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:
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, and hereby claims priority thereof to which it is entitled. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     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. 
     2. Description of the Related Art 
     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 modern firearms. 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 modern 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 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. 
     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 FAL, Soviet SVD and the Yugoslavian M76 rifle. 
     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, cool and slow the expanding 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. 
     Modern rifle designs such as the FN SCAR rifles incorporate adjustable gas blocks which have selectable 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 adversely. While designs with an adjustable gas block mitigate the potential problems associated with the increase of 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 counterproductive to the function of the silencer which is attempting to reduce the flash and sound from the muzzle of the host firearm. 
     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 firearm&#39;s 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 underpowered 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 
     Accordingly several objects and advantages of the present invention are
         (a) To provide the user an indexing means to adjust the flow of gas into the operating system of a firearm.   (b) To provide a device which restricts the flow of gas into the operating system without venting excess gas from the gas block.   (c) To provide an adjustment mechanism which does not require the use of special tools.   (d) To provide an adjustable gas block that may be utilized with an indirect gas system.   (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.       

     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 positions 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. 
     Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       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 to define the limits of the invention. 
         FIG. 1  is a side perspective view of an adjustable gas block for an indirect gas operated firearm in accordance with the present invention; 
         FIG. 2  is an exploded view of the gas block shown in  FIG. 1 ; 
         FIG. 3  is a partial cutaway view of the nozzle assembly and adjustment knob which are parts of the gas block shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a side cutaway view of the adjustable gas block for an indirect gas operated firearm shown in  FIG. 1 ; 
         FIG. 5  is a side perspective view of the adjustable gas block for an indirect gas operated firearm shown with the firearm receiver and barrel. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The adjustable gas block, generally designated by reference numeral  1 , for an indirect gas operated firearm 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, but it should be noted 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 of firearms. 
     As shown in  FIG. 1 , which illustrates the preferred embodiment of the present invention, the adjustable gas block  1  for an indirect gas operated firearm is a replacement for a standard gas block, well known in the prior art, for an autoloading firearm. The adjustable gas block  1  for an indirect gas operated firearm is comprised of a housing  10 , an adjustment knob  20 , a nozzle assembly  30 , also referred to as a gas nozzle, and a front sight  60 . 
     In  FIG. 2 , there is illustrated an exploded view of the adjustable gas block  1  for an indirect gas operated firearm and all of its components. The housing  10  has a gas nozzle receiving channel  13  which is located above the barrel receiving channel  12 . Near the distal end of the housing  10  is located a groove  14  for the adjustment knob  20 . The groove is transverse to the longitudinal axis of the barrel and is bounded on one side by a front surface of the gas block adjacent the gas nozzle receiving channel and on the other side by a solid rearwardly facing surface of the gas block. Located along the bottom of the housing  10  are two thru pin placements  15  which receive two taper pins that are utilized to secure the unit as a whole about the barrel  101  (see  FIG. 5 ). A front sight  60  is provided for on the distal end of the housing  10  along with a bayonet lug  70 . 
     The preferred embodiment gas nozzle  30  consists of a front end  33 , a back end and a middle portion. The front end  33  of the gas nozzle  30 , which does not have an opening, protrudes from the front of the gas nozzle receiving channel  13  and into the groove  14 . The back end protrudes from the rear of the housing and has an opening  31  into the gas nozzle which is in communication with gas ports  35 ,  36  and  37  (shown in  FIG. 3 ). The middle area consists of the structural features between the front end  33  and the opening  31  at the back end. Structural features found on the middle area are the connecting member  39 , the radial flange  40 , an opening  34  for a pin  21  and the diameter-reducing transition portion  41 . 
     The adjustment knob  20  has a front face, a rear face, and a generally annular body surrounding a central opening or bore  29 , said rotatable knob being received within said transverse groove with the knob rear face adjacent the front side of the gas nozzle receiving channel cylindrical bore and the knob front face adjacent a rearwardly facing surface of the housing. The adjustment knob  20  includes a series of slots  25 - 28  located about the periphery of the rear face of the adjustment knob  20 . The central opening or bore  29  of the adjustment knob  20  receives a front portion of the gas nozzle  30 . An opening  24  is present on the exterior of the adjustment knob  20  and is designed to receive a pin  21 . 
     In  FIG. 3  there is illustrated a view of the adjustment knob  20  assembled with the gas nozzle  30 . The gas nozzle  30  is partially cut away to reveal the three gas ports  35 ,  36  and  37 . Gas port  36  is at a 90 degree angle with respect to each of gas ports  35  and  37 , and gas ports  35  and  37  are positioned 180 degrees from one another. 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 gas nozzle  30 . Each of the gas ports is in communication with the opening  31  located at the front of the gas nozzle  30  and the bore  38  therethrough. 
       FIG. 4  illustrates a cutaway view of the adjustable gas block  1 . The housing  10  houses a spring  22  and ball detent  23  in a void  19 . A gas port  44  thru the housing  10  is in communication with both the gas nozzle  30  and the gas port of the barrel  101 . The gas nozzle  30  has a bore  38  which is in communication with an opening  31  of the gas nozzle  30  and the gas port  44  located in the housing  10 . The adjustment knob  20  is secured about the gas nozzle  30  by means of a pin  21  which is inserted through an opening  24  in the adjustment knob  20  and then through the opening  34  located on the gas nozzle  30 . 
