Patent Publication Number: US-6711842-B1

Title: Firing mechanism

Description:
BACKGROUND - FIELD OF INVENTION 
     This invention relates to firearms, specifically to the firing mechanism of a handgun designed for minimum overall length. 
     BACKGROUND - Description of Prior Art 
     The minimization of overall handgun length has long been recognized as a desirable design objective. 
     Shortly after the invention of the metallic cartridge, standing breech pistols designed for minimum size had already standardized around several features, including a firing mechanism incorporating a pivoted external hammer combined with a single action pivoted trigger, such as shown in U.S. Pat. No. 51,440 (Elliot) and U.S. Pat. No. 105,388 (Thuer). 
     The pivoted external hammer firing mechanism, as incorporated in these designs, suffers from several significant disadvantages. Foremost among these is a needless increase in overall firearm length. That portion of the gun set behind the breech end of the barrels is longer than necessary because it must both accommodate the long radius arc of hammer motion and still provide a handgrip extending beyond the rearwardmost point described by the arc, so as not to create interference between the hand and hammer while firing. The result is a waste of linear space which increases overall length. The corollary of this disadvantage is that the barrel is necessarily shorter for any given overall gun length than would otherwise be possible. 
     The pivoted external hammer creates another disadvantage in that it requires the gun to be grasped for firing below the lowest point of the hammer spur&#39;s arc. This results in a longer moment arm between hand and barrel axis and consequently creates an undesirable increase in the torque experienced by the shooter during recoil. 
     This design also suffers from the disadvantage of being slow to bring into a ready condition, as the pivoted external hammer must be manually cocked before firing. Since firearms of this class are frequently carried on the person, the pivoted external hammer suffers from a further inherent disadvantage. The protruding hammer may become snagged on a holster or clothing and thereby interfere with the drawing of the gun. 
     Despite these significant disadvantages of the prior art, standing breech pistols designed for minimum size have advanced little since the nineteenth century. Direct derivatives of nineteenth century designs are still currently in production. 
     Pistols with a firing mechanism consisting of a pivoted internal hammer combined with a self cocking pivoted trigger, such as shown in U.S. Pat. No. 3,193,960 (Stevens Jr.) mitigate some of the secondary disadvantages of traditional design. The pivoted internal hammer pistol however, still suffers from the primary disadvantage of needlessly large size. The long radius arc of hammer motion which needlessly increases the length of the gun is merely concealed, not eliminated. The corollary disadvantage of necessarily shorter barrel length for a given length gun is also not overcome. 
     Prior art attempts at maximizing barrel length for a given length handgun have focused on relatively large target arms, such as shown in U.S. Pat. No. 1,476,125 (Wesson et al). This design uses a longitudinally slidable external hammer for the purpose of reducing the length of that portion of the gun behind the breech end of the barrel. 
     Despite addressing the issue of barrel length, the longitudinally slidable external hammer design ignores the issue of overall gun length. In addition, this design also suffers from many of the same disadvantages as the previously discussed pivoted external hammer guns. 
     The gun must be grasped for firing below the path of the hammer&#39;s travel, so as not to create interference between the hand and hammer while firing. As before, this results in the disadvantage of a longer moment arm between hand and barrel axis and consequently creates an undesirable increase in the torque experienced during recoil. 
     This design likewise suffers from the disadvantage of being slow to bring into a ready condition, as the longitudinally slidable external hammer must be manually cocked before firing. 
     Although perhaps of little consequence on a target arm, the longitudinally slidable external hammer suffers from a further disadvantage if applied to a gun carried on the person. As with pivoted hammer designs, the protruding hammer may become snagged on a holster or clothing and thereby interfere with the drawing of the gun. 
     OBJECTS AND ADVANTAGES 
     Accordingly, among the objects and advantages of the present invention are: 
     (a) to provide a firing mechanism which minimizes overall gun length; 
     (b) to provide a firing mechanism which maximizes barrel length for a given overall gun length. 
