1036 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



of the ultimate work capacity of the magnet as related to the power 

 input and has been defined as S = oirG/Sio ergs per watt. 



The favorable low value of closed gap reluctance for the new relay- 

 results from adequate cross-sections of magnetic material, the absence 

 of joints, proper mating of the armature and core, and large pole face 

 areas. A low value of reluctance also insures less magnetic interference 

 to other relays and from other relays. 



Table I 



Closed Gap Reluctance (Ro, cm 



Coil Constant G, kilomhos 



Sensitivity S, ergs per watt. . . . 



AF Relay 



0.028 

 160 

 90,000 



U Relay 



0.065 

 160 

 39,000 



Although the coil constants are the same for the two relays, as can 

 be seen from Table I, the sensitivity of the new relay is more than 

 double that of the U relay, because of the lower closed gap reluctance. 



6. MOLDED WIRE SPRING SUBASSEMBLIES 



One of the major features of the new relay is the use of molded wire 

 spring subassemblies. Fig. 10 shows a wire spring relay with twelve make 

 contacts, and Fig. 11 shows a comparison of the wire spring assemblies 

 used in this relay and the corresponding parts of the U relay. From this 

 it is clear that the number of parts handled in the assembly of the con- 

 tact spring members is greatly reduced in the new relay. Not all relays 

 will have twelve contacts and in those cases where fewer contact springs 

 are needed the comparison will not be so unfavorable to the U relay. 

 For six contacts, about one-half of the parts shown will be needed for the 

 U relay, whereas the new relay will again require two \vire spring combs. 

 In the new relay three wire spring combs are needed for any contact 

 combination which includes both make and break contacts up to twelve 

 makes and twelve breaks. Four wire spring combs are needed for a relay 

 having twenty-four make contacts. 



Two problems had to be solved in providing molded wire spring combs, 

 namely, wire straightening and molding of a multiplicity of wires. Both 

 of these were studied cooperatively at Bell Telephone Laboratories and 

 the Western Electric Company. 



Wire is straightened by rotating cam and die members around the 

 unstraightened wire which causes alternating flexing of the wire. For 

 best results, it was found important to shape the cams properly and to 



