METHOD OF FOLDING AND USING STATIC CHARGE TO ALIGN AND RETAIN FOLDED MATERIAL

Abstract: A method of folding a material during the process of making disposable absorbent articles, such as sanitary napkins and the like, is disclosed. The method utilizes a static charge (72) to align the material to be folded and to, at least temporarily, retain the material in a folded configuration.

Description: METHOD OF FOLDING AND USING STATIC CHARGE TO ALIGN AND RETAIN FOLDED MATERIAL FIELD OF THE INVENTION This invention relates to a method of folding articles. More particularly, the invention relates to a method of folding a material during the process of making disposable absorbent articles, such as sanitary napkins and the like, which utilizes a static charge to align the material and, at least temporarily, retain the material in a folded configuration. BACKGROUND OF THE INVENTION All manner and variety of absorbent articles configured for the absoφtion of body fluids such as menses, urine, and feces are, of course, well known. Absorbent articles, particularly sanitary napkins, having wings or flaps are disclosed in the literature and are available in the marketplace. Generally, the flaps of such sanitary napkins extend laterally from a central absorbent means and are intended to be folded around the edges of the wearer's panties in the crotch region. Several preferred sanitary napkins having flaps are described in U.S. Patent No. 4,589,876 entitled "Sanitary Napkin", which issued to Van Tilburg on May 20, 1986, U.S. Patent No. 4,687,478, entitled "Shaped Sanitary Napkin with Flaps", which issued to Van Tilburg on August 18, 1987, U.S. Patent No. 5,389,094 entitled "Absorbent Article Having Flaps and Zones of Differential Extensibility", which issued to Lavash, et al. on February 14, 1995, and U.S. Patent No. 5,281,209 entitled "Absorbent Article Having Tucked Flaps", issued to Osborn, et al. on January 25, 1994 describes a particularly preferred sanitary napkin having flaps that are folded and tucked into recessed portions. One preferred diaper is described in PCT Publication No. WO 95/22951 entitled "Absorbent Article With Multiple Zone Structural Elastic-Like Film Web Extensible Waist Feature", published in the name of Roe, et al. on August 31, 1995. The diaper described in this PCT publication comprises a back waist feature comprising a pair of extensible side panels that comprise a structural elastic-like film web. Pjior techniques that would generally be used for folding the wings or flaps (or "side panels") of such absorbent articles would employ one or more geometrically shaped elements often referred to as "folding boards" or "folding plows" that would gradually turn one portion of the web of the material which formed these flaps over another portion ofthe web to form the fold. After the web was folded, the folded web would typically be run through a narrow space between pair of rollers, known as a nip, which would apply pressure on the folded material in order to hold the fold in place. These prior processes suffered from the drawback that they were subject to errors in the folding process that caused the folded portion of the web to be misaligned. The misalignment would generally cause the fold to be crooked, or in other words, aligned at an angle to the machine direction. This misalignment could occur even if a pre-formed folding line were formed in the web to be folded. If the web was not initially folded along the pre-formed folding line when it was passed through the nip, the pressure encountered in the nip would permanently crease the web at a fold line that did not correspond with the desired pre-formed folding line. Therefore, it is an object of the present invention to provide a method for accurately folding and retaining the flaps of an absorbent article, such as a sanitary napkin or diaper, in a folded configuration during the process of manufacturing such an absorbent article. It is an additional object of the present invention to provide a method for folding a continuous web that is provided with a mechanism that allows misalignment in the folding to be corrected before a permanent crease is formed in the web. These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in conjunction with the accompanying drawings. SUMMARY OF THE INVENTION This invention relates to a method of folding articles. More particularly, the invention relates to a method of folding a material during the process of making disposable absorbent articles which utilizes a static charge to align the fold in the material and, at least temporarily, retain the material in a folded configuration. The method of the present invention is preferably used as a step in a method of making an absorbent article having folded flaps. In one preferred embodiment, the method ofthe present invention comprises the steps of: (a) providing a main body portion for an absorbent article, the main body portion comprising a body-facing side, a garment side, an absorbent component between said body-facing side and the garment side, a principal longitudinal centerline, a principal transverse centerline, and two spaced apart longitudinal edges; (b) providing flap material for the absorbent article; (c) forming a pre-formed folding