Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Modular insert system for shoe soles
Technical Field of the Invention
The present invention relates to soles for articles of footwear, in particular
footwear for
correcting, supporting or accommodating the gait of the wearer.
Background of the Invention
In addition to providing general support for the wearer's feet while walking
or running,
shoe soles can be manufactured such that the degree of support for the foot
differs
between different regions of the sole. Thus the material of the heel region,
for example,
which experiences the greatest impact forces, is often manufactured to provide
greatest
impact cushioning effect. The desired variation in support may be achieved for
example by
varying mechanical properties of the material of the sole, such as the shape,
thickness,
density, hardness and flexural characteristics. In this way, the sole may be
manufactured
so as to provide optimum support for the typical wearer's feet. Since gait
characteristics
vary significantly from person to person, footwear manufacturers design the
soles of their
products to cater for a broad range of gait types, based around a putative
norm. Soles
may also be configured to suit different types of use. For example, soles may
be
configured for sprinting, long-distance running, playing particular sports
such as golf or
tennis or cross-country skiing, or for casual wear. Running shoes require
different sole
configurations for different distances, and for different types of terrain.
The wearer is therefore obliged either to settle for a sole which will cover a
wide range of
uses, but will not be well configured for any of those uses, or he may
purchase different
footwear for different uses; different shoes for road-running and for cross-
country running,
for example, or different shoes for different distances.
Specialist soles are also available which are configured to accommodate or
correct
particular types of gait, such as over-pronation or supination. Shoes are also
available
with soles which are customised to a particular combination of gait-type, or
sport, or use. It
is possible to have soles customised for a particular person, or even for a
particular foot.
However, bespoke soles are expensive, and the present invention is concerned
primarily
with soles for footwear which can be manufactured and distributed in
significant numbers
as a commercial retail product.
Prior art
It has been suggested to provide a certain customizability of the support
provided to a
wearers foot by means of an orthotic insole, laid on top of the integral sole
of a shoe.
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Such insoles may incorporate regions of different support, which are arranged
to suit the
particular use or gait-type. The hardness of the regions may be customised by
exchanging
portions of the orthotic, for example. Such a customisable orthotic is known
from
EP2383952, in which a shaped piece of the orthotic can be exchanged for a
similarly-
shaped piece having a different hardness. The orthotic described in this
document thus
provides a limited customizability of the support which is provided by the
insole.
W02016092353, from the same inventors as the present invention, describes a
sole
customising system in which hard inserts are located in cavities in the
midsole. The
application does not address the problem of ensuring constant and accurate
sensory-
motoric stimulus (see below), but nevertheless proposes an arrangement which
could
potentially offer a solution in that the inserts can be inserted into the
cavities from the top,
so that the cavity bottoms are closed by the outsole.
EP1352579 describes a midsole comprising regions of different hardnesses, so
that the
midsole can be customised for a particular wearer. The assembled portions of
the midsole
may be formed into a continuous moulding, in which case the customised sole is
no
longer customisable. Alternatively, the assembled portions can remain as
discrete
components of the sole, in which case the mechanical integrity of the sole as
a whole is
greatly reduced.
DE20320091 describes an adaptable insert which affords a limited
customizability of the
support provided at a particular region of the sole. The insert is introduced
from the medial
side of the sole (ie left-hand side of a right shoe or right-hand side of a
left shoe) or the
lateral side of the sole (ie right-hand side of a right shoe or left-hand side
of a left shoe),
and is held in place using a clip. The insert also includes vertical hexagonal-
shaped holes
into which can be inserted hexagonal pegs of a particular hardness. In this
way, the
effective hardness of the insert can be varied by inserting pegs which are
harder than the
material of the insert, which gives the wearer some control over the degree of
support
provided at that particular region of the sole when the insert is located in
position. The
midsole is provided with a wide horizontal cavity, open to one side, into
which the insert
can be pushed. The presence of a wide cavity reduces the overall mechanical
integrity of
the sole, even with the insert in place, and provides a path for water and
dirt to enter the
sole, and to work their way deep within the sole. The presence of the midsole
material
above and below the cavity means that the effectiveness of the lateral insert
is reduced, in
that the amount of vertical support it provides is reduced, and the total
amount of vertical
support provided may the sole in the region of the insert can be less
accurately defined.
