132 PARA RUBBER. 



between the surfaces of the two rollers can be adjusted, and varies 

 from | inch to practical contact. 



" The rollers revolve at different speeds and are driven by power 

 transmitted from belt and pulley through gear wheels to the rollers 

 themselves. 



" The axes of the two rollers may be on the same horizontal plane, 

 more usually one is slightly above the other ; a stream of water 

 flows over the surface of the rollers all the time they are in use. 



The Machine at Work. 



" When the machine is used, freshly-coagulated lumps of rubber 

 are put between the rollers, which are separated about J inch. The 

 rubber is passed through several times , the rollers being gradually 

 approximated to each other, and the rubber becomes compacted 

 and to some degree hardened. At the same time the effect of the 

 differential rate of movement of the two roller surfaces is to subject 

 the rubber to a shearing stress, which stretches and tears it to pieces, 

 and it is here that the peculiar property of rubber is clearly seen. 

 The elastic stretching and rebound kick out any gross mechanical 

 impurity that may be present, and when the machine is used on 

 scrap rubber there is a perfect shower of dirt, pieces of bark and 

 wood being thrown out from the front of the machine. Freshly-cut or 

 torn surfaces of rubber reunite on contact and pressure ; for this 

 reason the fragments, into which the rubber is torn by the machine, 

 reunite and emerge as a continuous sheet. At the same time the 

 stream of water thoroughly washes out any impurity soluble in 

 water that may be left in the rubber. The final product is a coherent 

 but granular sheet of rubber, the thickness of which can be regulated 

 by the distance left between the rollers. The function of the 

 machine is thus three-fold. : — 



" 1. — It ejects mechanically any solid impurity. 



" 2. — It breaks up the rubber, and subjects all portions of it to 

 the washing effect of flowing water. 



"3. — It produces a granular thin sheet of uniform thickness, 

 which is clean and which can be easily and rapidly dried. 



' ' The interests at stake are so great that I may be permitted 

 perhaps to put in condensed form the advantages of the use of a 

 washing machine in preparing rubber. — 



" 1. — The rubber produced will be as pure as it possibly can be 

 without costly chemical treatment. 



"2. — The rubber, being pure, will be of uniform quality. 



" 3. — The rubber, being washed, will be ready for immediate 

 use by the manufacturer. 



" 4. — It will effect a saving of labour to the planter by 

 eliminating the petty hand labour involved in preparing rubber in 

 small plates, rolling the sheets by hand, and manipulation of the 

 small biscuits. 



