Abstract:
Provided are systems and methods related to firearm trigger assemblies. An open design trigger assembly is provided to allow easier access to the trigger action. The trigger assembly is preferably an override trigger assembly, which may include adjustable trigger travel limiter and trigger bias force. Methods according to the present invention include a first step of removing either a direct-pull or a closed design trigger assembly from a firearm and replacing such removed assembly with an open design override trigger assembly.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/395,358, filed 12 May 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to firearms, but more particularly to systems and methods regarding firearm trigger assemblies. 
         [0003]    Generally, consistency and accuracy are understandably important in the art of firearms, especially in the field of competitive marksmanship. Regarding firearm trigger assemblies, inconsistency and inaccuracy may be attributed to at least two factors: friction and foreign particulates. 
         [0004]    In the art of firearms, trigger assemblies may generally be coarsely divided into two types: direct-pull and override. Each trigger assembly type includes a sear pin which is adapted to abut a firing pin in the associated firearm. However, the two types of trigger assemblies differ in the way that the sear pin maintains the firing pin in a retracted, pre-firing state. A direct-pull trigger assembly generally includes a sear pin that travels generally in a linear path, which is substantially perpendicular to and intersects the path of travel of the firing pin. The sear pin included in an override trigger assembly, on the other hand, is adapted to rotate away from the firing pin, where such rotation is caused by the force of the firing pin acting on the sear pin. The sear pin may be spring biased towards the firing pin, but when the trigger is pulled, the firing pin force is allowed to overcome the sear pin spring bias force, thus allowing the firing pin to contact the ammunition round placed in the firearm. 
         [0005]    As previously mentioned, two factors can contribute to undesirable inaccuracy and inconsistency in firearm trigger assemblies: friction and foreign particulates. Friction is of particular concern in direct-pull trigger assembly configurations. When in a cocked or pre-firing state, the direct-pull sear pin is in direct mechanical, frictional contact with a rear portion of the firing pin. To withdraw the sear pin and allow the firing pin to discharge the ammunition, the surface of the sear pin must be drawn across the surface of the portion of the firing pin, while the portion of the firing pin is biased towards the sear pin by a significant amount of force largely perpendicular to the direction of travel of the sear pin. Such interface creates a point of high frictional contact between the sear pin and the portion of the firing pin. Repeated firing actions begin to wear down both the sear pin and the portion of the firing pin, thereby altering the performance of the trigger assembly over time. 
         [0006]    Foreign particulates, such as oil, cleaning solutions, dust and dirt, can also affect accuracy and consistency. In an attempt to shield trigger assemblies from foreign particulates, prior after-market or replacement override trigger assembly designs were provided as closed design, or housed, triggers, some of which include small springs, screws and ball bearings in an effort to provide adequate functionality. The theory of such closed designs is believed to rest on the basis that the moving parts of the trigger assembly should be shielded from dust. However, it has been discovered that, contrary to the conventional wisdom that shielding moving parts from dust should improve functionality, the housing, or closed design, actually impedes functionality over time by allowing foreign particulates to accumulate therein. In turn, the closed design or housed trigger assemblies must be disassembled to be cleaned, such as by removing cover plates. Unfortunately, such disassembly creates the risk that the small springs, screws and ball bearings will be lost or damaged. Additionally, foreign particulates may extend what would otherwise be considered a normal lock time. A lock time is the amount of time that passes from the time the trigger mechanism is actuated until the time the firing pin strikes the primer of the ammunition round. Generally, the shorter the lock time, the better. Normal lock times for, e.g., a bolt action rifle such as the Mauser M98, range from about four to about seven milliseconds, with newer models ranging from 2.5 to about seven milliseconds. 
         [0007]    Accordingly, the art of firearm trigger assemblies would be enhanced by systems and methods suited to overcome at least the two mentioned causes of inconsistency and inaccuracy, while maintaining or reducing lock time. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides embodiments of systems and methods related to firearm trigger assemblies, which overcome one or more of the above mentioned drawbacks. In general, trigger assemblies according to the present invention will assist in preventing the accumulation of dust and other particulates within the assembly, and will assist in providing easy cleaning access in the event that any foreign particulates do interfere with operation. 
         [0009]    A first embodiment of a trigger assembly according to the present invention provides an override trigger assembly that may be adapted to replace a removed trigger assembly in a firearm. The override trigger assembly is preferably provided in an open design configuration. 
         [0010]    A first embodiment of a method according to the present invention comprises the steps of removing a direct pull trigger assembly from a firearm and coupling to the firearm an override trigger assembly, which may be an open design assembly. The firearm may be a bolt action rifle. 
