具体实施方式：
[0032]Embodiments of the collapsible tunnel system or segmented tubular structures may be printed on or otherwise attached to base layers on articles of apparel, articles of footwear, or other articles of manufacture. The collapsible tunnel systems have two or more tubular structures attached to the base layer, with tunnels extending through the tubular structures. A tensile strand such as a cable, lace, cord, or string may be laced through the tunnels in the tubular structure such that when tension is applied to the tensile strand the tunnels may collapse into a structure with a continuous tunnel through two or more tubular structures. In some embodiments, two or more segmented tubular structures each have two spaced-apart tubular structures joined by a connecting portion, and a tensile strand extending through tunnels in the tubular structures.
[0033]The collapsible tunnel systems or the segmented tunnels may be applied to articles of manufacture using three-dimensional printing systems, or by using other additive manufacturing techniques such as welding, applying adhesives, fusing or sewing. Three-dimensional printing systems and methods may be associated with various technologies including fused deposition modeling (FDM), electron beam freeform fabrication (EBF), selective laser sintering (SLS) as well as other kinds of three-dimensional printing technologies. Structures formed from three-dimensional printing systems can be used with objects formed by other manufacturing techniques. These include textile materials used in various articles of footwear, articles of apparel and/or protective articles.
[0034]In one aspect, embodiments of the collapsible tunnel system attached to a base layer may have a first tubular structure attached to the base layer. The first tubular structure may have a first end portion and a second end portion, and a first tunnel extending from the first end portion to the second end portion. The embodiments may also have a second tubular structure attached to the base layer. The second tubular structure may have a third end portion and a fourth end portion, with a second tunnel extending from the third end portion to the fourth end portion. The embodiments may have a tensile strand extending through the first tunnel and the second tunnel. The collapsible tunnel system thus can have a first configuration in which the second end portion of the first tubular structure is spaced apart from the third end portion of the second tubular structure and a second configuration in which the second end portion of the first tubular structure is closer to the third end portion of the second tubular structure than in the first configuration. Tension may be applied across a portion of the tensile strand to place the collapsible tunnel system in the second configuration.
[0035]In another aspect, embodiments of a collapsible tunnel system may be attached to a base layer and may include a first tubular structure attached to the base layer. The first tubular structure may have a first end portion, a second end portion, and a curved portion between the first end portion and the second end portion, and a first tunnel extending from the first end portion to the second end portion. The first tunnel may curve through the curved portion of the first tubular structure. Embodiments may also have a second tubular structure attached to the base layer that has a third end portion and a fourth end portion, with a second tunnel extending from the third end portion to the fourth end portion. The embodiments may also have a tensile strand extending through the first tunnel and the second tunnel. The collapsible tunnel system may have a first configuration in which the second end portion of the first tubular structure is spaced apart from the third end portion of the second tubular structure, and a second configuration in which the second end portion of the first tubular structure is in contact with the third end portion of the second tubular structure such that the first tunnel is continuous with the second tunnel in the second configuration. Tension may be applied across a portion of the tensile strand to place the collapsible tunnel system in the second configuration. In the second configuration, the first tunnel and second tunnel provide a nonlinear path for the tensile strand.
[0036]In another aspect, embodiments have a tensioning system attached to a base layer including a first segmented tubular structure that has a first tubular structure attached to the base layer and a second tubular structure attached to the base layer. The first tubular structure has a first tunnel and the second tubular structure has a second tunnel. The first tubular structure may be attached to the second tubular structure by a first connecting portion, such that the first tunnel is spaced apart from the second tunnel by the first connecting portion. Embodiments also have a second segmented tubular structure with a third tubular structure attached to the base layer and a fourth tubular structure attached to the base layer. The third tubular structure has a third tunnel and the fourth tubular structure has a fourth tunnel. The third tubular structure is attached to the fourth tubular structure by a second connecting portion. The third tunnel is spaced apart from the fourth tunnel by the second connecting portion. A tensile strand extends through the first tunnel, the second tunnel, the third tunnel, and the fourth tunnel. The first segmented tubular structure is spaced apart from the second segmented tubular structure.
