Note: Descriptions are shown in the official language in which they were submitted.
WO94/~5177 PCT/US93/08560
212249~
INTELLIqENT FOOT APPLIANCE
Related ApPlications
A patent application entitled "Method and Apparatus for
Evaluating a Load Bearing surface Such As a Seat", filed for
Clifford M. Gross on April 18, 1990, bearing Ser. No.
07/510,6~3l now U.S. 5,060,174 and assigned to the assignee
hereof, contains subject matter related to the subject matter
of the present application.
A patent application entitled "Feedback System for Load
Bearing 5urface",~ filed for Clifford M. Gross et al on
Decembe~ 6, 1990, bearing Ser. No. 07/623,220, and assigned to
~the~a~slgnee hereof,~contains;subject matter related to the
subject matter of ~he~present application.
The abo~e-identified related patent and patent
application are incorporated herein ~y reference.
Field of_the Invention~
The~present Invention relates to foot appliances such as
sne~kers, running~shoes and ski boots. In particular, the
present invention relates to a foot appliance incorporating an
electronic feedback~system for changing the shape of the foot
appliance to maintain~a desired level of support and/or
comfort for the foot of a user.
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SVBSTITUTE SHEEr
WO94/05177 PCT/US93/08560
212~492
Backqround of_the Invention
A foo~ appliance comprises a sole and side walls attached
to the sole. Generally, laces or a strap or some other
mechanism is provided for securing the side walls together.
The sole and side walls of a foot appliance deflne a load
bearing surface for supporting the foot of the user including
in some cases the ankle of the user. As used herein, the term
foot appliance includes but is not limited to sneakers,
running shoes, ski boots and orthopedic appliances for helpi~g
those with orthopedic problems or handicaps, walk or perform
other functlons.
In different circumstances, the nature of the support to
be provided by a particular foot appliance varies. Generally,
:::
shoes such as sneakers, running shoes, or ski boots are
oommercially a~ailable in a limited number of discrete sizes.
Howe~er, the feet of individuals have an infinite ~ariety of
~izes~and shapes. Accordingly, it is desirable for the shape
and~support of the load bearing surface defined by a shoe to
be automatically configurable to provide an optimum level of
upport and comfort for~an individual In other words, it is
desirabl~e for the foot appliance to include a mechanism for
automatically configuring the shape of its load bearing
surfa~e so that the load exerted on the load bearing surface
i3 distributed to achieve a desired level of comfort and
support for the individual user.
Furthermore, the physical dimensions of a foot and the
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amount of support required by a foot change over time in
response to ambient conditions and activity level and type.
For example, the ambient temperature of a skiing surface and
the temperature of the foot of a skier change moment by moment
while a person is skiing. The physical~properties of the
materials of which a ski boot is made (e.g., thë~resin of the
outer shell and foam plastic of the inner boot) also change.
Thus, the support provided by the ski boot changes over time.
In such a circumstance, it would be highly desirable if the ,
:: :
load bearing surface defined by the sole and side walls of a
skl~boot could~sens~e the changes in load distribution and
automatically reconfigure itself to provide a desired level of
support and/or c~mfort for the foot of the user.
Similarly, a human~foot changes in size during the course
of~a~day. It~ is~usually the smallest size in the morning and
tends~;to~expand toward~the night. It is desirable for the
load bearlng surface of a foot appliance to automatically
adjùstito the changes in~foot size of a user to maintain a
deslred level of~comfort~and support.~
In~other acti~ities~it is also desirable to have a foot
appliance~which automatically reconfigures itself. In
connection with athletic;~activities, such as tennis,
basketball, or running,;it is helpfuI if the foot appliance
worn by the athlete gives full support to the foot and ankle
to avoid sprain~ and~subluxations when vigorous movement is
undertaken by the athlete. However, when the athlete is
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SUBSTITUTE S~EET
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212~492
resting, it is undesirable to have the foot, in~luding the
ankle, subjected to substantial pressure (compressional
ischemia) as this may inhibit circulation (venous return) or
the like during the rest periods. Accordingly, it is
desirable to provide the athlete with a foot appliance which
senses the different distributions of load exer~ed during
different kinds of activity (i.e., vigorous movement and rest)
and automatically adjusts the load bearing surface to maintain
a desired level of support or comfort.
