Abstract:
A bullpup assembly for converting an AK-47 type firearm having an AK-47 stock in unmodified assembly into a bullpup configuration. The assembly includes a frame body coupleable with a body of the firearm, the frame body comprising a bullpup trigger, and the frame body being configured to replace the Ak-47 stock, and a trigger link coupled with the bullpup trigger and coupleable with a firearm trigger of the firearm, wherein actuation of the bullpup trigger actuates the firearm trigger via the trigger link.

Description:
[0001]    This application claims priority to U.S. Provisional Patent Application No. 61/513,749 filed on Aug. 1, 2011, and U.S. Provisional Patent Application No. 61/569,658 filed on Dec. 12, 2011, the entirety of each are hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the present invention relate to AK-47 and similar type firearms, and more particularly an apparatus and method for converting AK-47 type firearms to bullpup configurations. 
         [0004]    2. Background 
         [0005]    Firearms with and without a bullpup configuration are well known for military and private use. Generally, conventional firearms include an elongated stock, also known as a buttstock, to which the barrel and firing mechanism are attached, that is held against one&#39;s shoulder when firing the gun. The stock provides a means for the shooter to firmly support the device and easily aim it. The stock also transmits recoil into the shooter&#39;s body. 
         [0006]    Bullpups are firearm configurations in which the action is located behind the trigger group and alongside the shooter&#39;s face, so there is no wasted space for the stock as in conventional designs. This permits a shorter firearm length for the same barrel length for improved maneuverability, and reduces weight. Thus, firearm purchasers often prefer the bullpup configuration over the conventional configuration. 
         [0007]    In the related art, firearms are generally manufactured to either have a conventional configuration or a bullpup configuration. Thus, one must decide whether to purchase a conventional or bullpup configuration, and converting an already manufactured conventional configuration firearm, in the related art, typically requires substantial reengineering by a professional gunsmith. Once converted, the bullpup configured firearm likewise is not easily converted back into a conventional configuration without substantial reengineering. Thus, there is a need in the art for an apparatus and method for converting a firearm from a conventional configuration to a bullpup configuration and converting back to a conventional configuration without substantially reengineering the firearm, such as by a professional gunsmith. 
         [0008]    In particular, the AK-47 and similar type model firearms are generally manufactured with a conventional configuration. Thus, there is a need in the art for apparatuses and methods for converting conventional AK-47 type firearms to bullpup configurations and converting back to conventional configurations without substantially reengineering the firearm, such as by a professional gunsmith. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the present invention provide, among other things, features for reconfiguring a conventional AK-47 type firearm to a bullpup configuration. 
         [0010]    Aspects of an example bullpup assembly include a lower bullpup frame and an upper bullpup frame coupleable with a lower portion and an upper portion of a firearm respectively. The lower bullpup frame includes a bullpup trigger and trigger link, wherein a first end of the trigger link is coupled to or otherwise interoperates with the bullpup trigger. The other end of the trigger link abuttably connects or otherwise interoperates with the original trigger of the firearm (also interchangeably referred to herein as the “firearm trigger”) so that actuation of the bullpup trigger actuates the firearm trigger. 
         [0011]    Aspects of an example bullpup configured firearm in accordance with aspects of the present invention include a firearm body, a firearm barrel, a firearm trigger, a lower bullpup frame coupled to the firearm, and an upper bullpup frame coupled to the firearm. The lower bullpup frame includes or assembleably operates in conjunction with a bullpup trigger and trigger link, wherein a first end of the trigger link is coupled to or otherwise interoperates with the bullpup trigger. The other end of the trigger link abuts the trigger of the firearm so that actuation of the bullpup trigger actuates the firearm trigger. 
         [0012]    Aspects of the present invention further provide methods for modifying a conventional AK-47 type firearm to a bullpup configuration. The method includes removing a stock and handle from a conventional configuration firearm and then coupling a lower bullpup frame and an upper bullpup frame to the disassembled firearm, such that actuation of a trigger of the lower bullpup frame actuates a trigger of the disassemble firearm. 
