Shoe sole with dual energy management system

Details Shoe sole with dual energy management system Shoe sole with dual energy management system

1999-04-01

2003-03-04

Pyon, Harold (Department: 1772)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including aperture

C428S172000, C428S173000, C428S492000, C428S495000, C036S043000, C036S044000

Reexamination Certificate

active

06528140

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application incorporates by reference, and claims priority to, and the benefit of, German patent application serial number 19815132.2, which was filed on Apr. 3, 1998, and German patent application serial number 19914472.9, which was filed on Mar. 30, 1999.
TECHNICAL FIELD
The invention relates to an article of footwear that provides a dual energy management system to improve the biomechanical properties of the article of footwear.
BACKGROUND INFORMATION
During each footfall in walking, running and jumping, forces are acting between the ground and the foot. These forces are usually referred to as ground reaction forces (GRF). They can be quantified using appropriate measuring devices. The order of magnitude of the GRF for walking is typically 1 to 1.5 times an athlete's body weight (BW). In running, the forces are typically between 2 to 3 times BW, and in jumping the forces are typically between 5 and 10 times BW. To compensate for the forces occurring during walking, running and jumping, complex movements take place in the human body, which lead to considerable stress on the anatomy.
If an average runner runs a distance of approximately 1 kilometer, his feet contact the ground approximately 1,000 times. This leads to a considerable accumulation of arising impacts, i.e., resulting shocks. For example, a person with a body weight of approximately 68 kilograms who runs a distance of approximately 32 kilometers per week is exposed to a force equivalent to approximately 4 to 6 million kilograms per week. For an athlete to sustain such a stress without any damage it is necessary for the body to compensate for, or absorb, the shock in a harmless way.
To this end, the human body is provided with a number of natural mechanisms. A portion of the shock is already absorbed by the moving parts of the body consisting essentially of bones, muscles, and cartilage. Furthermore, the human foot comprises cushioning consisting of fat and cartilage for damping the impact and reducing the stress. In addition, the degree of bending of the knee can play an important role in the influence of the impact forces during running. For example, it has been shown that the vertical force impact peak (VFIP), i.e., the force that is measured when the heel contacts the ground, is reduced by an increase in the degree of bending of the knee during running. Experiments confirm that the VFIP values occurring in persons who contact the ground first with the midfoot or forefoot area are negligible. The VFIP A values depend heavily on boundary conditions, such as, the speed of running and the hardness of the ground.
For a long time, consideration has been given to protecting the human body against impacts by providing footwear with cushioning. If footwear cushioning is to be optimized for specific kinds of sports, it is helpful to obtain information about GRF, i.e., the forces occurring when the foot contacts the ground. GRF designates all forces which act upon the foot or the body during contact with the ground. Furthermore, it is helpful to consider the time dependence of the forces acting on the foot or body.
The force-time pattern for each foot-ground interaction typically shows two distinct phases; an impact phase when the foot collides with the ground followed by a push-off phase when the athlete is propelled forward and upwards.
FIG. 1
a
shows the landing motion of the foot in long distance running. About 80% of all runners contact the ground with the heel first.
FIG. 1
b
shows the following push-off of the midfoot and forefoot. The corresponding vertical component of the GRF is shown in
FIG. 1
c.
As can be seen, the curve consists of two distinct force maxima. The first maximum, corresponding to point P in
FIG. 1
c,
occurs after 20 to 40 milliseconds (ms) as a result of heel impact. This value P was designated above as the vertical force impact peak (VFIP). Sometimes this peak value P is also called the “passive peak value” because during this short time interval the human body can not react and adjust to it. The second maximum, corresponding to point A in
FIG. 1
c,
occurs after 80-100 ms and is caused by the push-off action of the midfoot or forefoot from the ground during running to move the runner forward and upwards for the next step. This peak value A is called the “active peak value” or the “propulsion peak value.”
Studies have shown that the relative height of the passive and active peak values can vary with respect to each other depending on; the kind of sport, speed of running, anatomical formation of the feet, etc. In some cases, the values shown in
FIG. 1
c
can change such that the active peak value has the same height as the passive peak value or even higher. It is, however, typical that two peak values occur which are separated by approximately 60 milliseconds.
The two types of forces have different consequences with respect to the human musculoskeletal system. Impact forces do not contribute to athletic performance. Impact forces, however, have been associated in a number of studies with chronic and degenerative injuries in various sports, especially, when the heel is involved. The goal, therefore, is to reduce impact forces under the heel using appropriate footwear sole constructions. The desired systems are the ones that deform easily under load and dissipate energy.
Magnitude and duration of active forces determine athletic performance, i.e., running speed and jumping height. This means, if an athlete wants to run at a certain speed, the appropriate level of active forces must be maintained. Thus, the intention is to enhance these forces with a footwear sole that minimizes energy dissipation as much as possible, and at the same time provides the necessary cushioning.
With respect to cushioning systems in footwear, and to deal with the undesired results of the forces, as discussed above, and to use these forces advantageously, the following approaches were used in the prior art. In U.S. Pat. No. 5,695,850, the concept is known to provide a sports shoe with a sole unit that is said to improve the performance of the shoe. This is to be achieved by using components of the shoe or the sole which “regain” the energy during running and transform it during the push-off phase from the ground, i.e., in the area of the active peak value in
FIG. 1
c,
into a forward movement. To this end, the use of elastic materials either in the complete sole area or limited to the forefoot area is disclosed. Suitable elastic materials are, among others, 1,4-polybutadiene/rubber compounds or, as an inlay for the shoe, a mixture of ethylene vinyl acetate (EVA) and natural rubber.
German patent no. DE 87 09 757 discloses a sole unit consisting of an outsole and a midsole mounted thereon. The midsole is formed by a comparatively narrow frame-like extending strip defining a seat that is downwards closed by the outsole. Inside the seat two sole parts are provided, one of which extends from the forefoot part of the shoe to the beginning of the heel part where the second sole part is provided. The first sole part consists preferably of a plastic supporting inlay being comparatively yielding under pressure so that during walking with such a shoe a foot bed can be formed on the sole part providing a certain level of comfort. The sole part arranged in the heel area provides a shock absorber and consists of impact or shock absorbing material, for example, silicon.
U.S. Pat. No. 4,108,886 also describes the use of shock absorbing inlays in the heel part of a sole unit. U.S. Pat. No. 4,316,335 discloses the use of a shock absorbing material not only in the forefoot part of a sole, but also in the heel part, wherein, the damping properties of the heel part are better than in the forefoot part.
European patent no. 0 272 082, discloses the use of a spring plate in the forefoot area of a sole unit. The spring plate is used to take up energy during each step and to release the energy during the push-off phase.
All of the above described known concepts have the disadvantage th

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