Patent Description:
An article of footwear typically includes a sole structure configured to be located under a wearer's foot to space the foot away from the ground. Sole structures in athletic footwear are typically configured to provide cushioning, motion control, and/or resilience.

Document <CIT> discloses a fluid-filled bladder formed of four superposed sheets.

The present disclosure relates to a sole structure for an article of footwear according to the independent claim <NUM>; additional features of the sole structure are disclosed by the dependent claims.

Referring to the drawings, wherein like reference numbers refer to like components throughout the views, <FIG> shows a sole structure <NUM> for an article of footwear. Only a portion of the sole structure <NUM> is shown. More specifically, a midsole <NUM> of the sole structure <NUM> is shown. The midsole <NUM> includes a bladder system <NUM>. The bladder system <NUM> shown is referred to as a full-length bladder system as it includes a forefoot region <NUM>, a midfoot region <NUM>, and a heel region <NUM>. The midfoot region <NUM> is between the heel region <NUM> and the forefoot region <NUM>. As is understood by those skilled in the art, the forefoot region <NUM> generally underlies the toes and metatarsal-phalangeal joints of an overlying foot. The midfoot region <NUM> generally underlies the arch region of the foot. The heel region <NUM> generally underlies the calcaneus bone. The bladder system <NUM> has a medial side <NUM> generally shaped to follow the medial side of an overlying foot, and a lateral side <NUM> generally shaped to follow the lateral side of an overlying foot.

Other components may be used in conjunction with the bladder system <NUM> to complete the midsole <NUM> and the sole structure <NUM>. For example, in some embodiments, other components of the sole structure <NUM> may be secured to the bladder system <NUM>. For example, an outsole or outsole components may be secured at a ground-facing surface, or a foam midsole layer may be secured at the ground-facing surface. Additionally or as an alternative, a foam midsole layer may be secured at a foot-facing surface <NUM>. For example, different foam midsole layers may be secured at both the foot-facing surface <NUM> and the ground-facing surface. Additionally, a footwear upper may be secured to the bladder system <NUM> at the foot-facing surface <NUM> and/or at side surfaces formed by the inflated top and bottom sheets at an outer perimeter <NUM> of the bladder system <NUM>.

The bladder system <NUM> includes four stacked polymeric sheets bonded together at a peripheral flange <NUM> as described herein. The peripheral flange <NUM> may extend entirely around an outer perimeter <NUM> of the bladder system <NUM>, and the four stacked polymeric sheets may be coextensive, each extending to the peripheral flange <NUM> and having an outer perimeter <NUM> at the peripheral flange <NUM>.

Only a first sheet <NUM> is visible in <FIG>. The first sheet <NUM> may also be referred to as an upper sheet. The upper sheet <NUM> includes and establishes a foot-facing surface <NUM> of the bladder system <NUM>. The four stacked sheets are best shown in <FIG>, which shows that the bladder system <NUM> also includes two middle sheets, referred to as a second sheet <NUM> and a third sheet <NUM>, as well as a fourth sheet <NUM>, referred to as a lower sheet or as a bottom sheet. The fourth sheet <NUM> includes and establishes a ground-facing surface <NUM> of the bladder system <NUM>. A first sealed chamber <NUM> is enclosed by the first sheet <NUM> and the second sheet <NUM>. The first sealed chamber <NUM> retains fluid as a first cushioning layer. The first sealed chamber <NUM> extends over the forefoot region <NUM>, the midfoot region <NUM>, and the heel region <NUM>. The first sealed chamber <NUM> is the only sealed chamber of the bladder system <NUM> that is disposed at and defines the foot-facing surface <NUM>. A foot supported on the bladder system <NUM> therefor has the first sealed chamber <NUM> underlying the expanse of the foot in each of the forefoot region <NUM>, the midfoot region <NUM>, and the heel region <NUM>. The inflation pressure of the first sealed chamber <NUM> significantly impacts a wearer's perception of the stiffness of the bladder system <NUM> as the first sealed chamber <NUM> is closer to the foot than any of the other sealed chambers formed by the bladder system <NUM> and described herein.

