具体实施方式：
[0046]Certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein in the context of various embodiments; however, the disclosed methods, systems, and apparatus are not limited to any specific aspect, feature, or combination thereof. For example, the embodiments may make use of any of the structures, components and/or methods as disclosed in U.S. Patent Application No. 62/263,916, filed Dec. 7, 2015, titled “Article of Footwear with Tubular Structures,” the entirety of which is herein incorporated by reference (hereafter referred to as the “Articles with Tubular Structures application”). The embodiments may also make use of any of the structures, components and/or methods as disclosed in U.S. Patent Application No. 62/263,891, filed Dec. 7, 2015, titled “Segmented Tunnels on Articles,” the entirety of which is herein incorporated by reference. The embodiments may make use of any of the structures, components and/or methods as disclosed in U.S. Patent Application No. 62/263,898, filed Dec. 7, 2015, titled “Article of Footwear with Tubular Structures Having Tab Portions,” the entirety of which is herein incorporated by reference (hereafter referred to as the “Articles with Tubular Structures and Tab Portions application”).
[0047]In one aspect, a tunnel spring structure is attached to a base layer, where the tunnel spring structure includes a plurality of tubular structures with each tubular structure having a tunnel. The tunnel spring structure further includes a plurality of connection portions. The plurality of tubular structures and the plurality of connecting portions are attached in alternating order in series. One of the plurality of tubular structures is attached to one of the plurality of connecting portions and another plurality of tubular structures is attached to the one of the plurality of connecting portions, and where each connecting portion is disposed between two tubular structures.
[0048]In one aspect, a tunnel spring structure is attached to a base layer, where the tunnel spring structure includes a plurality of tubular structures with each tubular structure having a tunnel. The tunnel spring structure further includes a plurality of connection portions. The plurality of tubular structures and the plurality of connecting portions are attached in alternating order in series. One of the plurality of tubular structures is attached to one of the plurality of connecting portions and another plurality of tubular structures is attached to the one of the plurality of connecting portions, and where each connecting portion is disposed between two tubular structures.
[0049]In another aspect, a tunnel spring structure is attached to a base layer. The tunnel spring structure includes a first tubular structure, a second tubular structure, a third tubular structure, a first connecting portion, a second connecting portion, and a tensile strand. The first tubular structure is attached to the base layer including a first end portion and a second end portion. The first tubular structure has a first tunnel extending from the first end portion to the second end portion. The second tubular structure attached to the base layer includes a third end portion and a fourth end portion. The second tubular structure has a second tunnel extending from the third end portion to the fourth end portion. The third tubular structure attached to the base layer includes a fifth end portion and a sixth end portion. The third tubular structure has a third tunnel extending from the fifth end portion to the sixth end portion. The first connecting portion is disposed between the first tubular structure and the second tubular structure. The first connecting portion is attached to the second end portion of the first tubular structure and the third end portion of the second tubular structure. The second connecting portion is disposed between the second tubular structure and the third tubular structure. The second connecting portion is attached to the fourth end portion of the second tubular structure and the fifth end portion of the third tubular structure. The tensile strand includes a first end and second end. The tensile strand extends through the first tunnel, the second tunnel, and the third tunnel. The tensile strand is partially exposed proximate the first connecting portion and is also partially exposed proximate the second connecting portion.
[0050]In another aspect, a method of forming a tunnel spring system coupled with a base layer, comprising printing a first tubular structure including a first end and a first opposite end. Then printing a second tubular structure including a second end and a second opposite end. Then printing a third tubular structure including a third end and a third opposite end, wherein the first tubular structure, the second tubular structure, and the third tubular structure are sequentially arranged on the base layer. Each tubular structure has a tunnel. Then printing a first connecting portion so that the first connecting portion attaches to the first opposite end of the first tubular structure and the second end of the second tubular structure. Then printing a second connecting portion so that the second connecting portion attaches to the second opposite end of the second tubular structure and the third end of the third tubular structure.
[0051]Other systems, methods, features, and advantages of the embodiments will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description and this summary, be within the scope of the embodiments, and be protected by the following claims.
