THE INDIA RUBBER WORLD 



The Manufacture of Blow -Out Patches. 



Bx .hthur C. 



s that are 



motorist v 

 icxpecledly 



Bi.ou-OLT PATCHES arc emergency 

 carried in the repair kit of every cautioi 

 ticipates the time, tliai usually comes 

 the need is ur- 

 gent. They are 

 intended for an 

 emergency re- 

 pair and a pro- 

 tection to the 

 inner tube in 

 case of a blow- 

 out or fabric 

 break, and may 

 be easily and 

 quickly applied 

 on the road. 



Blow - out 

 patches are 

 made by tire 

 and other rub- 

 ber manufac- 

 turers special- 

 izing in tire 

 sundries. There 

 are two types 



of inside blow-out patches, the fabric and the cord. The 

 is intended for fabric tires and is provided with flaps that 

 outwardly between the beads and the rim, thereby holdi 

 patch tirmly in place. The cord patch is designed for cor 



always 



ho an- 

 , when 



CORD TIRE PATCH 



former 

 extend 

 ng the 



C.\LF.NDERIXC THE F.\BR1C. 



although it may be used in a fabric tire repair. The cost of this 

 patch, however, does not warrant such use, n.s a fabric casing 

 break tends to increase, and therefore should be properly re- 

 paired and vulcanized. An injury to a cord casing does not 

 have a tendency to grow larger, hence the cord patch can be 

 applied with cold patching cement and may wear as IcMig as 

 the tire. However, a vulcanized repair is undoubtedly more 

 permanent. 



While the process of making inside blow-oul patches varies 

 somewhat among manufacturers, fabric patches are usually built 

 up from four superposed plies of bias frictioned fabric of equal 

 width, each ply being stepped down longitudinally. The cord 

 patch is built up from bias cord fabric in the same way and 

 the edges of both types are tapered to a fine edge. 



The manufacture of blow-out patches includes the wrapped 

 and molded processes, the former being the most commonly used, 

 method and is briefly described as follows: .\ roll of 13-ounce 

 cotton duck, 36 inches wide and about 50 yards in length, is 

 thoroughly dried to free it from moisture. .\ length of pipe is 

 passed through the center of the roll, which is then placed hori- 

 zontally in bearings, and the free end of the fabric is passed be- 

 tween the middle and lower roll of the calender and fastened 

 to the stock shell. Previously, the rubber stock is compounded 

 and mixed on a two-roll mill. The formula commonly used 

 consists of : 



Smoked sheet 22 pounds 



Whiting 12 pounds 



Litharge 3 pounds 



Sulphur 1 '. J pounds 



CALENDERING. 



The calendering is done on a three-roll calender. After the 

 rubber dough has been warmed up on a special warming mill, it 

 is placed between the upper and middle rolls of the calender, 

 and when the calender is started and adjusted, the rubbei; passes 

 in a thin sheet on the middle roll which is somewhat hotter than 

 the top roll. This sheet is transferred by pressure of the rolls 

 to the fabric that passed between the middle and lower rolls and 

 the frictioned-tabric is then wound up on the stijck shell with 

 a cotton liner between the rubber surfaces to prevent their 

 sticking together. The speed of the bottom roll is somewhat 

 slower than the other two for the purpose of forcing or friction- 

 ing the rubber through the interstices of the fabric. 



CUTTING. 



The roll of calendered fabric is then mounted at one end of the 

 cutting table and a length gf stock is unrolled and laid on the 

 table, meanwhile, the liner is stripped off and wound up for 

 further use. The stock is then cut on the bias according to 

 the sizes required. 



ASSEMBLINa 



The next operation is assembling or building up the patches. 

 This IS done on a hollow metal core that conforms in section 

 to the shape of 

 the tire casin.t; 

 in wliich the 

 patch is in- 

 tended to be 

 used. A coat- 

 ing of cetncnt 

 is first applied 

 to the core that 

 is mounted on 

 any ordinary 

 tire building 

 s.'t a n d. The 

 next step con- 

 sists in apply- 

 ing the largest 

 ply of fabric 

 to the core, al- 

 lowing the rim- 

 flaps to e.xtend 

 downward and 



over-hang the inside periphery of the core. This first-ply is given 

 a coating of cement and the second ply is laid on the first, and 

 so on until the four-ply patch is assembled. Each ply, however, 

 should be rolled down smoothly and all air pockets between the 

 plies carefully removed. As many patches as the circumference 



Building Operation 



