Patent Publication Number: US-2020298545-A1

Title: Apparatus and method of manufacturing an elastic composite structure for an absorbent sanitary product

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention is a continuation-in-part of and claims priority to U.S. Provisional patent application Ser. No. 16/721,414 filed Dec. 19, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62/789,058 filed Jan. 7, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Embodiments of the invention relate generally to absorbent sanitary products and, more particularly, to an improved apparatus and method for manufacturing an elastic composite structure for use in an absorbent sanitary product that minimizes or eliminates the use of consumable adhesives such as glue. 
     Absorbent sanitary products, such as disposable diapers, are typically equipped with elastic composite structures that include one or more elastic threads. These elastic composite structure s are positioned at various locations throughout the product, including in the waistbands, leg cuff regions, and throughout all or portions of the front or back panels of the product. During the typical manufacturing process of an elastic composite structure, the elastic threads are held in a tensioned state and an adhesive is used to secure the elastic threads between the two facing layers of non-woven materials or webs. The tension in the elastic threads is subsequently released, causing the web material to pucker or fold in the areas that contain the adhered elastic threads. 
     The use of adhesives to bond the elastic threads within elastic composite structures presents a number of disadvantages in both the end product and manufacturing method, including costs associated with the consumable material and undesirable tactile properties of the end product (e.g., stiffness). While thermal or ultrasonic welding techniques have been proposed as alternatives for bonding elastic threads within an elastic composite structure, movement or shifting of the elastic threads between or outside of notches on the anvil during the manufacturing process may result in a given elastic thread breaking or being unanchored over one or more portions of its length. 
     Accordingly, there is a need for an improved apparatus and method for fabricating an elastic composite structure of an absorbent sanitary product that reduces thread breakage and improves the reliability of bonds that anchor elastic threads in position within an elastic composite structure. It would further be desirable for such an apparatus and method to eliminate or minimize the use of consumable adhesives to secure the elastic threads to the facing web layers. 
     BRIEF STATEMENT OF THE INVENTION 
     In accordance with one aspect of the invention, a rotary anvil comprises a face surface, a plurality of non-linear ridges defined by a first plurality of grooves in the face surface, and a plurality of projections in each of the plurality of non-linear ridges. Each projection of the plurality of projections comprises a contact surface having parallel facing surfaces and parallel end surfaces. 
     In accordance with another aspect of the invention, a method of manufacturing a rotary anvil comprises providing a rotary anvil having a face surface, removing material from the face surface to form a plurality of non-linear welding lines in the rotary anvil, and forming a plurality of projections in the plurality of non-linear welding lines. Forming the plurality of projections comprises creating a contact surface for each projection of the plurality of projections, the contact surface having parallel facing surfaces and parallel end surfaces. The parallel facing surfaces of each contact surface are parallel to one another, and the parallel end surfaces of each contact surface are parallel to one another. 
     In accordance with another aspect of the invention, an elastic composite structure comprises a first web layer, a second web layer coupled to the first web layer by a non-linear bond pattern comprising at least non-linear one bond line having at least one pair of adjacent bonds, and at least one elastic thread extending through a passage defined by facing edges of the at least one pair of adjacent bonds. Each bond in the at least one bond line comprises parallel facing surfaces and parallel end surfaces orthogonal to the parallel facing surfaces. 
     These and other advantages and features will be more readily understood from the following detailed description of preferred embodiments of the invention that is provided in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate embodiments presently contemplated for carrying out the invention. 
       In the drawings: 
         FIG. 1  is a schematic perspective view of a portion of a manufacturing line for fabricating an elastic composite structure. 
         FIG. 2  is a schematic perspective view of a portion of the manufacturing line illustrated in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to one embodiment of the invention. 
         FIG. 4A  is a cross-sectional view of a portion of an elastic composite structure fabricated using the bonding unit of  FIG. 3  in its relaxed or non-tensioned state, according to one embodiment of the invention. 
         FIG. 4B  is a cross-sectional view of a portion of an elastic composite structure fabricated using the bonding unit of  FIG. 3  in its relaxed or non-tensioned state, according to another embodiment of the invention. 
         FIG. 5  is a cross-sectional view of an exemplary elastic strand of the elastic composite structure of  FIG. 4  in its relaxed or non-tensioned state. 
         FIG. 6  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 7  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 8  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 9  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 10  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 11A  is a cross-sectional view of a portion of a bonding unit usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 11B  is a cross-sectional view of a portion of an elastic composite structure fabricated using the bonding unit of  FIG. 11A  in its relaxed or non-tensioned state. 
         FIG. 12  is a front view of a rotary anvil usable with the manufacturing line of  FIG. 1 , according to an embodiment of the invention. 
         FIG. 12A  is a detailed view of a portion of the rotary anvil of  FIG. 12 . 
         FIG. 13  is a top view of a portion of an elastic composite structure shown in its elongated or tensioned state, according to an embodiment of the invention. 
         FIG. 13A  is a detailed view of a portion of the elastic composite structure of  FIG. 13  shown in its elongated or tensioned state. 
         FIG. 14  is a cross-sectional view of a multifilament elastic thread usable to manufacture the elastic composite structure of  FIG. 13 . 
         FIG. 15  is a front view of a rotary anvil usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 15A  is a front view of a rotary anvil usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 16  is a front view of a rotary anvil usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIG. 16A  is a front view of a rotary anvil usable with the manufacturing line of  FIG. 1 , according to another embodiment of the invention. 
