Patent Grant
9629415
Aspects of the present invention relate to sole structures for articles of footwear. More particularly, various examples relate to outsole structures having improved impact-attenuation and/or energy-absorption.
To keep a wearer safe and comfortable, footwear is called upon to perform a variety of functions. For example, the sole structure of footwear should provide adequate support and impact force attenuation properties to prevent injury and reduce fatigue, while at the same time provide adequate flexibility so that the sole structure articulates, flexes, stretches, or otherwise moves to allow an individual to fully utilize the natural motion of the foot.
High-action sports, such as the sport of skateboarding, impose special demands upon players and their footwear. For example, during any given run, skateboarders perform a wide variety of movements or tricks (e.g., carving, pops, flips, ollies, grinding, twists, jumps, etc.). During all of these movements, pressure shifts from one part of the foot to another, while traction between the skateboarder and the skateboard must be maintained. Further, for the street skateboarder, traction between the skateboarder's shoe and the ground propels the skateboarder.
Additionally, skateboarding requires the skateboarder to apply pressure to one or the other portions of the skateboard using his or her feet in order to control the board. This requires that skateboarders selectively apply pressure to the board through their shoes at different locations on the bottom and edges of the shoes. For example, for some skateboarding tricks, pressure is applied along the lateral edge of the foot, approximately at the outer toe line location. For other tricks, pressure is applied on the lateral edge of the foot somewhat forward of the outer toe line location. As the interaction between the skateboarder and the skateboard is particularly important when performing such tricks, skateboarders typically prefer shoes having relatively thin and flexible soles that allow the skateboarder to “feel” the board.
Importantly, however, over the past several years skateboard tricks have become “bigger,” involving higher jumps and more air time. These bigger skateboard tricks may result in uncomfortably high, even damaging, impact loads being felt by the skateboarder. Further, during many of the movements and particularly upon landing, significant impact loads may be experienced by various portions of the foot.
Accordingly, it would be desirable to provide footwear that allows the wearer to better feel and grip the ground or other foot-contacting surfaces, to achieve better dynamic control of the wearer's movements, while at the same time providing impact-attenuating features that protect the wearer from impacts due to these dynamic movements.
According to aspects of the invention, a sole structure for an article of footwear has one or more outsole portions. At least one of these outsole portions has a plurality of alternating upward-facing and downward-facing elongate channels. The channels may have a base element and two sidewalls, with adjacent upward-facing and downward-facing channels sharing a common sidewall. The base elements of the downward-facing channels form an upper surface of each outsole portion and the base elements of the upward-facing channels form a lower surface of each outsole portion. A first outsole portion has a pressure-versus-strain curve having a local maximum at a “trip point” pressure value and a first strain value and the pressure-versus-strain curve has a change in strain of at least approximately 10% before a second occurrence of the “trip point” pressure value is reached.
According to certain aspects, the first outsole portion may have a local minimum pressure value between the first and second occurrences of the “trip point” pressure value, and the local minimum pressure value may be greater than approximately 70% of the “trip point” pressure value.
According to other aspects, the first outsole portion may have a pressure-carrying capacity between the first and second occurrences of the “trip point” pressure value that varies by less than or equal to approximately 20% over a change in strain of at least approximately 15%.
According to further aspects, the first outsole portion may absorb a first amount of energy per unit area at the first occurrence of the “trip point” pressure value and absorb a second amount of energy per unit area between the first and second occurrences of the “trip point” pressure value. The value of the second energy per unit area may be at least 70% of the value of the first energy per unit area.
According to some aspects, the first outsole portion may have a height dimension of less than or equal to 8.0 mm, measured from the upper surface to the lower surface. The first outsole portion may absorb an energy per unit area of at least 600 J/mm2 without exceeding a pressure of 350 kPa. Alternatively, the first outsole portion may absorb an energy per unit area of at least 900 J/mm2 without exceeding a pressure of 500 kPa. Also, alternatively, the first outsole portion may absorb an energy per unit area of at least 1100 J/mm2 without exceeding a pressure of 700 kPa.
According to other aspects, the first outsole portion may have a “trip point” pressure value of between approximately 250 kPa and approximately 450 kPa, or alternatively, the first outsole portion may have a “trip point” pressure value of between approximately 450 kPa and approximately 650 kPa.