[0052]FIG. 1 illustrates a schematic isometric view of an embodiment of tunnel spring structure 100. Tunnel spring structure 100 may further comprise a plurality of discrete or disjoint tubular structures. As used herein, the term “tubular structure” refers to a tubular structure having a structure with a hollow tunnel extending through the structure. In the exemplary embodiment of FIG. 1, tunnel spring structure 100 is seen to include three tubular structures: first tubular structure 102, second tubular structure 104, and third tubular structure 106.
[0053]Each tubular structure may include two ends with a tunnel extending between the two ends. For example, first tubular structure 102 includes first end 118 and second end 120. First tunnel 130 extends through first tubular structure 102 between first end 118 and second end 120. Second tubular structure 104 includes first end 122 and second end 124. Second tunnel 132 extends through second tubular structure 104 between first end 122 and second end 124. Third tubular structure 106 includes first end 126 and second end 128. Third tunnel 134 extends through third tubular structure 106 between first end 126 and second end 128.
[0054]FIG. 1 also shows cross-section view 112 of an exemplary tubular structure. Third tubular structure 106 may include outer surface 114 and inner surface 116. Outer surface 114 extends between first end 126 and second end 128. Similarly, inner surface 116 extends between first end 126 and second end 128. Inner surface 116 bounds the third tunnel 134.
[0055]Any of the tubular structures of tunnel spring structure 100 may have any shape. FIG. 1 shows third tubular structure 106 as having a rounded outer cross-sectional geometry. Third tubular structure 106 could have outer cross-sectional geometries that are approximately rectangular or polygonal, ovoid, symmetrical, non-symmetrical or other geometries that need not be circular or approximately circular. Also, FIG. 1 shows third tubular structure 106 as having a rounded inner cross-sectional geometry. Third tubular structure 106 could have inner cross-sectional geometries that are approximately rectangular or polygonal, ovoid, symmetrical, non-symmetrical or other geometries that need not be circular or approximately circular. In some embodiments, each tubular structure of the tunnel spring structure could have the same shape. In other embodiments, every other tubular structure could have the same shape. Further, in other embodiments, each tubular structure could have a different shape. Any of the tubular structures can have these same provisions, and in some embodiments, the three tubular structures are identical in geometry. The structure, design, material(s), and construction for the tubular structures may be selected, including a number and configuration of tubular structures that is suitable for a desired type of article of footwear and/or article of apparel and intended use.
[0056]Any of the tubular structures of tunnel spring structure 100 may have any size. FIG. 1 shows first tubular structure 102 having axial length 146. Axial length 146 extends between first end 118 and second end 120 and could have a value in the range between 5.0 mm and 5.0 cm. In different embodiments, the outer diameter of a tubular structure could have any value in the range between 0.1 mm and 2 cm. Likewise, cross-section view 112 shows tubular structure thickness 144, characterized by the distance between the outer surface 114 and inner surface 116. Tubular structure thickness 144 could have any value in the range between 0.5 mm and 2.0 cm. It may be appreciated that the tunnel diameter may vary in accordance with the tubular structure thickness (i.e., the tunnel diameter is the diameter of the tubular structure minus twice the tubular structure thickness). Moreover, axial length, the outer diameter, and tubular structure thickness for a tubular structure may be selected according to various factors including desired tensile strand diameter, desired flexibility of the tubular structure, desired height of the tubular structure relative to an article of footwear and/or article of apparel as well as possibly other factors.
[0057]Any of the tubular structures can be configured with various physical properties. Exemplary physical properties of the tubular structures that could be varied include rigidity, strength, and flexibility or elasticity. In some embodiments, for example, any of the tubular structures could be configured as relatively rigid with little flexibility. In other embodiments, any of the tubular structures may be configured with some flexibility such that any of the tubular structures can undergo elastic deformation during tensioning.
[0058]Tunnel spring structure 100 may include provisions for connecting separate tubular structures. Some embodiments may include a plurality of connecting portions, where each connecting portion connects two nearby or adjacent tubular structures.
[0059]First connecting portion 108 has first end 136 connected to first tubular structure 102 and second end 138 connected to second tubular structure 104. First connecting portion 108 may be a hinge structure having an elastic or flexible characteristic. In some embodiments, first connecting portion 108 could flex so that first tubular structure 102 and second tubular structure 104 move closer together or farther apart. Second connecting portion 110 has first end 140 connected to second tubular structure 104 and second end 142 connected to third tubular structure 106. Second connecting portion 110 may be a hinge structure having an elastic or flexible characteristic. In some embodiments, second connecting portion 110 could flex so that second tubular structure 104 and third tubular structure 106 move closer together or farther apart.