         [0013]    Additional advantages and novel features of various aspects of the present invention will be set forth in part in the description that follows, and in part will become more apparent to those skilled in the art upon examination of the following or upon learning by practice thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0014]    In the drawings: 
           [0015]      FIG. 1  shows a side view of an example AK-47 type firearm having a conventional configuration; 
           [0016]      FIG. 2  shows a side view the firearm of  FIG. 1  with selected components removed; 
           [0017]      FIG. 3  shows a perspective exploded view of a bullpup assembly in accordance with aspects of the present invention; 
           [0018]      FIG. 4  shows a perspective partial visible view of the lower frame of the bullpup assembly of  FIG. 3 ; 
           [0019]      FIG. 5  shows a side partial visible view of the lower frame of the bullpup assembly of  FIG. 3 ; 
           [0020]      FIG. 6  shows a perspective view of the upper frame of the bullpup assembly of  FIG. 4 ; 
           [0021]      FIG. 7  shows a side partial visible view of a modified firearm having a bullpup configuration in accordance with aspects of the present invention; 
           [0022]      FIG. 8  shows a perspective partial visible view of the modified firearm of  FIG. 7 ; 
           [0023]      FIG. 9  shows a partial perspective exploded view of a bullpup assembly in accordance with another aspect of the present invention; 
           [0024]      FIG. 10  shows a partial perspective view of the bullpup assembly of  FIG. 9 ; 
           [0025]      FIG. 11  shows a side view of the bullpup assembly of  FIG. 9 ; and 
           [0026]      FIG. 12  shows the opposite side view of the bullpup assembly of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    Aspects of the present invention include a bullpup assembly for an AK-47 type firearm, a bullpup configured AK-47 type firearm, and a method for converting a conventional AK-47 type firearm into a bullpup configured AK-47 type firearm. 
         [0028]      FIG. 1  shows a side view of an example AK-47 type firearm  10  having a conventional configuration, i.e., does not have a bullpup configuration. The firearm  10  includes a body  12 , a stock  14 , a handle  16 , a grip  18 , a barrel  20 , a firearm trigger  22 , a magazine  24 , a gas tube holder  26 , a trigger guard  28 , a sight  30 , a gas tube  36 , a barrel retainer  40 , and other features known in the art. The stock  14  is attached to the main body  12  (e.g., via one or more screws and/or other attachment features), and in operation, is held against an operator&#39;s shoulder when firing the firearm  10 . The stock  14  allows the operator to firmly support the device and easily aim it. 
         [0029]      FIG. 2  shows a side view of an example AK-47 type firearm  50  having multiple components removed. In particular, the stock  14  and the handle  16  shown in  FIG. 1  have been removed. The other elements, including the body  12 , the firearm trigger  22 , the grip  18 , the guard trigger  28 , the gas tube holder  26 , the gas tube  36 , the barrel  20 , the magazine  24 , and the sight  30  remain. Generally, the mechanical parts of the firearm that contribute to firing operation remain operable in accordance with conventional operation. As shown in  FIG. 2 , when the stock  14  is removed, a mating piece  32  remains. The mating piece  32  may have, for example, a screw opening  34 , by which the stock  14 , having a corresponding threaded opening for receiving a screw threw the screw opening  34 , may be secured to the body  12 . 
         [0030]      FIG. 3  shows a perspective exploded view of a bullpup assembly  100 . More specifically,  FIG. 3  shows the elements of the bullpup assembly  100  before it has been assembled onto the firearm of  FIG. 2 . The bullpup assembly  100  includes a lower bullpup frame  102  (also interchangeably referred herein as a frame body), an upper bullpup frame  104  (also interchangeably referred herein as a mating frame assembly), a trigger link  106  and a bullpup trigger  108 . The lower bullpup frame  102  includes a hollow body (also interchangeably referred herein as an interior cavity)  110  integrally formed with a handle  112 , a trigger guard  114 , and screw receiver  116 . The lower bullpup frame  102  further includes a recessed opening  126  sized to mate with the barrel retainer  40 , a receiving member  128  sized to receive the gun barrel  20 , and a front opening  130  (also interchangeably referred herein as a barrel opening) sized to receive the barrel  20 .  FIG. 4  shows a perspective view of the lower bullpup frame  102 , where the body  110  is shown as transparent for clarity. As shown in  FIG. 4 , the bullpup trigger  108  may be located within the body  110 . Further, the bullpup trigger  108  may be linearly coupled within the body  110  via a coupling mechanism  108   a , such as screw, a pin, or the like. The bullpup trigger  108  may also be coupled with the trigger link  106 , which extends though the body  110 . Thus, force imparted on the bullpup trigger  108  (e.g., linear action during firing) may be transferred via the trigger link  106  toward the opposite end of the trigger link  106  from the end of the trigger link  106  that is coupled with or otherwise interoperable with the bullpup trigger  108 . 
