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. <CIT> describes that a bladder which is particularly useful for a sole assembly of a shoe is formed of multiple layers of barrier film to provide multiple pressurized layers of cushioning fluid or gas when the bladder is filled.

The claimed invention is defined by the subject-matter of the independent claim. Specific embodiments are defined by the dependent claims.

An article of footwear includes a sole structure with a midsole that has multiple cushioning layers of sealed chambers containing gas. The cushioning layers may each have a different compressive stiffness, and may be disposed relative to one another such that the midsole absorbs a compressive load, such as a dynamic compressive load due to impact with the ground, in stages of progressive cushioning (referred to as staged or graded cushioning) according to the relative stiffness values of the layers. Underfoot loads are "dosed" or "staged" to the wearer, with each stage having a different effective stiffness. In one example, the midsole initially provides a low, linear rate of change of load to displacement (i.e., compressive stiffness), followed by a higher, possibly nonlinear rate, and then a more rapid, exponentially increasing rate. The sole structure provides the graded cushioning while being lightweight and flexible. Moreover, various embodiments may exhibit an unloading behavior (i.e., behavior when the dynamic compressive force is removed) that provides significant energy return.

The inflation pressures of the respective sealed chambers of the cushioning layers may be selected to provide various sequences of load absorption by the cushioning layers, affecting the feel or "ride" of the sole structure. The inflation pressures affect the stiffness of the cushioning layers, with a higher inflation pressure resulting in a greater stiffness. Thus, the first cushioning layer has a first stiffness, the second cushioning layer has a second stiffness greater than the first stiffness, and the third cushioning layer has a third stiffness. A dynamic compressive load on the sole structure is absorbed by the first cushioning layer, the second cushioning layer, and the third cushioning layer in a sequence according to relative magnitudes of the first stiffness, the second stiffness, and the third stiffness. As used herein, "stiffness" is the rate of change of load to displacement in compression of a cushioning layer. A cushioning layer may have a constant stiffness (i.e., linear rate of change of load to displacement), a nonlinear stiffness, such as an exponentially increasing rate of change of load to displacement in compression, or may have a rate that is initially linear and changes to nonlinear or vice versa. The stiffness of the midsole may have an effective stiffness in a portion of the displacement range that is based on the stiffness values of more than one of the cushioning layers when two or more of the cushioning layers compress in series or in parallel.

Each sealed chamber retains a gas (e.g., air, nitrogen, or another gas) at a predetermined pressure when in an unloaded state, such as at a specific inflation pressure or at ambient pressure. For example, such a sealed chamber may be defined by and bounded by two adjacent polymeric sheets that are impervious to the gas. A gas-filled sealed chamber is empty (i.e., "structure-less"), yet can provide cushioning when compressed, with significant weight reduction in comparison to most foam. As used herein, a "predetermined pressure" is at a predetermined reference temperature.

More specifically, a sole structure for an article of footwear comprises a midsole having four stacked polymeric sheets bonded to one another to define a first cushioning layer, a second cushioning layer, and a third cushioning layer, each cushioning layer comprising a sealed chamber retaining gas in isolation from each other sealed chamber. For example, the four stacked polymeric sheets may include a first sheet at a ground-facing surface of the midsole, a second sheet stacked on the first sheet, a third sheet stacked on the second sheet, and a fourth sheet stacked on the third sheet at a foot-facing surface of the midsole. Bonds between adjacent ones of the sheets are arranged such that the third cushioning layer is stacked directly above the first cushioning layer with the second cushioning layer bordering both the first cushioning layer and the third cushioning layer. The sealed chamber of the second cushioning layer includes a plurality of elongated segments each extending lengthwise across a longitudinal midline of the midsole at a respective acute angle to the longitudinal midline. The elongated segments are sub-chambers of the sealed chamber of the second cushioning layer. They may be tubular in shape, and are also referred to herein as tubular sub-chambers. By extending over the longitudinal midline, especially where the elongated segments extend a substantial portion of the width of the midsole, such as from the lateral extremity to the medial extremity, the elongated segments provide torsional rigidity to the midsole. By extending at an acute angle to the longitudinal midline, the elongated segments encourage flexing in desired locations and directions, as described herein.

In one or more embodiments, the elongated segments may include a first elongated segment that angles forward in a direction from a lateral edge of the midsole to a medial edge of the midsole, and a second elongated segment that angles forward in a direction from the medial edge to the lateral edge and intersects the first elongated segment. The first and second elongated segments establish flexion axes about which the midsole flexes.

For example, in one aspect, the first elongated segment and the second elongated segment may together define an X shape in a forefoot region of the midsole. Moreover, the bonds between the second sheet and the third sheet may include a plurality of V-shaped bonds in the forefoot region that border the first elongated segment and the second elongated segment. The V-shaped bonds help to define the X shape of the elongated segments.

In another aspect, the first elongated segment and the second elongated segment together define an X shape in a heel region of the midsole. In such an embodiment, the bonds between the second sheet and the third sheet may include a plurality of V-shaped bonds in the heel region that border the first elongated segment and the second elongated segment.

In still another aspect, the bonds between the second sheet and the third sheet include a plurality of elongated bonds in the midfoot region that angle forward over the longitudinal midline from a lateral edge of the midsole to a medial edge of the midsole. In other embodiments, the bonds between the second sheet and the third sheet include a plurality of V-shaped bonds in the midfoot region that border at least one of the elongated segments in the midfoot region such that said at least one of the elongated segments in the midfoot region is V-shaped.

The first cushioning layer and the second cushioning layer may be adjacent to a ground-facing surface of the midsole, and the sole structure may also include an outsole secured to the ground-facing surface. The midsole and the outsole are configured in a complementary manner so that the outsole provides increasing ground contact area as the cushioning layers compress. For example, the outsole may be thicker under the first cushioning layer than under the second cushioning layer. The thicker portions of the outsole under the first cushioning layer protrude further from the midsole than thinner portions of the outsole under the second cushioning layer under a first compressive load, and are level with the thinner portions under a greater, second compressive load. The ground contact area of the outsole is thus greater under the larger loads, providing greater load distribution and traction.