The upper sheet <NUM> is bonded to the second sheet <NUM> at a plurality of dot bonds <NUM> spaced apart from one another in the forefoot region <NUM>, the midfoot region <NUM>, and the heel region <NUM>. The dot bonds <NUM> are shown as small circles, but may be other closed shapes instead, such as a square or a triangle. The dot bonds <NUM> are evenly spaced apart from one another in rows. The dot bonds <NUM> in adjacent rows may be offset from one another. In <FIG>, the evenly spaced pattern of the dot bonds <NUM> is somewhat obscured by slight waviness of the upper sheet <NUM> caused by the various inflation pressures of the underlying discrete chambers described herein. However, the dot bonds <NUM> are formed at evenly spaced circular areas not covered by blocker ink in a pattern of printed blocker ink applied to the bottom surface of the upper sheet <NUM> and a pattern of printed blocker ink applied to the upper surface of the second sheet <NUM>. The foot-facing surface <NUM> also has a plurality of dimples <NUM> at the plurality of dot bonds <NUM>. Each dot bond <NUM> causes the first sheet <NUM> to recess toward the dot bond <NUM>, creating a dimple <NUM>. A corresponding dimple is created in the second sheet <NUM> around where it is restrained at the bond <NUM>. Only some of the dimples <NUM> and dot bonds <NUM> are indicated with reference numbers in <FIG>. The dot bonds <NUM> act to limit the overall distance between the sheets <NUM>, <NUM> when the first sealed chamber <NUM> is inflated, limiting the height of the first sealed chamber <NUM>. The first sealed chamber <NUM> surrounds each of the dot bonds <NUM> between the first sheet <NUM> and the second sheet <NUM>, and communicates around the bonds <NUM>. During a forward foot roll in which dynamic loading begins at the heel region <NUM> and moves forward, gas in the first sealed chamber <NUM> is more easily displaced from rear to front, freely moving in the first sealed chamber <NUM> around the bonds <NUM>. The cushioning response of the bladder system <NUM> is therefore staged not only in relation to absorption of a vertical impact force by the bladder system <NUM> by sealed chambers working in stages as described herein, but also in relation to the forward roll of the foot from heel to toe.

<FIG> show that multiple discreet chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are disposed on a first side <NUM> of the first sealed chamber <NUM>, between the ground-facing surface <NUM> and the first sealed chamber <NUM>. Accordingly, the first sealed chamber <NUM> is disposed between the foot-facing surface <NUM> and the multiple discreet chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. With reference to <FIG>, multiple discreet chambers <NUM>, <NUM>, <NUM> and <NUM> are enclosed between and bounded by the third sheet <NUM> and the fourth sheet <NUM>. These chambers are fluidly isolated from one another by bonds <NUM> of the third sheet <NUM> to the fourth sheet <NUM> that separate the chambers. Two additional discreet chambers <NUM> and <NUM> are disposed between the second sheet <NUM> and the third sheet <NUM>. The chambers <NUM> and <NUM> are isolated from one another by bonds <NUM> of the second sheet <NUM> to the third sheet <NUM>.

The multiple discreet sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> retain fluid in isolation from one another, and each is also fluidly isolated from the first sealed chamber <NUM>. The multiple discreet chambers include a peripheral heel chamber <NUM> in the heel region <NUM>, a central heel chamber <NUM> in the heel region <NUM>, a peripheral lateral chamber <NUM> in the forefoot region <NUM>, and a medial forefoot chamber <NUM> in the forefoot region <NUM>. Additionally, the discreet chamber <NUM> underlies the entire first sealed chamber <NUM> except where the peripheral lateral chamber <NUM> extends along the lateral side <NUM>. The second sheet <NUM> may be bonded to the third sheet <NUM> at dot bonds <NUM>, similar to dot bonds <NUM>. The chamber <NUM> surrounds and is in fluid communication around the dot bonds <NUM>.

Each of the discreet chambers <NUM>, <NUM>, <NUM>, <NUM> and <NUM> is at least partially formed by the fourth sheet <NUM> and therefore is at the inner surface of the fourth sheet <NUM>, and influences the shape of the ground-facing surface <NUM>. An outer boundary of each of the discreet chambers <NUM>, <NUM>, <NUM>, <NUM> and <NUM> is schematically represented with dashed lines in <FIG> to illustrate the fluid isolation of each of the chambers <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. The boundary A is the boundary of the peripheral heel chamber <NUM>. The boundary B is the boundary of the central heel chamber <NUM>. The boundary C is the boundary of the peripheral lateral chamber <NUM>. The boundary D is the boundary of the medial forefoot chamber <NUM>. The ring-shaped boundaries E bound annular ring portions of a discreet chamber <NUM>. The annular ring portions may be in fluid communication with one another by connecting channels, or may be fluidly isolated from one another by bonds of the third sheet <NUM> to the fourth sheet <NUM> between the annular portions.

