Note: Descriptions are shown in the official language in which they were submitted.
CA 02419188 2003-02-17
~1-
COMPOSITE MA°fF'..RIA~ ~RTH~TIC INSERT. CONSTRUCTED
~° ~R ~' N~A~C~.'' D ~~~T~.~~.a A~D DU~A~yge~~°~
BACKGROCT1~ID OF THE INVEN~TODI
Field of the Invention
The present in~enti.on relates generally to orthotic
inserts for use in conjunction with various types of
footwear. More particularly, the present inventi~n relates
to an orthotic insert constructed of layers of fiberglass
and graphite fiber materials, with the graphite layers being
configured to provide enhanced control over the motions of
the foot, and the device further being particularly
configured to provide a long service life without cracking.
Dackc~round
a. Orthotic Devices
2~ Orthotic inserts are used in conjunction with various
types of footwear to enhance the functions of a pets~n's
foot. ~An orthotic insert can be eithex° soft or hard: a
hard insert is a substantially rigid. member, eiesirably
having a relatively thin vertical thickness dimension and
extending from the calcaneal area of the foot (the heel
portion) to at least the metatarsal head area of the foot
( i . a . , the "ball" of the foot ) . In general, the purpose of
the rigid orthotic (sometimes called a °'funct~.onal
orthotic") is to first position, and then control the
3~ movements of, the midtarsal and subtalar joints during the
gait cycle ~ahi.ch the body goes through in walking and
running, and possibly other weight bearing activities.
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b. The Gait Cycle
Before proceeding with a discussion of prior orthotic
devices and the problems which have been encountered with
the same, the "gait cycle" will be discussed here so as to
provide an improved understanding of the function of the
present invention. The discussion will include the
following: (i) the main components of the human leg and
foot, and how these function relative to one another;
(ii) the gait cycle which a person goes through in a normal
IO walking motion; and (iii) the intended function of a rigid
orthoti:c in optimizing the coordinated operation of the
person's foot arid leg throughout the gait cycle.
(i) The Main Components of the Human Leg
and Foot and How These Function Relative to
One Another
FIGS. I-3 show a typical human foot 10 and (in PIGS. 2-
3 ) the lower part i2 of the leg 14. The two lower bones of
the leg are the tibia If and the .fibula l8. Below the
tibia and fibula, there is the talas 20 (i.e. the "ankle
bone"). Positioned below and rearwardly of the taius 20 is
the calcaneus 22 (i.e, the °°heel hone"). Positioned
moderately below and forward of the talus 20 is the
navicular 24 and forward of the calcaneus is the cuboid 26.
Extending forwardly from the navicular are the three
cuneiform bones 28. Extending forwardly-.from the cuneiform
bones and the cuboid are the five metatarsals 30. Forwardly
of the metatarsals are the phalanges 32 which make up the
five toes 34.
The movement of the talus 20 relative to the tibia I6
and fibula 18 is such that it enables the entire foot to be
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-3-- ,
articulated upwardly and downwardly (in the motion of
raising or lowering the forward part of the foot}. However,
the talus is connected to the tibia and fibula in such a way
that when the entire leg is rotated about its vertical axis
(i.e. the axis extending the length of the leg), the
talus 20 rotates together withy the leg :14.
With regard to the relat~.onship of the talus to the
calcaneus, these two move relative to one another about what
is called the "subtalar joint" indicated at 36. The
I0 subtalar joint can be described generally as a hinge joint
about which the talus and calcaneus articulate relative to
one another. On average, the hinge axis extends upwardly
and forwardly at a slant angle of about 42° from the
horizontal, and also slants forwardly and inwardly at about
I5° from a straightforward direction. There is also a
midtarsal joint 38, and this will be discussed later.
To explain further the hinge motion of the subtalar
joint, reference is now made to FIGS. 4a and 4b. The talus
can be considered. as a vertical board 40, and the calcaneus
as a horizontally extending board 42, these being hinge
connected to one another along a diagonal hinge Sine 44,
with this hinge line corresponding to the subtalar joint 36.
It can be seen with reference to FIG. 4a that as the
talus is rotated inwardly about its vertical axis (i.e. the
front part of the leg is rotated toward the center of the
person's body), there is a corresponding rotation of the
calcaneus (i.e. the horizontal board.42) about a horizontal
axis. It can be seen in FIG. 4b that an opposite (i.e.
outward) rotation of the talus (i.e, the vertical board 40)
causes a corresponding rotation of the calcaneus (i.e. the
horizontal board 42) in the opposite direction to that shown
in FIG. 4a.
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With regard to the midtarsal joint 38, this is in
reality composed of two separate joints, the talo-navicular
and the calcaneal-cuboid. It is a complex joint, and n~
attempt will be made to illustrate or recreate its motion
accurately. Instead, a somewhat simplified explanation will
be presented as it relates to the present invention.
The main concern relative to the midtarsal joint is not
the precise relative motion of the parts of the foot which
make up this joint, but rather the locking and unlocking of
I0 the joint which occurs when there is an outward motion of
the leg and talus and an opposite inward motion,
respectively. When the leg is rotated inwardly, the
midtarsal joint 38 as in its unlocked position so ths;t the
portion of the foot 10 forwardly of the joint (i.e. the
f5 midfoot 45) is flexible, this being the ~°pronated" position
of the foot. ~n the other hand, when the leg and talus are
rotated outwardly, the foot is said to be ~supinated" and
the midtarsal joint is in its locked position and the
midfoot is essentially a part of a rigid lever. In
20 actuality, the midfoot never becomes completely rigid, so
that even in the totally supinated position, there is some
degree of flexibility in the midfoot.
