SHOE HAVING A COMPOSITE ROLL BAR

Technical Field

The present invention relates to shoes and sole components therefor, and more particularly, to a shoe having a sole with a wedge-shaped member therein.

Background of the Invention During an athletic activity, an athlete's feet can be subjected to large, repetitious, vertical ground reaction or impact forces. The impact forces associated with foot strike while walking are typically 1 to 1.5 times the athletes body weight. Runners impact the ground with vertical forces as high as three to four times their body weight, depending upon their speed. In more dynamic activities, such as aerobics and basketball, impact forces have been recorded as high as five to six times the athletes body weight.

The human body attenuates impact forces through a complex 3- dimensional motion of the foot at the subtalar joint area. This complex motion, known as pronation, occurs naturally and is an efficient biomechanism that attenuates the vertical forces through transverse rotation of the foot, ankle, and leg. During a walking or running gait, the athlete's foot initially contacts the ground in a fairly rigid supinated position. Pronation begins as the impact forces increase during full foot contact and continues to occur until the athlete reaches mid stance. During this pronation phase, the arch of the foot flattens, the ankle flexes, and the lower leg internally rotates. In addition, potential energy is stored in the bones and connective tissues of the body; i.e., ligaments, tendons, and muscles. As the athlete's gait reaches a propulsion phase, the potential energy stored in the connective tissues of the body is converted into kinetic energy, which is used for efficient toe off.

When the rate or range of pronation is excessive, the connective tissues of the body are subjected to high stress loads that greatly increase the risk of injury. Such excessive pronation has been attributed to many overuse injuries associated with athletics. Accordingly, it is highly desirable for a shoe to maintain functional foot biomechanics during movement while achieving a balance of adequate cushioning and stability. If a midsole is too soft, it will not provide sufficient stability or motion control, and excessive pronation may occur. If the midsole is too hard, it will not possess cushioning and dampening characteristics sufficient to adequately attenuate the impact forces.

Prior art shoes incorporate a midsole made of ethylvinylacetate (hereinafter referred to as "EVA") which is a closed-cell foam material. EVA is light weight and stable foam that possesses viscous and elastic qualities. In addition, the hardness or durameter of EVA can be altered by adjusting the manufacturing technique. The major drawback of EN A, however, is that the closed-cell structure collapses thereby resulting in compression set and a reduction in its impact attenuating and rebound qualities. An ENA heel wedge has been incorporated into a midsole to limit or control the extent of pronation experienced by the athlete. After a period of use, however, the ENA heel wedge breaks down and experiences compression set such that the heel wedge no longer controls pronation. Other closed-cell foam material such as polyurethane and polyethylene have been used in an attempt to achieve a proper balance of cushioning and stability. However, these closed-cell foams tend to be heavy and also suffer from some compression set.

The major limitation of closed-cell foam materials is that they are difficult to regulate and a single foam material must provide the two functional characteristics of a viscous shock attenuating system and an elastic rebound system. As a result, both characteristics are compromised. In addition, the protective midsole qualities are constantly deteriorating as the shoe is used. As such, the athlete cannot adapt to the change such that potential for injury increases. During the past several years, new materials and midsole concepts have been incorporated into shoe designs to enhance the protective qualities and overall durability of the midsole. These advances in materials have led to the development of midsoles having air, gel, or other viscous fluid therein that primarily enhance the shock attenuating quality of the shoe design.

To achieve a desirable balance of cushioning and elastic or "energy return" componentry, athletic shoes have used a single composite plate positioned within an ENA or polyurethane midsole to enhance its elastic quality, thereby providing stability for efficient propulsion during toe off. However, the benefit of these composite technologies has not reached its maximum potential because the surrounding ENA or polyurethane foam still breaks down over time when it becomes worn and fails to protect against excessive pronation.

Summary of the Invention

The present invention provides an improved roll bar for use in shoes, including, for example, athletic shoes, and shoes including such a roll bar. In a preferred embodiment, an athletic shoe may have an upper portion and a sole wherein the sole has a midsole attached to the upper portion, a composite wedge-shaped member or roll bar within the midsole in the heel area of the shoe, and an outer sole attached to the midsole.

The composite roll bar has top and bottom layers of carbon fiber composite material that communicates with the midsole, and medial and lateral sides that communicate with medial and lateral sides of the midsole. The composite roll bar further has a rear end that communicates with the heel area of the midsole and a front end that communicates with a midpoint between the heel and toe of the midsole. A resilient core is sandwiched between the top and bottom composite layers. The composite roll bar tapers laterally downward from the medial side to the lateral side, and it tapers longitudinally downward from the rear end to the front end. Thus, the composite roll bar tapers in two directions. In one embodiment of the present invention, the top and bottom composite layers of the composite roll bar are carbon fiber composite plates, and the resilient core is an elastic thermoplastic urethane core having channels therein extending laterally from the lateral side to the medial side between the top and bottom composite layers. The composite roll bar is positioned in the heel area of the midsole and is sandwiched between top and bottom portions of the midsole, wherein the top portion is attached to the heel area of the upper shoe portion, and the bottom portion is attached to the heel area of the outer sole.

