US 2617208 A
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Nov. 11, 1952 J. J. MARX EI'AL RUBBER FOOTWEAR Filed April 1, 1949 LEVEL OF OOAGOLANT DIPW LEVEL OF FIRST LATEX DIP- LEVEL OF 1 SECOND LATEX DlP-" INVENTOR. BY "32% ATTORNEYS Patented Nov. 11, 1952 UNITED "T'STTATES PA.-'l i?.N.-T OFFICE 2,617,208 "RUBBER FOOTWEAR JoeJsMarx and EdwardfMwDavis', Cincinnati, Ohio, assignors to" So-Lo WorksJncorporated, Loveland, Ohio, a corporation of Ohio 'fipplicationA-pril' 1, 194-9, Serial No; 84,952
, 1-; Claim.
This invention relates to novelliielastotmeric footwear, particularly overshoes J suitable for children, and to apro'cess-bywhich such footwear may be fabricated; lhe shoes of thi's invention are light, flexible, attractive in appearance and adapted to be manufaoturedihy the dipping-of forms in liquid latex compound; 'Whileelastomers other than nat'ura'l-latex maybe used, the following disclosure w ill bemade in relation to rubber overshoes so fabrioated.
Broadly, and from the-method point-of View, the invention comprises dipping a form in coagulant, then dipping it two or moretimes in latex compound, the depth of each dip being progressively less. This technique produces an overshoe, the'uppe'r portion of'which iscons'tituted by a single rubberfilm ofsub'stantial'flexibility to permit the top" ofthe' oversho'e' to be drawn over the foot. The lower or sole portion 'of the overshoe is constituted byi=twolayers .of' film, that is, the inner: layer .whiohieonstitutesvthe upper and the outer layerwhichl provides reinforcement over the sole portioniof theovershoe.
Preferably, the-compound? which deposits the outer layer is of composition" different from the liquid which: deposits the. inner layer. If there be no. difierence other than thatiofcolor; aibright attractive two-tone appearance is.provided. But it is within the contemplationof. this invention that the outerglayer. shouldtcontain materials which enhance the: resistance of the film t0 abrasion. "While the sole .po'rtionkof'the oversh'oe may not be so flexible.asi'the upperip'ortion; substantial resistance to. abrasion may be imparted to it without sacrificinglfiexibility unduly. Thus, this piece of. footwear combines the wear-resistance-so important in tchildrensi articles'with an easily stretchable :up'peririm: which ca-n bepulled apart almost like a' rubber band; even'by younger children. Further, theexpansible nature of the upper accommodates. the sovershoe to be worn for a long timeiwith'out the childstoutgrowingit. The overshoes are particularlywell adapted to this childrens market, especiallyfwhen ma'de in bright colors, although th .m'eth'od an'd the articles to be described are ini no way limited to those suita'ble'onlyv for children;
The overshoeof thisiinventionis sufiiciently flexible, that lovershoes lmanuiactu-red on a-'g iven form may be worniover sho'es thefsizes and shapes of which vary over considerable range. Itis not necessary to havea form correspondingto each size and'styleof shoe' of thelprospective purchaser. This chara'oteristi'c Lot :Lth'e. oversh'oe,
which isin partsdeterminedzb'y.the method-of its 'Thef-toe portion of the o'ver'shoe u finishof thetoprim of thefo'ver'shoe.
tread on the bottom of the form" because of the tendency of the tread to entrap airin the dipping operation. Onithis; account the oonfiguration of the tread of'the' ove'rshoe":v or: this-invention is fashioned in relation" to theTdippi-ng problem and consists of alternating grooves. and r idge's r'iinning transversely of the? overshoe ahdrapering from the central longitudinal line-of the overshoe to them'argi'ns "toionn a slightly convex sole surface. These lateral-treadspermit-air to escape tothe sides when the-for being dipp'ed. pper presents a substantial area of horizontal surface, in additionxtoqthat.of-'-theLsole'jitselfI l herefore, to
avoid the :formation io'fair pockets along these surfaces: and to facilitate drainage in the dippi'ng operation, the 2 form is turned dow'nwar'dly' at an angle from: toe to? heel so that as the sole is dipped from heel to toe, the airt'en'ds to escape forwardly. These angulations are ofsubstantial 1 importance to facilitate quantity production of the overshoes by the dipping'technique withoutproduction" of too much worthless scrap as a result of entrapment'of air.
