ELECTROFORMED CONDUCTOR FOR TELEPHONE DROP WIRE 1125 



3. Changes in the temperature or in the concentration of the electro- 

 lyte. 



4. Changes in the distance between the anode bed and the wire be- 

 cause of the wasting away of the anode bed during plating operations. 



5. Wire speed changes (by removal of the magnetic field from the sup- 

 ply-end capstan). 



6. Operation of the machine at less than its capacity number of chan- 

 nels. 



Control is justified by the savings in copper which accrue, by the re- 

 lieving of the operating personnel of tasks which could become tedious, 

 and by the resulting production of an exceptionally uniform product. 

 In view of the size tolerances available on steel wire, it was decided that 

 the most practicable approved way was to manufacture to uniform con- 

 ductivity and to ignore wire size within reasonable limits. 



Two systems produce the overall control function. A primary system 

 senses the total value of the dc current in the acid copper plate section 

 by means of a current transformer located in one phase of the common 

 ac feeder servicing all sixteen rectifiers. Changes in that current are im- 

 mediately detected and compensated for by adjustment of an induction 

 voltage regulator located at the head of the feeder. This system therefore 

 maintains the dc plating current essentially constant in value and cor- 

 rects for such fluctuations as are listed from 1 to 4 above before they can 

 seriously affect the product. 



Changes in certain other variables, as exemplified by 5 and 6 of the 

 above list, require that a new value of total current be established and 

 maintained constant by the primary system. Otherwise the maintaining 

 of the previous value of total plating current would result in a change in 

 the resistance of the product. Such variables are cared for in a secondary 

 control system which uses the resistance of one of the finished wires as 

 the control parameter. The secondary system automatically positions 

 the control point of the primary system, depending on the value of elec- 

 trical resistance of the pilot wire which is measured continuously. 



In addition to control equipment each machine has an inspection de- 

 vice which automatically measures the resistance of each of the twenty- 

 five wires and records the values on a chart. A cycle of all twenty-five 

 wires is completed each hour. 



Both the control and inspection resistance measuring equipments use 

 Kelvin Bridge circuits and measure approximately five feet of wire at 

 one time. Continuous contact with the wire being measured is made 

 through rotating sheaves and brushes. This avoids any scraping of the 

 soft lead and brass surfaces of the product. 