The first sealed chamber <NUM> underlies the entire expanse shown in the bottom perspective view of <FIG>, including underlying the discreet chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> and each of the areas bounded by the dashed line boundaries A, B, C, D, and E in <FIG> (and overlies these same areas when the bladder system <NUM> is not inverted as it is in <FIG>). The first sealed chamber <NUM> is indicated in <FIG> with reference lines in only some areas. Similarly, the discreet chamber <NUM> underlies the discreet chambers <NUM>, <NUM>, <NUM>, and <NUM> and each of the areas bounded by the dashed line boundaries A, B, and D in <FIG> (and overlies these same areas when the bladder system <NUM> is not inverted as it is in <FIG>), but is indicated in <FIG> with reference lines in only some areas Because the sheets <NUM>, <NUM>, <NUM>, and <NUM> may be transparent, some of the dot bonds <NUM> are indicated in <FIG>.

The bladder system <NUM> has protruding, domed pods <NUM> extending at the ground-facing surface <NUM> due to the shapes of the various sealed chambers, and sub-chambers within the sealed chambers. Each of the domed pods <NUM> is a portion of the fourth sheet <NUM> (e.g., the bottom sheet) where it forms a domed protrusion. For example, the peripheral heel chamber <NUM>, the central heel chamber <NUM>, the peripheral lateral chamber <NUM> in the forefoot region <NUM>, and the medial forefoot chamber <NUM> in the forefoot region <NUM> each include multiple fluidly-connected sub-chambers corresponding with the domed pods.

The peripheral heel chamber <NUM> has an arcuate portion <NUM> disposed at a rear of the heel region <NUM>, a lateral arm portion <NUM> extending forward from the arcuate portion <NUM> along the lateral side <NUM> of the bladder system <NUM> in the heel region <NUM>, and a medial arm portion <NUM> extending forward from the arcuate portion <NUM> along the medial side <NUM> of the bladder system <NUM> in the heel region <NUM>. The medial arm portion <NUM> is spaced apart from the lateral arm portion <NUM>, and the central heel chamber <NUM> is disposed between the arm portions <NUM>, <NUM>, and forward of the arcuate portion <NUM> of the peripheral heel chamber <NUM>.

The peripheral heel chamber <NUM> includes multiple fluidly-connected sub-chambers 42A, 42B, 42C, 42D, 42E, 42F, and <NUM>. Sub-chamber 42A is in the arcuate portion <NUM>, sub-chambers 42B, 42C, and 42D are in the medial arm portion <NUM>, and sub-chambers 42E, 42F, and <NUM> are in the lateral arm portion <NUM>. Bonds <NUM> between the third sheet <NUM> and the fourth sheet <NUM> narrow the peripheral heel chamber <NUM>, partially dividing it into the sub-chambers. However, the bonds <NUM> do not completely close the peripheral heel chamber <NUM> between adjacent sub-chambers, and all of the sub-chambers 42A, 42B, 42C, 42D, 42E, 42F, and <NUM> are in fluid communication with one another.

The central heel chamber <NUM> includes multiple fluidly-connected sub-chambers 44A, 44B, and 44C each corresponding with a domed pod <NUM> that extends at the ground-facing surface <NUM> of the bladder system <NUM>. The multiple fluidly-connected sub-chambers 44A, 44B, and 44C and the domed pods <NUM> that they correspond with are disposed in a longitudinally-extending row between the medial arm portion <NUM> and the lateral arm portion <NUM>. A bond <NUM> between the third sheet <NUM> and the fourth sheet <NUM> separates the peripheral heel chamber <NUM> from the central heel chamber <NUM>, and partially divides it into the sub-chambers 44A, 44B, and 44C. However, the bond <NUM> does not completely close the central heel chamber <NUM> between adjacent ones of the sub-chambers 44A, 44B, and 44C, and all of the sub-chambers 44A, 44B, and 44C are in fluid communication with one another. Some other areas where the third sheet <NUM> is bonded to the fourth sheet <NUM> are shown with reference numeral <NUM> in <FIG>, and may represent the same continuous bond <NUM> or different bonds <NUM> of the third sheet <NUM> to the fourth sheet <NUM>.