         FIGS. 17-21  illustrate cross-sectional views taken along line  17 - 21  of  FIGS. 15 and 16  showing steps for manufacturing the rotary anvils of  FIGS. 15 and 16  according to an embodiment of the invention. 
         FIGS. 22-23  illustrate steps for manufacturing the rotary anvils of  FIGS. 15 and 16  according to another embodiment of the invention. 
         FIG. 24  illustrates a rotary anvil manufactured using the step of  FIG. 23  according to another embodiment of the invention. 
         FIGS. 25A-28A  illustrate cross-sectional views taken along line  25 - 28  of  FIGS. 15 and 16  showing steps for manufacturing the rotary anvils of  FIGS. 15 and 16  according to another embodiment of the invention. 
         FIGS. 25B-28B  illustrate top views corresponding to the steps shown in  FIGS. 25A-28A . 
         FIGS. 29A-33A and 29B-33B  illustrate cross-sectional and top views of rotary anvils manufactured according to alternative embodiments of the invention. 
         FIGS. 34-36  illustrate orthogonal views of alternative electrodes according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention provide for a method and apparatus for manufacturing an elastic composite structure usable in an absorbent sanitary product such as, for example, a diaper, disposable adult pant, or feminine care product. 
     During the manufacture of absorbent sanitary products, it is often desirable to secure elastic threads between facing layers of non-woven material to form contoured or elasticized regions within the product. Such products are typically manufactured on an assembly or manufacturing line in which the product moves substantially continually longitudinally in what is referred to as the “machine direction.” 
     Referring now to  FIG. 1 , a portion of an exemplary manufacturing line  10  is illustrated according to one embodiment of the invention. As shown, a first web layer  12  is fed in the machine direction  14 . A second web layer  16  is similarly fed in the machine direction  14 . First web layer  12  and second web layer  16  are materials capable of fusing to one another upon application of an applied energy that causes one or both of the webs  12 ,  16  to soften or melt and join together. First and second web layers  12 ,  16  may be the same type of material or different materials according to alternative embodiments. As non-limiting examples, first and second web layers  12 ,  16  may include nonwoven materials, woven materials, films, foams, and/or composites or laminates of any of these material types. 
     A series of individual elastic threads  18  are positioned between the first and second web layers  12 ,  16 . The elastic threads  18  travel in the machine direction  14  under tension from a creel assembly (not shown) or similar device. The elastic threads  18  may be composed of any suitable elastic material including, for example, sheets, strands or ribbons of thermoplastic elastomers, natural or synthetic rubber, or LYCRA, as non-limiting examples. Each elastic thread  18  may be provided in the form of an individual elastomeric strand or be a manufactured multifilament product that includes many individual elastomeric filaments joined together, such as by a dry-spinning manufacturing process, to form a single, coalesced elastic thread  18 . Each elastic thread  18  may be in the range of approximately 200-1500 decitex (dTex), in non-limiting embodiments. In an embodiment where an elastic thread  18  is a multifilament product, the elastic thread  18  may have an overall decitex of 400 dTex, in an exemplary and non-limiting embodiment, with the individual elastomeric filaments of the elastic thread  18  individually having a decitex of ten percent or less of the overall 400 dTex value. As just a few examples, a multifilament thread with a decitex of 680 and up may include 55 individual elastomeric filaments while a multifilament thread with a decitex lower than 680 may include 47 individual elastomeric filaments. 
     Elastic threads  18  may have any suitable cross-sectional shape that facilitates formation of an elastic composite structure having desired elasticity, visual aesthetic, and manufacturability. As non-limiting examples, elastic threads  18  may have a cross-sectional shape that is round, rectangular, square, or irregular as may be the case where each elastic thread  18  is a multifilament product (as illustrated in detail in  FIG. 14 ). 
     While first web layer  12  and second web layer  16  are depicted in  FIG. 1  and described herein as physically separate components, it is contemplated that alternative embodiments may utilize a unitary web structure that is folded to capture the elastic threads  18  between upper and lower layers of the unitary web structure. In such an embodiment, the portion of the unitary structure positioned below the elastic threads  18  would be referred to as the first web layer  12  and the portion of the unitary structure positioned above the elastic threads  18  would be referred to as the second web layer  16 . 
     Manufacturing line  10  includes one or more guide rollers  20  that are employed to transport, accurately position and (optionally) tension the elastic threads  18  as it travels in the machine direction  14 . In some embodiments, manufacturing line  10  may include one or more optional tension monitoring devices  24  (shown in phantom) that are positioned along the path of travel of the elastic threads  18 . In such an embodiment, feedback from the tension monitoring devices  24  may be utilized to control the tension (i.e., elongation) in the elastic threads  18  as they travel in the machine direction  14 . 
     As shown in further detail in  FIG. 2 , each respective elastic thread  18  is positioned within a respective guiding section  26  of guide rollers  20 . Doing so maintains separation between the adjacent elastic threads  18 . In the illustrated embodiment, guiding section  26  includes notches that aid in alignment and guiding of the elastic threads  18 . Notches may be v-shaped as shown, have curved or other alternative geometries, or be omitted entirely in alternative embodiments. 