According to even other aspects, the upward-facing channels of the first outsole portion may undulate in the plane of the sole. Thus, for example, when viewed perpendicular to the plane of the sole (e.g., when viewed from above or from below), the channels may have a zigzag, sinusoidal, sawtoothed, or other regular or irregular wave-like configuration. Further, when viewed perpendicular to the plane of the sole, the base elements of the upward-facing channels (i.e., the lower base elements) may also have the zigzag (or other wave-like) configuration. Similarly, the downward-facing channels of the first outsole portion may undulate in the plane of the sole. Thus, as an example, when viewed perpendicular to the plane of the sole, the channels may have a zigzag, sinusoidal, sawtoothed, or other regular or irregular wave-like configuration. Correspondingly, when viewed perpendicular to the plane of the sole, the base elements of the downward-facing channels (i.e., the upper base elements) may have an undulating, wave-like configuration. The undulating configuration(s) of the lower base elements may be the same as the undulating configuration(s) of the upper base elements. Optionally, the undulating configuration(s) of the lower base elements may be different than the undulating configuration(s) of the upper base elements.
According to some aspects, the sidewalls of the channels may form acute, perpendicular, or obtuse angles from the upper surface. In some example embodiments, the angles of the sidewalls to the upper surface of the first outsole portion may be greater than or equal to approximately 70 degrees. The widths of the bases of the downward-facing channels of the first outsole portion may be approximately 3.0 mm and the widths of the bases of the upward-facing channels of the first outsole portion may be less than approximately 1.25 mm. The thickness of the sidewalls of the first outsole portion may be between approximately 0.8 mm and approximately 1.5 mm. The thickness of the bases of the upward-facing channels of the first outsole portion may be between approximately 1.0 mm and approximately 1.5 mm.
According to another aspect of the invention, a sole structure for an article of footwear includes one or more outsole portions. Each outsole portion has a plurality of alternating upward-facing and downward-facing elongate channels. Each channel has a base and two sidewalls, with adjacent upward-facing and downward-facing channels sharing a common sidewall. The bases of the downward-facing channels form an upper surface of each outsole portion and the bases of the upward-facing channels form a lower surface of each outsole portion. The sidewalls are arranged at a non-perpendicular angle to the upper surface of the first outsole portion. A first outsole portion has a monotonically increasing vertical pressure-carrying capacity as a function of strain, as measured over a 40 mm diameter area, until a local maximum “trip point” pressure value is reached. Beyond this first occurrence of the “trip point” pressure value the first outsole portion has a local minimum pressure value that is between 60% to 100% of the “trip point” pressure value.
An article of footwear including an upper attached to the sole structure disclosed herein is also provided.
The foregoing Summary, as well as the following Detailed Description, will be better understood when read in conjunction with the accompanying drawings.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of specific aspects of the invention. Certain features of the illustrated embodiments may have been enlarged or distorted relative to others to facilitate visualization and clear understanding. In particular, thin features may be thickened, for example, for clarity of illustration.
The following discussion and accompanying figures disclose articles of footwear having sole structures with sole geometries in accordance with various embodiments of the present disclosure. Concepts related to the sole geometry are disclosed with reference to a sole structure for an article of athletic footwear having a configuration suitable for the activity of skateboarding. However, the disclosed sole structure is not solely limited to footwear designed for skateboarding, and may be incorporated into a wide range of athletic footwear styles, including shoes that are suitable for rock climbing, bouldering, hiking, running, baseball, basketball, cross-training, football, rugby, tennis, volleyball, and walking, for example. In addition, a sole structure according to various embodiments as disclosed herein may be incorporated into footwear that is generally considered to be non-athletic, including a variety of dress shoes, casual shoes, sandals, slippers, and boots. An individual skilled in the relevant art will appreciate, given the benefit of this specification, that the concepts disclosed herein with regard to the sole structure apply to a wide variety of footwear styles, in addition to the specific styles discussed in the following material and depicted in the accompanying figures.
Sports generally involve consistent pounding of the foot and/or periodic high impact loads on the foot. For example, skateboarding is a sport that is known to involve high impact loading under the foot, especially when unsuccessfully or awkwardly landing tricks and/or inadvertently coming off the board on hard, unforgiving surfaces. Over the past several years, skateboarding tricks have gotten much bigger, resulting in even higher impact loads, especially in the medial and the heel regions of the foot. This is true whether the foot remains on the board during landing or, alternatively, if the landing is off the board. It is not unheard of for skateboarders to experience heel bruising and even micro-fractures.
A sole structure for an article of footwear having an impact-attenuation system capable of handling the high “big trick” impact loads, without sacrificing the intimate feel for the board desired by skateboarders, is sought. Thus, it may be advantageous to have a sole structure that responds somewhat stiffly when a user is walking or performing relatively low impact ambulatory activities, thereby maintaining a feel for the ground surface (or board), and that also responds more compliantly when the user is performing higher impact maneuvers, thereby lessening any excessively high impact pressures that would otherwise be experienced by the user.