This function of the midtarsal joint will now be
explained relative to FIGS. 5a and 5b. It can be seen that
25 FIGS. 5a-b are generally the same as FIGS. 4a-b, except that
a forward board member 46 is shown to represent the
midfoot 45, this member 46 having a downward taper in a
forward direction, and also a lower. horizontal plate
portion 48. This plate portion 48 is intended to represent
30 that the plantar surface (i.e. the lower support surface) of
the midfoot 45 engages the.underlying support surface in a
CA 02419188 2003-02-17
~T~a.
manner so as to remain generally horizontal to the support
surface.
It can be seen that when the two board members 40
and 42 are in the pronated position of F7LG. 5a, the
midtarsal joint represented at 50 in FIGS. 5a-b is in a
first position which will be presumed t~ be in unlocked
position. In the unlocked position of FIG. 5a, the
member 46 is not rigid with the horizontal member 42, and
the forward member 46 can flex upwardly relative to the
horizontal member 42. (This is the pronated position of the
foot I~.) However, in the position of F2G. 5b, the board
members 46 and 42 caill be presumed to be locked to one
' another so that the members 42 and 46 form a unitary lever.
For ease of illustration, no attempt has been made to
I5 illustrate physically the unlocking relationship of FIG. 5a
and the Locking relationship of FIG. 5b. Rather, the
illustrations of FIGS. 5a-b are to show the relative
movements and positions of these components, and the 1~cking
and unlocking mechanism is presumed t~ exist.
2~
(ii) The Gait Cycle inThich the Person Goes
Through in a I~Iormtal Walking I~totion
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_6_
the foot during the gait cycle, and this will be explained
in more detail below.
There is also the flexion and extension of the knee, as
illustrated in the five figures immediately below the graph
of FIG. 6a. Further, there is the flexion and extension of
the ankle joint. At the beginning of the gait cycle, the
heel of the forwardly positioned leg strikes the ground,
after which the forward part of the foot rotates downwardly
into ground engagement. After the leg continues through its
walking motion so as to extend rearwardly, the person pushes
off from the ball of the foot as the other leg comes into
ground engagement.
The motions described above are in large part apparent
.f.rom relatively casual observation. However, the motion
which is generally overlooked by those not familiar with the
gait cycle is the inward and outward rotation of the leg
about its lengthwise axis which must occur with the
pronating and supinating of the foot. This will be
described relative to FIG. 7a and FIG. 7b.
At initial ground contact the ieg ~a rotated moderately,
to the outside (i.e. the knee of the leg is at a more
outward position away form the center line of the body) so
that the foot is more toward the supinated position (i.e.
closer to the position shown in FIG. 4b)<, consequently, the
initial heel strike and loading of the foot takes place on
the lateral (i.e. outer) side of the heed., and the calcaneus
is normally inverted by approximately 2' at heel contact.
Immediately following heel strike and up to the 25$
position, the leg rotates about its vertical axis in ~.n
inward direction so that the subtalar joint pronates. This
pronation motion of the subtalar joint results in 4°6' of
aversion of the calcaneus, and ultimately this bane rests an
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average of 2-4° degrees averted to the vertical when the 25%
stance position is reached. The effect of this is to rotate
the heel of the foot so that the center of pressure moves
from a lateral heel location toward a location nearer the
center line of the foot, as indicated at 54 in FIG. °7b.
Also, the pronating of the subtalar joint produces a degree
of relaxation of the midtarsal joint 38 and subsequent
relaxation of the other stabilization mechanisms within the
arch of the foot. Furthermore, this inward. rotation of the
3.0 leg serves as a torque converter~ the internal rotation
takes the vertical force of the ieg at heel contact and
converts this into a frontal plane force which extends the
relaxed foot. From the foregoing, it will be understood
that shock absorption at heel contact is thus primarily a
I5 function of controlled pronation of the foot during the
first 25% of the stance phase.
With further movement from the 25% to the 75% position,
the leg rotates in an opposite direction (i.e. t~ the
outside), and the subtalar joint becomes supinated at the
20 ?5% position of FIG. 7a. This functionally locks the
midtarsal joint so that the person is then able to operate
his foot as a rigid lever so as to raise up onto the ball of
the foot and push off with this as the other leg moves into
ground contact.
25 With reference again to FIG. 7b, the initial pressure
point at ground contact is at 52, and moves medially across
the heel to the location at 54. Thereafter, the pressure
center moves rather quickly along broken line indicated
at 56 toward the ball of the foot. As the person pushes off
3~ o~ the ball ~~ the foot and to some extent from the toes,
the pressure moves to the location at 5~~ Accordingly, it
gill be appreciated that the pressure point or center shifts
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from. the lateral portion of the foot to the medial portion
in the course of the normal gait cycle.
(iii' The Intended Function of the Orthotic to
Improve ~peration of the Person°s Foot
and Leg Throughout the Gait Cycle
A primary function of most orthotic inserts is to
initially position the plantar surface of the calcaneus 22
and the midfoot 45 so that the subtalar and midtarsal
joints 3fi and 38 are positi~ned in the proper functional
relationship for the person's foot, and to thus control the
motion of the foot parts and the leg and hip throughout the
gait cycle. It will be understood that if the components of
i5 the foot have the proper initial pasition and movement about
the subtalar and midtarsal joints, the entire gait cycle,
all the way from the coordinated rotation of the hips
through the flexion and rotation of the leg, and also from
the initial heel strike to the final toe--off, will be
properly coordinated and balanced for~optimum movement.
The only practical way that a foot can be controlled in
this manner is by a three dimensional member which properly
conforms to the foot's plantar surface. The insoles of
mass-produced shoes, however, do not ordinarily conform to
the plantar surface of any particular foot so as to
optimally locate its components. Accordingly, it has been
the practice for many years to provide an orthotic insert
which engages both the shoe and the foot in a manner so as
to properly orientate the internal components of the latter.
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c. Deficiencies of Prior Orthotic Inserts
Orthotic inserts have been formed of many different
materials, including acrylic plastic, leather, metal, and
foam rubber, for example. One construction which has proven
extremely successful in recent years is a composite material
insert formed of fiberglass and graphite fiber in resin.