     Guide rollers  20  operate to accurately position and tension individual elastic threads  18  as they travel toward a strand guide roller  36  that is positioned upstream of bonding unit  38 , which is referred to hereafter as ultrasonic bonding apparatus  38 . Manufacturing line  10  also includes one or more structures that are configured to transport and guide the first and second web layers  12 ,  16  in the machine direction  14 . In the illustrated embodiment, these guide structures include an upper roller  40  and a lower roller  42  are positioned to guide the first web layer  12  and the second web layer  16 , respectively, toward the ultrasonic bonding apparatus  38 . 
     Ultrasonic bonding apparatus  38  may be a rotary ultrasonic welding system or a blade ultrasonic welding system in alternative embodiments. In the illustrated embodiment, ultrasonic bonding apparatus  38  is a rotary ultrasonic welding system that includes a rotary anvil  44  and a horn  46  that cooperate with each other to bond the first web layer  12  to the second web layer  16 . The elastic threads  18  are secured or anchored in position relative to the first and second web layers  12 ,  16  as described in detail below. Ultrasonic bonding apparatus  38  also includes one or more frames  48  that support and/or house a motor (not shown) that drives the horn  46 , a vibration control unit (not shown) that causes the horn  46  to vibrate, and a second motor (not shown) that drives the anvil  44 . The horn  46  and anvil  44  are positioned in a spaced relationship relative to one another to facilitate ultrasonically bonding the first and second web layers  12 ,  16  to one another while the elastic threads  18  are held in tension in the space between the horn  46  and anvil  44 . While horn  46  is illustrated as a rotary horn in  FIG. 1 , a stationary horn may be used in alternative embodiments. 
     The face  50  of the anvil  44  includes an arrangement of projections and notches that facilitate securing the combined elastic thread assemblies  34  in position relative to the first and second web layers  12 ,  16 . Exemplary embodiments of this arrangement of projections and notches are described in detail below relative to  FIGS. 3-11 . In one non-limiting embodiment, the face  52  of the horn  46  has a smooth or substantially smooth surface contour. In alternative embodiments, face  52  may include an arrangement of projections and/or notches that mate or align with the surface pattern of the anvil  44  to further facilitate bonding the first and second web layers  12 ,  16  together and securing the elastic threads  18  in position relative to the first and second web layers  12 ,  16 . 
     While embodiments of the invention are described relative to an ultrasonic bonding assembly and ultrasonic bonding technique, it is contemplated that the techniques described herein may be extended to any other known thermal or pressure bonding techniques. 
       FIG. 2  is a view of a portion of the manufacturing line  10  upstream of the ultrasonic bonding apparatus  38  looking into the machine direction  14 . As shown, the elastic threads  18  are fed outward from respective guiding sections  26  in the guide rollers  20  and toward strand guide roller  36 . In the embodiment, strand guide roller  36  includes an array of notches  54  that aid in aligning and guiding the elastic threads as they are received between the horn  46  and anvil  44 . These notches  54  may be evenly spaced across all of the strand guide roller  36  in the manner shown or may span only a portion thereof in an alternative embodiment. In yet other embodiments, the notches  54  may be positioned at uneven intervals along the length of strand guide roller  36  depending upon design specifications and the desired placement and spacing of the elastic threads  18  in the resulting elastic composite structure. 
     Referring now to  FIG. 3 , a cross-sectional view of a portion of the anvil  44  and horn  46  is provided according to one embodiment of the invention. As shown, the face  50  of the anvil  44  includes a welding line  68  that is defined by at least one notch  200 , which is positioned between a corresponding pair of projections  202 ,  204 . While only one instance of a notch  200  and corresponding pair of projections  202 ,  204  is illustrated in  FIG. 3 , it is contemplated that each welding line  68  on the anvil  44  may alternatively include multiple notches  200 , with each notch  200  similarly arranged between a corresponding pair of projections  202 ,  204 . In the embodiment shown, notch  200  has a u-shaped geometry defined by a bottom surface  206  and facing surfaces  208 ,  210  of the projections  202 ,  204 . One or more of surfaces  206 ,  208 ,  210  may be planar, as shown, or curved in alternative embodiments. 
     During the manufacturing process, the first and second web layers  12 ,  16  are positioned between the face  50  of the anvil  44  and the face  52  of the horn  46 . An elastic thread  18  is positioned between the first and second web layers  12 ,  16  in a tensioned state and aligned above notch  200 . As shown in  FIGS. 4A and 4B  and with continued reference to  FIG. 3 , the first and second web layers  12 ,  16  are bonded together by a pair of bonds  100 ,  101  at locations corresponding to the land surfaces  212 ,  214  of the respective projections  202 ,  204 . Thus bonds  100 ,  101  each have a width that corresponds to the width of land surfaces  212 ,  214 . Depending on the operating parameters of the ultrasonic bonding apparatus  38  and/or the geometry and configuration of the notches and projections on the anvil and/or horn, the resulting pair of adjacent bonds  100 ,  101  either may be discrete, discontinuous bonds  100 ,  101  as shown in  FIG. 4A , or part of a continuous fusion bond  103  that fuses the facing web layers  12 ,  15  together at bond points  100 ,  101  and fuses one or both of the facing web layers  12 ,  16  to the elastic thread  18 , as shown in  FIG. 4B . The bonding operation creates a manufactured elastic composite structure  86  as shown in  FIG. 13 . 
