Patent Application
20110023324
This invention relates generally to footwear and, more particularly to insoles for footwear having features that improve the comfort for the wearer during standing, walking and running.
Footwear has undergone significant evolutionary advances in technology, particularly since the development of the electrodynogram which has permitted researchers to measure dynamic forces and to better understand biomechanical action of a human foot within a shoe while the wearer is walking or running. Using this tool, many researchers have made technological advances directed towards the mid-sole of a shoe. Since the mid-sole functions primarily as a suspension system of the sole of the foot, and often provides both protective cushioning and a stable platform for the wearer's foot, many conventional technologies have focused on cushioning the impact associated with foot strike by varying the spring coefficients in the mid-sole to dispense shock.
In my earlier U.S. Pat. No. 4,597,195 I describe a discovery of a then previously misunderstood phenomena, functional hallux limitus, that is believed to affect a majority of the population. To treat functional hallux limitus I created an improved shoe sole design which permits the first metatarsal to better achieve plantarflex relative to the great toe and remaining metatarsal heads. As explained in my aforesaid '195 patent, plantarflex allows for the extension of the human great toe during human gate cycle in an efficient fashion. More particularly in accordance with my prior '195 patent, I created a human shoe sole having an area of reduced support underlying substantially only the location of the first metatarsal head of the wearer's foot. As described in my '195 patent, providing an area of reduced support substantially only under the head of the first metatarsal encourages eversion and plantarflexion of the first metatarsal head as weight shifts from the heel to the first ray. Thus the normal functioning of the foot for plantarflexion and supination is encouraged with beneficial results for improved walking comfort and shock absorption on subsequent heel contact. Following my discovery millions of pairs of shoes have been manufactured with foot beds having an area of reduced support underlying substantially only the location of the first metatarsal head of the wearer's foot, to encourage plantarflexion of the first metatarsal head.
The present invention provides an improved insole which incorporates an area of reduced support which includes an asymmetrically shaped depression under the first metatarsal head, fashioned with its lowest point skewed to the medial side of center. This unique shape further encourages the first metatarsal head into eversion as the wearer moves from midstance to propulsive phase.
As used herein the term “sole” and “inner sole” are used interchangeably. Moreover, a “sole” or “insole” may be an element built into or forming an integral element of a footwear product such as an insole board, or as a separate element, including, e.g. a sock liner or removable insole, an after-market insole device, or a custom or prefabricated foot orthotic, which may be inserted into a footwear product post-manufacture. The element also may be cut into or formed in the foot supporting surface of a shoe.
In general, the improved footwear of this invention comprises a sole having a forefoot section having a first region for supporting the first, second, third, fourth and optionally fifth metarsal heads of the foot and a second region surrounding the first region, for supporting the remainder of the foot, at least in part. The first region is designed to provide less support than portions surrounding the second region. Typically, the sole is formed so that the first region is formed of a resiliently deformable material that has a lower durometer or resistance to movement than the second region. Also, in order to further promote eversion, an area of the first region underlying substantially only the first metatarsal head has a depression relative to the surrounding portion having an asymmetric shape with its lowest point skewed to the medial side of center. In other words, the depression has a shallower slope on the lateral side. This has the effect of rotating the first metatarsal head into eversion as the wearer moves from midstance to propulsive phase. The remainder of the first region preferably is flat.
Further features and advantages of the present invention will be seen from the following detailed description, taking in conjunction with the accompanying drawings, wherein:
Referring to
The sole 10 is formed so that an area of reduced support or reduced resistance to downward loading or movement is located in the first region 28 of the forefoot section 16. The first region 28 is formed of a resiliently deformable material that offers less resistance to downward movement than the region surrounding the first region, i.e. the second region 30, and also the toe section region 18. Region 28 may be formed of a material having a lower durometer than the surrounding regions 30 and 18. Preferably, region 28 will have a Shore A hardness in the range of 30-35, which closely matches the hardness of the fat pad of a typical human foot. Alternatively, region 28 may be made thinner so as to at least in part fall below the surface of the second region 30 and toe section 18. Region 28 may be formed as a separate element, e.g. a plug or insert 40 cut or built into the sole 10, or as a recess formed in the top or bottom surface of the sole, e.g. by molding or by machining. Region 28 may be covered by a flexible liner (not shown).
Also, a region within region 28, underlying substantially only the first metatarsal head of the wearer includes a hollow or depression 42, relative to the remainder of region 28, of asymmetric shape, with the lowest point of the hollow or depression skewed to the medial side of center. That is to say, as seen particularly in
In practice, depression 42 is round or nearly round in plan, and the corresponding medial and lateral walls 44 and 46 are also somewhat rounded or curved. Accordingly, as used herein, “slope” is an imaginary line or cord running between the top edge of the side wall and a point where the side wall morphs into the bottom of the depression. This is best seen by phantom line 43 (
In dimensions, the hollow depression 42 should be large enough in plan to accommodate the first metatarsal head, at least in part. In a typical embodiment, depression 42 is substantially circular in plan, preferably having a diameter of about 2.54 cm. to about 3.81 cm., depending on foot size. The depression also may be oval, egg-shaped, or elongated in plan, and should have a nominal depth preferably in the range of about 2-3 mm measured from the top edge of the side walls to the lowest point of the depression. Despite this relatively small amount, this has a profound effect of rotating the first metatarsal head into eversion as the wearer moves from midstance to propulsive phase. In an alternative embodiment, the depression 42A is somewhat elongated and slightly wider at its toeward end, e.g. as shown in
The insoles described above may be used with street and sport footwear including sandals. As noted above, the insoles may be incorporated into an insole board at the time of manufacture, formed as a sock liner or as an aftermarket insole device or a custom or prefabricated (over-the-counter) orthotic for placing into a shoe by the wearer.
Various changes can be made in the above construction without departing from the scope of the invention. For example, an asymmetrically shaped hollow having tapered side walls skewed to the medial side of center may be formed extending downwardly from the bottom of an insole board or sock liner of a shoe, and underlying substantially only the first metatarsal head. Also, if desired, a device can be designed with a depression formed essentially half-way through, from side to side, e.g. as illustrated in
