Patent Publication Number: US-2022214126-A1

Title: Trigger Travel Stop Limit

Description:
CLAIM OF DOMESTIC PRIORITY 
     The present application claims the benefit of U.S. Provisional Application No. 63/134,935, filed Jan. 7, 2021, which application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to firearms and, more particularly, to a firearm and method of limiting travel of the trigger assembly by using limit stops. 
     BACKGROUND 
     Modern firearms are designed and manufactured to operate with multiple inter-operational components and often with modular construction. In one example, an AR-10 or AR-15 style sporting rifle  100  uses a modular construction with an upper receiver  102  and lower receiver  104 , as shown in  FIG. 1   a.  Lower receiver  104  is characterized by trigger guard  106 , trigger assembly  108 , pistol grip  110 , and magazine well  112 . Buttstock  114  attaches to lower receiver  104 . Upper receiver  102  is characterized by bolt carrier assembly, forward assist, charging handle, and gas-operated reloader. Barrel assembly  120  with handguard  122  attaches to upper receiver  102 . Lower receiver  104  is attached to upper receiver  102  by removable rear take-down pin  124  and forward pivot pin  126 . Removing rear take-down pin  124  allows upper receiver  102  to hinge and rotate about forward pivot pin  126 , see  FIG. 1   b.    
     The AR-10 and AR-15 platforms typically use a drop-in type trigger assembly. The trigger assembly includes a trigger housing, trigger body, disconnector, and hammer body. The trigger body includes an integral trigger pull and fits in and through the trigger housing. The disconnector is attached to the trigger body and inhibits automatic operation of the firearm. The trigger body engages a sear or notch in the hammer body to hold the trigger assembly in a cocked position, ready to fire. Upon applying pressure to the trigger pull, the trigger body releases or breaks from the hammer sear. The hammer body strikes the fire pin to discharge the weapon. 
     There is typically pre-travel or take-up, creep travel, and post-travel or over-travel in the trigger pull. In some contexts, creep travel is considered part of pre-travel, but in the interest of clarity, creep travel will be considered separately from pre-travel. Pre-travel is that movement for the trigger pull to bring the trigger body in pressure contact with the sear, up to the wall without releasing the hammer body. Creep travel is that movement of the trigger pull necessary to cause movement in the trigger body, breaking the wall and releasing the hammer to discharge the firearm. Post-travel is that movement of the trigger pull after discharge of the firearm. Pre-travel play and post-travel play can each be in the range of 0.15 to 0.32 centimeters (cm). With pre-travel and post-travel, the trigger pull and trigger body travel further than is actually necessary to release the hammer. The amount of pre-travel and post-travel is typically controlled using springs and generally follows the quality of the trigger assembly, i.e., high quality components tend to have less pre-travel and post-travel. Another method of reducing pre-travel is to reduce the trigger pull pressure, generally stated in terms of pounds of trigger pull, needed to break the wall and discharge the firearm. However, reducing trigger pressure tends to make the weapon susceptible to unintentional discharge, which is a major safety concern. Nonetheless, with pre-travel, the trigger pull travels further than necessary to reach creep travel. Pre-travel and post-travel cause undesired movement in the trigger and for the weapon as a whole. Shooting accuracy is reduced with excessive movement, as well as reliability in firing the weapon. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIGS. 1 a -1 b    illustrate a sporting rifle with conventional upper receiver, lower receiver, and trigger assembly; 
         FIGS. 2 a -2 b    illustrate a sporting rifle with an upper receiver, lower receiver, and improved trigger assembly; 
         FIGS. 3 a -3 n    illustrate the improved trigger assembly with a travel limit set screw and hammer limit set screw; 
         FIG. 4  illustrates implementing limit stops as solid shafts; and 
         FIGS. 5 a -5 e    illustrate the safety selector operating with the trigger body. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The following describes one or more embodiments with reference to the figures, in which like numerals represent the same or similar elements. While the figures are described in terms of the best mode for achieving certain objectives, the description is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the disclosure. 
