Abstract:
A kit for use with a modular weapon having a barrel and having an upper receiver defining a gas port and a barrel opening. The kit comprises an upper receiver plate for attaching to the upper receiver, and a barrel plate. The weapon barrel passes though concentric openings in the upper receiver plate and the barrel plate and is secured in the opening within the barrel plate. Another opening in the barrel plate receives a primary gas tube such that a rearward segment of the primary gas tube extends rearwardly from that opening and a forward segment of the primary gas tube extends forwardly from that opening. A forward end of a gas tube extension couples to a rearward end of the primary gas tube and a rearward end of the gas tube extension is received within the gas port when the kit is in use with the modular rifle. An assembly removably attaches the upper receiver plate and the barrel plate thereby creating a gas flow path beginning at the gas port and comprising the gas tube extension, the rearward segment of the primary gas tube, and the forward segment of the primary gas tube.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application claims the benefit of U.S. provisional patent application filed on Jul. 29, 2014 and assigned Application No. 62/030,260, incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     A method, system, and kit related to a removable and replaceable barrel and gas tube for modular rifles. 
     BACKGROUND OF THE INVENTION 
     M16 and AR15 rifles are air-cooled, gas-operated, magazine-fed assault rifles. These rifles are the primary assault weapons used by military and police forces. 
     A gas-operated rifle uses a portion of the high pressure gas formed as the ammunition round travels through the barrel to supply energy to operate the auto-loading feature of the rifle. The high pressure gas powers a mechanism to extract the spent casing and chamber a new cartridge. Energy from the gas is harnessed through either a port in the barrel or a trap in the muzzle. This high-pressure gas travels through a gas tube that is located parallel to the barrel and upon exiting the tube impinges on a surface such as a piston head to provide motion for unlocking the action, extracting the spent casing, ejecting the spent casing, cocking the hammer or striker, chambering a fresh cartridge, and finally locking the action. 
     Such a modular rifle is illustrated in  FIG. 1 . As shown in  FIG. 2 , the rifle comprises a lower receiver assembly  1  conveniently separable from an upper receiver assembly  2 . The lower and upper receiver assemblies  1  and  2  are connected using push pins with the pins carried by the lower receiver assembly  1  and extending through openings (not visible in  FIG. 2 ) in the upper receiver assembly  2 . 
     The lower receiver assembly  1  contains a lower receiver, fire control components, and a buffer assembly included in the butt-stock. These components are not separately designated in  FIG. 2  and are not pertinent to the structure and function of the present invention. Instead, the present invention relates generally to the upper receiver assembly  2  and its components. 
     Prior art  FIG. 3  illustrates the upper receiver assembly  2 , comprising an upper receiver  3  and a hand guard  4  surrounding a barrel  5 . The barrel  5  is affixed to the upper receiver  3  using a barrel nut that is obscured from view in  FIG. 3  but shown in  FIG. 4 . 
     Prior art  FIG. 4  illustrates the upper receiver assembly  2  with the hand guard  4  removed to expose a barrel nut  6 , a stock gas tube  7  and a gas block  8  that holds the stock gas tube  7  in place. The barrel  5  and the gas block  8  each define a small opening through which gas passes from the barrel, through the gas block, and into the stock gas tube  7 . 
     In the prior art modular rifles of  FIGS. 1-4 , the barrel  5  is affixed to the upper receiver  3  with the barrel nut  6  and this arrangement requires specialized tools and fixtures to remove and attach the barrel. For example, if the user wishes to change to a barrel of a different length. The prior art design makes it nearly impossible to remove the barrel in the field without use of these tools. Removal also requires a significant amount of time and familiarity with intricate mechanisms of the rifle. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The forgoing and other features of the present invention will be apparent to one skilled in the art to which the present invention relates upon consideration of the description of the invention with reference to the accompanying drawings. The use of the same reference numeral in the various figures refers to the same element. 
         FIG. 1  illustrates an exemplary prior art AR15/AR10 modular rifle. 
         FIG. 2  illustrates an exploded view of the prior art AR15/AR10 modular rifle of  FIG. 1 . 
         FIGS. 3 and 4  illustrate components of the prior art upper receiver assembly of  FIG. 2 . 
