VENTILATING 



141 



Fig. 80. Sliding- shaft system for operating ventilators 



This sliding movement is utilized to 

 operate the sash by means of a right angle 

 lever, pivoted at the angle with the short arm 

 attached to the shaft and the long arm to the 

 sash. It is claimed for this system that it 

 will operate a line of sash 500 feet long. 



