US2170376A - Method of stiffening shoes - Google Patents

Description

Patented Aug. 22, 1939 PATENT OFFICE METHOD or STIFFENING SHOES Karl Mayer, Landau Pi'alz, Germany No Drawing.

rial No. 38,847. In 1934 2 Claims.

The present invention relates to a cap-stiffening material for use in the manufacture of boots and shoes, and a method of applying same.

It is already known for stiffening the toe-caps 5 or heel-caps of footwear, to employ stiffening materials consisting of fabrics coated or impregnated with solutions of Celluloid or nitrocellulose.

Cap-stiffenings prepared from these materials are usually applied by dipping them for a few minutes in a solvent, such as acetone or methyl acetate and the like (or steaming them with the vapours of said solvents), in order to soften them, after which they are inserted between the upper leather and lining, so that, while in the softened condition, they adapt themselves to the shape of the last and unite with the leather and. lining,

when the upper is drawn on to the last, in a lasting machine.

These cap-stiffenings, however, have various considerable defects. A first, and highly important defect is that such stiffenings require very large amounts of solvents, both in dipping and steaming, for the purpose of softening the coating or impregnating agents, and therefore absorb large quantities of said solvents, so that the stiflenings become very wet'and smeary.

If such a softened cap stiffening be then inserted between the upper leather and the lining, the solvent absorbedby the stiffening readily penetrates through the leather-especially in the case of colored and patent-leather shoes-so that stained patches appear on the leather. Bubbles and wrinkles also appear, in the case of patentleather shoes. Moreover, owing to the very smeary character of the. impregnation, the cap stiffenings adhere but imperfectly to the leather, so that they ruck up whenthe upper is being drawn on to the last, and the stiffening has to be inserted over again; or else, if the rucking has 40 been overlooked, the footwear will be rendered defective and even become a throw-out. In addition, the drying of the adhesive takes a comparatively long time. i

Another defect is that, owing to the smeary nature of such cap stiffenings, the hands of the operative who inserts the stifienings become soiled and it becomes impossible to avoid soiling the leather itself, a circumstance which is specially detrimental in the case of leathers of delicate color, sincethe dirty stains can hardly be eradicated.

steaming be given, only the external layer of the coating or impregnation of the cap stiffening will 5 be softened, leaving the inner layers almost un- Application August 31, 1935, Se-

Germany November 3,

affected. In such case, the inconvenience results that no satisfactory adhesion can be obtained, because, unless the Celluloid or nitrocellulose impregnations have become sufliciently moist and soft, the cap stifienings adhere to the leather in 6 an imperfect manner.

In order to economize in the use of the solvent needed for the softening of the coating or impregnation, and especially to prevent such large amounts of the solvent, as would lead to the aforesaid inconveniences, from being absorbed by the cap stiffening during this treatment, it has already been proposed to apply the impregnating agent, not in the form of a layer, but by depositing it in a porous state on or in the fabric or felt, so that the latter is more easily acted upon and softened by the solvent employed in dipping or steaming. Nevertheless, the aforesaid inconveniences cannot be entirely obviated even with these cap stiffenings.

A further drawback in the employment of fabrics or hard felt, coated with celluloid solutions, consists in that such caps are diflicult to skive and that the skived surfaces'of such-caps curl up towards the coated side, so that the edge of the skivirig is palpable and discernible through the leather of the upper and, consequently, unsatisfactory footwear results.

It has now been ascertained that the aforesaid defects can be rectified completely by employing a felt--preferably felt that has not been fulled for the cap stiffenings, and impregnating said felt with a solution of a mixture of nitrocellulose and an artificial resin of strong adhesive power and miscible in nitrocellulose, such as a phenylformaldehyde resin.

When softened, such cap stiffenings are distinguished by a high adhesive capacity towards I leather, and, since they require only comparative- 1y small quantities of solvent for softening them, the aforesaid inconveniences cannot arise at all.

