CONTACT W KLOIXC I\ WIKK SPIMXC UKLAYS 017 



wires is held stationary and the contact block is moved to the wires to 

 make the weld. The speed of approach is an important factor in con- 

 trolling the arc duration and the impact force. \'arious speeds of the con- 

 tact block carriage from approximately 1 to 80 inches per second were 

 tried. The best welds were obtained by a spring actuated gun which 

 attained a \(^locity at impact of approximately 40 inches per second. 



AITOMATIC WELDEK OPKHATION 



The automatic percussion welder contains duplicate welder heads 

 which are miri'or images of each other. Two contacts are welded at a 

 time, one on each half of the comb, Fig. 18. After each welding opera- 

 tion or one cycle, the comb is indexed to the next pair of wire centers. 

 Six cycles complete the welding of tweh'e contacts, or a lessei- number if 

 rf^quired. The guns do not weld at exactly the same time. There is an 

 interval of one degree of revolution of the main shaft between the firing 

 l)oints to prevent electrical or mechanical interference. The welder was 

 designed to select the type of contact, cut it from the tape and weld it 

 in one eycle, to avoid the handling problems associated ^^^th precutting 

 and magazining contact blocks. 



TAPE SUPPLY AND SELECTOR 



One of four contact conditions ^\^ll apply for each ^^'ire; (1) no contact, 

 (2) contact ^^'ith palladium cap up, (3) palladium cap down, or (4) pal- 

 ladium cap both up and down. This requires three reels of tape on the 

 right for one head and three on the left for the other. Adjustable knobs 

 on both right and left tape feed cams are set for one of the four tape feed 

 conditions for each ^\•ire position of the comb. Thus, any combination of 

 contact conditions can be set up to make parts for any code of relay. 



CONTACT SHEAR AND TRANSFER 



The three tapes enter the shearing die through nidnidual openings. 

 However, only that tape selected by the tape selector is fed into the die 

 and subsequently sheared by one punch stroke. Fig. 18. The tape is 

 punched from such a direction that the base metal is not dragged over 

 the boundary line into the palladium zone. This avoids contamination 

 of the palladium. As the contact is blanked out, the walls of a notch 

 in the punch confine it on the precious metal sides to prevent (Hstortion. 

 The punch delivers the contact to a transfer position at the end of the 

 shearing stroke. There a transfer finger pushes the contact out of the 

 punch notch, through a guide channel and into the waiting gun jaws. 



