Patent Publication Number: US-8109025-B2

Title: Trigger engagement link for firearm

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/162,197, filed Mar. 20, 2009. 
     INCORPORATION BY REFERENCE 
     U.S. Provisional Patent Application No. 61/162,197, which was filed on Mar. 20, 2009, is hereby incorporated by reference for all purposes as if presented herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to firearm trigger assemblies, and in particular to a trigger engagement link for firearm trigger assemblies. 
     BACKGROUND INFORMATION 
     In most small arms-type firearms, such as handguns, shotguns and various other types of long guns including lever action and semiautomatic rifles, the firearm trigger assemblies or fire control systems thereof generally include a hammer that is held in a cocked position by a mechanical interface with a sear. The sear is connected either directly or through mechanical linkages to the trigger of the firearm. When the trigger is squeezed or moved rearwardly to fire a round of ammunition, the sear generally is moved out of locking engagement with the hammer so as to release the hammer. The hammer then is pivoted into contact with a firing pin of the firearm by a hammer spring. The engagement of the firing pin by the hammer causes the firing pin to strike a round of ammunition in the chamber of the firearm to initiate the firing of the round of ammunition. 
     In a conventional hammer sear interface, the sear typically includes a notched, hooked portion that engages a corresponding notch or hook formed in the rear hammer. Due to the sliding nature of this mechanical interface, the sear and hammer generally must be precisely machined so as to provide and ensure smooth and even surfaces on both the hammer and sear. This precise machining also provides a smooth and crisp trigger feel during shooting to avoid catching or hesitation during firing, which can lead to misfires and affect the aim of the shooter. The criticality of the components returning to full engagement upon release of the trigger thus further requires that the geometry and surface finishes of the hammer and sear be carefully and somewhat precisely machined and finished, such that the hammer and sear will regain full engagement in such a situation in which the trigger is released after a partial trigger pull without firing. Such precise and careful machining of these components, however, generally is expensive and requires significant quality control and review to ensure that such parts are precisely machined to within specific, narrow ranges of tolerances necessary to provide a smooth interface and function. 
     SUMMARY 
     In one embodiment of the disclosure, a fire control assembly for a firearm comprises a trigger engagement link comprising a forward end, a rearward end, and an intermediate portion. The fire control assembly further comprises a sear comprising a bottom portion engageable with the intermediate portion of the trigger engagement link, and a hammer moveable between cocked and firing positions. The hammer comprises a link displacement portion operable to displace the forward end of the trigger engagement link as the hammer is moved from its firing position to its cocked position, wherein the displacement of the forward end of the trigger engagement link by the link displacement portion of the hammer disengages the intermediate portion of the trigger engagement link from the bottom portion of the sear so as to at least temporarily deactivate the fire control assembly. 
     In another aspect of the disclosure, a firearm comprises a barrel defining a chamber and a fire control assembly comprising a trigger engagement link comprising a forward end, a rearward end, and an intermediate portion. The fire control assembly further comprises a sear comprising a bottom portion engageable with the intermediate portion of the trigger engagement link, and a hammer moveable between cocked and firing positions. The hammer comprises a link displacement portion operable to displace the forward end of the trigger engagement link as the hammer is moved from its firing position to its cocked position, wherein the displacing the forward end of the trigger engagement link by the link displacement portion of the hammer disengages the intermediate portion of the trigger engagement link from the bottom portion of the sear and at least temporarily deactivates the fire control assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other advantages, features, and aspects of the present invention will become apparent and more readily appreciated from the following detailed description of the embodiments taken in conjunction with the accompanying drawings, as follows. 
         FIG. 1  is a partial cutaway side view of a firearm showing a fire control assembly in an exemplary embodiment. 
         FIG. 2  is a partial cutaway perspective view of the fire control assembly of  FIG. 1 . 
         FIG. 3  is a side view of the fire control assembly of  FIG. 1  in which a trigger engagement link is disengaged from a roller sear in an exemplary embodiment. 