[0037]In another aspect, embodiments of a tensioning system attached to a base layer have a first tubular structure attached to a first portion of the base layer and a second tubular structure attached to a second portion of the base layer. The base layer has an intermediate portion extending between the first portion and the second portion. The first tubular structure has a first end portion and a second end portion, and includes a first tunnel extending from the first end portion to the second end portion. The embodiments have a second tubular structure that has a third end portion and a fourth end portion, with a second tunnel extending from the third end portion to the fourth end portion. A tensile strand extends through the first tunnel and the second tunnel. The first tubular structure and the second tubular structure are spaced apart so that an exposed portion of the tensile strand extends between the first tubular structure and the second tubular structure. The exposed portion of the tensile strand is next to the intermediate portion of the base layer. Applying tension across the tensile strand changes the geometry of the intermediate portion of the base layer.
[0038]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 disclosed herein 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. The embodiments may also make use of any of the structures, components and/or methods as disclosed in U.S. Patent Application No. 62/263,923, filed Dec. 7, 2015, titled “Tunnel Spring Structures,” 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. The embodiments may make use of any of the structures, components and/or methods as disclosed in U.S. Patent Application No. 62/263,834, filed Dec. 7, 2015, titled “Three-Dimensional Printing Utilizing a Captive Element,” the entirety of which is herein incorporated by reference.
[0039]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 of embodiments illustrated in the figures. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the embodiments, and be protected by the following claims.
[0040]The embodiments described below are illustrated schematically in the drawings as tubular structures and segmented tubular structures that have certain geometries and relative dimensions, as shown in the drawings. However, embodiments of the tubular structures and the segmented tunnel structures may have different shapes, such as curved, bent, or other nonlinear geometries, and may have any appropriate range of dimensions such as their inner diameters, their outer diameters, their wall thicknesses and their lengths. They may also have cross sections with any geometry, such as circular, oval, rectangular, square, hexagonal, or other polygonal geometry, or may have any combination of the foregoing.
[0041]Segmented tunnels may be applied to a base layer by using additive manufacturing techniques such as three-dimensional printing, welding, adhesive application, fusing, or sewing. Thus, although the embodiments described herein are described as being fabricated using three-dimensional printing, other additive manufacturing methods may alternatively be used to fabricate the articles of manufacture described herein.
[0042]FIG. 1 is a schematic diagram of an embodiment of a three-dimensional printing system 100, also referred to in this specification simply as printing system 100. FIG. 1 also illustrates several exemplary articles 130 that may be used with printing system 100. Referring to FIG. 1, printing system 100 may include printing device 102 in communication with CAD system 104 over network 106.
[0043]Embodiments may use various kinds of three-dimensional printing (or other additive manufacturing) techniques. Three-dimensional printing, or “3D printing,” comprises various technologies that may be used to form three-dimensional objects by depositing successive layers of material on top of one another. Exemplary 3D printing technologies that could be used include, but are not limited to, fused filament fabrication (FFF), electron beam freeform fabrication (EBF), direct metal laser sintering (DMLS), electron beam melting (EMB), selective laser melting (SLM), selective heat sintering (SHS), selective laser sintering (SLS), plaster-based 3D printing (PP), laminated object manufacturing (LOM), stereolithography (SLA), digital light processing (DLP) as well as various other kinds of 3D printing or additive manufacturing technologies known in the art.
[0044]In the exemplary embodiment shown in FIG. 1, printing device 102 of printing system 100 uses fused filament fabrication to produce three-dimensional parts. An example of a printing device using fused filament fabrication (FFF) is disclosed in Crump, U.S. Pat. No. 5,121,329, issued on Jun. 9, 1992, titled “Apparatus and Method for Creating Three-Dimensional Objects,” which application is herein incorporated by reference and referred to hereafter as the “3D Objects” application. Embodiments of the present disclosure may make use of one or more of the systems, components, devices, and methods disclosed in the 3D Objects application.