[0060]FIG. 2 is a schematic side view of the tunnel spring structure 100 of FIG. 1 in a first state or rest position. First tubular structure 102 is spaced a first predetermined distance D1 from second tubular structure 104. First predetermined distance D1 could be determined by the length of first connecting portion 108. For example, first predetermined distance D1 could be in the range of 5.0 mm to 3.0 cm. Similarly, the distance between second tubular structure 104 and third tubular structure 106 could be a first predetermined distance determined by the length of second connecting portion 110. The predetermined distance between first tubular structure 102 and second tubular structure 104 could be the same as the predetermined distance between second tubular structure 104 and third tubular structure 106. The predetermined distance between each tubular structure could also be different from one another.
[0061]FIG. 3 is a schematic side view of the tunnel spring structure 100 of FIG. 1 in a second state or biased position. First tubular structure 102 is spaced a second predetermined distance D2 from second tubular structure 104. Second predetermined distance D2 could be determined by the length of the contracted first connecting portion 108. For example, second predetermined distance D2 could be less than first predetermined distance D1. Similarly, the distance between second tubular structure 104 and third tubular structure 106 could be a second predetermined distance determined by the length of contracted second connecting portion 110.
[0062]Also shown in FIG. 3 is reactive force 302, which enables the connecting portions to contract. For example, in different embodiments, the geometry of the connecting portions change due to reactive force 302. In some embodiments, the connecting portions may be configured with some flexibility such that any of the connecting portions can undergo elastic deformation during tensioning. Upon elastic deformation of the connecting portions, the tubular structures move closer together.
[0063]Different embodiments could utilize different materials for any of the tubular structures and any of the connecting portions. Exemplary materials may include, but are not limited to, various kinds of polymers. In embodiments where a tubular structure and a connecting portion may be formed by a 3D printing process, the tubular structure and the connecting portion could be made of materials including, but not limited to, thermoplastics (e.g., PLA and ABS) and thermoplastic powders, high-density polyurethylene, eutectic metals, rubber, modeling clay, plasticine, RTV silicone, porcelain, metal clay, ceramic materials, plaster and photopolymers, flexible and castable resin, nylon powder, polyester-based filament as well as possibly other materials known for use in 3D printing. Such materials may be herein referred to as “printable materials.”
[0064]FIG. 4 is a schematic view of an embodiment of tunnel spring structure 426 and base layer 400. Tunnel spring structure 426 has first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412. Tunnel spring structure 426 also has first connecting portion 414, second connecting portion 416, third connecting portion 418, fourth connecting portion 420, and fifth connecting portion 422. A tubular structure and connecting portion are arranged in alternating order. A connecting portion is attached between two tubular structures. Although, six tubular structures and five connecting portions are shown, any number of tubular structures and connecting portions could be connected in alternating order to form a tunnel spring structure.
[0065]Tunnel spring structure 426 is positioned to receive tensile strand 424. As used herein, the term “tensile strand” refers to any elongated (e.g., approximately two dimensional) element capable of transferring tension across its length. Examples of various kinds of tensile strands that could be used with the embodiments include, but are not limited to, cords, laces, wires, cables, threads, ropes, filaments, yarns as well as possibly other kinds of strands. Tensile strands may be configured with different strengths as well as different degrees of stretch or elasticity.
[0066]Tensile strand 424 may comprise a cord-like element having an approximately rounded cross section. Tensile strand 424 includes first end portion 428 and second end portion 430. Although the length of tensile strand 424 could vary from one embodiment to another, in an exemplary embodiment, tensile strand 424 may be longer than tunnel spring structure 426 so that first end portion 428 and second end portion 430 extend outwardly from first tubular structure 402 and sixth tubular structure 412, respectively, of tunnel spring structure 426.
