts a simple sewn seam. In FIG. 3, fabric 13 is shown, with sewing stich seam 11, and fabric fold 15, wherein fabric is folded back on itself to create a seam. As shown, the simple seam is just a folding back of the two pieces of fabric to be stitched together. This simple seam prevents the interlocking weave from simply slipping off the edge of the fabric under the extreme pressures that are often found in bulk bag usage. This seam generally creates about a 58% joint strength.

[0153] FIG. 4 depicts a pre-hemmed seam, which is created by not only folding the fabric back prior to making the joint, but by sewing the folded back portion of the fabric to itself. FIG. 4 shows fabric 13 with sewing stitch seam 11 and stitch to hold the hem 12, wherein the folded back portion is sewn to the fabric itself. This extra step generally creates a seam with an average strength of 63%. 63% over 58% is a strength increase of 8.5%. Even though there is extra labor to hem the fabrics, a strength increase gain of this size is often considered important in the industry.

[0154] After the bag is made and filled, the pre-hemmed seam will be in the position shown in FIG. 5. FIG. 5 depicts heat seal joint 14. This means that the majority of the time, the seam is basically in a peel position whose strength is largely determined by the strength of the thread being used. But when seams are able to withstand forces only equal to 63% of the fabrics, then the fabrics must be overbuilt to take into account the seam's inefficiency.

[0155] When labor is taken into account as well, it is easily seen that the sewing operation is a very large factor in determining the final cost of making bulk bags.

[0156] Taking the same fabrics, and using the fusion heat seal seam method of the present invention, the graph shown in FIG. 6 shows that the seam strengths achieved, over 4 sets of tests, averaged 95.75% strength retention. This is a significant increase of strength retention with these fabrics.

[0157] When 95% of the original strength is being maintained through the fabric connections, equal fabrics may be used to carry heavier loads, or less fabric can be used to carry the same load. An embodiment of the present invention thus may provide a 50% gain in strength over the sewn seams.

[0158] The fusion heat seal seam not only creates a stronger seal, but it does it in a significantly different manner. The fusion heat seal seam of the present invention enables new bulk bag designs that will be able fill the needs of the bulk bag industry.

[0159] In the prior art, due to the nature of sewing machines and the size of bulk bags, the vast majority of seams must be sewn in an edge to edge peel position. The throat of a sewing machine is not big enough to easily allow an entire bulk bag to pass through the throat of the machine. Therefore, sewing is typically designed to place all seams in an edge to edge position as shown in FIG. 9. FIG. 7 depicts a fusion heat seal seam 16 of the fusion heat seal bag 10. FIG. 8 illustrates a prior art sewn seam 11.

[0160] Once a sewn seam prior art bag is made and filled, the sewn seam then is put into a peel position that depends entirely on the strength of the combination of the thread and needle punctured fabrics.

[0161] In FIG. 10, you can see the positions of the fabric as it was stitched by the machine above in FIG. 9. Stitch seam 11 is shown stitching together bag sidewall 17 and bag bottom wall 18. Fabric folds 15 are positioned so that fabric fold 15 of sidewall 17 is in contact with fabric fold 15 of bottom wall 18. In FIG. 11, the position of the stitch and fabric when the bag is in use are shown. Sewn stitch 11 and joint 14 are shown, wherein sidewall 17 and bottom wall 18 are attached. The fabric folds 15 of each wall 17, 18 are shown in an interior of the bag. Typically, a minimal fabric fold 15 will be 2 inches (5.08 cm) in depth on each side. This means the average sewn seam has 4 inches (10.16 cm) of doubled fabrics.

[0162] The fusion heat seal seam of the present invention is formed by over-lapping the fabrics to give the seal a wide shear area for strength. In an embodiment of the present invention, the fusion seam will get 95% of the original fabric strength. In a preferred embodiment, there will be an overlap of 1½ to 2 inches (3.81 cm to 5.08 cm). This saves a minimum of 2 inches (5.08 cm) of fabric in every joint as the prior art sewn method has 2 inches of doubled fabric layers on both sides of the seam.

