Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3L~7020~
This invention relates to a bandage material for
forming in place an orthopedic cast.
Orthopedic structures find wide use in the im-
mobilization of limbs in aiding the healing process. In the
maintenance of fixation of fractured bones, immobilization `
of inflamed or injured joints, in cases of disease or trauma
`~ and for the support and immobilization of ligamentous and
muscular structures in instances of sprains and strains, it
is necessary to encase the limb in a partially or completely
surrounding rigid form or cast. The immobilized limb may be
encased in such rigid structure for long periods of time,
frequently as much as 6 weeks or more~
There are t~o major considerations for a cast.
The first consideration concerns the formation of the
cast. A satisfactory cast material should be easily handleable, ~ ~`
should not have properties which deleteriously affect the
limb, particularly the skin~, should have a reasonable
setting time or work life, so as to allow a reasonable
period of time in which to mold the cast material about
the limb, should be flexible during application of the limb ;~i
so as to readily assume the shape of the limb, should be
free of offe~sive`or noxious solvents or othar chemical~,
and should set within a reIatively short time under rel-
atively mild conditions. In addition, it is desirable that
a minimum of equipment should be involved in formation of
the cast. Also it is desirable that during the forming of
the cast the mat~rial does not generate an uncomfortable `~
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exothermic reaction, and that upon drying, curing or setting ~ ~;
up it has negligible shrinkage factor. ;`
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The second consideration concsrns the properties
of the cast after it is formed. Desirably, the cast should
b~ of a light weight ma~erial so as to minimize the in-
convenience to the wearer, porous so as to allow the under-
lying skin to breathe and not become macerated or otherwise
irritated, should have sufficient structural strength so as
to retain its structure under normal usage, should ~e
sufficiently sturdy to maintain the joint or limb in the
immobilized position and protect the joint or limb from
jars, and should be easily removable. An optimum cast
should also be water-proof, (i.e., the impregnated fabric
material itself should not absorb and retain water), be
as x-ray transparent as possible, be highly impact a~d
abrasion resistant, and should exhibit a versatility to be
reformed, and repaired after the initial cast is formed in
place.
Because of the numerous and varied requirements
for an orthopedic ~ast material, none of the presently known
immediately available cast materials provide all or sub-
stantially all of the proper~ies indicated above.
In the prior art, U.S. Patent No. 3,692,023 issued
September l9j 1972, to Phillips et al describes the use of
polycaprolactone as a cast material employing permeable or
porous base webs impregnated with a polymer. U.S. Patents
Nos. 3,592,190 issued July 13, 1971, to Silverman, 2,301,426
is~ued July 13, 1971, to Silverman, 2,616,418 issued November
4, 1962, to Eberle, 3,420r231 issued January 7, 1969, to
Edenbaumr 3149t444 issued January 20, 1970, to Laaksor
3r592rl90 issued July 13, 1971, to Silvermanr 3,604,413
issued September 14, 1971, to Burg et al. also illustrates
various aspects of the prior art.
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he invention provides a bandage or wrapping of an
~' orthopedic cast comprising a large mesh flexible fabric
carrier (e.g., large mesh cotton knit~ impregnated with a ;
polycaprolactone polymer (or other resin having substan-
tially the same or equivalent property and behavioral
characteristics as hereinafter more fully identified) to
provide a relatively thick coating of the polymer while
, retaining substantially large openings in the mesh. The
resulting coated fabric is semi-flexible, capable of being
~'~ 10 wound into a cylindrical package, and upon heating above the ~'
softening point of the polymer softens to a highly flexible ,
, or pliable and readily moldable web. The web is readily
K:,` formable by the hands and may be applied without protective ,
covering and is not normally uncomfortable to the patient.
The formed orthopedic case rapidly cools to a hard durable
~ .