     When the manufactured elastic composite structure  86  shown in  FIG. 13  is permitted to relax, each elastic thread  18  will attempt to swell or expand to return to its non-tensioned or relaxed state within passage  104 . Passage  104  has a cross-sectional area  217  that is dictated by the cross-sectional area  216  of the notch  200  on anvil  44 . Thus, the cross-sectional area  217  of passage  104  is equal to or substantially equal to the cross-sectional area  216  of the notch  200 . Notch  200  is sized to have a cross-sectional area  216  that is less than the cross-sectional area  218  of the elastic thread  18  in its non-tensioned or relaxed state, which is illustrated in  FIG. 5 . As the elastic thread  18  expands, it becomes anchored or trapped in the passage  104  formed between the upward facing surface  106  of the first web layer  12 , the downward facing surface  108  of the second web layer  16 , and the facing edges  96 ,  98  of a pair of adjacent bonds  100 ,  101 . 
     As shown in  FIG. 4 , the elastic thread  18  deforms as it expands due to the relatively shallow geometry of the notch  200 . Depending on the shape and dimensions of notch  200  and the cross-sectional area  218  of the non-tensioned elastic thread  18 , the elastic thread  18  may expand to completely fill the passage  104 , as shown in  FIG. 4 . Alternatively, the elastic thread  18  may expand to a position where the elastic thread  18  fills only a portion of the passage  104 . In such an embodiment, the portion of the elastic thread  18  adjacent bonds  100 ,  101  would be secured in position relative to web layers  12 ,  16  by virtue of contact between the elastic thread  18  and facing surfaces  106 ,  108  of the web layers  12 ,  16  with a gap formed between the elastic thread  18  and one or both of the facing edges  96 ,  98  of adjacent bonds  100 ,  101 . 
       FIGS. 6, 7, 8, and 9  depict notch configurations according to alternative embodiments of the invention. A cross-sectional view of the resulting pair of adjacent bonds  100 ,  101  between the first and second web layers  12 ,  16  is provided above the land surfaces  212 ,  214  of the respective projections  202 ,  204  for ease of reference. Other portions of the elastic composite structure  86  are omitted for clarity purposes. In  FIG. 6 , notch  200  has a v-shaped geometry formed by opposing angled surfaces  218 ,  220 . The notches  200  in  FIGS. 7 and 8  have stepped configurations. In  FIG. 7 , notch  200  includes a u-shaped central region  222  defined by bottom surface  206  and two facing surfaces  208 ,  210  and two opposing side regions  224 ,  226 . The notch  200  of  FIG. 8  includes similarly configured side regions  224 ,  226  with a v-shaped central region  228  defined by opposing angled surfaces  218 ,  220 .  FIG. 9  depicts a modified stepped geometry where the angled surfaces  218 ,  220  of notch  200  have a different slope in the central region  228  of the notch  200  than in the opposing side regions  224 ,  226 . The surfaces that define the notches  200  in  FIGS. 6-9  may be straight, as shown, curved, or some mixture of curved and straight in alternative embodiments. 
     Each of notches  200  in  FIGS. 6-9  has a cross sectional area  216  that is smaller than the cross-sectional area of the elastic thread  18  in its non-tensioned state. The notches  200  of  FIGS. 6-9  define a resulting pair of adjacent bonds  100 ,  101  that are spaced apart by a gap or distance  102  that is greater than the strand diameter  112  of the elastic thread  18  when in its non-tensioned state. 
     As used herein the phrase “strand diameter” refers to the smallest measurable cross-sectional width of the elastic thread  18  in its non-tensioned state. In embodiments where a given elastic thread  18  is a monofilament structure, the strand diameter is the minor diameter or smallest measurable width of the monofilament structure in its non-tensioned state. In embodiments where a given elastic thread  18  is a structure that includes many individual filaments  116  (i.e., elastic thread  18  is a multi-filament structure), the elastic thread  18  typically will have an irregular cross-sectional area similar to that shown in  FIG. 14 . The strand diameter of such a multifilament structure is to be understood as the smallest distance  120  between opposite edges of an outline that generally defines the irregular cross-sectional area. The cross-sectional area of the multifilament structure may be measured as the cross-sectional area within a perimeter  118  drawn to surround all of the individual filaments  116  or calculated as the summed total of the cross-sectional area of each of the individual filaments  116 . 
       FIG. 10  depicts a portion of anvil  44  according to yet another embodiment of the invention. In this embodiment, notch  200  and the pair of flanking projections  202 ,  204  are formed atop a step  230  that is elevated above the face  50  of the anvil  44 . While only one notch  200  and corresponding pair of projections  202 ,  204  is illustrated atop step  230 , alternative embodiments may include any number of notches  200  and corresponding projections  202 ,  204 . Notch  200  may have the u-shaped geometry shown in  FIG. 3  or any of the alternative notch geometries illustrated in  FIGS. 6-9  or otherwise described herein. 
     Each of  FIG. 3 ,  FIG. 6 ,  FIG. 7 ,  FIG. 8 ,  FIG. 9 , and  FIG. 10  is to be understood as illustrating one exemplary and non-limiting configuration of notch  200 . In alternative embodiments, anvil  44  may include one or more notches  200  that has any shape or surface topology, including straight surfaces, curved surfaces, or any combination thereof that results in a notch  200  having a cross-sectional area  216  that is smaller than the cross-sectional area  218  of the corresponding elastic thread  18  when in its non-tensioned state. 
