Abstract:
A firearm including a barrel, receiver, indirect gas system and an adjustable gas block designed to interface with the indirect gas system is provided. Four indexable positions of adjustment are provided for on the adjustable gas block. Positions of adjustment are selected based on the use of a silencer, use of under-powered ammunition, the presence of un-burnt powder and debris in the host firearms operating system, or if the weapon is being fired under “ideal” circumstances. The provided gas block is designed to function with an indirect gas operating system. Excess gas from the operating system is not vented from the gas block thereby generating excess flash and sound. No tool is required to manipulate the adjustment mechanism of the gas.

Description:
[0001]    This application is a continuation of U.S. patent application Ser. No. 12/929,928, filed Feb. 24, 2011, now U.S. Pat. No. 8,752,473, which is a continuation of U.S. patent application Ser. No. 12/220,725, filed Jul. 28, 2008, the disclosure of each of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This present invention generally relates to self loading firearms, specifically to gas blocks for self loading firearms which facilitate user adjustment of the gas flow from the barrel into the operating system. 
         [0004]    2. Description of the Related Art 
         [0005]    The need to regulate the gas flow between the barrel and operating system of a firearm has been a concern since the introduction of autoloading firearms. Gas is generated during the combustion of gun powder present in the cartridges used in modem firearms;  20  This gas expands violently to push the bullet out of the firearm&#39;s barrel. These expanding gases are utilized as a means to operate the action of the host firearm. In modem firearms the preferred method of facilitating the function of an autoloading weapon is as follows. A hole is placed thru the barrel, generally on the top. Location of this hole or gas port varies between operating systems. Generally a gas port size is chosen to allow a broad range of 25 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 dealing with these problems is to incorporate an adjustable gas block into the operating system. 
         [0006]    An adjustable gas block allows for the flow of gas between the gas port in the barrel and the operating system of the firearm to be increased or decreased based on mitigating factors present at the time of use. These systems typically work by utilizing an oversized gas port with means to adjust the flow of gas into the operating system and by venting the unneeded gases from the barrel into the atmosphere thus generating flash and sound. Further, adjustment of the gas system typically requires a special tool and offers no way for the user to index the system and make adjustments due to mitigating circumstances quickly. Designs such as these are well known in the prior art and can be found on the Belgium F AL, Soviet SVD and the Yugoslavian M76 rifle. 
         [0007]    Recent firearm designs such as the FN SCAR rifles have incorporated adjustable gas blocks to be used in conjunction with noise suppressors. 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 during its full auto function, fouls the weapon leading to premature malfunction and to a variety of feeding and extraction problems. 
         [0008]    Modern rifle designs such as the FN SCAR Rifles incorporate adjustable gas blocks which have adjustable pre-set positions. Typically two or three positions of adjustment are afforded the user. A reduced gas flow setting on an adjustable gas block is generally present due to military and government agency requirements. Reducing the standard gas flow is desirable when a silencer is to be used. Silencers increase back pressure and the cyclic rate of the host firearm. By reducing the amount of gas directed to the operating system under normal circumstances, the silencer, with the increased pressure it generates, should not affect the weapon&#39;s operation significantly. While designs with an adjustable gas block mitigate the potential problems associated with the increased back pressure and fouling a noise suppressor generate, gases are still vented out of the gas block thus generating flash and sound. Generating flash and sound from the gas block is counter productive to the function of the silencer which is attempting to reduce the flash and sound from the muzzle of the host firearm. 
         [0009]    The present invention offers several advantages over the prior art. Four positions of adjustment are provided for. Position one offers a “standard” flow of gas. This position is optimized for the firearms barrel length and caliber. Position two reduces the flow of gas into the indirect gas operating system so that with the addition of a silencer the indirect gas operating system is still receiving an equivalent amount of gas as was being provided by position one when no silencer was being utilized. Position three blocks the flow of gas between the barrel gas port and the indirect operating system. This position optimizes the sound reduction capability of an attached noise suppressor. Position four increases the amount of gas being communicated to the operating system so that the firearm may operate properly while dirty or when under powdered ammunition is being utilized. Each of the aforementioned positions of adjustment are indexed with a spring and ball detent, and are pre-set at the factory. No tool is required to rotate the adjustment cylinder into one of the four positions. There is no vent in the gas block which allows for excess gas or un-burnt powder to exit. 
       SUMMARY OF THE INVENTION 
       [0010]    Accordingly several objects and advantages of the present invention are 
         [0011]    (a) To provide the user an indexing means to adjust the flow of gas into the operating system of a firearm. 
         [0012]    (b) To provide a device which restricts the flow of gas into the operating system without venting excess gas from the gas block. 
         [0013]    (c) To provide an adjustment mechanism which does not require the use of special tools. 
         [0014]    (d) To provide an adjustable gas block that may be utilized with an indirect gas system. 
         [0015]    (e) To provide an adjustable gas block with a means to provide gas that is in excess of what is required to help the weapon function in adverse conditions or with underpowered ammunition. 
