US2254711A - Insole - Google Patents

Description

Sept- 2, 1941- M. o. Scl-lun ETAL 2,254,711

INSOLE Filed May 24, 1938 Patented Sept, 2, igdi @25am INSLE Milton 0. Schur and Edward M. Archer, Eerlin,

N. lll., assignors to Brown Company, Berlin, N.. 1&2, a corporation of Maine Application May 24, 1933, Serial No. 2003i@ (Cl. Sci-44) Cia.

This invention relates to the manufacture of insoles and more especially articialleather insoles comprising a felted iiber base impregnated with rubber or other binder. Artificial leather insoles of this character are generally of deiicient scui-resistance especially when, as in the form of welt insoles, they are used in workmens and other shoes and are exposed in the presence of moisture or perspiration directly to the wear or scumng action of the foot.

The insole of the present invention compnses a binder-impregnated felted fiber base of substantial moisture-transmitting property or vresidual porosity (e. g. a rubber-impregnated paperlike base of substantial residual vo1d space) and containing a secondary water-resistant binder infused into the pores or surface port1on of its body only at and immediately below its foot side or surface, that is, to a depth constituting only a small fraction of its thickness and in the substantial absence of such secondary binder as a coating or film on the foot side or surface. We have found that such an insole 1s characterized by the desired high Wet-souilresistant quality on its foot side, part1cularly when the Wet-scuff-proofing material or secondary binder is a thermoplastic rubber derivative, e. g. a rubber halide or hydrohalide, which, besides being highly Water-resistant, evidently bonds or amalgamates well with the rubbercoated or rubber-enveloped fibers of the felted fiber base. I

While not limited thereto, the present invention will now be described with particular reference to the accompanying drawing in terms of the production ofv Welt-insole stock having the desired high wet-scui-resistance on its foot side. In the accompanying drawing:

Figure 1 depicts diagrammatically and conventionally the infusion of the wet-scui-proofing material into the superficial pores of the artificial leather stock;

Figure 2 shows the finished stock in the form of a welt-insole blank;

Figure 3 represents a section through the blank on the line 3'3 of Figure 2; and

Figure 4 is asimilar section after the blank has been channeled to develop the usual stitchreceiving rib.

The artificial leather stock used for producing the welt-insole hereof may consist of a threeply structure, all of whose plies consist essentially of a rubber-impregnated felted fiber base. Thus, each ply may be prepared by impregnatformed from reined Wood pulp and/or other suitable cellulose iiber, with a rubber-latex composition to the desired solids or binder content and ,then drying the impregnated web; and the impregnated plies may then be facially bonded together in superposed relationship, as with rubber latex or other'suitable binder, into a threeply structure. Such a three-ply structure may, as appears best in Figure 3, comprise afoot-side ply f and a central ply c of approximately equal thickness, say, about 0.055", and an outer or external ply e of about one-half the thickness of the other plies, say, about 0.027. Both the foot-side ply f and the external ply e may be impregnated with a similar rubber latex composition to practically the same solids or binder content, for instance, to a solids content of about '75%, based on the dry weight of ber. The central ply c is preferably impregnated, as with a rubber latex composition, to a much higher binder or solids content, for instance, to a latex solids or rubber content of about 150%, based on the weight of ber. Such comparatively high binder or solids content in the central ply imparts thereto suflicient toughness or internal ply adhesion to enable channeling thereof as usual for the p rpose of developing, as shown in Figure 4, a stitch-receiving rib r of requisite toughness and stitchRholding qualities, especially after the usual gem-duck or fabric (not shown) has been cemented to the external plyl e and the margins of such fabric are bonded as a reinforcement to the ribl It might be noted that the resulting composite or three-ply sheet is possessed of substantial residual void space and moisture-transmitting quality such as comport with comfort to the foot when the sheet is used as insole stock. Y The three-ply'sheet is treated or superiicially impregnated on its foot-side ply f with the appropriate wetscuii`proong material. Thus, as illustrated in Figure 1, such sheet S may be progressively unwound from a roll or other accumulation R and passed over successive applicator rolls I0, I0, each of which may rotate partially submerged in a bath of the wet-scui-prooiing material and progressively 'pick up and apply a iilm of such material to the foot-side surface or ply of the sheet. Specifically, the Wet-scuproong material thus applied to the sheet may consist of a solution of thermoplastic rubber halide or-hydrohalide (e. g. Pliolite or Tornesite) in a suitable volatile organic solvent, such as gasolene, carbon tetrachloride, or the like; and such solution may be, say, about 15% to ing an absorptive paper web, for instance, a web 20% solute content and exhibit a thick or syrupy consistency. As the sheet passes into contact with the applicator rolls I0, it is preferably pressed against such rolls by adjustable rolls I I, which ride or bear against the sheet and whose pressure against the sheet is correlated with the concentration of treating solution, rate of rotation of the applicator rolls, and linear speed of the sheet so that the desired or requisite amount of solution is infused locally into the surface pores or portion of the sheet in the substantial absence of any lm or coating on the surface. The surface-treated or locally Vreimpregnated sheet may then be passed through an air-drying chamber, in which it may be exposed while hanging from festooning bars to hot air currentsuntil it is dried and ready for accumulation as a roll I3. In the case of such wet-scuH-proong material as the thermoplastic rubber derivatives indicated, it is important that the temperature of the drying medium is not too high or that the time to which the sheet is exposed to the hot drying medium is not too long, since such material might be fused and caused to flow unduly from the surface portion into the body of the sheet, thereby detracting from the surface-proofing effect desired. It has been found that the desired retention or localization of such material at the surface portion of the sheet during drying may be realized by using as the drying medium air heated to a temperature downwards of about 212 F., say, about 180 F.

