Patent Publication Number: US-2015075031-A1

Title: Article Of Footwear Incorporating A Knitted Component With Monofilament Areas

Description:
BACKGROUND 
     Conventional articles of footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for comfortably and securely receiving a foot. The sole structure is secured to a lower area of the upper, thereby being positioned between the upper and the ground. In athletic footwear, for example, the sole structure may include a midsole and an outsole. The midsole often includes a polymer foam material that attenuates ground reaction forces to lessen stresses upon the foot and leg during walking, running, and other ambulatory activities. Additionally, the midsole may include fluid-filled chambers, plates, moderators, or other elements that further attenuate forces, enhance stability, or influence the motions of the foot. The outsole is secured to a lower surface of the midsole and provides a ground-engaging portion of the sole structure formed from a durable and wear-resistant material, such as rubber. The sole structure may also include a sockliner positioned within the void and proximal a lower surface of the foot to enhance footwear comfort. 
     The upper generally extends over the instep and toe areas of the foot, along the medial and lateral sides of the foot, under the foot, and around the heel area of the foot. In some articles of footwear, such as basketball footwear and boots, the upper may extend upward and around the ankle to provide support or protection for the ankle. Access to the void on the interior of the upper is generally provided by an ankle opening in a heel region of the footwear. A lacing system is often incorporated into the upper to adjust the fit of the upper, thereby permitting entry and removal of the foot from the void within the upper. The lacing system also permits the wearer to modify certain dimensions of the upper, particularly girth, to accommodate feet with varying dimensions. In addition, the upper may include a tongue that extends under the lacing system to enhance adjustability of the footwear, and the upper may incorporate a heel counter to limit movement of the heel. 
     A variety of material elements (e.g., textiles, polymer foam, polymer sheets, leather, synthetic leather) are conventionally utilized in manufacturing the upper. In athletic footwear, for example, the upper may have multiple layers that each include a variety of joined material elements. As examples, the material elements may be selected to impart stretch-resistance, wear-resistance, flexibility, air-permeability, compressibility, comfort, and moisture-wicking to different areas of the upper. In order to impart the different properties to different areas of the upper, material elements are often cut to desired shapes and then joined together, usually with stitching or adhesive bonding. Moreover, the material elements are often joined in a layered configuration to impart multiple properties to the same areas. As the number and type of material elements incorporated into the upper increases, the time and expense associated with transporting, stocking, cutting, and joining the material elements may also increase. Waste material from cutting and stitching processes also accumulates to a greater degree as the number and type of material elements incorporated into the upper increases. Moreover, uppers with a greater number of material elements may be more difficult to recycle than uppers formed from fewer types and numbers of material elements. By decreasing the number of material elements utilized in the upper, therefore, waste may be decreased while increasing the manufacturing efficiency and recyclability of the upper. 
     SUMMARY 
     Various configurations of an article of footwear may have an upper and a sole structure secured to the upper. A knitted component of the upper includes one or more monofilament areas. The monofilament areas are formed of unitary knit construction with the remaining portions of the knitted component. 
     In one aspect, the invention provides an article of footwear having an upper and a sole structure secured to the upper, the upper including a knitted component comprising: a first portion of the knitted component formed by a first yarn, the first yarn being a natural or synthetic twisted fiber yarn; at least one monofilament area disposed on the knitted component, the at least one monofilament area being formed by a monofilament strand; wherein the at least one monofilament area is formed of unitary knit construction with the first portion of the knitted component such that the knitted component is a one-piece element. 
     In another aspect, the invention provides an article of footwear having an upper and a sole structure secured to the upper, the upper including a knitted component comprising: a knit element including a first yarn, the knit element defining a portion of an exterior surface of the upper and an opposite interior surface of the upper, the interior surface defining a void for receiving a foot, the first yarn being a natural or synthetic twisted fiber yarn; and at least one monofilament area comprised of two knit layers, the two knit layers being overlapping and at least partially coextensive with each other, each knit layer including a monofilament strand; wherein the at least one monofilament area is formed of unitary knit construction with the knit element such that the knitted component is a one-piece element. 
     In another aspect, the invention provides an article of footwear having an upper and a sole structure secured to the upper, the upper including a knitted component comprising: a first portion of the knitted component formed by a first yarn, the first yarn being a natural or synthetic twisted fiber yarn; a second portion of the knitted component formed by a monofilament strand, wherein second portion is formed of unitary knit construction with the first portion such that the knitted component is a one-piece element; and an inlaid tensile element extending through the knitted component, including at least a portion of the first portion and a portion of the second portion. 
     Other systems, methods, features and advantages of the invention 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 invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is an isometric view of an exemplary embodiment of an article of footwear incorporating a knitted component with monofilament areas; 
         FIG. 2  is a medial side view of the exemplary embodiment of an article of footwear incorporating a knitted component with monofilament areas; 
         FIG. 3  is a lateral side view of the exemplary embodiment of an article of footwear incorporating a knitted component with monofilament areas; 
         FIG. 4  is a top plan view of the exemplary embodiment of an article of footwear incorporating a knitted component with monofilament areas; 
         FIG. 5  is a cross-sectional view of the exemplary embodiment of an article of footwear taken along the line shown in  FIG. 4 ; 
         FIG. 6  is a top plan view of an exemplary embodiment of the knitted component with monofilament areas; 
         FIG. 7  is a top plan view of the exemplary embodiment of the knitted component with monofilament areas including enlarged views of exemplary knit structures; 
         FIG. 8  is an isometric view of an exemplary embodiment of an article of footwear incorporating a knitted component with various monofilament areas; 
         FIG. 9  is a medial side view of the exemplary embodiment of an article of footwear incorporating a knitted component with various monofilament areas; 
         FIG. 10  is a lateral side view of the exemplary embodiment of an article of footwear incorporating a knitted component with various monofilament areas; 
         FIG. 11  is a top plan view of the exemplary embodiment of an article of footwear incorporating a knitted component with various monofilament areas; 
         FIGS. 12A-12C  are cross-sectional views of the exemplary embodiment of an article of footwear taken along different portions according to the section lines shown in  FIG. 11 ; 
         FIG. 13  is a top plan view of an exemplary embodiment of the knitted component with various monofilament areas; 
         FIG. 14  is a top plan view of the exemplary embodiment of the knitted component with various monofilament areas including enlarged views of exemplary knit structures; 
         FIGS. 15A-15C  are cross-sectional views of the exemplary embodiment of a knitted component taken along different portions according to the section lines shown in  FIG. 14 ; 
         FIG. 16A  is an enlarged view of a portion of an exemplary embodiment of a knitted component including a tensile element; 
         FIG. 16B  is an enlarged view of a portion of an alternate embodiment of a knitted component including a tensile element; and 
         FIG. 17  is a representation of a looping diagram for knitting a knit structure. 
     
    
    
     DETAILED DESCRIPTION 
     The following discussion and accompanying figures disclose a variety of concepts relating to knitted components and the manufacture of knitted components. Although the knitted components may be used in a variety of products, an article of footwear that incorporates one or more of the knitted components is disclosed below as an example.  FIGS. 1 through 17  illustrate exemplary embodiments of an article of footwear incorporating a knitted component including one or more monofilament areas formed of unitary knit construction with the remaining portions of the knitted component. The individual features of any of the knitted components described herein may be used in combination or may be provided separately in different configurations for articles of footwear. In addition, any of the features may be optional and may not be included in any one particular embodiment of a knitted component. 
       FIGS. 1 through 4  illustrate an exemplary embodiment of an article of footwear  100 , also referred to simply as article  100 . In some embodiments, article of footwear  100  may include a sole structure  110  and an upper  120 . Although article  100  is illustrated as having a general configuration suitable for running, concepts associated with article  100  may also be applied to a variety of other athletic footwear types, including soccer shoes, baseball shoes, basketball shoes, cycling shoes, football shoes, tennis shoes, training shoes, walking shoes, and hiking boots, for example. The concepts may also be applied to footwear types that are generally considered to be non-athletic, including dress shoes, loafers, sandals, and work boots. Accordingly, the concepts disclosed with respect to article  100  may be applied to a wide variety of footwear types. 
     For reference purposes, article  100  may be divided into three general regions: a forefoot region  10 , a midfoot region  12 , and a heel region  14 , as shown in  FIGS. 1 ,  2 , and  3 . Forefoot region  10  generally includes portions of article  100  corresponding with the toes and the joints connecting the metatarsals with the phalanges. Midfoot region  12  generally includes portions of article  100  corresponding with an arch area of the foot. Heel region  14  generally corresponds with rear portions of the foot, including the calcaneus bone. Article  100  also includes a lateral side  16  and a medial side  18 , which extend through each of forefoot region  10 , midfoot region  12 , and heel region  14  and correspond with opposite sides of article  100 . More particularly, lateral side  16  corresponds with an outside area of the foot (i.e., the surface that faces away from the other foot), and medial side  18  corresponds with an inside area of the foot (i.e., the surface that faces toward the other foot). Forefoot region  10 , midfoot region  12 , and heel region  14  and lateral side  16 , medial side  18  are not intended to demarcate precise areas of article  100 . Rather, forefoot region  10 , midfoot region  12 , and heel region  14  and lateral side  16 , medial side  18  are intended to represent general areas of article  100  to aid in the following discussion. In addition to article  100 , forefoot region  10 , midfoot region  12 , and heel region  14  and lateral side  16 , medial side  18  may also be applied to sole structure  110 , upper  120 , and individual elements thereof. 