[0163] FIG. 12 depicts a fusion heat seal seam of the present invention. In FIG. 12, fabric 13 is shown as a dark line. Coating or lamination 19 of the fabrics is shown as a dotted line. Line 20 depicts the sealed or joined area of fabric, which may be 1½ to 2 inches (3.81 cm to 5.08 cm).

[0164] In an embodiment of the present invention the width of the overlap can be much smaller, for example 0.5 inches (1.25 cm) to save even more fabrics.

[0165] It is preferable, that the seams be sealed in a manner that no graspable edge be left on any exterior seams of the bag. This will discourage any attempt to rip the seal open in the peel position which is the weak direction of the fusion joint.

[0166] In an embodiment of the present invention, the preferred method is to overlap the fabrics only 1½ inches (3.81 cm) and center this under a 2 inch (1.25 cm) wide, for example, seal bar 21 as shown in FIG. 13. In FIG. 13, line 20 depicts the sealed area, which may be 1½ inches (3.81 cm) wide. This intentionally leaves a ¼ inch (0.64 cm) gap or transitional area, represented by arrow 22, on either side of the joint or sealed area 20. This insures that the ending edges of the two halves of the seal are sealed to the very edge. This leaves no graspable edge to create an easily peelable area.

[0167] The ¼ inch (0.64 cm) transitional area is small enough to prevent damaging heat from overcoming the smaller material volume of the single layer and allows for some small misplacement of the fabric edge lineup.

[0168] In an embodiment of the method of the present invention, a pulse heat process is used. By using impulse heat, the top temperature can be controlled and held to a desired amount of heat for a desired amount of time. This then allows the process to bring the material temperatures up to the desired level without going so high as to damage the fabrics but to also hold it there long enough to allow a thorough and even heating of the joint area.

[0169] It is, also, useful to the process to keep equal amounts of materials under the seal at all times. The impulse heat process is injecting equal heat throughout the sealing process. If an uneven amount of materials under the seal bar is too diverse, then areas with less materials may absorb more heat than desired and material damage can occur.

[0170] In FIG. 12, with only a single seal being made, the amount of heat applied is minimal enough that the ¼ inch (0.64 cm) transitional area or gap 22 allows enough heat dissipation to provide a very good seal without damage to surrounding materials.

[0171] An embodiment of the present invention involves stacking this process and creating multiple seals simultaneously. When stacking the process, placement of materials should be considered and keeping material amounts equal throughout will enable safe repeatability of the sealing process.

[0172] What has been described and shown so far is the difference between sewing seams and heat sealing to make a simple seam using polypropylene fabrics. Hereafter, the construction of bulk bags, that may routinely carry one ton of dry flowable materials, for example, will be discussed.

[0173] An objective of the present invention is to find ways to reduce the cost of making a product commonly called by several names. These names include bulk bags, Flexible Intermediate Bulk Containers, FIBC's, Big Bags or even Super Sacks (a trademark name of B.A.G. Corporation). Herein the product has been and will be referred to mostly as bulk bags.

[0174] The present invention has useful applications with bulk bag production, and is also useful to a number of other packages or products, for example smaller bags used to carry 25 to 100 pounds (11 to 45 kilograms). Other products that will benefit from the present invention include products stored or transported in flexible fabric packaging, wherein a sterile and air tight package is preferred.

[0175] Current bulk bag technology, using sewing machines typically travels stitch by stitch around every inch (centimeter) of seam on every part of the bag on an individual basis. In an embodiment of the present invention, the invention will simplify this process to create a productive system that can seal or join the fill spout to the top sheet, the top sheet to the bag body, the bottom sheet to the bag body, and the bottom discharge spout to the bottom sheet in a single moment or step. This eliminates a tremendous amount of labor and time.

[0176] Further, in an embodiment of the present invention each heat sealed seam may be approximately 50% stronger than the sewn seam. Because each joint requires less fabric than the sewn seam, the present invention enables production of a fabric bag that is demonstrably less expensive and more economical to make.