Over time, the material of the midsole above and below the cavity, and the
material of the
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insert element surrounding the pegs, will lose elasticity and resilience due
to the repeated
compression during the gait cycle. Such insert elements are typically
positioned in regions
of the sole where greater support is required, which means that the repeated
compression, and the consequent crushing of the insert material and the
midsole material
above and below the insert, will be particularly susceptible to degradation,
and thereby
shorten the wearable life of the shoe.
It is also important for gait-correcting insert elements to retain a constant
proprioceptive
effect and to remain secured in the sole. If an insert works loose, or becomes
plastically
compressed, or if it is contaminated by ingress of dirt or water, the
customised
proprioceptive pressure effect of the insert will be altered.
Brief Description of the Invention
The invention described in this application seeks to overcome at least some of
the above
and other disadvantages inherent in the prior art. In particular, the
invention aims to
provide a customisable article of footwear according to claim 1, a method
according to
claim 23 and a method according to claim 25. Further variants are defined in
the
dependent claims.
A support customising system is described below for the sole of a shoe or
other article of
footwear. The sole comprises a relatively soft, resilient midsole and
(optionally) a harder
outsole. Insert elements of various hardnesses are provided for inserting into
vertical
cavities in the midsole. By customising the hardnesses of different inserts in
different
vertical cavities, a precisely-tunable pronation control effect on the
wearer's gait can be
effected. First-order, second-order and third-order pronation control effects
are described.
The invention and its advantages will further be explained in the following
detailed
description, together with illustrations of example embodiments and
implementations
given in the accompanying drawings. Note that the drawings are intended merely
as
illustrations of embodiments of the invention, and are not to be construed as
limiting the
scope of the invention. Where the same reference numerals are used in
different
drawings, these reference numerals are intended to refer to the same or
corresponding
features. However, the use of different reference numerals should not in
itself be taken as
an indication of any particular difference between the referenced features. In
this
description the terms hardness and durometer are used interchangeably, and
numerical
hardness values refer to the Shore A hardness scale.
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Figure la shows in side view a schematic cross-section of an example shoe
employing a
support-customising system of proprioception-enhancing inserts.
Figure 1b shows in isometric view an example of support adjustment inserts for
use in the
support customising system of figure la.
Figure 2 shows a schematic plan view, viewed from below, of a first example
sole
employing a support customising system.
Figures 3 to 8 show cross-sectional schematic views of various example
geometries of
proprioception-enhancing inserts.
Figures 9 to 11 show cross-sectional views of various example arrangements of
proprioception-enhancing inserts in a sole.
Figures 12 and 13 show transverse cross-sectional views of two example
arrangements of
proprioception-enhancing inserts.
Figure 14 shows a longitudinal cross-sectional view of an example arrangement
of
proprioception-enhancing inserts.
Figure 15 shows a transverse cross-sectional view of an example of an insert-
retention
arrangement.
Figures 16 to 24 show cross-sectional views of example geometries of
proprioception-
enhancing inserts.
Figures 25 to 27 show cross-sectional views of example sealing and retention
arrangements of proprioception-enhancing inserts.
Detailed Description of the Invention
An example of a support customising system is illustrated in figures la and
1b. Figure la
depicts a schematic cross-section of a shoe with a sole 1 comprising an
outsole 4, a
midsole 3, bonded to the outsole 4, and a liner or insole 6 laid on the upper
surface 7 of
the midsole 3. The midsole 3 may be made of a resilient material, for example
an
elastomer such as ethyl vinyl acetate (EVA) or other suitable material. The
outsole 4 may
for example be constructed from a hard, resilient elastomeric material such as
rubber/polyurethane, and may have a hardness which is greater than that of the
midsole
3, at least at the ground-facing surface of the outsole 4. Alternatively, the
midsole 3 and
outsole 4 may comprise the same or similar materials, or may be contiguous,
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homogenous regions of the same moulded shape. The liner or insole 6 may be of
relatively thin and/or softer material and serves to provide a comfortable
surface for the
sole of the wearers foot. The liner or insole 6 may be removed to expose the
upper
surface 7 of the midsole 3.
