Patent Publication Number: US-7594345-B2

Title: Article of footwear having sole with ribbed structure

Description:
FIELD OF THE INVENTION 
   Aspects of the present invention relate to athletic footwear for running, and in particular hurdling. Aspects of the invention concern, more particularly, an article of footwear having a rigid or semi-rigid plate. 
   BACKGROUND OF THE INVENTION 
   Athletic footwear generally includes an upper and a sole structure. Usually formed of leather, synthetic materials, or a combination thereof, the primary purpose of the upper is to comfortably secure the wearer&#39;s foot to the sole structure while providing necessary ventilation and protection from the elements. The sole structure is attached to the upper and typically has a multi-layer construction which includes a sock liner (insole), midsole, and outsole. The sock liner is located within the upper and improves the comfort of the footwear. The midsole forms the cushioning layer of the sole and may be formed of a soft, yet resilient foam material that attenuates the impact forces of running, walking, or other movement. The outsole may be fashioned from a durable synthetic, such as rubber, to resist wear during use and includes spikes and ridges. 
   Although the upper and sole structure may be considered universal elements of athletic footwear, the specific sport for which footwear is intended to be used determines the individual, specialized characteristics of each element. Commonly, running shoes include lightweight elements that minimize the harmful effects of over-pronation; basketball shoes require components that stabilize the foot during quickly-executed direction changes, jumps, and stops; and football shoes incorporate cleats to ensure adequate traction on a natural turf surface. Accordingly, the primary differences between sport-specific styles of athletic footwear relate to the highly-refined features that make footwear appropriate for the demands of a particular sporting activity. 
   Shoes for track, in particular for passing over hurdles, also include a highly-refined set of elements that combine to form an article of footwear having characteristics specific to the track. The ideal track shoe includes a low profile design that provides little or no support for the shoe. In general, the thicker the sole of an article of footwear, the more unstable the footwear becomes. A low profile design thereby lends stability to an article of track footwear. A track shoe generally has spikes on the forward portion of the shoe to aid in traction, but is otherwise made of a smooth, slippery, material. 
   Often, when hurdling, the heel portion of the bottom of the shoe contacts the hurdle. Such contact can slow down the hurdler or make the hurdler trip and possibly fall. 
   BRIEF SUMMARY OF THE INVENTION 
   Aspects of the present invention relate to an article of athletic footwear having an upper and a sole structure attached to the upper. The sole structure includes an optional midsole and rigid or semi-rigid ground contacting surface (outsole or plate). The optional midsole may be attached to at least a portion of the upper and may be formed of a thin resilient, shock-absorbing material. The plate is attached to at least a lower portion of the upper or optional midsole and provides a wear-resistant outer surface. 
   The sole structure includes a rigid or semi-rigid ground contacting surface having a plurality of ribs located in the heel portion. The plurality of ribs is located longitudinally in the heel portion. 
   The various advantages and features of novelty that characterize aspects of the present invention are pointed out with particularity in the appended claims. To gain an improved understanding of the advantages and features of novelty that characterize aspects of the present invention, however, reference should be made to the descriptive matter and accompanying drawings which describe and illustrate preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a medial side view of an article of footwear according to an aspect of the present invention. 
       FIG. 2  is a bottom view of the plate for an article of footwear depicted according to an aspect of the present invention. 
       FIG. 3  is a front view of the plate for an article of footwear depicted according to an aspect of the present invention. 
       FIG. 4  is a back view of the plate for an article of footwear depicted according to an aspect of the present invention. 
       FIG. 5  is a lateral side view of the plate for an article of footwear depicted according to an aspect of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings, wherein like numerals indicate like elements, an article of footwear in accordance with aspects of the present invention is illustrated. 
   The footwear of is described in terms of hurdling footwear, but the concepts can be applied to other types of footwear as well including athletic and casual footwear. 
   With reference to  FIG. 1 , the primary elements of footwear  10  are an upper  20  and a sole structure  30 . Sole structure  30  is attached to the lower portion of upper  20 . As footwear  10  is track footwear, in particular for passing over hurdles, the footwear may be of minimal construction. 
   Upper  20  is configured to receive a wearer&#39;s foot and secure the foot to footwear  10 . Typically, upper  20  includes a thin covering as is conventional in the art for track-style footwear. A sock liner may also be present and would be located within upper  20  and adjacent to the lower surface of the foot of the wearer and adjacent midsole  31 . The sock liner may be removable. 
   Sole structure  30  has a multi-layered configuration which includes an optional midsole  31  and rigid or semi-rigid ground contacting surface (“plate”)  33 . 
   Midsole  31  forms a layer of sole structure  30  above plate  33  and typically provides cushioning and attenuation of impact forces upon contact with the ground. Midsole  31  may be formed of a variety of materials, including polyurethane and ethyl vinyl acetate (e.g. PHYLON) and may include one or more supplemental shock-absorbing components. 
