Article of footwear

Shoes having foot support structures formed of arm portions and/or plates having variable flexibility are disclosed.

TECHNICAL FIELD

This disclosure relates to shoes.

BACKGROUND

Generally, shoes include an upper portion and a sole. When the upper portion is secured to the sole, the upper portion along with the sole define a void that is configured to securely and comfortably hold a human foot. Often, the upper portion and/or sole are/is formed from multiple layers that can be stitched or adhesively bonded together. For example, the upper portion can be made of a combination of leather and fabric, or foam and fabric, and the sole can be formed from at least one layer of natural rubber. Often materials are chosen for functional reasons, e.g., water-resistance, durability, abrasion-resistance, and breathability, while shape, texture, and color are used to promote the aesthetic qualities of the shoe.

SUMMARY

Generally, the disclosure relates to shoes having variable flexibility, e.g., laterally, or along a longitudinal axis of the shoe. For example, shoes are disclosed that have arm portions and/or plates having variable flexibility.

In one aspect, the disclosure features shoes having an assembly including a foot support structure and a plate mounted upon the foot support structure. The foot support structure includes a cross member, and a first pair of cantilevered arm portions extending from the cross member in a heelward direction, with a first, heelward-extending gap defined therebetween. If desired, the first pair of cantilevered arm portions can be, e.g., configured to reengage in a heelward direction, spaced from the cross member. In some configurations, the cross member can be, e.g., disposed in a forefoot region of the foot support structure.

In some implementations, the foot support structure includes a second pair of cantilevered arm portions extending from the cross member in a toeward direction, with a second, toeward-extending gap defined therebetween. If desired, the second pair of cantilevered arm portions can be, e.g., configured to reengage in a toeward direction, spaced from the cross member.

In some implementations, the foot support structure defines a first, upper surface directed towards a wearer's foot when the shoe is worn and an opposite surface. The plate can be, e.g., mounted upon the first surface.

The plate can, e.g., vary in beam stiffness along a longitudinal axis of the shoe. In such instances, the beam stiffness is measured as a product of an overall moment of inertia of a nominal cross-section and an effective modulus of elasticity (Young's modulus) of a material from which the plate is formed.

The plate can, e.g., vary in thickness along a longitudinal axis of the shoe and/or can be formed from materials that vary in hardness and/or flexural modulus.

In some implementations, the plate is formed from polymeric material, e.g., a thermoplastic (e.g., a thermoplastic polyurethane). The polymeric material can have, e.g., a flexural modulus of from about 5.0 MPa to about 2000 MPa, measured at 25° C. by DMA in a linear region of a stress strain curve. In specific implementations, the polymeric material has a flexural modulus that is from about 15.0 MPa to about 1200 MPa. In some implementations, the polymeric material has a hardness of from about 50 Shore A to about 80 Shore D, as measured using ASTM D2240 at 25° C. In specific implementations, the hardness is from about 70 Shore A to about 76 Shore D.

In some implementations, the plate has a toeward portion and a heelward portion, and the heelward portion has a relatively higher beam stiffness than the toeward portion. In specific implementations, the toeward portion and the heelward portion are each formed from a polyurethane material, e.g., a thermoplastic polyurethane. Each portion can be made, e.g., by molding (e.g., co-molding). In specific implementations, the material from which the toeward portion of the plate is made has a hardness of from about 50 Shore A to about 95 Shore A and a flexural modulus of from about 5.0 MPa to about 105.0 MPa; and the material from which the rearward portion of the plate is made has a hardness of about 90 Shore A to about 76 Shore D and a flexural modulus of from about 75.0 MPa to about 1700 MPa. In some implementations, a thickness of the toeward and/or heelward portion of the plate is from about 0.25 mm to about 2.5 mm.

In some implementations, the first, heelward-extending gap defined between the first pair of cantilevered arm portions extends along at least 50 percent of a total length of the foot support structure, e.g., at least 60 percent, 65 percent, 70 percent, 75 percent, or at least 85 percent of the total length of the foot support structure.

The foot support structure can made, e.g., from a material that includes a polyolefin, e.g., ethylene-vinyl-acetate copolymer (EVA) or linear, low density polyethylene (e.g., a copolymer of ethylene and a 5-20 carbon α-olefin such as 1-octene). The foot support structure can be made, e.g., by injection molding or compression molding. The material of the foot support structure can be foamed during the forming of the foot support structure, making it, e.g., advantageously low in density, and, therefore, weight. When the material of the foot support structure is foamed, the cellular structure of the foam can be open or closed. In implementations in which the material of the foot support structure is foamed, it can, e.g., have a hardness from about 30 ASKER C to about 75 ASKER C, e.g., 40 ASKER C to about 60 ASKER C, as measured using Japanese Standard SRIS 0101 at 25° C.