The example sole 1 illustrated in figure la is provided with a plurality (six
are shown) of
vertical cavities 2, each of which opens out through the outsole 4 and extends
up towards
the upper surface 7 of the midsole 3 along a vertical axis 8. The midsole 3,
apart from the
holes (cavities 2) which are formed in it, may be constructed of continuous
material, in
order to ensure the mechanical integrity of the sole as a whole. The vertical
direction is
understood in this text to be the vertical direction when the shoe is standing
flat on level
ground. The vertical axis 8 is thus substantially orthogonal to the general
plane 9 of the
sole 1, which is taken to be generally parallel to the upper, foot-facing
surface 7 of the
midsole 3 and/or to the lower surface of the outsole 4, at least in the heel
and/or midfoot
regions 13, 14 of the sole 1. The sole 1 illustrated in figure la has parallel
upper and lower
surfaces for clarity. In practice, the heel area of the sole may be thicker
than the forefoot
area ('positive drop'), or vice versa ('negative drop'), and/or the mid-foot
zone may be
thicker than both the heel and forefoot regions, for example.
The terms lower and upper used in this description are also defined in terms
of the vertical
axis 8. Note that the term vertical is used in this text to denote a general
rather than a
precise orientation of the vertical cavities 2, and includes orientations
which differ by up to
15 degrees, or alternatively even up to 40 degrees from the vertical axis 8
shown in figure
la.
While only six cavities/inserts are shown in particular cross-section of
figure la, all in the
heel and mid-foot parts of the sole, it should be understood that the sole may
also
comprise similar cavities/inserts in forward regions of the sole.
Figure lb shows a set of inserts or plugs 5, also referred to in this
description as support
adjustment inserts or proprioception-enhancing inserts, which are designed for
insertion
into the cavities 2 in the midsole 3. In the example shown in figures la and
lb, the inserts
5 may be inserted into the cavities 2 through openings in the outsole 4.
Inserting the
inserts from below has the advantage that the insertion openings are more
readily
accessible than if they are inserted from above. However, as discussed below,
inserting
the inserts through the outsole 4 renders the inserts liable to damage by over-
compression (for example if the wearer steps on a stone) or by incursion of
dirt or water.
The inserts 5 may also be made of an elastomeric material, for example, and
they may
have different hardnesses from the midsole 3 and/or from one another. Some of
the
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inserts 5 may have substantially the same hardness as the material of the
midsole 3, in
order to provide a null support adjustment at a particular cavity 2. It is
also possible to
provide inserts 5 with lower hardnesses than the midsole 3; this may for
example be
useful for providing a negative support adjustment in a particular region of
the sole 1 by
reducing the average hardness of the region by inserting one or more inserts 5
which are
softer than the material of the surrounding midsole 3.
The hardnesses of the inserts 5 may be selected from a set of predetermined
hardnesses.
For example, a pair of shoes having soles such as that illustrated in figures
la may be
purchased with a set of inserts 5 similar to those shown in figure lb, with
multiple
alternative inserts of different hardnesses available for insertion into each
cavity, and with
each insert having one of a predetermined selection of hardnesses. There may
be more
inserts 5 in the set than there are cavities 2 in the sole 1. The midsole 3
may have a
hardness in the range 30 to 70 Shore, or 45 to 60 Shore, for example, and the
supplied
set of inserts 5 may include some inserts having a hardness of 50 Shore, some
of 60
Shore, some of 70 Shore, some of 80, 90 or even 100 Shore, for example.
Different
inserts 5 of different hardnesses may then be fitted into the cavities 2
provided, so as to
achieve the desired local support hardness at each cavity location and
collectively in each
region of the sole 1 provided with cavities 2. If the midsole has a first
durometer, then the
set of inserts from which inserts can be selected for insertion into the
cavities may include
inserts, each of which may have one of a predetermined plurality of
durometers. The
plurality of durometers may include durometers which differ from each other by
between 5
and 20 Shore, including a durometer which is greater than the first durometer
by between
5 and 40 Shore. As will be discussed below, the plurality of durometers may
include a
durometer which is the same as the first durometer and/or one or more
durometers which
are less than the first durometer. The first durometer of the midsole 3 may be
constant for
all regions of the midsole 3, or it may vary between regions of the midsole 3.
In the latter
case, the first durometer may either be taken to be an average durometer of
the midsole 3
or a local durometer of a particular region of the midsole 3.
