Abstract:
A boresight verification device (BVD) comprised of a circular housing with a rear portion of smaller diameter and a front portion of larger diameter. The front portion securely holds a level. The circular housing also contains a plurality of spring plungers which grip the inside of a muzzle when BVD is inserted into a muzzle for use. A tooling ball provides a stable reference point.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein was made in the performance of official duties by one or more employees of the Department of the Navy, and the invention herein may be manufactured, practiced, used, and/or licensed by or for the Government of the United States of America without the payment of any royalties thereon or therefore. 
    
    
     FIELD OF INVENTION 
     The present invention relates to the field of sight mount adjustment components, and specifically to a device which verifies the continued alignment of a sight unit and the center line of a bore. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary embodiment of a boresight verification device (BVD). 
         FIG. 2  is a side view of an exemplary BVD. 
         FIG. 3  is a cross-sectional view of an exemplary BVD. 
         FIG. 4  is an exemplary embodiment of a BVD in use. 
     
    
    
     TERMINOLOGY 
     As used herein, the term “securing component” refers to any structure or device used to securely attach two components. Securing components may include, but are not limited to, screws, shoulder screws, set screws, screw/lock washer assemblies, adhesives, welding, brazing, nails, bolts, spring plungers, expanding jaws or collars, spring-loaded feet, tapered shafts and combinations of these and other structures or devices known in the art. Securing components may create permanent or temporary bonds. 
     BACKGROUND OF THE INVENTION 
     The current apparatus to accomplish bore sight verification is a large assembly of two parts, the M154 Alignment Device and the Bore Sight Adapter, both known in the art. The Bore Sight Adapter is inserted into the mortar bore and rotated to level. The M154 is then assembled onto the dovetail of the Bore Sight Adapter. The user views the crosshairs inside the M154 collimator through the sight mounted on the weapon, and uses the micrometer knobs to align the crosshairs of the M154 and the weapon&#39;s sight. The user then reads the angle measured from the micrometer knob and compares the new, measured value to the standard value. If the measured value is the same as the standard value within tolerance, the mortar is considered to have a verified bore sight. 
     The current method and equipment has a number of limitations and disadvantages. 
     The Bore Sight Adapter uses a rubber o-ring to locate and hold the assembly level in the bore. This o-ring must maintain a coat of grease. If ungreased, the o-ring will tear when the Bore Sight Adapter is leveled. However, excessive grease is also an issue; with excessive grease, the o-ring will no longer hold, allowing the weight of the M154 and the Bore Sight Adapter to pull the unit out of level. If the o-ring falls down the bore of the mortar, no tool exists to retrieve it. Therefore, the mortar must be taken back to the depot for special maintenance to disassemble the weapon in order to extract the o-ring. 
     The Bore Sight Adapter uses a dovetail-style mount to secure the M154. However, there is no physical locator to force the M154 to be in the same place from use to use, creating the problem of repeatability in measurements. The level vial used to level the assembly is located at the top of the Bore Sight Adapter. In this location, it is difficult to read, and it is unprotected from impact and the elements. 
     To use the weapon, the mortar must be elevated to a point near the extreme limit of travel. Not only does this take valuable emplacement time and effort, it also presents a set of optically-related challenges. The M154 must be in the same optical plane as the sight telescope for proper operation. When on solid ground before firing, the base plate of the mortar is sitting on the ground and this is not an issue. If the users must verify bore sight after firing, the base plate has sunk into the ground, and it may no longer be possible to elevate the mortar to the proper elevation for verifying bore sight. In this case, the weapon must be relocated, laid, and bore sight must be verified again before allowed to fire, which would take several minutes. 
     The manufacturing tolerance stack-up from the o-ring to the end of the M154 is excessive. Tolerance stack-up is a phenomenon which occurs when the individual parts of a component are all manufactured within required specifications, but the resulting larger component is out of tolerance as a result of the variances of its components. For example, if a 12-inch (±0.5) bar is needed out of three 4-inch (±0.2) components, it is possible to have a 12.6-inch bar, which is out of tolerance, comprised of three 4.2-inch components, each of which is in tolerance. 
