Patent Publication Number: US-2009229454-A1

Title: Field adjustable gas bleed assemblies for use with firearms

Description:
RELATED APPLICATION 
     This patent is a continuation of International Patent Application Serial No. PCT/EP2007/006780, filed on Jul. 31, 2007, which claims priority to German Patent Application 10 2006 036 309.4, filed on Aug. 3, 2006, and to German Patent Application 10 2006 056 130.9, filed on Nov. 28, 2006, each of which are hereby incorporated herein by reference in their entireties. 
     FIELD OF THE DISCLOSURE 
     This patent relates generally to firearms and, more specifically, to field adjustable gas bleed assemblies for use with firearms. 
     BACKGROUND 
     Typically, gas-operated firearms include a loading mechanism that is driven by ammunition gas pressure acting against a gas piston arranged in a gas cylinder to assist in loading and unloading cartridges. The gas cylinder is at least partially sealed at an end so that a pressure chamber is formed between a face of the gas piston and a front wall of the gas cylinder. A passage fluidly couples the pressure chamber to the interior of the barrel. After a round is fired and the projectile (e.g., the bullet) has passed the connecting point between the pressure chamber and the barrel bore, ammunition gases enter the pressure chamber. The ammunition gases increase a pressure in the pressure chamber and create a resulting force on the face of the piston. 
     The resulting force on the piston acts against a linkage that is part of a loading mechanism and causes the cartridges to feed and eject due to the movement of the piston relative to the pressure chamber. Additionally, the resulting force on the piston activates (e.g., cocks) the trigger mechanism. When firing a firearm that is fully automatic, each time a cartridge passes the connecting point, a portion of the ammunition gases are diverted through the passage and toward the pressure chamber to act against the piston and, thus, load and unload the firearm. As a result, the cartridges are continuously loaded and unloaded as long as the trigger is held in the firing position and the firearm is provided with ammunition. DE 196 15 181 describes a known gas-operated firearm arrangement. 
     Typically, the cross-sections governing the flow of the ammunition gasses and the design of the gas piston and the pressure chamber are configured to match the specifications of a particular firearm that fires at a determined frequency. Specifically, a firing cadence is selected to prevent overstress of firearm components. To control the pressure in the pressure chamber, the pressure chamber is provided with a gas outlet axially positioned toward the front of the pressure chamber. Through the gas outlet, at least a portion of the ammunition gasses that enter the pressure chamber exit into the environment to reduce the pressure within the pressure chamber. Specifically, the pressure chamber has a lower pressure as compared to the pressure within the barrel. An example of such an ammunition gas bleed device is described in DE 19615 181. 
     DE 648 391 describes a gas-operated firearm in which ammunition gasses enter the pressure chamber from the front of the pressure chamber. To control the amount of ammunition gasses that enter the pressure chamber, the described gas-operated firearm is provided with a locking screw. In contrast to the gas-operated firearms described above, to exhaust the ammunition gasses from the pressure chamber, the piston moves entirely out of the cylinder to create a gap through which the ammunition gasses exhaust. 
     By making structural changes to a firearm and/or using different types of ammunition, the gas pressure in the barrel and/or the pressure chamber may change. For example, firing a firearm that is typically provided with a flash suppressor instead with a silencer, increases the pressure in the barrel and the pressure in the pressure chamber. The increase in pressure increases the force acting on the gas piston and accelerates the loading process, especially if the firearm is an automatic weapon. Similarly, if a second type of ammunition (e.g., ammunition having a larger propellant charge, a higher bullet mass, etc.) is fired through the firearm instead of a first type of ammunition (e.g., ammunition having a smaller propellant charge, a smaller bullet mass, etc.), the gas pressure in the barrel and/or the pressure chamber also changes, which effects the firing cadence. 
     Accelerating the loading process, increases the firing cadence as well as ammunition consumption. Additionally, the mechanical load on the firearm components increases the wear and tear on the firearm, which decreases the time interval between needed maintenance. Further, unnecessary consumption of ammunition may pose a logistical problem during a military action, because additional ammunition must be brought along and provided at the location that the firearm is being fired without the firearm&#39;s performance being correspondingly improved. 