When the wearer puts weight on the sole, for example while walking, the
inserts 5 which
are harder than the surrounding midsole material serve to transfer a force
from between
the ground and the wearers foot which is greater than that transferred by the
surrounding
midsole material. Each of these harder inserts thereby provides increased
support for the
wearers foot at the location in the sole at which it is inserted. Because the
inserts 5 each
have one of a predetermined set of hardnesses, at least in the vertical
direction, and
because they extend along substantially the whole vertical depth 11 of the
sole 1, or at
least substantially the whole depth 11 of the midsole 3, the net vertical
hardness of the
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sole 1 at the location of each cavity 2 is determined exclusively, or in a
great majority, by
the hardness of the particular insert 5. The hardness of the outsole 4, if it
is different from
the hardness of the insert 5, may also contribute an effect to the net
vertical hardness of
the sole 1 at that location, but the contribution may be small, particularly
if the outsole 4 is
thin and/or the hardness difference between the outsole 4 and the insert 5 is
small.
Similarly, the contribution of the insole 6 or any minor part of the midsole
which extends
above or below the insert 5 when the insert 5 is inserted, will also have only
a small effect
on the net vertical hardness of the sole 1 at the particular cavity. The term
net vertical
hardness is used here to indicate a measure of the compressibility and
resilience of the
sole in an approximately vertical direction (ie as measured along the vertical
axis 8).
The vertical cavities 2 and the inserts 5 shown in the example of figures la
and lb have
substantially parallel vertical side-walls. The cavities 2 may thus have a
horizontal cross-
section which is substantially constant along their length 11, for example, or
they may
have a tapering cross-section, any other shape which allows them to be fitted
into the
cavities 2 and/or subsequently removed for exchange. The horizontal cross-
section of the
cavities 2 and inserts 5 may be of any regular shape, such as circular, oval,
ovoid,
hexagonal, triangular, square or rectangular, or it may have have an irregular
shape. The
inserts 5 and cavities 2 are advantageously dimensioned such that it is
possible to fit two
or more cavities/inserts into a particular gait control region of the sole 1,
as will be
discussed below. In this respect the cavities and inserts 5 may be formed with
a horizontal
cross-section which has a largest transverse dimension of between 5mm and 50mm
across, for example, or preferably between 10mm and 30mm.
Because the inserts 5 are oriented substantially vertically in the midsole 3,
and because
they have relatively small lateral dimensions, multiple inserts 5 and cavities
2 can be
located in a particular region of the sole 1 in order to adjust the net
vertical hardness of
sole with a fine resolution. Thus, a pronation control zone in the forefoot
area 12 of the
sole 1 may incorporate multiple (eg three to ten inserts), for example, each
with a
hardness suitable for the pronation control requirement of the wearer. The
hardnesses of
the three to ten inserts 5 may be the same, or they may be graded. For
example, the
hardnesses of the inserts may be increased from the rear-most insert 5 to the
foremost
insert 5.
The discussion above has related primarily to the inserts 5 and cavities 2 of
a single shoe.
In a pair of shoes, the inserts 5 and cavities 2 may similarly be made so that
the same
inserts 5 can be used in the cavities 2 of either shoe. The support
customising system
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may be arranged such that, multiple pairs of shoes can share the same set of
support
adjustment inserts 5.
The use of multiple, interchangeable inserts 5 having different hardnesses
means that the
support provided by the sole 1 can be finely tuned to the needs of the wearer.
The support
may be differently tuned between the left shoe and right shoe, between
different regions
12, 13, 14 of one sole 1, or even within the same region of the sole 1.
Figure 2 shows a plan view of a shoe sole 1 similar to the sole 1 shown in
figure la, and
shows in more detail how the support adjustment inserts 5 can be arranged in
the midsole
3 to achieve a customised support, for example as an aid to gait correction
for the wearer.
Figure 2 shows the midsole 3 of a left shoe, viewed from below, but it will be
understood
that the following description applies equally to a corresponding right shoe,
although the
arrangement of inserts 5 may be different between the left and right shoes.
In the example configuration of figure 2, the sole 1 comprises a heel region
19, a heel
medial region 21, a heel lateral region 22, a forefoot lateral region 23, a
metatarsal region
24 and a forefoot medial region 25. These regions are merely examples ¨ other
regions
may be chosen. If there are multiple inserts 5 in each region, as shown, the
support
offered by the region as a whole can be adjusted precisely by including
individual inserts
having different durometers ¨ either to give an overall average hardness which
is
equivalent to an intermediate durometer value between the available values of
the
available inserts, or to give a graded support across the region.