An exemplary orthotic insert having the latter
construction is disclosed in U.S. Pat. No. 4,439,934, the
inventor of which is the same as of the present invention.
The insert is fabricated by placing layers of fiberglass,
resin, and graphite fiber upon a positive cast. The first
layer is a continuous sheet constructed from a cloth such as
fiberglass or nylon mesh and impregnated with resin. The
second layer is a continuous sheet of graphite with the
woven graphite fibers prefernbly,running diagonally. The
next layer is also a glass and resin continuous sheet, and
then another graphite continuous sheet is added with the
woven graphite fibers running orthogoaalTy. Finally, there
is a bottom layer which may be a glass and resin continuous
sheet similar to the top layer. The assenebly_ is heat cured
to provide a bonded structure, and is triannted to the desired
size and shape by cutting and grinding.
Orthotic inserts having this construction are very
strong, yet extremely lightweight and relatively thin. In
practice, however, it has been found that they exhibit a
number of deficiencies. Firstly, devices of this type have
been prone to develop serious cracking with extended use.
The cracks usually develop along the medial and lateral
(i.e., side) edges of the insert and, once established,
quickly propagate and destroy the device. It has also been
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observed that the cracks sometimes occur In the toe or heel
areas and extend longitudinally into the structure.
As part of the present invent~_on, Applicant has
discovered the unexpected source of this problem. It has
keen found that the serious cracks initiate at the sites of
tiny, often microscopic "microcracks" which are formed along
the edges of the device during the cutting and grinding
phases of the manufacturing process; a goeat multiplicity of
these microcracks are formed all along the edges of the
device during final shaping and finishing. It has been
found that those along the side edges are the most likely to
enlarge, apparently due to the sagittal plane (i.e., end-to-
end) bending to which the device is subjected. as the person
walks. However, the cracks may also propagate
longitudinally in the heel and toe areas as a result of
frontal plane flexing or "cupping9' of the_ device~
As part of the present invention, Applicant has
discovered that the, severity of the, cracking problem which
is experienced by such composite material inserts stems
primarily from the fact that, once the cracks start an the
graphite fiber material, they propagatewith extreme speed.
Thus, even though the flexible fiberglass layers have been
found to be far more resistant to cracking, their integrity
is also destroyed once the associated graphite layer begins
to break.
Another deficiency of such prior devices is that they
have offered relatively little flexibility in terms of
allowing the rigidity or other characteristics of the .insert
to be adjusted to satisfy th.e requirements of a specific
~4 foot. At the time of their introduction, composite material
inserts having the construction described above represented
a significant advance in this respect. However, the
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-1I'
adjustments could only be made in the most general sense:
By varying the orientation of the graphite sheets so that
the fibers extended in various directions, the overall
rigidity of the structure (or possibly in certain
generalized areas) could be adjusted; also the rigidity of
certain areas could be increased by thickening the
structure, although this had the disadvantage of increasing
the thickness of the plate itself. In short, the
construction of the prior devices has offered little
I~ opportunity for "fine-tu~.ing" of rigidity/flexibility and
other control characteristics in specific areas where this
may be needed to satisfy the requirements of a particular
foot a
Accordingly, there has existed a need for a coanposite
I5 material orthotic constructed of layers of fiberglass and
graphite fiber material ~ihich minimizes or eliminates the
problem of cracks developing over a period~of extended use.
Moreover, there is a need for such a construction which
permits the rigidity and other contr~1 aspects of the i.a~sert
20 to be readily tailored to satisfy the spec~.fic needs of a
person-'s foot, and particuvariy for allowing this to be d~ne
without necessitating a substantial increase in the
thickness of the device. Mill further, there is a need for
such an improved orthotic which lends itself to being made
25 by a relatively quick, convenient, and economical method.
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SUMi~RY OF THE INVENTION
The present invention has solved the problems cited
above. Broadlyo this is a blank for an orthotic insert,
comprising a fiberglass/resin base lager having heel and
forefoot ends and medial and lateral edges, and at least one
graphite fiber/resin layer, the graphite fiber/resin layer
being configured t~ impart a first degree of rigidity to a
first portion of the blank, and a second degree of rigidity
1~ to a second portion of the blank. 'Phe fiberglass/resin
layer and graphite fiber/resin ~_ayer are bonded together to
form a unitary structure which is generally contoured to fit
a plantar surface of a person's foot, so that the first and
second portions of the b2ank having the first and second
Z5 degrees of rigidity support first and second portions of the
foot so as to provide control over the motions thereof.
Preferably, the graph~.te fiber/resin layer may comprise
a first graphite fiber/resin layer having a first
predetermined degree of rigidity which is bonded to the
2~ f~.herglass/resin base layer so as to be positioned beneath
the first portion of the foot, and a second graphite
fiber/resin layer having a second predetermined degree of
rigidity which is bonded to the base layer. so as to be
positioned beneath the second portion of the foot. The
25 first graphite fiber/resin layer may comprise a relatively
wide main reinforcement layer which extends through a
central portion of the fiberglass base layer so as to impart
the first degree of rigidity thereto. The second graphite
fiber/resin layer may comprise at least one relatively
30 narrow reinforcement strip which extends i.n a generally
longitudinal direction proximate to one of the edges of the
device so as to be positioned beneath an edge of the
CA 02419188 2003-02-17
-, ,
person°s foot. Preferably, the second graphite fiber/resin
layer may comprise first and second relatively narrow
reinforcement strips which are spaced apart across the
central portion of the base layer and extend proximate to
the medial and lateral edges of the base layer so as to be
positioned beneath the medial and lateral sides of the foot.
:Preferably, the first and second reinforcement strips are
positioned so as t~ extend beneath and generally parallel
to the first and the fifth rays of the foot.