     In an exemplary embodiment, sole structure  110  is secured to upper  120  and extends between the foot and the ground when article  100  is worn. In some embodiments, sole structure  110  may include one or more components, including a midsole, an outsole, and/or a sockliner or insole. In an exemplary embodiment, sole structure  110  may include an outsole  112  that is secured to a lower surface of upper  120  and/or a base portion configured for securing sole structure  110  to upper  120 . In one embodiment, outsole  112  may be formed from a wear-resistant rubber material that is textured to impart traction. Although this configuration for sole structure  110  provides an example of a sole structure that may be used in connection with upper  120 , a variety of other conventional or nonconventional configurations for sole structure  110  may also be used. Accordingly, in other embodiments, the features of sole structure  110  or any sole structure used with upper  120  may vary. 
     For example, in other embodiments, sole structure  110  may include a midsole and/or a sockliner. A midsole may be secured to a lower surface of an upper and in some cases may be formed from a compressible polymer foam element (e.g., a polyurethane or ethylvinylacetate foam) that attenuates ground reaction forces (i.e., provides cushioning) when compressed between the foot and the ground during walking, running, or other ambulatory activities. In other cases, a midsole may incorporate plates, moderators, fluid-filled chambers, lasting elements, or motion control members that further attenuate forces, enhance stability, or influence the motions of the foot. In still other cases, the midsole may be primarily formed from a fluid-filled chamber that is located within an upper and is positioned to extend under a lower surface of the foot to enhance the comfort of an article. 
     In some embodiments, upper  120  defines a void within article  100  for receiving and securing a foot relative to sole structure  110 . The void is shaped to accommodate the foot and extends along a lateral side of the foot, along a medial side of the foot, over the foot, around the heel, and under the foot. Upper  120  includes an exterior surface  121  and an opposite interior surface  122 . Whereas exterior surface  121  faces outward and away from article  100 , interior surface  122  faces inward and defines a majority or a relatively large portion of the void within article  100  for receiving the foot. Moreover, interior surface  122  may lay against the foot or a sock covering the foot. Upper  120  may also include a collar  123  that is located in at least heel region  14  and forms a throat opening  140 . Access to the void is provided by throat opening  140 . More particularly, the foot may be inserted into upper  120  through throat opening  140  formed by collar  123 , and the foot may be withdrawn from upper  120  through throat opening  140  formed by collar  123 . In some embodiments, an instep area  150  extends forward from collar  123  and ankle opening  140  in heel region  14  over an area corresponding to an instep of the foot in midfoot region  12  to an area adjacent to forefoot region  10 . 
     In some embodiments, upper  120  may include a tongue portion  152 . Tongue portion  152  may be disposed between lateral side  16  and medial side  18  of upper  120  through instep area  150 . In an exemplary embodiment, tongue portion  152  may be integrally attached to and formed of unitary knit construction with portions of upper  120  along lateral and medial sides through instep area  150 . Accordingly, as shown in the Figures, upper  120  may extend substantially continuously across instep area  150  between lateral side  16  and medial side  18 . In other embodiments, tongue portion  152  may be disconnected along lateral and medial sides through instep area  150  such that tongue portion  152  is moveable within an opening between a lateral portion and a medial portion on opposite sides of instep area  150 . 
     A lace  154  extends through a plurality of lace apertures  153  in upper  120  and permits the wearer to modify dimensions of upper  120  to accommodate proportions of the foot. In some embodiments, lace  154  may extend through lace apertures  153  that are disposed along either side of instep area  150 . More particularly, lace  154  permits the wearer to tighten upper  120  around the foot, and lace  154  permits the wearer to loosen upper  120  to facilitate entry and removal of the foot from the void (i.e., through throat opening  140 ). In addition, tongue portion  152  of upper  120  in instep area  150  extends under lace  154  to enhance the comfort of article  100 . Lace  154  is illustrated with article  100  in  FIG. 1 , while in  FIGS. 2 through 4 , lace  154  may be omitted for purposes of clarity. In further configurations, upper  120  may include additional elements, such as (a) a heel counter in heel region  14  that enhances stability, (b) a toe guard in forefoot region  10  that is formed of a wear-resistant material, and (c) logos, trademarks, and placards with care instructions and material information. 
     In some embodiments, upper  120  may include one or more portions that include monofilament strands, as will be described in more detail below. Monofilament strands may be made from a plastic or polymer material that is extruded to form the monofilament strand. Generally, monofilament strands may be lightweight and have a high tensile strength, i.e., are able to sustain a large degree of stress prior to tensile failure or breaking, so as to provide a large amount or degree of resistance to stretch to upper  120 . In an exemplary embodiment, portions of upper  120  that include monofilament strands may be located in one or more monofilament areas  160 . 
     In some embodiments, monofilament areas  160  may be located on various portions of upper  120 . In an exemplary embodiment, one or more monofilament areas  160  may be located on portions of article  100  where upper  120  will lay generally flat against a foot of a wearer disposed within upper  120 . In this embodiment, monofilament areas  160  include a medial monofilament portion  162  disposed on medial side  18  of upper  120  and a lateral monofilament portion  166  disposed on lateral side  16  of upper  120 . Medial monofilament portion  162  and lateral monofilament portion  166  may be generally located in midfoot region  12 . In some embodiments, monofilament areas  160  may further include a forefoot monofilament portion  164  that is disposed forward of instep area  150  in forefoot region  10  of upper  120 . 
     In some embodiments, monofilament areas  160  may be substantially continuous between each monofilament area  160  across upper  120 . For example, in one embodiment, medial monofilament portion  162  may be continuous with forefoot monofilament portion  164 , and lateral monofilament portion  166  may also be continuous with forefoot monofilament portion  164 . With this configuration, monofilament areas  160  may form a substantially continuous zone extending across upper  120  from lateral side  16  across forefoot region  10  to medial side  18 . In other embodiments, each monofilament area  160 , including medial monofilament portion  162 , forefoot monofilament portion  164 , and/or lateral monofilament portion  166 , may be discontinuous with other monofilament areas  160  disposed on upper  120 . In embodiments where monofilament areas  160  are discontinuous, each monofilament area  160 , for example, medial monofilament portion  162 , forefoot monofilament portion  164 , and/or lateral monofilament portion  166 , may be surrounded or circumscribed by the remaining portions of upper  120 . 
     Many conventional footwear uppers are formed from multiple material elements (e.g., textiles, polymer foam, polymer sheets, leather, synthetic leather) that are joined through stitching or bonding, for example. In contrast, in some embodiments, a majority of upper  120  is formed from a knitted component  130 , which will be discussed in more detail below. Knitted component  130  may, for example, be manufactured through a flat knitting process and extends through each of each of forefoot region  10 , midfoot region  12 , and heel region  14 , along both lateral side  16  and medial side  18 , over forefoot region  10 , and around heel region  14 . In an exemplary embodiment, knitted component  130  forms substantially all of upper  120 , including exterior surface  121  and a majority or a relatively large portion of interior surface  122 , thereby defining a portion of the void within upper  120 . In some embodiments, knitted component  130  may also extend under the foot. In other embodiments, however, a strobel sock or thin sole-shaped piece of material is secured to knitted component  130  to form a base portion of upper  120  that extends under the foot for attachment with sole structure  110 . In addition, a seam  129  extends vertically through heel region  14 , as depicted in  FIG. 4 , to join edges of knitted component  130 . 
     Although seams may be present in knitted component  130 , a majority of knitted component  130  has a substantially seamless configuration. Moreover, knitted component  130  may be formed of unitary knit construction. As utilized herein, a knitted component (e.g., knitted component  130 ) is defined as being formed of “unitary knit construction” when formed as a one-piece element through a knitting process. That is, the knitting process substantially forms the various features and structures of knitted component  130  without the need for significant additional manufacturing steps or processes. A unitary knit construction may be used to form a knitted component having structures or elements that include one or more courses of yarn, strands, or other knit material that are joined such that the structures or elements include at least one course in common (i.e., sharing a common yarn) and/or include courses that are substantially continuous between each of the structures or elements. With this arrangement, a one-piece element of unitary knit construction is provided. 
     Although portions of knitted component  130  may be joined to each other (e.g., edges of knitted component  130  being joined together) following the knitting process, knitted component  130  remains formed of unitary knit construction because it is formed as a one-piece knit element. Moreover, knitted component  130  remains formed of unitary knit construction when other elements (e.g., a lace, logos, trademarks, placards with care instructions and material information, structural elements) are added following the knitting process. 
