Abstract:
Disclosed is an anti-bounce firearm hammer including a hammer member mountable in a firearm for pivotal movement about an axis. The hammer member includes a head portion with a strike face radially spaced from the pivot axis. A mass is attached to and movable with the hammer member in a direction substantially toward and away from the strike face. The mass has freedom of movement such that the mass will continue to move a limited distance independent of the hammer member after pivotal movement of the hammer member has stopped.

Description:
RELATED APPLICATION 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/041,343 filed Aug. 25, 2014. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the fire control mechanism for a firearm. More specifically, it relates to a lightweight pivoting hammer carrying an independently movable mass to reduce bounce or recoil on impact with a firing pin. 
     BACKGROUND 
     In a fire control mechanism, pulling a trigger breaks the engagement of a sear with a hammer, which is then pivoted by spring force into contact with a firing pin. The inertia of the moving hammer provides an impact force to the firing pin to detonate an ammunition primer. 
     In an effort to reduce the overall weight of a firearm, material may be removed from virtually any part, or parts may be made from lower density materials. If the mass of the hammer is reduced too much, it will lack sufficient momentum or inertia to strike the firing pin with enough force or may rebound from the firing pin causing “hammer bounce.” If, in an effort to overcome the lack of hammer mass by increasing its velocity, the spring force is increased, other problems may be created by the significantly increased amount of force required to cock the hammer. 
     SUMMARY OF THE INVENTION 
     The present invention addresses these issues by providing a light weight hammer with a mass that is independently movable to a limited extent relative to the arcuate motion of the hammer. As a result, much like in a “dead blow” hammer, a portion of its mass continues moving after the initial impact, delivering its inertial force in a manner that counteracts rebound from the initial impact. 
     The invention provides an anti-bounce firearm hammer comprising a hammer member and a moveable mass attached thereto. The hammer member is mountable in a firearm for pivotal movement about an axis and includes a head portion with a strike face radially spaced from the pivot axis. A mass is attached to and movable with the hammer member in a direction substantially toward and away from the strike face. The mass has freedom of movement such that the mass will continue to move a limited distance independent of the hammer member after pivotal movement of the hammer member has stopped. 
     The mass may be located within the head portion. There may be a cavity in the head portion in which the mass is located, the cavity having an opening oriented substantially opposite the strike face, which may include a closure member for the cavity. The cavity may be an elongated bore situated substantially tangential to the pivot axis or may be an elongated arcuate bore situated substantially concentric with the pivot axis. 
     The mass may be made of a solid piece of material and may be made of material more dense than material from which hammer member is made. In one embodiment, the mass is comprised of tungsten. 
     Other aspects, benefits, and features of the present invention may be apparent to a person of skill in this art by reference to the following specification, drawing figures, and claims, all of which are part of the disclosure of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Like reference numerals are used to indicate like parts throughout the various figures of the drawing, wherein: 
         FIG. 1  is an isometric view of the fire control components in a typical AR15-style firearm; 
         FIG. 2  is a longitudinal sectional view of the lower receiver of a typical AR15-style firearm showing the fire control components with the hammer in a cocked or set position and partially cut-away to illustrate the hammer&#39;s internal structure; 
         FIG. 3  is a view like  FIG. 2 , but with the hammer illustrated in the dropped position; and 
         FIG. 4  is an enlarged fragmentary and partially cut-away view of the hammer upon initial contact with a firing pin. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to various figures of the drawing, and first to  FIG. 1 , therein as shown at  10  a typical fire control group (or mechanism) for a firearm. Typical components include a trigger  12 , a trigger spring  14 , a disconnector  16 , and a hammer  18 . The trigger  12  and disconnector  16  are pivotally mounted on a trigger pin  20 , supporting them for limited pivotal movement relative to the receiver (not shown in  FIG. 1 ). The trigger  12  includes or is directly connected to a sear  22 . The trigger  12  is a biased toward a set position by a trigger spring  14 . The hammer  18  is pivotally mounted on a hammer pin  24 , which is also supported by the receiver (not shown in  FIG. 1 ). The hammer  18  is biased toward a “dropped” position by a hammer spring  26 . The fire control group  10  illustrated herein is that of a typical AR15-style firearm. These same components, in various forms, are found in any firearm mechanism. The present invention is not limited to the illustrated embodiment and may be used in most any firearm having a pivoting hammer, whether single-shot, semi-automatic, or fully automatic. 