1~ The main reinforcement layer which extends across the
central portion~of the base layer may have a slot opening at
~.ts rearward end. The slot opening surrounds a center of
the heel cup portion of the blank, so as to minimize the
thickness of the blank under the heel of the person ~ s f~ot,
and so as to enable rearward ends of the main reinforcement
layer to deform independently around the slot ~pening so as
to conform to the curvature of the heel cup.
Preferably, a selected edge portion of the
fiberglass/resin base layer extends outwardly beyond ara edge
portion of the graphite fiber/resin Iayer so as to form a
substantially graphite-fiber free fiberglass border, the
border having a w~.dth which is sufficient to prevent
microcracks which are formed along the outer edge thereof
from propagating into the graphite fiber,/resin layer~ There
may be first and second such borders, extending along the
medial and lateral edges of the base layer so as to prevent
the microcracks from propagating into the graphite
fiber/resin layer due to sagittal plane bending of the
blank. There may also be borders extending across the ends
of the base layer so as to prevent the microcracks from
propagating due to frontal plane bending of the device.
CA 02419188 2003-02-17
_1.4_
A method is .also provided for forming a blank for an
orthotic insert, which method comprises the steps of (i)
forming a fiberglass/resin base layer having heel and
forefoot ends and medial and lateral edges, ( ii ) forming at
least one graphite fiber/resin layer which is configured to
impart a first degree of rigidity to a first portion of the
blank and a second degree of rigidity to a second portion of
the blank, and (iii) bonding the fiberglass/resin layer and
the graphite fiber/resin layer together to form a unitary
structure which is generally contoured to fit a plantar
surface of a person~s foot, so. that the first and second
portions of the blank having the first and second degrees of
rigidity support first and second portions of the foot so
as to provide control over the motions thereof.
The method may include the. steps of positioning the
graphite fiber/resin layers on the, fiberglass resin base
layer so as .to form a layup assembly, positioning the layup
assembly in .contact with a first mold having a contour which
is generally similar to that of the plantar surface of a
persons foot, and heating the mo3.d and layup assembly so
that the layers deform t~ match the contour of the mold, and
so that the resin portions of 'the layers fl~w together and
unite so as to bond the layers together i:n a unitary
structure.
The method may further comprise the steps of continuing
heating of the first mold and layup assembly at a
predetermined temperature and for a predetermined period of
time which are sufficient for full curing of the resin
portions of the layers, and then cooling the layup assembly
so that the fully cured resins harden and the unitary
structure permanently retains a contour which matches that
of the first mold.
CA 02419188 2003-02-17
~15~
Alternatively, the method may further comprise the
steps of continuing heating of the first mold and layup
assembly at a predetermined temperature and for a
predetermined time which are sufficient for only partially
curing the resin portions of the layers, cooling the layup
assembly so that the partially cured resin portions harden
and the unitary structure temporarily retains a contour
which matches that of the first mold, comparing the 'unitary
structure having the partially cured resin portions to a
contour of a plantar surface of the person's foot, reshaping
the. unitary structure having the partially cured resin
portions to have a contour which. matches that of the
person's foot to which the structure has been compared,
heating the reshaped unitary structure at a predetermined
temperature and for a predetermined period of time which are
sufficient to achieve full curing of the resin portions, and
cooling the unitary structure so that the fully cured resin
portions harden and the unitary structure permanently
xetains a contour which matches that of the person's f~ot.
The step of comparing the unitary structure to the
contour of_ the plantar surface of the person's foot may
comprise placing the unitary_structure having the partially
cured resin portions in contact with. a second mold having a
contour which matches that of the person's foot. The step
of reshaping the unitary structure may then comprise heating
the unitary structure in contact with the second mold, so
that the heated unitary structure deforms to match the
contour of the second mold. The step of heating the
reshaped unitary structure may comprise continuing heating
of the structure in contact with the second mold at a
predetermined temperature and for a predetermined period of
CA 02419188 2003-02-17
-16~
time which are sufficient to achieve full curing of the
resin portions.
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~17~
BRIEF I3ESCRIPTIO1>T of THE DRAHIIIdGS
FIG. 1 is a top plan view of the slteletal structure of
a person's right foot, with certain components of the foot
being separated from one another for purposes of
illustrations
FIG. 2 is a side elevational view looking toward the
inside of a person's left foot, with the autl.ine of the foot
and lower leg being shown as a shaded area
i~ FIG. 3 is a view similar to FIG. 2, but looking towards
the outside of the person's foot~
FIGS. 4a and 4b are perspective views illustrating
schematically the rotational movements of the talus and
calcaneus of a person's right foot about the subtalar joint~
1~ FIGS. 5a and 5b are schematic views similar to those of
FIGS. 4a-b, but further illustrating the relative movement
between the calcaneus and the midfoat about the midtarsal
~~ant~
FIG. 6a is a graph illustrating the ratat~.ona3. movement
2~ of the pelvis, femur, and tibia during one-~ha~.f of a gait
cycle;
FIG. 6b is a tap plan view illustrating the r~tation of
the person's pelvis during that portion of the gait cycle
illustrated in FIG. 7a~
25 FIG. 7a is a graph similar to FIG. ~6a, but illustrating
the timing of the pronating and supinating ~notian of the leg
and foot through one-half of a gait cyele.;
FIG. 7b is a view toaking upwardly toward. the plantar
surface of a person's left foot, and illustrating the
30 location of the center of pressure throughout the portion of
the gait cycle which is illustrated in FIGS. fa and 7b~
CA 02419188 2003-02-17
a
FIGm ~ is an isometric view Of a composite material
blank for an orthotic insert in accordance with the present
invention, with the view being taken from a location looking
from the side and downwardly toward the bottom surface of
the blank in an inverted position~ -
FIG. 9 is an exploded view of the blank of FIG.
showing the fiberglass and graphite fiber Iayers which are
bonded together to form this structure~
FIG. 10 is a bottom plan view of the blank of FIG.
