Abstract:
An article of footwear is constructed to dynamically provide width adjustment by cooperative expansion and contraction of a longitudinal split midsole with an expansion element integrated with an outsole that allows the midsole to expand from a narrow width to a wider width. The upper of the shoe has a corresponding section that can expand to a similar degree as the midsole and outsole to enable the volume of the upper to increase proportionally to the width of the sole.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to providing footwear with adjustable width to enable customized width fitting and adjustable width necessitated by changing conditions and activity during wear. The invention concerns, more particularly, articles of footwear having a longitudinal split midsole cooperating with a stretchable upper to enable dynamic fit adjustment.  
         [0003]     2. Background of the Invention  
         [0004]     Footwear sizing is generally based on the overall length of a wearer&#39;s foot with accommodation made for the width or girth of the foot as well. Footwear is generally purchased based on a static measurement of the wearer&#39;s foot without much regard to the change in the wearer&#39;s foot dimensions that may occur during a reasonable period of wear. Neither short term nor long term changes such as accommodation for the expansion of the foot at the end of a day, or growth of a child&#39;s foot within a few months from purchase are factored into the single static measurement at point of purchase.  
         [0005]     The shape of the last on which the article of footwear is formed is the primary influence on the fit of an article of footwear. In general a last is made by taking the following foot measurements into account: the overall length of the foot, the width of the foot, the height of the first digit, the contour of the instep, and at least six girth measurements. The general practice is to shape a last for mass production by utilizing foot measurements from a broad spectrum of the population to determine the characteristics of a statistically average foot. This will theoretically achieve a proper fit for a majority of the population. Most footwear manufacturers only provide consumers with footwear in limited length-width combinations.  
         [0006]     Prohibitive manufacturing and retail inventory challenges prevent mass manufacturers and marketers from offering footwear sizes in a full spectrum of length-width combinations. Since each length-width combination for an article of footwear generally requires a unique last that is correctly proportioned for that particular length-width combination, economics generally forces manufacturers and retailers to offer a limited spectrum of length-width combinations, based again, on a statistically average foot. The attempt is to cover as large a cross section of the population as possible. Research has demonstrated that this approach, while cost effective, yields little perceivable benefit to the consumer.  
         [0007]     Many individuals do not have feet with statistically average proportions so the usual length-width combinations would not provide a proper fit. Some people have feet of left and right feet of different widths, such as the dominant foot being slightly larger. In addition, some individuals have foot proportions that change in a relatively short period of time. Children, for example, often experience rapid growth in the feet that prevent footwear from being worn for a significant portion of the footwear&#39;s useful life. Individuals with certain medical conditions, such as pregnancy or edema, may experience day to day changes in foot proportions. Any of these factors necessitate fit adjustment to enable the wearer to receive the full benefit of an athletic shoe in particular.  
         [0008]     Due to these limitations, there have been multiple attempts in the prior art to provide for some measure of adjustment. The vast majority of prior art adjustment systems for footwear rely on some sort of mechanism for adjusting fit such as a lacing system, screw adjustments, or ratchet adjustments. The prior art sometimes combines the adjustment mechanisms in the midsole with inserts or other material variances to provide a measure of lateral or width adjustment.  
         [0009]     Some prior art attempts to address width adjustment and fit employ articulating midsole and outsole units that are sized with interchangeable plugs. These systems do not allay the inventory problem since often the extra pieces must be inventoried and managed by a retailer.  
       SUMMARY  
       [0010]     The present invention utilizes a longitudinal split midsole with an expansion element integrated with an outsole that allows the midsole to expand from a narrow width to a wider width for a given length. The expansion element shields the interior of the shoe from the elements such as dirt, water, debris. The upper of the shoe has a corresponding section that can expand to a similar degree as the midsole and outsole. This allows the volume of the upper to increase proportionally to the width of the sole.  
         [0011]     The footwear of the present invention includes specially designed midsole and outsole cooperating with an upper that is at least partially stretchable to provide customized width fitting and adjustable width necessitated by changing foot size, conditions and activity. The sole is designed with the requisite cushioning properties in a midsole, and at least one longitudinal expansion element integrated with the midsole. The expansion element allows the sole to expand laterally to provide width adjustment. The outsole is designed to accommodate and cooperate with a longitudinal split in the midsole in which the expansion element is disposed.  
