Patent Publication Number: US-7594465-B2

Title: In bore air regulation system

Description:
REFERENCE TO RELATED APPLICATION 
   The present application claims priority to U.S. Provisional Application No. 60/452,785, filed Mar. 7, 2003, and U.S. Provisional Application No. 60/520,419, filed Nov. 14, 2003. The identified provisional applications are hereby incorporated by reference in their entirety. 

   FIELD OF THE INVENTION 
   This invention provides a weapon system for firing rounds. More particularly, the present invention relates to a weapon system that uses in bore air regulation. 
   BACKGROUND OF THE INVENTION 
   Mortar rounds, which normally are used with muzzle loading weapon systems, can also be used in breech loading weapon systems employing a smooth bore gun tube, but only when the angle between the axis of the gun tube and horizontal is positive and sufficiently large for the force of gravity to assure the round is in proper engagement with the breech block of the gun. 
   Without such engagement, the percussion primer in the mortar round will not be activated causing the gun to misfire. The problem of holding the round against the breech face is aggravated with the additional system requirement of firing mortar systems from mobile platforms at negative elevation angles, i.e., at angles below horizontal. Under those circumstances, without some means of restraint, the round would be urged by the force of gravity to move down the gun tube away from the breech. 
   To compensate for such problems, the prior art has employed devices, such as stub cases and clips, which are attached to normal mortar rounds. An example of a stub case is shown in U.S. Pat. No. 6,257,148, wherein the stub case is mechanically attached to the base of the mortar round. The assignee of this patent is known to also attach a stub case by elastic straps engaging both the stub case and the fins of the round. 
   When stub case weapon systems are fired, the stub case separates from the round. Thereafter, the stub case must be removed from the breech. Because of the relatively high temperatures generated during the firing process, there are also issues relating to disposal of the hot stub case in a safe manner. 
   Another ordnance manufacturer is known to utilize a clip on the fins of the mortar round which engages a mating feature machined into the gun tube to hold the round against the breech face. Such prior art arrangements introduce complications of logistics, e.g., transportation, storage, and installation, and additional cost since both current and future rounds need hardware associated with them for use in breech loading systems, while increasing the complications and cost of using such specially configured rounds in traditional muzzle loading mortar systems. In addition, such prior art arrangements do not provide a means for safe misfire ejection, for clearing the gun bore of burning embers, or for forced convection cooling of the gun tube. 
   SUMMARY OF THE INVENTION 
   The in bore air regulation system of the present invention solves the problems associated with prior art weapon systems, while additionally providing a means for safely ejecting a misfired round without requiring handling by personnel and without moving the misfired projectile into the magazine of the vehicle, for clearing the gun tube of any residual burning embers, and for convection cooling of the gun tube when required by frequent firing. 
   The in bore air regulation system of the present invention holds the round in proper position within the breech by creating a low pressure vacuum in the breech block, i.e., reducing the pressure in the breech block below atmospheric, so that the pressure differential created thereby will cause the round to be pushed and held against the face of the breech block. 
   A valve is held open to connect the interior of the breech with a source of vacuum. Immediately prior to firing, the valve is closed so the integrity of the breech and chamber is maintained, and the vacuum components are protected from damage as the round is fired. 
   Even though the vacuum may begin to diminish as soon as the valve is closed, inertia and friction will retain the round in its proper position during the short interval of time between valve closing and firing of the round. The in bore air regulation system of the present invention achieves the attributes of ember clearing and forced convection cooling by selectively connecting the breech to a source of air under positive pressure through the same aforementioned valve. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially broken away perspective view of a weapon system having an in bore air regulation system. 
       FIG. 2  is a partially broken away perspective view of an alternate weapon system having an in bore air regulation system. 
       FIG. 3  is a partially broken away perspective view of another weapon system having an in bore air regulation system. 
       FIG. 4  is a partially broken away perspective view of yet another weapon system having an in bore air regulation system. 
       FIG. 5   a  is a perspective view of a breech loading gun having an in bore air regulation system in a battery position. 
       FIG. 5   b  is a perspective view of the gun shown in  FIG. 6   a  with the gun in a full recoil position. 
       FIG. 5   c  is a drawing illustrating the breech block used in the gun illustrated in  FIGS. 6   a  and  6   b.    
       FIG. 6   a  is a perspective view of the air system illustrating a break away connection in the battery position where the air system is in communication with the breech block. 
       FIG. 6   b  is a perspective view of the air system illustrating the break away connection in full recoil position where the air system is disconnected from the breech block. 
       FIG. 7  is a schematic drawing of one embodiment of the present invention illustrating its application to a gun having a sliding breech block utilizing a unidirectional pump in which the vacuum side is normally connected through a manually shiftable valve to a poppet valve in the breech block. The manual valve can be selectively shifted to connect the pressure side to the breech when the poppet valve is opened to eject a misfired round, to evacuate burning embers or to cool the gun tube. 