1~ illustrating the disposition of the fiberglass and graphite
layers relative to the calcaneus and medial and lateral rays
of the users foot~
FIG. I1 is an isometric view of the flat, unformed
layers of fiberglass and graphite fiber fabric arranged in
the desired configuration and disposed between convex and
concave molds for bonding together by heat cuffing;
FIG. 12 is a diagrammatical view of the graphite layers
which are incorporated in the blank of FIGS. ~-11,
indicating the various d~.rec~ions in which the graphite
2~ fibers may be oriented;
FIG. 13 is a atom plan view, similar t~ FIG. 1~,
showing a blank. for an orthotic insert in accordance with
the present invention, in which the graphite fiber layers
are recessed from the medial, lateral, and metatarsal edges
of the device so as to provide a protective fiberglass
border which prevents microcracks from propagating into the
graphite fiber layer~
FIG. 14 is a bottom plan view similar to FIG. 13,
showing an embodiment in which the graphite fiber layers are
3~ recessed from all edges of the device, so as to provide a
protective fiberglass border which ex.~tends continuously
around the ent~.re periaa~eter of the blank;
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-°19-
FIG. I5 is a bottom plan view similar to FIGS. 13-14,
showing an embodiment in which the graphite fiber Layer
extends annularly around the heel cup of the de~rice so as to
maximize the stiffness thereof for use in ski boots and
other specialized applications; and
FIG. 16 is an enlarged ~riew of the medial edge of the
device of FIG. 14, showing how the fiberglass border
prevents microcracks which are formed during the finishing
process from extending into the graphite fiber layers.
CA 02419188 2003-02-17
..2~~
DETAILED DESCRIPTION
a. Overview
Referring to the drawings in detail, wherein Like
reference numerals represent like parts throughout,
reference numeral 100 refers to a ragid, composite material
blank which is configured in the outline of the plantar
surface of a person°s foot. The blank 100 is shown in the
inverted position with its generaT.ly convex bottom
surface 102 positioned upwardly, and its generally concave
top surface (not shown) disposed downwardly; it will be
understood that, when in use, the concave tog surface of the
device will normally be disposed upwardly to receive the
bottom of the person's foot. It will also be understood
that the rigid blank 1Q0 will in many embodiments.serve as
the main structural member of an orthotic insert which
incorporates other elements in its construction, and in
particular may be covered with a layer of resilient
cushioning-material for the comfort of the wearer.
The blank 100 is an e5:ongate structure having a forward
edge 104 which is configured to lie proximate to the
metatarsal head area of 'the wearer's foot, and a rearward
edge 105 which generally surrounds a heel cup 106. Along its
sides, the device is bordered by medial and lateral
edges 108, 110.
The composite material blank 100 appears in FIG. 8. in
its fully assembled configuration, in which the graphite
fiber and fiberglass layers are permanently bonded together
to form a unitary structure. however, for the purpose of
describing the elements of this structure, reference is made
to the exploded view of FIG. 9. As can be seen, the primary
CA 02419188 2003-02-17
-21-
structural member or "foundation" of the assembly is
provided by a fibergiass/resin base layer lI2 which conforms
generally to the outline of the wearerDs foot and the
interior of the shoe. As was noted above, this fiberglass
layer is relatively soft and flexible. Moreover, in some
embodiments there may be both upper a,nd lower layers of
fiberglass/resin, so that the graphite material is fully
enclosed therein.
Strength, rigidity, and control characteristics, in
turn, are imparted by the graphite fiber/resin layers. As
can be seen in FIG. 9, the first of these is a' main
reinforcement layer I14. ~ The primary purpose of this member
is to impart a degree of strength and r~:gid~.ty to the blank
as a whole, while leaving enough flexibility to permit
further adjustment and "tuning" of the xigidity and control
characteristics by the additi~n of supplemental
strengthening members in specific. areas. For reasons which
will be discussed below, th.e medial and Lateral edges of the
reinforcement layer 11~ are r~cessed inwardly from the
medial and lateral edges of the fiberglass base layer 112,
and a ti-shaped cutout or slot 115 is provided in the region
of the heel cup.
In the embodiment which is ihlustrated, the main
reinforcement layer is supplemented by medial and lateral
graphite fiber reinforcement strips i16, 115, which serve to
provide additional rigidity and control under the medial and
lateral rays of the user's foot. Finally; medial and lateral
graphite fiber heel reinforcement strips 120 and 122 are
bonded over the rearward ends of the main reinforcement
strips, and serve to provide additional rigidity in the area
of the heel cup. As will be described in greater detail
below, one or more of these reinforcement strips may be
CA 02419188 2003-02-17
deleted, or additional strips may be added, as may be
desired for a particular application; moreover, the graphite
fiber/resin material and/~r the orientation of its fibers
may be selected in such a manner as to vary the rigidity of
each strip relative to the loading which. is imposed by the
user s foot .
The edges of the various graphite-fiber layers are
recessed inwardly from the boundaries of the fiberglass
foundation layer 112 so as to form "cleax-'~ fiberglass
1~ borders 124, 126 along the edges of the device. As will be
discussed below, this construction renders the edges of the
device relativdly soft and flexible,, enhancing wearer
comfort, and also prevents microcracks which are formed
during the finishing of the device from propagating into the
graphite fiber layers.
CA 02419188 2003-02-17
-23-
embodiment which is illustrated, the main reinforcement
layer is formed by a sheet of g~'aphite :Fiber material about
2 1/2" wide and about 6 1/2" long, both of these dimensions
being at least partly dependent on the size of the wearer~s
foot and hence the size of the finished device.