line in the flap material; (d) folding the flap material about a fold line to form folded flap material; and (e) applying a static electrical charge to the folded flap material to retain the flap material in a folded configuration. The flap material can be attached to the main body portion for the absorbent article either before, or after, the flap material is folded using the method of the present invention. The method of the present invention provides the advantage that it produces extremely accurate folds that were not possible using previously known folding techniques. The method of the present invention has also been found to be capable of correcting errors that may occur in the folding process. BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention. it is believed that the invention will be better understood from the following description which is taken in conjunction with the accompanying drawings in which: Figure 1 is a bottom plan view of a sanitary napkin having flaps of a type that can be folded according to the method ofthe present invention, shown with its flaps extended. Figure 2 is a bottom plan view ofthe sanitary napkin shown in FIG. 1, shown with its flaps folded and tucked. Figure 3 is a schematic top plan view of the main body portion of a sanitary napkin. Figure 4 is an enlarged plan view of the webs of flap material that are fed into the process shown in FIG. 5. Figure 5 is a schematic side view of the overall process for folding and retaining the flap material for the sanitary napkin shown in Figures 1 and 2. Figure 6 is a perspective view of one of the folding plows used in the folding process shown in Figure 5. Figure 7 is a perspective view of the other folding plow used in the folding process shown in Figure 5 (shown inverted from its orientation in Figure 5 for clarity of illustration). Figure 8A is a top plan view of a section of a continuous web of flap material before folding. Figure 8B is a cross-sectional view of the web of material shown in Figure 8A taken along line 8B-8B of Figure 8A. Figure 9 A is a top plan view of a section of a continuous web of flap material after it has been folded once. Figure 9B is a cross-sectional view of the web of material shown in Figure 9A taken along line 9B-9B of Figure 9A. Figure IOA is a top plan view of a section of a continuous web of flap material after it has been folded twice. Figure 1 OB is a cross-sectional view of the web of material shown in Figure 1 OA taken along line 10B-10B of Figure IOA. Figure 11 is a perspective view ofthe method ofthe present invention that uses a static charge to retain flap material in a folded configuration during the process of making the sanitary napkin shown in Figure 5. Figure 12 is a schematic plan view of a diaper that can have its side panels folded by the process ofthe present invention. DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of folding articles. More particularly, the invention relates to a method of folding a material during the process of making disposable absorbent articles, such as sanitary napkins and the like, which utilizes a static charge to align the fold in the material and, at least temporarily, retain the material in a folded configuration. The term "absorbent article", as used herein, refers to articles which absorb and contain body exudates. More specifically, the term refers to articles which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. The term "absorbent article" is intended to include sanitary napkins, pantiliners, incontinence pads, and diapers. The term "disposable" refers to articles which are intended to be discarded after a single use and preferably recycled, composted, or otherwise disposed of in an environmentally compatible manner. (That is, they are not intended to be laundered or otherwise restored or reused as an absorbent article.) A preferred embodiment of a sanitary napkin 20 made by the present invention is shown in FIG. 1. The term "sanitary napkin", as used herein, refers to an article which is worn by females adjacent to the pudendal region that is intended to absorb and contain the various exudates which are discharged from the body (e.g., blood, menses, and urine). The method of the present invention, however, is not limited to the production of the particular types or configurations of absorbent articles shown in the drawings. As shown in FIG. 1 , the sanitary napkin 20 basically comprises an absorbent means represented by central absorbent pad (or "main body portion") 22, and two flaps 24. FIG. 2 shows the sanitary napkin shown in FIG. 1 with its flaps folded and tucked. The sanitary napkin 20 has two centerlines, a principal longitudinal centerline L and a principal transverse centerline T. The term "longitudinal", as used herein, refers to a line, axis or direction in the plane of the sanitary napkin 20 that is generally aligned with (e.g., approximately parallel to) a vertical plane which bisects a standing wearer into left and right body halves when the sanitary napkin 20 is worn. The terms "transverse" or "lateral" used herein, are interchangeable, and refer to a line, axis or direction which lies within the plane of the sanitary napkin 20 that is generally perpendicular to the longitudinal direction. The