ELECTROFORMED CONDUCTOR FOR TELEPHONE DROP WIRE 1115 



unit consists of a cell and a small, individual reservoir with a small pump 

 which circulates the liquid in the reservoir through the cell, the overflow 

 returning to the reservoir. Makeup water to replace that lost by evapora- 

 tion in the associated plating section is added to the reservoir, serving 

 to continuously dilute the electrolyte washed from the wire. The reser- 

 voir operates at constant level, the excess of dilute electrolyte passing on 

 as makeup. The dragout recovery units act as an additional safeguard 

 to limit the loss of valuable plating solution and to minimize the con- 

 tamination of wash water going to sewer. 



Last in the design of the machine are the precautions taken to protect 

 against stray currents and to provide for expansion and contraction. 

 Protection against stray currents is an important consideration in any 

 equipment employing highly conductive liquids and heavy currents. All 

 plating cells are insulated from the machine frame by their supporting 

 blocks. Both positive and negative plating circuit buses are insulated. 

 All electrolyte pipe lines contain neoprene flexible joints which serve 

 both to sectionalize them electrically and to provide for expansion and 

 contraction. Contact rolls are insulated at their mountings. These are 

 the principal precautions taken. 



The expansion and contraction problem was rather complex. The three 

 trough sections of each machine are continuous units, the shortest 77 

 feet, the longest 300 feet in length. The plating cells in the trough are 

 supplied with current and electrolyte from a number of different loca- 

 tions in the building and the building itself is provided with a single 

 expansion joint in the center. To allow for relative motion between 

 machine and building, the machine sections are mounted on rollers. 

 Since these sections are required to operate at various temperatures, 

 from room conditions to 195°F, and are required to be supplied at fre- 

 quent intervals with current and electrolyte, all electrical connections 

 to bus bars are made with flexible joints and electrolyte is supplied to 

 each plating cell through a special flexible molded ell. 



Each machine section is anchored to the building steel to prevent 

 creep. An analysis was made of the several movements to be expected 

 under various operating conditions and ambient temperatures and the 

 anchor point was selected for each section so that the relative motions 

 are minimized. 



PLATING OPERATIONS 



From the chemical point of view, the electroforming process consists 

 of a series of unit processes in tandem, to clean the steel core wire and 

 to successively deposit the several metallic coatings required to make 



