BACKGROUND OF THE INVENTION
The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 60/598,363, filed Aug. 3, 2004, the content of which is hereby incorporated by reference in its entirety. The present application is also a Continuation-in-Part of and claims priority to U.S. patent application Ser. No. 10/142,353, filed May 8, 2002, which is hereby incorporated by reference.
Insoles currently exist to provide cushioning in articles of footwear such as shoes and boots. One type of insole is a removable insole that can often be purchased separately from the footwear article and used to replace an existing insole and/or to add additional cushioning. However, one problem associated with many such insoles is that they are usually padded, and thus, relatively thick. The added thickness often causes a wearer's foot to rub against the top and side inner surfaces of the shoe, boot or the like, which results in discomfort. Also, current padded insoles do not generally mitigate the negative effects of foot friction.
- SUMMARY OF THE INVENTION
An insole that address one, some, or all of the problems associated with prior art insoles would have significant utility.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention relates to an ultra-thin liquid-filled insole interface for use in footwear. An ultra-thin liquid-filled insole interface that is removable or non-removable is provided for an article of footwear.
FIG. 1 illustrates an assembly view of embodiment of the present invention.
FIG. 2 illustrates the embodiment illustrated in FIG. 1 as assembled.
FIG. 3 illustrates another embodiment of the present invention and potential features of further embodiments.
FIG. 4 illustrates another embodiment of the present invention and potential features of further embodiments.
FIG. 5 illustrates an article of footwear having an inserted ultra-thin liquid-filled insole of the present invention.
FIG. 6 illustrates a packaging of a pair of removable ultra-thin liquid-filled insoles of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 7 a-7 d illustrate alternate embodiments of the present inventions.
FIG. 1 illustrates ultra-thin liquid-filled insole interface or assembly 100. Insole interface or assembly 100 comprises at least one ultra-thin liquid-filled cell 102, 104 described in detail in pending U.S. Patent Application entitled ULTRA-THIN LIQUID-FILLED CELL FOR COMFORT ENHANCEMENT, Ser. No. 10/142,353 filed on May 8, 2002, which is incorporated by reference in its entirety.
In the embodiment illustrated, cell 102 is provided proximate first portion 101 of insole 100 to provide comfort to the ball of a foot, while cell 104 is provided proximate second portion 111 of insole 100 to provide comfort to the heel of a foot. One or both of cells 102, 104 can be provided in insole 100. As appreciated by those skilled in the art, the number of cells, as well as their size and shape can be adjusted as needed. Insole assembly 100 further comprises a top substrate 106, which is shaped and sized to fit into various articles of footwear as an insole, or portion thereof. Top substrate 106 can comprise a woven or knit textile fabric or a non-woven fabric such as natural or synthetic leather. Top substrate 106 can also comprise a moisture absorbing fabric such as terry cloth or other moisture management fabric.
Insole assembly 100 also can optionally comprise a bottom substrate 108 that is approximately identical in planar shape to top substrate 106. Bottom substrate 108 can comprise elastomeric materials such as but not limited to foam, rubber, or plastic. Top substrate 106 and bottom substrate 108 are typically affixed together with adhesive or affixing layer 113 such as formed with spray adhesives or lamination to sandwich and affix ultra-thin liquid filled cells 102, 104 therebetween.
Generally speaking, viscosity can be viewed as a measure of resistance to shear. Newtonian fluids, such as water or mineral oil, are unaffected by the magnitude and kind of motion to which they are subjected. Thus, Newtonian fluids have a constant viscosity regardless of the shear stress or shear rate applied. Water can be considered a low or relatively low viscosity liquid having a viscosity of approximately 1 cP at 273K (20° C.) and atmospheric pressure (about 1.0 atm). Generally, however, viscosity decreases (or loses resistance to shear) with increasing temperature.