[0045]Printing device 102 may include housing 110 that supports the devices and components used for three-dimensional printing on articles of manufacture. In some embodiments, printing device 102 may include printing nozzle assembly 116 and platform 112 for supporting the article to be printed on. In some embodiments, platform 112 may be controlled to move within housing 110 in the horizontal plane as well as in a vertical direction. In other embodiments, platform 112 may be fixed in one or more directions, and printing nozzle assembly 116 may be controlled to move in one or more directions. Moreover, in some cases, printing nozzle assembly 116 and/or platform 112 may be configured to rotate and/or tilt about one or more axes.
[0046]In the exemplary embodiment of FIG. 1, CAD system 104 may comprise central processing device 185, monitor 186, and input devices 187 (such as a keyboard and mouse), and software for designing a computer-aided design (“CAD”) representation 189 of a printed structure. In at least some embodiments, CAD representation 189 of a printed structure may include information related to the materials required to print various portions of the structure as well as information about the geometry of the structure.
[0047]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.
[0048]While the disclosed embodiments are described in the context of footwear, 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, undergarments, athletic support garments, gloves, wrist/arm bands, sleeves, headbands, 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, undergarments, athletic support garments, gloves, wrist/arm bands, sleeves, headbands, 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, knit, woven material, nonwoven material, mesh, leather, synthetic leather, polymer, rubber, and foam.
[0049]In an exemplary embodiment, printing device 102 may be configured to print one or more structures directly onto a portion of one of exemplary articles 130. Exemplary articles 130 comprise exemplary articles that may receive a printed structure directly from printing device 102, including article of apparel 132, as well as an upper for article of footwear 134. Printing device 102 may be used to apply printed material to flat articles or to articles that may be flattened, as shown in FIG. 1. Printing device 102 may also be used to print directly onto articles that have a three-dimensional configuration.
[0050]In order to apply printed materials directly to one or more articles, printing device 102 may be capable of printing onto the surfaces of various kinds of materials. Specifically, in some cases, printing device 102 may be capable of printing onto the surfaces of various materials such as a textile, natural fabric, synthetic fabric, knit, woven material, nonwoven material, mesh, leather, synthetic leather, polymer, rubber, and foam, or any combination of them, without the need for a release layer interposed between a substrate and the bottom of the printed material, and without the need for a perfectly or near-perfectly flat substrate surface on which to print. For example, the disclosed methods may include printing a resin, acrylic, thermoplastic materials, or other ink materials onto a fabric, for example a knit material, where the material is adhered/bonded to the fabric and where the material does not generally delaminate when flexed, rolled, worked, or subject to additional assembly processes/steps. Other possible ink materials may include, for example, polyurethane, polyethylene, eutectic materials, molding clay, silicone, and other materials, including heat-curable, UV-curable, and photo-curable materials. As used throughout this disclosure, the term “fabric” may be used to refer generally to materials chosen from any textile, natural fabric, synthetic fabric, knit, woven material, nonwoven material, mesh, leather, synthetic leather, polymers, rubbers, and foam.
[0051]Although some embodiments may use printing device 102 to print structures directly onto the surface of a material, other embodiments may include steps of printing a structure onto a platform or release paper, and then joining the printed structure to an article in a separate step. In other words, in at least some embodiments, printed structures need not be printed directly to the surface of an article.
[0052]Printing system 100 may be operated as follows to provide one or more structures that have been formed using a 3D printing process. CAD system 104 may be used to design a structure. This may be accomplished using CAD software or other kind of software. The design may then be transformed into information that can be interpreted by printing device 102 (or a related print server in communication with printing device 102). In some cases, the design may be converted to a 3D printable file, such as a stereolithography file (STL file).