         FIGS. 4A-4E  illustrate the position of the trigger engagement link, the sear, and a hammer during operation of the firearm. 
         FIG. 5  is a side view of the fire control assembly in which the trigger has not been released during or after the firing operation. 
         FIG. 6  is a side view of a fire control assembly in an alternative embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is provided as an enabling teaching of exemplary embodiments. Those skilled in the relevant art will recognize that many changes can be made to the embodiments described, while still obtaining the beneficial results. It will also be apparent that some of the desired benefits of the embodiments described can be obtained by selecting some of the features of the embodiments without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the embodiments described are possible and may even be desirable in certain circumstances, and are a part of the invention. Thus, the following description is provided as illustrative of the principles of the embodiments and not in limitation thereof, since the scope of the invention is defined by the claims. 
     The embodiments described are generally directed to a fire control for firearms where the trigger and sear are disengaged and non-operable as the hammer is cocked. While the embodiments described herein illustrate the use of the present invention with a long gun such as a rifle or shotgun, it will be understood that the present invention can be used with various types of long guns, including shotguns and rifles, handguns, and other types of firearms utilizing hammer driven trigger assemblies or fire control systems for firing rounds of ammunition. 
     As generally illustrated in  FIGS. 1-5 , the embodiments generally include a sear assembly  30  connected via a trigger engagement link  10  to a trigger  40  of a firearm fire control T. The trigger engagement link  10  is disengaged from the sear assembly  30  under certain conditions of the fire control T.  FIG. 1  illustrates a partially cutaway view of a firearm F with a stock S, receiver R, and barrel B. The receiver R contains a fire control T and a bolt and firing pin assembly P. A round  8  is shown in a chamber C at a proximal end of the barrel B. The firearm stock, receiver, bolt, firing pin, chamber, barrel, and round are shown generally and by way of example. Variation and omission of one or more of these elements for use with different types of firearms and firearm designs are considered to be within the scope of the present disclosure. 
     With reference to  FIGS. 1 and 2 , according to one example embodiment, the fire control assembly T of the firearm F includes a trigger engagement link  10 , a hammer  20 , a sear assembly  30 , and hammer springs  50 . The link  10  is pivotally attached to a trigger assembly  40  at a rearward end  11  by a pin  12 , while the forward end  14  of the link  10  can be supported by a roller bearing  42  and trigger return spring  44 , which provides resistance to forward and downward motion of the forward end  14  of the link. In other words, the spring  44  generally biases the forward end  14  rearwardly and upwardly as needed or desired. The roller bearing  42  engages the forward end  14  at a sloped surface  15 . The link  10  can further include a hammer engagement surface  16 , which is a generally flat surface at the top of the forward end  14  in the illustrated embodiment. The link  10  can also include a sear notch  18  defined in an intermediate portion  18   a  of the link  10 . The intermediate portion  18   a  and the sear notch  18  are shown as generally below the sear assembly  30  in the illustrated embodiment. 
     According to the illustrated embodiment of  FIG. 1 , the hammer  20  is pivotably supported by hammer pin  22  attached to the wall W of the receiver R so as to be moveable between a cocked position and a firing position. The hammer further generally includes a catch or notch  24  for engaging the sear assembly  30  and a link displacement protrusion  26  ( FIG. 2 ). The hammer engagement surface  16  can be situated generally below the link displacement protrusion  26  of the hammer  20  when the hammer is in the cocked position. The sear assembly  30  is pivotably attached to the receiver wall W by pin  32  and can include a pair of opposed side plates  34  ( FIG. 2 ), each typically formed from a metal such as steel or other durable, high strength materials and attached together via fasteners such as rivets, bolts, or other similar fastening mechanisms. Alternatively, the sear assembly  30  can be stamped, milled, metal injection molded, or otherwise formed as a single, unitary piece or component. A link interface flange  35  at a lower portion of the sear assembly  30  can be included for engaging the sear notch  18  of the link  10 . A roller bearing  36  for engaging the notch  24  of the hammer  20  is mounted between the sear side plates  34  adjacent the upper ends thereof. The sear assembly  30  further can include an intermediate flange  37  that engages a roller bearing  38  and spring  39  that biases the sear assembly  30  in a forward direction. 