Brief Description of the Drawings

Figure 1 is a schematic representation of a shoe with a composite roll bar in the shoe's sole in accordance with a preferred embodiment of the present invention.

Figure 2 is a rear elevation view of the shoe of Figure 1.

Figure 3 is an enlarged front isometric view of the composite roll bar of Figure 1 removed from the shoe's sole.

Figure 4 is a rear elevation of the composite roll bar of Figure 3.

Detailed Description of the Preferred Embodiment

The present invention will be more clearly understood from the following detailed description of a preferred embodiment taken in conjunction with the attached drawings. As seen in Figures 1 and 2, a shoe 10 including, for example, an athletic shoe, has an upper shoe portion 12, a shoe sole 16 that includes a midsole 18 and a wedge-shaped composite roll bar 20. The upper shoe portion 12 shaped and sized to receive a person's foot and is constructed such that it has a toe area 22 at its front end, a heel area 24 at its rear end, an inner or medial side 21, and an outer or lateral side 23. The upper shoe portion 12 is similar to the upper shoe portion 12, the sole 16 has a toe end 26, a heel end 28, a medial side 25, and a lateral side 27. The sole 16 runs the length of the shoe between the toe and heel areas 22 and 24 and between the medial and

lateral sides 21 and 23 of the upper shoe portion 12. Thus, the heel end 28 of the sole 16 communicates with the heel area 24 of the upper shoe portion 12, the toe end, 26 communicates with the toe area 22 of the upper shoe portion, and the sole's medial and lateral sides 25 and 27 communicate with the medial and lateral sides 21 and 23 of the upper shoe portion, respectively.

The sole 16 includes the midsole 18 which runs the length of the sole from the heel end 28 to the toe end 26, and receives the upper shoe portion 12 along the top of the midsole. In the preferred embodiment illustrated herein, the top of the midsole's heel end 28 is shaped to form an integral heel cup 30 that receives the heel area 24 of the upper shoe portion 12 and provides enhanced lateral support for the wearer's foot. The midsole 18 is constructed of a flexible, lightweight, and durable material, such as blown foam, so the midsole will flex in concert with the wearer's foot without excessive resistance. An outer sole 34 attaches to the bottom surface 35 of the midsole 18 and runs the length of the midsole. The outer sole 34 is attached to the midsole 18 in a convention manner such that tread (not shown) on the outer sole engages the ground or any other surface that the athlete may encounter.

The midsole 18 is also attached to the composite roll bar 20 that is positioned within the midsole. The composite roll bar 20 has a rear end 40, a front end 38, a medial side 42, and a lateral side 44. The composite roll bar 20 extends from the heel end 28 of the midsole 18 forward toward the toe end 26. The front end 38 of the composite roll bar 20 terminates within the midsole 18 rearward of the toe end 26 at a position under the arch of the wearer's foot and rearward of the first metatarsal head. In addition, the medial and lateral sides 42 and 44 of the composite roll bar 20 are coextensive with the medial and lateral sides 25 and 27 of the sole 16. The midsole 18 receives the composite roll bar 20 from a midpoint 41 rearward to the heel end 28 such that the midsole is divided into a top portion 43 that adheres to the upper shoe portion 12 from the midpoint rearward to the heel, and a bottom portion 45 that attaches to the outer sole 36 from the midpoint rearward to the heel. Thus, the composite roll bar 20 is sandwiched between the top and bottom portions 43 and 45 of the midsole 18. In the preferred embodiment, the composite roll bar 20 is adhered within the midsole 18 with a conventional adhesive. In addition, the midpoint 41 is under the arch of the wearer's foot rearward of the first metatarsal head, although the location of the midpoint can be at virtually any position between the heel and toe ends 28 and 26 of the midsole, depending upon the length of the composite roll bar 20.

As best seen in Figures 3 and 4, the composite roll bar 20 is a wedge- shaped member having a bottom layer or plate 48, a top layer or plate 50 and a resilient

core 52 between the top and bottom plates. The top and bottom plates 50 and 48, and the core 52 are assembled such that the composite roll bar 20 tapers downward in the longitudinal direction from a relatively thick rear end 40 to a relatively thin front end 38, and it tapers downward in a direction transverse to the longitudinal direction, hereinafter referred to as the lateral direction, from a relatively thick medial side 42 to a relatively thin lateral side 44. Thus, the composite roll bar 20 tapers in two directions.