     Referring now also to  FIG. 2 , therein, the fire control group  10  is shown mounted in an otherwise “stripped” AR15-type lower receiver  28 . In the cocked or set position ( FIGS. 1 and 2 ), the sear  22  engages a notch  30  on the hammer  18  against the force of the hammer spring  26 . 
     According to one embodiment of the invention, within a head portion  32  of the hammer  18 , a cavity  34  is provided which may extend in a direction substantially tangential to or along an arc of travel (arrow  36 ) along which the hammer  18  pivots. According to one embodiment, the cavity  34  may be formed, such as drilling, from a rear side of the head portion  32  toward, but short of, the striking face  38  of the head portion  32 . A moving mass  40  is provided that is sized and shaped to fit within and freely slide along the length of the cavity  34 . The moving mass  40  is typically of a relatively higher density material and can be a solid piece of material; a flowable dry material, such as metallic pellets or powder; or could be a high-density liquid, such as mercury. According to one embodiment, the moving mass  40  may be formed from a tungsten rod approximately ⅛ inch in diameter and 7/16 inch long. The open rear end  42  of the cavity  34  may be sealed in order to capture the moving mass  40  within the cavity  34  by any suitable means. According to one embodiment, a set screw  44  may be threaded into the open end  42  of the cavity  34  and then sealed in position by means of an adhesive or by staking. 
     When the hammer  18  is in the set or cocked position ( FIGS. 1 and 2 ) and as the hammer begins a forward movement, a movable mass  40  will remain at or toward the rear of the cavity  34 . Referring now in particular to  FIGS. 3 and 4 , when the hammer  18  reaches its forward or dropped position, the movable mass  40  will continue traveling forward (arrow  46  in  FIG. 4 ) until it reaches the forward-most end of the cavity  34  ( FIG. 3 ), transferring its momentum force to the firing pin  48  as it is struck by the hammer face  38 . Typically, the mass  40  will be made of a material more dense than that of the hammer  18 , such that the loss of weight resulting from formation of the cavity  34  is largely compensated or exceeded by the weight of the mass  40 . 
     In this manner, rebound or bounce of the hammer  18  against the firing pin  46  is offset by the slightly delayed transfer of momentum from the movable mass  40 . Accordingly, the overall mass of the hammer  18  and/or the tension of the hammer spring  26  may be reduced without the negative effect resulting from rebound or “bounce” that might otherwise occur. This reduction in weight may be accomplished by making a portion or all of the hammer  18  from a lower density material than usual or by removing nonessential material (i.e., “skeletalizing”) from the hammer  18 . Alternately, the hammer  18  may be made by metal injection molding (MIM) of powdered steel or aluminum, with the mass  40  being made of a higher density material. 
     The specific weight of the movable mass  40  as well as the amount travel it is permitted may be varied in order to meet specific needs and designs. Likewise the radial distance at which the mass  40  is located relative to the hammer&#39;s axis of rotation (on hammer pin  24 ) may be varied to affect the performance of the invention. While there are certain apparent advantages of having the movable mass  40  contained within a sealed cavity  34 , as illustrated, the same effect can be achieved with a moveable mass that is exposed or located on the exterior of the hammer  18  and guided by any suitable means along a limited path of travel. 
     While an exemplary embodiment of the present invention has been described in detail, it should be apparent that modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention disclosed herein. Therefore, the foregoing is considered as illustrative only of the principles of the invention and, since modifications and changes will be apparent to those skilled in the art, it is not intended to limit the invention to the exact construction and operation shown and described. Accordingly, all suitable modifications and equivalent may be resorted, falling within the scope of the invention.