CENTRIFUGAL SEPARATION 3 



from the limited and relatively small number of turns of the 

 crank shaft 45 to 60 turns per minute iwhich can be con- 

 venietly applied by hand. This is accomplished by transmis- 

 sion of the power by a series of gear wheels located between the 

 crank shaft and the spindle of the bowl. The type of gears varies 

 somewhat with different makes of machines, they may consist of 



Fig. 9. De Laval hand separator Fig. 10. Sharpies hand separator 



Courtesy De Laval Separator Co. Courtesy Sharpies Separator Co. 



cog wheels of various angles, worm wheels, friction wheels, or 

 chain, or belt wheels, or a combination of two or more of these 

 principles. 



The transmission by friction wheels has been almost com- 

 pletely abandoned, because they have been found unsatisfactory 

 for this purpose on account of uneven wear of friction surfaces 

 and therefore irregular speed of the bowl. 



The chain transmission also is of rare occurrence and the 

 belt transmission is generally installed only on those hand ma- 

 chines which are to be used for power as well as hand operation. 



