SOLDERLESS WRAPPED CONNECTIONS PART I 545 



wire connecting concept was proposed whereby a rotating spindle housed 

 a stationary terminal in an axial opening in the spindle and was pro- 

 vided with a second opening radially separated from the axial opening 

 and arranged to accommodate a wire. When the spindle was rotated 

 the wire was caused to form a spiral about the stationary terminal. One 

 method involved anchoring the wire in the second opening and feeding 

 the wire tangentially to the terminal as the spindle was rotated. Due to 

 certain limitations inherent in tangential feed onto a stationary ter- 

 minal an improved method was finally chosen. This is the axial feed 

 method which is particularly adapted to wrapping closely spaced ter- 

 minals of all cross sections. The operation of loading the wire and wrap- 

 ping the connection is shown in Fig. 23. Position A shows the tool tip, 

 Position B the bare wire 2 inserted into the feed slot 4, Position C the 

 anchoring of the wire by bending it into the notch 5, Position D the ter- 

 minal insertion and Position E the wrapping of the wire 2 by rotating 

 the spindle 1 around the terminal 3. Position F is the finished connec- 

 tion. A more detailed drawing of the tool tip is shown in Fig. 24. 



WRAPPING TENSION 



The tension in the wire is produced by rotating the spindle 1 around 

 the terminal 3 (Fig. 24) thus pulling the short skinner wire 2 out of the 

 feed slot 4. In the process of pulling the wire out of the slot and wrap- 

 ping it around the terminal each increment of the skinner wire length 

 undergoes several bending operations. The first bending occurs at the 

 edge R of feed slot 4 where the wire is bent through an angle of less than 

 90°. The second bending is the straightening out operation of the bent 

 wire. The third bending takes place as the wire is wrapped around the 

 terminal. All three bending processes contribute to the tension with 

 which the wire is wrapped. The dimensions which control the tension 

 and are therefore of engineering importance are the radius R at the tool 

 tip (See Figs. 25 and 25(a)) and the wall thickness W (Fig. 24). The bend- 

 ing forces are inversely proportional to the respective bending curva- 

 tures and the frictional forces in turn are proportional to the bending 

 forces. The tension imparted into the wire as it is wrapped around the 

 terminal, however, is not only due to the friction alone but to the com- 

 bined effect of friction and bending effort. If the wire were completely 

 elastic and the friction zero, no tension could be produced. But there 

 would be tension in the wire if the friction were zero and the wire only 

 partly elastic such as copper wire. There also would be tension if a com- 

 pletely elastic wire would be pulled around an edge having friction. 



