Patent Publication Number: US-8109194-B2

Title: Clamped gas block for barrel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/162,099, filed Mar. 20, 2009. 
     INCORPORATION BY REFERENCE 
     U.S. Provisional Patent Application No. 61/162,099, which was filed on Mar. 20, 2009, is hereby incorporated by reference for all purposes as if presented herein in its entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the disclosure are directed generally to gas operated firearms and, more particularly, to an apparatus for clamping a gas block to the barrel of a gas-operated firearm. 
     BACKGROUND INFORMATION 
     Semi-automatic firearms, such as rifles and shotguns, are designed to fire a round of ammunition, such as a cartridge or shot shell, in response to each squeeze of the trigger of the firearm, and thereafter automatically load the next shell or cartridge from the firearm magazine into the chamber of the firearm. During firing, the primer of the round of ammunition ignites the propellant inside the round, producing an expanding column of high pressure gases within the chamber and barrel of the firearm. The force of this expanding gas propels the bullet/shot of the cartridge or shell down the barrel. 
     In semi-automatic rifles and shotguns, a portion of the expanding gases typically are directed through a duct or port that interconnects the barrel of the firearm to a piston assembly that generally houses an axially moveable piston. This piston assembly further typically includes a gas block that connects the piston assembly to the barrel, and through which the explosive gases pass. In some systems, the gas blocks are one piece elements located on their firearms and aligned with the port in the barrel through which the gases from the fired cartridge flow into the gas block and back to the action for expelling the spent cartridge and for chambering a fresh cartridge. The portion of the explosive gases that are diverted from the barrel of the firearm act upon the piston so as to force the piston in a rearward direction to cause the rearward motion of the bolt of the firearm. This rearward motion of the bolt opens the chamber, ejects the empty shell or cartridge casing, and thereafter loads another shell or cartridge into the chamber, after which the bolt returns to a locked position for firing as the gases dissipate or are bled off. 
     SUMMARY OF THE DISCLOSURE 
     Briefly described, in one embodiment of the invention, a gas block clamping apparatus is provided for use with a gas-operated firearm. The gas block can comprise a plurality of sections, including an upper section and a lower cylindrical section to which the upper section is attached. The upper section further can have a profile that is shaped or configured to facilitate its fitting to and mounting along the barrel. A plurality of clamp sections are symmetrically disposed on opposite sides of the barrel. Each clamp section can have an upper surface for attaching the gas block to the barrel, an alignment surface that tends to facilitate alignment of the clamp section to the barrel when the clamp sections are tightened against the barrel, and a lower surface that aligns with the curved upper section of the gas block. A plurality of fasteners generally are disposed through a plurality of openings in the lower surface of the clamp sections and the upper surface of the gas block for securing each clamp section to both the barrel and gas block. 
     These and various other advantages, features, and aspects of the exemplary embodiments will become apparent and more readily appreciated from the following detailed description of the embodiments taken in conjunction with the accompanying drawings, as follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a gas-operated firearm showing the positioning of the clamped gas block in an exemplary embodiment. 
         FIG. 2  is a perspective view of clamped gas block attached to the firearm barrel in an exemplary embodiment. 
         FIG. 3A  is an isometric view of a clamp section of the clamped gas block of  FIG. 2 . 
         FIG. 3B  is an end view of the clamp section of  FIG. 3A  illustrating example force vectors applied to the clamp section. 
         FIG. 4A  is an end view of the clamp sections mounted to the firearm barrel and clamped gas block in an exemplary embodiment. 
         FIG. 4B  is a cross-sectional view of the clamped gas block and firearm barrel in an exemplary embodiment. 
         FIG. 5  is an enlarged perspective view of the clamp section attached to the firearm barrel and clamped gas block in an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     Referring now to the drawings in which like numerals indicate like parts throughout the several views, the figures illustrate one example embodiment of the clamped gas block apparatus or system according to the principles of the present disclosure for use in a firearm such as a rifle. However, it will be understood that the clamped gas block apparatus can be used in various types of firearms including shotguns and other long guns, hand guns, and other gas-operated firearms. The following description is provided as an enabling teaching of exemplary embodiments; and those skilled in the relevant art will recognize that many changes can be made to the embodiments described, while still obtaining the beneficial results. It will also be apparent that some of the desired benefits of the embodiments described can be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the embodiments described are possible and may even be desirable in certain circumstances, and are a part of the invention. Thus, the following description is provided as illustrative of the principles of the embodiments and not in limitation thereof, since the scope of the invention is defined by the claims. 
