Abstract:
The pendulum crosshair for a weapon sight incorporates a thin, rigid wire pivotally suspended at its upper end to a point at or immediately above the peripheral end point of the fixed vertical crosshair in the reticle of a weapon sight. If the weapon, and thus the sight, is tilted or canted from the vertical when aiming, the pendulum crosshair will misalign with the fixed vertical crosshair in the sight to indicate to the shooter that the weapon is canted. This allows the shooter to correct the cant or tilt of the weapon to avoid the lateral displacement of the shot that would otherwise occur due to lateral displacement of the elevation correction for the sight line.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/489,905, filed May 25, 2011. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to sighting devices for firearms and archery bows, and particularly to a pendulum crosshair for a weapon sight to alert the marksman of an out of plumb orientation of the weapon. 
         [0004]    2. Description of the Related Art 
         [0005]    Virtually all weapons intended for serious hunting and/or target use include sights that are adjustable for elevation, i.e., to compensate for the drop or fall of the projectile (bullet, arrow, etc.) between the time it is fired and the time it reaches the target. As an example of the above, a bullet or round traveling at an average velocity of 2,000 feet per second to a target that is 2,000 feet away from the shooter will be accelerated downward by the force of gravity at a rate of about 32 feet per second per second, for a drop or fall of about sixteen feet over the 2,000 foot distance. Of course, arrows travel at a considerably slower speed and over shorter distances, but the principle remains the same. Accordingly, weapon sights universally have some means to compensate for this factor by angling the sight slightly downward so that the weapon is aimed slightly high when the sight is precisely on the target. Ideally, the line of sight of the scope or other sights and the parabolic arc traveled by the projectile will meet at the range of the target, or very close to that range. At relatively longer ranges, the bullet will actually tend to rise somewhat above the line of sight of the scope before dropping back below the sight line as its energy is expended. 
         [0006]    A problem with the above is that such an elevation correction will only be absolutely accurate when the weapon is aligned vertically relative to gravity, i.e., the weapon is held in a plumb orientation. If the weapon is canted or tilted relative to the vertical, the elevation correction will be canted from the vertical accordingly. The lateral error induced will depend upon the angle of the cant of the weapon, as well as the angle subtended between the sight line and the alignment of the projectile when it is fired from the weapon (i.e., the bore of the firearm or the alignment of the arrow when released) and, of course, the distance to the target. All other things being equal, the greater the cant or tilt angle of the weapon from the vertical, the greater will be the resulting lateral error between the sight line to the target and the impact point of the projectile at the target distance. 
         [0007]    Thus a pendulum crosshair for a weapon sight solving the aforementioned problems is desired. 
       SUMMARY OF THE INVENTION 
       [0008]    The pendulum crosshair for a weapon sight comprises a sight reticle having a pivotally movable crosshair therein, formed of a thin, rigid wire or the like. The pivoting crosshair is suspended at its upper end at or immediately above the peripheral end point for the upper end of the fixed vertical crosshair in the reticle, the pivoting crosshair being free to pivot about its attachment point. The movable pivoting crosshair acts as a pendulum, always hanging vertically within the reticle, regardless of the lateral tilt or cant of the reticle. The shooter need only orient the weapon so that the pivotally attached crosshair is directly aligned with the fixed vertical crosshair of the sight reticle to assure that the weapon is being held vertically or plumb with no lateral tilt or cant. This assures the shooter that the elevation correction is entirely in the vertical plane, and will not throw off the aim laterally due to an undesired lateral component as a result of the cant or tilt of the weapon. The device may be applied at the focal plane of a telescopic sight for a firearm, e.g., a rifle, or may be applied to the sighting mechanism of an archery bow sight or other weapon sighting system. 
         [0009]    These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1A  is a diagrammatic view of a rifle with telescopic sight having a pendulum crosshair and sight reticle, shown enlarged separately, showing the general path of a bullet fired from the rifle when the rifle is canted, i.e., not plumb. 
           [0011]      FIG. 1B  is a diagrammatic view of a rifle with telescopic sight having a pendulum crosshair and sight reticle, shown enlarged separately, showing the general path of a bullet fired from the rifle when the rifle is plumb. 
           [0012]      FIG. 2  is an exploded environmental perspective view of a firearm scope and reticle incorporating a pendulum crosshair for a weapon sight according to the present invention, showing installation of the crosshair in the second or rear focal plane of the scope, the scope being shown in broken lines. 
           [0013]      FIG. 3  is an exploded detailed rear perspective view of a pendulum crosshair for a weapon sight according to the present invention, showing installation of the pendulum crosshair in the reticle. 