Many handicapped persons with conditions such as cerebral
palsy wear special foot appliances such as braces to provide
the handicapped person with sufficient support to engage in
certain common physical activities such as walking. It would
be hi3hly desirable to provide such handicapped persons with a
:
foot appliance which can sense the current distribution of
load exerted on the load bearing surface of the foot appliance
and which can reconfigure the load bearing surface in response
to the current load distribution to maintain a desired amount
of support or comfort.~
In short, there are a wide variety of circumstances in
which it would be desirable to utilize a foot appliance
includi~g a sensor apparatus for sensing the current
distribution of load exerted by the foot of the user on the
load bearing surface of the foot appliance, and an electronic
~ystem responsive to the sensor apparatus for adjusting the
load bearing surface to achieve a desired level of comfort.
SU8STlTlJTE S~g~ET
` WO 94/OS177 2 1 2 2~ PCT/US93/~8~60
. .
It is an object of the present invention to provide such a
foot appliance to improve fit and minimize discomfort and
injury potential.
The above-identified U.S. Patent 5,060,174 describes a
system for measuring the load or pressure distribution exerted
on a load bearing surface such as a seat or be'd';' The system
of this patent comprises a two or three dimensional array of
pressure sensors located within the load bearing surface and a
processor for processing the data generated by the pressure .
sensors. Using the data generated by the pressure sensors,
the processor evaluates certain attributes of the pressure
distribution on the load bearing surface. For example, it is
possible to divide the~load bearing surface into a plurality
of reg~ions to determine the fraction of the total exerted load
on each~region, the mean and median pressures of the various
regions, and the pressure gradients between regions.
The U.S. Patent~ 5,060,174 discloses that it is possible
to~statistically correlate subjective comfort sensations of
the~user with certain~attributes of the~objectively measured
pressure;~distribution~exerted on the load bearing surface by
the'~user.~ In the~exàmple~disclosed in U.S. Patent 5,060,174 a
seat~pan is divided into~eight regions, left thigh, right
thigh, left buttock, right ~uttock, two left~bolstexs and two
right bolsters. Similarly, a seat back may be divided into
eight regions: left bolster, right bolster, three lumbar
,
~ regions and three thoracic regions. It is possible to
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."~ ...~
statistically correlate the fraction of the total load which
is exerted on each of these regions with a user's comfort. In
this manner, it is possible to determine for each seat region
a desired range ~or the fraction of the total load which is
exerted on a region. A seat may then be objectively
classified as comfortable for a user if the actual
distribution of the load exerted by the user on a seat is such
that the fraction of total load in each region falls into the
corresponding desired range.
Qther attributes of the objectively measurable pressure
distribution may also be statistically correlated with
comfort. For example, small pressure gradients correlate with
high comfort levels and large pressure gradients correlate
with low comfort levels.
The U.S. Patent 5,060,174 also discloses that a
.
quantitative comfort level of a user of a load bearing surface
can~be evaluated as a function of attributes of the
objectively measurable~pressure distribution.
In the above-identified U.S. Patent application Ser. No.
.
07/623,220, an electronic feedback system for a load bearing; ; surface such as a eat or bed iQ disclosed. The feedback
ys~tem includes an array of sensors for outputting data
indicative of the actual pressure distribution pattern. A
processor receives this data and determines from this data the
actual comfort level of user supported by the seat or bed
using the techniques described in U.S. Patent 5,060,174. If
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the actual comfort level is not a predetermined desired
comfort level, a reconfiguration system is activated. The
reconfiguration system changes the shape of the load bearing
surface and, thus, changes the actual pressure distribution on
the load bearing surface until the actùal comfort level
reaches a desired comfort level. Illustratively, the
reconfiguration system comprises one or more air bladders
located within the load bearing surface and a valve system
controlled by the processor for adding or removing air from
the air bladders. By adjusting the amount of air in the air
bladders, it is possible to adjust the shape of the load
bearing sùrface.