The peripheral lateral chamber <NUM> extends along the lateral side <NUM> of the bladder system <NUM> in the forefoot region <NUM> and is disposed entirely between a longitudinal midline LM of the bladder system <NUM> and the lateral side <NUM> of the bladder system <NUM>. The peripheral lateral chamber <NUM> includes multiple fluidly-connected sub-chambers 46A, 46B, 46C, 46D, and 46E corresponding with domed pods <NUM> disposed in a longitudinally-extending row along the lateral side <NUM> of the ground-facing surface <NUM> in the forefoot region <NUM>. Rather than being separated by bonds, these sub-chambers 46A, 46B, 46C, 46D, and 46E are each disposed inward of and surrounded by a different one of the annular ring portions of the sub-chamber <NUM>.

The medial forefoot chamber <NUM> is disposed along the medial side <NUM> of the bladder system <NUM> in the forefoot region <NUM> and extends over the longitudinal midline LM. The bonds <NUM> between the third sheet <NUM> and the fourth sheet <NUM> partially divide the medial forefoot chamber <NUM> into sub-chambers 48A, 48B, 48C, 48D, 48E, 48F, <NUM>, <NUM>, 48I, and <NUM>. Domed pods <NUM> correspond with the sub-chambers 48A, 48B, 48C, 48D, 48E, 48F, <NUM>, <NUM>, 48I, and <NUM>. However, the bond <NUM> does not completely close the medial forefoot chamber <NUM> between adjacent ones of the sub-chambers 48A, 48B, 48C, 48D, 48E, 48F, <NUM>, <NUM>, 48I, and <NUM>, and all of the sub-chambers 48A, 48B, 48C, 48D, 48E, 48F, <NUM>, <NUM>, 48I, and <NUM> are in fluid communication with one another.

As shown, there are six domed pods <NUM> at the peripheral heel chamber <NUM>, three domed pods at the central heel chamber <NUM>, five domed pods <NUM> at the peripheral lateral chamber <NUM>, and ten domed pods <NUM> at the medial forefoot chamber <NUM>. As is evident in <FIG>, the domed pods <NUM> are not all of the same shape or size, and at least some of the domed pods <NUM> have different internal volumes. The different shapes and internal volumes of the domed pods <NUM> affect the cushioning provided during dynamic loading to the portions of the foot that they underlie.

The isolation of the discreet sealed chambers allows for different inflation pressures to effect different cushioning responses. For example, an inflation pressure of gas retained in the peripheral lateral chamber <NUM> may be greater than an inflation pressure of gas retained in the medial forefoot chamber <NUM>. Moreover, the inflation pressure of gas retained in the peripheral lateral chamber <NUM> may also be greater than an inflation pressure of gas retained in the peripheral heel chamber <NUM>, and greater than an inflation pressure of gas retained in the central heel chamber <NUM>. In one example, an inflation pressure of gas retained in the peripheral lateral chamber <NUM> is greater than an inflation pressure of gas retained in the peripheral heel chamber <NUM>, while the inflation pressure of gas retained in the peripheral heel chamber <NUM> is greater than an inflation pressure of gas retained in the central heel chamber <NUM>, and the inflation pressure of gas retained in the central heel chamber <NUM> is greater than an inflation pressure of gas retained in the medial forefoot chamber <NUM>. The first sealed chamber <NUM> may have a greater or lesser inflation pressure than one or more of the underlying sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and the sealed chamber <NUM> may have a greater or lesser inflation pressure than one or more of the other sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In other examples, different relative inflation pressures may be provided. Some of the discreet chambers may have the same inflation pressure, and/or at least some of the discreet chambers may be at ambient pressure when in an unloaded state.

<FIG> is a medial side view of the bladder system <NUM> that illustrates some of the many domed pods <NUM> descending and protruding at the ground-facing surface <NUM>, in contrast to the relatively flat foot-facing surface <NUM> provided due to the full-length sealed chamber <NUM> with a large number of small, spaced bonds <NUM> in a repeating pattern. There is an outer peripheral portion of the first sheet <NUM> to which the pattern of bonds <NUM> does not extend (e.g., the dot bonds <NUM> are somewhat inward of the peripheral flange <NUM>). The outer peripheral portion without bonds <NUM> forms a portion of a side wall <NUM> when the chambers of the bladder system <NUM> are inflated, and the bonds <NUM> are not visible in the side view of <FIG>.