The slot 115 in the heel area of the reinforcement
layer extends around the center of the heel cup, as
indicated at 130. This feature provides the device with
several significant advantages: firstly, this creates do
area of somewhat increased flexibility beneath the
calcaneus, allowing a degree of controlled motion of the
heel in some embodiments, in the form of frontal plane
cupping of the device as the medial and lateral sides of the
heel cup flex inwardly and outwardly; secondly, since only
the fiberglass foundation layer is present beneath the
center of the heel cup, and the graphite fiber layer is not,
the thickness of the device is minimized in this area, which
enhances wearer comf~rt and makes it much easier to achieve
a proper fit in a conventional shoe~ thirdly, the cutout 115
enables the rearward ends 132, 13~ of the graphite-fiber
layer to bend toward one another independently as the heel
cup is formed, ,making proper iay-up and molding of the
device much easier. In the exemplary embodiment which is
illustrated, the slot 115 extends approximately 3/~" on
e~.ther side of the center of the heel cup and 1/2° forwardly
thereof .
The next graphite-fiber layer comprises the medial and
lateral graphite fiber reinforcement strips 116, 118. s
is shown~ these generally overlie the medial and lateral
3~ edges of the main reinforcement layer 114, although (as
indicated. by dotted line image 136) the two edges do not
necessarily line up exactly, depending on the construction
CA 02419188 2003-02-17
-24-
and control characteristics which are desired. Preferably,
the two reinforcement strips 116, lI8 are splayed slightly,
so that they converge toward the heel end and diverge toward
the toe end. Referring back to FIG. 1 and then to FIG. I~,
it will be seen that this serves to position the
reinforcement strips II6, 11~ so that they extend parallel
to and beneath the long axes of the first and fifth rays of
the foot, as indicated by dotted line images I4~, I42. This
provides additional support under these high-load are as the
person's foot goes through a normal gait cycle. Also, the
first and fifth rays have independent axes of motion (2-4
move as a unit) the use of separate reinforcement strigs
therefore means that these areas of the device can be
adjusted to be more rigid or more flexible as may be needed
by the two independent rays for an individual foot or
particular activity. For example, this is advantageous in
connection with certain athletic applications, such as in
devices for basketball shoes or ice skates. .In the
exemplary embodiment which is illustrated, strips
approximately 5/8" wide and about equal in length~to the
main reinforcement Dyer have been found to provide suitable
rigidity and control characteristics.
The rigidity provided by the individual reinforcement
strips can be varied in a number of ways:. For example, the
strip may be made up of one or more layers of graphite-fiber
material, and the material may be selected to have a
particular degree of strength or rigidity. Furthermore, as
will be discussed in greater detail below, the orientation
of the graphite fibers can be adjusted relative t~ the long
axis of the foot so as to vary their resistance to frontal
and/or sagittal plane bending.
CA 02419188 2003-02-17
_2~_
Toward the heel end of the device, the reinforcement
strips 116, 118 converge somewhat (extending rearwardly in
line with the rays of the foot , so that their rearward ends
flank the heel cup. The reduced span between the strips in
this area .imparts additional strength and rigidity to the
heel cup. For the reasons discussed above, control of heel
position during the gait cycle is criiaical to the proper
functioning of the foot, and this configuration makes it
possible to achieve the desired degree of control without
having to build up an excessively thick structure beneath
the calcaneus.
Finally, the medial and lateral heel reinforcement
strips 120, 122 overlie the rearward portions of the main
reinforcement strips 116, 118~ preferably extending in line
I5 with. the latter. The separate heel reinforcement strips
serve to provide still more strength and rigidity in the
area of the heel cup, and to further increase the degree of
adjustability or °'tuning" which - is a~ra~.lable to the
practitioner. As with the main reinforcement .trips lls,
118, strips 120, I22 can be varied in n er, thickness,
material, or orientation to provide whatever degree of
rigidity is desired on either side of the heel cup.
Moreover, the reinforcement strips 120, 122 extend from
adjacent the heel cup to forward ends which lie near the
26 arch area of the device, and by varying the strength of
these strips, rigidity in this portion of the device can be
ad3usted as well.
The combined width of the graphite--fiber reinforcement
strips is preferably significantly lest than the overall
width of the main reinforcement layer 114, so that the
strips extend down the edges of the device while a
relatively broad central section 138 remains free of
CA 02419188 2003-02-17
~26-
additional reinforcement. This has the advantage of
providing the greatest rigidity and reinforcement where it
is most needed (i.e., under the medial and lateral rays of
the foot and adjacent to the heel cup),. while leaving the
area down the center of the device with more strength than
would be provided by unreinforced fiberglass, but still
flexible enough to bend as necessary for control functions
and user comfort. For example, in the exemplary embodiment
which is illustrated, the reinforcement strips are about
3/4" wide, leaving a span about 1 - 1 3/0" wide down the
center of the device in which the only strengthening is
provided by the main graphite layer.
F3G. 10 also shows that the combined width of the
graphite-fiber layers is significantly less than the overall
I5 width of the fiberglass foundation layer 112, leaving the
°'clear" fiberglass borders 124, 126 along the medial and
lateral edges of the device. this configuration provides
the device with several important advantages. Firstly,
because the unreinforced fiberglass is much more flexible
2~ than that which is reinforced with the graphite~-fiber
material, the medial and lateral edges. of the inset are
rendered relatively "soft" w~.thout compromising the overall
strength of the device; Chas greatly enhances wearer
comfort, since the soft sedges will flex somewhat where they
25 engage the edges of the user's foot and the inner surfaces
of the shoe. Secondly, the "clear" borders 124, 126 prevent
microcracks which are formed during the finishing of the
insert from propagating into the graphite ffiber layers of
the device~ this aspect of the present invention will be
30 described in greater detail in Section ;d) below.
It will also be uaaderstood that the sequence of the
layers in the device may be modified in some embodiments
CA 02419188 2003-02-17
-2~-
from that which has been described above. For example, the
main graphite-fiber reinforcement strips may be placed on
top of the secondary heel reinforcement strips, or the
graphite-fiber layers may be positioned above and below the
fiberglass foundation layer. Also, the graphite-fiber
layers may be fully encased in an envelope or "sandwich"
between upper and lower fiberglass layers so as to provide
additional strength and/or crack protection.
c. Materials and Fabrication
FIG. 11 illustrates schematically t:he manner in which
the blank 100 is constructed from sheets 'of fiberglass and
graphite fiber material.