main body portion 22 of the sanitary napkin 20 has two surfaces, a liquid pervious body-contacting surface or "body surface" 22A and a liquid impervious garment surface 22B. The sanitary napkin is shown in FIGS. 1 and 2 as viewed from its garment surface 22B, and in FIG. 3 as viewed from its body surface. The body surface 22A is intended to be worn adjacent to the body of the wearer. The garment surface 22B of the main body portion 22 is intended to be placed adjacent to the wearer's undergarments when the sanitary napkin 20 is worn. The main body portion 22 of the sanitary napkin 20, as shown in FIG. 3, is generally comprised of at least a topsheet 26, a backsheet 28, and an absorbent core 30. The topsheet, backsheet, and absorbent core can be comprised of any of the materials generally used for these particular purposes. Suitable materials for these components, and preferred arrangements for the assembly of the same, are described in greater detail in U.S. Patent No. 5,389,094 entitled "Absorbent Article Having Flaps and Zones of Differential Extensibility", which issued to Lavash, et al. on February 14, 1995, and U.S. Patent No. 5,281,209 entitled "Absorbent Article Having Tucked Flaps", issued to Osborn, et al. on January 25, 1994. The flaps 24 are each associated with main body portion 22 along a juncture. This is typically a longitudinally-oriented (or "longitudinal") juncture, such as lines of juncture 32. As used herein, the terms "juncture" (or "line of juncture") refer to regions where the flaps 24 extend from or are joined to the main body portion 22. The flaps 24 can be integral with the main body portion 22, or with components of the main body portion, or they can comprise separate elements (i.e., pieces of material) that are joined to the main body portion 22. In the embodiment shown in FIG. 1, the flaps 24 are comprised of separate pieces of material which are joined to the main body portion 22. The separate flap pieces are preferably joined to the main body portion 22 by applying adhesive to the flap pieces in the region that will form the juncture 32. The flaps 24 have a proximal edge 34 adjacent the line of juncture 32. A distal edge (or "free end") 36 is remote from the line of juncture 32. As shown in FIG. 1, each flap 24 is divided into a front half 38, and a back half 40 by a flap transverse centerline Tl . Preferably, as shown in FIG. 1, the flaps 24 of the sanitary napkin 20 are provided with four zones of differential extensibility 42, one in the front half of each flap, and one in the back half of each flap. The term "zone of differential extensibility", as used herein, refers to a portion of the sanitary napkin 20 (in this case, the portion of the flaps 24) which is capable of extending a differing amount (preferably a greater amount), than surrounding portions ofthe sanitary napkin 20. The zones of differential extensibility 42 relieve the stresses which develop in the flaps 24 when they are folded around a panty crotch. The zone(s) of differential extensibility 42 can comprise any structure capable of extending a greater amount than the surrounding portions ofthe sanitary napkin. Suitable structures for the zones of differential extensibility 42 are described in U.S. Patent 5,389,094 issued to Lavash, et al. In the preferred embodiment shown in FIG. 1, the zones of differential extensibility 50 comprise regions of the flaps 24 that have been pre- corrπgated or "ring rolled". The term "ring roll" refers to a process in which the material comprising the flaps is fed through intermeshing corrugated rolls. The flaps 24 can be ring rolled in accordance with methods described in U.S. Patent 4,107,364 issued to Sisson on August 15, 1978, U.S. Patent 4,834,741 issued to Sabee on May 30, 1989, U.S. Patent 5,143,679 issued to Gerald M. Weber, et al. on September 1, 1992, U.S. Patent 5,156,793 issued to Kenneth B. Buell, et al. on October 20, 1992, and U.S. Patent 5,167,897 issued to Gerald M. Weber, et al. on Decembr 1, 1992. The ring rolling forms corrugations in the zones of differential extensibility 42. The corrugations are defined by fold lines or ridges and valleys 44. The fold lines 44 may form any angle desired relative to the principal longitudinal centerline L. In the preferred embodiment shown in FIG. 1, the fold lines 44 form an angle of between about 40° - 45° with the principal longitudinal centerline L. This will provide the desired direction of extensibility. FIG. 1 also shows the fasteners, such as adhesive attachment means, central pad adhesive 46 and flap adhesive 48, which are adapted to secure the sanitary napkin 20 to the crotch region of an undergarment. The central pad adhesive 46 provides an adhesive attachment means for securing main body portion 22 in the crotch portion of a panty. The garment-facing surface of flap 24 is preferably coated with a flap adhesive 48. The flap adhesive 48 can be positioned adjacent the distal edge 36 of the flap as shown. Alternatively, the positions of the flap adhesive 48 and the unitary release material 50 (described below) can be reversed. The flap adhesive 48 is used to assist in maintaining the flap 24 in position after it is wrapped around the edge of the crotch portion of the wearer's panties. The