     During military actions and/or training exercises, it is impractical to continuously adjust the ammunition gas bleed device in an attempt to stabilize the firing cadence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  depicts a cross-sectional view of a portion of a barrel and an example field adjustable gas bleed assembly. 
         FIG. 2  depicts an enlarged cross-sectional view of a portion of the barrel and the example field adjustable gas bleed assembly of  FIG. 1 . 
         FIG. 3  depicts an enlarged side view of the barrel and the example field adjustable gas bleed assembly of  FIG. 1 . 
         FIG. 4  depicts an enlarged view of a different side of the barrel and the example field adjustable gas bleed assembly of  FIG. 1 . 
         FIG. 5  depicts another view of the example field adjustable gas bleed assembly of  FIG. 1 . 
         FIG. 6  depicts a cross-sectional view along A-A of  FIG. 5  that depicts an example fluid control apparatus and an example locking member of  FIG. 1 . 
         FIG. 7  depicts the example fluid control apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION  
     Certain examples are shown in the above-identified figures and described in detail below. In describing these examples, like or identical reference numbers are used to identify the same or similar elements. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity. Additionally, several examples have been described throughout this specification. Any features from any example may be included with, a replacement for, or otherwise combined with other features from other examples. Further, throughout this description, position designations such as “above,” “below,” “top,” “forward,” “rear,” “left,” “right,” etc. are referenced to a firearm held in a normal firing position (i.e., wherein the “shooting direction” is pointed away from the marksman in a generally horizontal direction) and from the point of view of the marksman. Furthermore, the normal firing position of the weapon is always assumed, i.e., the position in which the barrel runs along a horizontal axis. 
       FIG. 1  depicts a front portion of a firearm  100  having a barrel  1  that is coupled to a flash suppressor  2 . The barrel  1  may be any type of barrel such as, for example, a barrel that includes grooves and lands or a barrel that has a smooth interior surface. The firearm  100  includes a field adjustable gas bleed assembly  3  (herein after referred to as gas bleed assembly  3 ) that is coupled to the barrel  1  via a locking mechanism (not shown) and/or rods (not shown). 
     Firing a round of ammunition propels a bullet from a cartridge casing through a barrel bore  4 , which is concentric to a bore axis  6 , toward the flash suppressor  2  in a direction of a target. Once the bullet has traveled past the gas bleed assembly  3 , a portion of the ammunition gases enter a tap bore  8 , which in the example of  FIG. 1 , is substantially perpendicular to the barrel bore  4 . The portion of the ammunition gases flows from the tap bore  8  through a gas channel  10  into a pressure chamber  14  defined by a gas cylinder  12 . 
     Turning now to  FIG. 2 , the illustration depicts an enlarged view of the barrel  1  and the gas bleed assembly  3 . A piston  16  (e.g., a gas piston) is positioned in the gas cylinder  12 . The piston  16  is sized to slidably and sealingly engage an interior surface  202  of the gas cylinder  12 . The interior surface  202 , the gas cylinder  12 , and/or the piston  16  may be mechanically produced and/or finished via, for example, lathing, milling, grinding and/or honing (e.g., precision grinding). Additionally or alternatively, the interior surface  202 , the gas cylinder  12 , and/or the piston  16  may be treated using any suitable means such as, for example, the components may be hardened, chrome plated, coated, etc., to increase the durability of the contact surfaces. While not shown, the piston  16  may be provided with a plurality of rings (not shown) to provide a seal between the interior surface  202  and the piston  16 . 
     After a round is fired, the ammunition gasses flow to the pressure chamber  14  and increase the pressure in the pressure chamber  14 . Specifically, the pressure increases between a surface  204  of the piston  16  and a surface  206  of the pressure chamber  14 . Once the pressure within the pressure chamber  14  increases to a predetermined level, a force, created by the pressure (e.g., a pressure impulse), moves the piston  16  toward the rear of the firearm  100  ( FIG. 1 ) along with a rod (not shown). As the rod moves toward the rear of the firearm  100  ( FIG. 1 ), the rod transfers the pressure impulse to a weapon actuator (not shown) facilitating a breech block (not shown) and a loading mechanism (not shown) to, for example, cycle the firearm  100  ( FIG. 1 ). 