           [0014]      FIG. 4A  is a rear elevation view of an archery how sight having a pendulum crosshair for a weapon sight according to the present invention, showing the alignment of the crosshair with the vertical crosshair of the reticle to indicate that the weapon is plumb. 
           [0015]      FIG. 4B  is a rear elevation view of the archery bow sight of  FIG. 4A , showing misalignment of the crosshair with the vertical crosshair of the reticle to indicate that the weapon is not plumb. 
       
    
    
       [0016]    Similar reference characters denote corresponding features consistently throughout the attached drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The pendulum crosshair for a weapon sight provides the shooter with information regarding the vertical alignment of his or her weapon, thereby allowing the shooter to maintain true vertical alignment of the weapon and corresponding elevation adjustment between the sight system and the initial projectile path as defined by the firearm bore or arrow release. This is desirable in order to prevent the introduction of a lateral component to the plane defined by the sight line of the weapon sights and the parabolic path of the projectile after it has been fired. If the weapon is tilted or canted from the vertical, i.e., out of plumb, the resulting lateral offset of the sight line and projectile path will result in lateral displacement of the impact point of the projectile on the target, even when the sight line is aligned precisely with the center of the target. The pendulum crosshair is adaptable to any practicable weapon sight, including telescopic sights for firearms (rifles, etc.) and archery bow sights. 
         [0018]      FIGS. 1A and 1B  illustrate the vertical or plumb alignment of a firearm F 1  and the vertically tilted or out of plumb alignment of a firearm F 2 , respectively. In the case of  FIG. 1A  the firearm F 1  is plumb or vertically oriented, as noted. This places the plane defined by the sight line L 1  of the sight S 1  (e.g., telescopic sight, as shown in  FIGS. 1A and 1B ) and the vertical parabolic path P 1  of the bullet or projectile in flight in the vertical, i.e., with no lateral offset. Thus, the flight path of the bullet or projectile remains coplanar with the plane of the sight line L 1  and the projectile path P 1 , so that the projectile strikes the target T 1  in vertical alignment with the point of intersection of the sight line L 1  with the target T 1 . If the elevation correction has been set properly and all other factors (e.g., windage, etc.) properly accounted for, the projectile will strike the target T 1  at precisely the point of intersection of the sight line L 1  with the target T 1  with no lateral or vertical error. The vertical alignment of the firearm F 1  is clearly indicated by the weapon sight  10 , which has a pendulum crosshair  12  aligned vertically with the vertical crosshair  14  of the reticle of the sight  10 . 
         [0019]      FIG. 1B  provides an illustration of the error introduced when the firearm is tilted out of the vertical, or out of plumb. In  FIG. 1B , the firearm F 2  is tilted to the right, out of plumb with the vertical. The sight line L 2  of the sight S 2  is still aligned with the aiming point of the target T 2 , just as in the case of  FIG. 1A . However, the lateral tilt of the firearm F 2  has resulted in a corresponding lateral tilt of the plane defined by the sight line L 2  and the parabolic path of the projectile P 2 . This lateral tilt results in a horizontal offset of the impact point of the projectile with the target T 2 , as shown in  FIG. 1B  of the drawings. The lateral tilt or out of plumb orientation of the firearm F 2  is clearly indicated by the tilted weapon sight  10  in  FIG. 1B , the vertical crosshair  14  being tilted at an angle from the vertical corresponding to the tilt or cant of the firearm F 2 , the pendulum crosshair  12  remaining in the vertical to show the angular difference between the vertical crosshair  14  and pendulum crosshair  12 . 
         [0020]      FIG. 2  is an illustration of an exemplary installation of the weapon sight  10  with a telescopic sight S, with the sight S being shown in broken lines, The weapon sight  10  comprises a periphery or frame  16  surrounding a sight reticle  18 , the reticle  18  including the fixed vertical crosshair  14  described further above and a fixed horizontal crosshair  20 , which may be etched onto a lens, or onto a thin, transparent plastic disc, or onto any other crosshair support (a sight reticle support) known in the art, or which may be formed by fibers embedded into a lens, plastic disk, or other sight reticle support, or which may be formed on a sight reticle support in any other manner known in the art. The two fixed crosshairs  14  and  20  extend diametrically across the reticle  18  and periphery  16 . Each crosshair  14  and  20  has opposite ends terminating at the periphery  16  of the sight  10 , e.g., the upper end  22  of the vertical crosshair  14  terminating at the uppermost point of the periphery  16  of the sight  10 . The movable pendulum crosshair  12  is aligned with the fixed vertical crosshair  14  of the weapon sight  10  shown in  FIG. 2 , and is thus not visible separately. The weapon sight  10  may be installed at the rearward or second focal plane of the telescopic sight S by removing the eyepiece E of the sight and reinstalling the eyepiece E when the sight  10  has been installed, generally as shown in  FIG. 2 . Alternatively, the weapon sight  10  may be installed farther forward in the telescopic sight S in the forward or first focal plane (not shown), if desired. 