     Knitted component  130  may incorporate various types of yarn that impart different properties to separate areas of upper  120 . That is, one area of knitted component  130  may be formed from a first type of yarn that imparts a first set of properties, and another area of knitted component  130  may be formed from a second type of yarn that imparts a second set of properties. In this configuration, properties may vary throughout upper  120  by selecting specific yarns for different areas of knitted component  130 . The properties that a particular type of yarn will impart to an area of knitted component  130  partially depend upon the materials that form the various filaments and fibers within the yarn. Cotton, for example, provides a soft hand, natural aesthetics, and biodegradability. Elastane and stretch polyester each provide substantial stretch and recovery, with stretch polyester also providing recyclability. Rayon provides high luster and moisture absorption. Wool also provides high moisture absorption, in addition to insulating properties and biodegradability. Nylon is a durable and abrasion-resistant material with relatively high strength. Polyester is a hydrophobic material that also provides relatively high durability. In addition to materials, other aspects of the yarns selected for knitted component  130  may affect the properties of upper  120 . For example, a yarn forming knitted component  130  may be a monofilament yarn or a multifilament yarn. The yarn may also include separate filaments that are each formed of different materials. In addition, the yarn may include filaments that are each formed of two or more different materials, such as a bicomponent yarn with filaments having a sheath-core configuration or two halves formed of different materials. Different degrees of twist and crimping, as well as different deniers, may also affect the properties of upper  120 . Accordingly, both the materials forming the yarn and other aspects of the yarn may be selected to impart a variety of properties to separate areas of upper  120 . 
     In some configurations of knitted component  130 , materials forming yarns may be non-fusible or fusible. For example, a non-fusible yarn may be substantially formed from a thermoset polyester material and fusible yarn may be at least partially formed from a thermoplastic polyester material. When a fusible yarn is heated and fused to non-fusible yarns, this process may have the effect of stiffening or rigidifying the structure of knitted component  130 . Moreover, joining portions of non-fusible yarn using fusible yarns may have the effect of securing or locking the relative positions non-fusible yarns within knitted component  130 , thereby imparting stretch-resistance and stiffness. That is, portions of non-fusible yarn may not slide relative to each other when fused with the fusible yarn, thereby preventing warping or permanent stretching of knitted component  130  due to relative movement of the knit structure. Another feature of using fusible yarns in portions of knitted component  130  relates to limiting unraveling if a portion of knitted component  130  becomes damaged or one of the non-fusible yarns is severed. Accordingly, areas of knitted component  130  may be configured with both fusible and non-fusible yarns within the knit structure. 
     In an exemplary embodiment, upper  120  may include a first type of yarn that is knitted to form portions of knitted component  130  other than monofilament areas  160 . Monofilament areas  160  on upper  120  may be formed by knitting with a monofilament strand to form knitted component  130  of unitary knit construction with the portions knitted with the first type of yarn. That is, monofilament areas  160  are formed of unitary knit construction with the remaining portions of knitted component  130  so as to be a one-piece element. 
     In some embodiments, knitted component  130  may include one or more boundary zones. Boundary zones define the portion of knitted component  130  where the yarn used to knit knitted component  130  transitions from one yarn type to another yarn type. For example, knitted component  130  may transition from a first type of yarn to a monofilament strand forming monofilament areas  160  at one or more boundary zones on upper  120 . In an exemplary embodiment, the first type of yarn transitions from a natural or synthetic twisted fiber yarn to the monofilament strand at one or more boundary zones associated with each of monofilament areas  160 . In this embodiment, medial monofilament portion  162  includes a rear medial boundary  200  disposed towards heel region  14  of upper  120  where a monofilament strand forming medial monofilament portion  162  transitions to the first type of yarn used to form the remaining portions of knitted component  130 . Medial monofilament portion  162  may further include a top medial boundary  204  and a bottom medial boundary  206 . In one embodiment, top medial boundary  204  is located along medial side  18  of upper  120  and may be spaced apart from collar  123  and throat opening  140  by a first distance D1. In one embodiment, bottom medial boundary  206  is also located along medial side  18  of upper  120  and may be spaced apart from sole structure  110  by a second distance D2. 
     In some embodiments, forward medial boundary  202  may define a forward location of medial monofilament portion  162  on upper  120 . In embodiments where monofilament areas  160  are substantially continuous, forward medial boundary  202  may simply transition into forefoot monofilament portion  164 . In embodiments where each monofilament area  160  is discontinuous, however, forward medial boundary  202  may define the transition from the monofilament strand back to the first yarn type. It should be understood that in such discontinuous embodiments, forefoot monofilament portion  164  will be defined by another boundary zone where the yarn again transitions back to the monofilament strand. 
     Continuing along upper  120 , forefoot monofilament portion  164  may include a rear forefoot boundary  208  and a forward forefoot boundary  209 . In one embodiment, rear forefoot boundary  208  may be located forward of instep area  150  and spaced apart by a third distance D3. Similarly, forward forefoot boundary  209  may be located near a toe end of article  100  and spaced apart by a fourth distance D4. In this embodiment, lateral monofilament portion  166  includes a rear lateral boundary  210  disposed towards heel region  14  of upper  120  where a monofilament strand forming lateral monofilament portion  166  transitions to the first type of yarn used to form the remaining portions of knitted component  130 . Lateral monofilament portion  166  may further include a top lateral boundary  214  and a bottom lateral boundary  216 . In one embodiment, top lateral boundary  214  is located along lateral side  16  of upper  120  and may be spaced apart from collar  123  and throat opening  140  by a fifth distance D5. In one embodiment, bottom lateral boundary  216  is also located along lateral side  16  of upper  120  and may be spaced apart from sole structure  110  by a sixth distance D6. 
     In different embodiments, the distances associated with first distance D1, second distance D2, third distance D3, fourth distance D4, fifth distance D5, and/or sixth distance D6 may vary. For example, in some cases, first distance D1 and fifth distance D5 may vary from 1 cm to 4 cm. In an exemplary embodiment, first distance D1 and fifth distance D5 may be approximately 2 cm to 3 cm. In some cases, second distance D2 and sixth distance D6 may vary from 0.1 cm to 1 cm. In an exemplary embodiment, second distance D2 and sixth distance D6 may be approximately 0.25 cm to 0.5 cm. In some cases, third distance D3 may vary from 1 cm to 4 cm. In one embodiment, third distance D3 may be approximately 2 cm to 3 cm. In some cases, fourth distance D4 may vary from 2 cm to 6 cm. In one embodiment, fourth distance D4 may be approximately 3 cm to 5 cm. In other cases, the distances associated with first distance D1, second distance D2, third distance D3, fourth distance D4, fifth distance D5, and/or sixth distance D6 may be larger or smaller to provide monofilament areas  160  of varying shapes and/or sizes. 
     In some embodiments, a forward lateral boundary  212  may define a forward location of lateral monofilament portion  166  on upper  120 . Similar to forward medial boundary  202 , in embodiments where monofilament areas  160  are substantially continuous, forward lateral boundary  212  may simply transition into forefoot monofilament portion  164 . In embodiments where each monofilament area  160  is discontinuous, however, forward lateral boundary  212  may define the transition from the monofilament strand back to the first yarn type. It should be understood that in such discontinuous embodiments, forefoot monofilament portion  164  will be defined by another boundary zone where the yarn again transitions back to the monofilament strand. 
     In some embodiments, medial monofilament portion  162  and lateral monofilament portion  166  may have similar arrangements on each of medial side  18  and lateral side  16  so as to be approximately symmetric. In these embodiments, first distance D1 and fifth distance D5 may be approximately equal. Similarly, in second distance D2 and sixth distance D6 may also be approximately equal. In other embodiments, however, each of medial side  18  and lateral side  16  may have monofilament areas  160  that are different between each side. Accordingly, in such other embodiments, each of first distance D1 and fifth distance D5 may be different and/or second distance D2 and sixth distance D6 may be different to locate medial monofilament portion  162  and lateral monofilament portion  166  farther or closer to collar  123  and/or sole structure  110 . In still other embodiments, only one of medial side  18  or lateral side  16  may include monofilament areas  160 . It should be understood that other configurations of monofilament areas  160  of varying size, shape, and/or location may be arranged according to the processes described herein. 
     In some embodiments, monofilament areas  160  on upper  120  may be transparent, translucent, or opaque depending on the characteristics or properties of the material used to make the monofilament strand forming the respective monofilament area  160 . In one embodiment, a single monofilament strand having a diameter of approximately 0.114 mm may be used for forming monofilament areas  160 , including each of medial monofilament portion  162 , forefoot monofilament portion  164 , and lateral monofilament portion  166 . A monofilament strand having a larger or smaller diameter may be used in other embodiments. Additionally, in other embodiments, different monofilament strands may be used for each separate monofilament area  160  on upper  120  so as to provide different properties or characteristics to the respective monofilament area  160 . 