<FIG> shows that the multiple stacked polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are coextensive, each having an outer perimeter <NUM> at the peripheral flange <NUM>. Each of the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> extends from the forefoot region <NUM> to the heel region <NUM>, and from the medial side <NUM> to the lateral side <NUM>. Stated differently, there are only four polymeric sheets used to construct the bladder system <NUM>, and each sheet extends the width and length of the bladder system <NUM>.

The cross-sectional view of <FIG> shows that the first sealed chamber <NUM> is disposed between the foot-facing surface <NUM> and the multiple discreet chambers (only discrete chambers <NUM>, <NUM>, <NUM>, and <NUM> visible in <FIG>). Likewise, the multiple discreet chambers <NUM>, <NUM>, <NUM>, and <NUM> are disposed between the ground-facing surface <NUM> and the first sealed chamber <NUM>. The cross-sectional view of <FIG> shows that the first sealed chamber <NUM> is disposed between the foot-facing surface <NUM> and the discreet chambers <NUM>, <NUM>, and <NUM> (discreet chambers <NUM> and <NUM> not visible in <FIG>). Different bonds between the stacked sheets are illustrated in <FIG>, including the dot bonds <NUM> bonding the first sheet <NUM> to the second sheet <NUM>, the dot bonds <NUM> bonding the second sheet <NUM> to the third sheet <NUM>, bonds <NUM> bonding the third sheet <NUM> to the fourth sheet <NUM>, and bonds between adjacent ones of the stacked sheets <NUM>, <NUM>, <NUM>, <NUM> at the peripheral flange <NUM>. The dot bonds <NUM> are inward of the peripheral flange <NUM> and bond the lower surface of the first sheet <NUM> to the upper surface of the second sheet <NUM>.

Selection of the shape, size, and location of the various bonds between the sheets <NUM>, <NUM>, <NUM>, and <NUM> provides the desired contoured surfaces of the finished bladder system <NUM>, including the domed pods <NUM> and the relatively flat foot-facing surface <NUM>, and also provides or prevents fluid communication between different chambers of the bladder system <NUM>. Prior to bonding, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are stacked, flat sheets that are coextensive with one another. Anti-weld material is applied to interfacing surfaces of the sheets <NUM>, <NUM>, <NUM>, and <NUM> where bonds are not desired. For example, the anti-weld material may be referred to as blocker ink, and may be ink-jet printed according to a programmed pattern for each sheet <NUM>, <NUM>, <NUM>, and <NUM> at all selected locations on the sheets where bonds between adjacent sheets are not desired. The stacked, flat polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are then heat pressed to create bonds between adjacent sheets on all adjacent sheet surfaces except for where the anti-weld material was applied. No thermoforming molds or radio frequency welding is necessary. In the completed bladder system <NUM>, areas where the anti-weld material was applied will be at the internal volumes of the various sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

Once bonded, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> remain flat, and take on the contoured shape of the bladder system <NUM> only when the chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> are inflated and then sealed. The polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are not thermoformed in a mold. Accordingly, if the inflation gas is removed, and assuming other components are not disposed in any of the sealed chambers, and the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are not yet bonded to other components such as an outsole, other midsole layers, or an upper, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> will return to their initial, flat state.

The polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> can be formed from a variety of materials including various polymers that can resiliently retain a fluid such as air or another gas. Examples of polymer materials for the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> include thermoplastic urethane, polyurethane, polyester, polyester polyurethane, and polyether polyurethane. Moreover, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> can each be formed of layers of different materials. In one embodiment, each polymeric sheet <NUM>, <NUM>, <NUM>, and <NUM> is formed from thin films having one or more thermoplastic polyurethane layers with one or more barrier layers of a copolymer of ethylene and vinyl alcohol (EVOH) that is impermeable to the pressurized fluid contained therein as disclosed in <CIT>. Each polymeric sheet <NUM>, <NUM>, <NUM>, and <NUM> may also be formed from a material that includes alternating layers of thermoplastic polyurethane and ethylene-vinyl alcohol copolymer, as disclosed in <CIT> and <CIT>. Alternatively, the layers may include ethylene-vinyl alcohol copolymer, thermoplastic polyurethane, and a regrind material of the ethylene-vinyl alcohol copolymer and thermoplastic polyurethane. The polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> may also each be a flexible microlayer membrane that includes alternating layers of a gas barrier material and an elastomeric material, as disclosed in <CIT> and <CIT> Additional suitable materials for the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are disclosed in <CIT> and <CIT> Further suitable materials for the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> include thermoplastic films containing a crystalline material, as disclosed in <CIT> and <CIT>, and polyurethane including a polyester polyol, as disclosed in <CIT>, <CIT>, and <CIT> In selecting materials for the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM>, engineering properties such as tensile strength, stretch properties, fatigue characteristics, dynamic modulus, and loss tangent can be considered. The thicknesses of polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> can be selected to provide these characteristics.

