Note: Descriptions are shown in the official language in which they were submitted.
DO~LE-INS~LATED RUBBER FOOTWEAR PRODUCT
BRIEF SUMMARY OF T~E INVENTION
The present invention relates to insu-
lated rubber footwear ~roducts which a~ord
superior functional utility and versatility when
used under sub-arctic environmental conditions.
More particularly, the present invention relates
to an insulated rubber vulcanizate sized to
acco~modate a foot of a wearer and the removable
liner insert, and to the manufacture of such a
rubber footwear product.
BACKGROUND OF T~E INVENTION
.
For centuries, the footwear trade ha~
attempted to improve upon footwear to protect
sportsmen, military personnel, hunters and other
15 outdoorsmen against the peril4 of frostbite and
inclemen~ weather. External wetness and intern-
ally generated moisture, such as developed
through perspiration, present unique problems in
such footwear. Leather footwear generally pos-
20 sesses sufficient porosity to permit the transfer
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of internally developed moisture into the exter-
nal environment. Unfortunately, such leather
footwear provides inadequate insulative protec-
tion. Moreover, leather footwear is costly and
impractical for large scale usage, such as that
required by the military.
Rubber vulcanizate footwear has been
primarily used as protective outerwear. Rubber
vulcanizate~ have exceptional moisture barrier
characteristics. ~owever, this not only prevents
moisture from penetrating in~o the footwear~ but
also retains and entrap~ internally generated
moisture.
In general, ~omposite cold-weather
boot~ are knownl Examples are descri~ed in U.S.
Patents 395,664, issued on January 1~ 1889 to
M~Kie and 388,597, issued on Augu~t 28, 1888 to
Stickney.
Rubber boot~, fitted with a leather
top or legging, are also generally known, and
referred ~o by the trade a~ a "pac" boot. Such
pac boots may be oversized to accommodate a
separate felt insulative liner. 5uch pac boot~,
however, are not otherwise in~ulated.
The use of insulative compartments
built into foo~wear are also known. For example,
United States Patent No. 4,229,889, issued Octo-
ber 28, 1980 to Petrosy, has disclosed an air
cu~hion shoe base having a sole and a plurality
30 of vertical rims filled with foamed rubber and
sealed within compartmentalized rimmed section3
of a midsole. The foam rubber forms small meter-
ing orifices for restricting and delaying fluid
fxom flowing forward and rearward in re~ponse to
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wei~ht shifts. Similarly, United States Patent
No. 4,458,430, issued July 10, 1984 to Peterson,
discloses shock absorbing soles provided with
fluid-filled cushions interconnected by means of
a number of channels. Upon compression from
walking, the fluid flows Erom the rear cushion
to the forward cushion and vice versa.
Commercially, rubber vulcanizates have
been combined wi~h insulative materials. For
example, a rubber boot has been provided with
internally-disposed insulative pilings and means
for inflating the piling cavity with air. Its
utility has been primarily restric~ed to certain
military applica~ions wherein walking or other
foo~ activities are generally avoided. The par-
ticular construction of this boot includes a
plurality of synthe~ic insulative layers. The
two outermost layers have a rubber vulcanizate
backing which is intervulcanized (i.e., undergoes
vulcanization as a unit) with the sole, the inner
shell and outer shell components to provide an
airtight chamber within the footwear sidewall.
The sidewall insulative layers (which extend
Qeveral inches above the ankle bone) are sand-
wiched between the inner and outer shell vulcani-
zate component~ and are thus confined within an
air~igh~ chamber. The sidewall is equipped with
an air valve for air inflation. Thi~ boot also
has an insulated 501e portion comprised o~ a
plurality of felt layers, measuring approximately
~ hi~k, sandwiched between the inner sole and
outsole. These felt layers are compartmentalized
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within a separa~e airtight chamber (not communi-
cating with the sidewall compartments). The
excessive weight and bulkiness of this boot
readily contributes to user fatigue upon any
sust~ined physical exertion. Its design and
construction affords a narrow band of thermal
tolerance to externally and internally generated
heat. This sub-arctic boot is is generally imper-
vious to internally-generated moisture. Accord-
ingly, a wearer will typically encounter acutediscomfort due to internal sweat and moisture
accumulations, especially when the wearer is
reguired to engage in any appreciable physical
activity or exertion. Foot injury can readily
occur under sustained sub-arctic usage.