In implementations in which the support structure includes a second pair of cantilevered arm portions extending from the cross member in a toeward direction, with a second, toeward-extending gap defined therebetween, a combined length of the first gap and the second gap can be, e.g., at least 50 percent of a total length of the foot support structure, e.g., at least 60 percent, 65 percent, 70 percent, 75 percent, 85 percent, or at least about 90 percent of a total length of the foot support structure.

In some implementations, the assembly is used in a sandal or a boating shoe.

In some implementations, the foot support structure also includes straps, e.g., that extend through reinforced apertures defined in the foot support structure. If desired, straps can be made releasably engageable, e.g., by applying hook-and-loop type fasteners to the straps.

If desirable, the shoe assembly can further include a liner mounted to an outer surface of the plate. This can be advantageous, e.g., for additional shock-absorbing, when desired. The liner material can, e.g., define siping extending transversely to a longitudinal axis of the shoe. This can be advantageous when extra traction and slip resistance is desired. In specific implementations, the liner is formed from foamed EVA. When the liner is formed from foamed material, it can have, e.g., a hardness from about 25 ASKER C to about 65 ASKER C, e.g., 35 ASKER C to about 55 ASKER C, as measured using Japanese Standard SRIS 010 at 25° C. When the material of the liner is foamed, the cellular structure of the foam can be open or closed.

In some implementations, the shoe assembly further includes an outsole mounted to the opposite surface of the foot support structure. Such an outsole can, e.g., increase the wear-resistance of the shoe assembly. The outsole can define siping extending transversely to a longitudinal axis of the shoe. In specific implementations, the outsole is formed from vulcanized rubber material, e.g., a natural rubber material. In some implementations, the outsole is formed from a material having a hardness from about 40 Shore A to about 95 Shore A, e.g., from about 50 Shore A to about 80 Shore A, as measured using ASTM D2240 at 25° C.

In another aspect, the disclosure features shoes having an assembly having a foot support structure and a top plate mounted upon the foot support structure. The foot support structure includes a cross member, and a first pair of cantilevered arm portions extending from the cross member in a toeward direction, with a first, toeward-extending gap defined therebetween. If desired, the first pair of cantilevered arm portions can, e.g., be configured to reengage in a toeward direction, spaced from the cross member. In some configurations, the cross member can be, e.g., disposed in a forefoot region of the foot support structure. Any of the features described above with respect to the first aspect can be applied to this aspect.

In another aspect, the disclosure features a shoe that includes a plate formed of at least two different materials. For example, the plate can have a toeward portion and a heelward portion. In such implementations, the heelward portion can, e.g., have a relatively higher beam stiffness than the toeward portion. In specific implementations, the toeward portion includes a polymeric material having a hardness of from about 50 Shore A to about 95 Shore A and a flexural modulus of from about 5.0 MPa to about 115.0 MPa; and the rearward portion includes a polymeric material having a hardness of about 85 Shore A to about 80 Shore D and a flexural modulus of from about 75.0 MPa to about 1900 Mpa.

In another aspect, the disclosure features shoes having a foot support structure that includes a cross member, and a first pair of cantilevered arm portions extending from the cross member in a heelward direction, with a first, heelward-extending gap defined therebetween. If desired, the first pair of cantilevered arm portions can be, e.g., configured to reengage in a heelward direction, spaced from the cross member. In some configurations, the cross member can be, e.g., disposed in a forefoot region of the foot support structure. In some implementations, the foot support structure includes a second pair of cantilevered arm portions extending from the cross member in a toeward direction, with a second, toeward-extending gap defined therebetween. If desired, the second pair of cantilevered arm portions can be, e.g., configured to reengage in a toeward direction, spaced from the cross member. Any of the other features described herein with respect to the foot support structure can be applied to this aspect.

Implementations may include any one, or combination of the following advantages. The shoes described herein flex naturally along with the wearer's feet, allowing the wearer to control his/her movement as if they were barefoot, while at the same time providing adequate protection for the wearer. The shoes are lightweight. The shoes have enhanced breathability, providing many hours of continuous comfort.