flaps 24 can be maintained in position by attaching the flaps 24 to the undergarment, or to the opposing flap. Suitable adhesive fasteners are described in greater detail in U.S. Pat. No. 4,917,697. The central pad adhesive 46 is preferably covered with a removable release liner to keep the central pad adhesive from sticking to extraneous surfaces prior to use. Preferably, the flaps 24 are provided with a unitary release material 50 that superposes the flap adhesive 48 when the flap 24 is folded along a fold line. Such an arrangement is described in U.S. Patent Application Serial No. 08/402,769 filed in the name of Lavash, et al. on March 13, 1995 (published as PCT Publication No. WO 94/00093 on January 6, 1994). In a particularly preferred embodiment, after the flaps 24 are folded and tucked as described in U.S. Patent 5,281,209, the central pad adhesive 46 is covered by a releasable wrapper that not only covers the central pad adhesive 46, but also serves as an individual package for the sanitary napkin. Suitable release liners that serve as an individual package for a sanitary napkin are described generally in U.S. Patent 4,556,146 issued to Swanson, et al. and U.S. Patent 5,462,166 issued to Minton, et al. FIG. 5 is a schematic side view of the overall process for folding and retaining the flap material for the sanitary napkin shown in FIGS. 1 and 2. As shown in FIG. 5, the equipment used in the overall process basically comprises a cutting station 80, a folding apparatus 60, and an electrostatic charging device 68. The portion of the process that is of primary interest is the electrostatic charging process, which uses a static charge to align the material to be folded and to, at least temporarily, retain the flap material in a folded configuration. The static charging process will be discussed in greater detail in conjuction with FIG. 11. In the preferred embodiment of the process of making the sanitary napkin 20 shown in the drawings, the flap material comes into the process in the form of a single continuous web of material. The flap material preferably comprises a laminate, at least one layer of which comprises a polyethylene film similar to that used as a backsheet material. Overlying the polyethylene film and bonded thereto to form the laminate is preferably a layer of nonwoven material or an apertured film suitable for use as a topsheet material. The single continuous web of material is preferably cut along its length in a modified sine wave pattern as shown in FIG. 4 to form two continuous webs of flap material, one for each side ofthe sanitary napkin. Several steps are preferably performed on this single web of material before it is cut into two continuous webs of flap material. It should be understood, however, that the steps described herein are used to form the preferred sanitary napkin shown in the drawings. All of the steps described herein may not be necessary when folding components for other, more simple types of absorbent articles, or other articles. It should also be understood that the order of many of the steps described herein can be varied (at least to a certain extent) if desired. In a preferred embodiment of the process, the single web of material is preferably ring rolled before any ofthe stages ofthe folding process. The folding process begins with the forming of pre-formed folding lines, a first (or outer) pre-formed folding line Fi and a second (or inner) pre-formed line F2 in the single web of flap material. The pre-formed folding lines Fi and F2 are shown best in FIG. 4. The outer pre-formed folding line F] is closest to the portion of the web of flap material that will form the distal edge 36' ofthe flaps, after cutting the single continuous web into individual webs 24'. The pre-formed folding lines can be formed in any suitable manner known in the art. Preferably, the pre-formed folding lines are formed by forming a groove into (that is, by scoring) the web of flap material. A score line is formed in each place where the cut webs of flap material will be folded. The pre-formed fold lines Fj and F2 are preferably formed by scoring the garment-facing surface 24'B of the web of flap material. The patches of flap adhesive 48 and unitary release material 50 are then preferably applied to the continuous web of flap material. The unitary release material 50 can comprise any suitable material that will releasably adhere to and cover the flap adhesive 48. Preferably, the unitary release material comprises a silicone coating. The single continuous web of flap material then moves on to the cutting station 80. The cutting station 80 serves to cut the single continuous web of flap material into two continuous webs 24' that will form flaps for each side of the absorbent article. The cutting station shown in FIG. 5 preferably comprises a pair of metal rolls 82 and 84. One ofthe rolls is provided with a knife blade thereon that is configured to cut the webs in the area, A, shown in FIG. 4. As shown in FIG. 4, the continuous web of flap material is preferably cut so that there is a relatively small amount of waste material removed from between the cut webs of flap material 24'. Some material, however, is preferably removed between the webs of flap material 24' to obtain