In actual practice, the desired proofing of the foot side of the welt-insole stock may be realized with only about 2 to 6 grams of the wet-souffproofing rubber derivative per square foot of stock, provided that virtually all of such proofing material is sunk or infused immediately below the surface, insomuch that there is no sensible coating or film of such material left on the surface and the fibrous texture of the surface is apparent. Through such a surface proofing treatment, it was possible so to improve the weltinsoie stock that, whereas the untreated weltinsole stock quickly deteriorated and became unsightly on its foot side under drastic conditions of use, namely, in a workmans shoe, the treated welt-insole hereof used under the same conditions gave no sign of failure after months of use. It might be noted that the surface proofing treatment hereof, although increasing the surface-tightness of the insole, does not destroy its porosity. Thus, a number of Gurley airporosity tests made simply on the foot-side ply after the surface proofing treatment or impregnation hereof showed values ranging from 75 to 250 seconds for 100 cc. of air forced or transmitted through an area of 1" diameter, whereas similar tests on such ply before the surface treatment or impregnation hereof showed much lower values, namely, from less than l second to 10 seconds. These particular values were secured with a foot-side ply pf the particular characteristics of thickness and rubber latex impregnant content already indicated for the foot-side ply f. In many cases, the Gurley test on the bonded or plied-up and surface-treated or scuff-proofed insole product hereof (i. e. after the seuil-proofing treatment on the foot side) runs under 300 seconds, indicating that the residual voids in the plies of such product may inter-communicate'to a very great extent.

It is vitally important that the wet-scuf-proofing material be sunk or infused practically entirely and locally into the pores of the insole at and immediately below the foot side r surface in order to realize satisfactory results. When such material is deposited largely or to a substantial extent as an external coating or film on the surface of the foot-side ply, it tends to crack and check during wear and also to burn the foot on account of its practically complete destruction of the porosity or breathing quality of the insole; and perspiration stains the surface cracks and checks and quickly renders the insole unsightly. By sinking or infusing the wet-scuif-proong material to the proper degree locally into the surface pores or portion of the foot-side ply, it is possible desirably to retain the surface porosity or breathing quality of the insole and thus to avoid burning of the feet while at the same time realizing the marked surface-reinforcing effect or high wet-scuff-resistance with but very little usage of such material, since such material is not dissipated throughout the body of the insole but, rather, is

concentrated to only a limited depth in the insole, namely, a depth constituting only a very small fraction of the thickness of the binderimpregnated insole body or fibrous base.