In addition, the ability to “grip” the board is another important feature desired by skateboarders. Softer materials tend to provide higher coefficients of friction and, thus, generally provide better traction and “grip” than harder materials. However, softer materials also tend to wear out more quickly. Thus, another feature sought by skateboarders is a durable sole. Indeed, skateboarders and many other athletes desire sole structures that provide high traction and lasting durability
Even further, skateboarders and many other athletes desire sole structures that are light weight and low profile.
Various aspects of this disclosure relate to articles of footwear having a sole structure with an outsole structure capable of absorbing impact energies and mitigating impact loads.
As used herein, the modifiers “upper,” “lower,” “top,” “bottom,” “upward,” “downward,” “vertical,” “horizontal,” “longitudinal,” “transverse,” “front,” “back” etc., unless otherwise defined or made clear from the disclosure, are relative terms meant to place the various structures or orientations of the structures of the article of footwear in the context of an article of footwear worn by a user standing on a flat, horizontal surface.
Referring to
Referring to
The sole structure 200 of the article of footwear 10 further has a toe or front edge 14 and a heel or back edge 15. A lateral edge 17 and a medial edge 18 each extend from the front edge 14 to the back edge 15. Further, the sole structure 200 of the article of footwear 10 defines a longitudinal centerline 16 extending from the back edge 15 to the front edge 14 and located generally midway between the lateral edge 17 and the medial edge 18. Longitudinal centerline 16 generally bisects sole structure 200, thereby defining a lateral side and a medial side.
Referring to
The insole 212 (or sockliner), is generally a thin, compressible member located within the void for receiving the foot and proximate to a lower surface of the foot. The insole 212, which is configured to enhance footwear comfort, may be formed of foam. For example, the insole 212 may be formed of a 5.0 mm thick layer of polyurethane foam, e.g., injected Phylon. Other materials such as ethylene vinyl acetate or other foamed rubber may be used to form an insole. Typically, the insole or sockliner 212 is not glued or otherwise attached to the other components of the sole structure 200, although it may be attached, if desired.
In addition to outsole structures 210 and insoles 212, certain sole structures may also include midsoles 214. Conventionally, midsoles 214 form a middle layer of the sole structure 200 and are positioned between the outsole structure 210 and the insole 212. The midsole 214 may be secured to the upper 100 along the lower length of the upper. Midsoles 214 may have impact-attenuation capabilities, thereby mitigating ground (or other contact surface) reaction forces and lessening stresses upon the foot and leg. Further, midsoles 214 may provide stability and/or additional localized support or motion control for the foot or portions of the foot.
According to certain aspects, a midsole 214 need not be provided. This may be particularly appropriate when the sole structure 200 is designed to have a low profile and/or to be lightweight.
The outsole structure 210 may have one or more regions or portions 220 defined. For example, as shown in
According to some aspects of the present disclosure and referring to
Thus, according to aspects of the present disclosure, an outsole portion 220 may be designed with a particular structural configuration such that buckling occurs when the outsole structure is subjected to a predetermined pressure loading. For purposes of this disclosure, “buckling” refers to the occurrence of a relatively large deflection of a structure subjected to a compression load upon a relatively small increase in the compression load. The relatively large deflection in the direction of the application of the load may occur in conjunction with a large lateral deflection (i.e., a deflection lateral to the direction of the application of the load) of one or more components of the structure. For example, when a structure that consists of one or more relatively long, thin, slender members (e.g., plates or columns) is subjected to an initial compressive load, the long slender members may initially compress along their length in accordance with an essentially linear elastic stress-strain curve of the material. When this structure is then subjected to an increasing compressive load, at a certain critical load (referred to herein as a “trip point”) the long slender members may deflect laterally (bowing out) such that the structure experiences a large displacement in the direction of load application with a small increase in applied load. This large lateral deflection changes the load-carrying configuration of the structure, in essence, changing the stiffness of the structure. In the buckled configuration, the load required to compress the structure is less than the load required to compress the structure the same amount in the initial configuration. Thus, for a given increase in load, relatively large compressive displacements occur in the buckled structure. In other words, in the buckled configuration, the structure is “softened” and impact loads may be attenuated. If the structure continues to compress under the load, at some point it will “bottom out,” and once again, the compression will be governed by the stiffer stress/strain curve of the material.