         [0016]    In accordance with one embodiment of the present invention, a firearm is provided comprising a receiver, a barrel, an adjustable gas block for an indirect gas operated firearm and an indirect gas system. The adjustable gas block is fixedly secured to the barrel and aligned with the gas port hole located thereon. A rotating cylinder provides an indexing, adjustment means for the gas block. By rotating the provided cylinder the flow of gas between the barrel and the indirect gas system is either increased or decreased. Four position of adjustment are afforded the user: A standard gas flow, suppressed gas flow, no gas flow, and an adverse conditions gas flow setting. For adverse conditions the gas flow is increased over what the host weapon would typically require to compensate for a dirty operating system. 
         [0017]    Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0018]    The novel features believed to be characteristic of the present 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 as a definition of the limits of the invention. 
           [0019]      FIG. 1  is a side perspective view of an adjustable gas block for an indirect gas operated firearm in accordance with the present invention; 
           [0020]      FIG. 2  is an exploded view thereof; 
           [0021]      FIG. 3  is a partial cutaway view of the nozzle assembly and adjustment knob; 
           [0022]      FIG. 4  is a side cutaway view of the adjustable gas block for an indirect gas operated firearm; 
           [0023]      FIG. 5  is a side perspective view of an autoloading rifle, with the adjustable gas block for an indirect gas operated firearm in place. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0024]    The adjustable gas block for an indirect gas operated firearm  1  is designed to provide four positions of adjustment, each of which affects the flow of gas from the barrel gas port into the operating system of the host firearm. The herein disclosed device is designed for an indirect gas operating system, it should be noted however that this device is not limited to such operating systems and in fact could be utilized with a gas impingement operating system such as is found on the M16 family for firearms. 
         [0025]    Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is directed to  FIG. 1  which illustrates the preferred embodiment of the herein proposed invention. The adjustable gas block for an indirect gas operated firearm  1  is a replacement for a standard gas block, well known in the prior art, for an autoloading firearm. The adjustable gas block for an indirect gas operated firearm  1  is comprised of a housing  10 , adjustment knob  20 , nozzle assembly (piston)  30 , and a front sight  60 . 
         [0026]    In  FIG. 2 , there is illustrated an exploded view of the adjustable gas block for an indirect gas operated firearm  1  and all of its components. The gas piston block  10  has a piston receiving channel  13  which is located above the barrel receiving channel  12 . Near the distal end of the gas piston block  10  is located a placement  14  for the adjustment knob  20 . Located along the bottom of the gas piston block  10  are two thru pin placements which are utilized to secure the unit as a whole about a barrel. A front sight  60  is provided for on the distal end of the gas piston block  10  along with a bayonet lug  70 . 
         [0027]    The preferred embodiment piston  30  consists of a proximal end, middle and a distal end. On the proximal end is an end wall  33  which blocks the proximal opening entirely. A thru pin bore  34  is present proximate the proximal end. Near the middle of the piston  30  are the connecting member  39 , the radial flange  40 , and the diameter-reducing transition portion  41 . At the distal end is a nozzle  31  which provides an opening into the interior of the piston  30 . 
         [0028]    The adjustment knob  20  has a series of slots  25 - 28  which run transverse to the axis of the piston void  29  located in the center of the adjustment knob  20 . The slots  25 - 28  are located on the front of the adjustment knob  20 . A thru pin bore  24  is present on the exterior of the adjustment knob  20  and is designed to receive a thru pin  21 . 
         [0029]    In  FIG. 3  there is illustrated a view of the adjustment knob  20  and the nozzle assembly  30 . The nozzle assembly  30  is partially cut away to reveal the three gas ports which are 45 degrees offset from one another proximate the connecting member  39 . Gas port one  35 , gas port two  36 , and gas port three  37  are each unique in size. These gas ports  35 - 37  all intersect in the center of the nozzle assembly  30 . 
         [0030]      FIG. 4  illustrates a cutaway view of the adjustable gas block  1 . The gas piston block  10  houses a spring  22  and ball detent  23 . A porthole  44  thru the gas piston block  10  is in communication with the nozzle assembly  30 . The nozzle assembly has a bore  38  which is in communication with the nozzle  31  and the porthole  44  located in the gas piston block  10 . The adjustment knob  20  is secured about the nozzle assembly  30  by means of a thru pin  21  placed into the thru pin bore  24 . 
         [0031]      FIG. 5  illustrates a perspective view of a firearm receiver  90  connected to a barrel  101  utilizing a removable rail  91  which incorporates an indirect gas operating system  100  and the gas piston block  10 . 
         [0032]    As used herein, the word “front” or “forward” corresponds to direction right of the gas piston block  1  (i.e., to the right as shown in  FIGS. 1  thru  5 ); “rear” or “rearward” or “back” corresponds to the direction opposite the direction of the gas piston block  1  (i.e., to the left as shown in  FIGS. 1  thru  5 ); “longitudinal” means the direction along or parallel to the longitudinal axis of the gas piston block  1 ; and “transverse” means a direction perpendicular to the longitudinal direction. 