[0177] Use of heat sealing is known in the art. No matter what the shape of the seal to be made is, heat bars can be shaped to accomplish that seal and that shape. In an embodiment of the present invention, a square formed heat bar and structures to hold the fabric in place to allow the joining of the bottom of the bag to the sidewalls will be used to make a joint. Such equipment, however, may be large, bulky and expensive. Additional steps to complete the product and machines may be needed.

[0178] In an embodiment of the present invention, the method comprises using the fusion heat sealing method of the present invention for production of bulk bags, wherein individual joints are sealed sequentially, one after another. In another embodiment of the present invention, fewer steps and machines are used in fusion heat sealing a bulk bag. An objective of the present invention, is to simplify the number of steps when producing a bulk bag, as compared to prior art sewing methods.

[0179] There are many prior art designs in the bulk bag market but most of these designs fall into two basic categories. The body of the bag may be made from numerous pieces of flat panels sewn together or the body of the bag may be made from a single piece of tubular fabric that has no vertical seams.

[0180] All of the basic designs can be made using the system of the present invention. A preferred embodiment of the present invention will start with a tubular woven body.

[0181] Many bulk bags have a fill spout, a top panel, a circular woven body panel, a bottom panel and a discharge spout. The two spouts can be made with tubular fabric with no seams. The body of the bag may be made as tubular fabric with no seams. The top and bottom panels are generally square flat panels with a hole cut into them to accommodate the spouts that must be attached to them. FIG. 14 depicts a fill or discharge spout 23. Line 24 represents, for example, a 22 inch width for a (55.88 cm) spout tube, lying flat. Line 25 represents, for example, a 18 inch (45.72 cm) long fill or discharge spout.

[0182] FIG. 15 depicts example top or bottom panels 26. In FIG. 15, the top or bottom panel 26 is relatively square with sides being 41 inches (104.14 cm) for example, as represented by lines 29. Area 30 represents a connection area for the fill or discharge spout, with lines 28 being 11 inches (27.94 cm) for example.

[0183] FIG. 16 depicts a tubular fabric 27, without seams. Line 31 may represent a 45 inch (114.30 cm) height, for example, and line 32 may represent a 74 inch (187.96 cm) width, when the tubular fabric is lying flat.

[0184] Thus, FIGS. 14-16 depict five potential pieces of fabric, a fill spout 13, a discharge spout 13, a top panel 23, a bottom panel 23, and a tubular fabric piece 26.

[0185] In an embodiment of the present invention, a bulk bag may be produced, using fusion heat seal process, in a single step. In a preferred embodiment, the fabric pieces will be gusseted and placed in position for the heat fusion sealing process. The FIGS. 17-20 depict the final form of the fabrics in a preferred embodiment, just prior to making the basic bag.

[0186] In a preferred embodiment the coating side of the fabrics is on the outside of the tubes and on the inside of the flat panels, so that the coatings will be facing each other when the bag is formed.

[0187] These coating positions can be reversed and put inside of the tubes and outside of the flat panels for top and bottom, but since coating naturally comes on the outside of tubular fabric, the preferred method is the one shown in the drawings.

[0188] FIGS. 17-19 depict folding the bulk bag parts prior to heat sealing in a single step. As shown in FIGS. 17-19, the folded shape of every piece is basically the same shape. FIG. 17 depicts an end view of folded fill or discharge spouts 23, wherein the coating or lamination 19 is on the outside. Line 33 depicts an 11 inch (27.94 cm) width area, for example. FIG. 18 illustrates an end view of top or bottom panels 26 wherein the coating or lamination 19 is on the inside. Line 45 depicts a 41 inch (104.14 cm) area, for example. FIG. 19 illustrates an end view of a folded tubular bag body 27 wherein the coating or lamination 19 is on the outside. Line 46 depicts a 37 inch (93.98 cm) area. FIG. 20 depicts a side view of a folded top and bottom, wherein coating 19 is on the inside. Dotted line 34 represents a future fold line. Corner slits 35 are also shown. Approximately a 45 degree angle may be formed.