     By incorporating knitted component  130  with monofilament areas  160  into upper  120  for article  100 , monofilament areas  160  may provide strength, stretch resistance, reduced weight, and/or assist with airflow through upper  120  to provide ventilation to the interior of article  100 . For example, as shown in  FIG. 5 , medial monofilament portion  162  and lateral monofilament portion  166  are disposed along each of medial side  18  and lateral side  16  of upper  120  in midfoot region  12 . With this configuration, medial side  18  and lateral side  16  of upper  120  may have increased strength and resistance to stretch in these areas. Additionally, the structure of medial monofilament portion  162  and lateral monofilament portion  166  allows air to easily pass through upper  120  into the interior of article  100 . For example, when a foot of a wearer is disposed along a base portion  500  of upper  120  within the interior of article  100 , air may circulate into and out of upper  120  to assist with providing ventilation to article  100 . 
     Moreover, by forming upper  120  with one or more monofilament areas  160 , the overall weight of upper  120  may be significantly reduced compared with an upper formed wholly of a natural or synthetic twisted fiber yarn. For example, in one embodiment, an upper for an adult men&#39;s size 8 may weigh approximately 49 grams when knitted with a natural or synthetic twisted fiber yarn. In contrast, upper  120  with monofilament areas  160  may weigh only 29 grams for a similar size. Therefore, the weight savings associated with using the monofilament strand for monofilament areas  160  in upper  120  may be lighter by at least 40%. In addition, by varying the number, shape, and/or size of monofilament areas  160  on upper  120 , additional weight savings to increase the reduction in weight to more than 40% may be achieved. 
     Referring now to  FIGS. 6 and 7 , an exemplary embodiment of knitted component  130  is shown in a planar or flat configuration. In this embodiment, knitted component  130  has a generally Y-shaped configuration that is outlined by an outer perimeter edge  600 . In this embodiment, outer perimeter edge  600  extends around knitted component  130  from lateral side  16  to medial side  18 . The outer perimeter of knitted component  130  also includes a pair of heel edges  602  disposed on each of lateral side  16  and medial side  18 . In an exemplary embodiment, knitted component  130  may further include an inner perimeter edge along collar  123  that will be associated with and define throat opening  140 , described above. When incorporated into an article of footwear, including article  100 , outer perimeter edge  600  and at least a portion of heel edges  602  may lay against an upper surface of sole structure  110  as base portion  500 , shown in  FIG. 5 . In other embodiments, knitted component  130  may be joined to a strobel sock or sockliner for attachment to sole structure  110 . In addition, heel edges  602  are joined to each other and extend vertically in heel region  14  of article  100  to form seam  129 . In some embodiments of an article of footwear, a material element may cover seam  129  between heel edges  602  to reinforce seam  129  and enhance the aesthetic appeal of the article. 
     Knitted component  130  may include instep area  150  that is formed of unitary knit construction with the remaining portion of upper  120 , as described above. In some embodiments, instep area  150  includes plurality of lace apertures  153  disposed in knitted component  130 . Lace apertures  153  may extend through knitted component  130  from exterior surface  121  to interior surface  122  and are configured to receive a lace, including lace  154 . In an exemplary embodiment, lace apertures  153  may be formed directly into knitted component  130  by knitting. In other embodiments, however, lace apertures  153  may include additional reinforcing elements added to knitted component  130 . 
     In various embodiments, knitted component  130  may incorporate various types of yarn that impart different properties to separate areas of upper  120 . For example, one area of knitted component  130  may be formed from a first type of yarn that imparts a first set of properties, and another area of first knitted component  130  may be formed from a second type of yarn that imparts a second set of properties. In this configuration, properties may vary throughout upper  120  by selecting specific yarns for different areas of knitted component  130 . In an exemplary embodiment, knitted component  130  includes monofilament areas  160 , as described above. In one embodiment, monofilament areas  160  may include medial monofilament portion  162 , forefoot monofilament portion  164 , and/or lateral monofilament portion  166 . As described above, knitted component  130  is formed of unitary knit construction such that each of the areas of knitted component  130 , including monofilament areas  160 , are knitted as a one-piece element. 
     Referring now to  FIG. 7 , enlarged views of portions of monofilament areas  160  along various boundary zones are illustrated to show the unitary knit construction of knitted component  130 . As described above, boundary zones on knitted component  130  define the portion of knitted component  130  where the yarn used to knit knitted component  130  transitions from one yarn type to another yarn type. For example, knitted component  130  may transition from a first type of yarn  700  to a monofilament strand  701  forming monofilament areas  160  at one or more boundary zones on upper  120 . In an exemplary embodiment, first type of yarn  700  transitions from a natural or synthetic twisted fiber yarn to monofilament strand  701  at one or more boundary zones associated with each of monofilament areas  160 . 
     As shown in  FIG. 7 , at forward forefoot boundary  209  in forefoot region  10  of knitted component  130 , knitted component  130  transitions from forefoot monofilament portion  164  formed by monofilament strand  701  to the remaining portion of knitted component  130  formed by first type of yarn  700 . In this embodiment, a course of monofilament strand  701  is joined (e.g., by interlooping) to an adjacent course of first type of yarn  700 . That is, a course formed by knitting monofilament strand  701  is substantially continuous with a course formed by knitting first type of yarn  700 . With this configuration, monofilament areas  160  may be formed of unitary knit construction with knitted component  130 . 
     Similarly, adjacent wales of knitted component  130  may also transition from one type of yarn to a different type of yarn at boundary zones. As shown in  FIG. 7 , at top medial boundary  204 , knitted component  130  transitions from a portion formed by first type of yarn  700  to medial monofilament portion  162  formed by monofilament strand  701 . In this embodiment, wales of first type of yarn  700  are joined to an adjacent wale of monofilament strand  701 . In one embodiment, monofilament areas  160  may be knit using an intarsia knitting technique to transition between yarn types along boundary zones. For example, wales of first type of yarn  700  may joined to adjacent wales of monofilament strand  701  by using intarsia knit construction techniques. With this configuration, monofilament areas  160  may be formed of unitary knit construction with knitted component  130 . 
     By forming knitted component  130  with monofilament areas  160  of unitary knit construction, monofilament areas  160  may be surrounded or circumscribed by the remaining portions of knitted component  130  so as to place monofilament areas  160  under tension. That is, first type of yarn  700  may be configured to surround monofilament areas  160  formed by monofilament strand  701 . Because first type of yarn  700  may have a smaller stretch resistance than monofilament strand  701 , which is non-elastic and resists stretch, knitted component  130  may stretch in the portions surrounding monofilament areas  160  so as to apply a slight tensioning force on monofilament areas  160 . With this configuration, the tensioning force applied on monofilament areas  160  by the surrounding portion of knitted component  130  may assist with preventing or reducing kinks or sharp bends in monofilament strand  701  in monofilament areas  160  that may produce an uncomfortable feeling to a foot of a wearer. 
     In different embodiments, an article of footwear incorporating a knitted component having different features may be provided. In some embodiments, an article of footwear may be configured with a knitted component having different types of monofilament areas on an upper. Depending on the desired type and location, monofilament areas may be varied to provide different properties to an upper. For example, in some embodiments, a monofilament area with a natural or synthetic twisted fiber yarn interior layer may be configured to provide comfort to a foot of a wearer.  FIGS. 8 through 17  illustrate another exemplary embodiment of an article of footwear  800 , also referred to simply as article  800 , with multiple types of monofilament areas  860 . In some embodiments, article of footwear  800  may include an upper  820  that is attached to sole structure  110 , described above. In an exemplary embodiment, upper  820  may include multiple types of monofilament areas  860 . 
     In some embodiments, upper  820  may include multiple components that are substantially similar to components of upper  120 , described above. For example, upper  820  may include an exterior surface  821  and an opposite interior surface  822  that are substantially similar to exterior surface  121  and interior surface  122 , described above. Upper  820  may also include a collar  823  that is substantially similar to collar  123  and that is located in at least heel region  14  and forms a throat opening  840 , which provides access to the interior of upper  820 . Additionally, upper  820  may also include an instep area  850  that is substantially similar to instep area  150 , described above. 
     In some embodiments, instep area  850  may further include a tongue portion  852  that is disposed between lateral side  16  and medial side  18  of upper  820  through instep area  850 . In an exemplary embodiment, tongue portion  852  may be substantially similar to tongue portion  152 , described above, and may be integrally attached to and formed of unitary knit construction with portions of upper  820  along lateral and medial sides through instep area  850 . As with tongue portion  152 , in other embodiments, tongue portion  852  may be similarly disconnected along lateral and medial sides through instep area  850  such that tongue portion  852  is moveable within an opening between a lateral portion and a medial portion on opposite sides of instep area  850 . 