- Since the latex compound deposits. on?the form by virtue of the-exposure of the rubberin'ithe latex compound to a coagulant on the form, it has been a problem to obtain a uniform'and'substantial deposit of rubber on 'the-dipssubsequent to the first dip. Thisproblemhas been surmounted by inoorporatingin the-latex solution a stabilizer which impartsto the deposited :film'a permeability to the coagulant-solution,whereby the coagulant migrates through the unhardened filinafter its deposition and beoomes available to procure the deposition. of a-lilm of uniform and substantial thiokness onthenext dip.
AnadditionaYfeature or the invention is the Obviously it is desirable th'at this 'fi'nish'be even and "straight as trimming operations to obtain this result would "be unduly expensive from the point 'o'fview of both the labor invo'lv'ed 'and'the 'sorapresulting. We "have found '-'-that :if a1 coagulant solution possessed of the' proper physicaland' chemical properties is juti-li'Zed,--?and' if" the "dipping is performed sufiiciently slowly, then the first rubberfilm today be neutered "with "-such evenness that no trimming? operations are required. The
straight, smooth edge which results not only eliminates this expense but helps prevent tears from making a start in the film. While the slow clipping of the forms in the latex compound tends to expose the bottom of the form to the solution for a longer period of time than the top of the form, any inherent unevenness of deposit thus produced tends to provide a thicker sole portion and a thinner, more flexible upper portion, both of which characteristics are desirable.
The invention will be better understood by reference to the following drawings, in which Figure 1 is a side elevation of a form upon which layers of an elastomeric compound may be built up, showing the angle at which it is to be held during the dipping operations and the levels of successive dips to produce an overshoe of the type shown in Figure 2.
Figure 2 is a side view, partly in cross section, showing an overshoe constituted of two layers and stripped from the form of Figure 1.
Figure 3 is a section of the form of Figure 1 taken along line 3-3 showing the slightly convex sole surface.
Figure 4 is a side elevation of a boot or galosh made by the process of this invention, after having been stripped from a form of corresponding configuration.
As disclosed in Figure 1, a metallic, porcelain or other suitable form indicated generally as I is provided with a clipping portion 2 and a stem 3 having a hanger stud 4 by which it may be attached to a dipping rack, which is not shown. The hanger stud is angulated with respect to the bottom of the form so that when it is attached to a rack in horizontal position, the bottom of the form slopes downwardly from front to back at an angle of substantially 5-10". The bottom of the form is provided with ridges 5 separated by grooves B. Preferably each groove slopes upwardly from the central longitudinal line of the shoe to the margins to facilitate the escape of air on dipping and avoid the entrapment of air in the grooves. The degree of this slope may also be substantially 5-l0. The grooves and ridges extend for a short distance up the vertical sides of the form to provide channels for escape of air bubbles when the form is immersed in liquid. This arrangement also provides for the finished product a distinctive appearance otherwise unavailable, for normally the overshoe is displayed with the sole obscured, yet the corrugations are visible because of these extensions. Spaced above the bottom of the form, that is, at the portion of the form corresponding to the ankle or just below, is a depression 1 extending about the form, adapted to provide a tension band above the instep or about the ankle of the wearer. Preferably the heel of the sole portion of the form terminates in a ridge rather than a groove to provide a drip edge 8 to prevent too great a latex layer build-up at this point. The overshoe itself, as the two dip products shown in Figure 2 comprises an inner and flexible film of rubber constituting an envelope H for the foot and instep of the wearer reinforced by an outer layer 12 of rubber over the sole portion of the overshoe, and extending up above the sole and heel portion of the shoe of the wearer of the overshoe. As indicated, this outer layer may be of color different from that of the inner layer and may be of composition resistant to abrasion.
Corrugations on the overshoe consist of grooves l3 and ridges 14 corresponding to grooves 5 and sen es 4 ridges 6 of the form. Tension band 15 conforms to depression I of the form.