    
    
     Further objects and advantages are to provide a firing mechanism which does not require manual cocking, has no external projections to snag on a holster or clothing, and eliminates constraints to minimizing moment arm length between the shooter&#39;s hand and barrel axis. Still further objects and advantages will be made evident from a consideration of the following description and drawings. 
     DRAWING FIGURES 
     FIG. 1 is a right side view of a single shot pistol incorporating the invention. 
     FIG. 2 is a partial sectional right side view of the frame. 
     FIG. 3 is a partial sectional right side view of the frame showing rearward travel of the firing element. 
     FIG. 4 is a partial sectional right side view of the frame showing forward travel of the firing element. 
     FIG. 5 is an isometric view of the firing element. 
     FIG. 6 is a front view of the firing element. 
     FIG. 7 is a rear view of the firing element. 
     FIG. 8 is a right side view of the firing element. 
     FIG. 9 is an isometric view of the rebound spring guide. 
     FIG. 10 is an isometric view of the detachable backstrap and driving spring guide. 
     FIG. 11 is a right side view of an additional embodiment of the firing element. 
     FIG. 12 is a right side view of an additional embodiment of the firing element using a separate firing pin. 
     FIG. 13 is a partial sectional right side view showing an additional embodiment of the driving spring. 
     FIG. 14 is a rear view of the frame and firing element with the backstrap removed. 
    
    
     REFERENCE NUMERALS IN THE DRAWINGS 
       10  Single shot pistol 
       12  Right grip plate 
       14  Barrel 
       16  Hinge pin 
       18  Frame 
       20  Trigger 
       22  Triggerbar 
       24  Trigger return spring 
       26  Sear 
       28  Firing element 
       30  Sear catch 
       32  Driving Spring 
       33  Guide 
       36  Recess 
       38  Surface 
       40  Backstrap 
       46  Mandrel 
       48  Stop pin 
       100  Body of firing element 
       102  Projection of firing element 
       104  Firing pin 
       106  Well 
       108  Counterbore of body 
       110  Head of guide 
       112  Cross pin 
       114  Washer 
       116  Counterbore of projection 
       118  Rebound spring 
       120  Rebound spring guide 
       122  Rear radius 
       124  Head of rebound spring guide 
       126  Hole in body 
       128  Hole in projection 
       130  Countersink 
       132  Fillet 
       134  Separate firing pin 
       136  Parallel springs 
     DESCRIPTION—FIGS.  1  TO  14   
     FIG. 1 shows a standing breech single shot pistol  10  which incorporates the invention. Pistol  10  has a barrel  14 , a frame  18 , and a trigger  20 . FIG. 1 also shows a right grip plate  12 . Barrel  14  is pivotally mounted to frame  18  via a hinge pin  16 . 
     FIG. 2 shows a self cocking trigger mechanism comprising trigger  20 , a triggerbar  22 , and a trigger return spring  24 . A comparable trigger mechanism is disclosed in U.S. Patent application titled “Passive Safety Mechanism” filed 1997 October 31 which is hereby incorporated by reference in its entirety herein. Triggerbar  22  is pivotably connected to trigger  20 . Trigger  20  is longitudinally slidable and is maintained in battery position by trigger return spring  24 . Trigger return spring  24  is a left hand wound 90 degree torsion spring and is located within a recess  36  in frame  18 . Trigger return spring  24  is mounted on a cross pin mandrel  46  and is constrained from rotation by a stop pin  48 . Trigger return spring  24  bears upon triggerbar  22  and serves to place a forward bias on both trigger  20  and triggerbar  22 . Trigger return spring  24  also has a vertical component of force which urges the free end of triggerbar  22  upward into the battery position. Triggerbar  22  has an integral sear  26  which engages a firing element  28  via a sear catch  30 . Sear catch  30  has a rear radius  122  which facilitates clearance of sear  26  during the return of triggerbar  22  to battery after firing. Firing element  28  has a cylindrical body  100 , a vertical projection  102 , and a firing pin  104  fixed to projection  102 . Firing element  28  is longitudinally slidable within recess  36  and extends into a well  106 . A driving spring  32  of the helical compression type is mounted on a cantilever guide  33  and