Left and right feet naturally have slightly different pronation styles, due to
the natural
asymmetry in the person's posture and due to neurological effects which gives
rise to
asymmetries in gross motor control, reflected in the person's posture and
gait. However,
the characteristics of the landing portion 19 of the heel region should
preferably be the
same for left and right shoes.
Because the inserts 5 of a particular region, or of multiple regions of the
sole, may have
the same cross-sectional shape, the inserts 5 may be made interchangeable
between all
cavities 2 of a particular region or between all cavities 2 of the sole. In
this case many
different configurations of the support offered by the sole can be achieved
with a relatively
modest number of inserts 5.
Each insert 5 may be formed as a single contiguous piece of material, or it
may be formed
from two or more constituent pieces. It may be solid, for example to assure
its rigidity, or it
may be hollow, for example to cut down on shoe weight and material costs. It
may be
open at one or both ends, and it may have openings in its side wall(s).
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Also illustrated in figure 2 is an ideal gait line 20, also known as the
stability axis or "S-
tine", which indicates approximately how the wearers foot should pronate
during its heel-
to-toe contact (gait cycle) with the ground. The example regions 19, 21, 22,
23, 24 are
identified only approximately, and are used to illustrate how inserts 5 in the
various
regions can be used for controlling the wearer's gait.
The multiple cavities 2 may advantageously have the same size and shape, as
illustrated
in figure 2. The inserts 5 of a particular set, even if they have different
hardnesses, may
also have the same size and shape, so that multiple inserts 5 of different
hardnesses can
be interchangeably fitted into each cavity 2, and so that a particular insert
5 can be fitted
into multiple cavities 2. The hind-most heel part 19 of the midsole 3 in
figure 2 is shown
without any inserts 5 in this example. There may be instances when it may be
useful to be
able to adjust the hardness of this hind-most region 19, but the illustrated
example is
designed to show how the support adjustment inserts 5 can be used for
pronation/supination control, and the hindmost region 19 of the midsole 3
serves primarily
to cushion and control the landing impact of the heel on the ground and the
initial forward
motion of the foot.
Medial and lateral control regions 21 and 22 can be used to control the amount
of
pronation during the initial phase of the gait cycle (ie following initial
heel impact). By
judicious choice of the hardnesses of the inserts 51 of the medial region 21
and the
hardnesses of the inserts 51 and 52 of the medial 21 and lateral 22 control
regions, it is
possible to influence the degree of pronation of the foot around the stability
"S-line" 20.
Furthermore, the use of inserts 5 of graded hardnesses in a particular region
permits a
second-order control, in which not only the amount of pronation can be
controlled, but also
the rate of change of pronation with respect to the forward motion of the foot
during the
sole's contact with the ground when walking or running. Taking the six medial
control
inserts 51 illustrated in figure 2 as an example, a first-order pronation
control can be
obtained by selecting the hardness of the three inserts 52 relative to the
hardness of
midsole 3 and/or of the medial control inserts 51. Harder lateral inserts 52
will encourage
greater pronation, softer lateral inserts 52 will promote pronation less.
However, by varying
the difference between the durometers of the lateral inserts 52, it is
possible to achieve a
second-order control effect. If the hardness difference between inserts along
the heel to
toe direction is large, for example (ie the rear-most lateral insert 52 is
much harder than
the forward-most lateral insert 52, then the rate of pronation with respect to
the foot's
forward motion is greater. This means that the pronation occurs during a
shorter time,
when considered as proportion of the total contact time with the ground. On
the other
hand, if the hardness of the inserts 52 varies little along the heel to toe
direction, then the
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pronation-enhancing effect with respect to the foot's forward motion will be
less. If the
foremost lateral insert 52 is harder than the rear-most insert 52, then this
will act to reduce
the rate of pronation.
The lateral and medial inserts 51 and 52 can further be used to achieve a
third-order
control effect, in that inserts can be selected to vary the rate of pronation.