   Plate  33  forms the lower layer of the footwear and provides a wear-resistant, ground-contacting surface. In comparison with a conventional rubber outsole, plate  33  is formed from a harder, more rigid member and a generally slippery surface or, in other words, a surface having a lower coefficient of friction. The advantage of the plate surface being slippery is that the plate surface does not slow or bog the runner down. 
   As shown in  FIG. 2 , typically, the plate contains spikes  36  for traction. The spikes are located on the bottom forward portion of the plate. The spikes may be any suitable spikes for track or hurdling footwear. The spikes  36  may contain a disk-like portion with short pins as shown. The spikes may be formed integrally with the plate, or may be attached. A center pin (not shown) may also be attached through a center hole of the spike to the plate by glue or screw. This pin may be of a conical design. 
   In addition, as best shown in  FIGS. 1 ,  2 , and  5 , the bottom forward portion of the footwear may contain longitudinal ridges  38 . The ridges prevent the footwear from slipping sideways when running. Also present along the ridges may be several protrusions  39 . These protrusions may have the configuration of triangular points, for example. The protrusions also provide traction. 
   Near the toe region of the plate, several (approximately 3-10) protrusions such as triangular points  40  may be present to aid the runner in, for example, starting the race. The triangular points press into the ground at the start to prevent slippage. Protrusions, such as triangular or diamond-shaped points  41 , may also be present on the lateral side edge of the plate to prevent slippage. See  FIGS. 1 and 5 . 
   As shown in  FIGS. 2 ,  4  and  5 , in accordance with aspects of the invention, longitudinal ribs  50  are at least partially located in the heel region of the plate. The ribs are made of a slippery material and would typically be made of the same material as the plate. Generally, these ribs would contact the hurdle on the leading foot of the hurdler. That is, a leading foot generally goes over the hurdle in a straight forward motion since the leg is in a forward outstretched position. The likely point of contact of the leading foot is the heel region of the plate. 
   Ribs  50  allow only minimum contact of the footwear if contact is made to the hurdle. That is, instead of a flat heel surface which allows a large contact area, the ribs provide a significantly smaller contact area so that the footwear slides over the hurdle without slowing the hurdler or causing the hurdler to slip. In addition, since the ribs are longitudinal (correspond to the length of the footwear), the ribs do not get caught on the hurdle. The ribs typically wrap around the backside of the heel as shown in  FIGS. 4 and 5 . 
   Any suitable number of ribs  50  may be used, typically between three and ten. The ribs  50  may have any suitable cross-section, but generally are thicker next to the bottom of the plate and thinner at the portions of the ribs farthest from the plate. The portions of the ribs farthest from the plate are typically slightly rounded to avoid cutting into the hurdle. 
   At least one, generally 2-5 substantially vertically extending ribs,  52  may also be present along the medial side portion of the heel as shown in  FIGS. 1 and 2 . At least one, generally 2-10, substantially vertically extending ribs  56  may also be present along the medial side portion of the forefoot region of the plate as also shown in  FIGS. 1 and 2 . Generally, these medial ribs would contact the hurdle on the trailing foot. That is, the trailing foot tends to go over the hurdle at an angle such that the likely point of contact is the medial edge of the plate. The substantially vertically extending ribs may be slightly angled toward the rear as shown in  FIGS. 1 and 2  to accommodate the angle of the trailing foot going over the hurdle. 
   The footwear may be customized to provide leading foot footwear and trailing foot footwear. Thus the leading foot footwear may contain the longitudinal ribs  50  but no ribs on the side of the footwear. The trailing foot may contain the ribs on the medial side of the footwear, but not on the heel. 
   The plate may be made by an injection molding process, for example. The plate is made of a slippery material having a low coefficient of friction. Typically, the plate is made from a polymeric material such polyamides (e.g. NYLON 6/6), acetal homopolymers (e.g. DELRIN) and polyurethane. Nylon is a crystalline thermoplastic polymer with properties that include outstanding wear and abrasion resistance, high in use service temperature, excellent impact resistance, excellent chemical resistance, low friction and self lubricating. Polyamides are generally easy to machine. Acetal homopolymers have high modules of elasticity, high strength and stiffness, low coefficient of friction, good abrasion, and impact resistance. 
   The desired flexible modulus of elasticity is about 250,000 to about 500,000 psi, or about 300,000 to about 400,000 psi, or about 320,000 to about 340,000 psi. 
   For additional slipperiness, the ribs in the heel and medial part of the plate may be coated with a hydrophilic material in order to reduce the coefficient of friction. 
   Preferably, the ribs are integrally made with the plate in the same injection molding process for example. However, ribs may also be attached to the plate utilizing adhesive or other suitable methods. If not integrally made with the plate, the ribs also should be made with a slippery material having a low coefficient of friction. 
   The present invention is disclosed above and in the accompanying drawings with reference to a variety of preferred embodiments. The purpose served by disclosure of the preferred embodiments, however, is to provide an example of the various aspects embodied in the invention, not to limit the scope of the invention. One skilled in the art will recognize that numerous variations and modifications may be made to the preferred embodiments without departing from the scope of the present invention, as defined by the appended claims.