     Article  800  may further be used with lace  154 , described above, that extends through a plurality of lace apertures  853  in upper  820  and permits the wearer to modify dimensions of upper  820  to accommodate proportions of the foot. In some embodiments, lace  154  may extend through lace apertures  853  that are disposed along either side of instep area  850 . In some embodiments, lace apertures  853  may be lace-receiving members formed by a looped portion of an inlaid tensile element  832 , as will be further described below. More particularly, lace  154  permits the wearer to tighten upper  820  around the foot, and lace  154  permits the wearer to loosen upper  820  to facilitate entry and removal of the foot from the void (i.e., through throat opening  840 ). In addition, tongue portion  852  of upper  820  in instep area  850  extends under lace  854  to enhance the comfort of article  800 . Lace  154  is illustrated with article  800  in  FIG. 8 , while in  FIGS. 9 through 11 , lace  154  may be omitted for purposes of clarity. In further configurations, upper  820  may include additional elements, such as (a) a heel counter in heel region  14  that enhances stability, (b) a toe guard in forefoot region  10  that is formed of a wear-resistant material, and (c) logos, trademarks, and placards with care instructions and material information. 
     In some embodiments, upper  820  may include one or more portions that include monofilament strands, as described above. In an exemplary embodiment, portions of upper  820  that include monofilament strands may be located in one or more monofilament areas  860 . In this embodiment, monofilament areas  860  may include two or more different types of monofilament areas. For example, in one embodiment, different monofilament areas may have different knit structures. In another embodiment, different monofilament areas may be formed using a combination of monofilament strands and natural or synthetic twisted fiber yarns. 
     As with monofilament areas  160 , described above, monofilament areas  860  may be located on various portions of upper  820 . In an exemplary embodiment, one or more monofilament areas  860  may be located on portions of article  800  where upper  820  will lay generally flat against a foot of a wearer disposed within upper  820 . In this embodiment, monofilament areas  860  include a medial monofilament portion  862  disposed on medial side  18  of upper  820  and a lateral monofilament portion  866  disposed on lateral side  16  of upper  820 . Medial monofilament portion  862  and lateral monofilament portion  866  may be generally located in midfoot region  12 . In some embodiments, monofilament areas  860  may further include a forefoot monofilament portion  864  and a heel monofilament portion  868 . Forefoot monofilament portion  864  is disposed forward of instep area  850  in forefoot region  10  of upper  820  and heel monofilament portion  868  is disposed in heel region  14 . In an exemplary embodiment, heel monofilament portion  868  may extend substantially continuously around heel region  14  of upper  820  between lateral side  16  and medial side  18 . 
     In some embodiments, monofilament areas  860  may be substantially continuous between each monofilament area  860  across upper  820 . For example, in one embodiment, medial monofilament portion  862  may be continuous with forefoot monofilament portion  864 , and lateral monofilament portion  866  may also be continuous with forefoot monofilament portion  864 . Similarly, lateral monofilament portion  866  may be continuous with heel monofilament portion  868  and medial monofilament portion  862  may also be continuous with at least a portion of heel monofilament portion  868 . With this configuration, monofilament areas  860  may form a substantially continuous zone extending across upper  820  from lateral side  16  across forefoot region  10  to medial side  18  in the front portion of article  100  and may also form a substantially continuous zone extending across upper  820  from lateral side across heel region  14  to medial side in the rear portion of article  100 . 
     In other embodiments, each monofilament area  860 , including medial monofilament portion  862 , forefoot monofilament portion  864 , lateral monofilament portion  866 , and/or heel monofilament portion  868  may be discontinuous with other monofilament areas  860  disposed on upper  820 . In embodiments where monofilament areas  860  are discontinuous, each monofilament area  860  may be entirely surrounded or circumscribed by the remaining portions of upper  820 . 
     Knitted component  830  shown in  FIGS. 8 through 16  may include additional structures or elements as compared with knitted component  130 , described above. In an exemplary embodiment, the primary elements of knitted component  830  are a knit element  831  and an inlaid tensile element  832 . Knit element  831  may be formed from at least one yarn that is manipulated (e.g., with a knitting machine) to form a plurality of intermeshed loops that define a variety of courses and wales. That is, knit element  831  has the structure of a knit textile. Inlaid tensile element  832  extends through knit element  831  and passes between the various loops within knit element  831 . Although inlaid tensile element  832  generally extends along courses within knit element  831 , inlaid tensile element  832  may also extend along wales within knit element  831 . Inlaid tensile element  832  may impart stretch-resistance and, when incorporated into article  800 , operates in connection with lace  154  to enhance the fit of article  800 . In an exemplary embodiment, inlaid tensile element  832  may pass through one or more portions of knit element  831 , including portions of one or more monofilament areas  860 . 
     In some embodiments, inlaid tensile element  832  may extend upwards through knit element  831  in a vertical direction from sole structure  110  towards instep area  850 . In an exemplary embodiment, portions of inlaid tensile element  832  may form a loop that serves as lace aperture  853  and then may extend downwards back in the vertical direction from instep area  850  towards sole structure  110 . In addition, when article  800  is provided with lace  154 , inlaid tensile element  832  may be tensioned when lace  154  is tightened, and inlaid tensile element  832  resists stretch in upper  820 . Moreover, inlaid tensile element  832  assists with securing upper  820  around the foot and operates in connection with lace  154  to enhance the fit of article  800 . In some embodiments, inlaid tensile element  832  may exit knit element  831  at one or more portions, including along medial and lateral sides of instep area  850  so as to be exposed on exterior surface  821  of upper  820 . 
     As described above with reference to knitted component  130 , knitted component  830  may similarly include yarns formed of different materials, including any of the suitable materials for forming a yarn described above. In some embodiments, knitted component  830  may further include non-fusible yarns and fusible yarns, as described above. When a fusible yarn is heated and fused to non-fusible yarns, this process may have the effect of stiffening or rigidifying the structure of knitted component  830 . Moreover, by joining (a) one portion of a non-fusible yarn to another portion of a non-fusible yarn, and/or (b) non-fusible yarn and inlaid tensile element  832  to each other has the effect of securing or locking the relative positions of non-fusible yarns and inlaid tensile element  832 , thereby imparting stretch-resistance and stiffness. That is, portions of non-fusible yarns may not slide relative to each other when fused with fusible yarns, thereby preventing warping or permanent stretching of knit element  831  due to relative movement of the knit structure. Additionally, inlaid tensile element  832  may not slide relative to knit element  831 , thereby preventing portions of inlaid tensile element  832  from pulling outward from knit element  831 . Accordingly, areas of knitted component  830  may be configured with both fusible and non-fusible yarns within knit element  831 . 
     In some embodiments, knitted component  830  may include knit element  831  with multiple knit layers. Knit layers associated with knitted component  830  may be partially co-extensive and overlapping portions of knit element  831  that include at least one common yarn or monofilament strand that passes back and forth between the knit layers so as to join and interlock the layers to each other. With this configuration, the knit layers together form a single knit textile formed of unitary knit construction. 
     In an exemplary embodiment, knit element  831  may include at least two knit layers interlocked with each other at one or more portions to form knitted component  830 . In one embodiment, a first knit layer may form a majority of a first side of knitted component  830  and a second knit layer may form a majority of a second side of knitted component  830 . In some embodiments, the first knit layer may be associated with a majority of exterior surface  821  and the second knit layer may be associated with a majority of interior surface  822 . In an exemplary embodiment, inlaid tensile element  832  may extend through portions of the first knit layer, the second knit layer, and/or through portions of knit element  831  between the first knit layer and the second knit layer. 
     In some embodiments, knitted component  830  may include one or more boundary zones, as described above with reference to knitted component  130 . Boundary zones define the portion of knitted component  830  where the yarn used to knit a portion of knitted component  830  transitions from one yarn type to another yarn type. For example, knitted component  830  may transition from a first type of yarn to a monofilament strand forming monofilament areas  860  at one or more boundary zones on upper  820 . Additionally, in embodiments where knitted component  830  may further have the configuration of multiple knit layers, boundary zones may transition yarn types at only one of the first knit layer and the second knit layer, or may transition yarn types at both the first knit layer and the second knit layer. That is, the boundary zone may apply at the level of individual knit layers of knit element  831 . 
     In an exemplary embodiment, the first type of yarn transitions from a natural or synthetic twisted fiber yarn to the monofilament strand at one or more boundary zones associated with each of monofilament areas  860 . In this embodiment, medial monofilament portion  862  includes a rear medial boundary  900  disposed along a portion of upper  820  on medial side  18  towards heel region  14  where at least one monofilament strand forming one knit layer of medial monofilament portion  862  transitions to the first type of yarn in at least one knit layer of knit element  831  used to form the remaining portions of knitted component  830 . Medial monofilament portion  862  may further include a top medial boundary  904  and a bottom medial boundary  906 . In one embodiment, top medial boundary  904  is located along medial side  18  of upper  820  and may be spaced apart from collar  823  and throat opening  840  by first distance D1 and bottom medial boundary  906  is also located along medial side  18  of upper  820  and may be spaced apart from sole structure  110  by second distance D2, described above. 