     In the illustrated embodiment, the trigger assembly  40  can be pivotably connected to the wall W of the receiver R by a pin  46  and can include a safety mechanism  48  ( FIG. 2 ). The hammer springs  50  can be anchored to the receiver wall W on either side of the sear assembly  30  by a pin  54  located at one end and connected to the hammer  20  at the other end by pin  58 . In the present embodiment, each of the hammer springs  50  is coaxial with a respective hammer spring guide rod  52 . 
       FIG. 4A  illustrates a side view in which the notch  18  of the trigger engagement link  10  is engaged with the flange  35  of the sear assembly  30  with the roller bearing  38  and spring  39  biasing the sear assembly  30  forward, and the bearing  42  and spring  44  biasing the link  10  rearward. The notch  24  of hammer  20  is engaged with the sear roller  36  so as to lock the hammer  20  in a cocked or ready position. As the hammer  20  is moved into engagement with the sear assembly  30 , the hammer springs  50  are compressed, and the hammer spring guide rods  52  extend through the springs  50  towards the trigger  40 . When the trigger engagement link  10  is pushed downward by movement of the hammer  20  by engagement with the bolt, the trigger engagement link  10  depresses the roller bearing  42  and applies force to trigger return spring  44 . 
     When the trigger  40  is pulled to initiate a firing operation, the trigger engagement link  10  is pushed forward, depressing the roller bearing  42  against the spring force of spring  44  to provide the trigger pull force. The engagement between the link interface flange  35  of the sear assembly  30  and the sear notch  18  of the trigger engagement link  10  continues to push forward as the trigger  40  is pulled and eventually rotates the sear assembly  30  out of an engaged, cocked, and ready-to-fire position so as to release the hammer  20  to move to its firing position to strike the firing pin and fire the firearm. 
     After the firearm is fired, the bolt reciprocates over the top of the hammer  20 , pushing the hammer down toward its cocked, ready-to-fire position. At this point, as illustrated in  FIG. 3 , the protrusion  26  of the hammer  20  is now interfacing with the surface  16  of the trigger engagement link  10 . The protrusion  26  strikes or otherwise interacts with the engaging surface  16  to force the forward end  14  of the trigger engagement link  10  downwardly against the roller bearing  42  and spring  44 , causing a wide gap  60  between the surface  16  and the flange  35  to disengage the link and sear. This disengagement of the link and sear with the hammer substantially deactivates the firearm thus preventing the firearm from being fired even if the trigger  10  is not released to prevent full automatic operation of the firearm. 
       FIGS. 4A-4E  illustrate the position of the trigger engagement link  10 , the sear assembly  30 , and hammer  20  during operation of the firearm. In  FIG. 4A , the trigger engagement link is engaged with the sear assembly  30  of the firearm and the hammer thereof in its cocked, ready-to-fire position. The sear assembly  30  is biased forward by the spring  39  and the sear roller  36  is in engagement with the notch  24  of the hammer  20  while the springs  50 , shown in phantom, push against the hammer at the pin  58 . The link  10  is biased rearwardly and the trigger  40  is biased forward by the spring  44 . 