Thus, it has been determined, by experiment, .that, in order to make them workable, the soften- .ing of the cap stiffenings hitherto known requires the absorption of about three times the quantity of solvent needed for the new cap stiffenings. Consequently, when the new cap stiffenings are being applied, they are not smeary, but only slightly moist, so that all penetration of moisture through the leather, any soiling of the leather, and any rucking-up of the stiffening in drawing the upper on to the last, is avoided.

Since the new. cap s'tiffenings do not become smeary in softening, they can also be introduced, in packs or bundles, into the steamer, without any fear that they will stick together by contrast, the cap stiffenings hitherto known have to be placed separately in wire frames thus entailing substantially more labor.

At the same time, the employment of un-fulled felts has the advantage that, in the softened condition, the cap stiffenings adapt themselves very readily to the shape of the last when drawn on to the latter, so that no injurious creases are formed during the operation, and the usual beating out of such creases is obviated.

Owing to the high adhesive properties of the new cap stiifenings, their application and the building up of the footwear can be effected in a simpler manner than heretofore, a point which will be referred to later.

Forthe construction of the new cap stiffenings, an un-fulled hair or woolfelt can be used with'advantage, preferably a felt consisting of equal proportions of cotton fibres and sheeps wool, with-the usual dressings. Such felt can be impregnated, in the usual manner, by spreading, dipping or spraying. The impregnating agent may consist of a mixture of about 20-80 parts of nitrocellulose and 80-20 parts 'of an artificial resin. A preferred mixture is composed of parts of artificialresin and 50 parts of nitrocellulose, dissolved in a quantity of a solvent, such as acetone or methyl acetate, as will furnish a solution of low viscosity, for example, one of 30-60% strength. This mixture may be treated with an addition, in known manner, of plasticising agents such as striphenyl or tricresyl phosphate, or the like, (for example, with an amount corresponding with about 10% of that of the nitrocellulose and resin), and also with other fillers.

'If desired, the felt may also be impregnated successively with agents of different composition, for

example, by employing, for the first impregnation a solution containing a larger proportion of resin, and a solution lower in resin for the second treatment.

Example A sheet of dressed but un-fulled felt, about 1 mm. thick, and composed of equal parts of cotton and sheeps wool, is impregnated by dipping, spraying or spreading with a solution of 250 parts of artificial resin and 250 parts of mtrocellulose in 1000 parts of acetone (with which 50 parts of a plasticising agentsuch as triphenyl phosphate-and fillers may be incorporated if desired), the felt being then dried.

The cap stiffenings stamped out of a sheet of felt impregnated in this manner, can be applied as follows:

After skiving, the cap stiffenings are first softened again by exposing them, in known manner, to the vapours of a solvent (such as acetone) in a closed apparatus. The softened stiffeningwhich feels merely damp and, owing to the addition of resin, has not become smeary-is then inserted in the shoe upper, between the leather and the lining, the upper, with the assembled stiffening, being then placed in a. press, in which the stiffening is pressed into contact with the leather'and lining for a few moments. Owing to the high adhesive capacity of the cap stiffening, especially when pressed, the stiffening immediately attaches itself firmly to the leather and lining, so that the upper'can be further treated at once, and drawn on to the last without any fear of the stiffening rucking up. As the result of unfulled feltbei-ng employed, the softened stiffening readily adapts itself to the shape of the last in use, without becoming creased, so that beating out becomes unnecessary. Moreover, since the stifiening need only absorb a small quantity of solvent for softening, none of the solvent peneinsole with tacks and cemented on with an adhesive. The object of the nails is to hold the cap on to the insole until it is dry and the adhesive has set, which usually takes an hour or more. Afater this drying period, all the nails are taken .out again, and it is only after this has been done that the surplus, overlapped leather can be cut away in order to continue building up the shoe.

In the case of so-called welted goods (Goodyear), the cap after being drawn over on to the last is attached to the insole by means of a wire drawn along the lip of the insole, over the edge of the upper (instead of by tacking) until the inserted cap is dry, whereupon said wire is removed before sewing the lip of the insole, the edge of the upper, and the welt. To accelerate the drying of the capand of the aforesaid adhesive, if necessary-the shoes can also be put through drying stoves, though this increases the cost of production.

