United States Patent 3,201,812 LEATHER CONDHTIONIN G Hubert Q. Chaplin, Leicester, England, assignor to United Shoe Machinery Corporation, Boston, Mass, :1 corporation of New Jersey No Drawing. Fiied July 25, 1963, Ser. No. 297,691 (liaims priority, application Great Britain, July 27, 1962, 28,854/ 62 7 Claims. (Cl. 12-146) This invention relates to a method of conditioning leather and, more specifically, to a process of mulling or tempering an article of leather to distribute moisture therethrough.
The shoemaking industry has been involved throughout its history in a constant and penetrating search for technical improvements and, in recent years, for methods and apparatus which facilitate increased automation. One of the principal operations in the shoemaking cycle which has impeded the advancement toward complete automation is the mulling or tempering of the leather. The purpose of mulling or tempering is to render the leather more workable thereby to permit flexing and stretching thereof. Thus, mulling or tempering is an important prerequisite to a large number of shoemaking procedures.
Heretofore, a common method employed for mulling or tempering leather has been to house the leather in a moist atmosphere for an extended period of time thereby to ensure the distribution of water throughout the leather. Another method of tempering leather was accomplished by dipping it in cold water for a period of hours and allowing it to drain. The result of these operations was uniformly moistened leather which was easily worked. The procedure was, however, time consuming and, therefore, costly. Further, it did not lend itself to automation and diluted the value of the automation of appurtenant operations. The need for a method of mulling or tempering leather which would facilitate the integration of these operations into an automated shoemaking cycle has been long felt and desired. Adequate mulling or tempering could not be sacrificed for increased automation due to the detrimental effects on operations dependent thereon. To do so would be to thwart the purpose of automatation. tion is to provide an improved method of conditioning leather which materially decreases the time required for the mulling or tempering thereof.
A further object of this invention is to provide a novel method of conditioning leather which facilitates the integration of the mulling or tempering operations into an automated shoemaking cycle.
The specific application of the subject invention hereinafter delineated in the specification is concerned with the tempering of outsoles for welted shoes. The subject invention is disclosed by the definition of this specific application in order to facilitate a complete and facile description thereof. However, this is not to be construed to, nor is it intended to, limit the application of this invention. The method of the subject invention is intended for all applications wherein increased workability of leather or similar articles is desired.
A conventional method utilized in the manufacture of welted shoes comprises applying a coating of rubber latex to the flesh side of the outsole to facilitate adhesion of rubber solution to the damp outsole during the sole laying operation, the latex being allowed to dry and coagulate, tempering the outsole by dipping it in cold water for a period of from two to twelve hours, and allowing the outsole to drain. Thereafter, the operations of sole-laying, rounding and channelling, lip raising, stitching, channel laying and heel attaching are completed. The deficiencies stated hereinabove relative to the generic application of the sub- 3 ,Zh 1,8 l 2 Patented Aug. 24, 1965 ject invention are equally applicable tothe manufacture of welted shoes, as illustrated by the above defined method.
Accordingly, a more specific object of the subject invention is to provide a method of tempering outsoles during the manufacture of welted shoes, a correlative object being a reduction of the time required therefor and the adaptation thereof for integration into an automated shoemaking cycle.
To this end and in accordance with a feature of the present invention, there is provided a method of conditioning leather comprising subjecting the leather to a conditioning solution, applying a substantially impervious or continuous coating on one side thereof, and heating the coated side while maintaining the opposite side against a surface having a temperature lower than that of the heat ing means.
The above and other features of the invention will now be described.
