Two-phase projectile with a proximal compression chamber

Abstract

A man-powered system for pneumatically launching a pellet cluster includes a cartridge for holding the pellet cluster. A hollow propulsion shaft receives the cartridge for substantially free travel back and forth in the shaft to establish a variable-volume compression chamber in the shaft, between the cartridge and a closed end of the shaft. When a driving force acts to launch the combination of cartridge and shaft, the cartridge moves to compress gas in the compression chamber for a subsequent expansion that will propel the cartridge forward through the shaft. After launch, the compressed gas acts to separate the pellet cluster from the cartridge and to provide a pneumatic assist that increases the velocity of pellets after separation.

What is claimed is: 
     
         1 . A man-powered system for pneumatically launching a pellet cluster which comprises:
 an elongated tubular-shaped cartridge formed with a lumen for holding the pellet cluster therein, wherein the cartridge has an open distal end and a closed proximal end;   an elongated, cylindrical-shaped propulsion shaft formed with a lumen for receiving the cartridge therein for substantially free travel back and forth in the lumen of the shaft, wherein the shaft has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the shaft between the proximal end of the cartridge and the proximal end of the shaft, wherein a volume of the compression chamber changes in response to movements of a cartridge in the shaft; and   a launcher to impart a driving force on the proximal end of the shaft to launch the combination of cartridge and shaft, and to cause the cartridge to compress gas in the compression chamber for a subsequent expansion thereof to propel the cartridge forward in a distal direction through the lumen of the shaft, after launch, to separate the pellet cluster from the cartridge through the respective open ends of the cartridge and the propulsion shaft.   
     
     
         2 . A system as recited in  claim 1  wherein the cartridge further comprises:
 an O-ring assembly positioned in a retention groove formed at the proximal end of the cartridge to establish a substantially airtight seal between the proximal end of the cartridge and an inner sidewall defining the lumen of the propulsion shaft; 
 a plurality of retainer tubes positioned in the lumen of the cartridge at the distal end thereof to maintain the pellet cluster in the lumen of the cartridge prior to launch; and 
 a friction collar positioned on an outer surface of the cartridge for a snug engagement therewith to generate friction forces against the cartridge to retard movement of the cartridge for separation of the pellet cluster from the cartridge. 
 
     
     
         3 . A system as recited in  claim 2  wherein the retention groove is formed with at least one vent hole to establish fluid communication for equalizing pressure between the retention groove and the compression chamber, and wherein the O-ring assembly comprises:
 an outer ring positioned in the retention groove for contact with an inner surface of the propulsion shaft, wherein the inner surface defines the lumen of the propulsion shaft; and 
 an inner ring positioned in the retention groove to produce a force against the outer ring to urge the outer ring into contact against the inner surface of the propulsion shaft. 
 
     
     
         4 . A system as recited in  claim 3  wherein the inner ring is made of rubber and the outer ring is made of polytetrafluoroethylene (PTFE), and further wherein the outer ring is formed with a diagonal split to permit contraction and expansion of the outer ring. 
     
     
         5 . A system as recited in  claim 2  wherein the friction collar is made of aluminum and exerts a radial pressure against the cartridge of approximately 500 psi. 
     
     
         6 . A system as recited in  claim 2  further comprising a slide ring assembly positioned on the outer surface of the cartridge distal to the friction collar to mitigate impact forces against the friction collar at the launch of the pellet cluster. 
     
     
         7 . A system as recited in  claim 1  wherein the propulsion shaft further comprises:
 a pressure valve positioned at the proximal end of the propulsion shaft for use in pressurizing the compression chamber to a predetermined gauge pressure (psig) prior to imparting the driving force against the shaft; 
 a ferrule attached to the distal end of the propulsion shaft, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the shaft; and 
 a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the propulsion shaft to establish a distal limit for movement of the cartridge in the lumen of the shaft. 
 
     
     
         8 . A system as recited in  claim 7  wherein the pressure valve is mounted in a nock, and the nock is affixed to the proximal end of the propulsion shaft for operational interaction with the launcher. 
     
     
         9 . A system as recited in  claim 1  wherein pellets in the pellet cluster are made of a material selected from the group consisting of tungsten and steel. 
     
