Patent Publication Number: US-6981449-B2

Title: Projectile launch assembly and method

Description:
STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by the U.S. Government for Governmental purposes without the payment of any royalty thereon. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to the launching of small projectiles, and more specifically is directed to an assembly and method for launching such projectiles from firearms, such as rifles. 
   2. Description of the Prior Art 
   Launchers which facilitate the firing of a projectile such as, for example, a rifle grenade, from a rifle are generally known and in use. 
   However, in non-combat situations, as in training, or the like, the launch assemblies, which may be readily recoverable, are not reusable. That is, even on a practice range the launch assemblies are adapted only for one-time use. 
   It will be apparent that economies could be realized if launchers which are readily recoverable could be used multiple times before discarding. 
   SUMMARY OF THE INVENTION 
   An object of the invention is, therefore, to provide a projectile launch assembly which is suitable for providing a projectile launch capability for a rifle, and which can be used, for the most part, time and time again. 
   A further object of the invention is to provide a method for launching a projectile from a firearm, including providing a launch device capable of multiple reuses. 
   With the above and other objects in view, a feature of the present invention is the provision of a projectile launch assembly including a launch tube having distal and proximal ends and an inwardly extending dimple structure therebetween, the proximal end being adapted to receive a muzzle of a firearm. A receiver is disposed on the distal end of the launch tube, the receiver having connector structure at a distal end thereof for connection to a projectile. An energy absorbing plug is disposed in the launch tube and is provided with a proximal end portion adjacent the dimple and is provided with a body portion extending distally. An energy transfer piston is disposed in the launch tube and is provided with a proximal end configured complementarily to the plug and with a distal end configured complementarily to a proximal end of the receiver. A bullet leaving the firearm muzzle is absorbed by the plug which is thereby moved with the piston distally in the tube. The piston engages the receiver to propel the assembly and the projectile from the firearm muzzle. 
   In accordance with a further feature of the invention, there is provided a method for launching a projectile from a firearm, the method comprising the steps of providing a projectile launch assembly comprising a launch tube having distal and proximal ends and an inwardly extending dimple therebetween, a receiver disposed on the distal end of the launch tube, the receiver having connector structure at a distal end thereof for connection to a projectile, an energy absorbing plug having a proximal end portion adjacent the dimple, a body portion extending distally, and an energy transfer piston adjacent the plug and having a proximal end configured complementarily to the plug and having a distal end configured complementarily to a proximal end of the receiver; manipulating the receiver connector structure to connect a selected projectile to the receiver; sliding the launch tube onto a muzzle portion of a firearm until a distal end of the muzzle portion engages the dimple; and firing the firearm. A bullet leaving the firearm muzzle is absorbed by the plug which is thereby moved with the piston distally in the tube. The piston engages the receiver to propel the assembly and the projectile from the firearm muzzle. 
   The above and other features of the invention, including various novel details of construction and combinations of parts and steps, will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular assembly and method embodying the invention are shown and described by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is made to the accompanying drawings in which is shown an illustrative embodiment of the invention, from which its novel features and advantages will be apparent. 
     In the drawings: 
       FIG. 1  is an interrupted center line sectional view of one form of projectile launch assembly illustrative of an embodiment of the invention for low velocity ammunition; 
       FIG. 2  is a sectional view taken along line II—II of the whole assembly depicted in section in  FIG. 1 ; 
       FIG. 3  is similar to  FIG. 1  and is illustrative of an alternative embodiment of launch assembly for medium velocity ammunition; and 
       FIG. 4  is similar to  FIGS. 1 and 3  and is illustrative of a further alternative embodiment of launch assembly for high velocity ammunition. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1 and 2 , it will be seen that an illustrative embodiment of projectile launch assembly includes a cylindrically-shaped elongated launch tube  10  having a distal end  12  and a proximal end  14 . An inwardly extending dimple  16  is disposed between the launch tube distal and proximal ends  12 ,  14 . The dimple  16  may be a continuous single annular dimple, as illustrated, or a plurality of dimples arranged in annular fashion. 
   A collar  18  is mounted, as by threads or press-fit, on the distal end  12  of the launch tube  10 . The collar  18  is provided with connector structure  20 , such as screw threads. 
   The assembly further includes a receiver  22  which is provided at its proximal end  23  with connector structure  24 , such as screw threads, for connecting engagement with the collar connector structure  20 , to affix the receiver  22  to the launch tube distal end  12 . The receiver  22 , at a distal end  26  thereof, is provided with further connector structure  28 , such as a threaded bore, for connection to a stem  30  of a projectile. One such projectile for which the launch assembly described herein is well suited is a grappling hook generally of the type disclosed in U.S. Pat. No. 6,079,761, issued Jun. 27, 2000, in the name of James E. Sedeck, and incorporated herein by reference. 
   Mounted in the launch tube  10  is a circular plug  32  configured to fit snugly in the launch tube  10  abutting the dimple  16 . The plug  32  includes a frusto-conical portion  34  extending from a planar portion  36 . At a distal end  38  of the frusto-conical portion  34  there is disposed an end disc portion  40 , or other such protuberance. 
   Connected to the plug  32  is a piston  42  provided with a proximal end  44  adjacent the planar portion  36  of the frusto-conical portion  34  and having a recess  46  therein in which is disposed the frusto-conical portion  34  of the plug  32 . The piston  42  is further provided with a relief cut  48  which receives the end disc portion  40  of the plug  32 . The relief cut  48 , in cooperation with the end disc portion  40 , serves to interconnect the piston  42  and the plug  32 , both of which are slidably movable in the launch tube  10 . 