     In some embodiments, forward medial boundary  902  may define a forward location of medial monofilament portion  862  on upper  820 . In embodiments where monofilament areas  860  are substantially continuous, forward medial boundary  902  may simply transition into forefoot monofilament portion  864 . In embodiments where each monofilament area  860  is discontinuous, however, forward medial boundary  902  may define the transition from the monofilament strand back to the first yarn type for both knit layers forming knit element  831 . It should be understood that in such discontinuous embodiments, forefoot monofilament portion  864  will be defined by another boundary zone where the yarn again transitions back to the monofilament strand for forming at least one knit layer. 
     Continuing along upper  820 , forefoot monofilament portion  864  may include a rear forefoot boundary  908  and a forward forefoot boundary  909 . In one embodiment, rear forefoot boundary  908  may be located forward of instep area  850  and spaced apart by third distance D3 and forward forefoot boundary  909  may be located near a toe end of article  800  and be spaced apart by fourth distance D4, described above. In this embodiment, lateral monofilament portion  866  includes a rear lateral boundary  910  disposed on lateral side  16  of upper  820  towards heel region  14  at least one monofilament strand forming one knit layer of lateral monofilament portion  866  transitions to the first type of yarn in at least one knit layer of knit element  831  used to form the remaining portions of knitted component  830 . Lateral monofilament portion  866  may further include a top lateral boundary  914  and a bottom lateral boundary  916 . In one embodiment, top lateral boundary  914  is located along lateral side  16  of upper  820  and may be spaced apart from collar  823  and throat opening  840  by fifth distance D5 and bottom lateral boundary  916  may also be located along lateral side  16  of upper  820  and may be spaced apart from sole structure  110  by sixth distance D6, described above. 
     In some embodiments, a forward lateral boundary  912  may define a forward location of lateral monofilament portion  866  on upper  820 . Similar to forward medial boundary  902 , in embodiments where monofilament areas  860  are substantially continuous, forward lateral boundary  912  may simply transition into forefoot monofilament portion  864 . In embodiments where each monofilament area  860  is discontinuous, however, forward lateral boundary  912  may define the transition from the monofilament strand back to the first yarn type for both knit layers forming knit element  831 . It should be understood that in such discontinuous embodiments, forefoot monofilament portion  864  will be defined by another boundary zone where the yarn again transitions back to the monofilament strand for forming at least one knit layer. 
     In some embodiments, medial monofilament portion  862  and lateral monofilament portion  866  may have similar arrangements on each of medial side  18  and lateral side  16  so as to be approximately symmetric, as described in reference to knitted component  130  above. In these embodiments, first distance D1 and fifth distance D5 may be approximately equal. Similarly, in second distance D2 and sixth distance D6 may also be approximately equal. In other embodiments, however, each of medial side  18  and lateral side  16  may have monofilament areas  860  that are different between each side. Accordingly, in such other embodiments, each of first distance D1 and fifth distance D5 may be different and/or second distance D2 and sixth distance D6 may be different to locate medial monofilament portion  862  and lateral monofilament portion  866  farther or closer to collar  823  and/or sole structure  110 . In still other embodiments, only one of medial side  18  or lateral side  16  may include monofilament areas  860 . It should be understood that other configurations of monofilament areas  860  of varying size, shape, and/or location may be arranged according to the processes described herein. 
     Additionally, in an exemplary embodiment, knitted component  830  may further include boundary zones associated with heel monofilament portion  868 . In this embodiment, heel monofilament portion  868  may include a top heel boundary  920  and a bottom heel boundary  922 . Top heel boundary  920  may be spaced apart from collar  823  and throat opening  840  in heel region  14  of upper  820  and bottom heel boundary  922  may be spaced apart from sole structure  110 . In some embodiments, top heel boundary  920  may be spaced apart from collar  823  by a substantially similar distance as top medial boundary  904  and/or top lateral boundary  914  and bottom heel boundary  922  may be spaced apart from sole structure  110  by a substantially similar distance as bottom medial boundary  906  and/or bottom lateral boundary  916 . In other embodiments, the spacing of top heel boundary  920  and/or bottom heel boundary  922  may vary. 
     As described above, in some embodiments, knitted component  830  may include multiple types of monofilament areas  860  having different structures. For example, in an exemplary embodiment, monofilament areas  860  may include a first type of monofilament area formed from two knit layers knit with monofilament strands and a second type of monofilament area formed from two knit layers knit with a monofilament strand and natural or synthetic twisted fiber yarns. In an exemplary embodiment, monofilament areas  860  of the first type, i.e., two knit layers of monofilament strands, may be disposed along each of lateral side  16  and medial side  18 . In this embodiment, medial monofilament portion  862  and/or lateral monofilament portion  866  may be monofilament areas of the first type. That is, medial monofilament portion  862  and/or lateral monofilament portion  866  may include a first knit layer formed of a first monofilament strand and a second knit layer formed of a second monofilament strand. 
     In an exemplary embodiment, portions of knitted component  830  that are configured to rest against the toes and heel of a foot of a wearer when disposed within upper  820  may be configured with monofilament areas  860  of the second type, i.e., two knit layers having one knit layer formed of a monofilament strand and one knit layer formed of natural or synthetic twisted fiber yarns. In this embodiment, forefoot monofilament portion  864  and/or heel monofilament portion  868  may be monofilament areas of the second type. That is, forefoot monofilament portion  864  and/or heel monofilament portion  868  may include a first knit layer formed of a monofilament strand and a second knit layer formed of natural or synthetic twisted fiber yarns. 
     In an exemplary embodiment, the first knit layer formed of the monofilament strand in forefoot monofilament portion  864  and/or heel monofilament portion  868  may be associated with exterior surface  821  of upper  820  and the second knit layer formed of natural or synthetic twisted fiber yarns in forefoot monofilament portion  864  and/or heel monofilament portion  868  may be associated with interior surface  822  of upper  820 . For example, in one embodiment, the second knit layer associated with interior surface  822  may be made from a polyester yarn in forefoot monofilament portion  864  and/or heel monofilament portion  868 . With this configuration, the second knit layer of polyester yarn may provide a smooth and soft interior surface  822  for a foot of a wearer disposed within upper  820 . Additionally, the second knit layer may provide protection to the foot from sharp edges or bent portions of the first knit layer formed of the monofilament strand in forefoot monofilament portion  864  and/or heel monofilament portion  868 . 
     In another embodiment, the second knit layer associated with interior surface  822  may be made from a combination of polyester yarn and fusible yarn in forefoot monofilament portion  864  and/or heel monofilament portion  868 . With this configuration, the fusible yarn portion associated with the second knit layer may be configured to assist with setting forefoot monofilament portion  864  and/or heel monofilament portion  868  in place within knitted component  830  when heated, as described above. 
     By incorporating knitted component  830  with different types of monofilament areas  860  into upper  820  for article  800 , monofilament areas  860  may provide strength, stretch resistance, reduced weight, and/or assist with airflow through upper  820  to provide ventilation to the interior of article  800 , as described above. Additionally, by varying the two knit layer configuration of monofilament areas  860 , upper  820  may provide these features while also remaining comfortable to a foot of a wearer. Referring now to  FIGS. 12A through 12C , cross-sectional views of article  800  having upper  820  incorporating knitted component  830  with different types of monofilament areas  860  are illustrated. 
       FIG. 12A  shows a cross-section view of forefoot region  10  taken across upper  820 . In this embodiment, forefoot monofilament portion  864  is disposed along a top portion of upper  820 . In an exemplary embodiment, forefoot monofilament portion  864  may be a monofilament area  860  of the second type, described above. In this embodiment, forefoot monofilament portion  864  includes two knit layers, including a first knit layer formed by a monofilament strand that is associated with exterior surface  821  of knitted component  830  and a second knit layer formed by a natural or synthetic twisted fiber yarn that is associated with interior surface  822 . In some embodiments, the second knit layer of forefoot monofilament portion  864  may be made from the same yarn as the remaining portion of knit element  831  forming knitted component  830 . 
     With this configuration, when a foot of a wearer is disposed along a base portion  1200  of upper  820  within the interior of article  800 , air may circulate into and out of upper  820  to assist with providing ventilation to article  800  and forefoot monofilament portion  864  may include a softer knit layer along interior surface  822  to provide a comfortable feel to the foot. 
       FIG. 12B  shows a cross-section view of midfoot region  12  taken across upper  820 . In this embodiment, medial monofilament portion  862  and lateral monofilament portion  866  are disposed along each of medial side  18  and lateral side  16  of upper  820  in midfoot region  12 . In an exemplary embodiment, medial monofilament portion  862  and/or lateral monofilament portion  866  may be a monofilament area  860  of the first type, described above. In this embodiment, medial monofilament portion  862  and/or lateral monofilament portion  866  includes two knit layers, including a first knit layer formed by a first monofilament strand that is associated with exterior surface  821  of knitted component  830  and a second knit layer formed by a second monofilament strand that is associated with interior surface  822 . With this configuration, medial side  18  and lateral side  16  of upper  820  may have increased strength and resistance to stretch in these areas. 