       FIG. 8  is a schematic drawing, similar to  FIG. 8 , of another embodiment of the invention in which the poppet valve communicates with the breech through the side of the barrel rather than being incorporated into the breech block. 
       FIG. 9  is a schematic drawing, similar to  FIG. 9 , of another embodiment of the invention in which a reversible, positive displacement pump is connected directly to the breech through the poppet valve. 
       FIG. 10  is a schematic drawing of another embodiment of the invention illustrating its application to a gun having a sliding breech block and employing a reversible, positive displacement pump. 
       FIG. 11  is a schematic representation of the forces acting on a mortar round just prior to firing when in an arrangement according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention is directed to an in bore air regulation system for a weapon system. The in bore air regulation system of the present invention is particularly suited for use with breech loading weapon systems such as the M120 mortar system. The in bore air regulation system not only facilitates loading rounds into a firing position but also enables malfunctioning rounds to be easily and safely discharged from the weapon system. 
   It is possible to use the in bore air regulation system with all types of conventional rounds. The in bore air regulation system enables the weapon system to be oriented without respect to the angle of the barrel. The in bore air regulation system also operates in a highly reliable manner regardless of external factors such as temperature, humidity, dirt and dust. 
   Another advantage of the present invention is the in bore air regulation system of the present invention enables the weight of the weapon system to be significantly reduced compared to conventional breech loading weapon systems that utilize stub cases because the in bore air regulation systems do not use stub cases and stub case ejectors. Since stub cases are not required, it is also possible to use shorter magazines. 
     FIG. 1  depicts an in bore air regulation system  10  incorporated into a weapon system  8 . The weapon system  8  in this embodiment generally includes a gun barrel  30  with a first end  32  and a second end  34 . The gun barrel  30  has a bore  36  formed therein that extends from the second end  34  towards the first end  32  where a breech face  40  is located. The bore  36  is adapted to receive a round  38 . 
   The in bore air regulation system  10  is in communication with the bore  36  through an aperture  12  formed in a barrel wall  14 . A valve  16  is provided proximate the aperture  12  to protect the in bore air regulation system  10  during firing. 
   It is preferable to mount an air pressure generation portion  20  of the in bore air regulation system  10  on a portion of the weapon system  8  that does not recoil when firing. The air pressure generation portion  20  is in communication with the aperture  12  using a tube  24 . The tube  24  preferably has a sliding configuration that is similar to a trombone that allows the tube  24  to lengthen when the weapon system  8  is fired. 
     FIG. 2  illustrates use of the in bore air regulation system  110  with a screw breech weapon system  122 . Similar to the preceding embodiment, the weapon system  122  includes a gun barrel  130  having a bore  136  extending therethrough that is adapted to receive a round  138 . 
   In this embodiment, an aperture  112  is formed in a screw breech  118 . A valve  116  is provided in the screw breech  118  to protect the in bore air regulation system  110  during firing. 
   Similar to the embodiment illustrated in  FIG. 1 , the air pressure generation system  120  is connected to the aperture  112  with a tube  124  having a sliding configuration similar to a trombone. 
   Use of the in bore air regulation system  210  with another weapon system  222  is illustrated in  FIG. 3 . The weapon system  222  includes a gun barrel  230  with a bore  236  extending therethrough that is adapted to receive a round  238 . 
   This embodiment utilizes a sliding wedge breech  218 . An aperture  212  is formed in the sliding wedge breech  218 . A valve  216  is provided in the sliding wedge breech  218  to protect the in bore air regulation system  210  during firing. 
   A tube  224  connects an air pressure generation system  220  to the aperture  212 . The tube preferably has a sliding configuration that is similar to a trombone. 
   Still another embodiment of the present invention relates to mounting the air pressure generation system  320  behind the breech  318  of a weapon system  322 , as illustrated in  FIG. 4 . The weapon system  322  includes a gun barrel  330  having a bore  336  extending therethrough that is adapted to receive a round  338 . 
   In this embodiment, an aperture  312  is provided in the barrel wall  314 . Tubing  324  that connects the air pressure generation system  320  with the aperture preferably includes a trombone-like sliding configuration. 
     FIGS. 5   a - 5   c  and  6   a - 6   b  show a breech loading weapon system  500  into which an air pressure vacuum system  510  has been incorporated. A vacuum air pump  520  is carried by the elevating mass of the gun and connected to the breech through a break away connection  550 , which is most clearly illustrated in  FIGS. 6   a - 6   b.    
   The breakaway connection  550  reduces the mass to be absorbed by the gun&#39;s recoil mechanism by allowing the mass of the pump  520  to be attached to or otherwise carried by that portion of the weapon system  500  that does not move in recoil. 
   Since very low pressures differentials are involved and the flow is relatively high, this connection has negligible impact on the system performance. Thus, the break away connection  550  may be a cone shaped male member  552  mounted on either the recoil or movable mass engagable with a complementary shaped female member  554  mounted on the mass that does not move in recoil. 