~, porous cast, which is light and stable under normal usage
;~ conditions. The cast is easily removed by utilizing conven-
tional cast cutting or sawing techniques and equipment. -~
More specifically the invention is a bandage
;~ 20 material for forming,in place an orthopedic case, comprising
a pliant fabric carrier comprising low density strands of
relatively bulky and good heat insulating material and
,s~ defining openings of relatively large diameter; each strand `
~,; being coated and only partially impregnated with a polymer
~; 25 composition having a heat softening point of not less than
~ 125F and not greater than 165F; said polymer coated
,,, carrier defining openings having an area of not less than
, .020 square inches and not greater than about .25 square
,. :
', inches; said partially impregnated bulky strands being
5 ` 30 formed with multitudinous air voids providing increased ,''
'~ insulating properties to said bandage material. '~
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Aspects of the invention are illustrated, merely
~: by way of example, in the drawings in which:
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Figure 1 is a fragmentary, full scale plan view o
a cotton knit carrier before impregnation w.ith the resin
according to this invention;
Figure 2 is the same as Figure 1 after impreg-
nation with the resin and showing how the mesh openings need
not necessarily be maintained in perfectly square or rec-
tangular shape to provi.de a satisfactory bandage for forming
an orthopedic cast.
Figure 3 is an enlarged view of the knit carrier
shown in Figure 1.
Figure 4 is an enlarged view of the impregnated
carrier shown in Figure 2. ~:
Figure 5 is a diagrammatic view showing one method
of fabricating a resin impregnated bandage embodying the :
inventiOn
~ A novel hi~hIy advantageous material is provided
; for forming orthopedic casts. A fabric web is employed ~ .
having relatively large openings and reIativeIy heavy - s
strands. Preferably, the strands are~of a loose weave or .;
knit, so as to be porous and subject to at least partial
impregnation by the polymeric material. The web carrier
. serves as a structural element in the final product and is
coated with at least an equal weight of the polymeric
, ~ , .
composition, and preferably a greater weight of the poly-
:. 25 meric composition. .. In describing the subject invention, the elements -.
of the invention will be described as followso (I) the ~.
carrier material; (2) the polymeric composition; (3) a
: ~ . .,;
:. method of preparing the orthopedic cast forming bandage; and :
(4) the orthopedic cast forming bandage. .
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Ca_ri~r Material
Referring particularly to Figures 1 and 3, the
carrier material i5 a flexible large mesh fabric, preferably
knit, defining a lattice of relatively large openings
3. The smallest dimension of the openings will generally be
at least .015 sq. in. and preferably a minimum of .022 sq.
in., about .034 sq. in. and generally not-exceeding .25 sq.
in., more usually not exceeding .050 sq. in. The openings
may be of any configuration, such as square, polygonal, or
the like. The opening shall be large enough so that in the
finished product the polymer composition preferably does not
form air impervious windows across the opanings.
The s~rands 2 of the carrier which define the the
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openings are preferably formed of relatively coarse~ bulky,
staple, pOrous, low density and thermal insulating material
such as heavy yarn
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of 5 to 15 twist and having a raw diameter of at least n.13
in., preferably about .015 in. and generally not exceeding
.040 in., and when including the fluff or fuzz around the
yarn strands at least .030 in., preferably a minimum of
.050. in., about .075 in. ana generally not exceedinq .20n
in. and more usually not exceeding .100 in.
Materials which may be used include cellulosic
materials, such as cotton, synthetic materials, such as
acrylates and nylon, or combinations thereo~. For the most
part, organic materials are employed, rather than more
thermal conductive inorganic materials, such as glass fibers.
Some significant factors concerning the material are that
the material be a thermal insulator, that it provide struc-
tural stability to the final product, that it allow for
molding to form the orthopedic structure, that it is wett-
able by the polymer composition, and that it is stable under
normal usage. By way of more specific example, the low
., . ~ . , .
density strands of bulky Raschael type knits formed of ,.,~
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staple fibers of cotton and defining naturally occurring
multitudinous voids provides a de~irable carrier material.
A knit of the Raschael type inherently provides a highly
flexible carrier material~
Preferably, the material should be substantially
free of additives which may interfere with the bond between
the polymer and the fiber. Cellulosic materials are pre~
; ferably scoured to remove any binders or lubricants in-
,
hibiting the wetting properties of the polymer or other
~ possibly deleterious additives.