       FIG. 11A  depicts a portion of anvil  44  according to another embodiment of the invention. Welding line  68  of anvil  44  includes at least one notch  200  that has a cross-sectional area  216  that is smaller than the cross-sectional area  218  of a corresponding elastic thread  18  when in its non-tensioned state. Notch  200  forms a pair of adjacent bonds  100 ,  101  between first and second web layers  12 ,  16  that anchor the elastic thread  18  within a passage  104  defined between web layers  12 ,  16  and the pair of adjacent bonds  100 ,  101  as shown in  FIG. 11B . Depending on the geometry of notch  200 , operational parameters of ultrasonic bonding apparatus  38 , and material selection of web layers  12 ,  16  and elastic thread  18 , the resulting pair of bonds  100 ,  101  may be discrete, separated bond sites, similar to those shown in  FIG. 4A , or connected by virtue of fusion bonding between one or both of the web layers  12 ,  16  and the surface of the elastic thread  18 , similar to that shown and described relative to  FIG. 4B . While notch  200  is depicted with a notch geometry similar to that of  FIG. 8 , it is contemplated that notch  200  may have any of the alternative geometries described above with respect to  FIGS. 3, 6, 7, 9, and 10 . 
     In addition to the projections  202 ,  204  that form bonds  100 ,  101 , welding line  68  of  FIG. 11A  includes projections  230 ,  232  with land surfaces  234 ,  236  that form corresponding bonds  238 ,  240  between first and second web layers  12 ,  16 . Notch  242  is defined between projection  202  and projection  230 ; notch  244  is defined between projection  204  and  232 . Unlike notch  200 , notches  242 ,  244  have respective cross-sectional areas  246 ,  248  that are larger than the cross-sectional area  218  of the corresponding elastic thread  18 A,  18 B when in its non-tensioned state. As shown in  FIG. 11B , notches  242 ,  244  define passages  250 ,  252  between first and second web layers  12 ,  16  and respective bond pairs  100 / 238  and  101 / 240  in resulting elastic composite structure  254  that are larger than the cross-sectional area  218  of the non-tensioned elastic threads  18 A,  18 B. Elastic threads  18 A,  18 B are free to expand to their non-tensioned state within passages  250 ,  252 . Bond pairs  100 / 238  and  101 / 240  thus serve to define a channel that contains elastic threads  18 A and  18 B but does not anchor the elastic threads  18 A,  18 B in position relative to first and second web layers  12 ,  16 . 
     In one non-limiting embodiment notches  200 ,  242 , and  244  of anvil  44  are manufactured using a multi-step machining process that includes machining a pattern of similarly sized “anchoring” notches on the face  50  of the anvil at the desired location of each notch  200 ,  242 ,  244 . In the illustrated example, the manufacturing process would include initially machining notches  200 ,  242 , and  244  to all have the notch geometry or profile of notch  200 , as indicated by dashed lines  254 ,  256 . In a subsequent machining step, additional material is removed from select notch locations to define the final notch geometry of the larger, non-anchoring notches  242 ,  244 . 
       FIGS. 11A and 11B  are to be understood as depicting one exemplary and non-limiting configuration of anchoring notch  200  and non-anchoring notches  242 ,  244 . It is to be understood that alternative embodiments may include any combination or pattern of anchoring and non-anchoring notches  200 ,  242 ,  244  based on design considerations of the end product. Thus, a given welding line  68  may include a repeating pattern of one or more alternating anchoring notches and one or more non-anchoring notches or only one type of notch. Specific regions containing only anchoring notches or only non-anchoring notches may also be defined between two or more sequential welding lines  68  on the face  50  of the anvil  44 . 
     Referring now to  FIG. 12 , further details of the surface pattern of the anvil  44  is provided in accordance with one non-limiting embodiment of the invention. As shown, anvil  44  includes an array of welding lines  68  that are spaced apart from one another along the circumferential axis  70  of the anvil face  50 . As shown more specifically in the detailed view provided in  FIG. 12A , each welding line  68  contains a pattern of discrete projections  202 ,  204  that extend outward from the face  50  of the anvil  44 . The projections  202 ,  204  are spaced apart from one another, by a gap that is defined by the width  102  of the notch  200  positioned between a given pair of adjacent projections  202 ,  204 . Welding lines  68  are sinusoidal in the embodiment shown. However, may be straight lines, curved lines, or otherwise arranged to create a continuous and repeating pattern on the end product. 
     In the illustrated embodiment, the contact surfaces  78  of the projections  202 ,  204  have side surfaces  80  oriented at an angle  82  relative to the circumferential axis  70  such that no hypothetical arc  83  drawn from adjacent welding lines  68  is parallel to the circumferential axis  70  of the anvil  44 . In such an embodiment, the facing surfaces  80  of adjacent projections  202 ,  204  are non-parallel to the circumferential axis  70  as shown. As a result, projections  202 ,  204  of adjacent welding lines  68  are not aligned with one another along the circumferential axis  70 . Instead, a given projection  72 A in one welding line  68 A is offset from a given projection  72 B in an adjacent welding line  68 B by a pitch  84  defined by an angle  82 . Projections  202 ,  204  thus define a threaded pattern that extends around the circumferential face  50  of the anvil  44 . 
     It is contemplated that the contact surfaces  78  of the projections  202 ,  204  may have different geometries in alternative embodiments. As non-limiting examples, projections  202 ,  204  may be circular, rectangular, crescent shaped, or have irregular shapes that may be selected to form a desired overall pattern on the end product. In yet another embodiment, corresponding projections  202 ,  204  of adjacent welding lines  68 A,  68 B may be aligned with one another in a line parallel to the circumferential axis  70 . Alternatively, projections  202 ,  204  of sequential welding lines  68 A,  68 B may be offset from one another in the cross-machine direction thereby defining a stepped or non-linear passage through the bond lines that are formed on the first and second web layers  12 ,  16 . 