[0067]In some embodiments, tensile strand 424 may include provisions to prevent either first end portion 428 or second end portion 430 from being pulled into tunnel spring structure 426. Such an element may be herein referred to as a catching element or anchoring element. Catching elements could include knots formed in a tensile strand or other elements that clamp or tie onto the tensile strand. A catching element may generally have a cross-sectional size and/or shape that prevents the catching element from being pulled into a tubular structure. Instead, the catching element may press against the end of the tubular structure thereby allowing the other end of the tensile strand to be pulled for generating tension across the tensile strand.
[0068]FIG. 4 shows catching element 432 of tensile strand 424 that prevents second end portion 430 from being pulled into tunnel spring structure 426. Catching element 432 could also be located closer to first end portion 428 when second end portion 430 is inserted into tunnel spring structure 426 at first tubular structure 402.
[0069]In some embodiments, printed structures may be printed directly to one or more articles. The term “articles” is intended to include articles of footwear (e.g., shoes) and articles of apparel (e.g., shirts, pants, etc.), as well as protective gear and other articles of manufacture. As used throughout this disclosure, the terms “article of footwear” and “footwear” include any footwear and any materials associated with footwear, including an upper, and may also be applied to a variety of athletic footwear types, including baseball shoes, basketball shoes, cross-training shoes, cycling shoes, football shoes, tennis shoes, soccer shoes, and hiking boots, for example. As used throughout this disclosure, the terms “article of footwear” and “footwear” also include footwear types that are generally considered to be nonathletic, formal, or decorative, including dress shoes, loafers, sandals, slippers, boat shoes, and work boots.
[0070]The disclosed embodiments may further be equally applied to any article of clothing, apparel, or gear that bears additive components. For example, the disclosed embodiments may be applied to hats, caps, shirts, jerseys, jackets, socks, shorts, pants, scarves, undergarments, athletic support garments, gloves, wrist/arm bands, sleeves, headbands, sweatshirts, hoodies, any knit material, any woven material, any nonwoven material, sports equipment, etc. Thus, as used throughout this disclosure, the term “article of apparel” may refer to any apparel or clothing, including any article of footwear, as well as hats, caps, shirts, jerseys, jackets, socks, shorts, pants, scarves, undergarments, athletic support garments, gloves, wrist/arm bands, sleeves, headbands, sweatshirts, hoodies, any knit material, any woven material, any nonwoven material, etc. As used throughout this disclosure, the terms “article of apparel,”“apparel,”“article of footwear,” and “footwear” may also refer to a textile, natural fabric, synthetic fabric, any three-dimensional printed material, recycled materials, knit, woven material, nonwoven material, mesh, leather, synthetic leather, polymer, rubber, and foam. Base layer 400 could comprise a portion of any of these various kinds of articles.
[0071]FIG. 5 is a schematic view of an embodiment of tunnel spring structure 426 on base layer 400. In some embodiments, tunnel spring structure 426 could be attached to base layer 400 with an adhesive or other form of attaching mechanism. In other embodiments, tunnel spring structure 426 could be stitched or sewed onto base layer 400. In an exemplary embodiment, first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412 could be printed, using a three-dimensional printing system, onto base layer 400. Various methods of printing the tubular structures will be described with reference to FIGS. 17-24.
[0072]In some embodiments, first connecting portion 414, second connecting portion 416, third connecting portion 418, fourth connecting portion 420, and fifth connecting portion 422 could be three-dimensionally printed onto base layer 400 so that they are flush or positioned along a similar longitudinal axes with first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412. In other embodiments, first connecting portion 414, second connecting portion 416, third connecting portion 418, fourth connecting portion 420, and fifth connecting portion 422 could be printed onto base layer 400, so that they protrude outward or away from base layer 400.
[0073]Tensile strand 424 may extend through first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412 as shown in FIG. 5. Tensile strand 424 may be partially exposed proximate the connecting portions. For example, portion 502 of tensile strand 424 is seen to be exposed in the region between tubular structure 402 and tubular structure 404.
