6 BELL SYSTEM TECHNICAL JOURNAL 



auxiliary equipment was purchased and installed and the machine 

 converted to a fifty-wire basis. 



The installation was completed early in 1928 and the machine put 

 in experimental operation about March of that year. As rapidly as 

 possible crews were broken in and late that summer the machine was 

 placed on a regular operating basis with three complete crews on a 

 twenty-four-hour day and six-day week. It continued to operate on 

 this basis until 1931, when ten more wires were added. This product 

 was cabled into 26 and 24 A.W.G. cables on standard cabling equip- 

 ment with no major difficulties and installed in commercial telephone 

 plant by the operating companies. No serious operating trouble has 

 developed in any of this cable. 



The pulp insulated wire capacity now at the Hawthorne and 

 Kearny plants is approximately 225 million conductor feet per week 

 and all 24 and 26 A.W.G. exchange area cables are being manufactured 

 from pulp insulated wire. 



Process 



Essentially the process consists in forming simultaneously on a 

 modified cylinder paper machine 60 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 so as to form a 

 uniform cylindrical coating of wet pulp around the wire and then 

 driving the water from this coating by drying at a high temperature. 



The insulating material is given practically the same treatment in a 

 beater as it would receive in paper making, but without the addition 

 of sizing or loading. The beaten pulp is stored in a large tank from 

 which it is pumped to a mix box for dilution with water before passing 

 to the screen where coarse particles and lumps are removed. 



For the next operation a modified paper machine of the cylinder 

 type is used. The mixture of pulp and water is fed into the cylinder 

 vat by gravity from the screen. The cylinder mold itself is divided 

 into 60 narrow, uniform sections by dams or deckels on the surface of 

 the wire cloth covering. The bare conductors coming to the machine 

 are guided so that one conductor passes around the mold in each of 

 the sections. As the mold is rotated in the water suspension of pulp 

 in the vat, a narrow continuous sheet of paper with a conductor 

 embedded in it is formed in each section by the simple paper making 

 process of straining the fibres from the suspension as the water flows 

 through the fine wire cloth covering the mold, under the slight head 

 maintained outside the mold. These sheets are transferred from the 

 mold to a woolen felt by the pressure of a couch roll and carried by 

 it through two presses which take out a considerable part of the water 