[0189] The folding arrangement as described above, enables each piece to fit inside or around the piece it will be connected to in the production process.

[0190] Once the shapes are put together, the bag is ready to seal as shown in FIG. 21. At each of the four fusion heat seal areas or joints 41, the parts are positioned with the outer part having the coating 19 facing inward and the inner part having the coating 19 facing outward as shown in FIGS. 22-23.

[0191] This results in a total of 8 layers of fabric at all points from bottom to top. In FIGS. 22-23, layers 1-8 are shown.

Example; Connection of Top to Body of Bag

[0192]

TABLE-US-00002 1. Top layer Top Panel flat side 2. Second layer Body Panel flat side 3. Third Layer Body Panel Gusset side 4. Fourth layer Top Panel Gusset Side 5. Fifth layer Top Panel Gusset Side 6. Sixth Layer Body Panel Gusset Side 7. Seventh Layer Body Panel Flat Side 8. Eighth Layer Top Panel Flat Side

[0193] By lining up multiple layers in this fashion, heat fusion method of the present invention is able to completely join the top to the body panel in a single action. When the structure as depicted in FIGS. 22-23 is collapsed, the structure is always coating 19 to coating 19 for joint creation and fabric 13 to fabric 13 for not creating a joint. In the drawings the gussets may be positioned so as to fit together and during production, fabrics are collapsed to a flat condition.

[0194] All four joints are made in the same manner.

[0195] The method of the present invention using impulse sealing to make joints through multiple layers without exceeding the safe temperature limit, comprises controlled heating that will not rise above the desired level which is less than the melting point of the polypropylene fabric.

[0196] In a preferred embodiment, in order to get the entire group of intended joints to the right temperature level without damaging the fabric strength, time will be employed to allow the required heat to become universal throughout the 8 layers of materials.

[0197] Further, it will be useful if the heat mechanisms are mirrored on the top and bottom so that heat may need to travel only 50% of the total thickness. This process may also be achievable with one heating element by using a greater time for the heat to travel throughout the entire stack of fabrics. A preferred method uses heating elements on both top and bottom of the stack.

[0198] In an embodiment of the present invention, a single machine with 4 heating elements on top and four heating elements on the bottom can effectively seal, in a single action, all four of the joints shown in FIG. 21 of the complete bag.

[0199] The fabrics can be placed and positioned under the sealing mechanisms so that the heat sealing bars cover the area to be joined plus a ¼ inch (0.64 cm) overlap, for example, to enable sealing of all edges and to also make them ungraspable. In an embodiment of the present invention, the mechanisms can control heat, time and pressure. When this is done, the bags can be put together in a completely repeatable and dependable fashion with this stage of production requiring a single automatable machine.

[0200] When making bulk bags in this manner, different sizes of bags can be made by simply changing the length of the body panel. This would require only the movement of two heating elements to match the new distance between the top and bottom panel attachments. The relationship or distance between the spout joints and the top and bottom panel would be unchanged.

[0201] The method of the present invention may also be used to create different designs of bulk bags, for example baffle bags or bags with lifting loops, with heat fused seals or joints.

[0202] This system eliminates the need for threads and the resulting contamination that often occurs when a cut piece of thread is left inside the bag. It reduces contamination from sewing machines coming into contact with various parts of the bag. It reduces human contact with the inner surfaces of the bag.

[0203] Since the seams are solid without any needle holes, this system eliminates any need for sift-proofing that is often required for stitched bulk bags. The method of the present invention provides a bag that is nearly air tight.

[0204] Due to the airtightness and the cleanliness, it is perceived that this production system may eliminate the need for polyethylene liners that are often added to the inside of the bulk bag for cleanliness and/or moisture control. This will reduce the amount of plastic used in the industry and therefore reduce the amount of materials eventually going into landfill.