The top and bottom plates 50 and 48 are constructed of a composite material, such as a carbon fiber composite or a hybrid graphite composite. The composite top and bottom plates 50 and 48 are light weight, very durable, possess a superior strength to weight ratio, and provide an excellent elastic characteristic that gives the sole a high "energy return" during a gait. As such, the elastic properties of the composite top and bottom plates 50 and 48 do not deteriorate during repeated impacts over the life of the shoe 10. Thus, the composite roll bar 20 solves the major drawback of breakdown and consequent loss of cushioning due to deterioration of the elastic resilient character, with the deterioration-resistant composite roll bar of the present invention replacing a significant volume, e.g., from the midpoint 41 rearward to the heel end 28, of the foam midsole material used in the prior art. The resilient core 52 between the composite top and bottom plates is an elastic material, such as elastic thermoplastic urethane that has elastic qualities to dampen and attenuate impact forces generated during athletic activities, and it does not deteriorate or break down when subjected to repeated impacts. Although the preferred embodiment utilizes the elastic thermoplastic urethane core, other suitable elastic material can be sandwiched between the composite top and bottom plates 50 and 48 to provide the desirable cushioning and elastic characteristics of the shoe. Referring to Figures 1 and 2, the composite roll bar 20 is positioned within the midsole 18 between the top and bottom portions 43 and 45 of the midsole such that the bottom plate 48 is substantially horizontal or level with the ground, and the top plate 50 has a slanted orientation relative to the bottom plate. Accordingly, the top portion 43 has more blown foam material on the lateral side 27 of the sole 16 to accommodate the slanting top plate 50 and to maintain a relatively level surface within the heel cup area 30.

Referring now to Figures 1, 3, and 4, the resilient core 52 has a plurality of channels 54 extending through the composite roll bar 20 between the medial and lateral side 42 and 44. These channels 54 result in a lighter weight composite roll bar 20, and they allow the resilient core 52 to compress and deform somewhat into the area within the channels when subjected to a sufficient impact force. Thus, compression characteristics of the composite roll bar 20 can be altered during manufacturing by

increasing or decreasing the size of the channels 54 and by increasing or decreasing the amount of material between the top and bottom composite plates 50 and 48. The channels 54 are formed such that an inside surface 56 of the composite top and bottom plates 50 and 48 is exposed on the top and bottom areas of each channel, and the resilient core 52 essentially forms vertically oriented supported strips extending laterally across the composite roll bar 20. In the preferred embodiment, four channels 54 fully extend through the composite roll bar 20, however, the composite roll bar may be configured with greater or lesser number of channels and the channels may be configured with different orientations to achieve desired elastic and cushioning characteristics. The resilient core 52 is an especially formulated thermoplastic urethane core called Elastollan, manufactured by BASF Corporation of Parsippany, New Jersey. Elastollan is a very resilient material having superior strength to weight ratios and elastic qualities that do not deteriorate when subject to repeated impact.

The unique geometry and construction of the composite roll bar 20 works in conjunction with the natural kinematics of the foot to attenuate impact forces and control excessive pronation. For example, as a person's foot contact the ground, it is in a supinated position such that the lateral portion of the heel contacts the ground first and the rearward lateral side of the resilient core 52 will compress and partially attenuate the vertical impact forces. In addition, the composite top and bottom plates 50 and 48 slightly deflect to absorb and store potential energy therein. As the person's gait continues into the pronation phase, weight is rotated or transferred from the lateral side 44 of the composite roll bar 20 across to the medial side 42 such that a greater area of the resilient core 52 is compressed and a larger areas of the composite top and bottom plates 50 and 48 are deflected. The medial side 42 of the composite roll bar 20 is prevented from compressing too much because of the relatively thick core 52 at that side, thereby preventing excessive pronation while maintaining a stable platform for the foot. As the weight and forces are transferred during the toe off, the potential energy stored in the composite top and bottom plates 50 and 48 and in the resilient core 52 is released and transmitted back to the wearer's foot as rebound energy that propels the athlete into the next step.

Numerous modifications and variations of the shoe having a composite roll bar disclosed herein will occur to those skilled in the art in view of this disclosure. For example, the composite roll bar 20 can be assembled within the sole 16 of the shoe 10 such that it is sandwiched between the midsole 18 and the outer sole 36 of the shoe 10 or between the midsole and the upper shoe portion 12 such that the composite roll bar is not sandwiched between top and bottom portions of the midsole. Furthermore, other configurations of the channels 54 or the like may be formed within

the composite roll bar to achieve a desired shock attenuating characteristic and elastic rebound characteristic. Therefore, it is to be understood that these modifications and variations, and the equivalents thereof, may be practiced while remaining within the spirit and scope of the invention as defined in the following claims.