[0053]Before printing, an article may be placed onto the top surface 148 of platform 112 within the housing 110 of printing device 102. Once the printing process is initiated (by a user, for example), printing device 102 may begin depositing material onto the article. This may be accomplished by moving nozzle 118 (using printing nozzle assembly 116) to build up layers of a structure using deposited material. In embodiments where fused filament fabrication is used, material extruded from nozzle 118 may be heated so as to increase the pliability of the printable material as it is deposited.
[0054]Although some of the embodiments shown in the figures depict a system using filament-fused fabrication printing technologies, it will be understood that still other embodiments could incorporate one or more different 3D printing technologies. For example, printing system 100 may use a tack and drag printing method. Moreover, still other embodiments could incorporate a combination of filament-fused fabrication and another type of 3D printing technique to achieve desired results for a particular printed structure or part.
[0055]As previously noted, printing device 102 may be configured to print directly onto various articles. Similarly, printing device 102 may be configured to print on various surface topographies. For example, as shown in FIG. 1, platform 112 is substantially planar. In other embodiments, platform 112 may include one or more protrusions and/or one or more cavities. Moreover, printing device 102 may print on surfaces having various shapes. For example, as shown, platform 112 is generally rectangular. In other embodiments, platform 112 may be circular, triangular, shaped like an upper for an article of footwear, etc. As shown, platform 112 has a top surface 148 configured to receive exemplary articles 130 (such as article of apparel 132 or upper for an article of footwear 134) that will have segmented tunnels printed upon them, as described below.
[0056]The segmented tunnels may be printed on exemplary articles 130 using printable materials. The term “printable material” is intended to encompass any materials that may be printed, ejected, emitted, or otherwise deposited during an additive manufacturing process. Such materials can include, but are 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, as well as possibly other materials known for use in 3D printing.
[0057]In some embodiments, a printable material may be any material that is substantially moldable and/or pliable above a predetermined temperature, such as a glass-transition temperature and/or a melting temperature. In one embodiment, a printable material has one or more thermal properties such as a glass-liquid transition (“glass transition”) temperature and/or a melting temperature. For example, the printable material may be a thermoplastic material having a glass-transition temperature and a melting temperature. As used herein, thermoplastic materials may include, for example, acrylic, nylon, polybenzimidazole, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene (PTFE), and the like.
[0058]Segmented tubular structures may be used on articles of footwear, articles of apparel, or on other articles of manufacture to route tensile strands that may be pulled tight to alter the configuration of the article. Examples of such tensile strands include cables, cords, laces, and strings. The use of such segmented tubular structures may allow a wearer or user of the article to modify the configuration of the article in a controlled manner by applying tensile stress to the tensile strands.
[0059]The segmented tubular structures are generally printed on or otherwise attached to a base layer of the article of footwear, article of apparel, or other article of manufacture. The base layer may be, for example, a fabric layer, textile layer, woven layer, knit layer, nonwoven layer, natural leather layer, synthetic layer, plastic layer, or thermoplastic layer.
[0060]FIG. 2 and FIG. 3 are schematic diagrams illustrating two of the techniques that may be used to print segmented tubular structures on articles of manufacture. To produce tubular structure 200 shown in cross section in FIG. 2, a section of tensile strand 202 is placed on base layer 201 of an article. For convenience, the term “tensile strand” is used herein to designate any tensile strand including a cable, cord, lace, string, or other tensile strand. A layer 203 of printable material is then printed over directly onto base layer 201 and over tensile strand 202. Optionally, in some embodiments, tensile strand 202 is encased in a coating 205, such as a PTFE coating, that allows tensile strand 202 to be pulled or pushed smoothly through tunnel 206 formed by layer 203 of printable material with minimal resistance.
[0061]To produce the tubular structure shown in the cross section in FIG. 3, a layer 227 of printable material may first be printed onto base layer 221 of an article. Layer 227 is optional, and may be omitted in appropriate cases, as described below. Walls 223 are then printed on layer 227 (or if layer 227 is omitted, on base layer 221), and tensile strand 222 is then placed within walls 223 and on top of layer 227. The tubular structure is then capped by printing curved section 224 over the top of tensile strand 222 and over the top of walls 223. Optionally, in some embodiments, tensile strand 222 is encased in a coating 225, such as a PTFE coating, that allows tensile strand 222 to be pulled or pushed smoothly through tunnel 226 formed by layer 223 of printable material.