         FIG. 5  illustrates an exploded view of components of a upper receiver coupler and a barrel coupler. 
         FIG. 6  illustrates the upper receiver and  FIG. 7  the upper receiver with the upper receiver coupler attached thereto. 
         FIG. 8  illustrates the upper receiver coupler. 
         FIG. 9  illustrates the barrel coupler and the attached barrel. 
         FIG. 10  illustrates the barrel coupler. 
         FIGS. 11 and 12  illustrate the barrel with different length gas tubes. 
         FIG. 13  illustrates the barrel coupler, the barrel, and the hand guard. 
         FIG. 14  illustrates an exploded view of the upper receiver coupler (attached to the upper receiver) and the barrel coupler (attached to the barrel and hand guard). 
         FIG. 15  illustrates the barrel coupler mated to the upper receiver coupler. 
         FIG. 16  illustrates the barrel coupler attached to the upper receiver coupler. 
         FIG. 17  illustrates an AR15/AR10 rifle with the components of the present invention attached thereto. 
         FIG. 18  illustrates another embodiment of the barrel coupler and upper receiver coupler. 
         FIGS. 19-21  illustrate three different gas tubes. 
         FIGS. 22 and 23  illustrate different views of details of the hook and lever of the barrel coupler. 
         FIG. 24  illustrates an alternative embodiment of the upper receiver coupler. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Before describing in detail the particular methods and apparatuses related to a removable barrel and hand guard for modular rifles, it should be observed that the present invention resides primarily in a novel and non-obvious combination of elements and process steps. So as not to obscure the disclosure with details that will be readily apparent to those skilled in the art, certain conventional elements and steps have been presented with lesser detail, while the drawings and the specification describe in greater detail other elements and steps pertinent to understanding the inventions. 
     The presented embodiments are not intended to define limits as to the structures, elements or methods of the inventions, but only to provide exemplary constructions. The embodiments are permissive rather than mandatory and illustrative rather than exhaustive. 
     The components of the present invention when installed in a rifle allow the rifle user to easily and quickly remove the barrel without specialized tools and replace the removed barrel with a barrel of a different length. As is known by those skilled in the art, a longer barrel allows the ammunition round to exit the barrel with a greater velocity and thus travel farther (i.e., have a longer range) than a round shot from a shorter barrel. 
     Advantages of the present invention include at least: allowing the rifle barrel to be easily removed to store or transport the rifle in a smaller space; allowing the user to easily remove and replace the barrel with a different length barrel; allowing conversion of the rifle to a different caliber; and, simplifying cleaning of the weapon as specialized tools are not required to disassemble the rifle. With regard to different barrel lengths, a sniper prefers a longer rifle barrel while a shorter barrel is desired in close quarter combat. 
     The invention also permits the user to use any one of many different available hand guards. Alternatively, the barrel coupler of the present invention may be supplied with a hand guard permanently integrated with the barrel coupler. In this latter embodiment the barrel and hand guard can both be removed from the rifle as one unit without the user of tools. 
     The components of the present invention may be installed on any rifle or weapon having an appropriately styled barrel and receiver interface. 
     The components of the invention may also be considered a kit for adding and/or replacing the components of an existing rifle to allow the user to then easily and conveniently exchange a barrel of a first length for a barrel of a second length. The kit components can be installed on an existing rifle without any permanent modifications to the rifle. Alternatively, certain of the invention components can be integrated into a new rifle as it is manufactured, e.g., the upper receiver coupler integral with the upper receiver and/or the barrel coupler integral with the barrel. 
     The components of the invention generally comprise: an upper receiver coupler for attaching to an upper receiver of an existing rifle and a barrel coupler for attaching to a barrel of the existing rifle. The upper receiver coupler and the barrel coupler are removably joined or latched together using components attached to the upper receiver coupler, to the barrel coupler, and/or to both. Further, the invention comprises a novel gas tube that is attached to the barrel, passes through the upper receiver coupler and the barrel coupler, and via a gas tube extension attaches to the rifle upper receiver. 
       FIG. 5  is an exploded view illustrating an upper receiver coupler  100  and a barrel coupler  103  and their associated components. With the upper receiver coupler attached to the upper receiver, as described elsewhere herein, and the barrel coupler attached to the barrel, as described elsewhere herein, coupling the upper receiver coupler and the barrel coupler thereby attaches the barrel to the upper receiver to form a continuous path for the ammunition round. 