DETAILED DESCRIPTION

Referring toFIGS. 1,2,2A-2H and3A and3B, a sandal has an assembly10that includes a foot support structure20and a top plate30mounted upon foot support structure20. Support structure20includes a forefoot cross member40and a first pair of cantilever arm portions42extending from the forefoot cross member40in a heelward direction (direction indicated by arrow50), with a first, heelward-extending gap60defined therebetween. Foot support structure20also includes a second pair of cantilevered arm portions62extending from the forefoot cross member40in a toeward direction (direction indicated by arrow70), with a second, toeward-extending gap72defined therebetween. In the implementation shown, foot support structure20defines a recessed first, upper surface80directed towards a wearer's foot when the shoe is worn, and an opposite, second, lower surface82directed towards a walking surface. Recessed upper surface80is configured to accept the plate30, which is mounted via bottom surface95, e.g., by adhesive or solvent bonding, upon the first, upper surface80of the foot support structure20. As shown, plate30defines a plurality of apertures98in locations that correspond to first and second gaps60and72(perhaps best seen inFIG. 2). Shoe assembly10also defines a liner100that includes a plurality of apertures101that line up with apertures98of plate30when the liner100is mounted to a first, upper surface115of top plate30. Having the apertures101of liner100and apertures98of plate30in alignment can allow for effective air circulation through the sandal. In addition, assembly10includes an outsole120mounted to the opposite, second, lower surface82of the foot support structure20. As shown, the outsole120includes a first pair of cantilevered arm portions122extending from an outsole cross member124in a heelward direction, with a first, heelward-extending gap126defined therebetween, and a second pair of cantilevered arm portions128extending from the outsole cross member124in a toeward direction, with a second, toeward gap130defined therebetween. When outsole120is mounted by a top surface136to the lower surface82of foot support structure20, the first and second pair of cantilevered arm portions122and128are aligned with the first and second cantilevered arm portions42and62of foot support structure20. Such a construction can allow for the sandal to flex naturally along with the wearer's foot, allowing the wearer to control his/her movement as if they were barefoot, while at the same time providing adequate protection to the wearer's feet.

In some implementations, top plate30varies in beam stiffness along a longitudinal axis (indicated by double-headed arrow90) of the shoe. The beam stiffness is measured as a product of an overall moment of inertia of a nominal cross-section and an effective modulus of elasticity (Young's modulus) of a material from which the plate is formed. Beam stiffness can be varied by varying material hardness and/or flexural modulus and/or thickness of the plate30.

In some implementations, top plate30is formed of polymeric material, e.g., thermoplastic or thermoset polymeric material. The thermoplastic material can be, e.g., an elastomer, e.g., natural rubber, blends of styrenic block copolymers and polypropylene, elastomeric nylons (e.g., polyetheramides) or polyurethanes. In specific implementations, the thermoplastic is a polyurethane, e.g., polyether or polyester soft-segment polyurethane, such as those available from Dow Plastics under the tradename PELLETHANE™ AND ISOPLAST™. In some implementations, the polymeric material has flexural modulus of from about 2.5 MPa to about 2100 Mpa, e.g., from about 5.0 MPa to about 500 Mpa, as measured at 25° C. by DMA in a linear region of a stress strain curve. In some implementations, the polymeric material has hardness of from about 50 Shore A to about 85 Shore D, e.g., from about 75 Shore A to about 76 Shore D, as measured using ASTM D2240 at 25° C.

Referring again particularly toFIG. 1, plate30includes a toeward portion92and a heelward portion94(demarcation of portions indicated generally by dotted line105). The heelward portion94has a relatively higher beam stiffness than the toeward portion92, allowing toeward portion92to flex more easily than heelward portion94when the wearer walks. In the particular embodiment shown, the beam stiffness of portions92and94is varied by making the portions out of materials having a different hardnesses and/or flexural moduli. In such implementations, plate30can be formed, e.g., by molding (e.g., co-molding).

In some implementations, the material of the toeward portion92of plate30has hardness of from about 80 Shore A to about 95 Shore A, flexural modulus of from about 5.0 MPa to about 85.0 MPa and a thickness from about 0.25 mm to about 2.5 mm; and

the material of the rearward portion94of plate30has hardness of about 95 Shore A to about 80 Shore D, flexural modulus of from about 75.0 MPa to about 1700 MPa, and a thickness from about 0.25 mm to about 2.5 mm.

In a specific example, the material of the toeward portion92of plate30has hardness of from about 90 Shore A and a thickness of 1.5 mm; and the material of the rearward portion94of plate30has hardness of about 74 Shore D and a thickness 1.5 mm.

In some implementations, a combined length of the second, toeward-extending gap72and the first, heelward-extending gap60is at least 50 percent of a total length L (seeFIG. 3A) of the foot support structure, e.g., at least 60 percent, 65 percent, 70 percent, 75 percent, 80 percent, 85 percent, or at least about 90 percent of the total length of the foot support structure20.

