Propellant extrusion using shaped perforation pins

Abstract

An extruded stick-type propellant grain is disclosed that includes a length separated from a strand of extruded propellant material having a predetermined cross-sectional shape provided with a predetermined number of spaced, radially distributed, hollow non-round longitudinal perforations formed in said length of propellant material parallel to and extending along the length thereof and separated and surrounded by a web of the propellant material. The perforations have a geometric cross section selected from the group consisting of non-round shapes that enhance uniformity in unburned web thickness during a normal burn of said length of extruded propellant thereby reducing the amount of unburned slivers. A central perforation is also provided.

1 . An extruded stick-type propellant grain comprising: 
 (a) a length separated from a strand of extruded propellant material having a predetermined cross-sectional shape;    (b) a predetermined number of spaced, radially distributed, hollow longitudinal perforations formed in said length of propellant material parallel to and extending along the length thereof and separated and surrounded by a web of said propellant material; and    (c) wherein said perforations have a geometric cross section selected from the group consisting of non-round shapes that enhance uniformity in unburned web thickness during a normal burn of said length of extruded propellant thereby reducing the amount of unburned slivers.    
   
   
       2 . An extruded stick-type propellant grain as in  claim 1  further comprising a central perforation of a generally round geometry.  
   
   
       3 . An extruded stick-type propellant grain as in  claim 1  further comprising a central perforation of a generally star-shaped geometry.  
   
   
       4 . An extruded stick-type propellant grain as in  claim 1  wherein said perforations have a geometric cross section selected from generally star and trapezoid shapes.  
   
   
       5 . An extruded stick-type propellant grain as in  claim 1  wherein said radially distributed perforations have a geometric cross-sectional shape generally in the form of a trapezoid.  
   
   
       6 . An extruded stick-type propellant grain as in  claim 2  wherein said radially distributed perforations have a geometric cross-sectional shape generally in the form of a trapezoid.  
   
   
       7 . An extruded stick-type propellant grain as in  claim 3  wherein said radially distributed perforations have a geometric cross-sectional shape generally in the form of a trapezoid.  
   
   
       8 . An extruded stick-type propellant grain as in  claim 5  wherein at least one base of said trapezoids has a generally arcuate shape.  
   
   
       9 . An extruded stick-type propellant grain as in  claim 1  wherein said propellant grain has from 7 to 37 longitudinal perforations.  
   
   
       10 . An extruded stick-type propellant grain as in  claim 8  wherein said propellant grain has from 7 to 37 longitudinal perforations.  
   
   
       11 . An extruded stick-type propellant grain as in  claim 7  wherein said perforations include an array of six generally trapezoid-shaped perforations surrounding a central star-shaped perforation.  
   
   
       12 . An extruded stick-type propellant comprising: 
 (a) a length of extruded propellant material having a predetermined cross-sectional shape;    (b) a predetermined number of spaced, hollow longitudinal voids formed in said length of extruded propellant material parallel to and extending along the length thereof and separated and surrounded by a web of said propellant material; and    (c) wherein said voids have a geometric cross section selected from the group consisting of non-round shapes that enhance uniformity in unburned web thickness during a normal burn of a propellant grain made from the extruded propellant material thereby reducing the amount of unburned slivers.