The present teachings generally include a sole structure and an article of footwear having the sole structure.
Footwear typically includes a sole configured to be located under a wearer's foot to space the foot away from the ground or floor surface. Sole structure can be designed to provide a desired level of cushioning. Athletic footwear in particular sometimes utilizes polyurethane foam or other resilient materials in the sole structure to provide cushioning. It is also beneficial for the sole structure for an article of athletic footwear to have a ground contact surface that provides sufficient traction and durability for an athletic endeavor.
A sole structure for an article of footwear includes a midsole that has a first side with a first surface and an opposite second side with a second surface. The first side has a plurality of recesses extending toward the second side without extending to the second surface. The recesses are configured so that a thickness of the midsole between the second side and a deepest extent of each of the recesses is substantially uniform. By including recesses in the midsole, a higher density material can be used without increasing the overall weight of the midsole. A higher density foam may achieve greater resiliency and avoid compression set in comparison to a lower density foam. Compression set is the permanent loss of resiliency of a foam midsole after extensive use.
The midsole may be a foam material that has a first density in a first portion along the first surface, and a second density less than the first density in a second portion adjacent the first portion. By increasing the density of only the first portion, resiliency goals may be achieved with minimal overall weight. With such a construction, if the midsole with the recesses has a first weight, a volume of the foam material having the second density and equivalent to a volume of the midsole without any recesses will have a second weight at least as great as the first weight. In other words, volume is reduced due to the recesses, and since greater density foam is used strategically only in the first portion, resiliency is optimized without weight increase.
In one embodiment, the recesses are spaced from one another in correspondence with pressure zones of a predetermined foot pressure map. For example, with such a configuration, a first set of recesses in a relatively high pressure region of the foot pressure map are further from one another than a second set of recesses in a relatively low pressure region of the foot pressure map. Additionally, at least some of the recesses in the relatively low pressure region have a larger effective diameter than at least some of the recesses in the relatively high pressure region.
A method of forming a midsole for an article of footwear includes providing a plurality of recesses in the midsole that extend from a first side of the midsole toward a second side of the midsole opposite from the first side. The recesses are configured to extend from the first side only partway toward an outer surface at the second side so that a thickness of the midsole between the second side and a deepest extent of each of the recesses is substantially uniform. Providing the plurality of recesses may include spacing the recesses in correspondence with a predetermined foot pressure map so that the recesses are spaced further from one another in a relatively high pressure zone than in a relatively low pressure zone. The midsole may be a foam material, with the recesses provided by molding the midsole. The method may include controlling a temperature of mold tools used to mold the midsole such that a foam material contacting the mold tools forms an outer skin having a density greater than a density of the foam material not in contact with the mold tools.
The above features and advantages and other features and advantages of the present teachings are readily apparent from the following detailed description of the best modes for carrying out the present teachings when taken in connection with the accompanying drawings.
“A,” “an,” “the,” “at least one,” and “one or more” are used interchangeably to indicate that at least one of the item is present; a plurality of such items may be present unless the context clearly indicates otherwise. All numerical values of parameters (e.g., of quantities or conditions) in this specification, including the appended claims, are to be understood as being modified in all instances by the term “about” whether or not “about” actually appears before the numerical value. “About” indicates that the stated numerical value allows some slight imprecision (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring and using such parameters. In addition, a disclosure of a range is to be understood as specifically disclosing all values and further divided ranges within the range.
The terms “comprising,” “including,” and “having” are inclusive and therefore specify the presence of stated features, steps, operations, elements, or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, or components. Orders of steps, processes, and operations may be altered when possible, and additional or alternative steps may be employed. As used in this specification, the term “or” includes any one and all combinations of the associated listed items.
Those having ordinary skill in the art will recognize that terms such as “above,” “below,” “upward,” “downward,” “top,” “bottom,” etc., as used descriptively for the figures, do not represent limitations on the scope of the claims.
Referring to the drawings, wherein like reference numbers refer to like components throughout the several views,
The sole structure 14 may also be referred to as a sole assembly, as it may include multiple components. For example, the sole structure 14 may include the midsole 10, which can be a resilient sole component attached to and positioned under the footwear upper 16 when the sole structure 14 is resting on a level plane of the ground G. The midsole 10 may be a material that combines a desired level of resiliency and support, such as a polyurethane or an ethylene vinyl acetate (EVA) foam. For example, a desired level of resiliency, as measured by energy return, may be 55 percent. A desired level of compression set for the midsole 10 may be less than 20 percent under a standardized compression set test.
An outsole 24 or multiple outsole elements can be secured to a second side 26 of the midsole 10 that faces away from the upper 16. The outsole 24 can be a material configured to increase traction with the ground G, such as a rubber material. Alternatively, the midsole 10 can be a unitary sole component configured to serve the functions of both cushioning and fraction, without a separate outsole.
