US2447578A - Art of stiffening the uppers of shoes - Google Patents

Description

at the'time of manufacture.

Patented Aug. 24, 1 948 ART OF STIFFENING UPPERS F SHOES Maurice Godfrey Hill and Charles'Alan Cooper, Leicester, England, assignors to United Shoe Machinery Corporation, Flemington, N. J., a

corporation of New Jersey No Drawing. Application April 24, 1942, Serial No. 440,350. In Great Britain May 10, 1941 This invention relates to the stiffening of portions of the uppers of boots and shoes and more particularly to an improved shoe' stiffener blank and to a method of making it.

A stype of stiffener blank in commin use comprises a fibrous base such as felt or cotton flannel impregnated with a solution of a colloidal material such as an ester of cellulose. With stiffener blanks comprising bases of fibrous material charged or impregnated with such a stiffening substance it is usual practice to arrange that at the time of insertion. in shoe uppers the blanks shall be in a relatively limp condition so as to permit conformation to the desired shape of the last and that, after lasting of the upper has been" carried out, they shall harden in the desired shape to provide the stiffening effect. This result may be achieved by conditioning the dry 3 Claims. (01. 154-46) stiffener blank just before use to bring it into the relatively limp condition; for example by the' action on the dry stiffener blank of a solvent for the stiffening substance, or by maintaining the blank in a relatively limp condition from the time at which it is made until the time that it colloidal stiffening substance in a closed container, such as a sealed can, until they are required for insertion into' shoes. The closed container prevents evaporation of the solvent so that, until required for use, the blanks remain in the relatively limp condition, but, after removal from the container and insertion in the shoe and con forming to the last, evaporation of the solvent is permitted and the blanks pass into the desired hardened condition. The terms solvent and solution are used herein in a general sense as embracing respectively swelling or dispersing agents and the condition attained by the action of such agents.

Such blanks usually have a load or charge of stiffening substance which is less per unit area at some localities than at others; and, when the blanks are maintained in their limp state until required for use, trouble has been experienced in that during the period of storage in the rela-' tively limp condition the solution of stiffening substance tends to seep or migrate, thereby destroying any desired ineqiiality of the charge at different localities which may have been imposed For example, if, asis usual, it is desired that the rear margin of a toe stiffener blank should have a lesser'charge of stiffening substance than there is in the remainder of the blank in order that in the shoe the rear margin of the hardened stiffener shall be less stiff than the remainder, this result will be deleteriously effected, if, during storage as referred to, the solution of stiffening substance seeps from other parts of the blank into the rear margin.

Accordingly, the present invention relates to restricting the flow of a colloidal stiffening solution in a stiffener blank which is limp and ready to be inserted in the upper of a shoe and to be conformed with the upper to a last, by supplying the blank with a gelling agent for the solution. The blank, thus treated, which is particularly adapted to be stored while limp in a closed container, thus has part at least of its stiffening solution in gelled condition so that seepage or migration of the solution is prevented or greatly restricted.

Cellulose derivatives, such as esters of cellulose, are the stiffening substances most commonly employed in stiffener blanks intended for storage while maintained by solvent action in relatively limp condition. It has heretofore been proposed, to render handling more easy, to treat blanks charged with nitrocellulose solution with water, steam or other non-solvent for the nitrocellulose, before storage in a closed container, such treatment causing a reduction of stickiness of the blanks, apparently by reason of the nonsolvent effecting a superficial precipitation of the nitrocellulose from the solvent vehicle. Such precipitation action is to be distinguished from a gelling effect as above referred to. The gelling effect may be obtained by the action of an agent 1 selected to cause gelling of a solution of the particular stiffening substance that is in question. For example, in the case where the stiffening substance is nitrocellulose, the most appropriate gelling agent which we have found is borax, although other agents may be employed, such for instance as ammonia or derivatives thereof such as hexamethylene tetramine.

The above and other of the various objects of the invention will become apparent, from the following description which is now given, by way of example of illustrative methods of preparation of shoe stiffener blanks in accordance with the invention. The kind of shoe stiffener blank with reference to the preparation of which the illustrative methods are hereinafter exemplified is a toe stiffener blank of the nature of that described in Letters Patent of the United States No. 2,140,614 granted December 20, 1938 upon an application filed in the name of William H. Bancroft; and it will be assumed that the stiffenin substance employed is nitrocellulose.

