NEW GENERAL PURPOSE RELAY 1029 



4. PRINCIPLE OF CONTACT OPERATION OF THE AF RELAY 



The AF relay uses what has been called the "single card system" for 

 actuating the contacts. This is in contrast to other code card systems 

 wliich require two, three or four coded cards in each relay. The method 

 for obtaining individual make and break contacts with this system is 

 shown in Figs. 4a and 4b, and a means for obtaining transfer contacts, in 

 which both make and break twin contacts are associated with a common 

 stationary contact, is shown in Fig. 4c. As indicated on the figures, the 

 following principles are incorporated in this method of actuation: 



1. In general, three basic wire spring assemblies are required. Two of 

 these carry movable twin wires for make and break contacts and ai'e 

 identical except for some details in forming at the terminal ends for 

 convenience in wiring. The twin wire assemblies are mounted on either 



NORMAL /POSITION AFTER ASSEMBLY 



CONTACT 

 MOTION 



JTION f(| I — 



CDC I-ST^ "-''''''^ ■^nVree" POSITION OF TWIN 



r,^^, cr "nM f?"-^-?''' WIRES BEFORE ASSEMBLY 



DEFLECTION (r ---STATIONARY 



i ^t^ CONTACT 



Fig. 5 — Contact forces are controlled by relatively large predeflcctions of the 

 twin wires. 



side of the stationary wire assembly, which consists of a group of rela- 

 tively heavy wires molded into plastic sections, one a short distance be- 

 hind the contacts and one near the rear of the relay. These sections are 

 rigidly supported in the relay structure. 



2. Moving twin contacts on separate twin wires are used ^^'ith every 

 stationary contact. This arrangement assures good reliability and greater 

 freedom from open contacts in the presence of dust and dirt. In addition, 

 contact chatter is reduced as both contacts must be open simultaneously 

 in order to interrupt the circuit. 



3. As shown in Fig. 5, each group of twin wires is tensioned toward the 

 stationary wires by means of large predeflections before assembly, so 

 that the contact forces are determined by this predeflection. Good con- 

 trol of the contact force is assured without need for hand adjustment 

 because small variations in deflection of the low stiffness springs do not 

 result in appreciable changes in force. For this reason, the force is stable 

 and is not appreciably affected b}' wear of the contacts. 



4. The twin wires are actuated by a single pimched fiber card. Since 

 the tension in the twin wires is always in a direction to hold the contacts 

 closed, the card serves to hold the make contacts open when the relay 

 is unoperated and the break contacts open when the relay is energized. 