flaps of the preferred shape (that is, the webs 24' need not be in a fully nested arrangement, and preferably are not fully nested). During the cutting operation, and throughout the process described herein, the webs of flap material 24" move continuously in a machine direction, and are centered relative to a machine direction centerline (MD). The machine direction is the direction of movement of the webs of flap material 24'. The movement of a web of main body portions for the sanitary napkin will also typically be moving in the machine direction, and the webs of flap material 24' will be cut into individual flaps and joined to a main body portion in a continuous operation. As shown in FIG. 4, the webs of flap material 24' have been cut so that the distal edge 36' of each web defines a discontinuous portion comprising a plurality of tab portions 54. The distal edge 36' also has areas cut out thereof between the tab portions 54, and is not linear. The proximal edge 34' of each web of flap material 24', on the other hand, defines a continuous ribbon portion 56. The webs of flap material 24' in the particular embodiment of the process for making the sanitary napkin shown in FIG. 5 will each be folded twice. One fold, preferably the first fold, will position the flap adhesive 48 and the unitary release material 50 in an overlying relationship. Another fold, preferably the second fold, will fold the flaps so that they will be in a tucked position when they are attached to the main body portion 22 of the sanitary napkin 20. In other embodiments of the process, the webs of flap material may be folded only once, or more than twice. The scored webs of flap material 24' then pass through the folding apparatus 60. The folding apparatus 60 preferably comprises fold conveyors, such as a first fold conveyor 86 and a second fold conveyor 90, and a pair of folding plows such as first folding plow 88 and second folding plow 92. The pair of folding plows 88 and 92 will be used to sequentially form the two folds in both of the webs of flap material 24'. The folding plows 88 and 92 are provided in a configuration suitable for forming the particular folds in the webs of flap material 24'. The first folding plow 88 is shown in greater detail in FIG. 6. The second folding plow 92 is shown in greater detail in FIG. 7. The entire surface of each of the folding plows that will be contacted by the webs of flap material 24' are preferably hard coat annodized with Teflon impregnate according to techniques well known in the art. The sequence of folds formed by the process of the present invention is shown in FIGS. 8A-10B. FIGS. 8A and 8B show the position of one of the webs of flap material 24' relative to the machine direction centerline, MD, prior to folding the same. FIGS. 8A and 8B also show the position of one ofthe webs of flap material 24' relative to a folding centerline, C. There will be a folding centerline, C, for each of the webs of flap material 24'. The folding centerline C divides the discontinuous portion 54 and the continuous ribbon portion 56 of the web of flap material 24'. The other web of flap material 24', which is not shown in FIGS. 8A and 8B, will be on the other side of the machine direction centerline MD with its distal edge 36' facing the web of flap material shown. As shown in FIGS. 8 A and 8B, at this stage of the process, the web of flap material 24' is flat and unfolded, and the tab portion 54 is facing inwardly relative to the machine direction centerline, MD (that is, in the direction of the other web of flap material). The continuous portion 56 of the web of flap material 24' is held on the first fold conveyor 86, such as by vacuum pressure, while the web of flap material 24' moves into the first folding plow 88. The first folding plow 88 folds the tab portion 54 of the web of flap material 24' along the first fold line Fi over part ofthe rest ofthe web of flap material 24'. After folding, the tab portion 54 faces outwardly relative to the machine direction centerline, MD. FIGS. 9A and 9B show the position of the web of flap material 24' after the tab portion 54 has been folded by the first folding plow. This places the flap adhesive 48 over the unitary release material 50 (which have been omitted from FIGS. 8A to 10B for simplicity). The tab portion 54 of the web of flap material 24' is then held on the second fold conveyor 90, preferably also by vacuum pressure, while the web of flap material 24' moves into the second folding plow 92. FIGS. I OA and 10B show how the second folding plow 92 folds the continuous portion 56 of the web of flap material 24' along the second pre-formed fold line F2 under a portion of the web of flap material that was folded in the preceding step. The tab portion 54 remains facing outwardly relative to the machine direction centerline, MD. Thus, at this stage of the folding process of the present invention, unlike prior folding processes, the discontinuous portion (or tab portion) 54 defined by the distal edge 36' of the web of flap material 24' is preferably held in position relative to the machine direction centerline, MD, and the continuous portion (or continuous ribbon) 56 of the web of flap material 24' is folded. Conventional means, such as vacuum