According to the method of the patent a measured quantity of dope (very viscous nitrocellulose solution) is delivered locally upon an absorbent layer, such as cotton flannel, of the desired shape and is spread over and forced through the desired area of the layer by the pressing action of a die, the cotton flannel layer being located between a partly absorbent layer, such as filter paper, adhesively attached to one surface of the cotton flannel, and an impervious layer. such as grease-proof paper. The die, by which pressure is applied to cause spreading of the dope and impregnation of the cotton flannel layer, has a cavity which is or such size and shape that a marginal portion of all three layers will project beyond the cavity, so that the projecting portion will receive heavy pressure, thus preventing transmission of any substantial quantity of dope thereinto. Assuming that a band of substantial width at the rear margin of the toe stifiener blank is to be kept relatively free from the stiffening substance, the layers will project further beyond the die cavity at the said rear margin than elsewhere around their periphery. After the dopespreading operation, the toe stiffener blank is removed from the die, and piles of such articles are marketed in sealed containers which prevent any appreciable evaporation of the solvent during storage. When required for use, the relatively limp article is removed from the container, the grease-proof paper layer stripped off, and the toe stiffener blank inserted in the shoe upper. Evaporation of the solvent in the blank will thereafter cause the blank to harden to the desired stiff character.

When toe stiffener blanks have been made in the manner just described, we have found that there has been a tendency, during the storage of the blanks, in their relatively limp condition in their containers, for the dope to seep or migrate of the article, and the less stiff character desired at the rear margin of the toe stiffener in the finished shoe may not be realized. Such seepage will ordinarily manifest itself after short periods of storage, but the blanks may not be used until periods of weeks or months after manufacture; and it is important that seepage troubles should not develop during such longer periods of storage.

We have found that such undesired dope seepage may be avoided or reduced by causing the dope to undergo a gelling action which reduces any likelihood of its seeping during the storage period. For effecting such gelling of the dope, the most satisfactory manner of treatment known to us is subjection of the dope to the action of borax. The manner of introduction of the borax is not critical and it may be introduced in a number of different ways. For example, powdered borax may be lightly dusted upon the cotton flannel layer before or after the dope is applied thereto, or the borax may be in cluded in the adhesive used for uniting the cotton flannel layer and the filter paper layer, or the grease-proof paper layer may be treated with borax solution and dried before use. The gelling effect obtained by the action of the borax 4 on the dope does not exhibit itself immediately and therefore does not interfere with the spreading of the dope under the pressure, but develops over a period which may range from some hours to some days, being, however, shorter than any period within which seepage would normally occur. We have found that toe stiflener blanks in which the dope has been gelled, as referred to, maybe stored for any period (e. g. several months) likely to arise in practice before use of the blanks, without any appreciable seepage occurring, and, when the blanks are used, the stiffening effect obtained on evaporation of the solvent does not appear to have been adversely affected by the gelling treatment. A suitable borax solution for use as above referred to may be made by dissolving borax in water in the proportion of 60 grams of borax to one litre of water. A paper layer treated with such solution and dried will ordinarily provide a quantity of borax, in a toe stiflener blank as referred to, equivalent to about 0.9% of the weight of nitrocellulose in the dope in the .blank. A suitable adhesive for use as above referred to may comprise glue, borax and water in the respective proportions of 66, 84 and 225 parts by weight. Such an adhesive will provide, in the blank, up to about ten times the weight of borax provided by the use of a borax solution as referred to.

With toe stiffener blanks of the character in question it is commonly desired that the blank should bond itself firmly to the upper materials in which it is introduced, such bonding apparently assisting the strength of the stiffened toe obtained. Normally when the grease-proof paper layer is stripped off one surface of the cotton flannel layer to make ready for the insertion of the blank in the upper, the surface of the cotton flannel layer thereby exposed is sticky and in a condition suitable to allow of a good degree of such bonding occurring. Although with blanks in which the dope has been gelled as above described no undue weakness in the strength of toes produced has been observed, yet it may sometimes be the case that the reduction of stickiness of the said surface of the cotton flannel layer resulting from the gelling of the dope may appreciably reduce the strength of its .bond with the upper materials. Accordingly it may sometimes be desired to localize the gelling effect by carrying out the borax treatment only marginally of the stiffener (either around the whole margin or at the rear margin only), leaving the main central portion of the blank, where seepage troubles are not usually in evidence, in the best condition for bonding. Again, if the borax treatment is eifected only on the face of the cotton flannel layer adjacent the filter paper layer (e. g. by including borax in the adhesive uniting the two layers last referred to) we have found that, while seepage ls adequately avoided, the gelling effect is somewhat localized to the dope lying close to the side of the cotton flannel adjacent the filter paper layer, while the dope at the surface'exposed when the grease-proof paper is removed is left in a more sticky condition so as to ensure good bonding.