       FIG. 1  illustrates a gas-operated firearm  10  showing the positioning of the clamped gas block apparatus or system in one exemplary embodiment. Gas-operated firearm  10  generally includes barrel  12 , stock  20 , receiver  22 , fire control  24 , and the clamped gas block apparatus or system  40 , including a gas block  14 . The stock  20 , also known as the buttstock or shoulder stock, may be formed in any conventional manner to include cushioning, special curvatures, grips, etc. The receiver  22  houses and includes the firing mechanism or fire control  24 , including a trigger  23  for actuating the firearm a breech bolt or bolt assembly  25 , and a firing pin. The bolt assembly is translatable axially in both forward and rearward directions along the receiver during the firing cycle and generally is located behind a chamber portion  27  located at the proximal end of the barrel  12  adjacent the receiver  22 . The chamber receives a round of ammunition R, such as a shell or cartridge for firing. 
     In the gas-operated semi-automatic firearm  10  illustrated in  FIG. 1 , a gas-operated piston assembly  26  is provided for reloading the chamber after firing by way of mechanical interconnection and interaction between the gas redirecting piston assembly and the bolt. During a firing operation, a portion of the expanding gas in the barrel is redirected into the gas block assembly  14  to drive the gas piston rearward. The action of the gas piston, which in turn is translated to the bolt, functions to automatically clear or discharge a spent cartridge/shell casing from the chamber, load a new round R into the chamber, and recock the firing pin and bolt for a next firing cycle. 
     According to one embodiment of the clamped gas block apparatus or system  40 , as shown in  FIGS. 2 ,  4 A,  4 B, and  5 , generally symmetric clamp sections  42  of the clamped gas block apparatus  40  attach the gas block  14  to the barrel  12  by engaging one or more cut out sections (i.e., notches, recesses, or other depressions or other engaging areas)  16  formed along the outer surface of the barrel  12 . Each of the notches  16  generally is an elongate slot with a lower lip  16   a  adapted to engage or cooperate with one of the clamp sections  42 . The notches extend at least partially along the length of the barrel  12 , generally parallel with the central axis of the barrel, and can be situated below the horizontal centerline of the barrel. In a particular exemplary embodiment, the notches  16  can be machined into the outer surface of the barrel  12 . Additionally, various shapes and orientations of the notches  16  are considered to be within the scope of the present invention. For example, all or part of the notches, and/or the entirety or a portion of the notches themselves, can be formed or oriented generally transverse to the central axis of the barrel  12 . 
       FIG. 3A  shows an isometric view of a clamp section  42  according to one embodiment of the present disclosure. As illustrated, the clamp section  42  can include a generally C-shaped member  50 , a top portion  52 , a clamp protrusion  54 , and a lower flange  56 , which can include through-bores  58   a ,  58   b . In the illustrated embodiment, the top portion  52  is generally hook-shaped or otherwise configured to facilitate its engagement with its corresponding notch  16  ( FIGS. 4A ,  4 B, and  5 ) and to resist moments on the top portion  52  that would otherwise pivot the top portion away from the barrel  12 . Additionally, various shapes and orientations of the top portion  52  are considered to be within the scope of the present invention. For example, all or part of an alternative embodiment of the top portion can be generally vertically oriented or arranged. 
     The top portion  52  further can include a lip  53  that projects laterally and can have one or more beveled engaging surfaces  53   a . The lip  53  generally will be sized so as to engage and fit within a corresponding notch and create a substantially cantilevered, locked engagement between the clamp section and the barrel. The clamp protrusion  54  of each clamp section can be configured to engage a curved upper flange  18  supported by a bracket  17  of the gas block  14 . The bracket  17  generally is mounted to or integral with a gas expansion housing  19  of the gas block  14 . The upper flange  18  is mounted to or integral with the bracket  17 . In a particular exemplary embodiment shown in  FIG. 3B , the clamp protrusion  54  engages the curved flange  18  at a point where the outer surface of the flange extends at about a 30° angle (θ A ) with respect to the horizontal. Alternatively, the angle θ A  of the flange can be formed in a range of about 1° to about 89°. 