It is an object of the present invention to provide a
foot appliance with this kind of electronic feedback system to
maintain a desired level~of support and comfort for a foot of
a user under a variety of ~different conditions. This foot
appliance will improve the biomechanics of the foot through
the minimization of stréss risers, hysteresis and creep during
norma:~ and abnormal foot~ground loading patterns.
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SummarY of the Invention
In accordance with;a preferred embodiment of the present
invention, a foot appliance comprises a sole and side walls
' attached to the sole. The sole and side walls form a load
-.
bearing surface for the f oot of a user .
A plurality of air bladders are located within the load
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2 1 2 2 4 9 ~ r~ ~
bearing surface.
An electronic feedback system is provided for adjusting
the load bearing surface by controlling the amount of air in
the air bladders.
The electronic closed loop feedback system comprises a
pressure sensor apparatus for generating data indicating an
actual distribution~of load (or pressure) exerted by the foot
on the load bearing surface. An electronic processor receives
the actual load distribution data and determines if the actu~l
: : :
ioad distribution is a desired load distribution. For
example, to determine if an actual load distribution is a
desired load distribution, an actual comfort level may be
calculated as a function of attributes of the actual load
distribution. The actual comfort level may then be compared
wi;th a~range of comfort~levels predetermined to be desirable.
Additionally, through the use of artificial intelligence
ncorporating, f~or~example, fuzzy logic, the optional
comfort/support level~ can be determined in real-time. If the
actual`load distribution is not a desired or target load
distribution, a valve ~apparatus is activated by the electronic
processor to change~`the amount of air contained in the air
bladders. This changes the shape and mechanical
characteristics of the load bearing surface and thus changes
the actual distribution of load. A pump supplies air to the
air bladders via the~ valve apparatus. In a preferred
e~bodiment of the in~ention, the pump is loca~ed in the sole
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SUBSTITUTE SHEElr
WOg4/~177 PCT/US93/08560
2122~2
of the foot appliance and is activated by Yunning or walking
activity.
Brief Descri~tion of the Drawinq
FIGs lA, lB, lC, and lD illustrate a foot appliance with
air bladders in accordance with the present i~vëntion.
FIG 2 illustrates a feedback system for use in the foot
appliance of FIG 1.
FIG 3 is a flowchart of an algorithm carried out by a
processor in the feedback system of FIG 2.
FI~ 4 illustrates a pump for supplying air to the air
bladder of FIGs lA, IB, lC, and lD.
~:
etailed Description of_tke Invention
FIG lA schematically illustrates a foot appliance 10 in
~, ,
accordance with the invention. The foot appliance 10
~; comprises a sole 12 and side walls 14. The interior surfaces
of 13 and 15 of the sole and side walls ~shown in phantom)
: ~ :
form: a~loàd bearing surface for a foot of a user. A fastening
deYice in~the form of strap 16 is provided to hold the side
walls ~ogether although~other fastening means would accomplish
this, i.e., laces. ~
A plurality of air ~ladders are located within the load
bearing curface of the foot`appliance. These air bladders are
illustrated schematically in FIGs lB, lC and lD. FIG lB is an
ankle cross-section of the side walls 14 taken along the line
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A-A' of FIG lA. In FIG lB, the side walls 14 are shown as
having an exterior surface 17 and the interior surface 15. ~
pair of air bladders 19, 20 is located in between the exterior
and interior surfaces of the side walls. FIG lC is a cross-
section of the side walls along the line B-B' of FIG lA. The
side walls 14 are again shown as ha~ing the exterior surface
17 and the interior surface 15. Inbetween the exterior and
interior surfaces are a plurality of air bladders 21, 22, 23,
24, 25, 26. As shown in FIG lB and lC a sensor array 102 is~
located underneath the interior surface 15 of the side walls
14. This sensor array is discussed below. FIG lD il~ustrates
a cross-section of the sole 12 along the line C-C' of FIG lA.