         [0011]    A second embodiment of a method according to the present invention comprises the steps of removing a closed design override trigger assembly from a firearm and coupling to the firearm an open design override trigger assembly. The firearm may be a bolt action rifle. 
         [0012]    An embodiment of a firearm trigger assembly according to the present invention includes three levers, a first lever, a second lever, and a third lever. The first lever extends between a first lever first end and a first lever second end and includes a second-lever engagement means, which may comprise a notch and may be located closer to the first lever first end than to the first lever second end. The first lever is pivotable about a first lever axis and the first lever is biased in a first rotational direction about the first lever axis, which may be located closer to the first lever second end than to the first lever first end. The second lever extends between a second lever first end and a second lever second end and includes a protrusion, such as a wedge, formed thereon. The second lever is pivotable about a second lever axis and the second lever is biased in a second rotational direction about the second lever axis, which is at least substantially parallel with the first lever axis. The third lever extends between a third lever first end and a third lever second end and including a lower rocker surface and an upper pin surface, wherein the third lever is pivotable about a third lever axis, which is at least substantially parallel to the first lever axis. The levers generally cooperate in such a way to maintain a firearm firing pin in a cocked position. The second-lever engagement means rests in contact with the protrusion to prevent rotation of the second lever opposite the second and the third lever is prevented from rotating in a third rotational direction about the third lever axis by the contact of the lower rocker surface with the second lever. 
         [0013]    According to one aspect of an embodiment of a firearm trigger assembly according to the present invention, the first lever axis and the second lever axis may lie in a first plane, and the first lever axis and the third lever axis may lie in a second plane, which may be different from the first plane. The first plane and second plane may be arranged perpendicular to each other. 
         [0014]    According to another aspect of an embodiment of a firearm trigger assembly according to the present invention, the assembly may further comprise a support bracket, wherein one or more of the levers are pivotably mounted to the support bracket by a bearing disposed coaxial with the associated lever axis. The support bracket may further comprise a mounting structure to assist in coupling the bracket to a firearm, wherein the mounting structure may comprise a mounting yoke. 
         [0015]    According to yet another aspect of an embodiment of a firearm trigger assembly according to the present invention, one or more of the second rotational direction and the third rotational direction is/are eccentric to and opposite of the first rotational direction. 
         [0016]    According to still another aspect of an embodiment of a firearm trigger assembly according to the present invention, the first lever may be biased in the first rotational direction about the first lever axis by a spring. Additionally or alternatively, the second lever may be biased in the second rotational direction about the second lever axis by a spring acting on a surface of the second lever located between the second lever axis and the second lever second end. 
         [0017]    An embodiment of a method according to the present invention comprises the steps of providing a firearm having a firing pin and a first trigger assembly configured to cooperate with the firing pin to maintain the firing pin in a cocked position, removing the first trigger assembly from the firearm, and installing a second trigger assembly on the firearm. Embodiments of the second trigger assembly are described above and hereafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view of an embodiment of a trigger assembly according to the present invention. 
           [0019]      FIG. 2  is a left side elevation view of the embodiment of  FIG. 1 . 
           [0020]      FIG. 3  is a right side elevation view of the embodiment of  FIG. 1 . 
           [0021]      FIG. 4  is a left side elevation view of a prior direct-pull trigger assembly installed in a firearm. 
           [0022]      FIG. 5  is a second left side elevation view of the assembly of  FIG. 4  in a pulled orientation. 
           [0023]      FIG. 6  is a left side elevation view of a prior closed design, or housed, trigger assembly. 
           [0024]      FIG. 7  is a left side elevation view of the embodiment of  FIG. 1 , in a cocked position, installed on the same firearm depicted in  FIG. 4  after the direct-pull trigger was removed. 
           [0025]      FIG. 8  is the same view as  FIG. 7 , except that the trigger has been pulled. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0027]    Turning now to the figures,  FIGS. 1-3  depict a first embodiment  100  of a trigger assembly according to the present invention. The trigger assembly  100  generally includes a support bracket  110 , a trigger lever  150 , a transfer lever  170 , and a sear lever  190 . The support bracket  110  extends longitudinally throughout a bracket length  112  from a first bracket end  114  to a second bracket end  116 . The support bracket  110  has a top side  118  and a bottom side  120  coupled together by lateral sides  122 , which extend between the first bracket end  114  and the second bracket end  116 . Formed along at least a portion of the bracket length  112  and extending through the top side  118  and bottom side  120  is a sear channel  124 . Depending downward from and forming a part of the bracket bottom side  120  is a first bearing yoke  126  and a second bearing yoke  128 . Extending upward from and forming a part of the bracket top side  118  is a mounting yoke  130 . Extending through the bracket top side  118 , between the mounting yoke  130  and the first bracket end  114  is a stabilizing screw  140 , which is threadably engaged with the mounting bracket  110 . 