If a cap stiffening according to the invention be used, the fixing of the turned-in and cemented caps on the insole by tacks or wire staples, to prevent the still wet caps'from becoming detached from the insole, is obviated entirely.

Since, as already mentioned, the cap stiffening according to the invention absorbs only very little of the solvent, in the softening process, this small amount of solvent can be expelledfor example by a supply of hot air-in fixing the upper leather on the insole, so that the cemented cap can dry very quickly and thus retain its molded shape, without any fear of the cap becoming detached.

When a cap stiffening according to the invention is used, lasting can therefore be performed in the following manner. In the first place, the cap is turned in on the pulling-over machine in the usual way, over the last, or over the insole,

the edge of which has previously been coated d with an adhesive, such as the aforesaid impregnating medium, and dried again. Since, in this operation, the impregnating medium of the cap stiffener, penetrates slightly through the lining, the said adhesive on the insole is softened again, so that the desired adhesion between insole and upper is obtained. According to the invention, however, instead of securing the moulded damp cap to the insole, by means of tacks or a staple, until it is dry, a current of warm air is directed on to the molded cap for a short time, such as /21 minute, by which means the cap and, in particular, its adhesive dry at once, so that the cap remains attached to the insole without loss of shape, and the shoe can be further worked, immedesired connection between upper and insole can be ensured, in molding, through the penetratedimpregnating medium alone, without the application of adhesive-to the insole. Consequently, by employing the cap stiffening according to the invention, an intimate and durable connection can be established between upper and insole in a simple working operation, namely molding, without having to use any further adhesive, tacks or staples.

Instead of directing a current of warm air on the part to be cemented, the grippers or pincers may be heated, for example electrically, the same result being obtained. This procedure; however, is feasible only in the case .of the cap stiffenings according to the invention, since, ow-

ing to the special method of impregnation, theyabsorb but little of the solventv in softening, have very strong adhesive properties, owing to the joint use of the artificial resin, and set hard quickly and retain their shape, under the short drying treatment.

A further advantage of the new cap stiffening consists, finally, in that in the event of the lasting operation not proceeding quite satisfactorily, the stiffening can be again softened, by treatment with steam, after the first drying and setting, so that the said operation can be repeated very quickly.

In addition to toe-caps, the described capstifiening material.can of course be used for stifiening the. heel parts of the shoe, without requiring' any further adhesive, such as Vienna.

glue.

To sum up, the new cap stiffening therefore possesses over the known stifienings, the advantages that, by the employment of un-fulled felts, it readily adapts itself to lasts of all shapes, requires only a small amount of solvent for softening-so that, on the. one hand, solvent is economised, no solvent penetrates through the leather, and quick drying is possible-rand,

finally, that the lasting operation can be performed, without the use of tacks or staples, by

the simple evaporation of the solvent at the cemented places.

I claim: Y

1; Method of manipulating shoe tip stilfeners' of felt impregnated with a mixture of nitrocellulose and an artificial resin miscible with nitrocellulose, including the steps of inserting the softened tip stiffener between the upper leather and the shoe lining,.briefiy pressing together the upper,'stifiener, and lining to unite same, pulling the resultant reinforced upper over the last with the upper edge projecting beyond the last, turning in the projecting-upper edge over the inner sole resting on the last by means of the wipers onv the lasting machine, and directing hot air onto the juncture between the upper edge and the inner sole until the said juncture is dried.

' 2. Method of manipulating shoe cap stifieners cpmprising impregnating a cap stiffener material with a mixture of nitrocellulose and'an artificial resin miscible with nitrocellulose, coating the lower edge position of an inner sole with said mixture and then drying said coating, moistening the impregnated stiffener material with solvent for the impregnating material to soften said material, inserting the softened cap stiffener material between the upper leather and the lining, briefly pressing together the upper, the stiffener and the lining to unite same, pulling the resultant reinforced upper over the last with the edge of the upper projecting beyond the last and beyond theedges of an inner sole resting against the last, turningin the projecting edges of the upper over the edges of the inner sole, ano simultaneously heating the juncture between the edges of the upper and inner sole to dry same