The outsole may include lugs disposed directly under the first cushioning layer. The lugs are narrower than corresponding portions of the first cushioning layer disposed directly there above. A sufficient compressive load applied to the midsole can thus compress the first cushioning layer around the lugs so that the lugs are nested in the midsole below the first cushioning layer. In some embodiments, the lugs include central lugs and side lugs. The central lugs are centrally-disposed under corresponding portions of the first cushioning layer and the side lugs are disposed adjacent to the central lugs. Under a first compressive load, such as a relatively low load or no load, the ground-facing surface of the midsole is rounded under the first cushioning layer such that the central lugs are lower than the side lugs. Under a second compressive load greater than the first load, the first cushioning layer compresses, moving the side lugs level with the central lugs, thereby increasing ground contact area of the outsole. Accordingly, a dynamic compressive load as may occur with running or jumping increases the ground contact area of the outsole.

The bonds between adjacent sheets of the four stacked polymeric sheets may be arranged so that the second cushioning layer directly overlies only a first portion of the first cushioning layer, and the third cushioning layer directly overlies only a remaining portion of the first cushioning layer. The first cushioning layer thus absorbs the dynamic compressive load in series with the second cushioning layer at the first portion of the first cushioning layer, and the first cushioning layer absorbs the dynamic compressive load in parallel with the second cushioning layer and in series with the third cushioning layer at the remaining portion of the first cushioning layer.

The bonds may also be arranged so that the first cushioning layer and the second cushioning are disposed adjacent to a ground-facing surface of the midsole, and the third cushioning layer is displaced from the ground-facing surface of the midsole by the first cushioning layer and the second cushioning layer. The second cushioning layer and the third cushioning layer thus define a foot-facing surface of the midsole, and the first cushioning layer is displaced from the foot-facing surface of the midsole by the second cushioning layer and the third cushioning layer.

Referring to the drawings wherein like reference numbers refer to like components throughout the views, <FIG> show an embodiment of an article of footwear <NUM> that has a sole structure <NUM> with a midsole <NUM>. The midsole <NUM> has first, second, and third cushioning layers <NUM>, <NUM>, <NUM>, as best shown in <FIG>. At least some of the multiple cushioning layers <NUM>, <NUM>, <NUM> have a different stiffness. The multiple cushioning layers <NUM>, <NUM>, <NUM> are disposed relative to one another such that the midsole <NUM> absorbs a dynamic compressive load (such as due to impact with the ground) in stages of progressive cushioning in a sequence according to the relative stiffness of the cushioning layers. None of the cushioning layers <NUM>, <NUM>, <NUM> are foam. As used herein, "stiffness" of a cushioning layer is 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 midsole <NUM> includes four stacked polymeric sheets: a first polymeric sheet <NUM>, a second polymeric sheet <NUM>, a third polymeric sheet <NUM>, and a fourth polymeric sheet <NUM>. The sheets are bonded to one another to define a first cushioning layer <NUM>, a second cushioning layer <NUM>, and a third cushioning layer <NUM>. The first cushioning layer <NUM> is formed by the first and second polymeric sheets <NUM>, <NUM>, which form and define a first sealed chamber <NUM> bounded by the first polymeric <NUM> and the second polymeric sheet <NUM>. The second polymeric sheet <NUM> and the third polymeric sheet <NUM> form and define a second sealed chamber <NUM> bounded by the second polymeric sheet <NUM> and the third polymeric sheet <NUM>. The third cushioning layer <NUM> includes a third sealed chamber <NUM> that is formed, defined, and bounded by the third polymeric sheet <NUM> and the fourth polymeric sheet <NUM>. The first, second, third, and fourth polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are a material that is impervious to gas, such as air, nitrogen, or another gas. This enables the first sealed chamber <NUM> to retain a gas at a first predetermined pressure, the second sealed chamber <NUM> to retain a gas at a second predetermined pressure, and the third sealed chamber <NUM> to retain a gas at a third predetermined pressure.

<FIG> is a bottom view of the sole structure midsole <NUM>, with an outsole <NUM> removed. As is apparent in <FIG>, the midsole <NUM> is a full length, unitary midsole that includes a forefoot region <NUM>, a midfoot region <NUM>, and a heel region <NUM>.

The first and third sealed chambers <NUM>, <NUM> have the shape in plan view substantially the same as the various closed shapes shown in <FIG> (e.g., the V shapes, the W shape, and the rounded triangular shapes). The second sealed chamber <NUM> has the shape of the remaining area in <FIG> (i.e., the area surrounding the peripheries of each of the closed shapes in <FIG> and extending to the periphery of the midsole <NUM>).

Optionally, a foam or hard polymer support <NUM> shown in <FIG> forms a side wall that surrounds an outer periphery of the midsole <NUM> and extends up and around the heel region <NUM> of the upper <NUM>. A foot-facing outer surface <NUM> of the fourth polymeric sheet <NUM> (shown in <FIG>) may secure directly to a lower surface of the upper <NUM>, or to a strobel under the upper <NUM>, or the support <NUM> may extend under the foot and overlay the foot-facing outer surface <NUM>, with the fourth polymeric sheet <NUM> secured to the support <NUM>.

With reference to <FIG>, the four polymeric sheets <NUM>, <NUM>, <NUM>, <NUM> are stacked so that the second cushioning layer <NUM> partially overlies the first cushioning layer <NUM>, and the third cushioning layer <NUM> directly overlies a portion of the first cushioning layer <NUM> and partially overlies the second cushioning layer <NUM> when the article of footwear <NUM> is worn on the foot <NUM>. Accordingly, the sole structure <NUM> is disposed with the third cushioning layer <NUM> nearest the foot <NUM> and the first cushioning layer <NUM> nearest the ground surface G, such as when the outsole <NUM> is in contact with the ground surface G. The first cushioning layer <NUM> and the second cushioning <NUM> layer define the ground-facing outer surface <NUM> of the midsole <NUM>. Only the first polymeric sheet <NUM> is at the ground-facing outer surface <NUM>, but the contours of the ground-facing surface <NUM> are defined by the first sealed chamber <NUM> and the second sealed chamber <NUM>. The third cushioning layer <NUM> is entirely displaced from the ground-facing outer surface <NUM> by the first cushioning layer <NUM> and the second cushioning layer <NUM>. The second cushioning layer <NUM> and the third cushioning layer <NUM> together define the foot-facing outer surface <NUM> of the midsole <NUM>. Only the fourth polymeric sheet <NUM> is at the foot-facing outer surface <NUM>, but the contours of the foot-facing outer surface <NUM> are defined by the second sealed chamber <NUM> and the third sealed chamber <NUM>. The first cushioning layer <NUM> is entirely displaced from the foot-facing outer surface <NUM> by the second cushioning layer <NUM> and the third cushioning layer <NUM>.