conveyors, can hold the tab portion 54 in place while the continuous ribbon travels through the second folding plow 92 in order to fold the web of flap material 24' in the desired manner. The advantage of such a folding process is that it can be used to attach the folded flaps (after they have been cut into individual flaps) to the desired side of the main body portion of the sanitary napkin without making the webs of flap material cross over each other. The particular folding process used to fold the flaps of the sanitary napkin shown in FIGS. 1 and 2 is described in greater detail in U.S. Patent Application Serial No. 08/ entitled "Method of Folding and Handling A Web of Material In A Continuous Operation" (serial number to be filled in after one is assigned), which was filed in the name of Taub on the same date as the present application. As shown in FIG. 5, after folding, the folded webs of flap material 24' are preferably passed through the nip 66 between the pair of rollers 62 and 64. This will compress the folds into the webs of flap material 24'. The folds in the folded webs of flap material 24' will likely open slightly even though the folds are compressed into the webs of flap material 24'. As will be explained in greater detail below, it is acceptable, and even desirable for this to occur so that the folded flap material can have its fold adjusted and aligned about the pre-formed fold lines in the event that one or more folds are not made exactly on the pre-formed fold lines. The folded webs of flap material 24' then pass through the electrostatic charging device 68. The electrostatic charging device 68 places opposite static electrical charges on the folded webs of flap material 24'. The webs of flap material 24' are folded so there will be at least two layers of material through which the charges will penetrate. In the preferred embodiment of the process shown where each web of flap material is folded twice, the charges will be required to penetrate three layers of material. These charges attract the layers of film to each other resulting in a tight fold that remains folded during the manufacturing process. Because polyethylene is a good insulator, the charges will remain for about a week if not disturbed. The electrostatic charging process is shown in greater detail in FIG. 11. The equipment shown in FIG. 1 1 comprises the folding apparatus, (represented by box 60), the previously described pair of rollers 62 and 64 which form the fold compression nip 66 therebetween, and the electrostatic charging device 68. The electrostatic charging device 68 comprises a power source, 70, two pairs of electrodes 72 and 74 (one for each web of flap material 24'), and wires 76 connecting the electrodes 72 and 74 to the power source 70. The electrostatic charging device 68 can comprise any suitable apparatus for imparting a static electrical charge to at least one side of a web of material. In the preferred embodiment of the method of the present invention, the electrodes 72 and 74 and power source 70 respectively comprise cylindrical CHARGEMASTER® TETRA TM RC-3 electrostatic generating charging bars and a CH50 DC CHARGEMASTER electrostatic generating equipment power supply, obtained from the SIMCO Company, Inc. of Hatfield, PA, a subsidiary of Illinois Tool Works Company of Glenview, IL, or equivalent. The cylindrical charging bars 72 may have their longitudinal axes, A, oriented in the cross-machine direction (CD), or they may be turned so that their longitudinal axes are oriented in the machine direction, MD (the direction of the movement of the webs of flap material 24'). FIG 11 shows the cylindrical electrodes 72 and 74 tumed so that their longitudinal axes, A, are oriented in the machine direction, MD. Preferably, however, as shown in FIG. 5, the charging bars 72 have their longitudinal axes oriented in the cross- machine direction to conserve space in the area where the manufacturing line is located. Typically, relatively high voltages (in the range of between about 20,000 to 50,000 volts, and preferably about 40,000 volts) are needed to induce charges on the webs. However, very little amperage is generally required (approximately 2 milliamps). The electrostatic charging device 68 preferably imparts a static electrical charge to one side of the folded web and the opposite charge to the other side of the folded web as shown in FIG. 11. In another embodiment, rather than applying opposite charges to each side of the web, the electrostatic charging device 68 can impart a charge (either positive or negative) to one side ofthe web (i.e., to a first side ofthe web), and the air on the other side of the web (the second side of the web) can be ionized so that the charging bar on the first side ofthe web will attract only ionized particles ofthe opposite charge. In still other embodiments, the electrostatic charging device 68 can be used to impart a charge (either positive or negative) to one side of the web (the first side), and the other side of the web may be placed adjacent to a grounded surface, such as an anvil roll, a vacuum roll, or a plate, made of metal or another suitable material. The arrangements described above are in order with the arrangement that will tend to best retain