         [0012]     At least a portion of the upper, foot-covering portion is constructed to stretch for fit adjustment. The bottom insole panel of the upper may be made of a non-stretch material such as a woven fabric, with a longitudinal area of stretch fabric. The longitudinal area of stretch fabric is disposed to cooperate with the expansion element of the sole to enable the entire article of footwear to expand laterally, and for the internal volume to increase as a result.  
         [0013]     The insole panel of the upper is comprised of a combination of non-stretch material and a stretch material panel. The non-stretch material includes a number of stays extending laterally across the stretch panel material. The stays retain the shape of the insole panel and prevent it from expanding during lasting. The longitudinal stretch panel of the insole is aligned with the expansion element of the sole, and the upper and sole are attached. After the shoe is lasted and sole laying is completed, the stays of non-stretch material in the insole panel are severed. Severing the stays enables the longitudinal stretch panel to cooperate with the expansion element in the sole to provide width adjustment thus providing a dynamic and interactive fit.  
         [0014]     Alternatively, the insole panel may have a simpler construction of a non-material stretch with a cut-out along a longitudinal area to cooperate with the expansion element of the sole. For some sizes of footwear, a cut-out may be a sufficient expansion area for the insole panel. As with the earlier description, the insole panel with a cut-out includes a number of stays that extend laterally across the cut-out to retain the shape and dimensions of the upper prior to and during lasting.  
         [0015]     An upper with an integrated insole panel as described above lasted to a sole unit having an expansion element requires no user adjustment, no additional pieces or inserts and no additional molds of tooling. This substantially lowers production costs and allows the retailer to offer width sizing that is more individualized without additional inventory demands.  
         [0016]     An individual&#39;s foot geometry becomes the controlling element in determining the width of the shoe, as well as where the added width occurs relative to the length of the shoe. That is, whether the width increases near the toe area, the ball of the foot, or the waist of the foot. The stretch panel or cut-out can be tailored to meet the various demands or preferences of consumers. In general, the tighter fit of performance footwear would require more tension in the membrane, whereas a casual shoe may require less tension.  
         [0017]     Other configurations, features and advantages of the invention will be, or will became, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. In the drawings:  
         [0019]      FIG. 1  is a perspective view of an article of footwear in accordance with a preferred embodiment of the invention.  
         [0020]      FIG. 2  is a bottom view thereof.  
         [0021]      FIG. 3  is a schematic plan view of the insole panel viewed from inside the show prior to severing the non-stretchable stays.  
         [0022]      FIG. 4  is a perspective view of a footwear upper on a last, prior to lasting.  
         [0023]      FIG. 5  is a bottom plan view of the footwear upper of  FIG. 4 .  
         [0024]      FIG. 6  is an exploded assembly view of the footwear upper of  FIG. 4  shown with a sole unit as the pieces would be lasted together.  
         [0025]      FIG. 7  is a schematic cross-section of the sole unit of the article of footwear shown in the non-expanded condition.  
         [0026]      FIG. 8  is a schematic cross-section of the sole area similar to  FIG. 7  but shown in an expanded and flexed condition.  
         [0027]      FIG. 9  is an exploded assembly view of an alternative embodiment of the article of footwear, shown as the upper and sole unit would be lasted together. 
     
    
     DETAILED DESCRIPTION  
       [0028]     Article of footwear  10  shown in  FIG. 1  is formed generally of an upper  12  and a sole unit  14 . Sole unit  14  comprises a cushioning midsole  16  and a ground-engaging outsole  18 . In this particular shoe, outsole  18  is actually a set of elements on the ground contacting portions of the sole. For simplicity, whether the outsole is unitary or a set of elements, it is referred to as an outsole. Upper  12  has the customary foot opening  20  and a tongue or instep area  22 . The particular shoe shown in the figures features an upper made of a stretchable material along with lateral and medial panels extending upward from the sole to include lace loops. The present invention is applicable, however, to many variations on upper construction.  
         [0029]     As seen in  FIG. 2 , sole unit  14  of the particular shoe shown in the drawings comprises an outsole  18  which covers a substantial portion of the ground-engaging portion of the sole. Midsole  16  is exposed in a number of interstitial areas between portions of the outsole. Most prominently, along the longitudinal of the shoe bottom, a portion of the midsole is visible as an expansion element  24 . Expansion element  24  extends from the toe region  26  to the heel region  28 , and is shown in the figures to be a pleat in the midsole. In other words, the expansion element is a longitudinal expansion joint in the midsole which physically splits the midsole between a lateral side and a medial side.  