A schematic example of a load versus displacement curve, as may be used to generally characterize such a multi-regime load versus displacement response system, is shown in
Within the second regime (II) the pressure-versus-displacement curve of the outsole portions 220 may be described as being generally “S-shaped.” This S-shape is due to the presence of the “trip point,” which is a local maximum, a “point-of-inflection,” and a local minimum. For purposes of the present disclosure, the term “point-of-inflection” refers to a point on a curve at which the change in curvature changes sign, i.e., when the curve changes from being concave downward to concave upward, or vice versa. In other words, the “point-of-inflection” is the point on a curve at which the second derivative changes sign. Even more simply, the point of inflection is where the tangent to the curve crosses the curve. At the local minimum, the pressure is at its minimum in the buckled regime. Further, relative to the first and third regimes, the change in the pressure carrying capacity of the outsole portions 220 in the second regime remains relatively flat.
According to certain aspects, the buckling of the outsole portion 220 is elastic buckling. For purposes of the present disclosure, the phrase “elastically-buckled” (and variations thereof) refers to a configuration of a load-carrying element wherein an abrupt and large increase in the displacement (usually accompanied by a relatively large lateral deflection) of the load-carrying element(s) occurs with only a minimal increase in the applied load, while the stresses acting on the load-carrying element remain wholly elastic. In such case, when the load is removed, the load-carrying element or elements assume their original configuration (i.e., the zero-load configuration) without experiencing any permanent deformation or set. In other words, elastic buckling has occurred if the buckled structure regains its original configuration upon the release of the buckling load.
In
In
Looking at another curve in
In
In general, the curves of
According to aspects of the disclosure and referring now to
Thus, the outsole structure 210 may include one or more outsole portions 220 and one or more of these outsole portions 220 may have a multi-regime pressure load versus displacement response system as discussed above.
Referring again to
The elongate sidewall elements 234, 244 are plate-like elements that extend from the elongate base elements 242 of the top layer 222 to the elongate base elements 232 of the bottom layer 224, thereby forming the alternating upward-facing and downward-facing channels 230, 240. Specifically, each of the sidewall elements 234, 244 extends from an elongated edge of one of the base elements 242 of the top layer 222 to an elongated edge of one of the base elements 232 of the bottom layer 224. At least one of the sidewalls 234, 244 of each channel 230, 240 is arranged at an angle to the top layer 222 of the outsole portion 220 that is greater than 45 degrees. More typically the sidewalls 234, 244 may extend at an angle of 70 degrees or greater from the surface plane of the top layer 222.
Thus, according to aspects of the disclosure, the outsole portion 220 has a top layer 222 a bottom layer 224, and a plurality of sidewalls 234, 244 extending therebetween, wherein the top layer 222, the bottom layer 224 and the sidewalls 234, 244 are configured to provide an array of alternating upward-facing channels 230 (upper channels) and downward-facing channels 240 (lower channels). In the embodiment of
The particular dimensions of the outsole portion 220 and of the channels 230, 240 may depend upon the particular application for the article of footwear 10. Further, the dimensions of the outsole portion 220 and of the channels 230, 240 may depend upon the degree of impact-attenuation desired, the degree of flexibility desired, the locations of the channels 230, 240 under the foot, the existence and/or spacing of adjacent channels 230, 240, the material used to form the channels 230, 240, the user's “feel” preferences, etc.
For example, still referring to
According to other aspects, the thickness (TU, TL) of the base elements 232, 242 and the thickness (TS) of the sidewalls 234, 244 of the channels 230, 240 may depend upon the desired performance of the outsole portion 220. Thus, in certain embodiments, for example as shown in
Additionally, referring for example to
According to other aspects, the thickness (TU, TL) of any individual base element 242, 232 need not be constant. For example as shown in
According to even other aspects, and referring back to
In even other embodiments, referring to
According to even additional aspects and referring back to
In some embodiments, the width (WU, WL) of the base elements 242, 232 may depend upon their location in the outsole portion 220. Thus, the width (WU, WL) of the base elements 242, 232 in the heel portion 220c may be less than the width (WU, WL) of the base elements 242, 232 in the forefoot portion 220a. In certain other embodiments, the width (WU, WL) of the base elements 242, 232 in certain medial portions 220d, 220f, etc. may be greater than the width (WU, WL) of the base elements 242, 232 in certain lateral portions 220e, 220g, etc.
