Patent Publication Number: US-8528140-B1

Title: Adjustable scope mount

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/503,636, filed Jul. 1, 2011. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a mount for attaching optics or other sighting devices to a firearm. More specifically, it relates to a mount that may be adjustably reconfigured to attach the sighting device at multiple preselected angles of declination. 
     BACKGROUND 
     Optical scopes are mounted on rifles to provide a clear magnified image of a target and to provide an adjustable aiming point to indicate the point of impact of a projectile on a target. Scopes typically have an internal optical adjustment to shift the image or apparent location of the crosshairs or other reticle to compensate for the amount that the bullet drops below the axis of the barrel as it travels over a distance. A similar lateral adjustment is normally provided for windage compensation. 
     On firearms having a relatively short maximum effective range (under about 600 meters), the scope may be mounted such that its sighting axis is approximately aligned with the bore axis of the barrel and is adjusted vertically in elevation and adjusted laterally in windage such that the point of aim observed by the shooter is the point of impact of the projectile at the desired range. Other elevation and windage adjustments may be necessary based on number of well known factors including wind speed and direction, temperature, humidity, projectile shape and mass, and powder mass and burn characteristics. Since projectiles follow a ballistic path, adjustments of elevation may be a critical factor for hitting targets at ranges approaching the maximum range of the cartridge-rifle combination. Because all projectiles are affected by the Earth&#39;s gravitational pull, the ballistic path always follows a downward arc, requiring the bore axis of the barrel to be elevated relative to the target (or for the line of sight to be declined in elevation relative to the bore axis of the barrel). 
     The range in elevation adjustments needed for telescopic scopes mounted to high powered sporting and military rifles capable of hitting targets at distances greater than about 600 meters frequently exceeds the range in elevation adjustments achievable by adjustment mechanisms incorporated within the telescopic scope itself. Scope-mounting systems are available that provide a selected angular deviation that points the scope slightly downward with respect to the barrel bore axis. The angular deviation is typically less than one degree, with a deviation in the range of 10-50 minutes of angle (MOA) being typical. The deviation may be manufactured into a rail system to which a scope mount is attached or in a scope mount having rings encompassing a scope tube, with the rear ring at a higher elevation than the front ring. This allows use of a practical internal scope adjustment mechanism that employs the upper range of adjustment for nearer shots and the lower range below a neutral setting for more distant shots where bullet drop is greatest. 
     While a mount having a single, preselected angle of declination is effective for use with a given cartridge or firearm to hit targets within a selected range of distances, a single angled mount is not suitable for a varied range of cartridges or versatile for a wider range of target distances. Thus, numerous different-angled mounts must be manufactured and stocked, and users must buy multiple mounts to provide for different applications or settle for a compromise that is suboptimal at other extreme of the range. Changing the mount may be inconvenient for a sporting shooter who uses the same rifle to compete at  500  meters and 1,500 meters. But, for a sniper operating in a theater of war who may engage targets at as little as 350 meters and at well over 1,500 meters during the same mission, changing the mount is impractical, if not impossible. 
     In the past, field-adjustable mounts have been proposed. One type provides a pivot axis for moving the angle of a mounting rail. Another uses a pivot in one of the scope mounting rings with the other ring being adjustable in height. When sighting accuracy within ¼ MOA (or a 0.1 milliradian) is necessary and such mounts are subjected to the repeated recoil impact forces of a heavy caliber rifle, a pivotal mounting system may not provide sufficient stability and durability. 
     SUMMARY OF THE INVENTION 
     The present invention provides an adjustable mount for attaching a sighting device to a firearm. It includes an elongated base member and an elongated mount member that is longitudinally slidably engageable with the base member. Either the base member or the mount member includes a plurality of nonparallel longitudinal engagement slots. A longitudinal engagement tongue is provided on the other member. The tongue is selectively longitudinally slidably engageable in each of the plurality of slots to selectively position the mount member at different angles relative to the base member. At least one transverse clamping member is configured to secure the base member and mount member against relative longitudinal movement. 