         [0031]      FIG. 5  shows a side view of the lower bullpup frame  102  where the body  110  is shown as transparent for clarity. 
         [0032]      FIG. 6  shows a perspective view of the upper bullpup frame  104 . The upper bullpup frame  104  includes a hollow body  118 , a rear opening  120  sized to fit over a gas tube of an AK-47 type firearm, a recessed opening  122  sized to receive a barrel retainer  40  of an AK-47 type firearm, and a front opening  124  sized to receive the barrel  20  of the AK-47 type firearm. The top frame  104  may include openings to vent heat, such as may be produced by the barrel or other portions of the firearm when fired. The recessed opening  122  of the upper bullpup frame  104  (as shown in  FIG. 5 ) aligns with the recessed opening  126  of the lower bullpup frame  102  (as shown in  FIG. 4 ), and the front opening  124  of the upper bullpup frame (as shown in  FIG. 5 ) aligns with the front opening  130  of the lower bullpup frame (as shown in  FIG. 4 ). 
         [0033]      FIG. 7  shows a side view of an example AK-47 type firearm modified to a bullpup configuration, where the lower bullpup frame  102  and the upper bullpup frame  104  are shown as transparent for clarity.  FIG. 8  shows a perspective view of the example firearm of  FIG. 7 . In particular,  FIGS. 7 and 8  show the disassembled firearm  50  of  FIG. 2  after it has been coupled with the bullpup assembly  100 .  FIGS. 7 and 8  show various elements that are included in  FIGS. 2 and 3 , in an assembled configuration. As shown in  FIGS. 7 and 8 , the lower bullpup frame  102 , including the bullpup trigger  108  and the trigger link  106 , is abuttably assembled with the lower portion of the disassembled firearm  50 . The recessed opening  126  of the lower bullpup frame matably abuts the barrel retainer  40 , the receiving member  128  of the lower bullpup frame matably abuts with the gun barrel  20 , and the front opening  130  matably abuts the barrel  20 . 
         [0034]    The trigger link  106  may extend within the hollow body  110  of the lower bullpup frame  102 , around the magazine  24  and/or magazine well, and operably engage the firearm trigger  22 . Because the trigger link  106  operably engages the firearm trigger  22  on one end and is operably engaged with the bullpup trigger  108  on the other end, motion of the bullpup trigger  108  produces corresponding motion of the firearm trigger  22  via the trigger link  106 , such as when the firearm is fired. 
         [0035]    In assembly, the screw receiver  116  located at the end of the body  110  opposite the barrel  20  is aligned with the mating piece  32 , and the lower bullpup frame  102  is secured to the firearm body  12  via the mating piece  32 . For example, a screw may be inserted through the mating piece  32  and into a threaded screw receiver  116  in the lower bullpup frame  102 . Thus, the lower bullpup frame  102  may be secured to disassembled firearm  50  in a similar manner to that with which the stock was previously secured to the firearm. 
         [0036]    As shown in  FIGS. 7 and 8 , the upper bullpup frame  104  fits over the gas tube  36  via the rear opening  120 , which matably abuts the lower bullpup frame  102 . The upper bullpup frame  104  also mates with the barrel retainer  38  via the recessed opening  122 . 
         [0037]    The lower bullpup frame and upper bullpup frame may comprise any material suitable for use with a firearm. Of some concern may be the heat produced within the barrel of a gun during firing. Thus, the material chosen for the upper and lower bullpup frame must retain form and properties under high heat. In some variations, the frames may comprise a hard plastic having a high melting point. For example, because the lower bullpup frame includes portions near the handle, the lower bullpup frame may be formed such that it is capable of preventing or inhibiting heat transfer, so as to reduce the amount of heat reaching the operator&#39;s hand. Optionally, each of the upper and lower bullpup frames may further comprise one or more heat shielding elements that may be located within the upper or lower bullpup frames or that may be integral with one or both of these frames. Such heat shielding elements may comprise metal shielding, such as firearm grade aluminum, that is located within the lower bullpup frame. The upper bullpup frame, on the other hand, which, upon assembly, may be located further from the operator when the gun is fired, may allow sufficient heat dissipation without such shielding (e.g., via use of venting through one or more vent openings). 