The overshoe shown in Figure 4 is of the boot or galosh type and is constituted by three latex layers each progressively of lesser extent. In this form the inner layer of rubber constitute an en'- velope I6 extended not only over the foot and instep portions but up the ankle to whatever length is desired. The second or intermediate thickness ll of rubber covers the sole and instep portion of the first layer. The third or outer layer I8 of rubber reinforces the sole of the galosh and extends upwardly to a point slightly above the bottom, that is the sole and heel portion of the shoe.
The form itself is preferably fabricated from aluminum or aluminum alloy of the type commonly employed for forms to be dipped in latex. The coagulant may be any one of the many utilized for dipping forms in latex but should be chosen in respect to its capacity to penetrate a stabilized first film, in relation to its effect upon the strength and stability of the rubber films deposited over it and in relation to its immobility on the form. The coagulant film should be sufficiently immobile prior to the first dip to avoid downward drainage of the undipped coagulant which would mar the evenness of the top of the first deposited layer of rubber. A good coagulant of the following composition by weight has been found to be suitable for this purpose:
Per cent Anhydrous calcium chloride 27 Calcium nitrate, tetrahydrate 27 Zinc nitrate, hexahydrate 6 Wetting agent 1 Methanolto make Micronized talc (added to above) 5 The wetting agent utilized in the above formula is of the nonionic type, and may be a polymerized ethylene oxide condensation product. Such an item is manufactured under U. S. Patent Nos. 1,970,578 and 2,213,477 and is sold by the General Dyestuif Corporation of New York.
The latex compound in which the form is first dipped to deposit the envelope I l for the foot and instep, that is, the sole and upper portion, is of a type low in sulfur and low in accelerator, thus requiring a low cure. Low percentages of these constituents contribute to a relatively high tear resistance. Preferably there is no zinc oxide in this latex solution, although there is enough zinc, as the nitrate, present in the coagulant to obtain proper aging characteristics for the film.
The latex compound used for the first dip is almost of pure gum stock in order to get a low modulus. This compound must contain a stabilizer which, in the quantity used, will permit the coagulant to penetrate the film deposited so that the proper reinforcing film may be deposited over the sole portion of the overshoe. A small percentage of the condensation product of cetyl alcohol with ethylene oxide performs this function satisfactorily.
A product of this type is manufactured by General Dyestuff Corporation of New York under U. S. Patent No. 1,970,578. This stabilizer produces a first coat, which is uniformly penetrated by coagulant to permit a second coat to build up uniformly.
We have found any of the following formulae for latex compounds suitable for obtaining the proper physical properties inthe finished articles. The figures listed, asiwell as other similar referbeiormed .attthe top ofzthesolelayer.
iire eteseeti er rub Sulfur eue diamine Zinc'diethylclithiocarbaniate,
' dimethyldit -mate Mercaptobenz'othiazo Tetramethylthiurainrhsulfide.
-The second :latexsolution -is similar tqathei-first except that. a dyestufi-,; or a difl erent dyestufi, Y is usually employed to give: theoyer shoeta-tw0- toneefiect. The. cetyl alcohol-ethylene oxide condensation. productmaybe;- omi-tted frem gthe second-dip, forsits use may .cause thesoleedip to creep up the first dipzand nostraightglinerwou-ld preferable that the second: dippingpif-i" his. to
'- constitute theouter: layer-of the tsole-hfitheovershoe, be. more resistantcto. abrasion ,thanvthe flexible inner. layer. A.suitable tougheningmaterial is colloidal silicadispersed in water at a concentration of 30% by weight and stabilized. Products of this type are manufactured by E. I. Du Pont de-Nemour's- &. Companypf Wilmington,
. Delaware. As little as parts o t this -znaterial .latex to preyentthemfromcoming into ,contact with the. silica which, isv .to .be -.added :-later.-,and which would be.precipitatedithereby. :Next,.cne half partperhundred of potassium hydroxide is added in the ,form, of a %..aqueous-solution. This further,stabilizesthesolution and .tends to reduce Skinformationin the dipping tank. =.Preferably. these, materials ,shouldsbe added to the latex t east 2&1. rhou sbefore. adding the-siliceous sta il .A tholigh the amount. of silicav of,-the
toughenr may. be ...varied. dependin upon-,the
, am unt of abrasi n .resistancedesired, pod ,re-
it a tained byaddineienou h s cate-th t the relationship, ofthe drysilicato the dry rubber is 1 to 10. Coloring material may be added at any. stage of the mixing.