       FIG. 13  illustrates a portion of an elastic composite structure  86  output from the ultrasonic bonding apparatus  38 . The elastic composite structure  86  is illustrated in an elongated state with elastic threads  18  stretched to a point where the first web layer  12  and second web layer  16  are substantially flat. As shown, the elastic composite structure  86  includes the first web layer  12 , the second web layer  16 , and a number of elastic threads  18  that are located between the first and second web layers  12 ,  16  and oriented along a longitudinal axis  88  of the elastic composite structure  86 . While the illustrated embodiment includes three (3) elastic threads  18  it is contemplated that alternative embodiments may include a single elastic thread  18  or any number of multiple elastic threads  18  based on design specifications of the end product. 
     The ultrasonic bonding operation results in a continuous and repeating pattern of bond lines  90  that minor the welding lines  68  on the anvil  44  and bond or fuse the first web layer  12  to the second web layer  16 . Thus, in embodiments where welding lines  68  are sinusoidal, the resulting bond lines  90  have a similar sinusoidal bond pattern. As shown in the detailed view provided in  FIG. 13A , the tensioned elastic threads  18  extend along a passage  92  that is bounded by the gap  94  formed between the facing edges  96 ,  98  of a pair of adjacent bonds  100 ,  101  in each subsequent bond line  90 . The gap  94  has a width defined by the width  102  of the notches  200  on the anvil  44 . In the regions between the bond lines  90 , the elastic threads  18  are free to swell or expand to their non-tensioned state. In their non-tensioned state, each elastic thread  18  has a cross-sectional area  218  that is smaller than the cross-sectional area of the passage  104  formed between each pair of adjacent bonds  100 ,  101  and the first and second web layers  12 ,  16 . As a result, the elastic thread  18  is trapped or anchored between adjacent pairs of bonds  100 ,  101  and the first and second web layers  12 ,  16 . 
     Referring now to  FIG. 15 , details of the surface pattern of the anvil  44  illustrated in  FIG. 12  is provided in accordance with another non-limiting embodiment of the invention. As shown, anvil  44  includes an array of welding lines  68  that are spaced apart from one another along the circumferential axis  70  of the anvil face  50 . Each welding line  68  contains a pattern of discrete projections  202 ,  204  that extend outward from the face  50  of the anvil  44 . The projections  202 ,  204  are spaced apart from one another, by a gap that is defined by the width  102  of the notch  200  positioned between a given pair of adjacent projections  202 ,  204 . Welding lines  68  are sinusoidal in the embodiment shown. In the embodiment shown in  FIG. 16 , the welding lines  68  follow a repeating chevron pattern. However, the welding lines  68  may be straight lines, curved lines, or otherwise arranged to create a continuous and repeating pattern on the end product. 
     Referring to  FIGS. 15 and 16 , in the illustrated embodiments, the contact surfaces  78  of the projections  202 ,  204  have side surfaces  80  aligned with the circumferential axis  70 . Accordingly, the facing surfaces  80  of adjacent projections  202 ,  204  are parallel to the circumferential axis  70  as shown. End surfaces  260  of each projection  202 ,  204  are perpendicular to the facing surfaces  80  and are thus perpendicular to the circumferential axis  70 . As a result, the end surfaces  260  of the projections  202 ,  204  in any of the welding lines  68  are parallel with one another no matter the position of any individual projection  202 ,  204  along the sinusoid or chevron pattern of the welding lines  68 . The shape of at least the contact surfaces  78  of the projections is rectangular and may be square, for example. In addition, the shape of the entire projection may be a rectangular cuboid where any pair of opposite sides may be rectangular or square. The corners of the projections may be straight or radiused in alternative embodiments. 
     In an alternative embodiment, end surfaces  260  may be oriented at a common angle other than 90 degrees relative to the circumferential axis  70 , with the end surfaces  260  of all projections  202 ,  204  in all welding lines  68  remaining parallel with one another regardless of the position of any individual projection  202 ,  204  along the repeating pattern of the welding lines  68 . In such an embodiment, the shape of the contact surfaces  78  of the projections  202 ,  204  may be shaped as parallelograms. 
     It is contemplated that corresponding projections  202 ,  204  of adjacent welding lines  68  may be aligned with one another in a line parallel to the circumferential axis  70 . Alternatively, projections  202 ,  204  of sequential welding lines  68  may be offset from one another in the cross-machine direction thereby defining a stepped or non-linear passage through the bond lines that are formed on the first and second web layers  12 ,  16 . However, the alignment or misalignment of the adjacent welding lines  68  with respect to each other does not affect the arrangement of the end surfaces  260  of the projections  202 ,  204  being parallel to each other. 
       FIGS. 17-20  illustrate cross-sectional views taken along line  17 - 21  of  FIGS. 15 and 16  showing steps for manufacturing the rotary anvils of  FIGS. 15 and 16  according to an embodiment of the invention.  FIG. 17  illustrates a portion of a blank rotary anvil  44 , the face  50  of which is processed as described below. 
     As shown in  FIG. 18 , the face  50  of the anvil  44  is lowered as grooves  262  are formed through a removal process using, for example, a rotary milling or other cutting device  263 . In another embodiment, a removal process such as electrical discharge machining as known in the art may be used. As a result of the removal process, a plurality of ridges  264  are created above the anvil face  50 . The grooves  262  are spaced according to the desired positions of the welding lines  68 . The formation of the grooves  262  helps shape the welding lines  68  into sinusoid, chevron, alternative non-linear patterns, or linear patterns as desired. 