Another commercial variation of an
insulated rubber vulcanizate product employs a
pluràlity of wool or wool-like synthetic materL-
als sandwiched indiYidually and separately sealed
within a shoe upper which extends several inches
above the ankle bone. A felt sole, measuring
approxi~ately 3/4" thick, is ~andwiched and
~eparately compartmentalized between the rubber
outsole and insole. The boot'~ utility has been
generally restricted to rather specific applica-
~ion~ suc~ as for use by airflight maintenance
and ~ir runway personnel. The boot iq generally
unsati~factory for prolonged usage in sub-arctic
environments and cannot effec~ively dissipate
internally generated moisture or perspiration.
Another commercial variation, loosely
regarded as an insulated boot, embodies a separ-
ately compartmentalized rubber upper and sole
insulative materials comprising a closed-cell
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foamed rubber. Thi5 boot is neither designed
nor useful for sub-arc~ic applications.
The aforementioned commercial insulated
boots lack attributes normally required for sub-
arctic usage by the active outdoorsman and mili-
tary personnel. The insulated rubber vulcanizate
products of the prior art which afford the
highe~t degree of insulative protection again~t
coldness are generally regarded as unfit for
strenuous activity. Extreme discomfort, injury
and/or infections due to e~cessive accumulation
of sweat and moisture within the footwear remain
an inherent defective limitation. In contrast,
those rubber footwear vulcanizates offering
lessex insulatiYe protection ~e.g., those primar-
ily adapted for usa~e by flight attendant~, etc.)
inadequately protect ~he wearer against prolonged
exposure to sub-zero conditions. Accordingly,
the known insulated boots have been limited to
20 specialized applications. Unfortunately, sports-
men and other outdoorsmen are in need of footwear
more br~dly adaptable ~o thos~ environmental
and exertional requirement~ of a wearer in cold
climates.
2S A lightweight, nonbulky, insulated
rubber vulcanizate product which affords superior
protection against fro~tbite over a broad range
of cold tempera~ures and permits the wearer to
freely engage in phy~ical activities without
30 experiencing the discomforts associated with theprior ar~ products would fulfill a lons-elt
need. A rubber vulcanizate product which would
protect ~he foot against external wetness under
sub-arctic climate~ but also effectively remove
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and transfer perspiration an~ moisture away from
the foot area would overcome a particularly
troublesome prior art problem. Foot injurie~
and infections associated with the *xcessive
S accumulation of perspiration and moisture ~ould
thereby be avoided. The alleviation of these
prior art problems coupled with an ability to
mass produce an insulated rubber vulcanizate
inexpensively would constitute a significant
contribution to the insulated rubber footwear
trade.
BRIEI~ DE:SCRIPTION l)F THE DRA~IN~;
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~igure 1 is a .qide view of a double
insulated rubber ~ootwear product revealing the
exterior appearance of an insulated rubber vul-
canizate with a removable insulative liner insert
therewithin.
Figure 2 is a side view oE a removable
in~ulativ~ liner insert.
Figure 3 shows a side view of a leather
legging detached from the footwear product ~hown
in Pigure 1.
Figure 4 is a ~ide view of the insula-
ted rubber vulcanizate footwear product with anover~ized forming lact partially shown projectlng
from the internal shoe cavity of the vulcanizate.
Figure 5 ic a cross-sectional view
taken alons line 5-5 of Figure 4 showing in
greater detail the internal construction and
component part~ of an in~ulated rubber vulcani-
zate product.
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Pigure 6 is a cros3-~ectional view of
the toe section of the insulated rubber vulcani-
zate footwear taken along line 6-6 of Figure 5.
DETAILE:D DESCRIPTION OF 1~ INV~IO~
Referring to Figure 1~ a double-
insulated footwear product (generally designated
as 1) includes removable insulative liner insert
2 (mostly occluded from view) and an insulated
bottom (generally designated as 3) equipped with
a legging member 4.