the folded web in a folded configuration (which is also the most expensive arrangement) listed first. The static charge maintains the web of folded flap material 24' in their folded configuration so that they may be cut into individual flaps and joined to the main portion of the sanitary napkin. It has also been found that if the fold does not align with the pre¬ formed folding lines, since the electrostatic charging equipment does not produce as great of a perpendicular (or normal) force on the webs of flap material, the folded sections of the webs are free to move in the cross-machine direction or shift laterally. This tends to correct any misalignment of the folds because the webs inherently tend to fold along the score lines. Thus, the method ofthe present invention allows the manufacturer to initially impart a less precise and uncompressed (or loose) fold and thereafter correct the same using the static charging equipment. In addition, because there is no frictional drag similar to that encountered when using folding boards and folding plows, the electrostatic charge improves the accuracy ofthe folding relation and the score lines. The webs ofthe flap material 24' then move to a continuous cutting and fastening operation where a series of main body portions are being continuously fed into the process. The webs of flap material 24' are coated with adhesive along the proximal edge 34* thereof, cut into individual flaps, and attached to the garment side 22B of a main body portion 22. The central pad adhesive 46 is then applied to form the finished sanitary napkin 20. The present invention, thus, provides a temporary means for retaining a folded material in a folded configuration while it is being transported down a converting line used in the manufacturing process. This retention of the fold is achieved without the use of additional materials (such as adhesives) and without permanently altering the character of the material (such as that which occurs when crimping and heat sealing are used). In addition, unlike adhesives and heat sealing, the effects of this method dissipates with time and poses no problems for the consumer to open the folds when unfolding the flaps for use. Many variations of the method of the present invention are possible. For instance, the method could be performed on absorbent articles that either have integral flaps, or it could be performed on absorbent articles in which the flaps were already attached to the absorbent article before the folding operation takes place. In other embodiments, the method may be used to retain only one fold in a web of material, or it may be used to retain more than two folds in a web of material. The method of the present invention is also not limited to use with sanitary napkins. For example, FIG. 12 shows one preferred embodiment of a diaper that can have its side panels or flaps folded by the method of the present invention. The diaper 520 shown in FIG. 12 has a generally "T-shape". The diaper 520 comprises a chassis assembly 522 that preferably comprises a liquid pervious topsheet 524, a liquid impervious backsheet 526 joined with the topsheet 524, an absorbent core 528 positioned between the topsheet 524 and the backsheet 526. The diaper further comprises extensible leg cuffs 530 each comprising a leg flap panel 531 and one or more elastic members, and elastic strands 554, operatively joined with the leg flap panel 531. In addition, the diaper 520 preferably comprises an extensible back waist feature 532 comprising a central waistband panel 534, a pair of side panels 536, and a hip panel 538. The diaper 520 also comprises a closure system for fastening the diaper on the wearer preferably comprising at least a pair of tape tabs 540 and a landing member preferably comprising a reinforcing strip 541; and an extensible front waist feature 542 comprising a front waist panel 543. The back waist feature preferably comprises a pair of extensible side panels that comprise a structural elastic-like film web. The diaper 520 shown in FIG. 12 is described in greater detail in U.S. Patent Application Serial No. 08/203,456 entitled "Absorbent Article With Multiple Zone Structural Elastic-Like Film Web Extensible Waist Feature", filed in the name of Roe, et al. on February 28, 1994 (PCT Publication No. WO 95/22951, published August 31, 1995). In the case ofthe diaper 520 shown in FIG. 12, the side panels 536 are preferably folded inward toward the longitudinal centerline L on the topsheet 524 in the direction of the arrows. A plurality of diapers 520 will be continuously fed into the folding process in series with their longitudinal centerlines oriented in the machine direction. The side panels 536 of the diaper 520 will typically have already been joined to the chassis assembly (or main body portion of the diaper) prior to the folding operation. In such a case, the material forming the side panels may be continuous or discontinuous. In addition to sanitary napkins and diapers, other types of absorbent articles could be provided with flaps that are folded by the method of the present invention. Suitable absorbent articles in the form of pantiliners are disclosed in U.S. Pat. No. 4,738,676 entitled "Pantiliner" issues to Osborn on April 19, 