extends from the rear into an axial counterbore  108  within body  100 . The advantage of this construction is that since body  100  and driving spring  32  extend longitudinally forward of a breechface  136 , overall gun length is minimized and barrel length is maximized. A through hole  126  allows the free end of guide  33  to longitudinally extend out the front of body  100 . The free end of guide  33  terminates in a larger diameter head  110 . The fixed end of guide  33  is secured to a detachable backstrap  40  by a cross pin  112 . Driving spring  32  is preloaded by a washer  114  which is slidably mounted on guide  33  and retained by head  110 . Projection  102  has a through hole  128  and a counterbore  116  oriented in the opposite direction. Counterbore  116  accepts a helical compression rebound spring  118  which is supported by a cylindrical rebound spring guide  120  that extends through hole  128 . The preload of rebound spring  118  is much less than that of driving spring  32 ; thus, full rebounding of firing element  28  is achieved when washer  114  abuts against hole  126 . Rebound spring guide  2  has a larger diameter head  124  which retains rebound spring  118  and abuts against a surface  38  within frame  18 . Rebound spring guide  120  is not fixedly attached and is positioned solely by alignment within hole  128 . This simplifies assembly and manufacture. 
     Rebound spring guide  120  can be seen more clearly in FIG.  9 . FIGS. 5 through 8 depict firing element  28 . Sear catch  30  of firing element  28  has substantially the same transverse width as body  100  and projection  102 . FIG. 14 shows that firing element  28  also has substantially the same transverse width as recess  36 . Guide  33  is shown mounted to backstrap  40  in FIG.  10 . Washer  114  and driving spring  32  have been omitted for clarity. 
     In FIG. 3 trigger  20  has been translated rearward into the firing position. Trigger bar  22  and firing element  28  have translated with trigger  20 . Triggerbar  22  has also been cammed downward to disengage sears from sear catch  30 . Firing element  28  is about to be propelled fully forward by compressed driving spring  32 . Note that rebound spring  118  has no preload and that rebound spring guide  120  has enough length to stay aligned within hole  128  when firing element  28  is at the rearward limit of travel. 
     In FIG. 4 firing element  28  is shown after having moved fully forward for firing. Driving spring  32  has returned to the original preloaded deflection. Rebound spring  118  has received additional compression and rebound of firing element  28  is imminent. Releasing trigger  20  after rebound will allow trigger  20  and triggerbar  22  to automatically reset to the battery position. 
     FIG. 11 shows a variation in the design of firing element  28 . Hole  128  has received a countersink  130 . Countersink  130  facilitates the clearance of head  110  through hole  128 . In addition, firing pin  104  has received a fillet  132  which reduces the probability of breakage. 
     FIG. 12 shows an additional variation. Instead of firing pin  104  fixed on projection  102 , projection  102  acts upon a separate firing pin  134 . 
     FIG. 13 shows still another variation. Driving spring  32  has been replaced by two parallel springs  136 . Parallel springs  136  are concentric and have opposite helix directions to prevent entanglement. Parallel springs  136  offer the advantage of reduced solid height and further reduce the constraints to minimizing overall firearm length. 
     Conclusion, Ramifications, and Scope 
     The reader will see that the firing mechanism of this invention minimizes overall firearm length, maximizes barrel length for a given overall gun length, does not require manual cocking, has no external projections to snag on a holster or clothing, and eliminates constraints to minimizing the moment arm length between the shooter&#39;s hand and barrel axis. 
     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible. For example, the rebound spring guide could be fixedly attached to the backstrap or frame; the rebound spring guide could be made a captive component of the firing element; the head could be removed from the rebound spring guide, etc. 
     Accordingly, the scope of the invention should be determined not by the embodiment(s) illustrated, but, by the appended claims and their legal equivalents.