INSULATION OF WIRE WITH PAPER PULP 87 



wires of 22-gauge and smaller. The most practical size of commercial 

 machine (Fig. 3) was no less than three feet wide but by painting annular 

 rings on the cylinder screen surface the effect of a series of small cylinders 

 all immersed in a single vat could be produced. This was the scheme finally 

 adopted for preparing the paper making machine and we have standardized 

 on a cylinder three feet long with enough rings to simultaneously produce 

 sixty sheets of paper approximately \" in width. The layout of the re- 

 sultant machine is shown schematically in Fig. 4. 



Pulp Supply 



Kraft pulp is among the toughest of the wood fibers as well as one of the 

 cheapest. It is prepared by an alkaline process and our experience indi- 

 cated that this process produced pulp of a greater degree of permanence 

 than the acid processes unless special treatments were used. The chief 

 drawback to its use was its color, brown or tan, which necessitated a change 

 in the color code in the cables. Fortunately, cable designs could be made 

 using fewer colors than had previously been employed so that this obstacle 

 was not serious. Standard paper making beating equipment was purchased 

 and used for preparing the pulp to form the sheets although special beating 

 technique for our purpose had to be developed. The older beating method 

 consists of grinding the fibers in the presence of water under a heavy roll. 

 By this continuous maceration the pulp is softened and fibrilated and made 

 suitable for paper making. The longer the grinding the more parchmentlike 

 the final paper becomes, and as we desire as porous a paper as possible it is 

 necessary to control the beating to a point where good strong paper will be 

 made but will still contain a high degree of porosity. Within the last few 

 years a continuous beating system has been developed to replace the original 

 batch system. In this method the pulp mixed with water is run through a 

 preliminary hydrofiner grinder where the pulp is partially beaten before 

 being stored in a large tank. From this tank it is then fed to the various ma- 

 chines and colored by adding the proper dye. A further refiner in the line to 

 each machine finishes the beating for the particular insulation being made in 

 that position. Study showed that fiber from different sources of wood 

 supply handled differently so that standardization of sources of supply had 

 to be made and methods of test developed to check on new fibers or new 

 sources of pulp. 



Due to the small thin sheets made on the machine, the amount of pulp 

 required per unit of time is extremely small. No commercial means of 

 measuring such quantities accurately had been developed and it was neces- 

 sary to spend considerable time in this study. The suspension of pulp to 

 be measured contains only 1.5% fiber and this is further diluted to .05% in 

 the machine vat. The actual quantity of liquid measured is about 8 gallons 