In manufacturing the-overshoes the forms to be dipped are .preferablyicleansed in acidf -thensoap solution, particularly to remove anyJ-adhering particles of rubber remaining from prior dips. They are then rinsed in hot water and thoroughly dried. Next, the forms are disposed on racks and are heated to a temperature of substantially 120- 180 F., for instance, 160 F. They are then dipped, while still hot, in the coagulant which has been stirred to maintain uniformity. Preferably the depth of this dipping is appreciably greater than the contemplated dip in the first latex solution, for example, beyond the dot-dash line shown in Figure 1. The forms need not be held in the coagulant for any definite period of time, but they are removed from the coagulant very slowly for over a period of approximately tramte an at are midyear-in. air: -:;.b 1eun a 5 Th .99. is ot ub te i l,imeertanceinrtha rte sm e atio t mme 1 -I2r.e,clu s the. cpae nt n 1 du esi first/ atex. lip .t--- ladenwerext na ure a Shelf i:.=1atex-W -i0 hee.-er --r mnd a 1-, t e v sho wo ldh .im os b ew tbouthap d w-na't eor ab t-inc mh i op trimmi A a lt native, d pin a coatin .of
. coa ulant. may --be yestab1i,shed.- on; the 19m. by
; Sprayin a by. impregnating; a; porous -f ..,coagulant,, or. by. .any-; other conventional in s. The forms withthefilm oi coagulant-deposited thereon. are next dipped into the first latex, compound- .wh-ich is adapted to for-m; the over-all envelope. of the overshoe. The dipping iscarried outvery slowlyto prevent; trapping of-,air; underneath the sole of the form. After the solehas been covered, the-rateofimmersion maybe accel- ,erated-unt il,maximum depth is reached. -;The
. form aftertbeingimmersed tq the;dot-dash;;line
in i a din Eigure J g m t e t ema n; n-.. h latex mno d r: p r odef rom 1. 9 3 V mi utes depending. upon .the thickness- 01 the coating ,desired'. Ingeneral thicker coatings are desirable on the largersizes pto-vershoes. ;The;forms are then slowlylwithdrawn fro1n-,the late Q1 tion during a, period of approximately 2 minutes.
, The relatively even. drainagemesulting from; this l wi hd awa nd qrrev e a de Qsiedm which is adequately even and-uniform despite the irregularities of the for-m. On the. other hand,
this ratepfwithdrawal is sufficientto .draimthe latex frorn the vertical surfaces .of; the form to a thickness which .is still permeable to coagulant.
, Drainage is notso uniform irom-the toe. portion of .the form,, but the stabilizer in; the :latex compound is efiective- ,to render disproportionate thicknessesatthis point penetrable by coagulant,
,In the fabrication of the boot shown in ;Fiig,ure
-- h.eem a ire h fi st dimm r-be interup e talev l er es e d ee eeth yl idee ndiat e -flhe m-r he drin h sfixe i e ion er-s ve lm n te mo-all th est s hating ma istr tes as q msere meted-3 2 a;
l u d f ags w ich; 1
,heel and then. are allot v p 3 of, 3 .or. 1 minutes. to permit rela ment of an-area o intermediate thickness tols -u er-abette ely u i r ene rat n i fthefi riab h' u1. r y e peaant-.. Nextthe o ims. ar .si i e n-. h -,.-1ate compound adapted to provide the outer layer to the level of the lowermost dot-dash line of Figure 1. This dip is performed in the same manner as the first dip, but the forms are allowed to dwell in the latex compound for a period of from 6 to 8 minutes, depending upon the thickness of deposit desired. The additional time is provided to allow for migration of coagulant into the second layer. The three thicknesses shown in Figure 4 may also be obtained by an intermediate dip in latex, the dip being preferably of less depth but slightly greater duration than the first dip.