     Additionally, when the upper receiver coupler and the barrel coupler are joined, a gas tube running parallel to the barrel extends from a forward end of the barrel, passes through both couplers, and is received within the upper receiver of the rifle. Gas flowing through this path actuates various rifle functions as described above. 
     Turing to  FIG. 6 , it illustrates the conventional upper receiver  3  further comprising a threaded upper receiver extension  3 A and a gas port  3 B. In a prior art rifle, the barrel is received within the upper receiver extension  3 A and a barrel nut (not shown) holds the barrel within the upper receiver extension. A groove  3 C receives a tab on the barrel (not shown) to properly align the barrel to the upper receiver. 
     With reference to  FIGS. 5, 6, and 7 , to attach the upper receiver coupler  100  to the upper receiver  3 , the threaded upper receiver extension  3 A is inserted into an opening  10 A defined in an upper receiver plate  10 . Internal threads  11 A of a star nut  11  threadably engage external threads of the upper receiver extension  3 A, and the star nut  11  is tightened to fixedly join the upper receiver coupler  100  to the upper receiver  3 .  FIG. 7  illustrates the final configuration. 
     Semicircular grooves  16  in an outer circumference of the star nut  11  receive mating protrusions of a tool (not shown) for tightening the star nut  11 . However, this feature is not a required element of the invention instead it is merely a convenient technique for tightening the star nut  11 . 
       FIG. 8  also illustrates certain components and features of the upper receiver coupler  100  including the upper receiver plate  10  and the star nut  11 . The remainder of the illustrated components are described below. 
     In an alternative embodiment, in lieu of using the star nut  11 , the upper receiver plate  10  comprises internal threads  25  (see  FIG. 24 ) that threadably engage mating threads  3 D on the upper receiver extension  3 A of  FIG. 6 . 
     With reference to  FIGS. 5 and 9 , to position the barrel  5  within the barrel coupler  103 , the barrel is received within an opening  103 A that extends through the barrel coupler. A raised segment of the barrel, referred to as a collar (see a collar  5 A in  FIGS. 9, 11, and 12 ), is disposed within the opening  103 A and a rear surface of the collar  5 A abuts an internal surface of the barrel coupler  103 . 
     With continued reference to  FIGS. 5 and 9 , set screws  17  distributed around a circumference of a barrel plate  14  are urged against the barrel  5  to hold the barrel within the barrel coupler  103 . In one embodiment the set screws are spaced at 120 degrees although only one set screw  17  is illustrated in  FIG. 5 . Additionally, when the barrel coupler and the upper receiver coupler are mated, the barrel flange is captured and held in place between the mated barrel coupler and the upper receiver coupler. Also, in one embodiment the groove  3 C of the upper receiver extension  3 A of  FIG. 6  receives a tab (not shown) of the barrel to align the barrel in the upper receiver. Finally, the mated couplers exert additional forces on the barrel to secure the barrel within the barrel coupler. 
     As can be seen in  FIG. 9 , a barrel segment  5 B of the barrel  5  extends beyond a rear surface of the barrel coupler  103 . The barrel segment  5 B extends into the opening  10 A (see  FIGS. 5, 7, and 8 ) of the coupler plate  10  when the upper receiver coupler and the barrel coupler are mated. 
     In lieu of using the set screws  17 , the barrel can be held in place within the barrel coupler  103  by a compression fitting comprising a slot defined in the barrel plate  14  and a tension screw to close the slot after the barrel is inserted. Alternatively, an end of the barrel comprises a split cone feature with an outside-threaded nut for threading into mating threads extending from a rear surface of the barrel plate. 
     Returning to  FIG. 5 , in addition to the barrel plate  14 , the barrel coupler  103  further comprises hooks  12 , levers  13  for operating the hooks  12 , and a barrel plate extension  14 A. Only one hook  12  and lever  13  is illustrated in  FIG. 5  as the opposing hook and lever is not visible in  FIG. 5 . 
