Abstract:
A firearm includes a noise suppressor comprising ports in the barrel opening into an annulus provided between a barrel and a sleeve extending from adjacent the muzzle to adjacent the receiver. In the annulus are a series of baffles. The most upstream port opens upstream of the most upstream baffle and downstream ports open between adjacent baffles. In some embodiments, the upstream ports are considerably larger than the downstream ports. Propulsion gases escape from the barrel into the annulus before the projectile clears the muzzle. Sabot rounds or shotgun rounds can be safely fired in the weapon because the sabot carrier or shot cup don&#39;t begin to expand until it is past the muzzle end so it cannot damage the noise suppressor.

Description:
[0001]    This application is partly based on Provisional Application Ser. No. 61/396,065 filed May 12, 2010, priority of which is claimed. 
     
    
       [0002]    This invention relates to an assembly and noise suppressor for rifles, cannons, multibarrel weapons systems, automatic weapons, pistols, shotguns and similar firearms. 
       BACKGROUND OF THE INVENTION 
       [0003]    This invention is a modification or improvement over the device disclosed in PCT Application PCT/US2009/001062, the disclosure of which is incorporated herein by reference. 
         [0004]    Conventional silencers or noise suppressors are devices attached to the barrel of rifles, shotguns, pistols and similar firearms for reducing the noise attendant upon firing of ammunition. Silencers are typically attached by machining threads on the muzzle end of the barrel and then threading the silencer onto the barrel. 
         [0005]    There is always a problem aligning noise suppressors with the bore of the weapon so the projectile passes through the suppressor without grazing or otherwise impacting those components of the suppressor nearest the axis of travel of the projectile. 
         [0006]    Sabot ammunition are rounds where the projectile doesn&#39;t contact the barrel bore but is instead mounted on a carrier which separates from the projectile when the projectile clears the muzzle. The carrier tends to separate from the sabot inside conventional prior art noise suppressors which either destroys the suppressor or leaves debris in the suppressor to be contacted by the next round fired. Noise suppressors are known which are capable of being attached to a weapon through which sabot rounds are fired, e.g. U.S. Pat. Nos. 4,928,573; 5,992,291 and 6,065,384. 
         [0007]    Other disclosures of interest are found in U.S. Pat. Nos. 3,858,481; 4,576,083; 6,575,107 and 6,216,578 and PCT publication WO 2010/040886. 
       SUMMARY OF THE INVENTION 
       [0008]    A noise suppressor assembly is disclosed where ports are provided in the barrel adjacent the muzzle end, a sleeve or similar mechanism provides a receptacle into which propulsion gases flow and a series of baffles are disposed around the end of the ported barrel inside the sleeve. When a round is fired and the projectile enters the ported area of the barrel, expanding gases are delivered through the ports into the annulus between the barrel and sleeve. This allows expansion of the propulsion gases into a receptacle outside the barrel, reducing the energy of the gases, cooling the gases and reducing muzzle noise. Cooled propulsion gases bleed off through the baffle assembly between rounds. Those skilled in the art will recognize that the ported area of the barrel may comprise a muzzle brake so firing the weapon without the sleeve will act much like a similar weapon with only a muzzle brake. 
         [0009]    The muzzle end of the barrel is machined to provide a series of axially spaced ports upstream of the muzzle end in areas where rifling is provided in the bore. The ports may be positioned so they do not interfere with the rifling and may be along the lands. In preferred embodiments, the barrel end is machined to provide the ports. The size and spacing of the ports may be of many different configurations and/or sizes but are located adjacent the barrel end and are large in comparison to the bore of the barrel. In some embodiments, the furthest upstream port or ports are larger than downstream ports to divert a sizeable fraction of propulsion gases through the furthest upstream port. 
         [0010]    The receptacle disclosed may comprise an imperforate sleeve analogous to the heat shield or stabilizer tube disclosed in PCT application PCT/US2009/001062 and conveniently comprises a tube attached to the receiver, to the barrel adjacent its junction with the receiver or in any other suitable manner. 
         [0011]    The baffle assembly may comprise a series of baffles welded or otherwise secured to the muzzle end of the barrel between the ports or may be on a separate member inserted onto the barrel end. In some embodiments, the first or most upstream port or group of ports may be considerably larger than the downstream ports to allow a sizeable fraction of the propulsion gases to exit the barrel before reaching the more downstream baffles. The baffles may be slightly smaller than the internal dimension of the sleeve to allow gases exiting through downstream ports to escape into the sleeve interior or may fit more-or-less snugly against the sleeve interior so the cavity between each baffle traps and expands a small proportion of the propulsion gases. 