     
         10 . A cartridge for use with a man-powered launcher which comprises:
 a pellet cluster;   an elongated tubular-shaped sabot formed with a lumen for holding the pellet cluster therein, wherein the sabot has an open distal end and a closed proximal end with a retention groove formed at the proximal end of the sabot;   an O-ring assembly positioned in the retention groove;   a plurality of retainers positioned in the lumen of the cartridge at the distal end thereof to maintain the pellet cluster in the lumen of the cartridge prior to launch; and   a friction collar positioned on an outer surface of the sabot.   
     
     
         11 . A cartridge as recited in  claim 10  wherein the cartridge is dimensioned to interact with an elongated, cylindrical-shaped propulsion shaft formed with a lumen for receiving the cartridge therein for substantially free travel back and forth in the lumen of the shaft, wherein the shaft has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the shaft between the proximal end of the cartridge and the proximal end of the shaft, wherein a volume of the compression chamber changes in response to movements of a cartridge in the shaft. 
     
     
         12 . A cartridge as recited in  claim 11  wherein the combination of cartridge and propulsion shaft is mounted on a launcher, and the launcher is configured to impart a driving force on the proximal end of the shaft to launch the combination of cartridge and shaft, and to cause the cartridge to compress gas in the compression chamber for a subsequent expansion thereof to propel the cartridge forward in a distal direction through the lumen of the shaft to separate the pellet cluster from the cartridge through the respective open ends of the cartridge and the propulsion shaft after launch. 
     
     
         13 . A cartridge as recited in  claim 12  wherein the retention groove on the sabot is formed with at least one vent hole to establish fluid communication for equalizing pressure between the retention groove and the compression chamber, and wherein the O-ring assembly comprises:
 an outer ring positioned in the retention groove for contact with an inner surface of the propulsion shaft, wherein the inner surface defines the lumen of the propulsion shaft; and 
 an inner ring positioned in the retention groove to produce a force against the outer ring to urge the outer ring into contact against the inner surface of the propulsion shaft. 
 
     
     
         14 . A cartridge as recited in  claim 13  wherein the inner ring is made of rubber and the outer ring is made of polytetrafluoroethylene (PTFE), and further wherein the outer ring is formed with a diagonal split to permit contraction and expansion of the outer ring. 
     
     
         15 . A cartridge as recited in  claim 12  wherein the propulsion shaft further comprises:
 a pressure valve positioned at the proximal end of the propulsion shaft for use in pressurizing the compression chamber to a predetermined gauge pressure (psig) prior to imparting the driving force against the shaft; 
 a ferrule attached to the distal end of the propulsion shaft, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the shaft; and 
 a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the propulsion shaft to establish a distal limit for movement of the cartridge in the lumen of the shaft. 
 
     
     
         16 . A cartridge as recited in  claim 12  wherein the friction collar is made of aluminum and is dimensioned for a snug engagement with the sabot to exert a radial pressure against the cartridge of approximately 500 psi for generating friction forces to retard movement of the sabot for separation of the pellet cluster from the sabot, and wherein the cartridge further comprises a slide ring assembly positioned on the outer surface of the cartridge distal to the friction collar to mitigate impact forces against the friction collar at the launch of the pellet cluster. 
     
     
         17 . A propulsion shaft for use with a man-powered launcher which comprises:
 an elongated, cylindrical-shaped tube formed with a lumen for receiving a cartridge therein for substantially free travel back and forth in the lumen of the tube, wherein the tube has an open distal end and a closed proximal end to establish a compression chamber in the lumen of the tube between the proximal end of the cartridge and the proximal end of the tube, wherein a volume of the compression chamber changes in response to movements of the cartridge in the tube; and   a pressure valve positioned at the proximal end of the tube for use in pressurizing the compression chamber to a predetermined gauge pressure (psig).   
     
     
         18 . A propulsion shaft as recited in  claim 17  further comprising:
 a ferrule attached to the distal end of the tube, wherein the ferrule has a threaded extension projecting in a distal direction from the distal end of the tube; and 
 a plug joined in a threaded engagement with the ferrule to create an abutment around the open distal end of the tube to establish a distal limit for movement of the cartridge in the lumen of the tube. 
 
     
     
         19 . A propulsion shaft as recited in  claim 17  wherein the pressure valve is mounted in a nock, and the nock is affixed to the proximal end of the tube for operational interaction with the launcher. 
     
     
         20 . A propulsion shaft as recited in  claim 17  wherein the cartridge holds a pellet cluster, and pellets in the pellet cluster are made of a material selected from the group consisting of tungsten and steel.