; Polymer Composition
While for the most part, poly-~-caprolactone is ~ -
commerically available and therefore the product of choice,
~ ~ 7 ~7~ ~
other compositions resembling the properties of the poly-
caprolactone have been reported in the literature and to
that extent could be employed to replace the poly-
caprolactone. See the above U.S. Patent No. 3,692,023.
However, for the purposes of describing a preferred embod-
iment of this invention, only the poly- -caprolactone
i will be referred to and is to be considered illustrative of
this family of polymers. For purposes of convenience, the
formula set forth in the aforestated patent is repeated with
its definitions as inclusive of the types of polymers which
~ may be employed.
''r These polymers are characterized by the recurring
unit.
ot~(A~.~C~ :
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wherein each R, individually, is selected from the
class consisting of hydrogen, alkyl, halo and alkoxy; A is
the oxy group; x is an integer from 1 to 4; y is an integer
; from l to 4; z is an integer of zero or one; with the pro-
visos that (a) the sum of x + y ~ z is at least 4 and not
greater than 7, and (b) that the total number of R variables
, , :; which are substituents other than hydrogen perferably does
not exceed 3 per unit. Illustrative R variables include
methyl, ethyl, isopropyl, n-butyl, sec-butyl, t-butyl,
hexyl, chloro, bromo7 iodo, methoxy, ethoxy, n-butoxy, n~
hexoxy, dodecoxy, and the like. It is preferred that each
R, individually, by hydrogen, lower alkyl, e.g.
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methyl, ethyl, n-propyl, isobutyl, and/or lower alkoxy, e.g.
methoxy, ethoxy, propoxy, n-butoxy, and the like.
It is fur~her preferred that the total number of carbon
atoms in the R constituents does not exceed twenty. ;~
The polymers which are employed will normally have
a molecular weight of at least about 30,000 weight average
molecular weight and preferably about 40,000 weight average
molecular weight and will have reduced viscosities as
reported in the aforementioned patent of at least above 0.3
and generally not exceeding about 15, commonly above about
0.5 and up to about 10.
Small amounts, generally not exceeding 15 weight
`~ percent, more usually not exceeding 10 weight percent, and `~
preferably from about 3 to 8 weight percent of inert in-
sulative fillers may be included in the polymer composition.
Such fillers include titanium dioxide, talc, magnesium or
' calcium carbonate, clay or other suitable inorganic or
;~ organic materials.
In the present invention the polymer should
thermally soften at or above 125F, and below about 180 F,
and preferably between 145 - 165F.
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Method ~f;M~ki g Orthopedio;Cast Fo~ingii~a~dage
Turning now to Figure 5, a roll 10 of the appro-
priate knitted or loose carrier woven webbing 12 is pro-
vided. The web~ing 12 is passed under first tank roller 14
and immersed in coating solution 16.
Various coating solutions may be employed having
varying concentrations of polymer and fillers. A convenient
volatile solvent for the polymer is used, for example, a
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halocarbon such as methylene chloride. A formulation which
was found to be satisfactory is a mixture 95 weight percent
PCL-700 a poly--caprolactone having a weight average mole-
cular weight.of about 40,000 (available from Union Carbide)
and 5 weight percent titanium dioxide. The composition is
5 mixed with methylene dichloride to provide a mix having from
about 5% to 50~ solids and preferably 10% to 20% solids, the
solids content generally being dictated by the workable
viscosity required. It will be undexstood that coating
, techniques may be employed, such as hot melt coatings, where
10 a 100% solids content is used.
. The initially coated webbing is then passed be-
; tween ad.justable trunnion rolls 17 and past an air knife 18 :
'' and thence circuitously through oven 19 passing over rollers
20 adjacent the upper regions o the oven 19. The air knife
18 serves to blow out any polymer windows which may have
: formed in passing.through the wet polymer solution 16, and
;;~ the air knife also assists in the drying of the polymer
applied to the wet carrier 12. The webbing in passing
through the drying oven 20 is dried at an elevated tem-
.- . .
perature preferably around 180F. Where one coat does not
glve a suffi¢iently thick and h~avy coating of polymer, the
. knit fabric webbing 12, as' shown in Figure 5, is subjected
:. to a repeat process of reimmersion in a polymer solution and ' .