       FIG. 5  illustrates a perspective view of a firearm receiver  90  connected to a barrel  101  utilizing a removable rail  91  (also referred to as a handguard) which incorporates an indirect gas operating system  100  and the adjustable gas block  1 . 
     As used herein, the word “front” or “forward” corresponds to the direction right of the adjustable gas block  1  as shown in  FIGS. 1  thru  5 ; “rear” or “rearward” or “back” corresponds to the direction opposite the front direction of the adjustable gas 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 adjustable gas block  1 ; and “transverse” means a direction perpendicular to the longitudinal direction. 
     The adjustable gas block  1  is assembled as follows. The spring  22  and ball detent  23  are inserted in the void  19  located within the housing  10 . A placement area or groove  14  formed in the housing  10  receives the adjustment knob  20  therein and retains the spring  22  and ball detent  23  in place. The spring  22  provides a force to the ball detent  23  which interacts with the indexing notches  25 ,  26 ,  27  and  28  located about the adjustment knob  20  and provides an indexing means for the orientation of the gas nozzle  30 . The interaction between the ball detent  23  and the indexing notches  25 - 28  prevents the unintentional rotation of the adjustment knob  20  during routine use of the host firearm. The gas nozzle  30  is inserted through the gas nozzle receiving channel  13  and through the central opening  29  in the adjustment knob  20 . The gas nozzle  30  is initially oriented such that the openings  34  align with the openings  24  on the adjustment knob  20  where a pin  21 , preferably a roll pin type, is pushed through. This retains the adjustment knob  20  and the gas nozzle  30  in place. A portion of the barrel  101  is received by the barrel receiving channel  12  located on the housing  10 . Once the through pin placements  15  are aligned with the existing openings on the barrel  101 , two pins are then used to secure the adjustable gas block  1  to the barrel  101  and thus prevent the rotation and longitudinal movement of the housing  10 . 
     When a firearm is discharged, expanding gases travel down the barrel  101  with a small amount of this gas being vented through a gas port located on the top of the barrel  101 . This gas then travels through the gas port  44  located in the housing  10  into the bore  38  and out of the opening  31  of the gas nozzle  30  into the operating system  100 . A firearm equipped with the adjustable gas block  1  disclosed herein, through the use of the adjustment knob  20 , can rotate the gas nozzle  30  into a position which blocks gas from entering the bore  38 . This occurs when the adjustment knob  20  is rotated such that indexing notch  28  is in contact with the ball detent  23  thereby placing a non-ported portion of the gas nozzle  30  over the gas port  44  of the housing  10 . If the adjustment knob  20  and thereby the gas nozzle  30  are rotated in such a manner as to allow the flow of gas into the operating system  100 , one of the three gas ports  35 - 37  will be in direct communication with the gas port  44  located in the housing  10 . 
     Once the adjustable gas block  1  is fully assembled onto a rifle as shown in  FIG. 5 , the adjustment knob  20  is received within the transverse groove  14  with the rear face of the knob adjacent the front end of the gas nozzle receiving channel cylindrical bore and the knob front face adjacent a rearwardly facing surface of the housing. When coupled to the gas nozzle  30 , the adjustment knob  20  may be used to regulate the flow of gas between the barrel  101  and the operating system  100 . In the preferred embodiment of the herein disclosed design, the adjustment knob  20  has four indexed positions  25 ,  26 ,  27  and  28 . Also provided are the three gas ports  35 ,  36  and  37  which regulate the flow of gas into the bore  38 , through the gas nozzle  30 , and into the operating system  100 . The adjustment knob  20  and the gas nozzle  30 , when attached by the provided pin  21 , form an assembly where the rotation of the adjustment knob  20  rotates the gas nozzle  30  within the housing  10 . When the indexing notches  25 - 27  are in contact with the ball detent  23 , a specific gas port  35 - 37  of the gas nozzle  30  is in communication with the gas port  44  of the housing  10 . When indexing notch  28  is in contact with the ball detent  23 , the gas nozzle  30  is rotated to a position where there is no gas port to communicate with the gas port  44  of the housing  10 . Gas port three provides a flow of gas which is optimized for the proper functioning of the rifle based on its barrel length, caliber and operation under optimal conditions. Gas port three  37  is also referred to as the “standard” setting. Gas port one  35  has an opening which is larger than the opening of gas port three  37 , thereby providing an increased quantity of gas to the operating system  100  of the host firearm. Gas port one  35  is used when the host weapon is dirty or the firearm&#39;s rate of fire needs be increased. Gas port one  35  is also referred to as the “adverse condition setting”. The third gas port  36 , generally referred to as gas port two, has an opening which is smaller in diameter than the opening of the “standard” gas port  37 . Gas port two  36  is for use when a silencer is affixed to the muzzle of the barrel  101 . This gas port  36  is also referred to as the “silencer setting”. 
     In sum, an adjustable gas block is provided for an autoloading firearm which utilizes an indirect gas operating system. Four pre-set positions are afforded the user of this device. Gas settings which are optimized for suppressor use, harsh environments, dirty weapons or when firing under ideal circumstances are also 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. 
     Another embodiment of the adjustable gas block could eliminate the increased gas flow setting or the setting which blocks the flow of gas. 
     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. 
     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. 
     Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.