CA1255496A - Double-insulated rubber footwear product - Google Patents

Abstract

Abstract of the Disclosure The present invention provides a superior double insulated rubber vulcanizate footwear product for use in sub-artic climates. In general, the footwear product of this invention comrises a removable insulative liner insert sized so as to accommodate a foot of a wearer and an insulated rubber vulcanizate provided with an internal foot cavity of a size sufficient to accommodate a foot of a wearer and the removable liner insert. The insulated rubber vulcanizate construction includes an inner rubber vulcanizate portion generally defining the internal cavity of the rubber vulcanizate and contoured so as to permit for the insertion therein or removal therefrom of the removable insulative liner insert, an external vulcanizate shell circumscribing said inner vulcanizate portion and intervulcanized with said inner vulcanizate portion so as to form an internally disposed chamber within said rubber vulcanizate, gas molecules confined within said internally disposed chamber and an open-celled insulative layer sandwiched between said inner vulcanizate portion and said external vulcanizate shell with said open-celled insulative layer circumscribing and generally defining the contour of said inner vulcanizate portion.

Description

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
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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 - :. 1, . ~, . .
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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 ~, ' , 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 . ' , : ': ,.,,.. : .

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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_9_ 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 :
-: , 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 .~i : ' ~, .
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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 -13- '~

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 .i ,. ' .
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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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-lB-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~

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.

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Claims (24)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A double-insulated vulcanizate footwear product for protecting the foot of a wearer under sub-arctic climatic conditions, said footwear product comprising an insulative liner insert sized to fit the foot of the wearer and an insulated vulcanizate having an internal foot cavity sufficient to accommodate both the foot of the wearer and said liner insert, said insulated vulcanizate comprising an inner vulcanizate portion contoured to generally define the internal foot cavity of the vulcanizate, an external vulcanizate shell circumscribing said inner vulcanizate portion and inter-vulcanized with said inner vulcanizate portion to form an internally disposed chamber within said vulcanizate, gas molecules confined within said internally disposed chamber, and an open cell insulative layer housed within said internally disposed chamber and interposed between said inner vulcanizate portion and said external vulcanizate shell.

2. The double-insulated footwear product of claim wherein the liner insert is at least 3mm in thickness.

3. The footwear product of claim 2 wherein the open-cell insulative layer comprises an open-cell insulative sole portion and an open-cell upper insulative portion constructed of a foamed polymeric material.

4. The footwear product of claim 3 wherein the open-cell sole portion comprises a fibrous insulative material, the thickness of the liner insert is at least approximately 3mm, and the internal cavity of the vulcanizate exceeds the foot size of the wearer by at least the thickness of the insert liner.

5. The footwear product of claim 2 wherein the insert liner is characterized as possessing sufficient water absorption and capillary attributes to serve as a wicking device for internally generated moisture and perspiration and the thickness of the liner is from at least approximately 3mm and the internal cavity of the vulcanizate exceeds the foot size of the wearer by at least the thickness of the insert liner.

6. The footwear product of claim 5 wherein the uppermost portion of the vulcanizate is positioned below the anklebone of the wearer.

7. The double-insulated vulcanizate footwear product of claim 6 wherein a legging member is secured onto the vulcanizate.

8. The footwear product of claim 7 wherein the legging member is leather and extends from about 1 to about 2 inches below the ankle bone of the wearer.

9. The footwear product of claim 2 wherein the open-cell insulative layer is confined within a single gas-tight chamber, the insulative layer comprises an insulative sole portion and an insulative upper portion, and said liner insert and said insulative sole portion comprises wool fiber.

10. The footwear product of claim 9 wherein the insulative sole portion measures from about 8mm to about 12 mm in thickness and the open-cell upper insulative portion consisting essentially of polyurethane measures from about 4mm to about 8mm in thickness.

11. An insulated vulcanizate having an oversized internal foot cavity sized to accommodate a foot of a wearer and a removable insulative liner insert of at least 3mm in thickness therein, which vulcanizate, when combined with said liner insert, provides a double-insulated vulcanizate footwear product for protecting the foot of a wearer against sub-arctic climatic conditions, said insulated vulcanizate comprising:
an inner rubber portion of a contour generally defining the internal foot cavity of the vulcanizate, said cavity being sized to accommodate the foot of a wearer and said insulative liner insert without substantial deformation of said liner;
an external rubber shell circumscribing said inner vulcanizate portion and intervulcanized with said inner vulcanizate portion to provide an internally disposed sealed chamber within said vulcanizate; and an open-cell insulative layer internally disposed between said inner portion and said external shell.

12. The vulcanizate of claim 11 wherein the internal foot cavity exceeds the standard foot size of the wearer by a peripheral margin of at least 6mm.

13. The vulcanizate of claim 12 wherein the rubber inner portion comprises a rubber inner upper and a rubber bottom.

14. The vulcanizate of claim 12 wherein the open-cell insulative layer comprises an open-cell insulative sole portion and an open-cell upper insulative portion constructed of a foamed polymeric material.

15. The vulcanizate of claim 14 wherein the internal foot cavity of the vulcanizate exceeds the standard foot size of the wearer by a peripheral margin ranging from about 8mm to about 14mm.

16. The vulcanizate of claim 15 wherein the uppermost portion of the vulcanizate is positioned below the ankle bone of the wearer,

17. The vulcanizate of claim 15 wherein the external shell and rubber inner portion are intervulcanized together so as to provide a single gas-tight chamber for said sole insulative portion and said upper insulative portion.

18. Double-insulated footwear comprising a vulcanizate bottom;
a permeable legging affixed to said vulcanizate bottom; and an insulative liner adapted to be received within said vulcanizate bottom and legging;
said insulative liner having a foot portion of predetermined thickness and including an interior space configured to fit a foot;
said vulcanizate bottom comprising inner and outer intervulcanized rubber layers and an open-cell insulative layer;
said inner layer defining an interior cavity for receiving said insulative liner, said interior cavity generally conforming in shape to said insulative liner foot portion, and being of dimensions exceeding the dimensions of said insulative liner interior space by at least a predetermined amount of greater than said predetermined thickness;
said inner and outer intervulcanized layers forming a sealed chamber therebetween, said sealed chamber generally circumscribing said interior cavity;
said open-cell insulative layer being disposed in said sealed chamber.

19. The footwear of claim 18, wherein the dimensions of said bottom interior cavity exceed the dimensions of said liner interior space by at least 5mm.

20. The footwear of claim 19, wherein said insulative liner is at least 3mm thick.

21. The footwear of claim 18, wherein the dimensions of said bottom interior cavity exceed the dimensions of said liner interior space by at least 7mm.

22. The footwear of claim 18, wherein the dimensions of said cavity exceed the dimensions of said liner interior space by from about 6mm to about 14mm.

23. The footwear of claim 18, wherein the dimensions of said cavity exceed the dimensions of said liner interior space by from about 8mm to about 10mm.

24. The footwear of claim 18, wherein said insulative liner is removable from said bottom internal cavity.