As can be seen, the flat, unformed ~.ayers and strips of
i5 material are layered on top of one another to form a
generally planar layup assembly 150. As originally
supplied, the resin in these layers is soft and uncured, so
that the materials are very soft and pliable. The
layers 112, 114, .116, 118, 120, and 122 can therefore be cut
from sheets of ;the appropriate materials and then . placed on
tip of on another to form an assembly 150 which will readily
deform when subjected to pressure.
Flexible, heat-curable .fiberglass/resin and graphite
fibes/resin sheet materials which are suitable for forming
the layup assembly 150 are known to those skilled in the
art, and include the following examples: Graphite Fiber
material -- Product No. TXX145--12-F185--14, available from
Hexel Corporation, 5794 W. Positas Hlvd., Pleasanton,
California, 94588-8781~ Fiberglass Material -- Product No.
7781-38-F185-11, available from Hexel Corporation,
Pleasanton, California. The resin portions of these
CA 02419188 2003-02-17
i2S_
products are provided by compatible, highly modified
epoxies.
Also, although fiberglass and graphite--fiber materials
of the types which have been described are generally
preferred on the basis of both performance and econom.~c
factors, it will be understood that the terms "fiberglass"
and "graphite-fiber" when used with reference to materials
herein are intended to include these and similar matrices
which may include reinforcement fibers formed of other
1~ materials in addition to or in place oi: the giass/graphite
fibers. For example, high-strength, high-~rigidity f~.ber
materials which may be used an additior.~ to or in place of
graphite fibers include I~evlar(available from E.I. Du
Pont de Nemours & Co., of Wilmington, DE), Nextel~'M
( available f rom Minnesota ~5ining & N~anufacturing Co . , of St .
Paul, MN), Spectra~'M (available from Allied-Signal, Inc., of
Morristown, N3), and similar organic and inorganic fiber
materials. Similarly, the term fiberglass is aneant to
include materials which are substantially free of graphite
fibers, but which may incorporate other, relatively flexible
and fracture-resistant fa.ber reinforcement ynaterials in
addition to or in place of glass fiber.
The rigidity of the aphite fiber reinforcements may
be ad3usted by employing graphite fiber materials of varying
thic~nesses, widths, and fiber qualitiesJdensities. Adding
(i.e., stacking) additional layers can also be employed to
increase rigidity. Still further, the rigidity can be
ad3usted by orienting the graphite layers s~ that the fibers
run in various directions, as is illustrated in 1~IG. 12. If
3~ the graphite layer is configured with the graphite fibers
running horizontally, as seen at 152, then the strip or
layer will tend to flex more readily about the axis parallel
CA 02419188 2003-02-17
~29-
to the fibers, line C. Similarly, the fibers can be
arranged in any direction to create a series of axes about
which the material will flex more read~.Iy, as seen at 154,
156, and 158 in F°IG. 12. Thus, the arrangement and
configuration of the fibers relative to themselves and
relative to the fiberglass layer or layers can determine the
amount and direction of the flexibiiity,irigidity of various
regions of the completed device.
To farm the blank, the pliable layup assembly I50 is
placed between molds 160, i62 and subjected to heat in a
vacuum, autoclave, or other pressure blanket. The convex
and concave molds 160, 162 may be positive and negative dies
corresponding to an individual user°s foot; if desired,
however, the molds may be of a more ~unxversal~ nature, for
forming standardized devices which are generally suitable
for feet within a predetermined range of sizes or shapes.
The molds themselves may be formed as positive molds, such
as plaster casts taken from the patient°s feet, or molds
r~hich are computer-generated and~or machined (a.g~, by means
of a CAD°CAIri process ) from icceasaarements or . other data.
Positive force, such as mechanical, electromechanical
or hydraulic pressure, is applied to press the layup
assembly into conformance with the <;onvex and concave
engagement surfaces i64, 166 of the two mold halves. The
heat, in turn, causes the molten resins in the layers to
intermingle and become permanently bonded together. As this
is done, the various strips and layers are pressed into one
another, ensuring that the thickness of the device is
minimized (ae compared with a structure in which the layers
are simply stacked up on top of one another), and providing
the smooth, continuous surface which is seen in FIG. 8.
CA 02419188 2003-02-17
Continued heating of the lay-up assembly under positive
pressure at a temperature and for a period of time which are
specified by the manufacturer of the materials, followed by
a period of cooling, results in the resins in the several
layers curing and forming a semi-rigid matrix. Thus
permanently bonded together, the graphite fiber and
fiberglass layers cooperate as a unit to provide a device
having relatively more rigad and more flexible areas, as has
been described above.
After curing the now rigid assembly is trimmed to
provide a device having the desired outline, as indicated by
dotted line image 3.6~ in FIG~ 11. As this is done, the
edges may be tapered or "feathered" somewhat by grinding, in
order to provide greater flexibility and a smooth transition
I5 where the device meets the foot and sides of the shoe.
I~lso, as was noted above, a soft, resilient top cover and/or
additional structural features such as a heel post may then
be m~unted to the rigid blank.
~1s a part of the present invention,, it has been found
that the above process cah be carried out successfully in at
least two separate phases, and at different locations, which
is highly advantageous in several respects. In particular,
it has been found that the assembled fiberglass and graphite
layers can be initially heat molded for a limited period
~5 which is significantly less than that which is required for
the resins to fully cure and harden. Thus, when the first
phase of the process is completed, the various layers will
be bonded together in the correct orieni~ation/relationship,
and the device will have a semi-permanent shape which
corresponds at least roughly to that of the patient's foot.
~1t the same time, the device will remain somewhat soft and
CA 02419188 2003-02-17
-31-
deformable (usually at a somewhat elevated temperature) so
as to permit subsequent re--~sh.aping.
