Boots – shoes – and leggings – Soles – Cushion
C036S03000A, C036S037000, C036S071000
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a midsole of a shoe sole, particularly to a cushioning structure thereof.
2. Description of the Related Art
A shoe sole is required to have cushioning performance.
In a conventional shoe sole, in general, a landing shock at the time of walking is absorbed by dissipating energy through compression deformation of a midsole or the like. However, a sufficient cushioning property can not be obtained merely by the absorption (dissipation) of the energy through compression deformation, since the amount of the absorption is generally small.
On the other hand, if the midsole is made thick in order to make the dissipation of the energy large, the lightweight property of the shoe sole is lost.
) is a perspective view of a cushioning part disclosed in Japanese Patent Laid-Open No. Hei8-38211.
This cushioning part
is made of gel, and is provided with notch portions
for allowing compression deformation at the time of compression deformation of the part
. However, the notch portions
are not a significant factor in promoting shear deformation.
) is a cross-sectional vertical side view showing a cushioning structure disclosed in Japanese Patent Laid-Open No. Hei3-170102.
The cushioning structure shown in FIG.
) is provided with a columnar part
made of gel, and a coil spring
fitted around the part
for storing repulsive “spring-back” energy at the time of kicking and going forward.
) is a perspective view showing a part of an orthopedic shoe sole disclosed in U.S. Pat. No. 4,217,907.
is fixed to a heel of an outer sole. This part
includes a number of projecting ribs
arranged side by side in a circumferential direction. When receiving a repulsing force W from the ground, the projecting ribs
in the direction of the arrow
. The part
is for correcting and curing foot deformities by this rotation. Part
is made of a relatively hard material and is not designed to absorb shock.
) and FIG.
) are a front view and a plan view respectively showing a projection
of a sole disclosed in Peterson (U.S. Pat. No. 5,782,014).
A midsole unit of Peterson is provided with the helical or screw-like projection
is provided around the projection
in a range &agr;1 of rotation of 360 degrees or more, i.e., groove
completely circumscribes projection
. Since projection
thus has a shape like a screw and if a compression load is applied vertically to projection
, the projection
is vertically compression-deformed like a coil spring, i.e., there is only a minimal amount of shear deformation.
A cushioning structure disclosed in Japanese Patent Laid-Open No. 197503/2000 that includes a shearing transformation element at a rear foot portion of a midsole. The shearing transformation element is shear-deformed at the time of landing in such a manner that it falls forward. However, since the element is deformed in such a manner that it falls, it is difficult to apply this concept under the ball of the foot.
SUMMARY OF THE INVENTION
An object of the invention is to improve a cushioning property due to shear deformation by providing a new structure of a shoe sole.
In order to achieve the object, according to a first aspect of the invention, a midsole is provided between an outer sole and an upper that is suitable for absorbing a shock of landing that includes a thick plate-shaped or column-shaped cushioning portion. A plurality of grooves are formed on an outer peripheral surface of the cushioning portion. The respective grooves are helically formed around a substantially vertical axial line. The respective grooves are arranged substantially parallel with each other. A range &agr; in which each of the grooves is formed is larger than about 15 degrees around the axial line and smaller than about 180 degrees around the axial line.
When compression load is applied to the cushioning portion in the vertical direction, a rotating force to twist the cushioning portion around the vertical axial line is applied to the cushioning portion. Thus, shear deformation along the horizontal plane perpendicular to the axial line is generated in the inside of the cushioning portion.
This shear deformation has a cushioning function (i.e. an absorption function of energy) much greater than normal compression deformation. In the case where the cushioning part is required to be thin, e.g., the ball of the foot, the cushioning function due to shear deformation is greater and more effective than the cushioning function created by compression thereon. Further, since this shear deformation is generated around the axial line, in the case where the cushioning part is provided at a thin place, it has the cushioning function greater than such shear deformation as causes deformation in a state of falling, and therefore, it is more effective.
In the invention, the “midsole” is provided between an outer sole and an upper and has the cushioning function. The whole midsole may be integrally formed, or may be constructed by assembling a plurality of parts. Besides, the cushioning portion may be integrally formed with a midsole body, or may be constructed by a part different from the midsole body.
In the invention, the term “helix” denotes a line formed by simultaneously and continuously carrying out both rotation of a point around one axial line and translation thereof along the axial line. The term “helical” means “helix-like”, that is, includes not only a case where the ratio of a rotation angle by the rotation to a movement amount by the translation is constant, but also a case where the ratio of the rotation angle to the movement amount is inconstant. Further, the “helical” includes a locus formed by simultaneously carrying out the parallel movement of the translation, which accompanies the rotation, along the axial line, and the movement in a radial direction with respect to the axial line.
In the invention, since the plurality of helical grooves is provided in the cushioning portion or the cushioning part, a helical protrusion or convex portion (bank) is generally formed between the grooves.
In the case where the point is not moved in the radial direction, the groove and the convex portion become such groove and convex portion as those of a helical gear. In the case where the point is moved in the radial direction, in addition to the parallel movement along the axial line, the groove and the convex portion become such groove and convex portion as those of a helical bevel gear or a spiral bevel gear.
In the invention, it is preferable that a lead angle
between the groove and the horizontal plane is set within the range of 35 degrees to 60 degrees. In the case where the lead angle &thgr; is set within the range as stated above, since the projection between the grooves is deformed in such a manner that it largely falls, the cushioning performance becomes high.
According to a second aspect of the invention, a midsole provided between an outer sole and an upper and being suitable for absorbing a shock of landing includes a midsole body and a cushioning part (component).
The midsole body includes a cavity. The cushioning part is fitted in the cavity. The cushioning part is formed of an elastomer. Young modulus of a member constituting the cushioning part is set to be a value smaller than Young modulus of a member constituting the midsole body. The cushioning part includes a through hole passing through the cushioning part from its upper surface to its lower surface, so that it is formed into a ring shape having an outer peripheral surface and an inner peripheral surface. A plurality of grooves is helically provided on the outer peripheral surface of the cushioning part, the grooves being arranged substantially parallel with each other. A plurality of grooves is helically provided on the inner peripheral surface of the part, the grooves being arranged
Zall Michael E.
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