     In  FIG. 4B , trigger  40  is pulled rearwardly forcing the link  10  forwardly against the spring  44 . The sear notch  28  of the link  10  engages the flange  35  of the sear assembly  30  and pivots the sear roller  36  away from the hammer  20  against the spring  39 . The roller  36  is disengaged from the notch  24  so that the hammer  20  can pivot forwardly about the pin  22  into its firing position. In  FIG. 4C , the hammer  20  is shown rotating forwardly under the biasing force of the hammer springs  50  after firing is initiated and is shown completely clear of sear assembly  30 . In  FIG. 4D , the hammer  20  is continuing its forward motion as the hammer springs  50  extend between the pins  54 ,  58  and the guide rods  52  move forward into the springs  50 . In the case that the trigger was released after initiating firing, the spring  44  biases the roller bearing  42  up against the sloped surface  15  of the link  10 , forcing the link  10  rearwardly so that the sear notch  18  allows the flange  35  to pivot rearward. The rearwardly motion of the link  10  pivots the trigger  40  forward into the pre-firing position. The spring  39  forces the roller bearing  38  against the flange  37  to pivot the sear assembly  30  forward into position so the sear roller  36  can reengage the notch  24  after the firing operation. The link  10 , sear assembly  30 , and trigger  40  are now in a ready-to-fire position, as shown in  FIG. 4D , with the flange  35  situated in the notch  18 . Further, the sear assembly  30  is in position for the sear roller  36  to re-engage the notch  24  of the hammer  20  when the hammer is returned to the cocked position. 
     In the exemplary embodiment shown in  FIGS. 4D and 4E , the link  10 , sear assembly  30 , and trigger  40  can be returned to a ready-to-fire position as the released hammer  20  is pivoted from the cocked position to the firing position. It will be understood, however, that the link, sear, and trigger generally will be returned to their ready-to-fire position whenever the trigger  40  is released regardless of the position of the hammer  20 . 
     In  FIG. 4E , the hammer  20  is shown having reached its stop or firing position under the force of the hammer springs  50 . After firing a round, the bolt forces the hammer  20  rearward against the hammer springs  50  until the hammer  20  pivots down and the protrusion  26  engages the surface  16  to force the link  10  down against the spring  44 , as shown in  FIG. 3 . In a particular embodiment, as the hammer pivots rearward past the sear assembly  30 , the sloped surface of the protrusion  26  can engage the roller  36  and pivot the sear rearward slightly. After the notch  24  has passed the roller  36  as shown in  FIG. 3 , the sear is forced forward by the spring bias of the spring  39 . The bias of the spring  44  forces the forward end  14  of the link  10  and the hammer  20  upwardly, and the hammer springs  50  pivot the hammer  20  upwardly until the notch  24  reengages the roller  36 , as shown in  FIG. 4A . The fire control assembly T is now ready to fire again. 
     In the case that the trigger  40  is not released after initiating firing and/or prior to the hammer being properly reset to its cocked position, the firing operation proceeds normally. However, the hammer  20  disengages the link  10  from the sear assembly  30  until the trigger  40  is released. Particularly, when the trigger  40  is held during firing, the notch  18  remains in engagement with the flange  35  and prevents the sear assembly  30  from pivoting forward under the spring bias of the spring  39 . When the bolt forces the hammer  20  rearward and the protrusion  26  strikes the surface  16 , the link  10  is forced downward against the spring  44  similarly to the state shown in  FIG. 3 . The downward motion of the link  10  disengages the notch  18  from the flange  35 . The sear assembly  30  pivots forward and the roller  36  engages the notch  24  when the hammer  20  is pivoted upward by the hammer springs  50  as shown in  FIG. 5 . The flange  35  interferes with the link  10  at the intermediate portion  18   a  proximate to the notch  18  to maintain the link in a disengaged position against the spring  44 , and the firearm cannot be fired again until the trigger  40  is released. Thus, the hammer  20  substantially temporarily deactivates the operability of the fire control assembly and the flange  35  of the sear assembly  30  engages the intermediate portion of the link  10  to the rear of the notch  18  to maintain the fire control assembly in the deactivated state until the trigger  40  is released. 
     Releasing the trigger  40  when the fire control assembly T is in the disengaged state shown in  FIG. 5  allows the spring bias of the spring  44  to force the roller bearing  42  upward against the sloped surface  15  of the forward end  14  of the link  10 , which forces the link rearward and the trigger  40  forward to the ready-to-fire position. When the notch  18  passes the flange  35 , the link  10  is allowed to pivot upward under the bias of the spring  44 . The fire control assembly is now returned to the pre-firing state shown in  FIG. 4A , and the notch  18  can engage the flange  35  to pivot the sear assembly  30  and release the hammer  20  when the trigger  40  is pulled again. 