         [0021]      FIG. 3  of the drawings provides a detailed exploded perspective view of the weapon sight  10 , illustrating the installation of the pendulum crosshair  12  therewith. A small pin passage  24  is formed at the top of the frame or periphery  16  of the sight, adjacent the upper end  22  of the fixed vertical crosshair  14  and in vertical and axial alignment therewith. The pendulum crosshair  12  has a small eye  26  at its upper end. A pendulum crosshair attachment pin  28  is installed through the eye  26  of the pendulum crosshair  12 , the pin having a head with a diameter larger than the diameter of the eye  26 . A small spacer or washer  30  is placed over the shaft of the pin  28  after the shaft of the pin is passed through the eye  26  of the pendulum crosshair  12 , before installing the pin  28  in the passage  24  of the sight periphery  16 . 
         [0022]    The movable pendulum crosshair  12  is of very lightweight, preferably being formed of a very thin strand of metal wire or other suitable material. The pendulum crosshair  12  preferably has a length  32  of only about half the vertical span of the sight reticle  18  as subtended by the fixed vertical crosshair  14 , i.e., the pendulum crosshair  12  extends from its attachment pin  28  only to the center of the reticle  18 , as defined by the intersection of the fixed vertical and horizontal crosshairs  14  and  20  and as shown in  FIG. 1B  of the drawings. The spacer or washer  30  precludes binding of the movable pendulum crosshair  12  on the periphery or frame  16  and/or the reticle  18  of the sight  10 , thus permitting smooth arcuate motion of the pivotally suspended, lightweight pendulum crosshair  12  as the sight  10  is tilted or canted laterally. 
         [0023]      FIGS. 4A and 4B  of the drawings show the incorporation of a weapon sight having a pendulum crosshair, the sight being vertically oriented in  FIG. 4A , and having a cant or tilt in  FIG. 4B .  FIGS. 4A and 4B  are thus somewhat analogous to  FIGS. 1A and 1B , but the weapon sight of  FIGS. 4A and 4B  is adapted for use with an archery bow rather than a firearm. Accordingly, the archery sight of  FIGS. 4A and 4B  is designated as weapon sight  110 , and extends from an archery bow attachment bracket B 1  ( FIG. 4A ) and B 2  ( FIG. 4B ). The only difference between the brackets B 1  and B 2  is their orientation relative to the vertical. 
         [0024]    The two archery bow sights  110  of  FIGS. 4A and 4B  are configured identically to the weapon sights  10  of  FIGS. 1A through 3 , with the exception of their attachment means. Each of the archery bow sights  110  has a pivotally moving pendulum crosshair  12  aligned with the fixed vertical crosshair  14  of the sight  110  when the sight is oriented vertically, the pendulum crosshair  12  being pivotally attached to the upper center of the peripheral frame  16  of the sight, substantially as shown in  FIG. 3  for the sight  10  and described further above. A fixed horizontal crosshair  20  extends diametrically across the periphery  16 , the vertical and horizontal crosshairs  14  and  20  forming the sight reticle  18 . 
         [0025]    In the case of  FIG. 4A  the archery bow is plumb or vertically oriented, as evidenced by the orientation of its sight mounting bracket B 1 . This places the plane of the arrow or projectile path and the elevation sight line in the vertical, or parallel to the sight plane referenced by the vertical crosshair  14  of the sight  110 , with no lateral offset. Thus, the flight path of the arrow or projectile remains coplanar with the plane of the sight line and the arcuate projectile path, similar in principle to the scenario described further above, as shown with the firearm in  FIG. 1A . 
         [0026]      FIG. 4B  provides an illustration of the error introduced when the archery bow is tilted out of the vertical, or out of plumb. In  FIG. 4B , the archery bow is tilted or canted to the left, out of plumb with the vertical, as evidenced by the orientation of the sight mounting bracket B 2 . The lateral tilt or out-of-plumb orientation of the archery bow and its sight bracket B 2  is clearly indicated by the tilted weapon sight  110  in  FIG. 4B , the vertical crosshair  14  being tilted at an angle from the vertical corresponding to the tilt or cant of the bow and sight bracket B 2 , and the pendulum crosshair  12  remaining in the vertical to show the angular difference between the vertical crosshair  14  and pendulum crosshair  12 . 
         [0027]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.