Abstract:
An adjustable gas block for a gas operated firearm offering a means to adjust a volume of gas directed to the host rifle&#39;s operating system. The adjustable gas block provides two positions of adjustment that are selectable based on the presence of a pressure increasing device being mounted on the firearm. A first position provides an optimal volume of gas into the gas operating system absent a back pressure increasing device. A second position usable in the presence of a back pressure increasing device causing venting of a portion of the volume of gas into a secondary chamber prior to release into the atmosphere. The amount of gas received by the operating system due to venting is reduced to a volume that is substantially equal to the volume of gas that would be received by the operating system absent a back pressure increasing device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of Invention 
         [0002]    This present invention generally relates to autoloading firearms, specifically to gas blocks for autoloading firearms which facilitate user adjustment to change the volume of gas that flows between the barrel and the operating system. 
         [0003]    2. Description of the Related Art 
         [0004]    The need to regulate the flow of gas between the barrel and operating system of a firearm has been a concern since the invention of autoloading firearms. Gas is generated during the combustion of gun powder present in the cartridges used in firearms. This gas expands violently to push the bullet out of the firearm&#39;s barrel. These expanding gases are also utilized as a means to operate the action of the host firearm. In modern firearms, the preferred method of facilitating the function of an autoloading weapon is as follows. A hole, or gas port, is placed through the barrel, generally on the top. Location of the gas port varies between operating systems and gas port size is chosen to allow a broad range of ammunition to be utilized while guaranteeing the reliable function of the host firearm. Unfortunately, due to varying lengths of barrels, ammunition variance, and other factors, it is very difficult to choose a gas port size which universally works under all conditions. A popular way of compensating for these problems is to incorporate an adjustable gas block into the operating system. 
         [0005]    Traditionally, adjustable gas blocks have been used with autoloading rifles as a means to collect, restrict, and direct the flow of gas from the barrel into the gas operating system. By controlling the amount of gas directed into the operating system, reliable operation of the host firearm is ensured while also ensuring that recoiling parts are not actuated with undue force resulting in malfunctions or premature wear and breakage of parts. 
         [0006]    In response to military request and an increased interest in both civilian and police markets, recent firearm designs have incorporated adjustable gas blocks designed to be used in conjunction with noise suppressors or silencers. Noise suppressors provide a means to redirect and expand the gases generated from the discharge of a firearm so that the resulting flash and sound generated by the firearm is minimized or eliminated. As a result, back pressure is generated, forcing more gas into the firearm&#39;s operating system. This extra gas, or back pressure, increases the firing rate of a weapon when operating at full auto, fouls the weapon leading to premature malfunction, can cause a variety of feeding and extraction problems, and causes premature wear on the reciprocating parts of the operating system. As a result, regulating the flow of gas into a firearm&#39;s operating system and optimizing that flow for use with and without a noise suppressor has become a primary purpose of modern adjustable gas blocks. 
         [0007]    Prior art adjustable gas blocks can, in general, be characterized by the design disclosed in U.S. Pat. No. 2,748,662. Common in the prior art is the use of an oversized gas port located on the barrel which is in communication with the gas block and gas operating system of the host firearm. The adjustable gas block is provided with an indexing means that also turns a gas cylinder, or analogous structure. The gas cylinder has a series of openings, or ports, of differing size such that, when different ports are aligned with the port of the barrel, the flow of gas from the barrel into the operating system is thereby regulated. By rotating the gas cylinder with the provided indexing means, the user is able to select the most appropriate gas flow setting based on the ammunition being used, use of a rifle grenade or the presence of a noise suppressor. 
         [0008]    Prior art designs typically rely on the use of tools to adjust the position of the gas cylinder, an inconvenient requirement for civilian, law enforcement and military users alike. Further, many prior art designs are subject to carbon build up between the rotating gas cylinder and the gas block housing. The carbon build up can cause the gas cylinder to become locked up, making rotation very difficult without frequent maintenance. In consideration of these and other deficiencies found in the prior art, a new manner of constructing and operating an adjustable gas block is needed. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly several objects and advantages of the present invention are
       (a) To provide a means for regulating the volume of gas diverted from the barrel to the indirect gas operating system of the host rifle.   (b) To provide a means to divert excess gas from the operating system without directly venting the gas into the atmosphere.   (c) To provide an adjustable gas block having multiple functional positions which can be actuated by the user without the need of tools.   (d) To provide a means of regulating the flow of gas into the operating system that does not rely on a rotatable gas cylinder in direct communication with the gas port of the barrel.       