Below the inner surface 13 of the sole 12 is located a
plurality of air bladders 31, 32, 33, 34, 35, 36, and a pump
40.: The pump 40 is located in the heel portion 19 of the
sole. As is described in greater detail below, the purpose of
:he~pump 40 is to supply air to the air bladders 19-20, 21-26,
~ : ,
: 31-3~6. A portion of the sensor array 102 is also located just
undex tbe interior:surface 13 of the sole 12 of the foot
appl~iance.
A feedback æystem:for adjusting the amount of air in ~he
~ :
air bladders is incorporated into the oot appliance 10 of FIG
lA. The closed loop feedback system continuously or
discretely adjusts the amount of air in the air bladders to
control the shape of the load bearing surface 13, 15 to
provide a desired amount of comfort or support for the foot of
SUBSTITI ITE SI~EE;T
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the-user.
The feedback sy~tem 100 is illustrated in greater detail
in FIG 2. The feedback syctem 100 includes the pressure
sensor array 102. As indicated above, the pressure sensors
102 are located just underneath tne load bearing surface 13,
15 (see FIGs lA, lB, lC). Illustrati~ely, each of the
pressure sensors is a Force Sensing Resistor a~ailable from
Interlink Electronics, Santa Barbara, California. These
devices are flexible polymer thick fllm devices which exhibit
a decreasing resistance when an increasing force is applied
normal to the device surface. The sensors are arranged in
s~rips and connected to form a voltage divider network. The
load~bearing surface~13,15 may be divided~into a plurality of
regions. Assoclated with each region is a subset of the
pressure~sensors 102.~ In some embodiments of the invention,
d~f~ferent'~regions may overlap so that some~of the sensors
bel;ong to more than~one region.
;The~feedback~ system;also includes a multiplexer 104, an
interface 106, an~analog digital converter 107, and a
mlcroproce~60r~108.~ Thé multiplexer~104~connects a signal
'from~any;one~of the'pre6sure sensors~102~to~the interface 106.
The~equence in~ which~the pressure sensors are integrated is
transmitted from the microprocessor 108 to the interface 106.
Anal~g signals, generated by the pressure sensors and
~ , , . :
; tran6mitted via the~multiplexer 104, are converted to digital
form ~y.the analog-to-digital converter 107;. The digital
SUBSTITUTE SI~EET
WO94/~5177 2 1 ~ 2 ~ 9 2 PCT/US93/0856~
signals are then transmitted to the microprocessor 108-which
stores these signals in a memory.
The circuitry in the feedback system 100 is powered by a
battery or solar cell 112. The microprocessor 108 optionally
outputs two indicator signals. If battery operated, when the
battery needs to be changed, a first indicator'signal
activates a first light emitting diode 113. When the feedback
system 100 is operating, a second indicator signal activates a
`~ second light emitting diode 114. Returning briefly to FIG 1~,
the circuit elements 104, 106, 107, 108 are located in the
strap 16 as is the batter~y 112. The indicator diodes 113, 114
are located on the strap 16.
; The feedback system lO0 of FIG 2, also comprises a
:
plurality o~ val~es 12~0.~ The ~alves 120 are acti~ated by
eléctronic control~slgnals transmitted via the lines 109 from
the microprocessor 108.~; The~al~es 120 control the flow of
air~into or~out of the;air bladders 19, 20, 21, 22, 23, 24,
25~ 26,~ 31, 32, 33,~34,~35, 36.~ For purposes of clarity, only
,
three~;air bladders 19,~20, 21 are shown in FIG 2 and only
;three~corresponding valveæ 120 are illustrated.~ Howe~er, it
s ~ ld~be~understood that~in an actual~implementation there is
one~val~e 120 for each air bladder. Preferably, the valves
~ 12~0 occupy one of three~states: a first blocking state in
i~ which no air enters;or leaves the corresponding~air bladder, a
;second state in which air leaves the corresponding air
bladder, and a third state in which air is supplied to the
12
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.
corresponding air bladder. In an alternative embodiment of
the invention, there may be separate inlet and outlet valves
associated with each bladder, the inlet and outlet ~alves
being controlled by the microprocessor. In another
alternative embodiment, the bladders may be perforated to
allow for controlled steady leakage.