In certain embodiments, for example referring to
Another parameter shown in
Representative geometries for select outsole portions are presented in Table I (with reference to
Referring in general to
According to other aspects, the spacing (DU, DL) of the base elements 232, 242 between any two adjacent base elements may be constant along the elongated length of the base elements 232, 242 (and, thus, along the elongated length of the channels 230, 240), such that adjacent base elements (and adjacent channels) are arranged parallel (or substantially parallel) to one another. Optionally, however, the spacing (DU, DL) of the base elements 232, 242 need not be constant along the elongated length of the base elements, such that the base elements 232, 242 (and adjacent channels) may diverge from and/or converge toward one another. For example, referring to
According to certain aspects of the invention, a plurality of the alternating upper and/or lower channels 230, 240 may undulate in the horizontal plane of the outsole structure 210. As shown in
Referring to
As shown in
Optionally, the undulations in the plane of the sole may be irregular or even random. For example, as shown in
As shown in
Thus, according to certain other aspects, a plurality of the upper base elements 242 may undulate in the substantially horizontal plane of the upper layer 222. Similarly, a plurality of the lower base elements 232 may undulate in the horizontal plane of the lower layer 224. In other words, when viewed from above (or below), each of the base elements 242, 232 that forms the top or bottom layer 222, 224 of the outsole portion 220 may have a nonlinear two-dimensional aspect along their elongated axis. In certain embodiments, for example as shown in
Additionally, the undulating features of the base elements 242 of the top layer 222 may be identical to the undulating features of the base elements 232 of the bottom layer 224. However, in certain embodiments, the undulations of the upper base elements 242 need not be the same as the undulations of the lower base elements 232. Thus, in an example embodiment, the upper base elements 242 (when viewed perpendicular to the plane of the sole) may have a zigzag configuration, while the lower base elements 232 (when viewed from below) may be smoothly sinusoidal. As another example, the undulations of the upper base elements 242 may have an amplitude and/or a period that differs from the amplitude and/or period of the undulations of the lower base elements 232. Even further, the lower base elements 232 may undulate in the plane of the sole, while the upper base elements 242 do not (or vice versa). Thus, for example, as shown in
As even another alternative configuration and referring to
With such non-symmetric undulating configurations, the sidewalls 234, 244 connecting the upper base elements 242 to the lower base elements 232 would generally have complex, curvilinear configurations. The sidewall elements 234, 244 may generally be considered to be planar, plate-like elements, i.e., having a length and/or a width that are considerably greater than their thickness (TS). However, it is to be understood that the sidewall elements 234, 244 may be flat, curved in one dimension (such as a cylindrical sidewall of a can would be) or doubly curved (such as a portion of a sphere). Most typically, the sidewalls 234, 244 will be linear in the vertical cross-sectional plane of the outsole structure 210 and either linear or curved along the length of the undulating channel 230, 240 (i.e., to follow the linear or curved undulations of the undulating base elements 232, 242 of the top and bottom layers 222, 224).
The top layer 222 and the bottom layer 224, and their associated undulating base elements 242, 232, may remain essentially planar. A person of ordinary skill in the art would understand that “essentially planar,” in the context of the upper and lower layers 222, 224, encompasses slight curvatures or other out-of-plane geometries as would be in keeping with a sole structure 200 following the contours of a foot and allowing for a comfortable and/or efficient gait. Thus, when viewed from the side, the individual base elements 242, 232 may also be essentially planar—the undulations of the base elements 232, 242 lie in the plane of the top (or bottom) layer 222, 224. In other words, as with the top (or bottom) layer 222, 224 as a whole, each base element 232, 242 may be essentially planar, with slight curvatures or out-of-plane geometries as would be in keeping with a sole structure following the contours of a foot.
Alternatively, as shown in
As discussed above and referring, for example, back to
Referring back to
In certain embodiments, for example as shown in
As noted above and referring to
The one or more outsole portion 220a, 220b, 220c, etc. may cover at least a majority of the outsole area (e.g., at least 75% of the area, or even at least 85% or more of the area) of the outsole structure 210. Further, the one or more outsole portions 220 may be unitarily formed or, alternatively, the one or more outsole portions 220 may be made from different and/or separate pieces of material that are cemented or otherwise engaged to one another or with other portions of the outsole structure 210, if any.
Other conventional outsole configurations may also be provided within the outsole structure 210 where the one or more outsole regions 220, as disclosed herein, are not located. Thus, if desired, one or more regions of the outsole structure 210 may be provided without any channels 230, 240 or without any undulating elements 232, 242 without departing from the invention (see, for example,
The outsole portions 220 may further include a frame member 226 that extends around the perimeter of the outsole portion 220 and serves to connect the ends of the channels 230, 240 and/or the base elements 232, 242 together. The frame member 226 may lie in the same plane as the top layer 222 or the bottom layer 224. When the outsole structure 210 includes but a single outsole portion 220, the frame member 226 may extend around the perimeter of the outsole structure 210, which generally will coincide with the perimeter of the article of footwear.