1988. Such pantiliners could be provided with flaps having the configurations described herein. Suitable absorbent articles, at least some of which are in the form of adult incontinence products that could be provided with flaps that are folded by the method of the present invention, are described in U.S. Patents 5,300,054 issued to Feist, et al. on April 5, 1994, and 5,304,161 issued to Noel, et al. on April 19, 1994. It should be understood, that while the terms "flaps" and "side panels" have been used interchangeably herein, that this is only in the context of the method of the present invention, and it is expressly not admitted that such portions of these different types of absorbent articles are equivalent in terms of structure or function when in use. The present invention is also not limited to holding folds in webs during the process of manufacturing disposable absorbent articles. The method of the present invention can also be used to retain folds in materials during packaging. It can also be used for temporarily adhering materials, particularly film materials to either belts, rolls, or other equipment during manufacture while these materials are conveyed to faciliate processing (and as a result, may replace conventional vacuum equipment ordinarily used for these purposes). The disclosures of all patents, patent applications (and any patents which issue thereon, as well as any corresponding published foreign patent applications), and publications mentioned throughout this description are hereby incoφorated by reference herein. It is expressly not admitted, however, that nay ofthe documents incoφorated by reference herein teach or disclose the present invention. While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A method of folding and retaining a fold in a material during a process of making a disposable absorbent article, characterized in that said method comprises the steps of: (a) providing a material for use in a disposable absorbent article; (b) forming a pre-formed folding line in said material; (c) folding said material about at least one fold line to form a folded material; and (d) applying a static electrical charge to said folded material to retain said folded material in a folded configuration. 2. The method of Claim 1 wherein the material provided in step (a) is provided in the form of a continuous web of material which is separate from a main body portion for said absorbent article. 3. The method of Claim 2 wherein said continuous web of material provided in step (a) is traveling in a machine direction; said pre-formed folding line formed in step (b) is oriented in the machine direction; and said folded material is preferably joined to a main body portion of an absorbent article after step (d). 4. The method of Claim 1 wherein the material provided in step (a) is joined to a main body portion for an absorbent article prior to said method for folding said material. 5. The method of Claim 4 wherein said material provided in step (a) is discontinuous between adjacent absorbent articles. 6. The method of Claim 1 wherein the step of forming a pre-formed folding line in said material comprises scoring said material. 7. The method of Claim 1 wherein a step of compressing said folded material occurs between steps (c) and (d). 8. The method of Claim 1 wherein the following steps occur between steps (c) and (d): (1) compressing said folded material, and (2) allowing said folded material to open slightly; and the step (d) of applying a static electrical charge to said folded material also aligns the fold in said folded material about said pre-formed folding line. 9. The method of Claim 1 preferably comprising folding said material along two fold lines, wherein the step (d) of imparting a static electrical charge to said folded material comprises passing said folded material between a positive terminal and a negative terminal, and applying a static charge through at least two layers, and preferably three layers, of said folded material. 10. A method of folding and retaining a fold in a flap material during a continuous process of making a disposable absorbent article having folded flaps, said method comprising the steps of: (a) providing a main body portion for an absorbent article, said main body portion comprising a body-facing side, a garment side, an absorbent component between said body-facing side and said garment sides, a principal longitudinal centerline, a principal transverse centerline, and two spaced apart longitudinal edges; (b) providing flap material for said absorbent article; (c) forming a pre-formed folding line in said flap material; (d) folding said flap material about at least one fold line to form folded flap material; (e) compressing said folded flap material; (f) allowing said folded material to open slightly; and (g) applying a static electrical charge to said folded material to align the fold in said folded flap material about said pre-formed folding line and to retain said flap material in a folded configuration.

Inventors: LOKAR STOYAN, TAUB STEWART LAWRENCE, LOKAR, STOYAN, TAUB, STEWART, LAWRENCE
Applicants: PROCTER & GAMBLE, THE PROCTER & GAMBLE COMPANY
Application year: 1997
Main classification: A61F13
IPC codes: A61F5, A61F13, B29C53, B65H45