     The tolerance stack-up from the o-ring to the end of the M154 increases the angle tolerance, resulting in a large tolerance which is unacceptable in the artillery field. The size of the M154 and Bore Sight Adapter are also a potential hindrance due to the large protective case they are stored in. When loaded, the case is heavy and takes up a large amount of the valuable cargo area inside a vehicle. 
     SUMMARY OF THE INVENTION 
     The present invention is a boresight verification device (BVD) comprised of a circular housing with a rear portion of smaller diameter and a front portion of larger diameter. The front portion securely holds a level. The circular housing also contains a plurality of spring plungers that grip the inside of a muzzle and center the BVD in the muzzle when the BVD is inserted into a muzzle for use. A tooling ball provides a stable reference point. 
     DETAILED DESCRIPTION 
     For the purpose of promoting an understanding of the present invention, references are made in the text to exemplary embodiments of a boresight verification device, only some of which are described herein. It should be understood that no limitations on the scope of the invention are intended by describing these exemplary embodiments. One of ordinary skill in the art will readily appreciate that alternate but functionally equivalent materials, components, and devices may be used. The inclusion of additional elements may be deemed readily apparent and obvious to one of ordinary skill in the art. Specific elements disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present invention. 
     It should be understood that the drawings are not necessarily to scale; instead, emphasis has been placed upon illustrating the principles of the invention. In addition, in the embodiments depicted herein, like reference numerals in the various drawings refer to identical or near identical structural elements. 
     Moreover, the terms “substantially” or “approximately” as used herein may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. 
       FIG. 1  illustrates an exemplary embodiment of boresight verification device (BVD)  100 . Housing  10  is cylindrical with back section  14  having a smaller diameter and front section  16  having a larger diameter. Level  30  is shown contained in front section  16  and secured by screws  40   a ,  40   b . Spring plungers  50   a ,  50   b ,  50   c  are equally spaced on back section  14 , with indicator  55  attached to front section  16 . Indicator  55  acts as an aiming point for the crosshair of a sight unit, and therefore projects outward from BVD  100 . 
     In the exemplary embodiment shown, level  30  is a more sensitive level than others known in the art. Levels become more sensitive as both length and diameter increase. In the exemplary embodiment shown, level  30  is both longer and larger in diameter than the levels used with current Bore Sight Adapters known in the art. BVD  100  therefore provides a higher degree of accuracy and repeatability than the current Bore Sight Adapters. Level  30  is also positioned for easier viewing and is recessed into the body of BVD  100  to protect it from impact and other adverse conditions. 
       FIG. 2  is a side view of BVD  100 . Two spring plungers  50   a ,  50   c  are shown, with the third spring plunger  50   b  located on the opposite side of BVD  100  and not shown. Indicator  55  is connected to front section  16 . In the exemplary embodiment shown, spring plungers  50   a ,  50   b  and  50   c  are symmetrically arranged around BVD  100 . 
     Spring plungers  50   a ,  50   b  and  50   c  grip the inside of a muzzle and center BVD  100  within the muzzle. In further exemplary embodiments, BVD  100  may contain more or fewer spring plungers, and spring plungers may be positioned around BVD  100  in an unsymmetrical arrangement. 
     Spring plungers  50   a ,  50   b ,  50   c  act as independent yet equal springs, centering BVD  100  in muzzle  92  more accurately and with less physical effort than an o-ring as known in the art. Spring plungers  50   a ,  50   b ,  50   c  also require little to no maintenance, and cannot fall down muzzle  92  of mortar  95  since they are press-fit into place. 