[0205] Notably all four of the seams shown in the preferred embodiment put the final seams in the sheer position to withstand the forces of the heavy weights that bulk bags carry. Further, the act of carrying the weight will always stress these seams in only the shear position.

[0206] Thus, in the method of the present invention for automating production of flexible bags, packages or containers, it should be understood that this method would cover all kinds of flexible bags, packages or containers.

[0207] As previously discussed, the bulk bag industry uses a highly oriented woven polypropylene fabric. This is based on a cost versus strength matrix.

[0208] Polypropylene has historically been lower in cost per pound (kilogram) and historically stronger than similar polyethylene by about 30% in tensile strength. While it was always possible to use a thicker polyethylene material to make bulk bags, there has been limited interest in using that material due to the ensuing cost of getting the needed strength. Further, polyethylene fabrics have a lower melting point than polypropylene fabrics so once again, polypropylene has been a preferred material for nearly 40 years in this industry. Polypropylene is also a very inert material. It is unaffected by almost every chemical. This also makes it a good choice for making packaging bags. With all of these benefits for the industry, one area where polypropylene falls short of polyethylene, has been the result of polypropylene's inertness and its strength due to high levels of orientation.

[0209] Because of this inertness, the entire industry has relied upon a physical connection of materials for the container construction. It has relied nearly 100% on sewing as the method of construction.

[0210] One of the common alternate methods of connection to sewing that is automatable has been to use heat to form joints. When PE fabrics are used, this is very common. But polypropylene crystallizes at the level of heat needed to form a joint. This crystallization destroys the joint strength rendering this method previously unusable. There are currently no known methods of heat sealing polypropylene fabrics together that create usable seams for the construction of polypropylene bags such as bulk bags.

[0211] As stated earlier, the sewing process is very labor intensive and very poorly suited for any form of automation. Sewing machines have very high speed parts moving to allow sewing stitches to be applied at thousands of stitches per minute. At these speeds, even if the machines were operated robotically, needles and threads are continually breaking and needing human repair to be put back into operation. Therefore, due to the inability to run without constant human support, the bulk bag industry has never been able to automate its production in an efficient and cost effective manner. This has led to the loss of all of these jobs to overseas plants located in low labor cost countries.

[0212] Therefore, there is a need for an automatable system of bag construction that will reduce the high levels of labor currently required in the construction of bulk bags. This will allow the production to be positioned close to the end users and eliminate the extremely long lead times and high inventory needs that the industry suffers with under the current sewing construction methods.

[0213] An embodiment of the method of this invention comprises a method of constructing woven fabric bags using a new and unique heat sealing method. Use of a heat sealing process is well known and quite common in the joining of woven polyethylene fabrics. It is commonly understood that a joint efficiency of 80% to 85% is an extremely good joint efficiency level. Many operations accept much lower joint efficiencies that range down into the 70's of the percentage of efficiencies.

[0214] In the sewn seams, the efficiency is often only 65%. The strength of the polypropylene fabric takes these joint efficiencies into consideration when choosing the strength of the fabric that will be used in the construction of the final container.

[0215] Current methods of heat sealing usually involve high enough heat and high enough applied pressure to melt the basic fabrics and join them together. This method purposefully, melts any applied coating and squeezes it aside through the high pressure levels so that the base woven materials can be joined together. This method has been successful, with polyethylene fabrics for example, for several decades. It was necessary because the strength being relied upon came from the woven fabrics. The coatings that were generally applied, were applied for the purpose of providing dust and/or moisture control.

[0216] Because polypropylene is so inert, the coatings being applied had low attachment strength to the woven fabrics. Therefore, if they were to be used as the attachment point by welding the applied coatings together, the resulting strength would have no real relationship to the strength of the fabric. The resulting joint strength would only be related to the strength of the coating's attachment to the woven fabrics. When conducting testing with regard to the present invention, of making joints that relied on the strength of the coating's attachment using the present technology, results showed about a 27% joint efficiency on the particular strength of materials tested. In these tests, it was never the fabric that broke. It was always the coating detaching from the fabric that caused the joint to fail.