         [0030]     In the embodiment shown in  FIGS. 1-8 , expansion element  24  is actually made of a separate piece of material from midsole  16 . As best seen in  FIGS. 6-8 , expansion element  24  has laterally extending flange areas  25  which are attached to a recessed area in midsole  16 . The recessed area is of the same thickness as flanges  25 , so that the top surface of midsole  16  is flush. Midsole  16  actually has a split  17  to accommodate the insertion of expansion element  24 . The pleated portion of expansion element  24  is visible from the bottom of the shoe,  FIG. 2 .  
         [0031]     A dynamic, interactive adjustable width fit is accomplished by cooperation of the longitudinal expansion joint in the midsole with a particular construction of the upper. The bottom panel of the upper is referred to herein as the “insole panel.” The insole panel  34  is attached to the sides of the upper and forms the bottom fabric panel. Viewed from inside the upper, insole panel  34  is shown schematically in  FIG. 3 . It should be noted that when the shoe is finally assembled for sale, an additional cushioned insole or insole layer will be positioned above the insole panel so that this bottom panel is not visible to the wearer without removal of the insole.  
         [0032]     In this embodiment, insole panel  34  is comprised of a non-stretchable portion  36  surrounding a longitudinally oriented expansion portion  38 . The non-stretchable portion is preferably made of a woven fabric or the like. Expansion portion  38  is preferably made of a stretch fabric panel  40  that is stitched to non-stretch portion  36  along its periphery. Stretch panel  40  has a generally longitudinal shape which coincides with the location of the expansion element in the sole when the upper and sole unit are attached together. In the embodiment shown in the drawings, non-stretch portion  36  also includes a number of stays  42  integrally formed of the same fabric or material which extend across expansion portion  38 . Stays  42  help maintain the shape and dimensions of the upper and prevent insole panel  34  from expanding prior to assembly. Although stays  42  are shown to be integrally formed with the insole panel, they could also be made of a different non-stretch material and attached to insole panel  34  by other means. As long as they fulfill their purpose of maintaining the shape and dimensions of the upper during lasting, both integrally formed stays or stays made of a different material and attached to the insole panel are contemplated to be within the scope of the invention.  
         [0033]     In the assembly of the shoe components, upper  12  is fully stitched together and then fitted around a last L,  FIG. 4 . The bottom of the upper is shown in  FIG. 5 . Insole panel  34  includes non-stretch portion  36  surrounding the longitudinal stretch panel  40 . Stays  42  are shown in broken line since they are on the interior of the shoe. Stays  42  maintain the shape and dimensions of the upper and insole panel during lasting so that the upper has the desired shape and configuration. After lasting, the shoe undergoes a sole laying operation in which the sole unit is attached the lasted upper. The stays also maintain the shape and dimensions of the shoe during sole laying.  
         [0034]     It should be noted that the particular shape of stretch panel  40  shown in the drawings is generally for illustration purposes. In practice, stretch panel  40  may be narrower, have pointed ends or curve differently. The overriding factor in the shape of the stretch panel is that it should extend generally in a longitudinal direction with respect to the bottom of the shoe to accommodate lateral expansion.  
         [0035]     As best seen in  FIG. 6 , upper  12  is attached to sole unit  14  such that stretch panel  40  of the upper is vertically aligned to some degree with expansion element  24  in sole unit  14 . Both stretch panel  40  and expansion element  24  extend in a longitudinal direction with respect to the shoe. The upper and the sole unit are lasted together in a conventional manner. If any adhesive is used, care must be taken to ensure that the adhesive is not applied to the stretch panel so as not to inhibit any stretching expansion. Once the upper and sole unit are attached, stays  42  are severed from the inside of the shoe. Severing stays  42  enables expansion of stretch panel  40  as necessary to accommodate different widths of feet with respect to the length of the shoe. As can be seen, stretch panel  40  cooperates with expansion element  24  in the sole unit to enable the shoe to expand laterally to achieve a good fit.  
         [0036]     Since lateral expansion is function of the stretch panel and the expansion element, there is no reason to supply any additional mechanism or inserts. The fit of the shoe made in this manner is adjustable not just among wearers of different widths, but also to a single wearer whose foot expands during use. As discussed above, providing customized width adjustment reduces the inventory demands on retailers as separate width sizing need not be inventoried for a given length. Also, for some users, it is useful to provide a measure of lateral adjustability as the shape of their feet may change during wear. One example is for people with edema or pregnancy conditions whose feet may grow wider over a short period of time. Width adjustment by the cooperation of the stretch panel and the expansion element provides sufficient lateral range to accommodate such changes. Also for children whose feet are still growing, a shoe with the lateral adjustment of the present invention would accommodate some measure of growth before it must be replaced for a larger size.  