The first, second, third, and fourth 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 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 barriers layer 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.

The first, second, and third sealed chambers <NUM>, <NUM>, <NUM> are not in fluid communication with one another. Stated differently, the first and second sealed chambers <NUM>, <NUM> are sealed from one another by the second polymeric sheet <NUM>. The second and third sealed chambers <NUM>, <NUM> are sealed from one another by the third polymeric sheet <NUM>. This allows the first, second, and third sealed chambers <NUM>, <NUM>, <NUM> to retain gas at pressures that may be different from one another. The first sealed chamber <NUM> shown in <FIG> retains gas at a first predetermined pressure when the midsole <NUM> is in an unloaded state, the second sealed chamber <NUM> retains gas at a second predetermined pressure in the unloaded state, and the third sealed chamber <NUM> retains gas at a third predetermined pressure in the unloaded state. The unloaded state is the state of the midsole <NUM> when it is not under either steady state or dynamic loading. For example, the unloaded state is the state of the midsole <NUM> when it is not bearing any loads, such as when it is not on a foot <NUM>. In the embodiment shown, the second predetermined pressure is higher than the first predetermined pressure. The third predetermined pressure can be different than the first predetermined pressure and/or the second predetermined pressure. The lowest one of the predetermined pressures, such as the first predetermined pressure, may be ambient pressure rather than an inflated pressure. In one non-limiting example, the first predetermined pressure is <NUM> Pa (<NUM> pounds per square inch (psi)), the second predetermined pressure is <NUM> Pa (<NUM> psi), and the third predetermined pressure is greater than <NUM> Pa (<NUM> psi). The predetermined pressures may be inflation pressures of the gas to which the respective sealed chambers <NUM>, <NUM>, <NUM> are inflated just prior to finally sealing the chambers. The lowest one of the predetermined pressures, such as the first predetermined pressure, may be ambient pressure rather than an inflated pressure.

The first cushioning layer <NUM> has a first stiffness K1 that is determined by the properties of the first and second polymeric sheets <NUM>, <NUM>, such as their thicknesses and material, and by the first predetermined pressure in the first sealed chamber <NUM>. The second cushioning layer <NUM> has a second stiffness K2 that is determined by the properties of the second and third polymeric sheets <NUM>, <NUM>, such as their thicknesses and material, and by the second predetermined pressure in the second sealed chamber <NUM>. The third cushioning layer <NUM> has a third stiffness K3 that is determined by the properties of the third and fourth polymeric sheets <NUM>, <NUM>, such as their thicknesses and material, and by the third predetermined pressure in the third sealed chamber <NUM>.

A dynamic compressive load on the sole structure <NUM> due to an impact of the article of footwear <NUM> with the ground, is indicated in <FIG> by a footbed load FL of a person wearing the article of footwear <NUM> and an opposite ground load GL. The footbed load FL acts on the foot-facing outer surface <NUM>, and the ground load GL acts on a ground contact surface G of the outsole <NUM>, similar to as shown with respect to the corresponding surfaces of the article of footwear <NUM>. The footbed load FL is represented by all of the downward arrows on the foot-facing outer surface <NUM> in <FIG>. The ground load GL is represented by all of the upward arrows on the ground contact surface G of the outsole <NUM> in <FIG>. In an embodiment not forming part of the claimed invention, the dynamic compressive load is absorbed by the first cushioning layer <NUM>, the second cushioning layer <NUM>, and the third cushioning layer <NUM> in a sequence according to relative magnitudes of the first stiffness K1, the second stiffness K2, and the third stiffness K3 from least stiff to most stiff. According to the claimed invention, the magnitude of the stiffness of the cushioning layers <NUM>, <NUM>, <NUM> increases in the following order: first stiffness K1, third stiffness K3, and second stiffness K2.

Bonds <NUM> between adjacent ones of the sheets <NUM>, <NUM>, <NUM>, <NUM> are arranged such that the third cushioning layer <NUM> is stacked directly above the first cushioning layer <NUM> with the second cushioning layer <NUM> bordering both the first cushioning layer <NUM> and the third cushioning layer <NUM>. The second polymeric sheet <NUM> and the third polymeric sheet <NUM> are bonded to one another between the first sealed chamber <NUM> and the third sealed chamber <NUM> at bonds <NUM> each having an outer periphery <NUM> with a closed shape. The bonds <NUM> are also referred to herein as webbing. In the embodiment shown at the cross section of <FIG>, the closed shape is a zig-zag or "W" shape as best shown in <FIG>, where the webbing <NUM> is visible through the transparent and lowest first polymeric sheet <NUM>. Various bonds <NUM> connecting the second polymeric sheet <NUM> and the third polymeric sheet <NUM> are shown in <FIG>, such as at the portion bounded by the periphery <NUM>. The discrete bonds <NUM> have various shapes that interfit with one another. The shaded areas surrounding the bonds <NUM> in <FIG> are the outer peripheries of the separate sub-chambers of the first sealed chamber <NUM> that are disposed above the various bonds <NUM> in the bottom view of <FIG>, and are the same as the outer peripheries of the separate sub-chambers of the third sealed chamber <NUM> disposed below the bonds <NUM> in the bottom view. The sub-chambers of the first sealed chamber <NUM> are not in fluid communication with one another. The sub-chambers of the third sealed chamber <NUM> are not in fluid communication with one another. The second sealed chamber <NUM> is indicated in <FIG> by the entire remaining space surrounding the various discrete bonds <NUM> in the bottom view of <FIG>. The sub-chambers of the second sealed chamber <NUM> are in fluid communication with one another. All four of the first polymeric sheet <NUM>, the second polymeric sheet <NUM>, the third polymeric sheet <NUM>, and the fourth polymeric sheet <NUM> are bonded to one another at a peripheral flange <NUM> at an outer periphery of the midsole <NUM>.

An unrestrained portion of the first sealed chamber <NUM> tends to adopt a rounded shape, also referred to as a domed shape, due to the force of the internal pressure on the inner surfaces of the polymeric sheets <NUM>, <NUM> bounding the first sealed chamber <NUM>. As shown, each section of the ground-facing outer surface <NUM> under the first sealed chamber <NUM> is at least slightly rounded and is substantially centered under the webbing <NUM>. The rounded portions of the ground-facing outer surface <NUM> are thus also centered under and stabilized by the higher pressure second sealed chamber <NUM> of the second cushioning layer <NUM>. The second sealed chamber <NUM> borders and surrounds the outer peripheries <NUM> of all of the closed shaped bonds <NUM> between the second and third polymeric sheets <NUM>, <NUM> shown in <FIG>, and all surfaces of the first sealed chamber <NUM> except the domed, ground-facing outer surface <NUM>.