[0074]In another embodiment, tensile strand 424 could be laid down onto base layer 400. Then, first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412 could be three-dimensionally printed around and over tensile strand 424. First connecting portion 414, second connecting portion 416, third connecting portion 418, fourth connecting portion 420, and fifth connecting portion 422 could be three-dimensionally printed onto base layer 400 so that they are flush or positioned along a similar longitudinal axes with first tubular structure 402, second tubular structure 404, third tubular structure 406, fourth tubular structure 408, fifth tubular structure 410, and sixth tubular structure 412. In other embodiments, first connecting portion 414, second connecting portion 416, third connecting portion 418, fourth connecting portion 420, and fifth connecting portion 422 could be printed onto base layer 400, so that they protrude outward or away from base layer 400.
[0075]FIG. 6 is an isometric view of an embodiment of tunnel spring structure 602 in a first state or rest position. Tunnel spring structure 602 is attached to base layer 600. In some embodiments, three tubular structures and two connecting portions could be connected to form a tunnel spring structure. In other embodiments, multiple tubular structures and multiple connecting portions could be connected to form a tunnel spring structure. The number of tubular structures and connecting portions could be determined based on the location of the tunnel spring structure on the article of footwear and/or the article of apparel. In an embodiment, shown in FIG. 6, tunnel spring structure 602 includes first tubular structure 606, second tubular structure 608, third tubular structure 610, fourth tubular structure 612, fifth tubular structure 614, and sixth tubular structure 616, and first connecting portion 618, second connecting portion 620, third connecting portion 622, fourth connecting portion 624, and fifth connecting portion 626 arranged in alternating order with tensile strand 604 extending through the tubular structures. As shown in FIG. 6, the tubular structures could be spaced apart by first predetermined distance D3 in the first state or rest position. Similarly, the predetermined distance between the other tubular structures could be the same as D3.
[0076]FIG. 7 is an isometric view of an embodiment of tunnel spring structure 602 in a second state or biased position. Tunnel spring structure 602 is attached to base layer 600. Tension could be applied to tensile strand 604, shown by arrow 630. Upon application of tension, first tubular structure 606, second tubular structure 608, third tubular structure 610, fourth tubular structure 612, fifth tubular structure 614, and sixth tubular structure 616 are forced or urged closer together due to the flexible characteristic of first connecting portion 618, second connecting portion 620, third connecting portion 622, fourth connecting portion 624, and fifth connecting portion 626. As shown in call out 728, fifth connecting portion 626 elastically deforms when tension is applied to tensile strand 604. In the second state, fifth tubular structure 614 and sixth tubular structure 616 are spaced apart by distance D4. Similarly, in the second state, the distance between the other tubular structures will be less than first predetermined distance D3.
[0077]As shown in FIG. 7, as tension is applied on tensile strand 604, tunnel spring structure 602 shifts to the second state or biased position. Catching element 642 could be anchored at first tubular structure 606 urging second tubular structure 608 closer to first tubular structure 606 due to the flexible characteristics of first connecting portion 618. Base layer 600 could form first cinch 632 as first tubular structure 606 and second tubular structure 608 are urged closer together due to the flexibility of first connecting portion 618. Base layer 600 could form second cinch 634 as second tubular structure 608 and third tubular structure 610 are urged closer together due to the flexibility of second connecting portion 620. Base layer 600 could form third cinch 636 as third tubular structure 610 and fourth tubular structure 612 are urged closer together due to the flexibility of third connecting portion 622. Base layer 600 could form fourth cinch 638 as fourth tubular structure 612 and fifth tubular structure 614 are urged closer together due to the flexibility of fourth connecting portion 624. Base layer 600 could form fifth cinch 640 as fifth tubular structure 614 and sixth tubular structure 616 are urged closer together due to the flexibility of fifth connecting portion 626. Shifting tunnel spring structure 602 from a first state to a second state could provide an adjustable fit for the wearer.
[0078]FIG. 8 is an isometric view of an embodiment of tunnel spring structure 602 returning to the first state or rest position. As tension is released from tensile strand 604, first tubular structure 606, second tubular structure 608, third tubular structure 610, fourth tubular structure 612, fifth tubular structure 614, and sixth tubular structure 616 are urged to the first state due to the flexible characteristic of first connecting portion 618, second connecting portion 620, third connecting portion 622, fourth connecting portion 624, and fifth connecting portion 626. As shown in call out 828, fifth connecting portion 626 expands when tension is released from tensile strand 604, returning fifth tubular structure 614 and sixth tubular structure 616 to the first state. The expansion of fifth connecting portion is shown by arrows 830.