Referring now to Figure 2, liner 2
suitably includes a sole portion 5 and a sidewall
portion 6, both constructed of felt (e.g., 9mm
thick pressed felt (75% wool/25% synthetic
material manufactured and distributed by
Brandtfelt Companyr Ontario, Canada)), and sized
to f it a wearer's foot, yet fit within the over-
~ixed internal foot cavity of bottom 3. Liner 2
i~ provided with a liner heel reinforcement
portion 7 and ela~tic band 8 which permits liner
2 to fit snugly against the wearer's upper~ foot.
Referring to Flgure 3, legging 4 suit-
ably includes tongue 4a, a left lacing member 4b
and a right lacing member 4c, both of which are
equipped with lacing eyelets 4e. ~egging 4 may
be suitably secured onto bottom 3 by stitching,
adhe~ive cement~ or other suitable securing
mechanisms. Legging 4 may be formed of syn~hetic
or natural materials such as vinyl, synthetic
leatherr canvas, cloths of an animal or plant
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derivation, synthetic and natural rubbers, synthe-
tic fibrous materials and the like~ It is advan-
tageou~, however, for at least a major portion
(surface area basis) of the footwear product
above the ankle bone to be constructed of a gas-
permeable material. Leather and canvas are
illustrative of such gas-permeable materials.
The mirro capillary attributes of leather (which
generally permit the permeation of internally-
entrapped vapors and, at the same time, exhibit4ubstantial imperviousne~s to external moisture)
and its functional equivalents are particularly
effective materials for this purpose. Insulated
bottom 3 disposed with its uppermost portion
below the ankle bone of the wearer, and most
suitably abou~ 1 inch to about 2 inches below
the wearer' 5 ankle bone, and micro-capillary,
gas-permeable legging materials (e.g., leather)
have been found ~o be an especially beneficial
combination for excellent insulation and dissipa-
tion of perspiration.
Referring to ~igure 4, bottom 3 is
for~ed as a vulcanizate on an ovzrsized last L,
shown projecting from the internal cavity of the
vulcanizate~ T~.e vulcanizate components visually
observah~e rom Figure 4 include an external
vulcanizate 3hell 9 (e.g., a snag-proof, .04"
thick rubber with a .045" thick friction vamp)
reinforced with a corrugated rubber toe cap 10,
an outer rubber heel reinforcement .ection 11,
and a rubber brush guard 12 circumscribing the
uppermoct border of the vulcanizate 3. The lower
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section of vulcanizate 3 includes a 50le 13, a
heel 14, and a lower foxing band 15.
Referring to Figure 5 and Figure 6,
insulated vulcanizate (bot~om) 3 generally com-
prises, in addition to external shell 9, an innervulcanizate portion (generally designated as 16)
and an open-cell insulator ~generally designated
as 18). Inner portion 16 suitably comprises a
plurality of component parts: inner rubber upper
22 and inner rubber bottom 23. Inner rubber
upper 22 and inner rubber bottom 23 are ~uitably
intervulcanized to orm a gas-tight ~eal 24 ther~-
between. External shell 9 likewise suitably
includes a plurality of components: an outer
rubber upper 25 circumscribing inner rubber upper
22, and an outer rubber bottom 26. Outer rubber
upper 25 and outer rubber bottom 26 are suitably
intervulcanized to form a gas-tight seal 27 there-
between. The outer rubber upper 25 suitably
include~ a forward section 25a and a rear section
25b (both cons~ructed of a lightweight, ozone-
resi~tant na~ural rubber). A~ more fully
described later herein, the forward section 25a
may be appropriately prefabricated ~o as to
overlap the rear section 25b during its as~em-
blage upon the last L.