To supply air to the bladders 19, 20, 21, etc., the pump
40 is utilized. Illustratively, the pump 40 is located in the
heel portion 19 of the sole 12 (see FIG lA) and is activated
by running or walking activity. The operation of the pump 40
is discussed in greater detail below.
The feedback system 120 operates as follows. When there
is a load in the form of a foot on the load bearing surface
13, 15, the processor 108 receives from the array of pressure
: :,
sensors 102~data representative of the actual distribution of
pressure on the load bearing surface. This data is proces~ed
by the processor 108. In response to this data, the processor
108~outputs signals~on the lines 109 to control the valves 120
and~thereby control the amount of air in each of the bladders
.
s~ 2a,; 21, etc. In this manner, the proce~sor 108 controls
the~shape of the load bearing surface 13,15. In particular,
the processor 108 controls the shape of the load bearing
surface 12 to achieve a desired level of comfort and support
for the user.
An algorithm utilized by the processor 108 of FIG 2 to
control the shape of a load bearing surface is illustrated by
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r~t~
the flow chart of FIG 3. As shown in FIG 3, the first step of
the load bearing surface shape-changing process is to
interrogate the pressure sensors 102 (box 70 of FIG 3) to
obtain data representative of the actual distribution of
pressure exerted by a foot on the load bearing surface.
Because the shape reconfiguration mechanism o~eràtes
continuously, this data is time averaged (box 72 of FIG 3) to
a~oid changing the shape of the load bearing surface for each
small movement or other change of the user's foot or each
small change of the amblent conditions. Rather, the shape of
the load~bearing surface is preferably changed only in
response to larger, longer term or more~substantive movements
of the user's foot or larger longer term changes of the
ambient; conditions. ~
The processor 108 determines the~fraction of total load
exerted~on ach of~a plurality of regions of the load bearing
sùrface (box 74 of FIG 3~). The processor then determines if
thè~f~raction of~total;load exerted on each region is within a
des'~red~range (box~76~of~FIG 4). If the fraction of the total
load~;in each~region iæ~within the desired range no action is
taken.~If the fraction~of total load in~each region i~ not
within~the desired;range,~a linear programming algorithm tbox
78~of FIG 3) or other~optimization strategy is executed to
determine how to change the shape of the load ~earing surface
, .
with the fewest number~of ~djustments so that the fraction of
total load exerted on each region is within the desired range.
Once this is done, selected ones of the valves 120 are
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~ activated to change the shape of the load bearing surface.
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.,
Because a feedback system is utilized, after the shape of the
load bearing surface is changed, the pressure sensors are
again interrogated to determine if the fraction of total load
in each region is in the desired range and to determine if
further changes in shape are necessary to refine the load
bearing surface characteristic. ~ ~
It should be noted that the desired range of load
fraction for each reglon is determined experimentally by using
~ conventional statistical techniques to correlate the comfo~t
; ~ and support of a statistically valid sample of users with the
fraction of total load~exerted on each region by these users.
The linear programming algorithm utilized by the
processor 40 of FIG~2~to determine how t~ change the shape and
characteris~ic of the load bearing surface is as follows.
; An objective ~function:
: N
(W,) (Xi-Ai) (Bi-Xij
i9 maximized subject to the following constraints
Xl = 10 0
Xl ~ Ai~ >
Xi c B
where~
Xi = the fract~ion of total load exerted on region i,
for i = 1 to N
A4 --lower limit of region i load fraction range of a
~'"very comfortable and supportive" foot appliance
;~B, = upper limit of region i load fraction range of a
'ivery comfortable and supportive" foot appliance
Wi = priority~i.e. weighting) factor for region i
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Illustratively, the foot appliance is divided into N=16
regions.
