438 



BELL SYSTEM TECHNICAL JOURNAL 



modified cylinder paper machine, 50 narrow continuous sheets of 

 paper, with a single strand of wire enclosed in each sheet, pressing the 

 excess moisture from the sheets, turning them down by means of a 

 rapidly rotating polishing device, so as to form a uniform cylindrical 

 coating of wet pulp around the wire, and then driving the water from 

 this coating by drying. 



Fig. 5 — -Slitting of paper. 



The material used in making this insulation is Kraft pulp, which is 

 prepared for use on the machine by beating as in the ordinary paper- 

 making operation (Fig. 9) and fed to the machine in a somewhat more 

 diluted form than in standard paper making practice. 



In theory, the whole process is simple, but from a practical stand- 

 point, many interesting problems had to be solved before satisfactory 

 operation was possible. A continuous supply of wire must be fur- 

 nished, as it is not feasible to shut the machine down to change supply 

 spools. This was taken care of by removing the wire from the supply 

 spool by means of a flier without rotating the spool. This allows 

 time to braze the end of the wire from one spool to the next. Ordinary 

 annealed copper wire has a non-uniform surface due in part to the 

 residual drawing compound, h satisfactory surface is obtained by 