         [0038]    A method for assembling the modified firearm having a bullpup configuration will now be described. Starting with the conventional firearm  10  of  FIG. 1 , the stock  14  and the handle  16  are removed. The stock  14  and the handle  16  may be easily removed without the need for a gunsmith, for example, because the elements may be secured to the body  12  via screws and mating surfaces. For the stock  14 , the operator may simply unscrew the stock  14  from the mating piece  32  and slide the stock out of the body  12 . Similarly, the operator may remove the handle  16  by unscrewing and/or sliding the handle out of the body. Once the stock  14  and the handle  16  have been removed, the conventional AK-47 type firearm is in the state shown in  FIG. 2 . 
         [0039]    Next, the operator proceeds to couple the lower bullpup frame  102  ( FIGS. 3 to 5 ) to the firearm of  FIG. 2 . The lower bullpup frame  102  may be slid over the bottom portion of the firearm  50 . As shown in  FIGS. 7 and 8 , a portion of the body  12 , the firearm trigger  22 , trigger guard  28 , magazine  24 , and a portion of the barrel  20  of the firearm  50  may be located within the lower bullpup frame  102 . The recessed opening  126  may matably abut the barrel retainer  40 , and the receiving member  128  and the front opening  130  may each matably abut the barrel  20 . The screw receiver  116  may be aligned with the mating piece  32  and the trigger link  106  may be aligned with the firearm trigger  22 . The screw receiver  116  is then secured to the mating piece  32  via a screw or other securing mechanism. 
         [0040]    Then, the upper bullpup frame  104  ( FIGS. 3 and 5 ) may be coupled to the upper portion of the firearm  50 , such that the gas tube  36  fits within the rear opening  120 , barrel retainer  38  fits within the recessed opening  122 , and the barrel  20  fits within the front opening  124 . The upper bullpup frame  104  may be secured to the lower bullpup frame  102  by any suitable manner that sufficiently secures the frames  102 ,  104  together during operation of the firearm. For example, the upper bullpup frame  104  may include a bias tongue that allows one end of the upper bullpup frame to slide over and lock into a corresponding receiving portion at one end of the lower bullpup frame  102 . The opposite ends (and/or other suitable locations) may then be separately secured, such via one or more screws or other securing features. By securing the frames  102 ,  104  in this manner, assembly is made stable during operation of the firearm. Furthermore, the upper and lower bullpup portions  102 ,  104  may have grooves and/or other corresponding interoperating features (e.g., rail projections and corresponding receiving slots) to further allow the frames to securely mate together. 
         [0041]    After the above steps are taken, the bullpup configured AK-47 type firearm shown in  FIGS. 7 and 8  is completed. Whenever the operator desires to return the AK-47 type bullpup configuration back to a conventional AK-47 type configuration, the user need only reverse the above steps. One or all of the above steps of assembling or disassembling the bullpup configuration may be carried out so as to avoid the need for machining or other assistance by a professional gunsmith. Rather, a relatively unskilled operator need only screw/unscrew and assemble the relevant elements of the firearm. As shown in  FIGS. 1 ,  2 ,  7  and  8 , the complex functionality of the firing mechanism remains unaltered when the firearm is in the conventional state or the bullpup state. Thus, the above-described apparatus and method allows a firearm purchaser to easily and safely modify the firearm without the assistance of an expert. 
         [0042]      FIG. 9  shows a partial perspective exploded view of a bullpup assembly  200  in accordance with another aspect of the present invention. As shown in  FIG. 9 , a number of components of the bullpup assembly  200  are similar to those shown with the same numbers in  FIGS. 1-8 . Components having the same reference numbers as  FIGS. 1-8  are described above. As shown in  FIG. 9 , the assembly  200  includes an upper bullpup frame  204  and a lower bullpup frame  202 , similar to the assembly  100  of  FIGS. 1-8 . The assembly  200  additionally includes a shield member  206 . The shield member  206  may be shaped to fit within a portion of the upper bullpup frame  204 . The shield member  206  may fit over a front portion of the barrel  20 , near the sight  30 , and underneath/within the corresponding portion of the upper bullpup frame  204  that also covers the same portion of the barrel  20 , for example. The arrangement of the shield member  206  provides a second layering of protection (e.g., from heat) from the barrel  20 . Both the shield  206  and the corresponding portion of upper bullpup frame  204  may include a plurality of vent opening  224 ,  226  for allowing heat to dissipate from the barrel  20 . When assembled, the vent openings  224 ,  226  may be aligned ( FIGS. 11 ,  12 ). 
