Boots – shoes – and leggings – Soles – Cushion
Reexamination Certificate
2001-08-31
2003-11-18
Stashick, Anthony D. (Department: 3728)
Boots, shoes, and leggings
Soles
Cushion
C036S03000A, C036S031000, C036S037000, C036S103000
Reexamination Certificate
active
06647645
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a midsole structure of an athletic shoe, and more particularly, a midsole assembly having a corrugated sheet therein.
A sole for an athletic shoe used in various sports includes a midsole formed of a soft elastic material to secure cushioning properties and an outsole fitted to the bottom surface of the midsole and directly contacting the ground.
Not only cushioning properties but also running stability are required in an athletic shoe. That is, there is a need to prevent over-pronation or over-supination that causes an excessive lateral or transverse deformation of a shoe sole after striking onto the ground.
As shown in Japanese utility model application publication No. 61-6804 and Japanese patent application laying-open publication No. 11-203, Mizuno Corporation proposed a midsole assembly having a corrugated sheet therein to prevent such an excessive lateral or transverse deformation.
In the midsole assembly described in the above-mentioned publications, a corrugated sheet having a wavy corrugation is disposed in a heel portion of a midsole. Therefore, at the time of striking onto the ground, a resistance force occurs to restrain lateral or transverse deformation of the heel portion of the midsole.
Generally, by inserting a corrugated sheet into a midsole, compressive hardness or hardness with respect to deformation of the whole midsole caused by a vertical compressive force becomes higher, and the midsole tends to be less deformed in the transverse and vertical directions. Therefore, by inserting a corrugated sheet, required cushioning properties on landing are not necessarily achieved at portions that require cushioning properties.
On the other hand, when a relatively lower elastic material is used as a corrugated sheet, cushioning properties are achieved to some extent on landing but lateral deformation after landing may not be fully restrained.
An object of the present invention is to provide a midsole structure of an athletic shoe that can satisfy both stability and cushioning properties.
SUMMARY OF THE INVENTION
A midsole structure of an athletic shoe according to a first embodiment of the invention includes a midsole formed of a soft elastic material and extending from a heel region to a forefoot region of a shoe, and a corrugated sheet disposed at a heel portion and a midfoot portion of the midsole. The flexural rigidity of a medial portion of the corrugated sheet is different from that of a lateral portion of the corrugated sheet.
Generally, as the flexural rigidity of a corrugated sheet increases, the cushioning properties of a midsole on landing decrease but the stability of the midsole improves. In contrast, as the flexural rigidity of a corrugated sheet decreases, the stability of the midsole decreases but the cushioning properties of the midsole on landing improve.
Therefore, by decreasing flexural rigidity of a heel portion of a corrugated sheet at a medial portion (or a lateral portion) that requires cushioning properties on landing, in other words, by increasing flexural rigidity of a heel portion of a corrugated sheet at a lateral portion (or a medial portion) that requires stability after landing, cushioning properties of the midsole on landing can be secured and stability of the midsole after landing can be acquired.
In this case, when the flexural rigidity of the medial portion of the corrugated sheet is made higher than that of the lateral portion of the corrugated sheet, in an athletic shoe such as a running shoe that strikes onto the ground more often from the lateral side, the cushioning properties on landing are secured by the lateral portion of the corrugated sheet having a relatively lower flexural rigidity, and running stability after landing is secured by the medial portion of the corrugated sheet having a relatively higher flexural rigidity, thereby preventing over-pronation.
In contrast, when the flexural rigidity of the lateral portion of the corrugated sheet is made higher than that of the medial portion of the corrugated sheet, in an athletic shoe such as an indoor sports shoe or a tennis shoe that strikes onto the ground more often from the medial side, the cushioning properties on landing are secured by the medial portion of the corrugated sheet having a relatively lower flexural rigidity, and running stability after landing is secured by the lateral portion of the corrugated sheet having a relatively higher flexural rigidity, thereby preventing over-supination.
Preferably, a boundary line between the medial side portion and the lateral side portion of the corrugated sheet crosses a load transfer curve for a heel striker at the midfoot portion of the midsole. The heel striker tends to strike onto the ground from a heel region of a shoe.
Here, when the boundary line between the medial and lateral sides of the corrugated sheet is disposed on the load transfer curve, flexural rigidity of the midsole will change abruptly on opposite sides of the load transfer curve. Thus, the way of deformation of the midsole will abruptly change on opposite sides of the load transfer curve at the time of load transfer, which impedes running stability and makes a shoe wearer feel unpleasant. In contrast, when the boundary line crosses the load transfer curve, the way of deformation of the midsole will not abruptly change on opposite sides of the load transfer curve at the time of load transfer. Thus, running stability can be secured, and cushioning properties and stability can be adjusted according to the actual landing condition.
The boundary line between the medial and lateral sides of the corrugated sheet may cross a load transfer curve for a heel striker in zigzag. In this case, since the midsole comes to deform along the load transfer curve further smoothly, a smooth landing will be possible at the time of striking onto the ground. In addition, deflections of the boundary line from the load transfer curve may be equal or unequal on opposite sides of the load transfer curve.
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patent: 11000203 (1999-01-01), None
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Mizuno Corporation
Stashick Anthony D.
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