Patent Application
20060179683
The feet of an individual are subject to substantial impact forces during regular activities such as standing and walking. The impact forces are particularly strong during athletic activities such as running and jumping. Footwear which provides proper cushioning and support may prevent the feet from discomfort, soreness, fatigue and injury caused by such impact forces.
Numerous cushioning elements or inserts used in footwear to cushion a wear's foot have been developed over the years to absorb the impact forces. Many of such cushioning elements or inserts are made at least partially of compressible materials. For example, foam materials such as ethylene vinyl acetate (EVA) and polyurethane (PU) have been widely used in the footwear industry to form part of a sole, due to its advantageous properties such as light weight and isotropic cushioning property.
U.S. Pat. Nos. 5,092,060 and 5,369,896 to Frachey et al. disclose a sports shoe having an insert which includes a plurality of barrel-shaped elements that are elastically deformable under pressure and are enclosed in an airtight casing of a plastic material. The insert is arranged in a seat provided in a wedge in a position corresponding with the heel of the foot and is confined by the surrounding wall portion of the seat. However, the plurality of barrel-shaped elements may cause individual pressure points above each element, resulting in uneven pressure distribution. Furthermore, if a customer presses a side of the shoe by a thumb to check the pliability or elasticity of the shoe sole, which often happens in the process of selecting a pair of shoes to buy, the shoe may not satisfy the thumb test because it does not feel soft or pliable peripherally.
U.S. Pat. Nos. 4,874,640 and 5,235,715 to Donzis disclose a composite for absorbing and dispersing impacting forces. The composite includes a flexible plastic enclosure defining an internal cavity. The flexible enclosure is generally impermeable to air and capable of having its internal pressure changed. The composite further includes a foam core filling the cavity and retained within the cavity and adhered on substantially its entire external surface to the internal surface of the cavity. The cavity can be pressurized for higher impact absorbance. The method for producing the composites includes forming the outer enclosure by applying a solution/suspension of the prepolymer of controlled solids content to the core and also can include the step of preheating the core prior to coating it. To withstand the high inflation pressures in such air 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 air space available in the bladder. Consequently, the reduction in the amount of air in the bladder decreases the cushioning benefits provided by air. Furthermore, air bladders relying on elevated internal pressures to cushion are susceptible to punctures and leakage.
U.S. Pat. Nos. 5,343,639 and 5,353,523 to Kilgore et al. disclose a midsole for a shoe including one or more foam columns disposed between an upper and a lower plate. The foam columns may include grooves formed on the exterior surface. One or more elastic rings are disposed about the columns and are removably disposable in the grooves, allowing the stiffness of the columns to be adjusted. In a further embodiment, inflatable gas bladders are disposed in the hollow regions. The structure and manufacture of such midsoles are very complicated.
As described above, all of these constructions are not completely satisfactory. Furthermore, compressible materials such as foam in shoe soles tend to break down over time, especially notably when the shoe soles are frequently subject to abrasions and exposed to excessive heat and moisture, resulting in discoloration and mushy appearance of the soles, which are not only aesthetically undesirable, but also may affect their shock absorbing capacity. Therefore, there remains a need for a cushioning insert for footwear that has improved durability and pliability, while keeping all the advantageous properties of compressible materials and eliminating the drawbacks of the above described constructions.
It is an object of the present invention to provide an insert for footwear which properly cushions and supports a region of a foot and is durable and easy to manufacture.
It is another object of the present invention to provide an insert for footwear which when incorporated into an article of footwear, is aesthetically desirable and satisfies a thumb test of pliability.
In accordance with an aspect of the present invention, there is provided an insert for an article of footwear, comprising: a compressible core allowing pressure to be applied thereon by a foot, the compressible core having a top surface, a bottom surface and a peripheral surface; and a flexible casing for surrounding at least a portion of the compressible core, the flexible casing having a top portion, a bottom portion and a peripheral portion, the flexible casing having an open window, the window having a size which is sufficient for insertion of the compressible core into the flexible casing but leaving sufficient material to hold the compressible core, the peripheral portion of the flexible casing being spaced from at least a portion of the peripheral surface of the compressible core, while not interfering with the foot applying pressure to the compressible core.