       FIG. 19  illustrates an optional secondary material removal process that utilizes a second milling or cutting device  265  to remove additional bulk material from the grooves  262 . In the illustrated embodiment, the second milling device  265  is wider than the cutting device  263  of  FIG. 18 ; however, it can be sized differently in alternative embodiments. Milling device  265  creates larger grooves  266  that, when lined up with grooves  262  and when cutting to a shallower depth, create the steps  230  in the ridges  264 . In alternative embodiments, cutting device  263  of  FIG. 18  may be controlled to create the steps  230  in the ridges  254 , the steps  230  may be made using an alternative material removal device such as an electrical discharge machining device, for example, or the steps  230  may be omitted entirely. In embodiments where the steps  230  are omitted, welding lines  68  may be formed having a non-linear sinusoidal or chevron pattern as shown in  FIG. 15A  and  FIG. 16B , respectively, as non-limiting examples. 
     In a top view orientation,  FIG. 20  illustrates the formation of individual protrusions  202 ,  204  in a ridge  264  of one of the weld lines  68 . Another material removal device  268  such as a milling or cutting device may be used to remove material from the ridge  264  to create protrusions  202 ,  204  having parallel side surfaces  80  as well as parallel end surfaces  260  that are orthogonal to the side surfaces  80 . In one embodiment, material removal device  268  may be an electrode of an electrical discharge machining (EDM) device used to remove material from the ridge  264  via electrical current discharging between the electrode and the workpiece (i.e., the ridge  264 ). The material removal device  268  may be configured to translate in a linear motion to remove material, as shown in  FIG. 20 , or via rotary motion. Removal of the material of the ridge  264  by the material removal device  268  forms a step  269  above the optional step  230  when included such that a pair of steps may exist between the anvil face  50  and the protrusions  202 ,  204 . 
     A portion of a completed rotary anvil  44  is illustrated in  FIG. 21  manufactured according to the steps shown in  FIGS. 17-20 . 
       FIG. 24  illustrates a rotary anvil manufactured according to another embodiment of the invention. In this embodiment, the projections  202 ,  204  are built up from the face  50  of the rotary anvil  44  without creating the grooves  262  and steps  230  performed in the method illustrated in  FIG. 18 . Manufacture begins with the step shown in  FIG. 22 , wherein the face  50  of the anvil  44  provided in  FIG. 17  is lowered as the grooves  262  are formed through a removal process using, for example, a rotary milling or other cutting device  263 . Alternatively, material removal device  263  may be an electrode used in an electrical discharge machining device. Formation of the grooves  262  creates the steps  230  above the anvil face  50 . The grooves  262  are spaced according to the desired positions of the welding lines  68 . The formation of the grooves  262  helps shape the welding lines  68  into sinusoid or chevron patterns. 
     The manufacture of the projections  202 ,  204  occurs during a build-up or deposition process as illustrated in  FIG. 23 . The projections  202 ,  204  are grown from the surface of the individual steps  230  as material is deposited thereon. A controlled growing process creates the shapes of the contact surfaces  78  such that the facing surfaces  80  and the end surfaces  260  are aligned as described herein. In particular, the end surfaces  260  of each projection  202 ,  204  are parallel with each other no matter the position of the projection  202 ,  204  along the welding line pattern. 
       FIGS. 25A-28A  illustrate cross-sectional views taken along line  25 - 28  of  FIGS. 15 and 16  showing steps for manufacturing the rotary anvils of  FIGS. 15 and 16  according to another embodiment of the invention.  FIGS. 25B-28B  illustrate top views corresponding to the steps shown in  FIGS. 25A-28A . 
     As shown in  FIGS. 25A and 25B , from the portion of blank rotary anvil  44  illustrated in  FIG. 17 , the face  50  of the anvil  44  is lowered through a removal process using, for example, a rotary milling or other cutting device  270 . In another embodiment, a removal process such as electrical discharge machining as known in the art may be used. As a result of the removal process, a ridge  272  is created above the anvil face  50 . The ridge  272  is shaped into sinusoid, chevron, alternative non-linear patterns, or linear patterns as desired. 
       FIGS. 26A and 26B  illustrate a plurality of grooves  274  formed in the ridge  272  utilizing another milling or cutting device  276  to remove material from the ridge  272  to create land surfaces  278  of respective projections  280 . In the illustrated embodiment, the milling device  276  is narrower than the cutting device  270  of  FIG. 25A ; however, it can be sized differently in alternative embodiments. Alternatively, cutting device  276  may be a rotary cutting device such as a circular saw having an axis of rotation orthogonal to the axis of rotation of the milling device  276  illustrated in  FIGS. 26A, 26B . As illustrated, while the side surfaces  80  of the projections  280  are parallel to one another, the end surfaces  260  follow the path formed by the cutting device  270 . Accordingly, the end surfaces  260  may not be parallel with each other and may not be perpendicular to the circumferential axis  70 . 