If the lateral
control region 22 is provided with more cavities and inserts 52, (say five
inserts in a line
running parallel to the heel-toe axis, for example), then the hardnesses of
the five lateral
inserts 52 can be chosen so as to vary the rate pronation along the heel-to
axis. Thus, by
being able to select the hardnesses of the lateral inserts 52 it is possible
not only to vary
the amount of pronation (first-order effect), but also to vary the rate at
which pronation
occurs (second order effect) and the axial variation in the rate of pronation
(third-order
effect).
By using many cavities/inserts, it is possible to vary the
pronation/supination control with a
fine resolution, and in many different ways. For example, it is possible to
take set the
hardness of the inserts 5 to take account of individual bones or bone groups
in the foot.
Excessive calcaneal/talar tilt can be compensated for, for example, while
minimising the
effect on the metatarsal or forefoot regions.
The control effects described above in relation to the interchangeable inserts
52 of the
lateral region 22 also apply to the other illustrated regions in figure 2; the
medial control
region 21 with its multiple medial control inserts 51, and the forefoot
control regions 23 and
25, with their forefoot control inserts 53 and 55. A single mid-foot control
insert 54 is
illustrated in midfoot control region 24, which may be included in the midfoot
/metatarsal
region to discourage the wearer's arch from sinking. The sole 1 may comprise
such a
single midfoot insert 24 on its own or in combination with one or more other
inserts, as
shown in figure 2, for example.
As a consequence of such finely-adjustable and adaptable gait control, it is
possible to
improve the wearer's gait and straighten the wearer's axial skeleton, which
not only has
beneficial effects for the wearer, but also promotes even wear on the outsoles
4 and
therefore extends the life of the shoes.
Furthermore, if the individual inserts are replaceable, then the soles can be
"tuned" for
different uses, or for different wearers, or as the shoes age, or as the
wearer's gait
changes.
The following examples illustrate the insert hardnesses which could be chosen
for
different gait control purposes. The examples are based on a sole
configuration similar to
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that shown in figure 2, and the hardnesses given are relative to an example
midsole
material of hardness 50 Shore. Where different inserts hardnesses are listed
for a
particular region, these are listed on the order from rear-most to foremost).
Example 1: for correcting a slight supination
Lateral control region 22: 50 Shore, 60 Shore, 60 Shore
Medial control region 21: all 50 Shore or less
Forefoot lateral control region 23: all 60 Shore
Example 2: for correcting a delayed overpronation
Lateral control region 22: all 50 Shore (no correction)
Medial control region 21: 50, 60, 70, 80, 80, 60 Shore
Forefoot lateral control region 23: all 60 Shore
Example 3: for correcting severe general overpronation
Lateral control region 22: 50, 50, 60 Shore
Medial control region 21: 70, 80, 90, 80, 70, 60 Shore
Forefoot lateral control region 23: all 60 Shore
Example 4: for correcting early, slight overpronation
Lateral control region 22: 50, 50, 60 Shore
Medial control region 21: 70, 60, 50, 50, 50, 50 Shore
Forefoot lateral control region 23: 70, 60, 50, 50, 50 Shore
Example 5: for correcting delayed, slight overpronation
Lateral control region 22: all 50 Shore (no correction)
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Medial control region 21: 50, 50, 60, 60, 70, 70 Shore
Forefoot lateral control region 23: all 50 Shore (no correction)
The sole of figure 2 also shows how a stiffening plate 10 may optionally be
included to
maintain longitudinal and torsional stiffness of the part of the sole under
the arch of the
wearer's foot. The presence of such a plate can improve the stability of the
wearer's foot
with respect to the ground surface, and may increase the life of the shoe
sole. The plate
is also visible in figures 12 to 14.
Figures 3 to 8 illustrate various example arrangements for the cavities 2 and
inserts 5, as
mentioned above. In figure 3, the cavity 2 comprises an opening in the upper
surface 7 of
10 the midsole 3, and is closed at its lower end by outsole 4. In figure 4,
the cavity 2 is shown
with an opening above and below. Figures 5 to 8 show arrangements in which the
cavity 2
is closed at its upper end by a minority portion (eg 10% ¨ 20%) of the
thickness of the
material of the midsole 3. The inserts 5 may be secured in the cavities 2 by
any suitable
means. If an insert is intended to remain in its cavity permanently, then it
may be glued or
bonded or welded in place in the cavity 2. The insert 5 may even be supplied
as a liquid
which can be introduced into the cavity 2 and which then sets with a
predetermined
hardness. Figures 5 and 6 show the cavity with and without the insert 5
inserted. The
insert of this example comprises a body portion 5, which may have a hardness
selected to
give the desired proprioceptive stimulus pressure to the foot at that
location, and an
outsole portion 5', which may comprise a similar material to that of the
outsole 4.
