THE SEPARATION OF THE CRYSTALS. 



Motive Power for Centrifugals. Until recent years a belt 

 drive was the usual method of driving centrifugals but latterly many installa- 

 tions have adopted a water or electric drive. In Fig. 206 is shown a view of 

 an electrically driven spindle as made by Messrs. Pott, Cassels and Williamson. 

 The lettering is as under: C inside spindle, D intermediate spindle, H top 

 plate of motor case, K armature, L magnet coils, M brake, commutators, 

 P brushes, Q, driving disc, ft friction arms, S pulley, T brake pulley. On 

 switching on the current the magnet coils pull off the brake and the armature 



being loose on the outer spindle 

 immediately revolves at a high 

 speed and gradually communicates 

 motion to the spindle V by means 

 of the friction arms which are 

 pressed out against the pulley. 



In Fig. 207 (PLATE XVIII.) 

 is shown a view of the electric- 

 driven spindle as made by Messrs. 

 Watson, Laidlaw & Co. The let- 

 tering is as follows : C brushes, 

 D commutator, E motor spindle, 

 F field coils, G armature, L friction 

 shoes, N worm and wheel, E, 

 brake, T inner revolving spindle, 

 U stationary sleeve, Y outer 

 revolving spindle, Z switch. 



In Fig. 208 is given a view 

 of the water-driven machine of 

 Messrs. Watson, Laidlaw and Co. 

 This type of machine has in 

 recent years been very extensively 

 adopted. The head of water 

 necessary to drive the machine is 

 obtained from a double acting 

 pump ; no large supply is needed, 



as after discharge from the Pelton wheel fitted on the outer spindle, the water 

 flows back to the supply tank of the pump. Two jets are supplied, and after full 

 speed has been obtained, one is automatically cut off; if it is desired to 

 get up speed slowly one jet only is used, an advantage in curing low-grade 

 products. 



The motor and centrifugal head of the water-driven machine of Pott, 

 Cassels and Williamson is shown in Fig. 209 (PLATE XIX); the reference being 

 as follows: 38 centrifugal spindle; 33 ball-bearing; 35 rubber buffers; 29 



188 



FIG. 206. 



377 