         [0012]    This approach has many advantages. First, when firing sabot ammunition, there is no tendency of the sabot carrier to separate inside the noise suppressor. Second, the annulus between the barrel exterior and the sleeve interior provides an expansion chamber for cooling propellant gases thereby enhancing the silencing ability of the device. Third, because the sleeve is readily removable from the receiver, the firearm and noise suppressor are easy to clean without sophisticated cleaning equipment. Thus, in some embodiments, a novel noise suppressor is made having only one part that is removable from the weapon, i.e. the sleeve. The noise suppressor can be easily cleaned by removing the sleeve thereby exposing all of the components of the suppressor. In shotguns, which are normally unrifled, the suppressor allows a shot carrier to clear the ports and the barrel before it starts to expand so that the shot carrier does not damage or interfere with the suppressor. 
         [0013]    It is an object of this invention to provide an improved noise suppressor for a firearm. 
         [0014]    A further object of this invention is to provide a noise suppressor which may be used with a firearm using sabot rounds and preventing the sabot carrier from interfering with operation of the suppressor. 
         [0015]    Another object of this invention is to provide a firearm having a noise suppressor which includes a ported barrel section near the muzzle providing ports which are large in comparison to the bore area. 
         [0016]    These and other objects and advantages of this invention will become more apparent as this description proceeds, reference being made to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a pictorial view of a conventional rifle which is used in conjunction with a ported barrel and sleeve to provide a noise suppressed weapon; 
           [0018]      FIG. 2  is an isometric view of a ported barrel that is attached to the rifle of  FIG. 1 ; 
           [0019]      FIG. 3  is a broken side view of a sleeve that is attached to the rifle of  FIG. 1 ; 
           [0020]      FIG. 4  is a enlarged cross-sectional view of the muzzle end of the barrel onto which a baffle assembly has been added, taken substantially along line  4 - 4  in  FIG. 2 , as viewed in the direction indicated by the arrows; 
           [0021]      FIG. 5  is an isometric view of one embodiment of a baffle assembly used in conjunction with the barrel of  FIG. 2 ; 
           [0022]      FIG. 6  is a broken isometric view of another embodiment of a baffle assembly incorporated onto the end of a barrel; 
           [0023]      FIG. 7  is a cross-sectional view of the barrel of a weapon illustrating another embodiment of a noise suppressor; and 
           [0024]      FIG. 8  is a cross-sectional view, similar to  FIG. 7 , illustrating another embodiment of a noise suppressor. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring to  FIGS. 1-2 , a rifle  10  may be a bolt action type having a stock  12 , a bolt  14 , a receiver  16 , a barrel  18  which threads into the receiver  16  and a bipod support  20 . Those skilled in the art will recognize the rifle  10  as being a conventional rifle illustrated as a generic sniper rifle. 
         [0026]    As shown best in  FIGS. 2 and 4 , the barrel  18  is machined to provide a series of ports  22  that open into the bore  24 . Provided there are no burrs where the ports  22  intersect the bore  24 , the ports  22  do not scratch or mar the projectile passing through the barrel  18 . Thus, if a sabot round were to be fired through the barrel  18 , it stays intact as it passes the ports  22 , i.e. until the round clears the muzzle or muzzle end  26  of the barrel  18 . 
         [0027]    Rifling along the barrel, i.e. alternating lands  28  and grooves  30 , spin the projectile and thereby impart considerable stability to it. Grooves  30  may be formed using any suitable technique, e.g. cut rifling, button rifling, hammer forged rifling or the like. Rifling may be done before or after formation of the ports  22 . 
         [0028]    The ported section or area  32  around the ports  22  may be of the same outer diameter as the barrel  18  or may be of reduced diameter as suggested by the shoulder  34 . As will be explained more fully hereinafter, the ported section  32  is an area near the muzzle end  26  of the barrel and extends from adjacent the muzzle  26  along the barrel a distance not more than about one half the length of the barrel  18 . It may be preferred to have the ported section  32  much shorter, i.e. not more than about one quarter the length of the barrel or less. In some rifle calibers, the ported section  32  may be as small as one tenth the length of the barrel. 