     The hooks  12  and levers  13  are held together by pins not illustrated in  FIG. 5  but depicted as a pin  140  in  FIGS. 22 and 23 . With reference to  FIG. 5 , the pin is held in position by a set screw  22 , again, with only one illustrated in  FIG. 5 . 
     With the barrel coupler  103  in contact with the upper receiver coupler  100 , exerting an inwardly-directed force on the levers  13  forces the hooks  12  to each engage a hardened pin  21  within each recess  10 B in the upper receiver plate  10 . This action locks the barrel plate  14  to the receiver plate  10  and thereby locks the barrel coupler  103  to the upper receiver coupler  100 . Another hook, lever, recess and pin are disposed on an opposing side of the respective barrel plate and the upper receiver plate and thus are hidden from view in  FIG. 5 . 
     The illustrated pin  21  is held in position by action of a set screw  23 . 
     With the barrel  5  attached to the barrel coupler  103  with the set screws  17 , the barrel coupler  103  attached to the upper receiver coupler  100  with the hooks  12 , and the upper receiver coupler attached to the upper receiver  3  with the star nut  11 , the barrel is thereby coupled to upper receiver to provide a path for the round as it exits the upper receiver, enters and passes through the barrel segment  5 B (see  FIG. 9 ) and the barrel  5 , and exits from a forward end of the barrel  5 . 
     With this invention the barrel  5  can be easily and quickly changed by operating the levers  13  to release the hooks  12  and thereby separate the upper receiver coupler  100  from the barrel coupler  103  and loosening the set screws  17 . This operation is much simpler than the required operations to remove the barrel in a prior art rifle. 
     With reference to  FIG. 5 , when the barrel coupler  103  is brought into contact with the upper receiver coupler  100 , an alignment pin  19  extending rearward from a rear surface of the barrel plate  14  is received within an opening  20  in a front surface of the upper receiver plate  10  for aligning the upper receiver coupler  100  and the barrel coupler  103 . 
       FIG. 10  is a rear view of the barrel coupler  103 . In particular, this view shows an opening  29  through which a primary gas tube  33  passes, as described below. 
     As described above, a gas-operated rifle uses some of the high pressure gas generated as the ammunition round travels through the barrel to supply energy to operate the auto-loading feature of the rifle. In the present invention, a high pressure gas path extends from an entry point of the gas tube on the barrel  5 , along the barrel, through the barrel coupler  103 , through the upper receiver coupler  100  and finally to the upper receiver  3 . 
     As can be seen in  FIGS. 5 and 9 , a primary gas tube  33  extends forward from the barrel plate  14  runs parallel to the barrel  5  and connects to the barrel  5  at the gas block  8 . 
     Working toward the butt stock of the rifle and beginning at the barrel plate  14 , the primary gas tube  33  passes through the opening  29  (see  FIG. 10 ) in the barrel plate  14 . A rearward segment  33 A of the primary gas tube  33  (see  FIGS. 5 and 9 ) extends rearward out from the opening  29  in the barrel plate and through an opening  36  (see  FIG. 8 ) in the receiver plate  10 . An end  33 B of the rearward segment  33 A mates with a coupler  34  (that is, when the upper receiver coupler  100  and the barrel coupler  103  are coupled) that is in turn connected to a gas tube extension  35  (see  FIGS. 5 and 8 ). 
     To avoid interference between the rearward segment  33 A of the primary gas tube  33  and the upper receiver coupler  100  and its associated components, the rearward segment  33 A is disposed within one of the semicircular grooves  16  of the star nut  11 . 
     An end  35 A of the gas tube extension  35  (both of which are depicted in  FIG. 5 ) is received within the gas port  3 B of the upper receiver  3  as illustrated in  FIG. 6 . 
       FIG. 11  illustrates the barrel  5  with a stock or stock gas tube  7  installed in the gas block  8 . 
       FIG. 12  illustrates the barrel  5  with the shortened primary gas tube  33 , i.e., shorter than the stock gas tube  7 , installed in the gas block  8 . The shortened gas tube is required due to presence of the receiver coupler  100  and the barrel coupler  103  in the gas flow path between the gas block  8  and the gas port  3 B in the upper receiver  3 . 