[0062]A layer such as layer 227 (shown in FIG. 3) may also be used to produce a tubular structure such as the tubular structure shown in FIG. 2 by printing a layer of printable material onto the surface of the article prior to placing a tensile strand on the article. Use of a layer such as layer 227 may improve the adhesion of the tubular structure (FIG. 2) or the tunnel walls (FIG. 3). Thus, in cases where the printable material penetrates into the fabric of the article that is being printed upon and/or exhibits firm adhesion to the article, a layer such as layer 227 may be omitted. In other cases, where the adhesion of the walls of the tunnel themselves to the article may not be sufficient to prevent the possible separation of the tunnel segment to the article, printing a layer such as layer 227 may be an effective way of improving the attachment of the tunnel segment to the article.
[0063]FIG. 4 is a schematic diagram of a perspective view of an embodiment of a segment of a tubular structure 240 on a section of a base layer 241. Base layer 241 may be a fabric, such as the fabric used for an upper of an article of footwear or the fabric used for an article of apparel. In this embodiment, the lower portion 243 of tubular structure 240 is printed first on base layer 241. Tensile strand 242 is then placed within the lower portion 243 of tubular structure 240, and the upper portion 244 of tubular structure 240 is then printed over the lower portion 243 and over tensile strand 242, thus producing the tubular structure 240 shown in FIG. 4. Tensile strand 242 has catching element 247, which is illustrated inFIG. 4 as a knot, at one end. Catching element 247 prevents tensile strand 242 from passing entirely through tunnel 246 in tubular structure 240. Thus when end 248 of tensile strand 242 is pulled, tensile strand 242 is pulled through tunnel 246 in tubular structure 240 until catching element 247 abuts end 249 of tubular structure 240.
[0064]The opposite end 248 of tensile strand 242 may then be laced through one or more additional tunnel segments, as illustrated in FIGS. 7-10, which are described below.
[0065]Thus, in the embodiment of a tubular structure illustrated in FIG. 4, tensile strand 242 is completely encased by the printable tubular structure formed by printing layers of printable material on base layer 241 and over tensile strand 242, unlike the embodiment shown in FIG. 2, in which tensile strand 242 is in direct contact with the base layer 201 of an article. The embodiment illustrated schematically in FIG. 4 is also different from the structure of the embodiment illustrated in FIG. 2, because the FIG. 4 embodiment does not have a layer such as layer 227 that extends over the article beyond the periphery of the tunnel segment itself.
[0066]Optionally, in the embodiment illustrated in FIG. 4, tensile strand 242 may be coated with layer 245 of a material such as PTFE, which may allow tensile strand 242 to slip easily through tunnel 246 in tubular structure 240.
[0067]FIG. 5 is a schematic illustration of a perspective view of an embodiment of tubular structure 260 fabricated by the method described above with respect to FIG. 2, as it has been applied to a section of base layer 261. The cross section shows tensile strand 262 directly on the top surface of base layer 261, with optional coating 265 of a material such as PTFE, which allows tensile strand 262 to slip readily through tunnel 266 with minimal resistance from the inner surface of wall 263 of tubular structure 260. Thus when end 268 of tensile strand 262 is pulled, tensile strand 262 is pulled through tunnel 266 until catching element 267 abuts end 269 of tubular structure 260.
[0068]The tubular structures illustrated schematically in FIG. 4 and FIG. 5 may be applied sequentially to form collapsible tunnel systems. By collapsing two or more tubular structures, as illustrated in FIGS. 6-10, portions of a relatively flexible or bendable structure may be changed, for example, to a more rigid and less bendable structure and/or to have a different configuration or geometry.