Instead of using the foregoing algorithm, the processor
100 may evaluate a more complex algorithm. For example, an
actual comfort level of a user's foot may be set equal to a
linear combination of a variety of attributes of the actual
pressure distribution such as the standard deviation of the
pressure distribution in particular regions, pressure
gradients within or between particular regions, mean gradien~s
n particular regions, maximum gradients in particular
regions, median pressure in particular regions, fractions of
total load in particular regions and sums of l~ad fractions
over several regions.~ When a linear combination of such
attributes of the actual pressure distribution is sbtained so
as~to obtain~an ~actual comfort level of a user, the processor
comparès the actual comfort level to a desired comfort level
range.~ If the actual~comfort level i8 outside the desired
range,~the shape of the load bearing surface is altered until
the~actual comfort level is within the desired range.
The~pump 40 (~ee~FIG lA and FIG 2)~;is now discussed in
greater~detail. ~As shown in FIG 4, the pump 40 is formed as a
;chamber having upper;~and lower flexible side walls 42 and 44.
The~pump 40 has an inlet valve 46 and an outlet valve 48. A
.
,~ bent metal~spring 49 biases the chamber in its expanded volume
configuration. Alternatively,~the spring may be omitted and
the chamber filled by a resilient-open cell foam material to
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bias the chamber in its expanded volume configuration. When
the user steps down on the pump 40, the outlet valve 48 opens,
the inlet valve 46 closes and air is transmitted out of the
pump chamber. When the user's foot is raised and pressure
eased from the pump chamber, the resilient spring member 49
expands the pump chamber. In this case, air is arawn in
through the inlet valve 46 while the outlet valve 48 is
closed. Thus, as indicated above, the pump 40 is activated by
walking, running or other activity which causes the foot of ~
the user to step down on the pump chamber. This kind of pump
is~highly advantageous because its operation does not require
a motor and it does not require any source of electric or
other power. A pump of this type is disclosed in U.S. Patent
4,999,932, the contents of which are incorporated herein by
reference.
Returning~to FIG 2,~air is thus transmitted to the valves
120~via the ~alve 48 of the pump 40 and the air line 127.
Be~cause~the pump 40;is activated any time the user's foot
s;teps down on the sole~of the foot appliance, the situation
may arise wherein~air ic~transmitted out of the pump 40 and
none~of the~valves 120~leading to an air bladder are open.
For this~reason the air line 127 includes an additional valve
121-~which i9 controlled by the microprocessor 108. The
additional valve 121 is~open when all the valves 120 are~
closed or when some~of the valves 120 are open but not all of
the air emitted by the pump 40 is required by the air
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bladders. In these cases, the valve 120 transmits this excess
air ba k to the atmosphere.
In an alternative embodiment, a pump powered by a small
motor may be used to supply air to the bladders. Such a pump
and motor may be contained in a small pack which may, for
example, be mounted on the back heel portion of--the side walls
of the shoe or other foot appliance. This embodiment may be
especially useful in the case where the foot appliance is a
ski boot as ski boots are generally large and heavy enough to
support such a pack without discomfort to the user. Such a
pack containing a pump and motor is disclosed in U.S. Patent
4,583,305, the contents of which are incorporated herein by
reference.
In short a feedback system for use in connection with
footwear has been disclosed. The feedback system controls the
shape of the load bearing interior surface of the foo~wear to
provide support and/or comfort for the u~er depending on the
size and shape of the individual user's foot and the
activities the user is undertaking. The feedback syste~
sense8 the actual distribution of load exerted by the foot on
the load~bearing surface and automatically, electronically
changes the shape of the load bearing surface (e.g., by
ch~nging the amount of air in air bladders contained within
the load bearing surface) to change the actual distri~ution o~
load until a desired distribution of load is realized.
Finally, the above-described embodiments of the invention
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- 2122492
are intended to be illustrative only. Numerous alternative
embodiments may be devised by those skilled in the art without
departing from the scope of the following claims.
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