Alternatively, the insert may be of a single heterogenous piece of material.
The lower portion 5' (eg the outsole portion) of the insert 5 may
advantageously be wider
than the body portion which fits into the cavity 2. This has the following
advantages which
help to maintain a constant proprioceptive stimulus pressure provided by the
insert 5 at
the location. Firstly, the broader outer part 5' abuts the lower surface 15 of
the midsole
element 3. This prevents the insert from being over-compressed and receding
into the
cavity. It also distributes the load on the insert more evenly, thereby
ensuring a constant
proprioceptive stimulus effect from the insert as a whole on the wearer's foot
at that
location. Secondly, the broader outer part 5' covers the region where the
sidewall of the
insert body is in contact with the sidewall of the cavity. If sand, grit, dust
or water is
allowed to penetrate this region, which may happen in the arrangement of
figures 5 and 6,
for example, the accumulated matter may cause a hardening effect which will
alter the
proprioceptive pressure at the location and/or erode the material of the
midsole 3 or the
insert 5, such that the insert may work loose and drop out.
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Figure 8 shows an example variant in which the insert 5 extends downward
beyond the
outsole 4, thereby increasing the proprioceptive pressure effect at the
location. This is
made possible, with a reduced risk of the insert being pushed up into the
cavity, by the
shoulder which abuts the lower surface 15 of the midsole 3 as described above.
Figures 9 to 11 show variants in which an optional plate 16 is included over
all or some of
the inserts 5 in order to delocalise the pressure which occurs between the
foot and the
individual inserts 5. The plate 16 may be hard enough and flexible enough to
distribute the
pressure without influencing the proprioceptive or sensory-motoric effect of
graded or
varied hardnesses of the inserts. The plate 16 may optionally cover the whole
foot-contact
area of the sole or even the whole area of the sole. The plate 16 may
optionally be
recessed into the upper surface 7 of the midsole 3 as shown. The inserts 5 of
figure 9 are
shown flush with the lower surface of the outsole 4. The inserts 5 of figure
10 extend
slightly (1mm to 5mm) proud of the lower surface of the outsole 4, and the
inserts 5 of
figure 11 are profiled and extend further, thereby further increasing the
localised
proprioceptive stimulus pressure at the location.
Figures 12 to 14 show variants in which the cavities and inserts are angled
slightly from
the vertical, in a transverse direction as in figure 13 and/or in a
longitudinal direction as in
figure 14. The vertical axes 8, 81, 82, 8' of one or more cavities may be
angled slightly
outwardly or inwardly in order to enhance the effect of the choice of insert
hardness. The
cavities of the forefoot region may be angled forwards from the vertical in
order to
increase an acceleration effect at the end of the gait ground contact cycle,
thereby
enhancing a rolling or rocking in the gait of the wearer. With this
configuration it is thus
possible to perform a pronation control as discussed above, in addition to
enhancing a
rolling gait of the wearer. The tilt angles mentioned here are preferably less
than 30
degrees, or more preferably less than 15 degrees.
Figure 15 shows an example of an insert retention arrangement. The inserts may
be
retained in the midsole 3 by gluing, bonding, welding, or by form-fit,
compression fit or
other mechanical fitting. Advantageously, the inserts may be glued in position
using an
adhesive which allows the insert to be released (for example by application of
heat) and
replaced. Alternatively, or in addition to the gluing, bonding etc, a
retention element such
as a peg or pin 17 may be inserted, for example transversely, as shown in
figure 15, to
secure the insert 5 in position so that it cannot fall out or work its way out
of its cavity 2.
Inserts 5 may be made so that they can be inserted into the midsole 3 by hand,
for
example. Figures 16 to 27 show various configurations in which the lower
(outsole) part 5'
of the insert extends laterally outward of the insert body 5. The outsole 4 is
provided with
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an opening shaped and dimensioned to accommodate the corresponding lower part
5' of
the insert.