     The lower flange  56  can extend downward from the clamp protrusion  54  so that the bores  58   a ,  58   b  are generally aligned with through-bores  60  in the bracket  17 . Bore  58   b  can be configured to accommodate a fastener with an enlarged screw head at the outer surface of the clamp section  42  ( FIG. 5 ) and have a clearance fit with the shoulder of the fastener or screw head. The bore  58   a  also can be threaded or otherwise adapted to receive the end of another fastener as well. The clamp sections  42  can be generally identical so that the screw head of screw  46 , which is closest to the receiver  22  in the figures, is on the left in  FIG. 4A  and the screw head of screw  48  is on the right in  FIG. 4A . The bores  60  in the bracket  17  further can be configured for a clearance fit with screws or other fasteners  46 ,  48 . The fasteners  46 ,  48  can be, for example, low head socket cap screws such as a screw having a hexalobular internal driving feature, such as those sold under the trademark TORX®. Alternatively, the fasteners  46 ,  48  can include a variety of different type fasteners, including fasteners having a socket head cap, a low head socket cap, button head socket cap, flat head socket cap, or another fastener, including fasteners with a head diameter greater than the major diameter of the fastener. Such headed fasteners further can range from ASTM #0 to ½-inch diameter or greater fasteners and can have a pitch diameter as desired or needed for attachment of the clamp sections in view of the size and/or clamping engagement thereof. 
     In accordance with an alternative embodiment of the present disclosure, the bores  58   a ,  58   b  may be otherwise arranged without departing from the scope of this disclosure. For example, the bores can be configured so that both fastener openings or fastener heads are on the same side of the gas block. Alternatively, the bracket  17  can be provided with threaded bores  60  and four fasteners such as screws can secure the lower flange  56  to the bracket  17 . In a further alternative, the bore  58   b  can be a threaded blind bore. 
     As shown in  FIG. 4B , the upper flange  18  can have a contoured or shaped profile, including a concave inner surface for cradling a lower surface of an alignment element  62  situated in a recess  63  machined into or otherwise formed in the lower surface of the barrel  12 . The upper flange  18  can also have a convex outer surface for engaging the clamp protrusions  54  of the clamp sections  42 . A gas port  13   b  (shown in phantom in  FIG. 4A ) communicates from the upper flange  18  though the bracket  17  to the housing  19 . The gas port  13   b  is to be aligned with a gas duct  13   a  (shown in phantom in  FIG. 4A ), communicating between an interior of the barrel and an exterior of the barrel. The gas port and gas duct are shown in phantom in  FIG. 4A . 
     The alignment element  62  can have a curved, convex surface for engaging the upper flange  18  and a generally flat surface for engaging the barrel  12  in the recess  63 . In the illustrated embodiment, the element  62  fits tightly within the recess  63  in the direction of the length of the barrel  12 . The recess  63  allows the element  62  to be adjusted in the direction transverse to the length of the barrel. One or more alignment pins  64  each engages a blind alignment bore in the element  62  and a blind alignment bore in the bracket  17 . The alignment pin  64  can have an interference fit with the bracket  17 , the element  62 , or both. The alignment pin  64  and the alignment bores of the element  62  and the bracket  17  also can be offset along the length of the barrel  12  in the illustrated embodiment. In one particular exemplary embodiment, the element  62  and recess  63  can be shorter than the upper flange  18  and clamp sections  42  so that a portion of the upper flange  18  engages the element  62  and another portion of the upper flange  18  engages the barrel  12  directly. The gas duct  13   a  and gas port  13   b  can line up where the upper flange engages the barrel directly. In an another exemplary embodiment, the element  62  and recess  63  are substantially the same length as or longer than the upper flange  18  and claim sections  42  so that the upper flange  18  only engages the element  62 . The element  62  can include a through bore for communicating between the gas port  13   b  and the gas duct  13   a.    