External ~hell 9 and internal shell 16
are intervulcanized to form a gas-tight chamber
(generally de~ignated as 17). Inner rubber
bottom 23 and inner rubber upper 22 generally
provide the inner vulcanizate walls for ga~-tight
chamber 17, while the outer rubber upper 25 and
the outer rubber bottom 26 generally define the
external wall~ for e~ternal vulcanizate shell 9
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of chamber 17. Outer rubber upper 25 and inner
rubber upper 22 are intervulcanized to for~ upper
seal 28, defining the upper extremities of gas-
tight chamber 17. The interîor of the insulated
vulcanizate 3 (i.e., inner vulc~nizate 16) may
be provided, if desired7 with an inner liner 19,
such as a co~ton liner. The i~terior portion of
the vulcanizate as defined by internal walls of
inner vulcanizate portlon 16 i sized to accom-
modate the removable insulative liner insert 2without causing substantial deformation (e.g.,
compression) to the insert 2.
Internal insulative portion 1~ suitably
includes an open-cell insulati~e upper portion
20 and an open-cell insulative sole portion 21.
Insulative portion 18 ic ~onfined within said
gas-tight chamber 17, with upper portion 20 sand-
wiched between outer rubber upper 25 and inner
rubber upper 22. Sole portion 21 is similarly
sandwiched between outer rubber bottom 26 and
inner rubber bottom 23.
This particular combination coopsra-
tively provides for a circulatory movement of
gas mol~culeQ within gas-tight Ghamber 17 in
~5 re~pon~e to repetitive pneumatic compres~ive
expulsion and decompressive ab~orption of gas
molecules by open-cell upper in~ulative por~ion
20 and open-cell insulative sole portion 21,
such as oc urs when footwear product 1 is worn.
By intervulcanizing the open-cell upper insula-
tive portion 20 onto the outer rubber upper 25
and inner rubber upper 22, an accordion effect
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occurs when the inner and outer rubber uppers
(22 and 25) become ~eparated or compressed under
normal usage.
Other ~omponents of the illustrated
vulcanizate which may be incorporated into the
vulcanizate are an in~ole liner 29, an uncured
insole filler 30~ a steel shank 31, friction
tape 32 as well as the vulcanizate heel rein~orce-
ment sec~ion 11, the corrugated rubber toe cap
lDg a rubber brush guard 12, and a lower foxing
band 15~
The combined effect of the componerlt
parts uniquely enhance the functional utility of
the footwear product, In~ulative liner 2 and
the open-cell insulative layer~ within vulcani-
zate bottom 3 serve a multiplicity of functions.
Use of in~ula~ed vulcanizate 3 in conjunction
with ~he insulative liner effectively eliminates
the development of localized cold and hot spots.
The continuous circulatory movement of ga~e~ and
heat exchanging effect afforded thereby provides
a more uniform and desirable thermal control of
internal boot temper~turs. ~his ~ignificantly
enhance~ the versatllity and usefulness o the
footwear over a broad range of exertional~
environmental and climatic con~itions, effec-
tively alleviating the exce~Yive warmth~ coldness
and perspiration problems associated with the
prior art insulated boots.
Each of the open-cell in3ulative
materials have porous interstices for entraining
gaseou~ ~olecules, uch as air, in the relaxed
~noncompressed) state. Upon its use ~such as by
walking, running, etc.) the wearer's foot causes
~2~
these insulative materials to undergo repetitive
compression and decompression. The compres~ion
and decompreQsion in conjunction with the resili-
ent and open-cell structure of the in~ulative
S materials effectively serve~ a~ a pneumatic pump
for eontinual circulation of molecular gases
within the removable insulative liner insert 2
and ~he open-cell in~ernal insulative materials
18 of the vulcanizate. Th.is continuous circula-
tory movement of gaseous molecules allows for amore uniform distribution and exchange of inter-
nally generated heat within the footwear product.
The inability of prior footwear produc~s to
effectively dissipate heat and localized hot
spots (a major factor in contributing to thermal
and perspiration di~eomforts heretofore) are
thereby alleviated by the footwear product of
this invention.
An important function of the in~ulative
liner in.qert 2, in cooperation with the other
footwear component~, pertains to its ability ~o
transfer and remove exc2ssive perspira~ion and
moisture ~rom the foo~ surface. The con~inuous
circulation of air wi~hin the internal shoe
cavi~y in conjunctlon with the porou3, hydrophil-
llc construction and the capillary function of
the liner faeilitates the ab30rption of moisture
and its dissipation. The liner in er~ advan-
tageously possesses sufficien~ water absorption
and capillary attributes to serve ag a wicking
device for internally-generated moisture and
per~piration. The air current~ flowing through
the porous liner insert of the footwear product
are believed to enhance the rate of vaporization
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1 of liquid moisture absorbed by the liner insert.