The technical phenomenon which facilitates the implementation of the subject method is that moisture applied to one surface of a permeable article of manufacture can be rapidly and uniformly distributed within the article by the establishment of an appropriate temperature gradient thereacross. The rapidity with which the moisture is dispersed is dependent upon the temperature difference constituting the gradient, the inherent character of the article, and the condition thereof prior to the operation. The moisture on the high temperature side of the article would have a higher vapor pressure than that on the low temperature side and, thus, a pressure gradient is produced as a result of the temperature gradient. This pressure dilferential or gradient drives the moisture into and through the article. Thus, the establishment of hot and cold sinks on opposite sides of a piece of leather or similar article of manufacture can be utilized to distribute water or other conditioning solutions applied to the surface subjected to the hot sink.
In the application of the subject invention in the manufacture of welted shoes, the outsole is initially moistened by the application of a conditioning solution such as water. In the preferred embodiment, water having a wetting agent therein would be employed, the wetting agent preferably comprising sorbitol, phenol and aluminum sulphate. The soles are thereafter coated on the flesh side with rubber latex. The coating functions to seal the flesh side of the outsole against loss of moisture during the subsequent portion of the method. The coated flesh side is thereafter heated and the opposite grain side concurrently maintained against a smooth flat surface such as a wooden block which constitutes a cold sink. The heating means is preferably infra-red lamps or other radiant heating elements. The tempering is accomplished in two to four minutes and the leather remains in the tempered workable condition for approximately one hour. The radiant heat also assists in drying and coagulating the rubber latex employed in this particular application of the subject invention.
As stated above, the invention is not limited to the specific application defined in the preceding paragraph. Any article of manufacture which is permeable by water or other conditioning solution may be mulled or tempered by this method. Thus, upper leather can be prepared for the lasting operations by the use of this novel process. The particular conditioning solution and coating material may be varied in accordance with the requirements of the article being mulled or tempered. Rubber latex is used in the above defined procedure for welted shoes as it additionally facilitates adhesion of a rubber solution to the damp outsole. However, any substantially impervious or continuous coating material which would seal the moisture in the article is equally satisfactory.
Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:
1. The method of conditioning leather comprising subjecting a leather article to a conditioning medium, applying a susbtantia-llycontinuous coating to one side surface of the leather article, and heating the coated side while maintaining an opposite side surface at a temperature lower than the heated side.
2. The method of conditioning leather comprising subjecting a leather article to a conditioning medium, applying a substantially impervious coating to one side surface of the leather article, heating the coated side, and maintaining an opposite side surface against the surface of a member having a temperature lower than the heated side during the heating thereof.
3. The method of conditioning leather comprising sub jecting a leather article to an aqueous medium, applying a substantially continuous coating to one side surface of the leather article to prevent the passage of moisture therefrom, heating the coated side, and maintaining an opposite side surface at a temperature lower than the coated side during the heating thereof.
4. The method of conditioning leather comprising applying va conditioning solution to one side surface thereof, applying a substantially continuous coating to said side surface, and heating the coated side surface while maintaining an opposite side surface at a temperature lower than the heated coated side thereby to cause diffusion of the conditioning solution through the leather.
5. The method of tempering leather comprising first applying a conditioning solution to a leather article, thereafter heating one side surface of the leather article, and maintaining an opposite side surface at a temperature lower than the heated side during the heating thereof to cause diffusion of the conditioning medium through the leather.
6. The method of tempering leather comprising applying an aqueous medium to one side surface of a leather article, heating the said side surface by radiant heat, and maintaining an opposite side surface against the surface of a member having a temperature lower than the heated side thereby to cause diffusion of the aqueous medium through the leather.
7. In the manufacture of welted shoes, the method of conditioning an outsole comprising subjecting the outsole to a conditioning medium, applying a coating of rubber latex on one side surface thereof, heating the coated side, and maintaining an opposite side surface at a temperature lower than the heated side during the heating thereof.
References Cited by the Examiner UNITED STATES PATENTS 2,109,425 2/ 38 Hurxthal 69-21 2,421,053 5/47 Card 12--4l.5 2,586,985 2/52 Olson et a1 69--21 2,690,069 9/54 Kahn 69-21 JORDAN FRANKLIN, Primary Examiner.