       FIG. 2 a    shows an AR-10 or AR-15 style sporting rifle  200  designed for modular construction and manufactured for interchangeability of components. Sporting rifle  200  has upper receiver  202 , typically forged or casted then computer numerical control (CNC) machined, and lower receiver  204 , typically forged or casted then CNC machined. Lower receiver  204  includes trigger guard  206 , trigger assembly  208 , pistol grip  210 , and magazine well  212 . Buttstock  214  attaches to lower receiver  204 . Upper receiver  202  includes bolt carrier assembly, forward assist, charging handle, and gas-operated reloader. Barrel assembly  220  with handguard  222  attaches to upper receiver  202 . Lower receiver  204  is attached to upper receiver  202  by removable rear take-down pin  224  and forward pivot pin  226 . Removing rear take-down pin  224  allows upper receiver  202  to hinge and rotate about forward pivot pin  226 , see  FIG. 2 b   . 
       FIG. 3 a    illustrates an exploded view of lower receiver  204  and trigger assembly  208 , including trigger housing  230  and trigger assembly  232 . As a feature of sporting rifle  200 , trigger housing  230  and trigger assembly  232  use a travel limit set screw and hammer limit set screw to reduce or eliminate pre-travel and post-travel of the trigger pull. 
       FIG. 3 b    illustrates trigger housing  230  in isolation with slot  236  extending from surface  238  to surface  240 . Slot  244  is wider than slot  236  and extends from surface  238  to surface  240 . The combination of slot  236  and slot  244  will contain trigger assembly  232 . A rectangular opening  250 , with optional beveled edges and curved corners, is formed in surface  252  to receive trigger pull  284  of trigger body  280 . Slot  236 , slot  244 , and well  250  can be formed by CNC machining, sinker electrical discharge machining (EDM), and laser cutting. Threaded openings  256  and  258  are formed through surface  252  and receive column set screws to hold trigger housing  280  in place within lower receiver  204 . Threaded openings  260  and  262  are formed through surface  252  and extend to slot  236 . In one embodiment, threaded opening  260  and  262  are 0.635 cm in diameter and formed by tapping into surface  252  of trigger housing  232 . Circular openings  266  and  268  are formed through surface  270  and extend across slots  236  and  244  to exit corresponding openings in surface  272 . Circular openings  266  and  268  receive pins to permit movement of the trigger pull of trigger assembly  232  and hammer body  318  to strike the firing pin, respectively. 
       FIG. 3 c    shows trigger housing  230  from an opposing orientation with slot  236  extending from surface  238  to surface  240 , and slot  244  wider than slot  236  and extending from surface  238  to surface  240 . Rectangular opening  250 , with optional beveled edges and curved corners, is formed in surface  252  to receive trigger pull  284  of trigger body  280 . Threaded openings  256  and  258  are formed through surface  252  and cut partially into surface  276 . Threaded openings  260  and  262  are formed through surface  252  and extend to slot  236 . Circular openings  266  and  268  are formed through surface  270  and extend across slots  236  and  244  to exit corresponding openings in surface  272 . Circular openings  266  and  268  receive pins to permit movement of trigger assembly  232  and hammer body  318  to strike the firing pin. 
       FIG. 3 d    illustrates further detail of trigger assembly  232  including trigger body  280  with trigger pull  284  extending as a unitary portion of the trigger body. Trigger housing  232  and trigger assembly  232  can be applied to all drop-in trigger type firearms. Trigger shaft  286  extends through trigger body  280 . Trigger body  280  has notch  288  with concave surface  290  configured to accept a safety selector. Disconnector body  294  with locking neck  296  is held in place over trigger body  280  with rounded bar  297  disposed in rounded slot  299 . Disconnector spring  298  is disposed in opening  300  of disconnector body  294  and applies pressure to the bottom of the disconnector. Disconnector adjustment set screw  304  is screwed into threaded opening  306  in disconnector body  294 . Disconnector adjustment lock nut  308  is threaded onto disconnector adjustment set screw  304 . Trigger pull spring  310  is disposed within opening  312 . Trigger pull adjustment screw  314  sets the tension on trigger pull spring  310 . Hammer body  318  rotates with respect to trigger body  294  via hammer shaft  320  under tension from hammer spring  322 . Hammer spring  322  is a U-shaped spring, also known as dog spring. 
