December i, 1903.] 



THE INDIA RUBBER WORLD 



79 



over the older tubing machine method. The two principal ad- 

 vantages are much greater speed of covering ar.d consequently 

 increased output. Also more perfect insulation, due to the pos- 

 sibility of applying the stock in two or more plies, thus rem- 

 edying any defects in one ply by the stock in the next ply. By 

 using calendered sheets of different colors the plies of the insu- 

 lation are distinctly shown and the fact of double insulation in 

 this way easily verified. 



Several machines for performing this class of work have been 

 devised. In general principle they are much alike. The ma- 

 terial for insulation, in the form of thin sheet stock, is slit or 

 cut into bands or strips of appropriate widths varying with the 

 size and number of wires to be covered. The rubber strip is 

 then placed on reels arranged to feed into the covering device 

 folded around or laying both above and below the wires. The 

 covering mechanism consists of sharp edged grooved rollers 

 known as "caliper compression " type, because they both span 

 the wire and compress the stock upon it. The groove takes in 

 both wire and surrounding stock and by the revolving shear- 

 like action of the rollers on each side of the wire the rubber 

 sheet is compressed snugly to the wire and a butt joint or seam 

 is neatly formed in the insulation close to the wire as the ex- 



XX 



TWO HEAD RUBBER COVERING MACHINE. 



cess of stock is sheared off. The knitting of the two parts of 

 the sheet as it is sheared by the grooved edges of the rollers is 

 dependent on the adhesive property of raw or unvulcanized 

 rubber compound. By arranging the machine with the appro- 

 priate grooved covering rollers in two housings on the same 

 frame, several wires at once may be successfully covered as they 

 pass through and thus double insulation be effected with great 

 rapidity. 



Among recent developments in this class of rubber ma- 

 chinery may be mentioned that perfected by the New England 

 Butt Co. (Providence, Rhode Island). This is a two head 

 machine adapted for covering three wires with either one or 

 two seam rubber covering. It is shown in an illustration on 

 this page and consists of a rigid frame provided with heads 

 driven by bevel gearing from the main shaft which runs along 

 the side of the frame. The front head — that is, the head which 

 covers the outside layer of rubber — is positively driven, 

 while the rear heads are provided with friction devices 

 which permit slightly different speeds of the wire on 

 account of the differences in diameter. Each head is 

 provided with compensating gearing, which allows 

 the use of caliper compression rollers of different 

 diameters. By this arrangement the rollers can be 



turned down when dull and used until considerably reduced 

 in diameter. The heads are so arranged that the inside hous- 

 ing can be taken away in order to change the rollers, without 

 removing the shafts, gears and bearings. Each head is pro- 

 vided at the back with a wire guide and adjustable rubber 

 guide, and at the front with a pair of rollers to remove the rub- 

 ber scrap automatically. When desired the machine is pro- 

 vided with a taping head, placed at the extreme end of the 

 frame. 



The machine shown in the illustration is intended for cover- 

 ing single wires or strands from No. 20 Browne & Sharpe gage 

 to strands with an outside diameter over the covering of about 

 one inch. This machine will also cover three wires at once, in 

 sizes up to No. 12 Browne & Sharpe gage. Its capacity on No. 

 14 wire using the three groove cutters is 70,000 feet per day of 

 ten hours. A larger machine is built for large size wires and 

 cables, running from 1 inch to 2}£ inches outside diameter of 

 the covering. 



MOLDING SOLID CARRIAGE TIRES. 



In the manufacture of solid carriage tires the tubing machine 

 is indispensable. The stock must be mixed and handled at 

 a temperature that will insure its not being burnt in the pro- 

 cess. The various sizes are run as nearly as possible exact to a 

 template of the finished goods. In some factories it is the 

 practice to cold press the stock in wooden molds made in du- 

 plicate of the metal curing mold. In this way the tire is 

 shaped and all excess of stock saved in the unvulcanized con- 

 dition. The molding and curing takes place generally in 

 lengths of 14 feet in an hydraulic press. The old method of 

 clamping the stock in a mold and curing in open steam, being 

 too slow and expensive, is now in disuse. A few factories are 

 making solid tires in continuous length of any desired meas- 

 ure. This is merely a matter of making shift after shift and 

 splicing, on account of the wires, which are generally about 16 

 feet. 



The great difficulty formerly experienced in keeping the 

 holes in their proper locations in the base of the tire, has been 

 overcome by simply running the stock to exactly fit the molds 

 and, in that way, the overflow of surplus stock is reduced to a 

 minimum. In case there is much excess of stock in the mold; 

 its escape sidewise deflects the wires badly out of position and 

 renders the tire worthless. With the stock carefully run to fit 

 the molds it is only necessary to permit the straight wires to 



FIVE DIE ROTARY WIRE STRAIGHTENER WITH LOOSE PULLEY. 



lie in place during the curing with their ends protruding free. 

 The precaution must be observed to keep the wires constantly 

 straight. This can only be done by passing them regularly 

 through some form of power straightener, after each removal 

 from the tire. The usual form of straightener is the rotary 



SECTIONAL VIEW OF FIVE DIE ROTARY WIRE STRAIGHTENER. 