       FIG. 12C  shows a cross-section view of heel region  14  taken across upper  820 . In this embodiment, heel monofilament portion  868  is disposed along lateral side  16  and medial side  18  of upper  820 . In an exemplary embodiment, heel monofilament portion  868  may be a monofilament area  860  of the second type, described above. In this embodiment, heel monofilament portion  868  may have a substantially similar structure as forefoot monofilament portion  864 , including a first knit layer formed by a monofilament strand that is associated with exterior surface  821  of knitted component  830  and a second knit layer formed by a natural or synthetic twisted fiber yarn that is associated with interior surface  822 . In some embodiments, the second knit layer of heel monofilament portion  868  may be made from the same yarn as the remaining portion of knit element  831  forming knitted component  830 . 
     Additionally, in this embodiment, portions of inlaid tensile element  832  are shown extending through portions of knitted component  830 , including knit element  831 , as well as through monofilament areas  860 , for example, heel monofilament portion  868 . 
     Referring now to  FIGS. 13 and 14 , an exemplary embodiment of knitted component  830  is shown in a planar or flat configuration. As described above, knitted component  830  includes knit element  831  and inlaid tensile element  832 . In this embodiment, knitted component  830  may have an oblong offset configuration that is outlined by a top forefoot perimeter edge  1300 , a top side perimeter edge  1302 , a pair of heel edges, including a medial heel edge  1304  and a lateral heel edge  1314 , a bottom side perimeter edge  1312 , and a bottom forefoot perimeter edge  1310 . In addition, knit element  831  has a first side forming a portion of exterior surface  821  of upper  820  and an opposite second side that may form a portion of interior surface  822  of upper  820 , thereby defining at least a portion of the void within upper  820 . In many configurations, inlaid tensile element  832  may extend through portions of knit element  831 , including portions of monofilament areas  860 , between the first side and the second side of knit element  831 . 
     As shown in  FIGS. 13 and 14 , inlaid tensile element  832  repeatedly extends from top side perimeter edge  1302  toward instep area  850 , where a portion of inlaid tensile element  832  forms a loop to serve as lace aperture  853 , and back to top side perimeter edge  1302 . Inlaid tensile element  832  may follow a similar path on the opposite side of knitted component  830 . In this embodiment, inlaid tensile element  832  repeatedly extends from bottom side perimeter edge  1312  toward instep area  850 , where a portion of inlaid tensile element  832  forms a loop to serve as lace aperture  853 , and back to bottom side perimeter edge  1312 . In some embodiments, portions of inlaid tensile element  832  may angle rearwards and extend to medial heel edge  1304  and/or lateral heel edge  1314 . Additionally, inlaid tensile element  832  may pass through one or more monofilament areas  860  of knitted component  830 , including portions of medial monofilament portion  862  and/or lateral monofilament portion  866 , as inlaid tensile element  832  extends towards or away from top side perimeter edge  1302  and/or bottom side perimeter edge  1312 . Similarly, inlaid tensile element  832  may also pass through portions of forefoot monofilament portion  864  and/or heel monofilament portion  868  as inlaid tensile element  832  extends towards or away from medial heel edge  1304  and/or lateral heel edge  1314 . 
     In comparison with knit element  831 , inlaid tensile element  832  may exhibit greater stretch-resistance. That is, inlaid tensile element  832  may stretch less than knit element  831 . Given that numerous sections of inlaid tensile element  832  extend through knit element  831 , inlaid tensile element  832  may impart stretch-resistance to portions of upper  820  between instep area  850  and a lower area adjacent to sole structure  110 . Moreover, placing tension upon lace  154  may impart tension to inlaid tensile element  832 , thereby inducing the portions of upper  820  between instep area  850  and the lower area to lay against the foot. Additionally, given that numerous sections of inlaid tensile element  832  extend toward medial heel edge  1304  and/or lateral heel edge  1314 , inlaid tensile element  832  may impart stretch-resistance to portions of upper  820  in heel region  14 . Moreover, placing tension upon lace  154  may induce the portions of upper  820  in heel region  14  to lay against the foot. For example, inlaid tensile element  832  may assist with locating monofilament areas  860  along lateral side  16  and medial side  18  of upper  820  to lay flat against a foot of a wearer. As such, inlaid tensile element  832  operates in connection with lace  154  to enhance the fit of article  800 . 
     Knit element  831  may incorporate any of the various types of yarn discussed above for knitted component  130 . In some embodiments, the configuration of inlaid tensile element  832  may vary significantly. In addition to yarn, inlaid tensile element  832  may have the configurations of a filament (e.g., a monofilament), thread, rope, webbing, cable, or chain, for example. In comparison with the yarns forming knit element  831 , the thickness of inlaid tensile element  832  may be greater. In some configurations, inlaid tensile element  832  may have a significantly greater thickness than the yarns of knit element  831 . Although the cross-sectional shape of inlaid tensile element  832  may be round, triangular, square, rectangular, elliptical, or irregular shapes may also be utilized. Moreover, the materials forming inlaid tensile element  832  may include any of the materials for the yarn within knit element  831 , such as cotton, elastane, polyester, rayon, wool, and nylon. As noted above, inlaid tensile element  832  may exhibit greater stretch-resistance than knit element  831 . As such, suitable materials for inlaid tensile element  832  may include a variety of engineering filaments that are utilized for high tensile strength applications, including glass, aramids (e.g., para-aramid and meta-aramid), ultra-high molecular weight polyethylene, and liquid crystal polymer. As another example, a braided polyester thread may also be utilized as inlaid tensile element  832 . 
     U.S. Patent Application Publication 2012/0233882 to Huffa, et al., the disclosure of which is incorporated herein in its entirety, provides a discussion of the manner in which a knitted component (e.g., knitted component  130 ,  830 ) may be formed, including the process of inlaying or otherwise locating inlaid tensile element within a knit element. 
     In an exemplary embodiment, one or more of the perimeter edges of knitted component  830  may be joined to form upper  820 . In this embodiment, knitted component  830  may be folded at a folding point  1306  between top forefoot perimeter edge  1300  and bottom forefoot perimeter edge  1310  to place top forefoot perimeter edge  1300  and bottom forefoot perimeter edge  1310  in contact with each other. Similarly, top side perimeter edge  1302  may be placed in contact with bottom side perimeter edge  1312  and pair of heel edges, medial heel edge  1304  and lateral heel edge  1314 , may be placed in contact with each other. In an exemplary embodiment, medial heel edge  1304  and lateral heel edge  1314  may be joined along seam  829  disposed along medial side  18  of upper  820  in heel region  14 . In addition, seam  829  may further extend along and connect each of top forefoot perimeter edge  1300  and bottom forefoot perimeter edge  1310  and top side perimeter edge  1302  and bottom side perimeter edge  1312  to form upper  820 . 
     Referring now to  FIG. 14 , enlarged views of portions of knitted component, including knit element  831  and different types of monofilament areas  860 , are illustrated to show the unitary knit construction of knitted component  830 . As described above, monofilament areas  860  of knitted component  830  may include multiple types of monofilament areas  860  having different structures. For example, in an exemplary embodiment, monofilament areas  860  may include a first type of monofilament area formed from two knit layers knit with monofilament strands and a second type of monofilament area formed from two knit layers knit with a monofilament strand and natural or synthetic twisted fiber yarns. In this embodiment, medial monofilament portion  862  and/or lateral monofilament portion  866  may be monofilament areas of the first type. That is, medial monofilament portion  862  and/or lateral monofilament portion  866  may include a first knit layer formed of a first monofilament strand  1400  and a second knit layer formed of a second monofilament strand  1401 . Thus, as may be seen in  FIG. 15B , monofilament areas  860  of this first type include knit layers formed of monofilament strands on both exterior surface  821  and interior surface  822  of upper  820 . 
     In this embodiment, forefoot monofilament portion  864  and/or heel monofilament portion  868  may be monofilament areas of the second type. That is, forefoot monofilament portion  864  and/or heel monofilament portion  868  may include a first knit layer formed of monofilament strand  1400  and a second knit layer formed of a natural or synthetic twisted fiber yarn  1403 . In an exemplary embodiment, as may be seen in  FIG. 15A , the first knit layer formed of monofilament strand  1400  may be associated with exterior surface  821  of knitted component  830  and the second knit layer formed of natural or synthetic twisted fiber yarn  1403  may be associated with interior surface  822 . 
