IIIG THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



operate and release times, less contact chatter and increased mechanical 

 life. 



Normally, the armature is held against the card by the lightly pre- 

 tensioned armature hinge spring. However, when the relay is released, 

 the armature motion becomes quite complex. Overtravel at the front is 

 limited by the core plate backstop, and motion at the back, or heel sec- 

 tions, is limited by the heel stop studs. This freedom of movement is 

 intentional, its purpose being to dissipate armature energy into the core 

 plate and core rather than back into the card. 



Magnetic Circuit and Armature 



Analytical and experimental studies show that one per cent silicon 

 iron, with its higher resistivity, relative freedom from aging, and lower 

 eddy-current losses compared to ordinary magnetic iron, provides opti- 

 mum speed in the new fast relay. The contact load, about twelve grams 

 per twin contact pair, is about one-half the load required in the present 

 relay, and this together with winding space and heating, largely deter- 

 mines the size of the magnet. The magnetic structure is shown in Fig. 6. 

 The core is a one piece "E"-shaped section. The armature is a flat mem- 

 ber made of low carbon steel having specific magnetic characteristics. 

 This material simplifies manufacture, resulting in a cost saving with 



PRE- 

 DEFLECTION 



t 



Ql STATIONARY 



// ^'-CONTACT 



Si--_-_ '¥rEE POSITION OF TWIN 



I i- r , ~~~^------^__ ^^' WIRES BEFORE ASSEMBLY 



RMAL ^Ui 



.--.-^A,^ " 



NORMAL 

 CONTACT 

 MOTION '"POSITION AFTER ASSEMBLY 



CONTACT FORCES ARE CONTROLLED BY RELATIVELY 

 LARGE PREDEFLECTIONS OF THE TWIN WIRES ON 

 NEW WIRE SPRING RELAYS. 



NORMAL STATIONARY 



CONTACT MOTION CONTACT SPRING 



-=^ 



/' ^^^ 



■-■MOVING CONTACT SPRING 



OPERATING I "-^OPERATED POSITION OF 



STUD ARMATURE MOVING CONTACT SPRING 



ON FLAT SPRING RELAYS, CONTACT FORCE IS OBTAINED 

 BY "BUCKLING" THE MOVING CONTACT SPRING. 



Fig. 4 — Development of coiitaot forces in wire spring and fiat spring multi- 

 contact relays. 