         [0029]    The ports  22  may be of any desired number or configuration and may be formed in any suitable manner. Thus, the ports  22  may be square shouldered, round shouldered, round or the like but may preferably be elongate in the direction of the barrel. The ports  22  may be parallel to the barrel  18 , may be parallel to the rifling  30  or may be at any desired angle to the barrel or rifling. The ports  22  may be in a single file or any multiple of files commensurate with the diameter of the barrel. Water jet cutting may be desirable to avoid creation of any burrs around the ports  22 . The ports  22  may preferably include a first or most upstream set of ports  22   a  that are larger than the remaining ports to allow a major fraction of the propulsion gases to escape from the barrel  18  as soon as the projectile enters the ported area  30  of the barrel  18 . The volume in the annulus between the barrel exterior and the sleeve  44  open to the upstream ports  22   a , i.e. upstream of the most upstream baffle  42  is quite large compared to the volume between adjacent baffles  42 , the area of the upstream ports  22   a  may be large compared to the area of the downstream ports  22 . The ports  22   a  may accordingly be preferably at least two times as large as the ports  22  and, in some embodiments, about four times as large as the ports  22 . This promotes noise suppression as will become more fully apparent hereinafter. It will be evident that the sleeve  44  does not interfere with the forward stock  20 , meaning there is sufficient clearance between the barrel and the forward end of the stock  20  to accommodate and support the sleeve  44 . In the alternative, the stock  20  may be altered or of a different design. 
         [0030]    The cumulative area of the ports  22 ,  22   a  is large compared to the cross-sectional area of the bore  24  thereby allowing a substantial part of propulsion gases generated during firing of a round to pass through the ports  22 ,  22   a  into the annulus between the barrel  18  and the sleeve  44 . The cumulative area of the ports  22 ,  22   a  is at least four times the area of the bore  24  and can, in some embodiments, be much larger, i.e. on the order of 20-25 times. 
         [0031]    It will be apparent to those skilled in the art that the rifle  10 , as heretofore described, can be fired in a normal manner. Propulsion gases acting on the baffles  42  reduces recoil of the rifle  10 . If the ports  22 ,  22   a  on the top of the barrel  18  are larger than the ports  22 ,  22   a  on the bottom of the barrel, they will also act to minimize climbing of the muzzle during firing. 
         [0032]    As shown best in  FIG. 5 , a baffle assembly  36  may be provided having a tube  38  sized to fit over the ported area  32  and providing a series of slots or passages  40  allowing the passage of propulsion gases out of the barrel  18 . A series of baffles  42  spaced along the assembly  36  act in a manner analogous to noise suppression baffles as will be apparent to those skilled in the art. In some embodiments, the slots  40  in the tube  38  are aligned with the ports  22  in the barrel  18  as suggested in  FIG. 4 . The upstream slots  40   a  are considerably larger than the downstream ports  40  to allow a substantial fraction of propulsion gases to pass through the passages  40   a  to reduce firing noise. 
         [0033]    The baffle assembly  36  may be fixed to the barrel  18  in any suitable manner, as by welding or laser welding, or may be captivated by a sleeve  44  threaded into the receiver  16  or, as illustrated in  FIG. 2 , onto threads  46  provided at the inlet end of the barrel  18 . The sleeve  44  may be of any desired configuration and made of any suitable materials. The sleeve  44  may be made of carbon fiber and resin, or any other material, providing a heat shield capacity. A muzzle end  48  of the sleeve  42  may include an annular end wall  50  having a passage  52  larger than the rifle bore  24 . 
         [0034]    The baffle assembly  36  is assembled onto the ported area  32  of the barrel  18  and may be fixed to the barrel  18  or captivated by the end cap  50  of the sleeve  44  when the sleeve  44  is threaded onto the barrel  18 . It may be desirable to prevent the baffle assembly  36  from rotating relative to the barrel  18  so a suitable anti-rotating mechanism may be used, such as an interfitting rib and groove (not shown). When a round is fired from the rifle  10  and the projectile clears the most upstream ports  22   a , a sizeable fraction of the propulsion gases pass through the ports  40   a  into an annulus defined by the outside of the barrel  18  and the inside of the sleeve  44 . As the projectile clears successive ports  22 , additional propulsion gases flow through the ports  40  into the barrel/sleeve annulus or into the spaces between the baffles  42 , depending on the spacing of the baffles with the inside of the sleeve  44 . This cools the propulsion gases and suppresses noise generated by firing the rifle  10 . The outside diameter of the baffles  42  may be somewhat less than the internal diameter of the sleeve  44  to allow propulsion gases to escape from the barrel and flow into the annulus between the barrel  18  and sleeve  44  thereby attenuating energy of the propulsion gases and suppressing the noise of firing. In some embodiments, the baffles  42  more-or-less snugly slide inside the sleeve  44  so the smaller quantities of propulsion gases exiting through the downstream ports  22  expand into the gaps between the baffles  42 . 
