Boots – shoes – and leggings – Soles – Laminated
Reexamination Certificate
1997-05-30
2001-03-27
Patterson, M. D. (Department: 3728)
Boots, shoes, and leggings
Soles
Laminated
C036S031000, C036S107000, C036S102000, C036S114000
Reexamination Certificate
active
06205683
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel approach for integrating a means, in the rear of a shoe, for providing shock diffusion and torsional stiffness (rigidity) in a shoe construction methodology which lends itself to the economical production of shoes for performance applications including running, hiking and sustained walking. The shoe constructed by this methodology is lightweight and disperses pressure both throughout the top of the midsole and across more of the foot surface than in a shoe made according to more conventional construction techniques.
BACKGROUND OF THE INVENTION
The heel is generally the first part of the foot to impact the ground. This heel strike, as it is generally known, places extra stress on the heel and can lead to unnecessary repetitive motion injury. Shoe designers have long recognized that shock absorption and diffusion are necessary to reduce the stress on initial impact of the heel. Means have therefore been provided within the soles of shoes for some of the impact on the heel to be absorbed by the sole and diffused away from the heel area. The attempt has been to spread the force concentrated in a small area of the heel over a larger area to avoid a local “sore spot”.
Past attempts to diffuse the force of a heel strike have usually involved the addition of complicated structures to the shoe which added additional and sometimes complicated manufacturing steps. For example, in U.S. Pat. No. 1,566,364, Blair discloses a spring member made of steel which is disposed between the outsole and inner lining and extends into a recess under the heel. The spring member in conjunction with optional sponge rubber inserted in the recess is said to relieve the shock of the heel strike. As another example, in U.S. Pat. No. 5,185,943, Tong et al. disclose providing cushioning, stability and support in an athletic shoe by adding an insert which must be positioned between the midsole and outsole or encapsulated within the midsole or outsole. It is also known in the prior art to add a steel shank between the insole and outsole to support the shank area of the shoe and the arch of the foot. It is further known in the prior art to incorporate a tuck support into the insole board such as with a reinforced piece of texon board.
Basic shoe construction techniques have to some degree added inherent shock diffusion properties to the shoes manufactured by them. For example, a basic cement construction technique involves tacking an insole board to the shoemaker's last and cementing the marginal edges of the shoe upper—so called “lasting margins”—to the insole board. Such shoes are completed by the addition of an outsole and optionally a midsole. In addition, a sock liner or full orthotic was added to complete the interior of the shoe. Special purpose footwear incorporated lining materials to insulate the shoe and/or add waterproof-breatheability characteristics to the upper.
The use of a traditional full length insole board is a relatively poor structure to serve as the foundation for a shock diffusion system, even if combined with an appropriate sock liner or orthotic and a midsole with the appropriate elastic/damping properties. The material commonly used for such prior art insole boards (e.g. Texon board) is not sufficiently rigid to properly transmit and spread the localized force to the entire midsole because it must flex in the forefoot region in order to accommodate a normal walking or running gait. In addition, the use of a full length insole board does not permit the designer to select the area of the midsole which will bear the primary load in diffusing the shock of the initial heel strike.
The conventional use of a flat last to assemble shoes has also hindered the ability to diffuse the force of heel strike because the flat lasting technique does not permit the use of an insole board contoured to the shape of the foot. As a result, the force of the heel strike remains concentrated in the vicinity of the local sore spot.
There is therefore a need for achieving increased shock diffusion of the initial heel strike but limiting the shock diffusion to the heel and arch areas of the foot without compromising the maximum flexibility required in the forepart region of the shoe.
Another problem that has been addressed by the footwear industry is excess pronation (i.e., the outward rotation or twisting of the foot) which causes injuries. Solving this problem has led shoe designers to incorporate complex pronation control devices. For example, in U.S. Pat. No. 4,288,929, Norton et al. disclose a device which comprises an additional plastic piece attached between a lasted upper and the outsole, the plastic piece having medial and lateral walls formed around the heel. Another pronation control device, which is incorporated into the midsole, is disclosed in Kilgore et al. in U.S. Pat. No. 5,247,742.
It is therefore also advantageous to incorporate a device for reducing excessive pronation without adding additional components.
SUMMARY OF THE INVENTION
It is an object of this invention to provide in footwear a means which maximizes shock diffusion and torsional stiffness in the heel and midfoot area but, to reduce foot fatigue, does not compromise flexibility in the forefoot area where it would place undesirable stress on the metatarsals.
It is a further object of this invention to provide a means for shock diffusion which is simple and economical to fabricate.
It is a further object of this invention to provide a shoe wherein the pressure from the heel strike is dispersed directly under the foot and is further dispersed throughout the top of the midsole by exploiting more of the surface areas available under the foot as well as on top of the midsole for shock absorption.
It is a further object of this invention to provide a shoe construction methodology which uses a contoured last to construct a shoe having an insole board and sock liner which are contoured in the heel and arch areas.
It is a further object of this invention to provide arch support which cradles the foot and offers superior medial and lateral stability to reduce rearfoot motion during human locomotion.
It is a further object of this invention to provide a shoe whose properties will not degrade over time.
It is a further object of this invention to accomplish the above objectives while further enhancing the performance of multi-purpose outdoor footwear by providing an outsole with distinct zones, each zone maximized to perform the function specifically required at that portion of the gait cycle where such zone is utilized.
These objectives are accomplished in a shoe comprising a novel combination insole board in combination with a midsole and an outsole. The combination insole board comprises a semi-rigid shock diffusion plate in the heel and arch areas of the shoe to permit the diffusion of the force placed on the shoe during heel strike by a wearer. The combination insole board further comprises a flexible material in the forepart area of the shoe and attached to the shock diffusion plate. The shock diffusion plate, which may be loosely contoured to a foot morphology, also advantageously increases torsional stiffness.
In one preferred embodiment, the shoe comprises a single piece midsole extending substantially throughout the length of the shoe. In another embodiment, the midsole is comprised of two separate sections, a first section underlying the heel area and a second section underlying the forepart area. Depending on the type of end use for which the shoe is designed, the midsole may be made from either polyurethane, die cut ethylene vinyl acetate (EVA), compression molded EVA, polyvinyl chloride or thermoplastic rubber.
An orthotic, which is more closely contoured to the foot morphology than the shock diffusion plate, is preferably inserted into the shoe. A preferred orthotic comprises a blend of polyethylene and EVA.
The contoured orthotic, shock diffusion plate and midsole work in conjunction to diffuse the force of heel strike.
The shoe of the present invention may be constructe
Boyer Joseph D.
Clark Douglas E.
Roux Stephen R.
Schuette Lee A.
Todtfeld Bruce N.
Orrick Herrington & Sutcliffe LLP
Patterson M. D.
The Timberland Company
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