   An O-ring interface functions as a seal between the two members when the gun is in the battery position. Using such a configuration increases a contact surface area in the breakaway mechanism  550  to enhance the performance of the in bore air regulation system  510 . 
     FIG. 5   c  shows the poppet valve  560  in the breech block  562 . This valve  560  is urged by a compression spring  564  toward a closed position in which the integrity of the breech and the chamber is maintained and is cammed to an open position in which the chamber is in communication with the vacuum air pump  520 . 
   The poppet valve  560  is similar to the type of valves used for exhaust and intake on internal combustion engines. Thus, the poppet valve  560  is normally held tightly against a seat by the compression spring  564 , and is lifted off of its seat by a cam, which cam may be shifted by a solenoid, for example. 
     FIGS. 7-10  provide schematic illustrations of various configurations for the in bore air regulation system of the present invention. In particular,  FIG. 7  depicts the in bore air regulation system  610  using the valve  620  with a single direction pump  624 . 
   Changing the position of the valve  620  enables air to be drawn out of or into the barrel  630 . A breakaway connection  634  is preferably provided between the air pressure regulation system  610  and the gun barrel  630 . 
   A sliding seal  640  is preferably provided between gun barrel  630  and the breech  642  to enable the breech  642  to be removed from the gun barrel  630 . A valve  650  is provided in the breech  642  to separate the in bore air generation system  610  from the bore  652  when firing the round  654 . 
     FIG. 8  illustrates the in bore air regulation system  710  using a valve  720  with a single direction pump  724 . Changing the position of the valve  720  air to be drawn out of or into the barrel  730 . A breakaway connection  734  is preferably provided between the air pressure regulation system  710  and the gun barrel  730 . A valve  750  is provided in the barrel  730  to separate the in bore air generation system  710  from the bore  752  when firing the round  754 . 
     FIG. 9  is similar to the embodiment illustrated in  FIG. 8  but the in bore air regulation system  810  includes a reversible pump  824 . A breakaway connection  834  is preferably provided between the air pressure regulation system  810  and the gun barrel  830 . A valve  850  is provided in the barrel  830  to separate the in bore air generation system  810  from the bore  852  when firing the round  854 . 
     FIG. 10  is similar to the embodiment illustrated in  FIG. 7  but the in bore air regulation system  910  includes a reversible pump  924 . A breakaway connection  934  is preferably provided between the air pressure regulation system  910  and the gun barrel  930 . 
   A sliding seal  940  is preferably provided between gun barrel  930  and the breech  942  to enable the breech  942  to be removed from the gun barrel  930 . A valve  950  is provided in the breech  942  to separate the in bore air generation system  910  from the bore  952  when firing the round  954 . 
     FIG. 11  schematically illustrates the forces acting on the round. Force created by pressure is the product of the pressure and the area on which the pressure acts. Atmospheric pressure PA acting on the left end of the round creates a force equal to the cross sectional area of the round times the pressure PA that force urges the mortar round toward the right. i.e., the breech end of the gun tube. 
   The pressure in the breech PB creates a force acting in the opposite direction. Since the areas on which the pressure PA and PB act are equal, the two opposing pressure forces will be equal when the pressure in the breech PB is at atmospheric pressure PA. 
   Another force acting on the round is the force of gravity G, which force can be resolved into a force GA acting along the axis of the gun tube and a force GN, which is normal to the axis of the gun tube. The force GN creates a frictional force F, which is equal to the coefficient of friction times the normal force GN. 
   When the angle ø between the centerline of the gun tube and horizontal is sufficiently large, the force GA will be greater than the friction force F causing the round  10  to move into engagement with the face of the breech block. Since the coefficient of sliding friction for the materials involved is less than the coefficient of static friction, once the round begins to slide in the gun tube, it will move all the way into engagement with the face of the breech block. 
   However, as the angle ø is decreased, the axial component GA of the force of gravity G will also decrease and the friction force F will increase because the normal force GN will also increase. As a consequence, when the angle ø is sufficiently small, the component GA will be insufficient to assure the round is in engagement with the face of the breech block. 
   Under such circumstances, creating a vacuum in the breech, i.e., reducing the pressure PB in the breech block below atmospheric, will create a pressure differential on the round, which pressure differential will create a net force, which when added to the force GA, will urge the round into engagement with the face of the breech block. 
   In operation, the round is inserted through the breech end of the barrel. Thereafter, the breech is closed and the in bore air regulation system is activated to draw the round against the breech. 
   Just before it is desired to fire the weapon system, the in bore air regulation system is disconnected from the interior of the barrel with a valve. If the round fails to correctly fire, the defective round may be ejected from the weapon system by injecting air into the barrel with the in bore air regulation system. The force of the air is sufficiently high to eject the round but low enough not to cause the round to be fired. 
   It is contemplated that features disclosed in this application, as well as those described in the above applications incorporated by reference, can be mixed and matched to suit particular circumstances. Various other modifications and changes will be apparent to those of ordinary skill.