    
    
     
       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 one embodiment of the invention showing a riflescope mounted thereon; 
         FIG. 2  is an exploded isometric view of the adjustable mount; 
         FIG. 2   a  is a fragmentary enlarged isometric view of a forward portion of the base member showing the nonparallel configuration of the elongated slots; 
         FIG. 3  is a side plan view showing a mount member partially slidably engaged on a base member; 
         FIG. 4  is an isometric view of the mount member and base member assembled in a selected position; 
         FIG. 5  is an end plan view of the adjustable scope mount assembled in a first position; 
         FIG. 6  is an end plan view of the adjustable scope mount assembled in a second position; and 
         FIG. 7  is a transverse sectional view taken substantially along line  7 - 7  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the various figures of the drawings and first to  FIG. 1 , therein is shown at  10  a scope mount according an embodiment of the present invention with an internally adjustable telescopic sight  12  mounted thereon. The illustrated scope  12  is mounted using a pair of scope rings  14  which clamp to a standardized Picatinny mounting rail  16  presented at the top of the mount  10 . 
     Referring now also to  FIG. 2 , therein is shown the various components of this embodiment of the scope mount  10 . It includes a base member  18  and a mounting member  20 . The base member  18  includes a bottom portion  22  which is configured for secure attachment to a firearm receiver, barrel, or stock. Alternatively, the base member  18  may be manufactured integral with a firearm receiver, barrel, or stock (not shown). The base member  18  may include attachment openings  24  which are adapted to receive fasteners (not shown) for securely attaching the base member  18 . The scope mount  10  may be integrated into a more extensive accessory mounting system, portions of which may not need to be adjustable in angle. For example, a secondary mounting rail may extend forward of the mounting member  20  to hold a night vision device in a generally aligned position with the day scope  12 . Side accessory rails (not shown) may be integrated for attachment of target indicators or illuminators. Mounts for these other devices may not require the angle adjustment feature of the present invention. 
     Along opposite lateral sides of the base member  18  may be a plurality of nonparallel longitudinal engagement slots  26 ,  28 ,  30 . The engagement slots  26 ,  28 ,  30  are not parallel to each other, although one of them may be configured to be substantially parallel to the bore axis of a firearm barrel (not shown) to which the mount  10  is attached or integrated. The plurality of engagement slots  26 ,  28 ,  30  are precisely machined longitudinally at slight, preselected angles relative to one another. For example, the variance between two of the engagement slots  26 ,  28 ,  30  may be 10, 15, or 20 minutes of angle (MOA). Because the nonparallel configuration of the engagement slots  26 ,  28 ,  30 , being as little as 5 MOA ( 1/12 of one degree), may not be visually perceptible, the configuration is exaggerated for illustration in  FIG. 2   a.    
     The mounting member  20  may include a pair of flange portions  32 ,  34  which extend downwardly from a top portion  36  to form a downwardly-oriented longitudinal channel  38 . The top portion  36  is configured to receive a scope  12  mounted thereon, such as by way of integral scope rings (not shown) or a standardized Picattiny rail  16  to which scope rings  14  or other mounting devices may be secured. 
     Lateral inboard surfaces of the flange portions  32 ,  34  may include longitudinal tongue portions  40 ,  42 . The channel  38  is sized to closely engage sides of the base member  18  when the mounting member  20  is longitudinally slidably assembled thereon with each of the tongue portions  40 ,  42  respectively engaging an opposite pair of the plurality of longitudinal engagement slots  26 ,  28 ,  30 .  FIG. 3  shows base member  18  and mounting member  20  in a partially assembled position as the mounting member  20  is being slid into place on the base member  18 .  FIG. 4  shows the mounting member  20  assembled in position on the base member  18  with the tongue portions  40 ,  42  longitudinally engaged in the uppermost pair of longitudinal engagement slots  30 . 
     Referring now in particular, to  FIGS. 5 and 6 , it can be seen that the mounting member  20  can be longitudinally engaged on the base member  18  with the tongue portions  40 ,  42  in each of the opposed pairs of engagement slots  26 ,  28 ,  30 .  FIG. 5  shows the tongue portions  40 ,  42  engaged in the lowermost pair of engagement slots  26 .  FIG. 6  shows the tongue portions  40 ,  42  engaged in the uppermost pair of engagement slots  30 . Although not specifically illustrated, it is understood that the tongue portions  40 ,  42  may also be positioned to slidably engage the middle pair of engagement slots  28 . Thus, by sliding the mounting member  20  onto the base member  18  with the tongue portions  40 ,  42  in a selected pair of engagement slots  26 ,  28 ,  30 , the mounting member  20  may be positioned at preselected angles relative to the base member  18  and the bore axis of a firearm barrel (not shown). Because the tongue portions  40 ,  42  and engagement slots  26 ,  28 ,  30  may be of relatively small vertical dimensions, the difference in vertical height of the mounting member  20  is a relatively small variation. 