[0217] In the present invention, a coating that can be applied in a standard extrusion coating method attaches so completely to the polypropylene fabrics that it is no longer necessary to apply high pressure that will squeeze the coating out from under the heated jaws of the sealing mechanism. In fact, by sealing under less than 10 psi (68.9 kilopascal), it is an objective of this invention to utilize the strength of the applied coating as part of the strength of the final heat seal. The fabric itself is nearly undamaged during this heat sealing method. In an embodiment of the present invention, only the coating is intended to be melted to create the joint. Tests results show achievement of over 90% joint strengths. Some tests results are running up as high as 100% of the strength of the coated materials that have not been sealed. However, the resulting strength of the joints many times exceeds the strength of the original fabric itself prior to it having been coated.

[0218] Therefore in an embodiment of the method of the present invention, the method of heat sealing creates seams that are sometimes actually stronger than the original fabric before any process begins. Considering that the current methods are working with sewn seams that have a 65% joint efficiency, it is an objective of the present invention that this heat sealing method will makes heat joints with minimal damage to the original fabric and will allow not only lower costs through automation to reduce labor costs, but will provide many opportunities to reduce fabric weights and thicknesses while providing similar overall strengths through the higher seam efficiencies. An example would be as follows; if the sewn fabric had a tensile strength of 200 pounds per inch (3,572 kilograms/meter), after being sewn the seam would have a strength of 65% of the 200 pounds per inch (3,572 kilograms/meter) or only 130 pounds (58 kilograms). With a 90% joint efficiency, a fabric that had an original strength of 150 pounds per inch (2,678 kilograms/meter) would still create a seam strength of 135 pounds per inch (2,410 kilograms/meter). This would allow a 25% reduction in the strength of the fabric to create an equal seam. This obviously then will lead to long term reductions on the amount of fabrics needed with this system to create bags with similar strengths.

[0219] All seams have at least two measurements that are critical to its success. These are generally called shear and peel tests.

[0220] In the shear tests, the joint is made with two ends of the material being joined at opposite ends of the joint area. When the free ends of the materials are pulled in opposite directions, the entire sealed area supports the joint efficiently. This results in the highest possible demonstration of the sealed joint efficiency.

[0221] In the peel test, two free ends of the test materials are on the same side of the joint. In this case, when the two free ends are pulled apart, only one edge of the seal is stressed at any one time. This results in the peeling of the joint as the ends are pulled apart. This typically results in the lowest joint efficiency.

[0222] An embodiment of the present invention is illustrated in FIGS. 24-26. FIG. 24, depicts a joint wherein the fabric wall is doubled, in an upside down “T” shape construction. As the fabric meets the end wall, one leg goes to each side, and pressure from either side protects the opposite side with its shear strength. In FIG. 25, a fusion heat sealed bulk bag 10 can be designed in a manner such that lap seams as shown can be used. The product will always be pushing the joint in the shear direction, as illustrated by arrows 44 in FIG. 26, which depict pressure being applied from product held within a bag.

TABLE-US-00003 PARTS LIST PART NUMBER DESCRIPTION  1 layer  2 layer  3 layer  4 layer  5 layer  6 layer  7 layer  8 layer 10 heat Fusion Seam Bulk Bag 11 stich seam 12 stich to hold hem 13 fabric 14 sewn joint 15 fabric fold 16 fusion heat sealed seam 17 side wall 18 bottom wall 19 coating/lamination 20 line 21 heat seal bar 22 transitional gap 23 fill/discharge spout 24 line 25 line 26 top/bottom panel 27 body 28 sewn seam 29 line 30 area 31 line 32 line 33 line 34 future fold line 35 corner slit 36 gusseted fill spout 37 gusseted top panel 38 gusseted body 39 gusseted bottom panel 40 gusseted discharge spout 41 fusion seal area 42 double fabric wall 43 lap seam 44 pressure from bag contents 45 line 46 line

[0223] All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise.

[0224] The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.