Foot support structure20, liner100and outsole120can each independently be formed of thermoset material, e.g., natural rubber, or thermoplastic, e.g., polyolefin material. For example, the thermoplastic material can be an elastomer, e.g., styrenic block copolymer, polyethylene, linear, low density polyethylene (e.g., a copolymer of 1-octene and ethylene), polyurethane (e.g., a polyether or polyester soft-segment polyurethane), elastomeric polyester (e.g., polyether-polyester), and mixtures of these elastomers. In specific implementations, support structure20is formed by injection molding using ethylene-vinyl-acetate copolymer (EVA) and a foaming agent, e.g., an exothermic or endothermic foaming agent. Chemical foaming agents are available from Clariant Corporation under the tradename HYDROCEROL®. When the material is foamed, the cellular structure of the foam can be open or closed.

In some implementations, support structure20has a maximum thickness, measured from lower surface82to upper surface80, of from about 15.0 mm to about 35.0 mm, e.g., from about 18.0 mm to about 25.0 mm. In specific implementations, the material of support structure20is a foam having hardness of from about 30 ASKER C to about 75 ASKER C, e.g., 40 ASKER C to about 60 ASKER C, as measured using Japanese Standard SRIS 0101 at 25° C. In a specific example, the foam has hardness of about 53 ASKER C.

Referring toFIGS. 1 and 2, liner100and outsole120can define siping that extends transversely to a longitudinal axis, e.g., for enhanced traction or gripping. In some implementations, liner100and/or outsole120is between about 0.5 mm and 5.0 mm thick, e.g., between about 1.0 mm to about 4.0 mm, or between about 1.5 mm and 4.0 mm thick. In specific implementations, the material of liner100is a foam having hardness of from about 30 ASKER C to about 55 ASKER C, e.g., 35 ASKER C to about 50 ASKER C, as measured using Japanese Standard SRIS 0101 at 25° C. In a specific example, the foam has hardness of about 40 ASKER C. When the material is foamed, the cellular structure of the foam can be open or closed.

Referring toFIGS. 1 and 3A, foot support structure20can also include straps161that extend through apertures140, e.g., apertures reinforced with a collar (described below), defined in support structure20. In this particular implementations, straps are made releasably engageable by complementary hook150and loop160material, forming a hook-and-loop type fastener.

Other Embodiments

While implementations have been shown in which the foot support structure has both heelward and toeward extending cantilevered arm portions, in some implementations, the foot support structure has only heelward or only toeward cantilevered arm portions. For example, referring toFIG. 4, a foot support structure200is illustrated having only a pair of toeward extending cantilevered arm portions202. In such instances, the shoe assembly can generally include all the other features described herein in reference toFIGS. 1,2,2A-2H and3A and3B. For example, the shoe assembly can include a plate, e.g., a plate having two different beam stiffnesses, an outsole and a liner.

While implementations have been shown in which foot support structures have cantilevered arm portions that do not reengage, in some implementations, the arm portions may reengage. For example,FIG. 5illustrates a foot support structure210having only toeward extending cantilevered arm portions that reengage in a toeward direction;FIG. 6illustrates a foot support structure220having only heelward extending cantilevered arm portions that reengage in a heelward direction; andFIG. 7illustrates a foot support structure230having both heelward and toeward cantilevered arm portions that reengage. In any such instances, the shoe assembly can generally include all the other features described herein with reference toFIGS. 1,2,2A-2H and3A and3B. For example, any such shoe assembly can include a plate, e.g., a plate having two different beam stiffnesses, an outsole and a liner.

While implementations have been shown in which cross members are generally disposed in the forefoot of the foot support structure, in other implementations, such cross members may be disposed in other locations, e.g., locations central to the foot support structure.

FIGS. 8 and 9, which are inner and outer perspective views, respectively, illustrate a support member20having apertures that are reinforced with collars300. Collars can, e.g., strengthen the support member in the area about the apertures so that the support member resists tearing when the straps are tightened. In the particular embodiment shown, collar300is asymmetric in that the portion that is configured to reside on the inside of the support member includes a tab304. In some embodiments, the collars are press fit into the apertures, and then the tab304is bonded to, e.g., by using an adhesive, to the support structure. Tab304can, e.g., aid in reinforcing the area about the apertures by distributing an applied load over a larger surface area of the support structure. In some embodiments, tab304is made from a thermoplastic, e.g., a thermoplastic polyurethane.