     In operation, if the trigger  40  is pulled while cocking the firearm, the sear assembly  30  and trigger engagement link  10  are disengaged and the firearm cannot fire. If the trigger is released while cocking the firearm, and the sear assembly  30  and trigger engagement link  10  are disengaged, the firearm cannot fire. If the trigger  40  is released and the bolt is forward, the return spring  39  re-engages the sear catch with the hammer  20 . If the trigger  40  is not released during the bolt cycling, the sear assembly  30  and trigger engagement link  10  are disengaged and the firearm cannot fire. The trigger  40  must be released to enable release of the link and full recocking of the hammer to place the firearm in a condition for firing prior to being able to fire the firearm. 
     Various alternate configurations of the fire control assembly are considered to be within the scope of the present invention. In alternative embodiments, the roller bearing  42  and spring  44  can be otherwise oriented or arranged with respect to the forward end  14  of the link  10 . For example, the roller bearing  42  and the spring  44  can be arranged so that the spring extends in a direction generally normal to the sloped surface  15 . 
     In a further alternative embodiment shown in  FIG. 6 , the trigger engagement link  110  includes a rearward end  111 , an intermediate portion  118   a  having a sear notch  118  formed therealong, and a forward end  114 . As  FIG. 6  indicates, in this embodiment the intermediate portion  118   a  of the link  110  can have a substantially flat lower or bottom engaging surface that terminates at the forward end  114 , and with the forward end extending vertically, substantially normal to the intermediate portion. The forward end  114  can be supported and biased by roller bearings  142   a ,  142   b , sear engagement spring  144   a , and trigger return spring  144   b  that cooperate to provide resistance against the downward and forward motion of the forward end  114  of the link. In the configuration of the present embodiment, the link  110  acts on the orthogonal springs  144   a ,  144   b  generally in the direction in which each of the respective springs extend. Any force on the roller bearings  142   a ,  142   b  applied by link  110  in a direction that is transverse to the respective springs  144   a ,  144   b  generally can be reduced in the present configuration with respect to the sloped surface  15  of the link  10  in the previous embodiment. 
     As can be seen in  FIG. 6 , the biasing force acting on the forward end  114  is divided between the sear engagement spring  144   a  biasing the forward end  114  in a generally upward direction, while the trigger return spring  144   b  biases the forward end in a generally rearward or longitudinal direction. The roller bearing  142   a  engages the forward end  114  at a generally horizontal surface  115   a , and the roller bearing  142   b  engages the forward end at a generally vertical surface  115   b . The fire control of this alternate embodiment operates similarly to the fire control with link  10  except that the springs  144   a ,  144   b  bias the forward end  114  independently of each other. As the trigger  40  is pulled, the link  110  moves forwardly against the generally horizontally-extending trigger return spring  144   b , and when the hammer  20  forces the forward end  114  of the link  110  downwardly, as discussed with respect to the operation of the fire control assembly described above, the forward end  114  moves against the generally vertically-extending sear engagement spring  144   a . As a result, with the configuration of the present embodiment the resistance of the trigger or the trigger feel can be adjusted without significantly affecting the upward biasing force acting on the forward end of the trigger engagement link by the sear engagement spring  144   a . In particular, the trigger return spring  144   b  can be changed or adjusted to increase or decrease the rearward force on the link  110 , and thus the amount of force required for actuation of the trigger, without affecting the upward biasing force of the sear engagement spring  144   a  applied against the forward end of the trigger engagement link. 
     The corresponding structures, materials, acts, and equivalents of all means plus function elements in any claims below are intended to include any structure, material, or acts for performing the function in combination with other claim elements as specifically claimed. 
     Those skilled in the art will appreciate that many modifications to the exemplary embodiments are possible without departing from the scope of the invention. In addition, it is possible to use some of the features of the embodiments described without the corresponding use of the other features. Accordingly, the foregoing description of the exemplary embodiments is provided for the purpose of illustrating the principle of the invention, and not in limitation thereof, since the scope of the invention is defined solely be the appended claims.