     The clamped gas block self aligns so that the gas port  13   b  communicates with the gas duct  13   a . Particularly, the clamped gas block is aligned along the direction of the length of the barrel  12  when the alignment element  62  and the alignment pin  64  are assembled onto the bracket  17 , and the element  62  is inserted into the recess  63  as shown in  FIG. 4B . Each of the notches  16  provides clearance for the top portion  52  for adjusting the alignment of the respective clamp section  42  along the length of the barrel  12  and transverse to the length of the barrel so that the fasteners  46 ,  48  can be inserted into the bores  58   a ,  58   b  in the clamp sections  42  and the bores  60  in the bracket  17 . The tightening of the fasteners  46 ,  48  in an alternating fashion applies a laterally directed force against the clamp sections so as to generally pull the clamp sections  42  together and aligns the clamped gas block in the transverse direction so that the axis of the housing  19  is substantially aligned with the axis of the barrel  12  and the gas port  13   b  communicates with the gas duct  13   a . A guide rod (not shown) can be used to further align housing with a rearward portion  19   a  of the piston assembly  26  ( FIG. 2 ). A suitable clamping device such as a vise or locking pliers also can be used to hold the clamp sections  42  to the barrel  12  during assembly as needed. 
     Tightening the clamping screws  46 ,  48  or other, similar fasteners draws the gas block subassembly  14  to the barrel  12  to seal the system. When the clamp sections  42  are tightened, the top portions  52  of each clamp section  42  pull generally downwardly against the lower lips  16   a  of the notches  16  and the clamp protrusions  54  force the flange  18  against the alignment element  62 , which applies a generally upwardly directed clamping force to the lower surface of the barrel  12  in the recess  63 . The forces are distributed at the curved flange  18  and integrated into the gas block  14 . In the illustrated embodiment, each of the clamp sections  42  acts as a class 2 lever or cantilever, wherein the fasteners  46 ,  48  apply a lateral force drawing the lower flanges  56  inward causing the clamp protrusions  54  to clamp the upper flange  18  in inward and upward directions against the barrel  12  via element  62  while the top portions  52  resist the reaction forces pulling downwardly on the lips  16   a.    
       FIG. 3B  illustrates the force vectors applied to one of the clamp sections  42  during mounting of the gas block  14  to the firearm barrel  12 . The moments associated with the force of the gas block on the clamp (F GB/C ) and the force of the screw on the clamp (F S/C ) are substantially equal and opposite; i.e., the sum of the moments acting on the section  42  about any point on the section  42  generally are zero. With reference to  FIG. 3B , the clamp force analysis for the clamp gas block apparatus is as follows:
 
Σ M   0 =0 =F   GB/C ( R )− F   S/C ( Y )=&gt;
 
 F   GB/C =( Y/R ) F   S/C  
 
where:
 
     ΣM 0 =sum of the moments about the top portion  52   
     F S/C =force of the screws  46 ,  48  on the section  42 ; 
     F GB/C =normal contact force of the gas block  14  on the section  42  (“clamp force”). 
     In one exemplary embodiment, the distance Y can be about 0.376 inches, while the distance R can be about 0.266 inches, and the force applied by the screws F S/C  can be about 500 lbf. Using such example values, the clamp force applied in the exemplary embodiment is approximately F GB/C =706 lbf. 
     It therefore can be seen that the construction of the clamped gas block apparatus according to the principles of the present disclosure provides a clamp that allows accurate positioning and alignment of the gas block and efficiently transfers the screw force on the clamp to the gas block without requiring brazing or other permanent attachment methods. 
     The corresponding structures, materials, acts, and equivalents of all means plus function elements in any claims below are intended to include any structure, material, or acts for performing the function in combination with other claim elements as specifically claimed. 
     Those skilled in the art will appreciate that many modifications to the exemplary embodiments are possible without departing from the scope of the invention. In addition, it is possible to use some of the features of the embodiments described without the corresponding use of the other features. Accordingly, the foregoing description of the exemplary embodiments is provided for the purpose of illustrating the principle of the invention, and not in limitation thereof, since the scope of the invention is defined solely be the appended claims.