     In this example implementation, the gas bleed assembly  3  and the gas cylinder  12  are constructed from a single piece of material and are coupled to the barrel  1  via a collar  18 . The collar  18  may be fitted (e.g., shrunk) onto an exterior surface  208  of the barrel  1 . To ensure the position of the collar  18  relative to the barrel  1 , the barrel  1  defines a step or offset  20  that is engaged by a surface  210  of the collar  18 . Additionally, the collar  17  and the gas bleed assembly  13  are axially coupled in a circumferential direction to the barrel  1  via pins  22  (e.g., a spring pinning). The pins  22  may be any suitable pins  22  such as, for example, dowel pins, conical pins, etc. that draw the collar  18  downwards such that the gas channel  10  is adjacent the tap bore  8  to substantially prevent ammunition gasses from exhausting between the barrel  1  and the collar  18  during firing. 
     In the illustrated example, the piston  16  includes an elongated portion or auxiliary piston  16   a  that partially protrudes into an aperture or ventilation borehole  24  during a counter re-coil and/or in a rest position. In operation, after the pressure in the pressure chamber  14  increases to the predetermined level such that the piston  16  begins to move toward the rear of the firearm  100  ( FIG. 1 ), the elongated portion  16   a  moves out of the aperture  24 , which enables ammunition gases to exhaust to the atmosphere through the aperture  24  and a gas outlet or discharge nozzle  26 . As the ammunition gasses exhaust to the atmosphere from the pressure chamber  14 , the pressure in the pressure chamber  14  decreases, which reduces the resulting force acting against the piston  16  and the rod. By decreasing the pressure in the pressure chamber  14 , the stress on the breech block and the loading mechanism also decrease. 
     A flow control apparatus or inlet piece  30  is positioned in a bore or aperture  32  defined by the gas bleed assembly  3 . The aperture  32  is positioned approximately perpendicular relative to the bore axis  6  and intersects the gas channel  10 . As illustrated in  FIG. 2 , the flow control apparatus  30  defines a first borehole  10   a  that has a first cross-sectional area and a second borehole  10   b  that has a second cross-sectional area. The first and second boreholes  10   a  and  10   b  intersect at approximately a 90 degree angle and may have different cross-sectional areas and/or diameters. While  FIG. 2  depicts the boreholes  10   a  and  10   b  intersecting at approximately a 90 degree angle, the boreholes  10   a  and  10   b  may intersect at any other angle (e.g., a five degree angle, a ten degree angle, a fifteen degree angle, etc.). 
     As depicted in  FIG. 2 , the first borehole  10   a  is positioned to fluidly couple the tap bore  8  and the pressure chamber  14  and the second borehole  10   b  is positioned approximately parallel to the bore axis  6 . However, if the flow control apparatus  30  is rotated approximately 90 degrees, the second borehole  10   b  fluidly couples the tap bore  8  and the pressure chamber  14  and the first borehole  10   a  is positioned approximately parallel to the bore axis  6 . Changing which of the boreholes  10   a  or  10   b  fluidly couples the tap bore  8  and the pressure chamber  14 , changes the amount of the ammunition gasses that flows from the barrel bore  4  to the pressure chamber  14  because the cross-sectional area of the first borehole  10   a  is different from the cross-sectional area of the second borehole  10   b . The flow control apparatus  30  is designed to snuggly fit in the aperture  32  such that a plurality of first or second openings  214  or  216  of the boreholes  10   a  or  10   b  sealingly engage a surface  218  of the aperture  32  when the respective borehole  10   a  and  10   b  is not aligned with the tap bore  8 . 
