PUMPING WATERS. 



81 



of Stroud, Gloucestershire, and is known as the " Ex- 

 celsior " pump. Pumps with mitre valves must run 

 fairly slowly, under 60 revolutions per minute being 

 generally deemed advisable to allow the valves to 

 close and to avoid wear and tear on them. The 

 Excelsior pump, which is illustrated in figs. 68 and 

 69, has not the ordinary mitre valve but a special 

 valve known as the Guttermuth valve, which has 

 decided advantages over the ordinary type when 



I 



FIG. 68. 



FIG. 69. 



the pump has to run at a high speed. The valve 

 consists of a strip of phosphor bronze, one end of 

 which is coiled upon a spindle to form a spiral, 

 leaving part of the sheet flat to form the valve flap 

 proper. Referring to figs. 70 and 71, it will be seen 

 that the entire opening of the port only entails a 

 minimum coiling strain on the spiral, which increases 

 its durability while yet allowing it to exact sufficient 

 power to close the flap gently, directly the flow of 

 water ceases. An illustration of a complete set of 



Guttermuth valves appears in fig. 72. These valves 



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