Pyrotechnic launch tube

Abstract

A pyrotechnic launch tube made using fiberglass reinforced polymer (FRP) includes a cylindrical FRP tube having an inside wall, where the inside wall has a circumferential groove near a lower end of the tube. A bottom member made of FRP is molded for engagement with the tube at the groove. After forming the tube and the groove, a mold having a concave surface is placed inside the tube adjacent to the groove, and resin-coated fiberglass matting is laid on the mold. A fibrous material is placed over the fiberglass matting and a nonporous bag seals the fiberglass matting. A vacuum is drawn in the bag, and atmospheric air pressure compresses the fiberglass matting, forcing it into the groove. A counter mold can be used instead of vacuum setting to compress the fiberglass matting. The bottom member has a convex surface, and the convex surface and the inside wall of the tube define a chamber for receiving pyrotechnics.

1 . A method for making a fiberglass reinforced polymer (FRP) pyrotechnic launch tube, comprising the steps of: 
 providing an FRP tube having an upper end, a lower end, an inside wall and a circumferential groove in the inside wall near the lower end; and    engaging a bottom piece in the groove.    
     
     
         2 . The method of  claim 1 , wherein the step of engaging the bottom piece comprises molding FRP.  
     
     
         3 . The method of  claim 2 , wherein the molding step includes: 
 sealing a mold with the inside wall proximate to the groove;    laying fiberglass matting having a resin coating onto the mold;    placing a portion of the fiberglass matting within the groove for engagement with the tube; and    curing the resin.    
     
     
         4 . The method of  claim 3 , further comprising vacuum setting the fiberglass matting before the curing step.  
     
     
         5 . The method of  claim 4 , wherein the step of vacuum setting comprises placing a porous material over the fiberglass matting so that the matting is between the mold and the porous material; 
 sealing a nonporous sheet over the fiberglass matting; and    drawing a vacuum on the fiberglass matting so that the nonporous material collapses onto the fiberglass matting and forces the fiberglass matting into the groove.    
     
     
         6 . The method of  claim 3 , further comprising compressing the fiberglass matting between the mold and a counter mold before the curing step.  
     
     
         7 . The method of  claim 3 , wherein the curing step includes applying heat.  
     
     
         8 . The method of  claim 1 , wherein the step of engaging the bottom piece comprises: 
 providing a flexible, disc-shaped element;    pressing the disc-shaped element into the tube; and    allowing the disc-shaped element to expand into the groove.    
     
     
         9 . The method of  claim 1 , wherein the bottom piece has a convex surface, and the convex surface and the inside wall of the tube define a chamber for receiving pyrotechnics.  
     
     
         10 . The method of  claim 2 , wherein the mold has a concave surface, which forms the bottom piece with a convex surface, wherein the convex surface of the bottom piece and the inside wall of the tube define a chamber for receiving pyrotechnics.  
     
     
         11 . A pyrotechnic launch tube made according to the method of  claim 1 .  
     
     
         12 . A method for making a fiberglass reinforced polymer (FRP) pyrotechnic launch tube, comprising: 
 forming an FRP tube having an inside wall and upper and lower ends;    forming a groove in the inner wall about the circumference of the tube;    placing a mold inside the tube in sealed engagement with the inside wall adjacent to the groove;    laying a resin-coated fiberglass matting on the mold and in the groove;    placing a porous material on the fiberglass matting;    forming a sealed bag over the lower end of the tube;    evacuating the bag for pressing the fiberglass matting into the groove and onto the mold; and    curing the resin.    
     
     
         13 . The method of  claim 12 , wherein the mold has a concave surface so that a bottom is formed having a dome-shaped surface, wherein the dome-shaped surface and the inside wall define a chamber for receiving pyrotechnics.  
     
     
         14 . The method of  claim 12 , wherein the groove is formed as the tube is formed.  
     
     
         15 . The method of  claim 12 , wherein the groove is cut into the tube after the tube is formed.  
     
     
         16 . A method for making a fiberglass reinforced polymer (FRP) pyrotechnic launch tube, comprising: 
 forming an FRP tube having an inside wall and upper and lower ends;    forming a groove in the inner wall about the circumference of the tube;    placing a mold inside the tube in sealed engagement with the inside wall adjacent to the groove;    laying a resin-coated fiberglass matting on the mold and in the groove;    placing a counter mold on the fiberglass matting;    compressing the fiberglass matting between the mold and the counter mold; and    curing the resin.    
     
     
         17 . The method of  claim 16 , wherein the mold has a concave surface so that a bottom is formed having a dome-shaped surface, wherein the dome-shaped surface and the inside wall define a chamber for receiving pyrotechnics.  
     
     
         18 . The method of  claim 17 , wherein the counter mold has a convex surface sized to matingly engage the concave surface of the mold so the bottom has a relatively uniform thickness.  
     
     
         19 . A fiberglass reinforced polymer (FRP) pyrotechnic launch tube, comprising: 
 an FRP tube having an inside wall, an upper end, a lower end and a groove in the inside wall around the inner circumference of the tube; and    a bottom protruding into the groove.    
     
     
         20 . The pyrotechnic launch tube of  claim 19 , wherein the bottom has a convex surface, wherein the convex surface of the bottom and the inside wall of the tube form a chamber for receiving pyrotechnics.  
     
     
         21 . The pyrotechnic launch tube of  claim 20 , wherein the convex surface has the shape of a dome.  
     
     
         22 . The pyrotechnic launch tube of  claim 19 , wherein the bottom is a piece of FRP molded in place so as to mechanically engage the tube where the bottom protrudes into the groove, the bottom having a hemispherical shape extending toward the upper end so that as pyrotechnics explode within the tube, the bottom is pressed into deeper engagement with the tube at the groove.