Unlike the second sealed chamber <NUM>, the first sealed chamber <NUM> is provided as multiple separate sub-chambers (i.e., also referred to as pods) at the separate closed shapes in <FIG> not in fluid communication with one another or with the second sealed chamber <NUM> or third chamber <NUM>. This allows separate, discrete sub-chambers of the first sealed chamber <NUM> to be optimized in geometry and pressure for various areas of the foot. For example, the sub-chambers of the first sealed chamber <NUM> can be customized in number, size, location, and fluid pressure for a foot map of pressure loads of a specific wearer, or for a population average of wearers of the particular size of footwear. Alternatively, the sub-chambers of the first sealed chamber <NUM> could be fluidly connected by channels. The first sealed chamber <NUM> shown in the cross-section of <FIG> is a single one of the various sub-chambers. All portions of the single sub-chambers of the first sealed chamber <NUM> shown in <FIG> are in fluid communication.

The third sealed chamber <NUM> is also arranged in separate sub-chambers that are not in fluid communication with one another or with the first or second sealed chamber <NUM>, <NUM> similarly allows the separate, discrete sub-chambers of the third sealed chamber <NUM> to be optimized for various areas of the foot <NUM>. Alternatively, the sub-chambers of the third sealed chamber <NUM> could be fluidly connected by channels. The third sealed chamber <NUM> shown in <FIG> is a single one of the sub-chambers, with all portions of the single sub-chamber of the third sealed chamber <NUM> shown in fluid communication. The second sealed chamber <NUM> is a single large chamber that surrounds all of the discrete pods of the first sealed chamber <NUM> and third sealed chamber <NUM> as described.

The placement of the bonds <NUM> can be selected to tune (i.e., control) flexibility of the midsole <NUM>. The flexibility (e.g., bending stiffness) of the midsole <NUM> at any given location is at least partly dependent upon its height at that location. In the midsole <NUM>, the relative inflation pressures are such that the peak height of the second sealed chamber <NUM> is substantially equal to the peak height of the stacked first and third sealed chambers <NUM>, <NUM>. This helps provide a relatively flat foot-facing outer surface <NUM> to enable a uniform feel of the midsole <NUM> against the foot. The height of the midsole <NUM> at any given location is dependent upon the width (right to left in <FIG>) of the chambers <NUM>, <NUM>, <NUM>, as well as the overlap between the sealed chambers (i.e., portions where all three sealed chambers <NUM>, <NUM>, <NUM> are vertically stacked). These features are dependent upon the placement and width of the bonds <NUM>. The bonds <NUM> can be shaped and positioned to provide areas of relatively decreased bending stiffness (and therefore increased flexibility) where desired.

Referring to <FIG>, the first polymeric sheet <NUM> and the second polymeric sheet <NUM> are bonded to one another at a bond <NUM> along an outer peripheral portion <NUM> of an underside <NUM> of the second sealed chamber <NUM> such that the first sealed chamber <NUM> underlies the second sealed chamber <NUM> only inward of the outer peripheral portion <NUM> of the underside <NUM> of the second sealed chamber <NUM>. Similarly, the third polymeric sheet <NUM> and the fourth polymeric sheet <NUM> are bonded to one another at a bond <NUM> along an outer peripheral portion <NUM> of a top side <NUM> of the second sealed chamber <NUM> such that the third sealed chamber <NUM> overlies the second sealed chamber <NUM> only inward of the outer peripheral portion <NUM> of the top side <NUM> of the second sealed chamber <NUM>.

The bonds <NUM>, <NUM> at the outer peripheral portions <NUM>, <NUM> at both the underside <NUM> and the top side <NUM> create a double sheet thickness along the entire outer periphery <NUM>, <NUM> of the midsole <NUM> both above and below the peripheral flange <NUM>, which has a four-sheet thickness. The double-sheet thickness at outer peripheral portions <NUM>, <NUM> lessens ballooning outward of the midsole <NUM> under the dynamic compressive load and helps to even the pressure within the second fluid chamber <NUM> under a dynamic compressive load.

The second polymeric sheet <NUM> is also bonded to the first polymeric sheet <NUM> at lower bonds <NUM> at a lower periphery of the second sealed chamber <NUM> at the ground-facing outer surface <NUM> of the midsole <NUM> and inward of the bonds <NUM> at the outer periphery. The third polymeric sheet <NUM> is bonded to the fourth polymeric sheet <NUM> at upper bonds <NUM> at an upper periphery of the third sealed chamber <NUM> at the foot-facing outer surface <NUM> of the midsole <NUM> and inward of the bonds <NUM>. As is apparent in the cross-sectional view of <FIG>, the second polymeric sheet <NUM> and the third polymeric sheet <NUM> tether the first polymeric sheet <NUM> to the fourth polymeric sheet <NUM> between the upper and lower bonds <NUM>, <NUM>, and between bonds <NUM>, <NUM> and bonds <NUM>, <NUM> via the bonds <NUM>. Selection of the shape, size, and location of various webbing bonds <NUM>, <NUM>, <NUM>, <NUM>, <NUM> of a midsole, such as the midsole <NUM>, enables a desired contoured outer surface of the finished midsole. Prior to bonding at the bonds <NUM>, at the flange <NUM>, and at the bond <NUM> discussed below, the polymeric sheets <NUM>, <NUM>, <NUM> and <NUM> are stacked, flat sheets. Anti-weld material may be ink-jet printed at all selected locations on the sheets where bonds are not desired. For example, the anti-weld material may be printed on both sides of the second and third polymeric sheets <NUM>, <NUM> and/or on the upper surface of the first polymeric sheet <NUM>, the upper surface of the second polymeric sheet <NUM>, and the upper surface of the third polymeric sheet <NUM> in the four-sheet embodiment of the midsole <NUM>. The stacked, flat polymeric sheets are then heat pressed to create bonds between adjacent sheets on all adjacent sheet surfaces except for where anti-weld material was applied. No radio frequency welding is necessary.

Prior to bonding, the polymeric sheets <NUM>, <NUM>, <NUM>, <NUM> are stacked, flat sheets. Once bonded, the polymeric sheets <NUM>, <NUM>, <NUM>, <NUM> remain flat, and take on the contoured shape only when the chambers <NUM>, <NUM>, <NUM> are inflated and then sealed. In the embodiment shown, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> are not thermoformed. Accordingly, if the inflation gas is removed, and assuming other components are not disposed in the chambers and the polymeric sheets are not yet bonded to other components, such as the outsole <NUM>, the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> will return to their initial, flat state.