Because they are isolated from one another, the sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> may be filled with gas at the same or at different inflation pressures to achieve a desired cushioning response. For example, the discreet sealed chambers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM> which are closer to the ground than the first sealed chamber <NUM> may have a lower inflation pressure than the first sealed chamber <NUM>. Each sealed chamber <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> retains gas at a predetermined pressure to which it is inflated when the bladder system <NUM> is in an unloaded state. The unloaded state is the state of the bladder system <NUM> when it is not under either steady state loading or dynamic loading. For example, the unloaded state is the state of the bladder system <NUM> when it is not bearing any loads, such as when it is not worn on a foot. A dynamic compressive load on the bladder system <NUM> is due to an impact of the sole structure <NUM> with the ground, and the corresponding footbed load of a person wearing the article of footwear having the bladder system <NUM> and an opposite ground load. The dynamic compressive load may be absorbed by the chambers of the bladder system <NUM> in a sequence according to increasing magnitudes of the stiffness from least stiff to most stiff, with higher inflation pressures associated with greater stiffness. Generally, a smaller volume chamber will reach a maximum displacement under a given dynamic load faster than a larger volume chamber of the same or lower inflation pressure, providing return energy faster than the larger volume chamber.

Stiffness of a cushioning layer such as a sealed fluid chamber is indicated by a plot of force versus displacement under dynamic loading, with stiffness being the ratio of change in compressive load (e.g., force in Newtons) to displacement of the cushioning layer (e.g., displacement in millimeters along the axis of the compressive load). The compressive stiffness of different portions of the bladder system <NUM> would be dependent in part upon the relative inflation pressures. Assuming the four stacked sheets <NUM>, <NUM>, <NUM>, <NUM> are of the same material or materials and construction, and are of equal thickness, a chamber of equal volume and shape of another chamber but with a lower inflation pressure should experience greater initial displacement under dynamic loading, providing an initial stage of relatively low stiffness, followed by a subsequent stage of greater stiffness after reaching its maximum compression. The equal volume chamber of a greater inflation pressure or a lower volume chamber of equal inflation pressure should provide a steeper ramp in stiffness on a load versus displacement curve. Additionally, as the entire first sealed chamber <NUM> is in fluid communication from the heel region <NUM> to the forefoot region <NUM>, and the entire sealed chamber <NUM> is likewise in fluid communication from the heel region <NUM> to the forefoot region <NUM>, preloading of the midfoot region <NUM> and the forefoot region <NUM> will occur as the foot compresses the bladder system <NUM> with an initial heel strike and a roll forward, increasing the stiffness of the midfoot region <NUM>, and then of the forefoot region <NUM> during the forward roll. This may beneficially provide a relatively stiff, supportive platform for toe off.

Additionally, all references referred to are incorporated herein in their entirety.

The term "longitudinal" refers to a direction extending a length of a component. For example, a longitudinal direction of a shoe extends between a forefoot region and a heel region of the shoe. The term "forward" or "anterior" is used to refer to the general direction from a heel region toward a forefoot region, and the term "rearward" or "posterior" is used to refer to the opposite direction, i.e., the direction from the forefoot region toward the heel region. In some cases, a component may be identified with a longitudinal axis as well as a forward and rearward longitudinal direction along that axis. The longitudinal direction or axis may also be referred to as an anterior-posterior direction or axis.

The term "transverse" refers to a direction extending a width of a component. For example, a transverse direction of a shoe extends between a lateral side and a medial side of the shoe. The transverse direction or axis may also be referred to as a lateral direction or axis or a mediolateral direction or axis.