         [0028]    The trigger lever  150  generally extends from a first free end  152  to a second end  154 , and includes an upper transfer surface  156  extending therebetween. Disposed on the upper transfer surface  156 , closer to the first free end  152  than the second end  154  is at least one transfer lever engagement means  158 , such as a notch  159 . Extending upward from and forming part of the upper transfer surface  156 , closer to the second end  154  than the first free end  152 , is a mounting shank  160 . Extending from the trigger lever  150 , preferably between the mounting shank  160  and the second end  154 , is a trigger travel limiter  162 , which in one embodiment may be a hex screw  163  extending through and threadably engaged with the trigger lever  150 . Also provided is a trigger lever bias means  164 , which is preferably a coiled trigger bias spring  165  having a desirable spring constant. The trigger bias spring  165  may be sleeved over the travel limiting screw  163 , and may engage a bias adjustment nut  166 , which is threadably engaged with the screw  163 . Thus, as the nut  166  is threadably adjusted away from the trigger lever  150 , the spring  165  is compressed so as to increase the bias force of the trigger lever  150  in a trigger bias direction  167 . Extending downward from the trigger lever  150  is a preferably concave trigger engagement surface  168  extending from the trigger lever  150  to a free trigger end  169 . 
         [0029]    The transfer lever  170  generally extends from a free end  172  to a bias end  174 , and includes an upper sear interface surface  176  extending therebetween. The sear interface surface  176  extends generally planarly from the free end  172  towards the bias end  174 . The sear interface surface  176  is preferably generally smooth so as to provide a minimal frictional interface between the transfer lever  170  and the sear lever  190 . However, extending upward from and forming part of the sear interface surface  176 , preferably closer to the second end  174  than the first end  172 , is a mounting shank  178 . Extending downward from the transfer lever  170 , opposite the sear interface surface  176 , is a transfer wedge  180 , including a distal edge  182 , which may be peaked or slightly rounded. Extending from the transfer lever  170 , preferably between the mounting shank  178  and the bias end  174 , is a transfer lever bias means  184 , which is preferably a coiled transfer lever bias spring  185  having a desirable spring constant. 
         [0030]    The sear lever  190  generally extends from a free end  191  to a mounting end  192 , and includes an upper pin surface  193  and a lower rocker surface  194 . Extending upward from the upper pin surface  193  is a sear pin  195 . The sear pin  195  is preferably generally a parallelepiped, including a sloped, preferably planar safety surface  196  disposed between a front surface  197  and a rear firing pin engagement surface  198 . The safety surface  196  is preferably formed such that when the trigger assembly  100  is in its cocked position, the safety surface  196  is disposed at a desirable angle α with respect to the direction of travel of a firing pin  502 . A desirable angle α may be between five and sixty degrees, but a more preferred angle α is between ten and twenty degrees, with about fourteen degrees being most preferred. The lower rocker surface  194  is formed at a desired radius, preferably between about 0.100 inches and about 0.400 inches, with about 0.200 inches being preferred. 
         [0031]    Generally, the transfer lever  170  is pivotally mounted to the first bearing yoke  126  by a transfer bearing  171 , the trigger lever  150  is pivotally mounted to the second bearing yoke  128  by a trigger bearing  151 , and the sear lever  190  is situated at least partially within the sear channel  124  and is pivotally mounted to the support bracket  110  by a sear bearing  199 . The bearings  151 , 171 , 199  are preferably coaxially disposed with associated lever axes  151   a , 171   a , 199   a  about which each respective lever  150 , 170 , 190  is pivotable. 
         [0032]      FIGS. 4 and 5  depict a prior art direct pull trigger assembly  600  installed on a firearm action  500 . The prior assembly  600  includes a support bracket  610  and a trigger lever  650  pivotally connected thereto. The support bracket  610  includes a mounting yoke  630 , which is adapted to be pivotally mounted to the housing  504  of the firearm action  500 . Towards a free end  612  of the support bracket  610 , and extending upward therefrom, is a sear pin  690 , which extends into the firearm action  500  and is adapted to restrain the firing pin (not shown) when the action  500  is in a cocked position. At the top of the trigger lever  650 , there is formed a cam surface  652 . The cam surface  652  is adapted, when the trigger lever  650  is pulled in a first direction  520 , to rock against the housing  504  of the firearm action  500 . Such motion forces the support bracket  610 , and in turn the sear pin  690 , also to move in a second direction  522 , which allows the firing pin (not shown) to be released and to strike an ammunition round (not shown) loaded into the firearm action  500 . As the sear pin  690  is lowered in the second direction  522 , however, the top of the sear pin  690  is actually moving against the bias force of the firing pin (not shown), thereby increasing frictional forces, which may result in decreased performance over time. 