The second sealed chamber <NUM> directly overlies only a first portion <NUM> of the first sealed chamber <NUM>. The first portion <NUM> is that portion not directly underlying the bonds <NUM>, and is best shown in <FIG> between the lines representing the bonds <NUM> and the lines representing the outer periphery <NUM> of each discrete first chamber <NUM>. The areas bounded by the shape of each discrete first chamber <NUM> in <FIG> also represent where relatively thick portions <NUM> of the outsole <NUM> that have lugs <NUM>, <NUM> are disposed. The third sealed chamber <NUM> directly overlies only a remaining portion <NUM> of the first sealed chamber <NUM>. The remaining portion <NUM> is that portion directly under each of the various discrete bonds <NUM>. These portions <NUM>, <NUM> are also indicated in <FIG>, with the first portion <NUM> outside of the vertical dashed lines <NUM> extending downward from the outer periphery <NUM> (see <FIG>) of the respective bond <NUM> thereabove, and the remaining portion <NUM> inside of the dashed lines <NUM>.

With this arrangement of the sealed chambers <NUM>, <NUM>, <NUM>, the first cushioning layer <NUM> absorbs the dynamic compressive load in series with the second cushioning layer <NUM> and the third cushioning layer <NUM> at the first portion <NUM> of the first sealed chamber <NUM>, and the first cushioning layer <NUM> absorbs the dynamic compressive load in parallel with the second cushioning layer <NUM> and in series with the third cushioning layer <NUM> at the remaining portion <NUM> of the first sealed chamber <NUM>.

As described, the second cushioning layer <NUM> is disposed at least partially in series with the first cushioning layer <NUM> relative to the dynamic compressive load FL, GL applied on the midsole <NUM>. More specifically, the first cushioning layer <NUM> and the second cushioning layer <NUM> are in series relative to the load FL, GL at the portions <NUM>. The third cushioning layer <NUM> is also in series with the second cushioning layer <NUM> where the third cushioning layer <NUM> falls above the portions <NUM>. Accordingly, all three cushioning layers <NUM>, <NUM>, <NUM> are in series at the portions <NUM>. The third cushioning layer <NUM> is directly in series with the first cushioning layer <NUM> relative to the dynamic compressive load FL, GL at the portions <NUM>.

An outsole <NUM> is secured to the ground-facing outer surface <NUM> of the midsole <NUM>. In the embodiment, shown, the outsole <NUM> extends from the medial edge <NUM> (also referred to as medial extremity) to the lateral edge <NUM> (also referred to as lateral extremity) of the midsole <NUM> (i.e., from the flange <NUM> at the medial side to the flange <NUM> at the lateral side). The outsole <NUM> may extend as one piece under the entire midsole <NUM> from front to rear as well, or the outsole <NUM> may be multiple, discrete pieces. Relatively thick portions <NUM> of the outsole <NUM> that directly underlie the first sealed chamber <NUM> have lugs <NUM>, <NUM>. In the embodiment shown, relatively thin portions <NUM> of the outsole <NUM> directly underlying the second sealed chamber <NUM> do not have lugs. As used herein, "relatively thick" and "relatively thin" are used in comparison to one another, and do not denote any specific magnitudes of thickness. The thickness of the relatively thick portions <NUM> may include the thickness of the lugs <NUM> as well as the thickness of the base of the outsole from which the lugs <NUM>, <NUM> protrude. Central lugs <NUM> are substantially centered under the first sealed chamber <NUM> at the rounded portions of the ground-facing outer surface <NUM> of the first polymeric sheet <NUM> and are in contact with the ground surface G even when the sole structure <NUM> is only under a steady state load or is unloaded.

The outsole <NUM> also includes one or more side lugs <NUM> that surround the central lugs <NUM> and are disposed closer to the second sealed chamber <NUM> of the domed ground-facing outer surface <NUM> and/or are shorter than the central lugs <NUM> such that they are not in contact with the ground surface G when the sole structure <NUM> is unloaded or is under only a steady state load or a dynamic compressive load not sufficiently large to cause compression of the first sealed chamber <NUM> to the first stage of compression I of <FIG>. As is indicated in <FIG>, the lower surfaces of the lugs <NUM>, <NUM> generally follow the profile of the rounded shape of the ground-facing outer surface <NUM> under the first chamber <NUM>. The lugs <NUM>, <NUM> may be an integral portion of the outsole <NUM> as in the embodiment shown. In an alternative embodiment, either or both of the central lugs <NUM> and the side lugs <NUM> may be not integrally formed with the outsole <NUM>, but instead may be secured to the outsole <NUM> so that the outsole <NUM> with the lugs <NUM>, <NUM> functions as a unitary component.

Portions <NUM> of the outsole <NUM> that directly underlie the second sealed chamber <NUM> at the ground-facing outer surface <NUM> are not in contact with the ground surface G when the sole structure <NUM> is unloaded, or is under only a first load, such as a steady state load or a dynamic compressive load not sufficiently large to cause compression of the first sealed chamber <NUM> to the first stage of compression I of <FIG>. Stated differently, the relatively thin portions <NUM> do not form part of the ground contact surface of the outsole <NUM> under the first load. Portions <NUM> may have no lugs, may have other tread elements, such as tread elements in a herringbone orientation, or may have a smooth surface with no tread design or lugs.