     In contrast to the examples described herein, if a marksman intends to use a silencer (not shown) with a known firearm that typically is provided with flash suppressor (e.g., similar to the flash suppressor  2  of  FIG. 1 ), firing the firearm will result in the gas pressure in the barrel bore (e.g., similar to the barrel bore  4 ) and the pressure in the pressure chamber (e.g., similar to the pressure chamber  14 ) both being relatively higher as compared to when the firearm is fired with the flash suppressor, because a cross-sectional flow area of a channel that fluidly couples the pressure chamber and the barrel bore is configured to provide a particular firing cadence only in a single operation mode (e.g., firing the firearm with the flash suppressor). As discussed above, the increase in pressure accelerates the loading process and increases the force acting on the rod and the entire loading mechanism. In some instances, an increase in the firing cadence may result in the firearm jamming because the amount of time that is allotted to enable a cartridge (not shown) to move from a magazine (not shown) to a cartridge chamber (not shown) during reloading of the firearm is not adequate. 
     In contrast to known firearms, if a marksman intends to use a silencer (not shown) with the example firearm  100  that had previously been provided with the flash suppressor  2 , the marksman may rotate the flow control apparatus  30  to enable the borehole  10   a  or  10   b  that has a relatively smaller cross-sectional flow area to fluidly couple the tap bore  8  and the pressure chamber  14  instead of the borehole  10   a  or  10   b  that has a relatively larger cross-sectional flow area. Utilizing the borehole  10   a  or  10   b  that has the relatively smaller cross-sectional flow area as opposed to the borehole  10   a  or  10   b  that has the relatively larger cross-sectional flow area, enables the firearm  100  to be utilized with the silencer, which increases the pressure in the barrel bore  4 , without substantially effecting the pressure in the pressure chamber  14  and, thus, a desired firing cadence may be maintained. More generally, the examples described herein enable the firing speed of the firearm  100  implemented with the flash suppressor  2  to be substantially similar to the firing speed of the firearm  100  implemented with the silencer. Enabling a marksman to precisely and relatively quickly field adjust the cross-sectional flow area between the tap bore  8  and the pressure chamber  14  enables the firearm  100  to achieve a desired firing cadence in different operation modes and, thus, the versatility of the firearm is increased. 
     In some examples, if the firearm  100  is configured to fire NATO caliber 7.62 millimeter rounds, one of the boreholes  10   a  or  10   b  may have a diameter of approximately 1.7 millimeters (mm), which enables the firearm  100  to be fired with the flash suppressor  2  (e.g., a first operation mode) while maintaining a desired firing cadence. Additionally, the other of the boreholes  10   a  or  10   b  may have a diameter of approximately 1.2 mm to enable the firearm  100  to be fired with the silencer (e.g., a second operation mode) while maintaining a desired firing cadence. For other common calibers used with rifles, assault rifles or machine guns, the boreholes  10   a  and/or  10   b  may be between about 0.5 mm and 2 mm. However, the diameter and/or the cross-sectional area of the borehole  10   a  and/or  10   b  may vary depending on the type and size of the round and/or cartridge to be fired. 
     The flow control apparatus  30  is designed to be inserted and secured in the aperture  32  of the gas bleed assembly  3 . 
       FIG. 7  depicts an enlarged view of the flow control apparatus  30 . The flow control apparatus  30  includes a head or end  34  that includes an indicator or tab  36 . In operation, the position of the indicator  36  relative to the firearm  100  may indicate the position of the respective borehole  10   a  or  10   b  relative to the tap bore  8  and the gas channel  10 . 
     Turning to  FIG. 3 , to enable the flow control apparatus  30  to be relatively easily rotated in the aperture  32 , a surface  302  of the head  34  defines a hexagonal profile  38  (e.g., an opening) and a slot  40  (e.g., an opening). For example, a coin (not shown) may be inserted into the slot  40  and turned to rotate the flow control apparatus  30  such that the first borehole  10   a  fluidly couples the tap bore  8  and the pressure chamber  14 . Alternatively, a tool (not shown) may be inserted into the hexagonal profile  38  and turned to rotate the flow control apparatus  30  such that the second borehole  10   b  fluidly couples the tap bore  8  and the pressure chamber  14 . While  FIG. 3  depicts the head  34  having a hexagonal profile  38 , the head  34  may define any other profile and/or opening that corresponds to any suitable tool. 
