104 



ENGINEER'S BRAKE VALVES 



their use is not considered a sign of progress in the air-brake 

 field. 



B-ll Brake Valve. Next in order of invention was the B-ll 

 engineer's brake valve in 1876, shown in Fig. 2; it was the 

 first to have a rotary valve. In this an attempt was made 

 to have the valve automatic in closing the discharge of air 

 from the train pipe. The handle was connected to a quick- 

 thread screw in the top, which, when turned to the right, would 



To Tra/'n Pipe 



FIG. 2 



reduce the tension of the spring shown in the handle and 

 allow the train-pipe discharge valve to be raised off its seat 

 by train-pipe pressure; then train-pipe air would flow out 

 to the atmosphere until it was reduced so that the spring 

 could close the discharge valve and stop the flow of air. The 

 rotary valve had ports straight through it to feed air direct 

 from the main reservoir to the train pipe with rotary valve 

 in full-release position. Cavities in the face of the rotary 

 valve connected the train pipe direct to the atmosphere in 