So far as we are aware the inclusion of a small proportion of borax in the blank in the finished shoe is without adverse effect. It may be noted, however, that if, as above exemplified, the introduction of the borax is effected by impregnating the grease-proof paper layer with borax, sub-' stantially no excess of borax will remain in the toe stiffener in the finished shoe since the greaseproof paper layer is removed before the blank is inserted in the shoe upper.

Although the advantages of the gelling efiect have been set forth in connection with the dimculty arising from seepage of the untreated solution in stifieners which are stored while limp in sealed containers, it should be understood that such gelling efiect is of service in all cases in which a stifiener blank, limp by reason of the presence in it of a solvent, is inserted in the upper of a shoe. In all such cases it is desirable that the solvent should not be able readily to flow from the stiffener (as opposed to gradual evaporation) during the hardening of the stiffener, since, if such ready flow exists, the solvent is liable to penetrate the outer layer of leather and damage the finish on its exposed or display surface.

It has been stated hereinbefore that other gelling agents such for instance as ammonia or derivatives thereof such as hexamethylene tetramine may be employed. Such agents may be used in place of or in combination with borax. Moreover, as would be expected, we find other borates such as ammonium tetraborate, potassium tetraborate or sodium perborate are capable of giving similar results to borax.

Having thus described the invention, what we claim as new and desir to secure by Letters Patent of the United States is:

1. In a method of making a lamina ted stiffener blank which comprises assembling in superposed relation a plurality of layers of the desired shape one of which at least is pervious to a solution of a cellulosic ester impregnating stiflening substance, with a measured quantity of the solution between two of the layers, and subsequently exerting pressure upon both faces of the assembled stifiener to force the stiffening solution through the pervious layer, the pressure being greater on a. selected locality of the blank than on other localities of the blank whereby the locality sublected to greater pressure contains a smaller amount per unit area of stiffening substance than said other localities, that improvement which consists in supplying adjacent to said selected locality of the laminated article before the pressure is exerted, borax as a gelling agent to prevent seepage of said solution into said se lected locality.

2. A shoe stiffener blank of fibrous material impregnated with a solution of a cellulosic stifl'ening substance, 2. selected locality of said blank containing a smaller amount per unit area of stifiening substance than other localities of said blank, said stiiiener being in a limp condition and in a closed container so as to be adapted to be removed from the container and immediately incorporated in the upper of a shoe, borax being present adjacent said selected locality of the stiffener as a gelling agent to prevent seepage of said solution into said selected locality, the ratio of solvent to cellulosic stiffening substance remaining substantially unchanged.

3. The method of making and storing shoe stiffener blanks which comprises providing blanks made of a fibrous base impregnated with a solution of a cellulosic stiffening substance, a selected locality of said blank containing a smaller amount per unit area of stiffening substance than other localities of said blank, said blank being treated adjacent said selected locality with borax as a gelling agent which has substantially no efiect upon the ratio of solvent tostiifening substance and hence upon the degree of limpness of the blanks, and placing the blanks in a closed container which restricts evaporation of solvent whereby the solvent is prevented from migrating in the blanks during storage and shipment.

MAURICE GODFREY HILL. CHARLES ALAN COOPER.

REFERENCESl CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,537,848 Macdonald May 12, 1925 1,593,184 Lionne July 20, 1926 1,720,795 Lunde et al July 16, 1929 1,790,240 Lionne Jan. 27, 1931 1,920,564 Jochum et al. Aug, 1, 1933 1,980,810 Lovell Nov. 13, 1934 1,983,622 Lovell Dec. 11, 1934 2,036,588 Lovell Apr. 7, 1936 2,218,844 Lovell Oct. 22, 1940 FOREIGN PATENTS Number Country Date 136,927 Great Britain Dec. 31, 1919 783,407 France July 12, 1935 OTHER REFERENCES Technology of Cellulose Esters by Worden, published in 1921, Worden Laboratory and Library. Millburn, N. J., by Worden; pages 1739, 1786 and 2574 cited.