     In  FIG. 3 e   , trigger body  280  latchably engages with sear  334  to hold hammer body  318  under tension from hammer spring  322  when trigger assembly  232  is in a cocked position or ready to fire. That is, edge  344  of trigger body  280  engages sear or notch  334  in hammer body  318  to hold the trigger assembly in a cocked position, ready to fire. Disconnector  294  inhibits automatic operation of the firearm. Upon action of the discharge, hammer body  318  returns to a cocked position or ready to fire. However, hammer arm  326  momentarily engages with locking neck  296  to inhibit automatic operation. Once edge  344  engages with sear  334  and trigger pull  284  returns to the ready to fire position, hammer arm  326  disengages with locking neck  296  for a subsequent trigger pull to fire the weapon again, i.e., semi-automatic operation. 
     Pulling trigger pull  284  in the direction of arrow  328  causes a pressure contact between trigger body  294  and sear  334 , i.e., hitting the wall, followed by releasing sear  334  from edge  344  of trigger body  294 , i.e., breaking the wall. Once released, hammer body  318  rotates back in the direction of arrow  330  under tension of hammer spring  322  so that surface  332  of hammer body  318  strike the firing pin (not shown). Trigger limit set screw  340  and hammer limit set screw  342  limit the motion of trigger pull  284  and trigger body  280 , as discussed infra. 
       FIG. 3 f    illustrates a side view of trigger body  280  with trigger pull  284 , trigger shaft  286 , notch  288 , safety selector concave surface  290 , opening  300  for disconnector spring  298 , and opening  312  for trigger pull spring  310  and trigger pull adjustment screw  314 . Notch  346  accepts a portion of hammer body  318 . Rounded slot  299  accepts matching rounded bar  297  from disconnector body  280 . Edge  344  of trigger body  280  is adapted to latchably engage with sear  334  of hammer body  318  to hold the hammer body in a cocked position or ready to fire. 
     In  FIG. 3 g   , trigger assembly  232  is disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  350  is disposed through opening  266  of trigger housing  230  and trigger shaft  286  to provide rotational movement of trigger body  280  upon pulling trigger pull  284 . Pin  352  is disposed through opening  268  of trigger housing  230  and hammer shaft  320  to provide rotational movement of hammer body  318 . Trigger limit set screw  340  is threaded into opening  260 . Trigger limit set screw  342  is threaded into opening  262 . Hammer limit set screw  340  and hammer limit set screw  342  are driven from the outside of trigger housing  232  toward the inside of the trigger housing. 
       FIG. 3 h    illustrates another view of trigger assembly  232  disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  350  is disposed through opening  266  of trigger housing  230  and trigger shaft  286  to provide rotational movement of trigger body  280  upon pulling trigger pull  284 . Pin  352  is disposed through opening  268  of trigger housing  230  and hammer shaft  320  to provide rotational movement of hammer body  318 . Trigger limit set screw  340  is threaded into opening  260 . Hammer limit set screw  342  is threaded into opening  262 . Trigger limit set screw  340  and hammer limit set screw  342  are driven from the outside of trigger housing  232  toward the inside of the trigger housing. 
       FIG. 3 i    illustrates another view of trigger assembly  232  disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  350  is disposed through opening  266  of trigger housing  230  and trigger shaft  286  to provide rotational movement of trigger body  280  upon pulling trigger pull  284 . In  FIG. 3 j   , trigger limit set screw  340  is threaded into opening  260  and disposed to be capable of contacting bottom surface  360  of trigger body  280 . 