For each discrete pod of the first sealed chamber <NUM>, the total width W3 of all of the central lugs <NUM> at the ground contact surface G is less than a width W4 of the ground-facing outer surface <NUM> of the first polymeric sheet <NUM> at the pod, as indicated with respect to one of the grouping of lugs <NUM>, <NUM> in <FIG>. Because the central lugs <NUM> rest on the ground surface G and are not as wide as the ground-facing outer surface <NUM> of the overlying corresponding portion of the first cushioning layer <NUM> disposed directly there above, the reaction load (ground load GL) of the dynamic compressive load on the midsole <NUM> is initially applied through the central lugs <NUM> toward a center of the domed outer surface <NUM> of the first polymeric sheet <NUM> where the maximum available displacement of the first sealed chamber <NUM> exists. Because the portions of the outsole <NUM> with lugs <NUM>, <NUM> are not as wide as the portion of the ground-facing outer surface <NUM> where they are attached, the first sealed chamber <NUM> is compressed around the portions <NUM> with the lugs <NUM>, <NUM>. Moreover, the portions <NUM> are nested between portions of the higher pressure second sealed chamber <NUM>, increasing the force required to move the midsole <NUM> laterally as the nested portions of the outsole <NUM> are held in place against the ground by the surrounding second sealed chamber <NUM>. The midsole <NUM> and the outsole <NUM> are thus cooperatively configured to interact to increase traction and lateral stability during compression, such as during a lateral cutting motion in basketball. Stated differently, under a first compressive load, the ground-facing outer surface <NUM> of the midsole <NUM> is rounded under the first cushioning layer <NUM> such that the central lugs <NUM> are lower than the side lugs <NUM>, and under a second compressive load greater than the first load, the first cushioning layer <NUM> compresses, moving the side lugs <NUM> level with the central lugs <NUM>, thereby increasing ground contact area of the outsole <NUM>. Therefore, under a first compressive load, such as a load of a stationary wearer within a range of expected body weights, only the relatively thick portions <NUM> (and more specifically, the lugs <NUM> thereof) form a ground contact surface, and under a second compressive load greater than the first compressive load, the first sealed chamber <NUM> compresses such that both the relatively thick portions <NUM> and the relatively thin portions <NUM> form the ground contact surface. Moreover, even the relatively thick portions <NUM> have a greater contact area with the ground surface under the greater second load, as the side lugs <NUM> now also form part of the ground contact surface. The thicker portions <NUM> of the outsole <NUM> under the first cushioning layer <NUM> protrude further from the midsole <NUM> than thinner portions <NUM> of the outsole <NUM> under the second cushioning layer <NUM> under the first compressive load.

The material of the outsole <NUM> in the embodiment shown has a fourth stiffness K4 that is greater than the first stiffness K1 of the first cushioning layer <NUM>, and may be more or less stiff than either or both of the second stiffness K2 of the second cushioning layer <NUM> and the third stiffness K3 of the third cushioning layer <NUM>. For example, the outsole <NUM> could be a polymeric foam, such as an injected foam. In the embodiment shown, the fourth stiffness K4 is greater than the first stiffness K1 and the third stiffness K3, and is less than the second stiffness K1.

With reference to <FIG>, the stages of absorption of the dynamic compressive load FL, GL represented by the footbed load FL and the reaction ground load GL is schematically depicted assuming that the first stiffness K1 of the first cushioning layer <NUM> is less than the second stiffness K2 of the second cushioning layer <NUM>, and the third stiffness K3 is greater than the first stiffness K1 and less than the second stiffness K2. When the sole structure <NUM> initially receives the dynamic compressive load FL, GL, the least stiff, first cushioning layer <NUM> is the first to compress, both changing the shape of the first sealed chamber <NUM> and compressing the gas in the first sealed chamber <NUM> such that the overall volume of the first sealed chamber <NUM> is reduced in <FIG> (which represents the first stage of compression I) relative to the unloaded state shown in <FIG>. Compression of the second sealed chamber <NUM>, the third sealed chamber <NUM>, and the outsole <NUM> in the first stage of compression I, if any, is minimal. In the first stage of compression I shown in <FIG>, the compression of the first sealed chamber <NUM> straightens or inverts the rounded surface, causing the side lugs <NUM> to now form part of the ground contact surface over which the ground load GL is spread, increasing traction and stability. The relatively thin portions <NUM> of the outsole <NUM> directly underlying the second sealed chamber <NUM> are also in contact with the ground surface G and form part of the ground contact surface in the first stage of compression I. The ground contact surface of the sole structure <NUM> is thus larger in the first stage of compression I than in the unloaded state, increasing traction and stability of the outsole <NUM>. The midsole <NUM> has an effective stiffness during the first stage of compression I that is dependent on the first stiffness K1 that is substantially linear, and may be represented by the portion <NUM> of a stiffness curve <NUM> of <FIG>. The portion <NUM> of the curve <NUM> represents the absorption of the dynamic compressive load by the first cushioning layer <NUM> with the first stiffness K1.

In the second stage of compression II shown in <FIG>, the third cushioning layer <NUM> begins compressing by compression of the gas in the third sealed chamber <NUM>, as indicated by the smaller volume of the third sealed chamber <NUM>. Compression of the first sealed chamber <NUM> of the first cushioning layer <NUM> may continue in series with compression of the third cushioning layer <NUM> in the second stage of compression II assuming that the first cushioning layer <NUM> has not reached its maximum compression under the dynamic compressive load. The midsole <NUM> has an effective stiffness during the second stage of compression II that is dependent on the third stiffness K3 and potentially to a lesser extent on the first stiffness K1, and is represented by the portion <NUM> of the stiffness curve <NUM> in <FIG>. The portion <NUM> of the curve <NUM> represents the absorption of the dynamic compressive load by the third cushioning layer <NUM>.

In the third stage of compression III shown in <FIG>, the second cushioning layer <NUM> begins compressing by compression of the gas in the second sealed chamber <NUM>, as indicated by the smaller volume of the second sealed chamber <NUM> in <FIG> than in <FIG>. If compression of the first sealed chamber <NUM> has not yet reached its maximum compression, then compression of the first portion <NUM> of the first sealed chamber <NUM> will continue in series with the second cushioning layer <NUM>, and compression of the remaining portion <NUM> will continue in parallel with the second cushioning layer <NUM>. If compression of the third cushioning layer <NUM> has not already reached its maximum under the dynamic compressive load in the second stage of compression II, compression of a portion of the third sealed chamber <NUM> between the lines <NUM> above each webbing <NUM> will continue in parallel with compression of the second cushioning layer <NUM> and in series with compression of the first cushioning layer <NUM>, assuming compression of the first cushioning layer <NUM> has not already reached its maximum under the dynamic compressive load. Compression of a portion of the third sealed chamber <NUM> outward of the lines <NUM> above each webbing <NUM> will continue in series with the second cushioning layer <NUM> and in series with compression of the first cushioning layer <NUM>, assuming compression of the first cushioning layer <NUM> and the third cushioning layer <NUM> have not already reached their maximum under the dynamic compressive load.