   The receiver proximal end  23  is provided with a recess  50  shaped complementarily to a distal end  52  of the piston  42 . 
   The proximal end  14  of the launch tube  10  may be provided with stabilizing fins  54 . 
   Referring to  FIG. 3 , it will be seen that in an alternative embodiment, the plug  32  includes an end portion  38  which includes opposed frusto-conical shaped portions  60 ,  62  received in a complementarily shaped relief cut  48 . 
   A sealing ring  64  seals a joint between the receiver  22  and the collar  18 , preventing leakage of air from inside the launch tube  10  during movement of the piston  42 . Similarly, sealing rings  66  and  68  are seated in annular grooves  70 ,  72  in the piston  42  to prevent leakage of air between the piston and the launch tube  10 . 
   In this embodiment, the receiver recess  50  is of a curved configuration and the piston distal end  52  is complementarily shaped, providing for an even distribution of compressive force over the two surfaces  50 ,  52  and dissipation of heat in operation of the assembly. 
   In operation, the proximal end  14  of the launch tube  10  receives in a cavity  56  the muzzle and flash suppresser of a rifle (not shown) such that the flash suppresser is essentially flush with the plug planar portion  36 . The butt of the rifle is placed against the ground or other support and inclined at a selected launch angle. The rifle is fired in the usual manner. 
   A bullet leaving the rifle impacts the plug  32  which is of a selected material such as a polymer, lead, soft aluminum, copper, brass, and composites or alloys thereof, or other material adapted to receive and appreciably slow the bullet. The bullet embedding in the plug  32  drives the plug  32  and the piston  42 , which preferably is of hardened or cold-rolled steel, distally, such that the piston distal end  52  impacts the receiver  22  in the receiver recess  50  and compresses air in the recess  50 , such that the bullet is dynamically decelerated. The compressed air, and expanding powder explosion gases from the rifle cartridge, and the violent impact of the piston on the receiver proximal end recess  50 , serve to lift the launch assembly and the projectile  30  off of the rifle. 
   If the launch assembly is recovered, the receiver  22  can be unscrewed from the collar  18  and the piston  42  and plug  32  removed. The plug  32  can then be withdrawn from the piston  42 , the relative softness of the plug permitting withdrawal of the plug end disc portion  40  from the relief cut  48  in the steel piston. A new plug  32  is then inserted in the piston recess  46 . The piston  42  and new plug  32  are then slid down the launch tube  10  until the plug planar portion  32  is disposed adjacent the dimple  16 . The receiver  22  is threaded back onto the collar  18  to place the launch assembly in condition to receive another projectile for launch. 
   Referring to  FIG. 4 , it will be seen that in a further alternative embodiment, the plug  32  includes an end portion  38  which includes a frusto-conical portion  34  which, in turn, projects distally from a cylindrical portion  80  provided with a planar proximal end portion  36 . 
   The plug  32  is of a high-density metallic, polymeric or cellulose material and in this embodiment is held in the piston  42  by screws  82  disposed in bores  84 , the screws  82  projecting radially inwardly and engaging the plug cylindrical portion  80  to interconnect the plug  32  and the piston  42 . A circular rubber or polymer washer  86  is held on the proximal end  44  of the piston  42  by the plug planar portion  36 . 
   A circular bulkhead  88  is slightly oversized diameter-wise and is press-fitted into the launch tube  10  proximate the dimple structure  16 . The bulkhead  88  is provided with a central aperture  90  which is slightly larger than the caliber of bullet fired from the rifle being used for launch. 
   As shown in  FIG. 4 , the collar  18  may be sufficiently elongated to extend proximally on the launch tube  10  to slightly beyond the dimple structure  16 . The collar  18  may be provided with dimple structure  92  complementary to, and engageable with, launch tube dimple structure  16 . 
   Upon firing of the rifle, the bullet (not shown) passes through the aperture  90  and embeds in the plug  32 , and moves the plug  32  and the piston  42  distally in the launch tube  10 . The washer  86  moves with the plug  32  and piston  42 . The distal movement of the piston  42  compresses air between the piston and the receiver  22  and dynamically decelerates the bullet movement. Gas from the bullet powder charge enters the growing volume between the bulkhead  88 , which remains stationary, and the washer  86 , which moves distally with the plug  32 . The gas expansion in the space between the bulkhead  88  and the washer  86  exerts pressure on the washer, creating an improved seal between the washer and the interior sidewall of the launch tube  10 . The aforesaid space develops into a safety chamber which traps unburned powder particles and debris from the plug and the bullet. 
   Upon retrieval of the used launch assembly, the receiver  22  may be unscrewed from the collar  18  and the piston  42 , plug  32  and washer  86  removed from the launch tube  10 . The plug  32  and washer  86  are removed from the piston  42  by loosing the screws  82 . A new plug  32  and washer  86  are connected to the piston  42  and the piston, plug, and washer assembly is moved through the launch tube  10  to the position shown in  FIG. 4 . The receiver  22  is screwed onto the launch tube distal end  12  to complete the reassembly. The launch assembly is then in condition for re-use. 
   There is thus provided projectile launch assemblies suitable for providing a projectile launch capability for a rifle and which can be used multiple times with replacement of only a portion thereof, thereby realizing significant economies. There is further provided a method for launching a projectile from a rifle, including use of a launch device which is for the most part reusable. 
   It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention as expressed in the appended claims.