Boots – shoes – and leggings – Soles – Cushion
Reexamination Certificate
2000-03-16
2003-06-03
Kavanaugh, Ted (Department: 3728)
Boots, shoes, and leggings
Soles
Cushion
C036S03500R
Reexamination Certificate
active
06571490
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an improved cushioning member for a shoe, and more particularly to a fluid filled bladder having multiple layers of chambers of varying pressures to provide regionalized cushioning to predetermined areas of the bladder and a method of forming an improved cushioning member with inverted seam lines along its sidewalls.
BACKGROUND OF THE INVENTION
Considerable work has been done to improve the construction of cushioning members which utilize fluid filled bladders such as those used in shoe soles. Although with recent developments in materials and manufacturing methods, fluid filled bladders have greatly improved in versatility, there remain problems associated with obtaining optimum cushioning performance and durability. Fluid filled bladder members are commonly referred to as “air bladders,” and the fluid is generally a gas which is commonly referred to as “air” without intending any limitation as to the actual gas composition used.
There are numerous conventional articles of footwear having gas filled cushioning devices in their midsole or outsole. Gas filled cushioning devices are typically referred to as bladders or “air bladders,” and the gas is commonly referred to as “air” without intending any limitation as to the actual gas composition used. One well known type of bladder used in footwear is commonly referred to as a “two film bladder.” These bladders include an outer shell formed by welding the peripheral edges of two symmetric pieces of a barrier material together. This results in the top, bottom and sidewalls of the bladder being formed of the same barrier material. If any one part of a two film bladder needs to be formed of a specific material and/or to a specific thickness, the entire bladder must be formed of that specific material and/or to that specific thickness. Forming a bladder from only two pieces of a barrier material prevents the side, top and bottom walls from being customized.
Closed-celled foam is often used as a cushioning material in shoe soles and ethylene-vinyl acetate copolymer (EVA) foam is a common material. In many athletic shoes, the entire midsole is comprised of EVA. While EVA foam can easily be cut into desired shapes and contours, its cushioning characteristics are limited. One of the advantages of gas filled bladders is that gas as a cushioning compound is generally more energy efficient than closed-cell foam. This means that a shoe sole comprising a gas filled bladder provides superior cushioning response to loads than a shoe sole comprising only foam. Cushioning generally is improved when the cushioning component, for a given impact force, spreads the impact force over a longer period of time, resulting in a smaller impact force being transmitted to the wearer's body. Even shoe soles comprising gas filled bladders include some foam, and a reduction in the amount of foam will generally afford better cushioning characteristics.
The major engineering problems associated with the design of air bladders formed of barrier layers include: (I) obtaining complex-curved, contoured shapes without the formation of deep peaks and valleys in the cross section which require filling in or moderating with foams or plates; (ii) ensuring that the means employed to give the air bladder its complex-curved, contoured shape does not significantly compromise the cushioning benefits of air; (iii) providing regionalized cushioning to an air bladder to account for differences in load corresponding to the anatomical topology of a human foot especially during high loads; (iv) designing air bladders which maximize the cushioning properties of air and are made entirely of flat barrier films; and (v) designing bladders that provide the advantages of complex-contoured shapes and regionalized cushioning and which can be integrated easily into existing midsole manufacturing methods.
The prior art is replete with attempts to address these difficulties, but have only solved one, two or even three of the above-described problems often presenting new obstacles in the process. Most of the prior art discloses some type of tensile member. A tensile member is an element associated with a bladder which ensures a fixed, resting relation between the top and bottom barrier layers when the bladder is fully filled, and which often is in a state of tension while acting as a restraining means to maintain the general external form of the bladder.
Some prior art constructions are composite structures of bladders containing foam or fabric tensile members. One type of such composite construction prior art concerns bladders employing an open-celled foam core as disclosed in U.S. Pat. Nos. 4,874,640 and 5,235,715 to Donzis. These cushioning elements do provide latitude in their design in that the open-celled foam cores allow for complex-curved and contoured shapes of the bladder without deep peaks and valleys. However, bladders with foam core tensile member have the disadvantage of unreliable bonding of the core to the barrier layers. Another disadvantage of foam core bladders is that the foam core gives the bladder its shape and thus must necessarily function as a cushioning member which detracts from the superior cushioning properties of a gas alone. One reason for this is that in order to withstand the high inflation pressures associated with bladders, the foam core must be of a high strength which requires the use of a higher density foam. The higher the density of the foam, the less the amount of available volume in the bladder for a gas. Consequently, the reduction in the amount of gas in the bladder decreases the effectiveness of gas cushioning.
Even if a lower density foam is used, a significant amount of available volume is sacrificed which means that the deflection height of the bladder is reduced due to the presence of the foam, thus accelerating the effect of “bottoming out.” Bottoming out refers to the premature failure of a cushioning device to adequately decelerate an impact load. Most cushioning devices used in footwear are non-linear compression based systems, increasing in stiffness as they are loaded. Bottoming out is the point where the cushioning system is unable to compress any further and is a common failure in shoe soles comprised of foam. Also, the elastic foam material itself performs a significant portion of the cushioning function and is subject to compression set. Compression set refers to the permanent compression of foam after repeated loads which greatly diminishes its cushioning aspects. In foam core bladders, compression set occurs due to the internal breakdown of cell walls under heavy cyclic compression loads such as walking or running. The walls of individual cells constituting the foam structure abrade and tear as they move against one another and fail. The breakdown of the foam exposes the wearer to greater shock forces.
Another type of composite construction prior art concerns air bladders which employ three dimensional fabric as tensile members such as those disclosed in U.S. Pat. Nos. 4,906,502 and 5,083,361 to Rudy, which are hereby incorporated by reference. The bladders described in the Rudy patents have enjoyed considerable commercial success in NIKE, Inc. brand footwear under the name Tensile-Air® and Zoom™. Bladders using fabric tensile members virtually eliminate deep peaks and valleys, and the methods described in the Rudy patents have proven to provide an excellent bond between the tensile fibers and barrier layers. In addition, the individual tensile fibers are small and deflect easily under load so that the fabric does not interfere with the cushioning properties of air.
One shortcoming of these bladders is that currently there is no known manufacturing method for making complex-curved, contoured shaped bladders using these fabric fiber tensile members. The bladders may be of different heights, but the top and bottom surfaces remain flat with no contours and curves.
Another disadvantage of fabric tensile members is the possibility of bottoming out. Although the fabric fibers easil
Ager Colin D.
Aveni Michael A.
Colby Edward G.
Herridge David B.
MacGregor Alastair R.
Banner & Witcoff , Ltd.
Kavanaugh Ted
Nike Inc.
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