         [0035]    It will be seen there is provided a noise suppressor comprising the ports  22  in the barrel  18 , the baffle assembly  36  and the sleeve  44 . The sleeve  44  is readily removable from the barrel  18  and the baffle assembly  36  may be removable thereby allowing easy cleaning of the noise suppressor. 
         [0036]    It will be apparent to those skilled in the art that the ports  22  have an effect on muzzle velocity because some of the propulsion gases are sidetracked away from the projectile before it clears the muzzle  26 . This effect can be overcome if desired by firing hotter ammunition, i.e. ammunition with a greater quantity of powder or powder of greater energy. 
         [0037]    It is apparent that increased port area in a given bore diameter increases noise suppression but, like all variable parameters, there is a tendency to diminished returns as the variable increase. Thus, there is a trade off between noise suppression and muzzle velocity. When the ratio of cumulative port area to bore area becomes too large, muzzle velocity can be diminished too much or diminished more than can desirably be made up by a change in propellant charge. Extremely large ports can also affect the strength of the muzzle end of the rifle  10  thereby providing another limit of port size. 
         [0038]    Referring to  FIG. 6 , there is illustrated another embodiment of a baffle assembly  54 . In  FIG. 6 , a barrel  56  includes a bore  58  having rifling therein comprising alternating lands  60  and grooves  62 . A series of ports  64  are machined in a ported section  66  adjacent the muzzle end of the barrel  56 . An upstream port  64   a  is preferably larger than the remaining ports to allow a sizeable fraction of the propulsion gases to escape into an annulus between the barrel  56  and the sleeve  44 . A series of baffles  68  may be secured directly on the barrel  56  between adjacent ports  64 , in any suitable manner such as by welding, laser welding or the like. In the alternative, the baffles  68  may be machined from the same metal blank as the barrel  56 . The outside diameter of the baffles  68  may be somewhat less than the internal diameter of the sleeve  44  to allow propulsion gases to escape from the barrel  56  and flow into the annulus between the barrel  56  and sleeve  44  thereby attenuating energy of the propulsion gases and suppressing the noise of firing. The baffles  68  may fit more-or-less snugly against the sleeve interior so the cavity between each baffle traps and expands a small proportion of the propulsion gases. As in the embodiment of  FIGS. 1-5 , the ported section  66  is in the same proportions as the ported section  32  and the ports  64 ,  64   a  are as large as the ports  22 ,  22   a  in proportion to the bore  78 . 
         [0039]    Referring to  FIG. 7 , another rifle  70  is illustrated including a barrel  72  having rifling or grooves  74  therein in a conventional manner. A series of ports  76  open into the bore  78  of the barrel near the muzzle end  80  of the barrel, analogous to the ports  22 ,  64 . As in the embodiments of  FIGS. 2 and 6 , the upstream ports  76   a  are considerably larger than the ports  76 . Instead of simply turning down the exterior of the barrel  18 , the muzzle end is machined to remove metal between, and thereby provide, a series of baffles  82 . The baffles  82  accordingly act in the same manner as the baffles  42 ,  68  to provide gaps into which part of the propulsion gases can expand as the projectile is travelling through the barrel  72 . Surrounding the barrel  72  is a heat shield or sleeve  84  which may be connected to the receiver (not shown) of the rifle  70  or to the barrel  72  at a location adjacent the receiver. An end cap  86  may be provided to abut the muzzle end  80  of the barrel  72  in a manner analogous to the a fixed end wall  48 . As in the embodiment of  FIGS. 1-5 , the ported section  88  is in the same proportions as the ported section  32  and the ports  76 ,  76   a  can be as large as the ports  22 ,  22   a ,  64 ,  64   a.    
         [0040]    Referring to  FIG. 8 , there is illustrated another rifle  90  including a barrel  92  having a rifled bore  94 . A series of ports  96  open into the bore  94  near the muzzle end  98  of the barrel  92 , in a manner analogous to the ports  22 ,  64 ,  76 . The most upstream port  96   a  may, as in previous embodiments, be larger than the downstream ports  96 . The muzzle end  98  may be machined to remove metal between, and thereby provide, a series of baffles  100 . The baffles  100  accordingly act in the same manner as the baffles  44 ,  68 ,  82  to provide gaps into which part of the propulsion gases can expand as the sabot carrier or shot cup are travelling through the barrel  92 . Surrounding the barrel  92  is a heat shield or sleeve  102  which may be connected to the receiver (not shown) of the rifle  90  or to the barrel  92  at a location adjacent the receiver. An end cap  104  may thread onto the muzzle end  98  of the barrel  92  in a manner analogous to the fixed end wall  50  and thereby captivate the heat shield  102  in place. As in the embodiments of  FIGS. 1-7 , the ported section  106  is in the same proportions as the ported sections  32 ,  66 ,  88  and the ports  96 ,  96   a  are as large as the ports  22 ,  22   a ,  64 ,  64   a ,  76 ,  76   a  in proportion to the bore  94 . 