 
         [0014]    In accordance with one embodiment of the present invention, a firearm is provided comprising a receiver, an adjustable gas block for a gas operated rifle and an indirect gas operating system. The adjustable gas block is secured about the barrel such that the gas port of the barrel is in communication with the gas port of the gas block housing. In place of a rotatable gas cylinder, the adjustable gas block according to the present invention uses a fixed position gas nozzle which is in direct communication with the gas port of the barrel. The user is provided with an adjustment knob which allows for the selection of two distinct gas settings. The first position allows for a “standard” volume of gas to flow into the operating system. This position is optimized for rifle function when a noise suppressor is not being utilized. The second position, which is intended for use when a noise suppressor is being used, reduces the volume of gas which flows into the gas operating system by placing a channel and chamber located within the adjustment knob into communication with a secondary port located at the forward end of the gas nozzle. This secondary port vents a sufficient volume of excess gas from the adjustable gas block so that the firearm&#39;s operating system receives essentially the same volume of gas as it would in the absence of the noise suppressor. No tool is required to rotate the adjustment knob and select between the first and second positions. 
         [0015]    Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    The novel features believed to be characteristic of the invention, together with further advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a preferred embodiment of the present invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended to define the limits of the invention. 
           [0017]      FIG. 1  is a side perspective view of an adjustable gas block for a gas operated firearm in accordance with the present invention. 
           [0018]      FIG. 2  is an exploded view of the adjustable gas block shown in  FIG. 1 . 
           [0019]      FIG. 3  is a side cutaway view of the adjustable gas block shown in  FIG. 1 . 
           [0020]      FIG. 4  is a side cutaway view of the adjustable gas block with the adjustment knob rotated 90° from the position shown in  FIG. 3 . 
           [0021]      FIG. 5  is a side perspective view of a preferred embodiment rifle equipped with the adjustable gas block of  FIG. 1  and having its gas operating system exposed. 
           [0022]      FIG. 6  is a side cutaway view of the adjustable gas block in accordance with the present invention mounted on a barrel. 
           [0023]      FIG. 7  is a front perspective view of the adjustable gas block shown in  FIG. 1 . 
           [0024]      FIG. 8  is another perspective view of the adjustable gas block shown in  FIG. 7 . 
           [0025]      FIG. 9  is a side view of the preferred embodiment rifle shown in  FIG. 5  with an attached silencer. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    The adjustable gas block for a gas operated firearm in accordance with the present invention is designed to provide two positions of adjustment, each of which regulates the flow of gas between the barrel gas port and the indirect gas operating system, or operating system, of the host firearm. 
         [0027]    Turning now to the drawings, in which like reference characters indicate corresponding elements throughout the several views,  FIG. 1  shows an adjustable gas block, generally described by reference number  10 , in accordance with the present invention. The adjustable gas block  10  is generally comprised of a housing  11 , an adjustment knob  30 , and a gas nozzle  20 . In  FIG. 1 , the adjustment knob  30  is in the first position which provides an appropriate volume of gas for operating the host rifle  90 , shown in  FIGS. 5 and 9 , when a back pressure generating device such as a noise suppressor or silencer is not being used. 
         [0028]    As used herein, the word “front” or “forward” corresponds to the end of the adjustable gas block  10  where the adjustment knob  30  is located (i.e., to the right as shown in  FIGS. 1-5 ); “rear” or “rearward” or “back” corresponds to the direction opposite the end of the adjustable gas block  10  where the adjustment knob  30  is located (i.e., to the left as shown in  FIGS. 1-5 ). 
         [0029]      FIG. 2  illustrates an exploded view of the gas block  10 . The housing  11  has a barrel receiving channel  14  and a gas nozzle receiving channel  15 , with the central axis of each being in vertical alignment with the other. A spring  13  is configured to fit onto the housing  11  and is held in place by placing its two ends into two openings  16  located at the rearward end of the housing  11 , between the barrel receiving channel  14  and the gas nozzle receiving channel  15 . An opening  17 , which houses a roll pin  18 , is located at the forward end of the gas nozzle receiving channel  15 . The adjustment knob  30  has a slot  31  therein and the forward end of the gas nozzle  20  is provided with a side opening  22 . When the gas nozzle  20  is received within the adjustment knob  30 , the side opening  22  is aligned with the slot  31  and a roll pin  23  is inserted therethrough. On the exterior of the adjustment knob  30  are two notches  35 A and  35 B (see  FIG. 8 ) which interface with the spring  13 , shown in  FIG. 2 , thus preventing the unintentional rotation of the knob  30 . The bottom side of the housing  11  has two tapered holes  12  which receive a pair of taper pins  19 , shown in  FIG. 6 . The taper pins  19  prevent longitudinal and radial movement of the gas block housing  11  when it is mounted to the barrel  91 . 