Additionally, in one aspect, the outsole structure 210 may be a cupsole, formed as a single piece. According to this aspect, the outsole structure 210 may include a perimeter element 216 extending along at least a portion of the perimeter of the outsole structure 210. Typically, the perimeter element 216 forms a flange or sidewall that extends upward from the top layer 222 to form a structure that may cup and assist in retaining the upper 100 and/or the midsole 214, if any. The perimeter element 216 may be unitarily formed or co-molded with, or otherwise attached to, the top layer 222 or bottom layer 224. Further, the perimeter element 216 may also serve as a frame member 226 that connects the ends of the channels 230, 240 and/or base members 232, 242 together.
In operation, as the outsole structure 210 is initially compressed, energy is absorbed by the outsole structure's impact-attenuation system. As the outsole structure 210 is compressed even more, additional energy is absorbed by the system. For high-impact loading, it would be desirable to have a significant amount of energy absorbed by the system without the user's foot experiencing high impact loads. The disclosed impact-attenuation system provides a mechanism to absorb energy while at the same time minimizing or ameliorating the loads experienced by a user during the impact. As described below, the multi-regime outsole portions 220 disclosed herein may absorb significant amounts of energy, for example, as compared to conventional foamed midsoles with conventional outsoles, while minimizing or reducing the loads experienced by the user during the impact event.
Examples of energy absorption curves of various outsole portions 220 are shown in
Examining curve (A), it is seen that its “trip point” is from 300 kPa to 350 kPa, and that without exceeding the pressure of 350 kPa the outsole portion 220 associated with curve A absorbs from 700 J/mm2 to 800 J/mm2. In comparison, at a pressure of 350 kPa the foam block absorbs only about 330 J/mm2. In other words, at a pressure of 350 kPa, the outsole portion associated with curve A absorbs more than twice (approximately 2.3 times) the energy per unit area as the control foam block. Even further, when the “trip point” pressure value is first reached (i.e., its first occurrence), the energy per unit area is approximately 300 J/mm2, and when the “trip point” pressure value is next reached (i.e., its second occurrence), the energy per unit area is approximately 750 J/mm2. Thus, from the first occurrence to the second occurrence of the “trip point” pressure value, the amount of energy absorbed by the outsole portion 220 associated with curve A has more than doubled.
Examining curve (B), it is seen that its “trip point” is from 450 kPa to 500 kPa, and that at a pressure of approximately 470 kPa the outsole portion 220 associated with curve B absorbs approximately 1000 J/mm2—approximately 1.8 times the energy per unit area as the control foam block. Further, at a pressure of 550 kPa, the outsole portion absorbs from 1000 J/mm2 to 1100 J/mm2. In comparison, at a pressure of 550 kPa the foam block absorbs only about 740 J/mm2. Even further, when the “trip point” pressure value is first reached (i.e., its first occurrence), the energy per unit area of curve B is approximately 450 J/mm2, and when the “trip point” pressure value is next reached (i.e., its second occurrence), the energy per unit area is approximately 1000 J/mm2. Thus, from the first occurrence to the second occurrence of the “trip point” pressure value, the amount of energy absorbed by the outsole portion 220 associated with curve B has increased by approximately 70%.
Examining curve (C), it is seen that its “trip point” is from 600 kPa to 650 kPa, and that at a pressure of 650 kPa the outsole portion 220 associated with curve C absorbs approximately 1200 J/mm2—approximately 26% more energy per unit area as the control foam block. When the “trip point” pressure value is first reached (i.e., its first occurrence), the energy per unit area of curve C is approximately 600 J/mm2, and when the “trip point” pressure value is next reached (i.e., its second occurrence), the energy per unit area is approximately 1150 J/mm2. Thus, from the first occurrence to the second occurrence of the “trip point” pressure value, the amount of energy absorbed by the outsole portion 220 associated with curve C has increased by approximately 90%.
Another way of viewing the curves of
The outsole structure 210 may be formed of conventional outsole materials, such as natural or synthetic rubber or a combination thereof. The material may be solid, foamed, filled, etc. or a combination thereof. One particular rubber may be a solid rubber having a Shore A hardness of 74-80. Another particular composite rubber mixture may include approximately 75% natural rubber and 25% synthetic rubber. The synthetic rubber could include a styrene-butadiene rubber. By way of non-limiting examples, other suitable polymeric materials for the outsole include plastics, such as PEBAX® (a poly-ether-block co-polyamide polymer available from Atofina Corporation of Puteaux, France), silicone, thermoplastic polyurethane (TPU), polypropylene, polyethylene, ethylvinylacetate, and styrene ethylbutylene styrene, etc. Optionally, the material of the outsole structure 210 may also include fillers or other components to tailor its wear, durability, abrasion-resistance, compressibility, stiffness and/or strength properties. Thus, for example, the outsole structure 210 may include reinforcing fibers, such as carbon fibers, glass fibers, graphite fibers, aramid fibers, basalt fibers, etc.