It is known that shear viscosity can be a function of both shear force and shear rate in the following relationship:
where shear stress is a measure of shear force per unit area. Importantly, a low viscosity liquid has a lower shear stress when compared with a higher viscosity liquid assuming the same shear rate. Thus, boundary stress is lower for a low viscosity liquid than a higher viscosity liquid such as motor oil.
“Shear flow” is an idealize type of liquid flow near a solid surface. In shear flow, the velocity of the liquid increases linearly with distance from the surface. At the boundary between the liquid and the solid surface, the velocity of the liquid is zero. Thus, in shear flow the boundary between the liquid and solid surface has often been called a “non-slip” boundary.
It is believed that with footwear, during walking or running, shear stress between the shoe and walking surface can be transmitted to the interface or boundary between the shoe and wearer's foot. Constant back and forth rubbing between the shoe and the wearer's foot during walking or running thus can subject the wearer to harmful shear stress and friction, which is often associated with foot pain and blisters.
It has been discovered that positioning a low viscosity liquid-filled insole or interface into an article of footwear reduces or mitigates the negative effects of shear force, stress, and/or friction on a wearer. It is believed that the low-viscosity liquid results in less shear stress being transmitted across the boundary between the shoe and the wearer, especially when compared with a solid cushioning insole (which does not flow) or a high viscosity liquid or gel (which is more resistant to flow). Thus, it is believed that lower transmitted shear stress results in greater comfort for the wearer, especially over a prolonged period of time.
FIG. 2 illustrates an assembled ultra-thin liquid-filled insole 100 that has thickness 202, 208 of approximately 0.5 mm to 2.0 mm measured perpendicular or normal to the top surface of the top substrate when constant and equally distributed force is applied to the outer surfaces 204, 206. It is noted that such constant and equally distributed force (such producing 0.25 pound per square inch between two flat or planar surfaces) is adequate to ensure uniform thickness for measuring but does not compress the infill liquid nor distort surrounding substrates 106, 108. In most embodiments, the thickness 103, 105 of liquid-filled cells 102, 104 is less than 0.8 mm when constant and equally distributed pressure (such as 0.25 pound per square inch) is applied normal to its major surfaces. However, in other embodiments, thickness 103, 105 is no more than 0.4 mm., 0.2 mm., 0.1 mm., or 0.05 mm. Thickness 103, 105 can be identical or different as desired.
In other embodiments, thickness 202, 208 is in the range of approximately 0.75 mm to 1.5 mm. It is noted, if desired, thickness 202 can be slightly larger measured at one of the liquid-filled cells 102, 104 compared with thickness 208, which is measured where an interleaved cell 102, 104 is lacking. Although insole 100 is quite thin, insole 100 provides remarkable comfort due to reduced friction transmitted to the foot. Importantly, however, insole 100 is ideally sufficiently thin to not cause additional discomfort from raising the wearer's foot to be in greater contact with the shoe cavity or box. Also, it is believed that a thicker cushioning can cause increased shear to the body of the wearer at least partially due to greater “hammocking” or bowing across the surface of the liquid-filled insole. Hammocking or bowing in a thicker cushion is believed to cause a larger component of shear applied to the foot due to normal forces (e.g. the wearer's weight) applied to the foot of the wearer.
In most embodiments, the in-fill liquid is low viscosity and has a range of approximately 0.8 cP to 1.2 cP at approximately atmospheric pressure and 20° C. In other embodiments, the viscosity closely resembles the viscosity of water. However, it is noted that the liquid should be selected so that it does not tend to permeate the material enclosing the liquid when place in normal use. Also, a liquid that does not readily permit mold, bacteria, or other growth would be advantageous.