     In the exemplary embodiment described, spring plungers  50   a ,  50   b ,  50   c  are each made of a plunger, spring and ball nose. In further exemplary embodiments, BVD  100  could use any method to self-center in the bore, including, but not limited to, expanding jaws or collars, spring-loaded feet, tapered shafts and combinations of these and other structures or devices known in the art. An extra set of spring plungers or other centering structure could be added deeper in the bore to provide further stability. 
     In the exemplary embodiment shown, indicator  55  is a tooling ball comprised of a rod with a rounded knob-like structure at its end. However, in further exemplary embodiments, indicator  55  may be replaced with any other component known in the art to provide a reference point, such as a pointed dowel pin or square edge. 
       FIG. 3  is a cross-sectional view of BVD  100  taken along the line A-A. Spring plunger  50  is shown seated, and spring plungers  50  remain fully seated during assembly of BVD  100 . When inserted into a muzzle, spring plunger  50  exerts an outward force onto the inner surface of the muzzle in order to hold BVD  100  in place. 
     In the exemplary embodiment shown, spring plunger  50  must exert enough force to keep BVD  100  from falling into a muzzle or slipping out of position. In further exemplary embodiments, spring plungers may include a textured or coated surface to increase the friction between the spring plungers and muzzle&#39;s inner surface. For example, spring plungers may contain a rubber, silicone or other coating which increases a spring plunger&#39;s gripping ability. 
       FIG. 4  illustrates an exemplary embodiment of BVD  100  in use with boresight verification magnifier  90 . As illustrated, BVD  100  is in muzzle  92  of mortar  95 . BVD  100  is releasably secured in muzzle  92  through spring plungers  50   a ,  50   b ,  50   c  (not shown), which are manipulated to grip the inside of muzzle  92 . Using mortar&#39;s  95  sight unit and magnifier  90 , the sight unit is adjusted until the crosshairs align with indicator  55 . In some exemplary embodiments, BVD  100  may be used with a boresight verification magnifier (BVM) known in the art. 
     In the exemplary embodiment described, the vertical hairline of the crosshairs is brought tangent to the outer edge of indicator  55 . The value for the comparison is then read from the micrometer of the crosshairs and compared to the standard value. pring plungers  50   a ,  50   b  and  50   c , in combination with the other structures of BVD  100 , improves both the repeatability and accuracy of measurement. 
     In the exemplary embodiments described, BVD  100  is made of aluminum because of aluminum&#39;s high strength-weight ratio. However, in further exemplary embodiments, BVD  100  could also be made of any material capable of withstanding the press forces of assembly, including, but not limited to, aluminum, steel, cast iron, and some plastics and polymers. 
     In the exemplary embodiments shown, indicator  55  is press-fit into a tooled aperture in BVD  100  by a pneumatic or hydraulic press, or any other method which would provide even, mechanical pressure to indicator  55 . Indicator  55  has a rod with slightly larger dimensions than its corresponding aperture. When forced into the aperture, indicator  55  is therefore held in place by friction between its rod and its aperture. However, in further exemplary embodiments, indicator  55  may be held in place through any structure or method known in the art, including, but not limited to, corresponding threading, welding, clips, brackets and combinations of these and other joining structures. 
     Indicator  55  of BVD  100  is press-fit into place with a tightly held tolerance. Indicator  55  facilitates much simpler reference through the sight unit, and its simplicity eliminates much of the tolerance stack-up as seen with the Bore Sight Adapters known in the art, allowing for more repeatable, accurate measurements. 
     BVD  100  was designed to use a much lower weapon elevation than the Bore Sight Adapters known in the art, which allows for faster emplacement times, and, as a result, less time verification before the mortar is ready to fire rounds on target. The lower elevation also prevents the users from having to move the weapon to verify boresight after firing the mortar, which sinks the mortar baseplate into the ground, as the elevation required to use BVD  100  is always attainable. 
     Because BVD  100  does not rely on the alignment of optical planes, there is no longer a possibility of being forced to move mortar  95  to verify boresight. BVD  100  and its associated gear are smaller and lighter than the current equipment, allowing for a case almost half the size of the case currently issued. 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.