While any desired materials may be used for the outsole structure 210, in at least some examples, the rubber material of the outsole structure 210 may be somewhat softer than some conventional outsole materials (e.g., 50-55 Shore A rubber may be used), to additionally help provide the desired multi-regime characteristics. Optionally, if desired, a harder material (e.g., 60-65 Shore A rubber) may be used in the heel region and/or in certain medial regions.
Further, multiple different materials may be used to form the outsole structure 210 and/or the various outsole portions 220. For example, a first material may be used for the forefoot region 11 and a second material may be used in the heel region 13. Alternatively, a first material may be used to form the ground-contacting bottom layer 224 and a second material may be used to form the sidewalls 234, 244 and/or the top layer 222. The outsole structure 210 could be unitarily molded, co-molded, laminated, adhesively assembled, etc. As one non-limiting example, the ground-contacting layer 224 (or a portion of the ground-contacting bottom layer) could be formed separately from the sidewalls 234, 244 and/or the top layer 222 and subsequently integrated therewith.
The ground-contacting bottom layer 224 may be formed of a single material. Optionally, the ground-contacting bottom layer 224 may be formed of a plurality of sub-layers. For example, a relatively pliable layer may be paired with a more durable, abrasion resistant layer. By way of non-limiting examples, the abrasion resistant layer may be co-molded, laminated, adhesively attached or applied as a coating. Additionally, the material forming the abrasion resistant layer of the outsole structure 210 may be textured (or include texturing inclusions) to impart enhanced traction and slip resistance.
Further, with respect to another aspect of the disclosure, at least a portion of the outsole structure 210 may be provided with a grip enhancing material 218 to further enhance traction and slip resistance (see e.g.,
According to certain aspects and referring back to
Typically, a strobel 260 is a sole-shaped element that may include thin flexible materials, thicker and/or stiffer materials, compressible materials or a combination thereof to improve stability, flexibility and/or comfort. For example, the strobel 260 may include a cloth material, such as a woven or non-woven cloth supplied by Texon International, or a thin sheet of EVA foam for a more cushioned feel. An example strobel may be an EB-Strobel. The strobel 260 may have a thickness ranging from approximately 4.0 mm to approximately 10.0 mm, from approximately 5.0 to approximately 9.0 mm or even from approximately 6.0 to approximately 8.0 mm. For some applications, the strobel 260 would be thicker in the heel region than in the forefoot region. For certain applications, the strobel 260 may only be provided in the forefoot region, the midfoot region, the heel region, or select portions or combinations of these regions. A foam sockliner 212 such as described above, may be provided on top of the strobel 260.
It is to be understood that the addition of a strobel 260 or a sockliner 212 (or any other structure) will generally affect the stiffness characteristics of the outsole structure 210. Thus, the above discussion of outsole portions 220 and their stiffness characteristics is with respect to the outsole portions 220, in and of themselves, i.e., without the inclusion of any additional structure as may be part of the outsole structure 210 as a whole.
According to even other aspects of this disclosure and referring again to
For example, if desired, fill elements 250 may include an impact-attenuating material that at least partially fills, and in some instances completely fills, at least some of the upwardly-facing channels 230 of an outsole region 220. This additional impact-attenuating material, which may be somewhat softer than the material from which the channel is constructed, can also help provide a smooth and comfortable surface for user foot contact while still transmitting forces to the bottom layer 224 and to the downwardly-facing channels 240. The impact-attenuating material may include relatively soft polyurethane or other foam material. The fill elements 250, if any, may be co-molded in conventional manners along with the molding process used to form the outsole structure 210 or the fill elements 250 may applied to the outsole structure 210 in a separate manufacturing operation. The strobel 260 and the fill elements 250 are separate elements that may be provided independently of each other.
