DRIVES AND CONTROLS 



233 



Supply 



Piloi 

 circuii- 



■Pilof ^ 

 - circuit 



Jr-'-De/ivery No.1 



Supply 



• Delivery 

 No.2 



First Condition Second Condi+ion 



Fig. 473. — Three-way valve applied as convenient means of transferring one supply to either of two deliverie.s. 



Exhausi 



Supply 



Piloi 

 circuit 



Operating 

 ' rod 



Operating 

 cylinder 



Pilot 

 circuit 



J- Operating 

 rt rod 



Operating 

 cylinder 



First Condi+ion Second Condition 



Fig. 474 — Four-way valve arranged to control double-acting cylinder. Upon energization of solenoid, operating rod 



of cylinder reverses direction. 



Exhaust 



Power 

 lines 



Float 

 switch 



Power 

 lines 



Float 

 switch 



~~ Pressure -operated valve ' 



First Condition Second Condition 



Fig. 475.— Four-way valve arrangement, employing principle shown in Fig. 474, provides automatic control of tank 



level through pressure-operated valve. ' 



Emergency 

 supply "■ 



Normal — g 

 supply 



Delivery 



Normal Condition 



Fig. 476.— Three-way valve, utilizing inversion of principle shown in Fig. 473, offers means of transferring either of two 



supplies to a common delivery. Useful in appUcations where an emergency supply is provided. 