         [0030]    The gas nozzle  20  has an axial bore  24  therethrough with two gas ports  26  and  27 . The first gas port  26  is in direct communication with the gas port  25  of the housing  11  which, in turn, is in communication with the gas port  94  of the barrel  91  (see  FIG. 6 ). The second gas port  27  is located at the forward end of the axial bore  24 . 
         [0031]      FIGS. 3 and 4  show side cutaway views of the adjustable gas block  10  of  FIG. 1 . The rear portion of the adjustment knob is substantially cylindrical with a central bore generally designated by reference numeral  132 . A gas channel  32  is formed axially on the inner surface of the central bore. The gas channel is in communication with an expansion chamber  33  at the forward end of the bore  132 . Further, the expansion chamber  33  is in communication with a centrally located opening  34  extending through the front portion of the adjustment knob  30 . 
         [0032]    The front portion of the adjustment knob  30  is contoured to have two opposing substantially flat sides. A through-opening  134  passing through the two sides  130  is in communication with the opening  34 . By grasping the opposing sides with the thumb and at least one finger, the knob can be easily gripped by the user and manually rotated between the two predetermined positions of adjustment without the use of tools. In the first position of adjustment, shown in  FIGS. 1 ,  2  and  4 , the adjustment knob  30  is rotated so that the gas channel  32  is not in communication with the second gas port  27  located at the forward end of the gas nozzle  20 . In the second position of adjustment, shown in  FIGS. 3 and 5 , the adjustment knob  30  is rotated so that the gas channel  32  of the adjustment knob  30  is in direct communication with the second gas port  27 . According to the embodiment shown, the knob is rotated approximately 90° between the first and second positions. However, the gas block construction could be altered to require more or less rotation between the two positions. 
         [0033]      FIG. 5  illustrates a side view of a preferred embodiment rifle  90 . Shown is the lower receiver group  93  and the upper receiver group  92 , both well known in the prior art. The barrel  91  has a handguard  97  which is shown with its top portion removed to expose the indirect gas operating system  95  of the rifle  90 . Attached to the muzzle of the barrel  91  is a flash hider  98  which facilitates the mounting of a silencer  99  (see  FIG. 9 ). The indirect gas operating system  95  used with the preferred embodiment is described in U.S. Pat. No. 7,461,581 (“the &#39;581 patent”). The piston cup  28 , which is a portion of the gas operating system  95 , is nested over and around the rear portion of the gas nozzle  20 . Also shown is the adjustable gas block  10  according to the present invention, with the adjustable gas block in its second position of adjustment. 
         [0034]      FIG. 6  shows a cutaway view of the gas block housing  11  while mounted on the barrel  91 . This illustration provides clarity for how the taper pins  19  interact with the barrel  91  to prevent movement of the housing  11  during routine use of the host rifle  90 . Also shown is how the barrel gas port  94  is oriented in relation to the gas port  25  of the housing  11  and the gas port  26  of the gas nozzle  20 . 
         [0035]      FIG. 7  illustrates a front perspective view of the adjustable gas block  10  and shows the opening  34  in the adjustment knob  30  for gas to exit the expansion chamber  33  when the adjustment knob has been rotated into the second position (see  FIGS. 3 and 5 ). Also shown is one of the indexing notches  35 A of the adjustment knob  30 . This indexing notch  35 A is only in operational contact with the spring  13  when the adjustment knob  30  is rotated to the first position of adjustment as shown in  FIG. 4 . 
         [0036]      FIG. 8  illustrates another front perspective view of the adjustable gas block  10 . This view shows how the spring  13  interacts with the indexing notch  35 B when the adjustment knob  30  is in the second position. The spring  13  has a bend  36  about its centerline; the bend  36 , when nested in the indexing notch  35 B as shown, prevents unintentional rotation of the adjustment knob  30 . 
         [0037]      FIG. 9  illustrates a side perspective view of the preferred embodiment rifle  90  shown in  FIG. 5  with a silencer  99  attached to the flash hider  98 . 
         [0038]    To assemble the adjustable gas block  10  according to the present invention, the housing  11  is slid over the barrel  91 , with the barrel being received in the barrel receiving channel  14 . The two tapered holes  12  of the housing  11  are aligned with two dimples (not shown) located on the underside of the barrel  91 . Once aligned, the two taper pins  19  are inserted into the two tapered holes  12  to prevent rotational and longitudinal movement of the housing  11 . The location of the two dimples is selected so that the gas port  94  of the barrel  91  is in alignment with both the gas port  25  of the housing and the gas port  26  of the gas nozzle  20 , as best illustrated in  FIG. 6 . 