       FIG. 3 k    illustrates another view of trigger assembly  232  disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  352  is disposed through opening  268  of trigger housing  230  and hammer shaft  320  to provide rotational movement of hammer body  318 . In  FIG. 3   l,  hammer limit set screw  342  is threaded into opening  262  and disposed to be capable of contacting bottom surface  362  of trigger body  280 . 
       FIG. 3 m    illustrates another view of trigger assembly  232  disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  350  is disposed through opening  266  of trigger housing  230  and trigger shaft  286  to provide rotational movement of trigger body  280  upon pulling trigger pull  284 . Pin  352  is disposed through opening  268  of trigger housing  230  and hammer shaft  320  to provide rotational movement of hammer body  318 . Trigger limit set screw  340  is threaded into opening  260  and disposed to be capable of contacting bottom surface  360  of trigger body  280 . Trigger limit set screw  342  is threaded into opening  262  and disposed to be capable of contacting bottom surface  362  of trigger body  280 . 
       FIG. 3 n    illustrates another view of trigger assembly  232  disposed within trigger housing  230  with trigger body  280  located within slots  236  and  244 , and trigger pull  284  extending through rectangular opening  250 . Pin  350  is disposed through opening  266  of trigger housing  230  and trigger shaft  286  to provide rotational movement of trigger body  280  upon pulling trigger pull  284 . Pin  352  is disposed through opening  268  of trigger housing  230  and hammer shaft  320  to provide rotational movement of hammer body  318 . Trigger limit set screw  340  is threaded into opening  260  and disposed to be capable of contacting bottom surface  360  of trigger body  280 . Trigger limit set screw  342  is threaded into opening  262  and disposed to be capable of contacting bottom surface  362  of trigger body  280 . 
     Trigger limit set screw  340  and hammer limit set screw  342  are set to minimize the travel of trigger pull  284 , and correspondingly the movement of trigger body  280 . Upon trigger pull, trigger body  280  must exhibit some movement, i.e., creep travel, in order to pull edge  344  from sear  334  and release hammer body  318 . Trigger limit set screw  340  sets the starting point of trigger pull  284  to reduce or eliminate pre-travel. Hammer limit set screw  342  limits the travel of trigger pull  284  in the direction of arrow  368  to reduce or eliminate post-travel. In one embodiment, trigger limit set screw  340  is adjusted first to set the screw as close to the wall of hammer release as possible. Again, trigger limit set screw is positioned to have a small positive movement of trigger pull  284 , i.e., only creep travel, to reach the wall or release point of sear  334 . On the other hand, trigger limit set screw should not be set too close to the wall for unintended discharge of the weapon. In one embodiment, the creep travel of trigger pull  284  to release hammer body  318  is 1.0 degrees with 3-6 pound trigger pull. Pre-trigger pull, trigger limit set screw  340  contacts surface  360  of trigger body  280 , as shown in  FIG. 3 m   . Hammer limit set screw  342  is initially separated from surface  360  of trigger body  280 . Hammer limit set screw  342  is adjusted second to set the screw as close to the post release of hammer body  318 . Upon trigger pull, trigger pull  284  and trigger body  280  exhibit creep travel, i.e., the minimum travel required to release sear  334 . Post trigger pull, hammer limit set screw  342  contacts surface  362  of trigger body  280  stop further post travel, as shown in  FIG. 3 n   . Trigger limit set screw  340  is slightly separated from surface  360  of trigger body  280 . Accordingly, trigger limit set screw  340  and hammer limit set screw  342  reduce the travel of trigger pull  284  in the forward and backward directions to a minimum distance needed to release sear  334 . Trigger limit set screw  340  and hammer limit set screw  342  eliminate unnecessary travel of trigger pull  284 , i.e., pre-travel by setting the trigger starting point and post-travel in the direction of arrow  368 , leaving only the creep travel necessary to release the hammer to hit the fire pin. Trigger limit set screw  340  and hammer limit set screw  342  make sporting rifle  200  safer to operate and more accurate and reliable. 