         [0043]    The upper bullpup frame  204  includes a hollow body  218  and a recessed opening  222 , having the same functionality as in the bullpup assembly of  FIGS. 1-8 . The upper bullpup frame  204  further includes a rear opening  220  sized to fit over a gas tube of an AK-47 type firearm. However unlike the rear opening  120  of  FIGS. 1-8 , the rear opening  220  of  FIGS. 9-12  may extend partially along the surface of the hollow body  218 . In another aspect of the present invention, the upper bullpup frame may omit the rear opening  220 , and the upper bullpup frame may extend coextensively or partially coextensively with the lower bullpup frame. 
         [0044]    As seen in  FIGS. 9 and 10 , the bullpup assembly  200  further includes a trigger link  306  and a bullpup trigger  308 . The bullpup trigger  308  may include a receiving portion  310  for receiving an end portion of the trigger link  306 . The receiving portion  310  may comprise a groove or opening sized to receive and couple with the trigger link  306 . The trigger link  306  may be secured to the bullpup trigger  308  within the receiving portion via a pin, for example. The trigger link  306  extends along the length of the gun and may be coupled to firearm trigger engagement feature  312  at another end of the trigger link  306 . As shown in  FIG. 10 , upon assembly with the body of the firearm  10 , the firearm trigger engagement feature  312  may abut the trigger  22 . The trigger link  306  may surround the trigger engagement feature  312  and/or may couple to the trigger engagement feature via a pin, for example. The trigger link  306  may also extend beyond and surround the trigger  22 . As shown in  FIG. 10 , the trigger link  306  may be curved towards the body of the gun so that the trigger link is retained within the lower frame  202  when assembled, without interfering with the operator&#39;s hand. 
         [0045]    As shown in  FIG. 9 , the lower bullpup frame  202  includes a hollow body  210 , front opening  230 , a trigger guard  214 , a screwing feature  216 , such as screw receiver, a handle  212 , a recessed opening  226 , and a receiving member  228 , each having similar functionality to that described above with respect to the bullpup assembly of  FIGS. 1-8 . The lower bullpup frame  202  further includes a plurality of ports  232 ,  234 ,  236 . As shown in  FIG. 11 , upon assembly with the body of the firearm  10 , the first access port  232  and second access port  234  align with portions of a safety to allow access to and operation of the safety. As shown in  FIG. 12 , the third port  236  may be on a side of the lower bullpup frame  202  opposing the first and second ports  232 ,  234  and may accommodate projecting features of the firearm  10 , for example. 
         [0046]    The steps for converting an AK-47 into the bullpup configuration using the bullpup assembly  200  are similar to as discussed above with respect to the bullpup assembly shown in  FIGS. 1-8  and described in conjunction therewith 
         [0047]    Other aspects and modifications of the present invention would be readily apparent to one having ordinary skill the art. For example, the bullpup assembly may include an integrated or attachable rail system to the upper frame and the lower frame. In addition the rail system may be used to mount instruments according to an end user&#39;s preference. Examples of instruments include, but are not limited to flashlights, red dots, lasers, foregrips, halographic sighting systems, optical, targeting, and/or any instrument that improves accuracy and/or reduces muzzle rise. Additionally, aspects of the present invention may include a two shot injection molded or overmolded thermoplastic rubber, for example, Santoprene sold by Exxon Mobil, having a varying range of durometers and textures that may encompass the trigger grip partially or fully to aid end user in safe handling of firearm and positive grip position reinforcement. An injection molded stand alone part or overmolded or two shot injection molded integrated thermoplastic rubber buttstock recoil pad, manufactured in multiple sizes, durometers, textures and widths, for example, may also be utilized to aid in recoil absorption. The stand alone part may be attached by screw, channeled into position via flanges on either side or press fit into the assembly. The size and other features may be chosen according to the ergonomic preference of the user. For example, a user with smaller or larger hands may require a different size. Furthermore, any suitable polymer and color may be used in the bullpup assembly to provide desired texture and visuals. 
         [0048]    Example aspects have been described in accordance with the above advantages. It will be appreciated that these examples are merely illustrative of aspects of the invention. Many variations and modifications will be apparent to those skilled in the art.