As illustrated in Figure 1, the insulative liner
is advantageously designed so as to extend above
the vulcanizate and preferrably to coincide or
5 extend above the uppermost legging portion of
the footwear product. Such a design is believed
to create a chimneying effect for more effective
discharge of heated gases and moisture vapors
from the wearer's foot. Excessive accumulation
10 of moisture and the concomitant injury, disease
and/or discomfort to the wearer are thereby more
effectively alleviated by the present footwear
product. Moreover, the liner may also be removed
for drying, cleaning or replacement with another
15 insulative liner.
In its typical usage, the initial down-
step contact of the footwear product 1 upon a
walking surface will tend to compress the heel
portions of both the open-cell insulative sole
portion 21 and felt sole portion 5 of insert 2.
As the wearer's foot weight is shifted from the
heel to the toes, the more forward sole portion
is compressed. Similarly, the gas molecules
within the open-cell upper insulative portion 20
and felt sidewall portions of the liner 2 are
likewise respectively expelled and reabsorbed by
the compressive and decompressive forces exerted
against the upper insulative portion 20 by the
30 inner rubber upper 22 and outer rubber upper 25
and the biasing of liner 2 against the inner
vulcanizate portion 16 by the wearer's foot. As
previously mentioned, the intervulcanization of
the sole insulator 21 at its interfacing surfaces
35 to both the inner rubber upper 22 and the outer
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rubber upper 25 facilitates (via an accordion
effect) the circulation of gases therein. ~he
gas molecule~ within the confinement of the gag-
tight sealed chamber 17 as well as those within
the internal shoe cavity and liner 2 will undergo
repe~itive pneumatic compressive expulsion and
decompressiYe reabsorption from and into the
insulative materials of the vulcanizate 3 and
liner 2 during its normal and intended use.
Since the compre~sive ~orces exerted against the
upper or sidewall portion~ of the vulcanizate 3
a well as liner 2 are substantially less than
~hose exerted against the sole area, the outer
and inner sidewall~ of the vulcanizate are advan-
tageou~ly also con~tructed of relatively pliablean~ elastic rubber material such as a lightweight
ozone protected ~atural rubber~ Such a 3idewall
construction is suitably combined with a flex-
ible, pliable open-cell sidewall in~ula~or
material such as open-cell foaMed material (e.g.,
foamed open-Gell rubbers~ polyurethane~, poly-
ester~ etc.) to provide the desired elastici~y
and pliability to the ~idewall construction.
The thickne~s of the insulative
material u~ed within the vulca~izate may vary
and depend upon it~ in~ulative efficacy. ~n
open-cell upper insulative portion 20 of material
equivalent to at least 0.1" thick open-cell poly-
urethane foam is typically utilized for sub-
arc~ic conditions with about a 0.2" to about a0.4" thickness generally affording a more suit-
able insulation for most ~ub-arctic applications
thereofl Although the same insulative material
used within the vulcanizate a~ the open-cell
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upper insulative portion 20 m~y also be used as
a sole insulator 21 (and vice versa), open cell
insulative materials of a le~ser re~iliency s~lch
as synthetic or natural fiber are advantageously
u~ed to insula~e the sole area~ An in~ulative
ma~erial comparable to a~ least a 0.2" thick
felt ~e.g., pressed felt3 will typically be
required of the sole insulator 21 for sub-arctic
applications. The open-cell insulative sole
portion 21 will advantageously comprise from
about a Smm to about a 20mm thick felt insulator
and preferrably from about an 8mm ~o about a
12mm thick felt layer or it~ equivalent.