         [0039]    The gas nozzle  20  is then inserted into the gas nozzle receiving channel  15  and retained in place by inserting the roll pin  18  through the opening  17  to prevent both longitudinal and rotational movement. The adjustment knob  30  is slid over the forward end of the gas nozzle  20  which protrudes out of the gas nozzle receiving channel  15 . The roll pin  23  is inserted through the slot  31  in the adjustment knob  30  and through the opening  22  located at the forward end of the gas nozzle  20 . The roll pin  23  prevents longitudinal movement while the slot  31  defines the limits of the rotational movement of the adjustment knob  30 . The spring  13  is fitted into place between the adjustment knob  30  and the housing  11 , being retained in place by its two ends which are secured into openings  16  located on both sides of the housing  11 . The bend  36  of the spring  13  is shaped to removably fit into one of the two notches  35 A and  35 B located about the external surface of the adjustment knob  30 . The piston cup  28  is then slid over the rearward end of the gas nozzle  20  with the remainder of the indirect gas operating system  95  being assembled as disclosed in the &#39;581 patent. 
         [0040]    The adjustable gas block,  10  when secured to a rifle  90  equipped with an indirect gas operating system  95  as disclosed herein, functions in the following manner. When the adjustment knob  30  is in the first position of adjustment and a round is discharged from the rifle  90 , expanding gases which both precede and follow the projectile down the barrel are diverted through the gas port  94  of the barrel  91 , through the gas port  25  of the housing  11  and finally into the first gas port  26  located near the forward end of the gas nozzle  20 . As already disclosed, the first gas port  26  is in direct communication with the bore  24  in the gas nozzle  20 . Once the gas enters the bore  24  it further expands therethrough and impinges on the piston cup  28  of the operating system  95 , thereby reciprocating the action of the rifle  90 , the details and specifics of which are not discussed herein. Gas is prevented from exiting through the second gas port  27  located at the forward end of the gas nozzle  20  by a portion of the adjustment knob&#39;s  30  internal side wall which blocks the second port  27 . The first gas port  26 , in direct communication with the gas port  94  of the barrel  91  through gas port  25 , is calibrated to provide the optimal volume of gas for the reliable operation of the rifle  90  in the absence of a silencer  99  being attached to the muzzle of the barrel  91 . 
         [0041]    When the adjustment knob is rotated into its second position of adjustment (see  FIGS. 3 and 5 ), the gas channel  32  is placed into communication with the second gas port  27  located at the forward end of the gas nozzle  20 . While gas is expanding in the gas nozzle following the discharge of a loaded cartridge, as described above, a portion of the gas is ported through the second gas port  27 , through the provided gas channel  32  and into the expansion chamber  33  formed between the exterior of the gas nozzle  20  and the interior of the adjustment knob  30 . From the expansion chamber  33 , the gas is released into the atmosphere through the opening  34  in the adjustment knob  30 . Accordingly, the second position of the adjustable gas block  10  reduces the volume of gas which impinges on the piston cup  28  by releasing a portion of the expanding gases through the second gas port  27 . This is desirable when a silencer  99  is mounted to the flash hider  98  as shown in  FIG. 9 , because the silencer  99  increases the volume of expanding gases, or back pressure, forced through the gas port  25  into the gas nozzle  20 . The second gas port  27  at the forward end of the gas nozzle  20  reduces the volume of gas directed to the operating system  95  by diverting and venting a portion of it as described above. Through such venting, the volume of expanding gases which comes into contact with the piston cup  28  is approximately that which is desired to operate the rifle in the absence of a silencer  99  being affixed to the muzzle of the barrel  91 . In addition, venting a portion of the operating gases from the gas block housing serves to minimize fouling, reduce recoil and reduce premature wear of the host firearm when a silencer is in use. 
         [0042]    Still another embodiment of the adjustable gas block could be adapted to work with a direct gas impingement system such as found on M16 style rifles. The nozzle assembly can be modified to receive the prior art gas tube found on such systems, or even a non-standard straight profile gas tube, and thereby regulate the flow of gas between the barrel and the firearm&#39;s operating system. 
         [0043]    While the above drawings and description contain much specificity with respect to certain of the features of the present invention, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. 
         [0044]    It is now apparent to those skilled in the art that other embodiments, improvements, details, and uses can be made consistent with the letter and spirit of the foregoing disclosure and within the scope of this patent, which is limited only by the following claims, construed in accordance with the patent law, including the doctrine of equivalents.