THE INDIA RUBBER WORLD 



is passed through plunger rods and over a grooved roller. The 

 grooves are at equal distances and in them are knives which 

 cut and trim the cloth. After this the pieces of cloth are passed 

 through guide rollers to a wind-up roller operated by hand. 

 The knives are interchangeable and can be adjusted at will 

 from top to bottom, and from right to left, from groove to 

 groove. For trimming, sharp knives arc used, and for grooving, 

 blunt round ones. The latter knives impress a very distinct line 

 on the coated cloth where the belting will lattr be folded. 



The trimmed and grooved fabric then leaves the winder and 

 passes to a steam-heated warming table where the heat softens 

 the solution and makes it sticky. As soon as it is sufficiently 

 warmed, it is folded over where the grooving machine has made 

 lines, with the thick coating inside. Then it is pressed together 

 by hand-rollers and wound upon a reel at the end of the warm- 

 ing table, which usually consists of five heating plates, six feet 

 wide and ten feet long, placed end to end to form a slide about 

 52 feet long. 



The ne.xt and most important part of the work consists in 

 stretching, coating and fluting the belting. This takes place on 

 a stretching and coating calender. The belts are wound on a 

 braked winding roll and then passed over a steam-heated warm- 

 ing roller, under a heating plate and through the stretching 

 machines. These consist of a three-roll calender with a two-roll 

 calender of the same size standing 6 feet behind it. The two-roll 

 calender makes 15 per cent fewer revolutions, but has a 20 per 

 cent faster surface travel than the three-roll calender. When the 

 rolls are properly set, the higher surface speed of the two-roll cal- 

 ender causes the belting to be evenly stretched. In the stretching 

 operation, the rolls are well heated so that the balata in the fabric 

 may become as plastic as possible and penetrate farther into it. But 

 the warmer the rolls, the greater the danger of the belt being made 

 crooked. For instance, in a three-ply belt very hot rolls will 

 easily pull one side more than the other because one or the 

 other tends to slip. There is no standard for heat, but an 

 experienced and observant operator always finds the right heat 

 and accordingly adjusts the distances between rolls. 



The belt is later run again through the rolls of the stretching 

 machine. This time the rolls of the two-roll calender are not 

 set up ti.ght and the friction is just enough to rub against the 

 belt surface and make it smooth, .A.fter again rolling up, the 

 b. It i. i.rcpai-e.i f, .,- it, coatin:.; with balata. Tliis often takes 





Fig. 3. Belt-Coverj ng Machine. 



place on the two-roll calender above mentioned, but better 

 results are obtained with a special two-roll calender. The balata 

 needed for coating is prepared on a mixing mill. The stretched 

 and smoothed belt is wound on a reel, passed through the coating 

 calender, and is rolled up again on the other side. During the 



passage, the upper roll takes up a part of the balata mixture and 

 presses it against the belt. To obtain a coating of even thick- 

 ness, the distance of the rolls is fixed with chucks of metal or 

 wood, and a pair is needed for every size. These chucks are 

 arranged on a bridge mounted on the calender, are adjustable 



Trimming M.\chixe. 



and can be exchanged. They can therefore be adjusted over 

 the working width of the rolls according to the width of the 

 belt and at the same time act as guides. During the coating 

 process, the lower roll is cold, the upper being slightly warmed 

 so that the balata mixture has the softness needed to press it 

 on to the belt with ease. To prevent the coating from clinging 

 to the upper roll it is continually moistened with spirit. The 

 belt is now transferred to a table 90 feet long where it is 

 cleaned and trimmed with knives by hand to free the edges of 

 balata coating and of the mixture that has worked out of the 

 inside during calendering. 



The next operation is that of grooving. This takes place on 

 a grooving machine which consists of two horizontal rolls 

 mounted one above the other in stands. The belt passes through 

 these rolls once, and in order to make the grooved side glossy 

 it is slightly moistened with water before going through the 

 rolls. To make the grooves parallel to the edges, it is necessary 

 to guide the belt during the operations from start to finish. 

 The grooving machine is put up in front of a work table where 

 the belt is inspected before it is passed as being free of factory 

 defects. 



The above practice is not, however, universal, for some manu- 

 facturers mix with balata a certain amount of rubber, and some 

 add plastics of the refined elaterite variety. Others use only 

 the cleaned balata. As a matter of fact, the process of balata 

 belt making is very similar to that employed in the manufacture 

 of rubber belts. There is this difiference, however— no balata 

 belt is vulcanized; first, because it is not necessary, and second, 

 because it could not be done. As for the rest of the processes, 

 the frictioning of the fabric, the making up, the stretching, the 

 pressing for solidifying and surface, are almost identical. 



BALATA SOLING IN ENGLAND. 



-\ British branch of an American leather concern makes the 

 following announcement in a London trade journal: 



Balata, the satisfactory soling substitute. Like leather, it i» 

 adapted to be trodden under foot by the million. Light in weight, 

 absolutely waterproof and non-slipping, easy to work through 

 the factory, favorable in cost, economical in cutting, wears twice 

 as long as leather. Supplied in sheets, in various subsUnces, 

 providing a range for all soling requirements, from the h'ght 

 slipper to the gent's heavy boot. 



