134 



ENGINEER'S BRAKE VALVES 



spring will return the handle to running position if the handle 

 is let go. The spring exerts no influence on the brake- 

 valve handle between running and slow-application positions. 

 Moving the handle from slow- 

 to quick - application position 

 again puts the spring under 

 tension that returns the handle 

 to slow - application position if 

 the handle is let go. The brake 

 valve, therefore, will not stay in 

 either release or quick-applica- 

 tion position unless held there. 

 Action of Mechanism. The 

 return-spring mechanism is 

 operated through the medium 

 of the rotary-key stem and the 



FIG. 3 



brake- valve handle. The lower 



clutch has a lug on its lower end that by resting against the 

 return-spring stop, Fig. 3, prevents this clutch from being 

 turned to the left in the spring chamber. Its upper end is 

 notched out to fit a similar notch in the bottom end of the 

 upper clutch. These notches are such that the brake-valve 

 handle can turn the upper clutch from slow-application 

 position to release position without disturbing the lower 

 clutch. In moving the handle to the right, however, the 

 two clutches engage in slow-application position, so that 

 moving the handle beyond that position toward quick-appli- 

 cation position causes the upper clutch to rotate the lower 

 clutch to the right. As the casing holds the upper end of the 

 spring stationary, this places the spring under tension and fur- 

 nishes the power to move the handle back to slow-application 

 position. 



The lower end of the return spring rests against the far 

 side of the lug of the lower clutch, which holds it stationary; 

 the upper end of the spring rests against the stop lug of the 

 casing. In the running position of the brake valve, the lug on 

 the upper clutch strikes against the lug on the casing, and 

 moving the handle to release position causes the casing to be 

 rotated to the left. As the lower end of the spring is held 