     Turning to  FIG. 7 , the openings  214  and  216  of the boreholes  10   a  and  10   b  are positioned along an elongated member or cylindrical shank  42  of the flow control apparatus  30 . To secure and/or retain the flow control apparatus  30  in the aperture  32 , a groove or indentation  44  is defined toward an end  702  of the elongated member  42  that receives at least a portion of a locking member or locking device  46  ( FIG. 6 ). The locking member  46  is biased via a spring  48  that urges an end  52  of the locking member  46  toward the groove  44 . A stop or locking pin  50  ensures that the spring  48  maintains its position in a bore  49  and that the spring  48  urges the locking member  46  toward the flow control apparatus  30 . 
     The groove  44  includes a plurality of side walls, radial sides or lateral walls  54  and  56  between which the end of the locking member  46  may be positioned to secure the flow control apparatus  30  and to substantially ensure that the flow control apparatus  30  is not unintentionally removed from the aperture  32 . The side walls  54  and  56  are connected via connecting walls, corner arcs or lateral walls  58  and  60 . The position of the connecting walls  58  and  60  relative to the borehole  10   a  and  10   b  ensures that when the end  52  of the locking member  46  engages either of the connecting walls  58  and  60 , one of the boreholes  10   a  or  10   b  is aligned with the tap bore  8 . More generally, the connecting walls  58  and  60  form a stopper to substantially restrict the movement of the locking member  46  in a circumferential direction. 
     Additionally, the groove  44  includes a first surface  62  and a second surface  64 , which are separated by an edge  63 . For example, if the first borehole  10   a  initially fluidly couples the tap bore  8  and the pressure chamber  14 , the end  52  of the locking member  46  may engage the second surface  64 . As the flow control apparatus  30  is rotated to enable the second borehole  10   b  to fluidly couple the tap bore  8  and the pressure chamber  14 , a surface  66  of the locking member  46  follows the second surface  64  toward the edge  63 . Once the surface  66  of the locking member  46  engages the edge  63 , the locking member  46  is depressed toward the locking pin  50  against a force of the spring  48 . As the flow control apparatus  30  is further rotated, the force of the spring  48  urges the locking member  46  toward the groove  44  and, thus, the flow control apparatus  30  may be urged to rotate. As the flow control member  30  is rotated, the surface  66  of the locking member  46  follows the first surface  62  until the end  52  engages the connecting wall  60  at which point the second borehole  10   b  is aligned to fluidly couple the tap bore  8  and the pressure chamber  14 . 
     Turning to  FIG. 4 , to enable the flow control apparatus  30  to be removed from the aperture  32 , the firearm  100  is provided with a lever or actuating pin  68  that is positioned in a channel  70  such that the lever  68  is externally accessible. The lever  68  is operatively coupled to the locking member  46  such that by moving the lever  68  toward the rear of the firearm  100  ( FIG. 1 ), the locking member  46  is moved away from the groove  44 . Once the locking member  46  is completely removed from the groove  44 , the flow control apparatus  30  may be removed from (e.g., pushed out of) the aperture  32 . To prevent the locking member  46  from extending too far into the aperture  32  and/or to prevent the locking member  46  from being misplaced or lost, the locking member  46  includes a shoulder  72  that engages a step  73  after the flow control apparatus  30  is removed from the aperture  32 . 
     While the flow control apparatus  30  is depicted as including the first borehole  10   a  and the second borehole  10   b , the flow control apparatus  30  may include any number of boreholes (e.g., 1, 2, 3, 4, 5, etc.). In such examples, the groove  44  of the flow control apparatus  30  may include a corresponding number of surfaces to be engaged by the surface  66  on the end  52  of the locking member  46 . While not shown, in other examples, the flow control apparatus  30  may define a single borehole configured to be used with a particular operation mode. In such examples, a marksman may have a plurality of different flow control apparatus  30  each having a borehole having a different cross-sectional flow area. In operation, depending on the operation mode, different flow control apparatus  30  having different cross-sectional flow areas may be interchanged in the aperture  32 . 