Even further as shown in
Thus, from the above disclosure it can be seen that the enhanced impact-attenuation system due to the outsole portions 220 as disclosed herein provides better impact protection, while not sacrificing feel, for a wearer of the article of footwear. During use, one or more of the channels 230, 240 provide support for the wearer's foot. The channels 230, 240 in a first, unbuckled configuration carry or react at least some of the vertical, compressive load transmitted from the wearer to the ground. Thus, according to certain aspects of the disclosure, the channels 230, 240 in a first pressure-versus-displacement regime are designed to elastically react vertical compressive loads. In this first regime, the pressure versus displacement curve may be relatively stiff such that the wearer is able to get a good “feel” for the engaged surface. When a “trip point” load is reached, the channels 230, 240 are designed to assume a second, buckled, configuration. In such a second pressure-versus-displacement regime, the channels 230, 240 are designed to compliantly absorb additional impact energy without substantially any additional increase in load (for a given change in displacement). At some point in the post “trip point” regime, the buckling of the sidewalls 234, 244 will be at least partially arrested or physically limited and the stiffness of the outsole portion 220 will start to increase. For example, two adjacent sidewalls 234, 244 may lateral deflect until they contact one another, at which point, the lateral deflection of one sidewall will serve to limit the lateral deflection of the other sidewall (and vice versa). Upon release of the load, the channels 230, 240 return to their original configuration, without any permanent set or deformation. If the impact energy to be dissipated is great enough, the channels 230, 240 will eventually essentially “bottom out,” and the load experience by the wearer's foot in this third pressure-versus-displacement regime may increase above the “trip point” load.
The “trip point” load may be selected such that under normal walking or usage conditions the “trip point” is not reached. In other words, the channels 230, 240 may be designed with a high enough “trip point” such that the “trip point” is only achieved under relatively high impact loads. Further, the “trip point” may be selected based on expected loading events and peak pressure distributions under the foot. So, for example, for a skateboard shoe a target “trip point” of 350 kPa (+/−50 kPa, +/−75 kPa, or even +/−100 kPa) may be selected to accommodate expected loads during high impact tricks in the forefoot region of the foot, while a target “trip point” of 550 kPa (+/−50 kPa, +/−75 kPa, or even +/−100 kPa) may be selected to accommodate expected loads during high impact tricks in the heel region of the foot. Other “trip points” could be selected based on the expected impact event.
The disclosed multi-stage or multi-zoned vertical stiffness profile of this disclosed impact-attenuation system allows impact loading associated with normal activities such as walking to be reacted by the stiffer configuration of the outsole portions 220, thereby providing greater “feel” for the ground during low impact operation. The greater impact loading associated with jumping and tricks may be partly reacted by the softer, buckled, configuration of the outsole portions 220, thereby providing a “high-impact cushioning system,” i.e., a stiffness regime that provides superior protection for the wearer during such high impact activities.
This disclosed impact-attenuation system allows the sole structure 200 to be tailored to the specific application. The stiffness and compression characteristics (and particularly, the pressure-versus-displacement curves) of any particular outsole portion 220 is a function not only of its material (as would be the case with conventional cushions and foams) but also of its geometry. Thus, in essence, the geometry of the outsole portions 220 may be selected so that a particular pressure-versus-displacement characteristic may be achieved in the first regime, a desired “trip point” may be design to, and the post-buckling pressure-versus-displacement characteristics in the second regime may be tailored so that the expected impact energy is reacted without exceeding the desired “trip point” a second time. For certain embodiments, as compared to a sole structure having a solid foam midsole, the outsole portions 220 may be designed to be initially stiffer, but then softer than a solid foam midsole sole structure.
Thus, according to certain aspects, under expected low-impact loading conditions, the outsole portions 220 could be designed to act like a conventional, relatively stiff sole. Loads reacted at the ground (or other engaged surface) would be transmitted through the sole with relatively little attenuation such that a user would “feel” the reaction loads. Under high-impact loading conditions (i.e., when the “trip point” is reached), the sidewalls 234, 244 could be designed to buckle, resulting in a relatively short vertical displacement of the outsole portion 220 under a reduced (or possibly the same) pressure. During this buckling, post “trip point” regime, the user would feel a softening of the sole and experience a corresponding cushioning or “sinking-in” feel. Although the user will lose some “feel” for the ground during this “sinking-in” period, the loads experienced by the user will be attenuated, thus protecting the user's foot from injury. As the vertical displacement increases, at some point it is expected that the user will start to experience increasing reaction loads. Bottoming out occurs when the deflection due to buckling has reached it maximum, at which point impact force attenuation would be achieved by compression of the material of the outsole portion 220.
While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art, given the benefit of this disclosure, will appreciate that there are numerous variations and permutations of the above described structures, systems and techniques that fall within the spirit and scope of the invention as set forth above. Thus, for example, a wide variety of materials, having various properties, i.e., flexibility, hardness, durability, etc., may be used without departing from the invention. Finally, all examples, whether preceded by “for example,” “such as,” “including,” or other itemizing terms, or followed by “etc.,” are meant to be non-limiting examples, unless otherwise stated or obvious from the context of the specification.
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