`, subsequent drying. Corresponding parts of the equi,pment .''
~! 25 involved.in the repeat process are numbered correspondingly
,~ to those parts.already described but are suffixed by the
., letter "a" to distinguish them in the drawings. : :
A release film of polyethylene or similar materials
~' from an unwind roll-22 may be~employed in forming the take- :
up roll 23 of the impregnated web 12 if the roller handage
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~i~70;2~1
layers adhere to each other during rolling or when the roll
is heated to working temperature prior to its use in the
making of an orthopedic cast as more specifically described
hereinafter.
In the preferred embodiment the diameter of the
impregnated strands 2a of the web 12 (and as shown in
Figures 2 and 4) were measured in the range of between
t ~ ` " '
approximately .010 in. to .260 in. and generally between ;~
.075 in. and ~160 in................................................. -~
The size of the openings 3a (as shown in Figures 2
and 4) of the impregnated web should generally be in a
somewhat lower range of areas than given pre~iously with -
respect to the dimension of the openings of the unimpregnated
carrier material shown in Figures 1 and 3. The~smallest ~`
dimension of the coated opening will generally be at least
~;~ .010 sq. in., preferably a-minimum of .020 sq. in., about
.026 sq. in., generally not exceeding .250 sq. in. and
usually not exceeding .050 sq. in. The shape of the openings
shown in the impregnated web are disclosed as being in the
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form of a non-rectangular parallelogram as distinguished
` from the near square shaped openings of the unimpregnated
knit carrier of Figures 1 and 3. Such variation in shape
between the uncoated and coated carrier may result from the
. manner in which the carrier is handled during the coating
process. In manufacturing the impregnated web according to
the process described in reference to Figure 5 and without
utilizing rather special web tracking and handling equipment
~. ,j .,
it was found that the web could be better handled through
~' the impregnation and oven drying process by running the
- 30 fabric with the strandæ oriented paral~lel and perpendicular
.~ to the line of travel of the material through the-e~uipment.
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Where the carrier material is originally oriented in a
diagonal direction with respect to the strandsl it may be
desirable to cut the material on a bias and run it through
the coating process so that the strands are substantially
parallel and perpendicular inskead of diagonaI to the line
of travel. Such an orientation will give a more rectangular
finished product.
However, the disclosure of Figures 2 and 4 are
~ade to indicate that the orientation during coating is not
important and that in order to provide an entirely satis-
factory bandage it is not necessary that the openings be
square or rectangular. It is impoxtant, however, that the
openings after coating be of substantial area ranging for
example between not less than .010 sq. in. to not more than
.25 sq. in. and more preferably between .020 sq. in. and
.050 sq. in. and around .026 sq. in.
As earlier noted it is important that the openings
be large enough so that when a cast~is formed by spirally
wrapping and overlapping the material around the injured
limb, that air passages through the thickness of the cast
will be maintained to permit~the underlying skin of the
. .,
patient to breathe and to permit volatilization and dissi-
pation of moisture from the interior of the cast.
When utilizing a Raschael type knit carrier formed
of low density, staple fiber, bulky cotton strands as
hereinabove described, and by utilizing the process of
/ .
polycaprolactone polymer impregnation of said knit cotton
carrier described in reerence to Figure 5, the following
physical or mechanical characteristics of the impregnated
web 12 (other than those characteristics alrea~y specified)
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have been observed: `
1. Although both the polycaprolactone pol~mer
and the cotton yarn have individual specific gravities in
excess of the specific gravity of water which would lead to
the apparently obvious conclusion that a mere combination of ~;
the two material (i.e., impregnating the cotton yarn with
the polymer) would re~ult in a structure that would sink
water, the fact of the matter is that the final impregnated -~
; web 12 ~as herein described) will float on water indicating
that the specifi¢ gravity of the combined materials is less
than the mere sum of the specific gravities of the two
materials (polymer plus cotton yarn) divided by 2.