The midsole 10 has a heel portion 30, a midfoot portion 32, and a forefoot portion 34. The heel portion 30, the midfoot portion 32, and the forefoot portion 34 correspond with the heel region 18, the midfoot region 20, and the forefoot region 22, respectively, of the article of footwear 12. The heel portion 30 of the midsole is defined as approximately the rear third of the midsole 10, and is shown in
Referring to
As best shown in
The recesses 54 decrease the overall volume of the midsole 10 in comparison to a midsole having the same dimensions as midsole 10 but with foam in place of the recesses. With the reduced overall volume of the midsole 10, a more dense foam can be used without an increase in overall weight. A foam with greater density may better meet desired resiliency and compression set parameters. In the embodiment of
As discussed further herein with respect to
Referring again to
The recesses 54B are spaced from one another so that the foam of the midsole 10 has a second minimum wall thickness W2 between adjacent ones of the recesses 54B. In other words, the thinnest area of each of the wall portions 72 between the recesses 54B has a second minimum wall thickness W2. The second minimum wall thickness W2 is less than the first minimum wall thickness W1. During typical usage of the article of footwear 12, more of the wearer's weight is borne by the forefoot portion 34 than by the midfoot portion 32, both statically and dynamically. Because the first minimum wall thickness W1 is greater than the second minimum wall thickness W2, the forefoot portion 34 will provide greater cushioning than the midfoot portion 32, and sufficient resiliency for the greater loads in the forefoot portion 34. The recesses 54A are smaller in cross-sectional width W3 than the cross-sectional width W4 of the recesses 54B, as is evident in
The midsole 510 has recesses 554 spaced in correspondence with pressure regions Z1, Z2, Z3, Z4 of a predetermined foot pressure map 590 shown in
The magnitude of pressures in each pressure zone Z1, Z2, Z3, Z4 is indicated by the density of shading. Pressure zone Z1 covers the areas of the test midsole that experienced the highest range of pressures. Pressure zone Z2 covers an area of the test midsole that experienced a lower range of pressures than in pressure zone Z1. Pressure zone Z3 covers an area of the test midsole that experienced a lower range of pressures than either of zones Z1 and Z2. Pressure zone Z4 covers an area of the test midsole that experienced a lower range of pressures than any of zones Z1, Z2 and Z3. The various pressure zones Z1, Z2, Z3, and Z4 and boundaries L1, L2, and L3 are reproduced on the midsole 510 in
The recesses 554A are spaced from one another so that the foam of the midsole 510 has a first minimum wall thickness W1A between adjacent ones of the recesses 554A. In other words, the midsole 510 between the recesses 554A can be referred to as wall portions 572. The thinnest area of the wall portions 572 is the minimum wall thickness W1A in the pressure zone Z1. The recesses 554B in the pressure zone Z4 are spaced from one another so that the foam of the midsole 510 has a second minimum wall thickness W2A between adjacent ones of the recesses 554B. In other words, the thinnest area of each of the wall portions 572 between the recesses 554B has a second minimum wall thickness W2A. The second minimum wall thickness W2A is less than the first minimum wall thickness W1A.
The spacing of the recesses 554 in pressure zones Z2 and Z3 transition between the spacing in zone Z1 and Z2, with the recesses in pressure zone Z2 closer than those in zone Z3, but further than those in zone Z1, and the recesses in pressure zone Z3 closer than those in zone Z4. The recesses in the relatively low pressure zone Z4 have a larger effective diameter or cross-sectional width W4A than at least some of the recesses in the relatively high pressure region Z1, which have an effective diameter or cross-sectional width W3A.
The midsole 510 is manufactured so that a higher density first portion 66 is provided at the outer surface of the midsole 510. In other words, the first portion 66 includes the entire outer surface of the midsole 510, and extends inward to a boundary 68 at which the foam transitions to an adjacent second portion 70 of a lower density than the first portion 66. Additionally, the greater density of the first portion 66 bounds each of the recesses 554. Even though the first portion 66, including the surfaces 550, 552, is of a greater density than the second portion 70, because the recesses 554 decrease the overall volume of foam included in the midsole 510 in comparison to a midsole of the same dimensions but without the recesses 554, the overall weight of the midsole 510 is not more than that of the midsole having the same dimensions as midsole 510 but with foam in place of the recesses. In fact, the reduction in weight afforded by the recesses 554 may allow the density of the second portion 70 to be 30 to 40 percent greater than the density of a midsole of the same dimensions but without the recesses 554. The first portion 66 would be of even greater density with respect to the midsole of the same dimensions but without the recesses 554.
Referring to
Like midsole 10, the recesses 554 are configured so that a thickness 56 of portions of the midsole 510 between the second side 526 and a deepest extent 558 of each of the recesses 554 is substantially uniform, as shown with respect to midsole 10 in
A plurality of temperature sensors 318 are positioned on the mold tools 312, 314 to determine an operating temperature of the respective mold tool 312, 314 and/or of the foam material injected into the mold cavity 316 during formation of the midsole 10. The temperature sensors 318 are operatively connected to a controller 320 and are configured to transfer sensor signals to the controller 320, either by wiring, wirelessly, or otherwise. The controller 320, in turn, provides a control signal to a heater 322. The heater 322 heats foam material at a supply chamber 324 from which the foam material is provided via one or more conduits 326 to the cavity 316. The controller 320 is thus operable to control the temperature at the outer surface of the midsole 10 during formation. The temperature of formation affects the density of the midsole 10. By controlling the temperature of the outer surface of the midsole 10, the skin 66 is formed.
The recesses 54 can be provided in step 402 while controlling a temperature of mold tools 312, 314 used to mold the midsole 10 in step 404 such that the foam material contacting the mold tools 312, 314 forms an outer skin, also referred to as the first portion 66, that has a first density greater than a second density of the foam material not in contact with the mold tools. That is, the density of the first portion 66 of
While the best modes for carrying out the many aspects of the present teachings have been described in detail, those familiar with the art to which these teachings relate will recognize various alternative aspects for practicing the present teachings that are within the scope of the appended claims.
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