August 1, 1921 



THE INDIA RUBBER WORLD 



801 



A non-slip American compound is made up of these ingredients : 

 rubber, 18 pounds; litharge, 10 pounds; whiting, 20 pounds; 

 flowers of sulphur, 11 ounces; lampblack, 8 ounces; and to which 



A — Wire Brusil; B — Grindstone; C — Speed Counter; D — 



Levee on Which Sample Is Tested: E — Weight Forcing 



Sample Against Grindstone: F — Box for Rubber Soling 



Sample 



Device for Testing Rubber Soling Compounds 



is added coarse emery or other gritty substance in weight equaling 



the rubber and the other ingredients. 



A leather compound designed primarily for horseshoe pads, 



but. which it was stated could be used also for soling, is as 



follows : 



Parts 



Fine Para rubber 5 



Reclaimed rubber 3 



Golden sulphuret of antimony 5 



Lime 8 



Magnesia - 



Zinc oxide 1 



Rubber satvrated and coaled fibers 19 



Sulphur 5 



Total 48 



The batch is vulcanized under 2,000 pounds pressure for 40 

 minutes. If a more heat-resistant compound is desired, 2 parts 

 of asbestos fiber are added to the other 48 parts, the fiber being 

 either natural or rubber-coated. 



An artificial sole composition calls for crude rubber, ground 

 frictioned fabric, sulphur, and an alkali ground up in a mixing 

 mill. 



Standard soling for a large percentage of the high-grade rub- 

 ber shoes now worn is made up of four layers : rubber tread 

 surface, sheeting and friction, felt and cork, and sheeting lining. 

 UNUSUAL TYPES OF RUBBER SOLES 



A rubber sole having for its tread strands of stout cord held 

 together with rubber and stretched across the sole between the 

 toe and the shank — the shank and the heel being of rubber only, 

 or of rubber and fabric — is a comparatively recent invention. 

 In making the sole, after the pattern is stamped from a thin strip 

 or sheet of rubber, the cords are drawn under and over the sur- 

 face of this strip and held in place above with another and 

 stouter strip or sheet of rubber. The tread strands are cemented 

 with rubber solution to the under side of the lower strip, and 

 the whole vulcanized. 



While knurling and corrugations are much used on the soles 

 of rubber boots, rubber sole manufacturers either dispense with 

 them or use such "anti-skid" features in a much more modified 



form. The typical patterns shown in the illustration vary from 

 the soles having perfectly plain surfaces to the soles having 

 doubly-thickened taps and heels, soles with many small concavi- 

 ties like vacuum cups on thickened tap and heel portions, and 

 soles having crosswise ribbing and other designs intended to 

 give the wearer a firmer foothold. A rubberized crimped or 

 fluted fiber sole and a friction-plug rubber sole having a tough- 

 ened fabric inset in tap and heel are other types that have found 

 favor. 



MODERN SHOE MACHINERY USED 



One of the impediments to the progress of the rubber sole has 

 been the fact that such soles have not been adapted to modern 

 shoemaking machinery. Unable with standard apparatus and 

 ordinary factory methods to attach rubber soles to uppers in the 

 making of turn-shoes with single-faced stitches, manufacturers, 

 even though well-disposed toward the innovation, naturally side- 

 stepped the problem, and through this circiunstance rubber soles 

 failed to attain the vogue that they had fairly earned. Finally 

 United States Patent No. 1,296,894 was granted to Sidney W. 

 Winslow, Jr., of Beverly, Massachusetts, and assigned to the 

 United Shoe Machinery Co., of Paterson, New Jersey, that met 

 just such a condition, and whereby a rubber compound turn sole 

 could be produced which would enable a manufacturer of leather 

 shoes to make an attractive and serviceable rubber-soled turn shoe 

 with his regular machinery. The inventor contrived a rubber 

 compound sole having imbedded by vulcanization in its upper side 

 a low, upturned, folded fabric sewing-rib following the outline of 

 the sole and but a short distance from the edge. Thus another 

 great difficulty was surmounted and incidentally a decided impetus 

 given to the rubber sole indu.stry. The practically correct com- 

 pound having been found, an ideal method of attaching the rubber 

 soles to uppers had been devised, capping the climax, as it were. 

 RUBBER SOLE TESTING MACHINES 



Despite the fact that they have produced a material that amply 

 fills every reasonable requirement and more, rubber sole manu- 

 facturers are not yet wholly satisfied. They continue making and 



Bureau of Standards Rubber Sole Testing Machine 



testing out new compounds in the hope that a still better product 

 may yet be evolved. Simple but efficient is the device used for 

 determining the toughness or wearing quality of the various 

 samples of soling. A grindstone about 8 inches in diameter and 

 3 inches thick is mounted on a stand. Touching it above is a 

 revolving wire brush which keeps the stone clean, and beneath 

 the stone is a pivoted wooden lever. A sample of soling is 

 fastened to the lever near the grindstone and a IS-pound weight 

 is hung upon the other end of the lever, thus pressing the sample 