The apparent explanation for this observable fact
is that upon magnified visual inspection of the impregnated
strands 2a shows the existence of air voids still existing
in the body of the cotton year where complete wetting and
filling by the polyer has not occurred. It is theorized and
believe~, that this type of structure contributes materially
:: .
to the utility and practical operability of the impregnated
web as a~suitable orthopedlc cast bandage material. ~ore
`~ specificaIly, it is know that air pockets fundamentally form
.
relatively good heat insulating zones, and it is further
known that the better the heat insulating qualities of a
body the slower will be the rate of dissipation of stored
heat therefrom. It i9 therefore reasoned that in respect of
the intended and practical use of the present in~ention, the
. .~ .
existence of air voids (heat insulating zones) in the web
provides the unexpected advantages of providing a longer
"working time" with the material and accounts for the fact
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that a rolled bandage of such material can be imm~diately
removed from a hot water bath of over 165F and handled
comfortably in the ungloved and bare hands of a physician
user without his experiencing any discomfort as might be
expected in handling such a relatively heated object. r.rhe
"working time", and as will hereinafter be described, is the
time that a physician has to remove a bandage roll from a
hot water bath and unwind it with skill and care in a still
softened and pliant condition around a patient's limb to
form and mold an orthopedic aast.
Contributing also to the heat insulating proper-
ties of the impregnated web 12 (according to the present :~
invention) is the use of an organic carrier material, such
: :
: as cotton, which inherently is a relatively good heat
. .
insulator. In this connection, other resin impregnated .
-........... orthopedic cast bandages on the market today utilize a glass
fabric carrier which is not only less x-ray transparent, but
is a relatively good heat conductor and would not provide
~- the optimum advantages of heat insulating properties in the
` 20 environment of the present Invention as herein described.
. 2. The impregnated web 12 made according to the
` process, and using the polymer and fabric materials speci-
;; fically described herein, has a measured or determinable
ratio of approximately 4:1 polycaprolactone polymer weight
~ 25 to cotton yarn fabric weight, although this ratio may be
; varied substantially to produce reasonably satisfactory
: .
bandages within the range of 2. to 5:1 resin weight to fabric
carrier weight. :~.
Orthopedic Cast Forming Bandage and IJse Thereof
A typical bandage formed from the impregnated and :`~
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dried web 12 manufactured according to the process herein~
above described in reference to Figure 5 of the drawings may .~ ~ .
be approximately 6 ~eet long and:3 inches-wide i~ roll form
with a parting film of sheet polyethylene separating adja- ~ :
cent layers of impregnating fabric in the roll.
In using the bandage to make an orthopedic cast it ~ ;
is convenient simply to immerse the rolled bandage in a vessel
of hot water at a temperature above the thermal so~tening
point of the polymer. In a bandage utiliz.ing the preferred
lQ poly-~-caprolacton~ polymer, the same has been found to :~
soften readily when introduced into hot water a* about 155- ~,Q
~ 165F. Approximately.two minutes in the hot water bath is
.~ sufficient to bring the web to a readily moldable state.
While warm ai.r or oven heat or the like can be used at the
heat source to soften the polymer, the.water bath is pre-
ferred because of.its ability to rapidly a.nd uniformly
. aontact and heat all areas of:the rolled bandage to uniform
.` temperature... When removed fromlthe water, the bandage can
be readily wrapped about a limb without requiring any
protec~ive covering of~the:user's hands. When the usual `
-- no.rmal underlying stockinette or padding is employed, there
is no discomfort on the part of the patient. The heat . ~.
softened and pliant ban~age can be twisted, gathered, :~
formed, re-formed, molded., rolled and unrolled as desired,
there being ample time for the bonding hetween adjacent
.. layers and the formation;of the cast. Any release fïlm may
be peeled of and discarded as ~nwinding of the bandage
:
. proceeds. The cast.may be allowed to cool and:if desired, :
.i the rate of cooling~.can be enha~ced-by~applying cold water
~; 30 compresses over the cast. :Air cooling or oth2r means is
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1~70;20
employed to increase the rate of hardening.
