Note: Descriptions are shown in the official language in which they were submitted.
20~704~
1.
FOOTWEAR SOLE
This invention relates to soles for footwear.
The invention provides means for regulating the
rotational movement, or twist, between the forefoot
and rearfoot portions of a sole whilst providing
longitudinal stiffness of the sole when an article
of footwear incorporating the sole is in use.
The invention is especially advantageous for
use in sports and casual footwear, for example training
shoes, running and other athletic shoes, racket and
field game shoes, and plimsolls, but may be useful
also in other types of footwear.
According to the present invention there is
provided a sole for footwear, wherein the sole
incorporates a cruciate tension member located
predominantly between the forefoot and rearfoot portions
of the sole, the general directions of the linear
elements of the cruciform being oblique in relation
to the longitudinal axis of the sole, and the position
at which the linear elements of the cruciform intersect
being substantially in the shank portion of the sole.
It is found that, by means of such a tension
member, it is possible to provide an advantageously
controlled restraining force on the twisting of the
sole which frequently tends to occur in use, especially
for sports and play usage, without detriment to the
desired longitudinal flexibility/stiffness of the sole.
The tension member cruciform typically is oriented
obliquely to the longitudinal axis of the sole, i e
it has a general 'x' configuration as opposed to a
'+' configuration in relation to the sole length.
It is essentially a single cruciform, i e it is not
part of a grid pattern of similar cruciforms.
The linear elements of the cruciform need not
be orthogonal at the cruciform intersect. Suitably
the intersection angles facing forwardly and rearwardly
are up to 90, preferably acute, and the laterally
facing angles are at least 90, preferably obtuse.
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2047~4
_ 2.
The elements need not be rectilinear; one or
both of the elements may have a degree of linear
curvature. They may have a curved or polygonal cross-
section. One or both of them may have a surface profile
pattern at least on the ground-facing side, for instance
a ribbed pattern longitudinally of the element.
The tension member preferably is located
substantially between the heel portion of the sole
and the forefoot flex area of the sole which corresponds
with a position just behind the joint of the metatarsus
with the phalanges of the foot of a wearer of an article
of footwear incorporating the sole.
The position at which the linear elements of
the tension member intersect typically may be in the
middle third of the width of the sole in the shank
portion.
The tension member should be attached to the
body of the sole at least at or near to the ends of
the cruciform.
The tension member may be of integral construction
or it may comprise two separate linear elements which
may or may not be connected together at their cruciform
intersect. Separate members may be preferred to allow
greater independence of effect.
The dimensions, shapes and compositions of the
tension member elements, which may be similar or
different, may be selected to optimise the torsional
stiffness and other properties of each element, for
instance creep resistance, flex-fatigue resistance,
load-bearing ability, weight and colour. The shapes
of the elements may be uniform or non-uniform.
In one preferred embodiment of the invention,
one of the linear intersecting elements has a different
tensile stiffness or elasticity to that of the other
element, thereby conferring a twist-restraining force
in one direction at the shank (arch) portion which
is different to that in the other direction.
Accordingly, preferably the element extending between
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3.
the rearward outside edge and the forward inside edge
of the sole is designed to provide a greater degree
of torsional stiffness or sole twist-restraint between
its ends than that of the other element.
At least one of the elements may extend to at
least one of the lateral edges of the sole, preferably
the outside edge, and may be continued in the sidewall
of the sole.
In one preferred embodiment, one of the elements
extends from the outside edge of the sole adjacent
to the heel portion towards the medial inside edge
of the sole behind the forefoot flex area and may extend
completely to the medial inside edge. The other element
may extend from a position near to the inside edge
of the sole adjacent to the heel portion towards the
medial outside edge of the sole behind the forefoot
flex area and may extend completely to the medial
outside edge.
The tension member may be incorporated only in
the outsole, or in both the outsole and midsole, or
only in the midsole, if desired in association with
an appropriate cut-away feature in the outsole through
which the member would be visible. The member elements
may be substantially uniplanar with the sole or at
least one of the elements may intersect the general
plane of the sole especially when the tension member
is incorporated at least partially in the midsole.
Preferably the tension member does not project
significantly outwardly of the surface plane of the
outsole since such projection could be uncomfortable
to the wearer.