         [0033]      FIG. 6  shows a prior art closed design, or housed, override trigger assembly  700  installed on a firearm action  500 . The prior assembly  700  includes support plates  710 , which obscure and house the override trigger actuation mechanism. Indeed, the entire trigger action of the assembly  700 , except of course a trigger lever  750 , is obscured. The trigger lever  750  extends from between the plates  710  to allow for actuation. The trigger assembly  700  is mounted to the firearm action  500  by a mounting yoke  730 , and held stationary to the action  500  by a threaded stabilizing screw  740 . While the housed trigger assembly  700  may be disassembled to be serviced or cleaned, such as by removing, e.g., retaining rings  780 , such disassembly is accompanied by the high risk of component damage, loss, or misplacement. Another disadvantage of this design is an increased lock time over prior direct pull triggers. The cause of an increased lock time is thought to be the use of a relatively strong counterbalance spring that is used to decrease wear of the trigger action. 
         [0034]      FIG. 7  shows an embodiment  100  of a trigger assembly according to the present invention installed on a firearm action  500 , the trigger assembly  100  shown in a cocked position. After a factory or prior after-market trigger assembly is removed from the firearm as is known, the assembly  100  is installed by coupling the mounting yoke  130  to the firearm action  500  with a mounting pin  111 , and securing the assembly in place by tightening the stabilizing screw  140  against the firearm action  500 . Thus, a method according to the present invention includes the steps of removing a direct pull trigger assembly, such as the trigger assembly  600  shown in  FIG. 5 , from a firearm, such as a bolt action rifle, and installing an open design trigger assembly according to the present invention, thereby replacing the removed direct pull trigger assembly. A second method according to the present invention includes the steps of removing a closed design, or housed, override trigger assembly, such as the trigger assembly  700  of  FIG. 6 , from a firearm, such as a bolt action rifle, and installing an open design trigger assembly according to the present invention, thereby replacing the removed closed design, or housed, override trigger assembly. The method of removal of an extant direct pull or closed design override trigger assembly is generally within the skill of ordinary artisans in the trade. 
         [0035]    As can be seen, an open design assembly may provide access to substantially the entire trigger assembly from both lateral sides thereof. Preferably, such access is provided upon simple removal or separation from a firearm without further disassembly. In the depicted three-lever embodiment, there is a first contact point  301  between the transfer lever  170  and the trigger lever  150 . There is a second contact point  302  between the transfer lever  170  and the sear lever  190 . While the support bracket  110  has been shown manufactured in a way to allow access to both contact points  301 , 302  in both the cocked and pulled states, it is to be understood that the support bracket  110  may slightly cover one or both points. In this cocked state, the firing pin (not shown) has been automatically or manually retracted to allow the transfer bias means  184  to bias both the transfer lever  170  and the sear lever  190  upwards. The distal edge  182  of the transfer wedge  180  is then nestled into the transfer lever engagement means  158  so as to generally lock the assembly in the cocked position. The firing pin (not shown) is then automatically or manually allowed to rest against the sear pin  190 , and the weapon is ready for firing. 
         [0036]      FIG. 8  shows the trigger assembly  100  after the pulling of the trigger lever  150  in the first direction  520 . The force in such first direction  520  needs to overcome the biasing force of the trigger lever biasing means  164 , thus compressing  525  the trigger bias spring  165 . The travel of the trigger lever  150 , which may be limited by the trigger travel limit screw  163 , releases the distal edge  182  of the transfer wedge  180  from the transfer lever engagement means  158 . The bias force of the firing pin (not shown) is thus allowed to overcome the retention force supplied to the sear pin  190  by the transfer lever bias spring  185 , thus causing the sear lever to rotate in a third direction  526 , which in turn causes the transfer lever  170  to rotate in a fourth direction  527 , compressing  528  the transfer lever bias spring  185 . The trigger assembly  100  may be returned to the cocked position of  FIG. 7  by automatically or manually drawing the firing pin rearward to allow the biasing mechanisms  164 , 184  to bias the sear pin  195  upward to engage a portion of the firing pin. 
         [0037]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. For instance, while the design shown has been adapted and sized to cooperate with an M98 bolt action rifle available from Mauser Jagdwaffen GmbH of Isny, Germany, the general design of the support bracket  110 , including the bracket length  112  and mounting yoke  130  can be modified as required to accommodate the mounting mechanism included on other firearms, such as Springfield and Enfield bolt action rifles, onto which an embodiment according to the present invention may be installed. Such modification to the support bracket  110  is considered to be within the skill of the art, including various machining and casting techniques.