Atypical of conventional vulcanizates,
the vulcanizate 3 i9 ronstructed to accommodate
in3ulative liner 2 in addi~ion to the wearer's
foot. Thus, the internal ~hoe cavity of the
vulcaniza~e must be accordingly dimen~ionally
oversized to fully accommodate the re~ovable
liner. The required extent of over~izing will
depend primarily upon the thicknes~ of the insu-
lative liner 2. The manufacture of vulcanizate
3 generally neces~itates a orming devi~e (e.g.,
an aluminum ~hoe or boot last) specifically
designed to provide the over3ized internal 3hoe
cavity. An undersized shoe cavity will, upon
usage, cau~e the removable liner to be maintained
under con~tant compression and thu~ prevent the
circulatory movement o~ gase~ ~e.g., air)
therein. The forming last must necessarily be
larger than the wearer's foot ~ize in length,
width and depth and concomitant girth or total
surface area.
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The eircumscribing margin between the
wearer's foot and the internal surface of the
shoe cavity should be sufficient to prevent sub-
stantial compression such as occurs when the
wearer's foot is inserted into the footwear
product ~nd the product iq lifted above the
walking surface. It is typically desirable to
utilize a removable liner mea~uring at least 3mm
in thickne~. Special over~ized lasts which
exceed the outer margin of standard last~ by at
lea~t the liner thickness are appropria~ely used
to manufacture the insulated rubber vulcanizate.
An over~ized last exceeding a ~tandard last size
by at least 6mm in total length, depth and width
for any particular given foot 3ize will accommo-
da~e a 3mm thick removable liner, the 6mm over-
size providing an interior shoe cavity at least
3mm greater in dimension than ~he exterior of
the 3~m thick liner. The eficacy of the foot-
wear product is ~ignifioantly enhanced for sub-
arctic u~es by oversizing the internal cavity of
the vulcanizate by an external margin of at leat
5mm and preferably by at leaa~ 7mm. ~hu~, vul-
ca~;~ate 3 ia ~ypically con~tructed upon over-
~ized la~t~ eYceeding the external contour of astandard last by a margin ranging from about 6mm
to about 14mm and preferably by a margin ranging
from about 8mm to 19mm.
The dimen~ional size of ~tandard la~ts
are known and may be readily obtained by refer-
~n~e to the chart of Standard Scale of Last
Mea~urements in a book entitled Modern Pattern
utting and Desi~n, pages 129-130 ~1964 Second
Edition Printed in Great 3ritain by Dalketh
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Pre~s, Ltd., and Published by ~. J~ Patrick
SBFI, Mobbs and Lewis Ltd.,). Excessive over-
sizing of the internal shoe cavity is generally
undeqirable, since too loose a fit will not
provide the desired compres~ive and decompressive
effects up~n the insulative ~aterials. ~n
in~ulated rubber vulcanizate construction which
permits the wearer'~ foot to comfortably and
snugly fit against the removable liner without
causin~ substantial compres~ion will optimize
the effectivene~s of the footwear product.
The insulated vulcanizate 3 may be
~uitably manufactured by assembling the uncured
rubber components of the vulcanizate a~sembly
onto the oversized lastO Referring to Pigures 4
and S, the uncured rubber component part~ of the
insulated rubber vulcanizate are appropriately
precu~ or preabricated (e.g., see p~ges 1-65,
Modern Pattern and Cutting Designl and a~sembled
onto the over ized forming last. To accommodate
the ov~rsized internal shoe cavity~ the oonven-
~ion~l pattern~ are typically o~er~ized (yener-
ally by a .fac~or ~f the insulative thick~e~s
times ~ radius ~quared) to corre~pond~ngly
match the oversized di~ensions of the la~t. The
la~ted assemblage i~ then vulcanized to provide
the resultant in~ulated footwear vulcanizate.
