NEW GENERAL PURPOSE RELAY 



1053 



separation by use of separate twin wiics and a si<inilican( part of the 

 impro\(Mnenl witli respect to contact opens is dnc to this feature. 



The inii)ro\-enien(s in contact chatter and open contacts Ix'come e\'en 

 more evident duiing the hfe of the reia}'. As shown in Fijj;. 23, the con- 

 tact forces on U relays diminish rapidly with wear of the contacts result- 

 ing in increased chatter, more frequent opens and the need for earlier 

 readjustment. Card operation of wire springs with large predeflections, 

 however, assures substantially constant forces, thereby maintaining 

 the initial chatter-free performance and fewer open contacts. 



Lije 



Tests of relays with contacts protected electrically with resistance- 

 condenser networks indicate that the standard AF relays with winding 

 resistances of 700 ohms or greater will have a life in the order of 250- 

 500 million operations before readjustment becomes necessary. With 

 readjustment, of course, these figures can l)e increased several times. 



Where longer life is essential, special features are used to increase the 

 life. With these features a life, before readjustment, of a billion oper- 

 ations is expected for some relays and, with readjustment, all relays 

 equipped with the special features for long life should be capable of a 

 billion operations. 



The special features for long life include vibration dampers attached 

 to the twin wires and the stationary wire assembly as shown in Fig. 24, 

 wear-resistant nickel and chromium plate on the armature, core, and 

 core plate, and a long-wearing alloy for the nonmagnetic separators 



^ 



1 



^ 



i 



U TYPE 



3] 



J 0.33 L 

 ^ IN. I*" 



UB TYPE 



:bi 



-0.94 IN.-->j 



i 



AF TYPE 



-4 



Fig. 22 — Independent action of the twin contacts is limited on U and UB relays 

 because both contacts are mounted on a single spring which is notched. The AF 

 relay achieves complete independence by mounting the contacts on separate wires. 