After withdrawal from the final latex dip, the
approximately minutes and are then leached in running water at a temperature of substantially 125 F., for approximately one minute for each thousandth inch of film thickness. The overshoes are then heat treated for a period of between 1 and 1% hours at 160 F., depending upon film thickness and weather conditions. Next they are heated for substantially hour at a temperature of substantially 230 F. After this the overshoes are stripped from the forms, an operation which is greatly facilitated by the inclusion of tale in the coagulant. The overshoes are then given a chlorine treatment by being dipped for about 30 seconds in chlorine water containing substantially 300 parts of chlorine per million parts of water. Finally the overshoes are washed in running water and dried.
The chlorination imparts to the surfaces of the products a particularly smooth finish. This is important, for the inside of the article may thereby be more easily pulled over the shoe by the wearer.
Inasmuch as the composition of the rubber footwear just described is almost pure latex, the specific gravity of the finished article is only slightly greater than that of a pure gum product. Thus, overshoes may be fabricated as described to be light enough to float, even though filled with water. This is true as to all formulations described herein except that shoes with a substantial sole portion having colloidal clay as a toughener will not float; nor will an all-white product be light enough to float, for the white pigment, such as titanium dioxide, used in the composition is too dense. However, a two-tone shoe with either a white upper or sole portion and the other portion colored by dyestuffs can be made in the relative proportions shown and described and such a shoe will not sink.
Thus, rubber footwear produced by the method of our invention may not only be used as overshoes, but are peculiarly well-adapted to be used as beach shoes due to their buoyancy, the protection of the sole of the foot against sharp objects such as oyster shells, pebbles, etc., and the combinations of bright and attractive colors attainable. When such use is the main objective, the rubber shoes may preferably be supplied with a plurality of holes of varying sizes at various points of the vertical side portions or at or near the toe portion. These apertures act as ports to let air in and water out. The moistened interior of the beach shoes adheres more tightly to the bare skin of the wearer.
Having described our invention, we claim:
A light-weight protective overshoe comprisinga flexible envelope composed solely of latex adapted to completely enclose the sole and heel and at least a substantial portion of the upper of the shoe to be protected, said envelope being longitudinally and transversely circumferentially continuous, except for a single top aperture through which the shoe is inserted, the entire upper portion of said envelope including that portion which is adjacent said aperture being of substantially uniform thickness and relatively thin, flexible and resilient in comparison with the lower portion of the envelope to facilitate stretching it over the shoe, the said lower portion of the envelope beingof substantially uniform thickness and thicker than the upper portion and differentiated from said upper portion by a ridge extending continuously around the overshoe in an inclined plane which passes through the front of the overshoe somewhat above that portion thereof which embraces the forward edge of the sole of said shoe and which passes at a higher level through the rear of the overshoe at approximately the height of the top of that portion thereof whichembraces the counter portion of said shoe, and the top edge of said envelope which joins its exterior and interior surfaces and defines said aperture, being a smooth, even and unserrated surface deposit of latex disposed in a plane parallel to the plane of said ridge.
. JOE J. MARX.
EDWARD M. DAVIS.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 826,258 Lakin July 17, 1906 850,603 Reiter Apr. 16, 1907 1,522,890 Krap Jan. 13, 1925 1,537,778 Nyhagen May 12, 1925 1,560,995 Kaplan Nov. 10, 1925 1,607,375 Whipple Nov. 16, 1926 1,715,120 Costellow May 28, 1929 1,719,633 Teague July 2, 1929 1,746,478 Howland Feb. 12, 1930 1,828,990 Watkins Oct. 27, 1931 1,854,969 Walsh Apr. 19, 1932 1,885,327 Burnham Nov. 1, 1932 1,907,856 Murphy May 9, 1933 1,980,621 Innis Nov. 13, 1934 1,983,667 LHollier Dec. 11, 1934 2,115,561 Ogilby Apr. 26, 1938 2,149,102 Quennard Feb. 28, 1939 2,185,762 Cox Jan. 2, 1940 2,254,263 Bratring Sept. 2, 1941 2,315,310 'Bitter Mar. 30, 1943 2,326,160 Neiley Aug. 10, 1943 2,437,109 Maquat Mar. 2, 1948 v FOREIGN PATENTS Number Country Date 4,296 Great Britain -1 Feb. 26, 1896 385,138 'Great Britain Dec. 22, 1932 817,424 France May 24, 1939