In the manufacture of the particular
insulative footwear rubber vulcanizate depicted
by the accompanying ~igures, the inner rubber
bottom 23 (uncured rubber insole), fitted wi~h
cotton-woven fabric in~ole liner 29 and an
uncured filler 30, i3 initially placed onto the
last L (as a prea~sembled unit). An uncured
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inner rubber upper 22 coated upon a cotton liner
19 (prefabricated by applying about a lOOmm thick
uncured rubber coating onto a cot~on liner) is
next lasted onto insole 23. These eomponent3
collectively form the inner vulcanizate portion
16 of the vulcanizate. Next, the open cell
insulative sole portion 21 ~the interfacing upper
and lower surface4 of whi~h have been precoated
with an uncured rubber coating~ to which a ~teel
shank 31 has been preassembled onto the open-
cell insulative sole portion by means of an
encapsulating uncured rubber friction tape 32 is
placed on~o the filler 30. The heel reinforce-
ment se~tion 22h (rag counter about the upper
heel portion) i3 then placed onto the inner
rubber upper 22 and the interfacing edge of sole
portion 21. The open-cell upper insulative por-
tion 20 ~external interfacing ~urfaces of which
have been precoated with an uncured rubber
coa~ing3 is po~itioned onto the interfacing
surfaces of the uncured inner rubber upper 2~
~nd the uncured inner rubber heel reinforcement
section 22h. The uncured outer rubber upper 25
(compri ed o~ an overlapping uncured rubber gum
vamp 25a and an unc~red rubber counter 25b) is
then affixed onto the open cell upper in~ulative
portion 20 with extending margins thereof being
secured onto the upper interfacing margin of the
uncured inner rubber upper 22 and the lower
margin thereof primarily overlapping the inter-
facing peripheral edge of the open-cell insu-
l~tive sole portion 21 and the tangentially
interfacing portion of the uncured rubber heel
reinforcement section 22h (as illustrated in
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Figureq 5 and 6~. The corrugated rubber toe cap
lQ is lasted onto the gum vamp 25a of the outer
rubber upper 25, and the uncured ou~er rubber
bottom 26 secured onto interfacing margin~ or
surface3 of the outer rubber upper 25. Finally,
the open-cell insulative sole portion 21 and the
uncured rubber coated friction tape 32, followed
re~pectively by the lower foxing band 15, ~he
501e 13, the heel 14 and rubber brush guard 12
thereto are lasted onto the assemblage.
As recognized by those ver~ed within
the vulcanizate art, uncured rubbers convention-
ally used in the fabrication of rubber footwear
inherently pcssess suEficient tack to permit the
uncured components to be prea~sembled together
onto a Çorming last. The resultant uncured
la~ted assemblage may then be vulcanized to cure
the uncured lasted rubber componen~s into an
insulated rubber vulcanizate product equipped
with an internal cavity sized to accommodate the
insertion or removal of the liner ins~r~ from
the cured vulcanizate~ After allowiny the
vulcanizate to cool, the forming last L may be
removed thererom.
As illustrated by the cros~-sectional
views of Figure 5, the rubber brush guard 12
~rub~er coated ~abric) may appropriately extend
approximately O~S-loOI~ above seal 28 to provide
a margin onto which the leather legging 4 may be
secured by conventional adhe~ive or stitchery
techniques without rupturing gas-tight sealed
chamber 17. Seals 28, 27 and 24 ar~ r~spectively
obtained by overlapping of the uncured outer
rubber upper 25 onto the inner rubber upper 22,
- ,
,,
~z~
-20-
the uncured inner rubber upper 22 onto the
uncured inner rubber bottom 23 and the uncured
outer rubber bottom 26 onto the outer rubber
upper 25, respecti~ely, then intervulcanizing to
provide a gas-tight vulcaniza~e seal there-
between. It will be further observed that the
op~n-cell insulative 501e portion 21 and ~he
open-cell upper insulative portion 20 abut one
another about the outer periphery of the sole
area except for a minor portion in the heel
section which interfaces with heel reinforcement
~ection 22h. This construction allows ~he
entrapped gases within gas chamber 17 to flow
~ro~ the insulative ~ole portion 21 into the
upper insula~ive por~ion 20 and vice versa.
If desired~ ~he rubber vulcanizate may
be manufactured by other methods which would
generally provide an internal foot cavity suffici-
ently oversized so as to accommodate the wearerls
foot and the liner in ert while also retaining
the inner vulcanizate portion 16 and external
~hell with the internally disposed insulative
layer being disposed therebetween and ~onfined
therein by a chamber formed by the inner walls
o~ the inner vulcanizate portion and the external
~hell.
.
, ~
:
