Patent Publication Number: US-9410759-B2

Title: Burst firing device for firearm

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority of U.S. provisional application No. 62/103,394, filed Jan. 14, 2015, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a burst firing device for firearms and, more particularly, to a burst firing device utilizing more than one trigger. 
     In automatic firearms, burst mode or burst fire is a firing mode enabling the shooter to fire a predetermined number of rounds, usually two or three rounds on hand held weapons, with a single pull of the trigger. This firing mode is commonly used in submachine guns, assault rifles, and carbines. Other types of firearms, such as machine pistols may also have a burst mode. 
     Currently, a private citizen may have difficulty obtaining a burst fire automatic rifle. The burst fire weapons cost a lot of money, and the gun must be made before May 19, 1986, meaning that there is a finite supply of these particular firearms. With more collectors buying the burst fire rifles and keeping them, the availability of them has drastically gone down. There is the bump fire stock version; however the bump fire stock requires excellent technique and practice. Therefore, the bump fire stock may only fire one bullet at a time if not used properly. Further, the bump fire stock is inaccurate and is unreliable. 
     As can be seen, there is a need for a reasonably affordable and safe burst firing weapon. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a burst firing trigger mechanism comprises: a sear comprising a hammer engagement surface and a transfer mechanism; at least one trigger comprising, a lever, a base pivotally attached to the sear, and a plurality of trip fingers extending from the base, wherein each trip finger extends at a different angle relative to the lever; and a hammer biased by a spring away from the sear and comprising a cocking notch, wherein the burst firing trigger mechanism comprises a cocked position and a plurality of fired positions, wherein the cocked position comprises the hammer engagement surface engaging the cocking notch and suspending the hammer towards the sear, wherein each of the plurality of fired positions comprises the at least one trigger pivoted, wherein at least one of the trip finger engages the transfer mechanism thereby disengaging the hammer engagement surface from the cocking notch and thereby releasing the hammer. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of the first embodiment of the present invention incorporated on an AK-47 semi-automatic rifle. 
         FIG. 2  is a detail side elevation view with parts broken away, indicated by line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken on line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is an elevation view comparing the geometry of the three triggers of the first embodiment; 
         FIG. 5  is a cross-sectional view taken on line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a cross-sectional view taken on line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is a cross-sectional view taken on line  7 - 7  of  FIG. 3 ; 
         FIG. 8  is a side elevation view of the second embodiment of the present invention incorporated on an AR-15 semi-automatic rifle; 
         FIG. 9  is a detail side elevation view with parts broken away, indicated by line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a cross-sectional view taken on line  10 - 10  of  FIG. 9 ; 
         FIG. 11  is an elevation view comparing the geometry of the three triggers of the second embodiment; 
         FIG. 12  is a cross-sectional view taken on line  12 - 12  of  FIG. 10 ; 
         FIG. 13  is a cross-sectional view taken on line  13 - 13  of  FIG. 10 ; and 
         FIG. 14  is a cross-sectional view taken on line  14 - 14  of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims 
     Referring to  FIGS. 1 through 14 , the present invention includes a burst firing trigger mechanism  10 . The mechanism  10  includes a sear  20  having a hammer engagement surface  15  and a transfer mechanism  17 . The present invention further includes at least one trigger  14 , such as a plurality of triggers  14 . The plurality of triggers  14  each include a lever  14   a , a base  14   a ″ pivotally attached to the sear  20  by a pivot pin  16 , and a trip finger  14   a ′ extending from the base  14   a ″. Each of the trip fingers  14   a ′ extends at a different angle relative to the lever  14   a . The present invention further includes a hammer  24  biased by a spring  27  away from the sear  20 . The hammer  24  includes a cocking notch  25 . The burst firing trigger mechanism  10  includes a cocked position and a plurality of fired positions. The cocked position includes the hammer engagement surface  15  engaging the cocking notch  25  and suspending the hammer  24  towards the sear  20 . Each of the plurality of fired positions includes the plurality of triggers  14  pivoted so that at least one of the trip fingers  14   a ′,  14   b ′,  14   c ′ engages the transfer mechanism  17  thereby disengaging the hammer engagement surface  15  from the cocking notch  25  and thereby releasing the hammer  20 . 
     Referring to  FIGS. 1 through 7 , the present invention may be utilized with an AK-47 rifle  12 . The rifle  12  includes a trigger mechanism  10  and a safety  13 . The sear  20  of the AK-47 utilizes a latch mechanism  21 . The present invention may include three triggers  14   a ,  14   b ,  14   c . The triggers  14   a ,  14   b ,  14   c  are spring biased in the cocked position by springs  18 , such as a first spring  18   a , a second spring  18   b , and a third spring  18   c  each attached to each of the three triggers  14   a ,  14   b ,  14   c . The sear  20  of the present invention may also be spring biased in a cocked position by a spring  26 . The hammer  24  is spring biased in the firing position by a spring  27 . The three triggers  14   a ,  14   b ,  14   c  include three degrees of pivoting. A first degree of pivoting includes the first trip finger  14   a ′ engaging the transfer mechanism  17 , a second degree of pivoting includes the second trip finger  14   b ′ engaging the transfer mechanism  17 , and a third degree of pivoting includes the third trip finger  14   c ′ engaging the transfer mechanism  17 . 
     In certain embodiment, the transfer mechanism  17  includes a transfer pin  22  suspended within a slot formed in the sear  20 . A torsion spring  23  biases the transfer pin  22  towards the bases  14   a ″,  14   b ″,  14   c ″ of the triggers  14   a ,  14   b ,  14   c.    
     The triggers  14   a ,  14   b ,  14   c  align with one another, and are thereby pulled at the same time. After the first degree of pivoting is applied, the first trigger  14   a  presses the first trip finger  14   a ′ against the transfer pin  22 , pushing the transfer pin  22  back into the slot and rotating the sear  20  away from the hammer  24 . The hammer engagement surface  15  disengages from the cocking notch  25 , releasing the hammer  24 , and thereby firing the rifle  12 . The bolt of the rifle  12  pushes the hammer  24  back down so that the hammer engagement surface  15  engages the cocking notch  25 . After the second degree of pivoting is applied, the second trigger  14   b  presses the second trip finger  14   b ′ against the transfer pin  22 , pushing the transfer pin  22  back into the slot and rotating the sear  20  away from the hammer  24 . The hammer engagement surface  15  disengages from the cocking notch  25 , releasing the hammer  24 , and thereby firing the rifle  12 . The bolt of the rifle  12  pushes the hammer  24  back down so that the hammer engagement surface  15  engages the cocking notch  25 . After the third degree of pivoting is applied, the third trigger  14   c  presses the third trip finger  14   c ′ against the transfer pin  22 , pushing the transfer pin  22  back into the slot and rotating the sear  20  away from the hammer  24 . The hammer engagement surface  15  disengages from the cocking notch  25 , releasing the hammer  24 , and thereby firing the rifle  12 . The bolt of the rifle  12  pushes the hammer  24  back down so that the hammer engagement surface  15  engages the cocking notch  25 . 
     Referring to  FIGS. 8 through 14 , the present invention may be utilized with an AR-15 ® rifle  32 . The rifle  32  includes a trigger mechanism  30  and a safety  33 . The present invention may include three triggers  34   a ,  34   b ,  34   c . The triggers  34   a ,  34   b ,  34   c  are spring biased in the cocked position by a trigger bar  36  and a bar spring  38  spring biasing the trigger bar  36  against the triggers  34 . The sear  20  of the present invention may also be spring biased in a cocked position by a spring  46 . The hammer  50  is spring biased in the firing position by a spring  57 . The three triggers  34   a ,  34   b ,  34   c  include three degrees of pivoting. The first degree of pivoting includes the first trip finger  34   a ′ engaging the transfer mechanism  17 , a second degree of pivoting includes a second trip finger  34   b ′ engaging the transfer mechanism  17 , and a third degree of pivoting includes a third trip finger  34   c ′ engaging the transfer mechanism  17 . 
     The sear  20  of the present invention may be contained within a trigger group body  31 . In certain embodiment, the transfer mechanism  17  includes a transfer block  42  having a transfer block finger  43 . A spring  44  biases the transfer block  42  towards the bases  34   a ″,  34   b ″,  34   c ″ of the triggers  34   a ,  34   b ,  34   c . The trigger mechanism  30  may further include a disconnect  41  suspended on top of the sear  20  by a spring  48 . The hammer  50  includes a disconnect receiver  52  positioned to secure the disconnect  41  within during a transition between the cocked position and the fired position. 
     The triggers  34   a ,  34   b ,  34   c  align with one another, and are thereby pulled at the same time. After the first degree of pivoting is applied, the first trigger  34   a  presses the first trip finger  34   a ′ against the transfer block finger  43 , pushing the transfer block  42  against the sear  20 , thereby pushing the hammer engagement surface  15  away from the cocking notch  25 . The hammer engagement surface  15  disengages from the cocking notch  25 , releasing the hammer  50 , and thereby firing the rifle  32 . The bolt of the rifle  12  pushes the hammer  50  back down so that the disconnect  41  enters the disconnect receiver  52  and retains the hammer  50  in the cocked position. After the second degree of pivoting is applied, the second trigger  34   b  presses the second trip finger  34   b ′ against the transfer block finger  43 , pushing the transfer block  42  against the sear  20 , thereby pushing the disconnect  41  away from the disconnect receiver  52 . The disconnect  41  disengages from the disconnect receiver  52 , releasing the hammer  50  and thereby firing the rifle  32 . After the third degree of pivoting is applied, the third trigger  34   c  presses the third trip finger  34   c ′ against the transfer block finger  43 , pushing the transfer block  42  against the sear  20 , thereby pushing the disconnect  41  away from the disconnect receiver  52 . The disconnect  41  disengages from the disconnect receiver  52 , releasing the hammer  50  and thereby firing the rifle  32 . 
     It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.