         [0041]    As shown by a comparison of  FIGS. 7 and 8 , the baffles  82 ,  98  may be of any suitable shape, including relative straight as in  FIG. 7  and concave toward the breech end of the weapon  90  as in  FIG. 8 . 
         [0042]    There are a number of variables involved in designing noise suppressors of the type disclosed herein. The length of the ported section  34  is between 10-50% of barrel length and the cumulative area of the ports  22 ,  22   a  is 4-25 times the bore area. A preferred length of the ported section  34  can be about one quarter of barrel length and a preferred cumulative area of the ports  22 ,  22   a  can be about fifteen times bore area. There is a trade off between noise suppression provided by a large cumulative port area and a lessening of projectile muzzle velocity. At cumulative port areas that are too low, noise suppression is too low. At cumulative port areas that are too high, there is too much reduction of muzzle velocity. 
         [0043]    In one example, a standard .30 caliber military rifle has a barrel length of about 26 inches, meaning the ported section  34  is 2.6-13 inches long and can preferably be about 6½ inches long. The area of a 0.30 inch bore is 0.070686 square inches, meaning that the cumulative area of the ports  22 ,  22   a  is 0.2827-1.767 square inches and may preferably be about 1.0603 square inches. The ports  22 ,  22   a  may typically be elongate, i.e. longer in the direction of the barrel than transverse of the barrel. The area of each port  22  may vary widely, dependent partly on the bore diameter, but may be on the order of about 0.02-0.05 square inches, meaning that a size of 0.01″×0.02″ to 0.15″×0.33″ would be normal. In order to achieve the desired cumulative area, the ports  22  preferably extend at least half way between adjacent baffles  42 . The shorter ported sections  34  will likely be associated with smaller cumulative port areas because the cumulative axial lengths of the ports cannot be quite so long. 
         [0044]    When firing regular ammunition from the disclosed firearms, when the projectile passes the first set of ports, a substantial quantity of hot propulsion gases are sidetracked through the upstream ports into the annulus between the barrel exterior and the surrounding sleeve. This produces rapid cooling of a substantial quantity of the propulsion gases. When the projectile passes each successive downstream port, a smaller quantity of propulsion gases passes between the baffles and thereby expand and cool. This process continues until the projectile clears the muzzle end of the barrel whereupon gases accumulating between the barrel exterior and the sleeve leak out through the muzzle. Because the area of the ports is very large compared to the area of the bore, there is considerable room for the escape of propulsion gases into the annulus between the barrel exterior and the sleeve before the projectile clears the end of the barrel. This produces a large reduction in noise. There is a substantial reduction in muzzle flash because a high proportion of gases are sidetracked through the ports where they expand and cool before exiting the muzzle. 
         [0045]    In addition to superior noise suppression, the disclosed firearms are capable of firing regular and sabot ammunition without damage to the noise suppressor. It will be apparent that the carrier of a sabot round or a shot cup of a shotgun round will stay intact and be confined by the bore of the weapon until the sabot clears the muzzle end of the weapon. Because the carrier cannot expand until it passes the noise suppression ports in the barrel, the carrier cannot damage the noise suppressor and thereby endanger the user upon firing a subsequent round. 
         [0046]    It will be apparent that threading the sleeve  44  onto the barrel threads  46  until the end wall  50  or the end caps  86 ,  104  snug up to the end of the barrel  18  will cause the sleeve  44  to be placed somewhat in tension and the barrel  18  to be somewhat in compression. The extent of this is very minor and, in comparison with the strength of the barrel  18  and sleeve  44 , is minuscule. Even after firing a few rounds and the consequent heating up and lengthening of the barrel  18  and sleeve  44 , the extent of stressing of the barrel  18  is, for all practical purposes, non-existant. 
         [0047]    Although this invention has been disclosed and described in its preferred forms with a certain degree of particularity, it is understood that the present disclosure of the preferred forms is only by way of example and that numerous changes in the details of operation and in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention.