Abstract:
A sound suppressor for a firearm with a high rate of fire, such as a machine gun, conceals the location of the firearm during heavy use by rapidly dissipating heat through a foamed carbon core. A sound suppressing baffle core is coaxially located within a tubular housing, having flared ends extending beyond the core. An inlet nozzle and exit place close the ends of the suppressor and are held in place with threaded collars. The terminal portions of the collars are beveled, as are the corresponding terminal portions of the nozzle and end plate, and are used to capture the flared portions of the ends of the tubular housing. Diagonally opposing recesses in the collars enable their removal with a spanner wrench, along with the other components for maintenance and replacement. The suppressor lasts longer and has a less visible heat signature used in sustained fire on a machine gun.

Description:
PRIORITY CLAIM 
     The benefit of U.S. provisional patent application Ser. No. 61/906139, filed Nov. 19, 2013, is claimed, which application is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     A sound suppressor is intended to conceal the location of a gun when fired. When undergoing sustained fire, however, a gun, such as a machine gun, and its suppressor become hot, hot enough to glow a dull red, and therefore visible on a dark night. In addition, suppressors are subject to internal damage when a fired bullet does not pass cleanly through it. Slight impacts of the bullet damage the suppressor and firing residue deposits bits of metal inside it. In time, incremental build-up of these deposits, damage from bullet impacts, and heat deformation make frequent repair or replacement of suppressors inevitable. Perhaps more importantly, the ability of the suppressor to shed heat during sustained fire degrades its ability to conceal the location of a machine gun. 
     SUMMARY OF THE INVENTION 
     According to its major aspects and briefly recited, the present invention is a sound suppressor for a firearm, particularly for one capable of sustained firing, such as a machine gun. The suppressor is designed to be disassembled for maintenance and repair so that, when appropriate, only damaged components need to be replaced and all parts will last longer than otherwise. 
     Additionally, the present suppressor takes advantage of the heat transfer capabilities of graphite foam. Not only does the foam reduce the heat signature of the firearm when undergoing sustained firing but, by keeping all the components cooler, reduces damage to components both directly and indirectly from heat deformation to a surprising extent. 
     Those familiar with the art of suppressors and other components for firearms will take note of these and other features and their advantages of the present invention in a careful reading the following detailed description accompanied by the following drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the drawings, 
         FIG. 1  is a side, exterior, perspective view of the suppressor, according to an embodiment of the present invention; 
         FIG. 2  is a side, cross-sectional view of the suppressor of  FIG. 1 ; and 
         FIG. 3A and 3B  are detailed side cross-sectional views of the first and second ends, respectively, of the suppressor of  FIG. 1 . 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention is a suppressor for use with a firearm capable of sustained fire. The present suppressor, generally indicated by reference number  10 , comprises several components that can be disassembled for repair or for replacement of the individual components that are worn and reuse of the remaining components, which is a feature of the invention. Suppressor  10  includes a cylindrical baffle core  12  having a first end  24  and an opposing second end  26 . The baffle core is the part most likely to require replacement inasmuch as it is exposed to the highest temperatures and bullets are fired directly through its center. Baffle core  12  serves essentially as a frame for holding a series of integrally-formed, spaced-apart baffles  16  in position with respect to the axis of rotation of baffle core  12 . Baffle core  12  may be formed all of one piece by casting or machining or other convenient method of forming a three-dimensional object of homogeneous material. 
     Surrounding baffle core  12  is a thin metal, tubular housing  30  with a first end  34  and an opposing second end  36 . Tubular housing  30  is flared outwardly at both first end  34  and second end  36 . Tubular housing  30  slides over cylindrical baffle core  12 , with flared first end  34  and second end  36  extending beyond first end  24  and second end  26 , respectively, of baffle core  12 . Housing  30  conducts and redistributes axially the heat from the baffle core and the combustion gases traveling through the spaces between its baffles. 
     The terms first end and second end are arbitrarily assigned here but are used consistently to refer to the direction of a bullet fired through suppressor  10 . A fired bullet enters first end  24  of baffle core  24  and leaves second end  26 , which means the bullet travels from right to left in  FIGS. 1 and 2 . 
     The word flared means that the diameter of cylindrical housing  30  increases closer to first and second ends  34 ,  36 , axially lateral to first and second ends  24 ,  26 , baffle core  12  but is constant throughout most of the length of housing  30 . 
     An inlet nozzle  40  fits into first end  24  of baffle core  12  and an exit plate  50  covers opposing second end  26 . Both inlet nozzle  40  and exit plate  50  have radial flanges,  42 ,  52 , respectively. Flanges  42 ,  52 , carry exterior threads and are beveled on their respective peripheries,  44 ,  54 . The beveled portions of the peripheries  44 ,  54 , engage the flared first and second ends  34 ,  36 , respectively, of tubular housing  30 . 
     Both ends of suppressor  10  also carry collars. A collar  46  threads to flange  42  and has a beveled inner surface,  48  corresponding to the beveled portion of periphery  44 . Beveled periphery  44  and beveled inner surface  48  on collar  46  stop advancement of collar  46  with respect to flange  42  and capture the flared first end  34  of tubular housing  30 . Tightening collar  46  pinches first end  34  against the beveled portion of periphery  44  flange  42 . 
     A collar  56  threads to flange  52 , and has a beveled inner surface  58  corresponding to the beveled portion of periphery  54  on flange  52 . The beveled portion of periphery  54  on flange  52  and the beveled inner surface  58  of collar  56  stop advancement of collar  56  with respect to flange  52  and capture the flare at second end  36  of tubular housing  30 . Tightening collar  56  pinches second end  36  between the beveled portion of periphery  54  of flange  52  against the beveled inner surface  58  of collar  56 . 
     Collars  46 ,  56 , of inlet nozzle  40  and exit plate  50 , respectively, may carry surface features that facilitate their installation and removal. For example, collars  46 ,  56 , may have opposing recesses  60 , as shown in  FIGS. 1 and 2 , to receive the jaws of a spanner wrench, or other convenient means for tightening collars  46 ,  56  to flange  42  of inlet nozzle  40  and flange  52  of exit plate  50 , respectively. 
     The flared first and second ends  34 ,  36  of tubular housing  30 , flanges  42 ,  52  of inlet nozzle  40  and exit plate  50 , and collars  42 ,  52  together with their respective threaded and beveled portions, and recesses  60  enable the present suppressor  10  to be tightly assembled for use, yet to be disassembled for maintenance and repair, thus extending the useful life of suppressor  10  and its individual components, which is a feature of the invention. 
     The present suppressor  10  also may include a hollow cylinder  70  surrounding tubular housing  30 . Hollow cylinder  70  transfers heat generated by firing the gun radially from baffle core  12 . That heat is transferred through baffle core  12  and tubular housing and then through hollow cylinder  70 . This cylinder  70  may be made of graphite, such as foamed graphite, or other material with a high heat conductivity so as to transfer heat quickly away from baffle core  12  and tubular housing  30  and into the surrounding air, particularly when the firearm is being fired at high rates, in order to prevent the temperature at the exterior surface of the suppressor  10  from being elevated into the visible portion of the electromagnetic spectrum. 
     A thin tubular guard  80  may surround hollow cylinder  70  and have plural holes  82  formed in an array in it to protect hollow cylinder  70 , especially if hollow cylinder  70  is made of friable, foamed graphite. Tubular guard  80  may have a sufficient number of holes  82  or combination of total area of holes  82  so as not block the radiation of heat while still protecting hollow cylinder. Guard  80  provides structural protection for hollow cylinder  70 , which may be friable and therefore subject to damage from impact even if minor. 
     To secure tubular guard  80  to hollow cylinder  70 , bands  86  may be used. Bands may be moved axially to capture them between raised edges  90  formed in housing that will help to keep their axial position once bands  86  are in position. Tubular guard  80  may be formed as a resilient C-shaped sheet of metal that is placed over hollow cylinder  70  and then its ends squeezed together tightly, meeting at  94 , enough to allow bands  86  to be slipped into position and tightened with buckles  92 . Hollow cylinder  70  may also be conveniently made in two half cylinders. 
     Raised edges  90  are two parallel, low-relief, radially outward deformations of the edges of holes in tubular guard  80  to form lips spaced apart by the width of a band  86  and between which band  86  will be held, prevented from axial movement, until tubular guard  80  is squeezed with enough force to enable band  86  to be moved over the raised edges  90  on one side of it or the other. 
     Foamed graphite is a material well known in heat transfer, including in connection with firearm barrels. See for example, US Pub. 2013/0061503 filed by UT-Battelle, LLC, and which publication is incorporated herein in its entirety by reference. 
     Hollow cylinder  70  and tubular guard  80  are co-axial and co-terminal with baffle core  12 , that is, all stop just short of flared first and second ends  34 ,  36  of tubular housing  30 . Co-terminal means that they are the same length and are axially aligned; co-axial means that their respective axes of rotation are the same. 
     Baffle core  12  includes plural, integrally-formed, spaced-apart baffles  16  each with a central hole  18  and a radial cutout  20  that define passages radially outwardly from the major axis of suppressor  10  through which combustion gases can travel from the inlet nozzle  40  to exit plate  50  and mix turbulently as they travel. Baffle core  12  is an improvement in the baffle described in U.S. Pat. No. 8,167,084, which is incorporated in its entirety by reference. By integrally formed, it is meant that baffles  16  are made of the same material and permanently connected to the balance of baffle core  12 , preferably all made of one piece. Baffle core  12  has an axis of cylindrical rotation and each baffle  16  may canted with respect to that axis, that is, each may lie in a plane that is at a non-zero angle  0  with respect to to axis A of baffle core  12 . The orientation of a plane is defined by a vector normal to the plane. By separating and canting each baffle  16 , a portion of the combustion gases are diverted though the serpentine path across the axis of baffle core  12  and its central hole  18  and then through a radial passage  20  around each baffle  16 , with the longer path and the turbulent interaction with the remaining portion of the exhaust gases that follow the bullet through the series of central holes  86 , baffle core  12  acts as a heat exchanger to deliver combustion heat to cylindrical housing, which transfers it quickly to hollow core and thence to the surrounding environment. 
     The modularizing of the present suppressor, in combination with the choice of foamed graphite for the hollow cylinder reduces the rate at which heat accumulates during sustained firing, thereby dispersing the heat to a larger radius from the barrel and, with the larger surface area at that radius, radiating it to the surrounding air. It also reduces the temperature of the components of the present suppressor. Modularization makes it possible to replace only components damaged by a bullet strike, and thereby reduces cost of providing and maintaining a suppressor for a machine gun. For example, if baffle core  12  is damaged, but the remainder of suppressor  10  is sound, unthreading collars  46  and  56  allows release of tubular housing  30 , inlet nozzle  40 , and exit plate  50 . Baffle core  12  may then be removed and replaced. Being able to replace a baffle core  12  enables greater use of the remaining components. Importantly, keeping the baffle core cooler limits the rate of heat deformation significantly and thereby prolongs its life and reduces the incidents of bullet strikes that require baffle core replacement. 
     Those skilled in the art of firearms will appreciate that many modifications and substitutions may be made in the foregoing embodiments without departing from the spirit and scope of the present invention, which is defined by the appended claims. For example, improvements in material technology may produce hollow cylinders better than foamed graphite or better ways of protecting hollow cylinders than a tubular guard, such as a coating or fine mesh of metal or fabric.