     To shape the end surfaces  260  into a pattern where all end surfaces  260  of the projections  280  in any of the welding lines  68  are parallel with one another no matter the position of any individual projection  280  along the sinusoid, chevron, or other non-linear pattern of the welding lines  68 , an electrode  282  of an electrical discharge machining device may be used as illustrated in  FIGS. 27A, 27B  to remove material from the projections  280  via electrical current discharging between the electrode  282  and the workpiece (i.e., the ridge  272 ). The electrode  282  has an opening  284  formed therein that corresponds with the desired finished shape of the land surface  278 . As illustrated, a rectangular shape to the opening  284  creates rectangular land surfaces  278  where the end surfaces  260  of all projections  280  are parallel to each other and are perpendicular to the side surfaces  80  and to the circumferential axis  70 . 
     Referring now to  FIG. 34 , an orthogonal view of the electrode  282  is illustrated. The rectangular-shaped opening  284  corresponds to the shape of the land surfaces  278  illustrated in  FIG. 25B . As shown in  FIG. 35 , other shapes of the opening  284  are contemplated herein such as the parallelogram-shaped opening  286 , which created end surfaces  260  that are parallel to each other but which are not perpendicular to the side surfaces  80 .  FIG. 36  illustrates an electrode  288  with multiple openings  290  that can reduce manufacturing time by creating multiple projections  280  at the same time. 
     Referring back to  FIGS. 27A and 27B , while the electrode  282  with the rectangular opening  284  is illustrated, the parallelogram opening  286  of the electrode  282  of  FIG. 34  may be used instead, or an opening having a different shape than that illustrated in the figures herein may be used. For example, other shaped openings may be used that have circular, crescent shaped, or have irregular shapes that may be selected to form a desired overall pattern on the end product. 
     A portion of a completed rotary anvil  44  is illustrated in  FIGS. 28A, 28B  manufactured according to the steps shown in  FIGS. 25A-28A . 
       FIGS. 29A, 29B  illustrate a portion of a completed rotary anvil  44  manufactured according to another embodiment of the invention. The rotary anvil  44  of  FIGS. 29A, 29B  is manufactured similarly to the rotary anvil  44  of  FIGS. 28A, 28B  with the addition of an additional material removal step. As illustrated, in a bulk material removal step corresponding to a similar step illustrated in  FIG. 26A , a portion  292  of the rotary anvil is removed that is smaller than the portion removed in  FIG. 26A  using cutting device  270 . A step  294  may be created by removing an additional portion  296  of the anvil  44  such that less material is removed as compared with the rotary anvil  44  of  FIGS. 28A, 28B . While portions  292 ,  296  are referenced on one side of the anvil  44 , they are not shown on the other side of anvil  44  for clarity in illustrating the result of such removal. However, prior to the material removal, portions  292 ,  296  for material removal also correspond to the other side of the anvil  44 . 
     As illustrated in  FIGS. 30A, 30B , a portion of a completed rotary anvil  44  manufactured according to another embodiment of the invention. In the embodiment shown, portion  296  of anvil  44  refers to less material removed such that the ridge  272  is wider than that illustrated in  FIGS. 28A, 28B . The use of a cutting device such as cutting device  276  to remove portion  296  reduces the amount of material to be removed by electrode  282 . 
       FIGS. 31A-33A and 31B-33B  correspond with and are similar to the completed rotary anvils  44  illustrated in  FIGS. 28A-30A and 28B-30B  except for the depth of the grooves  274 . As illustrated in  FIGS. 31A-33A and 31B-33B , the depth of the grooves  274  extends to the depth of the anvil face  50 . Accordingly, islands of individual protrusions  280 , ridges  272 , and optional steps  294  are formed. 
     The apparatus and methods described herein can be used to make elastic composite structures for waist regions, below-waist regions, and/or leg cuff regions of a single-piece or three-piece diaper, as non-limiting examples, without the use of glue. By eliminating the use of glue, the resulting elastic composite is softer to the touch and has a more uniform ruffling pattern in the cross-machine direction (i.e., the direction perpendicular to the machine direction). From a manufacturing standpoint, the elastic threads are anchored within dedicated passages of the elastic composite structure that are defined based on notch geometries of the bonding assembly that improve the reliability of the bonds that anchor the elastic threads in position and reducing the likelihood of thread breakage during manufacture. Accordingly, embodiments of the invention disclosed herein provide a more reliable manufacturing process than existing prior art approaches and result in an end product that is visually and tactilely more pleasing to the end customer. 
     Therefore, according to one embodiment of the invention, a rotary anvil comprises a face surface, a plurality of non-linear ridges defined by a first plurality of grooves in the face surface, and a plurality of projections in each of the plurality of non-linear ridges. Each projection of the plurality of projections comprises a contact surface having parallel facing surfaces and parallel end surfaces. 
     According to another embodiment of the invention, a method of manufacturing a rotary anvil comprises providing a rotary anvil having a face surface, removing material from the face surface to form a plurality of non-linear welding lines in the rotary anvil, and forming a plurality of projections in the plurality of non-linear welding lines. Forming the plurality of projections comprises creating a contact surface for each projection of the plurality of projections, the contact surface having parallel facing surfaces and parallel end surfaces. The parallel facing surfaces of each contact surface are parallel to one another, and the parallel end surfaces of each contact surface are parallel to one another. 
     According to yet another embodiment of the invention, an elastic composite structure comprises a first web layer, a second web layer coupled to the first web layer by a non-linear bond pattern comprising at least non-linear one bond line having at least one pair of adjacent bonds, and at least one elastic thread extending through a passage defined by facing edges of the at least one pair of adjacent bonds. Each bond in the at least one bond line comprises parallel facing surfaces and parallel end surfaces orthogonal to the parallel facing surfaces. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.