[0079]A tunnel spring structure could have varying designs and shapes. As shown in the embodiments of FIGS. 5-8, a tunnel spring structure could be arranged linearly, or in a straight line. In other embodiments, a tunnel spring structure could be arranged in a serpentine shape, zigzag shape, triangular, irregular, geometric, or any other kind of shape. Also, multiple tunnel spring structures could be arranged together or intertwined depending on the desired or intended use. As shown in FIG. 9, in some embodiments, tunnel spring structure 902 is arranged in a wave pattern on base layer 900. Tunnel spring structure 902 is shown in a first state when there is no tension applied to tensile strand 908. FIG. 10 shows tunnel spring structure 904 in a second state when tension is applied to tensile strand 908. The connecting portions flex to urge tubular structures closer together. FIG. 11 shows tunnel spring structure 906 returning to the first state as tension is released from tensile strand 908. The connecting portions are no longer flexed and the tubular structures shift to the first state.
[0080]In other embodiments, as shown in FIGS. 12 and 13, tunnel spring structure 1002 is arranged in an arc-like shape on base layer 1000. FIG. 12 shows tunnel spring structure 1002 in a first state or rest position when there is no tension applied to tensile strand 1008. FIG. 13 shows tunnel spring structure 1004 in a second state or biased position when tension is applied to tensile strand 1008. As tension is applied by pulling on both ends of tensile strand 1008, connecting portions flex to urge tubular structures closer together.
[0081]In other embodiments, the tunnel spring structure could be formed of any variety of nonlinear paths to be able to form nonlinear paths for the structure and tensile strand. A nonlinear path of the tunnel spring structure could allow the tensile strand to be arranged in various nonlinear paths on articles to provide targeted support or tensioning, such as around bony structures. Also, nonlinear paths of the tunnel spring structure allow the path of the tensile strand to deviate around regions where you don't want the tensile strand passing through, such as pressure points underlying an article.
[0082]A tunnel spring structure includes tubular structures and connecting portions. FIGS. 14-16 show varying geometries of the connecting portions in the tunnel spring structures. In some embodiments, tunnel spring structure 1100 includes first connecting portion 1108 and second connecting portion 1110 have a high arch. First connecting portion 1108 extends away from first tubular structure 1102 and second tubular structure 1104. Distance 1120 measures the height of the arch. Distance 1120 is measured from the point of connection of first tubular structure 1102 and first connecting portion 1108 to the highest point of the arch. Second connecting portion 1110 extends away from second tubular structure 1104 and third tubular structure 1106. In some embodiments, the height of the arch of first connecting portion 1108 could be the same as the height of the arch of second connecting portion 1110. In other embodiments, the height of the arch of first connecting portion 1108 could be different from the height of the arch of second connecting portion 1110.
[0083]In other embodiments, as shown in FIG. 15, tunnel spring structure 1200 includes first connecting portion 1112 and second connecting portion 1114 have a medium arch. First connecting portion 1112 extends away from first tubular structure 1102 and second tubular structure 1104. Distance 1122 measures the height of the arch. Distance 1122 is measured from the point of connection of first tubular structure 1102 and first connecting portion 1112 to the highest point of the arch. Second connecting portion 1114 extends away from second tubular structure 1104 and third tubular structure 1106. In some embodiments, the height of the arch of first connecting portion 1112 could be the same as the height of the arch of second connecting portion 1114. In other embodiments, the height of the arch of first connecting portion 1112 could be different from the height of the arch of second connecting portion 1114.
[0084]Further, in other embodiments, as shown in FIG. 16, tunnel spring structure 1300 includes first connecting portion 1116 and second connecting portion 1118 have a low arch. First connecting portion 1116 extends away from first tubular structure 1102 and second tubular structure 1104. Distance 1124 measures the height of the arch. Distance 1124 is measured from the point of connection of first tubular structure 1102 and first connecting portion 1116 to the highest point of the arch. Second connecting portion 1118 extends away from second tubular structure 1104 and third tubular structure 1106. In some embodiments, the height of the arch of first connecting portion 1116 could be the same as the height of the arch of second connecting portion 1118. In other embodiments, the height of the arch of first connecting portion 1116 could be different from the