The tension member may be produced simultaneously
during moulding of the sole. Alternatively, the tension
member or the elements thereof may be produced
separately and then attached into the sole, for instance
by bonding.
The main body of the outsole may be of a rubber
material normally employed for outsoles of sports shoes
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4.
and the like, for instance a material based on a blend
of synthetic and natural rubber.
When the tension member is formed as an integral
part of, and of the same material as, the shank portion
of the sole, especially the outsole, such as when the
tension member is formed during moulding of the sole,
the thickness of the shank portion area adjacent to
at least the central part of the member should be less
than the thickness of the tension member in order to
allow the member to exert its requisite effect.
Suitably this thinner area is embodied as a 'depressed
area', i e an area of the shank portion having a surface
level below that of a substantial part, usually a major
part, of the tension member. The peripheral shape
and dimensions of the depressed area may be various,
provided that they are sufficient to enable the tension
member to exert the required twist-restraining force.
The peripheral shape may be substantially polygonal
(e g quadrilateral) or curved (e g circular, elliptical
or undulated) or a combination thereof. The depth
of the area below the surface level of the tension
member may be uniform throughout the area or it may
vary, for instance the depth may lessen, i e taper,
towards at least part of the area perimeter. An example
of a suitable depth is about 4 to 5 millimetres, for
an adult's shoe sole of average size, at least
immediately adjacent to the tension member.
When the tension member elements are of different
material to that of the shank portion incorporating
the tension member, a depressed area may not be
necessary. Such tension member elements may be of
organic polymeric material. Examples of polymers which
may be employed for the elements are thermoplastic
polyester elastomers, for instance that available under
the trade name 'Hytrel', and thermoset plastics such
as aromatic polyamides, for instance that available
under the trade name 'Kevlar'. A blend of polymers
may be employed, for instance a blend of one of the
2~704~
5.
aforementioned polymers with a rubber which may be
a rubber employed in the main body of the sole. If
desired, at least one of the tension member elements
may comprise a coloured core of material having the
requisite torsional stiffness encased by a clear
plastics material. One example of a suitable casing
plastics material is that available under the trade
name 'Nucrel'.
The outsole may have surface features such as
studs, channels, ridges, etc, which frequently are
included to confer properties such as grip, wear
resistance, flexibility, appearance, etc.
The invention is illustrated, by way of example
only, in the accompanying drawings, Figures 1 to 3,
which are diagrammatic representations of a right-foot
sole.
Figure 1 shows a schematic plan view
representation of the linear elements ABC and DBE of
a cruciate tension member in accordance with the
invention, B being the cruciform intersect, inside
a footwear sole outline. In the representation, the
angles ABD and CBE are acute and the angles ABE and
CBD are obtuse. Preferably, the element ABC has a
torsional stiffness between its ends A and C which
is greater than the torsional stiffness between the
ends D and E of element DBE.
Figure 2 shows a bottom plan view of an embodiment
of a sole incorporating a cruciate tension member,
in accordance with the invention, and Figure 3 shows
a left-hand side view of the sole of Figure 2.
With reference to Figures 2 and 3, the sole
comprises an outsole of moulded rubber material
incorporating a cruciate tension member (1) consisting
of two linear elements (2,3) having a ribbed surface
pattern. One of the elements (2) is thicker than the
other element (3), to confer a greater tensile stiffness
on that element (2). Both elements extend completely
to the outside edge (4) of the sole and are shown to
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6.
terminate at corresponding patterns (5,6) in the sole
sidewall (Figure 3). The central major part of the
tension member (1) is surrounded by a depressed area
(7) having a perimeter (8). The depth of the surface
of the depressed area (7) below the surface level of
the tension member (1) is substantially uniform
throughout the area (7) and may be about 4 mm.
Either or both of the elements (2,3) may be
lengthened to terminate near to the inside edge (12)
of the sole, if desired.
The illustrated sole has forefoot flex bars
comprising grooves (9), positioned approximately just
behind the joint of the metatarsus with the phalanges
of the right foot of a wearer of footwear having the
sole. The illustrated sole also has other surface
profile patterned areas providing enhanced
wear-resistance (10) and grip (11). It will be
appreciated that the illustrated surface patterns are
shown merely by way of example and are not essential
to the invention.