The resulting cast has a number of desirable
features. It is sufficiently transparent to x-rays, so that
close to skin quality x-rays can be achieved. This means
S lower x-ray voltage may be employed as compared to other
cast materials, such as plaster~ The cast is light weight
and a strong structure can be achieved with as li~tle as 2
layers of the material. Chan~els are retained, so that the
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skin is able to breathe through the cast and maceration over
the normal period of time for which the cast is worn is not
observed. Strong bonding is obtained between the layers of
the webbingj so that the cast does not come apart. In
addition, the cast can be immersed in water and because of
~` the porosity of the cast, the water will evaporate and the
skin underneath the cast will retain its healthy condition.
By employing a heavy webbing with large openings
t,~ .
and a relatively large proportion of polymeric composition,
the polymeric composition remains moldable for a substan-
tially long period of time. For example, a bandage roll of ~ -
6 feet in length upon heating in water of about 125-165
will remain soft and bondable for a period of at least 30-45
j....................................................................... ;
~ seconds at room temperature. A cast made of wound series of
1 3 rolls for example will remain hand pressure moldable or
; formable as a mass of approximately 3-4 minutes a~ter
application of the third roll. Thus, once the composition
has reached its softening point, it lS easily workable over
a reasonable time which is required in formin~ the cast and
insuring the proper positioning. ~he heavy strands of the
web provide structure to the material and remaln in place
when positioned, so as to insure that on hardening the
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immobilize~ limb is held in the desired position.
During use, the cast has good wet strength and
does not deteriorate upon repeated immersions in water, such
as during swimming or taking showers or baths. In addition,
the cast is highly abrasion resistant and capable of sus-
taining substantial impact. The cast provides pratection
- for the injured limb and can be used in most situations
normally encountered by the wearer.
Finally, the cast is readily removable as by
cutting with a conventional vibrating sawtooth disc. A cast
once formed in place over an injured limb can also be ~
readily reformed, repaired, and in many instances re-used. .
For example, i~ a patient complains of a discomforting
localized pressure point exerted by the cast, the cast can
be reformed by ease the pressure merely by applying to it
hot towels (or other type of heat) to cause the impregnated
: material to soften and be manually manlpulated and molded to
desired configuration.
In situations where it lS ne-cessary to cut out a
plug to form~a~window in a cast ~or~the physician to observe
or treat an underlying wound, the plug cut-out plu~ may be
readily~replaced simpIy by re-heating it and re-inserting it
::~
~ back in the window hole. If desired the plug can be more
~ .: ....
securely held in place by wrapping one or two layers o~ pre-
softened new ba~dage material around the cast and overlying
the re-inserted plugO -~
;~ It is also possible in some instances to re-use
:.~i . .
,!,;1 either a single or double slit cast after its entîre removal
from a limb. This can be done merely~by reheating in water
~ 30 or otherwise the removed cast parts and replacing and
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reforming them on the patient's limb, whereafter another
layer or two of new bandage material can be wrapped around
the original parts to hold them securely in place.
It will further be appreciated that the term
orthopedic "casts" as used herein is also meant to include
where applicable, the forming of splints and braces.
Further, although one manner of making and im-
pregnating carrier 12 has been described in particular
reference to Figure 5 of the drawings, it is contemplated
that the fabric carrier can be impregnated by other well
known processes such as by hot-melting the powderous resin
on the carrier, or by powder coating the carrier by passing
the carrier one or more times through a fluidized bed of
resin powder one or more times, and after each pass heating
- 15 the material to cause the powder to fuse and bond itself to
the carrier strands. ;
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Although the foregoing invention has been des-
cribed in some detail by way of illustration and example for
purposes of clarity of understanding, it will be obvious
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that certain changes and modifications may~be practiced
within the scope of the appended claims.
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