     In other examples, the boreholes  10   a  and  10   b  may be aligned along an axis  704  of the elongated member  42 . To align the different boreholes  10   a  or  10   b  with the tap bore  8 , the flow control apparatus  30  may be moved into or out of the aperture  32 . In this example, the flow control apparatus  30  may be configured as a slider and be provided with grooves (not shown), which are engaged by the locking member  46  to secure the flow control apparatus  30  relative to the aperture  32  once the desired borehole  10   a  or  10   b  fluidly couples the tap bore  8  and the pressure chamber  14 . 
     The examples described herein enable the cross-sectional flow area to be adjusted for the firearm  100  via the flow control apparatus  30 . Specifically, the flow control apparatus  30  enables the cross-sectional flow area to be tailored to a particular operation mode such as, for example, firing the firearm  100  with the flash suppressor  2 , firing the firearm  100  with a silencer, firing the firearm  100  with a first type of ammunition (e.g., ammunition having a smaller propellant charge, a smaller bullet mass, etc.) and/or firing the firearm  100  with a second type of ammunition (e.g., ammunition having a larger propellant charge, a higher bullet mass, etc.). 
     The flow control apparatus  30  may be tailored to a particular type of firearm and/or a particular application. Additionally, the flow control apparatus  30  may be relatively easily interchanged without additional necessary adjustments being performed on the firearm  100 . 
     As discussed above, the flow control apparatus  30  is insertable and removable from the aperture  32 . Additionally, once the flow control apparatus  30  is inserted into the aperture  32 , the flow control apparatus  30  may be adjusted (e.g., rotated or moved) to change the cross-sectional flow area between the tap bore  8  and the pressure chamber  14 . The design of the flow control apparatus  30  may be relatively easily produced and may be relatively easily implemented in different types of firearms and/or firearms configured to fire different size calibers. 
     As described above, the flow control apparatus  30  defines a plurality of boreholes  10   a  and  10   b  each having a cross sectional flow area that corresponds to a different operation mode. Generally, the flow control apparatus  30  enables the operation mode of the firearm  100  to be switched back and forth. In operation, the operation mode of the firearm  100  is changed by rotating and/or moving the flow control apparatus  30  relative to the aperture  32 . 
     As discussed above, the position of the flow control apparatus  30  may be secured to ensure that one of the boreholes  10   a  or  10   b  fluidly couples the tap bore  8  and the pressure chamber  14 . 
     As described above, the locking member  46  is urged toward the groove  44  via the spring  48 . The groove  44  includes the side walls  54  and  56  and the connecting walls  58  and  60 . The interaction between the locking member  46  and the groove  44  substantially prevents the locking member  46  from rotating beyond a certain point because the end  52  of the locking member  46  engages either of the connecting walls  58  and  60 . Additionally, the interaction between the locking member  46  and the groove  44  substantially ensures that the surface  66  on the end  52  of the locking member  46  engages either the first surface  62  or the second surface  64  when one of the boreholes  10   a  or  10   b  fluidly couples the tap bore  8  and the pressure chamber  14 . Further, the interaction between the locking member  46  and the groove  44  substantially prevents the flow control apparatus  30  from being unintentionally removed from the aperture  32  because of the interaction between the end  52  and the side walls  54  and  56  and/or the connecting walls  58  and  60 . The groove  44  may be produced, manufactured and/or fabricated via any suitable method such as, for example, turning, milling, grinding, precision casting, injection molding, etc. 
     As discussed above, the flow control apparatus  30  is provided with the indicator  36  that enables a marksman to feel and/or visually identify the position of the indicator  36  and, thus, which of the boreholes  10   a  or  10   b  is aligned with the tap bore  8  and/or the position of the flow control apparatus  30  relative to the aperture  32 . Readily identifying the position of the flow control apparatus  30  relative to the aperture  32  via touch and/or visual verification, enables the marksman to quickly determine if the firearm  100  is in the proper operation mode. 
     As described above, the surface  302  of the head  34  may include the hexagonal profile  38  and/or the slot  40 , which are to receive a tool to more easily enable the flow control apparatus  30  to be adjusted. 
     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.