The term "vertical" refers to a direction generally perpendicular to both the lateral and longitudinal directions. For example, in cases where a sole is planted flat on a ground surface, the vertical direction may extend from the ground surface upward. It will be understood that each of these directional adjectives may be applied to individual components of a sole. The term "upward" or "upwards" refers to the vertical direction pointing towards a top of the component, which may include an instep, a fastening region and/or a throat of an upper. The term "downward" or "downwards" refers to the vertical direction pointing opposite the upwards direction, toward the bottom of a component and may generally point towards the bottom of a sole structure of an article of footwear.

The "interior" of an article of footwear, such as a shoe, refers to portions at the space that is occupied by a wearer's foot when the shoe is worn. The "inner side" of a component refers to the side or surface of the component that is (or will be) oriented toward the interior of the component or article of footwear in an assembled article of footwear. The "outer side" or "exterior" of a component refers to the side or surface of the component that is (or will be) oriented away from the interior of the shoe in an assembled shoe. In some cases, other components may be between the inner side of a component and the interior in the assembled article of footwear. Similarly, other components may be between an outer side of a component and the space external to the assembled article of footwear. Further, the terms "inward" and "inwardly" refer to the direction toward the interior of the component or article of footwear, such as a shoe, and the terms "outward" and "outwardly" refer to the direction toward the exterior of the component or article of footwear, such as the shoe. In addition, the term "proximal" refers to a direction that is nearer a center of a footwear component, or is closer toward a foot when the foot is inserted in the article of footwear as it is worn by a user. Likewise, the term "distal" refers to a relative position that is further away from a center of the footwear component or is further from a foot when the foot is inserted in the article of footwear as it is worn by a user. Thus, the terms proximal and distal may be understood to provide generally opposing terms to describe relative spatial positions.

While various embodiments 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 embodiments. Any feature of any embodiment may be used in combination with or substituted for any other feature or element in any other embodiment unless specifically restricted. Accordingly, the embodiments are 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.

Claim 1:
A sole structure (<NUM>) for an article of footwear comprising:
a midsole (<NUM>) including a bladder system (<NUM>) having a forefoot region (<NUM>), a midfoot region (<NUM>), and a heel region (<NUM>),
wherein the bladder system (<NUM>) defines:
a first sealed chamber (<NUM>) retaining fluid as a first cushioning layer, the first sealed chamber (<NUM>) extending over the forefoot region (<NUM>), the midfoot region (<NUM>), and the heel region (<NUM>);
multiple discreet sealed chambers (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) retaining fluid in isolation from one another, each of the multiple discreet chambers (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) disposed at one side of the first sealed chamber (<NUM>), and fluidly isolated from the first sealed chamber (<NUM>); and
a foot-facing surface (<NUM>) and a ground-facing surface (<NUM>);
wherein the first sealed chamber (<NUM>) is disposed between the foot-facing surface (<NUM>) and the multiple discreet chambers (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>);
wherein the multiple discreet chambers (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are disposed between the ground-facing surface (<NUM>) and the first sealed chamber (<NUM>);
wherein:
the bladder system (<NUM>) includes multiple stacked polymeric sheets (<NUM>, <NUM>, <NUM>, <NUM>) including:
a first sheet (<NUM>) at least partially defining the foot-facing surface (<NUM>),
a second sheet (<NUM>) bonded to the first sheet (<NUM>), the first sealed chamber (<NUM>) enclosed by the first sheet (<NUM>) and the second sheet (<NUM>),
a third sheet (<NUM>) bonded to the second sheet (<NUM>), and
a fourth sheet (<NUM>) bonded to the third sheet (<NUM>) and at least partially defining the ground-facing surface (<NUM>);
wherein at least one of the multiple discreet chambers (<NUM>, <NUM>) is enclosed by the second sheet (<NUM>) and the third sheet (<NUM>), and at least one of the multiple discreet chambers (<NUM>, <NUM>, <NUM>, <NUM>) is enclosed by the third sheet (<NUM>) and the fourth sheet (<NUM>); and
wherein the multiple discreet chambers (<NUM>, <NUM>, <NUM>, <NUM>) include:
a peripheral heel chamber (<NUM>) in the heel region (<NUM>),
a central heel chamber (<NUM>) in the heel region (<NUM>),
a peripheral lateral chamber (<NUM>) in the forefoot region (<NUM>), and
a medial forefoot chamber (<NUM>) in the forefoot region (<NUM>).