Boots – shoes – and leggings – Soles – Spring heel
Reexamination Certificate
2001-09-21
2004-03-30
Kavanaugh, Ted (Department: 3728)
Boots, shoes, and leggings
Soles
Spring heel
C036S03500R, C036S03000A, C036S031000
Reexamination Certificate
active
06711834
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a sole structure of an athletic shoe, and more particularly, a sole structure that has a wavy plate inserted between an upper midsole and a lower midsole.
BACKGROUND OF THE INVENTION
A sole for an athletic shoe used in various sports includes a midsole and an outsole that is fitted on the bottom surface of the midsole and directly contacts the ground. The midsole is generally formed of a soft elastic material to ensure adequate cushioning properties as a shoe.
Incidentally, as a sports shoe, not only cushioning properties but also running stability is required. That is, there exists a need to prevent excessive lateral or transverse deformation of a sole, such as pronation or supination occurring at the time of striking onto the ground.
In order to prevent such a lateral deformation, as shown in Japanese patent application laying-open publication No. 11-203, Mizuno Corporation proposed a midsole structure having a wavy plate with a corrugation inserted thereinto. In this case, by the action of the wavy plate, a resistance force occurs to restrain a heel portion of a midsole from deforming in the transverse direction at the time of impacting onto the ground, thereby preventing the heel portion of a shoe from laterally deforming.
Such a wavy plate prevents lateral deformation of a shoe, but it decreases cushioning properties of the whole midsole. In the midsole structure shown in the above-mentioned publication, amplitude of a corrugation of a wavy plate is suitably varied between a front end and a rear end or between a medial side and a lateral side of the shoe heel portion to achieve cushioning properties. Although such a method of securing cushioning properties and preventing lateral deformation was adequate for runners whose pronation or supination is not so great, but it was inadequate for runners whose pronation or supination is greater. In athletic sports, such as tracks, field events, tennis, volleyball, basketball, or the like, an impact load three to five times an athlete's weight is applied on landing and especially on jumping, very high impact load about ten times an athlete's weight is applied. In these sports, adequate cushioning properties were not necessarily achieved by the above-mentioned midsole structure.
The present invention has been made in view of these conventional circumstances, and its object is to provide a sole structure of an athletic shoe that can not only effectively absorb an impact load applied to a heel portion of the shoe directly after contacting the ground but also securely prevent a pronation or supination of a shoe wearer's foot.
SUMMARY OF THE INVENTION
A sole structure of an athletic shoe according to a first invention includes an upper midsole that is formed of a soft elastic material and that extends from a heel portion of the shoe to a forefoot portion through a midfoot portion, a lower midsole that is formed of a soft elastic material and that is disposed at least at the heel portion of the shoe under the upper midsole, a wavy plate or a corrugated sheet having a wavy corrugation that progresses from a rear end side of the heel portion toward the midfoot portion and that is provided at least at the heel portion between the upper and lower midsoles, an outsole that is fitted on the bottom surface of the lower midsole, and a shock absorbing member that is fitted at a “heel strike region” of the heel portion of the shoe between the wavy plate and the outsole.
Here, the term, “heel strike region” used herein means a region of the heel portion of a shoe that contacts the ground at a first stage of landing when a shoe wearer lands on the ground from the heel portion of the shoe.
As a “shock absorbing member”, a high molecular compound having viscoelasticity is preferable. Specifically, polystyrene, polyurethane, or polyisoprene elastomer may be utilized. Also, a blend type of these mixed elastomers, or both solid and foamed types are included. The wavy plate is preferably formed of thermoplastic resin or thermosetting resin.
In this first invention, an impact load applied to the heel strike region of the shoe heel portion directly after contacting the ground is effectively absorbed by the shock absorbing member fitted at the heel strike region. And after landing onto the ground, pronation or supination of a shoe wearer's foot is securely prevented by the action of the wavy plate.
Also, in this case, because the shock absorbing member is provided between the wavy plate and the outsole, that is, on the side of the lower midsole, stability of the shoe heel portion on landing is secured to some extent by the upper midsole, and the impact load applied to the outsole is absorbed by the shock absorbing member. In contrast, when the shock absorbing member is provided on the upper midsole side, that is, between the upper and the wavy plate, lateral deformation of the shoe heel portion is easy to occur on landing and stability of the shoe heel portion is hardly maintained.
In a sole structure of an athletic shoe according to a second invention, the shock-absorbing member is formed of a viscoelastic material having 70% or more energy loss, or preferably, 85% or more energy loss.
Here, the term, “viscoelasticity” used herein means a phenomenon in which deformation caused by an external force appears as an overlap of elastic deformation and viscous flow, and such properties are especially remarkably seen in high molecular compound.
When an impact force is applied to the viscoelastic material, a portion of supplied energy by the impact force is converted into heat energy and the like, and by the amount of the converted energy, the impact force is absorbed and a shock is relieved. On the other hand, the other portion of supplied energy, which is not liveried converted into heat energy and the like, restores the deformed viscoelastic material to its original condition before deformation as a restoring energy by elastic rebound. In this case, the amount of supplied energy minus the restoring energy is an energy loss.
Generally, 70% or 85% or more energy loss is considerably high value. When a shock absorbing member formed of only a viscoelastic material having such a high energy loss is provided in the midsole, a shoe wearer receives a feeling of floating from the ground during activities, especially running, and as a result, he or she cannot exert a necessary kick power to the ground at the start of running and cannot control activities.
In contrast, according to the present invention, since such a shock absorbing member is used with the wavy plate, compressive and lateral deformations of the upper and lower midsoles after landing are restrained by the action of the wavy plate. Thus, a shoe wearer can exert a sufficient kick force to the ground and control activities.
In other words, as in the present invention, that the wavy plate is provided in the midsole enables to use the shock absorbing material formed of a viscoelastic material having 70% or more, or 85% or more high energy loss.
According to the present invention, even in sports where very high impact force is applied on jumping, a shock applied to the shoe heel portion is absorbed and relieved by the shock absorbing member having 70% or more, or 85% or more high energy loss, and lateral deformation of the shoe heel portion is prevented and activities are controlled by the action of the wavy plate.
In a sole structure of an athletic shoe according to a third invention, the shock absorbing member has hardness of 55 degrees or less, preferably, 45 degrees or less at Asker C scale. In this case, an impact force applied to the shock absorbing member is absorbed by converting a portion of supplied energy by the impact force into heat energy and the like. In addition, the reason why the hardness of 55 degrees or less at Asker C scale is employed is that less shock absorbing properties or less cushioning properties are acquired if the hardness is greater than 55 degrees at Asker C scale.
In a sole structure of an athletic shoe according
Fasse W. F.
Fasse W. G.
Mizuno Corporation
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