244 BELL SYSTEM TECHNICAL JOURNAL 



150 feet per minute with the electrically heated machines. \Mth an 

 overall efficiency of 90 per cent, the production per head is 13,000 

 feet per hour. 



Ample explosion reliefs have been included in the new machines. 

 F'or the chamber itself, a diaphragm of aluminum foil that will rupture 

 leads to an open space between the machines. On the top of the air 

 ducts above the machines, vents are located that will relieve any 

 explosive pressure in this part of the system before it reaches dangerous 

 proportions. 



Although the coating of textile served wire with cellulose acetate 

 is being performed successfully, it is felt that the ultimate design of 

 machine or maximum efficiency have not been reached. There is 

 promise in the possibility of using more viscous solutions of cellulose 

 acetate, thus reducing the amount of acetone to be evaporated and 

 recovered. Other solvents than acetone are to be tried. Higher ma- 

 chine speeds may be found possible and operating methods will be 

 developed that will increase the uniformity of the product. 