Using the materials described above, an initial "set"
of approximately 80~ of full curing has been found highly
satisfactory, with a level of cure down to approximately 40~
having been found to yield satisfactory results (the level
of cure being expressed as the completed portion of the
chemical reaction by which. the resins in the
fiberglass/graphite fiber materials harden). The actual
time and temperature necessary to achieve a given level of
cure (e.g., 80~, 95~, etc.) are dependent upon a number of
factors, including the resin compositions of the materials
being used, the thickness of the layup assembly {which will
in turn. vary with the amount of force applied to the molds),
and so forth. For a particular type of layup assembly, the
combinati~n of time, temperature, and pressure necessary to
achieve the desired lev~3. of cure can be determined by
varying these factors for a series of test batches and then
submitting the resulting devices to chemical analysis
28 (usually by the manufacturer of the materials) t~ determine
the level of cure which each set of parameters produces.
Thus, the devices can Y~e produced at the factory where
access to bulk materials and mass-production techniques are
available, and can then be shipped in semi:-finished form to
podiatrists and other .health practitioners/foot orthotic
laboratories in the field. There, the initial shape of the
device assists the practition~r/technician in positioning it
relative to the patient's foot, with the strengthening
strips and other elements in the proper orientation. The
practitioner/technician can then re-shape the device based
on his observations and measurements made locally, for
example, by means of a cast which the practitioner has
CA 02419188 2003-02-17
taken. As part of the present invention it has been found
unexpectedly that the partially cured fiberiresin materials
described above will soften and become deformable again
when re-heated to an elevated temperature in the range in
which the curing reaction resumes. Thus, when placed in
contact with a east taken from the patient's font and
heated, the softened device deforms to match the contour of
the mold, and heating continues for a period of time
sufficient for the materials to become fully cured as is
.~
commonly understood in the industry, the tern "fully cured"
when used with respect to these materials normally refers t~
a level of cure in excess of approximately 90~, although
this may vary somewhat depending on the manufacturer's
specifications.
i5 After the fully cured device is cooled, the desired
contour (e. g., that of the final moldj will be permanently
retained. It will also be understood that, in some
embodiments, if the temperature at which the partially-cured
materials become plastic la sufficientgy low and/or
sufficient insulation is provided, final .shaping may taken
directly from the plantar surface ~f the person's foot,
rather than from a separate mold.
CA 02419188 2004-09-02
- 33 -
the device (sometimes referred to herein as "sagittal plane
bending") as the foot goes through the gait cycle.
However, borders may also be provided to protect against
cracking in the toe and/or heel ends of the device, being
that in some embodiments there will be a degree of side-to-
side flexing around the longitudinal axis of the orthotic
(sometimes referred to herein as "frontal plane bending")
as well.
FIGS. 13 and 14 show embodiments of the present
invention which are particularly configured to protect the
graphite fiber layers from such cracking in the end areas.
In particular, FIG. 13 shows a blank 170 having a clear
fiberglass border 172 Which extends across the forward end
of the device, as well as medial and lateral crack
prevention borders 174, 176. Similarly, in the embodiment
which is illustrated in FIG. 14, the blank 180 is provided
with both heel and toe end borders 182, 184, in addition to
the medial and lateral borders 186, 188, so that a
continuous crack-prevention border is formed around the
entire perimeter of the device. The borders are all of
sufficient width to prevent microcracks from extending into
the graphite fiber layers, although the actual width may
vary somewhat (as shown) depending on factors such as the
anticipated degree of stress and bending in a particular
area and the amount of flexibility desired.
FIG. 15 shows an embodiment of the present invention
which is generally similar to those illustrated in FIGS.
13-14, except that the blank 190 includes a main graphite-
fiber reinforcement layer 192 having a closed-perimeter,
generally circular or oval opening 194 in the center of the
heel cup area, in place of the open-ended slot 115 which
was described above. As a result, an annular band 196 of
graphite reinforcement material extends around the entire
lip of the heel cup, the
CA 02419188 2004-09-02
- 34 -
band preferably being substantially uniform in width,
rendering this structure very tough and rigid. This
configuration is particularly useful for orthotic devices
which are intended for use in ski boots and similar
footwear (e.g., skate boots) in Which the user's foot is
immobilized, in that the rigid structure very rapidly
transfers even the slightest rotation of the user's leg
into rotation of the device and boot; for example, this
provides the skier with superior edge control and other
enhanced control characteristics. Any flexing or "cupping"
of the device in this area is also eliminated by the rigid
structure, but this flexibility is unneeded in a ski boot
because, unlike the embodiments described above, there is
no gait cycle involved and hence no heel-strike shock to be
absorbed. The reinforcement layer 192 is also more
difficult to lay up than those which have an open-ended
slot at the heel, but this configuration is still easier to
work with than a graphite sheet with no opening at all, and
the thickness under the heel is also kept to a minimum.
FIG. 16 provides an enlarged view of the portions of
the crack-prevention border and associated graphite fiber
layers which are indicated in FIG. 14. As can be seen, a
multiplicity of microcracks 198 (often microscopic a.n size)
are formed along the edges of the device during the
trimming and grinding process. However, the protective
fiberglass border 186 is of sufficient width that none of
these extends into the main graphite fiber reinforcement
layer 114 or into the reinforcement strips 116, 118; for
example, borders approximately 1/8"-I/2" Wide along the
medial and lateral edges of the device have been found
sufficient, although significantly narrower or wider
borders may be used depending on the nature of the
materials, the stresses to
CA 02419188 2003-02-17
~35_.
which the device is to be subjected, and the degree of
flexibility which is desired. Since the microcracks will
not propagate and extend in the fiberglass material, the
borders effectively eliminate cracking of the device,
ensuring a greatly extended service life.
Having thus described the present invention in its
preferred embodiments, it should be understood that numerous
modifications and adaptations may be resorted to without
departing from the spirit thereof. l~ccordingly, the present
1~ invention is not to be limited except as by the appended
claims.
