Chapter 7 — BASIC FIRE CONTROL 



Figure 7-8.- 



71.106 

 -Mechanical stop. 



the maximum safe quantity limit, however. In 

 other words, it allows the full value to be used 

 by some components, but still protects others 

 from accepting unsafe values. 



Electromechanical Devices 



Electromechanical devices combine two dif- 

 ferent types of action — electrical and mechanical. 

 These devices, such as the magnetic brake and 

 magnetic clutch, have wide usage and applica- 

 tion in fire control computing components. 



The magnetic brake can stop and hold a 

 shaft at a given value when certain conditions 

 are met. The magnetic brake is used to prevent 

 a line of gearing from turning. When the current 

 is off, no magnetic action takes place. In figure 

 7-9, an exploded view of a magnetic brake, 

 notice that the spring washer holds the cap away 



from the electromagnet, thus allowing the shaft 

 to turn freely. When the current is turned on, 

 the electromagnet exerts a force great enough 

 to overcome the effect of the spring washer 

 and pulls the cap tight against the electromagnet, 

 thereby locking the shaft in place. 



An electromagnetic clutch is used to engage 

 and disengage a line of gearing. An exploded 

 view of a magnetic clutch is shown in figure 

 7-10. When current is fed to the electromagnet, 

 the friction plate assembly and cap assembly 

 are in contact with each other, and the output 

 line transmits input rotation. When current to 

 the electromagnet is cut off, the friction plate 

 assembly and cap assembly separate by spring 

 action, losing contact with each other. The 

 output line does not rotate or transmit any input 

 to the clutchwhen these components are separated. 



BUSHING 



HOUSING 

 ELECTROMAGNET 



RETAINING RING 



SHIM WASHER 



FRICTION PLATE 

 ASSEMBLY 



SEARING 



71.59 71.60 



Figure 7-9. — Magnetic brake — exploded view. Figure 7-10. — Magnetic clutch— exploded view. 



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