366 



CHAPTER XVIII 



pression side of the pump all of the sleeves of the valve are forced together, 

 and the annular spaces C ' and D ^and the openings A i and B ^are all closed; 

 the compressed air escapes by e ' f ' and g ' ; on the aspirating side these 

 openings are closed by the spring H. The discharge valves are arranged 

 on the lower side of the pump so as to facilitate the removal of water. 



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Fig. 224 



A second type of high eiftciency operating without pressure equalization 

 is that of MuUan (U.S. patent), Fig. 225. In this design the suction ports, 

 a, are located round the middle of the cylinder and are closed and opened 

 by the movement of the piston, recalling the similar action in thefEdwards 

 pump. The discharge valves are placed at h in the ends of the cylinder, 

 the air finally escaping at c. 



Fig. 225 



Rotating Valve Reciprocating Pump. — Another type of pump, Fig. 226, 

 employs mechanically operated rotating valves, the arrangement and action 

 of which recall the movement in a CorHss engine. 



Rotary Vacuum Pumps. — This type is of comparatively recent introduc- 