The insoles to which the wet-scuff-proofing treatment hereof is applied are broadly of the binder-impregnated felted fiber or paper base variety and are possessed of substantial void space and moisture-transmitting quality. It is possible to use other than rubber as the primary binder or impregnant throughout the base, for instance, rubber 'latex compositions or compounds containing such other binders as casein, viscose, starch, or the like, or to use essentially a non-rubber binder, for instance, a starch binder such as is disclosed in Schur et al. application Serial No. 207,308, filed May 11, 1938. Insoles or insole stock embodying the present invention may be of various thicknesses and be of single-ply or multi-ply structure and of various primary binder contents. It is usually preferable, however, to build up the insole stock to the desired thickness from two or more binderimpregnated felted fibrous plies of similar or dissimilar contents of binder, such as rubber. Indeed, in the case of a welt-insole, it is, as already indicated, usually advantageous to build up the insole structure or body from at least three binder-impregnated plies, the central ply of which is of markedly higher binder content than the surface plies and the outer ply of which is thinner than the foot-side ply. However, the welt-insole might be made up of two plies with a foot-side ply of markedly lower rubber content than the outer or under ply, for instance, with a foot-side ply of a rubber content of about 60% to 90%, based on the weight of fiber, and an outer or under ply of a rubber content of about to 200%, based on the weight of fiber. A welt-insole structure thus produced and, in accordance with the present invention, scuff-proofed on its foot side has been found to be eminently satisfactory for use in lieu of a much more expensive leather welt-insole, especially when halogenated thermoplastic rubber derivatives constitute the wet-souff-Proong medium in combination with a rubber primary binder in the felted fibrous base or insole body.

We claim:

1. An insole consisting essentially of a porous, binder-impregnated, felted fiber base whose foot-side portion contains a halogenated, thermoplastic rubber derivative in the amount of about two to six grams per square foot practically completely confined to the pores at the foot-side surface and to pores extending from such surface to a depth constituting only a small fraction of the thickness of said base, said footside portion, despite its content of said derivative, being possessed of appreciable residual porosity, as determined by its capability of transmitting an appreciable amount of air under Gurley test.

2. 'An insole consisting essentially of a porous, rubber-impregnated, felted iiber base whose foot-side portion contains a halogenated thermoplastic rubber derivative in the amount of about two to six grams per square foot confined practically completely to the pores at the footside surface and to pores extending from such 15 surface to a depth constituting only a small fraction of the thickness of said base, said foot-side portion, despite its content of said derivative, being possessed of appreciable residual porosity, as determined by its capability of transmitting an appreciable amount of air under Gurley test.

3. An insole consisting essentially of a porous rubber-impregnated, felted fiber base containingl as an additional impregnant in its foot-side portion a thermoplastic rubber derivative practically 2.

completely concentrated in and immediately below the surface pores of the foot-side, said footside portion, despite its content of said derivative, being possessed of appreciable residual porosity, as determined by its capability of transmitting an appreciable amount of air under Gur--Y- ley test.

4. An insole consisting essentially of a porous, rubber-impregnated, felted fiber base containing as an additional impregnant in its foot-side portion a halogenated thermoplastic rubber derivative in the amount of about two to six grams per square foot practically completely concentrated in and immediately below the surface pores of the foot-side, said foot-side portion, despite its content of said derivative, being possessed of appreciable residual porosity, as determined by its capability of transmitting an appreciable amount of air under Gurley test.

5. An insole consisting essentially of a porous, binder-impregnated, felted ber base containing as an additional impregnant in its foot-side portion a thermoplastic rubber derivative practically completely concentrated in and immediately below the surface pores of the foot-side, said footside portion, despite its content of said derivative, being possessed of appreciable residual porosity, as determined by its capability of transmitting an appreciable amount of air under Gurley test.

MILTON O. SCHUR. EDWARD M. ARCHER.

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