     Referring now in particular to  FIGS. 1-4  and  7 , the mount  10  may include one or more transverse clamping member  44  to securely hold the mounting member  20  in place against longitudinal displacement on the base member  18 . For example, the mounting member  20  may include one or more opening  46  sized to receive a fastener, such as a bolt  48 . The bolt  48  may be sized to span the entire width of the mounting member  20  from one flange  32  to the other  34 . A transversely aligned complementary opening  50  (see  FIG. 7 ) may be provided in the opposite flange portion  34 , which may be threaded to engage the bolt  48  or a separate nut (not shown) can be used. A corresponding opening  52  may be provided transversely in the base member  18 . In preferred form, the corresponding opening  52  is sized to closely fit the bolt  48  along the longitudinal direction of the mount  10  but to be enlarged in vertical dimension so as to receive the bolt  48  no matter which of the engagement slots  26 ,  28 ,  30  is being used to receive the tongue portions  40 ,  42 . This is most clearly shown in  FIGS. 2 and 7 . In preferred form, a plurality of transverse clamping members  44  are used at longitudinally spaced intervals along the base member  18  and mounting member  20 . 
     In this manner, a substantial surface area of the base member  18  and mounting member  20  are firmly clamped together to provide a friction fit that resists longitudinal displacement. Moreover, longitudinal shear loads are carried by one or more bolts  48  engaged in corresponding openings  52  of the base member  18  and openings  46 ,  50  in the mounting member  20 . Vertical loads are carried by engagement of the tongue portions  40 ,  42  in the longitudinal engagement slots  26 ,  28 ,  30 . Despite the relatively small vertical and transverse dimensions of the tongue portions  40 ,  42  and engagement slots  26 ,  28 ,  30 , the substantial amount of overall area and clamping force provided transverse clamping members  44  make the mount  10  very strong while allowing for precise increments of declination to be selected. 
     Alternatively, the tongue portions  40 ,  42  may be formed on the mounting member  20  at a small angle, such as 5 MOA, relative to horizontal. In this manner, if the mounting member  20  is engaged on the Base member  18  is one orientation, the effective angle provided by each of the engagement slots  26 ,  28 ,  30  is reduced by this amount. If the orientation of the mounting member  20  is reversed, the effective angle provided is increased by 5 MOA. In this manner, angles in between those provided by the engagement slots  26 ,  28 ,  30  may be provided, effectively multiplying the number of preselected angles of adjustment available. 
     If desired, one end of each of the engagement slots  26 ,  28 ,  30  may be slightly narrowed and/or an opposite end of each tongue portion  40 ,  42  may be slightly widened in order to maximize the frictional fit between the base member  18  and mounting member  20  when fully longitudinally engaged together while allowing relatively easy sliding movement during the majority of longitudinal travel as the parts  18 ,  20  are assembled or disassembled. Alternatively, a mechanical stop (not shown) could be integrated into the base member  18  and/or mounting member  20  in order to further resist longitudinal displacement between the members, at least in one direction, when assembled. 
     Although it is not expected that adjustment of the mount  10  would be used to make rapid adjustments to the elevational position of a scope  12  or other sighting device, repositioning would not require the services a skilled armorer, but could be accomplished even in the field using no more than a simple tool for removing or tightening the transverse clamping members  44 . Precise and repeatable alignment is achieved after disassembly and reassembly of the mounting member  20  on the base member  18 . The base member  18  remains rigidly fixed and aligned with the bore axis of the barrel and is not disturbed by repositioning of the mounting member  20 . 
     As used herein, “forward” or “front” refers to the muzzle or discharge end or direction of a firearm, distal from the user. “Rearward” or “rear” refers to end of the firearm proximal to the user and opposite the direction of a projectile discharge. 
     The illustrated embodiment was chosen and described to provide the best disclosure of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by any allowed claims when interpreted in accordance with the breadth to which they are fairly, legally and equitably entitled. The drawings and preferred embodiments do not and are not intended to limit the ordinary meaning of the claims and their fair and broad interpretation in any way.