         [0033]    The adjustable gas block  1  receives a portion of a firearm barrel  101  inside of the gas piston block  10  in the barrel receiving channel  12 . Two thru pin placements  15  spaced apart along the bottom of the gas piston block  10  receive two thru pins which prevent rotation or longitudinal movement of the adjustable gas block  1  along the length of the barrel  101 . The piston receiving channel  13 , located above the barrel receiving channel  12 , has an opening which runs parallel to the bore line of the firearms barrel  101 . Between the front site  60  and the piston receiving channel  13  is a placement  14  which houses the adjustment knob  20 . The adjustment knob  20  has a centrally located void  29  which receives the proximal end of the nozzle assembly  30 . The nozzle assembly is  30  housed within the piston receiving channel  13  and void  29  located within the adjustment knob  20 . Thru pin bore  24  is located on the adjustment knob  20  and another thru pin bore  34  is located on the proximal end of the nozzle assembly  30 . These two thru pin bores are aligned and a thru pin  21  is utilized to secure both the nozzle assembly  30  and the adjustment knob  20  together. A spring  22  and ball detent  23  are located under the piston receiving channel  13  where the ball detent  23  interfaces with the four indexing notches  25 - 28  located about the distal or rear end of the adjustment knob  20 . 
         [0034]    Four positions of adjustment are provided for. Three gas ports  35 - 37  are provided to regulate the flow of gas into the operating system  100 . Nozzle assembly  30  and adjustment knob  20  are in operational communication. Toggling the adjustment knob  20  rotates the nozzle assemble  30  into one of four positions. One position  25  provides the standard flow of gas, for use when the weapon is being utilized in its factory configuration with no accessories. Another position  26  reduces the flow of gas for use of a silencer with the host firearm, well known in the prior art. Still another position  28  is provided which introduces more gas than is needed under normal circumstances, such as when the firearm is utilizing under powered ammunition or the weapon is fowled with un-burnt powder and debris. Finally, a position  27  which blocks the flow of gas from the porthole  44  in the gas piston block  10  from entering the nozzle assembly&#39;s  30  internal nozzle  38  and preventing the operating system of the firearm from cycling the weapon. The adjustment knob  20  is rotated by the user to select the desired flow of gas. Spring  22  and ball detent  23  prevent unintentional movement of the adjustment knob  20  by interfacing with the notches  25 - 28  located on the face of the adjustment knob  20 . 
         [0035]    When a firearm is discharged expanding gases travel down the barrel  101  and a small amount of this excess gas is vented through a gas port located at the top of the barrel  101 . This gas travels through the porthole  44  located in the gas piston housing  10 . If the adjustment knob  20  and thereby the nozzle assembly  30  are rotated in such a manner as to allow the flow of gas into the operating system  100 , one of three gas ports  35 - 37  will be in direct communication with the porthole  44  located in the gas piston housing  10 . Depending on the use of the firearm the user will utilize the adjustment knob  20  to select the appropriate gas setting. Gas will enter the nozzle assembly  30  through one of the three gas ports  35 - 37  located near the proximal end of the nozzle assembly  30 , travel thru the internal nozzle  38  and exit the nozzle  30  thereby entering the indirect gas operating system  100  of the host firearm. 
         [0036]    When the weapon is dirty, or under-powered ammunition is being utilized, the adjustment knob  20  and thereby the nozzle assembly  30  are rotated so that gas port three  35  is in communication with the porthole  44  located in the gas block  10 . When a silencer is being utilized, thereby increasing the flow of gas into the operating system  100 , gas port one  36 , which is smaller in diameter, should be chosen. This prevents the gas operating system  100  from becoming over-gassed and causing extraction problems, or increased wear of the operating systems  100  components. Under normal firing conditions, gas port two  37  is chosen which provides the necessary flow of gas into the operating system  100  for the firearm to operate under normal firing conditions. 
         [0037]    In sum, an adjustable gas block is provided for an autoloading firearm which utilizes and indirect gas operating system. Four pre-set positions are afforded the user of this device. Gas settings which are optimized for suppressor use, hard environments, dirty weapons or when firing under ideal circumstances are provided for. A position which prevents the flow of gas into the operating system is provided for. This system does not vent excess gas from the gas block into the atmosphere around it. Instead excess gas is trapped within the barrel and vented from the muzzle where a flash hider or silencer might allow the gasses to expand and cool. 
         [0038]    Another embodiment of the adjustable gas block could eliminate the increased gas flow setting or the setting which blocks of the flow of gas. 
         [0039]    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 assembled could be modified to receive the gas tube found on such system and thereby regulate the flow of gas from the barrel into the operating system. 
         [0040]    While the above drawings and description contain much specificity, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. 
         [0041]    Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.