         [0037]     This embodiment of the invention encompasses ensuring that at least a portion of the shoe upper which covers the instep of the wearer&#39;s foot has elasticity to some degree. For most categories of wearers it may be most comfortable if the shoe not only expands laterally at the sole, but can also expand around the instep to take into account any swelling or growth of the girth of the foot. This will provide the snug fit that is needed for most athletic activities.  
         [0038]     The expansion of the longitudinal split midsole in a completed shoe is illustrated schematically in  FIGS. 7-8 . In these cross-sections, midsole  16  has a longitudinal split  17 , and expansion element  24  is seen as a separate T-shaped element with flanges  26  that reside in a recess of corresponding thickness in midsole  16 . Insole panel  34  overlays the midsole with stretch panel  40  positioned generally over expansion element  24 . In the static condition, i.e. the unexpanded condition, expansion element  24  is retracted,  FIG. 7 , and the shoe is at its narrowest width. Stretch panel  40  and expansion element  24  are both biased to this retracted, static condition to provide a tight fit.  
         [0039]     When the width of the shoe is expanded, either by a wider foot or because of a flexure required by the wearer&#39;s activity, stretch panel  40  and expansion element  24  expand laterally to accommodate the width adjustment. The shoe therefore provides dynamic width adjustment by cooperative expansion of the stretch panel and expansion element. Flexure out of the horizontal plane is not necessarily contemplated to be required all of the time, but is illustrated in  FIG. 8 . Since the stretch panel and expansion element are biased to be retracted, even in their expanded state, they will provide a snug, secure fit to the wearer.  
         [0040]     The use of the insole stretch panel in cooperation with a longitudinal split midsole with expansion element enable a single length of shoe to accommodate a variety of widths. Moreover, even for a single wearer whose foot dimensions may change over a short period of time, a single sized shoe will be able to accommodate the changes. In this way, a single last can be used to manufacture a shoe that has a width sizing range from very narrow to extra wide. Of course the size and degree of elasticity of the stretch panel and the expansion element can be adjusted as necessary to provide a smaller or larger range of width sizes per each length size. In addition, these parameters may be customized for a particular shoe depending on the type of activity for which it is designed.  
         [0041]     Among the elements of the shoe that can be varied without changing the fit, function and advantages, are the construction of the insole panel, and the construction of the expansion element.  FIG. 9  illustrates variations on both of these elements. First, an alternative insole panel  34 ′ is shown in which a non-stretch portion  36  surrounds an expansion portion  38 . But instead of a stretch panel making up the expansion portion, expansion portion  38  is simply a cut-out  39  in the non-stretch portion  36 . Otherwise the insole panel  34 ′ is similar to that of the earlier described embodiment, stays  42  extend across the expansion portion  38  to maintain the shape and dimension of the upper prior to and during lasting and sole laying. In some applications, such as smaller sized shoes, the substitution of a cut-out for a stretch panel serves a corresponding expansion function.  
         [0042]     Secondly  FIG. 9  illustrates an alternative midsole expansion element  24 ′ which is integrally formed with the rest of the midsole material  16 . The pleated expansion element  24 ′ is molded together with the midsole and no separate attachment is needed. The integral pleated expansion element longitudinally splits the midsole between the lateral and medial sides to enable expansion therebetween.  
         [0043]     Either or both of these modifications are contemplated to be used with the earlier described constructions. That is, the insole panel with a cut-out expansion portion could be paired with a sole unit that has the separately formed pleated midsole element attached within the split midsole. Conversely, the insole panel with a stretch panel expansion portion could be paired with the sole unit with the integrally formed pleated midsole element.  
         [0044]     Although not a requirement, at least a portion of the upper should have some elasticity to hold the wearer&#39;s foot snugly for optimal fit. This is especially true for shoes using an insole panel with a cut-out expansion portion. Ideally any adjustment in width or internal shoe volume should occur at multiple areas around the wearer&#39;s foot, and not just at the bottom.  
         [0045]     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that may more embodiments and implementations are possible that are within the scope of the invention.