     Additionally, in embodiments where inlaid tensile element  832  extends through portions of knitted component  830  that include monofilament areas  860 , inlaid tensile element  832  may be located between exterior surface  821  and interior surface  822  of upper  820 . As shown in  FIG. 15C , inlaid tensile element  832  extends through heel monofilament portion  868  between the first knit layer formed of monofilament strand associated with exterior surface  821  and the second knit layer formed of natural or synthetic twisted fiber yarn associated with interior surface  822 . In some configurations, portions of inlaid tensile element  832  may be visible through one or both of surfaces. In other embodiment, portions of inlaid tensile element  832  may lay against one of exterior surface  821  and/or interior surface  822 , or knit element  831  may form indentations or apertures through which inlaid tensile element  832  passes. 
     In the remaining portions of knitted component  830  not including monofilament areas  860 , knit element  831  may have a similar two knit layer structure. For example, as shown in  FIG. 14 , a portion of knit element  831  may include a first knit layer formed of a first natural or synthetic twisted fiber yarn  1402  and a second knit layer formed of a second natural or synthetic twisted fiber yarn  1403 . In an exemplary embodiment, the first knit layer formed of first natural or synthetic twisted fiber yarn  1402  may be associated with exterior surface  821  of knitted component  830  and the second knit layer formed of second natural or synthetic twisted fiber yarn  1403  may be associated with interior surface  822 . In an exemplary embodiment, the same second natural or synthetic twisted fiber yarn  1403  may be used to knit monofilament areas  860  of the second type and the remaining portions of knitted component  830  that also include second natural or synthetic twisted fiber yarn  1403 . 
     By forming knitted component  830  with monofilament areas  860  of unitary knit construction, monofilament areas  860  may be surrounded or circumscribed by the remaining portions of knitted component  830  so as to place monofilament areas  860  under tension, as described above with reference to knitted component  130 . With this configuration, the tensioning force applied on monofilament areas  860  by the surrounding portion of knitted component  830  may assist with preventing or reducing kinks or sharp bends in monofilament strands in monofilament areas  860  that may produce an uncomfortable feeling to a foot of a wearer. 
     Referring now to  FIG. 16A , a portion of knitted component  830  that includes medial monofilament portion  862  is illustrated. In this embodiment, inlaid tensile element  832  extends through knit element  831  and medial monofilament portion  862 . In an exemplary embodiment, the portion of knitted component  830  at bottom medial boundary  906  may transition from monofilament strand  1400  forming medial monofilament portion  862  to natural or synthetic twisted fiber yarn  1402  forming the remaining portion of knit element  831 , as described above. As shown in the enlarged view of  FIG. 16A , a first course  1600  of knitted component  830  and a fourth course  1606  of knitted component  830  transition from monofilament strand  1400  forming medial monofilament portion  862  to natural or synthetic twisted fiber yarn  1402  at bottom medial boundary  906 . In one embodiment, a second course  1602  and a third course  1604  of knitted component  830  also include inlaid tensile element  832 . In this embodiment, second course  1602  and third course  1604  also transition from monofilament strand  1400  to natural or synthetic twisted fiber yarn  1402 , or another different type of yarn, at bottom medial boundary  906 , as with first course  1600  and fourth course  1606 . 
     In an exemplary embodiment, second course  1602  and third course  1604  may correspond with inlaid tensile element  832  as inlaid tensile element  832  extends through knit element  831 . With this configuration, inlaid tensile element  832  may extend through monofilament strand  1400  in medial monofilament portion  862 , and continue extending through natural or synthetic twisted fiber yarn  1402  in the remaining portion of knit element  831 . Accordingly, natural or synthetic twisted fiber yarn  1402  may substantially surround portions of inlaid tensile element  832  as it extends through the remaining portions of knit element  831  outside of medial monofilament portion  862 . With this configuration, inlaid tensile element  832  may be hidden from view on exterior surface  821  of knitted component  830  outside of monofilament areas  860 . 
     In other embodiments, one or more courses of knitted component  830  that include a monofilament strand may extend along through the remaining portions of knit element  831  beyond monofilament areas  860 . Referring now to  FIG. 16B , an optional configuration for a portion of knitted component  830  that includes medial monofilament portion  862  is illustrated. As with  FIG. 16A , inlaid tensile element  832  extends through knit element  831  and medial monofilament portion  862 . In this embodiment, however, one or more courses formed by a monofilament strand, for example monofilament strand  1400 , described above, may further extend through knit element  831  outside of medial monofilament portion  862  together with inlaid tensile element  832 . 
     In an exemplary embodiment, the portion of knitted component  830  at bottom medial boundary  906  may transition from monofilament strand  1400  forming medial monofilament portion  862  to natural or synthetic twisted fiber yarn  1402  forming the remaining portion of knit element  831 , as described above. As shown in the enlarged view of  FIG. 16B , a first course  1600  of knitted component  830  and a fourth course  1606  of knitted component  830  transition from monofilament strand  1400  forming medial monofilament portion  862  to natural or synthetic twisted fiber yarn  1402  at bottom medial boundary  906 . In one embodiment, a second course  1602  and a third course  1604  of knitted component  830  do not transition from monofilament strand  1400  to natural or synthetic twisted fiber yarn  1402 , or another different type of yarn, at bottom medial boundary  906 . Instead, second course  1602  and third course  1604  continue in a substantially continuous manner to be formed with the same monofilament strand  1400  forming medial monofilament portion  862 . 
     In this embodiment, second course  1602  and third course  1604  knit with monofilament strand  1400  may correspond with inlaid tensile element  832  as inlaid tensile element  832  extends through knit element  831 . With this configuration, inlaid tensile element  832  may extend through monofilament strand  1400  in medial monofilament portion  862 , as well as through the remaining portion of knit element  831 . Accordingly, monofilament strand  1400  may substantially surround portions of inlaid tensile element  832  as it extends through the remaining portions of knit element  831  outside of medial monofilament portion  862 . In other embodiments, one or more courses of monofilament strands may extend outside of each monofilament areas  860 , including medial monofilament portion  862 , forefoot monofilament portion  864 , lateral monofilament portion  866 , and/or heel monofilament portion  868 , to follow and correspond with the path of inlaid tensile element  832  throughout knitted component  830 . By enclosing or surrounding inlaid tensile element  832  with monofilament strand  1400 , additional strength and support may be provided to inlaid tensile element  832 . 
     In some embodiments, monofilament areas  860  of the second type, i.e., two knit layers having one knit layer formed of a monofilament strand and one knit layer formed of natural or synthetic twisted fiber yarns, may be knit with a knit structure that forms plurality of indentations during the knitting process in the knit layer formed of natural or synthetic twisted fiber yarns. Such a configuration may further provide ventilation to the interior of upper  820  while still providing a comfortable feel to a foot of a wearer along interior surface  822 . 
     A suitable knit structure for forming monofilament areas  860  of the second type includes a 1×1 inverted mock mesh knit structure or 2×2 inverted mock mesh structure. In contrast with a mesh knit structure, which may be used to form apertures that extend fully through a knit element, including both a first knit layer and a second knit layer, an inverted mock mesh knit structure forms indentations in second knit layer, i.e., the layer associated with interior surface  822  of upper  820 . An exemplary embodiment of a looping diagram  1700  for knitting an inverted 2×2 mock mesh structure is illustrated. In this embodiment, looping diagram  1700  illustrates the sequence of stitches and movements performed by a knitting machine, for example, a flat-knitting machine, to form an inverted 2×2 mock mesh structure making up a portion of monofilament areas  860  of the second type. As shown in  FIG. 17 , the spaced apart dots represent the needles of a knitting machine and the illustrated steps represent the direction of movement of a yarn or strand between the needles of each of a front bed and a back bed of a knitting machine. 
     As shown in  FIG. 17 , monofilament strand  1400  may be used to knit the first knit layer of monofilament area  860  that is associated with exterior surface  821  of upper  820 , while natural or synthetic twisted fiber yarn  1403  may be used to knit the second knit layer of monofilament area  860  that is associated with interior surface  822  of upper  820 . In contrast to the first knit layer, the second knit layer includes a number of tuck stitches performed with or natural or synthetic twisted fiber yarn  1403 . In this embodiment, the width or gap in second knit layer is associated with 2 needles to form the inverted 2×2 mock mesh structure. For example, such an inverted 2×2 mock mesh structure may be used to form one or more of forefoot monofilament portion  864  and/or heel monofilament portion  868 , described above. In other embodiments, however, a larger or smaller knit structure may be provided by making the gap associated with a larger or smaller number of needles. For example, an inverted 3×3 mock mesh structure may be formed by increasing the gap to 3 needles and an inverted 1×1 mock mesh structure may be formed by decreasing the gap to a single needle. 
       FIG. 17  illustrates one exemplary embodiment of a knit structure that may be used with knitted component  830  to form a portion of monofilament areas  860 . Mesh knit structures, mock mesh knit structures, and other suitable knit structures with accompanying loop diagrams for knitting such knit structures for use in the present embodiments are described in U.S. Patent Application Publication 2012/0233882 to Huffa et al., which was referenced above and incorporated herein. 
     While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.