In accordance with another aspect of the present invention, there is provided an insert for an article of footwear, comprising: a compressible core, the compressible core having a top surface, a bottom surface and a peripheral surface; and a flexible casing for surrounding at least a portion of the compressible core, the flexible casing having a top portion, a bottom portion and a peripheral portion, the flexible casing having an open window, the window having a size which is sufficient for insertion of the compressible core into the flexible casing but leaving sufficient material to hold the compressible core, the peripheral portion of the flexible casing being spaced from at least a portion of the peripheral surface of the compressible core, while not interfering with the foot applying pressure to the compressible core; wherein the insert has a first compressibility at its top or bottom surface and a second compressibility at its peripheral surface, the second compressibility being greater than the first compressibility preferably by at least about 10%, for example about 10-40%, more preferably by at least 20%, for example about 20-50%, and most preferably by at least about 30%, for example about 30-60%.
In accordance with yet another aspect of the present invention, the insert may further comprise a cap for at least partially covering the open window of the flexible casing.
In accordance with a further aspect of the present invention, there is provided an article of footwear, comprising a sole, the sole having a portion formed to receive an insert; and an insert in accordance with the present invention mounted in the portion formed to receive an insert.
In accordance with another aspect of the present invention, there is provided a method of making an insert for an article of footwear, comprising: providing a compressible core, the compressible core having a top surface, a bottom surface and a peripheral surface; forming a flexible casing for surrounding at least a portion of the compressible core, the flexible casing having a top portion, a bottom portion and a peripheral portion, the flexible casing having an open window, the window having a size which is sufficient for insertion of the compressible core into the flexible casing but leaving sufficient material to hold the compressible core; applying an adhesive to a predetermined area of the inner surface of the flexible casing; and bringing the compressible core into contact with the inner surface of the flexible casing.
In accordance with another aspect of the present invention, the method further comprises providing a sheet of flexible material; die cutting a cap from the sheet of flexible material; and sealing the cap to the bonded flexible casing and compressible core to at least partially cover the window of the flexible casing.
In accordance with yet another aspect of the present invention, there is provided a method of making an insert for an article of footwear, comprising: providing a compressible core, the compressible core having a top surface, a bottom surface and a peripheral surface; forming a flexible casing for surrounding at least a portion of the compressible core, the flexible casing having a top portion, a bottom portion and a peripheral portion, the flexible casing having an open window, the window having a size which is sufficient for insertion of the compressible core into the flexible casing but leaving sufficient material to hold the compressible core; turning the flexible casing inside out exposing the inner surface of the flexible casing; applying an adhesive to a predetermined area of the inner surface of the flexible casing; turning the flexible casing back; and bringing the compressible core into contact with the inner surface of the flexible casing.
The present invention can be better understood from the following description of preferred embodiments, taken in conjunction with the accompanying drawings. It should be apparent to those skilled in the art that the described embodiments of the present invention provided herein are merely exemplary and illustrative and not limiting. All features disclosed in the description may be replaced by alternative features serving the same or similar purpose, unless expressly stated otherwise. Therefore, numerous other embodiments of the modifications thereof are contemplated as falling within the scope of the present invention and equivalents thereto.
Referring to
The compressible core 5, 6 and the flexible casing 13, 14 may be bonded by an adhesive, for example, along the periphery of the window and/or at at least a portion of the bottom surface of the compressible core. Preferably, if an adhesive is used, it does not interfere with the transparency of the portion of the flexible casing that will be exposed after the insert is incorporated into an article of footwear.
The peripheral portion 19, 20 of the flexible casing 13, 14 is spaced from at least a portion of the peripheral surface 11, 12 of the compressible core 5, 6 by about 1 to 8 mm, preferably by about 1 to 5 mm, and more preferably by about 1 to 3 mm, forming a circumferential air gap between the compressible core 5, 6 and the flexible casing 13, 14. The peripheral portion 19, 20 of the flexible casing 13, 14 may not be uniformly spaced from the peripheral surface 11, 12 of the compressible core 5, 6 along the circumference and may be in contact with the compressible core at some locations.
