VENTILATING 



131 



When the shafting is hung from the sash 

 bars a hanger is attached to every second 

 or third bar, usually to every second. 



Fig. 71. 

 Open col- 

 umn ventil- 

 ator gearing 



Fig. 72.- 

 Open col- 

 umn chain 

 operated 

 ventilator 

 gearing 



Gearing. Generally speaking, there are 

 three types of gearing utilized for operating 

 overhead ventilator shafting. These are: 

 (i) The column gear, of which there are 

 many different forms; (2) the chain-oper- 