     Trigger limit set screw  340  and hammer limit set screw  342  operate as limit stops to physically stop undesired movement of trigger pull  284  and reduce or eliminate pre-travel and post-travel. The physical limit stop is achieved with the metal-to-metal contact between trigger limit set screw  340  and surface  360  of trigger body  280  and the metal-to-metal contact between hammer limit set screw  342  and surface  362  of trigger body  280 . The stop position of trigger limit set screw  340  and hammer limit set screw  342  can be tuned by adjusting the height of the set screws extending from threaded openings  260  and  262  of trigger housing  230  to provide only creep travel for trigger pull  288  and eliminate pre-travel and post-travel, for any trigger poundage. Accordingly, pre-travel and post-travel can be eliminated without down-scaling trigger poundage, as used in the prior art. 
     Other types of limit stops, providing a similar function as trigger limit set screw  340  and hammer limit set screw  342 , can be used to reduce or eliminate pre-travel and post-travel. For example, solid shafts or posts  367  and  369 , as shown in  FIG. 4 , can be inserted through non-threaded openings  260  and  262  and sealed or locked in place to set the proper distance between the top of the solid shafts and surfaces  360  and  362  of trigger body  280  to tune or calibrate to the desired limit stop for sporting rifle  200 . In another embodiment, solid shafts or posts  367  and  369  extend from trigger housing  230  at fixed distances between the top of the solid shafts and surfaces  360  and  362  of trigger body  280  to set to the desired limit stop for sporting rifle  200 . Solid shafts  367  and  369  function as limit stops, similar to trigger limit set screw  340  and hammer limit set screw  342 , as described in  FIGS. 3 m   - 3   n.  The limit stop trigger assembly  208  is applicable to virtually all types of weapons with a trigger release, including long guns, hand guns, cross-bows, bolt action, semi-automatic, automatic, and military launchers. 
       FIGS. 5 a -5 e    illustrate the operation of safety selector  370  working in conjunction with trigger assembly  232 . In  FIG. 5 a   , notch  288  of trigger body  280  has a concave surface  290  configured to accept safety selector  370 .  FIG. 5 b    shows a first position of safety selector  370  with curved surface  372  at least partially within concave surface  290 . In the first position of safety selector  370 , trigger body  280  and trigger pull  284  are prevented from moving by nature of curved surface  372  at least partially within concave surface  290 . The safety for sporting rifle  200  is active preventing the weapon from firing even if pressure is applied to trigger pull  284 .  FIG. 5 c    shows a second position of safety selector  370  with curved surface  372  still at least partially within concave surface  290 . In the second position of safety selector  370 , trigger body  280  and trigger pull  284  are prevented from moving by nature of curved surface  372  at least partially within concave surface  290 . The safety for sporting rifle  200  remains active preventing the weapon from firing even if pressure is applied to trigger pull  284 .  FIG. 5 d    shows a third position of safety selector  370  with curved surface  372  still at least partially within concave surface  290 . In the third position of safety selector  370 , trigger body  280  and trigger pull  284  are prevented from moving by nature of curved surface  372  at least partially within concave surface  290 . The safety for sporting rifle  200  remains active preventing the weapon from firing even if pressure is applied to trigger pull  284 .  FIG. 5 e    shows a fourth position of safety selector  370  with straight surface  374  over concave surface  290 . In the fourth position of safety selector  370 , trigger body  280  and trigger pull  284  are now free to move because curved surface  372  is no longer at least partially within concave surface  290 . The safety for sporting rifle  200  is deactivated and the weapon will fire if there is a round in the chamber, hammer body  318  is loaded, and pressure is applied to trigger pull  284 . 
     While one or more embodiments have been illustrated and described in detail, the skilled artisan will appreciate that modifications and adaptations to those embodiments may be made without departing from the scope of the present disclosure.