766 



HYDRAULICS AND ITS APPLICATIONS 



opens F 2 , thus opening the exhaust valve V E and putting the cylinder into 

 communication with the exhaust, while a second lever and valve admit 



FIG. 379. Details of 2^-inch Operating Valve for 420 tons Press. 



pressure water to the return cylinders. A smaller press for similar work 

 is illustrated in Fig. 380. 



ART. 204. THE HYDRAULIC FORGING PRESS. 



In the production of heavy forgings for large ingots of mild steel, it is 

 essential that every part of the ingot should be equally worked if the 

 resultant forging is to be homogeneous in structure. Where a steam 

 hammer is used, the energy of the blow is absorbed in producing dis- 

 tortion of the outer layers, while the interior is practically unaffected. 

 This disadvantage is overcome by the use of the hydraulic forging press, 

 with its slow and powerful compression, and this is gradually supplanting 

 the steam hammer for the production of very heavy forgings. The 

 principle of the press is the same as that of the ordinary flanging press, 