The material for the compressible core is preferably a foam material or any suitable elastic cushioning material. It may be selected from the following exemplary materials bearing in mind that other suitable materials are also contemplated: ethyl vinyl acetate (EVA) co-polymer, thermo-set polyether and poly-ester urethane, ethyl vinyl acetate co-polymer blends including isoprene rubber, poly-olefins, natural and synthetic rubbers, and blends or combinations thereof. The EVA co-polymer is the preferred material for the compressible core. The compressible core may also be a combination of more than one material, for example, in the form of a laminate.
The material for the flexible casing may be a plastic material or any durable and pliable material. Preferably, the material for the flexible casing is transparent or translucent such that the decorative patterns on the compressive core can be seen through the flexible casing for desired visual effects. It may be selected from the following exemplary materials bearing in mind that other suitable materials are also contemplated: thermoplastic polyurethane (TPU), polyester-TPU, polyether-TPU, polyester-polyether TPU, polyvinylchloride, polyester, thermoplastic ethyl vinyl acetate, styrene butadiene styrene, TPU blends including natural and synthetic rubbers, and blends or combinations thereof. TPU is the preferred material for the flexible casing.
It is also contemplated that the cap does not need to be a separate piece of a flexible material such as a plastic material. A part of a sole, such as midsole or insole, that overlies the insert can be construed as a cap.
The material for the cap is preferably the same as the flexible casing, for example a plastic material or any durable and flexible material. It may be selected from the following exemplary materials bearing in mind that other suitable materials are also contemplated: thermoplastic polyurethane (TPU), polyester-TPU, polyether-TPU, polyester-polyether TPU, polyvinylchloride, polyester, thermoplastic ethyl vinyl acetate, styrene butadiene styrene, TPU blends including natural and synthetic rubbers, and blends or combinations thereof. TPU is the preferred material for the cap.
Referring to
Furthermore, the decorative ribs 32 and additional decorative patterns 33 on the compressible core are visible through the transparent flexible casing. Therefore, the shoe incorporating the inserts of the present invention not only provide proper cushioning and support for a foot, but is also attractive to customers for providing desirable visual effects and satisfying the thumb test of pliability.
Preferably, at least a portion of the inserts is exposed peripherally from the shoe to touch, for example, along the medial and lateral sides of the shoe. It is also contemplated that the inserts may be exposed at any surface of the shoe including the bottom surface and the rear edge.
Referring to
Then an adhesive is applied to a predetermined area of the inner surface of the formed flexible casing. The flexible casing can be turned inside out to expose the inner surface of the flexible casing for convenient application of the adhesive and then turned back. The predetermined area is at least a portion of the area that will be in contact with the compressible core in the final insert product. In a preferred embodiment as shown in FIG. 13, the adhesive is applied along the periphery of the window 40 and/or at at least a portion of an area corresponding to the bottom surface of the compressible core 39.
Subsequently the compressible core is inserted or shoved into the flexible casing through the window to bring it into contact with the inner surface of the flexible casing such that the compressible core and the flexible casing are bonded through the adhesive. Although the flexible casing is preferably turned back before bringing the compressible core into contact with the inner surface of the flexible casing, it is contemplated that the flexible casing may be turned back after bringing the compressible core into contact with the inner surface of the flexible casing.
To prepare another preferred embodiment of the insert which has a cap for the window, a cap may be die cut from a sheet of plastic material. The cap is then sealed to the bonded flexible casing and compressible core to at least partially cover the window of the flexible casing.
While various embodiments and individual features of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the present invention. As will also be apparent to those skilled in the art, various combinations of the embodiments and features taught in the foregoing description are possible and can result in preferred executions of the present invention. Accordingly, it is intended that such changes and modifications fall within the scope of the present invention as defined by the claims appended hereto.