The stiffness K4 of the outsole <NUM> can be selected such that compression of the outsole <NUM> will not begin until after the third stage of compression III. The third stage of compression III has an effective stiffness that corresponds mainly with the relatively stiff second cushioning layer <NUM>. Sealed chambers of compressible gas tend to quickly ramp in compression in a nonlinear manner after an initial compression. The effective stiffness of the midsole <NUM> during the third stage of compression III is dependent upon the second stiffness K2, and potentially to a lesser extent on the first stiffness K1 and the third stiffness K3, and is represented by the portion <NUM> of the stiffness curve <NUM> in <FIG>. The reduced overall height of the midsole <NUM> throughout the first, second, and third stages of compression as indicated in <FIG> also reduces the tendency of tilting or tipping of the midsole <NUM>.

Referring again to <FIG>, it is evident that the bonds <NUM> between the second and third polymeric sheets <NUM>, <NUM> are shaped, arranged, and positioned to provide torsional stability while allowing forefoot flexing in multiple directions. More specifically, in the forefoot region <NUM>, the bonds <NUM> are disposed so that the second sealed chamber <NUM> forms multiple elongated segments, also referred to herein as tubular sub-chambers, extending transversely across the midsole <NUM> substantially from the medial edge <NUM> to the lateral edge <NUM>. A central axis CL1 of a first elongated segment 140A of the second sealed chamber <NUM> extends substantially or completely from the medial edge <NUM> to the lateral edge <NUM> establishing a first flexion axis FL1 about which the midsole <NUM> flexes in the forefoot region <NUM>. The bonds <NUM> are also disposed so that a central axis CL2 of a second elongated segment 140B of the second sealed chamber <NUM> extends substantially or completely from the medial edge <NUM> to the lateral edge <NUM> establishing a second flexion axis FL2 about which the midsole <NUM> flexes in the forefoot region <NUM>. The second flexion axis FL2 extends forward from the medial edge <NUM> to the lateral edge <NUM>. Both of the flexion axes FL1, FL2 are arranged at a respective acute angle A1, A2 measured from the portion of a longitudinal midline LM of the midsole <NUM> forward of a point P1 to the flexion axes FL1, FL2. The first flexion axis FL1 extends at an acute angle A1, and the second flexion axis FL2 extends at an acute angle A2. The acute angles A1 and A2 are <NUM> degrees in the embodiment shown. In other embodiments, the acute angles may range from <NUM> degrees to <NUM> degrees. The first and second elongated segments 140A, 140B and the flexion axes FL1, FL2 intersect at the point P1 along the longitudinal midline LM that serves as a pivot point. A plurality of V-shaped bonds border and define the elongated segments 140A, 140B (from above and at the lateral and medial sides). The first and second elongated segments 140A, 140B thus form an X shape in the forefoot region <NUM>.

The relatively thin portions <NUM> of the outsole <NUM> that directly underlie the second sealed chamber <NUM> at the ground-facing outer surface <NUM>, shown and described with respect to <FIG>, are disposed in the same pattern as the first and second elongated segments 140A, 140B. Additionally, the midsole <NUM> tends to flex with the flexion axes FL1, FL2 of the uninterrupted elongated segments 140A, 140B serving as pivot axes. When the forefoot region <NUM> of the midsole <NUM> (with the outsole <NUM> secured thereto) is planted on the ground G, a wearer can pivot either toward the lateral side (i.e., the side between the lateral edge <NUM> and the longitudinal midline LM) by flexing along the first flexion axis FL1, or toward the medial side (i.e., the side between the longitudinal midline LM and the medial edge <NUM>) by flexing along flexion axis FL2, lifting the heel portion <NUM> in either case.

A plurality of V-shaped bonds <NUM> in the heel region <NUM> border tubular sub-chambers 140C, 140D (that may also be referred to as first and second elongated members, respectively) with similarly angled flexion axes FL3 and FL4 arranged at acute angles A3, A4 within similar numerical ranges as angles A1 and A2. The flexion axes FL3 and FL4 extend from the medial edge <NUM> to the lateral edge and intersect at point P2.

Notably, in the midfoot region <NUM> of the midsole <NUM>, the bonds <NUM> are disposed such that each of the first sealed chamber <NUM>, the second sealed chamber <NUM>, and the third sealed chamber <NUM> extends across the longitudinal midline LM of the midsole substantially from the lateral edge <NUM> of the midsole <NUM> to the medial edge <NUM> of the midsole, providing torsional rigidity in the midfoot region <NUM>. The V-shaped bonds in the midfoot region <NUM> border an elongated segment 140E. The second chamber <NUM> extends from the medial edge <NUM> to the lateral edge <NUM> uninterrupted by the webbing <NUM> and stacked first and third chambers <NUM>, <NUM>. The symmetrical distribution of the webbing <NUM> relative to the longitudinal midline LM defines many elongated segments of the second sealed chamber <NUM> in the midfoot region <NUM> that extend nearly from the medial edge <NUM> to the lateral edge <NUM>, providing torsional rigidity (i.e., support and torsional stability in the midfoot region <NUM>). Stated differently, the midsole <NUM> discourages twisting of the midsole about the longitudinal midline LM in the midfoot region <NUM>.

Moreover, many of the closed shapes of the bonds <NUM> in <FIG> extend substantially the width of the midsole <NUM> from the medial edge <NUM> to the lateral edge <NUM>. The portions of the outsole <NUM> with lugs <NUM>, <NUM> underlie the bonds <NUM> as indicated in <FIG>, and are thus arranged to have a substantial and constant transverse footprint during all stages of loading, resisting lateral movement of the sole structure <NUM> when the sole structure <NUM> is planted on the ground with a lateral cut (i.e., with a laterally outward and downward force), such as in basketball.

<FIG> shows another embodiment of a midsole <NUM> in plan view, showing the forefoot-facing surface <NUM>. <FIG> is thus the opposite (top) surface of the midsole <NUM> than the bottom surface of midsole <NUM> shown in <FIG>). <FIG> is a fragmentary cross-sectional view at the lines <NUM>-<NUM> in <FIG>. The midsole <NUM> has many of the same features as midsole <NUM>, and these are referred to with like reference numbers. Similar to midsole <NUM>, the midsole <NUM> includes the four polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM>. The anti-weld material is applied to the adjacent surfaces of the polymeric sheets <NUM>, <NUM>, <NUM>, and <NUM> in a different pattern than in <FIG>. Like midsole <NUM>, the bonds <NUM> are disposed in the midsole <NUM> to establish the flexion axes FL1, FL2, FL3, and FL4. Moreover, the bonds <NUM> are disposed in the midfoot region <NUM> such that portions of each of the first sealed chamber <NUM>, the second sealed chamber <NUM>, and the third sealed chamber <NUM> extend across the longitudinal midline LM of the midsole <NUM> substantially from the lateral edge <NUM> to the medial edge <NUM> of the midsole <NUM>, providing torsional rigidity in the midfoot region <NUM>. The bonds <NUM> in the midfoot region <NUM> are arranged such that the second sealed chamber <NUM> includes elongated segments (also referred to as tubular sub-chambers) that extend substantially from the lateral edge <NUM> to the medial edge <NUM> providing torsional rigidity in the midfoot region <NUM>.

