Set-back rocket motor ignitor for shoulder-fired rockets

Abstract

A rocket motor ignitor assembly that may be used in a shoulder-fired rocket system. The rocket motor ignitor assembly may include a delay ignitor operable to ignite a rocket motor propellant, a stab firing pin operable to activate the delay ignitor by contacting the delay ignitor, and a biasing element coupled with the stab firing pin. The stab firing pin may have a length to diameter ratio greater than two, as well as relief grooves allowing air to vent past the stab firing pin as it travels toward the delay ignitor to activate it. The rocket motor ignitor assembly may also include a guide stop to limit penetration of the stab firing pin into the delay ignitor.

What is claimed is: 
     
         1 . A rocket motor ignitor assembly comprising:
 a delay ignitor operable to ignite a rocket motor propellant;   a stab firing pin operable to activate the delay ignitor by contacting the delay ignitor; and   a biasing element coupled with the stab firing pin,   wherein the delay ignitor is operable to ignite the rocket motor propellant after a predetermined amount of time upon contact by the stab firing pin;   wherein the biasing element is biased to space apart the stab firing pin and the delay ignitor when the rocket motor assembly is in a pre-fired condition and the stab firing pin is operable to contact the delay ignitor when the rocket motor assembly is in a firing condition.   
     
     
         2 . The rocket motor ignitor assembly according to  claim 1 , wherein the stab firing pin has a length and a diameter, the length to diameter ratio being greater than 2. 
     
     
         3 . The rocket motor ignitor assembly according to  claim 2 , wherein the stab firing pin length to diameter ratio is greater than 2.5. 
     
     
         4 . The rocket motor ignitor assembly according to  claim 2 , wherein the stab firing pin length to diameter ratio is greater than 3. 
     
     
         5 . The rocket motor ignitor assembly according to  claim 1 , wherein the stab firing pin comprises one or more relief grooves operable to vent air around the edge of the stab firing pin. 
     
     
         6 . The rocket motor ignitor assembly according to  claim 5 , wherein the relief grooves are operable to reduce air compression between the stab firing pin and the delay ignitor as the stab firing pin travels toward the delay ignitor. 
     
     
         7 . The rocket motor ignitor assembly according to  claim 5 , wherein the relief grooves are helically arranged. 
     
     
         8 . The rocket motor ignitor assembly according to  claim 5 , wherein the relief grooves are air venting relief grooves. 
     
     
         9 . The rocket motor ignitor assembly according to  claim 5 , wherein the relief grooves are cut into an outer surface of the stab firing pin. 
     
     
         10 . The rocket motor ignitor assembly according to  claim 1 , wherein the rocket motor ignitor assembly comprises an ignitor tube, wherein the delay ignitor, the stab firing pin, and the biasing element are disposed within an inner bore of the ignitor tube. 
     
     
         11 . The rocket motor ignitor assembly according to  claim 10 , wherein the stab firing pin and the biasing element are retained within the ignitor tube, the stab firing pin having one or more relief grooves formed therein operable to allow air between the stab firing pin and the delay ignitor to vent past the stab firing pin when the stab firing pin translates toward the delay ignitor within the inner bore. 
     
     
         12 . The rocket motor ignitor assembly according to  claim 1 , further comprising a guide stop disposed about an exterior surface of the delay ignitor, wherein the guide stop comprises an inner bore operable to receive at least a portion of the stab firing pin therethrough so as to limit penetration of the stab firing pin into the delay ignitor. 
     
     
         13 . The rocket motor ignitor assembly according to  claim 12 , wherein the guide stop comprises a first surface complementary to a second surface of the stab firing pin, such that the first surface is operable to engage the second surface of the stab firing pin so as to limit penetration of the stab firing pin into the delay ignitor. 
     
     
         14 . The rocket motor ignitor assembly according to  claim 12 , wherein the guide stop is operable to prevent over-penetration of the stab firing pin into the delay ignitor. 
     
     
         15 . The rocket motor ignitor assembly according to  claim 1 , wherein the rocket motor assembly is in a firing condition upon the ignition of an expelling charge coupled with the rocket motor ignitor assembly. 
     
     
         16 . The rocket motor ignitor assembly according to  claim 1 , wherein the rocket motor ignitor assembly is for use in a shoulder-fired rocket system. 
     
     
         17 . The rocket motor ignitor assembly according to  claim 16 , wherein the shoulder-fired rocket system is a rocket propelled grenade system. 
     
     
         18 . A rocket motor assembly comprising:
 a rocket motor propellant;   a delay ignitor operable to ignite the rocket motor propellant;   a stab firing pin operable to activate the delay ignitor by contacting the delay ignitor; and   a biasing element coupled with the stab firing pin,   wherein the delay ignitor is operable to ignite the rocket motor propellant after a predetermined amount of time upon contact by the stab firing pin;   wherein the biasing element is biased to space apart the stab firing pin and the delay ignitor when the rocket motor assembly is in a pre-fired condition and the stab firing pin is operable to contact the delay ignitor when the rocket motor assembly is in a firing condition.   
     
     
         19 . A shoulder-fired rocket system comprising:
 a rocket motor assembly, the rocket motor assembly comprising:
 a rocket motor propellant; 
 a delay ignitor operable to ignite the rocket motor propellant; 
 a stab firing pin operable to activate the delay ignitor by contacting the delay ignitor; and 
 a biasing element coupled with the stab firing pin, 
 wherein the delay ignitor is operable to ignite the rocket motor propellant after a predetermined amount of time upon contact by the stab firing pin; 
 wherein the biasing element is biased to space apart the stab firing pin and the delay ignitor when the rocket motor assembly is in a pre-fired condition; 
   an expelling charge coupled with a distal end of the rocket motor assembly; and   a warhead coupled with a proximal end of the rocket motor assembly.   
     
     
         20 . The shoulder-fired rocket system of  claim 19 , wherein upon actuation of the expelling charge, the stab firing pin is operable to contact the delay ignitor.