FIG. 3 illustrates an assembly view of another embodiment of the present inventions. Insole assembly 300 contains a top substrate 306 that is similar in structure to top substrate 106 illustrated in FIGS. 1 and 2. Ultra-thin liquid-filled cells 302, 304 are affixed to top substrate 306 such as with an adhesive layer. An optional adhesive layer 314 can be applied to a bottom surface of the insole assembly 300 to affix the insole into the article of footwear. A suitable removable layer, backing, or film 320 having any planar shape can be applied over adhesive layer 314, especially before packaging. Such layer 320 can be removed to expose adhesive layer 314 shortly before the insole is positioned in a shoe. Liquid-filled cells 302, 304 are illustrated with optional features 308, 310, 312 that can be included in other embodiments of the present invention. For example, liquid-filled cell 304 includes baffles 308, 310 herein exemplified as round although other shapes can be used, such as elongated. Typically, a baffle is formed by joining opposed portions of the walls of the cells. The baffles 308, 310 cause the liquid within the cells to flow around or between baffles 308, 310 when pressure is applied. Also illustrated is hole or perforation 312 through baffles 312, which is particularly advantageous for moisture wicking. In many embodiments, at least one baffle 308, 310 is positioned proximate outer longitudinal edge 332, rear lateral edge 333, or front lateral edge 336 of the insole. It is believed that baffles 308, 310 are especially helpful in mitigating shear stress in areas of the foot bearing most of the wearer's weight.
FIG. 4 illustrates an embodiment similar to the embodiment in FIG. 3. However, baffles 408 are elongated. In most embodiments, baffle elongation can be approximately parallel to the direction of movement (as indicated by reference 412) in order to mitigate the effects of friction on the skin of the foot during running or walking. However, in other embodiments, baffles can be selectively positioned at angles to one another to facilitate or control liquid flow. During walking or running, in-fill liquid moves through and around elongated baffles to reduce the amount of shear stress or force transmitted to the wearer as above described. FIG. 4 also illustrates that ultra-thin liquid-filled liner 406 can comprise a plurality of liquid-cells 402, 404. Liquid-filled liner 406 can also include adhesive layer 410 with or without a suitable removable backing (not illustrated).
FIG. 5 illustrates footwear assembly 500 comprising article of footwear 502 and inserted ultra-thin liquid-filled insole 100. Ultra-thin liquid-filled insole 100 can be affixed in footwear 502 (e.g. at point of manufacture) or be removable by the purchaser (such as before washing or during replacement of an existing insole). It is noted that insole 100 can be added to or completely replace an existing insole. Components of footwear assembly 500 should be sized so that the foot of the user does not rub against an inner surface of footwear 502 as often occurs with prior art insoles that are purchased separately and inserted into an article of footwear.
FIG. 6 illustrates packaging assembly 600 comprising packaging 602 with a pair of liquid-filled insoles 100 enclosed within. A portion of removable backing 602 is illustrated, which can be applied to an adhesive layer as described above. Such removable backing 602 is removed to expose an adhesive layer such as adhesive layer 113 (illustrated in FIG. 1) that affixes liquid-filled insoles 100 inside footwear such as footwear 502. Packaging assembly 600 can be purchased separately from an article of footwear for use therein.
FIGS. 7 a-7 d illustrate alternate embodiments of the present inventions. Insole 700 comprises liquid-filled cell 104 positioned in heel portion 111 of insole 700 to provide comfort to the heel of the wearer. In these embodiments, insole 700 can be adapted to cover substantially the entire insole surface of a shoe or other article of footwear. However, the insole can also be shortened or truncated so that insole 710 only covers a rear or heel portion of the insole area of the footwear.
It still other embodiments, insole 720 includes liquid-filled cell 102 positioned in first or ball portion 113 of insole 720 to provide comfort to the ball of the foot. Ball portion 101 includes ultra-thin liquid-filled cell 102. In these embodiments, insole 720 can be adapted to cover substantially the entire insole surface or truncated as illustrated as insole 730 to cover a front or ball portion of an article of footwear.
Finally, it is noted that although FIGS. 7 a-7 d illustrate insoles having both upper and lower substrates, it is understood that the bottom substrate can be eliminated as desired such as illustrated in FIGS. 3 and 4.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.