[0069]FIGS. 6-9 illustrate the structure and operation of an exemplary collapsible tunnel system comprised of two linear tubular structures. FIG. 6 is a schematic diagram of an exploded view of a section of base layer 281 with a collapsible tunnel system 280 that includes first tubular structure 283, second tubular structure 284, and tensile strand 282. FIG. 6 shows that tensile strand 282 may be laced through two sequential tubular structures, first tubular structure 283 and second tubular structure 284, to form a segmented structure of collapsible tunnel system 280. Dashed outline 285 shows the position of first tubular structure 283 on base layer 281, and dashed outline 286 shows the position of second tubular structure 284 on base layer 281.
[0070]FIG. 7 is a schematic diagram of a perspective view of an example of the embodiment of FIG. 6 as it is applied to a section of base layer 301. In this configuration, collapsible tunnel system 300 has first tubular structure 303 and second tubular structure 304 that are spaced apart from each other in this first configuration. First tubular structure 303 encloses first tunnel 315, and tubular structure 304 encloses second tunnel 316. Tensile strand 302 may be inserted into one back end 309 of first tubular structure 303 and laced through first tunnel 315 in first tubular structure 303 and through second tunnel 316 in second tubular structure 304 and out of the front end 310 of second tubular structure 304. Tensile strand 302 has a catching element 307 at one end, such that when tensile strand end 308 is pulled, first tubular structure 303 is forced toward second tubular structure 304. As shown in the cross section of first tubular structure 303, first tubular structure 303 completely encloses tensile strand 302 within first tunnel 315 in first tubular structure 303. Similarly, second tubular structure 304 completely encloses tensile strand 302 within second tunnel 316. However, in other embodiments, the structure illustrated in FIG. 5 may be used, such that the tensile strand is in direct contact with the underlying base layer.
[0071]FIG. 8 is a schematic diagram of the collapsible tunnel system 300 of FIG. 7 on base layer 301, as tensile strand 302 is pulled at its tensile strand end 308 in the direction indicated by arrow 312. Tensile strand 302 is laced through a back end 309 of first tubular structure 303, through first tunnel 315 in first tubular structure 303 and out of its front end 313. Tensile strand 302 is then laced into the back end 314 of second tubular structure 304 through second tunnel 316 of second tubular structure 304 and out of its front end 310. First Tubular structure 303 and second tubular structure 304 have been brought closer together, by first pulling on tensile strand 302 at tensile strand end 308 in the direction indicated by arrow 312 until catching element 307 (illustrated as a knot in FIG. 8) is forced against back end 309 of first tubular structure 303, and then pulling tensile strand 302 further such that front end 313 of first tubular structure 303 comes closer to back end 314 of second tubular structure 304. In this embodiment, the underlying base layer 301 now has a fold 311 below collapsible tunnel system 300, because the base layer has been pulled forward when first tubular structure 303 has been pulled forward as tensile strand 302 has been pulled forward.
[0072]FIG. 9 is a schematic diagram of a perspective view with a longitudinal cross section of the embodiment of collapsible tunnel system 300 of FIG. 7 and FIG. 8, showing the configuration of the fully collapsed collapsible tunnel system 300 after tensile strand 302 (shown with an optional PTFE coating 305) has been pulled fully forward through back end 309 of tubular structure 303 such that catching element 307 is forced against back end 309. Tensile strand 302 has also been pulled through first tunnel 315 and front end 313 of first tubular structure 303, then through back end 314 of second tubular structure 304, second tunnel 316, and front end 310 of second tubular structure 304 in the direction shown by arrow 312. In this configuration, front end 313 of first tubular structure 303 abuts back end 314 of second tubular structure 304, and fold 311 in underlying base layer 301 is essentially closed up, as shown in the cross section above the perspective view. FIG. 9 shows that, when fully collapsed, collapsible tunnel system 300 has a continuous tunnel 306 extending though first tubular structure 303 and second tubular structure 304, because first tunnel 315 in first tubular structure 303 and second tunnel 316 in second tubular structure 304 have me