<FIG> shows a first inflation port <NUM> that extends between the second and third polymeric sheets <NUM>, <NUM> at the periphery prior to sealing of the peripheral flange <NUM>. The inflation port <NUM> may be used to inflate the second sealed chamber <NUM>, and then sealed and trimmed. A second inflation port <NUM> is shown that may extend between the third and fourth polymeric sheets <NUM>, <NUM> and/or between the first and second polymeric sheets <NUM>, <NUM> and be used to inflate either or both of the stacked first and third sealed chambers <NUM>, <NUM>, and then sealed and trimmed.

Referring to <FIG>, the midsole <NUM> is shown in an unloaded state. The midsole <NUM> loads in a graded manner as described with respect to midsole <NUM>. The outsole <NUM> of <FIG> and <FIG> is not shown in <FIG>, but is secured to the ground-facing outer surface <NUM> in the same manner as in <FIG>. Except at the outermost periphery, where the middle, second and third polymeric sheets <NUM>, <NUM> tether the first and fourth polymeric sheets <NUM>, <NUM> to one another, the midsole <NUM> has a height H1 at the stacked first and third sealed chambers <NUM>, <NUM>. The height H1 is determined by selecting the width of the bonds <NUM> and bonds <NUM>, <NUM>, which in turn determines the width W1 of the first and third sealed chambers <NUM>, <NUM> and the width W2 of the second chamber <NUM>. In a non-limiting example, height H1 may be <NUM> if width W1 is <NUM>, width W2 is <NUM>, and width W3 is <NUM>. In another example, height H1 may be <NUM> if width W1 is <NUM>, width W2 is <NUM>, and width W3 is <NUM>.

In one non-limiting example, the various embodiments of midsoles disclosed herein may provide peak loads in Newtons from about <NUM> N to about <NUM> N, where peak load is defined as <NUM> percent displacement in average height of the midsole. Compressive stiffness can be evaluated using ASTM F1614-<NUM>(<NUM>), or ASTM F1976, Standard Test Method for Impact Attenuation of Athletic Shoe Cushioning Systems and Materials, or other test methods may be used.

In one non-limiting example, the various embodiments of midsoles disclosed herein may provide energy return from about <NUM>% to about <NUM>%, when energy return is measured as the percent restoration of initial drop height of an impact tester, or is measured with a mechanical tester such as an INSTRON® tester available from Instron Corporation, Norwood Massachusetts.

Assembled, ready to wear footwear articles (e.g., shoes, sandals, boots, etc.), as well as discrete components of footwear articles (such as a midsole, an outsole, an upper component, etc.) prior to final assembly into ready to wear footwear articles, are considered and alternatively referred to herein in either the singular or plural as "article(s) of footwear" or "footwear".

As used in the description and the accompanying claims, unless stated otherwise, a value is considered to be "approximately" equal to a stated value if it is neither more than <NUM> percent greater than nor more than <NUM> percent less than the stated value.

Those having ordinary skill in the art will recognize that terms such as "above", "below", "upward", "downward", "top", "bottom", etc., may be used descriptively relative to the figures.

The term "longitudinal" refers to a direction extending a length of a component. For example, a longitudinal direction of an article of footwear extends between a forefoot region and a heel region of the article of footwear. 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 an article of footwear extends between a lateral side and a medial side of the article of footwear. 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 structure 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 structure. 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.

Claim 1:
A sole structure for an article of footwear comprising:
a midsole (<NUM>) having four stacked polymeric sheets (<NUM>, <NUM>, <NUM>, <NUM>) bonded to one another at a peripheral flange (<NUM>) and defining a first cushioning layer (<NUM>) having a first sealed chamber (<NUM>), a second cushioning layer (<NUM>) having a second sealed chamber (<NUM>), and a third cushioning layer (<NUM>) having a third sealed chamber (<NUM>), each sealed chamber (<NUM>, <NUM>, <NUM>) retaining gas in isolation from each other sealed chamber (<NUM>, <NUM>, <NUM>);
wherein bonds (<NUM>) between adjacent ones of the four stacked polymeric sheets (<NUM>, <NUM>, <NUM>, <NUM>) are arranged such that the third cushioning layer (<NUM>) is stacked directly above the first cushioning layer (<NUM>) with the second cushioning layer (<NUM>) bordering both the first cushioning layer (<NUM>) and the third cushioning layer (<NUM>), and the sealed chamber (<NUM>) of the second cushioning layer (<NUM>) includes a plurality of elongated segments (140A, 140B) each extending lengthwise across a longitudinal midline (LM) of the midsole (<NUM>) at a respective acute angle to the longitudinal midline (LM);
wherein the four stacked polymeric sheets (<NUM>, <NUM>, <NUM>, <NUM>) include a first polymeric sheet (<NUM>), a second polymeric sheet (<NUM>), a third polymeric sheet (<NUM>), and a fourth polymeric sheet (<NUM>), the first sealed chamber (<NUM>) bounded by the first polymeric sheet (<NUM>) and the second polymeric sheet (<NUM>), the second sealed chamber (<NUM>) bounded by the second polymeric sheet (<NUM>) and the third polymeric sheet (<NUM>), and the third sealed chamber (<NUM>) bounded by the third polymeric sheet (<NUM>) and the fourth polymeric sheet (<NUM>);
wherein the first polymeric sheet (<NUM>) and the second polymeric sheet (<NUM>) are bonded to one another at a bond (<NUM>) along an outer peripheral portion (<NUM>) of an underside (<NUM>) of the second sealed chamber (<NUM>) such that the first sealed chamber (<NUM>) underlies the second sealed chamber (<NUM>) only inward of the outer peripheral portion of the underside of the second sealed chamber (<NUM>);
wherein the first cushioning layer (<NUM>) has a first stiffness, the second cushioning layer (<NUM>) has a second stiffness greater than the first stiffness, and the third cushioning layer (<NUM>) has a third stiffness less than the second stiffness; and
wherein the third stiffness is greater than the first stiffness.