Figure 16 shows a simple insert geometry in which the lower part 5' is flush
with the upper
and lower surfaces of the outsole 4.
Figure 17 shows an arrangement in which the upper surface of the lower part 5
is flush
with the upper surface of the outsole 4, and the lower surface of the lower
part 5' extends
proud of the lower surface of the outsole 4. As with any of the arrangements
described,
the lower surface of the lower part 5' of the insert may be provided with a
texture or tread
for improved grip.
Figure 18 shows an arrangement in which the shoulder formed by the upper
surface of the
lower part 5' abuts a corresponding shoulder formed in the sidewall of the
opening in the
outsole 4. In this example, the lower part 5' also extends proud of the
outsole 4.
Figure 19 shows an arrangement in which the lower part 5' abuts the outer
surface of the
outsole 4.
Figure 20 shows how the side surfaces of the lower part 5' of the insert may
have other
profile shapes such as the angled surface shown.
Figure 21 shows an arrangement in which the lower part 5' of the insert has
two
shoulders; a first, upper one which may be similar to the abutment arrangement
of figure
16 or 17, for example, and a second, lower shoulder similar to the abutment
arrangement
of figure 19. Two or more shoulders may be advantageous in that they provide
more
protection against dirt or water ingress. They also provide more surface area
for bonding
the insert's lower part 5' to the outsole 4 and/or the midsole 3.
Figure 22 shows how the upper part of the insert body 5 may be provided with a
cavity 12
which may help to retain the insert in the cavity by vacuum suction. When
vertical
pressure is exerted on the insert, compressing it slightly, air may be
expelled from the
cavity 12. When the pressure is release, the surfaces around the cavity may be
drawn
together by the resulting pressure differential so as to create a gas-tight
seal which
prevents air from re-entering the cavity 12. The cavity 12 may be deeper than
illustrated.
The hardness of the insert material may be increased so as to maintain the
propriocepive
(sensory motoric) stimulus effect with the reduced volume of solid insert
material.
Figure 23 shows a two-shoulder arrangement similar to that of figure 21, in
which the
lower should is adapted to accommodate bending movement of the outsole 4 by
being
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15
sufficiently elastic and/or sufficiently well bonded to the outsole 4 that the
lower should
forms a reliable permanent seal against the ingress of dirt or water.
Figure 24 shows how the insert may be shaped to be retained in the cavity by
mechanical
fitting. In the example shown, the middle part of the insert body may be
slightly wider than
the opening through which the insert is inserted, thereby preventing the
insert from falling
out or riding out of the cavity.
The inserts 5 may be provided with a positive-fit engagements, which may
engage with
corresponding recesses in the cavity wall, for example. The protrusions may
alternatively
be arranged in the cavity and the recesses on the insert. Figures 24 to 27
show illustrate
various further examples of how the inserts may be retained in the cavities by
such
positive fit or other mechanical interference. Such retention arrangements may
be used
alone or in combination.
Figure 25 shows an example in which the insert is retained in the cavity by
one or more
latch-rings or !aching or stepped protrusions 26, 27 in the body and/or
outsole part of the
insert 5.
Figure 26 shows an example in which the insert and cavity engage by means of a
thread
28, whereby the insert can be screwed into the cavity. A slot 29 or other
engagement
profile may be provided for ease of turning the insert.
Figure 27 shows how a form fit insert retention may be implemented by angled
or tapered
surfaces 30. In this case it may be advantageous to provide a special tool
configured to
compress the lower part 5' of the insert during insertion, so that it will
pass more easily
through opening of the outsole 4.
The inserts may extend up to 5 mm or more proud of the lower surface 15 of the
outsole
4, for example, thereby enhancing a sensomotoric (proprioceptive) loading-
response of
the wearer, in which the foot alters its orientation and movement in response
to localised
pressure from the inserts and thereby influences the gait of the wearer.
In the above examples, the inserts 5 have been shown inserted from below into
cavities 2
which extend vertically to a point below the upper surface 7 of the midsole 3.
The inserts
and cavities may alternatively be configured to extend right to the upper
surface 7 of the
midsole 3 or even to protrude above the upper surface 7 so as to create a
further
enhanced proprioception (sensory-motoric) stimulus in the sole of the wearer's
foot.
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