       FIG. 13  illustrates the hand guard  4  as mated with the barrel coupler  103  and covering a segment of the barrel  5  and the entire length of the primary gas tube  33 . To attach the hand guard  4 , inside threads of the hand guard threadably engage outside matching threads of the barrel plate extension  14 A depicted at least in  FIGS. 5 and 9 . 
       FIG. 13  also reveals that the hand guard  4  and the barrel  5 , when affixed to the barrel coupler  103 , can be removed from the rifle as a unitary structure by simply separating the barrel coupler  103  from the upper receiver coupler  100 . 
       FIG. 14  illustrates the upper receiver coupler  100  (and certain ones of its attached components) in position to mate with the barrel coupler  103  (and certain ones of its attached components). 
     To mate the upper receiver coupler  100  and the barrel coupler  103 , (see  FIGS. 5 and 14  in particular) the opening  10 A in the upper receiver plate  10  is aligned with the barrel segment  5 B, the pin  19  of the barrel coupler is aligned with the opening  20  in the receiver coupler, and the rearward segment  33 A of the gas tube is aligned with the coupler  34 . The upper receiver coupler and the barrel coupler are brought into contact and by the application of an inwardly directed force on the levers  13 , the hooks  12  on the barrel coupler are locked around the pins  21  in the recesses  10 B of the upper receiver coupler. 
       FIG. 15  illustrates the mated upper receiver coupler  100  and the barrel coupler  103  with the hooks  12  in an open position. 
       FIG. 16  illustrates the coupled upper receiver coupler  100  and the barrel coupler  103  with the hooks  12  in a closed position. 
       FIG. 17  illustrates an AR15/AR10  110  depicting the upper receiver coupler  100  and the barrel coupler  103  of the present invention. 
       FIG. 18  illustrates another embodiment of the present invention comprising an upper receiver coupler  111  for mating with a barrel coupler  113 . The upper receiver coupler  111  defines recesses  120  each for receiving a hook  122  (in lieu of the hook  12  of other embodiments) to attach the upper receiver coupler  111  to the barrel coupler  113 . 
     Each hook  122  comprises a head  130  affixed to a shaft  132  at a first end thereof. A second end of the shaft  132  terminates in a ring  133  concentrically mounted on a pin  136  that is in turn attached to or captured within a barrel plate  137 . The hooks  122  are pivoted into the recesses  120  to lock the upper receiver coupler  111  and the barrel coupler  113  together. 
     Pivoting of the hooks  122  out of the recesses  120  permits separation of the upper receiver coupler  111  and the barrel coupler  113 . Only one of the hooks  122  is depicted in its entirety in  FIG. 18 , another hook  122  and its associated components is hidden from view in  FIG. 18 . 
     In one embodiment the head  130  threadably engages mating threads (not shown) on the shaft  132 . The coupling force exerted by the hook  122  on the upper receiver coupler  111  is adjusted by turning the head  130  on the mating threads of the shaft  132 . 
       FIG. 19  illustrates a stock gas tube  7 .  FIG. 20  illustrates the shortened primary gas tube  33  connected to the gas tube extension  35  for use with the couplers of the present invention.  FIG. 21  illustrates an exploded view of the primary gas tube  33  and the gas tube extension  35 . 
       FIG. 22  is a close-up view of the hook  12  and the lever  13  including a pivot pin  140  and a tension adjustment screw  142 . Turning the screw  142  adjusts (increasing or decreasing) the force exerted by the hook  12  for holding the upper receiver coupler  100  and the barrel coupler  103  together and for increasing or decreasing the distance between the two couplers. 
       FIG. 23  depicts the hook  12 , the pivot pin  140  and the tension adjustment screw  142 . 
     Because the components of the present invention can be added to an existing rifle without modifying the existing rifle, these components can be easily removed and the rifle returned to its original configuration whenever desired. This is an advantage to the rifle owner who may wish to sell or trade-in a rifle that has been modified to implement the features of the present invention. 
     While the invention has been described with reference to various embodiments, it will be understood by those skilled in the art that various changes may be made and equivalent elements and process steps may be substituted for elements and steps thereof without departing from the scope of the present invention. The scope of the present invention further includes any combination of the elements and process steps from the various embodiments set forth herein. In addition, modifications may be made to adapt a particular situation to the teachings of the present invention without departing from its essential scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.