Resistor-based Ignition System for a Core Gun

Abstract

A core gun igniter assembly features a resistor under 50 ohms that is welded rather than soldered to a circuit. Upon energizing the circuit, the resistor creates the heat needed to directly set off the propellant to directly drive the core barrel into the surrounding formation to obtain the desired core sample. The use of a titanium powder ignition mix on a nichrome wire with its attendant safety risks is eliminated.

We claim: 
     
         1 . A core gun for subterranean use, comprising:
 a housing;   at least one barrel mounted to said housing for selective launching from said housing;   a propellant ignitable by a selectively energized resistor for selective launching of said barrel into a surrounding formation to collect a core sample therein.   
     
     
         2 . The gun of  claim 1 , wherein:
 said resistor has welded connections.   
     
     
         3 . The gun of  claim 1 , wherein:
 said resistor is less than 50 ohms.   
     
     
         4 . The gun of  claim 1 , wherein:
 said resistor and propellant are mounted in a cartridge in said housing.   
     
     
         5 . The gun of  claim 1 , wherein:
 said at least one barrel comprises a plurality of barrels each selectively launched.   
     
     
         6 . The gun of  claim 1 , wherein:
 said barrel is tethered to said housing for retrieval after launch.   
     
     
         7 . The gun of  claim 2 , wherein:
 said resistor is less than 50 ohms.   
     
     
         8 . The gun of  claim 7 , wherein:
 said resistor and propellant are mounted in a cartridge in said housing.   
     
     
         9 . The gun of  claim 8 , wherein:
 said at least one barrel comprises a plurality of barrels each selectively launched.   
     
     
         10 . The gun of  claim 9 , wherein:
 said barrel is tethered to said housing for retrieval after launch.