SPRiT  -  MX  Complex Rate Springs      
 
-   World Premier since Mar 20,  2020
    
-   Complex Rate v4.3  =  Progressive + Linear  
 
I have designed these Complex rate springs to be much lighter than normal springs by 5g - 7g until the actuation point by progressive rate as Graph 1.   
The force rises by linear rate after the actuation, results in the same bottom out weight as the conventional linear springs.  
Complex rate springs are hard to find any example in the electronics industry, the production is trickier and seems complicated.
  
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* No Polarity on the Complex rate springs.  
  According to the Newtonians,   Fab  =  - Fba 
  
Bottom out Force                Force ratio Before vs After actuation
 
63.5 C  (Actuation 43cN)      Force ratio  =  3 : 4   
 
68 C     (Actuation 47cN)      Force ratio  =  3 : 4   
 
72 C     (Actuation 50cN)      Force ratio  =  3 : 4  
 
78 C     (Actuation 53cN)      Force ratio  =  3 : 4   
 
 
For further info  >   spritdesigns.com/mx